JPS6241526B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a polyamide composition containing melamine cyanurate. It is already known that melamine cyanurate imparts an excellent flame retardant effect to polyamide (Japanese Patent Application Laid-Open No. 53-31759). Compared to the method of adding melamine and cyanuric acid separately or in combination to polyamide, this method shows the effect of being able to significantly suppress so-called plate-out and blooming phenomena, but transparency is lost and The inherent properties of polyamide are significantly impaired, such as poor colorability and poor molding fluidity. It also has the disadvantage that weld lines appear on injection molded products, impairing their commercial value. On the other hand, the present inventors have found that by adding melamine and cyanuric acid to polyamide under water-containing conditions during polymerization, a melamine cyanurate-containing polyamide composition can be obtained all at once, and the composition thus obtained can be used in the conventional method described above. It has been found that the dispersion state of melamine cyanurate is essentially a heterogeneous composition with no defects. This method has made it possible to economically advantageously produce flame-retardant polyamide compositions of extremely good quality, and it is said that good results can be obtained with approximately equimolar amounts of melamine and cyanuric acid. I was just gaining knowledge. However, based on this knowledge, when the reaction is carried out under normal polyamide polymerization conditions, air bubbles are likely to be mixed into the resulting composition;
It is very difficult to obtain a product with high commercial value that is free from air bubbles. This trend is especially true for nylon 66,
This is noticeable when polymerization is performed at relatively high temperatures, such as copolymers whose main components are nylon 6 and nylon 66. As a result of further investigation, we found that there is a close relationship between the molar ratio of melamine and cyanuric acid added to the reaction system and the rate of bubble inclusion, and that air bubbles can be prevented from being included in an extremely limited range of approximately equimolar amounts. We found that there are areas that show significant effects. That is, the present invention comprises a polyamide-forming monomer, cyanuric acid, and melamine in an amount of 1.02 to 1.15 times the molar amount of the cyanuric acid, in the presence of an amount of water necessary to cause an addition reaction between melamine and cyanuric acid. The present invention provides a method for producing a melamine cyanurate-containing polyamide composition by heating and reacting the composition. In the method of the present invention, well-known lactams, polymerizable ω-amino acids, combinations of diamines and dibasic acids can be used as polyamide-forming monomers, and specific examples include ε-caprolactam. , aminocaproic acid, enantholactam, 7-aminoheptanoic acid, 11-aminoundecanoic acid, 9-aminononanoic acid, α-pyrrolidone,
α-piperidone and hexamethylenediamine,
Combinations of diamines such as nonamethylene diamine, undecamethylene diamine, dodecamethylene diamine, and metaxylylene diamine with dicarboxylic acids such as terephthalic acid, isophthalic acid, adipic acid, sebacic acid, dodecanedicarboxylic acid, and glutaric acid are included. Ru. Particularly preferred are nylon 66, nylon 6, and copolymer-forming monomers thereof. Melamine and cyanuric acid are added to the reaction system in a strictly limited amount relationship such that melamine is 1.02 to 1.15 times the molar amount of cyanuric acid, thereby achieving the remarkable effect of preventing air bubbles from being mixed in. Cyanuric acid includes both enol and keto forms. Melamine and cyanuric acid may be added by any appropriate method, such as adding both in the form of fine powder or in the form of a slurry. It is added before high molecular weight polyamide is produced in the polymerization system, usually when monomers or oligomers are present.
Therefore, the copolymer-forming monomer in the present invention includes not only monomers in the narrow sense as exemplified above but also oligomers thereof. The amount of melamine and cyanuric acid added is preferably 2 to 25% by weight as melamine cyanurate in the final composition. If it is less than 2% by weight, sufficient flame retardant effect cannot be imparted, and if it exceeds 25% by weight, it is impossible to impart clear coloring using a normal amount of pigment during coloring molding, and molding fluidity is poor. Such shortcomings appear. When carrying out the method of the present invention, the presence of water in the polymerization system is essential. The amount of water is the amount necessary for causing the addition reaction between melamine and cyanuric acid, and is usually added in an amount of 5% by weight or more in the polymerization system. The method of the present invention is carried out by heating such a system, and it is desirable that the heating temperature be in the range of 200 to 300°C and avoid high temperature conditions as much as possible. The bubble-free flame-retardant polyamide obtained in this way has melamine cyanurate finely dispersed in the polyamide, but a composition obtained by mechanically mixing melamine cyanurate into a separately manufactured polyamide It differs not only in the size but also in the shape of the dispersed particles, and can be said to be a completely different composition. The flame-retardant polyamide of the present invention not only has excellent flame retardancy but also extremely excellent mechanical properties, colorability, and molding fluidity. In addition, the injection molded product has almost no weld lines, which were considered unavoidable in the past, and has extremely high commercial value. Next, the present invention will be explained with reference to Examples. The tests and measurement methods in each example are as follows. (1) Measurement of degree of polymerization of polyamide The relative viscosity ηr of a polyamide solution was determined according to JIS-K6810. (2) X-ray diffraction measurement A flat plate of the sample was molded, and the molded flat plate was placed on a Geigerflex DS model X-ray diffractometer (manufactured by Rigaku Denki) to draw a diffraction pattern in the diffraction angle range of 5 to 40° using a copper target. cyanurate, melamine,
The presence or absence of cyanuric acid was determined by the diffraction peak unique to cyanuric acid. (3) Flame retardancy A UL-94 vertical combustion test was conducted. (4) Colorability 97.5 parts by weight of pellets of the test composition were blended with 2.5 parts by weight of nylon pellets of a color masterbatch for black coloring (trade name Leona LCO20-M3300; manufactured by Asahi Kasei Corporation) and injection molded. The degree of blackness of the obtained molded product was observed with the naked eye, and Hunter whiteness was measured using a color difference meter. (5) Measurement of bubble inclusion rate After thoroughly mixing the obtained polyamide composition pellets, about 20 g of the pellets were sampled and the specific gravity d of the pellets was measured. The air bubble inclusion rate (%) was calculated from the pellet specific gravity do with no air bubbles and the specific gravity d using (d ₀ /d-1) x 100%. (6) Weld line To injection mold a rectangular shaped product measuring 5 inches long x 0.5 inches wide x 0.03 inches thick, a mold with gates at each end in the length direction is used, and injection molding is carried out at 250℃. did. The molded product has a central part where the molten resin that flowed from both ends merged, and this part was observed and evaluated with the naked eye. The evaluation ranks were 3: extremely conspicuous, conspicuous, and hardly conspicuous. Example 1 18.4 kg of nylon 66/6 copolymer (hereinafter abbreviated as Ny66/6=85/15) containing 85% by weight of bonding units corresponding to nylon 66 and 15% by weight of bonding units corresponding to nylon 6 was produced. The monomer aqueous solution necessary to
50% by weight aqueous solution of hexamethylenediammonium adipate salt (hereinafter abbreviated as 50% AH salt water)
It was prepared by mixing 36.3Kg and 2.76Kg of ε-caprolactam. Then 80 units equipped with heating device, pressure reducing device, stirrer, pressure gauge, thermometer and pressure regulating valve.
A slurry consisting of the monomer aqueous solution, 840 g (6.67 mol) of melamine powder, and 1 kg of water, 803 g (6.22 mol) of cyanuric acid powder, and 1 kg of water was placed in a pressure-resistant autoclave.
A slurry consisting of Kg was injected and immediately heated with stirring to initiate reaction and polymerization. The relationship between temperature and pressure and time during reaction and polymerization is shown in the figure. In the figure, curve 1 indicates the heating jacket temperature, 2 indicates the autoclave internal pressure, and 3 indicates the autoclave internal temperature. After the reaction was completed, the contents were discharged in a molten state into strands from a die having four 5 mmΦ holes at the bottom of the autoclave, and after cooling with water, the pellets were cut into cylindrical pellets of 3 mmΦ x 3 mm length using a cutter to produce a polyamide composition. Almost no air bubbles were observed in the discharged strands and pellets, and the appearance and shape were good. I measured the bubble inclusion rate, but the value was 6.
%, which was found to pose no practical problem. The degree of polymerization and X-ray analysis of the composition were performed. The degree of polymerization was a relative viscosity ηr=2.4, which was sufficient for practical use. Further, only melamine cyanurate was detected from the X-ray diffraction peak, and melamine and cyanuric acid were not detected. Further, when the composition was observed under an optical microscope, melamine cyanurate was found to be extremely uniformly and finely dispersed. Furthermore, when the composition was injection molded and its flame retardance was measured, it was ranked as V--O. Comparative Example 1 A polyamide composition was produced in the same manner as in Example 1 except that the amount of melamine added was 784 g (6.22 mol). After the reaction, when the composition was started to be discharged, air bubbles were gradually observed in the strands and pellets, and after the discharge, it was reported that the strands were swollen or broken due to the air bubbles. . As a result, the pellets had a foam appearance, the pellet sizes were uneven, and the pellets contained a large amount of water that came into contact with them during water cooling. Table 1 shows the bubble inclusion rate and degree of polymerization. Example 2 A polyamide composition was produced using the same composition and method as in Example 1, except that a reduced pressure of 350 mmHg was maintained for 1 hour from 3 hours and 40 minutes after the start of the reaction and polymerization until the end of the reaction. The bubble inclusion rate and degree of polymerization of the pellets obtained were measured. The results are shown in Table 1. Examples 3 to 4, Comparative Examples 2 to 4 A polyamide composition consisting of 90% by weight of a nylon 66/6 copolymer with Ny66/6 = 80/20 and 10% by weight of melamine cyanurate was prepared in the same manner as in Example 1 by 50%. AH brine,
When producing from ε-caprolactam, melamine and cyanuric acid, the molar ratio of melamine and cyanuric acid was 1.03:1.00 (Example 3) and 1.10:1.00.
(Example 4), 1.00:1.00 (Comparative Example 2), 1.00:1.10
(Comparative Example 3) and 1.20:1.00 (Comparative Example 4), reaction polymerization was carried out in the same manner as in Example 1. The bubble inclusion rate and degree of polymerization of the resulting composition were measured and subjected to X-ray analysis. The results are shown in Table 2.

【table】

[Table] Examples 5-6, Comparative Examples 5-6 Using the same equipment as used in Example 1, nylon 610 (92% by weight)/melamine cyanurate (8% by weight) composition and nylon 6 (92% by weight) were prepared. % by weight)/melamine cyanurate (8% by weight) composition was added to the polyamide-forming monomer-water system in the same manner as in Example 1, with melamine and cyanuric acid in the molar ratio shown in Table 3, and the reaction shown in Table 3 was carried out. It was produced by reaction polymerization under polymerization conditions. Table 3 shows the measurement results of the bubble inclusion rate of the obtained composition.

[Table] Comparative Example 7 Ny66/6 with ηr=2.4 using the same equipment as Example 1
= 85/15 nylon 66/6 copolymer was produced. 9.2 kg of the polyamide pellets and 0.8 kg of melamine cyanurate powder with an average particle size of 3 μm were premixed,
Supplied to a mmΦ extruder, extruded into strands at an extrusion temperature of 265℃, cooled with water, and cut with a cutter to 3mmΦ
A polyamide composition in the form of pellets with a length of 3 mm was obtained. In this composition, white secondary agglomerated melamine cyanurate particles that were visible to the naked eye were observed. Example 7 The weld lines and colorability of the compositions of Example 1 and Comparative Example 7 were evaluated. The results are shown in Table 4.

【table】 [Brief explanation of the drawing]

The figure is a diagram showing the relationship between temperature, pressure, and time during reaction/polymerization in Examples.

Claims (1)

[Claims] 1 A polyamide-forming monomer, cyanuric acid, and 1.02 to 1.15 times the molar amount of melamine relative to the cyanuric acid are heated in the presence of water in an amount necessary to cause an addition reaction between melamine and cyanuric acid. A method for producing a melamine cyanurate-containing polyamide composition.