JPH04325211A - Reactive injection molding method and manufacture of transmission type screen - Google Patents

Abstract

PURPOSE:To provide a reactive injection molding method and a manufacture of a transmission type screen which are able to efficiently effect the temperature up of a mold frame in a short period of time, and correctly readily perform the control of reactive temperature, wherein moreover, the workability is excellent. CONSTITUTION:Raw material resin liquid is injected by the use of a form 4 having two opposite mold surfaces and in used of previously heated hot buffer plates 6, 7, the aforegoing form 4 is contact-held for reaction-solidifying it, and then taking a molded article out of the form in order to obtain a transmission type screen. By the use of the hot buffer plates, the form can be made thin and the time to the start of reaction can be conducted in a short period of time, furthermore, since the hot buffer plates act to absorb the generation of heat due to polymerization heat, the reactive temperature is controlled easily.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a cast molding method and a method for manufacturing a transmission type screen such as a lens sheet for a projection screen.

0002

[Prior Art] Conventionally, as a reaction casting molding method, a fluidized resin or raw resin liquid such as a monomer is injected into a mold, polymerized and hardened, and then the mold is removed to obtain a molded product. Are known. For example, liquid initial reactants such as unsaturated polyester resin, prepolymers of methacrylic acid methyl ester, etc. are used as raw resins, and these resins undergo a polymerization reaction in a mold with a catalyst, solidify, and cast. A product is made. This method has been used, for example, as a method for manufacturing transmission screens by injecting methacrylic resin. In the conventional cast molding method, after injecting the raw material liquid into the mold and starting the polymerization reaction, a heating medium such as air or water is used to remove the polymerization heat and adjust the reaction temperature. Alternatively, the reaction was carried out in a water tank or the like equipped with a temperature control device. Furthermore, in the above-mentioned molding method, the thickness of the mold is made relatively thick in order to prevent the occurrence of defective products due to a decrease in the accuracy of the plate thickness of the molded body due to deformation of the mold.

0003

[Problems to be Solved by the Invention] However, in the above-mentioned prior art, when heating to the polymerization initiation temperature is performed using a hot air oven, the thick mold has a large heat capacity.
In a heating furnace with a small amount of heat, it takes a long time to reach the reaction starting temperature, and in order to uniformly react the resin, it is necessary to uniformly apply a large amount of hot air to the mold, making it difficult to obtain a molded product with high precision. Then, there was a problem in that large-scale equipment was required to raise the temperature of the mold and to uniformly heat it. In addition, when removing the heat of polymerization, it is necessary to lower the temperature to below the boiling point of the low-boiling components contained in the raw material liquid.If the heat of polymerization is large, rapid heat generation occurs, and the air volume of the heating furnace is reduced for cooling. It is difficult to control the temperature rise by increasing the temperature, and there is a risk that the temperature will rise too much and problems such as foaming will occur in the molded product. In addition, the amount of heat of polymerization changes due to variations in the composition of the raw material liquid, which causes the problem that the time from the start of the reaction to the generation of heat varies, requiring a great deal of effort to control the temperature of the equipment for each lot. Ta. In order to improve the above drawbacks, a method using water as a heat medium has been used, but
Although polymerization heat can be quickly removed due to its high thermal efficiency, water adhering to the formwork may remain as a stain when drying the formwork, or if you try to heat it above the boiling point of water during after-curing. , it is necessary to use hot air, it takes time and effort to change the heating device, and there are also problems such as it takes a long time to raise the temperature in the after-cure. The present invention was made in order to eliminate the drawbacks of the above-mentioned conventional techniques, and it is possible to raise the temperature of the mold efficiently and in a short time, and the reaction temperature can be easily controlled with accuracy. Another object of the present invention is to provide a reaction casting molding method and a method for manufacturing a transmission screen that are rational and have good workability.

0004

[Means for Solving the Problems] The reaction cast molding method of the present invention is a reaction cast molding method in which a raw resin liquid is injected into a mold having at least two opposing mold surfaces and reacted and cured to obtain a molded product. In this method, a reaction is carried out by bringing a preheated thermal buffer plate with good thermal conductivity into contact with the mold from the outside of the mold surface of the mold to sandwich the mold. Further, in the above method, it is preferable that the temperature of the preheated thermal buffer plate is set to a temperature that has enough heat to start the reaction of the raw resin liquid when brought into contact with the mold. Furthermore, when the thermal buffer plate is brought into contact with the formwork at a temperature that starts the reaction of the raw resin liquid,
It is more preferable to use one having a heat capacity capable of absorbing the reaction heat of the raw resin liquid and maintaining the temperature at a temperature below the boiling point of the raw resin liquid. Further, in the above method, it is preferable that the outside of the mold surface of the mold is formed into a shape that is curved toward the outside of the mold. A method for manufacturing a transmission screen, which is another invention of the present invention, uses the reaction casting method described above using a mold having a mold surface having a shape selected from the group consisting of a lenticular lens, a Fresnel lens, or a prism. This method uses a molding method.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below in detail with reference to the drawings. The drawings show one embodiment of the invention, and FIGS. 1 and 2
FIG. 1 is an explanatory diagram showing a method for manufacturing a transmission screen using the reaction casting method of the present invention. The present invention first begins with FIG. 1(a).
) As shown in FIG. The gap between the upper mold 2 and the lower mold 2 is adjusted using the sealing material 3 so as to have a predetermined thickness.
are assembled, and the raw resin liquid 5 is injected into the mold 4 (see the same figure (
b)). On the other hand, as shown in FIG. 1(a), thermal buffer plates 6 and 7 having good thermal conductivity are heated in advance in a heating furnace 8 as shown in the figure.

[0006] In the case of manufacturing a transmission screen, the molds 1 and 2 may have at least one mold surface formed in a shape selected from the group consisting of a lenticular lens, a Fresnel lens, or a prism. However, when producing molded products other than transmission screens, it is sufficient to form a desired mold surface. The material of molds 1 and 2 is nickel.
Copper alloy, aluminum, etc. are used. The sealing material 3 is used to hold the raw resin liquid 5 in the mold and to determine the thickness of the molded product. For example, using a vinyl chloride sealing material, etc., the sealing material 3 is used to hold the raw resin liquid 5 in the mold and to determine the thickness of the molded product. Provided between the molds. The mold 4 can also be formed into a shape in which the outside of the mold surfaces of the molds 1 and 2 (the surface opposite to the mold surface) is curved outward from the mold. Forming in this manner is preferable because when the formwork is held between the thermal buffer plates from both sides, the peripheral portion of the formwork is evenly pressed against the sealing material, and the shape of the formwork can be reliably maintained. As the raw resin liquid 5, a raw resin liquid used in this type of cast molding method can be used. For example, liquid initial reactants such as phenol resins, unsaturated polyester resins, and epoxy resins, prepolymers of methyl methacrylate, etc. are used, and if necessary, catalysts (initiators), light diffusion modifiers, antistatic agents, and antistatic agents are used. Additives such as fuel and coloring may also be added. In the production of transmission screens, a prepolymer of methyl methacrylate is usually used as a raw resin liquid. The raw resin liquid 5 can be cooled to a temperature below the boiling point of the raw resin liquid 5 when it generates heat due to polymerization heat after the polymerization reaction has started.

Next, as shown in FIG. 1(b), a thermal buffer plate 6 and a thermal buffer plate 7 are brought into contact with the mold 4 from the outside of the upper mold 1 and the lower mold 2, respectively, and the mold 4 is heated. It is held between buffer plates 6 and 7. Although not particularly shown, a thermal buffer plate 6,
The formwork 4 is clamped from the outside of the formwork 7 so that the formwork 4 and the thermal buffer plates 6 and 7 are in close contact with each other. The raw resin liquid 5 in the mold 4 is heated by the thermal buffer plates 6 and 7 that are in contact with each other, and a polymerization reaction begins.The mold is held in contact with the thermal buffer plates for a certain period of time, and the raw resin liquid 5
harden. Although the thermal buffer plates 6 and 7 may be used only on one side of the upper mold 1 or the lower mold 2, it is preferable to use them from both sides because uniform heating can be performed. Further, the shape of the thermal buffer plates 6 and 7 is preferably such that the surfaces in contact with the mold 4 cover the effective surface of the mold (the surface on the inside of the sealant 3), and the raw resin liquid 5 It is evenly heated, making it even more difficult for sink marks to occur due to partial heating. The temperatures of the thermal buffer plates 6, 7, the raw resin liquid 5, and the atmosphere vary depending on the type of the raw resin liquid, the capacity of the polymerization mold, etc., and may be appropriately determined accordingly, and the reaction may be adjusted as desired. Can be done. In this case, it is important to adjust each temperature so that the temperature inside the mold does not exceed the boiling point of the raw resin liquid due to heat generated by polymerization.

Thermal buffer plates 6 and 7 have a heat capacity that, when brought into contact with the formwork at a temperature at which the reaction of the raw resin liquid starts,
It is desirable that the amount be such that it absorbs the heat of the exothermic reaction and becomes below the boiling point of the raw resin liquid. The heat capacity is appropriately determined depending on the type and size of the material of the thermal buffer plate. thermal buffer plate 6,
The material 7 may be any material having good thermal conductivity, such as aluminum, copper, copper alloy, etc. By using the thermal buffer plates 6 and 7 having the heat capacity as described above,
It becomes easier to control the reaction temperature, and in particular, it is possible to prevent the temperature inside the mold from rising too much to exceed the boiling point and causing bubbles to form inside the molded product. Furthermore, thermal buffer plates 6 and 7
If the temperature of the raw resin liquid 5 is heated to a temperature that has a sufficient amount of heat to start the polymerization reaction of the raw resin liquid 5,
By selecting an appropriate ambient temperature, the curing reaction can be carried out with the simple operation of keeping the formwork held between thermal buffer plates at a constant ambient temperature, eliminating the troublesome task of adjusting the ambient temperature during the reaction. becomes unnecessary. However, the thermal buffer plate 6,
Even if 7 is set to a temperature at which the amount of heat does not start the reaction, it is sufficient to change the temperature in the heating atmosphere and heat until the reaction starts. Even in this case, since the thermal buffer plate has been heated in advance and has good thermal conductivity, heating until the start of polymerization can be completed in a short time. The time for the reaction to be carried out while being held between thermal buffer plates is not particularly limited, but it may be a period of time that usually ends the heat generation.

After the above-mentioned curing reaction has been carried out for a certain period of time, the thermal buffer plates 1 and 2 are removed from the polymerization form 4 as shown in FIG. 2(d), and the polymerization form 4 is placed in the hot air oven 10. Put it inside and do after cure. After the after-cure is completed, the cured molded body is taken out from the mold frame 4 and placed on the transparent screen 1.
2 is obtained [Figure (e)]. After-cure is performed to complete polymerization and eliminate unreacted monomers.
It is carried out at a higher temperature than the normal curing temperature. Although the above description has been made with the mold 4 lying horizontally (the mold surface is horizontal), the method of the present invention may also be carried out with the mold 4 being vertical (the mold surface is vertical). That is, in this case, if the upper mold 1 is the mold on the right side, the lower mold 2 is the mold on the left side.

FIG. 4 is an explanatory diagram showing the steps when molding is continuously performed by the method of the present invention. As shown in Figure 4, the present invention continuously performs reaction casting molding (manufacturing a transmission screen), which consists of five steps: ■ cell assembly, ■ resin liquid injection, ■ curing, ■ post-curing, and ■ cooling mold release. It can also be done. When the method of the present invention is carried out continuously, it is basically the same as the explanation of FIGS. 1 and 2, but as shown in FIG.
, 7 are heated with heat adjusters 31 and 32 respectively, and the formwork 4 is heated.
are held in contact and cured, and after curing is completed, the removed thermal buffer plates 6 and 7 are kept warm with heat controllers 31 and 32 and used for the next heating. On the other hand, the mold 4 is after-cured in a hot air oven 10, then cooled, the molded product is released and taken out, and the second process from cell assembly is performed again. As described above, in the case of a continuous process, the thermal buffer plates 6 and 7 are heated due to heat generated by polymerization, so heating in the heat controllers 31 and 32 requires extremely little energy and takes only a short time. The above description has been made using the reaction cast molding method of the present invention as an example of manufacturing a transmission screen, but the method of the present invention is not limited to the method of manufacturing a transmission screen, and can be used for molding other sheet-like and plate-like molds. It can also be optimally used when reaction casting is used to manufacture bodies.

[0011] Hereinafter, the present invention will be explained in more detail with reference to specific examples. Example 1 First, a rectangular nickel mold having a mold surface of a Fresnel lens (effective surface size is vertical width x width = 1020 x 76
4 mm thick and 1.5 mm thick) and an aluminum mold with a lenticular mold surface (the size is the same as Fresnel's nickel mold), with each mold surface facing each other, and a vinyl chloride sealant was applied. The mold was assembled by clamping the four sides so that the distance (gap) between the mold surfaces was 3 mm, and using methyl methacrylate raw resin liquid (manufactured by Mitsui Toatsu:
Esther MC1006 (with 1% initiator) was injected. Note that the temperature of the mold and the raw material liquid at the time of injection of the raw resin liquid was 0°C. Further, the mold was formed into a slightly curved shape so that the center of the outside of the mold surface (the part that contacts the thermal buffer plate) protruded. Next, two aluminum plates (length x width x thickness = 1020 x 764 x 1.5 mm) that had been previously immersed in hot water and heated to 80 ° C.
The polymerization mold was placed in contact with both sides of the polymerization mold injected with the above-mentioned raw resin liquid, and the polymerization mold was sandwiched and placed in a heat insulator (wind speed: 0 m/sec) adjusted to 75°C for 40 minutes. held. At this time, the relationship between the temperature of the raw resin liquid in the mold and time was measured and the results are shown in FIG. The temperature of the raw resin liquid drew a curve as shown in FIG. 3, and the maximum temperature of the raw resin liquid was 92°C, which was much lower than the boiling point (100°C) of the methyl methacrylate monomer. After the polymerization reaction is complete, remove the aluminum plates holding both sides of the formwork.
Dry the polymerized formwork in a drying oven (temperature: 130°C, wind speed: 10m/
sec) to perform after-curing, and then the mold was removed to obtain a transmission screen. The resulting transparent screen showed no defects such as sink marks or foaming.
In addition, the dimensional accuracy is good with no distortion or warping of the board,
It had excellent screen characteristics.

0012

[Effects of the Invention] As explained above, the reaction casting molding method of the present invention involves bringing a preheated thermal buffer plate of good thermal conductivity into contact with the mold surface of the mold from the outside of the mold to sandwich the mold. Since we adopted a method in which the reaction occurs using a thermal buffer, heating can be performed quickly using a thermal buffer plate, so there is no need to form a thick mold as with conventional methods, and heating can be performed in a short time, improving work efficiency. do. Furthermore, since a hot air stove with a small capacity can be used for heating, large-scale equipment is not required, and the cost of the equipment can be reduced. Furthermore, since the thermal buffer plate is made of a material with good thermal conductivity, heat generated by polymerization can be efficiently removed. In addition, if the temperature of the pre-heated thermal buffer plate is set to a temperature that has enough heat to start the reaction of the raw resin liquid upon contact with the mold, the reaction will start immediately upon contact with the thermal buffer plate. Furthermore, the thermal buffer plate can be
If it has a heat capacity that can absorb the reaction heat of the raw resin liquid and maintain it at a temperature below the boiling point of the raw resin liquid when it is brought into contact with the mold at a temperature that starts the reaction of the raw resin liquid, an appropriate atmosphere is used. Once the temperature is selected, the reaction can be carried out simply by maintaining the ambient temperature at a constant level.If the temperature inside the mold exceeds the boiling point of the raw resin liquid, or if the temperature is insufficient, it will take time for the reaction to take place. This eliminates the need for cumbersome adjustment of the atmosphere temperature during the reaction, improving work efficiency. Furthermore, for example, if the contact surface of the thermal buffer plate with the formwork is formed to have a size that covers at least the effective mold surface of the formwork, the transfer of heat from the raw resin liquid from the thermal buffer plate will be uniform. As a result, a molded product with more stable quality can be obtained. In addition, by forming the outside of the mold surface of the formwork into a shape that curves outward from the formwork, the formwork is securely clamped by the thermal buffer plates, making warping, distortion, deformation, etc. of the formwork less likely to occur. Become. The method for producing a transmission screen of the present invention adopts the above-mentioned reaction casting method, so compared to conventional production methods, the reaction temperature can be easily controlled, workability is improved, and production costs and production costs are reduced. This has the effect of shortening time and making it possible to easily obtain a high-quality transmission screen with good precision at a low cost.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an example of the reaction casting molding method of the present invention and showing the manufacturing process of a transmission screen.

FIG. 2 is an explanatory diagram showing an example of the reaction casting molding method of the present invention and showing the manufacturing process of a transmission screen.

FIG. 3 is a graph showing an example of the relationship between the temperature of the raw material liquid and time in the reaction casting method of the present invention.

FIG. 4 is an explanatory diagram showing an example of a process for continuously manufacturing a transmission screen using the reaction casting method of the present invention.

[Explanation of symbols]

1 Upper mold 2 Lower mold 4 Formwork 5 Raw resin liquid 6 Thermal buffer board 7 Thermal buffer board 8 Hot stove

Claims (5)

[Claims] Claim 1: In a reaction cast molding method in which a raw resin liquid is injected into a mold having at least two opposing mold surfaces and a molded product is obtained by reaction-curing, a preheated resin with good thermal conductivity is used. A reaction casting molding method characterized in that a reaction is carried out by bringing a buffer plate into contact with the mold from the outside of the mold surface of the mold to sandwich the mold. 2. The reaction cast molding method according to claim 1, wherein the temperature of the preheated thermal buffer plate is such that it has enough heat to start the reaction of the raw resin liquid when brought into contact with the mold. . 3. When the thermal buffer plate is brought into contact with the mold at a temperature at which the reaction of the raw resin liquid starts, it absorbs the reaction heat of the raw resin liquid and maintains the temperature at a temperature below the boiling point of the raw resin liquid. The reaction cast molding method according to claim 1 or 2, having a heat capacity of about 100%. 4. The reaction casting molding method according to claim 1, wherein the outside of the mold surface of the mold is curved outward from the mold. 5. Manufacturing by the method according to claim 1, 2, 3, or 4 using a mold having a mold surface having a shape selected from the group consisting of a lenticular lens, a Fresnel lens, or a prism. Features: A method for producing a transparent screen.