U.S. patent application number 11/568251 was filed with the patent office on 2007-09-20 for monofilament, surgical mesh having improved flexibility and biocompatibility, and process for preparing the same.
This patent application is currently assigned to SAMYANG CORPORATION. Invention is credited to Jun-Bae Kim, Guw-Dong Yeo.
Application Number | 20070219568 11/568251 |
Document ID | / |
Family ID | 36615112 |
Filed Date | 2007-09-20 |
United States Patent
Application |
20070219568 |
Kind Code |
A1 |
Yeo; Guw-Dong ; et
al. |
September 20, 2007 |
Monofilament, Surgical Mesh Having Improved Flexibility and
Biocompatibility, and Process for Preparing the Same
Abstract
The present invention relates to a monofilament with a segmented
pie structure formed by conjugated spinning of degradable polymers
and non-degradable polymers, a hernia mesh having improved
flexibility and biocompatibility, and a preparation method thereof.
More specifically, the hernia mesh of the present invention having
improved flexibility and biocompatibility is prepared using the
monofilament obtained by conjugated spinning of degradable polymers
and non-degradable polymers into a segmented pie form, to control
it to be gradually degraded in the body, whereby the stiffness of
the early stage is removed, and thereby the foreign body sensation
is also removed.
Inventors: |
Yeo; Guw-Dong;
(Daejeon-city, KR) ; Kim; Jun-Bae; (Seoul,
KR) |
Correspondence
Address: |
LEXYOUME IP GROUP, LLC
1233 TWENTIETH STREET, N.W.
SUITE 701
WASHINGTON
DC
20036
US
|
Assignee: |
SAMYANG CORPORATION
263, YEONJI-DONG, JONGRO-GU
SEOUL
KR
110-470
|
Family ID: |
36615112 |
Appl. No.: |
11/568251 |
Filed: |
December 22, 2005 |
PCT Filed: |
December 22, 2005 |
PCT NO: |
PCT/KR05/04455 |
371 Date: |
October 24, 2006 |
Current U.S.
Class: |
606/151 |
Current CPC
Class: |
A61F 2250/0031 20130101;
D01D 5/08 20130101; D01D 5/088 20130101; A61F 2002/0068 20130101;
D02G 3/448 20130101; D01D 5/16 20130101; D02J 1/229 20130101; B29C
48/0018 20190201; D01D 5/12 20130101; A61L 31/041 20130101; B29K
2023/12 20130101; A61L 31/148 20130101; B29L 2031/7546 20130101;
D03D 7/00 20130101; B29L 2028/00 20130101; D04B 21/12 20130101;
B29C 2948/92695 20190201; B29C 48/05 20190201; B29K 2995/0037
20130101; A61F 2/0063 20130101; B29C 48/92 20190201; D01D 10/00
20130101; D01D 5/32 20130101; D02J 1/22 20130101; D04B 1/22
20130101; B29K 2067/04 20130101; D01D 5/30 20130101; D02J 1/228
20130101; D01D 10/02 20130101; D01D 5/0885 20130101; B29C 48/345
20190201; A61L 31/041 20130101; C08L 67/04 20130101 |
Class at
Publication: |
606/151 |
International
Class: |
A61B 17/03 20060101
A61B017/03 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 29, 2004 |
KR |
10-2004-015443 |
Claims
1. A monofilament having a segmented pie structure formed by
conjugated spinning of a degradable polymer and a non-degradable
polymer.
2. The monofilament according to claim 1, wherein the content of
the degradable polymer is 30 to 70 vol %, and the content of the
non-degradable polymer is 30 to 70 vol %.
3. The monofilament according to claim 1, wherein the degradable
polymer is a homopolymer or copolymer comprising one or more
monomers selected from the group consisting of glycolide, glycolic
acid, lactide, lactic acid, caprolactone (.epsilon.-caprolactone),
dioxanone (p-dioxanone), trimethylene carbonate, polyanhydride, and
polyhydroxyalkanoate (PHA).
4. The monofilament according to claim 3, wherein the degradable
polymer is a glycolide/caprolactone copolymer or a
dioxanone/trimethylenecarbonate/caprolactone copolymer.
5. The monofilament according to claim 1, wherein the
non-degradable polymer is selected from the group consisting of
polyolefins, polyamides, polyurethanes, and fluoropolymers.
6. The monofilament according to claim 5, wherein the
non-degradable polymer is polypropylene, or a copolymer of
propylene and ethylene.
7. The monofilament according to claim 1, wherein the melt index of
the degradable polymer is not lower than the melt index of the
non-degradable polymer.
8. The monofilament according to claim 7, wherein the difference
between the melt indexes of the degradable polymer and the
non-degradable polymer is 10 or less.
9. The monofilament according to claim 1, wherein the
non-degradable polymer is divided into at least four strands.
10. A method of using the monofilament according to claim 1 in
hernia repair, vaginal sling procedures, artificial ligament and
tendon operations, or repairing fascial deficiencies that require
addition of an reinforcing material or a bridging material.
11. A hernia mesh having improved flexibility and biocompatibility,
comprising a monofilament having a segmented pie structure formed
by conjugated spinning of a degradable polymer and a non-degradable
polymer.
12. The hernia mesh according to claim 11, wherein the content of
the degradable polymer is 30 to 70 vol %, and the content of the
non-degradable polymer is 30 to 70 vol %.
13. The hernia mesh according to claim 11, wherein the degradable
polymer is a homopolymer or a copolymer comprising one or more
monomers selected from the group consisting of glycolide, glycolic
acid, lactide, lactic acid, caprolactone (.epsilon.-caprolactone),
dioxanone (p-dioxanone), trimethylenecarbonate, polyanhydride, and
polyhydroxyalkanoate.
14. The monofilament according to claim 13, wherein the degradable
polymer is a glycolide/caprolactone copolymer or a
dioxanone/trimethylenecarbonate/caprolactone copolymer.
15. The monofilament according to claim 11, wherein the
non-degradable polymer is selected from the group consisting of
polyolefins, polyamides, polyurethanes, and fluoropolymers.
16. The monofilament according to claim 15, wherein the
non-degradable polymer is polypropylene, or a copolymer of
propylene and ethylene.
17. The monofilament according to claim 11, wherein the melt index
of the degradable polymer is not lower than the melt index of the
non-degradable polymer.
18. The monofilament according to claim 17, wherein a difference
between the melt indexes of the degradable polymer and the
non-degradable polymer is 10 or less.
19. The monofilament according to claim 11, wherein the
non-degradable polymer is divided into at least four strands.
20. The monofilament according to claim 11, wherein the diameter of
the monofilament is 100 to 250 .mu.m.
21. The hernia mesh according to claim 11, wherein the stiffness of
the degradable polymer after degradation is decreased at least 70%
compared with that before degradation.
22. The hernia mesh according to claim 11, wherein the
non-degradable polymer is partitioned by the degradable polymer,
and the degradable polymer has a continuous form.
23. The hernia mesh according to claim 11, wherein the structure of
the mesh is a square, hexagonal, or network structure.
24. The hernia mesh according to claim 11, wherein the pore size is
0.1 to 4.0 mm and the thickness is 200 to 800 .mu.m,
25. The hernia mesh according to claim 11, wherein the density is 8
to 20 gauges/inch based on the distance between the needles in a
warp knitting machine.
26. The hernia mesh according to claim 11, wherein the degradable
polymer is partially dyed.
27. A method of preparing a hernia mesh, comprising the steps of
spinning, solidification, crystallization, and drawing to prepare a
monofilament, and the steps of warping, knitting, and curing to
prepare the hernia mesh, wherein: the spinning step is performed by
melting 30 to 70 vol % of a degradable polymer and 30 to 70 vol %
of a non-degradable polymer, and conducting conjugated spinning to
form a segmented pie structure; the drawing step is performed by
applying stress-relaxation to prepare the monofilament; and the
curing step is performed at 90 to 160.degree. C. for 1 to 30
minutes.
28. The method according to claim 27, wherein stress-relaxation of
at least 10% is applied.
Description
BACKGROUND OF THE INVENTION
[0001] (a) Field of the Invention
[0002] The present invention relates to a monofilament having a
segmented pie structure formed by conjugated spinning of degradable
polymers and non-degradable polymers, a hernia mesh comprising the
monofilament having improved flexibility and biocompatibility, and
a method for preparing the same. More specifically, the present
invention relates to a monofilament prepared by conjugated spinning
of degradable polymers and non-degradable polymers in the form of a
segmented pie; a hernia mesh that is prepared with the monofilament
and that is controlled to be gradually degraded in the body while
losing the stiffness of the early stage, causing no misfeelings,
and having improved flexibility and biocompatibility; and a method
of preparation thereof.
[0003] (b) Description of the Related Art
[0004] Tension-free hernioplasty (Lichtenstein I L, Am J Surg 1989;
157; 188-193) is considered to be a useful method for reparation of
hernias, because the relapse ratio thereafter is low, the operative
time is short, and the operative wound heals quickly, and thereby
the patient can rapidly return to normal life. Conventionally,
since the mesh used for hernia repair is required to have the
capability of maintaining its chemical and physical properties for
several years to strengthen the peritoneum, polypropylene
monofilaments have been used as the material for a hernia mesh.
However, it has been reported that the polypropylene mesh may have
the potential to generate fistulas in the intestine (Seelig M H, "A
rare complication after incisional hernia repair". Chirurg 1995;
66(7); 739-741, Leber G E, "Long-term complications associated with
prosthetic repair of incisional hernias", Arch Surg 1988; 133(4);
378-382). Further, as general side effects of the polypropylene
mesh, an edema, a restriction of abdominal wall mobility due to
stiffness of the peritoneum where the artificial membrane is
located and pain from misfeelings caused by the stiffness, a
chronic inflammatory response between the polypropylene fibers and
tissues in body, and the like have been reported (Amid P K,
"Biomaterials for abdominal wall hernia surgery and principles of
their applications", Lagenbecks Arch Chir 1994; 379(3): 168-171,
Waldrep D J, "Mature fibrous cyst formation after Marlex Vestweber
K, Results of recurrent abdominal wall hernia repair using
polypropylene mesh". Zentralblatt Fur Chirurgie 1997; 122:885-8,
Bellon J M, "Integration of biomaterials implanted into abdominal
wall: mesh ventral herniorrhaphy: a newly described pathologic
entity". Am Surg 1993; 59(11):716-8, "Process of scar formation and
macrophage response". Biomaterials 1995; 16(5):381-7, Klinge U,
"Changes in abdominal wall mechanics after mesh implantation".
Experimental changes in mesh stability. Lagenbecks Arch Chir 1996;
381(6): 323-32).
[0005] The hernia mesh needs stiffness in order to be positioned
and fixed on the surgical wound region when performing the surgical
operation. For that purpose, several methods to prepare the hernia
mesh using fibers in the monofilament form have been known. U.S.
Pat. No. 4,347,847, U.S. Pat. No. 4,452,245, U.S. Pat. No.
5,569,273, and U.S. Pat. No. 6,287,316 disclose a method to prepare
a hernia mesh consisting of polypropylene monofilaments. However,
since polypropylene is non-degradable, after performing the
surgical operation using the hernia mesh, the strength and
stiffness of the mesh that are necessary during the initial stage
after the surgical operation are continuously maintained in the
body. Therefore, the mesh has excessive stiffness even after the
wound has healed, causing pain to the patient due to misfeelings.
Further, U.S. Pat. No. 5,292,328 discloses a method of preparing a
hernia mesh consisting of polypropylene multifilaments in order to
improve the flexibility, in which the mesh has a somewhat improved
initial flexibility compared with that consisting of the
monofilaments. However, since the mesh consists of only
non-degradable materials, there are also some problems in that the
initial strength and stiffness of the mesh are continuously
maintained in the body, and an excessive amount of polypropylene
remains in the body. To solve these problems, studies on
development of a partially degradable mesh wherein the content of
polypropylene is decreased and the strength and stiffness necessary
for the initial stage is supplemented by additionally comprising
degradable materials, have been disclosed in U.S. Pat. No.
4,652,264 and U.S. Pat. No. 6,162,962. Herein, the degradable
materials are partially degraded after the wound has healed, to
improve the flexibility of the mesh. U.S. Pat. No. 4,652,264
discloses a method to prepare a mesh by combining threads
consisting of three different materials, of which two are
degradable and one is non-degradable. U.S. Pat. No. 6,287,316
discloses a method of preparing a mesh using a multifilament
consisting of degradable materials and non-degradable materials.
However, since the meshes prepared by the above methods consist of
several threads of degradable and non-degradable materials in the
combined form, there is a possibility of bacterial infection within
the spaces between the threads, which is an inherent defect of
multifilaments. Further, since the methods employ the multifilament
form wherein several strands of fiber are combined, the amount of
materials required for exhibiting the necessary stiffness is larger
than the case of using the monofilament. In addition, the
multifilament causes a strong foreign body response due to the
large surface area (Beets G L, "Foreign body reactions to
monofilament and braided polypropylene mesh used as preperitoneal
implants in pigs". Eur J Surg 1996; 162:823-825).
[0006] As known from the above prior art, although the use of a
hernia mesh has been regarded as a basic means in performing hernia
repairs, there are unsatisfactory results obtained from the studies
to develop a hernia mesh for improving the convenience in
performing the operation, reducing the misfeelings, and having
improved biocompatibility. Therefore, it is required to develop a
hernia mesh that can maintain its strength and stiffness at the
early stage, thereby ensuring convenience in performing the
operation, and be partially degraded as the surgical wound is
healed, thereby improving the flexibility of the remaining
mesh.
SUMMARY OF THE INVENTION
[0007] The object of the present invention is to provide a
monofilament having a segmented pie structure formed by conjugated
spinning of degradable polymers and non-degradable polymers.
[0008] Another object of the present invention is to provide a
hernia surgical mesh comprising the monofilament, having improved
flexibility and biocompatibility.
[0009] Another object of the present invention is to provide a
method of preparing the hernia mesh.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 A is an optical microscopic image of a cross section
of the conjugated filament in the segmented pie form according to
the present invention [1: degradable polymer, 2: non-degradable
polymer].
[0011] FIG. 1B is a SEM (scanning electron microscope) image of the
cross section of the conjugated filament in the segmented pie form
according to the present invention.
[0012] FIG. 2A is a SEM image prior to degradation of the mesh
prepared with the monofilament obtained by conjugated spinning.
[0013] FIG. 2B is a SEM image after degradation of the mesh
prepared with the monofilament obtained by conjugated spinning.
[0014] FIG. 3A is a SEM image of the cross section of the
monofilament prepared by conjugated spinning using 75 volume % of
degradable materials.
[0015] FIG. 3B is a SEM image showing a distortion of the
monofilament in the segmented pie form when the difference between
the melt indexes is more than 14 in conjugated spinning.
[0016] FIG. 3C is an SEM image showing fiber separation when the
stress-relaxation is not performed under the drawing conditions in
conjugated spinning.
[0017] FIG. 4 is a schematic diagram showing the flow of two
polymers at a distributing plate and a nozzle in the conjugated
spinning apparatus for preparing the monofilament in the segmented
pie form.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0018] The present inventors have conducted continued studies to
develop a novel hernia mesh with partial degradability, which
maintains its strength and stiffness at the early stage to secure
convenience in performing a surgical operation and then becomes
partially degraded during healing of the surgical wound to increase
the flexibility of the mesh remaining in the body, resulting in
alleviating the patient's pain and improving the biocompatibility
by remarkably reducing the amount of non-degradable materials used.
As the result, the present inventors found that when preparing a
monofilament in the segmented pie form by conjugated spinning of
degradable polymers and non-degradable polymers, the strength and
stiffness necessary for the early stage of the surgical operation
can be achieved by the stiffness characteristic of the monofilament
itself, and after performing the operation, the monofilament
becomes partially degraded in the body, and thereby the mesh
consisting thereof can remain in the body in the more flexible
structure, to complete the present invention.
[0019] Hereinafter, the present invention will be described in
detail.
[0020] The present invention relates to a hernia mesh with improved
flexibility and biocompatibility and a preparation method thereof,
wherein the mesh comprises monofilaments having the segmented pie
structure formed by conjugated spinning of degradable polymers and
non-degradable polymers, being controlled to be gradually degraded
in the body, to remove the initial stiffness of the mesh and to
avoid misfeelings due to the remaining mesh.
[0021] The monofilament in the segmented pie form, which composes
the hernia mesh of the present invention, consists of a degradable
polymer and a non-degradable polymer, wherein the non-degradable
polymer (2) is separated into several partitions by the degradable
polymer (1), and the degradable polymer (1) has a continuous form
[see FIG. 1A]. The monofilament in the segmented pie form of the
present invention is present in the monofilament form before
degradation, and then, as the degradable polymer becomes degraded,
the monofilament is divided into individual strands as a
multifilament form, to exhibit improved flexibility.
[0022] The degradable polymer used in the present invention may be
a homopolymer or a copolymer comprising one or more selected from
the group consisting of glycolide, glycolic acid, lactide, lactic
acid, caprolactone (.epsilon.-caprolactone), dioxanone
(p-dioxanone), trimethylenecarbonate, polyanhydride, and
polyhydroxyalkanoate, and is more preferably a
glycolide/caprolactone copolymer or a
dioxanone/trimethylenecarbonate/caprolactone copolymer.
[0023] The non-degradable polymer used in the present invention may
be selected from the group consisting of polyolefins such as
polypropylene, polyethylene, and a copolymer of propylene and
ethylene; polyamides such as nylon 6 and nylon 66; polyurethanes;
and fluoropolymers such as polyvinylidene fluoride, and is more
preferably polypropylene or a copolymer of propylene and
ethylene.
[0024] In particular, the content of the degradable polymer is
preferably 30 to 70 vol % and the content of the non-degradable
polymer is preferably 30 to 70 vol %, and more preferably, the
content of the degradable polymer is 40 to 60 vol % and the content
of the non-degradable polymer is 40 to 60 vol %. When the content
of the degradable polymer is less than 30 vol %, in spinning, the
volume of the degradable polymer is too small to separate the
non-degradable polymer, and thus the non-degradable polymer is in
the continuously linked form. When the content of the
non-degradable polymer is less than 30 vol %, the remaining amount
of the non-degradable polymer after degradation is too low to
maintain minimum strength, and further, the monofilament may be
prepared in a sea/islands type wherein the non-degradable polymer
is surrounded by the degradable polymer as shown in FIG. 3A.
[0025] The monofilament prepared by conjugated spinning may be
divided into several types, such as sea/islands type, a segmented
pie type, a side-by-side type, a sheath/core type, and the like,
depending on the structures, and the preferable type in the present
invention is the segmented pie type. The segmented pie type has
some advantages in that the degradable materials and the
non-degradable materials are uniformly spread on the surface of the
fibers to attain the mobility of the peritoneum by an appropriate
combination of fat tissue formed around the degradable material and
connective tissue appeared around the non-degradable material, and
to improve the adhesive property between the mesh and the tissues.
Further, different from the conjugated yarn type such as the
sea/islands type or the sheath/core type whereon the non-degradable
material is surrounded by the degradable material, the segmented
pie type monofilament can connect with the tissues in the body at
the early stage after the surgical operation, and thus induce
strong adhesion between the mesh and the tissues shortly after
performing the surgical operation [U. Klinge, "Influence of
polyglactin-coating on functional and morphological parameters of
polypropylene-mesh modifications for abdominal wall repair",
Biomaterials 1999;20:613-623, U. Klinge, "Foreign body reaction to
meshes used for the repair of abdominal wall" Hernias, Eur J Surg,
1999;1 65:665-673].
[0026] In mesh prepared with the segmented pie type monofilament,
in order to reduce the stiffness after healing of the surgical
wound to less than 70% of the initial stiffness and to improve the
flexibility of the mesh, it is preferable to divide the
non-degradable polymer into at least four strands, and more
preferably 6 to 10 strands.
[0027] In mesh prepared with the sea/islands type or sheath/core
type of monofilament, the sea or sheath which is an outside
component of the monofilament must be composed of the degradable
polymer, and the island or core which is an inside component of the
monofilament must be composed of the non-degradable polymer. In
these cases, as the degradable polymer located at the outside of
the monofilament is degraded and dispersed, the monofilament starts
exhibiting an excessive surface area and excessive fibrosis
(capsule formation) occurs, whereby the strong adhesion between the
mesh and the tissues in the body is inhibited. Further, in the
side-by-side type of monofilament wherein one of two components is
located at one side of the cross section and the other is located
at the other side, the non-degradable polymer causes an
inflammatory response, and rigid connective tissue is formed around
the mesh, inhibiting the mobility of the peritoneum. These types
are unsuitable for the object of the present invention which is to
improve the flexibility of the peritoneum, and are difficult to
prepare with two components having different melting behaviors and
different thermal contractibility. In addition, since the two
components have the same diameter, the diameter of the remaining
non-degradable fiber increases, and thereby there is a limitation
in improving the flexibility of the remaining mesh.
[0028] The diameter of the monofilament may be controlled so as to
have the strength and/or stiffness necessary at the early stage
after performing the surgical operation, and at the same time to
prevent a large amount of the non-degradable polymer from remaining
in the body, thereby improving the biocompatibility and the
flexibility. That is, in order to maintain the initial strength and
stiffness, it is required for the fiber to have a density and
diameter of a certain degree or higher, while in order to minimize
a foreign body response when inserted in the body, it is required
that the total amount of fibers used is minimized. In the present
invention, the diameter of the monofilament is preferably 100 to
250 .mu.m.
[0029] The mesh of the present invention may be prepared in various
shapes, and is preferably prepared as a net-structure such as a
square, hexagonal, or network shape. The density of the mesh is
preferably 8 to 20 gauges/inch based on the distance between the
needles in a flat warp knitting machine. When the mesh is cut in a
suitable size and shape for the surgical wound region of a patient
and is applied to the wound region, problems such as material
particles or an unraveling phenomenon may occur at the edge of the
cut-off mesh. Therefore, a structure that readily generates
particles or an unraveling phenomenon when cut may be relatively
undesirable, and the net-structure such as the square, hexagonal,
or network may be desirable in view of lesser particle generation
when cut.
[0030] In the present invention, the pore size of the mesh may be
0.1 to 4.0 mm, preferably 2.0 to 3.0 mm, and the thickness of the
mesh may be 200 to 800 .mu.m, preferably 500 to 600 .mu.m.
[0031] In the hernia mesh of the present invention, it is
preferable that the non-degradable polymer is partitioned by the
degradable polymer, and that the degradable polymer is continuously
linked. The present invention provides a method of preparing the
monofilament in the segmented pie structure formed by conjugated
spinning of the degradable polymer and the non-degradable
polymer.
[0032] In the present invention, to perform spinning, any
conventional conjugated spinning apparatus may be used. In detail,
the polymers are melted by two extruding apparatuses for conjugated
spinning. Each of the melted polymers is discharged in a desired
amount through each quantitative pump to control the content ratio
of each component. The polymers that are melted and passed through
the quantitative pump are subjected to conjugated spinning into one
strand of fiber through a conjugated spinning block. FIG. 4 is a
schematic diagram of the preparation of the monofilament in the
segmented pie form, showing the flows of the degradable polymer (3)
and the non-degradable polymer (4) in the conjugated spinning
block. The melted polymer discharged from each quantitative pump is
gathered at the distributing plate (5) in the conjugated spinning
block, and passed through the nozzle to prepare the monofilament in
the segmented pie form. The strand obtained by conjugated spinning
is solidified and crystallized in a cooling bath. The air gap
between the spinnerette and the surface of water in the cooing bath
is preferably 0.5 to 100 cm, and more preferably 1 to 30 cm. The
solidified fiber is drawn through a multi-stage drawing apparatus
and wound in a winder in order to obtain an improvement of the
property by orientation. A preferable embodiment of the
monofilament in the segmented pie form is shown in FIG. 1A.
[0033] To prepare the uniform and stable monofilament in the
segmented pie form by spinning process, the melt indexes (MI) of
the two polymers and the spinning conditions have to be exactly
controlled. The melt index of the degradable polymer may not be
lower than that of the non-degradable polymer to maintain the
segmented pie structure, and the difference between the melt
indexes of the degradable polymer and the non-degradable polymer is
preferably 10 or less. If the melt index of the degradable polymer
is lower than that of the non-degradable polymer, the segmented pie
structure may be obtained in a distorted and unequal form wherein
the distribution of the non-degradable polymer is not equally
distributed, being concentrated on a certain position as shown in
FIG. 3B. Further, if the difference between the melt indexes of the
two polymers is more than 10, phase separation easily occurs.
Therefore, it is preferable that the melt index of the degradable
polymer is not lower than that of the non-degradable polymer, and
that the difference between the melt indexes of the two polymers is
10 or less.
[0034] In addition, when the monofilament in the segmented pie form
is prepared by conjugated spinning of two polymers having different
properties such as the melting point, the degree of crystallinity,
the thermal contractibility and the like, improper drawing
conditions cause curling and phase separation of the two components
as shown in FIG. 3C. To prevent such a curling phenomenon, the
spinning temperature is controlled within a certain range so that
the melt index of the degradable polymer is the same as or higher
than that of the non-degradable polymer, to allow the melting
behavior of the two polymers to form the symmetric structure of the
segmented pie form. Further, to prevent the fiber phase separation
phenomenon, in a final drawing oven, stress relaxation of at least
10% and preferably 10 to 20% is applied in consideration of the
thermal contraction rate of the two polymer components to stabilize
the structure.
[0035] In order to easily distinguish the mesh when performing the
surgical operation, the mesh fibers may be dyed at regular
intervals. Herein, to prevent the dye from remaining in the body,
it is preferable to dye only the degradable polymer part. Any dye
that is conventionally employed in preparing sutures, such as
D&C violet No.2, D&C Green No.6, FD&C Blue No.2, and
the like, may be used.
[0036] The present invention also provides a method for preparing a
mesh using the above monofilament in the segmented pie form.
[0037] In the present invention, the mesh may be prepared through
three conventional steps of warping, knitting, and curing.
[0038] In the warping step, several strands are regularly wound on
a beam with a constant tension to equally supply a regular amount
of fiber before the knitting step. Then, the beam is equipped in a
flat warp knitting machine to prepare a mesh. In the present
invention, the mesh may be prepared by a Tricot flat warp knitting
machine or a Raschel flat warp knitting machine. When preparing the
mesh, the texture and shape may be controlled so as to give the
mesh the necessary strength and stiffness at the early stage and to
simultaneously prevent the non-degradable materials from remaining
in the body in a large amount to improve the biocompatibility and
flexibility, controlling the strength and stiffness of the texture
of the mesh. As a final step, the prepared mesh is cured to fix the
shape of the mesh. The curing step is performed under temperature
and time conditions such that yellowing and a change of the
properties are avoided. Conventionally, the mesh is cured at a
temperature 10.degree. C. to 15.degree. C. lower than the melting
point of the component constituting the mesh, e.g., at 90.degree.
C. to 160.degree. C., for 1 to 30 minutes. For example, in
preparing the mesh comprising polypropylene, if the melting point
of the degradable component is higher than that of polypropylene,
the curing temperature of the mesh is determined on the basis of
the melting point of polypropylene, that is, the mesh may be cured
at 100 to 155.degree. C. for 3 to 20 minutes.
[0039] In an embodiment of the present invention, a mesh having the
following texture may be used by a flat warp knitting machine.
(The warp knitted texture Example 1)
The number of gauge=18 (Gauges/inch)
[0040] G1=10 01 10 12 21 12 [0041] G2=00 11 00 22 11 22 [0042]
G=guide bar (The warp knitted texture Example 2) The number of
gauge=12 (Gauges/inch) [0043] G1=10 01 10 12 21 12 [0044] G2=00 11
00 22 11 22 [0045] G3=00 11 00 22 11 22 [0046] G4=00 11 00 11 00 11
(The warp knitted texture Example 3) The number of gauge=12
(Gauges/inch) [0047] G1=10 01 10 12 21 12.times.4 [0048] G2=00 11
00 22 11 22.times.4 [0049] G3=22 33 22 33 22 33 11 22 11 11 00 11
11 22 11 33 22 33 22 33 22 44 33 44 [0050] G4=11 22 11 33 22 33 22
33 22 44 33 44 22 33 22 33 22 33 11 22 11 22 00 22 (The warp
knitted texture Example 4) The number of gauge=18 (Gauges/inch)
[0051] G1=10 12 23 21 [0052] G2=23 21 10 12 (The warp knitted
texture Example 5) The number of gauge=18 (Gauges/inch) [0053]
G1=21 12 10 12 21 23 [0054] G2=12 21 23 21 12 10
[0055] FIG. 2A is an electronic microscopy image of the mesh
according to the present invention before degradation, and FIG. 2B
is that after degradation, showing that the component constituting
the mesh has the monofilament form prior to degradation, and is
converted to the multifilament form of several strands of the
non-degradable polymer after degradation.
[0056] In the present invention, the mesh is prepared with the
monofilament in the segmented pie form wherein the degradable
polymer and the non-degradable polymer are repeatedly and
alternatively distributed in all directions throughout the whole
fiber, to improve the biocompatibility and the adhesive strength to
the tissue in the body at the early stage after performing the
surgical operation. Further, the stiffness after degradation is
reduced by at least 70% compared with that before degradation, to
maximize the flexibility of the mesh remaining in the body after
the surgical wound is healed. Compared with the conventional mesh
that contains only non-degradable components or partially
degradable components, in the present invention the initial and
remaining amounts of the non-degradable components in the mesh are
lowered, and simultaneously the biocompatibility and the
flexibility of the mesh are improved.
[0057] Therefore, the mesh according to the present invention is
suitable for hernia repair, since the mesh maintains the strength
and the stiffness to attain the convenience of the surgical
operation at the early stage, and is partially degraded to improve
the flexibility as the surgical wound is healed.
[0058] According to the present invention, the monofilament with
the segmented pie structure formed by conjugated spinning of the
degradable polymer and the non-degradable polymer may be applied to
not only hernia mesh, but also to other operations, such as vaginal
sling procedures, artificial ligament and tendon operations,
fascial deficiencies which require the add an reinforcing material
or a bridging material, and the like.
[0059] Hereinafter, the present invention will be more specifically
described by the following examples, which should not be understood
to limit the scope of the invention.
EXAMPLE 1
[0060] The monofilament in the segmented pie form was prepared
through conjugated spinning of 55 vol % of a glycolide
(75)/caprolactone (25) copolymer as a degradable polymer and 45 vol
% of polypropylene as a non-degradable polymer under the conditions
shown in the following Table 1. The prepared monofilament in the
segmented pie form was warped with 150 yarns/7'' beam to prepare
the mesh according to the above warp knitted texture of Example 1.
The prepared mesh was cured at 150.degree. C. for 5 minutes. The
properties of the mesh, such as thickness, weight, tensile
strength, and stiffness were determined according to the
conventional measuring methods, and the results are shown in the
following Table 6. TABLE-US-00001 TABLE 1 glycolide (75)/
caprolactone Polymer polypropylene (25) copolymer Melt index (g/10
min, 230.degree. C.) 10 13 Spinning Conditions Extruder Ext. 1 Ext.
2 The number of segments of the non- 6 -- degradable polymer
Pre-pump pressure (kgf/cm.sup.2) 80 80 Temperature in Zone 1 150
150 Extruder (.degree. C.) Zone 2 160 165 Zone 3 170 180 Zone 4 175
190 Zone 5 175 195 Temperature in Manifold (.degree. C.) 180 198
Temperature in Quantitative Pump 180 186 (.degree. C.) Temperature
in Nozzle Pack Die (.degree. C.) 204 Capacity of Quantitative Pump
0.3 0.6 (cc/rev) Revolution speed of Quantitative 8.75 5.35 Pump
(rpm) Temperature in Cooling Bath (.degree. C.) 25 Drawing
Conditions First Roller velocity (m/min) 6.7 First Drawing Oven
Temperature (.degree. C.) 70 Second Roller velocity (m/min) 47
Second Drawing Oven Temperature 100 (.degree. C.) Third Roller
velocity (m/min) 55 Third Drawing Oven Temperature 140 (.degree.
C.) Fourth Roller velocity (m/min) 46 Total Drawing Ratio 6.86
Preparation Conditions of the Mesh Warping Conditions 150 yarns/7''
beam Warp Knitted Texture Warp Knitted Texture Example 1 Curing
Conditions 150.degree. C., 5 minutes
EXAMPLE 2
[0061] The monofilament in the segmented pie form was prepared
through conjugated spinning of 55 vol % of a glycolide
(75)/caprolactone (25) copolymer as a degradable polymer and 45 vol
% of a propylene (97)/ethylene (3) copolymer as a non-degradable
polymer under the conditions shown in the following Table 2. The
prepared monofilament in the segmented pie form was warped with 120
yarns/7'' beam to prepare the mesh according to the above warp
knitted texture of Example 2. The prepared mesh was cured at
155.degree. C. for 3 minutes. The properties of the mesh, such as
thickness, weight, tensile strength, and stiffness were determined
according to the conventional measuring methods, and the results
are shown in the following Table 6. TABLE-US-00002 TABLE 2
Propylene (97)/ ethylene (3) Glycolide (75)/ random caprolactone
(25) Polymer copolymer copolymer Melt index (g/10 min, 230.degree.
C.) 8 12 Spinning Conditions Extruder Ext. 1 Ext. 2 The number of
segments of the non- 6 -- degradable polymer Pre-pump pressure
(kgf/cm.sup.2) 80 80 Temperature in Zone 1 150 150 Extruder
(.degree. C.) Zone 2 160 165 Zone 3 165 180 Zone 4 170 190 Zone 5
170 195 Temperature in Manifold (.degree. C.) 175 198 Temperature
in Quantitative Pump 175 186 (.degree. C.) Temperature in Nozzle
Pack Die 203 (.degree. C.) Capacity of Quantitative Pump 0.3 0.6
(cc/rev) Revolution speed of Quantitative 8.75 5.35 Pump (rpm)
Temperature in Cooling Bath (.degree. C.) 25 Drawing Conditions
First Roller velocity (m/min) 6.1 First Drawing Oven Temperature 70
(.degree. C.) Second Roller velocity (m/min) 47 Second Drawing Oven
Temperature 100 (.degree. C.) Third Roller velocity (m/min) 55
Third Drawing Oven Temperature 140 (.degree. C.) Fourth Roller
velocity (m/min) 46 Total Drawing Ratio 7.54 Preparation Conditions
of the Mesh Warping Conditions 120 yarns/7'' beam Warp Knitted
Texture Warp Knitted Texture Example 2 Curing Conditions
155.degree. C., 3 minutes
EXAMPLE 3
[0062] The monofilament in the segmented pie form was prepared
through conjugated spinning of 55 vol % of a dioxanone
(90)/trimethylenecarbonate (9)/caprolactone (1) tri-block copolymer
as a degradable polymer and 45 vol % of polypropylene as a
non-degradable polymer under the conditions shown in the following
Table 3. The prepared monofilament in the segmented pie form was
warped with 120 yarns/7'' beam to prepare the mesh according to the
above warp knitted texture of Example 3. The prepared mesh was
cured at 95.degree. C. for 10 minutes. The properties of the mesh,
such as thickness, weight, tensile strength, and stiffness were
determined according to the conventional measuring methods, and the
results are shown in the following Table 6. TABLE-US-00003 TABLE 3
Dioxanone (90)/ trimethylene- carbonate (9)/ caprolactone poly- (1)
tri-block Polymer propylene copolymer Melt index (g/10 min,
230.degree. C.) 10 10 Spinning Conditions Extruder Ext. 1 Ext. 2
The number of segments of the non- 6 -- degradable polymer Pre-pump
pressure (kgf/cm.sup.2) 80 80 Temperature Zone 1 150 150 in Zone 2
160 155 Extruder Zone 3 165 160 (.degree. C.) Zone 4 165 160 Zone 5
165 160 Temperature in Manifold (.degree. C.) 170 165 Temperature
in Quantitative Pump (.degree. C.) 170 165 Temperature in Nozzle
Pack Die (.degree. C.) 175 Capacity of Quantitative Pump (cc/rev)
0.3 0.6 Revolution speed of Quantitative Pump 8.75 5.35 (rpm)
Temperature in Cooling Bath (.degree. C.) 25 Drawing Conditions
First Roller velocity (m/min) 5.8 First Drawing Oven Temperature
(.degree. C.) 70 Second Roller velocity (m/min) 45 Second Drawing
Oven Temperature (.degree. C.) 100 Third Roller velocity (m/min) 53
Third Drawing Oven Temperature (.degree. C.) 120 Fourth Roller
velocity (m/min) 42 Total Drawing Ratio 7.24 Preparation Conditions
of the Mesh Warping Conditions 120 yarns/7'' beam Warp Knitted
Texture Warp Knitted Texture Example 3 Curing Conditions 95.degree.
C., 10 minutes
EXAMPLE 4
[0063] The mesh was prepared by the same method as in Example 1,
except that the number of the segments of the non-degradable
polymer was 8. The properties of the prepared mesh, such as
thickness, weight, tensile strength, and stiffness were determined
according to the conventional measuring methods, and the results
are shown in the following Table 6.
EXAMPLE 5
[0064] The mesh was prepared by the same method as in Example 1,
except that the revolution speed (rpm) of the quantitative pump was
9.7 rpm for the polypropylene (50 vol %) and 4.9 rpm for the
glycolide/caprolactone copolymer (50 vol %). The properties of the
prepared mesh, such as thickness, weight, tensile strength, and
stiffness were determined according to the conventional measuring
methods, and the results are shown in the following Table 6.
EXAMPLE 6
[0065] The mesh was prepared by the same method as in Example 1,
except that the revolution speed (rpm) of the quantitative pump as
9.6 rpm for the polypropylene (40 vol %) and 7.2 rpm for the
glycolide/caprolactone copolymer (60 vol %). The properties of the
prepared mesh, such as thickness, weight, tensile strength, and
stiffness were determined according to the conventional measuring
methods, and the results are shown in the following Table 6.
COMPARATIVE EXAMPLE 1
[0066] The mesh was prepared by the same method as in Example 1,
except that the revolution speed (rpm) of the quantitative pump was
4.9 rpm for the polypropylene (25 vol %) and 7.3 rpm for the
glycolide/caprolactone copolymer (75 vol %). The obtained
monofilament was a sea/island type of monofilament wherein the
polypropylene component was surrounded by the
glycolide/caprolactone copolymer component as shown in FIG. 3A.
COMPARATIVE EXAMPLE 2
[0067] The mesh was prepared by the same method as in Example 1,
except that the melt index of polypropylene was 27. The
monofilament had the segmented pie structure, but the tensile
strength of the monofilament was poorer than that of Example 1, and
the segmented pie structure was not symmetrical (FIG. 3B).
COMPARATIVE EXAMPLE 3
[0068] The mesh was prepared by the same method as in Example 1,
except that the third roller velocity and the fourth roller
velocity of the drawing conditions were made the same at 55 m/min
such that no stress-relaxation was applied.
[0069] The intensity of the obtained monofilament in the segmented
pie form was improved compared with that of Example 1, but strand
separation of the two components occurred when preparing the mesh
(FIG. 3C).
COMPARATIVE EXAMPLE 4
[0070] The thickness, weight, tensile strength, and stiffness of a
conventional mesh product (Prolene Hernia mesh, Ethicon Co.)
consisting of only polypropylene monofilament were measured
according to the conventional measuring methods. The results are
shown in the following Table 6.
COMPARATIVE EXAMPLE 5
[0071] The thickness, weight, tensile strength, and stiffness of a
conventional mesh product (Vypro II Hernia mesh, Ethicon Co.)
comprising a glycolide/lactide copolymer multifilament as a
degradable component and a polypropylene monofilament as a
non-degradable component were measured according to the
conventional measuring methods. The results are shown in the
following Table 6.
EXPERIMENTAL EXAMPLE
[0072] The property measuring methods are summarized in the
following Table 4. TABLE-US-00004 TABLE 4 Measuring Methods and
Property Apparatuses Diameter, mm EP Regulation, Diameter Tensile
strength, kgf EP Regulation, tensile strength, Instron
corporation
[0073] The property measuring methods are described in the
following Table 5.
[0074] After measuring the initial properties, the properties of
the mesh, wherein the degradable component was completely degraded
under accelerated conditions (80.degree. C., 10 days in PBS, pH
7.4) and only the non-degradable component remained, were measured,
to compare the properties before and after degradation.
TABLE-US-00005 TABLE 5 Property Measuring Methods and Apparatuses
Thickness EP Regulation, Diameter (.mu.m) Weight (g/m.sup.2) The
weight of 10 cm .times. 10 cm mesh was converted on the basis of
m.sup.2. Tensile 1'' .times. 6'' mesh was sampled in the horizontal
and Strength vertical directions in preparing the warp knitted
texture, (Kgf/inch) and the tensile strength was measured by the
tensile strength tester (Instron, 4204, U.S.SA.) wherein the sample
was equipped with 50 mm tensile distance and tensed at 50 mm/min.
Stiffness The mesh was cut to a 1'' .times. 1'' size, to measure
(mgf) the stiffness by the stiffness tester (Gurley Precision
Instrument, U.S.A.) after setting the load at 5 g and the position
at 2.
[0075] The measured properties of the mesh prepared in Examples 1
to 6 and Comparative Examples 4 to 5 are shown in the following
Table 6. TABLE-US-00006 TABLE 6 Comparative Examples Examples
Property 1 2 3 4 5 6 4 5 Property Diameter (.mu.m) 150 145 140 150
150 200 150 100.about.150 of Fiber Tensile Strength (Kgf) 1 0.8 1.1
0.9 0.9 1.8 1 1.about.2 Property Initial Thickness (.mu.m) 550 540
540 550 550 600 600 650 of Mesh Property Weight (g/m.sup.2) 64 62
60 64 64 80 85 88 Tensile Vertical 20 18 21 18 20 22 26 20 Strength
Horizontal 6 5 6 5 6 8 16 6 (Kgf) Stiffness Vertical 22 19 24 18 20
24 28 18 (mgf) Horizontal 10 9 12 9 10 11 25 10 Property Thickness
(.mu.m) 450 450 440 470 470 420 600 470 after Weight (g/m.sup.2) 25
25 24 25 27 30 85 35 degradation Tensile Vertical 12 9 8 10 13 12
26 12 Strength Horizontal 5 4 4 4 5 6 16 4 (Kgf) Stiffness Vertical
2 2 2 1.5 2 2 28 9 (mgf) Horizontal 1 0.8 0.5 0.5 1 0.5 25 2
[0076] As shown in Table 6, when comparing the properties of the
mesh of Examples 1 to 6, wherein the mesh was prepared with the
monofilament in the segmented pie form consisting of the degradable
materials and the non-degradable materials, with those of
Comparative Example 4 to 5, wherein the mesh was prepared with only
the non-degradable monofilament or the mixture of the degradable
multifilament and the non-degradable monofilament, it is known that
the initial properties of the mesh of the present examples were
equal to those of the comparative examples, and the remaining
amount and the stiffness are relatively reduced compared thereto,
to improve the biocompatibility and the flexibility of the present
inventive mesh.
[0077] That is, in the case of the conventional hernia mesh
prepared with the polypropylene monofilament as in Comparative
Example 4, the initial strength and the stiffness were maintained
even after a certain time, while in the case of the mesh prepared
as in Example 1, the degradable material was degraded and the
amount remaining in the body was reduced to at least 3 times lower
than that of Comparative Example 4, and the stiffness was reduced
by at least 10 times to alleviate misfeelings of the patient.
[0078] Further, when comparing Examples 1 to 6 with Comparative
Example 5, it is known that in Examples 1 to 6, the initial amount
and the remaining amount after degradation is low, and the
stiffness is lowered three to four times, to remarkably improve the
biocompatibility and the flexibility.
[0079] Comparative Example 1 is a case in which the content of
polypropylene is 30 vol % or less, showing that the monofilament
obtained by conjugated spinning does not have the segmented pie
structure but rather has the sea/islands structure wherein the
polypropylene component is surrounded by the glycolide/lactide
copolymer component. When performing conjugated spinning of two
components with a big difference in the melt indexes as in
Comparative Example 2, the component with the low melt index pushes
the component with the high melt index to one side at the
distributing plate in the spinnerette, to generate the unequal
segmented pie structure. Further, when applying no
stress-relaxation at the last heating stage of the drawing step as
in Comparative Example 3, the stress is present between the fibers
of the two components with different thermal contractibilities,
which generates the fiber separation phenomenon when impacted from
the outside, especially when warping and knitting while preparing
the mesh.
[0080] As aforementioned, the present invention provides a useful
technique for preparing a mesh using a monofilament in a segmented
pie structure obtained by conjugated spinning of a degradable
polymer and a non-degradable polymer, to improve biocompatibility
and flexibility.
* * * * *