JP3227017B2 - Manufacturing method of cast polyamide resin molded body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a cast polyamide resin molded article, and more particularly, to a cast polyamide resin molded article having no voids such as air bubbles therein, and in particular, a narrow and long molded article. TECHNICAL FIELD The present invention relates to a method for producing a cast polyamide resin molded article effective for producing a molded article.

[0002]

2. Description of the Related Art In a method of manufacturing a cast polyamide rod-shaped product, a cylindrical die is heated in a hot blast stove until a predetermined temperature is reached, the die is taken out of the furnace, and a lactam polymerization solution is discharged. And the mold is again placed in a hot blast stove to polymerize the lactam. However, according to this method, the rod-shaped molded article has a disadvantage that air bubbles are likely to be contained in the center during the polymerization process.
In particular, it is well known that as the cast polyamide rod-shaped molded product becomes thinner and longer, a cavity defect is more likely to occur therein. Usually, volumetric shrinkage of about 15% occurs when the lactam polymerization solution is subjected to anionic polymerization molding. The volume shrinkage has been one of the causes for generating a void defects within the molded body. In the conventional method of manufacturing a cast polyamide rod-shaped molded body, it has been a technically important problem to reduce the occurrence of the above-described cavity defects.

[0003] In order to prevent the occurrence of void defects inside such a molded product, a method of polymerizing a lactam polymerization solution under pressure has conventionally been known. For example, Japanese Patent Publication No. 40-1
As disclosed in US Pat. No. 6,153, there is a method in which a lactam polymerization solution is subjected to pressure molding when the viscosity of the system is increased to a maximum by polymerization. In addition, Tokiko Sho 39
No. -25202 discloses that a mold maintained at a temperature at which polymerization proceeds and an auxiliary container maintained at a temperature at which polymerization does not proceed is insulated, and the auxiliary container is filled with a lactam polymerization solution. Is pressurized by an inert gas, and a lactam polymerization solution is constantly fed into a mold to press-mold a polyamide molded article. Furthermore,
Japanese Patent Publication No. 4-7966 proposes polymerizing a lactam polymerization solution under pressure by a piston.

[0004]

However, according to the conventional method of polymerizing a lactam polymerization solution under pressure, when a long molded article is produced, the pressure loss is extremely large, and the pressure loss is substantially large. The lactam polymerization solution could not be efficiently pressurized, and it was difficult to prevent cavity defects.
In addition, a thick mold that can withstand the pressurization is required, and the pressurizing device is required. Therefore, the equipment cost of the pressurizing device including the mold is increased, and there is a problem in terms of economy. . The present invention is intended to improve such problems, and by sufficiently considering the characteristics of the polymerization process of the lactam polymerization solution, the pressure is applied during the polymerization using a pressurizing mold or a pressurizing device. It is an object of the present invention to provide a production method capable of obtaining a cast polyamide resin molded article having no voids such as air bubbles therein without any problem.

[0005]

Means for Solving the Problems The present inventors consider that volume shrinkage due to crystallization is related to cavity defects in anionic polymerization molding of a lactam polymerization solution. As a result of intensive studies to solve the problem of the occurrence of defects, it was found that a method of cooling the molded article after the completion of the polymerization reaction was one of the solutions, and the present invention was reached. That is, the feature of the present invention is that anionically polymerizing a polymerizable lactam liquid comprising at least an anionic polymerization catalyst and an anionic polymerization initiator in a substantially anhydrous ω-lactam in a mold, into the mold. At the time when the surface temperature of the molded body of the injected polymerizable lactam liquid starts to decrease after the end of the polymerization reaction, the molded body is cooled in a heating medium at 50 to 100 ° C., which is a method for producing a cast polyamide resin molded body. .

According to this method, at the time of molding, the polymer is cooled when the surface temperature of the molded body of the polymerizable lactam liquid starts to fall after rising, so that the crystallization rate and the degree of crystallinity can be appropriately saved. In addition, the occurrence of cavity defects can be controlled. The cooling means is not particularly limited. For example, a mold in which a polymerizable lactam solution is injected is set at 50 to 100 °.
A furnace, hot water, hot air and oil adjusted to C can be used. However, when the polymer is cooled at a temperature lower than 50 ° C., the solidification by cooling from the surface to the inside becomes fast, and the inside becomes a reduced pressure state, and relatively large cavity defects occur. Also,
When cooled at a temperature exceeding 100 ° C., crystallization proceeds further, so that even when cooling and solidification is slow, the amount of shrinkage increases,
The center is in a reduced pressure state, and minute bubble-like cavity defects occur.

[0007] In the conventional method, after the heat generated by the polymerization reaction of the polymerizable lactam solution is terminated, the ambient temperature is usually lower, so that it is cooled from the surroundings and the whitening phenomenon due to crystallization from the surface toward the center occurs. move on. As the crystallization progresses, the center of the soft molded body in the course of crystallization is solidified into a ring shape by crystallization at the periphery, so that the central part is reduced in pressure due to shrinkage stress. For this reason, it is considered that the gas dissolved in the system is vaporized, which becomes the nucleus of the bubble, and grows as the shrinkage progresses to become a cavity defect.

The above-mentioned ω-lactam is substantially anhydrous α-piperidone, ε-caprolactam, ω-laurolactam or a mixture of two or more thereof. Industrially advantageous lactams are ε-caprolactam and ω-laurolactam. Lactam.

The anion polymerization catalyst used in the present invention includes sodium hydride, lithium hydride, sodium,
Known polymerization catalysts for ω-lactams such as potassium can be used, and the amount added is 0.1 to ω-lactam.
~ 2.0 mol%. And, as the initiator for anionic polymerization, for example, N-acetyl-ε-caprolactam,
Isocyanate, diisocyanate, urea derivative, urethane, isocyanurate derivative,
-A range of 0.05 to 1.0 mol% based on lactam is preferred.

In the above production method, the anion polymerization catalyst is used
A method of adding and mixing an anionic polymerization initiator at or after casting after adding and dissolving to a lactam, or injecting ω-lactam containing an anionic polymerization catalyst and ω-lactam containing an anionic polymerization initiator It is adjusted by a method of adding and mixing at the time of molding or after casting. Further, the polymerization temperature of ω-lactam can be carried out at a temperature of 100 to 210 ° C., preferably 130 to 180 ° C.

[0011] Incidentally, in practicing the method of the present invention, oils which does not inhibit polymerization in addition to the above components, waxes, zinc stearate, or a lubricant such as calcium stearate, carbon fiber, a reinforcing material such as U O Las preparative Night It is also possible to add.

[0012]

The present invention will be described in more detail with reference to the following examples. Example 1 8.0 kg of substantially anhydrous ε-caprolactam was added to 100 °
C, and the mixture was heated and melted, and 16 g of sodium hydride (63% oil-based) was added and dissolved therein. This lactam solution was heated to 125 ° C., and 7 g of trisphenyl isocyanurate was quickly mixed.
Aluminum inner dimensions 90φ, depth 1000m
m, and polymerized in a furnace adjusted to 170 ° C. After the mold surface temperature has finished rising due to reaction heat by the temperature sensor attached to the mold surface,
When the temperature drops by 1 ° C, the molded body is kept in the mold for 50 minutes.
Transferred to a furnace adjusted to ° C. After 30 minutes, the compact was removed from the mold. After the molded body was sufficiently cooled, the inside of the molded body was inspected with an ultrasonic flaw detector, and no void defect was recognized.

Example 2 As in Example 1, after the mold surface temperature was raised by the reaction heat and dropped by 1 ° C., the mold was taken out of the furnace and the molded product was released from the mold. This was immersed in hot water at 80 ° C. After 30 minutes, the molded body was taken out, cooled sufficiently, and then inspected with an ultrasonic flaw detector. As a result, no void defect was found.

EXAMPLE 3 900 g of substantially anhydrous ε-caprolactam was added at 100 ° C.
Then, 1.8 g of sodium hydride (63% oil-based) was added thereto and reacted and dissolved. The lactam solution was heated to 125 ° C., and 1.8 g of trisphenyl isocyanurate was quickly mixed.
Inner dimensions 50φ, depth 50 made of aluminum preheated to 0 ° C
The mixture was poured into a 0 mm cylindrical mold and polymerized in a furnace adjusted to 170 ° C. The temperature sensor attached to the surface of the mold causes the mold surface temperature to rise by the reaction heat, and then drops by 1 ° C. When the molded body is kept in the mold, the temperature is controlled to 70 ° C in a furnace. Moved to After 30 minutes, the compact was removed from the mold. After allowing the molded body to cool sufficiently,
When this was inspected with an ultrasonic flaw detector, no cavity defect was recognized.

COMPARATIVE EXAMPLE 1 In Example 1, polymerization was carried out in a furnace at 170 ° C., and after the mold surface temperature was lowered, the molded body was left in the furnace at 170 ° C. for 30 minutes. After being taken out and sufficiently cooled at room temperature, inspection with an ultrasonic flaw detector revealed many internal defects.

COMPARATIVE EXAMPLE 2 In Example 1, polymerization was carried out in a furnace at 170.degree. C., and after rising by reaction heat, the mold was taken out of the furnace when the temperature dropped by 1.degree. After release, remove 10
When immersed in cold water at ° C. and quenched, a large number of large void defects of φ1 mm to φ10 mm were observed inside the molded body.

[0017]

As described above, in the production method of the present invention, after the completion of the polymerization of the polymerizable lactam liquid, the molded body is cooled with a heating medium at 50 to 100 ° C. at the time when the temperature starts to drop, and Since the rate of crystallization and the degree of crystallinity are appropriately saved, the rate of shrinkage and the amount of shrinkage can be suppressed to a range that does not generate bubbles due to the reduced pressure inside the molded article, and a molded article without void defects can be obtained. At the time of polymerization molding, since the degree of reduced pressure inside the molded article is small, the molded article has an effect that a molded article having relatively small internal strain can be obtained.

────────────────────────────────────────────────── ─── Continuing from the front page Examiner Takeshi Sato (56) References JP-A-56-33916 (JP, A) JP-A-1-141914 (JP, A) (58) Fields investigated (Int. Cl. ⁷⁾ , DB name) C08G 69/00-69/50 B29C 39/00-39/44

Claims (1)

(57) [Claims] 1. An anion polymerization in a mold of a polymerizable lactam liquid comprising at least an anionic polymerization catalyst and an anionic polymerization initiator on a substantially anhydrous ω-lactam,
When the surface temperature of the molded article of the polymerizable lactam liquid injected into the mold starts dropping after the polymerization reaction, the molded article is cooled to 5%.
A method for producing a cast polyamide resin molded article, characterized by cooling in a heat medium at 0 to 100 ° C.