JPH06293053A - Screw planning method in twin-screw extruder - Google Patents

Abstract

PURPOSE:To design a proper screw shape at every raw material and product for a twin-screw extruder. CONSTITUTION:A pre-processor 11 divides the resin passage in a barrel by a hexahedral cell element three-dimensionally to form mesh data. A heat flow calculation part 12 performs not only numerical value analysis according to various boundary conditions and resin characteristics based on an actual phenomenon on the basis of the mesh data to perform separation but also heat flow analysis quantifying physical quantity history such as temp., a shearing speed or viscosity. A post-processor 13 displays the flow mark line in an area to be analyzed on the basis of the flow velocity separated by the numerical value analysis and draws respective physical quantities on the mesh data. By this heat flow analysis, the average number of times of the passage of a resin through a screw flight meshing part is indexed in the resin melting perfect filling part in an extruder and this index is used to plan a screw dimension.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. 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, a method of quantifying resin flow and pressure distribution in a screw portion of a twin-screw co-extruder (ANTEC'90) has been used to examine screw performance of a twin-screw extruder.
(P.135-138) Quantifying resin flow, operation characteristics and screw shape characteristics in the screw part by performing a three-dimensional analysis of the resin flow path in the twin-screw co-direction extruder (ANTEC'90
(P.139-142) Experimental results of kneading performance of screw element of twin-screw co-direction extruder (ANTEC'91 P.149-1
52) Quantification of the resin flow velocity, pressure, and shear rate in the resin flow path inside the twin-screw co-direction extruder (ANTEC'92 P.1311-131)
6) etc.

Further, as proposed by the inventor of the present invention, a three-dimensional numerical analysis is performed based on mesh data obtained by dividing a resin flow path in an extruder into three-dimensional minute elements (Japanese Patent Laid-Open No. 3-288620). JP-A-4-364921
Japanese Patent Laid-Open No. 3-28) and a method of determining a screw shape that meets the required quality by using these analysis results (JP-A-3-28).
8619).

[0004]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
In each of the above technologies published in EC, a test is performed for each raw material and product using the screw of the existing extruder, and the screw shape is determined based on the result, so there is little freedom in design, and It took a lot of time to complete the design.

Further, even in the one proposed by the present inventor, only the resin behavior in the extruder is quantified in the simulation for the heat flow in the extruder,
In addition, since the temperature is not taken into consideration, the simulation does not take into consideration the appearance and physical properties of the final extruded product.Therefore, there is a problem in the optimization of the specific screw shape for each raw material and product. Was left.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a screw design method for a twin-screw extruder capable of designing an appropriate screw shape for each raw material and product.

[0007]

In order to solve the above-mentioned problems, the screw design method in the twin-screw extruder of the present invention is such that a screw is provided in the barrel, and the rotation of the screw causes the resin in the barrel to be kneaded and melted. In a twin-screw extruder formed so as to be extruded, each equation governing heat flow is based on mesh data obtained by spatially dividing the resin flow path in the barrel into three-dimensional minute elements by hexahedral cell elements. All three-dimensionally, the resin flow path in the barrel is divided into a plurality of regions when performing numerical analysis and discretization based on various boundary conditions and resin characteristics based on actual phenomena. Each area is divided into minute elements, the boundary conditions are passed between each area, and numerical analysis is performed, and the analysis target is based on the velocity discretized by this numerical analysis. Using the values output by the thermal-hydraulic analysis method that quantifies the physical quantity history of temperature, shear rate, viscosity, etc. by displaying the trace line in the region, the resin is screw-flighted in the completely melted part of the resin in the extruder. The number of passes on average in the meshing portion is indexed, and the index is used to design the optimum screw size.

The twin-screw extruder in the present invention includes both those in which the rotation directions of the screws are opposite in each axis and those in which they are the same. Further, the resin in the present invention is a thermoplastic resin that melts by heat and energy by shearing, develops fluidity, and a thermosetting property that is insolubilized (curing reaction) by heat and energy by shearing and does not melt even when reheated. Resins may be mentioned. Examples of the thermoplastic resin include polyethylene, polypropylene, polystyrene, polycarbonate, hard vinyl chloride resin, soft vinyl chloride resin,
Examples thereof include nylon resin, 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.

Examples of the thermosetting resin include phenol resin, urea resin, melamine resin, aniline resin, unsaturated polyester resin, diallyl phthalate resin, epoxy resin, alkyd resin, silicon resin, polyimide resin, polyurethane resin and the like. Is mentioned.

In the present invention, the numerical analysis means that the flow field and the temperature field are finally determined by using the resin flow path data (mesh data) based on various conditions (screw rotation peripheral speed, wall surface temperature, inflow amount, etc.). It means to repeatedly calculate until a convergent solution is obtained, and examples thereof include a finite element method, a finite difference method, and a finite volume method. In the present invention, the completely melted portion of the resin in the extruder refers to a portion in the resin flow path between the barrel and the screw in the extruder in which the resin occupies 100% in the molten and molten state of the resin.

[0011]

[Effect] Based on the mesh data obtained by spatially dividing the resin flow path in the barrel by hexahedral cell elements into three-dimensional minute elements, each equation governing heat flow (continuous equation, kinetic equation, energy equation, composition) All equations are handled in three dimensions, and numerical analysis is performed based on various boundary conditions (screw rotation peripheral speed, wall temperature, inflow amount, etc.) and resin characteristics (flow characteristics, thermal characteristics, mechanical characteristics, etc.) based on actual phenomena. To discretize. At that time, the resin flow path in the barrel is divided into a plurality of regions, each region is divided into minute elements, and the boundary conditions are mutually passed between the regions to perform a numerical analysis. Then, based on the flow velocity discretized by this numerical analysis, the trajectory in the analysis target area is displayed, and the temperature,
Perform thermal-hydraulic analysis to quantify physical quantity history such as shear rate and viscosity.

Then, by using the value output by this thermal-hydraulic analysis method, in the completely melted portion of the resin in the extruder,
The average number of times the resin passes through the screw flight meshing part is indexed, and the index is used to design the optimum screw size.

That is, it is possible to design an appropriate screw for each raw material and product to be extruded, based on the result of thermal-hydraulic analysis taking into account the resin history in the completely melted portion of the resin in the extruder, which conforms to the detailed resin behavior in the twin screw extruder. Becomes

Therefore, the degree of freedom in design is widened, and the screw can be designed in an extremely short time. Also, since the design guidelines are clear and quantitative, it is possible to build a database for various screws.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a system configuration for executing the method for analyzing heat flow in the resin flow path in the extruder.

This system comprises a preprocessor (mesh generator) 11 for three-dimensionally dividing the resin flow path in the extruder by hexahedral cell elements to create mesh data for thermal-hydraulic analysis, the created mesh data and the actual mesh data. The three-dimensional discretization was performed by the thermal-hydraulic calculation unit 12 having an analysis program for repeatedly calculating the flow field and the temperature field using various boundary conditions defined by the phenomenon of It is constituted by a post processor 13 which plots each physical quantity on mesh data and displays the resin trajectory by using the flow velocity of each element.

The preprocessor 11 creates mesh data based on the input data defining the main parameters that characterize the resin flow path in the extruder and the number of divisions in each of the three-dimensional directions. The created mesh data is output as mesh information and accumulated in a mesh data file.

2 to 4 show input parameters for the twin-screw counter-rotating extruder. Here, in FIG.
The variables shown in the table of FIG. 4 are 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 includes flight Z direction division number (NWOB), groove section Z direction division number (NWCH), groove section X direction division number (NHCH), barrel section X direction division number (NHBA), basic block number (NBB).
N), screw non-meshing part circumferential division (NNC), screw meshing part circumferential division (NC), flight number (ISN)
), Screw inner radius (RI), screw outer radius (R
O), barrel inner radius (RB), screw shaft distance (R
L), flight pitch (PICH), flight top width (A),
This is done by setting the pressure angle (ALF).

When the resin flow behavior in the twin-screw extruder is analyzed, the shape becomes complicated. Therefore, 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. In the figure, a and c are regions where the screws do not mesh, and b is a region where the left and right screws mesh.

FIG. 5 shows an example of a mesh diagram when a mesh is generated using the numerical values in the table shown in FIG. However, this mesh diagram is a simplified representation in which the number of divisions of cell elements is reduced so that the configuration can be easily understood, but in actuality, it is divided into cell elements smaller than this.

Next, the operation of the heat flow calculation section 12 will be described with reference to the overall flow chart of the analysis program shown in FIGS. 7 and 8.

First, a constant is set and control data is read (steps S1 and S2). After that, these data are written to the output file (step S3).

Next, it is judged whether or not the mesh data is read, and if it is read, the mesh data is stored in a storage medium such as a magnetic disk (steps S4 and S5). If it is not read, mesh data is generated as it is (steps S4 and S6).

After this, it is judged whether or not there is an error in the mesh data generated or stored in the storage medium. If there is a data error, the error list is written to the output file and the operation is finished (steps S7, S8). ).
If there is no data error, it is determined whether or not the restart calculation is performed (steps S7, S).
9). Then, when restart calculation is performed, the restart file is read (step S10), and when restart calculation is not performed, initial values such as flow velocity, temperature, and pressure are set, and cell volume is calculated (steps S11 and S12). .

Next, it is judged whether or not the calculation of each block is continued, and if the calculation is continued, the data is read into the combining section (steps S13 and S14). If it is not continued, step S14 is skipped and the heat flow calculation described later is performed (step S15). Then, the result of this heat flow calculation is output and the data of the joint portion is output (steps S16 and S17). After that, information such as CPU time, normality, abnormality, and end is output (step S1
8) The process is completed.

Next, the process in step S15, that is, the process for calculating heat flow will be described.

The heat-and-fluid calculation is performed by the flow analysis unit and the temperature analysis unit of the heat-and-fluid calculation unit 12, and the convergence calculation of both analysis units is repeated until the whole enters the stable calculation stage.

As the calculation coordinates, both a rotating coordinate system on a screw rotating in the extruder and a stationary coordinate system can be selected. In addition, 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 stationary coordinates,
The peripheral speed defined by the screw rotation speed is set in the screw flight portion of FIG. Then, the convergence calculation is performed for each of the three regions a, b, and c shown in FIG. Where b
The calculation of the area is performed with the physical quantity of the elements adjacent to the areas b of the areas a and c as the boundary condition, and the calculation of the areas a and c is performed with the boundary of the physical quantities of the elements adjacent to the areas a and c of the area b. As a condition, the convergence calculation is continued until all three regions a, b, c enter the stable calculation stage.

The post-processor 13 uses the mesh data and the calculation result of the analysis program to display the distribution map of each physical quantity and the trace line based on the flow velocity of each element on the mesh diagram. At the same time, by switching the switch of the analysis control data, the convergence status of the convergence calculation and the history of each physical quantity are graphically output.

FIGS. 11 to 13 show the graphical output of the heat flow analysis results of the flow velocity and temperature in the twin-screw counter-rotating extruder.
However, in FIG. 11, the flow velocity vector is originally plotted on the mesh diagram shown in FIG. 5, but here it is a simplified representation by plotting the flow velocity vector on the external view. Further, the flow velocity vector diagram shown in FIG. 12 and the temperature distribution diagram shown in FIG. 13 are also simplified expressions for easy understanding.

Next, the trajectory display program will be described.

FIG. 9 shows a schematic flow chart of the trajectory display program.

In this program, first, the mesh data created by the preprocessor 11 and the analysis result by the analysis program of the thermal-hydraulic calculation unit 12 are read from each file (steps S21 to S27). Next, it is determined whether or not particle analysis is to be performed (step S28), and if it is to be performed, particle movement analysis processing is performed (step S29).

That is, the particle position coordinates within the analysis area defined by the input data are detected, and the particle flow velocity is interpolated from the element including this particle position coordinate and the flow velocity of the surrounding elements. . After that, the particles are moved at the flow velocity, the particle position coordinates after the movement are obtained, and the flow velocity is obtained repeatedly, and the process is repeated until the particles reach the coordinate values or the calculation time defined by the input data (step S29). ). After that, the trajectory of this particle movement is output as a diagram on the mesh data, and each physical quantity (temperature, shear rate,
The history of pressure etc. is graphically output (steps S30, S3).
1). In addition, the result of the streamline motion analysis is output (step S32), and then information such as CPU time, normality, abnormality, and end is output (step S33), and the process is completed.

FIG. 10 shows an example of the trace line display in the twin-screw counter-rotating extruder.

The particle history of the entire trajectory of the resin melt completely filled in the twin-screw extruder was quantified for 100 particles at the entrance of the analysis area, and the screw flight meshing portion of each particle was based on the trajectory. Average the number of passes.

Table 1 shows a comparison between the existing screw shape and the screw shape designed using the average number of passages at the meshing portion as an index. Table 2 shows the appearance and physical properties of a product (sheet having a thickness of 3 mm and a width of 1300 mm) produced by using this design screw.

[0041]

[Table 1]

[0042]

[Table 2]

The METERING portion, which is the comparison point shown in the ZONE section of Table 1, is the tip end portion of the screw shape shown in FIG. 14 (described as METERING in the drawing). Also, NUMBER OF FLIGHT and LEAD
The flight pitch PI is calculated from the following equation.

[0044]

[Equation 1] PI = LEAD / NUMBER OF FLIGHT Further, as shown in FIG. 6, ROLL CLEARANCE is a gap between the outer peripheral surface of one screw shaft and the outer peripheral end of the other screw, and MINIMUM FLIGHT CLEARANCE Means that in the region b in which the left and right screws engage with each other,
It is the gap where both flights are closest to each other.

The devices used in the examples and comparative examples shown in Table 2 are as follows.

Extruder used: twin-axis different direction conical type extruder (extruder tip shaft distance between shafts: 6 mm, extruder tip screw outer diameter: 80 mm, outer diameter conical angle: 1.2 °, inter-shaft conical angle: 1. 0 °), Resin used: Hard PVC (Tokuyama Sekisui,
Product name TS800E), mold used: product thickness 3 mm, width 1
Mold for 300 mm sheet, extrusion molding condition: extrusion amount 500
Kg / h, barrel temperature 180 ° C, sheet surface appearance evaluation: visual inspection, impact strength measurement: in accordance with JIS K7110.

As can be seen from Table 2, the design period of the newly designed screw using this design method is from 3 months to 0.
The product can be significantly shortened to 5 months, and a product having good physical properties and appearance can be produced.

Comparing this with Comparative Examples 1 and 2, in Comparative Examples 1 and 2, the mold back pressure and the screw rotation speed were increased to improve the appearance of the sheet.
Although the desired appearance was improved, on the other hand, Comparative Example 2
Indicates that the motor load rating (100%) has been exceeded and the impact value has decreased.

[0049]

According to the screw design method of the twin screw extruder of the present invention, the heat flow is controlled based on the mesh data obtained by spatially dividing the resin flow path in the barrel by hexahedral cell elements into three-dimensional minute elements. All the equations to be handled are handled in three dimensions, and when the numerical analysis is performed by various boundary conditions and resin characteristics based on the actual phenomenon to discretize, the resin flow path in the barrel is divided into a plurality of regions, Each area is divided into minute elements, and the boundary conditions are mutually passed between the areas to perform numerical analysis. Then, based on the flow velocity discretized by this numerical analysis, the trajectory in the analysis target area is displayed, and the value output by the thermal-hydraulic analysis method that quantifies the physical quantity history such as temperature, shear rate, and viscosity is displayed. By using the index to indicate how many times the resin passes through the screw flight meshing part on average in the completely melted part of the resin in the extruder, and using the index to design the optimum screw size, An appropriate screw design for each raw material and product to be extruded becomes possible based on the result of thermal-hydraulic analysis that takes into account the resin history in the completely melted portion of the resin in the extruder in accordance with the detailed resin behavior in the axial extruder. Therefore, the degree of freedom in design is widened and the screw can be designed in an extremely short time. Also, since the design guidelines are clear and quantitative, it is possible to build a database for various screws.

[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.

FIG. 2 is an explanatory diagram of input parameter variables of a preprocessor.

FIG. 3 is an explanatory diagram of input parameter variables of a preprocessor.

FIG. 4 is a table showing input parameter variables for a biaxial counter-rotating extruder.

FIG. 5 is a diagrammatic output diagram of mesh data of a twin-axis different-direction rotary extruder generated by a preprocessor.

FIG. 6 is a sectional view perpendicular to the axis of the twin-screw extruder.

FIG. 7 is an overall flow chart of the analysis program.

FIG. 8 is an overall flow chart of the analysis program.

FIG. 9 is a schematic flowchart of a trajectory display program.

FIG. 10 is a diagram showing a trace line display example in a twin-axis different-direction rotary extruder.

FIG. 11 is a perspective output diagram of a flow velocity vector as an analysis result by an analysis program.

FIG. 12 is a cross-sectional view perpendicular to an axis showing a flow velocity vector as an analysis result by an analysis program.

FIG. 13 is a cross-sectional view perpendicular to the axis showing the temperature distribution of the analysis result by the analysis program.

FIG. 14 is a diagram showing an example of a screw shape for comparison between old and new.

[Explanation of symbols]

 11 Pre-processor 12 Thermal-hydraulic calculation part 13 Post-processor

Claims (1)

[Claims] 1. A twin-screw extruder in which a screw is provided in a barrel, and the resin in the barrel is kneaded and melted and extruded by the rotation of the screw, wherein a resin flow path in the barrel is hexahedral. Spatial 3 with cell elements
When all equations governing heat flow are handled in three dimensions based on mesh data divided into three-dimensional minute elements, and numerical analysis is performed by various boundary conditions and resin characteristics based on actual phenomena In addition, the resin flow path in the barrel is divided into a plurality of areas, each area is divided into minute elements, and the boundary conditions are mutually passed between the areas to perform a numerical analysis. The trajectory in the analysis target area is displayed based on the converted flow velocity, and the resin in the extruder is used by using the value output by the heat flow analysis method that quantifies the physical quantity history of temperature, shear rate, viscosity, etc. In a twin-screw extruder characterized by indexing how many times the resin passes through the screw flight meshing part on average in the melt-completely filled part and using the index to design the optimum screw size. Screw design method.