Liu Xinjian, Wang Zeyun, Jing Suqin, Liu Xiao, Duan Weibo

Nafine Chemical Industry Co. Ltd., China

Jia Yanyu

Taiyuan Finechem Chemical Co. Ltd., China

Introduction

Over the recent decades, China experienced several emerging virus outbreaks including those by SARS coronavirus, H5N1 virus, and H7N9 virus. A series of health scares promoted the prosperity of antibacterial products market greatly. Bacteriostatic detergent is most popular with people. At present, most of the bacteriostatic liquid detergent formulations are anionic-nonionic surfactant systems with adding triclocarban (TCC) or triclosan (DP300),whose uniformity among antibacterial performance,washing performance, safety and consumer’s sensory demands is far from people’s expectation. For this reason,the study of the bacteriostatic liquid detergent has never been interrupted.

Dodecyl dimethyl benzyl ammonium chloride(1227), namely benzalkonium chloride or geramine, is a kind of non-oxidizing bactericide and has excellent antimicrobial performance. Owing to 1227 is low toxicity, no accumulation, easy to dissolve in water and not affected by hardness of water, it is widely used in medical, textile,dyeing and water treatment industry as disinfectants,fungicides.[1]Likewise, 1227 is a kind of cationic surfactant,which has many features of cationic surfactant such as emulsifying functions and making fabric soft, antistatic etc. Therefore, it indeed caters to the future trends of detergent’s functional requirements with the application of 1227 in liquid detergent formulation. Chen Youhong[2]and Zhang Hui[3]developed bacteriostatic liquid detergent formulations with 1227 in 1999 and 2013 respectively.However, none of them did evaluate the application performance of 1227. Because of this and considering the compatibility of cationic and anionic surfactants at the same time, in this paper, based on cationic-nonionic surfactant systems, the application and effect of 1227 in liquid detergent formulation was studied systematically.

Materials and methods

Materials

Polyethoxylated (7) fatty alcohols (AEO7, Dow Chemical Company, USA), Alkyl polyglucoside (APG 1214, 50%, Shanghai Fine Chemical Company, China),Fatty amide propyl amine oxide (CAO-35, 30%,Zhongshan Kemei Oil Chemical Company, China),Dodecyl dimethyl benzyl ammonium chloride (1227,45%, Taiyuan Finechem Chemical Company, China), Test cloths*(National Standardization Center of Surfactant and Detergent, China), Strains (Escherichia coli 8099 and Staphylococcus aureus ATCC 6538, China General Microbiological Culture Collection Center, China),Strains Mediums (Nutrient agar, Beijing Aoboxing Biotech Company, China), Other materials such as Sodium citrate, Ethylene diamine tetraacetic acid disodium(EDTA), Sodium chloride (NaCl), Preservative (KF-88*,10%), Perfume and Bacteriostatic laundry detergent were abtained from market.

In this paper, test cloths include carbon black grease cloth (JB-01), albumenized cloth (JB-02) and sebum cloth(JB-03), whose ingredients and methods of preparation are introduced in GB/T 13174-2008 Determination of detergency and cycle of washing property for laundry detergents.

KF-88 is mixture of Methylchloroisothiazolinone(CMIT) and Methylisothiazolinone (MIT) in a ratio of 1∶9, and the total concentration of two substances is 10% (wt).

Instruments

Ross-Miles and Vertical cleaner (RHLQ-III) were purchased from China Research Institute of Daily Chemical Industry, Fluorescence photometer (WSD-3C) was purchased from Beijing Kangguang Company,Incubator(LRH-150B) was purchased from Guangdong Medical Instrument Company.

Preparation of bacteriostatic laundry detergent

According to the formulation listed in Table 1 and the following procedure, the bacteriostatic laundry detergent was prepared. First of all, deionized water was added to mixing tank with agitation. Then, AEO7, APG1214,CAO-35 and 1227 were added in turn. Next, the liquid was heated to 40～50℃, stirring, ensure that all the materials dissolved fully. Afterward, sodium citrate,EDTA and KF-88 were added one after another. when the temperature of the mixture decreased below 30℃,the perfume was added. Finally, the product viscosity was adjusted with NaCl, the sample may be used after 8 hours. In order to confirm the antimicrobial performance of 1227, using the same method, bacteriostatic laundry detergent without preservative KF-88 was prepared too.

Table 1. Formulation of self-prepared bacteriostatic laundry detergent

Measurement and evaluation of sensory and physiochemical indices

The sensory and physiochemical indices of bacteriostatic laundry detergent were measured and evaluated referring to literature [4]*, the content of anionic or cationic surfactants in formulation was measured referring to literature [5] and [6].

Measurement [7]＊ and evaluation [4] of detergency

The test solution of 0.2% (wt) of self-prepared bacteriostatic laundry detergent and market product with similar functions were prepared by using standard hard water*separately, the detergency of two samples was measured at (30 ± 1) ℃. The results were expressed as decontamination ratio (the value of standard detergent is 1), the standard requires that the ratio of liquid laundry detergent must be greater than 1, and the greater the ratio, the stronger the detergency and the better decontamination performance.

Measurement of foaming performance [8]*

The test solution of 0.25% (wt) of self-prepared bacteriostatic laundry detergent and market product with similar functions were prepared by using standard hard water separately, the foaming performance of two samples were measured at (40 ± 0.5) ℃. The foam height at 0.5,3 and 5 min were recorded sequentially after the test solution was discharged.

Measurement [9]＊ and evaluation [10]＊ of antimicrobial performance

(1) The experimental strains on nutrient agar were cultured at 37℃ in incubator for 24 hours.

(2) Using 0.03 mol/L phosphate buffer solution (PBS)to clean (1), and bacterial suspension with concentration of 5×105～5×106cfu/mL was prepared.

(3) Aqueous solution of 1% (wt) of bacteriostatic laundry detergent as well as blank solution was prepared and 5 mL removed in sterile test tube (4 for each sample)separately.

(4) The bacterial suspension (2) of 100 μL was removed using pipette and added to each solution (3)respectively, mixed, after 2, 5, 10 and 20 min, the mixed solution of 0.5 mL was removed and placed in tube containing PBS of 5 mL sequentially, mixed.

(5) Solution of (4) was diluted again and again using PBS. Finally, 0.5 mL solution with concentration of 1×10～2×102cfu/mL(theoretical dilution concentration of blank sample) was removed, inoculated and cultured on nutrient agar with the pouring method for 48 h at 37℃,bacteria colony was counted and the antibacterial rate was calculated.

The experiment was repeated 3 times, taking arithmetic mean value of antibacterial rate of each sample. The higher the value, the better the antibacterial performance and the standard requires that the antibacterial rate of bacteriostatic laundry detergent must be higher than 50%.

Evaluation of practical application performance

The test was performed on underwears by hand washing at room temperature and filling out questionnaires. 150 volunteers were selected, of which the ratio of men to women was 19∶56. Among those volunteers, there were 40 persons whose age were below 25, 70 persons between the age of 25～45 and 40 persons over age 45. 200 mL (50～70 pieces of underwears can be washed in general) of self-prepared bacteriostatic laundry detergent as well as market product with similar functions respectively, and a questionnaire whose survey items including detergency, foaming performance, degree of easy rinsing, skin irritation and degree of comfort of clothes after washing were provided to each volunteer. Trial period was 15 days, and the results were represented by 5 points system, the higher the score,the higher the satisfaction.

Results and discussion

Sensory and physiochemical indices

Sensory and physiochemical indices of self-prepared bacteriostatic laundry detergent and market product with similar functions are shown in Table 2. The results show that all indices of the self-prepared bacteriostatic laundry detergent formulated with 1227 meet requirements specified in QB/T 1224-2012. Furthermore, it is to be noted that the pH value of self-prepared bacteriostatic laundry detergent is closer to neutrality, so it is more gentle on clothes and skin.

Table 2. Sensory and physiochemical indices of different kinds of bacteriostatic laundry detergent

Detergency

Detergency of self-prepared bacteriostatic laundry detergent and market product with similar functions are shown in Table 3. The results show that detergency of selfprepared bacteriostatic laundry detergent formulated with 1227 is slightly worse than market product with similar functions, this is consistent with the theoretical basis which the cationic surfactant is generally worse than the anionic surfactant. Analyzed the total active substance with 20.45% and 18.73% respectively of self-prepared bacteriostatic laundry detergent and market product with similar functions, it can be concluded that the detergency of product may meet the requirements of QB/T 1224-2012 by increasing the total active substance of formulation.Obviously, the cost of self-prepared bacteriostatic laundry detergent is about 20% higher than that product with similar functions and whose formulation is anionicnonionic surfactant systems. Nevertheless, as functional washing product, antibacterial performance is more important to consumers, according to the excellent antibacterial performance shown in Table 5, the selfprepared bacteriostatic laundry detergent has higher costperformance. As has been noted, it is feasible to develop detergent formulation of cationic-nonionic surfactant systems.

Table 3. Detergency of different kinds of bacteriostatic laundry detergent

Foaming performance

Foaming performance of self-prepared bacteriostatic laundry detergent and market product with similar functions are shown in Table 4. The results show that the foam of self-prepared bacteriostatic laundry detergent formulated with 1227 is far lower than market product with similar functions, and self-prepared bacteriostatic laundry detergent defoam fast, belonging to low foam and easy rinsing product. This indicates that foaming performance can be optimized with application of 1227 in laundry detergent formulation, the defect of high foam of detergent can be overcame by combination of cationic and nonionic surfactant instead of anionic and nonionic surfactant. This conclusion provides a new idea for formulation designer to develop low foam detergent. It can reduce the excessive dependence on defoaming agents in the design of low foam detergent formulations.

Table 4. Foaming performance of different kinds of bacteriostatic laundry detergent

Antimicrobial performance

The antimicrobial performance of self-prepared bacteriostatic laundry detergent and market product with similar functions was determined. The results are shown in Table 5. The results show that the antibacterial rate of aqueous solution of 1% mass fraction of selfprepared bacteriostatic laundry detergent for 2 min on Escherichia coli and Staphylococcus aureus may reach 94.51% and 100% respectively, and both reached 100%by 20 min, which is far higher than that of 39.43% and 65.02% of market product with similar functions on the same conditions (the bacteriostatic laundry detergent purchased from market declares that it’s target is only for Staphylococcus aureus). This indicates that self-prepared bacteriostatic laundry detergent formulated with 1227 has strong antimicrobial effect against Escherichia coli and Staphylococcus aureus. Also, we can make a conclusion that Escherichia coli is more bactericide resistance than Staphylococcus aureus from Table 5. This explains the reason of why the bacteriostatic laundry detergent purchased from market has only effect on Staphylococcus aureus, the limitation of bacteriostatic laundry detergent with anionic-nonionic systems was illustrated. In addition,from Table 5, it is to be noted that the preservative KF-88 has no obvious antimicrobial effect on two strains under the experimental conditions. This indicates that the antibacterial functions of bacteriostatic laundry detergent can be realized only by professional bactericide instead of preservative. In view of the fact that the preservatives are additives that prevent the growth of bacteria, while the total amount of preservatives used are usually no more than 0.5% (wt) in formulation.[11]Therefore, preservatives have limited inhibitor effects on extremely small bacterial colonies.

Table 5. Antibacterial performance of different kinds of bacteriostatic laundry detergent

Put the self-prepared bacteriostatic laundry detergent formulated with 1227 in 37～40℃ thermostat for 3 months, the antibacterial rate on Escherichia coli and Staphylococcus aureus was determined again. The results show (Table 6) that after 3 months of accelerated experiment, the antibacterial rate on two strains of selfprepared bacteriostatic laundry detergent was still greater than 90%. Thus, according to QB/T 2738-2012, we can judge that the antimicrobial effect of bacteriostatic laundry detergent formulated with 1227 is valid for 2 years.

Table 6. Accelerated test results for antibacterial performance of self-prepared bacteriostatic laundry detergent

Practical application performance

At the end of the 15-day trial period, the arithmetic mean of each item was obtained by analyzing the 141 returned questionnaires. The results are shown in Table 7.

Table 7. Trial results of different kinds of bacteriostatic laundry detergent

The results show that detergency, the scores of other items were higher than that of market product with similar functions. Especially, the scores of “easy rinse”and “skin irritation” were close to 5 points. This indicates that the self-prepared bacteriostatic laundry detergent containing 2% (wt) of 1227 has no obvious irritative effect to human skin. Particularly, the results in Table 7 show that the bacteriostatic laundry detergent formulated 1227 has low foam, easy rinse, and softening fabric property.In the background of that antibacterial performance,detergency, safety and consumer’s demands for products with anionic-nonionic surfactant systems has not yet been fully unified, it is a valuable way to develop an efficient,multifunctional and composite antibacterial detergent by application of 1227 in formulation without anionic surfactant.

Conclusions

In formulation without anionic surfactant, all indices of laundry detergent formulated with 1227 can meet requirements specified in relevant standards, and the foam of product is moderate and easy to rinse.

Bacteriostatic laundry detergent formulated with 1227 has strong antimicrobial performance and the effects can last long. And the bacteriostatic laundry detergent containing 2% of 1227 has no obvious irritative effect to human skin.

[1] Li Pengfei; Wang Donghai; Wang Yan; et al. Study on test methods of active matter content of 1227. Proceedings of the Symposium and 34thAnnual Meeting of Chinese Water Treatment Technology. 2014, 316-318.

[2] Chen Youhong. Ultra concentrated phosphorus free antibacterial disinfectant liquid laundry detergent. ZL. Pat.,CN 1222566A 1999-07-14.

[3] Zhang Hui; Li Wenbin. A kind of sterilizing liquid detergent formulated with anion and cation surfactant and preparation method thereof. ZL. Pat, CN 103194326A 2013-07-10.

[4] QB/T 1224-2012: Liquid detergent for fabric. Beijing: Ministry of Industry and Information Technology of the People’s Republic of China, 2012.

[5] GB/T 5173-1995: Surface active agents and detergentsdetermination of anionic-active matter by direct two-phase titration procedure. Beijing: General Administration of Technology Supervision, 1995.

[6] GB/T 5174-2004: Surface active agents-detergentsdetermination of cationic-active matter content. Beiing:General Administration of Quality Supervision, Inspection and Quarantine of the People’s Republic of China / Standardization Administration of the People’s Republic of China, 2004.

[7] GB/T13174-2008: Determination of detergency and cycle of washing property for laundry detergents. Beijing: General Administration of Quality Supervision, Inspection and Quarantine of the People’s Republic of China / Standardization Administration of the People’s Republic of China, 2008.

[8] GB/T7462-94: Surface active agents-measurement of foaming power-modified Ross-Miles method. Beijing: General Administration of Technology Supervision, 1994.

[9] QB/T2850-2007: The antibacterial and bacteriostatic detergent. Beijing: National Development and Reform Commission of the People’s Republic of China, 2007.

[10] QB/T2738-2012: Test methods for evaluating daily chemical products in antibacterial and bacteriostatic efficacy. Beijing:Ministry of Industry and Information Technology of the People’s Republic of China, 2012.

[11] He Xiaorong. Requirements and efficacy validation of preservatives for liquid household detergents. Detergent &Cosmetics, 2014, 37(10), 43-48.