JPH07137113A - Screw designing method for twin-screw extruder - Google Patents

Abstract

PURPOSE:To provide a screw designing method for a twin-screw extruder capable of designing a proper screw form at every material and product. CONSTITUTION:A preprocessor creates a mesh data by dividing a resin passage in a barrel with a hexahedron cell element three-dimensionally. A heat flow calculating section analyzes a numerical value by various boundary conditions and resin properties based on an actual phenomenon based on the mesh data and disperses it, and analyzes a heat flow for fixing physical quantity histories of temperature, shear rate, and viscosity. A postprocessor displays a trajectory in the area to be analyzed, based on the flow velocity dispersed by the numerical analysis and displays each physical quantity graphically on the mesh data. By using a value to be outputted by the heat flow analysis, any of a resin temperature distribution, a shear rate distribution, and a shearing stress distribution after passage of a melt resin through a full-filling part in an extruder is made to be an index. By using the index, a dimension of a screw is designed.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a screw design method for a twin-screw extruder.

[0002]

2. Description of the Related Art Conventionally, screw performance has been studied by quantifying resin flow and pressure distribution in the screw section of a twin-screw co-direction extruder (ANTEC'90 P.135-138), two-screw co-direction extruder. Three-dimensional analysis of the resin flow path inside the machine to quantify the resin flow in the screw part, operation characteristics and screw shape characteristics (ANTEC'90 P.139-142), screw for twin-screw co-direction extruder Experimental kneading performance of elements (AN
TEC'91 P.149-152) Quantification of resin flow velocity, pressure and shear rate in the resin flow passage in a twin-screw co-direction extruder (ANTEC '
92 P.1311-1316).

Further, the resin flow path in the twin-screw co-direction extruder is set to 3
Three-dimensional numerical analysis based on mesh data divided into three-dimensional microelements (JP-A-3-288620)
JP-A-4-364921), and a method of determining the screw shape that meets the required quality using these analysis results (JP-A-3-288619).

[0004]

Conventionally, there have been the following problems in the screw design method of the twin-screw extruder. That is, since a test is performed with an existing extruder screw for each raw material and product, and the screw shape is determined based on the result, the degree of freedom in design is small and it takes a lot of time to complete the design.

Further, in the simulation of heat flow in the extruder shown in the prior art, the resin behavior in the extruder is simply quantified without considering the temperature, and the simulation output value considering the appearance and physical properties of the final extrusion product is obtained. There is no handling. For this reason, it was not possible to optimize the specific screw shape for each raw material and product.

[0006]

In order to solve the above problems, the present invention provides a screw design method for a twin-screw extruder in which a resin in a barrel is extruded by rotation of the screw. The resin flow path of the resin melting completely filled part of is divided into three-dimensional minute elements by hexahedral cell elements,
Numerical analysis of all three-dimensional components of each equation (continuity equation, kinematic equation, energy equation, constitutive equation) that governs heat flow based on the mesh data by each boundary condition and resin property based on actual phenomenon In the case of discretization, the resin flow path in the extruder is divided into several elements and divided into minute elements, the boundary conditions between each area are transferred, and the analysis is performed within the symmetry area based on the discretized flow velocity. Display the resin trajectory of, the temperature, shear rate, by performing a simulation using the heat flow analysis method of the resin flow path in the extruder by quantifying the history of physical quantities such as viscosity, of the results, Based on the resin flow line every second at the completely melted portion of the resin in the extruder, the streamline is obtained when the particle coordinate value (X _i, Y _i, Z _i ) from the inlet to the outlet is obtained every second. Within the bending angle Θ of the trajectory segment The average value is indexed for all trace lines of the integrated value (ΣΘ) of those with a bending angle within 90 degrees,
The inventors invented a method for designing an optimum screw size using this design index by clarifying the relationship between the index and the appearance and physical properties of the final product.

In the twin-screw extruder according to the present invention, the screw rotation directions may be opposite or the same in each axis.

Further, the resin in the present invention is a thermoplastic resin which exhibits melting and fluidity by heat and energy by shearing, such as polyethylene, polypropylene, polystyrene, polycarbonate, hard vinyl chloride resin, soft vinyl chloride resin, nylon resin, Examples thereof include polyvinyl acetal resin, acrylic resin, acetal resin, polyester resin and the like. A plasticizer, a filler, and the like may be added to these thermoplastic resins. Further, heat, a thermosetting resin that is insolubilized (curing reaction) by energy due to shearing and does not melt even when reheated, such as phenol resin, urea resin, melamine resin, aniline resin, unsaturated polyester resin, diallyl phthalate resin, Epoxy resin, alkyd resin, silicon resin, polyimide resin, polyurethane resin, etc. may be used.

In the numerical analysis of the present invention, the resin flow path data (mesh data) is used to determine the flow field and temperature field under various conditions (screw rotation peripheral speed, wall surface temperature, inflow amount, etc.). It refers to iterative calculation until a convergent solution is obtained, and examples include finite element method, finite difference method, and finite volume method. Further, the completely melted portion of the resin in the extruder of the present invention means that in the resin flow path between the barrel and the screw in the extruder, the resin is in a molten and flowing state, and the proportion of the resin in the resin flow path is 100%. Is the part that is.

[0010]

According to the screw design method according to the present invention, each raw material and product to be extruded are based on the heat flow analysis result data in which the resin history in the completely melted portion of the resin in the extruder is taken into consideration in accordance with the detailed resin behavior in the twin screw extruder. The appropriate screw design can be done on the desk, and the degree of freedom in design is great and it can be done in a very short time. In addition, the design guideline is clear and quantitative, which makes it possible to construct a database for various screws.

[0011]

Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is an overall configuration diagram for executing a heat flow analysis method for a resin flow path in an extruder. This system is a pre-processor (mesh generator) that divides the resin flow path inside the extruder three-dimensionally with hexahedral cell elements and creates mesh data for thermal-hydraulic analysis, the mesh data and actual phenomena. The analysis program that repeatedly calculates the flow field and temperature field using various boundary conditions defined by the above, each physical quantity discretized three-dimensionally by the analysis program on the mesh data, and It consists of a post processor that displays the trajectory of the resin using the flow velocity.

The pre-processor creates mesh data based on the input data defining the main parameters characterizing the inside of the extruder and the number of divisions in each of the three-dimensional directions.

FIG. 2 and Table 1 show the input parameters for the twin-screw counter-rotating extruder. Here, the meaning of each variable in the figures and tables is as follows. That is, first, the resin flow path in the twin-screw extruder is divided into minute elements to form an assembly of hexahedral solid elements. This division is the number of divisions in the flight Z direction (NWO
B), number of divisions in groove Z direction (NWCH), number of divisions in groove X direction (NWCH)
HCH), the number of divisions in the X direction of the barrel part (NHBA), the number of divisions in the circumferential direction of the screw non-meshing part (NNC), the number of divisions in the circumferential direction of the screw meshing part (NC), and the screw inner radius (R
I), screw outer radius (RO), barrel inner radius (RB),
Screw shaft distance (RL), flight pitch (PICH),
This is done by setting the flight top width (A), flight pressure angle (ALF), basic block number (NBBN), and flight number (ISN).

[0014]

[Table 1]

When analyzing the resin flow behavior in a twin-screw extruder, the shape becomes complicated, so the analysis target is divided into three regions to create mesh data, and the boundary conditions are mutually passed between the regions for calculation. Proceed. The three areas are shown in FIG. Here, a and c are non-meshing regions in which the screws do not mesh, and b is a meshing region in which the left and right screws mesh.

Next, the heat flow calculation unit in FIG. 3 will be described. The heat-hydraulic calculation unit is composed of a flow analysis unit and a temperature analysis unit, and iterative calculation is performed by the convergence calculation of both until the whole reaches the stable calculation stage. As the calculation coordinate system, both a rotating coordinate system on a screw rotating in the extruder and a stationary coordinate system can be selected.

The temperature boundary condition sets the wall temperature of the barrel screw flight, which is defined by the actual phenomenon in the screw flight.

The flow boundary condition differs depending on the coordinate system used for calculation, but in the case of analysis in the stationary coordinate system, the peripheral speed defined by the screw rotation speed is set in the screw flight section.

Further, the above-mentioned three regions (a, b,
A convergence calculation is performed for each c). Here, the calculation of the b part is a,
As a boundary condition, the physical quantity of the element adjacent to the b part of the c part
In the calculation of the parts a and c, the physical quantity of the elements adjacent to the parts a and c of the part b is used as a boundary condition, and the convergence calculation is continued until all three regions enter the stable calculation stage. The post processor uses the mesh data and the calculation result of the analysis program to display a distribution map of each physical quantity and a trajectory line based on the flow velocity of each element on the mesh data. At the same time, by switching the analysis control data switch, the convergence status of the convergence calculation and the history of each physical quantity are graphically output.

Next, the trajectory display program will be described. FIG. 5 shows a schematic flow of the trajectory display program.
In this program, first, the mesh data created by the preprocessor and the analysis results by the analysis program are read from each file. Next, the particle position coordinates in the analysis region defined by the input data are detected, and the flow velocity of the particle is interpolated from the flow velocity of the element including this coordinate and the surrounding elements. After that, the particles are moved at the flow velocity, the particle position coordinates after the movement are obtained, and the process of obtaining the flow velocity is repeated, and this process is repeated until the particles reach the coordinate values or time specified by the input data (particle motion analysis unit). ). After that, the trajectory of this particle movement is graphically output on mesh data, and each physical quantity of the particle (temperature, shear rate, shear stress,
Output the history of pressure).

The history of particles in the entire portion of the resin melt completely filled in the twin-screw extruder of this trajectory is quantified for 100 particles at the entrance of the analysis region, and based on the trajectory, from the inlet to the outlet. When the particle coordinate value (X _i, Y _i, Z _i ) of each second is taken, the bending angle Θ of the trajectory segment over the entire streamline is

[Equation 2] Among them, the integrated value (ΣΘ) of bending angles within 90 degrees was averaged for all 100 trajectory lines, and the screw shape was designed and optimized using this value as a design index. Table 2 shows a comparison between the existing screw shape and the new screw shape designed using this design index. Also, after manufacturing this design screw, a product extruded using both screws (thickness 3 mm, width The appearance and physical properties of the 1300 mm sheet) are shown in Tables 3 and 4.

[0022]

[Table 2]

[0023]

[Table 3]

[0024]

[Table 4]

As can be seen from Table 4, the design period of the newly designed screw using this design method is 3 months to 0.5.
It is possible to significantly reduce the number of months, and under any extrusion condition, it is possible to manufacture a product in which the glass fiber is in a good dispersed state and the fiber length preservability is improved, and the bending property is excellent.

In comparison with this, Comparative Examples 1, 2 and 3 shown in Table 3
With No. 4, even if the extrusion conditions are changed with the existing screw, the uniform dispersibility of the glass fiber of the extruded sheet cannot be secured. Compared to the standard conditions of Comparative Example 1, in Comparative Examples 2, 3 and 4, for the purpose of improving the dispersibility of the glass fiber, mold back pressure,
Although the screw rotation speed was changed, the analysis index showing the degree of resin position exchangeability in the completely melted portion of the resin melt in the extruder did not change so much, and the glass fiber dispersibility was not improved even in the extruded sheet. Therefore, the bending property shows a low value.

The apparatus used in Examples and Comparative Examples is as follows.

Extruder used: Conical type twin-screw rotating extruder (screw tip outer diameter 50 mm). Resin used: polypropylene (MI value 3). Additive: glass fiber (content 20wt%, fiber diameter 13
μm, initial fiber length 3 mm). Mold used: Product thickness 3 mm, width 300 mm sheet mold. Extrusion molding conditions: extrusion rate 50 kg / h, barrel temperature 190
° C. Bending strength measurement: test (strength, elastic modulus), test piece shape JI
According to SK7113 Glass fiber length measurement: Quantification by image processing after resin sintering. Glass fiber distribution measurement: Visual inspection of soft X-ray photographs

[0029]

According to the screw designing method for a twin-screw extruder according to the present invention, analysis output data in accordance with the detailed resin behavior can be obtained, and based on the data, it is appropriate for each raw material and product to meet any required quality. The screw shape can be designed on the desk in a short time, and the degree of freedom in design is wide. In addition, the design guidelines are clear and quantitative, and it is possible to construct a database for various screws.

[0030]

[Brief description of drawings]

FIG. 1 is a system configuration diagram for performing a heat flow analysis of a resin flow path in an extruder.

Figure 2: Explanatory diagram of input parameter variables of the preprocessor

[Figure 3] Overall flow chart of the analysis program

FIG. 4 is a sectional view perpendicular to the axis of a biaxial counter-rotating extruder.

[Fig. 5] Overall flow chart of the trajectory display program

Claims (1)

[Claims] 1. A resin flow path of a twin-screw extruder, in which resin in a barrel is extruded by rotation of a screw, is divided into three-dimensional microelements by hexahedral cell elements, and based on mesh data, each equation governing heat flow is calculated. When handling all three-dimensional components and performing numerical analysis based on various boundary conditions based on actual phenomena and resin characteristics for discretization, the resin flow path inside the extruder is divided into minute elements to handle complex shapes. Boundary conditions are passed between each area, analysis is performed based on the discretized flow velocity, and the trajectory of the resin in the symmetrical area is displayed to quantify the history of physical quantities such as temperature, shear rate, and viscosity. By using the value output by the heat flow analysis of the resin flow path in the extruder by converting the resin flow path based on the resin flow line every second at the completely filled portion of the resin melt in the extruder, Particle constellation for each second Values (Xi, Yi, Zi) when a, the bending angle of Nagareato line across streamlines Θ
And, A method of designing a screw for a twin-screw extruder, characterized in that an average value is indexed with respect to all trace lines of an integrated value ΣΘ of a bending angle within 90 degrees, and an optimal screw dimension is designed using the index.