CN204874355U

CN204874355U - Device of preparation lactide

Info

Publication number: CN204874355U
Application number: CN201520575710.7U
Authority: CN
Inventors: 刘啸天; 王励申
Original assignee: Dongguan University of Technology
Current assignee: Dongguan University of Technology
Priority date: 2015-08-04
Filing date: 2015-08-04
Publication date: 2015-12-16
Anticipated expiration: 2025-08-04

Abstract

The utility model belongs to the technical field of mechanical equipment, in particular to device of preparation lactide, including reation kettle, water knockout drum and melting crystallization ware, the water knockout drum with reation kettle forms a return circuit, melting crystallization ware pass through the centrifugal pump with the reation kettle intercommunication. The utility model provides an in prior art the equipment of preparation lactide have the problem that structure complicacy, productivity are low, the energy consumption is high, the impurity content is high to make the industrial production enable of the lactide of low cost, high -purity.

Description

A kind of device preparing rac-Lactide

Technical field

The utility model belongs to mechanical equipment technical field, particularly a kind of device preparing rac-Lactide.

Background technology

The production of rac-Lactide and exploitation obtain in recent years to be paid attention to more and more widely, and its reason mainly utilizes the ring-opening polymerization of rac-Lactide to be the effective ways preparing poly-lactic acid in high molecular weight.Poly(lactic acid) is a kind of rising Biodegradable material, the final product decomposed in physical environment due to it is carbonic acid gas and water, nontoxic to environment, having good biocompatibility and biological degradability, excellent mechanical property simultaneously, be easy to the advantages such as machine-shaping, is a kind of medical macromolecular materials of excellence.And utilizing the ring-opening polymerization of rac-Lactide to be the effective ways preparing poly-lactic acid in high molecular weight, its polymerisate---polylactic acid molecule amount can reach up to a million.

Under existing Chemical Manufacture condition, the preparation of rac-Lactide uses decompression method or non-pressure process to be prepared to support equipment corresponding separately usually, no matter be non-pressure process or decompression method, its commercial synthesis is generally all divided into two steps: be first that monomer lactic acid polycondensation generates oligopolymer, then oligopolymer is depolymerized to ring under certain temperature and pressure, generates rac-Lactide.

(1) reduce pressure method

The reaction of decompression method in two steps, the first step is that lactic acid dehydrating polycondensation at 80 ~ 140 DEG C of temperature and reduced pressure forms oligopolymer (molecular-weight average 500 ~ 2000), this step can not use catalyzer, decompression operation can extract product moisture out on the one hand at any time, ensure that reaction forward is carried out, can system viscosity be reduced on the other hand, ensure that moisture is easy to steam from viscous solution, moreover decrease the probability that oxygen enters system generation oxidizing reaction.Under lower temperature conditions, steam moisture in system, promote that lactic acid oligomer is formed, and oligopolymer Pintsch process can be prevented; Second step is that thermolysis forms molecular structure to oligopolymer under reduced pressure in the presence of a catalyst, between 200 ~ 300 DEG C and is further hexa-atomic ring-like rac-Lactide product, this step is the committed step of rac-Lactide synthesis, oligopolymer chain rupture generates rac-Lactide and need at high temperature complete, this is because this step belongs to thermo-negative reaction, but excessive temperature can the side reaction such as accelerated carbonation, oxidation.Meanwhile, realize high vacuum operation and must use the equipment such as oil-sealed rotary pump or vapor jet pump, add the difficulty of equipment use and maintenance, initial reaction stage crosses high vacuum condition also can strengthen lactic acid loss, reduces rac-Lactide productive rate.

(2) non-pressure process

Non-pressure process reaction is that a step is carried out, and namely the building-up reactions of rac-Lactide is carried out between 100 ~ 150 DEG C, in reaction process, in system, passes into N ₂or CO ₂deng rare gas element, to reduce the dividing potential drop of rac-Lactide steam and the rac-Lactide of generation is taken out of continuously from reaction system, and solidify in curing area to obtain rac-Lactide product.The advantage of non-pressure process is that in reactor, oxygen is replaced by rare gas element, and avoid the side reaction such as variable color, coking being oxidized and causing, improve productive rate and the purity of rac-Lactide to a certain extent, and the method technical difficulty is low, successful operation is high; Its weak point is that dewatering time is long, and production efficiency is low, and productive rate is less.

The rac-Lactide that the method that no matter reduces pressure or non-pressure process obtain is all containing a certain amount of impurity, and the rac-Lactide containing impurity cannot be obtained poly-lactic acid in high molecular weight, so must carry out purification operations to the crude lactide obtained by polymerization.Industrially, the method for purification of rac-Lactide mainly contains recrystallization method, evaporation method of air aided and hydrolysis method etc., but these method techniques are all more loaded down with trivial details, and equipment is complicated, and rac-Lactide loss is larger; Report is also had to adopt the Methods For Purification crude lactide of rectifying, this method is relatively simple, be suitable for the serialization industrial production of rac-Lactide, but the fore-running component water of rectifying tower top and lactic acid are condensed into liquid, product rac-Lactide is then very easily cooled to solid, make operating process complicated, be unfavorable for being separated and collecting product.

As can be seen here, under existing industrial process conditions, no matter adopt which kind of method above-mentioned and support equipment to produce rac-Lactide, all there is the problems such as productive rate is low, Processes and apparatus is complicated, product foreign matter content is high.

Utility model content

The purpose of this utility model is: for the deficiencies in the prior art, and a kind of device preparing rac-Lactide is provided, which solves the problem that the equipment preparing rac-Lactide in the prior art exists complex structure, productive rate is low, energy consumption is high, foreign matter content is high, thus make low cost, the suitability for industrialized production of highly purified rac-Lactide becomes possibility.

For achieving the above object, the technical solution of the utility model is:

Prepare a device for rac-Lactide, comprise reactor, water trap and melting crystallizer, described water trap and described reactor form primary Ioops, and described melting crystallizer is communicated with described reactor by impeller pump.

Improve as the one preparing the device of rac-Lactide described in the utility model, water trap forms primary Ioops by return line, cooling tube and described reactor successively, and described return line and described cooling tube are provided with liquid feed valve.

Improve as the one preparing the device of rac-Lactide described in the utility model, the top of described water trap is communicated with vapor pipe, and the bottom of described water trap is provided with outlet valve.

Improve as the one preparing the device of rac-Lactide described in the utility model, described water trap is communicated with dimethylbenzene retrieving arrangement.

Improve as the one preparing the device of rac-Lactide described in the utility model, described water trap is provided with viewing window.

Improve as the one preparing the device of rac-Lactide described in the utility model, the upper inside wall of described melting crystallizer is set to cooling wall, and the inner wall lower of described melting crystallizer is set to heating-wall.

Improve as the one preparing the device of rac-Lactide described in the utility model, the inner chamber of described melting crystallizer is provided with scraper.

Improve as the one preparing the device of rac-Lactide described in the utility model, described melting crystallizer is communicated with equipment for separating liquid from solid.

Improve as the one preparing the device of rac-Lactide described in the utility model, described melting crystallizer is communicated with any residual aqueous phase liquid retrieving arrangement.

Relative to prior art, the utility model at least has the following advantages:

1) energy-efficient, by the setting of the utility model melting crystallizer, have employed production method and technique that solvent bank water and fusion-crystallization technology combine, make production temperature low, power consumption values only has 35% ~ 40% of distillation technology, and solving existing distillation technology has high reflux ratio and high thermal losses, problem that energy consumption is higher;

2) production temperature is lower, do not need to carry out pressurizeing or decompression operation, no matter the utility model is the production of rac-Lactide and the process pure processed of fusion-crystallization, its operational condition is atmospheric operation, service temperature is also lower, operating process is simple, safety, does not have excessive demand to equipment and materials, while reduction running cost, also save fixed investment;

3) prepare solvent in lactide process and can reclaim use, with decreasing pollution to greatest extent, the dimethylbenzene added in a kettle. both can be used as solvent, also can use as water entrainer, last added dimethylbenzene can be reclaimed by dimethylbenzene retrieving arrangement completely, both can reduce the pollution to environment, also can reduce production cost;

4) pure lactide process processed adopts fusion-crystallization method, and this method is different from solution crystallization, does not need to introduce other solvents again, has both avoided the pollution of solvent to product, has additionally reduced the cumbersome procedure of recycling design;

5) the pure system of rac-Lactide is effective, rectification method is produced in the process of rac-Lactide, the phenomenons such as easy appearance charing, coking, polymerization, so, product yield is low, is difficult to obtain high purity product, and utilizes fusion-crystallization technology just in time to solve this problem, the purity of rac-Lactide product is high, and foreign matter content is few.

Accompanying drawing explanation

Fig. 1 is structural representation of the present utility model.

Wherein: 1-reactor, 2-water trap, 3-melting crystallizer, 4-return line, 5-cooling tube, 6-liquid feed valve, 7-vapor pipe, 8-outlet valve, 9-viewing window, 10-cooling wall, 11-heating-wall, 12-scraper, 13-equipment for separating liquid from solid, 14-any residual aqueous phase liquid retrieving arrangement, 15-dimethylbenzene retrieving arrangement, 16-impeller pump.

Embodiment

Below in conjunction with embodiment and Figure of description, the utility model is described in further detail, but embodiment of the present utility model is not limited thereto.

As shown in Figure 1, a kind of device preparing rac-Lactide, comprises reactor 1, water trap 2 and melting crystallizer 3, and water trap 2 and reactor 1 form primary Ioops, and melting crystallizer 3 is communicated with reactor 1 by impeller pump 16.Water trap 2 forms primary Ioops by return line 4, cooling tube 5 with reactor 1 successively, return line 4 and cooling tube 5 are provided with liquid feed valve 6, liquid feed valve 6 on return line 4 is for controlling the refluxing xylene amount after getting rid of water, liquid feed valve 6 on cooling tube 5 is for controlling the mixture flow rate of dimethylbenzene and water, and cooling tube 5 plays the effect of the mixture of cooling dimethylbenzene and water.The top of water trap 2 is communicated with vapor pipe 7, plays the effect of exhaust, and the bottom of water trap 2 is provided with outlet valve 8, and outlet valve 8 is for the discharge of water in water trap 2.Water trap 2 is communicated with dimethylbenzene retrieving arrangement 15, for reclaiming dimethylbenzene, realizes again utilizing.Water trap 2 is provided with viewing window 9, for observing the response situation in water trap 2.

Preferably, the upper inside wall of melting crystallizer 3 is set to cooling wall 10, cooling wall 10 makes the upper temp of melting crystallizer 3 lower, the inner wall lower of melting crystallizer 3 is set to heating-wall 11, heating-wall 11 makes the temperature of lower of melting crystallizer 3 higher, thus the inner levels of melting crystallizer 3 forms differing temps region.The inner chamber of melting crystallizer 3 is provided with scraper 12, and scraper 12 can rotate, for being rooted out by reacted crystal.Melting crystallizer 3 is communicated with equipment for separating liquid from solid 13, for realizing solid-liquid separation.Melting crystallizer 3 is communicated with any residual aqueous phase liquid retrieving arrangement 14, for reclaiming liquid phase debris.

Working process of the present utility model is: first add commercial concentration be 85% lactic acid be initial feed, the inorganic oxides such as dry oxidation zinc or stannous octoate, organic metal salt is catalyzer (catalyst levels is the 1%-2% of added lactic acid weight), and dimethylbenzene as solvent and water entrainer (dimethylbenzene consumption be the 2-3 of added lactic acid weight doubly) in reactor 1, reacting by heating still 1 to 140 DEG C makes dimethylbenzene boiling reflux, first its reaction process is dehydration esterification reaction occurs between lactic acid molecules generate lactic acid oligomer, the less stable of lactic acid oligomer, the cyclic dimer rac-Lactide that cracking obtains lactic acid can be continued, the water generated must be got rid of to promote that the building-up reactions of rac-Lactide is carried out towards the positive direction as by product, the water of solvent xylene and generation is utilized in reactor 1, to form azeotropic mixture under 140 DEG C of conditions, the azeotropic mixture generated enters water trap 2 by cooling tube 5 again, in water trap 2, cooled dimethylbenzene and water stratification, water-mass density is deposited on greatly the bottom of water trap 2, after depositing in water accumulated amount is comparatively large, by outlet valve 8, water can be released from water trap 2, but the little meeting of dimethylbenzene density is positioned at the upper strata of water trap 2, getting rid of the dimethylbenzene after water can be come back in reactor 1 as solvent and water entrainer continuation use by return line 4.Until do not observe aqueous layer contg in water trap 2 to increase (being observed by viewing window 9), now preparation feedback end of processing, being distilled completely by dimethylbenzene residual in reactor 1 enters in water trap 2, and then reclaimed by dimethylbenzene retrieving arrangement 15, continue to recycle in the preparation process of upper once rac-Lactide.

Now, coarse liquid rac-Lactide has been generated in reactor 1, coarse liquid rac-Lactide enters into melting crystallizer 3 by impeller pump 16, upper inside wall due to melting crystallizer 3 is set to cooling wall 10, bottom is set to heating-wall 11, its inside is made to form certain thermograde up and down, when the temperature of cold zone, top is set as 65 DEG C, rac-Lactide pure substance in crude product is first at cooling wall 10 crystallization, crystal is rooted out by the scraper 12 rotated subsequently, because the density ratio density of liquid phase of solid phase is large, crystal also progressively enters high-temperature zone, bottom through liquid is mobile bottom melting crystallizer 3, when the design temperature of high-temperature zone is 90 DEG C, in the process, crystal constantly grows, in crystal, the impurity fusing of parcel enters liquid phase simultaneously, the continuous purifying of solid phase, then final discharge bottom melting crystallizer 3 enter equipment for separating liquid from solid 13, pure rac-Lactide crystallization is just obtained by the work of equipment for separating liquid from solid 13, and the up solid of crossing of any residual aqueous phase liquid adverse current containing impurity such as a large amount of lactic acid is to cold zone, gathered from top by any residual aqueous phase liquid retrieving arrangement 14, thus prepare the raw material use of rac-Lactide as next production cycle.

Thus, the preparation of a rac-Lactide and the production process of pure system complete, thus the pure rac-Lactide crystallization obtained, rac-Lactide crystallization can directly use as polymer raw.

The announcement of book and instruction according to the above description, the utility model those skilled in the art can also change above-mentioned embodiment and revise.Therefore, the utility model is not limited to above-mentioned embodiment, and any apparent improvement of every those skilled in the art done by basis of the present utility model, replacement or modification all belong to protection domain of the present utility model.In addition, although employ some specific terms in this specification sheets, these terms just for convenience of description, do not form any restriction to the utility model.

Claims

1. prepare a device for rac-Lactide, it is characterized in that: comprise reactor, water trap and melting crystallizer, described water trap and described reactor form primary Ioops, and described melting crystallizer is communicated with described reactor by impeller pump.

2. the device preparing rac-Lactide according to claim 1, is characterized in that: described water trap forms primary Ioops by return line, cooling tube and described reactor successively, and described return line and described cooling tube are provided with liquid feed valve.

3. the device preparing rac-Lactide according to claim 1, it is characterized in that: the top of described water trap is communicated with vapor pipe, the bottom of described water trap is provided with outlet valve.

4. the device preparing rac-Lactide according to claim 1, is characterized in that: described water trap is communicated with dimethylbenzene retrieving arrangement.

5. the device preparing rac-Lactide according to claim 1, is characterized in that: described water trap is provided with viewing window.

6. the device preparing rac-Lactide according to claim 1, it is characterized in that: the upper inside wall of described melting crystallizer is set to cooling wall, the inner wall lower of described melting crystallizer is set to heating-wall.

7. the device preparing rac-Lactide according to claim 1, is characterized in that: the inner chamber of described melting crystallizer is provided with scraper.

8. the device preparing rac-Lactide according to claim 1, is characterized in that: described melting crystallizer is communicated with equipment for separating liquid from solid.

9. the device preparing rac-Lactide according to claim 1, is characterized in that: described melting crystallizer is communicated with any residual aqueous phase liquid retrieving arrangement.