JP3362061B2 - Polyamide resin composition - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyamide resin composition, and more particularly to a polyamide resin composition which is useful as a housing for automobile parts and has excellent mechanical properties and heat resistance.

[0002]

2. Description of the Related Art In recent years, automobile parts housings, etc.
The use of polyamide resin compositions has been greatly expanded. In particular, a polyamide resin composition in which a copper-based heat stabilizer is added from a metal material to a housing that is required to have heat resistance is being used. In general, even when the polyamide resin composition containing the above-mentioned copper-based heat stabilizer is used, there are problems such as discoloration due to thermal oxidative deterioration in high temperature air, resulting in a black appearance.

[0003]

Generally, a polyamide resin composition reinforced with a filler has high rigidity and excellent dimensional stability, and is therefore used for housings of automobile parts and the like. Furthermore, the polyamide resin composition added with a copper-based heat stabilizer has excellent heat resistance, especially the ability to retain mechanical properties in heat aging, so it can be installed in high heat areas such as lamp sockets, lamp inner housings, and reflectors. Is used for housing In general,
The polyamide resin composition has a large discoloration due to thermal oxidative deterioration, and its improvement is desired. Conventionally, it is known to add a copper-based heat stabilizer as a polyamide-based composition in which the heat resistance of a polyamide resin is improved, but even if it is used in the above heat-resistant housing or the like, satisfactory results in thermochromism can be obtained. Has not been done.

Further, although the thermochromic property of polyamide is slightly improved by increasing the addition amount of copper, by adding a large amount of copper, the polyamide resin composition is extruded at the time of blending and processing such as housing molding. There is an upper limit to the amount of copper added, since metal corrosion of a machine and a molding machine and copper precipitation from the polyamide resin composition are likely to occur.

When an antioxidant other than a copper compound is used as a heat stabilizer for polyamide, for example, phosphorus-based, hindered phenol-based, and hindered amine-based ones are heated at a high temperature of 140 ° C. or higher, The effect as a stabilizer,
Smaller than copper-based heat stabilizers.

There is a method of preventing the discoloration of the polyamide resin composition by the hiding power of an inorganic pigment such as titanium oxide.
For example, it is known that red phosphorus such as a flame retardant prevents excessive coloring of polyamide by the hiding power of a white pigment of titanium oxide (JP-A-63-43952).

However, a polyamide resin composition obtained by blending titanium oxide with a polyamide resin containing no copper-based heat stabilizer has a remarkable decrease in mechanical properties due to thermal aging and an essential thermal discoloration of polyamide. Moldings made of such compositions cannot be used in heat-resistant housing applications.

Therefore, a technical problem in this field is to suppress the discoloration of the polyamide resin composition due to thermal oxidative deterioration in the hot air without deteriorating the mechanical properties due to thermal aging.

[0009]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventor has found that problems can be solved by adding titanium oxide and an inorganic filler to a polyamide resin containing a copper-based heat stabilizer. Found that is solved.
The present invention has been completed based on such findings.

That is, the gist of the present invention is that (A) 100 parts by weight of a polyamide resin containing a copper-based heat stabilizer, (B) _{2 to} 50 parts of titanium oxide (TiO ₂ ) and (C) an inorganic filler of 20 to 30 parts by weight. The polyamide resin composition comprises 120 parts by weight.

The details of the present invention will be described below.

The polyamide resin referred to in the present invention is a linear polymer having an amide bond, which is obtained by polycondensing an organic diamine and an organic dicarboxylic acid, obtained by polycondensing an aminocaproic acid, and a lactam. Are obtained by ring-opening polymerization. Examples of the organic diamine include tetramethylenediamine, hexamethylenediamine, metaxylylenediamine, and the like, and examples of the organic dicarboxylic acid include adipic acid, sebacic acid, dodecanedioic acid, terephthalic acid, isophthalic acid, and the like. Examples of aminocaproic acid include 11-aminoundecanoic acid, and examples of lactam include ε-caprolactam and ω-laurolactam. The polyamide may be a copolymer thereof or a polymer blend.
Of these polyamide resins, it is particularly preferable to use nylon 6 or nylon 6.6.

The copper-based heat stabilizer that can be added to the polyamide resin according to the present invention comprises a copper halide or a copper salt such as copper acetate and an alkali metal halide. In particular, copper iodide, or one composed of copper acetate and potassium iodide is preferable, and the amount of the copper component of the copper-based heat stabilizer is 0.001 to 0.02 parts by weight with respect to 100 parts by weight of the polyamide resin. Part especially 0.00
It is preferably from 3 to 0.015 parts by weight, and it is particularly preferable that the molar ratio of halogen is 8 to 25 times the molar number of the copper component of the copper-based heat stabilizer. When the amount of copper added is less than 0.001 part by weight, the effect of suppressing thermochromism is insufficient, and when the amount of copper added is more than 0.02 part by weight, the polyamide resin composition is blended and molded. In the processing steps such as, metal corrosion of the extruder and molding machine and copper precipitation from the polyamide resin composition tend to occur. Further, when the molar ratio of halogen to the number of moles of the copper component is less than 8 times, copper precipitation from the polyamide resin composition is likely to occur, and when it is more than 25 times, the above-described extruder and molding machine Metal corrosion is likely to occur.

The above-mentioned copper-based heat stabilizer may be added to the polyamide by adding it at the time of salt formation in the polymerization step of the polyamide, or by blending it with the polyamide at the time of melt-kneading in the extrusion step of the polyamide resin composition. There are things to add at times.

In addition to copper-based stabilizers, other stabilizers such as phosphorus-based and hindered phenol-based stabilizers may be used in combination if necessary.

The titanium oxide used in the resin composition of the present invention must have a purity of 90% or more. This may be of rutile type, anatase type or brookite type, preferably rutile type. The average particle diameter, that is, the upper and lower particle diameters (d ₅₀ ) of ₅₀ % by weight of the powder is 0.1 to 1.0 μm, especially 0.1.
It is preferably 1 to 0.3 μm. The chemical formula of this titanium oxide is generally TiO ₂ .

In the resin composition of the present invention, the mixing ratio of titanium oxide to the polyamide resin is 100 parts by weight of polyamide resin and 1 to 100 parts by weight of titanium oxide, preferably 100 parts by weight of polyamide resin and titanium oxide. Two
-50 parts by weight is selected. If the content of titanium oxide is less than 1 part by weight, the effect of suppressing thermochromism is insufficient, and if the content of titanium oxide is more than 100 parts by weight, the strength of the polyamide resin composition obtained is high. It tends to be extremely low.

The inorganic filler used in the present invention includes calcined kaolin, kaolin, wollastonite, mica, talc, calcium carbonate and the like, and wollastonite is particularly preferable. Instead of the inorganic filler, glass fiber, fibrous filler such as carbon fiber, or glass sphere may be used as the reinforcing filler.

In order to increase the adhesion between the inorganic filler and the polyamide resin, it is particularly preferable to treat the inorganic filler with a coupling agent such as a silane coupling agent or a titanate coupling agent. Of these, aminosilane coupling agents are particularly preferred.

In the polyamide resin composition of the present invention,
The mixing ratio of the inorganic filler to the polyamide resin is 100 parts by weight of the polyamide resin and 0 to 2 of the inorganic filler.
50 parts by weight, preferably 100 parts by weight of the polyamide resin and 20 to 120 parts by weight of the inorganic filler are selected. When the content of the inorganic filler is less than 10 parts by weight, the reinforcing effect on the polyamide resin composition as a reinforcing filler is insufficient, and the content of the inorganic filler is 25.
If the amount is more than 0 parts by weight, the mechanical strength of the polyamide resin composition tends to decrease, and the extrusion productivity largely decreases.

If necessary, it is possible to add a dye or another colored pigment other than titanium oxide to the polyamide resin composition of the present invention. Examples of the colored pigment mixed with titanium oxide include carbon black, titanium yellow, inorganic ultramarine blue, rouge, cobalt blue, yellow lead, and cyanine yellow, but are not particularly limited.

Further, as a dispersant for titanium oxide or an inorganic filler, or a lubricant or a plasticizer for a polyamide resin composition,
For example, an organic compound such as an alkali metal salt of stearic acid, a fatty acid amide, ε-caprolactam, or a fatty acid ester can be used, and among them, a fatty acid amide containing no metal component such as ethylenebisstearamide is particularly preferable. Be preferred. This is because the use of an organic compound containing a metal component other than ethylene bis-stearamide may impair the heat stabilization mechanism of copper with respect to the polyamide resin.

Further, the resin composition of the present invention can be appropriately blended with various additives generally used in the field of polymer processing, such as a nucleating agent and an ultraviolet absorber, if necessary.

The polyamide resin containing the copper-based heat stabilizer as described above, titanium oxide, the inorganic filler, and various additives used as necessary are mixed in a commonly used mixer such as a Henschel mixer. This is done with a ribbon blender, tumbler, etc. As the kneader, a single-screw or twin-screw extruder is generally used. With such an extruder, first, pellets made of the composition of the present invention are first produced, and the pellets are subjected to compression molding, injection molding, The desired resin product may be formed by molding into the housing shape of the automobile part by extrusion molding or the like.

The color tone of the above polyamide resin composition is
L, a, b color system or L according to JIS Z 8729
The lightness L value is used to represent the object color by the u and v color system, and the degree of thermal discoloration of the polyamide resin composition depends on the initial lightness L value and the lightness L after being left standing in air at 180 ° C. When expressed by the difference with the value (hereinafter referred to as ΔL), the composition in which the above-mentioned thermal discoloration is suppressed has an initial lightness L value of 35 or more, and has a ΔL after being left to stand in air at 180 ° C. for 72 hours. Is within the range of 15 or less.

[0026]

EXAMPLES Next, the present invention will be described more specifically with reference to Examples and Comparative Examples. The mechanical physical properties and color brightness in each example were measured as follows.

Immediately after molding, the test piece used for measuring the mechanical properties is left in a desiccator containing silica gel placed in a temperature-controlled room for 24 hours.

(1) Tensile test According to ASTM-D638, the crosshead speed was 50 mm / min.

(2) Bending test According to ASTM-D790, a crosshead speed was 5 mm / min.

(3) Izod impact test ASTM-D
According to 256, the test piece was cut with a V notch (0.25 mmR).

(4) Heat Aging Treatment in Air The test piece was heat aged in an oven heated to 180 ° C. in a normal atmosphere.

Color Lightness In accordance with JIS-Z8722, a color lightness L value (hereinafter referred to as L value) was measured using a spectrophotometer (ND-1001-DT type) manufactured by Nippon Denshoku Industries Co., Ltd. The degree of thermal discoloration is indicated by the difference ΔL between the initial L value and the L value after the heat aging treatment.

Example 1 (1) Nylon 66 (copper acetate (made by Wako Pure Chemical Industries KK) as a copper-based heat stabilizer and potassium iodide (Japan Natural Gas Industry K)
K), of which 0.006 parts by weight as a copper component and 0.15 parts by weight as an iodine component)
30 kg and aminosilane coupling agent (NUC S
ILICONES A-1100: Nippon Unicar KK
100 g) was blended with a V-type blender, and then wollastonite (NYAD325: Interface)
17.5 kg (made by KK) and ethylene bis-stearamide (armowax EBS powder: made by Lion KK) 1
00g and titanium oxide (R-TC30: made by ICIKK) 5
kg and carbon black (RCF # 50: Mitsubishi Kasei KK)
(Manufactured by Mitsui Chemicals Co., Ltd.) and added with a V-type blender.

The above blend was melt mixed at 290 ° C. using a 70 mmΦ single screw extruder, and pellets of a polyamide resin composition reinforced with wollastonite (diameter 2.5 m
m, length 3 mm) was obtained.

290 the above pellets were injected using an injection molding machine.
Test pieces for measuring physical properties and for measuring color difference were prepared at a temperature of ° C. Next, the test piece was measured for mechanical properties, brightness upon aging, and physical properties. The results are shown in Table 4.

Examples 2 to 4 In addition to blending the nylon 66 used in Example 1, the aminosilane coupling agent, wollastonite, ethylenebisstearamide, titanium oxide and carbon black in the proportions shown below, respectively. I went exactly as 1. The results of the evaluation are shown in Table 4.

Example 5 The procedure of Example 1 was repeated except that zinc stearate was used instead of ethylene bis-stearamide. The results of the evaluation are shown in Table 4.

Example 6 The same procedure as in Example 1 was carried out except that glass fiber (03MA416 manufactured by Asahi Fiber Glass KK) was used instead of wollastonite. The results of the evaluation are shown in Table 4.

The mixing ratios of Examples 1 to 6 are shown in Table 1 below.

[0040]

[Table 1]

Comparative Example 1 Nylon 66 (copper acetate (made by Wako Pure Chemical Industries KK) and potassium iodide (made by Japan Natural Gas Industrial Co., Ltd.) used in Example 1 were used as the copper component. 0.0
06 parts by weight, 12 kg containing 0.15 parts by weight as an iodine component), an aminosilane coupling agent (N
UC SILICONES A-1100: made by Nippon Unicar KK) 39 g was blended with a V-type blender, and then wollastonite (NYAD325: Interpa
ceKK) 8 kg and ethylene bis-stearamide (armowax EBS powder: Lion KK) 12 g
And titanium oxide (R-TC30: made by ICIKK) 96 g and carbon black (RCF # 50: made by Mitsubishi Kasei KK)
0.9 g was added and blended with a V-blender. 290 the above blend using a 70 mmΦ single screw extruder.
Polyamide resin pellets (diameter: 2.5 m) that were melt mixed at ℃, containing titanium oxide and reinforced with wollastonite
m, length 3 mm) was obtained. Then, the pellets were molded at 290 ° C. using an injection molding machine, and the mechanical properties, the brightness upon aging and the physical properties were measured. The results are shown in Table 4.

Comparative Example 2 The same molding as in Comparative Example 1 was carried out except that Nylon 66 containing no copper-based heat stabilizer was used and molded. The brightness and physical properties were measured. The evaluation results are shown in Table 4.

The mixing ratios of Comparative Examples 1 and 2 are shown in the following table.

[0044]

[Table 2]

Comparative Examples 3 to 6 Polyamide heat stabilizers were mixed in the proportions shown below, and the amount of titanium oxide used in Comparative Example 2 was adjusted to 2.0 parts by weight based on 100 parts by weight of the polyamide resin. Others were compounded and molded in exactly the same manner as in Comparative Example 2, and the brightness of the resulting molded piece during aging was measured. The evaluation results are shown in Table 5.

The phosphorus-based heat stabilizer is Irgafos 168 (tris (2,4-di-t-butylphenyl) phosphite: manufactured by Nippon Ciba-Geigy KK), and the hindered phenol-based heat stabilizer is Irganox 1098 (N, N'-hexamethylene bis (3,5-di-t-butyl-4-hydroxy-hydrocinnamamide): Nippon Ciba Geigy KK
), Hindered amine type is MARK PEP LA
57 (manufactured by Adeka Argus Chemical KK), the blending amount of each heat stabilizer is the amount added to 100 parts by weight of nylon 66.

The mixing ratios of Comparative Examples 3 to 6 are shown in the following table.

[0048]

[Table 3]

[0049]

[Table 4]

[0050]

[Table 5]

As described above, the polyamide resin composition of the present invention can suppress the discoloration of the polyamide resin composition even in high-temperature air without causing a significant deterioration in mechanical properties due to thermal aging.

─────────────────────────────────────────────────── --- Continued from the front page (56) References JP-A-62-167322 (JP, A) JP-A-1-156364 (JP, A) JP-A-4-222860 (JP, A) JP-A-53- 88857 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C08L 77/00-77/12 C08K 3/00-3/40

Claims (2)

(57) [Claims] 1. 100 parts by weight of a polyamide resin containing (A) a copper-based heat stabilizer and (B) titanium oxide (TiO ₂ ) 2.
To 50 parts by weight and 20 to 120 parts by weight of the inorganic filler (C), a polyamide resin composition. 2. The initial brightness is 35 or more and 180 ° C.
The polyamide resin composition according to claim 1, wherein the difference from the brightness after being left for 72 hours in air is 15 or less.