Masao Kunioka

Chemical Synthesis of Fully Biomass-Based Poly(butylene succinate) from Inedible-Biomass-Based Furfural and Evaluation of Its Biomass Carbon Ratio

We have produced fully biomass-based poly(butylene succinate) (PBS) from furfural produced from inedible agricultural cellulosic waste. Furfural was oxidized to give fumaric acid. Fumaric acid was hydrogenated under high pressure with a palladium-rhenium/carbon catalyst to give 1,4-butanediol, and with a palladium/carbon catalyst to give succinic acid. Dimethyl succinate was synthesized from fumaric acid by esterification and hydrogenation under normal pressure. Fully biomass-based PBS was obtained by polycondensation of biomass-based 1,4-butanediol and biomass-based succinic acid or dimethyl succinate. The biomass carbon ratio calculated from (14)C concentrations measured by accelerator mass spectroscopy (AMS) verified that the PBS obtained in this study contained only biomass carbon. The polycondensation of biomass-based 1,4-butanediol and petroleum-based terephthalic acid or dimethyl terephthalate gave partially biomass-based poly(butylene terephthalate), which is an engineering plastic.

Preparation conditions and swelling equilibria of hydrogel prepared by γ-irradiation from microbial poly(γ-glutamic acid)

Abstract Crosslinked microbial poly(γ-glutamic acid) (PGA) hydrogels were prepared by γ-irradiation, and their preparation conditions such as irradiation dose and PGA concentration were studied. When PGA solution was exposed to γ-radiation, PGA was crosslinked to yield high water sorption materials with specific water content of 100–1400 times their dry volume depending on the prepara tion conditions [e.g. irradiation dose (>20 kGy), PGA concentration (2–10 wt%)]. With an increase of γ-irradiation dosage, the gel content of PGA gels was inclined to increase but the specific water content decreased markedly. The equilibrium swelling behaviour in various aqueous solutions was investigated as a function of pH and concentration of electrolyte (NaCl, Na 2 SO 4 , CaCl 2 ). These PGA hydrogels exhibited reduced swelling when exposed to low pH or electrolyte solutions. The ionic contribution to swelling thus seems to be the main factor governing the swelling of these gels. In addition, the thermal hydrolytic degradability was measured in excess deionized water. PGA gels were almost completely degraded after about 1 h at 100°C.

Preparation conditions and properties of biodegradable hydrogels prepared by γ-irradiation of poly(aspartic acid)s synthesized by thermal polycondensation

Abstract Poly(aspartic acid) (PAsp) hydrogels have been prepared by the γ-irradiation of PAsp produced by thermal polycondensation reactions with an acid catalyst. The effects of the molecular weight of PAsp, pH, concentration of PAsp in the aqueous solution and dosage of γ-irradiation on the PAsp hydrogel preparation were investigated. PAsp hydrogels were prepared in the case when the PAsp weight-average molecular weight was 95 000, the pH of the solution was 7.5 or higher, the concentration of the solution was 5–10 wt/vol%, the dosage of γ-irradiation was 32 kGy or more and the preparation of PAsp solutions was done under N 2 . On the other hand, PAsp with low-molecular weight ( M w = 15 000) could not form hydrogel by γ-irradiation. The swelling of PAsp hydrogels in deionized water and artificial urine was measured. The maximum swelling by deionized water was 3400 g-water/g-dry hydrogel. Biodegradation of the hydrogel was checked using the activated sludge (Japanese Industrial Standards (JIS) K6950 method) indicating that the hydrogel showed about 50% biodegradation for 28 days.

Poly(γ‐glutamic acid) hydrogel prepared from microbial poly(γ‐glutamic acid) and alkanediamine with water‐soluble carbodiimide

Poly( y-glutamic acid) (PGA) hydrogels have been prepared from microbial PGA produced by Bacillus subtilis F-02-1, water-soluble carbodiimide (WSC), and alkanediamines such as 1,3-propanediamine (1,3-PD), 1,4-butanediamine (1,4-BD), and 1,6-hexanediamine (1,6-HD) in aqueous medium. The carboxyl groups of PGA were activated by the addition of WSC in deionized water, and the PGA-WSC adduct was produced. PGA hydrogels could be produced after the mixing of PGA-WSC and alkanediamine in deionized water. This alkanediamine to which both amino groups reacted with the carboxyl groups of PGA plays the role of a crosslinking point. When the amount of PGA was 100 mg, WSC was 50 mg or more, and 1,3-PD was 25 μL or more in 2 mL of deionized water, PGA hydrogels could be produced. Specific water contents (weight of absorbed water/weight of dry gel) ranged from 300 to 1,993 g/g in the case of 1,3-PD. If the PGA-WSC adduct was freeze-dried, the yield of the PGA hydrogel became higher than that when PGA-WSC was not freeze-dried. The highest yield of the PGA hydrogel from 100 mg of PGA, 100 mg of WSC, and 100 μL of 1,3-PD in 2 mL of deionized water using the freeze-dry method was 39.9 mg of dry PGA hydrogel with a 650 g/g specific water content. The order of yield was 1,6-HD > 1,4-BD > 1,3-PD from 100 mg of PGA-100 mg of WSC in 2 mL of deionized water. The order of the specific water content was 1,3-PD (462 g/g) > 1,4-BD (234 g/g) > 1,6-HD (199 g/g). This order may be due to the higher reaction probability between the activated carboxyl groups in the PGA-WSC and both amino groups in the alkanediamine with longer methylene chains, indicating that the crosslinking density of the PGA hydrogel is higher and the specific water content is lower.

Anaerobic Biodegradation Tests of Poly(lactic acid) under Mesophilic and Thermophilic Conditions Using a New Evaluation System for Methane Fermentation in Anaerobic Sludge

Anaerobic biodegradation tests of poly(lactic acid) (PLA) powder were done at the thermophilic (55 °C) and mesophilic temperature (35 °C) under aquatic conditions [total solid concentrations of the used sludge were 2.07% (at 55 °C) and 2.24% (at 35 °C)] using a newly developed evaluation system. With this system, the evolved biogas is collected in a gas sampling bag at atmospheric pressure. This method is more convenient than using a pressure transducer or inverted graduated cylinder submerged in water. PLA was degraded about 60% in 30 days, about 80% in 40 days and about 90% in 60 days at 55 °C. On the other hand, the PLA degradation started in 55 days at 35 °C and degradation rate was much slower than at 55 °C.

Utilization of a Biodegradable Mulch Sheet Produced from Poly(Lactic Acid)/Ecoflex®/Modified Starch in Mandarin Orange Groves

We have developed a mulch sheet made by inflation molding of PLA, Ecoflex® and modified starch, which all have different biodegradabilities. A field test of use as an agricultural mulch sheet for mandarin oranges was carried out over two years. The mechanical properties of the mulch sheet were weakened with time during the field test, but the quality of the mandarin oranges increased, a result of the controlled degradation of the sheet. The most degradable modified starch degraded first, allowing control of the moisture on the soil. Accelerator mass spectroscopy was used for evaluation of the biomass carbon ratio. The biomass carbon ratio decreased by degradation of the biobased materials, PLA and modified starch in the mulch sheet.

Biodegradability Evaluation of Polymers by ISO 14855-2

Biodegradabilities of polymers and their composites in a controlled compost were described. Polycaprolactone (PCL) and poly(lactic acid) (PLA) were employed as biodegradable polymers. Biodegradabilities of PCL and PLA samples in a controlled compost were measured using a Microbial Oxidative Degradation Analyzer (MODA) according to ISO 14855-2. Sample preparation method for biodegradation test according to ISO/DIS 10210 was also described. Effects of sizes and shapes of samples on biodegradability were studied. Reproducibility of biodegradation test of ISO 14855-2 by MODA was confirmed. Validity of sample preparation method for polymer pellets, polymer film, and polymer products of ISO/DIS 10210 for ISO 14855-2 was confirmed.

Biodegradation of Poly(butylene succinate) Powder in a Controlled Compost at 58 °C Evaluated by Naturally-Occurring Carbon 14 Amounts in Evolved CO2 Based on the ISO 14855-2 Method

The biodegradabilities of poly(butylene succinate) (PBS) powders in a controlled compost at 58 °C have been studied using a Microbial Oxidative Degradation Analyzer (MODA) based on the ISO 14855-2 method, entitled “Determination of the ultimate aerobic biodegradability of plastic materials under controlled composting conditions—Method by analysis of evolved carbon dioxide—Part 2: Gravimetric measurement of carbon dioxide evolved in a laboratory-scale test”. The evolved CO2 was trapped by an additional aqueous Ba(OH)2 solution. The trapped BaCO3 was transformed into graphite via a serial vaporization and reduction reaction using a gas-tight tube and vacuum manifold system. This graphite was analyzed by accelerated mass spectrometry (AMS) to determine the percent modern carbon [pMC (sample)] based on the 14C radiocarbon concentration. By using the theory that pMC (sample) was the sum of the pMC (compost) (109.87%) and pMC (PBS) (0%) as the respective ratio in the determined period, the CO2 (respiration) was calculated from only one reaction vessel. It was found that the biodegradabilities determined by the CO2 amount from PBS in the sample vessel were about 30% lower than those based on the ISO method. These differences between the ISO and AMS methods are caused by the fact that part of the carbons from PBS are changed into metabolites by the microorganisms in the compost, and not changed into CO2.

Composites consisting of poly(ε-caprolactone) and cellulose fibers directly molded during polymerization by yttrium triflate

Composite samples consisting of poly(e-caprolactone) (PCL) and cellulose fibers (CF) were prepared by the direct molding method during polymerization from e-caprolactone (CL) monomers. CL liquid was mixed with yttrium triflate as a catalyst and 2-propanol as an initiator. CF was easily added to CL liquid and was homogeneously mixed with CL liquid by this method. The mixture was put into a plastic tube. Heating temperature varied from 60 to 120 °C and heating time varied from 6 to 48 h. CF content varied from 0 to 30 wt%. After cooling, the sample was removed from the tube and cut into a column shaped specimen. PCL composites with CF dispersed homogeneously were obtained. The mechanical properties such as elastic modulus and strength of these PCL composites with CF were measured by compression test using the above specimen. The maximum values of modulus and strength of composite samples are the maximum values 654 and 13 MPa, when fiber content was 34% and these values are greater than those of PCL samples without CF. The biodegradability of PCL composites in an aqueous medium with commercial compost was evaluated measuring the biochemical oxygen demand (BOD). The biodegradability of composite samples was not affected by the presence of CF.

Preparation conditions and swelling equilibria of biodegradable hydrogels prepared from microbial poly(γ-glutamic acid) and poly(ε-lysine)

Biodegradable hydrogels prepared by γ-irradiation from microbial poly(amino acid)s are reviewed. pH-sensitive hydrogels were prepared by means of γ-irradiation of poly(γ-glutamic acid) (PGA) produced byBacillus subtilis IFO3335 and poly(e-lysine) (PL) produced byStreptomyces albulus in aqueous solutions. The preparation conditions, swelling equilibria, hydrolytic degradation, and enzymatic degradation of these hydrogels were studied. A hydrogel with a wide variety of swelling behaviors has been produced by γ-irradiation from a mixture solution of PGA and PL.