A photochemical preparation method of N-type parylene monomer

Abstract

The present invention relates to the technical field of organic synthesis, and specifically discloses a photochemical preparation method of an N-type parylene monomer. The preparation method comprises the steps of: heating and gasifying a mixed liquid of p-xylene and water to obtain a mixed vapor; heating the mixed vapor, irradiating the heated mixed vapor with ultraviolet light, and then passing it into an absorption solvent for dimerization reaction, and filtering and purifying after the reaction to obtain the N-type parylene monomer. The photochemical preparation method of the present invention avoids the high-temperature reaction of the Gorham synthesis method, avoids the stringent requirements on equipment and safety hazards, and has no coking phenomenon, high atomic utilization rate, and high yield. The entire preparation process is green and environmentally friendly, and is suitable for industrial production.

Description

Technical Field

[0001] The invention relates to the technical field of organic synthesis, and in particular to a photochemical preparation method of an N-type parylene monomer. Background Art

[0002] Parylene was first developed by Union Carbide Co. in the United States. The biggest features of Parylene film are no branching, high crystallinity, and ultra-large molecular weight. It can be applied to surfaces of various shapes, including sharp edges, and is known as "penetrating all holes" and can penetrate deep into cracks and inner surfaces. This nano-coating film prepared by room temperature deposition under vacuum has uniform thickness, is dense and pinhole-free, transparent and stress-free, does not contain additives, does not damage the workpiece, and has good electrical insulation and protection. At the same time, it is also a high-purity coating material with chemical inertness and good biocompatibility. It has been approved by the US FDA and is used for various types of in vivo implants. Devices coated with it can improve surface lubrication, biocompatibility, and reliability. Parylene's biocompatibility and biostability enable it to provide good moisture-proof, chemical-proof and dielectric protection.

[0003] Parylene film is inseparable from its parylene material monomer, whose structure is di-p-xylene and its substituted derivatives. At present, according to the different molecular structures, parylene materials can be divided into parylene N, parylene C, parylene F, parylene HT and other types. Among them, the raw materials of parylene C and parylene N are cheap and have the widest application range.

[0004] The structural formulas of Parylene N monomer, Parylene C monomer, Parylene D monomer and Parylene F monomer are as follows:

[0005]

[0006] In the late 1990s, China began to study the synthesis of parylene materials. The main synthesis methods are as follows:

[0007] Method 1: Gorham synthesis method, starting from p-xylene as raw material, pyrolyzes it with water vapor at high temperature, the temperature needs to be about 850-1000℃. Then dimerization reaction is performed to obtain di-p-xylene crystals. This method needs to be carried out at high temperature, is prone to coking, has strict requirements on equipment and high risk factor, and has a low yield, which is not suitable for industrial production.

[0008] The reaction route of this method is as follows:

[0009]

[0010] Method 2: Hofmann elimination method, which is currently the most commonly used method for synthesizing parylene monomer materials. After the benzyl halogen-substituted p-xylene and its derivatives react with trimethylamine to form quaternary ammonium salts, they undergo Hofmann elimination under the action of strong alkali and then dimerize to form the corresponding parylene monomer materials. The trimethylamine gas used in this method has a foul odor and produces a large amount of waste alkali, which is not environmentally friendly. Due to the high requirements for equipment under the halogen-containing strong alkali system, the equipment is also severely corroded, the yield is low, and the cost is high. And basically only the simplest parylene N and parylene C can be synthesized, and other substituted groups are more difficult to react.

[0011] The reaction route of this method is as follows:

[0012]

[0013] Method 3: Dihalogenated p-xylene derivatives are reduced and dimerized under the action of zinc powder to produce parylene monomer materials. This method can synthesize a variety of parylene monomers, but the amount of zinc powder used is large, there are safety risks, the product purity is low, separation is difficult, the yield is low, the atomic utilization rate is low, and the cost is difficult to control.

[0014] The reaction route of this method is as follows:

[0015]

[0016] Therefore, the prior art still needs to be improved and developed. Summary of the invention

[0017] In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide a photochemical preparation method of N-type parylene monomer, aiming to solve the problems that the existing method for preparing parylene monomer has strict equipment requirements, high safety risks and low yield.

[0018] The technical solution of the present invention is as follows:

[0019] The present invention provides a photochemical preparation method of N-type parylene monomer, comprising the steps of:

[0020] S1, heating and gasifying a mixed liquid of p-xylene and water to obtain mixed vapor;

[0021] S2, heating the mixed vapor, irradiating the heated mixed vapor with ultraviolet light, and then passing it into an absorbing solvent for dimerization reaction, filtering and purifying after the reaction to obtain the N-type parylene monomer (p-xylene ring dimer).

[0022] In step S1, optionally, the mass ratio of p-xylene to water in the mixed liquid is (0.8-2):1.

[0023] Preferably, the mass ratio of p-xylene to water in the mixed liquid is (1-1.5):1.

[0024] In step S2, optionally, the temperature of the heated mixed vapor is 140-260°C.

[0025] Preferably, the temperature of the heated mixed vapor is 180-200°C.

[0026] In step S2, optionally, the wavelength of the ultraviolet light irradiation is 254-300nm.

[0027] Preferably, the wavelength of the ultraviolet light irradiation is 275-285 nm.

[0028] In step S2, optionally, the absorption solvent includes one or more of benzene, chlorobenzene and p-xylene.

[0029] Optionally, the absorption solvent further comprises a polymerization inhibitor, and the polymerization inhibitor is selected from one or more of butylated hydroxytoluene, phenothiazine, p-benzoquinone and p-phenol.

[0030] Optionally, the mass fraction of the polymerization inhibitor in the absorption solvent is 0.4-0.6%.

[0031] In step S2, optionally, the temperature of the dimerization reaction is 15-75°C, preferably, the temperature of the dimerization reaction is 40-50°C.

[0032] Optionally, the dimerization reaction time is 6-8h.

[0033] Beneficial effects:

[0034] The present invention uses cheap and readily available p-xylene as a starting material, generates an active intermediate p-xylene by photochemical cracking of p-xylene, and then obtains an N-type parylene monomer by dimerization. The preparation method has a simple process and mild reaction conditions, avoids the high temperature reaction in the conventional Gorham synthesis method, thereby avoiding the stringent requirements on equipment and solving potential safety hazards. Moreover, the reaction raw material p-xylene can be reused, has no coking phenomenon, has high atomic utilization rate, and has a high yield. The whole process is green and environmentally friendly and suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 Schematic diagram of the reaction device used in the photochemical preparation method of N-type parylene monomer described in the embodiment of the present invention. DETAILED DESCRIPTION

[0036] The present invention provides a photochemical preparation method of N-type parylene monomer. In order to make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0037] Unless otherwise defined, all technical terms and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0038] The embodiment of the present invention provides a photochemical preparation method of N-type parylene monomer, comprising the steps of:

[0039] S1, heating and gasifying a mixed liquid of p-xylene and water to obtain mixed vapor;

[0040] S2, heating the mixed vapor, irradiating the heated mixed vapor with ultraviolet light, and then passing it into an absorption solvent for dimerization reaction, and filtering and purifying after the reaction to obtain the N-type parylene monomer.

[0041] In some specific embodiments, the following can be used: Figure 1 The reaction device shown is used for the photochemical preparation of N-type parylene monomer (i.e., p-xylene cyclic dimer). The specific process is as follows: first, a mixture of p-xylene and water is heated to boiling in a single-mouth reaction bottle to form a mixed vapor. The mixed vapor is heated again by a heating tube and then passed into a quartz tube. In the quartz tube, it is irradiated with ultraviolet light. At this time, gaseous p-xylene at high temperature is activated by the irradiation of high-energy ultraviolet light and photodegrades to form a highly active intermediate p-xylene benzene. After the gaseous p-xylene enters a receiving bottle with a lower temperature, a dimerization reaction occurs in the absorption solvent to polymerize to form an N-type parylene monomer. After the solid is gradually precipitated, the crude product is obtained by cooling and filtering, and then the fine product of N-type parylene monomer is obtained after purification.

[0042] In the preparation process, gaseous p-xylene forms gaseous free radical monomers under high temperature and ultraviolet light conditions, and then polymerizes to form N-type parylene monomers after cooling. The reaction route is as follows:

[0043]

[0044] The preparation method provided by the present invention has simple process and mild conditions, avoids the strict requirements on equipment and potential safety hazards of high-temperature reaction, has no coking phenomenon, has high atomic utilization rate, and improves the yield of N-type parylene monomer.

[0045] In step S1, in some embodiments, the mass ratio of p-xylene to water in the mixed liquid is (0.8-2):1.

[0046] In some preferred embodiments, the mass ratio of p-xylene to water in the mixed liquid is (1-1.5):1.

[0047] In step S2, in some embodiments, the temperature of the heated mixed vapor is 140-260°C.

[0048] In some preferred embodiments, the temperature of the heated mixed vapor is 180-200°C.

[0049] In step S2, in some embodiments, the wavelength of the ultraviolet light irradiation is 254-300 nm.

[0050] In some preferred embodiments, the wavelength of the ultraviolet light irradiation is 275-285 nm.

[0051] In a specific embodiment, ultraviolet external irradiation can use a high-pressure mercury lamp, a medium-pressure mercury lamp, or a 254-300nm LED ultraviolet lamp.

[0052] High-temperature gaseous p-xylene is activated under high-energy ultraviolet light and photodegrades to form the intermediate p-xylene. p-xylene is a highly active intermediate that is stable in the gaseous state at low pressure and high temperature, and rapidly polymerizes after dropping to a certain temperature. When a 280nm ultraviolet LED is selected for irradiation, it is easier for gaseous p-xylene to generate the intermediate p-xylene, thus achieving the highest yield.

[0053] In step S2, in some embodiments, the absorption solvent includes one or more of benzene, chlorobenzene and p-xylene.

[0054] In some embodiments, the absorption solvent further comprises a polymerization inhibitor, which is selected from one or more of butylated hydroxytoluene, phenothiazine, p-benzoquinone and p-phenol. The addition of the polymerization inhibitor can prevent the rapid generation of polymers and reduce the yield of the N-type parylene monomer.

[0055] In some embodiments, the mass fraction of the polymerization inhibitor in the absorption solvent is 0.4-0.6%.

[0056] In step S2, in some embodiments, the dimerization reaction temperature is 15-75° C., preferably, the dimerization reaction temperature is 40-50° C. In a specific embodiment, too high or too low temperature during the dimerization reaction will reduce the yield of N-type parylene monomer.

[0057] In some embodiments, the dimerization reaction time is 6-8 hours.

[0058] The following describes it in detail through specific embodiments.

[0059] The following examples all adopt Figure 1 The reaction device shown in the figure comprises: a single-mouth reaction flask, b metal heating tube, c quartz tube, d ultraviolet light irradiation (high-pressure mercury lamp or ultraviolet LED can be used) and e receiving bottle (three-necked flask). The connection order of each part in the reaction device is: the single-mouth reaction flask is connected to the metal heating tube, the metal heating tube is connected to one end (inlet) of the quartz tube, the high-pressure mercury lamp or ultraviolet LED is placed in parallel with the quartz tube, the other end (outlet) of the quartz tube is connected to the receiving bottle, and a condenser is configured to completely condense the tail gas. Among them, the receiving bottle can be placed on a magnetic stirrer.

[0060] Example 1

[0061] The route for synthesizing N-type parylene monomer using p-xylene as raw material is as follows:

[0062]

[0063] Add 500 g of p-xylene and 500 g of water into a single-necked reaction bottle, add 50 g of p-xylene and 0.25 g of butylated hydroxytoluene (BHT) into a receiving bottle (three-necked bottle), and turn on a 500 W high-pressure mercury lamp to irradiate the quartz tube.

[0064] Place the single-mouth reaction bottle in an oil bath (160°C) to heat the mixture of p-xylene and water to boiling. The mixed vapor is heated to 180°C through a metal heating tube, and then irradiated by a high-pressure mercury lamp in a quartz tube and enters the receiving bottle (three-necked flask). The temperature is controlled at 45°C to react for 6 hours. The p-xylene in the single-mouth reaction bottle is distilled to dryness. Solids begin to precipitate in the receiving bottle (three-necked flask). The temperature is lowered to 5°C for filtration to obtain 6g of crude product. 120mL of dichloromethane is added to the crude product. After heating and refluxing to dissolve, it is filtered while hot to remove polymers. The dichloromethane is concentrated to dryness to obtain 4g of N-type parylene monomer. The mass yield (calculated based on the amount of p-xylene consumed) is 12%. The melting point of the product mp: 285°C~287°C, 1 HNMR (CDCl3) δ: 6.54~6.69 (m, 8H), 3.03~3.10 (s, 8H), peak area ratio (about 3.90:4.0).

[0065] Example 2

[0066] Add 500 g of p-xylene and 500 g of water into a single-necked reaction bottle, add 50 g of p-xylene and 0.25 g of BHT into a receiving bottle (three-necked bottle), and turn on a 200 W ultraviolet LED (ultraviolet wavelength is 280 nm) to irradiate the quartz tube.

[0067] Place a single-mouth reaction bottle in an oil bath (160°C) to heat the mixture of p-xylene and water to boiling, heat the mixed vapor to 200°C through a metal heating tube, and then enter the receiving bottle (three-necked bottle) after being irradiated by an ultraviolet LED in a quartz tube, and react at 45°C for 8 hours. The p-xylene in the single-mouth reaction bottle is distilled to dryness. Solids begin to precipitate in the receiving bottle (three-necked bottle), cool to 5°C, and filter to obtain a crude product. Add 120mL of dichloromethane to the crude product, heat to reflux to dissolve, filter while hot to remove polymers, concentrate dichloromethane to dryness, and obtain N-type parylene monomer. The mass yield is calculated based on the amount of p-xylene consumed.

[0068] A series of comparative experiments 1-7 (wherein experiment 2 is the above-mentioned embodiment 2) as shown in Table 1 were carried out. The variable factors in the comparative experiments (ultraviolet wavelength, reaction temperature of the receiving bottle, whether to add an inhibitor) are listed in Table 1, and the rest are the same as the above-mentioned embodiment 2.

[0069] Table 1

[0070] UV wavelength Receiving bottle reaction temperature Inhibitor Mass yield Example 1 Mercury lamp broad spectrum 45℃ BHT 12％ 1 254nm 45℃ BHT 34％ 2 280nm 45℃ BHT 56％ 3 295nm 45℃ BHT 9.2％ 4 305nm 45℃ BHT 0％ 5 280nm 15℃ BHT 36％ 6 280nm 75℃ BHT 27％ 7 280nm 45℃ No 13％

[0071] It can be seen from the mass yield of the comparative experiment in Table 1 that the UV wavelength, the reaction temperature of the receiving bottle and the addition of the polymerization inhibitor during the preparation process have a significant impact on the yield of the N-type parylene monomer product. The conditions in Example 2 are preferably used: 280nm UV LED, the receiving bottle temperature is controlled at 45°C, and an appropriate amount of polymerization inhibitor dibutyl hydroxytoluene is added, and the mass yield of the N-type parylene monomer can reach 56%.

[0072] Example 3

[0073] Add 600 g of p-xylene and 400 g of water to a single-necked reaction bottle, add 50 g of p-xylene and 0.25 g of BHT to a receiving bottle (three-necked bottle), and turn on a 600 W ultraviolet LED (ultraviolet wavelength is 280 nm) to irradiate the quartz tube.

[0074] Heat the mixture of p-xylene and water in a single-mouth reaction bottle to boiling, heat the mixed vapor to 200°C through a metal heating tube, and then enter the receiving bottle (three-necked bottle) after being irradiated by an ultraviolet LED in a quartz tube, and react at 45°C for 8 hours. When solid precipitates in the receiving bottle, cool it to 5°C, filter it to obtain a crude product, replace the receiving bottle, and add the filtrate to the single-mouth reaction bottle to continue heating, and repeat the reaction for 48 hours. Combine the crude products, add dichloromethane, heat and reflux to dissolve, filter while hot, remove the polymer, and concentrate the dichloromethane to dryness to obtain 112g of N-type parylene monomer powder with a purity of 99%.

[0075] It should be understood that the application of the present invention is not limited to the above examples. For ordinary technicians in this field, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A photochemical preparation method of N-type parylene monomer, characterized in that: Includes steps: S1, heating and gasifying a mixed liquid of p-xylene and water to obtain mixed vapor; S2, heating the mixed vapor, irradiating the heated mixed vapor with ultraviolet light, and then passing it into an absorption solvent for dimerization reaction, and filtering and purifying after the reaction to obtain the N-type parylene monomer; The wavelength of the ultraviolet light irradiation is 254-300nm.

2. The photochemical preparation method of N-type parylene monomer according to claim 1, characterized in that: In step S1, the mass ratio of p-xylene to water in the mixed liquid is (0.8-2):

1.

3. The photochemical preparation method of N-type parylene monomer according to claim 2, characterized in that: The mass ratio of p-xylene to water in the mixed liquid is (1-1.5):

1.

4. The photochemical preparation method of N-type parylene monomer according to claim 1, characterized in that: In step S2, the temperature of the heated mixed steam is 140-260°C.

5. The photochemical preparation method of N-type parylene monomer according to claim 4, characterized in that: The temperature of the heated mixed steam is 180-200°C.

6. The photochemical preparation method of N-type parylene monomer according to claim 1, characterized in that: The wavelength of the ultraviolet light irradiation is 275-285nm.

7. The photochemical preparation method of N-type parylene monomer according to claim 1, characterized in that: In step S2, the absorption solvent includes one or more of benzene, chlorobenzene and p-xylene.

8. The photochemical preparation method of N-type parylene monomer according to claim 7, characterized in that: The absorption solvent further comprises a polymerization inhibitor, and the polymerization inhibitor is selected from one or more of butylated hydroxytoluene, phenothiazine, p-benzoquinone and p-phenol; And / or, the mass fraction of the polymerization inhibitor in the absorption solvent is 0.4-0.6%.

9. The photochemical preparation method of N-type parylene monomer according to claim 1, characterized in that: In step S2, the temperature of the dimerization reaction is 15-75°C.

10. The photochemical preparation method of N-type parylene monomer according to claim 9, characterized in that: The temperature of the dimerization reaction is 40-50° C., and the time of the dimerization reaction is 6-8 hours.

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