JPS5896651A - Polyamide resin composition - Google Patents

Abstract

PURPOSE:To obtain titled composition of high electromagnetic wave-shielding ability, lighter than metal products, capable of easy processing and molding, suitable as housing materials, by incorporating a polyamide resin with aluminum or its alloy in a powder form, etc. CONSTITUTION:The objective composition can be obtained by incorporating (A) 90-40vol% of a polyamide resin (pref. with a molecular weight 15,000-50,000, polymerization degree 150-500, viscosity (at 260 deg.C) 500-5,000 poises) with (B) 10-65vol% of aluminum or its alloy (contg. >=80wt% of aluminum) in the form of powder (250-20 mesh), fiber (diameter 0.0020-0.20mm.) and length <=10mm.) and/ or flake (section 0.1X0.1-5X5mm.<2>, especially width <=0.1mm. at a temperature between the softening point of the polyamide resin and 300 deg.C. Although any single form of the three kinds of aluminum (alloy) mentioned above may be used, combination of the three would show the objective effect with a lesser incorporation.

Description

DETAILED DESCRIPTION OF THE INVENTION Mark Object of the Invention The present invention relates to polyamide resin compositions. More specifically, France) amide resin and (B) aluminum metal or aluminum alloy powder, fibrous and/or
This relates to polyamide resin compositions consisting of flakes or flakes, which not only have high electromagnetic wave shielding properties, but are also lighter and easier to process and mold than those made of metal. The object is to provide a composition.

■ Background of the Invention The sources of electromagnetic radiation are increasing due to the advancement of industry and the standardization of home life. Therefore, leakage of electromagnetic waves can cause dangerous harm to the human body and damage to ICs in electronic equipment.
This has resulted in negative effects such as malfunction, and has become a serious social problem. In particular, electromagnetic waves emitted from computers and various office processing equipment are causing trouble to televisions and audio equipment.

For these reasons, various methods have been adopted in recent years to shield electromagnetic waves.

In general, since metal has the property of absorbing or reflecting electromagnetic waves, it is effectively used as an electromagnetic wave shielding material for microwave ovens and various communication devices. We also use thermal spraying, vapor deposition, and painting of metal on plastic for the same purpose.
Plating etc. are also applied. Furthermore, materials obtained by incorporating relatively large amounts of additives such as carbon powder and metal powder into plastics have also been used.

However, the methods of using metal as a material or applying treatments such as metal spraying to plastics have drawbacks such as high specific gravity, poor workability, difficult processing methods, and high processing costs. be.

Further, regarding the method of mixing additives, if a small amount of the additive is mixed, the effect cannot be fully exhibited. On the other hand, if a large amount is mixed in, the effect can be exhibited, but there is a drawback that the mechanical strength of the resulting molded product is significantly reduced.

l Structure of the Invention In view of the above, the present inventors have searched various ways to obtain a synthetic resin composition that has these drawbacks and has excellent electromagnetic wave shielding performance, and as a result, (A) polyamide resin. 90-40 capacity and (B) "powder, fibrous and/or flake-like materials of aluminum metal or alloys whose main component is aluminum" (hereinafter referred to as "powder-like materials of aluminum metal, etc.") ) 10 to 60 volume ratio, it was discovered that the polyamide resin composition not only has good electromagnetic wave shielding performance but also has various characteristics (effects), and the present invention was achieved.

Sub-effects of the invention, that is, the electromagnetic wave shielding material obtained by the present invention not only has extremely excellent electromagnetic wave shielding performance, but also has the following effects (features).

(1) It is lightweight.

(2) Good mechanical strength such as bending strength and impact strength.

(3) Since it has excellent moldability, it can be easily processed and molded into any shape.

(4) Secondary processing costs required for electromagnetic wave shielding treatment (for example, metal spraying, conductive coating, plating, etc.) are eliminated, resulting in a significant cost reduction.

The electromagnetic wave shielding material obtained by the present invention not only has extremely good electromagnetic wave absorption performance but also has the above-mentioned excellent effects, so it can be used in a wide variety of fields. Typical uses are shown below.

(1) Helding material for office equipment such as facsimiles, printers, food processors, etc. (2) Consumer home appliances and electronic equipment such as televisions and videos,
Internal parts of hesing machines for electrical and electronic equipment such as computers and communication equipment, ■Detailed description of the invention (A) Polyamide resin The polyamide resin used in the present invention is generally called nylon, and has an amide group. (-CONH-)
The main chain is composed of repetitions of . This polyamide resin is generally manufactured by the following method.

(1) Ring opening of lactam (2) Condensation of amino acid H2N-R2-C00H->(HNR2CO) +H2
0(2)(3) Condensation H2N of diamine and dicarboxylic acid
-R3-NH,,+HOOC-R' C0OH→1,000N
HR3NHCOR' Co+10H20(8)(1)~(
In the formula 3), cod is an alkylene group having 5 to 11 carbon atoms, R2 is an alkylene group having 5 to 16 carbon atoms, R3 is an alkylene group having 2 to 11 carbon atoms, and R4 is an alkylene group having 5 to 11 carbon atoms. is an alkylene group having 3 to 40 carbon atoms.

Typical examples of this polyamino resin include nylon 6 produced by ring-opening polymerization of ε-caglolactam, and similar examples include r-butyrolactam, δ-parellolactam, ξ-enaditractam, and η-caglolactam. Polyamino resin obtained by ring-opening polymerization, nylon 12 obtained by ring-opening polymerization of ω-laurolactam. Nylon 11 obtained by heating and condensing 1-aminoundecanoic acid. Examples include nylon 66 obtained by polycondensing hexamethylene diamine and adipic acid, and nylon 610 obtained by polycondensing hexamethylene diamine and sebacic acid. Furthermore, N-alkoxymethyl modified nylon (type 8 nylon), transparent nylon such as a polycondensate of trimethylhexamethylene diamine and terephthalic acid, and nylon 9. Nylon 1
3. Examples include Q2 nylon.

The molecular weight of these polyamide resins is generally 10,000 or more,
15,000 to 50,000 is preferred, especially 1
5,000 to 30,000 is suitable. Also 1
The degree of polymerization is 10.0 or more, preferably from 150 to 500, preferably from 150 to 300.

These polyamide resins are produced industrially and are used in a wide variety of fields.
(published by Nikkan Kogyo Shimbun, 1972), its manufacturing method, properties, etc. are known in detail. Among these polyamide resins, those with a viscosity of 50 at a temperature of 260°C
0 to 50,000 poise is preferred, especially 500 to 50,000 poise.
3000 poise is suitable.

(B) Aluminum metal powder Among the powder, fibrous and flake materials of aluminum metal or aluminum alloy used in the present invention, the average size of the powder is generally 250 mm. It is between 1 and 20 meshes. In addition, the diameter of fibrous materials is generally 0.0020 to 0.20 r.
trm, and a length of 10 mm or less is desirable because it is easy to process.

Furthermore, as a flake-like material, the cross-sectional area is 0.1×01
Any shape such as a circle, a square, a rectangle, or a rectangle measuring 5 x 5 m from the throat can be used, but it is particularly desirable that the thickness is 0.1 f+EI11 or less. Among these, those having a hexagonal shape with a cross-sectional area of about 1×1 and a thickness of about 0.03 haze have good dispersibility. These powdery, fibrous, or flaky materials may be used alone, but by using two or more of them together, it is possible to achieve the effect with a small mixing ratio in order to achieve the purpose of the present invention. This is suitable because it can be done. Further, the aluminum content in the aluminum alloy is usually 80% by weight or more.

(C) Blending ratio The blending ratio of the polyamide resin in the composition of the present invention is 90 to 40% by volume, preferably 85 to 45% by volume, particularly preferably 80 to 5% by volume, and particularly preferably 55% by volume. 20-5o capacity is suitable). The blending ratio of the aluminum 1 metal powder in the composition is i o
If the capacitance is less than 1, it will not provide enough conductivity for absorbing electromagnetic waves. On the other hand, when the volume is 60 or more, it is extremely difficult to mix it uniformly with the polyamide resin.Even if a uniform composition is made, it does not have enough strength to withstand practical use, so it is not practical. above is impossible.

(0) Production of composition, production of molded article To produce the composition of the present invention, tri-blending may be performed using a mixer such as a Henschel mixer, which is commonly used in the polyamide resin industry, or a Banbury mixer. -, by melt-kneading using a mixer such as a kneader, roll mill, or screw extruder.In this case, by tri-blending in advance and melt-kneading the resulting composition (mixture). A homogeneous composition can be obtained.

In particular, it is preferable to use the polyamide resin in the form of powder because it can be mixed more uniformly. In this case, the mixture is generally melt-kneaded, then molded into pellets, and subjected to the molding described later.

When preparing the compositions of the invention, oxygen and heat stabilizers, metal deterioration inhibitors, fillers, lubricants and flame retardants commonly used in the field of polyamide resins may also be added.

Both the above-mentioned melt mixing and molding must be carried out at temperatures above the softening point of the polyamide resin used, but if carried out at temperatures above 300°C, some of the polyamide resin may deteriorate due to heat. Therefore, it is natural that the process must be carried out at a temperature below this temperature.

Examples of the molding method include extrusion molding, injection molding, and press molding. Furthermore, molding methods commonly used in the field of polyamide resins such as stamping methods, press molding methods using extruded sheets, vacuum molding methods, etc. may also be applied.

As described above, the composition of the present invention has excellent processability, so it can be molded into various shapes by the molding method described above and used in many ways.

(2) Examples and Comparative Examples The present invention will now be explained in more detail with reference to Examples.

In the Examples and Comparative Examples, the melt viscosity was measured at a temperature of 250° C. and a shear rate of 1000 sec. Pull speed was measured according to ASTM D-638. In addition, the bending strength and bending modulus are AST
Measured according to MD-790. Additionally, Izot impact strength was measured with a notch according to ASTM D-256. In addition, the volume resistivity test was performed using a resistance meter (manufactured by Takeda Riken Co., Ltd., trade name: Digital Multimeter TR--6ss6), using a specimen with a thickness of 211 tll, and testing the specimen at a temperature of 25°C and a humidity of 60%. The resistance was measured and calculated according to the formula below.

Here, S is the electrode area of the specific resistivity measurement electrode, and R
is the resistance value of the specimen, and t represents the thickness of the specimen. , Also, to measure the shielding effect of electromagnetic waves, a sample box of 10 x 10 x 30 crn was made using a sheet of 3 sea bream thick.
A portable oscillator is placed in the box at a predetermined frequency (20'O
MHz).

This box was placed in an anechoic chamber, and the radio waves emitted by the transmitter inside the box were measured using a receiving antenna using a microwave power meter via a detector. The radio waves from the oscillator were measured in the same way when the box produced from the sheet was removed, and the ratio of power depending on the presence or absence of the sample box was expressed in decibels (dB) and was taken as the electromagnetic wave attenuation of the sample sheet.

Note that the polyamide resin, aluminum flakes, aluminum fibers, and aluminum powder used in the Examples and Comparative Examples have the following shapes and physical properties.

[Polyamide resin]

A polyamide resin produced by ring-opening polymerization of ε-caprolactam with a density of t 13//7 cm3 (melt viscosity at 250°C
3000 poise (hereinafter referred to as "nylon 6") and a polyamide resin obtained by polycondensation of hexamethylene diamine and adipic acid (melt viscosity at 280° C. 1500 poise, hereinafter referred to as "nylon 66") were used.

[Aluminum flakes]

As aluminum flakes, cross-sectional area 1 x 1 ml,
Square 7-lake aluminum with a thickness of 0.03 m (
Hereinafter referred to as "IT flakes") was used. - [Aluminum powder] As the aluminum powder, aluminum powder (hereinafter referred to as 1hl powder) having a particle size of 74 to 150 microns was used.

[Aluminum fiber]

As aluminum fiber, aluminum fiber (hereinafter referred to as J-AI!) has a length of approximately 61 m and a diameter of 65 microns.
fibers) were used.

, ◇ Examples 1-8, Comparative Examples 1-3 Nylon and A/flake, Al fiber and AI!
Each of the powders was tri-blended for 5 minutes using a Henschel mixer at the mixing ratio shown in Table 1. Each of the resulting mixtures was pelletized using an extruder (diameter 65) at a resin temperature of 240° C. while being melt-kneaded to produce a composition.

Each of the resulting compositions was molded into a 6-ounce injection molding machine preset at 240°C to a thickness of 311! l
A test piece of I was prepared.

Table 1 Examples 9 to 11, Comparative Examples 4 to 6 Same as Example 1 except that nylon 66 was used instead of nylon 6 used in Examples 1 to 8 and Comparative Examples 1 to 3. , under the condition that the resin temperature is 270℃)
The mixture was pelletized to produce a composition (the blending ratio is shown in Table 2). Next, injection molding was performed in the same manner as above to produce each test piece.

Table 2 The surface resistivity, transmission attenuation rate, tensile strength, elongation, bending strength, bending elastic modulus, and isot impact strength (notched) of each test piece obtained as shown in Table 2 were measured. The results are shown in Table 3.

Table 3 (Part 1) Section 3
Table (Part 2) 1) Impossible to measure (sample attachment sometimes destroys) 2) Notched From the results of the above examples and comparative examples, the composition obtained by the present invention always has excellent electromagnetic wave shielding properties. It is also clear that the mechanical properties such as tensile strength, flexural strength, flexural modulus and isot impact strength are also good.

Patent applicant: Showa Denko Co., Ltd. Agent: Patent attorney Sei Kikuchi

Claims (1)

[Scope of Claims] (A) Polyamide resin 90 to 4 o capacity, and (B) Powder, fibrous, and/or flake material of aluminum metal or an aluminum-based alloy from 10 to 60 capacity. A polyamide resin composition.