CN1176070C - Method of preparing lactide using recovered lactic acid polymer as raw material - Google Patents

Method of preparing lactide using recovered lactic acid polymer as raw material Download PDF

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CN1176070C
CN1176070C CNB021600724A CN02160072A CN1176070C CN 1176070 C CN1176070 C CN 1176070C CN B021600724 A CNB021600724 A CN B021600724A CN 02160072 A CN02160072 A CN 02160072A CN 1176070 C CN1176070 C CN 1176070C
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lactic acid
lactide
rac
poly
copolymer
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CN1429814A (en
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涂克华
王利群
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Zhejiang University ZJU
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Zhejiang University ZJU
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Abstract

The present invention discloses a method for preparing lactide by using recovered lactic acid polymerizing material as raw material, which comprises the following steps: 1, a recovered lactic acid polymer is pretreated, cleaned to remove impurities, dried, crushed, etc.; 2, the raw material is put in a kettle to be heated to 80 to 130 DEG C and then is dried at normal pressure or in vacuum; 3, the dried raw material can be thermally cracked (intermittently) in situ, for example, the temperature is raised to 150 to 310 DEG C to carry out heating cracking reaction under the condition with a catalyst in vacuum of which the pressure is higher than 0.04MPa. Thereby, a lactide product is obtained, or a horizontal thermal cracking device is utilized to carry out serialization production, and the catalyst is continuously added to a reactor by a metering pump according to setting scale. The temperature of the cracking reactor is divided into three stages, namely 190 DEG C, 210 DEG C and 240 DEG C. The lactide generated by cracking is directly pumped by a tie in line, and the refined lactide is collected and stored after condensed; 4, a lactide crude product is refined and purified by a solvent recrystallization method or a method of a thin membrane rotary evaporator. The yield of the lactide prepared by the present invention approaches the theoretical yield.

Description

To reclaim the lactic acid polymerizes material is the method for feedstock production rac-Lactide
Technical field
The present invention relates to a kind of preparation method of lactone organic compound, relating in particular to a kind of is the method for feedstock production rac-Lactide to reclaim the lactic acid polymerizes material.
Background technology
Macromolecular material is not dropped after in a single day finishing its application target, reclaims reshaping processing exactly.The macromolecular material that wherein is dropped accounts for more than 80% of spent high molecular material sum.Because at present the macromolecular materials of the overwhelming majority are derived from oil, so this method handles the huge waste that spent high molecular material had both caused valuable, non-renewable petroleum resources, causes " white pollution " for again people's living environment.Though can the recovery part spent high molecular material by simple process for subsequent treatment, but the heating for multiple times fusion will make high molecular polymer generation oxidation, a series of uncertain chemical reactions such as degraded, the overall performance of macromolecular material is reduced significantly, reclaim material processed and can only use as low-grade material.In reclaiming the machine-shaping process, tend to cause simultaneously to second environmental pollution.And many macromolecular materials, determined by structure of itself and character, be difficult to be for recycling and reuse.
Preparing high molecular weight polylactic acid by the rac-Lactide ring-opening polymerization, is one of important method of preparation biodegradable polylactic acid.The main method of preparation rac-Lactide is at present: starch is produced lactic acid through microbial fermentation, lactic acid pre-polymerization under the effect of certain process conditions and catalyzer obtains low-molecular-weight lactic acid oligomers, and this oligopolymer thermo-cracking is just prepared the raw material-rac-Lactide that can be used for synthesizing polylactic acid.
At present existing a large amount of synthetic about poly(lactic acid), the document that poly(lactic acid) degradation property and poly(lactic acid) are used at biomedical sector.Wherein United States Patent (USP) (US Pat 5053522, US Pat 6277951) is to preparing rac-Lactide by lactic acid, and is described in detail by the technology that the rac-Lactide ring-opening polymerization prepares poly(lactic acid).Some domestic investigators also are described (University Of Chongqing's journal, 112 pages of the 19th the 1st phases of volume) to the preparation of rac-Lactide.Preparation method about rac-Lactide in these documents all is by the lactic acid pre-polymerization, then the poly(lactic acid) oligopolymer that obtains is implemented thermo-cracking and obtains.
Summary of the invention
The purpose of this invention is to provide a kind of is the method for feedstock production rac-Lactide to reclaim the lactic acid polymerizes material.
To reclaim lactic acid polymer is the method for feedstock production rac-Lactide:
1) blend of poly(lactic acid) that at first recovery is obtained or lactic acid copolymer or poly(lactic acid) and macromolecular material carries out simple classification, cleaning impurity elimination, drying and pulverizes pre-treatment;
2) through the blend of pretreated poly(lactic acid) or lactic acid copolymer or poly(lactic acid) and macromolecular material by vertical pyrolysis reactor batch production, or send into enforcement serialization production in the horizontal cracking reactor continuously by e Foerderanlage;
3) the rac-Lactide crude product of Sheng Chaning carries out recrystallization more than 3 times with solvent, or can obtain meeting the rac-Lactide that polyreaction requires with the rectifying of film rotatory evaporator;
4) lactic acid of Hui Shouing and remaining rac-Lactide adopt lactic acid to prepare the in addition recycle of technology of rac-Lactide.
Though the polylactic acid article of finishing behind the application target can be degraded in the Nature fully, and final product is water and carbonic acid gas, but consider that from the repeated use and the production cost angle of resource it is rare good footpath that polylactic acid article is implemented recycle and reuse.We discover; poly(lactic acid) is a kind ofly can directly prepare polymer of monomers from macromolecular material by the method for chemical heat degraded; it is the preparation technology of feedstock production rac-Lactide with lactic acid at present both at home and abroad that the present invention has broken through; not only overcome low, the defect of high cost of preparation rac-Lactide yield; can recycle finishing the method for depleted poly-lactic acid material behind the application target again by chemistry; both can economize on resources, and help the protection of environment.The yield for preparing rac-Lactide with method of the present invention is near theoretical yield.
Embodiment
The process that batch process of the present invention is produced is: will place cracking still heating normal pressure or vacuum-drying through the blend of pretreated poly(lactic acid) or lactic acid copolymer or poly(lactic acid) and macromolecular material; After temperature is 150--310 ℃, decompression or normal pressure and in the presence of catalyzer or do not add catalyzer and carry out the heating pyrolyze reaction, treats that rac-Lactide distillates, accept the rac-Lactide that is steamed with receiver.
The process that continuous processing is produced is: will send in the horizontal cracking reactor through e Foerderanlage through the recovery poly(lactic acid) of pre-treatment and drying treatment, with volume pump with catalyzer, catalyst inlet through reactor joins in the reactor by preset proportion continuously, it is refining that the rac-Lactide crude product that cracking generates is collected the back, or directly the pipeline through connecting horizontal cracking reactor pumps into the film rotatory evaporator, collects after the rectifying to store.
Abandon after inferior waste product when the recovery poly(lactic acid) is macromolecular material production or the scrap stock in the molding process or the use and the poly(lactic acid) of short-term use back recovery or the blend of lactic acid copolymer or poly(lactic acid) and macromolecular material.
Poly(lactic acid) is L-type poly(lactic acid), D-type poly(lactic acid) and DL-type poly(lactic acid); Lactic acid copolymer is: oxyethane--lactic acid copolymer, amino acid--lactic acid copolymer, 6-caprolactone--lactide copolymer, Alpha-hydroxy acetate--lactic acid copolymer, acid anhydrides--lactic acid copolymer, polyester--copolymer of poly lactic acid, lactic acid--epoxy propane copolymer, ortho ester--lactic acid copolymer.Above-mentioned multipolymer can be random or block or graft copolymer;
Macromolecular material can be polyester, starch, Mierocrystalline cellulose, polyacrylic ester, polyvinyl acetate (PVA), polyethylene oxide, poly(propylene oxide), poly-epsilon-caprolactone, poly-Alpha-hydroxy acetate, Polyvinylpyrolidone (PVP), polyvinyl alcohol.
Catalyzer is zinc acetate, manganese acetate, Cobaltous diacetate, nickel acetate, zinc oxide, barium oxide, Neodymium trioxide, zirconium white, stannic oxide, tin protoxide, tin protochloride, stannous octoate, glass putty and zinc powder, titanium dioxide, germanium dioxide, zirconium dioxide, tindioxide, antimonous oxide, tin chloride, the inferior tin of lactic acid, ironic lactate, aluminum isopropoxide, titanium butoxide, zinc ethyl, etheric acid aluminium and butyl (tetra) titanate etc.Or one or both and two or more composite catalysts in the above-mentioned catalyzer.Catalyst consumption is 0~20%; When using two or more composite catalyst, use arbitrary ratio compound.
Solvent is one or both or the two or more mixed solvent that mixes mutually with arbitrary ratio in water, methyl alcohol, ethanol, propyl alcohol, Virahol, toluene, dimethylbenzene, ethyl acetate, butylacetate, pentyl acetate, ethylene glycol ethyl ether, butyl glycol ether, trichloromethane, ethylene dichloride, hexane, heptane, octane and the sherwood oil.
Elaborate below in conjunction with embodiment:
Embodiment 1:
Poly(lactic acid) 7000 grams, magnesium oxide 70 grams and tosic acid 50 grams that recovery is obtained place 10 liters of scission reaction devices that have airway, stirring, condensation, receiving system and heating and Controlling System, are heated to 80 ℃, and logical nitrogen dehydrated 1 hour; Be warmed up under 255 ℃ the condition and carry out scission reaction, treat that rac-Lactide distillates after, heating up gradually keeps its rate of cleavage, is warmed up to 310 ℃ at last, when cleaved residue darkens, finishes reaction after slipping out its colour changed into yellow of thing.Collection is obtained rac-Lactide make solvent, it is carried out recrystallization more than 3 times, can obtain meeting the rac-Lactide that polyreaction requires with butylacetate.The lactic acid that contains in the mother liquor after the filtration and a spot of rac-Lactide and solvent recovery cycle utilization.
Embodiment 2:
Lactic acid copolymer 7000 grams, zinc acetate 150 grams that recovery is obtained place 10 liters of scission reaction devices that have airway, stirring arm, condensation and receiving system, heating and Controlling System and pumped vacuum systems, be heated to 100 ℃, logical nitrogen dehydrated 0.5 hour; Reduce pressure vacuum 〉=0.06Mpa, be warmed up under 240 ℃ the condition and carry out scission reaction, after treating that rac-Lactide distillates, heating up gradually keeps its rate of cleavage, is warmed up to 300 ℃ at last, when cleaved residue darkens, finish reaction behind its colour changed into yellow of overhead product.Collection obtains rac-Lactide and makes solvent with toluene and ethyl acetate, and it is carried out recrystallization more than 3 times, can obtain meeting the rac-Lactide that polyreaction requires.To lactic acid and its recycling of a spot of rac-Lactide that contains in the mother liquor after filtering.
Embodiment 3:
Each 50 gram of the poly(lactic acid) that recovery is obtained--starch blend 7000 grams, zinc acetate and tosic acid place 10 liters of scission reaction devices that have airway, stirring, condensation and receiving system, heating and Controlling System and pumped vacuum systems, be heated to 120 ℃, logical nitrogen dehydrated 0.5 hour; Reduce pressure vacuum 〉=0.07Mpa, be warmed up under 240 ℃ the condition and carry out scission reaction, treat that rac-Lactide distillates after, heating up gradually keeps its rate of cleavage, is warmed up to 290 ℃ at last, finishes reaction later on when no longer including overhead product.Collection obtains rac-Lactide and makes solvent with toluene and ethyl acetate, and it is carried out recrystallization more than 3 times, can obtain meeting the rac-Lactide that polyreaction requires.Contain a certain amount of lactic acid and a spot of rac-Lactide in the mother liquor after filtration, can recycle it.
Embodiment 4:
30 parts in 1000 parts of poly(lactic acid)-polyoxyethylene copolymers, barium oxide and zinc oxide that recovery is obtained place cracker for 30 parts, vacuum 〉=the 0.05Mpa that reduces pressure is heated to 235 ℃, treat that rac-Lactide distillates after, heating up gradually keeps rate of cleavage, is warmed up to 280 ℃ at last.Collection obtains rac-Lactide and makes solvent with ethanol-toluene, and it is carried out recrystallization more than 3 times, can obtain meeting the rac-Lactide that polyreaction requires.Contain a certain amount of lactic acid and a spot of rac-Lactide in the mother liquor after filtration, can recycle it.
Embodiment 5:
The poly(lactic acid) 7000 that recovery is obtained restrains in 10 liters of scission reaction devices that have airway, stirring arm, condensation and receiving system, heating and Controlling System and a pumped vacuum systems, be heated to 80 ℃, the straight sky 〉=0.04Mpa that reduces pressure, logical nitrogen dehydrated 1 hour; Be warmed up under 230 ℃ the condition and carry out scission reaction, after treating that rac-Lactide distillates, heat up to keep its rate of cleavage gradually, be warmed up to 300 ℃ at last, when cleaved residue darkens and the color burn that goes out to heat up in a steamer to slip out thing does not have rac-Lactide and steamed the back and finishes to react.Collection is obtained injecting the film rotatory evaporator behind the rac-Lactide heating and melting, and the purified rac-Lactide is collected after condensation.
Embodiment 6:
To send in the horizontal cracking reactor through e Foerderanlage through the recovery poly(lactic acid) of pre-treatment and drying treatment, tin protochloride or other catalyst for cracking volume pump join in the reactor by preset proportion continuously through the catalyst inlet of reactor.The temperature of cracking reactor is divided into three sections, is respectively 190 ℃, 210 ℃ and 240 ℃.The rac-Lactide that cracking generates directly pumps into the film rotatory evaporator through connection line, and the purified rac-Lactide is collected storage after condensation.Lactic acid in the vaporizer and rac-Lactide are sent the opening for feed recycle of horizontal cracking reactor back to through reclaiming circulation line.

Claims (10)

1. one kind is the method for feedstock production rac-Lactide to reclaim the lactic acid polymerizes material, it is characterized in that:
1) blend of poly(lactic acid) that at first recovery is obtained or lactic acid copolymer or poly(lactic acid) and macromolecular material carries out simple classification, cleaning impurity elimination, drying and pulverizes pre-treatment;
2) through the blend of pretreated poly(lactic acid), lactic acid copolymer or poly(lactic acid) and macromolecular material by vertical pyrolysis reactor batch production, or send into enforcement serialization production in the horizontal cracking reactor continuously by e Foerderanlage;
3) the rac-Lactide crude product of Sheng Chaning carries out recrystallization more than 3 times with solvent, or can obtain meeting the rac-Lactide that polyreaction requires with the rectifying of film rotatory evaporator;
4) lactic acid of Hui Shouing and remaining rac-Lactide adopt lactic acid to prepare the in addition recycle of technology of rac-Lactide.
2. according to claim 1 a kind of be the method for feedstock production rac-Lactide to reclaim the lactic acid polymerizes material, it is characterized in that: the process that said batch process is produced is: will place cracking still heating normal pressure or vacuum-drying through the blend of pretreated poly(lactic acid) or lactic acid copolymer, poly(lactic acid) and macromolecular material; After temperature is 150--310 ℃, decompression or normal pressure and in the presence of catalyzer or do not add catalyzer and carry out the heating pyrolyze reaction, treats that rac-Lactide distillates, accept the rac-Lactide that is steamed with receiver.
3. according to claim 1 a kind of be the method for feedstock production rac-Lactide to reclaim the lactic acid polymerizes material, it is characterized in that: the process that said continuous processing is produced is: will send in the horizontal cracking reactor through e Foerderanlage through the recovery poly(lactic acid) of pre-treatment and drying treatment, with volume pump with catalyzer, catalyst inlet through reactor joins in the reactor by preset proportion continuously, it is refining that the rac-Lactide crude product that cracking generates is collected the back, or directly the pipeline through connecting horizontal cracking reactor pumps into the film rotatory evaporator, collects after the rectifying to store.
4. according to claim 1 a kind of be the method for feedstock production rac-Lactide to reclaim the lactic acid polymerizes material, it is characterized in that: inferior waste product when said recovery poly(lactic acid) is lactic acid family macromolecule material produce or the scrap stock in the molding process or use after abandon and short-term is used poly(lactic acid), lactic acid copolymer or the poly(lactic acid) of back recovery and the blend of macromolecular material.
5. according to claim 1 a kind of be the method for feedstock production rac-Lactide to reclaim the lactic acid polymerizes material, it is characterized in that: said poly(lactic acid) is L-type poly(lactic acid), D-type poly(lactic acid) or DL-type poly(lactic acid).
6. according to claim 1 a kind of be the method for feedstock production rac-Lactide to reclaim the lactic acid polymerizes material, it is characterized in that: said lactic acid copolymer is: oxyethane--lactic acid copolymer, amino acid--lactic acid copolymer, 6-caprolactone--lactide copolymer, Alpha-hydroxy acetate--lactic acid copolymer, acid anhydrides--lactic acid copolymer, polyester--copolymer of poly lactic acid, lactic acid--epoxy propane copolymer or ortho ester--lactic acid copolymer.Above-mentioned multipolymer can be random or block or graft copolymer.
7. according to claim 1 a kind of be the method for feedstock production rac-Lactide to reclaim the lactic acid polymerizes material, it is characterized in that: said macromolecular material can be polyester, starch, Mierocrystalline cellulose, polyacrylic ester, polyvinyl acetate (PVA), polyethylene oxide, poly(propylene oxide), poly-epsilon-caprolactone, poly-Alpha-hydroxy acetate, Polyvinylpyrolidone (PVP) or polyvinyl alcohol.
8. according to claim 2,3 described a kind of be the method for feedstock production rac-Lactide to reclaim the lactic acid polymerizes material, it is characterized in that said catalyzer is a zinc acetate, manganese acetate, Cobaltous diacetate, nickel acetate, zinc oxide, barium oxide, Neodymium trioxide, zirconium white, stannic oxide, tin protoxide, tin protochloride, stannous octoate, glass putty and zinc powder, titanium dioxide, germanium dioxide, zirconium dioxide, tindioxide, antimonous oxide, tin chloride, the inferior tin of lactic acid, ironic lactate, aluminum isopropoxide, titanium butoxide, zinc ethyl, etheric acid aluminium and butyl (tetra) titanate, or one or both and two or more composite catalysts in the above-mentioned catalyzer.
9. according to claim 4 a kind of be the method for feedstock production rac-Lactide to reclaim the lactic acid polymerizes material, it is characterized in that said catalyst consumption is 0~20%; When using two or more composite catalyst, use arbitrary ratio compound.
Root according to claim 1 a kind of be the method for feedstock production rac-Lactide to reclaim the lactic acid polymerizes material, it is characterized in that said solvent is one or both or the two or more mixed solvent that mixes mutually with arbitrary ratio in water, methyl alcohol, ethanol, propyl alcohol, Virahol, toluene, dimethylbenzene, ethyl acetate, butylacetate, pentyl acetate, ethylene glycol ethyl ether, butyl glycol ether, trichloromethane, ethylene dichloride, hexane, heptane, octane and the sherwood oil.
CNB021600724A 2002-12-26 2002-12-26 Method of preparing lactide using recovered lactic acid polymer as raw material Expired - Fee Related CN1176070C (en)

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