Note: Descriptions are shown in the official language in which they were submitted.
RC-1547~ g
IPROCESS FOR THE PRODUCTIOM
I
OF_AROMATIC POLYESTERS
, `
I ABSTRACT
IThe production of oxybenzoyl polyesters is facilitated
¦by the incorporation of a phosphite, particularly an organic phos-
¦phite, during the production enabling the production of molded
articles from these polyesters of improved appearance and excellent
Iproperties.
BACKGROUND OF THE INVFNTIGN
The present invention relates to an improved process for
~the prGduction of copolyesters. More particularly, it relates to
!a process for the production of oxybenzoyl polyesters of aromatic
¦dicarboxylic acids, bisphenols and p-hydroxybenzoic acid compounds
las the starting mat~rials.
It is known that such polyester resins can be produced
¦Iby various polymerization processes including suspension polymeri- '
¦Ization and bulk polymerization. Of these, the bulk polymerization
process is perhaps the most desirable process in terms of economy.
IHowever, since the arcmatic polyesters have a high melting point
las compared with aliphatic polyesters, such as polyethylene tereph-
Ithalat~, a higher temperature is required to maintain the aromatic
polyesters at their molten state. Consequently, the polymers are
1often colored and deteriorated in performance.
I Much effort has therefore been expended on the develop-
ment of a process which eliminates the disadvantages discussed
above and provides a polyester molding material from which articles
of pleasing and uniform appearance and properties can be obtained.
THE INVENTIOi~
Accordiny to the present invention, there can be pro-
I!duced a polymer having an extremely low degree of coloration and
~L2~Q~
an excellent heat stability which has hitherto not been obtainable
by the conventional bulk pol~nerization.
It is an object of the present invention to provide a
process for the production of aromatic polyesters having an
extremely low degree of coloration and an excellent heat stability.
It is another object of the invention to provide an
improved process for the economic production of aromatic polyesters
Other objects and further scope of the applicability of
the present invention will become apparent from the detailed
description given hereinafterO It should be understood, however,
that the detailed description and specific examples, while indi-
cating preferred embodiments of the invention, are given by way
of illustration only, since various changes and modifications
within the spirit and scope of the invention will become apparent
1~ to those skilled in the art from this detailed description.
In accordance with the present teachings, a bulk
polymerization process is provided for preparing a thermally
stable wholly aromatic polyester comprising heat condensing
wholly aromatic precursoxs to form a prepolymer, incorporating
into the reaction mixture a phosphite compound, after substan-
tial formation of the prepolymer and before advancing the
prepolymer, in an amount of between about 0.05 to 0.5 parts
per hundred by weight, and advancing the prepolymer to form a
thermally stable wholly aromatic polyester having the required
degree of polymerization.
It has been found that a process overcoming the problems
encountered in the practice of the prior art processes and provid-
ing polyester resins whose use is not attended by the noted draw-
backs is prov.ided by the improvement which comprises adding a
phosphite during the preparation of the resin and, particularly
to the prepolymer melt prior to advancement of the f:inal product
to the desired degree of polymerization.
The wholly aromatic polyesters towards whose prcduction
the present invention is directed consist of combinations of
repeating units of one or more of the following formulae:
~ ~ ~ )n ~ ~ c 3 ~oc ~ (x) ~ co ~
L ~3 (x) n~3 ~ ~ ~3 co ~
III ~ IV 5
~oc~coT fo~ol
V t VI u
.3
0~39
Iwhere x is O, S, - ¦¦ - , NH, or SO2 and ~ is 0 or 1 and the total
¦of the integers p + q + r + s ~ t + u in the moieties present is
from about 3 to about 800.
Combinations of the above units include union of the
carbonyl group of Formulae I, II, IV and V with the oxy group of
Formulae I, III, IV and VI. In the most general combination all
~units of the above formulae can be present in a single copolymer.
¦The simplest embodiment would be homopolymers of units I or IV.
IOther combinations include mixtures of units II and III, II and
¦VI, III and V, V and VI, and I and IV.
I The location of the functional groups are preferably in
¦the para (1,~) positions. They can also be located in meta (1,3)
position to each other. With respect to the naphthalene moiety,
the most desirable locations of the functional groups are 1,4i 1,5
land 2,6. Such groups can also be in the meta position to each
lother.
The symbols p, q, r, s, t and u are integers and indi-
Icate the number of moieties present in the polymer. The total
¦(P + q + r + s -~ t + u) can vary from 3 to 800 and, when present,
¦the ratio of q/r, q/u, t/r, t/u, q + t , q + t and t can
! r r + u r + u
jvary from about lO/ll to about ll/lO with the most preferable ratio
being lO/lO.
Exemplary of materials from which the moieties of For-
llmula I may be obtained are p-hydroxybenzoic acid, phenyl-p-hydroxy-
llbenzoate, p~acetoxybenzoic acid and isobutyl-p-acetoxybenzoate.
¦IThose from which the moiety of Formula II is derivable include
¦Iterephthalic acid, isophthalic acid, diphenyl terephthalate,
¦Idiethyl isophthalate, methylethyl terephthalate and the isobutyl
~ihalf ester of terephthalic acid. Among the compounds from which
¦Ithe moiety of Formula III results are p,p'-bisphenol; p,p'-oxybis- ¦
phenol; ~ dihydroxybenzophenone; resorcinol and hydroquinone.
Inspection will show which of these materials are also suitable
lfor supplying the moieties of Formulae VI - VII:[.
,
¦ Examples of monomers represented by Formula IV are
¦6-hydroxy-1-naphthoic acid; 5-acetoxy-1-naphthoic acid and phenyl
5-hydroxy-1-naphthoate. Monomers representing Formula V include
1,4-naphthalenedicarboxylic acid; 1,5~naphthalenedicarboxylic acid
and 2,6-naphthalenedicarboxylic acid. The diphenyl esters or
dicarbonyl chlorides of these acids can also be ~sed. Examples of ¦
monomers representative of Formula VI are 1,4-dihydroxynaphthalenei
2,6-diacetoxynaphthalene and 1,5-dihydroxynaphthalene.
Particularly preferred for use in the practice of the
lQ present invention are plastic ma~erials based upon oxybenzoyl
polyesters.
The oxybenzoyl polyesters useful in the present invention
are generally those repeating units of Formula VI:
(VI)
~o~ll~
, P
~where p is an integer of from about 3 to about 600.
I One preferred class of oxybenzoyl polyesters are those
¦of Formula VII:
(VII)
~3 ~,
P
¦wherein R1 is a member selected from the group consisting of ben- ¦
¦zoyl, lower alkanoyl, or preferably hydrogen; wherein R2 is hydro- ¦
gen, benzyl, lower alkyl, or preferably phenyl; and p is an integer
from 3 to 600 and preferably 30 to 200. These values of p corres-
pond to a molecular weight of about 1,000 to 72,000 and preferably
3,500 to 25,000. The synthesis of these polyesters is described
I
l. I
l ~
~in detail in Canadian Patent 822,194 entitled "Polyesters
Based on Hydroxybenzoic Acids". U.S. Patent Mo. 3,668,300
makes reference to the U.S. counterpart of the Canadian
Ipatent above.
Another preferred class of oxybenzoyl polyesters are
copolyesters of recurring units of Formulas VII, VIII and IX:
(VIII)
(IX)
~o~(X)L,~ =o~
. n r
¦wherein X is -O or -SO2-; m is 0 or 1; n is 0 or 1; q:r = 10 15 to
15:10; p:q = 1:100 to 100:1; p + q + r = 3 to 600 and preferahly
120 to 200. The carbonyl groups of the moiety of Formula I or III
¦are linked to the oxy groups of a moiety of Formula I or IV; the
joxy groups of the moiety of Formula I or IV are linked to the car- ¦
Ibonyl groups of the moiety of Formula I or III.
¦ The preferred copolyesters are those of recurring units
!f Formula X:
2s f ~c ~ 1l o~ 1 o 4~ o3
1 The synthesis of these polyesters is described in detail !
¦iin U.S. Pat- No. 3,637,595, entitled "P-Oxybenzoyl Copolyes~ers",
~ ' I
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1 ~2~38~ 1
¦I The bulk condensation oE aromatic polyesters is described
¦in the patent literature and broadly considered involves an alkan-
~¦oylation step in which a suitable dicarboxylic acid, hydroxyben-
¦!zoic acid and diol are reacted with an acid anhydride, a prepoly-
¦Imerization step in the reaction product of the first step is poly- ¦
condensed to prepare a prepolymer and the prepolymer is thereafter
lheated to produce a polycondensate of the desired degree of poly-
~merization.
¦ The polyesters useful in the present invention can also
llbe chemically modified by various means such as by inclusion in
¦Ithe polyester of monofunctional reactants such as benzoic acid or
¦Itri- or higher functional reactants such as trimesic acid or cyan-
luric chloride. The benzene rings in these polyesters are prefer-
iably unsubstituted but can be substituted with non-interfering
Isubstituents, examples of which include among others halogen such
~as chlorine or bromine, lower alkoxy such as methoxy and lower 1i
¦! alkyl such as methyl.
The phosphite can be an organic or inorganic phosphite.
IIHowever~ the use of an organic phosphite, such as an alkyl phos-
llphite, an aryl phosphite, an alkyl-aryl phosphite or a di- or
polyphosphite is preferred. More particularly, the follo~"ing
phosphites can be employed:
Diisooctyl Phosphite
I Di.stearyl Phosphite (Solid)
I; Triisodecyl Phosphite
Triisooctyl Phosphite
Trilauryl Phosphite
Diphenyl Phosphite
I Trisnonylphenyl Phosphite
Triphenyl Phosphite
Diphenylisodecyl Phosphite
Diphenylisooctyl Phosphi-te
Phenyldiisodecyl Phosphite
Diisodecyl Pentaerythritol Diphosphite
Tetraphenyl Dipropyleneglycol Diphosphite
Poly(dipropyleneglycol) Phenyl Phosphite
Dilauryl Phosphite
Ethyl He~yl Djphenyl Phosphite
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Il
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¦ Phenyl Neopentylglycol ~hosphi'te
Diisooctyl Octylphenyl Phosphite
~ Distearyl Pentaerythritol Diphosphite (Flake).
¦ While the addition of the phosphite at any stage of the
¦procedure is contemplated, it has been found to be particularly
¦effective, and to provide markedly superior properties in the
articles molded from the oxybenzoyl polyester resin, if the phos-
phite is added shortly before, for example about five minutes
before, the prepol~mer is transferred to the ne~t stage, as by
dumping into an insulated tray wherein an intermediate stage of
polymerization takes place before the thus advanced resin is trans-
ferred to suitable equipment, for example a rotary heating drum,
for advancement to the desired stage of polymerization.
In another approach to the determination of the optimum
point for addition of the phosphite, lt has been found that the
¦phosphite can most advantageously be added at about 95~ COnVersiQn
¦as indicated by the distillate yield of acetic acid.
The phosphite can be added as solid flakes or as a liquid
¦melt at a temperature above the melting point of the phosphite.
It is also possible to add the phosphite in a solution in acetic
lanhydride when incorporation is effected at a lower temperature.
¦Addition in melt form is in general preferred.
The amount of phosphite added is dependent on the purity
If the monomer. The purer the monomer, the less phosphite need be ¦
¦added to achieve the desired result. The purity is related to the
¦phenol and the amount of phenol employed and to the amount of ash
¦produced. Where there is a higher ash content, increased amounts
!f phosphite will be required to achieve optimum results, which
irequires a balancing of the achievement of the optimum levels for
¦!the achievement of optimum results in achieving the desired color
¦! and the desired level of thermal stability.
I Broadly, the phosphite has been addecl over a range of
¦Ifrom about 0.05 parts per hundred to about 0.5 parts per hundred.
IHowever, the preferred range is from about 0.1 to about 0.25 parts
_ 7 _
1~
~22~
~per hundred with 0.125 parts per hundred representing the optimum
~proportion.
The invention is illustrated by the following examples
which are not to be construed as limiting the present invention,
the scope of which is defined by the appended claims.
The following example provides a control in which no
~additive is present.
EXAMPLE 1
I CONTROL
A charge of 207.3 g (1.096 moles) of 4,4'-dihydroxybi-
phenyl (Assay 98.5%), 307.6 g (2.23 moles) of 4-hydroxybenzoic
acid, 185 g (1.11 moles) of terephthalic acid and 498 g (4.88
moles, 10% excess) of acetic anhydride was refluxed with stirring
for three hours. The contents of the reactor were then blanketed
with nitrogen and the mixture heated at an average rate of 30C/hr
to 295C and held for one-half hour at this temperature. At this
¦point, the reaction mixture was dumped into a pyrex dish lined
¦with aluminum foil and the resulting prepolymer ground and passed
Ithrough a 20 mesh screen.
I The above prepolymer (5.464 g) was inserted into a tube
¦furnace already preheated to 229~C. With a slight nitrogen sweep
¦the temperature of the material was raised to 360C in four hours
land held at 360C for one hour~
After cooling, the material was weighed and the weight
~5 lloss from prepolymer to advanced polymer was found to be 3.6~.
¦This polymer showed a peak endotherm at 417C as determined by
¦differential scanning calorimetry (DSC) under nitrogen. The resln
Ishowed a total weight loss in air of 3.6% when heated at 400C for
Ithree hours using thermogravimetric analysis (TGA). The rate of
iweight loss at 400C in air was 1.2~/hr after the first hour.
The following example illustrates the effect of the
~laddition of 0.28 pph oE clistearyl pentaerythritol diphosphite to
prepolymer melt before dump.
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1Z20~389
EXAMPLE 2
~ The charge and process were the same as in Example 1
¦¦except that at a point five minutes prior to the prepolymer dump,
¦1.75 g (0.28 pph based on theoretical advanced polymer yield) of
~distearyl pentaerythritol diphosphite was added to the prepolymer
~melt.
I This prepolymerl after grinding and screening, was also
¦advanced under a nitrogen sweep by the process described in Exam
ple 1. This time, the weight loss from 6.184 g of the prepolymer
was found to be 5.17~ from prepolymer to advanced polymer. The
peak endotherm by differential scanning calorimetry was found to
be at 410C. The weight loss of this resin as determined by TGA
was only 0.7~ after three hours at 400C in air. The rate of
weight loss after the first hour was only 0.2%/hr compared to
¦1.2%/hr as with the control sample.
The following examples compare the efficiency of addi-
¦tion of distearyl pentaerythritol diphosphite to the prepolymer
melt with addition of distearyl pentaerythritol diphosphite to
jprepolymer ln a rotary drum prior to advancing. Example 3 is a
,control in which no additive was added.
1 1
EX~PLE 3
A mixture of 301.1 g (2.18 moles) of 4-hydroxybenzoic
~lacid, 181.0~ g (1.09 moles) of terephthalic acid, 203.98 g (1.09
~moles, Assay 99.5%) of 4,4'-dihydroxybiphenyl and 525 g (5.15
Imoles, lB% excess) of acetic anhydride was refluxed for four hours.¦
IIJnder a nitrogen blanket, the mixture was heated at a rate of
140C/hr until 97.2% of the total theoretical distillate (including
llexceSS anhydride) was obtained. At this point the temperature in
¦Ithe reactor had reached 340C. The contents of the reactor were
lldumped into an aluminum pan, allowed to cool and qround in a Wiley
IMill through a 1 rnm screen. A yield of 603 g was obtained.
This prepolymer was then advanced with and without addi-
lltion of distearyl pentaerythritol diphosph:ite in a :rotary drum.
j _ 9 _
Il I
WITHOUT DISTEARYL PENTAERYTHRITOL DIPHOSPHITE
A total of 200 g of the prepolyner was placed in the
rotary drum and heated at a rate of 44C/hr under a nitrogen sweep
of 6 SCFH and a rotation of 15 rpm. When the temperature of the
resin reached 354C, the material was hleld at 354C for one hour
and then cooled rapidly. The yield of ,advanced polymer was 96%.
The resin had a peak endotherm at 420C and showed a weight loss
in air of 0.84% at 400C after three hours (TGA). The rate of
weight loss was 0.18%/hr after the first hour.
DISTEARYL_PENTAERYT~.~ITOL DIPHOSPHITE ADDED TO DRUM
A total of 200 g of prepolymer and 0.5 g (0.250 pph) of
distearyl pentaerythritol diphosphite was placed in a rotary drum
and advanced as above. The yield of advanced polymer from pre-
polymer was 96.5~. This advanced resin had a peak endotherm at
421C (differential scanning calorimetry). The total weight loss
at 400C in air after three hours was 0.87% with a rate of weight
loss of 0.14%/hr after the first hour.
The following example illustrates the effect of the addi-
Ition of 0.125 pph distearyl pentaerythritol diphosphite to the
Iprepolymer melt at 95% conversion.
i EXAMPLE 4
The charge and the process was the same as in Example 3
¦except that when the total distillate yield was 95% of theoretical~
j(including excess acetic anhydride), 0.81 g (0.125 pph based on
¦theoretical polymer weight) of distearyl pentaerythritol diphos-
¦phite was added. (The temperature of the melt was 330C at this
Ipoint.) The mixture was heated further to 340C in 15 minutes and
Ithe reactor content dumped into an aluminum pan. A total distil- ¦
Illate yield of 588 g (97.4~ of theoretical including excess acetic
I!anhydride) was obtained and the ~repolymer yield was 590 g.
I After grinding and screening oE the prepolymer as in
i! ~xample 3, 200 g was charged in a rotary drum and advanced to
1.
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~i ~
I :~22~38~
¦354OC and held one hour (as in Example 3). The resulting advanced
¦polymer had a reversible first peak endotherm at 421C (differen-
tial scanning calorimetry). Total weight loss in air after three
hours at 400C (TGA) was 0O75~ with a rate of weight loss of
0.08~/hr after the first hour. This represents a 2.25~ fold
decrease in the rate of weight loss over the unstabilized polymer
¦and a 1.75% fold decrease over that of resin prepared with twice
as much distearyl pentaerythritol diphosphite added to the drum.
I EXAMPLE 5
I The charge and the process were the same as in Example 4
¦for each of the additives and additive levels shown in Table I
¦below. The differences between additives and additive levels was
¦the only variation from the procedure of Example 4. The additives
Iwere introduced at the point at which the total distillate yield
Iwas 95~ of theoretical (including excess acetic anhydride). The
¦Irelative weight loss determined is set forth in Table I.
!
TA:~LE I
OTHER PHOSPHITE ADDITIVES AND LEVELSl
, Relative Rate of
1 2 Weight Loss
I _ Phosphite PPH_ 400C, Air
¦iDistearyl Pentaerythritol 0.00 3.8
' Diphosphite 0.10 1.2
0.125 1.0
, 0.250 1.8
ITrisnonylphenyl Phosphite 0.125 1.05
0.250 1.83
¦Bis(2,4-Di-t-Butylphenyl) 0.125 1.0
I Pentaerythritol 0.250 1.2
' Diphosphite
IDiisodecyl Pentaerythritol 0.125 1.2
Diphosphite 0.250 1.2
Triphenyl Phosphite 0.125 1.5
, ~
ll In addition to optimum level of phosphite regarding rate of
weight loss, too much or too little phosphite additive can
I affect the color and homogeniety. The above examples are based
li on high purity~low ash monomers.
1,2 Base on phosphorus content to give equivalent pph of dis-tearyl
I pentaerythritol diphosphite.
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3 Relative rate of weigh~ loss of advanced resin compared to
advanced resin using 0.125 of distearyl pentaerythritol diphos-
phite giving 1.0 rate of weight loss as the standard.
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