CA1261568A - Fibrous apatite and method for producing the same - Google Patents
Fibrous apatite and method for producing the sameInfo
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- CA1261568A CA1261568A CA000493540A CA493540A CA1261568A CA 1261568 A CA1261568 A CA 1261568A CA 000493540 A CA000493540 A CA 000493540A CA 493540 A CA493540 A CA 493540A CA 1261568 A CA1261568 A CA 1261568A
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- apatite
- product
- fibrous
- cotton
- hydroxy
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Abstract
Abstract of the Disclosure The present invention provides a fibrous product of apatite comprising one or more apatites selected from a group of apatites represented by the general formula:
M10(ZO4)6X2 wherein M represents Ca, Ba, Mg, Sr, Pb, Cd and Fe, ZO4 represents PO4, AsO4 and VO4, and X represents F, Cl and OH. This fibrous product of apatite has many applications such as uses for medical treatment, large scale microorganism cultivating media and others, and particularly it is useful as apatite implant materials having a good compatibility with living organism and superior workability. The fibrous apatite product of this invention may be produced by a method comprising the steps of:
(a) preparing a dispersion of apatite 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:
M10(ZO4)6X2 wherein M represents Ca, Ba, Mg, Sr, Pb, Cd and Fe, ZO4 represents PO4, AsO4 and VO4, and X represents F, Cl and OH;
(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 in the fibers;
(d) blowing said dewatered fiber stream upon a collector means to form a cotton-like product of apatite bonded together by the binder; and (e) if desired, calcining said cotton-like product.
M10(ZO4)6X2 wherein M represents Ca, Ba, Mg, Sr, Pb, Cd and Fe, ZO4 represents PO4, AsO4 and VO4, and X represents F, Cl and OH. This fibrous product of apatite has many applications such as uses for medical treatment, large scale microorganism cultivating media and others, and particularly it is useful as apatite implant materials having a good compatibility with living organism and superior workability. The fibrous apatite product of this invention may be produced by a method comprising the steps of:
(a) preparing a dispersion of apatite 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:
M10(ZO4)6X2 wherein M represents Ca, Ba, Mg, Sr, Pb, Cd and Fe, ZO4 represents PO4, AsO4 and VO4, and X represents F, Cl and OH;
(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 in the fibers;
(d) blowing said dewatered fiber stream upon a collector means to form a cotton-like product of apatite bonded together by the binder; and (e) if desired, calcining said cotton-like product.
Description
~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 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 ~;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 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 ~ 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.
~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 :~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 ~ 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 ~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 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:
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 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 ~;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 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 ~ 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.
~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 :~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 ~ 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 ~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 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 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 5~3
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 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 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.
~ 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 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 ~L2~
be made without departing from the spirit and scope of the invention.
~ 27 -
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.
~ 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 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 ~L2~
be made without departing from the spirit and scope of the invention.
~ 27 -
Claims (22)
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A fibrous apatite product characterized in that the product has an intertwined fibrous, cotton-like form and is made of one or more apatites selected from a group of apatites represented by the general formula:
M10(ZO4)6X2 wherein M represents Ca, Ba, Mg, Sr, Pb, Cd and Fe, ZO4 represents PO4, AsO4 and VO4, and X represents F, Cl and OH.
M10(ZO4)6X2 wherein M represents Ca, Ba, Mg, Sr, Pb, Cd and Fe, ZO4 represents PO4, AsO4 and VO4, and X represents F, Cl and OH.
2. The fibrous product of apatite according to claim 1 wherein M is at least one selected from Ca, Ba, and Sr, ZO4 is at least one selected from PO4 and VO4, and X is at least one selected from OH and F.
3. The fibrous product of apatite according to claim 1, substantially all of said apatite being hydroxy-apatite wherein M is Ca, ZO4 is PO4, and X is OH.
4. The fibrous product of apatite according to claim 3 said apatite containing calcium phosphate type compound in addition to said hydroxy-apatite.
5. The fibrous product of apatite according to claim 4 comprising 5 to 95 weight % of hydroxy-apatite and 95 to 5 weight % of calcium phosphate type compound.
6. The fibrous product of apatite according to claim 5 wherein said hydroxy-apatite is 20 weight % or more and said calcium phosphate type compound is 80 weight % or less.
7. The fibrous product of apatite according to claim 5 wherein said hydroxy-apatite is 50 weight % or more and said calcium phosphate type compound is 50 weight % or less.
8. The fibrous product of apatite according to any of claims to 6 wherein said calcium phosphate type compound is at least one selected from a group of calcium hydrogen phosphate, tri-calcium phosphate and tetra-calcium phosphate.
9. The fibrous product of apatite according to any one of claims 1 to 3 which has a mean fiber diameter of 1 µm to 30 µm and a mean fiber length of 1 mm to 1000 mm.
10. The fibrous product of apatite according to claim 1, 2 or 3 which is made in the form of cotton-like product or nonwoven fabric.
11. The fibrous product of apatite according to claim 1, 2 or 3 which is made in the form of cotton-like product or nonwoven fabric, and wherein the bests weight of said nonwoven fabric is in the range of 5 g/m2 to 200 g/m2.
12. A method of producing the intertwined fibrous, cotton-like apatite product of claim 1 comprising the steps of:
(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:
M10(ZO4)6X2 wherein M represents Ca, Ba, Mg, Sr, Pb, Cd and Fe, ZO4 represents PO4, AsO4 and VO4, and X represents F, Cl and OH;
(b) continuously 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 required, calcining said cotton-like product.
(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:
M10(ZO4)6X2 wherein M represents Ca, Ba, Mg, Sr, Pb, Cd and Fe, ZO4 represents PO4, AsO4 and VO4, and X represents F, Cl and OH;
(b) continuously 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 required, calcining said cotton-like product.
13. The method according to claim 12 further including the step of making the cotton-like product of apatite in the form of nonwoven fabric.
14. The method according to claims 12 or 13 wherein said apatite used is an apatite in which M is Ca, ZO4 is PO4 and X is OH.
15. The method according to claims 12 or 13 wherein said apatite used is a hydroxy-apatite in which M is Ca, ZO4 is PO4 and X is OH.
16. The method according to claims 12 or 13 wherein said apatite particles are in the form of stick having a mean particle diameter of 50 .ANG. to 1µm.
17. The method of claims 12 or 13 wherein said binder is a water-soluble high molecular compound.
18. The method according to claim 12 or 13, wherein said hinder is pullulan.
19. The method according to claims 12 or 13 wherein said apatite dispersion further contains fine particles of calcium phosphate type compound.
20. The method according to claims 12 or 13 wherein said fiber stream is heated so that the moisture content of the fibers is reduced to 10% or less.
21. The method according to claims 12 or 13 wherein said calcining temperature is in the range of 500°C to 1250°C.
22. The method according to claim 12 or 13 wherein said calcining temperature is in the range of 600°C to 1100°C.
Applications Claiming Priority (8)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP229283/1984 | 1984-10-31 | ||
| JP59229284A JPS61106167A (en) | 1984-10-31 | 1984-10-31 | Production of apatite fluffy material |
| JP229284/1984 | 1984-10-31 | ||
| JP59229283A JPS61106166A (en) | 1984-10-31 | 1984-10-31 | Apatite fluffy material |
| JP3526385A JPS61201019A (en) | 1985-02-26 | 1985-02-26 | Production of apatite wool |
| JP35262/1985 | 1985-02-26 | ||
| JP35263/1985 | 1985-02-26 | ||
| JP60035262A JPS61201018A (en) | 1985-02-26 | 1985-02-26 | Apatite wool |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1261568A true CA1261568A (en) | 1989-09-26 |
Family
ID=27460071
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000493540A Expired CA1261568A (en) | 1984-10-31 | 1985-10-22 | Fibrous apatite and method for producing the same |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1261568A (en) |
-
1985
- 1985-10-22 CA CA000493540A patent/CA1261568A/en not_active Expired
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