Molding method for injection stretch blow molding and temperature control rod

Abstract

To provide a molding method for injection stretch blow molding and a temperature control rod that can obtain a molded product with a variety of shapes by partially changing a thickness of a side wall of the molded product.MEANS FOR SOLVING THE PROBLEM: A molding method for injection stretch blow molding includes: an injection step of preforming a cylindrical preform with plasticized material; a temperature control step of adjusting a temperature of the preform after the injection step by means of a temperature control rod 31; a stretch blow step of stretch blow molding the preform after the temperature control step by blowing pressurized air from a nozzle in a closed mold; and a removing step of removing a product that has been cooled and solidified in the stretch blow step. By using the temperature control rod 31 provided with outer surface irregularities 34 on its rod side surface, inner surface irregularities 12 are formed on an inner surface of a side wall of a molded product 11, thereby partially changing a thickness of the side wall.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a molding method for injection stretch blow molding and a temperature control rod. [Background technology]

[0002] A known method for producing molded articles such as resin containers is to use a hot parison blow molding machine. The hot parison blow molding machine is configured to blow mold a resin container by utilizing the heat retained during injection molding of a preform, and is advantageous over the cold parison method in that it can produce a variety of resin containers with excellent aesthetic appearance.

[0003] Generally, a preform immediately after injection molding does not have a temperature distribution suitable for shaping a container. Therefore, in a hot parison blow molding cycle, a preform temperature adjustment process (hereinafter referred to as the temperature adjustment process) is performed between the injection molding process and the blow molding process to prevent temperature deviation in the preform or to impart to the preform a desired temperature distribution suitable for shaping a container. In this temperature adjustment process, a temperature adjustment rod conforming to the internal shape of the preform is generally inserted inside the preform, and the temperature is adjusted by bringing the inner peripheral surface of the preform into close contact with the temperature adjustment rod or by bringing them close to each other via an air layer.

[0004] Patent Documents 1 and 2 have proposed methods for this type of so-called injection stretch blow molding and temperature control rods used therein. Patent Document 1 proposes a molding method and a temperature control rod that can locally adjust the temperature in the axial direction from inside the preform while restricting shrinkage and deformation of the preform. Patent Document 2 points out the problem that when the contact surface of the temperature control rod with the preform is smooth and mirror-finished, the appropriate temperature range is narrow, at 60 to 75°C, and the preform will stick to the temperature control rod if the temperature is outside this range, and proposes roughening the contact surface of the temperature control rod with the preform. As described above, the proposals so far have focused on temperature control rods solely for adjusting the temperature of the preform, and have not been directed to partially changing the wall thickness of the molded product using the temperature control rod.

[0005] In injection stretch blow molding, some products have a bottom wall with a partially changed thickness, as in Patent Document 3, but the side wall of the container generally has a constant thickness. Molded products with irregularities on the side wall of a container are also known, but in all cases the thickness is constant, and no molded products with partially changed side wall thickness have been known. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2022 / 181618 Brochure [Patent Document 2] Japanese Patent Application Laid-Open No. 2003-103611 [Patent Document 3] Japanese Patent Application Publication No. 5-330535 Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a molding method for injection stretch blow molding that can obtain molded articles with a variety of shapes by partially changing the thickness of the side wall of the molded article. Another object of the present invention is to provide a temperature control rod that can realize variations in the unevenness and thickness of the molded product by changing the surface shape. [Means for solving the problem]

[0008] The present invention provides a molding method for injection stretch blow molding in which molding is performed while controlling the preform temperature using a temperature control rod, characterized in that the temperature control rod has outer surface irregularities on at least the side surface of the rod, thereby forming inner surface irregularities on the inner side of at least the side wall of the molded product and partially varying the wall thickness of the side wall. In practice, the injection stretch blow molding method can include an injection step of preforming a cylindrical preform from a plasticized material, a temperature control step of adjusting the temperature of the preform after the injection step using the temperature control rod, a stretch blow process of stretch blow molding the preform after the temperature control step by blowing pressurized air through a nozzle into a closed mold and stretch blow molding it, and a removal step of removing the product cooled and solidified in the stretch blow process. The present invention also provides the temperature control rod used in the injection stretch blow molding method. The temperature control rod has a rod side surface that faces a cylindrical preform preformed in the injection process, and the surface of the rod side surface can be a smooth surface or a finely rough surface. The surface of the rod side surface can be a rough surface that is the same as or finer than the surface roughness of sandpaper #300, or a smooth surface. In addition, the outer surface unevenness can be an uneven shape extending in the axial direction of the temperature control rod, an uneven shape extending in the circumferential direction of the temperature control rod, or or The temperature control rod may have an uneven shape extending at an angle to the axial direction of the temperature control rod. [Effects of the Invention]

[0009] The present invention aims to provide a molding method for injection stretch blow molding that can produce molded products with a variety of shapes by partially varying the thickness of the side walls of the molded product. The present invention also provides a temperature control rod that can realize variations in the unevenness and thickness of the molded product by changing the surface shape. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is an explanatory diagram of a blow molding device according to an embodiment of the present invention; [Figure 2] 1A is a front view of a temperature control rod according to an embodiment of the present invention, FIG. 1B is a cross-sectional view of the same, and FIG. 1C is a perspective view of a molded product. [Figure 3] (A) A longitudinal cross-sectional view of a conventional temperature control rod, (B) a front view and cross-sectional view of the same, (C) a front view and cross-sectional view of a temperature control rod according to another embodiment of the present invention, (D) a front view and cross-sectional view of a temperature control rod according to yet another embodiment of the present invention, (E) a front view and cross-sectional view of a temperature control rod according to yet another embodiment of the present invention. [Figure 4] (A) A front view and a cross-sectional view of a temperature control rod according to yet another embodiment of the present invention, (B) a front view and a cross-sectional view of a temperature control rod according to yet another embodiment of the present invention, and (C) a front view and a cross-sectional view of a temperature control rod according to yet another embodiment of the present invention. [Figure 5] (A) A front view and a cross-sectional view of a temperature control rod according to yet another embodiment of the present invention, (B) a front view and a cross-sectional view of a temperature control rod according to yet another embodiment of the present invention, and (C) a front view and a cross-sectional view of a temperature control rod according to yet another embodiment of the present invention. [Figure 6] 1A and 1B are a front view and a cross-sectional view of a temperature control rod according to still another embodiment of the present invention, respectively; [Figure 7] (A) A front view and a cross-sectional view of a temperature control rod according to yet another embodiment of the present invention, (B) a front view and a cross-sectional view of a temperature control rod according to yet another embodiment of the present invention, and (C) a front view and a cross-sectional view of a temperature control rod according to yet another embodiment of the present invention. [Figure 8] FIG. 8 is a perspective view of a temperature control rod according to the embodiment of FIG. 7(A). DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings, but the shape, dimensions, etc. of each element shown in the drawings are shown schematically and do not represent the actual shape, dimensions, etc. In addition, the same elements in each drawing will be described with the same reference numerals as a general rule.

[0012] The blow molding apparatus 20 of this embodiment, shown schematically in Fig. 1, is a hot parison type apparatus that uses the heat retained during injection molding (internal heat) without cooling the preform to room temperature to blow mold a molded article 11, such as a container, shown in Fig. 2. The container shown in Fig. 2(C) is an example of the molded article 11, and this container has a bottom-side portion 13 that includes the bottom of the container, a mouth portion 14, a neck portion 15, a shoulder portion 16 of the container, and a cylindrical body portion 17 between the bottom-side portion 13 and the shoulder portion 16.

[0013] This blow molding device 20 includes an injection molding section 21, a temperature adjustment section 22, a blow molding section 23, a take-out section 24, and a conveying mechanism 26. The injection molding section 21, the temperature adjustment section 22, the blow molding section 23, and the take-out section 24 are arranged at positions rotated by a predetermined angle (for example, 90 degrees) around the conveying mechanism 26.

[0014] (Transport mechanism 26) The conveying mechanism 26 includes a transfer plate 28 that moves so as to rotate around a central axis. The transfer plate 28 has one or more holding portions (not shown) that detachably hold the neck portions 15 of preforms (not shown) or molded articles 11 such as the resin container shown in FIG. 2, arranged at predetermined angles. The transfer mechanism 26 rotates the transfer plate 28 by 90 degrees at a time to convey the preforms or molded articles 11 whose neck portions are held by the holding portions to the injection molding section 21, the temperature adjustment section 22, the blow molding section 23, and the removal section 24, in that order. The conveying mechanism 26 further includes an elevation mechanism (a vertical mold opening / closing mechanism) and a mold opening mechanism for the holding portion, and is used to raise and lower the transfer plate 28 and perform mold release operations in the injection molding section 21, etc.

[0015] (Injection process: Injection molding section 21) The injection molding section 21 is equipped with an injection cavity mold and an injection core mold (not shown) and manufactures preforms. The injection molding section 21 is connected to an injection device 25 that supplies a resin material, which is the raw material of the preforms.

[0016] In the injection process of the injection molding unit 21, the injection cavity mold, the injection core mold, and the holding unit of the transport mechanism 26 are closed to form a mold space in the shape of a preform. A resin material is poured from the injection device 25 into this preform-shaped mold space, whereby a preform is manufactured in the injection molding unit 21. For example, the preform may be a cylindrical preform having an open end and a closed end, such as a bottomed cylindrical preform. A neck is formed at the open end of the preform.

[0017] The material of the molded article 11 and the preform is a thermoplastic synthetic resin, and can be appropriately selected depending on the application of the molded article 11. Specific types of material include, for example, PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PCTA (polycyclohexane dimethylene terephthalate), Tritan (Tritan (registered trademark): a copolyester manufactured by Eastman Chemical Company), PP (polypropylene), PE (polyethylene), PC (polycarbonate), PES (polyethersulfone), PPSU (polyphenylsulfone), PS (polystyrene), COP / COC (cyclic olefin polymer), PMMA (polymethyl methacrylate: acrylic), and PLA (polylactic acid).

[0018] It should be noted that even when the injection molding section 21 is opened, the holding section of the transport mechanism 26 does not open, but continues to hold and transport the preforms. The number of preforms that can be molded simultaneously in the injection molding section 21 (i.e., the number of molded articles 11 that can be molded simultaneously in the blow molding device 20) can be set as appropriate.

[0019] (Temperature adjustment process: Temperature adjustment section 22) Temperature adjustment section 22 equalizes the temperature of the preforms manufactured in injection molding section 21 and removes temperature deviations, adjusting the temperature of the preforms to a temperature suitable for blow molding (for example, about 90°C to 105°C) and to a temperature distribution suitable for the shape of molded article 11 to be formed. Temperature adjustment section 22 also has the function of cooling the preforms in a high-temperature state after injection molding.

[0020] Although not shown, the temperature adjustment unit 22 includes a cavity mold (temperature adjustment pot mold, heating pot mold) capable of accommodating a preform and a temperature adjustment rod 31, which is a mold component inserted inside the preform. The cavity mold has a temperature adjustment space having a shape substantially identical to the outer shape of the preform manufactured in the injection molding unit 21. The cavity mold may be divided into multiple sections along the axial direction of the preform, such as an upper-stage mold, a middle-stage mold, and a lower-stage mold. Each cavity mold is equipped with a heating element, such as a band heater (ring-shaped heater) or a rod-shaped heater, which maintains each section at a predetermined temperature. The outer periphery of the preform is heated by the heat from the cavity mold, thereby adjusting the temperature of the preform. The heated cylindrical body of the preform shrinks and deforms toward the inner diameter and neck. The temperature distribution along the axial direction of the preform can also be changed by changing the temperature of the heating element at each stage.

[0021] In the temperature adjustment section 22, the cavity mold and the temperature adjustment rod 31 adjust the temperature of the preform to a temperature suitable for the final blow. The temperature control rod 31 is configured to be movable axially forward and backward relative to the preform by the temperature control unit 22. The temperature control rod 31 includes a base portion 32 supported by the temperature control unit 22, and a main body portion 33 on the tip side. In this temperature control step, the preform held in the holder is placed in the cavity mold by the lowering of the transfer plate 28. Also, the temperature control rod 31 supported by the base 32 is lowered, so that the temperature control rod 31 is inserted into the preform, and the temperature of the preform is adjusted to a temperature suitable for blow molding, and furthermore, temperature deviations that occur during injection molding are reduced.

[0022] The diameter of the main body 33 of the temperature control rod 31 is set to a dimension smaller than the inner diameter of the preform. Furthermore, the tip of the temperature control rod 31 inserted inside the preform comes into contact with the bottom of the preform. The axial length of the temperature control rod 31 is set to a length that takes into account the amount of shrinkage of the preform after it is carried out from the injection molding section 21 until the temperature control rod 31 is inserted.

[0023] Although not shown, a flow path for a temperature control medium to flow along the axial direction is formed inside the temperature control rod 31, and the temperature control rod 31 is maintained at a predetermined temperature by the temperature control medium flowing inside. The temperature control rod 31 is set to a temperature lower than that of the preform, and the preform is cooled by the temperature control rod 31, but it is also possible to heat the preform by the temperature control rod 31.

[0024] The main body 33 of the temperature control rod 31 is inserted into the preform and has an outer peripheral surface that faces the inner peripheral surface of the preform. The outer peripheral surface of this main body 33 can have at least one of a portion that contacts the inner peripheral surface of the preform and a portion that faces the inner peripheral surface of the preform without direct contact, but through an air layer. The temperature of the main body 33 of the temperature control rod 31 is transferred to the preform by direct contact or through an air layer. Note that a tip piece or the like may be detachably provided on the outer peripheral surface or tip of the main body 33.

[0025] The body 33 of the temperature control rod 31 in the embodiment of the present invention has outer surface irregularities 34 (concave portions 35 and convex portions 36) on the cylindrical rod side. These outer surface irregularities 34 form inner surface irregularities 12 on the inner surface of at least the molded article side wall (body portion 17) of the molded article 11 obtained in the stretch blow process by the blow molding section 23 described below. The inner surface irregularities 12 of the molded article 11 obtained by the outer surface irregularities 34 of the temperature control rod 31 are characterized by partially varying thickness of the molded article side wall of the molded article 11, rather than the irregularities that maintain a constant thickness as in many conventional containers produced by injection stretch blow molding. Therefore, this does not include fine irregularities resulting from roughening the surface of the temperature control rod facing the preform, as shown in Patent Document 2, with the assumption that a molded article 11 with a constant thickness is obtained.

[0026] The outer surface unevenness 34 of the main body 33 of the temperature control rod 31 is formed by a recess 35 and a protrusion 3 6 andThis height difference is manifested by a difference in height toward the periphery of the molded article 11. This height difference can be achieved by modifying the thickness of the side wall of the molded article 11 as needed. Specifically, depending on the overall thickness of the side wall of the molded article, the thickness difference is preferably 0.1 mm to 6.0 mm, with 1.0 mm or more being preferable for achieving a more significant difference in thickness. However, it is preferable to modify the thickness difference depending on various conditions, such as the type of resin, molding conditions, and the shape and size of the molded article 11. The surface configuration of the outer surface irregularities 34 of the main body 33 can be a smooth surface, as with many conventional temperature control rods. However, it is also acceptable to form fine irregularities, such as a rough surface equivalent to or finer than the surface roughness of #300 grit sandpaper. Furthermore, the molded article 11, including the portion corresponding to the opening end portion 17 of the bottom end portion 13 of the molded article 11, may be implemented using other techniques, such as molding methods and conventional techniques related to temperature control rods.

[0027] The outer surface unevenness 34 can be implemented in various forms. For example, as shown in Figures 2(A) and (B), it can be implemented as unevenness extending in the axial direction of the temperature control rod 31. This unevenness has concave and convex portions 35 and 36 that appear alternately in the circumferential direction, but the concave and convex portions 35 and 36 are formed at offset positions in the circumferential direction at the upper and lower parts of the main body 33 of the temperature control rod 31. As shown in Figure 2(C), the outer surface unevenness 34 forms inner surface unevenness 12 on the inner surface of the body 17 of the molded product 11. On the other hand, the outer peripheral surface of the body 17 of the molded product 11 is cylindrical with a uniform diameter, and the convex portions of the inner surface unevenness 12 In the department The thickness is large and the concave In the department The wall thickness is small. The shape of the outer peripheral surface of the body portion 17 of the molded product 11 is mainly determined by the blow cavity mold of the blow molding section 23 in the subsequent stretch blow process, but in addition to a cylindrical shape, it can also be embodied in shapes with various irregularities, as with conventional molded products, and the overall shape of the molded product 11 can also be modified in various ways, such as a rectangular tube shape. In other words, in the practice of the present invention, the shape of the inner peripheral surface can be changed regardless of the shape of the outer peripheral surface of the body portion 17 of the molded product 11.

[0028] Figure 3~Fig.7 3 shows various modified examples of the shape of the outer surface unevenness 34 of the temperature control rod 31. Figure 3 shows an example in which uneven outer surface irregularities 34 extending in the axial direction of the temperature control rod are formed over almost the entire length of the main body 33. For comparison, Figures 3(A) and 3(B) show a temperature control rod 31 in which the outer surface irregularities 34 are not formed. The temperature control rod 31 in FIG. 3(C) has recesses 35 formed at every 90 degrees, and the portions between the recesses 35 are protrusions 36. The temperature control rod 31 in FIG. 3(D) has relatively wide recesses 35 formed at intervals of 60 degrees, and the portions between the recesses 35 are made into protrusions 36. The temperature control rod 31 of FIG. 3(E) has recesses 35 formed at intervals of 60 degrees, and the portions between the recesses 35 are protrusions 36 of the same width.

[0029] The temperature control rod 31 in Figure 4 (A) has an uneven shape extending in the axial direction of the temperature control rod, with flat recesses 35 formed every 36 degrees and curved protrusions 36 formed between the recesses 35. The temperature control rod 31 in FIG. 4(B) has arc-shaped recesses 35 formed in a groove shape at intervals of 36 degrees, and the portions between the recesses 35 are formed as protrusions 36. The temperature control rod 31 of FIG. 4(C) has groove-like angular recesses 35 formed at every 36 degrees, and the portions between the recesses 35 are curved convex portions 36.

[0030] The temperature control rod 31 in Figure 5 (A) has an uneven shape extending in the axial direction of the temperature control rod, with flat recesses 35 formed every 30 degrees and curved protrusions 36 between the recesses 35. The temperature control rod 31 in FIG. 5(B) has arc-shaped recesses 35 formed in a groove shape at intervals of 30 degrees, and the portions between the recesses 35 are formed as protrusions 36. The temperature control rod 31 of FIG. 5(C) has groove-like angular recesses 35 formed at every 30 degrees, and the portions between the recesses 35 are curved convex portions 36.

[0031] The temperature control rod 31 in FIG. 6(A) has three sections, top, middle and bottom, each of which has a concave-convex shape extending in the axial direction of the temperature control rod, and the sections are spaced apart at intervals of 60 degrees. Same width The recesses 35 are formed in the middle section, and the portions between the recesses 35 are formed as protrusions 36, and the middle section is formed so that its position in the circumferential direction is shifted from that of the upper and lower sections. The temperature control rod 31 in FIG. 6(B) has an uneven shape extending in the circumferential direction of the temperature control rod, with recesses 35 and protrusions 36 formed alternately in the axial direction.

[0032] The temperature control rod 31 in Fig. 7(A) has a spiral concave-convex shape that extends at an angle relative to the axial direction of the temperature control rod, with recesses 35 formed every 90 degrees and the portions between the recesses 35 serving as convex portions 36. A perspective view of this temperature control rod 31 is shown in Fig. 8. The temperature control rod 31 in Figure 7 (B) has a spiral-shaped uneven shape extending at an angle to the axial direction of the temperature control rod, with recesses 35 formed every 90 degrees and the parts between the recesses 35 being protrusions 36, with the upper and lower ends extending in the axial direction of the temperature control rod. The temperature control rod 31 in Figure 7 (C) has an uneven shape extending along the axial direction of the temperature control rod, with recesses 35 formed every 90 degrees in the middle of the axial direction, and the parts between the recesses 35 being protrusions 36. The shape of the outer surface irregularities 34 is not limited to the example shown in the figure and can be changed in various ways. For example, either the recesses 35 or the protrusions 36 can be made island-shaped, or can be in the form of letters, symbols, or figures, or can be an irregular pattern.

[0033] (Stretch blow process: blow molding section 23) Returning to FIG. 1, the blow molding section 23 performs a stretch blow molding process on the preform whose temperature has been adjusted in the temperature adjustment section 22, to produce a molded article 11 such as a container. Although not shown, the blow molding section 23 includes a blow cavity mold, which is a pair of split molds corresponding to the shape of the molded article 11, a bottom mold, a stretching rod, and an air introduction member (blow core mold, none of which are shown). The blow molding section 23 blow-moldes the preform while stretching it. As a result, the preform is shaped into the shape of the blow cavity mold, and a molded article 11 such as a container is manufactured.

[0034] Specifically, in the blow molding section 23, the blow cavity mold is first closed to place the preform in the mold space, and the air introduction member (blow core) is lowered to contact the neck of the preform. Next, a stretching rod (vertical axis stretching member) is lowered to press the bottom of the preform from the inside, and while vertical axis stretching is performed as necessary, blow air is supplied from the air introduction member to stretch the preform horizontally. As a result, the preform is shaped by expanding so as to fit closely into the mold space of the blow cavity mold, and is blow-molded into the molded product 11. Before the blow cavity mold is closed, the bottom mold waits in a lower position where it does not come into contact with the bottom of the preform, and then quickly rises to the molding position before or after mold closing.

[0035] The preform expands to fit closely into the mold space of the blow cavity mold, and the outer peripheral surface is shaped according to the irregularities of the blow cavity mold, while as described above, in the temperature control process, the outer surface irregularities 34 of the temperature control rod 31 create irregularities and temperature differences on the inner peripheral surface of the preform. As a result, reflecting these irregularities and temperature differences, inner surface irregularities 12 with varying wall thickness are formed on the inner peripheral surface of the molded product 11 in the blow molding process.

[0036] (Removal process: removal section 24) The removal section 24 is configured to release the neck portion 15 of the molded article 11 produced in the blow molding section 23 from the holding section, and remove the molded article 11 to the outside of the blow molding apparatus 20. When blow molding in the blow molding section 23 is completed, the blow cavity mold and bottom mold are opened, making it possible to remove the molded article 11 from the blow molding section 23. The transfer plate 28 of the conveying mechanism 26 rotates, and the molded article 11 is transported to the removal section 24. In the removal section 24, the neck portion 15 is released from the holding section, and the molded article 11 is removed to the outside of the blow molding apparatus 20.

[0037] As described above, the present invention is not limited to the above-described embodiments, and various improvements and design changes may be made within the scope of the spirit of the present invention, and the shape of the temperature control rod can also be changed in various ways depending on the type, use, and shape of the molded product 11. [Explanation of symbols]

[0038] 11: Molded product 12: Inner surface unevenness 13: Bottom edge portion 13 14: Mouth 15: Neck 16:Shoulder 17: Torso 20: Blow molding equipment 21: Injection molding section 22: Temperature adjustment section 23: Blow molding section 24: Removal section 25: Injection device 26:Transport mechanism 28:Transfer plate 31: Temperature control rod 32: Base 33: Main body 34: Outer surface unevenness 35: Recess 36: Convex part

Claims

1. In a molding method for injection stretch blow molding, molding is performed while controlling the preform temperature using a temperature control rod, By using a temperature control rod having outer surface irregularities at least on the side surface of the rod, A molding method for injection stretch blow molding, characterized in that inner surface irregularities are formed on at least the inner surface of the side wall of a molded product, and the thickness of the side wall is partially changed.

2. an injection step of preforming a cylindrical preform from the plasticized material; a temperature control step of controlling the temperature of the preform after the injection step using the temperature control rod; a stretch blowing process in which pressurized air is blown into the preform after the temperature adjusting process from a nozzle in a closed mold to stretch blow mold the preform; 2. The injection stretch blow molding method according to claim 1, further comprising a removal step of removing the product cooled and solidified in the stretch blow step.

3. The temperature control rod used in the injection stretch blow molding method according to claim 1, wherein the temperature control rod has a rod side surface facing a cylindrical preform preformed in an injection step, A temperature control rod characterized in that the surface of the side surface of the rod is a smooth surface or a finely rough surface.

4. 4. The temperature control rod according to claim 3, wherein the surface of the side of the rod is a rough surface having a surface roughness equal to or finer than #300 grit of sandpaper, or a smooth surface.

5. A temperature control rod as described in claim 3 or 4, characterized in that the outer surface unevenness is uneven extending in the axial direction of the temperature control rod, uneven extending in the circumferential direction of the temperature control rod, or uneven extending at an angle to the axial direction of the temperature control rod.

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