Use of Hydrolysis Lignin for the Production of Pulver-Bakelite-Type Resins
Abstract Generated abstract
This study examines the use of technical sulfuric acid hydrolysis lignin in lignophenol-formaldehyde resins intended as substitutes for pulverbakelite binders in shell molding sands. Resins were synthesized in two stages at phenol-to-lignin weight ratios of 2:1 and 3:1, varying the amount of formalin and recording phenol content, drop point, polymerization rate, and tensile strength of standard sand specimens prepared with urotropine. The experiments indicate that the 3:1 phenol-to-lignin ratio gave the best performance, with an optimal formaldehyde dosage of about 0.5 mole per mole of phenol. Under these conditions, the tensile strength of sand specimens was reported to be comparable to that obtained with commercial pulverbakelite, while resin yield based on phenol was higher than for phenol-formaldehyde resin.
Full Text
USE OF HYDROLYSIS LIGNIN FOR OBTAINING RESINS OF THE PULVERBAKELITE TYPE
Communication II: Preparation of resins at phenol-to-lignin ratios of 2:1 and 3:1
L. A. PERSHINA, A. N. NOVIKOV, A. I. GALOCHKIN
(Presented by the interuniversity conference dedicated to M. V. Lomonosov)
(For Communication I see Proceedings of the Tomsk Polytechnic Institute, vol. 112, 1962)
The lignophenol-formaldehyde resin previously obtained by us [1] at a phenol-to-lignin ratio of 1:1 makes it possible to prepare a substitute with tensile strength considerably inferior to that of pulverbakelite. In order to improve its quality indices, we prepared lignophenol-formaldehyde resin at phenol-to-lignin weight ratios of 2:1 and 3:1. As was to be expected, the optimum amounts of formalin at the indicated phenol-to-lignin ratio proved to be different; the influence of the remaining synthesis conditions (time, temperature, catalysts), however, did not change (see tables).
The lignophenol-formaldehyde resin was prepared in two stages, using lignin with the characteristics given earlier [1]. First phenol was condensed with lignin, then formalin was added. The resin was dried at atmospheric pressure to a drop-point temperature of 110–125°.
Molds for shell molding are prepared from quartz sand with the addition of 4 to 8% pulverbakelite. The indicated mixture is applied to a hot metal pattern (temperature 300°), and the mold is held in a furnace at a temperature of 350–400° for 2–3 minutes. The mold removed from the pattern must possess sufficient mechanical strength and meet a number of other requirements. In order to bring the conditions of mechanical testing of the pulverbakelite substitute closer to the conditions of its industrial use, we determined the quality of the resin by a value characterizing the tensile strength of sand specimens (figure-eights) prepared with a binder of lignophenol-formaldehyde resin with the addition of urotropine.
In order to obtain six specimens, 342 g of sand were moistened with 1.2 ml of kerosene (0.3% relative to the sand) in an iron tray measuring 20×20 cm and mixed thoroughly. To the resulting mass, distributed in an even layer over the tray, 16.2 g of resin were added, previously ground, sieved through a sieve with an aperture diameter of 0.08 mm, and mixed with 1.8 g of urotropine, in equal portions in three addi-
Fig. 1. General view of the mold for preparing specimens.
Fig. 2. Lower plate of the mold (part 3).
Fig. 3. Split die of the mold (part 2).
Fig. 4. Split die of the mold (part 1).
and all were thoroughly mixed. The mixture was divided into 6 portions of 60 g for each specimen. Then, into a lubricated metal mold, the form and section of which are shown in Figs. 1–4, at a mold temperature of 280–300° (heated in a muffle furnace), the mixture of three specimens was poured. The mold was placed in a muffle furnace at a temperature of 350° for 3 minutes. After cooling the specimens, their tensile strength was determined. The average value was found from six specimens. Factory-produced pulverized Bakelite was tested under analogous conditions.
The results of the investigations and the synthesis conditions are given in Tables 1, 2, 3, 4.
Table 1
Effect of the amount of formalin on the mechanical strength of the resin. Phenol 400 g, lignin 210 g, (5% moisture), hydrochloric acid 3% relative to phenol, time and temperature of the second stage 2 h and 90–95°C
| Resin No. | Amount of formalin 32%, ml | First stage temperature, °C | First stage time, h | Phenol content, %, first stage | Phenol content, %, second stage | Phenol content, %, dry resin | Tensile strength, kg/cm², corundum molds | Tensile strength, kg/cm², sand molds |
|---|---|---|---|---|---|---|---|---|
| 123 | 318.0 | 140 | 13 | 47.0 | 6.0 | 2.2 | 20.0 | — |
| 136 | 280.0 | 140 | 13 | — | 4.2 | 3.2 | 18.3 | — |
| 130 | 250.0 | 140 | 13 | — | 4.9 | 4.1 | 43.3 | — |
| 134 | 230.0 | 140 | 13 | — | 5.5 | 4.9 | 43.1 | — |
| 128 | 210.0 | 140 | 13 | — | — | 6.3 | 46.1 | — |
| 139 | 160.0 | 140 | 13 | — | 13.3 | — | 36.9 | — |
| 119 | 107.0 | 140 | 13 | — | 21.4 | 5.3 | 33.4 | — |
| 152 | 250.0 | 120 | 8 | — | — | — | — | 1.8 |
| 151 | 230.0 | 120 | 8 | — | — | — | — | 5.5 |
| 155 | 210.0 | 120 | 8 | — | 6.6 | — | — | 9.3 |
| 137 | 190.0 | 120 | 8 | — | — | — | 38.0 | — |
Table 2
Effect of the amount of formalin on the strength of specimens made from LFF resin. Phenol 400 g, lignin 200 g with 5% moisture, sulfuric acid 2.2 ml (sp. gr. 1.83). Temperature and time: first stage—120°C, 8 h; second—95–100°C, 2 h.
| Resin No. | Formalin 32%, ml | Phenol, %, first stage | Phenol, %, second stage | Phenol, %, dry resin | Polymerization rate, in seconds | Drip-melting temperature, °C, second stage | Drip-melting temperature, °C, dry resin | Tensile strength of sand molds, kg/cm² |
|---|---|---|---|---|---|---|---|---|
| 230 | 39.3 | 8.9 | — | 65 | — | 149 | 5.7 | |
| 210 | — | 7.0 | 3.6 | 85 | 67 | 132 | 9.2 | |
| 190 | 49.8 | 10.0 | 6.0 | 90 | 63 | 108 | 10.2 | |
| Pulverized Bakelite | 13.14 |
Table 3
Results of cooking FLF resins in a laboratory reactor. Phenol 4 kg, lignin 2.1 kg (with 5% moisture), sulfuric acid 1.83% by weight of the total phenol; temperature of the first stage 120°, of the second stage 95–100°, duration of the second stage 2 h
| Sample No. | Amount of formalin, 32%, ml | Time of first stage, h | Phenol, %, first stage | Phenol, %, middle stage | Phenol, %, dry resin | CH₂O, second stage, % | Polymerization rate, sec | Drop temperature, °C, second stage | Drop temperature, °C, dry resin | Tensile strength, kg/cm² |
|---|---|---|---|---|---|---|---|---|---|---|
| 7 | 2100 | 8 | 48.2 | 9.4 | 5.9 | 0.8 | 95 | 64 | 118 | 9.1 |
| 7-2 | 2100 | 8 | 49.1 | 7.7 | 5.9 | — | 93 | 74 | 110 | 7.5 |
| 15 | 2100 | 8 | — | 9.8 | 6.2 | — | 105 | 79 | 108 | 8.2 |
| 5 | 2100 | 6 | 49.7 | 10.5 | 7.7 | 0.5 | 75 | 90 | 136 | 9.6 |
| 9 | 2100 | 4 | 54.1 | 5.7 | 3.9 | — | 70 | 85 | 130 | 8.2 |
| 10 | 1900 | 8 | — | 11.4 | 9.7 | — | — | 52 | 114 | 9.0 |
| 11 | 1900 | 8 | 44.2 | — | 9.0 | — | 105 | 64 | 114 | 10.8 |
| 14 | 1900 | 8 | 42.4 | 11.8 | 8.8 | — | 105 | 57 | 114 | 11.0 |
| 13 | 1900 | 6 | — | 8.0 | 4.5 | 0.4 | 65 | 60 | 117 | 9.4 |
| Pulverbakelite (from phenol-formaldehyde resin) | — | 80–115 | — | 105–115 | 15.0 |
Tables 1, 2, and 3 include data obtained in syntheses of resins with a phenol-to-lignin ratio of 2 : 1; Table 4, 3 : 1. Information on the synthesis of resins in an 8-liter laboratory reactor made of stainless steel is given in Table 3.
The best lignophenol-formaldehyde resin in terms of quality was obtained at a phenol-to-lignin weight ratio of 3 : 1. In this case, 0.5 mole of formaldehyde must be taken per 1 mole of phenol. In terms of the tensile strength of sand specimens, the resin is not inferior to pulverbakelite. The yield based on phenol is 130% (for phenol-formaldehyde resin, 105%).
Table 4
Effect of the amount of formalin on the strength of specimens made from LPF resin.
Phenol 400 g, lignin 144 g with a moisture content of 8%, sulfuric acid 2.2 ml (specific gravity 1.83).
Temperature and time: first stage—125°C, 8 h; second stage—100–105°C, 2 h.
Free phenol after the 1st stage 48%. Phenol in the dry resin not more than 5%.
| Resin No. | Amount of formalin 38%, ml | Test results after the second stage: phenol, % | Test results after the second stage: drip point temperature, °C | Test results for dry resin: drip point temperature, °C | Test results for dry resin: tensile strength of sand molds, kg/cm² |
|---|---|---|---|---|---|
| 104 | 140 | — | 31 | 110 | 8.0 |
| 105 | 145 | 14.8 | 31 | 111 | 7.7 |
| 138 | 150 | 13.2 | 31 | 113 | 10.3 |
| 99 | 155 | 12.5 | 31 | 111 | 9.3 |
| 107 | 160 | 12.2 | 33 | 109 | 10.2 |
| 109 | 165 | 11.7 | 41 | 110 | 11.3 |
| 110 | 170 | — | 53 | 111 | 13.0 |
| 102 | 175 | 8.9 | 50 | 124 | 10.5 |
| 120 | 180 | 7.6 | 49 | 115 | 8.0 |
| 121 | 185 | — | 54 | 124 | 5.2 |
| 122 | 190 | 4.3 | 65 | 110 | 5.5 |
| pulverbakelite | — | — | — | 13–14 |
Conclusions
-
The optimal conditions have been established for obtaining lignophenol-formaldehyde resin at ratios of phenol to technical sulfuric-acid hydrolysis lignin of 2 : 1 and 3 : 1. The resin is intended for preparing a substitute for pulverbakelite.
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Tests showed that the strength of sand specimens prepared with a binder based on lignophenol-formaldehyde resin obtained at a phenol-to-lignin ratio of 3 : 1 is not inferior to specimens based on pulverbakelite.
References
- A. N. Novikov, L. A. Pershina, M. I. Moiseenko, V. I. Komarova. Izvestiya Tomskogo politekhnicheskogo instituta, vol. 112, 1962.