Calcium terephthalate

Health and Safety Factors. Terephthahc acid has a low order of toxicity. Inhalation by rats for 6 h/d, 5 d/wk for 4 wk produced no fatahties at a dust exposure level of 25 mg/m. The mean acute oral toxicity for rats is over 18 g/kg (86), and for mice over 6 g/kg (87). When terephthahc acid was fed as 3% of the diet to rats, urinary calcuh formed in 90 d, some of which led to cancer. High doses of terephthahc acid lead to formation of calcium terephthalate at levels exceeding its solubihty in urine. This insoluble material leads to the calcuh and provides a threshold below which cancer is not observed (88). Normal precautions used in handling industrial chemicals should be observed with terephthahc acid. If ventilation is inadequate, a toxic-dust respirator should be used to avoid prolonged exposure. 

The characteristic features of liquefaction described above necessarily result in unstable operation and high cost of liquefaction via pyrolysis. Recently, the operational problems have been solved by adding calcium hydroxide to control the evaporation and decomposition of terephthalate components such as calcium terephthalate [5]. 

Figure 8.32 shows the effect of filler type and concentration on the mode of fracture. Several factors are responsible for the behavior. CaT (calcium terephthalate) fillers have good adhesion to the matrix and have an elongated shape. CaCOs (1) and (2) are both untreated fillers of smaller particle sizes (2.2 and 4.1 (dm, respectively). CaCO (3) is a stearate coated filler (better dispersion, but poor adhesion to matrix) with a particle size of 6.1 im. The mode of fracture depends on filler concentration, the degree of adhesion to the matrix, and particle size. 

Synthesis of N,N -bis(p-carbomethoxybenzoyl) butanediamine (T4T-dimethyl). Dimethyl terephthalate (DMT) (275 g, 1.42 mol) is dissolved at 65°C in a mixture of 1100 mL anhydrous toluene and 85 mL anhydrous methanol in a 2-L flask equipped with a stirrer, condenser, calcium chloride tube, and nitrogen inlet. When all the DMT is dissolved, 15 mL lithium methoxide (1.25 M) is added. 1,4-Butanediamine (BDA) (34 mL, 0.34 mol), dissolved in 150 mL anhydrous toluene and 10 mL anhydrous methanol, is added dropwise in 4-6 h while the nitrogen flow is stopped. Three hours after the start of the BDA addition, the temperature is gradually increased up to 90°C (5°C/h) while the methanol is stripped off. After a total reaction time of 24 h the reaction is stopped. The white... 

Scratch resistance depends on the hardness of the added particles. The problem of a lack of this property can be addressed by adding chemically identical particles of different crystal modification and Mohs hardness. The preferred additives are silica, alumina, layered silicates such as kaolin, titania, barium sulfate and calcium carbonate. The latter is only suitable for the DMT process owing to side reaction caused by acidity during the terephthalic acid (TPA) route. 

Toluene, formaldehyde, HC.1, calcium hydroxide, and UNO , comprise the chargestock. In step 1 of this process, the toluene is reacted with concentrated HC1 at about 70°C along with paraformaldehyde. This accomplishes chloromethylation of approximately 98% of the toluene. In step 2, saponification of the chloromethyltoluene is effected with lime and H20 under pressure and at about 125°C. The product is methylbenzyl alcohol. In step 3. the methylbenzyl alcohol is oxidized with HNO3 (dilute) under a pressure of about 20 atmospheres and at a temperature of about 170°C. The main products are o-phthalic acid in HNO3 solution and insoluble terephthalic acid. 

Teijin aramid fiber, known as Technora (formerly as HM-50), is made slightly differently from the liquid crystal route described above. Three monomers, terephthalic acid, p-phenylenediamine (PDA), and 3,4-diamino diphenyl ether are used. The ether monomer provides more flexibility to the backbone chain which results in a fiber that has slightly better compressive properties than PPTA aramid fiber made via the liquid crystal route. An amide solvent with a small amount of salt (calcium chloride or lithium chloride) is used as a solvent (Ozawa et al., 1978). The polymerization is done at 0-80 C in 1-5 h and with a polymer concentration of 6-12%. The reaction mixture is spun from a spirmeret into a coagulating bath containing 35-50% CaClj. Draw ratios between 6 and 10 are used. 

A thin layer of the appropriate stationary phase is bonded to a suitable plate made of glass, aluminium foil, or plastic (polyethylene terephthalate). Adherence to the plate is usually assured by mixing a binding agent such as calcium sulphate with the stationary phase. Glass is the most popular plate material, but the others have the advantage that they... 

The pyrolysis of PET by Sakata [3] has been found surprisingly to yield no liquid products. It is widely known that compounds that undergo sublimation, such as tereph-thalic acid and benzoic acid, are produced by the thermal decomposition of PET and this causes problems in plastic pyrolysis plants. Interestingly Yoshioka et al. [4] found that the addition of calcium hydroxide (slaked lime) gives high selectivity for benzene formation without producing sublimation compounds such as terephthalic acid. The yield of benzene is around 35 wt% at 700°C and a 10.0 calcium hydroxide/PET molar ratio. 

In the second phase of the parametric study the removal of halogens from the reaction products was examined. Two different halogen removal methods were studied. The first method used a calcium oxide fixed bed placed between the reactor and condenser to remove organochloride vapours. However, it was found that the calcium oxide bed would plug up very rapidly if PET was present in the feed mixture and would become ineffective. This is because the PET would depolymerize into terephthalic acid and CO2 and would react with calcium oxide and cause it to plug up. The second method that was used for removal of chlorine was to add calcium oxide or hydroxide directly into the reactor with the plastic feed. It was found that this approach is far more effective than the previous method. Through trial and error it was found that calcium hydroxide feed of 10 wt% would remove the highest amount of chlorine (Table 19.7) [9]. 

Evacuated blood tubes may be made of soda-lime or borosflicate glass or plastic (polyethylene terephthalate). Because of the decreased likelihood of breakage and hence exposure to infectious materials, many laboratories have converted from glass tubes to plastic tubes. Tubes made from the soda-lime glass may release trace elements, particularly calcium and magnesium, into solutions. Special tubes are available for trace element determination (Table 2-2). 

Calcichrome has been used for determination of calcium in soil extracts [81] and in poly(ethylene terephthalate) [82], Calcium has been determined in river water with Propyl Orange after extraction with a crown ether [67]. 

Under model conditions ethyleneglycol as a hydrolysis product increases solubility of Ca (OH)2. However, its accumulation or introduction into the beaded mill as a component of the liquid phase does not lead to hydrolysis intensification. Probably it occurs because presence of ethyleneglycol promotes the growth of liquid phase viscosity that may be connected with increase in solubility of calcium salt of terephthalic acid in liquid phase of the reaction mixture. In consequence of this significant drop in efficiency of the beaded mill work is observed. 

Calcium salt of terephthalic acid that is slightly soluble in water remains on the surface of the solid part of the polymer and ethylene glycol that is soluble in water mainly goes into the liquid phase. Finally surface sediments of the products arise on particles of PET. Under conditions of intensive mechanical stirring and interaction of the particles with each other the sediments can move from particles of PET to ones of Ca(OH)2. It will lead to blocking of both particles of PET and ones of Ca(OH)2.In consequence of this the concentration of Ca(OH)2 in solution decreases that may be a reason of self-stopping to be met practice. 

A wide range of chemical agents, catalysts and conditions for the glycolysis of unsaturated polyester resins, used in the manufacture of buttons, have been described in a recent patent.34 In addition to different metal acetates, the following compounds have been proposed to be catalytically active in PET glycolysis sodium methylate, sodium ethylate, sodium hydroxide, methane-sulfonic acid, magnesium oxide, barium oxide and calcium oxide. Different applications of the depolymerization products were described, e.g., preparation of fresh unsaturated polyesters by reaction with maleic acid, maleic acid/ phthalic anhydride or maleic anhydride/terephthalic acid or the synthesis of polyurethane resins by reaction with a diisocyanate. 

In the first stage of tiie manufacture of polyethylene terephthalate, dimethyl terephthalate (1 mole) is caused to re t with ethylene glycol (2 moles) in the presence of a catalyst. Suital catalysts are litharge, zinc salts, calcium salts, magnesium salts, alkali metals or their alkoxides, etc. The catalyst concentration may vary from 0.005-0.1 per cent. The reaction begins at 150-160°C, and tiie methyl alcohol is distilled out through E. I. du Font de Nemours dc Company, Inc. 

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