JP5039636B2 - T-die for extrusion molding - Google Patents

Description

  The present invention relates to a T-die for extrusion molding, and in particular, in a flexible lip capable of adjusting the gap between lips provided at the tip of the T-die, the distance between the lips can be adjusted greatly or the durability of the lip The present invention relates to a lip structure that improves performance.

  In general, a resin film is manufactured by melting a resin material by an extruder and continuously extruding it from a film forming die lip provided at a tip portion into a wide thin film. Thickness uniformity is an important product quality of the resin film produced in this way. In order to make the thickness of the resin film uniform, it is necessary to adjust and maintain the slit interval in the width direction of the extrusion die so as to be uniform. For this purpose, a method of adjusting the slit (gap) of the lip utilizing the thermal expansion of the member due to the heating of the electric heater has been put into practical use in the extrusion die (see, for example, Patent Document 1). Is also used.

  Specifically, the T-die for extrusion molding is configured such that the upper part and the lower part are in close contact with each other, and the flow path leading the molten resin material extruded from the extruder to the contact surface of both members and the leading end from the flow path A die lip opening in the lip is formed. The upper end of the die forms a die lip, and the lower end of the die forms a fixed lip. A large number of sets of lip clearance adjusting devices are arranged at the top of the die in the entire width of the lip in the direction perpendicular to the extrusion direction of the extrusion die T. Are arranged in parallel to each other at a predetermined interval.

  A conventional extrusion T-die has a structure shown in FIG. FIG. 19 is a cross-sectional view of the main part in the extrusion direction of the molten resin material of a conventional extrusion T-die. The extrusion molding T-die 1 is configured such that a die upper part 2 and a die lower part 3 are in close contact with each other, and a flow path 1a and a flow path for guiding a molten resin material extruded from an unillustrated extruder to the contact surfaces of both members. A slit 1b that opens from 1a to the tip is formed. The extrusion T-die 1 and the slit 1b are configured to be wide with the direction perpendicular to the paper surface of FIG. 19 as the width direction, and the slit 1b is closed at both ends in the width direction. Further, a lip gap 1c is formed at the tip of the slit 1b on the surface which is the opening of the T die 1.

  A die lip 2a having a movable width direction is formed at the tip of the die upper part 2. In the width direction of the die lip 2a, a plurality of lip gap adjusting devices 10 are arranged in parallel at predetermined intervals. Each rod 11 of the lip gap adjusting device 10 is made of a heat bolt and has a heater 15. Each rod 11 is disposed between the die lip 2a and the protruding portion 2b, and a heat insulating material 4 is provided on the wall of the lateral groove 2c. The die lip 2a can be bent by the thin flexible portion 2d of the die upper portion 2, and thereby the lip gap 1c can be adjusted. The lip gap 1 c is adjusted by the expansion and contraction of the rod 11.

  More specifically, each lip gap adjusting device 10 includes a heat bolt 11, which is a rod, a lip fixing nut 12, a pressing adjusting nut 13, an attraction adjusting nut 14, and a heater 15 provided on the outer periphery of the intermediate portion of the heat bolt 11. And a heater heat insulating material 16 covering the outer periphery of the heater 15. A controller and an external power source (not shown) are connected to the heater 15 by a connection (not shown). The heat bolt 11 has a front end screw portion 11a at the front end portion and a rear end screw portion 11b at the rear end portion, and a lip fixing nut 12 and a pressing adjustment nut 13 are screwed into the front end screw portion 11a and the rear end screw 11b. Yes.

  The rear end threaded portion 11b of the heat bolt 11 is fixed to the protruding portion 2b by the pressing adjusting nut 13 and the pulling adjusting nut 14 while being inserted into the through hole 2g formed in the protruding portion 2b. On the other hand, the tip screw portion 11 a of the heat bolt 11 is screwed into a female screw 2 f formed on the back surface of the die lip 2 a and is fastened and fixed to the die lip 2 a by a lip fixing nut 12. When the pressing adjustment nut 13 and the pulling adjustment nut are tightened and fixed, the clearance of the slit 1b is set to a predetermined value, that is, the heater 15 is energized and heated to a predetermined temperature so that the predetermined clearance is obtained. Fixed by adjusting or attracting.

  The lip gap adjusting device 10 having the rod 11 is not limited to the above-described configuration, and the lip gap 1c can be adjusted by attaching the lip gap adjusting device 10 to the lower die 3 instead of the upper die 2. In the above-described configuration, the rod 11 is connected to the die lip 2a by fastening the screw at the tip of the rod 11 with the nut 12. However, as shown in FIG. It may be in the form.

  That is, the lip gap adjusting device 10 at a position corresponding to a location where the thickness of the resin film exceeds the allowable range controls the heating temperature of the heater 15 to expand and contract the heat bolt 11, so that the heat bolt 11 causes the die lip 2a to be extended. The gap between the slits 1b is adjusted by pushing and pulling, and the thickness of the extruded resin film is adjusted.

  The heat bolt 11 increases in temperature by increasing the amount of electric power to the heater 15 and expands, and decreases by shortening the temperature by decreasing the amount of electric power. In the die lip 2a, only the portion of the controlled lip gap adjusting device 10 is easily bent by the flexible portion 2d, the gap of the slit 1b is changed, and the thickness of the extruded resin film is returned within the allowable range. The heater 15 whose heating state changes during adjustment is prevented from affecting the heating state of the die upper portion 2 by the heater heat insulating material 16 and the heat insulating material 4.

The adjustment of the thickness by the heat bolt 11 is mainly a fine adjustment because the amount of expansion and contraction of the bolt by heat is small. When changing the distance between lips in mm units, for example, changing the material grade, changing the film thickness, or removing resin deposits that stick to the lip surface due to prolonged operation, use a slit. Adjustment is performed by an adjustment nut provided in the gap adjusting device 10. That is, the bolt 11 is moved in the axial direction by turning the adjusting nut to push and pull the lip, and the movable lip is bent to adjust the lip gap. In addition to this method, as shown by the reference numeral 74 in FIG. 21, the lip portion is configured to be removable, and there is also a method of changing the gap between the lips by exchanging with a die lip having a different thickness. is there. In the latter method, production of the film or sheet must be stopped and the die lip must be replaced. In the former case, it is necessary to adjust the overall width by turning the adjustment bolts with the lip gap arranged in the width direction one by one, but there is also a T die that can increase the width of the lip at once over the entire width. It has been developed (see, for example, Patent Document 2).
US Pat. No. 4,753,587 Japanese Patent No. 3229143

  In a flexible lip in which the lip is adjusted by bending the lip, the flexible portion 2d is bent with the base portion of the flexible portion 2d on the T die body (die upper portion 2) side as a fulcrum by pushing and pulling the adjustment bolt. . For this reason, if an attempt is made to obtain a large lip opening / closing degree, a large distortion occurs in the vicinity. That is, the maximum stress is generated in this vicinity. Therefore, the range in which the slit (gap) can be adjusted is limited to a range in which the vicinity of the fulcrum can be elastically deformed, that is, no stress greater than the yield stress is generated. Considering the safety factor of the material, the range becomes even smaller, and a large lip opening / closing degree cannot be obtained.

  Then, an object of this invention is to provide the T die for extrusion molding which can reduce the stress concentrated on a flexible part.

In order to achieve the above object, the T-die for extrusion molding of the present invention comprises a main body part, a lip part forming a lip gap through which molten resin is extruded, and a lip part with respect to the main body part in a direction in which the lip gap is opened and closed. In the T-die for extrusion molding having a flexible part that connects the main body part and the lip part so as to be displaceable , the flexible part has a tapered shape in which the thickness in the direction decreases from the main body part toward the lip part. At least a part of the flexible part has a constant thickness reduction rate, which is a value of a ratio of the thickness reduction amount to the unit length when the unit advances from an arbitrary position toward the lip part by a unit length. It is characterized in that it increases or becomes larger from the main body side toward the lip side .

  In the case of a conventional flexible part shape having a uniform thickness, stress is concentrated on the root part. On the other hand, in the T-die of the present invention, when the same lip opening degree is obtained by forming the flexible portion in a tapered shape, the stress concentration on the flexible portion is reduced. That is, a large lip opening / closing degree can be obtained by forming the flexible portion in a tapered shape. Even when a large lip opening / closing degree is not required, the stress generated when opening / closing the lip is reduced compared to the conventional case, so that it can be used for the purpose of improving the durability or safety of the lip. It is possible to expand the range of selection of materials that can be used, such as replacing the die material with an inexpensive material.

  In addition, the taper shape of the flexible portion of the present invention relates to the thickness reduction rate of the flexible portion,

Surface A: a surface parallel to the resin flow path of the flexible part,
Start position a: position where the flexible part starts,
Point b: a force point at which a force applied to adjust the lip gap acts,
Intersection c: intersection with a perpendicular drawn from point b to plane A,
Straight line bc: a straight line connecting point b and intersection c;
When
L: Distance from the start position a to the intersection point c l: Distance from the intersection point c to the force point b θ: A range with the upper limit of the value calculated by the expression 1 expressed by the angle between the straight line bc and the force application direction What is set by is preferable.

  In this case, almost the same stress can be generated over the entire flexible portion with respect to the moment from the adjusting bolt.

  Further, the lip portion of the T-die of the present invention may have an engagement portion that is detachably engaged with an engagement portion of an applying means that applies force to the lip portion.

  Furthermore, the lip portion of the T die of the present invention may have a contact surface with which the contact portion of the applying means for applying force to the lip portion contacts.

  According to the present invention, it is possible to reduce the stress concentrated on the flexible portion, and thus it is possible to obtain a large lip opening / closing degree or to improve the durability of the lip.

  The present invention is characterized in that the thickness of the flexible portion of the flexible lip is not a flat plate having a uniform thickness, and the thickness of the flexible portion is gradually reduced from the starting position of the flexible portion of the T-die body, that is, a tapered shape. .

  As a result, the stress concentrated on the starting point of the flexible part can be dispersed throughout the flexible part, and a large lip opening / closing degree can be obtained while keeping the stress generated in the flexible part low. Further, even when a large degree of lip opening / closing is not required, since the stress generated in the lip is reduced as compared with the conventional type, the durability (safety) of the lip can be improved. In addition, since a high-strength material is not required, it is possible to expand the range of materials that can be used for the T-die.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 and FIG. 2 are explanatory diagrams showing definitions of dimensions required when determining the taper shape of the T die in which the flexible portion of the present invention is tapered. FIG. 1 shows a case where a force in the opening direction is applied to the lip gap, and FIG. 2 shows a case where a force in the closing direction is applied to the lip gap. In FIG. 1 and FIG. 2, the subscript 1 indicates the time when a force is applied in the lip gap opening direction, and 2 indicates the time when a force is applied in the lip gap closing direction.

  The T-die 150 has a main body part 140, a lip part 130 that forms a lip gap through which molten resin is extruded, and a flexible part 100 that connects the main body part 140 and the lip part 130. It has the adjustment bolt 110 which is an application means which applies force to the part 130, and the engaging part 130a which engages detachably. The adjustment bolt 110 includes an engaging portion 110a that engages with the engaging portion 130a, and an abutting portion 110b that abuts against the abutting surface 130b of the lip portion 130.

  The flexible portion 100 of the T-die 150 of the present invention is characterized in that the shape thereof is a tapered shape that tapers from the main body portion 140 toward the lip portion 130. Details of the shape of the flexible part 100 will be described later.

  Further, the adjusting bolt 110 and the lip portion 130 are not coupled to each other and are detachably engaged with each other at the engaging portion 130a and the engaging portion 110a. When the lip gap is widened by the adjustment bolt 110, the adjustment bolt 110 is pulled in the direction indicated by the arrow B in FIG. Thereby, the engaging part 110a of the adjusting bolt 110 and the engaging part 130a of the lip part 130 are engaged, and a force is applied from the adjusting bolt 110 to the lip part 130 at a point b1 in FIG. On the other hand, when the lip gap is narrowed by the adjustment bolt 110, the adjustment bolt 110 is pushed in the direction indicated by the arrow C in FIG. Thereby, the contact part 110b which is a front-end | tip part of the adjustment bolt 110 contact | abuts to the contact surface 130b of the lip | rip part 130, and force is applied to the lip | rip part 130 from the adjustment bolt 110 at the point b2 in FIG. .

  The taper shape of the flexible part 100 is preferably set so that the thickness reduction rate (Tr) of the flexible part 100 does not exceed the value calculated by the following Equation 1. If the thickness of the flexible part 100 is designed to be close to the value calculated by Equation 1, the stress dispersion effect may not be sufficiently obtained.

  Here, the starting point a of the flexible part 100 is defined as a point b where the force applied to adjust the lip gap between the surface A of the flexible part 100 parallel to the resin flow path 160 of the flexible part 100 and the lip gap is applied. When the intersection point of the perpendicular line drawn from the point b to the surface A is the intersection point c and the straight line connecting the point b and the intersection point c is the straight line bc, L is the distance from the start position a to the intersection point c, and l is the intersection point c is the distance from the force point b, and θ is the angle between the straight line bc and the direction in which the force is applied.

  The thickness reduction rate is calculated in each case of lip opening and closing, and the smaller value is preferably used as a guide for the upper limit. However, the present invention defines the taper shape of the flexible portion 100 and does not define the shape of other portions.

  The thickness reduction rate (Tr) of the flexible part 100 used for defining the taper angle of the taper shape is defined as follows. The thickness reduction rate (Tr) is a distance between the start position a and the position c, where h0 is the thickness of the flexible part 100 at the start position a, and he is the thickness of the virtual flexible part 100 at the intersection c. This is a value indicating what percentage the thickness of the flexible part 100 is reduced with respect to the thickness h0, and can be expressed as follows.

  Next, the operation of the present invention will be described. In the conventional lip having a uniform thickness, the stress is most generated in the flexible portion having a small thickness, that is, a low rigidity due to the pushing and pulling force from the adjustment bolt at the tip of the lip. At this time, the stress generated in the flexible part is distributed, and the largest force is applied to the flexible part starting position on the T die body side that is farthest from the point where the force of the adjusting bolt is applied due to the moment of force. Acts and produces the greatest stress.

  Therefore, by reducing the thickness of the flexible portion as it approaches the lip tip, that is, by forming a taper shape, the stress generated by the moment from the adjusting bolt can be made equal over almost the entire area of the flexible portion. That is, in the conventional lip, the T-die main body side root portion is mainly bent, and distortion is concentrated on this portion, and this distortion mainly contributes to the opening / closing degree of the lip tip. On the other hand, in the tapered lip of the present invention, the flexible portion 100 is distorted little by little in the entire region, thereby contributing to the opening / closing degree of the lip tip. For this reason, when obtaining the same opening / closing degree of the lip tip as the conventional lip structure, the maximum stress generated in the flexible portion 100 is reduced by making the flexible portion 100 an appropriate taper shape as in the present invention. The range of strength that the flexible part 100 can withstand with respect to the degree of opening and closing can be widened.

  However, if the thickness of the taper shape is abruptly changed, the thickness of the end point of the flexible portion 100 becomes too thin and the rigidity becomes low. This portion is mainly distorted and stress concentration occurs. However, the stress dispersion effect cannot be obtained. Further, when the force application angle increases, the force in the in-plane direction parallel to the flexible part 100 increases, and this generates a substantially equal moment on the entire flexible part 100. Since this force is applied equally in the whole flexible part 100, the thickness of the flexible part 100 which balances with this force is the same over the whole flexible part 100, and there is no effect of the stress dispersion | distribution by a taper shape. As the force application angle increases, the force of the moment generated by this force becomes stronger. Therefore, if there is no thickness of the flexible part 100 corresponding to this, the portion having weak rigidity against the force, that is, the thinnest flexible part. The vicinity of the end point of 100 is concentrated, and distortion and stress are concentrated. The taper shape must be designed in consideration of such a force application angle, and the thickness reduction rate (Tr) is set with the upper limit around the value calculated by Equation 1 described above as a guide for the taper shape. It is preferable.

  As described above, according to the present invention, since the flexible portion of the T die 150 has a tapered shape, almost the same stress is generated over almost the entire flexible portion 100 with respect to the moment from the adjusting bolt 110. Therefore, in the case of the present invention, in the case of the conventional flexible portion shape having a uniform thickness, the stress generated in the flexible portion when the same lip opening / closing degree is obtained is reduced as compared with the case where the stress is concentrated on the root portion. That is, a large lip opening / closing degree can be obtained by forming the flexible portion 100 in a tapered shape. Even when a large lip opening / closing degree is not required, the stress generated when opening / closing the lip is reduced compared to the conventional case, so that it can be used for the purpose of improving the durability or safety of the lip. For example, the material of the die 150 can be replaced with an inexpensive material or the like.

  Hereinafter, derivation of Equation 1 will be described as a supplementary explanation of Equation 1. This equation 1 is derived by applying the problem of a cantilever having a rectangular cross section that receives a concentrated load at the so-called free end, which is taken up in material mechanics, to the tip of the T die. The maximum value of the bending stress caused by the bending moment of an arbitrary cross section can be expressed as follows, assuming that the tensile strength and compressive strength of the material are the same.

Where σ is the maximum stress in the cross section at a distance x from the fixed end of the cantilever beam, P is the load, L is the distance from the free end to the point where the load is applied, b is the beam width, and h is the beam thickness. , M (x) is the moment load, Z is shows a section modulus becomes bh ^{2/6-rectangular} cross-section (see FIG. 3). If the shape is such that the value of σ obtained from Equation 3 is the same at any x position, that is, at any cross-section of the beam, the stress concentration does not occur and the beam generates the same stress throughout the beam, so-called equal strength Become a beam.

  If x = 0, that is, if the thickness of the fixed end is h0 and the width is b, the maximum value of the bending stress generated at the fixed end is as follows from (Equation 3).

  Assuming that σ0 is equal to the value of stress in the cross section x, that is, substituting σ in Equation 3 for the right side of Equation 4, Equation 5 is derived.

  As described above, in a beam that receives a load at a distance L from the fixed end, the beam having the same stress over the entire area of the beam has a thickness x0 of the fixed end regardless of the load. It is determined by the distance L from the fixed end until the load is applied. When h and x are expressed as percentages when h0 and L are 100%, respectively, in this equation, the ideal shape of a beam with uniform strength is shown in FIG.

  As described above, an ideal uniform strength shape is calculated, but this equation cannot be applied to the lip of the T die as it is. Since the lip portion of the T die is a process of extruding resin from the lip tip and winding it with a roll, the tip of the T die is tapered as shown in FIG. In many cases, the structure is set parallel to this. For this reason, the load for opening and closing the lip is applied in a direction shifted from the direction perpendicular to the beam (flexible portion), and the position where this load is applied is a place away from the line of the beam. . Similar to FIG. 3, FIG. 5 shows a simplified model for considering how a load is applied to the T-die. When the load applied in the direction inclined by the angle θ is decomposed into a direction parallel to the beam and a direction perpendicular to the beam, the horizontal force Psinθ is applied to the position c where the beam is branched. The moment by is generated. It is considered that when a moment load is generated at the tip of the cantilever, a moment load Psinθ × l is generated uniformly over the entire flexible portion. Further, the load Pcos θ in the direction perpendicular to the beam is considered to be almost the same as in the case of FIG. 3, and the moment load is expressed as P cos θ × (L−x) and is considered to change depending on the distance from the fixed end. . Therefore, in reality, the above two types of moment loads are applied to the flexible part, and the moment load M (x) applied to the cross section x away from the fixed end is expressed by the following equation, The image is as shown in FIG.

  Substituting M (x) of this equation into Equation 3 and solving the equation assuming that x = 0, that is, the stress at the fixed end and the cross section of the flexible part are the same as when Equation 5 is derived, It becomes like this.

  σ (x) and σ0 are expressed as follows:

If these are equal,

Thus, the shape of an ideal beam that becomes a beam of uniform strength changes depending on the angle at which the load is applied and the position where the load acts. FIG. 7 shows an ideal beam thickness when θ = 20 °, L = 100, and l = 80. In Equation 7, when θ = 0, that is, when the load is applied perpendicular to the beam, Equation 7 is the same as Equation 5.

  In the present invention, the upper limit of the taper inclination is defined using Equation 7. Specifically, using the value x = L in Expression 7, that is, the virtual thickness value he at the position c where the load is applied, the point c obtained from Expression 7 from the fixed end thickness h0 is obtained. If the value when x = L in Equation 7 is substituted into Equation 2 is defined as follows:

The taper shape calculated by this equation has a change in thickness as shown in FIGS. 8 and 9 when θ = 0 and 20 °, respectively. In FIG. 8, the obtained shape deviates greatly from the ideal thickness represented by Equation 7, and becomes a shape thinner than the ideal shape. For this reason, since the rigidity of the load application position becomes weak and bending concentrates, it is not preferable to set this value as the upper limit of the tapered shape. Therefore, in order to correct these, an example will be shown later. The relationship between the stress generated per unit lip opening and the thickness reduction rate as shown in FIG. 10 using the finite element method based on the shape of FIG. The thickness reduction rate at which the stress was in the vicinity of the minimum value was obtained and the load application angle was plotted as shown in FIG. This plot was compared with the curve of Formula 8, and the values in Formula 8 were changed and fitted so that the plot and Formula 8 were close to each other, and Formula 1 was calculated.
(Example)
An embodiment of the present invention will be described below with reference to FIG. 11, and an example in which the shape of the lip portion of the conventional lip gap adjusting device of FIG. Although the adjustment mechanism using an adjustment bolt or the like is not limited to the use of the present invention, the adjustment mechanism shown in FIG. 19 will be described as an example.

  The shape of the flexible part 100 in FIG. 11 is such that the taper-shaped thickness reduction rate is 50%, the length of the flexible part is 35 mm, the distance from the tip of the lip to the base of the T die of the flexible part 100 is 69 mm, The thickness h0 at the start position is 6 mm, and each base has a radius of curvature R of 2 mm. A plurality of adjustment bolts 110 are provided in the T-die width direction, and a notch 111 as shown in FIG. 11 is provided at the tip of the adjustment bolt 110, and this notch 111 is a hook 120 at the tip of the lip. The force in the lip opening direction of the adjusting bolt 110 is transmitted through this portion. Further, the distances L and l to the location where the force defined in FIG. 1 is applied are 42 mm and 34.2 mm, respectively, and the installation direction θ of the bolt is 20 °. The force in the lip pushing direction of the adjustment bolt 110 is transmitted as the tip of the adjustment bolt 110 comes into contact with the lip portion 130.

  In this way, by forming the flexible portion 100 in a tapered shape, the lip has a substantially uniform strength against the force (moment) generated by the pushing and pulling force from the adjustment bolt 110, and the entire flexible portion 100 is evenly distributed. Bending and uniform stress occurs. That is, since the stress generated with respect to the lip opening / closing degree is reduced, the lip opening / closing degree can be set larger than that of the conventional shape even if the same material is used.

  The following shows the results of stress analysis using a finite element method for a T-die with a flexible portion having a tapered shape and a conventional shape. FIG. 12 shows an overall view of the model used for the analysis. As the model, a model in which a width corresponding to one interval of adjustment bolts installed in the width direction of the T die was cut out was used. The analysis was performed using COSMOSWORKS 2007 of Solidworks. The material constant used for the analysis was Young's modulus 210 GPa and Poisson's ratio 0.28. The load was set assuming that the force from the adjusting bolt acts on the lines on the points b1 and b2 in FIGS. Since the upper surface of the T die body and the lower portion of the die are joined with bolts and the surfaces are in close contact with each other, this surface is defined as a complete constraint, and the cut surface is defined as a symmetrical surface.

  FIG. 13 shows the conventional shape, and FIGS. 14 and 15 show the analysis results when the lip is opened with respect to the taper shapes having different thickness reduction rates of 50% and 75%, respectively. FIG. 16 shows the result of analysis by applying a force in the lip closing direction when the taper-shaped thickness reduction rate is 50%. In the analysis of FIGS. 13, 14 and 15, the load is applied on the line in the width direction passing through the point b1 in FIG. 1, and in the analysis of FIG. 16, the load is applied on the line in the width direction passing through the point b2 in FIG. . The load was 2000 N. In this case, since the installation angle of the adjusting bolt 110 was 20 °, the load was set along this direction.

  In the conventional shape of FIG. 13, the highest stress is generated at the T die side root portion of the flexible portion, whereas in the taper shape in which the thickness reduction rate is set to 50% in FIG. It can be seen that stress is generated and the stress is not concentrated but dispersed.

  On the other hand, in the taper shape in which the thickness reduction rate in FIG. 15 is 75%, that is, the taper inclination is set large, the stress is concentrated near the end of the flexible portion, and even if the taper shape thickness reduction rate is increased, a sufficient effect is obtained. It turns out that it cannot be obtained. When the upper limit of the thickness reduction rate in the shape used for the analysis is calculated by the formula for calculating the upper limit of the taper shape thickness reduction rate defined in the present invention, it is 63%, and the thickness reduction rate is 75% in the model of FIG. Therefore, it can be seen that the upper limit is exceeded. FIG. 16 shows a case where a force is applied to the model of FIG. 14 in the lip closing direction. In this case as well, it can be seen that the stress is dispersed throughout the flexible portion.

  FIG. 17 shows a graph in which the maximum stress generated in the flexible portion 100 is plotted with respect to the lip opening (the amount of displacement of the lip tip in the direction shown in the drawing). From the graph, it can be seen that, when the opening degree of the same lip tip is obtained, the maximum stress generated in the flexible part 100 is lower than that of the conventional shape by using the tapered shape.

  FIG. 18 shows a graph plotting the stress of the flexible portion generated when a 1 mm lip opening is obtained with respect to the taper thickness reduction rate. From the graph, it can be seen that when the taper shape is applied by increasing the thickness reduction rate from the conventional shape, that is, the thickness reduction rate of 0%, the stress of the flexible portion is reduced. However, as the thickness reduction rate increases, the reduction effect reaches its peak. This is because stress concentration occurs in the vicinity because the thickness near the end point of the flexible portion is thin as shown in FIG. The thickness reduction rate at which the stress reduction effect reaches its peak changes in relation to the load application angle θ and the distance between the flexible part starting point and the load application point. An effective upper limit of the taper-shaped thickness reduction rate with respect to this shape change can be calculated by the formula defined in the present invention.

It is explanatory drawing which shows the definition of the dimension required when determining the taper shape of T die which made the flexible part of this invention the taper shape (at the time of the force application of a lip clearance opening direction). It is explanatory drawing which shows the definition of the dimension required when determining the taper shape of T-die which made the flexible part of this invention the taper shape (at the time of the force application of a lip gap obstruction | occlusion direction). It is a model figure of the cantilever of the rectangular cross section which receives the concentrated load in a free end. It is a graph which shows the ideal thickness shape when it becomes a cantilever of equal strength which receives concentrated load in a free end. It is the model figure which simplified the front-end | tip part of T-die. It is the figure which showed the outline of the change by the cross-sectional position of the moment load concerning the flexible part of T-die. It is a graph which shows the ideal thickness shape when it becomes a cantilever of equal strength when a load application angle and a load application position are considered. It is a graph which shows the comparison with the thickness shape when it becomes a beam of theoretically uniform strength when (theta) = 0 and the thickness shape calculated by Formula 7. It is a graph which shows the comparison with the thickness shape when it becomes a beam of theoretically equal strength when the thickness shape calculated by Formula 7 when θ = 20 °. It is a graph which shows the comparison with the type | formula derived | led-out from the FEM calculation result of the relationship of the allowable thickness reduction | decrease rate with respect to a load application angle, the model, and the correction | amendment. It is a side view of the die | dye of the one side which shows one Example of T-die which made the flexible part of this invention the taper shape. It is a figure which shows the whole simplified model for using T-die of this invention for intensity | strength analysis. It is a figure which shows the result of having calculated the stress dispersion | distribution of the flexible part when a load is applied with respect to the T-die whose shape of a flexible lip is flat shape in the figure in the lip gap opening direction (θ = 20 °). Stress distribution in the flexible part when a load is applied in the direction of the opening of the lip gap indicated by the arrow (θ = 20 °) to the T-die having the flexible part of the present invention having a tapered shape (thickness reduction rate of about 49%). It is a figure which shows the result of having calculated. Stress distribution in the flexible part when a load is applied in the direction of the opening of the lip gap (θ = 20 °) indicated by an arrow in the figure with respect to the T die having the flexible part of the present invention having a tapered shape (thickness reduction rate of about 74%). It is a figure which shows the result of having calculated. Stress distribution of the flexible part when a load is applied in the lip gap closing direction (θ = 20 °) indicated by an arrow in the figure with respect to the T die having the flexible part of the present invention having a tapered shape (thickness reduction rate of about 49%). It is a figure which shows the result of having calculated. The relationship between the lip tip displacement (lip opening) and the maximum stress of the flexible part generated at this time. The figure is a graph comparing differences in the taper-shaped thickness reduction rate of the flexible part. It is the graph which showed the relationship between the maximum stress of the flexible part which arises per unit lip opening degree, and the thickness reduction rate of a flexible part taper shape. It is explanatory drawing which shows the slit adjustment mechanism of an example of T-die using the conventional flexible lip. It is a figure which shows the example of a lip | rip and an adjustment bolt connection mode. It is explanatory drawing which shows an example of the conventional lip exchange type T die.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Flexible part 110 Adjustment bolt 110a, 130a Engagement part 110b Contact part 130 Lip part 130b Contact surface 140 Main body part 150 T die 160 Resin flow path a Starting position of flexible part b Force applied in order to adjust lip gap C The intersection of the plane A parallel to the resin flow path of the flexible section and the perpendicular drawn from the point b to the plane A h0 The thickness of the flexible section at the start position a he of the virtually considered flexible section at the position c Thickness L Distance from start position a of flexible part to intersection c l Distance from intersection c to force point b θ Angle formed by straight line bc and force application direction

Claims (4)

A main body (140);
A lip portion (130) that forms a lip gap through which the molten resin is extruded;
For extrusion molding, comprising: a flexible portion (100) connecting the body portion (140) and the lip portion (130) so that the lip portion can be displaced relative to the body portion in a direction in which the lip gap is opened and closed . In the T-die,
The flexible part (100) has a tapered shape in which the thickness in the direction decreases as it goes from the main body part (140) to the lip part (130),
At least a part of the flexible part (100) is a thickness reduction rate which is a value of a ratio of the thickness reduction amount to the unit length when proceeding by a unit length from an arbitrary position toward the lip part. T-die for extrusion molding, characterized in that is constant or increases from the main body part (140) side toward the lip part (130) side. The taper shape of the flexible part (100) is related to the thickness reduction rate of the flexible part (100).

Surface A: a surface parallel to the resin flow path of the flexible part (100),
Start position a: position where the flexible part (100) starts,
Point b: a force point at which a force applied to adjust the lip gap acts,
Intersection c: Intersection c with an intersection with a perpendicular drawn from the point b to the surface A,
Straight line bc: A straight line connecting the point b and the intersection c is a straight line bc
When
L: distance from the start position a to the intersection point c l: distance from the intersection point c to the force point b θ: a value calculated by an expression 1 expressed by an angle between the straight line bc and the force application direction The T-die for extrusion molding according to claim 1, which is set in a range of   The said lip | rip part (130) has an engaging part (130a) detachably engaged with the engaging part (110a) of the application means (110) which applies a force to the said lip | rip part (130). Or T-die for extrusion molding according to 2.   The said lip | rip part (130) has any contact surface (130b) with which the contact part (110b) of the application means (110) which applies force to the said lip | rip part (130) contact | abuts. A T-die for extrusion molding according to item 1.

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