Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G65/00—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule
  • C08G65/34—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule from hydroxy compounds or their metallic derivatives
  • C08G65/46—Post-polymerisation treatment, e.g. recovery, purification, drying
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/26—Drying gases or vapours
  • B01D53/263—Drying gases or vapours by absorption
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C41/00—Preparation of ethers; Preparation of compounds having groups, groups or groups
  • C07C41/01—Preparation of ethers
  • C07C41/09—Preparation of ethers by dehydration of compounds containing hydroxy groups
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C41/00—Preparation of ethers; Preparation of compounds having groups, groups or groups
  • C07C41/01—Preparation of ethers
  • C07C41/34—Separation; Purification; Stabilisation; Use of additives
  • C07C41/36—Separation; Purification; Stabilisation; Use of additives by solid-liquid treatment; by chemisorption
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G65/00—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule
  • C08G65/34—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule from hydroxy compounds or their metallic derivatives

Definitions

• This invention relates to removal of color bodies from polytrimethylene ether glycol using solid adsorbents.
• PDO Polytrimethylene ether glycol
• P03G polytrimethylene ether glycol
• 1 ,3-propanediol may be prepared from: 1. ethylene oxide over a catalyst in the presence of phosphine, water, carbon monoxide, hydrogen and an acid (the “hydroformylation route”); 2. the catalytic solution phase hydration of acrolein followed by reduction (the "acrolein route”).
• Both of these synthetic routes to 1 ,3-propanediol involve the intermediate synthesis of 3-hydroxypropionaldehyde (hereinafter also termed "HPA").
• HPA 3-hydroxypropionaldehyde
• the HPA is reduced to PDO in a final catalytic hydrogenation step.
• Subsequent final purification involves several processes, including vacuum distillation.
• Biochemical routes to 1 ,3-propanediol have been described that utilize feedstocks produced from biological and renewable resources such as corn feed stock.
• PDO is hereinafter referred to as “biochemical PDO” or “biochemically-derived PDO”.
• biochemical PDO biologically-derived PDO
• bacterial strains able to convert glycerol into 1 ,3-propanediol are found in e.g., in the species Klebsiella, Citrobacter, Clostridium, and Lactobacillus.
• the technique is disclosed in several patents, including, US Patents 5,633,362, 5,686,276, and, most recently, 5,821 ,092, all of which are incorporated herein by reference.
• US Patent 5,821 ,092 Nagarajan et al.
• the process incorporates E. coli bacteria, transformed with a heterologous pdu diol dehydratase gene, having specificity for 1 ,2-propanediol.
• the transformed E. coli is grown in the presence of glycerol as a carbon source and 1 ,3-propanediol is isolated from the growth media.
• the process of the invention provided a rapid, inexpensive and environmentally responsible source of 1 ,3- propanediol monomer useful in the production of polyesters, polyethers, and other polymers.
• Precipitations e.g., with 1 ,2-propylene glycol, as well as carboxylates or other materials
• Precipitations have been used since the early 1980's to separate the colored and odiferous components from desired products
• Patent 5,527,973 discloses a process for providing a purified 1 ,3- propanediol that can be used as a starting material for low color polyester. That process has several disadvantages including the use of large equipment and the need for dilution with large quantities of water, which are difficult to remove from the product.
• 6,235,948 discloses a process for the removal color-forming impurities from 1 ,3-propanediol by a preheating, preferably with heterogeneous acid catalysts such as perfluorinated ion exchange polymers.
• the catalyst is filtered off, and the 1 ,3-propanediol is then isolated, preferably by vacuum distillation.
• Preparation of polytrimethylene ether glycol from purified diol gave APHA values of 30 - 40, however, the molecular weight of the polymers were not reported.
• the polyalkylene ether glycols are generally prepared by the acid- catalyzed elimination of water from the corresponding alkylene glycol or the acid-catalyzed ring opening of the alkylene oxide.
• polytrimethylene ether glycol can be prepared by dehydration of 1,3- propanediol or by ring opening polymerization of oxetane using soluble acid catalysts.
• Methods for making P03G from the glycol, using sulfuric acid catalyst are fully described in U.S. Patent Application publication Nos. 2002/0007043A1 and 2002/0010374A1 , all of which are incorporated herein by reference. It should be noted that polyol synthesis conditions largely determine amounts of impurities, color precursors, and color bodies formed.
• the polyether glycol prepared by the process is purified by the methods known in the art.
• the purification process for polytrimethylene ether glycol typically comprises (1 ) a hydrolysis step to hydrolyze the acid esters formed during the polymerization (2) water extraction steps to remove the acid catalyst, unreacted monomer, low molecular weight linear oligomers and oligomers of cyclic ethers, (3) a base treatment, typically with a slurry of calcium hydroxide, to neutralize and precipitate the residual acid present, and (4) drying and filtration of the polymer to remove the residual water and solids.
• the polytrimethylene ether glycol produced from the acid catalyzed polycondensation of 1 ,3-propanediol has quality problems, in particular the color is not acceptable to the industry.
• the polymer quality is in general dependent on the quality of the raw material, PDO.
• the polymerization process conditions and stability of the polymer are also responsible for discoloration to some extent.
• the polyether diols tend to have light color, a property that is undesirable in many end-uses.
• the polytrimethylene ether glycols are easily discolored by contact with oxygen or air, particularly at elevated temperatures, so the polymerization is effected under a nitrogen atmosphere and the polyether diols are stored in the presence of inert gas.
• a small concentration of a suitable antioxidant is added.
• Preferred is butylated hydroxytoluene (BHT, 2.6-di-t-butyl-4-methylphenol) at a concentration of about 100-500 microg/g (micrograms/gram) polyether.
• BHT butylated hydroxytoluene
• microg/g micrograms/gram
• SUMMARY OF THE INVENTION Disclosed is a process comprising contacting P03G having color with adsorbent and separating the P03G and adsorbent, wherein the P03G, after contact with the adsorbent, has a molecular weight of about
• adsorbent In using the term “adsorbent”, reference is made to materials that commonly are used to remove relatively small amounts of undesired components, whether such removal is by the process of adsorption or absorption, since many decolorization processes involve both mechanisms.
• color and “color bodies” are meant the existence of visible color that can be quantified by the use of a spectrocolorimeter in the range of visible light, using wavelengths of approximately 400 - 800 nm, and by comparison with pure water. Color precursors in PDO are not visible in this range, but contribute color after polymerization.
• the P03G made from the PDO of the present invention can be P03G homo- or co-polymer.
• the PDO can be polymerized with other diols (below) to make co-polymer.
• the PDO copolymers useful in the present invention can contain up to 50% by weight (preferably 20% by weight or less) of comonomer diols in addition to the 1 ,3-propanediol and/or its oligomers.
• Comonomer diols that are suitable for use in the process include aliphatic diols, for example, ethylenediol, 1 ,6-hexanediol, 1 ,7-heptanediol, 1 ,8-octanediol, 1 ,9-nonanediol, 1 ,10-decanediol, 1 ,12-dodecanediol, 3,3,4 ,4,5,5-hexafluro-1 ,5-pentanediol, 2,2,3,3,4,4,5,5-octafluoro-1 ,6-hexanediol, 3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10- hexadecafluoro-1 ,12-dodecanediol, cycloaliphatic diols, for example, 1 ,4-cyclohexanedio
• a preferred group of comonomer diol is selected from the group consisting of 2-methyl-1 ,3-propanediol, 2,2-dimethyl-1 ,3- propanediol, 2,2-diethyl-1 ,3-propanediol, 2-ethyl-2-(hydroxymethyl)-1 ,3- propanediol, 1,6-hexanediol, 1 ,8-octanediol, 1,10-decanediol, isosorbide, and mixtures thereof.
• Thermal stabilizers, antioxidants and coloring materials may be added to the polymerization mixture or to the final polymer if necessary.
• a process comprises contacting P03G having color with adsorbent and separating the P03G and adsorbent, wherein the P03G, after contact with the adsorbent, has a molecular weight of about 250 to about 5000 and a APHA color of less than about 50.
• the APHA color is less than about 40, more preferably, less than 30 and most preferably, less than about 20.
• APHA color values are a measure of color as defined in ASTM- D-1209 (see Test Method 1, below).
• the molecular weight of the P03G is about 250 to about 5000. More preferably, the molecular weight is about 500 to about 4000. Most preferably, the molecular weigh is about 1000 to about 3000.
• the adsorbent comprises-at least one of activated carbon, alumina, silica, diatomaceous earth, montmorillonite clays, Fuller's earth, kaolin minerals and derivatives thereof.
• the adsorbent comprises activated carbon.
• activated carbon includes “charcoal”.
• Activated carbon is an amorphous solid that has very large internal surface area and pore volume and has very low affinity for water.
• the amount of adsorbent used depends on the nature of the adsorbent, concentration of color bodies in the polytrimethylene ether glycol, interaction with the substrate and the process conditions such as contact time and temperature. For instance, in the practice of the present invention, 0.1 - 5%, and preferably 0.25 - 3%, activated carbon based on the weight of the polyether glycol is added to the P03G having color, with stirring under an inert atmosphere such as nitrogen. The contacting of the P03G with absorbent is carried out at a temperature such that the polymer is liquid and has a viscosity low enough to permit mixing and stirring.
• the mixing and stirring can be carried out at temperatures of about 10 - 150°C, preferably, about 25 - 100°C.
• the contacting is conducted for a period of about 5 to about 60 min., and preferably about 10 to about 30 min.
• Preferably contacting the P03G with the absorbent and the subsequent filtration are completed under an inert nitrogen atmosphere.
• Suitable processes for vacuum filtration are well known to those skilled in the art. Due to the viscosity of the P03G, filtration is conveniently accelerated by filtering at an elevated temperature. Typically, a temperature in the range of about 50° to about 100°C is sufficient.
• a filter bed of CELPURE C65 is firmly packed onto a 1 -micrometer Whatman filter paper, supported on a 250-mL fritted glass funnel, equipped with means to heat the filter.
• Other filter media may be used and will be well known to those skilled in the art, the requirements being a fineness of filter sufficient to retain the charcoal and inert to the glycol.
• the polytrimethylene ether glycol has a APHA color, before contact with adsorbent, of at least 50 APHA.
• the color, before contact with adsorbent can be about 70 to about 300.
• the APHA color, before contact with the absorbent can also be about 85-250 APHA, or about 100-200 APHA.
• a batch process may be used wherein the adsorbent is effectively contacted by mixing with the polyol and, after a period of time, separating the polyol from the adsorbent by suitable means, for example, by filtration, centrifugation, etc.
• the process of the invention may also be conducted in a continuous or semi-continuous fashion.
• the polyol may be pumped from a storage tank through a fixed bed of the adsorbent.
• the feed rate is adjusted for the kind, amount, and prior use of adsorbent in the bed and the color level of the feedstock so that the contact time of the polyol with the adsorbent is sufficiently long to give an effluent with the desired color reduction.
• the effluent may be kept in a holding tank for a short time, or used or shipped immediately.
• Other variations will be recognized by those skilled in the art.
• the APHA color of the polytrimethylene ether glycol is reduced by at least about 50%.
• the APHA color of the polytrimethylene ether glycol is reduced by at least about 60%, more preferably, by at least about 70%.
• the process of the present invention may be used for the decolorization of polytrimethylene ether glycol prepared by polymerization of PDO prepared from petrochemical sources, such as the process using acrolien, and also to the polyol prepared by polymerization of PDO prepared by biochemical routes.
• the activated carbon treatment can be performed either for the final polymer or it can be performed just prior to the filtration step of the purification process.
• the preferred way is to add the activated carbon to P03G polymer just prior to final filtration and store the filtered polymer in the presence of an antioxidant such as BHT.
• the activated carbon is available from many sources in different forms such as powder, granular, and shaped products.
• the preferred form is powdered activated carbon.
• Various brands of carbon may be used, including, but not limited to,
• a process comprises:
• the adsorbent comprises activated carbon
• the P03G is contacted with about 0.1 to about 5 weight % of the activated carbon based on the weight of the polytrimethylene ether glycol, and the contacting is conducted at a temperature of about 10° to about 150°C.
• a product comprises (i) P03G having color and (ii) adsorbent (as already described herein), wherein the P03G has a APHA color of less than about
• the APHA color is about 40, more preferably about 30, most preferably about 20.
• the product contains about 0.25 % to about 5 % adsorbent, more preferably about 1% to about 3% adsorbent.
• the P03G polymer prepared from1 ,3-propanediol is either from DuPont or from a commercially available source.
• Activated carbons (DARCO, CALGON, and CECA) and BHT are from Aldrich Chemicals (Milwaukee Wl).
• CELPURE products are from Advanced Minerals (Santa Barbara, CA). These products were used not only to remove color bodies from the polymer but also as filter aid.
• Test Method 1 Color Measurement and APHA Values.
• a Hunterlab ColorQuest Spectrocolorimeter [Reston, VA] was used to measure the polymer color before and after solid adsorbent treatment. Color numbers of the polymer are measured as APHA values (Platinum- Cobalt System) according to ASTM D-1209. The polymer molecular weights are calculated from their hydroxyl numbers obtained from titration method.
• the polymer was dried under reduced pressure at 90°C for 3 hours and then filtered through a Whatman filter paper precoated with a CELPURE filter aid.
• the purified P03G polymer obtained was analyzed for molecular weight and color.
• a 250-mL fritted glass funnel was securely assembled.
• CELPURE C65 (4.4 g, 1.2 kg/m 2 ) was packed firmly on 1 -micron size Whatman filter paper that was placed on the frit.
• a heating tape was wrapped around the funnel to provide heat to the polymer during filtration process.
• Activated charcoal O.OO ⁇ g, 0.01 wt%, DARCO G60 was added to the polymer.
• a magnetic stir was added to the polymer that was then stirred on a stirrer for 10 minutes under nitrogen at room temperature. Then the polymer, was filtered through the fritted glass funnel with the aid of house vacuum under a nitrogen blanket.
• the temperature was set at between 60°C - 70°C by adjusting the temperature controller (VARIAC).
• VARIAC temperature controller
• the final polymer was measured for color on a Hunterlab ColorQuest Spectrocolorimeter.
• BHT 200 micrograms/g polymer was added to the polymer as soon as finished.
• a control measurement on a sample for which the charcoal was omitted was made. The results are shown in Table 1.
• Example 3 The procedure of Example 2 was repeated using various amounts
• Example 5 The procedure of Example 5 was replicated to determine the reproducibility of the process.
• the P03G polymer used in these examples has a molecular weight of 2449, color of 145 APHA, and contains 200 micrograms BHT/g polymer. The results are shown in Table 2.
• Example 5 was repeated using higher amounts of carbon using P03G polymer having 2212 molecular weight and color of 70 APHA.
• Example 5 was repeated with the crude polymer rather than purific polymer.
• the crude polymer has color of 134 APHA.
• This polymer was hydrolyzed, neutralized with excess of calcium hydroxide and dried.
• a 0.25 wt% activated carbon was added to the dried P03G polymer containing residual base and salts and filtered as described above.
• the filtered P03G color was measured and found to be 80 APHA, indicating the activated carbon can be added just prior to final filtration step of the purification process.

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• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
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