JPH0373647B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Technical Field] The present invention relates to a method for melt-spinning polymeric chips such as polyester and polyamide in a non-drying state.

[Prior Art] When spinning polymers, generally the polymer chips are dried to reduce their moisture content to 0.05% or less so that the moisture does not affect the melt viscosity, and then melt spinning is carried out. For energy saving and other reasons, we would like to simplify the process by omitting the drying process if possible. To achieve this, it is necessary to remove water during the melt extrusion process, but conventionally, the degree of vacuum in the vent section of a single-screw or twin-screw vented extruder is maintained at 0.01 to 30 mmHg to remove water and polymer sublimates. It is known to do.

However, such a melt extrusion method has the problem that the remaining water content varies due to variation in the water content of the supplied polymer chips, and the degree of depolymerization by water changes, resulting in variation in the quality of the spun yarn.

In order to deal with this problem, it has been proposed to connect a hygrometer to the vent section and control the degree of vacuum in the vent section so that the humidity in the vent section is constant, as described in Japanese Patent Publication No. 57-54567. However, it is not only difficult to measure humidity in places where the degree of vacuum changes, but also
Even if the humidity in the vent section is controlled, there is no guarantee that the moisture content in the molten polymer will be constant.

[Structure of the Invention] The present invention has been made to solve the problems of the conventional method, and when melt-spinning non-dried polymer chips after melt-extruding them with a vented extruder, The intrinsic viscosity [η _F ] can be calculated by measuring the pressure drop of the molten polymer flowing in the downstream piping and calculating the intrinsic viscosity [η _F ] from the temperature (T) and flow rate (Q) of the molten polymer. The degree of vacuum in the vent section is controlled so that the calculated value [η _F ] is constant, and the limiting viscosity [η _F ] is constant regardless of the moisture content of the supplied polymer chips, resulting in a product of uniform quality. It is possible to obtain

Here, it is empirically known that the limiting viscosity [η _F ] can be expressed as ηF=AQ ^- 〓×△p〓×10 ^- 〓 ^T (A, α, β, γ are constants), and experimentally By changing the conditions and finding the constants of A, α, β, and γ, we can measure the differential pressure △p, temperature T, and flow rate Q, and use these as inputs to the control device to find the limiting viscosity [η _F ]. The degree of vacuum in the vent part can be controlled so that the limiting viscosity [η _F ] is constant. If the degree of vacuum in the vent section itself is detected and controlled to be constant, cascade control is used to control the set value of the vacuum degree control device using the output of the limiting viscosity [η _F ] control device. Just do it.

[Example] Hereinafter, the present invention will be explained in detail with reference to the drawings.

The figure is a process diagram showing an embodiment of the present invention, and in the figure, 1 is a vent type extruder, 1a is a vent part, and is connected to a vacuum suction device (not shown) via a pipe 1b. 1c is a screw, and 1d and 1e are an electric motor and a speed reducer for rotationally driving the screw 1c, respectively. Although not shown, the pressure at the discharge section 1f of the vented extruder 1 is normally detected, and the rotational speed of the screw drive electric motor 1d is controlled so that the pressure remains constant. 2 is a polymer chip supply hopper connected to a vented extruder. 3 is a molten polymer conduit (piping) downstream of the vented extruder. Reference numeral 4 denotes a pressure boosting metering pump provided as required, and its rotational speed is controlled so that the pressure at the outlet of metering pump 4 is constant, although not shown. In the present invention, a differential pressure converter 5 is provided to measure the differential pressure (pressure loss △p) between two points in the downstream piping 3 of the vent type extruder 1, and the pressure drop (△p) is fed back to the limiting viscosity control device 6. Then, the limiting viscosity [η _F ] is determined from the predetermined temperature and flow rate of the polymer, and the vacuum suction pipe 1b of the vent portion 1a is provided via the pressure control device 7 so that the limiting viscosity [η _F ] is constant. The opening degree of the control valve 8 is controlled. 5a and 5a' are diaphragm type pressure detection parts, and pressure transmission capillary 5b,
The pressure is transmitted to the differential pressure converter 5 via 5b' and converted into an electrical signal. 9 is a vacuum level detection transmitter for the vent section. Usually, the temperature of the molten polymer flowing through the pipe 3 is kept constant in the extruder 1.
Although not shown, the temperature of the heat-retaining heater in the pipe 3 is controlled, so it is sufficient to set it as a constant in the control device 6, but it is preferable to set a temperature detection terminal in the pipe 3. A temperature converter is installed to detect the temperature of the polymer in the piping and feed it back to the control device 6 via a temperature converter. Regarding the flow rate, in the case of a spinning machine, etc., it is constant once the brand (thickness) of the yarn is determined, and it can be given as a constant in advance, but if necessary (if you do not want to change the setting every time the conditions change), you can measure it. The rotation speed of the pump 4 may be fed back to the control device 6.

In addition, in the embodiment, the vacuum degree control device 7 controls the opening degree of the control valve 8 provided in the vacuum suction piping 1b so that it is constant based on the signal from the vacuum degree transmitter 9. 7 and the [η _F ] control device 6 are connected in cascade, and the output of the [η _F ] control device controls the set value of the vacuum degree control device 7. It is also possible to omit the device 7 and directly control the control valve 8 with the output of the [η _F ] control device 6. As a means for adjusting the degree of vacuum, it is also possible to control the suction force of a vacuum suction device (for example, in the case of a vacuum pump, the rotational speed of the pump) without relying on the control valve 8 or the like. Also, it is obvious from what has already been stated that when the temperature and flow rate of the polymer flowing through the pipe 3 are constant, the intrinsic viscosity [η _F ] and the differential pressure [△p] have a one-to-one correspondence. ,
In order to keep the limiting viscosity [η _F ] constant, it is sufficient to control the differential pressure Δp to be constant, and this is also included in the present invention.

This will be explained in more detail below.

The flow rate and temperature of the molten polyester polymer flowing through the pipe 3 with an inner diameter of 19.2 mm were varied, and the differential pressure △p between two points 580 mm apart was measured, and the intrinsic viscosity of the polymer was measured using the Ostwald method using sampling. Calculate the constant from the result [η _F ] = 1.312×Q ^-0.2047 ×△p ^0.2047 ×10 ^6.142×10-4
It turns out that it can be expressed as ^×T .

The units are Q: g/min, Δp: Kg/cm ² , and T: °C.

As the vacuum degree control device 7 and the [η _F ] control device 6, one commercially available (manufactured by Yokogawa Hokushin Electric) programmable controller (SLPC) was used as both control devices. In this case, non-dried polyester chips with an intrinsic viscosity of 0.650 are melt-extruded using this device [η _F ]=0.645±
I was able to control it to 0.002.

As described above, the present invention applies the principle of a capillary viscometer in the embodiment to determine the limiting viscosity [η _F ], but other viscometers may be used to determine the limiting viscosity. Empirically, the relationship between viscosity [μ] and intrinsic viscosity [η _F ], which can be measured with a general viscometer, can be expressed as log [μ] = αlog [η _F ] − βT−γ (α, β, γ constants). It is known that if α, β, and γ are determined experimentally, the intrinsic viscosity [η _F ] can be determined from the viscosity [μ] and the temperature T, so it is possible to control this.

[Effects of the Invention] The present invention has made it possible to melt-spun non-drying polymer chips with varying moisture content without going through a drying process, and the resulting effects were extremely large.

[Brief explanation of drawings]

The drawings are schematic process diagrams showing embodiments of the present invention. 1 is a vent type extruder, 1a is a vent part of the vent type extruder, 3 is a pipe through which the molten polymer flows, 4 is a differential pressure converter, and 4a, 4a' are detection parts. 6 is a limiting viscosity [η _F ] controller, 7 is a vacuum degree controller, 8 is
is a control valve provided in the vacuum suction piping of the vent portion 1b.

Claims (1)

[Claims] 1. When performing melt spinning after melting and extruding undried polymer chips using a vented extruder, the intrinsic viscosity [η _F ] of the molten polymer flowing through the downstream piping of the vented extruder is made to be constant. A method for melt-spinning a non-drying polymer, characterized in that the degree of vacuum in the vent section of the vented extruder is controlled.