Compact PE area i s a short distance from supply storage facilities. Both PE and sodium formate manufacture takes place here; formaldehyde and acetaldehyde are piped in. Soda ash stored in foreground
MORTON SALKIND, Associate Editor in collaboration with H. F. AHERN, Synthetics Department and A. A. ALBERT, Research Center Hercules Powder Co., Wilmington, Del.
Pentaerythritol
Fwmm
YEARS AGO, pentaerythritol (PE) looked like a real growth chemical -and grow it did indeed. By 1953, production was up more than 45070, and major expansion programs were in full swing. Since that time, however, the production curve has mainly moved sideways, and today is at relatively the same rate as 5 years ago. Reason for the change: PE’s main outlet is in surface coatings, and alkyd resins no longer enjoy the sharp growth of the late 1940’s and early 1950’s. This is keynoted in today’s recession; alkyd resin output is down sharply in 1958 from last year. ResultPE production in 1958’s first quarter was down Z6.6y0 from last year (77). But a lot of activity in the development of new uses is now going on throughout the industry. Chemists are looking at
Hercules’ Current Potential at Its Missouri Works (Annual basis) Million Pounds Methanol Formaldehyde Pentaerythritol Sodium formate Ammonia
1 106
50 100
24 12 78
PE with the idea that it’s a nearly untapped, relatively low-priced intermediate. While output has leveled off, domestic capacity has soared from 68,000,000 pounds in 1955 to 130,000,000 today. Either of the industry’s big two, Hercules Powder and Heyden Newport, could just about satisfy current demand by itself. Today’s line-up looks like this (according to each company’s management) : Million Lbs. per Year
Heyden Newport Garfield, N. J. Fords, N. J. Hercules Powder Mansfield, Mass. Louisiana, Mo. Trojan Powder Allentown, Pa. Reichhold Chemicals Tuscaloosa, Ala. Delaware Chemicals Staten Island, N. Y. Commercial Solvents Agnew, Calif. Gulf Oil (Warren Petroleum) Conroe, Tex.
51 26 25 44 20 24
15 12
6 1
1
monton, Alta., plant of its affiliate, Canadian Chemical Co., Ltd. Heyden also had Canadian PE tie-ins-a half interest (with Shawinigan) in St. Maurice Chemicals, Ltd., operating a 3,000,000-pound-per-year unit a t Varennes, Que, Shawinigan now has full ownership. However, a 2Oy0 duty into Canada makes it difficult for United States producers to compete in markets north of the border. Based on current sales and captive uses (more than lo%, mainly Hercules and Reichhold), no shortage is coming in the near future. Several companies not now in pentaerythritol have conducted market surveys, as a first step in a possible entry into the field. Celanese has considered the possibility of domestic manufacture. Likely location : Bishop, Tex., where it now has poly01 activity (4). Commercial Solvents still hasn’t decided about expanding. O n the other hand, Trojan Powder, which has partially installed another 10,000,000 pounds of PE capacity at Wolf Lake, Ill., stopped the project after 60% completion. One thing is certain-no one is rushing into a new PE plant just now. Pentaerythritol Chemistry
Imports, mainly from Canada, are a factor in the domestic market, even though duty of 12l/& ad valorem is charged. Celanese sells pentaerythritol from the 18,000,000-pound-per-year Ed-
INDUSTRIAL AND ENGINEERING CHEMISTRY
Basic PE chemistry appears simple. The product is made from acetaldehyde and formaldehyde in the presence of an alkaline condensing agent. Initial
reaction is three successive molecules of formaldehyde added to one of acetaldehyde by the classical aldol reaction: CHaCHO
--
+ HCHO OH-
HOCHzCHzCHO (1) HOCHzCHzCHO
+ HCHO
OH-
HOCHz
‘CHcHo
/
HOCHz HOCHz
-
(2)
+ HCHO OH-
‘CHCHO
/
HOCHz
CHzOH
I I
HOCHz-C-CHO
(3)
CHzOH These reactions are truly catalytic, and consume no base. They are also readily reversible and isolation of these intermediates is not practical. Fortunately, the equilibria are displaced continuously to the right by a second reaction possible between two aldehydes in the presence of base, the crossed-Cannizzaro. CHzOH HOcHz--b-cHO
+ H c H o + OH- -,
bHzoH CHzOH HOCH2--b-cH20H
HOCH2CHO
+ HCOO-
(4)
I t is not reversible and drives the system to a productive end. Here the base is a reactant, rather than catalyst and is consumed stoichiometrically. Many possible side reactions can take place. Luckily, many of these do not occur readily and others can be minimized by proper choice of reaction conditions. The aldol reaction, for example, can take place between any pair of aldehydes if at least one has a hydrogen on the carbon next to the aldehyde group. The most serious are the reactions of formaldehyde and of acetaldehyde with themselves. Aceraldehyde’s with itself is rapid, but can be minimized effectively by maintaining adequate formaldehyde concentration a t all times and by adding the acetaldehyde so its concentration never builds up. Formaldehyde can react with itself to form sugarlike products which eventually caramelize to impart color and odor to the products. The first step in this reaction is very slow, forming glycollic aldehyde.
OH-
HOCHzCHO
+ HCHO
OH-
(5)
This reaction becomes importanfat high concentrations of formaldehyde and at temperatures above GOo C., and is
erythritol.) Bis-pentaerythritol monoformal illustrates another group, the “pentaerythritol formals” : CHzOH HOCH~~-CHZO-CHZ-OCH~ -
CHzOH
HO(bHCH0
-bHzOH
ZHCHO
favored by presence of divalent metal ions. Once it takes place, the more normal and rapid aldol can follow.
(6)
As a result, formation of sugars appears to be “autocatalytic” and proceeds rapidly once started. Of the various possible Cannizzaro reactions, only the desired one and that of formaldehyde with itself take place to any appreciable extent. While aldol reactions in general are rapid even a t room temperature and under weakly alkaline conditions, the desired Cannizzaro does not progress rapidly below about 40’ C. and p H 10. The self-Cannizzaro of formaldehyde to form formate ion and methanol is still slower and is minimized by avoiding high concentrations of formaldehyde and/or high temperatures. Several materials containing the basic pentaerythritol structure are formed as coproducts by side reactions. One group is the ethers of PE with itself:
In general, the amounts of these polypentaerythritols decrease as n increases. (Common usage tends to reserve the term “polypentaerythritol” for the products with n greater than 2 and refer to the product with n = 2 as dipenta-
I
CHzOH O Z :H T :
(8)
bHzOH Two schemes have been proposed to account for the formation of these products. The first (7) is based on the fact that very little formaldehyde exists in a n aqueous solution as free HCHO. Rather it’s in the hydrated form of methylene glycol, H O C H 2 0 H , and the polyoxymethylene glycol polymers thereof. Reaction proceeds by splitting out water between these oxymethylene glycols and acetaldehyde. OH HO(CHz0)ZH CHaCHO ci HO(CHz0)S-1-CHzCHzCHO
+
+ HzO (9)
When x = 1, this is entirely analogous to Reaction 1 ; a continuation of the series, Reactions 2, 3, and 4 leads to PE. When x = 2, however, Reaction 9 leads to HOCH*OCH&H&HO, which, by the postulate made, can now react with a second molecule of acetaldehyde. OH CHaCHO HOCHzOCHzCHzCHO OHCCHzCHzOCHzCHzCHO HzO (10)
+
VOL. 50, NO. 8
+
AUGUST 1958
1107
Completing the series of reactions with monomeric methylene glycol in steps analogous to Reactions 2, 3, and 4 at both ends of this molecule leads directly to dipentaerythritol. Similarly when x = 3, the end product is bis-pentaerythritol monoformal; participation of two x = 2 in sequence with three acetaldehyde molecules leads to tripentaerythritol. Another mechanism ( 7 8 ) recognizes the low concentration of H C H O in aqueous solution, but capitalizes on its high reactivity compared to that of the methylene glycols. In detail, the aldol reaction proceeds as follows: CH3CHO
+ OH-
a
+ H10
-CH*CHO HCHO
+ -CH&HO
-OCH&H&HO
+
-0CHzCHzCHO HzO HOCHzCHzCHO
Each step in PE operations i s remotely controlled on this panel. Two operators :an easily handle the entire operations of the 24 million-pound-per-year PE works
(21)
F?
+ OH-
(12) (13)
The product of Reaction 13 is identical with that of Reaction 1. Reaction 2 then proceeds in a manner analogous to Reaction 11 ~
HOCHzCHzCHO
+ OH-
HOCH~CHCHO+ H ~ O(14)
Want to
Following through as in Reactions 12 and 13 the product is that written in Reaction 2. However, the hydracrolein anion in Reaction 14 is in equilibrium with acrolein.
Build a PE Plant?
Here, I/EC's editors tell you what it would cost today without an integrated operation: Needed facilities $4,3 15,000.
to build a 24,000,000
pound-per-year PE plant-
Material requirements to make 100 pounds of PE at 85% yield based on acetaldehyde are Formaldehyde (37%) Acetaldehyde (99%) Lime [95% Ca(OH)2] Soda ash (9870 Na2COJ
350.3 38.4 33.7 46.7
Ib. Ib. Ib. Ib.
Current market price for raw materials Formaldehyde Aceta Idehyde Lime Soda ash
3.5 10 0.9 1.55
cents cents cent cents
per per per per
pound pound pound pound
$14.67 1.28 0.40 1.32
5.55 0.30 1.80 $25.32
With PE now selling for $0.295 per pound, delivered east of the Rockies, there's no doubt why Hercules went basic in its latest PE plant-and pushed raw material costs down considerably. It's the only way to do it today.
INDUSTRIAL A N D ENGINEERING CHEMISTRY
+ OH-
(15 )
I n basic solution the following equilibria are known to set up rapidly. RO-
+ CH*=CHCHO
a
ROCH~CHCHO
(16)
KOCHZHCHO + H ~ Oa ROCHzCHzCHO
+ OH-
(17)
When R = H, Reactions 1 G and 17 are identical with Reactions 15 and 14, respectively. However, R may represent the residue of any hydroxylic compound in general. When the compound is pentaerythritol, the intermediate
I
So the Cost Sheet looks l i k e This for 100 Pounds of PE
1 108
CH*=CHCHO
CH20H
Other materials cost $0.70 per 1 0 0 Ib. of PE
Raw materials (including credits) Labor (all labor other than maintenance) Maintenance Utilities Overhead, indirect, taxes, others Container Depreciation Total
HOCH~CHCHO e
HOCH2-C-CH20CHz-CH2CHO CH20H 1
leads
directly by two aldols with formaldehyde and a cross-Cannizzaro to dipentaerythritol. Similarly, the reaction of methylene glycol with t w o acrolein molecules can lead eventually to bispentaerythritol monoformal. Neither mechanism has been established unequivocally and both suffer from lack of confirmatory data at critical points. Fortunately, both lead to the same qualitative conclusions in important areas.
PENTAERYTHRITOL
*
Flowsheet for the manufacture of methanol, Hercules Powder Co., Louisiana, Mo.
Another coproduct commonly found in many commercial pentaerythritols is pentaerythritol monoformal. 0-CH2
/ CH2 \0-CH!
CHzOH
‘d
‘CHIOH
Formation of this material can be rationalized by either mechanism but there is little reason to believe it is formed in the reaction to any appreciable extent. More likely it comes from the splitting of bis-pentaerythritol monoformal into one molecule of pentaerythritol monoformal and one molecule of PE during work-up of reaction mixtures. Pentaerythritol is isolated from reaction mixtures by successive fractional crystallizations. Precipitation may also form part of the scheme if a base such as lime is used. [Hercules uses lime, Heyden caustic. Other bases have been employed with varying degrees of success (Z).] Common precipitants for lime are sodium carbonate or sulfuric acid. The former replaces a moderately soluble formate with a very soluble one and changes the place a t which it is obtained in the crystallization scheme. Sulfuric acid can be used to precipitate most of the calcium or some of the calcium formate may be fractionated out first and the remainder of the calcium precipitated. In either case, the formic acid generated must be handled. Using sodium hydroxide as a condensing agent permits use of fractional crystallization throughout. Polypentaerythritols with n 2 3 are insoluble in water and are usually first to be separated. The remainder of the organic material is usually isolated as a mixture of PE, dipentaerythritol, and bis-pentaerythritol monoformal. This is further purified to produce “technical pentaerythritol,” containing small quantities of ash and formals in the form of bispentaerythritol monoformal or pentaerythritol monoformal.
The production of monopentaerythritol and of dipentaerythritol is a further operation on technical pentaerythritol. Solubilities of the two materials are sufficiently different to permit separation by crystallization once they are freed from the complicating factors of the reaction mixture. From Natural Gas to PE
Basic pentaerythritol chemistry goes back to Tollens’ work in 1882 with formaldehyde and barium hydroxide; U. s. commercial production did not begin until 1938. With current overcapacity in the industry, domestic producers slashed prices early in 1958 (6, 7) in obvious efforts to stimulate use. This was the first reduction in several years. Lower prices focus attention on the trend to new, efficient, well-integrated units, capable of low-cost volume output. Hercules’ year-old Louisiana, Mo., plant illustrates the move. Starting with natural gas, it now makes ammonia, methanol, formaldehyde, pentaerythritol, and sodium formate a t the single location. Urea production is a possible future addition (77) but no decision has yet been reached. Ammonia and carbon dioxide (needed raw materials) are already there.
Hercules’ original activity a t the site goes back to the early 1940’s. I t built and operated the ammonia plant for the Government during World War 11. Also in the plant’s history: Bureau of Mines’ coal hydrogenation activity. I n 1954, Hercules bought the entire site, cleared out unsuccessful coal hydrogenation operations, and made ammonia. Its moves into methanol, formaldehyde, and pentaerythritol came during 1957, and are natural. Carbon dioxide byproduct from the ammonia plant is a starting material for methanol synthesis. Methanol is converted into formaldehyde which in turn is a raw material for PE. The 70-ton-per-day-methanol unit, operating since last fall, uses the Swiss Inventa process. Natural gas, steam, and carbon dioxide are preheated and fed into reformer tubes filled with conventional nickel base catalyst. These strongly endothermic reactions yield hydrogen and carbon monoxide. Feed ratios are adjusted so the “synthesis gas” has a hydrogen-carbon monoxide ratio about 2.25. I t contains some residual nitrogen and uncracked carbon dioxide. From the reforming tubes, gases go through a feed preheater, waste heat boiler, cooler, and finally to the gas holder. Now, the synthesis gas enters a six-
STORE
STEAM
-YJ
SUPERHEATER
METHANOL WATER
BLOWER
Flowsheet for the manufacture of formaldehyde, Hercules Powder Co., Louisiana, Mo. VOL. 50,
NO. 8
AUGUST 1958
1109
0 I-
I
1 1 10
INDUSTRIAL AND ENGINEERING CHEMISTRY
stage compressor, and is brought to 5600 p.s.i.g. Monoethanolamine scrubbing removes any residual carbon dioxide between the third and fourth stages. Carbon dioxide returns to the reforming furnace for re-use. Feed gas and the recycle stream pass into a converter, where reaction to methanol takes place over modified chromium oxide-zinc oxide catalyst. Temperature is carefully controlled (about 350’ C.) to suppress unwanted side reactions which yield higher alcohols, dimethyl ether, and methane. After cooling, condensed crude methanol is separated, and unreacted gas recycled. Crude methanol goes through an initial fractionating column which removes the lowest boiling 2 or 3%, such as dimethyl ether and acetaldehyde. The higher boiling product goes to another column, where 99,85y0 methanol comes over. Water and higher alcohols remain. Next step is continuous formaldehyde manufacture. Methanol and deionized water are vaporized, superheated, then mixed with air. This mixture passes through finely divided silver catalyst a t high temperature. The converter is a vertical cylinder, with a tube bundle in a shell filled with water. Exothermic heat of reaction is removed in the exchanger section by boiling water iri the shell. This steam is used to heat the vaporizer. Combustion products are immediately cooled and passed through a condenser where water vapor absorbs much of the formaldehyde in condensate. The mixed phase stream enters the absorber bottom and the remaining formaldehyde is absorbed in deionized water. At this point the formaldehyde solution contains 2 to 3% methanol. Usually the methanol is then stripped off (some buyers prefer it to remain), and the stream goes through an ion exchange unit to remove acids. Storage is in heated tanks. Most of the plant’s formaldehyde goes for PE manufacture. Safety is essential. Each operation, from ammonia through pentaerythrito1 is well segregated; space was not a limiting factor in plant layout. In addition to the usual modern safety equipment, all flammables are carried in closed piping systems. A 30-inch gas line is 1400 feet long. Methanol is carried 1500 feet between manufacturing unit and formaldehyde production in a 4-inch pipe. Acetaldehyde (made by Hercules but not a t this site) goes through a closed system from tank cars, storage tanks, weigh tanks to the PE reactor. Again for safety, acetaldehyde is about 1000 feet from the PE unit, and a 11/2 inch pipeline carries it over 1300 feet. Acetaldehyde then moves into the
1
TO VACUUM n CO~DENSER rr ,
FROM P E PLANT
STORAGE STEAM
PENTAERYTHRITOL
mSTEAM %
%
CRYSTALLIZE EVAPORATOR E
---7
-
1‘
WATER OR STEAM
!Q STORE
--‘a
SODIUM FORMATE DRIER
to
ACTIVATED CARBON
WACTE
Flowsheet for the manufacture o f sodium formate, Hercules Powder Co., Louisiana, Mo.
pentaerythritol reactor by nitrogen pressure on the weigh tank. The stainless steel reactor is equipped with a high capacity agitator and cooling coils. I t rests on load cells, used for weighing throughout. Meanwhile formaldehyde, already in the area, is weighed directly. Lime is conveyed from the adjacent building as 2570 slurry in water. Temperature is critical and carefully controlled so the reaction a t no time exceeds 50’ C. Reaction time: about 2 hours. The completed reaction mixture is pumped to precipitator tanks (again stainless steel with agitator and coils). Sodium carbonate is added to precipitate calcium carbonate, leaving formates as sodium formate. Soda ash is added to precipitation tanks from a weigh hopper suspended from a load cell. The mixture-sodium formate, pentaerythritols, and suspended calcium carbonate-is pumped to a continuous rotary filter where the carbonate and insoluble polypentaerythritols are taken off. Washing frees any adhering soluble organics. Further filtration is an optional step. Filtrate and recycle streams are next held in an agitated stainless steel tank. These are concentrated in a triple effect, stainless evaporator. Combined effects have enough heating surface for future expansion as well as current capacity. Vacuum equipment and condensers maintain 3-inch Hg absolute pressure in the third effect; 15- to 20-inch in the first. Differential pressure cells actuating air-operated transfer and feed valves maintain levels in the effects. The system is automatic, requiring no manual attention. Performance is chart recorded, and each step in the entire PE operation is remotely controlled on a single panelboard.
From the evaporators, the stream goes to a hold tank, which is maintained a t 80’ to 100’ C. to hold material in solution. The stream next enters a vacuum crystallizer for cooling to room temperature by a controlled cycle. Pressure in the equipment can go to 4-mm. absolute. Both mono- and dipentaerythritol came out. The first of two rotary pan filters separates PE from the mother liquor. This filtrate goes to sodium formate operations for later processing and further pentaerythritol recovery. Years ago, this filter cake was commercially acceptable; today it’s far from that point. The second wash is recycled to the evaporator feed tank. After discharge, the cake is put into hot water solution a t high concentration. This passes through ion exchange columns to remove all sodium formate traces. Solids concentration for this step is measured by gamma ray absorption of solution passing through the recirculation line. It is next held in another crystallizer feed tank, at hot enough temperature to prevent any crystallization. Now, the purified pentaerythritol solution is again cooled to room temperature-along a well-defined timetemperature curve to get desired crystal growth. This takes place in another vacuum crystallizer, similar to the one Modern Technical Pentaerythritol Composition Monopentaerythritol Dipentaerythritol
Ash
70
88
11 0.01
Moisture 0.3 Formaldehyde (combined) 0.3 Four fifths of all PE sold in U. S. in this “technical” form.
VOL. 50, NO. 8
AUGUST 1958
1111
4 Looking at the heart of PE operations. Filter presses can remove insoluble organic material from reaction mixtures in foreground; background-centrifuge area. Pan filter used to separate crude PE crystals is round object in midground
Initial step in PE’s integrated manufacture i s methanol synthesis. This i s the heart o f the purification area with monoethanolamine scrubbing units
4 Drying operations are the final step in sodium formate manufacture. This d r y i n g unit handles plant capacity-1 2 million pounds per
year
4 Triple effect evaporators concentrate the react i o n mixture. Vacuum in t h e third effect keeps 3-inch Hg absolute pressure Methanol is used as raw material for formaldehyde, produced in this area. Total capacity: 100 million pounds annually
1 1 12
INDUSTRIAL A N D ENGINEERING CHEMISTRY
PENTAERYTHRITOL above. Purified PE crystals are separated from the mother liquor on the second rotary pan filter (a smaller one than that used for crude crystal removal). After final washing, the filter cake is dumped and dried. Filtrate and wash go to the evaporator feed tank. Drying equipment is a stainless steel steam tube rotary drier with forced air circulation. Dust collectors are used and air can be preheated. Dried PE moves to a holding bin for final bagging steps.
1958 Markets & Production Units for PE \
8.i
,,
Commercial Solvents, 1
Sodium Formate Recovery
Work-up of mother liquors to recover sodium formate and additional PE often makes the difference between profit and loss in pentaerythritol manufacture. At this plant, recovery units are an integral part of the operation, not separated in any way from main units. Mother liquor is concentrated in an evaporator-crystallizer to the point where sodium formate comes out of the solution. It is separated from the pentaerythritol in solution by centrifugation without cooling. This phase is batchwise-with automatically controlled loading and washing cycles. Formate is dried in smaller, but similar, equipment to that used for PE. Filtrate from the centrifuges is cooled, and PE crystallizes. After filtering in a pressure filter, these crystals are dissolved in water, and activated carbon is added. T h e solution goes through a plate and frame press-and then is recycled back to the PE evaporator feed tank. Today’s Market Situation, Sales Patterns
Capacity figures showing the industry a t 130,000,000 pounds in 1958 are somewhat misleading. The big two will favor their newer, more efficient operations-Hercules a t Louisiana, Mo., Heyden at Fords, N . J. Today, Hercules has its entire technical grade output coming from the new site, but continues monoand dipentaerythritol separation a t Mansfield, Mass. For many years, PE was sold at levels favorable for competing with glycerol. The latter fluctuated considerably between 1945 and 1953 but recently has leveled out owing to stabilizing influence of synthetic producers. At the same time PE prices have been relatively level. Over the last 15 years, pentaerythritol held between $0.27 and 0.34 per pound; glycerol shifted from $0.15 to 0.55 per pound. Currently synthetic glycerol is quoted a t $0.273/4 per pound; technical pentaerythritol a t $0.295 (both delivered). Lately, as consumers have paid more attention to properties rather than price,
--
I\ \
I
i !Annual Market, Millions of Pounds 0 Production Units, Millions of Pounds
PE has tended to become more independent in seeking its price level. Three times more glycerol is sold in the U. S. than PE. Reason: Unlike the latter, glycerol’s markets are highly diversified. Each has about the same tonnage going to the paint industry, but this outlet is less than one third of glycerol’s over-all sales. Other uses are in food, explosives, plasticizers, humectants, and toilet articles. However, some 9070 of domestic PE production goes into surface coatingsalkyd resins and rosin esters. In this major market, pentaerythritol enters principally into resin-forming esterifications with dibasic acids and into alcoholysis reactions with unsaturated oils. Here its competition with glycerol and other polyols is keenest (76). Synthesis of oil-modified alkyds is PE’s largest outlet-about 70% of sales. PE is widely used in coating vehicles where modification exceeds of semidrying oils (such as soybean, linseed, and tall oil). I n these, PE can be used as sole polyol, its tetrafunctionality producing higher viscosity and more rapidly drying vehicles than lower poly01s. The neopentyl structure contributes excellent hardness and durability characteristics. PE’s use in very high oil content alkyds for house paint vehicles is now attracting attention. This development would open up a large market now held almost exclusively by glyceride drying oils. I n alkyds containing less than 55% oil modification (so-called “short oil” alkyds), PB must be blended with less functional polyols (or ingredients such as benzoic acid and rosin) to prevent gelation. I n these alkyds, oils are either semidrying type or saturated types such as coconut oil, lauric acid, and pelargonic acid. Alkyds of this type are used with urea- and melamine-formalde-
hyde resins in baking enamels for metal finishes. Nondrying types are used with nitrocellulose in lacquers. PE contributes improved hardness, gloss retention, color stability, and water resistance in such coatings. PE’s second largest outlet is rosin esters, accounting for 20 to 25’% of sales. Pentaerythritol-based rosin esters and modified rosin esters go into a wide variety of end uses such as paints, varnishes, lacquers, printing inks, floor coverings, and adhesives. PE is also sold today for many old uses such as reconstituted drying oils, linoleum binders, and core oils, and some promising new applications such as plasticizers, vinyl stabilizers, and fireretardant paints. Today, after much sharp growth, the alkyd resin market has turned somewhat sour. This has been increasingly true during late 1957 and early 1958. November and December were extremely poor months-and the trend has continued into 1958. Total alkyd production of 365,000,000 pounds in ’57 is a sharp drop from the 430,000,000 pound level the year before (77), and far below the 620,000,000 figure predicted for 1955 by trade authorities just 5 years ago (74). Alkyd output never reached near that level. But the curve did show remarkable growth in the ’40’s and early ’50’s. First quarter 1958 production totaled 80,000,000 pounds, down 18% from last year. Looking back at early projections, it is easy to understand why few saw PE overcapacity. Forecasts of 70,000,000 pounds consumed for 1955 did not seem out of line. Spokesmen hesitated a bit by saying that conditions could change (74). The tremendous growth in latex paint-styrene/butadiene, poly(viny1 acetate), and acrylics-is up sharply in recent years, particularly in trade sales outlets (3). Alkyds have not yet made VOL. 50, NO. 8
0
AUGUST 1958,
1 1 13
Technical PL Prices vs. Glycerol D e l i v e r e d Prices, Cents
withstanding high humidities, elevated temperatures, and attack by many chemicals. Its excellent molding characteristics and dimensional stability make it highly desirable for precision moldings. Of particular interest to chemical process industry is its use in molded valve and pump parts (70, 75). A series of three-dimensional polymers made from PE and acrolein have attracted considerable attention for many years because of their unusual properties. They can be clear, nearly colorless, extremely tough resins but have suffered in that reactions forming the products are reversible. Important strides have been made in solving the stability problem ( 9 ) and this versatile group of p l y mers should soon reach the market. Through research, more information on the chemistry of the PE molecule is being developed and applied to fine new uses. Pentaerythritol producers have lived with overcapacity since 1955. They don’t like it. But the industry is optimistic that major new markets are coming. Acknowledgment
a splash in this field, but potential is there. Since 1950, the percentage of alkyd vehicles containing glycerol has decreased steadily, while those made with PE have increased (77). hTevertheless, few producers count on alkyd outlets to take care of existing surplus capacity in the short-term future. But other hopes come along. Pentaerythritol tetranitrate output has increased steadily since 1946 and now has annual production exeeding 2,000,000 pounds ( 2 ) . Known as an explosive since 1894, it could not price competitively until PE was commercially available. During World War 11, production increased sharply, hitting 14,200,000 pounds in 1944. Following the war, output dropped out of sight-only 162,000 pounds in 1946! But new blasting and medicinal applications give it a second life. Domestically, pentaerythritol tetranitrate is commercially made by batch nitration, with nitric acid, keeping temperature below 25” C. (8). Manufacturers include Hercules, Du Pont, Trojan, and Atlas Powder. About 270 of U. S. pentaerythritol went into explosives in 1957. Coming Uses for PE
Much of today’s installed pentaerythritol capacity is based on new marketsboth in resin synthesis and other outlet fields, Several are now in various stages of market development; others are currently undergoing laboratory and commercial development studies. Pentaerythritol esters of aliphatic
1 ;I 14
acids below 10 carbons are becoming increasingly popular as poly(viny1 chloride) plasticizers in applications where their stability and low volatility offset their somewhat higher cost. One is use of dipentaerythritol esters in high-temperature resistant wire insulation. Similar products show encouraging results in meeting challenges of hightemperature lubricant requirements for modern, high efficiency jet aircraft engines. PE itself, particularly when used with some metal salts, is being used in an unusually good heat stabilizer for vinyl chloride polymer and copolymer compositions (73). The stabilizer mixture is particularly good in rigid and semirigid compositions where high processing temperatures are needed. Pentaerythritol is also being used successfully in fire-retardant coatings which intumesce when exposed to high temperatures. Such coatings froth and swell up upon heating leaving a n incombustible, high-surface residue which tends to protect a combustible substrate from fire. Acetals of PE with a variety of aldehydes arouse considerable interest as textile creaseproofing agents. They are quite resistant to chlorine bleaches (72). Oxyalkylene ethers of PE are being developed as components of cross-linked foamed plastics. These tetrafunctional liquid polyols aid in obtaining proper balance of properties in such foams. One very promising PE-based polymer will soon go into commercial production. Hercules’ Penton [a polymer of 3,3-bis(chloromethyl) oxetane] is capable of
INDUSTRIAL A N D ENGINEERING CHEMISTRY
The authors wish to thank C. J. Campbell for his help in preparing the article, J. B. Talley and Harold R. Monfort for detailed information and guidance through Hercules’ Missouri Chemical Works, and Wheeler 0. Holmes for help in preparing photographs and related materials. literature Cited (1) Barth, R. H., Snow, J. E., Wood, E. H., presented before Meeting-
in-Miniature of the North Jersey Section, ACS, Jan. 8. 1951. (2) Berlow, E., Barth, R. H., Snow, J . E., The Pentaerythritols,” ACS Monograph, Reinhold, New York, 1958. (3) Chem. Eng. News 35, 14-6 (Jan. 14, 1957). (4) Ibid.,pp. 20-1 (Dec. 30, 1957). (5) Ibid.,36, 20-1 (Jan. 27, 1958). (6) Ibbid., p. 27 (Feb. 17, 1958). (7) Ibid.,p. 39 (March 17, 1958). (8) Cooley, R. A , Chem. Inds. 59, 745--9 (1946). (9) Guest, H. R., Organic Reactions and Processes Section, Gordon Research Conferences, June 11-15, 1956. (10) Hulse, G. E. ( t o Hercules Powder Go.), U. S. Patent 2,722,520 (Nov. 1, 1955). (11) J . Agr. Food Chem. 6 , 403 (May 1958). (12) Krees, B. H . (to Quaker Chemical Products Co.), U. S. Patent 2,785,996 (March 19,1957). (13) Lally, R. E. (to Ferro Gorp.), Ibid., 2,711,401 (June 21, 1955). (14) Morrison, W. D., Chem. Eng. News 31, 658-60 (Feb. 16, 1953). (15) Schilling, W. M. (to Hercules Powder Go.), U. S. Patent 2,794,027 (May 28, 1957). (16) Sherwood, P. W., Petrol. Rejner 35, NO. 11: 171-9 (1956). (17) United States Tariff Commission, Washington 25, D. C., “Synthetic Organic Chemicals,” 1943-58. (18) Wawzonek, S., Rees, D. A , , J . Am. Chem. Sac. 70, 2433 (1948).
