JP2005238716A - Manufacturing method and apparatus of polyamide resin molded body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem of white crystal generation by keeping a temperature of a polymerizable lactam liquid in a mold from going out via a pressing member to prevent decrease of the raw material temperature and prevent ununiform crystallization due to the decrease of the temperature. <P>SOLUTION: In the manufacturing method of a polyamide resin molded body comprising casting the polymerizable lactam liquid into a mold 1, inserting the pressing member 24 into the opening, pressing and heating it to polymerize it, the pressing member 24 has a thermal insulation portion 26 mounted between the downward portion 24b in contact with the polymerizable lactam and upper portion 24a out of the mold. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a production method for producing a polyamide resin molded article by casting a polymerizable lactam solution obtained by adding at least an anionic polymerization catalyst and an anionic polymerization initiator into anhydrous lactam into a mold and polymerizing in a pressurized state, and More particularly, the present invention relates to a manufacturing method and a manufacturing apparatus capable of eliminating non-uniformity of crystallization of a polyamide resin due to a decrease in temperature when molding a rod-shaped body and eliminating appearance defects.

  Polyamide resin molded bodies are often used as substitutes for metal gears, rollers, wheels, etc. for the purpose of weight reduction, oil-free operation, noise reduction, and the like, and rod-shaped bodies such as round bars are molded. As a manufacturing method thereof, for example, as described in Patent Document 1, a polymerizable lactam solution obtained by adding a polymerization catalyst and a polymerization initiator to anhydrous lactam is poured into a mold and polymerized by heating to obtain a desired one. There is a method for obtaining a molded body.

  However, in the case of molding by such a method, the top of the molded body may cause sink due to polymerization shrinkage, and the portion where the sink occurs is defective and must be removed. It was. There is also a problem that a void is generated in the center of the molded body.

  In order to solve the problem of sink marks and voids, there is a technique of performing polymerization while applying pressure by a pressure member during polymerization as shown in Patent Document 2. By performing polymerization and molding while applying pressure, generation of sink marks and voids due to polymerization shrinkage can be prevented, and a molded product with few defects can be obtained.

JP 7-237266 A JP-A 64-16614

  However, although problems such as sink marks and voids are less likely to occur, white rice-like white crystals are sometimes generated at the top of the molded product, and there is a problem in that the appearance is poor.

  The cause of the generation of the white crystals is that the temperature of the pressure member in contact with the lactam liquid at the time of polymerization is reduced by casting the polymerizable lactam liquid as a raw material, resulting in non-uniform crystallization at the time of polymerization. It is possible to end up.

  Therefore, the present invention prevents the pressure member from lowering in temperature, thereby eliminating the non-uniformity of crystallization during polymerization and generating white crystals in the vicinity of the top of the molded body that the pressure member contacts. It is a problem to prevent the utterance.

  In order to solve the above problems, in claim 1 of the present invention, a polymerizable lactam solution obtained by adding at least an anionic polymerization catalyst and an anionic polymerization initiator to a substantially anhydrous lactam is poured into a mold and added. In a method for producing a polyamide resin molded body in which a pressure member is inserted into an opening and polymerized by pressurization and heating, the pressure member has a heat insulating portion between a lower portion in contact with the polymerizable lactam in the mold and an upper portion outside the mold. It is provided.

  In Claim 2, it is set as the manufacturing method of the polyamide resin molded object which provided the cavity between the upper part and the lower part of a pressurization member.

  In Claim 3, it is set as the manufacturing method of the polyamide resin molded object which interposed the heat insulating material between the upper part and the lower part of a pressurization member.

  According to a fourth aspect of the present invention, there is provided a method for producing a polyamide resin molded body, wherein the heat insulating material is at least one material selected from polytetrafluoroethylene, polyetheretherketone, and asbestos.

  In claim 5, a mold for casting a polymerizable lactam solution obtained by adding at least an anionic polymerization catalyst and an anionic polymerization initiator to substantially anhydrous lactam, and pressurizing the polymerizable lactam liquid by inserting into the mold An apparatus for producing a polyamide resin molded body having a pressurizing member is characterized in that the pressurizing member is provided with a heat insulating portion between a lower part in contact with the polymerizable lactam in the mold and an upper part outside the mold.

  According to a sixth aspect of the present invention, a polyamide resin molded body manufacturing apparatus is provided in which a cavity is provided in the interior between the upper portion and the lower portion of the pressure member.

  According to a seventh aspect of the present invention, a polyamide resin molded body manufacturing apparatus is provided in which a heat insulating material is interposed between an upper portion and a lower portion of a pressure member.

  In Claim 8, it is set as the manufacturing apparatus of the polyamide resin molding which is at least 1 raw material in which a heat insulating material is chosen from polytetrafluoroethylene, polyetheretherketone, and asbestos.

  In Claims 1 and 6, since the heat insulating part is provided between the upper part and the lower part of the pressurizing member, the temperature of the polymerizable lactam liquid inside the mold escapes to the outside through the pressurizing member. In addition, since the temperature of the raw material is not lowered, the non-uniformity of crystallization caused by the temperature drop can be eliminated, and the problem of generating white crystals can be solved.

  In Claims 2 and 7, the heat insulating portion provided in the pressure member is a hollow portion provided in the pressure member, and the hollow portion can prevent heat from escaping to the outside through the pressure member. .

  In Claims 3 and 8, since a heat insulating material is interposed between the upper part and the lower part of the pressure member, the heat conduction is blocked by the heat insulating material to prevent a temperature drop of the raw material in the mold. Can do.

  In claims 4 and 9, the material of the heat insulating material is limited to polytetrafluoroethylene, polyether ether ketone, and asbestos. It is a material excellent in heat resistance, and even if the temperature of the pressurizing member rises, it does not melt and can retain the heat insulating effect.

  1 and 2 are a front view and a side view of a manufacturing apparatus used in the method for manufacturing a polyamide resin molded body according to the present invention, FIG. 3 is a cross-sectional view taken along line AA in FIG. 2, and FIG. FIG. 5 is a side view of the manufacturing apparatus when the cast polyamide resin molded body is removed from the cylindrical mold, and FIG. 6 is a pressure member. FIG. 7 is an enlarged view of part C in FIG.

  The shape of the molded body obtained by the method for producing a polyamide resin molded body of the present invention is not limited, and examples thereof include a rod-shaped body such as a round bar having a circular cross section, a square, or a rectangular prism.

  As shown in FIG. 1, a cylindrical mold 1 and a raw material pressing part 2 that constantly pressurizes a polymerizable lactam solution injected into the cylindrical mold 1 during polymerization, and a polyamide resin molded body after the polymerization is completed The mold moving unit 3 is configured to raise the mold so that it can be easily taken out from the mold.

  First, the cylindrical mold 1 has a flat plate-like support plate 12 having a raw material injection port 11 for injecting a polymerizable lactam liquid at the upper end portion and an elongated cylindrical cavity 13 for polymerizing the polymerizable lactam liquid. On the other hand, an openable and closable bottom lid 14 is attached to the lower end of the polyamide resin molded body that has undergone polymerization reaction. Further, in order to promote the polymerization of the polymerizable lactam solution, a heat medium introducing portion 15 is provided on the outer peripheral portion of the cavity 13 so as to keep the mold temperature constant.

  It is usually preferable to introduce and circulate a heat medium such as steam or oil in the heat medium introduction unit 15, and there are a heat medium introduction port 16 and a discharge port 17.

  The material of the cylindrical mold 1 used in the present invention is suitably a metal having good thermal conductivity such as aluminum and iron used for producing a polyamide resin molded body usually obtained by casting. However, copper alloys should not be used in contact with lactams because they interfere with lactam anionic polymerization. In addition, it is not necessary to coat the inner surface of the mold cavity 13 with a special release agent. However, in order to improve the take-out property, the product surface is finished as smoothly as possible. Plating treatment is desirable.

  The raw material pressing portion 2 is disposed above the support plate 12 of the cylindrical mold 1. The cylinder 22 constituting the raw material pressing portion 2 is fixed to the upper surface of the support base 23 fixed on the support plate 12. Further, a pressure member 24 fitted near the entrance of the cavity 13 of the cylindrical mold 1 is fixed to the rod 25 of the cylinder 22 so as to be removable. Accordingly, the pressurizing member 24 moves up and down the entrance of the cavity 13 by the operation of the cylinder 22 and constantly pressurizes the lactam liquid while the polymerizable lactam liquid injected into the cavity 13 undergoes the polymerization reaction. It is like that.

  A polyamide resin molded body can be pressure-molded using such a manufacturing apparatus, but in the process of pressurizing with a pressurizing member, heat has conventionally escaped through the pressurizing member and crystallization is uneven. As a result, there was a problem that white granular crystals of rice were formed in the vicinity of the upper portion of the molded body. Therefore, in the present invention, as shown in FIG. 6, by providing a heat insulating part 26 between the upper part 24a located outside the mold of the pressurizing member 24 and the lower part 24b in contact with the raw material, heat does not escape and crystallization is performed. It is made uniform so that defects such as white crystals are prevented.

  The pressure member 24 is preferably made of aluminum or an aluminum alloy. As the heat insulating part 26, a heat insulating part 26 is formed by providing a hollow part 26a inside the pressure member, or a heat insulating part 26b made of polytetrafluoroethylene, polyetheretherketone, asbestos or the like is arranged as a partition. The heat is cut off as 26. Of course, it is also Kano to use both together.

  The pressurizing member 24 is made of aluminum, an aluminum alloy, iron, or the like. When the cavity portion is provided as the heat insulating portion 26, the thickness is preferably 5 to 10 mm. If it is less than 5 mm, it is not preferable because sufficient mechanical strength cannot be ensured. Moreover, when arrange | positioning a heat insulating material as a partition, it is preferable to set it as the thickness of 5-15 mm. If it is less than 5 mm, a sufficient heat insulating effect cannot be obtained, and even if it exceeds 15 mm, the effect of preventing crystallization from becoming non-uniform does not change much.

  In the case of this embodiment, the pressure member 24 is a cylindrical rod-like body. In particular, the tip portion in contact with the injected lactam solution is communicated with a conical recess 27 and the recess 27 as shown in FIG. The concave portion 27 prevents unreacted substances and sink marks at the top of the molded body, and discharges air from the concave portion 27 to the outside through the groove portion 28. Furthermore, the ring-shaped sealing material 29 inserted in the vicinity of the tip portion prevents the lactam liquid from flowing out of the mold. Further, in the mold moving unit 3 constituting the manufacturing apparatus according to the present invention, a pair of opposing vertical frames 32 fixed to the substrate 31 and a horizontal frame 33 fixed to the top of the vertical frame 32 are provided. The guide bar 34 is located in the middle of the vertical frame 32 and is attached to the horizontal frame 33.

  One end of the bracket 35 inserted into the guide bar 34 is fixed to the cylindrical mold support plate 12, and the other end is fixed to the rod of the cylinder 36 attached to the side wall of the vertical frame 32. One end of the inserted bracket 35 is fixed to the cylindrical mold support plate 12, and the other end is fixed to the rod of the cylinder 36 attached to the side wall of the vertical frame 32. The bracket fixes almost the center of the cylindrical mold 1.

  Therefore, when the cylinder 36 is operated, the cylindrical mold 1 and the pressure member 14 connected thereto are moved upward as shown in FIG. As a result, the bottom lid 14 of the cylindrical mold 1 can be easily opened, and the cast polyamide molded body can be easily removed.

  Next, a method for molding the cast polyamide molded body according to the present invention will be described. First, the cylindrical mold 1 is installed at the lowest position, steam is introduced into the heat medium introduction part 15 of the mold and the mold temperature is maintained at 130 ° C. to 150 ° C., and then a predetermined composition is included. Ε-caprolactam having a liquid temperature of about 130 ° C. is injected into the cavity 13 from the raw material casting port 11. In this case, the pressurizing member 24 is located slightly above the raw material casting port 11.

Thereafter, the raw material pressing unit 2 is operated to lower the pressurizing member 24 to contact the lactam solution, and at the same time, pressurization is performed at a pressure of about 120 kg / cm ² or more, and then the length direction is obtained by polymerization and crystallization of the lactam solution. However, the pressure is continuously applied at a speed not lower than the contraction speed. When the pressurization time is about 20-25 minutes, the polymerization is almost completed.

  Thereafter, the mold moving unit 3 is operated. In this case, the cylindrical mold 1 is raised to a predetermined height by the operation of the cylinder 36. In this case, the temperature of the mold is maintained at 130 to 150 ° C. As a result, the bottom lid 14 of the cylindrical mold is opened, and then the pressure member 24 is lowered to expose a part of the cast polyamide molded body from the mold, and then the ring body is used as the molded body. After fitting and tightening, the top of the molded body and the pressure member 24 are released, and the molded body is extracted from the cylindrical mold.

  Mold with steam jacket for pressure molding of 155 ° C residual heat using an aluminum pressure member with upper and lower parts separated by a heat insulating material made of asbestos and having a cavity inside (inside dimension: inner diameter 53 mm x length 1220 mm, pressurizing member at the time of mold preheating is preheated in the state of being inserted into the mold), and a raw material liquid obtained by adding sodium hydride and isocyanate to heat-melted ε-caprolactam is cast, A polyamide resin round bar having a diameter of 50 mm × 1000 mm was molded (anionic polymerization) under a pressure of 20 MPa.

  The preheating time of the pressure member was set to 5 minutes, and the temperature at the tip of the pressure member and the generation depth of the white granular crystals of rice were measured. The results are shown in Table 1.

  A polyamide resin round bar was molded in exactly the same manner as in Example 1 except that the preheating time of the pressurizing member was 10 minutes, and the temperature at the tip of the pressurizing member and the generation depth of white granular crystals of rice were measured. The results are shown in Table 1.

  A polyamide resin round bar was molded in exactly the same manner as in Example 1 except that the remaining heat time of the pressure member was 15 minutes, and the temperature of the tip of the pressure member and the generation depth of white granular crystals of rice were measured. The results are shown in Table 1.

Comparative Example 1

  A polyamide resin round bar was molded under the same conditions as in Example 3 except that the pressurizing member was not provided with a partition of a heat insulating material and a cavity, and the temperature of the tip of the pressurizing member and the rice granular white crystals The generation depth was measured. The results are shown in Table 1.

  From the results of Table 1, in Examples 1 to 3, the generation depth of rice granular white crystals is the largest in Example 1, but the size is 8 mm, but there is no insulation partition or cavity. In the comparative example 1, the rice granular white crystal | crystallization has generate | occur | produced to the range of 20 mm, and can confirm the effect of this invention.

  The present invention relates to the production of a cast polyamide resin molded body in which a polymerizable lactam solution is polymerized in a mold and molded while being pressurized with a pressure member during polymerization in order to prevent sink due to polymerization shrinkage. The method can be applied to a method and an apparatus for producing a polyamide resin molded body in which heat is prevented from escaping from the pressure member and generation of defects due to non-uniform crystallization of the molded body is eliminated.

It is a front view of the manufacturing apparatus of the cast polyamide resin molding which concerns on this invention. It is a side view of a manufacturing apparatus. It is AA sectional drawing of FIG. The combination of a cylindrical metal mold | die and a raw material press part is shown. It is a side view when removing a cast polyamide resin molded product from a cylindrical mold. It is the C section enlarged view of FIG. It is a front view which shows the structure of a pressurization member.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cylindrical metal mold | die 2 Raw material press part 3 Mold moving part 11 Raw material casting part 14 Bottom cover 22 Cylinder 23 Support stand 24 Pressurization member 24a Upper part 24b Lower part 26 Thermal insulation part 26a Cavity part 26b Thermal insulation material

Claims (8)

  A polyamide resin in which a polymerizable lactam solution obtained by adding at least an anionic polymerization catalyst and an anionic polymerization initiator to substantially anhydrous lactam is poured into a mold, and a pressure member is inserted into the opening and is pressurized and heated to be polymerized. In the manufacturing method of a molded object, the pressurizing member provided the heat insulation part between the lower part which contact | connects polymerizable lactam in a type | mold, and the upper part outside a type | mold, The manufacturing method of the polyamide resin molded object characterized by the above-mentioned.   The method for producing a polyamide resin molded body according to claim 1, wherein a cavity is provided in the interior between the upper part and the lower part of the pressure member.   The manufacturing method of the polyamide resin molding of Claim 1 which interposed the heat insulating material between the upper part and the lower part of a pressurization member.   The method for producing a polyamide resin molded body according to claim 3, wherein the heat insulating material is at least one material selected from polytetrafluoroethylene, polyetheretherketone, and asbestos.   A mold for casting a polymerizable lactam solution obtained by adding at least an anionic polymerization catalyst and an anionic polymerization initiator to substantially anhydrous lactam, and a pressurizing member for pressurizing the polymerizable lactam liquid by inserting into the mold An apparatus for producing a polyamide resin molded body, wherein the pressure member is provided with a heat insulating portion between a lower part in contact with the polymerizable lactam in the mold and an upper part outside the mold.   6. The apparatus for producing a polyamide resin molded body according to claim 5, wherein a cavity is provided in the interior between the upper part and the lower part of the pressure member.   6. The apparatus for producing a polyamide resin molded body according to claim 5, wherein a heat insulating material is interposed between the upper part and the lower part of the pressure member. 9. The apparatus for producing a polyamide resin molded body according to claim 7, wherein the heat insulating material is at least one material selected from polytetrafluoroethylene, polyetheretherketone, and asbestos.

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