An isothiocyanate paste material, its preparation method and application

Abstract

This invention discloses an isothiocyanate paste material, its preparation method, and its applications. The isothiocyanate paste material is composed of isothiocyanate, bio-gel, and hydrophobically modified porous material, wherein the mass ratio of isothiocyanate to bio-gel and hydrophobically modified porous material is 1:(0.5-5):(0.5-2). The isothiocyanate paste material utilizes the confined adsorption effect of the hydrophobically modified porous material and the inclusion effect of the bio-gel to inhibit the rapid volatilization of isothiocyanate, achieving slow release of isothiocyanate and significantly extending its antibacterial time. The isothiocyanate paste material of this invention is low in cost, high in performance, has good repeatability, and high safety, and can be used in fields such as antibacterial and air purification; when used as an antibacterial agent in air conditioner antibacterial sheets, it can be used for antibacterial, mold removal, and odor reduction in the air conditioner cavity.

Description

Technical Field

[0001] This invention belongs to the field of antibacterial materials technology, specifically relating to an isothiocyanate paste material, its preparation method, and its application. Background Technology

[0002] Air conditioner odors mainly come from dust, dirt, bacteria, mites, and mold. During air conditioner use, the aerosol formed by the mixture of water and some particulate matter is an excellent "culture medium" for bacteria and microorganisms. When this aerosol circulates through the air ducts, it gradually deposits bacteria and microorganisms on the air conditioning pipes, evaporator, filter, and air outlet, leading to bacterial proliferation and odor. To reduce odor, regular cleaning of the air conditioner is usually required, which is both time-consuming and laborious. If a long-lasting antibacterial module could be added to the air conditioning system, effectively inhibiting bacteria for a long time, odors could be removed, and the frequency of air conditioner cleaning could be greatly reduced. The core technology to achieve this is to develop an antibacterial agent that can be used for a long period of time.

[0003] Isothiocyanates are a class of compounds with the general formula RN=C=S (R is usually allyl or aryl), and are the main active substances in horseradish and mustard. They are highly safe compounds that can be used in food. Numerous studies have shown that these substances have good broad-spectrum antibacterial effects, exhibiting strong inhibitory effects against bacteria, yeasts, and molds (Guangzhou Chemical Industry, 2017, 45, 64-69), and are therefore often used in food preservation and antibacterial applications. However, isothiocyanates have low solubility, high volatility, and a pungent odor, which limits their application to some extent. To reduce the irritation of isothiocyanates, prolong their action time, and improve their stability, it is necessary to control the slow release of isothiocyanates.

[0004] Currently, the commonly used method is microencapsulation technology. Microencapsulation technology typically uses cyclodextrin, sodium alginate, etc., as wall materials and isothiocyanate as the core material. Cyclodextrin is used to encapsulate isothiocyanate to address the problem of rapid volatilization and low residue during thermoplastic processing (Food Industry Technology, 2013, 34, 260-263). However, Chinese patent CN115926217A proposes that isothiocyanate microcapsules are mainly used to make antibacterial films for food preservation. Since the food preservation environment is a static airflow environment, only a low content of antibacterial agent (i.e., isothiocyanate) is needed in the antibacterial film. However, in air conditioning antibacterial agents, if isothiocyanate is used as the main component, the isothiocyanate content used will inevitably be significantly higher than in a static airflow environment due to the dynamic airflow environment of air conditioning. The required service time is also longer than that of traditional antibacterial films. Clearly, this places higher demands on the preparation of isothiocyanate antibacterial agents. Summary of the Invention

[0005] One objective of this invention is to overcome the limitations of isothiocyanates, such as high volatility, strong irritation, and short service life, by proposing a method for preparing isothiocyanate paste materials.

[0006] The present invention adopts the following technical solution:

[0007] Step (1): Dissolve isothiocyanate in ethanol at room temperature to prepare an isothiocyanate ethanol solution;

[0008] Preferably, the isothiocyanate in step (1) is one or two of allyl isothiocyanate and aromatic isothiocyanate;

[0009] Preferably, the mass ratio of isothiocyanate to ethanol in step (1) is 1:(5-20), and more preferably 1:(8-10);

[0010] Step (2): Mix the porous material, organosilanes, ethanol, and ammonia in a mass ratio of 1:0.5:(20-25):(3-5), heat and stir at 60-80℃ for 2 hours, then centrifuge, wash, and dry to obtain the hydrophobic modified porous material.

[0011] Preferably, the porous material in step (2) is at least one of mesoporous silica, aluminosilicate molecular sieve, activated carbon, and diatomaceous earth;

[0012] Preferably, the organosilane in step (2) is at least one of methyltrimethoxysilane, trimethylchlorosilane, phenyltrimethoxysilane, and phenyltriethoxysilane.

[0013] Preferably, the mass ratio of porous material, organosilanes, ethanol, and ammonia in step (2) is 1:0.5:20:3.

[0014] Step (3): Add the hydrophobically modified porous material to the isothiocyanate ethanol solution obtained in step (1) and stir for 1-3 hours to allow the porous material to fully adsorb the isothiocyanate and obtain a mixed solution.

[0015] Preferably, the mass ratio of the isothiocyanate in step (1) to the hydrophobic modified porous material in step (3) is 1:(0.5-2), and more preferably 1:(1-1.5).

[0016] Step (4): Dissolve the bio-glue in water to prepare a bio-glue solution;

[0017] Preferably, the bio-gum in step (4) is at least one of agar, gelatin, gum arabic, guar gum, xanthan gum, and cellulose gum; more preferably, it is agar.

[0018] Preferably, the mass ratio of the bio-adhesive to water in step (4) is 1:(10-100), and more preferably 1:(40-80);

[0019] Preferably, the water temperature in step (4) is 80-100℃; more preferably, the preparation is carried out by stirring thoroughly under heating conditions, with a heating temperature of 80-100℃.

[0020] Step (5): Under heating and stirring conditions, the bio-adhesive solution obtained in step (4) is slowly added to the mixed solution obtained in step (3). After the addition is complete, stirring is continued for a period of time. After cooling, the isothiocyanate paste material is obtained.

[0021] Preferably, the mass ratio of the isothiocyanate in step (1) to the bio-gel in step (5) is 1:(0.5-5), and more preferably 1:(1-2);

[0022] Preferably, the heating temperature in step (5) is 80-100℃.

[0023] A second objective of this invention is to provide an isothiocyanate paste material prepared using the method described above.

[0024] A third objective of this invention is to provide an application of the above-mentioned isothiocyanate paste material in antibacterial or air purification.

[0025] The fourth objective of this invention is to provide an air conditioner antibacterial sheet, which includes a housing and an antibacterial agent. The housing includes an upper cover and a lower cover that engages with the upper cover. The surfaces of the upper cover and the lower cover are provided with perforated grooves. The antibacterial agent is disposed in a cavity within the housing. The antibacterial agent contains the aforementioned isothiocyanate paste material.

[0026] The beneficial effects of this invention are as follows:

[0027] (1) This invention uses hydrophobically modified porous materials as carriers for isothiocyanates, which solves the problems of low water solubility and poor stability of isothiocyanates. It effectively increases the loading of isothiocyanates by utilizing their confined adsorption effect. After hydrophobic modification of the porous materials, their interaction with isothiocyanates is stronger, which reduces the volatilization of isothiocyanates.

[0028] (2) This invention uses bio-adhesive as an encapsulating material, utilizing its properties of high-temperature dissolution and low-temperature condensation to effectively and conveniently prepare a paste material, and uniformly distributes isothiocyanate and hydrophobically modified porous material in the paste. This isothiocyanate paste material can achieve high storage capacity by adsorbing and sealing isothiocyanate in the internal hydrophobically modified porous material, and can also achieve the purpose of sustained release and controlled release by utilizing the diffusion resistance of porous material and bio-adhesive encapsulating material, thereby inhibiting the volatilization of isothiocyanate, reducing its irritation, prolonging its action time, and improving its stability.

[0029] (3) The raw materials used in this invention, namely bio-glue, hydrophobically modified porous material and isothiocyanate, have good biocompatibility and safety. Attached Figure Description

[0030] Figure 1 The images are of isothiocyanate paste materials; in which (a) the mass ratio of isothiocyanate, hydrophobically modified mesoporous silica, and bio-adhesive is 1:1:2; and (b) the mass ratio of isothiocyanate, hydrophobically modified mesoporous silica, and bio-adhesive is 1:1:0.1.

[0031] Figure 2 This is a schematic diagram of the structure of the antibacterial sheet for air conditioning in Application Example 1. Detailed Implementation

[0032] As mentioned above, in view of the shortcomings of the prior art, the inventors of this invention, through long-term research and extensive practice, have proposed the technical solution of this invention. Its main basis includes at least the following: This invention uses hydrophobically modified porous materials as carriers for isothiocyanates, solving the problems of low water solubility and poor stability of isothiocyanates, and utilizing their confined adsorption effect to improve the loading capacity and stability of isothiocyanates; it uses bio-glue as an encapsulating material, utilizing its high-temperature dissolution and low-temperature condensation properties to effectively and conveniently prepare ointment materials, and ensuring that isothiocyanates / porous materials are uniformly distributed in the ointment. This isothiocyanate ointment material can achieve high fragrance storage capacity by adsorbing and sealing isothiocyanates within the internal hydrophobically modified porous material, and can also utilize the diffusion resistance of the porous material and the bio-glue encapsulating material to achieve the purpose of sustained and controlled release, thereby inhibiting the volatilization of isothiocyanates, reducing their irritation, prolonging their action time, and improving their stability.

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0034] In a first aspect, the present invention provides a method for preparing an isothiocyanate paste material for antibacterial purposes, comprising the following steps:

[0035] Step (1): At room temperature, dissolve isothiocyanate in ethanol to prepare an isothiocyanate ethanol solution; the isothiocyanate is at least one of allyl isothiocyanate and aromatic isothiocyanate or a mixture of both in any proportion; the mass ratio of isothiocyanate to ethanol is 1:(5-20).

[0036] Step (2): The porous material, organosilane, ethanol, and ammonia are mixed in a mass ratio of 1:0.5:(20-25):(3-5). After heating and stirring at 60-80℃ for 2 hours, the mixture is centrifuged, washed, and dried to obtain a hydrophobically modified porous material. The porous material is at least one of mesoporous silica, aluminosilicate molecular sieve, activated carbon, and diatomaceous earth. The organosilane is at least one of methyltrimethoxysilane, trimethylchlorosilane, phenyltrimethoxysilane, and phenyltriethoxysilane.

[0037] Step (3): Add the hydrophobically modified porous material to the solution obtained in step (1) and stir for 1-3 hours to allow the porous material to fully adsorb isothiocyanate to obtain a mixed solution;

[0038] Step (4): Pour hot water at 80-100℃ into the bio-glue powder and stir thoroughly under heating conditions at 80-100℃ until the bio-glue is completely dissolved; the bio-glue is at least one of agar, gelatin, gum arabic, guar gum, xanthan gum, and cellulose gum; the mass ratio of the bio-glue to the hot water is 1:(10-100);

[0039] Step (5): Under heating and stirring conditions at 80-100℃, slowly add the bio-glue solution obtained in step (4) to the mixed solution obtained in step (3). After the bio-glue solution is completely added, continue stirring for 1 hour. Then, cool the resulting suspension to room temperature to obtain a viscous paste.

[0040] In the preparation method, the mass ratio of isothiocyanate, hydrophobically modified porous material and bio-gel is 1:(0.5-2):(0.5-5).

[0041] Secondly, the present invention provides isothiocyanate paste materials prepared by the above method.

[0042] Thirdly, the present invention provides the application of the above-mentioned isothiocyanate paste material in antibacterial or air purification.

[0043] Fourthly, the present invention provides an air conditioner antibacterial sheet, the air conditioner antibacterial sheet comprising a shell and an antibacterial agent, the shell comprising an upper cover and a lower cover that engages with the upper cover, the upper cover and the lower cover having perforated grooves on their surfaces, the antibacterial agent being disposed in a cavity within the shell, the antibacterial agent containing the aforementioned isothiocyanate paste material.

[0044] The technical solution of the present invention will be further explained and described below with reference to several preferred embodiments, but the experimental conditions and setting parameters therein should not be regarded as limitations on the basic technical solution of the present invention. Furthermore, the scope of protection of the present invention is not limited to the following embodiments.

[0045] The following examples demonstrate the methods used in on-site testing of air disinfection effectiveness:

[0046] Pretreatment process: To more quickly differentiate the long-term stability of different isothiocyanate paste materials, this study conducted an accelerated aging pretreatment on the isothiocyanate paste materials. Specifically, the isothiocyanate paste materials were treated in a 45°C air-supply environment for 12 hours to accelerate the volatilization of isothiocyanates.

[0047] On-site test method for air disinfection effect: at 1m 3 In a confined space, samples were collected using a BY-300 airborne microbial sampler at a flow rate of 28.3 L / min. The sampler was placed in the center of the laboratory, with one sampling point, and the sampling time was 5 minutes. 20g of the pretreated paste sample was spread evenly on a petri dish, and a fan was used to blow air onto the dish. After 24 hours of incubation, Difco was added to the sampler. TM For D / E neutralized broth nutrient agar plates, air samples were taken from the same sampling point for 5 minutes. The sampling plates were then incubated at 37°C for 48 hours before the results were observed. The experiment was repeated three times.

[0048] The mortality rate N of naturally occurring bacteria in the air t The following formula is used for calculation.

[0049]

[0050] Where V0 is the bacterial count in the air before the test, V t The bacterial count in the air after the experiment.

[0051] Example 1

[0052] Step (1): Under stirring conditions, 2g of agar is completely dissolved in 100mL of hot water at 80℃ to obtain agar solution A.

[0053] Step (2): Mix mesoporous silica, methyltrimethoxysilane, ethanol and ammonia in a mass ratio of 1:0.5:20:3, heat and stir at 80°C for 2 hours, then centrifuge, wash and dry to obtain hydrophobic modified mesoporous silica.

[0054] Step (3): At 25°C, 1g of allyl isothiocyanate was dissolved in 10g of ethanol to prepare allyl isothiocyanate solution B. Then, 1g of hydrophobically modified mesoporous silica was added to isothiocyanate solution B and stirred for 1 hour to allow the mesoporous silica to fully adsorb the isothiocyanate, resulting in suspension C.

[0055] Step (4): Under heating and stirring conditions at 80°C, slowly add agar solution A to suspension C. After agar solution A has been completely added, continue stirring for 1 hour. Then cool to room temperature to obtain a viscous paste.

[0056] The mass ratio of allyl isothiocyanate, hydrophobically modified mesoporous silica, and agar is 1:1:2.

[0057] Example 2-12

[0058] The procedure was performed according to the method described in Example 1, the difference being the type of hydrophobic modified porous material used. Specific experimental parameters and antibacterial properties are shown in Table 1. Among these, the specific surface areas of mesoporous silica, aluminosilicate molecular sieves (clinoptilolite, mordenite, acridite, chalcogenite, 5A molecular sieve, 13X molecular sieve, Y molecular sieve, ZSM-5 molecular sieve), diatomaceous earth, and activated carbon were all greater than 300 m². 2 / g, while the specific surface area of ​​quartz sand is less than 20m². 2 / g. Based on the natural bacterial mortality data in the table, isothiocyanate pastes prepared from high specific surface area porous materials such as mesoporous silica, silica-alumina molecular sieves, diatomaceous earth, and activated carbon all exhibit good antibacterial effects. However, isothiocyanate pastes prepared using low specific surface area quartz sand have significantly poorer antibacterial effects. This is mainly because quartz sand has a very small specific surface area and cannot effectively adsorb isothiocyanates.

[0059] Examples 13-17

[0060] The method described in Example 1 was followed, except that the type of bio-adhesive used was different. Specific experimental parameters and antibacterial properties are shown in Table 1. The data in the table show that after adding hydrophobically modified porous materials as adsorbents, the type of bio-adhesive did not significantly affect the antibacterial effect. Isothiocyanate pastes prepared from various bio-adhesives all exhibited good antibacterial effects.

[0061] Example 18

[0062] The method described in Example 1 was followed, except that the isothiocyanate used in Example 17 was an aromatic isothiocyanate, and its antibacterial properties are shown in Table 1. The data in the table show that both aromatic and allyl isothiocyanates have good antibacterial effects.

[0063] Examples 19-26

[0064] The method described in Example 1 was followed, except that the mass ratio of isothiocyanate:porous material:biogel was different. Specific experimental parameters and antibacterial properties are shown in Table 1. Example 19 differs from Examples 1-11 in that hydrophobically modified porous material was not added in Example 19. Regarding the antibacterial effect, the isothiocyanate paste prepared solely from isothiocyanate and biogel without the addition of hydrophobically modified porous material showed significantly weaker antibacterial performance. This is mainly because the addition of hydrophobically modified porous material effectively adsorbs and stabilizes isothiocyanate. Without the addition of hydrophobically modified porous material, isothiocyanate is more volatile. After 12 hours of accelerated aging pretreatment, a large amount of isothiocyanate was lost, leaving less isothiocyanate in the paste, resulting in a weaker antibacterial effect. This result indicates that the addition of hydrophobically modified porous material plays an important role in improving the long-term stability of isothiocyanate paste materials.

[0065] The difference between Example 20 and Example 1 is that the mass ratio of isothiocyanate to mesoporous silica in Example 20 is 1:0.1. Compared to Example 1, Example 20 adds much less mesoporous silica, and its antibacterial effect is significantly worse. This indicates that the amount of porous material added has a significant impact on the long-term stability of the isothiocyanate paste material; when the amount of porous material added is too small, long-term antibacterial effect cannot be achieved. In Examples 21 and 22, the mass ratios of isothiocyanate to mesoporous silica are 1:0.5 and 1:2, respectively. The antibacterial effects of Examples 21 and 22 are similar to those of Example 1, indicating that a mass ratio of isothiocyanate to porous material between 1:(0.5 and 2) provides a good long-term antibacterial effect.

[0066] The difference between Example 23 and Example 1 is that in Example 23, the mass ratio of isothiocyanate to bio-glue is 1:0.1. Although both have good antibacterial effects, the isothiocyanate content in the isothiocyanate paste material in Example 23 is too high, resulting in oil spots and uneven color on the surface of the obtained paste sample. Figure 1 b), and the sample emitted a strong, pungent odor; while the ointment sample obtained in Example 1 had a smooth surface and uniform color. Figure 1a) The sample had a weaker pungent odor, better meeting the requirements of practical applications. In Examples 24 and 25, the mass ratio of isothiocyanate to bio-glue was 1:0.5 and 1:5, respectively, and their antibacterial effects and sample appearance / properties were similar to those of Example 1. However, in Example 26, the mass ratio of isothiocyanate to bio-glue was 1:10, at which point the isothiocyanate content was lower, and the antibacterial effect was significantly lower than that of Example 1. The above results indicate that 1:(0.5-5) is a relatively ideal mass ratio of isothiocyanate to bio-glue.

[0067] Example 27

[0068] The method described in Example 1 was followed, except that in Example 27, the paste material obtained in Example 1 was accelerated to age at 40°C for 100 hours. The antibacterial effect in Example 27 was similar to that in Example 1. This result further demonstrates that the isothiocyanate paste material, composed of isothiocyanate, bio-adhesive, and porous materials in a suitable ratio, possesses a long-term stable antibacterial effect.

[0069] Example 28

[0070] The method described in Example 19 was followed, except that in Example 28, the ointment material obtained in Example 19 was accelerated to 40°C for 100 hours. As shown in Table 1, without the addition of porous material, the ointment material almost completely lost its antibacterial ability after 100 hours of accelerated aging. This is mainly due to the loss of isothiocyanate during the accelerated aging process. A comparison of Example 28 and Example 27 shows that porous materials play an important role in improving the long-term stable antibacterial ability of the ointment.

[0071] Example 29

[0072] Agar, isothiocyanate, and mesoporous silica were added together to hot water at 80°C and stirred for 2 hours. The mixture was then cooled to room temperature to obtain a viscous paste. The mass ratio of agar to water was 1:50, and the mass ratio of allyl isothiocyanate, mesoporous silica, and agar was 1:1:2. Table 1 shows that the antibacterial effect of Example 29 was significantly lower than that of Example 1. Since Examples 1 and 29 used the same mass ratio of allyl isothiocyanate:mesoporous silica:agar, the only difference was the synthesis process—Example 1 used a stepwise method, while Example 29 used a one-pot method. Therefore, the significant difference in antibacterial effect indicates that the synthesis process of the paste material has a very important influence on its long-term antibacterial effect. A crucial technical point in the synthesis process of Example 1 was to first mix the isothiocyanate ethanol solution with the porous material, ensuring that the porous material fully adsorbed the isothiocyanate before mixing it with the bio-gel solution. This operation allows for full utilization of the adsorption and stabilizing effects of the porous material. In the one-pot process, the adsorption of isothiocyanates by porous materials is inevitably affected by the bio-gel, so its effect is not as good as the stepwise process.

[0073] Example 30

[0074] The method described in Example 1 was followed, except that the mesoporous silica used in Example 30 was not hydrophobically modified. Specific experimental parameters and antibacterial properties are shown in Table 1. From the natural bacterial mortality data in the table, the isothiocyanate paste prepared using unmodified mesoporous silica showed significantly weaker antibacterial effects. This is mainly because the interaction between the unmodified porous material and isothiocyanate is weaker, making the isothiocyanate more volatile. After 12 hours of accelerated aging pretreatment, a large amount of isothiocyanate was lost, leaving less isothiocyanate in the paste, thus resulting in a poorer antibacterial effect. This result indicates that hydrophobic modification plays an important role in improving the long-term stability of isothiocyanate paste materials.

[0075] Table 1. Experimental parameters and antibacterial effect data for each embodiment.

[0076]

[0077]

[0078] Application Example 1

[0079] The isothiocyanate paste material prepared in the examples was used as an antibacterial agent for air conditioning antibacterial sheets, such as... Figure 2 As shown, the air conditioner antibacterial sheet includes a housing and an antibacterial agent 2. The housing includes an upper cover 1 and a lower cover 3 that is fastened to the upper cover. The surfaces of the upper cover 1 and the lower cover 3 are provided with hollow grooves. The antibacterial agent 2 is disposed in the cavity of the housing.

Claims

1. A method for preparing an isothiocyanate paste material, characterized in that, The preparation method includes the following steps: Step (1): Dissolve isothiocyanate in ethanol at room temperature to prepare an isothiocyanate ethanol solution; Step (2): The porous material, organosilane, ethanol, and ammonia are heated and stirred at 60-80°C for 2 h in a mass ratio of 1:0.5:(20-25):(3-5). After centrifugation, washing, and drying, the hydrophobically modified porous material is obtained. The porous material is at least one of mesoporous silica, aluminosilicate molecular sieve, activated carbon, and diatomaceous earth. Step (3): Add the hydrophobic modified porous material to the isothiocyanate ethanol solution obtained in step (1) and stir for 1-3 hours to obtain a mixed solution; wherein, the mass ratio of the isothiocyanate in step (1) to the hydrophobic modified porous material in step (3) is 1:(0.5-2); Step (4): Dissolve the bio-gum in water to prepare a bio-gum solution, wherein the bio-gum is at least one of agar, gelatin, gum arabic, guar gum, and xanthan gum; wherein the mass ratio of the isothiocyanate in step (1) to the bio-gum in step (4) is 1:(0.5-5); Step (5): Add the bio-adhesive solution obtained in step (4) to the mixed solution obtained in step (3) under heating and stirring, and then continue stirring for a period of time. After the reaction is complete, cool to obtain the isothiocyanate paste material.

2. The preparation method according to claim 1, characterized in that, The isothiocyanate mentioned in step (1) is one or two of allyl isothiocyanate and aromatic isothiocyanate.

3. The preparation method according to claim 1, characterized in that, The mass ratio of isothiocyanate to ethanol in step (1) is 1:(5-20).

4. The preparation method according to claim 1, characterized in that, The organosilane mentioned in step (2) is at least one of methyltrimethoxysilane, trimethylchlorosilane, phenyltrimethoxysilane, and phenyltriethoxysilane.

5. The preparation method according to claim 1, characterized in that, The heating temperature in step (5) is 80-100℃.

6. An isothiocyanate paste material, characterized in that, It is prepared by the method described in any one of claims 1-5.

7. The application of the isothiocyanate paste material as described in claim 6 in antibacterial or air purification.

8. An air conditioner antibacterial sheet, comprising a housing and an antibacterial agent, wherein the housing includes an upper cover and a lower cover that engages with the upper cover, the surfaces of the upper cover and the lower cover having perforated grooves, and the antibacterial agent being disposed within a cavity in the housing, characterized in that, The antibacterial agent contains the isothiocyanate paste material as described in claim 6.

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