A crystalline polyamide which has improved tensile strength and which has a heat deflection temperature in excess of 240.degree. C. when filled is formed from dicarboxylic acid compounds comprising compounds of terephthalic acid and isophthalic acid in a molar ratio of at least 80:20 to about 99:1 and diamines comprising hexamethylene diamine and trimethylhexamethylene diamine in a molar ratio of about 98:2 to about 60:40.

FIELD OF THE INVENTION 
The field of this invention relates to crystalline polyamides obtained from 
compounds of terephthalic acid (TA) and isophthalic acid (IA) in 
combination with mixtures of hexamethylene diamine (HMDA) and 
trimethylhexamethylene diamine (TMHMDA) and filled compositions thereof. 
BACKGROUND 
Crystalline polyamides from mixtures of TA and IA and mixtures of TMHMDA 
and HMDA wherein the TA content is at least 80 percent of the total acid 
moieties have not been obtained by the prior art. In fact, U.S. Pat. No. 
3,382,216 (1968) teaches that the preparation of polyhexamethylene 
terephthalamide cannot be effected through melt condensation processes. 
U.S. Pat. No. 3,150,117 (1964) discloses that linear amorphous film forming 
polyamides can be prepared from dicarboxylic acids and alkyl-substituted 
saturated hydrocarbons; however, the mixture of trimethylhexamethylene 
diamine and hexamethylene diamine is not disclosed in this reference. 
U.S. Pat. No. 3,294,758 (1966) discloses a polyamide which is prepared from 
terephthalic and isophthalic acid and a mixture of diamines consisting of 
5-30 weight percent hexamethylene diamine and 95-70 weight percent 
trimethylhexamethylene diamines. This patent teaches that compositions 
having more than 30 weight percent hexamethylene diamine are brittle. 
U.S. Pat. No. 4,410,661 (1983) discloses a polyamide obtained from (i) a 
mixture of 70-100 weight percent trimethylhexamethylene diamines and 30-0 
weight percent hexamethylene diamine and (ii) 0-100 weight percent 
terephthalic acid and 100-0 weight percent isophthalic acid. 
Crystalline polyphthalamides obtained from terephthalic acid mixtures of 
hexamethylene diamine and trimethylhexamethylene diamine have been 
disclosed in commonly owned U.S. Pat. No. 4,495,328, which issued from 
application Ser. No. 601,909, which was a continuation-in-part of 
application Ser. No. 466,903 filed Feb. 16, 1983 concurrently with 
application Ser. No. 466,901. This patent is incorporated herein by 
reference. 
Other U.S. patents of interest include: U.S. Pat. Nos. 3,825,516 (1974); 
3,962,400 (1976); 3,941,755 (1976); 3,627,736 (1971); and 3,692,749 
(1972). All of these patents disclose amorphous polyamides. 
In reviewing all these references, it is clear that the crystalline 
polyphthalamides manufactured from mixtures of TA and IA and mixtures of 
HMDA and TMHMDA wherein the TA content is at least 80 percent of the acid 
moieties, which polymers have improved tensile strength, are unknown to 
the prior art. Additionally, such polyamides which, when filled, have heat 
deflection temperatures of about 240.degree. C. to about 305.degree. C. 
are unknown in the prior art. 
STATEMENT OF THE INVENTION 
The general object of this invention is to provide a crystalline polyamide 
with improved tensile strength. Another object is to provide reinforced 
molding compositions which have heat deflection temperatures of at least 
about 240.degree. C. and good tensile strengths. 
We have now found that these objects can be accomplished with a crystalline 
polyamide prepared from dicarboxylic acid compounds and diamines wherein 
said dicarboxylic acid compounds comprise compounds of terephthalic acid 
(TA) and isophthalic acid (IA) in a molar ratio TA to IA of at least 80:20 
to about 99:1 and said diamines comprise hexamethylene diamine (HMDA) and 
trimethylhexamethylene diamine (TMHMDA) in a molar ratio HMDA to TMHMDA of 
about 98:2 to about 60:40. These objects are also accomplished by a blend 
which comprises (1) about 80 to about 50 parts by weight of a polyamide 
resin of terephthalic acid (TA) and isophthalic acid (IA) and diamine 
wherein the molar ratio of TA to IA is at least 80:20 to about 95:5 and 
wherein said diamine comprises hexamethylene diamine (HMDA) and 
trimethylhexamethylene diamine (TMHMDA) in a molar ratio HMDA:TMHMDA of 
about 98:2 to about 60:40, and (2) about 20 to about 50 parts by weight of 
a filler selected from the group consisting of glass fibers, graphite 
fibers, and mixtures thereof. 
This crystalline polymer has improved tensile strength and, when filled, a 
heat deflection temperature in the range of at least about 240.degree. C. 
to about 305.degree. C., as determined by ASTM method, D648. The high heat 
deflection temperature is an unusual feature and completely unexpected, 
since amorphous polyphthalamides have much lower heat deflection 
temperatures. It is important to have high heat deflection temperatures 
since it enables the injection molded polyphthalamides to be used in 
applications such as the hood of an automobile, shroud for a lawn mower, 
chain saw guard, and an electrical connector application. In addition to 
the high heat deflection temperature, the tensile strengths of this filled 
polyamide are about 15,000 to about 40,000 psi, which is as high or higher 
than that of die cast aluminum or zinc, while the specific gravity is 
about one-half that of aluminum or zinc. Thus, this polyamide is 
particularly useful for application in transportation equipment. The 
molecular weight of the polyamide is about 5,000 to about 40,000. 
It is well known from the prior art that poly(hexamethylene phthalamide) 
materials with a high terephthalic acid content are difficult to produce 
due to the high melting temperature of the polymers. In fact, the prior 
art teaches that poly(hexamethylene phthalamide), for which the 
terephthalic acid content is greater than 80 mole percent, cannot be 
produced via melt polymerization. Chapman, et al., U.S. Pat. No. 4,022,756 
(1977), discuss this problem with respect to the formation of fibers from 
polymers containing greater than 80 mole percent terephthalic acid, but 
similar problems result with injection molding compounds in this range of 
TA content. Consequently, the prior art teaches that the polyamide of the 
instant invention would not be expected to be useful. 
The polyamide of this invention is preferably filled with about 10 to about 
60 weight percent glass fibers, graphite fibers or a mixture thereof. 
Other fillers such as glass beads and minerals can be used; however, the 
high heat deflection temperature may not be obtained. Advantageously, the 
molding composition may contain from about 20 to about 50 weight percent 
of glass fibers, graphite fibers or a mixture thereof. Our studies have 
shown that high heat deflection temperatures of the molded polyamide can 
be improved by using such fillers. The polyamide resin costs are also 
reduced when these fillers are substituted for part of the polyamide 
resin. 
Fibers can be prepared from this polyamide although the preferred use is as 
a molding resin. 
It is also possible to add to the polyamides of this invention various 
additives such as heat stabilizers, UV stabilizers, other particulate and 
fibrous reinforcing agents, toughening agents, flame retardants, 
plasticizers, antioxidants, and pigments before, during, or after the 
polymerization. 
Two critical properties of an injection molding composition are strength, 
especially tensile strength, and heat resistance, as measured, for 
example, by the heat deflection temperature of the material. These 
problems which are inherent in the polyamides of high terephthalic acid 
content prepared with only hexamethylene diamine are reflected in the data 
presented in Table 1. 
TABLE 1 
______________________________________ 
TA/IA-HMDA 
50/50- 65/35- 68/32- 72/28- 
molar ratio 
100 100 100 100 
Tensile 9,600 15,400 14,900 7,500 
strength, psi 
Elongation at 
152 5 14 2 
break, % 
HDT @ 264 154 253 269 267 
psi, .degree.F. 
Crystallinity 
No Yes Yes Yes 
______________________________________ 
The 50/50-100 TA/IA-HMDA composition is essentially amorphous. In terms of 
the tensile properties, this composition could be characterized as tough; 
yet, because of the low heat deflection temperature, the material would 
soften in hot water. The two intermediate materials, TA/IA-HMDA of 
65/35-100 and 68/32-100, could be characterized as strong. The presence of 
crystallinity, however, increases the heat deflection temperature by about 
100.degree. F. As used herein, a "crystalline" polymer is defined to be a 
polymer having a measurable, well-defined melting temperature. Above a 
terephthalic acid level of 70 mole percent, the tensile strength declines 
precipitously, and the material becomes very brittle. The heat deflection 
temperature is not further improved by increasing the level of TA. Also, 
as the level of TA is increased about 70 mole percent, it becomes more 
difficult, if not impossible, to prepare the polymer by usual melt 
polymerization methods. 
Quite surprisingly, it is possible to extend the limits of melt preparation 
for the poly(hexamethylene phthalamide) by incorporating a second 
hexamethylene diamine into the composition. Addition of the second diamine 
also improves the tensile strength and the filled heat distortion 
temperature of the high TA polyamide. This second hexamethylene diamine is 
trimethylhexamethylene diamine (TMHMDA) which is actually a mixture of 
2,2,4-trimethylhexamethylene diamine and 2,4,4-trimethylhexamethylene 
diamine. The effectiveness of the TMHMDA is illustrated in Table 2. 
TABLE 2 
______________________________________ 
TA/IA-HMDA/ 
65/35- 72/28- 85/15- 100/0- 
TMHMDA 100/0 100/0 96/4 65/35 
molar ratio 
Tensile 15,400 7,500 14,600 13,700 
strength, psi 
Elongation at 
5 2 5 6 
break, % 
HDT @ 264 253 267 273 273 
psi, .degree.F. 
______________________________________ 
The tensile properties of the 85/15-96/4 TA/IA-HMDA/TMHMDA formulation are 
virtually identical to those of the 65/35-100 TA/IA-HMDA formulation, 
while a 20.degree. F. improvement in heat deflection temperature (HDT) is 
also noted. 
The properties of these TMHMDA-containing compositions are further, 
dramatically improved by the incorporation of glass fibers as set forth in 
Table 3. 
TABLE 3 
______________________________________ 
TA/IA-HMDA/ 
65/35- 85/15- 85/15- 100/0- 
TMHMDA 100/0 96/4 96/4 100/0 
molar ratio 
Glass fiber, % 
33 30 45 45 
Tensile 31,100 17,200 36,300 8,300 
strength, psi 
Elongation at 
5 3 5 1 
break, % 
HDT @ 264 270 (132) 
Not Run &gt;580 (304) 
&gt;580 (304) 
psi, .degree.F. (.degree.C.) 
______________________________________ 
The injection moldable crystalline polyamide compounds of TA and IA of this 
invention comprise the following recurring structural units: 
##STR1## 
wherein R is a straight chain aliphatic hydrocarbon radical containing 6 
carbon atoms and R' is an alkyl-substituted aliphatic hydrocarbon chain, 6 
carbon atoms in length, in which the alkyl substitution comprises three 
methyl groups, with two of the three methyl groups on the same carbon 
atom. The preferred diamines for these compositions are 
2,2,4-trimethylhexamethylene diamine, 2,4,4-trimethylhexamethylene diamine 
or mixtures of these. 
The dicarboxylic acid compounds useful in preparing the polyamides of the 
instant invention are terephthalic acid (TA) and isophthalic acid (IA) and 
their derivatives which are capable of being reacted with diamines to form 
the instant polyamide. Useful derivatives include the corresponding acid 
halides, particularly terephthaloyl chloride and isophthaloyl chloride, 
and corresponding alkyl and aryl esters wherein preferably the alcohol 
component has at least two carbons, for example, ethyl terephthalate and 
phenyl terephthalate. The molar ratio of the TA and IA moieties can vary 
from at least 80:20 to about 99:1. Preferably, the molar ratio ranges from 
about 85:15 to about 95:5. Most preferably, the molar ratio is from about 
85:15 to about 90:10. It has been found that in order to obtain the heat 
deflection temperature in excess of 240.degree. C. and have high tensile 
strength, the content of the TA moiety must comprise at least 80 mole 
percent of the total TA and IA content. 
The diamines useful in preparing the instant polyamide are hexamethylene 
diamine (HMDA) and trimethylhexamethylene diamine (TMHMDA). The molar 
ratio of HMDA and TMHMDA can vary from about 55:45 to about 98:2, 
preferably from about 60:40 to about 95:5. As stated herein above, the 
preferred TMHMDA is a mixture of 2,2,4-trimethylhexamethylene diamine and 
2,4,4-trimethylhexamethylene diamine. The amount of TMHMDA required 
relative to the HMDA increases as the level of TA is increased in order to 
allow melt processing of the polymer. 
Injection molding of this polyphthalamide, filled or unfilled, is 
accomplished by injecting the polyamide melt into a mold maintained at a 
temperature of about 100.degree. to about 220.degree. C. In this process, 
a 20-second to 1-minute cycle is used with a barrel temperature of about 
300.degree. to 350.degree. C. These temperatures will vary depending on 
the glass transition temperature (Tg) and melting temperature (Tm) of the 
polyamide being molded. The polyphthalamide has excellent thermal and 
mechanical properties and can readily be molded into useful products or 
formed into fibers, laminates or coatings. 
The addition of reinforcing materials improves the material properties of 
the resulting blend. Particularly, the physical properties, such as 
flexural strength, are improved if the polyamides contain from about 10 to 
about 60 percent by weight glass fibers, glass beads, minerals, or 
mixtures thereof. In the preferred range, the polyamides contain about 20 
to about 50 percent by weight of glass fibers, glass beads, or graphite, 
or mixtures thereof. Suitably, the reinforcing materials can be glass 
fibers, glass beads, glass spheres, or glass fabrics. The preferred 
fillers are glass fibers and graphite fibers. The glass fibers are made of 
alkali-free, boron-silicate glass or alkali-containing C-glass. The 
thickness of the fibers is, on the average, between 3 microns and 30 
microns. It is possible to use long fibers in the range of from 5 mm to 50 
mm and also short fibers with each filament length of 0.05 mm to 5 mm. In 
principle, any standard commercial grade fiber, especially glass fibers, 
can be used. Glass beads ranging from 5 microns to 50 microns in diameter 
can also be used as a reinforcing material in combination with glass 
fibers. 
The glass fiber-reinforced polyamide polymers can be prepared by any 
conventional method. Suitably, so-called roving endless glass fiber 
strands are coated with the polyamide melt and subsequently granulated. 
The cut fibers and glass beads can also be combined with granulated 
polyamide compositions and the resulting mixture melted in a conventional 
extruder. Alternatively, uncoated fibers can be introduced into the molten 
polyamides through a suitable inlet in the extruder. 
The following procedures and examples illustrate a preferred embodiment of 
this invention. It is understood that these procedures and examples are 
illustrative only and do not purport to be wholly definitive with respect 
to the conditions or scope of the invention. While the desired polymer 
properties can be obtained regardless of the method of preparation, 
provided an adequate molecular weight is attained, the continuous process 
outlined in Example 4 represents a practical process for the commercial 
production of polyamides with high terephthalic acid content. The presence 
of high levels of terephthalic acid renders these polymers high melting 
and highly viscous. Chapman, et al., U.S. Pat. No. 4,022,756, describe the 
extraordinary means which must be employed in order to obtain acceptable 
polymer with terephthalic acid contents of 60 to 80 mole percent in 
conventional polycondensation polymerization equipment. 
The components used in the polymerization mixtures described below were 
polymerization-grade materials including: Amoco Chemicals Corporation 
grade TA-33 terephthalic acid and grade IPA-99 isophthalic acid; Monsanto 
Corporation aqueous hexamethylene diamine solution which is typically 
about 70 weight percent HMDA in water; TMHMDA was technical grade from 
Axon Company; benzoic acid (USP); and deionized water. The glass fibers 
used were 1/8-inch long with a diameter of about 9.7 micrometers and were 
supplied by Pittsburgh Plate Glass, grades PPG 3531 and PPG 3540, or 
similar materials. 
Procedure for Preparation of Polyamide 
While batch production of these polyamides can be carried out in one or two 
steps, it is convenient to carry out the process in two steps. In the 
first step, a polyamide of intermediate conversion is prepared in a 
stirred reactor which can process materials of high viscosity. For this 
process, feed materials consisting of the diacids (TA and IA in the 
desired ratios), the diamines (HMDA and TMHMDA in the desired ratios), and 
any additives are charged to the reactor at about room temperature to 
about 175.degree. F. Water, sufficient to attain a homogeneous solution 
before pressure letdown begins, is also added. For the equipment described 
in the examples which follow, the water content is about 15 percent of 
weight. The temperature of this polymerization mixture is then raised to 
between about 500.degree. F. and 600.degree. F. as rapidly as possible. 
Pressure, principally steam pressure, is allowed to build to the pressure 
limits of said reactor (in this case, 130 psig). Once the target 
temperature is reached, the pressure is reduced to atmospheric pressure 
over a period of 5 to 120 minutes. The polymer is then allowed to flow out 
of the reactor by gravity or is pumped out and collected under an inert 
atmosphere. This polymer has an inherent viscosity (TCE/phenol) of about 
0.10 dl/g to about 1.0 dl/g or greater. Preferably, the inherent viscosity 
is about 0.10 dl/g to about 0.40 dl/g. This polyamide of intermediate 
conversion is then granulated and fed to the final polycondensation 
section. This final polycondensation section is described below. 
Alternatively, if the inherent viscosity of this batch-prepared polymer 
exceeds about 0.8 dl/g, it can be compounded directly with the reinforcing 
filler materials. 
When these polyamides are prepared by the above-described process, and the 
resultant inherent viscosity is less than about 0.8 dl/g, the polyamide 
must be finished to an inherent viscosity of about 0.8 dl/g or greater in 
order to fully realize the improved properties of the instant polyamides. 
This finishing process is the final polycondensation step and utilizes a 
twin-screw extruder reactor such as a Werner-Pfleiderer ZSK-30. The 
twin-screw extruder allows these stiff, high melting resins to be easily 
handled. The screw configuration employed when the twin-screw extruder is 
used as a polycondensation reactor consists of four basic sections. The 
first section is a feed section which is composed of relatively long 
pitches for conveying the polymerization mixture away from the feeding 
port. The second section is a short compression section which compresses 
the polymerization mixture and provides a melt seal for the reaction zone. 
The reaction zone comprises about 70-80 percent of the entire length of 
the extruder. Typically, the screw flights have relatively long pitches, 
but various mixing elements or kneading blocks can be included in this 
section. The final section is also a compression section which feeds the 
die. Other types of finishing reactors such as disk ring reactors, 
agitated stranding devolatilizers, and thin film evaporators can be 
utilized; however, some of these can have difficulty in handling the high 
viscosity of our resins. 
Procedure for Compounding the Polyamide 
Two techniques are employed to prepare compounded samples for injection 
molding. The first of these is dry blending, which is especially 
convenient for the preparation of small samples. Dry blending involves 
combining weighed amounts of the resin, filler, and any other additives. 
These ingredients are then mixed by tumbling, stirring, etc., until the 
mixture is homogeneous. This dry blend can be either injection molded 
directly or used as a feed for melt compounding. 
Melt compounding involves melting the polymer resin in the presence of the 
filler or adding filler to the polymeric melt. This is conveniently 
accomplished in a twin-screw extruder, such as the above-mentioned ZSK-30. 
The basic screw configuration used for melt compounding is composed of 
three sections. The first section, the feed section, has screw flights of 
relatively long pitches for conveying the material away from the feeding 
port. The second section is a compression section in which the screw 
flights have shorter pitches. In this section, the resin is melted and 
further mixed with the filler. The third section is a decompression 
section in which the longer pitches are again used to degas the polymer 
melt. Advantageously, this section is vented. The polymer melt passes 
through a die to strand the compounded resin which is then chopped into 
pellets. The specific conditions employed in melt compounding, the 
compositions of the instant invention, and the comparative examples are 
presented in Table 4 below. 
TABLE 4 
______________________________________ 
ZSK-30 Conditions 
______________________________________ 
Screw 
Speed, Torque, Zone Temperature, .degree.F. 
Rpm Percent 1 2 3 4 5 
______________________________________ 
125 28 620 620 620 565 550 
______________________________________ 
Temperature, .degree.F. 
Product 
Final Rate, 
Die Melt lb/hr 
______________________________________ 
550 556 9.0 
______________________________________ 
Procedure for Forming of Objects from the Glass-Filled Compositions 
The compositions of the instant invention are melt processible. Injection 
molding is a common technique for forming polymeric materials into useful 
shapes and objects. The heat distortion temperature specimens used to 
exemplify this invention were prepared in a 1.5 oz Arburg injection 
molding machine, Model 221E, in accordance with ASTM procedures. 
Injection molding is an art. The precise conditions employed depend not 
only on the molding machine being used and the part being formed, but also 
on the melt viscosity of the polymeric resin and the level and nature of 
the fillers used. A thorough procedure for establishing an injection 
molding cycle is described in Nylon Plastics by Melvin I. Kohan in Chapter 
5, "Injection Molding of Nylons," pp. 156-205, John Wiley & Sons, 
Publishers (1973), incorporated herein by referece. General conditions for 
injection molding of ASTM specimens on the Arburg Model 221E injection 
molding machine are presented in Table 5 below. 
TABLE 5 
______________________________________ 
Mold Temperature 100.degree. to 200.degree. C. 
Injection Pressure 
6,000 to 15,000 psi and 
held for 10 to 20 seconds 
Back Pressure 100 to 1,000 psi 
Cycle Time 20 to 60 seconds 
Extruder 320.degree. to 340.degree. C. 
Nozzle Temperature 
Barrel 
Heated to 270.degree. to 370.degree. C. 
Screw 20 to 60 revolutions/ 
minute 
______________________________________ 
The temperature of the mold was controlled. This mold temperature is cited 
in each example. The aforementioned procedures were employed not only for 
the examples which embody the present invention, but they were also 
employed in the preparation of comparative examples from the prior art. 
The examples also demonstrate that the unexpected increase in heat 
deflection temperature upon filling is a property of the polymer and not 
of the method of preparation. 
The invention is explained in greater detail in the examples set forth 
below.

EXAMPLE 1 
Preparation of 85/15-94/6 (TA/IA-HMDA/TMHMDA) Polyamide 
In this example, the polyamide was produced by the continuous process 
described in Example 4. The 5-gallon salt reactor was charged with the 
following reactants: 
______________________________________ 
Reactant Amount, g 
______________________________________ 
TA 8742.6 
IA 1495.2 
HMDA 6763.2 
TMHMDA 570.0 
NaH.sub.2 PO.sub.2.H.sub.2 O 
13.8 
Silicone oil 13.8 
H.sub.2 O 3185.4 
______________________________________ 
Once the salt reactor was charged, it was purged with nitrogen and heated 
to about 470.degree. F. The pressure set point was 450 psig, and this was 
attained by a combination of steam pressure and nitrogen gas pressure. 
After about 85 minutes, the salt solution was then continuously passed 
through the reactor system. In the preheat zone, the pressure was 
increased to about 1500 to 2000 psig and the melt temperature was 
660.degree. F. The flash reactor was maintained at about 40 psig. The 
temperatures within the flash reactor ranged from 580.degree. to 
650.degree. F. depending upon the location within the flash reactor. The 
effluent from the flash reactor was injected directly into the twin-screw 
extruder/reactor. The operating conditions of the twin-screw 
extruder/reactor are shown in the following table. 
______________________________________ 
ZSK-30 Conditions 
______________________________________ 
Screw 
Speed, Torque, Zone Temperature, .degree.F. 
Rpm Percent 1 2 3 4 5 
______________________________________ 
150 40-60 635 560 570 570 560 
______________________________________ 
Temperature, .degree.F. 
Product 
Final Rate, Product 
Die Melt lb/hr IV 
______________________________________ 
560 -- 11 1.25 
______________________________________ 
The total production of this run was 26 lbs. The inherent viscosity of the 
resin measured in the solvent of 60/40 phenol/tetrachloroethane mixture at 
30.degree. C. was 1.25 dl/g. 
EXAMPLE 2 
Heat Stabilized Polyamide 
About 10 lbs of the 85/15-94/6 TA/IA-HMDA/TMHMDA polyamide produced by the 
continuous process was dried in a forced-air oven at 230.degree. F. 
overnight and then dry blended with 0.31% cupric acetate and 0.295% 
potassium iodide in a tumbler mixer for about 20 minutes. The well-mixed 
resin was then fed into the ZSK-30 extruder for extrusion compounding. The 
operating conditions of the extruder are shown in the following table: 
______________________________________ 
ZSK-30 Conditions 
______________________________________ 
Screw 
Speed, Torque, Zone Temperature, .degree.F. 
Rpm Percent 1 2 3 4 5 
______________________________________ 
200 15-20 615 615 645 615 620 
______________________________________ 
Temperature, .degree.F. 
Product 
Final Rate, 
Die Melt lb/hr 
______________________________________ 
610 -- 12 
______________________________________ 
EXAMPLE 3 
We have prepared monofilaments using our novel polyamides. To produce 
monofilament, the process starts with a single-screw extruder to supply a 
melt for conversion to fiber. The die for monofilament is similar to the 
multifilament die. The monofilament process is a slower operation, 
typically about 50 to about 200 feet/minute. For the melt spinning 
operations, about 40 to about 80 feet/minute was the speed used for the 
monofilament processing. The monofilament, on the other hand, is 
water-quenched with much less melt draw down. The monofilament is 
subsequently drawn with heated drawing systems. The monofilament drawing 
is done inline using heated ovens. 
TABLE 6 
______________________________________ 
Monofilament from 85/15-75/25 
(TA/IA-HMDA/TMHMDA) 
Melt Elonga- 
Tenac- 
Initial 
Draw 
Tm Temp. Denier tion ity Modulus 
Ratio 
(.degree.C.) 
(.degree.C.) 
(g/9000 m) 
(%) (g/d) (g/d) (X:1.0) 
______________________________________ 
302 321 1360 11.7 5.0 61.8 4.2 
1630 9.6 4.7 59.1 4.6 
1850 17.0 4.4 53.0 5.1 
1820 29.3 3.3 45.1 3.1 
______________________________________ 
EXAMPLE 4 
Continuous Preparation of 65/35-100 (TA/IA-HMDA) Copolymer 
The following charge was placed in the salt reactor: 
______________________________________ 
Component Amount, g 
______________________________________ 
TA 6447.1 
IA 3471.5 
BA (benzoic acid) 
73.3 
HMDA 7112.1 
H.sub.2 O 3100 
NaH.sub.2 PO.sub.2.H.sub.2 O 
13.8 
______________________________________ 
The salt reactor consisted of a 5-gallon stirred tank reactor with internal 
coils, an oil jacket for temperature control, and a pitched-blade turbine 
with a variable-speed drive. This reactor can accommodate a 60 g-mole 
charge of the polyammonium carboxylate salt components. 
Once the salt reactor has been charged, it is purged with nitrogen or other 
inert gas and heated to 420.degree. F. (216.degree. C.). The pressure is 
set to 480 psig by first allowing the water in the salt to reach its 
equilibrium pressure and then adjusting with nitrogen. In the feed batch 
operations, the salt is subjected to a range of residence times. They 
average about 100 minutes. Also, as a result of the fed-batch mode of 
operation, it is necessary to include a second surge vessel in the salt 
preparation section. This vessel, which is at 420.degree. F. (216.degree. 
C.) and 450 psig, is used to isolate the salt reactor during charge 
addition. 
Upon leaving the salt section, the salt is passed through a 140-micron 
filler into a two-headed positive displacement Bran-Lubbe pump. 
Temperature through the pump is maintained at 406.degree. F. (208.degree. 
C.). Pressures are increased to 1800 psig in the pump. After passing 
through the pump, the salt solution was passed through a preheat zone and 
heated to 622.degree. F. (328.degree. C.). The pressure prevents vapor 
formation in the preheater. Residence time in the preheater is 40 seconds. 
The salt enters the flash reactor through a valve manufactured by Research 
Control Valve (RCV) where pressure is reduced from about 1800 psig to 
about 0 to 400 psig. In ordinary operation, this flash reactor is a 
tubular reactor about 10 to 14 feet long with an internal diameter of 
0.375 to 0.5 inches. The wall temperature of this reactor is maintained at 
about 700.degree. to 750.degree. F. The necessary heat is supplied by hot 
oil jacket, electrical heaters, or other means. The internal temperature 
of this reactor is monitored along its length. The temperature of the 
reaction mixture is between about 525.degree. F. and 630.degree. F. within 
this reactor. The pressure within the flash reactor is controlled by a 
second RCV. The residence time in the flash reactor is about 10 seconds. 
The process conditions were: 
______________________________________ 
Process Conditions 
Preheat Reactor 
Temp, Press., Feed Rate, 
Press., 
Reactor Temperature, .degree.F. 
.degree.F. 
psig gal/hour psig 1/4 1/2 3/4 Final 
______________________________________ 
640 1850 1.8 50 541 556 576 592 
______________________________________ 
Upon exiting the flash reactor, the reaction mixture is injected directly 
onto the screws of a twin-screw extruder/reactor, the Werner-Pfleiderer 
ZSK-30, described above. The twin-screw extruder increases the molecular 
weight of the polymer, to provide an inherent viscosity of the finished 
polymer of about 0.8 dl/g or greater. The process conditions employed in 
the twin-screw reactor are presented below. 
______________________________________ 
ZSK-30 Conditions 
______________________________________ 
Screw 
Speed, Torque, Zone Temperature, .degree.F. 
Rpm Percent 1 2 3 4 5 
______________________________________ 
125 28 620 620 620 565 550 
______________________________________ 
Temperature, .degree.F. 
Product 
Final Rate, 
Die Melt lb/hr 
______________________________________ 
550 556 9.0 
______________________________________ 
The resin produced above had an inherent viscosity of 0.85 dl/g. This resin 
was compounded with 33 weight percent glass fiber by first dry blending 
the ingredients and then melt compounding the resins on the ZSK-30 
twin-screw extruder/reactor. The processing conditions employed were: 
______________________________________ 
Compounding Conditions, ZSK-30 
______________________________________ 
Pro- 
Die duct 
Screw Zone Temperature, .degree.F. 
Temp, Rate, 
Speed Torque 1 2 3 4 5 .degree.F. 
lb/hr 
______________________________________ 
90 41 535 600 600 600 600 600 17 
______________________________________ 
The filled and neat resins were injection molded. The 
following material properties were obtained: 
______________________________________ 
Ultimate Elonga- Izod HDT 
Glass Tensile tion at Flexural 
Modu- Impact 
@ 264 
Fiber Strength, 
break, Strength 
lus, ft-lb/ 
psi, 
% psi % psi M psi in .degree.F. 
______________________________________ 
0 15,400 5.0 22,800 444 0.8 241 
33 31,100 4.5 42,300 1,360 1.9 270 
______________________________________ 
EXAMPLE 5 
Preparation of 68/32-100 (TA/IA-HMDA) 
This polymer was prepared by the process described in Example 4 except that 
the charge to the reactor consisted of the following ingredients: 
______________________________________ 
Component Amount, g 
______________________________________ 
TA 5084 
IA 2392 
HMDA 6329 
H.sub.2 O 2272 
NaH.sub.2 PO.sub.2.H.sub.2 O 
12 
Silicone oil (DC-200) 
12 
______________________________________ 
The resin had the following material properties: 
______________________________________ 
Tensile Properties 
Yield Ultimate 
Tensile Tensile Elongation 
Strength, 
Elongation, Strength, 
at Break, 
psi % psi % 
______________________________________ 
17,400 7.9 14,900 14 
______________________________________ 
Flexural Properties 
Izod HDT 
Strength, 
Modulus, Impact, @ 264 psi, 
psi M psi ft-lb/in .degree.F. 
______________________________________ 
24,600 459 1.8 269 
______________________________________ 
EXAMPLE 6 
Preparation of 72/28-100 (TA/IA-HMDA) 
The polyamide of 72/28-100 TA/IA-HMDA composition was produced by the batch 
melt process on the 4CV Helicone reactor. The reactants, 358.84 g TA, 
139.55 g IA, 479.9 g HMDA including 25.9% water as received, 89 g 
deionized water, and 0.5 g sodium hypophosphite as catalyst, were loaded 
into the 4CV Helicone reactor, which was preheated to 
190.degree.-210.degree. F. The temperature controller was set at 
600.degree. F. The agitator was set at about 10 rpm. After about 26 
minutes, the pressure in the reactor rose to about 120 psi. The pressure 
was held at 120 psi for about 15 minutes as the melt temperature rose to 
about 506.degree. F. The pressure was then vented down to 100 psi in 3 
minutes and held at 100 psi for about 10 minutes. At this point, the 
temperature controller was set at 610.degree. F. The pressure was held at 
100 psi for an additional 7 minutes and then was vented down to 
atmospheric pressure in about 2 minutes. At this moment, the melt 
temperature rose to about 609.degree. F. and the current for the agitator 
started to increase. The polymer was then dumped into water. The inherent 
viscosity of the polymer measured in the solvent of 60/40 
phenol/tetrachloroethane mixture at 30.degree. C. was 0.91 dl/g. 
The polyamide resin produced by the batch melt process was ground and dried 
at 230.degree. F. in a pump vacuum oven overnight. One part was kept as 
neat resin. The other part was dry blended with 30% PPG 3540 glass fibers. 
The samples were injection molded into test bars on the Arburg molding 
machine by using a mold temperature of 250.degree. F. and barrel 
temperature profile of 580.degree., 610.degree., and 610.degree. F. Type I 
tensile bars were molded and tested at 2 in/min testing speed. The test 
results are shown in the table below: 
______________________________________ 
Ultimate Elonga- Izod HDT 
Glass Tensile tion at Flexural 
Modu- Impact 
@ 264 
Fiber Strength break, Strength 
lus, ft-lb/ 
psi, 
% psi % psi M psi in .degree.F. 
______________________________________ 
0 7,500 2 20,400 521 1.1 267 
30 29,300 4 43,900 1,370 2.7 &gt;560 
______________________________________ 
EXAMPLE 7 
Preparation of 75/25-100 (TA/IA-HMDA) Polyamide 
In this example, a series of a salt reactor, standpipe, and 
polycondensation reactor were employed to obtain a polycondensate with an 
inherent viscosity of about 0.1 to 0.2 dl/g. This polycondensate of low 
inherent viscosity was called a prepolymer. The high melt viscosity and 
high melt temperature of these polymers limited the inherent viscosity 
which could be obtained in the series of reactors. This low inherent 
viscosity material was then finished to a polymer of 0.85 dl/g inherent 
viscosity in the ZSK-30 extruder reactor. 
In this semi-continuous process, the reactants, 4984 g TA, 1661.2 g IA, 
6540.8 g HMDA including 26.8% water as received, 800 g deionized water, 
9.16 g NaH.sub.2 PO.sub.2.H.sub.2 O and 9.16 g silicone oil, were charged 
to a 5-gallon salt reactor. The salt reactor was operated at 445 psig and 
445.degree. F. (melt temperature). The effluent from this reactor was then 
passed to a standpipe which was operated at 420 psig and 470.degree. F. 
(heating oil temperature). The residence time in the polycondensation 
reactor was about 30 minutes. At the end of this time, the reactor was 
vented down to atmospheric pressure and the prepolymer was removed from 
the reactor. 
The prepolymer was dried in a forced-air oven at 80.degree. C. overnight 
and then ground to about a 3 mm size. The inherent viscosity was 
determined to be 0.11 dl/g, indicating the prepolymer was good enough for 
the feed of ZSK-30 extruder/reactor. The dried prepolymer was fed to the 
ZSK-30 twin-screw extruder/reactor. The extruder/reactor was operated at 
atmospheric pressure. The operating conditions are shown below. The 
residence time in the extruder was about 2 minutes. The inherent viscosity 
of the product was 0.85 dl/g. 
______________________________________ 
ZSK-30 Conditions 
______________________________________ 
Screw 
Speed, Torque Zone Temperature, .degree.F. 
Rpm Percent 1 2 3 4 5 
______________________________________ 
75 45-55 90 510 700 708 615 
______________________________________ 
Temperature, .degree.F. 
Product 
Final Rate, 
Die Melt lb/hr 
______________________________________ 
610 -- .about.8 
______________________________________ 
EXAMPLE 8 
In all the examples, the reactants, 1.317 lbs TA, 0.614 lbs HMDA, 0.462 lbs 
TMHMDA, and 0.87 gm of sodium hypophosphite, are loaded into a Helicone 
reactor that has been heated to 95.degree.-150.degree. C. The temperature 
control is set at 215.degree. C. The agitator is set at the maximum, 36 
rpm. In the examples given in Table 2, the reactor pressure rose to 105 
psi. The melt temperature was 205.degree. C. The temperature controller 
settings were gradually increased to 230.degree. C. The reactor pressure 
rose to 123 psi; the melt temperature was 220.degree. C. The temperature 
control was then increased to 315.degree. C. The reactor pressure was 
controlled at 123-125 psi for 16 minutes as the melt temperature increased 
to 260.degree. C. The reactor pressure was then vented down to 100 psi 
over a 17-minute period. The melt temperature increased to about 
310.degree. C. The reactor was then vented to atmospheric pressure over a 
2-minute period. The melt temperature reached 313.degree. C. The reaction 
was then stopped by dumping the resin into water. The resin had an I.V. of 
0.86 dl/g, measured in 60/40 phenol/tetrachloroethane at a temperature of 
30.degree. C. The filled molding compositions of this invention are 
prepared by blending the fillers and polymer and then extrusion 
compounding on an extruder. The extrusion compounding is carried out with 
the polymer in the molten state, generally at a temperature ranging from 
about 288.degree. to 355.degree. C., and preferably from about 310.degree. 
to 343.degree. C. 
Injection molding techniques which are used according to this invention are 
known to persons of skill in the art and are commonly referred to as 
"reciprocating screw injection molding." In reciprocating screw injection 
molding, powdered or pelletized polymer is delivered to a hopper and from 
there fed into the feed port of a barrel, typically cylindrical, which 
houses a screw adapted for rotation and reciprocal motion within the 
barrel along the length thereof. 
The barrel also has a nozzle end opposite the feed end, and may have a 
chamber located near the nozzle end. Polymer fed from the hopper into the 
barrel passes into and through the area between flights of the rotating 
screw and, during such passage, is plasticated due to heat and the working 
of the polymer between the interior surface of the barrel and the surfaces 
between screw flights. Working of the polymer between screw flights and 
the interior of the barrel compacts the polymer between screw flights. 
After passing between the screw flights, the compacted, plasticated 
polymer accumulates in the barrel or in a chamber near the nozzle. 
During rotation of the screw, pressure, commonly referred to as "back 
pressure", is applied to the end of the screw at the feed end of the 
barrel. An opposing pressure develops due to accumulation of polymer at 
the nozzle end of the barrel, and when this pressure exceeds the back 
pressure, the screw is pushed away from the nozzle. When the accumulating 
polymer fills the chamber or the portion of the barrel vacated by the 
screw or, in some instances, when the screw reaches a predetermined 
position, pressure, commonly referred to an "injection pressure", is 
applied to the screw and the accumulated polymer is forced through the 
nozzle into a mold, which is commonly heated. In some cases, a booster is 
used to aid the injection. Typically, a non-return check valve is employed 
to prevent polymer from flowing back towards the screw. Following 
injection of the polymer into the mold, the polymer is held therein, the 
mold is cooled, and the molded part removed. 
EXAMPLE 9 
The polymer of Example 9 is prepared by dry blending 45 percent by weight 
of glass fibers with the polyamide prepared in Example 8. 
EXAMPLE 10 
The polymer of Example 10 is prepared by dry blending 55 percent by weight 
of glass fibers with the polyamide prepared in Example 8. 
______________________________________ 
Material Properties of 
100/65/35 TA/HMDA/TMHMDA Polyamide 
Prepared as Shown in Example 8 
______________________________________ 
Tensile 
Glass ASTM Method D-638 
Example Fiber, Strength, 
Elongation, 
Number % M psi % 
______________________________________ 
8 0 13.1 5.2 
9 45 33.6 5.3 
10 55 34.2 4.9 
______________________________________ 
Notched 
Flexural Izod 
ASTM D-638 ASTM 
Example Strength, Modulus, D-256, 
Number M psi MM psi ft-lb/in 
______________________________________ 
8 21.3 0.46 0.77 
9 49.5 1.82 3.17 
10 52.4 2.32 3.88 
______________________________________ 
Tensile HDT 
Impact ASTM 
ASTM D-668 % Water 
Example D-256, (at 264 Absorption 
Number ft-lb/in.sup.2 
psi), .degree.C. 
ASTM D-570 
______________________________________ 
8 37 103 0.55 
9 33 303 0.23 
10 88 &gt;304 0.20 
______________________________________ 
Comparative examples 8, 9, and 10 show that in order to maintain tensile 
strength at high levels of TA, it is necessary to use higher levels of 
TMHMDA.