Semi-aromatic polyamide resin and method for producing the same

Abstract

This semi-aromatic polyamide resin has excellent heat resistance and heat discoloration resistance, and can further suppress mold contamination due to outgassing during melt molding. It also has excellent melt fluidity, gelling properties, and mechanical properties. The semi-aromatic polyamide resin contains structural units derived from hexamethylenediamine and terephthalic acid, and structural units derived from 11-aminoundecanoic acid or undecane lactam, has a relative viscosity (RV) in the range of 2.65 to 3.50, and the relationship between the amino end concentration (AEG), carboxy end concentration (CEG), and end concentration of blocked amino ends with monocarboxylic acid (EC) satisfies a specific formula.

Description

[Technical Field]

[0001] The present invention relates to a semi-aromatic polyamide resin that has excellent heat resistance and resistance to thermal discoloration, and furthermore can suppress mold fouling due to outgassing during melt molding. It also has excellent melt fluidity and gelling properties, and is suitable for use in resin compositions for molded products such as automobile parts, bicycle parts, and electric / electronic parts. [Background technology]

[0002] Among thermoplastic resins, polyamide resins have been used for clothing, industrial fiber, engineering plastics, etc., taking advantage of their excellent properties and ease of melt molding. As an engineering plastic, in particular, they are used in a wide range of applications, including not only automotive parts and industrial machinery parts, but also various industrial parts, housing parts, and electrical and electronic parts.

[0003] 6T nylon, composed of hexamethylenediamine (6) and terephthalic acid (T), is a widely known polyamide used in engineering plastics. For example, a copolymer polyamide obtained from an equivalent molar salt of hexamethylenediamine and terephthalic acid and 11-aminoundecanoic acid has been proposed. This copolymer polyamide has heat resistance, low water absorption, and excellent stability in surface mounting processes. Its glass transition temperature of 90°C allows injection molding at relatively low mold temperatures, resulting in satisfactory moldability. However, the resin's color tends to change during the manufacturing process or in the operating environment, leaving room for improvement in terms of color stability due to external factors. Furthermore, the various semi-aromatic polyamide resins mentioned above have drawbacks: a higher melting point and poorer melt fluidity than aliphatic polyamide resins, and they tend to thicken or gel during molten retention. Therefore, there is room for improvement in terms of processing stability and high fluidity (see, for example, Patent Document 1).

[0004] On the other hand, in order to solve the problems of resin color stability and gelation caused by such external factors, an invention has been made to provide a semi-aromatic polyamide resin that is suitable for resin compositions for molded products such as automobile parts, electrical and electronic parts, by adjusting a predetermined resin composition, melt viscosity, relative viscosity, and terminal group concentration, and that has excellent melt fluidity and color stability in addition to a high melting point of 290°C or higher and low water absorption (see, for example, Patent Document 2).

[0005] Furthermore, in order to solve the problems of color stability and gelation of resins, an invention has been made that provides a polyamide and a polyamide composition comprising the same, which have good thermal stability during drying and molding, do not deteriorate in color even when mixed with recycled materials, produce little foreign matter such as gel-like matter, and have excellent productivity during molding, by leaving a reducing phosphorus compound species in the resin (see, for example, Patent Document 3).

[0006] However, although this invention achieved improvements in terms of color stability and gelation, it had the problem of contaminating the mold with gas generated during melt molding, resulting in reduced productivity. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. WO2011 / 052464 [Patent Document 2] International Publication No. WO2017 / 077901 [Patent Document 3] Japanese Patent Application Laid-Open No. 2007-92053 Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention was made against the background of the problems of the conventional technology. That is, an object of the present invention is to provide a semi-aromatic polyamide resin that has excellent heat resistance and resistance to thermal discoloration, and furthermore, can suppress mold contamination due to outgassing during melt molding, and has excellent melt fluidity and gelling properties. Furthermore, in the course of conducting research to solve this problem, a demand has arisen for a semi-aromatic polyamide resin that, in addition to the above properties, also has excellent mechanical properties. The present invention also solves this new problem. [Means for solving the problem]

[0009] As a result of extensive investigations, the present inventors have found that the above problems can be solved by the following means, and have arrived at the present invention. That is, the present invention comprises the following configurations.

[0010] [1] A semi-aromatic polyamide resin containing structural units derived from hexamethylenediamine and terephthalic acid, and structural units derived from 11-aminoundecanoic acid or undecane lactam, having a relative viscosity (RV) within the range of formula (1), and in which the relationship between the amino end concentration (AEG), the carboxy end concentration (CEG), and the end concentration of monocarboxylic acid-blocked amino ends (EC) satisfies formulas (2) to (4). 2.65≦RV≦3.50 (1) 10eq / t≦AEG+CEG≦110eq / t ··· (2) 0.25≦(AEG+CEG) / (AEG+CEG+EC)≦0.75 ··· (3) 0.1≦AEG / CEG≦3.5 (4)

[0011] [2] The semi-aromatic polyamide resin according to [1], which contains 50 to 75 mol % of structural units derived from hexamethylenediamine and terephthalic acid, and 50 to 25 mol % of structural units derived from 11-aminoundecanoic acid or undecane lactam, and has a melting point of 270 to 330°C.

[0012] [3] A semi-aromatic polyamide resin according to [1] or [2], in which the sum (P3) of the phosphorus atom contents derived from phosphorus compounds detected in the semi-aromatic polyamide resin with the structures of structural formulas (P1) and (P2) is 30 ppm or more, and P3 is 10% or more of the total amount of phosphorus atoms remaining in the semi-aromatic polyamide resin.

[0013] [ka]

[0014] [ka]

[0015] (wherein R1 and R2 are hydrogen, an alkyl group, an aryl group, a cycloalkyl group, or an arylalkyl group; X1 to X3 are hydrogen, an alkyl group, an aryl group, a cycloalkyl group, an arylalkyl group, an alkali metal, or an alkaline earth metal; and one of X1 to X3 and one of R1 to R2 in each formula may be bonded to each other to form a ring structure.)

[0016] [4] The semi-aromatic polyamide resin according to any one of [1] to [3], wherein the amount of gas (outgas) generated when the semi-aromatic polyamide resin is pyrolyzed at 330°C for 20 minutes is 500 ppm or less.

[0017] [5] A step of preparing a raw material aqueous solution constituting a semi-aromatic polyamide resin; a raw material introduction step of continuously introducing a raw material aqueous solution into a tubular reactor; an amidation step in which the introduced raw material is passed through a tubular reactor to perform amidation, thereby obtaining a reaction mixture containing an amidated product and condensed water; a step of introducing the reaction mixture into a continuous reactor capable of separating and removing water to carry out melt polymerization; The method for producing a semi-aromatic polyamide resin according to any one of [1] to [4], comprising a step of carrying out solid-phase polymerization under vacuum or under a nitrogen gas flow. [Effects of the Invention]

[0018] The present invention can provide a semi-aromatic polyamide resin that has excellent heat resistance and resistance to thermal discoloration, can suppress mold contamination due to outgassing during melt molding, has excellent melt fluidity and gelling properties, and also has excellent mechanical properties. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 2 is a schematic diagram showing the shape of a test piece for evaluating weld strength in the examples. DETAILED DESCRIPTION OF THE INVENTION

[0020] The present invention will be described in detail below.

[0021] In the present invention, a "semi-aromatic polyamide resin" contains a polymerization catalyst compound, which will be described later. In that it contains substances other than the chemical substance "semi-aromatic polyamide," it can also be considered a type of "composition." However, since the amount of the polymerization catalyst compound is very small, it is referred to as a "semi-aromatic polyamide resin" in the present invention. Note that the term "semi-aromatic polyamide resin" may also be used to describe the chemical substance "semi-aromatic polyamide."

[0022] In the present invention, the semi-aromatic polyamide resin contains structural units obtained from hexamethylenediamine and terephthalic acid (hereinafter also referred to as 6T units), and structural units obtained from 11-aminoundecanoic acid or undecane lactam (hereinafter also referred to as 11 units). The ratios of 6T units and 11 units in the semi-aromatic polyamide resin are not particularly limited, but it is desirable that the 6T units be 45 to 85 mol % and the 11 units be 55 to 15 mol %.

[0023] The semi-aromatic polyamide resin preferably contains 50 to 75 mol% of 6T units and 50 to 25 mol% of 11 units, more preferably 60 to 70 mol% of 6T units and 40 to 30 mol% of 11 units, and even more preferably 62 to 68 mol% of 6T units and 38 to 32 mol% of 11 units. Having 50 mol% or more of 6T units tends to improve crystallinity and mechanical properties. Furthermore, having 75 mol% or less of 6T units keeps the melting point of the semi-aromatic polyamide resin below 330°C, preventing excessively high processing temperatures when molding the semi-aromatic polyamide composition by injection molding or the like, and ensuring the desired physical properties and appearance. Furthermore, suppressing an increase in amide bond concentration is also preferred from the viewpoint of water absorption of molded products.

[0024] The semi-aromatic polyamide resin may be copolymerized with copolymerizable components other than the 6T unit and 11 unit. Copolymerizable diamine components include 1,2-ethylenediamine, 1,3-trimethylenediamine, 1,4-tetramethylenediamine, 1,5-pentamethylenediamine, 2-methyl-1,5-pentamethylenediamine, 1,7-heptamethylenediamine, 1,8-octamethylenediamine, 1,9-nonamethylenediamine, 2-methyl-1,8-octamethylenediamine, 1,10-decamethylenediamine, 1,11-undecamethylenediamine, 1,12-dodecamethylenediamine, 1,13-tridecamethylenediamine, and 1,16-hexadecamethylenediamine. Examples of the diamine include aliphatic diamines such as amines, 1,18-octadecamethylenediamine, and 2,2,4 (or 2,4,4)-trimethylhexamethylenediamine; alicyclic diamines such as piperazine, cyclohexanediamine, bis(3-methyl-4-aminohexyl)methane, bis-(4,4'-aminocyclohexyl)methane, and isophoronediamine; aromatic diamines such as meta-xylylenediamine, para-xylylenediamine, para-phenylenediamine, and meta-phenylenediamine; and hydrogenated products thereof. These can be used alone or in combination. Examples of copolymerizable dicarboxylic acid components include aromatic dicarboxylic acids such as isophthalic acid, orthophthalic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 2,2'-diphenyldicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, 5-sodium sulfonate isophthalic acid, and 5-hydroxyisophthalic acid; and aliphatic or alicyclic dicarboxylic acids such as fumaric acid, maleic acid, succinic acid, itaconic acid, adipic acid, azelaic acid, sebacic acid, 1,11-undecanedioic acid, 1,12-dodecanedioic acid, 1,14-tetradecanedioic acid, 1,18-octadecanedioic acid, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 4-methyl-1,2-cyclohexanedicarboxylic acid, and dimer acid. Other examples include lactams such as ε-caprolactam, 12-aminododecanoic acid, and 12-lauryllactam, and aminocarboxylic acids having ring-opened structures of these.

[0025] Generally, the total number of terminals, which is the sum of the amino terminal concentration (AEG), carboxyl terminal concentration (CEG), and terminal concentration blocked with monocarboxylic acid and / or monoamine (EC), of a polyamide resin, correlates with the relative viscosity (RV). As a result of extensive investigations, it has been found that the semi-aromatic polyamide resin of the present invention, which satisfies the above-mentioned formula (1) and the ranges shown in formulas (2), (3), and (4), exhibits excellent heat resistance and heat discoloration resistance, suppresses mold contamination due to outgassing during melt molding, and exhibits excellent melt fluidity, gelation properties, and mechanical properties. In the present invention, EC refers to the terminal concentration of amino terminals blocked with monocarboxylic acid. For ease of explanation, the amino terminal, carboxyl terminal, and terminals blocked with monocarboxylic acid and / or monoamine may be referred to as AEG, CEG, and EC, respectively.

[0026] The (AEG + CEG) of the semi-aromatic polyamide resin of the present invention is 10 to 110 eq / t, preferably 20 to 100 eq / t, and more preferably 30 to 90 eq / t. When (AEG + CEG) is 10 eq / t or more, reactive terminal groups remain, making it possible to increase the viscosity to an RV that ensures the mechanical strength of the molded product. Furthermore, when (AEG + CEG) is 110 eq / t or less, the resin does not increase in viscosity and gel during melt molding.

[0027] The (AEG + CEG) / (AEG + CEG + EC) ratio of the semi-aromatic polyamide resin of the present invention is 0.25 to 0.75, preferably 0.30 to 0.70, and more preferably 0.35 to 0.65. When (AEG + CEG) / (AEG + CEG + EC) is 0.75 or less, thickening and gelation do not occur during melt molding, and heat-induced discoloration reactions can be suppressed. When (AEG + CEG) / (AEG + CEG + EC) is 0.25 or more, an appropriate amount of reactive end groups remain relative to the amount of endblocking, suppressing viscosity reduction during melt molding and resulting in molded articles with satisfactory mechanical properties. When it is important to ensure that molded articles obtained from the semi-aromatic polyamide resin have excellent mechanical properties, it is preferable that (AEG + CEG) / (AEG + CEG + EC) is greater than 0.50.

[0028] The (AEG / CEG) ratio of the semi-aromatic polyamide resin of the present invention is 0.1 to 3.5, preferably 0.3 to 2.5, and more preferably 0.5 to 1.5. Generally, polyamide resins thicken as a result of the reaction between the amino terminal and the carboxyl terminal. However, thickening can also occur when CEG reacts with EC. If the AEG disappears (becomes 0) during the amidation reaction, the terminals of the semi-aromatic polyamide resin become CEG and EC. In the absence of AEG, the acid catalytic effect of CEG causes CEG to attack the amide bond formed by the end-capping agent, resulting in an amidation exchange reaction. During this process, the thickening reaction proceeds while the end-capping agent is distilled out of the reaction system. This results in an increase in outgassing components derived from the end-capping agent. Furthermore, the acid component of CEG can cause a coloration reaction, resulting in a resin with poor color stability. Furthermore, if the (AEG / CEG) ratio exceeds 3.5, the residual amount of AEG is large, making it more susceptible to heat-induced coloring reactions. To avoid this phenomenon, it is important to satisfy equations (2), (3), and (4).

[0029] The AEG, CEG, and EC may be any as long as they satisfy the above-mentioned relationships, with their respective preferred ranges being as follows: AEG is preferably 10 to 80 eq / t, and more preferably 15 to 60 eq / t; CEG is preferably 10 to 80 eq / t, and more preferably 15 to 60 eq / t; EC is preferably 40 to 120 eq / t, more preferably 50 to 110 eq / t, and even more preferably 60 to 100 eq / t.

[0030] The semi-aromatic polyamide resin of the present invention has a relative viscosity (RV) of 2.65 to 3.50, preferably 2.70 to 3.40, and more preferably 2.75 to 3.35. When the RV is 2.65 or more, the mechanical strength of the molded product is satisfactory. When the RV is 3.50 or less, the fluidity during melt molding is high, which is preferable in terms of melt processability.

[0031] The semi-aromatic polyamide resin of the present invention generates 500 ppm or less of gas (outgassing) when pyrolyzed at 330°C for 20 minutes. The outgassing is measured by the method described in the Examples section below. By setting the specific end and RV, a semi-aromatic polyamide resin with low outgassing can be obtained. The outgassing is preferably 450 ppm or less, more preferably 400 ppm or less, and even more preferably 350 ppm or less. The lower limit of outgassing is preferably 0 ppm, but in the semi-aromatic polyamide resin of the present invention, it is approximately 250 ppm.

[0032] When the outgassing of the semi-aromatic polyamide resin of the present invention is within the above range, it becomes possible to suppress mold contamination during melt molding, and long-term production becomes possible.

[0033] The semi-aromatic polyamide resin of the present invention preferably has a sum (P3) of the phosphorus atom contents derived from phosphorus compounds detected in the structures of structural formulae (P1) and (P2) in the semi-aromatic polyamide resin of 30 ppm or more, and preferably P3 is 10% or more of the total phosphorus atom content remaining in the semi-aromatic polyamide resin. The phosphorus atoms are derived from the phosphorus compound used as a catalyst. P3 is more preferably 40 ppm or more, and even more preferably 50 ppm or more. When P3 is 30 ppm or more, peroxides generated by thermo-oxidative degradation can be suppressed, thereby preventing yellowing in a high-temperature atmosphere. Furthermore, the resin can be made to be one in which gelation due to peroxides generated by thermo-oxidative degradation is suppressed. If P3 is less than 10% of the total remaining phosphorus atom weight, this means that the resin has been thermally damaged by the thermal history during polymerization or has reacted with oxygen remaining in the polymerization system, causing oxidative degradation, resulting in a resin that is prone to coloration and gelation. There is no particular upper limit for the ratio of P3 to the total remaining phosphorus atom weight, but in the present invention, it is about 50%. To achieve a P3 of 30 ppm or more and a P3 of 10% or more of the total remaining phosphorus atoms, the oxygen concentration in the storage layer is set to 10 ppm or less, a low-order condensation product is obtained by polymerizing at a low temperature in the polycondensation process, and then the viscosity is adjusted to the specified level by solid-phase polymerization with little thermal history. In order to make P3 30 ppm or more relative to the total amount of remaining phosphorus atoms, the total amount of phosphorus atoms remaining in the semi-aromatic polyamide resin is preferably 200 to 400 ppm.

[0034] [ka]

[0035] [ka]

[0036] (wherein R1 and R2 are hydrogen, an alkyl group, an aryl group, a cycloalkyl group, or an arylalkyl group; X1 to X3 are hydrogen, an alkyl group, an aryl group, a cycloalkyl group, an arylalkyl group, an alkali metal, or an alkaline earth metal; and one of X1 to X3 and one of R1 to R2 in each formula may be bonded to each other to form a ring structure.)

[0037] The phosphorus compound used as the catalyst will be explained later, but when sodium hypophosphite is used as the catalyst, R1 and R2 are hydrogen, and X1 to X3 are each hydrogen or sodium.

[0038] By ensuring that the amount of P3 contained in the semi-aromatic polyamide resin of the present invention is within the above range, the ΔCo-b before and after heat treatment at 260°C for 10 minutes in air can be kept at 10 or less. It is also possible to obtain a semi-aromatic polyamide with a gelation time of 2 hours or more when heat treated at 330°C in a nitrogen stream. ΔCo-b and gelation time are measured using the method described in the Examples section below.

[0039] The method for producing a semi-aromatic polyamide resin of the present invention includes a step of preparing an aqueous raw material solution that constitutes the semi-aromatic polyamide resin, a raw material introduction step of continuously introducing the aqueous raw material solution into a tubular reactor, an amidation step of passing the introduced raw materials through the tubular reactor to perform amidation and obtain a reaction mixture containing an amidated product and condensation water, a step of introducing the reaction mixture into a continuous reactor capable of separating and removing water to perform melt polymerization, and a step of performing solid-state polymerization under vacuum or a nitrogen gas flow.

[0040] (1) Mixing process Predetermined amounts of hexamethylenediamine, terephthalic acid, and 11-aminoundecanoic acid or undecane lactam are each added to a pressure-resistant reactor. At the same time, water is added so that the raw material concentration is 30 to 90% by weight, and a phosphorus compound as a polymerization catalyst and a monocarboxylic acid as an end-blocking agent are also added. Furthermore, if foaming occurs in a subsequent process, a foam inhibitor is added.

[0041] Catalysts used in producing the copolymerized polyamide of the present invention include dimethylphosphinic acid, phenylmethylphosphinic acid, hypophosphorous acid, ethyl hypophosphite, phosphorous acid compounds, and their hydrolysates and condensates. Alternatively, metal salts, ammonium salts, and esters thereof may be used. Specific examples of metal species in metal salts include potassium, sodium, magnesium, vanadium, calcium, zinc, cobalt, manganese, tin, tungsten, germanium, titanium, and antimony. Examples of esters that can be added include ethyl esters, isopropyl esters, butyl esters, hexyl esters, isodecyl esters, octadecyl esters, decyl esters, stearyl esters, and phenyl esters. In the present invention, sodium hypophosphite is preferred as the catalyst. Furthermore, sodium hydroxide is preferably added to improve melt retention stability.

[0042] The timing of adding the end-capping agent is preferably when the raw materials are charged, but it may also be at the start of polymerization, in the latter stage of polymerization, or at the end of polymerization. The end-capping agent is not particularly limited as long as it is a monofunctional compound that is reactive with the amino group or carboxyl group at the polyamide terminal, and examples of the end-capping agent that can be used include monocarboxylic acids or monoamines, acid anhydrides such as phthalic anhydride, monoisocyanates, monoacid halides, monoesters, and monoalcohols. Examples of the end-capping agent include aliphatic monocarboxylic acids such as acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, caprylic acid, lauric acid, tridecanoic acid, myristic acid, palmitic acid, stearic acid, pivalic acid, and isobutyric acid; alicyclic monocarboxylic acids such as cyclohexanecarboxylic acid; aromatic monocarboxylic acids such as benzoic acid, toluic acid, α-naphthalenecarboxylic acid, β-naphthalenecarboxylic acid, methylnaphthalenecarboxylic acid, and phenylacetic acid; acid anhydrides such as maleic anhydride, phthalic anhydride, and hexahydrophthalic anhydride; aliphatic monoamines such as methylamine, ethylamine, propylamine, butylamine, hexylamine, octylamine, decylamine, stearylamine, dimethylamine, diethylamine, dipropylamine, and dibutylamine; alicyclic monoamines such as cyclohexylamine and dicyclohexylamine; and aromatic monoamines such as aniline, toluidine, diphenylamine, and naphthylamine. In the present invention, the end-capping agent is preferably a monocarboxylic acid, and among the above examples, acetic acid and benzoic acid are preferred.

[0043] The salt concentration of the raw material aqueous solution varies depending on the type of polyamide and is not particularly limited, but is generally desirably 30 to 90% by mass. If the salt concentration exceeds 90% by mass, even a slight change in temperature can cause salt to precipitate and clog piping. Furthermore, the need to increase the salt solubility requires equipment with high temperature and high pressure specifications, which is cost-inefficient. On the other hand, if the salt concentration is less than 30% by mass, the amount of water evaporated after the initial polymerization step increases, which is not only energy-intensive but also reduces productivity and increases costs. The preferred salt concentration is 35 to 85% by mass.

[0044] Although this varies depending on the type of polyamide and salt concentration, the salt solution is generally prepared at a temperature of 60 to 180°C and a pressure of 0 to 1 MPa. Temperatures above 180°C or pressures above 1 MPa require equipment with high-temperature and high-pressure specifications, which increases equipment costs and is disadvantageous. Conversely, temperatures below 60°C or pressures below 0 MPa not only cause problems such as clogged piping due to salt precipitation, but also make it difficult to increase the salt concentration, resulting in reduced productivity. The preferred conditions are a temperature of 70 to 170°C and a pressure of 0.05 to 0.8 MPa, more preferably 75 to 165°C and 0.1 to 0.6 MPa.

[0045] Basically, there is no problem with the storage tank for the aqueous salt solution as long as there is no salt precipitation, and the conditions for the salt formation step can be applied as they are.

[0046] The salt solution prepared in this manner is continuously supplied to the amidation process by a supply pump in the raw material introduction process. The supply pump used here must have excellent quantitative performance. Fluctuations in the supply amount will cause process fluctuations in the amidation process, resulting in polyamides with large deviations in relative viscosity (RV) and unstable quality. For this reason, it is recommended to use a plunger pump with excellent quantitative performance as the supply pump.

[0047] The oxygen concentration in the atmosphere during raw material blending significantly affects the color tone of the resulting polyamide. A concentration of 10 ppm or less in the atmosphere during raw material blending is not a problem, but if the oxygen concentration exceeds 10 ppm, the resulting polyamide tends to have a strong yellow tinge, resulting in poor product quality. While there is no specific lower limit for the oxygen concentration, it is, for example, 0.05 ppm or more. In polyamide production, an oxygen concentration of less than 0.05 ppm is not problematic, but achieving a concentration of less than 0.05 ppm simply makes the oxygen removal process unnecessarily complicated, with little effect on color tone or other physical properties. The preferred oxygen concentration range is 0.05 ppm to 9 ppm, and even more preferably 0.05 ppm to 8 ppm.

[0048] In the present invention, it is preferable to supply raw materials to a blending tank (melting tank or raw salt formation tank) from which oxygen has been removed in advance to an oxygen concentration of 10 ppm or less, or to charge the raw materials into the blending tank (melting tank or raw salt formation tank) and then remove oxygen to adjust the atmosphere in the blending tank to an oxygen concentration of 10 ppm or less, or to use both methods. This can be selected from the viewpoint of facilities or operation. It is also preferable to adjust the atmosphere in a storage tank to an oxygen concentration of 10 ppm or less.

[0049] Oxygen can be removed by vacuum substitution, pressure substitution, or a combination of these. The degree of vacuum or pressure applied to substitution and the number of substitutions can be selected based on the most efficient conditions for achieving the desired oxygen concentration.

[0050] (2) Raw material introduction process The aqueous salt solution prepared in the raw material preparation step is continuously introduced into the inlet of the tubular reactor of the amidation step by a feed pump through a pipeline.

[0051] (3) Amidation step In the amidation step, an aqueous salt solution is continuously introduced into the inlet of the tubular reactor and passed through the reactor to carry out amidation, thereby obtaining a reaction mixture containing an amidation product with a low degree of polymerization and water of condensation. Water is not separated and removed in the tubular reactor.

[0052] The tubular reactor preferably has an L / D of 50 or more, where D (mm) is the inner diameter of the tube and L (mm) is the length of the tube. Tubular reactors have the advantages of not requiring liquid level control due to their structure, high plug flow properties, excellent pressure resistance, and low equipment costs. When L / D is less than 50, a small L shortens the residence time of the reaction mixture flow and reduces the degree of increase in relative viscosity (RV). On the other hand, a large D reduces the plug flow properties, resulting in a residence time distribution, preventing the reactor from fulfilling its desired function. While the upper limit of L / D is not particularly specified, it is approximately 3000, taking into consideration the residence time and the degree of increase in relative viscosity (RV). The lower limit of L / D is preferably 60 or more, more preferably 80 or more, and the upper limit is preferably 2000 or less, even more preferably 1000 or less. Furthermore, the lower limit of L is preferably 3 m or more, more preferably 5 m or more, and the upper limit is preferably 50 m or less, more preferably 30 m or less.

[0053] The reaction conditions vary depending on the structure of the polyamide and the desired degree of polymerization, but for example, the internal temperature is 110 to 310°C, the internal pressure is 0 to 5 MPa, and the average residence time of the reaction mixture in the tube is 10 to 120 minutes. The degree of polymerization of the amidation product can be controlled by the internal temperature, internal pressure, and average residence time.

[0054] If the average residence time is shorter than 10 minutes, the degree of polymerization of the low-polymerization amidation product will be low, resulting in the diamine component being more likely to disperse during the polycondensation process, making it difficult to adjust the end groups. On the other hand, if the average residence time is longer than 120 minutes, the amidation will reach equilibrium, the increase in RV will plateau, and thermal degradation will progress, which is undesirable. The preferred average residence time is 12 to 110 minutes, and more preferably 15 to 100 minutes. The average residence time can be controlled by adjusting the inner diameter D and length L of the tube of the tubular reactor or by changing the feed rate of raw materials.

[0055] It is preferable that the polycondensation reaction in the amidation step increases the relative viscosity (RV) of the reaction mixture between the inlet and outlet of the tubular reactor by 0.05 to 0.6. If the increase in RV is less than 0.05, the diamine component is more likely to scatter during the polycondensation step, making it difficult to adjust the end groups. On the other hand, if the increase in RV is greater than 0.6, thermal degradation is more likely to occur due to the influence of coexisting condensation water (in the case of the salt formation method, the water used for salt formation and the condensation water). Furthermore, a reaction mixture with excessively high viscosity can cause pipe clogging, which can adversely affect operation. The desirable range of increase in RV in the amidation step is 0.15 to 0.5, more preferably 0.2 to 0.4.

[0056] (4) Polycondensation process The reaction conditions for the initial polymerization step are an internal pressure of 0 to 5 MPa, an average residence time of 10 to 150 minutes, and an internal temperature determined according to Flory's melting point depression formula based on the residual moisture content in the reactor. Desirable reaction conditions are an internal temperature of 230 to 285°C, an internal pressure of 0.5 to 4.5 MPa, and an average residence time of 15 to 140 minutes. More desirable reaction conditions are an internal temperature of 235 to 280°C, an internal pressure of 1.0 to 4.0 MPa, and an average residence time of 20 to 130 minutes. Reaction conditions outside the lower limits of the above ranges are undesirable, as the degree of polymerization achieved is too low or the resin solidifies inside the reactor. Reaction conditions outside the upper limits of the above ranges can result in decomposition of the P3 component and side reactions, resulting in a P3 concentration of less than 30 ppm, which is detrimental to heat yellowing resistance and gelation properties.

[0057] (5) Solid phase polymerization process In the present invention, solid-state polymerization refers to a process in which a polymerization reaction is carried out under vacuum or in a nitrogen gas flow at any temperature within a range in which the semi-aromatic polyamide resin does not melt. The equipment used for solid-state polymerization is not particularly limited, but examples include a blender or a vacuum dryer. Desirable reaction conditions are an internal temperature of 200 to 260°C and an internal pressure of 0.7 KPa or less, and even more desirable reaction conditions are an internal temperature of 210 to 250°C and an internal pressure of 0.4 KPa or less.

[0058] Although it is possible to melt-polymerize the polyamide prepolymer obtained in the polycondensation process of the present invention in a twin-screw extruder and thicken it to a predetermined RV, the thermal history during melting can cause decomposition of the P3 component and side reactions, which are disadvantageous in terms of heat yellowing resistance and gelation properties.Furthermore, low-molecular-weight substances such as oligomers remain in the semi-aromatic polyamide resin, making it unsuitable from the perspective of outgassing during the subsequent melt-molding process.

[0059] The semi-aromatic polyamide resin of the present invention is particularly preferably used in molding applications and can be made into a molded article. To produce a molded article from the semi-aromatic polyamide resin of the present invention or a composition containing the semi-aromatic polyamide resin of the present invention, a conventional molding method is used. Examples of molding methods include hot melt molding methods such as injection molding, extrusion molding, blow molding, and sinter molding. [Example]

[0060] The present invention will be specifically explained below by showing examples, but the present invention is not limited to these examples.

[0061] (1) Outgassing Three mg of polyamide resin was weighed and measured using a pyrolysis GC / MS (Shimadzu PY-2020iD) under helium at 330°C for 20 minutes. The quantitative values ​​were converted using dimethylsiloxane cyclic tetramer as the standard. Column: Rxi-5ms, injection port pressure: 80 kPa, split ratio: 30, column oven temperature: 40°C (2 min) - 300°C (15 min), 10 min / °C, mass measurement range: m / z 30-550.

[0062] (2)RV 0.25 g of a sample was dissolved in 25 ml of 96% sulfuric acid, and 10 ml of this solution was placed in an Ostwald viscosity tube and measured at 20°C, and the viscosity was calculated using the following formula. RV=t / t0 (where t0 is the number of seconds the solvent falls, and t is the number of seconds the sample solution falls)

[0063] (3)AEG, CEG, EC, composition 20 mg of semi-aromatic polyamide resin was dissolved in 0.6 ml of a mixed solvent of deuterated chloroform (CDCl3) / hexafluoroisopropanol (HFIP) = 1 / 1 (vol ratio), and diformic acid was added dropwise. Then, the resulting solution was analyzed using a 500 MHz Fourier transform nuclear magnetic resonance spectrometer (AVANCE500 manufactured by BRUKER). 1 H-NMR analysis was performed and the ratio was determined from the integral ratio.

[0064] (4) Melting point Five mg of the sample was placed in an aluminum sample pan and sealed. Measurements were performed using a differential scanning calorimeter (DSC) DSC-Q100 (TA Instruments Japan) at a heating rate of 20°C / min up to 350°C, and the maximum peak temperature of the heat of fusion was determined as the crystalline melting point.

[0065] (5) Quantitation of P compounds The sample was dissolved using the yttrium nitrate method and analyzed using an ICP (SPECTROBLUE, Hitachi High-Tech Science). 0.1 g of sample was weighed into a platinum crucible, and 5 mL of a 5% yttrium nitrate ethanol solution was added to perform a nitrate ashing process. 20 mL of 1.2 N hydrochloric acid was added to the ashing residue, and the solution was left to soak overnight. After confirming complete dissolution, the solution was placed in an ICP optical emission analyzer to measure the phosphorus emission intensity at a wavelength of 214 nm. The phosphorus concentration in the solution was quantified and converted to the phosphorus content in the sample.

[0066] (6) Structural analysis of P compounds 340-350 mg of sample was dissolved in 2.5 ml of a mixed solvent of deuterated chloroform (CDCl3) / hexafluoroisopropanol (HFIP) = 1 / 1 (vol ratio) at room temperature, and tri(t-butylphenyl) phosphoric acid (hereinafter abbreviated as TBPPA) was added as P to the polyamide resin at 100 ppm. 0.1 ml of trifluoroacetic acid was then added at room temperature, and after 30 minutes, the sample was analyzed using a Fourier transform nuclear magnetic resonance spectrometer (BRUKER AVANCE500). 31 P-NMR analysis was performed. 31The analysis was performed under the following conditions: P resonance frequency 202.5 MHz, detection pulse flip angle 45°, data acquisition time 1.5 seconds, delay time 1.0 seconds, number of integrations 1,000 to 20,000, measurement temperature room temperature, and complete proton decoupling. The molar ratio of the phosphorus compound represented by structural formula (P1) to the phosphorus compound represented by structural formula (P2) was calculated from the integral ratio.

[0067] (7) Calculation of P3 The amount of P compound determined by ICP above and 31 The amounts of P1 and P2 were calculated from the molar ratios of P1 and P2 determined by P-NMR, and the sum was taken as P3.

[0068] (8)ΔCo-b 10 g of polyamide resin was frozen using liquid nitrogen and then crushed at 15,000 rpm for 3 minutes in a crusher (Osaka Chemical Co., Ltd., ABLOLUTE 3) to obtain a powder. The Co-b of the crushed polyamide resin was measured using a color meter (Nippon Denshoku Co., Ltd., ZE 2000). The polyamide resin was thinly spread on a petri dish and placed in a Geer oven (TABAI Co., Ltd., GEER OVEN GHPS-222) heated to 260°C. The Co-b value of the resin was measured after 10 minutes of heat treatment in air, and the difference before and after heat treatment was defined as ΔCo-b.

[0069] (9) Gel time 3 g of polyamide resin was placed in an ampoule and heat-treated for a specified period of time in an inert oven (Tamato DN4101) heated to 330°C under a nitrogen gas flow of 10 L / min. 0.25 g of the heat-treated resin was dissolved in 25 ml of 96% sulfuric acid, and the time required for insoluble matter to appear was defined as the gelation time.

[0070] (10) Weld strength Using a Japan Steel Works J130-ADS injection molding machine, the cylinder temperature was set to the resin's melting point + 20°C, and the mold temperature was set to 140°C. The evaluation test specimens shown in Figure 1 were produced by injection molding. Figure 1 (A) is a top view of the test specimen, and (B) is a side view. The bending strength of the weld formed in the center of the test specimen was evaluated in accordance with ISO 178. The obtained weld strength was evaluated according to the following criteria. ◎:More than 120MPa ○: More than 100MPa and less than 120MPa ×: 100 MPa or less

[0071] Comparative Example 1' 8.66 kg (74.5 mol) of 1,6-hexamethylenediamine, 12.24 kg (73.7 mol) of terephthalic acid, 7.99 kg (39.7 mol) of 11-aminoundecanoic acid, 30.4 g of sodium hypophosphite as a catalyst, 95.8 g (1.6 mol) of acetic acid as an end-blocking agent, and 16.20 kg of ion-exchanged water adjusted to 0.5 ppm or less by nitrogen bubbling were charged into a 50-liter autoclave, pressurized from atmospheric pressure to 0.05 MPa with N2, released, and returned to atmospheric pressure. This operation was repeated 10 times, and after N2 replacement, the mixture was uniformly dissolved at 135 ° C and 0.3 MPa under stirring. The solution was then continuously supplied by a liquid pump, heated to 260 ° C in a heating pipe, and heated for 0.5 hours. The reaction mixture was then fed into a pressure reactor and heated to 270°C. Part of the water was distilled off so as to maintain the internal pressure of the reactor at 3 MPa, yielding a low-order condensate. The low-order condensate was then taken out into a container in the atmosphere at room temperature and normal pressure, and dried at 70°C and a vacuum of 0.07 KPa or less using a vacuum dryer. After drying, the low-order condensate was mixed in a blender (capacity 0.1 m) and the resulting mixture was mixed with water. 3 ) was reacted for 10 hours in an environment of 200°C and a vacuum of 0.07 KPa to obtain a semi-aromatic polyamide resin. The properties of the obtained semi-aromatic polyamide resin are shown in Table 1.

[0072] Comparative Example 2' Comparative Example 1' The same procedure was repeated up to vacuum drying to obtain a low-order condensation product.3 ) was reacted for 10 hours in an environment of 210°C and a vacuum of 0.07 KPa to obtain a semi-aromatic polyamide resin.

[0073] Example 3 The amount of 1,6-hexamethylenediamine was changed to 8.94 kg (76.9 mol), and the amount of acetic acid used as the end-capping agent was changed to 159.4 g (2.7 mol). Comparative Example 1' The same procedure was repeated up to vacuum drying to obtain a low-order condensation product. 3 ) was reacted for 6 hours at 225°C under a vacuum of 0.07 KPa to obtain a semi-aromatic polyamide resin.

[0074] Example 4 The mixture was changed to 1,6-hexamethylenediamine 7.20 kg (62.0 mol), terephthalic acid 9.89 kg (59.5 mol), 11-aminoundecanoic acid 11.99 kg (59.6 mol), and acetic acid as a terminal blocking agent 150.4 g (2.5 mol). Comparative Example 1' The same procedure was repeated up to vacuum drying to obtain a low-order condensation product. 3 ) was reacted for 12 hours at 235°C under a vacuum of 0.07 KPa to obtain a semi-aromatic polyamide resin.

[0075] Example 5 The mixture was changed to 10.38 kg (89.3 mol) of 1,6-hexamethylenediamine, 14.38 kg (86.6 mol) of terephthalic acid, 4.36 kg (21.7 mol) of 11-aminoundecanoic acid, and 118.9 g (2.0 mol) of acetic acid as a terminal blocking agent. Comparative Example 1' The same procedure was repeated up to vacuum drying to obtain a low-order condensation product. 3 ) was reacted for 11 hours at 235°C under a vacuum of 0.07 KPa to obtain a semi-aromatic polyamide resin.

[0076] Example 6 The amount of 1,6-hexamethylenediamine was changed to 8.91 kg (76.7 mol), and the amount of benzoic acid used as the end-blocking agent was changed to 344.7 g (2.8 mol). Comparative Example 1' The same procedure was repeated up to vacuum drying to obtain a low-order condensation product.3 ) was reacted for 8 hours at 230°C under a vacuum of 0.07 KPa to obtain a semi-aromatic polyamide resin.

[0077] Example 7 The amount of 1,6-hexamethylenediamine was changed to 8.75 kg (75.3 mol), and the amount of acetic acid used as the end-capping agent was changed to 73.8 g (1.2 mol). Comparative Example 1' The same procedure was repeated up to vacuum drying to obtain a low-order condensation product. 3 ) was reacted for 12 hours at 210°C under a vacuum of 0.07 KPa to obtain a semi-aromatic polyamide resin.

[0078] Example 8 The amount of 1,6-hexamethylenediamine was changed to 8.84 kg (76.1 mol), and the amount of acetic acid used as the end-capping agent was changed to 127.6 g (2.1 mol). Comparative Example 1' The same procedure was repeated up to vacuum drying to obtain a low-order condensation product. 3 ) was reacted for 10 hours in an environment of 210°C and a vacuum of 0.07 KPa to obtain a semi-aromatic polyamide resin.

[0079] Comparative Example 1 The amount of 1,6-hexamethylenediamine was changed to 8.98 kg (77.3 mol), and the amount of acetic acid used as the end-capping agent was changed to 217.3 g (3.6 mol). Comparative Example 1' The same procedure was repeated up to vacuum drying to obtain a low-order condensation product. 3 ) was reacted for 8 hours at 235°C under a vacuum of 0.07 KPa to obtain a semi-aromatic polyamide resin.

[0080] Comparative Example 2 The amount of 1,6-hexamethylenediamine was changed to 9.04 kg (77.8 mol), and the amount of acetic acid used as the end-capping agent was changed to 233.2 g (3.9 mol). Comparative Example 1' The same procedure was repeated up to vacuum drying to obtain a low-order condensation product. 3 ) was reacted for 8 hours at 240°C under a vacuum of 0.07 KPa to obtain a semi-aromatic polyamide resin.

[0081] Comparative Example 3 The amount of 1,6-hexamethylenediamine was changed to 8.78 kg (75.6 mol), and the amount of acetic acid used as the end-capping agent was changed to 75.7 g (1.3 mol). Comparative Example 1' The same procedure was repeated up to vacuum drying to obtain a low-order condensation product. 3 ) was reacted for 5 hours at 200°C under a vacuum of 0.07 KPa to obtain a semi-aromatic polyamide resin.

[0082] Comparative Example 4 The amount of 1,6-hexamethylenediamine was changed to 8.65 kg (74.4 mol), and the amount of acetic acid used as the end-capping agent was changed to 145.4 g (2.4 mol). Comparative Example 1' The same procedure was repeated up to vacuum drying to obtain a low-order condensation product. 3 ) was reacted for 6 hours at 235°C under a vacuum of 0.07 KPa to obtain a semi-aromatic polyamide resin.

[0083] Comparative Example 5 The amount of 1,6-hexamethylenediamine was changed to 9.04 kg (77.8 mol), and the amount of acetic acid used as the end-capping agent was changed to 123.5 g (2.1 mol). Comparative Example 1' The same procedure was repeated up to vacuum drying to obtain a low-order condensation product. 3 ) was reacted for 6 hours at 235°C under a vacuum of 0.07 KPa to obtain a semi-aromatic polyamide resin.

[0084] Comparative Example 6 The amount of 1,6-hexamethylenediamine was changed to 8.77 kg (75.5 mol), and the amount of acetic acid used as the end-capping agent was changed to 81.7 g (1.4 mol). Comparative Example 1' The same procedure was repeated up to vacuum drying to obtain a low-order condensation product. 3 ) was reacted for 18 hours in an environment of 210°C and a vacuum of 0.07 KPa to obtain a semi-aromatic polyamide resin.

[0085] Comparative Example 7 The amount of 1,6-hexamethylenediamine was changed to 9.10 kg (78.3 mol), and the amount of acetic acid used as the end-capping agent was changed to 279.2 g (4.6 mol). Comparative Example 1'The same procedure was repeated up to vacuum drying to obtain a low-order condensation product. 3 ) was reacted for 8 hours at 240°C under a vacuum of 0.07 KPa to obtain a semi-aromatic polyamide resin.

[0086] Comparative Example 8 The amount of 1,6-hexamethylenediamine was changed to 8.50 kg (73.1 mol), and the amount of acetic acid used as the end-capping agent was changed to 45.8 g (0.7 mol). Comparative Example 1' The same procedure was repeated up to vacuum drying to obtain a low-order condensation product. 3 ) was reacted for 10 hours at 200°C under a vacuum of 0.07 KPa to obtain a semi-aromatic polyamide resin. Table 1 shows the details of the properties of the semi-aromatic polyamide resins obtained in each example and each comparative example.

[0087] [Table 1]

[0088] In the table, AcOH represents acetic acid and BA represents benzoic acid.

[0089] Comparative Examples 1' and 2' Example 3 It can be seen that ~8 is satisfactory in all characteristics. However, Comparative Examples 1' and 2' were more colored than Examples 3-8. In Comparative Example 1, RV<2.65, indicating that the weld strength was low. In Comparative Example 2, (AEG+CEG) / (AEG+CEG+EC)<0.25, the proportion of end-blocked resin was high, which resulted in a decrease in viscosity during molding and reduced weld strength. In Comparative Example 3, (AEG+CEG)>110 eq / t, the amount of endblocking was small, the amount of remaining AEG and CEG was large, the heat yellowing resistance was poor, and gelation was likely to occur. In Comparative Example 4, since the AEG was 0 eq / t, the outgassing components derived from the end blocking increased, and the coloring reaction of the acid components occurred at the same time, resulting in a resin with poor heat yellowing resistance. In Comparative Example 5, since AEG / CEG>3.5, the amount of remaining AEG was large, and it was found that the resin was poor in heat yellowing resistance. It is clear that Comparative Example 6 has a RV>3.50, and therefore has poor fluidity during molding and is a resin that is prone to gelation. In Comparative Example 7, AEG+CEG<10eq / t, so (AEG+CEG) / (AEG+CEG+EC)<0.25eq / t, and the proportion of end-blocking is high, which means that viscosity decreases during molding and the weld strength is low. In Comparative Example 8, since (AEG+CEG) / (AEG+CEG+EC)>0.75, it is evident that the resin is prone to gelation and has poor heat yellowing resistance. [Industrial Applicability]

[0090] This provides a semi-aromatic polyamide resin that has excellent heat resistance and heat discoloration resistance, and furthermore, can suppress mold contamination due to outgassing during melt molding. It also has excellent melt fluidity, gelling properties, and mechanical properties, making it suitable for resin compositions used in molded products such as automobile parts, bicycle parts, and electrical and electronic parts. This is expected to make a significant contribution to industry.

Claims

1. A semi-aromatic polyamide resin containing a structural unit obtained from hexamethylenediamine and terephthalic acid, and a structural unit obtained from 11-aminoundecanoic acid or undecane lactam, having a relative viscosity (RV) in the range of formula (1), and in which the relationship between the amino terminal concentration (AEG), the carboxy terminal concentration (CEG), and the terminal concentration of blocked amino groups with monocarboxylic acid (EC) satisfies formulas (2) to (4). 2.65≦RV≦3.50 (1) 10eq / t≦AEG+CEG≦110eq / t... (2) 0.25≦(AEG+CEG) / (AEG+CEG+EC)≦0.65... (3) 0.3≦AEG / CEG≦2.5 (4)

2. 2. The semi-aromatic polyamide resin according to claim 1, wherein the structural units obtained from hexamethylenediamine and terephthalic acid are 50 to 75 mol % and the structural units obtained from 11-aminoundecanoic acid or undecane lactam are 50 to 25 mol %, and the melting point is 270 to 330°C.

3. A semi-aromatic polyamide resin according to claim 1 or 2, wherein the sum (P3) of the phosphorus atom contents derived from phosphorus compounds detected in the semi-aromatic polyamide resin with structures of structural formulas (P1) and (P2) is 30 ppm or more, and P3 is 10% or more of the total amount of phosphorus atoms remaining in the semi-aromatic polyamide resin. [Chemical formula 1] [Case 2] (However, R １ , R ２ is hydrogen, an alkyl group, an aryl group, a cycloalkyl group, or an arylalkyl group; X １ ~X ３ represents hydrogen, an alkyl group, an aryl group, a cycloalkyl group, an arylalkyl group, an alkali metal, or an alkaline earth metal; １ ~X ３ and R １ ~R ２ may be linked to each other to form a ring structure.

4. 4. The semi-aromatic polyamide resin according to claim 1, wherein the amount of gas generated (outgassing) when the semi-aromatic polyamide resin is pyrolyzed at 330° C. for 20 minutes is 500 ppm or less.

5. A step of preparing a raw material aqueous solution constituting a semi-aromatic polyamide resin; a raw material introduction step of continuously introducing a raw material aqueous solution into a tubular reactor; an amidation step in which the introduced raw material is passed through a tubular reactor to perform amidation, thereby obtaining a reaction mixture containing an amidated product and condensed water; a step of introducing the reaction mixture into a continuous reactor capable of separating and removing water to carry out melt polymerization; A method for producing the semi-aromatic polyamide resin according to any one of claims 1 to 4, comprising a step of carrying out solid-state polymerization under vacuum or nitrogen gas flow.

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