JPH0627191B2 - Method for producing ultra-high molecular weight polyamide molding - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a method for producing an ultra-high molecular weight nylon 6 molded article, and more particularly to a method for producing an ultra-high molecular weight molded article during melt molding. Here, the "ultra high molecular weight" means a molecular weight having an intrinsic viscosity of more than 2 which is obtained by the measuring method described later.

<Prior Art> Polyamides represented by nylon 6 and nylon 66 are widely used in the form of molded articles such as fibers, plastics and films. However, in recent years, the demand for improved tensile strength and toughness for these molded products has become even stronger, and therefore high molecular weight molded products have been strongly demanded. However, in order to obtain a high-molecular-weight molded product, the conventional method is to melt and mold the high-molecular-weight chips in a kneader such as an extruder, but in this case, when re-melting the chips, It has a drawback that the molecular weight is lowered and the terminal group is easily decomposed. Further, there is a method of performing a high temperature polycondensation reaction for a long time under a nitrogen atmosphere or under vacuum in order to prepare a high molecular weight chip, but in this case, the resulting polymer is difficult due to mechanical difficulty such as stirring. The molecular weight of is naturally limited. As another method, solid-phase polymerization of a polymer whose molecular weight has been increased to a certain extent is generally carried out,
In this case, the reaction is required for a long time, so that the productivity is low, and the side reaction is difficult to control.

On the other hand, as a method for obtaining a polyamide having a high degree of polymerization, British Patent No. 693645 discloses a method in which a bis-N-acyl lactam type chain linking agent is added during the polymerization of polyamide, and JP-A-61-171732. The official gazette proposes a method in which a carbamoyllactam type chain-linking agent is added to polyamide and reacted in an extruder. However, the former method has the problems of mechanical agitation and the decrease of the molecular weight at the time of re-melting, and the latter method has a low molecular weight of 1.8 or less as the intrinsic viscosity of the polymer. It didn't go.

In order to solve these problems, the present applicant previously proposed a method of reacting a bifunctional N-acyl lactam and a polyamide in an extruder (Japanese Patent Publication No. 57-53169), which facilitates ultra-high molecular weight conversion. Made possible However, according to the subsequent studies, in the molded product obtained by the method, the melting point thereof is considerably lowered, and the problem that the molded product contains a large amount of lactam monomer remains unsolved. It turned out.

<Object of the Invention> An object of the present invention is that there is a limit to the improvement of the molecular weight, and the melting point decrease is small regardless of the polymerization process involving frequent operations,
Another object of the present invention is to provide a method for obtaining a polyamide molded product having a low lactam monomer content.

<Structure of the Invention> The inventors of the present invention have conducted extensive studies to achieve the above object, and as a result, have found that a bifunctional N-acyl lactam compound as a chain linking agent, a relatively low amino terminal group amount, and a carboxyl group. When melt-kneading a polyamide in which the relationship with the amount of end groups is regulated in a specific range, a lactam monomer content is low, and an ultrahigh molecular weight polyamide molded product having good physical properties such as a melting point or lower is obtained. The inventors have found that and reached the present invention.

That is, in the present invention, nylon 6 satisfying the following formulas (1) and (2) is reacted with a bifunctional N-acyl lactam in a melt kneader to form a desired shape, and the following (3) to ( Five)
A method for producing an ultra-high molecular weight nylon 6 molded article, characterized in that a molded article having the characteristics shown in 1) is obtained.

(here, C _COOH represents the amount of terminal amino groups and the amount of terminal carboxyl groups in units of grams / equivalents / 10 ⁶ g.) Melting point of molded product ≧ 218 ° C. (3) Monomer content in molded product ≦ 1.0 wt% (( 4) [η] ≧ 2.5 of the molded product (5) Nylon 6 referred to in the present invention means a linear polymer obtained by polymerizing ε-caplactam.
Within the range that does not impair the basic properties of nylon 6, ε-
Monomers other than Caplactam may be copolymerized or blended. Here, in order to produce Nylon 6 having more amino terminal groups than carboxyl terminals, it is necessary to add a small amount of an amine component to ε-caprolactam for polymerization. In this case, the amine component may be a monoamine, but it is more advantageous to use a diamine from the viewpoint of polymerization rate. Examples of the diamine include aliphatic amines such as hexamethylenediamine and m-xylylenediamine, and aromatic amines such as p-phenylenediamine and m-phenylenediamine, but any diamine having heat stability may be used. .

Here, the important requirement required for the polymer is the amount of the terminal group, and it is essential to satisfy the above formulas (1) and (2) at the same time. If the formula (1) is not satisfied, finally a high intrinsic viscosity (hereinafter abbreviated as [η]) cannot be obtained. Further, when the expression (1) is satisfied but the expression (2) is not satisfied, not only the melting point of the molded product is lowered, but also the improvement of [η] cannot be expected, and the above (3) to (5) Molded parts with the indicated properties cannot be obtained.

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 residue, 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′-adipoylbis-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 a polyamide satisfying the above formulas (1) and (2) with a bifunctional N-acyl lactam, nylon 6 chips are previously dry-blended and melt-kneaded, or a bifunctional A method in which a solution of N-acyl lactam dissolved in ε-caprolactam or the like is metered into the extruder inlet may be adopted. Here, the amount of the bifunctional N-acyl lactam added to the nylon 6 is adjusted depending on the target molecular weight, but in order to obtain a high molecular weight, it is preferable that the addition amount is about the same as the amino terminal group of the polymer. If this amount exceeds the equivalent, on the contrary, the molecular weight decreases, the melting point decreases greatly, and the monomer content increases, which is not preferable from the viewpoint of physical properties of the molded product.

The melting temperature at this time is 10 to 150 ° C from the melting point of nylon 6.
(Preferably 50-80 ° C) High temperature, kneading time is 1
-20 minutes, preferably 2-6 minutes.

<Operations and Effects of the Invention> In the present invention, when a bifunctional N-acyl laclam is used as a chain linking agent to improve the molecular weight of nylon 6, the amount of terminal amino groups as a polymer is increased. Is less than 85 grams / equivalent / 10 ⁶ grams and the difference between the amount of terminal amino groups and the amount of carboxyl groups Is characterized by using a polyamide having an amino-terminal excess of 20 g · equivalent / 10 ⁶ g or more. This difference is 20
When it is less than gram-equivalent / 10 ⁶ grams, the initial [η]
Even if the value is high, the [η] of the final molded product obtained by reacting with the N-acyl lactam is not so high. Also,
Even if the above difference is 20 or more, when the amount of terminal amino groups is 85 g · equivalent / 10 ⁶ g or more, the obtained molded product has a low melting point and a high lactam monomer content. Also, N-
Since it is necessary to increase the amount of acyllactam added (equivalent to the amino terminal), not only is it economically disadvantageous, but a large amount of the agent causes uneven blending between the pellet and the agent. This leads to an unstable molding state (non-uniform parison thickness in blow molding), the amount of the final molded product,
There is a problem that uneven production occurs and stable production cannot be performed.

According to the present invention, it is possible to easily obtain pellets, fibers, films, and other injection-molded articles of ultra-high [η] polyamide, which were difficult in the past, and bring out new physical properties.

For example, as shown in Example 8 below, the Izod impact strength (with notch) of the ultra-high [η] nylon 6 according to the present invention
Is 2.5 times better than the conventional product, and new applications are expected.

<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] Dissolve 0.2 g, 0.4 g, and 0.8 g of polymer in 100 ml of meta-cresol, and measure η rel (t / to) at 35 ° C. Next, ηrel −1 / C is plotted for each concentration C (g / 100 ml), and [η] is obtained from the intercept of the straight line obtained from the three points.

The relationship between ηrel obtained in sulfuric acid and the above-mentioned intrinsic viscosity [η] is represented by [η] = 0.56 ηrel −0.26. For example, ηrel = 3.62 in Example 2 of JP-A-61-171732 is It corresponds to a 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 penzyl alcohol and titrating with 0.1 N sodium hydroxide.

c. Injection molding Using IS60B manufactured by Toshiba Corp., a test piece was prepared at a molding temperature of 260 ° C, a mold temperature of 60 ° C and a molding cycle of 40 seconds.

d. Evaluation of Characteristics of Molded Articles Tensile Properties ASTM D638, Bending Properties: ASTM D710, Izod Impact Strength: ASTM D256.

Examples 1-5, Comparative Examples 1-7 [epsilon] -caprolactam and m-xylenediamine (MXD)
Was added, melt-polymerized, washed with hot water, and dried to obtain various nylon 6 chips having different water content of 0.01 to 0.03% and monomer content of 0.20 to 0.30% and different terminal groups (Table 1).
This base chip was dry blended with N, N'-terephthaloylbiscaprolactam powder in an amount equivalent to the amount of amino terminal groups, melt-kneaded in an extruder at 270 ° C for 4 minutes, extruded, and then pelletized by cutting. It was created. These results are collectively shown in Table 1. When the polymer having an amino terminal excess according to the present invention is used for the base chip, the ultra-high [η] nylon having a melting point of 218 ° C. or more and a monomer content of 1% or less. It can be seen that 6 molded products can be obtained.

Comparative Example 4 is Example 1 of Japanese Patent Publication No. 57-53169.
Corresponding to the polymer. Further, Example 7 of the publication discloses that the amount of amino end groups is 46.1 equivalent / g, which is 96.1.
Is a typo. That is, in the seventh embodiment, the first embodiment is obviously the first embodiment.
It can be seen from [η] and the molecular weight that the same thing as is used. There is a certain relationship between the amount of end groups and the molecular weight, [η] 1.
In the case of 15, it was confirmed by the experiments of the present inventors that it becomes the terminal group of Example 1.

Example 6 In the place of m-xylylenediamine, 0.2% of hexamethylenediamine was added to ε-caprolactam, and melt polymerization, hot water washing and drying were carried out to obtain [η] = 1.60. A nylon 6 tip with C _COOH = 14 was made. N to this,
0.96 wt% N'-adipoylbis-ε-caprolactam
(57 grams / equivalent) After dry blending, pellets were prepared in the same manner as in Examples 1 to 5. As a result, [η] = 3.96, C _COOH = 17, melting point 219 ° C, monomer content 0.65% were obtained.

Example 7 In Example 6, N, N′-terephthaloylbis- was used instead of N, N′-adipoylbis-ε-caprolactam.
ε-caprolactam was added to the polymer in an amount of 1.00 wt% (57
As a result of using [gram / equivalent], [η] = 3.79, Pellets having a C _COOH = 17, a melting point of 218 ° C. and a monomer content of 0.68% were obtained.

Example 8 and Comparative Examples 8 to 9 A predetermined amount of N, N'-terephthaloylbis-ε-caprolactam was dry blended with the base chip shown in Table 2 and injection molding was performed. The characteristics of the test piece are shown in Table 2. The following is clear from this example. That is, a. By using the nylon 6 limited by the present invention, not only a super [η] nylon molded product having a low monomer content and a high melting point can be obtained, but also the notched impact strength of the molded product is significantly increased. .

b. On the other hand, Comparative Example 8 And an example of using nylon out of the scope of the present invention, in this case, the monomer content is high and only a molded product having a low melting point can be obtained.

c. In addition, Comparative Example 9 And using nylon outside the scope of the present invention,
The rise in [η] is insufficient, and improvement in notched impact strength cannot be expected.

Example 9 N, N′-Bisterehetaroyl-ε-caprolactam, cuprous iodide, and potassium iodide were added to the base chip used in Example 2 at 1.00 wt% (107 grams-equivalent) and 0.018 w, respectively.
t% and 0.24 wt% were dry blended. 22mm for this tip
Using a φ-extruder type melt spinning machine, a cylinder temperature of 280 ° C., a pack temperature of 305 ° C., a discharge rate of 10 g / min (zone retention time of about 6 minutes), and a spinning speed of 250 m were extruded from a nozzle having 12 holes and wound up. Then, it was stretched 3.5 times on a hot plate at 190 ° C. The [η] of this yarn is 2.75, the monomer content is 0.65% (by weight), the melting point is 219 ° C, C _COOH = 34, strength = 9.0 g / de, elongation = 16%.

Claims (1)

[Claims] 1. Nylon 6 satisfying the following formulas (1) and (2):
Is reacted with a bifunctional N-acyl lactam in a melt-kneader to form a desired shape to obtain a molded article having the characteristics shown in (3) to (5) below. Method for producing molded product of molecular weight nylon 6 (here, C _COOH represents the amount of terminal amino groups and the amount of terminal carboxyl groups in units of grams / equivalents / 10 ⁶ g.) Melting point of molded product ≧ 218 ° C. (3) Monomer content in molded product ≦ 1.0 wt% (( 4) [η] ≧ 2.5 of molded product (5)