Apparatus and method for reducing the acid value of polylactic polyol

Abstract

The application relates to a device and a method for reducing the acid value of polylactic acid polyol. The device for reducing the acid value of polylactic acid polyol comprises a reaction kettle and a distribution device arranged in the reaction kettle, the distribution device is communicated with a circulating feed port at the top of the reaction kettle and is used for distributing circulating materials, wherein the distribution device comprises a distribution cavity and N wire-wound screen pipes communicated with the side of the distribution cavity, and N>=2. The device can increase the contact area of polylactic acid polyol and an epoxide compound under inert gas conditions, improve the reaction rate, rapidly reduce the acid value of the product, reduce the reaction time of the materials and make the materials be heated more uniformly. In addition, the internal structure of the device is simple and the materials are not easy to be stored.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of polylactic acid polyol production, and particularly relates to a device and method for reducing the acid value of polylactic acid polyol. BACKGROUND

[0002] Polyester polyol is a main raw material for preparing polyurethane material, and can be used for preparing polyurethane elastomer, paint, adhesive, rubber, foam and other materials. Existing polyester polyol is generally synthesized by condensation of diacid and polyol. The raw materials such as diacid and polyol are basically derived from petroleum products. With the increasing consumption of petroleum resources, more and more attention is paid to the use of renewable resources to replace polyester polyol consuming petroleum resources to produce polyurethane material.

[0003] Polylactic acid polyol is synthesized from lactic acid as a monomer, which is a microbial fermentation product. It has the characteristics of non-toxicity, non-irritation, good biocompatibility and biodegradability, and is an ideal resin additive and modifier. It can be used to prepare biodegradable polyurethane material and replace polyester polyol to prepare polyurethane material. However, traditional polylactic acid polyol is usually prepared by direct polycondensation of lactic acid or ring-opening polymerization of lactide. Due to the existence of oxidation and cracking side reactions in the polycondensation or polymerization process, the polylactic acid polyol prepared by the above method contains a large amount of carboxyl-terminated polylactic acid, which makes the acid value of polylactic acid polyol high, thereby reducing the reaction performance of polylactic acid polyol. SUMMARY

[0004] The purpose of the present application is to overcome the shortcomings in the prior art and provide a device and method for reducing the acid value of polylactic acid polyol.

[0005] In a first aspect, the device for reducing the acid value of polylactic acid polyol comprises a reaction kettle and a distribution device arranged in the reaction kettle, the distribution device is connected with a circulating feed port at the top of the reaction kettle and is used for distributing the circulating material, wherein the distribution device comprises a distribution cavity and N wire-wound screen pipes connected with the side surface of the distribution cavity, and N≥2.

[0006] In some embodiments, the slit of the wire wrapped screen is 0.05 mm to 0.6 mm, for example, 0.07 mm, 0.09 mm, 0.1 mm, 0.13 mm, 0.15 mm, 0.17 mm, 0.19 mm, 0.2 mm, 0.23 mm, 0.25 mm, 0.27 mm, 0.29 mm, 0.3 mm, 0.33 mm, 0.35 mm, 0.37 mm, 0.39 mm, 0.4 mm, 0.43 mm, 0.45 mm, 0.47 mm, 0.49 mm, 0.5 mm, 0.55 mm, 0.57 mm, or any value therebetween. If the slit of the wire wrapped screen is too large, the effluent liquid column will be too thick, resulting in too small contact area with the epoxy compound, affecting the efficiency of acid value reduction. If the slit of the wire wrapped screen is too small, the pressure of the circulating pump will be increased, resulting in difficult circulation or too small circulation flow, thereby reducing the contact area of the material with the epoxy compound, and further affecting the efficiency of acid value reduction.

[0007] In some embodiments, the slit of the wire wrapped screen is 0.1 mm to 0.3 mm. In some embodiments, the slit of the wire wrapped screen is 0.15 mm to 0.2 mm.

[0008] In some embodiments, the length of the wire wrapped screen is 30% to 50% of the inner diameter of the reactor, for example, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, or any value therebetween. In some embodiments, the length of the wire wrapped screen is 35% to 45% of the inner diameter of the reactor.

[0009] In some embodiments, the length of the wire wrapped screen is 50 mm to 2000 mm, for example, 100 mm, 200 mm, 300 mm, 400 mm, 500 mm, 600 mm, 700 mm, 800 mm, 900 mm, 1000 mm, 1100 mm, 1200 mm, 1300 mm, 1400 mm, 1500 mm, 1600 mm, 1700 mm, 1800 mm, 1900 mm, or any value therebetween.

[0010] In some embodiments, the wire wrapped screen has an outer diameter of 20-50 mm, for example 21 mm, 22 mm, 23 mm, 24 mm, 25 mm, 26 mm, 27 mm, 28 mm, 29 mm, 30 mm, 31 mm, 32 mm, 33 mm, 34 mm, 35 mm, 36 mm, 37 mm, 38 mm, 39 mm, 40 mm, 41 mm, 42 mm, 43 mm, 44 mm, 45 mm, 46 mm, 47 mm, 48 mm, 49 mm, or any value therebetween. In some embodiments, the wire wrapped screen has an outer diameter of 25-40 mm.

[0011] In some embodiments, the distribution cavity is selected from a cylindrical cavity. In some embodiments, the distribution cavity has a diameter of 5-20% of the inner diameter of the reactor, for example 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, or any value therebetween. In some embodiments, the distribution cavity has a diameter of 6-15% of the inner diameter of the reactor.

[0012] In some embodiments, the distribution cavity has a height of 5-20% of the height of the reactor, for example 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, or any value therebetween. In some embodiments, the distribution cavity has a height of 8-15% of the height of the reactor.

[0013] In some embodiments, the wire wrapped screens are equidistantly annularly distributed on the side of the distribution cavity. In some embodiments, the wire wrapped screens are equidistantly annularly distributed on the side of the distribution cavity.

[0014] In some embodiments, 2≤N≤15, for example 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, or 14. In some embodiments, 5≤N≤10.

[0015] In some embodiments, the distribution device further comprises a feed inlet, which is in communication with the circulating feed inlet at the top of the reactor.

[0016] In some embodiments, the top of the reactor is further provided with a polylactic acid polyol feed inlet, an epoxide compound feed inlet, an inert gas inlet, and a vacuum inlet.

[0017] In some embodiments, the device further comprises a circulating pump, the inlet of which is in communication with the bottom of the reactor through a pipeline, and the outlet of which is in communication with the circulating feed inlet at the top of the reactor through a pipeline, for circulating the materials in the reactor.

[0018] In some embodiments, the circulation pump is selected from a forced circulation pump. In some embodiments, the pipeline is provided with a discharge port.

[0019] In some embodiments, the device further includes a monitoring and control unit, which includes a pressure control device and a liquid level monitoring device.

[0020] In some embodiments, the distribution device includes a feed inlet, a distribution box (distribution cavity), and a wire-wound screen tube.

[0021] In some embodiments, the device includes a reaction vessel, a forced circulation pump, and a distribution device disposed inside the reaction vessel. The top of the reaction vessel is provided with a polylactic acid polyol feed port, an epoxy compound feed port, an inert gas inlet, a circulation port, a vacuum port, and a pressure gauge from left to right. The circulation port is connected to the distribution device at its end. The bottom of the vessel is equipped with a level gauge, and the outlet of the circulation pump is connected to a discharge port.

[0022] In a second aspect, the present invention provides a method for reducing the acid value of polylactic acid polyol, comprising reacting a polylactic acid polyol with an acid value greater than or equal to 1.0 mg KOH / g with an epoxy compound represented by Formula I in the apparatus described in the first aspect.

[0023]

[0024] In the formula, n is 1, 2 or 3, and R is selected from hydrogen or C1-C4 alkyl.

[0025] In some implementations, the method includes the following steps:

[0026] S1: Under the condition of inert gas, polylactic acid polyol and epoxy compound are introduced into the reactor through the polylactic acid polyol feed port and the epoxy compound feed port, respectively. The reactor is kept sealed and preheated in the reactor to obtain preheated polylactic acid polyol and epoxy compound gas.

[0027] S2: The preheated polylactic acid polyol is circulated by a circulation pump and then enters the distribution device. After being distributed by the distribution device, it reacts with the epoxy compound gas to obtain a reaction intermediate.

[0028] In some embodiments, the method further includes step S3: when the acid value of the reaction intermediate in step S2 is less than or equal to 1.0 mg KOH / g, the reaction intermediate is subjected to devolatilization treatment through a vacuum port.

[0029] In some embodiments, R is selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, or tert-butyl.

[0030] In some embodiments, the epoxy compound is selected from one or more of ethylene oxide, 1,2-epoxypropane, 1,3-epoxypropane, and tetrahydrofuran.

[0031] In some embodiments, the amount of the epoxy compound is 0.1% to 20.0% of the mass of the polylactic acid polyol, for example, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0%, 6.0%, 7.0%, 8.0%, 9.0%, 10.0%, 13.0%, 15.0%, 17.0%, or any value between them.

[0032] In this application, the polylactic acid polyol is selected from polylactic acid polyol or modified polylactic acid polyol.

[0033] In some embodiments, the polylactic acid polyol has an acid value of 1.0-20 mg KOH / g.

[0034] In some embodiments, in step S1, the temperature of the preheating treatment is 80°C-170°C, for example, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C or any value between them.

[0035] In some embodiments, in step S2, the reaction temperature is 80°C-170°C, for example, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, or any value between them. In some embodiments, in step S2, the reaction time is 0.5h-8h, for example, 1h, 3h, 5h, or 7h.

[0036] In some embodiments, in step S3, the temperature of the devolatilization treatment is 100℃-180℃, for example, 110℃, 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, or any value between them. In some embodiments, in step S3, the temperature of the devolatilization treatment is 130℃-160℃.

[0037] In some embodiments, the method for reducing the acid value of polylactic acid polyols includes the following specific steps:

[0038] (1) After the reactor is purged with inert gas through the inert gas inlet 1-3 times, and the inert gas is kept at a slightly positive pressure, polylactic acid polyol and epoxy compound are then added to the reactor through the polylactic acid polyol inlet and the epoxy compound inlet, keeping the reactor sealed. Once the reactor temperature reaches 80-170℃, the pressure inside the reactor is maintained at positive pressure.

[0039] (2) Open the bottom valve and turn on the forced circulation pump to allow the material to circulate and then enter the reactor through the circulation inlet. The material is then redistributed by the distribution device. After redistribution, the circulating material comes into full contact with the vaporized epoxy compound and reacts. After reacting for 0.5-8 hours, take a sample to test the acid value of the reaction product in the reactor until the acid value is less than or equal to 1.0 mg KOH / g.

[0040] (3) Open the vacuum port and perform devolatilization on the material inside the reactor. After the devolatilization is completed, discharge the reactants through the outlet.

[0041] Thirdly, this application provides a low-acid-value polylactic acid polyol prepared using the method described in the second aspect.

[0042] In some embodiments, the low-acid-value polylactic acid polyol has an acid value less than or equal to 1.0 mg KOH / g.

[0043] In some embodiments, the number average molecular weight of the low acid value polylactic acid polyol is 300-20000, for example, 1000, 2000, 5000, 7000, 10000, 13000, 15000 or 17000.

[0044] Advantages of this application compared to existing technologies:

[0045] (1) The device provided in this application can increase the contact area between polylactic acid polyol and epoxy compound and improve the reaction rate under inert gas conditions, thereby achieving rapid reduction of product acid value, reducing material reaction time and more uniform heating. In addition, the internal structure of the device is simple and it is not easy to store materials.

[0046] (2) The method provided in this application overcomes the difficulty of high acid value in traditional polylactic acid polyol products, and the added epoxy compound has a low boiling point, is easy to remove, and has little impact on the molecular weight of the product. In addition, the preparation method of this invention is simple in process, low in production cost, convenient in operation, and has the characteristics of large-scale production. Attached Figure Description

[0047] Figure 1 This is a schematic diagram of a device for reducing the acid value of polylactic acid polyols in some embodiments of this application;

[0048] Wherein: 1 is the reaction vessel, 2 is the forced circulation pump, 3 is the polylactic acid polyol feed port, 4 is the epoxy compound feed port, 5 is the inert gas port, 6 is the circulating feed port, 7 is the vacuum port, 8 is the pressure gauge, 9 is the distribution device, 10 is the level gauge, and 11 is the discharge port.

[0049] Figure 2 for Figure 1 Front view of the distribution device;

[0050] Wherein: 12 is the feed inlet, 13 is the distribution cavity, and 14 is the wire winding screen tube.

[0051] Figure 3 for Figure 1 Side view of the distribution device;

[0052] Among them, 12 is the feed inlet, 13 is the distribution cavity, and 14 is the wire winding screen tube. Detailed Implementation

[0053] The preferred embodiments of this application will be described in detail below with reference to examples. It should be understood that the following embodiments are given for illustrative purposes only and are not intended to limit the scope of this application. Various modifications and substitutions made to this application by those skilled in the art without departing from the spirit and intent of this application are considered to fall within the technical scope of this invention.

[0054] The acid value involved in this application was determined by acid-base titration method according to national standard HG / T 2708-95.

[0055] A schematic diagram of the device for reducing the acid value of polylactic acid polyols in this application is shown below. Figure 1 As shown, it includes: a reaction vessel 1, a forced circulation pump 2, a polylactic acid polyol feed port 3, an epoxy compound feed port 4, an inert gas port 5, a circulating feed port 6, a vacuum port 7, a pressure gauge 8, a distribution device 9, a level gauge 10, and a discharge port 11.

[0056] A schematic diagram of the distribution device 9 is shown below. Figure 2 and Figure 3 As shown, it includes a feed inlet 12, a distribution cavity (distribution box) 13, and a wire-wound screen tube 14.

[0057] Specifically, reactor 1 is purged three times with nitrogen gas introduced through inert gas port 5, maintaining a slight positive pressure. Then, polylactic acid polyol and epoxy compound are added to the reactor through polylactic acid polyol feed port 3 and epoxy compound feed port 4, keeping the reactor sealed. After the reactor reaches a certain temperature, positive pressure is maintained inside, the bottom valve is opened, and the forced circulation pump 2 is activated, allowing the material to circulate. The circulated material then enters the reactor through circulation inlet 6 and is redistributed through distribution device 9. The redistributed material then fully contacts the vaporized epoxy compound to react. After a certain reaction time, a sample is taken to test the acid value of the reaction products in the reactor. Once the acid value decreases to a certain level, a devolatilization reaction is carried out. After the devolatilization reaction is completed, the reactants are discharged through outlet 11.

[0058] During the reaction, the appropriate reaction pressure (≤0.4MPa) and liquid level are controlled by vacuum port 7, pressure gauge 8 and liquid level gauge 10.

[0059] Example 1

[0060] 1m 3 Reactor 1 was purged three times with nitrogen gas introduced through inert gas port 5, maintaining a slight positive pressure. Subsequently, 0.6 ml of polylactic acid polyol was added to the reactor through polylactic acid feed port 3 and epoxy compound feed port 4. 3 Approximately 700 kg of polylactic acid polyol and 5.5 kg of ethylene oxide were added. The polylactic acid polyol has a theoretical molecular weight of 380 and an acid value of 6.3 mg KOH / g. The reactor 1 was kept sealed and heated to 120°C. Positive pressure was maintained inside the reactor. The bottom valve was opened, and the forced circulation pump 2 was turned on. The material was circulated and then entered the reactor through the circulation inlet 6. It was then redistributed by the distribution device 9. The distributed circulating material then came into full contact with the vaporized epoxy compound to react.

[0061] The distribution device includes a cylindrical dispensing box, the diameter of which is 8% of the diameter of the reactor body, and the height of which is 10% of the reactor body.

[0062] The side of the distribution box is connected to eight radially and evenly arranged wire-wound screen tubes, wherein the gap of the wire-wound screen tubes is 0.2 mm, the length is 40% of the diameter of the reactor, and the outer diameter of the screen tubes is 30 mm.

[0063] After reacting for 3.5 hours, a sample was taken and the acid value was measured to be 0.9 mg KOH / g. Vacuum port 7 was opened to start the devolatilization process at a temperature of 130℃. After devolatilization, polylactic acid polyol with an acid value of 0.7 mg KOH / g was obtained.

[0064] Example 2

[0065] 1m 3 Reactor 1 was purged three times with nitrogen gas introduced through inert gas port 5, maintaining a slight positive pressure. Subsequently, 0.6 ml of polylactic acid polyol was added to the reactor through polylactic acid feed port 3 and epoxy compound feed port 4. 3 Approximately 700 kg of polylactic acid polyol and 3.5 kg of ethylene oxide were added. The polylactic acid polyol has a theoretical molecular weight of 2000 and an acid value of 3.7 mg KOH / g. The reactor 1 was kept sealed and heated to 140°C. Positive pressure was maintained inside the reactor. The bottom valve was opened, and the forced circulation pump 2 was turned on. The material was circulated and then entered the reactor through the circulation inlet 6. It was then redistributed by the distribution device 9. The distributed circulating material then came into full contact with the vaporized epoxy compound to react.

[0066] The distribution device includes a cylindrical dispensing box, the diameter of which is 8% of the diameter of the reactor body, and the height of which is 10% of the reactor body.

[0067] The side of the distribution box is connected to eight radially and evenly arranged wire-wound screen tubes, wherein the gap of the wire-wound screen tubes is 0.2 mm, the length is 40% of the diameter of the reactor, and the outer diameter of the screen tubes is 30 mm.

[0068] After reacting for 3 hours, a sample was taken and the acid value was measured to be 0.7 mg KOH / g. Vacuum port 7 was opened to start the devolatilization process at a temperature of 140℃. After devolatilization, polylactic acid polyol with an acid value of 0.5 mg KOH / g was obtained.

[0069] Example 3

[0070] 1m 3 Reactor 1 was purged three times with nitrogen gas introduced through inert gas port 5, maintaining a slight positive pressure. Subsequently, 0.6 ml of polylactic acid polyol was added to the reactor through polylactic acid feed port 3 and epoxy compound feed port 4. 3 Approximately 700 kg of polylactic acid polyol and 4.7 kg of 1,2-epoxypropane were added. The polylactic acid polyol has a theoretical molecular weight of 5000 and an acid value of 5.6 mg KOH / g. The reactor 1 was kept sealed and heated to 150°C. Positive pressure was maintained inside the reactor. The bottom valve was opened, and the forced circulation pump 2 was turned on. The material was circulated and then entered the reactor through the circulation inlet 6. It was then redistributed by the distribution device 9. The distributed circulating material then came into full contact with the vaporized epoxy compound to react.

[0071] The distribution device includes a cylindrical dispensing box, the diameter of which is 8% of the diameter of the reactor body, and the height of which is 10% of the reactor body.

[0072] The side of the distribution box is connected to eight radially and evenly arranged wire-wound screen tubes, wherein the gap of the wire-wound screen tubes is 0.2 mm, the length is 40% of the diameter of the reactor, and the outer diameter of the screen tubes is 30 mm.

[0073] After reacting for 2.5 hours, a sample was taken and the acid value was measured to be 0.8 mg KOH / g. Vacuum port 7 was opened to start the devolatilization process at a temperature of 150℃. After devolatilization, polylactic acid polyol with an acid value of 0.6 mg KOH / g was obtained.

[0074] Example 4

[0075] 1m 3 Reactor 1 was purged three times with nitrogen gas introduced through inert gas port 5, maintaining a slight positive pressure. Subsequently, 0.6 ml of polylactic acid polyol was added to the reactor through polylactic acid feed port 3 and epoxy compound feed port 4. 3Approximately 700 kg of polylactic acid polyol and 3.3 kg of 1,3-epoxypropane were added. The polylactic acid polyol has a theoretical molecular weight of 10,000 and an acid value of 4.2 mg KOH / g. The reactor 1 was kept sealed and heated to 160°C. Positive pressure was maintained inside the reactor. The bottom valve was opened, and the forced circulation pump 2 was turned on. The material was circulated and then entered the reactor through the circulation inlet 6. It was then redistributed by the distribution device 9. The distributed circulating material then came into full contact with the vaporized epoxy compound to react.

[0076] The distribution device includes a cylindrical dispensing box, the diameter of which is 8% of the diameter of the reactor body, and the height of which is 10% of the reactor body.

[0077] The side of the distribution box is connected to eight radially and evenly arranged wire-wound screen tubes, wherein the gap of the wire-wound screen tubes is 0.2 mm, the length is 40% of the diameter of the reactor, and the outer diameter of the screen tubes is 30 mm.

[0078] After reacting for 2.0 hours, a sample was taken and the acid value was measured to be 0.9 mg KOH / g. Vacuum port 7 was opened to start the devolatilization process at a temperature of 160℃. After devolatilization, polylactic acid polyol with an acid value of 0.8 mg KOH / g was obtained.

[0079] Example 5

[0080] The 1m³ reactor 1 was purged three times with nitrogen gas introduced through the inert gas port 5, maintaining a slight positive pressure. Subsequently, 0.6m³ of polylactic acid polyol was added to the reactor through the polylactic acid feed port 3 and the epoxy compound feed port 4. 3 (Approximately 700 kg) and 4.2 kg of tetrahydrofuran, of which polylactic acid polyol has a theoretical molecular weight of 20,000 and an acid value of 4.3 mg KOH / g. Keep reactor 1 sealed and heat it to 170°C, maintain positive pressure inside the reactor, open the bottom valve, and turn on the forced circulation pump 2 to circulate the material. The material then enters the reactor through the circulation inlet 6 and is redistributed by the distribution device 9. The distributed circulating material then comes into full contact with the vaporized epoxy compound to react.

[0081] The distribution device includes a cylindrical dispensing box, the diameter of which is 8% of the diameter of the reactor body, and the height of which is 10% of the reactor body.

[0082] The side of the distribution box is connected to eight radially and evenly arranged wire-wound screen tubes, wherein the gap of the wire-wound screen tubes is 0.2 mm, the length is 40% of the diameter of the reactor, and the outer diameter of the screen tubes is 30 mm.

[0083] After reacting for 1.5 hours, a sample was taken and the acid value was measured to be 0.6 mg KOH / g. Vacuum port 7 was opened to start devolatilization at a temperature of 160℃. After devolatilization, polylactic acid polyol with an acid value of 0.5 mg KOH / g was obtained.

[0084] Example 6

[0085] 1m 3 Reactor 1 was purged three times with nitrogen gas introduced through inert gas port 5, maintaining a slight positive pressure. Subsequently, 0.6 ml of polylactic acid polyol was added to the reactor through polylactic acid feed port 3 and epoxy compound feed port 4. 3 4.7 kg of 1,2-epoxypropane was added, containing polylactic acid polyol with a theoretical molecular weight of 5000 and an acid value of 5.6 mg KOH / g. The reactor 1 was kept sealed and heated to 150°C. Positive pressure was maintained inside the reactor. The bottom valve was opened, and the forced circulation pump 2 was activated. The material circulated through the circulation inlet 6 and then entered the reactor, where it was redistributed by the distribution device 9. The redistributed circulating material then came into full contact with the vaporized epoxy compound to react.

[0086] The distribution device includes a cylindrical dispensing box, the diameter of which is 8% of the diameter of the reactor body, and the height of which is 10% of the reactor body.

[0087] The side of the distribution box is connected to eight radially and evenly arranged wire-wound screen tubes, wherein the gap of the wire-wound screen tubes is 0.05mm, the length is 40% of the diameter of the reactor, and the outer diameter of the screen tubes is 30mm.

[0088] The acid value was measured after 2.5 hours of reaction, 3.3 mg KOH / g, after 5.0 hours of reaction, 1.3 mg KOH / g, and after 10 hours of reaction, 0.8 mg KOH / g.

[0089] Vacuum port 7 is opened to begin the devolatilization process at a temperature of 150℃. After devolatilization, polylactic acid polyol with an acid value of 0.8 mg KOH / g is obtained.

[0090] Example 7

[0091] 1m 3 Reactor 1 was purged three times with nitrogen gas introduced through inert gas port 5, maintaining a slight positive pressure. Subsequently, 0.6 ml of polylactic acid polyol was added to the reactor through polylactic acid feed port 3 and epoxy compound feed port 4. 3 4.7 kg of 1,2-epoxypropane was added, containing polylactic acid polyol with a theoretical molecular weight of 5000 and an acid value of 5.6 mg KOH / g. The reactor 1 was kept sealed and heated to 150°C. Positive pressure was maintained inside the reactor. The bottom valve was opened, and the forced circulation pump 2 was activated. The material circulated through the circulation inlet 6 and then entered the reactor, where it was redistributed by the distribution device 9. The redistributed circulating material then came into full contact with the vaporized epoxy compound to react.

[0092] The distribution device includes a cylindrical dispensing box, the diameter of which is 8% of the diameter of the reactor body, and the height of which is 10% of the reactor body.

[0093] The side of the distribution box is connected to eight radially and evenly arranged wire-wound screen tubes, wherein the gap of the wire-wound screen tubes is 0.6 mm, the length is 40% of the diameter of the reactor, and the outer diameter of the screen tubes is 30 mm.

[0094] The acid value was 2.1 mg KOH / g after 2.5 h of reaction, 1.2 mg KOH / g after 5 h of reaction, and 1.1 mg KOH / g after 8 h of reaction.

[0095] Vacuum port 7 is opened to start the devolatilization process at a temperature of 150℃. After devolatilization, polylactic acid polyol with an acid value of 1.0 mg KOH / g can be obtained.

[0096] Comparative Example 1

[0097] 1m 3 Reactor 1 was purged three times with nitrogen gas introduced through inert gas port 5, maintaining a slight positive pressure. Subsequently, 0.6 ml of polylactic acid polyol was added to the reactor through polylactic acid feed port 3 and epoxy compound feed port 4. 3 Approximately 700 kg of polylactic acid polyol and 3.3 kg of 1,3-epoxypropane were added. The polylactic acid polyol has a theoretical molecular weight of 10,000 and an acid value of 4.2 mg KOH / g. The reactor 1 was kept sealed and heated to 160°C. Positive pressure was maintained inside the reactor. The bottom valve was opened, and the forced circulation pump 2 was turned on. The material was circulated and then entered the reactor through the circulation inlet 6. It was then redistributed by the distribution device 9. The distributed circulating material then came into full contact with the vaporized epoxy compound to react.

[0098] The distribution device is a conventional multi-hole pipe type.

[0099] After 2.0 hours of reaction, the acid value was measured to be 1.7 mg KOH / g, and after 5 hours of reaction, the acid value was measured to be 1.2 mg KOH / g. Vacuum port 7 was opened to start devolatilization at a temperature of 160℃. After devolatilization, polylactic acid polyol with an acid value of 1.1 mg KOH / g was obtained.

[0100] Comparative Example 2

[0101] 1m 3 Reactor 1 was purged three times with nitrogen gas introduced by inert gas 5, maintaining a slight positive pressure. Subsequently, 0.6 ml of polylactic acid polyol was added to the reactor through polylactic acid feed port 3 and epoxy compound feed port 4. 3Approximately 700 kg of poly(lactic acid) polyol and 30.2 kg of 1,2-epoxycyclohexane were added. The polylactic acid polyol has a theoretical molecular weight of 2000 and an acid value of 3.7 mg KOH / g. The reactor 1 was kept sealed and heated to 140°C. Positive pressure was maintained inside the reactor. The bottom valve was opened, and the forced circulation pump 2 was turned on. The material was circulated and then entered the reactor through the circulation inlet 6. It was then redistributed by the distribution device 9. The distributed circulating material then came into full contact with the vaporized epoxy compound to react.

[0102] The distribution device includes a cylindrical dispensing box, the diameter of which is 8% of the diameter of the reactor body, and the height of which is 10% of the reactor body.

[0103] The side of the distribution box is connected to eight radially and evenly arranged wire-wound screen tubes, wherein the gap of the wire-wound screen tubes is 0.2 mm, the length is 40% of the diameter of the reactor, and the outer diameter of the screen tubes is 30 mm.

[0104] After reacting for 3.0 hours, a sample was taken and the acid value was measured to be 1.6 mg KOH / g. Vacuum port 7 was opened to start the devolatilization process at a temperature of 140℃. After devolatilization, polylactic acid polyol with an acid value of 1.5 mg KOH / g was obtained.

[0105] Although the present invention has been described in detail above with general descriptions, specific embodiments, and examples, certain supplements or improvements can be made to the discrimination model of this method based on the present invention, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. An apparatus for reducing the acid value of polylactic acid polyols, comprising a reaction vessel and a distribution device disposed within the reaction vessel, the distribution device being connected to a circulating feed inlet at the top of the reaction vessel for distributing circulating materials, wherein, The distribution device includes a distribution cavity and N wire-wound screen tubes connected to the side of the distribution cavity, wherein 2≤N≤15; The gap of the wire-wound screen tube is 0.05mm-0.6mm; The wire-wound screen tubes are evenly spaced and distributed in a ring on the side of the distribution cavity; The distribution device also includes a feed inlet, which is connected to the circulating feed inlet at the top of the reactor; The top of the reactor is also equipped with a polylactic acid polyol feed port, an epoxy compound feed port, an inert gas inlet, and a vacuum port; The device also includes a circulation pump, the inlet of which is connected to the bottom of the reactor via a pipeline, and the outlet of which is connected to the circulation feed inlet at the top of the reactor via a pipeline, for circulating the material in the reactor. The device also includes a monitoring and control unit, which includes a pressure control device and a liquid level monitoring device.

2. The apparatus according to claim 1, characterized in that, The gap of the wire-wound screen tube is 0.1-0.3 mm; The length of the wire-wound screen tube is 30%-50% of the inner diameter of the reactor; The outer diameter of the wire-wound screen tube is 20mm-50mm.

3. The apparatus according to claim 1, characterized in that, The length of the wire-wound screen tube is 35%-45% of the inner diameter of the reactor.

4. The apparatus according to claim 1, characterized in that, The length of the wire-wound screen tube is 50mm-2000mm.

5. The apparatus according to claim 1, characterized in that, The outer diameter of the wire-wound screen tube is 25mm-40mm.

6. The apparatus according to claim 1, characterized in that, The dispensing cavity is selected from cylindrical cavities; and / or The height of the distribution chamber is 5%-20% of the height of the reactor.

7. The apparatus according to claim 6, characterized in that, The diameter of the distribution cavity is 5%-20% of the inner diameter of the reactor.

8. The apparatus according to claim 6, characterized in that, The diameter of the distribution cavity is 6%-15% of the inner diameter of the reactor.

9. The apparatus according to claim 1, characterized in that, The height of the distribution chamber is 8%-15% of the height of the reactor.

10. The apparatus according to claim 1, characterized in that, 5≤N≤10。 11. The apparatus according to claim 1, characterized in that, The circulation pump is selected from forced circulation pumps.

12. The apparatus according to claim 1, characterized in that, The pipeline is equipped with a discharge port.

13. A method for reducing the acid value of polylactic acid polyol, comprising reacting a polylactic acid polyol with an acid value greater than or equal to 1.0 mg KOH / g with an epoxy compound of Formula I in the apparatus of any one of claims 1-12. Equation I, In the formula, n is 1, 2 or 3, and R is selected from hydrogen or C1-C4 alkyl.

14. The method according to claim 13, characterized in that, The method includes the following steps: S1: Under the condition of inert gas, polylactic acid polyol and epoxy compound are introduced into the reactor through the polylactic acid polyol feed port and the epoxy compound feed port, respectively. The reactor is kept sealed and preheated in the reactor to obtain preheated polylactic acid polyol and epoxy compound gas. S2: The preheated polylactic acid polyol is circulated by a circulation pump and then enters the distribution device. After being distributed by the distribution device, it reacts with the epoxy compound gas to obtain a reaction intermediate.

15. The method according to claim 14, characterized in that, The method further includes step S3: when the acid value of the reaction intermediate in step S2 is less than or equal to 1.0 mg KOH / g, the reaction intermediate is subjected to devolatilization treatment through a vacuum port.

16. The method according to claim 13, characterized in that, The epoxy compound is selected from one or more of ethylene oxide, 1,2-epoxypropane, 1,3-epoxypropane, and tetrahydrofuran; and / or Based on the mass of the polylactic acid polyol, the mass of the epoxy compound accounts for 0.1%-20.0% of the mass of the polylactic acid polyol.

17. The method according to claim 15, characterized in that, In step S1, the preheating temperature is 80℃-170℃; and / or In step S2, the reaction temperature is 80℃-170℃, and the reaction time is 0.5h-8h; and / or In step S3, the temperature of the devolatilization treatment is 100℃-180℃.

18. The method according to claim 17, characterized in that, The temperature for the devolatilization treatment is 130℃-160℃.

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