JPH0627192B2 - Process for producing polyamide with increased amount of terminal carboxyl groups - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a method for producing a polyamide having an increased amount of terminal carboxyl groups. More specifically, in the present invention, a bifunctional N-acyl lactam is added to a polyamide and the mixture is melt-reacted to reduce the amount of terminal amino groups and simultaneously increase the number of terminal carboxyl groups to produce a polyamide that is difficult to be dyed with an acid dye. Regarding the method.

<Prior Art> Polyamides represented by nylon 6 and nylon 66 have excellent physical and chemical properties,
It is currently widely used for plastics and films.
In this case, in some applications such as fiber and film, it is sometimes required to have the property of being difficult to be dyed with an acid dye. For example, in polyamide fibers used in some fields of carpets or clothing, a combination of acid dyes that are easily dyed with acid dyes and dyes that are not easily dyed are used in the same bath to produce a shade effect, and the appearance and aesthetics of the product are shown. A method of increasing the sex is often used. When obtaining a light-dyeing polyamide that is difficult to dye with such an acid dye, it is necessary to increase the amount of terminal carboxyl groups and decrease the amount of terminal amino groups. In other words, the smaller the amount of terminal amino groups, the less likely it will be dyed with acid dyes.
When the amount of terminal amino groups is constant, the more terminal carboxyl groups, the more difficult it is to be dyed with an acid dye. There are several known methods for producing such a polyamide that is difficult to be dyed with an acid dye.

The most general and conventionally used method is to add a terminal terminating agent such as a monocarboxylic acid or a dicarboxylic acid at the beginning of the polymerization or during the polymerization. However, this method has the drawback that the polymerization rate is extremely slow and the productivity is low, and it is difficult to obtain a polymer having a very high degree of polymerization.

Another method is to add a monocarboxylic acid, a dicarboxylic acid or the like as a terminal stopper during the melt processing of the polyamide, but in this method, the terminal stopper is not limited to the polyamide terminal but also to the amide bond in the molecular chain. There is a fatal defect that it reacts and causes a decrease in molecular weight.

In order to solve these disadvantages, for example, Japanese Patent Publication No. 44-544 discloses a method in which a cyclic anhydride is used and reacted only with a terminal amino group as described below.

However, this reaction is not limited to the above amide formation, and partly proceeds to the next imide reaction to generate water, and this water causes a depolymerization reaction of the polyamide and at the same time causes yellowing of the polymer. There is.

<Objects of the Invention> The object of the present invention is to eliminate the above-mentioned conventional drawbacks, reduce the amount of terminal amino groups in an extremely short time and increase the amount of terminal carboxyl groups at the same time, without concern about yellowing of the decrease in molecular weight,
It is to provide a method for producing a polyamide that is difficult to be dyed with an acid dye.

<Structure of the Invention> As a result of intensive studies aimed at achieving the above-mentioned object, the present inventors have determined that a bifunctional N-acyl lactam compound known as a conventional chain extender has a specific end group concentration and water content. When melt-kneading with a polyamide regulated to a range, the amount of terminal amino groups was extremely limited, while the amount of terminal carboxyl groups increased all at once, and it was found that a polyamide in which the decrease in molecular weight was substantially suppressed was obtained. The invention has been reached.

Thus, according to the present invention, a polyamide satisfying the following formula (III) can be obtained by adding a bifunctional N-acyl lactam to a polyamide satisfying the following formulas (I) and (II) at the same time and performing a melt reaction. Provided is a method for producing a polyamide having an increased amount of terminal carboxyl groups, which is characterized by being modified.

(here, C _COOH represents the amount of terminal amino groups and the amount of terminal carboxyl groups in the unit of gram-equivalent / 10 ⁶ gram unit.) As the polyamide used in the present invention, if the above conditions (I) and (II) are satisfied, Anything is acceptable, among them nylon 6, nylon 66, nylon 4
Aliphatic polyamides such as 6, nylon 6/10 and nylon 12 are particularly preferably used.

In addition, to the extent that these polyamides can be melt-molded,
A third component, for example, an aromatic component such as terephthalic acid or isophthalic acid may be copolymerized. Of course, in such a polyamide, various additives such as an ultraviolet absorber, a heat stabilizer, a flame retardant, a whitening agent, a lubricant, a release agent, a pigment,
A filler or the like may be added, or these agents may be added during the reaction of the polyamide and the bifunctional N-acyl lactam.

Next, the conditions (I) and (II) of polyamide, which are important for achieving the object of the present invention, will be described.

First, regarding the amount of terminal groups, the value obtained by subtracting the amount of terminal carboxyl groups from the amount of terminal amino groups. Must be 20 or less (requirement of I). In the case of a polyamide having more than 20 groups, even if the polyamide is reacted with a bifunctional N-acyl lactam, the terminal amino groups are reduced but the terminal carboxyl groups are hardly expected to increase. And the present invention, the difference in the amount of the terminal groups is ± 15, more preferably ± 10 polyamide, that is, especially for a polyamide obtained by carrying out a normal polymerization in the presence of water without using a terminal regulator. It is useful.

Second, the moisture content (W) of the polyamide must be in the range of 0.05-0.4%. When the value of W is less than 0.05, for example, even if the requirement of (I) is satisfied, the peculiar phenomena such as the decrease of terminal amino groups and the increase of terminal carboxyl groups due to the acyllactam cannot occur. On the other hand, when W exceeds 0.4%, problems occur in polymer quality such as depolymerization.

The bifunctional N-acyl lactam compound used in the present invention is represented by the following general formula.

(Wherein X represents an alkyl group or an aromatic group, and R represents an alkyl group). Specific examples of the compound represented by the general formula include N,
N'-terephthaloylbis-ε-caprolactam, N,
N′-isophthaloylbis-ε-caprolactam, N,
N'-Adiboylbis-ε-caprolactam, N, N '
-Adiboylbis-ε-valerolactam, N, N'-isophthaloylbisvalerolactam, N, N'-isophthaloylbisbutyrolactam, N, N'-terephthaloylbisbutyrolactam and the like can be mentioned. I can. These compounds can be easily synthesized by reacting the corresponding carboxylic acid dihalide and lactam in the presence of an inorganic alkali such as amine or KOH.

In the present invention, in order to react the polyamide satisfying the above formulas (I) and (II) at the same time with the bifunctional N-acyl lactam compound, the lactam may be added and stirred in the polymerization vessel at the end of the polymerization of the polyamide. Well, it is possible to employ a means of melt-kneading both the fibers and the film in an extruder at the time of molding. Particularly, in the case of the latter method, the polyamide lactam is dry-blended with the acyllactam, and the mixture is kneaded and melted, or the acyllactam is dissolved in ε-caprolactam or the like,
There is a method of metering from the extruder inlet.

Here, the amount of the bifunctional N-aminolactam added to the polyamide varies depending on the target amount of terminal groups, but it is generally preferable to be about 2 to 2 equivalents to the terminal amino groups of the polymer. If this amount is too small, the difference between the terminal carboxyl group and the terminal amino group becomes small and the affinity for the acid dye increases, which is not preferable. or,
If it is used too much, the molecular weight will be greatly reduced, and moreover the amount of lactam monomer in the molded body will increase.

The reaction temperature during the melt-kneading may be in the range of 10 to 150 ° C. higher than the melting point of the polyamide used, preferably in the range of 20 to 80 ° C. The reaction time depends on the reaction temperature and the water content of the polymer, -20 minutes, preferably 2-6 minutes.

<Operation / Effect of the Invention> The present invention, when adding and reacting a bifunctional N-acyl lactam with a polyamide, the difference between the terminal amino group and the carboxyl group as a polymer This is based on a completely new finding that when a polyamide having a weight ratio of 20 g / 10 ⁶ g or less is used, a combined phenomenon of extremely reducing amino groups and increasing carboxyl groups occurs.

The bifunctional N-acyl lactam itself has a very high reactivity with the terminal amino group of the polyamide and forms an amide bond by reacting with the amino group, but when the reacting amino terminal is consumed, the water content in the polymer is reduced. Undergoes hydrolysis to generate a carboxyl group. Therefore, If but using 20 gram equivalent / 10 ⁶ g more polyamides, the need to add a large amount of N- acyl lactam occurs in order to obtain a hard polymer dyed acid dye purposes, only undesirable economically Not only that, the amount of lactam monomer in the molded product is large, and only the unfavorable product can be obtained.

In this way, according to the present invention, it becomes possible to easily obtain a polyamide which is difficult to be dyed with an acid dye having a large number of carboxyl terminal groups from a usual polyamide.

Incidentally, Japanese Patent Publication No. 57-53169 discloses that N-acyl lactam is melt-kneaded with polyamide in order to improve the molecular weight of polyamide. However, this method is only aimed at chain extension of the polyamide by the acyllactam, and there is no recognition that the amino terminal group is extremely reduced and the amount of the carboxyl group is remarkably increased as in the present invention. This is true even with reference to the examples of the publication.
Of the base polymer It can be seen from the fact that is far over 20.

<Example> Hereinafter, although an example is given and explained, the present invention is not limited to this.

Definition of test and measurement methods a. Intrinsic viscosity ([η] 0.2 g, 0.4 g and 0.8 g of polymer are dissolved in 100 ml of metacresol, and η rel (t / to) is measured at 35 ° C. Next, each concentration C ( g / 100 ml) for η rel-
1 / C was plotted, and [η] was calculated from the intercept of the straight line obtained from the three points.

The relationship between η rel obtained in sulfuric acid and the above-mentioned intrinsic viscosity [η] is represented by [η] = 0.56 _η rel-0.26. For example, η rel = of Example 2 of JP-A-61-171732. 3.62 corresponds to an intrinsic viscosity [η] = 1.77.

b. Terminal group quantity Terminal group quantity Was obtained by dissolving the polymer in m-cresol and titrating with 0.01 Np-toluenesulfonic acid. C _COOH was determined by dissolving the polymer in benzyl alcohol and titrating with 0.1N sodium hydroxide.

Examples 1 to 4 and Comparative Examples 1 to 4 Monomer content obtained by melt-polymerizing ε-caprolactam with water, washing and drying with hot water to adjust water content.
Nylon 6 tips with 0.5-1.0%, terminal amino group concentration 44, terminal carboxyl group concentration 47, [η] 1.34, N, N'-
The terephthaloylbiscaprolactam powder was dry blended in the predetermined amounts shown in Table 1 below, and the reaction temperature was maintained under a nitrogen stream.
When a melt-kneading reaction was carried out at 250 ° C. for a residence time of 4 minutes, a polyamide having the physical properties shown in Table 1 was obtained. The polyamide obtained at this time was neither colored nor gelled.

For comparison, when the same operation is performed without adding any additive, and The results are also shown in Table 1 for the case where the base polymer having an amount of more than 20 gram equivalent / 10 ⁶ gram was used.

Examples 5 to 7 and Comparative Example 5 Unreacted monomer content of about 10%, terminal amino group concentration 45, terminal carboxyl group concentration 48, [η] 1.24 obtained by melt polymerization of ε-caprolactam with water. Nylon 6 chips were dry-blended with N, N'-terephthaloylbiscaprolactam powder in a predetermined amount shown in Table 2 below, and melt-kneaded under a nitrogen stream at a reaction temperature of 250 ° C and a residence time of 4 minutes. . The obtained polyamide was washed with hot water for 4 hours and dried under vacuum for 16 hours to measure polymer properties.
It was as shown in.

The polyamide obtained at this time was neither colored nor gelled, and even if it contained an unreacted monomer, there was no problem in reactivity. For comparison, the results are also shown in Table 2 when the same operation was performed without adding any additives.

Example 7 and Comparative Example 3 ε-caprolactam was melt-polymerized with water, washed with hot water, and dried to obtain a water content of 0.15%, a monomer content of 0.5 to 1.0%, and a terminal group concentration. Nylon 6 tips with 46, terminal carboxyl group concentration 48, [η] 1.34, N, N'-
Dry blend 1.25 wt% terephthaloyl biscaprolactam powder, and in a nitrogen stream, 65 mm melt kneading extruder,
While performing a melt-kneading reaction at a reaction temperature of 250 ° C. and a residence time of 4 minutes, melt spinning and drawing were performed using a spinneret having a diameter of 0.6 mm and 68 holes. Table of polyamide properties after melting reaction
3 (2) shows the yarn physical properties of the drawn yarn, and Table-3 (3) shows them.

For comparison, the water content was adjusted to 0.10%, the same operation was performed without adding any additives, and the properties of the obtained polyamide and the yarn physical properties of the drawn yarn are shown in Table 3 as a comparative example. .

Then, using a 36 gauge tubular knitting machine, the two types of samples were dyed in the same acidic dye bath below at 90 ° C. for 45 minutes to obtain L, a and b.
The value was measured.

Acid dye bath Green dye-Tectilon Yellow 4R 0.1% owt-Telon Red FRLL 0.02% owt-Tectilon Blue 6G 0.114% owt-Aborane AV 2.0% owt Bath ratio 1: 100 PH6.5 (sodium phosphate dibasic phosphate) Adjust with soda). The results are shown in Table-3 (4).

The L, a, and b values are OPTICAL SENSOR of Nippon Denshoku Industries Co., Ltd.
Measured in Z.

As is clear from Table 3, according to the present invention, the amount of terminal amino groups is decreased and the amount of terminal carboxyl groups is increased while suppressing decrease of [η] of polyamide. As a result, it is recognized that the L value with respect to the acid dye is increased and a marked light dyeing is exhibited.

Claims (2)

[Claims] 1. A bifunctional N-acyl lactam is added to a polyamide satisfying the following formulas (I) and (II) at the same time, and the mixture is melt-reacted to be modified into a polyamide satisfying the following formula (III). A method for producing a polyamide having an increased amount of terminal carboxyl groups, comprising: (here, C _COOH represents the amount of terminal amino groups and the amount of terminal carboxyl groups in units of grams / equivalents / 10 ⁶ grams respectively) 2. A bifunctional N-acyl lactam is used in an equivalent amount or more based on the amount of amino end groups of the polyamide.
The method for producing a polyamide having an increased number of terminal carboxyl groups according to the item (1).