JPH05170895A - Highly white polyamide and production thereof - Google Patents

Abstract

PURPOSE:To efficiently obtain a highly white polyamide having excellent mechanical properties by prepolymerizing a salt obtained from a diamine and a dicarboxylic acid at a temperature not higher than the melting point of the polymer and then conducting solid phase polymerization. CONSTITUTION:An aqueous solution of a salt or a salt and a lactam is produced from at least two raw materials selected from among an aliphatic diamine (e.g. hexamethylenediamine), an aliphatic dicarboxylic acid (e.g. adipic acid), an aromatic dicarboxylic acid (e.g. terephthalic acid) and epsilon-capro-lactam. The aqueous solution is heated always in a uniformly molten state under conditions such that the maximum attainable temperature T is within the range of formula I (wherein Tm is the melting point of a crystalline polymer or the glass transition point of an amorphous polymer plus 200 deg.C), and that the maximum attainable pressure P satisfies formula II with respect to the pressure Pmin at which the salt or a formed prepolymer begins crystallization and solidification. The resultant solid prepolymer is subjected to solid polymerization at a temperature T' satisfying formula III to thereby obtain a polyamide.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a polyamide and a method for producing the same. More specifically, the present invention relates to a polyamide having a low thermal history during polymerization and therefore stable quality, high whiteness and excellent mechanical properties, and a method for efficiently producing the same.

[0002]

Polyamide is excellent in heat resistance and mechanical properties and is applied to automobile parts and electric / electronic parts. Conventionally, these polyamides are usually produced by a melt polymerization method. For example, nylon 66 is made to have a high molecular weight by melting and staying at a temperature above the melting point of the polymer. However, in this method, the polymer is exposed to a high temperature for a long time, so that a thermal decomposition reaction occurs, and a gelled product is deposited in the polymerization tank, which requires periodic cleaning, and the deposited product is mixed in the product. However, thermal deterioration causes a decrease in mechanical strength, particularly toughness, and a polymer of excellent quality could not be obtained.

Further, Japanese Patent Laid-Open No. 163927/1985,
There is a method, as disclosed in JP-A-61-159422, for carrying out melt polymerization in an extremely limited polymerization temperature range. However, in this method, the polymer is heated to a temperature equal to or higher than the melting point even in a limited polymerization temperature region, so that the thermal decomposition reaction cannot be avoided, and therefore, the polymer having excellent toughness can be obtained. There wasn't. JP-A-60-206828 and JP-A-2-
There is a method for producing a polyamide as disclosed in Japanese Patent No. 187427, that is, a method in which a salt aqueous solution is heated under a pressure condition to prepare a prepolymer, and the prepolymer is solid-phase polymerized to increase the molecular weight. Also in this method, in order to proceed the polymerization at a considerably high temperature in order to obtain a prepolymer,
A polymer having excellent toughness could no longer be obtained no matter how much solid phase polymerization was carried out at a temperature below the melting point due to a certain degree of thermal deterioration at the prepolymerization stage.

[0004]

DISCLOSURE OF THE INVENTION The present invention is to provide a stable quality and a whiteness degree by polymerizing in the production process of polyamide without causing the thermal decomposition reaction, gelation and the like as seen in the conventional method. It is intended to efficiently produce a polyamide having high mechanical properties and high properties.

[0005]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that by polymerizing a polyamide under specific polymerization conditions, the quality is stable and the whiteness is high, Further, they have found a method for efficiently producing a polymer having excellent mechanical properties, particularly toughness. That is, the present invention relates to a method for producing a polyamide and a copolyamide obtained by polycondensing at least two components selected from aliphatic diamine, aliphatic dicarboxylic acid, aromatic dicarboxylic acid, and ε-caprolactam. ) A salt or an aqueous solution of a salt and a lactam is always heated under uniform melting, and the maximum attainable temperature (T) is Tm-80 ° C ≤ T ≤ Tm (Tm is the melting point (° C) of the polymer in the case of a crystalline polymer). , Glass transition point (℃) + for amorphous polymers
It represents 200 ° C. ), And the final ultimate pressure (P) is prepolymerized under the condition that Pmin <P <Pmin + 15 kg / cm ² with respect to the pressure (Pmin) at which the salt or the generated prepolymer begins to precipitate and solidify, (2) Further, the prepolymer in a homogeneously melted state under heating and pressurization is discharged as a solid by paying out under the temperature and / or pressure conditions at which the prepolymer solidifies, and (3) the obtained solid prepolymer At a polymerization temperature (T ′) of Tm−130 ° C. ≦ T ′ ≦ Tm−10 ° C. (Tm is the same as above), and a method for producing a polyamide, wherein the whiteness is 80 or more. The present invention relates to a copolyamide containing hexamethylene adipamide and hexamethylene terephthalamide having a whiteness of 70 or more as a component.

The present invention will be described in detail below. Polyamides applicable to the present invention include aliphatic diamines (eg, hexamethylenediamine, tetramethylenediamine, trimethylhexamethylenediamine, etc.), aliphatic dicarboxylic acids (eg, adipic acid, sebacic acid, dodecanedioic acid, dimer acid, etc.). , A polyamide and a copolyamide obtained by polycondensing at least two components selected from aromatic dicarboxylic acids (for example, terephthalic acid, isophthalic acid, etc.) and ε-caprolactam. That is, for example, homopolyamide such as nylon 66, 46, nylon 6T / 66, 6T / 6I, 6T / 6, 6T / 66/6,
6T / 66/612, 6T / 6I / 66, 6T / 6I /
Copolymerized polyamides such as 6,6T / 6I / 612 may be mentioned.

The prepolymerization reaction in the production method of the present invention can be easily carried out using a pressure vessel such as a batch type autoclave or a continuous type reactor which is usually used, but it is not always necessary to use only such an apparatus. It's not limited. The starting material is a salt consisting of the above components or an aqueous solution of salt and lactam. The aqueous solution is constantly heated and pressurized under uniform melting conditions to remove water out of the reaction system, thereby prepolymerization. The term "uniform melting condition" as used herein means that the salt and / or the produced prepolymer is uniformly dissolved or melted without precipitation and solidification. At this time, the maximum ultimate temperature (T) is in the range of Tm-80 ° C ≤ T ≤ Tm (Tm is the same as above. The same applies hereinafter), and the final ultimate pressure (P) is when the salt or the produced prepolymer is Prepolymerization is performed under the condition of Pmin <P <Pmin + 15 kg / cm ² with respect to the pressure (Pmin) at which precipitation and solidification start. Preferably Tm
-70 ° C ≤ T ≤ Tm -15 ° C and Pmin + 1kg /
cm ² <P <Pmin + 12 kg / cm ² . T <
If it is in the range of Tm-80 ° C, the reaction does not proceed sufficiently or the reaction is too slow to be efficient. In the range of T> Tm, the thermal decomposition reaction cannot be ignored and the physical properties of the polymer are adversely affected. If it is in the range of P <Pmin, salt or prepolymer will be precipitated in the reaction system, and it will be difficult to dispense the prepolymer from the reaction system. P> Pmin + 15kg / c
If it is in the range of m ² , the reaction may not proceed sufficiently or the reaction may be too slow to be efficient.

The next step is a step of taking out the homogeneous molten prepolymer obtained under the above conditions under heating and pressure in a solid state. That is, it is a step of paying out the prepolymer in a uniformly molten state under the temperature and / or pressure conditions under which the prepolymer solidifies. For example, when the homogeneously melted prepolymer under heating or pressurization is sprayed at its autogenous pressure or under pressure into an inert gas at atmospheric pressure through a nozzle or the like, dissolved water is evaporated and the prepolymer is powder solidified by latent heat. It In addition, when pre-pressurized around the polymerization pressure P and pressure-extruded into water maintained at a temperature at which the prepolymer is solidified, a prepolymer solid without foaming can be taken out in a strand shape. The extruded strands can also be made into chips using a cutter. Further, by dropping the prepolymer onto the stirred pressurized water, a crumb-shaped or bead-shaped prepolymer can be obtained. The above method is only a representative example, and does not limit the scope of the present invention.

The final step is to increase the molecular weight by solid-phase polymerizing the obtained prepolymer. This step can be easily carried out by a batch type solid-state polymerization apparatus such as a tumbler or a continuous-type solid-state polymerization apparatus such as a paddle dryer, but it is not necessarily limited to the use of such an apparatus. The polymerization temperature (T ′) is Tm−130 ° C. ≦ T ′ ≦ Tm−10 ° C. When T '<Tm-130 ° C, the reaction is slow and inefficient, or the desired degree of polymerization is not reached. When T '> Tm-10 ° C, thermal decomposition cannot be ignored, and the surface of the polymer is colored and deteriorated. Also, the solid prepolymers may be fused together.

Conventionally, the molten polymer was discharged in the latter half of the polymerization reaction while keeping the pressure at normal pressure. However, in this method, it is necessary to raise the temperature to Tm or higher so as not to solidify the polymer, which causes thermal decomposition and gelation. Further, when the molecular weight was increased to some extent, it was difficult to completely dispense due to the high melt viscosity, no matter how much the polymer was dispensed at a temperature above the melting point, and the residual polymer was thermally decomposed and gelled.

A feature of the production method of the present invention is that the reaction temperature is kept below the Tm of the polymer at any stage of the polymerization reaction in order to suppress thermal decomposition and gelation.
Further, by paying out at the stage of the prepolymer having a relatively low melt viscosity, the residual polymer can be minimized and the thermal decomposition and gelation due to the retention can be suppressed. Each step of the production method of the present invention may be a continuous type or a batch type. The obtained polymer may be granulated within a range that does not impair the object of the present invention, for example, by using an extruder. Further, usual additives such as heat stabilizer, weathering agent, defoaming agent, flame retardant, and reinforcing material such as glass fiber may be used.

The high whiteness polyamide of the present invention means hexamethylene adipamide (nylon 66) having a whiteness of 80 or more and hexamethylene terephthalate having a whiteness of 70 or more evaluated by the measuring method described in Examples. A copolyamide containing amide as a component. Here, the copolyamide containing hexamethylene terephthalamide as a component means, for example, nylon 6T / 66, 6T / 6I, 6
T / 6, 6T / 66/6, 6T / 66/612, 6T /
It is a copolyamide such as 6I / 66, 6T / 6I / 6, 6T / 6I / 612.

[0013]

EXAMPLES The present invention will be described in detail below with reference to examples and comparative examples. The evaluations in Examples and Comparative Examples were performed by the following methods. Melting point: The peak temperature when the temperature was raised at a temperature rising rate of 20 ° C./min using DSC-7 manufactured by Perkin Elmer.

Glass transition point: A test piece immediately after molding was measured with a viscoelasticity spectrometer manufactured by Iwamoto Seisakusho Co., Ltd. at a frequency of 35H.
It was defined as the peak temperature of the tensile loss elastic modulus when measured by z. Relative viscosity: 95.50 ± 0.03% 1.0 g / d in sulfuric acid
Dissolve the polymer or prepolymer at a concentration of 1
It was measured at.

Tensile properties: Measured according to ASTM D638. The test piece was created with an IS-50EP injection molding machine manufactured by Toshiba Machine Co., Ltd. Whiteness W: ND-100DP manufactured by Nippon Denshoku Industries Co., Ltd. was used, and the whiteness was calculated by the formula 1.

[0016]

[Equation 1]

[0017]

Example 1 4 liters of a 50 wt% aqueous solution of equimolar salts of adipic acid and hexamethylenediamine were charged into a 5 liter autoclave, and the temperature was changed from room temperature to 22 with stirring.
The temperature was raised to 0 ° C in 1 hour, water was removed from the reaction system while maintaining the pressure at 18 kg / cm ² , and the temperature was raised to 25 ° C over 2 hours.
The temperature was raised to 0 ° C. After the reaction, the powder prepolymer was sprayed from the bottom of the autoclave through a spinneret of 2 mmφ in a nitrogen stream at normal pressure and room temperature to obtain 1.9 kg of a powder prepolymer. The obtained prepolymer was subjected to solid phase polymerization at 230 ° C. for 6 hours under a nitrogen stream using an evaporator type solid phase polymerization apparatus having an internal volume of 10 liters.

[0018]

Example 2 An equimolar salt of adipic acid and hexamethylenediamine and an equimolar salt of terephthalic acid and hexamethylenediamine were mixed in a molar ratio of 55:45, and a 25 wt% aqueous solution was charged into a 5 liter autoclave and stirred. the temperature from room temperature to 225 ° C. the temperature was raised at 1 hour, while maintaining the pressure to 23 kg / cm ² to remove water from the reaction system 2
The temperature was raised to 250 ° C. over time, and the state was kept for 3 hours. After the reaction, the powder prepolymer (0.9 kg) was obtained by spraying from the bottom of the autoclave into a nitrogen stream at normal pressure and room temperature through a 2 mmφ spinneret. The obtained prepolymer was subjected to solid phase polymerization at 250 ° C. for 6 hours in a nitrogen stream using an evaporator type solid phase polymerization apparatus having an internal volume of 10 liters.

[0019]

Example 3 Equimolar salts of terephthalic acid and hexamethylenediamine and ε-caprolactam were mixed in a molar ratio of 55:45 and charged as a 25 wt% aqueous solution in a 5 liter autoclave, and the temperature was raised from room temperature to 225 ° C. with stirring. The temperature was raised in 1 hour, water was removed to the outside of the reaction system while maintaining the pressure at 23 kg / cm ² , the temperature was raised to 250 ° C. in 2 hours, and the state was kept for 3 hours. After the reaction, 2 mm from the bottom of the autoclave in a nitrogen stream at normal pressure and room temperature
The powder was sprayed from the spinneret of φ to obtain 0.9 kg of powder prepolymer. The obtained prepolymer was heated under a nitrogen stream at 250 using an evaporator type solid phase polymerization apparatus with an internal volume of 10 liters.
Solid phase polymerization was carried out at 6 ° C for 6 hours.

[0020]

Example 4 An equimolar salt of isophthalic acid and hexamethylenediamine and an equimolar salt of terephthalic acid and hexamethylenediamine were mixed in a molar ratio of 50:50, and a 25 wt% aqueous solution was charged into a 5 liter autoclave and stirred. The temperature is raised from room temperature to 225 ° C. in 1 hour, water is removed from the reaction system while maintaining the pressure at 25 kg / cm ² , the temperature is raised to 250 ° C. in 2 hours, and the state is maintained for 3 hours. Held After the reaction, the autoclave was pressurized to 30 kg / cm ² with nitrogen gas and 25.5 kg from the bottom.
0.9 kg of a solid prepolymer was obtained by extruding from a spinneret of ² mmφ into water under stirring at room temperature at room temperature. The obtained prepolymer was subjected to solid phase polymerization at 230 ° C. for 6 hours under a nitrogen stream using an evaporator type solid phase polymerization apparatus having an internal volume of 10 liters.

[0021]

Comparative Example 1 4 liters of a 50 wt% aqueous solution of equimolar salts of adipic acid and hexamethylenediamine were charged into a 5 liter autoclave and the temperature was changed from room temperature to 22 while stirring.
The temperature was raised to 0 ° C in 1 hour, water was removed from the reaction system while maintaining the pressure at 18 kg / cm ² , and the temperature was raised to 25 ° C over 2 hours.
The temperature was raised to 0 ° C. Then, the temperature is set to 280 for 1 hour.
The temperature was raised to 0 ° C., the pressure was adjusted to normal pressure while flowing nitrogen, and the state was maintained for 1 hour for melt polymerization, followed by natural cooling.

[0022]

[Comparative Example 2] An equimolar salt of adipic acid and hexamethylenediamine and an equimolar salt of terephthalic acid and hexamethylenediamine were mixed in a molar ratio of 55:45, and a 25 wt% aqueous solution was charged into a 5 liter autoclave and stirred. the temperature from room temperature to 225 ° C. the temperature was raised at 1 hour, while maintaining the pressure to 23 kg / cm ² to remove water from the reaction system 2
The temperature was raised to 250 ° C. over time, and the state was kept for 3 hours. After this, the temperature is raised to 310
The temperature was raised to 0 ° C., the pressure was adjusted to normal pressure while flowing nitrogen, and the state was maintained for 1 hour for melt polymerization, followed by natural cooling.

[0023]

[Comparative Example 3] An equimolar salt of adipic acid and hexamethylenediamine and an equimolar salt of terephthalic acid and hexamethylenediamine were mixed in a molar ratio of 55:45, and a 25 wt% aqueous solution was charged into a 5 liter autoclave and stirred. the temperature from room temperature to 225 ° C. the temperature was raised at 1 hour, while maintaining the pressure to 23 kg / cm ² to remove water from the reaction system 2
The temperature was raised to 300 ° C. over a period of time, the state was maintained for another 3 hours, the tube was sealed, and then naturally cooled. 0.9 kg of the obtained prepolymer was subjected to solid phase polymerization at 250 ° C. for 4 hours under a nitrogen stream using an evaporator type solid phase polymerization apparatus having an internal volume of 10 liters.

[0024]

[Comparative Example 4] Equimolar salts of terephthalic acid and hexamethylenediamine and ε-caprolactam were mixed at a molar ratio of 55:45, and charged as a 25 wt% aqueous solution in a 5 liter autoclave, and the temperature was raised from room temperature to 225 ° C with stirring. The temperature was raised in 1 hour, water was removed to the outside of the reaction system while maintaining the pressure at 23 kg / cm ² , the temperature was raised to 250 ° C. in 2 hours, and the state was kept for 3 hours. After this, 1
The temperature was raised to 310 ° C. over a period of time, the pressure was adjusted to normal pressure while flowing nitrogen, and the state was maintained for 1 hour for melt polymerization, followed by natural cooling.

[0025]

[Comparative Example 5] An equimolar salt of isophthalic acid and hexamethylenediamine and an equimolar salt of terephthalic acid and hexamethylenediamine were mixed in a molar ratio of 50:50, and charged as a 25 wt% aqueous solution in a 5 liter autoclave and stirred. The temperature is raised from room temperature to 225 ° C. in 1 hour, water is removed from the reaction system while maintaining the pressure at 25 kg / cm ² , the temperature is raised to 250 ° C. in 2 hours, and the state is maintained for 3 hours. Held After this, the temperature is raised to 31
The temperature was raised to 0 ° C., the pressure was adjusted to normal pressure while flowing nitrogen, and the state was maintained for 1 hour for melt polymerization, followed by natural cooling.

Polymerization conditions and evaluation results of the above Examples and Comparative Examples are summarized in Tables 1 and 2.

[0027]

[Table 1]

[0028]

[Table 2]

[0029]

EFFECTS OF THE INVENTION According to the present invention, it is possible to efficiently produce a polyamide having little heat deterioration, stable quality, high whiteness and excellent mechanical properties.

Claims (3)

[Claims] 1. An aliphatic diamine, an aliphatic dicarboxylic acid,
In a method for producing a polyamide and a copolyamide obtained by polycondensing at least two components selected from an aromatic dicarboxylic acid and ε-caprolactam, (1) a salt or an aqueous solution of a salt and a lactam is always melted uniformly. The maximum temperature reached (T) is Tm-80 ° C ≤ T ≤ Tm (Tm is the melting point (° C) of the polymer in the case of a crystalline polymer, the glass transition point (° C) in the case of an amorphous polymer). +
It represents 200 ° C. ), And the final ultimate pressure (P) is Pmin <P <Pmin + 15 kg / cm ² with respect to the pressure (Pmin) at which the salt or the generated prepolymer begins to precipitate and solidify. (2) Further, the prepolymer in a homogeneously melted state under heating and pressure is discharged as a solid by paying out under a temperature and / or pressure condition where the prepolymer is solidified, and (3) the obtained solid prepolymer Polymerization temperature (T ')
Is a solid-state polymerization at Tm-130 ° C. ≦ T ′ ≦ Tm-10 ° C. (Tm is the same as above). 2. Hexamethylene adipamide having a whiteness of 80 or more. 3. A copolymerized polyamide containing hexamethylene terephthalamide having a whiteness of 70 or more as a component.