JP2003145610A - Method for extrusion-molding polyamide resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent strength change, discoloration, and defective appearance such as a depression of an extrusion-molded article by the deterioration of the article caused by the water incorporation and oxidation of a polyamide elastomer and to provide a method for efficiently producing a tube which has a dimensional precision applicable to a medical tube, etc., and is reduced in nonuniformity of a tensile modulus of elasticity, tensile elongation, etc. SOLUTION: In the extrusion molding of the polyamide elastomer which is the block copolymer of nylon 12 and a polyether, during the operation of an extrusion molding apparatus, the polyamide elastomer is extruded while the water content of the elastomer to be supplied is kept to be 100-500 ppm, and the variation of the water content is kept within 20% of the average water content.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for extrusion-molding a polyamide resin. More specifically, it is possible to obtain an extruded product having a stable extrusion system, less appearance defects such as dents and coloring, and stable quality (dimensional accuracy, tensile properties (tensile elastic modulus, elongation at break)). The present invention relates to a method for extrusion-molding a polyamide elastomer.

[0002]

2. Description of the Related Art Polyamide-based elastomers are engineering plastic-based thermoplastic elastomers with excellent properties such as toughness, high flexibility, heat resistance, oil resistance, and good adhesiveness, and excellent practical moldability. In addition to being used for sports shoes such as ski boots, extruded products are air, water, soft drinks, various tubes for alcohol, corrugated tubes for wiring insulation, medical tubes such as catheters, textiles for clothing. It is used for etc.

When the polyamide elastomer is subjected to a molding process such as extrusion molding, it is necessary to dry the resin using a blower dryer, a dehumidifying dryer or the like to sufficiently reduce the water content of the resin. is there. If extrusion molding is carried out while the water content is high, the strength characteristics of the obtained extrusion molded product may change,
It will discolor. Also, the sorbed water in the resin is vaporized and dissipated during the extrusion, which may cause a defective appearance such as a dent in the extrusion.

For example, Japanese Patent Laid-Open No. 2001-55632 discloses a fiber in which two kinds of polyamide resins having a difference in bending stress are bonded in a side-by-side type, and a high stress polymer has a bending characteristic value of 0.025 gf · cm. ^2/24
Nylon 12 / polyether block copolymer of 0f or less, low stress polymer has a bending property value of 0.035 gf · c.
Nylon 6 with m ² / 240f or more, elongation rate of 30
A polyamide elastic yarn having a content of 0% or more is disclosed, and it is preferable to adjust the moisture content of the high stress polymer chip to be 0.05 to 2.0 weight (500 to 20000 ppm). . It is described that the polyamide fiber is susceptible to deterioration such as hydrolysis in a molten state, and it is described that the coloring and discoloration of the obtained fiber increase as the moisture content increases.

Further, Japanese Patent Publication No. 9-509860 discloses a block copolymer elastomer catheter balloon, wherein polyamide elastomer pellets having a Shore hardness D of 60 or more are used in 0.10 weight prior to extrusion molding. It is described that it is dried to below a water content of%.

[0006] Furthermore, the site of EMS-CHEMIE (www.emsc
hem.com), Product Data Bulle-tin,
When a polyamide elastomer having a Shore hardness D of 62 or 63 is subjected to extrusion molding, first, the water content is set to 0.1.
It is stated that it should be less than or equal to%, and then 8
It is recommended that the resin stay in the hopper dryer at 0 ° C for 2 hours or more.

On the other hand, it is known that, when drying the polyamide resin, if it is left at a too high temperature for a long time, it is oxidatively deteriorated and discolored.

For example, Japanese Patent Publication No. 2001-511690 discloses a balloon useful for a medical device manufactured from a material containing a plasticized polyamide having a glass transition temperature of less than about 32 ° C., which is described therein. In particular, when extruding a nylon 12 homopolymer tube, the nylon feedstock (ie, the nylon material prior to heating and extruding) in the hopper must be kept moisture free. This is usually accomplished by using a dryer and heater installed in the hopper. A nylon 12 homopolymer is typically maintained at about 250 ° F. (about 121 ° C.) with a dryer. However, even with these precautions, nylon 12 homopolymer
It is stated that it should be used within about 1 hour 30 minutes to 2 hours, otherwise it will decompose and become unusable.

Here, the special table 2001-511690
The content described in the publication is technical knowledge in extrusion-molding a nylon 12 homopolymer and is strictly different from that of the polyamide elastomer in the present invention, but in order to obtain a high-strength extrusion-molded product. In the case of the polyamide-based elastomer having a Shore hardness D of 60 to 75, which is also preferably used in the present invention, the content of the hard segment nylon 12 is about 75 to 95% by weight, which is a reference. .

Regarding the oxidative deterioration of polyamide-based elastomers, see, for example, the website of Degussa-Huels (www.degussa).
-hpp.com) Technical data, Handling and Processing o
It is disclosed in fVESTAMID, and it is described that discoloration due to oxidation occurs when dehumidifying and drying at 80 ° C. or higher. For example, the water content is 2600 ppm.
When the resin of a certain degree is dried by a dehumidifying dryer, 8
Even if it is dried at 0 ° C. for 48 hours, the water content cannot be reduced to 500 ppm, and discoloration occurs in about 32 hours. On the other hand, although the water content becomes about 500 ppm when dried at 110 ° C. for about 5 hours, the reason why discoloration occurs is also described here.

On the other hand, even if the water content of the polyamide-based elastomer can be adjusted to a low level without causing discoloration, the inventors have studied and found that the resin viscosity fluctuates greatly and that the quality of the tube usable for medical use is stable. It was difficult to obtain the extruded product. In this case, the dimensional stability can be improved to some extent by using a constant-volume supply device such as a gear pump, but the size required for medical tubes, especially small-diameter medical tubes requiring dimensional accuracy. It is difficult to satisfy the accuracy, and there are problems that the yield is low and the labor cost is high because they are selected and used. In addition, especially when using some medical tubes or this tube after reprocessing, unevenness such as tensile elastic modulus and tensile elongation is not allowed in the tube, and the above method does not meet this requirement. It is necessary to process in anticipation that a defective product will occur in order to select and remove defective products after reprocessing, because it is impossible to obtain a tube filled with It was

[0012]

In view of these circumstances, the first object of the present invention, which the present inventor intends to solve, is a change in strength due to deterioration of the extruded product due to water absorption and oxidation of the polyamide elastomer. , It is to prevent discoloration and defective appearance such as dents.

A second object of the present invention is to provide a method for efficiently producing a tube having dimensional accuracy usable for medical tubes and the like and having reduced unevenness in tensile elastic modulus, tensile elongation and the like. It is in.

[0014]

The present invention has been made based on the above-mentioned prior art and technical knowledge. That is, in extrusion molding of a polyamide elastomer, which is a block copolymer of nylon 12 and polyether,
During the operation of the extrusion molding apparatus, the polyamide-based elastomer is extruded while maintaining a water content of 100 to 500 ppm and a variation in the water content within 20% of the average water content. This is a resin extrusion molding method.

Further, the polyamide resin has a Shore hardness D of 60 to 75, wherein the polyamide resin is extrusion-molded.

Further, the water content is maintained by a dehumidifying dryer, and the temperature inside the dehumidifying dryer is 35 to 60 ° C.
Relative humidity is 3 to 20%, The extrusion molding method of the said polyamide resin characterized by the above-mentioned.

Further, the water content is previously set to 1 by using a vacuum dryer.
The extrusion molding method as described above, which uses a polyamide elastomer adjusted to a range of 00 to 500 ppm.

Further, the obtained extruded product has an outer diameter of 0.3.
The method for extrusion molding of a polyamide resin as described above, which is a medical tube having a diameter of up to 2.5 mm.

Further, the present invention relates to a method of biaxially stretching the tube obtained by the above-mentioned extrusion molding method to form a balloon with good yield.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. According to the present invention, in extrusion molding of a polyamide-based elastomer which is a block copolymer of nylon 12 and polyether, the water content of the polyamide-based elastomer supplied during the operation of the extrusion molding apparatus is 100 to 500 pp.
m, and a method for extrusion molding a polyamide resin, which comprises extruding while maintaining the variation of the water content within 20% of the average water content.

The polyamide-based elastomer is known and is easily available. For example, EMS-CHEMIE's "Gr
ilamid ELY (trademark) ”, Degussa-Huels“ VESTAMI
"D (trade name) E-series" and "PEBAX (trade name)" manufactured by elf atochem.

The polyamide elastomer is obtained by changing the weight fraction of nylon 12 which is a hard segment and polyether which is a soft segment.
The shore hardness can be changed, and the higher the weight fraction of the nylon 12 component, the higher the shore hardness.
On the other hand, the equilibrium water content increases under the same conditions, and the change in viscosity due to the change in water content increases. Therefore, in the present invention, a polyamide elastomer having a Shore hardness D of 60 to 75 and a relatively high hardness is preferably used. Further, a polyamide elastomer having a Shore hardness D of 68 to 75 is more preferably used.

The polyamide elastomer may be mixed with one or more plasticizers, stabilizers, antibacterial agents, release agents, dyes, pigments and the like. Further, another resin that is compatible with the polyamide-based elastomer or exhibits a phase-separated structure to improve the properties of the polyamide-based elastomer, such as a polyamide resin, may be added.

As the extrusion molding apparatus, any of conventionally known extruders and wire coating apparatuses can be applied.

As the extruder, both single-screw and twin-screw extruders can be applied. Further, it is preferable to add a constant volume supply device such as a piston type or a gear pump (melt pump), because the excellent effect of the present invention will be more remarkably exhibited.

When the extrusion molding apparatus is in operation, when a hopper drier or the like is used, temperature control and humidity control are started by the hopper drier or the like or equipment attached thereto when a polyamide elastomer is present inside. It means the time from the given time to the end of the production of the desired extrudate. Various types of hopper dryers are known, and those that only heat with a heater cannot be used, but especially 90% or more of the gas in the hopper is replaced with nitrogen or dry air, or dehumidification. It is preferable to use a dehumidifying and drying type such as an air circulation type because the moisture content can be maintained within a certain range at a relatively low temperature and oxidative deterioration can be suppressed or prevented.

The water content of the polyamide elastomer is a weight fraction of the sorbed water content of the polyamide elastomer supplied to the extruder from a hopper having a function such as a hopper dryer. For example, a method such as ASTM D570 can be used for measurement. However, in this method, when the water content is a small amount of less than 0.1% (1000 ppm), the effective number becomes one digit, and the measurement accuracy decreases. Therefore, it is preferable to use a trace moisture measuring device such as a coulometric titration method.

The variation of the water content means the percentage of the value obtained by dividing the difference between the maximum water content and the average water content of the polyamide elastomer during the operation of the extruder by the average water content, and the average water content and the minimum water content. It is the larger of the percentages of the values obtained by dividing the difference in water content by the average water content.

In the present invention, the water content of the polyamide elastomer supplied during the operation of the extrusion molding apparatus is 100 to 5%.
00 ppm, and change the water content to 20% of the average water content.
It is characterized by extruding while maintaining within%. This not only prevents the first problem of the present invention, such as appearance change such as strength change, discoloration, and further dent due to deterioration of the extruded product due to water absorption and oxidation of the polyamide-based elastomer, The second problem is that it is necessary to efficiently produce a tube that has dimensional accuracy that can be used for medical tubes and the like and has reduced unevenness in tensile elastic modulus and tensile elongation.

More specifically, as disclosed in the prior art, by controlling the water content to 0.1% (1000 ppm) or less, it is possible to prevent some deterioration of the physical properties of the polyamide elastomer such as coloring and discoloration. What I can do, but not enough, 50
It is preferably 0 ppm or less. As a result of the examination, it was confirmed that the water content of the polyamide elastomer can be reduced to 500 ppm or less by an industrially applicable method by performing vacuum drying.

On the other hand, the resin viscosity at the time of extrusion increases as the water content decreases, but when the water content is too low, the rate of resin viscosity fluctuation due to the water content change becomes very large, and extrusion molding with stable quality is achieved. It is difficult to get things. In this case, the dimensional stability can be improved to some extent by using a constant volume supply device such as a gear pump, but the dimensional accuracy required for a medical tube, especially a small-diameter medical tube requiring dimensional accuracy, In particular, it is not possible to satisfy the uniformity of the tensile elastic modulus, the tensile elongation and the like of some medical tubes and the tubes required when the tube is reprocessed and used. For the above reasons, the water content of the polyamide elastomer is 1 in order to achieve the object of the present application.
It is necessary to be at least 00 ppm.

Further, even if the water content is in the above range, the water content of the resin in the hopper is increased by the water absorption of the resin in the hopper during the operation of the extruder or vice versa. If the rate changes, the viscosity of the molten resin in the extruder changes and the extrusion pressure changes with the change in viscosity, and the size required for medical tubes, especially small-diameter medical tubes that require dimensional accuracy. It is not possible to satisfy the accuracy, particularly the uniformity of the tensile elastic modulus, the tensile elongation, etc. of a part of the medical tubing, and the tubing required when this tube is reprocessed and used. For the above reasons, it is necessary to maintain the variation of the water content of the polyamide elastomer within 20% of the average water content.

The fluctuation of the extrusion pressure caused by the fluctuation of the viscosity of the molten resin in the extruder due to the fluctuation of the water content is, for example, at the die inlet with the constant volume feeding device added and the extrusion amount kept constant. It is evaluated by measuring the change with time of the extrusion pressure measured with a pressure gauge installed. The change over time of the extrusion pressure is due to rotation of a screw, rotation of a gear when a gear pump is added, or the like, and a periodic fluctuation of a relatively short cycle, and a change in water content of a polyamide-based elastomer as a raw material. Can be divided into gentle and irregular fluctuations due to the change in viscosity. Since these two pressure fluctuations have completely different fluctuation patterns, they can be easily separated. Among them, the former can be relatively easily improved by those skilled in the art by adjusting the gear pump, but the latter is especially problematic in terms of smooth and irregular fluctuations.

In the present invention, the stability of the extrusion system can be evaluated, for example, by the smooth and irregular fluctuation of the extrusion pressure. For example, when the polyamide-based elastomer in the hopper is adsorbing moisture, the extrusion pressure is gently and irregularly changed at intervals of several minutes to several tens of minutes for a few minutes or a small upward movement. While having a peak of, the overall decline.
On the contrary, when the drying is progressing in the hopper, it rises on the contrary.

In the following examples, the smooth and irregular fluctuation of the extrusion pressure was quantitatively defined using the rate of change (MPa / h) of the extrusion pressure. The rate of change of the extrusion pressure is a value obtained by averaging the rate of change of the extrusion pressure during the continuous operation for a minimum of 2 hours while keeping the extrusion rate constant. Therefore, the rate of change of the extrusion pressure is positive when the drying is progressing, the viscosity is increasing, the extrusion pressure is increasing, the water absorption is progressing, the viscosity is decreasing, and the extrusion pressure is decreasing. It becomes a negative value, and in any case, it is not preferable that the absolute value of the changing speed of the extrusion pressure is large, and 0 is the optimum value.

The maintenance of the water content is carried out by a dehumidifying dryer,
For example, a dehumidifying air circulation type hopper dryer is used, and the temperature inside the dehumidifying dryer is 35 to 60 ° C., preferably 35 to 55 ° C., more preferably 37 to 55 ° C .; relative humidity is 3 to 20%, preferably 3 to It is preferably 15%, more preferably 5 to 15%.

When the temperature is lower than 35 ° C., the dehumidifying dryer must be provided with a cooling function, which is not preferable because it is costly. On the other hand, when the temperature is higher than 60 ° C., the operating time of the extruder is low. Is longer, the polyamide-based elastomer is apt to be oxidized and deteriorated, which is not preferable.

The amount of fluctuation of the water content is calculated as the average water content of 20.
By maintaining the ratio within%, the quality of the extrudate can be stabilized. For example, the Shore hardness D is 6
When the tensile properties of the extruded product using a polyamide-based elastomer such as 0 to 75, especially the elongation at break are considered important, the extrusion amount, die shape, screw shape, extrusion temperature, take-up speed, etc. Even when the process factors other than the water content are constant, if the water content is different, the resin viscosity is different, the extrusion pressure is different, and the stretching degree of the extruded product thus obtained is changed, As a result, the elastic modulus and elongation at break of the extruded product greatly change. According to the research conducted by the present inventors, for example, in extrusion molding of the polyamide-based elastomer having a Shore hardness D of 69,
With constant extrusion conditions other than water content, an outer diameter of 1.18 mm,
A tube with an inner diameter of 0.58 mm was molded. In this case,
The extrusion pressure changed from 2.0 MPa (water content 1000 ppm) to 4.0 MPa (water content 200 ppm), and the extrusion pressure was not stable at all. Furthermore, the tubes obtained at each extrusion pressure were stored for 1 week in an environment of 23 ° C. and 50% RH, and then the distance between chucks was 50 m.
When the tensile measurement was performed at m and a tensile speed of 50 mm / min, the extrusion pressure was 2.0 MPa (water content 1000 pp.
In m), the elongation at break was 700% (n = 5 average value), while the extrusion pressure was 4.0 MPa (water content 200
(ppm), the elongation at break was 530%.

From the above, it is clear that the quality of the extruded product obtained greatly changes depending on the water content of the raw material resin, and it is difficult to stabilize the quality only by setting the conventionally known water content of 1000 ppm or less. Therefore, in order to stabilize the quality, it is clear that it is necessary to strictly control the water content in a narrower range.

The present invention also has an outer diameter of 0.3 to 2.5.
When applied when extruding a mm medical tube,
It is preferable because the effect is remarkable. Such a medical tube is used to improve the blood flow on the peripheral side of the blood vessel by expanding the narrowed or blocked portion of the blood vessel when the blood vessel or the like becomes narrowed or blocked. Plastic surgery (PTA: Percutaneous Transluminal)
Angioplasty, PTCA: Percutaneous Transluminal
Coronary Angioplasty) used as a constituent material of balloon catheters.

The cross-sectional shape of the medical tube is not particularly limited, and the internal lumen may be one or plural.

In the extrusion molding of the parison to be the balloon portion of the balloon catheter by the medical tube, particularly the catheter tube, or the blow molding, the extruded product obtained is inserted into the human body, and therefore the appearance thereof is particularly remarkable. And performance is strictly checked. Above all, stability of tube quality such as dimensional accuracy and tensile properties (tensile elastic modulus, elongation at break) is important. In particular, when the tube is reprocessed into a balloon or the like to be used, the uniformity of the tensile modulus of elasticity and tensile elongation of the tube required is very high. In this case, not only the uniformity of tensile elastic modulus and tensile elongation within one tube used for a balloon but also the uniformity among a large number of produced tubes are very important in terms of productivity.

When used as a constituent material of the balloon catheter, an internal pressure is applied to the tube in order to inflate the balloon in the vessel. Therefore, a constant pressure resistance is required for all constituent materials,
For this purpose, it is necessary to keep the wall thickness of the tube above a certain value.

On the other hand, since it is inserted into a vessel, the outer diameter of the tube naturally has an upper limit, and it is necessary to shorten the deflation time or maintain the slidability of the guide wire. It is necessary that the inner diameter of the above is above a certain value.

Therefore, in order to obtain a balloon catheter of which the pressure resistance and the limits of the inner and outer diameters are simultaneously satisfied and the quality is stable, it is necessary to suppress the variation of the inner and outer diameter dimensions to the utmost limit. Strict requirements such as ± 30 μm or less are made.

Naturally, the appearance abnormality such as foreign matter and dents undergoes a strict check that cannot be compared with other extruded products, and they are selected and used.

From the above, a tube of stable quality obtained by the extrusion molding method of the present invention is
When used as a medical tube, it is obvious that it is particularly effective.

[0048]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Example 1 As a polyamide elastomer, "PEBAX7033SA01" (Shore hardness D69, moisture content 700 ppm) manufactured by elf atochem was used. After drying the polyamide-based elastomer pellets in a vacuum dryer at 80 ° C for 6 hours, immediately store them in an aluminum bag in a sealed state, and
It was left for 5 hours. Then, it was moved into a dehumidified air circulation type hopper dryer attached to the extruder, and the operation was started at a set temperature of 50 ° C. A portable thermo-hygrometer was installed in the hopper dryer, and the temperature and humidity during operation of the extruder were measured. The temperature was 50 ° C and the relative humidity was 6%. Run for 12 hours, collect resin pellets from the sampling port under the hopper dryer every 2 hours, quickly seal in an aluminum bag, leave for 15 hours or more, and then use Mitsubishi Chemical's trace moisture analyzer (electro titration method). Automatic moisture analyzer) CA
The water content of the sampling pellets at a total of 7 points was measured at −07 (measured weight 0.8 to 1.0 g, measured temperature 230 ° C.,
Nitrogen flow rate 200-250ml / min, end judgment 0.1
μg / S), the water content and the variation of the water content were calculated. The average water content was 204 ppm, and the variation of the water content was 15
%Met.

Also, about 1 hour after the start of the operation of the extruder, the φ25 extruder was started up, the conditions were set, the extrusion pressure when the extrusion system became stable was 3.5 MPa (gauge), and the average outer diameter was 1. A medical single-lumen tube having a length of 18 mm and a length of about 30 cm was produced. A gear pump having a discharge capacity of 1.2 cc / rev was installed and operated in order to stabilize the extrusion rate of the extruder.

The φ25 extruder was operated for about 11 hours after startup (the operating time of the extruder was 12 hours), and changes in the extrusion pressure during that time were monitored.
It did not fluctuate at all from 5 MPa (gauge), and therefore the rate of change of extrusion pressure was 0 MPa / h.

During the last hour of operation of the extruder, medical tubes for evaluation were taken. Randomly extract 50 tubes from the obtained medical tubing, and measure a total of 3 points at about 5 cm, 15 cm, and 25 cm from one end of each tube.
Outer diameter at all 150 points, standard deviation σ _n-1
Was calculated to be 2.9 μm. In addition, a two-axis laser outer diameter measuring machine (Mitsutoyo Laser
Scan Micrometer LSM-201X) was used as the outer diameter value by averaging the measured values on the two axes.

Further, the same 50 as that of the outer diameter was measured.
The number of appearance defects such as foreign matters and dents and the presence or absence of discoloration were observed for the medical tubes of the book. As a result, the number of appearance defects was 0.13 pieces / m, and a good medical tube without discoloration was obtained.

Regarding the main operating conditions and conditions, and the quality of the obtained extruded medical tubing,
It is summarized in Table 1 (the same applies to the following examples and comparative examples).

(Example 2) Extrusion molding was carried out in the same manner as in Example 1 except that the extrusion pressure at the start-up of the extruder was 1.4 MPa and the outer diameter of the extruded medical tube was 0.54 mm. I went. The average water content of the polyamide-based elastomer during the operation of the extruder was 204 ppm, and the variation was 15%, which was the same as in Example 1. The rate of change of extrusion pressure was also 0 MPa / h. The standard deviation of the outer diameter of the obtained medical tube is 1.3 μm, and the number of appearance defects is 0.07.
It was a good medical tube having a number of pieces / m and no discoloration.

Example 3 A polyamide elastomer was used
elf atochem "PEBAX7233SA01" (Shore D hardness 7
Extrusion molding was performed in the same manner as in Examples 1 and 2 except that the water content was 850 ppm and the outer diameter of the medical tube was 0.95 mm. The water content of the resin at the start of the operation of the extruder is 240 ppm, and the water content during the operation of the extruder is 245 p.
pm, and the variation of the water content was 7%. The extrusion pressure at the time of starting the extruder was 6.2 MPa, and the rate of change of the extrusion pressure was 0 MPa / h. The standard deviation of the outer diameter of the obtained medical tube is 2.3 μm, and the number of appearance defects is 0.13.
It was a good medical tube having a number of pieces / m and no discoloration.

Comparative Example 1 A medical tube made of a polyamide elastomer was extruded in the same manner as in Example 1 except that the hopper dryer was not operated.
The temperature inside the hopper was 22 ° C. and the relative humidity was 47%. Therefore, the water content at the start of the operation of the extruder was 200 ppm, which was the same as in Example 1, but the moisture absorption of the resin proceeded in the hopper, and the average of the water content measurement values at 7 points was 900.
The amount of change in ppm was 78%. The extrusion pressure at the start-up of the extruder was set to 3.5 MPa as in Example 1, but the extrusion pressure was gradual and irregularly varied, and the extrusion pressure decreased with time, and the rate of change was −0.17 MPa / h. Became. The obtained medical tube has an average outer diameter of 1.18 mm.
However, the standard deviation was 6.7 μm, and compared with Example 1 (standard deviation 2.9), the outer diameter variation was about 2.3 times larger, and the number of appearance defects was larger. Also 0.4
The number was 7 / m, which was 3.6 times that of Example 1 (0.13 / m), and although there was no discoloration, it was unusable as a constituent material of the balloon catheter.

(Comparative Example 2) A medical tube having an outer diameter of 1.18 mm was extruded in the same manner as in Example 1 except that the set temperature of the dehumidifying and drying type hopper dryer was set to 110 ° C. The relative humidity inside the hopper dryer was 6%. The water content at the start of the operation of the extruder was 200 ppm, which was similar to that in Example 1, but the temperature of the hopper was high and the drying of the resin proceeded in the hopper, so the water content during the operation of the extruder was 70 ppm, and the variation was It became 186%. The extrusion pressure at the time of starting the extruder is the same as in Example 1.
Although the pressure was set to 5 MPa, the extrusion pressure gradually fluctuated irregularly, the extrusion pressure increased with time, and the rate of change was +
It was 0.14 MPa / h. The standard deviation value of the outer diameter of the obtained medical tube was 5.8 μm, and the variation in the outer diameter dimension was 2.0 times that of Example 1 (2.9 μm in the same). The number of appearance defects was 0.07 pieces / m, which was the same as that of Example 1, but the discoloration of the tube which is considered to be caused by the oxidative deterioration of the resin in the hopper was observed, and it cannot be used as the constituent material of the balloon catheter. It was a thing.

[0059]

As described above, according to the extrusion molding method of the present invention, the extrusion system is stabilized, whereby an extrusion molded article having stable physical properties can be easily obtained.

[0060]

[Table 1]

Claims (6)

[Claims] 1. In extrusion molding of a polyamide elastomer, which is a block copolymer of nylon 12 and polyether, the average water content of the polyamide elastomer supplied during operation of an extrusion molding apparatus is 100 to 500 p.
An extrusion molding method of a polyamide-based resin, which comprises extruding while maintaining the pm and the variation of the water content within 20% of the average water content. 2. The extrusion molding method for a polyamide resin according to claim 1, wherein the Shore hardness D of the polyamide elastomer is 60 to 75. 3. The maintenance of the water content is carried out by a dehumidifying dryer, and the temperature inside the dehumidifying dryer is 35 to 60 ° C. and the relative humidity is 3 to 20%. Extrusion molding method of polyamide resin. 4. A water content of 100 using a vacuum dryer in advance.
The extrusion molding method according to claim 3, wherein a polyamide-based elastomer adjusted to a range of ˜500 ppm is used. 5. The obtained extruded product has an outer diameter of 0.3 to
It is a 2.5 mm medical tube,
The extrusion molding method of the polyamide resin according to claim 1. 6. A balloon molding method for biaxially stretching a tube obtained by the extrusion molding method according to claim 1.