JPS59143614A - Manufacture of polypropylene board with saw-dust mixed-in - Google Patents

Abstract

PURPOSE:To obtain a compound board made of polypropylene by one process by a monospindle extruder, by adding a mixing medium to a mixture of polypropylene resin and saw dust. CONSTITUTION:Polyethylene of low molecular weight or ataxic polypropylene is added in addition with polypropylene resin and saw dust. Although mean molecular weight of a medium differs with grades and blending rates of the saw dust to be used, it can be limited within a comparative narrow range of 1,000- 4,000. When the mean molecular weight exceeds 4,000 it becomes not only that a bite into an extruder is not favorable and an extruding quantity is deteriorated extremely but also that an extrusion pattern and ruggedness are generated on the surface of a board to be extruded, through which a good board is not obtained. Even if the mean molecular weight is less than 1,000, the bite into the extruder is deteriorated and an effect as a mixing medium can not be displayed to its full capability. As for an additive rate of the medium, 20-40pts.wt. polypropylene resin is appropriate against 100pts.wt. polypropylene.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a composite material of plastic and wood flour, and in particular provides a method for easily and inexpensively manufacturing a polyprohylene composite board containing a large amount of wood flour. be.

Attempts have been made for quite some time to partially replace plastics, particularly polypropylene resin, with inexpensive wood flour and to use it in fields where full strength such as impact resistance is not required. The advantages of this multi-layered composite material are its wood-like double-layered feel, rigidity, and writability.

Some have excellent paintability, adhesion, and processability, extrusion molding,
One advantage is that it can be molded using general plastic molding methods such as vacuum molding, injection molding, and press molding.

Conventionally, when producing a material that is a mixture of plastic and wood flour, a twin-screw extruder or a single-screw extruder is used to first make plasticized composite pellets, and then injection molding or extrusion molding is used. A method has been adopted to do so. The reason for this is that high blends of wood flour have poor extrusion stability, and the extrusion fit fluctuates, resulting in sheets or plate-like products of a certain thickness. This is due to the fact that the resin and wood flour are not rubbed together, but also because the resin and wood flour are not sufficiently kneaded, resulting in problems such as a severely roughened surface and hollow sounds inside. Therefore, once containing wood flour 1
At present, after the tt fat pellets are completely produced, they are shaped again through an extruder or an injection molding machine.

In the method of No. 39, two extrusion steps are required, and the processing cost is high (i'j'), so cheap wood flour is mixed in. II point is lost.

The inventors of 4C have devoted themselves to research into a method for easily and inexpensively manufacturing polypropylene plates with a high content of this powder by eliminating the drawbacks of this conventional method. The present invention has been completed by discovering a method for efficiently producing beautiful composite plates of constant thickness without surface roughness or cavities during the extrusion process.

In manufacturing the polypropylene composite board of the present invention, a third substance is added in addition to the polypropylene resin and wood flour. This substance can be called a type of mediator that promotes the miscibility of resin and wood flour, and as a result of research, it has been found that
Mouse polyethylene or atactic polypropylene were suitable for this purpose. The average molecular weight of the mediator varies depending on the fineness of the wood flour used and the blending ratio of wood flour, but i, o
oo~ Target 4, (Can be limited to a relatively narrow range of Kawaguchi. If the average molecular weight △ exceeds 4.O[]O, it will not penetrate into the extruder properly,
Not only does extrusion become extremely poor, but also extrusion patterns and irregularities occur on the surface of the extruded plate, making it impossible to obtain a high-quality plate. Furthermore, if the average molecular weight is less than 1,000, the penetration will similarly deteriorate and the effect as a miscibility mediator cannot be exhibited. The appropriate addition rate of the mediator was 20 to 40 parts by weight per 100 parts by weight of the polypropylene resin.

The polypropylene resin used in the present invention is preferably in the form of a powder, while the pellet-like one is unsuitable because it has poor stabilization in the extruder. Also, the fluidity of the resin is 1;1 lower lj
Good results were obtained with a melt index of about 5.

In the present invention, the powder is mixed with polypropylene resin (regardless of the tree species, sawdust from ordinary wood can be used, and sawdust from processed materials such as plywood and particle board can also be used. Wood powder) The particle size of the powder should be finer than 25 meters per millimeter; if the particle size is coarser than 25 meters, the extrusion stability will be poor and the extrusion rate will be reduced. First, air drying will cause a decrease in the extrusion rate.The mixing ratio of wood flour is 50 parts by weight per 100 parts by weight of polypropylene 8I fat depending on the use of the composite board.
Although the amount can be increased or decreased within the range of ~150 parts by weight/h1, the present invention is particularly directed toward high-compound blends of this powder. Furthermore, when mixing the resin and wood flour, add less than 1 part of a low-melting substance such as carunium stearate as a lubricant, and if the mixture is heated at a temperature that does not melt the resin, extrusion stability is 1'8.
I---improved further, and extrusion-1 can also be increased.

As is clear from the explanation in Section 4-2 below, when extrusion molding a mixture of polypropylene resin and wood flour using an extruder/machine, the stability of biting in the extruder hopper and, ultimately, the extrusion 4
This is an important factor and can be improved by adding a miscibility mediator such as low-molecular polyethylene or atactic polypropylene and a lubricant such as carunium stearate, but it is important to ensure that there is sufficient crosstalk in the extruder to achieve smoother extrusion. In order to do this, it is necessary to make some modifications to the extruder itself. That is, in a single-screw extruder, 1) the inner diameter of the extruder barrel is changed between the supply section and the metering section, and a two-stage barrel system is adopted in which the inner diameter of the metering section is 1/1.

2] Add a tapered groove to the barrel wall of the supply section.

6] It is necessary to make the entire gap between the screw shaft of the metering part and the barrel wall an appropriate depth.

FIGS. 1 and 2 show longitudinal and transverse sections of a single screw extruder barrel in which the present invention is practiced. In the figure, ■ is the hopper, ■ is the barrel of the supply section, ■ is the barrel of the metering section, ■ is the screw, and ■ is the tapered groove made on the wall of the barrel of the supply section.

■ is the gap between the metal ring screw shaft and the barrel wall.

Among the six modifications listed in Item L, [1] is a known method used in ordinary extruders, but in the present invention, the barrel inner diameter ratio el: [J, 6 to 0.8] is particularly used in the present invention. do. As a result of research, it was found that extrusion becomes difficult if the barrel inner diameter of the metering section is less than 0.6 times that of the supply section. 2) By forming shallow tapered grooves on the wall of the barrel of the feed section, the mixture of resin and wood flour fed from the hopper is bitten by several degrees i'1, resulting in an increase in the extrusion rate. The groove may be shallow, with a width of 5 to 20 nm and a depth of 1 to 5 nm, but the length is 1.5 to 6 mm, which is the inner diameter of the supply barrel.
It is safe to set the depth to about double the diameter, and it should be provided vertically on the screw shaft and in row F, so that it gradually becomes shallower as it goes from the hopper side to the extrusion side, and finally disappears. Although the number of grooves may be one, it is even more preferable to provide six grooves. 6] is a measure to ensure that the gap between the screw shaft and the barrel wall in the metering part is adjusted to an appropriate level so that the mixture of resin and wood flour is combed in all stages and the extrusion is performed smoothly. If kneading is not sufficient, surface roughness and internal hollowing of the composite plate will be induced.

If the gap is too narrow, gas is likely to be generated due to overheated decomposition of the wood powder, making it impossible to obtain a satisfactory board. The thickness of the gap is 5~
A 10 m crow was appropriate.

Using an extruder modified as described above and adding the above-mentioned admixture agent, a beautiful plate-like product in which 50 to 150 parts of wood flour is mixed with 100 parts of polypropylene 4L fat and 100 parts of heavy iron can be easily produced. It can be extruded.

The resulting plate? By further sandblasting,
A board with significantly improved paint applicability, printability, antistatic properties, etc. can be obtained.

According to the production method of the present invention, resin and wood powder? There is no need to make pellets in advance and re-extrude the entire knot to form the desired polypropylene composite tray, and the desired polypropylene composite tray can be obtained in one step using a simple single-screw extruder, which not only saves processing costs, but also There is no doubt that this method is extremely advantageous economically compared to conventional methods, as it requires less investment in equipment for an extruder.Examples will be further explained below.

In the examples, all references to "part-4" refer to "part-4".

Example 1 Powdered polypropylene resin (trade name, Yucalon TA-5. Manufactured by Mitsubishi Yuka) 100 parts Hon powder, 25 mesh baths (manufactured by Dezumi Kokusaku Pulp) 100 parts low molecular weight resin
Polyethylene (trade name: Mitsui Iwanox 110P.

Made by Mitsui Petrochemical Co., Ltd.] 20 parts Stearin Calcium 0.5 fB is mixed well, and the barrel inner diameter ratio of the supply part and the metering part is 1.
: 0.75 (130gJ-98ρ) extruder,
The barrel wall of the supply section has six tapered grooves with a length six times the inner diameter of the barrel, and there is a gap between the screw shaft of the metering section and the barrel wall. jji total 8〃1. The entire extrusion of the plate-like material was carried out by putting it into a single-screw extruder adjusted to m.

The extrusion stability was good and it was possible to obtain the desired product with no surface roughness or internal voids for a long time.

The surface of this plate-like object was sandblasted, and the paint coating was good, and the plate had a beautiful woody feel.

Example 2 100 parts of powdered polypropylene (trade name, Yucalon TA-5, manufactured by Mitsubishi Yuka) 100 parts of wood flour, 150 parts of 10 Rometsuyupas (Mitoyo Kakoki Co., Ltd.) 40 parts of atactic polypropylene (Sumitomo Chemical Co., Ltd. #) After mixing well, the mixture was fed to the same single-screw extruder as in Example 1 and continuously extruded for a long time. The extrusion stability was good, and the thickness variation of the plate with a thickness of 10 was ±Q, 5 m. , m.

It was below. The obtained composite plate had no surface roughness and no cavities were formed inside.

The entire surface of this plate was sandblasted in the same manner as in Example 1, resulting in a wood-like warm board with good paint applicability and adhesion.

[Brief explanation of drawings]

FIG. 1 shows a longitudinal section of the barrel of a single screw extruder, and FIG. 2 shows a cross section thereof. In the figure: ■3. Hopper ■・Supply section Barrel ■・Metering section Barrel ■・Screw ■・Storage section Tapered groove on the barrel wall ■・Metering section Gap between screw shaft and barrel wall Figure 2 ■

Claims (1)

[Scope of Claims] 1. A method for producing a wood flour-containing polypropylene board, which comprises completely adding a miscibility promoter to a mixture of polypropylene resin and wood flour, and extruding the mixture using a single-screw extruder. 2. The method for producing a wood flour-containing polypropylene board according to claim 1, wherein the miscibility mediator is low molecular weight polyethylene. 6. The method for producing a wood flour-containing polypropylene board according to claim 1, wherein the miscibility mediator is atactic polypropylene. 4 The single-screw extruder has a barrel inner diameter ratio of 1:0.6 to 0.8 between the feeding section and the medalling section, and a tapered wall with a length of 1.5 to 6 times the barrel inner diameter on the barrel wall of the feeding section. Any one of claims 1 to 6, which is a two-stage barrel metal having a groove and having a gap between the metal cylinder part screw shaft and the barrel wall adjusted to 5 to 10 islands. The method for manufacturing the wood flour-containing polypropylene board described in .