Pulp and Paper

Pulp and Paper PHILIP E. NETHERCUT Technical Association of the Pulp and Paper Industry, 1 55 East 44th St., New York 1 7 , Ν. Υ.

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NITED STATES paper and paperboard production for 1958 was ex­ pected to equal the 30,700,000 tons produced in 1957. During the first 6 months of the year production was almost 4 % below that for the comparable period in 1957. After the summer months, however, the industry saw a notable upturn in the demand for its products, partic­ ularly paperboard. Recent announcements of new expansion plans and reactivation of deferred ones indicate that the paper industry is preparing for a continua­ tion of the phenomenal growth which characterized the decade following World War II. The Stanford Research Institute recently forecast that U . S . paper and board consumption by 1965 will be about 49,000,000 tons, an in­ crease of about 40% over 1957. By 1970 it should rise to 58,000,000 tons. On the basis of these data the increase over the next 7 years will exceed that in the past 10 years, and in the next 12 years will be as much as in the whole period from 1929 to 1957. World consumption of pulp and paper products should double in the next 18 years, according to the UN Food and Agriculture Organiza­ tion, if the rate of increase does not exceed 4 % a year. However, evi­ dence presented by the agency's forestry division suggests that the momentum may be considerably more rapid. In retrospect it is apparent that the paper industry maintained a reasonably strong position during the recent decline in general business activity. Even though substantial increases in pulp, paper, and board capacity had been added during 1957—58 to meet the long-term growth needs of our economy, the ratio of production to capacity for both paper and paperboard ranged from 85 to 90% for most of the last 18 months. Since September 1958 these ratios varied between 90 and 9 5 % of capacity.

In spite of the encouraging upturn in production, however, the earnings of the paper industry have suffered as a result of higher material and wage costs and the expense of operat­ ing at less than optimum capacity. This has led to intensified efforts to raise productivity, reduce manufac­ turing costs, and improve product qualities through new developments in pulping and papermaking tech­ nology. Pulpwood Developments

Wood is the basic raw material of the pulp and paper industry and one of the major economic factors in end-product costs. The price of pulpwood delivery to the mill varies widely with different pulp-producing regions, depending primarily upon accessibility of the timber stands, yield per acre, and labor, trans­ portation, and stumpage costs. To minimize handling and labor costs many west coast mills have switched from storage of pulpwood in stick form to storage of pulpwood chips at the mill sites. Anticipated bene­ fits from this new practice include the elimination of roundwood de­ terioration during outside storage, a reduction in wftod handling costs due to a smaller yard labor force and exclusive use of efficient chiphandling equipment, and an increase in storage volume for a given ground area. Recent tests have demonstrated that chip piles containing west coast wood species do not seriously de­ teriorate when left for up to 3 years. Another innovation in pulpwood handling is the first installation in the South to produce pulpwood chips in the forest. By debarking and chipping pulpwood in its timber stands at Fargo, Ga., the St. Regis Paper Co. hopes to reduce the cost of wood fiber for kraft paper manu­ facture by greater utilization of the tree and lower handling costs. The chips are shipped in hopper cars to the St. Regis pulp and paper mill at Jacksonville, Fla.

In the past year several new pulp­ ing developments of great technical interest to the industry have been described. Magnesium base recovery, applied to the acid sulfite process, has resulted in a major advance in pulping technology, but this proc­ ess has not been suitable for certain wood species. Recent studies have led to the development of the Magnefite process by the Howard Smith Paper Mills, Ltd., of Canada. This process involves cooking wood chips with a magnesium bisulfite solution without the normal excess of sulfur dioxide and using a higher combined sulfur dioxide concentration than for acid sulfite production. Such liquor has a pH in the range of 3.5 to 5.0. The digestion can be carried out rapidly and at relativelyhigh temperature and has many advantages over regular sulfite pulp­ ing, even with species that are normally readily cooked by acid sulfite liquor. Extensive pilot plant data have indicated that pulps su­ perior to regular sulfite pulps can be produced and that, by increasing the combined sulfur dioxide concen­ tration, faster pulping, lower re­ jects, and greater pulp brightness may be obtained. By varying the cooking times, superior pulps have been produced over a wide range of yields. This new cooking process retains the simplicity and advantages of a magnesium-base recovery system in which the residual cooking liquor is collected, evaporated, and burned, yielding heat recoverable as steam, VOL. 5 1 , NO. I

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JANUARY 1959

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I/EC ANNUAL REVIEW sulfur dioxide, and a highly reactive magnesium oxide. The Sivola sulfite cooking and recovery process represents another outstanding development in pulping technology. This technique has been in successful use in Finland for 5 years, but process details were disclosed only recently. The Sivola process consists of an acid first stage, followed by an alkaline stage in the same vessel without reducing pressure and temperature. The major portion of the delignification is accomplished in the first stage, in which sodium bisulfite liquor at pH 3.5 to 4.5 is employed. In this first stage, which lasts 5 to 6 hours, the digester is brought up to a cooking temperature of 300° to 320° F. Sufficient liquor is drained off during and at the end of the first stage, so that sodium carbonate can be injected into the digester for the second stage at a pH of 7.5 to 9.0. The second stage lasts 1 to 1.5 hours. By adjusting the time, temperature, and pH of the two stages, a wide range of pulp types can be prepared from the wood species investigated. The Sivola recovery process is similar to a conventional kraft recovery cycle and may be operated in conjunction with kraft or semichemical mills. In this case the liquor may be mixed and burned in the same recovery unit. The Sivola process, however, does not require causticizing or lime reburning.

1958

After more than 5 years of successful mill operation, the advantages claimed for the Sivola process are: (1) For the same wood species it yields a pulp with the strength of kraft and the bleaching ease of sulfite; (2) either softwoods or hardwoods may be pulped to produce a high quality product; (3) compared to other sulfite processes it produces stronger pulps at the same yield; (4) compared to other sulfite processes bleaching costs are reduced, and ultrahigh brightness can be achieved with fewer bleaching steps; (5) air pollution is virtually eliminated because of the closed process cycle, and stream pollution abatement is comparable to that in a kraft mill; (6) over-all thermal efficiencies are high, as in the kraft process, because of the steam generated in the recovery unit and the digester heat recovered by conventional blow-flashing procedures; and (7) it provides a means of purging spent liquors of such impurities as iron sulfides, silicates, phosphates, thiosulfates, and sodium chloride, which are corrosive or have an adverse effect on pulp quality. In the field of mechanical pulping, where wood is reduced to pulp by a grinding process, two interesting processes have been proposed recently. One is the production of mechanical pulp from wood chips rather than from pulpwood in log form. Advantages claimed for the chip grinding process include closer

A recent development in continuous pulping is the S p r o u t - W a l d r o n 48 A

INDUSTRIAL AND ENGINEERING CHEMISTRY

digester

control of grinding, superior strength of the pulp produced, and utilization of any shaped wood. A second innovation is the production of groundwood pulp using stones for coarse grinding and finishing with double-disk refiners. It is claimed that this two-stage grinding process produces pulps of superior strength, increases production from present grinding equipment, and reduces power consumption by roughly 10%. Although only a small fraction of the country's pulp is produced by continuous pulping processes, the tonnage is rising steadily, and several mills have recently installed such units. Continuous digesters have been used primarily for making coarse grades of pulp for corrugating medium, roofing felt, and building papers, but they are finding increased application in the production of higher quality pulps. A recent development in continuous pulping is the Sprout-Waldron continuous digester, which has been installed at the Sonoco Products Co. plant at Hartsville, S. C , and the Continental Can Co. plant at Hodge, La. This digester is really two independent operating units in one. Each of the digester halves is divided into an upper and lower section. Presteamed chips pass through a specially designed rotary valve which brings them into the pressure zone of the digester with minimum steam loss. As the chips pass along the perforated metal trough in the digester, they receive a continuous spray of cooking liquor, the strength of which is maintained by controlled additions of white liquor. The speed of the conveyor screws in the digester governs cooking time. As the chips reach the end of the upper trough, they drop by gravity to another conveyor in the trough just below and are carried back to the opposite end of the digester for discharge. While traveling in the lower trough they are continually sprayed with liquor as it drops from the perforated tray above. Cooking time in the digester is approximately 10 to 15 minutes for semichemical and 30 to 45 minutes for chemical pulp. Advantages claimed for this equipment are a short cooking time, a low liquorwood ratio made possible by an efficient recirculating system, improved yields, improved pulp uniformity, and a twin or duplex design

w h i c h permits h a n d l i n g t w o woods or two different chemicals at t h e same t i m e . I n the p r o d u c t i o n of bleached p u l p chlorine dioxide continues to play a n increasingly i m p o r t a n t role. F o r m e r l y considered expensive a n d h a z a r d o u s to use, it c a n n o w b e m a n u f a c t u r e d a t t h e p u l p mill b y a n y one of several reasonably safe processes a t a cost to c o m p e t e economically w i t h s o d i u m h y p o ­ chlorite. At t h e start of 1958, 43 p u l p mills in N o r t h A m e r i c a w e r e using chlorine dioxide, a n d six mills m o r e w e r e scheduled to install chlorine dioxide bleaching processes d u r i n g t h e year. A t present chlo­ rine dioxide is most widely used for bleaching kraft p u l p , w h e r e the n u m b e r of requisite stages has b e e n reduced to t h r e e or four for 80 t o 86 G . E . brightness a n d to five for 87 to 91 G . E . brightness. T h e present trend is to eliminate h y p o ­ chlorite altogether in kraft p u l p bleaching. T h e sequence chlorine, caustic extraction, chlorine dioxide, caustic extraction, a n d chlorine d i ­ oxide has gained w i d e acceptance, as it will bleach a n y t y p e of p u l p to high brightness with m i n i m u m color reversion, while retaining a s t r e n g t h e q u a l t o t h a t of u n b l e a c h e d p u l p .

By-product Utilization T h e major p u l p - p r o d u c i n g com­ panies h a v e intensified their efforts to develop n e w a n d profitable uses for their r a w m a t e r i a l a n d for t h e by-products of the p u l p i n g reaction. A n economical process for t h e large scale p r o d u c t i o n of q u e r c e t i n from Douglas fir bark, developed by the W e y e r h a e u s e r T i m b e r C o . , in­ volves m e c h a n i c a l refining of t h e bark to yield cork flakes, w h i c h a r e t h e n extracted w i t h h o t w a t e r to yield d i h y d r o q u e r c e t i n a n d t a n n i n s in solution. Air oxidation t h e n d e hydrogenates t h e d i h y d r o deriva­ tive to quercetin. T h i s is recover­ able in purities of over 9 5 % by cooling a n d filtering t h e solution. Q u e r c e t i n finds application in a n t i ­ oxidants, chemical syntheses, a n d pharmaceuticals. I n the field of alkaline p u l p i n g tall oil has assumed n e w i m p o r t a n c e . T a l l oil, a n a t u r a l m i x t u r e of rosin acids related to abietic acid, fatty acids related to oleic acid, a n d nonacidic bodies, is t h e p r o d u c t of t h e acidification of the skimmings from

D A N G E R S of launching a NEW PRODUCT Snell Research can help overcome them H e r e ' s h o w , in s o m e t y p i c a l c a s e h i s t o r i e s of S n e l l c l i e n t s : Product Research and Development Toxicology—One of the largest frozen —A few years ago Snell was retained to food companies began getting complaints on the flavor of one of their green vege­ develop new products, applications, and markets for sugar. Extensive research tables. Since hundreds of thousands of and development work by Snell resulted dollars were at stake, they consulted in the creation of a new synthetic deter­ Snell to find out what was wrong. Snell by analyzing tests, and checking on the gent—based on sugar! farm, was able to prove that the taste— Product Application—A Snell client in actually toxic—was due to a new type of the paper industry, for whom we had insecticide sprayed on the fields hundreds developed a fine additive, wanted to of yards away on a windy day long before explore uses in other fields. Unfortunately, the harvest! their highly qualified staff's experience Engineering—A large midwestern firm was limited to the one field. Snell, with desired to produce its own brand of experts in practically every product field, instant coffee, to possess outstanding found the new product has potentialities flavor, body, and bouquet. They engaged as both a good emulsifier and a paint Snell to handle all details, from design to plasticizer. Only the very largest manu­ engineering, to supervision of actual proc­ facturing companies can duplicate the ess startup. The fine qualities "built into" breadth of experience and background this resultant product made it such a the Snell "brain-trust" of technical ex­ success that Snell was commissioned to perts can offer you! enlarge the plant, which has recently gone into production. Product Improvement — One Snell client found their product, an adhesive What's Your Product Problem?— bandage, slipping in quality. Tape was Whatever it is, and whatever your prod­ going gooey in storage on druggists' uct field—chemicals, chemical specialties, shelves. Snell research helped this client personal products, pulp and paper, pro­ bring his product quality up to equal the tective coatings, plastics, textiles, foods, best on the market, and retain his share petroleum, rubber—Snell has men who "know the score" in that field, and who of sales. can work with you creatively and profit­ Product Evaluation—A Snell brewery ably in developing, producing, protecting, client wanted to expand production and and marketing new ideas. This broad take advantage of a more efficient pro­ experience can be decisive in protecting not only your ideas, but also the thou­ duction technique but feared the taste of the beer might suffer. Snell food tech­ sands of dollars you spend developing nologists, taste panels, and engineers them. And the cost of Snell service is less than you might imagine! Half the jobs checked the new process and hundreds of samples of beer made under new and old we do cost less than $1000! systems, recommended the switch to the SEND FOR more profitable modern process. The change went unnoticed by the customers, FREE BOOKLET and sales continued to climb. Our brochure, " H o w to Market Research—A Snell client with a waste product had briefly considered building a plant to use it to manufacture another product; but had given up after their own brief survey showed the new product to be already overproduced. When they consulted Snell for checking, how­ ever, Snell predicted there would be a shortage within three years. The client waited two years, built the plant—and now has a profitable new product instead of a waste!

D e v e l o p S u c c e s s f u l NewProducts," tells the whole Snell story. Why not send for it today? No obligation, of course. Foster D. Snell, Inc., Dept. I E - 1 , 29 West 15th Street, N.Y. 11, Ν . Υ.

FDS

SNELL New York, Ν. Υ. Baltimore, Md. Bainbridge, Ν. Υ. Worcester, Mass.

VOL. 51, NO. 1 ·

JANUARY 1959

49 A

Sonic

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ULTRASONICS to work ^ W H ^ 5 1 H ^ ? ? . ! J art, engineering, and witchcraft are the ingredients for good wax emulsion. When Commonwealth Color and Chemical brought in some wax emulsions for tests, our spirits waned a little because as every good chemist knows, wax emulsions are fickle. However, the art was good, and our Rapisonic was soundly engineered. The immediate test results were very gratifying. A short while later our happiness was complete when we added Commonwealth Color and Chemical to our ever growing list of friends and users. The tremendous disruptive forces of cavitation developed right inside the liquid by the Rapisonic gave them results at a speed which had to be seen to be believed. Thus another happy marriage of chemistry and engineering and...-a little more grist to our mill. f

. . i n Adhesives ultrasonics puts stickem in adhesives, too. Apparently someone who was frustrated as a child pasting with flour and water finally developed a really sticky adhesive. But his s u c c e s s story stuck in his customers' mind only afte r h e r a n it t h r o u g h the Rapisonic. Result: the finest texture and stickiest film yet. Sonic Homogenizers develop and use all the energy right in the liquids with only 1/6 to 1/10 the power, and at a fraction of the first cost, of conventional equipment . . . maintenance-negligible.

The Minisonic.

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T h e v a p o r phase is r e m o v e d a n d stripped of its d i m e t h y l sulfide con­ tent. T h e yield of c r u d e d i m e t h y l sulfide is a b o u t 3 % of the total black liquor solids; this corresponds, to a b o u t half t h e methoxyl g r o u p s pres­ ent in the lignin. T h e largest p o ­ tential use of this p r o d u c t is as a chemical i n t e r m e d i a t e . As a result of their dispersing properties, purified lignosulfonates from the sulfite p u l p i n g process h a v e found a wide variety of industrial applications. Lignosulfonates es­ sentially free of c a r b o h y d r a t e m a ­ terial h a v e been p r o d u c e d by t h e H o w a r d lime precipitation process, by t h e fermentation of coniferous spent sulfite liquors to ethyl alcohol, a n d by t h e torula yeast p r o d u c t i o n processes o p e r a t e d by t h e R h i n e lander P a p e r Co. a n d C h a r m i n P a p e r Products Co. T w o recently developed processes for p r o d u c i n g carbohydrate-free lignosulfonates a r e being considered for c o m m e r c i a l development. T h e first is a re­ active solvent extraction process of spent sulfite liquor solids w i t h acid a c e t o n e to remove sugars as dio-oisopropylidene derivatives. Several lignosulfonated materials of v a r y i n g molecular weight a r e o b t a i n e d as by-products. I n the second process spent sulfite liquor is fractionated into lignosulfonate a n d c a r b o h y ­ d r a t e fractions by ion e x c h a n g e resins. A n o t h e r recent d e v e l o p m e n t has been t h e l a b o r a t o r y p r e p a r a t i o n of polyesters from hydroxyalkyl ethers of vanillic acid p r e p a r e d from lignin

. for small batches

Other Models RAPISONIC

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the black liquor of the alkaline p u l p ­ ing industry. T a l l oil a n d its de­ rivatives a r e t h e least expensive source of organic acids available t o d a y ; it is predicted t h a t by 1960 the p u l p a n d p a p e r industry will p r o d u c e 1,440,000,000 p o u n d s of tall oil annually. T a l l oil a n d its deriva­ tives find application in the p r e p a r a ­ tion of alkyl resins for the protective coatings industry, as air-entraining agents in c e m e n t m a n u f a c t u r e , in washing citrus fruit, in mineral flotation, in the r u b b e r industry, in t h e m a n u f a c t u r e of synthetic organic detergents, a n d in cleaning c o m p o u n d s , degreasing agents, metal soaps, disinfectants, a n d oil well drilling c o m p o u n d s . O t h e r by-products of the kraft p u l p i n g process a r e the terpenes. S t e a m released from the p u l p i n g digesters is condensed to yield c r u d e sulfate t u r p e n t i n e . T h e refined prod­ uct can be used as a solvent for paint, waxes, a u t o polish, shoe polish, floor polish, wood stain, a n d in insecticides. At the C r o w n Zellerbach C o r p . laboratories in C a m a s , Wash., a pilot p l a n t is now in operation, designed to p r o d u c e nearly 2,000,000 p o u n d s per y e a r of d i m e t h y l sulfide from kraft black liquor. T h e proc­ ess involves evaporating black liquor to a b o u t 5 0 % solids content, a d d i n g sulfur c o m p o u n d s , heating the reac­ tion m i x t u r e to 4 5 0 ° to 500° F., a n d r e d u c i n g the t e m p e r a t u r e a n d pressure of the mixture in a flash t a n k , t o the point at which the bulk of the d i m e t h y l sulfide is vaporized.

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. . . production homogenizer

SANISONIC . . . meets sanitary requirements

AUTOSONIC . . . continuous supply

DISPERSONIC . . . abrasive emulsions

Sonic homogenizers can give you a superior emulsion, too. Send for technical bulletin

Sonic SONIC ENGINEERING CORPORATION 146 Selleck Street, Stamford, Conn. 50 A

Figure 1 . In the nip a r e a o f the Clupak extensible unit a tough k r a f t p a p e r is m a d e with considerable stretch

INDUSTRIAL AND ENGINEERING CHEMISTRY

I/EC

ANNUAL

REVIEW

vanillin. The Rayonier laboratories at Shelton, Wash., have obtained this polyester through condensation of the hydroxyethyl ether of vanillic acid or its methyl ester by means of heat and catalyst. The linear polyester can be extruded in the form of fibers or filaments, molded in a press, or cast from a melt. The process has been placed in pilot plant production, to produce a new synthetic textile fiber that is more elastic than wool, heavier and harder than nylon, and lighter than cotton. Papermaking

Developments

An unusually tough and stretchable paper product called Clupak has been developed by the West Virginia Pulp and Paper Co. As a result of laboratory tests and experience in the field, it is claimed that such paper is, on basis weight comparisons, up to five times tougher than regular kraft paper. Its greater toughness results from its stretching characteristic which absorbs the shock. The process was invented by Cluett, who developed the Sanforizing process for textiles. It is a simple mechanical process utiliz-

1958

ing a heated steel roll and a rubber blanket. The extensible unit consists of an endless rubber blanket with two carrier rolls and a third roll which forms a nip between the rubber blanket and the dryer drum. The outer ply of the rubber blanket stretches as it enters and passes through the nip, and then returns to its normal dimensions. In Figure 1 the outer ply in section 1 is of normal dimensions. In section 2 it is starting to stretch as it enters the nip. Maximum stretch is attained in section 3, and after passing through the nip, the rubber blanket returns to normal dimensions, even contracting slightly in section 4 because of the curvature of the dryer roll. The paper is led into this nip, coming in contact with the surface of the stretched rubber blanket, and then while tightly held between dryer roll and blanket is compressed from its original state as the blanket's outer ply contracts. This process produces a tough kraft paper, which· might be considered preshrunk, and which has considerable stretch in the machine direction. Clupak, compared to conventional paper, is said to have greater machine direction stretch by 500% and less tensile strength by about 25%. Stretch in the cross-machine direction is slightly increased, and cross-direction tensile is about the same. The toughness of this paper may enable sack and bag manufacturers to use less paper and still improve the performance of their products. The first commercial unit has been installed on West Virginia Pulp and Paper Co.'s new $25,000,000 fourdrinier machine at its Charleston, S. C , mill. Trends in Paper Converting

Multiwall sacks of Clupak stand up in butt-drop tests 52 A

In the field of paper converting the recent growth in the production of nonwoven fabrics has excited great interest. Several paper companies have entered this field on either a pilot plant or full production basis. In the 10-year history of nonwoven fabrics, production has grown from practically zero to over 90,000,000 pounds in 1957, and is expected to double during the next 3 years. These nonwoven prod-

INDUSTRIAL AND ENGINEERING CHEMISTRY

ucts are generally fabricated by combining soft creped sheets of paper with a reinforcing textile scrim which provides the necessary strength. The past growth and future potential of this segment of the industry result from the almost unlimited end uses to which nonwoven products can be adapted: in the industrial field for filters, wiping clothes, padding, backing for coated fabrics, and insulation; in the household and sanitary markets for napkins, table cloths, towels, draperies, backing for upholstery, bed pads, dressing, sanitary products, diapers, and bibs; and -in the apparel market for interlining, padding, petticoats, aprons, and skirts. New products envisioned for the near future and now in research or the pilot plant stage are leathertype articles for the shoe industry, upholstery, and bookbindings, disposable work clothing for medical and industrial applications, and printed materials for outerwear. Another interesting development on the horizon is the metalizing of paper to produce decorative and protective effects for packaging uses. Vacuum metalizing permits the deposition of an extremely thin, continuous layer of metal upon a paper base. In this way it may be possible to produce a versatile and attractive material at a cost low enough to be sold competitively with a foil laminate. The metal can be vaporized under high vacuum by either high frequency induction heating or resistance heating. In either case the metal travels as a vapor to the surface of the paper web. Because the paper is at a relatively low temperature, the vapor condenses on it, cooling quickly from liquid to the solid form and producing an extremely thin continuous layer of metal on the paper. These metalized papers may have several advantages over the foil laminated papers: They retain paper properties better, contain less metal and therefore are less costly, and show less tendency to be "dead" on handling or bending. Because they will spring back into original shape without permanent deformation, these metalized papers may be less troublesome in further converting operations such as sheeting, printing, and bag making than the conventional foil laminated papers.