JPS6258379B2 - - Google Patents

Description

[Detailed description of the invention]

The method of the present invention relates to a method for producing polyamide compositions containing melamine cyanurate. The present inventors have discovered that by first 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 contains melamine cyanurate. We have found a method that can produce a heterogeneous composition in which the dispersion state of melamine cyanurate is essentially different without the drawbacks of the method of adding melamine cyanurate to polyamide, and have filed an application. However, in the field of electrical component materials, which is the main field of use of the flame-retardant polyamide obtained by the method of this invention, a high degree of heat resistance, especially heat aging resistance, is required in addition to flame retardancy. It has been found that the flame-retardant polyamides are not always satisfactory. The method of the present invention solves such problems and provides a method for producing a high quality flame-retardant polyamide containing melamine cyanurate with a high degree of heat resistance by adding a certain limited heat stabilizer in combination. It is something to do. That is, the method of the present invention involves heating a polyamide-forming monomer obtained by adding melamine and cyanuric acid in a substantially equimolar amount to the polyamide-forming monomer in the presence of at least 5% by weight of water based on the polyamide-forming monomer. This is a method for producing a flame-retardant polyamide, which comprises polymerizing the flame-retardant polyamide, and adding one type of heat stabilizer selected from the following during or after the polymerization. 0.001-0.2% by weight of copper compounds based on polyamide 0.001-0.2% by weight of copper compounds and 0.005-1.0% by weight of alkali metal halide compounds based on polyamide 0.001-0.2% by weight of copper compounds and 0.005-1.0% by weight based on polyamide % of an alkali metal halide compound and 0.001 to 0.5% by weight of a tin compound. Polyamide-forming monomers used in the method of the present invention include nylon 6, nylon 66, nylon
It is also possible to use any monomer capable of forming polyamides, such as 12, nylon 612, and nylon 66/6 copolymers. Specifically, ε-caprolactam or a copolymer system containing the same is included.
Melamine and cyanuric acid are added to the polymerization system in substantially equimolar amounts. For example, if one is added in an amount that cannot be said to be substantially equimolar, such as 1.5 times the mole of one, the degree of polymerization of the polyamide will be lowered and plate-out and blooming phenomena will occur. Of course, it is not necessarily necessary that the molar ratio be strictly equimolar, and a slight variation is allowed as long as the above-mentioned drawbacks do not actually occur. Both enol and keto forms of cyanuric acid can be used. Melamine and cyanuric acid can be added by any appropriate method, such as adding them in powdered form or slurry form. It is added before high molecular weight polyamide is produced in the polymerization system, usually when monomers or oligomers are present. Therefore, the polyamide-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 25
If the percentage by weight is exceeded, it will be impossible to provide clear coloring using a normal amount of pigment during color molding.
Further, there are drawbacks such as a decrease in molding fluidity. When carrying out the method of the present invention, the presence of water in the polymerization system is required to be at least 5% by weight, preferably at least 8% by weight, based on the polyamide-forming monomers.
The amount of water is also related to the amount of melamine and cyanuric acid added; as the amount of melamine and cyanuric acid added increases, the amount of water required increases. water is 5
If the amount is less than % by weight, a sufficient amount of melamine cyanurate will not be produced and the degree of polymerization of the polyamide will decrease, making it impossible to obtain a polyamide containing finely dispersed melamine dianurate. The upper limit of the amount of water can be adjusted by adding a large amount of water and then concentrating the system, and is not particularly limited, but it is preferably 300% by weight or less at the start of the polymerization reaction. For example, a method of polymerizing ε-caprolactam using about 1% by weight of water as a catalyst is well known, but the presence of water in the method of the present invention is necessary to produce a melamine cyanurate dispersion within the polymerization system. It is essential and its effects are essentially different from water in conventional polyamide production technology, which functions exclusively as a polymerization catalyst. The method of the present invention is carried out by heating such a system, and the heating temperature is in the range of 200 to 300°C.
It is desirable to avoid high temperature conditions as much as possible. The heat stabilizer added and blended in the method of the present invention is one type of additive selected from the following. Copper Compounds Copper Compounds and Alkali Metal Halides Compounds Copper Compounds, Alkali Metal Halides and Tin Compounds The above copper compounds are organic/inorganic copper salts or copper chelate compounds that can be uniformly blended into polyamide. For example, cuprous chloride, cupric chloride, cuprous iodide, cupric sulfate, cupric nitrate, etc.
Examples include copper, cupric salicylate, cupric stearate, cupric acetate, cupric benzoate, and copper sebacate. Among these, cuprous chloride and cupric acetate are preferred. Examples of the alkali metal halide compounds include potassium iodide, potassium bromide, potassium chloride, sodium iodide, sodium bromide, and sodium chloride. Furthermore, tin compounds include inorganic tin salts such as stannous chloride and stannic chloride, tin salts of organic acids such as tin oxalate,
Examples include hydroxides such as stannous hydroxide and stannous hydroxide, preferred are inorganic acid salts of divalent tin, and stannous chloride is most preferred. The amount of these heat stabilizers to be used is 0.001 to 0.2% by weight, preferably 0.01 to 0.05% by weight of the copper compound, and 0.005 to 1.0% by weight, preferably 0.05 to 0.5% by weight of the alkali metal halide compound, based on the polyamide resin. %, and tin compounds from 0.001% to 0.5% by weight,
Preferably 0.005% to 0.1% by weight is desirable.
The effect of heat resistance stability by these heat stabilizers is that heat resistance is improved even when a copper compound is used alone, but it is further improved by a combination of a copper compound and an alkali metal halide compound, and even more so when a copper compound, an alkali metal halide compound, and a tin compound are combined. Improved by combination with other compounds. Any heat stabilizer will not be sufficiently effective if used in an amount below the lower limit mentioned above, and if the amount exceeds the upper limit, the polymer may noticeably discolor, deteriorate mechanical properties, or in some cases. degrades polyamide. In addition, in the combination of a copper compound and an alkali metal halide compound, it is preferable to use the latter in an amount of 5 to 15 times (by weight) the former because the effect becomes noticeable. In the method of the present invention, the heat stabilizer is added to the polyamide composition during polymerization of the polyamide composition, that is, the heat stabilizer is added to the polyamide-forming monomer to which melamine and cyanuric acid are added. A method in which polymerization is initiated in the presence of water by adding melamine and cyanuric acid, or a method in which polymerization is initiated in the presence of water of a polyamide-forming monomer to which melamine and cyanuric acid have been added, and the heat stabilizer is added and blended during the polymerization. , or a method of adding and blending the polyamide composition after polymerization, that is, a method of melt-mixing and blending the heat stabilizer into the melamine acrylate-containing polyamide composition produced by polymerization using an extruder or injection molding machine, etc. method can be used. The flame-retardant polyamide thus obtained is
In addition to being highly heat resistant, melamine cyanurate is extremely uniformly and finely dispersed in polyamide, and it is simply different from a composition obtained by mechanically mixing melamine shea slate into polyamide. The dispersed particles differ not only in size but also in shape and can be said to be completely different compositions. The flame-retardant polyamide of the present invention not only has excellent flame retardancy and heat resistance, 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. Furthermore, high quality fibers and films with excellent flame retardancy and heat resistance can be produced by melt spinning and melt film forming. Next, the method of the present invention will be explained in more detail with reference to Examples and Comparative 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-direction diffraction measurement A flat plate of the sample was molded, and the molded product was applied to a Geigerflex DS model X-ray diffractometer manufactured by Rigaku Denki, and a diffraction pattern was drawn in the diffraction angle range of 5 to 40° using a copper target. The presence or absence of melamine cyanurate, melamine, and cyanuric acid was determined by diffraction peaks specific to melamine and cyanuric acid. (3) Flame retardancy A UL-94 vertical flame test was conducted on injection molded specimens with a thickness of 1/16 inch. (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) and injection molded. The degree of blackness of the molded product was observed with the naked eye, and Hunter whiteness was measured using a color difference meter. (5) Plate-out and blooming Regarding plate-out, when molding test pieces for combustion tests were injection-molded using an injection molding machine, the mold during molding was observed to determine the presence or absence of plate-out. Regarding blooming, the molded test pieces for combustion tests were left in a hot air oven at 150° C. for 10 days, and the surface of the molded products was observed. (6) Mechanical properties Tensile strength of injection molded test pieces was measured according to ASTM-D638. (7) Heat Resistance A dumbbell piece for tensile testing specified in ASTM-D638 was molded and left in a hot air oven at 150°C, and the tensile strength retention rate and degree of discoloration due to thermal deterioration were measured. Example 1 18.0 kg of ε-caprolactam and 990 g (7.8 mol) of melamine powder were placed in an 80 pressure autoclave.
Add 1010g (7.8mol) of cyanuric acid and 4.5kg of water, and then dissolve 4g of cupric acetate in water to make 2.5kg of cyanuric acid.
A wt % aqueous solution and a 20 wt % aqueous solution made by dissolving 36 g of potassium iodide in water were added.
Immediately, the container was sealed and heated while stirring to initiate a polymerization reaction. The polymerization reaction begins at the heating jacket temperature.
The container was kept sealed at 200℃ for 4 hours, and then the internal pressure was lowered to normal pressure over about 1 hour while gradually releasing the pressure.
Furthermore, while flowing nitrogen gas, maintain the pressure at normal pressure for 8 hours.
During this time, the internal temperature was raised from 200°C to 250°C. After completing the reaction polymerization for a total of 13 hours, the contents were discharged in the form of a strand, cooled with water, and cut into 3 mm pieces with a cutter.
A polyamide composition was prepared by cutting into cylindrical pellets with a length of 3 mm. The degree of polymerization of the resulting composition was measured. The result was a relative viscosity ηr=2.4, which was a sufficiently practical degree of polymerization. Next, X-ray diffraction measurements were performed. From the X-ray diffraction diagram, only the peak of melamine cyanurate was detected, and melamine and cyanuric acid were not detected. Furthermore, the flame retardancy, mechanical properties, plate-out and blooming, and coloring properties of the composition were measured. The results are shown in Table 1. Heat resistance was also measured. The results are shown in Table 2. Comparative Example 1 A polyamide composition was produced using the same composition and polymerization conditions as in Example 1, except that an aqueous cupric acetate solution and an aqueous potassium iodide solution were not added. The same measurements as in Example 1 were performed on the polyamide composition.
The results are shown in Tables 1 and 2. Comparative Example 2 A polyamide composition was produced under the same conditions as in Example 1 except that the amount of water added was 0.6 kg.
The degree of polymerization, X-ray diffraction, mechanical properties, plate-out and blooming of the resulting composition were measured.
The results are shown in Table 1. Comparative Example 3 The amounts of melamine and cyanuric acid to be added are
A polyamide composition was produced under the same conditions as in Example 1 except that the weights were 1.19Kg and 0.81Kg and the molar ratio was 1.5:1.0. The same measurements as in Comparative Example 2 were performed on the obtained composition. The results are shown in Table 1. Comparative Example 4 Using the apparatus of Example 1, 18 kg of ε-caprolactam, the same amounts of copper acetate aqueous solution and potassium iodide aqueous solution as in Example 1 were added, and further 0.6 kg of catalyst water was added. Heat stabilizer-containing nylon 6 pellets with ηr=2.4 were produced under similar polymerization conditions. 9.0kg of the nylon 6 pellets and 1.0kg of melamine cyanurate powder with an average particle size of 3μ are premixed to form a 40mm powder.
〓Feed it to an extruder and extrude it into a strand at an extrusion temperature of 265℃, cool it with water, and cut it with a cutter to 3mm × 3
A polyamide composition in the form of pellets with a length of mm was obtained. The composition was evaluated in the same manner as in Example 1. The results are shown in Tables 1 and 2. Examples 2, 3, 4 Nylon 6 pellets with ηr = 2.5 and various heat stabilizer powders of the type and amount listed in Table 3 were premixed, and the extrusion temperature was adjusted using the same extruder as used in Comparative Example 4.
Three types of heat stabilizer concentrated polyad composition pellets were produced by extrusion at 265°C. Next, the composition pellets and the melamine cyanurate-containing polyamide pellets of Comparative Example 1 were premixed at a weight ratio of 1:19, and the mixture was sent to an injection molding machine to form a test piece for measuring heat resistance. Then, the heat resistance of the test piece was measured. The results are shown in Table 2. Example 5 50% by weight of the monomer aqueous solution required to produce 18.8 kg of a nylon 66/6 copolymer containing 90% by weight of bonding units corresponding to nylon 66 and 10% by weight of bonding units corresponding to nylon 6. % aqueous solution of hexamethylene diammonium adipate and 1.9 kg of ε-caprolactam. The aqueous monomer solution was then concentrated to a monomer concentration of 70% by weight and injected into the same apparatus used in Example 1. Furthermore, 590 g (4.7 mol) of melamine was added to 1 kg of water to make a slurry, and 610 g (4.7 mol) of cyanuric acid was added.
1 kg of water was added to make a slurry, and then 6 kg of cupric acetate was dissolved in water to make a 2.5% aqueous solution by weight, and 90 g of potassium iodide was dissolved in water to make a slurry. % aqueous solution was added and immediately heated while stirring, and the temperature and pressure were adjusted to conduct a polymerization reaction for about 4 hours and 40 minutes. The figure shows the relationship between temperature, pressure, and time during the polymerization reaction. In the figure, curve 1 shows the heating jacket temperature, 2 shows the autoclave internal pressure, and 3 shows the autoclave internal temperature. A polyamide composition was thus produced. The same measurements as in Example 1 were performed on the composition. The results are shown in Tables 1 and 2. Example 6 The polyamide compositions of Example 1, Example 5, and Comparative Example 4 were evaluated for weld lines. i.e. 5 inches long x 0.5 inches wide x 0.03 thick
A mold with gates at each end of the length is used to injection mold a 250-inch rectangular shaped product.
Injection molded at ℃. There is a part in the center of the molded product where the molten resin flowing from both ends joins together.
The part was observed with the naked eye. As a result, in the molded pieces of the compositions of Examples 1 and 5, the weld lines were hardly noticeable, whereas in the composition of Comparative Example 4, the weld lines were very noticeable.

【table】

【table】

【table】

[Table] Weight percentage added to the product
Example 7 The composition of Example 5 and the composition of Comparative Example 4 were evaluated for impact resistance, tensile elongation, colorability, and appearance of weld lines. The results are shown in Table 4, and it can be seen that the composition of Example 5 is excellent. (1) Impact resistance (a) Falling weight impact strength Measured on a 1 mm thick test piece according to ASTMD-1709. (b) Dine-stud impact strength Measured on a 1 mm thick test piece according to the dynamic test method of British standard BS1330. (c) Tensile impact strength Measured on an S type test piece according to ASTMD-1822. (2) Tensile elongation Measured according to JIS K6301 using a No. 3 type test piece with a thickness of 1 mm, and calculated using the following formula. Tensile elongation (%) = Tensile elongation (cm) / Distance between chucks (
cm) x 100 (3) Weld mark Add 1 part by weight of blue color masterbatch (manufactured by Asahi Kasei Corporation, Color Concentrate M-8800) to 19 parts by weight of sample pellet and inject into a rectangular mold (65 x 90 mm). Molded. At this time, a square nylon plate with a side of 20 mm was set as a resin flow inhibiting plate at a position 1 cm from the mold gate in a direction whose diagonal line coincided with the longitudinal center line of the mold.
A weld mark appearing on the rear part was observed. (4) Colorability The coloring state of the weld mark test piece was also observed at the same time.

【table】 [Brief explanation of the drawing]

The drawing shows a graph showing changes over time in polymerization conditions in Example 5, which is an embodiment of the method of the present invention.

Claims (1)

[Scope of Claims] 1. A polyamide-forming monomer obtained by adding melamine and cyanuric acid in a substantially equimolar amount to the polyamide-forming monomer, at least 5% of the polyamide-forming monomer.
A method for producing a flame-retardant polyamide with excellent heat resistance, characterized by carrying out thermal polymerization in the presence of % by weight of water, and adding a heat stabilizer selected from the following during or after the polymerization. . 0.001-0.2% by weight of copper compounds based on polyamide. 0.001-0.2% by weight of copper compounds and 0.005-1.0% by weight of alkali metal halide compounds based on the polyamide. 0.001-0.2% by weight of copper compounds, 0.005-1.0% by weight of alkali metal halides compounds and 0.001-0.5% by weight of tin compounds based on the polyamide.