JPH0325448B2 - - Google Patents

Description

[Detailed description of the invention] <Industrial application field> The present invention relates to a new method for producing polyamides.

More specifically, the present invention relates to a method for producing a high melting point polyamide at a low temperature below its melting point.

<Prior Art> Various methods for producing thermoplastic polyamides are known, but the most common method is melt polymerization. This method is a method in which ring-opening or condensation polymerization is carried out at a temperature higher than the melting point of the polyamide from which lactams or salts of dicarboxylic acids and diamines are obtained. This method uses general-purpose nylon-6, nylon-
Although this method is extremely effective for producing 6, 6, etc., it is difficult to use to obtain high melting point polyamides when aromatic dicarboxylic acids are used because of decomposition at high temperatures.

For this reason, in the production of special polyamides such as high melting point polyamides, interfacial polymerization methods and solution polymerization methods using acid chlorides and the like are generally used. However,
In this method, it is necessary to use expensive acid chlorides, etc., and chlorine ultimately becomes salt, calcium chloride, and other substances with low utility value, which significantly impairs the economic efficiency of the obtained polymer.

<Problems to be Solved by the Invention> The present invention aims to provide a method for easily producing a high melting point polyamide that easily decomposes at high temperatures without using expensive raw materials such as acid chlorides. be.

<Means for Solving the Problems> The present inventors have conducted repeated studies to find a method for easily obtaining a high melting point polyamide by a polycondensation reaction of a dicarboxylic acid or its lower alkyl ester and a diamine. The present invention was based on the discovery that a high molecular weight polyamide can be easily obtained by carrying out a polymerization reaction at a temperature below the melting point in the presence of a substantially non-volatile and stable liquid substance. .

That is, the present invention produces a polyamide by reacting at least one dicarboxylic acid selected from terephthalic acid and adipic acid and/or a lower alkyl ester thereof with a linear primary aliphatic diamine having 2 to 12 carbon atoms. In this case, the temperature of the polycondensation reaction after the polyamide precursor is at least lower than the melting point of the polyamide, and is selected from ethylene, propylene, and styrene, which is substantially non-volatile and stable under the polycondensation reaction conditions. A method for producing polyamide, characterized by carrying out a polycondensation reaction in the presence of a polymer obtained by polymerizing at least one type of monomer.

In the present invention, the acid component of the polyamide is a dicarboxylic acid selected from terephthalic acid and adipic acid, and esters of lower alcohols having 3 or less carbon atoms such as methyl esters of these dicarboxylic acids are also used.

On the other hand, the diamine is preferably a linear primary amine having 2 to 12 carbon atoms, such as ethylene diamine, hexamethylene diamine, dodecamethylene diamine, and the like.

The combination of these dicarboxylic acids (or esters) and diamines may be used alone or in combination of two or more, but the melting point of the resulting polyamide is 200°C or higher, preferably 220°C or higher, more preferably 220°C or higher. The present invention is effective for temperatures of 250°C or higher.
This is because products with a low melting point, such as less than 200°C, can be sufficiently produced by conventional methods such as melt polymerization without particularly applying the present invention.

A polymer that is substantially non-volatile and stable under the polycondensation conditions used in the present invention is such that when placed under the temperature and pressure conditions for polyamide polycondensation without substantially refluxing, the polymer itself undergoes decomposition polymerization. A polymer is used that is liquid under polycondensation conditions and does not substantially cause such reactions and does not react with polyamide or its precursor. Such polymers include, in particular, homopolymers or copolymers produced by addition polymerization using ethylene, propylene, styrene, etc. as raw materials. This polymer needs to be fluid under the reaction conditions, and high molecular weight materials with a melt viscosity exceeding 10,000 poise are not preferred. In addition, if it is less than 10 poise, it is difficult to disperse the target polyamide, which is undesirable.
~2000 poise is preferred.

As such polymers, those that dissolve the obtained polyamide are often undesirable because it is difficult to separate the obtained polyamide, so it is preferable to use a polymer that is as incompatible as possible.

In the present invention, such dicarboxylic acid and/or
Alternatively, the lower ester thereof and the diamine are polycondensed in the presence of the non-volatile and stable polymer, for example, the following method is employed.

(A) Equimolar salts of dicarboxylic acids and diamines, or diamines, are charged in an excess of 0.2 mole or less, water, catalysts, etc. are added if necessary, and the temperature is raised under normal pressure or increased pressure to produce water and A step in which the added water is removed from the reaction system to form a prepolymer, or a lower alcohol ester of a dicarboxylic acid and a diamine in an amount of 1 to 1.2 times the mole (based on the dicarboxylic acid ester) are added, if necessary, with a catalyst, and heated under normal pressure. or a step of producing a prepolymer by raising the temperature under pressure and removing the alcohol produced by the reaction from the system, (B) a step of further reacting the prepolymer under reduced pressure or an inert gas stream to produce a high molecular weight polyamide. When producing by , the polymer is made to exist at least before the step (B). Although the polyamide manufacturing process is described here as being divided into two steps (A) and (B) for convenience, it is not necessary to carry out these steps separately and they may be carried out consecutively. Needless to say.

Moreover, the prepolymer herein refers to an oligopolyamide having a molecular weight below which the prepolymer becomes liquid under the reaction conditions (particularly the reaction temperature) for ultimately obtaining a high molecular weight polyamide. Of course, whether the prepolymer becomes liquid or not depends not only on the molecular weight of the oligopolyamide but also on the substances present in the oligopolyamide, such as water. Normally, when water is present, the oligopolyamide is easily liquefied, and the limit molecular weight at which it becomes liquid becomes large.

In the present invention, the amide forming component is
(A) If the solid state is to be maintained from the beginning of the process, it is preferable to add the non-volatile and stable polymer from the beginning, and the polyamide-forming component should be 1 mm
It is preferable to keep the particle size as follows.

The amount of such non-volatile and stable polymer added is 10 to 900 parts by weight per 100 parts by weight of the polyamide obtained.
Preferably 20 to 500 parts by weight, more preferably 50 to 500 parts by weight
It is 300 parts by weight. If the amount added is less than this, the polyamide particles will become stuck, which is undesirable, and if it is more than this, the yield of the desired polyamide will decrease, which is not preferable.

Regarding the polycondensation reaction conditions in the present invention, ordinary melt polymerization methods are used, except that the final reaction temperature is at least lower than the melting point of the polyamide. In particular, after adding the polymer, stirring is not necessary until the polyamide component solidifies. Preferably, the polyamide component is dispersed in the polymer. The reaction temperature is generally 20 to 300°C below the melting point of the polyamide, particularly preferably 10°C or more lower than the melting point. Moreover, it is preferable to carry out the reaction under reduced pressure. Any catalyst that is generally known as a polyamide polymerization catalyst can be used, and if necessary, an end-blocking agent can also be used.

As the apparatus for carrying out the polymerization reaction of the present invention, any apparatus can be used as long as it is capable of mixing and can perform the reaction under reduced pressure or an inert gas stream, and conventional melt polymerization apparatus can be used as is.

The mixture containing the highly polymerized polyamide thus obtained can also be formed as it is. At this time, the polyamide may be melted at a temperature higher than the melting point of the polyamide and then molded, and depending on the conditions, it is also possible to contain the polyamide in the form of fibers.

Furthermore, in the polyamide obtained in the present invention, the polyamide and the polymer are generally separated. As this separation method, a method is generally used in which the polymer component is dissolved and removed using a solvent. This solvent may be any solvent as long as it does not dissolve the polyamide or react with the polyamide, but can dissolve the polymer. For example, in the case of polyethylene and polypropylene, aromatic hydrocarbons such as toluene and xylene, decahydronaphthalene, and tetrahydronaphthalene are used. etc. are often used.

The polyamide thus obtained can be used as fibers, films, and other molded products by melt molding, powder molding, solution molding, etc.

Example 1 194 parts of dimethyl terephthalate, 122 parts of hexamethylene diamine, high pressure polyethylene 948 with a melt viscosity of 250 poise at 265°C (under a shear rate of 1000/sec)
1 part and 0.045 part of phosphoric acid were charged into a reactor equipped with a stirrer, and methanol was removed from the system while gradually increasing the temperature from 200°C. When the temperature reached 265°C, the reaction was further carried out for 1 hour under normal pressure. Then gradually reduce the pressure to 30
After a few minutes, the pressure was increased to 50 Pa, and the reaction was further continued for 2 hours.
The obtained reaction product was made into chips and the polyethylene was extracted with xylene to obtain powdered polyamide. The intrinsic viscosity of this product measured with metacresol at 35°C was 0.85.

Example 2 A salt obtained by neutralizing adipic acid and ethylenediamine in water was charged into a pressurized reactor, and the salt was heated at 240℃ for 1
After standing for a while, the pressure was returned to normal, and 100 parts of the taken out prepolymer was charged into a container with a stirrer together with 200 parts of polystyrene (viscosity 320 poise under 1000/sec shear at 240°C), and heated at 250°C under normal pressure for 30 minutes. After standing, the pressure was gradually reduced to 50 Pa or less after 30 minutes, and the reaction was continued for an additional 3 hours. The remaining polymer after polystyrene was extracted from the resulting polymer mixture had an intrinsic viscosity of 0.93 when measured in sulfuric acid at 35°C.

Example 3 100 parts of a salt obtained by neutralizing adipic acid and hexamethylene diamine in water was added to polypropylene (1000/
250 parts of viscosity (250 poise) at 230°C under shearing for 2 seconds and put into a container equipped with a stirrer and sealed in a nitrogen atmosphere.
After heating to 215°C, the mixture was allowed to stand for 90 minutes without stirring, and then the pressure was gradually released while stirring, and the temperature was raised to 230°C. After returning to normal pressure over 30 minutes, the pressure was further reduced to 50 Pa, and the reaction was carried out for a total of 4 hours. The resulting mixture was extracted with decahydronaphthalene,
Polyamide, which is an insoluble component, was obtained. The intrinsic viscosity of this polyamide is 1.15, and once at 290℃
The melting point was 265°C, which was measured by heating to melt, rapidly cooling, and then increasing the temperature at 10°C/min with a differential scanning calorimeter.
It was hot.

This extracted polymer was spun at 400 m/min using a silver plate spinning machine at 290°C.
It was found that spinning was possible in the same manner as in Example 6. Further, the strength of the yarn after drawing was 7.0 g/de, and no difference was observed from that obtained by a conventional method.

<Effects of the Invention> According to the present invention, polyamide, which conventionally required expensive raw materials such as acid chlorides, can be produced in the same manner as ordinary melt polymerization using inexpensive versatile raw materials such as dicarboxylic acids or lower alkyl esters thereof. It can be easily manufactured. Further, even if the polymer is obtained by melt polymerization reaction, the reaction is carried out at a lower temperature according to the present invention, so that a polymer with less coloring etc. can be obtained.

Claims (1)

[Claims] 1. Polyamide is produced by reacting at least one dicarboxylic acid selected from terephthalic acid and adipic acid and/or a lower alkyl ester thereof with a linear primary aliphatic diamine having 2 to 12 carbon atoms. In the production, the temperature of the polycondensation reaction after the polyamide precursor is at least lower than the melting point of the polyamide, and the polyamide is made of ethylene, propylene, and styrene, which are substantially nonvolatile and stable under the polycondensation reaction conditions. A method for producing polyamide, which comprises carrying out a polycondensation reaction in the presence of a polymer obtained by polymerizing at least one selected monomer. 2 Polyamide 100 from which the polymer used is obtained
The method for producing polyamide according to claim 1, wherein the amount is 10 to 900 parts by weight.