JPH05124077A - Manufacture of plastic molding - Google Patents

Abstract

PURPOSE:To provide the manufacture of a plastic molding, in which a slow cooling time can be shortened while equalizing the temperature distribution of a resin in a cavity and the productivity of a molding can be improved. CONSTITUTION:When a resin temperature reaches a temperature close to a glass transition temperature by slowly cooling a mold, slow cooling is stopped for a fixed time, and slow cooling is started again.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a plastic molded product, and more particularly to a method for manufacturing a plastic molded product suitable for manufacturing a plastic molded product such as a plastic lens in a short time and with high precision.

[0002]

2. Description of the Related Art In a conventional method for manufacturing a plastic molded article of this kind, a molten resin is injected and filled in a cavity, and then the temperature of the resin in the cavity is once made uniform at a softening temperature or a glass transition temperature or higher. After that, it is gradually cooled. By the way, in such a manufacturing method, the temperature distribution of the mold can be made uniform by slowing the slow cooling rate.

That is, when the slow cooling time is set to 5 ° C./minute or more, the temperature distribution of the resin in the cavity becomes large, and a highly accurate molded product cannot be obtained. Therefore, the slow cooling rate is 2 ° C./minute. The following settings are made to cool the resin in the cavity while maintaining a uniform temperature. However,
If the slow cooling rate is set to be slow in this way, it takes a lot of time for slow cooling, resulting in a problem that productivity of molded products is significantly deteriorated.

As a solution to such a problem,
For example, there is one described in JP-A-61-19327. In this product, the mold temperature is set low before the resin is injected, and in this state, the molten resin is injected and filled, and then the mold temperature is heated to reach the softening temperature of the resin. After the temperature distribution of the resin inside is once made uniform in the softening temperature range, the resin is gradually cooled to the heat distortion temperature of the resin at a constant cooling rate and then rapidly cooled. For this reason, the molding time can be shortened, and the resin can be cooled while minimizing the temperature nonuniformity of the resin due to cooling.

[0005]

However, in such a conventional method for manufacturing a plastic molded article,
Although the mold temperature is set low before the injection of the resin in order to shorten the production time of the molded product, a constant cooling rate is still required for slow cooling. The solid line indicates the resin temperature of the wall surface (mirror surface part) that defines the cavity of the mold, and the dotted line indicates the resin temperature at the center of the cavity.) The temperature distribution of the resin can be made uniform once in a region much higher than the transition temperature, but the temperature distribution again occurs in the resin in the cavity as the resin is homogenized and then gradually cooled.

In order to prevent the temperature distribution from becoming non-uniform as described above, the slow cooling rate may be made extremely slow to 2 ° C./min or less after the above-mentioned uniform distribution. In addition, a long time is required for the slow cooling time, which causes a problem that the productivity of the molded product is significantly deteriorated. Therefore, the present invention provides a method for producing a plastic molded article, which can shorten the annealing time while making the temperature distribution of the resin in the cavity uniform and improve the productivity of the molded article. It is an object.

[0007]

The invention according to claim 1 is
In order to solve the above problems, they are arranged to face each other,
After inserting the thermoplastic base material preprocessed into the final shape into a pair of molds having at least one mirror surface forming at least one cavity, the plastic base material is heated to a glass transition temperature or higher and melted. By doing
Manufacture of a plastic molded product in which a predetermined resin pressure is generated in the cavity to transfer the mirror surface to the plastic base material, and then the mold is gradually cooled and taken out from the cavity when the temperature is below the heat deformation temperature of the resin. In the method, when the resin temperature reaches the vicinity of the glass transition temperature by gradually cooling the mold, the slow cooling is stopped for a certain period of time, and then the slow cooling is restarted.

In order to solve the above-mentioned problems, the invention according to claim 2 provides a pair of molds, which are arranged to face each other and have one or more mirror surfaces forming at least one or more cavities, with a final shape in advance. After inserting the pre-processed thermoplastic base material into the, by heating and melting the plastic base material above the glass transition temperature, a predetermined resin pressure is generated in the cavity to transfer the mirror surface to the plastic base material, Next, in the method for producing a plastic molded product in which the mold is slowly cooled and taken out from the cavity when the temperature becomes equal to or lower than the thermal deformation temperature of the resin, the resin temperature is brought to near the glass transition temperature by gradually cooling the mold. It is characterized in that when the temperature becomes low, the slow cooling is stopped, then the mold is rapidly heated, and then the slow cooling is restarted.

In order to solve the above-mentioned problems, a third aspect of the present invention is to provide a pair of molds, which are arranged to face each other and have one or more mirror surfaces forming at least one or more cavities, with a final shape in advance. After inserting the pre-processed thermoplastic base material into the, by heating and melting the plastic base material above the glass transition temperature, a predetermined resin pressure is generated in the cavity to transfer the mirror surface to the plastic base material, Next, in the method for producing a plastic molded product in which the mold is slowly cooled and taken out from the cavity when the temperature becomes lower than the heat deformation temperature of the resin, the plastic base material is heated to a temperature higher than the glass transition temperature and melted, and then the mold It is characterized in that it is rapidly cooled and then gradually cooled.

In order to solve the above-mentioned problems, the present invention provides a pair of molds, which are arranged to face each other and have one or more mirror surfaces forming at least one or more cavities, to have a final shape in advance. After inserting the pre-processed thermoplastic base material into the, by heating and melting the plastic base material above the glass transition temperature, a predetermined resin pressure is generated in the cavity to transfer the mirror surface to the plastic base material, Next, in the method for producing a plastic molded product in which the mold is slowly cooled and taken out from the cavity when the temperature becomes equal to or lower than the heat distortion temperature of the resin, when the process of rapidly cooling, heating, and slowly cooling the mold is one cycle After heating and melting the plastic base material to the glass transition temperature or higher, the cycle is repeated at least twice or more.

In order to solve the above-mentioned problems, the invention according to claim 5 is characterized in that the slow cooling rate is controlled by using a pair of molds having a highly conductive material in the vicinity of the cavity.

[0012]

According to the present invention, when the mold temperature is gradually cooled and the resin temperature reaches the vicinity of the glass transition temperature, the slow cooling is stopped for a certain period of time, and then the slow cooling is performed again. Be started. Therefore, after the resin temperature distribution in the cavity is made uniform above the glass transition temperature, the resin temperature distribution in the cavity is made uniform again near the glass transition temperature at which the molten resin begins to solidify, and residual stress and It is possible to obtain a highly accurate molded product by suppressing the generation of strain. In addition, since the resin temperature in the cavity is made uniform again near the glass transition temperature, it is not necessary to spend a lot of time in the slow cooling after the temperature distribution becomes uniform, and the slow cooling time is shortened and the productivity of molded products is reduced. Is improved.

According to the second aspect of the invention, when the mold temperature is gradually cooled and the resin temperature is close to the glass transition temperature, the slow cooling is stopped, and then the mold is rapidly heated and then gradually cooled. Is started again. Therefore, after the resin temperature distribution in the cavity is made uniform at the glass transition temperature or higher, the resin temperature distribution in the cavity is made uniform again near the glass transition temperature at which the resin begins to solidify in a short time. For this reason,
The slow cooling time is greatly shortened, the productivity of the molded product is improved, and residual stress and strain are suppressed from being generated in the resin, and a highly accurate molded product is obtained.

According to the third aspect of the present invention, the plastic base material is heated to the glass transition temperature or higher and melted, and then the mold is rapidly cooled, and then gradually cooled. Therefore, the mold is rapidly cooled until the resin temperature distribution in the cavity becomes uniform at the glass transition temperature or higher, and the slow cooling time is greatly shortened, improving the productivity of the molded product. Thus, generation of residual stress or strain in the resin is suppressed, and a highly accurate molded product can be obtained.

In the invention according to claim 4, when the step of rapidly cooling, heating and gradually cooling the mold is defined as one cycle, after the plastic base material is heated and melted to the glass transition temperature or higher, the cycle is at least Repeated twice or more. Therefore, the resin is cooled in multiple stages near the glass transition temperature, and the resin is homogenized a plurality of times. As a result, generation of residual stress or strain in the resin is significantly suppressed, and a highly accurate molded product is obtained, and the slow cooling time is shortened to improve the productivity of the molded product.

In a fifth aspect of the invention, a pair of molds having a highly conductive material is used in the vicinity of the cavity,
The die controls the slow cooling rate. Therefore, the responsiveness of the slow cooling is significantly improved, and the slow cooling time is easily controlled.

[0017]

EXAMPLES The present invention will be described below based on examples.
1 and 2 are views showing a first embodiment of a method for manufacturing a plastic molded product according to the invention, and this embodiment is applied to a plastic lens. 1 shows a configuration diagram of a main part of a mold for achieving the production method of the present invention, and FIG. 2 shows a resin temperature pattern in the slow cooling step of the production method of the plastic molded product of the present invention.

First, the structure will be described. In FIG.
Reference numerals 1 and 2 are a movable side template and a fixed side template, respectively.
The movable-side mold plate 1 and the fixed-side mold plate 2 are arranged so as to face each other, and the movable-side mold plate 1 is operated by a cylinder (not shown) so that the movable-side mold plate 1 is brought into contact with and separated from each other to close the mold, and the mold is clamped and opened. It is like this. The movable mold plate 1 and the fixed mold plate 2 are respectively provided with a movable insert piece 3 and a fixed insert piece 4 made of iron or the like.

Mirror surfaces 3a and 4a corresponding to the surfaces of the lenses are formed on the facing surfaces of the movable-side insert piece 3 and the fixed-side insert piece 4, respectively, and between these mirror surfaces 3a and 4a, a final shape is formed beforehand. A cavity 5 into which a thermoplastic base material made of a processed polycarbonate resin (hereinafter, also simply referred to as PC resin) is inserted is defined.

Around the movable insertion piece 3 and the fixed insertion piece 4, a heat insulating layer 6a made of copper as a highly conductive material,
6b is provided, and the heat insulating layers 6a and 6b are interposed between the movable side mold plate 1, the fixed side mold plate 2, the movable side insert piece 3 and the fixed side insert piece 4, respectively. The movable side insert piece 3 and the fixed side insert piece 4 each have a plurality of heaters 7.
a and 7b are provided, are connected to the heaters 7a and 7b and a heating source (not shown), and are heated by the heating source. Further, cooling holes 8a and 8b are arranged around the movable insertion piece 3 and the fixed insertion piece 4 so that a cooling catalyst can be introduced into the cooling holes 8a and 8b from a cooling device (not shown). Is becoming

Therefore, the movable insertion piece 3 and the fixed insertion piece 4 have heaters 7a, 7b and cooling holes 8a,
The temperature and cooling rate are controlled by being heated and cooled by 8b. In addition, the movable side mold plate 1, the fixed side mold plate 2, the movable side insert piece 3, the fixed side insert piece 4, the cavity 5, the heat insulating layers 6a and 6b, and the heater 7 described above.
The a and 7b and the cooling holes 8a and 8b constitute a mold 9 for molding a plastic lens.

The method of manufacturing a plastic molded article of this embodiment is for processing a PC resin which has been molded into a final shape in advance in the previous step, that is, an injection molding step.
The manufacturing method will be described with reference to FIG. In FIG. 2, the solid line indicates the resin temperature near the mirror surfaces 3a and 4a, and the broken line indicates the resin temperature at the center of the cavity 5. First, the PC resin pre-processed to the final shape is inserted into the cavity 5, the movable side mold plate 1 is closed to the fixed side mold plate 2 and the mold is clamped, and then the heaters 7a and 7b are operated to move the movable side mold piece. 3 and the fixed side insert piece 4 are heated. Therefore, the PC resin in the cavity 5 expands to generate a resin pressure in the cavity 5, and the mirror surfaces 3a and 4a are transferred to the surface of the PC resin.

After heating, a cooling catalyst is supplied to the cooling holes 8a and 8b to gradually cool the insert pieces 3 and 4. When cooled to about 175 ° C., the temperature distribution of the resin becomes uniform at point A. Next, when the insert pieces 3 and 4 are cooled to near the glass transition temperature (about 145 ° C.), the supply of the cooling catalyst is stopped to temporarily stop the slow cooling of the insert pieces 3 and 4. Therefore, the temperature distribution of the resin is made uniform again near the glass transition temperature at which the resin begins to solidify, as indicated by point B. After that, the cooling catalyst is again supplied to the cooling holes 8a and 8b to gradually cool the insert pieces 3 and 4 again, and after the heat distortion temperature (about 135 ° C.) is reached, the insert pieces 3 and 4 are rapidly cooled to obtain the temperature. Is further lowered, and when the internal pressure of the resin matches approximately atmospheric pressure, the resin molded product is taken out from the cavity 5.

As described above, in this embodiment, when the resin temperature reaches the vicinity of the glass transition temperature by gradually cooling the insert pieces 3 and 4, the slow cooling is stopped for a certain time, and then the slow cooling is restarted. Therefore, after homogenizing the resin temperature distribution in the cavity 5 above the glass transition temperature, it is possible to homogenize the resin temperature distribution in the cavity 5 again near the glass transition temperature at which the molten resin begins to solidify. Therefore, it is possible to suppress the occurrence of residual stress and strain in the resin, and obtain a highly accurate molded product. Further, since the resin temperature in the cavity 5 is made uniform again near the glass transition temperature, it is not necessary to spend a lot of time on the annealing after the temperature distribution is made uniform, and the annealing time is shortened. Therefore, the productivity of the molded product can be improved.

A heat insulating layer 6a is formed around the insert pieces 3 and 4.
Since 6b is provided and the slow cooling rate is controlled by the mold 9, the slow cooling response can be significantly improved, and the slow cooling time can be easily controlled. In this embodiment, the cooling catalyst is supplied to the cooling holes 8a and 8b, but the present invention is not limited to this, and air or the like may be supplied. Also,
Although copper is used for the heat insulating layers 6a and 6b, the present invention is not limited to this,
You may use copper alloy, aluminum, an aluminum alloy, etc. In addition, the cavity 5 can be formed without using the heat insulating layers 6a and 6b.
The insert pieces 3 and 4 in the vicinity may be formed of a highly conductive material such as copper.

Further, in this embodiment, the PC resin is heated and melted at a temperature not lower than the glass transition temperature to generate the resin internal pressure. In addition to such a molding method, the mold temperature is previously set to the glass transition temperature. After the above heating and injection filling, the mold is gradually cooled, and the mold temperature is set low before the resin is injected.In this state, the molten resin is injected and filled, and then the mold temperature is set. You may apply to the manufacturing method which heats so that it may reach the glass transition temperature or higher of the resin, and then slowly cools the mold.

FIG. 3 is a diagram showing a second embodiment of the method for manufacturing a plastic molded product according to this embodiment. In this embodiment, since the same mold as that of the first embodiment is used, 1
A description will be given using the mold of the embodiment. In this embodiment, FIG.
As shown in FIG. 4, after inserting the PC resin into the cavity 5 and heating the insert pieces 3 and 4, the insert pieces 3 and 4 are gradually cooled to gradually cool the resin when the resin temperature is close to the glass transition temperature. Stop. Then, after the mold is rapidly heated, gradual cooling is started again. Therefore, after the resin temperature distribution in the cavity 5 is made uniform (shown by A1) above the glass transition temperature, the resin temperature distribution in the cavity 5 is kept in the vicinity of the glass transition temperature at which the molten resin begins to solidify for a short time. Can be made uniform again (shown by B1). As a result, the slow cooling time can be greatly shortened to improve the productivity of the molded product, and at the same time, it is possible to suppress the occurrence of residual stress or strain in the resin and obtain a highly accurate molded product.

FIG. 4 is a diagram showing a third embodiment of the method for manufacturing a plastic molded product according to this embodiment. In this embodiment, since the same mold as that of the first embodiment is used, 1
A description will be given using the mold of the embodiment. In this embodiment, the PC
After the resin is inserted into the cavity 5 and heated to a temperature above the glass transition temperature and melted, the insert pieces 3 and 4 are rapidly cooled and then gradually cooled, so that the resin temperature distribution in the cavity 5 is above the glass transition temperature. The insert pieces 3 and 4 can be cooled rapidly before being made uniform (indicated by A2). As a result, the slow cooling time can be greatly shortened to improve the productivity of the molded product, and at the same time, it is possible to suppress the occurrence of residual stress or strain in the PC resin and obtain a highly accurate molded product. ..

FIG. 5 is a view showing a fourth embodiment of the method for manufacturing a plastic molded product according to this embodiment. In this embodiment, the same mold as that of the first embodiment is used, 1
A description will be given using the mold of the embodiment. In this embodiment, when the process of rapidly cooling a, the heating b, and the gradually cooling c of the insert pieces 3 and 4 is one cycle, the PC resin is inserted into the cavity 5 and heated to a temperature not lower than the glass transition temperature and melted. Cycle 2
Since it is repeated, the PC resin can be cooled in multiple stages near the glass transition temperature, and the resin can be homogenized twice (indicated by B2 and B3) after the first homogenization (indicated by A3). it can. As a result, it is possible to significantly suppress the generation of residual stress and strain in the PC resin and obtain a highly accurate molded product, and shorten the annealing time to improve the productivity of the molded product. .. In this example,
You may repeat the said cycle 2 or more cycles. By doing so, it is possible to further cool the resin in multiple stages to further homogenize the resin, and it is possible to obtain a highly accurate molded product.

[0030]

According to the first aspect of the present invention, when the resin temperature reaches near the glass transition temperature by gradually cooling the mold, the slow cooling is stopped for a certain time, and then the slow cooling is performed again. Since it has started, after homogenizing the resin temperature distribution in the cavity above the glass transition temperature, it is possible to homogenize the resin temperature distribution in the cavity again near the glass transition temperature at which the molten resin begins to solidify. .. For this reason,
Generation of residual stress or strain in the resin can be suppressed, and a highly accurate molded product can be obtained. In addition, since the resin temperature in the cavity is made uniform again near the glass transition temperature, it is not necessary to spend a lot of time on the annealing after the temperature distribution is uniform, and the annealing time can be shortened. The productivity of molded products can be improved.

According to the second aspect of the present invention, when the mold temperature is gradually cooled and the resin temperature becomes close to the glass transition temperature, the slow cooling is stopped, the mold is rapidly heated, and then the slow cooling is performed again. Since it has started, the resin temperature distribution in the cavity can be made uniform above the glass transition temperature, and then the resin temperature distribution in the cavity can be made uniform again in a short time near the glass transition temperature at which the resin begins to solidify. .. Therefore, the slow cooling time can be greatly shortened to improve the productivity of the molded product, and at the same time, it is possible to suppress the occurrence of residual stress and strain in the resin and obtain a highly accurate molded product.

According to the third aspect of the invention, since the plastic base material is heated and melted at the glass transition temperature or higher, the mold is rapidly cooled, and then gradually cooled. The mold can be rapidly cooled until the resin temperature distribution of the resin is made uniform, and the slow cooling time can be greatly shortened to improve the productivity of the molded product and the residual stress on the resin. It is possible to obtain a highly accurate molded product by suppressing the occurrence of strain and distortion.

According to the invention described in claim 4, when the step of rapidly cooling, heating and gradually cooling the mold is one cycle, after heating and melting the plastic base material to the glass transition temperature or higher, at least the cycle is performed. Since it is repeated twice or more, the resin can be cooled in multiple stages near the glass transition temperature, and the resin can be homogenized a plurality of times.
As a result, it is possible to significantly suppress the occurrence of residual stress and strain in the resin to obtain a highly accurate molded product, and shorten the annealing time to improve the productivity of the molded product.

According to the invention of claim 5, a pair of molds having a highly conductive material is used in the vicinity of the cavity,
Since the slow cooling rate is controlled by the mold, the slow cooling response can be significantly improved, and the slow cooling time can be easily controlled.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a main part of a mold for achieving a manufacturing method of a first embodiment of a manufacturing method of a plastic molded product according to the present invention.

FIG. 2 is a diagram showing a resin temperature pattern in a slow cooling step of the method for manufacturing a plastic molded article of the first example.

FIG. 3 is a diagram showing a resin temperature pattern in the slow cooling step showing a second embodiment of the method for producing a plastic molded product according to the present invention.

FIG. 4 is a diagram showing a resin temperature pattern in the slow cooling step showing a third embodiment of the method for producing a plastic molded product according to the present invention.

FIG. 5 is a diagram showing a resin temperature pattern in the slow cooling step showing a fourth embodiment of the method for producing a plastic molded product according to the present invention.

FIG. 6 is a diagram showing a resin temperature pattern in a slow cooling step of a conventional method for producing a plastic molded product.

[Explanation of symbols]

 9 mold

Claims (5)

[Claims] 1. A thermoplastic base material pre-processed into a final shape is inserted into a pair of molds having one or more mirror surfaces which are arranged to face each other and which constitute at least one or more cavities, and By heating and melting the plastic base material above the glass transition temperature, a predetermined resin pressure is generated in the cavity to transfer the mirror surface to the plastic base material, and then the mold is gradually cooled to below the heat deformation temperature of the resin. In the method for producing a plastic molded product that is taken out from the cavity when the temperature reaches, when the resin temperature reaches the vicinity of the glass transition temperature by gradually cooling the mold, after gradually stopping the cooling for a certain period of time A method for producing a plastic molded article, which comprises restarting slow cooling again. 2. A thermoplastic base material pre-processed into a final shape in advance is inserted into a pair of molds having one or more mirror surfaces which are arranged to face each other and which constitute at least one or more cavities, By heating and melting the plastic base material above the glass transition temperature, a predetermined resin pressure is generated in the cavity to transfer the mirror surface to the plastic base material, and then the mold is gradually cooled to below the heat deformation temperature of the resin. In the method for producing a plastic molded product that is taken out of the cavity when the temperature reaches, the gradual cooling of the mold stops the gradual cooling when the resin temperature becomes close to the glass transition temperature, and A method for producing a plastic molded article, which comprises rapidly heating a mold and then restarting slow cooling. 3. After inserting a thermoplastic base material pre-processed into a final shape into a pair of molds having one or more mirror surfaces which are arranged to face each other and which constitute at least one or more cavities, By heating and melting the plastic base material above the glass transition temperature, a predetermined resin pressure is generated in the cavity to transfer the mirror surface to the plastic base material, and then the mold is gradually cooled to below the heat deformation temperature of the resin. In the method of manufacturing a plastic molded product that is taken out from the cavity when the temperature reaches, the plastic base material is heated to a temperature above the glass transition temperature and melted, and then the mold is rapidly cooled,
Then, a method for producing a plastic molded product, which comprises slowly cooling. 4. After inserting a thermoplastic base material pre-processed into a final shape into a pair of dies arranged to face each other and having one or more mirror surfaces forming at least one or more cavities, By heating and melting the plastic base material above the glass transition temperature, a predetermined resin pressure is generated in the cavity to transfer the mirror surface to the plastic base material, and then the mold is gradually cooled to below the heat deformation temperature of the resin. In the method for producing a plastic molded product that is taken out of the cavity when the temperature reaches, the plastic base material is heated and melted at the glass transition temperature or higher when the process of rapidly cooling, heating, and gradually cooling the mold is one cycle. Then, the above-mentioned cycle is repeated at least twice or more. 5. The method for producing a plastic molded article according to claim 1, wherein the slow cooling rate is controlled by using a pair of molds having a highly conductive material in the vicinity of the cavity.