Chemical analysis of 1,2,3,4-butanetetracarboxylic acid
Chemical Analysis of 1,2,3,4-Butanetetracarboxylic Acid1
Polycarboxylic acids have been the most promising durable press finishing agents for cotton to replace traditional formaldehyde-based reagents. Among the various polycarboxylic acids investigated in recent years, 1,2,3,4-butanetetracarboxylic acid (BTCA) has been the most effective crosslinking agent. Cottons treated with BTcA have shown superior durable press performance with high levels of laundering durability. In this research, we analyze a reagent grade and an industrial grade BTCA using elemental analysis and acid-base titration. The titration data indicate that the industrial grade product contains approximately 95% BTcA. The two BTCA products are studied by Fm and Fr-Raman spectroscopy, proton magnetic resonance spectroscopy , mass spectroscopy (MS), and liquid chromatography/mass spectroscopy . All the instrumental analysis data indicate the low level of impurities in the industrial BTCA. Cotton fabrics treated with the two products show similar durable press performance, indicating that the differences in effectiveness for crosslinking cotton between these two BTCA products are insignificant. The data also show that the impurity in the industrial grade BTCA does not cause fabric yellowing.
Since the late 1980s, extensive efforts have been made to use multifunctional carboxylic acids to replace the traditional dimethyloldihydroxylethyleneurea (DMDHEU) due to increasing concern with the toxicity of formaldehyde [9]. Polycarboxylic acids have shown high levels of effectiveness for crosslinking cotton when sodium hypophosphite (NaH^sub 2^P0^sub 2^) is used as a catalyst [ 12-14, 17]. A new finishing system consisting of citric acid and a polymer of maleic acid has been commercialized [18]. Polycarboxylic acids have also been used as crosslinking agents for wood pulp cellulose to improve paper wet strength [4, 16, 17, 19]. Among the various effective polycarboxylic acids investigated, BTCA has proved to be the most efficient crosslinking agent for cotton fabrics [12-13].
BTCA can be synthesized by two different methods. The first is to subject the Diels-Alder reaction product of maleic anhydride and 1,3-butadiene to hydrolysis followed by oxidative cleavage [1, 8, 10]. The Diels-Alder reaction takes place in the temperature range of 100140(deg)C with 1,3-butadiene as the solvent [8]. The reaction forms cis-1,2,3,6-tetrahydrophthalic anhydride, which is hydrolyzed to become cis-1,2,3,6-tetrahydrophthalic acid. Finally, cis-1,2,3,6-tetrahydrophthalic acid is subjected to oxidative cleavage by hydrogen peroxide in water in the presence of a catalyst, such as tungstic acid, to form BTCA. The second method is electrolytic hydrodimerization of dialkyl maleate followed by hydrolysis of the hydrodimerization product [2, 3, 6].
Even though BTCA is the most efficient nonformaldehyde crosslinking agent for cotton, it has not been used as a durable press finishing agent by the textile industry because of its high cost and unavailability on a commercial scale. A Chinese producer recently succeeded in manufacturing an industrial grade BTCA at a very competitive price, thus making commercial applications of BTCA likely [11]. In this research, we use both chemical and instrumental analytical techniques to investigate industrial grade BTCA (BTCA-I) and compare it with a reagent grade BTCA (BTCA-R). We also evaluate the performance of these two BTCA products as durable press finishes for cotton fabrics.
Experimental
Measuring moisture content: A BTCA sample was weighed and heated in a vacuum oven at 100(deg)C for 30 minutes, transferred into a desiccator to cool to room temperature, then weighed again. This procedure was repeated until the sample reached a constant weight. The moisture content (%) was calculated using the following formula:
{[Initial weight (g) - dry weight (g)]
/ [initial weight (g)]} X 100%
Elemental analysis: The concentrations of carbon, hydrogen, and oxygen (C, H, 0) of the BTCA samples were analyzed with a PE 240C C, H, N analyzer. Approximately 2 mg of a sample was first combusted, then separated by chemical chromatography, and measured by a thermal conductivity detector to determine the C, H, N concentrations.
Acid/base titration: Approximately 4 g of BTCA was accurately weighed and dissolved in CO^sub 2^-free distilled water in a 1000 ml volumetric flask; 20 ml of the BTCA solution were then titrated with a standard sodium hydroxide solution (0.0540M). The equivalent point (pH = 8.5) was determined by a pH meter. Carboxylic acid concentration (mmol/g) was calculated using the following formula:
[Volume of NaOH (ml)
x concentration of NaOH (mmol/ml)]
X [1000 (ml)/20 (ml)] / [the weight of sample (g)]
The purity of the BTCA sample was calculated using the following formula:
{[Carboxylic acid concentration of the sample (mmol/g)]
/ [theoretical value of the carboxylic
acid concentration of BTCA (mmol/g)]} X 100%
FTIR spectroscopy: A Nicolet Magna 760 FTIR spectrometer was used to collect the transmission spectra of a BTCA powder. Resolution for all the infrared spectra was 4 cm^sup -1^ , and there were 100 scans for each spectrum. No smoothing functions and baseline correction were used.
FT-Raman spectroscopy: A Nicolet 950 FT-Raman spectrometer with a powder sample accessory and an InGaAs detector was used to collect all the Raman spectra of BTCA powders. The resolution was 4 cm^sup -1^, and there were 300 scans for each spectrum.
1H–NMR spectroscopy: NMR data were acquired at 20(deg)C on a Varian Inova 500 spectrometer (500 MHz) using a 10 mg sample dissolved in 0.5 ml D^sub 2^0. The ^sup 1^H chemical shift at 20(deg)C (4.81 ppm) was referenced to DSS (2,2dimethyl-2-silapentane-5-sulfonate) by means of HDo resonance. The coupling constant was computed by multiplying the difference in chemical shift by 500 (Hz).
Mass spectroscopy: The mass analysis was conducted with a Perkin Elmer Sciex API I plus quadrupole mass spectrometer, which scanned negative ions from 100– 600 m/z using a 0.2 m/z step and a 2.0 millisecond dwell time. The samples were dissolved in a mixed solvent of H^sub 2^O/CH^sub 3^CN (50:50) and infused at a rate of 0.2 ml/min.
LC/MS: The HPLC used a Kromasil C-18 column (1 mm X 250 mm with a 5 (mu)m particle size and 100 Angstrom pore size) made by Keystone Scientific and an Applied Biosystems (ABi) solvent delivery system. Solvent A was H^sub 2^O and solvent B was acetonitrile (CH^sub 3^CN). A sample was injected with 100% A. A was held at 100% for 7 minutes, and B was ramped to 70% in 30 minutes and then to 100% in 5 minutes. 100% B was held for the remainder of the run. The HPLC flow rate was 30 (mu)L per minute. The uv at 220 nm was measured using an ABt 759A absorbance detector. After flowing through the detector, the effluent was split so that it went at a rate of 16 (mu)L per minute into the PE Sciex API I plus quadrupole mass spectrometer equipped with an electrospray source. The mass spectrometer scanned from 100 to 600 m/z with a 2.0 millisecond dwell time and a 0.2 u step size.
Material: The cotton fabrics were desized and bleached print cloth (Testfabrics style 400). Sodium hypophosphite, sodium hydroxide, and BTCA were reagent grade chemicals supplied by Aldrich. Industrial grade BTCA was supplied by Hangzhou Green Additives Institute, Hangzhou, China (green@public 1.hz.zj.cn). The fabric softener was a high-density polyethylene (Mikon HD) supplied by Omnova Solution, South Carolina.
Cotton fabric treatment. The cotton was first impregnated in a solution containing the reagents, padded through two dips and two nips to reach an average wet pickup of 98-103%, dried at 80(deg)C for 3 minutes, and finally cured in a Mathis curing oven at a specified temperature. All the BTCA solutions contained sodium hypophosphite (NaH^sub 2^PO^sub 2^) as a catalyst with a 3:2 (w/w) acid-to-catalyst ratio.
Evaluation of cotton fabric performance: The conditional wrinkle recovery angle (WRA) and durable press (DP) rating of the treated cotton fabric were measured according to AATCC Standard Methods 66-1990 and 124-1992, respectively. Fabric tensile strength was measured according to ASTM Method D5035-90. The fabric ciE whiteness index was measured before washing with a Macbeth Color-Eye 7000A spectrometer according to AATCC Standard Method 110-1995. Initial fabric WRA, DP rating, and tensile strength were evaluated after one home laundering washing/drying (HLWD) cycle without a detergent. Fabric wRA and Dr rating were also evaluated after different numbers of HLWD cycles.