JPH10235660A - Manufacture of bucket-shape cast polyamide resin formed body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method for a comparatively thin bucket- shape boxy cast polyamide resin formed body without internal defect, in which the temperature controlling of the mold is easy. SOLUTION: In order to manufacture thin bucket-shape cast polyamide resin formed body, after a polymerizable lactam liquid is poured in a bottom mold 15 heated with circulating heating medium, a top mold 1 heated similarly with the circulating heating medium is fitted to the bottom mold 15 so as to reduce the volume between the top mold 1 and the bottom mold 15, between which the polymerizable lactam liquid is housed, by moving either one of the molds during a process ranging from a time point, at which the temperature rise of a system reaches equibrium due to the polymeric heat generation of the polymerizable lactam liquid, to a time point, at which the temperature of the system after the above-mentioned heat generation starts to descend due to the recrystallization of the liquid. After the further processing of the polymerization of the liquid, the polymerization is brought in an end. After that, the top mold 1 and the bottom mold 15 are separated from each other so as to remove a formed body.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a cast-shaped bucket-shaped polyamide resin molded article, and more particularly, to a method of manufacturing a cast-shaped box-shaped cast polyamide resin molded article having a relatively thin thickness without internal defects. It is about the method.

[0002]

2. Description of the Related Art In a method for producing a cast polyamide molded article, a mold is heated to a predetermined temperature in a hot blast stove, the mold is taken out of the furnace, a lactam polymerization solution is poured into the mold, and the mold is again heated. The lactam is polymerized by placing the mold in a hot blast stove. However, according to this method, there is a drawback that the molded body tends to contain bubbles in the polymerization process. Usually, volumetric shrinkage of about 15% occurs when the lactam polymerization solution is subjected to anionic polymerization molding. This volume shrinkage has been one of the causes of generating cavity defects inside the compact. In the conventional method for producing a cast rod-shaped molded article, it has been a technically important task to reduce the occurrence of the above-mentioned internal defects.

[0003] In order to prevent the occurrence of such internal defects in a molded article, a method of polymerizing a lactam polymerization solution under pressure has been conventionally known. For example, Japanese Patent Publication No. 40-16153
As disclosed in Japanese Patent Application Laid-Open Publication No. H10-209, 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, Japanese Patent Publication No. 39-252
No. 02, insulated connection between a mold maintained at a temperature at which polymerization proceeds and an auxiliary container maintained at a temperature at which polymerization does not proceed, encloses the lactam polymerization solution in the auxiliary container There is disclosed a method of press-molding a polyamide molded article by pressurizing with an inert gas so that a lactam polymerization solution is always fed into a mold.

[0004]

However, in the method of manufacturing a molded article such as a bucket having a relatively small thickness, the outer mold and the inner mold are used.
The height of the polymerizable lactam liquid cast between the outer mold and the inner mold fluctuates due to the movement of the inner mold during the initial stage of polymerization, and it is substantially difficult to manufacture buckets with good dimensional stability such as thickness. there were. Also, when polymerizing in an oven, the mold is taken out of the oven when casting the polymerizable lactam liquid,
It is difficult to control the temperature in the mold and the oven, and the heat capacity of the upper and lower molds is different. Therefore, it is very difficult to control the temperature of the mold by the oven heating method.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and is intended to provide a box-shaped cast polyamide resin molded article such as a bucket having a relatively small thickness, which facilitates temperature control of the mold and has no internal defects. It is to provide a manufacturing method.

[0006]

That is, the invention according to claim 1 of the present application is a method for forming a polymerizable lactam liquid obtained by adding at least an anionic polymerization catalyst and an anionic polymerization initiator to substantially anhydrous ω-lactam. In the method for producing a bucket-shaped cast polyamide resin molded article by anionic polymerization after casting, the polymerizable lactam liquid is cast into a lower mold heated by a circulating heat medium, and then circulated in a similar manner. The upper mold heated by the medium and the lower mold are fitted to each other, and when the temperature rise of the system due to the heat generated by the polymerization of the polymerizable lactam liquid reaches an equilibrium, the temperature of the system after the heat generated by the crystallization starts to decrease. In the meantime, one of the molds is moved so as to reduce the volume of the upper mold and the lower mold in which the polymerizable lactam liquid is contained, and the polymerization is further advanced to complete the polymerization. Molded separately from mold There the production method of the bucket-shaped casting polyamide resin molded body taken out, the temperature of the mold is uniform,
In addition, the polymerizable lactam liquid is poured into the mold, and from the time when the temperature rise of the system reaches equilibrium due to the heat generation of the polymerization system until the time when the temperature of the system after the heat generation accompanying the crystallization starts to decrease, Since the volume in the mold containing the polymerizable lactam liquid is reduced, it is possible to obtain a molded article having a uniform thickness and preventing the occurrence of internal cavity defects.

[0007] The invention according to claim 2 of the present application relates to a method in which the temperature from the time when the temperature rise of the system due to the polymerization heat of the polymerizable lactam liquid reaches an equilibrium to the time when the temperature of the system after the heat generation accompanying the crystallization starts to decrease. This is a method for producing a bucket-shaped cast polyamide resin molded article having a range of 155 to 170 ° C.

According to a third aspect of the present invention, the heat medium chambers provided in the upper mold and the lower mold are provided with at least one partition plate forming a flow path of the heat medium. By preventing the stagnation, the temperature of the upper mold and the lower mold can be further adjusted.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a plan view of an upper die used in a method for producing a bucket-shaped cast polyamide resin molded article of the present invention, FIG. 2 is a sectional view taken along the line AA of FIG. 1, and FIG. FIG. 4 is a plan view of a lower mold used in the method for producing a bucket-shaped cast polyamide resin molded product of FIG.

The upper die 1 includes a main body 2 made of aluminum, iron or the like having a relatively high thermal conductivity, and a molded portion 3 projecting outward from the main body 2.
A closed heat medium chamber 5 in which a heat medium such as oil flows by fixing the upper plate 4 to the main body 2 with screws or the like is provided inside the molded portion 3. The heat medium chamber 5 is provided with a partition plate 6 therein to improve the flow of the heat medium. In the embodiment, the heat medium chamber 5 is divided into four chambers 7 by a cross plate 6 provided in a cross shape, and is discharged from the inlet 8. The heat medium is circulated to the outlet 9 to accurately control the temperature.

The lower die 15 has a recessed accommodation portion 17 into which the protruding molded portion 3 of the upper die 1 is fitted, and a closed heat medium chamber 18 through which a heat medium flows is formed by an outer wall 19 outside. . A heat insulating material (not shown) is attached to the outer wall 19. A partition plate 20 is also provided in the heat medium chamber 18 so that the heat medium flowing from the inlet 21 flows smoothly without stagnation and flows out from the outlet 22 to the outside.

FIG. 5 shows a state in which the upper mold 1 and the lower mold 15 are respectively set in a molding machine 25. According to this, the upper mold 1 is fixed in position to the support portion 26, and the lower mold 15 is
The movable table 28 mounted on the movable table 28 connected to the ball screw 29 is moved up and down by the operation of the motor 27 to be fitted or separated from the upper mold 1.

FIG. 6 shows a state in which the lower die 15 is raised and fitted to the upper die 1, and FIG. 7 shows a state in which the lower die 15 is lowered to take out the molded body 30 from the upper die 1.

Thus, in this embodiment, the ω-lactam is dehydrated in a dehydration tank under reduced pressure to make it substantially anhydrous, and then replaced with an inert gas such as nitrogen. The ω-lactam in the dehydration tank is weighed into two casting tanks, and then a predetermined amount of an anion polymerization catalyst is added to the ω-lactam.
One casting tank containing lactam and a predetermined amount of an anionic polymerization initiator are charged into the other casting tank containing ω-lactam. And the upper mold 1 for forming the bucket
And the lower mold 15 are prepared, and the upper mold 1 and the lower mold 15 are respectively set at predetermined positions of the molding machine 25 as described above.

After the polymerizable lactam liquid discharged from each casting tank is mixed and stirred in the mixing section, it is poured into a lower mold 15 whose temperature is controlled at 130 to 160 ° C. as shown in FIG. 15 is raised by the operation of the prime mover 27 and fitted to the upper mold 1 to form a cavity 32 between the lower mold 15 and the upper mold 1. This state is shown in FIG.
A gap 33 of about 2 to 5 mm is provided between the lower mold 15 and the upper mold 1. This gap 33 can be freely adjusted by the prime mover 27.

A lower mold 15 in which a polymerizable lactam liquid is temperature-controlled.
As shown in FIG. 10, the temperature of the system rises due to the polymerization heat of the polymerizable lactam solution, but after a certain period of time, the temperature of the system after the heat generation due to crystallization decreases from time A when the temperature reaches almost equilibrium. The lower mold 15 is slightly raised and brought into close contact with the upper mold 1 until a time point B at which the operation is started. At this time, the molded body 30 is in a pressurized state, and as crystallization proceeds further, the volume of the molded body 30 gradually shrinks, so that the molded body 30 has a uniform thickness with no void defect inside. Can be finished.

If the lower mold 15 and the upper mold 1 are brought into close contact with each other until the temperature of the above-mentioned system reaches substantially equilibrium, the polymerizable lactam liquid flows because the viscosity has not sufficiently increased at the initial stage of the polymerization, and the molded product is molded. When the lower mold 15 and the upper mold 1 are brought into close contact with each other after the thickness of the lactam becomes insufficient or the temperature of the system after heat generation due to crystallization starts to decrease, the crystallization of the polymerizable lactam solution proceeds and the volume shrinks greatly. Therefore, the pressure is insufficient and not only a cavity defect is generated inside the molded body, but also a concave portion is easily generated on the appearance of the molded body. The temperature range from the point A at which the temperature rise of the system due to the heat generated by the polymerization of the polymerizable lactam liquid reaches equilibrium to the point B at which the temperature of the system after the heat generated by the crystallization starts to fall is specifically 155 to 170 °. C, which is approximately equal to the mold temperature. When measuring the mold temperature, it is preferable to embed a temperature sensor (not shown) in one or both of the upper mold 1 and the lower mold 15.

Generally, the relationship between the polymerization time of the polymerizable lactam liquid and the system is shown in FIG. 10 as a model diagram showing the relationship between the polymerization time of the polymerizable lactam liquid and the system. It consists of two stages, a stage and a later stage of crystallization heat generation. First, the temperature of the system rises due to the heat generated by polymerization of the polymerizable lactam liquid, and after a certain period of time, the temperature rise of the system reaches almost equilibrium. This point is A. After that, the exothermic curve falls, but instead rises again due to the appearance of the exotherm accompanying the crystallization of the polymerizable lactam liquid, and then starts to fall smoothly. The point at which this descent begins is B. From time A, when the temperature rise of the system reaches equilibrium, to time B, at which the temperature of the system after heat generation due to crystallization starts to decrease, reducing the volume in the mold is caused by the subsequent crystallization shrinkage. It became clear that it would prevent the generation of the internal space that occurs at the time.

The 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.

Further, the anionic 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 ω
A method of adding and mixing an anionic polymerization initiator at or after casting after adding and dissolving to a lactam, or injecting an ω-lactam containing an anionic polymerization catalyst and an 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.

In carrying out the method of the present invention, other than the above components, oils, waxes, lubricants such as zinc stearate and calcium stearate, and reinforcing materials such as carbon fiber and wollastonite which do not inhibit polymerization may be added. It is possible.

[0023]

The present invention will be described in more detail with reference to the following examples. Examples 1-2, Comparative Examples 1-2 After dehydration, ε-caprolactam in the dehydration tank was weighed and put into two casting tanks, 1,250 g into one casting tank and the other casting tank. After adding 1,250 g to the casting tank, 5 g of sodium hydride (6
(3% oil) was added and dissolved, and 7 g of trisphenyl isocyanurate was further added to the other casting tank.
During this time, the polymerizable lactam solution was mixed while the temperature was raised to 125 ° C. while flowing nitrogen in the casting tank under atmospheric pressure.

An upper mold and a lower mold made of aluminum (length: 200 mm, width: 305 mm, depth: 160 mm) are set on a molding machine, heated to 150 ° C. with oil, and the above-mentioned mixed polymerizable lactam solution is placed in an outer mold. After pouring, the lower mold was raised and fitted to the upper mold, and polymerized in a state where a gap of about 8 mm was provided between the upper mold and the lower mold. Then, after 3 minutes, 8 minutes, 12 minutes, and 15 minutes have elapsed after casting the polymerizable lactam liquid,
The polymerization was completed by bringing the upper mold and the lower mold into close contact, and the lower mold was lowered to take out a 6 mm-thick bucket molded body. FIG. 11 shows the polymerization time of the polymerizable lactam liquid and the temperature of the system in this example. The time A at which the temperature rise of the system reached equilibrium was 5 minutes,
Further, the time point B at which the temperature of the system after the heat generation accompanying the crystallization starts to decrease is 12 minutes.

After the molded body was sufficiently cooled, the results of observing the inside with naked eyes and observing cavity defects are shown in Table 1.

[0026]

[Table 1]

As a result, the polymerizable lactam solution was cast into 8
When the upper mold and the lower mold were brought into close contact with each other after a lapse of 12 minutes and 12 minutes, no internal cavity defect was observed in the molded body. Was not sufficiently raised, the polymerizable lactam liquid overflowed, and insufficient thickness of the molded article and internal cavity defects were observed. Also,
After 15 minutes from casting of the polymerizable lactam liquid, crystallization shrinkage has started, and the pressurization of the molded body during polymerization is insufficient, so that only void defects are generated inside the molded body. No recesses were formed in the appearance of the molded product.

Comparative Example 3 The same polymerizable lactam solution as in Example 1 was added with
After pouring into the lower mold heated to 50 ° C, raise the lower mold and fit it into the upper mold to polymerize with 8 mm gap between the upper and lower molds, and complete the polymerization in that state did. Observation of cavity defects of the obtained molded body revealed that void defects were present in the entire inside of the molded body, and a concave portion was also generated in the appearance of the molded body.

[0029]

As described above, according to the first aspect of the present invention, the polymerizable lactam liquid is poured into the lower mold heated by the circulating heat medium, and then the upper mold heated by the circulating heat medium. And the lower mold are fitted to each other, from the time when the temperature rise of the system due to the heat generated by the polymerization of the polymerizable lactam liquid reaches an equilibrium to the time when the temperature of the system after the heat generated by the crystallization starts to decrease, After moving one of the molds so as to reduce the volume of the upper mold and the lower mold in which the acidic lactam liquid is contained, and further proceeding the polymerization and terminating the polymerization, the upper mold and the lower mold are separated. In the method of manufacturing a bucket-shaped cast polyamide resin molded product to take out the molded product, the temperature of the mold is uniform, and the polymerizable lactam liquid is poured into the mold. The temperature of the system after the heat generated by the crystallization Until the time to begin, in order to reduce the volume of the mold containing the polymerizable lactam solution, it is possible to obtain a blocked the generation of the internal cavity defects with a uniform thickness molded body.

Further, in the invention according to claim 2 of the present application, from the time when the temperature rise of the system due to the heat generated by the polymerization of the polymerizable lactam liquid reaches an equilibrium, to the time when the temperature of the system after the heat generated by the crystallization starts to decrease. Is in the range of 155 to 170 ° C., and by detecting this temperature with the mold temperature, one of the upper mold and the lower mold can be accurately moved.

According to a third aspect of the present invention, the heat medium chambers provided in the upper mold and the lower mold are provided with at least one partition plate for forming a flow path of the heat medium. By preventing the stagnation, the temperature of the upper mold and the lower mold can be further adjusted.

[Brief description of the drawings]

FIG. 1 is a plan view of an upper mold used in a method for producing a bucket-shaped cast polyamide resin molded article of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a plan view of a lower mold used in the method for producing a bucket-shaped cast polyamide resin molded article of the present invention.

FIG. 4 is a sectional view taken along line BB of FIG. 3;

FIG. 5 is a view showing a state in which an upper mold and a lower mold are respectively installed in a molding machine.

FIG. 6 is a view showing a state where the lower mold is raised and fitted to the upper mold.

FIG. 7 is a view showing a state in which a lower die is lowered to take out a molded body.

FIG. 8 is a cross-sectional view showing a state where the lower mold and the upper mold are fitted to each other with a gap provided between them.

FIG. 9 is a cross-sectional view showing a state in which a lower mold and an upper mold are in close contact with each other.

FIG. 10 is a representative graph showing a model of the relationship between the polymerization time of a polymerizable lactam liquid and the temperature of the system.

FIG. 11 is a graph showing the relationship between the polymerization time of the polymerizable lactam liquid and the temperature of the system in Example 1.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Upper die 2 Main body 3 Molding part 4 Upper plate 5 Heat medium chamber 6 Partition plate 8 Inlet 9 Outlet 15 Lower die 17 Housing part 18 Heat medium chamber 19 Outer wall 20 Partition plate 21 Injection 22 Outlet 30 Molded object

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08G 69/18 C08G 69/18 // B29K 77:00 B29L 22:00

Claims (3)

[Claims] 1. A bucket-shaped cast polyamide obtained by casting a polymerizable lactam liquid obtained by adding at least an anionic polymerization catalyst and an anionic polymerization initiator to substantially anhydrous ω-lactam, and then performing anionic polymerization. In the method for producing a resin molded article, after casting the polymerizable lactam liquid into the lower mold heated by the circulating heat medium, the upper mold and the lower mold heated by the circulating heat medium are fitted together, The upper mold containing the polymerizable lactam liquid between the time when the temperature rise of the system due to the heat generated by polymerization of the polymerizable lactam liquid reaches an equilibrium and the time when the temperature of the system after the heat generation due to crystallization starts to decrease. A bucket characterized in that one of the molds is moved so as to reduce the volume of the mold and the lower mold, polymerization is further advanced to complete the polymerization, and then the upper mold and the lower mold are separated to take out a molded body. Shape cast polyamide Method for producing a resin molded article. 2. The temperature range from the point in time when the temperature rise of the system due to the heat generated by the polymerization of the polymerizable lactam liquid reaches an equilibrium to the point in time when the temperature of the system after the heat generated by the crystallization starts to decrease is 155.
The method for producing a bucket-shaped cast polyamide resin article according to claim 1, wherein the temperature is from 170 to 170 ° C. 3. The bucket-shaped cast polyamide resin molded article according to claim 1, wherein at least one partition plate forming a flow path of the heat medium is provided in the heat medium chambers provided in the upper mold and the lower mold. Manufacturing method.