JPH0295377A - Medical resin composition and method for producing medical molded articles - Google Patents

Abstract

PURPOSE:To produce the molding for treatment with high accuracy and grade by incorporating an org. solvent which does not dissolve a base polymer, can be mixed with a plasticizer and evaporates by depriving of sufficient latent heat without foaming at the time of curing by heating into the resin compsn. CONSTITUTION:The hard 1st molding part is formed at the temp. lower than the processing temp. at the time of curing by molding (molding) of the soft 2nd molding part by using the resin compsn. for treatment (particularly, PVC plastisol) contg. the base polymer (more particularly, polyvinyl chloride), the plasticizer (for example, di-2-ethylhexyl phthalate) and the org. solvent (for example, synthetic isoparaffinic hydrocarbon) which has substantially no dissolving power to the base polymer and can be mixed with the plasticizer at the time of producing cannula. The soft 2nd molding part is formed by a heating and curing treatment after the hard 1st molding part is brought into contact with the resin compsn. for treatment (more particularly, PVC plastisol) which does not contain the plasticizer. This org. solvent can evaporate by sufficiently depriving of the latent heat of evaporation without foaming at the time of curing by heating.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to medical resin compositions (especially polyvinyl chloride (P
VC') plastisol), and medical molded articles (e.g.
This invention relates to a method for producing canyule.

BACKGROUND OF THE INVENTION In recent years, progress has been made in the development of artificial hearts for supplementary and temporary replacement of the functions of the heart outside the body during targeted surgeries and other surgeries. For example, as shown in Figure 4,
A stick-type blood pump device 11 is connected between the right atrium and the pulmonary artery of the living body's heart 10, and between the left atrium and the aorta.

In such a blood device 111C, the blood introduction tube 3 and the blood discharge tube 4 are formed upward and substantially parallel. Each cannile 12 and each blood conduit 3 and 4 connected to the heart of the living body by anastomosis are connected from both ends of each connector 13 to the ring-shaped flange 14 provided at the center thereof. are inserted respectively.

By the way, since the tubular tip of the cannula 12 is connected to the living body by anastomosis as described above, it is desirable that this tip is hard so that the anastomosis can be easily performed. In particular, it is desirable for the tip portion to have a small outer diameter so as to minimize the damage inevitably caused to the living body, and a large inner diameter to ensure sufficient blood flow. Therefore, since it is desired to be small and thin, the tip portion is preferably hard.

On the other hand, the living body and the blood pump device are connected via a cannula, but in order to facilitate this connection work and the performance of surgery, the tubular body of the cannula other than the above-mentioned tip should be flexible. desired.

However, for antithrombotic purposes, the entire cannula is integrally molded, so the tip and tubular body are made of exactly the same material and there is no difference in physical or mechanical properties between them. Therefore, no cannula that satisfies the above-mentioned requirements has been known so far, and neither the tip nor the tubular body satisfy the required hardness and flexibility at the same time, making it difficult to handle while using the cannula. is the current situation.

On the other hand, there is a conventional method in which the tip of a cannula made of soft polyvinyl chloride is immersed in a poor solvent for vinyl chloride (such as alcohol) to extract the plasticizer and harden the cannula. However, in this case, there are problems such as reduction in dimensional accuracy and occurrence of devitrification phenomena due to shrinkage and deformation accompanying extraction.

In addition to the cannula, the above-mentioned problems also occur in drain tubes and the like used for draining bleeding blood and body fluids.

C. Object of the Invention The object of the present invention is to provide a resin composition for molding, which is suitable for selectively imparting desired physical or mechanical properties to medical molded articles such as the above-mentioned cannula; Another object of the present invention is to provide a method for manufacturing medical molded articles with high precision and high quality using this resin composition.

2. Structure of the invention That is, the present invention provides a medical resin composition (particularly PvC plastisol) containing a base polymer (particularly polyvinyl chloride) and a plasticizer (such as di-2-ethylhexyl phthalate). Contains an organic solvent (for example, a synthetic isoparaffinic hydrocarbon) that has substantially no dissolving power for the base polymer and is miscible with the plasticizer, and this organic solvent does not cause foaming during heat curing. This invention relates to a medical resin composition characterized in that it can evaporate by sufficiently removing latent heat of vaporization.

The present invention also provides a medical molded product (for example, a cannula) in which a first molded part (for example, a hard tubular tip part) and a second molded part (for example, a soft tubular body) are integrally connected to each other. ), (a) a base polymer (especially polyvinyl chloride), a plasticizer (e.g., di-2-ethylhexyl phthalate), and a base polymer having substantially no dissolving power for the base polymer and the above-mentioned The plasticizer contains a miscible organic solvent (for example, a synthetic isoparaffinic hydrocarbon) (however, this organic solvent can sufficiently remove the latent heat of vaporization and evaporate without causing foaming during heat curing). Forming the first molded part using the medical resin composition (particularly PVC plastisol) at a temperature lower than the processing temperature during heat curing (molding) of the second molded part (i.e., with underchire air). (b) After bringing the first molded part into contact with the medical resin composition that does not contain an organic solvent (in particular, PVC plastisol), the second molded part is heated and cured (i.e., the present invention). The present invention also provides a method for manufacturing a medical molded article, which comprises a step of forming a molded part.

E, Example The present invention will be explained in detail below.

1 to 3 show an example in which the present invention is applied to a cannula.

First, the PvC plastisol used when molding the hard tip of the cannula of this example separately from the tubular body will be described.

This PVC glastisol is made by dispersing polyvinyl chloride as a pace polymer (for example, a particulate polymer with an average particle size of 1 μm) in a plasticizer. It is distinctive in that it contains an organic solvent.

In other words, this organic solvent has substantially no dissolving power for the pace polymer, is miscible with the plasticizer, and can sufficiently absorb the latent heat of vaporization to evaporate (or vaporize) without causing foaming during molding. It is non-toxic and can be dispersed. However, this organic solvent is
The boiling point range is selected so that there is virtually no evaporation during under-chire (particularly above 80° C.) during molding of the hard tip.

These organic solvents preferably have a low molecular weight, such as linear paraffin series, branched paraffin series, cyclic 7-tene series, etc.
Selected from terpenes, aromatic hydrocarbons, alcohols, glycol ethers, etc. Among these, especially
Synthetic imparaffins with boiling points of 60-210'C are preferred and are approved by the FDA (Food and Drug A).
It is an approved product and has very low toxicity. However, the boiling point of the organic solvent can be selected from various types depending on the purpose.

The amount of this organic solvent to be blended varies depending on the molding temperature, the wall thickness of the molded article, etc., but it is preferably 2 to 15 parts by weight, particularly 3 to 10 parts by weight, based on 100 parts by weight of the resin. If the amount is too small, the mixing effect described below will be poor, and if it is too large, the viscosity of the plastisol will drop significantly, making it difficult to increase the thickness of the molded product during processing. The amount of latent heat of vaporization removed during molding changes depending on the blending amount.

The cannula of this example is PvC as shown in Figures 1B and 1F.
Since the molding is performed by dipping plastisol, appropriate viscosity control of the PvC plastisol is required to obtain the desired wall thickness. All of the above-mentioned organic solvents have significantly lower viscosity than plasticizers, so if they are substituted in the same amount as the plasticizer in plastisol, the viscosity will decrease significantly, making processing difficult to obtain the desired wall thickness. However, the addition of organic solvents makes it possible to reduce the amount of plasticizer as a result.

Therefore, to adjust the viscosity of PVC plastisol,
In the raw material PvC plastisol for the hard tip of the cannula (corresponding to the first molded part) described above, the amount of plasticizer blended can be lower than the usual amount, and the resin 100
60 to 30 parts by weight (preferably 50 to 40 parts by weight)
parts by weight). That is, by reducing the amount of plasticizer, the desired hard tip can be formed without changing the normal processing conditions.

However, if the amount of plasticizer is too small, moldability will drop significantly.

Since the above-mentioned organic solvent is added to this PVC plastisol, a predetermined amount of this organic solvent remains in the molded part during the molding of the tip part or under the under-cure condition, but during the next main cure (tubular Body molding) Sometimes PVC
It scatters and evaporates from the sol composition. At this time, since the organic solvent sufficiently removes the latent heat of vaporization, the temperature rise at the tip is suppressed (heating is temporarily delayed), and thermal decomposition due to reheating can be avoided. In other words, even when heat is applied for the second time, processing (heat hardening) similar to that of the raw material plastisol for the tubular body proceeds without thermal decomposition, producing high-quality molded products with the same physical properties for both the tip and the main body with high precision ( (No need to extract plasticizer, etc.)

In addition, in the raw material plastisol composition of the tip part mentioned above,
As a heat stabilizer, for example, a Ca-based or Zn-based organic composite or a metal salt (such as zinc stearate) is added. In order to further improve the thermal stability of the sol and make it resistant to strong heating conditions, it is better to use Sn-based or Cd-based heat stabilizers, but since it is for medical use, toxicity must be taken into account. Good. In the molding process of PvC, the thermal decomposition temperature of the resin and the processing temperature are often close to each other, so the selection and addition of a strong thermal stabilizer as described above is important from this point of view as well. Thus, using the latent heat of the solvent to retard thermal decomposition by reheating is an effective thermal aid.

Next, a method of molding a medical molded article, such as a cannula, using the above-mentioned PVC plastisol will be described with reference to FIG.

First, as shown in FIG. 1A, a mold 20 for molding the hard tip of the cannula is prepared, and a ring 21 made of plastic or metal is fitted and fixed near the tip.

Next, as shown in Fig. 1B, the gold is heated at a specified temperature (usually 1
40 to 200[deg.] C.), and its lower end is dipped into the above-mentioned organic solvent-containing PvC plastisol composition 23 in the container 24.

First, as shown in FIG. 1C, a thin layer 22 of polyvinyl chloride gelled by the heat of the mold 20 is formed on the surface of the mold 20, and then pulled out from the plastisol composition 23 and left to stand for a predetermined time. Furthermore, remove (shake off) excess plastisol that has adhered to it.

By repeating these heating and dipping operations,
As shown in the figure, a polyvinyl chloride coating film 32 is formed to a predetermined thickness.

Next, the coating film 32 is heated and cured, and then cooled to form the trap coating film 3 as shown in FIG. 1D.
2 is removed from the mold 20. However, the above-mentioned curing is not performed sufficiently, and the material is heated to 130 to 150° C. for about 10 minutes to bring it into an incompletely cured state. That is, preliminary processing (under-chire) is performed at a temperature lower than the temperature of the next main-chire (see Fig. 1G), and mechanical properties are imparted that will not cause any trouble in handling during the main-chire. In this case, the underchire is performed for a short time at a temperature around or slightly below the boiling point of the organic solvent in the plastisol composition 23 to form the desired hard tip 32.

This is because if the organic solvent were to be completely cured at this point, the organic solvent would evaporate and would be decomposed by reheating the mold used at that time in the process of forming the tubular body later.

After releasing the above-mentioned undercarriage air trap and the mold 20, the tip of the cannula is cut, as shown in Figure 1D, and the inner wall of the atrium, etc. A side hole 16 is formed to prevent the flow rate from decreasing due to suction. However, this side hole 16 can also be formed at the final stage of manufacturing.

The composition of the above plastisol composition 23 is, for example, as follows.

Polyvinyl chloride (PVC) plastisol (pace polymer): 100 parts by weight Di-2-ethylhexyl phthalate (warming agent): 40 parts by weight Synthetic isoparaffin hydrocarbon (organic solvent): 5 parts by weight Calcium-zinc heat stabilizer : 3 parts by weight, then 1E
As shown in the figure, a cylindrical mold 36 is fitted into the tip 32 and fixed. The mold 36 has a portion 36 made of highly magnetic material.
a and a part 36b made of a low magnetic material, and the tip 32 is fitted into the part 36b made of a low magnetic material so as to be adjacent to the part 36a made of a high magnetic material. The mold portion 36b made of a low magnetic material may be made of ceramics instead of metal.

Next, as shown in FIG. 1F, the mold 36 is immersed in polyvinyl chloride plastisol 37 housed in a container 38, with the portion 36a made of highly magnetic material facing down. At this time, a portion of the lower end side of the tip portion 32 is slightly immersed in the plastisol 37. Next, the highly magnetic material portion 36a of the mold is heated by high frequency induction using a coil 39 disposed outside the container 38. Highly magnetic material part 3 of the mold
6a, the surface layer is rapidly heated by high-frequency induction heating,
The plastisol 37 is gelled in the region in contact with the highly magnetic material portion 36a of the mold, and a gelled layer 34 is formed as shown by the dashed line in the figure. The gelled layer 34 becomes a tubular body through curing which will be described later.

At this time, since the tip portion 32 is in an under-air condition,
The gelled layer 34 is easily fixed to the tip (lower end) K.

The formulation of plastisol 37 used here and the conditions for high frequency induction heating are as follows.

Polyvinyl chloride (PVC) plastisol (base polymer>: IOO parts by weight Di-2-ethylhexyl phthalate (plasticizer) 280 parts Calcium-zinc heat stabilizer: 3 parts by weight
Applied voltage: 200 V Current: 0.3 to 8 A (0.5 A in this example) Frequency: 400 KHz Heating time: 10 to 30 minutes (15 minutes in this example) Next, as shown in Fig. 1G, mold 36 is heated. Pull out from plastisol 37. After cutting the sauce, heat it to 185℃ for 20 minutes.
The gelled layer 34 adhered by heating for a minute is cured to form the molded part 33, and the tip part 32 is cured.
Completely cure. This curing may be accomplished by placing the metal ferromagnetic material in a cylinder made of ferromagnetic material and heating the cylinder by high-frequency induction, or by using a combination of high-frequency induction heating and external heating using hot air. good.

In this main curing, the tip 32 is heated a second time (and at a higher temperature) in addition to the previous under-chire, but at this time, since the tip 32 contains the above-mentioned organic solvent, The heat generated during the main heating evaporates the organic solvent and removes sufficient latent heat, thereby providing the effect of temporarily delaying (slowly slowing down) the heating of the tip 32. Therefore, during main curing, the molded part (i.e., the tubular body)
33 can proceed to the tip 32 without thermal decomposition, resulting in a completely hardened molded part. Therefore, the molded part 32 has the same mechanical and physical properties as the molded part 33. If the tip 32
If the main body molded part 33 is relaxed in order to suppress heat hardening, the hardening of the main body molded part 33 will be insufficient, and conversely, under the conditions of this key air, the tip part 32 will be heated too hard and decompose. The presence of the above-mentioned organic solvent of the invention eliminates this problem, resulting in a satisfactory hardening of both the molded parts 32 and 33.

After the above-mentioned main curing, remove the gold m36 and cut off the excess portion 33a attached to the gold end face to obtain the cannula 31 as shown in cross-sectional view in Fig. 1H and in perspective view in Fig. 2. . The tip portion 32 and the tubular main body 33 are made of the same type of polyvinyl chloride, differing only in hardness and flexibility, and are therefore firmly fixed to each other.

In addition, 1E is used for forming the tip (20 in Figure 1A).
The distal end portion 32 and the tubular body 33 may be sequentially formed in a pre-process and a post-process using a common mold 36 using the low magnetic material portion 36b of the mold 36 shown in the figure. In this case, the most extreme end of the tip and the side hole 16 are provided in the final step.

An annular protrusion 45 is formed at the rear end edge of the distal end portion 32 so as to be covered by the distal end edge of the tubular body 33 . By forming the annular protrusion 45 in addition to the collar 15, the following advantages are brought about.

When connecting the cannula to a living body, as shown in FIG.
Connect 1 with 8i! - (kick) to stop bleeding. At this time, the collar 15 comes into close contact with the atrial wall 50 from the inside, effectively preventing the cannula 31 from being pulled out, while the thread 54 firmly connects the cannula 31 to the atrial wall 50 (anastomoses). .

The annular protrusion 45 formed at the rear of the collar 15 is positioned so as to sandwich the incision 50a of the atrial wall 50 together with the collar 15, and the position of the cannula 31 after being joined by the annular protrusion 45 and the collar 15 is Misalignment is prevented, the cannula is always accurately positioned, and the surgery is performed safely.

Although the present invention has been illustrated above, the above-mentioned example can be further modified based on the technical idea of the present invention.

For example, the composition and blending ratio of the above-mentioned PvC plastisol may be changed in various ways, and the pace polymer may be a copolymer of vinyl chloride and other monomers, a combination of polyvinyl chloride and other polymers, or a polychloride polymer. It may be other than vinyl, and other known plasticizers (for example, dioctyl adipate) may be used as the plasticizer. The organic solvent to be added is
Various materials can be selected from among those having the above-mentioned properties and having a relatively low molecular weight and a low boiling point. In order to firmly fix the tip portion and the tubular body to each other, it is preferable that the materials of both the tip portion and the tubular body are the same.

Furthermore, instead of repeating the heating and dipping of the mold as described above, the cannula tip may be manufactured by casting into a plastisol mold.

Further, the heating during molding of the main body can also be done by any other appropriate method that allows rapid heating.

Although the above-mentioned example is an example in which the present invention is applied to the manufacture of a cannula, the present invention can be similarly applied to the manufacture of catheters and other medical conduits other than cannulae. In addition to tubular bodies, for example, sheet-like bodies are integrated (one is hard and the other is soft), and the surface of a hard molded part is partially covered with a soft molded part (secondary It may also be applied to coated products by processing).

As described above, the present invention contains an organic solvent in the resin composition that does not dissolve the pace polymer, is miscible with the plasticizer, and evaporates by removing sufficient latent heat without foaming during heat curing. Therefore, during the molding process, the latent heat removal effect of the organic solvent suppresses the temperature increase in the molded part (heating is temporarily delayed), and thermal decomposition due to heating can be avoided. This is particularly effective when forming the second molding section in a continuous manner with the first molding section. Even if heat is applied to the first molded part again during curing of the first molded part, the rising temperature of the first molded part is suppressed and the same processing (heat curing) as in the second molded part proceeds without thermal decomposition, and both the image molded part and the image molded part are cured. High-quality molded products with equivalent physical properties can be produced with high precision.Moreover, the first molded part can be easily processed into a hard product due to the inclusion of the above-mentioned organic solvent, and the second molded part can be made soft.

[Brief explanation of the drawing]

1 to 3 show embodiments of the present invention. Figure 1, Figure 1B, Figure 1C, Figure 1D, Figure 1E,
Figures 1F, 1G, and 1H are cross-sectional views of each main part showing the main steps of the cannula manufacturing method, Figure 2 is a perspective view of the cannula, and Figure 3 is the main points when the cannula is bonded to a living body. FIG. FIG. 4 is a schematic diagram showing how the blood pump device is used. In addition, in the symbols shown in the drawings, 15...Brim portion 16...20.36...23.37.・・・ 31 ・・・・・・・・・・・・ 32・・・・・・・・・・・・ 33・・・・・・・・・・・・ 36a・・・・・・・・・・ 39・・・・・・・・・・・・ 45・・・・・・・・・・・・

Claims (1)

[Claims] 1. A medical resin composition containing a pace polymer and a plasticizer, which contains an organic solvent that has substantially no dissolving power for the pace polymer and is miscible with the plasticizer. , and the organic solvent can be evaporated by sufficiently removing the latent heat of evaporation without causing foaming during heating and curing. 2. When manufacturing a medical molded article in which a second molding part is integrated and connected to a first molding part, (a) the dissolving power of the pace polymer, the plasticizer, and the pace polymer is substantially reduced. and an organic solvent that is miscible with the plasticizer (however, this organic solvent can sufficiently remove the latent heat of vaporization and evaporate without causing foaming during heating and curing). (b) forming the first molded part using the composition at a temperature lower than the processing temperature during heat curing of the second molded part; (b) adding the first molded part to the medical resin composition that does not contain the organic solvent; A method for manufacturing a medical molded article, the method comprising: bringing the first molded part into contact with each other, and then forming the second molded part by heat curing treatment.