A polyvinyl chloride resin with high time-space yield and preparation method thereof

Abstract

The present application proposes a polyvinyl chloride resin with high space-time yield and a preparation method thereof, and relates to the field of polymer technology. A preparation method of polyvinyl chloride resin with high space-time yield comprises the following steps: emulsifying an initiator and adjusting the concentration with a diluent before storing to obtain an initiator preparation solution; adding a pH regulator, a dispersant, deionized water and a premixed vinyl chloride monomer into a reaction container, heating and stirring to obtain a mixed solution; when the mixed solution is suspended and polymerized, adding the initiator preparation solution into the reaction container in stages; when the pressure in the reaction container begins to drop for the first time, adding vinyl chloride monomer into the reaction container, adding an antioxidant after the reaction to obtain an aqueous slurry; sending the aqueous slurry to steam stripping, centrifugal drying and homogenization treatment to obtain a polyvinyl chloride resin product with high space-time yield. The polyvinyl chloride resin prepared by this method has the advantages of high space-time yield and low water content.

Description

Technical Field

[0001] The present application relates to the field of polymer technology, and in particular to a polyvinyl chloride resin with high time-space yield and a preparation method thereof. Background Art

[0002] Polyvinyl chloride (PVC) is a widely used polymer material, which is classified into various types according to its melt index or molecular weight. PVC is polymerized from vinyl chloride monomer (VCM), and PVC can also be further chlorinated to obtain chlorinated polyvinyl chloride (CPVC).

[0003] With the continuous development of the industrialization process of polyvinyl chloride, people have been committed to the research of improving the production intensity of polymerization kettles for many years. For a specific polymerization kettle, the main method to improve the production intensity is to shorten the system reaction cycle, reduce the production auxiliary time, etc. The above methods are restricted by public works, polymerization equipment and other conditions. Today, with the improvement of raw material matching, it is not advisable to simply rely on shortening the system reaction cycle or reducing the production auxiliary time to improve the production intensity of the polymerization kettle, and the space-time yield of the obtained polyethylene resin is low and the water content is high. Summary of the invention

[0004] The purpose of the present application is to provide a polyvinyl chloride resin with high time-space yield and a preparation method thereof. The polyvinyl chloride resin prepared by this method has the advantages of high time-space yield and low water content.

[0005] To solve the above problems, the technical method adopted by the present invention is:

[0006] On the one hand, the present invention provides a method for preparing a polyvinyl chloride resin with a high space-time yield, comprising the following steps:

[0007] emulsifying the initiator and adjusting the concentration with a diluent before storing to obtain an initiator preparation solution;

[0008] Add a pH regulator, a dispersant, deionized water and premixed vinyl chloride monomer into a reaction container, raise the temperature and stir evenly to obtain a mixed solution;

[0009] During suspension polymerization of the mixed solution, the initiator preparation solution is added into the reaction container in stages;

[0010] When the pressure in the reaction container begins to drop for the first time, vinyl chloride monomer is added to the reaction container, and an antioxidant is added after the reaction to obtain an aqueous slurry;

[0011] The aqueous slurry is sent to steam stripping, centrifugal drying and homogenization treatment to obtain a polyvinyl chloride resin product with high time and space yield.

[0012] On the other hand, an embodiment of the present application provides a polyvinyl chloride resin with a high space-time yield, comprising the following raw materials in parts by weight: 0.01 to 0.03 parts of a pH adjuster, 0.05 to 0.15 parts of a dispersant, 140 to 160 parts of deionized water, 100 to 125 parts of a vinyl chloride monomer, 0.3 to 0.35 parts of an initiator, 0.1 to 0.15 parts of a diluent and 0.05 to 0.15 parts of an antioxidant.

[0013] Compared with the prior art, the invention of this application has at least the following advantages or beneficial effects:

[0014] This application combines the kinetic evolution law of the reaction system and adopts a single high-activity or high-low-activity composite initiator configuration liquid to add to the suspension polymerization system in stages at the reaction temperature set by the material type. The volume shrinkage of the suspended polymerization material is utilized. When the pressure drop of the reaction container begins, vinyl chloride monomer is added to the suspension polymerization reaction system, and the heat exchange conditions of the polymerization device are fully utilized to shorten the reaction cycle of the system and improve the space-time yield of the suspended polymerization material. This application can obtain polyvinyl chloride resin with a water content of less than 4% and a space-time yield of more than 90%. At the same time, this application is also suitable for continuous suspension polymerization reactions. This application can also improve the space-time yield of the reaction container.

[0015] The present application realizes the safe operation of suspension polymerization. Specifically, since the half-life of the selected initiator is extremely short, when the segmented feeding of the initiator stops, the suspension polymerization reaction stops immediately. That is, if the operation process of the present application encounters device abnormalities, power outages, emergency stops, etc. that affect normal operation, the feeding can be stopped immediately, which can improve the safety of the operation. However, the present application itself is not limited by the above-mentioned safety factors.

[0016] The reaction process of the present application is stable, and the dosage of the initiator preparation liquid and the feeding frequency can be adjusted at any time according to the changes in the suspension polymerization reaction system, and the polymerization rate can be extremely well controlled. More specifically, by means of segmented feeding, the free radical concentration inside the suspension polymerization reaction system reaches the optimal value at the set material type reaction temperature, thereby preventing overheating, overpressure, explosion and agglomeration, and avoiding unstable product quality caused by too fast or too slow reaction rate of the system.

[0017] In the present application, vinyl chloride monomer is added to the suspension polymerization reaction system at a later stage. Since the reaction system has a high conversion rate at this time, a large number of loose polyvinyl chloride molecules have been formed, and the friction dispersion force of the interaction between the resins is much higher than the polymerization ability between the monomers, no additional dispersant is required for the addition of vinyl chloride monomer. In addition, the amount of residual gas-phase vinyl chloride monomer in the aqueous slurry treatment process is extremely low, which can reduce the recovery rate of vinyl chloride while improving the space-time yield of the device, thereby reducing the auxiliary time consumption.

[0018] The suspension polymerization reaction and the heat exchange centered on the polymerization kettle in this application are completed by a complete distributed automatic control system (DCS automatic control system). This stage can effectively reduce the possibility of errors caused by human operation and ensure the control of the device and the accurate addition of raw / auxiliary materials.

[0019] The polyvinyl chloride resin produced by the present application has extremely low internal residual content (vinyl chloride monomer, initiator, dispersant). The resin residual content in the polyvinyl chloride resin obtained according to the aqueous slurry post-treatment process of the present application is less than 1ppm. And after testing the initial colorability of the polyvinyl chloride resin of the present application, it is confirmed that when the mixing process step is carried out, the polyvinyl chloride resin obtained by the present invention has excellent initial colorability. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0021] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to specific embodiments.

[0022] The present invention provides a method for preparing a polyvinyl chloride resin with a high space-time yield, comprising the following steps:

[0023] emulsifying the initiator and adjusting the concentration through a diluent and storing the emulsified initiator to obtain an initiator preparation solution;

[0024] Add a pH regulator, a dispersant, deionized water and premixed vinyl chloride monomer into a reaction container, raise the temperature and stir evenly to obtain a mixed solution;

[0025] During suspension polymerization of the mixed solution, the initiator preparation solution is added into the reaction container in stages;

[0026] When the pressure in the reaction container begins to drop for the first time, vinyl chloride monomer is added to the reaction container, and an antioxidant is added after the reaction to obtain an aqueous slurry;

[0027] The water-containing slurry is sent for steam stripping, centrifugal drying and homogenization treatment to obtain a polyvinyl chloride resin finished product with a water content of less than 4% and a time-space yield of more than 90%.

[0028] This application combines the kinetic evolution law of the reaction system and adopts a single high-activity or high-low-activity composite initiator configuration liquid to add to the suspension polymerization system in stages at the reaction temperature set by the material type. The volume shrinkage of the suspended polymerization material is utilized. When the pressure drop of the reaction container begins, vinyl chloride monomer is added to the suspension polymerization reaction system, and the heat exchange conditions of the polymerization device are fully utilized to shorten the reaction cycle of the system and improve the space-time yield of the suspended polymerization material. This application can obtain polyvinyl chloride resin with a water content of less than 4% and a space-time yield of more than 90%. At the same time, this application is also suitable for continuous suspension polymerization reactions. This application can also improve the space-time yield of the reaction container.

[0029] In some embodiments of the present application, the pH adjuster, dispersant, deionized water and premixed vinyl chloride monomer can be added to the reaction container in sequence; or, after the pH adjuster, dispersant and deionized water are mixed, they can be added to the reaction aeration at the same time as the premixed vinyl chloride monomer.

[0030] In some embodiments of the present application, after the pH adjuster, dispersant, deionized water and premixed vinyl chloride monomer are added to the reaction container, a cold start method is adopted to simultaneously feed and heat up until the reaction temperature of the reaction container and the material type is consistent. This premixing and heating method can reduce production auxiliary time and improve the space-time yield of suspension polymerization.

[0031] In some embodiments of the present application, the above-mentioned initiator emulsification is specifically.

[0032] In some embodiments of the present application, the temperature rise time after the pH adjuster, dispersant, deionized water and premixed vinyl chloride monomer are added to the reaction container is 0.4 to 0.7 hours, and the temperature is raised to 55 to 60° C.; the water-oil ratio in the mixed liquid is 1 to 2.5:1.

[0033] In some embodiments of the present application, the heating time after the pH adjuster, dispersant, deionized water and premixed vinyl chloride monomer are added to the reaction container is 0.6 to 0.7 hours.

[0034] In some embodiments of the present application, the water-oil ratio in the above-mentioned mixed liquid is 1.5:1.

[0035] Since the temperature control of suspension polymerization depends on the heat transfer capacity of the reaction container, in other words, the container should have good heat transfer effect, uniform polymer particle size, concentrated molecular weight distribution, and high production control ability, the inventor of this application has tried a mixed liquid with a water-oil ratio of 0.5:1, but the experiment failed. Therefore, a lower water-oil ratio is the key to the success of the present invention.

[0036] In some embodiments of the present application, the above-mentioned segmented addition is specifically when the suspension polymerization conversion rate of the mixed liquid is 1-50%, the initiator preparation liquid is added at time intervals of 0.1-0.3 hours according to the segmented feeding amount of 30-95 ppm; when the suspension polymerization conversion rate of the mixed liquid is 50-90%, the initiator preparation liquid is added in 10-30 segments, and the segmented feeding amount of each segment is 25-65 ppm.

[0037] After the temperature inside the container reaches the reaction temperature, the initiator preparation liquid is intermittently added into the reaction container. The specific interval time is the half-life of a single initiator at the set material reaction temperature or the longer half-life of a composite initiator at the set material reaction temperature. The residual amount of the polyvinyl chloride resin initiator obtained by this method is extremely low.

[0038] In some embodiments of the present application, the above-mentioned segmented addition is specifically when the suspension polymerization conversion rate of the mixed liquid is 1-50%, the initiator preparation liquid is added at time intervals of 0.1-0.3 hours according to the segmented feeding amount of 45-95 ppm; when the suspension polymerization conversion rate of the mixed liquid is 50-90%, the initiator preparation liquid is added in 10-30 segments, and the segmented feeding amount of each segment is 35-65 ppm.

[0039] In some embodiments of the present application, the above-mentioned segmented addition is specifically when the suspension polymerization conversion rate of the mixed liquid is 1-50%, the initiator preparation liquid is added at time intervals of 0.1-0.3 hours according to the segmented feeding amount of 65-95 ppm; when the suspension polymerization conversion rate of the mixed liquid is 50-90%, the initiator preparation liquid is added in 10-30 segments, and the segmented feeding amount of each segment is 45-65 ppm.

[0040] In some embodiments of the present application, the above-mentioned segmented addition is specifically when the suspension polymerization conversion rate of the mixed liquid is 1-50%, the initiator preparation liquid is added at time intervals of 0.1-0.3 hours according to the segmented feeding amount of 30-65 ppm; when the suspension polymerization conversion rate of the mixed liquid is 50-90%, the initiator preparation liquid is added in 10-30 segments, and the segmented feeding amount of each segment is 45-65 ppm.

[0041] By adding the initiator in the above-mentioned staged feeding method, the adverse thermal effect caused by the automatic acceleration phenomenon of the suspension polymerization reaction can be reduced, the normal progress of the reaction can be ensured, and the time-space yield of the polyvinyl chloride resin can be improved.

[0042] It should be clear that the "conversion rate" mentioned in this application is calculated after the single initiator configuration liquid or the composite initiator configuration liquid is first added to the suspension polymerization reaction system. In this application, the single initiator configuration liquid or the composite initiator configuration liquid are both initiator emulsions. Therefore, the present invention does not limit the segmented feeding position of the single initiator configuration liquid or the composite initiator configuration liquid.

[0043] In some embodiments of the present application, when the pressure in the reaction container begins to drop to 0.05-0.1 MPa for the first time, vinyl chloride monomer is added into the reaction container.

[0044] It should be clear that the "addition" mentioned in the present application refers to the intermittent or continuous addition of vinyl chloride monomer to the suspension polymerization reaction system, that is, the vinyl chloride monomer is added to the suspension polymerization reaction system at least once.

[0045] It should be clear that in this application, the pressure drop in the reaction container refers to the phenomenon that the suspension polymerization conversion rate reaches 70%, the low molecular forces are converted into covalent bonds between the links, and the volume shrinks and the pressure decreases, and does not refer to the pressure fluctuations that occur during the suspension polymerization reaction. At this time, the liquid phase monomers in the system basically disappear, and the addition of vinyl chloride monomers at this time will not affect the already formed polyvinyl chloride resin. At the same time, there is no need to worry about the occurrence of the system temperature runaway due to the excessive reaction rate of the system.

[0046] In the present application, the addition of vinyl chloride monomer to the reaction container is not affected by the staged feeding of the initiator, that is, the addition of vinyl chloride monomer to the suspension polymerization reaction can be carried out simultaneously with the staged feeding of the initiator.

[0047] In some embodiments of the present application, the centrifugal drying homogenization treatment is specifically to dry the water-containing slurry after steam stripping through a cyclone drying bed at 30 to 90° C. for 0.5 to 0.7 hours.

[0048] In the present application, the slurry post-treatment includes sending the aqueous slurry after the suspension polymerization reaction to a stripping tower to separate the gaseous vinyl chloride monomer, sending the separated gaseous vinyl chloride monomer to a high-pressure recovery system for compression, condensation and recovery, sending the slurry to a drying system for dehydration and drying it in a cyclone drying bed at 30 to 90°C for 0.5 to 0.7 hours, and supplying the finished product for packaging, storage and transportation after homogenization treatment. The time used in this stage is auxiliary time and should be included in the calculation of the space-time yield of the suspension polymerization.

[0049] It should be clear that the "auxiliary time" mentioned in this application refers to the sum of the time used for the feeding, discharging, recovery and other processes in the suspension polymerization cycle. In this application, the time used for the addition of vinyl chloride monomer coincides with the time used for the suspension polymerization reaction, so the addition of vinyl chloride monomer is not included in the auxiliary time.

[0050] The present application also provides a polyvinyl chloride resin with high space-time yield prepared by the aforementioned method, comprising the following raw materials in parts by weight: 0.01 to 0.03 parts of a pH regulator, 0.05 to 0.15 parts of a dispersant, 140 to 160 parts of deionized water, 100 to 125 parts of vinyl chloride monomer, 0.3 to 0.35 parts of an initiator, 0.1 to 0.3 parts of a diluent, and 0.05 to 0.15 parts of an antioxidant.

[0051] In some embodiments of the present application, the decomposition activation energy of the above-mentioned initiator is 100-125 kJ / mol.

[0052] In some embodiments of the present application, the pH adjuster is specifically a carbonate. Preferably, the pH adjuster is sodium bicarbonate, calcium carbonate or calcium bicarbonate.

[0053] In some embodiments of the present application, the antioxidant is one or more of bisphenol A or a high-efficiency water-soluble antioxidant.

[0054] In some embodiments of the present application, the decomposition activation energy of the above-mentioned initiator is 105-125 kJ / mol.

[0055] In some embodiments of the present application, the half-life of the above-mentioned initiator at the set material type reaction temperature of the present application is less than 1.0 hour.

[0056] Since the concentration of this type of initiator decreases with the progress of suspension polymerization, causing the polymerization rate to decay, it can compensate for the increase in polymerization rate caused by the automatic acceleration effect of the reaction system, allowing the suspension polymerization reaction system to proceed smoothly and at a uniform speed.

[0057] In some embodiments of the present application, the above-mentioned initiator includes one or more of diisobutyryl peroxide, isopropyl peroxyneodecanoate, bis(3-methoxybutyl) peroxydicarbonate, 1,1,3,3-tetramethylbutyl peroxyneodecanoate, bis(2-ethylhexyl) peroxydicarbonate and tert-butyl peroxyneodecanoate.

[0058] The activation energy of decomposition of diisobutyryl peroxide is 109.06 kJ / mol, and the half-life is less than 0.1 hour at a reaction temperature above 57°C;

[0059] Cumyl peroxyneodecanoate, the decomposition activation energy is 114.59 kJ / mol, and the half-life is less than 1.0 hour at a reaction temperature above 56°C;

[0060] Bis(3-methoxybutyl)peroxydicarbonate, the decomposition activation energy is 143.29 kJ / mol, and the half-life is less than 0.1 hour at a reaction temperature above 72°C;

[0061] 1,1,3,3-Tetramethylbutyl peroxyneodecanoate, decomposition activation energy is 115.79 kJ / mol, and the half-life is less than 1.0 hour at a reaction temperature above 57°C;

[0062] Bis(2-ethylhexyl)peroxydicarbonate, the decomposition activation energy is 122.45 kJ / mol, and the half-life is less than 1.0 hour at a reaction temperature above 64°C;

[0063] Tert-butyl peroxyneodecanoate has a decomposition activation energy of 115.47 kJ / mol and a half-life of less than 1.0 hour at a reaction temperature above 64°C.

[0064] In some embodiments of the present application, the initiator mentioned above includes at least one high-activity initiator.

[0065] In some embodiments of the present application, the highly active initiator is diisobutyryl peroxide and / or bis(3-methoxybutyl)peroxydicarbonate.

[0066] At least one of the initiators used is a high-activity initiator. In the later stage of the suspension polymerization reaction, the concentration of the high-activity initiator is extremely low, and the attenuation of the polymerization rate cannot be compensated by the automatic acceleration effect. In order to obtain a high space-time yield, it is necessary to extend the system reaction time.

[0067] In some embodiments of the present application, the initiator includes at least one high-activity initiator and one medium-low-activity initiator.

[0068] By combining it with medium or low activity initiators, the suspension polymerization reaction can have a considerable polymerization rate in the later stage, and the reaction can be completed in a shorter time, thus shortening the reaction cycle of the system.

[0069] In some embodiments of the present application, the vinyl chloride monomer comprises premixed vinyl chloride monomer and additional vinyl chloride monomer in a weight ratio of 100:10-18; the diluent is a polyvinyl alcohol solution and / or dodecane with a volume concentration of 5%.

[0070] When the selected initiator is water-soluble, the diluent used is a low-concentration polyvinyl alcohol solution; when the selected initiator is oil-soluble, the diluent used is dodecane; when the selected initiator includes an oil-soluble initiator and a water-soluble initiator, the diluents used are a low-concentration polyvinyl alcohol solution and dodecane.

[0071] In some embodiments of the present application, the vinyl chloride monomer comprises a premixed vinyl chloride monomer and an additional vinyl chloride monomer in a weight ratio of 100:12-12.5. The premixed vinyl chloride monomer and the additional vinyl chloride monomer are both vinyl chloride monomers.

[0072] The above-mentioned additional amount of vinyl chloride monomer has both operational flexibility and can improve the space-time yield of suspension polymerization.

[0073] It should be clear that the calculation of the "suspension polymerization space-time yield" mentioned in the present invention should include the total time used for heating, feeding, suspension polymerization reaction, discharging, and slurry post-treatment.

[0074] The features and performance of the present application are further described in detail below in conjunction with the embodiments.

[0075] Example 1

[0076] A method for preparing a polyvinyl chloride resin with high time-space yield comprises the following steps:

[0077] raw material Weight / g pH Adjusters 0.02 Dispersants 0.1 Deionized water 150 Premixed vinyl chloride monomer 100 Addition of vinyl chloride monomer 12.5 Initiator (diisobutyryl peroxide) 0.32 Dilution (5% polyvinyl alcohol solution) 0.12 Antioxidants 0.1

[0078] emulsifying the initiator and adjusting the concentration through a diluent and storing the emulsified initiator to obtain an initiator preparation solution;

[0079] Add a pH regulator, a dispersant, deionized water and premixed vinyl chloride monomer into a reaction vessel, and heat the vessel to 57° C. with synchronous steam to obtain a mixed solution;

[0080] When the mixed liquid is suspended and polymerized, 95 ppm of initiator configuration liquid is first added to the reaction container, and the suspension polymerization reaction starts to be timed. When the suspension polymerization conversion rate is 1-50%, 4 stages of initiator configuration liquid are added to the reaction container in stages with a feed amount of 95 ppm at a time interval of 0.3 hours. When the suspension polymerization conversion rate is 50-90%, 5 stages of initiator configuration liquid are added to the reaction container in stages with a feed amount of 75 ppm.

[0081] When the pressure in the reaction container initially drops, vinyl chloride monomer is added to the reaction container, and the polymerization reaction is continued until the pressure in the reaction container drops by 0.075 MPa. The reaction time is 3.25 h. An antioxidant is injected into the suspension polymerization reaction system to obtain an aqueous slurry.

[0082] The water-containing slurry is sent for steam stripping and centrifugal drying and homogenization treatment (dried in a cyclone drying bed at 45°C for 0.5 hour) to obtain a polyvinyl chloride resin product with a time-space yield of 94.12% and a water content of less than 4%. The gaseous vinyl chloride monomer after separation is sent to a high-pressure recovery system for compression, condensation and recovery.

[0083] Example 2

[0084] This embodiment is basically the same as embodiment 1, except that: when the suspension polymerization conversion rate is 1-50%, 5 stages of initiator configuration liquid are added to the reaction container at a time interval of 0.25 hours and a stepwise feed amount of 90 ppm; when the suspension polymerization conversion rate is 50-90%, 6 stages of initiator configuration liquid are added to the reaction container at a stepwise feed amount of 65 ppm.

[0085] The space-time yield of the polyvinyl chloride resin product obtained in this example is 92.5%.

[0086] Example 3

[0087] This embodiment is basically the same as Embodiment 1, except that: when the suspension polymerization conversion rate is 1-50%, 6 stages of initiator configuration liquid are added to the reaction container at a time interval of 0.2 hours and a stepwise feed amount of 75 ppm; when the suspension polymerization conversion rate is 50-90%, 8 stages of initiator configuration liquid are added to the reaction container at a stepwise feed amount of 55 ppm; the reaction time is 2.95 h.

[0088] In this embodiment, the space-time yield of the obtained polyvinyl chloride resin product is 92.25%.

[0089] Example 4

[0090] This embodiment is basically the same as Embodiment 1, except that: when the suspension polymerization conversion rate is 1-50%, 8 stages of initiator configuration liquid are added to the reaction container at a time interval of 0.16 hours and a staged feeding amount of 65 ppm; when the suspension polymerization conversion rate is 50-90%, 9 stages of initiator configuration liquid are added to the reaction container at a staged feeding amount of 45 ppm; the reaction time is 2.5 h.

[0091] In this embodiment, the space-time yield of the obtained polyvinyl chloride resin product is 92.5%.

[0092] The differences between Examples 1-4 are shown in Table 1 below.

[0093] Table 1

[0094] Feeding Difference Example 1 Example 2 Example 3 Example 4 1~50% conversion rate single feed amount / ppm 95 90 75 65 Adding time interval / h 0.3 0.25 0.2 0.16 1~50% conversion rate addition times / stage 4 5 6 8 50~90% conversion rate single feed amount / ppm 75 65 55 45 50~90% conversion rate adding times / stage 5 6 8 9 Reaction time 3.25 3.25 2.95 2.5 Polyvinyl chloride yield / % 94.12 92.5 92.25 92.5

[0095] By comparing Examples 1-4, it can be seen that the space-time yield of the polyvinyl chloride resin obtained is higher when the reaction is carried out on the basis of a higher single feed amount and a longer interval time.

[0096] Example 5

[0097] A method for preparing a polyvinyl chloride resin with high time-space yield comprises the following steps:

[0098]

[0099] emulsifying the initiator and adjusting the concentration through a diluent and storing the emulsified initiator to obtain an initiator preparation solution;

[0100] Add a pH regulator, a dispersant, deionized water and premixed vinyl chloride monomer into a reaction vessel, and heat the vessel to 57° C. with synchronous steam to obtain a mixed solution;

[0101] When the mixed liquid is suspended and polymerized, 95 ppm of initiator solution is first added to the reaction container, and the suspension polymerization reaction starts to be timed. When the suspension polymerization conversion rate is 1-50%, 8 stages of initiator solution are added to the reaction container in stages with a feed amount of 65 ppm at a time interval of 0.16 hours. When the suspension polymerization conversion rate is 50-90%, 9 stages of initiator solution are added to the reaction container in stages with a feed amount of 45 ppm.

[0102] When the pressure in the reaction container initially drops, vinyl chloride monomer is added to the reaction container, and the polymerization reaction is continued until the pressure in the reaction container drops by 0.075 MPa. The reaction time is 3 hours. An antioxidant is injected into the suspension polymerization reaction system to obtain an aqueous slurry.

[0103] The aqueous slurry is sent to steam stripping, centrifugal drying and homogenization treatment (dried in a cyclone drying bed at 45°C for 0.5 hour) to obtain a polyvinyl chloride resin product with a time-space yield of 92.81%. The gaseous vinyl chloride monomer after separation is sent to a high-pressure recovery system for compression, condensation and recovery.

[0104] Example 6

[0105] This embodiment is basically the same as embodiment 5, except that: when the suspension polymerization conversion rate is 1-50%, 65ppm is added for the first time at a time interval of 0.1 hour, and then 14 stages of initiator configuration liquid are added to the reaction container at a staged feeding amount of 35ppm; when the suspension polymerization conversion rate is 50-90%, 15 stages of initiator configuration liquid are added to the reaction container at a staged feeding amount of 25ppm; the reaction time is 3.25h.

[0106] In this embodiment, the space-time yield of the obtained polyvinyl chloride resin product is 94.19%.

[0107] The differences between Examples 5 and 6 are shown in Table 2 below.

[0108] Table 2

[0109]

[0110]

[0111] By comparing Examples 5-6, it can be seen that when a composite initiator is selected, the space-time yield of the obtained polyvinyl chloride resin is higher when the single feed amount is small and the number of additions is large.

[0112] Example 7

[0113] A method for preparing a polyvinyl chloride resin with high time-space yield comprises the following steps:

[0114]

[0115]

[0116] emulsifying the initiator and adjusting the concentration through a diluent and storing the emulsified initiator to obtain an initiator preparation solution;

[0117] Add a pH regulator, a dispersant, deionized water and premixed vinyl chloride monomer into a reaction vessel, and heat the vessel to 57° C. with synchronous steam to obtain a mixed solution;

[0118] When the mixed liquid is suspended and polymerized, 30 ppm of initiator configuration liquid is first added to the reaction container, and the suspension polymerization reaction starts to be timed. When the suspension polymerization conversion rate is 1-50%, 5 stages of initiator configuration liquid are added to the reaction container in a stepwise manner with a feed amount of 65 ppm at a time interval of 0.1 hour. When the suspension polymerization conversion rate is 50-90%, 15 stages of initiator configuration liquid are added to the reaction container in a stepwise manner with a feed amount of 25 ppm.

[0119] When the pressure in the reaction container initially drops, vinyl chloride monomer is added to the reaction container, and the polymerization reaction is continued until the pressure in the reaction container drops by 0.05 MPa, and an antioxidant is injected into the suspension polymerization reaction system to obtain an aqueous slurry;

[0120] The aqueous slurry is sent to steam stripping, centrifugal drying and homogenization treatment (dried in a cyclone drying bed at 45°C for 0.5 hours) to obtain the finished polyvinyl chloride resin. The gaseous vinyl chloride monomer after separation is sent to a high-pressure recovery system for compression, condensation and recovery.

[0121] Example 8

[0122] A method for preparing a polyvinyl chloride resin with high time-space yield comprises the following steps:

[0123]

[0124]

[0125] emulsifying the initiator and adjusting the concentration through a diluent and storing the emulsified initiator to obtain an initiator preparation solution;

[0126] Add a pH regulator, a dispersant, deionized water and premixed vinyl chloride monomer into a reaction vessel, and heat the vessel to 57° C. with synchronous steam to obtain a mixed solution;

[0127] When the mixed liquid is suspended and polymerized, 30 ppm of initiator configuration liquid is first added to the reaction container, and the suspension polymerization reaction starts to be timed. When the suspension polymerization conversion rate is 1-50%, 10 stages of initiator configuration liquid are added to the reaction container in a stepwise manner at a feed rate of 95 ppm at a time interval of 0.3 hours. When the suspension polymerization conversion rate is 50-90%, 10 stages of initiator configuration liquid are added to the reaction container in a stepwise manner at a feed rate of 65 ppm.

[0128] When the pressure in the reaction container initially drops, vinyl chloride monomer is added to the reaction container, and the polymerization reaction is continued until the pressure in the reaction container drops by 0.1 MPa, and an antioxidant is injected into the suspension polymerization reaction system to obtain an aqueous slurry;

[0129] The aqueous slurry is sent to steam stripping, centrifugal drying and homogenization treatment (dried in a cyclone drying bed at 45°C for 0.5 hours) to obtain the finished polyvinyl chloride resin. The gaseous vinyl chloride monomer after separation is sent to a high-pressure recovery system for compression, condensation and recovery.

[0130] Example 9

[0131] This example is basically the same as Example 1, except that the initiators used are tert-butyl peroxyneodecanoate and diisobutyryl peroxide, and the diluent is dodecane.

[0132] A method for preparing a polyvinyl chloride resin with high time-space yield comprises the following steps:

[0133]

[0134] emulsifying the initiator and adjusting the concentration through a diluent and storing the emulsified initiator to obtain an initiator preparation solution;

[0135] Add a pH regulator, a dispersant, deionized water and premixed vinyl chloride monomer into a reaction vessel, and heat the vessel to 57° C. with synchronous steam to obtain a mixed solution;

[0136] When the mixed liquid is suspended and polymerized, 95 ppm of initiator solution is first added to the reaction container, and the suspension polymerization reaction starts to be timed. When the suspension polymerization conversion rate is 1-50%, 8 stages of initiator solution are added to the reaction container in stages with a feed amount of 65 ppm at a time interval of 0.16 hours. When the suspension polymerization conversion rate is 50-90%, 9 stages of initiator solution are added to the reaction container in stages with a feed amount of 45 ppm.

[0137] When the pressure in the reaction container initially drops, vinyl chloride monomer is added to the reaction container, and the polymerization reaction is continued until the pressure in the reaction container drops by 0.075 MPa. The reaction time is 3 hours. An antioxidant is injected into the suspension polymerization reaction system to obtain an aqueous slurry.

[0138] The aqueous slurry is sent for steam stripping, centrifugal drying and homogenization treatment (dried in a cyclone drying bed at 45°C for 0.5 hour) to obtain a polyvinyl chloride resin product with a time-space yield of 93.51%. The gaseous vinyl chloride monomer after separation is sent to a high-pressure recovery system for compression, condensation and recovery.

[0139] The finished polyvinyl chloride resin products of Examples 1-7 and Example 9 were tested for thickness, yellowness index, light transmittance and haze according to Q / TCPVC 001-2022 "Special polyvinyl chloride resin for suspension method", and the results are shown in Table 3 below.

[0140] Table 3

[0141] sample Thickness / mm Yellowness Index (YID) Light transmittance / % Haze Example 1 10.00 24.14 83.21 16.57 Example 2 10.00 22.28 84.45 14.05 Example 3 10.00 30.41 82.17 16.18 Example 4 10.00 28.17 83.32 13.38 Example 5 10.00 28.34 83.46 13.11 Example 6 10.00 23.46 84.30 13.10 Example 7 10.00 20.14 84.87 13.17 Example 9 10.00 20.48 83.79 12.73

[0142] From observing Table 3, it can be seen that the polyethylene resin prepared in the examples of the present application has a low yellowness index, high light transmittance and low haze, which indicates that the polyvinyl chloride resin obtained in the present invention has excellent initial colorability.

[0143] Comparative Example 1

[0144] This comparative example is basically the same as Example 1, except that the vinyl chloride monomer is added at one time.

[0145] A method for preparing a polyvinyl chloride resin with high time-space yield comprises the following steps:

[0146] raw material Weight / g pH Adjusters 0.02 Dispersants 0.1 Deionized water 150 Vinyl chloride monomer 112.5 Initiator (diisobutyryl peroxide) 0.32 Dilution (5% polyvinyl alcohol solution) 0.12 Antioxidants 0.1

[0147] emulsifying the initiator and adjusting the concentration through a diluent and storing the emulsified initiator to obtain an initiator preparation solution;

[0148] Add a pH regulator, a dispersant, deionized water and vinyl chloride monomer into a reaction vessel, and heat the vessel to 57° C. with steam to obtain a mixed solution;

[0149] When the mixed liquid is suspended and polymerized, 95 ppm of initiator configuration liquid is first added to the reaction container, and the suspension polymerization reaction starts to be timed. When the suspension polymerization conversion rate is 1-50%, 4 stages of initiator configuration liquid are added to the reaction container in stages with a feed amount of 95 ppm at a time interval of 0.3 hours. When the suspension polymerization conversion rate is 50-90%, 5 stages of initiator configuration liquid are added to the reaction container in stages with a feed amount of 75 ppm.

[0150] The polymerization reaction was continued until the pressure in the reaction vessel dropped by 0.075 MPa. The reaction time was 3.25 h. An antioxidant was injected into the suspension polymerization reaction system to obtain an aqueous slurry.

[0151] The water-containing slurry is subjected to steam stripping, centrifugal drying and homogenization treatment (dried in a cyclone drying bed at 45°C for 0.5 hour) to obtain a polyvinyl chloride resin product with a time-space yield of 70.68% and a water content of less than 4%. The gaseous vinyl chloride monomer after separation is sent to a high-pressure recovery system for compression, condensation and recovery.

[0152] The space-time yield of the finished polyvinyl chloride resin obtained by adding vinyl chloride monomer in batches is 94.12%, while the space-time yield of the finished polyvinyl chloride resin obtained by adding vinyl chloride monomer all at once is 70.68%. It can be seen that adding vinyl chloride monomer in batches can significantly improve the space-time yield of polyvinyl chloride resin.

[0153] In summary, the present application combines the kinetic evolution law of the reaction system, adopts a single high-activity or high-low-activity composite initiator configuration liquid to add the suspension polymerization system in stages at the reaction temperature set by the material type. The volume shrinkage characteristic of the suspended polymerization material is utilized. When the pressure drop of the reaction container begins, vinyl chloride monomer is added to the suspension polymerization reaction system, and the heat exchange conditions of the polymerization device are fully utilized to shorten the reaction cycle of the system and improve the space-time yield of the suspended polymerization material. The present application can obtain polyvinyl chloride resin with a water content of less than 4% and a space-time yield of more than 90%. At the same time, the present application is also suitable for continuous suspension polymerization reaction, and the present application can also improve the space-time yield of the reaction container.

[0154] The embodiments described above are part of the embodiments of the present application, rather than all of the embodiments. The detailed description of the embodiments of the present application is not intended to limit the scope of the present application for protection, but merely represents the selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present application.

Claims

1. A method for preparing a polyvinyl chloride resin with high space-time yield, characterized in that: The steps include: emulsifying the initiator and adjusting the concentration through a diluent and storing the emulsified initiator to obtain an initiator preparation solution; Adding a pH regulator, a dispersant, deionized water and a premixed vinyl chloride monomer into a reaction container, heating and stirring to obtain a mixed solution; wherein the water-to-oil ratio of the mixed solution is 1 to 2.5:1; During suspension polymerization of the mixed solution, the initiator preparation solution is added into the reaction container in stages; When the pressure in the reaction container begins to drop for the first time, vinyl chloride monomer is added to the reaction container, and an antioxidant is added after the reaction to obtain an aqueous slurry; The aqueous slurry is subjected to steam stripping, centrifugal drying and homogenization treatment to obtain a polyvinyl chloride resin product with high time and space yield; The staged addition specifically comprises adding the initiator preparation liquid at a time interval of 0.1 to 0.3 hours when the suspension polymerization conversion rate of the mixed liquid is 1 to 50%, according to a staged feeding amount of 30 to 95 ppm; when the suspension polymerization conversion rate of the mixed liquid is 50 to 90%, adding the initiator preparation liquid in 10 to 30 stages, and according to a staged feeding amount of 25 to 65 ppm each time.

2. The method for preparing a polyvinyl chloride resin with high space-time yield according to claim 1, characterized in that: The initiator emulsification specifically comprises emulsifying the initiator and the emulsifier in a ratio of 100:(1-3), wherein the emulsifier is polyvinyl alcohol, and the concentration of the initiator preparation liquid is 15-25%.

3. The method for preparing a polyvinyl chloride resin with high space-time yield according to claim 1, characterized in that: The pH regulator, dispersant, deionized water and premixed vinyl chloride monomer are added to the reaction container and the temperature is raised to 57° C. for 0.4 to 0.7 hours.

4. The method for preparing a polyvinyl chloride resin with high space-time yield according to claim 1, characterized in that: When the pressure in the reaction container begins to drop to 0.05-0.1 MPa for the first time, vinyl chloride monomer is added to the reaction container.

5. The method for preparing a polyvinyl chloride resin with high space-time yield according to claim 1, characterized in that: The centrifugal drying homogenization treatment specifically involves drying the water-containing slurry after steam stripping at 30-90° C. for 0.5-0.7 hours in a cyclone drying bed.

6. A polyvinyl chloride resin with high space-time yield prepared by the method according to any one of claims 1 to 5, characterized in that: The invention comprises the following raw materials in parts by weight: 0.01 to 0.03 parts of pH regulator, 0.05 to 0.15 parts of dispersant, 140 to 160 parts of deionized water, 100 to 125 parts of vinyl chloride monomer, 0.3 to 0.35 parts of initiator, 0.1 to 0.3 parts of diluent and 0.05 to 0.15 parts of antioxidant.

7. A polyvinyl chloride resin with high space-time yield according to claim 6, characterized in that: The initiator comprises one or more of water-soluble organic peroxides or oil-soluble organic peroxides, and the decomposition activation energy of the initiator is 100-150 kJ / mol.

8. A polyvinyl chloride resin with high space-time yield according to claim 7, characterized in that: The initiator includes one or more of diisobutyryl peroxide, cumyl peroxyneodecanoate, bis(3-methoxybutyl)peroxydicarbonate, 1,1,3,3-tetramethylbutyl peroxyneodecanoate, bis(2-ethylhexyl)peroxydicarbonate and tert-butyl peroxyneodecanoate.

9. A polyvinyl chloride resin with high space-time yield according to claim 7, characterized in that: The vinyl chloride monomer comprises premixed vinyl chloride monomer and additional vinyl chloride monomer in a weight ratio of 100:10-18; the diluent is a polyvinyl alcohol solution and / or dodecane with a volume concentration of 5%.

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