JP2004359903A - Method for compressing unreacted vinyl monomer gas - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for suppressing occlusions in piping and strainers in the circulation line of lubricant oil, enabling the realization of stable operation of the circulation line of the lubricant oil over a long period by suppressing the sedimentation of a polymerization inhibitor for inhibiting the polymerization of VCM (vinyl chloride monomer) even in the case of using a rotary gas compressor having a large gas-treating volume, and almost completely preventing the production of a vinyl chloride-based polymer caused by the above in the gas compressor. <P>SOLUTION: This method for compressing unreacted vinyl chloride monomer gas by using the rotary gas compressor under contact with the lubricant oil for circulation supplied into the compressor is characterized in that the lubricant oil contains 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００４２】
＜評価＞
実施例１〜３のように、潤滑油として、４−ヒドロキシ−２，２，６，６−テトラメチルピペリジン−Ｎ−オキシルを含有するものを、本発明の用件を満たす濃度で使用した場合には、ストレーナ閉塞回数がいずれの場合にも０〜１回であり、回転式ガス圧縮機を長期間に渡って安定的に運転できる。
一方で、比較例１または２のように、潤滑油として、４−ヒドロキシ−２，２，６，６−テトラメチルピペリジン−Ｎ−オキシルの代わりに、３，５−ジ−ｔｅｒｔ−ブチル−４−ヒドロキシトルエン（ＢＨＴ）またはビスフェノールＡを含有するものを使用した場合には、ストレーナ閉塞回数が１０〜１１回であり、回転式ガス圧縮機を長期間に渡って安定的に運転するのは困難である。
【００４３】
【発明の効果】
本発明によれば、未反応ＶＣＭガスの圧縮工程で、該ＶＣＭに含まれる水分が、回転式ガス圧縮機内に供給される潤滑油へ移行、蓄積しても、ＶＣＭの重合を阻害する添加剤である重合禁止剤の析出が起こらないため、長期間該潤滑油を循環用潤滑油として、循環、再利用しても塩化ビニル系重合体の生成、付着がほとんど起こらず、潤滑油の循環ライン中の配管およびストレーナ内部等の閉塞が抑制される。そのため、ガス処理容量の大きい回転式ガス圧縮機を使用した場合においても、塩化ビニル系重合体の生成が効果的に阻害されるため、潤滑油の循環ラインの分解、掃除等を行う必要がなく、長期間に渡って回転式ガス圧縮機の運転を安定的に行うことが可能となる。
【図面の簡単な説明】
【図１】本発明の圧縮方法の一例の工程図である。
【符号の説明】
１…塩化ビニルモノマーの供給ライン配管
２…回転式ガス圧縮機
３、６、１０…循環ライン配管
４…気液分離器兼潤滑油貯蔵タンク
５…圧縮塩化ビニルモノマーの凝縮器への供給ライン配管
７…潤滑油用冷却器
８…潤滑油ストレーナ
９…送液ポンプ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for compressing a vinyl chloride monomer gas, for example, an unreacted vinyl chloride monomer gas containing water recovered from a process for producing a vinyl chloride polymer.
[0002]
[Prior art]
In the production process of a vinyl chloride polymer, a vinyl chloride polymer is obtained by polymerizing a vinyl chloride monomer (VCM) by a polymerization vessel, while gaseous unreacted vinyl chloride monomer (VCM gas) is recovered and gaseous. After compression by a compressor, it is common to liquefy and condense with a cooling condenser and reuse it.
[0003]
As a gas compressor used for compressing the recovered VCM gas, there are a reciprocating type, a rotary type, a centrifugal type, and the like. Above all, a rotary gas compressor is preferably used because of its high operation stability, almost no parts worn by mechanical sliding, maintenance-free operation for a long period of time, and the like.
When the recovered VCM gas is compressed by the rotary gas compressor, the temperature of the VCM gas (compressed VCM gas) discharged from the gas compressor is suppressed from rising, and the driving and sliding parts of the gas compressor are cooled and lubricated. For this purpose, a method of injecting and supplying a lubricating oil into a gas compressor and compressing it together with a VCM gas has been adopted. The lubricating oil discharged from the gas compressor together with the compressed VCM gas is separated from the compressed VCM gas by a gas-liquid separator, sent to a lubricating oil storage tank once, passed through a lubricating oil cooler, etc. Used as lubricating oil injected and supplied into the compressor.
[0004]
In the process of compressing the recovered VCM gas by the above method, if the lubricating oil circulation line is operated for a long period of time, the VCM slightly polymerizes in the gas compressor in the circulation line, thereby causing the vinyl chloride heavy load. Coalescence forms. When the vinyl chloride polymer accumulates in the lubricating oil, the pipes and strainers in the lubricating oil circulation line are blocked, or the lubricating oil cooler is installed in the lubricating oil circulation line. It is known that covering the inner wall causes a problem such as a decrease in the cooling effect of the cooler. In order to prevent such troubles and enable stable long-term operation, a method has been proposed in which an oil-soluble polymerization inhibitor is contained in lubricating oil (Patent Document 1).
[0005]
According to the above method, the polymerization of VCM in the gas compressor is inhibited by the effect of the polymerization inhibitor contained in the lubricating oil, and compared to the case where the lubricating oil containing no polymerization inhibitor is used, for a certain period of time. The stable operation of the lubricating oil circulation line can be achieved over the entire period. However, when a gas compressor having a large gas processing capacity is used, in a very short period of time, the polymerization inhibitor precipitates in the circulation line and starts to adhere to the inside of the strainer. Next, it was found that the vinyl chloride-based polymer was generated and adhered in the circulation line, causing a problem that the inside of the strainer and the piping was blocked. In order to prevent these problems, it is necessary to frequently disassemble the lubricating oil circulation line and remove the vinyl chloride polymer by cleaning.
[0006]
[Patent Document 1]
JP 2001-48919 A
[Problems to be solved by the invention]
The present invention solves the above problems, and even when a rotary gas compressor having a large gas processing capacity is used, a polymerization inhibitor having an action of inhibiting polymerization of VCM, which is dissolved in lubricating oil, precipitates. By preventing the formation of a vinyl chloride polymer in the gas compressor due to this almost completely, thereby suppressing the blockage of the piping and strainer in the lubricating oil circulation line and circulating the lubricating oil. It is an object of the present invention to provide a method capable of realizing stable operation of a line for a long period of time.
[0008]
[Means for Solving the Problems]
As a result of intensive studies on the above problems, the present inventors have found that the unreacted VCM gas introduced into the gas compressor contains moisture, and the moisture gradually migrates and accumulates in the lubricating oil. If the water content exceeds a certain level, the oil-soluble polymerization inhibitor dissolved in the lubricating oil is precipitated, and the precipitated polymerization inhibitor adheres to the inside of the strainer in the lubricating oil circulation line. It was found that a sufficient amount of a polymerization inhibitor to inhibit the polymerization of VCM was not present in the lubricating oil that was injected and supplied again into the compressor. Since the amount of water in the lubricating oil increases in proportion to the amount of gas to be processed by the gas compressor, if a gas compressor with a large gas processing capacity is used, the amount of water as described above will be shorter. Will invite the situation.
[0009]
Once such a state is reached, even if a polymerization inhibitor is further added to the lubricating oil, the polymerization inhibitor hardly dissolves in the lubricating oil. Also, even if a series of gas compression operations is restarted, the polymerization inhibitor precipitates out immediately and adheres to the inside of the strainer, so that the polymerization of VCM cannot be inhibited and the vinyl chloride-based heavy It was also found that the formation of coalescence could not be suppressed.
[0010]
Thus, the present inventors have studied various reagents that do not precipitate as described above and effectively inhibit the polymerization of VCM over a long period of time even when the amount of water contained in the lubricating oil increases, 4-Hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl, which is soluble (oil-soluble) in a lubricating oil, is also water-soluble and has a very high polymerization inhibiting ability of VCM, is used as a lubricating oil. It has been found that the addition is effective, leading to the present invention.
[0011]
In view of the above, the present invention provides a method for compressing vinyl chloride monomer gas by a rotary gas compressor under contact with a circulating lubricating oil supplied into the machine, wherein the lubricating oil is 4-hydroxy The present invention provides a method for compressing unreacted vinyl chloride monomer gas, comprising -2,2,6,6-tetramethylpiperidine-N-oxyl.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in more detail. In this specification, “(meth) acrylic acid” means “acrylic acid” and “methacrylic acid”.
[0013]
The method of the present invention is used, for example, in the production process of a vinyl chloride polymer, and preferably, the unreacted VCM gas recovered from the polymerization vessel used in the production of the vinyl chloride polymer (the present invention). When unreacted VCM gas such as “recovered VCM gas” in the specification is compressed by a rotary gas compressor (also simply referred to as “gas compressor” in this specification), 4 This is performed by injecting and supplying a circulating lubricating oil containing -hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl, and compressing the VCM gas while contacting the lubricating oil.
[0014]
-Rotary gas compressor-
The rotary gas compressor used in the present invention is not particularly limited as long as the rotary gas compressor has a structure in which unreacted VCM gas is compressed while being in contact with the lubricating oil supplied into the compressor. For example, a rotary screw gas compressor, a rotary roots gas compressor, a rotary movable blade gas compressor, and the like can be given. In the present invention, it is particularly preferable to use a rotary screw gas compressor. In this rotary screw gas compressor, the oscillator and the mess rotor with different numbers of teeth mesh in the casing, and the meshing space of the widely opened teeth narrows with the rotation of the rotor, thereby reducing the volume of the space. Is a gas compressor that compresses gas by reducing the pressure with rotation. When the space is maximized, both walls of the rotor are closed by walls, and the gas sucked from outside is sealed in the space together with the lubricating oil. On the other hand, when the rotation proceeds and the space becomes minimum, the space is connected to the discharge port, and the compressed gas is discharged together with the lubricating oil. These series of steps are performed continuously.
[0015]
The present invention can be applied without any particular limitation on the gas processing capacity of this rotary gas compressor, but the gas processing capacity of the gas compressor is 2,000 m ³ / standard state (0 ° C., 1 atm). it is preferably hr or more, more preferably 2,000~10,000m ³ / hr, and particularly preferably 3,000~5,000m ³ / hr. When the gas treatment capacity is 2,000 m ³ / hr or more in a standard state, the gas treatment capacity is higher than when a polymerization inhibitor containing no 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl is used. The effect of the present invention can be more remarkably recognized.
[0016]
-VCM gas-
The VCM gas to which the method of the present invention is applied is not particularly limited, but a typical example is an unreacted VCM gas recovered from a vinyl chloride-based polymer production process. The polymer recovered from the production process of the polymer (having a vinyl chloride homopolymer content of 60 to 100%, preferably 80% or more, particularly preferably 90% or more of the whole polymer) is preferable. Examples of such unreacted VCM gas include those recovered from a process for producing a vinyl chloride homopolymer, a copolymer of a vinyl chloride monomer and another copolymerizable monomer, and the like.
[0017]
Other copolymerizable monomers include, for example, butenes such as ethylene, propylene, 1-butene and isobutene, amylenes, 1-hexene, hexene such as 4-methyl-1-pentene, heptene, octene, nonene, decene and the like. Alkenes, vinyl acetate, vinyl stearate, vinyl benzoate, monoallyl esters of saturated carboxylic acids such as various monoallyl phthalates, acrylates such as methyl (meth) acrylate, ethyl (meth) acrylate, etc. Unsaturated carboxylic acids such as di- or tri (meth) acrylates of polyhydric alcohols, di- or triallyl ethers of polyhydric alcohols, monovinyl ethers, monoallyl ethers, acrylic acid, methacrylic acid, crotonic acid, and maleic acid Acids, aromatic monovinyls such as styrene, acrylonitrile, etc. It is below.
[0018]
Further, the VCM gas may contain moisture. As described above, when moisture is present in the VCM gas, the polymerization inhibitor in the lubricating oil tends to precipitate, thereby generating a vinyl chloride-based polymer in the lubricating oil circulation line. According to the method of the present invention, such a problem does not occur even if moisture is present in the VCM gas.
[0019]
The VCM gas usually contains about 0.01% by weight of water, more typically 0.001 to 0.1% by weight. The method of the present invention can be applied even when such an amount of water is contained.
[0020]
The VCM gas is usually supplied to a gas compressor at a normal temperature (20 ° C.) and a low to medium pressure of 1 kPa G to 0.3 MPa G (gauge pressure) to be compressed. The pressure at the time of compression depends on the gas compressor, but is usually 0.5 to 0.7 MPaG.
[0021]
-Lubricant-
The lubricating oil injected and supplied to the gas compressor contacts the unreacted VCM gas in the process of compressing the unreacted VCM gas, and thereby the unreacted VCM gas and the compressed VCM discharged from the gas compressor. In addition to suppressing the temperature rise of gas (also referred to as “compressed VCM gas” in the present specification), it lubricates the compression section of a gas compressor (comprising a gas compression section and a casing surrounding the same) to compress and compress the gas. It has a function of sealing the inside of the section and between the compression section and the casing.
[0022]
Such lubricating oil is suitably that kinematic viscosity at 40 ° C. as measured by kinematic viscosity test method JIS K2283 is in the range of 60~170mm ² / s, in the range of 65~150mm ² / s Certain ones are preferred, and those in the range of 80 to 120 mm ² / s are particularly preferred. Specific examples of the lubricating oil having a kinematic viscosity in the range of 60 to 170 mm ² / s include ISO VG68, ISO VG100, and ISO VG150, which are ISO viscosity grades according to ISO viscosity classification (JIS K2001).
[0023]
The amount of lubricating oil supplied into the gas compressor is preferably such that the temperature of the compressed VCM gas discharged from the gas compressor is in the range of 60 to 120C, preferably 75 to 95C. When lubricating oil is supplied in such an amount that the temperature of the compressed VCM gas is in the range of 60 to 120 ° C., the liquid returns to the gas compressor, and the formation of a vinyl chloride polymer in the lubricating oil circulation line is promoted. Problem can be prevented.
[0024]
The lubricating oil used in the present invention needs to contain 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl. 4-Hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl is a kind of N-oxyl compound, and is known to have a property of preventing polymerization of vinyl monomers such as vinyl chloride monomers. (Table 2001-505601). This 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl can be obtained, for example, under the trade name of Polystop 7300P (manufactured by Hakuto K.K.).
[0025]
N-oxyl compounds are generally poorly soluble in water, whereas 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl is soluble in oil and water, and especially soluble in water. It is characterized by extremely high solubility (50% by weight or more dissolved at 25 ° C.). Therefore, even if water is added in a state where 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl is dissolved in a lubricating oil, the compound does not precipitate at all, and the object of the present invention is to be solved. It can be suitably used to achieve.
[0026]
The content of 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl in the lubricating oil can be arbitrarily set, but is preferably in the range of 1 to 1,000 ppm, and more preferably 10 to 500 ppm. The range is more preferable, and the range of 50 to 300 ppm is particularly preferable. When the content is in the range of 1 to 1,000 ppm, not only is the fluidity and lubricity of the lubricating oil excellent, but also the production of the vinyl chloride polymer is suppressed, and the lubricating oil flows to the inner wall of the circulation line piping and the like. The effect of preventing the adhesion of the vinyl chloride polymer is improved. When starting a series of operations for compressing unreacted VCM gas, since the operation of the gas compressor is unstable and a vinyl chloride polymer is easily generated, the content is preferably set to 100 ppm or more, The content is more preferably 200 to 800 ppm, particularly preferably 300 to 500 ppm. After the operation of the gas compressor is stabilized, the content of 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl in the lubricating oil may be reduced.
[0027]
4-Hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl contained in the lubricating oil is consumed to inhibit polymerization of unreacted VCM in the lubricating oil, and its content is reduced. Decrease gradually. Therefore, lubricating oil is periodically collected and analyzed for the content of 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl in the lubricating oil by a method such as gas chromatography mass spectrometry. 4-hydroxy-2,2 as appropriate so as not to be less than 1 ppm, preferably not less than 10 ppm, more preferably 10 to 500 ppm, particularly preferably 50 to 300 ppm. It is preferred to add 2,6,6-tetramethylpiperidine-N-oxyl.
[0028]
The lubricating oil of the present invention is not particularly limited as long as it satisfies the above conditions.For example, lubricating oil is separated from a compressed gas containing a lubricating oil generated in the compression step, and then the gas It may be reused in a compressor.
[0029]
-Compression process-
Next, a preferred embodiment of the method of the present invention will be described in detail with reference to FIG.
FIG. 1 is a process chart of an example of the compression method of the present invention. In FIG. 1, reference numeral 1 denotes a supply line pipe for supplying unreacted VCM gas to the rotary gas compressor 2, 2 denotes a rotary gas compressor, and 4 denotes a compressed VCM gas mixed with the rotary gas compressor 2 and lubricating oil. A gas-liquid separator serving also as a storage tank for the separated lubricating oil, and a supply line piping for the compressed VCM gas to a condenser (not shown); 7 is a lubricating oil cooler, 8 is a lubricating oil strainer, 9 is a liquid sending pump, and 3, 6, and 10 are lubricating oil circulation line piping.
[0030]
Unreacted VCM gas from a polymerization vessel (not shown) used in the production process of the vinyl chloride-based polymer passes through the supply line piping 1 at a low or medium pressure as described above, and is supplied to the rotary gas compressor. 2. The low- or medium-pressure unreacted VCM gas supplied into the rotary gas compressor 2 is introduced into the space of a pair of male and female rotors provided in the rotary gas compressor 2 and has a pressure of 0.5. Compressed to a high-pressure gas of 0.7 MPaG.
[0031]
On the other hand, in this compression process, the lubricating oil for circulation is injected and supplied into the rotor space of the male and female pair in the rotary gas compressor 2 through the circulation line pipe 10, and is supplied into the rotary gas compressor 2. Unreacted VCM gas is compressed while contacting the lubricating oil. By supplying and contacting the lubricating oil, the temperature of the obtained compressed VCM gas is suppressed in the range of 60 to 120 ° C., and at the same time, the lubrication of the rotor and the sealing between the rotors and between the rotor and the casing are performed.
[0032]
After the compression step, a mixture of the compressed VCM gas and the lubricating oil is discharged from the rotary gas compressor 2, and the mixture is sent to the gas-liquid separator 4 through the circulation line pipe 3. At the top of the gas-liquid separator 4, the mixture is separated into compressed VCM gas and lubricating oil. The compressed VCM gas thus separated is sent through a supply line pipe 5 to a condenser (not shown), where it is liquefied and condensed by a cooling condenser to become a crude liquefied VCM. On the other hand, the lubricating oil separated by the gas-liquid separator 4 is accumulated at a lower part of the gas-liquid separator 4.
[0033]
The lubricating oil collected in the lower part of the gas-liquid separator 4 is sent through a circulation line pipe 6 into a cooler 7, where the lubricating oil is usually at a temperature in the range of 20 to 60C, preferably 40 to 50C. Is cooled. Next, the lubricating oil cooled by the cooler 7 is supplied to the rotary gas compressor 2 through the lubricating oil strainer 8 through the circulation line piping 10 by the liquid feed pump 9, and thereafter circulates similarly. .
[0034]
【Example】
Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. In addition, this invention is not limited to a following example.
[0035]
<Examples 1-3, Comparative Examples 1-2>
As shown in FIG. 1, the rotary gas compressor 2, the gas-liquid separator 4, the lubricating oil cooler 7, the lubricating oil strainer 8, and the lubricating oil strainer 8, which are connected by the supply line piping 1, the circulation line pipings 3, 6 and 10, Using the pump 9, a compression process of the unreacted VCM gas including a lubrication oil circulation process was performed. As the rotary gas compressor 2, a rotary screw gas compressor having a pair of male and female rotors is used, and specifically, a gas compressor P-1 or P1 having the following specifications with different gas processing capacities. -2 was used. As the cooler 7, a horizontal shell-and-tube condenser was used, and as the VCM gas, a low-pressure VCM gas having an average pressure of 2.0 kPa G at ordinary temperature was used.
[0036]
Before the compression of the VCM gas, the inside of the rotary gas compressor 2, the inside of the gas-liquid separator 4, the inside of the tube of the cooler 7, the inside of the strainer 8, the inside of the pump 9, and the circulation line of the lubricating oil are previously set. Dirt in the formed circulation line pipes 3, 6, and 10 was sufficiently removed. The following lubricating oils A to D were respectively injected into the circulation line piping 10, from which the lubricating oils A to D were supplied into the rotary gas compressor 2 by the pump 9.
[0037]
At the same time, the VCM was supplied and compressed into the rotary gas compressor 2, and a mixture of the compressed VCM gas and the lubricating oil was discharged from the rotary gas compressor 2. The obtained mixture is introduced into the gas-liquid separator 4 through the circulation line piping 3, and the compressed VCM gas and the lubricating oil are separated from the mixture, and the average pressure is 0.6 to 0.7 MPa G and the average temperature is 80 ° C. Was obtained.
[0038]
The compression step of the unreacted VCM gas including the lubrication oil circulation step was continuously operated for 12 months while maintaining the temperature of the supplied lubrication oil at 50 ° C. or lower. During this time, in the circulation step, when the strainer 8 is closed and continuous operation becomes difficult, the gas-liquid separator 4, the tube of the cooler 7, the strainer 8, the pump 9, and the lubricating oil The vinyl chloride polymer was removed and cleaned in the circulation line pipes 3, 6, 10 and, in some cases, in the rotary gas compressor 2, and the operation was resumed. This operation was counted as the number of strainer closures, and the results are shown in Table 1. The type of rotary gas compressor used and the type of lubricating oil used are as shown in Table 1.
[0039]
-Gas compressor-
-Gas compressor P-1 (manufactured by Kobe Steel Ltd., trade name: KS20S-12S, gas processing capacity: 1,000 m ³ / hr under standard conditions, suction pressure: 2.0 kPa G, discharge pressure: 0.6 MPa G , Motor output: 16kW)
-Gas compressor P-2 (manufactured by Kobe Steel Ltd., trade name: KS30TVB, gas processing capacity: 3,000 m ³ / hr under standard conditions, suction pressure: 2.0 kPa G, discharge pressure: 0.7 MPa G, electric motor Output: 380kW)
[0040]
-Lubricant-
All of the following lubricating oils A to D used Daphne oil KP-100 (trade name) (manufactured by Idemitsu Kosan, ISO viscosity grade: ISO VG100).
Lubricating oil A: The concentration of 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl (manufactured by Hakuto K.K., trade name: Polystop 7300P) is 20 ppm with respect to the lubricating oil. Added as follows.
Lubricating oil B: The concentration of 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl (manufactured by Hakuto K.K., trade name: Polystop 7300P) is 100 ppm with respect to the lubricating oil. Added as follows.
Lubricating oil C: 3,5-di-tert-butyl-4-hydroxytoluene (BHT) added to a lubricating oil so that the concentration becomes 1,000 ppm.
Lubricating oil D: Lubricating oil to which bisphenol A has been added to a concentration of 1,000 ppm.
[0041]
[Table 1]

[0042]
<Evaluation>
As in Examples 1 to 3, when lubricating oil containing 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl is used at a concentration satisfying the requirements of the present invention. In any case, the number of times the strainer is closed is 0 to 1 in each case, and the rotary gas compressor can be stably operated for a long period of time.
On the other hand, as in Comparative Example 1 or 2, instead of 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl, 3,5-di-tert-butyl-4 was used as the lubricating oil. -When using a compound containing hydroxytoluene (BHT) or bisphenol A, the strainer is clogged 10 to 11 times, and it is difficult to operate the rotary gas compressor stably for a long period of time. It is.
[0043]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, even if the water | moisture content contained in this unreacted VCM gas transfers and accumulates in the lubricating oil supplied in a rotary gas compressor in the compression process of VCM gas, the additive which inhibits the polymerization of VCM is added. Since the polymerization inhibitor does not precipitate, the generation and adhesion of the vinyl chloride polymer hardly occurs even if the lubricating oil is circulated and reused as a lubricating oil for a long period of time. Blockage of the inside piping and the inside of the strainer is suppressed. Therefore, even when a rotary gas compressor having a large gas processing capacity is used, the generation of the vinyl chloride polymer is effectively inhibited, so that there is no need to disassemble or clean the lubricating oil circulation line. In addition, the operation of the rotary gas compressor can be stably performed over a long period of time.
[Brief description of the drawings]
FIG. 1 is a process chart of an example of a compression method according to the present invention.
[Explanation of symbols]
1 ... supply line piping of vinyl chloride monomer 2 ... rotary gas compressor 3, 6, 10 ... circulation line piping 4 ... gas-liquid separator and lubricating oil storage tank 5 ... supply line piping of compressed vinyl chloride monomer to the condenser 7: Cooler for lubricating oil 8 ... Strainer for lubricating oil 9: Pump for feeding liquid

Claims (6)

A method of compressing a vinyl chloride monomer gas by a rotary gas compressor under contact with a circulating lubricating oil supplied into the machine, wherein the lubricating oil is 4-hydroxy-2,2,6,6- A method for compressing unreacted vinyl chloride monomer gas, comprising tetramethylpiperidine-N-oxyl. The compression method according to claim 1, wherein the vinyl chloride monomer gas contains moisture. 3. The compression method according to claim 1, wherein the vinyl chloride monomer gas is unreacted vinyl chloride monomer gas recovered from a vinyl chloride polymer production process. 4. 4. The lubricating oil according to claim 1, wherein the 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl is contained in the lubricating oil in a range of 1 to 1,000 ppm. The compression method according to claim 1. The lubricating oil is separated from a compressed gas containing the lubricating oil generated in the compression step, and then the lubricating oil is reused in the gas compressor. The compression method described in the section. The compression method according to claim 1, wherein the rotary gas compressor has a gas processing capacity of 2,000 m ³ / hr or more in a standard state.

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