Process and systems for molding thermosetting plastics

Abstract

Process and systems for molding or forming products from thermosetting plastics. The system utilizes a deformable container that is placed within the cavity of the housing of the mold with the resins and initiator mixed therein. As a piston slides into the cavity, the upper edges of the container engage between the housing and the piston to seal the housing form leakage. The pressure of the piston along with heat on the housing enable the curing process to be controlled to minimize shrinkage and porosity.

Claims

1. A system for creating molded thermosetting plastic products, said system includes: a housing having an inner cavity; a base attached to the bottom of said housing; a piston slidable within said inner cavity of said housing; and a container for holding resins and initiator mixed together; said container engaging between said piston and said housing to create a seal between the housing and piston and prevent leakage of said mixed resins and initiator during a controlled curing process, the controlled curing process forming a cured dental material puck that may be extracted from the container.

2. The system of claim 1 wherein said container is formed of a rigid material.

3. The system of claim 1 wherein the portion of the container is formed of a deformable plastic.

4. The system of claim 1, wherein at least a portion of the container comprises: an edge of the container.

5. The system in claim 1, wherein the piston does not contact the housing.

6. The container in claim 1 wherein the container lacks a top side or a bottom side.

7. The system of claim 1, wherein at least a portion of the container comprises a deformable material to enable impressions to be created in said thermosetting plastic through the piston sliding into the housing.

8. A system for creating dental material puck, said system includes: a housing having an inner cavity; a base attached to the bottom of said housing; a container for holding resins and initiator mixed together, the container configured to seat in the inner cavity of the housing and deform into the shape of the dental material puck.

9. The system of claim 8 further comprising a piston that may apply pressure into the container holding the resins and initiator mixed together, wherein an interaction between the container, piston and the base of the housing utilizes heat and pressure to create the dental material puck.

10. The system in claim 9, wherein dental material puck may further comprise a groove configured from the interaction.

11. The system in claim 10, wherein the groove is an annular groove.

12. The systems of claim 1 or 8 wherein said resins include: acrylic resins.

13. The system of claim 1 or 8, the container having curved aspects.

14. The system of claim 1 or 8, the container having linear aspects.

15. The system in claim 9, wherein the interaction does not include the piston contacting the housing or base.

16. The system in claim 8, wherein the container lacks a top side or a bottom side.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is an exploded view of the system of a preferred embodiment of the present invention.

(2) FIG. 2 is a bottom view of the system of FIG. 1.

(3) FIG. 3 is a top view of the system of FIG. 1.

(4) FIG. 4 is a view of the assembled system of FIG. 1.

(5) FIG. 5 is a cutaway view of the system of FIG. 1.

(6) FIG. 6 is a detail view showing the area D of FIG. 5.

(7) FIG. 7 is a detail view showing the area E of FIG. 5.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(8) The present invention provides systems and methods for manufacturing dentures, and more particularly, to the fabrication of the blank for the denture. It is to be expressly understood that this exemplary embodiment is provided for descriptive purposes only and is not meant to unduly limit the scope of the present inventive concept. Other embodiments and variations of the molding process and systems of the present invention are considered within the present inventive concept as set forth in the claims herein. Also, the present invention is primarily discussed for use with dentures for descriptive purposes only and is not meant to be limited solely to this use. It is to be expressly understood that other objects could be fabricated within the present invention as set forth in the claims.

(9) Certain plastics are preferred for particular characteristics. An example of one such material is acrylic. Acrylic is a general term used for any one of the plastics generated through chemical reaction by applying a polymerization initiator and heat to a monomer resin. The monomer resin polyermizes to harden into a solid polymer material. These thermosetting plastics are formed from resins derived from acrylic acid, methacrylic acid or other related compounds. The chemical name for the resin produced from the methyl methacrylate monomer (MMA) is polymethyl methacrylate (PMMA). This particular material is highly durable, resistant to environmental factors and does not easily discolor.

(10) The PMMA resin is mixed with a catalyst, hardener or initiator (collectively referred to as catalyst or initiator) to harden the plastic into a desired shape. The resin and catalyst are mixed together to form a liquid which can then be poured into a mold. The hardening or curing process begins once the two components, resin and catalyst, are mixed together to create a chemical process to form a hard polymer. Two important factors occur during the curing process that affect the final product. These factors are shrinkage of the combined components and heat.

(11) While heat is necessary to initiate the curing process, the exothermic chemical process of curing also generates considerable heat. The exothermic process occurs from the center outward causing considerable temperature gradients and internal stresses. This generated heat can cause bubbles to form in the acrylic creating air porosity in the material. Additional air bubbles may occur due to the initial mixing of the two components and from pouring the liquid into the mold.

(12) An additional problem with casting acrylics into molds is the shrinkage that occurs during the curing process. This shrinkage can range from eight percent to twenty one percent, thus is a significant factor in precisely forming an object from casting acrylic.

(13) These factors are addressed by a number of techniques. These techniques include careful selection of the catalysts to control the exothermic process, utilization of vacuum chambers to remove air, multiple stages of heat application to control the heat of the curing process, and other techniques. One preferred technique is to apply pressure during the curing process. The use of high pressure on the resin and catalyst during the curing process will decrease the cooking of the acrylic during curing, decrease any thermal expansion during the curing, minimize any polymerization shrinkage, decrease the porosity of the acrylic by increasing the evaporation of the polymer and compressing air bubbles created during mixing. The pressure also compensates for the shrinkage factor.

(14) System for Molding or Casting Acrylic

(15) A preferred embodiment of a system for molding acrylic is illustrated in FIGS. 1-4. The system 10 includes a base 20 with housing 30 mounted thereon. Piston 50 slides within housing 30. A driving force, such as a mechanical force, hydraulic, pneumatic or other force application device (not shown) drives the piston 50 through the housing to create pressure within the housing. Cup 40 is mounted within the housing 30 to form a seal between the housing and piston.

(16) The bottom 32 of the housing 30 is mounted to the base 20 by a series of spaced bolts securing the housing to the base as shown in FIGS. 2, 3, 4 and 5 to form a sealed container. The housing 30 is cylindrical with inner opening 32 forming a space for the cup 40, the combined resin and catalyst and the piston 50. A heating element (not shown) applies heat to the housing 30 to initiate the curing process. Temperature and pressure gauges may also be utilized in housing 30 along with ventilation openings to assist in controlling the curing process.

(17) The resin and catalyst are mixed in cup 40 which is then placed within housing 30. Force is applied to piston 50 to apply pressure on the combined resin and catalyst. As shown in FIG. 5, the upper edges 42 of the cup 40 engage in the spacing between the housing 30 and piston 50 to form a seal to prevent leakage of the material. This is shown in greater detail in FIG. 6.

(18) The cup 40 can also be used to create special impressions in the shape of the cured acrylic. For example, as shown in FIG. 7, the cup deforms under the pressure from the piston 50 to form a groove in the corner of the final product. Other impressions may be created as well as desired by the interaction of the cup and the housing.

(19) The cup may be formed of plastic or other materials to be deformable under pressure or can be formed of more rigid materials to create a precise shape. The cup 40 also serves other purposes for the molding/casting process. The resin and catalyst can be carefully mixed in the cup which allows the cup to then be inserted into the housing. The cup also protects the housing 30 and base 20 from cured acrylic to minimize later clean-up.

(20) Process of Molding Acrylic

(21) The resins and catalysts are mixed together in the cup 40 to innate the curing process. The cup containing the combined components is then placed in the bottom of housing 40. Force is applied to piston 50 to apply pressure against the cup and combined components along with heat through the housing 30. The combined heat and pressure controls the curing process. The edges of the cup 40 engage between the piston 50 and the housing 40 to seal the housing to prevent leakage of the acrylic material. Once the acrylic has cured, the piston is retracted and the cured acrylic product is removed. The cup allows easy release of the product from the housing. The cup can then be removed from the cured product and discarded.

(22) Applications

(23) One application of the preferred embodiment of the present invention is to create precise blanks for manufacturing dentures. Blanks are formed using the above described system in the steps of the above described process to create manufacturing pucks. These pucks are then fabricated into dentures using CAD/CAM or other machining processes.

(24) It is to be expressly understood that the above described embodiments are intended for explanatory purposes only and are not meant to limit the scope of the claimed inventions.