JP2006002009A - Method for imparting function to polymer substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for imparting function to a polymer substrate, which controls surface precipitation of a functional additive from a fluid occurring on pressure reduction and removal of the functional additive injected to the substrate after function imparting. <P>SOLUTION: The improved method for imparting function to a polymer substrate by supplying a supercritical fluid having dissolved a functional additive to a pressure container storing a polymer substrate comprises further a process for introducing liquid carbon dioxide to the pressure container, replacing the supercritical liquid having dissolved the functional additive in the pressure container with the liquid carbon dioxide and reducing pressure in the pressure container, into which the liquid carbon dioxide is introduced, to atmospheric pressure as an aftertreatment process after imparting function to the polymer substrate. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for imparting a function to a polymer substrate that imparts a function of modifying the surface of the substrate to a polymer substrate.

By utilizing the properties of supercritical fluids, various additives are supported on the polymer to control the release rate of the additive, to form a uniform fine particle catalyst, physical properties of the substrate, chemical properties, heat resistance or stability. Many methods have been proposed for improving the performance and modifying the operation characteristics.
For example, a polymer substrate, an additive, and a polymer swelling aid are placed in a pressure vessel, held in contact with the supercritical fluid to impregnate the polymer substrate with the additive and the polymer swelling aid, and the supercritical fluid is placed in the pressure vessel. Disclosed is a method for modifying a polymer base material with an additive, characterized in that after the polymer swelling aid flows out and separated, the pressure is reduced in a pressure vessel and the additive is contained in the polymer base material. (For example, refer to Patent Document 1). In the modification method disclosed in Patent Document 1, a low molecular weight compound that is soluble in a supercritical fluid and that can be impregnated into a polymer base material as a polymer swelling aid is used as an additive. Is used. By using this method, high molecular weight additives can be impregnated, and water, physiological saline, tears, body fluids, and the like from the polymer base material obtained into liquids that come into contact with the polymer base material during actual use. It is possible to provide a highly functional polymer base material that is substantially free from elution of the additive or is extremely small.
JP-A-11-255925 (Claim 1, paragraph [0039])

Functional addition to the polymer base material is made by contacting the polymer base material with a supercritical fluid in which the functional additive is dissolved to swell the surface of the base material with the supercritical fluid, and a part of the functional additive. Alternatively, the functional additive is fixed on the surface of the polymer base material by injecting the whole into the surface of the polymer base material.
Conventionally, a method for imparting a function to a polymer substrate has been performed as follows. That is, first, a polymer substrate is put into a pressure vessel, and the pressure vessel is sealed. Next, the supercritical fluid in which the functional additive is dissolved is supplied to the pressure vessel, the supercritical fluid is filled in the pressure vessel, and the supercritical fluid in which the functional additive is dissolved is brought into contact with the polymer substrate. By this contact, the functional additive is injected onto the surface of the polymer substrate. Next, the inside of the pressure vessel was depressurized to atmospheric pressure, and the polymer base material having a function was taken out from the pressure vessel.

However, the above method has the following problems.
After injecting the functional substance onto the surface of the polymer substrate, the supercritical fluid changes from the supercritical state to the normal pressure state by rapidly reducing the pressure vessel to atmospheric pressure. Due to this phase change, firstly, the solubility of the functional additive in the fluid is drastically decreased, and the functional additive dissolved in the fluid is precipitated, and the deposit adheres to the surface of the polymer substrate. was there. Second, there is a problem that a part of the functional additive injected onto the surface of the polymer base material easily escapes from the polymer base material together with the fluid. The first problem is that the precipitate is only attached to the surface of the polymer substrate, and the bond strength between the polymer substrate and the precipitate is weak and easy to peel off. When it comes to trouble. Therefore, the polymer base material modified using a cleaning solvent must be cleaned to remove surface precipitates, which is complicated. As for the second problem, the pressure difference between the surface layer of the polymer base material and the fluid phase in the pressure vessel rapidly increases due to the sudden pressure reduction, and a part of the functional additive injected into the polymer base material surface It becomes easy to escape from the polymer substrate together with the fluid. As a result, the concentration of the functional additive in the polymer substrate is lowered, and the efficiency of the imparted function is lowered.

  The object of the present invention is to provide a function for a polymer base material that can suppress the surface precipitation of the functional additive from the fluid and the escape of the functional additive injected into the base material when the pressure is reduced after imparting the function. It is to provide a grant method.

The invention according to claim 1 is an improvement of a method for imparting a function to a polymer substrate by supplying a supercritical fluid in which a functional additive is dissolved to a pressure vessel containing the polymer substrate.
The characteristic configuration is that, as a post-treatment step after imparting a function to the polymer substrate, liquid carbon dioxide is introduced into the pressure vessel and the supercritical fluid in which the functional additive in the pressure vessel is dissolved is liquid carbon dioxide. After the replacement, the method further includes a step of reducing the pressure in the pressure vessel into which liquid carbon dioxide has been introduced to atmospheric pressure.
In the invention according to claim 1, the supercritical fluid in which the functional additive in the pressure vessel is dissolved is replaced with liquid carbon dioxide, and then the pressure vessel is depressurized to atmospheric pressure. Adhesion of additives can be suppressed, and by reducing the pressure to atmospheric pressure, liquid carbon dioxide is vaporized and absorbs a lot of heat to form a carbon dioxide solid layer on the substrate surface. The escape of the functional additive injected into the inside can be suppressed.

The invention according to claim 2 is the invention according to claim 1, wherein the functionality imparting temperature is not less than the critical temperature of the fluid and less than the melting temperature of the polymer substrate, and the functionality imparting pressure is not less than the critical pressure of the fluid and 30 MPa. The method is as follows.
The invention according to claim 3 is the method according to claim 1, wherein the temperature of the liquid carbon dioxide is 31 ° C. or lower and the pressure of the liquid carbon dioxide is 7 MPa or higher.
The invention according to claim 4 is the invention according to claim 1, wherein the supercritical fluid is CO ₂ .
The invention according to claim 5 is the invention according to claim 1, wherein the supercritical fluid is CH ₃ OH, NH ₃ , H ₂ S, benzene, toluene or C _n H _m (n = 2 to 5, m = 2n or 2n + 2).
The invention according to claim 6 is the invention according to claim 1, wherein the supercritical fluid is CO ₂ and 5% by volume or less of CH ₃ OH, NH ₃ , H ₂ S, benzene, toluene or C _n H _m ( n = 2 to 5, m = 2n or 2n + 2).

  The method for imparting a function to a polymer base material of the present invention is a method of introducing a liquid carbon dioxide into a pressure vessel and dissolving a functional additive in the pressure vessel as a post-treatment step after imparting the function to the polymer base material. After replacing the critical fluid with liquid carbon dioxide, the method further includes the step of reducing the pressure in the pressure vessel into which the liquid carbon dioxide has been introduced to atmospheric pressure, whereby the supercritical fluid in which the functional additive is dissolved is liquid carbon dioxide. Since the pressure vessel is depressurized to atmospheric pressure after replacement with, the precipitation of the functional additive due to the decrease in solubility due to the phase change of the fluid is greatly suppressed. Adhesion can be suppressed, and by reducing the pressure to atmospheric pressure, liquid carbon dioxide is vaporized to form a carbon dioxide solid layer on the substrate surface. Break out It is possible to win.

Next, the best mode for carrying out the present invention will be described with reference to the drawings.
The supercritical fluid used in the function-imparting method of the present invention is a physically or chemically stable fluid, and is selected from environmentally friendly substances having low critical temperatures and critical pressures. A supercritical fluid is a fluid maintained above a critical temperature and a critical pressure, exhibits both properties of gas and liquid, is easily diffused like gas, and exhibits solubility of liquid. An example of the supercritical fluid of the present invention is CO ₂ . Other fluids that can be used as the supercritical fluid of the present invention include CH ₃ OH, NH ₃ , H ₂ S, benzene, toluene, C _n H _m (n = 2 to 5, m = 2n or 2n + 2), etc. In addition, a combination of CO ₂ and 5% by volume or less of CH ₃ OH, NH ₃ , H ₂ S, benzene, toluene or C _n H _m (n = 2 to 5, m = 2n or 2n + 2) is desirable. If a function can be provided to a polymer base material using a property additive, it will not be limited to these. The functionality imparting temperature of the present invention is preferably not less than the critical temperature of the fluid and less than the melting temperature of the polymer substrate, and the functionality imparting pressure is preferably not less than the critical pressure of the fluid and not more than 30 MPa. When the supercritical fluid is supercritical CO ₂ , a particularly preferable functional application temperature is 31 ° C. to 150 ° C., and a particularly preferable functional application pressure is 10 to 25 MPa.

The polymer substrate used in the function-imparting method of the present invention is all polymers as well as molded articles made from these polymers. Specific materials include PP (polypropylene), PE (polyethylene), PS (polystyrene), PET (polyethylene terephthalate), ABS (acrylonitrile-butadiene-styrene) resin, PVC (polyvinyl chloride), PVDC (polychlorinated). Vinylidene), methacrylic, zeonex, cyclopolyolefin, cellulosic, unsaturated polyester, phenol, polyurethane, silicone, and other resins. Pipes, tanks, plates, fibers, or products of various shapes made using these materials However, it is not limited to these as long as it is a base material capable of imparting a function with a functional additive.
In addition, the functional additive used in the function-imparting method of the present invention is physically and chemically very stable, does not decompose by the supercritical fluid, and is 5% by volume or less in the supercritical fluid or CO _2. It is an organic compound that can be dissolved in a supercritical fluid containing ₃ OH, NH ₃ , H ₂ S, benzene, toluene, or C _n H _m (n = 2 to 5, m = 2n or 2n + 2). Examples include dyes, ultraviolet absorbers, antiglare agents, photochronic agents, softeners, agricultural chemicals, drugs, proteins, antibiotics, anti-inflammatory agents, nutrients, vitamins, fluorinating agents, surfactants, and the like.

  As shown in FIG. 1, an apparatus 10 suitable for the method for imparting a function to a polymer substrate of the present invention includes a pressure vessel 11 that imparts a function to a polymer substrate 12 with a functional additive dissolved in a supercritical fluid, The pressure vessel 11 is provided with a supply passage 13 for supplying a supercritical fluid in which a functional additive is dissolved, and a discharge passage 14 for discharging the supercritical fluid from the pressure vessel 11. In this supply path 13, the fluid in which the functional additive is dissolved is pressurized to the functionality imparting pressure, and the pressure pump 17, the first valve 18 and the fluid in which the functional additive is dissolved are supplied into the pressure vessel 11. Each of the heaters 16 for heating up to the temperature for imparting functionality is provided. In addition, a second valve (pressure reducing valve) 19 is provided in the discharge path 14. Further, the supply path 13 is provided with a supply pump 21 and a third valve 22 for introducing liquid carbon dioxide into the pressure vessel 11.

  The polymer substrate 12 is accommodated in the pressure vessel 11 of the apparatus 10 configured as described above, and a supercritical fluid in which the functional additive is dissolved by the pressure pump 17 and the heater 16 is supplied to the pressure vessel 11 through the supply path 13. By supplying the pressure vessel 11, the supercritical fluid in which the functional additive is dissolved is filled in the pressure vessel 11, and the polymer base 12 and the supercritical fluid come into contact with each other. Next, each of the first valve 18 and the second valve (pressure reducing valve) 19 is closed, and the contact between the polymer substrate 12 and the supercritical fluid in which the functional additive is dissolved is maintained for a certain period of time. The surface of the base material swells, and a part or all of the functional additive is injected into the surface of the polymer base material, thereby imparting a function to the polymer base material. In addition, a function may be imparted to the polymer base 12 while continuously supplying the supercritical fluid in which the functional additive is dissolved to the pressure vessel 11, and in this case, the first valve 18 and the second valve ( Each of the pressure reducing valves 19 is opened, and the supercritical fluid in which the functional additive is dissolved is continuously supplied to the pressure vessel 11 through the supply path 13, so that the concentration of the functional additive dissolved in the supercritical fluid is increased. Can be maintained. The supercritical fluid in which the functional additive discharged from the inside of the pressure vessel 11 is discharged through the discharge path 14 is adjusted to a predetermined concentration, and then supplied again by the pressurizing pump 17 and the heater 16. You may circulate through.

A characteristic configuration of the present invention is a super-process in which liquid carbon dioxide is introduced into the pressure vessel 11 and the functional additive in the pressure vessel is dissolved as a post-treatment step after imparting a function to the polymer base material with a supercritical fluid. After replacing the critical fluid with liquid carbon dioxide, the method further includes a step of reducing the pressure in the pressure vessel 11 into which liquid carbon dioxide has been introduced to atmospheric pressure.
In this post-processing step, first, the first valve 18 of the supercritical fluid in which the functional additive connected to the supply path 13 side of the pressure vessel 11 is dissolved is closed, and the functional additive into the pressure vessel 11 is closed. The supply of the supercritical fluid in which is dissolved is stopped. Subsequently, the second valve (pressure reducing valve) 19 and the third valve 22 are each opened to supply liquid carbon dioxide that does not dissolve the functional additive while maintaining the pressure inside the pressure vessel 11 within a predetermined range. 21 is introduced into the pressure vessel 11 through the supply path 13 to replace the supercritical fluid in which the functional additive in the pressure vessel is dissolved with liquid carbon dioxide. The supercritical fluid in which the substituted functional additive is dissolved is removed from the pressure vessel 11 through the discharge path 14. When the introduction of liquid carbon dioxide into the pressure vessel 11 is completed, the third valve 22 is closed and the introduction of liquid carbon dioxide is stopped.

  Next, the second valve (pressure reducing valve) 19 provided on the discharge path 14 side of the pressure vessel 11 is opened to reduce the pressure vessel 11 to atmospheric pressure. The liquid carbon dioxide introduced into the pressure vessel 11 by this decompression is vaporized, and a lot of heat of absorption is generated by this vaporization. The temperature of the polymer substrate surface rapidly decreases due to the generation of vaporization absorption heat, and a solid layer of carbon dioxide is formed on the polymer substrate surface. Since the solid layer formed on the surface of the polymer substrate 12 reduces the electrical activity of the substrate surface, even if the functional additive remains in the pressure vessel 11, the functional addition to the substrate surface The precipitation of the agent is suppressed. Further, by forming a solid layer of carbon dioxide on the surface of the base material, it is possible to suppress the escape of the functional additive applied to the base material surface, which has been caused by reducing the pressure in the past. The solid layer of carbon dioxide formed on the surface of the polymer substrate 12 is removed by natural sublimation by taking the polymer substrate 12 out of the pressure vessel 11 and allowing the substrate to cool at room temperature.

Next, examples of the present invention will be described in detail together with comparative examples.
<Example 1>
First, polypropylene was prepared as a polymer substrate, bronone 204 as a functional additive, carbon dioxide as a fluid, and liquid carbon dioxide as a post-treatment introduction solvent. Next, using the function providing apparatus shown in FIG. 1, polypropylene was accommodated in the reaction vessel 11 and the reaction vessel was sealed. Next, supercritical carbon dioxide in which bronone 204 is dissolved by heating and pressurizing to 40 ° C. and 10 MPa is supplied into the reaction vessel 11 through the supply path 13, and supercritical carbon dioxide in which bronone 204 is dissolved in the reaction vessel 11. Filled with carbon and contacted with polypropylene. Next, each of the first valve 18 and the second valve (pressure reducing valve) 19 was closed, and this state was maintained for 1 hour, so that bronone 204 was injected onto the polypropylene surface to impart a function to the polypropylene. Subsequently, the pressure in the reaction vessel 11 is adjusted to a predetermined pressure with the second valve (pressure reducing valve) 19, the third valve 22 is opened, and the liquid maintained in the reaction vessel 11 at 31 ° C. or lower and 7 MPa or higher. Carbon dioxide was introduced, and the supercritical carbon dioxide in which the bronone 204 in the reaction vessel 11 was dissolved was replaced with liquid carbon dioxide. The second valve (pressure reducing valve) 19 on the discharge path 14 side was opened, the inside of the reaction vessel 11 was reduced to atmospheric pressure, and the polypropylene was removed from the pressure vessel 11 and allowed to cool at room temperature. . When the obtained polypropylene surface after imparting the function was observed, the function of bronon 204 was sufficiently imparted.

<Example 2>
A function was imparted to polypropylene in the same manner as in Example 1 except that the supercritical temperature was maintained at 120 ° C. When the obtained polypropylene surface after imparting the function was observed, the function of bronon 204 was sufficiently imparted.

<Comparative Example 1>
After imparting a function to polypropylene in the same manner as in Example 1, the second valve (pressure reducing valve) 19 on the discharge path 14 side is opened, the inside of the reaction vessel 11 is reduced to atmospheric pressure, and the polypropylene is further added to the pressure vessel. The polypropylene which was taken out from No. 11 and given a function was allowed to cool at room temperature. That is, liquid carbon dioxide was not introduced into the pressure vessel 11 after the function was imparted. Bronone 204 deposits were adhered to the obtained polypropylene surface after imparting the function. Therefore, it has been necessary to further perform a washing step using methanol as a washing solvent. By performing this cleaning step, it is considered that not only an environmental load is applied, but also the cost increases. Further, when the polypropylene surface after removing the precipitates by washing was observed, the application of bronone 204 was not partially sufficient, and once injected, the bronone 204 abruptly reached the atmospheric pressure in the reaction vessel 11. It is thought that it escaped when decompressing.

The figure which shows the apparatus used for the function provision method to the polymer base material of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Function provision apparatus 11 Reaction container 12 Polymer base material 13 Supply path 14 Discharge path 16 Heater 17 Pressurization pump 18 1st valve 19 2nd valve (pressure reduction valve)
21 Supply pump 22 3rd valve

Claims (6)

In a method of imparting a function to the polymer substrate by supplying a supercritical fluid in which a functional additive is dissolved in a pressure vessel containing the polymer substrate,
As a post-treatment step after imparting a function to the polymer base material, after introducing liquid carbon dioxide into the pressure vessel and replacing the supercritical fluid dissolving the functional additive in the pressure vessel with liquid carbon dioxide A method for imparting a function to a polymer substrate, further comprising the step of reducing the pressure in the pressure vessel into which the liquid carbon dioxide has been introduced to atmospheric pressure.   The method according to claim 1, wherein the functional application temperature is not lower than the critical temperature of the fluid and lower than the melting temperature of the polymer substrate, and the functional application pressure is not lower than the critical pressure of the fluid and not higher than 30 MPa.   The method according to claim 1, wherein the temperature of the liquid carbon dioxide is 31 ° C or lower, and the pressure of the liquid carbon dioxide is 7 MPa or higher. The method of claim 1 wherein the supercritical fluid is CO _2. Supercritical fluid _{CH 3 OH, NH 3, H} 2 S, benzene, toluene or _{C n H m (n = 2~5} , m = 2n or 2n + 2) The method of claim 1, wherein. Supercritical fluid and CO ₂ 5% by volume or less of _{CH 3 OH, NH 3, H} 2 S, benzene, according to claim 1, wherein toluene or _{C n H m (n = 2~5} , m = 2n or 2n + 2) the method of.

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