JPS5842218B2 - Flame retardant polyamide composition - Google Patents

Description

Detailed Description of the Invention The present invention has low toxicity, excellent heat resistance and mechanical properties,
And 5! , relates to a flame-retardant polyamide composition with excellent shape processability.

Polyamides, especially nylon 66 and nylon 6, have excellent heat resistance and mechanical properties, and are used as molding materials in a wide range of fields including electrical and mechanical parts.

However, in the field of electrical components, recent revisions to UL standards have required molding materials to have higher flame retardancy.

On the other hand, sanitary laws and regulations have been tightened, and products with lower toxicity are now required.

In response to these circumstances, halogen-based flame retardants that have conventionally been used as flame retardants for polyamides have a toxicity problem.

On the other hand, melamine and cyanuric acid are known as relatively low-toxic flame retardants for polyamide (the former is disclosed in Japanese Patent Publication No. 47-1714 and U.S. Patent No. 366034).
No. 4 (for the latter, see Japanese Patent Application Laid-open No. 51-39750)
.

However, melamine has a limited flame retardant effect, but has sublimation properties, so when a polyamide composition containing melamine is melt-molded, the melamine sublimes and adheres to the mold, contaminating the mold. A so-called mold deposit phenomenon occurs, and if the composition molded product is left unattended, melamine comes out on the surface of the molded product, a so-called bleed-out phenomenon, which significantly impairs the appearance of the molded product and impairs molding processability. There is a big problem with this.

Cyanuric acid also lacks high-temperature stability and foams when melt-kneading cyanuric acid and polyamide, and when a cyanuric acid-containing polyamide composition is melt-molded, air bubbles are mixed into the molded product, making it impractical.

Polyamide compositions in which both melamine and cyanuric acid are mixed with polyamide are also known (Japanese Patent Laid-Open No. 51-54
(Refer to No. 655), the composition cannot prevent mold deposits during molding or fleet out of molded products.O The present inventors took these circumstances into account and conducted extensive studies, and found that melamine and cyanuric acid It was discovered that melamine cyanurate, which is a reaction product of polyamide, has a flame retardant effect on polyamide. When blended with melamine cyanurate, it has both high heat resistance and mechanical properties, and has excellent molding processability without mold deposits during molding, no air bubbles in the molded product, and no bleed-out of the molded product. The present inventors have discovered that it is possible to obtain a polyamide composition having the same properties as above and exhibiting excellent flame retardancy, leading to the present invention.

That is, the present invention is composed of polyamide and melamine cyanurate, and the polyamide contains 95 to 65% by weight of bonding units corresponding to nylon 66 and 5 to 35% by weight of bonding units corresponding to nylon 6 as polymer components. /6 copolymer and has a melamine cyanurate content of 2 to 30% by weight.

The effects of the present invention are that a high degree of flame retardancy can be imparted without substantially impairing excellent heat resistance and mechanical properties, and there is no need to worry about hygienic problems. There is no mold deposit, no air bubbles in the molded product, and no bleed-out of the molded product.

The polyamide of the present invention is a nylon 66/6 copolymer, with 95 to 65% by weight of bonding units corresponding to nylon 66,
It preferably consists of 93 to 85% by weight, 5 to 35% by weight of bonding units corresponding to nylon 6, preferably 7 to 15% by weight.

If the bonding units corresponding to nylon 6 are less than 5%,
Air bubbles are mixed in when the composition is molded, which not only significantly impairs the appearance of the molded product, but also significantly reduces mechanical properties, making it impractical.

In addition, the copolymer has 35 bonding units corresponding to nylon 6.
If the content exceeds 5%, the mechanical properties of the nylon 66/6 copolymer itself will be poor, and the flame retardant effect of melamine cyanurate will be insufficient, which is not preferable.

The nylon 66/6 copolymer is industrially manufactured by copolymerizing a salt of adipic acid and hexamedenediamine (AH salt) with ε-caprolactam. It is not necessarily limited to this, and ε−
ε-aminocaproic acid may be used instead of caprolactam, or nylon 66 and nylon 6 may be melt-kneaded,
It may also be produced by an amidation exchange reaction.

The polymer component ratio in the present invention is the weight of the portion based on the AH salt and the portion based on ε-caprolactam in the main chain of the copolymer, that is, the weight percent of each monomer participating in the copolymerization is , calculated by taking into account the amount of water dehydrated during copolymerization.

The melamine cyanurate of the present invention is a reaction product of melamine [see structural formula (I)] and cyanuric acid.

Note that cyanuric acid can have two tautomers as shown in the structural formula (If), and chemically, the enol type is usually called cyanuric acid and the keto type is called incyanuric acid, but the cyanuric acid used in the present invention The name acid is not a chemical name that refers only to the enol form, but a general name that refers to both the enol and keto forms.

That is, cyanuric acid as used in the present invention is enol-type cyanuric acid or keto-type isocyanuric acid.

The reaction between melamine and cyanuric acid usually occurs via water.

Melamine is slightly soluble in water and its aqueous solution is weakly alkaline, and cyanuric acid is also slightly soluble in water and its aqueous solution is weakly acidic. When mixed to equimolar proportions, melamine cyanurate reacts immediately and forms a white precipitate, and the supernatant liquid becomes neutral.

In this reaction, as shown in formula (I), melamine as a base undergoes a neutralization reaction with cyanuric acid as an acid, and it is thought that melamine cyanurate as a neutralized salt is produced.

C3N6H6+C3N303H3→CaNaHa・C3
N303H3 (Melamine) (Cyanuno 14) (Melamine Cyanurate) (I) The fact that proves that the white precipitate produced by this reaction is not just a mixture of melamine and cyanuric acid but a different compound is ( 1) The solubility of melamine in water is 2.5 g/l
00 & water (80°C), the solubility of dianuric acid in water is 2.5 g/l 00.9 water (80°C), whereas the solubility of the white precipitate, which is melamine cyanurate, in water is (2) Even if the molar ratio of melamine and cyanuric acid as reaction raw materials is changed, the elemental analysis value of the white precipitate produced is always C6N903) TQ, i.e. , CaNaHa・
(3) When the infrared absorption spectrum of the white precipitate is measured, the absorption spectrum is completely different from that of melamine, cyanuric acid, or a mixture of melamine and cyanuric acid (Figures 1 to 4). ), etc.

The method for producing the melamine cyanurate of the present invention is not particularly limited.

Usually, a method is used in which melamine cyanurate, which is produced by mixing an aqueous melamine solution and an aqueous cyanuric acid solution, is added to the polyamide.

The method of producing melamine cyanurate by blending melamine and cyanuric acid with polyamide and mixing the three is not preferred because it is difficult to actually produce melamine cyanurate.

The melamine cyanurate used for the purpose of the present invention does not necessarily need to be completely pure, and can be used even if it contains very small amounts of unreacted substances, impurities, etc.

In addition, the shape of melamine cyanurate has an average particle size of 200 μm.
The following fine powders are preferred.

When the average particle size exceeds 200μ, it becomes difficult to uniformly disperse the particles into the polyamide, and the mechanical properties of the polyamide composition are significantly deteriorated.

In the polyamide composition of the present invention, the melamine cyanurate content is 2 to 30% by weight, preferably 4 to 15% by weight.

If the content is less than 2% by weight, flame retardancy will be insufficient, and if it is included in excess of 30% by weight, molding fluidity will be poor and mechanical properties will also be degraded, making it impractical.

The flame-retardant polyamide composition of the present invention may also contain dyes and pigments, lubricants, plasticizers, stabilizers, antistatic agents, and other commonly used additives as long as they do not impair the effects of the present invention.

In the present invention, there are no particular limitations on the method for mixing melamine cyanurate with polyamide, and methods commonly used for mixing powdered additives with polymers can be applied.

However, in order to improve the dispersion of melamine cyanurate, it is generally preferable to knead melamine cyanurate into the polymer using an extruder or the like.

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

Measurement and evaluation of evaluation items in each example were performed as follows.

O] Flammability: UL-94 vertical combustion test with 1/3 thickness
The test was conducted on a 2-inch molded test piece.

(2) Molding Processability Regarding the two-mold deposit, when molded test pieces for combustion tests were injection molded using a 5-ounce injection molding machine, the presence or absence of the mold deposit was determined by observing the mold during molding.

6 inches x 1/2 inch x 1 for bleed out
A rectangular molded product of /8 inch was left in a hot air oven at 150°C and an atmosphere of 60°C x 95% relative humidity for 10 days, and the surface of the molded product was observed.

■ Mechanical properties: ASTM l)- for tensile strength and elongation.
638, A for isot impact strength (notch)
Measured according to STM-D-256.

(4) Heat resistance: Heat distortion temperature was measured according to ASTM-D-648.

Example 1 (Synthesis of melamine cyanurate) Melamine s
A melamine aqueous solution in which 4g (4 mol) of o4g (4 mol) was dissolved in 251 water at 80°C and 516.9 (4 mol) of cyanuric acid were mixed at 80°C.
A cyanuric acid aqueous solution dissolved in 25A of water at ℃ was mixed with stirring to react, and the resulting precipitate was separated in a furnace, then dried and milled to form a white powder with an average particle size of 50 μm.
Obtained 0g.

Elemental analysis of this powder revealed that C28.3%;
When the infrared absorption spectrum was measured, the absorption spectrum shown in Figure 1 was obtained, confirming that this white powder was melamine cyanurate. .

Nylon 66/6 copolymer (hereinafter abbreviated as Ny66/6=90/10) containing 10% by weight of nylon 6 component (9.20%) pellets! g and 0.80 kg of melamine cyanurate prepared as described above were mixed in a tumbler, and then granulated by cross-wire extrusion at 260°C using a 40 mmφ extruder to obtain a composition of 3 diameter x 3. Obtained pellets.

This composition pellet was molded using a 5-ounce injection molding machine, and its flammability, moldability, mechanical properties, and heat resistance were measured and evaluated.

The results are shown in Table 1, and it can be seen that it has excellent flame retardancy, moldability, mechanical properties, and heat resistance.

Examples 2-3, Comparative Examples 1-5 A polyamide composition (Example 2) containing 96% by weight of NY 66/6=90/10 copolymer and 4% by weight of melamine cyanurate in the same manner as in Example 1, and **N,y 66
/6 = 75% by weight of a 90/10 copolymer and 25% by weight of melamine cyanurate (Example 3)
) was produced and evaluated in the same manner as in Example 1.

For comparison, a bag containing 1 weight melamine cyanurate (Comparative Example 1) and a bag containing 35% by weight (Comparative Example 2),
Furthermore, as flame retardants, 10% by weight of melamine (Comparative Example 3), 10% by weight of cyanuric acid (Comparative Example 4),
A mixture of 5% by weight of melamine and 5% by weight of cyanuric acid (Comparative Example 5) was produced and evaluated in the same manner.

The results are shown in Table 1.

Table 1 shows that mere mixing of melamine and cyanurate does not improve moldability.

Examples 4 to 5, Comparative Examples 6 to 8 In the same manner as in Example 1, using several types of copolymers with different component ratios of nylon 66/6 copolymer and nylon 66, the melamine cyanurate content was 8 weight. % composition was created.

Table 2 shows the composition ratio and evaluation results.

Table 2 shows that when the copolymer contains less than 5% by weight of the component corresponding to nylon 6 (Comparative Example 6) or the copolymer containing nylon 66 (Comparative Example 8), air bubbles are mixed into the molded product, impairing the appearance, and the product is not satisfactory. Molded specimens for measuring mechanical properties cannot be obtained.

Furthermore, if the content of the component corresponding to nylon 6 exceeds 35% (Comparative Example 7), the mechanical properties and heat resistance deteriorate, resulting in a lack of practicality.

[Brief explanation of the drawing]

Figure 1 shows the infrared absorption spectrum of melamine cyanurate obtained in Example 1 of the present invention, Figure 2 shows the infrared absorption spectrum of an equimolar mixture of melamine and cyanuric acid,
Figure 3 shows the infrared absorption spectrum of melamine, and Figure 4 shows the infrared absorption spectrum of cyanuric acid.

Claims (1)

[Claims] 1 Nylon 66/6 copolymer consisting of polyamide and melamine cyanurate, where the polyamide contains 95 to 65% by weight of bonding units corresponding to nylon 66 and 5 to 35% by weight of bonding units corresponding to nylon 6 as a polymer fraction. 1. A flame-retardant polyamide composition characterized in that it is a melamine cyanurate content of 2 to 30% by weight.