JPS5841296B2 - 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 polyamide composition that has excellent flame retardancy and can provide molded articles with good appearance using a simplified process.

Due to its excellent properties, polyamide is widely used in fields such as fibers, molded products, and adhesives, but depending on the application, a high degree of flame retardancy is often required.

A commonly known method for making polyamide flame retardant is to add flame retardants such as phosphorus, halogen, and nitrogen compounds.
There are various problems such as inhibition of the physical properties of polyamide itself, toxicity due to flame retardants, environmental pollution, corrosion of metals, etc., and it is strongly desired to realize flame-retardant polyamide that improves the above problems. Ta.

Recently, certain nitrogen-based compounds have attracted attention as effective flame retardants for polyamides, such as melamine (Japanese Patent Publication No. 49-1714), cyanuric acid (Japanese Patent Publication No. 1714-1982),
-105744) and melamine cyanurate (
JP-A-53-31759) and the like have been proposed.

However, in polyamide compositions containing melamine or cyanuric acid, the compound used as a flame retardant itself is sublimable, so plate-out of the flame retardant occurs during molding, which not only significantly impairs the surface appearance of the molded product. In particular, when the molded product is left in a high-temperature atmosphere, the flame retardant bleeds onto the surface of the molded product, causing a whitening phenomenon (bleed-out), resulting in a decrease in flame retardancy over time. be.

Furthermore, in a composition containing cyanuric acid melamine, which is an equimolar addition salt of melamine and cyanuric acid, plate-out and bleed-out as described above are improved;
Since cyanuric acid melamine has poor dispersibility in polyamide, in order to maintain the mechanical properties of a polyamide composition mixed with cyanuric acid melamine, for example, Japanese Patent Laid-Open No. 54
Measures such as using a dispersant as described in Japanese Patent No. 15955 are required.

In addition, to produce cyanuric acid melamine, melamine and cyanuric acid are added to about 20 times the amount of water, and this is mixed with 80 to 90 times the amount of water.
Melamine cyanurate produced in this way is naturally expensive, and requires many steps such as precipitation, filtration, drying, and pulverization after reacting at a high temperature of ℃. , economically disadvantageous.

Therefore, the present inventors conducted intensive studies with the aim of obtaining a polyamide composition that has excellent flame retardancy and mechanical properties, and can provide molded products with good surface appearance without plate-out or bleed-out. The inventors have discovered that the above objects can be achieved all at once by selecting a means for mixing cyanuric acid with polyamide, and have arrived at the present invention.

That is, the present invention provides flame retardancy characterized by melt-mixing a melt mixture of polyamide and melamine and a melt mixture of polyamide and cyanuric acid so that the melamine and cyanuric acid in the final composition are substantially equimolar. A method of manufacturing a polyamide composition is provided.

When polyamide is melt-mixed with an equimolar mixture of melamine and cyanuric acid, not only the flame retardance of the resulting composition is insufficient, but also plate-out and bleed of the molded product occur when the composition is molded. Surprisingly, the above-mentioned two-step melt-mixing method was adopted, in which melamine and cyanuric acid were melt-mixed separately for polyamide, and the molten mixtures were further melt-mixed. In some cases, it has been found that flame-retardant polyamide compositions with sufficiently excellent flame retardancy and without plate-out or bleed-out of molded products during molding can be economically advantageously obtained by a simplified process. It was.

As will be described later in Examples, this effect of the present invention is due to the fact that melamine and cyanuric acid easily react during melt mixing to form cyanuric acid melamine.

Although it is not clear why the reaction between melamine and cyanuric acid is accelerated during melt-mixing, it is thought that this is probably due to the fact that melamine and cyanuric acid are melt-mixed separately in polyamide, which improves their compatibility. It will be done.

In this way, the present invention does not involve melt-mixing preformed cyanuric acid melamine into polyamide as in the conventional method.
It is characterized by forming cyanuric acid melamine during melt mixing of polyamide, and this has the effect of improving the dispersibility of cyanuric acid melamine and shortening the process compared to conventional methods. .

The polyamide used in the present invention includes all kinds of polyamides obtained by polymerizing lactams or aminocarboxylic acids, or by reacting diamines with dicarboxylic acids or derivatives thereof, and includes homopolyamides. , copolyamides or blends of these polyamides can also be used.

For example, nylon 6.66.8.11.12.69.6
Homopolyamide such as 10.612, nylon 6/66
．． 6/12.6/6T, 667BAC·6 (T represents terephthalic acid, and BAC represents each residue of 1.3 or 1.4-bisaminomethylcyclohexane.

) copolyamides such as 6/66/12.6/610/
Also included are terpolyamides such as PACM.10 (PACM represents the residue of 4,4'-diaminodicyclohexylmethane).

However, as fibers and molding materials, nylon 6.66.610.11.12 and copolymers thereof are generally used from the viewpoint of economy, physical properties, etc., and are also preferable in view of the effects of the present invention.

The melamine used in the present invention is not particularly limited, but normal melamine powder manufactured and sold on the market as a raw material for so-called melamine-formaldehyde resin may be used as it is, or it may be recrystallized from water or pulverized. May be used.

However, more preferably, fine-grained melamine having an average particle size of 50 μm or less is used.

These melamines may be used in combination with derivatives in which part of their amino groups are substituted with other substituents, such as acetoguanamine, ethylmelamine, benzoguanamine, ammeline, etc., within the scope of the present invention.

The cyanuric acid used in the present invention may be either enol type (cyanuric acid) or keto type (incyanurate) represented by the following general formula (■), and fine-grained cyanuric acid with an average particle size of 50μ or less is preferably used. can.

These cyanuric acids also include cyanuric acid derivatives in which part of the -NH group or hydroxyl group is substituted with other substituents, such as thiocyanuric acid, 2-ethoxy-4,6-
Hydroxy S-triazine, tris(2-carboxyethyl)in cyanurate, etc. can be used in combination without departing from the spirit of the present invention.

The total amount of melamine and cyanuric acid in the final composition is 3 to 30% by weight, especially 5% by weight.
A range of ~20% by weight is effective; below 3% by weight, the effect of improving flame retardancy is insufficient, and above 30% by weight, the effect of improving flame retardancy is saturated and the properties of the polyamide itself deteriorate. Undesirable.

The amount of melamine and cyanuric acid blended is such that the two are substantially equimolar, and if the equimolar ratio of the two in the final composition deviates significantly, plate-out or bleed-out may occur in the composition. It is not desirable because

In the present invention, it is important to first melt-mix melamine and cyanuric acid separately to polyamide, and then further melt-mix these molten mixtures, and simultaneously melt and mix an equimolar mixture of melamine and cyanuric acid to polyamide. Even if mixed, the desired effect cannot be obtained.

Melt mixing in the present invention means heating the polyamide above its melting point and mixing the polyamide in a state where it is completely melted, and there is no need to heat it to a state where even melamine and cyanuric acid are melted.

The preferred melt mixing temperature is 5 to 80 degrees higher than the melting point of the polyamide.
℃ higher temperature range.

When preparing the melt mixture of polyamide and melamine and the melt mixture of polyamide and cyanuric acid,
It is only necessary to select conditions that can achieve homogeneous mixing of both.
The molten mixture herein includes both a state in which the polyamide is still molten after melt mixing and a state in which the molten mixture is shredded into pellets and solidified by cooling.

Next, examples of embodiments of the present invention include the following construction method.

(N) Add a predetermined amount of melamine to polyamide polymerized using a normal polymerization method, pre-mix using a Henschel mixer as necessary, melt mix using an extruder, and pelletize to form a polyamide/melamine molten mixture into pellets. Get it.

Similarly, a polyamide/siameric acid melt mixture is obtained in the form of pellets.

Next, in step L, both pellets are mixed so that the melamine and cyanuric acid in the final composition are substantially equimolar, and this is melt-mixed again in an extruder to form the desired composition into pellets. Alternatively, the mixture can be directly molded after being melt-kneaded by supplying it to an injection molding machine having a screw cylinder.

(B) In method (4) above, two extruders are
The polyamide/melamine molten mixture and the polyamide/siameric acid molten mixture are remixed in the molten state without pelletizing.

For example, a molten mixture of melamine and cyanuric acid is quantitatively taken out from two extruders so that the moles thereof are substantially equimolar, and then this is transferred to a molten mixer such as a high mixer or further installed. The mixture is fed to another extruder or an injection molding machine equipped with a screw cylinder, and mixing in the molten state is continued to obtain the desired composition in the form of pellets or directly as a molded product.

Among these, method (B) is advantageous in that it can shorten the steps.

Note that the embodiments of the present invention are not limited to the above methods (A) and (B), and other conditions may be set, for example, in the molten state immediately after polymerization, as long as the molten mixture can be melt-mixed again. It is possible to incorporate conditions such as a method of mixing a certain polyamide with melamine or cyanuric acid, a method of further melt-mixing a polyamide/melamine mixture in a molten state and a polyamide/cyameric acid mixture in a pellet state.

Further, when carrying out the present invention, when a small amount of water is present during melt mixing, the reaction and dispersion of melamine and cyanuric acid are further promoted, and more favorable results can be obtained.

Water can be added at any stage, but it is advantageous, for example, to use polyamide pellets containing moisture or to use wet, wet pellets during the second melt-mixing.

However, the amount of water used here is sufficient as long as it does not interfere with the melt-mixing operation; too much water is not preferable because it foams during melt-mixing, making the operation difficult and adversely affecting the physical properties of the polyamide.

When carrying out the method of the present invention, conventional dyes, pigments, fillers, fibrous reinforcing agents, plasticizers, heat and light resistance agents (e.g. hindered phenol compounds, phosphite compounds, copper compounds, etc.), lubricants and Mold release agents (e.g. higher fatty acids or their esters, amides, metal salts, paraffin, silicone oil, etc.), nucleating agents (e.g. talc, zeolite, clay, alumina, etc.) and antistatic agents (e.g. polyalkylene glycol, dodecylbenzenesulfonic acid) Additives such as soda, etc.) can be added at any stage.

According to the method of the present invention described above, the following advantages can be obtained.

(1) A polyamide composition with excellent flame retardancy can be obtained.

(2) Molded products made from the composition have a good appearance as there is no plate-out or blooming, and they can be safely used in precision parts, etc., and there is no need to worry about poor release during molding or contamination of the molded products. .

(3) A composition consisting of polyamide and cyanuric melamine can be obtained directly from inexpensive melamine and cyanuric acid without using cyanuric acid melamine obtained through a complicated and multi-branched process, and the process can be shortened.

(4) Melamine cyanurate in the resulting composition is well dispersed in polyamide.

The present invention will be specifically explained below with reference to Examples, but the present invention is not limited to the following Examples unless it exceeds the gist thereof.

The flammability in the examples is the result of measuring a test piece with a length of 5 inches, a width of 1/2 inch, and a thickness of 1/16 inch using a vertical combustion test specified in UL-94. Sometimes Black Master Pellet M
A UL-94 combustion test piece made by tri-blending 5 parts of 100B-1 (Toshi ■) with the pellet to be tested was processed in a constant temperature and humidity chamber at 40°C and 95% relative humidity for 7 days to produce a molded product. The appearance of precipitates on the surface was examined, and the evaluation was rated as ○ if no precipitation occurred at all, and × if white precipitation occurred.

The tensile test was measured according to ASTM-D638.

Example 1 After uniformly mixing 10 parts by weight of melamine with 6.100 parts by weight of nylon having a relative viscosity of 2.35 using a Henschel mixer, this was melt-mixed at 240°C using a 30 mm extruder to obtain a mixture containing melamine. Nylon 6 pellets were prepared.

Similarly, 10 parts by weight of cyanuric acid was melt-mixed with 6.100 parts by weight of nylon to prepare cyanuric acid-containing nylon 6 pellets.

After drying the melamine-containing nylon 6 pellets and cyanuric acid-containing nylon 6 pellets at 80°C for 16 hours under reduced pressure,
Equal amounts were blended in a tumbler and remelted and kneaded at 240°C using a 30mm extruder to form a 3.0 mm diameter x 3. OmmL
A white pellet was obtained.

A test piece was molded from this pellet using an injection molding machine and used for evaluation.

As shown in Table 1, the results were fully satisfactory in both flame retardancy and bleed-out characteristics.

For comparison, 10 parts of an equimolar mixture of melamine and cyanuric acid, which had been thoroughly mixed in advance, was added to 100 parts by weight of the nylon 6 used above, premixed in a Henschel mixer, and then mixed in a 30 mm IJ extruder. A melt-mixed polyamide composition was obtained.

Test pieces were molded from this composition using an injection molding machine and subjected to evaluation in the same manner as above, but as shown in Table 1, both flame retardancy and bleed-out properties were unsatisfactory.

From the results in Table 1, it is clear that the method according to the present invention provides a flame retardant material with sufficiently satisfactory bleed-out properties.

Next, 1/16" obtained by the above method of the present invention and comparative example
X-ray diffraction was performed on the thick UL test piece using an X-ray generator manufactured by Rigaku Denki ■.

The X-ray diffraction chart of the test piece obtained by the method of the present invention is shown in FIG. 1, and the X-ray diffraction chart of the test piece obtained by the method of the comparative example is shown in FIG.

As is clear from Figures 1 and 2, when an equimolar mixture of melamine and cyanuric acid is melt-mixed with polyamide (Figure 2), peak A of melamine and peak B of cyanuric acid are clearly recognized. On the other hand, when the mixing means of the present invention is selected (FIG. 1), the peaks of melamine and cyanuric acid disappear and a peak C of melamine cyanuric acid is formed.

Example 2 Using the melamine/nylon 6 composition, cyanuric acid/nylon 6 composition, and nylon 6 pellets prepared in Example 1, the ratios of melamine and cyanuric acid in the final composition were as shown in Table 2. The pellets were triblended, then melt mixed, molded, and evaluated in the same manner as in Example 1.

The results were as shown in Table 2.

Example 3 30-: Two IJ extruders were installed in parallel, the tip of each extruder was stationary, and an in-tube mixer (Imixer manufactured by Toshi ■)
The nylon/melamine and nylon/cyameric acid compositions kneaded by both extruders are continuously melt-mixed in a high-mixer, and a nozzle is provided at the other end of the high-mixer. We prototyped a device that

Using this equipment, the hopper of each extruder was filled with nylon 6
/melamine 85/15 (wt%) and nylon 6/cyanuric acid = 85/15 (wt%) were supplied and melt-kneaded at a polymer temperature of 250°C.

The test result of the obtained product was that the flame retardancy was UL94-V-0, and there was no bleed-out of the flame retardant.

In addition, it was found that the tensile strength was 790 kg/cvt, which was an excellent physical property value.

[Brief explanation of the drawing]

FIG. 1 shows an X-ray diffraction chart of a composition obtained by the method of the present invention, and FIG. 2 shows an X-ray diffraction chart of a composition obtained in a comparative example.

Claims (1)

[Claims] 1. A flame-retardant polyamide composition characterized in that a melt mixture of polyamide and melamine and a melt mixture of polyamide and cyanuric acid are melt-mixed so that the melamine and cyanuric acid in the final composition are substantially equimolar. manufacturing method.