JPS6168209A - Molding of polyamide molded shape - Google Patents

Abstract

PURPOSE:To manufacture a molded product free from foams and having a smooth surface by a method wherein lactam and catalyst are injected into heated molds, polymerized, and molded at a low speed compacting, at a high speed compacting by a press equipment. CONSTITUTION:Lactam and catalyst, lactam and co-catalyst are heated and melted at 80-120 deg.C. The mixed liquid is injected into a set of forces composed of the top force 8 and the bottom force 9 which are controlled previously at 140-170 deg.C and the forces are operated by a press assembly 10-12. Manufacture is executed by (a) stock solution 13 injection process, (b) polymerization process, (c) low speed mold compacting process, (d) high speed mold compacting process. When the manufacturing speed of the top force 8 inserted into the inner wall of the bottom force 9 is changed from the low speed to the high speed, foam, etc. in the stock solution 13 are removed at the low speed as the viscosity of the stock solution 13 increases, the manufacturing speed of the top force 8-increases, a molded product 16 having a smooth surface and free from shrink can be obtained.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention provides nylon R using rapid polymerization reaction of lactam.
This relates to an IM resin molding method.

(Public Art) The known art related to the present invention is JP-A-56-3391.
No. 6 ``Method for producing a plate-shaped polyamide molded article'' discloses a method for producing a plate-shaped polyamide molded article by a monomer casting method. That is, in a method in which molten lactam is polymerized in the presence of an alkali catalyst and a co-catalyst in a polymerization molding machine that gives a plate-shaped molded product, a presser lid that can vertically slide between the inner walls of a female mold and a male mold is used. A gap is formed between at least one arbitrary side surface of the presser cover and the inner wall of the male mold facing thereto, and the bottom surface of the presser cover is sloped upward toward the gap. As the polymerization and solidification of the molten lactam progresses, the presser lid is pressed down to an extent that the contents do not overflow to produce a plate-shaped polyamide product. This manufacturing method involves injecting raw materials into a half-open mold, Mold clamping is performed as polymerization progresses, and mold clamping is completed when polymerization is complete, that is, shrinkage is complete, to prevent sink marks, voids, and underfilling.

However, this method of injecting raw materials in a half-open state and clamping the mold as polymerization progresses is difficult because in rapid polymerization reactions, the viscosity changes rapidly as the raw materials polymerize, and the timing of mold clamping and the timing of mold clamping speed must be adjusted. is rarely constant, and this method has the disadvantage that it is difficult to match it to the optimal timing.

(Problems to be Solved by the Invention) Therefore, the present invention provides a technical method for forming a molded product that does not cause any sink marks, voids, or underfilling when press molding is performed using a mold using the monomer casting method. This is a subject to be addressed.

[Structure of the invention]

(Means for solving the problem) The technical means taken to solve the above technical problem are:
Nylon RI using rapid polymerization reaction of caprolactam
In the production of M resin molded products, the stock solution is mixed and injected into a half-opened mold, held for a certain period of time, and then the press ram is lowered at low speed, and the processing pressure is automatically set at a preset timing when polymerization shrinkage is almost complete. The molded product is manufactured by switching the molding press ram from low speed to high speed.

(Operation) The above technical means operates as follows. That is, lactam and catalyst, lactam and cocatalyst are heated at 80°C to 120°C.
The mixed liquid is injected into a mold consisting of an upper mold and a lower mold which are heated and melted at 140 to 170°C, and the mold is operated by a press device. (Al stock solution injection step) , (blii joining process, (C) low-speed mold clamping process, (d) high-speed mold clamping process,
By rapidly changing the machining speed of the upper mold inserted into the inner wall of the lower mold from low speed, air bubbles etc. in the stock solution are removed at low speed, and as the viscosity of the stock solution increases, the processing speed of the upper mold is increased. , to produce molded products with smooth surfaces and no sink marks.

(Example) Examples will be described below. 2 is the present apparatus, 2 is an injection device, 3 and 4 are tanks with a stirrer, and lactam and catalyst, lactam and co-catalyst are heated and melted at 80°C to 120°C.

5 is a pump, 6 is a mixture injection head, 7 is a mold, and upper mold 8. It is divided into a lower mold 9, and the lower mold has an injection port 9a. 10 is a press, 11 is a press-ram, and 12 is a hydraulic pressure generator for the press.

In the above configuration, its function is as follows: (a) Stock solution injection step A specified amount of stock solution is poured into the lower mold. 13 is the stock solution in the lower mold.
33 is its surface.

(b) Polymerization step Immediately after injection of the stock solution, the upper mold 8 is lowered by the press ram 11. Immediately after injection, the undiluted solution has an extremely low viscosity, and it is maintained in this state for a certain period of time. When the undiluted solution becomes viscous (state 14), the press ram 11 starts to descend at low speed, and at the same time, air bubbles in the undiluted solution are degassed. do.

(c) Low-speed mold clamping process On the other hand, the stock solution in the mold rapidly increases in viscosity from a viscous state as polymerization progresses, and when the polymerization reaches the final stage, that is, state 15 where shrinkage due to polymerization is almost completely completed. The processing pressure of the press 10 increases rapidly.

(d) High-speed mold clamping process The processing pressure at this point is set in advance, and the moment this pressure is reached, the processing speed of the press ram 11 is automatically switched to high speed, changing the mold state from (c) to (d) at once. The mold is clamped until the end, the shaping is completed, and the molded article 15 is formed.

In the lactam, catalyst, and cocatalyst used as raw materials in the present invention, a lactam having a five-membered ring or more is used as the lactam. For example, pyrrolidone.

These include caprolactam, laurolactam, todecanolactam, etc., and two or more of these lactams may be used in combination.

Catalysts are alkali metals, alkaline earth metals, and their hydrogen compounds or organic compounds. Furthermore, examples of co-catalysts include acyl compounds, finite isocyanates, and carposisides.

Example-1 One tank of ε-caprolactam was added to each of the two tanks of the injection device.
0 kg was added, approximately 140 g of 1.5 mol% sodium tyrate was added as a catalyst to one tank, and 1°5 of N, acetyl ε-caprolactam was added as a co-catalyst to the other tank.
After adding about 400 g of mol%, it was heated and melted at 95°C. On the other hand, the molding die has a box-shaped cavity with a wall thickness of 400L x 200W x 70H, and the temperature is controlled to 160°C using a heating medium.

Next, connect this molding mold to the head of the injection device, mix the liquid, and inject about 500g into the half-opened mold.
160T until the upper part of the mold comes into contact with the liquid surface immediately after injection.
The press ram of the ON press was lowered, and the gap between the upper and lower molds was held at approximately 19+n, and this state was maintained for approximately 2 minutes. After holding for 2 minutes, the stock solution becomes viscous to the point where it does not flow.From this point, the press ram starts to descend at a low speed of 0.1 crane/sec, and after about 60 seconds, the descending pressure suddenly increases to 30T.
As soon as it reaches ON, the press automatically starts at a high speed of 5m/s.
After switching to eC and completing mold clamping, a processing pressure of about 607 ON was applied, and the molding was completed in 4 minutes as a total cycle, yielding a good molded product with no voids or sink marks.

[Brief explanation of the drawing]

FIG. 1 is a simplified explanatory diagram of the entire apparatus according to the present invention, and FIG. 2 is a cross-sectional view of a mold for this manufacturing method, in which (a) is the stock solution injection process, (b) is the polymerization process, and (c) is a low-speed mold clamping process, (
D) is a high-speed mold clamping process.

Claims (1)

[Claims] A method in which a stock solution consisting of a molten lactam, a catalyst, and a co-catalyst is mixed and polymerized in a mold consisting of an upper mold and a lower mold in a polyamide molding apparatus comprising an injection device and a press device, (b) Immediately after injection of the stock solution, the upper mold is lowered and held for a certain period of time, and when the stock solution becomes viscous, the press ram is moved at low speed. (c) a polymerization process in which the viscosity of the stock solution rapidly increases in the mold and the downward pressure of the press is rapidly increased after contraction due to polymerization has finished; (d) A molding process for a polyamide molded product, which molds the molded product in a molding process comprising: a mold clamping step in which the descending speed of the press ram increases to a high speed to clamp the mold when the descending pressure reaches a constant pressure.