JPS63207824A - Post-treatment of polyamide based polymer - Google Patents

Abstract

PURPOSE:To efficiently remove an anionic polymerization catalyst in a polyamide based polymer in a relatively short time, by bringing the polyamide based polymer into contact with an aqueous solution of a weak acidic organic compound having a specific acid dissociation constant. CONSTITUTION:(A) A polyamide based polymer obtained by anionic polymerization of a lactam is brought into contact and post-treated with (B) an aqueous solution of a weak acidic organic compound having 2-12 acid dissociation constant (e.g. ethyl acetoacetate). Furthermore, the concentration of the component (B) in the aqueous solution is preferably, e.g. 0.0001-0.5wt.% and the amount of the component (B) is preferably 0.05-20pts.wt. based on 100pts.wt. component (A).

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for treating a polyamide-based polymer obtained by anionic ring-opening polymerization of a lactam, which is widely used as nylon, after polymerization.

In particular, it relates to a method for removing catalyst components used in polymerization.

<Prior art> Polyamide polymers obtained by anionic polymerization of lactams are processed in a molten state, and due to the action of anionic polymerization catalysts remaining in the polymers, the viscosity becomes unstable, the amount of residual lactams increases, etc. It is known that it has the following disadvantages.

For example, the instability of the viscosity of polycaprolactam in the molten state is explained by Sorenson and Campbell's Preparative Methods of Polymer Chemistry (Preparative Methods of Polymer Chemistry).
active Methods of PolymerC
hemistry) 2nd plate Shinbelay & Sons Co. 19
It was published in 1968.

The instability of the viscosity of polycaprolactam in its molten state is described in Japanese Patent Publication No. 54339/1983.

Due to these drawbacks, polyamide polymers obtained by anionic polymerization of lactams have not been widely used in melt processing such as injection molding.

Therefore, as methods for stabilizing polyamide polymers obtained by anionic polymerization, methods such as washing out the anionic polymerization catalyst and deactivating the anionic polymerization catalyst with additives have been studied.

First, as a method for washing out anionic polymerization catalysts,
A method of cleaning with an aqueous solution of hydrogen phosphate or an alkali metal salt is known, as disclosed in Japanese Patent No. 0-123688.

Furthermore, as a method for deactivating anionic polymerization catalysts with additives, Japanese Patent Publication No. 56-54338 describes the general formula (wherein R1 and R2 are an alkyl group or an alkoxy group, and R3 is hydrogen or an alkyl group). ) A method for adding the compound shown in
6-54339 discloses a method of adding a tertiary alcohol.

<Problems to be solved by the invention> However, the conventionally known stabilization method, that is, the method of washing out the anionic polymerization catalyst with an aqueous aqueous alkali hydrogen phosphate solution,
Any method of adding additives to the polymer to deactivate the anionic polymerization catalyst is insufficient.

In addition, in the method of deactivating the anionic polymerization catalyst with an additive, it is necessary to add the additive in an amount equal to or more than the anionic polymerization catalyst, and this additive bleeds out onto the surface of the polyamide polymer, resulting in product damage. It spoils the appearance.

Means for Solving the Problems> The present invention provides polyamide polymers obtained by anionic polymerization of lactams with an acid dissociation constant (hereinafter referred to as pKa) of 2.
This is a method for post-treatment of a polyamide-based polymer, characterized by bringing it into contact with an aqueous solution of a weakly acidic organic compound.

The organic weakly acidic compound having a pKa of 2 to 12 used in the present invention may be any compound having a pKa of 2 to 12 in water at 25°C.

Specifically, acetic acid, propionic acid, hydroxyacetic acid, chloroacetic acid, formic acid, butyric acid, benzoic acid, phthalic acid, tartaric acid, citric acid, malic acid, phenylacetic acid, maleic acid, fumaric acid, malonic acid, methylmalonic acid, dimethyl Carboxylic acids such as malonic acid; General formula (wherein R1 and R1 are each independently selected from the group consisting of a saturated aliphatic hydrocarbon group, an aromatic hydrocarbon group, and an alkoxy group, and R3 is hydrogen or an aliphatic hydrocarbon group) ), such as diethyl malonate, dimethyl malonate, ethyl acetoacetate, methyl acetoacetate, acetylacetone, diethyl methylmalonate, diisopropyl acetoacetate, methyldipropionylmethane, benzoylacetone, etc. can be given.

Preferred are ethyl acetoacetate, methyl acetoacetate and acetylacetone.

The acidity of these compounds is sufficient to remove the anionic polymerization catalyst, but not so strong as to cleave the polyamide polymer chains.

Therefore, even if the above-mentioned compound remains after the polyamide polymer is washed by the method of the present invention, it does not affect the processing stability of the polyamide polymer.

In addition, pKa as used in the present invention refers to the pKa of a certain acidic compound.
When HA is dissociated in water, it is given by the following formula.

HA:H" +A- Kam(H"") (A-)/ ()(A)pKa-
-1og+oKa Langes is a data collection containing this pKa value.
Handbook Op Chemistry (LANGE'S
HANDBOOK OF CHHMISTRY),
J.A.

Dean (J, A, DI! 8N AI, published by McGraw-Hill Publishing), Chemistry Handbook Fundamentals mn (Japan Chemical Society is famous).

The polyamide polymer to which the method of the present invention is applied may be any polyamide polymer obtained by anionic polymerization of lactam, such as a homopolymer, a block copolymer, or a graft copolymer.

These polyamide-based polymers are known to contain lactams having 4 to 12 carbon atoms, such as ε-caprolactam and ω-dodecalactam, at a temperature above or below the melting point of the polyamide-based polymer in the presence of an anionic polymerization catalyst. It is manufactured according to the method of

Methods for producing homopolymers such as polycaprolactam and polydodecalactam are described in Sorenson and Camben's Preparative Materials of Polymer Chemistry (Pr.
eparative? Letho-ds of Po
The method for producing polyamide block copolymers consisting of a polylactam polymer portion and other polymer portions is described in detail in the second plate (published by John Belay & Sons, 1968).
-40120 publication, U.S. Patent No. 3862262, U.S. Patent No. 40
Journal Op.
Polymer Science (Journal of Po-
Po-1y 5science) -Volume 34 309-3
17 pages (published in 1959), US Patent No. 3,136,738
etc. are shown.

As shown in these known documents, anionic polymerization catalysts for lactam include alkali metals, alkaline earth metals,
These hydrides, oxides, carbonates, alkoxides, Grignard reagents, and reaction products of the above metal compounds with lactams, such as sodium salts, potassium salts, chloromagnesium salts, bromomagnesium salts of C-caprolactam, and i. Odomagnesium salt etc. are used.

Note that these anionic polymerization catalysts remain active in the polymer even after completion of polymerization.

Among the polyamide-based polymers mentioned above, the polymers that exhibit more remarkable effects according to the present invention are block copolymers, especially those selected from the group consisting of polyoxyalkylene, polybutadiene, polydimethylsiloxane, and aliphatic polyester. A block copolymer of one or more polylactam polymer moieties and a polylactam polymer moiety, and further a polyether polylactam block copolymer.

Applying the method of the present invention to these block copolymers not only stabilizes the polylactam polymer portion of the block copolymer, but also thermally decomposes the polymer chains of polyoxyalkylene, polybutadiene, polydimethylsiloxane, and aliphatic polyester portions. It also suppresses oxidative decomposition and exhibits particularly high effects.

Furthermore, thermally unstable water-insoluble oligomers can also be extracted and removed.

Further, the polyamide polymer is preferably in the form of a powder, a thin film, or a flake (fine shapes are preferable).

Methods for obtaining fine polyamide-based polymers include pulverizing polymers obtained by bulk polymerization, lactam solution-precipitation polymerization, non-aqueous suspension polymerization, etc. There is a way to get it.

Among these, suspension polymerization is suitable for the present invention.

In this suspension polymerization, lactam is polymerized in an anionic polymerization catalyst in an anionic polymerization activator in an anionic polymerization catalyst at a temperature below the melting point of the resulting polyamide-based polymer to obtain a polyamide-based polymer in the form of powder particles. It's a method.

This polymerization method itself is well known and is disclosed, for example, in Japanese Patent Publication No. 10636/1983.

Polyamide polymers produced in the form of powder by suspension polymerization not only have a small particle size, but also are porous and have a large specific surface area.

Therefore, for the purpose of the present invention, it is more suitable than a powder produced by pulverization, and the anionic polymerization catalyst can be efficiently extracted in a short time even under mild washing conditions.

Moreover, it is preferable that the polyamide polymer obtained by this suspension polymerization does not contain coarse particles.

For this purpose, a basic nitrogen-containing polymer as shown in JP-A No. 57-98513 or a carboxyl group-containing polymer as shown in JP-A-57-98512 is used as a suspension stabilizer during suspension polymerization. It is better to use polymers.

The aqueous solution concentration of the organic weakly acidic compound of the present invention is about 0.00
01% to 0.5% by weight.

If it is thinner than 0,0001% by weight, the amount of aqueous solution will be large,
This is not preferable because it takes time to handle and the device becomes large.

If it is 0.5% by weight or more, the effect may be exhibited even though the concentration is high, but it is not economically preferable.

The weakly acidic compound is used in an amount of 0.01 parts by weight or more and 50 parts by weight or less, preferably 0.05 parts by weight or more and 20 parts by weight or less, based on 100 parts by weight of the polyamide polymer.

If it is less than 0.01 part by weight, the residual anionic polymerization catalyst will not be removed sufficiently, which is undesirable, and if it exceeds 50 parts by weight, it will be ineffective and economically wasteful.

A well-known solid-liquid mixing method may be used to bring the aqueous solution of the organic weakly acidic compound into contact with the polyamide polymer.

Examples include a method in which a tower is filled with a polyamide polymer and the aqueous solution is passed through the tower, and a method in which the polyamide polymer and the aqueous solution are charged in a tank and stirred.

The treatment temperature is 0°C or higher and lower than the softening temperature of the polymer, preferably 20°C or higher and 200°C or lower.

If the temperature is lower than 0°C, the removal rate of the anionic polymerization catalyst becomes significantly slow, which is not preferable.

The contact time varies depending on the temperature, the type of weakly acidic organic compound, etc., but most of the anionic polymerization catalyst can be removed within about 5 hours.

After contact, the mixture of the aqueous solution and the polymer becomes a normal solid.
It is separated by a liquid separation method such as filtration, centrifugation, sedimentation, etc., and if necessary, it is further washed with only water and then dried.

When the polyamide polymer from which the anionic polymerization catalyst has been removed by the method of the present invention is actually used, for example, as a molding material, in order to further enhance the stabilizing effect of the present invention, it is necessary to use known antioxidants used for polyamide polymers. Agents, heat stabilizers, and light stabilizers can be used.

In addition, pigments, dyes, fillers, etc. may be mixed.

<Effects of the Invention> According to the method of the present invention, most of the anionic polymerization catalyst in the polyamide polymer can be efficiently removed in a relatively short time.

Therefore, stability during melt processing is increased, and foaming and coloring due to thermal decomposition of the polyamide polymer itself can be suppressed.

The effects of the present invention are particularly remarkable when applied to polyamide block copolymers, such as polyether polyamide block copolymers obtained by anionic polymerization. Improvement in mechanical properties can be seen.

<Example> In this example, the metal content in the polyamide polymer was determined using a dry atomic absorption spectrophotometer.

Examples 1-3 ■Synthesis of suspension agent 62 g of 2-ethylhexyl acrylate and N.

4.66 g of N-dimethylaminoethyl methacrylate and 0.333 g of azobisisobutyronidonyl were added to 300 mj of isooctane! and charged into a 500ml round bottom flask.

After bubbling nitrogen into the liquid in this flask for 30 minutes, stirring was started and the temperature was raised to 60°C over 30 minutes.

The mixture was stirred as it was at 60°C for 3 hours, the reaction temperature was raised to 70°C, and the mixture was further stirred for 2 hours to obtain an isooctane solution of 2-ethylhexyl acrylate-N,N-dimethylamine ethyl methacrylate copolymer.

■Manufacture of nylon 6 by suspension polymerization 2! Add the above 2-ethylhexyl acrylate N to the flask.
, 36.8 g of isooctane solution of N-dimethylaminoethyl methacrylate copolymer and 1200 g of isooctane
ml to make it uniform.

This solution was heated to 98° C., and about 120 mff of isooctane was distilled out while dry nitrogen was blown into the solution, making the system substantially anhydrous.

In another container A, 4 g of adipoyl biscaprolactam and 193.6 g of caprolactam were dissolved and mixed and kept at 80°C. In another container B, 1 g of anhydrous ε-caprolactam was dissolved and mixed.
A mixture of 94.4 g and 8 g of 6-caprolactam magnesium iodide was kept at 80°C.

The liquids in containers A and B are mixed by rapid shaking at a temperature of 80 ° C., poured into the above isooctane solution kept at 98 ° C., and dispersed by stirring at a rotation speed of 400 μm.
Suspension polymerization was performed.

The polymerization reaction was completed in one hour, and the resulting slurry was filtered and dried to obtain 320 g of nylon-6 powder.

The particle size of the sieved portion was 540 μm, and the magnesium content was 1830 ppm.

(2) Post-treatment of nylon 6 50 g of the above nylon 6 powder, 150 mN of water, and 1 g of the weak acids and compounds shown in Table 1 were mixed and heated at 80° C. for 3 hours with stirring.

Thereafter, the nylon 6 powder was separated from the cleaning solution by filtration and recovered.

The nylon 6 powder was further washed with 150 ml of pure water in a defilter.

Nylon 6 powder taken out from the defilter was heated to 100°C under reduced pressure.
to obtain a dried nylon 6 powder.

The magnesium content in the obtained nylon 6 powder is shown in Table 1.

95% of the polymerization catalyst was removed in about 3 hours.

Example 4 ■ Production of nylon 6 by bulk polymerization 29.4 g of dried ε-caprolactam and 0.6 g of adipoyl biscaprolactam synthesized by reacting adipic acid chloride with caprolactam were mixed and the mixture was heated at 80°C. A homogeneous solution was prepared by heating and stirring and was designated as Solution A.

In a separate container, 28.8 g of dried ε-caprolactam and 1.2 g of caprolactam magnesium iodide were charged and dissolved to prepare a B solution.

After uniformly mixing these two liquids at a temperature of 80°C,
The mixture was poured into a glass cast cavity with a thickness of 3 cranes and kept warm for 10 minutes.

After that, the frame was cooled and the frame was opened to form a plate-like nylon hexapolymer, approximately 60%
I got g.

■ Post-treatment of nylon 6 The resulting plate-shaped polymer was finely ground with a hammer and sieved to produce an average particle size of 970μ and magnesium content of 1800p.
40 g of pm powder was obtained.

This was washed with the weakly acidic compound shown in Table 1 in the same manner as in Examples 1 to 3, and then dried to obtain 36 g of polymer.

Table 1 shows the magnesium content in this polymer.

Examples 5 to 7 (Treatment of polyamide block copolymer by suspension polymerization) In Example 1-■, the contents of container A were
12825 Example 6, except that 197.6 g of terminally carbonyl lactamated polytetramethylene glycol (number average molecular weight: about 3130) was used, and 380 g of nylon 6-polytetramethylene glycol block copolymer powder was prepared in the same manner. Obtained.

The particle size of the sieved portion by method was 630 μm, and the magnesium content was 1880 ppm.

50 g each of this powder was mixed with 150 mJ of water and 1 g of the weakly acidic compound shown in Table 1, and washed by the method of the present invention in the same manner as in Examples 1 to 3.

The magnesium content in the dried nylon 6-polytetramethylene glycol block copolymer obtained is shown in Table 1.

Table 1 Example 8 (When the catalyst residue contains sodium salt) ε-caprolactam 194.
The procedure of Example 5 was repeated, except that 201.4 g of ε-caprolactam and 1.0 g of sodium hydride were used instead of 4 g of ε-caprolactam magnesium iodide and 8 g of ε-caprolactam magnesium iodide. 360 g of methylene glycol block copolymer powder was obtained.

The sodium content in this powder is 2430 ppm
Met.

50 g of this powder was mixed with 150 mjt of pure water and 1 g of acetic acid, and treated in the same manner as in Example 5.

Sodium content is 7 ppm, 99% of total sodium
．． It can be seen that 7% was removed in just 3 hours of washing.

Claims (1)

[Claims] (1) A polyamide polymer obtained by anionic polymerization of lactam has an acid dissociation constant (hereinafter referred to as pKa) of 2 to
1. A method for post-treatment of a polyamide-based polymer, which comprises bringing it into contact with an aqueous solution of a weakly acidic organic compound according to No. 12.