JPH09234242A - Production method of bone jointing material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable to easily produce an excellent bone jointing material no requiring re-operation. SOLUTION: This bone jointing material is produced in such a manner that a crystalline thermoplastic high molecular weight material with in vivo decomposition and absorptivity is melted and formed to make a pre-forming body, it is cold-plastic-deformed and press-oriented in the narrow space of a forming mold 2 with closed its bottom end to produce an oriented forming body. This oriented forming body is crystallized in such a manner that crystals are oriented in parallel to multiple reference axes. For the press-orientation, a pre-forming body is cold-plastic-deformed, press-filled, and press-oriented in the narrow space of the forming mold 2 with closed its bottom end which has smaller cross-sectional area than the pre-forming body, or a pre-forming body is cold- plastic-deformed, press-filled, and press-oriented in the narrow space of a forming mold with smaller cross-sectional area, thickness, and width than the pre-forming body, or in a forming mold with smaller space than the pre-forming body.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an osteosynthetic bone cement material having high mechanical strength and biodegradability.

[0002]

In the field of surgery such as orthopedic surgery, plastic surgery, thoracic surgery, oral surgery, and brain surgery, metal or ceramic plates, screws, and pins are used as bone-bonding materials for fixing and joining living bones. Etc. are used.

However, since these bone cements have much higher mechanical strength and elastic modulus than that of living bone, there is a problem in that the strength of surrounding bone is lowered by stress protection after healing. In particular, since metal bone-bonding materials may cause poisoning to the living body by elution of metal ions, when a fracture or the like is healed, it is necessary to perform re-operation to remove it from the body as soon as possible. I have a problem.

Under these circumstances, research using a biodegradable and absorbable polymer material as an osteosynthesis material has been actively carried out mainly in Northern Europe, and a self-reinforced type in which polyglycolic acid fibers are welded is welded. Although an osteosynthesis device has been proposed (see US Pat. No. 4,968,317) and used clinically, it is rapidly decomposed, and delamination between fused fibers and its disintegrated strips cause the living body to be destroyed. The drawback was that it stimulated and caused inflammation.

In addition, Japanese Patent Laid-Open No. 59-97654 discloses a method for synthesizing polylactic acid or a lactic acid-glycolic acid copolymer which can be used as a biodegradable and absorbable bone-joining device. In this case, what is listed as the bone-bonding material is the polymerization product itself, and nothing has been described regarding the moldability of this material, and attempts to raise its strength to the level of human bone are shown. It has not been. In addition, this bone-joining device is not strong enough and may be broken.

[0006] Therefore, as one contrivance in the manufacturing method for increasing the strength, a biodegradable and absorbable polymer material such as polylactic acid containing a small amount of hydroxyapatite (hereinafter abbreviated as HA) is molded, and then molded. A method for producing an osteosynthesis pin that is stretched with heating in the longitudinal direction (Japanese Patent Laid-Open No. 63-68155)
No.) was proposed. In addition, a high-strength bone cement material obtained by stretching a molded product of polylactic acid or a lactic acid-glycolic acid copolymer having a viscosity average molecular weight of 200,000 or more after melt molding (Japanese Patent Laid-Open No. 1-19
8553).

Bone-bonding materials or pins obtained by these manufacturing methods are bent essentially because the crystal axes (molecular chain axes) of polymer materials are uniaxially oriented parallel to the long axis direction which is the reference axis. Strength and tensile strength in the major axis direction are improved. In particular, when the viscosity-average molecular weight of polylactic acid or the like after melt-molding is 200,000 or more like the latter bone-bonding material, the strength is high even at a low draw ratio to the extent that fibrillation does not occur, which is useful. However, the bone cement obtained by stretching essentially only in the major axis direction has the following problems.

[0008]

Usually, when a living bone is bonded and fixed by using a bone cement, forces in various directions act on the bone cement. For example, in the case of a plate-shaped bone cement, various forces such as bending force, tensile force, compression force, tearing force, shear force, etc. act individually or in combination, and in the case of a screw-shaped bone cement. In addition to these forces, a large torsional force acts when screwed into a living bone and when in a living body. However, in the bone cement obtained by stretching in the long-axis direction as described above, the molecules are oriented only in the long-axis direction that is the molecular chain axis [the machine direction that is the stretching axis]. The anisotropy of the molecular orientation is large with respect to the lateral direction, which is a direction perpendicular to.

Therefore, it is weak against the tear strength from the long axis direction and the shearing force from the lateral direction, and is also weak against the twisting force with the long axis as the rotation axis. Therefore, when the above-mentioned tearing force or shearing force acts on the bone cement in the bone, the bone cement may relatively easily crack, tear, or shear fracture along the long axis direction. Further, when a torsional force acts with the long axis as a rotation axis, such as a screw embedded in bone while applying torque, there is a problem that the bone cement causes torsional fracture.

Such a problem becomes more remarkable as the degree of stretching increases and the degree of fibrillation increases as the polymer material goes from the spherulite structure to the lamella orientation and further reaches the fiber structure. The present invention has been made in view of the above problems, and an object thereof is to have less anisotropy in strength and to have greater strength than a uniaxially oriented material obtained by long-axis (uniaxial) stretching. However, it is another object of the present invention to provide a method capable of easily producing a biodegradable and resorbable bone cement whose crystals are oriented essentially parallel to a plurality of reference axes.

[0011]

Means for Solving the Problems As a result of various studies on the above problems, the present inventors preliminarily produced a preform containing a crystalline thermoplastic polymer material that is biodegradable and absorbable, According to the present invention, it is possible to easily produce an oriented molded article having a strength higher than that of a uniaxially oriented material by performing indentation and pressurizing orientation while cold plastically deforming in a narrow space of an essentially closed forming die. Has been completed.

That is, the present invention is as follows: A crystalline thermoplastic polymer material that is biodegradable and absorbable is melt-molded to form a preform, and the preform is essentially closed at the lower end. The present invention provides a method for producing an osteosynthesis material, which comprises producing an oriented compact by pressing and orienting it while cold plastically deforming it into a narrow space.
It is also characterized in that the oriented compact is crystallized, and that the crystals have a crystal morphology that is essentially oriented parallel to a plurality of reference axes. Further, the pressure orientation is such that the preform described is press-fitted into the mold having a substantially lower end having a cross-sectional area smaller than the cross-sectional area of the green body while being plastically deformed and compressed and oriented. There is also a feature in that it consists of things. Also,

The pressure orientation allows the preform described to be in a narrow space of a mold, or a mold in which a cross-sectional area, a thickness, or a width of the molded body is partially or wholly small. It is also characterized in that it is formed by forging, filling and orienting while cold plastically deforming a forming die having a space smaller than the volume of the preformed body. The initial viscosity average molecular weight of the polymer material is 200,000-6.
It is also characterized in that it has a viscosity average molecular weight of 100,000 and a subsequent melt-molded preform has a viscosity average molecular weight of 100,000 to 400,000. Another feature is that the preform is press-fitted into the cavity of the mold having a cross-sectional area of ⅔ to ⅙ of the cross section of the preform. In addition, the molding die is also characterized in that it has a storage cylindrical portion with a large cross-sectional area for accommodating the preform, a cavity with a smaller cross-sectional area to be compressed and filled, and a reduced-diameter portion with a tapered surface connecting them. Have. It is also characterized in that the plastic deformation temperature of the preformed body is a temperature at which the thermoplastic polymer material can be crystallized between the glass transition temperature and the melting temperature. It is also characterized in that the oriented molded body is cut into a desired shape of the bone cement.

The present invention will be described in detail below. In addition, here, "compression molding in which it is essentially pressed and oriented in a closed mold or pressure-oriented by a press-fitting method" is simply referred to as "compression molding, compression orientation" or "forging molding". , Forging orientation ”. However, the compression molding and the forging molding referred to in the present invention are different in the following points.

Both of them are not a molding method in which a material (pressure chain) is pressure-molded to orient a crystal (molecular chain) only in the major axis direction (machine direction) such as uniaxial stretching, but in a certain direction having a plurality of axes. This is a molding method for the purpose of The methods of the two are different, and the orientation form of the obtained molded article is also essentially different. That is, compression molding is performed as shown in FIGS.
A billet, which is a preform, has a smaller cross-sectional area and is cold-press-filled into a relatively simple shaped mold whose bottom end is essentially closed to form and orient while plastically deforming. Is the way.

On the other hand, the forging is carried out by forming the billet in FIGS.
In the space of the mold as shown in FIG. 4, which has a more complicated shape and has a space in which the thickness or the width of its cross section is partially or wholly small, or the space of the mold is a billet. This is a molding method in which a mold having a volume smaller than the volume is cold forged and filled so as to be oriented while being plastically deformed. Therefore, the lower end of the mold does not necessarily have to be closed, and a compression-orientated molecular chain (crystal) form can be obtained at a portion pressed into a space having a small cross-sectional area (or thickness or width). However, there is also a part of the molded product that has the same or larger cross-sectional area and is only deformed by rolling or the shape of the mold by press fitting at the part, and the material is completely filled up to every corner of such a complicated shape. To let
It is necessary to adjust the method of molding appropriately by making the press-fitting stronger or weaker or by continuously or discontinuously press-fitting.

The forming method itself by such a press-fitting method is a forming method called forging. That is, the molded body obtained by forging as referred to in the present invention includes a mixture of a portion having a compression-oriented form and a portion having a form oriented by casting as in the compression molding. In addition, “a crystalline thermoplastic polymer material that is biodegradable and absorbable” is simply referred to as “polymer material”. The “crystal orientation” in the present invention means the orientation of the molecular chain of the polymer at the same time in some cases.

(A) [General] Manufacturing Method of Bone Joint Material: (a) Oriented bone joint material of the present invention, that is, an orientation having a crystal morphology in which crystals are essentially oriented in parallel along a plurality of reference axes The method for producing a molded article is basically (a) biodegradable and absorbable,
The first step of making a preform by melt-molding a crystalline or thermoplastic polymer material using an extruder or the like, (b) a mold whose bottom end is essentially closed A second step of producing an oriented molded body by pressing and orienting while cold plastically deforming into a narrow space formed by

Alternatively, the billet is formed into a mold space having a space in which the diameter, thickness, or width of the molded body is partially or wholly small, or the mold space is smaller than the volume of the billet. The second step is to manufacture the oriented compact while plastically deforming it by forging and filling, and (c) if necessary, further cutting or the like to produce the desired shape. Here, "cold" means
It means a crystallizable temperature (Tc) between the glass transition temperature (Tg) and the melting temperature (Tm) of the thermoplastic polymer material and lower than the molding temperature at the melting temperature or higher that is usually performed.

In other words, a large-diameter billet is closed into a small-diameter mold cavity through a reduced-diameter portion having a gradient of θ as shown in FIG. When it is pushed in, a polymer having a low fluidity of Tm or less, which does not have a thermal fluidity like a molten polymer at the time of press-fitting, undergoes large shear due to friction between the billet and the inner surface of the molding die while being plastically deformed. The shearing force acts as an oblique or lateral external force for orienting the polymer, so that the molecular chains (crystals) of the polymer are oriented along the direction of press-fitting into the mold.

That is, it is possible to obtain a crystal morphology that is oriented in parallel along a plurality of reference axes according to the method of press-fitting the billet. In this case, the more the orientation reference axis is, the less the physical strength anisotropy is. Then, in such a state, the molded body is pressed in the vertical or diagonal direction which is the press-fitting direction, so that the molded body becomes qualitatively dense. As a result, the physical strength anisotropy is small unlike the simple uniaxial stretching in the long axis direction, and the mechanical properties such as bending strength, tensile strength, tear strength, shear strength, torsional strength, and surface hardness are generally An improved oriented compact is obtained. This oriented molded product is finally processed into a predetermined shape by subjecting it to a cutting process or the like to manufacture a bone cement having various shapes with high strength.

(B) Crystal morphology of the pressure-oriented compact:
5 and 6 are schematic views showing the orientation state of the crystals of the columnar and plate-like bone cements 11, respectively, (a) showing the orientation state of the longitudinal section, and (b) the orientation state of the plane. Show. Basically, as shown schematically in FIG. 5, the crystal of the pressure-oriented compact has an axis L (simply referred to as a central axis) L that serves as a mechanical core of the compact, that is, a force from the outside is concentrated during the compaction. Along a number of reference axes N that are inclined obliquely from the outer peripheral surface toward the axis L of the center of continuous mechanical points, they are continuously and diagonally oriented in parallel from the upper side to the lower side in FIG. It has a form.

In other words, a large number of reference axes N having a radial oblique orientation around the central axis L are connected circumferentially as shown in FIG. 5B to form a substantially conical shape, which is shown in FIG. As shown in (a), the crystals are connected in the vertical direction, and the crystals are oriented parallel to these reference axes N to form a continuous phase having a substantially conical surface. That is, it can be regarded as an oriented structure in which the conical crystal planes are continuous in the vertical direction of the central axis L, and the crystal planes extending from the outer circumference to the center are oriented in the central axis direction. Such a crystalline state is formed by subjecting the billet to large shear due to friction during compression molding, and at the same time as crystallization progresses, the billet is obliquely oriented toward the central axis L.

In this case, when a large billet having a rectangular cross section is compression-molded in a molding cavity having a rectangular cross section, the obtained oriented molded product has a plate shape, as schematically shown in FIG. , The axis that becomes a mechanical core by receiving large shear from both sides of its long side is not the center line,
A plane M is formed that includes this axis and is parallel and equidistant to opposite sides of the plate. Therefore, the crystal state of the oriented compact is
The plate is oriented parallel to a diagonal reference axis N extending from both facing surfaces of the plate toward the surface.

Further, since the axis L or the surface M including the axis L, which is the mechanical core of the molded body, is the point where the external force is concentrated, the diameter of the molding die 2 shown in FIG. 1, for example, is reduced. When the bottomed mold 2 in which the inclination angle θ of the reduced diameter portion 20a is gradually changed over the entire circumference or partially is used, the point where the external force is concentrated is decentered, and the crystal is centered. Off axis L
It is oriented parallel to the reference axis N that changes corresponding to the inclination angle θ inclined from the outer peripheral surface toward (there may be a plurality of cases). Further, if the oriented molded body has the plate shape shown in FIG. 6, a plane M having a continuous axis L serving as a mechanical core.
However, it deviates from the center equidistant from both sides and is biased to either side. Although the crystal orientation state is described in FIGS. 5 and 6 in the case where the axis L or the plane M passes through the center or the middle of the molded body, these figures are, of course, conceptually the axis L or The case where the surface M is deviated to the left or right from the center or the center of the molded body is also included.

(C) Manufacture of a pressure-oriented molded body: 1) Compression-oriented molding; a polymer material is melt-molded to form a pre-molded body, and the pre-molded body is essentially molded into a closed mold. It consists of press-fitting and compressing orientation while cold plastically deforming into a narrow space. 2) Forging orientation molding; a preform is produced by melt-forming a polymer material, and the preform is defined as above, and either the thickness or width of the cross-sectional area of the preform is partial or Press into the narrow space of the mold that is small as a whole or into the mold of the total volume with the space of the mold smaller than the volume of the preform while cold or plastically deforming continuously or discontinuously. And forging orientation.

3) Deformation Degree: When the billet is press-filled (pushing pressure) into the cavity of the molding die having a cross-sectional area of ⅔ to ⅙ of the cross-sectional area of the billet, the resulting pressure-oriented molded body is obtained. Deformation degree R = So
/ S (where So is the cross-sectional area of the billet and S is the cross-sectional area of the compression-oriented compact) is a value substantially in the range of 1.5 to 6.0, which is shown in the data of Examples described later. Thus, the improvement in strength is remarkable. Further, a mold having a value of R in this range and having a partially different value (the cross-sectional area in the direction in which the polymer proceeds by press fitting is partially different,
When the other part except this part has the same cross-sectional area as the billet), the orientation axis is complicated and disturbed, and the anisotropy is not simple either.

The portion of the molded article having a large R has a higher degree of orientation than the portion having a small R, and therefore generally has a high mechanical strength. Therefore, it is possible to intentionally form a molded product having a partially different strength according to the application. this is,
This can be achieved only by a method of forming an oriented molded body by press-fitting into a mold by plastic deformation like the method of the present invention, and a stretching method in which a portion having a different stretching ratio cannot be partially formed during the stretching operation. It can be said that this is a remarkable advantage of the present invention in comparison with the above.

That is, the reason why the method according to the pressure orientation of the present invention is very advantageous as compared with the conventional method based on the stretch orientation also exists here. Here, if the cross-sectional area of the cavity is made larger than 2/3 of the cross-sectional area of the billet, the orientation and compression rate of the molecular chains and crystals during press-fitting are low, and it is difficult to obtain a compression-oriented molded article having high strength and hardness. On the other hand, 1 /
If it is smaller than 6, not only is it difficult to press-fill the cavity of the billet into the cavity, but also the polymer may become fibrillated. When fibrillation occurs, the strength of the molded body in the lateral direction is improved, but that in the longitudinal direction is decreased, and shearing forces tend to tear between the fibrils in the longitudinal direction.

4) Plastic Deformation Temperature The plastic deformation temperature of the billet is preferably a crystallizable temperature (Tc) between the glass transition temperature (Tg) and the melting temperature (Tm) of the thermoplastic polymer material. . Specifically, for example, in the case of polylactic acid or lactic acid-glycolic acid copolymer, 60 to 160 within the range shown in the examples below.
C, preferably 80 to 110 C is desirable. When the billet is press-filled into the cavity at this temperature, the press-fitting is relatively easy, the orientation of the molecular chains (crystals) is effectively performed, and the crystallinity can be adjusted as desired. Also, at that time, an appropriate speed (for example, 8 to 80 mm / min) to suppress the springback phenomenon in the press-fitting process.
It is necessary to choose.

5) In either case of pressure orientation molding such as compression orientation molding or forging orientation molding, a high pressure suitable for the molding die (for example, 100 to 4000 kg / cm ² , preferably 2).
00~2500kg / cm ²⁾ cold under (glass transition temperature (Tg of the polymer material) above the melting temperature (Tm) crystallizable temperatures between below (Tc), such as polylactic acid or lactic acid - glycolic acid In the case of a copolymer, 60 to 160 ° C,
Friction is generated between the mold wall and the mold wall during press-fitting while plastically deforming (preferably 80 to 110 ° C.), and this acts as an external force in a lateral or oblique direction for orienting the polymer. A crystal structure oriented in parallel is formed. Further, at this time, the molded body is pressed in the vertical direction to be qualitatively dense, and the density of the bone cement increases, and as a result, high strength can be obtained.

(B) [Specification] Manufacturing method of bone cement:
A specific description will be given with reference to the drawings. FIG. 1 is a cross-sectional view showing a state before press-filling a billet into a cavity of a mold in compression orientation molding. FIG. 2 is a cross-sectional view showing a state after press-filling a billet into a cavity of a mold in compression orientation molding. FIG. 3 is a front view showing an example of an osteosynthesis screw finally obtained by cutting.

The manufacturing method of the present invention will be described for the case of manufacturing an osteosynthesis screw S as shown in FIG. 3, for example. It basically consists of the following three steps. A primary molding step in which a biodegradable and absorbable, crystalline, thermoplastic polymer material is melt-molded to form a preform, for example, a thick cylindrical billet 1, and then the billet 1 is molded into a mold as shown in FIG. Two
2 in the cavity 2c of the molding die 2 as shown in FIG. 2 by continuously or intermittently pressurizing the billet 1 by a piston (ram) or other pressurizing means 2b. Secondary molding step in which a thin columnar compression-oriented molded body 10 is formed by press-fitting while cold plastically deforming, and the compression-oriented molded body 10 taken out from the molding die 2 is joined to the bone as shown in FIG. A processing step of cutting into screws S.

(A) Raw material composition: The polymeric material used in the present invention is not particularly limited as long as it is a biodegradable and absorbable crystalline crystalline linear polymer.
Polylactic acid, which has been confirmed to be biocompatible and is already in practical use, and various polylactic acid copolymers (for example, lactic acid-glycolic acid copolymer, lactic acid-caprolactone copolymer, etc.) are preferably used. As polylactic acid, L-lactic acid or D-
A homopolymer of lactic acid is suitable, and the lactic acid-glycolic acid copolymer has a molar ratio of 99: 1 to 75:25.
Those having a range of 10 are preferable because they have better hydrolysis resistance than homopolymers of glycolic acid. In addition, amorphous D,
A small amount of L-polylactic acid or an amorphous lactic acid-glycolic acid copolymer may be mixed in order to facilitate plastic deformation, or to impart toughness to the obtained oriented molded article by pressure orientation.

(B) Molecular weight of raw material and preform: The above-mentioned polymeric material is required to have strength as at least a certain value as a bone bonding material and physical properties such as maintaining it for a certain period of time. Since the molecular weight of the polymer material is inevitably lowered at the stage of melt molding into a preform such as a billet, the viscosity average molecular weight of the raw material polymer is about 200,000 to 600,000, preferably 300,000 to 550,000. desirable. When a polymer material having a viscosity average molecular weight in this range is used,
Usually, the viscosity average molecular weight of the billet after melt molding is 100,000 to 400,000, but it is preferable to adjust it to 180,000 to 350,000.

Since the subsequent crystal orientation operation by press-fitting into the mold is carried out in the above temperature range for a short time,
A high-strength pressure-oriented molded body can be obtained without substantially lowering the molecular weight, and if the temperature rise due to friction is suppressed even in the step of cutting out the bone cement by cutting, etc. An osteosynthesis material having a maintained molecular weight is obtained. In this case, when a polymer material having an initial viscosity average molecular weight of more than 600,000 is used, high temperature and high pressure are required when producing a billet by melt molding, which causes a significant decrease in the molecular weight. Since it is lower than when using less than 10,000 raw material polymers, it is meaningless.

Finally, as shown in FIG.
The bone-bonding screw S obtained by cutting the pressure-oriented molded body obtained from the billet having a molecular weight of about 400,000 is the same as the living bone for 2 to 4 months which is an average period required for bone fusion in the living body. It is desirable because it maintains a certain level of strength, and thereafter, the debris formed by the decomposition of the bone cement gradually hydrolyzes at a decomposition rate that does not cause an inflammatory reaction due to a strong foreign body reaction with surrounding tissue cells. is there.

When the viscosity average molecular weight of the billet after melt-molding becomes lower than 100,000, the pressure-molded oriented molded body is
Since it is difficult to obtain a high initial strength and the strength may be decreased by hydrolysis faster than two months, there is a concern that the strength cannot be maintained for a period required for bone fusion. In addition, since low-molecular-weight debris may be generated at one time within a short period of 1.5 to 2 years after living body implantation, surrounding cells cannot completely process it and there is a risk of inflammation due to foreign body reaction. On the other hand, the bone-bonding material, which is an orientation-molded body pressure-molded using a billet having a viscosity average molecular weight of more than 400,000 after melt-molding, is decomposed in vivo after bone union and is not completely absorbed until it is absorbed. It requires a long time. In addition, there is a concern that a foreign substance reaction may occur in a living body due to many small particles having a low molecular weight that are generated at a time after a long period of 2 years or more after being implanted in the living body, and may be expressed as inflammation.

(C) Melt molding: In the primary molding step, as a method for melt molding the billet 1 from a polymer material,
The melt extrusion molding method is preferably adopted, but other molding methods such as an injection molding method and a press molding method may be adopted if consideration is given to avoiding a decrease in molecular weight. When adopting the melt extrusion molding method, it is important to adopt a temperature condition slightly higher than the melting point of the polymer material and a minimum extrudable pressure condition in order to minimize the decrease in the molecular weight of the polymer material. .
For example, when the polymer material is poly-L-lactic acid (PLLA) having a viscosity average molecular weight of about 200,000 to 600,000, the temperature is not lower than the melting point and not higher than 220 ° C., preferably not higher than 200 ° C. and 260 kg. / Cm ² or less, preferably 1
It is preferable to adopt a pressure condition of about 70 to 210 kg / cm ² .

(D) Compression orientation molding: As shown in FIGS. 1 and 2 exemplified as compression orientation molding, the billet 1 is
It is desirable to perform melt-molding so as to have a cross-sectional shape similar to the cross-sectional shape of the cavity 2c of the mold 2, and when the cavity 2c has a circular cross-sectional shape as in the present embodiment, a larger circular cross-sectional shape. It is desirable to melt-form the billet 1 so as to form a cylindrical body having
In this way, if the cross-sectional shape of the billet 1 is similar to the cross-sectional shape of the cavity 2c, the billet 1 can be plastically deformed while being uniformly compressed from the surroundings and press-filled into the cavity 2c, resulting in a uniform degree of deformation. Compression orientation molded body 10
Can be obtained.

However, the cross-sectional shape of this billet is not limited to a circular shape, and it is needless to say that it may be a polygonal shape or another irregular shape. It may have a desired shape corresponding to the cross section. In addition, the billet 1 has a cross-sectional area of the cavity 2c.
The cross-sectional area is preferably 1.5 to 6.0 times. That is, the billet 1 is set to 2/3 to 1 of the cross-sectional area of the billet 1.
Deformation degree R of the compression-oriented molded body 10 obtained by press-filling into the cavity 2c having a cross-sectional area of / 6
So / S (where S0 is the cross-sectional area of the billet 1 and S is the cross-sectional area of the compression-oriented compact 10) can be processed to be 1.5 to 6.0.

By doing so, the strength and hardness of the compression-oriented molded body 10 are remarkably improved, as shown in the data of Examples described later. Then, by performing cutting, threading, slicing, or the like on this, ideal bone-bonding materials such as bone-bonding screws S, nails, pins, and plates can be obtained. When the billet 1 is press-fitted into the cavity 2c larger than ⅔ of the cross-sectional area of the billet 1, it is difficult to obtain the compression-oriented molded body 10 having high strength and hardness because the orientation and compression rate of the molecular chains and crystals are low. Become. On the other hand, the cross-sectional area is 1/6
Even if it is attempted to press fit into the smaller cavities 2c, it is difficult to press fit, and even if it is possible, the orientation of the polymer becomes excessive, fibrillation may occur, and cracks are likely to occur between the fibrils, which is not preferable.

Next, the mold used for compression orientation molding, the mechanism of orientation and the method thereof will be described. FIG. 1 is a cross-sectional view illustrating a state before press-filling a billet into a cavity of a mold in compression orientation molding. 1) As shown in FIG. 1, a molding die 2 used in the secondary molding step.
Is a thick cylindrical storage cylinder portion 2a for storing the billet 1.
And a thin cylindrical molding cavity 2c for press-filling the billet 1 by the pressurizing means 2b are coaxially connected vertically via a diameter-reduced portion 20a having a tapered bottom. A pressurizing means 2b such as a piston (ram) that pressurizes the billet 1 continuously or intermittently is provided on the upper part of the housing tubular portion 2a. Then, in the bottom of the cavity 2c, very minute air vent holes and gaps (not shown) are formed.

[0044] 2) the radius r ₂ of a radius r ₁ and the cavity 2c of the housing cylinder portion 2a, the inequality for the reasons described above: 1.5
It is set so that ≦ (r ₁ / r ₂ ) ² ≦ 6.0, and a cylindrical billet 1 having a cross-sectional area of 1.5 to 6.0 times the cross-sectional area of the cavity 2c is accommodated. It can be housed in the tubular portion 2a.

3) Further, the taper inclination angle θ of the reduced diameter portion 20a is set within the range of 10 to 60 °. When the inclination angle θ is smaller than 10 °, the pressure when the billet 1 is press-fitted into the cavity 2c does not become high, and the orientation of the molecular chains (crystals) of the obtained compression oriented molded body 10 (not shown) is low, so that it is high. No strength can be obtained. On the other hand, the tilt angle θ is 6
When it is larger than 0 °, press-fitting and filling becomes difficult. Therefore, the inclination angle θ is 10 ° to 60 °, preferably 15 ° to 4
It is desirable to set it to 5 °. And (r ₁ / r ₂ ) ²
When the value of is in the range of 1.5 to 6.0, the smaller the inclination angle θ is, the smaller the inclination angle θ is set.

4) As shown in FIG. 2, the billet 1 is housed in the housing cylinder portion 2a by using such a mold 2, and the billet 1 is continuously or intermittently pressed by the pressing means 2b, If the cavity 2c is press-fitted while being plastically deformed in the cold, large shear due to friction occurs between the inner surface of the reduced diameter portion 20a and the inner surface of the cavity 2c at the time of press-fitting. Acts as an external force (vector force) in the direction of. Therefore, the polymer is essentially oriented along the inner surface of the reduced diameter portion 20a to promote crystallization, and at the same time, the press-fitting into the center of the molding cavity 2c is prioritized over the peripheral portion. The crystallographic axes of the compression-oriented compact 10 molded as described above are oriented obliquely with respect to the longitudinal axis thereof according to the inclination angle θ of the taper of the reduced diameter portion.

5) Then, the obtained compression oriented molded body is oriented concentrically along the inner surface of the cavity 2c,
It is considered to have many reference axes. At the same time, the polymer is compressed in the longitudinal direction (machine direction), so that a qualitatively compact thin columnar compression-oriented compact 10 is obtained.
In that case, the orientation angle of the crystal (the angle of the crystal with respect to the axis that serves as the mechanical core of the compression-oriented compact) is determined by the inclination angle θ of the reduced diameter portion 20a and the area of the cross-sectional surface of the containing cylinder portion 2a and the cavity 2c. It is approximately determined by the ratio.

That is, as shown in FIG. 7, the radius of the accommodating tubular portion 2a is r ₁ , the radius of the cavity 2c is r ₂ , the inclination angle of the reduced diameter portion 20a with respect to the central axis Lc of the molding die 2 is θ, and the accommodating portion 20a is accommodated. The area ratio of the cross section of the cylindrical portion 2a and the cavity 2c is A = r ₁
² / r ₂ ^2, and the distance at which the point Y on the central axis Lc is press-fitted while the point X on the outer peripheral portion of the billet 1 is press-fitted along the tapered inner surface by the distance d in the direction of the axis Lc. , The crystal is considered to be oriented in the direction of the line segment Lm. When the orientation angle (angle with respect to the axis Lc) of the crystal oriented in the direction of the line segment Lm is θm, tan θm = r ₂ / (D−d), and D−d = A · d, so tan θm = r ₂ /
It becomes A · d ·· [1]. d = (r ₁ −r ₂ ) / tan
Since it is θ, substituting this into [Equation 1], tan θ
m = r ₂ tan θ / [A (r ₁ −r ₂ )] ... [Equation 2]
Since r ₁ = r ₂ · A ^0.5 , substituting this into [Equation 2], tan θm = tan θ / [A · (A
^0.5 -1)] ... [Equation 3].

6) Therefore, the crystal is oriented obliquely with respect to the axis at the orientation angle θm satisfying the above [Formula 3], and the larger the inclination angle θ of the inner surface of the taper, the more the orientation angle θm of the crystal becomes. It becomes large, and the storage cylinder 2a and the cavity 2
The larger the area ratio A of the cross section of c, the smaller the orientation angle of the crystal. Therefore, the crystal can be adjusted to a desired orientation angle θm by changing the tilt angle θ and the area ratio A.

7) As described above, the compression-oriented compact 10 having a crystal form oriented parallel to many reference axes is anisotropic in strength as compared with a compact uniaxially stretched in the major axis direction. Since it has little property and is qualitatively dense, mechanical properties such as compressive bending strength, compressive bending elastic modulus, tensile strength, tearing strength, shearing strength, torsional strength, and surface hardness are improved, and fracture is less likely to occur. . In particular, when the deformation degree R of the compression-oriented molded body 10 is in the range of 1.5 to 6.0, the strength is remarkably improved. For example, the billet 1 of polylactic acid (viscosity average molecular weight: 100,000 to 400,000). The compression-oriented molded body 10 having the above-mentioned deformation degree obtained by press-filling with the above-mentioned material has a compressive bending strength of 160 to 300 MPa, and polylactic acid is uniaxially stretched to a stretching ratio which is substantially the same as the above-mentioned deformation degree. Physical strength such as compressive bending strength, torsional strength and surface hardness is generally higher than that of the stretched material.

8) On the other hand, in the case of free width uniaxial stretching in which the billet of the polymer material is stretched in the major axis direction, external force is not applied from the lateral direction (side surface), and the thickness of the molded product is increased during the stretching process. Thins. Further, the stretched product is qualitatively thin because it is stretched in the major axis direction which is the orientation axis. Therefore, the stretch-formed compact 1 according to the present invention has a compression-oriented compact 1 having a crystalline morphology which is essentially oriented along many reference axes.
Compared with 0, the anisotropy is large and the mechanical strength is also generally small.

9) Depending on the type of polymer material, the press-fitting of the billet 1 may be carried out at room temperature lower than the glass transition temperature (Tg), but the ease of press-fitting and the orientation of the molecular chains (crystals). In order to achieve the effect, the adjustment of the crystallinity, and the like, the billet 1 is moved to the glass transition temperature (T
It is desirable to heat to a temperature (Tc) that can be crystallized between g) and a melting temperature (Tm) and lower, and press-fill into the cavity 2c. In the case of the polylactic acid billet 1 described above, the temperature for press-fitting and plastic deformation is 60 to
The temperature is 160 ° C, preferably 80 to 110 ° C.

10) The press-fitting / filling pressure is 100-4.
000 kg / cm ² , preferably 200 to 2500 kg
/ Cm ² . Press-fit / fill pressure is 4000 kg / cm ²
If it is excessively press-fitted over the range, the molecular weight is significantly reduced by the shearing force and heat generated thereby, and it becomes difficult to obtain a high-strength compression-oriented molded body 10. Further, if the press-fitting / filling pressure is less than 100 kg / cm ² , it becomes difficult to press-fit and fill the billet 1 into the cavity 2c having a cross-sectional area smaller than 2/3, and it becomes impossible to obtain a compression-oriented compact having high strength and hardness. .

11) The press-fitting speed is 8 to 80 mm / min, preferably 40 to 80 mm when a mold used for general molding is used or when the metal surface is not subjected to a special surface treatment for improving sliding. 60 mm / min is suitable. When pressed at a speed slower than 8 mm / min, the billet 1 still has a cavity 2
The part that is not press-fitted into c is hardened by the progress of crystallization, and press-fitting becomes difficult. On the other hand, when press-fitting and filling at a speed faster than 80 mm / min, stick-slip occurs,
This is not preferable because it results in a non-uniform molded body. The crystallinity of the compression-oriented compact 10 obtained by press-filling the billet 1 into the cavity 2c as described above depends on the deformation degree R of the compact 10, the temperature at the time of press-fitting, the pressure, the time (press-fit speed), etc. In general, the degree of deformation R is large, the temperature is high, the pressure is large, and the time is long, the crystallinity is high.

12) The crystallinity of the compression-oriented compact 10 is 3
It is desirable to be in the range of 0 to 60%, preferably 40 to 50%. Compressed orientation molded body 10 having such a crystallinity
The bone-bonding material such as the bone-bonding screw S obtained by subjecting the material to the cutting has a good balance of the ratio of the crystalline phase and the amorphous phase of the polymer. Since it is well balanced with the flexibility of the crystalline phase, it does not have the brittleness as in the case of only the crystalline phase, and does not show the soft and weak property as in the case of only the amorphous phase. Therefore, the bone joint material has toughness and a sufficiently high strength overall.

When the crystallinity is less than 30%, it is generally not expected that the crystal will improve the strength. On the other hand, when the crystallinity is high, the strength is correspondingly improved, but when the crystallinity is higher than 60%, the lack of toughness causes the brittle property of being easily broken when an impact is applied. Also,
The polymer material used in the present invention generally has a gradual increase in crystallinity in the process of hydrolysis progressing to a low molecule in vivo, and the progress of hydrolysis decreases as the crystallinity increases. It is known that a low molecular weight is not easily reached until it is absorbed in a living body. However, as described above, a polymer having a crystallinity of 30 to 60% is present in a living body and from a living body. Since the decomposition product is further fragmented by the force, there is not much concern that the hydrolysis rate in the living body may be reduced.

For these reasons, the compression-oriented molded body 10
Processability R and temperature, pressure, time, etc. at the time of press fitting are controlled within the above range, or heat treatment is carried out for a short time at a crystallization temperature (for example, a temperature of 90 to 160 ° C.) after press fitting to perform compression orientation molding. The crystallinity of the body 10 is 30 to 6
It is desirable to adjust it to 0%. 13) When the press-fitting and filling of the billet 1 is completed, the compression-oriented molded body 10 is cooled and taken out from the mold 2, and the non-oriented blank material portion 10a of the compression-oriented molded body 10 is cut to perform cutting or thread cutting. By performing processing, slicing, etc., an osteosynthesis screw S having a screw shaft portion S ₁ , a screw head S ₂ , and a rotary jig insertion hole S ₃ as shown in FIG. 3 is obtained.

The bone-joining screw S may have various shapes other than the shape shown in FIG. 3, and bone-bonding materials other than the screw, such as pins, nails, plates, buttons, and cylindrical objects, may be used as desired. It goes without saying that the shape of the material may be cut, threaded, punched, sliced or the like. When the thin columnar compression-oriented molded body 10 with the margin material portion 10a cut off is used as it is as an osteosynthesis rod, the above-mentioned cutting work is unnecessary. The osteosynthesis screw S manufactured according to the above-described embodiment has a dense compression orientation molding with a deformation degree R of 1.5 to 6.0, which has a crystalline morphology that is oriented essentially parallel to many reference axes. Since the body 10 (viscosity average molecular weight: 100,000 to 400,000, crystallinity: 30 to 60%) is cut, etc., the strength anisotropy is higher than that of the conventional uniaxially stretched bone cement. It has less mechanical properties such as compressive bending strength, compressive bending elastic modulus, tensile strength, tearing strength, shearing strength, torsional strength, surface hardness, etc. Moreover, it has moderate hydrolysis resistance and bone in vivo. It is a near-ideal implant material because it maintains the same strength as living bone for several months required for fusion, and is gradually decomposed and absorbed at an appropriate decomposition rate without causing an inflammatory reaction thereafter.

14) In the above-described embodiment, as the molding die 2, a cylindrical housing cylinder portion 2a having a large radius and a cylindrical cavity 2c having a small radius are mounted with a taper having the same inclination angle .theta. What is connected vertically through the conical diameter-reduced portion 20a is used. However, in the case of manufacturing a plate-shaped bone bonding material such as a bone bonding plate,
A molding die may be used in which a housing cylinder portion having a rectangular cross section and a cavity having a small rectangular cross section similar to this are connected through a reduced diameter portion. In this case, if the taper of the reduced diameter portion is provided on the four sides, a plate-shaped molded body is formed which is oriented obliquely from the four sides toward the vertical axis, but the reduced diameter portion in which only the two sides in the long side direction are tapered is formed. When provided, the plate-shaped molded product is oriented obliquely from both sides toward the plane including the vertical axis.

15) In the embodiment of the cylindrical body described above, the inclination angle θ of the reduced diameter portion 20a is constant, but it can be changed over the entire circumference or partially, or the two sides in the long side direction of the prismatic body. By changing the inclination angle θ of the above, the axis L or the plane M including the axis L, which is the mechanical core of the molded body, is decentered, and is oriented obliquely toward the displaced axis L or plane M.
For example, as shown in FIG. 8, compression molding is performed from a rectangular billet 1 having a large cross-sectional area by using a molding die 2 in which the inclination angles θ ₁ and θ ₂ (θ ₁ <θ ₂ ) of the reduced diameter portion 20a are different on the left and right. Then, when a rectangular compression oriented molded body is molded, an oriented molded body in which the surface M is displaced to the right is obtained.

As shown in FIG. 9, the crystals of this oriented compact are oriented parallel to the reference axes N and N'which are inclined obliquely from both sides toward the plane M which is offset to the right. This compression-oriented molded body has different crystal orientation angles on the left and right, so it becomes a plate-shaped molded body with different strength on both sides.
It is preferably used for applications requiring bone cements having different strengths on both sides. The strength on both sides can be changed by changing the tilt angle in various ways.
Since it can be deflected by changing the position of, it can be freely adjusted according to the application. in this way,
The molding die may be selected according to the shape and application of the bone cement to be manufactured.

(E) Forging orientation molding FIG. 4 is a sectional view showing a state before the billet 1 is press-fitted into the cavity 2c of the molding die 2 in the forging orientation molding which is another embodiment of the present invention. 1) The molding die 2 used in this embodiment includes a cylindrical or (multi-) polygonal tube 2a having a hollow disk shape or a hollow shape having an area of a projection plane larger than the cross-sectional area of the tube 2a. It is provided in the center of a (multi-) square plate-shaped (different shape) cavity 2c, and a pressurizing means 2b such as a piston (ram) is provided above the housing cylinder 2a.

However, the thickness of the cavity 2c (the area of the cross section in the press-fitting direction) is the diameter of the accommodating cylinder portion 2a (the area of the cross section).
The basic condition is to be smaller. This is because even in the forging method, the purpose is to press and orient the crystals. This condition may be satisfied in all or a part of the cavity 2c, but the volume of the billet 1 is larger than that of the cavity 2c in order to fill the cavity 2c with the material to be molded. It needs to be big. In particular, when this condition is partially (partially) satisfied (in other words, the cavity 2
In the case of a molded body in which the thickness (diameter) of c partially has a diameter larger than the diameter of the billet 1 and the remaining portion is small or the same), the material is pressed all the way into the mold. The volume of the billet 1 needs to be much larger than the total volume of the cavity in order to be spread.

2) In the embodiment shown in FIG. 4, the cross-sectional shape is the same as the cross-sectional shape of the accommodating cylinder portion 2a, and the volume is a columnar shape or a (multi-) prismatic shape (an irregular shape) larger than the volume of the cavity 2c. The billet 1 made of a polymer material, which is obtained by melt molding, is housed in the housing cylinder 2a and continuously or intermittently pressurized by the pressurizing means 2b, so that the billet 1 is cold and the area of the projection plane is Of the large cavity 2c is pressed and filled from the central portion to the peripheral portion while being expanded by punching to obtain a disc-shaped or (multi) square plate-shaped (different shape) forged oriented molded body.

The forged oriented compact obtained in this embodiment is different from the above-mentioned compression oriented compact in that the molecular chains and crystals are radially oriented with many axes from the central part to the peripheral part of the molding cavity 2c. There are essentially many forged oriented compacts oriented parallel to the reference axis. This is obviously a molded product having a different orientation form from a simple uniaxially stretched product. 3) The method according to such an embodiment is a bone-shaped bone prosthesis material having a hole inside such as a cylindrical shape, a (multi) square plate shape, or a button shape, or a deformed plate-shaped bone prosthesis material having a part having a different thickness. It is particularly effective in the case of manufacturing (bone filling material).

4) Further, the cavity 2d shown by the dotted line in FIG. 4 shows an example in which R gradually increases toward the tip. That is, an example is shown in which the same molded body has a portion in which R changes in the range of 2/3 to 1/6. In this case, the orientation axis forms a state of biting in the thickness direction (towards the bottom) as it goes to the tip of the cavity 2d, so that the state of being radially oriented from the central portion of the molding cavity 2c to the peripheral portion thereof. And, a molded product having a complicated orientation form in which the orientations of the mutually intertwined states are established. 5) Also, the various conditions shown in the case of compression orientation molding (d) can be similarly adopted in the case of forging orientation molding (e).

[0067]

EXAMPLES The present invention will now be specifically described with reference to examples, but these do not limit the scope of the present invention. The physical properties and the like of the bone cement of the present invention are values obtained by the following measurements. Crystallinity: A value calculated from the analysis result by a differential scanning calorimeter (DSC). Bending strength: A value measured by a method according to [JIS K 7203]. Flexural modulus: A value measured by a method according to JIS K7203. Density: Numerical value calculated from the volume and weight of the obtained oriented compact. Breaking torque: Torque tester (manufactured by Shinpo Industry Co., Ltd.,
It is a value measured by a screw tester).

Example 1 <Example of Compressive Orientation; Example 1> Poly L lactic acid having a viscosity average molecular weight of 400,000 is used in an extruder 19
Melt extrusion was performed at 0 ° C. to obtain a prismatic billet having a length × width = 60 mm × 60 mm, a length of 50 mm, and a viscosity average molecular weight of 300,000. This billet is put in a container of a mold having the same cross-sectional shape and heated to 110 ° C., and pressure 2 is applied through the reduced diameter portion.
000kg / cm ² length x width x length = 35mm x 35m
It was press-fitted and filled into a cavity of m × 120 mm. And
After cooling, a prismatic compression-oriented molded body (deformation degree R
≈3) was taken out, the blank material portion was cut out, and the molded body was sliced in the longitudinal direction into a plate having a thickness of 30 mm to manufacture an osteosynthesis plate.

The following Table 1 compares the physical properties of the obtained osteosynthesis plate and a comparative example, a polylactic acid osteosynthesis plate of the same shape stretched 3 times in the longitudinal direction. In addition,
The density of the billet was determined before press-filling, and the results are shown in Table 1.

[Table 1] However, in the stretched plate of the comparative example, the same billet was used at 110 ° C.
It was obtained by a method of stretching in the paraffin bath by 3 times in the long axis direction.

As shown in Table 1, the bone-bonding plate made of the compression-oriented molded body has a higher density and higher bending strength, bending elastic modulus, and shear strength than the bone-bonding plate made of the uniaxially stretched product. Of course, the density is higher than that of the billet before press-filling. That is, in the osteosynthesis plate according to the manufacturing method of the present invention, when the billet is press-fitted into the cavity of the mold, shearing force due to friction is exerted on the surface of the reduced diameter portion, and the crystals are essentially oriented along the surface of the reduced diameter portion. However, since it was oriented obliquely from the outer periphery toward the central axis, there was no strength anisotropy and it became qualitatively denser due to the compressive force. It is considered that the strength was generally higher than that of the oriented body. The crystallinity was kept relatively low because the forming temperature and speed for plastic deformation were properly selected. Therefore, this plate has good toughness, and the decomposition rate is within a range that does not interfere with biological reaction.

Example 2 <Example of Compressive Orientation; Example 2> Poly L lactic acid having a viscosity average molecular weight of 400,000 was used in an extruder 19
Melt extruded at 0 ° C, diameter 13mm, length 50mm,
A cylindrical billet having a viscosity average molecular weight of 300,000 was obtained. This billet was put in a cylindrical accommodating cylinder part having a diameter of 13 mm and heated to 110 ° C., and the diameter was 8.5 m.
A cylindrical compression-oriented molded body having the same size as the cavity (deformation degree R = 2.3), which was press-fitted into the cylindrical cavity having a length of m and a length of 92 mm while being plastically deformed at a pressure of 1800 kg / cm ^2. Got

Then, the compression-oriented molded body was cut to manufacture an osteosynthesis pin having a diameter of 3.2 mm and a length of 40 mm, and the same physical property test as in Example 1 was conducted. Moreover, the breaking torque value by the torque tester was also measured. Table 2 shows the results. In addition, as a comparative example, the same physical properties were measured and compared using an osteosynthesis pin of the same shape made of poly-L-lactic acid having a stretching ratio of 2.3 times obtained by stretching the same billet in the long axis direction. Table 2 shows the results.

[Table 2]

As shown in Table 2, the bone-bonding pin produced by the manufacturing method of the present invention had a high bending strength, a high flexural modulus and a high density as compared with the bone-bonding pin produced by stretching. Further, the breaking torque value is also large, and it can be seen that the former is stronger against torsion than the latter. As described above, in the latter, the crystal axes are uniaxially oriented only in the major axis direction, whereas in the former, the crystal axes are essentially along the surface of the reduced diameter portion, and Since it is oriented obliquely from the outer peripheral surface toward the central axis, the strength anisotropy decreases,
This is considered to support the fact that it showed great strength against the twist around the long axis.

Example 3 <Example of Compressive Orientation; Example 3> Poly L-lactic acid having a viscosity average molecular weight of 300,000 was used in an extruder 18
Melt extruded at 8 ° C, diameter 13mm, length 50mm,
A cylindrical billet having a viscosity average molecular weight of 220,000 was obtained. This billet was put into a cylindrical accommodating cylinder part having a diameter of 13 mm and heated to 100 ° C. to have a diameter of 10.6 m.
pressure of 400 m in a cylindrical cavity with a length of 60 mm
By press-fitting and filling with kg / cm ² , a columnar compression-oriented compact having a size similar to that of the cavity (degree of deformation R = 1.5) was obtained. Then, a bone joining pin having a diameter of 3.2 mm and a length of 40 mm was manufactured by cutting this formed body, and the same physical property test as in Example 1 was performed. Table 3 shows the results.

(Example 4) <Example of forging orientation: Example 1> Poly-L-lactic acid having a viscosity average molecular weight of 250,000 was extruded using an extruder.
Melt extruded at 8 ° C, diameter 50mm, length 43mm
A cylindrical billet (including a blank material portion) and a viscosity average molecular weight of 200,000 was obtained. Then, using a molding die having a shape shown in FIG. 4, in which a cylindrical accommodating cylinder portion having a diameter of 50 mm and a hollow disk-shaped cavity having a diameter of 100 mm and a thickness of 10 mm are coaxially connected vertically, The billet is put in the housing cylinder and heated to 100 ° C., and while being plastically deformed, it is press-fitted into the cavity at a pressure of 2500 kg / cm ² , and a disk-shaped forged orientation molded body of the same size as the cavity (diametrically deformed Degree = 2.0) was obtained. Physical properties were measured by cutting a test piece in the radial direction of the forged compact, excluding the central cylindrical portion. Table 3 shows the results. This test piece is a molded product having a large crystallographic plane, in which the crystallographic plane is different from that of Example 3 and the orientation axis is radially oriented in a multi-axial manner from the center portion of the disk shape toward the outer peripheral direction.

(Example 5) <Example of compression orientation; Example 4> Polylactic acid having a viscosity average molecular weight of 400,000 is extruded in the same manner as in Example 2 to obtain a billet having a viscosity average molecular weight of 300,000. It was Then, this billet is formed into a mold having a diameter of 13 m.
m into a cylindrical accommodating cylinder portion, and a cylindrical cavity having a diameter of 11.9 mm and a length of 46 mm was press-fitted at a pressure of 80 kg / cm ² under the same conditions as in Example 2, and the degree of deformation R was 1.2. A compression oriented molded body of A pin having a diameter of 3.2 mm and a length of 40 mm was produced from this molded body by cutting, and the same physical property test as in Example 1 was conducted.

The results are shown in Table 3.

[Table 3] This value showed higher flexural strength and density than a stretched product uniaxially stretched at a stretch ratio of the same ratio as the deformation degree R. However, the compression bending strength of this molded body was lower than the lower limit of 150 to 200 MPa which is the strength of general cortical bone.
Therefore, in order to obtain the strength of 150 MPa or more, it seems that the deformation degree R is at least 1.5 or more as in Example 2.

Example 6 <Example of Compressed Orientation; Example 5> The same polylactic acid billet as obtained in Example 5 was put into a cylindrical accommodating cylinder portion having a diameter of 13.0 mm and a diameter of 5 was obtained. ．
A cavity having a length of 3 mm and a length of 220 mm was press-filled under the same conditions as in Example 2, and an attempt was made to obtain a compression-oriented molded body having a deformation degree R of 6.0. However, 1000 for press-fit filling
A very high pressure of 0 kg / cm ² was required. Also,
The obtained molded product had cracks. Similarly, trial production was performed when the deformation degree R was 5.5. The obtained molded product had partial cracks and was not sufficiently satisfactory. However, when a treatment for making the inclination angle of the diameter-reduced portion small (15 °) and making the surface of the mold slippery, a good compression-oriented molded body was obtained.

(Example 7) <Example of compression orientation; Example 6> Example 2 using a copolymer of poly L-lactic acid and polyglycolic acid (molar ratio = 95: 5) having a viscosity average part of 400,000. In the same manner as described above, a compression-oriented molded body of a cylindrical body was made, and its physical properties were measured. The results are also shown in Table 3. Since the copolymer has a lower crystallinity than the homopolymer, its strength is slightly lower than that of the homopolymer, but this compression-oriented molded article has strength enough for use as an osteosynthetic material, and in vivo. Has the advantage that it decomposes faster than a homopolymer.

<Proof experiment> An experiment for demonstrating that the oriented molded body obtained by the present invention has an orientation form different from that of the oriented molded body obtained by stretching in the longitudinal direction by uniaxial stretching. Was performed as follows. (1) A small-diameter through hole is opened in the transparent poly-L-lactic acid billet obtained by the above-described melt molding as shown in FIG. 10, and a white opaque of the same diameter is obtained by mixing the same-quality poly-L-lactic acid with an inorganic white pigment. The poly-L-lactic acid round bar was inserted and completely packed. This was filled in the mold described in the example, and compression orientation molding was performed to a deformation degree of 2.8 by the same method. As a result, FIG.
A round bar shaped as 1 was obtained. The white opaque round bar having a small diameter was bent at an angle of θm = 28 ° with the center as a boundary. The thickness of the round bar was deformed to be thick (to a thickness corresponding to the degree of deformation) not in the radial direction but in the length direction in the molded poly-L-lactic acid transparent body.

(2) Similar to (1), as shown in FIG. 12, three small holes are opened from the lower end in a transparent poly-L-lactic acid billet,
The same round bar as the white opaque poly L lactic acid round bar used in (1) was inserted. Then, compression orientation molding was performed at a deformation degree of 2.8. As a result, a molded product as shown in FIG. 13 was obtained. Θ _m = 2 for the round bars of A and C inserted near the outer circumference of the same diameter as the small round bar of B inserted in the center of the billet
At an angle of 8 °, B reached the bottom, but A
And C were in the state of FIG. 13 which floated from the bottom.

Θm of (1) and (2) is the inclination angle (45 ° in this case) of the taper portion of the molding die and the degree of deformation (in this case, 2.
Although it is affected by 8), the theoretical formula tan θm = tan θ /
[A (A ^0.5 -1)] (where θ = 45 °, A = 2.
It was 28 ° which is a value close to θm≈30 ° obtained from 8). As is clear from the experiments of (1) and (2), the compact obtained by compression orientation molding with the mold as shown in Fig. 1 is the material near the center among the materials on the same diameter of the billet. It advances in the molding cavity earlier, and is pushed into the molding cavity later as it approaches the outer periphery.

Therefore, although the angle formed by the material of the central portion and the outer peripheral portion depends on the angle of the tapered surface portion, the fact that an angle close to the theoretical angle of θm is formed corresponding to the degree of deformation is supported. . From a different point of view, materials on the same diameter form a "mortar-shaped" orientation plane like an ant hell with an angle of θm where the orientation axes are radially continuous. It has a form of orientation in which the surfaces can be said to be continuous in the major axis direction. Such a form is distinctly different from the simple uniaxially oriented form obtained by stretching in the long axis direction. The applied form is obtained in FIG. 9, and it is easily understood that a more complicated form of orientation is obtained in the case of forging forming in FIG.

[0084]

As is clear from the above description, according to the manufacturing method of the present invention, the crystals are oriented essentially parallel to a plurality of reference axes, and the anisotropy is small and the strength is high. A bone cement composed of oriented moldings, which has an adequate hydrolyzability and maintains sufficient strength for the time required for bone fusion, and is decomposed and absorbed at a rate that does not cause an inflammatory reaction after the fracture is healed. The excellent bone-bonding material that does not require re-operation is easily produced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a state before compression-filling a billet into a cavity of a mold in compression orientation molding.

FIG. 2 is a cross-sectional view showing a state after press-filling a billet into a cavity of a mold in compression orientation molding.

FIG. 3 is a front view showing an example of an osteosynthesis screw finally obtained by cutting.

FIG. 4 is a cross-sectional view showing a state before press-filling a billet into a cavity of a mold in forging orientation molding.

FIG. 5 is a schematic view showing a crystal orientation state of a columnar bone cement. FIG. 5A shows the orientation state of the vertical section.
(B) shows the orientation state of the plane.

FIG. 6 is a schematic view showing a crystal orientation state of a plate-shaped bone cement. FIG. 6A shows the orientation state of the vertical cross section.
(B) shows the orientation state of the plane.

FIG. 7 is a schematic cross-sectional view explaining a mechanism of crystal orientation in compression orientation molding.

FIG. 8 is a schematic cross-sectional view illustrating a state before the press-filling of the billet into the cavity of the molding die in the compression orientation molding using the molding die in which both the inclination angles of the reduced diameter portion are different.

FIG. 9 is a schematic diagram showing a crystal orientation state of a plate-shaped bone cement. FIG. 2A shows the orientation state of the vertical section.
(B) indicates a plane orientation state.

10 (a) is a side view of the billet used in the proof experiment (1), and FIG. 10 (b) is a plan view thereof.

FIG. 11 is a side view of a round bar after compression orientation molding in proof experiment (1).

FIG. 12 (a) is a side view of the billet used in the proof experiment (2), and FIG. 12 (b) is a plan view thereof.

FIG. 13 is a side view of the molded body after the compression orientation molding in the proof experiment (2).

[Explanation of Codes] 1 Billet 2 Mold 2a Housing cylinder 2b Pressurizing means 2c, 2d Cavity 10 Compression orientation molded body 10a Blank material part 11 Bone bonding material 20a Reduced diameter θ Tilt angle S Bone bonding screw r ₁ Storage cylinder Radius of the part r ₂ radius of the cavity

Claims (9)

[Claims] 1. A biodegradable and absorbable crystalline thermoplastic polymer material is melt-molded to prepare a preform, and the preform is essentially placed in a narrow space of a mold whose lower end is closed. A method for producing an osteosynthesis material, which comprises producing an oriented molded body by cold pressing and plastically deforming and orienting. 2. The osteosynthesis material according to claim 1, wherein the oriented shaped body is crystallized, and the crystal has a crystal morphology that is oriented essentially parallel to a plurality of reference axes. Manufacturing method. 3. The press orientation press-fits the preform according to claim 1 into a mold having a substantially closed lower end having a cross-sectional area smaller than the cross-sectional area of the green compact while plastically deforming it. The method for producing an osteosynthesis material according to claim 1 or 2, which comprises filling and compressing and orienting. 4. A narrow space of a mold in which the pressure orientation is such that the preform according to claim 1 has a small volume either partially or wholly in the cross-sectional area, thickness or width of the preform. The bone according to claim 1 or 2, characterized in that it is formed by forging, filling and orienting the mold with the space of the mold smaller than the volume of the preform while cold plastically deforming it. Manufacturing method of bonding material. 5. The polymer material has an initial viscosity average molecular weight of 200,000 to 600,000, and a subsequent melt-molded preform has a viscosity average molecular weight of 100,000 to 400,000. The method for manufacturing the bone cement according to any one of claims 1 to 4. 6. The area of the cross section of the preform is 2/3 to 1 of the area.
The preform is press-fitted and filled into a cavity of a mold having a cross-sectional area of / 6.
The method for producing a bone cement according to any one of 1. 7. A molding die is composed of a housing cylinder portion having a large cross-sectional area for accommodating a preformed body, a cavity having a smaller cross-sectional area to be compressed and filled, and a reduced diameter portion having a tapered surface connecting these. The method for producing an osteosynthesis material according to any one of claims 1 to 6, characterized in that. 8. The plastic deformation temperature of the preform is a crystallizable temperature between the glass transition temperature and the melting temperature of the thermoplastic polymer material.
7. The method for producing a bone cement according to any one of 7. 9. The method for producing a bone bonding material according to claim 1, wherein the oriented molded body is cut into a desired shape of the bone bonding material.