CN103819658B - A kind of production has the method for the poly(lactic acid) of low lactide monomer content - Google Patents
A kind of production has the method for the poly(lactic acid) of low lactide monomer content Download PDFInfo
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Abstract
The invention discloses a kind of method that production has the poly(lactic acid) of low lactide monomer content, comprise the following steps: a) under the effect of catalyzer, be polymerized by the rac-Lactide of melting, lactide conversions is 10 ~ 30%; B) product of step a) is carried out polymerization and obtain poly(lactic acid), lactide conversions reaches more than 90%; C) rac-Lactide residual in the poly(lactic acid) in removed under reduced pressure step b), then by poly(lactic acid) granulation, the pressure of described decompression is-0.07 ~-0.09MPa, and rac-Lactide residual in poly(lactic acid) pellet 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 the poly(lactic acid) with low lactide monomer content, wherein the poly(lactic acid) of low lactide monomer content refers to that in poly(lactic acid), the content of lactide monomer is below 0.1wt%.According to method and apparatus provided by the invention, can the lower poly(lactic acid) of production residual lactide monomer content, the poly(lactic acid) formability obtained and better heat 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 low poly-lactic acid in high molecular weight of production lactide monomer content.
Background technology
In recent years, along with the plastics such as polyethylene, polypropylene, polystyrene and polyvinyl chloride are widely used, the process of the waste after using also becomes one of day by day serious environmental problem.Usually by these castoff burning process and bury process.Burning disposal can produce obnoxious flavour.Because the chemical stability of above-mentioned plastics is high, after burying process, there is microbial decomposition hardly, but left behind in semipermanent state.
For solving the problem, the eco-friendly biodegradable polymkeric substance of investigators' Devoting Major Efforts To Developing, one of them is poly(lactic acid).The polycondensation of gained lactic acid by the amylofermentation as main raw material is obtained lactic acid, then is prepared by poly(lactic acid).Poly(lactic acid) has the processing characteristics of good biological degradability, biocompatibility, physical and mechanical properties and excellence, is widely used in many aspects such as packaging, housing, container, tableware, medical product.Polylactic acid article, after use is dropped, can become carbonic acid gas and water in microbial decomposition under composting conditions, thus alleviates the day by day serious environmental stress brought by plastics waste.
At present, poly(lactic acid) is mainly through indirect synthesis technique (i.e. rac-Lactide ring-opening polymerization method, also referred to as two-stage polymerization method) preparation, wherein lactic acid or lactate are used as raw material, by the low-molecular-weight poly(lactic acid) of oligomeric for described raw material dehydration acquisition, then poly(lactic acid) Pintsch process is obtained monomers lactide, finally rac-Lactide ring-opening polymerization is obtained poly(lactic acid).
Patent CN1068011C discloses a kind of method preparing poly(lactic acid), and described method comprises: (a) uses the rac-Lactide making main raw material to be polymerized in molten state, obtains poly(lactic acid); (b) by the heating temperatures at the fusing point lower than final polymkeric substance, the poly(lactic acid) obtained in step (a) is polymerized further in solid phase.Although this method can obtain the low poly(lactic acid) of lactide monomer content, the reaction times is very long, is unsuitable for large-scale industrial production.United States Patent (USP) 6,214,967 disclose two-step approach rac-Lactide being polymerized to poly(lactic acid), described method comprises and wherein rac-Lactide is polymerized to the first step that poly(lactic acid) proceeds to the transformation efficiency of at least 50 % by weight, and wherein rac-Lactide is polymerized to further the second step of high conversion under the condition avoiding melt-mixing and rac-Lactide evaporation, wherein temperature 180 ~ 250 DEG C in second step.Wherein the first step is carried out in an extruder, and second step can carry out in tubular reactor.Chinese patent CN101353417A discloses the multistage reaction continuous polymerization unit by rac-Lactide class monomer synthesize polylactic acid material, wherein in prepolymerization kettle, monomer being carried out pre-polymerization to monomer conversion is 5 ~ 40%, be 70 ~ 90% at twin screw extruder by monomer polymerization to monomer conversion, finally monomer be polymerized further making monomer conversion to reach 80 ~ 99% in tubular reactor.
But, there is the fusing point of the poly(lactic acid) of the high molecular of more than 100000 more than 175 DEG C.When being taken out from reactor with molten state by the final polymerisate of above-mentioned poly(lactic acid), owing to there is the balance between poly(lactic acid)-rac-Lactide, make the lactide monomer still remaining about 5 % by weight in polymkeric substance.These residual lactide monomer, being easy to distillation by being used as in the poly(lactic acid) injection moulding of raw material or spinning process, adhering on mould or nozzle, thus hindering operation.In addition, residual rac-Lactide reduces second-order transition temperature and the melt viscosity of polymkeric substance, and formability and thermostability are deteriorated.
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 on the basis keeping poly(lactic acid) performance, lactide monomer remaining in poly(lactic acid) can be removed, the poly(lactic acid) obtained 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 method that production has the poly(lactic acid) of low levels lactide monomer, comprise the following steps:
A) under the effect of catalyzer, be polymerized by the rac-Lactide of melting, lactide conversions is 10 ~ 30%;
B) product of step a) is carried out polymerization and obtain poly(lactic acid), lactide conversions reaches more than 90%;
C) rac-Lactide residual in the poly(lactic acid) in removed under reduced pressure step b), then by poly(lactic acid) granulation, the pressure of described decompression is-0.07 ~-0.09MPa, and rac-Lactide residual in poly(lactic acid) pellet 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 the poly(lactic acid) with low levels lactide monomer, wherein the poly(lactic acid) of low levels lactide monomer refers to that in poly(lactic acid), the content of lactide monomer is below 0.1wt%.
In the above-mentioned methods, the polymerization temperature in described step a) is 130 ~ 160 DEG C, and polymerization pressure is 0.1 ~ 0.4MPa, and polymerization time is 0.5 ~ 2h.During initial polymerization, lactide monomer content is higher, and thermal discharge is comparatively large, adopts tank reactor, and the temperature of material and the transformation efficiency of lactide monomer are easy to control, and prevent material excessively sticky.
In the above-mentioned methods, in described step b), the weight-average molecular weight of gained poly(lactic acid) is 100000 ~ 500000, preferably 140000 ~ 300000.Polymerization temperature in described step b) 150 ~ 210 DEG C, is preferably 160 ~ 190 DEG C; Polymerization pressure is 0.3 ~ 1.5MPa, and polymerization time is 2 ~ 5 hours.
In the above-mentioned methods, the removal temperature in described step c) is 180 ~ 210 DEG C, and the time of removing is 5 ~ 10 minutes.Described granulation can adopt various suitable granulation process, in a concrete example, have employed 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 the specific surface area increasing material, is conducive to the follow-up operation removing remaining lactide monomer.
In the above-mentioned methods, 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 consumption of described catalyzer is 0.01 ~ 0.1wt% based on the weight of lactide monomer.
In the above-mentioned methods, the temperature of the rare gas element in described step d) higher than poly(lactic acid) second-order transition temperature and lower than the fusing point of poly(lactic acid), preferably 50 ~ 180 DEG C, duration of contact is 1 ~ 10h.Removed by the vaporization selecting suitable temperature to be both conducive to lactide monomer remaining in poly(lactic acid), also advantageously avoid the adhesion of poly(lactic acid) pellet in subtractive process.Preferably, the temperature of described rare gas element is 100 ~ 140 DEG C, and duration of contact is 3 ~ 5h.Described rare gas element is preferably nitrogen.Rare gas element and poly(lactic acid) pellet counter current contact, make the residual lactide monomer in poly(lactic acid) can be pulled away along with the flowing of rare gas element, makes lactide monomer content remaining in poly(lactic acid) to be reduced to below 0.1wt%.
In a specific embodiment of aforesaid method, the poly(lactic acid) with low levels lactide monomer finally obtained after cooling, can obtain poly(lactic acid) material, then for subsequent use.
According to another aspect of the present invention, provide a kind of equipment performing aforesaid method, comprise successively be connected with lower device:
Perform the first poly-unit of step a), comprise fritting still and tank reactor;
Perform the second poly-unit of step b), comprise tubular reactor;
Perform step c) first removes device, comprises forcing machine and tablets press;
Perform step d) second removes device, comprises degassing tower.
In aforesaid device, the tubular reactor in described second poly-unit can be 1, also can multiplely be cascaded.In a concrete example, described tubular reactor is for be 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, and in doline at the bottom of tower, outside is provided with chuck.In another specific examples, degassing tower is also provided with external heater.Can by the thermal medium in external heater or degassing tower chuck for rare gas element provides temperature.Poly(lactic acid) pellet enters degassing tower from tower top, and with the rare gas element counter current contact entered 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 synthesized 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 is benchmark with the gross weight of poly(lactic acid) containing lactide monomer.
By method and apparatus provided by the invention, lactide monomer remaining in poly(lactic acid) can be removed on the basis keeping poly(lactic acid) performance, the poly(lactic acid) obtained has low-down lactide monomer content, injection moulding or spinning can be directly used in, 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 skill in the art can know easily.
Accompanying drawing explanation
Fig. 1 shows the equipment drawing of production poly(lactic acid) according to an embodiment of the invention.
Embodiment
Hereafter by the present invention is described further in conjunction with the accompanying drawings and embodiments and illustrate, but do not form any limitation of the invention.
In a specific embodiment, the equipment in the present invention comprises fritting still 1, catalyzer storage tank 2, melt metering pump 11,12 and 13, catalyst dosing 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 and forms.Wherein fritting still 1 is in advance by lactide monomer melting, melt metering pump 11 is for measuring the amount of the rac-Lactide feeding vertical autoclave 3, catalyst dosing pump 14 is for measuring the amount of the catalyzer feeding vertical autoclave, vertical autoclave 3 is for generating the product of low-conversion by rac-Lactide polymerization, melt metering pump 12 is for feeding tubular reactor 4 by the material in vertical autoclave 3 and measuring, tubular reactor 4 generates the poly(lactic acid) of high molecular for the poly(lactic acid) of low-conversion being polymerized further, melt metering pump 13 is for sending the poly(lactic acid) of high molecular into forcing machine 5 and measuring, forcing machine 5 is for tentatively removing lactide monomer residual in resulting polymers, the high temperature strip poly(lactic acid) cooling of cold rinse bank 6 for flowing out from forcing machine, dicing machine 7 is for the strip poly(lactic acid) granulation by cooling, degassing tower 8 is for removing rac-Lactide residual in poly(lactic acid) further, cooling reactor 9 is for cooling the poly(lactic acid) after removing residual lactide.
In said device, tubular reactor 4 can be 1, also can be more than 2 uses of connecting, can constant temperature polymerization or the polymerization of segmentation constant temperature.Degassing tower 8 top is cylindrical, and bottom is doline, outside with chuck, and in chuck, logical thermal medium is with the particles of polylactic acid in heat de-airing tower and rare gas element.Rare gas element is also by entering degassing tower after external heater heating.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, after rac-Lactide vaporization residual in poly(lactic acid) with rare gas element from tower top 81 mouthfuls outflow, enter water cooler 15, heat exchange is carried out with the cold medium in water cooler, rac-Lactide gas cooling in rare gas element is liquid or solid, degassing tower is entered after remaining rare gas element and the fresh rare gas element heater via 16 supplemented heat, or the temperature needed after directly entering degassing tower, is heated by the thermal medium in degassing tower chuck.The kettle of cooling reactor 9 is cylindrical, and, outside with chuck, in chuck, logical water coolant is down to less than 40 DEG C to make the temperature of poly(lactic acid) pellet at the bottom of still conically.
Utilize vacuum pump to be vacuumized by fritting still 1, then stop vacuumizing, then inflated with nitrogen or rare gas element, preferred inflated with nitrogen.Repeat to vacuumize and the air in fritting still discharged and is nitrogen or rare gas element is full of with thorough with inflated with nitrogen or rare gas element several times.Lactide monomer 21 fed in fritting still, the temperature by the thermal medium in chuck lactide monomer being heated to 120-140 DEG C under stirring is with by its complete melting.When lactide monomer used is two or more mixing, the blending ratio that those skilled in the art can determine 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, catalyzer feeds vertical autoclave in the ratio certain with lactide monomer from catalyzer storage tank 2 by catalyst dosing pump 14 simultaneously, at 130 ~ 160 DEG C, be polymerized to lactide conversions is 10 ~ 30%, polymerization pressure is 0.1 ~ 0.4MPa, and polymerization time is 0.5 ~ 2h.Can be provided with as chuck heating outside vertical autoclave, heat by making the resistant to elevated temperatures oil such as silicone oil or high-pressure water vapor circulation be undertaken by described chuck, can agitator being provided with in still, molten lactide and catalyzer fully being mixed and is beneficial to heat exchange to make polymerization temperature keep constant by stirring.The form of agitator can if anchor formula, helical-ribbon type, turbine type, paddle or their combination be as turbine and the combination of anchor formula and the combination of 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 conventional and known to those skilled in the art in this area.Those skilled in the art can as the case may be as the output of required poly(lactic acid) determines diameter and the length of tubular reactor used.Tubular reactor can be one or more, serial operation time multiple.Each tubular reactor is equipped with the entrance and exit of heat-conducting medium, and by independent heat supply, to be regulated further by the molecular weight of sectional temperature-controlled mode to lactide conversions and resulting polymers.The temperature of polymerization controls at 150 ~ 210 DEG C, and preferred temperature range is 160 ~ 190 DEG C.Polymerization pressure is 0.3 ~ 1.5MPa, and polymerization time is 2 ~ 5 hours, is entirely full of operation.
In the course of the 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 such as lauryl alcohol, tridecanol, tetradecyl alcohol, ethylene glycol, glycerol, polyoxyethylene glycol, the high-boiling point alcohols such as polypropylene glycol.The consumption of described alcohol is 0.001 ~ 10 % by weight based on the weight of lactide monomer.
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 consumption of described catalyzer is 0.01 ~ 0.1wt% based on the weight of lactide monomer.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 being located at tubular reactor outlet and forcing machine entrance, the poly(lactic acid) generated in tubular reactor is fed in forcing machine.Any suitable forcing machine well known by persons skilled in the art can be used as twin screw extruder, such as hing surface, non-hing surface, 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 DEG C, and the polymkeric substance residence time is in an extruder 5 ~ 10 minutes.For as much as possible by the residual lactide monomer removal in polymkeric substance, forcing machine generally operates at reduced pressure conditions, and pressure is-0.07 ~-0.09MPa, and such as pressure can be-0.09MPa.The lactide monomer 22 of the remnants removed from forcing machine can be recycled or for other purposes after condensation.From the poly(lactic acid) that outlet of extruder obtains, the residual quantity of lactide monomer is less than 5% based on the weight of poly(lactic acid).
Owing to there is the balance between poly(lactic acid)-rac-Lactide, in the poly(lactic acid) of molten state, still remain a certain amount of lactide monomer.In order to remove lactide monomer residual in polymkeric substance further, the present invention carries out pelletizing after the melting strip poly(lactic acid) obtained from forcing machine being introduced and carrying out water-cooled in cold rinse bank 6 in dicing machine 7.Cold rinse bank and dicing machine known to those skilled in the art.The particle diameter of gained particles of polylactic acid is 1.5 ~ 2.0mm, and particle weight is 1 ~ 2 gram.
Poly(lactic acid) pellet containing the remaining lactide monomer of the 5wt% that has an appointment enters degassing tower from the import 82 at degassing tower 8 top, 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 higher than poly(lactic acid) second-order transition temperature but lower than the fusing point of poly(lactic acid), preferred temperature range is 100 ~ 140 DEG C, 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.The duration of contact of nitrogen and poly(lactic acid) particle is 1 ~ 10h, 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 conventional and known to those skilled in the art in this area.Those skilled in the art can as the case may be as the flow of poly(lactic acid) and monomer content determine diameter and the length of degassing tower used.Lactide monomer residual in poly(lactic acid) particle forms mixed gas with rare gas element after being heated and vaporizing and flows out from the outlet 81 of tower top, enter water cooler 15, heat exchange is carried out 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 the heating of supplementary fresh rare gas element 25 heater via 16, or after directly entering degassing tower, be heated the temperature needed by the thermal medium in degassing tower chuck.From the poly(lactic acid) particle that degassing tower outlet at bottom obtains, the residual quantity of unreacted lactide monomer is below 0.1wt% based on the weight of poly(lactic acid).
Remove the poly(lactic acid) particle after residual lactide monomer and enter cooling reactor 9 by valve 17.Cooling reactor kettle is cylindrical, outside with chuck at the bottom of still conically, and logical water coolant in chuck, that is discharged by the valve 18 of cooling reactor 9 is the poly(lactic acid) particle 26 that temperature is less than 40 DEG C.
In the present invention, molecular weight adopts gel chromatography (GPC) to measure, and wherein solvent for use is chloroform.Transformation efficiency adopts the heavy method of conventional difference to measure.
Embodiment 1
To cross with nitrogen pump drainage and temperature is add 200kgL-rac-Lactide in the 500L molten-bath of 130 DEG C, supplied the vertical autoclave of 20L continuously with the mass flow rate of 5kg/h by melt metering pump after the whole melting of L-rac-Lactide, by catalyst pump, sub-for octoate catalyst tin is supplied continuously 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 DEG C and 0.4MPa simultaneously.Lactide conversions reaches 30%.With melt metering pump, resulting polymers is delivered to tubular reactor, polymerization 2.5 hours under the pressure of the polymerization temperatures of 160 ~ 190 DEG C and 0.8MPa.Lactide conversions reaches 91%, and the weight-average molecular weight of gained poly(lactic acid) is 161000.
Fed in twin screw extruder by the polymkeric substance obtained from tubular reactor by melt metering pump, the service temperature of forcing machine is 190 DEG C, and pressure is-0.09MPa, and the residence time is 8min.The residual lactide monomer content of the poly(lactic acid) obtained from outlet of extruder is 5 % by weight, and molecular weight is 158000.Diameter 1.5mm is cut to through dicing machine, the poly(lactic acid) particle of weight about 1.5 grams after water-cooled.
Gained poly(lactic acid) particle is entered degassing tower from degassing tower top, be that the hot nitrogen of 120 DEG C is from degassing tower bottom infeed degassing tower by temperature simultaneously, nitrogen containing rac-Lactide steam after counter current contact 4h flows out from tower top, Separation and Recovery rac-Lactide after cooling, remaining nitrogen and the fresh nitrogen heater via heating Posterior circle supplemented use.The residual lactide monomer content of the poly(lactic acid) obtained bottom degassing tower is 0.08 % by weight, and molecular weight is 158000.Remove the poly(lactic acid) particle after residual lactide monomer further and enter cooling reactor bottom degassing tower, in cooling reactor, by the water coolant of chuck, the temperature of poly(lactic acid) particle is down to about 35 DEG C.Data are as shown in table 1.
Embodiment 2
Step is with embodiment 1, and difference is: the temperature of molten-bath is 120 DEG C; 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 that poly(lactic acid) particle and nitrogen are heated to 140 DEG C, poly(lactic acid) particle and nitrogen counter current contact 3h; The temperature of the poly(lactic acid) particle obtained after cooling in cooling reactor is about 30 DEG C.Data are as shown in table 1.
Embodiment 3
Step is with embodiment 1, and difference is: the temperature of molten-bath is 140 DEG C; Supply vertical autoclave continuously with the mass flow rate of 4.0kg/h after the melting of raw material D, L-lactide monomer, 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 DEG C, counter current contact 5h.Data are as shown in table 1.
Embodiment 4
Step is with embodiment 1, and difference is: supply vertical autoclave continuously with the mass flow rate of 8kg/h after the melting of raw material D-lactide monomer, and 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 DEG C, counter current contact 5h; The temperature of the poly(lactic acid) particle obtained after cooling in cooling reactor is about 40 DEG C.Data are as shown in table 1.
Embodiment 5
Step is with embodiment 1, and difference is: the temperature of molten-bath is 140 DEG C; 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 that poly(lactic acid) particle and nitrogen are heated to 120 DEG C, 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, can production residual lactide monomer content lower, the poly(lactic acid) of high molecular.The method is simple to operation, is conducive to suitability for industrialized production, has broad application prospect.
It should be noted that above-described embodiment only for explaining the present invention, not forming any limitation of the invention.By referring to exemplary embodiments, invention has been described, but to should be understood to word wherein used be descriptive and explanatory vocabulary, instead of limited vocabulary.Can modify the present invention by the scope being defined in the claims in the present invention, and the present invention be revised not deviating from scope and spirit of the present invention.Although the present invention wherein described relates to specific method, material and embodiment, and do not mean that the present invention is limited to particular case disclosed in it, on the contrary, easily extensible of the present invention is 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, be polymerized by the rac-Lactide of melting, lactide conversions is 10 ~ 30%;
B) step product a) is carried out polymerization and obtain poly(lactic acid), lactide conversions reaches more than 90%;
C) removed under reduced pressure step b) in poly(lactic acid) in residual rac-Lactide, then by poly(lactic acid) granulation, the pressure of described decompression is-0.07 to-0.09MPa, rac-Lactide residual in poly(lactic acid) pellet is below 5wt%, described step c) in removal temperature be 180 ~ 210 DEG C, the time of removing is 5 ~ 10 minutes;
D) under normal pressure by step c) in granular poly(lactic acid) contact with rare gas element is reverse, remove lactide monomer, obtain the poly(lactic acid) with low lactide monomer content, wherein, the temperature of described rare gas element is 100 ~ 140 DEG C, duration of contact is 3 ~ 5h, and the poly(lactic acid) of low lactide monomer content refers to that in poly(lactic acid), the content of lactide monomer is below 0.1wt%.
2. method according to claim 1, is characterized in that, described rare gas element is nitrogen.
3. method according to claim 1 and 2, is characterized in that, described step a) in polymerization temperature be 130 ~ 160 DEG C, polymerization pressure is 0.1 ~ 0.4MPa, and polymerization time is 0.5 ~ 2h.
4. method according to claim 1 and 2, is characterized in that, described step b) in the weight-average molecular weight of gained poly(lactic acid) be 100000 ~ 500000.
5. method according to claim 4, is characterized in that, described step b) in the weight-average molecular weight of gained poly(lactic acid) be 140000 ~ 300000.
6. method according to claim 1 and 2, is characterized in that, described step b) in polymerization temperature 150 ~ 210 DEG C, polymerization pressure is 0.3 ~ 1.5MPa, and polymerization time is 2 ~ 5 hours.
7. method according to claim 6, is characterized in that, described step b) in polymerization temperature be 160 ~ 190 DEG C.
8. method according to claim 1 and 2, 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.
9. according to Claim 8 described in method, it is characterized in that, the consumption of described catalyzer is 0.01 ~ 0.1wt% based on the weight of lactide monomer.
10. method according to claim 1 and 2, described comprise successively be connected with the equipment of lower device in carry out:
Perform step the first poly-unit a), comprise fritting still and tank reactor;
Perform step b) the second poly-unit, comprise tubular reactor;
Perform step c) first remove device, comprise forcing machine and tablets press;
Perform steps d) second remove device, comprise degassing tower.
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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 |
| KR101713215B1 (en) * | 2015-08-11 | 2017-03-07 | 롯데케미칼 주식회사 | Preparation method of polylactic 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 |
| 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 |
| CN111450792B (en) * | 2020-05-20 | 2020-12-15 | 吉林中粮生化有限公司 | Polylactic acid and device and method for preparing polylactic acid |
| CN111484604B (en) | 2020-06-28 | 2020-09-15 | 中粮营养健康研究院有限公司 | 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 |
| CN113024850B (en) * | 2021-03-23 | 2022-05-20 | 江南大学 | Method for preparing polylactic acid microspheres by free radical polymerization without solvent |
| 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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