CN103819658A - Method for producing polylactic acid with low lactide monomer content - Google Patents
Method for producing polylactic acid with low lactide monomer content Download PDFInfo
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Abstract
The invention discloses a method for producing polylactic acid with low lactide monomer content. The method comprises the following steps: a) under the action of a catalyst, polymerizing molten lactide, wherein the conversion rate of the lactide is 10-30 percent; b) polymerizing a product in the step a) to obtain the polylactic acid, wherein the conversion rate of the lactide is greater than 90 percent; c) removing the lactide remained in the polylactic acid in the step b) under reduced pressure, and then granulating the polylactic acid, wherein the reduced pressure is minus 0.07MPa to minus 0.09MPa, and the content of the lactide remained in polylactic acid granulates is less than 5 weight percent; d) reversely contacting granulated polylactic acid in the step c) with inert gas under normal pressure, and removing a lactide monomer to obtain the polylactic acid with the low lactide monomer content, wherein the content of the lactide monomer in the polylactic acid is less than 0.1 weight percent. According to the method and equipment provided by the invention, the polylactic acid with lower remained lactide monomer content can be produced, and the obtained polylactic acid is better in formability and thermal stability.
Description
Technical field
The present invention relates to a kind of production method of poly-lactic acid in high molecular weight, more specifically, relate to the method for the poly-lactic acid in high molecular weight that production lactide monomer content is low.
Background technology
In recent years, along with the plastics such as polyethylene, polypropylene, polystyrene and polyvinyl chloride are widely used, the processing of the waste after use also becomes one of day by day serious environmental problem.Conventionally processing is processed and buried to these castoff burnings.Burning disposal can produce obnoxious flavour.Because the chemical stability of above-mentioned plastics is high, bury and microorganism can occur hardly after processing and decompose, left behind but be semipermanent state.
For addressing the above problem, the eco-friendly biodegradable polymkeric substance of investigators' Devoting Major Efforts To Developing, one of them is poly(lactic acid).Poly(lactic acid) can pass through the amylofermentation as main raw material to obtain lactic acid, then prepared by the polycondensation of gained lactic acid.Poly(lactic acid) has good biological degradability, biocompatibility, physical and mechanical properties and excellent processing characteristics, is widely used in many aspects such as packing, housing, container, tableware, medical product.Polylactic acid article, after use is dropped, can resolve into carbonic acid gas and water in microorganism under composting conditions, thereby alleviates the day by day serious environmental stress being brought by plastics waste.
At present, poly(lactic acid) (is mainly rac-Lactide ring-opening polymerization method by indirect synthesis technique, also referred to as two-stage polymerization method) preparation, wherein lactic acid or lactate are used as to raw material, by the described raw material low-molecular-weight poly(lactic acid) of oligomeric acquisition of dewatering, then poly(lactic acid) Pintsch process is obtained to monomer rac-Lactide, finally rac-Lactide ring-opening polymerization is obtained to poly(lactic acid).
Patent CN1068011C discloses a kind of method of preparing poly(lactic acid), and described method comprises: (a) use the rac-Lactide of making main raw material in molten state polymerization, obtain poly(lactic acid); (b) by the temperature heating of the fusing point lower than final polymkeric substance, make the poly(lactic acid) obtaining in step (a) in the further polymerization of solid phase.Although this method can obtain the poly(lactic acid) that lactide monomer content is low, the reaction times is very long, is unsuitable for large-scale industrial production.United States Patent (USP) 6,214,967 disclose the two-step approach that rac-Lactide is polymerized to poly(lactic acid), described method comprises the first step that wherein rac-Lactide is polymerized to poly(lactic acid) and proceeds to the transformation efficiency of at least 50 % by weight, and wherein rac-Lactide is further polymerized to the second step of high conversion under the condition of avoiding the evaporation of melt-mixing and rac-Lactide, wherein 180 ~ 250 ℃ of temperature in second step.Wherein the first step is carried out in forcing machine, and second step can carry out in tubular reactor.Chinese patent CN 101353417A discloses the multistage reaction continuous polymerization unit by rac-Lactide class monomer synthesizing polylactic acid class material, wherein in prepolymerization kettle, monomer being carried out to pre-polymerization to monomer conversion is 5 ~ 40%, be 70 ~ 90% at twin screw extruder by monomer polymerization to monomer conversion, finally in tubular reactor, make monomer conversion can reach 80 ~ 99% further monomer polymerization.
But, there is the fusing point of poly(lactic acid) of more than 100000 high molecular more than 175 ℃.In the time that the final polymerisate of above-mentioned poly(lactic acid) is taken out from reactor with molten state, due to the balance existing between poly(lactic acid)-rac-Lactide, make in polymkeric substance the still lactide monomer of residual 5 % by weight left and right.These residual lactide monomer, by being easy to distillation in the poly(lactic acid) injection moulding as raw material or spinning process, adhere on mould or nozzle, thereby hinder operation.In addition, residual rac-Lactide has reduced second-order transition temperature and the melt viscosity of polymkeric substance, makes formability and thermostability variation.
Summary of the invention
For deficiency of the prior art, the invention provides a kind of method that production has the poly(lactic acid) of low lactide monomer content, the method is keeping on the basis of poly(lactic acid) performance, can remove lactide monomer remaining in poly(lactic acid), the poly(lactic acid) obtaining can be directly used in injection moulding or spinning, and in the course of processing, there will not be distillation phenomenon, formability and the better heat stability of rac-Lactide.The method is simple to operation, is conducive to suitability for industrialized production, has broad application prospect.
According to an aspect of the present invention, provide a kind of production to there is the method for the poly(lactic acid) of low levels lactide monomer, comprised the following steps:
A) under the effect of catalyzer, the rac-Lactide of melting is carried out to polymerization, lactide conversions is 10 ~ 30%;
B) product of step a) is carried out to polymerization and obtain poly(lactic acid), lactide conversions reaches more than 90%;
C) under decompression, remove rac-Lactide residual in the poly(lactic acid) in step b), then by poly(lactic acid) granulation, the pressure of described decompression is-0.07 ~-0.09MPa, and in poly(lactic acid) pellet, residual rac-Lactide is below 5wt%.
D) under normal pressure, the granular poly(lactic acid) in step c) is contacted with rare gas element is reverse, remove lactide monomer, obtain having the poly(lactic acid) of low levels lactide monomer, wherein the poly(lactic acid) of low levels lactide monomer refers to that the content of lactide monomer in poly(lactic acid) is below 0.1wt%.
In aforesaid method, the polymerization temperature in described step a) is 130 ~ 160 ℃, and polymerization pressure is 0.1 ~ 0.4MPa, and polymerization time is 0.5 ~ 2h.When initial polymerization, lactide monomer content is higher, and thermal discharge is larger, adopts tank reactor, and the temperature of material and the transformation efficiency of lactide monomer are easy to control, and prevent that material is excessively sticky.
In aforesaid method, in described step b), the weight-average molecular weight of gained poly(lactic acid) is 100000 ~ 500000, preferably 140000 ~ 300000.150 ~ 210 ℃ of polymerization temperatures in described step b), are preferably 160 ~ 190 ℃; Polymerization pressure is 0.3 ~ 1.5MPa, and polymerization time is 2 ~ 5 hours.
In aforesaid method, the temperature that removes in described step c) is 180 ~ 210 ℃, and the time of removing is 5 ~ 10 minutes.Described granulation can adopt various suitable granulation processs, in a concrete example, has adopted water-cooled granulation process.In a concrete example, after granulation, the particle diameter of gained poly(lactic acid) pellet is 1.5 ~ 2.0mm, and particle weight is 1 ~ 2 gram.Poly(lactic acid) granulation obtains pellet, is conducive to increase the specific surface area of material, is conducive to the follow-up operation that removes remaining lactide monomer.
In aforesaid method, described catalyzer is selected from the compound of glass putty, tin protochloride, stannous octoate, benzoic acid stannous, antimonous oxide, organic acid rare earth compound and iron, the sub-tin of preferably octanoic acid.The weight of the consumption of described catalyzer based on lactide monomer is 0.01 ~ 0.1wt%.
In aforesaid method, the temperature of the rare gas element in described step d) is higher than the second-order transition temperature of poly(lactic acid) and lower than the fusing point of poly(lactic acid), preferably 50 ~ 180 ℃, be 1 ~ 10h duration of contact.Remove by the vaporization of selecting suitable temperature to be both conducive to lactide monomer remaining in poly(lactic acid), also advantageously avoided the adhesion of poly(lactic acid) pellet in subtractive process.Preferably, the temperature of described rare gas element is 100 ~ 140 ℃, and be 3 ~ 5h duration of contact.Described rare gas element is preferably nitrogen.Rare gas element and poly(lactic acid) pellet counter current contact, can be pulled away along with the mobile of rare gas element the residual lactide monomer in poly(lactic acid), and lactide monomer content remaining in poly(lactic acid) can be reduced to below 0.1wt%.
In a specific embodiment of aforesaid method, the poly(lactic acid) with low levels lactide monomer finally obtaining can be after cooling, obtains poly(lactic acid) material, then for subsequent use.
According to another aspect of the present invention, provide a kind of equipment of carrying out aforesaid method, comprise be successively connected with lower device:
Execution step the first poly-unit a), comprises fritting still and tank reactor;
Execution step the second poly-unit b), comprises tubular reactor;
Execution step c) first remove device, comprise forcing machine and tablets press;
Execution step d) second remove device, comprise degassing tower.
In aforesaid device, the tubular reactor in described the second poly-unit can be 1, also can multiplely be cascaded.In a concrete example, described tubular reactor is for being entirely full of operation.
In aforesaid device, also comprise other as the auxiliary facility such as volume pump, well heater.
In a specific embodiment of aforesaid device, degassing tower tower body is hollow cylindrical, is doline at the bottom of tower, and outside is provided with chuck.In another specific examples, degassing tower is also provided with external heater.Can provide temperature for rare gas element by the thermal medium in external heater or degassing tower chuck.Poly(lactic acid) pellet enters degassing tower from tower top, and with the rare gas element counter current contact entering from tower bottom, the residual lactide monomer in poly(lactic acid) pellet is discharged from tower top with rare gas element after being heated and vaporizing.
Term as used herein " rac-Lactide " refers to DL-rac-Lactide, L-rac-Lactide, D-rac-Lactide or its any mixture.The present invention's lactide monomer used is commercially available or synthesize by method known to those skilled in the art.
Term as used herein " poly(lactic acid) " refers to poly DL-lactide, PLLA, poly-D-rac-Lactide.
In the present invention, lactide monomer content is take the gross weight containing the poly(lactic acid) of lactide monomer as benchmark.
By method and apparatus provided by the invention, remaining lactide monomer in can removing poly(lactic acid) on the basis that keeps poly(lactic acid) performance, the poly(lactic acid) obtaining has low-down lactide monomer content, can be directly used in injection moulding or spinning, and in the course of processing, there will not be distillation phenomenon, formability and the better heat stability of rac-Lactide.The method is simple to operation, is conducive to suitability for industrialized production, has broad application prospect.
Advantage of the present invention is after considering in conjunction with following accompanying drawing entirety, and those of ordinary skills can know easily.
Accompanying drawing explanation
Fig. 1 has demonstrated the equipment drawing of production poly(lactic acid) according to an embodiment of the invention.
Embodiment
Below in connection with drawings and Examples, the present invention is described further and explanation, but do not form any limitation of the invention.
In a specific embodiment, the equipment in the present invention comprises that fritting still 1, catalyzer storage tank 2, melt metering pump 11,12 and 13, catalyzer volume pump 14, vertical autoclave 3, tubular reactor 4, forcing machine 5, cold rinse bank 6, dicing machine 7, degassing tower 8 and cooling reactor 9 form.Wherein fritting still 1 is in advance by lactide monomer melting, melt metering pump 11 is for measuring the amount of the rac-Lactide that feeds vertical autoclave 3, catalyzer volume pump 14 is for measuring the amount of the catalyzer that feeds vertical autoclave, vertical autoclave 3 is for generating rac-Lactide polymerization the product of low-conversion, melt metering pump 12 is for feeding the material of vertical autoclave 3 tubular reactor 4 metering, tubular reactor 4 is for generating further the poly(lactic acid) of low-conversion polymerization the poly(lactic acid) of high molecular, melt metering pump 13 is for sending into the poly(lactic acid) of high molecular forcing machine 5 metering, forcing machine 5 is for tentatively removing the residual lactide monomer of resulting polymers, cold rinse bank 6 is for by cooling the high temperature strip poly(lactic acid) flowing out from forcing machine, dicing machine 7 is for by cooling strip poly(lactic acid) granulation, degassing tower 8 is for further removing the residual rac-Lactide of poly(lactic acid), cooling reactor 9 is for the cooling poly(lactic acid) removing after residual lactide.
In described device, tubular reactor 4 can be 1, can be also 2 series connection uses above, can constant temperature polymerization or the polymerization of segmentation constant temperature.Degassing tower 8 tops are cylindrical, and bottom is doline, outside with chuck, and in chuck, logical thermal medium is with poly(lactic acid) particle and rare gas element in heat de-airing tower.Rare gas element enters degassing tower after also can heating by external heater.Degassing tower is connected with cooling reactor 9 by valve 17.Rare gas element is (as nitrogen, argon gas) enter degassing tower from the mouth 83 of degassing tower bottom, poly(lactic acid) particle enters from the mouth 82 of tower top, hot inert gas and poly(lactic acid) particle counter current contact, in poly(lactic acid) after the vaporization of residual rac-Lactide with rare gas element from 81 mouthfuls of outflows of tower top, enter water cooler 15, carry out heat exchange with the cold medium in water cooler, rac-Lactide gas cooling in rare gas element is liquid or solid, after heating, remaining rare gas element and the fresh rare gas element heater via 16 supplementing enter degassing tower, or directly enter the temperature that is heated needs after degassing tower by the thermal medium in degassing tower chuck.The kettle of cooling reactor 9 is cylindrical, is conical at the bottom of still, outside with chuck, in chuck, leads to water coolant so that the temperature of poly(lactic acid) pellet is down to below 40 ℃.
Utilize vacuum pump that fritting still 1 is vacuumized, then stop vacuumizing, then inflated with nitrogen or rare gas element, preferably inflated with nitrogen.Repeat to vacuumize with inflated with nitrogen or rare gas element several times with thoroughly by the Bas Discharged in fritting still and be nitrogen or rare gas element is full of.Lactide monomer 21 is fed in fritting still, under stirring, by the thermal medium in chuck, lactide monomer is heated to the temperature of 120-140 ℃ with by its complete melting.In the situation that lactide monomer used is two or more mixing, those skilled in the art can determine the blending ratio between described different monomers according to the performance of required poly(lactic acid).
By melt metering pump 11, the lactide monomer of complete melting is fed vertical autoclave 3 from fritting still 1, simultaneously catalyzer by catalyzer volume pump 14 in feeding vertical autoclave from catalyzer storage tank 2 with the certain ratio of lactide monomer, at 130 ~ 160 ℃, being polymerized to lactide conversions is 10 ~ 30%, polymerization pressure is 0.1 ~ 0.4MPa, and polymerization time is 0.5 ~ 2h.Vertical autoclave is outer can be provided with as chuck heating, heating can be by can carrying out by described chuck the resistant to elevated temperatures oil such as silicone oil or high-pressure water vapor circulation, in still, can be provided with agitator, molten lactide fully be mixed with catalyzer and be beneficial to heat exchange to make polymerization temperature keep constant by stirring.The form of agitator can be if anchor formula, helical-ribbon type, turbine type, oar formula or their combination be as the combination of the combination of turbine and anchor formula and anchor formula and helical-ribbon type.
By melt metering pump 12, the polymerisate of low-conversion is fed tubular reactor 4 from vertical autoclave 3.The present invention's tubular reactor used is routine and known to those skilled in the art in this area.Those skilled in the art can be as the case may be as diameter and the length of the production determining tubular reactor used of required poly(lactic acid).Tubular reactor can be one or more, serial operation when multiple.Each tubular reactor is equipped with the entrance and exit of heat-conducting medium, and by independent heat supply, to the molecular weight of lactide conversions and resulting polymers is further regulated by sectional temperature-controlled mode.The temperature of polymerization is controlled at 150 ~ 210 ℃, and preferred temperature range is 160 ~ 190 ℃.Polymerization pressure is 0.3 ~ 1.5MPa, and polymerization time is 2 ~ 5 hours, is entirely full of operation.
In polymerization process, alcohol can be added with by the molecular weight control of final gained poly(lactic acid) within the required range.Suitable alcohol is for example lauryl alcohol, tridecanol, tetradecyl alcohol, ethylene glycol, glycerol, polyoxyethylene glycol, the high-boiling point alcohols such as polypropylene glycol.The weight of the consumption of described alcohol based on lactide monomer is 0.001 ~ 10 % by weight.
In the present invention, described catalyzer is conventional lactide open-ring polymerization catalyst, as being selected from the compound of glass putty, tin protochloride, stannous octoate, benzoic acid stannous, antimonous oxide, organic acid rare earth compound and iron.The weight of the consumption of described catalyzer based on lactide monomer is 0.01 ~ 0.1wt%.In a concrete example, described catalyzer is stannous octoate.
The transformation efficiency of tubular reactor outlet rac-Lactide reaches more than 90%, and the weight-average molecular weight (Mw) of resulting polymers is 100000 ~ 500000, and preferably 140000 ~ 300000.
By the melt metering pump 13 that is located at tubular reactor outlet and forcing machine entrance, the poly(lactic acid) generating in tubular reactor is fed in forcing machine.Can use any suitable forcing machine well known by persons skilled in the art as twin screw extruder, such as engagement type twin screw extruder, non-engagement type twin screw extruder, co-rotating twin screw extruder or Heterodromy double-screw extruder etc.The service temperature of forcing machine, higher than the fusing point of poly(lactic acid), is generally 180 ~ 210 ℃, and the residence time of polymkeric substance in forcing machine is 5 ~ 10 minutes.For as much as possible the residual lactide monomer in polymkeric substance being removed, forcing machine generally operates under reduced pressure, and pressure is-0.07 ~-0.09MPa, can be-0.09MPa of for example pressure.After condensation, can be recycled or for other purposes from the remaining lactide monomer 22 removing forcing machine.The poly(lactic acid) obtaining from outlet of extruder, the weight of the residual quantity of lactide monomer based on poly(lactic acid) is below 5%.
Due to the balance existing between poly(lactic acid)-rac-Lactide, in the poly(lactic acid) of molten state, still remain a certain amount of lactide monomer.In order further to remove lactide monomer residual in polymkeric substance, the present invention introduces the melting strip poly(lactic acid) obtaining from forcing machine in cold rinse bank 6 and carries out in dicing machine 7, carrying out pelletizing after water-cooled.Cold rinse bank and dicing machine are known to those skilled in the art.The particle diameter of gained poly(lactic acid) particle is 1.5 ~ 2.0mm, and particle weight is 1 ~ 2 gram.
The poly(lactic acid) pellet that contains the remaining lactide monomer of the 5wt% that has an appointment enters degassing tower from the import 82 at degassing tower 8 tops, and rare gas element enters degassing tower from the import 83 of degassing tower bottom simultaneously, rare gas element 25 and poly(lactic acid) particle counter current contact.The temperature of rare gas element is higher than the second-order transition temperature of poly(lactic acid) but lower than the fusing point of poly(lactic acid), preferred temperature range is 100 ~ 140 ℃, rare gas element preferred nitrogen.The temperature of rare gas element is provided by the thermal medium in external heater 16 or degassing tower chuck.Be 1 ~ 10h the duration of contact of nitrogen and poly(lactic acid) particle, is preferably 3 ~ 5h.The working pressure of degassing tower is normal pressure.Degassing tower tower body is cylindrical, and bottom is doline.The present invention's degassing tower used is routine and known to those skilled in the art in this area.Those skilled in the art can be as the case may be determine diameter and the length of degassing tower used as the flow of poly(lactic acid) and monomer content.In poly(lactic acid) particle, residual lactide monomer flows out from the outlet 81 of tower top with rare gas element formation mixed gas after being heated and vaporizing, enter water cooler 15, carry out heat exchange with the cold medium in water cooler 15, lactide monomer in mixed gas is cooled to liquid or solid, these liquid or solid-state lactide monomer 22 are discharged from water cooler, can be recycled or for other purposes; And enter degassing tower after rare gas element and fresh rare gas element 25 heater vias 16 heating that supplement, or directly enter the temperature that is heated needs after degassing tower by the thermal medium in degassing tower chuck.The poly(lactic acid) particle obtaining from degassing tower outlet at bottom, the weight of the residual quantity of unreacted lactide monomer based on poly(lactic acid) is below 0.1wt%.
The poly(lactic acid) particle removing after residual lactide monomer enters cooling reactor 9 by valve 17.Cooling reactor kettle is cylindrical, is conical at the bottom of still, outside with chuck, logical water coolant in chuck, and the temperature that is of discharging by the valve 18 of cooling reactor 9 is 40 ℃ of following poly(lactic acid) particles 26.
In the present invention, molecular weight adopts gel chromatography (GPC) to measure, and wherein solvent for use is chloroform.Transformation efficiency adopts conventional poor heavy method to measure.
Embodiment 1
To crossing with nitrogen pump drainage and temperature is to add 200kg L-rac-Lactide in the 500L molten-bath of 130 ℃, after the whole meltings of L-rac-Lactide, supply with continuously the vertical autoclave of 20L with the mass flow rate of 5kg/h by melt metering pump, by catalyst pump, sub-octoate catalyst tin is supplied with continuously to the vertical autoclave of 20L with the mass flow rate of 1.5g/h, polymerase 10 .9 hour under the pressure of the temperature of 160 ℃ and 0.4MPa simultaneously.Lactide conversions reaches 30%.Resulting polymers is delivered to tubular reactor, polymerization 2.5 hours under the pressure of the polymerization temperatures of 160 ~ 190 ℃ and 0.8MPa with melt metering pump.Lactide conversions reaches 91%, and the weight-average molecular weight of gained poly(lactic acid) is 161000.
By melt metering pump, the polymkeric substance obtaining from tubular reactor is fed twin screw extruder, the service temperature of forcing machine is 190 ℃, and pressure is-0.09MPa that the residence time is 8min.The residual lactide monomer content of the poly(lactic acid) obtaining from outlet of extruder is 5 % by weight, and molecular weight is 158000.After water-cooled, be cut to diameter 1.5mm through dicing machine, the poly(lactic acid) particle of 1.5 grams of left and right of weight.
Gained poly(lactic acid) particle is entered degassing tower from degassing tower top, the hot nitrogen that by temperature is simultaneously 120 ℃ feeds degassing tower from degassing tower bottom, the nitrogen that contains rac-Lactide steam after counter current contact 4h flows out from tower top, Separation and Recovery rac-Lactide after cooling, recycles after remaining nitrogen and the fresh nitrogen heater via supplementing heat.The residual lactide monomer content of the poly(lactic acid) obtaining from degassing tower bottom is 0.08 % by weight, and molecular weight is 158000.The poly(lactic acid) particle further removing after residual lactide monomer enters cooling reactor from degassing tower bottom, and the temperature of poly(lactic acid) particle is down to 35 ℃ of left and right by the water coolant by chuck in cooling reactor.Data are as shown in table 1.
Embodiment 2
Step is with embodiment 1, and difference is: the temperature of molten-bath is 120 ℃; The mass rate of the sub-tin of octoate catalyst is 2.5g/h; Use two tubular reactors of series connection; The poly(lactic acid) particle weight of pelletizing after water-cooled is 1.0g; Nitrogen enters degassing tower from degassing tower bottom, utilizes the thermal oil in degassing tower chuck poly(lactic acid) particle and nitrogen to be heated to 140 ℃, poly(lactic acid) particle and nitrogen counter current contact 3h; The temperature of the poly(lactic acid) particle obtaining after cooling in cooling reactor is 30 ℃ of left and right.Data are as shown in table 1.
Embodiment 3
Step is with embodiment 1, and difference is: the temperature of molten-bath is 140 ℃; Raw material D, the mass flow rate with 4.0kg/h after the melting of L-lactide monomer is supplied with vertical autoclave continuously, and the mass rate of the sub-tin of octoate catalyst is 3.2g/h; The poly(lactic acid) particle weight of pelletizing after water-cooled is 2.0g; The temperature of hot nitrogen is 100 ℃, counter current contact 5h.Data are as shown in table 1.
Embodiment 4
Step is with embodiment 1, and difference is: after the melting of raw material D-lactide monomer, supply with continuously vertical autoclave with the mass flow rate of 8kg/h, the mass rate of the sub-tin of octoate catalyst is 2.4g/h; ; Use two tubular reactors of series connection; The poly(lactic acid) particle weight of pelletizing after water-cooled is 1.0g; The temperature of hot nitrogen is 130 ℃, counter current contact 5h; The temperature of the poly(lactic acid) particle obtaining after cooling in cooling reactor is 40 ℃ of left and right.Data are as shown in table 1.
Embodiment 5
Step is with embodiment 1, and difference is: the temperature of molten-bath is 140 ℃; Raw material is D, L-rac-Lactide; The mass rate of the sub-tin of octoate catalyst is 2.5g/h; Use two tubular reactors of series connection; The poly(lactic acid) particle weight of pelletizing after water-cooled is 1.0g; Nitrogen enters degassing tower from degassing tower bottom, utilizes the thermal oil in degassing tower chuck poly(lactic acid) particle and nitrogen to be heated to 120 ℃, poly(lactic acid) particle and nitrogen counter current contact 5h.Data are as shown in table 1.
Table 1
As can be seen from the table, according to method and apparatus provided by the invention, poly(lactic acid) can production residual lactide monomer content lower, high molecular.The method is simple to operation, is conducive to suitability for industrialized production, has broad application prospect.
It should be noted in the discussion above that above-described embodiment, only for explaining the present invention, does not form any limitation of the invention.By with reference to exemplary embodiments, invention has been described, be descriptive and explanatory vocabulary but should be understood to word wherein used, rather than limited vocabulary.Can in the scope of the claims in the present invention, modify the present invention in accordance with regulations, and the present invention be revised not deviating from scope and spirit of the present invention.Although the present invention who wherein describes relates to specific method, material and embodiment, and does not mean that the present invention is limited to wherein disclosed particular case, on the contrary, the present invention can extend to other all methods and applications with identical function.
Claims (10)
1. production has a method for the poly(lactic acid) of low lactide monomer content, comprises the following steps:
A) under the effect of catalyzer, the rac-Lactide of melting is carried out to polymerization, lactide conversions is 10 ~ 30%;
B) product of step a) is carried out to polymerization and obtain poly(lactic acid), lactide conversions reaches more than 90%;
C) under decompression, remove rac-Lactide residual in the poly(lactic acid) in step b), then by poly(lactic acid) granulation, the pressure of described decompression is-0.07 ~-0.09MPa, and in poly(lactic acid) pellet, residual rac-Lactide is below 5wt%.
D) under normal pressure, the granular poly(lactic acid) in step c) is contacted with rare gas element is reverse, remove lactide monomer, obtain having the poly(lactic acid) of low lactide monomer content, wherein the poly(lactic acid) of low lactide monomer content refers to that the content of lactide monomer in poly(lactic acid) is below 0.1wt%.
2. method according to claim 1, is characterized in that, the temperature of the rare gas element in described step d) is 50 ~ 180 ℃, and be 1 ~ 10h duration of contact.
3. method according to claim 2, is characterized in that, the temperature of described rare gas element is 100 ~ 140 ℃, and be 3 ~ 5h duration of contact; Described rare gas element is preferably nitrogen.
4. according to the method described in any one in claim 1 ~ 3, it is characterized in that, the polymerization temperature in described step a) is 130 ~ 160 ℃, and polymerization pressure is 0.1 ~ 0.4MPa, and polymerization time is 0.5 ~ 2h.
5. according to the method described in any one in claim 1 ~ 4, it is characterized in that, in described step b), the weight-average molecular weight of gained poly(lactic acid) is 100000 ~ 500000, preferably 140000 ~ 300000.
6. according to the method described in any one in claim 1 ~ 5, it is characterized in that 150 ~ 210 ℃ of the polymerization temperatures in described step b) are preferably 160 ~ 190 ℃; Polymerization pressure is 0.3 ~ 1.5MPa, and polymerization time is 2 ~ 5 hours.
7. according to the method described in any one in claim 1 ~ 6, it is characterized in that, the temperature that removes in described step c) is 180 ~ 210 ℃, and the time of removing is 5 ~ 10 minutes.
8. according to the method described in any one in claim 1 ~ 7, it is characterized in that, described catalyzer is selected from the compound of glass putty, tin protochloride, stannous octoate, benzoic acid stannous, antimonous oxide, organic acid rare earth compound and iron, the sub-tin of preferably octanoic acid.
9. the method described according to Claim 8, is characterized in that, the weight of the consumption of described catalyzer based on lactide monomer is 0.01 ~ 0.1wt%.
10. execute claims in 1 ~ 9 an equipment for method described in any one, comprise be connected successively with lower device:
Execution step the first poly-unit a), comprises fritting still and tank reactor;
Execution step the second poly-unit b), comprises tubular reactor;
Execution step c) first remove device, comprise forcing machine and tablets press;
Execution step d) second remove device, comprise degassing tower.
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| CN201210469847.5A CN103819658B (en) | 2012-11-19 | 2012-11-19 | A kind of production has the method for the poly(lactic acid) of low lactide monomer content |
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| CN201210469847.5A Active CN103819658B (en) | 2012-11-19 | 2012-11-19 | A kind of production has the method for the poly(lactic acid) of low lactide monomer content |
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| CN105439874A (en) * | 2014-08-20 | 2016-03-30 | 中国石油化工股份有限公司 | Ligand compound and preparation method and application thereof |
| CN107922599A (en) * | 2015-08-11 | 2018-04-17 | 乐天化学株式会社 | It is used to prepare the method for polylactic acid |
| CN109796584A (en) * | 2018-12-26 | 2019-05-24 | 万华化学集团股份有限公司 | A kind of preparation system and preparation method of aromatic series thermotropic liquid crystal polymer |
| CN111074374A (en) * | 2019-12-31 | 2020-04-28 | 吉林中粮生化有限公司 | Method for preparing high-quality polylactic acid fiber by continuous polymerization melt direct spinning |
| CN111450792A (en) * | 2020-05-20 | 2020-07-28 | 吉林中粮生化有限公司 | Polylactic acid and device and method for preparing polylactic acid |
| CN111514606A (en) * | 2020-04-29 | 2020-08-11 | 吉林中粮生化有限公司 | Polylactic acid crystallization system |
| CN112210200A (en) * | 2020-10-29 | 2021-01-12 | 银金达(上海)新材料有限公司 | Environment-friendly PLA (polylactic acid) film material and application thereof |
| CN112979929A (en) * | 2021-02-20 | 2021-06-18 | 深圳安特生物科技有限公司 | Lactide-containing polymer, preparation method thereof, medical material and surgical article |
| CN113024850A (en) * | 2021-03-23 | 2021-06-25 | 江南大学 | Method for preparing polylactic acid microspheres by free radical polymerization without solvent |
| US11118006B1 (en) | 2020-06-28 | 2021-09-14 | Nutrition & Health Research Institute, COFCO Corporation | Method for producing polylactic acid |
| CN114573797A (en) * | 2022-04-01 | 2022-06-03 | 温州邦鹿化工有限公司 | Continuous polymerization process for producing polylactic acid slices from lactide |
| CN115707725A (en) * | 2021-08-20 | 2023-02-21 | 中国石油化工股份有限公司 | Method for removing residual monomers in polyglycolic acid |
| CN115707725B (en) * | 2021-08-20 | 2024-06-28 | 中国石油化工股份有限公司 | Method for removing residual monomers in polyglycolic acid |
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| CN105439874B (en) * | 2014-08-20 | 2017-05-31 | 中国石油化工股份有限公司 | A kind of ligand compound, preparation method and applications |
| CN105439874A (en) * | 2014-08-20 | 2016-03-30 | 中国石油化工股份有限公司 | Ligand compound and preparation method and application thereof |
| CN107922599A (en) * | 2015-08-11 | 2018-04-17 | 乐天化学株式会社 | It is used to prepare the method for polylactic acid |
| US10487174B2 (en) | 2015-08-11 | 2019-11-26 | Lotte Chemical Corporation | Method for preparing polyactic acid |
| CN109796584B (en) * | 2018-12-26 | 2021-04-20 | 万华化学集团股份有限公司 | Preparation system and preparation method of aromatic thermotropic liquid crystal polymer |
| CN109796584A (en) * | 2018-12-26 | 2019-05-24 | 万华化学集团股份有限公司 | A kind of preparation system and preparation method of aromatic series thermotropic liquid crystal polymer |
| CN111074374A (en) * | 2019-12-31 | 2020-04-28 | 吉林中粮生化有限公司 | Method for preparing high-quality polylactic acid fiber by continuous polymerization melt direct spinning |
| CN111514606A (en) * | 2020-04-29 | 2020-08-11 | 吉林中粮生化有限公司 | Polylactic acid crystallization system |
| CN111450792A (en) * | 2020-05-20 | 2020-07-28 | 吉林中粮生化有限公司 | Polylactic acid and device and method for preparing polylactic acid |
| US11118006B1 (en) | 2020-06-28 | 2021-09-14 | Nutrition & Health Research Institute, COFCO Corporation | Method for producing polylactic acid |
| CN112210200A (en) * | 2020-10-29 | 2021-01-12 | 银金达(上海)新材料有限公司 | Environment-friendly PLA (polylactic acid) film material and application thereof |
| CN112979929A (en) * | 2021-02-20 | 2021-06-18 | 深圳安特生物科技有限公司 | Lactide-containing polymer, preparation method thereof, medical material and surgical article |
| CN113024850A (en) * | 2021-03-23 | 2021-06-25 | 江南大学 | Method for preparing polylactic acid microspheres by free radical polymerization without solvent |
| CN113024850B (en) * | 2021-03-23 | 2022-05-20 | 江南大学 | Method for preparing polylactic acid microspheres by free radical polymerization without solvent |
| CN115707725A (en) * | 2021-08-20 | 2023-02-21 | 中国石油化工股份有限公司 | Method for removing residual monomers in polyglycolic acid |
| CN115707725B (en) * | 2021-08-20 | 2024-06-28 | 中国石油化工股份有限公司 | Method for removing residual monomers in polyglycolic acid |
| CN114573797A (en) * | 2022-04-01 | 2022-06-03 | 温州邦鹿化工有限公司 | Continuous polymerization process for producing polylactic acid slices from lactide |
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