JPH1067023A - Manufacture of casting polyamide resin molded object - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent that a cavity part or flow pattern is formed to the upper layer of a molded object by dripping liquid paraffin on the surface of polymerizable lactam liquid injected into a mold to form a film before polymerizing the lactam liquid. SOLUTION: Immediately after a polymerizable lactam liquid is injected into a mold 5, the lid of the mold 5 is opened and a predetermined amt. of heated liquid paraffin is dripped on the lactam liquid to form a film 10 and, after the lid is again closed, the mold 5 is introduced into an oven of which the atmospheric temp. is regulated to 100-210 deg.C, pref., 130-180 deg.C to advance the polymerization of the lactam liquid. The film thickness of liquid paraffin is set to 0.2-5.0mm. By this method, it can be prevented that a cavity part or flow pattern is formed to the upper layer of a molded object.

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 in an upper layer. The present invention relates to a method for producing a cast polyamide resin molded article effective for producing such a rod-shaped molded article.

[0002]

2. Description of the Related Art In a method of manufacturing a cast polyamide rod-shaped molded body, a cylindrical mold is heated to a predetermined temperature in a hot blast stove, and the mold is removed from the furnace to remove a polymerizable lactam liquid. The lactam was injected into the mold, and the mold was placed in a hot-blast furnace again to polymerize the lactam. The obtained cast polyamide rod-shaped molded product is the most representative engineering plastic, and has excellent mechanical strength, impact resistance, heat resistance, chemical resistance, and good moldability. Used as many mechanical parts such as boards.

However, according to this method, since the polymerizable lactam liquid injected into the mold is in contact with air, the difference in polymerization shrinkage due to the temperature difference between the inner layer and the upper layer, the inhibition of polymerization due to moisture in the air, Alternatively, the oxidative deterioration of the polymerizable lactam liquid causes cavities and flow patterns to occur frequently on the upper part of the rod-shaped body, and the upper part of the rod-shaped body is unavoidably cut to a predetermined length and shipped as a product. For this reason, conventionally, a method of replacing the air layer in contact with the polymerizable lactam liquid injected into the mold with heated nitrogen has been adopted.

[0004]

However, since the volume of the polymerizable lactam liquid changes during the polymerization process, the mold lid cannot be closed, and thus the above method cannot provide a sufficient effect of nitrogen replacement. Further, a method has been proposed in which heated nitrogen is continuously fed into the mold during the polymerization process. However, equipment costs are increased and there is a problem in terms of economic efficiency. The present invention has been made to solve such problems, and by fully considering the characteristics of the polymerization process of the polymerizable lactam liquid, a cast polyamide resin free of void defects such as air bubbles and a flow pattern in an upper layer. An object of the present invention is to provide a manufacturing method capable of obtaining a molded body.

[0005]

That is, the invention of claim 1 of the present application provides a substantially anhydrous ω-lactam with a polymerizable lactam liquid comprising at least an anionic polymerization catalyst and an anionic polymerization initiator in a mold. In the anionic polymerization, after forming a film by dropping liquid paraffin on the surface of the polymerizable lactam liquid injected into the mold, there is a method for producing a cast polyamide resin molded body in which the polymerization proceeds, particularly the liquid paraffin After the film was formed, polymerization was carried out, whereby a cavity and a flow pattern could be prevented in the upper layer of the molded article.

According to the invention of claim 2 of the present application, the thickness of the liquid paraffin is set to 0.2 to 5.0 mm so that the polymerizable lactam liquid injected into the mold is kept warm and the air is cut off. Polymerization can be carried out uniformly and uniformly, and a cast polyamide resin molded article free of void defects such as air bubbles in the upper layer can be obtained more reliably.

[0007] The invention according to claim 3 of the present application is the invention in the range of 80 to 140 °.
C. A liquid paraffin heated to C is dropped to form a film, and the temperature difference between the heated liquid paraffin film and the polymerizable lactam liquid injected into the mold is reduced, so that a cavity like an air bubble is more reliably formed in the upper layer. A cast polyamide resin molded article without defects can be obtained.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic view of a polymerization apparatus used in a method for producing a cast polyamide resin molded article according to the present invention. This apparatus 1 is divided into a storage tank 2 in which an anionic polymerization catalyst is put in a molten lactam and a storage tank 3 in which an anion polymerization initiator is put in a molten lactam. A tube 7 equipped with a valve 6 is connected. The molten lactam flowing out of each of the storage tanks 2 and 3 is mixed and stirred in the mixing section 4 and then cast into a mold 5 having a relatively high thermal conductivity such as aluminum or iron heated to 150 to 180 ° C. Is done.

A pipe 8 for supplying nitrogen and a pipe 9 for discharging the nitrogen are provided in each of the storage tanks 2 and 3 so that the pressure in the tanks is always kept constant. A metering pump (not shown) can be installed below the valve 6 provided in each of the storage tanks 2 and 3.

Immediately after casting the polymerizable lactam liquid into the mold 5, the lid of the mold 5 is opened as shown in FIG. 2, and a predetermined amount of heated liquid paraffin is dropped to form the film 10. Then, the mold 5 is closed again and the mold 5 is heated to an ambient temperature of 100 to 21.
After placing in an oven controlled at 0 ° C, preferably 130-180 ° C, the polymerization is allowed to proceed.

In this case, the liquid paraffin is heated to 80 to 140 ° to approximate the temperature of the castable polymerizable lactam liquid.
By heating to C, the temperature of the surface layer of the polymerizable lactam liquid is maintained at the internal temperature without lowering to reduce the temperature gradient between the surface layer and the internal layer so that unreacted monomers do not remain. Also, the thickness of the liquid paraffin is 0.2 to 5.0 m.
m must be set. If the film thickness is less than 0.2 mm,
The effect is small as a heat insulating film and an air blocking film, and cavities and flow patterns frequently occur in the upper layer of the molded body, and cavities and flow patterns are generated in the surface layer of the molded body. On the other hand, if the film thickness exceeds 5.0 mm, the effect of the film thickness is not expected, and it is rather disadvantageous economically.

The liquid paraffin used here is a mixture of a chemically inert colorless, odorless liquid hydrocarbon,
It does not dissolve in the polymerizable lactam liquid, and includes, for example, Christol (trade name) manufactured by Esso Oil Co., Ltd.

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.

[0015] In the above production method, the anionic 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 which do not inhibit polymerization, waxes, lubricants such as zinc stearate, calcium stearate, reinforcing materials such as carbon fiber and wollastonite, polyvinylidene chloride, etc. It is also possible to add a coloring agent.

[0017]

The present invention will be described in more detail with reference to the following examples. Examples 1-3, Comparative Example 1 8.0 kg of substantially anhydrous ε-caprolactam was added at 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.
Pre-heated aluminum inner dimensions 90φ, depth 1000m
m into a cylindrical mold. Thereafter, a predetermined amount of liquid paraffin heated to 85 ° C. was dropped into 0.1 mm,
After forming films of various thicknesses of 0.2 mm, 1.0 mm and 5.0 mm, they were polymerized in a furnace adjusted to 170 ° C. By the temperature sensor stuck on the mold surface,
When the mold surface temperature was lowered by 1 ° C. after the rise in the reaction heat, the molded body was transferred into a furnace adjusted to 50 ° C. while being kept in the mold. After 30 minutes, the compact was removed from the mold. Table 1 shows the results of observation of the upper layer of the molded article after the molded article was sufficiently cooled.

[0018]

[Table 1]

As a result, the thickness of the liquid paraffin was 0.2
At 1.0 mm, 1.0 mm, and 5.0 mm, no cavity or flow pattern was observed in the upper layer of the molded body, but at 0.1 mm, a cavity or flow pattern was observed in the upper layer of the molded body.

Comparative Example 2 Instead of liquid paraffin, 5.9 g of silicone was added dropwise to form a 1.0 mm thick film, which was polymerized in the same manner as in Example 1. And flow patterns were observed.

Comparative Example 3 Instead of liquid paraffin, 5.9 g of polyethylene wax was dropped to form a 1.0 mm-thick film, which was polymerized in the same manner as in Example 1. Parts and flow patterns were observed, and it was observed that the polyethylene wax was dissolved in the upper layer of the molded article.

Comparative Example 4 In place of liquid paraffin, powder of ultra-high molecular weight polyethylene (particle diameter: 0.1 mm) was dropped, and a uniform film was not formed. In this state, polymerization was performed in the same manner as in Example 1. However, cavities and flow patterns were observed in the upper layer of the molded body.

Comparative Example 5 Instead of liquid paraffin, a circular aluminum wheel having a thickness of 0.015 mm and a diameter equal to the inner diameter of the mold was placed on the surface of the polymerizable lactam liquid injected into the mold, and then the process was carried out. When polymerization was carried out in the same manner as in Example 1, no cavity or flow pattern was observed in the upper layer of the molded product, but the diameter of the upper layer was small and thin. Table 2 shows the results of Example 1 and Comparative Examples 2 to 5 described above.

[0024]

[Table 2]

From this result, it can be seen that the liquid paraffin having a predetermined thickness has a large effect as a heat insulating film and an air barrier film, and that no cavity or flow pattern is observed in the upper layer of the molded product.

[0026]

As described above, the invention of claim 1 of the present application is
In anionically polymerizing a polymerizable lactam solution comprising at least an anionic polymerization catalyst and an anionic polymerization initiator onto substantially anhydrous ω-lactam in a mold, liquid paraffin is added to the surface of the polymerizable lactam solution injected into the mold. After forming a film by dropping, a method for producing a cast polyamide resin molded body in which polymerization proceeds is performed.In particular, after forming a film of liquid paraffin, polymerization is performed, so that a cavity or the like is formed in the upper layer of the molded body. There is an effect that the flow pattern can be prevented.

According to a second aspect of the present invention, a liquid paraffin having a film thickness of 0.2 to 5.0 mm is used to keep the polymerizable lactam liquid injected into the mold warm and relatively uniformly polymerize. Thus, there is an effect that a cast polyamide resin molded article free of void defects such as air bubbles in the upper layer can be more reliably obtained.

[0028] The invention of claim 3 of the present application is the invention in which
C. A liquid paraffin heated to C is dropped to form a film, and the temperature difference between the heated liquid paraffin film and the polymerizable lactam liquid injected into the mold is reduced, so that a cavity like an air bubble is more reliably formed in the upper layer. There is an effect that a cast polyamide resin molded article having no defect can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic view of a polymerization apparatus used in a method for producing a cast polyamide resin molded article according to the present invention.

FIG. 2 is a cross-sectional view showing a state in which a polymerizable lactam solution is cast into a mold and then a predetermined amount of liquid paraffin is dropped to form a film.

[Explanation of symbols]

 2 Storage tank 3 Storage tank 4 Mixing 5 Mold 10 Membrane

Claims (3)

[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,
A method for producing a cast polyamide resin article, comprising: forming a film by dropping liquid paraffin on the surface of a polymerizable lactam liquid injected into a mold, and then proceeding with polymerization. 2. A liquid paraffin having a film thickness of 0.2 to 5.0.
The method for producing a cast polyamide resin molded article according to claim 1, wherein 3. The method according to claim 1, wherein liquid paraffin heated to 80 to 140 ° C. is dropped to form a film.