WO2008118495A1

WO2008118495A1 - Lower-color polytrimethylene ether glycol using zero-valent metals

Info

Publication number: WO2008118495A1
Application number: PCT/US2008/004083
Authority: WO
Inventors: Yanhui Niu; Zuohong Yin
Original assignee: EI Du Pont de Nemours and Co
Current assignee: EIDP Inc
Priority date: 2007-03-27
Filing date: 2008-03-27
Publication date: 2008-10-02
Anticipated expiration: 2009-09-27
Also published as: US20080242831A1; TW200904853A

Abstract

The present invention relates to a process for preparing lower-color polytrimethylene ether glycol polymer, comprising contacting said polytrimethylene ether glycol polymer, or its precursor reaction-mixture, with a zero-valent metal during at least one stage of the process of manufacture, or on the polytrimethylene glycol resulting form such process, such that the polytrimethylene ether glycol polymer demonstrates a reduced color (as compared to using no zero-valent metal).

Description

TITLE

LOWER-COLOR POLYTRIMETHYLENE ETHER GLYCOL USING ZERO-VALENT

METALS

FIELD OF THE INVENTION

The present invention relates to a process for preparing lower-color poly- thmethylene ether glycol polymer, comprising contacting said polythmethylene ether glycol polymer, or its precursor reaction-mixture, with a zero-valent metal during at least one stage of the process of manufacture, or on the polytrimethylene glycol resulting form such process, such that the resulting polytrimethylene ether glycol polymer demonstrates a reduced color (as compared to using no zero-valent metal).

BACKGROUND OF THE INVENTION

Polytrimethylene ether glycol (PO3G) and its uses have been described in the art. Preferred methods for preparation of a polytrimethylene ether glycol involve acid catalyzed polycondensation of 1 ,3-propanediol. For example, US6720459 and US6977291 disclose processes for preparation of a polytrimethylene ether glycol from 1 ,3-propanediol using a polycondensation catalyst, preferably an acid catalyst such as sulfuric acid.

Specifically, US6977291 describes a purification procedure for a crude polytrimethylene ether glycol obtained from an acid catalyzed polymerization process com- prising: (1 ) a hydrolysis step to hydrolyze the acid esters formed during the acid catalyzed polymerization; (2) phase separation and water extraction steps to remove soluble acid catalyst, thereby generating an organic phase and a waste aqueous phase; (3) a base treatment of the organic phase to neutralize and precipitate the residual acid present; and (4) drying and filtration of the polymer to remove residual water and sol- ids. It is clear from the disclosure that, when sulfuric acid is used as a catalyst to make polyether glycols from their corresponding diols, it is preferred to include a hydrolysis step because a substantial portion of the acid catalyst is converted to an ester (alkyl hydrogen sulfate).

US 2005/0272911A1 and US Application Serial No. 1 1/654865 (filed January 18, 2007) disclose polycondensation processes for preparing polyether polyols, includ- ing preparing polytrimethylene ether glycol from 1 ,3-propanediol, utilizing a polycon- densation catalyst system that contains both an acid and a base. It is disclosed that the use of this catalyst system produces polyether polyol with a high degree of polymerization and low color under mild conditions. The purification processes utilize a hy- drolysis step wherein water and organic solvent that has affinity for both water and the polyether polyol are used and subsequent separation into aqueous and organic phases. In one example of US 2005/0227911 A1 , there is disclosed the use of calcium hydroxide to treat the organic phase after the phase separation.

US7161045 relates to a process of manufacture of polytrimethylene ether gly- col comprising: (a) polycondensing reactant comprising a diol selected from the group consisting of 1 ,3-propanediol, 1 ,3-propanediol dimer and 1 ,3-propanediol trimer or mixtures thereof in the presence of an acid polycondensation catalyst to form polytrimethylene ether glycol; (b) adding water to the polytrimethylene ether glycol and hy- drolyzing the acid esters formed during the polycondensation to form a hydrolyzed mix- ture containing the polytrimethylene ether glycol and the hydrolyzed acid esters; (c) adding an organic solvent that is immiscible with water to the hydrolyzed mixture to form an aqueous-organic mixture comprising (i) an organic phase containing polytrimethylene ether glycol and residual acid polycondensation catalyst from the polycondensing, and (ii) a water phase; (d) separating the water phase and the organic phase; (e) adding a base to the separated organic phase to neutralize the residual acid polycondensation catalyst by forming salts of the residual acid polycondensation catalyst; (f) separating the organic phase into (i) a liquid phase comprising the polytrimethylene ether glycol, the organic solvent and any residual water, and (ii) a solid phase comprising the salts of the residual acid polycondensation catalyst and the base which is unreacted; and (g) removing the organic solvent and the residual water from the organic phase to obtain polytrimethylene ether glycol. The organic solvent added in step (c) helps to promote phase formation and separation.

US7157607 discloses a process of manufacture of polytrimethylene ether glycol that is similar to that disclosed in previously incorporated US7161045, except that an organic solvent that is miscible with polytrimethylene ether is added to the hydrolyzed aqueous mixture.

US7164046 and US Application Serial No. 11/599861 (filed November 15, 2006) disclose the addition of one or more water-soluble, inorganic compounds to the hydrolyzed mixture to promote phase formation and separation, wherein the water- soluble, inorganic compounds are selected from the group consisting of an inorganic salt and an inorganic base.

In the PO3G polymer manufacturing processes described above, it is com- monly found that the polytrimethylene ether glycol polymers have residual color that results into a lower-quality polymer, not adequate for many of the polymer applications.

The quality of 1 ,3-propanediol, the polymerization process conditions, and polymer degradation are most likely responsible for the polymer discoloration. In addition, the color of the final polymer can be affected by factors such as temperature of polymeri- zation, oxidizing agents present in the reaction mixture, acidity, etc.

The presence of color is a major impediment to providing a high-quality polytrimethylene glycol polymer. Because a majority of the current PO3G processes involve high-temperature processing, discoloration could happen essentially at any step during the process, especially with a strong oxidizing agent (such as H₂SO₄) present in the mixture.

The present invention reduces color of the resulting polymeric P03G, without substantially compromising polymer properties, preferably in a shorter cycle time and at a lower cost, by using a zero-valent metal at one or more stages of the PO3G.

SUMMARY OF THE INVENTION

In one aspect, the present invention is directed to a process for the manufacture of a polytrimethylene ether glycol, comprising the steps of:

(a) polycondensing reactant comprising a diol selected from the group consisting of 1 ,3-propanediol, 1 ,3-propanediol dimer, 1 ,3-propanediol trimer and mixtures thereof, in the presence of an acid polycondensation catalyst to form a polytrimethyl- ene ether glycol and an acid ester of the acid polycondensation catalyst;

(b) adding water to the polytrimethylene ether glycol and hydrolyzing the acid ester formed during the polycondensation to form a hydrolyzed aqueous-organic mixture containing polytrimethylene ether glycol and residual acid polycondensation catalyst; (c) forming an aqueous phase and an organic phase from the hydrolyzed aqueous-organic mixture, wherein the organic phase contains polytrimethylene ether glycol and residual acid polycondensation catalyst,

(d) separating the aqueous phase and the organic phase;

(e) optionally adding base to the separated organic phase to neutralize residual acid polycondensation catalyst by forming salts of the residual acid polycondensation catalyst;

(f) removing residual water from the organic phase; and

(g) in the event that a base is added in step (e), and optionally otherwise, separating the organic phase into (i) a liquid phase comprising polytrimethylene ether glycol, and (ii) a solid phase comprising the salts of the residual acid polycondensation catalyst and base which is unreacted,

wherein a zero-valent metal is (1 ) added at least once during at least one of said steps . (a), (b), (c), (d), (e), (f) and (g), and/or (2) is contacted with polytrimethylene ether gly- col from step (g).

Preferably, the forming of the aqueous and organic phases in step (c) (and thus the separation in step (d)) is enhanced by adding to the hydrolyzed aqueous-organic mixture:

(i) a water-soluble, inorganic compound selected from the group consisting of an inorganic salt and an inorganic base, and/or

(ii)(1 ) a water-immiscible organic solvent that is miscible with polytrimethylene ether glycol, or

(ii)(2) an organic solvent that is miscible with water and the polytrimethylene ether glycol.

In a preferred embodiment, the zero-valent metal is added during hydrolysis

(b); during the forming of the aqueous and organic phases (c), including during addition of inorganic compound/organic solvent; during phase separation (d); during neutralization (e); and/or during drying (f). In another preferred embodiment, the zero-valent metal is added more than once, preferably during neutralization (e) and/or drying (f).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

All publications, patent applications, patents and other references mentioned herein, if not otherwise indicated, are explicitly incorporated by reference herein for all purposes as if fully set forth.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In case of conflict, the present specification, including defini- tions, will control.

Except where expressly noted, trademarks are shown in upper case. Unless stated otherwise, all percentages, parts, ratios, etc., are by weight.

When an amount, concentration, or other value or parameter is given as either a range, preferred range or a list of upper preferable values and lower preferable val- ues, this is to be understood as specifically disclosing all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether ranges are separately disclosed. Where a range of numerical values is recited herein, unless otherwise stated, the range is intended to include the endpoints thereof, and all integers and fractions within the range. It is not intended that the scope of the invention be limited to the specific values recited when defining a range.

When the term "about" is used in describing a value or an end-point of a range, the disclosure should be understood to include the specific value or end-point referred to. As used herein, the terms "comprises," "comprising," "includes," "including,"

"has," "having" or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such process, method, article, or appara- tus. Further, unless expressly stated to the contrary, "or" refers to an inclusive or and not to an exclusive or. For example, a condition A or B is satisfied by any one of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present).

Use of "a" or "an" are employed to describe elements and components of the invention. This is done merely for convenience and to give a general sense of the in- vention. This description should be read to include one or at least one and the singular also includes the plural unless it is obvious that it is meant otherwise.

The materials, methods, and examples herein are illustrative only and, except as specifically stated, are not intended to be limiting. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described herein.

Starting Materials

The starting material for the process is reactant comprising at least one of 1 ,3-propanediol, 1 ,3-propanediol dimer and 1 ,3-propanediol trimer, or mixtures thereof.

The 1 ,3-propanediol reactant employed in the process of the present invention may be obtained by any of the various chemical routes or by biochemical transformation routes. Preferred routes are described in US5015789, US5276201 , US5284979, US5334778, US5364984, US5364987, US5633362, US5686276, US5821092, US5962745, US6140543, US6232511 , US6235948, US6277289, US6284930, US6297408, US6331264, US6342646, US2004/0225161A1 , US2004/0260125A1 , US2005/0069997A1 and US Application Ser. No. 11/599861 (filed November 15, 2006).

The preferred source of 1 ,3-propanediol is via a fermentation process using a renewable biological source. As an illustrative example of a starting material from a renewable source, biochemical routes to 1 ,3-propanediol (PDO) have been described that utilize feedstocks produced from biological and renewable resources such as corn feed stock. For example, bacterial strains able to convert glycerol into 1 ,3-propanediol are found in the species Klebsiella, Citrobacter, Clostridium, and Lactobacillus. The technique is disclosed in several patents, including US5633362, US5686276 and US5821092. For example, US5821092 discloses, inter alia, a process for the biologi- cal production of 1 ,3-propanediol from glycerol using recombinant organisms. The process incorporates E. coli bacteria, transformed with a heterologous pdu diol dehy- dratase 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. Since both bacteria and yeasts can convert glucose (e.g., com sugar) or other carbohydrates to glycerol, the processes disclosed in these publications pro- vide a rapid, inexpensive and environmentally responsible source of 1 ,3-propanediol monomer.

The biologically-derived 1 ,3-propanediol, such as produced by the processes described and referenced above, contains carbon from the atmospheric carbon dioxide incorporated by plants, which compose the feedstock for the production of the 1 ,3- propanediol. In this way, the biologically-derived 1 ,3-propanediol preferred for use in the context of the present invention contains only renewable carbon, and not fossil fuel-based or petroleum-based carbon. The polytrimethylene ether glycol and personal care compositions of the present invention utilizing the biologically-derived 1 ,3- propanediol, therefore, have less impact on the environment as the 1 ,3-propanediol used in the compositions does not deplete diminishing fossil fuels and, upon degradation, releases carbon back to the atmosphere for use by plants once again. Thus, the compositions present invention can be characterized as more natural and having less environmental impact than similar compositions comprising petroleum based glycols.

The biologically-derived 1 ,3-propanediol, and polytrimethylene ether glycols, may be distinguished from similar compounds produced from a petrochemical source or from fossil fuel carbon by dual carbon-isotopic finger printing. This method usefully distinguishes chemically-identical materials, and apportions carbon in the copolymer by source (and possibly year) of growth of the biospheric (plant) component. The isotopes, ¹⁴C and ¹³C, bring complementary information to this problem. The radiocarbon dating isotope (¹⁴C), with its nuclear half life of 5730 years, clearly allows one to apportion specimen carbon between fossil ("dead") and biospheric ("alive") feedstocks (Cur- rie, L. A. "Source Apportionment of Atmospheric Particles," Characterization of Environmental Particles, J. Buffle and H. P. van Leeuwen, Eds., 1 of Vol. I of the IUPAC Environmental Analytical Chemistry Series (Lewis Publishers, Inc) (1992) 3-74). The basic assumption in radiocarbon dating is that the constancy of ¹⁴C concentration in the atmosphere leads to the constancy of ¹⁴C in living organisms. When dealing with an isolated sample, the age of a sample can be deduced approximately by the relationship t = (-573O/O.693)ln(A/Ao)

where t = age, 5730 years is the half-life of radiocarbon, and A and A₀ are the specific ¹⁴C activity of the sample and of the modern standard, respectively (Hsieh, Y., Soil Sci. Soc. Am J., 56, 460, (1992)). However, because of atmospheric nuclear testing since 1950 and the burning of fossil fuel since 1850, ¹⁴C has acquired a second, geochemi- cal time characteristic. Its concentration in atmospheric CO₂, and hence in the living biosphere, approximately doubled at the peak of nuclear testing, in the mid-1960s. It has since been gradually returning to the steady-state cosmogenic (atmospheric) baseline isotope rate (¹⁴C/¹²C) of ca. 1.2 x 10^"12, with an approximate relaxation "half- life" of 7-10 years. (This latter half-life must not be taken literally; rather, one must use the detailed atmospheric nuclear input/decay function to trace the variation of atmospheric and biospheric ¹⁴C since the onset of the nuclear age.) It is this latter biospheric ¹⁴C time characteristic that holds out the promise of annual dating of recent biospheric carbon. ¹⁴C can be measured by accelerator mass spectrometry (AMS), with results given in units of "fraction of modern carbon" (f_M). f_M is defined by National Institute of Standards and Technology (NIST) Standard Reference Materials (SRMs) 4990B and 4990C, known as oxalic acids standards HOxI and. HOxII, respectively. The fundamental definition relates to 0.95 times the ¹⁴C/¹²C isotope ratio HOxI (referenced to AD 1950). This is roughly equivalent to decay-corrected pre-lndustrial Revolution wood. For the current living biosphere (plant material), f_M M .1.

The stable carbon isotope ratio (¹³C/¹²C) provides a complementary route to source discrimination and apportionment. The ¹³C/¹²C ratio in a given biosourced material is a consequence of the ¹³C/¹²C ratio in atmospheric carbon dioxide at the time the carbon dioxide is fixed and also reflects the precise metabolic pathway. Regional variations also occur. Petroleum, C₃ plants (the broadleaf), C₄ plants (the grasses), and marine carbonates all show significant differences in ¹³C/¹²C and the corresponding δ ¹³C values. Furthermore, lipid matter of C₃ and C₄ plants analyze differently than materials derived from the carbohydrate components of the same plants as a consequence of the metabolic pathway. Within the precision of measurement, ¹³C shows large variations due to isotopic fractionation effects, the most significant of which for the instant invention is the photosynthetic mechanism. The major cause of differences in the carbon isotope ratio in plants is closely associated with differences in the pathway of photosynthetic carbon metabolism in the plants, particularly the reaction occurring during the primary carboxylation, i.e., the initial fixation of atmospheric CO₂. Two large classes of vegetation are those that incorporate the "C₃" (or Calvin-Benson) pho- tosynthetic cycle and those that incorporate the "C₄" (or Hatch-Slack) photosynthetic cycle. C₃ plants, such as hardwoods and conifers, are dominant in the temperate climate zones. In C₃ plants, the primary CO₂ fixation or carboxylation reaction involves the enzyme ribulose-1 ,5-diphosphate carboxylase and the first stable product is a 3-carbon compound. C₄ plants, on the other hand, include such plants as tropical grasses, corn and sugar cane. In C₄ plants, an additional carboxylation reaction involving another enzyme, phosphoenol-pyruvate carboxylase, is the primary carboxylation reaction. The first stable carbon compound is a 4-carbon acid, which is subsequently decarboxylated. The CO₂ thus released is refixed by the C₃ cycle.

Both C₄ and C₃ plants exhibit a range of ¹³C¹²C isotopic ratios, but typical values are ca. -10 to -14 per mil (C₄) and -21 to -26 per mil (C₃) (Weber et al., J. Aqric. Food Chem., 45, 2942 (1997)). Coal and petroleum fall generally in this latter range. The ¹³C measurement scale was originally defined by a zero set by pee dee belemnite (PDB) limestone, where values are given in parts per thousand deviations from this material. The "<J¹³C" values are in parts per thousand (per mil), abbreviated %o, and are calculated as follows:

J ¹³C ≡ (¹³C/¹²C)sample - (¹³C/¹²C)standard x 1000%o (¹³C/¹²C)standard

Since the PDB reference material (RM) has been exhausted, a series of alternative RMs have been developed in cooperation with the IAEA, USGS, NIST, and other selected international isotope laboratories. Notations for the per mil deviations from PDB is 5¹³C. Measurements are made on CO₂ by high precision stable ratio mass spectrometry (IRMS) on molecular ions of masses 44, 45 and 46.

Biologically-derived 1 ,3-propanediol, and compositions comprising biologically- derived 1 ,3-propanediol, therefore, may be completely distinguished from their petrochemical derived counterparts on the basis of ¹⁴C (f_M) and dual carbon-isotopic fingerprinting, indicating new compositions of matter. The ability to distinguish these products is beneficial in tracking these materials in commerce. For example, products comprising both "new" and "old" carbon isotope profiles may be distinguished from products made only of "old" materials. Hence, the instant materials may be followed in commerce on the basis of their unique profile and for the purposes of defining competition, for determining shelf life, and especially for assessing environmental impact.

Preferably the 1 ,3-propanediol used as the reactant or as a component of the reactant will have a purity of greater than about 99%, and more preferably greater than about 99.9%, by weight as determined by gas chromatographic analysis. Particularly preferred are the purified 1 ,3-propanediols as disclosed in US20040260125A1 , US20040225161A1 and US20050069997A1 , and polytrimethylene ether glycol made therefrom as disclosed in US20050020805A1.

The purified 1 ,3-propanediol preferably has the following characteristics:

(1 ) an ultraviolet absorption at 220 nm of less than about 0.200, and at 250 nm of less than about 0.075, and at 275 nm of less than about 0.075; and/or

(2) a composition having L^*a^*b* "b^*" color value of less than about 0.15 (ASTM D6290), and an absorbance at 270 nm of less than about 0.075; and/or

(3) a peroxide composition of less than about 10 ppm; and/or

(4) a concentration of total organic impurities (organic compounds other than

1 ,3-propanediol) of less than about 400 ppm, more preferably less than about 300 ppm, and still more preferably less than about 150 ppm, as measured by gas chromatography.

The starting material for making polytrimethylene ether glycol will depend on the desired polytrimethylene ether glycol, availability of starting materials, catalysts, equipment, etc., and comprises "1 ,3-propanediol reactant." By "1 ,3-propanediol reactant" is meant 1 ,3-propanediol, and oligomers and prepolymers of 1 ,3-propanediol preferably having a degree of polymerization of 2 to 9, and mixtures thereof. In some instances, it may be desirable to use up to 10% or more of low molecular weight oli- gomers where they are available. Thus, preferably the starting material comprises 1 ,3- propanediol and the dimer and trimer thereof. A particularly preferred starting material is comprised of about 90% by weight or more 1 ,3-propanediol, and more preferably 99% by weight or more 1 ,3-propanediol, based on the weight of the 1 ,3-propanediol reactant. The starting material for the present invention may also contain small amounts, preferably no more than about 30%, and more preferably no more than about 10%, by weight, of the starting material, of comonomer diols in addition to the reactant 1 ,3-propanediol or its dimers and trimers without detracting from the efficacy of the process. Examples of preferred comonomer diols include ethylene glycol, 2-methyl- 1 ,3-propanediol, 2,2-dimethyl-1 ,3 propanediol, and C₆-C₁₂ diols such as 2, 2-diethyl-1 ,3- propanediol, 2-ethyl-2-hydroxymethyl-1 ,3-propanediol, 1 ,6-hexanediol, 1 ,8-octanediol, 1 ,10-decanediol, 1 ,12-dodecanediol, 1 ,4-cyclohexanediol and

1 ,4-cyclohexanedimethanol. A more preferred comonomer diol is ethylene glycol. Polytrimethylene ether glycols prepared from 1 ,3-propanediol and ethylene glycol are described in US2004/0030095A1.

The polytrimethylene ether glycols of this invention can also be prepared using from about 10 to about 0.1 mole percent of an aliphatic or aromatic diacid or diester, preferably terephthalic acid or dimethyl terephthalate, and most preferably terephthalic acid, as described in detail in US6608168.

Additives

Stabilizers (e.g., UV stabilizers, thermal stabilizers, antioxidants, corrosion inhibitors, etc.), viscosity boosters, antimicrobial additives and coloring materials (e.g., dyes, pigments, etc.) may be added to the polymerization mixture or final product if necessary.

Acid Catalysts

Any acid catalyst suitable for acid catalyzed polycondensation of 1 ,3-propanediol may be used in present process. Preferred acid polycondensation catalysts are described in previously incorporated US6977291 and US6720459. They are preferably selected from the group consisting of Lewis acids, Bronsted acids, super acids and mixtures thereof, and they include both homogeneous and heterogeneous catalysts. More preferably, the catalysts are selected from the group consisting of inorganic acids, organic sulfonic acids, heteropolyacids and metal salts. Still more preferably, the catalyst is a homogeneous catalyst, preferably selected from the group consisting of sulfuric acid, hydriodic acid, fluorosulfonic acid, phosphorous acid, p-toluenesulfonic acid, benzenesulfonic acid, methanesulfonic acid, phosphotungstic acid, trifluoromethanesulfonic acid, phosphomolybdic acid, 1 ,1 ,2,2-tetrafluoro- ethanesulfonic acid, 1 ,1 ,1 ,2,3,3-hexafluoropropanesulfonic acid, bismuth triflate, yttrium triflate, ytterbium triflate, neodymium triflate, lanthanum triflate, scandium triflate and zirconium triflate. The catalyst can also be a heterogeneous catalyst, preferably selected from the group consisting of zeolites, fluorinated-alumina, acid-treated alumina, heteropolyacids and heteropolyacids supported on zirconia, titania alumina and/or silica. An especially preferred catalyst is sulfuric acid.

Preferably, the polycondensation catalyst is used in an amount of from about 0.1 wt% to about 3 wt%, more preferably from about 0.5 wt% to about 1.5 wt%, based on the weight of reactant.

The process of this invention may also be carried out using a base or a salt as a component of the catalyst system, such as the polycondensation catalyst that contains both an acid and a base described in previously incorporated US2005/0272911A1 and US Application Serial No. 11/654865 (filed January 18, 2007). When base is used as a component of the polycondensation catalyst, the amount of base should be such that it insufficient to neutralize all of the acid present in the catalyst.

Optional additives may also be present during the polycondensation, for example, an inorganic compound such as an alkali metal carbonate, and an onium com- pound.

Preferred inorganic compounds are alkali metal carbonates, more preferably selected from potassium carbonate and/or sodium carbonate, and still more preferably sodium carbonate.

By onium compound is meant a salt which has onium ion as the counter cation. Generally, the onium salt has a cation (with its counterion) derived by addition of a hy- dron to a mononuclear parent hydride of the nitrogen, chalcogen and halogen family, e.g. H₄N⁺ ammonium ion. It also includes CI₂F⁺ dichlorofluoronium, (CH₃)₂S⁺H di- methylsulfonium (a secondary sulfonium ion), CICH₃)₃P⁺ chlorotrimethylphosphonium, (CH₃CH₂)₄N⁺ tetraethylammonium (a quaternary ammonium ion). Preferred are qua- ternary ammonium compounds, phosphonium compounds, arsonium compounds, sti- bonium compounds, oxonium ions, sulfonium compounds and halonium ions. Pre- ferred compounds also include derivatives formed by substitution of the parent ions by univalent groups, e.g. (CH₃)₂S⁺H dimethylsulfonium, and (CH₃CH₂)₄N⁺ tetraethylam- monium. Onium compounds also include derivatives formed by substitution of the parent ions by groups having two or three free valencies on the same atom. Such deriva- tives are, whenever possible, designated by a specific class name, e.g. RC≡O⁺ hydro- carbylidyne oxonium ions R₂C=NH₂ ⁺ iminium ion, RC ≡NhT nitrilium ions. Other examples include carbenium ion and carbonium ion. Preferred onium compounds also include Bu₄N⁺HSO₄ ^", (Me₄N)₂ ⁺SO₄ ^2", Py⁺Cl^", Py⁺OH^", Py⁺(CH²)¹⁵CH³CI^", Bu₄P⁺CI^" and Ph₄ ⁺PCI^".

Zero-Valent Metals

A zero-valent metal is added in at least one step during polymerization or preparation of the PO3G polymer to remove and/or reduce the color of the resulting polymer.

For the present invention, useful zero-valent metals include the following: lith- ium, sodium, rubidium, cesium, beryllium, magnesium, calcium, strontium, barium, scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, yttrium, zirconium, niobium, molybdenum, technetium, ruthenium, rhodium, palladium, silver, cadmium, lanthanum, hafnium, tantalum, tungsten, rhenium, osmium, iridium, platinum, gold, gallium, indium, germanium, tin, antimony, bismuth, selenium, and tellurium.

A preferred zero-valent metal is selected from scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper and zinc.

A further preferred zero-valent metal is selected from zinc and nickel.

Combinations and alloys of any two or more of the above are also useful.

The zero-valent metals may have various shapes or sizes, ranging from a fine powder to granules, particles, porous metal structures, tablets, pellets, extrudates, or other structured supports. It can also be supported on a substrate. The support could be from any support material known in the art, such as at least one of carbon, alumina, silica, titania, silica-alumina, silica-titania, titania-alumina, clays, aluminosilicates, water insoluble salts of calcium, barium, barium sulfate, calcium carbonate, strontium carbonate, and compounds and combinations thereof.

In one embodiment, the zero-valent metal comprises Raney nickel and/or Ra- ney cobalt, which can optionally be modified with at least one of iron, molybdenum, chromium, palladium, zinc or other modifying elements, or metals made as dispersions of these elements, or supported metals from the group consisting of palladium on carbon, palladium on calcium carbonate, palladium on barium sulfate, palladium on alumina, palladium on titania, platinum on carbon, platinum on alumina, platinum on silica, iridium on silica, iridium on carbon, iridium on alumina, rhodium on carbon, rhodium on silica, rhodium on alumina, nickel on carbon, nickel on alumina, nickel on silica, rhenium on carbon, rhenium on silica, rhenium on alumina, ruthenium on carbon, ruthenium on alumina, and ruthenium on silica.

An example of the preferred zero-valent metal is nickel, which may be in the form of a Raney metal (which may be doped with other active metals) or extrudates supported on silica/alumina.

Preferably, the zero-vaient metal is used in an amount in the range of from about 0.01 wt% to about 5 wt%, more preferably from about 0.03 wt% to about 2 wt%, based on the weight of reactant. The zero-valent metal can also be used in the amounts that are in increments of 0.01% between the range of 0.01 and 5%, for exam- pie, 0.01 , 0.02, 0.03,...so on, and so forth.

Step (a) - Polymerization Process

The polymerization process can be batch, semi-continuous, continuous, etc. A preferred batch process is described in previously incorporated US2002/0007043A1. In this embodiment, the polytrimethylene-ether glycol is prepared by a process com- prising the steps of: (a) providing (1 ) reactant, and (2) acid polycondensation catalyst; and (b) polycondensing the reactants to form a polytrimethylene ether glycol. The reaction is conducted at an elevated temperature of at least about 150⁰C, more preferably at least about 160⁰C, up to about 21 OX, more preferably about 200⁰C. The reaction is preferably conducted either at atmospheric pressure in the presence of inert gas or at reduced pressure (i.e., less than 760 mm Hg), preferably less than about 500 mm Hg in an inert atmosphere, and extremely low pressures can be used (e.g., as low as about 1 mm Hg or 133.3X10^'6 MPa).

A preferred continuous process for preparation of the polytrimethylene ether glycols of the present invention is described in previously incorporated US6720459. Thus, in this embodiment the polytrimethylene ether glycol is prepared by a continuous process comprising: (a) continuously providing (i) reactant, and (ii) polycondensation catalyst; and (b) continuously polycondensing the reactant to form polytrimethylene ether glycol.

Step (b) - Hydrolysis

Regardless of whether the process is a continuous or batch process, or otherwise, a substantial amount of acid ester is formed from reaction of the catalyst with the hydroxyl compounds, particularly when a homogeneous acid catalyst (and most particularly sulfuric acid) is used. In the case of sulfuric acid, a substantial portion of the acid is converted to the ester, alkyl hydrogen sulfate. It is important to remove these acid esters because, for example, they can act as emulsifying agents during the water washing used to remove catalyst and therefore cause the washing process to be difficult and time consuming. Moreover, the hydrolysis step is also important in order to obtain polymer with the high dihydroxy functionality required to use the polymer as a reactive intermediate. Furthermore, the hydrolysis step is also important in order to obtain polymer at conversion (yield).

Thus, the next step comprises hydrolyzing the acid esters formed during the polycondensing that are in the aqueous-organic mixture.

The hydrolysis step is preferably carried out by adding water to the polymer. The amount of water added can vary and is preferably from about 10 to about 200 wt%, more preferably from about 50 to about 100 wt%, based on the weight of the polytrimethylene ether glycol. Hydrolysis is preferably carried out by heating the aqueous-organic mixture to a temperature in the range from about 50 to about 110⁰C, preferably from about 90 to about 110⁰C (and more preferably from about 90 to about 100⁰C when carried out at atmospheric pressure), for a period of sufficient time to hy- drolyze the acid esters. The hydrolysis step is preferably conducted at atmospheric or slightly above atmospheric pressure, preferably at about 700 mmHg to about 1600 mmHg. Higher pressures can be used, but are not preferred. The hydrolysis step is carried out preferably under inert gas atmosphere.

Steps (c) and (d) - Phase Formation/Separation

The next steps involve forming and separating the water phase and the organic phase.

Phase formation and separation is preferably promoted by either adding an inorganic compound such as a base and/or salt, or by adding an organic solvent to the reaction mixture, as disclosed in previously incorporated US7157607, US7161045, US7164046 and US Application Serial No. 1 1/599861 (filed November 15, 2006).

Specifically, previously incorporated US7157607 and US7161045 disclose processes for preparing polytrimethylene ether glycol by acid polycondensation wherein the phase separation after hydrolysis is promoted by addition of organic solvent miscible with polytrimethylene ether glycol in the case of previously incorporated US7157607, and miscible with water in the case of previously incorporated US7161045. The solvents disclosed in these two publications also may be used conjunction with the water-soluble inorganic compounds disclosed in previously incorporated US7164046 and US Application Serial No. 11/599861 (filed November 15, 2006) herein to promote phase separation.

Preferred is the use of the water-soluble inorganic compounds as disclosed in previously incorporated US7164046 and US Application Serial No. 11/599861 (filed November 15, 2006), which are added to the aqueous polytrimethylene ether glycol mixture after hydrolysis.

Preferred water-soluble, inorganic compounds are inorganic salts and/or inorganic bases. Preferred salts are those comprising a cation selected from the group consisting of ammonium ion, Group IA metal cations, Group HA metal cations and Group IUA metal cations, and an anion selected from the group consisting of fluoride, chloride, bromide, iodide, carbonate, bicarbonate, sulfate, bisulfate, phosphate, hydrogen phosphate, and dihydrogen phosphate (preferably chloride, carbonate and bicarbonate). Group IA cations are lithium, sodium, potassium, rubidium, cesium and fran- cium cations (preferably lithium, sodium and potassium); Group MA cations are beryllium, magnesium, calcium, strontium, barium and radium (preferably magnesium and calcium); and Group IMA cations are aluminum, gallium, indium and thallium cations. More preferred salts for the purposes of the invention are alkali metal, alkaline earth metal and ammonium chlorides such as ammonium chloride, lithium chloride, sodium chloride, potassium chloride, magnesium chloride, calcium chloride; and alkali metal and alkaline earth metal carbonates and bicarbonates such as sodium carbonate and sodium bicarbonate. The most preferred salt are sodium chloride; and alkali metal carbonates such as sodium and potassium carbonate, and particularly sodium carbonate.

Typical inorganic bases for use in the invention are ammonium hydroxide and water-soluble hydroxides derived from any of the above-mentioned Group IA, HA and MIA metal cations. The most preferred water-soluble inorganic bases are sodium hydroxide and potassium hydroxide.

The amount of water-soluble, inorganic compound used may vary, but is preferably the amount effective in promoting the rapid separation of the water and inor- ganic phases. The preferred amount for this purpose is from about 1 to about 20 wt%, more preferred amount from about 1 to about 10 wt%, and still more preferably from about 2 to about 8 wt%, based on the weight of the water added to the polytrimethyl- ene ether glycol in the hydrolysis step.

Preferably the time required for phase separation is less than about one hour. More preferably this time period is from less than about 1 minute to about one hour, and most preferably about 30 minutes or less.

Separation is preferably carried out by allowing the water phase and the organic phase to separate and settle so that the water phase can be removed. The reaction mixture is allowed to stand, preferably without agitation until settling and phase separation has occurred.

Once phase separation has occurred, the water phase and the organic phase can be split, preferably by decantation or draining. It is advantageous to retain the organic phase in the reactor for subsequent processing. Consequently, when the organic phase is on bottom it is preferably to decant off the aqueous phase and when the organic phase is on top, it is preferred to drain off the aqueous phase. A preferred phase separation method when high molecular weight polymer is obtained is gravity separation of the phases.

Step (e) - Neutralization

Following the hydrolysis and phase separation steps, a base, preferably a sub- stantially water-insoluble base, may be added to neutralize any remaining acid. During this step residual acid polycondensation catalyst is converted into its corresponding salts. However, the neutralization step can be optional.

Preferably, the base is selected from the group consisting of alkaline earth metal hydroxides and alkaline earth metal oxides. More preferably, the base is se- lected from the group consisting of calcium hydroxide, calcium oxide, magnesium hydroxide, magnesium oxide, barium oxide and barium hydroxide. Mixtures may be used. A particularly preferred base is calcium hydroxide. The base may be added as a dry solid, or preferably as an aqueous slurry. The amount of insoluble base utilized in the neutralization step is preferably at least enough to neutralize all of the acid poly- condensation catalyst. More preferably a stoichiometric excess of from about 0.1 wt% to about 10 wt% is utilized. The neutralization is preferably carried out at 50 to 90⁰C for a period of from 0.1 to 3 hours under nitrogen atmosphere.

Step (f) - Water/Solvent Removal

Next, the organic solvent, if it was used in the process, and the residual water is preferably removed from the organic phase by vacuum stripping (e.g., distillation at low pressure), generally with heating, which will also remove organic solvent if present and, if desired, unreacted monomeric materials. Other techniques can be used, such as distillation at about atmospheric pressure.

Step (q) - Further Purification

When base is added in step (e) such that residual acid catalyst salts are formed, and optionally otherwise, the organic phase is separated into (i) a liquid phase comprising the polytrimethylene ether glycol, and (ii) a solid phase comprising the salts of the residual acid polycondensation catalyst and unreacted base. Typically, this occurs by filtration (preferably with use of filter-aid material, for example as disclosed in US2005/028302A1 , or centrifugation, to remove the base and the acid/base reaction products. Centrifugation and filtration methods are generally well known in the art. For example, filtration under the earth's gravity, centrifugal filtration, or pressure filtration can be used. Filter presses, candle filters, pressure leaf filters or conventional filter papers are also be used for the filtration, which can be carried out batch wise or con- tinuously. Filtration in the presence of a filter-aid is preferred at a temperature range from 50 to 100⁰C at a pressure range from 0.1 MPa to 0.5 MPa.

Even if base is not added in step (e), purification techniques like centrifugation and filtration may still be desirable for refining the final product.

Addition of Zero-Valent Metal Compound

As indicated previously, the zero-valent metal is added at least once during at least one of the steps (a), (b), (c), (d), (e), (f) and (g), and/or is contacted with poly- trimethylene ether glycol from step (g). Preferably, the zero-valent metal is added at least once during at least one of the steps (b), (c), (d), (e), (f) and (g), and/or is contacted with polytrimethylene ether glycol from step (g). More preferably, the zero- valent metal is added at least once during at least one of steps (d), (e), (f) and (g), and still more preferably at least once during at least one of steps (d) and (e).

The zero-valent metal compound added at any time may be added as one single zero-valent metal or as a mixture/alloy of more than one zero-valent metal.

The zero-valent metal may be added all at one time in a single step, or it may be added in increments in a single step, or it may be added in increments over two or more steps. For example, if the amount of zero-valent metal to be added is X g, all of X g may be added in one step or, for example, X/Y g may be added over Y time intervals during one or more steps. The Y intervals need not be equal to each other in length of time.

The zero-valent metal addition to the water-removal or the drying step may not remove color as efficiently as the addition to other steps of the process.

The zero-valent metal can be of any size or shape such as powders, particles, nanopariticles, dust, foils and sticks, in nanometers to centimeters size. In principle, smaller size provides larger surface area and hence improved efficiency as known to a person of ordinary skill in the art; however it is also known to a person of ordinary skill of art that smaller size also results in difficulties in complete removal. The preferred range of sizes is from about 1 μm to about 5mm.

Sufficient agitation is preferred during and after the addition of zero-valent metal. Preferably, the agitation is higher than about 25 rpm, and more preferably higher than about 100 rpm, for better dispersibility.

Other Purification Techniques

It should be noted that the present invention is not limited to using the addition of the zero-valent metal as the sole purification/color reduction technique, but can be combined with other well-known techniques as, for example, described in the previ- ously incorporated publications, or with other techniques such as disclosed in commonly owned U.S. Application Serial No. 11/728630 (filed concurrently herewith and entitled "LOWER-COLOR POLYTRIMETHYLENE ETHER GLYCOL USING HYDRIDE COMPOUNDS").

Resulting PO3G

The polytrimethylene ether glycols preferred for use herein generally have a number average molecular weight from about 250 to about 7000, preferably from about 250 to about 5000. Mn of 500 to 5000 is preferred for many applications. Mn of 1000 to 3000 is further preferred.

The polytrimethylene ether glycols preferred for use herein are typically polydisperse polymers having a polydispersity of preferably from about 1.0 to about 2.2, more preferably from about 1.2 to about 2.0, and still more preferably from about 1.2 to about 1.8.

The polytrimethylene ether glycols made in accordance with the present invention preferably have a color reduction of greater than about 10%, more preferably greater than about 30%, as compared with the process where a zero-valent metal is not used. The zero-valent metal is preferably added in an amount so as to achieve at least this level of color reduction.

The polytrimethylene ether glycols for use in the present invention preferably have a color value of less than about 100 APHA, and more preferably less than about 40 APHA. Polytrimethylene ether glycol as described above should in general have low acute oral toxicity, and not be a skin or eye irritant, or a skin sensitizer.

The invention is illustrated in the following examples. All parts, percentages, etc., referred to in the examples are by weight unless otherwise indicated.

EXAMPLES

The examples below utilized either a petrochemical-based 1 ,3-propane diol ("chem-PDO") or a biologically-derived 1 ,3-propane diol ("bio-PDO"). The bio-PDO had a purity of higher than 99.99%.

Example 1 (COMPARATIVE) - No Zinc (0) Added

1 ,3-propanediol (chem-PDO, 3010 g) and Na₂CO₃ (4.05g) were charged into a

5 L glass flask and then heated to 170 +/- 1 °C under nitrogen with overhead stirring. Then 41.3g of sulfuric acid was injected to the reaction flask and heating was continued at 170 +/- 1 °C for 12 hrs to produce polytrimethylene ether glycol. During the reaction, by-product water was removed with a condenser.

The resulting product is referred to as the "Crude PO3G Product 1" for examples 1-8.

Crude PO3G Product 1 (50 g) and equal amount of Dl water (50 g) were charged into a 250 mL batch reactor and mixed by overhead stirring at 120 rpm, and under nitrogen blanketing. The polymer-water mixture was heated to 95°C and held at that temperature for 3 hrs.

Subsequently, the mixture was cooled to about 70°C and the aqueous-rich portion was removed.

The polymer-rich portion was further hydrolyzed, upon addition of another 50 g of Dl water, for one hr, under the same conditions at 95°C to complete the hydrolysis step.

The aqueous phase was removed upon phase separation. The remainder polymer-rich phase was neutralized with 0.25 g of Ca(OH)₂ (0.5% wt/wt of crude polymer) at 70⁰C for 2 hrs. The mixture was subsequently dried at about 85°C, under 6 torr (1 torr = 133.32x10^"6 MPa) pressure, for 2 hrs. The dried mixture was filtered with filter aid (Celpure® C65) at 80^°C (Steam Temp.).

The APHA number was calculated from absorbance data collected every 5 nm from 780 nm to 380 nm. Absorbance data were converted to transmittance. A calibra- tion of APHA vs. Yellowness index was performed using PtCo standards ranging from APHA 15 to 500 according to the ASTM standard 5386-93b. The APHA color number of the PO3G was found to be at 278.6.

Example 2 - 4% Zinc (0) Added during Hydrolysis

Crude P03G Product 1 (50 g) and equal amount of Dl water (50 g) were charged into a 250 mL batch reactor and mixed by overhead stirring at 120 rpm, and under nitrogen blanketing. The polymer-water mixture was heated to 95°C and held at that temperature for 30 min. Subsequently, 2 g or 4% of zinc dust (Tyler mesh size of 28 mesh to 100 mesh; equivalent to about 150 μm to 600 μm average particle size) were added to the mixture, and the mixture was further heated for 2.5 hrs.

Subsequently, the mixture was cooled to about 70⁰C and the aqueous-rich portion was removed.

The polymer-rich portion was further hydrolyzed, upon addition of another 50 g of Dl water, for one hour, under the same condition at 95°C to complete the hydrolysis step.

The aqueous phase was removed upon phase separation. The remainder

PO3G-rich phase was neutralized with 0.25 g of Ca(OH)₂ (0.5% wt/wt of crude polymer) at 70⁰C for 2 hrs. The mixture was subsequently dried at about 85°C, under 6 torr (1 torr = 133.32x10⁶ MPa) pressure, for 2 hrs. The dried mixture was filtered with filter aid (Celpure® C65) at 80⁰C (Steam Temp.). The APHA color number of the PO3G was found to be at 162.7. Example 3 - 4% Zinc (0) Added During Hydrolysis, No Neutralization

Crude PO3G Product 1 (50 g) and equal amount of Dl water (50 g) were charged into a 250 mL batch reactor and mixed by overhead stirring at 120 rpm, and under nitrogen blanketing. The polymer-water mixture was heated to 95°C and held at that temperature for 30 min. Subsequently, 2 g or 4% of zinc dust (Tyler mesh size of 28 mesh to 100 mesh; equivalent to about 150 μm to 600 μm average particle size) were added to the mixture, and the mixture was further heated for 2.5 hrs.

The polymer-rich portion was further hydrolyzed, upon addition of another 50 g of Dl water, for one hr, under the same condition 95°C to complete the hydrolysis step.

The aqueous phase was removed upon phase separation. The remainder PO3G-rich phase was dried at about 85°C, under 6 torr (1 torr = 133.32x10^'6 MPa) pressure, for 2 hrs. The dried mixture was filtered with filter aid (Celpure® C65) at 80^°C (Steam Temp.). The APHA color number of the PO3G was found to be at 196.4.

Example 4 - 4% Zinc (0) Added during Hydrolysis, 2% Zinc(0) Added During Drying

Crude PO3G Product 1 (50 g) and egual amount of Dl water (50 g) were charged into a 500 mL batch reactor and mixed by overhead stirring at 120 rpm, and under nitrogen blanketing. The polymer-water mixture was heated to 95°C and held at that temperature for 30 min. Subsequently, 2 g or 4% of zinc dust (Tyler mesh size of 28 mesh to 100 mesh; equivalent to about 150 μm to 600 μm average particle size) were added to the mixture, and the mixture was further heated for 2.5 hrs.

The polymer-rich portion was further hydrolyzed, upon addition of another 50 g of Dl water, for one hour, under the same condition 95°C to complete the hydrolysis step.

The aqueous phase was removed upon phase separation. The remainder PO3G-rich phase was neutralized with 0.25 g of Ca(OH)₂ (0.5% wt/wt of crude poly- mer) at 70°C for 2 hrs and 1 g of zinc dust was added to the resulting mixture. Subsequently, the resulting mixture was dried at about 85°C, under 6 torr (1 torr = 133.32x10^" ⁶ MPa) pressure, for 2 hrs. The dried mixture was filtered with filter aid (Celpure® C65) at 80⁰C (Steam Temp.). The APHA color number of the PO3G was found to be at 165.3.

TABLE 1

Example 5 - 4% Zinc (0) Added before Hydrolysis, No Neutralization

Crude PO3G Product 1 (50 g), equal amount of Dl water (50 g), and 2 g or 4% of zinc dust were charged into a 250 ml. batch reactor and mixed by overhead stirring at 120 rpm, and under nitrogen blanketing. The polymer-water mixture was heated to 95°C and held at that temperature for 3 hours.

Subsequently, the mixture was cooled to about 70⁰C and the aqueous-rich portion was removed by decantation or with a syringe.

The aqueous phase was removed upon phase separation. The remainder PO3G-rich phase was dried at about 85°C, under 10 torr (1 torr = 133.32x10⁶ MPa) pressure, for 2 hrs. The dried mixture was filtered with filter aid (Celpure® C65) at 80⁰C (Steam Temp.). The APHA color number of the PO3G was found to be at 209.6. Example 6 - 4% Zinc (0) Added before Hydrolysis

Crude PO3G Product 1 (50 g), equal amount of Dl water (50 g), and 2 g or 4% of zinc dust were charged into a 250 ml_ batch reactor and mixed by overhead stirring at 120jpm, and under nitrogen blanketing. The polymer-water mixture was heated to 95°C and held at that temperature for 3 hours.

The aqueous phase was removed upon phase separation. The remainder

PO3G-rich phase was neutralized with 0.25 g of Ca(OH)₂ (0.5% wt/wt of crude polymer) at 70⁰C for 2 hrs, and dried at about 85°C, under 10 torr (1 torr = 133.32x10⁶ MPa) pressure, for 2 hrs. The dried mixture was filtered with filter aid (Celpure® C65) at 80°C (Steam Temp.). The APHA color number of the PO3G was found to be at 171.2.

Example 7 - 2% Zinc (0) Added before Hydrolysis

Crude PO3G Product 1 (50 g), equal amount of Dl water (50 g), and 1 g or 2% of zinc particles (Tyler mesh size of 28 mesh to 100 mesh; equivalent to about 150 μm to 600 μm average particle size) were charged into a 250 ml. batch reactor and mixed by overhead stirring at 120 rpm, and under nitrogen blanketing. The polymer-water mixture was heated to 95°C and held at that temperature for 3 hours.

The aqueous phase was removed upon phase separation. The remainder PO3G-rich phase was neutralized with 0.25 g of Ca(OH)₂ (0.5% wt/wt of crude polymer) at 70°C for 2 hrs, and dried at about 85°C, under 10 torr (1 torr = 133.32x10⁶ MPa) pressure, for 2 hrs. The dried mixture was filtered with filter aid (Celpure® C65) at 80⁰C (Steam Temp.). The APHA color number of the PO3G was found to be at 183.9.

Example 8 - 1% Zinc (0) Added before Hydrolysis

Crude PO3G Product 1 (50 g), equal amount of Dl water (50 g), and 0.5 g or 1 % of zinc particles (Tyler mesh size of 28 mesh to 100 mesh; equivalent to about 150 μm to 600 μm average particle size) were charged into a 250 mL batch reactor and mixed by overhead stirring at 120 rpm, and under nitrogen blanketing. The polymer- water mixture was heated to 95°C and held at that temperature for 3 hours.

The aqueous phase was removed upon phase separation. The remainder PO3G-rich phase was neutralized with 0.25 g of Ca(OH)₂ (0.5% wt/wt of crude polymer) at 70⁰C for 2 hrs, and dried at about 85°C, under 10 torr (1 torr = 133.32x10⁶ MPa) pressure, for 2 hrs. The dried mixture was filtered with filter aid (Celpure® C65) at 80⁰C (Steam Temp.). The APHA color number of the PO3G was found to be at 245.3.

TABLE 2

Example 9 (COMPARATIVE) - No Zinc (0) Added

1 ,3-propanediol (bio-PDO, 602 g) and Na2CO3(0.81g) were charged into a 1 L glass flask and then heated to 170 +/- TC under nitrogen with overhead stirring. Then 8.26g of sulfuric acid was injected to the reaction flask and continue to heat at 170 +/- TC for 10 hrs to produce polytrimethylene ether glycol. During the reaction, byproduct water was removed with a condenser.

The resulting polymeric product was called the "Crude PO3G Product 2" for examples 9-10.

Crude PO3G Product 2 (50 g) and equal amount of Dl water (50 g) were charged into a 250 ml_ batch reactor and mixed by overhead stirring at 120 rpm, and under nitrogen blanketing. The polymer-water mixture was heated to 95°C and held at that temperature for 3 hrs.

The polymer-rich portion was further hydrolyzed, upon addition of another 50 g of Dl water, for one hr, under the same condition at 95°C to complete the hydrolysis step.

The aqueous phase was removed upon phase separation. The remainder

PO3G-rich phase was neutralized with 0.25 g of Ca(OH)₂ (0.5% wt/wt of crude poly- mer) at 70⁰C for 2 hrs. The mixture was subsequently dried at about 85°C, under 6 torr (1 torr = 133.32x10⁶ MPa) pressure, for 2 hrs. The dried mixture was filtered with filter aid (Celpure® C65) at 80^°C (Steam Temp.).

The APHA number was calculated from absorbance data collected every 5 nm from 780 nm to 380 nm. Absorbance data were converted to transmittance. A calibra- tion of APHA vs. Yellowness index was performed using PtCo standards ranging from

APHA 15 to 500 according to the ASTM standard 5386-93b. The APHA color number of the PO3G was found to be at 69.4. Example 10 - 4% Zinc (0) Added during Hydrolysis

Crude PO3G Product 2 (50 g) and equal amount of Dl water (50 g) were charged into a 250 mL batch reactor and mixed by overhead stirring at 120 rpm, and under nitrogen blanketing. The polymer-water mixture was heated to 95°C and held at that temperature for 30 min. Subsequently, 2 g or 4% of zinc dust (Tyler mesh size of 28 mesh to 100 mesh; equivalent to about 150 μm to 600 μm average particle size) were added to the mixture, and the mixture was further heated for 2.5 hrs.

The aqueous phase was removed upon phase separation. The remainder PO3G-hch phase was neutralized with 0.25 g of Ca(OH)₂ (0.5% wt/wt of crude polymer) at 70⁰C for 2 hrs. The mixture was subsequently dried at about 85°C, under 6 torr (1 torr = 133.32x10⁶ MPa) pressure, for 2 hrs. The dried mixture was filtered with filter aid (Celpure® C65) at 80⁰C (Steam Temp.). The APHA color number of the PO3G was found to be at 23.6.

TABLE 3

Example 11 (COMPARATIVE) - No Zinc (0) Added

1 ,3-propanediol (bio-PDO, 3000 g) and 28.42g of sulfuric acid were charged into a 5 L glass flask and then heated at 166 +/- 1 °C under nitrogen for 24 hrs to produce polytrimethylene ether glycol. During the reaction, by-product water was removed by nitrogen sparging. The resulting polymeric product was called the "Crude PO3G Product 3" for examples 11-12.

Crude PO3G Product 3 (100 g) and equal amount of deionized water (100 g) were charged into a 300 ml_ batchjeactor and mixed by overhead stirring at Ji 20 rpm under nitrogen blanketing. The polymer-water mixture was heated to 95°C and held for 3 hrs. Subsequently, the mixture was cooled to 70⁰C and the aqueous portion was removed. The polymer-rich portion was hydrolyzed by addition of deionized water (100 g) under the same conditions for another one hour to complete the hydrolysis step. The aqueous phase was removed upon phase separation.

The remainder PO3G-rich phase was neutralized with 0.5 g of Ca(OH)₂ (0.5%, wt/wt of crude polymer) at 70⁰C, for 2 hrs and the mixture stirred at 86°C for 15 minutes.

The mixture was subsequently dried at 85°C under 3 torr pressure (1 torr = 133.32X10⁶ MPa; therefore 3 torr = 400X10⁶ MPa) for 3 hrs. The dried polymer was used for Examples 1 1-12.

The dried PO3G product (20 g) was stirred at 80°C for 25 min. The mixture was then pumped dry at 80⁰C, under the pressure of 3 torr (1 torr = 133.32x10^'6 MPa) pressure, for 1 hr. The dried mixture was filtered with filter aid (Celpure® C65) at 80⁰C (Steam Temp.). The APHA color was found to be at 133.8.

Example 12 - 10% Zn (0) Added after Drying

The dried PO3G product form Example 11 (20 g) and 2 g (10%) of Zn dust were stirred at 80⁰C for 25 min. The mixture was then pumped dry at 80°C, under the pressure of 3 torr (1 torr = 133.32x10^"6 MPa) pressure, for 1 hr. The dried mixture was filtered with filter aid (Celpure® C65) at 80°C (Steam Temp.). The APHA color was found to be at 84.5. TABLE 4

Example 13 (COMPARATIVE) - No Raney Ni Added

1 ,3-propanediol (Bio-PDO, 3000 g) and 28.42g of sulfuric acid were charged into a 5 L glass flask and then heated at 166 +/- 1 °C under nitrogen for 24 hrs to produce polytrimethylene ether glycol. During the reaction, by-product water was removed by nitrogen sparging.

The resulting polymeric product was called the "Crude PO3G Product 4" for examples 13-15.

Crude PO3G Product 4 (40 g) and equal amount of deionized water (40 g) were charged into a 250 mL batch reactor and mixed by overhead stirring at 120 rpm under nitrogen blanketing. The polymer-water mixture was heated to 95°C and held for 3 hrs. Subsequently, the mixture was cooled to 70⁰C and the aqueous portion was removed. The polymer-rich portion was hydrolyzed by addition of deionized water (40 g) under the same conditions for another one hour to complete the hydrolysis step. The aqueous phase was removed upon phase separation.

The remainder PO3G-rich phase was neutralized with 0.2 g of Ca(OH)₂ (0.5%, wt/wt of crude polymer) at 70⁰C, for 2 hrs and the mixture stirred at 86°C for 15 minutes.

The mixture was subsequently dried at 85°C under 3 torr pressure (1 torr =

133.32X10⁶ MPa; therefore 3 torr = 400X10⁶ MPa) for 3 hrs. The dried mixture was filtered with filter aid (Celpure® C65) at 80⁰C (Steam Temp.). The APHA color was found to be at 92.0. Example 14 - 10% Raney Ni Added after Neutralization

The remainder PO3G-rich phase was neutralized with 0.2 g of Ca(OH)₂ (0.5%, wt/wt of crude polymer) at 70⁰C, for 2 hrs. 4 g or 10% Raney Nickel slurry (10% wt/wt, Aldrich Raney 2800) was added, and the mixture stirred at 86°C for 15 minutes.

The mixture was subsequently dried at 85°C under 3 torr pressure (1 torr = 133.32X10^"6 MPa; therefore 3 torr = 400X10^"6 MPa) for 3 hrs. The dried mixture was filtered with filter aid (Celpure® C65) at 80⁰C (Steam Temp.). The APHA color was found to be at 38.9.

Example 15 - 10% Ranev Ni Added to Dried PO3G

The mixture was subsequently dried at 85°C under 3 torr pressure (1 torr = 133.32X10^"6 MPa; therefore 3 torr = 400X10⁶ MPa) for 3 hrs. The dried PO3G product (20 g) and 2 g (10%) of Raney Nickel slurry (10% wt/wt, Aldrich Raney 2800) were stirred at 86°C for 15 min. The mixture was then pumped dry at 86°C, under the pressure of 3 torr (1 torr = 133.32x10⁶ MPa) pressure, for 1 hr. The dried mixture was filtered with filter aid (Celpure® C65) at 80⁰C (Steam Tempr)-T-he APHA color was fΘund-tΘτbe-at-35:6: —

TABLE 5

Claims

CLAIMSWhat is claimed:

1. A process for the manufacture of a polytrimethylene ether glycol, comprising the steps of:

(a) polycondensing reactant comprising a diol selected from the group consisting of 1 ,3-propanediol, 1 ,3-propanediol dimer, 1 ,3-propanediol trimer and mixtures thereof, in the presence of an acid polycondensation catalyst to form a polytrimethylene ether glycol and an acid ester of the acid polycondensation catalyst;

(b) adding water to the polytrimethylene ether glycol and hydrolyzing the acid ester formed during the polycondensation to form a hydrolyzed aqueous-organic mixture containing polytrimethylene ether glycol and residual acid polycondensation catalyst;

(c) forming an aqueous phase and an organic phase from the hydrolyzed aqueous-organic mixture, wherein the organic phase contains polytrimethylene ether glycol and residual acid polycondensation catalyst,

(d) separating the aqueous phase and the organic phase;

(f) removing residual water from the organic phase; and

wherein a zero-valent metal is (1 ) added at least once during at least one of said steps (a), (b), (c), (d), (e), (f) and (g), and/or (2) is contacted with polytrimethylene ether glycol from step (g).

2. The process of claim 1 , wherein the zero-valent metal is (1 ) added at least once during at least one of said steps (b), (c), (d), (e), (f) and (g), and/or (2) is contacted with polytrimethylene ether glycol from step (g).

3. The process of claim 1 , wherein the zero-valent metal is added at least once during at least one of said steps (d), (e), (f) and (g).

4. The process of claim 1 , wherein the zero-valent metal is added at least once during at least one of said steps (d) and (e).

5. The process of claim 1 , wherein the zero-valent metal is added under agitation.

6. The process of claim 1 , wherein the zero-valent metal is added in an amount so as to achieve a color reduction in the polytrimethylene ether glycol of greater than about 10%, as compared with the process where a zero-valent metal is not used.

7. The process of claim 1 , wherein the zero-valent metal is added in an amount so as to achieve a color reduction in the polytrimethylene ether glycol of greater than about 30%, as compared with the process where a zero-valent metal is not used.

8. The process of claim 1 , wherein the zero-valent metal is used in an amount in the range of from about 0.01 wt% to about 5 wt% based on the weight of reactant.

9. The process of claim 1 , wherein the zero-valent metal is used in an amount in the range of from about 0.03 wt% to about 2 wt% based on the weight of reactant.

10. The process of claim 1 , wherein the zero-valent metal is selected from the group consisting of scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper and zinc, and combinations and alloys thereof.

11. The process of claim 1 , wherein the zero-valent metal is selected from the gorup consisting of nickel and zinc, and combinations and alloys thereof.

12. The process of claim 1 , wherein the zero-valent metal comprises Raney nickel and/or Raney cobalt.

13. The process of claim 1 , wherein the zero-valent metal is added in increments in a single step.

14. The process of claim 1 , wherein the zero-valent metal is added in increments over two or more steps.

15. The process of claim 1 , wherein the following is added to the hydrolyzed aqueous-organic mixture:

16. The process of claim 1 , wherein the 1 ,3-propane diol is biologically-derived.

17. The process of claim 1 , wherein the 1 ,3-propane diol has the following characteristics:

(2) a composition having L^*a^*b^* "b^*" color value of less than about 0.15 (ASTM D6290), and an absorbance at 270 nm of less than about 0.075; and/or

(3) a peroxide composition of less than about 10 ppm; and/or

(4) a concentration of total organic impurities (organic compounds other than 1 ,3-propanediol) of less than about 400 ppm, as measured by gas chromatography.

18. The process of claim 1 , wherein the 1 ,3-propane diol has the following characteristics:

(1) an ultraviolet absorption at 220 nm of less than about 0.200, and at 250 nm of less than about 0.075, and at 275 nm of less than about 0.075; and

(2) a composition having L^*a^*b^* "b^*" color value of less than about 0.15 (ASTM

D6290), and an absorbance at 270 nm of less than about 0.075; and (3) a peroxide composition of less than about 10 ppm; and

19. The process of claim 1 , wherein the acid polycondensation catalyst comprises a base in an amount less than that required to neutralize the acid.

20. The process of claim 15, wherein a water-soluble inorganic compound selected form the group consisting of sodium carbonate and potassium carbonate is added to the hydrolyzed aqueous-organic mixture.

21. The process of claim 1 , wherein the zero-valent metal is added at least once during at least one of said steps (d) and (e); the zero-valent metal is added under agitation; the zero-valent metal is selected from the group consisting of nickel and zinc, and combinations and alloys thereof, or comprises Raney nickel and/or Raney cobalt; and the zero-valent metal is used in an amount in the range of from about 0.01 wt% to about 5 wt% based on the weight of reactant, and is added in an amount so as to achieve a color reduction in the polytrimethylene ether glycol of greater than about 10%, as compared with the process where a zero-valent metal is not used.