JPH055251B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to an improvement in a method of treating the inner surface of a plastic tube with low temperature plasma to improve its inner surface characteristics. [Prior Art] Treatment of plastic surfaces with low-temperature plasma to improve the hydrophilicity and adhesion of the surfaces, or to prevent the elution of plasticizers, has been practiced since before the filing of the present invention. Another known method is to bring a radically polymerizable monomer into contact with a large amount of radicals generated on the surface of a plastic treated with low-temperature plasma to cause a polymerization reaction, thereby performing graft copolymerization on the surface of the plastic. The method of surface graft copolymerization using this low-temperature plasma treatment is superior to other methods, such as methods of irradiating with radiation such as gamma rays and electron beams, methods of irradiating with ultraviolet rays, and methods of treating with ozone. This method is known to be superior in terms of efficiency and safety. [Problems to be Solved by the Invention] In the conventional low-temperature plasma treatment method for the inner surface of a plastic tube, a sample is placed between positive and negative electrodes and discharge is performed, thereby causing plasma to be applied to the area between the two electrodes. It was difficult to treat the inner surface of the tube efficiently by generating . In other words, the usual method is to install electrodes at both ends of a plastic tube to generate a discharge, so the length of the tube that can be processed is inevitably limited by the distance between the electrodes. Moreover, there was a drawback that there was a natural limit to the number of tubes that could be processed in one operation. Therefore, the conventional methods are not suitable for the purpose of efficiently processing a large number of tubes. In order to solve such problems,
A method such as that described in Publication No. 29505 has been proposed. In this method, a tube whose interior is maintained under reduced pressure is inserted into a cylindrical electrode, and low-temperature plasma is generated while the tube is continuously moved, thereby treating the inside of the tube with low-temperature plasma. However, this method has the disadvantage that it is technically difficult to uniformly treat the inner surface of the tube, and the device itself must be large and require a complicated mechanism. ,
A more serious defect is that, as with conventional methods, the electrode and the surface to be treated must be brought close to each other, so the temperature rise in the tube to be treated becomes so large that it cannot be ignored, causing the tube to become deformed due to heat. This means that fine irregularities are formed on the treated surface. This defect can lead to serious consequences when used in medical plastic tubes such as artificial blood vessels, such as blocking the normal flow of blood or causing the risk of blood clots. This could not be said to be a desirable method for obtaining the desired results. The present invention has been made with the aim of eliminating these drawbacks, and the first object is to prevent uneven distortion from occurring on the inner and outer surfaces of the tube when treating the inner surface of the plastic tube, and to prevent the inner surface from being distorted. The second purpose is to provide a low temperature plasma treatment method that can uniformly finish plastics.The second purpose is to provide a tube inner surface graft copolymerization method using low temperature plasma treatment method. The object of the present invention is to provide a method for efficiently treating the inner surface of a tube with low-temperature plasma. [Means for solving the problems] These objectives are to generate low-temperature plasma gas by non-polar discharge using microwaves, and to introduce the generated plasma gas into a plastic tube placed at a location away from the plasma generation area. The basic condition is to bring this into contact with the inner surface of the tube, and the inner surface graft copolymerization is achieved by further bringing a radically polymerizable monomer into contact with the inner surface of the tube that has been treated with low temperature plasma. Ru. [Operation] In microwave non-polar discharge, there is no electrode inside the discharge space (area), and the amount and density of generated plasma is significantly higher than in other methods.
In the method of the present invention, a sufficient amount of low-temperature plasma-containing gas can be continuously extracted from the discharge space by performing the discharge treatment while continuously supplying reduced pressure gas. If this is introduced into the plastic tube and brought into contact with the inner surface of the tube, the inner surface of the tube can be treated at a location away from the discharge area, and therefore the object to be treated (the tube) is exposed to microwaves and This has the advantage of not being directly affected by discharge. Therefore, if the distance from the discharge section is appropriately selected, there is no risk that the object to be treated will be abnormally heated and deformed or deteriorated, or that the inner and outer surfaces will become uneven due to electric discharge. be. Furthermore, if a radically polymerizable monomer is introduced in the form of a gas or liquid into the plastic tube treated in this manner and is brought into contact with the inner surface, a polymerization reaction occurs there and a graft copolymer is formed on the inner surface. A polymer is produced and the inner surface of the tube is improved. [Example] The present invention will be described below based on the accompanying drawings.
FIG. 1 is a basic configuration diagram of a microwave plasma processing apparatus used in the present invention, which includes an oscillation device 1, a conversion waveguide 2, an isolator 3, a power monitor 4, a matching box 5, It consists of a furnace 6, an activation chamber 7, a processing chamber 8, a conduit 9, and an exhaust pump for reducing the pressure in the activation chambers 7-8. Microwaves with a frequency of 2450MHz are used as the energy source. The isolator 3 is installed for the purpose of stably operating the oscillation device 1 even when the microwave power from the oscillation device is under no load. The power monitor 4 is provided to monitor reflected power. Now, to explain the operating status of this device, the microwave oscillated from the oscillator 1 is ultimately sent to the activation furnace 6, and a quartz tube is inserted into the activation furnace at the position of the maximum electric field of the microwave. It is absorbed by the gas in the activation chamber 7 and excites the gas in the chamber into a plasma state. This excited plasma gas is introduced into the processing chamber 8 through a conduit 9. Since a plastic tube 10 to be treated is attached to the tip of the conduit 9 as shown in the figure, the plasma gas is introduced into the inner surface of the tube. will come into contact with the inner surface and activate it. The processing chamber 8 is used to house the plastic tube 10 and perform plasma treatment, and also has the role of preventing the tube from being crushed by outside air pressure. Therefore, if there is no risk of the tube being crushed by outside air pressure, it is not necessary to provide it. Note that the pressure inside the processing chamber and the tube is preferably about 0.01 to 10 mmHg. Although the apparatus shown in FIG. 1 can only process one tube at a time, if it is desired to process a plurality of tubes at the same time, the tip of the conduit 9 can be branched as shown in FIG. In this case, it is preferable to maintain the mounting position of the tube at an equal distance from the branch. Next, a case in which graft copolymerization is performed on the inner surface of the tube will be described. This is carried out by bringing a radically polymerizable monomer solution or vapor into contact with the inner surface of the plastic tube which has been plasma treated by the method described above. In this case, the polymerization reaction proceeds at room temperature, but may be heated or cooled to an appropriate temperature to control the progress. In addition, the radically polymerizable monomers used include acrylamide, dimethylacrylamide,
Examples include methacrylamide, vinylpyrrolidone, acrylic acid, methacrylic acid, esters of acrylic acid or methacrylic acid, vinyl acetate, styrene, and vinyl chloride, but those that produce water-soluble polymers when polymerized alone are preferred. Practical example 1 Using the apparatus shown in Figure 1 (microwave output 1 kW), the inner surfaces of a polyurethane tube and an ethylene-vinyl acetate copolymer (EVA) tube with an inner diameter of 3 mm and a length of 30 cm were treated with low-temperature plasma. did. Oxygen gas is used as the processing gas, and the pressure is 0.07.
Treatments were performed with mmHg for 10 and 60 seconds. Next, these low-temperature plasma-treated tubes were immersed in a 10% aqueous solution of acrylamide and polymerized at 60°C for 6 hours, and then the tubes were washed with warm water to remove unreacted monomers and the produced homopolymer. Removed. The amount of graft polymerization at both ends and the inner surface of the central portion of the tube thus obtained was measured to evaluate the uniformity of the treatment. The results are shown in Table 1. In addition, the amount of graft polymerization was measured as follows. First, each measurement part of the tube was cut, each part was immersed in 1.5NHCl, and the polyacrylamide was hydrolyzed in an autoclave at 1.5 atmospheres for 30 minutes. Then, the mixture was neutralized with NaOH, a ninhydrin solution was added, and the mixture was allowed to react again for 5 minutes in an autoclave at 1.5 atmospheres, and the absorbance of the reaction solution at 570 nm was measured. The amount of graft polymerization was calculated from this measured value and a calibration curve determined in advance.

[Table] Comparative Example 1 A polyurethane tube with an inner diameter of 3 mm and a length of 30 cm was plasma treated for 5 seconds and 30 seconds at a pressure of 0.8 mmHg using a glow discharge device equipped with a needle electrode. Acrylamide was graft-polymerized onto the obtained tube in the same manner as in Example 1, and the amount of polymerization was measured. The results are shown in Table 2.

[Table] Comparative Example 2 An EVA tube with an inner diameter of 3 mm and a length of 30 cm was subjected to plasma treatment for 10 seconds at a pressure of 0.2 mmHg using a high frequency discharge device with a frequency of 13.56 MHz and an output of 50 W. Acrylamide was graft-polymerized onto the obtained tube in the same manner as in Example 1, and the amount of polymerization was measured. The results are shown in Table 3.

〔Effect of the invention〕

As described above, according to the present invention, the plastic tube is not directly affected by the discharge, so the tube is not deformed or deteriorated by heat, and the inner and outer surfaces are not uneven. can be processed smoothly. Further, since long tubes can be processed quickly and uniformly, products of stable quality can be efficiently manufactured. Therefore, when the present invention is applied to the production of medical plastic tubes, blood clots are less likely to form when the inner surface of the tube comes into contact with blood, compared to those obtained by other plasma treatment methods. When the antithrombotic properties of the inner surface of the tube are improved by graft copolymerization, both effects combine to produce a significantly favorable effect. The invention is therefore particularly suitable for the manufacture of medical tubes in contact with blood, such as artificial blood vessels, catheters and blood circuits.

[Brief explanation of the drawing]

FIGS. 1 and 2 show basic configuration diagrams of a low-temperature plasma processing apparatus used in the method of the present invention. DESCRIPTION OF SYMBOLS 1... Oscillator, 2... Conversion waveguide, 3... Isolator, 4... Power monitor, 5... Matching box, 6... Activation furnace, 7... Activation chamber, 8... Processing chamber, 9... Conduit, 1
0...Plastic tube.

Claims (1)

[Scope of Claims] 1. Low-temperature plasma is generated in an activation chamber by a non-polar discharge using microwaves, and the generated plasma gas is introduced into a plastic tube located at a position away from the activation chamber. A medical plastic tube characterized in that the surface is activated and then a radically polymerizable monomer is introduced into the plastic tube to graft-copolymerize the polymer onto the activated inner surface of the plastic tube. Production method. 2. The method for producing a medical plastic tube according to claim 1, wherein the radically polymerizable monomer is a monomer that produces a water-soluble polymer by itself.