JPH0593063A - Production of polyamide with increased content of terminal carboxyl group - Google Patents

Abstract

(57) [Summary] [Objective] To provide a process for producing a polyamide which is less likely to be dyed with an acid dye by suppressing the change in molecular weight, preventing yellowing of the polymer, decreasing the amount of terminal amino groups and simultaneously increasing the amount of terminal carboxyl groups. [Structure] A polyamide polymer is mixed with a bifunctional N-acyl lactam such as N, N'-terephthaloylbis-ε-caprolactam and a cyclic acid anhydride such as succinic anhydride 9: 1 to 1: 9. By adding at a ratio of (equivalent ratio) and performing a melt reaction, a polyamide having a terminal carboxyl group amount larger than the terminal amino group amount by 30 g equivalent / 10 ⁶ or more is modified.

Description

Detailed Description of the Invention

[0001]

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, by adding a predetermined ratio of a bifunctional N-acyl lactam and a cyclic acid anhydride to a polyamide and performing a melt reaction, the amount of terminal amino groups is reduced while suppressing the change in molecular weight, and at the same time the amount of terminal carboxyl groups is reduced. The present invention relates to a method for producing a polyamide which is less likely to be dyed with an acid dye by increasing the amount of water.

[0002]

Polyamides represented by nylon 6 and nylon 6,6 are widely used for fibers, plastics, films and the like because they have excellent physical and chemical properties. In fiber and film applications, the property of being difficult to dye with an acid dye is sometimes required.

For example, in polyamide fibers used in some fields of carpets or clothing applications, a combination of acid dyes that are easily dyed with acid dyes and dyes that are not easily dyed are combined and dyed in the same bath to produce a shade effect, The method of enhancing the appearance and aesthetics of is often used.

In order to obtain a light-dyeing polyamide that is difficult to be dyed with such an acid dye, it is necessary to increase the amount of terminal carboxyl groups and decrease the amount of terminal amino groups. That is, the smaller the amount of terminal amino groups, the less likely it is to dye with an acid dye, and when the amount of terminal amino groups is constant, the more terminal carboxyl groups there are, the less likely it is to dye with an acid dye.

There are several known methods for producing such a polyamide that is difficult to be dyed with an acid dye, and the most common and conventionally used methods are monocarboxylic acid and dicarboxylic acid at the beginning of polymerization or during polymerization. This is a method of adding the end-stopping agent. However, this method has the drawbacks that the polymerization rate is very slow and 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 terminating agent at the time of melt processing of the polyamide, but in this method, the terminal terminating agent is not limited to the polyamide terminal and may be added in the molecular chain. There is a fatal drawback that it also reacts with an amide bond and causes a decrease in molecular weight.

In order to eliminate these disadvantages, for example, in Japanese Examined Patent Publication No. 44-544 and Japanese Examined Patent Publication No. 1-229810, a cyclic acid anhydride is used and only a terminal amino group as shown in the following chemical formula 1 is used. A method of reacting has been proposed.

[Chemical 1]

However, this method is not limited to the reaction with a terminal amino group to form an amide, and a part thereof proceeds to an imide reaction to produce water as shown in the following chemical formula 2, and this water is a polyamide. It causes a depolymerization reaction and lowers the molecular weight. Furthermore, when a large amount of cyclic acid anhydride is used, there is a problem that it also causes yellowing of the polyamide, and using only the cyclic acid anhydride, it is not possible to obtain a polyamide that is difficult to be dyed with a practical acid dye. It was

[Chemical 2]

Further, Japanese Patent Laid-Open No. 1-236238 proposes a method using a bifunctional N-acyl lactam. According to this method, it is possible to reduce the amount of terminal amino groups in an extremely short time and increase the amount of terminal carboxyl groups in a very short time without fear of coloring the polyamide, thereby producing a polyamide that is not easily dyed with an acid dye. ..

However, this method is characterized in that the molecular weight is increased. When the polyamide obtained by this method is used as the fiber, the spinnability becomes poor due to the increase in the packing pressure of the polymer melter, and the texture of the fiber becomes poor. It may become too hard and not preferable.

Therefore, in order to obtain a polyamide having a desired molecular weight, it is necessary to raise the water content of the polyamide before the melting reaction to a predetermined water content. However, by increasing the water content, foaming easily occurs, When manufacturing a fiber, there is a problem that the spinnability is significantly reduced.

[0012]

DISCLOSURE OF THE INVENTION The present invention solves the drawbacks of the conventional method, suppresses the change in molecular weight, does not cause yellowing of the polymer, and extremely easily reduces the amount of terminal amino groups in a short time. At the same time, it is an object of the present invention to provide a method for producing a polyamide that is difficult to be dyed with an acid dye by increasing the amount of terminal carboxyl groups.

[0013]

DISCLOSURE OF THE INVENTION In order to solve the drawbacks of the conventional method and to obtain a polyamide which is difficult to be dyed with an acid dye, the present inventors have made earnest studies, and as a result, as a result, a cyclic acid anhydride and a bifunctional N-acyl were obtained. By using lactam in a specific ratio,
The present inventors have found that it is possible to obtain a polyamide in which a change in molecular weight is suppressed, yellowing does not occur, and a terminal carboxyl group amount is increased, and the present invention has been completed.

That is, according to the present invention, a polyamide is mixed with a bifunctional N-acyl lactam and a cyclic acid anhydride in a ratio of 9: 1 to 1: 9.
The amount of the terminal carboxyl groups is 30 g more than the amount of the terminal amino groups by adding them in a ratio of (equivalent ratio) and performing a melting reaction.
It is intended to provide a method for producing a polyamide having an increased amount of terminal carboxyl groups, which is characterized in that the polyamide is modified to have an equivalent amount of 10 ⁶ g or more.

Examples of polyamides used in the present invention include aliphatic polyamides such as nylon 6, nylon 6,6, nylon 4,6, nylon 6,10 and nylon 12.

Further, the polyamide may be a copolymer of a third component, for example, an aromatic component such as terephthalic acid and isophthalic acid, within the range of being melt-moldable.
Of course, in such a polyamide, various additives such as an ultraviolet absorber, a heat stabilizer, a flame retardant, a whitening agent, and
Lubricants, nucleating agents, release agents, pigments, fillers and the like may be added.

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

[Chemical 3] (In the formula, X represents an alkylene group or an aromatic group, and R represents an alkylene group.).

Among the compounds represented by the above general formula [I], compounds in which X is an alkylene group having 4 to 8 carbon atoms, a terephthaloyl group or an isophthaloyl group, and R is an alkylene group having 3 to 5 carbon atoms are preferable. ..

Examples of the compound represented by the general formula [I] include N, N'-terephthaloylbis-ε-caprolactam, N, N'-isophthaloylbis-ε-caprolactam and N, N '. -Adipoylbis-ε-caprolactam, N, N'-adipoylbis-ε-valerolactam, N, N'-isophthaloylbisvalerolactam,
N, N'-isophthaloylbisbutyrolactam, N,
N'-terephthaloyl bis butyro etc. can be mentioned. 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.

Further, examples of the cyclic acid anhydride used in the present invention include succinic anhydride, phthalic anhydride, maleic anhydride, trimellitic anhydride, and the like. Those which do not impair the thermal stability of (1) and promote photoyellowing are desirable.

In the present invention, polyamide and difunctional N are used.
In order to react the acyl lactam and the cyclic acid anhydride, these compounds may be added and stirred in a polymerization kettle at the final stage of the polymerization of the polyamide, or in an extruder when molding into a fiber or film. It is also possible to employ means for melting and kneading both.

Particularly in the case of the latter method, a method of dry blending a predetermined ratio of a bifunctional N-acyl lactam and a cyclic acid anhydride on a polyamide chip and kneading and melting the mixture, or a predetermined ratio of a bifunctional N-acyl compound. There is a method in which a lactam and a cyclic acid anhydride are dissolved in ε-caprolactam and the like and then metered from an extruder inlet.

When the bifunctional N-acyl lactam and the cyclic acid anhydride are added, the polyamide is usually adjusted to a water content of 0.01 to 0.15% by weight which is controlled for fibers and resins. Is desirable.

In the present invention, the addition ratio of the bifunctional N-acyl lactam and the cyclic acid anhydride is 9: 1 to an equivalent ratio.
It should be 1: 9, preferably 4: 1 to 1: 4. If the proportion of the bifunctional N-acyl lactam exceeds 9 equivalents, the melt viscosity of the polymer will increase and the spinnability will be poor, while if it is less than 1 equivalent the resulting polymer will yellow and the melt viscosity will decrease. Therefore, the object of the present invention cannot be achieved.

The total amount of the bifunctional N-acyl lactam and the cyclic acid anhydride added to the polyamide is preferably 0.3 to 4.0 times the equivalent of the terminal amino groups of the polyamide, and particularly preferably 0.1. It is 5 to 2.5 times equivalent. If the total addition amount is less than 0.3 times equivalent, 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. On the other hand, when the amount is more than 4 times the equivalent, the decrease in the molecular weight of the polyamide becomes large, the amount of lactam in the molded product increases, and yellowing coloring of the polyamide becomes noticeable, which is not preferable.

[0026]

When a bifunctional N-acyl lactam and a cyclic acid anhydride are added to a polyamide at an equivalent ratio of 9: 1 to 1: 9 and melt-reacted, the terminal amino groups of the polyamide are extremely reduced and the carboxyl group is reduced. The merging phenomenon of increasing
Moreover, the change in the molecular weight of the polyamide is small. The present invention is an application of such a phenomenon.

[0027]

The present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.
In the examples, each characteristic value and evaluation were as follows. a. Intrinsic viscosity : Shows the intrinsic viscosity obtained by dissolving in m-cresol at 35 ° C. b. Amount of terminal amino group : Polyamide was dissolved in m-cresol and titrated with 0.01N para-toluenesulfonic acid. c. Amount of terminal carboxyl group : Polyamide was dissolved in benzyl alcohol and titrated with 0.1N sodium hydroxide.

[0028] d. Coloring property of polyamide: A polyamide chip was observed and evaluated as follows. ◯: No coloration Δ: Some yellowing x: Yellowing e. Spinnability : Evaluation was made as follows. ◯: Good silk forming property Δ: Slightly bad ×: Bad

Examples 1 to 4 ε-caprolactam was melt-polymerized with water, washed with hot water and dried to adjust the water content to obtain a monomer content of 0.5 to 1.0% and a terminal amino group. 45g equivalent / 10
⁶ g polyamide, terminal carboxyl group amount 47 g equivalent / 1
N, N'-terephthaloylbiscaprolactam powder and succinic anhydride powder were dry-blended in an amount shown in Table 1 onto ⁶ g of polyamide, nylon 6 chips having an intrinsic viscosity of 1.34, and reacted under a nitrogen stream. When a melt-kneading reaction was carried out at a temperature of 250 ° C. and a residence time of 4 minutes, a polyamide having the physical properties shown in Table 1 was obtained.

The obtained polyamide had little decrease in intrinsic viscosity, and was neither colored nor gelled. Further, when this polyamide was directly spun and drawn using a spinneret having a diameter of 0.6 mm and 12 holes, the spinnability was very good.

Comparative Examples 1 to 3 For comparison, N, N'-terephthaloylbiscaprolactam powder and succinic anhydride powder were not added (Comparative Example 1),
Alternatively, a polyamide was obtained in the same manner as in Example 1 except that succinic anhydride alone was added in the amounts shown in Table 1 (Comparative Examples 2 and 3). The results are shown in Table 1.

As shown in Table 1, the polyamides obtained in Comparative Examples 2 and 3 showed a large decrease in intrinsic viscosity and yellowing coloring.

Comparative Example 4 A polyamide was obtained in the same manner as in Example 1 except that N, N'-terephthaloylbiscaprolactam powder was added in the amount shown in Table 1 without adding succinic anhydride powder. .. The results are shown in Table 1.

As shown in Table 1, the obtained polyamide did not show any coloring, but the intrinsic viscosity was greatly increased, and when the yarn was spun, not only the pack pressure increased largely but also the drawability was lowered. The sexual deterioration was seen.

Comparative Example 5 The same procedure as in Comparative Example 5 was carried out except that the polyamide chips were made to absorb moisture up to the moisture content shown in Table 1, and then N, N'-terephthaloylbiscaprolactam powder was added in the amount shown in Table 1. A polyamide was obtained. The results are shown in Table 1.

In the case of this comparative example, the increase in the intrinsic viscosity was small and the pack pressure was stable, but the result was that many yarn breakages occurred on the spinneret surface due to foaming.

[0037]

[Table 1]

Example 5 Epsilon-caprolactam was melt-polymerized with water, washed with hot water and dried to obtain a water content of 0.10%, a monomer content of 0.5 to 1.0%, and a terminal amino group. Nylon 6 chips having a base amount of 46, a terminal carboxyl group amount of 48, and an intrinsic viscosity of 1.34 were added to 0.89% by weight of N, N'-terephthaloylbiscaprolactam powder (50 g equivalent / 10 ⁶ g) and succinic anhydride. 0.30% by weight of powder (30 g equivalent / 10 ⁶ g) was dry blended, and a diameter of 0 was obtained while performing a melt kneading reaction at a reaction temperature of 250 ° C. and a residence time of 4 minutes with a 22 mm melt kneading extruder under a nitrogen stream. Melt spinning and drawing were performed using a 12 mm spinneret with a diameter of 6 mm. Table 2 shows the polyamide properties after the melt reaction and the yarn physical properties of the drawn yarn.

Then, after tubular knitting using a 34 gauge tubular knitting machine, dyeing was performed in the following acidic dye bath at 90 ° C. for 45 minutes, and L,
The a and b values were measured. The results are shown in Table 2. (Acid dye bath) Green dye: Tectilon Yellow 4R 0.1% owf Telon Red FRLL 0.02% owf Tectilon Blue 6G 0.114% owf Aborane AV 2.0% owf Bath ratio 1: 100, pH 6.5 (sodium phosphate, diphosphorus) Adjustment with acid soda) The L, a, and b values were measured by Nippon Denshoku Industries Co., Ltd. OPTICAL SENSORZ.

Comparative Example 6 For comparison, without adding N, N'-terephthaloylbiscaprolactam powder and succinic anhydride powder,
A polyamide was obtained in the same manner as in Example 5, melt-spun and stretched to form a tubular knit, and dyeing evaluation with an acid dye was performed. The results are also shown in Table 2.

As is clear from Tables 1 and 2, according to the present invention, the amount of terminal amino groups can be reduced and the amount of terminal carboxyl groups can be increased while suppressing the change in the intrinsic viscosity of the polyamide to be small, and the acidity can be improved. It can be seen that a significantly lightly dyed polyamide can be obtained by increasing the L value for the dye.

[0042]

[Table 2] Note) In the table, TL is N, N'-terephthaloylbis-ε-
Caprolactam and SA indicate succinic anhydride.

[0043]

Industrial Applicability According to the present invention, it becomes possible to easily obtain a polyamide from an ordinary polyamide which is difficult to be dyed with an acid dye having a large amount of terminal carboxyl groups, and to produce an ordinary fiber, film and resin molding. In addition, it is possible to manufacture a polyamide product having a small change in physical properties, no coloring, and more excellent practicality.

Claims (1)

[Claims] 1. A bifunctional N-acyl lactam and a cyclic acid anhydride are added to polyamide at a ratio of 9: 1 to 1: 9 (equivalent ratio) and melt-reacted, whereby the amount of terminal carboxyl groups is changed to terminal amino groups. A method for producing a polyamide having an increased amount of terminal carboxyl groups, which comprises modifying the polyamide to have an amount of 30 g equivalent / 10 ⁶ g or more in excess of the base amount.