Impact modified polyester

Provided is an impact modified copolyester prepared from a reaction of an aromatic dicarboxylic acid component and a diol component. The aromatic dicarboxylic acid component is terephthalic acid or an ester derivative thereof, and the diol component comprises a mixture of 1,4 butanediol and an alkoxylated bisphenol A. The combination of the 1,4 butanediol and alkoxylated bisphenol A provides for a polyester exhibiting superior impact properties.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to polyesters prepared from an aromatic 
dicarboxylic acid component and a diol component. More particularly, the 
present invention relates to polyesters prepared from terephthalic acid or 
an ester derivative thereof and a diol component comprising 1,4 
butanediol, which polyester exhibits improved impact properties. 
2. Description of the Prior Art 
Many different polyesters, modified to one extent or another, are known to 
the prior art. Polyethylene terephthalate (PET) is well known, and in view 
of its excellent physical properties and resistance to attack by chemicals 
is widely used commercially. Other polyesters such as polybutylene 
terephthalate (PBT) are also known, but not as widely accepted as PET. 
One particular field of application for polyesters, and particularly 
polyethylene terephthalate, is the fiber industry. Therein, much of the 
modification of the polyesters is attempted in order to alter the spinning 
or mechanical properties of the polyesters, or the other properties 
important to films and fibers, e.g., such as improved dyeability. For 
example, see Muenster et al, U.S. Pat. No. 2,973,339, which discloses a 
process for the production of polyesters by reacting terephthalic acid or 
the dimethyl ester thereof with ethylene glycol and 5-30 mole percent 
(with respect to the terephthalic acid) of an aromatic glycol. The patent 
relates to a polyester useful in films and fibers. 
Hrach et al, U.S. Pat. No. 3,651,016, discloses a process for the 
production of polyesters comprising reacting at least one lower alkyl 
ester of a dicarboxylic acid (including dimethyl terephthalate) with at 
least one diol selected from the group consisting of ethylene glycol, 
1,4-butanediol, 1,4-(hydroxymethyl)-cyclohexane and 
2,2'-bis(4'-beta-hydroxyethoxyphenyl)-propane. In Example 3 of the patent, 
there is disclosed the preparation of a polyester from a mixture of 200 
parts terephthalic acid dimethyl ester, 150 parts ethylene glycol and 31.6 
parts bisphenol A-diglycol ether. The result is an allegedly color stable 
polyester useful in forming films and filaments. 
U.S. Pat. No. 4,067,850 issued to Kohler et al, discloses a process for the 
production of copolyesters by the transesterification of dimethyl 
terephthalate or the esterification of terephthalic acid with a glycol, 
such as ethylene glycol, in the presence of such quantity of 
bishydroxyethyl tetramethyl bisphenol A that the resulting polyester 
contains 4-15 weight percent of this bisphenol A in chemically 
co-condensed form. The filaments and fibers formed allegedly have improved 
dyeability properties. 
Ohguchi et al, U.S. Pat. No. 4,377,682, discloses copolyesters formed from 
dicarboxylic acid components (which can include terephthalic acid and 
esters thereof) and an aliphatic glycol component containing mostly one or 
more glycols selected from ethylene glycol, tetramethylene glycol and 
1,4-cyclohexane dimethanol, with a small portion of an additional glycol, 
and in addition small amounts of bisphenol A or bis-ethoxylated 
2,2-bis(2,5-dimethyl-4-hydroxyphenyl)propane. The foregoing copolyesters 
are alleged to possess improved dyeability. 
U.S. Pat. No. 3,972,852 issued to Inata et al, discloses a process of 
preparing aromatic polyesters from aromatic dicarboxylic acids or esters 
thereof (including terephthalic acid), diphenols and aliphatic dihydroxy 
compounds having 2 to 12 carbon atoms. The inclusion of the aliphatic 
dihydroxy compounds is said to permit the preparation of polyesters having 
a high deflection temperature under load as well as superior dimensional 
stability, thermal resistance and resistance to attack by chemicals. 
See also Login, U.S. Pat. No. 4,263,370, which discloses graft polyesters 
prepared by grafting a monovinyl monomer to an unsaturated polyester which 
is the reaction product of at least one polycarboxylic acid reactant 
(including terephthalic acid and its esters) and at least on polyhydric 
alcohol reactant, with the provision that part of at least one of these 
reactants is alpha, beta-ethylenically unsaturated. 
PBT is another known polyester, although generally not as widely employed a 
PET. A fire retardant PBT is known which comprises a brominated, 
ethoxylated bisphenol A component. Such polymers generally have a problem 
with color due to the bromine. The use of PBT in mechanical applications 
has been somewhat limited, however, as there is a need for a tougher PBT 
polyester, i.e., having improved impact properties. The prior art to date 
has not successfully addressed this problem. An improved, impact modified 
PBT type polymer would be of great commercial value to the industry. 
It is an object of the present invention, therefore, to provide an impact 
modified polyester. 
More particularly, it is an object of the present invention to provide an 
impact modified polybutylene terephthalate. 
Another object of the present invention is to provide a polybutylene 
terephthalate copolyester having improved strength as well as improved 
impact toughness. 
These and other objects, as well as the scope, nature and utilization of 
the invention, will be apparent to those skilled in the art from the 
following description, the Drawing and the appended claims. 
SUMMARY OF THE INVENTION 
Provided by the present invention is a copolyester prepared from the 
reaction of terephthalic acid or an ester derivative thereof with a diol 
component comprising a mixture of 1,4 butanediol and an alkoxylated 
bisphenol A. It is preferred that the terephthalic acid component is its 
methyl ester derivative, i.e., dimethyl terephthalate, and that the 
alkoxylated bisphenol A is ethoxylated bisphenol A (EBPA). The combination 
of the 1,4 butanediol and alkoxylated bisphenol A as the diol component 
provides for a polyester exhibiting superior impact properties, improved 
toughness, and at higher levels of alkoxylated bisphenol A, an amorphous 
(clear) polymer. 
The proces for preparing the foreging copolyester comprises reacting the 
terephthalic acid or ester derivative thereof which a mixture of the 1,4 
butanediol and alkoxylated bisphenol A. The reaction is preferably 
conducted in the presence of a catalyst and comprises first an 
esterification or ester interchange reaction, and then polymerization at a 
higher polymerization temperature.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The acid component employed in the preparation of the polyester of the 
present invention is terephthalic acid or an ester derivative thereof. It 
is preferred that an ester derivative of terephthalic acid be employed, 
with the methyl ester derivative, i.e., dimethyl terephthalate, being most 
preferred. However, other lower alkylester derivatives may be employed, 
e.g., ethyl, propyl and butyl terephthalates. 
While it is preferred that the acid component be comprised wholly of 
terephthalic acid or an ester derivative thereof, it is within the scope 
of the present invention to employ small amounts of other dicarboxylic 
acid components, and preferably aromatic dicarboxylic acids. The amount is 
limited, however, so that the quality of the copolyester obtained is not 
impaired. Examples of suitable dicarboxylic acid esters include 
isophthalic acid, naphthalene dicarboxylic acid or their ester forming 
derivatives. The amount of such additional dicarboxylic acid component is 
generally limited to no more than about 5 mole percent of the carboxylic 
acid component. 
The diol component, with which the terephthalic acid or ester derivative 
thereof is reacted; comprises a mixture of 1,4 butanediol and a 
alkoxylated bisphenol A. The alkoxylated bis phenol A is preferably a 
lower alkoxylated compound, i.e., from 1 to about 4 carbons in the alkoxy 
group. Ethoxylated bisphenol A is the most preferred alkoxylated bisphenol 
A for purposes of the present invention. It is also important that the 
bisphenol A be non-halogenated. 
The amount of bisphenol A compound employed can be any amount sufficient to 
provide an improvement in the impact properties of polyester product, as 
compared to a polyester product containing none of the bisphenol A 
reaction component. Generally, the non-halogenated, alkoxylated bisphenol 
A will comprise from about 1% to about 25 mole % of the polymer, with the 
remainder of the diol component being comprised of the 1,4 butanediol. 
Special preference is given to having from 2 to about 8, and most 
preferably from about 4 to 6 mole % of alkoxylated bisphenol A in the 
polymer since such a combination of 1,4 butanediol and non-halogenated, 
alkoxylated bisphenol A surprisingly provides a polyester product showing 
improved impact properties and improved strength. When a more transparent 
product is desired, the amount of alkoxylated bisphenol A employed is 
preferably at least 20 mole % of the polymer. 
The amount of total diol component employed in preparing the polyester of 
the present invention, as compared to the amount of acid component 
employed, is generally such that the mole ratio of diol/acid is between 
about 1.0/1.0 and 3.0/1.0. In general, it is preferred that the diol/acid 
molar ratio be greater than 1, with the ratio approaching 3 when a 
continuous or semicontinuous operation is employed in order to facilitate 
the feeding of the diol/acid slurry to the reaction. 
The copolyesters of the present invention can generally be obtained by the 
usual processes employed in producing polyesters. For example, the 
conventional process comprising an ester-exchange reaction of the 
terephalate (dicarboxylic acid ester) with the diol component. The ester 
exchange-reaction is then followed by a polycondensation reaction to 
provide the polyester product. If the terephthalic acid is employed as the 
reaction component, a conventional process comprising esterification of 
the terephthalic acid and the diol component can be employed, followed by 
a polycondensation reaction. 
As a general rule, the temperature of the reaction may lie anywhere between 
the normal boiling point of the diol component, and about 300.degree. C. 
Above 300.degree. C., it has generally found that decomposition becomes 
excessive and, consequently, it is most advantageous to complete the 
esterification reaction at a temperature close to that required for 
subsequent polycondensation. Generally, the temperature employed in the 
initial esterification or ester-exchange will be about 170.degree. to 
200.degree. C. For the polymerization or polycondensation reaction 
subsequent thereto, the temperature is generally raised to about 
225.degree. to 275.degree. C. It is preferred that the heating be effected 
under conditions such that any displaced alcohol can be removed from the 
reaction zone, usually by means of conventional distillation equipment. 
The heating is usually at atmospheric pressures, but higher or lower 
pressures may be used if desired. Preferably, the heating is also effected 
in an inert atmosphere, e.g., in the presence of an inert gas such as 
nitrogen or hydrogen. 
During the initial reaction, the presence of a catalyst is generally 
preferred. Without the catalyst, the reaction generally proceeds very 
slowly. Any of the well known and conventional catalysts may be used, for 
example, lithium, sodium, potassium, calcium, beryllium, magnesium, zinc, 
cadmium, aluminum, chromium, molybdenum, manganese, iron, cobolt, nickel, 
copper, silver, mercury, tin, lead, bismuth, antimony, platinum and 
palladium. In some cases small amounts of an alkali metal may be used in 
combination with one of the foregoing metals, for example, from about 
0.025% to 0.1% by weight. 
The catalysts may be added in the form of powder, chips, shavings, ribbon, 
wire or in any other convenient form. The alkaline metals, the 
alkaline-earth metals or magnesium are conveniently used in the form of 
alcoholates, formed by dissolving them in the diol to be used or in 
another alcohol such as methyl or ethyl alcohol. Further, the alkaline 
metals may be used in the form of their carbonates or other alkaline 
reacting salts, for example the borates. Magnesium may also be used in the 
form of its oxide. 
Other additives which may be used include delustrants, stabilizers, etc. 
Any conventional additive may be added to the reaction pot so that it is 
incorporated into the final polyester product. 
After the initial reaction, the subsequent polymerization or 
polycondensation reaction takes place. As noted previously, the 
temperature is generally raised during this reaction. During the heating 
or during part of the heating, the pressure is also generally reduced so 
as to facilitate the rapid distillation of excess diol present. The 
pressure may be reduced in successive stages so that the heating begins at 
normal pressure, but is continued at a reduced pressure and is completed 
at a still further reduced pressure. Pressures from 20 down to 1 
millimeter of mercury are particularly suitable. Higher or lower pressures 
may be used if desired. The reaction can also take place in its entirety 
at a pressure of about 1 millimeter of mercury or so. Metal catalysts may 
also be used and be present during this subsequent reaction. If desired, 
additional catalyst may be added prior to the polyermization. 
During the heating, the melting point and the viscosity of the melt 
gradually increase. The temperature is maintained high enough to keep the 
mass in the molten state during the entirety of the heating period. 
Generally, the inherent viscosity is monitored during the polymerization 
reaction until the desired inherent viscosity is reached, which will 
determine the termination of the reaction. 
The resulting polymer can therefore be molded into articles useful in 
mechanical applications. The molding can be achieved using any of the 
conventional molding operations. 
The following Example is given as a specific illustration of the claimed 
invention and the advantages thereof. It should be understood, however, 
that the specific details set forth in the Example are merely illustrative 
and in no wise limitative. All parts and percentages in the Example and in 
the remainder of the specification are by weight unless otherwise 
specified. 
EXAMPLE 
Several polymerizations in accordance with the subject invention were 
performed in a 4 gallon stirred autoclave reactor. In each instance, the 
reactor was charged initially with dimethyl terephthalate, 1,4 butanediol, 
ethoxylated bisphenol A and catalyst. This mixture was heated to 
175.degree. C., where the ester interchange occurs and methanol is 
liberated. Upon completion of the reaction, i.e., little or no additional 
methanol was evolved, additional catalyst was then added and the solution 
was heated to 254.degree. C. under 1.0 millimeter of mercury vacuum, 
whereupon polymerization occured. A product intrinsic viscosity (I.V.) was 
determined by agitator amp load increase during the polymerization. A 
stabilizer was added just before the target I.V. was achieved. Upon 
completion of the polymerization, the polymer was then gravity drained 
from the reactor through a strand bath and chopper. 
Various samples of the polyester were then molded using a conventional 
molding apparatus, i.e., a 5 oz., 75 ton Van Dorn molding machine. Certain 
samples of the polymers were also compounded with 15% glass and molded. 
The physical properties of izod impact strength, flexural strength 
modulus, flexural strength stress, tensile strength, tensile elongation 
and Gardner impact strength were then measured for the various samples 
prepared, as well as for two additional control samples. The tensile 
measurements were made in accordance with ASTM D638-77a; the izod impact 
strength measurements were made in accordance with ASTM D256-78; the 
elongation measurements were made in accordance with ASTM D638-77a; and, 
the flexural strength measurements were made in accordance with ASTM 
D790-71. Control Sample A involved a conventional PBT polymer, i.e., no 
bisphenol A in the diol component, and control compound B employed 2.0 
mole % of brominated bisphenol A with respect to the polymer. 
The measured physical properties of the molded samples of the unfilled 
polymer are listed below in Table I. The physical properties of the molded 
samples of the filled polymer (15% glass) are noted below in Table II. As 
well, the different measured properties for the various samples are 
graphically depicted in FIGS. 1-5. 
It is evident upon a review of the foregoing that the combination of 
alkoxylated bisphenol A with 1,4 butanediol as the diol component provides 
a polyester exhibiting a definite increase in impact properties. 
Furthermore, it is noted that when from about 2-8 mole %, and particularly 
from 4-6 mole %, alkoxylated, non-halogenated bisphenol A is employed, not 
only are the impact properties superior, but the tensile properties, i.e., 
the strength, are also improved. 
TABLE I 
__________________________________________________________________________ 
PHYSICAL PROPERTIES-MOLDED SAMPLES, UNFILLED POLYMER 
Tensile Gardner 
Polymer 
EBPA, 
Intrinsic 
Izod Impact 
Flexural Strength 
Strength 
Elongation 
Impact 
Sample Mole % 
Viscosity 
Strength 
Mod .times. 10.sup.6 
Stress 5% 
(Yield/Break) 
(Yield/Break) 
Strength 
__________________________________________________________________________ 
Control A.sup.(a) 
0 0.74 0.580 0.383 13,190 
8545 -- -- 
14.0 
1 1.00 0.77 0.560 0.388 13,525 
8220/8220 
3.3/5.0 
8.6 
Control B 
2.0.sup.(b) 
0.70 0.610 0.371 13,348 
8630 -- -- 
15.9 
2A 4.3 0.70 0.768 0.366 13,265 
8570/7775 
4.8/15 37.8 
2B 4.3 0.70 0.816 0.337 12,115 
8395/3805 
4.56/69 37.8 
3 10.0 0.74 1.12 0.325 9,854 
7430/2800 
4.14/240 
50.6 
__________________________________________________________________________ 
.sup.(a) Conventional PBT polymer 
.sup.(b) 2.0 mole percent brominated, ethoxylated bisphenolA in polymer. 
TABLE II 
__________________________________________________________________________ 
PHYSICAL PROPERTIES, MOLDED SAMPLES, 
FILLED POLYMER (15% GLASS) 
Tensile 
Polymer 
EBPA, 
Izod Impact 
Flexural Strength 
Strength 
Elongation % 
Sample Mole % 
Strength 
Mod .times. 10.sup.6 
Stress 5% 
(Yield) 
(Yield) 
__________________________________________________________________________ 
Control C.sup.(c) 
0 0.89 0.781 22,349 
12,840 
3.10 
4 1.0 0.91 0.803 22,599 
13,440 
3.22 
Control D.sup. 
2.sup.(d) 
1.11 0.833 23,629 
14,800 
3.27 
5 4.3 1.14 0.824 20,640 
14,170 
3.15 
6 10.0 1.54 0.680 13,615 
10,980 
4.19 
__________________________________________________________________________ 
.sup.(c) Conventional PBT polymer 
.sup.(d) 2.0 mole percent brominated, ethoxylated bisphenolA in polymer. 
Although the invention has been described with preferred embodiments, it is 
to be understood that variations and modifications may be resorted to a 
will be apparent to those skilled in the art. Such variations and 
modifications are to be considered within the purview and the scope of the 
claims appended hereto.