JPH1034674A - Manufacture of reproduced model using photosensitive resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a reproduced model with high dimensional accuracy and being rigid and hardly broken and without defect. SOLUTION: This method for manufacturing a reproduced model prepares the reproduced model by preparing a mold with a UV permeable silicone rubber based on a master model and pouring a photosensitive resin in this mold and irradiating it with UV rays. In this case, temp. of a silicone rubber mold at which the photosensitive resin compsn. is poured and curing is performed by irradiating it with UV rays us made 30-50 deg.C higher than temp. for curing the silicone rubber.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a duplicate model by casting using a photosensitive resin.

[0002]

2. Description of the Related Art A small number of prototype models and small-scale production of duplicate models are obtained by taking a silicone rubber mold from a master model, injecting a thermosetting resin into the mold in a vacuum, and then heating and curing. Has been done in However, thermosetting resins are usually of two-part type, and the mixing of the two parts takes a short time until the start of curing.Therefore, the subsequent injection work into the silicone mold must be performed in a short time. However, in some cases, there is a problem in that curing may start during the pouring operation, resulting in a defective product. Furthermore, the container used for mixing and casting must be washed each time before the resin is cured, which is troublesome. In addition, this method requires a long time of about two hours for heat curing, and requires one day. There was also a disadvantage that the number that could be copied was limited.

On the other hand, Japanese Patent Application Laid-Open No. 58-80587 discloses a one-pack type UV-curable synthetic resin, which is a one-pack type, and irradiates it with UV light under reduced pressure. This shows how to duplicate a watch plastic case. As the resin which is cured by ultraviolet rays, a synthetic resin for casting such as a spirane resin containing benzophenone as a sensitizer or an unsaturated polyester resin containing a reaction accelerator is used.

Japanese Patent Application Laid-Open No. 3-114711 discloses a method of injecting a photosensitive resin into a transparent silicone rubber mold and curing the resin by irradiating ultraviolet rays, wherein a bisphenol A ethylene oxide adduct is used as the photosensitive resin. There has been proposed one obtained by adding a photopolymerization initiator to a mixture of a diacrylate and an acrylate of phenylglycidyl ether.

The applicant of the present invention has proposed a photosensitive resin composition in which the above-mentioned disadvantage that the photosensitive resin is easily broken is improved in Japanese Patent Application Nos. 7-78408 and 7-152770.

Although high dimensional accuracy is required for a duplicate product obtained by casting, the size of the duplicate product obtained is smaller than that of the master model because the photosensitive resin shrinks when cured by irradiation with ultraviolet light. However, the problem of becoming a problem remained. It is possible to deal with this by correcting the shrinkage by making the master model large, but it is inefficient to create a prototype model for initial shape evaluation and a master model for duplication separately, and the Had to be limited.

[0007] Further, in order to inject a photosensitive resin composition into a silicone rubber mold and to irradiate and cure it with an ultraviolet ray, an exposing machine in which a light source is arranged in a vertical direction as used in printing plate manufacturing is used. When exposed, there is also a problem that a portion corresponding to a side surface of the model is not sufficiently cured, resulting in a defective product.

[0008]

SUMMARY OF THE INVENTION A method for producing a replica model by preparing a mold from an ultraviolet-permeable silicone rubber based on a master model, injecting a photosensitive resin composition into the mold and irradiating the mold with ultraviolet rays. In addition to providing the manufacturing conditions for obtaining a duplicate model having high dimensional accuracy and also being hard and resistant to cracking, a duplicate model using an exposure apparatus capable of completely curing a three-dimensional model is provided. It is an object to provide a manufacturing method.

[0009]

Means for Solving the Problems The present inventors set the temperature at which a photosensitive resin is injected and irradiated with ultraviolet rays to be cured at a temperature of 30 ° C. or less from the temperature at which silicone rubber is cured. The present inventors have found that the problem can be solved by raising the temperature by 50 ° C. and completed the present invention.

Hereinafter, the present invention will be described in detail. The silicone rubber used as a mold in the present invention may be any silicone rubber as long as it has a property of transmitting ultraviolet light. Usually, a commercially available RTV silicone rubber which is curable at room temperature is used. Any material can be used as long as it is capable of transmitting the necessary amount of ultraviolet light for curing the photosensitive resin for casting. Silicone rubber is classified according to its curing mechanism into addition type and condensation type, but the condensation type is not preferable in terms of dimensional accuracy because the low molecular weight compound produced during condensation shrinks when it goes out of the system. An additional type that does not have the above is suitable.

Usually, a silicone rubber mold is prepared by fixing a master model in a mold frame, and then pouring silicone rubber which has been mixed with a curing agent in advance and defoamed under vacuum.
This is carried out by leaving at a temperature of ４０40 ° C. to cure.
After the cured silicone rubber is cut open and the master model is taken out, it is used as a casting mold.In order to exhibit the effects of the present invention, the silicone rubber mold is poured with the casting photosensitive resin composition poured. It is necessary to keep the temperature 30 to 50 ° C. higher than the curing temperature and to irradiate with ultraviolet rays to cure.

It is preferable to heat the silicone rubber mold in advance and then pour the photosensitive resin composition for casting into the mold. May be raised to a predetermined temperature. However, in this case, the silicone rubber mold swells with the rise in temperature as compared with the injected photosensitive resin composition, and a gap is formed. Therefore, it is necessary to additionally inject the photosensitive resin composition into the gap.

Since the thermal expansion of the silicone rubber is several steps larger than that of the photosensitive resin, the photosensitive resin composition cures while the silicone rubber mold is swollen beyond the size of the master model. Since the shrinkage due to the temperature difference is small even when the temperature decreases, the shrinkage during curing is corrected, and a duplicate product with good dimensional accuracy can be obtained.

The point that the curing temperature is easily maintained constant is 2
Preferably, the silicone rubber is cured at 5 to 40 ° C. More preferably, it is 30 to 40 ° C. Considering the ease of handling of the silicone rubber mold during the casting operation, the temperature of the silicone rubber mold is desirably 80 ° C. or lower. More preferably, it is 70 ° C. or less.

Although it is desirable for handling that the photosensitive resin composition used for casting is heated to some extent, it is not always necessary to keep the same temperature as the silicone rubber mold.
While the thickness of the silicone rubber mold is as large as 20 to 30 mm or more, the thickness of the model to be duplicated is usually as small as 2 to 3 mm, so that the temperature of the silicone rubber mold is hardly affected. . However, when the thickness of the model to be duplicated is large, it is desirable that the temperature of the photosensitive resin be raised to the same level as the temperature of the silicone rubber mold. Usually, it is used by heating to 50 to 60 ° C.

The dimensional accuracy of the duplicate is required to be within ± 0.3% of the master model, but this can be achieved by the method of the present invention.

There are no particular restrictions on the composition of the photosensitive resin composition for casting in order to exhibit the effects of the present invention. Considering that the molecular weight having an ethylenically unsaturated bond in the molecule is 80
It is preferable to use a photosensitive resin composition comprising a polymer having a molecular weight of 0 to 9000 and an ethylenically unsaturated compound having a molecular weight of less than 800 and a photopolymerization initiator as an essential component.

Examples of the polymer having a molecular weight of 800 to 9000 having an ethylenically unsaturated bond in the molecule include unsaturated polyurethane and unsaturated polyester. From the viewpoint of the balance between hardness and resistance to cracking, unsaturated polyurethane is more preferred. Unsaturated polyurethane is
It can be obtained by reacting a diol compound, a diisocyanate compound, a compound having both a hydroxyl group or an isocyanate group and an ethylenically unsaturated bond or a compound having both an isocyanate group and an ethylenically unsaturated bond.

In a method of first synthesizing a polyurethane polymer having isocyanate groups at both terminals and reacting it with a compound having a hydroxyl group and an ethylenically unsaturated bond at the same time, the compound having both a hydroxyl group and an ethylenically unsaturated bond is treated at both ends. In order to facilitate the reaction with the polyurethane polymer having an isocyanate group, to suppress the side reaction and complete the reaction in a short time, add and react so that the number of hydroxyl groups is excessive relative to the number of isocyanate groups. Is preferred. Usually, an excess of about 2 to 5 times is added. The result is a mixture of a polyurethane polymer having ethylenically unsaturated bonds and an excess of hydroxyl-containing ethylenically unsaturated compounds.

In a method of first synthesizing a polyurethane polymer having hydroxyl groups at both ends and reacting it with a compound having an isocyanate group and an ethylenically unsaturated bond simultaneously, the compound having both an isocyanate group and an ethylenically unsaturated bond is a polyurethane polymer. It is generally added in the same or less range as the number of hydroxyl groups of the polymer, but in this case, in order to facilitate stirring and suppress side reactions,
It is preferable to reduce the viscosity of the reaction system by using a component not involved in the urethanization reaction as a diluent. When a compound having both an isocyanate group and an ethylenically unsaturated bond is added in excess, it is necessary to eliminate the isocyanate group by adding a compound having an active hydrogen such as a hydroxyl group after completion of the reaction.

As the diol compound, compounds having two hydroxyl groups in one molecule, for example, polyester glycols such as polypropylene glycol adipate diol, polyneopentyl glycol adipate diol, polycaprolactone diol, polyvalerolactone diol, polyethylene glycol, polypropylene Examples thereof include polyether diols such as glycol and polytetramethylene glycol. The molecular weight of the diol compound is usually about 400 to 2,000, but from the viewpoint of obtaining a stronger one,
It is preferable to use one having a molecular weight of about 100 to 1,000.

Examples of the diisocyanate compound include compounds having two isocyanate groups, such as tolylene diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, and isophorone diisocyanate. Among these, tolylene diisocyanate is preferable because it does not increase the viscosity so much and a hard and tough product is easily obtained.

Examples of the compound having both a hydroxyl group and an ethylenically unsaturated group include hydroxyethyl methacrylate,
Examples include hydroxypropyl methacrylate, N-methylol acrylamide, polyoxyethylene glycol monomethacrylate, polyoxypropylene glycol monomethacrylate, and the like. Among these, hydroxyethyl methacrylate and hydroxypropyl methacrylate are preferred from the viewpoint of hardness and toughness, and hydroxypropyl methacrylate from which higher hardness is obtained is most preferred.

Examples of the compound having an isocyanate group and an ethylenically unsaturated group at the same time include those obtained by adding a diisocyanate compound one to one to a compound having a hydroxyl group and an ethylenically unsaturated group at the same time. it can.

The unsaturated polyurethane obtained as described above preferably has a number average molecular weight of 800 to 9000 determined by GPC measurement using polystyrene as a standard. Although having the advantage that the viscosity of the obtained photosensitive resin composition can be lowered as the molecular weight is smaller, when the molecular weight is smaller than this, the cured product becomes hard and brittle and loses toughness, and when cutting and removing unnecessary portions of a duplicated product, It is not preferable because cracks easily occur.

When the molecular weight is large, the toughness of the cured product is easily ensured, but when the molecular weight is larger than this, the viscosity of the obtained photosensitive resin composition becomes high, so that the photosensitive resin can be spread to every corner of the mold in the casting process. In addition to the above, it becomes difficult to obtain the cured product, and the resulting cured product becomes soft, resulting in unfavorable characteristics of the duplicated product.

Examples of the ethylenically unsaturated compound include N-methylol acrylamide, diacetone acrylamide,
N-substituted acrylamides such as N, N-dimethylacrylamide, N- (2-methoxyethyl) acrylamide, N-methylol methacrylamide, N, N-dimethylmethacrylamide, N-substituted methacrylamides, hydroxyethyl methacrylate and acrylate, hydroxy Hydroxyalkyl methacrylates and acrylates such as propyl methacrylate and acrylate, ethylene glycol dimethacrylate and acrylate, diethylene glycol dimethacrylate and diacrylate, tetraethylene glycol dimethacrylate and diacrylate such as polyoxyethylene glycol dimethacrylate and diacrylate,

Polyoxypropylene glycol dimethacrylate and diacrylate such as propylene glycol dimethacrylate and diacrylate, dipropylene glycol dimethacrylate and diacrylate, tripropylene glycol dimethacrylate and diacrylate, butanediol dimethacrylate and diacrylate, hexanediol Examples thereof include dimethacrylate and diacrylate, nonanediol dimethacrylate and diacrylate, trimethylolpropane trimethacrylate and triacrylate, and diacrylate and dimethacrylate having a bisphenol A skeleton.

Among these, N-methylolacrylamide and methacrylamide are preferred from the viewpoint of increasing hardness and heat resistance without significantly lowering toughness. From the viewpoint of increasing toughness without significantly lowering hardness and heat resistance. Diacetone acrylamide is preferred. Further, from the viewpoint of lowering the viscosity of the photosensitive resin composition and increasing the elongation properties and hardness, etc., hydroxyethyl methacrylate, hydroxypropyl methacrylate, trimethylolpropane trimethacrylate, etc., while further maintaining toughness From the viewpoint of increasing hardness and heat resistance, diacrylate and dimethacrylate having a bisphenol A skeleton are suitable. Usually, these are used in combination.

Usually, an ethylenically unsaturated compound is used in an amount of from 60 to 200 parts by weight based on 100 parts by weight of a polymer having an ethylenically unsaturated bond in the molecule and having a molecular weight of 800 to 9000.

As the photopolymerization initiator used in the photosensitive resin composition for casting, a photopolymerization initiator having a capability of initiating polymerization by absorbing ultraviolet rays having a wavelength of 300 to 400 nm is used. . For example, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzoin-n-butyl ether, α-methylol benzoin methyl ether, α-methoxy benzoin methyl ether, benzoin derivatives such as α-ethoxy benzoin ethyl ether, Examples thereof include 1-hydroxycyclohexylphenylacetophenone and 1-benzyl-1-dimethylaminopropyl-p-morpholinoketone. Of these, α-methoxybenzoin methyl ether is particularly preferred in that it has a high effect rate and can be cured to a large thickness.

The amount of the photopolymerization initiator may be any as long as it is an effective amount for initiating polymerization, but is usually used in the range of 0.1 to 10% by weight based on the total weight of the photosensitive resin composition. If the amount is less than this, the photopolymerization initiation efficiency becomes poor, and in particular, the curing on the surface in contact with the silicone rubber becomes poor, and the adhesiveness may remain on the surface of the duplicate product, which is not preferable. Conversely, if the amount is too large, the mechanical properties of the cured product are undesirably reduced. A preferred range is 1-4% by weight, a more preferred range is 1.5% by weight.
~ 3.5% by weight.

In addition, a stabilizer such as a known thermal polymerization inhibitor can be added in order to secure the stability during the production or storage of the photosensitive resin composition. Examples of such stabilizers include p-methoxyphenol, 2,6-di-t-butyl-p-cresol, and the like. Further, a releasing agent, a plasticizer, and other additives can be contained as needed.

The viscosity of the photosensitive resin composition should be 120 P or less at 20 ° C. so that air bubbles mixed during the work can be easily removed and can be easily spread to every corner of the silicone rubber mold.
Preferably, it is 100 P or less. The viscosity of the photosensitive resin composition can be reduced by increasing the blending ratio of the ethylenically unsaturated compound, particularly the liquid ethylenically unsaturated compound. Among the liquid ethylenically unsaturated compounds, those having a small molecular weight are particularly effective in lowering the viscosity.
It is also effective to reduce the viscosity by adding a liquid plasticizer such as silicone oil in a range that does not significantly affect other properties.

When the viscosity of the photosensitive resin composition is high, the viscosity at the time of use can be lowered by increasing the temperature of the photosensitive resin at the time of casting, but the deterioration may occur depending on the temperature. Yes, it must be used in a temperature range where this does not occur.

The light source used for photocuring is 300 to 400.
Anything that emits ultraviolet light having a wavelength of nm may be used, and an ultraviolet fluorescent lamp, a high-pressure mercury lamp, a metal halide lamp, a xenon lamp, or the like that is usually used for curing a photosensitive resin can be used.

Unlike the production of a printing plate and the baking of a resist, the production of a duplicate model requires that ultraviolet rays be irradiated from the six directions of the top, bottom, left, right, front and rear during photocuring, and is used for that purpose. It is desirable that the light sources are arranged in six directions, that is, up, down, left, right, front and rear. Although the number of light source arrangements can be reduced by using a reflector, it is necessary to determine the shape and arrangement of the reflectors so that light is emitted from six directions even in such a case. If the light irradiation is performed only from the same vertical direction as for the printing plate preparation, the portion corresponding to the side surface is insufficiently cured, resulting in a defective product.

[0038]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below with reference to Examples and Comparative Examples, but the present invention is not limited to these.

[0039]

【Example】

Example 1 Using an ABS master model having the shape shown in FIG. 1, 30 g of room temperature curing type transparent silicone rubber GT-9000 (manufactured by Janome Sewing Machine Industry Co., Ltd.), which had been defoamed under vacuum in advance, was used.
The composition was cured at a temperature of ° C. to prepare a casting mold.

A 2 L separable flask has a molecular weight of 500
Of polycaprolactone diol was added, and 410 g of tolylene diisocyanate was added thereto to carry out a urethanization reaction to obtain a polymer having both ends having isocyanate groups. Then, 410 g of 2-hydroxypropyl methacrylate (307 g of which is an excess addition as a diluting monomer) was added to react with isocyanate groups of the polymer, and the number average molecular weight having a methacrylate group at both terminals was 8
000 urethane polymers were obtained.

120 g of this polymer (including 20 g of 2-hydroxypropyl methacrylate as a diluent monomer), 20 g of N-methylolacrylamide, 20 g of methacrylamide, 40 g of 2-hydroxypropyl methacrylate, α-methoxybenzoin methyl ether 5 g
g, 0.2 g of 2,6-di-t-butyl-p-cresol
Was mixed to obtain a photosensitive resin composition having a viscosity at 20 ° C. of 80P.

This photosensitive resin, which has been previously heated to 50 ° C., is stirred and defoamed under reduced pressure, and then poured into the above-mentioned transparent silicone rubber mold heated to 65 ° C.
The silicone rubber mold was placed in an exposing machine in which 40 W ultraviolet fluorescent lamps having a center wavelength of 70 nm were arranged in six directions, up, down, left, right, front and rear, and ultraviolet irradiation was performed for 10 minutes.

After the irradiation, the mold was opened to take out the duplicate made of the cured photosensitive resin, and the dimensions of each location of the duplicate were measured using calipers. Table 1 shows the measurement results. Further, the Shore D hardness at 20 ° C. of this duplicate product was 82 degrees, and no crack was generated even when cut using a nipper.

Examples 2-A to C and Comparative Example 1 The same photosensitive resin composition as in Example 1 was used, except that the curing temperature of the silicone rubber and the heating temperature of the silicone rubber mold were variously changed. In the same manner, a duplicate product using the photosensitive resin for casting was produced. Table 1 shows the dimensions of each part of the obtained duplicate.

[0045]

[Table 1]

[0046]

According to the method for producing a duplicate model of the present invention, a duplicate model with high dimensional accuracy can be produced. Further, a hardened and hard-to-break duplicate model can be produced in a defect-free form.

[Brief description of the drawings]

FIG. 1 is a plan view showing a shape of a master model used in an embodiment of the present invention.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location B29K 75:00 105: 24

Claims (3)

[Claims] 1. A method for preparing a mold using an ultraviolet-permeable silicone rubber based on a master model, injecting a photosensitive resin composition into the mold, and irradiating the mold with ultraviolet light to produce a duplicate model. The temperature of the silicone rubber mold at the time of injecting the photosensitive resin composition and irradiating ultraviolet rays to cure the resin is set at 30 ° C.
A method for producing a duplicate model using a photosensitive resin composition, wherein the method is performed at a temperature higher by 50 ° C. 2. A photosensitive resin composition having an ethylenically unsaturated bond in the molecule and having a molecular weight of 80.
A polymer model having a molecular weight of 0 to 9000, an ethylenically unsaturated compound having an ethylenically unsaturated bond and a molecular weight of less than 800, and a photopolymerization initiator. Production method. 3. The method for producing a duplicate model according to claim 1, wherein the exposure is performed by using an exposure device provided with a light source so that the ultraviolet light is emitted from the six directions of the top, bottom, left, right, front and rear.