JPS6318311B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a method for manufacturing a surface heater, and its purpose is to produce a surface heater that is sophisticated and has a uniform heat generation temperature, temperature distribution, and strength, and is sophisticated and strong. The objective is to provide a smooth molding operation without traffic jams.

(Prior art and its problems) Conventionally, as shown in Fig. 3, in the manufacture of a surface heater, a molding material b mixed with carbon fiber a is compressed and kneaded in an injection molding machine c, and this kneaded material is put into a mold. This is done by supplying it into the cavity e of d and molding it.

However, in this conventional method, carbon fibers (a) are solidified into pellets in a fixed amount with synthetic resin (f) and mixed into the molding material (b), and when the injection molding machine (c) is used, the L/D is 20 or less and the shaft taper is The following problems arose because screws exceeding 0.02 were used.

In other words, carbon fiber a that can be mixed into pellets
Since the length is about 0.3 to 0.4 mm, it is not possible to impart sufficient strength to the molded product, and since the carbon fibers a in the pellet are dispersed in no direction, they become entangled with each other during compression kneading. As a result, the heat generation temperature, heat distribution, and intensity of the individual surface heaters were uneven.

In addition, since the injection molding machine c uses a screw with an L/D of 20 or less and a shaft taper of more than 0.02, the material becomes pressurized and kneaded, causing the carbon fibers a to be cut and the fiber length to be shortened (original). 1/5 of
~1/10), which may further weaken the strength of the molded product and lead to a decrease in electrical conductivity.
Furthermore, the dispersion state of the carbon fibers a deteriorated due to the pressurized kneading, so that the heat generation temperature, heat generation temperature distribution, and strength of the surface heater became nonuniform.

In addition, since molding is performed by injection molding, the injection of molten material into the mold d must be performed by high-pressure injection through a small diameter nozzle g, which may become clogged with carbon fibers a, resulting in molding. There was a risk that work would be frequently interrupted.

(Means for solving the problem) In this invention, the length of carbon fiber is 5 to 50 mm.
In addition, this carbon fiber is bundled with synthetic resin powder interposed between them and mixed into the molding material while being coated with a synthetic resin film of the same quality as the powder, and is used as a pressurized conveyor. Using a screw with an L/D of 25 or more and a shaft taper of 0.02 or less,
All of the above problems are solved by performing the molding by the injection pressure expansion method.

(Example) An example of the present invention will be described based on the drawings.

FIG. 1 is a diagram illustrating a molding apparatus according to a manufacturing method according to an embodiment of the present invention.

In order to mold a surface heater using the molding apparatus according to the embodiment of the present invention, a molding material 2 mixed with carbon fibers 1 is melted and transported by a heating transporting machine 3, and this molten material is transferred into a cavity 5 of a mold 4. is supplied to perform molding.

As the carbon fiber 1, one having a length of 5 to 50 mm is used. If it is shorter than this, sufficient strength cannot be imparted to the molded product, while if it is longer than this, the resistance during conveyance will increase, and only the carbon fibers 1 will remain in the heating conveyance machine 3, resulting in uneven dispersion. It is. Note that within this range, a diameter of 20 to 30 mm is most effective.

Moreover, the thickness used is 7 to 30 μm in diameter. If it is thinner than this, sufficient strength cannot be imparted to the molded product, while if it is thicker than this, when it is made into a bundle, as will be described later, the thickness of the bundle will be thicker and the resistance during transportation in the heating conveyor 3 will be large. This is because only the carbon fibers 1 become stagnant in the heating conveyance machine 3 and the dispersion state becomes non-uniform. Note that within this range, a thickness of 15 to 20μ is most effective.

Furthermore, the blending amount is 10 to 50% by weight.

This is because if the amount is less than this, sufficient strength cannot be imparted to the surface heater, and on the other hand, if it is more than this, the resistance during conveyance in the heating conveyor 3 increases as described above. Note that within this range, 25 to 35% by weight is most effective.

As the material for the molding material 2, both thermoplastic resins and thermosetting resins can be used, but non-crystalline thermoplastic resins such as ABS are most effectively used.

In order to mix the carbon fibers 1 into the molding material 2, a plurality of carbon fibers 1 are bundled with synthetic resin powder 7 interposed between them and coated with a synthetic resin film 6, and then mixed into the molding material 2. do. The reason for interposing the synthetic resin powder 7 is to maintain the spacing between the carbon fibers 1 and ensure a dispersed state in advance, and also to give flexibility to the bundle and prevent it from being cut due to bending during transportation. This is to prevent this. The reason why the synthetic resin film 6 is used is to maintain the above-mentioned dispersed state until near the end of conveyance and to improve the dispersion of the carbon fibers 1 in the surface heater.

The quantity to be bundled is 100 to 3000.

If the amount is less than this, the number of bundles will inevitably increase, and the directionality of each bundle of carbon fibers dispersed in the heating conveyor 3 will vary greatly, and the dispersibility will deteriorate due to mutual entanglement. This is because if the number is too large, the bundle will become thick and the conveyance resistance will increase, making it impossible to achieve sufficient dispersion.

Further, the diameter of the bundle is suitably 0.2 to 8 mm.

Further, as materials for the synthetic resin powder 7 and the synthetic resin coating 6 in this case, any of various thermoplastic resins or thermosetting resins can be suitably used.

As the heating conveyor 3, a screw having an L/D of 25 or more and a shaft 10 with a taper of 0.02 or less is used.
The taper of shaft 10 is less than the conventional L/D20.
This is because, if the screw exceeds 0.02, the material to be conveyed will be in a pressurized kneading state, and the strength of the surface heater will be reduced due to the cutting of the carbon fibers 1, while the dispersibility will be inhibited by the entanglement of the carbon fibers 1.

The injection pressure expansion method was used for molding. What is the injection pressure expansion method?
Mold 4 with shear edge opened as shown in Figure 1
The inner diameter of the injection nozzle 8 is at least 6 mm.
I can do more than that. In injection molding, the inner diameter of the injection nozzle must be made very small because it is necessary to perform high-pressure injection into the mold, and there is a risk of congestion in the molding operation due to clogging of the carbon fiber 1. In addition, in compression molding, the molding material is This is because it is necessary to measure and add the solid form (sheet-like, etc.), and the complexity of the feeding process reduces productivity.

In addition, in injection compression molding, the molten material is injected into a slightly open parting line mold, and then the mold is closed and the molten material is forced into the mold to form the mold. This is because it can only be used for specific purposes and lacks versatility.

Incidentally, during the compounding process, additives such as plasticizers and stabilizers that are effective for ordinary plastic molding are naturally added in arbitrary amounts. In addition, 9 in the figure is an accumulator for feeding the molten material into the mold in a measured state.

Incidentally, FIG. 2 shows a modification of the molding apparatus according to the molding method according to the embodiment of the present invention, and in this example, an injection extrusion is used as the heating conveyor 3.

(Effects) As explained above, in this invention, carbon fibers with a length of 5 to 50 mm are used, and moreover, these carbon fibers are bundled in plural with synthetic resin powder interposed between them and coated with a synthetic resin coating. The molding material is mixed into the molding material in this state, a screw with an L/D of 25 or more and a shaft taper of 0.02 or less is used as the heating conveyor, and the molding is carried out by the injection pressure expansion method, so the following effects are achieved.

That is, since the length of the carbon fiber is 5 to 50 mm, sufficient strength can be imparted to the surface heater.

In addition, since multiple carbon fibers are bundled with synthetic resin powder interposed between them and mixed into the molding material,
The carbon fibers can be transported and molded in a state in which they are dispersed in advance, and the carbon fibers can be prevented from entangling with each other to make the dispersion uniform, and it is possible to provide a surface heater with uniform heat generation temperature, heat generation temperature distribution, and strength. In addition, since the bundle of carbon fibers is coated with a synthetic resin film, the above-mentioned dispersion of the carbon fibers can be maintained until the middle of transportation, and the dispersion state of the carbon fibers in the surface heater can be made uniform, resulting in improved heat generation temperature, temperature distribution of heat generation, and strength. A uniform surface heater can be provided.

In addition, since a screw with an L/D of 25 or more and a shaft taper of 0.02 or less is used as the heating conveyor, there is no entanglement of carbon fibers that accompanies pressurized kneading of the molding material, the carbon fibers are uniformly dispersed, and the exothermic temperature is This is further advantageous in providing a surface heater with uniform heat generation temperature distribution and strength.

Furthermore, since the molding is carried out by the injection pressure expansion method, there is no need to use a small-diameter injection nozzle as in conventional injection molding, there is no clogging of the injection nozzle, and there is no congestion in the molding operation.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a molding apparatus according to a molding method according to an embodiment of the present invention, FIG. 2 is an explanatory diagram of a modification of the same molding apparatus, and FIG. 3 is an explanatory diagram of a molding apparatus according to a conventional molding method. . 1... Carbon fiber, 2... Molding material, 3... Heating conveyance machine, 4... Mold, 5... Cavity, 6...
...Synthetic resin film, 7...Synthetic resin powder.

Claims (1)

[Claims] 1. In a method for manufacturing a surface heater in which a molding material mixed with carbon fibers is melted and transported by a heating transporter, and the melted material is fed into the cavity of a mold for molding, the carbon fibers have a length of 5 to 50 mm. In addition, a plurality of carbon fibers are bundled with a synthetic resin powder interposed between them and coated with a synthetic resin film of the same quality as the powder, and mixed into the molding material, and as the heating conveyor. Using a screw with L/D25 or more and a shaft taper of 0.02 or less,
A method for manufacturing a surface heater, characterized in that the forming is performed by a jet pressure expansion method.