JP5639326B2 - Method for producing polyamide - Google Patents

Description

The present invention relates to a novel method for producing a polyamide. Specifically, the present invention relates to a method for producing a polyamide which is excellent in performance such as mechanical performance, heat resistance and chemical resistance and is suitable as an engineering plastic.

  Conventionally, crystalline polyamides represented by nylon 6, nylon 66 and the like have been widely used as clothing, industrial material fibers, or general-purpose engineering plastics because of their excellent characteristics and ease of melt molding. On the other hand, problems such as insufficient heat resistance and poor dimensional stability due to water absorption have been pointed out. In particular, in the electrical and electronic fields that require heat resistance due to reflow soldering accompanying the recent development of surface mount technology (SMT), or in the engine room parts of automobiles where the demand for heat resistance is increasing year by year, It has become difficult to use, and there is an increasing demand for polyamides that are more excellent in heat resistance, dimensional stability, mechanical properties, and physicochemical properties.

  Various semi-aromatic polyamides based on terephthalic acid and 1,6-hexanediamine have been proposed and some of them have been put into practical use in response to such demands in the world. However, a polyamide composed of terephthalic acid and 1,6-hexanediamine (hereinafter abbreviated as PA6T) has a melting point near 370 ° C., which exceeds the decomposition temperature of the polymer. It is not a thing. Therefore, in practice, by copolymerizing a dicarboxylic component such as adipic acid and isophthalic acid, or an aliphatic polyamide such as nylon 6 in an amount of 30 to 40 mol%, the temperature can be lowered to an actual use temperature range, that is, about 280 to 320 ° C. It is currently used in a composition having a melting point.

  As described above, normally, a high heat-resistant semi-aromatic polyamide is used in a composition whose decomposition temperature and melting point are close to each other. Therefore, conventional polymerization methods such as batch melt polymerization do not involve polymer decomposition. It was difficult to increase the molecular weight by polymerization. Therefore, many methods have been proposed as a method for polymerizing semi-aromatic polyamides. Among them, the solid phase polymerization method can be carried out at a temperature several tens of degrees C lower than the melting point of polyamide throughout, so that there are many research examples as an effective method capable of suppressing the deterioration of the resin during the polymerization.

For example, JP-A-62-252727 discloses equimolar salts of 1,6-hexanediamine and terephthalic acid, and equimolar salts of 1,12-dodecanediamine and terephthalic acid, respectively, under reduced pressure or in a nitrogen stream. It is disclosed that polyamides can be obtained by phase polymerization. In addition, Polymer Chemistry, Vol. 29, no. In 323, 159-163 (1972), as a method for producing PA6T, first, an oligomer is synthesized from a nylon salt, and then solid-state polymerization is performed under a nitrogen stream or under reduced pressure to increase the molecular weight. It has been reported that the polycondensation reaction proceeds without this. JP-A-60-163928 discloses that the same method can be applied to the case where 15 to 40 mol% of the third component is copolymerized with respect to PA6T. In JP-A-61-228022, as a method for producing a semi-aromatic polyamide, a low-order condensate formed from an aromatic dicarboxylic acid component unit and an alkylenediamine component unit is subjected to a polycondensation reaction under melt shear conditions. A method of increasing the degree of polymerization by solid phase polymerization after performing a low-order condensate is disclosed.
JP-A-2-251532 discloses that a polyamide having a low degree of gel and a high degree of polymerization is obtained by performing solid-phase polymerization using a low-order condensate of PA6T as a raw material in the presence of a metal salt of hypophosphorous acid. Is disclosed.
JP 62-20527 A JP-A-60-163928 JP-A-61-228022 JP-A-2-251532 Polymer chemistry, Vol. 29, no. 323, 159-163 (1972)

  According to the study by the present inventors, even when a polyamide is polymerized by using a solid-phase polymerization method of a conventionally known semi-aromatic polyamide as described above, for example, the intrinsic viscosity measured at 30 ° C. in concentrated sulfuric acid [η When a polyamide having a high degree of polymerization having an intrinsic viscosity [η] of 1.0 dl / g or more is produced by solid-phase polymerization from a low-order condensate having a viscosity of 0.2 dl / g or less, a gel is added to the obtained polyamide. It was found that the mechanical performance and heat resistance of the product using this were inferior. Further, it has been found that the formation of this gel is partly due to the formation of a crosslinked structure starting from triamine produced as a by-product by polycondensation of diamine components. Controlling the amount of triamine in the polyamide is a problem of gel suppression.

  As a result of intensive studies to solve the above problems, the present inventors have obtained a case where semi-aromatic polyamide is polymerized by solid phase polymerization using a salt or a low-order condensate as a polymer precursor. In view of the fact that a polyamide is contained in the polyamide, the present inventors have found that the gel can be suppressed by classifying or pulverizing a salt or a low-order condensate and solid-phase polymerization, thereby completing the present invention.

  That is, the present invention relates to a method for producing a polyamide in which a salt formed from a dicarboxylic acid component and a salt formed from a diamine component or a low-order condensate thereof is heated and polycondensed in a solid phase, and the particle size is 2 mm or less. The present invention provides a method for producing a polyamide, characterized by solid-phase polymerization of a salt of a dicarboxylic acid component and a diamine component, or a low-order condensate thereof.

  According to the method for producing a polyamide of the present invention, a polyamide gel obtained by a solid phase polymerization method is suppressed, and a polyamide that is excellent in performance such as mechanical performance, heat resistance, and chemical resistance and suitable as an engineering plastic is obtained. Can do.

Hereinafter, the present invention will be described in detail.
In the present invention, the polymer precursor before solid-phase polymerization is composed of a carboxylic acid component mainly composed of terephthalic acid and a diamine component mainly composed of an aliphatic diamine having 6 to 18 carbon atoms. Subcondensate. The salt is synthesized by a conventionally known method in a solvent such as water or alcohol, and the solvent is removed as it is, or it is isolated by a method such as filtering by cooling the precipitated salt, and then dried. use. The low-order condensate is prepared by heating the raw material dicarboxylic acid and diamine or the above salt to 150 to 350 ° C. in a water solvent and reacting them while gradually distilling off water, and then drying or autoclave. The container is sealed in such a pressure-resistant container, reacted at the above temperature and pressure of 1 to 5 MPa, and then dried.

  The polymer precursor before the solid phase polymerization is preferably a low-order condensate from the viewpoint of the solid phase polymerization rate. The intrinsic viscosity [η] of the low-order condensate is preferably 0.05 dl / g or more, and the residual monomer content of the low-order condensate is preferably 5% or less.

  The dicarboxylic acid component used in the method for producing the polyamide of the present invention is selected from aromatic dicarboxylic acids and / or aliphatic dicarboxylic acids. The proportion thereof is 30 to 100 mol% of terephthalic acid component, 0 to 70 mol% of aromatic dicarboxylic acid component other than terephthalic acid and / or 0 to 70 mol% of aliphatic dicarboxylic acid component having 4 to 20 carbon atoms. . The terephthalic acid component is preferably 45 mol% or more, more preferably 50 mol% or more. When the terephthalic acid component is less than 30 mol%, the heat resistance and chemical resistance of the resulting polyamide are lowered, which is not preferable. Other dicarboxylic acid components other than the terephthalic acid component include malonic acid, dimethylmalonic acid, succinic acid, glutaric acid, adipic acid, 2-methyladipic acid, trimethyladipic acid, pimelic acid, 2,2-dimethylglutaric acid, Aliphatic carboxylic acids such as 3,3-diethylsuccinic acid, azelaic acid, sebacic acid and suberic acid; alicyclic dicarboxylic acids such as 1,3-cyclopentanedicarboxylic acid and 1,4-cyclohexanedicarboxylic acid; isophthalic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,4-phenylenedioxydiacetic acid, 1,3-phenylenedioxydiacetic acid, diphenic acid, dibenzoic acid 4,4′-oxydibenzoic acid, diphenylmethane-4,4′-dicarboxylic acid, diphenylsulfate Down-4,4'-dicarboxylic acid, aromatic dicarboxylic acids such as 4,4'-biphenyl dicarboxylic acid, or can be given any mixture thereof. Of these, aliphatic carboxylic acids such as adipic acid and aromatic dicarboxylic acids such as isophthalic acid are preferably used. Furthermore, polyvalent carboxylic acids such as trimellitic acid can be used within a range where melt molding is possible.

  The didiamine component used in the method for producing a polyamide of the present invention is selected from diamines having 4 to 25 carbon atoms having a straight chain and / or a side chain. Examples of the aliphatic diamine component having 4 to 25 carbon atoms include 1,6-hexanediamine, 1,7-heptanediamine, 1,8-octanediamine, 1,9-nonanediamine, 1,11-undecanediamine, , 10-decanediamine, linear aliphatic diamine such as 1,12-dodecanediamine, 3-methyl-1,5-pentanediamine, 2,2,4-trimethyl-1,6-hexanediamine, 2,4, Branched chain aliphatic diamine such as 4, -trimethyl-1,6-hexanediamine, 2-methyl-1,8-octanediamine, 5-methyl-1,9-nonanediamine; cyclohexanediamine, methylcyclohexanediamine, Cycloaliphatic diamines such as isophorone diamine and bis (4-aminocyclohexyl) methane, or any of these Mixture can be mentioned. Of these, 1,6-hexanediamine, 1,7-heptanediamine, 1,8-octanediamine, 1,9-nonanediamine, 1,10-decanediamine, , 11-undecanediamine, 1,12-dodecanediamine, 2-methyl-1,8-octanediamine, and 5-methyl-1,9-nonanediamine are preferred. In particular, 1,6-hexanediamine is preferable because a polyamide that is remarkably excellent in any of mechanical properties, heat resistance, chemical resistance, and moldability can be obtained.

  A diamine component other than the aliphatic diamine component having 4 to 25 carbon atoms may be used as a minor component, for example, p-phenylenediamine, m-phenylenediamine, xylenediamine, 4,4′-diaminodiphenylmethane, 4,4 ′. -Aromatic diamines such as diaminodiphenyl ether, or any mixture thereof.

  Phosphorus catalyst such as phosphoric acid, phosphorous acid, hypophosphorous acid, or a salt or ester thereof, for increasing the polycondensation rate and preventing deterioration during polymerization when synthesizing the low-order condensate or salt Is preferably added. Of these, hypophosphorous acid derivatives are preferred from the quality of the polymer produced, and sodium hypophosphite is particularly preferred from the viewpoint of cost and ease of handling. The addition amount of these catalysts is preferably 0.01 to 5% by weight, more preferably 0.05 to 2% by weight, particularly preferably 0.07 to 1% by weight, based on the weight of the total raw material. is there. When the addition amount is less than 0.01% by weight, the polymerization rate is almost the same as when these catalysts are not added, and the quality of the obtained polymer such as coloring and deterioration is not sufficient. On the other hand, when the addition amount is more than 5% by weight, the polymerization rate is decreased, and only a polymer with deterioration such as coloring and gelation can be obtained.

  Furthermore, when synthesizing the low-order condensate, it is preferable to add a terminal blocking agent in order to adjust the molecular weight and improve the melt stability. The end capping agent is not particularly limited as long as it is a monofunctional compound having reactivity with the amino group or carboxyl group at the end of the polyamide, but from the viewpoint of reactivity and stability of the capping end, monocarboxylic acid is used. An acid or a monoamine is preferable, and a monocarboxylic acid is more preferable from the viewpoint of easy handling. In addition, acid anhydrides such as phthalic anhydride, monoisocyanates, monoacid halides, monoesters, monoalcohols, and the like can also be used.

  The monocarboxylic acid that can be used as the end-capping agent is not particularly limited as long as it has reactivity with an amino group. For example, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, caprylic acid, lauryl Aliphatic monocarboxylic acids such as acids, tridecylic acid, myristic acid, palmitic acid, stearic acid, pivalic acid and isobutyric acid; cycloaliphatic monocarboxylic acids such as cyclohexanecarboxylic acid; benzoic acid, toluic acid, α-naphthalenecarboxylic acid , Β-naphthalenecarboxylic acid, methylnaphthalenecarboxylic acid, aromatic monocarboxylic acid such as phenylacetic acid, or any mixture thereof. Of these, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, caprylic acid, lauric acid, tridecylic acid, myristic acid, palmitic acid, stearic acid from the viewpoint of reactivity, stability of the sealing end, price, etc. Benzoic acid is particularly preferred.

  When a monocarboxylic acid is used as the terminal blocking agent, the amino group terminal of the polyamide is blocked with these monocarboxylic acid to form a blocked terminal represented by the following general formula (I).

(In the formula, R is a residue obtained by removing a carboxyl group from the above monocarboxylic acid, preferably an alkyl group, a cycloalkyl group, an aryl group, or an aralkyl group.)

  The monoamine used as the end-capping agent is not particularly limited as long as it has reactivity with a carboxyl group. For example, methylamine, ethylamine, propylamine, butylamine, hexylamine, octylamine, decylamine, stearyl Aliphatic monoamines such as amine, dimethylamine, diethylamine, dipropylamine, dibutylamine; cycloaliphatic monoamines such as cyclohexylamine, dicyclohexylamine; aromatic monoamines such as aniline, toluidine, digenylamine, naphthylamine, or any of these Can be mentioned. Of these, butylamine, hexylamine, octylamine, decylamine, stearylamine, cyclohexylamine, and aniline are particularly preferred from the standpoints of reactivity, boiling point, stability of the sealing end and price.

  When a monoamine is used as the terminal blocking agent, the carboxyl group terminal of the polyamide is blocked with these monoamines to form a blocked terminal represented by the following general formula (II).

(In the formula, R ¹ is a residue obtained by removing an amino group from the above monoamine, preferably an alkyl group, a cycloalkyl group, an aryl group, or an aralkyl group. R ² represents a hydrogen atom or an amino group from the above monoamine. The residue is preferably a hydrogen atom, an alkyl group, a cycloalkyl group, an aryl group or an aralkyl group.)

  In the method of the present invention, the amount of the end-capping agent that can be used when producing the polyamide varies depending on the reactivity, boiling point, reaction apparatus, reaction conditions, etc. of the end-capping agent used. It is used in the range of 0.1 to 15 mol% with respect to the total number of moles of acid and diamine.

  The salt or low-order condensate used in the solid phase polymerization preferably has a particle size of 2 mm or less. When solid phase polymerization is performed using a salt having a particle diameter of 2 mm or higher, and a low-order condensate, triamine is produced as a by-product due to the condensation of diamine components. This is not preferable. The lower limit of the particle size is not particularly limited, but is desirably 1 μm or more in terms of handling. Moreover, there is no restriction | limiting in particular as a method of controlling the salt or low-order condensate used for solid-phase polymerization to a particle size of 2 mm or less by the method of this invention, A well-known classifier and a grinder can be used.

  According to the method for producing a polyamide of the present invention, the salt and the low-order condensate obtained by the above method are heated and polycondensed in a solid phase under an inert gas stream to obtain a polyamide. Nitrogen, helium, argon, etc. can be used as the inert gas. In addition, the inert gas can be dried, deoxygenated, heated, etc. before being sent into the reaction system. The solid phase polymerization in the production method of the present invention is not particularly limited in pressure and temperature, but the pressure is preferably normal pressure or reduced pressure from the viewpoint of reactivity. Further, the solid phase polymerization in the production method of the present invention can be applied to both continuous and batch reactors.

  In the method for producing the polyamide of the present invention, additives other than those described above, such as conventionally known colorants, ultraviolet absorbers, light stabilizers, antioxidants, antistatic agents, flame retardants, crystallization accelerators, plasticizers, Other additives such as lubricants can be added at any stage during the polycondensation reaction.

  The polyamide obtained by the production method of the present invention can also be used in the form of a reinforcing system containing glass fibers, carbon fibers, inorganic powder fillers, organic powder fillers, and alloys with various polymers. Injection molding, blow molding, extrusion molding, compression molding, stretching, vacuum molding, and other molding methods can be applied. Furthermore, it can be molded not only in a normal molded body as an engineering plastic but also in the form of a film or fiber, and can be suitably used for industrial materials, industrial materials, household goods and the like.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. The intrinsic viscosity and triamine analysis in the examples were measured by the following methods.
Intrinsic viscosity [η]: Analysis was performed in concentrated sulfuric acid at 30 ° C. by a conventional method.
Confirmation of gel: Using a solution for limiting viscosity analysis, the presence or absence of jelly-like insoluble matter was visually confirmed.
Triamine: GC analysis was performed under the following conditions.

  The polyamide sample is hydrolyzed with an aqueous hydrochloric acid solution, the resulting treatment solution is filtered, and the filtrate is made up to a volume of 100 ml. Collect 5 ml of the solution and add concentrated sodium hydroxide solution (about 1 g / 20 ml) to make it alkaline. Check that it is alkaline with pH test paper and leave it for 4 hours. After standing, dry using an evaporator, add 5 ml of toluene, and apply ultrasonic waves for 10 minutes to make a GC measurement solution. HMTA standard solution is used for quantification.

<GC conditions>
Equipment: HP6890 manufactured by Agilent
Column: HP-1 0.32mm × 30m
Column flow rate: 1.8 ml / min Oven temperature: 40 ° C-15 ° C / min-320 ° C
Injection volume: 1μl

[Example 1]
1827 g (11.0 mol) of terephthalic acid, 2343 g (20.2 mol) of 1,6-hexanediamine, 1315 g (9.0 mol) of adipic acid, 30.5 g (0.25 mol) of benzoic acid, hypophosphorous acid Sodium monohydrate (4.7 g) (0.08% by weight with respect to the raw material) and distilled water (445 g) were placed in an autoclave having an internal volume of 13.6 L and purged with nitrogen. Stirring was started from 190 ° C, and the internal temperature was raised to 250 ° C over 4 hours. At this time, the autoclave was pressurized to 3.1 MPa. The reaction was continued for 1 hour as it was, and then the low-order condensate was extracted from the spray nozzle installed at the bottom of the autoclave. Then, after cooling to room temperature, it grind | pulverized to the particle size of 1.5 mm or less with the grinder, and it dried at 110 degreeC for 24 hours. The obtained low-order condensate had a water content of 4520 ppm and an intrinsic viscosity [η] of 0.15 dl / g. Next, this low-order condensate was put into a shelf type solid phase polymerization apparatus, and after nitrogen substitution, the temperature was raised to 220 ° C. over about 2 hours. Then, it reacted for 4 hours and cooled to room temperature. The obtained polyamide had an intrinsic viscosity [η] of 1.1 dl / g and bishexamethylene triamine was 0.24% by weight. In addition, formation of insoluble matter (gel) in the concentrated sulfuric acid was not observed when measuring the intrinsic viscosity [η].

[ Reference example]
1,423 g (8.6 mol) of terephthalic acid, 1750 g (10.2 mol) of 1,10-decanediamine, 221 g (1.5 mol) of adipic acid, 7.7 g (0.063 mol) of benzoic acid, hypophosphorous acid 2.35 g of sodium monohydrate (0.07% by weight with respect to the raw material) and 2785 g of distilled water were placed in an autoclave and heated to the same temperature as in Example 1. At this time, the autoclave was pressurized to 3.7 MPa. The low-order condensate obtained by taking out in the same manner as in Example 1 was classified with a classifier, and only those having a particle size of 2 mm or less were dried at 110 ° C. for 20 hours. The obtained low-order condensate had a water content of 3580 ppm and an intrinsic viscosity [η] of 0.07 dl / g. In addition, it carried out by the same method as Example 1 except having made solid phase polymerization time into 10 hours. The polyamide obtained had an intrinsic viscosity [η] of 0.9 dl / g and bisdecamethylenetriamine of 0.35% by weight. In addition, formation of insoluble matter (gel) in the concentrated sulfuric acid was not observed when measuring the intrinsic viscosity [η].

[Comparative Example 1]
The same procedure as in Example 1 was performed, except that the low-order condensate was classified and only those having a particle size larger than 2.5 mm were used. In order to measure the intrinsic viscosity of the obtained polyamide, an attempt was made to dissolve it in concentrated sulfuric acid at 30 ° C., but a jelly-like insoluble matter (gel) was observed, which could not be analyzed. Further, bishexamethylene triamine was 1.3% by weight.

Claims (5)

A salt or low-order condensate formed from a dicarboxylic acid component and a diamine component and having an intrinsic viscosity [η] measured in concentrated sulfuric acid at 30 ° C. of 0.2 dl / g or less is heated and polycondensed in a solid state. In the method for producing polyamide,
A step of setting the particle size of the salt or low-order condensate of the dicarboxylic acid component and the diamine component to 1.5 mm or less;
Drying the salt or low-order condensate of the dicarboxylic acid component and diamine component having a particle size of 1.5 mm or less;
And a step of solid-phase polymerization of the salt or low-order condensate of the dicarboxylic acid component and the diamine component after drying.   The method for producing a polyamide according to claim 1, wherein the salt or low-order condensate of the dicarboxylic acid component and the diamine component is reduced to 1.5 mm or less by classification or pulverization.   The method for producing a polyamide according to claim 1, wherein the amount of triamine in the polyamide is 1% by weight or less.   Polyamide is 30 to 100 mol% of terephthalic acid component units, 0 to 70 mol% of aromatic dicarboxylic acid component units other than terephthalic acid, and / or 0 to 70 mol% of aliphatic dicarboxylic acid component units having 4 to 20 carbon atoms. 2. The method for producing a polyamide according to claim 1, comprising a dicarboxylic acid component unit and a diamine component unit having 4 to 25 carbon atoms having a straight chain and / or a side chain. A polyamide which is formed from a dicarboxylic acid component and a diamine component and heats and polycondenses a low-order condensate having an intrinsic viscosity [η] measured in concentrated sulfuric acid at 30 ° C. of 0.2 dl / g or less in a solid phase. In the manufacturing method,
A step of condensing a dicarboxylic acid component and a diamine component in an aqueous solvent to prepare a low-order condensate;
A step of setting the particle size of the low-order condensate to 1.5 mm or less;
Drying the low-order condensate of 1.5 mm or less;
A process for solid-phase polymerization of the low-order condensate after drying.