JP2005319289A - Catheter balloon - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flexible catheter balloon with a good adhesiveness which is excellent in dimensional stability and has a high disruptive strength in the catheter balloon. <P>SOLUTION: The catheter balloon which is flexible and dimensionally stable and has the high disruptive strength is provided by forming the biaxially stretched catheter balloon using a polyamide base elastomer tube which is a thermoplastic resin, and by setting a calculated elasticity of the balloon at the pressure during expansion to 1,300 MPa or more. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a catheter balloon, and more particularly to a catheter balloon suitably used for blood vessel dilation.

  When a stenosis or occlusion occurs in a blood vessel such as a blood vessel, an angioplasty (PTA: Percutaneous Transluminal Angioplasty) is performed to improve the blood flow to the blood vessel peripheral side by expanding the stenosis or occlusion site of the vessel. , PTCA: Percutaneous Transiental Coronary Angioplasty, etc.) have many examples in many medical institutions, and it has become common for surgery in this type of case.

  Balloon catheters are used in a set of guide catheter and guide wire, mainly to dilate the stenotic site of the coronary artery. Angioplasty using this balloon catheter, after first inserting the guide catheter from the puncture site of the femoral artery, brachial artery, radial artery, etc., after positioning the tip of the guide catheter at the entrance of the coronary artery through the aorta, The guide wire that penetrates the balloon catheter is advanced beyond the stenosis site of the coronary artery, and then the balloon catheter is advanced along the guide wire, and the balloon catheter balloon is inflated with the balloon positioned at the stenosis site, and the stenosis site The procedure is expanded, and the balloon is deflated and removed outward. However, balloon catheters are not limited to treating arterial stenosis and are useful for many medical applications including insertion into blood vessels as well as insertion into various body cavities.

  The balloon is usually manufactured by biaxially stretching blow molding a single lumen tube. A single lumen tube for a balloon is usually manufactured by extruding a thermoplastic resin.

  This single lumen tube for balloon is required to be thin and have high accuracy in outer diameter and thickness. If the accuracy of the outer diameter and the thickness is low, the characteristics of the balloon made from the tube are lowered and the variation becomes large, and the reliability of the product is impaired. Moreover, the single lumen tube for balloons is required to have high tensile elongation at break. If the tensile elongation at break is small, the tube tends to be ruptured when it is biaxially stretched to form a balloon, and the balloon is easily damaged even if it does not rupture. The ratio of non-defective products to the total number decreases.

  Examples of the material for the balloon portion include PVC (polyvinyl chloride), PET (polyethylene terephthalate), POC (polyolefin copolymer), nylon, polyurethane, and the like. The selection criteria for the balloon material greatly depend not only on the properties of the material but also on the processing technology.

  In recent years, many technologists expect the appearance of so-called semi-compliant balloons with a compliance characteristic located between compliant balloons and non-compliant balloons. Nylon is the material used to meet this demand. Among these nylons, nylon 12 which has little influence on moisture absorption is used as a semi-compliant balloon or a balloon material for stent delivery. However, due to the hardness of nylon, the problem as a catheter has become obvious, and a polyamide elastomer material having more hydrophobicity and flexibility has appeared in a corresponding form.

  This polyamide elastomer is rich in flexibility and is a material that can improve the performance (trackability) of passing through a complicated path in a blood vessel. Furthermore, in the catheter procedure, after expanding the balloon and expanding the stenosis site, the balloon is once deflated in order to treat the affected area or another stenosis site. A catheter balloon having excellent rewrap performance can be provided.

  However, when expanding a so-called calcified lesion or chronic total occlusion lesion (CTO) that is highly constricted in a blood vessel close to the heart, flexibility is required to reach the lesion, and the lesion is once passed and expanded. The polyamide elastomer, which is a flexible material, must be thin and have high pressure resistance. Due to its softness, the polyamide elastomer has excellent dimensional stability, which is the opposite of flexibility, and high breaking strength. It was difficult to mold a balloon that had both.

  In addition, it has been necessary to use a plurality of catheters in a single procedure so far, but there has been a restriction on catheter procedures that can be used at a time since the revision of medical insurance. As a result, there has been a demand for a method for optimal treatment with few procedures, and the need for a balloon catheter having flexibility, excellent dimensional stability and high breaking strength has increased.

  Therefore, when a balloon catheter having the above-mentioned characteristics is realized, it can cope with calcified lesions or chronic total occlusion lesions (CTO) that require high expansion force, and can further reduce the time required for the procedure. Thus, it is possible to provide a catheter balloon that can reduce the burden on the operator and the patient.

  In order to meet these requirements, the development of a balloon with a thin balloon membrane and high breaking strength was considered, but in reality, thinning the balloon membrane deteriorates the dimensional stability and fracture strength, and there is a risk of bursting during use. was there.

  As a result of intensive studies to solve these problems, it has been found that a balloon having the above-mentioned characteristics can be provided by developing a balloon having a high elastic modulus, and the present invention has been achieved.

  In the prior art, a number of methods relating to high strength and high flexibility have been disclosed. For example, Patent Document 1 discloses a balloon made of PET (polyethylene terephthalate). Although this balloon is thin, it has high strength and excellent dimensional stability. However, the inherent hardness of PET cannot be wiped off, and it lacks flexibility, and when the balloon is folded, it produces a constriction that is small and difficult to fold. In addition, pinhole destruction occurs as a demerit, and pinhole destruction is particularly high when high pressure is locally applied to the blood vessel wall when the balloon breaks in the blood vessel, causing damage to the blood vessel wall. Therefore, it is not preferable.

  Patent Document 2 discloses a balloon formed using an aromatic polyamide or a polyamide-based alloy containing aromatic polyamide as a constituent component. In Patent Document 3, although a balloon having high strength and high flexibility is provided, this balloon is composed of a polyesteramide block copolymer in which the hard segment is made of polyamide and the soft segment is made of aliphatic polyester. is there. Since these are not so-called high pressure resistant balloons, they do not have sufficient breaking strength and are unsuitable for insertion into sites where stenosis is severe due to calcified lesions.

On the other hand, Patent Document 4 describes a balloon made of a polyamide-based elastomer, and the molded balloon is flexible and satisfies the requirement for trackability. However, the bursting pressure is about 1.83 MPa (18 atm) and lacks the fracture strength, so that it is unsuitable for insertion into a site where stenosis is severe due to a calcified lesion or the like.
JP-A-3-37949 Japanese Patent Laid-Open No. 5-95996 JP 2001-87375 A Japanese Patent No. 3494654

  An object of the present invention is to provide a catheter balloon that can reach a stenosis site without damaging the inner wall of a blood vessel, and has excellent dimensional stability and high breaking strength.

  As a result of intensive studies to improve the above problems, the balloon catheter according to the present invention is a balloon molded from a polyamide-based elastomer that is a thermoplastic resin, and has a calculated elastic modulus at the pressure when the balloon is expanded. It is characterized by being at 1300 MPa or more.

  Further, the catheter balloon according to the present invention is manufactured by biaxial stretch blow molding of the material. In the present invention, the pressure at the time of expansion refers to a pressure from a specified pressure (Nominal Pressure) to a rated burst pressure (Rated Burst Pressure).

  Furthermore, the polyamide elastomer according to the present invention is a polyamide whose hard segment is selected from the group consisting of nylon 6, nylon 6-6, nylon 6-10, nylon 6-12, nylon 11 and nylon 12, etc. Is a glycol selected from the group consisting of polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and the like, and is composed of a block copolymer of a hard segment and a soft segment.

  Furthermore, the weight percentage of the hard segment in the block copolymer according to the present invention is 90% to 99%, and the weight percentage of the soft segment is 1% to 10%.

  The catheter balloon according to the present invention is characterized in that the average burst pressure is 2.53 MPa (25 atm) or more.

  As described above, according to the present invention, it is possible to reach a stenosis site without damaging the inner wall of a blood vessel, excellent in dimensional stability and fracture strength, and highly calcified lesion or chronic complete occlusion lesion ( It is possible to provide a catheter balloon that can expand the blood vessel of CTO with high pressure and can reduce the burden on the operator and the patient.

  The polyamide elastomer, which is a tube material used in the present invention, will be described below, but the present invention is not limited thereby. As the polyamide elastomer used in the present invention, a block copolymer composed of a hard segment and a soft segment is used, and preferably a block copolymer using a hard segment composed of polyamide and a soft segment composed of polyether is used. It is done.

  Furthermore, nylon 6, nylon 6-6, nylon 6-10, nylon 6-12, nylon 11 and nylon 12 can be used as the polyamide constituting this hard segment, but nylon 12 having a particularly low hygroscopic effect is used. preferable. Furthermore, polyethylene glycol, polypropylene glycol and the like can be used as the polyether constituting the soft segment, and polytetramethylene glycol is particularly preferable.

  On the other hand, the polyamide elastomer has any hardness depending on the flexibility required of the balloon, but preferably has a Shore D hardness of 25 to 75, more preferably a Shore D hardness of 50 to 72. Is used.

The calculated elastic modulus in the present invention is calculated by the following formula 1.

_{P = (4 × T 0 ×} D 0 × (D-D 0) × E) / (D × D × (D + D 0)) ··· Equation 1
here,
E: Calculated elastic modulus (MPa)
P: Balloon pressure (MPa)
D: Outer diameter at the time of balloon pressurization (mm)
D ₀ : Initial balloon outer diameter (mm)
T ₀ : initial balloon thickness (mm)
It is. The outer diameter and the film thickness are values at the center of the balloon straight section.

Equation 1 is derived based on the following concept. First, the balloon should behave elastically. Second, it is assumed that the balloon is an isotropic material and the elastic modulus is constant. Third, the balloon is treated as a thin cylinder for the straight tube. Fourth, the effect of the balloon taper is not considered. Based on the above concept, a circumferential strength formula, an axial strength formula, and a constant balloon material volume formula are derived, and the pressure P applied to the balloon is the straight film thickness T ₀ , When the outer diameter D ₀ , the calculated elastic modulus E, and the outer diameter D at the time of balloon pressurization are replaced with each other, Equation 1 is obtained.

  A specific method for deriving the calculated elastic modulus is shown below.

Circumferential strength formula ((π × D−π × D ₀ ) / (π × D ₀ )) × E = P × D / (2 × T)
((D−D ₀ ) / D ₀ ) × E = P × D / (2 × T) (1)
Axial strength formula ((L−L ₀ ) / L ₀ ) × E = P × D / (4 × T) (2)
Here, L ₀ is the initial axial length (mm), L is the balloon axial length (mm) at the pressure P applied in the balloon, and T is the balloon membrane at the pressure P applied in the balloon. It is thick.

Also, since the balloon material volume is constant,
π × D × L × T = π × D ₀ × L ₀ × T ₀
(D / D ₀ ) × (L / L ₀ ) × (T / T ₀ ) = 1 (3)

From (1) and (2), L / L ₀ = ((D / D ₀ ) +1) × (1/2) (4)

From (3) and (4), (D / D ₀ ) × (1/2) × ((D / D ₀ ) +1) × (T / T ₀ ) = 1
T = (2 × T ₀ ) × (D ₀ / D) × (D ₀ / (D + D ₀ )) (5)
From (1) and (5), ((D−D ₀ ) / D ₀ ) × E
= P × D / ((4 × T ₀ ) × (D ₀ / D) × (D ₀ / (D + D ₀ )))
Therefore, the following formula 1 is obtained.
_{P = (4 × T 0 ×} D 0 × (D-D 0) × E) / (D × D × (D + D 0)) ··· Equation 1
The catheter balloon of the present invention can be obtained by suitably setting the annealing temperature, the hoop ratio, and the axial stretch ratio.

  Annealing is a process for achieving dimensional stability of a balloon molded in a mold in balloon molding. By setting the annealing temperature to a temperature at least above the glass transition temperature and below the recrystallization temperature, a balloon with better dimensional stability can be formed.

  The hoop ratio is the ratio between the inner diameter of the balloon molding parison (in the present invention, polyamide elastomer, Shore D hardness 72) and the inner diameter of the balloon molding die. A larger hoop ratio is preferable.

  Next, the axial stretching ratio will be described. In the balloon forming step, the balloon forming parison is previously stretched in the axial direction and reduced in diameter. At this time, the portion not reduced in diameter is inserted into a mold, and a balloon is formed by heating, pressurizing, stretching and cooling. The ratio between the length of the parison of the portion not reduced in diameter and the length of the formed balloon is referred to as the axial stretch ratio. A higher axial stretching ratio is preferred.

  Calculation of the calculated elastic modulus can be performed as follows.

First, the straight part central film thickness T ₀ immediately after the balloon molding is actually measured. Next, the balloon compliance behavior at the time of balloon pressurization, that is, the change of the balloon outer diameter when fluid pressurization is performed on the balloon is measured and plotted. The calculated elastic modulus E and the balloon are calculated by the least square method so that the equation 1 can be approximated to a plot point group of the outer diameter of the balloon in the pressure range from 1.22 MPa (12 atm) to 2.23 MPa (22 atm). An initial outer diameter D ₀ is obtained.

  The present invention uses a flexible polyamide elastomer as the balloon material, makes it easy to reach the stenosis by thinning the balloon, and stabilizes the dimensions by making the calculated elastic modulus of the balloon 1300 MPa or more. Provided is a catheter balloon having excellent properties and high breaking strength. The catheter balloon molded according to the present invention can be used for all body cavities and blood vessels of the human body, and more preferably for coronary arteries, limb blood vessels, kidneys, liver blood vessels, and the like.

EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example and a comparative example, these do not restrict | limit this invention at all.
Example 1
A balloon-forming tube was manufactured by extrusion molding using a polyamide elastomer, Pebax 7233 (manufactured by Elf Atochem), which is a thermoplastic elastomer, and biaxial stretch blow molding was performed using this tube. In biaxial stretch blow molding, a balloon-forming tube manufactured by extrusion molding is placed in a mold, the inside of the tube is heated in a pressurized state, and expanded when stretched in the axial direction to form a balloon. Thereafter, a balloon with good dimensional stability is formed through annealing and cooling processes. The heating temperature of the mold was 90 ° C., nitrogen was applied to pressurize the tube, and a pressure of about 5.0 MPa was applied. A 3.00 mm vasodilator catheter balloon was molded at a temperature of 100 ° C.
(Example 2)
A balloon forming tube made of the same material as in Example 1 was used, the heating temperature of the mold was 90 ° C., and nitrogen was used to pressurize the tube, and a pressure of about 5.0 MPa was applied. A 3.00 mm vasodilator catheter balloon was molded at a stretch rate of about 230 percent, a hoop ratio of 7.14, and an annealing temperature of 120 ° C.
(Comparative Example 1)
A balloon forming tube made of the same material as in Example 1 was used, the heating temperature of the mold was 90 ° C., and nitrogen was used to pressurize the tube, and a pressure of about 5.0 MPa was applied. A 3.00 mm vasodilator catheter balloon was molded at a stretch ratio of about 230 percent, a hoop ratio of 7.14, and an annealing temperature of 140 ° C.
(Comparative Example 2)
A balloon forming tube made of the same material as in Example 1 was used, the heating temperature of the mold was 90 ° C., and nitrogen was used to pressurize the tube, and a pressure of about 5.0 MPa was applied. A 3.00 mm vasodilator catheter balloon was molded at a stretch ratio of about 200 percent, a hoop ratio of 5.88, and an annealing temperature of 100 ° C.
(Comparative Example 3)
A balloon forming tube made of the same material as in Example 1 was used, the heating temperature of the mold was 90 ° C., and nitrogen was used to pressurize the tube, and a pressure of about 5.0 MPa was applied. A 3.00 mm vasodilator catheter balloon was molded at a stretch ratio of about 200 percent, a hoop ratio of 5.88, and an annealing temperature of 120 ° C.
(Comparative Example 4)
A balloon forming tube made of the same material as in Example 1 was used, the heating temperature of the mold was 90 ° C., and nitrogen was used to pressurize the tube, and a pressure of about 5.0 MPa was applied. A 3.00 mm vasodilator catheter balloon was molded at a stretch ratio of about 200 percent, a hoop ratio of 5.88, and an annealing temperature of 140 ° C.

  The balloons molded in Examples 1-2 and Comparative Examples 1-4 were gradually pressurized in 37 ° C. physiological saline using a leak tester, and the outer diameter of the balloon was measured. The balloon was pressurized until bursting, and the average burst pressure was measured. The number of samples was N = 3. Table 1 shows the measurement results of pressure (atm) and outer diameter (mm).

この外径の変化量を記録することで、バルーン内加圧１．２２ＭＰａ（１２ａｔｍ）から２．２３ＭＰａ（２２ａｔｍ）までの外径変化率を求めた。さらにマイクロメータを用い直管部中央膜厚を測定し、バルーン内加圧１．２２ＭＰａ（１２ａｔｍ）から２．２３ＭＰａ（２２ａｔｍ）までの範囲におけるバルーン加圧時外径のプロット点群が上記式１と近似できるように最小二乗法に基づいてフィッティングを行い、計算弾性率を算出した。算出には、Sma4Winという計算ソフトを使用した。表２に計算弾性率及び外径変化率を示す。

By recording the amount of change in the outer diameter, the rate of change in the outer diameter from 1.22 MPa (12 atm) to 2.23 MPa (22 atm) was determined. Further, the thickness of the central part of the straight pipe portion is measured using a micrometer, and the plotted point group of the outer diameter at the time of balloon pressurization in the range from 1.22 MPa (12 atm) to 2.23 MPa (22 atm) is shown in the above formula 1. Fitting was performed based on the least square method so as to approximate, and the calculated elastic modulus was calculated. For the calculation, a calculation software called Sma4Win was used. Table 2 shows the calculated elastic modulus and the outer diameter change rate.

外径変化率とは、バルーン内加圧１．２２ＭＰａ（１２ａｔｍ）から２．２３ＭＰａ（２２ａｔｍ）までの、バルーン外径の変化率のことをいう。所謂石灰化病変或いは慢性完全閉塞病変（ＣＴＯ）に適したカテーテルはこの変化率が小さい値ほど良い。

The outer diameter change rate refers to the change rate of the balloon outer diameter from the pressure in the balloon of 1.22 MPa (12 atm) to 2.23 MPa (22 atm). For catheters suitable for so-called calcified lesions or chronic total occlusion lesions (CTO), the smaller the rate of change, the better.

  As shown in Table 2, in the balloons obtained in Examples 1 and 2 of the present invention, the calculated elastic modulus in the range from 1.22 MPa (12 atm) to 2.23 MPa (22 atm) is 1300 MPa. The average burst pressure was sufficiently high at 2.53 MPa (25 atm) or more, and it was confirmed that the balloon had flexibility, excellent dimensional stability, and high fracture strength.

Claims (5)

  A catheter balloon characterized in that it is a balloon molded from a polyamide-based elastomer that is a thermoplastic resin and has a calculated elastic modulus at a pressure during expansion of 1300 MPa or more.   The catheter balloon according to claim 1, wherein the catheter balloon is manufactured by biaxial stretch blow molding.   The polyamide elastomer is a polyamide whose hard segment is selected from the group consisting of nylon 6, nylon 6-6, nylon 6-10, nylon 6-12, nylon 11 and nylon 12, and the soft segment is polyethylene glycol, polypropylene. The catheter balloon according to claim 1, which is a glycol selected from the group consisting of glycol, polytetramethylene glycol and the like, and is a block copolymer of a hard segment and a soft segment.   The catheter balloon according to claim 3, wherein a weight percentage of the hard segment in the block copolymer is 90% to 99%, and a weight percentage of the soft segment is 1% to 10%. The catheter balloon according to claim 1, wherein the average burst pressure is 2.53 MPa (25 atm) or more.