Antibacterial resin additive and antibacterial resin composition

Abstract

To provide an antibacterial resin additive, capable of maintaining antibacterial performance for a long duration without impairing the mechanical properties of resin, and a resin composition which enables retention of antibacterial performance for a long duration.SOLUTION: The present invention provides an antibacterial resin additive that contains a mixture of a quaternary ammonium salt or a long-chain alkylpyridinium salt having surface activity and a polyhydric alcohol or a carboxylic acid, and an antibacterial resin composition that contains 0.1-5 wt.% of the antibacterial resin additive. It is preferable that the quaternary ammonium salt having surface activity is benzalkonium chloride.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an antibacterial resin additive that enables the maintenance of antibacterial properties for a long period of time without impairing the mechanical properties of the resin, and to a resin composition that maintains antibacterial properties for a long period of time. [Background technology]

[0002] Due to the recent increase in hygiene awareness, antibacterial properties of resins have come to be positioned as a basic performance. Conventionally, methods of imparting antibacterial properties to resins have been considered, such as kneading antibacterial agents into the resin or applying paint containing antibacterial agents to the surface. Surface-active quaternary ammonium salts (with chloride ions as the counter ion), such as benzalkonium chloride, are widely used as antibacterial agents, and by incorporating them into resins, antibacterial properties are imparted to resin products. However, many of the commonly used surface-active quaternary ammonium salts are crystalline solids at room temperature and have low compatibility with many resins, resulting in very poor solubility and diffusibility in resins. This makes it difficult for the antibacterial agent inside the resin to bleed out, posing the problem of short-lasting antibacterial properties in resin products.

[0003] To address these issues, a method has been proposed for controlling antibacterial bleeding (Patent Document 1) in which a methosulfate-type quaternary ammonium salt with antibacterial activity is used in combination with a base resin with low compatibility. Didecyldimerammonium methyl sulfate, the methosulfate-type quaternary ammonium salt used in Example 1 of Patent Document 1, is a liquid at room temperature and dissolves in organic solvents such as benzene, and is therefore thought to easily move through gaps in polymers. On the other hand, surface-active quaternary ammonium salts widely used as antibacterial agents are solid at room temperature, have even lower compatibility with common resins than methosulfate-type quaternary ammonium salts, and are insoluble in low-polarity organic solvents such as benzene. Therefore, it is thought that the method described in Patent Document 1 cannot control bleeding.

[0004] In order to control the bleeding of the surface-active quaternary ammonium salt, it is necessary to improve its solubility or diffusibility in the resin, or both. Patent Document 2 describes that a mixture containing a hydrogen bond donor and a hydrogen bond acceptor (deep eutectic solvent) has excellent affinity with a resin having a functional group capable of forming a hydrogen bond. Because quaternary ammonium salts are exemplified as substances that constitute deep eutectic solvents, using surface-active quaternary ammonium salts as deep eutectic solvents may be one way to improve the affinity of surface-active quaternary ammonium salts for resins.

[0005] However, the exemplified quaternary ammonium salts do not include those generally known as cationic surfactants and also used as antibacterial agents. Furthermore, the exemplified quaternary ammonium salts have no or very weak surface activity, which differs from the physical properties of quaternary ammonium salts with strong surface activity. Therefore, it is unclear whether quaternary ammonium salts with surface activity can be used as deep eutectic solvents. Furthermore, deep eutectic solvents are merely considered to have excellent affinity with resins having functional groups capable of forming hydrogen bonds. Therefore, it is unclear whether the solubility and diffusibility of quaternary ammonium salts with surface activity in resins will be improved when quaternary ammonium salts with surface activity are used as deep eutectic solvents. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2020-7266 [Patent Document 2] Japanese Patent Application Publication No. 2020-105336 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide an antibacterial resin additive that enables the maintenance of antibacterial properties for a long period of time without impairing the mechanical properties of the resin, and a resin composition that maintains antibacterial properties for a long period of time. [Means for solving the problem]

[0008] The present invention is characterized by the following configuration and solves the above-mentioned problems. [1] An antibacterial resin additive containing a mixture of a surface-active quaternary ammonium salt or a long-chain alkylpyridinium salt and a polyhydric alcohol or a carboxylic acid, wherein the surface-active quaternary ammonium salt is represented by the following general formula (1): [ka] (In the formula, R1 represents one of a C1 to C10 linear or branched alkyl group, a benzyl group, and a phenoxyethyl group; R2 represents one of a C6 to C18 linear or branched alkyl group and a phenoxyethoxyethyl group having a substituent; and X represents one of Cl or Br.) The polyhydric alcohol is represented by the following general formula (2): [ka] (In the formula, R1, R2, R3, and R4 each independently represent one of H, a C1 to C10 linear or branched alkyl group, an alkyloxymethylene group, and a C5 to C10 cyclic alkyl group in which two of R1 to R4 are bonded to form a ring, with the proviso that at least one of R1, R2, R3, and R4 is not H, and n represents an integer of 0 or 1.) An antibacterial resin additive, wherein the carboxylic acid is a C1 to C12 linear, branched or cyclic alkyl or alkenyl mono- or dicarboxylic acid, or an aromatic mono- or dicarboxylic acid. [2] The antibacterial resin additive according to [1], wherein the surface-active quaternary ammonium salt is benzalkonium chloride. [3] An antibacterial resin composition containing 0.1 to 5% by weight of the resin additive according to [1] above. [Effects of the Invention]

[0009] According to the present invention, surface-active quaternary ammonium salts whose counterions are chloride or bromide ions are highly hydrophilic and polar, but when mixed with a polyhydric alcohol or a carboxylic acid, their hydrophilicity and polarity decrease. Such mixtures have improved solubility in resins compared to the surface-active quaternary ammonium salts alone, thereby improving the solubility of the surface-active quaternary ammonium salts in resins. Furthermore, by using such mixtures as antibacterial resin additives, it is possible to provide resin compositions that maintain antibacterial properties for a long period of time. DETAILED DESCRIPTION OF THE INVENTION

[0010] Preferred embodiments of the present invention will be described below, but the present invention is not limited to these embodiments.

[0011] The antibacterial resin additive of the present invention comprises a mixture of a surface-active quaternary ammonium salt and a polyhydric alcohol or a carboxylic acid.

[0012] The surface-active quaternary ammonium salt is represented by the following general formula (1): [ka] In the formula, R1 represents one of a C1 to C10 linear or branched alkyl group, a benzyl group, and a phenoxyethyl group, R2 represents one of a C6 to C18 linear or branched alkyl group and a phenoxyethoxyethyl group having a substituent, and X represents one of Cl or Br.

[0013] Specific examples include benzalkonium chloride, benzethonium chloride, methylbenzethonium chloride, cetylpyridinium chloride, dophanium chloride, didecyldimethylammonium chloride, dequalinium chloride, hexadecyltrimethylammonium bromide, etc., which can be used alone or in combination. Among these, benzalkonium chloride is most preferred.

[0014] The polyhydric alcohol is represented by the general formula (2): [ka] In the formula, R1, R2, R3, and R4 each independently represent one of H, a C1 to C10 linear or branched alkyl group, an alkyloxymethylene group, or a C5 to C10 cyclic alkyl group in which two of R1 to R4 are bonded to form a ring, provided that at least one of R1, R2, R3, and R4 is not H, and n represents an integer of 0 or 1.

[0015] Specific examples of polyhydric alcohols include ethylene glycol, propylene glycol, 1,4-butanediol, 1,3-butanediol, 1,2-hexanediol, 1,2-octanediol, 2-ethyl-1,3-hexanediol, and ethylhexylglycerin.

[0016] The carboxylic acid is a C1 to C12 linear, branched, or cyclic alkyl or alkenyl mono- or dicarboxylic acid, or an aromatic mono- or dicarboxylic acid. Specific examples include saturated aliphatic carboxylic acids such as acetic acid, 2-ethylhexanoic acid, decanoic acid, myristic acid, and cyclohexanecarboxylic acid, and polycarboxylic acids such as citric acid, maleic acid, phthalic acid, and succinic acid.

[0017] A hydrogen bond may exist between the surface-active quaternary ammonium salt and the polyhydric alcohol or carboxylic acid. Specifically, the chloride ion or bromide ion, which is the counter anion of the quaternary ammonium salt, may act as the hydrogen bond acceptor, and the hydroxyl group proton of the alcohol or the proton of the carboxylic acid may act as the hydrogen bond donor to form the hydrogen bond (e.g., DIM Al-Risheq et al. Separation and Purification Technology 255 (2021) 117737, DV Wagle et al. ACS Sustainable Chem. Eng. 6 (2018) 7525-7531). This hydrogen bond formation can be confirmed by measuring the proton NMR of the mixture, where the hydroxyl protons of the alcohol shift downfield from their chemical shift position when alone, and the carboxylic acid protons shift upfield when water is present (e.g., H. Kivela et al., J. Phys. Chem. B 126 (2022) 513-527, S. Spittle et al., Nat.Commun 13 (2022) 219).

[0018] The mixing ratio of the surface-active quaternary ammonium salt to the polyhydric alcohol or alkyl carboxylic acid is preferably within the range of 1:0.25 to 1:4 moles, preferably 1:0.33 to 1:3 moles, and more preferably 1:0.5 to 1:2 moles, of quaternary ammonium salt:polyhydric alcohol or carboxylic acid. If the amount of polyhydric alcohol or carboxylic acid is less than 0.25 moles per mole of quaternary ammonium salt, the solubility of the mixture in the resin decreases. If the amount of polyhydric alcohol or carboxylic acid is more than 4 moles per mole of quaternary ammonium salt, the polyhydric alcohol or carboxylic acid will be in excess.

[0019] A mixture of a surface-active quaternary ammonium salt and a polyhydric alcohol or alkyl carboxylic acid can be prepared, for example, by placing 1 mole of a surface-active quaternary ammonium salt and an arbitrary molar amount of a polyhydric alcohol or alkyl carboxylic acid in a container, stirring the mixture at a temperature ranging from room temperature to 100°C until a uniform, transparent liquid is obtained, and then returning the mixture to room temperature.

[0020] The antibacterial resin composition of the present invention contains the antibacterial resin additive in an amount of 0.1 to 10 wt %, preferably 0.2 to 8 wt %, and more preferably 0.3 to 7 wt %. If the amount is less than 0.1 wt %, the antibacterial properties will not last. More than 10 wt % is not necessary.

[0021] Resins used in antibacterial resin compositions include thermoplastic resins such as polyethylene, polypropylene, polycycloolefins, ethylene-vinyl acetate copolymers, acrylonitrile-butadiene-styrene copolymers, acrylonitrile-styrene copolymers, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyamides, polyesters, polyimides, polyamideimides, polymethyl methacrylate, polycarbonates, liquid crystal resins, polyurethanes, and modified resins thereof; curable resins such as silicone resins, epoxy resins, and modified resins thereof; and rubbers such as polybutadiene, polyisoprene, styrene-butadiene copolymers, acrylonitrile-butadiene copolymers, and modified resins thereof. Resins with melting, curing, or crosslinking temperatures lower than the decomposition temperature of the surface-active quaternary ammonium salt used in the present invention are preferably used. In this specification, the decomposition temperature of the quaternary ammonium salt is defined as the extrapolated onset temperature of the weight loss curve (TG curve) observed in thermogravimetric analysis (TGA) above the weight loss due to the water contained therein.

[0022] The antibacterial resin composition of the present invention can be prepared by a dry blending method in which the antibacterial resin additive is directly mixed with the resin; a melt kneading method in which the resin and the antibacterial resin additive are mixed in a molten state; a solution method in which the resin and the antibacterial resin additive are mixed using a solvent that dissolves the antibacterial resin additive; or a method in which the antibacterial resin additive is directly dissolved in a liquid resin. For example, if the resin is a thermoplastic resin, the antibacterial resin composition of the present invention can be obtained by mixing the antibacterial resin additive of the present invention by melt kneading and then cooling. If the resin is a liquid curable resin, the antibacterial resin composition of the present invention can be obtained by dissolving the antibacterial resin additive of the present invention and then curing the solution using an appropriate curing agent and curing conditions. If the resin is a rubber, the antibacterial resin composition of the present invention can be obtained by mixing the antibacterial resin additive of the present invention by kneading and then curing the solution. A crosslinking agent can be added during mixing to crosslink the resin. Furthermore, if the resin has a melting temperature higher than the decomposition temperature of the surface-active quaternary ammonium salt used in the present invention but is soluble in organic solvents, the antibacterial resin composition of the present invention can be obtained by mixing the antibacterial resin additive of the present invention with a resin solution and then removing the solvent. In this case, the organic solvent is preferably a solvent in which the antibacterial resin composition of the present invention is soluble.

[0023] In addition, additives generally used in resin products, such as colorants, plasticizers, ultraviolet absorbers, flame retardants, metal soaps such as aluminum stearate, and fillers such as silica, clay, talc, glass fibers, carbon nanofibers, and cellulose nanofibers, may also be added. [Example]

[0024] The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these examples.

[0025] Each evaluation was carried out by the following method. <Antibacterial property test of antibacterial resin composition> The antibacterial properties of the antibacterial resin composition sheet were evaluated by an antibacterial test in accordance with JIS Z 2801. Specifically, the test was carried out according to the following procedure. (1) The sheet was irradiated with UV light for 5 minutes on each side to sterilize the surface. (2) The cultured Staphylococcus aureus (NBRC 12732 strain) was diluted with 1 / 500 NB medium to adjust the concentration. (3) 0.4 ml of the adjusted bacterial solution was dropped onto the surface of the sheet. (4) A 4 x 4 cm PE film was placed over the container, and the bacterial solution was spread over the entire surface of the film. (5) The dish was closed with a lid, placed in a humidified box, and left to stand in a constant temperature bath at 35°C for 24 hours. (6) The PE film and the surface of the test piece were washed with recovery buffer (JIS Z2801 specified, SCDLP medium). (7) The washed fluid was diluted 10 to 100,000 times with phosphate buffered saline. (8) 1 mL of each diluted solution was dropped onto a film medium for microbiological testing, EasyPlate (Kikkoman Corporation). (9) The film medium was cultured at 35°C for 24 hours, and the number of colonies formed was counted.

[0026] The antibacterial activity of the antibacterial resin composition sheet was calculated by the method described in JIS Z2801. According to the standards set by the Society of Antibacterial Products and Technology (SIAA), a product is considered to have antibacterial effects if its antibacterial activity is 2 or higher.

[0027] <Antibacterial durability test of antibacterial resin composition> The sample subjected to the above antibacterial test was designated the first test. After rinsing the surface with sterilized Milli-Q water, the sample was air-dried and left at room temperature for 7 days. The dried and left sample was then used as the second sample for the persistence test and subjected to the above antibacterial test. For the third test, the sample after the second antibacterial test was dried and air-dried in the same manner as the first test, and left at room temperature for 1 day, after which the third antibacterial test was performed. For the fourth test, the sample after the third antibacterial test was dried and air-dried in the same manner, and left at room temperature for 5 days, after which the fourth antibacterial test was performed. The antibacterial test was performed, and samples that maintained an antibacterial activity score of 2 or higher by the fourth test were deemed to have persistence.

[0028] Example 1 <Preparation of antibacterial resin additive 1> To 1 mole of benzalkonium chloride (manufactured by Nacalai Tesque, calculated based on a molecular weight of 354.02), 1 mole of 2-ethylhexanoic acid (manufactured by Nacalai Tesque) was added, followed by stirring at 80°C for approximately 20 minutes using a stirrer. The mixture was then cooled to room temperature to obtain a mixture.

[0029] Thermogravimetric measurements were performed on the above mixture, benzalkonium chloride alone, and 2-ethylhexanoic acid alone. 2-Ethylhexanoic acid began to lose weight around 90°C and disappeared at 175°C. Benzalkonium chloride showed weight loss due to adsorbed water up to 100°C, then began to lose weight around 175°C and disappeared at 250°C. On the other hand, the weight loss observed for the mixture closely overlapped with the weight loss curve for benzalkonium chloride alone, and no weight loss was observed solely for 2-ethylhexanoic acid. This suggests that the mixture is not simply a mixture of two components, but that there is some kind of interaction between them, causing them to behave thermally as a single molecule.

[0030] Tetramethylsilane was added to this mixture as an internal standard, and proton NMR was measured at 50°C. Benzalkonium chloride and 2-ethylhexanoic acid were also measured separately. The proton NMR spectrum showed that benzalkonium chloride contained two water molecules. Comparing the NMR charts of both samples, the carboxyl group proton of 2-ethylhexanoic acid was observed at 12.3 ppm, but in the mixture it was observed at 6.4 ppm, showing a high field shift, suggesting that the carboxyl group proton of 2-ethylhexanoic acid forms a hydrogen bond with the chloride ion of benzalkonium chloride.

[0031] When the solubility of the above mixture in organic solvents (concentration 10 wt%) was investigated, it dissolved in hexane at 25°C. It also dissolved in tetrahydrofuran, ethyl acetate, and toluene at 22°C. On the other hand, benzalkonium chloride alone did not dissolve in these solvents. It can be said that benzalkonium chloride becomes more soluble in organic solvents with low polarity when it is in the form of a mixture.

[0032] Example 2 <Preparation of antibacterial resin additive 2> To 1 mole of benzalkonium chloride (manufactured by Nacalai Tesque, calculated based on a molecular weight of 354.02), 1 mole of decanoic acid (manufactured by Nacalai Tesque) was added, and the mixture was stirred at 80° C. for about 20 minutes using a stirrer, and then cooled to room temperature.

[0033] A 1:1 molar mixture of benzalkonium chloride and decanoic acid was dissolved in deuterated chloroform, and tetramethylsilane was added as an internal standard to measure proton NMR. Decanoic acid alone was also measured separately. Comparing the NMR charts of both samples, the carboxyl group protons of decanoic acid were observed at 12.2 ppm, while in the mixture they were observed at 5.82 ppm, showing an upfield shift. This suggests that the carboxyl group protons of decanoic acid form hydrogen bonds with the chloride ions of benzalkonium chloride.

[0034] Thermogravimetric measurements were performed on the above mixture, benzalkonium chloride alone, and decanoic acid alone. Decanoic acid began to lose weight at approximately 150°C and disappeared at 200°C. Benzalkonium chloride showed weight loss due to adsorbed water up to 100°C, then began to lose weight at around 175°C and disappeared at 250°C. On the other hand, the weight loss observed for the mixture almost overlapped with the weight loss curve for benzalkonium chloride alone, and no weight loss was observed for decanoic acid alone. This suggests that the mixture is not simply a mixture of two components, but that there is some kind of interaction between the two, causing them to behave thermally as a single molecule.

[0035] When the solubility of the above mixture in organic solvents (concentration 10 wt%) was investigated, it dissolved in hexane at 40°C. It also dissolved in ethyl acetate and toluene at 22°C. Benzalkonium chloride alone does not dissolve in these solvents, so it can be said that the solubility of benzalkonium chloride in organic solvents changed when it was mixed.

[0036] Example 3 <Preparation of antibacterial resin additive 3> One mole of ethylene glycol (manufactured by Nacalai Tesque) was added to one mole of benzalkonium chloride (manufactured by Nacalai Tesque, calculated based on a molecular weight of 354.02), and the mixture was stirred at 80° C. for about 20 minutes using a stirrer, and then cooled to room temperature.

[0037] Tetramethylsilane was added to the mixture as an internal standard and proton NMR was measured (measurement temperature 20°C). Separately, ethylene glycol alone was measured. Comparing the NMR charts of both, it was found that the hydroxyl group protons of ethylene glycol were observed at 5.35 ppm, but in the mixture they were observed at 5.15 ppm, indicating a high magnetic field shift. This suggests that the hydroxyl group protons of ethylene glycol form hydrogen bonds with the chloride ions of benzalkonium chloride.

[0038] Thermogravimetry was performed on the above mixture, benzalkonium chloride alone, and ethylene glycol alone. Ethylene glycol began to lose weight at approximately 50°C and disappeared at 160°C. Benzalkonium chloride showed weight loss due to adsorbed water up to 100°C, then began to lose weight at around 175°C and disappeared at 250°C. On the other hand, the weight loss curve of the mixture was observed to be shifted overall to a lower temperature by approximately 10°C compared to the weight loss curve of benzalkonium chloride alone. Since no weight loss of ethylene glycol alone was observed, it is believed that the mixture behaves thermally as a single molecule.

[0039] When the solubility of the above mixture in organic solvents (concentration 10 wt%) was investigated, it was found to be soluble in ethyl acetate and toluene at 22°C. Since benzalkonium chloride alone does not dissolve in these solvents, it can be said that the solubility of benzalkonium chloride in organic solvents changed when it was mixed.

[0040] Example 4 <Preparation of antibacterial resin composition by melt kneading method 1> 2 g of the mixture from Example 1 was mixed with 98 g of polyethylene pellets (Novatec, manufactured by Nippon Polyethylene) and melt-mixed using a Toshin Lab Kneader Mill TDR100-3 (mixing temperature: 150°C, rotation speed: 50 rpm, mixing time: 5 min). After mixing, the resulting resin composition was recovered and then press-molded using a vacuum press manufactured by Imoto Machinery Works at 150°C, a pressure of 0.4 MPa, and for 1 min to form a sheet 1 mm thick x 50 mm long and wide.

[0041] Example 5 <Preparation of antibacterial resin composition by melt kneading method 2> A sheet was produced in the same manner as in Example 4 using 2 g of the mixture of Example 2.

[0042] Example 6 <Preparation of antibacterial resin composition by melt kneading method 3> A sheet was produced in the same manner as in Example 4 using 2 g of the mixture of Example 3.

[0043] (Comparative Example 1) In the same manner as in Example 4, a polyethylene sheet was prepared and subjected to an antibacterial activity test and a durability test.

[0044] (Comparative Example 2) In the same manner as in Example 4, a sheet containing 2% by weight of benzalkonium chloride was prepared and subjected to an antibacterial activity test and a durability test.

[0045] Example 7 <Preparation of antibacterial resin composition by melt kneading method 4> 2 g of the mixture from Example 1 was mixed with 98 g of polypropylene pellets (Novatec (registered trademark) manufactured by Japan Polypropylene) and melt-mixed using a Toshin Lab Kneader Mill TDR100-3 (mixing temperature: 180°C, rotation speed: 50 rpm, mixing time: 5 min). After mixing, the resulting resin composition was recovered and then press-molded using a vacuum press manufactured by Imoto Machinery Works at 180°C, a pressure of 0.4 MPa, and for 1 min to form a sheet measuring 1 mm thick and 50 mm long and wide. The resulting sheet had good transparency.

[0046] (Comparative Example 3) A sheet containing 2% by weight of benzalkonium chloride was produced in the same manner as in Example 7. The obtained sheet was cloudy and had poor transparency.

[0047] Example 8 <Preparation of antibacterial resin composition by solution method 5> 9.8 g of polystyrene (manufactured by Toyo Styrene) was dissolved in 40 g of tetrahydrofuran, and 0.2 g of the mixture from Example 1 was added to the solution and stirred at room temperature for 5 minutes with a stirrer to produce a transparent mixture. The mixture was poured into a glass container (4.9 mm diameter), left to dry at room temperature with the lid on for 3 days, and then dried under reduced pressure at 40°C for 8 hours. After drying, the mixture was recovered from the glass container to produce a transparent sheet with a thickness of approximately 0.5 mm.

[0048] <Analysis of benzalkonium chloride in the prepared sheets> For the sheets of Example 4 and Comparative Example 2, the distribution of benzalkonium chloride in the thickness direction of the sheet was examined by detecting chlorine in the cross section of the sheet by EDS measurement. Since the location of chlorine in the sheet of Example 4 was unclear by EDS analysis, the sample surface was treated with a 1% silver nitrate aqueous solution to convert chlorine to silver chloride and perform indirect analysis. After treatment with the silver nitrate aqueous solution, a uniform distribution of fine particles of about 1 μm was observed on the sample surface using an SEM, and these were identified as silver chloride by EDS analysis. The sheet of Comparative Example 1 was also treated with a silver nitrate aqueous solution, but no silver chloride particles were produced. From these findings, it is believed that the mixture containing benzalkonium chloride is dispersed in polyethylene in the form of particles of about 1 μm at most. The sheet of Example 5 gave similar results.

[0049] On the other hand, in the sheet of Comparative Example 2, SEM observation revealed that particles of about 10 to 150 μm were scattered throughout the polyethylene, and EDS analysis detected high concentrations of chlorine in the particle areas. Furthermore, when the sample was washed with water, the particles dissolved and became voids. From these findings, it is believed that benzalkonium chloride was phase-separated within the polyethylene and dispersed as particles of about 10 to 150 μm.

[0050] From the above, the antibacterial resin additive of the present invention existed even in a non-polar resin such as polyethylene without phase separation to form large particles. Furthermore, in polypropylene, benzalkonium chloride alone produced a cloudy sheet, whereas the antibacterial resin additive of the present invention produced a transparent sheet, suggesting good solubility in resin.

[0051] <Antibacterial activity of antibacterial resin composition> The results of testing the antibacterial activity and durability of antibacterial activity of each sample are shown in the table below.

[0052] [Table 1]

[0053] In the first test, no bacteria were recovered, and all samples showed antibacterial activity. This is thought to be the effect of the mold release agent used during molding. From the second test onwards, polyethylene samples alone showed almost no antibacterial activity. The antibacterial activity of polyethylene samples that had only benzalkonium chloride kneaded into them decreased. On the other hand, polyethylene samples kneaded with the antibacterial resin additive of the present invention maintained high antibacterial activity. Antibacterial activity was maintained even when the surface was repeatedly exposed to bacteria, and it is thought that bleeding was appropriately controlled due to the good solubility of the antibacterial resin additive in the resin. [Industrial Applicability]

[0054] According to the present invention, by mixing a surface-active quaternary ammonium salt having antibacterial activity and a counter ion of chloride or bromide with a polyhydric alcohol or a carboxylic acid, the solubility of the quaternary ammonium salt in a resin can be indirectly improved. By using such a mixture as an antibacterial resin additive, a resin composition can be provided that maintains antibacterial activity for a long period of time. Furthermore, the improved solubility does not impair the transparency of the resin, allowing for the provision of antibacterial resin products with excellent design.

Claims

1. An antibacterial resin additive comprising a mixture of a surface-active quaternary ammonium salt or a long-chain alkylpyridinium salt and a polyhydric alcohol or a carboxylic acid, wherein the surface-active quaternary ammonium salt is represented by the following general formula (1): 【Chemical 1】 (In the formula, R1 represents one of a C1 to C10 linear or branched alkyl group, a benzyl group, and a phenoxyethyl group; R2 represents one of a C6 to C18 linear or branched alkyl group and a phenoxyethoxyethyl group having a substituent; and X represents one of Cl or Br.) The polyhydric alcohol is represented by the following general formula (2): 【Chemistry 2】 (In the formula, R1, R2, R3, and R4 each independently represent one of H, a C1 to C10 linear or branched alkyl group, an alkyloxymethylene group, or a C5 to C10 cyclic alkyl group in which two of R1 to R4 are bonded to form a ring, with the proviso that at least one of R1, R2, R3, and R4 is not H, and n represents an integer of 0 or 1.) An antibacterial resin additive, wherein the carboxylic acid is a C1 to C12 linear, branched or cyclic alkyl or alkenyl mono- or dicarboxylic acid, or an aromatic mono- or dicarboxylic acid.

2. 2. The antibacterial resin additive of claim 1, wherein the surfactant quaternary ammonium salt is benzalkonium chloride.

3. An antibacterial resin composition comprising 0.1 to 5% by weight of the resin additive according to claim 1.

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