JP2929076B2 - Master Badge - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a masterbatch used for foam extrusion molding having excellent dispersibility, and more particularly to a masterbatch suitably used for producing a foamed coaxial cable.

[0002]

2. Description of the Related Art A foamed extruded product of a polyolefin resin is widely used in various fields, for example, applied to an insulator of a foamed coaxial cable. Conventionally, an organic nucleating agent such as ADCA (azodicarbonamide) and OBSH (4,4′-oxybisbenzenesulfonylhydrazide) is used for a polyolefin-based resin in a foamed extruded product. As a method of mixing the polyolefin resin and the nucleating agent, the following two methods have been adopted. One method is a method in which a polyolefin-based resin and a nucleating agent are kneaded and extruded in advance using a Banbury mixer or the like, and then pelletized by a pelletizer or the like, which is directly supplied to an extruder and foamed and extruded. Another method is a method using a master batch. That is, a master batch in which a nucleating agent is contained at a high concentration in a polyolefin resin is prepared, and the master batch and a raw polyolefin resin are supplied to an extruder to thereby obtain a nucleating agent in the polyolefin resin. This is a method in which foaming extrusion molding is carried out by reducing the concentration to the above.

[0003] In any of the above methods,
Usually, the production of pellets and masterbatch and the foam extrusion molding are performed in separate steps. That is, pellets and a master batch are prepared in advance, and then, if necessary, a production plan is made by, for example, receiving an order from a customer, and then foam extrusion is performed using these pellets and the master batch as needed.
Therefore, it may take time from the production of the pellets or the masterbatch to the actual production of the foamed extruded product, and during this time, moisture adheres to the pellets or the masterbatch containing the nucleating agent that easily absorbs moisture. When a foamed extruded product is formed using the pellets or the masterbatch, a small amount of water remains in the foamed extruded product. For example, when the foamed coaxial cable is used as an insulator, the electrical characteristics of the foamed coaxial cable are reduced. The problem arises that is worse. Therefore, it is necessary to store the pellet containing the nucleating agent and the masterbatch in a low humidity environment. In particular, the former method has a problem that the amount of the pellet is large and the management is difficult. Further, when ADCA, OBSH, etc. are used as nucleating agents in the master batch, the foamed extruded product has a variation in the degree of foaming in the length direction. For example, when the foamed coaxial cable is used as an insulator, There has been a problem that electrical characteristics, particularly voltage standing wave ratio characteristics (hereinafter, also referred to as VSWR characteristics) are reduced, and radio waves of a certain frequency range cannot be transmitted. Further, it is desired that the foam insulator of the foamed coaxial cable has a fine and uniform cell structure and a high foaming degree from the viewpoint of electrical characteristics.

[0004]

DISCLOSURE OF THE INVENTION The present invention solves the above problems and provides a masterbatch used for foam extrusion molding having excellent dispersibility, and a masterbatch suitably used for producing a foamed coaxial cable. The purpose is to provide.

[0005]

DISCLOSURE OF THE INVENTION The present inventors have developed a masterbatch used for foaming extrusion molding of a polyolefin resin, wherein the polyolefin resin has an average particle diameter of 3 to 50 μm and a specific surface area of 1 to 50 μm as a nucleating agent. By adding 10 m ² / g of boron nitride, mixing the polyolefin-based resin with boron nitride at a mixing ratio of 30:70 to 90:10, and forming the pellets, a masterbatch having excellent dispersibility can be obtained. It was also found that the cell structure of a foamed extruded product using the masterbatch of the present invention was finer and more uniform. Furthermore, it has been found that the use of a scaly boron nitride makes the cell structure of a foamed extruded product finer. Also,
By using the masterbatch of the present invention for producing a foamed coaxial cable, it has been found that a foamed coaxial cable having excellent electrical properties can be produced.

The polyolefin resins used in the present invention include, for example, high-density polyethylene, medium-density polyethylene, low-density polyethylene, polypropylene, ethylene-
A propylene copolymer and the like can be mentioned. In the present invention, the above-mentioned various polyolefin resins can be used alone or as a mixture of two or more. From the viewpoint of the degree of foaming, high-density polyethylene and / or low-density polyethylene are preferably used. And low-density polyethylene are preferably used. The mixing ratio of the high-density polyethylene to the low-density polyethylene in the above mixture is suitably about 10:90 to 90:10 by weight, and those having a ratio of 20:80 to 50:50 are particularly preferably used. In the present invention, the high-density polyethylene has a density exceeding 0.940 g / cm ³ and 0.965 g / cm ^3.
/ Cm ³ or less, and medium density polyethylene has a density exceeding 0.925 g / cm ³ and 0.940 g / cm ^3
3 or less one, the low density polyethylene density 0.910 g / cm ³ or more, and of 0.925 g / cm ³ or less.

The preferred range of the melt flow rate (hereinafter referred to as MFR) of the polyolefin resin used in the present invention is about 0.5 to 10 g / 10 minutes for polyethylene, and 1 to 20 g / 10 minutes for polypropylene. It is about. In the present invention, the MFR is JIS K721.
It is a value measured according to 0.

In the present invention, the nucleating agent has an average particle size of 3 to 3.
Use 50 μm boron nitride. If the average particle size is less than 3 μm, the boron nitride is liable to agglomerate and the dispersibility decreases, which is not preferable. On the other hand, when the average particle size exceeds 50 μm, the cell structure of the foamed extruded product becomes uneven, which is not preferable. The average particle size in the present invention is determined by placing about 10 mg of boron nitride in an ethanol / water (1: 1) solution based on a laser diffraction method (microtrack particle size analyzer), and using an ultrasonic cleaner (28 KHz). For 5 minutes and then disperse the dispersion in Laser
It was measured using a Granulometer Model 715 device.

In the present invention, among the above-mentioned boron nitrides, those having a specific surface area of 1 to 10 m ² / g are particularly used. If the specific surface area is less than 1 m ² / g, the cells of the foamed extruded product tend to be non-uniform, and if it exceeds 10 m ² / g, the cells of the foamed extruded product tend to be coarse and non-uniform. The hygroscopicity tends to increase. The specific surface area in the present invention is a value measured based on BET (Brunauer-Emmett-Taylor method). Further, in the present invention, boron nitride having an appearance form such as flakes or granules can be used, but from the viewpoint of miniaturization of cells of the foamed extruded product, in particular, flaky boron nitride may be used. preferable.

[0010] In the masterbatch of the present invention, the compounding ratio of the polyolefin resin and boron nitride is from 30:70 to
90:10. If the compounding amount of boron nitride is too large, the dispersibility tends to decrease, and if the compounding amount of boron nitride is too small, the amount of the master batch used for foam extrusion molding increases, so that the management tends to be difficult. is there.

A conventionally known nucleating agent other than the above-mentioned boron nitride can also be used in combination with boron nitride as long as the object of the present invention is not lost. For example, alumina, zirconia, inorganic compounds such as talc, azodicarbonamide,
Organic foaming compounds such as 4,4'-oxybisbenzenesulfonyl hydrazide and the like can be mentioned. Further, an antioxidant, a copper damage inhibitor, a coloring agent, and the like may be appropriately added to the masterbatch of the present invention, if necessary.

In the present invention, the master batch needs to be in the form of pellets. In the present invention, the pellet shape has a cylindrical shape, a cylindrical shape, a cubic shape, a rectangular parallelepiped shape, a spherical shape or the like, and one side or diameter is 0.5.
About 5.0 mm. Note that, for example, a powdery master batch has poor dispersibility, and the object of the present invention is hardly sufficiently achieved.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The master batch of the present invention is used for foaming extrusion molding of a polyolefin resin, and is particularly suitably used for molding an insulator of a foamed coaxial cable. When the masterbatch of the present invention is used, the mixing ratio of the polyolefin resin and the masterbatch to be foamed and extruded is such that when the polyolefin resin and the masterbatch are sufficiently kneaded in the extruder, the polyolefin resin 100 Boron nitride is 0.1 to 5.0 parts by weight.
What is necessary is just to make it about a weight part. If the amount of boron nitride is less than 0.1 part by weight, the appearance of the molded article tends to deteriorate, and if it exceeds 5.0 parts by weight, the degree of foaming tends to decrease. In this case, a foaming agent is used, and the foaming agent is not particularly limited. For example, nitrogen gas, argon gas, inert gas such as carbon dioxide gas, fluorocarbon,
Chlorofluorocarbon, hydrocarbon and the like can be mentioned.

Example 1 Each material shown in Table 1 was heated to 130 ° C.
The mixture was sufficiently mixed for 20 minutes with two rolls held at a constant temperature, and then pelletized at room temperature to obtain a cylindrical master batch having an outer diameter of 3.0 to 4.0 mm and a length of 3.0 to 4.0 mm.
The masterbatch and the polyolefin-based resin are supplied to a hopper of an extruder having a barrel temperature of 200 ° C. and an L / D of 24, and a foaming agent is pressed into the extruder through a pump, mixed in the extruder, and extruded and foamed on a conductor. The insulation of the foamed coaxial cable was formed. The amounts of the master batch and the foaming agent are 5 parts by weight and 1.0 part by weight, respectively, based on 100 parts by weight of the polyolefin resin. (Examples 2 to 4) The same as Example 1. (Examples 5 and 6) The same as Example 1 except that the blending amount of the master batch was changed to 10 parts by weight with respect to 100 parts by weight of the polyolefin resin. (Embodiment 7) This is the same as Embodiment 1. (Embodiment 8) The shape of the master batch is 1.0 to 1.0
It is the same as Example 1 except that a 2.0 mm cube was used. (Embodiment 9) The shape of the master batch is changed to an outer diameter of 1.0 to 2.
Example 1 is the same as Example 1 except that the columnar shape is 0 mm and the length is 3.0 to 4.0 mm. (Comparative Examples 1 to 3) Same as Example 1. (Comparative Example 4) The same as Example 1 except that the shape of the master batch was changed to powder.

Tables 1 and 2 show the mixing ratios of the materials used in the examples and comparative examples, and the evaluation results. The evaluation method is as follows. <Fineness> The fineness of the cell structure of the foamed extruded product was evaluated based on the average cell diameter. The average cell diameter is obtained by observing the cross section of the foamed insulator, measuring the longest diameter of ten randomly selected cells, and calculating the average length. Criteria A: Average cell diameter is 0.5 mm or less. ：: The average cell diameter is more than 0.5 mm and less than 1.0 mm. X: The average cell diameter is 1.0 mm or more. <Uniformity> The cell uniformity of the foamed extruded product was determined by visually observing the cross section of the foamed insulator. Judgment criteria A: A state in which the size of all cells is almost the same. ：: A state in which slightly larger cells are mixed with cells of average size. ×: A state in which half or more large cells are mixed. <Dispersibility> The dispersibility of the masterbatch was evaluated from the VSWR characteristics of the foamed coaxial cable manufactured using the masterbatch. The VSWR is a maximum voltage (Vma) of a wave (standing wave) that does not seem to travel due to interference between the traveling wave and the reflected wave.
x) and the minimum voltage (Vmin), and is a value calculated from the following equation. VSWR = Vmax / Vmin The obtained VSWR value was 1.2 or less, and the result was ×.

The average particle size, specific surface area, and shape of boron nitride used in Examples and Comparative Examples are as follows. BN-1: average particle size 8 μm, specific surface area 5.5 cm ² /
g, scaly. BN-2: average particle size 40 μm, specific surface area 2.0 cm ² /
g, scaly. BN-3: average particle size 7 μm, specific surface area 4.0 cm ² /
g, scaly. BN-4: average particle size 20 μm, specific surface area 3.0 cm ² /
g, granular. BN-5: average particle size 5 μm, specific surface area 3.0 cm ² /
g, scaly. BN-6: average particle size 2 μm, specific surface area 10.0 cm ² /
g, scaly. BN-7: average particle size 55 μm, specific surface area 1.0 cm ² /
g, scaly.

[0017]

[Table 1]

[0018]

[Table 2]

[0019]

According to the present invention, there is provided a masterbatch used for foam extrusion extrusion of a polyolefin resin, wherein the polyolefin resin has an average particle size of 3 as a nucleating agent.
Since a masterbatch having excellent dispersibility can be obtained by containing boron nitride having a thickness of about 50 μm and forming a pellet, the cell structure of the foamed extruded product using the masterbatch of the present invention is fine and uniform. become. Further, by using the boron nitride having a specific surface area of 1 to 10 m ² / g, the cell structure of the foamed extruded product becomes finer and more uniform. In addition, by using the above-mentioned boron nitride having a scale shape, the cell structure of the foamed extruded product is further reduced. Further, by using the masterbatch of the present invention for forming an insulator of a foamed coaxial cable, a foamed coaxial cable having excellent electrical characteristics can be obtained.

Continued on the front page (72) Inventor Mutsumi Wada 8 Nishinocho, Higashimukaijima, Amagasaki City, Hyogo Prefecture Inside Mitsubishi Cable Industry Co., Ltd. Ryuichi Ide, Examiner, Fukui Works, Cable Industries, Ltd. (56) References JP-A-4-348141 (JP, A) JP-A-53-67750 (JP, A) JP-A 8-208873 (JP, A) ( 58) Field surveyed (Int.Cl. ⁶ , DB name) C08J 3/22, 9/06 H01B 13/14

Claims (3)

(57) [Claims] 1. A masterbatch used for foam extrusion extrusion of a polyolefin resin, wherein the polyolefin resin has an average particle diameter of 3 to 50 μm and a specific surface area of 1 as a nucleating agent.
10 to 10 m ² / g of boron nitride, and the compounding ratio of the polyolefin resin and boron nitride is 30:70.
A masterbatch characterized by being in the form of a pellet, having a particle size of up to 90:10. 2. The method according to claim 1, wherein said boron nitride is in the form of scale.
Master batch described. 3. The master batch according to claim 1, which is used for producing a foamed coaxial cable.