The Combination of Itaconic Acid and Sodium Hypophosphite as a

Article pubs.acs.org/IECR

The Combination of Itaconic Acid and Sodium Hypophosphite as a New Cross-Linking System for Cotton Huitao Peng,†,‡ Charles Q. Yang,†,* Xilie Wang,§ and Shanyuan Wang‡ †

Department of Textiles, Merchandising and Interiors, The University of Georgia, Athens, Georgia 30602, United States College of Textiles, Donghua University, Shanghai 201620, China § Beijing Institute of Microchemistry, 39 Xinjian Gongmen Road, Beijing 100091, China ‡

ABSTRACT: In this research, we studied cross-linking of cotton fabrics using the combination of itaconic acid (ITA) and sodium hypophosphite (NaH2PO2). ITA, a bifunctional carboxylic acid, was able to esterify cotton cellulose to form a single ester linkage, but it was not able to form cross-linking between two cellulose molecules. In the presence of NaH2PO2, the amount of ester formed on cotton fabric was increased substantially and the esterification temperature of ITA was reduced. Therefore, NaH2PO2 functioned as a catalyst for esterification of cotton by ITA. Moreover, we found that wrinkle resistance of the cotton fabric was significantly improved when cotton fabrics were treated with the combination of ITA and NaH2PO2.We also found that phosphorus was bound to the treated cotton fabric and that the increase in the wrinkle recovery angle of the treated fabric was correlated to the increase in the amount of phosphorus bound to cotton. All the data indicated that H−P−H of sodium hypophosphite probably reacts with the >CC< of two ITA molecules, which are also esterified with cellulose, thus forming a cross-linkage between the two cellulose molecules. The cotton fabrics treated with the ITA/NaH2PO2 system demonstrated a high level of durable press performance with significantly lower tensile strength loss than those treated with the formaldehydebased dimethyloldihydroxyethyleneurea.

1. INTRODUCTION Cross-linking agents are commonly used by the industry to produce wrinkle-resistant cotton fabrics and garments. Dimethyloldihydroxyethyleneurea (DMDHEU) and its modified versions have been the most widely used cross-linking agents, and they are efficient and cost-effective with little changes on fabric color and whiteness.1 However, DMDHEU is a formaldehyde-based cross-linking agent. Formaldehyde vapor is continually and gradually released from DMDHEU-treated cotton fabrics and garments during processing, storage, and consumer use. In 1979, a study of the effect of formaldehyde on rats by the Chemical Industry Institute of Toxicology indicated that cancer occurred in rats as a result of exposure to 15 ppm formaldehyde.2 Scientists of U.S. federal government concluded in 1982 that formaldehyde induced both gene mutations and chromosomal aberrations in rats under laboratory conditions.3 The impact of formaldehyde on human health has gained contentiously increasing worldwide attention. In 1987, the U.S. Environmental Protection Agency classified formaldehyde as “a suspected carcinogen”.4 Most recently, a working group of WHO International Agency for Research on Cancer concluded that formaldehyde was “carcinogenic to humans” based on the sufficient evidence of nasopharyngeal cancer in humans and nasal cancer in animals.5 The risk of formaldehyde was upgraded from ″Group 2A″ (probably carcinogenic to human) to ″Group 1″ (carcinogenic to human).6 Studies conducted on textile industrial workers by the National Cancer Institute and National Institute of Occupational Safety and Health have shown that formaldehyde exposure caused lumphohematopoietic malignancies, particularly myeloid leukemia.7−11 Other studies also demonstrated that exposure to formaldehyde increased the risk of lung cancer.12,13 © 2012 American Chemical Society

Among the nonformaldehyde cross-linking agents investigated, 1,2,3,4-butanetetracarboxylic acid (BTCA) in particular is able to impart high levels of wrinkle resistance and smooth drying properties to cotton fabrics when sodium hypophosphite (NaH2PO2) was used as the catalyst.14 We found that a polycarboxylic acid esterifies cotton cellulose in two steps: formation of a five-membered cyclic anhydride intermediate by the dehydration of two carboxylic groups bound to the adjacent carbons in its backbone, and the reaction between cellulose and the anhydride intermediate to form an ester linkage as shown in Scheme 1.15,16 BTCA was also used as a cross-linking agent for the stabilization of antimicrobal agents, carbon nanotubes, and silica nanoparticles on cotton as reported most recently.17−19 Maleic acid (MA), an α,β-unsaturated olefinially bifunctional acid shown in Scheme 2, has only two carboxylic groups, therefore can only form one ester linkage with cellulose, and is not capable of forming a cross-linkage between two cellulose molecules. However, the MA-treated cotton fabric showed a significantly increased wrinkle recovery angle when NaH2PO2 was present.20,21 The data revealed that H−P−H of sodium hypophosphite likely reacts with >CC< of MA which is also esterified by cellulose, thus forming a cross-linkage between two cellulose molecules. We also studied the use of oligomers of MA as a cross-linker for cotton.22 Itaconic acid (ITA), also shown in Scheme 2, is another olefinically unsaturated dicarboxylic acid. ITA has been widely used in industries in such applications as the synthesis of resins, Received: Revised: Accepted: Published: 11301

March 2, 2012 August 1, 2012 August 5, 2012 August 5, 2012 dx.doi.org/10.1021/ie3005644 | Ind. Eng. Chem. Res. 2012, 51, 11301−11311

Industrial & Engineering Chemistry Research

Article

Scheme 1. Esterification of Cotton Cellulose by BTCA

performance of the combination of ITA and NaH2PO2 as a nonformaldehyde DP finishing system for cotton fabrics.

Scheme 2. Chemical Structures of MA and ITA

2. EXPERIMENTAL SECTION 2.1. Materials. Two cotton fabrics were used in this study: (a) a desized, scoured, and bleached printcloth weighting 109 g/m2 (Testfabrics Style 400) and (b) a 3/1 twill weave Khaki fabric weighing 264 g/m2 produced by Milliken, Blacksburg, SC. ITA, NaH2PO2 which contained ≤ 1 H2O in its molecular formula, and sodium phosphite dibasic pentahydrate (Na2HPO3·5H2O) were reagent grade chemicals supplied by Aldrich (Milwaukee, WI). A modified low-formaldehyde DMDHEU with the commercial name of “Freerez 845″, which was premixed with the catalyst (MgCl2), was supplied by Emerald Carolina Chemical (Charlotte, NC). A nonionic wetting agent with commercial name “Triton X-100” was supplied by Bio-Rad Laboratories (Hercules, CA). The aminofunctional silicon softener with the commercial name of ″DM-3362″ was supplied by Dymatic Chemicals, Shunde, China. The concentrations (w/w) of ITA, NaH2PO2, and Na2HPO3 were based on the weight of 100% active ingredient, whereas those of DMDHEU, the silicon softener, and the

textile dyeing, biomedical fields and papermaking.23−26 The density, melting point, solubility, and acidity of ITA are listed in Table 1.27 The use of ITA in a cross-linking system for cotton was first reported by Choi.28 The cotton fabric was treated with MA and ITA (1:1 mol ratio) in combination with a free radical initiator (K2S2O8, 1.5% of the acids) and an esterification catalyst (NaH2PO2). Choi concluded that copolymerization of MA/ITA took place on cotton.28 On the same topic, we discovered that the concentration of sodium persulfate played a critical role in the in situ polymerization or copolymerization of ITA and a much higher sodium persulfate concentration is needed for the treated cotton fabric to achieve desirable laundering durability.29 In our previous research, we also studied the use of oligomers of ITA and in situ polymerization of ITA as cross-linking agents for cotton.30 In this research, we studied the cross-linking of cotton by the combination of ITA and NaH2PO2 and the Table 1. The Physical Properties of ITA.27 name

molecular formula

density (g/cm−3)

melting point (°C)

solubility in water (g/L, 20 °C)

acidity (pKa, 25 °C)

itaconic acid

C5H6O4

1.63

165−169

83.3

pKa1 = 3.85 pKa2 = 5.45

11302

dx.doi.org/10.1021/ie3005644 | Ind. Eng. Chem. Res. 2012, 51, 11301−11311


Article

homogeneous powder. The powder stored in a 20 mL scintillation vial was kept in the conditioning room for 24 h before the analysis. Approximately 0.1 g of the powder was accurately weighted (four significant figures) and was then transferred to a 100 mL beaker, where the wet digestion procedure was carried out. A 10 mL portion of 30% H2O2 was added dropwise into the beaker, allowing the reactions to subside between drops. The reaction mixture was then heated up to 250 °C to digest the powder and to evaporate the water until a dense SO3 vapor was generated. After the digestion, the sample became a clear solution without any particles, in which all the phosphorus bound to cotton was converted to soluble compounds. The solution was transferred to a 50 mL volumetric flask, and then diluted with deionized water to the marker. The solution thus prepared was analyzed using a Thermo-Farrell-Ash model 965 inductively coupled plasma atomic emission spectrometer (ICP/AES) to determine the percent concentration (w/w) of phosphorus on the fabric. The percent phosphorus concentration was calculated using equation 2, where M (mg/L) was the phosphorus concentration in the solution provided by an ICP/AES measurement and W was the weight of the sample (g). The ICP−AES instrument was calibrated using a standard phosphorus solution prepared by dissolving the accurately weighed (∼4.4 g with four significant figures) anhydrous KH2PO4 and diluting the solution in a 1000 mL volumetric flask with distilled water. Phosphorus 213.618 nm emission line was used in the ICP− AES measurement. The coefficient of variance for ICP−AES phosphorus measurement was CC< of ITA. A band at 1842 cm−1 appears to be very weak in Figure 1B when the curing temperature reaches 190 °C. The band at 1842 cm−1 is due to the stretching mode of a five-membered cyclic anhydride.35 Another band at 1767 cm−1 due to the asymmetric stretching mode of the cyclic anhydride carbonyl emerges in Figure 1C as the temperature increases to 210 °C.35 The data indicated that, in the absence of NaH2PO2, ITA forms anhydride at exceedingly high temperatures. The infrared spectrum of the cotton fabric treated with the combination of 6.7% ITA and 4.0% NaH2PO2 and cured at temperatures ranging from 120 to 200 °C are shown in Figure 2. When NaH2PO2 is present, the anhydride carbonyl symmetric stretching band at 1842 cm−1 appears when the curing temperature is increased to 140 °C (Figure 2B). The two anhydride carbonyl bands at 1842 and 1769 cm−1 become significantly more intense at 160 °C (Figure 2C). It is evident that formation of the cyclic anhydride of ITA takes place at 11303



Article

Figure 2. The infrared spectra of the cotton fabric treated with the combination of 6.7% ITA and 4.0% NaH2PO2 and cured at different temperatures (°C) for 2 min: (A) 120, (B) 140, (C) 160, (D) 180, (E) 200.

Figure 1. The infrared spectra of the cotton fabric treated with 6.7% ITA and cured at different temperatures (°C) for 2 min: (A) 170, (B) 190, (C) 210.

much lower temperatures when NaH2PO2 is present on cotton. The data presented here undoubtedly demonstrate that NaH2PO2 catalyzes the formation of the cyclic anhydride intermediate. The intensities of those two anhydride carbonyl bands decrease as the curing temperature increases further to 180 and 200 °C, possibly due to the sublimation of the anhydride (Figure 2D and E). Since the carbonyl bands of ester and free acid are overlapped around 1730 cm−1 in the infrared spectra of the treated cotton fabric, we use a 0.1 M NaOH solution to convert the free carboxylic group to carboxylate anion so that the ester carbonyl band can be used as the basis for quantitative analysis of the ester formed on the treated cotton as the result of esterification.31,32 Presented in Figure 3 are the ester carbonyl band intensity of the cotton fabric treated with ITA and that treated with the combination of ITA and NaH2PO2. Without NaH2PO2, esterification of cotton starts to take place at 160 °C, and the ester carbonyl band intensity is very low (0.08). It increases marginally to 0.14 as the curing temperature is increased to 200 °C (Figure 3). In the presence of NaH2PO2, however, the esterification starts at much lower temperatures. The carbonyl band intensity is 0.25 when the curing temperature is 130 °C, and it increases to 0.48 when the curing temperature is increased to 160 °C (Figure 3). It is evident that NaH2PO2 is an effective catalyst for the esterification of cotton by ITA. 3.2. Cross-Linking of Cotton by the Combination of ITA and NaH2PO2. The cotton fabric was treated with 8.0% ITA in combination with 4.0% NaH2PO2, cured at temperatures ranging from 130 to 190 °C, and finally subjected to one

Figure 3. The ester carbonyl band intensity of (1) the cotton fabric treated with 6.7% ITA and (2) that treated with 6.7% ITA and 4.0% NaH2PO2, cured at different temperatures for 2 min, subjected to one home laundering cycle, and finally rinsed with a 0.1 M NaOH solution.

home laundering cycle. Presented in Figure 4 is the weight gain of the cotton fabric thus treated as a function of curing temperature. The data presented show that the weight of the ITA-treated cotton fabric steadily increases from 3.25 to 7.13% as the curing temperature is increased from 130 to 190 °C (Figure 4). The esterification of cotton by ITA is evidently the cause for the weight gain of the treated fabric shown in Figure 4. We 11304



Article

Figure 4. The weight gain of the cotton fabric treated with 8.0% ITA and 4.0% NaH2PO2, cured at different temperatures for 2 min and subjected to one home laundering cycle.

Figure 6. The adjusted weight gain of the cotton fabric treated with 8.0% ITA and 4.0% NaH2PO2, cured at different temperatures for 2 min, and subjected to one home laundering cycle.

reaction must have taken place above 160 °C on the treated fabric, which causes the additional weight gain of the fabric. To investigate the second reaction on the treated cotton fabric, we measured the phosphorus content on the cotton fabric treated with 8.0% ITA and 4.0% NaH2PO2. The phosphorus concentration of the cotton fabric thus treated is presented as a function of the curing temperature in Figure 5. The data presented here clearly demonstrate that phosphorus is bound to cotton. The phosphorus on cotton can only come from NaH2PO2. It can also be seen that the phosphorus concentration versus curing temperature curve shows a significant increase in its slope at 150 °C in Figure 5, indicating that the amount of phosphorus bound to the cotton fabric increases with a much higher magnitude as the curing temperature is increased beyond 150 °C. The weight of the NaH2PO2 bound to cotton, calculated based on the phosphorus concentration of the treated cotton fabric, is presented in Table 2. The total weight increase of the cotton fabrics treated with 8.0% ITA and 4.0% NaH2PO2, cured and subjected to one home laundering cycle (Figure 4) is the sum of the weight of ITA and that of NaH2PO2, both bound to cotton. The weight of ITA bound to cotton can be calculated by subtracting the weight of the bound NaH2PO2 from the total weight increase. The adjusted weight gain after the subtraction is presented against the curing temperature in Figure 6, which shows the same pattern as the ester carbonyl band intensity versus curing temperature curve in Figure 3. The two curves are independently generated by two different sets of samples using two different methods. Both the adjusted weight gain and ester carbonyl band intensity show a significant increase from 130 to 150 °C and then level off as the curing temperature is increased from 160 to 190 °C. Thus, the data presented here confirm our assumption that the weight increase shown in Figure 4 is also partly due to the bonding of NaH2PO2 to the cotton fabric when it is treated with ITA and NaH2PO2. The weight increase of treated cotton fabric is due to (1) esterification of cotton by ITA and (2) bonding of NaH2PO2 to cotton. The esterification of cotton reached the optimum range at 160 °C, whereas the bonding of NaH2PO2 to cotton mostly takes place as the curing temperature is increased beyond 150 °C. Consequently, the total weight increase shows a steady increase in the entire curing temperature range (130−190 °C). The H−P−H of

Figure 5. The phosphorus concentration of the cotton fabric treated with (1) 8.0% ITA and 4.0% NaH2PO2 and (2) 8.0% ITA and 8.2% Na2HPO3, cured at different temperatures for 2 min, and subjected to 1 home laundering cycle.

Table 2. The Phosphorus Concentration, NaH2PO2 Concentration, And Adjusted Weight Gain of Cotton Fabrics Treated with 8.0% ITA/4.0% NaH2PO2, Cured at Different Temperatures for 2 min and Subjected to One Home Laundering Cycle curing temperature (°C)

phosphorus concentration (%)

NaH2PO2 concentration (%)

adjusted weight gain (%)

130 140 150 160 170 180 190

0.06 0.09 0.16 0.28 0.45 0.58 0.75

0.17 0.26 0.45 0.80 1.28 1.65 2.13

3.08 4.19 4.72 5.12 5.15 5.17 5.00

discover, however, the weight gain of the fabric treated with ITA/NaH2PO2 steadily increase in the entire curing temperature range (Figure 4), whereas the ester carbonyl band intensity levels off above 160 °C (Figure 3). The discrepancy in the data presented in the two figures indicates that a second 11305



Article

Scheme 3. Bonding of NaH2PO2 to Cotton by Its Reaction with ITA Esterified to Cotton

Figure 8. The breaking strength retention of cotton fabric treated with 8.0% ITA and 4.0% NaH2PO2, cured at different temperatures for 2 min, and subjected to one home laundering cycle.

Figure 7. The WRA of (1) cotton fabric treated with 8.0% ITA and 4.0% NaH2PO2 and (2) that treated 8.0% ITA and 8.2% Na2HPO3, cured at different temperatures for 2 min, and subjected to one home laundering cycle.

different temperatures. Presented in Figure 7 is the WRA of the treated cotton fabric as a function of the curing temperature. The WRA of the treated fabric is 193° when it is cured at 130 °C, and it increases to 229° when the fabric is cured at 160 °C. The WRA becomes 261° as the curing temperature is increased further to 190 °C (Figure 7). The increase of WRA is another experimental evidence of the reactions of NaH2PO2 forming cross-linking among cellulose molecules, thus imparting wrinkle

NaH2PO2 is probably added to the >CC< of ITA, which is also esterified by cotton cellulose as shown in Scheme 3. Consequently, the NaH2PO2 reacting with ITA cotton becomes durable to laundering. To investigate the reactions of NaH2PO2 further, we measured the WRA of the cotton fabric treated with the combination of 8.0% ITA and 4.0% NaH2PO2 and cured at

Scheme 4. Crosslinking of Two Cellulose Molecules by the Reaction of NaH2PO2

11306



Article

Scheme 5. Molecular Structures of Sodium Hypophosphite and Dibasic Sodium Phosphite

Figure 10. The WRA and breaking strength retention of the cotton fabric treated with 8.0% ITA and NaH2PO2 of different concentrations, cured at 180 °C for 2 min and subjected to one home laundering cycle.

Table 4. The NaH2PO2-to-ITA Mole Ratio of the ITA/ NaH2PO2 of the Solutions Used for Treating the Cotton Fabrics

Figure 9. The weight gain and phosphorus concentration of cotton fabric treated with 8.0% ITA and NaH2PO2 of different concentrations, cured at 180 °C for 2 min, and subjected to one home laundering cycle.

Table 3. The Total Weight Gain, Weight Gain Due to NaH2PO2 and That Due to ITA of the Cotton Fabrics Treated with 8.0% ITA and NaH2PO2 of Different Concentration, Cured at 180 °C for 2 min and Subjected to One Home Laundering Cycle NaH2PO2 concentration (%)

total weight gain (%)

NaH2PO2 bound to cotton (%)

ITA bound to cotton (%)

0.5 2.0 4.0 6.0 8.0 10.0 12.0

3.29 5.85 7.29 7.74 7.93 8.58 8.70

0.28 0.99 1.56 1.99 2.10 2.24 2.33

3.01 4.86 5.73 5.75 5.83 6.34 6.37

resistance to the treated cotton fabric.36 The cross-linking is probably formed between the two hydrogen atoms of NaH2PO2 and two ITA molecules which are also esterified with cotton cellulose shown in Scheme 4. We can also see that the slope of the WRA versus temperature curve significantly increases above 150 °C. This is consistent with the pattern of the phosphorus concentration versus temperature curve in Figure 5. Shown in Figure 8 is the percent breaking strength loss in warp direction of the cotton fabric treated with ITA/NaH2PO2 as a function of the curing temperature. The percent breaking strength loss is calculated based on the breaking strength of the cotton fabric before and after the ITA/NaH2PO2 treatment. The percent breaking strength loss of the treated cotton fabric increases from 27 to 49% as the curing temperature is increased from 130 to 190 °C (Figure 8). In our previous research, we

NaH2PO2 concentration (%)

ITA concentration (%)

NaH2PO2/ITA mole ratio

0.5 2.0 4.0 6.0 8.0 10.0 12.0

8.0 8.0 8.0 8.0 8.0 8.0 8.0

0.09 0.37 0.74 1.10 1.45 1.85 2.22

Figure 11. The weight gain and phosphorus concentration of the cotton fabric treated with 8.0% NaH2PO2 and ITA of different concentrations, cured at 180 °C for 2 min, and subjected to one home laundering cycle.

discovered that the strength loss of the cotton fabrics crosslinked by a polycarboxylic acid is caused by acid-catalyzed cellulose depolymerization and cross-linking of cotton cellulose.37 The strength loss of the treated cotton fabric shown in Figure 8 provides another piece of evidence to support the hypothesis that the reactions between NaH2PO2 and ITA cross-link cotton cellulose. 11307



11308

F

77 60 67 49

W

a

All the formulations contained 3.0% silicon softener and 0.1% wetting agent. bAbbreviations: SD, standard deviation; W, warp direction; F, filling direction.

F

6.6 ± 0.2 5.2 ± 0.1 8.6 ± 0.2 3.8 ± 0.2 2.8 ± 0.1 5.7 ± 0.2

W F

45 37 49 39

W F

89 ± 4 72 ± 5 197 ± 10 144 ± 7 114 ± 8 296 ± 4

W 30

3.0 3.0 3.3 3.2

20 10

3.4 3.4 3.7 3.6

1 30

249 251 252 253

20 10

180 °C /2 min 160 °C /2 min

257 260

1

270 268 190

curing temperature/time cross-linking agents

a

8.0% ITA 8.0% NaH2PO2 10.5% DMDHEU control

tearing strength (N) ± SD breaking strength retention (%) breaking strength, (N) ± SDb

The infrared spectra of the cotton fabric treated ITA/ NaH2 PO2 presented in Figure 2 also provides direct experimental evidence for the reaction between ITA and NaH2PO2 on the fabric. In the infrared spectra of the cotton fabric treated and cured at 120 °C (Figure 2A), the weak and broad band at 2352 cm−1 is due to the P−H stretching mode of the hypophosphite anion, whereas the band at 1637 cm−1 is attributed to the stretching mode of >CC< of ITA.38 As the curing temperature is increased from 120 to 200 °C, both the band at 2352 cm−1 due to P−H stretching and band at 1636 cm−1 due to >CC< stretching decrease their intensities. Thus the data clearly confirm the reaction between P−H of hypophosphite anion and the >CC< of ITA shown in Schemes 3 and 4. The band at 2352 cm−1 decreases its frequency to 2335 cm−1 as the curing temperature is increased to 160 °C and above (Figure 2C−E). The broadening of the P−H stretching band at 2352 cm−1 in the spectra (Figure 2B,C) is probably due to the intermolecular hydrogen-bonding among H−P−H of hypophosphite anions. As the curing temperature is increased to 160 °C and higher, this band becomes sharper and its frequency decreases to 2335 cm−1 (Figure 2C−E). The change in band shape indicates the decrease in the hydrogen-bonding of H−P−H of hypophosphite anions as a result of the reactions shown in Schemes 3 and 4. To elucidate the reaction between NaH2PO2 and ITA on cotton, we compared the performance of two different catalysts, that is, NaH2PO2 and Na2HPO3, for the esterification of ITA on cotton. Na2HPO3 has been one of the effective catalysts for esterification.39 The cotton fabric was treated with 8.0% ITA in combination of 8.2% Na2HPO3 of different concentrations, cured at different temperatures for 2 min and finally subjected to one home laundering cycle. The mole concentration of Na2HPO3·5H2O (8.2% w/w) is similar to that of 4.0% NaH2PO2, therefore the two ITA solutions have approximately the same concentration of phosphorus. The phosphorus concentration and WRA of the cotton fabric treated with ITA/Na2HPO3 are presented in Figures 5 and 7, respectively. It is apparent in Figure 5 that the concentration of phosphorus of the cotton fabric treated with ITA/Na2HPO3 increases as the curing temperature is increased following the similar pattern of that treated with ITA/NaH2PO2. However,

DP rating, no. of laundering cycles

Figure 12. The WRA of the cotton fabric treated with 8.0% NaH2PO2 and ITA of different concentrations, cured at 180 °C for 2 min, and subjected to one home laundering cycle.

WRA (w + f, deg), no. of laundering cycles

Table 5. The Durable Press Performance and Mechanical Properties of the Plain Weave Cotton Fabric Treated with ITA/NaH2PO2 and DMDHEU

b

tearing strength retention (%)

Article


All the formulations contained 3.0% silicon softener and 0.1% wetting agent. bAbbreviations: SD, standard deviation; W, warp direction; F, filling direction. a

F

113 78 128 90

W

the WRA of the two treated fabric is different as shown in Figure 7. As the curing temperature is increased from 130 to 190 °C, the WRA of the cotton treated with ITA/NaH2PO2 increases from 192 to 261°, indicating a drastic rise in fabric wrinkle resistance as a result of cellulose cross-linking. For the fabric treated with ITA/Na2HPO3, however, its WRA increases only slightly from 193 to 219°. The increase in phosphorus concentration of the two treated cotton fabrics is due to the adding of P−H of NaH2PO2 and Na2HPO3 to the >CC< of ITA. The higher wrinkle resistance of the cotton fabric treated with ITA/NaH2PO2 and lower wrinkle resistance of that treated with ITA/Na2HPO3 can be explained by the difference in the molecular structure between NaH2PO2 and Na2HPO3 shown in Scheme 5. NaH2PO2 has two hydrogen atoms which are able to add to two ITA molecules esterified by cotton cellulose, thus forming cross-linking between two cellulose molecules. Na2HPO3, on the other hand, has one reactive hydrogen atom; therefore it can only be bound to one ITA molecule. Thus, the comparison between the two cotton fabrics treated with ITA/NaH2PO2 and that treated with ITA/ Na2HPO3 also supports the reaction mechanism shown in Schemes 3 and 4. The low level of wrinkle resistance of the cotton fabric treated with ITA/Na2HPO3 is probably due to the esterification of bifunctional phosphorous acid by cotton under acidic conditions. In our previous research, we discovered that cotton treated with MA and monobasic sodium phosphate also shows a marginal increase in fabric wrinkle resistance.20 The cotton fabric is treated with 8.0% ITA in combination with NaH2PO2 of different concentrations, cured at 180 °C for 2 min and finally subjected to one laundering washing/drying cycle. Presented in Figure 9 is the weight gain and percent phosphorus concentration of the treated fabric as functions of the NaH2PO2 concentration. As discussed above, the weight gain of the treated cotton fabric is due to (1) esterification of ITA on cotton, which is catalyzed by NaH2PO2 and (2) NaH2PO2 bound to cotton as shown in Schemes 3 and 4. On the basis of the percent phosphorus concentrations presented in Figure 9, the weight gain due to the bound NaH2PO2 and that due to the esterified ITA are calculated and presented in Table 3. It can be seen that the weight gain due to esterified ITA increases at low NaH2PO2 concentrations (0.5 and 2.0%), but its increase levels off when the NaH2PO2 concentration reaches ≥4.0% (Table 3). This is evidently because NaH2PO2 functions as a catalyst for the esterification of ITA. The amount of NaH2PO2 bound to the cotton fabric has a different dependency on the NaH2PO2 concentration of the solutions for the treatment (Figure 9). It increases steadily in the entire NaH2PO2 concentration range because NaH2PO2 functions as a reactant for the bonding of phosphorus to cotton. The WRA and breaking strength retention of the cotton fabric treated with 8.0% ITA and NaH2PO2 of different concentrations and cured at 180 °C for 2 min are shown in Figure 10. The NaH2PO2-to-ITA mole ratio of those solutions for treating the cotton fabric is presented in Table 4. The WRA increases from 212 to 260° as the NaH2PO2 concentration is increased from 1.0 to 8.0%, respectively. The increase in fabric WRA reveals the increase of the amount of cross-linking by the esterification of ITA and the reaction between ITA and NaH2PO2 as shown in Schemes 3 and 4. The decrease in the fabric strength retention is also a result of the cross-linking of cotton as reported previously.37 The WRA reaches its maximum of 260° as the NaH2PO2 is increased to 8.0% (NaH2PO2-to-ITA mole ratio, 1.45). Theoretically, 0.5

22.1 ± 0.4 15.3 ± 0.2 19.5 ± 0.6

F

Article

21.1 ± 0.5 14.8 ± 0.2 16.5 ± 1.1

W F

52 37 53 37

W F

179 ± 19 139 ± 12 377 ± 10 353 ± 16 244 ± 20 662 ± 4

W 30

3.0 3.0 3.2 3.3

20 10

3.4 3.6 3.6 3.7

1 30

231 239 234 243

20 10

180 °C/3 min 160 °C/3 min 8.0% ITA 8.0% NaH2PO2 12.5% DMDHEU control

238 249

1

251 257 190

curing temperature/time cross-linking agentsa

tearing strength (N) ± SDb WRA (w + f, deg), no. of laundering cycles

DP rating, no. of laundering cycles

breaking strength, (N) ± SDb

breaking strength retention (%)

Table 6. The Durable Press Performance and Mechanical Properties of the Twill Weave Cotton Fabric Treated with ITA/NaH2PO2 and DMDHEU

tearing strength retention (%)


11309



Article

treated with ITA/NaH2PO2 is also 36 and 27% higher than that treated with DMDHEU in warp and filling directions, respectively. Since the fabrics treated with two different crosslinking systems have similar wrinkle resistance, we can conclude that ITA/NaH2PO2 as a DP finishing system has significantly higher strength retention in addition to being a nonformaldehyde system. The same cross-linking systems were also applied to a 3/1 twill cotton fabric. The twill fabric treated with ITA/NaH2PO2 has WRA of 251° after one laundering cycle, whereas that treated with DMDHEU has WRA of 257°, indicating the DMDHEU-treated fabric has modestly higher wrinkle resistance than the fabric treated with ITA/NaH2PO2 (Table 6). The WRA data of the two treated cotton fabrics after 10, 20, and 30 home laundering cycles show the same phenomenon. The DP rating data also demonstrate that the DMDHEU-treated fabric has a moderately higher smooth drying property than the fabric treated with ITA/NaH2PO2 (Table 6). The breaking and tearing strength between the two treated fabrics are drastically different. The breaking strength of the cotton fabric treated with ITA/NaH2PO2 are 42 and 29% higher than that of the DMDHEU-treated fabric, whereas its tearing strength is 43 and 44% higher than that of the DMDHEU-treated fabric in warp and filling directions, respectively. Therefore, the data of the treated twill cotton fabric also confirm the superior mechanical strength of cotton fabrics treated with the ITA/NaH2PO2 cross-linking system.

NaH2PO2-to-ITA mole ratios are required for cross-linking ITA by NaH2PO2, which has two reactive hydrogens. But the experimental data indicate that the amount of NaH2PO2 required to achieve maximum WRA is much higher than the theoretical value. The WRA versus NaH2PO2 concentration curve in Figure 10 takes a sharp turn and the WRA decreases from 260 to 236° as the NaH2PO2 concentration increases from 8.0 to 12.0% (NaH2PO2-to-ITA mole ratio from 1.45 to 2.22). At such excessively high NaH2 PO 2 -to-ITA ratios, the NaH2 PO 2 becomes so abundant that most of the ITA forms a single bond with NaH2PO2 shown as II in Scheme 3, which cannot react further to form cross-linking. Consequently, the fabric WRA decreases and strength retention increases as shown in Figure 10. The breaking strength retention versus NaH2PO2 concentration curve also reverses its slope when NaH2PO2 concentration reaches 8.0% (Figure 10). The weight gain, phosphorus concentration, and WRA of the cotton fabric treated with 8% NaH2PO2 and ITA of different concentrations are shown in Figures 11 and 12. It is obviously that both the weight gain and phosphors concentration increases linearly as the ITA concentration is increased with R2 of 0.98 and 0.99, respectively. The linear dependency of the phosphorus concentration of the treated fabric on ITA concentration supports the reaction between NaH2PO2 and ITA on cotton discussed previously. The WRA of the treated cotton fabric also shows a linear relationship with the ITA concentration with R2 of 0.98, indicating that the cross-linking of cotton increases linearly with the ITA concentration (Figure 12). It should be pointed out that bonding phosphorus, a very effective flame retarding element, to cotton will have profound impact on a fabric’s flammability and heat release properties. The reduced peak heat release rate and reduced flammability of the cotton fabrics treated with MA are discussed with details elsewhere.40,41 3.3. Performance of Cotton Fabrics Treated with the Combination of ITA and NaH2PO2. The ITA/NaH2PO2 system in combination of an aminofunctional silicone softener and a wetting agent was applied to the plain weave fabric. A low-formaldehyde DMDHEU premixed with MgCl2 (catalyst) commonly used in the textile industry was included in the study for the purpose of comparison. The formulas, curing conditions, WRA, DP rating, and mechanical properties of the treated plain weave fabric are presented in Table 5. The fabric treated with ITA and the modified DMDHEU have the WRA of 270° and 268° after one home laundering cycle, indicating similar wrinkle resistance for the two treated fabrics. After 30 laundering cycles, the WRA of the two treated fabrics (249° and 251°) are still very close to each other (Table 5). The DP ratings for the two treated cotton fabrics are also very similar after 1, 10, 20, and 30 laundering cycles (Table 5). Therefore, the cotton fabric treated with ITA/NaH2PO2 and that treated with DMDHEU demonstrate the same level of wrinkle resistance, smooth drying property and similar laundering durability. The breaking strengths of the fabric treated with ITA/ NaH2PO2 are 144 and 89 N, whereas those of the fabric treated with DMDHEU are 114 and 72 N in warp and filling directions, respectively (Table 5). The data show that the fabric treated with ITA/NaH2PO2 has breaking strengths 26 and 24% higher than that treated with DMDHEU in warp and filling directions, respectively. The tearing strength of the fabric

4. CONCLUSIONS (1) Esterification of cotton by ITA requires exceedingly high temperature (>200 °C). NaH2PO2 catalyzes both the formation of five-member cyclic anhydride intermediate of ITA and esterification of cotton by ITA. In the presence of NaH2PO2, the esterification temperature is significantly reduced and the amount of ester formed on cotton reaches its optimum when the curing temperature is increased to ≥160 °C. (2) All the data presented here indicate that the cotton treated with the combination of ITA and NaH2PO2 has a second reaction, that is, H−P−H of H2PO2− is added to >C C< of ITA. The addition reaction of one NaH2PO2 with two ITA molecules, which is also esterified by cotton, cross-links two cellulose molecules, thus imparting wrinkle resistance to cotton. (3) ITA/NaH2PO2 is a nonformaldehyde DP finishing system for cotton. The cotton fabrics treated with ITA/ NaH2PO2 show high levels of durable press performance with significantly higher strength retention than those treated with the modified DMDHEU.

■

AUTHOR INFORMATION

Corresponding Author

*Tel.: +1 706 542 4912. Fax: +1 706 542 4890. E-mail: cyang@ uga.edu. Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS This research project was partially supported by the USDA Agriculture Experimental Station grants (csrees/USDA GE000668). 11310



■

Article

(20) Yang, C. Q.; Chen, D.; Guan, J.; He, Q. Cross-linking cotton cellulose by the combination of maleic acid and sodium hypophosphite. I. Fabric wrinkle resistance. Ind. Eng. Chem. Res. 2010, 49, 8325−8332. (21) Peng, H.; Yang, C. Q.; Wang, S. Nonformaldehyde durable press finishing of cotton fabrics using the combination of maleic acid and sodium hypophosphite. Carbohydr. Polym. 2012, 87, 491−499. (22) Chen, D.; Yang, C. Q.; Qiu, X. Aqueous polymerization of maleic acid and cross-linking of cotton cellulose by poly(maleic acid). Ind. Eng. Chem. Res. 2005, 44, 7921−7927. (23) Kin, R.; Sai, T.; So, S. Itaconate copolymer with quadratic nonlinear optical characteristic. JP Patent 10,293,331,1998. (24) Tate, B. E. Itaconic acid and derivatives. Kirk-Othmer Encyclopaedia of Chemical Technology; Grayson, M., Eckroth, E., Eds.; Wiley: New York, 1981; Vol. 3, pp 865−873. (25) Willke, T.; Vorlop, K. D. Biotechnological production of itaconic acid. Appl. Microbiol. Biotechnol. 2001, 56, 289−295. (26) Okabe, M.; Lies, D.; Kanamasa, S.; Park, E. Y. Biotechnological production of itaconic acid and its biosynthesis in Aspergillus terreus. Appl. Microbiol. Biotechnol. 2009, 84, 597−606. (27) Budavari, S., The Merck Index: An Encyclopedia of Chemicals, Drugs, And Biologicals, 12th ed.; Merck: Whitehouse Station, NJ, USA, 1996; p 842.. (28) Choi, H. M. Nonformaldehyde polymerization-crosslinking treatment of cotton fabrics for improved strength retention. Text. Res. J. 1992, 62, 614−618. (29) Yang, C. Q.; Lu, Y. In-situ polymerization of maleic acid and itaconic acid and crosslinking of cotton fabric. Text. Res. J. 1999, 69, 782−789. (30) Mao, Z.; Yang, C. Q. Polymeric multifunctional carboxylic acids as crosslinking agents for cotton cellulose: Poly (itaconic acid) and in situ polymerization of itaconic acid. J. Appl. Polym. Sci. 2001, 79, 319− 326. (31) Yang, C. Q. Characterizing ester crosslinkages in cotton cellulose with FT-IR photoacoustic spectroscopy. Text. Res. J. 1991, 61, 298−305. (32) Yang, C. Q.; Bakshi, G. D. Quantitative analysis of the nonformaldehyde durable press finish on cotton fabric: Acid-base titration and infrared spectroscopy. Text. Res. J. 1996, 66, 377−384. (33) Feldman, C. Perchloric acid procedure for wet-ashing organics for the determination of mercury (and other metals). Anal. Chem. 1974, 46, 1606−1609. (34) Rezic, I.; Steffan, I. ICP-OES determination of metals present in textile materials. Microchem. J. 2007, 85, 46−51. (35) Gu, X.; Yang, C. Q. FT-IR and FT-Raman spectroscopy study of the cyclic anhydride intermediates for esterification of cellulose: I. Formation of anhydrides without a catalyst. Res. Chem. Intermed. 1998, 24, 979−996. (36) Wei, W.; Yang, C. Q. Predicting the performance of durable press finished cotton fabric with infrared spectroscopy. Text. Res. J. 1999, 69, 145−151. (37) Kang, I.; Yang, C. Q.; Wei, W.; Lickfield, G. C. Mechanical strength of durable press finished cotton fabrics Part I: Effects of acid degradation and crosslinking of cellulose by polycarboxylic acids. Text. Res. J. 1998, 68, 865−870. (38) Bellamy, L. J. The Infrared Spectra of Complex Molecules, 3rd ed.; Chapman and Hall: London, 1975; pp 357−358. (39) Brown, R.; Tomasino, C. Catalysis of 1,2,3,4-butanetetracarboxylic acid in the durable press finishing of cotton textiles. In Book of Papers, 1991 AATCC International Conference; American Association of Textile Chemist and Colorist: Research Triangle Park, NC, 1991; pp 168−185. (40) Wu, X.; Yang, C. Q. Flame retardant finishing of cotton fleece fabric: Part IIIThe combination of maleic acid and sodium hypophosphite. J. Fire Sci. 2008, 26, 351−368. (41) Yang, C. Q.; He, Q.; Voncina, B. Crosslinking of cotton cellulose by maleic acid in the presence of sodium hypophosphite, part II. Fabric fire performance. Ind. Eng. Chem. Res. 2011, 50, 5889−5897.

REFERENCES

(1) Peterson, H. A. Crosslinking with formaldehyde-containing reactants. In Chemical Processing of Fibers and Fabrics: Functional Finishes. Part A.; Lewin, M., Sello, S. B., Eds.; Marcel Dekker: New York, 1983; pp 51−53. (2) Swenberg, J. A.; Kerns, W. D.; Mitchell, R. I.; Gralla, E. J.; Pavkov, K. L. Induction of squamous cell carcinomas of the rat nasal cavity by inhalation exposure to formaldehyde vapor. Cancer Res. 1980, 40, 3398−3401. (3) Griesemer, R. Report of the federal panel on formaldehyde. Environ. Health Perspect. 1982, 43, 139−168. (4) U.S. Environmental Protection Agency (EPA). Assessment of Health Risks to Garment Workers and Certain Home Residents from Exposure to Formaldehyde; Office of Pesticides and Toxic Substances, EPA: Washington, DC, 1987. (5) Cogliano, V.; Grosse, Y.; Baan, R.; Straif, K.; Secretan, B.; El Ghissassi, F. Advice on formaldehyde and glycol ethers. Lancet Oncol. 2004, 5, 528. (6) International Agency for Research on Cancer (IARC) IARC Monograph on the Evaluation of Carcinogenic Risks to Humans: Formaldehyde, 2-Butoxyethanol and 1-tert-Butoxy-2-propanol. World Health Organization: Lyon, France, 2006; Vol. 88. (7) Pinkerton, L.; Hein, M.; Stayner, L. Mortality among a cohort of garment workers exposed to formaldehyde: An update. Occup. Environ. Med. 2004, 61, 193−200. (8) Hauptmann, M.; Lubin, J. H.; Stewart, P. A.; Hayes, R. B.; Blair, A. Mortality from lymphohematopoietic malignancies among workers in formaldehyde industries. J. Natl. Cancer Inst. 2003, 95, 1615−1623. (9) Hauptmann, M.; Lubin, J. H.; Stewart, P. A.; Hayes, R. B.; Blair, A. Mortality from solid cancers among workers in formaldehyde industries. Am. J. Epidemiol. 2004, 159, 1117−1130. (10) Hauptmann, M.; Stewart, P. A.; Lubin, J. H.; Beane Freeman, L. E.; Hornung, R. W.; Herrick, R. F.; Hoover, R. N.; Fraumeni, J. F.; Blair, A.; Hayes, R. B. Mortality from lymphohematopoietic malignancies and brain cancer among embalmers exposed to formaldehyde. J. Natl. Cancer Inst. 2009, 101, 1696−1708. (11) Beane Freeman, L. E.; Blair, A.; Lubin, J. H.; Stewart, P. A.; Hayes, R. B.; Hoover, R. N.; Hauptmann, M. Mortality from lymphohematopoietic malignancies among workers in formaldehyde industries: The National Cancer Institute Cohort. J. Natl. Cancer Inst. 2009, 101, 751. (12) Coggon, D.; Harris, E. C.; Poole, J.; Palmer, K. T. Extended follow-up of a cohort of British chemical workers exposed to formaldehyde. J. Natl. Cancer Inst. 2003, 95, 1608−1615. (13) Bosetti, C.; McLaughlin, J.; Tarone, R.; Pira, E.; La Vecchia, C. Formaldehyde and cancer risk: A quantitative review of cohort studies through 2006. Ann. Oncol. 2008, 19, 29−43. (14) Welch, C. M. Tetracarboxylic acids as formaldehyde-free durable press finishing agents. Text. Res. J. 1988, 58, 480−486. (15) Yang, C. Q. Infrared spectroscopy studies of the cyclic anhydrides as the intermediate for the ester cross-linking of cotton cellulose by polycarboxylic acids: I. Indentification of the cyclic anhydride intermediate. J. Polym. Sci. Part A 1993, 31, 1187−1193. (16) Yang, C. Q.; Wang, X. Formation of cyclic anhydride intermediates and esterification of cotton cellulose by multifunctional carboxylic acids: An infrared spectroscopy study. Text. Res. J. 1996, 66, 595−603. (17) Montazer, M; Afjeh, M. G. Simultaneous X-linking and antimicrobal finishing of cotton fabric. J. Appl. Polym. Scie. 2007, 103, 178−185. (18) Alimohammadi, F.; Gashti, M. P.; Shamei, A. A novel method for coating of carbon nanotube on cellulose fiber using 1,2,3,4butanetetracarboxylic acid as a cross-linking agent. Prog Org. Coat. 2012, 74, 470−478. (19) Gashti, M. P.; Alimohammadi, F.; Shamei, A. Preparation of water-repellent cellulose fibers using a polycarboxylic acid/hydrophobic silica nanocomposite coating. Surf. Coat. Technol. 2012, 206, 3208−3215. 11311


The Combination of Itaconic Acid and Sodium Hypophosphite as a

Recommend Documents