JP4209293B2 - Flame retardant polyamide resin composition - Google Patents

Description

  The present invention relates to a flame retardant polyamide resin composition. Specifically, the present invention relates to a flame retardant polyamide resin composition excellent in tracking resistance and heat discoloration resistance, which is suitable for colored electrical parts such as electromagnetic switches and breaker casings.

A flame retardant resin composition containing polyamide resin as a main component is used as a material for housings such as electromagnetic switches and breakers. These devices have been reduced in size in order to reduce the installation space. However, if the device is reduced in size, heat tends to be trapped inside during energization, and the temperature of the casing may partially reach nearly 140 ° C. Conventionally, the color tone of the molded product has been mostly black, but in recent years there has been an increasing demand for a bright gray color, and when used in such a high-temperature atmosphere, the polyamide resin is discolored, causing a problem in appearance.
It has been proposed to add a heat stabilizer as a method for solving this problem. For example, Patent Document 1 discloses a resin composition in which a hindered phenol stabilizer is added as a stabilizer in addition to a polyamide resin, a brominated flame retardant, an antimony compound, magnesium hydroxide, and glass fiber. Patent Document 2 discloses a resin composition containing a heat stabilizer and a polyamide resin having a melting point of 280 to 340 ° C., an inorganic filler, a flame retardant containing bromine or chlorine, an antimony compound, an oxide, and the like. The literature describes the use of heat stabilizers such as copper iodide as examples of heat stabilizers.
However, according to the study by the present inventors, a copper heat stabilizer represented by copper iodide has no effect on resin discoloration at 120 ° C., and a hindered phenol stabilizer has an effect. The discoloration suppressing effect was insufficient and the discoloration was large. Furthermore, zinc sulfide is often used as a concealing component in order to adjust the molded product to a light gray color. However, contamination at the metal contacts inside the housing occurs at high temperatures as described above. There was a problem that the electrical characteristics as a circuit breaker deteriorated.

JP-A-11-172101 Special Table 2002-506910

  An object of the present invention is to provide a flame-retardant polyamide resin composition having excellent tracking resistance and excellent heat resistance and little thermal discoloration. Another object of the present invention is to provide a flame retardant polyamide resin composition free from contamination of metal contacts in addition to these characteristics.

  The inventors of the present invention have made studies to solve the above-mentioned problems, and have found that the problem can be solved by using a specific phosphorus-based stabilizer, and have achieved the present invention. That is, the gist of the present invention is that the polyamide resin (A), ethylene-bis (pentabromobenzene) (B), flame retardant aid (C), inorganic filler (D), and pentaerythritol-type phosphorus stabilizer (E ), Wherein the blending ratio is (B) 18 to 35 parts by weight, (C) 9 to 17 parts by weight, and (D) with respect to (A) + (D) = 100 parts by weight. 10) to 70 parts by weight, (E) 0.1 to 1.5 parts by weight, and the color change ΔE after being treated at 120 ° C. for 3000 hours is 15 or less. It exists in things.

Hereinafter, the present invention will be described in detail.
The polyamide resin (A) used in the present invention is obtained by ring-opening polymerization of lactams having 3 or more members, polymerizable ω-amino acids, or polycondensation or copolymerization reaction of dibasic acid and diamine. A polymer having acid amide as a repeating unit or a mixture thereof.
Specific examples of the lactams having three or more members include ε-caprolactam, enantolactam, capryllactam, lauryllactam, α-pyrrolidone, α-piperidone and the like. Specific examples of ω-amino acids include 6-aminocaproic acid, 7-aminoheptanoic acid, 9-aminononanoic acid, and 11-aminoundecanoic acid.
Specific examples of the dibasic acid include malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecadionic acid, tridecadionic acid, tetradecadionic acid, Aliphatic dicarboxylic acids such as hexadecadioic acid, hexadecenedioic acid, octadecadioic acid, octadecenedioic acid, eicosandioic acid, eicosendioic acid, docosandioic acid, 2,2,4-trimethyladipic acid, and terephthalate Aromatic dicarboxylic acids such as acid, isophthalic acid, phthalic acid, and xylylene dicarboxylic acid can be mentioned.
Specific examples of the diamine include ethylene diamine, trimethylene diamine, tetramethylene diamine, pentamethylene diamine, hexamethylene diamine, heptamethylene diamine, octamethylene diamine, nonamethylene diamine, undecamethylene diamine, dodecamethylene diamine, 2, 2,4- (or 2,4,4) -trimethylhexamethylenediamine, cyclohexanediamine, bis- (4,4′-aminocyclohexyl) methane, metaxylylenediamine and the like can be mentioned.

The terminal of the polyamide resin used in the present invention may be sealed with a carboxylic acid or an amine, and a polyamide resin sealed with a carboxylic acid or amine having 6 to 22 carbon atoms is particularly preferable. Specific examples of the monocarboxylic acid used for sealing include aliphatic monocarboxylic acids such as caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, and behenic acid. Examples of monoamines include aliphatic primary amines such as hexylamine, octylamine, decylamine, laurylamine, myristylamine, palmitylamine, stearylamine, and behenylamine. Furthermore, the above-mentioned dibasic acid and diamine used for polyamide production can also be used. The amount of carboxylic acid or amine used for sealing is preferably about 5 to 60 μeq / g of resin.
Polyamide resin (A) is a poly-ε-caprolactam (polyamide 6), a copolymer of ε-caprolactam, adipic acid and hexamethylene diamine (polyamide 6/66) considering the heat resistance, moldability and cost of the flame retardant. And mixtures thereof. The ratio of ε-capramide in polyamide 6/66 is preferably 50% by weight or more, more preferably 80% by weight or more based on the whole polyamide 6/66.
The relative viscosity of the polyamide resin (A) is 2.0 to 3.5 as measured in 98% sulfuric acid, at a concentration of 1% and at a temperature of 25 ° C. according to JIS K6810-1994, more preferably 2.2. To 3.2. When the relative viscosity is lower than 2.0, the melt viscosity is too low to make injection molding difficult, and the mechanical strength of the molded product also decreases. On the other hand, if the relative viscosity is higher than 3.5, the melt fluidity is poor and it is not suitable for injection molding.

  In the present invention, ethylene-bis (pentabromobenzene) (B) is used as a halogen flame retardant. This flame retardant has good tracking resistance, and has higher whiteness and higher degree of freedom in coloring than general brominated flame retardants, so it is suitable for electrical parts that are colored bright gray or the like.

  Examples of the flame retardant aid (C) used in the present invention include antimony compounds such as antimony trioxide and antimony pentoxide, and metal borate salts such as zinc borate, preferably zinc borate and antimony trioxide. And antimony trioxide is most preferred.

  The flame retardant resin composition of the present invention further contains an inorganic filler (D) in order to increase the strength and rigidity of the composition. Any inorganic filler may be used as long as it is normally used for reinforcing thermoplastic resins. Specifically, glass fiber, carbon fiber, glass flake, glass bead, mica, talc, kaolin, wollastonite, potassium titanate whisker, aluminum borate whisker, barium sulfate, ferrite, expansive mica, calcium carbonate, etc. Illustrated. These inorganic fillers may be used in combination of two or more. Among the inorganic fillers, glass fiber is particularly preferable. The glass fiber may be one normally used as a reinforcing material for thermoplastic resin, and chopped strand made from E glass (non-alkali glass) is particularly preferable. The fiber diameter of the glass fiber is usually 1 to 20 μm, preferably 5 to 15 μm. Moreover, it is preferable that the glass fiber is surface-treated with a silane coupling agent such as aminosilane in order to improve adhesiveness with polyamide.

Furthermore, the composition of the present invention contains a pentaerythritol type phosphorus stabilizer (E). Specifically, bis (2,6-di-t-butyl-4-methylphenyl) -pentaerythritol-diphosphite, di (2,4-di-t-butylphenyl) -pentaerythritol-diphosphite, distearyl pentaerythritol -Diphosphite and the like can be mentioned, but bis (2,6-di-t-butyl-4-methylphenyl) -pentaerythritol-diphosphite is most preferred.
The composition of the present invention contains such a specific phosphorus stabilizer (E) as a stabilizer, and thus has excellent resistance to thermal discoloration as compared with a composition using other heat stabilizer. .

Polyamide resin (A), ethylene-bis (pentabromobenzene) (B), flame retardant aid (C), inorganic filler (D), pentaerythritol phosphorus stabilizer (E) in the resin composition of the present invention The blending ratio of (A) and (D) is 100 parts by weight of the total amount of (A) and (D), (B) 18 to 35 parts by weight, (C) 9 to 17 parts by weight, (D) 10 to 70 parts by weight, (E) 0.1 to 1.5 parts by weight. If it is out of this blending ratio, a composition that sufficiently satisfies flame retardancy, electrical properties, and heat discoloration cannot be obtained. A more preferable blending ratio is (B) 20 to 30 parts by weight, (C) 10 to 15 parts by weight, (D) 13 to 65 parts by weight with respect to 100 parts by weight of the total amount of (A) and (D). (E) 0.3 to 1.0 part by weight.
The composition of the present invention has a color tone change ΔE of 15 or less after being kept at 120 ° C. for 3,000 hours. The composition showing such color change is, for example, using the components (A) to (E) in the above ratio, mixing components other than the inorganic filler (D), adding and mixing the inorganic filler thereto, The melting point of the polyamide resin (A) can be obtained by employing a resin temperature of + 20 ° C. or higher and melting and kneading.

Further, when a concealing pigment is used to color the resin composition of the present invention in gray or the like, it is possible to prevent contamination of metal contacts at high temperatures by using titanium oxide (F) as the pigment. According to the study of the present inventors, when using zinc sulfide which has been conventionally used as a concealing pigment, black contamination occurs on the surface of the contact parts silver-plated on the surface of the copper plate by treatment at 120 ° C. for 3000 hours, Analysis of this revealed that sulfur is present as an inorganic element. From this, it is presumed that a sulfonic acid-based gas containing sulfur is generated from zinc sulfide, and this gas reacts with the metal surface to cause black contamination. On the other hand, in the molded product using titanium oxide as a pigment, it has been found that the surface of the contact part is not contaminated even if the same treatment is performed.
0.01-3 weight part is preferable with respect to 100 weight part of total amounts of (A) and (D), and, as for the compounding quantity of a titanium oxide (F), 0.5-2 weight part is more preferable. When the amount of (F) is less than 0.01 parts by weight, there is no concealing effect, and when it is more than 3 parts by weight, the mechanical strength is greatly reduced.

  In addition to the components (A) to (F), a release agent and a pigment can be blended in the resin composition of the present invention as long as the object of the present invention is not impaired. Examples of the release agent include fatty acid amide compounds such as ethylenebisstearylamide, polycondensates of ethylenediamine and stearic acid and sebacic acid, fatty acid metal compounds such as fatty acid ester compounds and calcium stearate, and ethylenediamine and stearic acid and sebacic acid. The polycondensate is more preferred. As the pigment, pigments usually used for polyamide resins can be used. However, a pigment containing no sulfur is particularly preferable from the viewpoint of contamination of metal contacts.

  The method for producing the resin composition of the present invention is not particularly limited as long as the composition having the target characteristics of the present invention can be obtained, and each component is blended at a predetermined ratio and biaxial or single. After melt-kneading by a shaft extruder, it is produced by a method of cooling and pelletizing by a conventional method. The feeding method of each component to the extruder can be blended and fed from the main hopper, but when using a filler with a large aspect ratio such as glass fiber as the inorganic filler, It is preferable to manufacture by a method in which the component is supplied from the main hopper and made into a molten state, and then the filler is side-fed to reduce the strength of the molded product. The resin temperature is preferably the melting point of the polyamide resin (A) used + 20 ° C. or higher and 320 ° C. or lower. When it becomes higher than 320 degreeC, a flame retardant decomposes | disassembles and a flame retardance falls.

  The resin composition of the present invention is excellent in heat discoloration resistance and tracking resistance, and has the advantages of less contamination of metal contacts, and is suitable as a material for electrical parts. The method for obtaining an electrical component from the resin composition of the present invention is not particularly limited, and various known molding methods such as injection molding, extrusion molding, and compression molding can be applied. In order to obtain it, the injection molding method is preferable in terms of industrial productivity. When the injection molding method is used, the resin temperature is preferably set to the melting point + 20 ° C. or higher, and the mold temperature is preferably about 80 ° C.

The flame retardant resin composition of the present invention is excellent in flame retardancy and tracking resistance, has little heat discoloration, is free from metal contact contamination, and is suitable as a material for electrical parts such as breakers and electromagnetic switch casings. .

EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, this invention is not restrict | limited to the following examples, unless the summary is exceeded.
The materials and resin composition test methods used in the following examples are as follows.
<Material>
(A) Polyamide resin: Polyamide 6, relative viscosity 2.2 (98% sulfuric acid, concentration 1%, 25 ° C.).
(B) Flame retardant 1: ethylene-bis (pentabromobenzene), melting point 345 ° C., specific gravity 3.25, L value by Hunter chromaticity measuring method = 95 to 96.
(B) 'Flame retardant 2: poly-dibromophenylene oxide, melting point 210-240 ° C.
(C) Flame retardant aid: antimony trioxide.
(D) Inorganic filler: glass fiber, fiber diameter 10 μm, aminosilane-treated product.
(E) Stabilizer 1: Bis (2,6-di-t-butyl-4-methylphenyl) -pentaerythritol-diphosphite.
(E) 'Stabilizer 2: Tris (2,4-di-t-butylphenyl) phosphite.
(E) "Stabilizer 3: Tetrakis- (methylene-3- (3 ', 5'-di-t-butyl-4'-hydroxyphenyl) propionate) methane.
(F) Pigment 1: Titanium oxide.
(F) 'Pigment 2: Zinc sulfide.

<Test method>
(1) Tracking resistance: The comparative tracking index was evaluated in an absolutely dry state in accordance with IEC60112.
(2) Flame retardancy: Evaluation was performed using a test piece having a thickness of 0.8 mm based on the UL94 combustion test.
(3) Heat resistance test: The color difference of a 100 × 100 × 3 mm thick test piece treated at 120 ° C. for 3000 hours in a hot air oven was measured with a spectrophotometric colorimeter, and the color difference based on the color tone before treatment Was evaluated. The color difference is preferably 15 or less.
(4) Contact contamination evaluation: In a glass petri dish, four test pieces each having a thickness of 50 × 50 × 3 mm are sandwiched between staples (thickness 0.5 mm) so that the test pieces are not in contact with each other. On top of this, a silver-plated contact (a copper plate (10 × 20 × 3 mm thickness) silver-plated on the surface) was placed. The petri dish lid was closed and the whole was wrapped and sealed with aluminum foil, then placed in a hot air oven and treated at 120 ° C. for 3000 hours. The silver plating contact was taken out from the petri dish after processing, the surface was observed visually, and the following reference | standard evaluated.
○: No abnormalities on the surface ×: The surface is darkened or contaminated

[Examples 1 to 4 and Comparative Examples 1 to 4]
After blending the materials with the formulations shown in Table-1 and Table-2, and pelletizing by melting and kneading at a resin temperature of 250 ° C. in a twin screw extruder TEX30HCT manufactured by Nippon Steel Works, 200 Pa or less at 120 ° C. Was dried for 8 hours or more to produce resin composition pellets.
Using the pellets, the above test pieces were molded with a 75-ton molding machine manufactured by Nippon Steel Works, Ltd., and the tracking resistance evaluation based on IEC60112 and the flame retardance evaluation based on UL94 were performed. Furthermore, after the test piece for the heat resistance test was processed in a 120 ° C. hot air oven for 1000 hours, the color difference from the untreated product was evaluated. Similarly, contact contamination was evaluated for the contact contamination evaluation test piece by the above method.
The evaluation results are shown in Table-1 and Table-2.

Claims (4)

Resin composition containing polyamide resin (A), ethylene-bis (pentabromobenzene) (B), flame retardant aid (C), inorganic filler (D), and pentaerythritol-type phosphorus stabilizer (E) The blending ratio is (B) 18 to 35 parts by weight, (C) 9 to 17 parts by weight, and (D) 10 to 70 parts by weight with respect to 100 parts by weight of the total amount of (A) and (D). Part (E) 0.1 to 1.5 parts by weight, and a color change ΔE after being held at 120 ° C. for 3000 hours is 15 or less, a flame retardant polyamide resin composition. The flame-retardant polyamide resin composition according to claim 1, wherein the polyamide resin (A) is polyamide 6 or polyamide 6/66. The resin composition further comprises 0.01 to 3 parts by weight of titanium oxide (F) with respect to 100 parts by weight of the total amount of (A) and (D). The flame-retardant polyamide resin composition as described. The electrical component formed by shape | molding the flame-retardant polyamide resin composition in any one of Claims 1-3.