JPS61159422A - Production of copolyamide molding - Google Patents

Abstract

PURPOSE:To increase the yields of a molding without detriment to polymer qualities, by copolymerizing hexamethylenediammonium adipate with hexamethylenediammonium terephthalate at a specified temperature and specifying the degree of polymerization of the copolymer. CONSTITUTION:A copolyamide is obtained by copolymerizing hexamethylenediammonium adipate (A) with hexamethylenediammonium terephthalate (B) under conditions in which the maximum attainable temperature (T deg.C) is represented by the formula (wherein Tm deg.C is the crystal m.p. of the formed copolyamide). This copolyamide is melt-extruded under conditions in which the degree of polymerization during melt extrusion is 2.0-2.5 in terms of a relative viscosity (etar) in sulfuric acid. The proportion of component (B) in said copolyamide is preferably about 20-60wt%. It is preferable in order to control the degree of polymerization during melt molding to add 0.7-4mol%, based on the salts as materials, viscosity stabilizer (e.g., aliphatic dicarboxylic acid).

Description

Detailed Description of the Invention [Industrial Application Field] The present invention copolymerizes hexamethylene diammonium adipate and hexamethylene diammonium terephthalate, and when melt-dispensing, the excellent properties of this copolyamide are utilized. The present invention relates to a method for producing copolyamide molded articles that can be melt-discharged in high yield without damage.

[Prior Art] Polycapramide and polyhexamethylene adipamide are highly crystalline polyamides that can be easily melt-molded, so they are widely used as clothing and industrial fibers, engineering plastics, and the like.

Although these polyamide fibers and plastics have excellent mechanical properties, they have the disadvantage of poor dimensional stability due to their low Young's modulus and low glass transition point.

In order to overcome this drawback, various attempts have been made to introduce rigid copolymer units such as terephthalamide units into the polymer main chain. One type of such polyamide is a copolyamide (hereinafter referred to as 66/6T copolyamide) formed by copolymerizing hexamethylene diammonium adipate and hexamethylene diammonium terephthalate.

This 66/6T copolyamide has almost no deterioration in crystallinity due to copolymerization, and can be produced by a normal polyamide polymerization method in which a salt of a dicarboxylic acid and a diamine, or an aqueous solution thereof is polymerized by heating and melting under pressure. It has a higher melting point, higher Young's modulus, and higher glass transition point than polyhexamethylene adipamide, and has dyeing properties.
Made of useful polyamide with excellent light resistance and chlorine resistance. These useful properties are due to the terephthalamide units introduced into the polymer main chain, so the more terephthalamide units are copolymerized, the better the polyamide can be obtained.

However, when the copolymerization ratio of terephthalamide units is increased, the melt viscosity of this 66/6T copolyamide significantly increases, resulting in a significant deterioration in melt discharge properties, making it difficult or impossible to discharge. polymerizes into
It was difficult to melt and discharge it into product chips.

That is, by a method similar to the industrial polymerization method of polyhexamethylene adipamide, about 0.1 to 0.4 mol% of a viscosity stabilizer is added, and the crystalline melting point of the polymer (Tm > 2
When polymerization is carried out at a temperature as high as 0'C, the viscosity of the polymer when melted and discharged becomes as high as 2.8 or more in terms of sulfuric acid relative viscosity (ηr), and the higher the copolymerization ratio of terephthalamide units, the higher the degree of melting and discharge. This made it difficult. If melting and dispensing becomes difficult in this way, air bubbles will get mixed into the gut and the gut will break frequently, resulting in a decrease in chip yield.Also, since the dispensing time will be prolonged, the difference in polymer properties depending on the dispensing time will become large. This causes the problem that the quality is not constant.

This problem can be avoided to some extent by raising the polymer temperature during polymerization, but when polymerization is performed at such high temperatures, thermal denaturation such as thermal decomposition and gelation of the polymer becomes noticeable. It cannot be used industrially because it causes significant quality deterioration such as deterioration of the color tone of the polymer and deterioration of mechanical properties.

[Problems to be Solved by the Invention] The present invention improves the discharge performance of the polymer from a polymerization apparatus without causing a deterioration in the quality of the polymer, and improves the yield of 66/6 copolyamide molded products. 6 of excellent quality
The main object of the present invention is to provide a method for producing a copolyamide molded product that enables industrial production of a 6/6T copolyamide molded product.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides hexamethylene diammonium adipate and hexamethylene diammonium terephthalate with a maximum temperature (T'C) of (Tm
+5)≦T≦(Tm+15) (Tm °C: crystal melting point of the resulting copolyamide). is the relative viscosity of sulfuric acid (η”), which is 2
．． It is characterized by being melted and discharged under conditions of 0 to 2.5.

The copolyamide (66/6T copolyamide) obtained by copolymerizing hexamethylene diammonium adipate and hexamethylene diammonium terephthalate according to the present invention is terephthalate in order to increase the melting point, Young's modulus, and glass transition point. It is preferable to increase the copolymerization ratio of ramid units, but if it is too large, melt spinning and molding become difficult, so in practice, the copolymerization ratio of terephthalamide units should be 20 to 60% by weight. The content is preferably 25 to 50% by weight, and more preferably 25 to 50% by weight.

The sulfuric acid relative viscosity (ηr) of the polymer is a value measured by the following method, and the sulfuric acid relative viscosity (ηr) of the polymer during melt-discharge in the method of the present invention is a value measured by the viscosity of the melt-discharged polymer. You can know by

A polymer solution with a concentration of 1% by weight dissolved in 98% sulfuric acid,
25°C by Ostwald viscometer (improved Nakano type)
The number of seconds of flow under constant temperature was measured, and the viscosity ratio to 98% sulfuric acid was calculated from the value of the number of seconds of flow.

[Function] In order to suppress thermal deterioration of the polymer during polymerization, especially from the final stage of polymerization to the period between melt discharge and to prevent quality deterioration, it is important not to raise the polymer temperature too high at this time; It is necessary that the ultimate temperature (T>) be 15 °C higher than the crystal melting point (Tm'C) of the copolyamide. However, if this maximum temperature is too low, polymerization may not proceed sufficiently. I can't do it, and
No matter how you adjust the degree of polymerization during polymer discharge, it is difficult to improve the discharge performance, so it is also necessary to set it to (Tm+5>'C or higher.This maximum temperature (T) is
Roughly, (Hm +7.5) ~ (Tm +12.5>
It is preferable to set the temperature range to 'C.

Further, the discharge properties of the polymer during melt discharge can be improved by adjusting the degree of polymerization during discharge to a relative viscosity of sulfuric acid (ηr) of 2.0 to 2.5.

That is, the sulfuric acid relative viscosity (ηr) of the polymer is 2.0 to 2.
．． It is important to complete the polymerization when it reaches 5. Melting and dispensing with a degree of polymerization in which ηr is 2.5 or less results in good dispensing properties, which increases the chip yield (the number of product chips obtained relative to the total amount of dispensed polymer). It is possible to suppress variations in quality of polymer chips. On the other hand, if the degree of polymerization is in the range where ηr is less than 2.0, the degree of polymerization is too low to stably form chips, and the resulting polymer has insufficient properties, making it difficult to put it to practical use. I can't.

In order to adjust the degree of polymerization at the completion of polymerization to such a level, it is sufficient to add a large amount of viscosity stabilizer to carry out the polymerization. A stabilizer may be added.

As the viscosity stabilizer, there are conventional viscosity stabilizers such as aliphatic dicarboxylic acids, aromatic dicarboxylic acids, aliphatic monocarboxylic acids, aromatic monocarboxylic acids, aliphatic diamines, aromatic diamines, aliphatic monoamines, and aromatic monoamines. nylon 6
The viscosity stabilizer compound used in the polymerization method of 6 may be used.

Also, during polymerization, in addition to the viscosity stabilizer, ordinary nylon 6
Other additives added in the 6-polymerization method, such as heat-resistant/light-resistant agents, matting agents, plasticizers, etc., may also be added. In particular, it is preferable to add a phosphorus-based heat resisting agent to suppress oxidation and thermal decomposition of the polymer.

The method of the invention may be applied to batch polymerization or
It may also be applied to continuous polymerization.

In addition, the polymer obtained by the method of the present invention may be used after solid-phase polymerization in order to roughly increase the degree of polymerization.

[Examples and Comparative Examples] - Example 1 A 50% aqueous solution of hexamethylene diammonium adipate (66 salt) and a 13% aqueous solution of hexamethylene diammonium terephthalate (6T salt) were prepared into a concentrated color with the composition shown in Table 1. , after completely replacing with nitrogen gas,
While maintaining the water vapor pressure at 1.0k(]/c+fG, it was heated and concentrated to obtain an aqueous solution with a concentration of 60-70%.Next, ordinary additives such as viscosity stabilizers were added, and the mixture was transferred to a batch-type polymerization tank with a capacity of 20OL. , after replacing with nitrogen gas, the water vapor pressure was 17.5
Heating was continued under a pressure of kMo+fG.

After reaching 250 to 270°C, pressure relief was started and heating was continued until the maximum temperature was reached. Next, while maintaining this maximum temperature, after the pressure release is completed, the polymerization is maintained under a reduced pressure of 100 to 300 mm and 1 to 1 g for 5 to 15 minutes to complete polymerization, and the obtained polymer is discharged into water and cut into chips. did. In addition, the amount of the viscosity stabilizer added to the polymerization raw material salt is as shown in Example N.
It is 1.3 mol% in the case of No. 2, and 1.2 mol% in the case of No. 5, and the degree of polymerization at the time of melt discharge is shown in Table 1 by changing the amount of viscosity stabilizer added. Adjusted to the value shown.

The crystal melting point (Tm) and yellowness index (YI), which indicates the quality, of the obtained polymer chips were measured by the following method.

Crystal melting point (Tm): Polymer chips (3m) were heated from room temperature at a heating rate of 10'C/min under a nitrogen stream using a DSC-24 (differential scanning calorimeter) manufactured by PERKIN-ELMER. , the temperature at the top of the endothermic peak of the thermograph was defined as 1'-m.

Yellowness index (YI): Measure the tristimulus values X, Y, and Z of the polymer chip using a digital colorimetric color difference calculator (Suga AUO-3CH2 model), and calculate the yellowness index (YI) from the measured values as YI= (1,28X-1,06Z) /YX100
Calculated by. The higher this value is, the more yellow the polymer is.

As can be seen from the results in Table 1, the method of the present invention had a good chip yield of 90% or more, and the obtained polymer chips were of excellent quality without yellowing. On the other hand, the conventional method
Alternatively, in the case of a comparative example under conditions other than those of the present invention, the yellowness was high and the quality was poor, and the chip yield was also low.

By the way, in the case of comparative example No. 16, the maximum temperature reached (T)
Polymerization was carried out under the same conditions as Comparative Example No. 15, except that the sulfuric acid relative viscosity at the time of discharge was not measured. is estimated to be about 2.90.

・Example 2 The copolymerization ratio of 6-ton salt was increased to 50% or 60% by weight, and the maximum temperature reached during polymerization (T>) and the degree of polymerization during melt discharge were adjusted to the values shown in Table 2. Other than that, Example 1
Polymerization was carried out in the same manner as in the case of 66/6T copolyamide chips.

In addition, in Comparative Example No. 16, the amount of viscosity stabilizer added (based on the raw material salt) was 0.3 mol%, and the viscosity of the chip could not be measured because it was impossible to eject. The relative viscosity of sulfuric acid is estimated to be as shown in Table 2.

[Effects of the Invention] According to the method of the present invention, by improving the polymer discharging property from the polymerization equipment without causing a deterioration in the quality of the polymer during polymerization, it is possible to produce 66/6T copolyamide molded products of excellent quality with high chips. It can be produced with high yield. Therefore, according to the method of the present invention, even when the copolymerization ratio of terephthalamide units is 20 to 60% by weight, it is possible to produce molded products of excellent quality at a high yield. It is possible to industrially produce 66/6T copolyamide molded articles with a polymerization composition in high yield.

Claims (2)

[Claims] (1) Conditions for hexamethylene diammonium adipate and hexamethylene diammonium terephthalate such that the maximum temperature (T°C) achieved is (Tm+5)≦T≦(Tm+15) (Tm°C: crystal melting point of the resulting copolyamide) The copolymerized polyamide is then copolymerized to form a copolymerized polyamide, and then the copolymerized polyamide is melted and discharged under conditions such that the degree of polymerization at the time of melting and discharge is 2.0 to 2.5 in terms of sulfuric acid relative viscosity (ηr). A method for producing a copolyamide molded product characterized by: (2) The method for producing a copolyamide molded article according to claim 1, wherein the copolymerization ratio of hexamethylene diammonium terephthalate in the copolyamide is 20 to 60% by weight.