KR20090056121A - Denture base resin composition excellent in impact resistance - Google Patents

Abstract

The denture resin composition according to the present invention is a denture resin composition comprising a liquid component comprising a functional monomer and a crosslinking agent, and a solid phase component comprising PMMA, an initiator, and core-shell particles for reinforcing impact resistance. The core-shell particles are composed of a core of a urethane-based resin and a shell of a material having high affinity with PMMA, and are incorporated in an amount of 5% by weight or less based on the weight of the composition. It has the advantage that the impact resistance is very excellent without falling transparency.

Description

Resin Composition for Denture Base with Excellent Impact Resistance}

The present invention is a denture base resin composition excellent in impact resistance, and more specifically, a solid component comprising a liquid component comprising a functional monomer and a crosslinking agent, and a core-shell particle for reinforcing impact resistance, PMMA, an initiator, and impact resistance. A denture base resin composition comprising: the core-shell particles are composed of a core of a urethane-based resin and a shell of a material having high affinity with PMMA, and are incorporated in an amount of 5% by weight or less based on the weight of the composition. The denture base resin composition characterized by the above-mentioned.

Polymethyl methacrylate (PMMA) resin is not only excellent in transparency by transmitting about 95% of visible light, but also has high surface appearance and glass transition temperature, so it is applied as a molding material for glass. It is stable in the normal oral environment, and the physical properties are suitable for oral application. Most denture bases have been made of PMMA resin since the 1940s.

However, in order to use it as a denture base composite material, although both impact resistance and transparency must be satisfied, PMMA resin has a weak impact strength and is easily broken by external force such as a drop impact. In addition, due to low surface strength and fragility, the wear and scratch of the surface is likely to occur, there is a disadvantage that the transparency is reduced.

Accordingly, various studies and discussions have been conducted to reinforce the impact resistance of PMMA.

For example, a blending method of mixing or copolymerizing a polymer having a low glass transition temperature, which is a temperature at which physical properties begin to change, and a PMMA, or a physically dispersed polymer having a rubbery phase that is resistant to impact, has been discussed.

However, in the case of strengthening the properties of PMMA by the copolymer, the properties are often influenced by the monomers of the polymer having a low glass transition temperature, and thus improvement of mechanical properties such as surface strength and impact resistance cannot be greatly expected. In addition, the blending method has a problem in that the phase separation occurs between the polymer having a strong rubber phase and PMMA, thereby decreasing transparency.

As another attempt to increase the impact strength of PMMA resins, studies on the addition of metal materials or fiber reinforcements have been discussed. For example, US Pat. No. 6,103,779 discloses the use of fiber reinforcements in PMMA. To improve the impact strength of the technique is disclosed. However, it has been found that the above-mentioned techniques cause problems that degrade the transparency of the PMMA resin, or are incompatible with the polymer compound used as the substrate, resulting in phase separation.

Therefore, there is an urgent need to develop a technology for denture base material having excellent impact resistance and compatibility with PMMA used as a substrate without affecting transparency.

Accordingly, an object of the present invention is to solve the problems of the prior art as described above and the technical problem that has been requested from the past.

Specifically, in the PMMA-based denture base resin composition, specific core-shell particles are mixed in a predetermined amount so that the transparency of the denture base resin is excellent and excellent in impact resistance without deterioration in transparency. It is to provide a composition.

The denture resin composition according to the present invention for achieving this object comprises a liquid component comprising a functional monomer and a crosslinking agent, and a solid phase component comprising a PMMA, an initiator, and core-shell particles for reinforcing impact resistance. The denture base resin composition, wherein the core-shell particles are composed of a core of a urethane-based resin and a shell of a material having high affinity with PMMA, and are incorporated in an amount of 5% by weight or less based on the weight of the composition. .

That is, the denture base resin composition according to the present invention includes a predetermined core-shell particle, and can improve the impact resistance of the PMMA substrate by a urethane-based resin, which is a core material, and a shell made of a material having excellent affinity with PMMA. By this method, phase separation with the PMMA substrate may be uniformly dispersed. At this time, the core-shell particles may be added in a predetermined content to have a moldability suitable as a denture base material, it is possible to prevent a decrease in transparency of the PMMA substrate.

Polymerization of the denture base resin composition produces a PMMA substrate and the core-shell particles are distributed evenly dispersed on such PMMA substrate. The PMMA substrate forms a network structure while polymerizing the functional methacrylate monomer of the liquid component between the solid phase components to form PMMA.

Although not related to the present invention, there are some examples of composite materials that add core-shell particles to PMMA resins in the prior art. However, the industrial PMMA composite material, since the core-shell particles are mixed during the melt extrusion process, the material constituting the shell is melted together with the PMMA resin, so that the core material itself is melt-dispersed in the PMMA resin. Thus, when polymerizing the composition of the present invention, the core-shell particles themselves are clearly distinguished from the morphologies incorporated into the PMMA substrate in the form of independent particles.

The core-shell particles are included in an amount of 5% by weight or less based on the weight of the solid component, as defined above. According to the experiments performed by the present inventors, when the content of the core-shell particles exceeds 5% by weight, the distance between the particles is very short and the viscosity is increased, thereby reducing the moldability and transparency of the PMMA substrate. It was found that the resin was not suitable for use as a denture base material by lowering it. On the other hand, when the content of the core-shell particles is too small, the effect of improving the desired impact resistance can not be exhibited, so that the core-shell particles are preferably contained in an amount of 0.1 to 5% by weight based on the weight of the solid component. Do.

In the present invention, the core material of the core-shell particles is made of a urethane resin so as to exhibit excellent impact resistance, and the urethane resin may be urethane acrylate.

As the core material, an elastomer such as butyl acrylate, butadiene, acrylonitrile may be considered, but according to the experiments conducted by the inventors of the present application, it is difficult to control the size of the particles when synthesizing the core particles. It was confirmed that not only the impact resistance can be exhibited but also that there is a problem of decreasing transparency due to the difference in refractive index (> 0.02) from the PMMA shell (refractive index: PMMA: 1.4893, PBA (Poly Butyl Acrylate): 1.466, PUA ( Poly Urethane Acrylate): 1.4914). However, it is possible to use the above materials copolymerized with urethane acrylate.

Furthermore, it is generally known that fragile polymers, such as PMMA, are enhanced by shear yield formed between dispersed elastic particles, and that the addition of smaller particles can effectively induce shear bands.

Therefore, when synthesizing the core particles using urethane acrylate, which is a polymer having a polyoxyethylene group, it is possible to control the size of the core during the synthesis of the core by the polyoxyethylene group, and consequently to control the size of the core-shell particles Is possible.

In the present invention, since the urethane acrylate is located at one end of the PEG, and the polyoxyethylene group acts as a polymeric surfactant when the PEG oligomer is emulsified, the amount of PEG is increased. In this case, the size of the core tends to decrease regularly. In this way, the core size of the core-shell can be adjusted to about 10 to 200 nm, preferably 10 to 100 nm.

On the other hand, the shell material is a material having high affinity with PMMA which is a component of the core-shell particles. Here, the high affinity means that the physical and chemical properties of PMMA are similar, so that phase separation does not occur by mixing well with PMMA. Such shell material may preferably be a methacrylate-based resin, more preferably PMMA.

In one preferred example, the core material and / or shell material may be crosslinked. Since the strength of the core shell particles is further increased by the formation of the network structure by crosslinking, excellent impact resistance can be exhibited even when a relatively small amount is added.

In addition, if the molecular weight of the core material is too small, the degree of impact absorption is small and can not exhibit the desired impact resistance improvement effect, if the molecular weight of the shell material is too small, there is a problem that the bond strength with the core material is low and unstable. . On the contrary, if the molecular weight is too large, the size of the molecules constituting each material increases, the distance between the particles is too close, the elasticity of the PMMA substrate is lowered, and thus the problem that can not impart the desired impact resistance have. Therefore, preferably the molecular weight of the core material is 100,000 to 1,000,000, the molecular weight of the shell material may be 100,000 to 1,000,000.

In addition, if the size of the core-shell particles is too small, it may not be uniformly distributed in the PMMA substrate due to the cohesive force, and thus it is difficult to exert the impact resistance of homogeneous properties. not. In consideration of this, the core-shell particles may be preferably having a size of 20 to 400 nm, more preferably 20 to 250 nm.

The method for preparing the core-shell is not particularly limited, and may be preferably synthesized by emulsion polymerization, and more preferably by continuous emulsion polymerization.

In one preferred embodiment, the core-shell comprises the steps of (1) synthesizing the seed of the core material in an emulsion polymerization manner, and semi-continuously loading the shell material without purification to the core material seeds prepared in step (1); It can synthesize | combine continuously by dropping by fixed amount by semi-continuous). Since the process of preparing the core-shell by such a continuous emulsion polymerization method is known in the art, a detailed description thereof is omitted herein.

In one preferred example, the core material and / or shell material may be of a crosslinked structure, and in particular, between the mixed core material, between the shell material or between the core material and the shell material may be crosslinked with each other. The cross-linked structure can improve the binding force between materials or particles, thereby increasing the impact strength of the PMMA substrate, which has been demonstrated through examples and experimental examples described below.

As described above, the PMMA substrate is prepared by polymerizing a liquid component including a functional methacrylate monomer and a crosslinking agent, and a solid phase component including PMMA and an initiator in addition to the core-shell particles.

The functional monomer in the liquid component may be 1 or 2 or more selected from the group consisting of acrylic acid monomer, methacrylic acid monomer, acrylic monomer, methacrylic monomer, and vinyl ester monomer, preferably MMA (methyl methacryl) Rate) or EMA (ethyl methacrylate), but is not limited thereto.

The crosslinking agent is a dimethacrylate-based monomer to cross-polymerize during polymerization in a liquid composition, and serves to increase the strength of the PMMA substrate and provide sufficient bonding strength to improve impact resistance. It is not particularly limited. In a preferred example, ethylene glycol dimethacrylate (EGDMA), Bis-GMA (2,2-bis- (4- (2-hydroxy-3-methacryloyloxypropoxy) phenyl) propane), TEGDMA (triethylene glycol di Methacrylate), UDMA (urethane dimethacrylate), Bis-EMA (ethoxylate bisphenol A dimethacrylate), polyethylene glycol dimethacrylate (PEGDMA), and glycerol dimethacrylate (GDMA) It may be one or two or more selected from the group consisting of.

The liquid component may further include a stabilizer as necessary to prevent polymerization of the monomer during storage, and the stabilizer may be hydroquinone, methyl ether of hydroquinone, and the like. It is not limited only to these.

The content of the functional methacrylate monomer in the liquid component may be preferably 70 to 98% by weight, more preferably 85 to 98% by weight based on the total weight of the liquid component. In addition, the crosslinking agent may be preferably included in an amount of 2 to 30% by weight, more preferably 2 to 15% by weight, based on the total weight of the liquid component, the stabilizer is a small amount in consideration of the relationship with other components Can be added.

On the other hand, an initiator of the azo series, an initiator of the peroxide series, etc. may be used as the initiator among the solid phase components. In addition, the solid component may further include fibers or fillers or pigments for increasing strength, as necessary.

The fibers are gum wool fibers, preferably acrylic fibers, rayon fibers, and the like, but are not limited thereto. The pigment may be a metal oxide-based pigment such as iron oxide or zinc oxide or a white pigment such as titanium oxide, but is not limited thereto.

In one preferred example, the solid component may consist of PMMA, an initiator, a fiber and a pigment. At this time, the content of the PMMA may be preferably 80% by weight or more based on the total weight of the solid phase component, more preferably 90% by weight or more. The initiator may preferably be from 0.1 to 3% by weight, more preferably from 0.5 to 2% by weight based on the total weight of the solid phase components. In addition, the fiber and the pigment may be added as needed in consideration of the relationship with other components, the fiber may be preferably added in 2% by weight or less, more preferably 1% by weight or less The pigment may be preferably added in less than 0.5% by weight.

The method for producing a denture base using the denture base resin composition according to the present invention may be carried out by a series of processes including, for example, the following steps (i) to (iv).

(i) mixing the PMMA, initiator and core-shell particles to produce a solid phase component;

(ii) mixing the functional monomer and the crosslinking agent to produce a liquid component;

(iii) mixing the solid component prepared in step (i) with the liquid component prepared in step (iii); And

(iv) polymerizing the mixture prepared in step (iii).

Step (i) is a process of mixing the core-shell particles into a solid component including PMMA, fibers, pigments and the like in a mechanical manner such as a blender.

In the step (ii), the liquid component may be prepared by putting a functional monomer, a crosslinking agent, a stabilizer and the like into a blender and mechanically mixing, and the solid component prepared in step (i) Mix (step (iii)). At this time, the mixing ratio of the solid phase component and the liquid component may preferably be a volume ratio of 3: 1. The mixture becomes a paste state by mixing of such a liquid component and a solid component.

Step (iv) is a process of polymerizing the mixture paste of step (iii), wherein the functional monomers contained in the liquid component are polymerized to become PMMA. In this way, the network is formed while the solid phase components are connected to each other during the polymerization of the monomer. The state of the mixture paste in the polymerization process will be described as follows.

First, the mixture paste is in the form of wet sand and is called the sandy stage. After this sandy stage, the solid phase begins to mix with the liquid phase, and the state becomes thick and is called a stringy stage. After the stringy stage lasts for about 5 to 15 minutes, the solid phase component mixed with the monomer and the solid phase component are not mixed. This stage is called a dough stage, and after the dough stage, the monomer is a solid component. It penetrates deep into me and becomes a rubbery stage that appears to be missing.

When fabricating dentures using the denture base resin composition according to the present invention, it is preferable to perform the molding step in the dough stage, and this operation is preferably performed before the rubbery stage.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the following Examples are provided to illustrate the present invention, and the scope of the present invention is not limited thereto.

Example 1

First, 93.5 to 98% by weight of PMMA and 1% by weight of BPO (initiator), core-shell particles made of urethane acrylate core and uncrosslinked PMMA shells were added with varying contents and mechanically mixed to obtain solid component composition A ~. D was prepared. At this time, the particle diameter of the core of the core-shell has a distribution of 40 to 50 nm, the content was changed as shown in Table 1 below.

In addition, about 90% by weight MMA monomer, about 10% by weight EGDMA (crosslinking agent), and a small amount of hydroquinone (stabilizer) were added to the blender and mixed to prepare a liquid component.

23 g of the solid component was mixed with 10 ml of the liquid component to prepare a denture resin composition, and a test piece was prepared using the same.

TABLE 1

Example 2

A denture base resin composition and a test piece were prepared in the same manner as in Example 1, except that core-shell particles consisting of a PMMA shell crosslinked with a urethane acrylate core were used. At this time, the particle diameter of the core showed distribution of 40-50 nm.

Comparative Example 1

The denture base resin composition and the test piece were produced in the same manner as in Example 1, except that no core-shell particles were added to the solid phase component.

Comparative Example 2

The denture base resin composition and the test piece were prepared in the same manner as in Example 1, except that 5 wt% of the core-shell particles composed of the crosslinked polybutylacrylate core and the crosslinked PMMA shell were added. At this time, the particle diameter of the core exhibited a distribution of 150 nm to 180 nm.

Comparative Example 3

The denture base resin composition and the test piece were prepared in the same manner as in Example 1 except that the core-shell particles composed of the PMMA shell crosslinked with the urethane acrylate core were added at 10 wt%.

Experimental Example 1

The impact strength of a total of 12 test pieces prepared through Examples 1 to 3 and Comparative Examples 1 and 2 were tested. Impact strength was measured by the Charpy impact strength test of the notch type according to ISO 1567: 1999 Dentistry-Denture base polymers / Amd 1: 2003. The impact strength specimens were 60 mm long, 6 mm wide, and 4 mm high, with a notch depth of 1.2 mm. The distance of the test piece support was 50 mm, and the capacity of the hammer was 0.5 J. Through the impact strength test, the test piece was placed on the support and measured by applying a hammer by rotating the hammer opposite the notch, and the results are shown in Table 2 below.

TABLE 2

As shown in Table 2, it can be seen that all 12 test pieces of Examples 1 and 2 according to the present invention exhibit excellent impact strength compared to the test piece according to Comparative Example 1. In addition, the impact strength increases as the content of the core-shell particles increases, and it can be seen that the crosslinked particles appear higher than those without crosslinking. On the other hand, when comparing the composition D (5 wt%) of Comparative Example 2 and Examples 1 and 2 including the core-shell particles of the cross-linked polybutylacrylate core, compared to the same content of the core-cell (5 wt%) It can be seen that the impact strength of the test piece according to the embodiments is much better. This is presumably because the core-shell having a relatively large particle size is included in Comparative Example 2, so that the shear band cannot be effectively induced at the same content.

On the other hand, in the case of Comparative Example 3 in which the content of the core shell is added in excess of 5% by weight can be expected to improve the impact strength, it can be seen that the results are lower than the composition D of Examples 1 and 2. This is presumably because the viscosity increases in the dough stage as the content of the nano-sized particles increases, which makes it difficult to form, thereby creating a lot of bubbles in the test piece.

Therefore, it can be confirmed that the impact resistance is greatly improved by adding a predetermined amount of particles composed of the core of the urethane acrylate and the shell of the PMMA affinity polymer to the denture base resin composition.

Experimental Example 2

The transparency of the test specimens prepared in Examples 1 and 2 and Comparative Examples 1 to 3 was confirmed. Transparency measurement was calculated according to the following formula after measuring the absorbance at 500 nm using a UV visible spectrophotometer. The thickness of the test piece was 3 mm.

T = P / P _O = e ^-A

(T: transparency of sample, P and P _O : intensity of light before and after absorption, A: absorbance measured)

As a result, all of the test pieces of Examples 1 and 2 exceeded 95% of transparency based on the transparency (PMMA) of Comparative Example 1. On the other hand, the test piece of Comparative Example 2 showed a low transparency of about 90%. This is presumably due to not easy to control the size of the polybutyl acrylate core has a large particle diameter of 150 to 180 nm, as well as due to the difference in refractive index between the polybutyl acrylate and PMMA. In addition, even in the case of the test piece of Comparative Example 3 shows a low transparency of about 90%, it can be seen that the desired transparency can not be exhibited when the content of the core shell exceeds 5 wt%.

Therefore, the denture base resin composition according to the present invention can be seen that the impact resistance is significantly improved without lowering the transparency.

As described above, the denture base resin composition according to the present invention contains specific core-shell particles having excellent compatibility and affinity with PMMA in a predetermined amount, and thus has excellent impact resistance without deteriorating transparency.

Those skilled in the art to which the present invention pertains will be able to perform various applications and modifications within the scope of the present invention based on the above contents.

Claims (13)

A denture base resin composition comprising a liquid component comprising a functional monomer and a crosslinking agent and a solid phase component including a PMMA, an initiator, and core-shell particles for reinforcing impact resistance, wherein the core-shell particles are formed of a urethane resin. A denture resin composition comprising a core and a shell of a material having a high affinity for PMMA and incorporated in an amount of 5% by weight or less based on the weight of the composition. The denture resin composition according to claim 1, wherein the core material of the core-shell particles is urethane acrylate. The denture resin composition according to claim 1, wherein the shell material is PMMA. The denture resin composition according to claim 1, wherein the core material and / or the shell material are crosslinked. The denture resin composition according to claim 1, wherein the core material has a molecular weight of 100,000 to 1,000,000, and the shell material has a molecular weight of 100,000 to 1,000,000. The denture resin composition according to claim 1, wherein the core-shell particles have a size of 20 to 400 nm. The denture resin composition according to claim 1, wherein the core-shell core has a size of 10 to 100 nm. The denture resin composition according to claim 1, wherein the core-shell particles are prepared by continuous emulsion polymerization. The denture resin composition according to claim 1, wherein the monomer is at least one monomer selected from the group consisting of an acrylic acid monomer, a methacrylic acid monomer, an acrylic monomer, a methacrylic monomer, and a vinyl ester monomer. . The denture resin composition according to claim 9, wherein the monomer is MMA (methyl methacrylate), EMA (ethyl methacrylate), or a mixture thereof. The method of claim 1, wherein the crosslinking agent is ethyleneglycol dimethacrylate (EGDMA), Bis-GMA (2,2-bis- (4- (2-hydroxy-3-methacryloyloxypropoxy) phenyl) propane), TEGDMA (Triethylene glycol dimethacrylate), UDMA (urethane dimethacrylate), Bis-EMA (ethoxylate bisphenol A dimethacrylate), polyethylene glycol dimethacrylate (PEGDMA), and glycerol dimethacryl Denture resin composition, characterized in that 1 or 2 or more selected from the group consisting of a rate (GDMA). The denture resin composition according to claim 1, wherein the liquid component further comprises a stabilizer. The denture resin composition according to claim 1, wherein the initiator is an azo initiator, a peroxide initiator, or a mixture thereof.