JPH0371245B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for manufacturing a synthetic resin flat plate with an empty interior, which is excellent in terms of hygiene, has a good feeling of use, is lightweight, and is easy to mass produce. It is something.

[Prior art]

The fact is that wood is one of the synthetic resin flat plates, and today there is a shift from wood to synthetic resin from the viewpoint of saving capital and sanitary reasons.

In the past, various proposals have been made regarding synthetic resin mats that are homogeneous and have a good feel when used. Kosho 49-16551
This is shown in the issue of the publication, etc.

By the way, since conventional synthetic resin moldings were focused on heavy weight, solidity, and durability, compression molding, which has relatively low equipment costs, was not always sufficient. , sink marks, warpage, etc. were likely to occur, the rate of defective products that were fatal to the product was high, and there were also problems in mass production.

For this reason, injection molding, which has expensive equipment costs, is used.
We are equipped with a large injection molding machine to meet mass production requirements.
The reality is that they are cut into appropriate sizes (for business use and home use).

[Problem to be solved by the invention]

However, whether it is compression molding or injection molding, in order to minimize the incidence of defective products, many considerations must be made regarding various conditions during molding, such as raw materials, molding temperature, molding time, molding pressure, degassing, and cooling. The molding process required a high degree of skill, which also caused problems in terms of economy and mass production.

The present invention focuses on specific conditions that are seen as problematic and should be avoided during conventional molding, and rather uses them to the contrary, thereby extremely simply reducing the incidence of defective products to almost zero, without requiring any special molding technology. This has improved mass productivity and made manufacturing easier, and it is also lighter than conventional products.
In addition, the purpose is to provide at a low price a flat plate made of synthetic resin that is suitable for use as a maenatata and has appropriate elasticity (repulsion) so that when used as a mainatata, the blade has good contact and does not cause the blade to spill. .

[Means to solve the problem]

The present invention is a method of synthesizing an air-filled material, which is characterized in that a pellet-like synthetic resin material is compression-molded into a flat plate under heating conditions of 200°C or higher, and then cooled while unmelted pellets remain in the core of the flat plate. The present invention provides a method for manufacturing a resin flat plate.

[Effect]

Since the pail manufactured according to the present invention has air (bubbles) contained in the core, it is lighter than conventional products, has appropriate elasticity, and has no warping on the front or back surface. The blade has good contact and maintains a good feeling of use over a long period of time.

To manufacture such synthetic resin flat plates, pellet-shaped thermosetting synthetic resins such as vinyl chloride, polyethylene, and polypropylene are used as materials, and pellets of these materials are weighed and loaded into molds. Then, the mold is placed on the mold stand 1 of a downward compression molding machine as shown in FIG. In the illustrated example,
The mold 2 used is one that can mold two pieces at a time, and the mold stand 1 is shown in three stages, making it possible to compression mold six pieces at a time. It is also possible to use a known compression molding machine with improved mass productivity.

Next, the ram 3 is pushed down and the press plate 4 presses all the materials in the mold 2 at the same time, as shown in FIG. 2, and heat-forms them. The optimum temperature for compression molding varies depending on the material, but is generally between 130 and 180°C.
℃, and is controlled at this temperature, but in the present invention, molding is performed under heating conditions above this optimum temperature. That is, the heating temperature is determined depending on each material, but by setting it to 200° C. or higher, for example around 230° C., the heating temperature becomes common to various materials. This heating does not melt down to the core of the flat plate, and some unmelted pellets still remain in the core, and the pellet surface melts slightly and the pellets weld together to form a void. It will take about 30 minutes.

After compression molding under such heating conditions, cold water is sent into the mold 2 and circulated to cool the molded product S. The molded product S shrinks in the mold 2 and becomes easier to release from the mold. In molding, problems such as shrinkage and warping after water cooling are less likely to occur as in injection molding.

In conventional compression molding of synthetic resins, excessive heating can cause so-called bubbles to form inside the product, resulting in a defective product. Even at low temperatures, air bubbles were prevented from staying inside by repeating the degassing operation as appropriate.
In the present invention, such precise temperature control is unnecessary, and a special intentional degassing operation may also be unnecessary or insufficient.

That is, in the case of the present invention, the shrinkage of the molded product due to water cooling after molding is observed to be significantly large, and when the heating is completed at the above-mentioned heating temperature and the pressure plate 4 is raised by the ram 3, the upper Since the mold is lifted by the internal pressure of the resin, this results in easier degassing.

In addition, there is almost no need to consider maintaining the optimum molding temperature range and degassing operations, which require particularly precise control during conventional compression molding, and compression molding can be performed under conditions that were previously considered taboo. This is an extremely easy molding technique.

As shown in FIG. 3, it is a partially enlarged cross-sectional explanatory view of a molded article S according to the embodiment of the present invention.
The molded material (in the case of a thickness of 15 mm) is completely melted from the front surface A and the back surface B by about 5 mm toward the center, and over the approximately 5 mm width of the core C, only the surface of the pellet P of the material (high-pressure polyethylene) is melted. They melt, weld together, and form a void naturally without the need for any special operations.

As described above, the present invention makes it possible to manufacture a flat plate made of synthetic resin whose core portion contains air bubbles.

〔Example〕

Next, examples of the present invention will be shown.

(1) Material High-pressure polyethylene pellets (Note) The required amount of raw material is determined by the size of the pellets and the volume of the mold.
Loaded with 1050g.

(2) Compression molding machine 4-column hydraulic press 28 ton vertical multi-stage type (3) Molding mold Two molds consisting of an upper mold and a lower mold for producing molded material (Mainata) of 230 mm x 410 mm x 15 mm thickness. Place it on the mold stand under 3 tiers.

(4) Molding conditions Heating temperature: 230°C Heating time: 6 minutes Cooling time: 5 minutes 40 seconds Cooling water is provided using a cooling tower method. Assuming that a flat plate manufactured under the above conditions is, for example, a product, it is 230 mm long x 410 mm wide x 15 mm thick. When cut into two pieces, there was an empty space approximately 5 mm thick parallel to the top and bottom surfaces in the center, and the usability was extremely good.

〔Effect of the invention〕

As described above, according to the present invention, a flat plate made of synthetic resin is obtained which is suitable as a container, which was completely unthinkable in the past, and when used, it is tasteless, odorless, completely non-toxic, and free from germs and bacteria. It is hard to clean, hygienic, does not deteriorate over a long period of time, has fewer defective products, is easy to mass produce, is lighter than conventional products, has a good grip on the blade, and does not cause the blade to spill. It has extremely beneficial effects such as being elastic and being inexpensive.

[Brief explanation of drawings]

FIG. 1 is a front view showing an example of a compression molding machine for manufacturing a synthetic resin flat plate of the present invention, and FIG.
The figure is a perspective view during pressure molding, and FIG. 3 is a partially enlarged cross-sectional explanatory view of the molded product. 1... Mold stand, 2... Mold, 3... Ram, 4... Pressure plate, S... Molded product, K... Empty, P... Pellet.

Claims (1)

[Claims] 1. An air-filled synthetic resin flat plate characterized in that a pellet-like synthetic resin material is compression-molded into a flat plate under heating conditions of 200°C or higher, and the flat plate is cooled while unmelted pellets remain in the core of the flat plate. manufacturing method.