JP3734623B2 - Manufacturing method of polyamide resin molded body - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a polyamide resin molded body having a predetermined shape such as a rod shape or a plate shape by anionic polymerization of lactam, and particularly when there are no internal residual bubbles and when additives such as a filler and a reinforcing material are added, The present invention relates to a method for producing a uniformly dispersed molded body.
[0002]
[Prior art]
In the method in which molten lactam heated to a predetermined temperature is injected into a preheated mold and anion polymerization is performed to form polyamide, a cavity defect called a bubble is generated inside the molded body depending on the size and shape of the molded body. Is a problem.
[0003]
This is due to a large volume shrinkage at the time of molding, and it takes a certain amount of time from the injection of the lactam solution into the mold until the start of polymerization, so the progress of polymerization varies at each site, or convection occurs after the lactam solution is injected. It is considered that one of the factors is that the upper solution temperature rises in the mold height direction and polymerizes from the upper part.
[0004]
In order to prevent the generation of such internal residual bubbles, a method for polymerizing a lactam solution under pressure has been proposed. In addition, when an additive such as a filler or a reinforcing material having a specific gravity different from that of the lactam solution is added, the particle size can be reduced for the problem that it is difficult to obtain a uniformly dispersed molded body that settles during polymerization. The method of increasing the viscosity of the lactam solution has been taken.
[0005]
[Problems to be solved by the invention]
The conventional method for eliminating the internal residual bubbles has been difficult to apply when the molding size is increased or a molded body having a different shape in the height direction is obtained. Furthermore, the equipment cost of the molding apparatus including a metal mold is high, which is a problem in terms of economy.
[0006]
In addition, when various additives are added to the lactam solution, the variation in the polymerization progress rate at each part becomes remarkable, the occurrence rate of internal residual bubbles increases in addition to poor dispersion, and it is difficult to suppress both by the conventional method. It is.
[0007]
[Means for Solving the Problems]
The present invention solves the above problems, and relates to a method for producing a polyamide resin molded body having no internal residual bubbles regardless of the size and shape of the molded body. In the presence of a cocatalyst, a method of producing a polyamide resin molding by injecting heat detection means into the molds provided in the lower, middle and upper parts of the mold, and maintaining the entire mold at a constant temperature The molten lactam was confirmed while detecting the temperature rise from the lower part of the mold to the middle part and the upper part by detecting the temperature rise due to the heat generated by polymerization of the molten lactam injected into the molded mold. The method for producing a polyamide resin molded body is characterized in that the injection speed of the resin is adjusted .
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described with reference to the drawings.
[0009]
FIG. 1 is a perspective view of a molding die used in the present invention, in which a thermocouple 2 is set at three locations of a lower portion, a middle portion, and an upper portion in a molding die 1 having a height of 600 mm, a width of 1200 mm, and a thickness of 20 mm. The entire mold was kept at 160 ° C.
[0010]
In the present invention, specific means for sequentially solidifying the polymer in the mold from the lower part to the upper part of the mold, or the temperature rise due to the polymerization heat of the polymer in the mold from the lower part to the upper part of the mold. As a specific means for sequentially developing, the rate at which the lactam solution is injected into the mold shown in FIG. 1 is adjusted.
That is, while the lactam solution is being injected into the mold, the polymerization reaction of the solution starts at the lower part of the mold and the solidification of the polymerization proceeds. The polymerization reaction generates heat and the thermoelectric set in the lower part of the mold 1. Pair 2 shows the high temperature value.
While confirming the value of this thermocouple, polymerization molding is performed while adjusting the injection rate of the lactam solution into the mold so that the exothermic temperature due to polymerization rises sequentially in the lower, middle and upper portions.
[0011]
FIG. 2 is a graph showing the relationship between the temperature rise of each part in the mold and the time when molten lactam is injected into the mold. It rises, then rises to the middle and upper part, and finally the temperature of each part in the mold becomes a constant value.
[0012]
Thus, polymerization solidification progressed from the lower part to the upper part of the mold, and a polyamide resin molded body having no internal residual bubbles could be obtained. In addition, when a filler having a specific gravity different from that of molten lactam or an additive for a reinforcing material is added, the thickening of the lactam solution is superior to the sedimentation of the additive, so that it can be uniformly dispersed.
[0013]
Here, if the polymerization rate is extremely increased by adjusting the composition and temperature of the lactam solution to be injected, the temperature of the mold, etc., there will be an extreme difference in the polymerization solidification speed in the mold height direction, and the polymer molded product As a result, irregularities appear on the surface of the film, resulting in poor appearance and no uniform physical properties. In addition, when the injection rate is extremely slow, similar defects occur in the polymer molded product.
[0014]
【Example】
Hereinafter, the present invention will be described with reference to examples and comparative examples.
Example 1
As the molding die, a molding die shown in FIG. 1 held at 160 ° C. was used.
In a stainless steel container, 14 kg of anhydrous ε-caprolactam was taken and heated to a temperature of 140 to 160 ° C., to which 33 g of tolylene diisocyanate as a polymerization promoter and 2 kg of graphite were added and mixed. ... Although it is called “Liquid A”, 1 kg of anhydrous ε-caprolactam was taken in another stainless steel container, and 9 g of sodium hydride (63% oily) as a polymerization catalyst was added to this to adjust to 140 to 160 ° C. . …… Using two pumps called “Liquid B”, liquid A is 5.65 kg / min, liquid B is 0.35 kg / min, and molten lactam liquid is poured into the mold at a total injection rate of 6 kg / min. Injected simultaneously. At the same time as the injection, the temperature rise due to the polymerization exotherm of the mixed solution at each part of the mold was measured with the thermocouple 2, and it was expressed sequentially from the lower part to the middle part and the upper part.
In about 30 minutes, the molded body was taken out from the mold and subjected to internal inspection with an ultrasonic flaw detector, but no internal residual bubbles were found. The appearance was also good, and the dispersion of graphite was good at each part of the compact. When the tensile strength was measured according to ASTM D638, it showed a strength of 85 MPa or more, and the difference in each part was within 5 MPa, which was good. In addition, the tensile test piece was extract | collected by making the height direction of a metal mold | die into the length direction of a test piece.
The melted lactam solution injected into the mold was polymerized as the solidification proceeded sequentially from the bottom to the top of the mold.
[0015]
Comparative Example 1
Evaluation was made in the same manner as in Example 1 except that the injection rate ratio of the solution A and the solution B was the same and the total injection rate of the molten lactam solution was changed to 15 kg / min.
The temperature rise due to the polymerization exotherm of the mixed solution in each part of the mold appeared from the top to the middle and the bottom.
The molded body had internal residual bubbles, and the appearance was good, but the dispersion of graphite was poor and the tensile strength was good.
Further, the molten lactam solution injected into the mold proceeded to solidify from the upper part of the mold to the middle part and the lower part.
[0016]
【The invention's effect】
By the present invention, regardless of size and shape, the molded body has no internal residual bubbles, and the outer surface is free of irregularities. Further, when an additive such as a filler or a reinforcing material is added, the polyamide is uniformly dispersed. A compact can be supplied.
[Brief description of the drawings]
FIG. 1 is a perspective view of a molding die used in the present invention.
FIG. 2 is a diagram showing the relationship between the temperature rise and time of each part in the mold when molten lactam is injected into the mold.
[Explanation of symbols]
1 Mold 2 Thermocouple

Claims (1)

The molten lactam in the presence of an anionic polymerization catalyst and a cocatalyst, the thermal detection means of the inner mold bottom, a method is injected into a mold provided in the middle and upper producing polyamide resin moldings, gold The temperature is increased so that the temperature rises from the lower part to the middle part and the upper part of the mold by detecting the temperature rise caused by the heat generated by polymerization of the molten lactam injected into the mold with the whole mold held at a constant temperature. A method for producing a polyamide resin molded article, wherein the injection rate of molten lactam is adjusted while confirming the rise .

Images