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acrylic acid) and its application in leather finishing agent
European Polymer Journal 44 (2008) 2695–2701
Contents lists available at ScienceDirect
European Polymer Journal journal homepage: www.elsevier.com/locate/europolj
Synthesis of alkali-soluble copolymer (butyl acrylate/acrylic acid) and its application in leather finishing agent Jing Hu *, Jianzhong Ma, Weijun Deng College of Resource and Environment, Shaanxi University of Science and Technology, Xi’an, Shaanxi 710021, People’s Republic of China
a r t i c l e
i n f o
Article history: Received 29 November 2007 Received in revised form 16 May 2008 Accepted 21 May 2008 Available online 3 July 2008
Keywords: Alkali-soluble copolymer Synthesis Leather finishing agent Emulsifier
a b s t r a c t Alkali-soluble copolymer (butyl acrylate/acrylic acid) was synthesized via solution polymerization and used as the emulsifier to prepare acrylic resin for leather finishing agent. The influence of the synthetic conditions, such as the contents of acrylic acid and the initiator types on the properties of P(BA/AA) was investigated in detail. Fourier Transform Infrared Spectrometer (FTIR) indicated that the polymerization reaction of P(BA/AA) was complete without ‘‘AC@CA” absorption peak. Differential Scanning Calorimeters (DSC) analysis confirmed that the glass transition temperature (Tg) of P(BA/AA) was 44 °C, Transmission Electron microscope (TEM) indicated that the copolymer latex particles dispersed evenly and were less than 100 nm. Moreover, in contrast to acrylic resin prepared with sodium dodecylsulfate (SDS) and alkylphenol ethoxylates (OP-10) as the emulsifiers, the applied properties of light leather finished by acrylic resin in use of P(BA/AA) as the emulsifier were measured: The air permeability increased by 18.5% as well as the waterresistance by 28.08% and the wet rub fastness by half class, respectively. Ó 2008 Elsevier Ltd. All rights reserved.
1. Introduction With the improvement of the environment safeguards and the finishing materials requirement, water-soluble finishing materials has become the research hotspot in the leather finishing agent. However, the water-solubility finishing agent prepared via the conventional emulsion polymerization also exhibited the disadvantages [1]: the large use of small molecular surfactants pollute the environment and limit the finishing materials properties such as the freezing stability, the mechanical stability, the wet and dry rubbing resistance and so on. In order to avoid these disadvantages, The polymer surfactants was applied to the emulsion polymerization [2–9]. Liu et al. [3] reported that the alkali-soluble copolymer P(methyl methacrylate/ethyl acrylate/methacrylic) was used to synthesize the emulsion polymerization of n-butyl methacrylate as the surfactants and the nucleus-shell latexes * Corresponding author. Tel./fax: +86 29 86132559. E-mail address: [email protected] (J. Hu). 0014-3057/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.eurpolymj.2008.05.016
of 40–80 nm were obtained. Sun et al. [4] prepared a novel macromolecule surfactant of PS21-acrylamide/acrylic acid/MMA copolymer via the homogeneous polymerization. Muller et al. [5] used polyelectrolyte block copolymers to prepare the emulsion of 100 nm. Doug et al. [6] studied the preparation of PBA emulsion in the presence of polystyrene/a-methylphenylene/AA copolymer; Satoshi et al. [7] investigated the kinetic process of styrene emulsion polymerization with MMA/methacrylic acid copolymer as the emulsifiers. Although the results that the properties of the macromolecule emulsifiers are better than low-molecular-weight emulsifier have been reported already, the macromolecule emulsifiers usually have be used after the purification. In a word, the process seems to be time-consuming. If the mixture of the macromolecule emulsifiers with the excellence emulsifier property was obtained without the separation, this will be useful for the industry manufacture. In this paper, the mixture of the macromolecule emulsifiers synthesized via solution polymerization without any purification ways was employed to be copolymerized with
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J. Hu et al. / European Polymer Journal 44 (2008) 2695–2701
acrylate monomers for preparing leather finishing agent directly. Besides, the influence of synthesized conditions such as the contents of AA and the different initiator types on the physical properties of alkali-soluble copolymer (BA/ AA) was investigated in detail. At last, acrylic resin prepared with P (BA/AA) as the emulsifier was applied in leather finish and the applied properties were determined.
2. Experimental 2.1. Materials Acrylic acid (AA), kalium persulfate (KPS), sodium bisulphite (NaHSO3), iso-propyl alcohol (IPA), MMA, BA, ammonium persulfate (APS), sodium thiosulfate (Na2S2O3) and sodium hydroxide (NaOH) were all purchased from Tianjin No. 3 Chemical Reagent Factory and used without further purification; Sodium dodecylsulfate (SDS) and alkylphenol ethoxylates (OP-10) were bought from China Research Institute of Daily Chemical Industry. Deionized water was applied for the polymerization processes. APV (cationic aromatic polyurethane), black pigment and black dye liquid were industry class and provided by Lanxsess LTd. 2.2. Preparation of alkali-soluble copolymer (BA/AA) A 250-mL 3-necked round-bottom flask was equipped with a reflux condenser, a thermometer and a magnetic stirring bar. The reactor flask, charged with dionized water (60 g), AA (variable) and BA (5.00 g) were immersed in a water bath at 82 °C. It was stirred at 350 rpm for 20 min. Then 10 g aqueous solution of variable initiators (1.5 wt%) was added to the flask. The reaction was kept at the same temperature for 1.5 h and pH was adjusted to 7.0 using an aqueous solution of NaOH (20 wt%). 2.3. Preparation of acrylic resin emulsion 1# Acrylic resin: A 250-mL 3-necked round-bottom flask was equipped with a reflux condenser, a thermometer and a magnetic stirring bar. The reactor flask charged with 70 g of latex including water and P (BA/AA) was heated to 80 °C in a water bath. It was stirred at 350 rpm for 20 min. Then, the polymerization was started with 10 g aqueous solution of KPS (1.5 wt%) and the mixture of MMA (10 g) and BA(6 g) monomers added dropwise and finished within 1 h. The reaction was kept at 85 °C for 2 h. 2# Acrylic resin: A 250-mL 3-necked round-bottom flask was equipped with a reflux condenser, a thermometer and a magnetic stirring bar. The reactor flask charged with 2 g of SDS, OP-10 (the molar ratio of SDS and OP-10 is 1:2) and deionized water (40 g) were heated to 50 °C for 20 min; After the mixture of MMA (3 g) and BA (2 g), 5 g aqueous solution of KPS (1 wt%) were charged to the reactor for 30 min at 80 °C. Then, the polymerization was started with 15 g aqueous solution of KPS (1 wt%) and the mixture of MMA (12 g) and BA (6 g) added dropwise and finished within 1 h. The reaction was kept at 85 °C for 2 h.
2.4. The application in the leather finishes Acrylic resin leather finishing agent (1#) prepared with the emulsifier of copolymer P(BA/AA) and conventional acrylic resin (2#) prepared with the emulsifiers of SDS and OP-10 were applied in the parallel leather finish experiments. Then the applied properties of the leather after finished were determined. The formula of leather finished was shown in Table 1. Operations: The mixture of aqueous solution of ammonia (15 N), anhydrous ethanol and water were used to clean the crust in the ratio 3:2:95 (mass ratio). The leather was sprayed once with the prebase coat materials and hung up. Then the same procedure as outlined above was followed with the base coat materials (total mass of the finishing materials: 9 g). 2.5. Determination of applied property Measurement of water vapor permeability: In accordance with method DIN EN 14268, DIN 53333*, IUP 15. Measurement of water resistance of light leathers: In accordance with reference [10,11]. Measurement of fastness to rubbing (wet and dry) of light leathers: In accordance with method DIN EN ISO 11640, DIN 53339*, IUF450. Measurement of flexing endurance of light leathers: In accordance with method IUP20. 2.6. Characterization 2.6.1. Thermogravimetric analysis (TGA) Thermogravimetric analysis (TGA) was performed using a PerkinElmer thermogravimetric analyzer under a stream of air. P(BA/AA) films were heated from 50 °C to 800 °C at a scanning speed of 10 °C/min. 2.6.2. FTIR analysis Fourier transform infrared spectrometer (FTIR) analysis of P(BA/AA) film after purification, BA and AA were performed by VETOR-2 FTIR (Bruker Company in German). 2.6.3. Thermal analysis (DSC) Differential Scanning Calorimeters analysis was carried out on SHIMADZU DSC-204 (Netzsch Company in German). The samples were quickly cooled to 100 °C and equilibrated at that temperature for 3 min, then heated to 100 °C at the scan rate of 10 °C/min under nitrogen atmosphere.
Table 1 Formula of leather finishes
APV(Cationic Polyu’ethane) H20 IPA(iso-Propy1 alcohol) Black pigment Black dye liquid Resin
Prebase coat/g
Base coat/g
100 250 10
350 100 20 300
Resins of two base coat formulas were 1# acrylic resin and 2# acrylic resin dividedly. Crust material: black cow crust.
J. Hu et al. / European Polymer Journal 44 (2008) 2695–2701
2.6.4. TEM analysis Emulsion of P(BA/AA) after the phosphomolybdic acid coloration was observed by JEM-10OCXII TEM (JOEL company in Japan). 3. Results and discussion 3.1. Surface tension analysis The influence of AA amount and the initiator type on the surface tension of alkali-soluble copolymer was investigated during the preparation of P(BA/AA). The surface tension of alkali-soluble copolymer (BA/AA) is dependent upon the contents of AA, which belongs to the strong hydrophilic polyacrylic acid and sodium polyacrylate used as the hydrophilic groups of the surfactants [12]. When the copolymer (BA/AA) molecule assembles the surface layer between air and liquid state, the polar groups of copolymer (BA/AA) can interact with H2O molecule but their non-polar groups extend outside, which decreases the interface area of air and liquid state and the surface tension of the solution. Besides, the remnant sulfate ion of initiators after polymerization initiated can become the polar end group of copolymer like the polymer emulsifiers. Fig. 1 shows that the surface tension of alkali-soluble copolymer (BA/AA) increases with the contents of AA rising, when the initiators of APS/NaHSO3 and KPS/NaHSO3 are used during the preparation. This is because that the interaction between the hydrophilic group (ACOOH) of copolymer and H2O molecule increases the interface area of air and liquid state. But the surface tension of alkali-soluble copolymer (BA/AA) with the initiators of APS/Na2S2O3 and KPS/Na2S2O3 decreases, which belongs to the different reducers. 3.2. Instability analysis Fig. 2 displays that the instability of P(BA/AA) with different initiators is dependent on the contents of AA. This is
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because the increase of the contents of AA leads to the improvement of the system interface area and the surface Gibbs function. Besides, with the hydrophilic groups in P(BA/AA) rising, the copolymer molecule cannot be effectively adsorbed the interface layer between the air and liquid state to form the interface film. Fig. 2 also demonstrates that the stability of P(BA/AA) is best using oxidation–reduction initiator system of APS, which is attributed to the only sodium ion after the copolymer neutralized by NaOH. However, the stability of P(BA/ AA) using oxidation–reduction initiator system of KPS is low. In conclusion, the different cations influence the stability of P(BA/AA) drastically, which belongs to more water molecules accompanied by Na+ and larger electrostatic repulsive force caused by the hydrated cation(Na+). 3.3. TGA analysis Fig. 3 and Table 2 demonstrate the thermogravimetric analysis (TGA) curves of P(BA/AA) with different AA amount and the initiator of KPS and NaHSO3 (samples a, b, c, d in Fig. 3). Three weight-loss stages are observed for P(BA/AA). These correspond to the evaporation of physically adsorbed water, the decomposition of P(BA/AA), and the decomposition of P(BA), respectively. With the contents of AA increased, the amount of P(BA/AA) increases but the amount of P(BA) decrease. Fig. 3 also shows that the weight of P(BA/AA) decreases at lower temperature for P(BA/AA) with higher content of AA. 3.4. FTIR analysis The structures of alkali-soluble copolymer (BA/AA), BA monomer and AA monomer shown in Fig. 4 display that BA and AA were copolymerized completely. In P(BA/AA) curve, the unsaturated carbonous bonds monomers have been copolymerized completely without the extending vibration of C@C absorption peak 1680–1620 cm 1. The
Fig. 1. Effect of AA contents and initiator types on the surface tension of P(BA/AA).
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Fig. 2. Effect of AA contents and initiator types on the instability of P(BA/AA).
Fig. 3. TGA ana1ysis (a-0.3AA, b-0.9AA, c-1.5AA, d-2.1AAt1; the initiator of KPS/NaHSO3).
Table 2 TGA results of P(BA/AA) AA(g)
The first weight loss (wt%)
The second weight loss (wt%)
The third weight loss (wt%)
0.3
16.68 (below 289.4 °C) 10.54 (below 266.989 °C) 10.77 (below 221.16 °C) 10.863 (below 202.63 °C)
55.18 (289.4–432.63 °C) 70.25 (266.98–455.69 °C)
16.78 (432.63–657.43 °C) 11.45 (455.699– 695.28 °C) 7.84 (464.39–670.21 °C) 5.4 (471.38–687.05 °C)
0.9
1.5 2.1
74.65 (221.16–464.39 °C) 75.86 (202.63–471.38 °C)
wide absorption peak 3000 cm 1 and the absorption peak 2600–2800 cm 1 of ACOOH are disappeared and instead of another wide absorption peak 3836 cm 1 of P(BA/AA) affected by extending vibration of AOH. The absorption peak 1733 cm 1 belongs to the extending vibration of C@O and the absorption peak 2872 cm 1 is the extending vibration of ACH3. 3.5. DSC analysis Fig. 5 shows that there is the only glass transition temperature (Tg = 44 °C) in alkali-soluble copolymer P(BA/
J. Hu et al. / European Polymer Journal 44 (2008) 2695–2701
AA), which may be that of P(BA/AA) and P(BA) mixtures. Based on FOX Formulation, the glass transition temperatures (Tg) of P(BA/AA) with 0.3 g AA and the initiator of KPS/NaHSO3 calculated is about 45.7 °C. The glass transition temperature of PBA is 54 °C. 3.6. TEM analysis Fig. 6 demonstrates that the latex particles of alkali-soluble copolymer(BA/AA)is kept below 100 nm and disperses even, which is because the addition of AA increase the hydrophilic groups of the emulsifiers and ensure the
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water–oil latex particles formed during the early period of the copolymer. 3.7. Applied properties Table 3 demonstrates that the physical mechanical properties of light leather finished by acrylic resin using P(BA/AA) as the emulsifier was improved evidently in contrast to the conventional emulsifiers such as the water resistance increased by 28.08% and the water vapor permeability improved by 18.5%. Besides, the wet rubbing fastness is improved by half class. The reason for these is
Fig. 4. FTIR analysis (a-AA, b-BA, c-P (BA/AA); AA = 0.3 g, KPS/NaHSO3).
Fig. 5. DSC analysis of P(BA/AA) (AA = 0.3 g, KPS/NaHSO3.
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Fig. 6. TEM analysis of P(BA/AA) (AA = 0.3 g, the initiator of KPS/NaHSO3).
Table 3 Physical and mechanical properties of finished leather Type
Leather finished by 1# acrylic resin Light leather finished by 2# acrylic resin Ratio in contrast to 2# acrylic resin
Water vapor permeability ml (cm2 h)
Water resistance (the quality of leather after 0.25/h water uptaking)
Dry rubbing fastness class
Wet rubbing fastness class
Flexing endurance
Perfect coating after 100,000 Times flex Perfect coating after 100,000 Times flex 0
1.99
67.49
4/5
1/2
1.68
93.84
4/5
3
28.08%
0
0.5
18.5%
that acrylic resin prepared by the emulsifier of alkali-soluble copolymer (BA/AA) avoids the water-uptaking reaction of the small surfactants and the obtained film is even and transparent.
use of P(BA/AA)as the emulsifier were measured: The air permeability increased by 18.5% as well as the water-resistance by 28.08% and the wet rub fastness by half class, respectively.
4. Conclusion
Acknowledgements
Alkali-soluble copolymer (BA/AA) was synthesized via solution polymerization and used as the emulsifier to prepare acrylic resin for leather finishing agent. The properties of the copolymer P(BA/AA) are dependent on the synthetic conditions, such as the contents of acrylic acid and the initiator types. Fourier Transform Infrared Spectrometer (FTIR) indicated that the polymerization reaction of P(BA/ AA) was complete without ‘‘AC@CA” absorption peak. Differential Scanning Calorimeters (DSC) analysis confirmed that the glass transition temperature (Tg) of P(BA/AA) was 44 °C, Transmission Electron microscope (TEM) indicated that the copolymer latex particles dispersed evenly and were less than 100 nm. Moreover, in contrast to acrylic resin prepared with sodium dodecylsulfate (SDS) and alkylphenol ethoxylates (OP-10) as the emulsifiers, the applied properties of light leather finished by acrylic resin in
This investigation was supported by National 863 Foundation (Item No.: 2008AA03Z311), National Natural Science Foundation (Item No.: 20674047) and the Team Work Project of Science Innovation of Shaanxi University of Science and Technology (Item No.: SUST-A03). References [1] Zhang GY, Liu XH. Leath Chem 2003;20(4):6–11. [2] Cao TY, Liu QP, Hu JS. Synthesis theory and application of polymer emulsion. Beijing: Chemical Industry Press; 1997. [3] Liu J, Zheng C, Ding XB, et al. Acta Polymerica Sinica 2005;1:149–52. [4] Sun LL, Yang X, Yang SG. J Southwest Petrol Univ 2006;4(4):52–5. [5] Muller H, Leube W, Tauer K, et al. Macromolecules 1997;30:2288–93. [6] Doug YL, Young JP, Mei CK, et al. Macromolecules 2000;151:479–85. [7] Satoshi Kato, Kiyoshi Suzuki, Mamoru Nomura. European Polym 2005;33:1–15.
J. Hu et al. / European Polymer Journal 44 (2008) 2695–2701 [8] Doug YL, Jin SS, Young JP, et al. Surf Interface Anal 1999;28:28–35. [9] Zhang MG, Weng ZX, Huang ZM, et al. European Polym J 1998;34(9):1243–7. [10] Pan JS, Yang ZS. Leather analysis and measurement. Beijing: China Light Industry Press; 1979.
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[11] National Quality Standards, Department of Light Industry Bureau. China light industry standards of leather, Beijing: China Standards Press; 1999. [12] Zhang GX. Principle of the surfactants. Beijing: China Light Industry Press; 2003.
Contents lists available at ScienceDirect
European Polymer Journal journal homepage: www.elsevier.com/locate/europolj
Synthesis of alkali-soluble copolymer (butyl acrylate/acrylic acid) and its application in leather finishing agent Jing Hu *, Jianzhong Ma, Weijun Deng College of Resource and Environment, Shaanxi University of Science and Technology, Xi’an, Shaanxi 710021, People’s Republic of China
a r t i c l e
i n f o
Article history: Received 29 November 2007 Received in revised form 16 May 2008 Accepted 21 May 2008 Available online 3 July 2008
Keywords: Alkali-soluble copolymer Synthesis Leather finishing agent Emulsifier
a b s t r a c t Alkali-soluble copolymer (butyl acrylate/acrylic acid) was synthesized via solution polymerization and used as the emulsifier to prepare acrylic resin for leather finishing agent. The influence of the synthetic conditions, such as the contents of acrylic acid and the initiator types on the properties of P(BA/AA) was investigated in detail. Fourier Transform Infrared Spectrometer (FTIR) indicated that the polymerization reaction of P(BA/AA) was complete without ‘‘AC@CA” absorption peak. Differential Scanning Calorimeters (DSC) analysis confirmed that the glass transition temperature (Tg) of P(BA/AA) was 44 °C, Transmission Electron microscope (TEM) indicated that the copolymer latex particles dispersed evenly and were less than 100 nm. Moreover, in contrast to acrylic resin prepared with sodium dodecylsulfate (SDS) and alkylphenol ethoxylates (OP-10) as the emulsifiers, the applied properties of light leather finished by acrylic resin in use of P(BA/AA) as the emulsifier were measured: The air permeability increased by 18.5% as well as the waterresistance by 28.08% and the wet rub fastness by half class, respectively. Ó 2008 Elsevier Ltd. All rights reserved.
1. Introduction With the improvement of the environment safeguards and the finishing materials requirement, water-soluble finishing materials has become the research hotspot in the leather finishing agent. However, the water-solubility finishing agent prepared via the conventional emulsion polymerization also exhibited the disadvantages [1]: the large use of small molecular surfactants pollute the environment and limit the finishing materials properties such as the freezing stability, the mechanical stability, the wet and dry rubbing resistance and so on. In order to avoid these disadvantages, The polymer surfactants was applied to the emulsion polymerization [2–9]. Liu et al. [3] reported that the alkali-soluble copolymer P(methyl methacrylate/ethyl acrylate/methacrylic) was used to synthesize the emulsion polymerization of n-butyl methacrylate as the surfactants and the nucleus-shell latexes * Corresponding author. Tel./fax: +86 29 86132559. E-mail address: [email protected] (J. Hu). 0014-3057/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.eurpolymj.2008.05.016
of 40–80 nm were obtained. Sun et al. [4] prepared a novel macromolecule surfactant of PS21-acrylamide/acrylic acid/MMA copolymer via the homogeneous polymerization. Muller et al. [5] used polyelectrolyte block copolymers to prepare the emulsion of 100 nm. Doug et al. [6] studied the preparation of PBA emulsion in the presence of polystyrene/a-methylphenylene/AA copolymer; Satoshi et al. [7] investigated the kinetic process of styrene emulsion polymerization with MMA/methacrylic acid copolymer as the emulsifiers. Although the results that the properties of the macromolecule emulsifiers are better than low-molecular-weight emulsifier have been reported already, the macromolecule emulsifiers usually have be used after the purification. In a word, the process seems to be time-consuming. If the mixture of the macromolecule emulsifiers with the excellence emulsifier property was obtained without the separation, this will be useful for the industry manufacture. In this paper, the mixture of the macromolecule emulsifiers synthesized via solution polymerization without any purification ways was employed to be copolymerized with
2696
J. Hu et al. / European Polymer Journal 44 (2008) 2695–2701
acrylate monomers for preparing leather finishing agent directly. Besides, the influence of synthesized conditions such as the contents of AA and the different initiator types on the physical properties of alkali-soluble copolymer (BA/ AA) was investigated in detail. At last, acrylic resin prepared with P (BA/AA) as the emulsifier was applied in leather finish and the applied properties were determined.
2. Experimental 2.1. Materials Acrylic acid (AA), kalium persulfate (KPS), sodium bisulphite (NaHSO3), iso-propyl alcohol (IPA), MMA, BA, ammonium persulfate (APS), sodium thiosulfate (Na2S2O3) and sodium hydroxide (NaOH) were all purchased from Tianjin No. 3 Chemical Reagent Factory and used without further purification; Sodium dodecylsulfate (SDS) and alkylphenol ethoxylates (OP-10) were bought from China Research Institute of Daily Chemical Industry. Deionized water was applied for the polymerization processes. APV (cationic aromatic polyurethane), black pigment and black dye liquid were industry class and provided by Lanxsess LTd. 2.2. Preparation of alkali-soluble copolymer (BA/AA) A 250-mL 3-necked round-bottom flask was equipped with a reflux condenser, a thermometer and a magnetic stirring bar. The reactor flask, charged with dionized water (60 g), AA (variable) and BA (5.00 g) were immersed in a water bath at 82 °C. It was stirred at 350 rpm for 20 min. Then 10 g aqueous solution of variable initiators (1.5 wt%) was added to the flask. The reaction was kept at the same temperature for 1.5 h and pH was adjusted to 7.0 using an aqueous solution of NaOH (20 wt%). 2.3. Preparation of acrylic resin emulsion 1# Acrylic resin: A 250-mL 3-necked round-bottom flask was equipped with a reflux condenser, a thermometer and a magnetic stirring bar. The reactor flask charged with 70 g of latex including water and P (BA/AA) was heated to 80 °C in a water bath. It was stirred at 350 rpm for 20 min. Then, the polymerization was started with 10 g aqueous solution of KPS (1.5 wt%) and the mixture of MMA (10 g) and BA(6 g) monomers added dropwise and finished within 1 h. The reaction was kept at 85 °C for 2 h. 2# Acrylic resin: A 250-mL 3-necked round-bottom flask was equipped with a reflux condenser, a thermometer and a magnetic stirring bar. The reactor flask charged with 2 g of SDS, OP-10 (the molar ratio of SDS and OP-10 is 1:2) and deionized water (40 g) were heated to 50 °C for 20 min; After the mixture of MMA (3 g) and BA (2 g), 5 g aqueous solution of KPS (1 wt%) were charged to the reactor for 30 min at 80 °C. Then, the polymerization was started with 15 g aqueous solution of KPS (1 wt%) and the mixture of MMA (12 g) and BA (6 g) added dropwise and finished within 1 h. The reaction was kept at 85 °C for 2 h.
2.4. The application in the leather finishes Acrylic resin leather finishing agent (1#) prepared with the emulsifier of copolymer P(BA/AA) and conventional acrylic resin (2#) prepared with the emulsifiers of SDS and OP-10 were applied in the parallel leather finish experiments. Then the applied properties of the leather after finished were determined. The formula of leather finished was shown in Table 1. Operations: The mixture of aqueous solution of ammonia (15 N), anhydrous ethanol and water were used to clean the crust in the ratio 3:2:95 (mass ratio). The leather was sprayed once with the prebase coat materials and hung up. Then the same procedure as outlined above was followed with the base coat materials (total mass of the finishing materials: 9 g). 2.5. Determination of applied property Measurement of water vapor permeability: In accordance with method DIN EN 14268, DIN 53333*, IUP 15. Measurement of water resistance of light leathers: In accordance with reference [10,11]. Measurement of fastness to rubbing (wet and dry) of light leathers: In accordance with method DIN EN ISO 11640, DIN 53339*, IUF450. Measurement of flexing endurance of light leathers: In accordance with method IUP20. 2.6. Characterization 2.6.1. Thermogravimetric analysis (TGA) Thermogravimetric analysis (TGA) was performed using a PerkinElmer thermogravimetric analyzer under a stream of air. P(BA/AA) films were heated from 50 °C to 800 °C at a scanning speed of 10 °C/min. 2.6.2. FTIR analysis Fourier transform infrared spectrometer (FTIR) analysis of P(BA/AA) film after purification, BA and AA were performed by VETOR-2 FTIR (Bruker Company in German). 2.6.3. Thermal analysis (DSC) Differential Scanning Calorimeters analysis was carried out on SHIMADZU DSC-204 (Netzsch Company in German). The samples were quickly cooled to 100 °C and equilibrated at that temperature for 3 min, then heated to 100 °C at the scan rate of 10 °C/min under nitrogen atmosphere.
Table 1 Formula of leather finishes
APV(Cationic Polyu’ethane) H20 IPA(iso-Propy1 alcohol) Black pigment Black dye liquid Resin
Prebase coat/g
Base coat/g
100 250 10
350 100 20 300
Resins of two base coat formulas were 1# acrylic resin and 2# acrylic resin dividedly. Crust material: black cow crust.
J. Hu et al. / European Polymer Journal 44 (2008) 2695–2701
2.6.4. TEM analysis Emulsion of P(BA/AA) after the phosphomolybdic acid coloration was observed by JEM-10OCXII TEM (JOEL company in Japan). 3. Results and discussion 3.1. Surface tension analysis The influence of AA amount and the initiator type on the surface tension of alkali-soluble copolymer was investigated during the preparation of P(BA/AA). The surface tension of alkali-soluble copolymer (BA/AA) is dependent upon the contents of AA, which belongs to the strong hydrophilic polyacrylic acid and sodium polyacrylate used as the hydrophilic groups of the surfactants [12]. When the copolymer (BA/AA) molecule assembles the surface layer between air and liquid state, the polar groups of copolymer (BA/AA) can interact with H2O molecule but their non-polar groups extend outside, which decreases the interface area of air and liquid state and the surface tension of the solution. Besides, the remnant sulfate ion of initiators after polymerization initiated can become the polar end group of copolymer like the polymer emulsifiers. Fig. 1 shows that the surface tension of alkali-soluble copolymer (BA/AA) increases with the contents of AA rising, when the initiators of APS/NaHSO3 and KPS/NaHSO3 are used during the preparation. This is because that the interaction between the hydrophilic group (ACOOH) of copolymer and H2O molecule increases the interface area of air and liquid state. But the surface tension of alkali-soluble copolymer (BA/AA) with the initiators of APS/Na2S2O3 and KPS/Na2S2O3 decreases, which belongs to the different reducers. 3.2. Instability analysis Fig. 2 displays that the instability of P(BA/AA) with different initiators is dependent on the contents of AA. This is
2697
because the increase of the contents of AA leads to the improvement of the system interface area and the surface Gibbs function. Besides, with the hydrophilic groups in P(BA/AA) rising, the copolymer molecule cannot be effectively adsorbed the interface layer between the air and liquid state to form the interface film. Fig. 2 also demonstrates that the stability of P(BA/AA) is best using oxidation–reduction initiator system of APS, which is attributed to the only sodium ion after the copolymer neutralized by NaOH. However, the stability of P(BA/ AA) using oxidation–reduction initiator system of KPS is low. In conclusion, the different cations influence the stability of P(BA/AA) drastically, which belongs to more water molecules accompanied by Na+ and larger electrostatic repulsive force caused by the hydrated cation(Na+). 3.3. TGA analysis Fig. 3 and Table 2 demonstrate the thermogravimetric analysis (TGA) curves of P(BA/AA) with different AA amount and the initiator of KPS and NaHSO3 (samples a, b, c, d in Fig. 3). Three weight-loss stages are observed for P(BA/AA). These correspond to the evaporation of physically adsorbed water, the decomposition of P(BA/AA), and the decomposition of P(BA), respectively. With the contents of AA increased, the amount of P(BA/AA) increases but the amount of P(BA) decrease. Fig. 3 also shows that the weight of P(BA/AA) decreases at lower temperature for P(BA/AA) with higher content of AA. 3.4. FTIR analysis The structures of alkali-soluble copolymer (BA/AA), BA monomer and AA monomer shown in Fig. 4 display that BA and AA were copolymerized completely. In P(BA/AA) curve, the unsaturated carbonous bonds monomers have been copolymerized completely without the extending vibration of C@C absorption peak 1680–1620 cm 1. The
Fig. 1. Effect of AA contents and initiator types on the surface tension of P(BA/AA).
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Fig. 2. Effect of AA contents and initiator types on the instability of P(BA/AA).
Fig. 3. TGA ana1ysis (a-0.3AA, b-0.9AA, c-1.5AA, d-2.1AAt1; the initiator of KPS/NaHSO3).
Table 2 TGA results of P(BA/AA) AA(g)
The first weight loss (wt%)
The second weight loss (wt%)
The third weight loss (wt%)
0.3
16.68 (below 289.4 °C) 10.54 (below 266.989 °C) 10.77 (below 221.16 °C) 10.863 (below 202.63 °C)
55.18 (289.4–432.63 °C) 70.25 (266.98–455.69 °C)
16.78 (432.63–657.43 °C) 11.45 (455.699– 695.28 °C) 7.84 (464.39–670.21 °C) 5.4 (471.38–687.05 °C)
0.9
1.5 2.1
74.65 (221.16–464.39 °C) 75.86 (202.63–471.38 °C)
wide absorption peak 3000 cm 1 and the absorption peak 2600–2800 cm 1 of ACOOH are disappeared and instead of another wide absorption peak 3836 cm 1 of P(BA/AA) affected by extending vibration of AOH. The absorption peak 1733 cm 1 belongs to the extending vibration of C@O and the absorption peak 2872 cm 1 is the extending vibration of ACH3. 3.5. DSC analysis Fig. 5 shows that there is the only glass transition temperature (Tg = 44 °C) in alkali-soluble copolymer P(BA/
J. Hu et al. / European Polymer Journal 44 (2008) 2695–2701
AA), which may be that of P(BA/AA) and P(BA) mixtures. Based on FOX Formulation, the glass transition temperatures (Tg) of P(BA/AA) with 0.3 g AA and the initiator of KPS/NaHSO3 calculated is about 45.7 °C. The glass transition temperature of PBA is 54 °C. 3.6. TEM analysis Fig. 6 demonstrates that the latex particles of alkali-soluble copolymer(BA/AA)is kept below 100 nm and disperses even, which is because the addition of AA increase the hydrophilic groups of the emulsifiers and ensure the
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water–oil latex particles formed during the early period of the copolymer. 3.7. Applied properties Table 3 demonstrates that the physical mechanical properties of light leather finished by acrylic resin using P(BA/AA) as the emulsifier was improved evidently in contrast to the conventional emulsifiers such as the water resistance increased by 28.08% and the water vapor permeability improved by 18.5%. Besides, the wet rubbing fastness is improved by half class. The reason for these is
Fig. 4. FTIR analysis (a-AA, b-BA, c-P (BA/AA); AA = 0.3 g, KPS/NaHSO3).
Fig. 5. DSC analysis of P(BA/AA) (AA = 0.3 g, KPS/NaHSO3.
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J. Hu et al. / European Polymer Journal 44 (2008) 2695–2701
Fig. 6. TEM analysis of P(BA/AA) (AA = 0.3 g, the initiator of KPS/NaHSO3).
Table 3 Physical and mechanical properties of finished leather Type
Leather finished by 1# acrylic resin Light leather finished by 2# acrylic resin Ratio in contrast to 2# acrylic resin
Water vapor permeability ml (cm2 h)
Water resistance (the quality of leather after 0.25/h water uptaking)
Dry rubbing fastness class
Wet rubbing fastness class
Flexing endurance
Perfect coating after 100,000 Times flex Perfect coating after 100,000 Times flex 0
1.99
67.49
4/5
1/2
1.68
93.84
4/5
3
28.08%
0
0.5
18.5%
that acrylic resin prepared by the emulsifier of alkali-soluble copolymer (BA/AA) avoids the water-uptaking reaction of the small surfactants and the obtained film is even and transparent.
use of P(BA/AA)as the emulsifier were measured: The air permeability increased by 18.5% as well as the water-resistance by 28.08% and the wet rub fastness by half class, respectively.
4. Conclusion
Acknowledgements
Alkali-soluble copolymer (BA/AA) was synthesized via solution polymerization and used as the emulsifier to prepare acrylic resin for leather finishing agent. The properties of the copolymer P(BA/AA) are dependent on the synthetic conditions, such as the contents of acrylic acid and the initiator types. Fourier Transform Infrared Spectrometer (FTIR) indicated that the polymerization reaction of P(BA/ AA) was complete without ‘‘AC@CA” absorption peak. Differential Scanning Calorimeters (DSC) analysis confirmed that the glass transition temperature (Tg) of P(BA/AA) was 44 °C, Transmission Electron microscope (TEM) indicated that the copolymer latex particles dispersed evenly and were less than 100 nm. Moreover, in contrast to acrylic resin prepared with sodium dodecylsulfate (SDS) and alkylphenol ethoxylates (OP-10) as the emulsifiers, the applied properties of light leather finished by acrylic resin in
This investigation was supported by National 863 Foundation (Item No.: 2008AA03Z311), National Natural Science Foundation (Item No.: 20674047) and the Team Work Project of Science Innovation of Shaanxi University of Science and Technology (Item No.: SUST-A03). References [1] Zhang GY, Liu XH. Leath Chem 2003;20(4):6–11. [2] Cao TY, Liu QP, Hu JS. Synthesis theory and application of polymer emulsion. Beijing: Chemical Industry Press; 1997. [3] Liu J, Zheng C, Ding XB, et al. Acta Polymerica Sinica 2005;1:149–52. [4] Sun LL, Yang X, Yang SG. J Southwest Petrol Univ 2006;4(4):52–5. [5] Muller H, Leube W, Tauer K, et al. Macromolecules 1997;30:2288–93. [6] Doug YL, Young JP, Mei CK, et al. Macromolecules 2000;151:479–85. [7] Satoshi Kato, Kiyoshi Suzuki, Mamoru Nomura. European Polym 2005;33:1–15.
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