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Synthesis of Dimethyl Succinate Using Carbon Monoxide and Its Application to Biodegradable Polymers
B i o d e g r a d a b l e Piaslics and P o l y m e r s 596
Y . D o i and K . Fukuda ( e d i i o r s ) 1994 Elsevier S c i e n c e B . V .
Synthesis of Dimethyl Succinate Using Carbon Monoxide and Its Application to Biodegradable Polymers Ikuo Takahashi and Kenji Koumoto Research Institute of Innovative Technology for the Earth (RITE), c/o National Institute of Materials and Chemical Research, 1-1 Higashi, Tsukuba, Ibaraki, 305, Japan AkioMatsuda and Takashi Masuda* National Institute of Materials and Chemical Research, 1-1 Higashi, Tsukuba, Ibaraki, 305, Japan
1. Abstract An effective synthesis of dimethyl succinate was carried out by hydroesterification of metiiyl acrylate in the presence of Co2(CO)g-pyridine derivative catalyst. This reaction is characterized by a single-stage process which proceeds at low carbon monoxide pressure. 3,5-Lutidine was the most effective promoter among various pyridine derivatives on the hydroesterification of methyl acrylate by using Co2(CO)8. High molecular weight aliphatic polyesters were obtained from dimethyl succinate and some glycols by transesterification. The polyesters thus produced gave strong film and showed biodegradability by soil burying test. Enzymatic degradation of the copolymer increased with increasing the content of comonomer in the polymer chain.
2.
Introduction Many works on aliphatic polyesters have been carried out, and efforts have been made to
use them in the industry. But, so far, only few reports dealing with industrial utilization of aliphatic polyesters have appeared because of their properties such as low melting point, low heat resistance and a trend to hydrolysis. However, application of aliphatic polyester to biodegradable polymer has recentiy been attracting attention. In this study, we describe results of synthesis of dimethyl succinate using carbon monoxide and its application to biodegradable aliphatic polyesters.
597
3.
Experimental Tlie hydroesterification of methyl acrylate was carried out in the presence of Co2(CO)8-
pyridine derivative catalyst in a stainless steel autoclave under CO pressure of 50kg/cm2. Polymerization of dimetyl succinate (SDM) with glycols was carried out by transesterification at 160-220°C in the presence of Zn(OAc)2.2H20 catalyst for 8-12hrs.
4. Results and Discussion In this paper, we report the synthesis of dimethyl succinate using carbon monoxide and its application to biodegradable aliphatic polyesters [1]. We have developed a new technology for synthesizing dimethyl succinate in good yield in a single-stage synthesis process by using methyl acrylate,carbon monoxide and methanol as the raw material. An effective synthesis of dimethyl succinate was carried out by hydroesterification of methyl acrylate in the presence of Co2(CO)8-pyridine derivative catalysts as shown in Equation(l). Dimethyl methylmalonate and dimethyl-y-ketopimelate were found as by-products. CH3OC ^ C02(C0)8/3.5-Liitidine - ^ ^ C 0 C H 3 O
.
^
CO.CH3OH
C O / H 2 50kg/cm2 1 1 0 ° C 1.5hr
Ö
COCH3 Ö
CH3OGA COCH3
(1)
η " ^ ° CH30^(CH2)^{CH2)^COCH3< 1 %
Table 1 shows effect of various pyridine derivatives on the hydroesterification of methyl acrylate by using Co2(CO)8. 3,5-Lutidine was found to be the most effective promoter. The synthesis was possible at a lower CO pressure of 50Kg/cm2 than the originally reported pressure [2], and the yield was approximately 90% in the presence of Co-3,5-lutidine Table 1. Effect of various pyridine derivatives on the hydroesterification of methyl acrylate by using Co2(CO)8 . ^ ) Run
1 2 3 4 5
Base
3,5-Lutidine Pyridine 3,4-Lutidine 2,4-Lutidine 4-Dimethylaminopyridine
Conversion (%) 98.3 99.0 92.0 11.0 0.0
Selectivity(%) ^ ) SDM 90.6 86.0 80.3 40.0
-
MMDM
MP
4.6 3.0 6.8 4.8
2.7 2.5 3.5 55.0
-
-
a)Reaction conditions: Methyl acrylate; lOOmmol, Methanol; ISOmmol, Toluene;30g,Co2(CO)8; 5mmol, Base;15mmol , C 0 pressure; SOkg/cm^, H2 content of the carbon monoxide;0.5%, Reaction Temp.;110°C , Reaction time; 1.5hr. b ) S D M : Dimethyl succinate, M M D M : Dimethyl methylmalonate, M P : Methyl propionate
598
catalyst. Further, hydroesterification of butadiene with carbon monoxide and methanol using Co-pyridine catalyst gave dimethyl adipate (ADM) in good yield [3]. By-products were dimethyl 2-methylglutarate, dimethyl ethylsuccinate and dimethyl propylmalonate. These aliphatic dimethylesters were polymerized with various glycols to synthesize aliphatic polyesters, and high molecular weight polyesters were obtained by using these dimethylesters [4]. For example, dimethyl succinate was polymerized with glycols by transesterification as shown by Equation(2). CH3COOCH2CH2COOCH3
4-
HOROH — • 4 C O C H 2 C H 2 C O O R O h r + 2 C H 3 O H (2)
Table2 shows results of the polymerization and biodegradation test of the polyesters in the soil (compost). The molecular weight of the aliphatic polyesters was between 16,0(X) and 40,(XX). The melting point of the polyesters was between 70 and 119 °C, and the thermal Table 2, Run
Biodegradation test of some kinds of polyesters in soil (compost)^)
Monomei*>)(mol ratio)
Rl-(COOCH3)2 R2-(OH)2 1 2 3 4 5 6 7 8 9
Molecular weight (before test) MnxlO'^ Mw/Mn
SDM EG SDM 1,4BG SDM CHDM ADM CHDM SDM/ADM 1,4BG 80 / 20 SDM/MMDM 1,4BG 80 / 20 SDM EG/1,4BG 30 / 70 ADM 1,4BG/CHDM 40 / 60 Polycaprolactone(H-7 Daicel)
Biodegradation (after test) Weightless Molecular weight (%) MnxlO-^ Mw/Mn
3.43 3.74 3.09 1.78 2.72
1.7 2.0 2.0 1.7 1.7
5.0 22.0 1.5 1.2 35.0
3.02 3.06 2.99 1.79 2.56
1.9 2.0 2.0 1.7 1.8
2.55
1.7
46.6
2.50
1.7
3.71
1.8
47.0
3.39
1.9
1.64
1.6
18.6
1.54
1.6
3.45
2.0
15.8
3.23
2.0
a) Degradation condition: Polymer film;40x40x0.15mm, Soil;Commercial compost, 30*C, 3(Mays. b) S D M (Dimethyl succinate), A D M (Dimethyl adipate), M M D M (Dimethyl methylmalonate), EG (Ethylene glycol), 1.4BG (1,4-Butanediol), C H D M (Cyclohexanedimethanol)
decomposition temperature exceeded 300°C. The biodegradation test of tiie aliphatic polyesters in the soil showed that when the polyester films were buried for 30 days, the weight loss of homopolyesters was accelated by the copolymerization which used the third component. The molecular weight of polymer samples did not practically change after the biodegradation test. From this result, it is suggested that biodegradation of the polyester samples occured on the surface of the polymer film. Table3 shows results of the copolymerization of dimethyl succinate and dimethyl adipate with l,4-butanediol(l,4-BG), and their molecular weight and thermal properties. The number-average molecular weight(Mn) of the aliphatic polyesters was between 20,000 and
599 Table 3. Copolymerization of dimethyl succinate (SDM) and dimetiiyl adipate(ADM) witii 1,4-butanedioia) Run
Feed ratio SDM/ADM
Thennal properties
Molecular weight
Monomer(mol ratio) Unit ratio SDM/ADM
MnxlQ-'* Mw/Mn
Tm
AHm
CQ
(J/g)
Td(-2wt%) CC)
1
100/0
100/0
3.44
1.8
119
84
-33
336
2
80/20
80/20
3.28
1.8
98
66
-43
310
3
60/40
60/40
3.26
1.8
71
45
-44
320
4
40/60
39/61
2.05
1.9
45
38
-50
318
5
20/80
20/80
2.66
1.8
50
60
-58
318
6
0/100
0/100
2.26
1.8
60
83
-60
322
a) Reaction condition: Catalyst Zn(OAc)2-2H20; 0.13mol%/diester, Temp;160'C, Time; 8-12hrs, Final degree o f vaccum; 0.3-0.5Torr b)Determined by GPC based on PSt. standards c)Tm and A H m values were measured by DSC at IsL heating.
35,000. These polyesters gave sturdy films when the number-average of moleculare weight exceeded 25,000. The melting point of the polyesters was between 45 and 119°C, and the thermal decomposition temperature exceeded 300°C. Glass transition temperature was between -33and-60°C. Entiialpy of melting (AHm) of the polyesters was between 38 and 84 J/g. Further, from this and related results obtained by measurement of X-ray diffraction of the polyesters, a 100 80
o Co 2
60
40 20 Οά 0
20
40
60
80
100
Ratio of A D M ( m o l % )
Fig.l.
Enzymaric degradation of polyesters ( ( S D M / A D M ) -1,4BG) with Lipase (from Rhizopus delemer ) Enzyme : Lipase {Rhizopus delemer),
120units
Polymer : Copolyester [ ( S D M / A D M ) -1,4-BG ] O.lg Conditions : 25mmol phosphate buffer ( P h 6.86) 20cc, 3 0 ° C . 20h.
600 correlation between AHm and the degree of crystallinity of the polyesters was observed. As shown in Table3, AHm of the polyesters decreased with increasing content of A D M to 60mol%. This decrease in AHm shows a decrease in the degree of crystalhnity of the poly estes. Fig.l shows results of enzymatic degradation of the copolyesters((SDM/ADM)-l,4-BG) using lipase from Rhizopus delemer. Degradation of polymer increased with increasing the content of ADM in the polymer chain. Biodegradation of aliphatic polyesters was accelated by the copolymerization. The polyesters of dimethyl adipate with 1,4-butanediol was degraded easily by Upase. Also, biodegradability of the copolymer was furthermore accelated with decreasing the degree of crystallinity of the copolymer.
Acknowledgement This work was supported by New Energy Industrial Technology Development C)rganization(NEDO).
References 1.1.Takahashi, et al., Abst. Papers presented at 65th National Meeting, Chem. Soc. Japan, p259 (1993). 2. A.Matsuda, Bull. Chem. Soc. Jpn., 42, 571(1969). 3. A.Matsuda, Bull, Chem. Soc. Jpn. 46, 524(1973). 4.1.Takahashi, et al.. Polymer preprints, Japan, 42, No.9, 3688(1993).
Y . D o i and K . Fukuda ( e d i i o r s ) 1994 Elsevier S c i e n c e B . V .
Synthesis of Dimethyl Succinate Using Carbon Monoxide and Its Application to Biodegradable Polymers Ikuo Takahashi and Kenji Koumoto Research Institute of Innovative Technology for the Earth (RITE), c/o National Institute of Materials and Chemical Research, 1-1 Higashi, Tsukuba, Ibaraki, 305, Japan AkioMatsuda and Takashi Masuda* National Institute of Materials and Chemical Research, 1-1 Higashi, Tsukuba, Ibaraki, 305, Japan
1. Abstract An effective synthesis of dimethyl succinate was carried out by hydroesterification of metiiyl acrylate in the presence of Co2(CO)g-pyridine derivative catalyst. This reaction is characterized by a single-stage process which proceeds at low carbon monoxide pressure. 3,5-Lutidine was the most effective promoter among various pyridine derivatives on the hydroesterification of methyl acrylate by using Co2(CO)8. High molecular weight aliphatic polyesters were obtained from dimethyl succinate and some glycols by transesterification. The polyesters thus produced gave strong film and showed biodegradability by soil burying test. Enzymatic degradation of the copolymer increased with increasing the content of comonomer in the polymer chain.
2.
Introduction Many works on aliphatic polyesters have been carried out, and efforts have been made to
use them in the industry. But, so far, only few reports dealing with industrial utilization of aliphatic polyesters have appeared because of their properties such as low melting point, low heat resistance and a trend to hydrolysis. However, application of aliphatic polyester to biodegradable polymer has recentiy been attracting attention. In this study, we describe results of synthesis of dimethyl succinate using carbon monoxide and its application to biodegradable aliphatic polyesters.
597
3.
Experimental Tlie hydroesterification of methyl acrylate was carried out in the presence of Co2(CO)8-
pyridine derivative catalyst in a stainless steel autoclave under CO pressure of 50kg/cm2. Polymerization of dimetyl succinate (SDM) with glycols was carried out by transesterification at 160-220°C in the presence of Zn(OAc)2.2H20 catalyst for 8-12hrs.
4. Results and Discussion In this paper, we report the synthesis of dimethyl succinate using carbon monoxide and its application to biodegradable aliphatic polyesters [1]. We have developed a new technology for synthesizing dimethyl succinate in good yield in a single-stage synthesis process by using methyl acrylate,carbon monoxide and methanol as the raw material. An effective synthesis of dimethyl succinate was carried out by hydroesterification of methyl acrylate in the presence of Co2(CO)8-pyridine derivative catalysts as shown in Equation(l). Dimethyl methylmalonate and dimethyl-y-ketopimelate were found as by-products. CH3OC ^ C02(C0)8/3.5-Liitidine - ^ ^ C 0 C H 3 O
.
^
CO.CH3OH
C O / H 2 50kg/cm2 1 1 0 ° C 1.5hr
Ö
COCH3 Ö
CH3OGA COCH3
(1)
η " ^ ° CH30^(CH2)^{CH2)^COCH3< 1 %
Table 1 shows effect of various pyridine derivatives on the hydroesterification of methyl acrylate by using Co2(CO)8. 3,5-Lutidine was found to be the most effective promoter. The synthesis was possible at a lower CO pressure of 50Kg/cm2 than the originally reported pressure [2], and the yield was approximately 90% in the presence of Co-3,5-lutidine Table 1. Effect of various pyridine derivatives on the hydroesterification of methyl acrylate by using Co2(CO)8 . ^ ) Run
1 2 3 4 5
Base
3,5-Lutidine Pyridine 3,4-Lutidine 2,4-Lutidine 4-Dimethylaminopyridine
Conversion (%) 98.3 99.0 92.0 11.0 0.0
Selectivity(%) ^ ) SDM 90.6 86.0 80.3 40.0
-
MMDM
MP
4.6 3.0 6.8 4.8
2.7 2.5 3.5 55.0
-
-
a)Reaction conditions: Methyl acrylate; lOOmmol, Methanol; ISOmmol, Toluene;30g,Co2(CO)8; 5mmol, Base;15mmol , C 0 pressure; SOkg/cm^, H2 content of the carbon monoxide;0.5%, Reaction Temp.;110°C , Reaction time; 1.5hr. b ) S D M : Dimethyl succinate, M M D M : Dimethyl methylmalonate, M P : Methyl propionate
598
catalyst. Further, hydroesterification of butadiene with carbon monoxide and methanol using Co-pyridine catalyst gave dimethyl adipate (ADM) in good yield [3]. By-products were dimethyl 2-methylglutarate, dimethyl ethylsuccinate and dimethyl propylmalonate. These aliphatic dimethylesters were polymerized with various glycols to synthesize aliphatic polyesters, and high molecular weight polyesters were obtained by using these dimethylesters [4]. For example, dimethyl succinate was polymerized with glycols by transesterification as shown by Equation(2). CH3COOCH2CH2COOCH3
4-
HOROH — • 4 C O C H 2 C H 2 C O O R O h r + 2 C H 3 O H (2)
Table2 shows results of the polymerization and biodegradation test of the polyesters in the soil (compost). The molecular weight of the aliphatic polyesters was between 16,0(X) and 40,(XX). The melting point of the polyesters was between 70 and 119 °C, and the thermal Table 2, Run
Biodegradation test of some kinds of polyesters in soil (compost)^)
Monomei*>)(mol ratio)
Rl-(COOCH3)2 R2-(OH)2 1 2 3 4 5 6 7 8 9
Molecular weight (before test) MnxlO'^ Mw/Mn
SDM EG SDM 1,4BG SDM CHDM ADM CHDM SDM/ADM 1,4BG 80 / 20 SDM/MMDM 1,4BG 80 / 20 SDM EG/1,4BG 30 / 70 ADM 1,4BG/CHDM 40 / 60 Polycaprolactone(H-7 Daicel)
Biodegradation (after test) Weightless Molecular weight (%) MnxlO-^ Mw/Mn
3.43 3.74 3.09 1.78 2.72
1.7 2.0 2.0 1.7 1.7
5.0 22.0 1.5 1.2 35.0
3.02 3.06 2.99 1.79 2.56
1.9 2.0 2.0 1.7 1.8
2.55
1.7
46.6
2.50
1.7
3.71
1.8
47.0
3.39
1.9
1.64
1.6
18.6
1.54
1.6
3.45
2.0
15.8
3.23
2.0
a) Degradation condition: Polymer film;40x40x0.15mm, Soil;Commercial compost, 30*C, 3(Mays. b) S D M (Dimethyl succinate), A D M (Dimethyl adipate), M M D M (Dimethyl methylmalonate), EG (Ethylene glycol), 1.4BG (1,4-Butanediol), C H D M (Cyclohexanedimethanol)
decomposition temperature exceeded 300°C. The biodegradation test of tiie aliphatic polyesters in the soil showed that when the polyester films were buried for 30 days, the weight loss of homopolyesters was accelated by the copolymerization which used the third component. The molecular weight of polymer samples did not practically change after the biodegradation test. From this result, it is suggested that biodegradation of the polyester samples occured on the surface of the polymer film. Table3 shows results of the copolymerization of dimethyl succinate and dimethyl adipate with l,4-butanediol(l,4-BG), and their molecular weight and thermal properties. The number-average molecular weight(Mn) of the aliphatic polyesters was between 20,000 and
599 Table 3. Copolymerization of dimethyl succinate (SDM) and dimetiiyl adipate(ADM) witii 1,4-butanedioia) Run
Feed ratio SDM/ADM
Thennal properties
Molecular weight
Monomer(mol ratio) Unit ratio SDM/ADM
MnxlQ-'* Mw/Mn
Tm
AHm
CQ
(J/g)
Td(-2wt%) CC)
1
100/0
100/0
3.44
1.8
119
84
-33
336
2
80/20
80/20
3.28
1.8
98
66
-43
310
3
60/40
60/40
3.26
1.8
71
45
-44
320
4
40/60
39/61
2.05
1.9
45
38
-50
318
5
20/80
20/80
2.66
1.8
50
60
-58
318
6
0/100
0/100
2.26
1.8
60
83
-60
322
a) Reaction condition: Catalyst Zn(OAc)2-2H20; 0.13mol%/diester, Temp;160'C, Time; 8-12hrs, Final degree o f vaccum; 0.3-0.5Torr b)Determined by GPC based on PSt. standards c)Tm and A H m values were measured by DSC at IsL heating.
35,000. These polyesters gave sturdy films when the number-average of moleculare weight exceeded 25,000. The melting point of the polyesters was between 45 and 119°C, and the thermal decomposition temperature exceeded 300°C. Glass transition temperature was between -33and-60°C. Entiialpy of melting (AHm) of the polyesters was between 38 and 84 J/g. Further, from this and related results obtained by measurement of X-ray diffraction of the polyesters, a 100 80
o Co 2
60
40 20 Οά 0
20
40
60
80
100
Ratio of A D M ( m o l % )
Fig.l.
Enzymaric degradation of polyesters ( ( S D M / A D M ) -1,4BG) with Lipase (from Rhizopus delemer ) Enzyme : Lipase {Rhizopus delemer),
120units
Polymer : Copolyester [ ( S D M / A D M ) -1,4-BG ] O.lg Conditions : 25mmol phosphate buffer ( P h 6.86) 20cc, 3 0 ° C . 20h.
600 correlation between AHm and the degree of crystallinity of the polyesters was observed. As shown in Table3, AHm of the polyesters decreased with increasing content of A D M to 60mol%. This decrease in AHm shows a decrease in the degree of crystalhnity of the poly estes. Fig.l shows results of enzymatic degradation of the copolyesters((SDM/ADM)-l,4-BG) using lipase from Rhizopus delemer. Degradation of polymer increased with increasing the content of ADM in the polymer chain. Biodegradation of aliphatic polyesters was accelated by the copolymerization. The polyesters of dimethyl adipate with 1,4-butanediol was degraded easily by Upase. Also, biodegradability of the copolymer was furthermore accelated with decreasing the degree of crystallinity of the copolymer.
Acknowledgement This work was supported by New Energy Industrial Technology Development C)rganization(NEDO).
References 1.1.Takahashi, et al., Abst. Papers presented at 65th National Meeting, Chem. Soc. Japan, p259 (1993). 2. A.Matsuda, Bull. Chem. Soc. Jpn., 42, 571(1969). 3. A.Matsuda, Bull, Chem. Soc. Jpn. 46, 524(1973). 4.1.Takahashi, et al.. Polymer preprints, Japan, 42, No.9, 3688(1993).