JP7168936B2 - Hydrophilic surface treatment agent - Google Patents

Description

TECHNICAL FIELD The present invention relates to a hydrophilizing surface treatment agent for improving the hydrophilicity of the surface of a resin denture base or the like.

Dentures, which are worn every day to replace missing teeth and are used for mastication, are required to be durable so that they can be used for a long period of time. The characteristic that there is is required. Therefore, high-strength and hydrophobic resin materials such as acrylic resins, polycarbonate resins, and polyamide resins are used as denture base materials.

Another feature required for dentures is a sense of stability when worn. In order to allow long-term use in the oral cavity, hydrophobic materials are used for the denture base portion, while the oral mucosa with which the denture base portion contacts has hydrophilic properties. Therefore, the denture base material and the oral mucosa have contradictory properties from the viewpoint of hydrophilicity and hydrophobicity, and there is a problem that the stable feeling of wearing the denture is insufficient. In other words, the surface of the denture base material is preferably hydrophilic in order to give the user a more stable wearing feeling.

On the other hand, in so-called denture stabilizers, which are interposed between the denture and the oral mucosa to temporarily fix the ill-fitting denture to the palatal mucosa, serine is blended with a thickening agent such as glycerin, sorbitol, polyethylene glycol, and the like. Or, a technology that enhances the stability of dentures and oral mucosa by blending water-soluble polymer compounds such as carboxymethyl cellulose and making them absorb water such as saliva to give them adhesive power is adopted. (See Patent Documents 1 and 2).

JP 2018-1999723 A JP 2007-254287 A JP 2007-051266 A Japanese Patent No. 5836361 JP 2017-205683 A JP-A-2005-270891 Japanese Patent Application Laid-Open No. 2015-142900

The denture fixatives described in Patent Documents 1 and 2 are recommended for temporary use mainly for ill-fitting dentures. In other words, dentures are originally made according to the condition of the remaining teeth, gums, and jawbone. Improper use of the dentures leads to uneven resorption of the alveolar ridge and further deterioration of the fit of the denture. In addition, many of the ingredients are sticky, and cases have been reported in which leftover stabilizers stick to the mouth or dentures.

Thus, denture stabilizers are basically not intended for fitted dentures, and their use also requires caution. As far as the present inventors know, there is no treatment agent that can be made hydrophilic and that does not use adhesive components such as stains.

Accordingly, the present invention provides a hydrophilizing agent for hydrophilizing the hydrophobic surface of an article having a hydrophobic surface, which agent does not contain adhesive components such as stains and can be used easily. for the purpose.

As a result of repeated studies, the inventors found that cellulose nanofibers (hereinafter sometimes abbreviated as "CNF") used for fiber reinforcement such as resin are suspended in an aqueous dispersion medium. The present inventors have found that when the denture is immersed, the surface of the denture base becomes more hydrophilic, and the affinity between the surface of the denture base and the oral mucosa also increases, leading to the completion of the present invention.

That is, the first aspect of the present invention is a hydrophilizing agent for hydrophilizing the surface of a poly(meth)acrylate resin denture base , wherein cellulose nanofibers are dispersed in water or a solvent containing water. The hydrophilic treatment agent is characterized in that the content of the cellulose nanofibers in the hydrophilic treatment agent is 0.02 to 0.5 wt % .

In the hydrophilizing agent, the cellulose nanofiber preferably has an average fiber width of 3 nm or more and 200 nm or less and an average fiber length of 0.1 μm or more and 5.0 μm or less. In addition, the content of cellulose nanofibers is preferably 0.05 wt % to 0.20 wt %, and more preferably, it is a hydrophilizing agent for hydrophilizing the surface of the resin denture base.

The second aspect of the present invention is a method for treating a denture, comprising the step of immersing a denture having a denture base made of a poly(meth)acrylate resin in the hydrophilizing agent.

According to the present invention, a simple operation of immersing a denture in a CNF suspension can increase the hydrophilicity of a hydrophobic surface such as a denture base surface. For example, a surface with a contact angle to water of 94° can be a surface with a contact angle to water of 77°-80°. In the denture treated with the hydrophilizing agent of the present invention, the surface of the denture base film surface is changed to be hydrophilic, so the affinity with the oral mucosa is increased, and the adhesion between the oral mucosa and the denture is improved. It is possible to obtain a stable wearing feeling.

The hydrophilizing agent of the present invention can increase the hydrophilicity of the surface by a simple operation of immersing the object to be treated in it. In addition, since it does not contain adhesive ingredients such as thickening agents and water-soluble polymers, it can be applied to compatible dentures, and adhesive ingredients do not remain in the oral cavity or on the surface of dentures, and stains do not adhere to the ingredients. It is hygienic. Furthermore, although it does not contain such an adhesive component, the active ingredient CNF is relatively stably retained on the surface to be treated, and its effect can be maintained, for example, even after washing with water several times. It is possible.

The hydrophilizing agent of the present invention is a cellulose nanofiber (CNF) having an average fiber width of 3 nm or more and 200 nm or less and an average fiber length of 0.1 μm or more and 5.0 μm or less in water or a solvent containing water. becomes dispersed. Here, CNF is known as a reinforcing material used for fiber reinforcement of resin as described in Patent Documents 3 and 4, but examples of using it as a surface reforming agent are As far as the inventors know, it is not known.

That is, CNF is known as a lightweight and high-strength material, and not only is it attracting attention as a fiber reinforcing material in so-called fiber-reinforced resin, but research and development is also progressing on using itself as a structural material. . However, due to its hydrophilicity, CNF is difficult to be compatible with resin, and when mixed with resin, it aggregates and has a problem that it is difficult to obtain the desired effect. Therefore, when using CNF as a fiber reinforcing material, it was necessary to devise such as hydrophobizing the hydroxyl groups present in the cellulose units of CNF as described in Patent Document 4. The inventors of the present invention do not regard the inherent hydrophilicity of CNF as a drawback, but try to actively utilize it, conceived of its use as a surface hydrophilization treatment agent, and as a result of examination, as described above. It was confirmed that a good effect can be obtained, and the present invention has been completed. Although CNF is hydrophilic , it is believed that the reason why it is relatively stably retained on the hydrophobic resin surface is due to intermolecular forces such as van der Waals force, polar attraction, and hydrogen bonding. be done. For example , when CNF aggregates, a region with a high density of hydrophobic parts in the cellulose molecule is generated, etc., the Van der Waals force between the hydrophobic surface of the object to be treated and the CNF aggregates increases, and simple It is presumed that a holding force was generated that would not wash away with water washing.

The present invention will be described in detail below.

The CNF used in the hydrophilizing agent of the present invention is not particularly limited, and those available industrially or as reagents can be used. From the viewpoint of the adsorptivity between the denture base surface and the oral mucosa and the cost and labor required for CNF defibration, those having an average fiber width of 3 to 200 nm and an average fiber length of 0.1 to 5.0 μm, It is more preferable to use those having an average fiber width of 3 nm to 80 nm, particularly 5 nm to 50 nm. Moreover, from the viewpoint of the rigidity and strength of the CNF fiber itself, it is more preferable to use one having a degree of crystallinity of 50% or more. Such CNF is formed, for example, by defibrating cellulose with a high-pressure water stream. The average fiber width and average fiber length can be measured using an electron microscope or the like.

Such CNF can be obtained by defibrating pulp to nanosize. The fibrillation method of pulp is not particularly limited as long as it is known, and examples thereof include chemical treatment such as TEMPO oxidation method, enzymatic hydrolysis method, ion-selective liquid dissolution method, underwater counter-impingement method, and hydraulic penetration refinement method. , a high-pressure homogenizer method, a microfluidizer method, a grinder method, a twin-screw kneading method, a ball mill pulverization method, and the like. Moreover, you may defibrate by combining these methods. For example, by the underwater facing collision treatment method described in Patent Document 5, the polysaccharide wet pulverization method described in Patent Document 6, the nano-miniaturized product manufacturing method described in Patent Document 7, etc. A method of colliding high-pressure water of about 50 to 400 MPa against cellulose fibers suspended in 5 to 10% by weight of water can be suitably employed.

The CNF raw material pulp is not particularly limited as long as it is known, and any material can be used. Examples include linter pulp, rag pulp, bamboo pulp, esparto pulp, bagasse pulp, hemp pulp, straw pulp, softwood pulp, and hardwood pulp. good too. As raw material pulp, it is preferable to use pulp having an α-cellulose content of 60% to 99% by weight. If the purity of the α-cellulose content is 60 wt% or more, the fiber width and fiber length can be easily adjusted and the entanglement of the fibers can be suppressed, compared to the case where the α-cellulose content is less than 60 wt%. , the coloring suppression effect is good.

In the CNF used in the present invention, at least part of the hydroxyl groups on the surface may be substituted with other functional groups as long as the effects of the present invention are not impaired. As the functional group substituted for the hydroxyl group on the CNF surface, any functional group can be introduced as long as it can be chemically reacted with the hydroxyl group and introduced. In order to effectively impart hydrophilicity, the introduced functional group preferably has high hydrophilicity, and the dielectric constant is preferably 5 or more, more preferably 10 or more, and 15 or more. is more preferred. Examples of such functional groups include a carboxyl group and a phosphoric acid group.

Water or a solvent containing water is used as the dispersion medium for CNF in the hydrophilic treatment agent of the present invention from the viewpoint that CFN is uniformly dispersed. The solvent containing water is preferably a mixture of water and a water-soluble organic solvent. Water-soluble organic solvents include alcohols such as methanol, ethanol, propanol, and ethylene glycol; acetone, ethyl methyl ketone, and methyl isobutyl ketone. ketones can be suitably used, among which alcohols are most preferable.

The CNF content in the hydrophilic treatment agent of the present invention is 0.001 wt% or more and 3.0 because it prevents excessive use of CNF, efficiently attaches an effective amount of CNF to dentures, and is easy to handle. %, preferably 0.01 wt % to 1.0 wt %, more preferably 0.02 wt % to 0.5 wt %, most preferably 0.03 wt % to 0.3 wt %.

For the reasons described above, the hydrophilizing agent of the present invention preferably does not contain a substance that becomes an adhesive component. It may contain moisturizing ingredients. Examples of such moisturizing ingredients include polyhydric alcohols such as glycerin and butylene glycol, and polymers having moisturizing properties such as polyethylene glycol.

The article to be treated with the hydrophilic agent of the present invention (article to be treated) is not particularly limited as long as it has a hydrophobic surface. Here, the term "hydrophobic surface" means a surface having a contact angle with water of 90° or more, and usually a synthetic resin surface corresponds to this. As the article to be treated, an article having such a hydrophobic surface and to which it is desired to impart hydrophilicity to the surface is appropriately used. preferable. Examples of resin materials used for the denture base portion of dentures include homopolymers of methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, n-propyl (meth) acrylate, and butyl (meth) acrylate. Or poly (meth) acrylate resin selected from at least one of these copolymers, as well as polyolefin resin (e.g., polypropylene), polyamide resin (e.g., nylon 66 (registered trademark)), polyester resin (e.g., polycarbonate), polyether resins (e.g., polyacetal, polysulfone), polynitrile resins (e.g., polyacrylonitrile), polyvinyl resins (e.g., polyvinyl acetate), cellulose resins (e.g., cellulose acetate), fluorine resins ( Examples include polychlorofluoroethylene), imide-based resins (eg, aromatic polyimide), and the like. The denture base may be one that has been restored with a backing layer material, and examples of resin components used in the backing layer material include silicone-based resins, (meth)acrylate-based resins, fluorine-based resins, polyolefin-based resins, and the like. be able to.

In order to treat an article to be treated with the hydrophilic treatment agent of the present invention, the dispersion medium (water or a solvent containing water) may be removed by contacting the hydrophobic surface with the hydrophilic treatment agent of the present invention. . When the hydrophobic surface and the hydrophilic treatment agent are brought into contact, the CNF dispersed in the dispersion medium sorbs on the hydrophobic surface, and even if the dispersion medium is removed by intermolecular forces such as van der Waals force, An effective amount of CNF is retained on the hydrophobic surface without being washed away with the dispersion medium. Contact conditions such as contact method and contact time may be appropriately determined according to the article to be treated, etc. However, when the article to be treated is a denture, the denture can be immersed in the hydrophilizing agent of the present invention. preferable. The longer the immersion time, the more stably the CNF adheres to the denture base surface. Immersion for hours or more is more preferable, and immersion for 12 hours or more is even more preferable.

In addition, since the attached CNF is considered to be attached only by intermolecular force, it will be detached (removed) during mechanical cleaning of the denture, so the frequency of treatment (immersion of the denture) is , preferably once or more a week, particularly once or more every three days, more preferably once or more a day. Furthermore, although the denture surface may be washed with water after treatment, it is preferable to use the denture as it is without washing in order to maintain a state in which more CNF is attached and to maximize the effect.

EXAMPLES The present invention will be specifically described below with reference to Examples, but the present invention is not particularly limited to these Examples.

(Preparation of denture base)
A thermosetting acrylic resin denture base (manufactured by Akron, GC) was cured into a rectangular parallelepiped (64.0×10.0×3.3 mm) by the method described in the package insert and ISO20795-1. Both surfaces of the obtained cured product were polished with #600, #800, #1000 and #1200 emery abrasive papers. After the cured product was washed with water for 15 seconds, it was immersed in distilled water at room temperature (23±2° C.) for 24 hours.

(Method for producing CNF)
CNF was produced using bamboo-derived pulp as a raw material by the underwater facing collision treatment method described in Patent Document 5 (Japanese Patent Application Laid-Open No. 2017-205683).
In the underwater facing impingement method, cellulose fibers suspended in water are introduced into two nozzles facing each other in a chamber, and the polysaccharide surface is nanofibrillated by injecting them from these nozzles under high pressure and causing facing collisions. and peeled off, and finally reach a state close to dissolution in the carrier water. In this method, cellulose nanofibers can be obtained in a state in which there is no structural change in the cellulose molecules and the decrease in the degree of polymerization due to cleavage is minimized because the refining is performed by cleaving only the interaction between the fibers. can be done.

(Immersion in CNF suspension)
0.05 wt%, 0.10 wt%, and 0.20 wt% CNF suspensions were prepared by diluting a 1.34 wt% cellulose nanofiber aqueous dispersion with distilled water. After immersing the cuboid denture base piece prepared in the section of denture base preparation in each concentration of CNF suspension for 1 week under conditions of 23±2° C., it is removed from the CNF suspension and washed with distilled water. performed the operation. The operation from immersing the denture base piece in the CNF suspension to washing with distilled water was regarded as one cycle, and this cycle was repeated. The contact angle was measured for the samples after 4 cycles (28 days of total immersion) and 8 cycles (56 days of total immersion). Table 1 shows the results. As a reference, Table 1 shows the contact angle of the surface of the denture base piece not immersed in the CNF immersion liquid as the initial contact angle. The test was conducted by preparing 7 test pieces for each concentration (n=7), and the average values are shown in the table.

(Fiber width measurement)
The average fiber width of CNF can be measured by observation using an atomic force microscope (AFM). The average value of 20 or more randomly selected fibers was taken as the average fiber width. As a result of fiber width measurement, the average width of the CNF used in this example was 12 nm.

(Polymerization degree measurement)
Dissolve 0.15 g of the CNF sample solid content of the CNF suspension so that it becomes 30 ml of 0.5 M copper ethylene diamine solution, use a Canon Fenske kinematic viscosity tube, keep warm at 25 ° C., then measure the flowing time. The viscosity was measured by Assuming that the viscosity of this CNF copper ethylenediamine solution is η and the viscosity of the 0.5M copper ethylenediamine solution is η0, the degree of polymerization was calculated by the following formula. In addition, the average value which tested by n= 3 was made into the average degree of polymerization.
Intrinsic viscosity [η] = (η / η0) / {c (1 + A × η / η0)} (where c is the fibrous cellulose concentration (g / dL) at the time of viscosity measurement, A is a unique value depending on the type of solution and A = 0.28 for a 0.5M copper ethylenediamine solution)
Degree of polymerization DP = [η]/aK (K and a are values determined by the polymer and the type of solvent used. In the case of cellulose dissolved in copper ethylenediamine, K = 5.7 x 10-3, a = 1 )
As a result of measuring the degree of polymerization, the CNF of this example had an average degree of polymerization of 700.

(contact angle measurement)
The denture base was removed from the CNF soak and the surface was dried. Accurately 2 μL water droplets were dropped on the surface of the denture base using an autopipette and a goniometer, and the contact angle was measured. The contact angle was measured using a portable contact angle measuring machine (PCA-1, manufactured by Kyowa Interface Science Co., Ltd.). All contact angle measurements, with the average value as the contact angle of each test piece, were carried out at room temperature and 50% humidity.

(3-point bending test)
After being immersed in the CNF suspension for 168 days, a three-point bending test was performed to measure the bending properties of the specimen. As a three-point bending test, using a material testing machine (Model 5565; Instron Co., MA, USA), it was performed according to ISO 20795-1, with a 2 kN load cell (serial No.: UK268) at a crosshead speed of 5 mm / min, at room temperature. went below
Elastic modulus (E) was calculated using the following formula.
E=F ₁ ·l ³ /4bh ³ d
In addition, F1 represents the load when the test piece breaks, _l represents the distance between the fulcrums (50.0 mm), b represents the h test piece width (10.0 mm), and h represents the thickness of the test piece (3 .0 _mm ), and d represents the deflection under load F1.
What is the bending strength (δ)? It was calculated using the following formula.
δ=3Fl/2bh ²
Note that F represents the maximum load during the bending test.

Claims (3)

A hydrophilizing agent for hydrophilizing the surface of a poly(meth)acrylate resin denture base ,
The cellulose nanofibers are dispersed in water or a solvent containing water, and the content of the cellulose nanofibers in the hydrophilic treatment agent is 0.02 to 0.5 wt%.
The hydrophilic treatment agent characterized by: The hydrophilic treatment agent according to claim 1, wherein the cellulose nanofibers have an average fiber width of 3 nm or more and 200 nm or less and an average fiber length of 0.1 µm or more and 5.0 µm or less. A method for treating dentures, comprising the step of immersing a denture having a denture base made of poly(meth)acrylate resin in the hydrophilizing agent according to claim 1 or 2 .