JPH04302Y2 - - Google Patents

Description

[Detailed description of the invention] Industrial application field The invention relates to a flow testing device for thermoplastic plastics, and more specifically, for extruding hard plastics with a low melt index value (hereinafter referred to as MI value). Regarding the improvement of tubules in cases.

Prior Art Flow testing of thermoplastic plastics is an important test when supplying plastics with fluidity that meets customer needs, or when required for quality control in polymerization processes, etc. The test method is specified in ASTM D1238, JIS K7210, etc. JIS K7210 specifies the extrusion speed when a molten thermoplastic is extruded through a die with a specified length and diameter under conditions of temperature and pressure determined by the nature of the thermoplastic being tested. It is something to be measured. The method of expressing this result is the melt index (MI) value or melt value, which is the mass of the sample extruded in 10 minutes in grams, or the value converted from the mass of the sample extruded in a given time to the mass of the sample extruded in 10 minutes. Calculated as flow rate (MFR) value. This test method was established because the melt flowability of polymeric substances depends on the shear rate, but it is a discontinuous process and is not suitable for mass production. Therefore, during the production process, samples are continuously collected for testing. In this method, the sample is forced into a capillary and extruded by a constant flow pump rotationally driven by a servo motor, and the servo motor is driven by a servo system so that the pressure loss within the capillary is constant. The MI value is calculated from the flow rate that is proportional to the rotation speed of the constant flow pump. In other words, the principle of this method is based on Hagen-Poiseuille's law, which states that the flow rate through a capillary is inversely proportional to the viscosity of the sample when the pressure difference in the capillary is constant, and the viscosity of the sample extruded in a given time. In the definition where the product of the sample mass, that is, the flow rate and the density, is the MI value, the density is almost constant under these conditions, so the MI value is
There is a proportional relationship between the value and the flow rate, and the flow rate in the capillary is also
Since both MI values are functional forms that are inversely proportional to viscosity, the flow rate can be converted into MI values for testing.

FIG. 2 is a diagram showing an example of a conventional continuous MI value testing device. In the figure, indicates a detection section, and indicates an operation panel section. A gear pump 3 for feeding the fluid to be tested from the main line 1 to the thin tube 2 (capillary), a servo motor 4 for rotating the gear pump 3, a pump-side heater 5, temperature sensing elements 6, 6',
It has a capillary-side heater 7, temperature sensors 8, 8', a differential pressure detector 9 for detecting the differential pressure between the inlet and outlet of the capillary 2, a constant temperature bath 10, etc., and the operation panel section includes a pump-side temperature controller 11. , temperature indicator 11', capillary side temperature controller 12,
Temperature indicator 12', MI value indicator 13, resistance voltage converter 14, magnetic amplifier 15, non-indicating regulator 16,
It has a converter 17, etc., and controls the rotation speed of the pump 3 by a servo motor 4 so as to always keep the differential pressure between the inlet and the outlet of the capillary 2 constant.
The temperature controllers 11 and 12 are activated by the detection signals from the temperature sensors 6 and 8 to control the heaters 5 and 7 of the pump section and the capillary section, thereby controlling the temperature inside the thermostatic chamber 10 to be constant. Therefore, the rotation speed of the pump that sends fluid to keep the differential pressure in the capillary constant constant is proportional to the pump's discharge amount, that is, the flow rate.Therefore, the rotation speed of the servo motor that controls the rotation of the pump is also proportional to the flow rate. Since it is proportional to , if a tachogenerator is connected to a servo motor and its rotation is extracted, the output of the tachogenerator will display the flow rate, and from this the MI value can be obtained.

Problems to be solved by the present invention In the MI value test device as described above,
For thermoplastics with a low MI value, that is, a high viscosity, it is necessary to increase the pumping pressure to obtain a predetermined flow rate, but in this case, the pressure conditions specified in the standard will not be satisfied. Increasing the pumping load means increasing the capacity of the drive servo motor, and because of this problem, conventionally the thickness of the capillary was increased to satisfy the conditions of shear rate and shear stress. ing. on the other hand,
In recent years, with the development of fine chemicals, resins with low MI values have appeared, and these plastics also have excellent high-temperature properties and are super-resistant materials. In such a plastic flow test, problems occur such as the extruded resin pushing up the test device and the inability to judge the sample. The present invention attempts to solve these problems.

Embodiment FIG. 1 is a configuration diagram for explaining an embodiment of the test apparatus according to the present invention. In the figure, 21 is a feed pipe for feeding plastic, which is the fluid to be tested, and 22 is a resin pressure feed pipe. pump, 23 is the motor, 2
4 is a heater, 25 is a temperature measuring element, 26 is a pressure detection unit,
27 is a capillary (thin tube), 27a is a capillary end, 27b is a porous part, 27c is a discharge plastic, 28 is a constant temperature bath, and the pump 22 to the pressure detection section 26 are the conventional test equipment shown in FIG. It has a similar effect. That is, the pressure detection section 26 detects the differential pressure between the predetermined sections A and B of the capillary 27, and the motor 23 is driven by a control device (not shown) so that the differential pressure becomes constant. The resin pressure feeding pump 22 is driven, and the plastic in the capillary 27 is pumped by the resin pressure feeding pump 22. The test plastic is fed under pressure to the resin pressure feeding pump 22 in a constant temperature bath 28 through a feed pipe 21, and is heated and kept at the constant temperature in the constant temperature bath 28, which is maintained at a constant temperature determined for the test plastic. There is.
At this test temperature, the test plastic has a predetermined viscosity. The capillary end 27a of the capillary 27 is an enlarged part with a larger diameter than the capillary 27.
A porous portion 27b is provided in 7a. The porous portion 27b is provided with a large number of pores, and the total area of the pores is selected to be approximately equal to the cross-sectional area of the capillary 27. The plastic that has been forced to flow through the capillary 27 passes through the capillary end 27a and is discharged from the porous portion 27b to form a rod-shaped outflow plastic 27c having the inner diameter of the porous portion 27b.

For plastics with low MI values, generally
As mentioned above, the measurement time is shortened and the accuracy is improved by applying a larger load or increasing the capillary size.In the case of a continuous MI meter, for example, the extrusion pressure corresponding to a load of 2160g is 3.04
A differential pressure of Kg/cm ² G is used. However, in the case of bottom MI plastic, when measured directly using a capillary specified by JIS, the extrusion amount is small;
As the test error increases, the capillary size is increased as described above. In the case of hard plastics with an MI value of 0.1 or less, plastics with a thickness of approximately 10 mmφ are discharged from the capillary.
Post-treatment of this discharged resin is difficult. According to the present invention, the discharge plastic is made thinner by forming the discharge plastic 27c.
The disposal of the discharged plastic becomes easier and easier to handle.

Effects As is clear from the above explanation, according to the present invention, the discharged resin is made thinner and can be taken out using a porous capillary, so that post-processing of the discharged resin becomes very easy.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram for explaining an embodiment of the MI test device according to the present invention, and Fig. 2 is a configuration diagram for explaining an embodiment of the MI test device according to the present invention.
FIG. 2 is a configuration diagram for explaining an example of an MI test device. 21...Resin feed pipe, 22...Pump, 2
3... Motor, 24... Heater, 25... Temperature sensing element, 26... Pressure detection section, 27... Porous capillary, 28... Constant temperature chamber.

Claims (1)

[Scope of utility model registration request] A constant temperature bath that maintains the thermoplastic at a constant temperature determined by the type of thermoplastic; a thin tube with a constant cross-sectional area that flows through the plastic kept at a constant temperature in the constant temperature bath; It has a pump that pumps plastic at a constant differential pressure in a predetermined section of the thin tube, and a means for measuring the flow rate of the plastic flowing in the thin tube, and calculates the flow rate of the plastic from the flow rate of the plastic flowing in the thin tube at a constant differential pressure. Melt Index (MI)
In a flow test device for thermoplastic plastics for determining the value, the capillary is composed of the capillary and an enlarged portion integrally provided on the outlet side of the capillary, and the enlarged portion has a cross-sectional area smaller than the cross-sectional area of the capillary. A thermoplastic plastic flow testing device characterized by having a porous section having a plurality of pores.