JP2003003026A - Medical resin composition and molded article for medical use - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a medical resin composition which has flexibility, kink resistance and high frequency processability similar to those of an existing soft polyvinyl chloride-based resin and has no problem of plasticizer elution nor difficulty in waste disposal. SOLUTION: The medical resin composition is composed of 40-92.5 wt.% of an ethylene-α-olefin copolymer of which the α-olefin contains 3-20 carbon atoms, the α-olefin content is 8-50 wt.%, the density is 0.85-0.90 g/cm<3> and the ratio (Mw/Mn) of the weight-average mol.wt. (Mw) and the number-average mol.wt. (Mn) is 1.5-2.5 and 7.5-60 wt.% of an ethylene-vinyl ester copolymer.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a specific ethylene
The present invention relates to a medical resin composition comprising an α-olefin copolymer and an ethylene / vinyl ester copolymer, and a medical molded article such as a medical tube or a catheter comprising the resin composition.

[0002]

2. Description of the Related Art At present, a polyvinyl chloride resin is used as a soft resin material most often used for medical molded articles such as infusion sets. This is because the flexibility of the polyvinyl chloride resin can be easily controlled by the type and addition amount of the plasticizer, it has a transparent feeling, and it is
This is because it has advantages such as excellent secondary processability and relatively low cost.

However, in recent years, in order to deal with environmental problems such as dioxins and endocrine disrupters, there has been a strong demand for a soft resin material that can substitute for a polyvinyl chloride resin.

Further, in an infusion set using an infusion tube made of polyvinyl chloride resin, there is a problem that the plasticizer contained in the polyvinyl chloride resin is eluted into the infusion solution or the like. Therefore, there is a strong demand for an infusion tube (infusion set) that can substitute for polyvinyl chloride resin.

From such a point of view, it has been considered to use a polyolefin resin such as a polyethylene resin or a polypropylene resin for an infusion tube or an infusion bag as an alternative material to the polyvinyl chloride resin ( For example, JP-A-8-131537 and JP-A-2
000-93490).

However, an infusion tube made of polyethylene resin or polypropylene resin cannot be said to be satisfactory in terms of flexibility and kink resistance (folding resistance). Among polyethylene-based resins, low-density polyethylene resin has relatively good flexibility, but even infusion tubes made of low-density polyethylene resin do not have sufficiently satisfactory flexibility and kink resistance. . Further, ordinary polyolefin resins have a problem that secondary processing by high frequency dielectric heating is almost impossible.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has the same flexibility, kink resistance, and high-frequency processability as those of conventional soft polyvinyl chloride resins. Another object of the present invention is to provide at low cost a medical resin composition which does not have the problem of plasticizer elution and has no difficulty in disposal, and a medical molded article made of the resin composition.

[0008]

According to the present invention, the α-olefin has a carbon number of 3 to 20, and the α-olefin content is 8 to 5.
0% by weight, the density is 0.85 to 0.90 g / cm ³ , and the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is 1.5 to 2.5. Ethylene / α
An olefin copolymer 40 to 92.5% by weight and an ethylene / vinyl ester copolymer 7.5 to 60% by weight, which is a medical resin composition. As the polymer, an ethylene / vinyl acetate copolymer is particularly suitable. Further, another aspect of the present invention is a medical molded article characterized by comprising the above-mentioned medical resin composition, and a preferable example of the medical molded article is a medical tube or catheter. Hereinafter, the present invention will be described in detail.

The α-olefin, which is one of the copolymerization components of the ethylene / α-olefin copolymer contained in the medical resin composition of the present invention, has 3 to 20 carbon atoms.
Those having 6 to 10 carbon atoms are preferably used. That is, 1-hexene, 4-methyl-1
-Pentene, 1-heptene, 1-octene, 1-nonene, 1-decene are preferably used. These α
-The olefins may be used alone or in combination of two or more. Among these α-olefins,
An α-olefin having 8 carbon atoms, that is, 1-octene is particularly suitable as a copolymerization component.

The ethylene-α-olefin copolymer contained in the medical resin composition of the present invention has an α-olefin content (α-olefin copolymerization ratio) of 8 to 50% by weight, preferably Is 10 to 45% by weight, more preferably 15 to 45% by weight. This is because if the α-olefin content is less than 8% by weight, the bending elasticity of the molded product becomes too large, and conversely, if it exceeds 50% by weight, the adhesiveness of the molded product becomes high.

The density of the ethylene / α-olefin copolymer contained in the medical resin composition of the present invention is 0.
It is limited to 85 to 0.90 g / cm ³ , and preferably 0.
87-0.90 g / cm ³ , more preferably 0.86-
It is 0.88 g / cm ³ . This has a density of 0.85 g /
This is because if it is less than cm ³ , the mechanical strength of the molded product becomes insufficient, and conversely, if the density exceeds 0.90 g / cm ³ , the flexibility and kink resistance of the molded product become insufficient. In addition, the said density is measured based on ASTM D792.

Further, the ethylene / α-olefin copolymer contained in the medical resin composition of the present invention has a ratio (Mw) of its weight average molecular weight (Mw) to its number average molecular weight (Mn).
/ Mn) is 1.5 to 2.5, and preferably 1.8 to 2.5. This is Mw
This is because that / Mn exceeds 2.5 is inferior in bending fatigue resistance and impact resistance of the molded product. The weight average molecular weight (Mw) and the number average molecular weight (Mn) are values measured by gel permeation chromatography (GPC).

The melt index (measured in accordance with ASTM D 1238) of the ethylene / α-olefin copolymer contained in the medical resin composition of the present invention is 0.3 to 3.0 g. / 10 minutes is preferable from the viewpoint of moldability and mechanical strength, and the melt flow rate (I ₁₀ / I ₂ : measured in accordance with ASTM D 1238) is 5.0 to 10.0. Is also preferable from the viewpoints of molding processability and mechanical strength.

The above ethylene / α-olefin copolymer can be obtained by copolymerizing ethylene and α-olefin using, for example, a metallocene catalyst.

The above metallocene catalyst is a compound in which at least one ligand having a cyclopentadienyl skeleton is coordinated with a metal of Groups 3 to 10 of the periodic table such as titanium or zirconium or a lanthanoid series metal, Specific examples thereof include, but are not particularly limited to, for example, cyclopentadienyl titanium tris (dimethylamide), methylcyclopentadienyl titanium tris (dimethylamide), bis (cyclopentadienyl) titanium dichloride, Dimethylsilyltetramethylcyclopentadienyl-t-butylamide zirconium dichloride, dimethylsilyltetramethylcyclopentadienyl-t-butylamide hafnium dichloride,
Dimethylsilyltetramethylcyclopentadienyl-p
-N-butylphenylamide zirconium chloride, methylphenylsilyltetramethylcyclopentadienyl-t-butylamide hafnium dichloride, indenyl titanium tris (dimethylamide), indenyl titanium tris (diethylamide), indenyl titanium tris (di- n-propyl amide), indenyl titanium bis (di-n-butyl amide) (di-n-propyl amide) and the like. These metallocene catalysts may be used alone or in combination of two or more kinds. A cocatalyst such as methylaluminoxane or a boron compound may be used in combination with these metallocene catalysts.

The method for copolymerizing ethylene and α-olefin to obtain the ethylene / α-olefin copolymer used in the present invention is not particularly limited, but for example, a solution using an inert medium is used. Examples of the polymerization method include a bulk polymerization method and a gas phase polymerization method in which an inert medium does not substantially exist, and any polymerization method may be adopted.

With the above catalyst and polymerization method, a density of 0.
85 to 0.90 g / cm ³ , and the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is 1.5 to
A substantially linear ethylene / α-olefin copolymer having a value of 2.5 can be obtained.

The medical resin composition of the present invention contains an ethylene / vinyl ester copolymer in addition to the above ethylene / α-olefin copolymer.

Examples of the vinyl ester which is a copolymerization component of the ethylene / vinyl ester copolymer include vinyl acetate, vinyl propionate, vinyl 2-methylpropionate, and the like. As the united product, an ethylene / vinyl acetate copolymer is most preferably used.

Among the above ethylene / vinyl acetate copolymers, those having a vinyl acetate content of 1 to 50% by weight are preferable, and those having a vinyl acetate content of 10 to 30% by weight are more preferable.

The resin composition of the present invention comprises the above ethylene / α
-Olefin copolymer 40 to 92.5 wt% and the ethylene / vinyl ester copolymer 7.5 to 60 wt%, more preferably the ethylene / α-olefin copolymer 60 to 92. 5% by weight and 7.5 to 40% by weight of the above polyolefin resin. This is because when the proportion of the ethylene / α-olefin copolymer is less than 40% by weight, flexibility and kink resistance are lowered, and conversely 92.
This is because if it exceeds 5% by weight, the high frequency processability is deteriorated. The ethylene / α-olefin copolymer and the polyolefin resin may be used alone or in combination of two or more.

In the medical resin composition of the present invention, in addition to the above resin components, other polyolefin-based resins may be added, if necessary, within the range not impairing the object of the present invention. As such a polyolefin resin,
Examples thereof include polyethylene resin, polypropylene resin, polybutene resin, methylpentene resin and the like.

Examples of the polyethylene resin include low density polyethylene, medium density polyethylene, high density polyethylene, linear low density polyethylene, ethylene / propylene copolymer, ethylene / (meth) acrylic acid copolymer, ethylene. Examples thereof include (meth) acrylic acid ester copolymers. Examples of polypropylene resins include homopolypropylene, block polypropylene, random polypropylene, propylene / α-olefin copolymer, propylene / ethylene copolymer, propylene / butene copolymer, propylene / ethylene / butene copolymer. And so on.

The method for producing the medical resin composition of the present invention comprises:
The ethylene / α-olefin copolymer and the ethylene / vinyl ester copolymer, which are essential components, are not particularly limited, and for example, using an ordinary kneader such as a stirring kneader, an extruder, a Banbury mixer, or a roll. By uniformly kneading each predetermined amount of the polymer and one or more predetermined amounts of the above-mentioned resins or various additives which are added as necessary at room temperature or under heating, A resin composition can be obtained.

In the medical resin composition of the present invention, if necessary, for example, a filler, a bulking agent, a softening agent, a surfactant,
One or more of various additives such as coupling agents, antioxidants (anti-aging agents), heat stabilizers, light stabilizers, UV absorbers, colorants, lubricants, antistatic agents, flame retardants, etc. are added. It may be done.

The method for producing the molded article of the present invention is not particularly limited, and may be, for example, an extrusion molding method, a calender molding method, or the like, depending on the kind and intended use of the desired molded article.
A desired molded product can be obtained by adopting a normal molding method such as a press molding method and an inflation molding method and molding conditions accompanied therewith.

The form of the above-mentioned molded article is not particularly limited, and examples thereof include film or sheet-like products, bottles, tubes, box-like products, and the like, although the use is not particularly limited, but medical tubes or catheters. Etc. are preferable, and particularly suitable as a tube for an infusion set.

[0028]

EXAMPLES The following examples are given to illustrate the present invention in more detail, but the present invention is not limited to these examples.

(Examples 1 to 6 and Comparative Examples 1 to 8) Using a resin composition prepared by mixing the resins shown below in the proportions shown in Table 1, an inner diameter of 6.5 mm and an outer diameter were measured by an extrusion molding apparatus. The 9.0 mm tubes of Examples 1-6 and Comparative Examples 1-8 were molded.

Ethylene / α-olefin copolymer (Table 1
Resin A): The α-olefin has 8 carbon atoms, the α-olefin content is 20% by weight, and the density is 0.868 g / cm 3.
³ , Mw / Mn is 2.1, melt index is 0.5
g / 10 minutes, melt flow rate (I ₁₀ / I ₂ ) 7.
6, ethylene / 1-octene copolymer ethylene / vinyl acetate copolymer (I) (resin B in Table 1): vinyl acetate content 20% by weight, JIS K72
Ethylene / vinyl acetate copolymer ethylene / vinyl acetate copolymer (II) (resin C in Table 1) having a hardness based on 15 of A90: vinyl acetate content of 28% by weight, JIS K72
Ethylene / vinyl acetate copolymer polyvinyl chloride resin (resin D in Table 1) having a hardness based on 15 of A82: 100 parts by weight of polyvinyl chloride having an average degree of polymerization of 1000 and a plasticizer of 50
Soft polyvinyl chloride resin made by adding parts by weight

The performances of the tubes of Examples 1 to 6 and Comparative Examples 1 to 8 ((1) flexibility, (2) kink resistance, (3) high frequency workability) were evaluated by the following methods. The results are shown in Table 1.

(1) Flexibility A sus rod having a cross section of 15 mmφ was attached to the upper part of a compression tester and the tube was compressed to test the flexibility. The compression condition was a compression speed of 10 mm / min, and the load when pressing 4.5 mm was used as the evaluation value of flexibility.
In addition, the said evaluation was performed in 25 degreeC-50% RH atmosphere.

(2) Kink resistance FIG. 1 is a schematic view showing a compression tester for evaluating kink resistance. The tube is compressed under the condition that the chuck distance is 200 mm and the compression speed is 100 mm / min.
(Chuck movement distance: mm) was obtained and used as an evaluation value of kink resistance. In addition, the said evaluation was performed in 25 degreeC-50% RH atmosphere.

(3) High Frequency Machinability After each tube was once cut, the cut surface was welded again by high frequency dielectric heating using a high frequency welder processing machine. Each end of the tube having the cut surface welded was fixed to a tensile tester to perform a tensile test, and the strength when the welded surface was broken was measured. The strength at break of 98 N or more is shown in Table 1, and the less than 98 N is shown in Table 1.

[0035]

[Table 1]

From Table 1, the tubes of the present invention (Examples 1 to 1)
It can be seen that 6) exhibits flexibility, kink resistance, and high-frequency processability comparable to those of the conventional tube made of polyvinyl chloride resin (Comparative Example 8). Further, the tube of the present invention is superior in high-frequency processability to the tubes of Comparative Examples 1 and 6 and 7, and is superior in flexibility and kink resistance to the tubes of Comparative Examples 2 to 5. I understand.

[0037]

As described above, the present invention is excellent in flexibility and kink resistance, and is also excellent in high-frequency processability. Furthermore, there is no problem of elution of the plasticizer, and there is no difficulty in disposal. It is also possible to perform EOG sterilization or γ-ray sterilization. Therefore, the resin composition of the present invention is extremely useful particularly for medical tubes or catheters.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a compression tester for evaluating kink resistance.

FIG. 2 is a diagram showing a method for obtaining a value (L) indicating kink resistance.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4F071 AA15 AA28 AA81 AA82 AF17                       AF26 AH19 BB03 BB04 BB06                       BC01 BC04 BC05                 4J002 BB15W BF03X GB00 GB01

Claims (4)

[Claims] 1. An α-olefin having 3 to 20 carbon atoms, α
-Olefin content 8-50% by weight, density 0.85
˜0.90 g / cm ³ , and the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is 1.5 to
An ethylene / α-olefin copolymer 40 having a ratio of 2.5
9 to 92.5% by weight and ethylene / vinyl ester copolymer 7.5 to 60% by weight, a medical resin composition. 2. The medical resin composition according to claim 1, wherein the ethylene / vinyl ester copolymer is an ethylene / vinyl acetate copolymer. 3. A medical molded article, comprising the medical resin composition according to claim 1 or 2. 4. The medical molded article according to claim 3, wherein the medical molded article is a medical tube or a catheter.