KR20200061740A - Method for preparing polyamide resin - Google Patents

Abstract

Disclosed in the present invention is a method for preparing a straight chain aliphatic polyamide resin, which reduces annular by-products generated during polymerization and reduces color discoloration caused at a high temperature and a high pressure by using a novel method without a need for a flash process when preparing a straight chain aliphatic polyamide resin comprising cadaverine. The present invention provides a method for preparing a straight chain aliphatic polyamide resin, comprising the steps of: (a) preparing a pre-polymer by preliminarily polymerizing dicarboxylic acid and diamine in a first reactor; (b) discharging and pelletizing the preliminarily polymerized pre-polymer while maintaining a temperature of the first reactor higher than a melting point of the preliminarily pre-polymer; and (c) inputting the pelletized pre-polymer into a second reactor to polymerize the same at a solid state at a temperature of less than 200°C.

Description

Method for preparing polyamide resin{Method for preparing polyamide resin}

The present invention relates to a method for producing a polyamide resin, and more particularly, to a method for producing a straight-chain aliphatic polyamide resin by an economical method.

Polyamide (PA) is one of the engineering plastics widely used in automobiles, electrical and electronic parts, etc., and has different physical properties depending on the number of carbons in a component, and is used in various fields according to physical properties suitable for industrial use.

These polyamides are mainly produced through two methods of ring opening reaction and condensation reaction. Polyamide resins PA66, PA610, PA612, PA6T, etc. produced through condensation reaction are mainly amide monomers, and are mainly hexamethylene diamine. ; HMDA) is used.

Diamine monomers used in addition to HMDA, 1,4-butanediamine, 1,10-decanediamine, 1,12-dodecanediamine, etc. Monomers with an even number of carbons were mainly used. This was because petrochemical-based diamines with an odd number of carbons were used as monomers for polymers, which was accompanied by economic problems.

However, as a technology capable of biologically producing monomers has been developed, various diamine monomers have been produced, and an odd number of carbon cadaverine (CAD) has emerged. The cadaverine possesses 5 carbons, and is bioavailable through the decarbonation reaction of lysine produced from biomass, and has economic feasibility applicable as a polymer monomer.

Non-Patent Document 1 (Dyetec vision 139, 2016, p12-15) shows that PA56, which introduced odd-numbered carbon-derived cadaverine, has superior dyeing and moisture absorption properties compared to PA66, and the reason is cadaverine. It is stated that, due to the lack of one carbon number compared to hexamethylenediamine, all NH does not fully participate in hydrogen bonding, and thus the space for receiving dye and moisture increases. However, this document is a document about the properties of a polymer containing cadaverine and does not describe a manufacturing technique.

Synthesizing a novel polyamide resin incorporating cadaverine can develop a polyamide resin having new physical properties, and is expected to expand various uses. However, when a new resin incorporating cadaverine is produced under high temperature and high pressure, there is a problem that cyclic by-products are generated by deammonia reaction, and color discoloration by high temperature also occurs. Do.

WO2010-113736 discloses a method for producing an aliphatic polyamide resin by melt polycondensation reaction of an aliphatic long-chain diacid with biologically produced cadaverine. This patent limits the content of cyclic byproducts of biologically produced cadaverine, but does not mention cyclic byproducts produced through polymerization, and only describes methods for manufacturing through melt polymerization.

Korean Patent Publication No. 2015-0062943 discloses the production of an aliphatic polyamide resin through solid-phase polymerization of a prepolymer, but uses an alicyclic diamine as a main monomer and uses cadaverine as a monomer. It is not mentioned. At this time, the solid phase polymerization of the prepolymer of the polyamide resin must include a process performed at a temperature of 200°C or higher. In addition, in order to introduce the prepolymer into a solid-state polymerizer, it includes a flash process that discharges from high temperature and high pressure to room temperature and normal pressure, but for high-temperature and high-pressure instantaneous discharge to room temperature and normal pressure, equipment suitable for commercialization There is a problem that must be introduced.

Japanese Patent Publication No. 1999-228690 discloses a method for producing a polyamide resin through solid phase polymerization of a prepolymer, but only mentions an aromatic polyamide resin, and also performs a solid phase polymerization in two steps to prevent fusion. In the first stage of the disclosure, solid phase polymerization is performed at a temperature of 195° C. or lower in the first stage and 205 to 280° C. in the second stage, and the technology is disclosed. In order to prevent fusion, in the first step, solid phase polymerization is performed at a temperature of less than 200°C, but in the end, there is a problem that solid phase polymerization must be performed at a temperature of 200°C or higher. In addition, in order to introduce the prepolymer into a solid-state polymerization reactor as in the previous patent, there is a problem that includes a flashing process of flashing and discharging from high temperature and high pressure to room temperature and pressure.

In addition, the prepolymer produced by the flash process is difficult to deal with in the process, such as fusion between powders during solid phase polymerization in powder form, piping scaling and clogging due to powder blowing, and a large amount of adhesion to the inner wall of the device.

The present invention reduces the cyclic by-products generated during polymerization in the production of a straight-chain aliphatic polyamide resin containing cadaverine, while reducing the color discoloration generated under high temperature and high pressure, and a new type of straight-chain method without the need for a flash process. It is intended to provide a method for producing an aliphatic polyamide resin.

In order to solve the above problems, the present invention, (a) preparing a prepolymer by prepolymerizing dicarboxylic acid and diamine in a first reactor; (b) discharging and pelletizing the prepolymerized prepolymer while maintaining the temperature of the first reactor above the melting point of the prepolymerized prepolymer; (c) a step of solid-phase polymerization at a temperature of less than 200° C. by introducing the pelletized prepolymer into a second reactor.

In addition, the dicarboxylic acid is a straight-chain aliphatic dicarboxylic acid having 4 to 14 carbon atoms, and the diamine provides a method for producing a straight-chain aliphatic polyamide resin characterized by being cadaverine.

In addition, the step (a) is a straight-chain aliphatic polyamide resin characterized in that pre-polymerization is performed in the presence of 20 to 70 parts by weight of solvent compared to 100 parts by weight of the total weight of dicarboxylic acid and diamine input to the first reactor. Provide a manufacturing method.

In addition, a terminal sealant, which is a monocarboxylic acid, is further added to the first reactor, and the amount of the terminal sealant is 0.001 to 0.1 equivalent to that of the dicarboxylic acid, thereby providing a method for producing a straight-chain aliphatic polyamide resin. do.

In addition, when the prepolymer is discharged, the pressure of the first reactor is the same as the external pressure of the first reactor.

In addition, in the step (b), the prepolymer provides a method for producing a straight-chain aliphatic polyamide resin, characterized in that it is discharged in a strand form.

In addition, the pellet to be introduced into the second reactor of step (c) is pelletized is performed within 30 minutes, provides a method for producing a straight-chain aliphatic polyamide resin, characterized in that the moisture content is less than 10% by weight.

In addition, the pellet has a relative viscosity (RV, 98% (w/w) sulfuric acid as a solvent at a concentration of 1 g/㎗ at 25° C.) of 1.0 to 2.0, and a zero shear viscosity of 10,000 to 30,000. cP, Shore D hardness of 70 to 80 provides a method for producing a straight-chain aliphatic polyamide resin.

In addition, the solid phase polymerization provides a method for producing a straight-chain aliphatic polyamide resin characterized in that it is performed under vacuum conditions of 1 torr or less.

In addition, after the step (c), the relative viscosity of the polymerized product (RV, 98% (w/w) sulfuric acid as a solvent at a concentration of 1 g/mm 2 at 25° C.) is 2.0 to 4.0. It provides a method for producing an aliphatic polyamide resin.

In addition, after the step (c), a cyclic by-product content of the polymerized product is 10 mol% or less.

According to the present invention, in preparing a straight-chain aliphatic polyamide resin containing cadaverine, solid phase polymerization is performed after prepolymer preparation, while prepolymer is discharged and pelletized while maintaining the temperature of the reactor higher than the melting point of the polymerized prepolymer when discharging the prepolymer. By performing a solid phase polymerization at a low temperature of less than 200°C without introducing a conventional flash process, it is possible to reduce cyclic by-products generated during polymerization and reduce color discoloration occurring under high temperature and high pressure. By introducing the strand pelletizing method used in the factory, it is possible to provide a method of manufacturing a straight-chain aliphatic polyamide resin that does not require the introduction of special equipment and high-level technology of the flash process.

In addition, instead of applying the conventional melt polymerization process, by manufacturing a straight-chain aliphatic polyamide resin at a low temperature of less than 200°C, it is possible to increase the thermal efficiency to give the final product a price competitiveness. There is an advantage that the manufacturing method of the new method according to the present invention can be applied directly to the existing production line without.

Hereinafter, preferred embodiments of the present invention will be described in detail. In the description of the present invention, when it is determined that a detailed description of related known technologies may obscure the subject matter of the present invention, the detailed description will be omitted. Throughout the specification, when a part “includes” a certain component, this means that other components may be further included instead of excluding other components, unless specifically stated to the contrary.

The present inventors repeatedly researched to derive a method capable of performing solid phase polymerization at a low temperature of less than 200°C without introducing a flash process in manufacturing a straight-chain aliphatic polyamide resin, and surprisingly, the temperature of the reactor was higher than the melting point of the prepolymer polymerized. When discharging and pelletizing the prepolymer while maintaining a high level, solid phase polymerization is performed at a low temperature of less than 200°C without introducing a flash process to reduce cyclic by-products generated during polymerization and to reduce color discoloration occurring under high temperature and high pressure. It has been discovered that it is possible to provide a method for producing a straight-chain aliphatic polyamide resin, which has led to the present invention.

Thus, the present invention comprises the steps of: (a) preparing a prepolymer by prepolymerizing dicarboxylic acid and diamine in a first reactor; (b) discharging and pelletizing the prepolymerized prepolymer while maintaining the temperature of the first reactor above the melting point of the prepolymerized prepolymer; (c) a step of solid-phase polymerization at a temperature of less than 200° C. by introducing the pelletized prepolymer into a second reactor.

First polymerization step

The first polymerization step in the present invention is a step of prepolymerizing and discharging a polyamide resin by solution polymerization in a first reactor to prepare a prepolymer and then pelletizing it. The method of solution polymerization, discharge and pelletizing of the following polyamide resin It can be performed according to.

First, dicarboxylic acid and a solvent are introduced into the first reactor, and then diamine in a liquid form is subsequently introduced into the first reactor. Here, the first reactor is not particularly limited as long as it is a reactor capable of solution polymerization of a known polyamide resin.

The dicarboxylic acid component used as a raw material for producing a polyamide resin in the present invention is a straight-chain aliphatic dicarboxylic acid, preferably a straight-chain aliphatic dicarboxylic acid having 4 to 14 carbon atoms, for example, succinic acid ), glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecane diacid (undecanedioic acid), dodecanedioic acid, brassylic acid, tetradecanedioic acid, and the like, preferably sebacic acid or dodecanedioic acid Can be used.

In addition, the diamine component used as a raw material for producing a polyamide resin in the present invention is a straight-chain aliphatic diamine, and the diamine component used in the production of a polyamide resin can be used without limitation, but in the present invention, cadaverine is introduced as a conventional diamine component. In view of the problem to be solved in the light of the present invention to solve the problem of presenting a method capable of performing solid phase polymerization at a low temperature of less than 200°C without introducing a conventional flash process, while improving problems such as cyclic by-product generation and color discoloration due to high temperature. It is preferred to choose cadaverine as an ingredient. At this time, the cadaverine may be used both petrochemical derived or bio-derived, purity of 95% or more, preferably 98% or more.

On the other hand, in the present invention, the equivalent ratio of the dicarboxylic acid component and the diamine component is preferably in the range of 1:1 to 1:4, and more preferably in consideration of the reaction yield and prepolymer production efficiency, 1:1 to 1: It may be in the range of 1.2, and most preferably in the range of 1:1 to 1:1.05.

The solvent is not particularly limited as long as it is a solvent used for solution polymerization of a conventional polyamide resin. For example, water, methanol, ethanol, etc. may be used, and preferably water. By performing polymerization using the solvent, deterioration and solidification of the polymer generated during polymerization can be prevented. The solvent content is preferably 20 to 70 parts by weight, more preferably 30 to 60 parts by weight, and most preferably 40 to 50 parts by weight compared to 100 parts by weight of the total weight of the raw materials to be added. When the content of the solvent is less than 20 parts by weight, the effect of introducing a solvent for preventing deterioration and solidification occurring during polymerization may be insignificant, and when it exceeds 70 parts by weight, the time required to remove the solvent may increase and efficiency may be reduced.

Next, a catalyst and an end-sealing agent may be added to the first reactor in addition to the monomer component and a solvent, and the catalyst and the end-sealing agent may be introduced by itself or dissolved in a solvent.

As the catalyst in the present invention, a phosphorus-based catalyst may be used, for example, phosphoric acid, phosphorous acid, hypophosphite, phosphate, phosphite, hypophosphite, and the like, and more preferably hypophosphite may be used. However, the catalyst is not particularly limited as long as it is a substance that does not inhibit the polymerization reaction among the phosphorus compounds. When the phosphorus-based catalyst is applied to the polymerization reaction, the catalyst not only speeds up the polymerization reaction, but also acts as a thermal stabilizer for the polymerization reaction. Therefore, it is preferable to apply the phosphorus-based compound as a catalyst, the amount of which is preferably 10 to 5,000 ppm, more preferably 30 to 1,000 ppm, and most preferably 50 to 300 ppm, compared to the resulting polymer. When the amount of the catalyst used is 10 ppm or less, the action of the catalyst may not be sufficiently exhibited, and when it exceeds 5,000 ppm, decomposition reaction may occur during processing due to the catalyst remaining in the final product, thereby deteriorating physical properties.

In the present invention, the terminal sealing agent is introduced to adjust the molecular weight, for example, monocarboxylic acids or monoamines of a monofunctional group may be used, but in the present invention, monocarboxyl is used to prevent gel formation during solid phase polymerization. It is preferred to use acids.

The monocarboxylic acid end sealant is acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, carboxylic acid, lauric acid, tridecyl acid, myristic acid, palmitic acid, stearic acid, pivalic acid, isobutyl acid, etc. It may be an aliphatic monocarboxylic acid or an aromatic monocarboxylic acid such as alicyclic monocarboxylic acid such as cyclohexane carboxylic acid, benzoic acid, toluic acid, naphthalenecarboxylic acid or phenylacetic acid, preferably economical as aliphatic And acetic acid having excellent solubility.

The content of the terminal sealant is preferably 0.001 to 0.1 equivalents, more preferably 0.002 to 0.1 equivalents, and most preferably 0.005 to 0.1 equivalents compared to the dicarboxylic acid to be added. When the content of the terminal sealant is less than 0.001 equivalent, the molecular weight control effect may be insignificant, and when it exceeds 0.1 equivalent, it may be difficult to obtain a polymer product having a desired high molecular weight.

Next, a prepolymer is prepared by performing a prepolymerization reaction after forming a salt state before polyamide polymerization in the first reactor in which the components are added.

For the salt formation, for example, after sufficiently replacing the first reactor with an inert gas such as nitrogen or argon at room temperature, the reactor is completely sealed and 1 to 20°C, preferably 1 to 10°C, than the melting point of the input dicarboxylic acid. The temperature is raised to a high temperature, and when the temperature rise is completed, the mixture can be stirred for 10 minutes to 3 hours, preferably 30 minutes to 1 hour at that temperature, so that a perfect salt is formed.

Thereafter, the temperature of the first reactor is raised to 200 to 250°C, preferably 210 to 230°C, and then 30 to 300 minutes at that temperature, preferably 5 to 30 bar for 60 to 180 minutes, preferably 15 to 20 The prepolymerization reaction is performed while maintaining the pressure of the bar to prepare a prepolymer. At this time, in order to maintain the pressure inside the first reactor, the inside solvent and the resulting condensate can be removed. After that, the pressure inside the reactor is gradually lowered to normal pressure, that is, after the pressure is equal to the outside pressure of the first reactor. The produced prepolymer can be discharged. Here, the'same pressure' means that after opening the discharge portion, no external pressure is applied to the reactor, so that the reactor pressure is completely matched to the external pressure, as well as the case where an external pressure is applied, but can be normally employed for smooth discharge. It can be understood as meaning including a state in which there is a slight pressure difference within approximately 1 atmosphere, preferably 0.5 atmosphere, by means such as blowing.

The prepolymer may be discharged into a water bath from a reactor at atmospheric pressure with all of the solvent removed. In order to discharge without using a flash process at normal pressure, the temperature of the reactor can be set to 5 to 30°C, preferably 10 to 20°C, higher than the melting point of the generated polymer. Specifically, the temperature of the reactor may be 200 to 250°C, preferably 210 to 240°C, and most preferably 225 to 235°C. At this time, the water temperature of the discharged water bath may be room temperature.

Hereinafter, a process of pelletizing after discharging with a water bath is illustrated.

The prepolymer discharged into the water bath is in the form of a strand, and after being solidified in a strand form in a water bath at room temperature, it is directly introduced into a pelletizer to be made into a pellet form. Before the strand is introduced from the water bath to the cutter of the pelletizer, most of the water from the strand derived from the water bath is removed through a drying system included in the pelletizing system, and the drying system is mainly air. Use The dried strand is introduced into a pelletizer, wherein the entire pelletizing is preferably completed within 30 minutes, preferably between 20 and 30 minutes. If the pelletizing time is shorter than 20 minutes, the polymer may not be discharged in a strand form, and if it is longer than 30 minutes, discoloration may occur, and if it is longer than 1 hour, the properties of the front and rear ends of the discharged resin are different. Can be. At this time, the viscosity of the resulting prepolymer pellet is a low molecular weight in the range of 1.0 to 2.0 in the RV standard analyzed at 25°C with 98% (w/w) sulfuric acid as the solvent at a concentration of 1 g/mm 2, and the ejection process is smooth in the viscosity range. It was confirmed that it was possible to perform polymerization at low temperature during subsequent solid-phase polymerization. In addition, the pellet has a value of 10,000 to 30,000 cP of zero shear viscosity analyzed at a temperature 10 to 20°C higher than the melting point, and the Shore D hardness is 70 to 80, which has a hardness capable of pelletizing. have. The particle size of the pellets is 0.5 to 3 mm, preferably 1.0 to 2.0 mm, and the moisture content of the pellets is 10% by weight or less, preferably 5% by weight or less.

In the conventional polyamide manufacturing process, due to the high melting point (Tm), melt polymerization is difficult, and solid phase polymerization is performed. For example, in the case of polyphthalamide (PPA), solid phase polymerization is mainly carried out, which requires a temperature of 300°C or higher for melt polymerization with a melting point of 300°C or higher, and thus a temperature below the melting point of polyphthalamide resin instead of melt polymerization. The solid phase polymerization is performed. Therefore, in this case, discharge is not possible unless a flash process is used in the pre-polymerization process. That is, in the case of polyphthalamide, pre-polymerization is carried out at a temperature of about 230 to 250°C. At this temperature, polyphthalamide is hardly discharged in the absence of a solvent, and thus, in a state of partially containing water as a solvent, about 5 bar conditions. Therefore, it is necessary to employ a flash process that allows instantaneous discharge with water.

On the other hand, in the first polymerization step of the present invention, in particular, when a polyamide resin having a certain level of melting point is scheduled, a flash process used in conventional polyamide polymerization is not employed, and the prepolymer is stranded after removing all of the solvent to atmospheric pressure. Since it is not necessary to introduce additional equipment for the flash process by discharging and solidifying in the form and pelletizing, there is an advantage that can be applied directly to an existing production line, and as described later, solid phase polymerization is performed at a low temperature of less than 200°C. If it does, there is an effect to prepare a polyamide resin having physical properties and qualities equal to or higher than those of conventional melt polymerization.

Second polymerization step

The second polymerization step in the present invention is a step of performing solid phase polymerization using a prepolymer in the pellet phase prepared in the first polymerization step in a second reactor.

The second reactor used for solid phase polymerization is not particularly limited as long as it is a reactor capable of solid phase polymerization of a known polyamide resin, and may be performed using, for example, a tumbler reactor.

The solid-phase polymerization reaction is performed by introducing pelletized pellets into the second reactor in the first polymerization step, but in the present invention, the pellets injected into the second reactor as described above are not obtained through a conventional flash process, but upon discharge By using the one obtained by maintaining the temperature of the first reactor higher than the melting point of the prepolymer to be polymerized and discharged, poly having the physical properties and quality of equal or higher despite being performed in a low temperature environment compared to the production under melt polymerization of a conventional polyamide resin This will allow amide resins to be produced.

Therefore, in the present invention, the solid phase polymerization is carried out at a temperature of less than 200 ℃, preferably more than 150 ℃ less than 200 ℃, more preferably can be carried out at a temperature of more than 170 ℃ less than 200 ℃. At this time, the polymerization time may be appropriately set in the range of 1 to 48 hours in consideration of cyclic by-product formation and color discoloration, and preferably may be performed for 5 to 24 hours.

In addition, the solid-phase polymerization may be performed while releasing by-products generated during the reaction by making the inside of the reactor under a vacuum of 1 torr or less, and the tumbler reactor during polymerization can be rotated at 1 to 20 rpm. As described above, the moisture content of the pelletized prepolymer introduced into the solid phase polymerization is 10% by weight or less, preferably 5% by weight or less, and drying performed by the pelletizing system is sufficient, and 5% by weight or less In the case of containing water, it does not affect the solid-phase polymerization result even without an additional drying process.

The polymer that has undergone solid phase polymerization may be rotated in a reactor in a vacuum state, cooled to 100° C. or less, and then discharged into the air, or continuously flow nitrogen flow at room temperature and cooled to 100° C. or less to be discharged into the air. There is no need to cool using any of the above two methods, but in order to prevent discoloration of the polymerized polymer, it is preferable that the polymerized product is cooled to a temperature of 100° C. or less and then discharged into the air. In addition, it may be directly discharged into a water bath or liquid nitrogen, which is a medium capable of rapid cooling.

The polymer produced through the solid-phase polymerization has a relative viscosity (RV, 98% (w/w) of sulfuric acid as a solvent at a concentration of 1 g/㎗ and analyzed at 25°C) in the range of 2.0 to 4.0, and has excellent color characteristics. Not only that, it is easy to process and is suitable for applications such as automobiles and electric and electronic materials. In addition, the cyclic by-product content of the polymer produced through the solid-phase polymerization is 10 mol% or less, preferably 8 mol% or less, more preferably 5 mol% or less, and even more preferably 3 mol% or less to produce cyclic by-products. Can be significantly reduced.

The manufacturing method including the solid-phase polymerization step as described above does not include a flash process used in the conventional polyamide solid-phase polymerization, and after removing all solvents up to atmospheric pressure to be discharged, strands commonly used in petrochemical plants By introducing the pelletizing method, there is an advantage that it can be applied directly to an existing production line because it does not require the introduction of high-precision technology and special equipment of the flash process. In addition, the prepolymer produced by the flash process has a difficult problem to be handled in the process of fusion between powders during solid phase polymerization in powder form, piping scaling and clogging due to powder blowing, and a large amount of adhesion to the inner wall of the device. The prepolymer according to the present invention is in the form of pellets, and does not cause fusion and clogging during solid phase polymerization, and has an advantage of being easier to handle than powder.

In addition, in the second polymerization step of the present invention, solid phase polymerization is performed at a low temperature of less than 200° C. to reduce discoloration, thereby providing excellent color characteristics, and to dramatically generate cyclic by-products generated during polymerization of polyamide resin containing cadaverine. It can provide a method for producing a polyamide resin that can be reduced. In particular, when polymerizing a polyamide resin containing cadaverine, it is possible to reduce the production of piperidine end groups by cyclization of cadaverine at the end of the reactor, thereby minimizing the inhibition of the polymer production reaction by end group capping to achieve high molecular weight. It is possible to make it possible to manufacture a straight-chain fatty acid polyamide resin containing cardaline.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.

Example 1

Sebacic acid 1,260 g (6.23 mol, 1.00 eq), cadaverine 650 g (6.36 mol, 1.02 eq), distilled water 1,700 g (total 100 parts by weight 47 parts by weight), sodium hypophosphite 132 mg (1.25 mmol, based on final polymer) 79 ppm) and acetic acid 1.87 g (0.03 mol, 0.005 eq) was added to a 10L high pressure reactor and nitrogen was replaced at room temperature for 10 minutes. After the reactor was completely sealed, the temperature was raised to 140°C. After the heating was completed, the mixture was stirred at 140°C for 30 minutes to prepare a salt state before polyamide polymerization. Thereafter, the temperature was set to 230°C and the temperature was gradually raised to 210°C, so that the pressure became 17.2 bar, and the pressure was maintained while gradually removing water. To maintain the pressure, the reaction temperature gradually reached 230°C. When the pressure can no longer be maintained after reaching 230°C, the pressure in the reactor was gradually reduced to normal pressure. When the pressure reached normal pressure, the discharge part at the bottom of the reactor was opened to discharge the produced prepolymer in a strand form in cooling water. The total reaction time was 300 minutes including the heating time.

After discharging, the solidified prepolymer is put into a single screw extruder and extruded, followed by pelletizing for 30 minutes through a pelletizer, size 1~2mm, relative viscosity (RV) 1.0~2.0, zero point shear viscosity 15,000~20,000 cP, and Pellets having Shore D hardness of 70-80 were prepared.

The pellet-formed PA510 prepolymer prepared as described above was dried in a vacuum oven at 50° C., 1 torr or less for 2 hours, then put 200 g into a 5 L tumbler reactor, sealed, and slowly rotated at 10 rpm. The internal oxygen was first removed by rotating the vacuum for 15 minutes at room temperature while applying an internal pressure of 1 torr or less. Thereafter, the temperature was gradually increased to reach 190°C, and solid phase polymerization was performed at 190°C for 9.5 hours, including a heating time. The polymerized solid-phase polymer product was discharged into liquid nitrogen or cooling water to prepare a final polyamide resin.

Here, the zero point shear viscosity (rheology analysis) and hardness of the pellets were analyzed by the following method.

[Prepolymer rheology analysis]

A 2 mm thick specimen was inserted into a rotational rheometer heated to 230°C. Geometry was used for parallel-plate, and after confirming that the specimen was completely melted, it was rotated at a rate of angular frequency 0.5[1/s] to perform rheology analysis of the prepolymer.

[Hardness analysis]

After preparing a 6T specimen according to ISO868, shore D hardness was analyzed.

Example 2: Solid phase polymerization of water-containing pellets

A polyamide resin was prepared in the same manner as in Example 1, except that 5% by weight of water (10.53 g) was optionally added to the dried prepolymer pellet sample in Example 1.

Comparative Example 1: Melt polymerization

Sebacic acid 1,260g (6.23mol, 1.00eq), cadaverine 650g (6.36mol, 1.02eq), distilled water 1,700g (total 100 parts by weight 47 parts by weight), sodium hypophosphite 132mg (1.25mmol, 79ppm based on final polymer) And acetic acid 1.87 g (0.03 mol, 0.005 eq) was added to a 10 L high-pressure reactor and nitrogen was substituted at room temperature for 10 minutes. After the reactor was completely sealed, the temperature was raised to 140°C. After the heating was completed, the mixture was stirred at 140°C for 30 minutes to obtain a salt state before polyamide polymerization. Thereafter, the temperature was set to 230°C and the temperature was gradually raised to 210°C, so that the pressure became 17.2 bar, and the pressure was maintained while gradually removing water. To maintain the pressure, the reaction temperature gradually reached 230°C. When the pressure can no longer be maintained after reaching 230°C, the pressure in the reactor was gradually reduced to normal pressure. After the temperature of the reactor at normal pressure was raised to 270° C. for 20 minutes, the temperature was further increased for 50 minutes at normal pressure and 10 minutes under a vacuum of 1 torr or less. After the polymerization was completed, the discharge portion at the bottom was opened to discharge the resulting polymer into cooling water to pelletize the final polyamide resin. The total reaction time was 380 minutes including the heating time.

Comparative Example 2: Powder solid phase polymerization

A polyamide resin was prepared in the same manner as in Example 1, except that the prepolymer discharged in Example 1 was pulverized to form a powder to perform solid phase polymerization.

Test example

For the polyamide resin prepared according to the Examples and Comparative Examples, the melting point (Tm), crystallization temperature (Tc), relative viscosity (RV), cyclic by-product content, and color were measured in the following manner and the results are shown in Table 1 below. Shown.

[How to measure]

1) Melting point (Tm)

Melting points were confirmed by differential scanning calorimetry (DSC). It is a result of heating up from 20°C to 300°C at a rate of 10°C/min, gradually cooling to 10°C/min, and then raising the temperature again.

2) Relative viscosity (RV)

Using 98% (w/w) sulfuric acid as a solvent, a sample having a concentration of 1 g/mm 2 was analyzed according to Equation 1 below using a Ubelroad viscosity tube at 25°C.

[Equation 1]

RV=η/η ₀

(η: the number of seconds in which the sample is dissolved, η ₀ : the number of seconds in which only the solvent is not dissolved)

3) Structure of the polymer product and the content of end group piperidine by cadaverine cyclization reaction

The NMR (Nuclear Magnetic Resonance) analysis confirmed the structure of the polymer product and the content of piperidine in the terminal group by the cyclization reaction of cadaverine. A small amount of polyamide to be analyzed was dissolved in a solution of Hexafluoro-2-propanol (HFIP), and a small amount of the solution was taken to perform ¹ H-NMR analysis with CDCl ₃ NMR solvent. ¹ H-NMR analysis was performed by confirming the structure of the polymerized product through the position and integral of ¹ H-NMR peak. Hydrogen bound to carbon adjacent to the nitrogen atom of the amide bond of the polyamide main chain (chemical shift value of 3.0 to 3.5 ppm) and hydrogen bound to carbon adjacent to the nitrogen atom of the heterocycle of nitrogen (chemical shift value of 3.5 to 4.0 ppm) ), the content of the piperidine end groups was calculated through the integral value of) to calculate the content of cyclic by-products.

4) Color

The polymerized product was observed with the naked eye.

Referring to Table 1, the thermal properties and viscosity characteristics of the final product through melt polymerization (Comparative Example 1) and solid phase polymerization (Examples 1 and 2) are not different, but solid phase polymerization is used in terms of cyclic by-product content and color characteristics. It can be seen that the embodiment was significantly superior in the embodiment.

That is, in the prepolymerization of the polyamide resin according to the present invention, when the prepolymer is discharged, the temperature of the prepolymer is maintained above the melting point of the prepolymer to be polymerized, and discharged and solidified in a strand form to apply pelletization, without employing a conventional flash process. It can be seen that solid phase polymerization proceeds effectively at a temperature of less than 200°C to obtain a polymer product having a high molecular weight, as well as dramatically reducing the formation of cyclic by-products generated during polymerization and color discoloration occurring under high temperature and high pressure. .

In addition, in the case of performing solid phase polymerization by making the prepolymer into a powder form (Comparative Example 2), it is fused to the reactor and attached to the reactor in a lump form, whereas recovery of the product is difficult and impossible to carry out. If you do, you can see that you can proceed without problems.

In addition, it can be seen that even when the solid phase polymerization contains 5% by weight of water, it does not affect the solid phase polymerization result, and thus it is understood that no further drying process is required after pelletizing.

As described above, according to the present invention, cyclic by-products are reduced through solid phase polymerization, and the color can be polymerized into an aliphatic straight-chain polyamide resin superior to a melt polymer product, and the polyamide is suitable for use in automobiles, electrical and electronic materials Do.

The preferred embodiments of the present invention have been described above in detail. The description of the present invention is for illustrative purposes, and those skilled in the art to which the present invention pertains will appreciate that other specific forms can be easily modified without changing the technical spirit or essential features of the present invention.

Therefore, the scope of the present invention is indicated by the following claims rather than the above detailed description, and it should be construed that all changes or modified forms derived from the meaning, scope and equivalent concepts of the claims are included in the scope of the present invention. do.

Claims (11)

(a) preparing a prepolymer by prepolymerizing dicarboxylic acid and diamine in a first reactor;
(b) discharging and pelletizing the prepolymerized prepolymer while maintaining the temperature of the first reactor above the melting point of the prepolymerized prepolymer;
(c) solidifying the pelletized prepolymer into a second reactor at a temperature of less than 200° C.;
Method for producing a straight-chain aliphatic polyamide resin comprising a. According to claim 1,
The dicarboxylic acid is a straight chain aliphatic dicarboxylic acid having 4 to 14 carbon atoms, and the diamine is a cadaverine. According to claim 1,
The step (a) is a method for producing a straight-chain aliphatic polyamide resin, characterized in that pre-polymerization is performed in the presence of a solvent of 20 to 70 parts by weight compared to 100 parts by weight of the total weight of dicarboxylic acid and diamine input to the first reactor. . According to claim 1,
A method for preparing a straight chain aliphatic polyamide resin, wherein a terminal sealant, which is a monocarboxylic acid, is further added to the first reactor, and the terminal sealant input amount is 0.001 to 0.1 equivalents compared to the dicarboxylic acid. According to claim 1,
When the prepolymer is discharged, the pressure of the first reactor is the same as the external pressure of the first reactor. According to claim 1,
In the step (b), the prepolymer is a straight-chain aliphatic polyamide resin production method characterized in that it is discharged in a strand form. According to claim 1,
A method for producing a straight-chain aliphatic polyamide resin, wherein pellets introduced into the second reactor in step (c) are pelletized within 30 minutes and have a water content of 10% by weight or less. The method of claim 7,
The pellet has a relative viscosity (RV, 98% (w/w) sulfuric acid as a solvent at a concentration of 1 g/㎗ and analyzed at 25° C.) of 1.0 to 2.0, a zero shear viscosity of 10,000 to 30,000 cP, , Shore D hardness is 70 to 80, characterized in that the straight-chain aliphatic polyamide resin production method. According to claim 1,
The solid-phase polymerization method of manufacturing a straight-chain aliphatic polyamide resin, characterized in that to be carried out in a vacuum condition of 1 torr or less. According to claim 1,
After the step (c), the relative viscosity of the polymerized polymer (RV, 98% (w/w) sulfuric acid as a solvent at a concentration of 1 g/mm 2 at 25° C.) is 2.0 to 4.0. Manufacturing method of amide resin. According to claim 1,
After the step (c), the cyclic by-product content of the polymerized polymer is 10 mol% or less, characterized in that the straight-chain aliphatic polyamide resin production method.