•
INDUSTRY ss*?-^^''"% f'^?*-.^
:
V4
COOH BENZOIC m^ — TOUJIC ACID MIXTURE (CO-PRODUCT)
CLARIFICATION, CARBON
A MIME FILTRATION HYDROLYSIS
ISOPHTHALIC /SLCID
1 ^
D I M E T H Y L TEREPHTHALATE' X
surface coatings which will make them more versatile, leading to greater production of such e n d products; as an intermediate chemical, isophthaJic will Last phthalic a c i d r e a c h e s commercial production supplement present supply of phthalic anhydride, since it gives results that a r e a s S t a n d a r d ( C a l i f . ) starts its isophthalic plant not obtainable with phthalic anhydride i n a n u m b e r of applications. per-day pilot unit. Major uses for isoo UT AT RICHMOND, Calif., Standard > Production Process. Standard, Oil (Calif.) is now turning valves and phthalic v^ill b e i n alkyd resins, sat- only producer of all three xylenes a n d flipping switches bringing its n e w $10 urated and unsaturated polyester plas- only producer of isophthalic, h a s been million plant on stream for the pro- tics, and plasticizers, according to d e - reticent about disclosing process d e duction of isophthalic acid. W i t h iso- velopment work carried out so far b y tails. Developments leading to isophthalic acid being produced from Oronite a n d by otxiers i t has furnished phthalic production stem from w a r m-xylene, phthalic anhydride from o- development samples t o . T h e s e fields fostered needs for aromatics—among xylene, and dimethylterephthalate from are served by isoplhthalic's competitors, them xylenes—for high octane gasop-xylene, all three of the xylene isomers notably phtthalic anhydride, to t h e ex- line. Problems for postwar chemical will at last b e serving as chemical inter- tent of about 3 5 0 million p o u n d s p e r use o f the phthalic acids were first to mediates in commercial scale production year. Standard will increase tfie n a - separate t h e isomers, then t o find suitwhen Standard's plant gets into full tion's production o f these chemicals b y able oxidation techniques f o r producing production, probably in January. Sales about one seventh in one m o v e . the various phthalic acids. will be as Oronite Isophthalic. Oronite led the way with o-xylene Standard expects the immediate Although, iso—hthalic max-r b e t h e effect ost lilcely b e a sliorhf dis- with a commercial nlant in 194-5, using third and final of the phthalic acids t o location o f pbthalic anhydride b u t the isomer to make phthalic anhydride. move into commercial production, it is thinks demand will eventually become Oronite likewise led the way t o comcoming out in no small quantities: greater than t h e present production mercial production of p-xylene with a .Standard is starting immediately a t t h e capacity for both- Oronite's reasons: plant in 1950, and a second p-xylene JO million-pound-per-year range in a As an end product, isophthalic appar- plant joined t h e Standard family at El one-step scale-up from a 100-poimd- ently provides improved plastics a n d Segundo, Calif., in mid-1953. A plant
Isophthalic-- 50 Million Pounds
NOV.
2 I,
I 95 5
C&EN
5017
INDUSTRY for separating m-xylene is part of the new isophthalic plant at Richmond. Only two oxidation agents have been used commercially in the past in any volume to make phthalic acids—air a n d nitric acid—and no single process appears t o b e completely satisfactory for use on all three isomeric xylenes, according to W. G. Toland of Cal Research, Standard's research subsidiary. O-xylene can be oxidized directly b y air in the vapor phase over a v a n a d i u m oxide catalyst, but other xylenes u n d e r g o degradation under these conditions. Suitability of o-xylene for vapor p h a s e oxidation apparently hinges on its ability to stabilize as a cyclic anhydride. A n added complication in liquid p h a s e oxidation of the m e t a and para isomers is apparently d u e to one carboxyl group's introduction making oxidation t o the dibasic acid much more difficult, Toland says. Cal Research, with some 15 years of xylene oxidation development b e h i n d it, side-stepped this difficulty with the discovery that if t h e first carboxylic acid g r o u p is changed to another functional g r o u p , such as an ester, then oxidation of t h e second group proceeds m u c h more easily. Thus, one Cal Researchdeveloped process for oxidation of m- a n d p-xylene involves four steps: oxidation of the xylene to toluic acid, esterification with methanol, oxidation of t h e ester to the methyl hydrogen phthalate, a n d final esterification with methanol to the dimethyl phthalate. This process is n o w being used commercially by Hercules to produce dimethyl terephthalate under a nonexclusive license from Cal Research (C&EN, Jan. 11, 1954, page 1 2 8 ) . In addition to this broad general process involving methyl esterification, Cal Research has a patent structure on several additional xylene oxidation methods, including straight air oxidation. While Standard has thus never admitted publicly what its isophthalic process is, worth noting is a series of four patents assigned to Cal Research Nov. 1, 1 9 5 5 - U . S . Patents 2,722,546, 2,722,547, 2,722,548, and 2 , 7 2 2 , 5 4 9 w h i c h add yet a fifth method to Standard's xylene patent structure. These take a different approach and could well b e t h e basis of Standard's commercial plant. This fifth process uses some form of sulfur as the oxidizing agent in an aqueous medium also containing ammonia and or an ammonium salt. Reaction temperatures disclosed in these patents vary from 200° to a b o u t 700° F. at pressures "great e n o u g h to maintain at least part of the w a t e r in the liquid state." I n this system, t h e
ALKYD RESINS
ALKYD OILS
UNSATURATED POLYESTERS (Polyester S t yrene ix» Copolymers) SATURATED POLYESTERS ( F i l m s , Rig id ond Flexible Fooms, SilicoTie-modif ied Resin)
POLYAMIDE RESINS (Molding Moteriols^ Adhesive*)
- : PLASTICI2ERS; Ju { Mon o;m>ri c^ E s t e r s
5018
C&EN
NOV.
2 1,
1 9 55
acid ends u p as t h e amide and as a m monium salts in t h e oxidation reactor, a n d subsequent hydrolysis liberates the free isophthalic acid. > A l k y d s , Plastics, Plasticizers O u t lets. Perhaps the greatest market development work on isophthalic has gone into its potentialities in alkyds (C&EN, May 9 , page 2 0 1 4 ) . H e r e Oronite is banking o n w h a t it believes are a n u m b e r of advantages over phthalic anh y d r i d e alkyds, including t h e important ability of p e r m i t t i n g alkyd oil (alkyds of very long oil length) production because of isophthalic's greater reactivity than pbthalic a n h y d r i d e . T h e s e alkyd oils a r e expected to find a substantial outlet in exterior paints a n d possibly in printing inks. It is worth noting in passing t h a t a n u m b e r of alkyl aromatic acids, such as benzoic acid, are suitable as short oil alkyd madifiers. Co-product from Standard's isophthalic p l a n t will b e a mixture of benzoic a n d m-toluic acids ( 8 0 to 90% benzoic), which is expected to find a spot in this market, too. Standard is also looking t o a n u m b e r of plastic outlets in addition to coatings. Unsaturated polyesters (polyester-styrene copolymers) h a v e better strength properties a n d h e a t distortion characteristics than similar resins from phthalic anhydride, Oronite says, while silicon-modified resins show good results in high t e m p e r a t u r e electrical insulation. E t h y l e n e glycol isophthalate high polymers give a resin with a softening point of a~bout 140° F . Further reaction with diisocyanates gives polyurethane t y p e rubbers, while introduction of water into this reaction gives rigid foams with high t h e r m a l stability. A 20:80 mixture of isophthalic and terephthalic acids gives a crystalline polymer, while high polymers of isophthalic a n d hexanaethylenediamine give polyamide resins for molding compounds a n d adhesive applications. Monomeric ester plasticizers have lower volatility than d o phthalic anhydride plasticizers, resulting in better efficiency on long aging, while polymeric plasticizers for polyvinylchloride resins and alkyd type plasticizers for nitrocellulose are likewise improved through u s e of isophthalic, Oronite says. • Marketing. About 7 5 % of the Richmond plant's production will be marketed in t h e East, considering the geographic distribution of t h e paint and plastic industries, a n d Standard will take a d v a n t a g e of inexpensive ocean shipment t o get its p r o d u c t to market. T h e California plant will also t u r n out about 5 million p o u n d s of m-xylene a year for direct sales to others. •
