JP2002322272A - Method for producing polyamide prepolymer and polyamide, and polyamide obtained from the production method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a polyamide resin comprising caprolactam as the main raw material, which enables the omit or time shortage of a hot water extraction process and lowers an unreacted caprolactam content and an oligomer content. SOLUTION: The polyamide prepolymer having an amino group content of >=0.1 mmol/g and a cyclic oligomer content of <=0.6 wt.% is prepared by thermally treating an aqueous caprolactam solution having a water content of 2 to 20 wt.% at 250 to 330 deg.C for 1 to 30 min under pressurization. For example, the prepared polyamide prepolymer is fed into an atmospheric pressure polymerization device and then polymerized under a temperature condition that the highest value of the polymerization temperature is less than or equal to 10 deg.C + the melting point of the obtained polyamide, thus obtaining the polyamide having an unreacted caprolactam content of <=15 wt.% and an oligomer content of <=1.8 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyamide prepolymer, a polyamide resin, and a method for producing a polyamide resin, which are produced mainly from caprolactam. More specifically, in a process for producing a polyamide prepolymer having a very small amount of cyclic oligomers and a caprolactam-based polyamide resin when subjected to heat treatment for a specific time using caprolactam as a main material, unreacted caprolactam content and oligomer content And a method for producing the polyamide resin, which can be prepared with high efficiency and low energy.

[0002]

2. Description of the Related Art Polyamide resins containing caprolactam as a main raw material are used in clothing fibers and industrial fibers by taking advantage of their excellent properties. Furthermore, they are used as injection molded products in the fields of automobiles, electric and electronic fields, and the like. It is widely used as an extruded film and a stretched film mainly for food packaging.

[0003] A polyamide resin mainly composed of caprolactam is usually produced by heating caprolactam in the presence of a small amount of water. This manufacturing method is a relatively simple process, and is a manufacturing method widely used in the world. An outline of a general-purpose polycapramide polymerization method described on pages 63 to 65 of "Polyamide Resin Handbook" (Osamu Fukumoto, Nikkan Kogyo Shimbun) is described below.

[0004] Caprolactam is melted and supplied to an atmospheric pressure polymerization tower heated to about 260 ° C. After staying in this polymerization tower for about 10 hours, the mixture is discharged from the lower part of the tower into a strand and discharged into a water tank to be pelletized. You. Since the polycapramide resin pellets thus obtained contain caprolactam monomers and oligomers generated at the polymerization equilibrium, they are then supplied to a hot water extraction tower, countercurrently extracted with hot water sent from the bottom of the tower, and then removed from the bottom. . Since the pellets after extraction contain a large amount of water, they are dried at about 100 ° C. in a vacuum or an inert gas atmosphere.

[0005] Since the polyamide after caprolactam polymerization contains unreacted caprolactam and oligomers, a hot water extraction step after polymerization is considered to be essential. This hot water extraction step requires a lot of energy, and the unreacted monomer reduces the productivity. Therefore, it is required to omit this step or shorten the time. In particular, it is required to reduce oligomers which have low solubility in water and are difficult to extract.

As a means for omitting the hot water extraction step, there is a method of removing unreacted caprolactam and oligomers by treating the polyamide after polymerization in a molten state at a high temperature and under a high vacuum (US Pat. 35585
No. 67). However, there are few examples applied to actual production, especially since it is difficult to remove oligomers.
The degree is not enough.

Another approach is to reduce unreacted monomers and oligomers to reduce the time required for the hot water extraction step. That is, in order to omit the hot water extraction step or shorten the time, the idea is to reduce unreacted caprolactam and oligomers after polymerization. Several methods have been proposed for reducing such unreacted caprolactam and oligomers.

For example, JP-A-59-164327 proposes a method in which a prepolymer of caprolactam is polymerized and then further polymerized under pressure to reduce oligomers and gels.

[0009] In this method, caprolactam is added to 220-
After prepolymerization at 280 ° C, 240-29
A method for obtaining a polyamide polymer having a low oligomer or gel content by further polymerizing at 0 ° C. is disclosed. Although this method is effective for gel reduction, the effect of oligomer reduction in this step is insufficient due to the large thermal history of the prepolymerization step.

Furthermore, Japanese Patent Publication No. 50-26594 proposes a method for lowering the polymerization temperature to reduce the amount of oligomers.

According to this method, the polyamide which forms caprolactam having a water content of 0.5% by weight or less has a melting point equal to or higher than the melting point of the polyamide.
A method for producing a polyamide resin having a low cyclic oligomer content by polymerizing in a temperature range of 20 ° C. or less is taught. However, looking at the examples, it was shown that a polyamide having a cyclic oligomer content of 0.9% by weight was obtained, but the amount of unreacted caprolactam at that time was 1%.
At least 5%, the reduction of unreacted substances is insufficient. That is, there is a problem that the yield of polyamide is low and the productivity is low.

The present inventors have previously described Japanese Patent Application Laid-Open No. 11-34334.
No. 1, in the presence of dicarboxylic acid and diamine,
A polyamide resin having a small amount of oligomers is produced by polymerizing at or below the melting point of the generated polyamide, and caprolactam is obtained by heating the obtained polyamide resin under reduced pressure.
Although a method for removing oligomers has been proposed, the development of a polymerization method having a low unreacted product and oligomer amount and high productivity has been demanded.

As described above, in the method for producing a polyamide resin using caprolactam as a main raw material, a method capable of producing a high-quality polyamide resin having low caprolactam content and oligomer content at low cost has been known. Did not.

[0014]

SUMMARY OF THE INVENTION Accordingly, the present inventors
An object of the present invention is to provide a method for producing a polyamide resin having a low unreacted caprolactam content and a low oligomer content in order to solve the above-mentioned problems of the prior art and to omit or shorten the time for the hot water extraction step. And

[0015]

As a result of intensive studies to solve the above problems, a caprolactam aqueous solution having a specific water content is heat-treated under pressure and at a specific temperature for a short time in the presence of a specific additive. By producing a polyamide prepolymer having a large amino group content and a small cyclic oligomer content, and polymerizing under a temperature condition equal to or lower than the melting point of the polyamide for producing the prepolymer, the caprolactam content and the oligomer content are reduced. Have been found to be able to produce a polyamide resin with low values of both, and have reached the present invention.

That is, the object of the present invention is to provide (1) an aqueous solution of caprolactam having a water content of 2 to 30% by weight and at least one selected from dicarboxylic acids, diamines and salts thereof in an amount of 0.05 to 5 mol% based on the caprolactam. The amount of amino groups obtained by heat-treating a mixture consisting of various components for a period of 30 minutes or less is 0.1 mmol.
A polyamide prepolymer having a content of 1/1 g or more and a cyclic oligomer content of 0.6% by weight or less.

(2) The amount of amino groups is 0.15 mmol / 1
g or more and the cyclic oligomer content is 0.4% by weight or less.

(3) An aqueous solution of caprolactam having a water content of 2 to 30% by weight and 0.05 to 5
mol% of at least one component selected from dicarboxylic acids, diamines and salts thereof, and heating the mixture under pressure at a temperature of 200 to 330 ° C. for 1 to 30 minutes. .1 mmol / 1 g or more,
And a method for producing a polyamide prepolymer having a cyclic oligomer content of 0.6% by weight or less.

(4) The amino group content is 0.15 mmol /
(3) The method for producing a polyamide prepolymer according to (3), wherein the content of the cyclic oligomer is 1 g or more and the content of the cyclic oligomer is 0.4% by weight or less.

(5) An aqueous solution of caprolactam having a water content of 2 to 30% by weight and 0.05 to 5 m
A polyamide having the following properties, which is produced by a melt polymerization of a mixture of at least one component selected from diol acids, dicarboxylic acids, diamines and salts thereof in a polymerization time of 20 hours or less. Caprolactam content: 15% by weight or less, oligomer content: 1.8% by weight or less, total content of cyclic dimer to tetramer: 0.9% by weight or less.

(6) A method for producing a polyamide containing a capramide unit as a main component, wherein the polyamide has a water content of 2 to 30.
% By weight of a caprolactam aqueous solution and 0.05 to 5 mol% of at least one component selected from dicarboxylic acids, diamines and salts thereof based on the caprolactam are mixed, and the mixture is heated to 200 to 330 ° C. under pressure. A polyamide prepolymer having an amino group content of 0.1 mmol / 1 g or more and a cyclic oligomer content of 0.6% by weight or less, obtained through a step of heating at a temperature of 1 to 30 minutes, is supplied to a normal pressure polymerization apparatus, A polyamide having a caprolactam content of 15% by weight or less and an oligomer content of 1.8% by weight or less, characterized in that the polymerization is carried out under the temperature condition of the melting point of the polyamide capable of obtaining the highest polymerization temperature + 10 ° C or less. Production method.

(7) The process for producing a polyamide according to (6), wherein the polymerization is carried out under a temperature condition in which the maximum value of the polymerization temperature is not higher than the melting point of the obtained polyamide.

(8) The method for producing a polyamide according to (6) or (7), wherein the polyamide prepolymer has a water content of 4% by weight or less when supplied to an atmospheric pressure polymerization apparatus.

(9) The process for producing a polyamide according to any one of (6) to (8), wherein the prepolymer is flushed at an upper portion of the atmospheric pressure polymerization apparatus to evaporate and remove water before supplying the polyamide prepolymer to the atmospheric pressure polymerization apparatus. .

(10) The method for producing a polyamide according to any one of (6) to (9), wherein the atmospheric pressure polymerization apparatus is a continuous atmospheric pressure polymerization apparatus.

(11) A polyamide obtained by the production method according to any one of (6) to (10).

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below.

The polyamide prepolymer referred to in the present invention is a composition obtained as a raw material for polyamide through the following steps, and is a mixture mainly composed of a polyamide chain oligomer (including aminocaproic acid), a cyclic oligomer, and unreacted raw materials. Say

Caprolactam is mainly used as a raw material of the polyamide used in the method for producing a polyamide prepolymer or the method for producing a polyamide of the present invention. One or more other lactams may be used in combination within a range not exceeding 20 mol% of the entire raw material of the polyamide, as long as the object of the present invention is not hindered. If it exceeds 20 mol%, the crystallinity of the obtained polyamide polymer may be too low, which may limit the practical use.

Specific examples of other lactams include valerolactam, enantholactam, capryllactam, undecalactam, laurolactam, and the like.
Of these, undecalactam and laurolactam are preferably used because they are effective for controlling the crystallinity.

In the method for producing a polyamide prepolymer of the present invention, an aqueous solution of caprolactam is prepared. The water content at this time is in the range of 2 to 30% by weight, preferably 3 to 30% by weight, more preferably 4 to 27% by weight, and particularly preferably 5 to 2% by weight based on the total amount of the raw materials.
5% by weight. If the water content is outside the range of 2 to 30% by weight, the amount of oligomers in the polyamide prepolymer increases until the required amount of amino groups is obtained, and the object of the present invention cannot be achieved.

In the present invention, the water content is 2 to 30% by weight.
To the caprolactam together with the caprolactam of 0.1.
At least one component selected from a dicarboxylic acid, a diamine and a salt thereof in an amount of from 0.5 to 5 mol% is mixed with the aqueous solution of caprolactam and used. Among them, it is preferable to use a dicarboxylic acid or a diamine.

Examples of the dicarboxylic acid include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecandioic acid, dodecandioic acid, brassic acid, and tetradecanedioic acid. Acids, pentadecandioic acid, aliphatic dicarboxylic acids such as octadecandioic acid, alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid, phthalic acid, isophthalic acid,
Examples thereof include aromatic dicarboxylic acids such as terephthalic acid and naphthalenedicarboxylic acid. Sebacic acid, adipic acid, terephthalic acid, and isophthalic acid are preferred. Of these, adipic acid and terephthalic acid are particularly preferably used.

Examples of the diamine include ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 1,7-diaminoheptane, and 1,8-diaminohexane. Diaminooctane, 1,9-diaminononane, 1,10-diaminodecane, 1,11-diaminoundecane, 1,12-
Diaminododecane, 1,13-diaminotridecane,
1,14-diaminotetradecane, 1,15-diaminopentadecane, 1,16-diaminohexadecane, 1,
17-diaminoheptadecane, 1,18-diaminooctadecane, 1,19-diaminononadecane, 1,20-
Examples thereof include aliphatic diamines such as diaminoeicosane, cyclohexanediamine, alicyclic diamines such as bis- (4-aminohexyl) methane, and aromatic diamines such as xylylenediamine. 4
-Diaminobutane, 1,6-diaminohexane, xylylenediamine are preferably used.

Examples of the salt of a dicarboxylic acid and a diamine include the salts of the dicarboxylic acid and the diamine. Among them, a salt of adipic acid and 1,6-diaminohexane, and a salt of terephthalic acid and 1,6-diaminohexane are preferable. Used.

Although the effect is not necessarily clear, at least one component selected from the group consisting of dicarboxylic acids, diamines and salts thereof has a reaction promoting effect. It seems that the content of cyclic oligomer in the polymer can be reduced, the polymerization time can be shortened, and the content of oligomer in the polyamide can be reduced. The mixing ratio of this component is preferably 0.07 to 4 mol% or less, more preferably 0.1 to 3 mol%, based on caprolactam. If the mixing ratio of the components exceeds 5 mol%, problems such as a decrease in the degree of polymerization obtained, a decrease in the melting point and crystallinity of the polyamide polymer, and a decrease in the moldability and physical properties of the molded product occur.
If it is less than 05 mol%, there is no effect of reducing cyclic oligomers in the polyamide prepolymer and polyamide.

In the method for producing a polyamide prepolymer of the present invention, it is necessary to perform a heat treatment under pressure at 200 to 330 ° C. for 1 to 30 minutes.

The pressure is not particularly limited as long as it is under pressure, but is preferably 0.111 to 6.08 MPa (1.1 to 60 a
tm, preferably in the range of 1.14 to 62.00 kg / cm 2, and 0.152 to 5.065 MPa (1.5 to 50 MPa).
atm, 1.55 to 51.67 kg / cm 2). Under a pressure of less than 0.111 MPa, the efficiency of amino group generation during prepolymerization decreases, so that the amount of oligomers in the polyamide prepolymer increases until the required amount of amino groups is obtained. On the other hand, 5.065 MPa
When the value exceeds, the increment of the effect corresponding thereto is small, but rather the burden on the handling and the apparatus is large, which is disadvantageous in terms of productivity and economy.

The processing temperature for preparing the polyamide prepolymer of the present invention is in the range of 200 to 330 ° C. Preferably from 205 to 325 ° C, particularly preferably from 210 to 32 ° C.
0 ° C. If it is lower than 200 ° C., the content of the cyclic oligomer at the time when the required amount of amino group is obtained is large, and if it is higher than 330 ° C., it is difficult to control the amount of amino group in the reaction product and lacks industrial stability.

The heating time for preparing the polyamide prepolymer of the present invention is 1 to 30 minutes. The upper limit is preferably 25 minutes or less, particularly preferably 20 minutes or less.
If the time exceeds 30 minutes, the content of the cyclic oligomer in the reaction product increases, and if the time is less than 1 minute, the amino group content fluctuates, and it becomes difficult to control the degree of polymerization of the polyamide in the polymerization step.

The amount of amino groups in the polyamide prepolymer of the present invention is at least 0.1 mmol / 1 g. Further, it is preferably at least 0.15 mmol / 1 g reactant, particularly preferably at least 0.2 mmol / 1 g. 0.1mmo
If the amount is less than 1/1 g, the content of the oligomer in the polyamide increases when the polyamide is produced from the obtained polyamide prepolymer, and the object of the present invention cannot be achieved. Although there is no upper limit to the amount of the amino group, it is usually 1.0 mm in consideration of productivity.
ol / g or less.

The content of the cyclic oligomer in the polyamide prepolymer of the present invention is 0.6% by weight or less. It is preferably at most 0.4% by weight, particularly preferably at most 0.3% by weight. If the content exceeds 0.6% by weight, the content of oligomers in the polyamide polymer increases when the polyamide polymer is produced from the obtained polyamide prepolymer. The lower limit of the cyclic oligomer content is not particularly limited, but is usually 0.01% by weight.

When the polyamide of the present invention is produced by melt polymerization within 20 hours, the unreacted caprolactam content is 15 wt% or less, the oligomer content is 1.8 wt% or less,
It is necessary to have a total of 0.9% by weight or less of the total content of the cyclic dimer to tetramer, and by satisfying this requirement, it is possible to produce a high quality polyamide with high productivity. It becomes possible.

In the method for producing a polyamide of the present invention, caprolactam can be additionally added to the polyamide prepolymer at the start of the polymerization to carry out the polymerization. The additional amount of caprolactam is not particularly limited as long as the amino group content in the raw material composition comprising the polyamide prepolymer and the additional caprolactam is within a range of 0.1 mmol / 1 g or more.

In the method for producing a polyamide of the present invention, the reaction product obtained by the above reaction is supplied to a polymerization apparatus under normal pressure to carry out the polymerization reaction. The polymerization apparatus used at this time is not particularly limited. An apparatus used for the polymerization of caprolactam can be used. Specifically, a liquid-phase polymerization apparatus such as a continuous-type normal-pressure polymerization apparatus and a batch-type polymerization apparatus can be used.
Among them, a continuous atmospheric pressure polymerization apparatus is preferable from the viewpoint of productivity.

In the method for producing a polyamide of the present invention, the maximum value of the polymerization temperature is determined by the melting point of the obtained polyamide + 1
Polymerization is performed under a temperature condition of 0 ° C. or less. If the polymerization temperature exceeds the melting point of the polyamide at which the highest temperature is obtained + 10 ° C., the oligomer content increases, and if the polymerization temperature is too low, the time required for the polymerization increases, and the production efficiency decreases. Therefore, the polymerization temperature is preferably carried out in the range of 160 to 232C, more preferably in the range of 170 to 222C,
A range from 180 to 220 ° C. is particularly preferred. The melting point is determined by using a differential scanning calorimeter (D) using a sample obtained by removing caprolactam, oligomers, and the like from the obtained polyamide by hot water extraction, melting the polyamide, and then rapidly cooling the polyamide.
SC) is defined as a peak top temperature of an endothermic peak based on crystal melting measured at a heating rate of 20 ° C./min.

If the above conditions are satisfied, the polymerization temperature profile can be arbitrarily set according to a conventional method. In the method for producing a polyamide of the present invention, the polymerization time is within 20 hours.
It is preferably within 8 hours, more preferably within 16 hours. If the time exceeds 20 hours, the practical value decreases in terms of production efficiency.

In the method for producing a polyamide of the present invention, the content of caprolactam in the finally obtained polyamide is 1
5% by weight or less. It is preferably at most 13% by weight, more preferably at most 11% by weight. If it exceeds 15% by weight, the time and energy required for the hot water extraction step increase. Although the lower limit of the caprolactam content is not limited, it is usually about 3% by weight.

In the method for producing a polyamide of the present invention, the oligomer content in the finally obtained polyamide is 1.8.
% By weight or less. It is preferably at most 1.5% by weight, more preferably at most 1.3% by weight. 1.8
Exceeding the weight percent increases the time required for the hot water extraction process,
The caprolactam and oligomer content after removal of oligomer volatilization increases. The lower limit of the oligomer content is not limited, but is usually about 0.6% by weight.

In the polyamide of the present invention, the total content of cyclic dimer and tetramer in the finally obtained polyamide is 0.9% by weight or less. It is preferably at most 0.85% by weight, more preferably at most 0.8% by weight.
If it exceeds 0.9% by weight, the time required for the hot water extraction step will increase, and the content of oligomers after removal of caprolactam and oligomers will increase. The lower limit of the total content of the cyclic dimer to tetramer is not limited, but is usually about 0.2% by weight.

In the method for producing a polyamide of the present invention, there is no limitation on the water content when supplied to the atmospheric polymerization apparatus, but it is preferably 4% by weight or less, particularly preferably 2.5% by weight or less. If the amount exceeds 4% by weight, a large amount of heat is required for heating during the production of the polyamide, so that the productivity tends to decrease and the oligomer content in the polyamide tends to increase.

In the method for producing a polyamide polymer of the present invention, when the polyamide prepolymer obtained by the heat treatment under pressure is supplied to the atmospheric polymerization apparatus, the reactant after the heat treatment under pressure is flushed to the upper part of the atmospheric polymerization apparatus. It is preferably employed to remove water by evaporation. By removing water by evaporation, the amount of heat required for heating when producing the polyamide can be reduced, and the control of the polymerization temperature can be facilitated.

In the method for producing a polyamide polymer of the present invention, caprolactam and oligomers may be further removed from the obtained polyamide by hot water extraction, or may be volatilized and removed by heating under reduced pressure. After removing the caprolactam and oligomer by heating at, hot water extraction may be further performed.

The volatilization and removal of caprolactam and oligomer by heating under reduced pressure may be carried out in a solid phase or in a molten state after the polymerization reaction product is solidified such as pellets. Volatilization removal in the molten state may be carried out by solidifying the polymerization reaction product into pellets or the like, followed by melting and heating under reduced pressure using an extruder, thin film evaporator, etc., and the polymerization in the molten state discharged from the polymerization tower. The reaction product may be directly supplied to an extruder, a thin film evaporator, or the like.

In addition, the degree of polymerization of the polyamide can be adjusted to a suitable value according to the application in volatilization and removal of caprolactam and oligomer by heating under reduced pressure.

The polyamide obtained by the method for producing a polyamide of the present invention has a melting point lower than the melting point of the polyamide so as to obtain a suitable viscosity for applications requiring a high viscosity of the polyamide such as extrusion molding. It is preferable to adjust the degree of polymerization to a desired degree by a solid phase decompression treatment in which a heat treatment is performed at a temperature and a reduced pressure.

The degree of polymerization of the polyamide obtained by the method for producing a polyamide according to the present invention is such that the sample concentration is 0.01 g / mL.
As a relative viscosity at 25 ° C. of a 98% sulfuric acid solution of
Preferably it is 2.2 to 8.0. Furthermore, preferably 2.2 to 7.0, particularly preferably 2.2 to 6.5,
Most preferably, it is 2.2 to 6.0. 1. The relative viscosity is 2.
If it is less than 2, the mechanical properties are insufficiently developed, and if it exceeds 8.0, the melt viscosity is too high and molding becomes difficult.

In the method for producing a polyamide of the present invention, the terminal can be blocked with a carboxylic acid compound, if necessary. When adding a monocarboxylic acid to block the end,
The terminal group concentration of the obtained polyamide resin is lower than when no terminal blocking agent is used. On the other hand, when the terminal is blocked with dicarboxylic acid, the total amount of terminal groups does not change, but the ratio of amino terminal groups to carboxyl terminal groups can be changed. Specific examples of the carboxylic acid compound include acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid,
Caprylic acid, pelargonic acid, undecanoic acid, lauric acid, tridecanoic acid, myristic acid, myristoleic acid,
Aliphatic monocarboxylic acids such as palmitic acid, stearic acid, oleic acid, linoleic acid, and arachinic acid, cyclohexanecarboxylic acids, alicyclic monocarboxylic acids such as methylcyclohexanecarboxylic acid, benzoic acid, toluic acid, and ethylbenzoic acid Aromatic monocarboxylic acids such as phenylacetic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecandioic acid, dodecanedioic acid, brassic acid, Aliphatic dicarboxylic acids such as tetradecandioic acid, pentadecandioic acid, and octadecandioic acid, alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid, and aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, and naphthalenedicarboxylic acid And the like.

In addition, as a method of adding the terminal blocking agent, in the case of a monocarboxylic acid, a method of charging the polyamide prepolymer with a raw material such as caprolactam at the beginning of the heat treatment, a method of adding during the heat treatment, and a method of adding after the heat treatment, A method of adding before the addition to the atmospheric pressure polymerization apparatus, a method of adding the polyamide resin in a molten state when removing unreacted caprolactam and oligomers, and the like can be adopted. A method of adding the polyamide resin in a molten state before removing the unreacted caprolactam and oligomer in a molten state, and the like are used. The terminal blocking agent may be added as it is, or may be added after being dissolved in a small amount of a solvent.

In the production method of the present invention, for example, antioxidants and heat stabilizers (hindered phenols, hydroquinones, phosphites and their substitutes, copper halide, iodine compounds, etc.) Weathering agents (resorcinol-based, salicylate-based, benzotriazole-based, benzophenone-based, hindered amine-based, etc.), mold release agents and lubricants (such as aliphatic alcohols, aliphatic amides, aliphatic bisamides, bis-ureas and polyethylene waxes), pigments (sulfurized) Cadmium, phthalocyanine, carbon black, etc., dyes (nigrosine, aniline black, etc.), crystal nucleating agents (talc, silica, kaolin, clay, etc.), plasticizers (octyl p-oxybenzoate, N-butylbenzenesulfonamide, etc.) , Antistatic agent (alkyl sulfate type anio -Based antistatic agents, quaternary ammonium salt-type cationic antistatic agents, nonionic antistatic agents such as polyoxyethylene sorbitan monostearate, betaine amphoteric antistatic agents, etc.), flame retardants (melamine cyanurate, water) Hydroxides such as magnesium oxide and aluminum hydroxide, ammonium polyphosphate, brominated polystyrene, brominated polyphenylene oxide, brominated polycarbonate, brominated epoxy resin, or a combination of these brominated flame retardants with antimony trioxide), Fillers (graphite, barium sulfate, magnesium sulfate, calcium carbonate, magnesium carbonate, antimony oxide, titanium oxide, aluminum oxide, zinc oxide, iron oxide, zinc sulfide, zinc, lead, nickel, aluminum,
Copper, iron, stainless steel, glass fiber, carbon fiber, aramid fiber, bentonite, montmorillonite, synthetic mica, and other particulate, fibrous, acicular, and plate-like fillers), and other polymers (other polyamides, polyethylene, polypropylene) , Polyester, polycarbonate, polyphenylene ether,
Polyphenylene sulfide, liquid crystal polymer, polysulfone, polyether sulfone, ABS resin, SAN resin,
Polystyrene, etc.) can be added at any time.

The polyamide obtained by the production method of the present invention can be formed into a molded product by a usual molding method, similarly to a conventional polyamide. There is no particular limitation on the molding method, and known molding methods such as injection molding, extrusion molding, blow molding, and press molding can be used. The term "molded article" used herein refers to a molded article in a narrow sense by injection molding or the like, as well as fibers,
It also includes excipients such as films, sheets, tubes, and monofilaments.

[0062]

EXAMPLES The present invention will be specifically described below with reference to examples. The analysis and measurement described in Examples and Comparative Examples were performed according to the following methods.

(1) Amount of amino group in polyamide prepolymer About 0.2 g of an object to be measured was precisely weighed and dissolved in 25 cc of a phenol / ethanol mixed solvent (83.5: 16.5, volume ratio). Titration was performed using a 02N hydrochloric acid aqueous solution.

(2) Content of Cyclic Oligomer in Polyamide Prepolymer The object to be measured was pulverized, passed through a JIS standard sieve, 24 mesh, and the non-passable 124 mesh was collected, and about 20 g of the powder was collected. The mixture was extracted with 200 ml of methanol for 3 hours using a Soxhlet extractor, and the cyclic oligomer contained in the extract was quantified using a high performance liquid chromatograph. In the following examples, cyclic oligomers of 7-mers or more were not detected. The measurement conditions are as follows. High-performance liquid chromatograph: Waters 600E Column: GL Sciences ODS-3 Detector: Waters 484 Tunable Absorbance Detector Detection wavelength: 254 nm Injection volume: 10 μl Solvent: methanol / water (The composition of methanol / water is 20: 80 → 80 : 20 gradient analysis) Flow rate: 1 ml / min.

(3) Water content of polyamide prepolymer Measured using Hiranuma trace water content measuring device AQ-6.

(4) Caprolactam Content in Polyamide The polyamide was pulverized, passed through a JIS standard sieve 24 mesh, the non-passed polyamide powder was collected in 124 mesh, and about 20 g of the powder was subjected to Soxhlet extraction with 200 ml of methanol for 3 hours. Caprolactam contained in the extract was quantified using a high performance liquid chromatograph. The measurement conditions are as follows. High performance liquid chromatograph: Waters 600E Column: GL Sciences ODS-3 Detector: Waters 484 Tunable Absorbance Detector Detection wavelength: 254 nm Injection volume: 10 μl Solvent: methanol / water (20:80 (volume ratio)) Flow rate: 1 ml / min.

(5) Oligomer Content in Polyamide The polymerization reaction product was pulverized, passed through a JIS standard sieve 24 mesh and collected without passing through 124 mesh, and about 20 g of the powder was subjected to Soxhlet extraction with 200 ml of methanol for 3 hours. Then, after caprolactam contained in the extract was quantified by the above-mentioned method, the residue was evaporated to dryness by an evaporator, and further dried at 80 ° C. for 8 hours to obtain a residue, which was determined in the above section (4). The amount of caprolactam was subtracted to obtain the oligomer content.

(6) Relative viscosity of sulfuric acid (ηr) Measurement was carried out in 98% sulfuric acid at a concentration of 0.01 g / ml at 25 ° C. using an Ostwald viscometer.

(7) Content of Cyclic Dimer to Polymer in Polyamide The polyamide was pulverized, passed through a JIS standard sieve 24 mesh, and the non-permeated polyamide powder was collected in 124 mesh. About 20 g of the powder was dissolved in 200 ml of methanol for 3 hours. Soxhlet extraction was performed, and the content of the cyclic dimer to tetramer contained in the extract was quantified using a high performance liquid chromatograph. The measurement conditions are as follows. High performance liquid chromatograph: Waters 600E Column: GL Sciences ODS-3 Detector: Waters 484 Tunable Absorbance Detector Detection wavelength: 254 nm Injection volume: 10 μl Solvent: methanol / water (20:80 (volume ratio)) Flow rate: 1 ml / min.

A. Raw Materials Used The following raw materials were used in the following Examples and Comparative Examples.

The caprolactam was prepared by melting a special grade product of Tokyo Chemical Industry Co., Ltd. and drying it with a molecular sieve.

For 1,6-diaminohexane, terephthalic acid and adipic acid, special grade products of Tokyo Chemical Industry Co., Ltd. were used as they were.

The 1,6-diaminohexane adipate and 1,6-diaminohexane terephthalate used in the Examples and Comparative Examples were prepared by dissolving the above diamines and dicarboxylic acids in equimolar amounts in hot water. After cooling, the precipitated crystals were filtered and vacuum dried at 80 ° C. for 8 hours.

B. FIG. 1 shows a schematic diagram of an apparatus used for the heat treatment and the normal pressure continuous polymerization experiment, and the explanation will be made with reference to the drawings.

An aqueous solution of caprolactam having a predetermined composition was charged into the raw material storage tank 1, and then supplied to the pressurized heat treatment tank 4 using the raw material supply pump 2, and heat treatment was continuously performed under predetermined conditions. Next, the obtained polyamide prepolymer was supplied to the atmospheric pressure continuous polymerization tower 7 and polymerized under predetermined conditions to obtain a polymerization reaction product.

The pressure during the pressurizing and heating treatment was controlled by the opening of the valve 5 in the middle of the flow path.

In the analysis of the prepolymer, the polyamide prepolymer sampling port 6 was supplied before the supply to the atmospheric pressure continuous polymerization tower 7.
, A sample was collected and subjected to various analyses.

C. Melt volatilization removal of unreacted caprolactam / oligomer A twin screw extruder with a 30 mmφ vent manufactured by Nippon Steel Works was used. The conditions are as follows. L / D = 45.5, same direction rotation, deep groove type Barrel temperature: The temperature from the raw material supply side is 160/240/250/260/260/260/2
60/250/250 ° C ・ Decompression degassing from the second, fourth and sixth zones at 133 Pa (1 Torr) ・ Rotation speed 200 rpm.

D. Solid phase volatilization removal of unreacted caprolactam / oligomer 133 Pa (1 To
rr), volatile removal was performed at 150 ° C. for 6 hours.

E. Removal of unreacted caprolactam oligomer by hot water extraction Unreacted caprolactam in the polymerization reaction product is 0.05
The extraction time required to reduce the weight of the oligomer to 1.0% by weight or less was measured. For the extraction, cylindrical pellets of polyamide resin (diameter about 2 mm, length about 3
mm). The extraction conditions are as follows. Extraction solvent: water Extraction bath ratio: polyamide / water = 1/20 Extraction temperature: 98 ° C.

Examples 1 to 6 and Comparative Examples 1 and 2 Heat treatment and normal pressure continuous polymerization were carried out under the conditions shown in Tables 1 and 2.

As can be seen from a comparison between Examples 1 to 5 and Comparative Examples 1 to 4, the polyamide polymer obtained by the production method of the present invention has a small amount of both unreacted caprolactam and oligomer, and particularly has a large amount of oligomer. Was found to decrease.

Examples 7 and 8 and Comparative Example 3 Caprolactam and oligomers were removed from the polyamide obtained in Examples 1 and 4 or Comparative Example 1 by melting and volatilization. Table 3 shows the results. As a result, according to the method of the present invention, it is possible to obtain a polyamide having a small content of caprolactam and oligomer, having an unreacted caprolactam content of 0.05% by weight or less and an oligomer content of 0.98% by weight or less. all right.

Examples 9, 10 and Comparative Example 4 Caprolactam and oligomers were subjected to solid phase volatilization removal from the polyamide obtained in Examples 3 and 4 or Comparative Example 1. Table 4 shows the results. As a result, it was found that a polyamide having a small content of caprolactam and oligomers having an unreacted caprolactam content of 0.07% by weight or less and an oligomer content of 1.15% by weight or less was obtained.

Examples 11 and 12 and Comparative Example 5 Caprolactam and oligomers were removed from the polyamide obtained in Examples 1 and 4 or Comparative Example 2 by hot water extraction. Table 5 shows the results.

From the comparison of the required extraction time, it was found that the polyamide obtained by the production method of the present invention requires a short extraction time.

Further, when the polyamides of Examples 6 to 11 were injection-molded and their handling properties were confirmed, they were as good as those obtained by the conventional method.

[0088]

[Table 1]

[0089]

[Table 2]

[0090]

[Table 3]

[0091]

[Table 4]

[0092]

[Table 5]

[0093]

As described above, by using the production method of the present invention, a polyamide having reduced unreacted caprolactam and oligomer can be obtained. As a result, the hot water extraction step can be omitted or the time can be shortened, and the polyamide resin can be manufactured with high production efficiency and low energy cost.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a polymerization reaction apparatus used in Examples.

[Explanation of symbols]

 1: raw material storage tank 2: raw material supply pump 3: pressure gauge 4: pressurized heat treatment tank 5: pressure regulating valve 6: polyamide prepolymer sampling port 7: normal pressure continuous polymerization tower

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4J001 DA01 DB02 DB04 EA06 EB04 EB05 EB06 EB07 EB08 EB09 EB10 EB14 EB35 EB36 EB37 EB46 EC05 EC06 EC07 EC08 EC09 EC10 EC14 EC47 EC48 EC85 FA03 FB03 FC03 FD01 GA01 GB02 GB03 GB03 GB01 JA12 JB50

Claims (11)

[Claims] An aqueous solution of caprolactam having a water content of 2 to 30% by weight and 0.05 to 5 mol% based on the caprolactam.
The amount of amino groups obtained by heat-treating a mixture of at least one component selected from the group consisting of dicarboxylic acids, diamines and salts thereof for 30 minutes or less is 0.1
mmol / g or more and a cyclic oligomer content of 0.1 g / g.
A polyamide prepolymer that is not more than 6% by weight. 2. The polyamide prepolymer according to claim 1, wherein the amount of amino group is at least 0.15 mmol / 1 g and the content of cyclic oligomer is at most 0.4% by weight. 3. An aqueous solution of caprolactam having a water content of 2 to 30% by weight and 0.05 to 5 mol% based on the caprolactam.
A dicarboxylic acid, a diamine and at least one component selected from salts thereof, and a step of heating the mixture under pressure at a temperature of 200 to 330 ° C. for 1 to 30 minutes, wherein the amount of amino groups is 0.1 mmol. / 1 g or more and a method for producing a polyamide prepolymer having a cyclic oligomer content of 0.6% by weight or less. 4. The method for producing a polyamide prepolymer according to claim 3, wherein the amount of amino group is 0.15 mmol / 1 g or more and the content of cyclic oligomer is 0.4% by weight or less. 5. An aqueous solution of caprolactam having a water content of 2 to 30% by weight and 0.05 to 5 mol% based on the caprolactam.
A mixture comprising at least one component selected from dicarboxylic acids, diamines and salts thereof,
A polyamide having the following properties, produced by melt polymerization for a polymerization time of 0 hours or less. Caprolactam content: 15% by weight or less, oligomer content: 1.8% by weight or less, total content of cyclic dimer to tetramer: 0.9% by weight or less 6. A process for producing a polyamide containing a capramide unit as a main component, comprising an aqueous solution of caprolactam having a water content of 2 to 30% by weight and a caprolactam having a water content of 0 to 30% by weight.
0.5 to 5 mol% of at least one component selected from dicarboxylic acids, diamines and salts thereof are mixed, and the mixture is heated under pressure at a temperature of 200 to 330 ° C. for 1 to 1 mol.
The amount of amino groups obtained through the step of heating for 30 minutes is 0.1
mmol / g or more, and the cyclic oligomer content is 0.1 g / g.
A polyamide prepolymer having a caprolactam content of not more than 6% by weight is supplied to a normal pressure polymerization apparatus, and is polymerized under a temperature condition of a melting point of a polyamide capable of obtaining the highest polymerization temperature + 10 ° C. or less. A method for producing a polyamide having a content of 15% by weight or less and an oligomer content of 1.8% by weight or less. 7. The method for producing a polyamide according to claim 6, wherein the polymerization is carried out under a temperature condition in which the maximum value of the polymerization temperature is lower than the melting point of the obtained polyamide. 8. A polyamide prepolymer having a water content of 4% by weight or less when supplied to an atmospheric pressure polymerization apparatus.
Or a method for producing a polyamide according to 7. 9. The method for producing a polyamide according to claim 6, wherein before feeding the polyamide prepolymer to the atmospheric pressure polymerization apparatus, the prepolymer is flushed at the upper portion of the atmospheric pressure polymerization apparatus to remove water by evaporation. 10. The method for producing a polyamide according to claim 6, wherein the atmospheric pressure polymerization apparatus is a continuous atmospheric pressure polymerization apparatus. 11. A polyamide obtained from the production method according to claim 6.