REDUCTION IN PROCESSING T I M E OF UNSATURATED POLYESTERS M. P. STEVENS A N D J . D . GARDNER California Research Corp., Richmond, Gal$.
Catalysts and combinations of catalyst and solvent were studied as agents for reducing processing of unsaturated polyesters containing isophthalic acid. Effectiveness of catalysts varied with polyester formulation. The effect of catalysts and residual solvent on polyester properties was also studied. Catalysts had no effect on mechanical and thermal properties of the polyesters, and the traces of solvent remaining after a run did not significantly alter resin properties.
ATALYSTS S U C H A S
H2SOr or p-toluenesulfonic acids which
C are effective for simple esterification
are generally not suitable for preparing pol>-esters because they cause poor resin color and tend to demmpose gl>-cols. These difficulties have been avoided in the p a t by using trans-esterification to prepare high molecular weight saturated polyesters or direct esterification in the absence of catalyst to prepare loiver molecular \veight unsaturated pol>-esters. I n recent years. several patents ( 5 - 7 ) have been issued which describe the use of metals. metal salts, or organometallic compounds as catalysts for direct esterification. In thcse laboratories. a n investigation of a variety of catalysts in isophthalic acid--based polyesters revealed a selectivit)- not obvious in the patent literature. Catal>-st activity \vas so dependent on po1yestt.r formulation that it was impossible to piedict effectiveness of catalysts from one formulation to another. Even metals of the same periodic subgroup exhibited different activit>-. a n effect noticed earlier by D u n l a p and Heckles in their stud>-of oleic acid esterification ( 3 ) . 'l'his investigation was limited to unsaturated pol\-esters containing isophthalic acid. I t \vas prompted py the Jvork of Carlston a n d colvorkers ( 2 ) \vho sho\ved that isophthalicmaleic pol>-esters had properties superior to the corresponding phthalic resins. Processing times of isophthalic resins are generally longrr. ho\$:ever. because isophthalic acid is less soluble than phthalic anhydride. a n d isophthalic resins are normally proressed to higher molecular \$-rights. Some time is saved by iising the tico-step method (2'1 of preparation. ivhereby the isophthalic acid is esterified with all the glycol in the first step. a n d maleic anh>-dride (or fumaric acid) is reacted in the second step to form polyester; however, when secondary glycols such as propylene glycol are used. reaction raws are still very low. Numerous compounds were tested as catalysts in both onea n d tkvo-step preparations (Table I): but only the most effective ones are discussed here-namely, tetrabutyl and tetraoctyl titanates. te trabutyl zirconate. zirconium naphthenate, and stannous oxalate in combination Tvith sodium a n d zinc acetates. \Vhile catalysts were tested only in fusion processes. the feasibility of solvent processing in conjunction \vith esterification catalysts was investigated. Results show that u p to SOTc of processing time can be saved using catalysts or catalysts in combination with solvent. T h e effect of catalysts and residual solvent on pol,).ester properties \vas also studied.
t h a n those d u e to ether formation. This condenser was replaced with a straight take-off tube \-col, LIE(; = diethylene
Table 1.
Compounds or Combinations Tested as Catalysts for Polyestersa
a
Most Effective Trtrahutyl titanate Tetraoctyl titanate Tetrabutyl zirconate Zirconium naphthenate 3/1 Stannous oxalate/sodium acetate 3/1 Stannous oxa1ate;sodinm acetate with zinc acetatc Less Effective Tetraphenyltin Ilihutyltin dichloridr Zinc acetate Stannous oxalate Zinc naphthenate ferrous acrtylacetonate Manganese naphthenate Triphenylantimony Tributylantimony Triphenylhismuth Magnesium titanate Magnesium zirconate Ineffective Boric acid Chloroacetic acidb Trimethylamineboraneh Dimet hylaminrboraneb Pyridineboraneh Dibasic lead phthalate Cobalt naphthenate Magnesium zirconium silicate .Magnesium hypophosphite Compounds tesied at a m r i e t y of concentrations up to 0.77; mftal or
0.; 7'
compound (in t h r cast of orqanic compounds) bastd on reactor rliorte.
Experimental
Unsaturated polyesters were prepared on a l a b o r a t o n scale with the equipment shown in Figure 1 . T h e steam-jacketed zig-zag condenser practically eliminated glycol losses other
.Molar Ratio
Caused ethtri$cation of g l j c o l .
VOL. 4
NO. 1
JANUARY
1965
67
THERMOMETER
I STEAM INLET
I 1 01 II
PARTIAL CONDENSER
TOTAL CONDENSER I
0
CW O U T L E T - d l STEAM
ELCTEAM
co;;:wC.+d
TRACED
PACKED TOWER
AND
@ O d
CW I N L E T
KETTLE CHARGEINERT GAS SPARGE STEAM OR COOLING WATER
CONDENSATE RECEIVER
,RESIN KETTLE HEATED
_W- H
Gate ~a'.e-Normdl'i
-6ate
E INERT GAS OUTLET
Gon
+zlve-?srmal'r C o i e d
L T o THINNING
TANK
P-
>e''ef
TO DRAIN
Figure 2. Ten-gallon resin kettle for preparing unsaturated polyesters I. RECEIVER
2.
3.
Minimum height above p a r t i a l condenser; line to total condenser to slope downward Cooling water outlet for total condenser when p a r t i a l condenser contains steam a t end of cook Vent valve and relief valve; vent valve open with cooling water, closed with steam Cooling water Steam High-temperature alarm Low-temperature alarm Temperature controller
2 ' =
LAB J A C K
CW.
Figure 1. Laboratory equipment for preparing unsaturated polyesters
glycol. and EG = ethylene glycol. Commercial dibasic acids and g l y o l s \ v e x used. These formulations \\ere studied at processing temperatures t)-pical of those found in practice. Esterification rate \vas follo\\-ed by periodically Lvithdraxving samples from the reactor. dissolving them in a 3 to 1 tolueneisopropyl alcohol solution. a n d titrating to a phenolphthalein end point with niethanolic KOH. Acidity \\-as expressed as acid number (milligrams of potassium h>-droxide required to iieutralize 1 %ram of sample). I n some cases. the extent of reaction \\-as also follo\\ed by measuring increase in G a r d n r r Iioldt viscosity of 30 to '0 or 40 to GO styrene-pol!-estcr soiulions. but generally resins \\ere processed to the same viscosit). and acid number. For this study. emphasis !vas placed on acid number because this properly reflects esterification rate. Clear castings and glass-filled laminates prepared from the polyrsters were tested according to the usual ASTM methods ( / ) ,
PROCESS DESIGN A N D
SECOND STEP
uib
O L ' I L
2
4
6
8
L
1 0 2
T I M E , HOURS
Figure 3. Effect of catalysts on two-step processing time of 1 / 1 / 2 IP/MA/PG polyester at 390" F. 0
N o catalyst
0 3 to 1 stannous oxalate-sodium acetate (0.05% Sn) A 3 to 1 stannous oxalate-sodium acetate with zinc acetate (0.05%
A
I t should be emphasized that this discussion is concerned mainly tvith laboratory experirnents under controlled conditions. I t is riot al\rays possible to relate these methods directly to large-scale commercial equipment because reaction rates are dependent on such design factors as rate of inert gas flo~v. agitation. type of overhead sk-stem. and so on. Some overhead systems. Tor example. ma)- flood a t very high esterification rates because they cannot handle the rapid distillation of \vater, .4 few successrul runs \\ere made, hoLvever. in a resin kettle Lvhich. although small. is of comparable design to commercial kettles. Laboratory runs \vcre very reproducible. Differences in processing time to rcach specific acid numbers \\ere never more than 1 5 minutes. Figures 3 to 8 shoiv representative runs that were duplicated a t least three times. Effect of Esterification Catalysts. Propylene glycol is a common ingredient i n pol>-esters because it is loiv in cost and the products are generally compatible with styrene. the most common cross-linking monomer. I t s srcondary h>-drox>-l I&EC
TAL. TC.
Sn, 0.1 7 0 zn)
Results and Discussion
68
ST. TAH.
DEVELOPMENT
0
Tetrabutyl zirconate (0.1% Zr) Tetrabutyl titanate (0.0370 Ti)
group. howcver. makes it more difficult to esterify than glycols \vith only primary hydroxyls. Figure 3 sho\vs the effect of the tin. titanium. and zirconium catalysts in reducing the reaction time of a 1 1 2 IP ;M:l PG polyester prepared by the rivo-step method at 390' F. CataIl-st concentrations are expressed as \\-eight per cent of the first step char5e to the flask. T o avoid difyerences in upheat rates. reaction times are from the first \vater condensed in the receiver. 'The stannous oxalate-sodium acetate and stannous oxalate-sodium acetate- zinc acetate combinations are most effective. although the latter imparts a haze to the resin. U n expectedly. stannous oxalate-sodium acetate had no effect in a one-step preparation (Figure 4), [This combination has been recommended for use in neopentyl glycol polyesters ( - I ) . ] '1-etrabutyl titanatc. effective in the first step, has no effect in the second. Catal>-sts generally have a n adverse effect on resin color.
eoy
,-.so:
'\
FIRST STEP
\
TIME, HOURS
Figure 5. Effect of catalysts on two-step processing time of 1 / 1 /2 IP/MA/PG polyester a t 390" F. in 1 0-gallon resin kettle
Figure 4. Effect of stannous oxalatesodium acetaie on one-step processing time of 1 / I IP/MA/PGpolyester at 3 9 0 " F.
/>?
0
N o catalyst 3 to 1 stannous oxalate-sodium
1
\
v
TIME, HOURS
0
\
STEP
t
A No catalyst 0 3 to 1 stannous oxalate-sodium (0.05% Sn, 0.1 % Znl
acetate
a c e t a t e with zinc a c e t a t e
3 to 1 stannous oxalate-sodium a c e t a t e
L-
(0.0570Sn)
naphrhenate ('containing 6 7 , Zr) acts similarly to tetrabutyl zirconate. lyhile tetraoctyl titanate acts like tetrabutyl titanate. An added bonus tvith zirconium catalysts is that they consistently give lighter colored resins than \\.hen no catalyst is used. Also, unlike the titanates, they form no color with inhibitor. I n view of the fact that D u n l a p a n d Heckles ( 3 ) found catalyst effectiveness to be inversely proportional to ionic volume of metals in a given group, it is surprising that zirconium is more active here than titanium. It can be argued that changes in catalyst activit!- might arise froin changing from maleic to fumaric. T h a t this is unlikely is shown by the processing d a t a of a 3,'4, 5.6 '1.4 IP, FA/ DE[;, EG polyester. \Vith 20%; of the diethylene glycol replaced with ethylene glycol, tetrabutyl zirconate \vas ineffective. but tetrabutyl titanate reduced reaction time by 25Yc (Figure 8). Diethylene glycol by itself apparently favors zirconium. but addition of other gl>-cols destroys zirconium's effectiveness as a catalyst. This was also demonstrated by the fact that tetrabutyl zirconate did not catalyze preparation of the prop>-lene g l y o l resin byhen 10 mole of the propylene glycol 11'3s replaced \vith diethylene glycol. I t appears. therefore, that the glycol has a greater influence on the catalyst than does the dibasic acid.
Styrene solutions of resins catalyzed with titanates have exceptionally dark color. apparently because of interaction bet\veen catalyst a n d inhibitor. (This color is absent \\.hen n o inhibitor is present.) T h e color mostly clears u p . hoivever, during curing. Figure 5 demonstrates the effectiveness of stannous oxalate-. sodium acetate a n d stannous oxalate-sodium acetatr-zinc acetate in preparing [ h e I, 1 2 IP, MA PG resin in a 10-gallon resin kettle. T h e three-part catal) st system is most effective. reducing over-all processing time some 42%. O p t i m u m concentration appears to be 0.05i;C Sn based on first-strp charge. \\'hen prop>-leiir glycol is replaced Lvith diethylene glycol. catalyst activity changes markedly. Figures 6 a n d 7 show the effect of catalysrs in reducing reaction time of a 1, 1, 2 IP/ FA DEG resin prepared in one step a t 420" F. In contrast to the propylene glycol resin. tetrabutyl zirconate, at a n optimum concentration of 0.023cc Z r based on total charge. is the most effective catal!-st. reducing processing time 457,. Tetrabutyl titanate. even at relatively higher concentrations (Figures 6 and 7 ) . is not so effectivt: as the zirconate. Lo\ver acid n u m bers a t comparable viscosities obtained Tvith tetrabutyl titanate a n d zirconate prohabl>- are due to lower glycol losses from etherification during t h r shorter reactlon times. Zirconium
70
2-
I
Yh
ZVI 40-
8 30-
x-
2 v
w-
2
v-
z
u-
0
T-
>
I o z ;0 5
>
t
WZL
-I
6L 20-
"
2
s-
Y
za
0 10-
z
s
R-
aP-
2--+ 0
TIME, HOUR:;
OO
I
I
,
I
I
,
I
I
I
I
2
3
4
5
8
7
8
0
1011
1
I
' 0
I2
1
I
I
2
3
4
5
6
7
TIME, HOURS
Figure 6. Effect of cotalysts on processing time of 1 / 1 / 2 IP/FA/ DEG polyester a t 4 2 0 " F.
Figure 8. Effect of catalystson processing time of 3/4/5.6/1.4 IP/FA/DEG/ EG polyester a t 4 4 6 " F.
0
0
0
No catalyst Tetrabutyl titanate (0.07770Ti) 3 to 1 stannous oxalate-sodium acet a t e ( 0 . 0 3 9 % Sn) Tetrabutyl zirconate (0.02370Zr)
0
fl
N o catalyst Tetrabutyl titanate (0.02270Ti) 3 to 1 stannous oxalate-sodium (0.036% Sn) Tetrabutyl zirconate (0.02270Zr)
VOL. 4
NO. 1
JANUARY
acetate
1 9 6 5
69
Table II.
Effect of Esterification Catalysts on Polyester Properties 0.25-Inch Clear Castingsb ~ _ _ Ilejec',ls-Inch Glass-Filled LaminatesC tion temp. Flexural Flexural Flexural Strength,e Flexural .\lodulus,e under strength,e modulus,e Impact P.S.I. x 7 0 - 3 P.S.I. 70-6 load,d p.s.i. p.s.i. strength,/ A/t er .4ft er Viscosity. "C. X J0-3 X J0-5 ft.-lb./in. Initial boil0 Initial bod@ - -~
--
-~
x
Formulation and Catalyst
Acid .\-o.
111/ 2 IPIMAjPGh
No catalyst 18 z+ 113 17 5.5 2.1 72 61 2.9 2.8 3 to 1 stannous oxalatesodium acetate 18 x115 17 5.4 3.3 75 56 3.0 2.8 3 to 1 stannous oxalatesodium acetate-zinc acctate 18 Y117 17 5.4 3.3 73 53 2.9 2.6 Tetrahutpl titanate 18 X 111 17 5.5 2.4 68 62 3.0 2.8 11112 I P r.l DEG' No catalyst 15 x-Y 61 16 4 5 1 72 53 2 9 2 6 Tetrahuiyl zirconate 10 163 16 4.6 5.1 68 58 3.0 2.8 'z Gnrdner-tloldt. Catalyzed w i t h 1 'b Lupel-co '4 7'C ( 7 0 5 , benzoyl peroxide), 0.55'; Lupersol DU.M (0'0',1 AIIEKperoxide), and 0.15 naphthenate (ij',C Co): cured J hours at 3 8 " C. and 7 hour each at (io", K O 2 , and 135" C. 12-plj, 787 glass cloth, VolanJinish, catalyzed hencoyl peroxide. preis cured 7 hour at 210' F.,jost-cured J hour at .3UO" F. dST.1.I I) 618-56 ( 7 ) . e A5'T.M D 790-59T( 7 ) . Izod unnotched, .-ISI'.\d U 276-56 ( 7 ) . 2.1 hours' irnmprsion in boiling dictillecl water. ' -lo',; styrene. 30' 1 styrene. Q
Table 111.
Solient,
yoh
0 Xvlerie 0 1 0 5.
1.n 2 0
Effect of Solvents on Polyester Propertiesa
Viscosityc X-
\v -
U e j c r t ion Temp. undu L.oad, C.
FlPsural Strength, P.S.I. X 7 V 3
Fl exural .llodulus, P.S.I. x 10-5
Impact Strength, Ft. -L b. ,IIn.
111
16
5.3
2.2
111 110 103 98
15 14
2.6
15 16
5,3 5 3 5 4 5 3
2 5
110 106 1176
14 13 14
5.4
2.6 2.2
93
15
5,3 5.3 5 3
111 109 106
17
5.3
1.7
15
5.4
2.3 2.5
,Y
w-c it' v - \v
2.2 1 6
roiueile 0 1
05 1. o
2.0 Chrirron 265 thinnfr 0 1
05 1 . (! 2.0
'I
5.4 14 5.3 B a e d on resin-styrene solution. 16
98 7 / 7 / 2 JP,I.LfAiPG polypstpr, dear castings: see T a b l e I I f o i prqharation nnd te.cfing.
2.5 2 6
2.3 Gardner-Holdt, 40?c
rlycne.
Catallsts h a l e no apparent effect on mechanical and thcrrnal p r o p i t i r s of pol\esters ( I a b l e 11) I h e 1 1 2 I P M 1 PG and 1 1 2 I P F 2 DEG iesins \\ere tested as cleai castings and glass-hllt-d laminate?. \\ithin experimental < I i o i . properties \\el? thp snine \\hcther catal\stu were used or not Resistdnce to boiling distilled \later (24 hours' exposure) \\as also not affected r h e onl\ noticeable difference ~ \ n sail apparent slight increase in gel time of the ambient cured 1 1 2 I P M.4 PG resin \\hen the stannous oxalate-sodium acetatezinc acetate combination \\as used as catal\st Solbent reflux to remove \Later of Solvent Processing. esterification i b a common procedure There is some pieludice against its comniercial use. ho\vever. because of difficulnes in remobing last traces of solLent from the resin Labolator\ scale solvt-nt proct-ssing \\as applied to the second step of a 390' F two-step 1 1 2 I P MA PG preparation using w l e n e toluene and Chevron 265 thinner as solbents The latter is a paraffinic solvent 4 common firststep product prepared in the 10-gallon resin kettle mith tetrab u t \ l titanate aq catalxst was used for all subsequent solvent runs Second-step processing time \cas reduced 55Yc with 70
I&EC
PROCESS DESIGN A N D DEVELOPMENT
xylene, 62TCirith toluene. and 41YC \vith Chevron 265 thinner \\-hen resins \yere reacted to acid numbers of 16 or less and Gardnrr-Iloldt viscosities of about X (40Yc s t y e n e ) . Residual solvent xias reduced to less than O.5Yc of total resin solids by replacing the Dean-Stark t r a p with a straight take-off tube when the acid number {vas do\vn to about 22 a n d bloiring the resin \vith about 0.05 cubic foot of inert gas per minute per gallon for 2 to 3 hours. Solvent analysis was done b>- gas chromatography. Success in removing solvent from small laboratory preparations does not necessarily mean it can be removed so readily from large resin kettles. \Vith good agitation and adequate inert gas pressure. hoivever. it should be possible to remove most solvent. T o determine the effect of residual solvent on pol>-ester properties. solvents \vere added to a batch of 1 1 '2 I P MA 'PG resin (40Yc styrene) a t concentrations up to 2 7 , based on total solution. Clear castings were prepared from each of the solutions. and properties of the cured resins Jvere measured. Results are shoirn in Table 111. A4part from a moderate do1vnivar-d trend in deflection temperature under load. resin
properties are virtiiall~;unchanged by addition of solvent. ..Ic.oinl)lairit sorrictitnes heard is that r e s i d u a l solvent caiiscs blistering at thc t.esii.l surface i n a molding operation. ' I his problem \vas not rncl3untered i n inaking X 9 X 2.5-inch boxes i t t a n A L P ( : hlodrl 5200 niatclird-metal die inold with those resiiis containing 1 L;.; solvent.
Acknowledgment
Conclusions
literature Cited
Proccssing c>cles of unsaturated polyrstcrs c a n he effrctivcly Icduced with csrcrilicatioti catal>sis. It is ditlicult t o pwdict i n advancr. however. ~vtiirhcatalyst to use. O n e should not be discouragrd by initial failurrs. s i n c r this studv has sho\vn that difleretit foirriulatioii~~ favoi difIc-rciit ( atalyst s>.stcnls. 'l'his stud!- c n v r t s those g l ~ c o l s\vhic.h are most cornrnoiil) u s t ~ but I aril!, i n a liniitcd s r t oi'LrSiiis. Catal!st sclt,ctivity \\.it11 less cotninon gl!c~ols is (,iirrrtitly undrr irivcsrigation i n thrse I a bora t orics. I V h c i i catalysts are not sufficiciitlb- effective. solvent processitig rail he used. It inay not bc iiccessar) to remove last tiaces of solvent a t t h c end of a r u n because they apparently d o not signiiicantl>- altrr msin propcrtirs. A cornbination o f catal\.st aiid solvrnt in t \ v o - s t r p p i cparations ma!. somrtirnrs be profitable.
(I)
-
I lie authors are gi-atcf'ul to J. \'. Prcoriotn arid I'. E . I h t y lor help i n obtaining marib of these data. a n d to the Oronite Divisioti of (hlifor-ilia Chcniical C h . for suppot tirig this \voi.k.
: h i .
Soc. 'I'rsting Matrrials.
Philadrlphia, Pa.. ' V S ' I M (;,,
Hugginr, I>.(;,:
( 3 ) 1)unlap. 1.. H.. H r c k l r s . .J. S . , J . Ani. O i l Cherrii.c/.r' ,Sue. 37, 285 (1900). (4) Enctirian Kodak (Io,, 'l'rcli. 1)ata Kcpt. N-106, Kochrster. S . I,., 1959.
( 5 ) 1.r B i n s . 1.. K.. Stalir. 1). F. ( t o Pittst)rit.gh Plat(%G l a s s Ch.), L..S. l'atcnts 3,055,867 (Scpt. 25, 1962) : 3,057,824 (Oct. 9,
1962).
(0)'\Vriher. F'. S. ( t o R . t . Goodiicli C o . ) , / b i d . , 3,056,818 (Ocr. 2 > 1962). ( 7 ) LViIson t. LV.. Hiitc~liins. .T. F,. (tci l..astrndn Kodak Co.)? / h i d . . 3,055,869 (Srpt. 2.3, 1 9 6 2 ) .
RASCHIG SYNTHESIS OF HYDRAZINE
The hydrazine-forming stage of the Raschig synthesis has been investigated in a continuous tubular reactor operating a t 480 p.s.i.g., 160" C., and residence times up to 12.5 seconds using 2.070 (ethylenedinitril0)tetraacetic (acid (EDTA) as inhibitor. Four methods of operation have been studied: direct reaction of aqueous chloramine, reaction of chloramine with anhydrous and with 3570 ammonia, and direct reaction of sodium hypochlorite with ammonia. The optimum reactor outlet temperature was found to be between 1 6 0 " and 200" C. and hydrazine yield was shown to increase linearly with reciprocal residence time in the first system. Mole ratios of NH I/NH,CI effect in all four systems.
gave increased yields and chloramine molarity exerted an important
€ I t , t i n t stag
