JP2752213B2 - Extrusion molding method of polyolefin-vegetable fiber composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for extruding a polyolefin-vegetable fiber composition.

[Conventional technology and its problems] When a polyolefin resin such as polyethylene or polypropylene is used for a building material, an industrial material, or the like, a plant fiber is blended with the polyolefin as a reinforcing material or an expanding material. Have been done.

As a molding method of such a polyolefin-vegetable fiber composition, a general compression molding method, a transfer molding method, an injection molding method, an extrusion molding method, and the like are employed.
For example, to obtain a long product, an extrusion molding method is employed.

The extrusion molding method extrudes a kneaded polyolefin-vegetable fiber composition while being heated and melted in a cylinder containing a screw from a molding die having a predetermined cross-sectional shape, and forms a molten state formed by the molding die. In this method, the composition is passed through a sizing die, cooled, and sized to a predetermined size to obtain a desired molded product. Here, the sizing die is usually provided at a predetermined interval (3 cm to 20 cm) from the forming die.

By the way, when a relatively thick solid deformed product obtained from the above-mentioned polyolefin-vegetable fiber composition is used for building materials, industrial materials, etc., its specific gravity is as heavy as about 1.16, so that the workability is high. It is desired to reduce the weight in terms of cost and cost. Therefore, it has been studied and attempted to reduce the apparent specific gravity to about 0.6 and to reduce the thickness (about 1.5 mm to 2 mm in thickness) by making the shape of the molded article hollow.

However, as described above, by reducing the thickness of the molded article to a hollow irregular shape, the cooling rate is increased, and the polyolefin-vegetable fiber composition itself is difficult to mold. Various problems have occurred.

For example, the frictional resistance between the polyolefin-vegetable fiber composition and the sizing die wall surface increases, and it becomes difficult to obtain a molded article having a uniform shape, and the surface of the molded article becomes a matte state, and the surface is smooth and glossy. There is a problem that a molded product cannot be obtained.

Therefore, it is conceivable to add general calcium stearate or silicone oil as a lubricant to the polyolefin-vegetable fiber composition as a molding material,
Almost no improvement in moldability due to calcium stearate is observed. As for the silicone oil, a molded product with a uniform and smooth surface can be obtained at the beginning of extrusion molding, but as the molding proceeds, the silicone oil adheres to the screw of the extruder, causing uneven discharge, and furthermore, molding is not possible There is a problem that becomes.

Further, as a problem derived from the difficulty of molding of the polyolefin-vegetable fiber composition itself, the plant fiber has a molding temperature (20%).
(At around 0 ° C.) to generate an acidic gas, and there is a problem that the vaporization of the acidic gas and the water adsorbed on the plant fiber causes a large number of air bubbles, resulting in a decrease in strength and rigidity.

Although the problem in the case of extrusion molding of a hollow shaped article has been described above, the same problem occurs in the case of extruding a relatively thin shaped article which has no hollow portion but is relatively thin.

Accordingly, an object of the present invention is to suppress the frictional resistance with the wall surface of a sizing die, which is observed when producing a polyolefin-vegetable fiber-based composition having a hollow deformed product or a relatively thin deformed product having no hollow portion. , Excellent in shape uniformity,
Another object of the present invention is to provide a method for extruding a polyolefin-vegetable fiber composition, which can provide a molded article having a smooth and glossy surface. Another object of the present invention is to provide a polyolefin-vegetable fiber composition. An object of the present invention is to provide a method for extruding a polyolefin-vegetable fiber composition, which can prevent the generation of bubbles due to its own difficulty in molding and can obtain a molded article having excellent strength and rigidity.

[Means for Solving the Problems] That is, according to the present invention, a polyolefin-vegetable fiber composition kneaded in a heated and molten state is extruded into a required shape from a forming die having a through-hole having a predetermined cross-sectional shape. The shaped polyolefin-vegetable fiber composition is cooled by passing through a sizing die provided coaxially with the molding die, and forming an extruded product of the polyolefin-vegetable fiber composition, 100 parts by weight of the polyolefin-vegetable fiber composition to be used as a molding material is 1 part by weight of a silicone rubber-based polymer in terms of silicone.
Compounded in a range of 3.5 parts by weight, the sizing die is arranged coaxially with the molding die in contact with the molding die,
The method further comprises cooling the polyolefin-vegetable fiber composition formed into the shape while controlling the temperature of the sizing die to a predetermined temperature between 80 ° C and 140 ° C.

The molding material used in the present invention is mainly composed of a composition obtained by blending a plant fiber with a polyolefin. Examples of the polyolefin include polyethylene, modified polyethylene, polypropylene, modified polypropylene, and copolymers thereof.
Used as a mixture of more than one species. Examples of the plant fiber include wood pulp, wood flour, rice husk, linter, linter pulp, finely ground newspaper, magazine, and waste paper such as corrugated cardboard. These may be used alone or in combination of two or more. Is used. The mixing ratio of the polyolefin and the plant fiber is not particularly limited, but it is preferable that the plant fiber is mixed with the polyolefin in a range of 40% by weight to 60% by weight.

The molding material used in the present invention is a composition in which a silicone rubber-based polymer is blended in an amount of 1 part by weight to 3.5 parts by weight in terms of silicone content, with 100 parts by weight of the composition of the polyolefin and the vegetable fiber. . As the silicone rubber-based polymer, And n is 6000 to 14000 ° C. (for example, melting point: −40 ° C., glass transition point: −123 ° C.) is preferable. The reason why the amount of such a silicone rubber-based polymer was set to be 1 part by weight to 3.5 parts by weight in terms of silicone based on 100 parts by weight of the polyolefin-vegetable fiber-based composition, is that the compounding amount was 1 part by weight. If it is less than 3, lubricating effect cannot be sufficiently obtained, so that a molded article having a uniform shape cannot be extruded stably, and if it exceeds 3.5 parts by weight, the extrusion speed will decrease. .

In the extrusion molding method of the polyolefin-plant fiber composition of the present invention, a hopper used for ordinary resin molding,
Equipped with screw, cylinder, drive, heating unit, etc. For example, the ratio of screw length to diameter (L / D) is 10
An extruder having a compression ratio (CR) of about 1.5 to 4.0 is used. A molding die having a through-hole having a cross-sectional shape corresponding to the outer peripheral shape of the molded product to be obtained is provided at the outlet side of the extruder. When a hollow molded product is to be obtained, a breaker plate holding a core having an outer peripheral shape corresponding to the inner peripheral shape of the hollow molded product is installed inside the molding die.

In addition, the extruder uses a sizing die in contact with the forming die and coaxially with the forming die. As a result, the pressurized state is maintained from the extrusion process to the cooling process by the sizing die, the generation of acidic gas due to the decomposition of plant fibers and the evaporation of water adsorbed on the plant fibers are suppressed, and high strength and high rigidity molding is performed. Goods are obtained.

In the present invention, first, a polyolefin-vegetable fiber composition containing a silicone rubber-based polymer is kneaded while being heated and melted in a cylinder containing a screw of an extruder as described above. The temperature of the polyolefin-vegetable fiber composition in the cylinder or in the forming die varies depending on the type of polyolefin, the size and shape of the molded product, and the like, but is generally 180 ° C to 230 ° C. The reason is that if the temperature is lower than 180 ° C., the polyolefin-vegetable fiber composition hardens, and if the temperature exceeds 230 ° C., the polyolefin and the vegetable fiber deteriorate.

Next, the polyolefin-vegetable fiber composition in the molten state is continuously extruded from a molding die to shape the polyolefin-vegetable fiber composition into a required shape, and then passed through a sizing die to obtain a predetermined shape. It is sized to a shape and dimensions to obtain a molded product having a predetermined shape, for example, an irregular shape.

Here, the polyolefin-vegetable fiber composition extruded from the molding die is cooled by a sizing die controlled to a predetermined temperature between 80 ° C and 140 ° C. The reason for limiting the temperature of the sizing die to the above range is as follows. That is, when the temperature of the sizing die is less than 80 ° C., the solidification of the polyolefin-vegetable fiber-based composition proceeds rapidly, the frictional resistance between the molded product and the sizing die wall surface increases, and the uniformity of the molded product decreases, This is because the smoothness of the surface of the molded article is lost, and furthermore, extrusion becomes impossible. On the other hand, when the temperature exceeds 140 ° C, the cooling becomes insufficient, and the molten composition is extruded before being sufficiently solidified in the sizing die, and the molten composition oozes out from the surface of the molded article, and has a high density, high strength, and high rigidity. In addition, it becomes impossible to obtain a glossy molded product having a smooth surface.

The reason for controlling the temperature of the sizing die to a predetermined temperature within the above range is to reduce the frictional resistance between the surface of the molded product and the wall surface of the sizing die by balancing the extrusion speed and the cooling speed as described above. In addition, it is for cooling the polyolefin-vegetable fiber composition under pressure.

The extrusion molding method of the polyolefin-vegetable fiber composition of the present invention is particularly suitable for extrusion molding of a hollow shaped article, but is also suitable for extrusion of a relatively thin shaped article having no hollow portion but having a relatively small thickness. is there.

[Operation] In the extrusion molding method of the polyolefin-vegetable fiber composition of the present invention, the lubricating effect is improved by the silicone rubber-based polymer compounded in a predetermined amount in the molding material, and the temperature of the sizing die is controlled to a predetermined temperature. By doing so, the frictional resistance between the molded product and the wall surface of the sizing die is reduced, and it is possible to perform extrusion molding while keeping the shape of the molded product uniform, and a smooth and glossy molded product surface can be obtained.

Controlling the temperature of the sizing die;
The sizing die is placed in contact with the forming die, and the polyolefin-vegetable fiber-based composition can be cooled under pressure while maintaining the balance between the extrusion rate and the cooling rate. The generation of gas and the evaporation of water adsorbed on plant fibers are suppressed,
A high strength, high rigidity molded product can be obtained.

EXAMPLES Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples.

Embodiment 1 FIG. 1 shows an extrusion molding apparatus used in this embodiment.
In FIG. 1, reference numeral 1 denotes a cylinder for containing a molding material, and a heater 2 for heating and melting the molding material is provided on the outer periphery of the cylinder 1. A screw 3 is provided in the cylinder 1 to knead the injected molding material and guide it toward one end (in the direction of the molding die). A hopper 4 for supplying a molding material is provided on the other end side of the cylinder 1, and these constitute an extruder 5.

At one end of the cylinder 1 of the extruder 5, a molding die 6 for molding the molding material exiting the extruder 5 into a required shape is provided. This forming die 6
A sizing die 7 having the same cross-sectional shape as the forming die 6 is provided coaxially at the end of the side opposite to the cylinder 1. The sizing die 7 contacts the end of the forming die 6. It is arranged.

As shown in FIG. 2, the molding die 6 has a through-hole 6a having a cross-sectional shape corresponding to the outer peripheral shape of the hollow molded product. A core 8 for holding the core and a breaker plate 9 for holding the core 8 are provided. The center 8 is provided so as to protrude into the saijin die 7.

Further, inside the sizing die 7, a jacket portion 10 having an inlet 10a and an outlet 10b for the heat medium for temperature control is provided, and the temperature of the sizing die 7 is controlled by the jacket portion 10. The sizing die 7 having the temperature-controllable jacket portion 10 is sized so that the molding material exiting the molding die 6 can maintain a predetermined hollow shape.

Using the extrusion molding apparatus having the above configuration, the polyolefin-plant fiber composition was extruded according to the following procedure.

First, a polyolefin comprising 30% by weight of a polypropylene resin J130G (trade name, manufactured by Ube Industries, Ltd.), 20% by weight of a maleic anhydride-modified polypropylene resin, 45% by weight of wood pulp and 5% by weight of magnesium hydroxide
The plant fiber composition was melt-kneaded and pelletized. Next, 3 parts by weight of silicone rubber-based polymer pellet BY27-001 (trade name, manufactured by Toray Silicone Co., Ltd., silicone polymer content: 50% by weight) was added to 100 parts by weight of the pellet, and the mixture was dried. It was blended to form a molding material.

Next, the molding material was supplied from the hopper 4 into the cylinder 1. The diameter of the cylinder 1 was 20 mm. The molding material supplied into the cylinder 1 was kneaded by the screw 3 while being heated and melted by the heater 2, and was guided to the molding die 6. The screw 3 used had an L / D of 24 and a CR of 2.8, and the rotation speed of the screw 3 was set to 60 rpm.
Further, the temperature of the cylinder 1 was given a temperature gradient in the range of 180 ° C to 200 ° C.

In addition, as shown in FIG.
The building material used had a cross-sectional shape for the peripheral edge, and the core 8 used had a shape corresponding to the peripheral edge.

Next, the kneading die 6 is kneaded by the screw 3.
The molding material guided to the side was formed into a predetermined hollow shape through the molding die 6, and then guided to a sizing die 7 provided coaxially with and in contact with the molding die 6. The temperature of the sizing die 7 was controlled to a constant temperature of 120 ° C. by using a heat medium circulation type temperature controller.

The surface of the extruded product (surrounding edge of the building material) leaving the sizing die 7 had a smooth luster, and the outer peripheral shape and the shape of the hollow portion were clearly reproduced.

Next, the hollow shaped extruded product thus obtained was cut at a length of 1 m, and the weight (single weight) and the coefficient of linear expansion were measured. In addition, 120mm × 5mm ×
A 7 mm test piece was cut out, and the density, flexural strength and flexural modulus were measured. Table 1 shows the results of these measurements. Table 1 also shows the maximum extrusion speed at the time of extrusion molding in the above example.

Comparative Example 1 In Example 1, the molding material was cooled in a temperature range of 10 ° C. to 30 ° C. by simply passing cooling water through the sizing die 7 without providing a temperature controller in the sizing die 7. Molding was performed in the same manner as in Example 1.

However, immediately after the molding material entered the sizing tie 7, the discharge pressure rose sharply and exceeded the allowable pressure value of the extruder, so molding was stopped. Therefore, no molded product was obtained.

Comparative Example 2 A hollow shaped article was extruded in the same manner as in Example 1 except that no silicone rubber-based polymer pellets were added to the molding material.

As a result, under the same temperature conditions as in Example 1, the molded product stopped in the sizing die 7 due to frictional resistance with the die wall surface, and could not be extruded. By raising the temperature in the sizing die 7 to 160 ° C., extrusion became possible, but the obtained molded product was only a very brittle product with poor filling. The physical properties of the extruded product obtained in Comparative Example 2 were measured in the same manner as in Example 1. Table 1 also shows the results.

As is clear from the results in Table 1, the hollow extruded product obtained in Example 1 was higher in density, bending strength, flexural modulus, and flexural strength than the hollow extruded product obtained in Comparative Example 2.
It is excellent in all points of linear expansion coefficient, and it can be seen that it is suitably used as a building material, an industrial material and the like. This is because, in the above embodiment, a predetermined amount of the silicone rubber-based polymer pellet was added to the molding material, and the molding material exiting the molding die 6 was cooled by the sizing die 7 controlled at a constant temperature. This is because an appropriate sliding property is provided in the sizing die 7 and an appropriate cooling rate is obtained.

Comparative Example 3 In Example 1, instead of adding the silicone rubber-based polymer pellets to the molding material, the surface of the molding material was
Silicone oil SH200 for 100 parts by weight of molding material
(Trade name, manufactured by Toray Silicone Co., Ltd., 10000 cs) Extrusion molding of a hollow deformed product was performed in the same manner as in Example 1 except that the treatment was performed with 1 part by weight.

As a result, molding was possible immediately after the start of extrusion molding, but the discharge amount gradually decreased, and after one hour, the screw 3
The molding material did not penetrate into the mold, making molding impossible.

Comparative Example 4 In Example 1, calcium stearate was added to the molding material in place of the silicone rubber-based polymer pellets.
Extrusion molding of a hollow product was carried out in the same manner as in Example 1 except that parts by weight were added.

As a result, almost the same phenomenon as in Comparative Example 2 was observed, and the effect of adding calcium stearate 4 was not recognized at all.

Example 2 A hollow extruded product was obtained in the same manner as in Example 1, except that 2 parts by weight of silicone rubber-based polymer pellet BY27-001 was added in terms of silicone. The appearance and physical properties of the obtained molded article were almost the same as those of the molded article of Example 1, and were excellent.

Comparative Example 5 A hollow extruded product was obtained in the same manner as in Example 1 except that 4 parts by weight of silicone rubber-based polymer pellet BY27-001 was added in terms of silicone content, which was outside the limited range of the present invention. In this comparative example, a molded product was obtained, but there was a problem that the allowable pressure value of the extruder would be exceeded unless the discharge rate was reduced so that the extrusion speed was 4 cm / min or less. Moreover, the surface of the obtained molded product is slightly sticky,
The gloss was poor. Physical properties of the addition the obtained molded article is bending modulus ^{3.1 × 10 4 kg / cm 2} , the flexural strength was lower than in the molded article of 510kg / cm ² in Example 1.

Example 3 Extrusion was performed in the same manner as in Example 1 except that a forming die having a through-hole having a substantially L-shaped cross section was used (an extrusion speed of 6.
4 cm / min) to obtain a relatively L-shaped, relatively thin, irregularly shaped article having no hollow portion as shown in FIG. 3 (a). The appearance and physical properties of the obtained molded article were excellent with almost no difference from the appearance and physical properties of the molded article of Example 1.

Further, in the same manner as above, an odd-shaped product having a sectional shape shown in FIGS. 3 (b) and 3 (c) was obtained. The obtained molded product was excellent with almost no difference in appearance and physical properties of the molded product of Example 1.

Comparative Example 7 Except that the silicone rubber-based polymer pellet was not used, the same procedure as in Example 3 was carried out to obtain a shaped article having a cross-sectional shape shown in FIGS. 3 (a), (b) and (c) by extrusion molding. However, the molding material stopped in the sizing die due to frictional resistance with the die wall surface, and could not be extruded. Therefore, no molded product was obtained.

[Effects of the Invention] As described above, according to the present invention, the shape uniformity is excellent,
In addition, a molded article of a polyolefin-vegetable fiber composition having a smooth and glossy surface can be obtained with good reproducibility by extrusion molding. This molded article is excellent in that it has denseness, high strength, high rigidity, and a low coefficient of thermal expansion.

[Brief description of the drawings]

FIG. 1 is a view showing a schematic configuration of an extrusion molding apparatus used in Examples 1 and 2 of the present invention, FIG. 2 is a view showing a sectional shape of a forming die and a core used in Examples 1 and 2, 3 (a),
(B), (c) is a figure which shows the cross-sectional shape of the molded product obtained in Example 3. 1 ... cylinder, 2 ... heater, 3 ... screw, 4
... Hopper, 5 ... Extruder, 6 ... Forming die, 6a ...
... Through hole, 7 ... Sizing die, 8 ... Center, 9 ...
Breaker plate, 10 ... Jacket part, 10a ... Heat medium inlet, 10b ... Heat medium outlet.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI B29K 105: 12

Claims (2)

(57) [Claims] 1. A polyolefin-vegetable fiber composition kneaded in a heated and melted state is extruded into a required shape from a forming die having a through-hole having a predetermined cross-sectional shape, and the polyolefin-vegetable fiber shaped into this shape is obtained. The system composition is cooled by passing through a sizing die provided coaxially with the molding die to form an extruded product of the polyolefin-plant fiber composition, wherein the polyolefin-plant fiber as a molding material is formed. System composition
100 parts by weight of a silicone rubber-based polymer is compounded in a range of 1 part by weight to 3.5 parts by weight in terms of silicone, and the sizing die is coaxially arranged with the forming die so as to be in contact with the forming die; 80 ° C die temperature
A method for extruding a polyolefin-vegetable fiber-based composition, comprising cooling the polyolefin-vegetable fiber-based composition shaped into the shape while controlling the temperature to a predetermined temperature of about 140 ° C. 2. An extrusion molding composition comprising 100 parts by weight of a polyolefin-vegetable fiber composition and 1 part by weight to 3.5 parts by weight of a silicone rubber-based polymer in terms of silicone.