JP5087949B2 - Polyamide fiber - Google Patents

Description

  The present invention relates to a polyamide fiber. More specifically, the present invention relates to a polyamide fiber comprising a polyamide composition which is suitable as a polyamide fiber for tire cords and airbags, hardly produces spherulites and exhibits a unique crystallization behavior. Higher strength, higher toughness, and higher fatigue resistance for tire cords, especially for aircraft tires that can reduce weight and increase the number of take-offs and landings, and for airbags, particularly less generation of fluff The present invention also relates to the provision of a polyamide fiber suitable for an air bag base fabric having excellent warping and weaving properties and excellent quality.

  Polyamide fiber, especially polyhexamethylene adipamide (hereinafter referred to as nylon 66) fiber, is useful for tire cords and airbags, taking advantage of its high strength, high toughness, high fatigue resistance, and high heat resistance. Has been.

  As a tire code, it is useful as a tire for heavy vehicles such as trucks, buses, construction vehicles, and aircraft. In particular, aircraft tires are required to have higher strength, higher toughness, and higher fatigue resistance in order to reduce weight and increase the number of take-offs and landings.

  In recent years, for airbags, demand for airbag fabrics has increased due to the expansion of global automobile production, improvement of airbag mounting rates, 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 high strength, high toughness and high fatigue resistance required for tire cords and low fluffy nylon 66 fiber required for airbags is achieved by removing the common main causes that hinder them. Achievable. That is, one of the hindering factors is that the spherulites generated during spinning cooling hinder the high orientation during drawing, making it difficult to produce high strength and high toughness fibers. This is because thread breakage and fluff are generated by the mixed foreign matter, so that it is difficult to obtain higher strength and high toughness fibers, and fluff cannot be reduced.

  The former is a polyamide polymer polymerization process and a melt spinning process, in which the polyamide polymer is thermally decomposed and minute foreign matters generated by the thermal decomposition become spherulite nuclei, and additives such as a heat-resistant agent are thermally decomposed and become minute. New foreign matters are produced and they become spherulite nuclei. 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 generate minute foreign substances that become spherulite nuclei. Further, since spherulite formation is formed by spherulite growth in addition to the above spherulite nucleus generation, it also depends on the crystallization rate of the polyamide polymer. In particular, since nylon 66 has a high crystallization speed, the formation of spherulites and the resulting yarn-making trouble are remarkable. Therefore, as a spherulite formation suppression technique, thermal decomposition, the addition of a gelling inhibitor, a method of reducing the crystallization rate by copolymerizing a small amount of a copolymer component, and the like are 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.

  Further, as another method for suppressing spherulites, a spinning technique of quenching in the spinning cooling process and passing through the crystallization temperature range in a short time is generally applied.

  On the other hand, the foreign matter mixed in the latter polyamide fiber is such that the additive such as a heat-resistant agent does not sufficiently dissolve in the molten polyamide polymer and remains as a foreign matter, or the additive is thermally decomposed to cause a polyamide polymer insoluble substance, that is, a foreign matter. In many cases, the polyamide polymer that is generated or pyrolyzed becomes a foreign substance by gelation. In particular, in a polymerization kettle or a melt spinning apparatus, it often stays for a long time at a portion where the flow of the molten polymer is poor, and it is often pyrolyzed and gelled. Then, the gelled material is laminated and occasionally becomes a foreign matter in the yarn and causes a yarn-making trouble.

  Therefore, for the purpose of suppressing the spherulite to improve the yarn-making property and producing a high-quality polyamide fiber, a method of suppressing the spherulite by using a copolymerized polyamide and reducing the crystallization rate of the polymer, and For example, Patent Documents 1 to 4 relate to methods for suppressing thermal decomposition and gelation of polyamide polymer to suppress spherulites.

  Patent Document 1 aims to improve the spinning performance by suppressing the spherulites (spherical aggregates) of nylon 66 and increasing the gelation time. The problem is that 2-methylpentamethylenediamine and other amide units are used. It is disclosed that it can be solved by preparing ternary polyamides and multi-component polyamides containing bismuth and products produced therefrom. According to the technique described in Patent Document 1, spherulite formation can be reduced and gelation time can be increased, and useful effects such as stretchability of BCF yarn, optical transparency, and dyeing speed can be obtained. It is shown.

  However, the copolymer polymer produced by the technique described in Patent Document 1 has a relatively large melting point drop, and even in the examples, the melting point drop is 2.1 ° C., most of which is 5 to 10 ° C. Such a melting point drop may not be particularly disadvantageous in terms of performance in products that are normally used at room temperature, such as BCF for carpets. However, in the tire cord and airbag targeted by the present invention, the melting point Along with the descent, the shrinkage rate increases, the thermal dimensional stability decreases, and the heat resistance decreases. In addition, since the product performance deteriorates such that the high strength intended by the present invention cannot be obtained, it cannot be employed.

  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 a small amount of nylon 6 as a main component. Specifically, it is disclosed to apply N66 copolymer polyamide containing 94-96% hexamethylene adipamide, 1-6% caprolactam, and 0.001-2% water-soluble inorganic calcium salt. .

  In the technology described in Patent Document 2, by reducing the crystallization rate of nylon 66 by copolymerizing caprolactam, in fibers that have a large single yarn fineness and are difficult to cool, such as BCF for carpets, The effect of suppressing spherulite is noticeable. However, the method of copolymerizing caprolactam has a great effect of suppressing spherulite, but also has a large melting point drop. Although not described in Patent Document 2, the melting point drop is inferior in quality for the tire cord and airbag of the present invention and cannot be applied.

  Patent Document 3 aims to improve the thermal stability of polyamides containing polyhexamethylene adipamide as the main constituent, to suppress gel generation and spherulite, and to improve the continuous batch property. Polyamide consisting of hexamethylene adipamide units is copolymerized with amide units consisting of a specific linear aliphatic diamine and dicarboxylic acid, and the ratio between the carboxyl group concentration and amino group concentration is specified. It is disclosed that it can be achieved by controlling the end group concentration to fall within the range.

  Further, in the examples, a polyamide obtained by copolymerizing 2.9 mol% of 1,4 diaminobutane / adipic acid as an amide unit composed of a specific linear aliphatic diamine and dicarboxylic acid in hexamethylene diamine / adipate. Examples are described and techniques similar to the present invention are disclosed.

  However, since the melting point of polyamide obtained by copolymerizing 2.9 mol% of 1,4 diaminobutane / adipic acid is 4 ° C. lower than the melting point of hexamethylene adipamide homopolymer, thermal dimensional stability and heat resistance are reduced. It is difficult to apply the present invention to a tire cord or an airbag. Further, the cooling crystallization temperature was relatively high at 219 ° C., and the effect of suppressing spherulite was not sufficient because of a slight difference of 2 ° C. from 221 ° C. of the homopolymer (Comparative Example 1).

  Patent document 4 makes it a subject to improve the thermal stability of polyamide which has polyhexamethylene adipamide as a main constituent, gel generation and spherulite suppression, and improvement of continuous batch property. A copolymerized polyamide comprising an amide unit comprising 0.5 to 20 mol% of a diamine and a dicarboxylic acid containing an aromatic structure in a polyamide comprising 99.5 mol% of hexamethylene adipamide units, It is disclosed that it is achieved by controlling the terminal group concentration so that the ratio between the group concentration and the amino group concentration falls within a specific range.

  In the examples, there is an example of a polyamide obtained by copolymerizing 2.9 mol% of hexamethylene adipic acid / terephthalic acid as an amide unit composed of a diamine and a dicarboxylic acid containing an aromatic structure in hexamethylene diamine / adipate. It is disclosed.

However, the cooling crystallization temperature of polyamide obtained by copolymerizing 2.9 mol% of hexamethylenediamine / terephthalic acid is relatively high at 219 ° C., which is a slight difference of 2 ° C. from 221 ° C. of the homopolymer (Comparative Example 1). The effect of suppressing spherulite was not sufficient.
: JP-T 6-502671 (Claims) : U.S. Pat. No. 4,919,874 : JP 2000-38444 A (Claims) : JP 2000-53762 A (Claims)

  The present invention is a polyamide fiber obtained by suppressing the formation of spherulites, suitable as a tire cord or airbag fiber, and is less likely to cause yarn breakage and fluff, and has excellent yarn production yield and fluff quality. An object is to obtain a polyamide fiber.

In order to solve the above problems, the present invention has the following configuration.
1. The following (1), (2), in which a powder of a compound having a melting point of 270 to 300 ° C. is finely dispersed in polyamide mainly composed of hexamethylene adipamide units.
) And (3), a polyamide fiber having the following fiber characteristics (A) to (E).
Tc (270) −Tc (300) ≧ 15 ° C. (1)
Tc (300) ≦ 188 ° C., Tc (270) ≧ 200 ° C. (2)
Tm ≧ 260 ° C. (3)
Here, Tc (T) is a cooling crystallization peak temperature measured by melting at a temperature T ° C., and Tm is a melting point.
(A) Fineness = 150 to 5000 dtex
(B) Strength = 7-11.5 cN / dtex
(C) Elongation = 15-35%
(D) Boiling water shrinkage = 2.5 to 9.5%
(E) Birefringence = 35 to 65 × 10 −3
2. Made of Polyamide is polyamide fiber of the 1, wherein the polyhexamethylene adipate Pami de.
3. 3. The polyamide fiber as described in 2 above, wherein the compound having a melting point of 270 to 300 ° C. is polyamide.
4). 4. The polyamide fiber as described in 2 or 3 above, wherein the polyamide having a melting point of 270 to 300 ° C. is polytetramethylene adipamide and / or a copolymer thereof.
5. 5. The polyamide fiber as described in any one of 1 to 4 above, wherein the polyamide fiber is used for tire cords and / or airbags.

  According to the present invention, a polyamide fiber in which the formation of spherulites is suppressed can be obtained. Particularly in the case of a tire cord, higher strength, higher toughness, and higher fatigue resistance can be achieved. Further, in the case of an airbag, polyamide fibers having little yarn breakage and fluff generation, excellent yarn production yield, and excellent quality can be obtained. As a result, an airbag base fabric excellent in warping and weaving properties and excellent in quality can be obtained.

  The present invention is described in detail below.

  The polyamide fiber of the present invention can be obtained by spinning a polyamide composition satisfying the following formulas (1) to (3) containing a polyamide mainly composed of hexamethylene adipamide units.

Although the polyamide composition used in the polyamide fiber of the present invention has a remarkable effect of suppressing spherulite, crystallization is likely to proceed in the process of forming the fiber structure. Few. As a result, effects such as higher strength, higher toughness, improved yarn production, and reduced fluff are obtained, while there is an advantage that dimensional stability and fatigue resistance are not deteriorated. The polyamide composition of the present invention having such effects is characterized by satisfying the following formulas (1) to (3).
Tc (270) -Tc (300) ≧ 15 ° C. (1)
Tc (300) ≦ 188 ° C., Tc (270) ≧ 200 ° C. (2)
Tm ≧ 260 ° C (3)

  Here, Tc (T) indicates a cooling crystallization peak temperature measured by melting at a temperature T ° C., and Tm indicates a melting point. The melting point Tm was measured by using a differential scanning calorimeter and completely melting at a sample amount of 4 mg at a heating rate of 80 ° C./min, then cooling at a cooling rate of 80 ° C./min, and further at a heating rate of 80 ° C./min. The peak top temperature of the endothermic peak based on melting when the temperature is raised is defined as 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.

  In the above formula (1), 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. Indicates that it is lower by 15 ° C. or more than the crystallization temperature Tc (270) when it is cooled and crystallized after melting at 270 ° C., which is a relatively low temperature.

  That is, the polyamide composition of the present invention has a low cooling crystallization rate when melted at a relatively high temperature, and conversely, a high crystallization rate when melted at a relatively low temperature. In this case, the component that becomes the crystal nucleus is almost completely dissolved, whereas when it melts at 270 ° C., it means that the component that becomes the crystal nucleus remains.

  When Tc (300) is low, crystallization in the melt spinning process is difficult to proceed, and the effect of suppressing spherulite is large, so that deterioration of the spinning property and fluff generation due to spherulite can be suppressed. On the other hand, when Tc (270) is high, crystallization is likely to proceed in the fiber structure formation process, and the fiber structure oriented by stretching is easily heat-fixed. Therefore, highly oriented fibers with little dimensional change can be obtained. That is, the large crystallization temperature difference between Tc (270) and Tc (300) satisfies both the spherulite suppression effect in the melt spinning process and the fiber structure heat setting effect in the stretching orientation process at the same time. This means that it is easy to obtain a polyamide fiber having high strength, high toughness and excellent dimensional stability. This crystallization temperature difference needs to be 15 ° C. or higher, and is preferably 16 ° C. or higher. As an upper limit, it is preferable that it is 50 degrees C or less at the point that sufficient effect of the said characteristic is acquired.

  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 (300) and Tc (270), but decrease Tc (270) more than Tc (300). Since it is large, the melting temperature dependency is small. Further, when a polyamide having a melting point of 300 ° C. such as inorganic fine particles such as talc and silica or polyhexamethylene terephthalate (hereinafter referred to as nylon 6T), which is known as a crystal nucleating agent, is added, Tc (270) Although both Tc (300) rise, since the rise of Tc (300) is larger than Tc (270), the melting temperature dependency is small as in the case of lactam copolymerization.

  The above formula (2) shows that the cooling crystallization peak temperature Tc (300) of the polyamide composition measured by melting at 300 ° C. is 188 ° C. or less, and measured by melting at 270 ° C. It shows that the cooling crystallization peak temperature Tc (270) of the polyamide composition is 200 ° C. or higher. That is, Tc (300) of the polyamide composition of the present invention is 5 ° C. or more lower than 193 ° C., which is Tc (300) of polyhexamethylene adipamide, and the Tc (270) of the polyamide composition is 200 ° C. or more obtained by adding 12 ° C. which is the difference in crystallization temperature between Tc (300) and Tc (270) of polyhexamethylene adipamide alone to 188 ° C. which is the maximum temperature of Tc (300) of the polyamide composition It means that.

  That is, this indicates that the polyamide composition of the present invention has a large spherulite suppression effect and can simultaneously satisfy both the fiber structure heat setting effect in the stretching orientation process, and has high strength, high toughness, and dimensions. It means that it is easy to produce a polyamide fiber having excellent stability. If the Tc (300) of the polyamide composition exceeds 188 ° C., it cannot be said that the crystallization rate was sufficiently slow, and the effect of suppressing spherulite cannot be clearly obtained. Further, when the Tc (270) of the polyamide composition is less than 200 ° C., the fiber structure heat fixation in the stretching orientation process cannot be sufficiently performed as in the case of the conventional copolymerized polyamide polymer. A polyamide fiber excellent in certain high strength, high toughness and dimensional stability cannot be obtained. Tc (300) is 186 ° C. or lower and preferably 180 ° C. or higher, and Tc (270) is 201 ° C. or higher and preferably 225 ° C. or lower. When Tc (300) is less than 180 ° C., crystallization at the time of forming the fiber structure does not proceed sufficiently, it is difficult to obtain high strength and high toughness, and dimensional stability and heat resistance are lowered. In addition, a polyamide composition having a Tc (270) exceeding 225 ° C has not been found, but a sufficient effect can be obtained when the Tc (270) is in the range of 200 to 225 ° C.

  Further, the above formula (3) indicates that the melting point Tm of the polyamide composition of the present invention is 260 ° C. or higher, that is, the melting point drop from the 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 not particularly defined as long as melt spinning is possible under general conditions. When the melting point drop exceeds 3 ° C., that is, when the melting point Tm is 260 ° C. or less, the thermal dimensional stability is lowered and the heat resistance is lowered, so that the high strength fiber intended by the present invention cannot be obtained.

  That is, a polyamide composition having crystallization characteristics represented by the above formulas (1) and (2) and having a melting point represented by the above formula (3) has not been obtained in the prior art.

In the present invention, a polyamide fiber having the following fiber characteristics (A) to (E) can be obtained by spinning the above-mentioned unique polyamide composition.
(A) Fineness = 150 to 5000 dtex
(B) Strength = 7-11.5 cN / dtex
(C) Elongation = 15-35%
(D) Boiling water shrinkage = 2.5 to 9.5%
(E) Birefringence = 35 to 65 × 10 ⁻³

  The polyamide fiber of the present invention has a fineness of 150 to 5000 dtex, preferably 150 to 2500 dtex. Although the technology of the present invention can be applied to fine yarns of less than 150 dtex or thick yarns of more than 5000 dtex, the airbags and tire cords targeted by the present invention are usually used in this fineness range.

  The strength is 7 to 11.5 cN / dtex, preferably 7.5 to 10.5 cN / dtex. If it is less than 7, the strength is insufficient even for an airbag, and it cannot be applied. A high-strength yarn exceeding 11.5 cN / dtex is difficult to achieve as a production technology even when the present technology is applied.

  The elongation is 15 to 35%, preferably 20 to 30%. If it is less than 15%, the frequency of yarn breakage and fluffing increases, and stable production is difficult. On the other hand, if the elongation exceeds 35%, high-strength fibers cannot be obtained.

  The boiling water shrinkage is 2.5 to 9.5%, preferably 3.0 to 9.0%, more preferably 4.0 to 7.0%. If it is attempted to obtain less than 2.5%, it is difficult to achieve the high strength of the present invention. On the other hand, if it exceeds 9.5%, the thermal dimensional stability is inferior and the characteristics as polyhexamethylene adipamide are lost.

The birefringence is 35 to 65 × 10 ^−3, preferably 35 to 63 × 10 ⁻³ , more preferably 40 to 63 × 10 ⁻³ . Birefringence is a parameter indicating the degree of orientation of molecular chains, and high-strength fibers cannot be obtained unless the birefringence range of the present invention is satisfied.

  Next, the polyamide composition used for the polyamide fiber of the present invention is preferably a polyamide composition characterized by containing polyhexamethylene adipamide and a compound having a melting point of 270 to 300 ° C. In the case of a polyamide composition using a compound of less than 270 ° C., the cooling crystallization peak temperature Tc (300) measured by melting at 300 ° C. is sufficiently lowered, but measured by dissolving at 270 ° C. The cooling crystallization peak temperature Tc (270) also decreases at the same time. Such a polyamide composition is not preferred because, like conventional copolymerized polymers, crystallization during fiber structure formation does not proceed sufficiently, high strength and high toughness are difficult to achieve, and dimensional stability and heat resistance are reduced. On the other hand, a polyamide composition using a compound having a temperature exceeding 300 ° C. is difficult to obtain a stable polymer, and therefore, it is difficult to produce a polyamide fiber. When a compound having a melting point of 270 ° C. or higher and lower than 300 ° C. is added, when it is melted at 270 ° C., the additive acts as a crystal nucleating agent, Tc (270) can be maintained high, and it is melted at 300 ° C. In this case, the additive acts as a crystallization inhibitor and Tc (300) is lowered.

  The amount of the compound having a melting point of 270 to 300 ° C. is preferably 0.5 to 5 parts by weight with respect to 100 parts by weight of nylon 66 monomer which is a raw material of polyamide mainly composed of hexamethylene adipamide units. More preferably, it is 4 parts by weight. If the amount is less than 0.5 part by weight, the effect of suppressing the spherulite of the polyamide composition is not sufficient, and the effects of the present invention tend to be small, such as higher strength, higher toughness, improved yarn-making property, and reduced fluff. On the other hand, if the amount exceeds 5 parts by weight, crystallization during the formation of the fiber structure is difficult to proceed, and high strength, high toughness, dimensional stability, heat resistance, etc. are reduced, and the tire cord and air targeted by the present invention are reduced. It becomes difficult to obtain a bag.

  The above compound is not particularly limited as long as it satisfies the temperature range of 270 to 300 ° C., but is preferably similar in structure to polyhexamethylene adipamide, It is a polyamide that can be finely dispersed in it. Particularly preferred is polytetramethylene adipamide (nylon 46) and / or a copolymer thereof. In order to satisfy the characteristics of the polyamide composition of the present invention, these polymers are added in an amount of 0.5 to 5 parts by weight with respect to 100 parts by weight of nylon 66 monomer which is a raw material of polyamide comprising hexamethylene adipamide units. Is preferred. The polyamide having a melting point of 270 to 300 ° C. may be added alone, but two or more other polyamide components may be added.

  The polyamide fiber of the present invention is suitable for tire cords and / or airbags. As a tire code, it can usually be used for reinforcing tires for trucks, buses, construction vehicles and aircraft. In particular, it is used favorably as a tire that is lightweight and can significantly increase the number of take-offs and landings by taking advantage of its high strength, high toughness, high fatigue resistance, and the like. Moreover, even when designing the highest strength raw yarn and base fabric required for the market for airbags, the polyamide fiber of the present invention has high strength and high elongation potential. There can be obtained a base fabric for an air bag having little yarn breakage, excellent passability in the warping process and weaving process, and good quality.

  Below, the manufacturing method of the polyamide fiber of this invention is outlined.

  In the production of the polyamide composition used in the polyamide fiber of the present invention, a terminal blocking agent such as monocarboxylic acid, a matting agent such as titanium oxide, a polymerization catalyst such as a phosphorus compound, and heat resistance, as long as the effects of the present invention are not impaired. 1 type or 2 or more types of lactam units other than an antioxidant, heat resistance stabilizers, such as an agent, a copper compound and a halide of an alkali metal or an alkaline earth metal, and a tetramethylenediamine unit and an adipic acid unit as main constituent units, A polyamide having a dicarboxylic acid unit and a diamine unit can be added at any time. The liquid phase polymerization can be produced by either a continuous polymerization method or a batch polymerization method, and then a solid phase polymerization can be performed to increase the degree of polymerization. A method for producing a polyamide fiber obtained from the polyamide composition of the present invention is shown as an example as follows.

  Nylon 66 monomer 100, which is a polyamide raw material consisting of hexamethylene adipamide units, is added to an autoclave, an equimolar amount of hexamethylenediamine and adipic acid in an aqueous solution of 50 to 90% by weight, and a compound having a melting point of 270 to 300 ° C. Charge 0.5 to 5 parts by weight with respect to parts by weight. Nitrogen replacement was performed, and hermetic heating was performed until the internal pressure reached 1.7 to 1.8 MPa. While maintaining the internal pressure 1.7-1.8 MPa until the autoclave internal temperature reaches 250-260 ° C., the internal pressure is gradually released to atmospheric pressure over about 1-2 hours while continuing the heating, During this time, the internal temperature is raised to 280-290 ° C. Then, after reducing the pressure in the autoclave and proceeding the polymerization, the pressure is increased, and the polymer is extruded into a strand having a diameter of about 2 to 4 mm and cut to about 3 to 5 mm to obtain a polymer chip. The relative viscosity of the polymer chip is preferably 2.5 to 3.3.

  Next, an aqueous copper acetate solution as an antioxidant is added to and adsorbed on the polymer chip in an amount of 50 to 100 ppm as copper with respect to the polymer weight, and an aqueous potassium iodide solution and an aqueous potassium bromide solution are added to 0.01 parts by weight based on 100 parts by weight of the polymer. Add 0.5 parts by weight to adsorb. After the antioxidant is adsorbed on the surface of the polymer chip, it is left for 3 to 10 hours to be impregnated into the polymer chip.

  Next, the polymer chip is subjected to solid phase polymerization by a batch type solid phase polymerization apparatus or a tower type continuous solid phase polymerization apparatus, and the relative viscosity of the polymer chip is increased to 3.7 to 3.9. The solid phase polymerization is performed at 150 to 170 ° C. for 10 to 30 hours. The polymer chip subjected to solid-phase polymerization is conditioned to a moisture content of 0.07 to 0.10 and then supplied to a yarn making hopper.

  As the spinning machine, an extruder type is usually used. The polymer chip is melted in a spinning machine, filtered in a spinning pack, and then spun from the nozzle hole. The melting temperature is 290 to 300 ° C. The spun yarn is passed through a 280 to 320 ° C. heating tube atmosphere provided immediately below the base, and then cooled and solidified by blowing cold air. Then, after applying the oil, it is taken up by a take-up roll. The take-up speed is 300 to 1000 m / min. The taken yarn is usually drawn continuously. Stretching is performed by winding the yarn around Nelson type rolls with different speeds. In a preferred drawing process, after the stretched yarn is stretched by less than 10%, the necking is drawn in the first stage, and then the second or third stage is drawn. The first stage stretching is preferably cold stretching, and the second and subsequent stages are preferably performed by hot stretching. The stretching ratio is 4.0 to 6.0 times, and the stretching speed is 2500 to 4500 m / min. The thermal stretching is performed by heating the stretching roll temperature to 100 to 250 ° C. When producing a polyamide fiber of 9 cN / dtex or more, multi-stage drawing of 3 or more stages is advantageous. The hot-drawn yarn continues to give 2 to 12% relaxation with the relaxation roll, and after being drawn and strained, it is wound up by a winder.

  Thus, the polyamide fiber of the present invention having the above characteristics is obtained.

Hereinafter, the present invention will be specifically described by way of examples. Definitions of characteristic values and measurement methods described in the specification text and examples are as follows.

  (1) Relative viscosity: 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) Moisture content: Measured using a Karl Fischer measuring device (vaporizer: SE-24 type, electrolytic cell: AQ-6 type) manufactured by Hiranuma Sangyo Co., Ltd. The sample was 3 g, and the nitrogen used for water vaporization was 220 ° C. and 200 ml / min.

  (3) Melting point (Tm): Measured using a differential scanning calorimeter of Diamond DSC manufactured by Perkin-Elmer. The sample amount was 4 mg, the temperature was increased at a rate of 80 ° C./min, and the peak temperature of the melting endothermic curve was taken as the melting point.

  (4) Crystallization temperature (Tc): Measured using a DSC-7 type differential scanning calorimeter manufactured by Perkin-Elmer. The sample amount was 4 mg, the temperature was raised to a temperature T ° C. at a temperature rising rate of 80 ° C./minute, held at the temperature T ° C. for 6 minutes, then cooled at a temperature falling rate of 80 ° C./minute, and the peak temperature of the crystallization exothermic curve Was Tc (T).

  (5) Fineness: Measured according to JIS L1017 8.3 with an initial load of 0.045 cN / dtex and a predetermined yarn length of 90 m.

  (6) Strength, strength, elongation, intermediate elongation: JIS L1017 8.5 a) Measurement was performed under constant speed elongation conditions shown in the standard time test. The sample was “TENSILON” UCT-100 manufactured by Orientec Co., Ltd., and the gripping interval was 25 cm and the pulling speed was 30 cm / min. The number of tests was 10 and the average value was obtained. In addition, elongation was calculated | required from elongation of the point which showed the maximum strength in a SS curve. The intermediate elongation is the elongation at the time of 4.0 cN / dtex stress.

  (7) Boiling water shrinkage ratio: Measured at an initial load of 0.045 cN / dtex according to JIS L1017 8.14.

  (8) Dry heat shrinkage rate: Measured at an initial load of 0.045 cN / dtex, a predetermined temperature of 150 ° C., and a predetermined time of 30 minutes in accordance with JIS L1017 8.10 (Method B).

  (9) GY fatigue resistance: Tested according to the tube fatigue strength (Goodyear method) of Appendix 2.2.1 of JIS L1017, and the time until the tube burst was measured.

(10) Vulcanized cord strength, vulcanized cord strength, vulcanized strength retention rate: Dip cords are arranged in parallel to an unvulcanized rubber sheet, set together with another unvulcanized rubber sheet in a mold, and 175 ° C. Was vulcanized for 30 minutes with a heat press machine set to 1. Immediately after taking out the mold from the heat press machine, the mold was cooled, and the cord in the rubber was suddenly and freely shrunk. Next, the cord was removed from the rubber sheet, and the strength of the vulcanized cord after being left in a temperature / humidity adjusting chamber at 20 ° C. and 65% RH for 24 hours or more was measured, and the vulcanized cord strength was also obtained. Further, the strength retention after vulcanization was determined by the following formula from the ratio to the cord strength before vulcanization.
Strength retention after vulcanization = (Vulcanization cord strength / Cord strength before vulcanization) x 100 (%)

  (11) Heat resistant strength retention: The strength of the drawn yarn filament wound up with a measuring instrument and the drawn yarn filament subjected to thermal degradation in a constant temperature bath at 180 ° C. in air for 40 hours was measured by The ratio of strength after deterioration was determined.

  (12) Birefringence: Measured by a Belek compensator method using a white light source.

  (13) Degree of spherulite formation: unstretched yarn filament as a sample, embedded in paraffin to obtain a section, and this section was dropped on a slide glass by adding xylene and dissolving and removing the paraffin as a sample for observation. . The sample was observed with a polarizing microscope at 200 times, and the image was printed to determine the area (%) of spherulites in the cross section.

  (14) Thread breakage frequency: The number of yarn breaks per 1 ton of production was obtained, and the yarn breakage frequency was indicated by times / t.

  (15) Fluff occurrence frequency: Fluff was counted by a fluff sensor in the warping process, and the number of fluffs per 10 million m of the raw yarn was determined.

Example 1
Autoclave 6 m ^3, triturated with 90 wt% aqueous solution of 3000kg and advance mixer is a salt of hexamethylene diamine and adipic acid hexamethylene diammonium adipate (AH salt), 36 passes through the mesh, the powder to stay 100 mesh Nylon 46 (manufactured by Aldrich Chemical Co., Ltd., melting point: 293 ° C.) was charged in the amount shown in Table 1, and liquid phase polymerization was performed. In addition, the space was replaced with nitrogen in order to drive out oxygen in the autoclave before polymerization.

  The liquid phase polymerization conditions were as follows. The autoclave was heated at 300 ° C. in a closed system, and when the internal pressure rose to 1.7 MPa (internal temperature 210 ° C.), the pressure was controlled by opening the valve on the top of the autoclave 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 obtained by polymerization was extruded into cold water in the form of a strand having a diameter of about 3 mm and cut to a length of about 4 mm to obtain a polymer chip. The relative viscosity of the obtained polymer chip was 3.12.

  Next, copper acetate as an antioxidant is added to the polymer chip as a 5% by weight aqueous solution, and 80 ppm of copper is added and adsorbed with respect to the polymer weight, and 50% by weight aqueous solution of potassium iodide and 20% by weight aqueous solution of potassium bromide. As shown in FIG.

  Next, solid phase polymerization was performed using a batch type solid phase polymerization apparatus, and the relative viscosity of the polymer chip was increased to 3.90. Solid phase polymerization was performed at 160 ° C. under a reduced pressure of 13 Pa or less for about 20 hours to obtain a polyamide composition.

  Next, the polyamide composition was conditioned to a moisture content of 0.10, then supplied to a yarn-making hopper, and melt-spun with a 110 mmφ extruder-type spinning machine. Spinning temperature 300 ° C. After filtration using a 20 μm metal filter in a spinning pack, spinning was performed using a die having a diameter of 0.3 mm and a hole number of 204. A 20 cm heating cylinder was attached directly under the base, and a high temperature atmosphere of 300 ° C. was formed between 25 cm from the base surface, and the spun yarn was cooled and solidified with 18 ° C. cold air after passing through the high temperature atmosphere. Next, an oil agent containing a smoothing agent as a main component and an activator and additives (such as an antistatic agent, an extreme pressure agent and an antiseptic agent) is applied to the yarn, and then a take-up roll rotating at 600 m / min ( 1FR). The take-up yarn is a first stage of 2.9 times between the 2FR and the first drawing roll (1DR) after 5% stretch is applied to the feeding roll (2FR). Stretching 1.2 times the second stage stretching between 1DR and the second stretching roll (2DR), performing 1.4 times the third stage stretching between the 2DR and the third stretching roll (3DR), Next, the drawn yarn was relaxed by 8% with the relaxation roll (RR), and then wound with a winder. 1FR and 2FR were 40 ° C, 1DR was 135 ° C, 2DR was 209 ° C, 3DR was 235 ° C, and RR was 140 ° C. Each roll is a Nelson type roll consisting of two pairs. Thus, a 1400 dtex-204 filament polyamide fiber was obtained. The undrawn yarn used for the evaluation of the spherulite degree was sampled by winding a small amount on the take-up roll.

  Next, the obtained drawn yarns were each subjected to 39 times of twisting per 10 cm, and then the two twisted cords were put together and the same number of twisted yarns were applied in the opposite direction to the twisted to obtain raw cords. The raw code was applied with an adhesive using a “compute reader” dipping machine manufactured by Riller (USA), followed by heat treatment. An RFL liquid was used as the adhesive, and the liquid concentration and liquid draining conditions were adjusted so that the amount of adhesion was 5 parts by weight with respect to 100 parts by weight of the raw cord.

  The heat treatment conditions were as follows: a passage through the drying zone at a constant length of 120 ° C. for 120 seconds, a heat treatment zone at 235 ° C. for 40 seconds, and a stress at the exit of the heat treatment zone (value obtained by dividing the tension by the fineness of the dimple cord) of 1 g / d. It was stretched and passed. Subsequently, in the normalizing zone, heat treatment was performed by giving 1% relaxation at 230 ° C. for 40 seconds.

  Table 1 shows the properties of the polyamide composition, fibers and dip cords obtained by the above liquid phase polymerization conditions, solid phase polymerization conditions, yarn making conditions and higher processing conditions.

Example 2
A polyamide composition was obtained in the same manner as in Example 1 except that the addition amount of nylon 46 was changed as shown in Table 1. The relative viscosities of the polymer chip after liquid phase polymerization and after solid phase polymerization were 3.11 and 3.88, respectively. Further, melt spinning of the polyamide composition obtained in the same manner as in Example 1 was performed. The properties of the obtained polyamide composition, polyamide fiber and dip cord are shown in Table 1.

Example 3
A polyamide composition was obtained in the same manner as in Example 1 except that the addition amount of nylon 46 was changed as shown in Table 1. The relative viscosities of the polymer chip after liquid phase polymerization and after solid phase polymerization were 3.10 and 3.89, respectively. Further, melt spinning of the polyamide composition obtained in the same manner as in Example 1 was performed. The properties of the obtained polyamide composition, polyamide fiber and dip cord are shown in Table 1.

Example 4
Instead of nylon 46, a copolymer of nylon 46 / nylon 66 described in Table 1 (molar ratio: nylon 46/66 = 95/5, melting point Tm = 288 ° C., tetramethylene adipamide (nylon 46 component) and hexa A polyamide composition was obtained in the same manner as in Example 1 except that a copolymer of methylene adipamide (nylon 66 component) (hereinafter, “/” means copolymerization)) was used. The relative viscosities of the polymer chip after liquid phase polymerization and after solid phase polymerization were 3.09 and 3.88, respectively. Further, melt spinning of the polyamide composition obtained in the same manner as in Example 1 was performed. The properties of the obtained polyamide composition, polyamide fiber and dip cord are shown in Table 1.

Example 5
A polyamide composition was obtained in the same manner as in Example 1 except that a nylon 46 / nylon 66 copolymer shown in Table 1 was used instead of nylon 46. The relative viscosities of the polymer chip after liquid phase polymerization and after solid phase polymerization were 3.11 and 3.91, respectively. Further, melt spinning of the polyamide composition obtained in the same manner as in Example 1 was performed. The properties of the obtained polyamide composition, polyamide fiber and dip cord are shown in Table 1.

Comparative Example 1
A polyamide composition was obtained in the same manner as in Example 1 except that nylon 46 was not added. The relative viscosities of the polymer chip after liquid phase polymerization and after solid phase polymerization were 3.10 and 3.88, respectively. Further, melt spinning of the polyamide composition obtained in the same manner as in Example 1 was performed. Table 2 shows the properties of the obtained polyamide composition, polyamide fiber and dip cord.

Comparative Example 2
A polyamide composition was obtained in the same manner as in Example 1 except that the amount of nylon 46 was changed as shown in Table 2. The relative viscosities of the polymer chip after liquid phase polymerization and after solid phase polymerization were 3.11 and 3.89, respectively. Further, melt spinning of the polyamide composition obtained in the same manner as in Example 1 was performed. Table 2 shows the properties of the obtained polyamide composition, polyamide fiber and dip cord.

Comparative Example 3
A polyamide composition was obtained in the same manner as in Example 4 except that 8 parts by weight of a nylon 46 / nylon 66 copolymer was used. The relative viscosities of the polymer chip after liquid phase polymerization and after solid phase polymerization were 3.11 and 3.91, respectively. Further, melt spinning of the polyamide composition obtained in the same manner as in Example 1 was performed. Table 2 shows the properties of the obtained polyamide composition, polyamide fiber and dip cord.

Comparative Example 4
A polyamide composition was obtained in the same manner as in Example 3 except that nylon 6 shown in Table 1 (“CM1010” melting point Tm = 220 ° C., manufactured by Toray Industries, Inc.) was used instead of nylon 46. The relative viscosities of the polymer chip after liquid phase polymerization and after solid phase polymerization were 3.08 and 3.88, respectively. Further, melt spinning of the polyamide composition obtained in the same manner as in Example 1 was performed. Table 2 shows the properties of the obtained polyamide composition, polyamide fiber and dip cord.

Comparative Example 5
A polyamide composition was obtained in the same manner as in Example 1 except that nylon 6T shown in Table 1 (“AE4200” melting point Tm = 320 ° C., manufactured by Aalen) was used instead of nylon 46. The relative viscosities of the polymer chip after liquid phase polymerization and after solid phase polymerization were 3.09 and 3.90, respectively. Further, melt spinning of the polyamide composition obtained in the same manner as in Example 1 was performed. Table 2 shows the properties of the obtained polyamide composition, polyamide fiber and dip cord.

  Examples 1 to 5 and Comparative Examples 1 to 5 are evaluations of high-strength yarns for tire cords. From Tables 1 and 2, all of the examples satisfy the polymer characteristics and fiber characteristics of the present invention, and sufficiently satisfy the important strength, dimensional stability, heat resistance and fatigue resistance as tire cords. I understand. On the other hand, since all of the comparative examples do not satisfy any of the polymer characteristics of the polyamide composition of the present invention, it is understood that the fiber characteristics and the tire cord characteristics are inferior.

Example 6
The polyamide composition after solid phase polymerization obtained in the same manner as in Example 1 was melt-spun with a 90 mmφ extruder type spinning machine. The spinning temperature was 300 ° C. After filtration using a 20 μm metal filter in a spinning pack, spinning was performed using a die having a diameter of 0.3 mm and a hole number of 36. A 20 cm heating cylinder was attached directly under the base, and a high temperature atmosphere of 300 ° C. was formed between 25 cm from the base surface, and the spun yarn was cooled and solidified with 18 ° C. cold air after passing through the high temperature atmosphere. Next, an oil agent containing a smoothing agent as a main component and an activator and additives (such as an antistatic agent, an extreme pressure agent and an antiseptic agent) is applied to the yarn, and then a take-up roll rotating at 600 m / min ( 1FR). The take-up yarn was stretched by 6% between the yarn supply roll (2FR) and then the first stage of 2.9 times between 2FR and the first draw roll (1DR). Stretching 1.2-fold second stage stretching between 1DR and second stretching roll (2DR), and 1.1-fold third stage stretching between 2DR and third stretching roll (3DR), Next, the drawn yarn was relaxed by 7% with the relaxation roll (RR) and then wound by a winder. 1FR and 2FR were 40 ° C, 1DR was 135 ° C, 2DR was 200 ° C, 3DR was 224 ° C, and RR was 140 ° C. Each roll is a Nelson type roll consisting of two pairs. Thus, a polyamide fiber of 235 dtex-36 filament was obtained. The drawn yarn thus obtained was warped at a speed of 200 m / min, an infrared fluff sensor manufactured by ENKA was installed on the running warp, and the number of fluff was counted. The properties of the obtained polyamide composition and polyamide fiber are shown in Table 3.

Example 7
Example 6 except that the polyamide composition after solid phase polymerization obtained in the same manner as in Example 2 was used instead of the polyamide composition after solid phase polymerization obtained in the same manner as in Example 1. The same was done. The properties of the obtained polyamide composition and polyamide fiber are shown in Table 3.

Example 8
Example 6 is the same as Example 6 except that the polyamide composition after solid phase polymerization obtained in the same manner as in Example 3 was used instead of the polyamide composition after solid phase polymerization obtained in the same manner as in Example 1. The same was done. The properties of the obtained polyamide composition and polyamide fiber are shown in Table 3.

Example 9
Example 6 except that the polyamide composition after solid phase polymerization obtained in the same manner as in Example 4 was used instead of the polyamide composition after solid phase polymerization obtained in the same manner as in Example 1. The same was done. The properties of the obtained polyamide composition and polyamide fiber are shown in Table 3.

Example 10
Example 6 is the same as Example 6 except that the polyamide composition after solid phase polymerization obtained in the same manner as in Example 5 was used instead of the polyamide composition after solid phase polymerization obtained in the same manner as in Example 1. The same was done. The properties of the obtained polyamide composition and polyamide fiber are shown in Table 3.

Comparative Example 6
Instead of the polyamide composition after solid phase polymerization obtained in the same manner as in Example 1, a polyamide composition after solid phase polymerization obtained in the same manner as in Comparative Example 1 was used. The same was done. The properties of the obtained polyamide composition and polyamide fiber are shown in Table 4.

Comparative Example 7
Example 6 is the same as Example 6 except that the polyamide composition after solid phase polymerization obtained in the same manner as in Example 1 was used instead of the polyamide composition after solid phase polymerization obtained in the same manner as in Example 1. The same was done. The properties of the obtained polyamide composition and polyamide fiber are shown in Table 4.

Comparative Example 8
Example 6 is the same as Example 6 except that the polyamide composition after solid phase polymerization obtained in the same manner as in Example 1 was used instead of the polyamide composition after solid phase polymerization obtained in the same manner as in Example 1. The same was done. The properties of the obtained polyamide composition and polyamide fiber are shown in Table 4.

Comparative Example 9
Example 6 is the same as Example 6 except that the polyamide composition after solid phase polymerization obtained in the same manner as in Example 1 was used instead of the polyamide composition after solid phase polymerization obtained in the same manner as in Example 1. The same was done. The properties of the obtained polyamide composition and polyamide fiber are shown in Table 4.

Comparative Example 10
Example 6 is the same as Example 6 except that the polyamide composition after solid phase polymerization obtained in the same manner as in Example 1 was used instead of the polyamide composition after solid phase polymerization obtained in the same manner as in Example 1. The same was done. The properties of the obtained polyamide composition and polyamide fiber are shown in Table 4.

  Examples 6 to 10 and Comparative Examples 6 to 10 are evaluations of high strength yarns for airbags. It can be seen from Tables 3 and 4 that all of the examples satisfy the polymer characteristics and fiber characteristics of the present invention, and sufficiently satisfy the strength, heat resistance, and warping properties important as an airbag. On the other hand, since the comparative examples do not satisfy any of the polymer properties of the polyamide composition of the present invention, it is understood that the fiber properties and warping properties are inferior.

  The present invention is a polyamide fiber produced by using a polyamide composition that produces less spherulites and exhibits a unique crystallization behavior, and is particularly suitable as a fiber for tire cords and airbags. When used for tire cords, it is possible to obtain an aircraft tire that is lightweight and can significantly increase the number of take-offs and landings by taking advantage of high strength, high toughness, and high fatigue resistance. In addition, when used for airbags, even when designing the highest-strength raw yarn and base fabric required in the market, there are few fuzz and yarn breakage in the yarn-making process, excellent warping and weaving process, A good base fabric for an air bag can be obtained.

  The polyamide fiber having high strength, high toughness, and high fatigue resistance of the present invention can be useful not only for the above-mentioned use but also for heavy cloth, tent, hood, string, conveyor belt, narrow belt, rope and the like.

Claims (5)

It consists of a polyamide composition satisfying the following formulas (1), (2) and (3) obtained by finely dispersing a powder of a compound having a melting point of 270 to 300 ° C. in a polyamide mainly composed of hexamethylene adipamide units. A polyamide fiber having fiber characteristics (A) to (E).
Tc (270) −Tc (300) ≧ 15 ° C. (1)
Tc (300) ≦ 188 ° C., Tc (270) ≧ 200 ° C. (2)
Tm ≧ 260 ° C. (3)
Here, Tc (T) is a cooling crystallization peak temperature measured by melting at a temperature T ° C., and Tm is a melting point.
(A) Fineness = 150 to 5000 dtex
(B) Strength = 7-11.5 cN / dtex
(C) Elongation = 15-35%
(D) Boiling water shrinkage = 2.5 to 9.5%
(E) Birefringence = 35 to 65 × 10 −3 Made of Polyamide is polyamide fiber according to claim 1, characterized in that the polyhexamethylene adipate Pami de. The polyamide fiber according to claim 2, wherein the compound having a melting point of 270 to 300 ° C is polyamide. The polyamide fiber according to claim 2 or 3, wherein the polyamide having a melting point of 270 to 300 ° C is polytetramethylene adipamide and / or a copolymer thereof. The polyamide fiber according to any one of claims 1 to 4, wherein the polyamide fiber is used for tire cords and / or airbags.