JP2008163227A - Polyamide composition, polyamide fiber and manufacturing methods thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyamide composition which can inhibit the formation of spherulites on spinning and results in the preparation of a polyamide fiber with reduced formation of fluff and excellent in thermal dimensional stability. <P>SOLUTION: The polyamide composition mainly contains polyhexamethylene adipamide, has a crystallization temperature Tc and a melting point Tm which meet formula a: Tc(270)-Tc(300)≥15, formula b: Tc (300)≤188, and formula c: Tm≥260 [wherein Tc(T) is a crystallization temperature measured by melting the composition at a temperature of T°C and Tm is a melting point], and contains nylon 12. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a polyamide composition, a polyamide fiber, and a method for producing them. Specifically, the present invention relates to a polyamide composition, a polyamide fiber, and a method for producing the same, which show excellent characteristics for textiles, particularly for airbag base fabrics, by improving crystallization characteristics.

  Polyamide fibers, particularly polyhexamethylene adipamide (hereinafter referred to as nylon 66) fibers, have high mechanical strength and are excellent in wear resistance and heat resistance. Therefore, as industrial fibers, tire cords and airbags are used. It is useful for use.

  In particular, for airbags, the demand for airbag fabrics has increased in recent years due to the expansion of global automobile production, the improvement of airbag mounting rates, the expansion of airbag mounting sites, and the like. Along with the demand for increased production of nylon 66 fibers for airbags, nylon 66 fibers excellent in high-speed weaving properties have been demanded in order to increase the production efficiency of airbag fabrics. In other words, the supply of nylon 66 fibers with less fluff is the biggest issue.

  The production of nylon 66 fibers with less fluff can be achieved by suppressing the spherulites that are generated during spinning cooling. The main factors for the formation of spherulites are fine foreign matters generated by the thermal decomposition of nylon 66 polymer and fine foreign matters generated by thermal decomposition of additives such as heat-resistant agents in the polymerization process and melt spinning process of nylon 66. is there. In particular, during polymerization and melt spinning, the flow of the polymer is poor and it stays for a long period of time, often causing thermal decomposition and gelation to produce minute foreign substances that become spherulite nuclei. In addition to the formation of the above spherulite nuclei, the spherulite formation depends on the crystallization rate because it is formed by the growth of spherulites. In particular, since nylon 66 has a high crystallization speed, the formation of spherulites and the resulting yarn-making trouble are remarkable.

  As a spherulite formation suppression technique, a method of copolymerizing a small amount of a copolymer component to reduce the crystallization rate has been performed. In addition, a method has been proposed in which a specific copolymer component is added to obtain a copolyamide that hardly gels even if thermal decomposition occurs. Regarding these, there are, for example, Patent Document 1 and Patent Document 2.

  Patent document 1 makes it a subject to improve the spinning property by suppressing the spherulite (spherical aggregate) of nylon 66 and increasing the gelation time, and the subject is 2-methylpentamethylenediamine and other amide units. It is disclosed that it can be solved by preparing ternary polyamides and multi-component polyamides containing benzene, and products produced therefrom. According to the patent document, it is possible to reduce the formation of spherulites and increase the gelation time, and a fiber having useful effects such as stretchability, optical transparency, and dyeing speed can be obtained and used after crimping. It has been shown that

  However, the copolymer polymer described in the patent document has a relatively large melting point drop, and the specifically prepared copolymer polymer has a minimum melting point drop of 2.1 ° C., at most about 5 to 10 ° C. The melting point falls in the range of. Such a melting point drop may not be particularly disadvantageous in performance for products that are normally used at room temperature, such as bulky crimped yarn (BCF) for carpets, but the shrinkage rate increases with the melting point drop. Since the thermal dimensional stability is lowered, it is extremely difficult to employ it in some applications, for example, in airbag applications.

  Patent Document 2 has an object to provide nylon 66 fiber that suppresses spherulite of nylon 66 fiber for BCF carpet, has a smooth filament surface, and can be dyed at room temperature. It is disclosed that it is achieved by copolymerizing nylon 6 in a small amount. Specifically, nylon 66 copolymer polyamide containing 94-96% hexamethylene adipamide, 1-6% caprolactam, and 0.001-2% water-soluble inorganic calcium salt is used for the nylon 66 fiber. It is disclosed. By reducing the crystallization rate of nylon 66 by copolymerizing caprolactam, the effect of suppressing spherulite is observed in fibers that are thick and difficult to cool, such as BCF for carpets. However, the method of copolymerizing caprolactam has a great effect of suppressing spherulite, but at the same time, the field where the melting point drop can be used greatly is limited.

  Further, Patent Documents 3 and 4 are techniques for improving the physical properties of the resulting resin composition by containing nylon 12 or nylon 12 monomer (laurolactam) in the polymerization composition.

In Patent Document 3, an initial polymer of polyester and a polyamide having a degree of polymerization of about 10 are mixed and subjected to polycondensation in a molten state, whereby both components of polyamide and polyester are dispersed and mixed uniformly and finely. And a method for providing a polymer composition having a high degree of polymerization and a high crystallinity substantially having the polymer characteristics of polyester. It has also been shown that resin compositions by this approach have properties different from polymer blends and copolymers.
In the examples, there is a description in which nylon 12 is added to an initial polymer of polybutylene terephthalate and polycondensed. However, the relative viscosity only increased to 1.2, and it was impossible to use as an industrial fiber which is the object of the present invention. In addition, both Tm and Tc are low, it is possible to suppress the formation of spherulites during spinning, and since there is little generation of fluff, it was not possible to obtain a polyamide fiber excellent in yarn production yield and quality and excellent in thermal dimensional stability. .

Patent Document 4 discloses ternary copolymerization of nylon 6 monomer (ε-caprolactam), nylon 66 monomer, an equimolar salt of adipic acid and hexamethylenediamine (hereinafter referred to as AH salt), and nylon 12 monomer (laurolactam). A method for providing a polyamide having excellent transparency is disclosed. However, the purpose was to obtain a polyamide having excellent flexibility and stretchability, and a polyamide composition having excellent thermal dimensional stability could not be obtained.
Japanese Patent Publication No. 6-502671 (Claims) US Pat. No. 4,919,874 (Claims) JP 58-42645 A (Claims) JP-A-11-71455 (Claims)

  As a result of studying a technique for suppressing the melting point drop due to copolymerization and reducing the crystallization rate, the present inventors have found that the melting point is 270 ° C. in either the pre-polymerization stage or the intermediate polymerization stage of the process for producing nylon 66. A technology for adding a compound having a temperature of less than 300 ° C. to a raw material or a polymerization system has been developed. When this method is used, it is possible to obtain a polyamide fiber which can suppress spherulites and is excellent in thermal dimensional stability. However, since the melting point of the additive compound is 270 ° C. or higher, it is not easy to melt or dissolve in the polymerization stage, and the additive compound is processed into a fine powder for uniform fine dispersion in nylon 66. A process was required. Further, depending on the particle size of the powder and the polymerization time, it was considered that the dispersion was insufficient and it became a spherulite nucleating agent contrary to the effect of suppressing spherulite. Therefore, there has been a demand for a technique in which the additive compound is finely dispersed even without a step of processing into a fine powder, the melting point drop due to copolymerization is suppressed, and the crystallization rate is reduced.

  An object of the present invention is to provide a polyamide composition, a polyamide fiber, and a method for producing the same, which show excellent properties for textiles, particularly for airbag fabrics, by improving crystallization characteristics.

In order to solve the above problems, the present invention has the following configuration.
(1) A polyamide composition comprising mainly polyhexamethylene adipamide, having a crystallization temperature Tc and a melting point Tm satisfying the following formulas a, b and c, and containing nylon 12:
Tc (270) −Tc (300) ≧ 15... A
Tc (300) ≦ 188... B
Tm ≧ 260... C
Here, Tc (T) is a crystallization temperature measured by melting at a temperature of T ° C., and Tm indicates a melting point.
(2) A polyamide fiber comprising the polyamide composition described in (1) above.
(3) The polyamide fiber according to (2) above, wherein the single yarn fineness is 4 dtex or more.
(4) A process for producing polyhexamethylene adipamide using hexamethylenediamine and adipic acid as a polymerization raw material, wherein nylon 12 is added in a pre-polymerization stage or a polymerization intermediate stage. Production method.
(5) A method for producing a polyamide fiber, comprising melt-spinning the polyamide composition obtained by the production method according to (4) above.

  According to the polyamide composition of the present invention, excellent properties for textiles, particularly for airbag base fabrics, that is, spherulite generation during spinning is possible, and since there is little generation of fluff, the yarn production yield and quality are excellent. In addition, a polyamide fiber having excellent thermal dimensional stability can be obtained.

The present invention is described in detail below.
The main component of the polyamide composition of the present invention is polyhexamethylene adipamide, and in order to sufficiently obtain the effects of the present invention, the content of polyhexamethylene adipamide is preferably 80% by weight or more, and more preferably Is 90 to 99.9% by weight.

  The polymerization method of hexamethylenediamine and adipic acid is not particularly limited. The polymerization method of polyhexamethylene adipamide generally includes a continuous polymerization method and a batch polymerization method. The outline of the production method of the polyamide composition of the present invention by the batch polymerization method is as follows.

  AH salt aqueous solution is charged into a pressure-resistant reaction vessel and hermetically heated until the internal pressure reaches 1.7 to 1.8 MPa (pressure increase step), and heated until the internal temperature reaches 250 to 260 ° C. while maintaining the internal pressure. Then, the internal pressure is gradually released to atmospheric pressure while continuing heating, and the internal temperature is raised to 275-290 ° C. during this time (pressure releasing step). Then, the inside of the pressure-resistant reaction vessel is depressurized, and after the polymerization is advanced (decompression step), the pressure is increased and the polymerized polymer is discharged.

  More specifically, an autoclave is charged with an AH salt as an aqueous solution of 50 to 90% by weight. In order to expel oxygen in the autoclave, after replacing the space with nitrogen, heating is performed so as not to release the pressure until the internal pressure rises and reaches 1.7 to 1.8 MPa (pressure raising step). When the internal pressure rises and reaches 1.7 to 1.8 MPa, heating is continued while adjusting the internal pressure so as to maintain the internal pressure until the internal temperature reaches 250 to 260 ° C. (pressure suppression step). When the internal temperature reaches 250 to 260 ° C., the internal pressure is gradually released to atmospheric pressure (0.1 MPa) over about 1 to 2 hours while continuing the heating, and the internal temperature is increased to 275 to 290 ° C. during this time. (Pressure release process). Further, the pressure is reduced to 0.09 to 0.03 MPa, and the polymerization is advanced for 10 to 60 minutes (decompression step). The polymerized polyamide composition is extruded into a strand having a diameter of about 2 to 4 mm and cut to a length of about 3 to 5 mm to obtain a polymer chip.

The sulfuric acid relative viscosity of the polymer chip is preferably about 2.2 to 3.5, and more preferably 2.5 to 3.3. The sulfuric acid relative viscosity is obtained by dissolving 0.25 g of a sample in 25 ml of 98% sulfuric acid, measuring at 25 ° C. using an Ostwald viscometer, and determining the ratio of the polymer solution and sulfuric acid falling seconds.

  The polyamide composition of the present invention contains nylon 12. Nylon 12 is contained in polyhexamethylene adipamide at a stage until the polymerization raw materials hexamethylenediamine and adipic acid are charged, that is, in the pre-polymerization stage or in the middle of the polymerization stage. It is preferably added so that it is finely dispersed, and in order to sufficiently finely disperse the added compound, it is more preferable to add it at the raw material charging stage, the pressurizing step or the pressure reducing step, and it is added at the raw material charging step or the pressurizing step. More preferably. When added after completion of the polymerization, the added nylon 12 is not sufficiently finely dispersed in polyhexamethylene adipamide, and the crystallization inhibiting effect is not sufficient.

  Although there is no restriction | limiting in particular about the addition amount of nylon 12, In order to express the effect of this invention efficiently and fully, it is 0.1-5 weight part with respect to 100 weight part of polyhexamethylene adipamide raw material monomers. Preferably, 0.5 to 3 parts by weight is particularly preferable.

  Further, the addition shape of the nylon 12 to be added is not particularly limited, but when the polymerization time is short or the addition time is the late polymerization time, it is 0.1 mm to 2 mm in order to finely disperse in the polyhexamethylene adipamide. It is preferable to make it a powder. (The above range corresponds to 9.2 mesh pass and 150 mesh on when classification using JIS standard sieves.)

  The polymerization time is preferably 0.5 to 5 hours from the start of heating after the raw material is charged until the polymerization is completed and discharged from the autoclave. If it is less than 0.5 hours, it may not be sufficiently finely dispersed depending on the added form of nylon 12 to be added, and if it is more than 5 hours, the added compound may be decomposed and the original purpose may not be obtained.

  In the method for producing a polyamide composition of the present invention, the end of polyhexamethylene adipamide can be blocked by adding a monocarboxylic acid as long as the purpose of the present invention is not impaired as required. Examples 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, palmitic acid, stearic acid, oleic acid, Aliphatic monocarboxylic acids such as linoleic acid and arachidic acid, cycloaliphatic monocarboxylic acids such as cyclohexanecarboxylic acid and methylcyclohexanecarboxylic acid, aromatic monocarboxylic acids such as benzoic acid, toluic acid, ethylbenzoic acid and phenylacetic acid Examples thereof include carboxylic acid. The preferable usage-amount of the said monocarboxylic acid is 0-1 mol normally with respect to 100 mol of AH salts which are polymerization raw materials, Preferably it is 0-0.5 mol%.

  Further, in the method for producing a polyamide composition of the present invention, polyhexamethylene adipamide is used in addition to the main constituent units of hexamethylene diamine units and adipic acid units as long as the purpose of the present invention is not impaired. These may contain one or more other lactam units, dicarboxylic acid units, and diamine units. Examples of raw materials (copolymerization components) for forming these units include valerolactam, enantolactam, capryllactam, undecalactam, laurolactam, oxalic acid, malonic acid, succinic acid, glutaric acid, pimelic acid, and suberin. Acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassic acid, tetradecanedioic acid, pentadecanedioic acid, aliphatic dicarboxylic acid such as octadecanedioic acid, cyclohexanedicarboxylic acid, phthalic acid, isophthalic acid, terephthalic acid , Naphthalenedicarboxylic acid, 1,4-diaminobutane, 1,5-diaminopentane, 1,7-diaminoheptane, 1,8-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane, 1,11- Diaminoundecane, 1,12-diaminododecane, 1,1 -Diaminotridecane, 1,14-diaminotetradecane, 1,15-diaminopentadecane, 1,16-diaminohexadecane, 1,17-diaminoheptadecane, 1,18-diaminooctadecane, 1,19-diaminononadecane, 1 , 20-diaminoeicosane, diethylaminopropylamine, cyclohexanediamine, bis- (4-aminohexyl) methane, xylylenediamine and the like. The amount of these copolymer components used is preferably 0 to 0.8 parts by weight, preferably 0 to 0.4 parts by weight, based on 100 parts by weight of the raw material monomer of polyhexamethylene adipamide. From the viewpoint of sex.

  In the method for producing a polyamide composition of the present invention, after the polyamide composition is polymerized in the liquid phase, solid phase polymerization is performed as necessary to further increase the degree of polymerization within a range that does not impair the object of the present invention. In addition, depending on the application, for example, antioxidants and heat stabilizers (hindered phenols, hydroquinones, phosphites and their substitutes, copper halides, iodine compounds, etc.), weathering agents (resorcinols, Salicylates, benzotriazoles, benzophenones, hindered amines, etc.), mold release agents and lubricants (aliphatic alcohols, aliphatic amides, aliphatic bisamides, bisureas, polyethylene waxes, etc.), pigments (cadmium sulfide, phthalocyanine, carbon black) Etc.), dyes (nigrosine, aniline black, etc.), plasticizers (p-oxy) Non-ionic such as octyl benzoate, N-butylbenzenesulfonamide, etc., antistatic agents (alkyl sulfate type anionic antistatic agents, quaternary ammonium salt type cationic antistatic agents, polyoxyethylene sorbitan monostearate Antistatic agents, betaine amphoteric antistatic agents, etc.), flame retardants (hydramines such as melamine cyanurate, magnesium hydroxide, aluminum hydroxide, ammonium polyphosphate, brominated polystyrene, brominated polyphenylene oxide, brominated polycarbonate , Brominated epoxy resins or combinations of these brominated flame retardants and antimony trioxide), fillers (graphite, barium sulfate, magnesium sulfate, calcium carbonate, magnesium carbonate, antimony oxide, titanium dioxide, 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, needle-like, plate-like fillers ) Can be added at any time.

  The polyamide composition of the present invention is required that the crystallization temperature Tc and the melting point Tm satisfy the following formulas a, b and c.

When the crystallization temperature Tc and the melting point Tm satisfy the following formulas a, b and c, a polyamide composition having a remarkable spherulite suppression effect and an extremely low melting point drop like a copolymerized polyamide of the prior art can be obtained. As a result, the thermal dimensional stability is excellent, and the effect of improving the yarn production and reducing the fluff can be obtained. The polyamide composition of the present invention having such an effect is characterized by satisfying the following formulas a to c.
Tc (270) −Tc (300) ≧ 15... A
Tc (300) ≦ 188... B
Tm ≧ 260... C
Here, Tc (T) is a crystallization temperature measured by melting at a temperature of T ° C., and Tm indicates a melting point.

  The melting point Tm is obtained by using a differential scanning calorimeter and completely melting at a sample amount of 4 mg at a temperature rising rate of 80 ° C./min, then cooling at a temperature falling rate of 80 ° C./min, and further a temperature rising rate of 80 ° C./min. The peak top temperature of the endothermic peak based on melting when the temperature is raised at is the melting point Tm (however, it is determined as an average value where n is 5). The crystallization temperature (Tc) is also observed when the temperature is raised to a temperature T ° C., held at the temperature T ° C. for 6 minutes, and then lowered at a rate of temperature drop of 80 ° C./min using a differential scanning calorimeter. The peak top temperature of the exothermic peak due to crystallization is defined as the crystallization temperature Tc (T) (however, it is determined as an average value where n is 5). The average value of polyhexamethylene adipamide polymerized only from hexamethylenediamine and adipic acid (hereinafter referred to as polyhexamethylene adipamide alone) measured under the above conditions is Tc (300) = 193 (each measurement The value variation is 193.0 ± 0.2) ° C., and Tm = 263 (variation of each measurement value 263.3 ± 0.2) ° C.

  The physical properties of the polyamide composition in the present invention vary depending on conditions such as the timing of addition, the addition method, and the form of the additive. Therefore, it was difficult to simply define the polyamide composition in the present invention.

  Therefore, the polyamide composition of the present invention is measured using the crystallization temperature Tc, which is an index of easiness of crystallization when cooled and crystallized, and the melting point Tm of polyhexamethylene adipamide, which is an index of thermal dimensional stability. Defined as above.

  The above formula a shows that the crystallization temperature Tc (300) when cooling and crystallizing after heating and melting to 300 ° C., which is a general melt spinning temperature of nylon 66, is equal to or higher than the melting point of nylon 66. This indicates that the temperature is lower by 15 ° C. or more than the crystallization temperature Tc (270) when it is melted at 270 ° C. which is a low temperature and then cooled and crystallized. That is, when the polyamide composition of the present invention is melted at a relatively high temperature, the crystallization temperature is low and difficult to crystallize. Conversely, when it is melted at a relatively low temperature, the crystallization temperature is high and it is easy to crystallize. Yes.

  That is, when the polyamide composition of the present invention is heated to 300 ° C. and melted, a component that becomes a crystal nucleus is difficult to be generated in the cooling process, whereas when melted at 270 ° C., a polymer component that becomes a crystal nucleus. Means that it remains.

  A low Tc (300) means that it is easy to obtain polyamide fibers with less glomer and less fluff, and a high Tc (270) means that crystallization proceeds in the fiber structure formation process of the polyamide composition. Indicates that it is easy. This means that the fiber structure oriented by stretching is easily heat-set, and means that a polyamide fiber excellent in thermal dimensional stability is easily obtained. In order to achieve both the effect of suppressing spherulite during spinning and thermal dimensional stability, the temperature difference needs to be 15 ° C. or higher, and preferably 16 ° C. or higher. The upper limit is preferably 50 ° C. or less in that a sufficient effect of the above characteristics can be obtained.

  In the case of polyhexamethylene adipamide alone, the temperature difference between Tc (300) and Tc (270) is usually about 12 ° C. In addition, copolymer polyamides such as lactam, which have been conventionally known as a spherulite suppression technique, decrease both Tc (270) and Tc (300), but decrease Tc (270) more than Tc (300). The temperature difference is small because it is large. Further, when inorganic fine particles such as talc and silica are added as a crystallization nucleating agent, both Tc (270) and Tc (300) rise, but since the rise in Tc (300) is larger than Tc (270), Similar to the case of copolymerization, the temperature difference becomes small. A polyamide composition having a temperature difference of less than 15 ° C. cannot achieve both the effect of suppressing spherulite during spinning and the thermal dimensional stability.

  The above-mentioned formula b shows that the crystallization temperature Tc (300) when the polyamide composition of the present invention is cooled and crystallized after being heated to 300 ° C. and melted is 188 ° C. or less. This means that it is lower by 5 ° C. or more than the crystallization temperature of polyhexamethylene adipamide alone (193 ° C.), and the temperature was raised and melted to 300 ° C., which is a general melt spinning temperature of nylon 66. In this case, the crystallization rate is slower than that of polyhexamethylene adipamide alone, which means that the generation of spherulites can be suppressed. When the crystallization temperature Tc (300) is not lower than the crystallization temperature (193 ° C.) when the polyhexamethylene adipamide alone is measured by 5 ° C. or more, that is, when the Tc (300) exceeds 188 ° C. Since the crystallization rate is not sufficiently slow, the generation of spherulites cannot be suppressed, and polyamide fibers with less fluff formation cannot be obtained. Tc (300) is preferably 186 ° C. or lower. The lower limit is 178 ° C. or higher.

  The above formula c indicates that the melting point of the polyamide composition of the present invention is 260 ° C. or higher. This means that the melting point drop from polyhexamethylene adipamide alone is within 3 ° C. The melting point drop is preferably within 2 ° C., that is, the melting point is 261 ° C. or more. The upper limit is preferably 270 ° C. or less from the viewpoint of suitability in melt spinning. When the melting point drop exceeds 3 ° C., that is, when the melting point is less than 260 ° C., the shrinkage rate becomes high and the decrease in thermal dimensional stability increases, and the fields that can be used are limited. I can't.

  Copolymer polyamide polymer, which is a conventional spherulite suppression technique, can satisfy the condition of the above-mentioned formula b, depending on the copolymerization ratio. However, a copolyamide satisfying the formula c at the same time was not obtained due to the melting point drop.

  Although the polyamide composition of the present invention has the above-mentioned characteristics, Tc (270) is preferably 200 ° C to 225 ° C. When it is in the above range, crystallization at the time of forming the fiber structure is extremely good, and a fiber having excellent dimensional stability can be obtained.

  The polyamide composition of the present invention can be produced by adding nylon 12 in the pre-polymerization stage or in the middle of the polymerization process of polymerizing hexamethylenediamine and adipic acid to produce polyhexamethylene adipamide. .

  As a result of studying a technique for suppressing the melting point drop due to copolymerization and reducing the crystallization rate, the present inventors have found that the melting point is 270 ° C. in either the pre-polymerization stage or the intermediate polymerization stage of the process for producing nylon 66. A technology for adding a compound having a temperature lower than 300 ° C. to a raw material or a polymerization system has been developed. When this method is used, it is possible to obtain a polyamide fiber which can suppress spherulites and is excellent in thermal dimensional stability. However, since the melting point of the additive compound is 270 ° C. or higher, it is not easy to melt or dissolve in the polymerization stage, and the additive compound is processed into a fine powder for uniform fine dispersion in nylon 66. A process was required. Further, depending on the particle size of the powder and the polymerization time, it was considered that the dispersion was insufficient and it became a spherulite nucleating agent contrary to the effect of suppressing spherulite.

  The polyamide composition of the present invention is not a compound having a melting point of 270 ° C. or higher and lower than 300 ° C., but by adding nylon 12 having a low melting point, the added compound is finely dispersed even without a step of processing into a fine powder. In addition, the melting point drop due to copolymerization can be suppressed, and the crystallization rate can be reduced. Although the detailed structure of the obtained polyamide composition is not clear, it is presumed that the above characteristics are achieved by the fine dispersion of the additive at the molecular level.

  When the polyamide composition of the present invention is melted at 300 ° C., which is the spinning temperature of polyamide fibers, the crystallization rate is slow and spherulites are unlikely to occur. Therefore, when the polyamide fiber is used, the single yarn fineness is preferably 4 dtex or more. When the single yarn fineness is less than 4 dtex, the cooling of the yarn is fast, and although the effect of the polyamide composition of the present invention is effective, the improvement effect is small. The single yarn fineness shall be measured by the method of 8.3 of JIS L1017: 2002.

  Since the fiber comprising the polyamide composition of the present invention has few fuzz, it is particularly useful for fabrics that are woven at high speed, particularly for airbag base fabrics.

  Hereinafter, the present invention will be described in detail by way of examples. The measurement methods of characteristic values described in the examples are as follows.

  (1) Relative viscosity of sulfuric acid: 0.25 g of a sample was dissolved in 25 ml of 98% sulfuric acid and measured at 25 ° C. using an Ostwald viscometer. The relative viscosity was determined from the ratio of the number of seconds that the polymer solution and sulfuric acid dropped.

  (2) Melting point (Tm): Samples with a melting point range of 0 to 730 ° C. use a differential scanning calorimeter of Diamond DSC manufactured by Perkin-Elmer, and samples with a melting point range of 730 to 1000 ° C. are DSC-2 manufactured by Perkin-Elmer. Measurement was performed using a mold. After completely melting at a sample amount of 4 mg and a temperature increase rate of 80 ° C./min, the sample was cooled at a temperature decrease rate of 80 ° C./min, and further the endothermic peak based on melting when the temperature was increased at a temperature increase rate of 80 ° C./min. The peak top temperature was defined as the melting point Tm (measured with an n number of 5 and the average value was determined).

  (3) Crystallization temperature (Tc): Measured using a DSC-7 type differential scanning calorimeter manufactured by Perkin-Elmer. Based on crystallization, observed when the sample amount is 4 mg, the temperature is raised to a temperature T ° C. at a temperature rising rate of 80 ° C./minute, held at the temperature T ° C. for 6 minutes, and then the temperature is lowered at a temperature falling rate of 80 ° C./minute The peak value of the exothermic peak was measured at an n number of 5 with the crystallization temperature Tc (T), and the average value was obtained.

  (4) Fineness: Measured according to 8.3 of JIS L1017: 2002.

  (5) Boiling water shrinkage: measured in accordance with JIS L1017: 2002, 8.14.

  (6) Spherulite formation rate: unstretched yarn filament as a sample, embedded in paraffin to take a section, this section was dropped on a slide glass by adding xylene and dissolving and removing it as a sample for observation . The sample was observed with a polarizing microscope (Nikon / ME-600) at 200 times, and the image was printed to determine the area (%) of spherulites in the cross section.

  (7) Fluff occurrence frequency: Fluff was counted with an infrared fluff sensor manufactured by ENKA, and the number of fluffs per 10 million m of raw yarn was determined.

Example 1
In a 0.2 m ³ autoclave, 120 kg of 90% by weight aqueous solution of hexamethylene diammonium adipate (AH salt), which is a salt of hexamethylene diamine and adipic acid, and nylon 12 pellets (manufactured by Aldrich Chemical Co., melting point: 178 ° C.) 2.2 kg (2 parts by weight per 100 parts by weight of raw material monomer) was charged, and the space was replaced with nitrogen in order to drive out oxygen in the autoclave. Thereafter, the autoclave was heated at 300 ° C. in a closed system, and when the internal pressure increased to 1.7 MPa (internal temperature 210 ° C.), the valve at the top of the autoclave was opened to control the pressure so as to maintain the pressure. When the internal temperature reached 250 ° C., the internal pressure was gradually released to 0.1 MPa in 1 hour. Further, the pressure in the system was reduced to 0.05 MPa using a vacuum pump and maintained for 30 minutes to complete the polymerization. The internal temperature at this time was 285 degreeC. The polymerization time was 4 hours. Next, the polyamide composition obtained by the polymerization was extruded into a strand having a diameter of about 3 mm and cut to a length of about 4 mm to obtain a pellet. The relative viscosity of sulfuric acid of the polyamide composition was 3.1. The pellet was held at 267 Pa for 15 hours, dried and conditioned to obtain a polyamide composition having a sulfuric acid relative viscosity of 3.3 and a moisture content of 0.08%. The properties of the obtained polyamide composition are shown in Table 1.

  Next, the polyamide composition was melt-spun with an extruder-type spinning machine. After spinning using a 20 μm metal filter in a spinning pack at a spinning temperature of 300 ° C., spinning was performed using a die having a diameter of 0.3 mm and a hole number of 36. A heating cylinder of 20 cm was attached directly under the base, and spinning was carried out at a high temperature atmosphere of 300 ° C. between 25 cm from the base. The spun yarn was cooled and solidified with cold air at 18 ° C. after passing through a high temperature atmosphere. Subsequently, after applying an oil agent to the yarn, the yarn was wound around a take-up roll (1FR) rotating at 600 m / min.

  Next, the take-up yarn is subjected to a 5% stretch with the yarn supply roll (2FR), and then the first stretch between the 2FR and the first draw roll (1DR). Second-stage stretching was performed between 1DR and the second stretching roll (2DR). Next, the drawn yarn was relaxed by 8% with the relaxation roll (RR), and then wound with a winder. 1FR and 2FR were 30 ° C, 1DR was 120 ° C, 2DR was 245 ° C, and RR was 100 ° C. Each roll is a Nelson type roll consisting of two pairs. Thus, a polyamide fiber of 235 dtex-36 filament was obtained.

  The evaluation of the degree of spherulite formation was performed with undrawn yarn sampled with a small amount of squeezing roll. The properties of the obtained polyamide fiber are shown in Table 1.

Example 2
Polymerization was carried out under the same conditions as in Example 1 except that 1.1 kg (1 part by weight per 100 parts by weight of raw material monomer) of nylon 12 pellets was charged to obtain a polyamide composition. Further, a polyamide fiber was obtained in the same manner as in Example 1. The properties of the obtained polyamide composition and polyamide fiber are shown in Table 1.

Example 3
Polymerization was carried out under the same conditions as in Example 1 except that 0.54 kg (0.5 parts by weight per 100 parts by weight of raw material monomer) of nylon 12 pellets was charged to obtain a polyamide composition. Further, a polyamide fiber was obtained in the same manner as in Example 1. The properties of the obtained polyamide composition and polyamide fiber are shown in Table 1.

Example 4
Polymerization was carried out under the same conditions as in Example 2 except that nylon 12 obtained by pulverizing with a mixer in advance and passing through 36 mesh and separating the powder remaining at 100 mesh was added to the polymerization raw material to obtain a polyamide composition. Further, a polyamide fiber was obtained in the same manner as in Example 2. The properties of the obtained polyamide composition and polyamide fiber are shown in Table 1.

Example 5
Polymerization was carried out under the same conditions as in Example 2 except that nylon 12 pellets were added in the middle of the polymerization (controlling step) to obtain a polyamide composition. Further, a polyamide fiber was obtained in the same manner as in Example 2. The properties of the obtained polyamide composition and polyamide fiber are shown in Table 1.

Comparative Example 1
Polymerization was carried out under the same conditions as in Example 1 except that only the AH salt was used without using nylon 12, and a polyamide composition was obtained. Further, a polyamide fiber was obtained in the same manner as in Example 1. The properties of the obtained polyamide composition and polyamide fiber are shown in Table 2.

Comparative Example 2
Polymerization was carried out under the same conditions as in Example 1 except that 12-aminododecanoic acid was used in place of nylon 12, to obtain a polyamide composition. Further, a polyamide fiber was obtained in the same manner as in Example 1. The properties of the obtained polyamide composition and polyamide fiber are shown in Table 2.

Comparative Example 3
Example 2 was used in place of nylon 12 except that nylon 46 (Aldrich Chemical Co., melting point: 293 ° C.), which had been pulverized with a mixer in advance and passed through 36 mesh and separated into 100 mesh, was used. Polymerization was performed under the conditions described above to obtain a polyamide composition. Further, a polyamide fiber was obtained in the same manner as in Example 2. The properties of the obtained polyamide composition and polyamide fiber are shown in Table 2.

Comparative Example 4
Polymerization was carried out under the same conditions as in Comparative Example 3 except that the nylon 46 pellets were not pulverized and were directly added to the polymerization raw material. However, the polymerization was completed, and unmelted nylon 46 pellets remained when the polyamide was extruded, making it impossible to extrude the polyamide and making it impossible to pelletize it.

  As shown in Tables 1 and 2, all of the examples have the crystallization temperature characteristics and melting point of the present invention, the spherulite formation of the fiber by the polyamide composition of the present invention is small, and the fiber is excellent in thermal stability. I understand.

  Further, according to Comparative Examples 3 and 4, nylon 46 also has the crystallization temperature characteristics and melting point of the present invention, but in order to uniformly disperse in nylon 66, the additive compound is processed into a fine powder. The process to do is necessary. On the other hand, according to Examples 1 to 5, the nylon 12 does not need to be crushed. Further, in Example 5, even when nylon 12 pellets are added in the course of polymerization, they are uniformly finely dispersed in nylon 66, showing the crystallization temperature characteristics and melting point of the present invention, and excellent in melting and dispersibility. I understand that.

  Based on the small-scale test results of Examples 1 to 5 and Comparative Examples 1 to 4, the raw yarn fluff was evaluated using 2000 kg of the polyamide composition by an expansion evaluation using a representative example.

Example 6
A 6 m ³ autoclave was charged with 3000 kg of a 90% by weight aqueous solution of hexamethylene diammonium adipate (AH salt), which is a salt of hexamethylene diamine and adipic acid, and 27 kg of nylon 12 (1 part by weight per 100 parts by weight of raw material monomer) The space was purged with nitrogen in order to expel oxygen in the autoclave. Thereafter, the autoclave was heated at 300 ° C. in a closed system, and when the internal pressure increased to 1.7 MPa (internal temperature 210 ° C.), the valve at the top of the autoclave was opened to control the pressure so as to maintain the pressure. When the internal temperature reached 250 ° C., the internal pressure was gradually released to 0.1 MPa in 1 hour. Further, the pressure in the system was reduced to 0.05 MPa using a vacuum pump and maintained for 30 minutes to complete the polymerization. The internal temperature at this time was 285 degreeC. The polymerization time was 4 hours. Next, the polyamide composition obtained by the polymerization was extruded into a strand having a diameter of about 3 mm and cut to a length of about 4 mm to obtain a pellet. The relative viscosity of sulfuric acid of the polyamide composition was 3.1. The pellet was held at 267 Pa for 15 hours, dried and conditioned to obtain a polyamide composition having a sulfuric acid relative viscosity of 3.3 and a moisture content of 0.08%.

  Next, a 235 dtex-36 filament polyamide fiber was obtained in the same manner as in Example 1, and the occurrence frequency of fluff was examined when 2000 kg of polyamide fiber was wound. Table 3 shows the properties of the obtained polyamide composition and polyamide fiber, and the occurrence frequency of fluff.

Comparative Example 5
Polymerization was carried out in the same manner as in Example 6 without using nylon 12, and a polyhexamethylene adipamide simple substance was obtained, and a 235 dtex-36 filament polyamide fiber was obtained by spinning. In the same manner as in Example 6, the occurrence frequency of fluff was examined when winding the polyamide fiber. Table 3 shows the properties of the obtained polyamide composition and polyamide fiber, and the occurrence frequency of fluff.

  The polyamide composition, the polyamide fiber, and the production method thereof of the present invention are suitable as a polyamide fiber raw material for textiles, particularly for airbag base fabrics, and obtain a polyamide fiber with less fuzz generation and excellent thermal dimensional stability. be able to.

Claims (5)

A polyamide composition comprising mainly polyhexamethylene adipamide, having a crystallization temperature Tc and a melting point Tm satisfying the following formulas a, b and c, and containing nylon 12:
Tc (270) −Tc (300) ≧ 15... A
Tc (300) ≦ 188... B
Tm ≧ 260... C
Here, Tc (T) is a crystallization temperature measured by melting at a temperature of T ° C., and Tm indicates a melting point. A polyamide fiber comprising the polyamide composition according to claim 1. The polyamide fiber according to claim 2, wherein the single yarn fineness is 4 dtex or more. A method for producing a polyhexamethylene adipamide using hexamethylenediamine and adipic acid as a polymerization raw material, wherein nylon 12 is added in a pre-polymerization stage or a polymerization intermediate stage.   A method for producing a polyamide fiber, comprising melt-spinning the polyamide composition obtained by the production method according to claim 4.