JP6560560B2 - Contamination resistant surface modifier and surface treatment method - Google Patents

Description

The present invention relates to a stain-resistant surface modifier, particularly a stain-resistant surface modifier suitable for ceramic materials, and a surface treatment method using the surface modifier.

Ceramic materials are used in various fields such as medicine, architecture, environment, and hygiene. Among them, ceramic materials are often used for water supply equipment, but such water supply equipment is exposed to various types of dirt on a daily basis, so it is necessary to impart antifouling properties to the surface of the materials used there. There is.

In general, as a means for imparting antifouling properties to the surface of a material, it is known to perform a treatment for making the surface super water-repellent or super hydrophilic. A super-water-repellent surface is a surface having the property that the static contact angle of water is 150 degrees or more and the hysteresis is 10 degrees or less, while the superhydrophilic surface is a static contact angle of water of 10 degrees. The surface has the following properties.

Although the super-water-repellent surface is easy to remove the attached water-based dirt, it is not expected to be effective against oil-based dirt, and has a drawback that the structural strength is low. On the other hand, the superhydrophilic surface exhibits a self-cleaning action that removes dirt by allowing water droplets to enter between the dirt and the substrate surface (for example, Non-Patent Document 1), and forms a water film on the surface. Dirt is difficult to adhere to, and can be removed with a small amount of water.

However, the conventional hydrophilic treatment of the material surface with a hydrophilic polymer coating or the like does not provide long-term stability of the effect, and particularly when applied to inorganic materials such as ceramics, the adhesion and durability of the coating film It is known that the performance deteriorates with time in an environment where the wet and dry conditions such as water facilities are frequently repeated. Furthermore, when using a hydrophilic polymer containing a hydrophobic functional group for physical adsorption to a material, a pretreatment such as immersion in water is required to reorient the hydrophilic functional group to the outermost surface (for example, Non-patent document 2). On the other hand, it is also known that a hydrophilic surface can be obtained by a photocatalyst, but there is a problem that it is unsuitable for indoor use with an insufficient amount of ultraviolet rays.

Bhushan et al., RSC Advances, 3, 617, 2013 Yamasaki et al., Colloids and Surfaces B: Biointerfaces, 28, 53, 2003

Therefore, the present invention does not require pre-treatment such as immersion in water for materials such as ceramics, can easily make the surface hydrophilic, and can provide a polymer-type surface modification that can impart antifouling properties with excellent durability. It is an object of the present invention to provide an agent and surface treatment means.

As a result of intensive studies to solve the above problems, the present inventor has determined that the structure design of the surface-modified polymer is a hydrophilic part that imparts hydrophilicity to the surface of the material, a hydrophobic part that enhances film formation, and a material. By forming a block polymer consisting of the three components of the adhesive part that can be bonded to each other by covalent bonding, the surface hydrophilicity can be achieved even under dry conditions without the need for pretreatment such as immersion in water, simply by coating the surface of the polymer. The present inventors have found a polymer-type surface modifier that can easily and stably provide the property and antifouling property, and have completed the present invention.

That is, the present invention in one aspect,
<1> A monomer unit (A) having a zwitterionic structure and / or an ether structure in the side chain; a monomer unit (B) having a hydrophobic group containing a Si atom in the side chain; and a trialkoxysilyl group in the side chain A surface modifier comprising a monomer unit (C), wherein the monomer unit (A) forms a block segment;
<2> The surface modifier according to <1>, wherein the monomer units (B) and (C) are randomly polymerized in the copolymer.
<3> The surface modifier according to the above <1> or <2>, wherein the monomer unit (A) has a phosphorylcholine group, a betaine group, or polyethylene glycol in a side chain;
<4> The surface modifier according to any one of the above <1> to <3>, wherein the monomer unit (B) has a tris (trialkylsilyloxy) silyl group;
<5> The monomer units (A) to (C) are present in a molar ratio in the range of (A) :( B) :( C) = 2: 1: 1 to 8: 1: 1. The surface modifier according to any one of> to <4>;
<6> The surface modifier according to any one of <1> to <5> above, wherein the copolymer has a weight average molecular weight (Mw) in the range of 1.0 × 10 ^{4 to} 1.0 × 10 ⁵ ;
<7> In any one of the above items <1> to <6>, wherein the ratio (Mw / Mn) of the weight average molecular weight to the number average molecular weight in the copolymer is in the range of 1.0 to 1.5. The surface modifier as described;
<8> The surface modifier according to any one of the above <1> to <7>, wherein the main chain of the copolymer has a skeleton selected from polyalkyl acrylate or polyalkyl methacrylate; and <9> The surface modifier according to any one of the above <1> to <8>, wherein the copolymer is obtained by reversible addition-fragmentation chain transfer (RAFT) polymerization.
About.

In another aspect, the present invention provides:
<10> A surface treatment method including a step of applying the surface modifier according to any one of <1> to <9> above to a surface of a material;
<11> The method according to <10> above, which does not include a step of treating the surface of the material with water after the step of applying the surface treatment agent;
<12> The method according to <10> or <11> above, wherein the material is ceramics.
<13> The material according to <13>, wherein the material is surface-treated with the surface modifier according to any one of <1> to <89>; and <14> ceramics.

According to the present invention, it is possible to provide a polymer-type surface modifier and a surface treatment method that are efficient and simple and excellent in durability. In particular, even for materials such as ceramics, the adhesion and durability of the coating can be greatly improved by simply coating the surface with the surface modifier, without requiring a pretreatment step such as immersion in water. it can.

In addition, according to the surface modifier of the present invention, it is possible to provide a hydrophilic surface that is always present on the surface even under dry conditions (in the air), that is, a hydrophilic surface that is not influenced by the environment. This is extremely useful in that the hydrophilicity and antifouling effect of the surface can be stably maintained over a long period even in an environment where water and moisture are repeatedly used.

FIG. 1 is a graph showing the measurement results of the hysteresis of the dynamic contact angle of the substrate surface-modified with the surface modifier of the present invention. FIG. 2 is a graph showing the measurement results of the protein (BSA) adsorption amount of the substrate surface-modified with the surface modifier of the present invention.

Hereinafter, embodiments of the present invention will be described. The scope of the present invention is not limited to these descriptions, and other than the following examples, the scope of the present invention can be appropriately changed and implemented without departing from the spirit of the present invention.

1. Surface modifier The surface modifier of the present invention comprises (A) a monomer unit having a zwitterionic structure and / or an ether structure in the side chain; (B) a monomer unit having a hydrophobic group containing a Si atom in the side chain; C) It has a monomer unit having a trialkoxysilyl group in the side chain, and the monomer unit (A) includes a copolymer forming a block segment.

(1) The copolymer as a main component of the copolymer surface modifier is a polymer obtained by copolymerizing the monomer units (A) to (C), a so-called terpolymer (terpolymer). is there. Furthermore, in the said copolymer, the monomer unit (A) corresponds to what is called a block polymer at the point which forms the block segment. On the other hand, the monomer units (B) and (C) do not necessarily have to form block segments, and may be combined in a manner having random or some regularity / periodicity. That is, the copolymer in the surface modifier of the present invention is a copolymer of the mode of “A-block-B-block-C” as long as the monomer unit (A) forms a block segment. Or “A-block- (B-random-C)”, “A-block- (B-stat-C)”, “A-block- (B-alt-C)”, etc. It can also be a copolymer of the embodiment. In a preferred embodiment, the monomer units (B) and (C) are randomly polymerized, and the copolymer has a structure of “A-block- (B-random-C)”. As a result, on the surface of the material treated with the surface modifier of the present invention, the adhesion portion or the like due to the monomer unit C exists evenly without aggregation, and the hydrophilic block segment due to the monomer unit (A) is dispersed on the material surface. This is preferable in that a stable and uniform surface coating can be obtained.

In addition, the said copolymer does not exclude including other monomer units other than monomer unit (A)-(C). In addition, the other monomer units are typically bonded at random, but embodiments having some regularity and periodicity are also included in the scope of the present invention. A segment of a periodic polymer or a block polymer can be formed. In some cases, a segment of a graft polymer can also be formed.

The monomer unit (A) in the copolymer has a zwitterionic structure and / or an ether structure in the side chain. As described above, the monomer unit (A) forms a hydrophilic block segment (hydrophilic portion) in the copolymer and imparts hydrophilicity to the surface of the material after surface modification. Examples of such functional groups include zwitterionic structures such as phosphorylcholine groups (PC groups) and betaine groups, or polyethylene glycol chains. Moreover, it can also have an ether group in addition to a zwitterionic structure. Here, the PC group is a polar group having the same structure as the polar group of phospholipid (phosphatidylcholine) which is a main component of the biological membrane. Therefore, by including a PC group in the side chain, the copolymer has hydrophilicity (wetability), specifically, very good biocompatibility possessed by the surface of the biomembrane, particularly non-adsorption of biomolecules. And non-activation properties can be imparted, and non-specific adsorption to various molecules such as proteins and blood cells can be effectively suppressed, so that excellent antifouling properties can be imparted to the surface of the material to be treated. .

On the other hand, the monomer unit (B) in the copolymer has a hydrophobic group containing a Si atom in the side chain. This mainly functions to improve the film-forming property of the coating during the surface treatment, and can also contribute to the improvement of the stability of the coating surface by physical adsorption to the material surface by hydrophobic interaction. The hydrophobic group containing an Si atom is, for example, a substituent having an alkylsilyl group or an alkylsilyloxysilyl group, preferably a tris (trialkylsilyloxy) silyl group, more preferably tris (trimethylsilyloxy). It can be a silyl group or a tris (triethylsilyloxy) silyl group.

Furthermore, the monomer unit (C) in the copolymer is dehydrated and condensed to form a covalent bond (—SiO— bond) by a chemical reaction such as a silane coupling reaction with an OH group or the like present on the surface of the material. In addition, the side chain has a functional group that can be chemically adsorbed on the material surface. Such a functional group is preferably a trialkoxysilyl group. By the monomer units (B) and (C), the stability and uniformity of the surface coating film by the copolymer are improved.

The skeleton site in the monomer unit forming the main chain (skeleton) in the copolymer is not particularly limited as long as it can form a polymer by polymerization reaction with each other. Are preferably, for example, vinyl monomer residues, acetylene monomer residues, ester monomer residues, amide monomer residues, ether monomer residues, urethane monomer residues, etc. Among these, vinyl monomers Residues are more preferred. The vinyl monomer residue is not particularly limited, and examples thereof include a methacryloxy group, a methacrylamide group, an acryloxy group, an acrylamide group, a styryloxy group, and a styrylamide group in a state where the vinyl moiety is addition-polymerized. Among these, an acryloxy group and a methacryloxy group are particularly preferable. The above-mentioned skeletal site can be the same for each monomer unit or can be independently different, but an embodiment in which both are the same is preferable.

Therefore, the main chain in the copolymer preferably has a skeleton selected from polyalkyl acrylate or polyalkyl methacrylate.

Specific examples of the copolymer are not limited to these, but preferred examples include a polymer having a structure represented by the following formula (I).

In the formula, the monomer unit (A) is MPC (2-methacryloyloxyethyl phosphorylcholine), the monomer unit (B) is MPTSSi (3- (methacryloyloxy) propyltris (trimethylsilyloxy) silane), and the monomer unit (C ) Is MPTMSi (3-methacryloyloxytrimethoxylsilane). N, m, and l each independently represent an integer of 2 or more, but each may be 2000 or less, preferably 1000 or less.

The monomer composition ratio in the copolymer is preferably such that the monomer units (A) to (C) are in the range of (A) :( B) :( C) = 2: 1: 1 to 9: 1: 1. Is the molar ratio. More preferably, the molar ratio is in the range of (A) :( B) :( C) = 4: 1: 1 to 8: 1: 1. An increase in the proportion of the monomer unit (A) is preferable in that the hysteresis of the dynamic contact angle on the material surface decreases. This is presumably because the region of the copolymer physically and chemically bonded to the material surface can be sufficiently covered with the hydrophilic portion derived from the monomer unit (A).

Although the weight average molecular weight (Mw) of the said copolymer is not specifically limited, For example, 1.0 * ¹⁰ < ⁴ > -5.0 * 10 < ⁵ > is preferable, More preferably, it is 5.0 * ¹⁰ < ⁴ > -1.0 * ¹⁰ < ⁵ >.

The ratio of the weight average molecular weight to the number average molecular weight (Mw / Mn) in the copolymer is not particularly limited, but is preferably in the range of 1.0 to 2.0, more preferably 1.0 to 1. .5.

As described above, the copolymer may include a structural unit derived from another monomer other than the monomer units (A) to (C), if necessary. The proportion of structural units derived from other monomers is preferably 30 mol% or less, more preferably 10 mol% or less, based on all structural units constituting the polymer.

The synthesis of the copolymer can be performed by a conventional method based on the technical level of those skilled in the art, but from the viewpoint of being suitable for obtaining the block segment of the monomer unit (A), as a polymerization method, Preferably, a living radical polymerization method can be used, and among them, a reversible addition-fragmentation chain transfer (RAFT) polymerization method can be more preferably used. Here, the RAFT polymerization method is a radical polymerization reaction using a thiocarbonyl compound as a chain transfer agent (RAFT agent). Since a RAFT residue is present at the terminal at the end of the polymerization, a monomer is newly added for polymerization. Can be used to obtain a block copolymer. Such RAFT polymerization method does not require the use of a metal catalyst, is easy to operate, and has advantages such as a wide range of applicable monomer species.

In addition, the synthesis | combination of the monomer compound used as said monomer unit can be performed by a conventional method based on the technical level of those skilled in the art.

2. Surface modification treatment The surface modifier of the present invention can be used to modify the surface of an inorganic or organic material. It is particularly suitable for inorganic materials such as ceramics. In this case, the surface modifier may include any other component that is generally used as a component of the surface modifier of the substrate, in addition to the above-mentioned surface modification copolymer.

The solvent is preferably a polar solvent such as alcohol, but any solvent that can dissolve the copolymer can be appropriately changed according to its use, material, and the like. Preferred is methanol, ethanol, or 1-propanol, and more preferred is ethanol.

In general, the surface treatment agent is preferably in the form of a solution, and the concentration of the surface-modifying copolymer of the present invention contained as a main component is preferably 0.01 to 3.0 weight percent, for example. More preferably, it is 0.05-2.0 weight percent, More preferably, it is 0.1-1.0 weight percent.

The material subject to surface modification according to the present invention may be either an inorganic material or an organic material, and is not particularly limited. For example, silicon-containing polymer, glass, polyethylene terephthalate, polyurethane, nylon, and polyurethane = Examples thereof include nylon copolymers, and can also be applied to metals, alloys, metal oxides, ceramics, and the like. It is particularly suitable for ceramic materials.

The shape of the material is not particularly limited, and examples thereof include a film shape, a plate shape, a bead shape, a fiber shape, and a hollow tubular shape, and holes and grooves provided in a plate-like base material. Further, the use is not particularly limited, and examples thereof include a watering facility, various medical devices, an artificial organ, a biochip, a biosensor, and a cell storage device.

  As a method of performing surface modification using the surface modifier of the present invention, the surface modification copolymer is applied to the surface of the substrate by immersing an inorganic or organic material as a target substrate in the surface modifier. Application may be mentioned. In addition, surface modification can be performed by a technique known in the technical field.

In general, in the case of surface modification using MPC (2-methacryloyloxyethyl phosphorylcholine) polymer copolymerized with a monomer unit containing a hydrophobic part, it is more hydrophobic than PC group in the atmosphere (dry state) in terms of surface energy. It is known that the sex part is preferentially oriented on the surface of the material. Therefore, in order to reorient the PC group on the surface to obtain a hydrophilic surface, a pretreatment step such as immersion in water is required before use. On the other hand, in the surface treatment using the surface modifier of the present invention, the above polymer contains three monomer units, and the hydrophilic part (monomer unit (A)) forms a block segment. However, since hydrophilic groups such as PC groups are always oriented on the material surface, a hydrophilic surface can be obtained without performing such a pretreatment step. In a preferred embodiment, the monomer units (B) and (C) are randomly polymerized, and the copolymer has a structure of “A-block- (B-random-C)”. Adhesive parts and the like due to are uniformly present without agglomeration, and the hydrophilic block segment due to the monomer unit (A) is dispersed on the material surface, whereby a stable and uniform surface coating can be obtained.

  The material surface-modified with the surface modifier of the present invention has the above-mentioned copolymer coating film on the surface, so that the surface is made hydrophilic and excellent in antifouling property, and in addition to materials such as ceramics. Since it is suitable and has a stabilized surface coating, the antifouling property by surface modification can be maintained for a long time.

EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited by these.

1. Synthesis of copolymer As monomer units, 2-methacryloyloxyethyl phosphorylcholine (MPC), 3- (methacryloyloxy) propyltris (trimethylsilyloxy) silane (MPTSSi), and 3-methacryloxypropyltrimethoxysilane (MPTMSi) are used. It was. These used the commercially available thing.

These monomer units were polymerized by two-step RAFT polymerization to synthesize a copolymer poly (MPC-block) (MPTSSi-ran-MPTMSi) in which MPC formed block segments. A synthesis scheme is shown below.

In the first stage reaction, a polymer (PMPC) containing only MPC monomer was synthesized. MPC was dissolved in 1-propanol at a concentration of 0.5M, then RAFT agent 4-cyano-4- (thiobenzoylthio) pentanoic acid (CPD), 2,2′-azobisisobutyroyl as initiator. Nitrile (AIBN) was added, bubbled with Ar gas for 15 minutes, and then polymerized in an oil bath at 65 ° C. for 24 hours. The concentration of the initiator was set to about one fifth of that of the RAFT agent. After the polymerization, the second-stage polymerization was performed as it was without reprecipitation.

In the second stage reaction, MPTSSi, MPTMSi, and 1-propanol were added to the PMPC polymerization solution obtained in the first stage reaction so that the total monomer concentration was 0.25M. After bubbling the solution with Ar gas for 15 minutes, a polymerization reaction was performed at 65 ° C. for 24 hours. Thereafter, it was reprecipitated with diethyl ether: hexane = 7: 3 (v / v) and recovered as a solid. This was not vacuum dried and stored as a coating solution.

The obtained copolymer, the chemical structure of the obtained polymer was identified by H ¹ -NMR, the molecular weight was determined by gel permeation chromatography (JASCO Corp.). Table 1 shows the results of the copolymers obtained by carrying out the polymerization reaction in the same manner while changing the monomer ratios.

2. Preparation of polymer thin film Each of the copolymers obtained in Example 1 was dissolved in ethanol to prepare a 0.2 wt% coating solution. As the substrate, a glass substrate and a Si / SiO ₂ substrate were used. Each substrate was subjected to ultrasonic cleaning in the order of ethanol and acetone for 10 minutes, and then subjected to oxygen plasma. Next, it was immersed for 2 hours in the above coating solution to which 10% by weight of 0.1M acetic acid was added as a catalyst, dried at room temperature in a solvent atmosphere for 2 hours, and then subjected to thermal annealing at 70 ° C. for 3 hours.

3. Physical property evaluation of polymer film surface (1) Calculation of hysteresis of dynamic contact angle In order to evaluate the physical property of the film surface formed by the copolymer, Wilhelmy plate method, which is one of surface tension measurement methods, is used. Dynamic surface characteristics were analyzed. Specifically, after the polymer-coated substrate obtained in Example 2 was sufficiently dried with a desiccator, the dynamic contact angle was measured. In addition, it produced hysteresis in advancing and receding angles. From the result of the hysteresis, the surface state in the atmosphere and the surface state in water can be evaluated. The calculation result of the hysteresis of the dynamic contact angle is shown in FIG. As a comparative example, poly (MPC-co-n-butyl methacrylate) (PMB30), which is well known as an MPC polymer copolymerized with a hydrophobic component, was used. The broken line in FIG. 1 is the value of PMB30.

As a result, it was found that the hysteresis decreased as the ratio of MPC (that is, the ratio of hydrophilic block segment by MPC) increased. This is considered to be because when the hydrophilic block segment by MPC increases, the polymer region (region derived from MPTSSi and MPTMSi) that physically and chemically bonds to the substrate surface can be sufficiently covered with the hydrophilic block segment. . In particular, with P-160 having the highest MPC ratio, the contact angle was about 10 degrees, and high hydrophilicity comparable to the superhydrophilic state was obtained.

(2) Protein adsorption measurement by μBCA method Next, the amount of bovine serum albumin (BSA) adsorbed was measured by the μBCA method, and the antifouling property of the membrane surface was evaluated. The polymer coated substrate was used without being immersed in water. The polymer-coated substrate was immersed in a 4.5 mg / ml BSA solution at 37 ° C. for 3 hours. The substrate was immersed in a sufficient amount of 6 ml of sodium n-dodecyl sulfate (SDS) solution and subjected to ultrasonic cleaning for 5 minutes to separate the BSA and polymer adsorbed on the surface. Three such treatments were performed per sample. In addition, the substrate not immersed in the BSA solution was similarly subjected to ultrasonic cleaning with the SDS solution. The obtained solution was weighed out in a 96-well plate by 150 μL. A Micro BCA Protein Assay Reagent kit was prepared at A: B: C = 25: 24: 1, mixed with 150 μL of each sample, and incubated at 37 ° C. for 2 hours. Thereafter, the absorbance at 560 nm in each well was measured using a plate reader. The BSA concentration (μg / ml) in each sample was produced from the absorbance and calibration curve obtained for each sample. The obtained results are shown in FIG. The broken line in FIG. 2 is the value of PMB30.

As a result, it was found that the amount of BSA adsorbed decreased compared to PMB30. In particular, it was found that p-120 and P-160 can sufficiently suppress the BSA adsorption amount. Moreover, when the result of FIG. 1 was also taken together, it was suggested that the amount of adsorption | suction of BSA reduces with the reduction | decrease of hysteresis.

(3) Uniformity evaluation of polymer film using ceramic substrate A ceramic substrate (1 cm × 4 cm) was subjected to ultrasonic cleaning in the order of ethanol and acetone for 10 minutes, and then subjected to oxygen plasma. Next, a coating solution was prepared by adding 10% by weight of 0.1M acetic acid as a catalyst to an ethanol solution of 0.2% by weight P-160 copolymer. The substrate was immersed in the coating solution for 2 hours, dried at room temperature in a solvent atmosphere for 2 hours, and then subjected to thermal annealing at 70 ° C. for 3 hours. The obtained polymer-coated substrate was immersed five times in rhodamine 6G solution (200 ppm) and washed with pure water for about 20 seconds. Thereafter, the glass substrate was observed with a fluorescence microscope. As a result, even when a ceramic substrate was used, uniform film formation was confirmed.

The above results demonstrate that by using the surface modifier of the present invention, a surface modification excellent in hydrophilicity and antifouling property can be provided easily and stably.

Claims (14)

Monomer unit (A) having zwitterionic structure and / or ether structure in side chain; Monomer unit (B) having alkylsilyl group or alkylsilyloxysilyl group in side chain; and monomer having trialkoxysilyl group in side chain has a unit (C), seen containing a copolymer of the monomer units (a) form a block segment,
The surface modifier, wherein the copolymer has a weight average molecular weight to number average molecular weight ratio (Mw / Mn) in the range of 1.0 to 2.0 . The surface modifier according to claim 1, wherein in the copolymer, the monomer units (B) and (C) are polymerized randomly. The surface modifier according to claim 1 or 2, wherein the monomer unit (A) has a phosphorylcholine group, a betaine group, or polyethylene glycol in a side chain. The surface modifier according to any one of claims 1 to 3, wherein the monomer unit (B) has a tris (trialkylsilyloxy) silyl group. The monomer units (A) to (C) are present in a molar ratio ranging from (A) :( B) :( C) = 2: 1: 1 to 9: 1: 1. The surface modifier of any one of Claims 1. The surface modifier of any one of Claims 1-5 whose weight average molecular weight (Mw) of the said copolymer is the range of 1.0x10 < ⁴ > -5.0x10 < ⁵ >. The surface modifier according to any one of claims 1 to 6, wherein a ratio (Mw / Mn) of a weight average molecular weight and a number average molecular weight in the copolymer is in a range of 1.0 to 1.5. . The surface modifier of any one of Claims 1-7 in which the principal chain of the copolymer has a skeleton selected from polyalkyl acrylate or polyalkyl methacrylate. The surface modifier according to any one of claims 1 to 8, wherein the copolymer is a living radical polymer . The surface treatment method including the process of apply | coating the surface modifier of any one of Claims 1-9 on the surface of material. The method of Claim 10 which does not include the process of treating the surface of material with water after the process of apply | coating the said surface treating agent. The method according to claim 10 or 11, wherein the material is ceramics. The material by which surface treatment is carried out with the surface modifier of any one of Claims 1-9. The material according to claim 13, which is a ceramic.

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