Hirokuni Ono

Rapid liquefaction of lignocellulosic waste by using ethylene carbonate.

Abstract Cyclic carbonates were selected as novel liquefying reagents in order to establish a rapid liquefaction technique converting lignocellulosic waste into useful chemicals. Lignocellulosic materials such as wood and cellulose were liquefied using ethylene carbonate (EC) or propylene carbonate (PC) in the presence of acid catalyst at elevated temperature (120–150°C). Very rapid and complete liquefaction occurred in the EC-liquefaction of cellulose and white birch (hardwood). The rate of the EC-liquefaction of cellulose was approximately 10 times faster than that of current polyhydric alcohol liquefaction. Conversely, liquefaction was not accomplished due to the formation of insoluble lignin derivatives when applied to softwood (Japanese cedar and Japanese cypress). Satisfactory liquefaction is dependent on the type of lignin, i.e. hardwood lignin or softwood lignin. This problem was solved by blending ethyleneglycol (EG) with EC. 13 C-NMR revealed that the EC liquefaction products from cellulose include levulinic acid compounds, which also results from EG liquefaction of cellulose.

Characterization of the products resulting from ethylene glycol liquefaction of cellulose

The composition of liquefied cellulose in the presence of ethylene glycol (EG) was studied. The liquefied products were fractionated and analyzed with highperformance liquid chromatography and nuclear magnetic resonance. EG-glucosides were detected as the only saccharides and 2-hydroxyethyl levulinate as the highly decomposed compound derived from cellulose. Quantitative analysis of the EG-glucosides and levulinic acid that comes from the levulinate shows the presence of the following mechanism in the EG-liquefaction of cellulose. First, cellulose is degraded and produces considerable amounts of EG-glucosides during the early stage of liquefaction. Then, when liquefaction is prolonged, the glucosides are decomposed, leading to a large quantity of levulinates.

Network structures and thermal properties of polyurethane films prepared from liquefied wood

Polyurethane (PU) films were prepared by solution-casting after co-polymerization of liquefied woods (LWs) and polymeric methylene diphenylene diisocyanate (PMDI). The resulting PU films had various [NCO]/[OH] ratios ranging from 0.6 to 1.4 and contained 5.0-16.8% dissolved woody components at the [NCO]/[OH] ratio of 1.0. The crosslink densities of the films with [NCO]/[OH] ratios of 0.6-1.4 increased remarkably with increasing [NCO]/[OH] ratio. Similarly, there were large increases in glass transition temperatures (Tg). These characteristics could be attributed to effective incorporation of PMDI into the LW. The crosslink densities and Tg of the PU films prepared at the [NCO]/[OH] ratio of 1.0 increased because the amounts of dissolved woody components in the films increased. It is concluded that the dissolved woody components acted as crosslinking points in PU network formations. The thermal degradation of the PU films at an [NCO]/[OH] ratio of more than 0.8 or with more than 10.6% dissolved wood started above 262 degrees C under an N2 atmosphere. The thermostability was lost at low crosslink density or with large amount of co-polymerized glycerol structures in the PU networks.

Wood species effects on the characteristics of liquefied wood and the properties of polyurethane films prepared from the liquefied wood

Abstract Polyurethane (PU) films were prepared by solution-casting through co-polymerization between liquefied wood (LW) and polymeric methylene diphenylene diisocyanate (PMDI) at [NCO]/[OH] ratios of 1.0 and 1.2. The LWs tested were made from six wood species through liquefaction using glycerol–polyethylene glycol (PEG) co-solvent, in the presence of sulfuric acid at 150°C. The viscosity of the LWs at 25°C varied from 1.37 to 2.31 Pa s with the wood species, whereas the hydroxyl number, moisture content, and amount of dissolved woody components (DWC) were almost constant. The PU films prepared from LW with high viscosity were found to be more rigid than the films prepared from LW with low viscosity. The increase in the viscosity contributed to the increases in the crosslink density of the PU films. Varying the viscosity is a way to control the mechanical properties of PU films at a constant [NCO]/[OH] ratio.

Preparation of low-molecular weight alginic acid by acid hydrolysis

Abstract Three kinds of low-molecular weight alginic acid fractions, Alg.A, B, and C, were prepared from a commercial alginic acid by acid hydrolysis using phosphoric acid. Alg.A was obtained as an insoluble fraction by the filtration of mixture. Alg.B was obtained as a precipitate by pouring the filtered solution into water. Alg.C was obtained as a precipitate by pouring the filtrate into methanol. Measurements with 13 C NMR, GPC and WAXS were performed on the prepared fractions for characterization. Alg.A was composed of rich M and G blocks, and had DP n and DP w /DP n values of 79 and 3.11, respectively. Alg.B was mainly composed of M block, and had DP n and DP w /DP n values of 38 and 2.57, respectively. Alg.C had a random structure including many alternating sequences, and had DP n and DP w /DP n values of 35 and 2.11, respectively. Alginic acid oligomers prepared in this study, Alg.B and C, were improved regarding in solubility in water and the viscosity of their aqueous solution.

Chemical analysis of the product in acid-catalyzed solvolysis of cellulose using polyethylene glycol and ethylene carbonate

Degradation and decomposition of cellulose were studied in an acid-catalyzed solvolysis treatment of biomass using polyethylene glycol (PEG) and ethylene carbonate (EC). The solvolysis reaction was followed by a typical reaction system of wood liquefaction that uses sulfuric acid catalyst at 140° or 150°C at atmospheric pressure. The methods of fractionation and chemical analysis of the degraded cellulose in the solvolyzed product are discussed. The solvolyzed product was separated into several fractions, and they were hydrolyzed to release glucose and levulinic acid to determine the quantity of glucosides and levulinates in the solvolysis product. The data clearly showed that the solvolysis reaction had the same mechanism when using PEG or EC. Degradation of cellulose leads to the formation of glucosides, which then decompose, resulting in a levulinic acid structure, and producing a water-insoluble fraction. The conversion rates of both glucosides and levulinates strongly depend on the reaction conditions of the solvolysis. In particular, EC promotes faster conversion of the reactions. The method discussed here is a chemical analytical technique for characterization of the products of wood liquefaction.

Miscibility and pressure-sensitive adhesive performances of acrylic copolymer and hydrogenated rosin systems

Relationship between the miscibility of pressure-sensitive adhesives (PSAs) acrylic copolymer/hydrogenated rosin systems and their performance (180° peel strength, probe tack, and holding power), which was measured over a wide range of time and temperature, were investigated. The miscible range of the blend system tended to become smaller as the molecular weight of the tackifier increased. In the case of miscible blend systems, the viscoelastic properties (such as the storage modulus and the loss modulus) shifted toward higher temperature or toward lower frequency and, at the same time, the pressure-sensitive adhesive performance shifted toward the lower rate side as the Tg of the blend increased. In the case of acrylic copolymer/hydrogenated rosin acid systems, a somewhat unusual trend was observed in the relationship among the phase diagram, Tg, and the pressure-sensitive adhesive performance. Tg of the blend was higher than that expected from Tgs of the pure components. This trend can be due to the presence of free carboxyl group in the tackifier resin. However, the phase diagram depended on the molecular weight of the tackifier. The pressure-sensitive adhesive performance depended on the viscoelastic properties of the bulk phase. A few systems where a single Tg could be measured, despite the fact that two phases were observed microscopically, were found. The curve of the probe tack of this system shifted toward a lower rate side as the Tg increases. However, both the curve of the peel strength and the holding power of such system did not shift along the rate axis.

Effects of miscibility and viscoelasticity on shear creep resistance of natural-rubber-based pressure-sensitive adhesives

Natural rubber (NR) was blended in various ratios with 29 kinds of tackifier resins. Miscibilities of all the blend systems were illustrated as phase diagrams. From these blend systems, we selected 8 systems having typical phase diagrams (completely miscible, immiscible, lower critical solution temperature [LCST] types) and carried out measurements of shear creep resistance (holding power). Holding time was recorded as required time for the pressure-sensitive adhesive (PSA) tape under shear load to completely slip away from the adherend. Holding time of miscible PSA systems tended to decrease as the tackifier content increased. This is attributable to a decrease in plateau modulus of the PSA with increasing tackifier content. There was rather large difference in holding time by tackifier among the miscible PSA systems; the reason for this is also considered to be a difference in plateau modulus. Holding time of an immiscible PSA system scarcely changed by tackifier content. But in another immiscible system, holding time tended to increase with increasing tackifier content. In fact, in the case of immiscible PSAs, the effect of tackifier content on holding time was different from tackifier to tackifier. This may be caused by difference in extent of phase separation.

Effects of miscibility on peel strength of natural-rubber-based pressure-sensitive adhesives

Natural rubber (NR) was blended in various ratios with 29 kinds of tackifier resins, which were prepared from rosin, terpenes, and petroleum. Miscibilities of all the blend systems were illustrated as phase diagrams. From these blend systems, we selected 7 systems having typical phase diagrams [completely miscible, completely immiscible, and lower critical solution temperature (LCST) types] and carried out measurements of peel strength. Peel strength was measured at the angle of 180° at 20°C over the wide range of pulling rates. In the case of pressure-sensitive adhesives (PSAs), which showed phase diagrams of the completely miscible or LCST type, the peak positions in the pulling rate–peel strength curves shifted to the lower velocity as the tackifier content increased. On the contrary, completely immiscible PSAs had a smaller peel strength than miscible ones and did not give manifest shift of peaks. In most of the adhesives, the fracture mode changed from cohesive failure to interfacial failure (between adhesive and adherend), slip-stick failure, and glassy failure (between the tape and adhesive) as the pulling rate increased.

Adhesives from waste paper by means of phenolation

Abstract Recently the effective use of woody materials has been of interest from the viewpoint of forestry preservation. Newsprint is one of the most abundant of woody materials which are discarded into the environment after use. They would be, however, easily recovered from the market. The application of phenolation to cellulosic materials is one possibility for the utilization of waste papers. Phenolation is a newly-established method by which lignocellulosic materials are completely converted to substances soluble in some polar organic solvents. Waste newsprint is subjected to phenolation in the presence of an acidic catalyst. The phenolated product was then methylolated in order to prepare alkaline curable adheisve resins. The chemical characteristics of the phenolated products were studied and the properties of plywood adhesives from them were evaluated. The results indicated that cellulose decomposed and reacted with phenol, producing complicated compound having a phenolic moiety during phenolation ...