JPS6345410B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for producing flame-retardant polyester. (Prior Art and Problems to be Solved by the Invention) It is already known that melamine cyanurate can be added to thermoplastic polyester to impart excellent flame retardant effects to the polyester (Japanese Patent Laid-Open No. 53
−88854). Compared to the method of adding melamine and cyanuric acid alone or in combination to polyester, this method has the effect of significantly suppressing so-called plate-out and blooming phenomena, but the transparency of the resulting composition The inherent properties of polyester are significantly impaired, such as poor coloring properties and poor molding fluidity. Furthermore, it is virtually impossible to obtain flame-retardant fibers or films of good quality by melt spinning or melt film forming. The present inventors have studied to establish a method for producing flame-retardant polyester that can effectively express the characteristics of melamine cyanurate without impairing the inherent properties of polyester, and have completed the present invention. I came to the conclusion. (Means for Solving the Problems) That is, the present invention provides monomers consisting of melamine and a thermoplastic polyester-forming dicarboxylic acid and diol to which cyanuric acid is added in a substantially equimolar amount to the polyester-forming monomer. This is a method for producing flame-retardant polyester, which comprises heating and polymerizing the monomers in the presence of at least 20% by weight of water. As the thermoplastic polyester-forming monomer used in the method of the present invention, any monomer capable of forming a well-known thermoplastic polyester, such as polyethylene terephthalate, polybutylene terephthalate, and copolyester containing these as main components, is used. is also possible. Specific examples include a combination of terephthalic acid and ethylene glycol or 1,4-butanediol, and a combination of dimethyl terephthalate and ethylene glycol or 1,4-butanediol. Melamine and cyanuric acid are added to the polymerization mixture in substantially equimolar amounts. For example, if one of the two is added in a 1.5-fold molar excess, which cannot be said to be substantially equimolar, plate-out or blooming phenomena occur in the resulting composition. Of course, it is not necessarily necessary that the moles be strictly equimolar, and a slight variation, for example, a variation of about 0.1 mole, is allowed as long as the above-mentioned drawbacks do not actually occur. In addition, both enol type and keto type of cyanuric acid can be used. 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 polyester is produced in the polymerization system, usually when monomers or oligomers are present. Therefore, the thermoplastic polyester-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 2 to 30% by weight as melamine cyanurate in the final composition.
It is preferable that If it is less than 2% by weight, sufficient flame retardant effect cannot be imparted, and if it exceeds 30% by weight, disadvantages arise such as it becomes impossible to impart clear coloring using a normal amount of pigment during colored molding. A method for adjusting the amount of melamine cyanurate in the final composition is to add an amount corresponding to the amount of melamine cyanurate that produces melamine and cyanuric acid when producing the composition by direct polymerization. or by pre-polymerizing to produce a composition with a high concentration of melamine cyanurate,
There is a method in which the composition is melt-mixed with monomers to obtain a predetermined amount of melamine cyanurate during the production of polyester. In carrying out the process of the invention, the presence of at least 20% water by weight based on the polyester-forming monomers in the polymerization system is required. 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. If water is present in an amount less than 20% by weight, a sufficient amount of melamine cyanurate will not be produced and a polyester containing finely dispersed melamine cyanurate will not be obtained. Plate-out and blooming also occur in the resulting composition. The upper limit of the amount of water can be adjusted by adding a large amount of water and then concentrating the system, and there is no particular limit, but the upper limit of the amount of water can be adjusted by adding a large amount of water and then concentrating the system.
It is preferably less than % by weight. The method of the present invention is carried out by heating such a system to remove added water, methanol, water, etc. generated during esterification, and further remove glycols generated during polycondensation. 200
It is desirable to avoid high temperature conditions as much as possible in the range of ~300°C. Further, during polycondensation, appropriate additives such as a polyester polymerization catalyst, pigment, antistatic agent, heat stabilizer, and antioxidant may be added. The flame-retardant polyester thus obtained has melamine cyanurate uniformly and finely dispersed in the polyester, and is different from a composition obtained by mechanically mixing melamine cyanurate into polyester, which is simply dispersed particles. They differ not only in size but also in shape, and can be said to be completely different compositions. The flame-retardant polyester of the present invention not only has excellent flame retardancy, but also has extremely excellent mechanical properties, colorability, and molding fluidity, and has extremely high commercial value.
Furthermore, high quality flame retardant fibers and films can also be produced by melt spinning and melt film forming. (Example) Next, the present invention will be explained in detail using Examples and Comparative Examples. The tests and measurement methods in each example are as follows. (1) Degree of polymerization of polyester The reduced viscosity ηsp/C was measured. That is, the specific viscosity of a 1% solution in orthochlorophenol was measured, and the calculation was made based on that value. (2) X-ray diffraction measurement A flat plate of the sample is molded, and the molded product is subjected to a Geigerflex DS model X-ray diffractometer manufactured by Rigaku Denki.
A diffraction pattern was drawn using a copper target within a diffraction angle range of 5 to 40 degrees, and the presence or absence of melamine cyanurate, melamine, and cyanuric acid was determined based on their unique diffraction peaks. (3) Flame retardancy A UL-94 vertical combustion test was conducted on injection molded specimens with a thickness of 1/16 inch. (4) Plate-out and blooming Regarding plate-out, when a test piece for flame retardancy measurement was molded using an injection molding machine, the mold during molding was observed to determine the presence or absence of plate-out. For blooming, use the test piece for flame retardancy measurement.
The molded product was left in a hot air oven at 150°C for 7 days, and the surface of the molded product was observed. (5) Colorability 100 parts by weight of sample pellets were mixed with 0.1 part by weight of carbon black black pigment and injection molded, and 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. It was measured. Example 1 13.6Kg of high purity terephthalic acid, 18.4Kg of 1.4-butanediol (18.0Kg of polybutylene terephthalate)
equivalent), 0.6g sodium hydroxide, 2.5g antimony oxide, 0.99Kg melamine, 1.1Kg cyanuric acid (equivalent to 2.0Kg melamine cyanurate), and
Put 10.0Kg of water into a pressure-resistant autoclave, and raise the pressure to 4.5Kg/cm ² and the temperature to 230℃ while stirring.
Hold at that pressure and temperature for 2 hours. Thereafter, the internal pressure was lowered to normal pressure, the internal temperature was raised to 250°C, the pressure was further reduced to 0.2 mmHg, and the temperature was maintained at 280°C for 2 hours to carry out polymerization. The obtained polymer was discharged from the lower part of the autoclave in the form of a rope, cooled with water, and then cut with a cutter to produce a polyester composition in the form of pellets with a diameter of 3 mm and a length of 3 mm. The degree of polymerization and X-ray diffraction of the obtained polyester composition were measured. Regarding the degree of polymerization, the reduced viscosity was 0.52, which was a sufficiently practical degree of polymerization. From the measurement of the X-ray diffractogram, only the peak of melamine cyanurate was detected, and the peaks of melamine and cyanuric acid were not detected at all. Next, flame retardancy, plate-out and blooming, and colorability were measured. The results are shown in Table 1. Comparative Example 1 A polyester composition was produced under the same composition and polymerization conditions as in Example 1, except that the amount of water added was 0.1 kg. In X-ray diffraction measurements of the resulting composition, only a faint peak of melamine cyanurate was detected, indicating that a sufficient amount of melamine cyanurate was not produced. Plate out and blooming of the composition was measured. Table 1 shows the results.
Shown below. Comparative Example 2 9.0 kg of polybutylene terephthalate pellets with a reduced viscosity of 0.52 and 1.0 kg of melamine cyanurate fine powder with an average particle size of 3 μm were premixed, supplied to a 40 mmφ extruder, and extruded into a strand at an extrusion temperature of 260°C.
The mixture was cooled with water and cut with a cutter to obtain a polyester composition in the form of pellets with a diameter of 3 mm and a length of 3 mm. The same measurements as in Example 1 were performed on the composition. The results are shown in Table 1. Example 2 Using the apparatus of Example 1, 13.8 kg of terephthalic acid,
Starting materials: 10.3Kg of ethylene glycol (equivalent to 16.0Kg of polyethylene terephthalate), 0.5g of sodium hydroxide, 1.5g of antimony oxide, 1.48Kg of melamine, 1.52Kg of cyanuric acid (equivalent to 3Kg of melamine cyanurate) and 5.0Kg of water. Polymerization was carried out under the same polymerization conditions as in Example 1. However, considering the melting point of polyethylene terephthalate, the internal temperature in the latter stage of polymerization was set at 265 to 270°C. When the obtained polymer composition was subjected to X-ray diffraction measurement, only melamine cyanurate was detected, and melamine and cyanuric acid were not detected. Example 1 of other measurement evaluations
I did it in the same way. The results are shown in Table 1. Comparative Examples 3 and 4 A polyester composition was produced under the same composition and polymerization conditions as in Example 1, except that the amounts of melamine and cyanuric acid added were changed to the ratios shown in Table 2. Plate out and blooming of the resulting compositions were measured. The results are shown in Table 2.

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Claims (1)

[Claims] 1 consisting of a thermoplastic polyester-forming dicarboxylic acid and diol to which melamine and substantially equimolar amount of cyanuric acid are added;
A method for producing a flame-retardant polyester, which comprises heating and polymerizing a monomer in the presence of at least 20% by weight of water based on the polyester-forming monomer.