Preparation method of octafluoro [2, 2] dimer p-xylene

Abstract

The invention discloses a preparation method of octafluoro [2, 2] parylene dimer, which comprises the following steps: uniformly mixing parylene N monomer, polar organic solvent, photosensitizer and additive to obtain mixed solution; and carrying out light treatment on the mixed solution, and adding a fluorinating reagent into the mixed solution to obtain the octafluoro [2, 2] dimer p-xylene. Starting from the N-type parylene monomer, photochemical reaction byproducts are few, the yield is high, purification is easy, and the N-type parylene monomer is commercialized, cheap and easy to obtain, so that industrialization of the preparation method is easier to realize.

Description

Technical Field

[0001] The invention relates to the technical field of organic synthesis, and in particular to a method for preparing octafluoro[2,2]dipoly-p-xylene. Background Art

[0002] Parylene, whose English name is Pary l ene, is a new type of conformal coating material. It is a polymer of paraxylene. According to different molecular structures, Pary l ene can be divided into N type, C type, D type, F type, HT type and other types.

[0003] The biggest features of parylene film are no branching, high crystallinity, and super 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, 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. The devices coated with it can improve surface lubrication, biocompatibility, and reliability. Among them, parylene HT, compared with other parylenes, the performance of parylene HT film is equally excellent or even better: low friction coefficient; excellent anti-penetration performance to water vapor, O2, N2 and CO2; low dielectric constant, dielectric strength, and dielectric loss factor. In addition, compared with other parylene films, the thermal stability and UV stability of Parylene HT film are much better, which means that Parylene HT film can fully maintain physical and chemical integrity at high temperatures. At the same time, it has very obvious advantages in terms of heat aging resistance, UV aging resistance, and radiation aging resistance. For example, Parylene HT can withstand high temperatures above 450 degrees Celsius for a long time, and can work stably for more than 2000 hours under ultraviolet rays. These excellent properties make Parylene HT have special applications in national defense, aerospace, military industry, etc. The synthesis of its monomer AF4 has always been a difficult point, and there are generally problems such as low yield, difficult purification, and high cost.

[0004] Therefore, the prior art needs to be further improved and enhanced. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the present invention provides a method for preparing octafluoro[2,2]dipoly-p-xylene, aiming to solve the problems of low yield, difficult purification and high cost in the existing preparation of octafluoro[2,2]dipoly-p-xylene.

[0006] The technical solution adopted by the present invention to solve the above technical problems is as follows:

[0007] A method for preparing octafluoro[2,2]dipoly-p-xylene, comprising:

[0008] Mixing parylene N monomer, polar organic solvent, photosensitizer and additives uniformly to obtain a mixed solution;

[0009] The mixed solution is subjected to light treatment. During the light treatment, a fluorination agent is dispersed into the mixed solution to obtain the octafluoro[2,2]dipoly-p-xylene.

[0010] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. Through the following preferred technical solutions, the objectives and beneficial effects of the present invention can be better achieved and realized.

[0011] As a preferred technical solution, in the method for preparing octafluoro[2,2]dipoly-p-xylene, the polar organic solvent is selected from one or more of acetonitrile, benzyl cyanide, cyclohexane, cyclohexanol and methanol.

[0012] As a preferred technical solution, the method for preparing octafluoro[2,2]dipoly-p-xylene, wherein the photosensitizer is selected from one or more of 9-fluorenone, benzophenone, diethoxyacetophenone, tris(2-phenylpyridine)iridium and 2,4,5,6-tetrakis(diphenylamino)-isophthalonitrile.

[0013] As a preferred technical solution, in the method for preparing octafluoro[2,2]dipoly-p-xylene, the additive is selected from one or more of butylated hydroxytoluene, phenothiazine, p-benzoquinone and p-phenol.

[0014] As a preferred technical solution, the method for preparing octafluoro[2,2]dipoly-p-xylene, wherein the fluorination agent is selected from one or more of 1-chloromethyl-4-fluoro-1,4-diazobicyclo[2.2.2]octane di(tetrafluoroborate), 1-fluoro-4-methyl-1,4-diazabicyclo[2.2.2]octane tetrafluoroborate, N-fluorobisbenzenesulfonamide, a mixed gas of F2 and N2 and N-fluoropyridine trifluoromethanesulfonate.

[0015] As a preferred technical solution, in the method for preparing octafluoro[2,2]dipoly-p-xylene, the wavelength of light used for the light treatment is 365-480nm.

[0016] As a preferred technical solution, the method for preparing octafluoro[2,2]dipoly-p-xylene, wherein the parylene N monomer, polar organic solvent, photosensitizer and additive are uniformly mixed to obtain a mixed solution, specifically comprising:

[0017] Parylene N monomer, polar organic solvent, photosensitizer and additive are respectively added into a photoreaction container, and a magnet is added into the photoreaction container for magnetic stirring to obtain a mixed solution.

[0018] As a preferred technical solution, the method for preparing octafluoro[2,2]dipoly-p-xylene, wherein the photoreaction container has a transparent cover; the mixed solution is subjected to light treatment, and a fluorination agent is added to the mixed solution to obtain the octafluoro[2,2]dipoly-p-xylene, specifically comprising:

[0019] At a preset temperature, irradiating the mixed solution in the photoreaction container with light through the cover;

[0020] The fluorination reagent is added into the photoreaction container in multiple times, and the octafluoro[2,2]dipoly-p-xylene is obtained after the reaction.

[0021] As a preferred technical solution, the method for preparing octafluoro[2,2]dipoly-p-xylene, wherein the fluorination agent is the mixed gas of F2 and N2; the photoreaction container has a transparent cover; the mixed solution is subjected to light treatment, and the fluorination agent is added to the mixed solution to obtain the octafluoro[2,2]dipoly-p-xylene, specifically comprising:

[0022] At a preset temperature, irradiating the mixed solution in the photoreaction container with light through the cover;

[0023] The F2 and N2 mixed gas is introduced into the photoreaction container multiple times through a pipeline, and the octafluoro[2,2]dipoly-p-xylene is obtained after the reaction.

[0024] As a preferred technical solution, in the method for preparing octafluoro[2,2]dipoly-p-xylene, the preset temperature is 20-60°C.

[0025] Beneficial effects: Compared with the prior art, the present invention starts from N-type parylene monomer, has few photochemical reaction byproducts, high yield and easy purification, and N-type parylene monomer has been commercialized, cheap and easy to obtain, making the preparation method easier to realize industrialization. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The present invention provides a preparation circuit diagram of octafluoro[2,2]dipoly-p-xylene;

[0027] Figure 2 This is the high performance liquid chromatogram of octafluoro[2,2]dipoly(p-xylene). DETAILED DESCRIPTION

[0028] The present invention provides a method for preparing octafluoro[2,2]dipoly-p-xylene. To make the purpose, technical scheme 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.

[0029] In addition, the features, operations or characteristics described in the specification can be combined in any appropriate manner to form various implementation methods. At the same time, the steps or actions in the method description can also be interchanged or adjusted in a manner that is obvious to those skilled in the art. Therefore, the various sequences in the specification and the drawings are only for the purpose of clearly describing a certain embodiment and do not mean that they are necessary sequences, unless otherwise specified that a certain sequence must be followed. The serial numbers themselves, such as "first", "second", etc., assigned to the components herein are only used to distinguish the objects described and do not have any order or technical meaning. The instruments used are all commercially available products.

[0030] Combination Figure 1 The method for preparing octafluoro[2,2]dipoly-p-xylene provided by the present invention comprises:

[0031] Step 10: Evenly mix the parylene N monomer, polar organic solvent, photosensitizer and additive to obtain a mixed solution.

[0032] Specifically, the parylene N monomer, polar organic solvent, photosensitizer and additive are weighed according to the addition ratio, and the above materials are mixed evenly to form a mixed solution. The structural formula of the parylene N monomer is: Polar organic solvents include but are not limited to acetonitrile, benzyl cyanide, cyclohexane, cyclohexanol, methanol and the like.

[0033] Photosensitizers include but are not limited to 9-fluorenone, benzophenone, diethoxyacetophenone, tris(2-phenylpyridine)iridium, 2,4,5,6-tetrakis(diphenylamino)-isophthalonitrile, etc., and the amount of photosensitizer added can be 3% of the substrate weight. Additives include but are not limited to butylated hydroxytoluene (BHT), phenothiazine, p-benzoquinone, p-phenol, etc., and the amount of addition can be 0.1% of the substrate weight.

[0034] Step 20: subjecting the mixed solution to light treatment and adding a fluorination agent to the mixed solution to obtain the octafluoro[2,2]dipoly-p-xylene.

[0035] Specifically, the mixed solution can be irradiated with blue light, the wavelength of the blue light can be 365-480nm, and the temperature of the irradiation reaction can be 20-60°C. Fluorination agents include but are not limited to: 1-chloromethyl-4-fluoro-1,4-diazobicyclo[2.2.2]octane di(tetrafluoroborate) (SelectfluorS). 1-Fluoro-4-methyl-1,4-diazabicyclo[2.2.2]octane tetrafluoroborate (Selectfluor II), N-fluorobisbenzenesulfonamide (NSFI), N-fluoropyridine trifluoromethanesulfonate, F2 / N2 mixed gas (10%), etc. Preferably, the mixed system of SelectfluorS and F2 / N2 gas (10%) is added in an amount of 8-20 times the molar equivalent of the reactants.

[0036] The above technical solution provided by the present invention is further explained below through a specific preparation method.

[0037] Example 1

[0038] In the photoreaction cup, add 10g of parylene N monomer, 500mL of acetonitrile, 0.3g of photosensitizer 2,4,5,6-tetrakis(diphenylamino)-isophthalonitrile, 0.01g of phenothiazine, add a magnet, turn on the constant temperature magnetic stirrer to stir evenly, set the temperature to 40℃, cover the quartz plate, turn on the flat LED lamp (120w, 420nm), irradiate the reaction solution through the quartz cover, add 160g of selective fluorine reagent (Se l ectfluorS) in 8 times, add it within 4 hours, continue to react for 8h after adding, and after the reaction is completed, reduce the pressure to concentrate most of the solvent, cool to 0-10℃ for crystallization for 1h, and filter. Add 1000mL of water to the filter cake, heat it to 50℃ and stir for 1h. Filter and dry to obtain 14.3g of AF4 crude product with a yield of 85%.

[0039] Example 2

[0040] In the photoreaction cup, add 10g of parylene N monomer, 500mL of acetonitrile, 0.3g of photosensitizer 9-fluorenone, 0.02g of BHT, add a magnet, connect the ventilation line, turn on the constant temperature magnetic stirrer to stir evenly, set the temperature to 35°C, cover the quartz plate, turn on the flat LED lamp (120w, 420nm), irradiate the reaction solution through the quartz cover, open the F2 / N2 gas (10%) valve, slowly introduce F2 / N2 gas, maintain a flow rate of about 0.2L / min, continue to ventilate and continue to react for 8h, after ventilation is completed, continue to react for 4h, switch to nitrogen and continue to blow nitrogen for 1h, reduce pressure and concentrate most of the solvent, cool to 0-10°C for crystallization for 1h, and filter. Add 800mL of water to the filter cake and heat to 50°C and stir for 1h. Filter and dry to obtain 13.5g of AF4 crude product with a yield of 79.8%.

[0041] Example 3

[0042] In the photoreaction cup, add 10g of parylene N monomer, 500mL of acetonitrile, 0.3g of photosensitizer 2,4,5,6-tetrakis(diphenylamino)-isophthalonitrile, 0.01g of phenothiazine, add a magnet, turn on the constant temperature magnetic stirrer to stir evenly, set the temperature to 40℃, cover the quartz plate, turn on the flat LED lamp (120w, 420nm), irradiate the reaction solution through the quartz cover, add 16g of selective fluorine reagent (SelectfluorS), open the F2 / N2 gas (10%) valve, slowly introduce F2 / N2 gas, maintain the flow rate of about 0.2L / min, continue to ventilate and continue to react for 8h, after ventilating, continue to react for 4h, switch to nitrogen and continue to ventilate for 1h, concentrate most of the solvent under reduced pressure, cool to 0-10℃ for crystallization for 1h, and filter. Add 800mL of water to the filter cake, heat to 50℃ and stir for 1h. Filtration and drying gave 15.1 g of crude AF4 with a yield of 89.3%.

[0043] Purification: Add 15g of crude AF4 to the sublimation bottle, cover it with a desublimation plate and lid, and heat under reduced pressure for sublimation purification. The temperature is 100℃, and the vacuum pressure is -0.09Mpa, which is maintained for 20 minutes. Cool, release the gas, remove the initial condensate on the desublimation plate, install the device and continue to heat to 160℃, and the vacuum pressure is maintained at -0.09Mpa for 1.5 hours. Cool, and remove 13.6g of AF4 fine product on the desublimation plate, with a yield of 90.7% and a purity of 99.1%. 1HNMR (200MHz, CDC l 3) δ7.16 (s, 8H); 19F NMR (376.5MHz, CDC l3) δ118.2 (s, 8F). Its spectrum is as follows Figure 2 shown.

[0044] Example 4

[0045] In the photoreaction cup, add 10g of parylene N monomer, 500mL of cyclohexane, 0.3g of photosensitizer diethoxyacetophenone, 0.01g of dibutylhydroxytoluene, add a magnet, turn on the constant temperature magnetic stirrer to stir evenly, set the temperature to 45℃, cover the quartz plate, turn on the flat LED lamp (120w, 450nm), irradiate the reaction solution through the quartz cover, add 160g of selective fluorine reagent (Selectfluor II) in 8 times, add it within 4 hours, continue to react for 8h after adding, and after the reaction is completed, reduce the pressure to concentrate most of the solvent, cool to 8℃ for crystallization for 1h, and filter. Add 1000mL of water to the filter cake, heat it to 50℃ and stir for 1h. Filter and dry to obtain 14.1g of AF4 crude product with a yield of 83.8%.

[0046] Example 5

[0047] In the photoreaction cup, add 10g of parylene N monomer, 500mL of benzyl cyanide, 0.3g of photosensitizer tris(2-phenylpyridine)iridium, 0.01g of p-benzoquinone, add a magnet, turn on the constant temperature magnetic stirrer to stir evenly, set the temperature to 60℃, cover the quartz plate, turn on the flat LED lamp (120w, 450nm), irradiate the reaction solution through the quartz cover, add 160g of selective fluorine reagent (Selectfluor II) in 8 times, add it within 4 hours, continue to react for 8h after adding, and after the reaction is completed, reduce the pressure to concentrate most of the solvent, cool to 8℃ for crystallization for 1h, and filter. Add 1000mL of water to the filter cake, heat it to 50℃ and stir it for 1h. Filter and dry to obtain 13.2g of AF4 crude product with a yield of 78.5%.

[0048] Example 6

[0049] In the photoreaction cup, add 10g of parylene N monomer and 500mL of benzyl cyanide.

[0050] Photosensitizer 2,4,5,6-tetrakis (diphenylamino)-isophthalonitrile 0.3g, BHT 0.02g, add magnet, connect ventilation line, turn on constant temperature magnetic stirrer to stir evenly, set temperature to 40℃, cover with quartz plate, turn on flat LED lamp (120w, 420nm), irradiate reaction solution through quartz cover plate, open F2 / N2 gas (10%) valve, slowly introduce F2 / N2 gas, keep flow rate about 0.3L / min, continue ventilation and continue reaction for 8h, ventilation is completed, continue reaction for 4h, switch nitrogen and continue nitrogen blowing for 1h, reduce pressure and concentrate most of solvent, cool to 10℃ for crystallization for 1h, filter. Add 800mL water to filter cake, heat to 50℃ and stir for 1h. Filter and dry to obtain 13.8g crude AF4 with a yield of 81.5%.

[0051] Example 7

[0052] In the photoreaction cup, add 10g of parylene N monomer, 200mL of benzyl cyanide, 300mL of acetonitrile, 0.3g of photosensitizer 2,4,5,6-tetrakis(diphenylamino)-isophthalonitrile, 0.02g of BHT, add a magnet, connect the ventilation line, turn on the constant temperature magnetic stirrer to stir evenly, set the temperature to 40℃, cover the quartz plate, turn on the flat LED lamp (120w, 420nm), irradiate the reaction solution through the quartz cover, open the F2 / N2 gas (10%) valve, slowly introduce F2 / N2 gas, maintain the flow rate of about 0.2L / min, continue to ventilate and continue to react for 8h, after the ventilation is completed, continue to react for 4h, switch to nitrogen and continue to blow nitrogen for 1h, reduce pressure to concentrate most of the solvent, cool to 8℃ for crystallization for 1h, and filter. Add 1000mL of water to the filter cake, heat to 50℃ and stir for 1h. Filtration and drying were performed to obtain 13.6 g of crude AF4 with a yield of 80.3%.

[0053] Example 8

[0054] In the photoreaction cup, add 10g of parylene N monomer, 200mL of benzyl cyanide, 300mL of acetonitrile, 0.3g of photosensitizer 2,4,5,6-tetrakis(diphenylamino)-isophthalonitrile, 0.02g of phenothiazine, add a magnet, turn on the constant temperature magnetic stirrer to stir evenly, set the temperature to 40℃, cover the quartz plate, turn on the flat LED lamp (120w, 450nm), irradiate the reaction solution through the quartz cover, add 160g of selective fluorine reagent (SelectfluorS) in 8 times, add it within 4 hours, continue to react for 8h after adding, and after the reaction is completed, reduce the pressure to concentrate most of the solvent, cool to 8℃ for crystallization for 1h, and filter. Add 1000mL of water to the filter cake, heat it to 50℃ and stir it for 1h. Filter and dry to obtain 14.2g of AF4 crude product with a yield of 83.9%.

[0055] Example 9

[0056] In the photoreaction cup, add 10g of parylene N monomer, 200mL of benzyl cyanide, 300mL of acetonitrile, 0.3g of photosensitizer 2,4,5,6-tetrakis (diphenylamino)-isophthalonitrile, 0.02g of phenothiazine, add a magnet, turn on the constant temperature magnetic stirrer to stir evenly, set the temperature to 40℃, cover the quartz plate, turn on the flat LED lamp (120w, 450nm), irradiate the reaction solution through the quartz cover, add 160g of N-fluoropyridine trifluoromethanesulfonate in 8 times, add it within 4 hours, continue to react for 7h after adding, and after the reaction is completed, reduce the pressure to concentrate most of the solvent, cool to 10℃ for crystallization for 1h, and filter. Add 800mL of water to the filter cake, heat it to 50℃ and stir for 1h. Filter and dry to obtain 13.9g of AF4 crude product with a yield of 82.2%.

[0057] In summary, the present invention provides a method for preparing octafluoro[2,2]dipoly-p-xylene, using N-type parylene monomer as raw material, blue light irradiation reaction, the wavelength range is 365-480nm, preferably 420nm, the photosensitizer includes 9-fluorenone, benzophenone, diethoxyacetophenone, tris(2-phenylpyridine)iridium, 2,4,5,6-tetrakis(diphenylamino)-isophthalonitrile, etc.

[0058] 2,4,5,6-Tetrakis(diphenylamino)-isophthalonitrile is preferred. The added amount is 3% of the substrate weight.

[0059] Fluorination agents include: 1-chloromethyl-4-fluoro-1,4-diazobicyclo[2.2.2]octane di(tetrafluoroborate) (SelectfluorS), 1-fluoro-4-methyl-1,4-diazabicyclo[2.2.2]octane tetrafluoroborate (SelectfluorII), N-fluorobisbenzenesulfonamide (NSFI), N-fluoropyridine trifluoromethanesulfonate, F2 / N2 mixed gas (10%), etc. Preferably, a mixed system of SelectfluorS and F2 / N2 gas (10%) is used, and a reaction solvent added in an amount of 8-20 times the molar equivalent of the reactants includes acetonitrile, benzyl cyanide, cyclohexane, cyclohexanol, methanol, etc., preferably acetonitrile. The additives include butylated hydroxytoluene (BHT), phenothiazine, p-benzoquinone, p-phenol, etc., and the added amount is 0.1% of the substrate mass. The reaction temperature range of phenothiazine is preferably 20-60°C, preferably 40°C. Starting from the N-type parylene monomer, the starting raw material has been commercialized, cheap and easy to obtain, with few by-products, and only the product AF4 and its intermediates are generated. The intermediates can continue to react to obtain products. The photochemical reaction is green and environmentally friendly, and it is easy to realize industrialization.

[0060] 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 method for preparing octafluoro[2,2]dipoly-p-xylene, characterized in that: include: Mixing parylene N monomer, polar organic solvent, photosensitizer and additives uniformly to obtain a mixed solution; The mixed solution is subjected to light treatment. During the light treatment, a fluorination agent is dispersed into the mixed solution to obtain the octafluoro[2,2]dipoly-p-xylene.

2. The method for preparing octafluoro[2,2]dipoly-p-xylylene according to claim 1, characterized in that: The polar organic solvent is selected from one or more of acetonitrile, benzyl cyanide, cyclohexane, cyclohexanol and methanol.

3. The method for preparing octafluoro[2,2]dipoly-p-xylylene according to claim 1, characterized in that: The photosensitizer is selected from one or more of 9-fluorenone, benzophenone, diethoxyacetophenone, tris(2-phenylpyridine)iridium and 2,4,5,6-tetrakis(diphenylamino)-isophthalonitrile.

4. The method for preparing octafluoro[2,2]dipoly-p-xylylene according to claim 1, characterized in that: The additive is selected from one or more of butylated hydroxytoluene, phenothiazine, p-benzoquinone and p-phenol.

5. The method for preparing octafluoro[2,2]dipoly-p-xylylene according to claim 1, characterized in that: The fluorination agent is selected from one or more of 1-chloromethyl-4-fluoro-1,4-diazobicyclo[2.2.2]octane di(tetrafluoroborate), 1-fluoro-4-methyl-1,4-diazabicyclo[2.2.2]octane tetrafluoroborate, N-fluorobisbenzenesulfonamide, a mixed gas of F2 and N2, and N-fluoropyridine trifluoromethanesulfonate.

6. The method for preparing octafluoro[2,2]dipoly-p-xylylene according to claim 1, characterized in that: The wavelength of light used in the phototreatment is 365-480nm.

7. The method for preparing octafluoro[2,2]dipoly-p-xylylene according to claim 1, characterized in that: The parylene N monomer, polar organic solvent, photosensitizer and additive are uniformly mixed to obtain a mixed solution, specifically comprising: Parylene N monomer, polar organic solvent, photosensitizer and additive are respectively added into a photoreaction container, and a magnet is added into the photoreaction container for magnetic stirring to obtain a mixed solution.

8. The method for preparing octafluoro[2,2]dipoly-p-xylylene according to claim 7, characterized in that: The photoreaction container has a transparent cover; the mixed solution is subjected to light treatment, and a fluorination agent is added to the mixed solution to obtain the octafluoro[2,2]dipoly-p-xylene, specifically comprising: At a preset temperature, irradiating the mixed solution in the photoreaction container with light through the cover; The fluorination reagent is added into the photoreaction container in multiple times, and the octafluoro[2,2]dipoly-p-xylene is obtained after the reaction.

9. The method for preparing octafluoro[2,2]dipoly-p-xylylene according to claim 7, characterized in that: The fluorination agent is the mixed gas of F2 and N2; the photoreaction container has a transparent cover; the mixed solution is subjected to light treatment, and the fluorination agent is added to the mixed solution to obtain the octafluoro[2,2]dipoly-p-xylene, specifically comprising: At a preset temperature, irradiating the mixed solution in the photoreaction container with light through the cover; The F2 and N2 mixed gas is introduced into the photoreaction container multiple times through a pipeline, and the octafluoro[2,2]dipoly-p-xylene is obtained after the reaction.

10. The method for preparing octafluoro[2,2]dipoly-p-xylylene according to claim 8 or 9, characterized in that: The preset temperature is 20-60°C.

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