JP2980694B2 - Short fiber composite rubber composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a short fiber composite rubber composition, and more particularly, to an extrusion, transfer and injection molding.

[0002]

2. Description of the Related Art Generally, in the field of elastomers, for example, in the field of elastomers, short-fiber composite rubber products are used as FRPs on compression rubber layers of power transmission belts, vibration-isolating rubber, cushioning materials, sealing materials, shoe soles, flooring materials, and covers of tracks. In the field of, it can be used for applications such as sliding materials and reinforcing parts, and is useful. Conventionally, as a processing method for orienting fibers in a short fiber composite rubber product, using an unvulcanized short fiber composite rubber composition in which short fibers are dispersed in a matrix rubber, the above fibers are calendered in a calendering direction. There is known a method of orienting the resin in an extrusion direction and a method of mainly orienting the material in an extrusion direction and a direction orthogonal thereto using an annular die.

[0003]

However, in the former processing method described above, it is possible to obtain a homogeneous oriented product regardless of the characteristics of the compound. However, in the latter processing method, transfer molding in which alignment is achieved through holes. In addition, in injection molding, there is a problem that voids exist inside the molded product, and it is difficult to obtain a uniform molded product as a whole due to uneven distribution of short fibers and local disturbance of the degree of short fiber orientation. Was.

[0004] The present invention has been made in view of such a point, and an object thereof is to eliminate internal defects by specifying the flow characteristics of a matrix rubber in extrusion, transfer, injection molding, and the like. Moreover, it is an object of the present invention to provide a short-fiber composite rubber composition in which short fibers are uniformly dispersed and oriented to obtain a uniform molded product as a whole.

[0005]

In order to achieve the above-mentioned object, a solution of the present invention is a short fiber composite rubber for unvulcanized extrusion, transfer and injection molding, in which short fibers are dispersed in a matrix rubber. As the composition, the following viscosity formula (I) of the matrix rubber alone and the relaxation die swell (I
In (I) and the viscosity formula (I ′) and the relaxation die swell (II ′) of the short fiber composite rubber, the absolute temperature is 353 to 4
Each coefficient in the region of 33 ° K and a shear strain rate of 2 to 500 sec ^-1

[0006]

(Equation 2)

[0007]

[0008]

According to the present invention, the viscosity formula (I) and the relaxation die swell (II) of the matrix rubber alone and the viscosity formula (I ') and the relaxation die swell (II') of the short fiber composite rubber are used in the present invention. ), The absolute temperature is 353
Each coefficient in a region of ４433 ° K and a shear strain rate of 2 to 500 sec ⁻¹

[0009]

(Equation 3)

[0010] Therefore, the elastic recovery of the short fibers causing voids and the change in viscosity causing the disorder of the fiber dispersion orientation are reduced, and there are no internal defects and the short fibers are uniformly dispersed. Orientation results in a molded product that is homogeneous as a whole.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

A short fiber composite rubber composition according to an embodiment of the present invention is for unvulcanized extrusion, transfer and injection molding in which short fibers are dispersed in a matrix rubber,
The viscosity formula (I) and the relaxation die swell (II) of the matrix rubber alone and the viscosity formula (I
') And the relaxation die swell (II'), the absolute temperature is 353-433 ° K and the shear strain rate is 2-50.
Each coefficient in the region of 0 sec ^-1 is

[0013]

(Equation 4)

Is set to The relaxation die swell is also described as a function of the absolute temperature and the shear strain rate similarly to the viscosity, but is omitted because the contribution of the temperature term is smaller than that of the shear strain rate.

As the matrix rubber, for example, a compound obtained by adding a compounding agent to a crosslinkable elastomer such as natural rubber, styrene / butadiene rubber, chloroprene rubber, acrylonitrile / butadiene rubber and ethylene propylene rubber is used.

Examples of the short fibers include natural fibers such as cotton, silk and wool, synthetic fibers such as nylon, aramid, polyester, acrylic and vinylon, and inorganic fibers such as glass, carbon, silica, silicon nitride and alumina. And metal fibers are used.

In the viscosity formula (I) and the relaxation die swell (II) of the matrix rubber alone and the viscosity formula (I ′) and the relaxation die swell (II ′) of the short fiber composite rubber, the absolute temperature is 353 to The coefficient a ′ in the region of 433 ° K. and a shear strain rate of 2 to 500 sec ⁻¹ is represented by a ′.
The reason for setting ≦ 1000 is that when a ′> 1000, the viscosity change due to the temperature difference is large, and the temperature variation of the compound during the flow is remarkably exhibited as the viscosity variation, which causes turbulence and causes the uniform short fibers. This is because it becomes impossible to obtain a proper alignment state.

The reason why the coefficient b 'is set to 0.70≤b'≤0.95 is that when b'<0.70, an apparent increase in the viscosity in the flow path expanding portion from the molding flow path to the cavity or the die is caused. While small, voids are easily generated in the molded product, b
When '> 0.95, a change in the flow path dimension causes a sudden change in viscosity, and at the change point, the flow is disturbed, and a high fiber orientation product cannot be obtained.

The reason why the coefficient c ′ is set to 5.1 ≦ c ′ ≦ 5.6 is that when c ′ <5.1, it is considered that the back pressure is insufficient. This is because an extrudate that is extruded and corresponds to the shape of the die outlet cannot be obtained, and in transfer molding or injection molding, a gate-shaped material is filled in a random direction. On the other hand, when c ′> 5.6, it is not possible to pass through a flow path having a size sufficient for orientation at a sufficient speed, the back pressure is increased, and in extrusion molding, the extrusion speed is extremely slow, and scorch or deterioration is caused. For it will occur. Also,
This is because transfer molding or injection molding results in insufficient filling.

The relationship between the coefficient b 'and the coefficient b is represented by b' / b≤
The reason for setting to 1.5 is that although b ′ / b> 1.5, the cause is not always clear, but it is considered that there is a difference in fluidity at the high and low portions of the microscopic fiber concentration in the channel size changing portion. And
This is because macroscopic fiber shading appears in the final molded product.

The relationship between the coefficient d 'and the coefficient d is represented by d' / d ≧
The reason for setting to 0.1 is that voids are generated inside the molded product when d '/ d <0.1. This phenomenon is caused when a large amount of short fibers are mixed in the matrix rubber with a low filler content. Many appear. This is because it is considered that the elastic recovery of the matrix rubber is in a form in which the elastic recovery is forcibly suppressed by short fibers, and the shape can be maintained when a substantially complete uniaxially oriented material is extruded by a capillary rheometer or the like. In actual product molding, elastic recovery occurs when pressure is released, and voids are generated.

Next, an example of the present invention in which a molded product (sheet) is extruded using the short fiber composite rubber composition having the above-described structure will be described.

First, the following compounding materials were mixed by an internal kneader to obtain a matrix rubber compound. In the following blending materials, the blend ratio of neoprene W and neoprene WHV was varied, and FT (20 to 150 parts by weight) and SR as carbon black were used.
F (15 to 100 parts by weight), FEF (10 to 70 parts by weight) and ISAF (10 to 60 parts by weight) were added in varying amounts.

<Ingredients> Chloroprene rubber 100 parts by weight (neoprene W / WHV) Stearic acid 1 Calcium oxide 5 Magnesium oxide 4 Zinc oxide 5 Antioxidant 2 Dioctyl phthalate 5 Vulcanization accelerator NA-22 0.8 Carbon black variant -Variation Next, 1 to 25 VOL% of aramid, nylon and cotton fibers cut to a length of 0.5 to 6.0 mm with a roll were mixed with the matrix rubber compound to obtain a short fiber composite rubber compound. The viscosity and relaxation die swell were measured with a capillary rheometer at 80, 100,
120, 140 ° C,

[0025]

(Equation 5)

The coefficients a to e and a 'to e' were calculated using the above viscosity equation and relaxation die swell.

Thereafter, a mold (die) having two arc-shaped openings 4A and 4B as shown in FIGS.
1 was attached to the tip of an extruder (not shown), and an extruded sheet was obtained from the short fiber composite rubber compound. The test results are shown in Table 1 (Example of the present invention) and Table 2 (Comparative Example), FIG. 3A (fiber orientation ratio), and FIG. 3B (presence or absence of voids). In FIG. 1, reference numeral 2 denotes a main molding passage;
Is an annular molding passage, and the short fiber composite rubber compound flows out from the main molding passage 2 through the annular molding passage 3 through the openings 4A and 4B.
The annular forming passage 3 has a first passage 3A which communicates with the main forming passage 2 and gradually increases in radius, and a second passage 3B having a diameter substantially equal to the maximum diameter of the first passage 3A. In the middle of the second passage 3B, a minimum dimension portion (dam portion) 5 which is a constricted portion for reducing the passage sectional area is provided. Also, ho is the dimension of the openings 4A and 4B corresponding to the sheet thickness direction, hm is the dimension corresponding to the sheet thickness direction in the minimum dimension section 5 (the minimum dimension in the second passage 3B), and lmo is the minimum dimension section. 5
The flow path length from the opening to the openings 4A and 4B is shown. And
In this embodiment, ho = 5 mm, hm = 0.5 mm, lmo =
It is set to 40 mm. Further, in FIG. 3A, a mark ○ indicates that the fiber orientation rate is 55% or more, and a mark ● indicates that the fiber orientation rate is 50% or less. Also,
In FIG. 3B, a mark ○ indicates that there is no gap, and a mark ● indicates that there is a gap.

The shape was visually determined, the presence of voids was determined by visual observation and measured specific gravity / calculated specific gravity, and the macroscopic uniformity of the fiber was determined by microscopic observation of the cross section of the vulcanized rubber. The fiber orientation ratio H was 20 mm x 2 after vulcanization.
A test piece of 0 mm × 2 mm was cut out by cutting, and the linear swelling ratio after immersion in toluene for 48 hours was determined by the following equation.

[0029]

(Equation 6)

[0030]

[Table 1]

[0031]

[Table 2]

As a result, as apparent from the data shown in Tables 1 and 2 and FIGS. 2 and 3, the viscosity formula (I) and the relaxation die swell (II) of the matrix rubber alone were In the viscosity formula (I ′) and the relaxation die swell (II ′) of the short fiber composite rubber, the absolute temperature is 3
53-433 ° K and shear strain rate of 2-500 sec ^-1
Each coefficient in the region of is

[0033]

(Equation 7)

At the time, a molded product (extruded sheet) homogeneous as a whole without any voids or disturbance in fiber dispersion orientation could be obtained.

[0035]

As described above, according to the present invention,
The viscosity formula (I) and the relaxation die swell (II) of the matrix rubber alone and the viscosity formula (I
') And the relaxation die swell (II'), the absolute temperature is 353-433 ° K and the shear strain rate is 2-50.
Each coefficient in the region of 0 sec ^-1 is

[0036]

(Equation 8)

Since the setting is set to be extruded, transferred, injection-molded, etc., there is no internal defect, and the short fibers are uniformly dispersed and oriented, so that a uniform molded product as a whole can be obtained.

[Brief description of the drawings]

FIG. 1 is a vertical sectional side view of a molding die.

FIG. 2 is a front view of a molding die.

FIG. 3A is a view showing data of fiber orientation ratio.
(B) is a diagram showing data on the presence or absence of a void.

Continuation of the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) C08L 7/00-21/02 C08J 5/04-5/08 C08K 7/02-7/14

Claims (1)

(57) [Claims] An unvulcanized short fiber composite rubber composition for extrusion, transfer and injection molding wherein short fibers are dispersed in a matrix rubber, wherein the viscosity formula (I) and relaxation of the following matrix rubber alone are In the die swell (II), the viscosity formula (I ') of the short fiber composite rubber, and the relaxation die swell (II'), the absolute temperature is 353 to 433 ° K and the shear strain rate is 2 to 500 sec ^-1 . Each coefficient in the area is Short fiber composite rubber composition characterized by being set to: