JPH02251532A - Polymerization of high molecular weight polyhexamethylene terephthalamide - Google Patents

Abstract

PURPOSE:To polymerize the subject polyhexamethylene terephthalamide while preventing the formation of gel by polymerizing a prepolymer composed mainly of a specific polyhexamethylene terephthalamide in the presence of a hypophosphorous acid metal salt under specific condition. CONSTITUTION:The objective polyhexamethylene terephthalamide having high polymerization degree is produced by adding 0.05 to 5wt.% (preferably 0.1 to 2wt.%) of preferably sodium hypophosphite, etc., in the form of a solution of water, alcohol, etc., to a prepolymer composed mainly of a polyhexamethylene terephthalamide having an intrinsic viscosity of >=0.1dl/g (preferably >=0.2dl/g) and polymerizing the prepolymer at a temperature above 150 deg.C and below the melting point (preferably 240 to 300 deg.C) under reduced pressure or in an inert gas stream.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for polymerizing high molecular weight polyhexamethylene terephthalamide (also referred to as Nine 6T). More specifically, the present invention relates to a method for polymerizing polyhexamethylene terephthalamide with a high degree of polymerization that minimizes gel formation.

The polymer mainly composed of polyhexamethylene terephthalamide obtained by the present invention is a high melting point nylon having a benzene nucleus in the polymer chain.This polymer has excellent heat resistance and chemical resistance, and has various physical properties. It is expected that fibers, films, etc. with excellent properties can be obtained.

[Conventional technology]

Nylon 6T has a high melting point and its decomposition temperature is close to the melting point, so
Melt polymerization, which is commonly used for polyamides such as nylon 6.6 and nylon 6, cannot be used; instead, it is made from interfacial polymerization of hexamethylene diamine and terephthalic acid dichloride, or from a salt of hexamethylene diamine and terephthalic acid. Synthesized by solid phase polymerization of nylon 6T salt.

Synthesis by interfacial polymerization is difficult to handle due to the high reactivity of terephthalic acid chloride, and is also very expensive, making it difficult to produce it industrially.

The latter solid phase polymerization has also been extensively studied. For example, in Japanese Patent Application Laid-Open No. 62-20527, nylon 6T salt was
A method is disclosed in which solid phase polymerization is carried out at a temperature above .degree. C. and below the melting point under reduced pressure or under an inert gas.

However, this method cannot produce a polymer with a high degree of polymerization because the temperature at which nylon 6T salt starts to polymerize under normal pressure or reduced pressure is lower than the temperature at which it decomposes and hexamethylene diamine begins to escape. . Furthermore, in Japanese Patent Publication No. 41-11634, USP 3, 365.428, nylon 6T salt is heated at 260-300°C 125-50°C.
A method is disclosed in which initial polymerization is carried out under pressure of kg/cd, and then the pressure is returned to normal pressure and solid phase polymerization is carried out at 260 to 300° C. under an inert gas. It is also disclosed that a slight excess of hexamethylene diamine is added at this initial polymerization stage. However, with this method, the intrinsic viscosity is 2. Oa/
When solid phase polymerization is carried out for a long period of time in an attempt to obtain a polymer with a high degree of polymerization of more than 100 g, there is a problem in that a large amount of gel-like material that is insoluble in concentrated sulfuric acid is produced.

[Problem to be solved by the invention]

An object of the present invention is to provide a polymerization method for obtaining polyhexamethylene terephthalamide with a high degree of polymerization, which can prevent the formation of gel as described above as much as possible.

(Means for Solving the Problems) That is, the present invention uses a prepolymer mainly composed of polyhexamethylene terephthalamide having an intrinsic viscosity of 0.ld1/g or more, and a prepolymer containing 0.05 to 5% by weight of hypophosphorus. in the presence of a metal salt of an acid at a temperature of 150' C or more and below the melting point,
This is a method for polymerizing high molecular weight polyhexamethylene terephthalamide, which is characterized by polymerizing under reduced pressure or an inert gas stream.

The prepolymer used in the present invention is an amide polymer having 70% or more, preferably 80% or more of polyhexamethylene terephthalamide skeletons in repeating units. Such a prepolymer can be obtained by a conventional method such as solid phase polymerization of a dicarboxylic acid compound and a diamine compound or solution polymerization using a phenolic solvent. At that time, as a copolymerization component other than terephthalic acid and hexamethylene diamine, a dicarboxylic acid compound having a carbon number of 4, for example,
-12 straight chain aliphatic dicarboxylic acids, cyclohexanedicarboxylic acid, isophthalic acid, orthophthalic acid, naphthalene dicarboxylic acid, diphenyldicarboxylic acid, and the like. In addition, as a diamine compound, for example, a carbon number of 2 to 1
2, straight chain aliphatic diamine, cyclohexane diamine, phenylene diamine, diaminomethylcyclohexane xylylene diamine, and the like.

It is important that the prepolymer thus obtained has substantially no unreacted monomer remaining, and its intrinsic viscosity is 0.1 d17g or more, preferably 0.2 d17g.
It is necessary that it is above. The intrinsic viscosity here is 0
．． The value was measured in a concentrated sulfuric acid solution at a concentration of 4 a/g at a temperature of 35°C. If unreacted sulfur remains, the monomer escapes during the polymerization step of the present invention, disrupting the molar balance and making it difficult to obtain a high molecular weight. In order to solve this problem, a prepolymer having an intrinsic viscosity of 0.1 a/g or more is needed, and by doing so, it is possible to prevent molar balance collapse due to escape.

In the present invention, a metal salt of hypophosphorous acid is added to the prepolymer prior to polymerization, which is extremely effective in improving the degree of polymerization and suppressing gel-like substances in the subsequent polymerization. The metal salt of hypophosphorous acid can be added in one stage or in multiple stages at any stage before or during the polymerization reaction. Although it can be added in advance before prepolymer synthesis, it is preferable to add it before polymerization because it may deteriorate or escape during prepolymer synthesis or purification.

As the metal salt of hypophosphorous acid, sodium salt, calcium salt, etc. are preferably used. Further, the amount applied is 0.05 to 5% by weight, preferably 0.1 to 2% by weight based on the prepolymer. If it is less than 0.05% by weight, there is no effect of increasing the degree of polymerization, and if it is less than 5% by weight, the polymerization reaction will be hindered. The granting method is not particularly stipulated;
For example, it can be applied in the form of a solution such as water or alcohol.

In this case, in terms of suppressing the amount applied, it is better to have a smaller particle size of the prepolymer, and the particle size is preferably III
1 or less, more preferably 0.1M or less.

In the present invention, polymerization is carried out without melting the prepolymer to which hypophosphite has been added. Specifically, this prepolymer is charged into a container through which an inert gas can be circulated under pressure, and heated to 150° C. or higher to distill generated and remaining water and other substances out of the system, thereby increasing the molecular weight. At this time, sufficient consideration must be given to the incorporation of oxygen into the polymerization system, as this may cause coloration of the polymer, gelation due to partial crosslinking, etc. The temperature conditions for this reaction are 150°C or higher, preferably 180°C below the melting point, more preferably 2
0 reaction temperature is 40°C or more and less than 300°C 150
If the temperature is lower than .degree. C., the reaction will not proceed, which is not preferable, and if the temperature is above the above-mentioned temperature, decomposition, coloring, etc. may occur, which is not preferable.

The reaction time varies depending on the temperature, the amount of hypophosphite applied, the equipment, etc., so it is difficult to define it unambiguously, but it is generally 1 to 10 minutes.
0 hours, preferably 30 to 40 hours. When using reduced pressure, the pressure is 1000 Pa or less, preferably 300 Pa or less.

In carrying out the present invention, additives such as antioxidants, light stabilizers, and heat stabilizers may be added as necessary.

〔Example〕

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples. The intrinsic viscosity in the Examples was measured at a temperature of 35°C using a concentrated sulfuric acid solution at a concentration of 0.4 g/a.

Example 1 A stainless steel autoclave equipped with a stirrer and a pressure gauge was charged with 7 g of hexamethylene diammonium terephthalate salt and 28 g of nitrogen bubbled baracresol, replaced with nitrogen, and heated to 200 g over the course of 1 hour.
The temperature was raised to .degree. C. and maintained at that temperature for 2 hours. At that time, the internal pressure was 1 kg/ajG. Thereafter, the internal temperature was raised to 225°C over 1 hour and maintained at that temperature for 20 hours. At that time, the internal pressure gradually rose and finally reached 4.4k.
It became g/c+IIG. Thereafter, the mixture was cooled to 120'C, purged, and reacted in a pressurized system at 260'C for 3 hours and then at 280°C for 4 hours. The final pressure at each temperature is 3.5 kg/cnG at 260°C.
, 4.8 kg/dG at 280° C. After completion of the reaction, the product was cooled, precipitated using methanol, washed, and dried in vacuum.

The obtained prepolymer is white and its intrinsic viscosity is 0.
．． It was 32d1/g. This prepolymer was crushed and passed through a 60 mesh sieve to obtain prepolymer particles.

5 g of the obtained prepolymer particles were placed in a 100-meter volumetric flask, and 12.5 g of water and 10 g of methanol in which sodium hypophosphite had been dissolved at a concentration of 0.2% by weight were added.
The mixture was stirred at 65°C for 3 hours under a nitrogen atmosphere. Thereafter, it was concentrated using an evaporator and dried under vacuum.

This prepolymer was pulverized and subjected to solid phase polymerization at 295°C for 5 hours under a nitrogen stream using a solid phase polymerization apparatus equipped with a stirrer, and the intrinsic viscosity of the product was 1.9 a/g, and it was polymerized for 35 hours. The intrinsic viscosity of the solid-phase polymerized product was 2.8 a/g.

These polymers were white in color and did not contain gel-like substances that were insoluble in concentrated sulfuric acid.

Comparative Example By performing the same operation as in Example 1, the intrinsic viscosity was 0.34 d1/
g of prepolymer was obtained. This prepolymer was heated at 295° under a nitrogen stream without adding sodium hypophosphite.
Solid phase polymerization was carried out at C for 5 hours. The intrinsic viscosity of the obtained polymer was 1.4 a/g. A gel-like substance insoluble in concentrated sulfuric acid was observed in the product subjected to solid phase polymerization for 35 hours, and its intrinsic viscosity was 1.9 a/g.

〔Effect of the invention〕

The present invention is an extremely effective polymerization method for obtaining high molecular weight polyhexamethylene terephthalamide while preventing the formation of gel-like substances as much as possible.

Moreover, by using this polymer, molded products such as fibers and films that have excellent heat resistance and chemical resistance, and various excellent physical properties can be obtained.

In recent years, attempts have been made to apply the gel stretching method developed for ultra-high molecular weight polyethylene to various polymers. In order to apply this technology, a polymer with a high molecular weight is required, and it is expected that it will be useful when applying such technology in the future.

Patent applicant: Asahi Kasei Industries, Ltd.

Claims (1)

[Claims] A prepolymer mainly composed of polyhexamethylene terephthalamide with an intrinsic viscosity of 0.1 dl/g or more,
．． In the presence of 05-5% by weight of metal salts of hypophosphorous acid, 1
A method for polymerizing high molecular weight polyhexamethylene terephthalamide, which is characterized by polymerizing at a temperature of 50°C or higher and lower than the melting point under reduced pressure or an inert gas stream.