JPS6279225A - Manufacture of high viscosity polyhexamethyleneadipamide - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to high viscosity polyamide resin (R1), particularly polyhexamethylene adipamine P ( The present invention relates to a method for producing polyamide-6,6).

The relative viscosity (ηrel) of polyamides specified for processing by extrusion is between 6.7 and 7.5, measured at 25°C in a solution of 1% in 96es sulfuric acid.

This means that the average molecular weight (Mn) is 23000~4s
Corresponds to ooo.

Prior Art Known processes for the production of such polyamides, for example by bulk post-polycondensation of particulate, low viscosity polymers at temperatures below their melting point, are described in U.S. Pat. and in West German Patent Specification No. 1210183 and East German Patent Specification No. 91566.

In general, the bulk postpolycondensation of polyamides is carried out under inert gas or vacuum in drying apparatuses operating discontinuously or continuously. This method requires a sufficiently large viscosity (ηrel
5.0 and above), which allows the production of polyamides that are suitable for subsequent processing in an extruder. However, this bulk postpolycondensation has quite decisive disadvantages.

First, since the temperature is low, the process time is not long.

Generally this is 24 hours and longer.

Second, large amounts of protective gas heated to temperatures above 200° C. are used. Furthermore, the polymers obtained by bulk post-polycondensation have a wide molecular track distribution due to the uneven rate of removal of condensation water through the particle thickness. Furthermore, this deteriorates the processing properties.

Another method for producing high viscosity polyamides is continuous post-condensation in the melt using a wide variety of screw devices.

A method for increasing the molecular t' of polyamide P1, such as polyhexamethylene adipamide, is known (US Pat. No. 3,509,107). In this case, a low viscosity melt of presynthesized polyhexamethylene adipamide (90% relative viscosity of a 11% solution in acid 17, corresponding to a molecular weight Mn 4000) is fed into a horizontal single-screw extruder, So this is 0.
0.275 in countercurrent at 200-295°C for 1-1.5 hours
~25.711 kg (polymer), preferably 1.28-6.
285 supplied in an amount of 9 (polymer) in 42 l/
Treated with nitrogen at °C. The highest relative viscosity thus obtained is 75-77 units, which is equal to the average molecular jjkM
n19000, or a relative viscosity of 6 measured in sulfuric acid solution.

Similarly, a method known to increase the molecular weight of polyhexamethylene adipamide is pre-metallized resin, which has a K value of 60 to 60.
Low viscosity polyhexamethylene adipamide having a molecular f of 4000 to 15000 has a water vapor of 1 to 1
0% by weight, into a two-screw reactor with tightly interlocking self-cleaning screws and at least one vent hole ([IIF Italian Patent Specification No. 1720349]). . This polymer lasts for 5-45 minutes! ! 11270~285°C and pressure 50~23
00) Energy supply by screw in le, 10.03
Processed with ~0.2 kWh/kg (polymer).

The highest molecular weight achievable by this method is K value 69.
~72, corresponding to Mn==18000.

A disadvantage of the above-mentioned known methods for increasing the molecular weight of polyamide 6, O is that it is not possible to produce polymers with molecules greater than 1t2DOOO. However, for producing tubes, profiles and sheets, polymers with a molecular weight of at least 23,000 are required.

Furthermore, it is known to increase the molecular weight of polyamides, in particular polyhexamethyleneadipamide, by using polyamide P in the form of granules, pellets or tablets.
65 to 1.3 m of inert gas skin to be fed to the feed hopper of the axial screw extruder, in which case to remove atmospheric oxygen
J/ is a method in which 9 (polymer) is supplied to the hopper (
No. 3,040,005). As it passes through the extruder, the polymer melts and is treated with a cocurrently flowing inert gas, which removes the low molecular weight reaction products formed during the polycondensation. The temperature of the polymer varies as it passes through the extruder. The temperature starts from room temperature and rises to 296°C. Total residence time is 4-8 minutes.

The polyamide melt is degassed under vacuum. To promote polycondensation, a phosphorus-containing compound is added to polyamide 6.6.
For example, sodium hypophosphite is 0.05~
It is added in an amount of 1.0mF%.

The average molecular weight (Mn) of polyamide is 17,000 to 3
Increased to 9000.

Although this known method increases the molecular weight,
However, it has the following drawbacks: 1. During the vacuum treatment of the melt, it is impossible to completely seal the extruder, so the polyamide is oxidized due to the inflow of atmospheric oxygen into the extruder.

2. The amount of inert gas consumed to obtain the desired molecular weight is large (0.65 to 1.3 m'/yu (polymer)).

6. Wide molecular weight distribution.

4. Formation of del particles.

The last two disadvantages are due to the excessive dehydration of the polyamide melt that occurs when applying a vacuum or bubbling the degassing zone of the polymer with an inert gas. This results in
Excessively long polymer chains are formed and reactions between chains (
So-called overamidation) cannot proceed.5
, low equipment efficiency and large specific energy consumption values.

Therefore, the output when using a twin screw extruder with a diameter of 3 (82,5 m) is 1-2 Kg/h with a specific energy consumption of 0.4-0.6 kTh/) C9 (polyamide). there were.

Problem to be Solved by the Invention The object of the invention is to produce polyamides with very homogeneous macromolecules without containing del particles, increasing the capacity of the equipment and reducing the energy costs.

Means to solve the problem In order to solve this problem, the relative viscosity ηrel is 2.5~
2.7 polyhexamethylene adipamide is polycondensed by processing in successive zones of an extruder in which the pressure is alternately increased or decreased, in which case in the pressure increase zone , water vapor superheated to the temperature of the melt is supplied in an amount of 0.05 to 0.7 kg/kg (polymer), the introduced water vapor and condensed water are removed in a reduced pressure I-/, and The melt temperature varies over the length of the extruder, from 260-280°C in the first zone to 280-280°C in the last zone.
It is evenly raised to 610°C.

For example, processing of a polyamide melt can be carried out in six pressure increase zones and six pressure reduction zones.

For example, the amount of superheated steam supplied to each pressure increase zone may be 50 to 100 times the amount of steam introduced into the preceding zone. The pressure in the vacuum zone is reduced over the length of the extruder from 0500-300 mbar in the first zone to 50-30 mbar in the last zone.

The method according to the invention is carried out as follows.

A polymer melt having a relative viscosity Bel of 2.5 to 2.7 is fed to a twin-screw extruder via a feed hole (see FIG. 1). This melt flows into a first pressure increase zone, into which steam superheated to the temperature of the melt is supplied under pressure.

The increased pressure in this zone prevents the diffusion of vacuum from the reduced pressure zone into the feed zone, and thereby prevents atmospheric oxygen from entering the extruder in tight screw closures or other non-tight locations. Eliminate the possibility of inflow through

Furthermore, the supply of superheated steam causes foaming and thereby an increase in the specific polymer surface area.

Thereafter, the polymer melt enters a first vacuum zone where, by means of vacuum action, the previously supplied superheated steam and the resulting condensation water are removed and polyamide 6.6 is removed for the purpose of increasing the molecular weight. Subsequently, the conditions for polycondensation are established.

This melt then enters the next pressure increase zone, where it is also supplied with superheated steam. The presence of water in vapor form slows down the removal of condensed water from the polymer melt in this zone and thus also the increase in polymer molecular weight. The reaction between the individual macromolecules continues to proceed, although the molecular weight distribution will shift from a broad distribution (in the case of rapid polycondensation) to a standard distribution.

During its passage through the extruder, the polyamide 6.6 melt is passed through the pressure and vacuum zones successively, in relation to the desired molecular weight, a number of times, but not more than twice in each case. will be processed. If a polyamide melt is treated in this way, i.e. if the molecular weight growth is carried out stepwise with compensation of the molecular weight distribution by overamidation and under conditions that do not allow excessive dehydration of the polymer melt, the delta A polymer with very homogeneous macromolecules without inclusion of particles is obtained. The melt temperature is increased evenly along the extruder from 260-280°C in the first zone to 280-610°C in the last zone. Increasing the melt temperature allows greater reaction rates to be obtained even though the number of reactive end groups on the polyamide P decreases with the progress of the reaction and the polymer molecular weight increases.

On the other hand, increasing temperature reduces the effective viscosity of the polymer melt. This facilitates the removal of water from the polymer and thus reduces the influence of the diffusion process on the course of the chemical reaction. Increasing the polycondensation temperature significantly enhances this process, with residence times of the polyamide melt in the extruder ranging from 1.0 to
It is 4.0 minutes. In this case, the specific energy consumption is approximately 0.
1-0.3 kWh/kg (polymer). The short residence time of the polyamide in the extruder, together with the slight moisture in the melt due to superheated steam, prevents thermal decomposition of the polymer as well as the formation of del particles. Starting from the second zone, the amount of superheated steam supplied to each pressure increase zone is between 50 and 100 times the amount of steam supplied to the preceding zone.

The amount of superheated steam supplied into the intensification zone allows the molecular weight balance of polyamide H4 in each successive zone to be maintained at a high level, but this level is greater than the amount of superheated steam supplied to this zone. commensurate with the quantity.

In the extruder, the pressure in the vacuum zone is 50% lower than that in the first zone.
It is reduced from 0-600 mbar to 50-30 mbar in the last zone. In this way, the water vapor partial pressure on the melt surface in these zones is continuously reduced, thereby ensuring a sufficiently rapid removal of the condensed water even if the effective melt viscosity increases continuously, and this also contributes to process enhancement. For additional process acceleration purposes, phosphorus-containing compounds such as orthophosphoric acid, sodium hypophosphite, phenylphosphinic acid, etc. are added in amounts of 0.06 to 1.0% based on the amount of polyamide.
Used at 0 weight it-%.

A novel feature of the process according to the invention is the following sequence: 1. The polyamide 6.6 melt is placed in series-connected zones with alternately increased and decreased pressures 1. , processed for the purpose of increasing viscosity.

According to a known method (West German Patent Specification No. 1720349) polyamide y6. <5 The melt is degassed in at least one vacuum zone at pressures between 50 Torr and 2300 Torr, in which case the viscosity increases to 2.7 to 2.8 (relative viscosity of a 1H solution in H2S04). can get.

According to the process according to US Pat. No. 3,040,005, the processing of low-viscosity polyamide P is carried out in a vacuum zone, although in this case, according to the description, a discolored product is obtained.

The use of alternating zones with increased and decreased pressure ensures the production of a homogeneous structure of high viscosity polyamide 6.6 (relative viscosity>4) without discoloration.

2. In order to facilitate the removal of condensed water in the depressurization zone and to create the necessary conditions for the proceeding of the overamidation process in the pressure increase zone, superheated steam is added to the extruder for the purpose of increasing the surface area of the melt. is added to the polyamide 6°6 melt in multiple zones over the length of the polyamide 6°6 melt.

According to German Patent Specification No. 17 20 549, the continuous postpolycondensation of a low-viscosity polyamide 6.6 is carried out in the presence of 1 to 10 degrees of water vapor fed together with the polymer, in which case this water vapor is actually The first part of the extruder
completely removed in the degassing zone.

In the case of this known process, the presence of water vapor is not intended to enhance the postpolycondensation, but is a consequence of the use of rubolimers in which water was not completely removed during the synthesis.

In the case of the process according to the invention, the use of water vapor added to the polyamide 6.6 melt in two and more zones
High-quality, high-viscosity polyamide 6 with enhanced post-polycondensation process
．． 6, which is absolutely new.

Furthermore, what has not yet been described is that polyamide 6.6 is continuously postpolycondensed in an extruder and
When passing through the extruder, the temperature is raised uniformly and the pressure is reduced in multiple zones. West German Patent Specification No. 17
In the case of the known method according to No. 20349 and U.S. Pat. Nos. 3,509,107 and 3,040,005,
The postpolycondensation is carried out at a temperature of 275 DEG to 295 DEG, provided that this temperature is not varied over the length of the extruder. In these methods, the pressure in the degassing zone is within a certain range (e.g. U.S. Pat. No. 3,040,005
20-100 Torr; according to German Patent Specification No. 1720349, 50-2300 Torr), provided that this pressure does not vary over the length of the extruder.

The uniform variation of these parameters over the extruder length according to the invention ensures optimal conditions for carrying out the postpolycondensation and the subsequent overamidation over the entire extruder length and at the same time increasing polymer viscosity.

Example In the following, the present invention will be explained in detail with reference to examples.

Example 1 Relative viscosity ηrel measured in 100% solution in 96% sulfuric acid
A polyamide 6.6 melt having a molecular weight of 2.5 (corresponding to a molecule f17000) is continuously fed at a rate of 8 to 9/hour by tightly meshing and co-rotating screws [diameter 60 tm and length-to-diameter ratio (l/d) 42 and equipped with 6 pressure increase zones and 6 pressure reduction zones] at a Hessfrill rotation speed of 10 rpm (for example type ZSK 30).

The temperature of the polyamide melt was reduced to 270°0 in these zones.
．． Maintain at 285°C and 300°C.

The amount of superheated steam supplied to the pressure increase zone was 0.2i each.
? /It is time. The pressure in the vacuum zone is adjusted to 43 mbar.

Energy consumption is 0.18 kwh/* (polymer)
It is.

After being processed in the extruder, the outlet polyamide 6.6 has a relative viscosity ηrel 5.4, which corresponds to Mn=3400
Corresponds to 0.

Note 6: This molecular distribution indicates the polydispersity of the polyamide, provided that: Mw represents the weight average value of the molecular weight, Mn represents the number average value of the molecular weight, and when Mw −<2.2, There are polymers whose macromolecules have a large homogeneous character.

Table 1 summarizes other examples.

Example 15 The process is carried out analogously to Example 1, using 0.05% by weight of orthophosphoric acid, based on the amount of polyamide, as accelerator.

At the outlet, the polyamide 6.6 has a relative viscosity w ηrel 6.8 k and a polydispersity=2.6. There are no del particles. Energy consumption is 0.28kw
h/K9 (polymer).

polyamide r6. When carrying out post-polycondensation, an increase in the number of alternating pressure increase and decrease zones to 3 or more ensures an increased output when the residence time of the polymer in the extruder is kept the same. . However, in this case, the extruder length is 1744
It is necessary to increase the number by more than 2, but this is technically difficult to implement.

A comparison between the method according to the invention and known methods is summarized in Table 2.

As is clear from this wc2 table, the method according to the invention:
Polyamide 6 with a relative viscosity of 7.5 or less, suitable for example for producing tubes, profiles and sheets in an extruder
．． We guarantee the production of 6.

The dead polymers produced in this way are distinguished by a high macromolecular homogeneity and the absence of del particles, which ensure good properties, processability and high quality of the products produced therefrom. Furthermore, the obtained polymer is colorless. The process for producing high viscosity polyamide 6.6 according to the present invention has high productivity, in which case the required viscosity is higher than that of the next known technology (US Pat.
obtained with a shorter post-polycondensation time.

[Brief explanation of drawings]

FIG. 1 is a schematic longitudinal sectional view of an embodiment of a device for carrying out the method according to the invention.

Claims (1)

[Claims] 1. Rotating in the same direction a melt of a polymer having a relative viscosity of 2.5 to 2.7 (measured as a 1% solution in 96% sulfuric acid);
2 with tightly meshing screws and degassing zones
In producing highly viscous polyhexamethylene adipamide by postpolycondensation in a axial screw extruder, the polymer melt is placed in series in the extruder and subjected to alternatingly increased pressure and The polycondensation is carried out by processing in a number of zones with reduced pressure, in which case in the pressure increase zone the water vapor superheated to the temperature of the melt is
0.7 kg/kg (polymer) is fed to the melt, in a vacuum zone the introduced vapor phase and condensation water are removed, and the temperature of the melt is maintained at the first level over the length of the extruder. from 260-280℃ in the zone to 280℃ in the last zone
A method for producing high viscosity polyhexamethylene adipamide, characterized in that the temperature is uniformly increased to ~310°C. 2. Process for producing high viscosity polyhexamethylene adipamide according to claim 1, characterized in that the treatment of the melt is carried out in at least two pressure increase and pressure reduction zones, respectively. 3. Claims 1 or 2, characterized in that the amount of superheated steam supplied to each subsequent pressure increase zone is 50 to 100% of the amount of steam supplied to the preceding zone. A method for producing high viscosity polyhexamethylene adipamide according to any one of the above. 4. The pressure in the decompression zone is 500 to 500 in the first zone.
High viscosity polyhexamethylene azimuth according to any one of claims 1 to 3, characterized in that it is uniformly reduced from 300 mbar to 50-30 mbar in the last zone. Production method of Pamid. 5. Polyamide melt is 0.03 to 1 to polyamide
Any of claims 1 to 4, characterized in that it is polycondensed in the presence of phosphorus-containing compounds, such as orthophosphoric acid, sodium hypophosphite and phenylphosphinic acid, in an amount of % by weight. A method for producing high viscosity polyhexamethylene adipamide according to item 1. 6. According to any one of claims 1 to 5, characterized in that the temperature distribution and the pressure distribution are selected in such a way that a polyamide with a predetermined polydispersity is obtained. A method for producing high viscosity polyhexamethylene adipamide.