JPH10146846A - Manufacture of plastic cast article and mold therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a plasticizing process efficient. SOLUTION: Adhesive tapes 2 are wound on the outer peripheral faces of two molds 1 facing each other at the given interval to form a cavity A between two molds 1, and then an elastic body 3 of rubber-like elasticity is bonded on the adhesive tapes 2. Then the elastic body 3 and the adhesive tapes 2 are thrust by a nozzle and an exhaust pipe, and the ends of the elastic bodies and the adhesive tapes are inserted into the cavity A. Then the injection of a plastic raw material from the nozzle into the cavity A is started, and when the inside of the cavity A is filled with the plastic raw material, the injection of the plastic raw material from the nozzle is discontinued, and the nozzle and the exhaust pipe are drawn out of the elastic body 3 and the adhesive tapes 2, and the process is moved over to a plastic raw material polymerization process as the following process while keeping the above-said state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic casting method suitable for manufacturing plastics for eyeglasses.

[0002]

2. Description of the Related Art As a method for producing plastic lenses such as spectacle lenses having different required specifications (frequency, size, etc.) for each customer at low cost and with high quality, Japanese Patent Application Laid-Open No. 64-2483 described below is known. There is known a plastic lens casting method described in the publication (hereinafter, referred to as a plastic lens casting method). In this plastic lens casting method, a tape is wound around the outer peripheral surfaces of the two molds so as to keep a space between the two opposing molds, and a cavity is formed. Then, an injection tube is inserted into the cavity, This is a method of molding a plastic lens by injecting a plastic material into the cavity.
Then, as a method of inserting the injection pipe into the cavity, (1) a joint at the end of the tape is peeled to form an injection port, and the tip of the injection pipe is inserted into the cavity from the injection port. Method (hereinafter, referred to as the first injection tube insertion method)
Or (2) a method of using a self-sealing tape as a tape to be wound around the outer peripheral surfaces of the two molds, piercing the tape with an injection needle as an injection tube, and inserting the tip into the inside of the cavity (hereinafter, referred to as a second step). (Referred to as two injection tube insertion methods).

According to the plastic lens casting method,
Since the two molds are fixed with a flexible tape, the capacity of the cavity changes according to the shrinkage of the plastic raw material during polymerization and curing, and the separation between the two molds and the plastic raw material is prevented. be able to. Therefore,
The surface shape of the mold can be transferred well. Further, since cavities at various intervals can be formed using the same tape, new capital investment is not required every time the required specifications of the plastic lens are changed. Therefore, it is possible to manufacture low-cost, high-mix low-volume products such as plastic lenses for eyeglasses.

[0004]

However, in the conventional plastic lens casting method, when the first injection tube insertion method is used, it takes time to peel off the tape end and to position the injection tube with respect to the injection port. Problem arises. Further, after the injection of the plastic raw material into the cavity is completed, it is necessary to adhere the peeled tape end portions again to close the injection port, which requires much more time and effort. Then, the plastic raw material may flow out of the inlet through handling until the inlet is closed.

[0005] Further, as the above-mentioned second injection tube insertion method,
Although there is a proposal to use self-sealing tape,
It is completely unknown what a self-sealing tape is and how to achieve this. Also, common sense, it can be assumed that this self-sealing tape is a rubber sheet having organic solvent resistance and heat resistance, but such tapes have to be very expensive. .

Accordingly, an object of the present invention is to provide a concrete means for giving a tape a self-sealing property, thereby realizing efficient casting of a high-quality plastic casting.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention is directed to an interior of a cavity formed between a plurality of molds and a tape adhered to an outer peripheral surface of the plurality of molds. A plastic casting is formed by injecting a plastic raw material with a plastic raw material injection nozzle to form a plastic casting, wherein the plastic raw material is injected through an elastic body attached to the surface of the tape facing the outside of the cavity. Inserting the tip of the plastic material injection nozzle into the cavity by penetrating the tape, and injecting the plastic material into the cavity from the plastic material injection nozzle; Pulling and pulling an injection nozzle from the elastic body and the tape. To provide a method of manufacturing a plastic casting characterized.

According to the method of manufacturing a plastic casting, when the plastic material injection nozzle is pulled out, the hole formed in the tape by the plastic material injection nozzle is naturally closed by the elasticity of the elastic material attached to the tape. Therefore, it is possible to promptly shift to a subsequent process without taking time and effort for completely closing a hole formed in the tape by the plastic material injection nozzle. Accordingly, the efficiency of the casting process of the plastic casting can be improved accordingly.

[0009] Further, since the hole opened in the tape is not left open, the plastic raw material filled in the cavity does not flow out due to careless handling. Therefore, the frequency of occurrence of casting defects due to insufficient filling of the plastic raw material is reduced, and a plastic cast product with stable quality can be obtained.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for manufacturing a plastic casting according to an embodiment of the present invention will be described with reference to the accompanying drawings. Here, a case where a plastic lens is molded using an appropriate monomer (for example, diethylene glycol bisallyl carbonate or the like) as a plastic raw material will be described as an example.

First, a cavity for molding a plastic lens is formed according to the following procedure. That is, using a well-known positioning device or the like capable of adjusting the interval between the two held molds 1, the molding surface 1a of the two molds 1 is used.
The two molds are fixed in a state where they are facing each other at a predetermined interval t (a distance obtained by adding a correction amount corresponding to the molding shrinkage of the monomer used as a raw material to the design value of the thickness of the plastic lens). After that, an adhesive tape is wound around the outer peripheral surface to form a space A (that is, a cavity) for filling the monomer between the two molds.

When the formation of the cavity A is completed according to the above procedure, as shown in FIG. 1, a nozzle or the like described later is smoothly penetrated into an appropriate region (for example, the uppermost surface) on the surface of the adhesive tape 2. Possible thickness (about 1 to 3 mm
The elastic body 3 having the degree is bonded with an adhesive. Or,
As shown in FIG. 2, a reaction-curable liquid resin is applied to an appropriate area on the surface of the adhesive tape 2 so as to have a rubber-like elasticity and an appropriate film thickness (about 1 mm to 3 mm). The layer 4 may be formed.

The pressure-sensitive adhesive tape 2 used here is made of a material having excellent heat resistance and organic solvent resistance (in particular, resistance to a monomer used as a plastic raw material), for example,
Desirably, it is formed of polyethylene terephthalate (PET) or the like. The shape and thickness of the adhesive tape 2 may be appropriately determined for convenience in handling.

The elastic body 3 used here is excellent in heat resistance and organic solvent resistance (in particular, resistance to a monomer used as a plastic raw material) and completely closes a hole formed by a nozzle or the like described later. It is desirable to use a material which has rubber-like elasticity to the extent that it can be used and does not contain a pigment which may migrate to a monomer used as a plastic raw material. However, (1) materials that are generally excellent in heat resistance and organic solvent resistance are expensive,
(2) The amount of the monomer that leaks out of a hole formed in the adhesive tape by a nozzle or the like described later and adheres to the elastic body 3 is extremely small. (3) The elastic body 3 is a monomer filled in the cavity A. It is used to prevent the outflow of (since it will be unnecessary after the monomer is cured,
At most, the elastic body 3 needs to have heat resistance enough to withstand the thermal environment in the monomer polymerization step.
In selecting a material for forming the compound, a certain degree of compromise is allowed in heat resistance and organic solvent resistance. In view of the above, when using diethylene glycol bisallyl carbonate, which is considered to be optimal as a raw material for plastic lenses for spectacles, as the material of the elastic body 3, a suitable resistance to diethylene glycol bisallyl carbonate and a temperature of about 100 ° C. An elastomer having heat resistance and a Shore hardness of about A20 to A50 (specifically,
Silicon rubber, nitrile rubber, chloroprene rubber, urethane rubber, etc.) and thermoplastic elastomers are selected.

The adhesive used to adhere the elastic body 3 to the adhesive tape 2 is suitable for the material properties of the adhesive tape 2 and the elastic body 3 and, after curing, is made of the material of the elastic body 3. Similar properties (e.g., organic solvent resistance, hardness,
(For example, a silicone adhesive, an acrylic adhesive, a rubber adhesive, etc.). Furthermore, an adhesive is used for this purpose as long as it has the same organic solvent resistance and heat resistance as the adhesive of the adhesive tape 2 and has a sufficient adhesive force to adhere the elastic body 3. can do.

On the other hand, when the coating layer 4 is formed instead of adhering the elastic body 3 to the adhesive tape 2, after curing, the same properties as the material of the elastic body 3 (for example, organic solvent resistance, hardness , Heat resistance, etc., and a liquid resin having relatively low wettability (for example, urethane resin, acrylic resin, silicon resin, etc.) is desirably used.

After the elastic body 3 is adhered to the surface of the pressure-sensitive adhesive tape 2 (or the coating layer 4 is formed), the elastic body 3 (or the coating layer 4) is then supplied by a nozzle for supplying a monomer.
And the adhesive tape 2, and the tip is inserted into the cavity A. Similarly, the elastic body 3 (or the coating layer 4) and the adhesive tape 2 are pierced by an exhaust pipe for discharging air from inside the cavity A during monomer injection, and the tip is inserted into the cavity A. In this embodiment, the nozzle and the exhaust pipe are respectively provided so that an excessively large hole that cannot be closed by the rubber-like elasticity of the elastic body 3 (or the coating layer 4) is not opened in the adhesive tape 2. And an injection needle having an appropriate diameter.

When the above setting is completed, supply of the monomer from the nozzle to the inside of the cavity A is started. At this time, with the supply of the monomer from the nozzle to the inside of the cavity A, the air inside the cavity A is naturally discharged from the exhaust pipe to the outside, but it is particularly necessary to prevent appearance defects such as bubbles from occurring. If this is taken into account, it is desirable to further reduce the pressure inside the exhaust pipe to promote the discharge of air from inside the cavity A.

When the filling of the monomer into the cavity A is completed, the nozzle and the exhaust pipe are pulled out from the elastic body 3 (or the coating layer 4) and the adhesive tape 2. At that time, due to the rubber-like elasticity of the elastic body 3 (or the coating layer 4),
The two holes formed in the adhesive tape 2 by the nozzle and the exhaust pipe are naturally closed.

Thereafter, this is left in a heating furnace heated to about 100 ° C. for about 10 to 15 hours, and when the monomer is completely cured, it is taken out of the heating furnace and placed in an atmosphere at about 50 ° C. to about 80 ° C. Cool with. Then, the adhesive tape is peeled off from the outer periphery of the two molds, and further, the two molds are peeled off from the surface of the cast plastic lens. The two molds are usually reused after cleaning.

As described above, according to the present manufacturing method, when the nozzle and the exhaust pipe are pulled out, the nozzle and the exhaust pipe are adhered due to the rubber-like elasticity of the elastic body (or the coating layer 4) on the surface of the adhesive tape. Since the hole made in the tape is naturally closed, after the step of filling the monomer into the cavity A is completed,
The process can be promptly shifted to the monomer polymerization step without any trouble in the process of completely closing the hole of the adhesive tape. Accordingly, the efficiency of the casting process of the plastic casting can be improved accordingly. Also, since there is no need to work with the hole of the adhesive tape left open, the cavity A
There is almost no danger of the monomer escaping from the interior. Therefore, the frequency of occurrence of casting failure due to insufficient filling of the plastic raw material is reduced, and a plastic lens of stable quality can be obtained. Further, since the monomer inside the cavity A and the elastic body hardly come into contact with each other, there is almost no danger of foreign matter (a constituent component of the elastic body) being mixed into the monomer inside the cavity A. Also in this respect, the quality of the plastic lens is guaranteed. In addition, (1) the material of the elastic material to be attached to the tape can be obtained relatively inexpensively, and (2) the tape itself can be a tape similar to the conventionally used one. It seems that the manufacturing cost can be reduced as compared with the case where the self-sealing tape described in the technical section is used.

Although the present invention has been described with reference to an example of application to a casting process of a plastic lens, the present manufacturing method is applied to a casting process of another plastic casting (for example, a plastic sheet for a window). However, it goes without saying that a similar effect is achieved.

[0023]

According to the method of manufacturing a plastic casting according to the present invention, a plastic casting having a stable quality can be efficiently molded.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a setting in a casting process of an eyeglass plastic lens by a method of manufacturing a plastic casting according to an embodiment of the present invention.

FIG. 2 is a view showing an example of a setting in a casting process of a plastic eyeglass lens by a method of manufacturing a plastic casting according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Mold 2 ... Adhesive tape 3 ... Elastic body having rubber-like elasticity 4 ... Coating layer having rubber-like elasticity

Claims (3)

[Claims] A plastic material is injected into a cavity formed between the plurality of molds with a plurality of molds and a tape adhered to an outer peripheral surface of the plurality of molds by a plastic material injection nozzle, and a plastic injection is performed. A method for producing a plastic cast article for molding a mold article, wherein the tip of the plastic material injection nozzle is formed by penetrating the tape through an elastic body attached to a surface of the tape facing the outside of the cavity. A first step of inserting the plastic raw material into the cavity from the plastic raw material injection nozzle, a first step of inserting the plastic raw material from the plastic raw material injection nozzle, the elastic body and the tape through the plastic raw material injection nozzle. And a third step of extracting from the plastics. 2. The plastic lens casting method according to claim 1, wherein, in the first step, a tip of an exhaust pipe for discharging air inside the cavity when injecting the plastic raw material is provided with the elasticity. A method for casting a plastic lens, wherein the tape is penetrated through a body and inserted into the cavity. 3. A molding die in which a cavity is formed between a plurality of molds by a plurality of molds and a tape adhered to an outer peripheral surface of the plurality of molds, wherein a surface of the tape facing outside the cavities. A molding die characterized in that an elastic body is attached to the mold.