JPH0119684B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing oligomers by continuous hydrolytic polymerization of lauryllactam. Nylon 12 is produced from lauryllactam by ring-opening polymerization, and especially when the polymer is obtained on an industrial scale, a hydrolysis polymerization method is used as the ring-opening polymerization method. Hydrolytic polymerization of lauryllactam is a method of adding water to lauryllactam and raising the temperature to obtain nylon 12 oligomer. As is well known, in a subsequent step water is removed from this oligomer and it is converted into a condensation polymer to become nylon 12. However, the hydrolytic polymerization rate of lauryllactam is extremely slow, about 1/10 to 1/30 of the hydrolytic polymerization rate of caprolactam, which is a monomer of nylon 6. For this reason, high temperature and high pressure conditions are used, but the reaction time still takes a long time. For example, temperature 280℃~290℃, added moisture content 2~5%, pressure 15
A reaction time of ~15 hours is required under conditions of ~30 Kg/ ^cm2 . For this reason, even a batch polymerization method using an autoclave requires large-scale high-pressure equipment, and a continuous polymerization method requires an even larger-scale and more complicated high-pressure equipment. It is also estimated that the hydrolytic polymerization rate of lauryllactam will further increase by increasing the temperature and the amount of water added, but increasing the temperature and the amount of water added will increase the pressure during polymerization. It is estimated that it will increase extremely, for example to 100Kg/cm ² or more. For this reason, it was considered that such conditions could not be achieved industrially due to the limits of the pressure resistance of the polymerization container, and instead attention has been focused on how to make polymerization possible under low pressure conditions. An object of the present invention is to provide a method for producing oligomers by continuously hydrolyzing and polymerizing lauryllactam in a short reaction time using small-scale equipment. For this purpose, the present inventors changed their thinking and conceived the idea of carrying out hydrolytic polymerization of lauryllactam under extremely high temperature and pressure, and arrived at the present invention. In other words, the relationship between heating temperature and added moisture content is as follows with heating temperature as the vertical axis:
On a graph with added water content on the horizontal axis (370℃, 2
%), (340℃, 3%), (325℃, 10%), (310℃,
20%), (300℃, 30%) (295℃, 50%), (360℃,
It has been found that the object of the present invention can be achieved by continuously hydrolyzing and polymerizing lauryllactam within the range surrounded by lines connecting the points of 40%). That is, it has been found that when hydrolysis polymerization is carried out under such conditions, the reaction time can be shortened to within 30 minutes. In batch polymerization, the monomer charging time, temperature raising time, product removal time, etc. are long, so shortening the polymerization time may not have much meaning, but in continuous polymerization, , the residence time in a high-temperature, high-pressure state is reliably shortened to less than 30 minutes, which reduces the capacity of the high-temperature, high-pressure vessel used, which not only allows for the overall scale of the equipment, but also makes it extremely easy to construct a small-capacity high-temperature, high-pressure vessel. It will be possible to manufacture it in In other words, the method of the present invention combines the hydrolytic polymerization of lauryllactam in an extremely short period of time under high temperature and high pressure with the continuous polymerization method. A method for continuous production of advantageous lauryllactam oligomers is provided. Specifically, the range of heating temperature and amount of added water used in the method of the present invention is the range shown in FIG. Here, the amount of added water refers to lauryl lactam,
The amount of water is expressed in % by weight based on the weight of the entire polymerization system including copolymerizable monomers and additives. If the temperature is lower than the range shown in FIG. 1, the polymerization rate will be slow; if the temperature is higher than the range shown in FIG. 1, problems such as coloring and formation of by-products will occur. Moreover, if the water content is less than the range shown in FIG. 1, the polymerization rate will be slow, whereas if it is too much, the pressure will become unnecessarily high, and the degree of polymerization of the obtained oligomer will be extremely reduced. As the continuous polymerization device used to carry out the method of the present invention, it is preferable to use a tubular container connected to a heating device, such as a heat exchange coil, as shown in the examples below, and a high-pressure pump. lauryl lactam and water are fed into the tubular container through a heating device, and polymerization takes place. The gist of the present invention is to continuously polymerize lauryl lactam, which has a slow hydrolytic polymerization rate, using simple equipment, and the method according to the present invention uses not only lauryl lactam alone, but also lauryl lactam as a monomer component and a monomer that can be copolymerized therewith. A copolymer oligomer can be obtained by hydrolytic copolymerization. Further, as long as the monomer is copolymerizable, it can be copolymerized not only with polyamide monomers but also with polyester monomers. For example, terpolymers of lauryllactam, caprolactam and adipic acid hexamethylene diamine salt useful as hot melt adhesives may also be suitably polymerized. Furthermore, additives such as a polymerization degree regulator, a polymerization accelerator, and a stabilizer can be added in addition to the monomer. The nylon 12 oligomer or copolymerized oligomer obtained by the method of the present invention usually has a number average molecular weight of Mn
is 700 to 4000, and heat condensation is performed under reduced pressure, normal pressure, or increased pressure to obtain high molecular weight nylon 12 or copolymer. In this case, the condensation conditions are
The reaction is carried out at a temperature of 250 to 350°C for 2 minutes to 5 hours under a nitrogen stream at normal pressure or reduced pressure. Continuous condensation is preferably carried out by moving the oligomer at a constant speed while stirring. Furthermore, the oligomers according to the invention can be used as raw materials for other polymers, such as by reacting with other compounds, for example polytetrahydrofuran. The present invention will be described below with reference to Examples, but the present invention is not limited to these Examples. Examples 1 to 4 The present invention was carried out using the apparatus shown in FIG. In Figure 2, 1 is the lower part of the heater 1a.
It is a silo heated to 200℃ and contains lauryl lactam. This silo is filled with lauryllactam and then replaced with nitrogen, with a small amount of nitrogen constantly flowing to prevent air from entering the silo. The lauryl lactam is melted in the lower part of this silo, and is fed under constant pressure into a corrugated pipe 6 by a high-pressure pump 2. The corrugated tube 6 is immersed in a night bath 7 that is kept at a constant temperature and stirred, and has an inner diameter of 10 mmφ and an outer diameter of 12 mm.
It is made of stainless steel and has a diameter of 30m. 3 is a silo with a steam pipe 3a at the bottom, and pure water is contained therein in a boiling state. The boiling pure water is fed under constant pressure to a flexible pipe 5 in a night bath 7 by a high-pressure pump 4. The serpentine pipe 5 has an inner diameter of 6 mmφ,
It is made of stainless steel and has an outer diameter of 8 mmφ and a length of 5 m. The pure water is heated through the corrugated tube 5 and then sent to the corrugated tube 6 where it is mixed with the lauryllactam. The mixture of lauryl lactam and water, which has been heated in the corrugated pipe 6 and partially polymerized, is heated to a constant temperature from the outside with a band heater 8a, with an inner diameter of about 50 mmφ,
The reaction tube 8 is made of stainless steel and has an outer diameter of about 60 mmφ and a length of 5 m. Reaction tube 8 is approximately 50cm inside.
I have a total of 10 Mel blenders (static mixers) made by Sulzer Co., Ltd. at intervals. The mixture of oligomers and water polymerized in the reaction tube 8 flashes through a relief valve 9 that opens when the pressure reaches 150 Kg/cm ² or more, and is sent to the cyclone 10 . In the cyclone 10, the heated steam is separated from the upper part and the molten oligomer is separated from the lower part, and the oligomer is cooled and solidified in the cooling water tank 11. Using this device, the flow rate of the lauryl lactam pressure pump 2, the flow rate of the pure water pressure pump 4, the temperature of the night bath 7, and the reaction tube 8 were determined as shown in Table 1.
Various oligomers were produced at different temperatures. After drying, the solidified oligomer was Soxhlet-extracted with acetone for 24 hours, and the amount of acetone extracted was measured. This corresponds to the amount of residual monomer. Further, the moisture content of the dried oligomer was measured at 250° C. using a coulometric titration moisture meter manufactured by Mitsubishi Kasei Corporation to determine the approximate condensed moisture content. The larger this value is, the lower the degree of polymerization of the oligomer is. The results are shown in Table-1. When the oligomer obtained in Example 1 was heated at 250° C. for 2.5 hours in a nitrogen stream, a nylon 12 polymer was obtained. The obtained nylon 12 had good color and physical properties, and a degree of polymerization with a relative viscosity of 1.72 in a 0.5% m-cresol solution at 25°C.

[Table] Example 5 Put 44.4% caprolactam aqueous solution in place of pure water in the hot water bath of 3, and carry out the same procedure as in Examples 1 to 4.
A copolymerized oligomer of lauryllactam and caprolactam was polymerized. However, the amount of lauryl lactam pumped is 12.8Kg/hr, the amount of 44.4% caprolactam aqueous solution pumped is 7.2Kg/hr, and the night bath temperature is 345
℃, and the reaction tube temperature was 340℃. The polymerization ratio of lauryllactam and caprolactam is 80/20, the amount of added water corresponds to 20%, and the residence time is 20 to 22 minutes. The amount of residual monomer in the obtained oligomer is 1.5%
Most of it was caprolactam. The condensed water content was 1.05%. This polymer was heated in a nitrogen stream.
A copolymer was obtained by heating at 240℃ for 5 hours, and 25
The relative viscosity of a 0.5% m-cresol solution at °C is
1.70, and the melting point was 150°C. Comparative Examples 1 to 3 In the same manner as Examples 1 to 4, lauryllactam was hydrolyzed and polymerized under conditions outside the scope of the present invention shown in Table 2. The results are also shown in Table 2. From Table 2, it can be seen that a large amount of monomer remains at the same residence time as in Examples 1 to 4.

【table】 [Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between the heating temperature and the amount of added water in the present invention, and FIG. 2 is a schematic diagram of the apparatus used for carrying out the present invention. 1 is a silo, 2 is a high pressure pump, 3 is a hot water tank, 4
is a high-pressure pump, 5 is a serpentine pipe, 6 is a serpentine pipe, 7 is a night bath, 8 is a reaction tube, 9 is a relief valve, 10 is a cyclone, and 11 is a cooling water tank.

Claims (1)

[Claims] 1 The relationship between heating temperature and added moisture content is shown in Figure 1 (370℃, 2%), (340℃, 3%), (325℃, 10%)
,
(310℃, 20%), (300℃, 30%), (295℃, 50%)
,
(360℃, 40%) Continuous hydrolytic polymerization or copolymerization of lauryllactam or a monomer that can be copolymerized with lauryllactam within the range surrounded by the line connecting each point. Characteristic method for producing oligomers.