JP3216893B2 - Manufacturing method of precision cast products - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an object of the present invention to provide a more convenient precision castings of production how.

2. Description of the Related Art At present, there are many established methods for mass-producing precision molded products, and high-precision molded products are manufactured at low cost. This is because, if a high-volume production is carried out using high technology and high-priced equipment is used, the unit price per unit is reduced, and it is economically balanced. However, for example, such a manufacturing method cannot be adopted in the production of a precision molded product that requires only one piece in the world, and even if expensive and expensive products are manufactured, the accuracy is low. Often bad. One example is a method for manufacturing a denture base. This is a method for producing a plastic precision molded article of the same form from a wax model of a desired form (lost wax method), but is sufficiently applicable to the production of precision molded articles in other fields. . At present, the method of preparing a denture base, which has become mainstream, is a system developed by Kurtour in Germany in 1938, and is classified as a compression molding method of a heat-polymerizable resin. The denture base is prepared by charging a heat-curable resin prepared by mixing a PMMA powder and a liquid agent containing MMA as a main component into a plaster mold, which is a negative type of the denture base, and polymerizing the resin in the mold. Is made. When the manufacturing process is listed,

(Work in a dental clinic) 1. Acquisition of the affected area with an impression material 2. Reproduction of affected part form with gypsum (production of working model) (work in laboratory) 3. Manufacture of wax denture using wax based on working model (work in dental clinic) 4. Intraoral trial and occlusal adjustment of wax dentures (work in a laboratory) 5. Implantation of wax dentures in gypsum in flask 6. Wax wax (mold removal by wax removal; production of split molds) 7. Filling (inserting) floor resin into mold 8. Removal of excess resin by pre-pressing the mold (the mold is opened and closed several times to remove burrs) Final molding of molded product by main press of mold 10. Heat polymerization 11. The process includes removal, deburring, and polishing of the polymer (molded product). Of these, steps 1 and 4 are indispensable as a therapeutic action. Also, considering the fact that gypsum is the cheapest and most reliable as a model agent for taking the form of a wax denture, steps 1 to 6 are inevitable.
Therefore, the conventional denture base preparation method and improvement of the denture base material mainly relate to the improvement of 7 to 10 steps.

[0003] One such method is an injection molding method.
In the injection molding method, when molding an article from a granular or powdered plastic (resin = resin) material, the material is supplied from a hopper to a heating cylinder, in which the material is plasticized, and then the material is pressed with a plunger or a screw. From the nozzle, through the sprue (runner gate),
This is a method in which a molded product is taken out after being poured into a closed mold and cooled. As a modification of this method, an injection molding system has been proposed in which a heat-polymerizable or room-temperature polymerizable resin mixed with a powdery liquid into a rice cake is injected into a mold. The advantage of this system is that when the molds (split molds) are fitted together, the resin can be fitted without intervening resin, so that they can be perfectly fitted. This is a point that a molded article with few defects can be obtained because air bubbles mixed at the time of resin injection are crushed at a high pressure. On the other hand, the problem with this method is that a large amount of high-viscosity resin must be supplied and injected into a closed mold, or high pressure must be applied to the resin to eliminate bubbles in the resin. It is essential to have an injection molding machine and a sturdy mold that can withstand the heat. In other words, this method has many problems as a method for producing a precision molded product that produces only a small amount in terms of economy.

[0004]

The problem to be solved by the present inventor is to develop a precision cast product manufacturing system which can manufacture a precision molded product with high accuracy by a simple method without the need for expensive equipment. .

The reason why an expensive apparatus is required in the injection molding method is that an injection molding machine which can withstand high temperature and high pressure is required. The present inventor has studied an injection molding method that can be performed with a simple apparatus and method, and as a result,
It has been found that the object of the present invention can be achieved by using the following means.

First, in order to operate an injection molding machine at a temperature as low as room temperature, a heat-polymerizable or room-temperature polymerizable resin is used rather than using a normal thermoplastic resin as a resin for injection molding. It is desirable to use. Further, in order to inject and inject the plastic resin into the mold at a relatively low pressure, it is necessary to provide a discharge hole for discharging air into the mold.
In this case, the pressurizing means for supplying the resin may be one for relatively low temperature and low pressure, and it is not necessary to use an expensive device. Next, in order to obtain a molded product without voids, high pressure is applied to the resin in the mold to eliminate bubbles mixed during resin preparation and filling, and complete filling of the resin to the part where the resin did not spread. In the present invention, apart from the pressurizing means for supplying the resin, the pressurizing means for eliminating the voids is provided independently, so that a simpler pressurizing means is used in the mold. It was found that a sufficient pressure could be applied to the resin.

That is, according to the present invention, a polymerizable resin is injected and filled at a low temperature and a low pressure into a mold having an exhaust hole, and one of the resin supply hole and the exhaust hole is closed, and then the resin supply hole or the unopened resin supply hole or the exhaust hole is connected. After applying a pressure equal to or higher than the filling pressure to the resin in the mold via an incompressible medium by a pressurizing means having a pressurizing surface with a relatively small cross-sectional area to completely fill the resin in the mold, the resin is removed. This is a method for producing a precision cast product characterized by curing.

After supplying a sufficient amount of raw resin into the mold, only a small amount of resin needs to be newly supplied to further pressurize the resin, and the pressurizing means for eliminating voids is very small. A small capacity device is sufficient. The second pressurizing means has a cylinder and a plunger as main components, and the pressure acting surface, that is, the pressure surface of the pressurizing means has a small cross-sectional area. It was found that large pressure can be applied to the resin in the mold by applying only a small force to the plunger.

As the polymerizable resin used in the present invention, a heat-curable resin in one package form is used in principle. However, when it does not take much time to supply the resin to the mold or when the polymerization time of the polymerizable resin is sufficient. When the resin is long, a resin of a heat polymerization type or a room temperature polymerization type prepared by mixing two packaging materials immediately before use can also be used. The polymerizable resin that can be used in the present invention is an acrylic resin,
Any resin such as epoxy resin, urethane resin, and silicon resin that can be easily polymerized without exposure to special reaction conditions can be used. ) -Based resins are preferred. The meta (acrylate) resin used in the present invention contains a polymerizable monomer, a polymer powder, and a polymerization initiator as main components. The polymerizable monomer used for the polymerizable resin is a (meth) acrylate (in the case of an alkyl ester, the alkyl group has 1 to 1 carbon atoms).
2, esters containing aromatic groups have 6 to 12 carbon atoms, and those containing a substituent such as a polyethylene glycol chain in these groups also include those carbon atoms), polyalkylene glycol di (meth) acrylates (of alkylene groups) Carbon number 2
-20), ethylene glycol oligomer di (meth) acrylate (2-10 mer), bisphenol A di (meth) acrylate, 2.2-bis [p- (r-methacryloxy-β-hydroxypropoxy) phenyl] propane, Monofunctional or polyfunctional such as 2-di (4-methacryloxypolyethoxyphenyl) propane (2 to 10 ethoxy groups per molecule), trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate (Meth) acrylates or urethane (meth) acrylates which are the reaction products of 2 moles of (meth) acrylate having a hydroxyl group with 1 mole of diisocyanate,
Preferred are monomers disclosed in JP-A-336687 and JP-A-56-152408.

Further, the polymer powder is not particularly limited, and a homopolymer of the above-mentioned polymerizable monomer or a copolymer containing the same is insoluble in the above-mentioned monomer. Alternatively, polyethylene, polypropylene, polybutadiene, polyvinyl chloride, polycarbonate, nylon, polyurethane, polychloroprene, polyvinyl fluoride, cellulose tributyrate, cellulose trinitrate,
Polyethylene oxide, polyoxymethylene, polyacrylonitrile, collagen, polyvinyl alcohol, polyvinylidene chloride, polyvinyl butyral, epoxy resin, poly-4-methylpentene, polyester, phenolic resin, urea resin, melanin resin, diallyl phthalate resin, silicone resin, etc. Or a copolymer containing two or more repeating units constituting these polymers, a crosslinked product of these polymers, or a blend of these polymers.

As a polymerization initiator, a platinum compound or a polymerization initiator for cationic polymerization may be used depending on the type of monomer. In the case of an acrylic monomer, a radical polymerization initiator is preferably used. The radical polymerization initiator has a 10-hour half-life temperature of 50 to 110.
Organic peroxides at ℃ and azo-based initiators. Further, to the denture base material used in the present invention, a polymer that is soluble in the above-mentioned acrylic monomer is added by dissolving it in advance in the monomer for viscosity adjustment, or the average particle diameter is 0.1.
For example, ultrafine silica having a particle size of from 0.1 to 0.1 μm can be blended. It may also contain coloring agents, fibers such as mimetic blood vessels, storage stabilizers (polymerization inhibitors), discoloration inhibitors (such as ultraviolet absorbers), preservatives, and fragrances.

The polymerization temperature of the heat-curable resin is from 50 to 150 degrees. Regarding the heating temperature, it is preferable to polymerize at a lower temperature for a long time to improve the precision of precision castings, but it is preferable to polymerize at high temperature to pursue high mechanical strength of precision castings . After polymerization at a low temperature of about 70 ° C., it may be further processed at a high temperature of 120 to 150 ° C. The heating means heats the mold in a water bath, heats the mold by putting it in a device that heats the air in a cooking oven or the like, heats the mold with steam, or incorporates a heating element into the mold and electrically connects it. Heating or use of a microwave oven may be used.

Hereinafter, the present invention will be described by taking a method of manufacturing a denture base as an example. First, a plastic tube is attached to the wax denture as two passages, a resin supply hole and an air discharge hole. The denture is buried in gypsum, and after the gypsum hardens, the wax of the denture is run off to form a mold for denture base preparation. These tubes should be appropriately flexible so that they can be conveniently connected to the pressurizing means for supplying the polymerizable resin. The resin can be supplied into the mold by manually pressing the resin supply pressurizing means or by mechanically pressurizing the resin. The inner diameter of the cylinder constituting the resin supply device is preferably 5 mm or more and 50 mm or less. When the resin is supplied mechanically, it is preferable to provide a mechanism in the air discharge hole attached to the mold, in which air is easily leaked and discharged but the resin is not easily discharged.

After the resin supply into the mold is completed, one of the resin supply hole and the exhaust hole is closed. Then, a second pressurizing means is connected to the resin supply hole or the exhaust hole which is not closed, and pressure is applied to the supplied resin by applying a force to the second pressurizing means. The inner diameter of the cylinder constituting the second pressurizing means is preferably 3 mm or more and 10 mm or less. The second pressurizing means has a pressurizing surface having a sufficiently small cross-sectional area as compared with the resin-supplying pressurizing means, and pressurizes the pressurized medium such as the resin supplied previously or an uncompressed liquid such as a liquid inert to the resin. It is necessary to use a conductive medium. With this structure, a high pressure can be applied to the resin in the mold with a small force. If the voids in the mold are large, it is advantageous to use the resin supplied earlier as the pressurizing medium, because refilling of the resin and pressurization are performed simultaneously.

After a sufficient pressure is applied to the polymerizable resin in the mold, the mold and the polymerizable resin in the mold are polymerized by heating. In this step as well, it is desirable to carry out the polymerization while continuing to pressurize and replenish the resin. The pressure of the resin before and during polymerization is 2 kg / cm ² to 20 k
g / cm ² is preferred. If the pressure is lower than this, the effect of pressurization is insufficient, and if it exceeds this range, problems such as the rupture of the plastic tube and leakage of the polymerizable resin from the joint of the mold occur. The polymerization temperature is desirably 100 ° C.

[0015] Next explained is that apparatus employed in the present invention. The resin pressurizing means of these apparatuses is provided with a means such as a chuck for surely or easily attaching and detaching the connecting means to and from the mold so that the resin can be removed when pressure is no longer necessary, such as during annealing after resin polymerization. You may have. In order to make the images of these devices concrete, FIG.
Attach ~ 3. In the figure, 1 denotes a casting mold, 2 denotes a resin supply flow path, 3 denotes an exhaust hole, and 4 denotes a first resin supply.
Pressurizing means, 5 is a polymerizable resin, 6 is a second pressurizing means for pressurizing a resin having a relatively small cross-sectional area, 7 is an opening / closing means for a flow path, particularly when the opening / closing means is closed. As long as it is described. In addition, the above-described resin filling automatic stop device and the second pressurizing device can be shared by the same device.

[0016]

【Example】

Example 1 An edentulous jaw model (upper jaw) made of gypsum manufactured from Nissin's full-jawed edentulous model negative type (H3-402) for upper jaw was used as a working model, and wax dentures were produced according to a conventional method. Next, the working model is used as a dental resin casting flask (perm flask manufactured by GC).
Was fixed using gypsum in the lower wheel. Then, the inner diameter 5
mm, outside diameter 7 mm, length 4 cm, inside diameter 3 mm, outside diameter 5 mm, length 3 cm, prepared a soft PVC tube for sprue, one end of which was made using a small amount of utility wax,
Temporarily attached to both distal ends of the wax denture. An alginate-based separating material (Acrosep, manufactured by GC) was applied to the gypsum exposed surface of the working model fixed to the lower wheel, the upper wheel was attached to the flask, plaster was poured, and the wax denture was embedded. After the gypsum was cured, the upper and lower rings of the flask were separated, and hot water was poured into wax to flow wax to prepare a split mold. The above-mentioned separating material was applied again to the inside and the seam of the split mold, the upper ring and the lower ring were perfectly fitted, and the upper and lower sides of the flask were clamped and fixed with a clamp to form a mold.

In order to use a disposable syringe made of polypropylene (catheter tip with a capacity of 30 ml) as a pressurizing means for supplying a polymerizable resin, a lid is provided at the tip thereof, and a heat shock type denture resin (trade name, manufactured by GC Corporation) is placed therein : Quick Akron) 7g, and powder (11.
5 g) was poured in, mixed quickly, a plunger was attached to the rear end, the lid of the syringe tip was removed, and air was pushed out with the tip up. The flask was fixed on a base so as not to fall down, and a disposable syringe for supplying a polymerizable resin was attached to a thicker tube for filling the resin. Further, in order to use a disposable syringe made of polypropylene (capacity: 2.5 ml, inner diameter: 9 mm) as a second pressurizing means, the cylinder was connected to a thin tube for discharging air from a mold.

Next, a pressure was applied to the polymerizable resin supply syringe using a caulking gun, and the resin was supplied to the mold. The supply of the resin was continued even when the mold became full and the resin protruded from the air vent tube, and was continued until 2 ml or more of the resin entered the second pressurizing means. next,
The resin filling tube was closed, and the plunger of the resin pressing device attached to the air discharging tube was pressed with a force of 6 kg using a spring to pressurize the inside. next,
The mold kept pressurized was placed in a water bath while leaving only a part of the vinyl tube protruding from the water surface, and the temperature of the water was gradually raised. Thereafter, the mold was allowed to cool to the next day while being immersed in water, then the mold was disassembled and the denture base was taken out. The denture base prepared by this method did not contain air bubbles and showed good compatibility with the original working model.

Example 2 2 parts by weight of benzoyl peroxide, 0.1 part by weight of butylhydroxytoluene, 40 parts by weight of triethylene glycol dimethacrylate, 30 parts by weight of urethane dimethacrylate, 2,2-di (4-methacryloxypolyethoxyphenyl)
Propane (2-4 ethoxy groups per molecule, average 2.6)
By mixing and kneading 55 parts by weight of a powder of methyl methacrylate-ethylene glycol dimethacrylate copolymer (weight ratio 90:10) with 45 parts by weight of a monomer mixture consisting of 30 parts by weight, a heat-polymerizable denture base material is obtained. Prepared. This material was filled into a disposable syringe and stored at room temperature until ready for use. Next, in the same manner as in Example 1, wax teeth were prepared on the working model, the working model was fixed to the lower ring of the flask, and a mold with two tubes for resin filling and air discharging was prepared. did. Fix the flask to the stand so that it does not fall over, attach the disposable syringe containing the above polymerizable resin to the thicker tube for resin loading, and attach the disposable syringe with an inner diameter of 9 mm and a capacity of 2.5 ml to the remaining air discharging tube. Of the cylinder. Resin filling, pressurization, and heating of the flask were performed in the same manner as in Example 1, and the time for adding the polymerization was set to 2 hours after the boiling of water. After that, the water bath was turned off, and the mold was left until the next day.
The mold was disassembled and the denture base was removed. The denture base prepared by this method did not contain air bubbles and showed good compatibility with the original working model.

Example 3 2.5 parts by weight of t-butyl perbenzoate, 0.1 part by weight of butylhydroxytoluene, 50 parts by weight of triethylene glycol dimethacrylate, 2,2-di (4-methacryloxypolyethoxyphenyl) propane (per molecule) Ethoxy group 2 to
4 parts, average 2.6 parts) 50 parts by weight of a monomer mixture in a glass mortar, 10 parts by weight of PMMA (PMMA beads manufactured by Negami Kogyo Co., Ltd., Hyper 250ML), 40 parts by weight of the above monomer, and described in Example 2. The polymer powder was mixed and kneaded with 50 parts by weight, and the mixture was used as a thermopolymerizable resin in a disposable syringe. Using a wax model in which the shape of the top of the human skull was made of wax, the thermopolymerizable resin was charged into a mold according to the method of Example 1, pressurized, and heat-polymerized to obtain a model of the top of the skull. It could be made well.

Example 4 Titanium oxide and various bengara were blended with the liquid A of room-temperature-curable silicone rubber TSE3450 manufactured by Toshiba Silicon Co., Ltd., to produce a product having the same color as human skin. In order to prepare a material for a cervical facial prosthesis (epitesis) for a patient with an ear defect, an ear-shaped wax model was prepared on a gypsum working model prepared from an impression of the affected area. Next, according to the method described in Example 1, a mold was prepared through steps such as burying in gypsum. The coloring agent A of TSE3450 was mixed with the curing agent B, and the degassed product was transferred under reduced pressure to a polypropylene disposable syringe, connected to the plastic tube containing the mold, and the liquid silicone rubber was removed. Injected.
(At this time, the surplus of the liquid silicone rubber mixed with the above curing agent was stored in a refrigerator.) After the liquid silicone rubber was injected, the inside was pressurized as in Example 1 to crush bubbles, Silicon rubber was completely filled. Next, the silicone rubber was cured by heating this mold to 90 ° C. for 1 hour. After taking out the cured product, liquid silicone rubber left in the refrigerator to smooth the surface of the cured product is thinly applied to the surface of the cured product and stored at room temperature overnight to be cured, which is used for the intended prosthesis. Materials were made.

Example 5 Instead of the methyl methacrylate-ethylene glycol dimethacrylate copolymer particles described in Example 2, instead of the nylon fine powder, the above monomer was used and the operation described in Example 2 was repeated. The denture base which did not include and showed good compatibility with the original working model was obtained.

Example 6 Instead of the methyl methacrylate-ethylene glycol dimethacrylate copolymer particles described in Example 2, a fine powder of polyvinyl chloride was prepared by repeating the operation described in Example 2 using the above-mentioned monomer. It was possible to obtain a denture base that did not contain air bubbles and showed good compatibility with the original working model.

[0024]

According to the present invention, the resin can be completely filled in the mold by a simple method and apparatus, and a high-quality precision cast product can be manufactured.

[Brief description of the drawings]

1 is a schematic sectional view showing the structure of one example of being that casting production apparatus used in the present invention.

2 is a schematic cross-sectional view showing a structure of an example other castings manufacturing apparatus that is used in the present invention.

3 is a schematic cross-sectional view showing a structure of an example other castings manufacturing apparatus that is used in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Casting mold 2 Resin supply flow path 3 Exhaust hole 4 Resin supply pressurizing means 5 Polymerizable resin 6 Second pressurizing means 7 Opening / closing means

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B29C 39/02-39/24 B29C 45/00 B29C 45/46-45/57

Claims (1)

(57) [Claims] 1. A polymerizable resin is injected and filled at a low temperature and a low pressure into a mold having an exhaust hole, one of the resin supply holes and the exhaust hole is closed, and then the resin is connected to the resin supply hole or the exhaust hole which is not closed. After applying a pressure equal to or greater than the filling pressure to the resin in the mold through an incompressible medium by a pressing means having a pressing surface with a small cross-sectional area, after completely filling the resin in the mold,
A method for producing a precision cast product, comprising curing a resin.