CA1256638A - Polymer and its production - Google Patents
Polymer and its productionInfo
- Publication number
- CA1256638A CA1256638A CA000486142A CA486142A CA1256638A CA 1256638 A CA1256638 A CA 1256638A CA 000486142 A CA000486142 A CA 000486142A CA 486142 A CA486142 A CA 486142A CA 1256638 A CA1256638 A CA 1256638A
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- CA
- Canada
- Prior art keywords
- acid
- weight
- lactic acid
- copolymer
- catalyst
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
- C08G63/02—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds
- C08G63/06—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds derived from hydroxycarboxylic acids
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
- A61K9/00—Medicinal preparations characterised by special physical form
- A61K9/14—Particulate form, e.g. powders, Processes for size reducing of pure drugs or the resulting products, Pure drug nanoparticles
- A61K9/16—Agglomerates; Granulates; Microbeadlets ; Microspheres; Pellets; Solid products obtained by spray drying, spray freeze drying, spray congealing,(multiple) emulsion solvent evaporation or extraction
- A61K9/1605—Excipients; Inactive ingredients
- A61K9/1629—Organic macromolecular compounds
- A61K9/1641—Organic macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds, e.g. polyethylene glycol, poloxamers
- A61K9/1647—Polyesters, e.g. poly(lactide-co-glycolide)
Abstract
POLYMER AND ITS PRODUCTION
Abstract of the Disclosure A polymer or copolymer of lactic acid and/or glycolic acid which has a weight-average molecular weight of not less than about 5,000 and a dispersity of about 1.5 to 2 is advantageously used as a biodegradable polymer or copolymer for medical preparation.
Abstract of the Disclosure A polymer or copolymer of lactic acid and/or glycolic acid which has a weight-average molecular weight of not less than about 5,000 and a dispersity of about 1.5 to 2 is advantageously used as a biodegradable polymer or copolymer for medical preparation.
Description
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The present invention relates to a polymer of lactic acid or glycolic acid, a copolymer of lactic acid and glycolic acid and a method for producing the polymer or the copolymer by a polycondensation reaction in the presence of a solid inorganic acid catalyst.
In recent years, degradable polymers have attracted a good deal of attention, for example, as readily degradable poly-mers serving to mitigate environmental pollution and also as biodegradable polymers for medical use.
A method for producing a copolymer of lactic acid and glycolic acid is disclosed in UOS. Patent No. 4,273,920. In this Patent, it is stated that a copolymer substantially free of poly-merization catalyst is obtained by reacting lactic acid with glycolic acid in the presence of a readily removable strong acid ion-exchange resin, and removing the resin therefrom.
However, the copolymers produced by the above- described method all exhibit a dispersity in molecular weight as high as nearly 3 or more, an~ in use, give great complexity in fac~ors involving solubility and other aspects, thus presenting major problems in controlling such factors. Therefore, they cannot be said to be very favorable, when they are used, for example, as a biodegradable polymer for medical use. In addition, this method allows the strong acid ion exchange resin being used as a poly-merization catalyst to deteriorate due to heat during a polycon-densation reaction under heating and to get dissolved in the resulting copolymer, thereby contributing to the development of coloration oE the copolymer. Furthermore, it is difficult to eliminate such coloration, and it is practically impossible to remove such coloration completely, and the coloration shows that the catalyst, i.e. the strong acid ion-exchange resin, cannot be completely removed. Such coloration not only diminishes value as an article of commerce but also is undesirable by virtue of i~s impurities.
In view of such circumstances, the present inventors conducted repeatedly intensive research, and found a method for 3~
~5~i63~
producing a polymer of lactlc acid or glycolic acid and a copoly-mer of lactic acid and glycolic acid, which are effective and substantially free from the above-mentioned disad~antages. Based on this finding and a further research, the present inventors have completed the present invention.
The present invention is directed to:
(1) A polymer or copolymer of lactic acid and/or glycolic acid, which has a weight-average molecular weight of not less than about 5,000 and a dispersity of about 1.5 to 2, and (2~ A method for producing a polymer or copolymer of lactic acid and/or glycolic acid comprising subjecting lactic acid and/or glycolic acid to a polycondensation reaction, with a solid inorganic acid catalyst as a polycondensation catalyst.
In the method of the present invention, lactic acid and/or glycolic acid are/is employed, as the starting materials, in the form of crystals, powders or granules as such, or in the form of an aqueous solution. The concentration of the solution is arbitrarily selected, preferably as high as possihle, and more preferably not lower than about 85 ~ (w/w).
As the lactic acid and/or glycolic acid starting material, low molecular polymers of lactic acid or glycolic acid or low molecular copolymers of lactic acid and glycolic acid may be employed in the present method.
Such low molecular polymers of ]actic acid or glycolic acid, may be oligomers (e.g. dimers, trimers, etc.) of lactic acid, or glycolic acid.
One SUCh low molecular polymer or copolymer starting material is produced by sub~ecting lactic acid and/or glycolic acid to a polycondensation reaction in the absence of a catalyst under for example about 100 to 150C/350 to 30 mmHg ~or more than about 2 hours, normally about 2 to 10 hours, more preferably while increasing the temperature and reducing the pressure stepwise from about 105C/350 mmHg to 150C/30 mmHg for about 5 to 6 hours, to remove water. In this process, a low molecular polymer or co-polymer of molecular weight of about 2000 to 4000 is obtained.
~256638 Furthermore~ as the low molecular copolymers, there are mentioned, or example, ones which are obtainable by processes described in Kogyo Kagaku Zasshi (Journal of the Chemical Society of Japan), vol. 68, pp. 983-986 (1965), i.e. lactic acid and gly-colic acid are reacted in a normal atmospheric pressure and in the absence of a catalyst at 202C for 6 hours, or U.S. Patent No. ~,362,511, i.e. lactic acid and glycolic acid are reacted at a temperature of 200~C holding the mixture at that temperature for a period of about 2 hours and subsequently continuing the heating for another period of about 2 hour under vacuum.
The ratio of lactic acid to glycolic acid in the copoly-mer, when the object compound is a copolymer of these compounds, is preferably about 50 to 95 weight % of lactic acid and about 50 to 5 weight % of glycolic acid, preferably about 60 to 95 weight of lactic acid and about 40 to 5 weight ~ of glycolic acid, more preferably about 60 to ~5 weight % of lactic acid and about ~0 to 15 weight % oE glycolic acid. The ratio is more preferably about 75+2 mol ~ of lactic acid and about 25+2 mol ~ of glycolic acid~
A solvent may be employed, when the starting material is in crystal, powder or granule form. Such solvents are, for example, water, methanol, ethanol and acetone.
The solid inorganic acid catalyst inclu3es acid clay, activated clay, bentonite, kaolin, talc, aluminum silicate, mag-nesium silicate, alumina bolia, and silicic acid. These can all be used, either solely or as a mixture and each may be employed as such or after being washed with, for example, hydrochloric acid at a concentration of 5 to 20 ~, to remove metal ions, if necessary.
The amount of the solid inorganic acid catalyst used in the present method is normally about 0.5 to 30 ~ w/w, preferably abo~t 1 to 20 ~ w/w, based on the total amount of lactic acid and glycolic acid. The catalyst can be used in one or several portions.
The catalyst may be added to the reaction system during the reaction.
The method is preferably carried out with heating and ~:256~;31~
under reduced pressure. The heating is carried out by heating reaction system at about 150 to 250~C, preferably about 150 to 200C. The reduced pressure is normally about 30 to 1 mmHg, preferably about 10 to 1 mmHg. The reaction time of the present polycondensation reaction is normally not less than about 10 hours, preferably about 10 to 150 hours, more preferably about 10 to 100 hours~
When lactic acid and/or glycolic acid are/is employed as the starting materials, the following conditions are preferred:
Heating under reduced pressure at about 100 to 150C/350 to 30 mmHg for not less than about 2 hours, normally about 2 to 10 hours, for example, for about 5 to 6 hours while increasing the temperature and the degree of reduced pressure stepwise to about 105C/350 mmHg to 150C/30 mmHg, to remove water, followed by a dehydration polycondensation reaction at about 150 to 200C/10 to 1 mmHg for not less than about 10 hours, normally up to about 100 hours may be adequate.
When a low molecular polymer or copolymer is employed as starting material, preferred reaction conditions are as follows-A dehydration polycondensation reaction is carried out at about150 to 200C/10 to 1 mmHg for not less than about 10 hours, nor-mally up to about 100 hours may be adequate.
After termina-tion of the reaction, the objective polymer or copolymer is readily obtained by removing the used solid in-organic acid catalyst. The solid acid catalyst oE the present invention can easily be removed for example by filtration with suction using ordinary qualitative filter paper. Mere hot filtra-tion of the reaction solution or filtration after dissolution of the polymer or copolymer in a suitable solvent such as methylene chloride, dichloroethane, chloroform or acetone, (in an amount of about lO-times that of the polymer or copolymer), is sufficient.
No subsequent treatment is required, either in the former case in which the reaction solution is filtered as such and the solvent is concentrated or distilled off, or in the latter case in which the reaction solution is filtered after being dissolved in a solvent.
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If desired, a conventional separation may be used, for example, by pouring the filtered reaction solution, either directly or in the form of a concentrated Eiltrate where a solvent is used, into a large amount of a precipitant. If required, further purification may be carried out by reprecipitation, etc.
The present invention provides a polymer or copolymer consi~ting of lactic acid and/or glycolic acid units having a weight-average molecular weight oE not less than about 5,000, preferably about 5,000 to 30,000, and having a dispersity of about 1.5 to 2. Furthermore, the polymer or copolymer is colorless to almost white.
As the polymer or copolymer oE the present invention has a low degree of dispersity, the distribution of the molecular weight of the polymer or copolymer is not wide.
Furthermore, as the solid inorganic acid catalyst is insoluble in the polymer or copolymer and in a solven'c, the catalyst is substantially completely removed from the reaction product and the resulting polymer or copolymer is substantially free of catalyst discoloration.
The polymer or copolymer obtained can be utilized as a base for drug preparation. For example, by incorporating steroid hormones, peptide hormones or anti-tumor agents, etc. into them for embedded or microcapsule type controlled release preparations or by preparing fine particles containing an ~256 E;3~
anti-tumor agent to process into a therapeutlc agent for embolization.
The ~periment Examples and Examples are described below to illustrate the present invention in more detail.
Experimen _Example 1 To 160 g (1.5 mole as lactic acid) of a 85 %
aqueous solution of lactic acid was added 6.8 g of a solid acid catalyst, and heating under reduced pressure was carried out for 6 hours under the stepwise varyins conditions of lO0 to 150C/350 to 30 mmHg under a stream of nitrogen gas to remove the resulting water.
Subsequently, 6.8 g of the solid acid catalyst was added additionally, followed by a dehydration polycondensation reaction at 175C/5 mmHg for 72 hours.
Shown in Table 1 is the relationship between reaction time and weight-average molecular weight attained and its dispersity in the production of lactic acid polymers.
Also shown in Table l for the purpose of comparison are the results obtained with Dowe~ 50 (a cross-linked polystyrene resin, Dow Chemical Co., U.S.A.), a strongly acidic ion-exchange resin being commercially available, which was used as a polymerization reaction.
The weight-average molecular weight and dispersity (d;spersity = weiaht-averaae molecular weignt) in th~
number-aver2ge molecular we1ght present specification were measured by gel permea~ion chromatography utilizing the standard polystyrene with the known molecular weight.
* Trade Mark ~L~S~
Table 1 Type of polyme~ization catalysts and molecular weight attained and its dispersity Catalyst: Alumin~m Actlvated Acid clay silicate clay Dowex 50W
Added amount (1) 6.8 g 6.8 g 6.8 g 6.8 gAdded amount (2) 6.8 g 6.8 g 6.8 ~ 6.8 g . _ _ . _ . _ _ . . _ _ ~ . _ . . _ _ 12 hours of 6,200 5,000 reaction time (1.71) (1.63) 24 hours o~ 8,90011,200 8,800 s,ioo reaction time (1.88) (1.66) (1.61) (2.43) 36 hours of ï6,60015,600 12,700 1_,400 reaction time (1.72) (1.6~) ' (1.62) (2.63) 48 hours of 19,100 16,700 1~,900 reaction time _ (1.65) (1.50) (2.80) 60 hours oE 26,50022,500 19,900 17,800 reaction time (1.73) (1.66) (1.67) (2.81) i2 hours of 29,300*25,800 23,700 20,200 reaction time (1.77) (1.6c) (1.81) (2.80) Appearance ofAlmostAlmost Almost Dark brown (thë
the polymer**whitewhite white color deepens _ with time) - -- -- _ . ._ Note: * ; Reaction time of nearly 65 hours.
** ; Each of the polymers obtained after the respective reactlon time was dissolvea in methylene chloride of the volume four tlmes that of the polvmer, and the solution was filtered using Toyo'Filter Paper No. 131 [?oyo Roshl Co., Ltd., Japan] to remove the c-_al st, and then concentrated to distill o f the solvent; the resulting polymers were examined in accordance with JIS K 8004-2 (namely, a~out 3 g of the specimen is taken on a watch glass, which is placed on a sheet of white paper and examined.).
In the Table 1, the added amount (1) of catalyst and the added amount (2) of catalyst deno-te an initially added amount of catalyst and an amount of catalyst additionally added at the time of the polycondensation ' Trade Mark ~2S6~i313 s reaction at 175C/5 mmHg after removal of water, respectively while the reaction time means that at 175C/5 mmHg. In the table, the parenthesized value beneath the molecular weight attained indicates a dispersity.
As is clear from Table 1, the present invention can permit readily the production of high molecular weight polymer with a weight-average molecular weight of not less than about 5,000 being almost free from polymerization catalyst, whereby the resulting polymers show that colored appearance is hardly observed and the polymers have dispersity of not more than 2, with the polymerization reaction rate being evidently promoted by the addition of the catalyst.
Ex~eriment Exam~le 2 After 160 g (1.5 mole) of a 85 % aqueous solution of lactic acid and 38 g tO.5 mole) of glycolic acid were mixed, 8.7 g of a solid acid catalyst was added to the mixture, and heating under reduced pressure was carried out at 100 to 150C/350 to 30 mmHg under a stream of nitrogen gas for 6 hours to remove the distilled water.
Subsequently, 8.7 g of the solid acid catalyst was adaed additionally, followed by a dehydration condensation reaction at 175C/6 to 5 mmHg for 72 hours.
Shown in Table 2 is the relationship between reaction time and weight-average molecular weight attained in the production of copolymers of lactic acid and glycolic acid.
Also, shown in Table 2 for the purpose of comparison are the results obtained with a strongly acidic ion-exchange resin (Dowex*50W) which was used as a polymerization catalyst.
* Trade Mark ~5~;~3~
g Table 2:
Type of polymerlzation catalysts and molecular weights attained Catalyst: Type Aluminum Activated Acid clay silicate clayDowex 50W
.
Added amount (1) 8.7 g 8.7 g 8.7 g 8.7 g Added amount (2) 8.7 g 8.7 g 8.7 g 8.7 g 12 hours of 5,100 reaction time (1.72) 24 hours of 12,600 11,700 10,200 10,500 10 reaction time (1.72) (1.72) _ (1.69) (2 47) 36 hours of 18,600 17,800 16,100 1~,400 reaction time (1.73) (1.74) (1.65) (2.44) 48 hours of 22,900 22,000 20,400 18,900 reaction time (1.65) (1.64) (1.64) (2.46) 60 hours of 25,400 25,800 22,800 22,200 reaction ti~e (1.68) (1.68) (1.63) _ (2.47) 15 72 hours of 27,900 28,600 26,000 25,300 reac-tion ti~e (1.76) (1.66) (1.63) (2.76) Almost AlmostAlmost Dark brown (the the polymer* white white white color deepens Note: ~ ; Each of the polymers obtained after the respective reaction time was dissolved in methylene chloride of the volume :Eour times that of the polymer, and the solution was filtered using Toyo Filter Paper No. 131 to remove the catalyst, and then, concentrated to distill off the solvent; the resulting polymers were examined in accordance with JIS K 8004-2 (namely, about 3 g of the specimen is taken on a watch glass, which is placed on a sheet of white paper and examined.).
In the Table 2, the added amount (1) of catalyst and the added amount (2) of catalyst denote an initially added amount of catalyst and an amount of catalyst additionally added at the time of the polycondensation reaction at 175C/5 mmHg after removal of water, respectively, while the reaction time means tha-t at 175C/5 mmHg. In the Table 2, the parenthesized value ~LZ5~;63~
. - 10 -beneath the molecular weiqht attained indicates a dispersity.
As is clear from Table 2, the present invention can - permit readily the production or high molecular weight lactic acid-glycolic acid copolymers with a weight-average molecular weight of not less than about 5,000 being almost free from polymerization catalyst, whereby the resulting copolymers show that colored appearance is hardly observed, and all has dispersity as small as not more than 2, with the polymerization reaction rate being evidently promoted by the additlon of the catalyst.
Furthemore, analysis of nuclear magnetic resonance spectrometry on said resulting copolymer of the present invention in CDC13 solution indicates the followin~
composition of lactic acid and glycolic acid.
~ ~ 2~i3~
Copolymer ratio of the present copolymer mol %
(weight %) Catalist Aluminum Activated Reaction~~- _ Acid Clay time ~ _ _ slllcate Clay 12 hours _ _ _ 75.5:24.5 (79.3:20.7) ._ __ _ ___ _ .. __ 75 ~25 75 ~25 75.5:24.5 24 hours l(78.8:21.2) (78.8:21.2) (79.3:20.7) ... _ .__ I _ ._ ', 75 :25 75 :25 75 :25 36 hours (78.8:21.2) (78 8:21.2) (78.8:21.2) ._ ,,_ , __ 75 :25 76 :24 75 :25 48 hours (78.8:21.2) (79.7:20.3) (78.8:2102) _ _ _ _ _ !
75.5:24.5 75.5:24.5 76 :24 60 hours (79.3:20.7) (79.3:20.7) (79.7:20.3) . _ .
75.5:24.5 75.5:24.5 75.5:24.5 1 72 hours (79.3:20.7) (79.3:20.7) (79.3 20.7)1 ~:~S~63~
Example 1 Placed in a four-necked flask equipped with a thermometer, condenser and inlet tube for nitrogen gas were 160 g of a 85 % aqueous solution of lactic acid and 13.6 g of acid clay, and heating under reduced pressure was carried out under a stream of nitrogen gas over the period of 6 hours, while increasing the internal temperature and the degree of internal reduced pressure stepwise from 105C and 350 mmHg to 150C and 30 mm~g, and then the resulting water was removed. Successively, heating was conducted under reduced pressure of 3 mmHg and at the internal temperature of 175C for 50 hours.
The reaction solution was cooled to room temperature, and 400 m~ of methylene chloride was added to it, followed by stirring to a solution. Then, the acid clay was removed by fil-tration using Toyo Filter Paper No 131, and the filtrate was concentrated to dryness to give 100 g of an almost colorless polyer, which has a weight-average molecular weight of 22,000 and a dispersity of 1.75.
In order to determine the remaining catalyst in the resultina copolymer, a specimen of the copolymer was weighed out onto a dish of platinum and subjected to a fusing treatment with sodium carbonate, and then aluminum and silicon were determined colorimetrically by ~S~631~
application of the aluminon method and molybdenum blue method, with the result that neither of the metals was detected, leading to the conclusion that there was no contamination of the catalyst observed.
Example 2 A reaction was carried out in the manner of Example 1, except that 27.2 g of aluminum silicate was used as a catalyst, and there was obtained 92 g of an almost colorless polymer, which has a weight-average molecular weight of 21,900 and a dispersity of 1.70. The similar results were obtained when kaolin and talc were used in place of aluminum silicate as a catalyst.
In order to determine the remaining catalysts in the resulting copolymers, detection of the remaining catalysts was carried out in the manner of Example l, with the result that there was no contamination of catalysts observed.
Example 3 In the manner of Example 1, 160 g of a 85 % aqueous solution of lactic acid was used, but 6.8 g of activated clay was charged in place of acid clay, whereupon after removal of the resulting water, a heating reaction was conducted at the internal pressure of 5 mmHg and at the internal temperature of 185C for 96 hours to give 90 g of an almost white polymer. The resulting polymer has a weight-average molecular weight of 29,600 and a dis-persity of 1.85.
In order to determine the remaining catalyst in the resulting polymer, detection of the remaining catalyst was carried out in the manner of Example l, with the result that there was no contamination of catalyst observed.
Example 4 A reaction was conducted in the manner of Example l, except that 160 g of a 85 % a~ueous solution of lactic ~256~3g~
acid, 38 g of glycolic acid and 17.4 g of activated clay were used, and there was obtained 122 g of an almost white copolymer, which has a weight-average molecular weight of 20,100 and a dispersity of 1.70, and shows a copolymerization composition of lactic acid and glycolic acid of 76 mol % : 24 mol % (79.7 weight % : 20.3 weight %).
In order to determine the xemaining catalyst in the resulting copolymer, detection of the remaining catalyst was carried out in the manner of Example 1, with the result that there was no contamination of catalyst observed.
Example 5 Charged were 191 g of a 85 ~ aqueous solution of lactic acid, 17.5 g of glycolic acid and 9 g of acid clay, and after removal of the distilled water, a heating reaction was carried out at the internal pressure of 3 mmHg and at the internal temperature of 170C for 96 hours to give 130 g of an almost white copolymer. The resulting copolymer has a weight-average molecular weight of 28,100 and a dispersity of 1.73, and a copolymeriza-tion composition of lactic acid and glycolic acid of 89 mol % : 11 mol %~90.9 weight ~ : 9.1 weight %).
The similar results were obtained, when the similar reaction was carried out with aluminum silicate, bentonite and kaolin being used as a catalyst instead.
In order to determined the remaining catalysts in the resulting copolymers, detection of the remaining catalysts was conducted in the manner of Example 1, with the result that there was no contamination of catalysts observed.
Example 6 146 g of a 93 % aqueous solution of lactic acid and 38 g of glycolic acid was used, a heating reaction was ~2S6Ei3~
conducted at the temperature of 202C for 6 hours, whereby a copolymer with a welght-average molecular weight of 2,700 and a composition of lactic acid and glycolic acid of 75 mol % : 25 mol % was obtained.
Weighed in the same polymerization apparatus as usedin Example 1 were 100 g of this copolymer and 10 g of aeid clay, and heating was earried out under redueed pressure of 5 mmHg at internal temperature of 180C for 50 hours.
The reaction solution was eooled to room temperature, and 500 ml of methylene ehloride was added to it, followed by stirring to a solution. Then, the acid clay was removed by filtration using Toyo Filter Paper No. 131 and the filtrate was concentrated to dryness to give 82 g of an almost colorless polymer, which showed a weight-average moleeular weight of 23,700 and a dispersity of 1~73, and a eopolymerization composition of laetie acid and glycolie acid of 75 mol % : 25 mol %(78.~ weight ~: 21.2 weight ~).
In order to determine the remaining eatalyst in the resulting polymer, deteetion of the remaining catalyst was carried out in the manner of Example 1, with the result that there was no contamination of catalyst observed.
Example 7 A reaetion was eonducted in the manner of Example 6, exeept that 97 g of laetie acid dimer (Lactic acid lactate) and 54 g of glycolic acid dimer (Glycologlycolic acid) and 7.5 g of acid clay were used, and there was obtained 98 g of an almost white copolvmer, which has a weight-average molecular weight of 21,000 and a dis-persity of 1~ 75, and a copolymerization composition oflaetic aeid and glycolie acid of 59.5 mol % : 40.5 mol (64.6 weight % : 35.4 weight %).
In order to determine the remaining catalyst in the resulting copolymer, detection of the remaining catalyst was carried out in the manner of Example 1, with the result that there was no contaminatiOn of eatalyst observed.
The present invention relates to a polymer of lactic acid or glycolic acid, a copolymer of lactic acid and glycolic acid and a method for producing the polymer or the copolymer by a polycondensation reaction in the presence of a solid inorganic acid catalyst.
In recent years, degradable polymers have attracted a good deal of attention, for example, as readily degradable poly-mers serving to mitigate environmental pollution and also as biodegradable polymers for medical use.
A method for producing a copolymer of lactic acid and glycolic acid is disclosed in UOS. Patent No. 4,273,920. In this Patent, it is stated that a copolymer substantially free of poly-merization catalyst is obtained by reacting lactic acid with glycolic acid in the presence of a readily removable strong acid ion-exchange resin, and removing the resin therefrom.
However, the copolymers produced by the above- described method all exhibit a dispersity in molecular weight as high as nearly 3 or more, an~ in use, give great complexity in fac~ors involving solubility and other aspects, thus presenting major problems in controlling such factors. Therefore, they cannot be said to be very favorable, when they are used, for example, as a biodegradable polymer for medical use. In addition, this method allows the strong acid ion exchange resin being used as a poly-merization catalyst to deteriorate due to heat during a polycon-densation reaction under heating and to get dissolved in the resulting copolymer, thereby contributing to the development of coloration oE the copolymer. Furthermore, it is difficult to eliminate such coloration, and it is practically impossible to remove such coloration completely, and the coloration shows that the catalyst, i.e. the strong acid ion-exchange resin, cannot be completely removed. Such coloration not only diminishes value as an article of commerce but also is undesirable by virtue of i~s impurities.
In view of such circumstances, the present inventors conducted repeatedly intensive research, and found a method for 3~
~5~i63~
producing a polymer of lactlc acid or glycolic acid and a copoly-mer of lactic acid and glycolic acid, which are effective and substantially free from the above-mentioned disad~antages. Based on this finding and a further research, the present inventors have completed the present invention.
The present invention is directed to:
(1) A polymer or copolymer of lactic acid and/or glycolic acid, which has a weight-average molecular weight of not less than about 5,000 and a dispersity of about 1.5 to 2, and (2~ A method for producing a polymer or copolymer of lactic acid and/or glycolic acid comprising subjecting lactic acid and/or glycolic acid to a polycondensation reaction, with a solid inorganic acid catalyst as a polycondensation catalyst.
In the method of the present invention, lactic acid and/or glycolic acid are/is employed, as the starting materials, in the form of crystals, powders or granules as such, or in the form of an aqueous solution. The concentration of the solution is arbitrarily selected, preferably as high as possihle, and more preferably not lower than about 85 ~ (w/w).
As the lactic acid and/or glycolic acid starting material, low molecular polymers of lactic acid or glycolic acid or low molecular copolymers of lactic acid and glycolic acid may be employed in the present method.
Such low molecular polymers of ]actic acid or glycolic acid, may be oligomers (e.g. dimers, trimers, etc.) of lactic acid, or glycolic acid.
One SUCh low molecular polymer or copolymer starting material is produced by sub~ecting lactic acid and/or glycolic acid to a polycondensation reaction in the absence of a catalyst under for example about 100 to 150C/350 to 30 mmHg ~or more than about 2 hours, normally about 2 to 10 hours, more preferably while increasing the temperature and reducing the pressure stepwise from about 105C/350 mmHg to 150C/30 mmHg for about 5 to 6 hours, to remove water. In this process, a low molecular polymer or co-polymer of molecular weight of about 2000 to 4000 is obtained.
~256638 Furthermore~ as the low molecular copolymers, there are mentioned, or example, ones which are obtainable by processes described in Kogyo Kagaku Zasshi (Journal of the Chemical Society of Japan), vol. 68, pp. 983-986 (1965), i.e. lactic acid and gly-colic acid are reacted in a normal atmospheric pressure and in the absence of a catalyst at 202C for 6 hours, or U.S. Patent No. ~,362,511, i.e. lactic acid and glycolic acid are reacted at a temperature of 200~C holding the mixture at that temperature for a period of about 2 hours and subsequently continuing the heating for another period of about 2 hour under vacuum.
The ratio of lactic acid to glycolic acid in the copoly-mer, when the object compound is a copolymer of these compounds, is preferably about 50 to 95 weight % of lactic acid and about 50 to 5 weight % of glycolic acid, preferably about 60 to 95 weight of lactic acid and about 40 to 5 weight ~ of glycolic acid, more preferably about 60 to ~5 weight % of lactic acid and about ~0 to 15 weight % oE glycolic acid. The ratio is more preferably about 75+2 mol ~ of lactic acid and about 25+2 mol ~ of glycolic acid~
A solvent may be employed, when the starting material is in crystal, powder or granule form. Such solvents are, for example, water, methanol, ethanol and acetone.
The solid inorganic acid catalyst inclu3es acid clay, activated clay, bentonite, kaolin, talc, aluminum silicate, mag-nesium silicate, alumina bolia, and silicic acid. These can all be used, either solely or as a mixture and each may be employed as such or after being washed with, for example, hydrochloric acid at a concentration of 5 to 20 ~, to remove metal ions, if necessary.
The amount of the solid inorganic acid catalyst used in the present method is normally about 0.5 to 30 ~ w/w, preferably abo~t 1 to 20 ~ w/w, based on the total amount of lactic acid and glycolic acid. The catalyst can be used in one or several portions.
The catalyst may be added to the reaction system during the reaction.
The method is preferably carried out with heating and ~:256~;31~
under reduced pressure. The heating is carried out by heating reaction system at about 150 to 250~C, preferably about 150 to 200C. The reduced pressure is normally about 30 to 1 mmHg, preferably about 10 to 1 mmHg. The reaction time of the present polycondensation reaction is normally not less than about 10 hours, preferably about 10 to 150 hours, more preferably about 10 to 100 hours~
When lactic acid and/or glycolic acid are/is employed as the starting materials, the following conditions are preferred:
Heating under reduced pressure at about 100 to 150C/350 to 30 mmHg for not less than about 2 hours, normally about 2 to 10 hours, for example, for about 5 to 6 hours while increasing the temperature and the degree of reduced pressure stepwise to about 105C/350 mmHg to 150C/30 mmHg, to remove water, followed by a dehydration polycondensation reaction at about 150 to 200C/10 to 1 mmHg for not less than about 10 hours, normally up to about 100 hours may be adequate.
When a low molecular polymer or copolymer is employed as starting material, preferred reaction conditions are as follows-A dehydration polycondensation reaction is carried out at about150 to 200C/10 to 1 mmHg for not less than about 10 hours, nor-mally up to about 100 hours may be adequate.
After termina-tion of the reaction, the objective polymer or copolymer is readily obtained by removing the used solid in-organic acid catalyst. The solid acid catalyst oE the present invention can easily be removed for example by filtration with suction using ordinary qualitative filter paper. Mere hot filtra-tion of the reaction solution or filtration after dissolution of the polymer or copolymer in a suitable solvent such as methylene chloride, dichloroethane, chloroform or acetone, (in an amount of about lO-times that of the polymer or copolymer), is sufficient.
No subsequent treatment is required, either in the former case in which the reaction solution is filtered as such and the solvent is concentrated or distilled off, or in the latter case in which the reaction solution is filtered after being dissolved in a solvent.
~s~
If desired, a conventional separation may be used, for example, by pouring the filtered reaction solution, either directly or in the form of a concentrated Eiltrate where a solvent is used, into a large amount of a precipitant. If required, further purification may be carried out by reprecipitation, etc.
The present invention provides a polymer or copolymer consi~ting of lactic acid and/or glycolic acid units having a weight-average molecular weight oE not less than about 5,000, preferably about 5,000 to 30,000, and having a dispersity of about 1.5 to 2. Furthermore, the polymer or copolymer is colorless to almost white.
As the polymer or copolymer oE the present invention has a low degree of dispersity, the distribution of the molecular weight of the polymer or copolymer is not wide.
Furthermore, as the solid inorganic acid catalyst is insoluble in the polymer or copolymer and in a solven'c, the catalyst is substantially completely removed from the reaction product and the resulting polymer or copolymer is substantially free of catalyst discoloration.
The polymer or copolymer obtained can be utilized as a base for drug preparation. For example, by incorporating steroid hormones, peptide hormones or anti-tumor agents, etc. into them for embedded or microcapsule type controlled release preparations or by preparing fine particles containing an ~256 E;3~
anti-tumor agent to process into a therapeutlc agent for embolization.
The ~periment Examples and Examples are described below to illustrate the present invention in more detail.
Experimen _Example 1 To 160 g (1.5 mole as lactic acid) of a 85 %
aqueous solution of lactic acid was added 6.8 g of a solid acid catalyst, and heating under reduced pressure was carried out for 6 hours under the stepwise varyins conditions of lO0 to 150C/350 to 30 mmHg under a stream of nitrogen gas to remove the resulting water.
Subsequently, 6.8 g of the solid acid catalyst was added additionally, followed by a dehydration polycondensation reaction at 175C/5 mmHg for 72 hours.
Shown in Table 1 is the relationship between reaction time and weight-average molecular weight attained and its dispersity in the production of lactic acid polymers.
Also shown in Table l for the purpose of comparison are the results obtained with Dowe~ 50 (a cross-linked polystyrene resin, Dow Chemical Co., U.S.A.), a strongly acidic ion-exchange resin being commercially available, which was used as a polymerization reaction.
The weight-average molecular weight and dispersity (d;spersity = weiaht-averaae molecular weignt) in th~
number-aver2ge molecular we1ght present specification were measured by gel permea~ion chromatography utilizing the standard polystyrene with the known molecular weight.
* Trade Mark ~L~S~
Table 1 Type of polyme~ization catalysts and molecular weight attained and its dispersity Catalyst: Alumin~m Actlvated Acid clay silicate clay Dowex 50W
Added amount (1) 6.8 g 6.8 g 6.8 g 6.8 gAdded amount (2) 6.8 g 6.8 g 6.8 ~ 6.8 g . _ _ . _ . _ _ . . _ _ ~ . _ . . _ _ 12 hours of 6,200 5,000 reaction time (1.71) (1.63) 24 hours o~ 8,90011,200 8,800 s,ioo reaction time (1.88) (1.66) (1.61) (2.43) 36 hours of ï6,60015,600 12,700 1_,400 reaction time (1.72) (1.6~) ' (1.62) (2.63) 48 hours of 19,100 16,700 1~,900 reaction time _ (1.65) (1.50) (2.80) 60 hours oE 26,50022,500 19,900 17,800 reaction time (1.73) (1.66) (1.67) (2.81) i2 hours of 29,300*25,800 23,700 20,200 reaction time (1.77) (1.6c) (1.81) (2.80) Appearance ofAlmostAlmost Almost Dark brown (thë
the polymer**whitewhite white color deepens _ with time) - -- -- _ . ._ Note: * ; Reaction time of nearly 65 hours.
** ; Each of the polymers obtained after the respective reactlon time was dissolvea in methylene chloride of the volume four tlmes that of the polvmer, and the solution was filtered using Toyo'Filter Paper No. 131 [?oyo Roshl Co., Ltd., Japan] to remove the c-_al st, and then concentrated to distill o f the solvent; the resulting polymers were examined in accordance with JIS K 8004-2 (namely, a~out 3 g of the specimen is taken on a watch glass, which is placed on a sheet of white paper and examined.).
In the Table 1, the added amount (1) of catalyst and the added amount (2) of catalyst deno-te an initially added amount of catalyst and an amount of catalyst additionally added at the time of the polycondensation ' Trade Mark ~2S6~i313 s reaction at 175C/5 mmHg after removal of water, respectively while the reaction time means that at 175C/5 mmHg. In the table, the parenthesized value beneath the molecular weight attained indicates a dispersity.
As is clear from Table 1, the present invention can permit readily the production of high molecular weight polymer with a weight-average molecular weight of not less than about 5,000 being almost free from polymerization catalyst, whereby the resulting polymers show that colored appearance is hardly observed and the polymers have dispersity of not more than 2, with the polymerization reaction rate being evidently promoted by the addition of the catalyst.
Ex~eriment Exam~le 2 After 160 g (1.5 mole) of a 85 % aqueous solution of lactic acid and 38 g tO.5 mole) of glycolic acid were mixed, 8.7 g of a solid acid catalyst was added to the mixture, and heating under reduced pressure was carried out at 100 to 150C/350 to 30 mmHg under a stream of nitrogen gas for 6 hours to remove the distilled water.
Subsequently, 8.7 g of the solid acid catalyst was adaed additionally, followed by a dehydration condensation reaction at 175C/6 to 5 mmHg for 72 hours.
Shown in Table 2 is the relationship between reaction time and weight-average molecular weight attained in the production of copolymers of lactic acid and glycolic acid.
Also, shown in Table 2 for the purpose of comparison are the results obtained with a strongly acidic ion-exchange resin (Dowex*50W) which was used as a polymerization catalyst.
* Trade Mark ~5~;~3~
g Table 2:
Type of polymerlzation catalysts and molecular weights attained Catalyst: Type Aluminum Activated Acid clay silicate clayDowex 50W
.
Added amount (1) 8.7 g 8.7 g 8.7 g 8.7 g Added amount (2) 8.7 g 8.7 g 8.7 g 8.7 g 12 hours of 5,100 reaction time (1.72) 24 hours of 12,600 11,700 10,200 10,500 10 reaction time (1.72) (1.72) _ (1.69) (2 47) 36 hours of 18,600 17,800 16,100 1~,400 reaction time (1.73) (1.74) (1.65) (2.44) 48 hours of 22,900 22,000 20,400 18,900 reaction time (1.65) (1.64) (1.64) (2.46) 60 hours of 25,400 25,800 22,800 22,200 reaction ti~e (1.68) (1.68) (1.63) _ (2.47) 15 72 hours of 27,900 28,600 26,000 25,300 reac-tion ti~e (1.76) (1.66) (1.63) (2.76) Almost AlmostAlmost Dark brown (the the polymer* white white white color deepens Note: ~ ; Each of the polymers obtained after the respective reaction time was dissolved in methylene chloride of the volume :Eour times that of the polymer, and the solution was filtered using Toyo Filter Paper No. 131 to remove the catalyst, and then, concentrated to distill off the solvent; the resulting polymers were examined in accordance with JIS K 8004-2 (namely, about 3 g of the specimen is taken on a watch glass, which is placed on a sheet of white paper and examined.).
In the Table 2, the added amount (1) of catalyst and the added amount (2) of catalyst denote an initially added amount of catalyst and an amount of catalyst additionally added at the time of the polycondensation reaction at 175C/5 mmHg after removal of water, respectively, while the reaction time means tha-t at 175C/5 mmHg. In the Table 2, the parenthesized value ~LZ5~;63~
. - 10 -beneath the molecular weiqht attained indicates a dispersity.
As is clear from Table 2, the present invention can - permit readily the production or high molecular weight lactic acid-glycolic acid copolymers with a weight-average molecular weight of not less than about 5,000 being almost free from polymerization catalyst, whereby the resulting copolymers show that colored appearance is hardly observed, and all has dispersity as small as not more than 2, with the polymerization reaction rate being evidently promoted by the additlon of the catalyst.
Furthemore, analysis of nuclear magnetic resonance spectrometry on said resulting copolymer of the present invention in CDC13 solution indicates the followin~
composition of lactic acid and glycolic acid.
~ ~ 2~i3~
Copolymer ratio of the present copolymer mol %
(weight %) Catalist Aluminum Activated Reaction~~- _ Acid Clay time ~ _ _ slllcate Clay 12 hours _ _ _ 75.5:24.5 (79.3:20.7) ._ __ _ ___ _ .. __ 75 ~25 75 ~25 75.5:24.5 24 hours l(78.8:21.2) (78.8:21.2) (79.3:20.7) ... _ .__ I _ ._ ', 75 :25 75 :25 75 :25 36 hours (78.8:21.2) (78 8:21.2) (78.8:21.2) ._ ,,_ , __ 75 :25 76 :24 75 :25 48 hours (78.8:21.2) (79.7:20.3) (78.8:2102) _ _ _ _ _ !
75.5:24.5 75.5:24.5 76 :24 60 hours (79.3:20.7) (79.3:20.7) (79.7:20.3) . _ .
75.5:24.5 75.5:24.5 75.5:24.5 1 72 hours (79.3:20.7) (79.3:20.7) (79.3 20.7)1 ~:~S~63~
Example 1 Placed in a four-necked flask equipped with a thermometer, condenser and inlet tube for nitrogen gas were 160 g of a 85 % aqueous solution of lactic acid and 13.6 g of acid clay, and heating under reduced pressure was carried out under a stream of nitrogen gas over the period of 6 hours, while increasing the internal temperature and the degree of internal reduced pressure stepwise from 105C and 350 mmHg to 150C and 30 mm~g, and then the resulting water was removed. Successively, heating was conducted under reduced pressure of 3 mmHg and at the internal temperature of 175C for 50 hours.
The reaction solution was cooled to room temperature, and 400 m~ of methylene chloride was added to it, followed by stirring to a solution. Then, the acid clay was removed by fil-tration using Toyo Filter Paper No 131, and the filtrate was concentrated to dryness to give 100 g of an almost colorless polyer, which has a weight-average molecular weight of 22,000 and a dispersity of 1.75.
In order to determine the remaining catalyst in the resultina copolymer, a specimen of the copolymer was weighed out onto a dish of platinum and subjected to a fusing treatment with sodium carbonate, and then aluminum and silicon were determined colorimetrically by ~S~631~
application of the aluminon method and molybdenum blue method, with the result that neither of the metals was detected, leading to the conclusion that there was no contamination of the catalyst observed.
Example 2 A reaction was carried out in the manner of Example 1, except that 27.2 g of aluminum silicate was used as a catalyst, and there was obtained 92 g of an almost colorless polymer, which has a weight-average molecular weight of 21,900 and a dispersity of 1.70. The similar results were obtained when kaolin and talc were used in place of aluminum silicate as a catalyst.
In order to determine the remaining catalysts in the resulting copolymers, detection of the remaining catalysts was carried out in the manner of Example l, with the result that there was no contamination of catalysts observed.
Example 3 In the manner of Example 1, 160 g of a 85 % aqueous solution of lactic acid was used, but 6.8 g of activated clay was charged in place of acid clay, whereupon after removal of the resulting water, a heating reaction was conducted at the internal pressure of 5 mmHg and at the internal temperature of 185C for 96 hours to give 90 g of an almost white polymer. The resulting polymer has a weight-average molecular weight of 29,600 and a dis-persity of 1.85.
In order to determine the remaining catalyst in the resulting polymer, detection of the remaining catalyst was carried out in the manner of Example l, with the result that there was no contamination of catalyst observed.
Example 4 A reaction was conducted in the manner of Example l, except that 160 g of a 85 % a~ueous solution of lactic ~256~3g~
acid, 38 g of glycolic acid and 17.4 g of activated clay were used, and there was obtained 122 g of an almost white copolymer, which has a weight-average molecular weight of 20,100 and a dispersity of 1.70, and shows a copolymerization composition of lactic acid and glycolic acid of 76 mol % : 24 mol % (79.7 weight % : 20.3 weight %).
In order to determine the xemaining catalyst in the resulting copolymer, detection of the remaining catalyst was carried out in the manner of Example 1, with the result that there was no contamination of catalyst observed.
Example 5 Charged were 191 g of a 85 ~ aqueous solution of lactic acid, 17.5 g of glycolic acid and 9 g of acid clay, and after removal of the distilled water, a heating reaction was carried out at the internal pressure of 3 mmHg and at the internal temperature of 170C for 96 hours to give 130 g of an almost white copolymer. The resulting copolymer has a weight-average molecular weight of 28,100 and a dispersity of 1.73, and a copolymeriza-tion composition of lactic acid and glycolic acid of 89 mol % : 11 mol %~90.9 weight ~ : 9.1 weight %).
The similar results were obtained, when the similar reaction was carried out with aluminum silicate, bentonite and kaolin being used as a catalyst instead.
In order to determined the remaining catalysts in the resulting copolymers, detection of the remaining catalysts was conducted in the manner of Example 1, with the result that there was no contamination of catalysts observed.
Example 6 146 g of a 93 % aqueous solution of lactic acid and 38 g of glycolic acid was used, a heating reaction was ~2S6Ei3~
conducted at the temperature of 202C for 6 hours, whereby a copolymer with a welght-average molecular weight of 2,700 and a composition of lactic acid and glycolic acid of 75 mol % : 25 mol % was obtained.
Weighed in the same polymerization apparatus as usedin Example 1 were 100 g of this copolymer and 10 g of aeid clay, and heating was earried out under redueed pressure of 5 mmHg at internal temperature of 180C for 50 hours.
The reaction solution was eooled to room temperature, and 500 ml of methylene ehloride was added to it, followed by stirring to a solution. Then, the acid clay was removed by filtration using Toyo Filter Paper No. 131 and the filtrate was concentrated to dryness to give 82 g of an almost colorless polymer, which showed a weight-average moleeular weight of 23,700 and a dispersity of 1~73, and a eopolymerization composition of laetie acid and glycolie acid of 75 mol % : 25 mol %(78.~ weight ~: 21.2 weight ~).
In order to determine the remaining eatalyst in the resulting polymer, deteetion of the remaining catalyst was carried out in the manner of Example 1, with the result that there was no contamination of catalyst observed.
Example 7 A reaetion was eonducted in the manner of Example 6, exeept that 97 g of laetie acid dimer (Lactic acid lactate) and 54 g of glycolic acid dimer (Glycologlycolic acid) and 7.5 g of acid clay were used, and there was obtained 98 g of an almost white copolvmer, which has a weight-average molecular weight of 21,000 and a dis-persity of 1~ 75, and a copolymerization composition oflaetic aeid and glycolie acid of 59.5 mol % : 40.5 mol (64.6 weight % : 35.4 weight %).
In order to determine the remaining catalyst in the resulting copolymer, detection of the remaining catalyst was carried out in the manner of Example 1, with the result that there was no contaminatiOn of eatalyst observed.
Claims (19)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method for producing a polymer of lactic acid or glycolic acid or a copolymer of lactic acid and glycolic acid, which comprises subjecting a member selected from the group con-sisting of lactic acid, glycolic acid or a combination thereof, to a polycondensation reaction with a solid inorganic acid cata-lyst as a polycondensation catalyst, wherein the solid inorganic acid catalyst is selected from the group consisting of acid clay, activated clay, bentonite, kaolin, talc, aluminium silicate, mag-nesium silicate, alumina bolia and silicic acid.
2. A method according to claim 1, wherein the weight-average molecular weight of the polymer or copolymer is not less than about 5,000 and the dispersity of the polymer or copolymer is about 1.5 to 2.
3. A method according to claim 1, wherein the weight-average molecular weight of the polymer or copolymer is about 5,000 to 30,000 and its dispersity is about 1.5 to 2.
4. A method according to claim 1, 2 or 3, wherein lactic acid is polymerized to obtain a polymer of lactic acid.
5. A method according to claim 1, 2 or 3, wherein a combin-ation of lactic acid and glycolic acid is polymerized to obtain a copolymer of lactic acid and glycolic acid.
6. A method according to claim 1, 2 or 3, wherein a com-bination of lactic acid and glycolic acid is polymerized to obtain a copolymer having a ratio of about 50 to 95 weight % of lactic acid and about 50 to 5 weight % of glycolic acid.
7. A method according to claim 1, 2 or 3, wherein a combin-ation of lactic acid and glycolic acid is polymerized to obtain a copolymer having a ratio of about 60 to 95 weight % of lactic acid and about 40 to 5 weight % of glycolic acid.
8. A method according to claim 1, 2 or 3, wherein a combin-ation of lactic acid and glycolic acid is polymerized to obtain a copolymer having a ratio of about 60 to 85 weight % of lactic acid and about 40 to 15 weight % of glycolic acid.
9. A method according to claim 1, 2 or 3, wherein a combin-ation of lactic acid and glycolic acid is polymerized to obtain a copolymer having a ratio of about 75?2 mol % of lactic acid and about 25?2 mol % of glycolic acid.
10. A method according to claim 1, 2 or 3, wherein the solid inorganic acid catalyst is kaolin.
11. A method according to claim 1, 2 or 3, wherein the solid inorganic acid catalyst is one selected from the group consisting of acid clay, activated clay, kaolin, bentonite and aluminium silicate.
12. A method according to claim 1, 2 or 3, wherein the solid inorganic acid catalyst is acid clay.
13. A method according to claim 1, 2 or 3, wherein the solid inorganic acid catalyst is activated clay.
14. A method according to claim 1, 2 or 3, wherein the solid inorganic acid catalyst is alauminium silicate.
15. A method according to claim 1, 2 or 3, wherein a combination of lactic acid and glycolic acid is polymerized to obtain a copolymer having a ratio of about 50 to 95 weight % of lactic acid and about 50 to 5 weight % of glycolic acid and the solid inorganic acid catalyst is selected from the group consisting of acid clay, activated clay, bentonite, kaolin, talc, aluminium silicate, magnesium silicate, alumina bolia and silicic acid.
16. A method according to claim 1, 2 or 3, wherein a combination of lactic acid and glycolic acid is polymerized to obtain a copolymer having a ratio of about 60 to 85 weight % of lactic acid and about 40 to 15 weight % of glycolic acid and the solid inorganic acid catalyst is one selected from the group consisting of acid clay, activated clay, kaolin, bentonite and aluminium silicate.
17. A homopolymer lactic acid or glycolic acid, which has a weight-average molecular weight of not less than about 5,000 and a dispersity of about 1.5 to 2.
18. A polymer according to claim 17, wherein the weight-average molecular weight is about 5,000 to 30,000.
19. A polymer according to claim 17 or 18, which is a homopolymer of lactic acid.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP140356/1984 | 1984-07-06 | ||
| JP59140356A JPH0678425B2 (en) | 1984-07-06 | 1984-07-06 | New polymer manufacturing method |
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| CA000486142A Expired CA1256638A (en) | 1984-07-06 | 1985-06-28 | Polymer and its production |
| CA000486283A Expired CA1236641A (en) | 1984-07-06 | 1985-06-28 | Copolymer of lactic acid and glycolic acid and method for producing same |
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| CA000486283A Expired CA1236641A (en) | 1984-07-06 | 1985-06-28 | Copolymer of lactic acid and glycolic acid and method for producing same |
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| US (2) | US4683288A (en) |
| EP (2) | EP0171907B2 (en) |
| AT (2) | ATE39936T1 (en) |
| BG (1) | BG61520B2 (en) |
| CA (2) | CA1256638A (en) |
| DE (2) | DE3567471D1 (en) |
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| US1995970A (en) * | 1931-04-04 | 1935-03-26 | Du Pont | Polymeric lactide resin |
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-
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- 1985-06-28 CA CA000486142A patent/CA1256638A/en not_active Expired
- 1985-06-28 CA CA000486283A patent/CA1236641A/en not_active Expired
- 1985-07-03 DE DE8585304734T patent/DE3567471D1/en not_active Expired
- 1985-07-03 DE DE8585304733T patent/DE3567470D1/en not_active Expired
- 1985-07-03 EP EP85304733A patent/EP0171907B2/en not_active Expired - Lifetime
- 1985-07-03 EP EP85304734A patent/EP0172636B2/en not_active Expired - Lifetime
- 1985-07-03 AT AT85304734T patent/ATE39936T1/en not_active IP Right Cessation
- 1985-07-03 US US06/751,671 patent/US4683288A/en not_active Expired - Lifetime
- 1985-07-03 US US06/751,672 patent/US4677191A/en not_active Expired - Lifetime
- 1985-07-03 AT AT85304733T patent/ATE39935T1/en not_active IP Right Cessation
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1991
- 1991-12-24 SG SG1081/91A patent/SG108191G/en unknown
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1992
- 1992-03-12 HK HK195/92A patent/HK19592A/en not_active IP Right Cessation
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1994
- 1994-02-11 BG BG98460A patent/BG61520B2/en unknown
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| US4677191A (en) | 1987-06-30 |
| DE3567471D1 (en) | 1989-02-16 |
| HK19592A (en) | 1992-03-20 |
| CA1236641A (en) | 1988-05-10 |
| EP0172636A1 (en) | 1986-02-26 |
| EP0171907B1 (en) | 1989-01-11 |
| US4683288A (en) | 1987-07-28 |
| ATE39936T1 (en) | 1989-01-15 |
| ATE39935T1 (en) | 1989-01-15 |
| EP0172636B1 (en) | 1989-01-11 |
| SG108191G (en) | 1992-06-12 |
| EP0171907A1 (en) | 1986-02-19 |
| EP0172636B2 (en) | 1992-11-11 |
| BG61520B2 (en) | 1997-10-31 |
| EP0171907B2 (en) | 1994-08-10 |
| DE3567470D1 (en) | 1989-02-16 |
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