CN103254409A - Preparation method of high-molecular-weight polylactic acid based on metal alkoxide dehydrating agent - Google Patents
Preparation method of high-molecular-weight polylactic acid based on metal alkoxide dehydrating agent Download PDFInfo
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Abstract
The invention relates to a preparation method of high-molecular-weight polylactic acid based on a metal alkoxide dehydrating agent, and belongs to the technical field of macromolecular materials. The method comprises the following steps of placing catalyst into a dehydrated prepolymer under a vacuum condition, controlling the reaction temperature at 160 to 180 DEG C, enabling the prepolymer and the catalyst to be reacted for 0 to 16 hours, and continuing the reaction for 1 to 24 hours after adding the metal alkoxide to obtain the product polylactic acid. The metal alkoxide powder material which can be high efficiently reacted with the water so as to remove the water in the system is adopted, little metal alkoxide powder can be added in the later stage of the polycondensation of a lactic acid body, the water in the polycondensation process can be effectively removed, and the reaction process can be greatly promoted. Moreover, the price of the metal alkoxide is cheap, and the cost is much lower by adding little metal alkoxide.
Description
Technical field
The present invention relates to a kind of preparation method of the poly-lactic acid in high molecular weight based on the metal alkoxide dewatering agent, belong to technical field of polymer materials.
Background technology
Poly(lactic acid) is a kind of non-petroleum base novel high polymer material of mechanical strength, unreactiveness and easy processing preferably that has, and has good biological degradation and biocompatibility.Based on poly(lactic acid) to the nontoxic non-stimulated biocompatibility of human body, U.S. food and drug administration (FDA) approval can be used for the material of medical field, is widely used in fields such as medical implantation, surgical sutures, medicine controlled releasing system, fracture internal fixing, tissue regeneration at present.Can substitute petroleum-based plastics etc. in certain limit.Simultaneously, poly(lactic acid) has the physical and mechanical properties very similar to general-purpose plastics, alternative nondegradable general-purpose plastics, because it is degraded by hydrolysis method, final product is nontoxic carbonic acid gas and water, can in body or in the environment, not accumulate, prevent the pollution of the environment, thereby have tempting prospect.
At present, the main method of poly(lactic acid) preparation has direct method and indirect method.Indirect method is by lactic acid elder generation synthesis of lactide from, again by rac-Lactide reaction synthesizing polylactic acid, by this method can the synthetic macromolecule amount poly(lactic acid), but reaction cost is higher, and the purity of rac-Lactide is had high requirements.Direct method is to be reaction raw materials with lactic acid, and at certain direct synthesizing polylactic acid of reaction conditions, though synthetic molecular weight is relatively low, this method technology is simple, flow process is short, productive rate is high, cost is lower, so need carry out more deep research to this method.
In the direct polycondensation method, temperature of reaction is higher than the fusing point of polymkeric substance, reaction system is carried out under molten state, is the bulk polymerization without any medium, and formed by product (water, rac-Lactide etc.) carries by rare gas element or constantly gets rid of by means of the vacuum tightness of system.Advantage is that product is pure, does not need separating medium, but the product relative molecular mass that melt-polycondensation obtains is not high, because along with the carrying out that reacts, the viscosity of system is increasing, small molecules is difficult to discharge, and balance is difficult to carry out to direction of polymerization.In melt polymerization process, catalyzer, reaction times, temperature of reaction and vacuum tightness are very big to the influence of product relative molecular mass.The problem that is difficult to get rid of at the micromolecular water later stage.
Summary of the invention
The objective of the invention is in order to propose a kind of preparation method of the poly-lactic acid in high molecular weight based on the metal alkoxide dewatering agent, poly(lactic acid) is a kind of high molecular degradable material that the good physical mechanical property is arranged, and is widely used in plastic wrapping, medical, aquatic products and agricultural every field at present.
The objective of the invention is to be achieved through the following technical solutions.
The preparation method of a kind of poly-lactic acid in high molecular weight based on the metal alkoxide dewatering agent of the present invention, its concrete preparation process is as follows:
1) at first under 65-150 ℃ of temperature lactic acid aqueous solution is dewatered, dewatering time is 12-24; Obtain lactic acid prepolymer, number-average molecular weight is 200～400g/mol, is used for next step body polycondensation;
2) under vacuum condition, catalyzer is joined in the poly(lactic acid) prepolymer that the first step obtains, 160～180 ℃ of control temperature of reaction, reaction is 0-16 hour under agitation condition; Afterwards, add the metal alkoxide with dehydration reaction activity, reacted 1～24 hour, obtain the product poly(lactic acid).
Above-mentioned steps 2) catalyzer in is one or more the mixture in tin protochloride, stannous octoate, the tosic acid, is preferably three's mixture.When containing tin protochloride in the catalyzer, the quality of tin protochloride is 0.33% of lactic acid prepolymer quality, when containing stannous octoate in the catalyzer, the quality of stannous octoate is 0.167% of lactic acid prepolymer quality, when containing tosic acid in the catalyzer, the quality of tosic acid is 0.5% of lactic acid prepolymer quality.
Above-mentioned steps 2) metal alkoxide in is one or more the mixture in magnesium methylate, aluminum methylate, methyl alcohol iron, magnesium ethylate, the aluminum ethylate, is preferably magnesium methylate, aluminum methylate and magnesium ethylate.
Above-mentioned steps 2) catalyzer in can have other to select, and not interacting, do not disturbed the catalysis polycondensation with catalyzer with the metal alkoxide that adds is principle.
Above-mentioned steps 2) metal alkoxide in can be micron-scale, also can be nano-scale.The metal alkoxide reactive behavior height of nano-scale, but it is very important to add the back dispersing uniformity; Though micron-scale metal alkoxide reactive behavior is high not as nano-powder, interpolation and dispersion are easier.
The quality of the metal alkoxide above-mentioned steps 2) is the 0.1%-5% of lactic acid prepolymer quality, is preferably 0.47%-1%.
The joining day of the metal alkoxide in above-mentioned second step is preferably 10～16h for reaction back 0-16h, namely reacts the later stage adding.Reason is that polycondensation antecedent moisture product amount is big, and is violent with the reaction of metal alkoxide, makes reaction wayward.
Whether the time control after metal alkoxide in above-mentioned second step adds can and allow factor adjustment, changes such as the unreacted metal alkoxide is residual according to the target value of temperature of reaction, metal alkoxide add-on, polylactic acid molecule amount.
After above-mentioned steps, can obtain the poly-lactic acid in high molecular weight product.Contain little metal oxyhydroxide in the poly(lactic acid) product that obtains, during as employing magnesium methylate powder or methyl alcohol aluminium powder, be magnesium hydroxide or aluminium hydroxide, for the poly(lactic acid) plastics, be a kind of solid packing, because content is very little, can not bring disadvantageous effect to its color or performance.Because magnesium hydroxide and aluminium hydroxide can be used as fire retardant to plastics and uses, be very favourable to the fire-retardant of poly(lactic acid) therefore.
Beneficial effect
The present invention has used a kind of new cheap reactive metal alkoxide reactant matter, can efficiently remove the moisture in the prepolymer, obtain the poly(lactic acid) product of higher molecular weight, and processing ease, condition are simple, good reproducibility, reaction efficiency height, cost are low, are fit to the production of expansion property.And, alcoholate reactive behavior height, basic noresidue in the product, one of reaction product is methyl alcohol or ethanol, direct disengaging system under the vacuum condition, another product metal fire retardant magnesium hydroxide or aluminium hydroxide can improve the flame retardant properties of product but not influence the colour properties of product.The present invention relates to a class and can efficiently remove the metal alkoxide powder body material of the moisture in the system with water, middle and later periods in the lactic acid polycondensation adds on a small quantity, the water that later stage is difficult to discharge is converted into methyl alcohol or the ethanol that is easy to discharge, can promote the process of reacting greatly, and small molecules product wherein is that methyl alcohol or ethanol can not remain in the system, another bottom product is that metal hydroxides not only can not exert an influence to color and luster or the performance of poly(lactic acid), is of value to the flame retardant properties of product on the contrary.
Embodiment
The invention will be further described below by embodiment, but embodiment does not limit protection scope of the present invention.
Embodiment 1
1) 88% lactic acid aqueous solution with 300mL progressively is warming up to 150 ℃ under vacuum, and reaction 24h obtains lactic acid prepolymer, and number-average molecular weight is 301g/mol, and quality is 214.82g;
2) in the flask of the lactic acid prepolymer that 214.82g is housed, add 1.07g tosic acid, 0.72g tin protochloride and 0.36g stannous octoate, whole system is connected on the device of taking back stream prolong, temperature regulating device and stirring, under vacuum condition, progressively be warming up to 170 ℃, add stirring rake after the fusion, react and add the 1.1g magnesium methylate after 16-18 hour, reacted 6-8 hour, and obtained the product poly(lactic acid), its weight-average molecular weight is 20756g/mol.
Embodiment 2
1) 88% lactic acid aqueous solution with 300mL progressively is warming up to 150 ℃ under vacuum, and reaction 24h obtains lactic acid prepolymer, and number-average molecular weight is 321g/mol, and quality is 213.76g;
2) in the flask of the lactic acid prepolymer that 213.76g is housed, add 1.07g tosic acid, 0.71g tin protochloride and 0.36g stannous octoate, whole system is connected on the device of taking back stream prolong, temperature regulating device and stirring, under vacuum condition, progressively be warming up to 170 ℃, add stirring rake after the fusion, add the 5g magnesium methylate simultaneously, reacted 24 hours, and obtained the product poly(lactic acid), its weight-average molecular weight is 6989g/mol.
Embodiment 3
1) 88% lactic acid aqueous solution with 300mL progressively is warming up to 150 ℃ under vacuum, and reaction 24h obtains lactic acid prepolymer, and number-average molecular weight is 287g/mol, and quality is 221.58g;
2) in the flask of the lactic acid prepolymer that 221.58g is housed, add 1.10g tosic acid, 0.73g tin protochloride and 0.37g stannous octoate, whole system is connected on the device of taking back stream prolong, temperature regulating device and stirring, under vacuum condition, progressively be warming up to 170 ℃, add stirring rake after the fusion, add the 0.45g aluminum methylate simultaneously, reacted 24 hours, and obtained the product poly(lactic acid), its weight-average molecular weight is 20414g/mol.
Embodiment 4
1) 88% lactic acid aqueous solution with 300mL progressively is warming up to 150 ℃ under vacuum, and reaction 24h obtains lactic acid prepolymer, and number-average molecular weight is 276g/mol, and quality is 241.14g;
2) in the flask of the lactic acid prepolymer that 241.14g is housed, add 1.2g tosic acid, 0.8g tin protochloride and 0.4g stannous octoate, whole system is connected on the device of taking back stream prolong, temperature regulating device and stirring, under vacuum condition, progressively be warming up to 170 ℃, add stirring rake after the fusion, add the 0.56g magnesium ethylate simultaneously, reacted 24 hours, and obtained the product poly(lactic acid), its weight-average molecular weight is 18069g/mol.
Embodiment 5
1) 88% lactic acid aqueous solution with 300mL progressively is warming up to 150 ℃ under vacuum, and reaction 24h obtains lactic acid prepolymer, and number-average molecular weight is 237g/mol, and quality is 258.20g;
2) in the flask of the lactic acid prepolymer that 258.20g is housed, add 1.29g tosic acid, 0.86g tin protochloride and 0.43g stannous octoate, whole system is connected on the device of taking back stream prolong, temperature regulating device and stirring, under vacuum condition, progressively be warming up to 170 ℃, add stirring rake after the fusion, add the 0.6g aluminum ethylate simultaneously, reacted 24 hours, and obtained the product poly(lactic acid), its weight-average molecular weight is 16860g/mol.
Claims (7)
1. preparation method based on the poly-lactic acid in high molecular weight of metal alkoxide dewatering agent is characterized in that reactions steps:
1) at first under 65-150 ℃ of temperature lactic acid aqueous solution is dewatered, dewatering time is 12-24; Obtain lactic acid prepolymer, the number-average molecular weight of lactic acid prepolymer is 200～400g/mol;
2) under vacuum condition, catalyzer is joined in the lactic acid prepolymer that step 1) obtains, 160～180 ℃ of control temperature of reaction after the reaction certain hour, add metal alkoxide under agitation condition, reacted 1～24 hour, obtain the product poly-lactic acid in high molecular weight;
Above-mentioned steps 2) catalyzer is one or more the mixture in tin protochloride, stannous octoate, the tosic acid in; When containing tin protochloride in the catalyzer, the quality of tin protochloride is 0.33% of lactic acid prepolymer quality, when containing stannous octoate in the catalyzer, the quality of stannous octoate is 0.167% of lactic acid prepolymer quality, when containing tosic acid in the catalyzer, the quality of tosic acid is 0.5% of lactic acid prepolymer quality;
Above-mentioned steps 2) metal alkoxide in is one or more the mixture in the following material: magnesium methylate, aluminum methylate, magnesium ethylate, aluminum ethylate.
The quality of the metal alkoxide above-mentioned steps 2) is the 0.1%-5% of lactic acid prepolymer quality;
Above-mentioned steps 2) certain hour in is 0-16h.
2. the preparation method of a kind of poly-lactic acid in high molecular weight based on the metal alkoxide dewatering agent according to claim 1, it is characterized in that: catalyzer is tin protochloride, stannous octoate, tosic acid three's mixture.
3. the preparation method of a kind of poly-lactic acid in high molecular weight based on the metal alkoxide dewatering agent according to claim 1, it is characterized in that: metal alkoxide is magnesium methylate, aluminum methylate or magnesium ethylate.
4. the preparation method of a kind of poly-lactic acid in high molecular weight based on the metal alkoxide dewatering agent according to claim 1, it is characterized in that: the quality of metal alkoxide is the 0.47%-1% of lactic acid prepolymer quality.
5. the preparation method of a kind of poly-lactic acid in high molecular weight based on the metal alkoxide dewatering agent according to claim 1, it is characterized in that: certain hour is 10～16h.
6. the preparation method of a kind of poly-lactic acid in high molecular weight based on the metal alkoxide dewatering agent according to claim 5, it is characterized in that: certain hour is 16h.
7. the preparation method of a kind of poly-lactic acid in high molecular weight based on the metal alkoxide dewatering agent according to claim 1 is characterized in that: reaction unit and the step 2 of this step 1)) reaction unit all have condensation reflux unit, temperature regulating device and whipping appts.
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Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH072987A (en) * | 1993-06-18 | 1995-01-06 | Mitsui Toatsu Chem Inc | Production of poly(hydroxy carboxylic acid) |
| US5917010A (en) * | 1996-09-02 | 1999-06-29 | Mitsui Chemicals, Inc. | Preparation process of aliphatic polyester |
| CN1326997A (en) * | 2001-06-28 | 2001-12-19 | 华东理工大学 | Method for preparing high molecular weight poly lactic acid by direct polycondensation |
| CN1563139A (en) * | 2004-03-25 | 2005-01-12 | 同济大学 | Direct fusion method for preparing poly lactic acid in high molecular weight |
| CN101402723A (en) * | 2008-09-15 | 2009-04-08 | 青岛生物能源与过程研究所 | Method for preparing high molecular weight poly lactic acid by direct polycondensation |
| CN101735429A (en) * | 2009-12-29 | 2010-06-16 | 江西省科院生物技术有限责任公司 | Melt polycondensation method for preparing high molecular weight polylactic acid |
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2013
- 2013-06-03 CN CN201310217589.6A patent/CN103254409B/en active Active
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH072987A (en) * | 1993-06-18 | 1995-01-06 | Mitsui Toatsu Chem Inc | Production of poly(hydroxy carboxylic acid) |
| US5917010A (en) * | 1996-09-02 | 1999-06-29 | Mitsui Chemicals, Inc. | Preparation process of aliphatic polyester |
| CN1326997A (en) * | 2001-06-28 | 2001-12-19 | 华东理工大学 | Method for preparing high molecular weight poly lactic acid by direct polycondensation |
| CN1563139A (en) * | 2004-03-25 | 2005-01-12 | 同济大学 | Direct fusion method for preparing poly lactic acid in high molecular weight |
| CN101402723A (en) * | 2008-09-15 | 2009-04-08 | 青岛生物能源与过程研究所 | Method for preparing high molecular weight poly lactic acid by direct polycondensation |
| CN101735429A (en) * | 2009-12-29 | 2010-06-16 | 江西省科院生物技术有限责任公司 | Melt polycondensation method for preparing high molecular weight polylactic acid |
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