Note: Descriptions are shown in the official language in which they were submitted.
~2~5~
SPEC IF ICATION
l;ibrous Apatite and Method
for Prod_cin~ the Same
Tech~ical Field
This invention relates to an apati-te rna-terial in fibrous
form and a me-thod ~or producing the same, and particuIarly
to apatite materials in fibrous form, particularly in cotton-
like and ~nwoven fabric form having many applications such
as uses for medical treatment, large scale microorganism
cultivating media or others, and a method for manufacturing
such materials. More particularly, this invention relates
to apatite implant materials having good compatibility with
living organism and a high working efficiency, and a method
for fabricating the same.
Background Art
Artificial implant mater.ials conventionally used for
remedying breaks or voids made in bones or tooth roots by
e~cision include the patient's own bones, similar bones
provided by close relatives, other dissimilar bones, and
metallic, organic and carbon materials. However, if a
patient's own bone is to be used, the patient would suffer
a severe pain in that a bone organization must be cut from a
location other than the affected part. In addition, there
may not always be sufficient bone available to provide an
,3?~'
~L26~68
adequate amount oE bone required for the xemedy, so that it
is often required to use a substitute to make up the shortage.
In order to utilize similar or dissimilar bones other than
a patient's o~m as a substitute, it is required to perform
a suryical opera-tion on an other living organism,' which would
impose a heavy burden on the bone donor.
On the other hand, metallic implant materials do not
only lack affinity wikh living organism, but also have the
disadvantage that metallic ions will plate out of the implant
material into the human body, resulting in deterioration of
the material. Such metallic ions may also be poisonous to
man. For these reasons, metallic implant materials have
pxoven unsuitable for permanent use. This is also true of
organic and carbon materials.
In an attempt to overcome the aforesaid disadvantages,
single-crystal or polycrystal alumina, silica, alumina or
calcium phosphate-based glass, and ceramics such as apatite
(see Japanese Patent Application Public Disclosure No. 52-
6~199, for example) have recently been proposed for use as
implant materials. Composite materials comprising a metallic
core flame spray coated with hydroxy-apatite powders are also
known as disclosed in Japanese Patent Application Public
Disclosure No. 52-~2893. These ceramic materials are superior
to other materials in that they have a high afEinity with
living organism and provide direct and intimate connection
-- 2 --
with bone organization. Especially, hydroxy-apatite is known
to be a main inorganic ingredient of a bone or tooth. In
this regard, calcined synthetic hydroxy-apatite draws an
increasing attention as so-called ar-tificial implant materials
Eor artificial tooth, bone and the like since such apatite
e~hibits so good affinit~ with bone and tooth OrCJaniZatiOnS
as to bond directly and chemically with the bone organization
and gums. (See, Eor example, The Chemistry and Indus-try,
Vol. 37, No. ~, P.2~3, 198~.) Arti~icial tooth roots of
calcined apatite and artificial bones of porous apatite have
reached the stage of practical use.
However, calcined apatike is a brittle material which
is vulnerable to tension, although highly resistant to
compression, so that such apatite tends to have its tensile
strength greatly reduced if a hair crack should be developed
on the surEace of the apatite due to a shock. This narrows
down the width oE application of calcined apatite to living
organism. The use of such material has thus been limited
only to artiEicial tooth roots Eor molar teeth or the like
where no excessi~e tensile stress will be exerted. Moreover,
when such material is to be used as fillers Eor breaks in
bone, diEEiculties are involved in shaping the material in
conFormity with the intricate contour oE the aEfected part.
In an attempt to eliminate the shortcomings oE the
calcined apatite described above, Japanese Patent Application
-- 3 --
~;26~6~
Public Disclosures No. 57-117621 and No. 58-54023 disclose
inorganic apatite fiber in which the apatite is made fibrous
so as to suit the use as implant material for breaks or
voids in bone. However, the apati-te fiber as disclosed in
these patent application public disclosures is fabricated by
the so-called melt spinniny process involving the steps of
meltincJ apatitc at a high tempera-ture and spinniny it. As
stated also in said disclosures, such melt spinning process
requir~s that apatite be melted at a high temperature of
1500C. As a result, the apatite is deprived of its hydroxy
group, and hence the 'affinity'. The apatite fiber thus has
a serious disadvantage in that it does not provide adequate
compatibility with living organism in contrast to hydroxy
apatite. For this reason, such melt spun apatite fiber
required a post-treatment for providing it with 'affinity'.
If apatite is to be madé fibrous without being deprived
of the hydroxy group, the melt spinning process cannot be
employed, but an other method such as the solution spinning
process should be taken into consideration. However, since
no binder or no spinning or calcining method suitable for
use with the solution spinning process has been developed,
it has heretofore been impossible to make apatite in Eibrou~
particularly in/
--- n-like or fabric form with the hydroxy group retained
as such.
After extensive researches and studies with a view to
26~6~
overcoming the prior art shortcomings as described above,
the inventors of the present invention have discovered that
~ ibrous a~atite ~articularl
it is possible to ~ e andnonwoven
fabric thereof by solution spinning apatite with the use of
special binder to make the apatite in fibrous form,
particularly in cotton-like and h~nWoven fabric form, and
calcininy the thus made apatite.
It is accordingly an object of this invention to provide
apatite material in fibrous form, particularly in cotton-like
and ~woven fabric form having many applications such as
uses for medical treatment, large scale microorganism
cultivating media and others.
Another object of this invention is to provide hydroxy-
apatite material in fibrous form, particularly in cotton-like
and ~nwoven fabric form which has excellent compatibility with
living organism and superior physical properties such as
tensile strength and the like.
Still another object of this invention is to provide a
method of producing the apatite material of the type described
in fibrous form, particularly in cotton-like and~woven
fabric form.
Yet another object of this invention is to provide
apatite implant material having a good compatibility with
living organism and a high workability.
: - 5 -
Summary of the Invention
Briefly, the present invention ~rovides a fibrous
product of apatite comprising one or more apatites selected
from a group of apatites represented by the general formula:
Mlotzo4)6~
wherein M represents Ca, Ba, Mg, Sr, Pb, Cd, Fe and the like,
ZO4 represents POq, AsO4, VO4, CO3 anA the like, and X
represents F, CQ, OH and the like, and more particularly a
fibrous product of apatite in which the apatite is
substantially hydroxy-apatite.
This invention may also provide a fibrous product
of apatite having calcium phosphate type compound incorporated
therein for reinforcement.
A fibrous product of apatite according to this
~ cotton-like product or /
invention may be manufactured in the form ofY~woven fabric,
if desired.
In another aspect, the present invention provides a
method of producing a fibrous product of apatite of the
type described, comprising the steps of preparing a dispersion
of fine apatite particles with the use of a water-soluble
high molecular compound, and spinning this dispersion by
solution spinnin~ p~ocess.
In a ~urther aspect of the present invention there
i6 provided a method ~or producing the inkertwined
fibers, cotton-like apatite product as described above
comprising the steps of:
~26~5~3
(a) preparing a dispersion of one or more of the
selected apatites by dispersing fine apatite particles
uniformly in a solution of binder in water, said apatite
being one or more apatites selected from a group of
apatites represented by the general formula:
Ml o ( Z~ ) 6X2
wherein M represents Ca, Ba, Mg, Sr, Pb, Cd and Fe, ZO4
represents PO4, ~sO~ and VO~, and X represents F, Cl and
OH;
(b) contlnuously extruding the dispersion through a
plurality of spinning orifices while simultaneously
stretching the dispersion into a fibrous state with the
aid of a high speed air flow to form a stream of fine
fibers;
(c) heating said fiber stream to evaporate the water
in the fibers to dewater the stream to a moisture content
of 10% or less;
(d) blowing the so dewatered fiber stream onto a
collector means to form the cotton-like product of
intertwined fibrous apatite bonded by the binder; and
(e) if re~uired, calcining said cotton-like product.
~rief Description of the Drawings
These and other objects and features of the present
invention will be fully understood from the following detailed
- 6a -
C
~6~6~3
description of the invention taken with reference to the
accompanying drawings, in which:
Fig. 1 is a schematic side elevational view of one form
of apparatus used for producing a cotton-like product of
apatite according to this invention;
Fig. 2 is a schemat.ic side elevational view of one Eorm
of apparatus used for manufacturing nonwoven fabric of apatite
according to this invention;
Fig. 3 is an X-ray diffraction pattern of a cotton-like
product of hydroxy-apatite according to this invention;
Fig. 4 is an X-ray diffraction pattern of the cotton-like
product of hydroxy-apatite shown in Fig. 3 prior to being
calcined; and
Fig. 5 is electron micrographs of a cotton-like product
of apatite according to this invention prior to and after
being calcined, respectively.
Detailed Descriptlon of the Preferred Embodiments
According to this invention, a fibrous product of
particularly in cotton-like form or nonwoven fabric form
apat1teVis provided which comprises one or more apati ~
selected from a group of apatiteq represented by the general
formula:
Mlo~Z04)6X2
wherein M represents Ca, Ba, Mg, Sr, Pb, Cd, Fe and the like,
ZOg represents P04, As04, VOgl C03 and -the like, and X
represents F, CQ, OH ancl the like.
~;26~i6~3
The term "cotton-like product" herein used is intended
to mean what is formed by intertwined ~ibers as if they were
cotton. If desired, a cotton-like product of apatite may
be made in the form ofh~woven fabric.
According to this invention, any one or more oE apatites
as represen-ted by the aforesaid general formula may be
selected and employed alone or in combination to obtain a
fibrous product of the apatite or apatites used. When
producing medical implant materials, calcium phosphate type
apatite is pre~erably used because of its similarity to bone
organization. More preferably, hydroxy-apatite (compound
as represented by the aforesaid general formula where M is
Ca, ZO4 is PO4 and X is OH) is employed from a view point
of compatibility with liviny organism~ However, it should
be understood that this invention does not preclude the use
oE such compounds as having members other than Ca, PO4 and
OH in the locations of M, ZO4 and X, respectively represented
by the aforesaid formula, so long as such other members
would not impair the compability with living organism. In
other words, two or more kinds of apatite may be employed.
According to a particularly preferred embodiment of this
invention, a Eibrous product oE apatite wherein the
apatite is substanti~lly hydroxy-apatite is provided.
Such fibrous product of apatite substantially all
o~ which comprises hydroxy-apatite, however, may not be
~26~6~
satisfactory with respect to its strength. In this regard,
the fibrous product of apatite may contain inorganic
compound such as calcium phosphate type compound, for example
therein to enhance the physical properties such as strength
and the like. Accordingly, in another preferred embodiment
of the invention, a ~ibrous product of apatite containing
a calcium phosphate type compound in addition to hydroxy-
apatite is provided. Such compound may be at least one
selected Erom a group o~ calcium hydrogen phosphake (CaHPO4),
tri-calcium phosphate (Ca3(PO4)2), and tetra-calcium phosphate
(Ca4O(PO4)2). These compounds may be contained in the apatite
product in an amount of generally 5 to 95 weight %, preferably
80 weight ~ or less, more preferably 50 weight % or less.
Calcium phosphate type compound may be incorporated by initially
blending an amount of the compound required into the main
ingredient(s), or alternatively by subjecting the hydroxy-
apatite to a high temperature treatment to produce such
compound from a part of the hydroxy-apatite, as will be
described hereinafter.
In a fibrous product of apatite according to this
invention the fibers may have generally a mean diameter of
1 ~m to 30 ~m and a mean lenyth of 1 mm to 1,000 mm. Of
course, this is not limitative but just illustrative. As
stated before, a Eibrous product of apatite according to
this invention may be made particularly in cotton-like form or
nonwoven fabric.
_ g _
~6~
For suchnonwoven fabric the basis weight may generally be
in the range of 5 g/m2 to 500 g/m2, but this is not limitative.
\in cot-ton-like form/
A fibrous apatite~oE this invention may be produced
by a method comprising the steps of:
(a) preparing a dispersion of apa-tite by dispersing
fine apatite particles uniformly in a solution of binder in
water, said apatite being one or more apatites select.ed from
a group o~ apatites represented by the general formula:
Mlo (Z~l ) 6X2
wherein M represents Ca, Ba, Mg, Sr, Pb, Cd, Fe and the like,
Z04 represents P04, As04, V04, C03 and the like, and X
represents F, CQ, OH and the like;
(b) continuously extruding the thus prepared dispersion
through a plurality of spinning orifices in a spinning
apparatus while simultaneously stretching the dispersion into
a fibrous state with the aid of a high speed air flow to form
a stream of fine fibers;
(c) heating said fiber stream to evaporate the water
off from the fibers;
(d) blowing said water-removed ~iber stream upon a
collector means to form a cotton-like product of apatite
bonded by the binder; and
(e) if desired, calcining said cotton~like product.
According to a preferred embodiment of this invention,
a hydroxy-apatite represented by the general formula wherein
-- 10 --
M is Ca, ZO~ is PO~, and X is OH is employed.
Apati-te for the purpose of this invention may be either
any suitable one synthesized in a known manner or any natural
one. The apatite may be fine particles having a mean particle
diameter of 50 A to 1 ~m, and preferably 70 to 500 A. In
this case, while the conEiguration of apatite particle.s is
not limited to any particular one, it is preferable to use
apatite particles in the form o:E stick since such stick
\fibrous Eorm or /
particles facilitate the formation oE the apatite in~
cotton like form. Although the reason for this has not
completely been elucidated, it is presumed that it may be
easy to orient the stick-like particles in a predetermined
direction during the spinning step. Stick-like particles of
apatite such as hydroxy-apatite may be prepared by dropping
an aqueous solution of phosphoric acid gradually into an
alkaline solution (pH: 7 to 11) containing calcium ions,
for example.
Binders used to produce a fibrous product of apatite
according to this invention may be commonly known water-
soluble binders. Such binders may be water-solublè, cotton-
like high molecular compounds having -OH, -COOH, -CONH2 groups
or the like in their molecules, including pullulan which is
a linear cJlucan wherein rnaltotrioses are bonded by recurring
~-1, 6-glycoside linkages, polyvinyl alcohol, polyacrylamide,
polyacrylic acid, polymethacrylic acid, polyitaconic acid,
6~3
polyethylene oxide, polyvinyl pyrolidone, polyvinyl methylene
ether, hydroxypropyl cellulose, xanthane gum, guar gum,
collagen, hydroxyethyl cellulose, carborymethylcellulose and
the like. While there is no particular limitation as to the
molecular weight, such high molecular compounds may have a
molecular weight o~ preEerably 20,000 to 2,000,000, and more
preferably 50,000 to 1,000,000.
When fibrous products o apatite according to this
invention are to be used particularly as medical materials,
it is desirable that binders should meet at least two
conditions that they be harmless to living organism and
water-soluble. Suitable examples of such binders may include
high molecular compounds such as polyvinyl alcohol, carboxy-
methylcellulose, hydroxypropylcellulose, collagen and the
like and high molecular polysaccharides such as pullulan,
chitin, dextran and the like. Pullulan is particularly
suitable.
According to this invention, a dispersion comprising
apatite particles dispersed in an aqueous solution of the
binder as described above is subjected to a spinning step.
Thus, the composition o~ the feed dispersion should be in a
predetermined range. By way of example, ~or hydroxy-apatite,
its composition may comprise 10 to 90 weight %, prePerably
50 to 70 weight %, more preferably 60 to 65~ of water, 5 to
70 weight ~, preferably 15 to 30 weight %, more preEerably
- 12 -
~ 26~3
15 to 20 weight % of hydroxy-apatite, and 5 to 40 weight %,
preferably 15 to 30 weight %, more preferably 20 to 25
weight % of binder. If the amount of hydroxy-apatite is less
than 5 weight %, it would not be able to provide a fibrous
apatite material having sufficient strength. Conversely,
more than 70 weight % of hydroxy-apatite would undesirably
increase the vi~cosity excessively.
For the purpose of improving the dispersion of hydroxy-
apatite in feedstock liquid, organic carboxylic acid, or
plasticizers or softening agents including polyhydric alcohol
such as glycerin, sorbitol, maltitol, ethylene glycol,
propylene glycol or the like may be added.
Further, inorganic compounds other than apatite, such as
calcium phosphate, for example may be added in an amount of
less than 5% as a dispersing medium to improve the physical
propertieS of fibrous apatite material obtained.
In the present invention it is preferable to prepare the
feedstock solution described above at a temperature of about
20 to 70C. The thus prepared dispersion is continuously
extruded through spinning orifices while simultaneously
discharging a gas through gas discharge orifice means adjacent
to the spinning orifices at a high speed to form the dispersion
into a stream of fibers. The ~iber stream is rid of water
lin cotton-like form/
and collected as a fibrous ~ , if desired,
the product may be calcined.
- 13 -
~2~ ;6~
In case of hydroxy-apatite, it has been experimentally
found by X-ray diffraction and infrared spectrophotometry
that the fibrous apatite material, if not calcined or if
calcined at a temperature lower than 1250C, will have the
structure of Ca10(PO~)6OH2 or Ca5(PO~)30H, whereas if calcined
at higher than 1250C, it will be transformed into the
structure o ~-Ca3(PO4)2. Such transformed product does not
retain the hydroxy group, resultincJ in reduced compatibility
with living organism. In order to retain substantially the
structure of hydroxy-apatite, it is preferable to carry out
the calcining step at a temperature lower than 1250C,
preferably lower than 1200C.
One embodiment of the method of producing a fibrous
product of apatite according to this invention wherein fine
hydroxy-apatite particles are used as a raw material will
now be described with reference to Fig. 1.
First, hydroxy-apatite, binder and water, and if required,
dispersant, plasticizer and/or softener are introduced through
a feed line 1 into a feedstock tank 2 to prepare a viscous
spinning solution. Such feed spinning solution may be
prepared preferably at about 20 to 70C. This viscous spinning
solution is fed through a conduit 15 and then extruded through
a spinning nozzle means 5 by a gear pump ~ driven by a motor
3, while simultaneously gas is discharyed throuyh an air nozzle
means 7 positioned around the spinniny nozzle means at a high
1:~6~S6~
velocity by a multi-stage blower 6. The spinning nozzle may
include a plurality of dies arranged in a straight line in
a widthwise direction. A stream 8 of fine fibers stretched
and cut in length is formed by discharging gas such as air
at about 20 to 60C from around the spinning nozzle means at
a velocity of about 5 to 1000 m/sec. The diameter and length
of the fibers may be adjusted so as to be in the ranges of
about 1 to 30 ~m and 2 to 1,000 mm, respectively by varying
the pressure of yas discharged.
Then, the thus formed stream 8 o fine fibers is heated
by a heater such as an infrared heater 9 or the like underlying
the spinning nozzle means to evaporate the water off from the
fibers to a moisture content of less than 10 weight %,
preferably less than about 7 weight % to thereby solidify the
fiber stream. It should be noted that excessive removal of
water would result in failure to produce a fibrous apatite
in cotton-like form,
~-Vcomposed of fine fibers. In this regard, the temperature of
the heater may be generally in the range of about 200 to 500C
for the fiber stream at about 80 to 150C. The heating
temperature for the fiber stream is selected depending upon
the extrusion rate of the spinning solution, and the temperature
and volume of the gas blown. Excessively hi~h heating
temperature is not desirable in that it would cause decomposi-
tion of the binder during the heating step.
The fine fiber stream 10 as stretched, cut in length
- 15 -
:~LZ6~56~3
and water-removed is then blown onto a suitable collector
means 11 in the form of a screen type collector vessel or a
screen-type collecting belt to be collected and deposited
thereon._fibrous apatite in
abric is to be manufactured, the fine fiber
stream as stretched and water-removed as described above is
caused to drop onto a moving collector means in the form of
a screen type rotary drum a8sembly 16 as shown in Fig. 2 or
a moving belt conveyor with the fibers intertwined to form
an ~woven fabric. If the stream of fibers is blown down
into the nip between the two rotating screen type drums 16,
a bulky n~woven fabric 17 having the intertwined fibers
oriented in a direction of thickness of the ~woven fabric
(that is, in a three-dimensional configuration) will be
obtained. In an alternate embodiment, if the fiber stream
is blown down onto those areas of the rotating drums other
than the nip between the drums or onto a planar collecting
belt conveyor, an ~mwoven fabric will be produced in which
the fibers are oriented parallel in a plane (that is, in a
two-dimensional manner). The basis weight of the ~woven
fabric may be regulated so as to be in the range of 5 g/m2
to 500 g/m2, for example by varying the speed at whiah the
collector means moves.
fibrous a~atite, namel~
The thus pr ~ otton-like product or ~woven fabric
of apatite fibers bonded together by the binder provides a
- 16 -
~ 2~
feeling soft and agreeable to the touch. Further, owing to
its hydrophilic nature, moisture-absorption characteristics
and non-electrifying property as well as its cultivation
promoting effect, such cotton-like product or ~nwoven fabric
oE apatite in an uncalcined state may be employed as a
culture mediurn for microorganisms.
Uncalcined cotton-like product or ~V~woven fabric may be
calcined at a temperature oE about 500 to 1250C, preferably
about 600 to 1200C, more preferably 650 to 1100C to burn
the binder of whereby a fibrous apatite material of this
invention is obtained. At the calcining temperature lower
than 1200C there is very little loss of the hydroxy group,
so that no account may be taken of the loss of hydroxy group
although it depends somewhat upon the calcining temperature.
If required, the calcining temperature higher than 1200C
may be used to produce Ca3(PO4)2 in the hydroxy-apatite to
thereby enhance the physical properties such as strength of
the cotton-like product or ~woven fabric of hydroxy-apatite
when it is used as implant material.
The thus obtained cotton-like product or ~woven fabric
may be subjected to a further process according to the purpose
for which it is to be used. By way of example, collagen may
be applied to or impregnated into such product or fabric to
further improve the desired properties thereof. It may also
be combined with a culti~ating substance such as pullulan to
- 17 -
~L2~
suit the use as a large scale culture medium.
A fibrous apatatite material according to another
preferred embodiment of this invention containing calcium
phosphate--type compound in addition to hydroxy-apatite may
be produced by a method comprising the steps of: adding a
water-soluble binder to an aqueous solution containing fine
par-ticles of hydroxy-apatike and calcium phosphate-type
compound to form a viscous dispersion, continuously spinning
the dispersion through a plurality of spinning orifices of
a spinning machine while simultaneously discharging a gas
through gas discharge orifice means adjacent to the spinning
orifices at a high velocity to s-tretch the fibers from the
spinning orifices into a stream of fine fibers, heating the
fiber stream to remove the water therefrom, and blowing said
water-removed fiber stream onto a collector means as in the
form of a collecting plate to form a cotton-like product of
apatite.
In this case, the composition of the starting dispersion
may preferably comprise 5 to 90 weight % of water, 5 to 70
Weight % of apatite, 5 to 70 weight % of calcium phosphate
and 2 to 30 weight %. More suitable composition is 25% of
water, 35% of hydroxy-apatite, 30% of calcium phosphate, and
10% of pullulan on the basis oE weight. The other manufacturing
conditions may be the same as for the production of the
fibrous product as describecl hereinbefore substantially
- 18 -
all of which comprises apatite.
Examples of the present invention will be described
hereinbelow, it being understood that this is not to limit
the invention.
Example 1
11 weight % of pullulan particles having a mean molecular
weiyht of 200,000, 17 weight ~ of hydroxy-apatite particles
having a particle diameter of 50 to 800 ~, and 72 weight 5~
of water were kneaded toyether to disperse the hydroxy-apatite
uniformly in the aqueous pullulan solution. The thus prepared
solution was defoamed and fed into a spinning apparatus as
shown in Fig. 1 at a room temperature (25C), said apparatus
equipped with a die having a plurality of 0.3 mm diameter
spinning nozzles arrayed in a straight line in a transverse
direction. The solution was extruded through the nozzles at
a pressure of 1.4 kg/cm2 while discharging air through the
air gaps at a velocity of 250 m/sec to thereby form a stream
of fibers. This fiber stream was heated on its opposite sides
at a temperature of 400C by a far infrared heater (wavelength:
2 to 50 ~m) underlying the spinning nozzles to evaporate the
water off and was blown onto a screen type belt to produce
\in co-tton-like form/
a fibrous produ~V~ hydroxy-apatite bonded by pullulan.
I'he thus produced cotton-like product was heated at a heating
r~te of ~0C/hr. to be calcined at 1100C for an hour, whereby
a cotton-like product oE hydroxy-apatite having a mean fiber
-- 19 --
1 Z6,~ B
diameter of 5 ~m and a mean fiber length of 50 mm was
obtained as -the pullulan was burned off. It was determined
by X~ray diffraction and infrared ray spectrophotometry that
the thus obtained cotton-like product contained substantially
the same amount of hydroxy group as the starting material had.
Figs. 3 and 4 show X-ray dif~raction patterns prior to and
after the calcining s-tep, respectively.
Example 2
Pullulan particles with a mean molecular weight of
200,000 were dissolved in water to prepare 21 weight ~ of
aqueous solution into which 6 weight ~ of hydroxy-apatite
particles having a particle diameter of 50 to 300 A was mixed.
The solution was then defoamed. The thus prepared feed
solution was fed into the apparatus used in the Example 1 at
a room temperature and extruded at a pressure of 1.4 ~g/cm2
while discharging air through the air gaps at a velocity of
500 m/sec. to thereby form a stream of fibersO This fiber
stream was heated on its opposite sides at a temperature of
400C by a far infrared heater (wavelength: 2-50 ~m)
underlying the spinning nozzles to evaporate the water off
and was blown onto a screen type belt to produce a Eibrous
in cotton-like fo~l
pr~ r-----droxy-apatite bonded by pullulan. The thus
produced cotton-like product was heated at a heating rate of
50C/hr. to be calcined at 1400C or two hours, whereby a
cotton-like product of apatite having a mean fiber diameter
- 20 -
5~3
3 ~m and a mean flber length of 30 mm was obtained as the
pullulan was burned off. It was determined by X-ray
diffraction and infrared ray spectrophotometry that the thus
obtained cotton-like product had been deprived of the hydroxy
group.
Example 3
A cotton-like product of hydroxy-apatite having a mean
fiber diameter o 15 ~m and a mean iber length of 70 mm after
calcined was obtained by the same procedure as the Example 1
excep-t that the amounts of the pullulan particles, hydroxy-
apatite particles, and water used were 19%, 31~, and 50~ by
weight, respectively.
Example 4
A cotton-like product of hydroxy-apatite having a mean
fiber diameter of 7 ~m and a mean fiber length of 65 mm after
calcined was obtained by the same procedure as the Example 1
except that polyvinyl alcohol with a molecular weight of
190,000 was used as a binder.
Example 5
A cotton-like product of hydroxy-apatite having a mean
fiber diameter of 3 ~m and a mean fiber length of 35 mm was
obtained by forming a stream oE Eibers under th~ same conditions
as in the Example 1 except that a feed solution containing 50
weight % of hydroxy-apatite particles and 15 weight % of
pullulan particles was used and that the air was discharged
~ 26~LS~E~
at a velocity of 1200 m/sec..
Example 6
11 weight ~ of pullulan particles having a mean molecular
weight of 200,000, 17 weight % of hydroxy-apatite particles
having a particle diameter of 50 to 800 A, and 72 weight
of water were kneaded together to disperse the hydroxy-
apatite uniformly in the aqueous pullulan solution. The thus
prepared solution was defoamed and fed into a spinning
apparatus as shown in Fig. 2 at a room temperature (25C).
The solution was extruded through the nozzles at a pressu~e
of 1.4 kg/cm2 while discharging air through the air gaps at
a velocity oE 250 m/sec to thereby form a stream of fibers.
This fiber stream was heated on its opposite sides at a
temperature of 400C by a far infrared heater (wavelength:
2 to 50 ~m~ underlying the spinning nozzles to evaporate the
water off and was blown onto a screen type belt to produce
~ nonwoven fabric form/
a fibrous produ-~V-----droxy-apatité bonded by pullulan.
The thus produced ~woven abric was heated at a heating
rate of 50C/hr. to be calcined at 1100C for an hour, whereby
a ~woven fabric of hydroxy-apatite having a mean fiber
diameter of 5 ~m and a basis weight of 200 g/m2 was obtained
as the pullulan was burned off. It was determined by X-ray
diffraction and infrared ray spectrophotometry that the thus
obtained ~woven fabric contained substantially the same
amount of hydroxy group as the starting material had. Fig. 5
- ~2 -
i8
shows the fibers of the ~woven fabric prlor to and after
the calcining step observed by electron micrographs.
Example 7
Pullulan particles with a mean molecular weight of
200,000 were dissolved in water to prepare 21 weight % of
aqueous solution into which 6 weight % oE hydroxy-apatite
particles having a particle diameter of 50 to 300 A was mixed.
The solution was then defoamed. The thus prepared feed
solution was fed into the apparatus used in the Example 6
at a room temperature and extruded at a pressure of 1~4 kg/cm2
while discharging air through the air gaps at a velocity of
500 m/sec. to thereby form a stream of fibers. This fiber
stream was heated on its opposite sides at a temperature of
400C by a far infrared heater (wavelength: 2-50 ~m)
underlying the spinning nozzles to evaporate the water off
and was blown onto a screen type belt to produce a fibrous product
\in nonwoven fabric form/
Vof hydroxy-apatite bonded by pullulan. The thus
produced ~woven fabric was heated at a heating rate of
50C/hr. to be calcined at 1~00C for two hours, whereby a
nonwoven fabric of apatite having a mean fiber diameter
3 ~m and a basis weight of 200 g/m2 was obtained as the
pullulan was burned off. It was determined by X-ray diffraction
and infrared ray spectrophotometry that the thus obtained
~o~woven fabric had been deprived of the hydroxy gxoup.
- 23 -
~ 2~ 5~8
Example 8
A ~woven fabric of hydroxy-apatite having a mean fiber
diamter of 15 ~m after calcined was obtained by the same
procedure as the Example 6 except that the amounts of the
pulluran par-ticles, hydroxy-apatite particles, and water used
were ].9~, 31~, and 50~ by weight, respectively.
Example 9
~ woven fabric of hydroxy-apatite having a mean
diameter of 7 ~m after calcined was obtained by the same
procedure as the Example 6 except that polyvinyl alcohol with
a molecular weiyht of 190,000 was used as a binder.
Example 10
This example was conducted according to the Example 6
except that the composition of the viscous dispersion in the
feedstock tank 2 comprised 25% of water, 35% of hydroxy-
apatite, 30% of calcium phosphate and 10% of pullulan on the
basis of weight. The spinning nozzles were 0.3 mm in diameter,
the spinning temperature was a room temperature (25C), and
the pressure of the air discharged was 300-1000 mm H2O.
Further, the far infrared heater 9 was 800 to 1000 mm
in length, had an output of ~ to 10 kw and provided heating
temperature of ~00C. The ~woven fabric of apatite was
heated at a heatiny rate oE 50Cthr. -to be calcined at 1100C
for two hours.
The calcined apatite fibers produced in the examples
- 2~ -
described above had a mean fiber diameter of 3-15 ~m and
high mechanical streng-th, that is, high tensile strength and
impact resistance.
Advantaqes of the Invention
From the foreyoing, it is ko be appreciated that since
the apatite is solution spun at a room kemperature rather
han being melted at a hiyh temperature, the present invention
l cotton-like form and _onwoven fabric fo~
provides a f.ibrous product of ~ ~ich lS not~~ - lVed
of the hydroxy group loss of which would spoil the affinity
with living organism in contrast to the prior art.
Consequently, there is no need for after-treatments for
imparting 'affinity' to the fabric product of apatite,
lending itself to simplification of the manufacturing process
and improved operating efficiency. It is believed that the
solution spinning at a room temperature has been made possible
by the fact that binders such as pulluran has been found out
which meet the three conditions of non-toxicity to living
organism, water-solubility and decomposability at a high
temperature without melting, and that a conventional spinning
apparatus used for the so-called melt blow process or melt
spinning process has been so modified that a Eibrous
product of apatite may be produced b~ spinning feed solution
khrough the spinning nozzles to form a stream of ~ibers without
melting the material at a high temperature, heating the stream
o fibers to evaporate -the water o:E the fibers, and blowing
- 25 -
L568
the fiber stream onto a collector such as a collector plate
or a screen type drum collector conventionally used for the
melt blow process.
The present invention is the first that has succeeded
in obtaining a high strength fibrous apatite by
the solution spinning process by which it has heretofore
~ fibrous produc ~ articularlyl
been considered impossible to produce such apatite. Avcotton
like product or ~woven fabric of apatite produced according
to this invention is not deprived of the hydroxy group,
exhibiting much the same affinity with living organism as
the conventional sintered apatite. Furthermore, the content
of hydroxy apatite in the fibrous apatite may be
adjusted by varying the calcining temperature to control the
physical properties such as strength. In addition, owing to
its fibrous form, the apatite material according to this
invention provides high resistance to impact and superior
processing characteristics, so that it may be easily conformecl
to intricate contours of breaks in a bone. Thus, the
fibrous apatite of this invention may be used not only
for artificial teeth but also for reconstruction of various
bones and artificial joints. Further, it may be used for
three-dimensional culture media in biotechnology.
While various embodiments of the invention have been
described hereinabove, -the present invention should not be
limited to these, but various changes and modificat:Lons may
- 26 -
~L2~
be made without departing from the spirit and scope of the
invention.
~ 27 -
