Semichemical and Sulfite Pulping Experiments and Production of Semichemical Corrugated Board from Red Gum (Liouidampar Styraciflua)

AGRICULTURE ROOM

SEMICHEMICAL AND SULFITE PULPING EXPERIMENTS AND PRODUCTION OF SEMICHEMICAL CORRUGATED BOARD FROM RED GUM (LIOUIDAMPAR STYRACIFLUA)

August 1939

UNITED STATES DEPARTMENT OF AGRICULTURE FOREST SERVICE LFOREST—PRODUCTS LABORATORY L- Madison, Wisconsin In Cooperation with the University of Wisconsin SEMICEEMIC AL AND SULFITE PULPING EXPERIMENTS AND PRODUCTION OF SEMI-

CHEMICAL CORRUGATED BOARD FROM RED GUM (LIQUIDAMBAR STYRACIFLUA)

G. H. CHIDESTER, Senior Engineer, and J. N. McGOVERN, Assistant Technologist

Large quantities of red gum, among other hardwoods, are available in pulpwood size in various parts of the South. A. market for rid gum pulpwood would provide an outlet for thinnings and cleanings to supplement its present use for lumber and be of material aid in improving forestry practice in many of these areas.

The experiments reported here were made to determine the suitability of red gum for the manufacture of corrugating board, a high tonnage product in growing demand. Also, preliminary trials were made to furnish information on the suitability of the wood for sulphite pulp. For corrugating board the semichemical pulping process, which has given a high yield of pulp suitable for this purpose from other hardwoods with a con- sequently low cost, was used.

WOOD USED

The sample of red gum (Liouidambax styraciflua) consisting of about 5 cords, supplied through the courtesy of the Arkansas State Forest Service, was cut in Prairie County, Arkansas. The stand was second growth and contained about 200 trees per acre, averaging 10 inches d.b.h. The properties reportegl for the wood are given in tables 1, 2, and 3. The evaluation of the wood showed no abnormalities except for irregularity of the heartwood. The chemical analysis shows the hip pentosan content typical of hardwoods. attermeisterg reports a fiber length of 1.55 mm. and a diameter of 0.031 mm. for red gum.

-Schafer,1 E. R. and Pew, J. C. Physical and Chemical Properties of Red Gum (Libuidaribar styraciflua) Pulpwood,. Shipment No.. 150S. U. S.. Forest Products Laboratory report, Project L-168-5, Problem D-172. 2 -Sutermeister, Edwtn. Chemistry of Pulp and Paper Making.,

R1415 In contrast to blackjack oak which was investigated similarly," red gum had a higher cellulose content and lower extractive contents. In spite of having considerably less bark and larger volume of solid wood per cord, its lower density resulted in a somewhat lower weight of oven-dry wood per cord. Although the color of the red gum heartwood was dark as in the oak, the sapwood was considerably lighter than the oak. Because of the light color of the sapwood and the much smaller volume of heartwood, the red gum would be expected to give considerably lighter-colored semichemical pulp than the oak.

=IC REMIC AL PULPING

Semichemical pulping studies were made in a steam-jacketed, stainless alloy-lined autoclave to determine the conditions suitable for a pulp yield range ef about 70 to 80 percent. Larger scale digestions were then made in a 69-cubic-foot rotary digester to give pulps representative of those obtainable in high and low yield for the preparation of nine-point corrugating beard, The results of the digestions are given in table 4.

The first digestion of the autoclave series gave a relatively. low yield for this type of product (68.1 percent). In the following digestions the concentration of chemicals in the impregnating liquor was reduced and shorter times were used for both penetration and cooking to give higher yields. The highest yield obtained in the series was 76.9 percent.

The results indicated that red gum was more readily reduced by the semichemical process than was blackjack oak in previous trials, 3 in that less concentrated liquor and less drastic conditions were necessary to produce similar yields.

Very little difference was indicated in the strength properties of the pulps obtained in the different yields. The tearing strength at the lower freeness was slightly lower for the highest yield pulp and the beating time was longer. The strength values of all of the red gum pulps were about double those obtained from blackjack oak, and the color, in some instances, much lighter.

The two larger-scale digestions gave pulp yields of 73.8 and 79.2 percent. The higher yield pulp developed slightly lower bursting and tearing strengths and required a longer time for processing than the lower yield pulp. The color of the higher yield pulp was considerably lighter than that of the other, probably owing to the fact that the digestion of the lower yield pulp was carried more nearly to exhaustion of the chemicals in the liquor.

"VbGovern, J. N. and Chidester, G. H. Semichemical and Sulfite Pulping Experiments and Production of Semichemical Corrugating Boards from Blackjack Oak. Project L-168-5, Problem B-189.

R1415 -2- 44P4RATION OF CORRUGATING BOARD

Three machine runs were made on the two pulps from the larger= scale digestions to make nine-point corrugating board:. The differences in the strength of the boards obtained from the two pulps, were again very small; the tearing strength. obtained from the lower yield pulp was slightly higher than that obtained from the other (table 5).

The strength of the boards was superior to that of blackjack oak boards, but may have been partly due to differences in processing. The strength was much superior to most commercial corrugating boards and ex- cellent products were obtained in corrugating trials.

SULFITZ PULPING

Two sulfite digestions of red gam were made, one under conditions which would be considered representative of commercial conditions and the other at comparatively high temperatures in .a short time (table 6). The total cooking times were 10.1 and S.3 hburs, respectively. The results showed red gwm to be readily reducible by the sulfite,process. The pulps were comparatively dark colored, but required a comparatively small amount of bleach to produce a standard whiteness. The strength was characteristically low.-

The results, except for the darker color of the unbleached pulps, were quite similar to. thee° obtained in pulping other hardwoods, such as black gum' and aspen, by the sulfite process.

R14f5

Table 1.--Physical characteristics of red gum pulpwood, shipment 1508

Weight of cord: (Basis 4-foot unbarked logs, 128 cubic feet gross volume) Unbarked, as received. 5,670 pounds Barked, as received 4,880 pounds Barked, oven-dry (Weight barked x percentage nonvolatile) 2,320 pounds (Solid volume x density) 2,340 pounds Solid-volume of wood in cord as received 80.9 cu.ft. Number of logs in cord 81 Straightness (basis number logs in cord) -- Nearly straight, less than a deviation of 0.5 inch 56 percent Crooked, greater than a deviation of 0.5 inch 44 percent Average deviation of crooked logs from straight 0.8 inch Logs with large protruding knots or bumps -- (Basis total in cord) . 2.5 percent Knots, average number per log (Basis sample logs) -- Small 7.6 Medium 1.4 Large .5 Loss through barking -- In weight (Basis unbarked logs, as received) 13.9 percent (Basis unbarked discs, oven-dry) 16.0 percent Specific gravity -- (Basis discs i • oven-dry weight, green volume).. 0.462 (Basis discs, oven-dry weight, oven-dry volume) ...... 537 Density (Basis discs, oven-dry weight per cu.ft. green volume) 28.8 pounds Nonvolatile at 105° C. (Basis discs as received) -- Uhbarked 48.7 percent Barked 4..4 47.4 percent Bark 57.8 percent Diameter of barked logs -- Maximum , 10.3 inches Minimum 4.0 inches Average 6.6 inches Volume of heartwood (Basis discs) 6.2 percent Age (Average of discs) 34.5 years Rate of growth, average per inch 10.3 rings

-R1415 Table 2.--Color analysis of red Aum_pulpwoodi. shipment 1908

: Ives readings : Color analysis from Ives readings

Material : : : : : Primary hue : Secondary hue : Red : Green : Blue : White : • : : : : Tint : Lumi- : Tint : Lumi- : : : : : :nosity : : nosity

: Percent :Percent: :Percent: : Percent

• • • • Sapwood...: 78 : 65 55 : 55 :Orange : 8.3 :Yellow : 3.2 . : : • : . . • ' Heartwood.: 36 : 23 : .28 : 18 :Orange : 6.4 :Red : .6

Table 3.- 213 aical wood shipment 1508

Cellulose 60.5 percent Alpha-cellulose Oeoe o 44.5 percent Lignin 21.4 percent Total pentosans 20.7 percent Pentosans in cellulose.. 22.6 percent Solubility in -- Hot 1 percent sodium hydroxide solution 12.0 percent Hot water 2.5 percent .Alcohol-benzene 2.0 percent Ether .5 percent

81415

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Table 5.--Properties of red gum corrugating boards

Kind Physical properties Machine: Diges-: of : run : tion : proc- : :Bursting:Tearing :Tensile : Solid : : : essing :Caliper:strength:strength:strength: frac- :Stretch . : : tion

No. : No. : :Points :Pt./lb./:Gm./lb./:Lb./so. : • : : : ream : ream : la. : : : : . . '• '• : Ream size -- 25 x 40 - 500

. :Beater : : . : . : 1412 : 2498-N: and : 9.70: 0.49 : 1.15 ; 4,135 : 0.40 : 2.8 . : Jordan : : : : : : : .. . :Beater : .: .: 1413 : 2498-N: and : 9.50 : .52 .. 1.07 : 4,570 .46 : 3.7 . : Jordan : : : : :

. :Beater .: : . . 1414 : 2496-N: and : 8.12 : .48 : 1.28 : 4,500 :. .50 : : : Jordan : ; :

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