JP2885555B2 - Denture base resin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a resin composition for dental denture base.

[0002]

2. Description of the Related Art
Polymethyl methacrylate (abbreviated as PMMA) is generally used as a denture base resin material. This resin is chemically stable in the oral cavity, has low toxicity to the human body, and is easily colored and excellent in transparency, so that a clear color tone can be obtained. Polymethacrylic acid dentures are manufactured by mixing a powdered acrylic polymer (powder) made of polymethyl methacrylate and a liquid monomer (liquid) containing methyl methacrylate as a main component at a predetermined ratio, and sealed at room temperature. After standing for a predetermined period of time, the adhesiveness and adhesiveness are not shown but plasticity of appropriate hardness is exhibited (mochi state).
This rice cake-like material is filled into a right plaster mold made from an impression in the oral cavity of a patient, and is formed by pressurizing and heating. When the powder and liquid are mixed in the above method, the mixture first becomes a sandy state wet with water, then the monomer dissolves the surface of the polymer powder and draws a thread when touched State. Further, when the monomer is absorbed and diffused into the polymer powder and plasticization of the polymer proceeds, the polymer powder becomes a soft rice cake-like state (sticky state) which is easy to operate without sticking to hands or containers. After that, it becomes a hard state through a rubbery state showing elasticity. The most important thing in producing a denture base in this way is that the mixture is put into a gypsum mold while the mixture is in the form of a rice cake. In a state like sand or wet thread that is not mochi-like,
When the mold is filled, the pressurization cannot be performed sufficiently, so that air bubbles are easily generated, which causes a decrease in the strength of the denture base and a cause of breakage. On the other hand, in a state of pasting the rice cake and showing elasticity, the details of the mold are not filled in, resulting in molding failure.

However, since the period of the rice cake-like state is short in the conventionally used resin composition, when a large number of denture bases are manufactured, the dentures must be divided into small portions and mixed many times. There has been a long-awaited demand for a resin composition having a long period of rice cake-like state, which has problems in terms of technical operations and costs, such as the resin cannot be stored and must be discarded.

[0004] Japanese Patent Application Laid-Open No. 57-203006 discloses a composition comprising two such powdery liquids and having a long rice cake-like period when mixed. This composition comprises a powder containing a high molecular weight polymethyl methacrylate having an average molecular weight of 300,000 to 800,000 and a low molecular weight polymethyl methacrylate having an average molecular weight of 50,000 to 200,000, and a liquid comprising a polymerizable liquid monomer. The two kinds of polymethyl methacrylates having different molecular weights in the powder have different solubilities with respect to the liquid monomer, so that the period of the mixture becomes longer. However, this composition has a problem that the strength of the obtained denture base is inferior because it contains a large amount of low molecular weight polymer. Therefore, it is clear that creation of a resin composition that solves the above problems is desired.

Thus, according to the present invention, crosslinked methyl methacrylate polymer particles 5 to 45 formed by suspension polymerization of methyl methacrylate and 0.01 to 0.5 mol% of a bifunctional or more crosslinkable monomer. Parts by weight, a powder comprising methyl methacrylate resin particles produced by absorbing and polymerizing 95 to 55 parts by weight of methyl methacrylate with respect to the particles, and optionally a powder comprising a polymerization initiator, methyl methacrylate and a crosslinking agent. A resin composition for a denture base comprising a combination with a liquid is provided.

[0006] The powder in the composition of the present invention comprises methyl methacrylate resin particles and a polymerization initiator. Here, the methyl methacrylate resin particles are subjected to suspension polymerization of methyl methacrylate and a bifunctional or more cross-linking monomer to obtain cross-linked methyl methacrylate polymer particles (first step), and the methyl methacrylate resin particles are absorbed and polymerized. It can be obtained by making it into methyl methacrylate resin particles (second step).

The methyl methacrylate resin particles of the present invention require that a non-crosslinked methyl methacrylate polymer be held by a crosslinked methyl methacrylate polymer. Here, holding does not include the case where both are simply mixed. The holding is performed, for example, by preparing a cross-linked polymethyl methacrylate,
This can be achieved in the process by making non-crosslinked polymethyl methacrylate. Preferably, non-cross-linked polymethyl methacrylate is formed within the cross-linked polymethyl methacrylate molecular structure.

The ratio of cross-linked polymethyl methacrylate to non-cross-linked polymethyl methacrylate in the methyl methacrylate resin particles is suitably from 5:95 to 45:55 (weight ratio), more preferably from 10:90 to 30:50. 70 (weight ratio). If the amount of the non-crosslinked polymethyl methacrylate is less than 55% by weight, the hardness of the rice cake becomes insufficient, pressure cannot be sufficiently applied when filling into the mold, and the arrival to the rice cake becomes extremely delayed. If the cross-linked polymethyl methacrylate is less than 5% by weight, the effect of prolonging the rice cake period is not recognized.

The first step for producing the crosslinked methyl methacrylate polymer particles as a raw material of the composition of the present invention is obtained by suspension polymerization of methyl methacrylate. At that time, crosslinking polymerization is carried out by the presence of 0.01 to 0.5 mol%, preferably 0.03 to 0.3 mol% of a crosslinking monomer. The amount of the crosslinking monomer used is one of the characteristics of the raw material of the present invention.
One of the components. In the use of 0.01 mol% or less,
For example, even if the resin of the present invention is used as a powder of the denture base composition, the desired prolongation of the rice cake period is not recognized. Also 0.
If the amount is more than 5 mol%, the hardness of the rice cake is insufficient, and sufficient pressure cannot be applied when filling the rice cake into the mold, and the arrival at the rice cake is extremely delayed.

[0010] The crosslinkable monomer used herein includes a monomer having two or more functional groups capable of crosslinking polymethacrylate in one molecule. For example, ethylene glycol dimethacrylate, propylene glycol dimethacrylate, triethylene glycol dimethacrylate, pentaerythritol trimethacrylate,
And trimethylolpropane trimethacrylate or their corresponding acrylates. Other examples include diallyl phthalate. One type of these crosslinkable monomers is generally used, but a mixture of two or more types may be used.

In the first step, it is essential to add a polymerization initiator. The amount of the polymerization initiator used can be arbitrarily excessive. As the polymerization initiator, an organic peroxide (for example, benzoyl peroxide, lauroyl peroxide, etc.) is usually used. Other azo compounds (for example, 2,
2'-azobisisobutyronitrile).

The dispersion medium in the first step is water. A dispersant (eg, polyvinyl alcohol, tertiary calcium phosphate, metathetical method magnesium pyrophosphate, etc.) is usually added to the dispersion medium. Also, the use of a surfactant (e.g., sodium alkyl sulfate such as sodium lauryl sulfate) may help control particle size.

In the first step, heating is usually carried out with stirring (for example, 40 to 40).
80 ° C). The reaction time is usually tens of minutes to several hours. Thus, crosslinked polymethacrylate is generated as fine particles in the reaction system.

Next, in a second step, a second polymerization is carried out by adding methyl methacrylate to the above reaction system. However, by classifying the crosslinked methyl methacrylate polymer particles obtained after the completion of the first step and then performing the second step, it is possible to efficiently produce a resin powder having an arbitrary particle size distribution.

The addition of methyl methacrylate in the second step is preferably performed gradually so that it is at least adsorbed on the crosslinked polymethacrylate fine particles and absorbed in the macromolecule. For example, the addition is performed gradually over a long period of time while heating at 60 ° C to 80 ° C.

After the completion of the first step, the polymerization initiator necessary for the second step may be dissolved in a small amount of a monomer at the polymerization temperature or at room temperature and then added dropwise, or the monomer may be added dropwise in the second step. Or by utilizing the polymerization initiator remaining in the first step.

The reaction in the second step is carried out at 40 to 80 ° C. for several tens of minutes to several hours after the addition of the monomer is completed. In this reaction, it is considered that a non-crosslinked methyl methacrylate polymer is formed in the molecule of the crosslinked methyl methacrylate polymer. The molecular weight of the polymer produced at this time is 0.5 to 2,000,000 (GP
Method C standard polystyrene calibration). The powder of the methyl methacrylate resin particles thus formed can be easily isolated by a conventional method. The average particle size of this powder is 20 to
Preferably it is 200 μm. Such a particle diameter can be obtained mainly by adjusting the stirring speed in the first step, the amount of the surfactant added, and the like.

As the polymerization initiator contained in the powder component of the composition of the present invention, an organic peroxide such as benzoyl peroxide and lauroyl peroxide is used. The content is not particularly limited, but is about 0.2 to 2% by weight based on the weight of the polymer in methyl methacrylate. The method of adding the polymerization initiator to the powder may be a blending method, but an excess polymerization initiator may be used in suspension polymerization for producing methyl methacrylate particles, and a part of the polymerization initiator may be left.

The liquid component in the composition of the present invention is basically composed of methyl methacrylate and a crosslinkable monomer. For the purpose of improving the physical properties, a polymerizable compound such as an alkyl ester other than (meth) acrylic acid is used. A vinyl monomer may be used in combination. As the (meth) acrylate,
For example, esters such as ethyl, butyl, and 2-ethylhexyl are exemplified.

Examples of the crosslinkable monomer include polyfunctional methacrylate and diallyl phthalate, and one type or a mixture of two or more types may be used. Examples of the polyfunctional methacrylate include ethylene glycol bis methacrylate, trimethylolpropane trimethacrylate, and the like. The content of the crosslinkable monomer in the liquid may be increased or decreased according to the desired properties of the product, but is preferably 0.1 to 15 wt%.

The mixing ratio of the powder component and the liquid component in the composition of the present invention is preferably from 10: 4 to 10: 5.

[0022]

Embodiments of the present invention will be described below. A. Production of Resin Particles: Examples 1 to 3 and Comparative Examples 1 to 2 In a method in which crosslinked poly (methyl methacrylate) particles are produced in the first step by suspension polymerization and then the monomers are absorbed in the second step to carry out polymerization. Resin particles of Examples 1 to 3 and Comparative Examples 1 and 2 were prepared with the compositions shown in Table 1 and below. Table 2 shows the results of these test evaluations. Next, specific manufacturing conditions will be described. Methacrylic acid was added to a stainless steel autoclave at 2000 parts by weight of a 1% by weight aqueous solution of saponified polyvinyl alcohol (Gohsenol GH-20 manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) and a ratio as described in the first stage column of Table 1. A mixture of methyl, a crosslinking monomer and benzoyl peroxide was charged, and the space was replaced with nitrogen.
And heated for 3 hours to produce a crosslinked polymer. For example, in Example 1, the obtained crosslinked polymer had an average particle size of 5
The polymerization conversion ratio was 6 μm, and the polymerization conversion rate was 92%. The unpolymerized component was benzoyl peroxide and its decomposition product and methyl methacrylate by liquid chromatography, and it was confirmed that the unpolymerized component of the crosslinking monomer did not remain. The gel fraction is 91%
It was also confirmed that almost all of the produced polymer was crosslinked. Following the polymerization of the crosslinked polymer, methyl methacrylate described in the second stage column of Table 1 was quantitatively added at a rate of 100 g / hour to proceed with the polymerization. The polymerization was terminated by holding. Samples were appropriately taken during the polymerization process and observed at a magnification of 100 times. As a result of the addition of methyl methacrylate, the diameter of the polymer particles increased, and almost no new particles were formed. In addition, the collected particles are uniformly plasticized and softened by the absorbed methyl methacrylate with no difference between the particle surface and inside, and the generation of non-crosslinked polymethyl methacrylate occurs almost uniformly inside the particles. Conceivable. After the polymerization was completed, the suspension was cooled to 30 ° C., and the suspension was taken out, filtered, washed with water, and air-dried to obtain powder of methyl methacrylate resin particles.

[Table 1]

Comparative Examples Comparative examples 3 and 4 show examples in which ordinary suspension polymerization was carried out without using the method of the present invention.

Comparative Example 3 An average particle diameter of 123 μm was obtained by suspension polymerization.
%, A polymethyl methacrylate powder having a weight average molecular weight of 1.37 million (GPC standard polystyrene calibration) was obtained.

Comparative Example 4 Crosslinked poly (methyl methacrylate) resin particles having an average particle diameter of 110 μm, a polymerization conversion rate of 96%, and a gel fraction of 96% were obtained by suspension polymerization of methyl methacrylate containing 0.1% by weight of ethylene glycol dimethacrylate. I got The crosslinked poly (methyl methacrylate) resin particles and the poly (methyl methacrylate) resin particles of Comparative Example 3 were mixed at a weight ratio of 1/4 and subjected to a test. B. Evaluation of denture base resin composition (Explanation of test and evaluation method) Rice cake-like, pot life 50 g of polymer particles and 20 g of methyl methacrylate liquid containing a crosslinkable monomer are placed in a glass container in the order of liquid and powder, and the lid is closed. A portion of this resin mud is taken out and put into a number of stainless steel cylinders having an inner diameter of 13 mm and a volume of 2 cm ³ to obtain a cylindrical resin. The spreading diameter of the cylindrical resin is read every 5 to 10 minutes from the start of mixing. The point at which the resin diameter was 35 mm was defined as the start of rice cake formation, and the pot life was defined as 35 to 28 mm. Test environment is 23 ± 2 ℃,
RH 50% 2. Anti-bending test, breaking load
After heating for 1.5 hours, the molded body obtained by heating in boiling water for 30 minutes was used as a sample, and the molding was performed according to JIST6501.
The load continued to be increased even after 5 kgf, and the load at which breakage occurred was determined, and the average of 10 specimens was taken as the breakage load. From Table 2, it can be seen that the use of the resin composition for denture base of the present invention does not impair the strength and the like, and the rice cake shape suitable for filling has a pot life of 170-150.
It can be seen that the time is dramatically extended to 260 minutes.

[Table 2]

[0026]

EFFECT OF THE INVENTION The resin composition for denture base of the present invention can maintain the optimal mixing state of the powder and liquid (mochi state) for filling in the mold for a long time without impairing the mechanical strength and various physical properties. Hold. This has the effect of increasing the efficiency of the technical operation and reducing the cost.

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁶ Identification symbol FI C08L 33/12 C08L 33/12 (56) References JP-A-2-212407 (JP, A) JP-A-57-203006 (JP) JP-A-5-93004 (JP, A) JP-A-2-305808 (JP, A)

Claims (1)

(57) [Claims] (1) Methyl methacrylate and 0.01 to 0.5
5 to 45 parts by weight of cross-linked methyl methacrylate polymer particles formed by suspension polymerization with a mole% of bifunctional or more cross-linkable monomer, and 95 to 55 parts by weight of methyl methacrylate are absorbed and polymerized with the particles. A denture base resin composition comprising a combination of a powder comprising methyl methacrylate resin particles and optionally a polymerization initiator, and a liquid comprising methyl methacrylate and a crosslinking agent.