WO2014180205A1

WO2014180205A1 - Method for continuously preparing high molecular weight polyhydroxy acid

Info

Publication number: WO2014180205A1
Application number: PCT/CN2014/074806
Authority: WO
Inventors: 陈群; 崔爱军; 何明阳; 周维友; 陈圣春
Original assignee: 常州大学
Priority date: 2013-05-06
Filing date: 2014-04-04
Publication date: 2014-11-13
Also published as: CN103304786A; GB201520339D0; GB2528814A; CN103304786B

Abstract

The present invention relates to the technical field of environmentally friendly high molecular material. Disclosed is a method for continuously preparing high molecular weight polyhydroxy acid, the method comprising: employing a single-stage or multi-stage temperature-controllable screw reactor; utilizing organic or inorganic Lewis acid as a catalyzer, controlling the temperature, dosage of the catalyzer, and revolutions of the screw, and continuously feeding cyclic ester monomer and the catalyzer for polymerization reaction, the product being obtained quickly through continuous discharge; and in the middle and latter stages, directly adding antioxidizer and end-capping reagent to adjust the chromaticity of the polyhydroxy acid, and improve the stability thereof. The prepared polyhydroxy acid has advantages such as high molecular weight and low chromatic value.

Description

Method for continuously preparing high molecular weight polyhydroxy acid

The invention relates to a method for continuously preparing polyhydroxy acid, belonging to the technical field of environmentally friendly polymer materials. technical background

Traditional polymer materials are generally derived from non-renewable petroleum resources and are difficult to degrade. Although it plays an irreplaceable role in the socio-economic development process, it faces the problem of white pollution and energy shortage.

At present, polyhydroxy acid is a kind of degradable environmentally friendly polymer material, which has the advantages of easy processing, convenient recycling, non-toxic and harmless, and reduced pollution. Among them, polyglycolic acid and polylactide have good gas barrier properties, excellent mechanical properties, good biocompatibility and excellent degradability, and are widely used in medical absorbable surgical sutures, drug controlled release, High value-added products simulating human tissue materials, biodegradable polymer scaffolds, high-strength fibers (fishing lines); modified materials are used in multi-layer bottle materials for beverage packaging, PET composite bottles for beer packaging, shrink films and Single (multi) layer of soft packaging materials such as containers, thermoformed teacups, and composite papers, and agricultural biodegradable films.

The methods for preparing the polyhydroxy acid mainly include a lactide ring opening method, a solution condensation polymerization method of a hydroxy acid or a halogenated acid, and a melt solid phase polycondensation method. The high-molecular weight PGA can also be obtained by the melt/solid phase polycondensation method. However, since the oligomer is solidified, it is necessary to take out the crushing, and it is difficult to complete the continuous production, so that it is difficult to form an industrialization. The chloroacetic acid solution polycondensation method is simple and the process is simple, but the PGA product obtained by the synthesis has a small molecular weight and is difficult to meet the standards for material application. Relatively speaking, the lactide ring-opening method is a relatively mature method. The PGA product prepared by the method has high molecular weight, low chroma and wide application range, and can be modified with materials such as PET to form a variety of materials with special functions.

U.S. Patent No. 3,297,033 discloses a technique for preparing high molecular weight polyglycolic acid. The method is to first purify glycolic acid, then make glycolic acid into an oligomer, and depolymerize the oligomer to form a cyclic ester containing a dimer of a hydroxycarboxylic acid. Finally, the cyclic ester is heated and melted in the presence of a catalyst, and then the cyclic ester in a molten state is subjected to ring-opening polymerization. Although this method can produce a high molecular weight polyglycolic acid, the process is complicated and the cost is high, and in particular, the purity of the cyclic ester is high.

Chinese Patent No. CN101374883A discloses a synthetic method for preparing an aliphatic polyester, characterized in that, when a cyclic polyester is used for ring-opening polymerization to prepare an aliphatic polyester, the cyclic ester is first prepolymerized, and then the prepolymer is melted. The product was continuously introduced into a twin-screw stirring device, and a prepolymer in a solid pulverized state was continuously obtained, and further solid phase polymerization was carried out, and then the produced polymer was melt-kneaded together with a stabilizer to be pelletized. The method has long process flow and complicated equipment, and the overall process is discontinuous, and a long-term solid phase polycondensation reaction is required to obtain a high molecular weight polyhydroxy acid.

Chinese patent CN1544503A discloses a technique for preparing polyglycolic acid. The method is to select soluble chloroacetic acid The low boiling point solvent and the selective alkaline reagent are used as catalysts, and the suitable reaction concentration, temperature and reaction time, and suitable washing conditions are controlled to prepare polyglycolic acid. The molecular weight of the polyglycolic acid obtained by the method is not high, and the standard of practical application is not obtained, and the raw material chloroacetic acid is highly toxic and corrosive.

Yamagen and Line, etc. (Specially Open 2009-185065) 70% industrial grade glycolic acid aqueous solution is stirred at 170~200 °C under normal pressure for 2 hours, and the water is distilled off; then the reaction is kept at 5 kPa and 200 °C. 2h, the unreacted raw material contained in the low boiling point was distilled off, and a high yield of PGA oligomer was obtained, and the molecular weight was about 2 to 100,000.

Takahashi et al. (Polymer, 2000, 41(24): 8725-8728) using zinc acetate dihydrate as a catalyst, mixing glycolic acid with a catalyst, stirring at 190 ° C, 20 kPa for 1 h, then decompressing to 4 kpa for 4 h. , let the system change from liquid to solid, quickly heat up to 230 Γ to make the solid melt evenly, and then quickly cool down to 190 ° C to solidify the product for 20 h distribution solid phase polycondensation method (Formula 2), or get Mw is 91000, and A product having similar properties to the PGA obtained by the ring opening polymerization of glycolide can be obtained.

Nanjo Yicheng et al. (Specially Open 2006-182017) used a similar direct synthesis process, adding 20kg of glycolic acid to the stirred reactor, purging with dry nitrogen for 20min at room temperature, adding 4g of SnCl ₄ · 6.5Η ₂ 0 catalyst, 170Γ After holding for 2 hours, the material was polymerized and cooled to room temperature. The polymer was taken out and pulverized into particles of about 3 mm, and dried at 150 ° C under O.lkpa vacuum for 24 hours to eliminate residual monomers, and the Tm was 228 Γ, Tg was 38 Γ, and the melt was obtained. Viscosity (250 Γ, 100 s - ^ 2200 Pa · s can be used to make PGA resin for biaxially oriented film.

In summary, the current polyhydroxy acid synthesis process mainly adopts the reactor batch preparation method, and also has some continuous process preparation processes, but has not fully achieved continuous production. This condition leads to a long reaction time, a deep coloration of the product, difficulty in removing the material from the reaction system, and the like, which are unfavorable for industrial production. Therefore, the present invention proposes to directly input the cyclic ester as a raw material into a screw type reactor for continuous rapid preparation of polyhydroxy acid, which has short reaction time and light coloration; and directly adds an antioxidant in the middle and rear stages of the reactor. , a blocking agent to adjust the color of the polyhydroxy acid and improve its stability. The entire process of the present invention is continuous and is a route method that can accommodate large-scale production. Summary of the invention

SUMMARY OF THE INVENTION The object of the present invention is to overcome the above deficiencies of the prior art and to provide a rapid process for the preparation of polyhydroxy acids by chemical synthesis.

A method for continuously preparing a high molecular weight polyhydroxy acid is carried out according to the following steps:

(1) Under the protection of an inert gas (nitrogen or argon), in a screw reactor with one or more stages of temperature control, the cyclic lipid monomer and the catalyst are continuously and uniformly added to the reactor for polymerization. Respond The material speed is basically the same as the discharging speed, and the product is quickly obtained by continuous discharging. (2) In the middle and the back of the reactor, the method of directly adding an antioxidant and a blocking agent is used to blend with the polyhydroxy acid. To adjust the color of the polyhydroxy acid and improve its stability.

The cyclic ester monomer of the present invention is glycolide, lactide, γ-butyrolactone, δ-valerolactone, _ε -caprolactone, and a mixture of two or more of the above monomers, preferably B. The lactide or lactide; wherein the mixed cyclic ester, the mass fraction of glycolide or lactide is not less than 90%.

The catalyst of the present invention is a Lewis acid, specifically: an organic phosphonium salt, an organic ammonium salt, calcium acetate, zinc acetate, zinc acetate dihydrate, antimony trioxide, antimony dioxide, antimony trisulfide, stannous chloride. , stannous chloride dihydrate, stannous octoate, tin chloride, tin oxide, chromium oxide, titanium dioxide, complex titanium catalyst, etc., preferably zinc acetate dihydrate, antimony trioxide, stannous chloride dihydrate One, or any two or more kinds of composite catalysts.

The catalyst of the present invention is an oxide or metal salt of zinc, ruthenium, osmium, tin, or titanium.

The amount of the catalyst in the present invention is from 20 to 2,000 ppm, preferably from 50 to 1,000 ppm, based on the amount of the cyclic ester monomer, and the molecular weight of the polyhydroxy acid can be more than 200,000, and the intrinsic viscosity is more than 1.0. At the same time, the amount of the catalyst also has a significant effect on controlling the chromaticity of the polyhydroxy acid. When the amount of the catalyst is less than 1000 ppm, the yellowness index of the polyhydroxy acid is not higher than 50.

The monomer feeding method of the invention may be selected by uniformly mixing the catalyst and the monomer into powder, or granulating the catalyst and the monomer, or mixing the two by a melt pump and then adding to the reactor. in.

The reaction temperature of each section of the reactor of the present invention is preferably carried out under the conditions of 160-260 Torr, more preferably at a temperature of 190-230 Torr, and has a large regulating effect on the molecular weight and yellowness index of the polyhydroxy acid. . The reaction temperature can be appropriately changed according to the properties of the product in the reaction, and the temperature range can be adjusted to obtain a polymer having a molecular weight of 5 to 1,000,000, and the yellowness index ranges from 2 to 50.

The one-stage or multi-stage temperature-controlled screw type reactor of the present invention preferably has a plurality of stages of 2-10 stages, more preferably 6 stages, and each stage is programmed to be heated to a reaction temperature by electric heating or oil bath heating; The reactor described has a semi-closed device for controlling the reaction time and the screw advancement speed, and the screw may be a single screw or a twin screw.

The stirring speed of the reactor of the present invention is important for the mass transfer and heat transfer of the reaction material, and has a certain influence on the uniform distribution of the molecular weight of the polymer. The preferred rate is controlled at 5-150 rpm, more preferably 20 -80 rpm, at the same time, it can be changed according to the product properties in the reaction, and the molecular weight distribution is expressed by the weight average molecular weight/number average molecular weight (Mw/Mn) ratio in the range of 0.8 to 3.0.

The reaction time of the present invention has a great influence on the properties of the polymer. As the reaction time increases, the intrinsic viscosity of the polyhydroxy acid increases first and then decreases within a range, for example, at 200 Torr, the catalyst is 500 ppm. Reaction 8 The intrinsic viscosity of the polyhydroxy acid is about 0.91dL/g, and reaches a maximum value; then, as the reaction time increases, the intrinsic viscosity begins to decrease, and when the reaction time increases to 40 minutes, the intrinsic viscosity decreases to 0.61d. /g. Therefore, the reaction time should be controlled from 1 to 100 minutes, more preferably from 3 to 30 minutes;

In order to reduce the chromaticity of the polyhydroxy acid, the antioxidant inlet is designed in the middle and the back of the screw reactor, and the phosphate or phosphite antioxidant can be blended to prevent the polyhydroxy acid. The chromaticity is deepened during discharge or subsequent processing. Preferred antioxidants include bis-octadecyl phosphate, bis-dodecyl phosphate, bis 2,4-di-tert-butyl phenyl phosphate, octadecyl phosphite, dodecyl phosphite Ester, triphenyl phosphite, tris(2,4-di-tert-butyl)phenyl phosphite, and the like. The antioxidant is preferably used in an amount of from 0.1 to 5% by mass based on the amount of the cyclic ester, more preferably from 0.5 to 2% by mass.

In order to obtain a polymer having a stable molecular weight, a feed port of a carboxyl blocking agent is designed in the last stage of the screw reactor to meet different requirements for water resistance of the polymer. Preferred carboxyl blocking agents include N,N-2,6-diisopropylcarbamoylamine, N,N-dicyclohexylcarbamoylamine, 2-phenyl-2-oxazoline, carbonized cyclohexane The olefin blocking agent is preferably used in an amount of from 0.01 to 2% by mass, more preferably from 0.1 to 1% by mass based on the mass of the cyclic ester.

In order to obtain a polymer having a small amount of residual monomers, the prepared polyhydroxy acid is subjected to solid phase polycondensation under reduced pressure at a temperature of 120 to 180 Torr to extract unreacted residual monomers, and molecular weight distribution of the polymer. Narrowed. The preferred pressure conditions are 0. 01-5 Kpa, more preferably the pressure condition is 0.1-lKpa; the solid phase polycondensation time is preferably from 1 to 50 hours, more preferably from 2 to 10 hours.

The preparation method of the polyhydroxy acid provided by the invention, when the reaction temperature is 180-240 Torr, the obtained polyhydroxy acid has a relatively stable viscosity range, and the viscosity (? ₆ ) measured at 250 Γ after 60 minutes is maintained at 250 Γ. The ratio of the initial viscosity (7.) measured after preheating for 5 minutes [(7 _{6 .} / 7.) 100], the melt viscosity retention rate is more than 45%. Therefore, the polyhydroxy acid has better durability and shape retention.

The polyhydroxy acid of the present invention is characterized in that it has:

(1) Weight average molecular weight (Mw) in the range of 10,000 to 1,000,000;

(2) The molecular weight distribution range is 0.8 3.0 when expressed by the weight average molecular weight / number average molecular weight (Mw / Mn) ratio;

(3) The sheet obtained by compression molding and crystallization has a yellowness index (YI) of up to 50.

(4) A relatively stable viscosity range, after 60 minutes of holding at 250 Torr, the melt viscosity retention is greater than 45%. The polyhydroxy acid is preferably a polyglycolic acid, a polylactic acid or a copolymer of the two.

The invention provides a preparation method of a polyhydroxy acid. By selecting suitable reaction conditions, a polymer excellent in melt stability can be obtained, which has high intrinsic viscosity, high strength and shape, and less coloration. Used directly as a degradable plastic. The method for preparing a polymer has the advantages of high yield, continuous, and is suitable for industrial production. DRAWINGS

1 is an infrared spectrum of the polyglycolic acid prepared in Example 1;

2 is an iHNMR spectrum of the polyglycolic acid prepared in Example 1;

Figure 3 is a DSC curve of the polyglycolic acid prepared in Example 1;

4 is an XRD spectrum of the polyglycolic acid prepared in Example 1;

Figure 5 is a flow chart of the polymerization reaction of the present invention. detailed description

Hereinafter, the present invention will be further described by using a glycoly glycol and a lactide which are preferred embodiments of the present invention as a raw material in a twin-screw stirred reactor having a temperature control of 6 stages (Hecker Reomex OS PTW16 system). It is not intended to limit the scope of the invention.

In the following description, "%" and "ppm" indicating the proportion of the quantity mean the weight basis unless otherwise specified. Unless otherwise stated, the starting materials, reagents and equipment of the present invention are commercially available for purchase.

The detection method of the present invention is a conventional technical method in the art:

The infrared spectrum was measured by a Fourier transform infrared spectrometer (KBr tablet method).

The ¹ H-NMR was determined by deuterated trifluoroacetic acid (CF ₃ COOD) as a solvent and TMS as an internal standard.

The X-powder diffraction conditions are: current 30 mA, slit DS = SS = 1 °, RS = 0.3 mm, scanning speed

10 min, graphite monochromator, copper target, scanning range 5°~80°.

The ratio of the area of the crystalline region to the total area in the X-ray diagram is defined as the crystallinity (Cryst _a llinity). Calculated using equation (a):

Crystallinity = Α / (Α + Α) * 100% (a)

Where: Λ—Crystal peak area 非晶—Amorphous peak area The DSC analysis conditions are as follows: N ₂ flow rate 40 mL/min, starting from 50 ,, heating to 250 20 at 20 ° C/min, maintaining l.Omin at 250 ,, then Cool down to 50 °C at 10 °C / min.

The intrinsic viscosity method is as follows: accurately weigh 25 mg of ground polymer particles, dissolved in a solution of 5 mM sodium trifluoroacetate in hexafluoroisopropanol, under a condition of 25 Torr, using a diameter of 0.5 to 0.6 mm The viscometer tests the outflow time t _Q and t intrinsic viscosity of pure solvent and polymer solution respectively. The calculation of the intrinsic viscosity is obtained by the "one point method" formula:

[77]=[2(77 _sp -ln77 _r )] ^1/2 /c (b)

Where: =t/t _c is the relative viscosity; = -1 is the specific viscosity Each sample was measured in parallel three times, and the difference in the outflow time of each measurement could not exceed 0.2 s. Finally, the average of the three results is taken as the outflow time of the liquid to be tested.

The weight average relative molecular weight and distribution were measured: The sample was dissolved in a solution of 5 mM sodium trifluoroacetate in hexafluoroisopropanol to prepare a solution of 0.05 to 0.3% by mass. It was filtered through a Teflon filter, and then 20/L was added to a gel permeation chromatograph (GPC) injector, and molecular weight correction was performed using five standard polymethyl methacrylates having different molecular weights.

The melt viscosity was measured: 10 g of polyhydroxy acid ester sandwiched between aluminum plates was placed on a press preheated to 240 Torr, and after preheating for 30 s, pressed at 5 MPa for 15 s, and then rapidly cooled to prepare a sheet. material. Such an amorphous sheet was crystallized by heating in an oven at 150 ° C for 15 minutes. A sample of 7 g was placed in a cylinder having an inner diameter of 9.55 mm on a Capirograph 3C manufactured by Toyo Seiki Co., Ltd., and the temperature was set to 240 Torr. After preheating for 5 min, the sample was extruded from a die having an inner diameter of 1 mm and a length of 1 mm at a shear rate of 122 / sec, and the melt viscosity (Pa_s;) of the sample was obtained from the stress at this time.

The percent weight loss rate was determined: using a TG50 manufactured by Metier, the polyhydroxy acid was heated from 50 Torr at a heating rate of 2 ° C/min in a nitrogen atmosphere dominated by a nitrogen flow rate of 10 ml/min. The sample was accurately read at a temperature at which the weight (W _5Q ) at 50 ° C showed a loss of 1%.

Determination of the amount of residual monomer: Approximately 300 mg of the sample was heated in about 6 g of dimethyl sulfoxide at 150 Torr for about 10 min, dissolved, cooled to room temperature, and then filtered. A certain amount of the internal standard 4-chlorobenzophenone and acetone were added to the filtrate. 2 μl of this solution was weighed and injected into a GC apparatus to carry out measurement. The numerical value obtained by the measurement was calculated as the residual monomer amount in the form of % by weight contained in the polymer. Gas phase analysis conditions:

Installation: Shimadzu GC-2010

Pillar: TC-17

Vaporization chamber temperature: 200Γ

Column temperature: After 5 min at 50 °C, the temperature was raised to 270 °C at a temperature increase rate of 20 °C/min, and kept at 270 °F for 4 min.

Detector: FID (hydrogen ionization detector), temperature: 300 °C.

Determination of the yellowness (YI):

10 g of polyhydroxy acid was placed on a high-temperature tableting machine, and pressed into a sheet having a thickness of 0.5 mm under 240 Torr, and sufficiently crystallized by heating under 100 Torr to determine yellowness. The measuring instrument was carried out with the SF600 model Datacolor color measuring instrument produced by Swiss Plus CT. The yellowness value was measured under the conditions of 2° field of view, standard light C and reflected light, and the average was taken as the yellowness of the sample. value.

Example 1 1000 g of high-purity glycolide was taken, 50 ppm of SnCl ₂ *2H ₂ 0 was added, and the two were uniformly mixed by a pulverizer and then uniformly fed into the screw-stirred reactor through an addition funnel, and the feeding speed was kept consistent with the discharge speed. The reactor comprises a total of 6 heating zones (as shown in Figure 5, i.e., n = 6), and the temperature of each zone is set separately in advance. The reactor was set up as follows: Feeding rate: 1 kg / h; Screw speed: lOrpm;

Reactor temperature: 1, 2 zone = 200 ° C; 3, 4 zone = 210 ° C; 5, 6 zone = 190 ° C;

The residence time was 10 min, and the obtained polyglycolide had a molecular weight average of 180,000, a molecular weight distribution range of 2.5, a yellowness index (YI) of 25.6, and a melt viscosity of 500 Pa·s.

Example 2

1000 g of glycolide having the same purity as in Example 1 was added, 500 ppm of SnCl ₂ *2H ₂ 0 was added, and both were uniformly mixed by a pulverizer, and then uniformly fed into a screw-stirred reactor through an addition funnel, and the feeding rate was maintained. The discharge speed is the same. The reactor is set up as follows:

Feeding rate: 1kg / h; screw speed: 30rpm;

Reactor temperature: 1, 2 zone = 210 ° C; 3, 4 zone = 220 ° C; 5, 6 zone = 190 ° C

The residence time was 3 min, and the obtained polyglycolide had a weight average molecular weight of 250,000, a molecular weight distribution range of 1.8, a yellowness index (YI) of 28.8, and a melt viscosity of 620 Pa*s. Example 3

1000 g of glycolide having the same purity as in Example 1 was added, 2000 ppm of SnCl ₂ *2H ₂ 0 was added, and both were uniformly mixed by a pulverizer and then uniformly fed into a screw-stirred reactor through an addition funnel, and the feeding rate was maintained. The discharge speed is the same. The reactor is set up as follows:

Feeding rate: 1kg / h; screw speed: 80rpm;

The residence time was 1. Omin, and the obtained polyglycolide had a weight average molecular weight of 245,000, a molecular weight distribution range of 2.0, a yellowness index (YI) of 47.1, and a melt viscosity of 610 Pa*s. Example 4

1000 g of glycolide having the same purity as in Example 1 was added, 200 ppm of SnCl ₂ *2H ₂ 0 was added, and both were uniformly mixed by a pulverizer, and then uniformly fed into a screw-stirred reactor through an addition funnel, and the feeding rate was maintained. The discharge speed is the same. The reactor is set up as follows: Feeding rate: 1kg / h; screw speed: 5rpm;

Reactor temperature: 1, 2 zone = 200 ° C; 3, 4 zone = 210 ° C; 5, 6 zone = 190 ° C

The residence time was 30 min, and the obtained polyglycolide had a weight average molecular weight of 160,000 and a molecular weight distribution range of 2.1. The yellowness index (YI) is 43. 6; the melt viscosity is 480 Pa · s.

Example 5

1000 g of glycolide having the same purity as in Example 1 was added, 200 ppm of SnCl ₂ * 2H ₂ 0 was added, and both were uniformly mixed by a pulverizer, and then uniformly fed into a screw-stirred reactor through an addition funnel, and the feeding rate was maintained. The discharge speed is the same. The reactor is set up as follows:

Feeding rate: 1kg / h; screw speed: 45rpm;

Reactor temperature: 1, 2 zone = 220 ° C; 3, 4 zone = 210 ° C; 5, 6 zone = 190 ° C

The residence time was 3. Omin, and the obtained polyglycolide had a weight average molecular weight of 355,000, a molecular weight distribution range of 2.2, a yellowness index (YI) of 21.6, and a melt viscosity of 780 Pa·s.

Example 6

Feeding rate: 1kg / h; screw speed: 150rpm;

The residence time is l. Ornin, and the obtained polyglycolide has a weight average molecular weight of 235,000, a molecular weight distribution range of 1.5, a yellowness index (YI) of 20.3, and a melt viscosity of 600 Pa*s. Example 7

1000 g of glycolide having the same purity as in Example 1 was added, 500 ppm of SnCl ₂ * 2H ₂ 0 was added, and both were uniformly mixed by a pulverizer, and then uniformly fed into a screw-stirred reactor through an addition funnel, and the feeding rate was maintained. The discharge speed is the same. The reactor is set up as follows:

Feeding rate: 1kg / h; screw speed: 50rpm;

Reactor temperature: 1, 2 zone = 240 ° C; 3, 4 zone = 210 ° C; 5, 6 zone = 160 ° C

The residence time is 2. Omin, the obtained polyglycolide has a weight average molecular weight of 265,000 and a molecular weight distribution range of 2.4; The yellowness index (YI) was 16.3; the melt viscosity was 660 Pa·s.

Example 8

1000 g of high-purity lactide was taken, 300 ppm of SnCl ₂ *2H ₂ 0 was added, and both were uniformly mixed by a pulverizer and then uniformly fed into a screw-stirred reactor through an addition funnel, and the feeding speed was kept consistent with the discharge speed. The reactor is set up as follows:

Feeding rate: 1kg / h; screw speed: 40rpm;

Reactor temperature: 1, 2 zone = 220 ° C; 3, 4 zone = 220 ° C; 5, 6 zone = 200 ° C

The residence time was 2.4 min, and the obtained polylactide lactide had a weight average molecular weight of 305,000, a molecular weight distribution range of 2.2, a yellowness index (YI) of 24.2, and a melt viscosity of 750 Pa*s. Example 9

Take 500g of high-purity glycolide and lactide, add 600ppm of SnCl ₂ «2H ₂ 0, mix the material with a pulverizer and then add it to the screw stirring reactor through the feeding funnel. The feeding speed is maintained and discharged. The speed is the same. The reactor is set up as follows:

Feeding rate: 1kg / h; screw speed: 130rpm;

Reactor temperature: 1, 2 zone = 180 °C; 3, 4 zone = 190 °C; 5, 6 zone = 170 °C

The residence time was 1.6 min, and the obtained polyglycolide copolymer had a weight average molecular weight of 195,000, a molecular weight distribution range of 2.1, a yellowness index (YI) of 33.1, and a melt viscosity of 480 Pa*s. Example 10

Take high-purity glycolide 1000g, ε_caprolactone 50g, add 600ppm of SnCl ₂ *2H ₂ 0, mix the material with a pulverizer and then add it to the screw stirring reactor through the feeding funnel at a constant rate. The discharge speed is the same. The reactor is set up as follows:

Feeding rate: 1kg / h; screw speed: 30rpm;

Reactor temperature: 1, 2 zone = 220 °C; 3, 4 zone = 210 °C; 5, 6 zone = 190 °C

The residence time was 3. Omin, and the obtained polyglycolide copolymer had a weight average molecular weight of 295,000, a molecular weight distribution range of 2.8, a yellowness index (YI) of 28.2, and a melt viscosity of 720 Pa*s. Example 11 1000 g of high-purity glycolide was taken, 600 ppm of SnCl ₂ *2H ₂ 0 was added, and the material was uniformly mixed by a pulverizer and then uniformly fed into the screw-stirred reactor through an addition funnel, and the feeding speed was kept consistent with the discharge speed. 100 g of polyhydroxy acid masterbatch containing 10% (mass fraction) of antioxidant triphenylphosphite was added to the fifth stage of the reactor, and the reactor was set up as follows:

Glycolide feed rate: 1kg / h; Antioxidant feed rate: 100g / h _; Screw speed: 30rpm;

The residence time was 3. Omin, and the obtained polyglycolide copolymer had a weight average molecular weight of 225,000, a molecular weight distribution range of 2.3, a yellowness index (YI) of 18.2, and a melt viscosity of 650 Pa*s.

Example 12

1000 g of high-purity glycolide was taken, 600 ppm of SnCl ₂ *2H ₂ 0 was added, and the material was uniformly mixed by a pulverizer and then uniformly fed into the screw-stirred reactor through an addition funnel, and the feeding speed was kept consistent with the discharge speed. In the fifth stage of the reactor, 100 g of a toluene solution containing 10% (mass fraction) of the blocking agent N,N-dicyclohexylcarbamoylamine was added, and the reactor was set as follows:

Feeding rate of glycolide: 1kg / h; feeding rate of blocking agent: 100g / h _; screw speed: 30rpm;

The residence time was 3. Omin, and the obtained polyglycolide copolymer had a weight average molecular weight of 252,000 and a molecular weight distribution range of 2.0; a yellowness index (YI) of 23.5; and a melt viscosity of 680 Pa*s.

Example 13

1000 g of the polyglycolic acid prepared in Example 5 was placed in a closed stirred high-pressure reaction vessel under nitrogen atmosphere, the temperature was raised to 160 ° C, the pressure was raised to 2 MPa, and the reaction was continuously stirred for 5 hours. Then, the pressure is released, and the pressure is reduced to 1 Kpa under reduced pressure for 2 hours. The obtained polyglycolic acid has a weight average molecular weight of 552,000 and a molecular weight distribution range of 2.3; a yellowness index (YI) of 33.5; a melt viscosity of 880 Pa * s. 1 is an infrared spectrum of polyglycolic acid prepared in Example 1, and it can be seen that ΠΑόοηι· ¹ is a polymer ester carbonyl group C=0 stretching vibration peak; 1154 cm" ¹ and ΙΟδ^ηι· ¹ are ester groups. C_0_C absorption peak; 3515 cm" ¹ is the polymer terminal hydroxyl-OH absorption peak. The 2993 cm" ¹ is the C_H stretching vibration peak in the polymer; the C-H absorption peak at 1419 cm" ¹ is the characteristic absorption peak of CH ₂ in the PMG. From the above analysis, the synthesized polymer was polyglycolic acid.

2 is an iHNMR spectrum of the polyglycolic acid prepared in Example 1, and it is understood that the molecular structure of the polyglycolic acid is known. Its molecular structure is single, in the ¹ H NMR spectrum, (5 11.5 is the solvent peak of ? ₃ 000, (55.160 is the peak on (0. 3⁄4. 0)).

Figure 3 shows the X-powder diffraction pattern of polyglycolic acid. As can be seen from the figure, the polyglycolic acid is a semi-crystalline polymer, 2 straight at 22.2° and 29.1°. The crystallinity was 63.33% by peak calculation.

The DSC curve of the polyglycolic acid prepared as shown in Fig. 4 shows that the glass transition temperature of the product of this example was 36.4 ° C, the crystallization temperature was 175.1 ° C, and the melting point was 219.7 ° C.

Figure 5 shows a schematic diagram of the polymerization reactor. The diagram includes the feed section. A continuous addition funnel or melt pump can be used. The reactor is a tubular type with a screw agitator in the middle. The reactor can be heated in sections. In the middle and the back stage, an antioxidant and a carboxyl blocking agent may be added, and after discharging, the solvent is cooled or air-cooled, and dried and then pelletized.

Claims

WO 2014/180205 Quanhej Letter of Request PCT/CN2014/074806

1. A method for continuously preparing high molecular weight polyhydroxy acid, which is characterized by following the following steps: (1) Under the protection of nitrogen or argon, in a screw reactor with one or more stages of temperature control , the cyclic lipid monomer and the catalyst are continuously added to the reactor at a uniform speed to perform the polymerization reaction, keeping the feed speed and the discharge speed basically consistent, and the product is quickly obtained in a continuous discharge manner; (2) in the reactor In the middle and later stages, antioxidants and end-capping agents are directly added and blended with polyhydroxy acid to adjust the color of the polyhydroxy acid and improve its stability.

2. A method for continuously preparing high molecular weight polyhydroxy acid according to claim 1, characterized in that the cyclic ester monomer is glycolide, lactide, γ-butyrolactone, δ- Valerolactone, f-caprolactone and mixtures of two or more of the above monomers, preferably glycolide or lactide; wherein the mass fraction of glycolide or lactide in the mixed cyclic ester is not less than 90%.

3. A method for continuously preparing high molecular weight polyhydroxy acid according to claim 1, characterized in that the catalyst organic guanidine salt, organic ammonium salt, calcium acetate, zinc acetate, zinc acetate dihydrate, trioxide Antimony, germanium dioxide, antimony trisulfide, stannous chloride, stannous chloride dihydrate, stannous octoate, tin chloride, tin oxide, chromium oxide, titanium dioxide, titanium complex catalyst, etc., preferably dihydrate One of zinc acetate, antimony trioxide, stannous chloride dihydrate, or a composite catalyst of any two or more.

4. A method for continuously preparing high molecular weight polyhydroxy acid according to claim 1, characterized in that the catalyst is an oxide or metal salt of zinc, antimony, germanium, tin, or titanium.

5. A method for continuously preparing high molecular weight polyhydroxy acid according to claim 1, characterized in that the amount of catalyst used in the cyclic ester monomer is 20-2000 ppm, preferably 50-1000 ppm, It can make the molecular weight of the polyhydroxy acid reach more than 200,000, and the intrinsic viscosity is greater than 1.0.

6. A method for continuously preparing high molecular weight polyhydroxy acid according to claim 1, characterized in that the monomer feeding method of the present invention can be to beat the catalyst and the monomer into powder and mix them evenly, or Pelletize the catalyst and monomer, or use a melt pump to mix the two and add them to the reactor.

7. A method for continuously preparing high molecular weight polyhydroxy acid according to claim 1, characterized in that the one or more stages of the temperature-controllable screw reactor, the multi-stage is preferably 2-10 stages, more preferably It is 6 segments.

8. A method for continuously preparing high molecular weight polyhydroxy acid according to claim 1, characterized in that the stirring speed of the reactor is controlled at 5-150 rpm, more preferably 20-80 rpm At the same time, it can be changed in time according to the properties of the product in the reaction. The molecular weight distribution is expressed by the weight average molecular weight/number average molecular weight (Mw/Mn) ratio, which ranges from 0.8 to 3.0.

9. A method for continuously preparing high molecular weight polyhydroxy acid according to claim 1, characterized in that The reaction time is controlled at 1-100 minutes, more preferably 3-30 minutes; antioxidants and end-capping agents can be added to the polyhydroxy acid in the middle and rear sections of the screw reactor to facilitate the adjustment of the polyhydroxy acid. Chroma and stability.