JPH06287298A - Amorphous polyamide resin and its production - Google Patents

Abstract

PURPOSE:To obtain the subject resin having excellent gas-barrierness, transparency, moldability and mechanical properties by carrying out the polycondensation of a mixture of m-xylylenediamine and a specific dicarboxylic acid, etc., under specific condition. CONSTITUTION:The objective resin is produced by preparing a neutral salt of (A) m-xylylenediamine and (B) a dicarboxylic acid mixture of (i) one or more kinds of 7-20C aromatic dicarboxylic acid (derivative) such as isophthalic acid and (ii) one or more kinds of 5-20C saturated aliphatic dicarboxylic acid (derivative) such as adipic acid and containing 10-60mol% of the component (ii) based on the sum of the components (i) and (ii), preparing an aqueous solution of the neutral salt in nitrogen gas atmosphere to obtain a solution having an APHA value of <=50 (at 40wt.% concentration), concentrating the salt solution to 85-95wt.% under internal pressure of 2-4kg/cm<2>.G and subjecting to polycondensation under an internal pressure of <=2kg/cm<2>.G at an internal temperature of 200-240 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an amorphous polyamide having excellent gas barrier properties under low and high humidity, transparency, moldability and mechanical properties, and a method for producing the same.

[0002]

2. Description of the Related Art Recently, as a material excellent in gas barrier property, polyvinylidene dichloride containing halogen and ethylene / vinyl alcohol copolymer (EVOH) which is an alternative material of polyvinyl chloride have been used. E
VOH has problems such as poor thermal stability during molding and reduced barrier properties under high humidity. Therefore, there has been a demand for a material that does not deteriorate the barrier property even under high humidity.

As a resin excellent in gas barrier property, a polyamide resin (MXD.6) composed of metaxylylenediamine and adipic acid is also known (Japanese Patent Application Laid-Open No. 5 (1998) -5160).
8-11129), this resin also has a low gas barrier property under high humidity, and requires high temperature for melting due to its crystallinity, and is not a suitable material for coextrusion molding with a low melting point material such as polypropylene. There wasn't. Further, it is known that such a metaxylylenediamine-containing polyamide is liable to form a metaxylylenediamine dimer as a side reaction during polymerization and easily gelate with this as a cross-linking point (Japanese Patent Publication No. 35-7596). .

A polyamide resin composed of metaxylylenediamine, isophthalic acid and adipic acid, which is described in JP-A-48-36296, has a high gas barrier property even under high humidity and is amorphous, so that it is molded. Since the temperature can be lowered, it is useful for molding and the like. However, during the polymerization, a temperature much higher than 240 ° C. (about 270 ° C.) is required as in the case of the crystalline polymer, and it was difficult to suppress the dimerization of metaxylylenediamine at the temperature.

[0005]

When a metaxylylenediamine dimer, which is such a cross-linking point, is by-produced, the entire polymerization time is prolonged especially when the polymerization reaction is repeated and when the scale is increased. In such a case, the deterioration reaction extremely progresses, and the fluidity is lost due to gelation. Therefore, there is a strong demand for improvement for industrially stable production of a polyamide resin having a high gas barrier property even under high humidity by using a production method in which a metaxylylenediamine dimer is hardly produced as a by-product. It was

[0006]

Means for Solving the Problems As a result of intensive studies on the above problems, the present inventors have found that a polyamide resin containing specific components has a high gas barrier property even under high humidity, and The present invention has been accomplished by finding a stable manufacturing method. That is, the gist of the present invention is (1) metaxylene diamine, (2) (a) at least one aromatic dicarboxylic acid having 7 to 20 carbon atoms or a derivative thereof, and (b) at least one carbon atom having 5 to 20 carbon atoms. A mixture of saturated aliphatic dicarboxylic acids or derivatives thereof, which is obtained by polycondensation with a mixture of dicarboxylic acids in which the ratio of (b) to the total of (a) and (b) is 10 to 60 mol%. In the crystalline polyamide, the proportion of crosslinking points is 1 mol% of all diamine units in ¹ H-NMR analysis.
The present invention resides in an amorphous polyamide resin characterized by the following and a method for producing the same.

The present invention will be described in detail below. Metaxylylenediamine is used as the diamine component constituting the amorphous polyamide resin in the present invention. Also,
As the dicarboxylic acid component, aromatic dicarboxylic acids,
A mixture of aliphatic dicarboxylic acids is used.

The aromatic dicarboxylic acids include 7 to 20.
A dicarboxylic acid having 8 carbon atoms, preferably 8 to 14 carbon atoms, or a derivative thereof is used, and monocyclic dicarboxylic acids having a carboxyl group at the meta position are particularly preferable. Specifically, isophthalic acid, 2,5-pyridinedicarboxylic acid, 4,4′-diphenyldicarboxylic acid,
1,4-naphthalene dicarboxylic acid, 1,5-naphthalene dicarboxylic acid, 2,6-naphthalene dicarboxylic acid, 4,
4'-diphenyl sulfone dicarboxylic acid and the like,
Of these, isophthalic acid is preferable.

These aromatic dicarboxylic acids may be used alone or as a mixture. The aliphatic dicarboxylic acids have 5 to 20 carbon atoms, preferably 6 carbon atoms.
Dicarboxylic acids or derivatives thereof having ˜12 carbon atoms are used. Specific examples thereof include adipic acid, 2-methylglutaric acid, pimelic acid, corkic acid, azelaic acid, sebacic acid, and 1,10-decanedicarboxylic acid, and adipic acid is particularly preferable. These aliphatic dicarboxylic acids may be used alone or as a mixture. As the derivative of the aromatic dicarboxylic acid or / and the aliphatic dicarboxylic acid, an ester with a lower alcohol or the like is used.

The ratio of the aliphatic dicarboxylic acid to the total dicarboxylic acid component is 10 to 60 mol%, preferably 40 to
It is 60 mol%. When the proportion of the aliphatic dicarboxylic acid is less than 10 mol%, the gas barrier property of the obtained polyamide resin is extremely lowered and it is not suitable as a gas barrier material. If it is more than 60 mol%, the polyamide resin obtained will show crystallinity, so that the polycondensation temperature must be 250 ° C. or higher during the production, and if the polycondensation temperature becomes high in this way, it will deteriorate. Since the reaction becomes remarkable, stable production becomes difficult, which is not preferable.

Generally, a polyamide containing metaxylylenediamine as a diamine component is much more likely to cause a side reaction than a polyamide containing an aliphatic diamine, and deterioration reactions such as coloring and gelation are likely to proceed. It has been known. These conventionally known amorphous polyamides have a high production ratio of metaxylylenediamine dimer, which is a crosslinking point, of about 2 mol% of all diamine units. It has been found that the formation of dots is associated with poor flowability of the polyamide, i.e. deterioration of the resin. Furthermore, it has been found that by suppressing the cross-linking point to 1 mol% or less, it has an excellent effect on the deterioration reaction, and polycondensation is performed under specific conditions to provide such an amorphous polyamide. It was possible.

That is, the proportion of crosslinking points of the amorphous polyamide obtained by the present invention is 1 mol% or less of all diamine units according to the analysis using ¹ H-NMR. When the cross-linking point exceeds 1 mol%, the fluidity at the time of molding is deteriorated, and when the polymerization is repeated or scale-up is performed, the number of cross-linking points is increased, and finally a state of not flowing (gelation) is obtained. Therefore, it is not preferable.

The number average molecular weight of the polyamide in the present invention is 5,000 to 20,000, preferably 7,
It is in the range of 000 to 15,000. The polyamide resin in the present invention is manufactured by a melt polymerization method. That is, a neutral salt (hereinafter referred to as "nylon salt") composed of a mixture of (1) metaxylylenediamine, (2) a dicarboxylic acid mixture of an aromatic dicarboxylic acid or a derivative thereof and a saturated aliphatic dicarboxylic acid or a derivative thereof. A method is used in which the aqueous solution is heated and concentrated under pressure and polymerized in a molten state while removing added water and condensed water.

In the production of the polyamide resin of the present invention,
A particularly suitable method consists of the following four steps. That is,
(1) An aqueous solution of nylon salt is prepared, and (2) while keeping the aqueous solution at an internal pressure of ² to 4 kg / cm ² · G, water is evaporated to a concentration of 85% by weight or more and less than 95% by weight, (3) In a state where the internal pressure is reduced to ² kg / cm ² · G or lower, the temperature is heated to 200 ° C. or higher and lower than 240 ° C., and further condensed and condensed to synthesize a low polymer, and (4) temperature 200 to It is composed of a step of synthesizing a high polymer while further removing the condensation water while keeping the internal pressure of 2 kg / cm ² · G or less at 240 ° C.

In step (1), a nylon salt composed of a mixture of dicarboxylic acids of metaxylylenediamine and the above-mentioned aromatic dicarboxylic acids and saturated aliphatic dicarboxylic acids,
Add to water thoroughly degassed with nitrogen, stir and dissolve. The salt solution obtained is preferably not colored, and the APHA value at a concentration of 40% by weight is 50 or less, preferably 4
It is 0 or more, more preferably 30 or less.

The water used for dissolution needs to be degassed under a nitrogen atmosphere, but when oxygen removal is insufficient, the salt aqueous solution is colored yellow (APHA value of 50 or more) to obtain. Polyamide will also be colored. The polyamide resin obtained from the salt aqueous solution colored in this way is not preferable because the content of the metaxylylenediamine dimer is larger than that of the polyamide resin obtained from the uncolored salt aqueous solution and the gelation becomes extremely easy.

From the solubility curve of the nylon salt, the concentration of the salt aqueous solution is preferably about 40% to 50% (70 ° C to 80 ° C) in industrialization. Incidentally, a polymerization control agent such as acetic acid or an antioxidant such as phosphorous acid may be added to the nylon salt aqueous solution. In the step (2), the nylon salt aqueous solution prepared in the step (1) is charged into an autoclave sufficiently replaced with nitrogen, and heated and heated. Specifically, the internal pressure of the autoclave is 2-4 kg /
When the pressure reaches cm ² · G, open the valve and increase the internal pressure to 2
Gradually remove water while maintaining ~ 4 kg / cm ² · G. During this time, the temperature is continuously raised, and the salt concentration is 85% by weight or more,
Concentrate to less than 95% by weight.

At this time, when the concentration is concentrated to 80% by weight or more at an internal pressure lower than ² kg / cm ² · G, salt is precipitated during the concentration, and the obtained polyamide resin has a haze. Is not preferable. This is because, in the polyamide resin according to the present invention, the reactivity of the aliphatic dicarboxylic acid is considerably higher than the reactivity of the aromatic dicarboxylic acid, and therefore, one molecule of the aliphatic dicarboxylic acid and two molecules of metaxylylenediamine are used in the concentration step. React with each other to produce a new diamine, and the diamine and the aromatic dicarboxylic acid form a new salt. The newly formed salt is much less soluble than the initial nylon salt and is therefore prone to precipitation. Therefore, it is necessary to concentrate at an internal pressure of ² kg / cm ² · G or more to avoid the supersaturated region of the salt.

Further, if the internal pressure is higher than 4 kg / cm ² · G, the temperature at the end of the concentration must be raised, and in this case, the dimerization of metaxylylenediamine is promoted, which is not preferable. In step (3), the valve of the autoclave was gradually opened to reduce the pressure, and the internal pressure was 2 kg / cm ² ·.
G or less. Usually, when polymerizing 6-nylon or 6,6-nylon, the reaction is carried out under pressure after the concentration step, but in the case of the present polyamide resin, the metaxylylenediamine dimer is under pressure. The production of
Moreover, this tendency is particularly remarkable when the salt concentration is 90 to 100% by weight. Therefore, about 90% by weight of Nanron salt
It is preferable to quickly depressurize after concentrating the solution to the concentration.

After reducing the internal pressure to 2 kg / cm ² · G or less, the internal temperature of the autoclave is increased to 200 ° C. or more and less than 240 ° C., preferably 220 to 230 ° C.,
It is concentrated and condensed to form a low polymer. At this time, the internal temperature is 2
If the temperature is lower than 00 ° C, the polyamide does not flow and cannot be taken out from the polymerization tank after the polymerization, and if the temperature is higher than 240 ° C, the polyamide is significantly deteriorated and a phenomenon such as color gelation occurs, which is not preferable.

In the step (4), while maintaining the internal temperature at 200 ° C. or higher and lower than 240 ° C., preferably 220 to 230 ° C., the pressure in the autoclave is reduced and further condensation is carried out to obtain a high polymer of polyamide resin. To manufacture. Even in this case, if the internal temperature is 240 ° C. or higher, the deterioration reaction is promoted, which is not preferable. As described above, the polyamide resin according to the present invention specifically maintains the non-crystallinity, and its tendency does not change even in the middle stage of the polycondensation, so that the polymerization temperature is the lowest temperature at which the condensation proceeds. Even if the temperature was lowered to 200 ° C., melt polymerization proceeded without any problem, and at the same time, dimerization of metaxylylenediamine, which is a deterioration reaction, could be extremely reduced.

[0022]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples unless it exceeds the gist thereof. The following measured values in the examples were measured as follows.

(1) Ratio of Crosslinking Point Polyamide was hydrolyzed with 6N HCl, made basic with NaOH, and then extracted with chloroform. Next, chloroform was distilled off, the remaining oily substance was dissolved in deuterated chloroform, and ¹ H-NMR was measured. From the strength ratio of the methylene group adjacent to the primary amine and the methylene group adjacent to the secondary amine, the ratio (mol%) of the metaxylylenediamine dimer to the total base component was determined, and this was calculated as the crosslinking point ratio ( The number of crosslinking points).

(2) UV Absorbance Polyamide was dissolved in 98% H ₂ SO ₄ to prepare a 1% solution, and the UV-visible spectrum was measured. Λ = 468 nm
Absorbance (g ⁻¹ · dl · cm ⁻¹ ) was obtained and used as an evaluation scale of the degree of coloring of the product.

(3) Melt viscosity Using a flow tester CFT-SOO type (manufactured by Shimadzu Corp.), the melt viscosity at j = 100 1 / sec and a temperature of 230 ° C. was measured and used as a scale for melt molding.

(4) APHA value The color tone was measured according to ASTM D-1209. (5) Number average molecular weight The number of equivalents of all end groups (total equivalent of amino groups and carboxyl groups μeq / g) was determined and calculated by the following mathematical formula.

[0027]

[Equation 1]

Example 1 480 kg of water and 149 kg of metaxylylenediamine
And 91 kg of isophthalic acid and 80 kg of adipic acid were added under a nitrogen atmosphere and dissolved by stirring.
An aqueous nylon salt solution with a value of 25 (pH = 7.0) was obtained. Further, 986 g of acetic acid was added as a polymerization degree control agent and then charged into a 1 m ³ autoclave. The jacket temperature was set to 238 ° C, the internal temperature was raised, and the pressure was 3.5 kg /
When the pressure reached cm ² · G, water was distilled off so that the valve of the autoclave was opened to keep the pressure at the same pressure, and the mixture was concentrated for 8 hours until the salt concentration reached 90%. After the concentration is complete, open the autoclave valve further and the pressure becomes 0 kg.
/ Cm ² · G was gradually released over about 3 hours. After depressurization, the temperature was continuously raised while maintaining the same pressure, and when the internal temperature reached 230 ° C., the pressure was reduced to 300 mmHg, and the reaction was further continued for 1 hour. After the reaction was completed, the molten polyamide was extracted from the bottom of the autoclave in a strand form, cut into chips, and dried. This polyamide is colorless and transparent, and the ratio of crosslinking points (the number of crosslinking points) is 0.
It was 45 mol%. Next, as a result of repeating the polymerization four times, the number of cross-linking points of the obtained polyamide resin did not change, and no gel or the like was mixed. No haze, UV
The absorbance is as low as 0.02 g ⁻¹ · dl · cm ^−1, and the measurement result of the melt viscosity is also shown in Table 1,
It was confirmed that the fluidity during molding was good. Also,
The number average molecular weight was 10,000.

Examples 2 to 6 Using the amounts of isophthalic acid and adipic acid shown in Table 1,
A polyamide resin was produced in the same manner as in Example 1 except that the concentration step and the polymerization step were performed under the conditions shown in Table 1. Table 1 shows the analysis results of the obtained polyamide resin.

Example 7 Polymerization was carried out in the same manner as in Example 1 except that the concentration was carried out at 2.0 kg / cm ² · G up to 95%. The polyamide obtained had few crosslinking points and had good fluidity during molding, but haze was observed throughout the polymer.

Comparative Example 1 Polymerization was carried out in the same manner as in Example 1 except that the APHA value of the aqueous nylon salt solution was 200. The number of cross-linking points of the obtained polyamide was high as shown in Table 1, and the coloring was remarkable.

Comparative Example 2 Polymerization was carried out in the same manner as in Example 1 except that the polymerization pressure was 13.0 kg / cm ² · G. The number of cross-linking points of the obtained polyamide was as high as 1.40 as shown in Table 1, and when the polymerization was repeated 4 times, the number of cross-linking points increased to 1.90, which was further increased.

Comparative Example 3 Polymerization pressure was 4.0 kg / cm ² · G, and polymerization end temperature was 2
Polymerization was performed in the same manner as in Example 1 except that the temperature was 60 ° C. The cross-linking number of the obtained polyamide is 1.7 as shown in Table 1.
It is as high as 5, and by repeating the polymerization four times, it is further 2.3
It increased to 5, and at the end of the polymerization, it became difficult to extract it as a strand from the bottom of the autoclave.

Comparative Example 4 Polymerization pressure was 13 kg / cm ² · G and polymerization end temperature was 26.
Polymerization was performed in the same manner as in Example 1 except that the temperature was 0 ° C. The number of cross-linking points of the obtained polyamide is as shown in Table 1, and as a result of repeated polymerization, it was impossible to extract it at the fourth time.

Comparative Example 5 36 kg of water, 149 kg of metaxylylenediamine,
91 kg of isophthalic acid and 80 kg of adipic acid were charged into an autoclave in which the atmosphere was sufficiently replaced with nitrogen. The autoclave was sealed and the contents were melted and stirred at 220 ° C. for 1 hour. Then, after 1 hour, the internal pressure was reduced to atmospheric pressure, and at the same time, the internal temperature was raised to 275 ° C. The mixture was stirred at this temperature for 30 minutes while flowing nitrogen. Then the internal pressure is 0.3mmHg
It was depressurized to and stirred for 30 minutes. After the reaction was completed, the polyamide was extracted from the bottom of the autoclave. The obtained polyamide was colored yellow and the number of crosslinking points was 2.8 mol%.

[0036]

[Table 1]

[0037]

The amorphous polyamide resin of the present invention has a high gas barrier property even under high humidity and has an extremely excellent fluidity during molding. Further, the method for producing the polyamide resin of the present invention is a method suitable for industrialization because stable production is possible without affecting quality even when polymerization is repeatedly performed in the same polymerization tank.

Front page continued (72) Inventor Satoshi Yoshishima, 370 Enzo, Chigasaki, Kanagawa Mitsubishi Kasei Co., Ltd., Chigasaki Plant (72) Inventor, Yamamoto, No. 1000, Kamoshida-cho, Midori-ku, Yokohama, Kanagawa Sanryo Kasei Co., Ltd.

Claims (2)

[Claims] 1. A metaxylylenediamine, (2) (a) at least one aromatic dicarboxylic acid having 7 to 20 carbon atoms or a derivative thereof, and (b) at least one having 5 to 20 carbon atoms. Amorphous mixture obtained by polycondensation with a mixture of saturated aliphatic dicarboxylic acid or its derivative, wherein the ratio of (b) to the total of (a) and (b) is 10 to 60 mol% In the organic polyamide, the ratio of crosslinking points is 1 mol% or less of all diamine units in ¹ H-NMR analysis, and the number average molecular weight is 5,0.
An amorphous polyamide resin characterized by having a content of 00 to 20,000. 2. (1) Metaxylylenediamine, (2) (a) at least one aromatic dicarboxylic acid having 7 to 20 carbon atoms or a derivative thereof, and (b) at least one having 5 to 20 carbon atoms. A mixture of a saturated aliphatic dicarboxylic acid or a derivative thereof, wherein the water-solubility of a neutral salt of a mixture of dicarboxylic acids in which the ratio of (b) to the total of (a) and (b) is 10 to 60 mol%. The salt solution having an APHA value of 50 or less (concentration 40% by weight) is prepared under a nitrogen atmosphere, and the salt solution is then fed to an internal pressure of ^{2 to 4} kg / cm ^2.
G is concentrated to 85% by weight or more and less than 95% by weight, and then polycondensed at an internal pressure of 2 kg / cm ² G or less and an internal temperature of 200 ° C. or higher and 240 ° C. or lower.
A method for producing the described polyamide resin.