JPH0240095B2 - UNMOJUTENNETSUKASOSEIJUSHISOSEIBUTSU - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a thermoplastic resin composition having excellent mechanical strength such as tensile strength and bending strength as well as high weld strength. Recently, mica-containing thermoplastic resin compositions that use mica as a reinforcing material have been found to have superior rigidity, phosphorus-free properties, and high electrical insulation properties compared to compositions reinforced with fillers such as glass fiber and calcium carbonate. It is widely used because of its However, when such a mica-filled molded product is molded, particularly by injection molding, so-called welds may occur in the molded product. When a weld occurs in a molded product, the strength of this part is lower than the strength of unreinforced resin, which is a disadvantage, and in order to prevent this disadvantage, attention has traditionally been paid to the design of molds. It's here. However, in order to prevent welding, it is impossible to completely prevent welding by simply paying attention to the design of the mold, and it is necessary to consider the resin composition as well. It is known that the strength of the weld portion of a thermoplastic resin containing mica varies depending on the mica flake diameter, and the smaller the flake diameter, the better the strength of the weld portion. However, if the diameter of the mica flakes is reduced in order to increase the strength of the weld portion, the aspect ratio also decreases, which causes a problem in that the reinforcing effect decreases. Furthermore, the cost of crushing to reduce the diameter of mica flakes increases significantly. As a result of intensive studies to obtain a mica-filled resin composition with high weld strength without the above-mentioned drawbacks, the present inventors found that by blending mica with a specific shape into a thermoplastic resin, the reinforcing effect could be sacrificed. We have discovered that it is possible to obtain a resin composition having high weld strength without any process, and have arrived at the present invention. That is, the present invention uses 10 to 80% by weight of mica flakes with an average shape factor of 0.76 or more and 90% by weight of thermoplastic resin.
It is a resin composition consisting of ~20% by weight. The shape factor in the present invention is calculated by adding 4π to the area (s) obtained from the projection view from the top of the mica flake.
The value multiplied by the circumference obtained from the projection diagram
It is a value expressed as 4πs/l ² divided by the square of (l).
By the way, this value is 1 for a circle, 0.785 for a square,
For an equilateral triangle, it is 0.605. The area and circumference of the mica flake projection can be determined by the following method. First, a scanning electron micrograph of the mica flakes is taken and a projected image is taken. Next, a sensor is traced along the image of the projection to measure the circumference and the area of the area surrounded by the circumference. Figures 1 and 2
The figure shows a scanning electron micrograph of mica flakes (magnification
190 times). The shape factor of each mica flake is calculated from the area and circumference measured by such a method, and a cumulative frequency curve of the shape factor is drawn as shown in FIG. The point at which the cumulative number of flakes reaches half of the measured number, that is, the shape coefficient of the average value, is taken as the shape coefficient of that mica flake. The resin composition of the present invention has a particle size of 2000 μm or less, an aspect ratio of 10 or more, and an average shape factor of 0.76 or more (preferably 0.79).
It is obtained by blending the above mica flakes into a thermoplastic resin. Further, it is preferable that the number of mica flakes having a shape factor of 0.70 or less in 100 pieces is 20 or less (preferably 15 or less). Usually, mica is crushed using a crushing method that applies strong impact energy to the mica, such as in a jet mill type crusher, but the shape of mica flakes obtained by such conventional crushing methods is shown in Figure 2. Therefore, the average value of the shape factor is only about 0.65 to 0.73.
However, in the present invention, in order to crush mica with weak impact energy and to smooth sharp edges, for example, using a fine micron type crusher, mica is crushed with a shape factor of 0.76 or more as shown in Figure 1. can be obtained. Mica flakes used in the present invention can be efficiently obtained with a shape factor of 0.76 or more by using the above-mentioned fine micron type crusher, but the use of the above-mentioned crusher is limited. Any pulverization method may be used as long as it produces mica flakes having the above-mentioned specific shape. Examples of mica used in the present invention include muscovite, phlogopite, biotite, and synthetic mica. In addition, thermoplastic resins used in the present invention include polyolefins such as polyethylene and polypropylene, polyamides such as nylon 6 and nylon 66,
Polyesters such as polyethylene terephthalate and polybutylene terephthalate are used. Furthermore, the resin composition of the present invention is a thermoplastic resin of 90 to
20% by weight of mica flakes with a shape factor of 0.76 or more
It is carried out by blending 10 to 80% by weight. When the amount of mica flakes is less than 10% by weight, the effect of the present invention is low, and when it is more than 80% by weight, molding becomes difficult. In carrying out the present invention, it is also possible to use an alkylsilane compound as a surface treatment agent for mica,
A titanium compound may be used as an auxiliary agent to help disperse the mica. Further, various reinforcing materials and fillers such as glass fiber, carbon fiber, talc, calcium carbonate, and wollastonite can be used. especially,
The combined use of small amounts of glass fiber and carbon fiber is effective in improving strength, impact strength, heat distortion temperature, etc. In addition, known additives such as colorants, lubricants, stabilizers, plasticizers, and antistatic agents may be added. The composition of the present invention can be manufactured using a conventional injection molding machine.
Although it is molded into structural parts, mechanical parts, electrical parts, etc., other molding methods such as extrusion molding, compression molding, and calender molding may also be employed. The present invention will be specifically explained below with reference to Examples.
The present invention is not limited in any way by these Examples. Example 1 and Comparative Example 1 Phlogopite was pulverized using a fine micron type pulverizer (manufactured by Hosokawa Micron Co., Ltd.), and 10% of the fine powder portion was cut off by air classification, resulting in an average flake diameter of 40 μm.
Phlogopite flakes with an average shape factor of 0.80 and an aspect ratio of 30 were obtained (Figure 1). Furthermore, out of 100 mica flakes, there were 7 flakes with a shape factor of 0.70 or less. The shape factor of mica was determined by measuring the area and circumference using a scanning electron micrograph of mica using an image analysis system (MOP-Modular System, manufactured by Hideko Seiki Sangyo Co., Ltd.). The cumulative frequency curve of these shape factors is shown in FIG. Also,
A mixture of isotactic polypropylene 4 and carboxyl-modified polypropylene 1 was used as the thermoplastic resin. The ratio of mica and resin is 40/60 by weight, and this mixture is fed to a single screw extruder, melted and kneaded at 230°C, and the resulting pellets are injection molded to improve tensile strength, bending strength, and A test piece was obtained for measuring the tensile strength of the weld part. The shapes of the test pieces for measuring tensile strength and bending strength are ASTM D638 and ASTM
D790, and the shape of the test piece for measuring the tensile strength of the weld part was determined by Kobunshi Papers (edited by the Society of Polymer Science and Technology), 38 ,
209 (1981). The physical properties of these test pieces were measured and shown in Table 1 (Example 1). In addition, using the same resin as in Example 1, phlogopite pulverized by a jet mill with an average flake diameter of 38 μm, an aspect ratio of 28, and an average shape factor of 0.70 was mixed in the same manner as in Example 1 to prepare a test piece. It was prepared and its physical properties were measured and are also shown in Table 1 (Comparative Example 1). However, out of 100 flakes in the mica, 50 flakes had a shape factor of 0.70 or less. The cumulative frequency curve of the shape factor is shown in FIG. From this result, the tensile strength and bending strength are almost the same, but
It is clear that the weld strength has been greatly improved. Example 2 and Comparative Example 2 Phlogopite was pulverized using the pulverizer used in Example 1, and further air classified to reduce the fine powder to 5% and the coarse powder to 30%.
Phlogopite flakes having an average flake diameter of 20 μm, an aspect ratio of 30, and a shape factor of 0.78 were obtained by cutting. The shape factor was measured in the same manner as in Example 1. In addition, out of 100 flakes, there were 11 flakes with a shape factor of 0.70 or less. 40 parts by weight of this mica flake was used in the resin 60 used in Example 1.
A test piece was prepared in the same manner as in Example 1, and the physical properties were measured and shown in Table 1 (Example 2). In addition, using the same resin as in Example 2, this was mixed with phlogopite crushed by a roller mill with an average flake diameter of 20 μm, an aspect ratio of 31, and an average shape factor of 0.68 in the same manner as in Example 2, and a test piece was prepared. Created.
The physical property values were measured and shown in Table 1 (Comparative Example 2).
However, out of 100 mica, 55 had a shape factor of 0.70 or less. From this result, it is clear that the tensile strength and bending strength are almost the same, but the weld strength is greatly improved. Example 3 and Comparative Example 3 Nylon 640 with relative viscosity 2.6 as thermoplastic resin
The weight part contains 60 parts by weight of muscovite having an average diameter of 45 μm, an aspect ratio of 45, and an average shape factor of 0.78, which were obtained by pulverizing with the pulverizer used in Example 1, air classifying, and cutting off 10% of the fine powder part. part and mixed. The shape factor was measured in the same manner as in the examples. The shape factor of 100 muscovite flakes is 0.70.
There were 15 of the following items. This mixture was fed to a single screw extruder, melted and kneaded at 260°C to obtain pellets. This pellet was made into a test piece in the same manner as in Example 1, dried completely, and its physical properties were measured, and the results are shown in Table 1 (Example 3). The same resin used in Example 3 was crushed with a jet mill, with an average flake diameter of 43 μm and an aspect ratio.
47, muscovite having an average shape factor of 0.65 was mixed in the same manner as in Example 3. Among the 100 muscovite flakes, 60 had a shape factor of 0.70 or less.
This mixture was pelletized in the same manner as in Example 3, and the physical properties were measured using test pieces as shown in Table 1 (Comparative Example 3). From this result, it is clear that the tensile strength and bending strength are almost the same, but the weld strength is greatly improved. Example 4 and Comparative Example 4 Phlogopite was crushed using the crusher used in Example 1, and then air classified to cut 20% of the fine powder into flakes with an average diameter of 60 μm, an aspect ratio of 33, and an average shape factor of 0.81. Obtained some phlogopite flakes. The shape factor was measured in the same manner as in Example 1. In addition, out of 100 flakes, there were 7 flakes with a shape factor of 0.70 or less. 40 parts by weight of this mica flake and 60 parts by weight of polybutylene terephthalate with a melt flow rate of 12 g/10 min were mixed, a test piece was prepared in the same manner as in Example 1, and the physical properties were measured and shown in Table 1. (Example 4). In addition, 60 parts by weight of the same resin used in Example 4,
A test piece was prepared in the same manner as in Example 4 by mixing with 40 parts by weight of phlogopite flakes having an average flake diameter of 57 μm, an aspect ratio of 33, and an average shape factor of 0.70, which were crushed with a Dispa Mill (manufactured by Hosokawa Micron Co., Ltd.). The physical properties were measured and shown in Table 1 (Comparative Example 4).
In addition, the shape factor of mica flakes in this case is 0.70
It was hot. Comparing Example 4 and Comparative Example 4, it is clear that the tensile strength and bending strength are almost the same, but the weld strength is significantly improved. Example 5 and Comparative Example 5 Phlogopite was pulverized using the pulverizer used in Example 1, and 10% of the fine powder portion was cut off by air classification, and the average flake diameter was 80 μm, the aspect ratio was 50, and the average shape factor was 0.82. Mica flakes were obtained. The mica flakes and the resin used in Example 1 were mixed at a weight ratio of 20/80, a test piece was prepared in the same manner as in Example 1, and the physical properties were measured and shown in Table 1. Example 5).
Further, out of 100 mica flakes, there were 5 flakes with a shape factor of 0.70 or less. In addition, using the same resin as in Example 1, phlogopite pulverized with a jet mill having an average flake diameter of 80 μm, an aspect ratio of 53, and an average shape factor of 0.69 was mixed in the same manner as in Example 5, and a test piece was prepared. was created. The physical property values were measured and shown in Table 1 (Comparative Example 5). However, the shape factor of the 100 mica is
There were 52 items below 0.70. From this result, it is clear that the tensile strength and bending strength are almost the same, but the weld strength is greatly improved.

【table】

【table】 [Brief explanation of drawings]

Figure 1 is a scanning electron micrograph of mica flakes with an average shape factor of 0.80 used in Example 1, and Figure 2 is a scanning electron micrograph of mica flakes with an average shape factor of 0.70 used in Comparative Example 1. This is an electron micrograph. Figure 3 shows the cumulative frequency curves of the mica flakes used in Example 1 and Comparative Example 1, where 1 is the cumulative frequency curve of the mica flakes used in Example 1, and 2 is the cumulative frequency curve of the mica flakes used in Comparative Example 1. It is.

Claims (1)

[Claims] 1. Mica flakes with an average shape factor of 0.76 or more
A resin composition consisting of 10 to 80% by weight and 90 to 20% by weight of a thermoplastic resin. 2. Claim 1, in which the number of mica flakes having a shape factor of 0.70 or less is 20 or less out of 100.
The resin composition described in .