JP2006272794A - Method for manufacturing polyamide resin molding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a polyamide resin molding which can avoid the problems such as voids or blow holes, which is free from the problem that a raw material leaks even though the size of the mold product is large, and which can be carried out by a small pressuring force without using a large size device. <P>SOLUTION: A lid body 6 having a gap of 0 to 10 mm from the lid side in the state of being inserted in the opening portion 5 of the mold 1 with the raw material G being cast and having a through opening 8 is placed to come into contact with the raw material G. The raw material G located in the gap between the mold 1 and the lid body 6 is solidified to seal the lid 6, and then pressurized air is blown through the hole 8 to pressurize the raw material G in the mold to cause polymerization to proceed. Thus, the molding is completed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a production method for producing a polyamide resin molded article by casting a polymerizable lactam solution in which at least an anionic polymerization catalyst and an anionic polymerization initiator are added to anhydrous lactam into a mold and polymerizing in a pressurized state. In particular, the present invention relates to a method for producing a polyamide resin molded body that can sufficiently press the lower part of the raw material when molding a rod-shaped body and has few internal defects.

  Polyamide resin molded bodies are often used as substitutes for metal gears, rollers, wheels, and the like for the purpose of weight reduction, oil-free operation and noise reduction, 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 a sink due to polymerization shrinkage, and the portion where the sink occurred becomes 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, it is possible to prevent the occurrence of sink marks and voids due to polymerization shrinkage, and it is possible to obtain molded products with few defects.

  Patent Document 3 discloses a method of forming a cast nylon pipe using a material in which a lubricant is blended with a polymerization catalyst and a polymerization promoter in lactam.

JP 7-237266 A JP-A 64-16614 JP-A-2-241708

  By performing polymerization while applying pressure as in Patent Document 2, problems such as sink marks and voids are somewhat less likely to occur, but it is still not sufficient. In particular, when forming a rod-shaped body such as a round bar, the pressure due to pressurization is sufficiently transmitted to the entire raw material at the initial stage of polymerization, but as the polymerization proceeds, the viscosity of the raw material rapidly increases, and the high-viscosity raw material Due to this friction, the entire raw material is not sufficiently pressurized. For this reason, problems such as voids in the molded body can be considerably reduced by pressure molding, but it has not yet reached the stage where it is completely eliminated. In particular, problems such as voids and nests occurred in the lower part of the raw material.

  In the case of small-diameter round bars and small-size molded products, the effect was achieved by pressing the raw material in the mold with a piston during molding as described above. In the case of a plate-like body, it has been difficult to seal the liquid raw material from leaking from the gap between the pressure piston and the inner surface of the mold. Furthermore, there is friction between the raw material and the mold, and when the raw material begins to solidify, the frictional force becomes particularly large. Therefore, the pressurizing method using a piston requires a large pressure device to apply sufficient pressure to the raw material. It was difficult to actually do because it was necessary.

  Therefore, in the present invention, since the raw material is pressed during molding, problems such as voids and nests can be prevented in the obtained molded product, and the raw material leaks even if the size of the molded product is large. It is an object of the present invention to provide a method for producing a polyamide resin molded body which can be carried out without problems and without using a large apparatus with a very small pressure.

  In order to achieve such an object, 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 as a raw material, In the method for producing a polyamide resin molded body that is polymerized by pressurization and heating, after the raw material is cast, the lid body is sized to have a gap of 0 to 10 mm from the mold in a state of being fitted into the mold opening, and the through hole The lid body provided with the material is disposed so as to be in contact with the raw material, and the raw material located in the gap between the mold and the lid body is solidified by heating the raw material, and the cover body is sealed, and the pressurized gas is supplied from the through hole. While the raw material in the mold is pressurized, the polymerization is advanced to complete the molding.

  According to a second aspect of the present invention, the lid body has a concave portion on the surface in contact with the raw material, and is arranged so that the concave portion is filled with the raw material when the lid is arranged, and the through hole is provided in the concave portion. It is set as the manufacturing method of the polyamide resin molding of Claim 1.

  The method for producing a polyamide resin molded body according to claim 2, wherein the recess has a conical shape, and the through hole is located at the apex of the conical shape.

  According to the present invention, a lid having substantially the same size as the opening is disposed at the opening of the mold into which the raw material is poured, and the pressurized gas is released from the through-hole of the lid after the raw material located in the gap between the lid and the mold is solidified. The raw material in an uncured state is polymerized while being pressurized by blowing in, and this pressurization method can perform sufficient pressurization with relatively small pressurization, so a large round bar In addition, it is not necessary to prepare a large-scale apparatus even when molding a plate-like body, and a good molded body free from voids and nests can be produced.

  In claim 2, since the polymerization is performed while pressurizing with gas from the through hole in the state where the recess is first filled with the raw material in the lid, the amount of polymerization shrinkage is compensated with the raw material in the recess, Sinking of the upper part of the molded body can be prevented, and a molded body with few defective parts due to shrinkage can be obtained.

  According to claim 3, the concave portion has a conical shape, the raw material in the concave portion is not easily heated from the mold, and the raw material is supplied in response to shrinkage occurring in the final stage of polymerization, so that the sink on the upper portion of the molded body is less. It can be set as a molded body.

  FIG. 1 is a schematic view of a mold used in the method for producing a polyamide resin molded body according to the present invention, FIG. 2 is a cross-sectional view when a raw material is cast into the mold, and FIG. 3 is a cross-sectional view when a lid is disposed. 4 is a cross-sectional view showing a state in which the mold surface and its vicinity are polymerized and solidified, FIG. 5 is a cross-sectional view where nitrogen is pressurized, and FIG.

  The mold 1 used in the method for producing a polyamide molded body of the present invention will be described by taking a mold for molding a plate-like body as an example. In the mold 1, a cavity 4 having an opening 5 above is formed between the side plate 2 and the spacer 3 by moving two side plates 2 in the direction of the arrow in FIG. Then, a polymerizable lactam solution to be the raw material G is poured into the cavity 4 and heated to polymerize and cure the raw material to form a plate-shaped molded body.

  Although not shown in the mold 1, a heat medium passage such as steam or oil can be arranged, or a raw material poured into the cavity 7 can be heated by contacting a heater from the back. The lid 6 has a size substantially the same as that of the opening 5, and after the raw material G is cast into the cavity 4, the lid 5 closes the opening 5. The lid 6 has a through hole 7 for blowing pressurized gas into the cavity 4 when it is disposed in the opening 5 so that the pressurized gas supply pipe 8 can be detached. .

  Using such a mold 1, a polyamide resin molded body is manufactured in the following steps. First, as shown in FIG. 2, a substantially anhydrous polymerizable lactam solution is poured into the cavity 4 from the opening 5 as a raw material G. Next, as shown in FIG. 3, the opening 5 is closed with the lid 6, and the raw material G is heated. Since the polymerizable lactam liquid is polymerized by heating, it is gradually polymerized and cured from the portion in contact with the mold 1, and the raw material located in the gap between the lid 6 and the mold 1 when the surface vicinity 7 of the mold 1 is cured. G is cured as shown in FIG. Then, the gap between the lid 6 and the mold 1 is the same as that sealed with the cured resin. In the entire mold 1, only a small portion in contact with the mold 1 is polymerized and cured, but most other parts are still The polymerization is not progressing. In this situation, the inside of the mold 1 is pressurized by connecting a pressurized gas supply pipe 9 to the through hole 8 of the lid 6 and blowing the gas into the cavity 4 as shown in FIG. When the polymerization is completed and the resin is cured as shown in FIG. 6, the polyamide resin molded body 11 is removed from the mold 1 by cooling as appropriate.

  By adopting such a method, it is possible to perform molding while pressurizing the inside of the mold in polymerization molding of a plate-like body or a large-sized molded article, generation of voids or nests due to polymerization shrinkage, and sink marks on the upper part of the molded article. Defects due to generation or the like can be prevented.

  The gap between the side surface of the lid 6 and the mold 1 is preferably set in the range of 0 to 10 mm, more preferably 1 to 5 mm. If the gap exceeds 10 mm, polymerization of the raw material G located there proceeds and cures, and the time required until the gap between the lid 6 and the mold 1 is sealed is undesirably long. Further, if the gap is too narrow, it is difficult to attach and detach the lid 6 from the mold 1 at the time of molding or after completion of molding, so it is preferable to have a gap of about 1 mm if possible.

  The magnitude of pressurization with gas is set in the range of 50 to 500 kPa. If it is less than 50 kPa, the applied pressure is too small and problems such as voids, nests and sink marks due to polymerization shrinkage may not be solved, which is not preferable. There is no difference in the effect even if the pressure is further increased beyond 500 kPa, and the equipment for pressurization becomes a large scale and is not practical. It can be seen that the range of 50 to 500 kPa is significantly smaller than the pressure applied (15 to 30 MPa), which has been conventionally performed using a piston that matches the size of the mold.

  In the method of pressurizing using a piston when forming a round bar, since the raw material in the mold remains almost liquid at the beginning of polymerization, the piston is effectively pressurized. In this case, the raw material near the mold surface has already been polymerized and hardened, but in the central part, the degree of polymerization is low and liquid raw material still remains.In the central part, polymerization shrinkage still occurs. It is necessary to press. However, since the piston is pressurized including the part where polymerization has already progressed near the surface of the surrounding mold, a very large pressing force is required to give a sufficient pressing force to the central portion. On the other hand, in the method according to the present invention, the pressure is applied with gas, and the already hardened portion in the vicinity of the mold surface can be pressurized without becoming an obstacle. Therefore, sufficient pressure can be applied with a relatively small pressure. be able to.

  A conical recess 10 is provided on the surface of the lid 6 in contact with the raw material G. The concave portion 10 has a volume equivalent to the polymerization shrinkage amount of the raw material G (for example, preferably 80 to 120% of the polymerization shrinkage amount), and has a through hole 7 at the apex position. When placing in the opening 5 of the cast mold 1, the through hole 7 is placed open, and the raw material G is lowered to a position that fills the recess 10. Then, the raw material G located in the gap between the lid 6 and the mold 1 is polymerized and effective, and a pressurized gas is blown from the through hole 7 in a state where the seal is made. In order to prevent voids and sink marks, pressurization is continued until polymerization is completed and molding is completed. By providing the lid 6 with the recess 10 and placing the raw material G in the concave portion 10, the heat from the mold 1 is not easily transmitted, and the liquid raw material G can be maintained even when the polymerization is completed.

  The raw material cast into the mold 1 is polymerized by heating the polymerizable lactam solution in the cavity 7 for about 20 to 100 minutes while maintaining the low temperature in the range of 130 to 160 ° C.

  The polymerizable lactam solution is obtained by adding an anionic polymerization catalyst and an anionic polymerization initiator to ω-lactam, and the ω-lactam is substantially anhydrous α-piperidone, ε-caprolactam, ω-laurolactam, Alternatively, industrially advantageous lactams, which are mixtures of two or more of these, are ε-caprolactam and ω-laurolactam.

  As the anionic polymerization catalyst, a known ω-lactam polymerization catalyst such as sodium hydride, lithium hydride, sodium, potassium and the like can be used, and the addition amount thereof is 0.1 to 2.0 with respect to ω-lactam. Mol%. Examples of the initiator for anionic polymerization include N-acetyl-ε-caprolactam, isocyanate, diisocyanate, urea derivative, urethane, isocyanurate derivative, and the addition amount thereof is 0.05 to 1. A range of 0 mol% is preferred.

  Also, a method in which an anionic polymerization catalyst is added to ω-lactam and dissolved, and then an anionic polymerization initiator is added and mixed at the time of casting, or ω-lactam containing an anionic polymerization catalyst and an anionic polymerization initiator Are adjusted by a method of adding and mixing at the time of casting.

  In carrying out the method of the present invention, it is also possible to add lubricants such as oils, waxes, zinc stearate, calcium stearate, etc. that do not inhibit polymerization, and reinforcing materials such as carbon fibers and glass fibers, in addition to the above components. is there.

  Next, in order to confirm the effect of the present invention, the molded body obtained in the example in which the production method included in the scope of the present invention was implemented and the comparative example performed in the conventional method were compared.

(Example)
A polymerizable lactam solution was cast as a raw material into a cylindrical mold having an inner diameter of 150 mm and a height of about 1,200 mm adjusted to 150 ° C. to a height of 1,100 mm. Next, it is lowered to the liquid level of the raw material cast with an aluminum lid having a conical recess having an outer diameter of 145 mm, a thickness of 150 mm, an opening diameter of 125 mm and a height of 125 mm on the bottom and a through hole at the apex. Is arranged at a position that fills the substantially conical recess. When 15 minutes passed in this state, since the raw material located in the gap between the lid and the mold was solidified, a nitrogen pipe was connected to the through-hole of the lid and the inside of the cavity was pressurized with a pressure of 200 kPa. After 1.5 hours, the round bar molded body that had been polymerized and solidified was released and cooled.

  As a result of ultrasonic flaw detection on the obtained round bar, it was a good molded body with no internal defects found and almost no sink marks on the upper part.

(Comparative example)
Except that the lid used in the example was not used and no pressurization with nitrogen was performed, the same mold as in the example was used and cast and polymerized in the same manner to obtain a round rod molded body made of polyamide resin. . However, a lid was installed above the liquid level in order to prevent the polymerizable lactam liquid as a raw material from cooling during the polymerization.

  As a result of ultrasonic flaw detection on the obtained round bar molded product, five internal defects having a size of 1 mm or less were found near the center. In addition, sink marks having a depth of 60 mm were observed in the upper part.

  As described above, according to the method for producing a polyamide resin molded body of the present invention, the inside of the molded body can be sufficiently pressurized to obtain a molded body having no internal defects, and there is little sinking at the upper part of the molded body. You can stay in things. Moreover, the pressing force may be smaller than that in the case of using a conventional piston, and can also be applied to molding a large-sized round bar or plate-like body.

  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 is molded while being pressurized with a pressure member during polymerization in order to prevent sink marks due to polymerization shrinkage. This method can be applied to a method for producing a polyamide resin molded product in which defects such as voids are prevented from occurring.

It is the schematic of the type | mold used for the manufacturing method of the polyamide resin molding of this invention. It is sectional drawing when the raw material was cast into the type | mold. It is sectional drawing of the place which has arrange | positioned the lid | cover. It is sectional drawing which shows a mode that mold surface vicinity solidified and solidified. It is sectional drawing of the place which is pressurizing with nitrogen. It is sectional drawing of the place where superposition | polymerization was completed.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Type | mold 2 Side surface 3 Spacer 4 Cavity 5 Opening part 6 Cover body 7 Mold surface vicinity 8 Supply pipe 9 Through-hole 10 Recessed part 11 Polyamide resin molding G Raw material

Claims (3)

  In a method for producing a polyamide resin molded body 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 as a raw material and polymerized by pressurization and heating. After casting the raw material, the lid body is sized to have a gap of 0 to 10 mm from the mold in a state of being fitted into the mold opening, and the lid body having a through hole is arranged so as to contact the raw material, The raw material located in the gap between the mold and the lid is heated and solidifies, and with the lid sealed, a pressurized gas is blown through the through-hole and polymerization proceeds to complete the molding. A process for producing a polyamide resin molded product characterized by comprising:   The said cover body has a recessed part in the surface which contacts a raw material, and when arrange | positioning a cover, it arrange | positions so that this recessed part may be filled with a raw material, and the said through-hole is provided in this recessed part. A method for producing a polyamide resin molded body. The method for producing a polyamide resin molded body according to claim 2, wherein the concave portion has a conical shape, and the through hole is located at the apex of the conical shape.

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