Apparatus and method for adjusting the lip gap of a sheet molding die.

Abstract

To provide a lip gap adjustment device that can timely adjust film thickness distribution and has a short reaction time.SOLUTION: The present invention is a lip gap adjustment device for a sheet molding die using a heat bolt, in which twill-like unevenness is formed on a surface of a heating part of the heat bolt.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a lip gap adjusting device for a sheet forming die and a lip gap adjusting method using the lip gap adjusting device.

Background Art

[0002] In recent years, due to the high functionality and thinning of films, film thickness unevenness in the width direction has been emphasized. Since the sheet material discharged in a sheet shape from the lip gap of the sheet forming die is formed into a film, by adjusting the lip gap, the film thickness distribution can be adjusted and the thickness unevenness in the width direction can be reduced. As a device for adjusting this lip gap, there is a lip gap adjusting device that heats and expands a plurality of heat bolts arranged in the width direction and pushes and pulls the lip of the sheet forming die. In order to reduce the thickness unevenness in the width direction, this lip gap adjusting device controls the amount of thermal expansion of each heat bolt according to the measured film thickness distribution. At this time, since the film thickness distribution changes moment by moment, if the time from when the heat bolt starts to be heated until it finishes thermal expansion, that is, the time until the lip gap changes (hereinafter referred to as the "response time") is long, the film thickness distribution cannot be adjusted in a timely manner. Therefore, in order to adjust the film thickness distribution in a timely manner, a lip gap adjusting device with a short response time is desired.

[0003] Incidentally, two technologies that appear at first glance to be similar to a preferred embodiment of the present invention are the extrusion die disclosed in Patent Document 1 and the film manufacturing apparatus disclosed in Patent Document 2. Patent Document 1 discloses an extrusion die that detects the gap shape of the discharge port with a detector in order to reduce the skill required to adjust the adjustment bolt. Figure 5 is a cross-sectional view perpendicular to the width direction of the extrusion die of Patent Document 1. As shown in Figure 5, the extrusion die of Patent Document 1 comprises an extrusion die 1 composed of lips 2 and 3 that form a discharge port 4, an adjustment bolt 5 installed in a bolt holding part 21 that pushes and pulls the lip 2, a heater 6 built into the adjustment bolt 5 that makes the adjustment bolt 5 function as a heat bolt, a detection body 22 installed on the lower surface of the lip 2, and a proximity sensor 23 installed on the lower surface of the bolt holding part 21 that detects the distance to the detection body 22, and the gap shape of the discharge port 4 can be detected by a detector composed of the detection body 22 and the proximity sensor 23. Generally, the gap shape of the discharge port 4 adjusted with the adjustment bolt 5 is estimated from the film thickness downstream, so adjustment requires skill. In contrast, with the extrusion die described in Patent Document 1, the gap shape of the discharge port 4 can be confirmed with a detector, thus reducing the skill required for adjustment.

[0004] Furthermore, Patent Document 2 discloses a film manufacturing apparatus for applying a slit gap adjustment mechanism using a heat bolt to solution film formation, which involves supplying and exhausting gas into a cover that encloses the entire heat bolt. Figure 6 is a cross-sectional view perpendicular to the width direction of the film manufacturing apparatus of Patent Document 2. As shown in Figure 6, the film manufacturing apparatus of Patent Document 2 comprises a nozzle 1 composed of lips 2 and 3 that form a slit gap 4, a heat bolt 5 that pushes and pulls the lips 2, a heating element 6 that heats the heat bolt 5, a cover 31 that encloses the entire heat bolt 5, and a gas supply pipe 32 for supplying gas into the cover enclosed by the cover 31, and a gas exhaust pipe 33 for exhausting gas. By supplying and exhausting gas through the gas supply pipe 32 and the gas exhaust pipe 33, it is possible to prevent the solvent scattered during solution film formation from coming into contact with the heat bolt 5 or the heating element 6. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Patent No. 5998697 [Patent Document 2] Patent No. 3932711 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] However, since the technologies described in Patent Documents 1 and 2 do not focus on reaction time, the reaction time is long, similar to other conventional technologies, and the film thickness distribution cannot be adjusted in a timely manner.

[0007] Therefore, the present invention provides a lip gap adjustment device with a short reaction time that can adjust the film thickness distribution in a timely manner, and a lip gap adjustment method using the lip gap adjustment device. [Means for solving the problem]

[0008] (1) The present invention, which solves the above problems, is a lip gap adjustment device for a sheet molding die using a heat bolt, wherein a cross-shaped pattern of irregularities is formed on the surface of the heating portion of the heat bolt.

[0009] The lip gap adjustment device for the sheet molding die of the present invention is preferably in any of the following embodiments (2) to (3). (2) A lip gap adjustment device for the sheet molding die of (1) above, wherein the height of the above-mentioned twill-like irregularities is 200 μm or more and 600 μm or less. (3) A lip gap adjustment device for the sheet molding die according to (1) or (2), which is equipped with a circulation device for circulating the air around the heating section.

[0010] (4) The present invention, which solves the above problems, is a method for adjusting the lip gap of a sheet molding die using the lip gap adjustment device for a sheet molding die described in (3) above, wherein the air velocity around the heating section is 7 m / s or more.

[0011] Next, the meaning of each term used in this invention will be explained. "Sheet material" refers to the material that makes up the sheet. As sheet material, for example, polyolefin resins such as polyethylene, polypropylene, polystyrene, and polymethylpentene; alicyclic polyolefin resins; polyamide resins such as nylon 6 and nylon 66; aramid resins; polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polypropylene terephthalate, polybutyl succinate, and polyethylene-2,6-naphthalate; polycarbonate resins; polyarylate resins; polyacetal resins; polyphenylene sulfide resins; fluororesins such as tetrafluoroethylene resin, trifluoroethylene resin, trifluoroethylene chloride resin, tetrafluoroethylene-hexafluoropropylene copolymer, and vinylidene fluoride resin; acrylic resins; methacrylic resins; polyacetal resins; polyglycolic acid resins; and polylactic acid resins can be used in a fluidized form by dissolving or melting them in a solvent. Furthermore, these thermoplastic resins may be homopolymers, copolymers, or blends of two or more types. Furthermore, various additives may be added to each thermoplastic resin, such as antioxidants, antistatic agents, nucleating agents, inorganic particles, organic particles, viscosity reducers, heat stabilizers, lubricants, infrared absorbers, ultraviolet absorbers, and doping agents for refractive index adjustment. A "sheet forming die" refers to a device that extrudes sheet material in a sheet shape from a gap formed by a pair of lips. Examples of sheet forming dies include T-dies, coat hanger dies, L-dies, and fishtail dies, but are not limited to these. A "lip gap adjustment device" is a device that adjusts the lip gap of a sheet molding die in order to adjust the film thickness distribution. A "heat bolt" is a bolt that expands and contracts due to thermal expansion caused by heating and cooling, pushing and pulling the lip of a sheet molding die. The "heating section" refers to a part of the heat bolt that is primarily heated between the part fixed to the sheet molding die and the part fixed to the lip. The "circulation device" refers to a device that circulates the air around the heating part. Examples of the circulation device include, but are not limited to, air nozzles, air supply and exhaust mechanisms, and fans.

Advantages of the Invention

[0012] According to the present invention, the film thickness distribution can be adjusted in a timely manner.

Brief Description of the Drawings

[0013] [Figure 1] Cross-sectional view perpendicular to the width direction of the lip gap adjusting device of the present invention [Figure 2] Enlarged view and cross-sectional view of an example of the mesh-like unevenness formed on the surface of the heating part in the present invention [Figure 3] Enlarged view and cross-sectional view of another example of the mesh-like unevenness formed on the surface of the heating part in the present invention [Figure 4] Cross-sectional view perpendicular to the width direction of the lip gap adjusting device of the present invention provided with a circulation device [Figure 5] Cross-sectional view perpendicular to the width direction of the die for extrusion molding of Patent Document 1 [Figure 6] Cross-sectional view perpendicular to the width direction of the film manufacturing apparatus of Patent Document 2

Embodiments for Carrying Out the Invention

[0014] The present invention will be described in detail below, but the present invention is not limited to the embodiments including the following examples. FIGS. 1 to 4 are diagrams related to the lip gap adjusting device 10 of the present invention. In addition, members having the same uses and functions as those of the prior art may have the same reference numerals.

[0015] The lip gap adjustment device of the present invention will now be described. Figure 1 is a cross-sectional view perpendicular to the width direction of the lip gap adjustment device 10 of the present invention. As shown in Figure 1, the lip gap adjustment device 10 of the present invention comprises a sheet molding die 1 composed of lips 2 and 3 that form a lip gap 4, a plurality of heat bolts 5 arranged in the width direction on the lip 2, and a heater 6 housed inside the heat bolts 5. By heating with the heater 6, the heating portion 7 of the heat bolt 5 expands due to heat and pushes the lip 2, narrowing the lip gap 4. At this time, the time from when the heating portion 7 starts to heat until it has fully expanded, that is, until the lip gap 4 has completely changed, is called the reaction time.

[0016] Through repeated experiments and theoretical calculations, the inventors discovered that by making the surface of the heating element 7 of the heat bolt 5 uneven, the reaction time can be shortened and the film thickness distribution can be adjusted in a timely manner. From the heat conduction equation, the larger the product of the amount of heat transferred on the surface of the heating element 7, i.e., the heat transfer coefficient and the surface area, the shorter the reaction time is during both heating and cooling. By making the surface of the heating element 7 uneven, the surrounding airflow becomes turbulent, increasing the heat transfer coefficient, and further increasing the surface area, the amount of heat transferred is greatly increased, thus shortening the reaction time.

[0017] However, depending on the shape of the unevenness, the reaction time cannot be sufficiently shortened. For example, in the case of unevenness in one direction such as a thread, since the direction of the airflow that becomes turbulent is limited, the reaction time cannot be sufficiently shortened. Moreover, if the unevenness is too deep, the strength of the heat bolt 5 will be reduced, making it impossible to push and pull the lip 2. In addition, in the case of unevenness with a roughened surface by blasting or the like, the height of the unevenness is too low, making it difficult to become turbulent. As a result of further intensive studies by the inventors, it has been found that by making the surface of the heating portion 7 into a lattice-shaped unevenness, the amount of heat transfer can be maximally increased. By making the unevenness lattice-shaped, the airflow can be made turbulent regardless of the direction, and even with shallow unevenness, the amount of heat transfer can be sufficiently increased, so the strength of the heat bolt 5 is not reduced. FIGS. 2 and 3 are enlarged views and cross-sectional views of the lattice-shaped unevenness of the present invention. The lattice-shaped unevenness of the present invention is, for example, a pyramid shape as shown in FIG. 2 or a shape with a flat upper portion as shown in FIG. 3, but is not limited thereto. Also, the formation range of the lattice-shaped unevenness is preferably 70% or more of the surface area of the heating portion 7.

[0018] The lip gap adjusting device 10 of the present invention preferably includes a circulation device that circulates the air around the heating portion 7. FIG. 4 is a cross-sectional view perpendicular to the width direction of the lip gap adjusting device of the present invention provided with the circulation device 11. As shown in FIG. 4, by circulating the air around the heating portion 7 with the circulation device 11, the effect of making it easier to become turbulent due to the lattice-shaped unevenness becomes more prominent, and the reaction time can be further shortened.

[0019] Also, when adjusting the lip gap 4 using the lip gap adjusting device 10 provided with the circulation device 11, it is preferable that the wind speed around the heating portion 7 is 7 m / s or more. By setting the wind speed around the heating portion 7 to 7 m / s or more, the effect of making it easier to become turbulent due to the lattice-shaped unevenness becomes more prominent, and the reaction time can be further shortened. More preferably, the wind speed around the heating portion 7 is 10 m / s or more.

[0020] In the lip gap adjustment device 10 of the present invention, it is preferable that the height of the twill-patterned irregularities is 200 μm or more and 600 μm or less. By making the height of the twill-patterned irregularities 200 μm or more, the effect of making turbulence easier to occur becomes more pronounced, and the reaction time can be further shortened. Also, by making the height of the irregularities 600 μm or less, sufficient strength of the heat bolt 5 can be maintained to push and pull the lip 2. More preferably, the height of the twill-patterned irregularities is 300 μm or more and 500 μm or less.

[0021] In this invention, "height of unevenness" refers to the height distance from the bottom of the concave portion to the top of the convex portion, and the average value of any five points is used.

[0022] Typical applications of films manufactured using the lip gap adjustment device 10 of the present invention include, but are not limited to, general optical applications, general industrial applications, adhesive tapes, displays, backlight reflectors, touch panels, window coverings, capacitors, battery separators, solar cells, release agents, and ribbons. [Examples]

[0023] [Example 1] The results of actually manufacturing and evaluating a sheet using the lip gap adjustment device shown in Figure 1 will be explained. The specific sheet molding method in this embodiment is as follows. (1) Sheet material: Polyethylene terephthalate (PET) resin (Toray Industries, Inc. thermoplastic resin F20S) (2) Preparation: The sheet material was supplied to the extruder after drying. The extrusion rate was set to 100 kg / h, and the temperature from the extruder to the die was set to 280°C. (3) Sheet forming die: Slit width 500 mm, slit gap 2 mm. (4) Dispensing: The sheet material was extruded from the die into a sheet shape, then rapidly cooled and solidified with cold water to form a sheet with a thickness of 1 mm. (5) Sheet thickness: The sheet thickness was continuously measured during molding using a thickness gauge "WEBFREX NV" (manufactured by Yokogawa Electric). (6) Lip gap adjustment device: The heat bolt is cylindrical with a diameter of φ16 mm, and a cross-shaped pattern of irregularities (irregularity height 150 μm, pitch 600 μm) is formed on the surface of the heating section by knurling. A cartridge heater is inserted inside the heat bolt as the heating element. The cross-shaped irregularities are 5300 mm 2 It is formed within the range, with a heating surface area of ​​7500 mm². 2 This corresponds to 71% of the total. (7) Evaluation of reaction time: The cartridge heater was turned on, and the change in sheet thickness over time was observed at the location corresponding to the heat bolt position. The time required for the sheet thickness to change from the start of the change to 95% of the final change was defined as the reaction time.

[0024] [Example 2] The sheet was formed in the same manner as in Example 1, except that a slit air nozzle was installed as a circulation device to blow air and ensure that the average air velocity around the heating section was 5 m / s.

[0025] [Example 3] The sheet was formed in the same manner as in Example 1, except that the height of the twill-patterned unevenness was set to 300 μm.

[0026] [Example 4] The sheet was formed in the same manner as in Example 2, except that the average air velocity around the heating element was set to 8 m / s.

[0027] [Comparative Example 1] The sheet was formed in the same manner as in Example 1, except that the surface of the heating section was smoothed.

[0028] [Comparative Example 2] The sheet was formed in the same manner as in Example 1, except that the surface of the heating element was made to have M16 screw threads (height of unevenness 1083 μm).

[0029] [Comparative Example 3] The sheet was formed in the same manner as in Example 1, except that the surface of the heated section was blasted to an arithmetic mean roughness of Ra 60 μm.

[0030] [Evaluation Results] The effectiveness of each example and comparative example was evaluated based on how much the reaction time was shortened compared to Comparative Example 1.

[0031] Comparative Example 1 had a reaction time of 20 minutes. Comparative Example 2, in which screw threads were formed on the surface of the heating section, had a reaction time of 19 minutes, a 5% reduction. Comparative Example 3, in which the surface of the heating section was treated with blasting, had a reaction time of 17 minutes, a 15% reduction. Although the reaction time was slightly shorter compared to Comparative Example 1 due to the uneven surface of the heating section, it was almost the same.

[0032] On the other hand, in Example 1, where a twill-like pattern of irregularities with a height of 150 μm was formed on the surface of the heating section, the reaction time was reduced by 60% to 8 minutes, which was significantly shorter than in Comparative Example 1. Furthermore, in Example 2, where air was blown around the heating section at an average wind speed of 5 m / s, the reaction time was reduced by 70% to 6 minutes. In Example 3, where the height of the twill-like pattern of irregularities was set to a preferred range of 300 μm, the reaction time was reduced by 75% to 5 minutes. In Example 4, where air was blown around the heating section at a preferred average wind speed of 8 m / s, the reaction time was reduced by 85% to 3 minutes. In all cases, the reaction time was even shorter compared to Example 1. [Industrial applicability]

[0033] According to the present invention, by having a twill-like pattern of irregularities on the surface of the heating section, the reaction time can be shortened and the film thickness distribution can be adjusted in a timely manner. [Explanation of symbols]

[0034] 1: Sheet molding die 2, 3: Lip 4: Lip gap 5: Heat Bolt 6: Heating element 7: Heating part 10: Lip gap adjustment device 11: Circulation device 21: Bolt holding part 22: Detected object 23: Proximity sensor 31: Cover 32: Gas supply pipe 33: Gas discharge pipe

Claims

1. A lip gap adjustment device for a sheet molding die using a heat bolt, wherein a cross-shaped pattern of irregularities is formed on the surface of the heating portion of the heat bolt.

2. The lip gap adjustment device for a sheet molding die according to claim 1, wherein the height of the aforementioned twill-like irregularities is 200 μm or more and 600 μm or less.

3. A lip gap adjustment device for a sheet molding die according to claim 1, further comprising a circulation device for circulating air around the heating section.

4. A method for adjusting the lip gap of a sheet molding die using the lip gap adjustment device of claim 3, A method for adjusting the lip gap of a sheet molding die, wherein the air velocity around the heating element is set to 7 m / s or more.

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