JPH05230205A - Production of polyamide resin - Google Patents

Abstract

PURPOSE:To facilitate the formation of a specified crystalline copolyamide excellent in heat resistance, etc., and having low water absorptivity by forming a lower condensate under specified conditions and subjecting this condensate to a treatment for increasing its molecular weight. CONSTITUTION:A process for producing a crystalline copolyamide comprising hexamethylenephthalamide units (A) of formula I and hexamethyleneisophthalamide units (B) of formula II, hexamethyleneadipamide units (C) of formula III and capramide units (D) of formula IV in a comonomer ratio (by weight) of A/B, A/C or A/D in a specified range, which process comprises forming a lower condensate of a relative viscosity of 1.01-1.6 when measured in a 1% sulfuric acid solution at 25 deg.C at 150-300 deg.C and feeding a dicarboxylic acid component (e.g. terephthalic acid) in an amount 0.3-10mol%- excess over the amount which is the total of the numbers of moles of monomers of A-D, the number of moles of the dicarboxylic acid component in the form of a salt and the number of moles of the diamine component.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
Further, the present invention relates to a method for producing a polyamide resin by forming a low-order condensate from an aqueous solution of a salt and increasing the degree of polymerization thereof, and particularly to a method for producing a polyamide resin suitable for automobile parts and electric / electronic parts.

[0002]

2. Description of the Related Art Polyamides have been widely used in the fields of automobiles, electric and electronic fields, etc. by utilizing their excellent properties as engineering plastics.

Conventionally, nylon 6 and nylon 66 reinforced with glass fiber have been used for these molded products (Japanese Patent Laid-Open No. 59-161461). However, due to recent technological innovation, the temperature rise of the engine room of automobiles and With the progress of microelectronics, there has been a demand for a material for an ultra-thin molded product that can withstand use in a higher temperature atmosphere. However, the melting points (Tm) of nylon 6 and nylon 66 are 220 ° C. and 260 ° C., respectively, and the limits of the heat distortion temperature are only the melting points even when reinforced with glass fiber.

Recently, many copolyamide resin compositions containing terephthalic acid and isophthalic acid, or glass fiber reinforced products thereof have been proposed as copolyamide resin compositions that can withstand use under these high temperature atmospheres. JP-A-59-161428, JP-A-59-155426,
(JP-A-59-53536, JP-A-62-156130)
. As a production method, a method of performing a polymerization reaction in a solid state from a nylon salt to a polymer has been proposed (JP-A-62-20527).

[0005]

However, these terephthalic acid- and isophthalic acid-containing copolyamide resin compositions have a high melt viscosity when the number of terephthalic acid component units is large, and discharge is impossible by a usual melt polymerization method. Since the melting point of the polymer is close to the thermal decomposition temperature of the polymer, it has been decomposed or deteriorated during melt polymerization. In addition, the method of carrying out the polymerization reaction in the solid state from the nylon salt to the polymer is
There is a problem that the composition of the polymer is not stable.

[0006]

In view of the above situation, the present inventors have found that the polyamide resin has high rigidity and high heat distortion temperature that can sufficiently withstand use in a high temperature atmosphere, is inexpensive, and has good fluidity. As a result of extensive studies on a method for producing a stable composition, a low-order condensate having a large amount of terminal carboxyl groups is produced, and the degree of polymerization of the low-order condensate is increased to achieve an efficient and stable high degree of polymerization. The inventors have found that a polymer can be obtained and arrived at the present invention. That is, the present invention provides (1) a repeating unit (I) a hexamethylene terephthalamide unit represented by the following structural unit,

[Chemical 5] And any unit selected from the following repeating units (II) to (IV), (II) a hexamethylene isophthalamide unit represented by the following structure,

[Chemical 6] (III) a hexamethylene adipamide unit represented by the following structural unit,

[Chemical 7] (IV) a caproamide unit represented by the following structural unit,

[Chemical 8] And the copolymerization ratio is (I) / (II) = 55 by weight.
/ 45 to 80/20 or (I) / (III) = 20/8
0-80 / 20 or (I) / (IV) = 55 / 45-9
In producing the crystalline copolyamide in the range of 0/10, 0.3 to 1 is used with respect to the total number of moles of the monomers (I) to (IV), the dicarboxylic acid component and the diamine component.
Excessively charged 0 mol% of dicarboxylic acid component, and heated at 150 ° C.
~ 300 ° C, 1% under the condition of 20kg / cm ² -G or less
Relative viscosity (ηr) of sulfuric acid solution at 25 ° C is 1.01
It is a method for producing a polyamide resin, which comprises producing a low-order condensate satisfying the requirements of up to 1.6 and then increasing the degree of polymerization of the low-order condensate.

The crystalline copolyamide of the present invention is any one selected from (I) hexamethylene terephthalamide unit, (II) hexamethylene isophthalamide unit, (III) hexamethylene adipamide unit and (IV) caproamide unit. And a copolymerization ratio of (I) / (II) is 55/4 by weight.
5 to 80/20, (hereinafter referred to as 6T / 6I copolyamide) or (I) / (III) copolymerization ratio of 2 by weight.
0/80 to 80/20 (hereinafter referred to as 6T / 66 copolyamide). Alternatively, the copolymerization ratio of (I) / (IV) is in the range of 55/45 to 90/10 (hereinafter referred to as 6T / 6 copolyamide) in weight ratio.

According to the invention, the copolymerization ratio of 6T / 6I is 55 / 45-80 / 20, preferably 60 / 40-8.
It should be 0/20, and more preferably 60/40 to 70/30. The copolymerization ratio of 6T / 66 is 20/80 to 80/20, preferably 35/65.
~ 70/30, more preferably 40/60 to 60/40
Must be within the range. The copolymerization ratio of 6T / 6 is 55/45 to 90/10, preferably 60/4.
0-85 / 15, more preferably 60 / 40-80 / 2
It must be in the 0 range. 6T / 6 here
The copolymerization ratios of I, 6T / 66 and 6T / 6 copolyamide relate to crystalline copolyamides having a polymer melting point in the range of approximately 270 ° C to 340 ° C. 6T /
When the copolymerization ratios of 6I, 6T / 66 and 6T / 6 are less than 40/60, 20/80 and 55/45, respectively, the polymer melting point is lowered, so that heat resistance such as heat distortion temperature is lowered, which is preferable. Absent. Also, 6T / 6I, 6T
The copolymerization ratio of / 66 and 6T / 6 is 80/2, respectively.
When it is more than 0, 80/20, 90/10, the melting point of the polymer becomes high and the heat resistance is improved, but the processing temperature becomes high and the polymer is thermally decomposed, which is not preferable. The degree of polymerization of the crystalline copolyamide is not particularly limited, and the relative viscosity (ηr) of a 1% sulfuric acid solution at 25 ° C. is usually 1.5 to 5.
Those at 0 can be used arbitrarily.

According to the present invention, 150 ° C. to 300 ° C., 20 kg /
The low-order condensate produced under the conditions of cm ² -G or less means an aqueous solution of the above-mentioned monomer or salt in a pressure polymerization kettle usually used for the polymerization of nylon 66 and the like, and the mixture is stirred under the conditions of 150.
Heat to ℃ ~ 300 ℃. The reaction temperature is 150 ° C to 300
It is necessary to adjust the temperature to 180 ° C, preferably 180 ° C to 280 ° C,
More preferably, it is 190 ° C to 270 ° C. If the reaction temperature is lower than 150 ° C., the reaction time becomes long, which is not preferable, and if the reaction temperature is higher than 300 ° C., the viscosity of the low-order condensate becomes too high and discharge of the low-order condensate becomes difficult. However, a low-order condensate is deposited and discharge becomes impossible, which is not preferable.

The pressure for producing the low-order condensate of the present invention means the equilibrium pressure due to the mixture of the low-order condensate and water at that time, and the pressure rises as the internal temperature rises.
20 kg / cm ² -G or less in the system, preferably 10-18
It is operated so as to keep it at kg / cm ² -G. Since the low-order condensate gives a remarkable freezing point depression due to the presence of a small amount of water, it can be discharged from the polymerization vessel in a molten state at a temperature of 150 ° C to 300 ° C.

The low-order condensate having a large amount of terminal carboxyl groups of the present invention means the total amount of COOH groups and total NH contained in monomers and salts in ordinary polyamide polymerization.
_It is common to charge the raw materials so that the amount of the _two groups becomes equal, but in the present invention, the dicarboxylic acid component is made excessive at the time of charging the raw materials, and a low-order condensate having a large amount of terminal carboxyl groups is positively produced. In particular, the dicarboxylic acid component is charged in an excess of 0.3 to 10 mol% with respect to the number of moles of the constituent monomer monomer and the total number of moles of the dicarboxylic acid component unit and the diamine component unit of the salt. Means that.
The excess dicarboxylic acid component is not particularly limited,
Examples thereof include aliphatic dicarboxylic acids such as adipic acid and sebacic acid, and aromatic dicarboxylic acids such as terephthalic acid and isophthalic acid. Isophthalic acid and terephthalic acid are preferable, and terephthalic acid is particularly preferable.
The amount of excess dicarboxylic acid added is 0.3 to 10 mol%, preferably 0.5 to 8 mol%, and more preferably 0.5 to 8 mol%.
It must be in the range of 7 mol%. Addition amount is 0.
If it is less than 3 mol%, the conditions for increasing the degree of polymerization are narrowed and stable operation becomes impossible, which is not preferable. Also, 10
When it is more than mol%, it is difficult to increase the degree of polymerization, which is not preferable. In order to facilitate the control of the degree of polymerization of the low-order condensate and the degree of polymerization when the degree of polymerization is increased, it is effective to add a degree-of-polymerization regulator. As the polymerization degree regulator, monoamine compounds and monocarboxylic acid compounds are usually used, but benzoic acid and stearic acid are preferable, and benzoic acid is particularly preferable. The degree of polymerization modifier is 0 to 0.1 times mol, preferably 0.0001 to 0.05 times mol, based on the mol number of the constituent monomer and the total mol number of the dicarboxylic acid component unit and the diamine component unit of the salt. Used.

The relative viscosity (ηr) of the low-order condensate of the present invention must be 1.01 to 1.6, preferably 1.0 to 1.5, and more preferably 1.01 to 1. It must be in the range of 0.4. Relative viscosity (ηr) is 1.0
When it is lower than 1, it is not preferable because it causes the composition ratio to vary in the step of increasing the degree of polymerization or the degree of increasing the degree of polymerization is insufficient. Further, if the relative viscosity is larger than 1.6, the melt viscosity of the low-order condensate becomes too high, causing ejection failure,
Alternatively, a low-order condensate may be deposited to cause ejection failure, which is not preferable.

The apparatus for producing the low-order condensate of the present invention is not particularly limited, and a known apparatus such as a batch reaction kettle or a 1 to 3 tank type continuous reaction apparatus can be used.

As the method for increasing the degree of polymerization of the low-order condensate of the present invention, a method using a melter, a method of solid-phase polymerization,
A method of using a melting machine or a solid phase polymerization machine in combination can be used. When using a melting machine, the melting temperature is preferably in the range of 10 to 70 ° C. higher than the melting point of the low-order condensate. 6T
When a low-order condensate having a large content and a high melting point is used, it is necessary to set the upper limit temperature to 360 ° C. or lower in order to prevent thermal decomposition and thermal deterioration of the polymer. As a melt extruder, an extruder, a
Although a doubler can be used, a twin-screw extruder and a twin-screw kneader are preferable.

The residence time in the melting machine is not particularly limited, but it is preferably 1 minute or longer, particularly preferably 2 minutes or longer. A short residence time is not preferable because the degree of polymerization cannot be effectively increased. It is also effective to connect two or more melting machines in series in order to increase the residence time and increase the degree of polymerization. The presence of a phosphorus-based catalyst is effective for increasing the degree of polymerization, but it has the drawback of impairing the heat resistance of the obtained polyamide resin, and it is therefore preferable not to add it.

If necessary, the polymer having a high degree of polymerization may be solid-phase polymerized to further increase the degree of polymerization.

The solid-state polymerization of the low-order condensate of the present invention is carried out under pressure or normal pressure in the presence of an inert gas,
Alternatively, the method may be performed under reduced pressure, or any of these may be combined. The solid-state polymerization temperature needs to be 150 ° C to the melting point, and preferably 200 ° C to
Melting point -10 ° C, more preferably 220 ° C to melting point -15
℃. If the solid phase polymerization temperature is lower than 150 ° C, the reaction rate becomes slow, which is not preferable. The solid-state polymerization time is such that the relative viscosity (ηr) of the copolyamide used for ordinary molded products is 1.
Any time can be selected until it becomes 5 to 5. The solid-state polymerization apparatus of the present invention is not particularly limited, and any known method can be used. Specific examples of the solid-state polymerization apparatus include a kneader, a twin-screw paddle type, a tower type, a rotary drum type and a double cone type solid-state polymerization apparatus.

A filler is preferably added to the polyamide resin obtained in the present invention. Fillers include glass fibers or beads, talc, kaolin, wollastonite, mica, silica, alumina, diatomaceous earth, clay, gypsum, red iron oxide, graphite, titanium dioxide, zinc oxide, copper, stainless steel, etc. Inorganic compounds in the form of powder or plate, other polymer fibers (carbon fibers), etc., and preferably glass fibers. As the glass fiber, glass fiber is generally used as a reinforcing agent for thermoplastic resin or thermosetting resin, but particularly preferred is a diameter of 3 to
Examples include glass rovings, glass chopped strands, and glass yarns made from strands of continuous long fibers of about 20 μm. The blending ratio of such a filler is the polyamide 1
It is necessary to be in the range of 0 to 200 parts by weight with respect to 00 parts by weight, preferably more than 0 and 150 parts by weight, particularly preferably 10 to 100 parts by weight. When the blending ratio of the filler exceeds 200 parts by weight, the fluidity at the time of melting is deteriorated, it is difficult to injection-mold a thin molded product, and the appearance of the molded product is deteriorated, which is not preferable.

There is no particular limitation on the method of adding the filler to the crystalline copolyamide of the present invention, and any known method can be used. A specific example of the compounding method is a method in which a filler is dry-blended with crystalline copolyamide pellets, and the resulting mixture is melt-kneaded with a single-screw or twin-screw extruder. When the polymerization degree is increased in the melting machine, the method of adding the filler from the middle of the melting machine is preferable because of high production efficiency.

The crystalline copolyamide resin composition obtained according to the present invention contains a catalyst, a heat stabilizer, a weathering agent, etc., when necessary, when a low-order condensate is prepared, such as melt extrusion, high polymerization degree, compound or molding step. Stability stabilizer, plasticizer, release agent,
Lubricants, crystal nucleating agents, pigments, dyes, other polymers and the like can be added.

In order to improve the color tone of the polyamide resin, it is effective to add an antioxidant in any step such as polymerization, increasing the degree of polymerization or compounding, and especially soda hypophosphite and hindered phenol. It is preferable to add an antioxidant.

[0022]

The present invention will be described in more detail with reference to the following examples. The various properties in the examples and comparative examples were measured by the following methods.

1) Melting point (Tm) Samples 8 to 10 using DSC (PERKIN-ELMER7 type)
Let (T) be the temperature at which the maximum value of the melting curve obtained by measuring mg at a temperature rising rate of 20 ° C./min. Sample 8-
10 mg is heated at a temperature rising rate of 20 ° C / min to obtain T + 20 ° C.
For 5 minutes, and then at a temperature decrease rate of 20 ° C / min for 3 minutes.
After cooling to 0 ° C and holding at 30 ° C for 5 minutes, 20
Heat up to T + 20 ° C. at a heating rate of ° C./min. The maximum value of the melting curve at this time was defined as the melting point (Tm).

2) Concentration of end groups of copolyamide [NH ₂ ] 1 g of copolyamide was added to 100 ml of phenol / ethanol.
Dissolved in a mixed solvent (50/50 wt ratio), 1 / 50N
It was determined by titration with an aqueous hydrochloric acid solution.

3) Terminal group concentration of copolyamide [COOH] 0.5 g of copolyamide was added to 50 ml of hot benzyl alcohol.
Dissolved in methanol and titrated with a 1/50 N-KOH methanol solution.

4) Tensile Strength It was measured according to ASTM-D638.

5) Bending strength It was measured according to ASTM-D790.

6) Flexural Modulus Measured according to ASTM-D790.

7) Izod impact strength It was measured according to ASTM-D256. 8) Heat distortion temperature (HDT) It was measured according to ASTM-D648, load 4.6 kgf / cm ² and load 18.6 kgf / cm ² .

Example 1 Hexamethylene ammonium adipate (66 salt) 9.
00 kg, 6.72 kg of terephthalic acid, 7.02 kg of a 64.5 wt% aqueous solution of hexamethylenediamine and 6.40 kg of ion-exchanged water were charged into a 0.10 m ³ batch type pressure polymerization kettle (diamine component unit and dicarboxylic acid component unit). (1 mol% terephthalic acid was added to the total number of total moles of the above), and after sufficient nitrogen substitution, the water vapor pressure was 1
Heating was continued under a pressure of 7.5 kg / cm ² -G. After heating to 240 ° C over 3.5 hours with stirring, 30 m
After the reaction was completed by maintaining the temperature at 240 ° C. to 245 ° C. for 1 hour, the lower condensate was discharged into water from the bottom of the polymerization kettle at a differential pressure of 17.5 kg / cm ² -G. The viscosity of this low-order condensate is ηr
= 1.14, melting point 304 ° C., [COOH] = 113 × 10
^-5 mol / g, [NH ₂ ] = 88 × 10 ^-5 mol / g, and was a low-order condensate of 25 × 10 ^-5 mol / g [COOH] rich. The obtained low-order condensate is heated at 100 ° C for 24 hours.
After vacuum drying, antioxidant Irganox 1098
0.2 parts by weight of (Ciba Geigy's antioxidant) was blended, and the residence time was 5 minutes with a 30 mmφ bent type twin-screw extruder.
The maximum resin temperature was 320 ° C. and the degree of polymerization was increased by melting. White pellets having a polymer viscosity ηr = 2.70 and a polymer melting point of 302 ° C. were obtained. 3 mm length for 100 parts by weight of this pellet
× 6 glass fiber chopped strands with a diameter of 13 μm
The mixture was supplied from the side feeder of the extruder so as to be 5 parts by weight and melt-mixed. This mixture was molded by an injection molding machine to prepare a test piece. Table 1 shows the results of evaluation of the obtained test pieces.

Example 2 8.76 kg of terephthalic acid, 8.93 kg of a 64.5 wt% aqueous solution of hexamethylenediamine, 6.00 kg of ε-caprolactam and 6.66 kg of deionized water were added.
A 10 m ³ batch type pressure polymerization kettle was charged (2 mol% terephthalic acid was excessively charged with respect to the total moles of the monomer and dicarboxylic acid components and the diamine component), nitrogen substitution was sufficiently performed, and then the steam pressure was adjusted to 15 Heating was continued under a pressure of 0.0 kg / cm ² -G. After the temperature was raised to 225 ° C. over 5 hours under stirring, the reaction was further allowed to proceed at 225 ° C. to 232 ° C. for 30 minutes, then the stirring was stopped and the pressure difference from the bottom of the polymerization vessel was 1
The low-order condensate was extracted at 5.0 kg / cm ² -G. The melting point of the obtained low-order condensate is 303 ° C., ηr is 1.12,
[COOH] = 129 × 10 ⁻⁵ mol / g, [NH ₂ ] = 92
× 10 ^-5 mol / g, and 37 × 10 ^-5 mol / g
It was a [COOH] -rich low-order condensate. This low-order condensate was melted to have a high degree of polymerization by the method of Example 1, compounded and molded, and evaluated. The results are shown in Table 1.

Example 3 8.12 kg of terephthalic acid and 4.12 k of isophthalic acid
g, 64.5 wt% aqueous solution of hexamethylenediamine 1
2.76 kg and 5.50 kg of ion-exchanged water are added to 0.1
Charge to a 0 m ³ batch type pressure polymerization kettle (2 mol% terephthalic acid was excessively charged with respect to the total mol number of the diamine component unit and the dicarboxylic acid component unit), and after sufficiently purging with nitrogen, the water vapor pressure was 17. Heating was continued under a pressure of 5 kg / cm ² -G. After the temperature was raised to 230 ° C. over 5 hours under stirring, the temperature was further maintained at 235 ° C. to 240 ° C. for 30 minutes to complete the reaction, and then the differential pressure from the bottom of the polymerization kettle was 17.5 k.
The low-order condensate was discharged into water at g / cm ² -G. The viscosity of this low-order condensate was ηr = 1.11 and the melting point was 317 ° C. The resulting low-order condensate was vacuum dried at 100 ° C. for 24 hours, and then melt-polymerized to a high degree of polymerization by the method of Example 1 except that described in Table 1, compounded and molded, and evaluated. The results are shown in Table 1.

Examples 4 to 5 Table 1 shows the results of evaluation in accordance with the method of Example 1 while changing the amount of raw material charged, the amount of terephthalic acid and the amount of glass fiber added, and the like.

In each of the methods of Examples 1 to 5, a polyamide resin having a high degree of polymerization was stably obtained, and the physical properties of the molded articles were excellent.

Comparative Example 1 6.48 kg of terephthalic acid, 9.00 kg of 66 salt, 7.02 k of a 64.5 wt% aqueous solution of hexamethylenediamine.
g and 6.36 kg of deionized water, Example 1
A low-order condensate was prepared by the method of. The viscosity of this low-order condensate is ηr = 1.20, the melting point is 301 ° C., and [COOH] = 67 × 1.
It was 0 ⁻⁵ mol / g, [NH ₂ ] = 66 × 10 ⁻⁵ mol / g, and was a low-order condensate having almost the same concentration of end groups. The obtained low-order condensate was vacuum-dried at 100 ° C. for 24 hours, and then melted to have a high degree of polymerization by the method of Example 1. It was not possible to obtain a fisheye with a stable degree of polymerization.

Comparative Example 2 6.68 kg of terephthalic acid, 6.38 kg of a 64.5 wt% aqueous solution of hexamethylenediamine, 10.00 kg of ε-caprolactam and 5.50 kg of ion-exchanged water were added to a 0.10 m ³ batch type pressure polymerization kettle. (3 mol% terephthalic acid was excessively charged relative to the total number of moles of the diamine component unit and the dicarboxylic acid component unit), and a low-order condensate was prepared by the method of Example 1. The melting point of this low-order condensate is 252 ° C., ηr = 1.33, [COOH] = 69 × 10 ⁻⁵
mol / g, [NH ₂ ] = 21 × 10 ⁻⁵ mol / g, and it was a low-order condensate of 48 × 10 ⁻⁵ mol / g [COOH] rich. This low-order condensate was vacuum-dried at 100 ° C. for 24 hours, and then melted to have a high degree of polymerization according to the method of Example 1. The melting point of the obtained pellets is 253 ° C., ηr = 2.9.
It was 5.

The results of evaluation by the method of Example 1 using these pellets are shown in Table 1. The rigidity and heat distortion temperature were low.

Comparative Example 3 1.19 kg of terephthalic acid, 1.21 kg of a 64.5 wt% aqueous solution of hexamethylenediamine, 0.10 k of 66 salt
g and ion-exchanged water 0.650 kg to 0.005 m ³
(3 mol% terephthalic acid was excessively charged relative to the total mol number of the diamine component unit and the dicarboxylic acid component unit) into the batch type pressure polymerization kettle of No. 3, and a low-order condensate was prepared by the method of Example 1. The melting point of this low-order condensate is 361 ° C.,
ηr = 1.05. This low-order condensate was vacuum dried at 100 ° C. for 24 hours, and then melted to have a high degree of polymerization at a maximum resin temperature of 375 ° C. Good pellets could not be obtained because foaming due to thermal decomposition and fish eyes coexisted.

[0039]

[Table 1]

[0040]

INDUSTRIAL APPLICABILITY The crystalline copolyamide obtained according to the present invention is not only high in rigidity and heat distortion temperature but also low in water absorption and good in moldability, so that it is particularly used as a material for automobile parts and electric / electronic parts. Suitable as

Claims (1)

[Claims] (1) Repeating unit (I) Hexamethylene terephthalamide unit represented by the following structural unit: And any unit selected from the following repeating units (II) to (IV), (II) a hexamethylene isophthalamide unit represented by the following structural unit, (III) a hexamethylene adipamide unit represented by the following structural unit: (IV) a caproamide unit represented by the following structural unit, And the copolymerization ratio is (I) / (II) = 55 by weight.
/ 45 to 80/20 or (I) / (III) = 20/8
0-80 / 20 or (I) / (IV) = 55 / 45-9
In producing the crystalline copolyamide in the range of 0/10, 0.3 to 1 is used with respect to the total number of moles of the monomers (I) to (IV), the dicarboxylic acid component and the diamine component.
Excessively charged 0 mol% of dicarboxylic acid component, and heated at 150 ° C.
~ 300 ° C, 1% under the condition of 20kg / cm ² -G or less
Relative viscosity (ηr) of sulfuric acid solution at 25 ° C is 1.01
A method for producing a polyamide resin, which comprises producing a low-order condensate satisfying the requirement of ˜1.6 and then increasing the degree of polymerization of the low-order condensate.