JP6930718B2 - A method for producing a high-strength gel having a low-friction surface - Google Patents

Description

The present invention relates to a method for producing a high-strength gel. In particular, the present invention relates to a method for producing a high-strength gel capable of imparting a low-friction surface to the high-strength gel.

Hydrogels containing hydrophilic polymers are useful materials that are attracting attention because they have excellent properties such as water absorption, water retention, and flexibility, and are used in various technical fields such as medicine, food, and civil engineering. It is expected to be used in.
On the other hand, the fields of application of hydrogels are often limited due to insufficient strength, and efforts have been made to improve the mechanical strength of hydrogels.

For example, WO 2003/0933337 discloses a hydrogel having a structure in which two or more polymers, particularly polymers having a crosslinked network structure, or a polymer having a crosslinked network structure and a linear polymer are intertwined with each other. There is. The double network gel (hereinafter, also referred to as "DN gel") using such a mutually invading network structure hydrogel has an excellent balance between strength and elongation, and can also reduce the cost of raw materials and processes. Conceivable.

Further, Japanese Patent Application Laid-Open No. 2008-163055 discloses a hydrogel having a structure in which a second polymer has penetrated into a crosslinked network structure of fine particles containing a first polymer having a crosslinked network structure. It is considered that this hydrogel is excellent in moldability as compared with the conventional DN gel while retaining the advantages of the strength and the like of the DN gel.

It is being studied to use a high-strength hydrogel with improved mechanical strength for applications requiring low friction, such as artificial joints.
However, since the gel material is soft, it is not suitable for processing such as molding and cutting using a mold. In addition, the dimensions change easily due to changes in moisture content due to drying, salt content, etc., making precise processing difficult. Therefore, it is difficult to impart a low-friction surface to a high-strength gel by surface processing such as texturing.
It is also conceivable to apply a lubricant such as oil to the surface of the gel material to reduce the friction on the surface of the high-strength gel, but the applied oil may change the chemical properties of the gel material. Is not desirable.

Therefore, there is a demand for a method for producing a high-strength gel, which can easily impart a low-friction surface to the high-strength gel without adversely affecting the chemical properties of the gel material.

International Publication 2003/0933337 Pamphlet Japanese Unexamined Patent Publication No. 2008-163055

In the present invention, a low-friction surface can be relatively easily applied to a high-strength gel without applying a lubricant or the like to the surface of the gel material, so that low friction is required as in an artificial joint. It is an object of the present invention to provide a method capable of producing a high-strength gel having a low-friction surface that can be used for various purposes.

The present inventors have found that the above problems can be solved by processing a block of high-strength gel to increase its surface roughness.
Normally, in the friction between objects, the frictional force F has a proportional relationship with the load N. That is, there is a relationship of F = μN with respect to the dynamic friction coefficient μ. Further, the coefficient of friction does not depend on the contact area A between objects and the pressure P = N / A.
However, in the case of gel, if the load F is increased while keeping the contact area A constant, the friction coefficient is reduced. The present inventors have focused on the fact that this relationship, in other words, means that the smaller the contact area A, the lower the friction coefficient for the same load N, and the surface roughness of the gel. The present invention was derived from the idea that the load between the gel and the friction partner substrate should be substantially increased and the apparent friction should be reduced by increasing the amount of friction.

That is, the present invention
A method for producing a high-strength gel having a low-friction surface.
The process of creating blocks of high-strength gel,
A step of imparting a low friction surface to the block of high strength gel by processing the block of high strength gel to increase the surface roughness of at least a part of at least one surface.
The production method, which comprises the above.
In the production method of the present invention, the step of processing the block of the high-strength gel can include a step of cutting the block of the high-strength gel with a laser cutter to obtain a surface having an increased surface roughness.
Further, in this case, it is desirable to further include a step of swelling the block of the high-strength gel to which the low friction surface is imparted.

Further, in the production method of the present invention, the step of processing the block of the high-strength gel includes a step of processing the surface of the block of the high-strength gel with sandpaper to obtain a surface having an increased surface roughness. can do.

In the production method of the present invention, the step of producing the block of the high-strength gel is
A step of producing a first polymer having a network structure, and a step of producing the second polymer so that the second polymer penetrates into the network structure of the first polymer.
Can be included.

According to the present invention, it is possible to relatively easily apply a low-friction surface to a high-strength gel without applying a lubricant or the like to the surface of the gel material, so that low friction can be achieved like an artificial joint. It is possible to produce a high-strength gel having a low-friction surface that can be used in a required application.

In one embodiment of the present invention, it is a conceptual diagram of a process of cutting a block of high-strength gel with a laser cutter. It is an overall schematic view of the apparatus used for surface processing of gel and evaluation of surface friction in an Example. It is a schematic diagram of the main part of the apparatus used for surface processing of gel and evaluation of surface friction in an Example. It is a micrograph which observed the surface of the high-strength gel prepared in Example 1. It is a micrograph which observed the surface of the high-strength gel prepared in Example 4. It is a micrograph which observed the surface of the high-strength gel prepared in the comparative example.

Hereinafter, modes for carrying out the present invention will be described.

In the method for producing a high-strength gel having a low-friction surface of the present invention, first, a block of the high-strength gel is prepared. The block of the high-strength gel uses, for example, a first polymer, a photopolymerization initiator, a monomer that forms a second polymer by polymerization using the photopolymerization initiator, and a light absorber. The first polymer and the second polymer are produced by producing a first polymer having a network structure and then producing a second polymer so that the second polymer penetrates into the network structure of the first polymer. The polymer can be such that it constitutes a hydrogel.

The first polymer that can be used in the present invention is, for example, 2-acrylamide-2-methyl-1-propanesulfonic acid sodium salt solution (NaAMPS) or 2-acrylamide-2-methylpropanesulfonic acid (AMPS) as a raw material monomer. , Acrylamide (AAm), Acrylic Acid (AA), Methacrylate, N-Isopropylacrylamide, Vinyl pyridine, Hydroxyethyl Acrylate, Vinyl Acetate, Dimethylsiloxane, Styrene (St), Methyl Methacrylate (MMA), Trifluoroethyl acrylate (TFE) ), Stylonic acid (SS) or dimethylacrylamide such as N, N-dimethylacrylamide (DMAAm).
In addition, 2,2,2-trifluoroethyl methyl acrylate, 2,2,3,3,3-pentafluoropropyl methacrylate, 3- (perfluorobutyl) -2-hydroxypropyl methacrylate, 1H, 1H, 9H-hexadeca It may be obtained by using a fluorine-containing monomer such as fluorononi methacrylate, 2,2,2-trifluoroethyl acrylate, 2,3,4,5,6-pentafluorostyrene or vinylidene fluoride.
Further, polysaccharides such as gellan, hyaluronic acid, carrageenan, chitin or alginic acid, or proteins such as gelatin and collagen may be used as the first polymer.

The first polymer preferably has a network structure. The first polymer is also preferably fine particles.

The monomers forming the second polymer that can be used in the present invention are those that can be polymerized using a photopolymerization initiator, for example, 2-acrylamide-2-methylpropanesulfonic acid (AMPs), N. N-dimethylacrylamide (DMAAm), 2- (dimethylamino) ethyl methacrylate, lauryl acrylate (LA), stearyl acrylate (SA), acrylate (AA), methacrylic acid, styrene sulfonic acid, or salts thereof, For example, 2-acrylamide-2-methylpropanesulfonate sodium, sodium acrylate, sodium styrenesulfonate and the like.

In the present invention, preferred examples of the second polymer are polyacrylamide-2-methylpropanesulfonic acid obtained by polymerizing 2-acrylamide-2-methylpropanesulfonic acid (AMPs) as a monomer and 2-acrylamide-2-methyl. Polyacrylamide-2-methylpropanesulfonate polymerized with sodium propanesulfonate (NaAMPs) as a monomer, polyN, N-dimethylacrylamide (PDMAAm) polymerized with N, N-dimethylacrylamide (DMAAm) as a monomer, etc. Can be mentioned.

The second polymer preferably has a network structure.
Further, it is desirable that the hydrogel composed of the first polymer and the second polymer has a structure in which the second polymer penetrates into the network structure of the first polymer, and further, the first polymer and the first polymer. It is preferable to have a network structure in which the two polymers penetrate each other.

The photopolymerization initiator that can be used in the present invention may be any as long as it initiates the polymerization of the above monomer by light such as ultraviolet rays and visible light. For example, α-ketoglutaric acid, benzophenone, acetophenone benzyl, benzyl dimethyl ketone, benzoin. , Benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, dimethoxyacetophenone, dimethoxyphenylacetophenone, diethoxyacetophenone, diphenyldisulfite, methyl orthobenzoyl benzoate, ethyl 4-dimethylaminobenzoate, 2,4-diethylthioxane Son, 2-methyl-1- [4- (methyl) phenyl] -2-morpholinopropanone-1, tetra (t-butylperoxycarbonyl) benzoinone, benzyl, 2-hydroxy-2-methyl-1-phenyl- Propane-1-one, 4,4-bisdiethylaminobenzophenone, 2,2'-bis (2-chlorophenyl) -4,5,4', 5'-tetraphenyl-1,2'-bimidazole, etc. You can.
The light absorber can be contained in an amount of 1: 3 to 3: 1 in molar ratio with respect to the photopolymerization initiator.

The gel material used in the present invention may further contain a cross-linking agent for cross-linking the second polymer. As the cross-linking agent, a polyfunctional vinyl-based monomer having two or more radically polymerizable unsaturated groups can be used. Divinyl compounds such as N, N'-methylenebisacrylamide (MBAA), ethylene glycol dimethacrylate (EDMA), and N, N'-diethylene glycol dimethacrylate (DEGDMA) can be preferably used.

The method for producing the block of high-strength gel used in the present invention is not particularly limited, and for example, the following method can be adopted.
That is, first, the first monomer, the cross-linking agent, and the photopolymerization initiator are mixed at a predetermined molar ratio (for example, 1: 4: 0.1), and bubbling is performed using nitrogen for about 10 minutes. Then, UV light is irradiated for about 7 hours to prepare a first polymer. The prepared first polymer is dried and pulverized into fine particles.
Next, the second monomer, the cross-linking agent, and the photopolymerization initiator are mixed at a predetermined molar ratio (for example, 1: 0.01: 0.01), and a light absorber such as an ultraviolet absorber is added thereto. Mix at a ratio of 0.25 mol to 1 mol of the photopolymerization initiator to prepare a mixed solution for forming the second polymer. The prepared mixed solution and the first polymer fine particles are mixed so as to have a weight ratio of 30: 1, and by irradiating with light, a gel material in which the first polymer and the second polymer form a gel can be obtained. Prepare.

The block of high-intensity gel used in the present invention is a 3D gel printer in which the gel material before UV irradiation is placed in a bathtub-shaped container, and only the portion irradiated by UV laser irradiation is radically polymerized to gel. , Can also be produced.

In the method for producing a high-strength gel having a low-friction surface of the present invention, a block of the prepared high-strength gel is then processed to increase the surface roughness of at least a part of at least one surface. Gives the block of high-strength gel a low-friction surface.
As a step of processing the high-strength gel block, a step of cutting the high-strength gel block with a laser cutter to obtain a surface having an increased surface roughness can be adopted.
The laser cutter is not particularly limited, but for example, one that uses a carbon dioxide laser as a light source can be used, and the output is several watts to several tens of watts, and a wooden board, acrylic board, etc. with a thickness of several millimeters can be cut. Those that can be used can be preferably used.
Specifically, a plate-shaped block of high-strength gel is first cut with a laser cutter to form a strip shape having a laser-processed surface, and the laser-processed surface (surface roughness is increased) of this strip-shaped high-strength gel. A columnar high-intensity gel having a circular laser-processed surface is cut out by laser processing from a strip-shaped high-intensity gel so that the surface) remains. In this way, a high-strength gel having a low-friction surface can be obtained as a cylindrical high-strength gel block having an upper surface with an increased surface roughness.
Further, a block of high-strength gel provided with a low-friction surface may be swollen.
In this method, for example, in the above processing example, a plate-shaped block of a high-strength gel that has been equilibrium-swelled during the production of a high-strength gel is laser-processed and equilibrium-swelled again.
Specifically, at room temperature, a block of high-strength gel having a low-friction surface is placed in a bat filled with a large amount of water so that the low-friction surface of the block does not come out of the water surface and the block sinks. Let stand for the time of.

As a step of processing the block of the high-strength gel, a step of processing the surface of the block of the high-strength gel with sandpaper to obtain a surface having an increased surface roughness can also be adopted.
The sandpaper is not particularly limited, but waterproof sandpapers such as # 1000, # 1500, and # 2000 can be used, and # 1500 sandpaper can be preferably used. For example, sandpaper can be pressed against the surface (surface to be processed) of a block of high-strength gel with a load of 100 g, and slid at a sliding speed of 10 mm / sec and a sliding cycle of 1000 to perform processing. At that time, the number of sliding times is 500 times or more, for example, 1500 times or more, preferably 2000 times or more.
In the present invention, the surface roughness can be evaluated by, for example, observing the unevenness of the low-friction processed surface of the high-strength gel by microscopic observation. Alternatively, the surface roughness can be evaluated by measuring the line roughness and the surface roughness with a three-dimensional confocal laser scanning microscope.
In the present invention, the surface friction uses the dynamic friction coefficient as an evaluation index, and can be evaluated by using a known method capable of measuring the dynamic friction coefficient.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

(Example 1)
<Preparation of the first polymer>
2-acrylamide-2-methylpropan-sulfonic acid monomer (AMPS) 1M, 4 mol% N, N'-methylenebisacrylamide (MBAA) as a cross-linking agent for cross-linking this monomer, and as a photopolymerization initiator , 60 mL of a monomer solution containing 0.1 mol% α-ketoglutaric acid (α-keto) was prepared.
The monomer solution in which each of the above components was weighed was stirred with a stirrer for 15 minutes. Next, in order to prevent the inhibition of gelation due to the oxygen contained in the monomer solution absorbing the radicals generated by the photoinitiator, nitrogen substitution (bubbling) is performed for about 20 minutes in the monomer solution. Oxygen was removed.
This monomer solution is filled between two glass plates sandwiching a U-shaped spacer having a thickness of 2 mm, and is irradiated with UV light (wavelength 365 nm) for about 8 hours using a UV lamp to carry out polymerization. The polymer of the above was prepared.

<Preparation of monomer solution for the second polymer>
Monomer containing 0.02 mol% MBAA as a cross-linking agent for cross-linking this monomer with respect to N, N-dimethylacrylamide (DMAAm) 2M and 0.1 mol% α-keto as a photopolymerization initiator. 400 mL of solution was prepared.
This monomer solution was also stirred and bubbling in the same manner as in the case of the monomer solution for producing the first polymer.

<Preparation of second polymer and hydrogel>
An amount such that the ratio of the first polymer to the monomer solution for the second polymer is about 1:20 by weight is added to the monomer solution for the second polymer prepared as described above. 1 polymer was charged.
The first polymer was immersed in a monomer solution for the second polymer for 2 days to swell.
Take out the first polymer swollen with the monomer solution for the second polymer, cut it into a size of about 10 cm × 10 cm × 1.5 cm, sandwich it between two glass plates, and use a UV lamp. The second polymer was polymerized by irradiating with UV light (wavelength 365 nm) for about 8 hours to prepare a block of high-intensity hydrogel (moisture content of about 60 to 80%).
After that, the one immersed in a large amount of pure water for two weeks (equilibrium swelling (moisture content of about 90%)) was used for the subsequent processing.

<Processing of high-strength gel blocks with a laser cutter>
The block of high-strength hydrogel obtained as described above was processed by a laser cutter under the following conditions.
As the laser cutter, a laser processing machine HAJIME (wavelength 10 to 10.6 μm, maximum output 30 W) manufactured by Oh-Laser was used at a laser output of 80% and a laser feed rate of 2 mm / sec.
With reference to FIG. 1, first, a plate-shaped block of high-strength hydrogel that has been equilibrium-swelled is cut with a laser cutter to form a strip shape (about 10 cm × 0.2 cm × 1.5 cm) having a laser-processed surface. ). Next, this strip-shaped hydrogel was arranged so that the laser-processed surface was on top, and a columnar hydrogel having a circular (diameter 5 mm) laser-processed surface was cut out by laser processing.

(Example 2)
First, a block of high-strength hydrogel having a size of about 9 cm × 3 cm × 0.5 cm was prepared by the same method as in Example 1.

<Processing of high-strength gel blocks with sandpaper>
The obtained high-strength hydrogel block was processed with sandpaper under the following conditions.
FIG. 2 shows an overall schematic view of the apparatus used for surface processing of hydrogel in the examples. This same device was also used to evaluate the surface friction of the gel.
With reference to FIG. 2, a holder to which sandpaper was attached as a head 3 was attached to the lower end of the load cell 2 on which the weight set 1 for applying a vertical load (contact load 100 g weight) was placed.
FIG. 3 shows a schematic view of the head 3 which is a main part of the apparatus used for the surface processing of the gel and the evaluation of the surface friction of the gel in the examples.
With reference to FIG. 3A, in the case of processing a block of high-strength gel with sandpaper, the sandpaper 12 was attached to the resin holder 11. The tip of the holder 11 is a semi-cylindrical shape with a radius of 5 mm. Here, # 1500 water resistant paper (water resistant sandpaper) was attached with an adhesive. The head prepared in this way was slid on the surface of the hydrogel block 16 to perform processing.
With reference to FIG. 2 again, the sample container 6 containing the block 5 of the hydrogel immersed in the pure water 4 was placed on the moving table 7. With the sandpaper at the tip of the head 3 pressed against the surface of the block 5, the head 3 is slid at a sliding speed of 10 mm / sec, a sliding cycle of 1000, and the number of sliding times of 2000, and the hydrogel block 5 is slid. The surface of was processed.

<Swelling of high-strength gel blocks>
(Example 3)
A block of high-strength hydrogel was prepared by the same method as in Example 1 and processed by a laser cutter.
The processed blocks were then swollen in pure water for 1 day.

(Example 4)
The processed block was inflated for 1 week by the same method as in Example 3.

(Comparison example)
A block of high-strength hydrogel was prepared by the same method as in Example 1. The created block was not processed as in the examples.

<Evaluation of gel surface friction>
A sample for friction measurement was cut out from the blocks obtained in Examples 1 to 4 and Comparative Example, and the surface friction of the gel was measured under the following conditions.
First, for the sample of Example 2 (a block of high-strength gel processed by sandpaper), a glass ball (BK7) 14 having a diameter of 6 mm is attached to the tip of the stylus holder 13 with reference to FIG. 3 (b). rice field. The head prepared in this way was slid on the surface of the block 17 of the hydrogel to perform the measurement. That is, referring to FIG. 2 again, with the stylus holder 13 as the head 3, the tip (glass ball 14) thereof is pressed against the surface of the sample contained in the sample container 6 not filled with water. The surface friction of the sample was measured by sliding the head 3 at a sliding speed of 1 mm / sec and removing the vertical load from the frictional force measured by the load cell. At that time, water was dropped on the sample surface to prevent drying.
Next, for samples other than Example 2 (a block of high-strength gel processed by a laser cutter and a block of high-strength gel of Comparative Example), a glass ball was placed in the stylus holder 13 with reference to FIG. 3 (c). The gel sample 15 processed into a columnar shape using No. 14 was pressed and fixed so that the processed surface was exposed. The head prepared in this way was slid on the surface of the glass plate 18 to perform the measurement. That is, the surface friction of the sample was measured by using the stylus holder 13 as the head 3 as in the case of the second embodiment.
The measurement results are shown in Table 1.

<Evaluation of gel surface roughness>
From the blocks obtained in Example 1, Example 3 and Comparative Example, a sample for surface roughness evaluation was cut out under the following conditions.
Using this sample, the surface roughness of the gel was evaluated under the following conditions.
The surface roughness of the gel was evaluated by observing the surface of the sample at a magnification of 10 times using a metallurgical microscope.
The observation results are shown in FIG. 4 (Example 1), FIG. 5 (Example 4) and FIG. 6 (Comparative example), respectively. As is clear from the figure, the surface roughness of the examples is increased as compared with the comparative examples.

As described above, according to the present invention, it is possible to impart a low friction surface to the high-strength gel block by processing the high-strength gel block to increase the surface roughness.

Claims (2)

A method for producing a high-strength gel having a low-friction surface.
The process of making blocks of high-strength gel,
A step of imparting a low friction surface to the block of high strength gel by processing the block of high strength gel to increase the surface roughness of at least a part of at least one surface.
The step of swelling the block of high-strength gel to which the low-friction surface is imparted,
Only including,
The production method, wherein the step of processing the surface of the block of the high-strength gel with sandpaper to obtain a surface having an increased surface roughness is performed in water. The step of creating the block of high-strength gel
A step of producing a first polymer having a network structure, and a step of producing the second polymer so that the second polymer penetrates into the network structure of the first polymer.
The production method according to claim 1 , wherein the production method comprises.

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