JPS6233060B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention mainly relates to a method for manufacturing thick-walled acrylic resin products that can be manufactured in small quantities and in a wide variety of types in the form of thick-walled containers at low cost and easily.

Conventionally, methods for manufacturing thick-walled container-shaped synthetic resin products include (1) the in-die extension method, (2) the press method, (3) the vacuum or compressed air method, and (4) the in-die extrusion blow method.

The first injection method is to create a gap between a male mold and a female mold that has the same shape as the synthetic resin product to be manufactured, and after flowing the molten synthetic resin into the gap, it is cooled and solidified. This is a method of manufacturing a synthetic resin product as a final product by dividing or pulling out a male mold and a female mold from a synthetic resin product.
If the shape of the synthetic resin product is such that the bottom part is larger than the mouth part, or if there are irregularities on the sides, it is extremely difficult to create a structure in which the mold consisting of a male mold and a female mold can be removed from the synthetic resin product. In addition, since the precision of the mold must be high, the manufacturing cost becomes high, and there is a drawback that it cannot be implemented in the case of synthetic resin products that are only manufactured in small quantities.

In the second pressing method, first a flat synthetic resin intermediate product is produced, and while the synthetic resin intermediate product is still in a high temperature state, the synthetic resin intermediate product is placed on a female mold, and the male mold is used to press the synthetic resin intermediate product. This is a method of molding the synthetic resin product into the desired shape by pressing it into a female mold. However, with this method, the shape of the synthetic resin product to be obtained may be such that the shape of the bottom is larger than the shape of the mouth or there are irregularities on the sides. If it is, it is impossible to press mold it,
Moreover, since a male mold and a female mold are required, the equipment cost is high, and the work must be carried out while the synthetic resin intermediate product is still in a high temperature state, so it has to be manufactured on a consistent large-scale equipment line. It was hot.

The third vacuum or compressed air method is to first manufacture a flat synthetic resin intermediate product, place this synthetic resin intermediate product on a female mold, chuck the surrounding area, heat the chucked area, and then mold the female mold. The synthetic resin intermediate product is inflated by suctioning air between the female mold and the synthetic resin intermediate product through an air vent hole drilled in the mold, or by blowing compressed air onto the inner surface of the synthetic resin intermediate product. This is a method of manufacturing synthetic resin products by pressing them into a mold, and it does not require a male mold, and the bottom part is slightly larger than the mouth part, and the synthetic resin products have some unevenness on the sides. However, because it is a method for immediately manufacturing synthetic resin products from flat synthetic resin intermediate products, the depth is deep and the shape of the bottom is significantly larger than the mouth. It had the disadvantage that it was not suitable for manufacturing synthetic resin products that required uniform wall thickness.

Furthermore, the fourth in-die extension blowing method is to produce a synthetic resin intermediate product with a shape similar to the synthetic resin product by the in-die extension method, and then remove the female mold while the synthetic resin intermediate product is still in a high temperature state and blow the male mold. Inserting the synthetic resin intermediate product formed around the mold together with the male mold into a female mold having an internal shape that is the same as the external shape of the synthetic resin product to be manufactured,
This is a method of manufacturing synthetic resin products by injecting compressed air through a hole drilled through a male mold to inflate a synthetic resin intermediate product and press it against a female mold. Since the method uses the residual heat of the synthetic resin intermediate products manufactured, the synthetic resin intermediate products do not have a uniform temperature throughout, making it impossible to produce stable synthetic resin products. Once the intermediate product is manufactured, it must be immediately transferred to the synthetic resin product manufacturing process, so the equipment must be placed online, making it large and expensive, making it unsuitable for manufacturing synthetic resin products that are only produced in small quantities. It was hot.

The present inventors have solved the drawbacks of the conventional method for manufacturing thick-walled container-shaped synthetic resin products, particularly the drawbacks of the method for manufacturing thick-walled acrylic resin products that are susceptible to external influences due to their high thermal conductivity. It is possible to manufacture thick-walled acrylic resin products whose bottom shape is larger than the shape of the mouth part or where there are irregularities on the sides, and it is also possible to manufacture thick-walled acrylic resin products in small quantities and in a wide variety of products using inexpensive and compact equipment. We have succeeded in developing the method of the present invention suitable for this purpose.

That is, in the present invention, a thick-walled container-shaped acrylic resin intermediate product, which is smaller than the thick-walled acrylic resin product to be manufactured, is manufactured in advance by an injection method, and after cooling to room temperature, a fixing device is placed inside the acrylic resin intermediate product. After inserting the heating element into the fixture and heating the acrylic resin intermediate product to a temperature exceeding the heat deformation temperature and below the decomposition temperature, after removing the heating body from the fixture. Compressed air is injected into the inner surface of the acrylic resin intermediate product through a ventilation hole drilled through the fixture to inflate it and press it against a female mold whose inner surface has the outer shape of the desired thick acrylic resin product, thereby increasing the thickness. The present invention relates to a method for producing a thick acrylic resin product, which is characterized by producing a thick acrylic resin product.

EMBODIMENT OF THE INVENTION Hereinafter, one embodiment of the method for manufacturing a thick acrylic resin product according to the present invention will be described in detail with reference to the drawings.

Fig. 1 is a perspective view of one embodiment of the acrylic resin intermediate product, Fig. 2 is a vertical cross-sectional view of the state before inserting the fixture into the acrylic resin intermediate product and further inserting the heating element, and Fig. 3 The figure is a longitudinal cross-sectional view showing a state in which a fixture is inserted into the inner surface of an acrylic resin intermediate product and a heating element is further inserted, and Figure 4 is a longitudinal cross-sectional view showing a state in which a heated acrylic resin intermediate product is installed inside a female mold. Figure 5 is a vertical cross-sectional view showing the acrylic resin product inflated by injecting compressed air, and Figure 6 is a vertical cross-sectional view showing the female mold divided to take out the manufactured thick-walled acrylic resin product. Figure 7 is a perspective view of a thick acrylic resin product manufactured through the steps shown in Figures 4 to 6, and Figure 8 is a perspective view of another thick acrylic resin product manufactured by the method of the present invention. FIG. 9 is a perspective view of the embodiment as viewed diagonally from above, and FIG. 9 is a perspective view of the thick acrylic resin product shown in FIG. 8 as viewed diagonally from below.

In the drawing, reference numeral 1 indicates an acrylic resin intermediate product that has been prefabricated by the injection extrusion method to form a thick-walled container shape that is smaller than the thick-walled acrylic resin product to be manufactured, and has been cooled to room temperature. Since the acrylic resin intermediate product is manufactured by the in-die extension method, the thickness of the final thick acrylic resin product is more uniform than that of products manufactured by other methods, and uneven thickness portions do not occur in the final thick-walled acrylic resin product. This acrylic resin intermediate product 1 is made of the same acrylic resin as the thick-walled acrylic resin product to be manufactured, that is, polymethyl methacrylate. Reference numeral 2 denotes a fixture inserted into the thick-walled container-shaped acrylic resin intermediate product 1, and this fixture 2 is made of a material with good thermal conductivity such as aluminum or copper, and has a ventilation hole 2a at a predetermined position. is drilled through. A heating element 3 is inserted into the fixture 2 and heats the acrylic resin intermediate product 1 via the fixture 2. The means for heating the heating body 3 is not limited to the method of applying electricity in the illustrated embodiment, but various methods such as a method of flowing a high-temperature fluid inside can be adopted. The heating temperature of the acrylic resin intermediate product 1 heated by this heating body 3 via the fixture 2 is then inflated without being destroyed by the pressure of compressed air injected through the ventilation hole 2a of the fixture 2. The temperature must be higher than the heat distortion temperature and lower than the decomposition temperature, and the appropriate temperature range for polymethyl methacrylate is 150 to 180°C. 4 is a splittable female mold, and this female mold 4 has a clamping part 4a that clamps the outer periphery near the mouth of the acrylic resin intermediate product 1 to which the fixture 2 is attached when assembled, and a clamping part 4a that clamps the outer periphery of the acrylic resin intermediate product 1 to which the fixture 2 is attached, and a Inner surface 4 with the same shape as the outer shape of the meat acrylic resin product
b, and an exhaust hole 4c that reaches the inner surface 4b from the outside. Reference numeral 5 denotes a sealing body that seals the mouth of the acrylic resin intermediate product 1 held between the female molds 4 near the mouth, and a hose connected to a compressed air source (not shown) is connected to the sealing body 5. 5b are connected,
A ventilation hole 5a is bored near the connection part of the hose 5b, and compressed air is supplied from the hose 5b to the ventilation hole 5a.
a into the fixture 2 through the ventilation hole 2 of the fixture 2.
It is sprayed onto the inner surface of the heated acrylic resin intermediate product 1 through step a.

Next, the operation of manufacturing a thick-walled container-shaped acrylic resin product by the method of the present invention using each of these parts will be explained.

First, a thick-walled container-shaped acrylic resin intermediate product 1 smaller than the thick-walled acrylic resin product to be manufactured.
was prepared in advance by the injection method and cooled to room temperature. By manufacturing the thick-walled container-shaped acrylic resin intermediate product 1 in advance in this way, even when manufacturing a thick-walled acrylic resin product as shown in FIG. 7, for example, the product as shown in FIG. 8 and FIG. Even when manufacturing thick-walled acrylic resin products, it is possible to manufacture them using acrylic resin intermediate products 1 of the same shape, so in factories that manufacture a wide variety of thick-walled acrylic resin products in small quantities, a large number of the above-mentioned acrylic resin intermediate products 1 are separately produced. Alternatively, there is an advantage that it can be purchased and prepared in advance. In this way, for example, the first
After preparing an acrylic resin intermediate product as shown in the figure, a fixture 2 is then inserted into this acrylic resin intermediate product 1, a heating element 3 is inserted into this fixture 2, and the heating element 3 is heated. The acrylic resin intermediate product 1 is heated via the fixture 2 to a temperature exceeding the thermal deformation temperature of the resin and below the decomposition temperature. In this way, in the method of the present invention, a separate heating step is provided before the acrylic resin intermediate product 1, which has been produced in advance by the in-die extension method and cooled to room temperature, is molded into the next final product, which is a thick-walled acrylic resin product. , it is possible to control the heating temperature to suit the shape of thick-walled acrylic resin products, which have high thermal conductivity and are easily affected by external influences, and also to quickly transfer synthetic resin intermediate products to the final molding process, such as with the in-die extension blow method. There is an advantage that there is no restriction on the necessity of transporting and molding. After heating the acrylic resin intermediate product 1 to a desired temperature in this manner, the heating body 3 is removed from the fixture 2, and the majority of the acrylic resin intermediate product 1 attached around the fixture 2 is located within the inner surface 4b. A splittable female mold 4 is installed so that the vicinity of the mouth part is held between the clamping parts 4a, and after the mouth part of the acrylic resin intermediate product 1 is sealed with the sealing body 5, the sealing body 5 is passed through the hose 5b. Compressed air is supplied into the fixture 2 through the pores 5a, and the compressed air is injected onto the inner surface of the acrylic resin intermediate product 1 through the vent hole 2a of the fixture 2, thereby inflating the acrylic resin intermediate product 1 and blowing the inner surface of the female mold 4. 4
A thick acrylic resin product having a desired external shape can be manufactured by pressing the material with b. Therefore, as shown in FIG. 6, the female mold 4 is divided, the opening portion is unblocked by the sealing body 5, the fixture 2 is removed, and the unnecessary portion of the female mold 4 near the clamping portion 4a is removed, for example. By cutting along the line AA in FIG. 6, thick acrylic resin products as shown in FIGS. 7, 8, and 9 can be obtained.

The method of the present invention as detailed above has various advantages as listed below, and its industrial value is extremely large.

(1) A thick-walled container-shaped acrylic resin intermediate product smaller than the thick-walled acrylic resin product to be manufactured is made in advance, cooled to room temperature, and then used when manufacturing the desired thick-walled acrylic resin product. Since this is a method of heating and inflating resin intermediate products with compressed air and molding them, the same acrylic resin intermediate products can be used to manufacture thick-walled acrylic resin products of various shapes, making it suitable for manufacturing a wide variety of products in small quantities. .

(2) Since the production of acrylic resin intermediate products and the production of the final product, thick-walled acrylic resin products, can be completely separated, there is no need to concentrate large-scale production equipment in one place, so it can be used in small factories, etc. But it can be easily implemented.

(3) Since the acrylic resin intermediate product is manufactured by the in-die extension method, its wall thickness is more uniform than that of products manufactured by other methods, resulting in a good thick wall with no uneven thickness. Acrylic resin products can be manufactured.

(4) Heating as a pre-treatment for molding acrylic resin intermediate products into acrylic resin products is not done by using the residual heat from the production of acrylic resin intermediate products, but rather by producing acrylic resin intermediate products in advance using the in-die extension method and allowing them to cool to room temperature. Since the product is cooled down to a completely different stage, it is made of acrylic resin, which has a higher thermal conductivity than other synthetic resin products and is more susceptible to external influences, as well as being thick and difficult to control temperature. Despite this, temperature control is very easy, and thick acrylic resin products of good quality can be manufactured.

(5) Suitable for manufacturing thick acrylic resin products with complex shapes or shapes where the bottom is larger than the mouth.

Examples of the method of the present invention are shown below.

Example Polymethyl methacrylate resin (trade name Delpet 60N, manufactured by Asahi Kasei Corporation) was heated and melted and injected for 10 seconds at an average pressure of 100 kg/cm ² to obtain an inner diameter of 400 mm.
mm, depth 120mm, inner radius of curvature around the bottom 25mm,
Wall thickness with a 500mm outer diameter flange on the upper outer periphery
A 2.5 mm thick container-shaped injection molded acrylic resin intermediate product was produced, and inside the acrylic resin intermediate product cooled to room temperature, an outer diameter of 393 mm, a height of 120 mm, and a thickness of 3 mm were placed.
A fixing device with a heating element consisting of a ring-shaped surface heater is inserted all around the inside surface of the pot-shaped container, which is made of aluminum and has 10 ventilation holes of 3 mm in diameter evenly bored in the bottom surface. An infrared heater is installed 20cm away from the bottom of the resin intermediate product.
The acrylic resin intermediate product is simultaneously heated from the inner and outer surfaces for 90 seconds using the fixture and the infrared heater to uniformly heat the acrylic resin intermediate product to about 160°C, excluding the flange, and then immediately heated with the infrared heater. At the same time, the heating element was removed from the fixture, and the lower part of the acrylic resin intermediate product had a mouth part with a diameter of 400 mm and a thickness of 30 mm. It is machined into an inner shape with a chamfered part with a radius of 40 mm around the periphery, and is divided into upper and lower parts at a position of 70 mm from the upper part, and the upper part can be divided into two left and right from the center. Pressure from ventilation hole 4Kg/cm ²
The acrylic resin intermediate product was inflated by injecting room-temperature compressed air for 10 seconds, and when taken out from the female mold after about 4 minutes, it had the same external shape as the female mold and no flesh except for the flange. It was possible to manufacture a thick acrylic resin product with a uniform thickness of about 2 mm throughout.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of one embodiment of the acrylic resin intermediate product, Fig. 2 is a vertical cross-sectional view of the state before inserting the fixture into the acrylic resin intermediate product and further inserting the heating element, and Fig. 3 The figure is a longitudinal cross-sectional view showing a state in which a fixture is inserted into the inner surface of an acrylic resin intermediate product and a heating element is further inserted, and Figure 4 is a longitudinal cross-sectional view showing a state in which a heated acrylic resin intermediate product is installed inside a female mold. Figure 5 is a vertical cross-sectional view showing the acrylic resin product inflated by injecting compressed air, and Figure 6 is a vertical cross-sectional view showing the female mold divided to take out the manufactured thick-walled acrylic resin product. Figure 7 is a perspective view of a thick acrylic resin product manufactured through the steps shown in Figures 4 to 6, and Figure 8 is a perspective view of another thick acrylic resin product manufactured by the method of the present invention. FIG. 9 is a perspective view of the embodiment as viewed diagonally from above, and FIG. 9 is a perspective view of the thick acrylic resin product shown in FIG. 8 as viewed diagonally from below. In the drawings, 1... acrylic resin intermediate product, 2...
Fixture, 2a...Vent hole, 3...Heating element, 4...
Female mold, 4a... holding part, 4b... inner surface, 4c...
Exhaust hole, 5...Closing body, 5a...Vent hole, 5b...
…hose.

Claims (1)

[Claims] 1. A thick-walled container-shaped acrylic resin intermediate product smaller than the thick-walled acrylic resin product to be manufactured is produced in advance by an in-die extension method, and after cooling to room temperature, the product is placed inside the acrylic resin intermediate product. After inserting a fixture and inserting a heating body into the fixture and heating the acrylic resin intermediate product to a temperature above the heat distortion temperature and below the decomposition temperature, the heating body is removed from inside the fixture. After that, compressed air is injected into the inner surface of the acrylic resin intermediate product through a vent hole drilled through the fixture to inflate it and press it into a female mold having the outer shape of the desired thick-walled acrylic resin product on the inner surface. A method for manufacturing a thick-walled acrylic resin product, the method comprising: manufacturing a thick-walled acrylic resin product. 2. The method of manufacturing a thick acrylic resin product according to claim 1, wherein the fixture is made of a material with good thermal conductivity.