Viscosities of Solutions of Pine Wood Lignin from Kraft Black Liquor

IN SOLUTION. Figure 7. Relationship of 2 with concentration for samples of ..... weight-viscosity relationship to be a straight-line function,. Figure...
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in raw materials. T h e relationship of 2 to concentration is useful in comparing the viscosity behavior of different cellulose a c e t a t e s in concentrated solutions. It may a l s o point t o the manufacturing variables which affect t h e viscosity properties of the product. CONCL US IONS

N

a2

1

I

I

I

I

I

I

I

LITERATURE CITED

01

oh

T h e 2 power of t h e concentrated solution viscosities of secondary cellulose a c e t a t e in acetone w a s found t o b e approximately a linear function of intrinsic viscosity and concentration. A coefficient w a s introduced into t h e Baker-Philippoff equation t o give a n equation which would approximate the experimental data. T h i s coefficient varies with both intrinsic viscosity and concentration.

3

I 10

1 I5

I

I

I

20

25

30

I

WEIGHT PER CENT OF ESTER IN SOLUTION

Figure 7. Relationship of 2 with concentration for samples of cellulose acetate of different intrinsic v i s c o s i t i e s Using solvent of acetone containing 2.5% of water

There a r e factors which affect concentrated solution viscosities without affecting intrinsic viscosities. T h e y would, of course, a l s o affect 2. Some of t h e s e factors a r e methods of acetylation, s a l t s i n t h e product, or differences

(1) Am. Soc Testing Materials, Philadelphia, Pa., “ASTM Standards,” D 1343-54T, Tentative Method of T e s t for Viscosity of Cellulose Derivatives by Ball-Drop Method. (2) Baker, F., J . Chem. SOC. 103, 1653 (1913). ‘ ( 3 ) Browning, B. L . , Sell, L. O . , Joint TAPPI-ACS-ASTM, Disperse Viscosity Subcommittee, Project 1592, Progress Rept. 3, J a n 13, 1956 (not published). (4) Kauppi, T. A., B a s s , S. L., Znd. Eng. Chem. 29, 800 (1937). (5) Malm, C. J . , Tanghe, L. J . , Laird, B. C., Ibid., 38, 77 (1946). (6) Markwood, W. H., Jr., Am. SOC. Testing Materials, Proc. 51, 441 (1951). (7) Ott, Emil, Spurlin, H. M., eds., “Cellulose and Cellulose Derivatives,” High Polymers, vol. V, pp. 1212-22, Intclc science, New York, London, 1955. (8) Philippoff, W., H e s s , K., Z. physik. Chem. 831, 237 (1936). (9) Wagner, R. H . , others, Anal. Chem. 20, 151 (1948). Received for review September 13, 1956. Accepted April 25, 1957. Division of Cellulose Chemistry, 130th Meeting, ACS, Atlantic City, N. J., September 1956.

Viscosities of Solutions of Pine W o o d Lignin from Kraft Black Liquor LOUIS R. LAWSON, Jr., ond J. BAYNE DOUGHTY Research Laboratory, West Virginia Pulp and Paper Co., Charleston, S.

T h e lignin studied w a s a commercial pine wood lignin (Indulin A, Polychemicals Division, West Virginia Pulp and Paper Co.), recovered by acidification of kraft black liquor from the pulping of pine woods of the Southeast. A typical analysis a s offered by t h e manufacturer i s : moisture 4.3%, a s h 0.4%, methoxyl 13.9%, and sulfur 1.4%. Four fractions of the lignin prepared by fractionation with acetone and with methanol, and a chemically modified form were a l s o studied. T h e commercial lignin w a s fractionated according t o the procedure outlined in Figure 1. An oxidized lignin w a s prepared by passing oxygen g a s through an aqueous alkaline solution of the commercial lignin. A solution containing 20% of the commercial lignin w a s prepared in which 4 moles of alkali were used to each 840 grams of t h e lignin. T h e solution w a s heated to 7OoC. and oxygen g a s w a s passed in for 11.5 hours at a rate of 0.04 cu. foot per minute per 1000 grams of lignin. When oxygen addition had been completed, the mixture w a s heated to 90’C. and 1 2 1 sulfuric acid w a s added with good stirring until a pH of 2.0 w a s obtained. T h e acidified mixture w a s allowed to cool to 70°C. and then filtered. T h e oxidized lignin cake w a s washed with water until the wash water had a pH of 4.5. T h e lignin w a s then dried to constant weight at 105OC.

128

INDUSTRIAL AND ENGINEERING CHEMISTRY

C.

PREPARATION OF PYRIDINE SOLUTIONS FOR VISCOSITY TESTS

After being dried to constant weight, the lignin and lignin fractions were stored in ground-glass weighing bottles, which were kept in desiccators containing both concentrated sulfuric acid and sodium hydroxide p e l l e t s as desiccants. T h e pyridine used to make the t e s t solutions w a s Baker’s analyzed reagent grade 0 . T. Baker Chemical Co., Phillipsburg, N. 3.1. TESTS OF VISCOSITY OF LIGNIN-PYRIDINE SOLUTIONS

T h e viscometers used in the tests were the CannonFenske-Ostwald T y p e 50 (Cannon Instrument Co., S t a t e College, Pa.), standardized by the instrument company under t h e direction of M. R. Cannon. They held a charge of approximately 7.0 ml. and had a driving head of approximately 9.0 c m . , and t h e working diameter of t h e lower reservoir w a s 3.0 c m . Their suggested range of operation w a s 0.8 to 3 centistokes. T h e v i s c o s i t i e s of t h e pyridine solutions were determined at 20.00’ f 0.01’C. by the testing procedure recommended by t h e Cannon Instrument Co. T h e kinematic viscosity in centistokes for t h e pyridine solvent and the lignin solutions w a s obtained by multiplying the efflux t i m e i n s e c o n d s by the calibrated viscometer V O L . 3, NO. 1

ACETONE

PYRIDINE

PYRIDINE

PYRl D l NE

100% SOLUBLE

METHANOL

PYRl DI NE

PYRIDINE

1 0 0 %SOLUBLE

37% SOLUBLE

Figure

Table 1. Lignin Material in Solution

Lignin Concn., G/IOO G Soh.

Specific Gravity

None

i

1

63% INSOLUBLE

56% SOLUBLE

1. Solvent fractions o f p i n e

4 4 % INSOLUBLE

wood l i g n i n

V i s c o s i t y o f P i n e Wood L i g n i n Solutions

of Soh.

Flow Time of Liquid in Viscometer, Sec.

Centistokes

Centipoises

None

0.9836

505

0.975

0.969

...

0.31 0.45 0.81 1.07 1.43 1.96 2.58

0.9852 0.9853 0.9867 0.9875 0.9888 0.9899 0.9915

524 528 547 558 612 653

1.011 1.019 1.056 1.077 1.119 1.181 1.260

0.996 1.004 1.042 1.064 1.106 1.171 1.249

Methanolsoluble fraction

0.36 0.57 0.98 1.36 1.77 2.35

0.9854 0.9857 0.9868 0.9878 0.9888 0.9902

523 525 539 545 560 578

1.009 1.013 1.040 1.052 1.081 1.116

Methanolinsoluble pyridine soluble

0.22 0.37 0.59 0.75 1.03

0.9848 0.9850 0.9862 0.9861 0.9867

519 526 530 540 552

Acetonesoluble fraction

0.34 0.55 0.97 1.18 1.60 2.22

0.9819 0.9855 0.9867 0.9876 0.9883 0.9896

Acetoneinsoluble pyridinesoluble

0.12 0.22 0.71 1.06 1.40

0.9846 0.9859

Oxidized

0.54 0.88 1.04 1.53

Pine wood lignin

'Concentration,

g.

/loo

In N r Relative

C*

Specific

...

...

1.038 1.046 1.083 1.105 1.149 1.212 1.293

0.038 0.046 0.083 0.105 0.149 0.212 0.293

0.127 0.108 0.095 0.098 0.098 0.097 0.099

0.994 0.999 1.027 1.039 1.069 1.105

1.036 1.040 1.067 1.079 1.109 1.145

0.036 0.040 0.067 0.079 0.109 0.145

0.109 0.069 0.069 0.057 0.059 0.060

1.002 1.015 1.023 1.042 1.065

0.987 1.000 1.009 1.028 1.051

1.028 1.042 1.050 1.069 1.093

0.028 0.042 0,050 0.069 0.093

0.134 0.106 0.083 0.090 0.084

518 524 538 550 563 584

1.000 1.011 1.038 1.062 1.087 1.127

0.985 0.996 1.024 1.049 1.074 1.115

1.026 1.038 1.065 1.089 1.115 1.156

0.026 0.038 0.065 0.089 0,115 0.156

0.087 0.071 0.070 0.073 0.071 0.070

1.000 1.011 1.050 1.077 1.108

0.985 0.997

0.9874 0.9881

518 524 544 558 574

1.063 1.095

1.026 1.038 1.077 1.105 1.137

0.026 0.038 0.077 0.105 0.137

0.247 0.178 0.109 0.099 0.094

0.9867 0.9874 0.9888 0.9903

554 577 617 679

1.069 1.114 1.191 1.310

1.055 1.100 1.178 1.279

1.086 1.131 1.210 1.330

0.086 0.131 0.210 0.330

0.160 0.139 0.185 0.187

...

s ao

...

g, solution

constant. T h e v i s c o s i t y in c e n t i p o i s e s w a s obtained by multiplying t h e c e n t i s t o k e v a l u e s by t h e d e n s i t y of t h e solutions. T h e d e n s i t i e s of t h e solvent and s o l u t i o n s a t 20.00' f O.0loC. were determined with a 25-ml. pyrometer. Throughout t h i s work t h e concentration of solution is s t a t e d a s grams per 100 grams of solution, which is very close t o t h a t of grams per 100 ml. of solution commonly used i n v i s c o s i t y s t u d i e s , b e c a u s e t h e density of t h e pyridine is so near unity. 1958

Viscosity

COMPARISON SOLUTION

OF

VISCOSITIES

OF

PINE

WOOD

LIGNIN

T h e laboratory-determined concentration, s p e c i f i c gravity, and viscometer flow time of the lignin solutions tested, with five c a l c u l a t e d v i s c o s i t y relationships, a r e given in T a b l e I. T h e relative viscosity, Nr and t h e s p e c i f i c visc o s i t y a r e relations of the viscosity of t h e solution t o that of t h e solvent (Equations 1 and 2). CHEMICAL AND ENGINEERING DATA SERIES

129

I 0.3

I

1

I

0.6

0.0

I 2

I 1.8

I 5

I

1 2.1

2.4

2.7

CONCENTRATION. #/I% SOLUTION CONCENTRATION,

2. Specific v i s c o s i t y

Figure

Figure

VS. concentration of pyridine pine wood l i g n i n solutions

3000

PINEWOOD

OXIDIZED

SOLUTION

Logcrithm of r e l a t i v e v i s c o s i t y VS. concentration o f pyridine pine wood lignin solutions

03

I

I

3.

4 /io04

LIGNIN

0 30

ZOO0 MOLECULAR WEIGHT OF

I

I

I

I

CETONE

SOLUBLE

METHANOL SOLUBLE

FRACTION

0 06

ow SPECIFIC

OF

FRACTION OF

I

0 03

I

LIGNIN LIGNIN

I

0 le

VISCOSITY

PINEWOOD

PINEWOOD

0 15

0 I0

0.21

I?. S O L U T I O N S

OF

L

I 0.3

0.6

I

I

0.0

1.e

CONCENTRATION,

F i g u r e 4. Empirical r e l a t i o n s o f molecular weight of l i g n i n s to specific v i s c o s i t y o f 1% solutions

Specific viscosity (N P'

viscosity of solution

-

viscosity of solvent ) = Nr 1

-

( 1)

(2)

For comparative purposes the specific v i s c o s i t i e s of the solutions of lignins are plotted against concentrations in Figure 2, and in Figure 3 the logarithms of the relative viscosities divided by the concentration a r e plotted against concentration.

130

I N D U S T R I A L AND E N G i N E E R l N G C H E M I S T R Y

1.8

I

I

I

2.1

2.4

2.7

SOLUTION

Figure 5. Specific v i s c o s i t y VS. concentrution o f pyridinelignin and water-lignosulfonate solutions

Prepared from data of Staudinger and Dreher (J), assuming all values were straight-line functions

Relative viscosity (Nr) =

f,/lGU~

1 1 5

T h e differences in t h e viscosities of the lignin materials shown in T a b l e I and Figures 2 and 3 suggest differences in chemical structure. T h e s e may be due entirely t o differe n c e s i n molecular weights, In general, the materials of lower molecular weight are more soluble in organic solvents than homologous materials of greater weight. T h i s could explain the lower v i s c o s i t i e s of the solutions of t h e solventseparated lignins and the greater v i s c o s i t i e s of t h e solutions of the oxidized lignin. One theory of the oxidation of such lignins from kraft liquors proposes that oxidation occurs VOL. 3, NO. 1

between t h e mercaptan groups of e a c h of two molecules of lignin and t h u s molecules of greater size a r e formed. T h e lower v i s c o s i t i e s of t h e solutions of t h e pyridine-soluble portions of t h e acetone- and methanol-insoluble fractions of t h e lignin would be expected. If s o l u t i o n s were prepared of t h e pyridine-insoluble materials of t h e s e fractions, their v i s c o s i t i e s would probably b e greater than t h a t of t h e unchanged p i n e wood lignin in t h e same solvent. INDICATED MOLECULAR WEIGHT O F LIGNIN MATERIALS

In a s t u d y of lignins isolated from wood by phenol and resorcinol it w a s noted t h a t t h e s p e c i f i c v i s c o s i t i e s of t h e chloroform s o l u t i o n s of t h e s e lignins a t concentrations of 1%or below w e r e directly proportional t o t h e concentrations and t h a t viscosity-concentration curves were linear (6). T h e s p e c i f i c v i s c o s i t i e s of t h e s e s o l u t i o n s a t the lower concentrations were 0.030 t o 0.065. More detailed s t u d i e s of similar lignins in acetone, a c e t i c acid, and dioxane solutions (5) confirmed t h e earlier work. T h e s p e c i f i c v i s c o s i t i e s of 1%s o l u t i o n s of phenol lignin, acetylphenol lignin, o-cresol lignin, a c e t y l - e c r e s o l lignin, beechwood lignin, and a sodium lignosulfonate i n acetone and a c e t i c a c i d were from 0.030 t o 0.065. T h e s e v a l u e s corresponded very c l o s e l y t o t h a t of c e l l o p e n t a o s e a c e t a t e , w h o s e molecular weight w a s 1542. A lignin obtained by digestion of s p r u c e wood in concentrated formic a c i d g a v e a molecular weight of 1000 by freezing point depression of dioxane. T h e s p e c i f i c v i s c o s i t y of a 1%solution of t h e s a m e lignin in dioxane or formic a c i d w a s 0.065 t o 0.070. By using t h e molecular weight of t h e formic acid s p r u c e lignin a s 1000 and i t s specific viscosity of 0.065, and assuming t h e weight-viscosity relationship to b e a straight-line function, F i g u r e 4 w a s prepared. From F i g u r e 2 s p e c i f i c v i s c o s i t i e s at 1% concentration were obtained and a r e indicated on F i g u r e 4. T h e molecular weights a s indicated i n F i g u r e 4 vary from 900 t o 2900. In a s t u d y of native black spruce lignin, t h e v i s c o s i t i e s

of some d i l u t e solutions of t h e lignin in dioxane were determined (2). Various fractions of the lignin having molecular w e i g h t s estimated a t 2800 t o 5800 were studied. T h e reduced v i s c o s i t i e s ( s p e c i f i c v i s c o s i t y per unit concentration) of 1 and 2% solutions varied from 0.05 t o 0.10. C a l c u l a t i o n s of t h e reduced v i s c o s i t i e s of t h e pine wood lignin-pyridine s o l u t i o n s from t h e c u r v e s of F i g u r e 2 give v a l u e s of 0.06 t o 0.23. A s u m i n g t h e s p e c i f i c viscosityconcentration relationships for t h e native black spruce lignin-dioxane s o l u t i o n s and t h e pine wood lignin-pyridine solutions a r e comparable, i t a p p e a r s that t h e two lignins a r e of about t h e s a m e molecular weight. T h e v i s c o s i t i e s o f s o m e dilute s o l u t i o n s of purified (by exhaustive dialysis) sodium lignosulfonates and lignin sulfonic a c i d s from a sulfite w a s t e liquor have been determined (1). T h e s p e c i f i c viscosity-concentration relations h i p of t h e s e aqueous s o l u t i o n s w a s shown t o be a lineal function. A plot of t h i s viscosity-concentration relationship is shown in Figure 5 , with similar p l o t s of l i k e v a l u e s of solutions of t h r e e pine wood lignins. T h e two t y p e s of lignins appear t o have molecular weights of t h e s a m e magnitude. Estimated molecular weights of 3000 t o 20,000 h a v e been obtained for lignosulfonates f r o m s p e n t s u l f i t e liquors by c a l c u l a t i o n s f r o m light-scattering measurements (3) and determinations of diffusion coefficients (4). L I T E R A T U R E CITED (1) Heister, K., McCarthy, J. L., Benson, H. K., Zbid., 126, 58-61 (1948). (2) H e s s , L., TAPPZ 35, 312-319 (1952). (3) Moacanin, Jovan, Felicetta, V. F.,Haller. Wolfgana, McCarthy, J. L . , J . Am. Chem. S O C .77, 3470-75 (1955). (4) Olleman, E. Ritter, D. M ,Zbid., 69, 665 (1947). (5) Staudinger, H.,Dreher, E., Ber. 698, 1729-37 (1936). (6) Wedeking, E., Engel, O., Storch, K., Tauber, L., Cellulosechemie 12, 1163-73 (1931). Received for review December 3, 1956. Accepted August 29, 1957. Division of Cellulose Chemistry, Lignin Symposium, 130th Meeting, ACS, Atlantic City, N. J., September 1956.

W e a t h e r i n g of Poly (vinyl Chloride) Effect of Composition J. 6. DeCOSTE, J. 6. HOWARD, and V. T. WALLDER Bell Telephone Laboratories, Inc., Murray Hill, N. J.

P l a s t i c i z e d poly(viny1 chloride) (PVC) is being used i n a n increasing number of outdoor applications, particularly in t h e outside telephone plant, where it a p p e a r s a s extruded wire coatings, injection molded parts, and dispersion coati n g s on textiles. Serviceable outdoor compositions a r e p o s s i b l e through t h e judicious c h o i c e of s t a b i l i z e r s and pigments (8). T h e s e r i e s of colored poly(viny1 chloride) c o a t i n g s used on t h e two new t y p e s of outdoor telephone wire known as B Urban and B Rural Wire a r e practical applications of t h e s e principles (20). On t h e b a s i s of a 4year study in Florida, a minimum outdoor life of 10 y e a r s h a s been predicted by G r i e s s e r and Higgins (15) for properly pigmented materials. Poly(viny1 chloride) p l a s t i c s a r e not inherently weatherr e s i s t a n t and derive their properties in t h i s r e s p e c t mainly through formulation. T h e purpose of t h e present s t u d i e s h a s been t o a s s e s s t h e e f f e c t s of weathering on various r e s i n s , p l a s t i c i z e r s , and light absorbers. Through work of 1958

t h i s kind, it is hoped to accumulate technical d a t a useful in formulating outdoor compositions d e s i e n e d for s p e c i f i c applications. T h e formulations reported h e r e a r e not intended for any s p e c i f i c applications, however, and should be viewed only as v e h i c l e s in which t h e variables a r e being investigated. .As t h e s a m p l e s weathered, their attrition w a s followed primarily by t h e measurement of physical properties. Natural weathering w a s u s e d exclusively, with d i v e r s e climates, t o obtain the maximum p o s s i b l e effect. MATERIALS

T h e mixing procedures were e s s e n t i a l l y t h o s e followed in t h e previous investigation (8). Compositions were mixed on hot rolls and press-molded to t e s t s h e e t s 0.030 inch thick, e x c e p t where noted. T h r e e s e r i e s of experimental compositions were studied i n which t h e resin, plasticizer, and organic ultraviolet absorber were varied. CHEMICAL AND ENGINEERING D A T A SERIES

131