JP2024044447A - polyamide resin composition - Google Patents

Abstract

The present invention relates to a polyamide resin composition having excellent polymer color tone and excellent dyeability. The present invention relates to a polyamide resin composition comprising a diamine component and sebacic acid, the resin composition having a 98% by weight sulfuric acid relative viscosity ηr in the range of 2.4 to 3.0, an amino terminal group amount of more than 10.0×10-5 mol/g, and a value obtained by subtracting the amount of carboxyl terminal groups from the amount of amino terminal groups of more than 6.5×10-5 mol/g. [Selected Figure] None

Description

The present invention relates to a polyamide resin composition that is produced by polycondensation of a diamine component and sebacic acid, and that has excellent dyeability when made into fibers.

Thermoplastic resins such as polyamide and polyester are widely used as clothing fibers, industrial fibers, and resin molding applications, and are excellent in strength, durability, heat resistance, stretchability, and color fastness. In recent years, due to growing interest in environmental issues, there is a demand for polyamides that use plant-derived ingredients and polyamides that have low wastewater load from dyes and excellent dyeability.

Polyamides made by polycondensing diamines and sebacic acid are in high demand as environmentally friendly polyamide resins because sebacic acid is a plant-derived component and because it has strength, durability, and heat resistance that are comparable to those of polyhexamethylene adipamide (N66) and polycapramide (N6), which are general-purpose polyamides derived from petroleum. However, the issue is that it is significantly inferior to N66 and N6 in terms of dyeability, which is the most important aspect of clothing fibers.

In light of this background, there is a demand to improve the dyeability of polyamides obtained by polycondensation of diamines and sebacic acid in order to solve environmental issues.

Regarding the development of polyamides made by polycondensing diamine and sebacic acid, for example, in the development of polypentamethylene sebaamide (N510), which is made by polycondensing 1,5-pentanediamine and sebacic acid, sterically hindered N atom It has been proposed that a polyamide with excellent color tone can be obtained by adding a heat-resistant agent having a nitrogen-containing functional group that can react with at least one of an amino group, a carboxyl group, and an amide group constituting the polyamide. (For example, see Patent Document 1). A polyamide whose main components are 1,5-pentamethylene diamine and an aliphatic carboxylic acid having 7 or more carbon atoms, a fibrous filler, an impact modifier, and a flame retardant, which have high heat resistance and low water absorption. A method for obtaining a polyamide resin composition with excellent retention stability has been proposed (see, for example, Patent Document 2). A method for obtaining a long fiber reinforced polyamide resin composition having excellent strength, heat strength, and durability using a polyamide with a constant amount of cyclic amino terminal groups and a weight average fiber length within a constant range has been proposed (for example, Patent Document 3). reference).

International Publication No. 2013/129371 International Publication No. 2010/113736 JP 2012-172086 A

In the case of polyamides obtained by polycondensation of diamines and sebacic acid, they contain sebacic acid, which has a higher carbon number, than the general-purpose nylons N6 and N66. Therefore, when attempting to obtain a polyamide resin composition with a degree of polymerization suitable for clothing fibers, the amide groups and amino terminal groups that act as dyeing sites for dyes are significantly reduced, resulting in inferior dyeability. Therefore, in order to improve dyeability, it is sufficient to increase the amount of amino terminal groups, and a commonly known method is to add an excess of diamine components at the time of polymerization.

In addition, since polyamide resin compositions have a wide range of uses, including plastic molded products, films, and fibers, they are generally designed with a degree of polymerization that prioritizes durability. If the diamine component is used in large excess, the molar balance between the diamine component and the dicarboxylic acid component is disrupted. In other words, there is a trade-off between the degree of polymerization and the amount of amino terminal groups.

The polyamide resin composition described in Patent Document 1 is a technology for improving yellowing caused by heat, while the polyamide resin composition described in Patent Documents 2 and 3 is a technology for improving impact resistance, heat stability, and durability. Although the durability is excellent, the amount of amino terminal groups is general, and the dyeability is still inferior.

The objective of the present invention is to obtain a polyamide resin composition that, when made into fibers, has excellent dyeability and strength when made from a polyamide obtained by polycondensing a diamine component and sebacic acid.

In order to solve the above problems, the present invention comprises the following configuration.
(1) A polyamide resin composition comprising a diamine component and sebacic acid, the resin composition having a 98 wt% sulfuric acid relative viscosity ηr in the range of 2.4 to 3.0, an amino terminal group amount of more than 10.0× ^10-5 mol/g, and a value obtained by subtracting the amount of carboxyl terminal groups from the amount of amino terminal groups of more than 6.5× ^10-5 mol/g.
(2) The polyamide resin composition according to (1) above, characterized in that the filtration pressure increase rate ΔP using a 5 μm filter is 3.0 MPa/hour or less.
(3) The polyamide resin composition according to (1) or (2), in which the yellowing index YI of pellets of the polyamide resin composition is 6.0 or less. (4) The polyamide resin composition according to (1) or (2), which contains, as a diamine component, one or more of 1,4-diaminobutane, 1,5-diaminopentane, and 1,6-diaminohexane.
(5) A fiber made of the polyamide resin composition according to (1) or (2).

The polyamide resin composition of the present invention can provide a polyamide resin composition that has excellent dyeability and strength when made into fibers.

The present invention relates to a polyamide resin composition obtained by polycondensation of a diamine component and sebacic acid.

The polyamide resin composition of the present invention is preferably a polyamide resin composition in which 90 mol % or more of the repeating units are composed of sebacic acid units. By containing a large amount of sebacic acid units, orientation crystallization becomes easier during the spinning process, and the regularity of the molecular chains of the obtained fiber increases, resulting in a fiber with excellent mechanical properties, boiling water shrinkage rate, and heat resistance. Therefore, the ratio of sebacic acid units is more preferably 95 mol % or more, and even more preferably 98 mol % or more.

As long as the effect of the present invention is not impaired, dicarboxylic acid components other than sebacic acid may be contained in an amount of, for example, 10 mol% or less. Examples of other dicarboxylic acids include, but are not limited to, aliphatic dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, undecane diacid, dodecane diacid, brassic acid, tetradecane diacid, pentadecanedioic acid, and octadecanedioic acid, and aromatic dicarboxylic acids such as cyclohexane dicarboxylic acid, phthalic acid, isophthalic acid, terephthalic acid, and naphthalenedicarboxylic acid.

Sebacic acid is available in two types: one made from petroleum and one made from biomass such as plants. In the present invention, however, sebacic acid obtained from biomass such as plant-derived materials is preferred. One method for identifying whether sebacic acid is derived from biomass is, for example, measuring the radioactive carbon (C14) content. Details of the measurement method are standardized by ASTM (American Society for Testing and Materials), CEN (Committee on Standardization in Europe), etc., and in the United States, the ASTM-D6866 method has been presented as a measurement standard for the biomass ratio. This measurement method was originally a standardization of the radioactive carbon dating method for determining the age of fossils, and has been used for 60 years, so it is an established technique and technology. Currently, the ASTM-D6866 method is also used to measure the biomass degree as specified by JBPA and JORA.

The diamine component of the present invention can be selected arbitrarily. Examples of the diamine include aliphatic diamines such as ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 1,7-diaminoheptane, 1,8-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-diaminoeicosane, and 2-methyl-1,5-diaminopentane; alicyclic diamines such as cyclohexanediamine and bis-(4-aminohexyl)methane; and aromatic diamines such as xylylenediamine. One type of diamine component may be used, or two or more types of diamine components may be used. When a mixture of multiple diamine components is used, the diamine component of the main component is preferably 90 mol% or more of the repeating units relative to the total of the diamine components of the subcomponents. By setting it in this range, the order of the molecular chains of the obtained fiber is increased because it becomes easier to crystallize in an oriented manner during the spinning process, resulting in a fiber with excellent mechanical properties, boiling water shrinkage, and heat resistance. The ratio of the diamine units of the main component is more preferably 95 mol% or more, and even more preferably 98 mol% or more.

When the polyamide resin composition of the present invention is used as a clothing fiber, an industrial fiber, or for resin molding, the melting point of the polymer is preferably 200 to 300°C from the viewpoint of processability and heat resistance, and it is preferable to select a diamine component that falls within this range. In order to obtain a polymer with this melting point range, the diamine component is preferably 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, or 1,10-diaminodecane. Furthermore, from the viewpoint of industrial availability, 1,4-diaminobutane, 1,5-diaminopentane, and 1,6-diaminohexane are more preferable.

The polyamide resin composition of the present invention may also include amino acids such as 6-aminocaproic acid, 11-aminoundecanoic acid, 12-aminododecanoic acid, para-aminomethylbenzoic acid, ε-caprolactam, Structural units derived from lactams such as ω-laurolactam can be included.

It is important that the polyamide resin composition of the present invention has dyeability and strength suitable for clothing fibers, and that the amount of amino terminal groups is increased while maintaining the degree of polymerization, i.e., the composition satisfies both the following characteristics: a 98% sulfuric acid relative viscosity of 2.4 or more, and an amino terminal group amount of more than 10.0× ¹⁰ mol/g.

The polyamide resin composition of the present invention has a relative viscosity of 2.4 to 3.0 in a 98% sulfuric acid solution with a sample concentration of 0.01 g/mL at 25°C (hereinafter referred to as the 98% sulfuric acid relative viscosity). By setting the relative viscosity in this range, the excellent strength required for clothing fibers can be achieved. The relative viscosity is preferably 2.5 to 2.9, and more preferably 2.6 to 2.8. If the 98% sulfuric acid relative viscosity is lower than 2.4, the strength when fiberized decreases. If the 98% sulfuric acid relative viscosity is higher than 3.0, the total amount of terminal groups in the polymer decreases, and dyeability decreases.

The polyamide resin composition of the present invention has an amount of amino terminal groups greater than 10.0×10 ⁻⁵ mol/g. By making the amount larger than 10.0×10 ⁻⁵ mol/g, excellent dyeability suitable for clothing fibers will be exhibited.

Since the dicarboxylic acid component of the polyamide resin composition of the present invention is sebacic acid, the methylene chain in the molecule is longer than that of N66 or N6, and there are fewer amide bonds that serve as dyeing sites for acidic dyeing. In addition, since the methylene chain becomes longer, the hydrophobicity of the polymer becomes higher and the affinity with water-soluble dyes becomes worse. Therefore, in the present invention, the dyeability is improved by significantly increasing the amount of amino terminal groups compared to N66 and N6. On the other hand, although dyeability improves by increasing the amount of amino terminal groups, the degree of polymerization decreases and the strength, which is a textile mechanical property, also decreases, so from the viewpoint of strength, it is set to 12.0 × 10 ^-5 mol/g or less. It is preferable. When the amount of amino terminal groups is less than 10.0×10 ⁻⁵ mol/g, the dyeing property is decreased and a particularly deep color cannot be obtained.

In the polyamide resin composition of the present invention, the value obtained by subtracting the amount of carboxyl end groups from the amount of amino end groups is greater than 6.5×10 ⁻⁵ mol/g. By setting it within this range, a polyamide with a high degree of polymerization and a sufficiently large amount of amino terminal groups can be obtained, and when it is made into fibers, it can exhibit excellent strength and dyeability. If the value obtained by subtracting the amount of carboxyl end groups from the amount of amino end groups is less than 6.5×10 ⁻⁵ mol/g, a polyamide with a high degree of polymerization cannot be obtained and excellent strength will not be exhibited when it is made into fibers. The value obtained by subtracting the amount of carboxyl end groups from the amount of amino end groups is preferably larger than 6.5×10 ⁻⁵ mol/g, and more preferably larger than 7.5×10 ⁻⁵ mol/g.

The polyamide resin composition of the present invention preferably has a filtration pressure rise rate ΔP of 3.0 MPa/hour or less using a 5 μm filter. More preferably, it is 1.0 MPa/hour or less. By lowering the temperature during polymerization, thermal degradation is sufficiently suppressed, and adhesion to the polymerization can wall and the like and gelling due to localized thermal degradation are sufficiently suppressed, so that the content of gel, which is a thermal degradation product, in the polyamide resin composition is reduced, and the rise in filtration pressure can be reduced even during melt spinning. If there is a large amount of gel in the polyamide resin composition, the orientation of the polymer deteriorates during melt spinning, and the strength decreases.

The polyamide resin composition of the present invention is a polyamide with a sufficiently increased amount of amino terminal groups, and the generation of substances that cause coloration is sufficiently suppressed by suppressing thermal deterioration, so the polyamide resin composition has a good color tone. can get things. If the color tone is good, more excellent dyeing properties can be exhibited when it is made into fibers. Coloring can be affected by even a very small amount of coloring substances, so the identification of the substances and the generation mechanism are unknown, but it is assumed that this was achieved by optimizing the polymerization temperature, time, and pressure to suppress thermal deterioration. There is. The yellowing degree YI of the pellets is preferably 6.0 or less. Incidentally, the yellowing degree YI refers to a value measured by a method described below. A lower YI means less coloring. If the coloration is large, the range of use will be limited and the product value will be lowered, so a lower YI is preferable. The yellowing degree YI of the pellets of the polyamide resin composition of the present invention is more preferably 2.0 or less, and even more preferably 0.0 or less. The lower limit of yellowing degree YI is about -10.

Other additives may be added to the polyamide resin composition of the present invention depending on the intended use within a range that does not impede the effects of the present invention. These additives can be added during copolymerization of polyamide, or can be blended by melt-mixing with the polyamide resin composition. When melt-mixing, an extruder can also be used for melt-mixing.

Furthermore, master chips containing these additives can be chip-blended or physically mixed with pellets of the polyamide resin composition, and then subjected to molding such as spinning, extrusion molding, and injection molding to form the compound.

Examples of such additives include antioxidants, heat stabilizers (hindered phenol-based, hydroquinone-based, phosphite-based and substituted products thereof, copper halides, iodine compounds, etc.), weathering agents (benzophenone-based , hindered amines, etc.), mold release agents and lubricants (aliphatic alcohols, aliphatic amides, etc.), pigments (titanium oxide, carbon black, etc.), dyes (nigrosine, aniline black, etc.), crystal nucleating agents (talc, silica, kaolin, etc.) , clay, etc.), antistatic agents (polyetheramide antistatic agents, polyetheresteramide antistatic agents, etc.), flame retardants (melamine cyanurate, magnesium hydroxide, etc.), fillers (graphite, barium sulfate, sulfuric acid) magnesium, calcium carbonate, magnesium carbonate, etc.), other polymers (other polyamides, polyethylene, polypropylene, polyester, polycarbonate, etc.).

Although the method for polycondensation of polyamide in the present invention is not particularly limited, a preferred manufacturing method for obtaining the polyamide resin composition of the present invention will be shown.

Polycondensation methods for polyamides generally include continuous polymerization methods and batch polymerization methods, and production is possible using either method. The outline is shown below.

An aqueous solution of equimolar salts of sebacic acid and 1,6-diaminohexane is prepared and concentrated by heating in a pressure-resistant container (concentration step). The moisture content of the equimolar salt aqueous solution may be adjusted in consideration of handling and lightweight considerations, but is preferably 10 to 60%, more preferably 10 to 50%. Concentration can be carried out once in an apparatus separate from the polycondensation apparatus to an arbitrary moisture content; in this case, the moisture content after concentration is preferably 10 to 30%, more preferably 10 to 20%.

1,6-diaminohexane is additionally added to the equimolar salt aqueous solution after concentration to reach the desired amount of amino terminal groups. In the present invention, by additionally adding a diamine component after the concentration step, polymerization can be performed with a good molar balance between the diamine component and the sebacic acid component during the polymerization reaction while suppressing a decrease in the degree of polymerization, and the desired degree of polymerization (98 % sulfuric acid relative viscosity), the amount of amino end groups, and the value obtained by subtracting the amount of carboxyl end groups from the amount of amino end groups. If it is added before concentration, the amount of evaporation of the diamine component with a relatively low boiling point will increase, and the molar balance will be greatly disrupted, making it impossible to increase the degree of polymerization to the desired range. Furthermore, the diamine component additionally added to increase the amino end groups necessary for improving dyeability also evaporates, making it impossible to obtain the desired amount of amino end groups. The additional amount may be adjusted as appropriate to achieve the target amino terminal group amount, but it is preferably 0.016 to 0.024 mol based on the equimolar 1,6-diaminohexane/sebacic acid salt. This is preferable because the amount of evaporation of 1,6-diaminohexane can be suppressed and the molar balance between sebacic acid and 1,6-diaminohexane can be maintained.

The concentrated equimolar salt aqueous solution is sealed and heated until it reaches the target pressure (pressurization process). The maximum pressure inside the vessel is preferably 1.0 MPa or more, more preferably 1.3 MPa (absolute pressure) or more, and even more preferably 1.7 MPa or more. If it is 1.0 MPa or more, evaporation of 1,6-diaminohexane can be reduced. There is no particular upper limit, but taking into consideration the pressure resistance of the polycondensation apparatus, it is preferably 3.0 MPa or less, and even more preferably 2.0 MPa or less.

While maintaining the above pressure, water is distilled off until the internal temperature of the container reaches 240 to 250°C (pressure control step), and then the internal pressure of the container is gradually reduced to 0.1 MPa (atmospheric pressure) while continuing heating. Release the pressure (pressure release process). If the temperature at which pressure release starts is 240°C or higher, polycondensation can occur without solidifying the internal liquid in the pressure release step, and if the temperature is 250°C or lower, thermal deterioration of the polymer can be suppressed.

To proceed with polycondensation after the pressure release step, there are two methods: one is to remove the condensation water by passing an inert gas through the container at atmospheric pressure (normal pressure polymerization), and the other is to reduce the pressure inside the container (reduced pressure polymerization). When the pressure inside the container is reduced, the water in the polymer evaporates and foams rapidly, causing the polymer to adhere to the container wall and heat up on the container wall, causing thermal degradation. When this thermal degradation product is mixed back into the polymer liquid, microgels are generated. This microgel causes an increase in filtration pressure during fiberization, affecting the raw yarn properties, so normal pressure polymerization is preferred in the present invention. Examples of inert gases include helium gas, argon gas, and nitrogen gas, with nitrogen gas being the preferred gas from the standpoint of cost.

The normal pressure reaction time to advance the polycondensation to the desired degree of polymerization is preferably 20 to 50 minutes. More preferably, the time is 20 to 40 minutes.

The maximum temperature in the vessel for atmospheric polymerization is preferably 240 to 250°C. By setting the temperature in this range, thermal degradation can be suppressed even when atmospheric polymerization is carried out for a long period of time, and the deterioration of the polymer's color tone and the occurrence of microgels can be reduced. A temperature of 245 to 250°C is more preferable. If the temperature is 240°C or higher, the melt viscosity of the polymer does not increase too much, and good fluidity can be maintained in the vessel. If the temperature is 250°C or lower, the deterioration of the polymer's color tone and the occurrence of microgels due to thermal degradation can be suppressed, and the YI value and ΔP can be controlled within the preferred range.

Preferred polymerization conditions for polypentamethylene sebacamide consisting of 1,5-diaminopentane and sebacic acid are the same as the preferred polycondensation method for polyhexamethylene sebacamide described above.

In the case of polytetramethylene sebacamide consisting of 1,4-diaminobutane and sebacic acid, the maximum temperature in the container for normal pressure polymerization is preferably 250 to 260 ° C., more preferably is 255-260°C. When the temperature is 250° C. or higher, the melt viscosity of the polymer does not increase too much, and good fluidity in the container can be maintained. Further, if the temperature is 260° C. or lower, deterioration of the color tone of the polymer can also be suppressed.

The polyamide resin composition thus obtained is preferably extruded from the container into strands, cut, and formed into pellets. The molecular weight can also be increased by solid-phase polymerization of the pellets. Solid-phase polymerization proceeds by heating in a vacuum or in an inert gas at a temperature range of 100°C to the melting point, and can increase the molecular weight of polyamide resin compositions that have insufficient molecular weights when subjected to heated polycondensation.

The polyamide resin composition of the present invention is preferably used for fiber applications, and is particularly preferably used for clothing fiber applications.

The fibers obtained from the polyamide resin composition of the present invention are produced by known melt spinning. For example, molten polyamide pellets are metered and transported by a gear pump, discharged from a spinneret, and passed through a steam injection device that injects steam toward the spinneret surface located directly below the spinneret, and an area where cooling air is blown from a cooling device located downstream of the steam injection device, where the threads are cooled and solidified to room temperature, then oiled by an oiling device to concentrate the threads, entangled by a fluid entanglement nozzle device, and passed through a take-up roller and a stretching roller. At this time, the threads are stretched according to the ratio of the peripheral speeds of the take-up roller and the stretching roller. Furthermore, the threads are heat-set by heating the stretching roller, and wound up by a winder (winding device).

EXAMPLES The present invention will be described in more detail with reference to Examples below, but the present invention is not limited to the description of these Examples.

[Sulfuric acid relative viscosity ηr]
0.25 g of the pellets were dissolved in 100 ml of 98% sulfuric acid to give a total weight of 1 g, and the flow time (T1) was measured at 25° C. using an Ostwald viscometer. Subsequently, the flow time (T2) of only the 98% sulfuric acid was measured. The ratio of T1 to T2, i.e., T1/T2, was defined as the sulfuric acid relative viscosity ηr.

[Amino terminal group amount]
1 g of the pellets was dissolved in 50 mL of a phenol/ethanol mixed solution (phenol/ethanol = 80/20) by shaking at 30°C to obtain a solution, and this solution was neutralized by titrating with 0.02 N hydrochloric acid to determine the amount of 0.02 N hydrochloric acid required. In addition, the phenol/ethanol mixed solvent (same amount as above) alone was neutralized by titrating with 0.02 N hydrochloric acid to determine the amount of 0.02 N hydrochloric acid required. The amount of amino groups per 1 g of sample was calculated from the difference.

[Carboxyl terminal group amount]
Precisely weigh 0.5 g of pellets, add 20 ml of benzyl alcohol and dissolve at a temperature of 195°C. The amount of carboxyl terminal groups (mol/g) was determined by titration.

[Yellowing Index YI]
The yellowing degree of the pellets was measured using a color computer manufactured by Suga Test Instruments Co., Ltd. The measurement method was in accordance with JIS standard K7105 (test method for optical properties of plastics).

[Filtration pressure increase rate ΔP]
The pellets were dried at 105° C. for 8 hours under a vacuum of 133 Pa or less, and the rate of increase in filtration pressure was measured using a filtration tester (Melt Spinning Tester CII manufactured by Fuji Filter Industries, Ltd.). A Dynalloy filter X5 (opening 5 μm, filtration area 4.5 cm ² ) manufactured by Giichi Watanabe Seisakusho Co., Ltd. was used as a filter, and filtration was performed at a polymer temperature of 280° C. and a throughput of 4 g/min. The difference between the filtration pressure 1 hour after the filter was attached and the filtration pressure 2 hours after attachment was measured and defined as the filtration pressure increase rate ΔP (MPa/hour).

[Strength (raw yarn properties)]
A. Strength and elongation Fiber samples were measured according to JIS L1013 (2010) tensile strength and elongation. The test conditions were constant speed tension type, grip distance 50 cm, and tensile speed 50 cm/min. When the strength at break was smaller than the maximum strength, the maximum strength and the elongation at that time were measured.
The strength and strength-strain product were calculated using the following formula.
Strength = Strength at break (cN) / Fineness (dtex)
Elongation = percent elongation at break.

B. Fineness A fiber sample was set on a measuring scale of 1.125 m/turn and rotated 500 times to prepare a looped hank. After drying in a hot air dryer (105±2°C, 60 minutes), the mass of the hank was weighed on a balance and multiplied by the official moisture regain to calculate the fineness (dtex). The strength of the fiber samples obtained in the above items A and B was evaluated according to the following three-level scale.
S: 4.75 cN/dtex or more, 5.0 cN/dtex or less A: 4.5 cN/dtex or more, less than 4.75 cN/dtex B: less than 4.5 cN/dtex.

[Stainability]
A. Production of tubular knitted fabric A tubular knitted fabric was produced by doubling four fiber yarns of 22 dtex obtained in the example (total fineness of 88 dtex) and adjusting the fineness to 50 using a tubular knitting machine. .

B. Refining of tubular knitted fabric The tubular knitted fabric obtained in above A was prepared with 100 ml of a 2 g/l aqueous solution of nonionic surfactant (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Neugen SS) per 1 g of knitted fabric, and heated at 60°C for 30 minutes. After washing, it was washed with running water for 20 minutes, dehydrated with a dehydrator, and air-dried.

C. Dyeing of tubular knitted fabric A. above. Section, B. The tubular knitted fabric obtained in Section 1 was dyed using the following dyes and dyeing aids.
Acidic dye: Erionyl Blue AR 2.0% by mass
Dyeing aid: Acetic acid 1.5%
After dyeing in a dyeing bath containing an acid dye and a dyeing aid at normal pressure at 98°C for 45 minutes, the fabric was washed with running water for 20 minutes, dehydrated in a dehydrator, and air-dried.

D. Color development C. The color development of the dyed tubular knitted fabric obtained in Section 1 was evaluated on the following three levels. A polymer with an ηr of 2.6, an amount of amino end groups of 3.5×10 ⁻⁵ mol/g, and a value obtained by subtracting the amount of carboxyl end groups from the amount of amino end groups is −10.5×10 ⁻⁵ mol/g. The color development property is designated as B.
S: The whole body is uniformly colored in a medium color (light to dark color) to a dark color A: The whole body is uniformly colored in a light color to a medium color (light to dark color) B: The whole body is uniformly colored in a light color.

Reference Example 1 (Preparation of 40% by weight aqueous solution of 1,6-diaminohexane sebacate)
While stirring an aqueous solution of 1,6-diaminohexane diluted with ion-exchanged water, sebacic acid (manufactured by Kirk Corporation) having an equimolar amount to 1,6-diaminohexane and a radioactive carbon (C14) content of 70% or more was added little by little, and near the neutralization point, the solution was heated in a 40° C. water bath to an internal temperature of 33° C., thereby preparing a 40% by weight aqueous solution of an equimolar salt of 1,6-diaminohexane and sebacic acid. In a similar manner, a 40% by weight aqueous solution of an equimolar salt of 1,5-diaminopentane and sebacic acid and a 40% by weight aqueous solution of an equimolar salt of 1,4-diaminobutane and sebacic acid were prepared.

Example 1
300 kg of the 40 wt% aqueous solution of 1,6-diaminohexane-sebacic acid obtained in Reference Example 1 was charged into a jacketed autoclave, and the inside of the vessel was thoroughly replaced with nitrogen, and then heated. The aqueous solution was concentrated until the water content in the aqueous solution reached 15 wt% while controlling the temperature inside the vessel to 200°C and the pressure inside the vessel to 0.2 MPa (gauge pressure) (concentration step). The aqueous solution concentration in the vessel was determined from the amount of distilled water. After completion of concentration, 0.022 moles of 1,6-diaminohexane was added to the equimolar salt of 1,6-diaminohexane-sebacic acid so as to achieve the target amount of amino terminal groups, and then the solution was transferred to an autoclave equipped with a stirrer and a heat medium jacket, and the heat medium temperature was heated to 290°C, and the pressure inside the vessel (gauge pressure) was increased to 1.7 MPa while stirring at 30 rpm (pressure increase step). After this, the pressure inside the vessel (gauge pressure) was controlled at 1.7 MPa, and the pressure inside the vessel was maintained until the temperature inside the vessel reached 245°C (pressure control step). Then, the pressure was released to atmospheric pressure over 50 minutes (pressure release step). While adjusting the heating temperature so that the internal temperature at the end of the atmospheric polymerization was 245°C or higher but less than 250°C, nitrogen gas was passed through at 0.5 L/min (50 L/min) per 1 kg of polymer, and blown for 30 minutes to increase the degree of polymerization (atmospheric pressure step). Then, nitrogen pressure of 0.5 MPa (absolute pressure) was applied to the inside of the container, and the polyamide resin composition obtained by polycondensation was extruded into a strand shape with a diameter of about 3 mm, cut into a length of about 4 mm, and 100 kg of pellets were obtained (discharge step). The results of the obtained polyamide resin composition are shown in Table 1.

The resulting polyamide resin composition was dried to a moisture content of 0.135% by weight or less, and then melt-extruded at a spinning temperature of 280°C from a spinneret with 96 nozzle holes (hole diameter 0.2 mm, hole elongation 0.7 mm) at a discharge rate of 38.6 g/min. After melt-extrusion, the fiber was cooled, oiled, entangled, and then taken up with a godet roller at 3532 m/min. It was then stretched 1.3 times and heat-set at 170°C, yielding a fiber with a total fineness of 22 decitex and 24 filaments at a take-up speed of 4500 m/min. There were zero breakages when 100 kg of the polyamide resin composition was spun.

(Example 2)
Polyamide resin composition pellets were obtained under the polymerization conditions shown in Table 1, except that 0.017 mol of 1,6-diaminohexane was additionally added to the equimolar salt of 1,6-diaminohexane and sebacic acid after completion of the concentration. Note that the stretching ratio during fiberization was arbitrarily changed so that the elongation was in the range of 45 to 55%.

(Example 3)
A 40% by weight aqueous solution of 1,5-diaminopentane/sebacic acid was used, and after completion of concentration, 0.022 mol of 1,5-diaminopentane was additionally added to the equimolar salt of 1,5-diaminopentane/sebacic acid. Except for the above, polyamide resin composition pellets were obtained under the polymerization conditions shown in Table 1.

(Example 4)
Polyamide resin composition pellets were obtained under the polymerization conditions shown in Table 1, except that 0.017 mol of 1,5-diaminopentane was additionally added to the equimolar salt of 1,5-diaminopentane and sebacic acid after completion of the concentration.

(Example 5)
Except for using a 40% by weight aqueous solution of 1,4-diaminobutane/sebacic acid and adding 0.022 mol of 1,4-diamibutane to the equimolar 1,4-diaminobutane/sebacic acid salt after completion of concentration. Polyamide resin composition pellets were obtained under the polymerization conditions shown in Table 1.

Example 6
After the concentration was completed, polyamide resin composition pellets were obtained under the polymerization conditions shown in Table 1, except that 0.022 moles of 1,6-diaminohexane and 5% by weight of ε-caprolactam were additionally added relative to the amount of 1,6-diaminohexane·sebacic acid.

(Comparative Example 1)
Polyamide resin composition pellets were obtained under the polymerization conditions shown in Table 2, except that 1,6-diaminohexane was not added after the concentration was completed.

(Comparative example 2)
Polyamide resin composition pellets were obtained under the polymerization conditions shown in Table 2, except that 0.013 mol of 1,5-diaminopentane was additionally added after the completion of concentration.

(Comparative example 3)
Polyamide resin composition pellets were obtained under the polymerization conditions shown in Table 2, except that 0.017 mol of 1,6-diaminohexane was additionally added to the equimolar salt of 1,6-diaminohexane and sebacic acid before concentration.

(Comparative example 4)
Polyamide resin composition pellets were obtained under the polymerization conditions shown in Table 2, except that 0.035 mol of 1,6-diaminohexane was additionally added after the completion of concentration.

Claims (5)

A polyamide resin consisting of a diamine component and sebacic acid, the resin composition has a relative viscosity ηr of 98% sulfuric acid in the range of 2.4 to 3.0, and an amino terminal group amount of 10.0×10 ⁻⁵ mol/ g, and the value obtained by subtracting the amount of carboxyl end groups from the amount of amino end groups is larger than 6.5×10 ⁻⁵ mol/g. The polyamide resin composition according to claim 1, in which the filtration pressure increase rate ΔP through a 5 μm filter is 3.0 MPa/hour or less. The polyamide resin composition according to claim 1 or claim 2, in which the yellowing index YI of the pellets of the polyamide resin composition is 6.0 or less. The polyamide resin composition according to claim 1 or 2, wherein the diamine component is one or more types selected from 1,4-diaminobutane, 1,5-diaminopentane, and 1,6-diaminohexane. A fiber made of the polyamide resin composition according to claim 1 or 2.