JP2009113324A - Method of manufacturing resin hollow tube - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a resin hollow tube to eliminate various faults when manufacturing a hollow tube by conventional extrusion molding processes. <P>SOLUTION: This method of manufacturing a resin hollow tube has a step Y to successively form a hollow part in the stretching direction of a strand, as follows. In a heating and stretching device having a strand-feed unit, a take-off unit and an infrared-focusing heating unit disposed between the strand-feed unit and the take-off unit, a thermoplastic resin strand is stretched under heat while infrared rays including a wavelength to be absorbed by the thermoplastic resin are focused toward the strand from a plurality of directions so that the viscosity of the strand at the center part in the stretching direction becomes lower than that in the peripheral parts. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing a resin hollow tube.

A resin hollow tube formed from a thermoplastic resin is used as, for example, a medical tube, a hollow tube for forming an optical fiber cladding material or a core material.
Conventionally, hollow tubes for forming cores of optical fibers, clad hollow tubes of optical fibers, medical tubes, etc. have high roundness as well as smoothness of the inner wall of the tube as the dimensional accuracy of the tubes. Is required.

These hollow tubes are generally manufactured by a melt extrusion method, and a method using a mandrel (core wire) and a method not using it are known.
Regardless of whether or not a mandrel (core wire) is used, the melt extrusion method is manufactured by extruding a molten resin from a die having a tubular base part, so that the resin stays inside the extruder. There is a problem that the longer the time is, the easier it is to generate a staying degradation product such as a thermal decomposition product or a gelled product.

  In addition, when a hollow tube is manufactured by an extruder without using a mandrel (core wire), the inner wall of the hollow tube is extruded from a state in contact with the tubular die. It is easy for deposits and foreign substances to accumulate on the part. As a result, there is a problem in that contaminants adhere to the inner wall of the hollow tube or streaks are likely to occur in the flow direction, and the smoothness of the inner surface of the hollow tube is liable to be impaired.

  Furthermore, when reducing the thickness of the hollow tube, it becomes possible to extrude if the width of the opening of the die corresponding to the thickness of the hollow tube is narrowed and the temperature of the molten resin is increased to lower the viscosity. However, the resin is likely to be thermally deteriorated and the cooling time is prolonged. In particular, in the case of a crystalline resin, if the cooling time is long, crystallization proceeds during cooling, which causes a problem that the smoothness of the hollow tube is deteriorated.

  On the other hand, in the extrusion molding method using a mandrel, for example, the mandrel is supplied to an extrusion molding machine, the polymer is coated, cut into a predetermined length, and after opening both ends, the mandrel is pulled out to obtain a hollow tube. Is the method. However, since the hollow tube is pulled out from the mandrel, it is difficult to produce a long hollow tube. Further, when the hollow tube is pulled out from the mandrel, there are problems that the hollow tube is deformed to cause residual distortion or the inner wall of the hollow tube is damaged. Furthermore, there has been a problem that a part of the metal or lubricant desorbed from the mandrel surface migrates to the inner wall of the hollow tube and becomes a contaminant.

The resin hollow tube obtained by the above manufacturing method has a problem in ensuring the quality reliability and safety of the hollow tube particularly in applications such as optical fibers and medical tubes.
Various methods for solving these problems have been proposed in the past (see, for example, Patent Documents 1 and 2).

  The method described in Patent Document 1 is a method of controlling the spherulites of the resin by controlling the cooling temperature during extrusion molding. The method described in Patent Document 2 is a method in which a crystalline polymer and an amorphous polymer are mixed and used as a raw material resin.

However, both of these methods are methods for controlling the crystallization of the resin, and in these methods, problems derived from the above-described extrusion molding method itself (for example, problems such as easy generation of staying deterioration products, mandles are not used). In some cases, contaminants adhere to the inner wall of the hollow tube, or streaks are likely to occur in the flow direction, and the smoothness of the inner surface of the hollow tube is liable to be damaged. The hollow tube is deformed when pulling out, resulting in residual strain, the inner wall of the hollow tube is damaged, the metal that was detached from the mandrel surface and a part of the lubricant migrated to the inner wall of the hollow tube, As a means to solve the problem of becoming a pollutant), it was insufficient and there was still room for improvement.
Japanese Patent Laid-Open No. 2004-249606 JP 2005-258297 A

  An object of this invention is to provide the manufacturing method of the resin hollow tube which does not produce the various problems originating in the said extrusion method itself.

As a result of intensive studies to solve the above problems, the present inventors have found a method for producing a resin hollow tube that does not depend on an extrusion molding method, and have completed the present invention.
That is, the method for producing a resin hollow tube according to the present invention includes a strand supply unit, a take-up unit, and a heating and stretching apparatus having an infrared condensing heating unit disposed between the supply unit and the take-up unit.
By concentrating infrared rays including wavelengths absorbed by the thermoplastic resin from a plurality of directions toward the strand, the viscosity of the central portion in the stretching direction of the strand is reduced in the outer peripheral portion. It has the process Y which forms a hollow part continuously in the extending | stretching direction of this strand by extending | stretching, heating so that it may become lower than a viscosity.

In the step Y, it is preferable that stretching is performed while heating so that the temperature of the central portion in the stretching direction of the strand is higher than the temperature of the outer peripheral portion.
The method for producing a hollow resin tube of the present invention includes a step X of stretching a strand made of a thermoplastic resin while heating so as to be in a fluid stretch state,
It is preferable to have the process Y performed by changing the heating and / or stretching conditions of the process X to reduce the amount of infrared heat input to the strand and increasing the take-up tension.

In the step Y, the infrared rays are monochromatic light, and the absorption coefficient K (m ⁻¹ ) of the thermoplastic resin in the monochromatic light and the diameter D (m) of the strand before heating are expressed by the following formula ( It is preferable that the relationship 1) is satisfied and the diameter D is 0.5 × 10 ⁻³ m or more.

0.1 <K · D <2.6 (1)
When the strand supply speed in Step X is Vf1, the light collecting intensity is I1, and the take-up speed is Vt1,
It is preferable that the strand supply speed in the process Y is Vf1, the light collecting intensity is I1, and the take-up speed is Vt2 faster than Vt1.

The infrared ray is an infrared ray irradiated from a carbon dioxide laser,
It is preferable that the strand made of the thermoplastic resin is polyethylene.

  The method for producing a hollow resin tube of the present invention differs from the conventional extrusion molding method in that a hollow portion is formed in a non-contact state at the time of hollowing by stretching a strand of thermoplastic resin under specific conditions. Therefore, it is possible to eliminate various drawbacks when a hollow tube is produced by an extrusion molding method.

Next, the present invention will be specifically described.
The method for producing a resin hollow tube according to the present invention includes a strand supply unit, a take-up unit, and a heat-stretching apparatus having an infrared condensing heating unit disposed between the supply unit and the take-up unit. By concentrating infrared rays including wavelengths absorbed by the thermoplastic resin from a plurality of directions toward the strand, the viscosity of the central portion in the stretching direction of the strand is lower than the viscosity of the outer peripheral portion. It has the process Y which forms a hollow part continuously in the extending | stretching direction of this strand by extending | stretching, heating so that it may become.

  In the step Y, the hollow portion is continuously formed in the stretching direction of the strand by stretching the strand while heating, but in order to form the hollow portion, the viscosity of the hollow portion in the stretching direction of the strand is It is necessary to stretch while heating so as to be lower than the viscosity of the outer peripheral portion.

  That is, even if infrared rays are directed toward the strand from multiple directions and heated, the resin hollow tube is obtained when the viscosity of the central portion in the stretching direction of the strand is higher than the viscosity of the outer peripheral portion. It is difficult.

  Unless otherwise specified in the present invention, when simply described as “manufacturing method”, it indicates “method of manufacturing the resin hollow tube of the present invention”, and when “strand” is described as “from thermoplastic resin” "Strand".

  Moreover, the fluid drawing state in this invention means that the outer peripheral part temperature of a strand is extended | stretched in the state more than the melting temperature of a thermoplastic resin. In the flow-stretched state, usually, even if the stretching speed is increased, almost no increase in the stretching stress following the stretching speed is observed, and the strand can be confirmed by thinning without becoming a neck shape in the infrared light collecting region. . The strand outer peripheral temperature immediately after passing through the infrared condensing region can be measured using an infrared radiation thermometer.

In the production method of the present invention, a heating and stretching apparatus having a strand supply unit, a take-up unit, and an infrared condensing heating unit arranged between the supply unit and the take-up unit is used.
An example of a schematic diagram of a heating and stretching apparatus used in the present invention is shown in FIG. 1, and the production method of the present invention is shown below with FIG.

  As a strand supply part (A), what is necessary is just to be able to supply the strand which consists of a thermoplastic resin composition used for this invention toward an infrared condensing heating part. As the strand supply unit (A), for example, a feeding roller for sending out a strand made of a thermoplastic resin prepared in advance, an extrusion molding device for producing a strand made of a thermoplastic resin by an extrusion molding method, a spinning device, etc. Can be mentioned. In addition, in this invention, the speed at the time of sending out a strand with a sending roller (feeding speed) and the speed at the time of manufacturing and sending out a strand are collectively called a strand supply speed.

  As the take-up section (3), it is sufficient that the strand made of the thermoplastic resin supplied from the strand supply section (A) and heated by the infrared ray condensing heating section can be taken, and examples thereof include a take-up roller. Further, as another aspect of the apparatus having the heating and stretching means, there is an aspect in which a strand made of a thermoplastic resin is gripped and stretched instead of the take-up roller. In the present invention, the speed at which the strand is taken up by the take-up section (3) such as a take-up roller is called the take-up speed.

The take-up tension in the present invention means a tension acting on the strand between the take-up part and the take-up part. The take-up tension can be adjusted by providing a tension controller in the take-up part.

  In the heating and stretching apparatus shown in FIG. 1, the ratio between the take-up speed and the supply speed (take-off speed / supply speed) becomes the draw ratio, and the draw ratio and take-up tension are changed by adjusting the supply speed and take-up speed. Can be made. In order to produce a stable resin hollow tube, it is preferable to change the draw ratio and take-up tension by changing the take-up speed while keeping the feed rate constant.

  There is no limitation in particular as an infrared condensing heating part (2), if infrared rays can be condensed toward a strand from two or more directions, ie, two or more directions. As an infrared condensing heating part (2), it usually has a light source which generates infrared rays, and an optical system for condensing infrared rays irradiated from the light sources toward the strand from two or more directions. The wavelength of this light source is preferably 0.8 to 12 μm.

  As a light source that generates infrared rays, for example, a laser, a light emitting diode, or an infrared radiation heater (hereinafter, abbreviated as an infrared heater) can be used. In particular, a laser can be suitably used as a monochromatic light source.

  When the light source is a laser, any of solid laser, semiconductor laser, fiber laser, disk laser, gas laser, dye laser, and chemical laser may be used as the type of laser.

  For example, as a solid-state laser, a YAG laser doped with Nd (neodymium) having a light source wavelength in the range of 0.94 to 1.4 μm (hereinafter referred to as Nd: YAG laser), a light source wavelength of 1.8 to 3 is used. YAG laser doped with Ho (holmium), Tm (thulium), and Er (erbium) in the range of 0.0 μm, Y (yttrium) doped with Er and Cr (chromium), Sc (scandium), Ga (gallium) ), Er, Cr: YSGG laser using Garnet crystal (light source wavelength: 2.78 to 2.79 μm), Cr using Y, Sc, Ga, Garnet crystal doped with Cr, Ho, Tm, Ho, Tm: YSGGG laser (light source wavelength: 2.09 μm).

For example, the semiconductor laser includes a semiconductor laser having a light source wavelength in the range of 0.8 to 1.0 μm.
Examples of the fiber laser include a Yb (ytterbium) fiber laser, a Tm fiber laser, a Ho fiber laser, and an Er fiber laser. Examples of the gas laser include a carbon monoxide laser (CO laser, light source wavelength 5 to 6 μm) and a carbon dioxide laser (CO ₂ laser, light source wavelength 9 to 11 μm).

As other lasers, a quantum cascade laser (light source wavelength: 4.7 μm, 5.7 μm) or a laser composed of an optical parametric resonator may be used.
When the strand material made of the thermoplastic resin composition is made of a non-fluorinated thermoplastic resin, a YAG laser doped with Ho, Tm, Er or the like having an oscillation wavelength in the range of 1.8 to 3.0 μm. A CO ₂ laser, a fiber laser, or the like can be preferably used.

Above all, when the material of the strands of a thermoplastic resin composition is polyethylene, it is preferred to use a CO ₂ laser.
When the strand material is made of a fluorine-based thermoplastic resin, a CO laser, Er
, Cr: YSGG laser can be used.

On the other hand, when the light source is an infrared heater, a xenon heater, a halogen heater, a carbon heater in which a carbon wire is sealed in a quartz tube, or the like can be used.
Two or more infrared rays emitted from these light sources are directed toward the strand using an optical system composed of a mirror, a half mirror, a spectroscope, an elliptical mirror, a lens, a prism, a mask, an optical fiber, a wavelength filter, and the like. By condensing from the direction, in the step Y, the strand of the thermoplastic resin can be stretched while being heated so that the viscosity of the central portion in the stretching direction is lower than the viscosity of the outer peripheral portion. This condensing is preferably performed such that the temperature distribution in the cross section of the strand passing through the condensing region (infrared condensing heating part) is close to the central axis symmetry.

  In order to make the temperature distribution of the cross section of the strands symmetrical about the central axis, the plurality of infrared beam shapes and spatial intensity distributions are made equal to each other around the central axis of the strand, and then toward the central axis of the strand. It is preferable to collect the infrared beam. For example, in consideration of simplification of the optical system, by collecting infrared beams having equal beam shapes, spatial intensity distributions, and angles formed by the beams from three directions toward the strands, around the central axis of the strand. A temperature distribution with high contrast can be formed.

The optical axis of the infrared beam may be inclined rather than perpendicular to the central axis of the strand, but is preferably perpendicular to the central axis, that is, within the cross section of the strand.
In the present invention, the infrared light source is a laser, and an infrared beam having the same beam shape, spatial intensity distribution, and the angle formed by the beams is condensed from three directions toward the central axis of the strand. Is shown in FIG.

  In FIG. 2, the laser beam emitted from the laser (B) is divided into four laser beams of the same intensity using three half mirrors (4a-c), one of which is a power meter ( C) and the intensity of the laser beam can be monitored. Further, the remaining three laser beams are condensed from the three directions of the plane perpendicular to the central axis of the strand (1) using the mirrors (5a to f). Further, the laser beam that has passed through the strand (1) made of the thermoplastic resin is absorbed using a beam stopper. In FIG. 2, the laser beam (10) passes through the central axis in the stretching direction of the strand (1), and the intersection of the laser beams (10) collected from three directions corresponds to the central axis in the stretching direction of the strand. To do.

  As the material of the strand made of the thermoplastic resin used in the present invention, polyolefin such as polyethylene, polypropylene, polybutene, poly-4methyl-1-pentene, ethylene-cyclic olefin copolymer, ethylene-acrylic acid copolymer, ethylene Polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyamides such as nylon 6, nylon 66, nylon 46, nylon 12, and MXD nylon, acrylic polymers such as polymethyl methacrylate, polyacrylic acid, polystyrene, polyacrylonitrile , Acrylonitrile-butadiene-styrene copolymer, vinyl chloride, polyvinylidene chloride, tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene Synthesis of polyfluoroethylene such as oloethylene / hexafluoropropene copolymer, ethylene / tetrafluoroethylene copolymer, halogen-containing polymer such as ethylene / chlorotrifluoroethylene copolymer, polyvinylidene fluoropolymer, polybutadiene, polyisoprene, etc. Examples thereof include rubber and its hydrogenated products, thermoplastic elastomers such as styrene-butadiene-styrene block copolymers and their hydrogenated products, liquid crystal polymers, polyurethane, polycarbonate, polysulfone, polyetheretherketone, polyimide, and the like.

  The thermoplastic resin may contain various known additives. Examples of the additive that may be contained in the thermoplastic resin include an infrared absorber, and specifically, a pigment such as carbon black, a near infrared absorbing dye such as phthalocyanine, and the like. Moreover, a plasticizer may be added to the thermoplastic resin having a high melt viscosity for the purpose of facilitating melt plasticization.

  In the present invention, the wavelength of the infrared light emitted from the light source can be appropriately determined according to the material of the thermoplastic resin. In the present invention, since heating is performed by infrared irradiation, the thermoplastic resin used needs to absorb infrared rays emitted from the light source. That is, the infrared light emitted from the light source needs to have an infrared wavelength that is absorbed by the thermoplastic resin.

  In addition, if the absorption coefficient of the thermoplastic resin with respect to the wavelength of the collected infrared light is too large, most of the infrared light is absorbed on the surface of the strand, and the vicinity of the center of the cross section of the strand is not sufficiently heated. In some cases, the viscosity of the central portion in the direction is not lower than the viscosity of the outer peripheral portion, and the resin hollow tube cannot be suitably manufactured.

In the step Y, when the light source for performing infrared irradiation is a laser and the condensed infrared light is monochromatic light, the absorption coefficient K (m ⁻¹ ) of the thermoplastic resin at the laser oscillation wavelength (monochromatic light). The diameter D (m) of the strand satisfies the relationship of the following formula (1), and the diameter D is preferably 0.5 × 10 ⁻³ m or more.

0.1 <K · D <2.6 (1)
Further, the diameter D of the strand is more preferably 1 × 10 ⁻³ m or more, and the upper limit thereof is preferably 10 × 10 ⁻³ m or less.

In the said range, a resin hollow tube can be manufactured suitably.
When the K · D value exceeds the upper limit, the viscosity of the outer periphery of the strand (surface viscosity) tends to be higher than the viscosity of the central portion in the strand drawing direction. For this reason, hollowing becomes difficult, and there may be a case where stretching is broken. On the other hand, when the K · D value is below the lower limit range, the viscosity at the center of the strand in the drawing direction becomes too higher than the viscosity (surface viscosity) at the outer periphery of the strand, and the drawing may be broken.

When the K · D value is within the above range, the viscosity of the central portion in the stretching direction of the strand is higher than the viscosity (surface viscosity) of the outer peripheral portion of the strand, and a viscosity condition enabling hollowing is obtained.
Further, in the step Y, even when a light source other than laser light is used as the light source, when monochromatic light is irradiated as infrared rays using a wavelength filter or the like, the above formula (1) is satisfied and the diameter D is preferably 0.5 × 10 ⁻³ m or more, and more preferably 1 × 10 ⁻³ m or more. The upper limit of D is preferably 10 × 10 ⁻³ m or less.

Furthermore, in the said process Y, it is preferable to extend | stretch, heating, so that the temperature of the center part of the extending | stretching direction of a strand may become higher than the temperature of an outer peripheral part.
When the above temperature condition is not satisfied, that is, when the temperature (surface temperature) of the outer periphery of the strand is higher than the temperature of the central portion in the strand drawing direction, hollowing becomes difficult and heat such as thermal decomposition occurs on the strand surface layer. Deterioration or stretching may occur.

In the present invention, the strand needs to be heated so that the viscosity of the central part in the stretching direction of the strand is lower than the viscosity of the outer peripheral part. Whether or not the heating conditions are lower than the viscosity of can be confirmed by the following preliminary test. Further, it can be confirmed by the same preliminary test that the temperature of the central portion in the stretching direction of the strand is heated so as to be higher than the temperature of the outer peripheral portion in the process Y.

  That is, when the strand is set in an apparatus having a heating and stretching means, and infrared rays are collected from a plurality of directions toward the strand in an unstretched state, the heat-affected zone is caused by heat generated by infrared absorption of the strand. Occurs. The presence or absence of the heat affected zone can be determined by confirming whether or not a birefringence change occurs before and after the infrared irradiation. Therefore, by examining whether the birefringence change in the center part of the strand is observed before the birefringence of the outer periphery part of the strand is changed by infrared irradiation, the viscosity of the central part in the stretching direction of the strand is more than the viscosity of the outer periphery part. It can be determined whether or not it has a heating characteristic that becomes low.

  Specifically, in the process of irradiating infrared rays toward the strand, the infrared intensity and the infrared irradiation time at which the outer periphery of the strand starts to melt are confirmed in advance. 2: Next, change in birefringence between the outer peripheral portion and the central portion before and after infrared irradiation is confirmed with the same infrared intensity and shorter infrared irradiation time. Here, as a means for examining the birefringence change at the outer periphery and the central portion of the strand, after stopping the infrared irradiation toward the strand and cooling, a cross-section sample perpendicular to the central axis of the strand is taken from the infrared irradiation portion of the strand. An example is to cut out with a uniform thickness using a microtome or the like, and to examine the birefringence distribution of the cross-section sample before and after infrared irradiation using a phase contrast microscope. 3: When the strand can be hollowed with the infrared intensity, that is, when the viscosity of the central portion of the strand in the drawing direction is lower than the viscosity of the outer peripheral portion, in the preliminary test, infrared irradiation is usually performed. Compared with before, it is possible to find an infrared irradiation time such that the birefringence of the central portion of the strand cross-section sample after infrared irradiation is lowered and the birefringence of the outer peripheral portion is not changed. On the other hand, when it is difficult to hollow the strand, in such a preliminary test, the birefringence of the outer periphery of the strand cross-section sample after infrared irradiation is more complex at the center than before infrared irradiation. Observed in a form that changes before refraction.

Examples of the phase contrast microscope that can be used for such a preliminary test include a polarizing microscope and a micro area birefringence meter (manufactured by Oji Scientific Instruments, KOBRA CCD).
Furthermore, when concentrating infrared rays on the strand, as an auxiliary means for keeping the viscosity of the central portion of the strand higher than the viscosity of the outer peripheral portion, the outer periphery of the strand is forcibly applied to the strand surface when heating is performed by infrared condensing. Cooling air such as cooling air lower than the section temperature may be blown. In addition, before the infrared rays are collected, between the strand supply unit and the infrared ray condensing heating unit, the strands are once passed through a heating furnace such as a hot air furnace or a hot plate furnace, and the strands are sufficiently heated to the center. In addition, the strand may be passed through a refrigerant tank such as a water tank or a cold air tank in advance, and the strand is kept in a solid state at a higher center temperature than the outer peripheral portion and then passed through the infrared condensing heating unit. .

In the production method of the present invention, the strand made of the thermoplastic resin supplied from the strand supply section usually has a circular cross section defined by a plane perpendicular to the central axis in the stretching direction of the strand. Although preferred, it may have a modified cross section. Moreover, when extending | stretching a strand between a supply part and a taking-up part, it is preferable that a central axis does not meander along the extending | stretching direction, but becomes linear. In addition, the central axis of a strand means the central axis along the extending direction of a strand.
Further, the diameter of the cross section is 0.5 to 10 mm, preferably 1.0 to 3.0 mm in the case of polyethylene. Within the said range, a resin hollow tube can be manufactured suitably.

  Further, in the present invention, before the step Y, a step X is provided in which a strand made of a thermoplastic resin is drawn while being heated so as to be in a fluid drawing state, and the heating and / or drawing conditions in the step X are changed. Therefore, it is preferable to change to the step Y performed by decreasing the amount of infrared heat input to the strand and increasing the take-up tension. It is preferable to provide the step X before the step Y because it is possible to suppress strand stretching and uneven stretching and to form a stable stretched state.

  Further, in the present invention, when the strand supply speed in the step X is Vf1, the light collection intensity is I1, and the take-up speed is Vt1, the strand supply speed in the process Y is Vf1, the light collection intensity is I1, and the take-up speed is It is preferable that the take-up speed Vt2 is faster than Vt1.

  In the production method of the present invention, when changing from the step X to the step Y, the method for changing the light collecting intensity by changing the heating conditions, the supply rate and the take-up rate are adjusted, the drawing conditions are changed, and the drawing rate is changed. There is a method of changing the heating condition and the drawing condition, but as described above, the strand supply speed Vf1 and the light collecting intensity I1 are made constant in the process X and the process Y, and the take-up speed is set to the process X. It is preferable to change from Vt1 to Vt2 in step Y (however, Vt2 is faster than Vt1). Thus, when the take-up speeds (Vt1, Vt2) are adjusted without changing the strand supply speed Vf1 and the light collecting intensity I1, it is easy to manage the operating conditions of the heating and stretching apparatus.

  Furthermore, in the manufacturing method of this invention, it is preferable to pass through the process W whose condensing intensity is weaker than the process X before the said process X. That is, it is preferable to perform the process Y by performing the process W, increasing the condensing intensity of the process W, performing the process X, and further changing the heating and / or stretching conditions of the process X.

By passing through the process W before the process X, in the process of forming the state of the process X, an unstable stretching state such as stretching breakage and stretching unevenness can be suppressed, and a stable stretching state can be created.
When the strand supply speed of process X is Vf1, the light collection intensity is I1, and the take-up speed is Vt1, the supply speed of process W is usually Vf1 and the take-up speed Vt1, and the light collection intensity is I0 which is weaker than I1. is there. In the production method of the present invention, as an aspect having the above-described Step W, Step X and Step Y, for example, an infrared ray including the absorption wavelength of the thermoplastic resin is directed to the strand with respect to the strand made of the thermoplastic resin. By collecting light from a plurality of directions at a light collecting intensity I0, heating is performed under the condition that the viscosity of the central portion of the strand in the drawing direction is lower than the viscosity of the outer peripheral portion, while the supply speed Vf1 and the take-up speed Vt1. Stretching (process W) and condensing infrared rays with a condensing intensity I1 larger than the condensing intensity I0 to form a fluid stretched state (process X), and then changing the take-up speed to Vt2 faster than Vt1 Thus, by reducing the amount of infrared heat input to the strand and increasing the take-up tension, the hollow portion is continuously formed in the stretching direction of the strand. It is preferable to produce the resin hollow tube by (step Y).

  It is preferable that the intensity ratio of the light collection intensity I0 and the light collection intensity I1 (light collection intensity I0: light collection intensity I1) is 1: 1.2 to 1: 3, and 1: 1.5 to 1: 2. .5 is more preferable.

  Further, the rate of change when changing from the condensing intensity I0 to the condensing intensity I1 is usually 0.5 to 1.5% / s, preferably 0.6 to 0.8% / s. Note that the rate of change is defined as ((condensation intensity I1−condensation intensity I0) / condensation intensity I0 / (time [s] required for the change in the concentration of condensing) × 100%). Is changed from 0.8 W to 1.5 W in 140 seconds, (1.5 W−0.8 W) /0.8 W / 140 s × 100% = 0.6% / s.

Furthermore, in the process Y, it is preferable to extend | stretch on the conditions which exceed 1 and satisfy | fill less than 30 as a range of draw ratio (Vt / Vf), More preferably, it exceeds 5 and is less than 25 conditions.
The reason why the resin hollow tube can be obtained by the method for producing a resin hollow tube of the present invention is not clear, but the present inventors estimated as follows.

That is, in the present invention, infrared rays are collected from a plurality of directions toward the strands, but the strands made of thermoplastic resin pass through the light collection region, so that the vicinity of the central axis of the strands in the light collection region ( The viscosity of the center portion is lower than that near the outer surface (outer peripheral portion). By stretching in this state, the resin in the vicinity of the central axis having a low viscosity is pulled toward the outer surface side having a high viscosity, and a tear is formed on the strand surface, and at the same time, a hole is opened in the vicinity of the central axis of the strand. Immediately thereafter, the tear on the strand surface is closed, and a continuous cavity is formed from around the central axis. For the reasons described above, the inventors estimated that a resin hollow tube having a continuous hollow portion can be obtained by the production method of the present invention.

Moreover, in the manufacturing method of this invention, the present inventors estimated the reason why it is preferable to provide the process X as follows.
By passing the strand made of the thermoplastic resin through the light collecting region, the viscosity in the vicinity of the central axis of the strand in the collecting region becomes lower than that of the outer surface. First, the supply speed Vf1, the take-up speed Vt1, and the light collecting intensity I1 are changed to the flow-drawn state, and then the heating and / or drawing conditions are changed to reduce the amount of infrared heat input to the strand and increase the take-up tension. In this case, preferably, the resin in the vicinity of the central axis having a low viscosity is pulled toward the outer surface side having a high viscosity, and a tear is formed on the strand surface, and at the same time, a hole is formed in the vicinity of the central axis of the strand. Immediately thereafter, the tear on the strand surface is closed, and a continuous cavity is formed from around the central axis. For the reasons described above, the inventors estimated that a resin hollow tube having a continuous hollow portion can be obtained by the production method of the present invention.

Since the production method of the present invention does not depend on an extrusion method at the time of hollowing, various disadvantages in the case of producing a resin hollow tube by a conventional extrusion method can be solved.
Moreover, the resin hollow tube obtained by the said manufacturing method is excellent in the surface smoothness of the inner wall of a resin hollow tube normally.

Since the resin hollow tube is excellent in surface smoothness of the inner wall, it can be used as, for example, a medical tube, a resin hollow tube for forming an optical fiber clad material or a core material, and a hollow fiber.
〔Example〕
EXAMPLES Next, although an Example is shown and this invention is demonstrated further in detail, this invention is not limited by these.

(Production of strands made of thermoplastic resin)
High density polyethylene (weight average molecular weight 150,000, JIS K as thermoplastic resin)
190 ° C. measured according to 7210, melt flow rate 0.33 g / 10 min with a load of 2.16 kgf, melting point 134 ° C., absorption coefficient 6.5 × 10 ² m ^{−1 at} carbon dioxide laser oscillation wavelength 10.6 μm) The polyethylene is melt-extruded by a nozzle (inner diameter 2).
mm, land length 10 mm), and melt extrusion was performed at an extrusion temperature of 155 ° C. to obtain an unstretched strand having a diameter of 2.5 mm.

(Laser heating drawing device)
The laser heating and stretching apparatus used for the production of the resin hollow tube has the configuration shown in FIG. 1, and the infrared condensing and heating unit has the configuration shown in FIG.

In addition, in an Example, A of FIG. 1 is a sending roller which can control the supply speed Vf of the unstretched strand with a diameter of 2.5 mm.
In the infrared condensing and heating unit used in the examples, the light source is a laser oscillator [carbon dioxide laser PIN-30S (laser wavelength (oscillation wavelength) 10.6 μm, rated output 30 W, irradiation spot diameter 6 mm) manufactured by Onitsuka Glass Co., Ltd.]. 2 has an optical system shown in FIG. 2 for irradiating a laser beam from three directions. The laser irradiation power density has a Gaussian distribution symmetrical about the optical axis, and the irradiation spot diameter has a radius at a position where the irradiation power density becomes e ^{−2 of the} laser optical axis. Note that e is the base of the natural logarithm.

Further, the laser heating and stretching apparatus used in the examples has a take-up roller for controlling the take-up speed Vt and take-up tension T of the strand.
The laser heating and stretching apparatus used in the present invention feeds an unstretched strand having a diameter of 2.5 mm from a delivery roller and takes it out by a take-up roller, during which the laser beam is condensed from three directions toward the central axis of the strand. An infrared condensing heating unit.

(Manufacture of resin hollow tubes)
The strand made of the thermoplastic resin is sent out from the feed roller of the laser heating drawing apparatus at a supply speed Vf1 (0.06 m / min), taken up at a take-up speed Vt1 (0.17 m / min) by a take-up roller, and a draw ratio. A stretched state was formed at (Vt1 / Vf1) 2.8 times. The laser output at this time was 0.8 W per direction (total I0 = 0.8 × 3 = 2.4 W).

  Next, while maintaining the stretched state, the laser output was increased at a rate of change of 0.6% / s and changed to 1.5 W per direction (total I1 = 1.5 × 3 = 4.5 W). A stretched state was formed. The time required for changing the laser output was 140 seconds. The take-up tension T1 at this time was (5N).

  Next, while the supply speed Vf is kept at Vf1 (= Vf2) and the laser output total I is kept at I1 (= I2), the take-up speed Vt is changed from the take-up speed Vt1 (0.17 m / min) to the take-up speed Vt2 (1.02 m). ) To increase the take-up tension T from the take-up tension T1 (5N) to the take-up tension T2 (12N), thereby reducing the infrared heat input of the strand and increasing the take-up tension.

  Along with this, a tear is temporarily generated in the vicinity of the take-up roll side of the laser irradiation portion (infrared ray condensing heating portion) of the strand made of thermoplastic resin, and then the tear is quickly closed and the outer peripheral surface is closed. Empty tubes were formed continuously and stably.

(Properties of resin hollow tube)
The obtained resin hollow tube had an outer diameter of 1.2 mm and an inner diameter of 0.98 mm.
The obtained resin hollow tube was cut out obliquely, and the inner wall of the hollow tube was coated with osmium, and then using a scanning electron microscope (Hitachi: S-4700), an acceleration voltage of 5 kV, a magnification of 250 times, and 10, The inner wall of the resin hollow tube was observed at a magnification of 000. The results are shown in FIGS. The resin hollow tube of the present invention had a smooth surface with no flow direction streaks observed.

(Manufacture of resin hollow tubes)
It was carried out using a strand made of the same thermoplastic resin as in Example 1 and a laser heating stretching apparatus.

  In Example 1, the take-up speed Vt is from the take-up speed Vt1 (0.17 m / min) to the take-up speed Vt2 (1.02 m / min), and the take-up tension T is from the take-up tension T1 (5N) to the take-up tension T2 (12N). In Example 2, stretching was performed by reducing the amount of infrared heat input from the fluid stretching state and increasing the take-up tension. In Example 2, the take-up speed Vt1 (0.17 m / min) was changed to the take-up speed Vt2 (1.25 m / min). Min) and by changing the take-up tension T1 (5N) to the take-up tension T2 (14N), the amount of infrared heat input was reduced from the flow-stretched state, and the take-up tension was increased to perform stretching.

The rest was performed in the same manner as in Example 1 to produce a resin hollow tube.
(Properties of resin hollow tube)
The obtained resin hollow tube had an outer diameter of 1.1 mm and an inner diameter of 0.93 mm.

(Manufacture of resin hollow tubes)
It was carried out using a strand made of the same thermoplastic resin as in Example 1 and a laser heating stretching apparatus.

  In Example 1, the take-up speed Vt is from the take-up speed Vt1 (0.17 m / min) to the take-up speed Vt2 (1.02 m / min), and the take-up tension T is from the take-up tension T1 (5N) to the take-up tension T2 (12N). In the example 3, the drawing speed Vt1 (0.17 m / min) was changed from the drawing speed Vt2 (1.53 m / min). Min), and by changing from the take-up tension T1 (5N) to the take-up tension T2 (15N), the amount of infrared heat input was reduced from the flow-stretched state, and the take-up tension was increased to perform stretching.

The rest was performed in the same manner as in Example 1 to produce a resin hollow tube.
(Properties of resin hollow tube)
The obtained resin hollow tube had an outer diameter of 1.1 mm and an inner diameter of 0.90 mm.

(Production of strands made of thermoplastic resin)
High density polyethylene (weight average molecular weight 150,000, JIS K as thermoplastic resin)
190 ° C. measured according to 7210, melt flow rate 0.33 g / 10 min with a load of 2.16 kgf, melting point 134 ° C., absorption coefficient 6.5 × 10 ² m ^{−1 at} carbon dioxide laser oscillation wavelength 10.6 μm) The polyethylene is melt-extruded by a nozzle (inner diameter 2).
mm, land length 10 mm), and melt extrusion was performed at an extrusion temperature of 155 ° C. to obtain an unstretched strand having a diameter of 1.5 mm.

(Manufacture of resin hollow tubes)
The same laser heating and stretching apparatus as in Example 1 was used.
In Example 1, the strand diameter was 2.5 mm, the initial laser output was 0.8 W per direction (total I0 = 0.8 × 3 = 2.4 W), and the laser output was increased while maintaining the stretched state. The direction of flow stretching was changed to 1.5 W per direction (total I1 = 1.5 × 3 = 4.5 W). Thereafter, the supply speed Vf is Vf1 = Vf2 (0.06 m / min), the take-up speed Vt is from the take-up speed Vt1 (0.17 m / min) to the take-up speed Vt2 (1.02 m / min), and the take-up tension T is By changing the take-up tension T1 (5N) to the take-up tension T2 (12N), the amount of infrared heat input was reduced from the flow-stretched state and the take-up tension was increased. The initial laser output is 0.8 W per direction (total I0 = 0.8 × 3 = 2.4 W) and the laser output is increased while maintaining the stretched state, and 1.3 W per direction. (Total I1 = 1.3 × 3 = 3.9 W) was changed to form a fluid stretched state. Thereafter, the supply speed Vf is Vf1 = Vf2 (0.12 m / min), the take-up speed Vt is the take-up speed Vt1 (0.36 m / min) to the take-up speed Vt2 (2.26 m / min), and the take-up tension T is By changing the take-up tension T1 (3N) to the take-up tension T2 (12N), the amount of infrared heat input was lowered from the flow-stretched state, and the take-up tension was increased to perform stretching. The rest was performed in the same manner as in Example 1 to produce a resin hollow tube.

(Properties of resin hollow tube)
The obtained resin hollow tube had an outer diameter of 0.7 mm and an inner diameter of 0.4 mm.
[Comparative Example 1]
(Manufacture of resin hollow tubes)
High density polyethylene (weight average molecular weight 150,000, JIS K as thermoplastic resin)
Resin hollow by melt extrusion using an extruder equipped with a hollow die using 190 ° C measured in accordance with 7210, melt flow rate 0.33 g / 10 min with a load of 2.16 kgf, melting point 134 ° C) A tube was made. The annular part size corresponding to the molten resin outlet of the hollow die was 4 mm in outer diameter and 3 mm in inner diameter.

The extrusion temperature was 155 ° C., the extrusion flow rate was 1.57 cm ³ / min, and the hollow tube drawing speed was 3.0 m / min.
(Properties of resin hollow tube)
The obtained resin hollow tube had an outer diameter of 1.2 mm and an inner diameter of 0.92 mm.

  The inner wall of the resin hollow tube was observed in the same manner as in Example 1. The results are shown in FIGS. Many stripes in the flow direction were observed at a magnification of 250 times. Further, the surface was rough even at a magnification of 10,000 times.

[Comparative Example 2]
(Manufacture of resin hollow tubes)
A resin hollow tube was produced in the same manner as in Comparative Example 1 except that the extrusion temperature was 170 ° C. and the take-up speed was 3.6 m / min.

(Properties of resin hollow tube)
The obtained resin hollow tube had an outer diameter of 1.1 mm and an inner diameter of 0.84 mm.
The inner wall of the resin hollow tube was observed in the same manner as in Example 1. The results are shown in FIGS. Many stripes in the flow direction were observed at a magnification of 250 times. Further, the surface was rough even at a magnification of 10,000 times.

  Table 1 shows the production conditions of the examples and the dimensions of the obtained resin hollow tubes.

As described above, the method for producing a hollow resin tube of the present invention does not have the disadvantages derived from the conventional extrusion method. The obtained resin hollow tube is usually excellent in the surface smoothness of the inner wall of the hollow tube, and can be used as, for example, a medical tube, a resin hollow tube for forming an optical fiber clad material or a core material.

It is the schematic which shows one embodiment of the method of manufacturing the resin hollow tube of this invention. It is the schematic which shows one structural aspect of the infrared condensing heating part of the laser heating extending | stretching apparatus used for this invention. It is a photograph which shows the result of 250-times multiplication factor when the inner wall of the resin hollow tube obtained in Example 1 was observed. It is a photograph which shows the result of magnification 10,000 times when the inner wall of the resin hollow tube obtained in Example 1 was observed. It is a photograph which shows the result of 250 times the magnification at the time of observing the inner wall of the resin hollow tube obtained in Comparative Example 1. It is a photograph which shows the result of the magnification 10,000 times when the inner wall of the resin hollow tube obtained in Comparative Example 1 is observed. It is a photograph which shows the result of 250 times the magnification at the time of observing the inner wall of the resin hollow tube obtained in Comparative Example 2. It is a photograph which shows the result of the magnification 10,000 times when the inner wall of the resin hollow tube obtained in Comparative Example 2 is observed.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Strand consisting of thermoplastic resin 2 ... Infrared condensing heating part 3 ... Taking-up part 4a ... Half mirror 4b ... Half mirror 4c ... Half mirror 5a ... Mirror 5b ... Mirror 5c ... Mirror 5d ... Mirror 5e ... Mirror 5f ... Mirror 6a ... Beam stopper 6b ... Beam stopper 6c ... Beam stopper 10 ... Laser beam A ..Strand supply unit B ... Laser oscillator C ... Power meter

Claims (6)

In a heating and stretching apparatus having a strand supply unit, a take-up unit, and an infrared condensing heating unit arranged between the supply unit and the take-up unit,
By concentrating infrared rays including wavelengths absorbed by the thermoplastic resin from a plurality of directions toward the strand, the viscosity of the central portion in the stretching direction of the strand is reduced in the outer peripheral portion. By stretching while heating to be lower than the viscosity,
The manufacturing method of the resin hollow tube which has the process Y which forms a hollow part continuously in the extending | stretching direction of this strand.   The method for producing a hollow resin tube according to claim 1, wherein in the step Y, the resin hollow tube is stretched while being heated so that the temperature of the central portion in the stretching direction of the strand is higher than the temperature of the outer peripheral portion. A step X of stretching a strand made of a thermoplastic resin while heating so as to be in a fluid stretch state;
The step Y is performed by changing the heating and / or stretching conditions of the step X to reduce the amount of infrared heat input to the strand and increasing the take-up tension. 3. A method for producing a hollow resin tube according to 1 or 2. In the step Y, the infrared rays are monochromatic light, and the absorption coefficient K (m ⁻¹ ) of the thermoplastic resin in the monochromatic light and the diameter D (m) of the strand before heating are expressed by the following formula ( The method for producing a hollow resin tube according to claim 1, wherein the relationship of 1) is satisfied and the diameter D is 0.5 × 10 ⁻³ m or more.
0.1 <K · D <2.6 (1) When the strand supply speed in Step X is Vf1, the light collecting intensity is I1, and the take-up speed is Vt1,
The method for producing a resin hollow tube according to claim 3 or 4, wherein the strand supply speed in step Y is Vf1, the light collecting intensity is I1, and the take-up speed is Vt2 higher than Vt1. The infrared rays are infrared rays emitted from a carbon dioxide laser;
The method for producing a resin hollow tube according to any one of claims 1 to 5, wherein a material of the strand made of the thermoplastic resin is polyethylene.