JP3427446B2 - Solid state polymerization method of polyamide - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state polymerization method for increasing the degree of polymerization of a polyamide resin. In particular, the present invention relates to a solid-phase polymerization method for obtaining a polyamide having a high degree of polymerization, which has a small amount of by-product gelation and is adjusted to a predetermined viscosity, and is therefore suitable as a fiber or other industrial raw material. More specifically, the present invention relates to a solid-state polymerization method for obtaining the high-quality polyamide having a high degree of polymerization by performing a solid-state polymerization reaction at a relatively low temperature in a steam atmosphere. [0002] Conventionally, as a method of obtaining a polyamide having a high degree of polymerization suitable for a raw material such as fiber, a monomer compound is first polycondensed in a liquid phase, extruded into a linear form, cooled, solidified, and then cut. A method is known in which pellets are formed and solid-phase polymerization is performed at a temperature equal to or lower than the melting point until a predetermined degree of polymerization is reached. As a method for solid-phase polymerization of polyamide, conventionally, a temperature lower than the melting point (usually 30 degrees above the melting point) in an inert gas (nitrogen) atmosphere or under reduced pressure.
(A temperature as low as about ° C.) is known. Further, in order to shorten the reaction time of the solid-phase polymerization, prior to the solid-state polymerization, a pretreatment step of adding water to the pellets to increase the water content to 1.0% by weight or more, followed by heating under pressure, and then drying was performed. A method of post-solid phase polymerization is also known (Japanese Patent Publication No. 50-219).
7). Furthermore, polyamide precondensed to a low degree of polymerization
In an inert gas atmosphere with a water content of 5 to 100% by volume
Also known is a method of solid-state polymerization at a relatively high temperature (European Patent
No. 207539). However, relatively high weight
Solid polyamide at relatively low temperature in the wet state
By polymerizing, there are few gel products produced as by-products,
To produce a polyamide adjusted to a predetermined viscosity
Not done conventionally. [0003] According to the conventional solid-state polymerization method, it is inevitable that by-products, in particular, gelled products confirmed in accordance with the measurement method described later, are produced to some extent. Adverse effects such as clogging. Therefore, in this field, it is important to suppress the by-product of the gelled product. In addition, in order to obtain a product with constant quality, it is necessary to obtain a polymer adjusted to a predetermined viscosity, and therefore, it is also an important issue in this field that the viscosity can be easily adjusted. SUMMARY OF THE INVENTION The present invention is directed to a method for solid-state polymerization of polyamide, wherein the reaction is carried out in a steam atmosphere so that a by-product of a gel is reduced and the viscosity is adjusted to a predetermined value. Is based on the new finding that a high degree of polymerization polyamide can be obtained.
8% Sulfuric acid Polycondensation to a relative viscosity of 2.0 or more, pelletized polyamide is subjected to solid phase polymerization under an inert gas atmosphere or under reduced pressure, under a steam atmosphere and at a melting point of the polyamide of 50 to 100 ° C. The present invention relates to a method characterized in that the reaction is performed at a low temperature. [0005] The most important requirement in the solid-state polymerization method of the present invention is that the reaction is carried out in a steam atmosphere. In addition,
Although some water may be generated during the solid-state polymerization reaction, the amount is extremely small, and the amount of water generated during the reaction alone is substantially unsuitable for being under a steam atmosphere. is there. Therefore, in order to achieve the object of the present invention, it is necessary to introduce water by any means other than the water generated during the reaction. [0006] The amount of water vapor introduced is such that the content in the reactor is from 2.8 × 10 ^-3 mol / l to 5.5 × 10 ^-3.
The amount is desirably such as to be mol / l (3.9% by weight to 7.3% by weight). Incidentally, the amount of water generated by the solid-state polymerization reaction is about 1/100 or less. If the amount of water vapor is less than this range, the suppression of side reactions will be insufficient, and the rate of increase in relative viscosity will increase, making it difficult to control the viscosity to a predetermined value. Further, when the amount of water vapor is larger than the above range, the rate of increase in relative viscosity decreases, and in some cases, may not reach the predetermined viscosity, and the obtained polymer has a high moisture content and is not desirable. Become. In the solid-state polymerization method of the present invention,
The use of such polyamide raw materials is also an important requirement.
Polyamide used as a raw material has a relatively high degree of polymerization
Having a relative viscosity of 98% sulfuric acid of 2.0 or more
Things. The melting point of the nylon pellets used
It is usually about 240 ° C. Temperature of the solid-phase polymerization reaction of the present invention, Ri by melting point of nylon pellets to be used as a raw material 5
Temperatures 0-100 ° C lower are preferred. If the solid-state polymerization reaction is performed at a temperature higher than this, that is, at a temperature close to the melting point, partial fusion of the polymer occurs, making it difficult to withdraw the polymer from the reactor, and oxidizing the polymer with a small amount of mixed oxygen. Deterioration occurs. Further, the insoluble content when the obtained polymer is dissolved in a formic acid solvent, that is, a by-product of a gelled product increases. In addition, when the solid-state polymerization reaction is performed at a temperature lower than the melting point by 100 ° C. or more, the reaction rate is reduced, so that the reaction is not industrially feasible, and thermal degradation occurs during a long-time reaction. The solid-state polymerization method of the present invention is not limited to typical ones such as nylon 6, nylon 66 and the like, and can be applied to all nylons or polyamides. Further, the solid phase polymerization method of the present invention can be applied to both a continuous type and a batch type. [Measurement method] (1) Gelled product The gelled product contained in the polyamide obtained by the solid-state polymerization method of the present invention was weighed by weighing 1 g of a sample and formic acid 1
The solution was dissolved in 00 ml, filtered through a glass filtration filter (3G) of known weight, the glass filter was washed with fresh formic acid, dried (drying conditions: 105 ° C. × 16 hours), weighed, and the formic acid insoluble matter (gelled product) ) Is calculated. (2) Dissolve 200 mg of the relative viscosity sample in 20 ml of 98% sulfuric acid, measure the falling seconds of this solution using an Ubellose viscometer (at 20.0 ° C.), and determine the ratio to the falling seconds of the sulfuric acid solvent alone as follows: The relative viscosity of the sample is determined by the following equation. [0010] As is apparent from the above description, according to the solid-state polymerization method of the present invention, the content of by-products (expressed as a gel) is small, and the viscosity is accurately adjusted. Therefore, it is possible to obtain a high polymerization degree polyamide having uniform quality. Hereinafter, the present invention will be described in detail with reference to examples. Example 1 Nylon 6 pellets having a relative viscosity of 98% sulfuric acid of 2.6 were placed in a nitrogen gas atmosphere containing 4.4 × 10 ⁻³ mol / l (6.0% by weight) of water vapor. A solid-state polymerization reaction was performed at atmospheric pressure. As the reaction temperature and time, conditions of 150 ° C. for 32 hours, 170 ° C. for 32 hours, and 190 ° C. for 16 hours were employed. The amount of gelled product in the obtained product was measured. Similarly, when no steam was added, the amount of the gelled product was measured. Table 1 shows these results.
Shown in As is clear from Table 1, according to the solid-state polymerization method of the present invention, the by-product of the gelled product is reduced to about 1/10 as compared with the case where steam is not added. [Table 1] Example 2 In Example 1, in order to examine the change over time of the relative viscosity, in each case, 4 hours after the start of the reaction,
The relative viscosities were measured after 12, 24, 28 and 32 hours. Table 2 shows the results when water vapor was added.
Table 3 shows the results when no addition was made. As is clear from the comparison of these tables, when steam is added, the relative viscosity increases more slowly than when water is not added,
It is understood that it is easy to obtain a product having a predetermined viscosity. [Table 2] [Table 3] Example 3 In Example 2, the reaction temperature was 150 ° C.
Experiments were carried out with the water vapor content varied between 1.5% and 7.3% by weight, and the relative viscosity over time in each case was measured. Table 4 shows the results. As is clear from Table 4, it can be understood that when the content of water vapor is small, the relative viscosity continues to increase, and it is difficult to control the relative viscosity. [Table 4]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 Changes in relative viscosity over time when solid-state polymerization reaction temperatures of 150 ° C., 170 ° C., and 190 ° C. are employed when the water vapor content is 6.0% by weight (Table 1) 2)
A graph showing. FIG. 2 is a graph showing a change over time in relative viscosity (Table 3) when 150 ° C., 170 ° C., and 190 ° C. are employed as solid-state polymerization reaction temperatures when water vapor is not added. FIG. 3 shows a water vapor content of 1.5% by weight, 3.9% by weight, and 6.0% by weight at a solid-state polymerization temperature of 150 ° C.
5 is a graph showing a change over time in relative viscosity (Table 4) when 7.3% by weight and 7.3% by weight are employed.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C08G 69/00-69/50

Claims (1)

(57) [Claim 1] When solid-phase polymerizing a polyamide having a relative viscosity of 98% sulfuric acid of 2.0 or more in an inert gas atmosphere or under reduced pressure, the polyamide is used in a steam atmosphere and a raw material polyamide. A method for solid-phase polymerization of polyamide, wherein the reaction is carried out at a temperature lower by 50 to 100C than the melting point.