JPS5835610B2 - Method for producing flame retardant polyamide composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a flame-retardant polyamide composition having excellent heat resistance and mechanical properties and excellent moldability.

Polyamide is an excellent engineering resin that is widely used as a material for electrical parts, mechanical parts, etc. However, in recent years, the standards for use of electrical parts materials have been gradually raised, and higher flame retardancy has been required.

Until now, halogen-based flame retardants have been the mainstream flame retardants for polyamides, but although they provide excellent flame retardant effects, the decomposition gas generated during molding can corrode equipment, and when used There are drawbacks such as the generation of toxic gas and pollution problems when incinerating finished products.
There is a tendency to gradually replace them with nitrogen-based flame retardants.

By the way, among these nitrogen-based flame retardants, melamine (%B) is attracting particular attention in terms of its great flame retardant effect.
B47-1714) and cyanuric acid (Japanese Unexamined Patent Application Publication No. 1983)
-39750).

However, when melamine is blended with polyamide and molded, it becomes a white powder that adheres to the mold surface, forming a so-called mold deposit that may damage the shape of the molded product, or cause the molded product to be exposed to high temperature and humidity. When it is brought down, it stands out on the surface of the molded product, resulting in so-called bleed-out, which significantly impairs the appearance of the molded product.

On the other hand, cyanuric acid has the disadvantage that when it is blended with polyamide, it foams during melt-kneading or molding, causing strand breakage or creating air bubbles in the molded product, deteriorating the properties of the polyamide.

In order to improve these drawbacks of melamine and cyanuric acid, it has recently been proposed to use an equimolar reaction product of melamine and cyanuric acid, ie, melamine cyanurate, as a flame retardant.

However, although this product has improved the drawbacks of melamine and cyanuric acid mentioned above, it is still not fully satisfactory in terms of providing a higher degree of flame retardancy required for electrical component materials. .

The present inventors have conducted intensive research to develop a flame retardant that can overcome the drawbacks of melamine and cyanuric acid and provide superior flame retardant effects for polyamides. We proposed melamine percyanurate obtained by reacting with acid.

This melamine percyanurate is usually blended into polyamide by a method of melt-mixing it with polyamide in an extruder or injection molding machine.

However, this method is not economically efficient because the polyamide is once polymerized to form a solid in the form of pellets or powder, which is then remelted and mixed with melamine percyanurate.

As a result of further research into this compounding method, the present inventors found that by adding 103 to 150 moles of cyanuric acid per 100 moles of melamine to melamine during polymerization of polyamide, melamine percyanurate was added at once. We have found a way to obtain polyamide compositions.

Cyanuric acid reacts with many bases to form neutralized salts, and melamine also acts as a base and reacts with many acids to form neutralized salts.

Furthermore, when cyanuric acid alone or melamine alone is added during polyamide polymerization, cyanuric acid reacts with the amino end groups of the polyamide and blocks the ends, while melamine reacts with the carboxyl end groups of the polyamide. In both cases, it is known that the degree of polymerization of the polyamide is reduced because the terminal groups are blocked.

However, when 103 to 150 moles of cyanuric acid are added to melamine and cyanuric acid per 100 moles of melamine during polymerization of polyamide, the polyamide-forming monomer polymerizes with the polyamide-forming monomer or the polyamide end, and the melamine and cyanuric acid react with the polyamide. The melamine-cyanurate-containing polyamide composition is formed by selectively reacting between melamine and cyanuric acid to form melamine percyanurate without interfering with the polymerization of melamine or reacting with the polyamide-forming monomers or the polyamide ends. What I got was completely unexpected.

The present invention was made based on these findings, and in producing polyamide by polymerizing polyamide-forming monomers in the presence of water, melamine and a molar ratio of 103 to 150 to 100 of the melamine are used during polymerization. The present invention provides a method for producing a flame-retardant polyamide composition comprising polyamide and melamine percyanurate, which comprises adding and reacting cyanuric acid.

In the present invention, the method of polymerizing polyamide using an aqueous solution of a polyamide-forming monomer or a polyamide-forming monomer to which water is added as a starting material does not require any special method or polymerization conditions, and various well-known methods may be used. I can do it.

That is, a monomer such as a lactam such as ε-caprolactam, water, and if necessary a viscosity stabilizer such as a monocarboxylic acid or a reaction accelerator such as ε-aminocaproic acid are placed in a reaction vessel, and while passing an inert gas, the mixture is heated to
A normal pressure batch polymerization method for lactams in which the polymerization reaction is carried out by heating to 290°C for several hours to 20 hours, a method in which in the above polymerization method, the polymerization is sealed and pressurized at the beginning of the polymerization, and the polymerization is carried out under normal pressure or reduced pressure in the later stages; An aqueous solution of a polyamide monomer salt consisting of a diacid and a dibase such as ethylene diammonium salt (AH salt) and sebacic acid hexamethylene diammonium salt (SH salt) is heated to 220 to 290°C, and the generated water vapor pressure is reduced to 10 It is possible to optionally use a condensation polymerization method in which the pressure is concentrated and condensed while maintaining the pressure at an appropriate value between ~20 atmospheres, and finally the water vapor pressure is removed and the pressure is maintained at normal pressure or reduced pressure to complete the polymerization.

Of course, it is also possible to use a continuous polymerization method that is practiced industrially.

However, methods such as a method of polymerizing anhydrous lactam with an alkali catalyst, a method of heating polymerization of 11-aminoundecanoic acid, etc.
A method in which polymerization is initiated using a monomer system in the absence of water cannot be used because a sufficient amount of melamine percyanurate is not produced even if melamine and cyanuric acid are added.

Furthermore, melamine cyanurate is approximately 290°C at normal pressure.
Since decomposition starts from 200° C., it is necessary to maintain the temperature within the polymerization system at 290° C. or lower, preferably at 280° C. or lower.

Further, in order to uniformly disperse the produced melamine cyanurate into the polyamide, it is preferable to include a mixing device such as a stirrer.

As the melamine and cyanuric acid used in the present invention, commercially available powder or granule products may be used.

Cyanuric acid can have two tautomers; chemically, the enol form is usually called cyanuric acid and the keto form is called incyanuric acid, but the name cyanuric acid used in the present invention refers to only the enol form. It should be understood to include both the enol and keto forms.

There is no need to adopt any special method for adding melamine and cyanuric acid to the polyamide polymerization system, and a conventional method can be used.

For example, you can add powdered melamine and cyanuric acid as is, add water to melamine or cyanuric acid and make a slurry and inject it, mix melamine and cyanuric acid powder and then make a mixed powder, or make a mixed powder. A method can be used in which water is added as a mixture slurry IJ-.

However, the method of adding solid powder to the polymerization system is not very desirable as an industrial method because of the difficulty in handling the powder and the deterioration of the polymer caused by the introduction of air with the powder into the polymerization system. , a method of adding it as a slurry fluid is preferred.

Furthermore, if an aqueous solution of melamine or cyanuric acid is prepared and added to the polymerization system, the solubility of melamine or cyanuric acid in water is extremely low (2.5 f/1 in the case of melamine).
00 da water, 80°C: 2.5 f/10 for cyanuric acid
0 f? Water, 80°C), so adding a large amount of water to the polymerization system significantly delays the polymerization reaction, and in the case of batch polymerization, the reaction vessel must be significantly larger than the amount of polymer produced. There are many inconveniences (unfavorable).

The molar ratio of melamine and cyanuric acid in the present invention is melamine/cyanuric acid=-100/103 to Z
oo/150 (melamine/cyanuric acid-100/103
means that the molar ratio of melamine and cyanuric acid is 100:103
), preferably melamine/cyanuric acid=100/105 to 100/130, more preferably 100/110 to 100/130.

If the cyanuric acid content is less than 103 to melamine 100, high flame retardancy cannot be obtained, and if the cyanuric acid content exceeds 150, the degree of polymerization of the polyamide cannot be sufficiently increased, and the polyamide composition containing melamine percyanurate cannot be obtained. Mechanical and thermal properties deteriorate.

In the present invention, the amount of melamine and cyanuric acid added to the polymerization system is such that the sum of the amount of melamine and the amount of cyanuric acid is 2 to
It is preferably selected to be 30% by weight, particularly in the range of 3 to 15% by weight.

If this amount is less than 2% by weight, the flame retardance will be insufficient, and if it exceeds 30% by weight, the mechanical properties will be significantly reduced.

In addition, it is preferable that all of the added melamine and cyanuric acid be converted into melamine percyanurate, but melamine percyanurate should be used as long as there is no adverse effect on the polymerization reaction of polyamide or on the moldability of the melamine percyanurate composition. It is acceptable even if the production rate is slightly less than 100%.

Regarding the timing of addition of melamine and cyanuric acid during polyamide polymerization in the present invention, it is preferable to add them at the beginning of polymerization of the polyamide-forming monomer system, or at the early stage of polymerization when most of the polymerization system still exists as monomers or oligomers. .

If it is added in the late stage of polymerization, when most of the polymerization system is present as high molecular weight polyamide, melamine percyanurate will not be sufficiently produced, which is not preferable.

As the polyamide in the present invention, any of various commonly used polyamides can be used as long as it is a polyamide obtained by polymerizing an aqueous solution of a polyamide-forming monomer or a polyamide-forming monomer to which water is added.

Examples include nylon 6, nylon 66, nylon 12, nylon 610, nylon 612, and nylon 66/6 copolymer.

However, nylon 6 and nylon 66/6 copolymer are particularly preferred in consideration of the polymerization temperature and melt molding temperature of the polymer and the flame retardancy of the composition.

In addition, during polyamide polymerization in the present invention, pigments, heat stabilizers, antioxidants, light stabilizers, viscosity stabilizers, reaction accelerators, and other commonly used There is no problem even if additives are added in combination.

The method for producing the flame-retardant polyamide composition of the present invention involves three processes at once: synthesis of melamine percyanurate, polymerization of polyamide, and mixture of melamine percyanurate and polyamide. It has the advantage of being much cheaper to produce and more economical than independent methods.

The effects of the present invention will be explained in more detail with reference to Examples below.

The measurement method and evaluation method in each example were performed as follows.

Measurement of each component in the composition: Molding a flat plate of the composition, applying the molded flat plate to a Geigerflex DS type X-ray diffraction device manufactured by Rigaku Denki, and drawing a diffraction pattern at a diffraction angle in the range of 10 to 400 using a copper target. The presence or absence of melamine percyanurate, melamine cyanurate, melamine, and cyanuric acid was determined by the presence or absence of their characteristic diffraction peaks.

Flammability: UL-94 vertical flame testing was conducted on 1/16 inch thick injection molded specimens.

Molding processability: Regarding mold deposit, when injection molding molded test pieces for combustion test with a 5 oz injection molding machine,
The mold after 100 shots was observed to determine the presence or absence of mold deposits.

For bleed out, 6 inches x 172 inches x
A 1/8-inch rectangular injection molded product was left in a hot air oven at 150° C. for 10 days, and the surface of the molded product was observed.

Mechanical properties: ASTM-D-63 for tensile strength and elongation
8.For Izotsu impact strength (with notch), refer to AST
Measured according to M-D-256.

Example 1 (1) Preparation of polyamide-forming monomer aqueous solution: 90% by weight of bonding units corresponding to nylon 66 as a polymer component
, a nylon 66/6 copolymer containing 10% by weight of bonding units corresponding to nylon 6 (hereinafter Ny 66/6=90/1
The monomer aqueous solution necessary to produce 18.8 kg of adipic acid hexamethylenediammonium salt (hereinafter abbreviated as 50% AH salt) is converted into a 50% by weight adipic acid hexamethylene diammonium salt aqueous solution (hereinafter abbreviated as 50% AH salt).
It was prepared by mixing 39.2 kg of ε-caprolactam and 1.7 liters of ε-caprolactam.

(2) Concentration of polyamide-forming monomer aqueous solution: The polyamide-forming monomer aqueous solution prepared in (1) has a monomer concentration of 52% by weight, and the monomer aqueous solution is heated to remove water by evaporation and concentrated to a monomer concentration of 70% by weight. did.

(3) Addition of polyamide-forming monomer aqueous solution, melamine and cyanuric acid to the polymerization apparatus: heating jacket using Dowsum A as a heating medium, stirrer,
First, 30.7 kg of the polyamide-forming monomer aqueous solution concentrated in (2) was poured into an 801 pressure-resistant autoclave equipped with a pressure gauge, a thermometer, and a pressure regulating valve, and then melamine powder 551F (4.37 mol) and 1.5 mol of water were poured into it. A slurry of 5 kg was injected, and finally a slurry of 649 g (5.03 mol) of cyanuric acid powder and 8 kg of water was injected.

(4) Polyamide polymerization: Immediately after the injection operation shown in (3), the autoclave is sealed, and polyamide polymerization is started at a heating jacket temperature of 230°C.

FIG. 1 shows the relationship between the control of the heating jacket temperature and autoclave internal pressure during polymerization and the autoclave internal temperature time.

The broken line in the figure is the heating jacket temperature, the chain line is the autoclave internal temperature, and the solid line is the internal pressure.

After completing the polymerization in this way, open the valve at the bottom of the autoclave while lowering the internal pressure of the autoclave with nitrogen gas, and pour the molten polymer composition into strands from a die with four holes of 5 mm in diameter attached to the end of the valve. After discharging and cooling with water, the pellets were cut into cylindrical pellets with a diameter of 3 mm and a length of 3 mm using a cutter.

(5) Measurement and evaluation of polymer composition: Polymer composition obtained by the above operation, melamine percyanurate powder, melamine cyanurate powder, mixture of melamine powder and cyanuric acid powder, melamine cyanurate powder and cyanuric acid The mixture with the powder was subjected to X-ray analysis and an X-ray diffraction pattern was drawn.

The melamine percyanurate powder mentioned here and that of Comparative Example 1 are melamine/cyanuric acid-100/11.
Add 2 kg of water to 1 kg of a mixture of melamine powder and cyanuric acid powder with a molar ratio of 5 to form a slurry,
It was stirred at ℃ for 2 hours, dried and ground.

The results are shown in Figures 2a-e. The X-ray diffraction diagram of melamine percyanurate is characterized by a diffraction angle of 10° to 12°.

That is, for melamine percyanurate (Fig. 2b), a single peak is observed at 11° in this range, whereas for melamine cyanurate (Fig. 2C) and a mixture of melamine cyanurate and cyanuric acid ( In Figure 2 e), two peaks are seen, one each at 11° and 12°, and no peak is seen in the mixture of melamine and cyanuric acid (Figure 2 d).

The X-ray diffraction diagram (Figure 2a) of the composition of Example 1 shows an angle of 11°.
One peak was observed, indicating the presence of melamine percyanurate in the composition.

Moreover, from the above facts, it can be seen that what is present in the composition is not just a mixture of melamine and cyanuric acid, but also neither melamine cyanurate nor a mixture of melamine cyanurate and cyanuric acid.

Next, the flammability and moldability of the polymer composition were evaluated, and the results are shown in Table 1, indicating excellent flame retardancy and moldability.

Furthermore, the polyamide in the polymer composition was free from coloration or discoloration, and judging from the melt viscosity during injection molding, no signs of polymer deterioration or decrease in the degree of polymerization were observed.

Comparative Example 1 (1) Polyamide polymerization: The same nylon 66/6 copolymer (Ny 6
6/6=90/10) was polymerized and produced under the same polymerization conditions as in Example 1 without adding any melamine or cyanuric acid.

(2) Incorporation of melamine percyanurate into polyamide: The polyamide obtained in (1) (Ny66/6=90/I
O) Pre-mix 18.8 kg of pellets and 1.2 kg of melamine percyanurate powder, feed it to a 40 mm diameter extruder, extrude it into a strand at an extrusion temperature of 265°C, cool it with water, cut it with a cutter, and 3 door diameter rrt. A melamine percyanurate-containing polyamide composition in the form of a pellet having a length of 3 was obtained.

(3) Evaluation of composition: The polyamide composition containing melamine percyanurate was subjected to X-ray analysis under exactly the same conditions as in Example 1, and an X-ray diffraction pattern was drawn.

The results are shown in Figure 2f.

According to this, a diffraction peak peculiar to melamine percyanurate is seen, but when this is compared with Figure 2g, the intensity of the diffraction peak corresponding to melamine percyanurate is almost the same, so the polymer composition of Example 1 It is thought that the composition contains melamine percyanurate in a proportion comparable to that of the melamine percyanurate-containing polyamide composition of Comparative Example 1.

Next, the flammability and moldability of the polyamide composition containing melamine percyanurate were evaluated.

The results are shown in Table 1, and it can be seen that, like Example 1, it has excellent flame retardancy and moldability.

Comparative Example 2 Melamine powder 551f (4,37 mol) and cyanuric acid powder 649 were used instead of melamine percyanurate in Comparative Example 1.
A polyamide composition was produced in the same manner as in Comparative Example 1 using a mixture with P (5.03 mol), and X-ray analysis and evaluation of flame retardancy and moldability were performed.

The X-ray diffraction pattern is shown in Figure 2g, and it shows that melamine percyanurate was not detected, but diffraction peaks specific to melamine and cyanuric acid were detected, indicating that melamine and cyanuric acid were produced by extrusion with polyamide. It can be seen that no reaction occurred during melt mixing.

Furthermore, the evaluation results of flame retardancy and moldability are shown in Table 1, and it can be seen that the moldability is poor.

Example 2 and Comparative Example 3 Instead of the method of Example 1 in which melamine and cyanuric acid are added at the start of polymerization, a method of adding melamine and cyanuric acid after the start of polymerization was tried.

That is, the polyamide of Example 1 (Ny 66/6=9
o7'10) alone, and 30 minutes after the start, when the internal pressure was about 8 kg/crA (see Figure 1), a paste consisting of melamine 5511 and water 50 (l) and cyanuric acid 6491 and water 600f were added. A paste consisting of the following was injected under pressure and polymerized to produce a polymer composition (Example 2).

Further, 3 hours and 50 minutes after the start of polymerization, when the internal pressure was normal pressure, the same melamine paste and cyanuric acid paste as in Example 2 were injected, polymerization was continued, and a polymer composition was manufactured (Comparative Example 3).

When the polymer composition of Example 20 and the polymer composition of Comparative Example 30 were subjected to X-ray analysis, melamine persia nude was detected from the polymer composition of Example 20 as in Example 1, whereas in Comparative Example 30, melamine persia nude was detected from the polymer composition of Example 20. It was found that melamine percyanurate was not sufficiently produced in the polymer composition.

In addition, the flame retardancy and moldability of the polymer composition of Example 20 were evaluated.

The results are also shown in Table 1.

Example 3 and Comparative Example 4 In the same manner as in Example 1, a monomer aqueous solution to produce 18 kg of a nylon copolymer of Ny66/6-70/30, melamine 919f (7.3 mol), and cyanuric acid 108]
1 (8.4 mol) was used to produce a polymer composition (Example 3).

In addition, Ny66/6=70/30 nylon copolymer 1
Monomer aqueous solution and cyanuric acid 1081 to produce 9 kg
Polymerization was carried out using 1 kg (Comparative Example 4).

Table 1 shows the results of X-ray analysis, flammability, and moldability of the polymer composition obtained in Example 3.

On the other hand, in Comparative Example 4, when the discharge valve of the autoclave was opened after the polymerization was completed, a solution with extremely low melt viscosity was discharged, and a strand-like product could not be obtained.Therefore, composition pellets could not be obtained and the evaluation sample Could not be manufactured.

Examples 4 to 6, Comparative Example 5 200rnl equipped with a pressure gauge, pressure control valve, and stirrer
In an autoclave, monomers forming various polyamides 47.5P, melamine 1.15P, and cyanuric acid 1.
A mixture powder of 35f was added, and polymerization was carried out under standard polymerization conditions for various polyamides in order to obtain a polymer composition of 50P. I looked into it.

These experimental conditions and results are shown in Table 2.

In addition, in Example 4, when it was investigated whether melamine percyanurate was already formed at the time of starting polymerization by adding a mixture of melamine and cyanuric acid to the nylon 66 monomer aqueous solution, it was found that melamine and cyanuric acid were already formed. It existed as a precipitate without being dissolved, and melamine percyanurate was not detected.

Examples 7-11. Comparative Examples 6-8 Nylon 66/6 = 90/10 polymer at 18.8
The monomer aqueous solution required to produce 1 kg was concentrated in the same manner as in Example 1, and melamine and cyanuric acid were each added in the form of water paste in the following proportions, and the mixture was heated under the same conditions as in Example ①. Polymerization was performed to obtain a pelletized polymer composition.

Melamine 593'1f (4,70 mol), cyanuric acid 6
01' (4,70 mol) / Removal / Comparative Example 6 Melamine 58
7f (4,66 mol), cyanuric acid 61.1' (4,7
5 mol) --- Comparative Example 7 Melamine 584P
(463 mol), cyanuric 616 g (4.78 mol).
...Example 7 Melamine 578S' (459 mol), cyanuric acid ★★622P (4,82 mol)...
...Example 8 Melamine 564S' (4,48 mol), cyanuric acid 636 g (L93 mol)...°°°°
゛°Example 9 Melamine 51.5S' (4.09 mol),
Cyanuric acid 685f (5,31 mol)...Example 1 Melamine 473S' (3,75 mol), cyanuric acid 727y' (5,64 mol)...Execution Example 11 Melamine 43B? (3,48 mol), cyanuric acid 762P (5,91 mol) Comparative Example 8 The flammability and mechanical properties of the obtained composition were measured.

The results are shown in Table 3. It can be seen that if the molar ratio of cyanuric acid to 100 parts of melamine is less than 103, the flame retardancy will decrease, and if it exceeds 150, the viscosity of the polymer will decrease and the mechanical properties will also decrease.

[Brief explanation of drawings]

Figure 1 shows the polymerization conditions (internal pressure, heating temperature, internal temperature) for melamine and cyanuric acid-added polyamide polymerization in the method of the present invention.
A graph showing changes over time in FIG. 2 is a polyamide composition containing melamine percyanurate according to the present invention a, melamine percyanurate b1 melamine cyanurate C, and a mixture of melamine and cyanuric acid d1 melamine cyanurate and cyanuric acid. It is an X-ray diffraction diagram of a composition f in which a mixture e1 of melamine percyanurate and polyamide with an acid is cross-mixed using an extruder, and a polyamide composition g containing melamine and cyanuric acid.

Claims (1)

[Claims] 1. In producing a polyamide by polymerizing a polyamide-forming monomer in the presence of water, melamine and cyanuric acid in a molar ratio of 103 to 150 to 100 of the melamine are added and reacted during the polymerization, A method for producing a flame-retardant polyamide composition comprising polyamide and melamine percyanurate.