JP3840610B2 - Processing method and continuous processing equipment for plastic tube inner surface - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an inner surface treatment method for a plastic tube, in particular to prevent elution of the additives added to the plastic tube, particularly harmless to the human body, it also relates to an inner surface treatment how friendly plastic tube to the environment.
[0002]
[Prior art]
Currently, medical plastic tubes are used in various medical fields including infusion tubes for infusion, blood collection tubes, dialysis tubes, and the like. There are many types of materials, from various and expensive fluororesin-based materials to inexpensive vinyl chloride-based materials. In particular, vinyl chloride-based materials are easy to mold and inexpensive, so they are common as disposable medical devices, but measures against environmental hormones that have been a problem for several years are extremely important. Furthermore, how to stop the elution of the plasticizer is a big problem for soft vinyl chloride. The infusion tube for infusion, the tube for blood collection, especially the tube for dialysis are dialyzed at about 40 ° C., which is considerably higher than the body temperature in consideration of natural cooling.
Other plastic tube materials include urethane resins, liquid crystal polymers, and polyolefin resins such as polyethylene and polypropylene. These plastics include, for example, antioxidants, UV absorbers, flameproofing agents, and light stability. It contains many chemical substances such as chemicals, some of which have adverse effects on the environment and are also harmful to the human body.
Therefore, there has been a demand for a technique that can be applied with good workability at low cost to the inner surface treatment of tubes used not only for medical purposes but also for all purposes.
[0003]
[Problems to be solved by the invention]
The present inventors have and no effect on the human body for a variety of plastic tube including the plastic tube for these medical result of various studies about the process how friendly tube inner surface to the environment, and completed the present invention, the It is an object of the invention to provide a method for treating the inner surface of a plastic tube that does not affect the human body without the elution of additives from the inner surface of the plastic tube.
[0004]
[Means for Solving the Problems]
The gist of the present invention is to apply an alkoxysilane compound on the inner surface of a plastic tube, replace the air inside the tube with helium or a mixed gas of helium and argon, and excite plasma by atmospheric pressure glow discharge to form a silica thin film. a processing method for a plastic tube surface, characterized in that allowed to, as an apparatus for use in this treatment method, wrapped two fine copper pipe at intervals greater than the outer diameter of the tube a quartz glass tube, which electrodes The air in the plastic tube placed in the quartz glass tube is replaced with helium or a mixed gas of helium and argon, and a high frequency voltage is applied to the electrode while flowing the gas to generate glow discharge in the plastic tube to excite the plasma. inner surface processing apparatus according to an atmospheric pressure glow discharge process the tube inner surface allowed It is preferred.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described in detail.
The plastic tube to be treated in the present invention is a commonly used plastic tube having an inner diameter of about 3 to 15 mm, and is particularly preferable for treating the inner surface of a medical tube.
In the present invention, plasma is excited by atmospheric pressure glow discharge. Usually, plasma treatment is performed by glow discharge in a vacuum or induction heating with a high frequency of 13.56 MHz. However, it is impossible to perform a plasma treatment only inside the tube in a vacuum, especially for soft plastics. In some cases, if only the inside is evacuated, it will collapse.
The present invention is an application of the fact that a plasma is excited when a high frequency voltage is applied to helium or a mixed gas of helium and argon gas under atmospheric pressure. Only the inner surface can be plasma treated.
[0006]
As described above, the apparatus for performing the plasma treatment on the inner surface of the plastic tube by the atmospheric pressure glow discharge can be carried out continuously with the apparatus as shown in FIG. It is not limited to.
An experimental example of plasma processing by atmospheric pressure glow discharge according to the present invention will be described with reference to FIG. In this experiment, a quartz glass tube having a length of 1000 mm, a diameter (outer diameter) of 9 mm, and an inner diameter of 6 mm is used as the reaction tube 1. The electrode 2 was made of a copper tube having an inner diameter of 3 mm. The copper tube electrode was a ground electrode 2a and a high voltage electrode 2b, and the distance between them was set to 11 mm, which was larger than the outer diameter of the reaction tube. This is to prevent the spark discharge or creeping discharge from occurring between the copper tubes and stop the glow discharge. One end of both electrodes is the electrode connection portion, and the other end is shown in FIG. As shown, slightly shorten and round the tip with solder to prevent tip discharge.
When the frequency of the high frequency is increased, the temperature of the copper tube electrode is increased. In such a case, it is necessary to take a method of passing water without soldering so that water can flow and cool in the copper tube electrode.
[0007]
The principle diagram of this discharge is shown in FIG. FIG. 2 is a cut surface perpendicular to the quartz glass tube (reaction tube 1). Thus, the copper tube electrodes 2a and 2b are in a state in which both electrodes are parallel electrodes on all surfaces of the quartz glass tube 1. When a high frequency voltage is applied to the copper tube electrode 2 while replacing the air inside the quartz glass tube with helium or a mixed gas of helium and argon gas, glow discharge occurs between the copper tube electrodes 2 facing each other as shown in FIG. appear. This is because quartz is filled with glow discharge in the entire lath tube, and a plastic tube is inserted into the quartz glass tube 1 and the air in the tube is replaced as described above. Is applied, glow discharge is generated in the same manner inside the tube.
[0008]
The above is an explanation of the important plasma generation of the present invention. In the present invention, a silica film is formed on the inner surface of a plastic tube by plasma treatment.
Next, silica film formation will be described. A common silane compound that can be used in the present invention is an alkoxysilane compound. Specifically, the alkoxysilane compound is at least one selected from the group consisting of tetramethoxysilane, trimethoxysilane, tetraethoxysilane, triethoxysilane, tetrapropoxysilane, tripropoxysilane, tetrabutoxysilane, and tributoxysilane. A particularly preferred alkoxysilane compound is tetraethoxysilane, also known as ethyl silicate, and is a compound. This is a colorless liquid having a boiling point of about 140 ° C., but upon hydrolysis, ethyl alcohol is liberated to silica, that is, SiO ₂ .
[0009]
Experimental Example Next, an experimental example of forming a silica coating inside the tube is shown. A soft vinyl chloride having a diameter of 5 mm, an inner diameter of 3 mm and a length of 1 m is used. First, a normal liquid detergent is poured into the tube, followed by washing with fresh water and drying. To dry, warm air can be passed through the tube. Next, if ethyl silicate is mixed with petroleum ether in a ratio of 10:10, the viscosity is lowered to a smooth liquid. However, the concentration is 50%. Since this liquid does not contain any water, it flows into the tube and wets the inner wall uniformly. Although this tube has not yet completely evaporated the petroleum ether, it is put into a quartz glass tube and helium gas that does not dehydrate is allowed to flow from one side of the tube. Since petroleum ether evaporates in an instant, if a high frequency voltage is immediately applied to the electrode connection, all of the tube becomes pink with a power of 1.3 MHz 2000 V 20 W and glow discharge is generated. A film formation that was not sticky at all when energized for 15 seconds was observed.
[0010]
The solvent used to lower the viscosity of the silane compound used here and to form a uniform film with a low boiling point is a non-aqueous aliphatic hydrocarbon that does not mix with water at all. Examples include petroleum ether, petroleum benzine, N heptane, and N hexane used.
Of course, to increase the thickness of the coating, the amount of the solvent mixed may be reduced, and in some cases, the inside may be wetted with only the silane compound without using the solvent.
However, if it is not used after making sure that there are no water droplets or moisture inside, powder will be formed or uneven film formation will occur.
[0011]
The high frequency power supply is not particularly specified. In this experiment, the vibration part of the induction coil was removed to make a normal AC high-voltage transformer, and the primary coil was wound with 3 mm aluminum wire 5 times at 7 mm intervals, and 1 mm enameled wire was wound 2000 times with air at the center. If spark discharge occurs in the gap, the LC oscillation circuit generates a high frequency of 1.3 megahertz, which was used. The frequency was specified with an oscilloscope. As a high-frequency power source, there are an inverter system that generates a high frequency by a switching circuit and a normal VFO system that multiplies from a crystal oscillation, in addition to a combination of this spark discharge and an LC circuit, both of which can be used.
As for the frequency of the high frequency, if it is 1 kHz or more, it can be used up to 13.56 MHz, which is generally used for industrial purposes, such as long wave, medium wave, short wave, ultra short wave, but in the case of radio wave, it is completely so that the radio wave does not go out to the outside at all. A strong shield is required. In particular, those that gel with a plasticizer and paste resin such as soft vinyl chloride and polyethylene, and those that are molded at low temperatures, are vulnerable to heat, so they must be kept low in frequency or dissolved and decomposed unless the voltage is reduced and the power is reduced with low power. In addition, since the plasticizer is evaporated, the frequency range is 10 kHz to 100 kHz, and 100 kHz to 2 MHz is preferable for processing with low power (50 W or less).
Also, use inert gas such as helium or a mixed gas of helium and argon that is used as the plasma excitation gas in this patent, or do not dehydrate it, and do not saturate it with water in the washing bottle. What is necessary is just to include the water | moisture content of the grade which passes.
[0012]
FIG. 3 shows an overall view of an apparatus that continuously performs this process. Normally, plastic medical tubes such as vinyl chloride, which is an object to be processed, are commercially available with a length of about 20 m, and it is the most efficient processing method to process them continuously.
FIG. 4 shows an enlarged view of the tube connecting portion of the tube inner surface continuous processing apparatus of the present invention. In FIG. 4, each of the winding portion 3 and the unwinding portion 4 has a sliding connection portion 5 for flowing a mixed gas of helium or helium argon, and a tube connecting portion 6 is provided at the central axis of the unwinding portion 4. It is provided. Since each of the winding center 3 and the unwinding portion 4 has a double gas inlet or outlet sliding center, even if it is rotated, it is connected at the sliding portion so that the gas flows in at all Can be discharged.
The tube is preliminarily coated with a silane compound to evaporate petroleum ether as a solvent while flowing gas. Next, simultaneously with the application of the high frequency voltage, the winding portion is wound in the direction of the arrow. As already mentioned, it takes 15 seconds to process 1m, so at the beginning of winding, it is energized for 15 seconds and then winding starts, and if the speed is moved 1m in 15 seconds good.
[0013]
The inner surface of the vinyl chloride tube was treated using this device, and the conditions were as follows.
The gas used is helium 80 capacity part argon 20 capacity part high frequency 1.3 kHz voltage 2000V power 20W
The inside of a 10 m vinyl chloride tube was treated beforehand with a 50% petroleum ether solution of ethyl silicate, and the entire inner surface was wetted with the above solution.
Thereafter, a silica film was formed, and a part of the film was cut to measure the film thickness. The film thickness was measured from the weight before and after the treatment of vinyl chloride having a diameter of 5 mm.
A tube length of 20 mm of vinyl chloride before treatment is accurately cut with a cutter, and this is used as an untreated sample. Next, 20 mm of the tube on which the silica film was formed by the above test was accurately cut out and used as a treated sample.
The weight was 0.2268 g for the untreated sample and 0.2372 g for the treated sample.
Then results of untreated samples was measured the area making rectangular cut vertically, 16 mm × 20 mm = the 320 mm ² in the specific gravity of the silicic anhydride to measure the thickness from 2.6 weight difference 0.0104g So this The film thickness is calculated to be 12 μm. This silica film has no migration of plasticizer, and is characterized by the fact that the inorganic film is formed so that no sticking occurs when pressure is applied with a soft vinyl chloride tube held between fingers. Moreover, the adhesion of the formed film was very good, and peeling did not occur at all in the peel test using cello tape (registered trademark).
[0014]
Next, a method of processing the inner surface using the plastic tube itself as a processing object as a dielectric will be described with reference to FIG.
FIG. 5a shows a method of making an air core electrode used in this method. Two copper pipes with an outer diameter of about 4 mm and an inner diameter of about 3 mm are spirally wound around a metal pipe or rod having a diameter of 10 mm, the outer periphery is sandwiched between insulators 8, and then the metal pipe or rod 7 is attached. When extracted, a spiral copper pipe is obtained, which is used as a high voltage electrode and a low voltage electrode (see FIG. B). Thereafter, a plastic tube 9 as an object to be processed is inserted into the center portion of the air core electrode, and the air in the tube is replaced with helium or a mixed gas of helium and argon through the plastic tube through a mixed gas of helium or helium and argon. (See Fig. C). If a high frequency voltage is applied to the air core electrode in this state, the plastic tube of the object to be processed becomes a dielectric, and there is no quartz glass tube as the reaction tube shown in the previous example, so glow discharge is generated at an extremely low voltage. Occurs, and the inside of the plastic tube can be processed. In this case, a thick plastic tube can be processed regardless of the diameter of the quartz glass tube as the reaction tube. However, in this state without a quartz glass tube, if the frequency of the high frequency is high, plastic tubes that are vulnerable to heat may melt, so tubes made of materials such as polyethylene and vinyl chloride that are not heat resistant are particularly When the treatment is performed at a low frequency of 1 kHz to 5 kHz, the plastic tube is not melted by heat and the inner surface treatment is possible.
[0015]
【Example】
EXAMPLES Next, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.
Example 1
An inner surface treatment was performed on a urethane soft tube having a diameter of 5 mm according to the conditions of the experimental example.
That is, as shown in FIG. 1, a quartz glass tube having a length of 1000 mm, a diameter (outer diameter) of 9 mm, and an inner diameter of 6 mm was used as the reaction tube 1. The electrode 2 was made of a copper tube having an inner diameter of 3 mm. The copper tube electrode was a ground electrode 2a and a high voltage electrode 2b, and the distance between them was set to 11 mm, which was larger than the outer diameter of the reaction tube. One end of both electrodes was used as an electrode connection portion, and the other end was slightly shortened and rounded with solder to prevent tip discharge, as shown in FIG. A vertical cut surface with respect to the quartz glass tube (reaction tube 1) is shown in FIG. The copper tube electrodes 2a and 2b are in a state in which both electrodes are parallel electrodes on all surfaces of the quartz glass tube 1, and the copper tube is replaced while replacing the air inside the quartz glass tube with helium or a mixed gas of helium and argon gas. When a high frequency voltage is applied to the electrodes 2, glow discharge is generated between the opposing copper tube electrodes 2 as shown in FIG. This is because all the inside of the quartz glass tube is filled with glow discharge, so a plastic tube is put in this quartz glass tube 1 and the air in the tube is replaced as described above, so that a high frequency voltage is applied to the electrode. When G was applied, glow discharge was generated in the same manner inside the tube.
Next, a plastic tube made of soft vinyl chloride having a diameter of 5 mm, an inner diameter of 3 mm, and a length of 1 m was used. First, a normal liquid detergent was poured into the tube, and the tube was washed thoroughly with fresh water and dried. In the experimental example, a solution in which ethyl silicate was mixed with petroleum ether in a ratio of 10:10 was used. However, in Example 1, a 50% petroleum ether solution of tetramethoxysilane was used instead of ethyl silicate, and the other examples were completely experimental examples. As well as. That is, a high frequency voltage was applied to the electrode connection portion. With a frequency of 1.3 MHz, a voltage of 2000 V, and a power of 20 W, everything in the tube became pink and glow discharge was generated, and energized for 15 seconds . As a result, formation of a silica coating was observed.
[0016]
Example 2
Using the apparatus in which the soft vinyl chloride tube having a diameter of 5 mm was used in Example 1, the inner surface was processed according to the conditions of the experimental example. However, helium alone was used as the inert gas, and a 50% N-hexane solution of ethyl silicate (tetraethoxysilane) was used as the silane compound. The frequency of the high-frequency power source was 1.3 MHz, but in the case of helium, glow discharge was generated at a lower voltage of 1800 V, and a silica coating was formed in exactly the same manner.
[0017]
Example 3
Using the apparatus in which the soft polyethylene tube having a diameter of 5 mm was used in Example 1, the inner surface was treated in exactly the same manner as in the experimental example. As a result, a silica film was formed.
Example 4
The inner surface of a 9 mm diameter vinyl chloride tube is wetted with a 50% petroleum ether solution of ethyl silicate, and is inserted into the air core electrode shown in FIG . When a high frequency voltage of 5 kHz was applied, a glow discharge was generated at a low voltage of 2000 V or less, but a silica film was formed in the same manner.
[0018]
【The invention's effect】
As described above, the present invention hydrolyzes the inner surface of a tube coated with a silane compound with atmospheric pressure glow discharge plasma, forms a thin film of silica on the inner surface of the tube, and forms a coating of an inorganic material in the tube including a plasticizer. The elution of the additive can be prevented, and as a result, a medical tube that is inexpensive and harmless to the human body can be provided.
[Brief description of the drawings]
FIG. 1 is an explanatory view of an atmospheric pressure glow discharge generator used in the present invention. FIG. 2 is a principle diagram of the atmospheric pressure glow discharge generator in FIG. 1. FIG. 4 is an enlarged view of a connecting portion of a tube in the apparatus of the present invention. FIG. 5 is an explanatory view of the present invention using an air core electrode. (A) A copper wire is spirally wound around a metal pipe. (B) The metal pipe is pulled out. Air core electrode (c) Inner surface treatment through a plastic tube in the center of the air core electrode
DESCRIPTION OF SYMBOLS 1 Reaction tube 2 Electrode 2a Ground electrode 2b High voltage electrode 3 Tube unwinding part 4 Tube winding part 5 Gas inlet / outlet connection part 6 Tube connection part 7 Metal pipe or rod 8 Insulator

Claims (6)

After applying an alkoxysilane compound to the inner surface of the plastic tube and replacing the air inside the plastic tube with helium or a mixed gas of helium and argon, a plasma of atmospheric pressure glow discharge is excited to form a silica thin film on the inner surface of the plastic tube. processing method for a plastic tube surface, characterized in that allowed to form. The alkoxysilane compound is at least one selected from the group consisting of tetramethoxysilane, trimethoxysilane, tetraethoxysilane, triethoxysilane, tetrapropoxysilane, tripropoxysilane, tetrabutoxysilane, and tributoxysilane. processing method for a plastic tube surface according. Plastic tubing vinyl chloride polymer which is an object to be treated, ethylene - polyvinyl alcohol copolymer, urethane resin, or the processing method for a plastic tube surface according to claim 1 or 2, wherein either the tube made of a polyolefin polymer . Alkoxysilane compounds of low boiling aliphatic processing method for a plastic tube surface of any of claims 1 to 3 for use by dilution with a non-aqueous solvent such as a hydrocarbon. Processing method for a plastic tube surface of any of claims of claims 1 to 4 mixed gas of helium or helium and argon containing water vapor. Insert a long soft plastic tube into the air core electrode, flow helium or a mixed gas of helium and argon into the tube, rotate the winding part and the unwinding part, move the tube and apply a high frequency voltage of 1 kHz to 5 kHz A plastic tube continuous inner surface treatment method in which a glow discharge is generated inside the tube by using the plastic tube itself as a dielectric material to excite atmospheric pressure plasma to decompose a silane compound wetted inside the tube in advance to form a silica coating.

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