Full-continuous production process of dioctyl terephthalate

Abstract

The invention relates to a full-continuous production process of dioctyl terephthalate, and belongs to the technical field of high-molecular compound synthesis processes. The invention discloses a full-continuous production process of dioctyl terephthalate, which comprises the following steps: by taking a three-stage gradient reaction device as an esterification tower, increasing the esterification rate by controlling gradient temperature and pressure, connecting an esterification separator to the top of the esterification tower, separating water vapor and alcohol vapor, cooling the vapor, and carrying out oil-water separation, and freezing and standing the separated octanol to flow back into the esterification tower, enabling the material reacted in the esterification tower to flow out from the bottom of the tower, introducing into a secondary distillation tower, carrying out reduced pressure distillation, cooling and dehydrating, and filtering to obtain a finished product.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high polymer compound synthesis process, and relates to a full-continuous production process of dioctyl terephthalate. BACKGROUND

[0002] Dioctyl terephthalate (DOTP) is a kind of excellent main plasticizer for polyvinyl chloride (PVC) plastic, which has the advantages of heat resistance, cold resistance, low volatility, anti-extraction, softness and good electrical insulation performance, and shows excellent durability, resistance to soapy water and low-temperature softness in products. Because of its low volatility, the use of DOTP can fully meet the temperature rating requirements of electric wires and cables. DOTP, in addition to being used as a plasticizer for cables and PVC, can also be used as a plasticizer for acrylonitrile derivatives, polyvinyl butyral, nitrile rubber, nitrocellulose, synthetic rubber, coating additives, precision instrument lubricants, lubricant additives, and paper softening agents.

[0003] Compared with the traditional batch production, the continuous production can significantly improve the production efficiency, reduce the energy consumption and cost per unit product, and ensure the stability and consistency of product quality. The advantage of this process is that it can realize continuous input of raw materials, continuous output of products and automatic control of the production process, thereby reducing the possibility of human intervention and operation errors. In addition, the continuous production process helps to maximize the use of resources and minimize the discharge of waste, in line with the current green and environmentally friendly production concept. SUMMARY

[0004] The application relates to a full-continuous production process of dioctyl terephthalate, and belongs to the technical field of high polymer compound synthesis process. The full-continuous production process of dioctyl terephthalate disclosed by the application takes a three-stage gradient reaction device as an esterification tower, controls the gradient temperature and pressure to improve the esterification rate, connects an esterification separator to the top of the esterification tower, separates water vapor and alcohol vapor, separates oil and water after the vapor is cooled, and the separated octanol is cooled, frozen and placed to flow back to the esterification tower. The material reacted in the esterification tower flows out from the bottom, is subjected to reduced pressure distillation, cooling and dehydration operation in a secondary distillation tower, and is filtered to obtain a finished product.

[0005] The object of the application can be achieved by the following technical scheme.

[0006] A full-continuous production process of dioctyl terephthalate, which comprises the following steps.

[0007] (1) The pretreated terephthalic acid, the pretreated octanol and the catalyst are put into the first-stage reaction device of the three-stage gradient reaction device, and then the temperature is raised and the mixture is stirred;

[0008] (2) connecting the esterification separator with the first-stage reaction device, separating water vapor and alcohol vapor, and separating the alcohol after cooling the vapor;

[0009] (3) passing the material generated in step (1) from the third-stage reaction device of the three-stage reaction device into a two-stage distillation column, distilling under reduced pressure, filtering after cooling and dewatering, and obtaining the finished product.

[0010] Further, the mass ratio among the pretreated terephthalic acid, the pretreated octanol and the catalyst in step (1) is 1-2:3-4:0.02, wherein the catalyst is composed of stannous octoate and sulfuric acid with a mass ratio of 1-1.2:1, and the mass fraction of the sulfuric acid is 70-72%.

[0011] Further, the preparation method of the pretreated terephthalic acid in step (1) is as follows: freezing the terephthalic acid at a temperature of -15℃ for 40-60 minutes, and then dewatering under vacuum at 80-90℃ until the water content is 0.1%, and the vacuum degree is 0.01-0.04 MPa.

[0012] Further, the preparation method of the pretreated octanol in step (1) is as follows: freezing the octanol at a temperature of -15 to -18℃ for 30 minutes, and then centrifuging to take the supernatant.

[0013] Further, the three-stage gradient reaction device in step (1) is composed of the first-stage reaction device, the second-stage reaction device and the third-stage reaction device from top to bottom, and the temperatures of the first-stage reaction device, the second-stage reaction device and the third-stage reaction device are 210-225℃, 215-230℃ and 220-235℃, respectively.

[0014] Further, the time of the first-stage reaction device, the second-stage reaction device and the third-stage reaction device is 25-30 min, 20-25 min and 13-15 min, respectively, and the pressure of the first-stage reaction device, the second-stage reaction device and the third-stage reaction device is 30-50 KPa, 35-70 KPa and 45-90 KPa, respectively.

[0015] Further, the cooling in step (2) is cooling to 80-100℃, and the temperature and time of the freezing and standing treatment are -15 to -18℃ and 30 min, respectively.

[0016] Further, the two-stage distillation column in step (3) is composed of the first-stage distillation and the second-stage distillation, and the temperature, time and pressure of the first-stage distillation and the second-stage distillation are 120-150℃, 180-220℃, 10-20 min, 20-25 min, -0.02 to -0.03 MPa and -0.02 to -0.001 MPa, respectively.

[0017] Advantages of the present application:

[0018] 1. The full continuous production process of dioctyl terephthalate is disclosed, a three-stage gradient reaction device is used as an esterification tower, the esterification rate is controlled by controlling the gradient temperature and pressure, an esterification separator is connected to the top of the esterification tower, water vapor and alcohol vapor are separated out, the vapor is separated into oil and water after cooling, the separated octanol is frozen and placed to flow back to the esterification tower, the raw material octanol is recycled to reduce the cost of raw materials, and in addition, a two-stage distillation tower is used to remove residual impurities by reduced pressure distillation, and the flash point and purity of the product are improved. DETAILED DESCRIPTION

[0019] In order to further illustrate the technical means and effects adopted by the present application to achieve the predetermined object, the specific embodiments, structures, features and effects according to the present application are described in detail as follows.

[0020] Example 1

[0021] A full continuous production process of dioctyl terephthalate, the full continuous production process of dioctyl terephthalate, specifically the following steps:

[0022] (1) Put the pretreated terephthalic acid, pretreated octanol and catalyst into the first stage reaction device of the three-stage gradient reaction device, then heat and stir the mixture;

[0023] (2) Connect an esterification separator to the first stage reaction device, separate out water vapor and alcohol vapor, separate the vapor into oil and water after cooling, and freeze and place the separated octanol for treatment before being put into the first stage reaction device;

[0024] (3) The material generated in step (1) flows out from the third stage reaction device of the three-stage reaction device and is introduced into a two-stage distillation tower for reduced pressure distillation, and after cooling and dehydration, filtration is performed to obtain the finished product.

[0025] The mass ratio between the pretreated terephthalic acid, pretreated octanol and catalyst in step (1) is 1:3:0.02, wherein the catalyst is composed of stannous octoate and sulfuric acid with a mass ratio of 1:1, and the mass fraction of the sulfuric acid is 70%.

[0026] The preparation method of the pretreated terephthalic acid in step (1) is as follows: the terephthalic acid is frozen at a temperature of-15℃ for 40 minutes, then vacuum dehydrated at 80℃ to a water content of 0.1%, and the vacuum degree is 0.01 MPa.

[0027] The preparation method of the pretreated octanol in step (1) is as follows: the octanol is frozen and placed in a-15℃ environment for 30 minutes, and the upper clear liquid is separated by centrifugation.

[0028] The third-stage gradient reaction device in step (1) is sequentially composed of a first-stage reaction device, a second-stage reaction device, and a third-stage reaction device from top to bottom, and the temperatures of the first-stage reaction device, the second-stage reaction device, and the third-stage reaction device are 210°C, 215°C, and 220°C, respectively.

[0029] The time of the first-stage reaction device, the second-stage reaction device, and the third-stage reaction device is 25 min, 20 min, and 13 min, respectively, and the pressure of the first-stage reaction device, the second-stage reaction device, and the third-stage reaction device is 30 KPa, 35 KPa, and 45 KPa, respectively.

[0030] The cooling in step (2) refers to cooling to 80°C, and the temperature and time of the freezing and standing treatment are -15°C and 30 min, respectively.

[0031] The second-stage distillation column in step (3) is divided into a first-stage distillation and a second-stage distillation, and the temperature, time, and pressure of the first-stage distillation and the second-stage distillation are 120°C, 180°C, 10 min, 20 min, -0.02 MPa, and -0.02 MPa, respectively.

[0032] Example 2

[0033] A full-continuous production process of dioctyl terephthalate, specifically comprising the following steps:

[0034] (1) Put pretreated terephthalic acid, pretreated octanol, and a catalyst into the first-stage reaction device of a three-stage gradient reaction device, and then heat and stir the mixture;

[0035] (2) Connect an esterification separator to the first-stage reaction device, separate water vapor and alcohol vapor, separate the octanol after the vapor is cooled, and then put the separated octanol into the first-stage reaction device after freezing and standing treatment;

[0036] (3) The material generated in step (1) flows out from the third-stage reaction device of the three-stage reaction device and is subjected to reduced-pressure distillation in a second-stage distillation column, and then the product is obtained after cooling, dehydration, and filtration.

[0037] The mass ratio among the pretreated terephthalic acid, the pretreated octanol, and the catalyst in step (1) is 1.5:3.5:0.02, wherein the catalyst is composed of stannous octoate and sulfuric acid with a mass ratio of 1.1:1, and the mass fraction of the sulfuric acid is 71%.

[0038] The preparation method of the pretreated terephthalic acid in step (1) is as follows: freeze the terephthalic acid at a temperature of -15°C for 50 minutes, and then dehydrate the terephthalic acid under vacuum at a temperature of 85°C until the water content is 0.1%, and the vacuum degree is 0.03 MPa.

[0039] The preparation method of the pretreated octanol in step (1) is: freezing and standing treatment of octanol in-16℃ environment for 30 minutes, and centrifugal separation to take the upper clear liquid.

[0040] The third-stage gradient reaction device in step (1) is sequentially composed of a first-stage reaction device, a second-stage reaction device and a third-stage reaction device from top to bottom, and the temperatures of the first-stage reaction device, the second-stage reaction device and the third-stage reaction device are 220℃, 220℃ and 230℃ respectively.

[0041] The time of the first-stage reaction device, the second-stage reaction device and the third-stage reaction device is 28min, 22min and 14min respectively, and the pressure of the first-stage reaction device, the second-stage reaction device and the third-stage reaction device is 40KPa, 55KPa and 65KPa respectively.

[0042] The cooling in step (2) refers to cooling to 90℃, and the temperature and time of the freezing and standing treatment are-16℃ and 30min respectively.

[0043] The second-stage distillation column in step (3) is divided into a first-stage distillation and a second-stage distillation, and the temperature, time and pressure of the first-stage distillation and the second-stage distillation are 135℃, 200℃, 15min, 22min, 0.01MPa and-0.01MPa respectively.

[0044] Example 3

[0045] A full-continuous production process of dioctyl terephthalate, specifically the following steps:

[0046] (1) Put pretreated terephthalic acid, pretreated octanol and catalyst into the first-stage reaction device of a third-stage gradient reaction device, and then heat and stir the mixture;

[0047] (2) Connect an esterification separator to the first-stage reaction device to separate water vapor and alcohol vapor, and after cooling, the vapor is subjected to oil-water separation, and the separated octanol is subjected to freezing and standing treatment before being put into the first-stage reaction device again;

[0048] (3) The material generated in step (1) flows out from the third-stage reaction device of the third-stage reaction device, and is subjected to reduced pressure distillation in a second-stage distillation column, and after cooling and dehydration, filtration is performed to obtain a finished product.

[0049] The mass ratio among the pretreated terephthalic acid, the pretreated octanol and the catalyst in step (1) is 2:4:0.02, wherein the catalyst is composed of stannous octoate and sulfuric acid with a mass ratio of 1.2:1, and the mass fraction of the sulfuric acid is 72%.

[0050] The preparation method of the pretreated terephthalic acid in step (1) is: freezing the terephthalic acid at a temperature of -15°C for 60 minutes, and then dehydrating under vacuum at 90°C to a water content of 0.1%, with a vacuum degree of 0.04 MPa.

[0051] The preparation method of the pretreated octanol in step (1) is: freezing the octanol in an environment at -18°C for 30 minutes, and then centrifuging to take the upper clear liquid.

[0052] The third-stage gradient reaction device in step (1) is sequentially arranged from top to bottom as a first-stage reaction device, a second-stage reaction device, and a third-stage reaction device, and the temperatures of the first-stage reaction device, the second-stage reaction device, and the third-stage reaction device are 225°C, 230°C, and 235°C, respectively.

[0053] The time of the first-stage reaction device, the second-stage reaction device, and the third-stage reaction device is 30 min, 25 min, and 15 min, respectively, and the pressure of the first-stage reaction device, the second-stage reaction device, and the third-stage reaction device is 50 KPa, 70 KPa, and 90 KPa, respectively.

[0054] The cooling in step (2) is cooling to 100°C, and the temperature and time of the freezing standing treatment are -18°C and 30 min, respectively.

[0055] The second-stage distillation column in step (3) is divided into a first-stage distillation and a second-stage distillation, and the temperature, time, and pressure of the first-stage distillation and the second-stage distillation are 150°C, 220°C, 20 min, 25 min, 0.03 MPa, and -0.001 MPa, respectively.

[0056] Comparative Example 1

[0057] On the basis of Example 2, a fully continuous production process of dioctyl terephthalate, which specifically comprises the following steps:

[0058] (1) The pretreated terephthalic acid, the pretreated octanol, and the catalyst are subjected to a mono-esterification reaction, and then are added into a second esterification kettle, while the catalyst is added to perform a di-esterification reaction, wherein the mass of the two added catalysts is equal;

[0059] (2) The material generated in step (1) is subjected to a vacuum distillation in a second-stage distillation column, and after cooling and dehydration, is filtered to obtain a finished product.

[0060] The mass ratio among the pretreated terephthalic acid, the pretreated octanol, and the catalyst in step (1) is 1.5:3.5:0.02, wherein the catalyst is composed of stannous octoate and sulfuric acid with a mass ratio of 1.1:1, and the mass fraction of the sulfuric acid is 71%.

[0061] The preparation method of the pretreated terephthalic acid in step (1) is: freezing the terephthalic acid at a temperature of -15°C for 50 minutes, and then vacuum dehydrating at 85°C to a water content of 0.1%, a vacuum degree of 0.03 MPa.

[0062] The preparation method of the pretreated octanol in step (1) is: freezing the octanol in a -16°C environment for 30 minutes, and then centrifugally separating to take the supernatant.

[0063] The secondary distillation column in step (2) is divided into a first-stage distillation and a second-stage distillation, and the temperature, time and pressure of the first-stage distillation and the second-stage distillation are 135°C, 200°C, 15 min, 22 min, 0.01 MPa, -0.01 MPa, respectively.

[0064] Comparative Example 2

[0065] On the basis of Example 2, a fully continuous production process of dioctyl terephthalate, specifically the following steps:

[0066] (1) The pretreated terephthalic acid, the pretreated octanol and the catalyst are put into the first-stage reaction device of the two-stage gradient reaction device, and then the temperature is raised and the mixture is stirred;

[0067] (2) The first-stage reaction device is connected with an esterification separator, and water vapor and alcohol vapor are separated out, the vapor is cooled and then subjected to oil-water separation, and the separated octanol is frozen and statically treated before being put into the first-stage reaction device again;

[0068] (3) The material generated in step (1) flows out from the second-stage reaction device of the two-stage reaction device, and is subjected to reduced pressure distillation in a two-stage distillation column, and then filtered after cooling and dehydration to obtain the finished product.

[0069] The mass ratio among the pretreated terephthalic acid, the pretreated octanol and the catalyst in step (1) is 1.5:3.5:0.02, wherein the catalyst is composed of stannous octoate and sulfuric acid with a mass ratio of 1.1:1, and the mass fraction of the sulfuric acid is 71%.

[0070] The preparation method of the pretreated terephthalic acid in step (1) is: freezing the terephthalic acid at a temperature of -15°C for 50 minutes, and then vacuum dehydrating at 85°C to a water content of 0.1%, a vacuum degree of 0.03 MPa.

[0071] The preparation method of the pretreated octanol in step (1) is: freezing the octanol in a -16°C environment for 30 minutes, and then centrifugally separating to take the supernatant.

[0072] The third-stage gradient reaction device in step (1) is sequentially provided with a first-stage reaction device and a second-stage reaction device from top to bottom, and the temperatures of the first-stage reaction device and the second-stage reaction device are 220℃ and 230℃, respectively.

[0073] The time of the first-stage reaction device and the second-stage reaction device is 28min and 14min, respectively, and the pressure of the first-stage reaction device and the second-stage reaction device is 40KPa and 65KPa, respectively.

[0074] The cooling in step (2) is cooling to 90℃, and the temperature and time of the freezing and standing treatment are -16℃ and 30min, respectively.

[0075] The second-stage distillation column in step (3) is divided into a first-stage distillation and a second-stage distillation, and the temperature, time and pressure of the first-stage distillation and the second-stage distillation are 135℃, 200℃, 15min, 22min, 0.01MPa and -0.01MPa, respectively.

[0076] Comparative Example 3

[0077] On the basis of Example 2, a full-continuous production process of dioctyl terephthalate, specifically the following steps:

[0078] (1) The pretreated terephthalic acid, pretreated octanol and catalyst are put into the first-stage reaction device of the third-stage gradient reaction device, and then the mixture is heated and stirred;

[0079] (2) The first-stage reaction device is connected with an esterification separator, and water vapor and alcohol vapor are separated out, the vapor is cooled and then subjected to oil-water separation, and the separated octanol is subjected to freezing and standing treatment and then put into the first-stage reaction device again;

[0080] (3) The material generated in step (1) flows out from the third-stage reaction device and is subjected to reduced-pressure distillation in a distillation column, and then the product is obtained after cooling, dehydration and filtration.

[0081] The mass ratio among the pretreated terephthalic acid, pretreated octanol and catalyst in step (1) is 1.5:3.5:0.02, wherein the catalyst is composed of stannous octoate and sulfuric acid with a mass ratio of 1.1:1, and the mass fraction of the sulfuric acid is 71%.

[0082] The preparation method of the pretreated terephthalic acid in step (1) is as follows: the terephthalic acid is subjected to freezing treatment at a temperature of -15℃ for 50 minutes, and then vacuum dehydration is performed at 85℃ until the water content is 0.1%, and the vacuum degree is 0.03MPa.

[0083] The preparation method of the pretreated octanol in step (1) is: freezing and standing the octanol in -16°C environment for 30 minutes, and centrifugally separating to take the supernatant.

[0084] The third-stage gradient reaction device in step (1) is sequentially composed of a first-stage reaction device, a second-stage reaction device and a third-stage reaction device from top to bottom, and the temperatures of the first-stage reaction device, the second-stage reaction device and the third-stage reaction device are 220°C, 220°C and 230°C respectively.

[0085] The time of the first-stage reaction device, the second-stage reaction device and the third-stage reaction device is 28 min, 22 min and 14 min respectively, and the pressure of the first-stage reaction device, the second-stage reaction device and the third-stage reaction device is 40 KPa, 55 KPa and 65 KPa respectively.

[0086] The cooling in step (2) is cooling to 90°C, and the freezing and standing temperature and time are -16°C and 30 min respectively.

[0087] The temperature, time and pressure of the distillation column in step (3) are 135°C, 15 min and 0.01 MPa respectively.

[0088] Performance test

[0089] Conversion rate: taking the dioctyl terephthalate prepared in Examples 1-3 and Comparative Examples 1-3 as samples, the mass of the samples is weighed respectively, and the conversion rate is calculated as = mass of sample / total mass of raw material x 100%;

[0090] Acid value and flash point test: taking the dioctyl terephthalate prepared in Examples 1-3 and Comparative Examples 1-3 as samples, the acid value and flash point of the samples are tested, and the above test results are shown in Table 1.

[0091] Table 1 evaluation results

[0092] Sample Conversion % Acid value (≤) Flash point (°C, ≥) Example 1 99.69 0.2 218 Example 2 99.72 0.21 219 Example 3 99.70 0.2 218 Comparative Example 1 86.93 0.10 202 Comparative Example 2 99.14 0.2 218 Comparative Example 3 99.70 0.11 198

[0093] From the results in Table 1, it can be seen that the conversion rate of Examples 1-3 is as high as 99.6% or more, which is higher than that of Comparative Examples 1-3, and the acid value is small and the flash point is high. Comparative Example 1 uses a batch production process to produce dioctyl terephthalate, and the raw material loss in this process is large, which results in a low conversion rate. Since the conversion rate is low, the material fed into the distillation column contains a large amount of unreacted raw material acid, and there is still acid residue after distillation, which increases the acid value of the product and reduces the purity, thereby reducing the flash point. Comparative Example 2 uses a two-stage reaction device, which affects the conversion rate and reduces it, but since the acid content of the material fed into the distillation column is small, the acid value and flash point of the product are not affected. Comparative Example 3 uses a single-stage distillation, which reduces the removal effect of the acid and impurities in the material, and thus reduces the purity of the product, which affects the flash point and acid value of the product.

[0094] The above merely describes preferred embodiments of the present application, and is not intended to limit the present application in any form. Although the present application has been described above with reference to preferred embodiments, the present application is not intended to be limited to the above-described embodiments, and any person skilled in the art, without departing from the technical scope of the present application, can make some changes or modifications to the above-described embodiments, or make equivalent embodiments with equivalent changes, as long as the changes or modifications do not depart from the technical scope of the present application. Any modification, change, or equivalent change made to the above-described embodiments, based on the technical essence of the present application, still falls within the scope of the present application.

Claims

1. A fully continuous production process for dioctyl terephthalate, characterized in that, The fully continuous production process for dioctyl terephthalate specifically includes the following steps: (1) Pretreated terephthalic acid, pretreated octanol and catalyst are added to the first stage of the three-stage gradient reaction apparatus, and then heated and stirred to mix. (2) Connect an esterification separator to the first-stage reaction unit to separate water vapor and alcohol vapor. After the vapor is cooled, oil and water are separated. The separated octanol is frozen and allowed to stand before being fed into the first-stage reaction unit. (3) The material generated in step (1) flows out from the third stage of the three-stage reaction device and is fed into the second stage distillation tower for vacuum distillation. After cooling and dehydration, it is filtered to obtain the finished product.

2. The fully continuous production process for dioctyl terephthalate according to claim 1, characterized in that, In step (1), the mass ratio of pretreated terephthalic acid, pretreated octanol and catalyst is 1-2:3-4:0.02, wherein the catalyst is composed of stannous octoate and sulfuric acid in a mass ratio of 1-1.2:1, and the mass fraction of sulfuric acid is 70-72%.

3. The fully continuous production process for dioctyl terephthalate according to claim 1, characterized in that, The preparation method of the pretreatment of terephthalic acid in step (1) is as follows: terephthalic acid is frozen at -15℃ for 40-60 minutes, and then vacuum dehydrated at 80-90℃ to a water content of 0.1% with a vacuum degree of 0.01-0.04MPa.

4. The fully continuous production process for dioctyl terephthalate according to claim 1, characterized in that, The preparation method of pretreated octanol in step (1) is as follows: place octanol in an environment of -15 to -18℃ for freezing and standing for 30 minutes, and then centrifuge to separate the supernatant.

5. The fully continuous production process for dioctyl terephthalate according to claim 1, characterized in that, In step (1), the three-stage gradient reaction device is arranged from top to bottom as a first-stage reaction device, a second-stage reaction device, and a third-stage reaction device. The temperatures of the first-stage reaction device, the second-stage reaction device, and the third-stage reaction device are 210~225℃, 215~230℃, and 220~235℃, respectively.

6. The fully continuous production process for dioctyl terephthalate according to claim 5, characterized in that, The reaction times for the first-stage reaction device, the second-stage reaction device, and the third-stage reaction device are 25-30 min, 20-25 min, and 13-15 min, respectively, and the pressures for the first-stage reaction device, the second-stage reaction device, and the third-stage reaction device are 30-50 kPa, 35-70 kPa, and 45-90 kPa, respectively.

7. The fully continuous production process for dioctyl terephthalate according to claim 1, characterized in that, In step (2), cooling refers to cooling to 80-100℃, and the temperature and time of the freezing and settling treatment are -15 to -18℃ and 30 min, respectively.

8. The fully continuous production process for dioctyl terephthalate according to claim 1, characterized in that, The secondary distillation column in step (3) is divided into a first-stage distillation and a second-stage distillation. The temperature, time and pressure of the first-stage distillation and the second-stage distillation are 120~150℃, 180~220℃, 10-20min, 20-25min, -0.02~0.03MPa and -0.02~-0.001MPa, respectively.