CA2239905A1 - Production of poly(trimethylene terephthalate) - Google Patents

Abstract

Disclosed herein is a novel crystalline form of low molecular weight poly(trimethylene terephthalate). This crystalline form may be produced from molten or glassy low molecular weight poly(trimethylene terephthalate) material by means of rapid heat transfer to or from the material. The poly(trimethylene terephthalate) composition is suitable for use as a starting material for solid-state polymerization in order to produce polymers of higher molecular weight.

Description

CA 0223990~ 1998-06-08 W O 97/23543 PCT~US96/19647 TITLE
PRODUCTION OF POLY(TRIM[ETHYLENE TEREPHTHALATE) FTELD OF THE rNVENTION
This invention concerns a process for producing a low molecular weight poly(trimethylene terephth~l~te~ which can be used in so}id-state polymerization to obtain a higher molecular weight polymer. A novel crystalline form of the polymer is also disclosed.
TECHNICAL BACKGROUND
Poly(trimethylene terephth~l~te), herein abbreviated 3GT, may be useful in many materials and products in which polyesters are currently used, for example,films, carpet fibers, textile fibers, mi.sc~ neous industrial fibers, containers and p?~r.k~ging For use in carpet fibers, 3GT may offer advantages because of built-in stain rçsi~t~nc~e and superior resiliency. See, for example, an article by H. ~.Chuah et al., in IFJ (October 1995) on pages 50-52 concerning poly(trimethylene terephth~ te) as a new pelrulllldllce carpet fiber.
British Patent 578,097 disclosed the synthesis of poly(trimethylene terephth~l~te) in 1941. The polymer, however, is not available commercially.
There is a lack of published literature on processes for producing the polymer on other than a laboratory scale.
Many of the proposed uses for 3GT require a polymer of relatively high molecular weight. Other polyesters such as poly(ethylene terephthalate), referred to herein as PET or 2GT, have been commercially made by increasing, either in melt and/or solid-state polylll~li,.~Lion, the molecular weight of a lower molecular weight polymer, sometimes referred to as a prepolymer or oligomer. In general, melt polymerizations require higher telllp~l~Lul~s, which are more likely to cause polymer decomposition and require expensive equipment. Solid-state polymerizations, in contrast, are usually run at somewhat lower telllpel~LIlres.Solid-state polyll,eli~aLions can also have the advantage, compared to melt polymerizations, that very high molecular weights, where melt viscosities would be extremely high, are more readily obtained. In commercial use, however, solid-state polymerizations may be relatively slow.
In the case of PET, solid-state polymerizations usually require that lower molecular weight polymer, in the form of particles or pellets, undergo a relatively lengthy cryst~lli7~tion process prior to being polymerized in the solid-state, in order that the particles do not agglomerate in the solid-state reactor. The ~ cryst Illi7~tion process for PET is usually accomplished by annealing the lower molecular weight polymer at an elevated temperature at which the desired cryst~lli7.~tion occurs.

CA 0223990~ 1998-06-08 W O 97/23543 PCT~US96/19647 It would be desirable to obtain a higher molecular weight 3GT polymer without having to expose a lower molecular weight 3GT polymer to lengthy and problematic cryst~ 7~tiQn and ~nn~ling steps.
SUMMARY OF THE INVENTION
This invention concerns a composition, comprising, poly(trimethylene terephth~l~te) having an average appal ellL crystallite size of at least 1 B .0 nm determined from the 010 reflection.
This invention also concellls a process for cryst~ ing poly(trimethylene terephth~l~te), comprising cooling at a rate sufficient to lower the temperature of a molten poly(trimethylene terephth~l~te) mass or, alternatively, heating at a rate s lffi~ nt to raise the temperature of a glassy poly(trimethylene terephth~l~te)mass to a telll~el~L~lre of about 60~C to about 190~C. This process produces a crystalline poly(trimethylene terephth~l~te) having an average appa,Glll crystallite size of 18.0 nm or more.
More particularly, disclosed herein is a process for the crystallization of pellets of poly(trimethylene terephth~l~te), comprising:
heating a glassy poly(trimethylene terephth~l~te) mass to a bulk average temperature of 60~C to about 1 90~C within a specified maximum period oftime and, furthermore, ~ g the mass at that buLtc average temperature for a specified minimllm period oftime; or cooling a molten mass of a poly(trimethylene terephth~te) so that the bulk average temperature of the molten mass is brought to a temperature in the range of 60~C to about 1 90~C within a specified m~ximllm period of time and, furthermore""~ ioh~g the cryst~lli7ing mass at that buL~ average temperature fora specified minimllm period oftime.
In a ~ d embodiment, the glassy mass may be in the form of particles or pellets or the molten mass may be in the form of small portions or droplets.
This invention also concerns a process for the solid-state polymerization of poly(trimethylene terephth~l~te), wherein the improvement comprises, starting with poly(trimethylene terephth~l~te) having an average appalellL crystallite size of18.0 nm or more and an I.V. (intrinsic viscsosity) of 0.05 to 0.9 dl/g. Finally, a 3GT polymer product of a solid-state polyln~ aLion process is ~ r~losed which product has an average ~palellL crystallite size of 18.0 nm or more and an L.V. of 0.5 dl/g or more.
BRIEF D~SC~IPTION OF THE DRAWINGS ~
Figure 1 is an illustration of a wide-angle x-ray diffraction pattern of a sample of 3GT polymer produced according to the present invention.

CA 0223990~ 1998-06-08 W O 971~3543 PCT~US96/19647 Figure 2 is an illustration of the region of interest of the diffraction patternshown in Figure 1.
Figure 3 is an illustration of the wide-angle X-ray diffraction pattern of Figure 2 after being deconvoluted into two o~ ping Pearson VII peaks.
DETAILS OF THE INV~NTION
A novel process for producing poly(trimethylene terephth~ e), also referred to as 3GT, is disclosed herein. A novel polymer composition characterized by a certain kind of crystalline morphology and other desirable characteristics is also disclosed. By 3GT or poly(trimethylene terephth~l~te) herein is meant poly(trimethylene terephth~l~te) which may be modified with small amounts, less than 10 mole percent, and more preferably less than 5 mole percent, of polymer repeat units derived from copol~ eli~ed monomers (or "co-repeat units"), so long as the cryst~lli7~tion behavior of the polyester is subst~nti~lly the same as "homopolymer" 3GT.
The present 3GT has an average appale.. l crystallite size of about 18.0 nm or more, preferably 19.0 nm or more, more p.~r~ly about 20.0 nm to about 35 nm, which mea~u~ ents are based on the 010 reflection. In particular, the average appa. ~llL crystallite size is measured by wide angle X-ray powder diffraction, the method or procedure for which is as follows.
Polymer samples of 3GT having uniform thic.kness for X-ray measurements are produced by cryogrinding the 3GT in a SPEX Freezer/Mill (Met~l~.hPn, NJ) under liquid nitrogen for 30 seconds and then col--pressing the 3GT into disks app.~x;"~ Ply 1 mm thick and 32 mm in ~i~mP~tPr~ While it is preferable that thesample's patterns are collected over the range 14.5-18.5~ 2~ (as shown in Figure 2), the patterns of the s~mples can be collected over the range 10-35~ 2~ in some cases, as was obtained for some of the samples (as shown in Figure 1). The diffraction data are collected using an automated Philips diffractometer operating in the tr~n~mi~.cion mode (CuKa radiation, curved diffracted beam monochrometer, fixed step mode (0.05~/step), 65 sec/step, 1~slits, sample rotating). Lorentz-polarization corrections are applied to each powder pattern.
To remove the local background scattering from the 14.5~-18.5~ 2~3 region of each powder pattern, a straight line e~tPn~ing from 14.5~ to 18.5~ 2~3 is defined and subtracted, as shown in Figure 2. This region of the diffraction pattern has~ been found to contain two crystalline reflections, at appl~ aLely 15.6~ and 17.1~

2~, that have been defined as the (010) and (012) reflections, referred to by S. Poulin-Dandurand, et al., in Polymer, Vol. 20, p. 419-426 (1979).
Figures 1 and 2 show the diffraction patterns, corrected as detailed above, collected over the 2~3 range 10-35~ and 14.5-18.5~, respectively. In addition to the CA 0223990~ 1998-06-08 Miller indices of the reflections of interest, the local "artificial" backgroundbetween 14.5~ and 18.5~ 2~, labeled "b", and described above, is shown.
The 14.5-18.5~ 2~ region is then deconvoluted into two overlapping Pearson VII peaks corresponding to the two crystalline reflections, and the S position, width, height, and exponential Pearson VII fiKing parameters of both peaks are extracted. See ~uation 2 3.3.16 on page 67 from the standard reference by A. J. C. Wilson, ed., International Tables :~or Crystallo~raphy, Vol. C, Published for The International Union of Crystallography by Kluwer ~r~ çmic Publishers, Doldl~chl (1992). An example ofthis deconvolution is shown in Figure 3. Below the deconvoluted peaks is plotted the residuals, i.e., the observed minus r~lç~ te~ intensity as a filnt.ti-~n of the scattering angle. The appal el.L
crystallite size for the (010) reflection (herein so~netimçs also referred to simply as appalt;.ll crystallite size), ACSolo, is ç~lclll~ted from the reflection's position and full width at half height using the Scherrer equation, as for instance described by L. E. ~ n-1Pr, X-~ay Diffraction Methods in Polymer Science~ p. 335 et seq.
(John Wiley & Sons, New York, 1969):

ACSolo = ~O10C~S~OlO

where ACSolo is the mean ~lim~nciQn ofthe crystal, K is ~c~nmed to be 1.0, ~ is the wavelength, 13 is the full width at half height of the profile, in radians, and ~3 has its normal m~ning By the term "average" with respect to apl)a~ellL crystallite size is meant the numerical average of one or more (pl~.ably 3 or more) measurements on the same batch of polymer. Such multiple measurements may be used to insure reproducibility because of the relatively small sample size used in the X-ray measurement.
It is also ~-erell~d if the 3GT has no distinct prçm~lting endotherrn. By a "pr~m~l~ing endotherm" is meant an endothermic peak in the DSC due to a melting endotherm at a lower temperature than (before) the main melting endotherm. By "distinct" is meant the melting occurs over a temperature range of 70~C or less,p.t;rel~bly less than 50~C. By having "no distinct pr~melting endotherm" is meant that if one or more such endotherms are detected, the total heat of fusion is less than 1 J/g, preferably less than 0.5 J/g. Pr~m~lting endotherms are believed to be indicative of small and/or relatively imperfect cryst~llitç.c, and when present, the 3GT particle may have a tendency to more readily stick to other particles when heated, usually at or around the temperature of a prçm.olting endotherm, which is very undesirable in solid-state polymerization.

CA 0223990~ 1998-06-08 W O 97/23543 PCT~US96/19647 The 3GT ofthe present invention, as a starting material for solid-state polymerization of poly(trimethylene terephth~l~te), has an average appalellL
crystallite size of 18.0 nm or more and an I.V. (intrinsic viscosity) of 0.05 to0.9 dVg, preferably about 0.1 to about 0 5 dl/g. The 3GT polymer product of a 5 solid-state polymerization process according to the present process has an average a~pale-lL crystallite size of 18.0 nm or more and an I.V. of 0.5 or more, preferably about 0.7 to about 2.0 dVg.
The 3GT of the present invention may be made, as indicated above, by rapidly heating glassy 3GT to a certain temperature range or by cooling molten 10 3GT to that same temperature range. By "glassy 3GT" is meant 3GT below its Tgthat contains a quantity of crystalline material that produces a heat of fusion, in a DSC measurement, of less than about 10 J/g, preferably less than about 5 J/g, and most preferably less than 1 J/g. The amount of crystalline 3GT present can be determined by using a standard DSC method heating at 10~C/min to determine the 15 heat of fusion of the crystallites present. Since the 3GT sample will be mostly amorphous, an exothermic cryst~lli7~tion peak will occur in the DSC trace as well as an endothermic melting peak. The crystallinity of the starting material, given in J/g, is d~Le~ ed by taking the difference in the areas under the curves of the two peaks. By a "molten 3GT" is meant a 3GT in the liquid (not glassy) state.
20 Preferably, it co--L~i..s less than ten weight percent (10%), more preferably less than five weight percent (5%), and most preferably less than one weight percent ( 1.0%) crystalline 3 GT. It is pl t:rt;..ed if the initial temperature of the molten 3GT
is about 230~C or higher, p.ert;ldbly about 240~C or higher, since this is apl,loxilllaLely at or above the common melting point of 3GT. In order to obtain a 25 large a~pa-t;-l~ crystallite size, it is plt;Ç~I~ed to have as little crystallinity in the starting 3GT as possible.
It has been found that the desired 3GT crystalline morphology may be formed by rapidly heating or cooling amorphous 3GT to a preselected temperature range, which process step may be referred to as thermal shock cryst~lli7~tion. A30 temperature range of 60~C to about 190~C has been found to produce the desired result; 80~C to 170~C is p-er~ d for Illd~imUIIl cryst~lli7~ti~n rate of 3GT.
Accordingly, in this process, not only must a temperature gradient be imposed between the 3GT and its surrolln-1ingc but heat (or another apl)~oplidle~ form of energy~ should be removed or added to the polymer at a relatively high 35 rate. If he~ting conductive and/or radiant heat as obtained in conventional ovens may be employed. For example, ovens in which heat flows primarily by radiation and/or conduction from the surroundings into the 3GT material or particle may beemployed.

CA 0223990~ 1998-06-08 W O 97/23543 PCT~US96/19647 This }equires that the surroundings or environment of the 3 GT be able to transfer this heat rapidly. Preferably, the cross-sectional area of the mass of 3GT
should not be so large that the change of temperature of the 3GT is relatively rapid on the surface of the mass but inadequate or too slow in the center.
When cryst~11i7ing from molten 3GT, in order to obtain rapid heat transfer into the molten 3GT, it is plerelled if the 3GT is in good contact with a heat-transfer material that has a relatively high overall heat capacity (derived from both its mass and its actual heat capacity) and thermal conductance. Metals are particularly useful for this purpose, especially metals with high coefficients of heat transfer. However, coated metals, plastics and other materials may be employed for ~l~n~r~ling heat to molten 3GT during cryst~11i7~tinn The surfiace ofthe molten 3GT may be exposed to a colllbill~Lion of heat ~l ~lsr~l materials, for example, a part of the surface may be exposed to a metal surface and another part of the surface may be exposed to, for example, a gas.
Although a gas may be used to transfer heat to or from the 3GT, the heat capacities of gases are relatively low, and so such cooling would be more difflcult to achieve by itself. Liquids at the apl,.o~,iate temperature may also be used, but they may be less plt;r~ d because of concerns that co"i ~ ticm may occur and because ofthe need to separate the li~uid from the 3GT. Thus, it is ~l~r~lled to at least partially cool the molten 3GT by contact with a heat conductive solid.
Conversely, when starting with glassy 3GT instead of molten 3GT, the glassy 3GT should be rapidly heated instead of cooled. One way to accomplish this is to expose the glassy 3GT to a very high te~nll)el~lule environment, about 300~C to 800~C or higher for up to about 120 seconds. Generally speaking, the 25 higher the tcl~ L.Ire or the smaller the cross section of the 3GT ~eing treated, the less time that will be needed. In forming the desired crystalline form of 3GT by heating or cooling, it is plt;ft;lled that the entire cryst~11i7~tion process, i.e., heating or cooling and crystal formation, be complete in less than 5 min, more plt;~el~bly less than 3 min, more preferably less than 2 min, and most preferably about 3 toabout 60 sec. When cryst~11i7ing molten 3GT, the particles may be ~ ed at the temperature of cryst~11i7~tion for longer periods of time. When cryst~l1i7:ing glassy 3GT, however, prolonged exposure to the temperature of cryst~11i7~tion may be deLlill-~llL~I to the desired result.
The m~imllm linear ~ t~nce from any point in a particle to its surface is used to determine how fast the bulk of the 3GT is heated or cooled. Generally, it is p. er~l, ed if the llld~dnlum linear ~lict~nc.e for the 3GT particles to be heated or cooled is about I cm or less, more preferably, about 0.6 cm or less.

CA 0223990~ 1998-06-08 W O 97~3~43 PCT~US96/19647 The shape ofthe crystallized 3GT may vary, and may be, for example, a film, a ribbon or particles of various shapes. In one l"~r~ d embodiment, the 3GT is in the form of particles (or, more accurately, small discrete units, masses, or droplets in the case of molten 3GT). Crystalline 3GT in the form of particles isparticularly useful in solid-state polymerization. The particles herein have average diameters of 0.05 cm to 2 cm. Preferred forms and/or sizes for particles are spherical particles with (1i~met~rs of 0.05 cm to 0.3 cm, hemispherical particles with a ~ ~ ~, x; ~ ~ 1l 1 1 1 l cross section of 0.1 cm to O. 6 cm, or right circular cylinders with a ~ meter of 0.05 cm to 0.3 cm and a length of 0.1 cm to 0.6 cm. If shapes such as films or ribbons are formed, then if desired, they can be later ground, cut, or otherwise divided into particles, such as are suitable for solid-state polymerization.
Since it is preferred if the pellets are produced on an economically advantageous commercial scale, the pellets would pl~ bly be produced and collected together in commercial quantities of greater than 10 kg, more preferably greater than 50 kg.
The pellets may be used in the same plant soon after being made, stored for later use, or p~c~ged for transport, all in commercial quantities.
Before reaching a stable shape, molten or cryst~lli7ing 3GT may be affected by the shape of the means into which it can flow or within which it is confined before solidification, whether such means employs physical or other forces.
Glassy 3GT, for use as a starting material in a cryst~ 7~tion process according to a method of the present invention, may be made by very rapidly cooling the a~lup~iate m~lec~ r weight molten 3GT to below the glass transition temperature of 3GT. This can be done in bulk or while r~"l"hlg particles of the 3GT. The 3GT itself can be made from applop,iate methods known to the artisan.
See, for example, British Patent 578,097. Also, methods for pl~l.a,illg PET (2GT) may, to a large extent, be applicable to 3GT. See, for example, with respect to PET polyester, B . Elvers, et al., Ed., Ullmann' s Encyclopedia of Industrial ChemistrY, Vol. A21, p. 232-237 (VCH Verlagsgesrll~r.h~ft mbH, Wf~inh~im 1992). Such a glassy polymer may be stored or shipped (preferably in a relatively dry state) for later polymerization to higher molecular weight, whether a solid-state polymerization, melt polymerization, or other processing.
It is pl~rell~d if the instant process starts with molten 3GT, which is then cooled. It is convenient, and therefore preferred, if the 3 GT is formed into "particles" just before or escenti~lly .cim~llt~neous with the cooling ofthe molten 3GT to form the desired crystalline morphology. The ple~lled eventual sizes and shapes of such particles are as given above.
The molten 3GT may be formed into particles by a variety of methods, inc.h~ding pastillation, see copending commonly assigned application U.S.S.N.

CA 0223990~ 1998-06-08 08/376,599; and U.S. 5,540,868, these applications hereby incorporated by reference in their entirety, or U.S. Patent 5,340,509, prilling as desribed in numerous patents such as U.S Patent No. 4,165,420, melt cutting, dripping (see Examples 1-5 below), or extruding (see Co,-,p~ Li~te Examples 7-9 for an 5 extrusion step).
Pastillation, broadly termed, is employed for particle formation in a pl~r~--ed embodiment ofthe present invention. P~till~ti~ln typically employs an outer, rotating, cylindrical container having a plurality of orifices circu...Ç~ ially spaced on its periphery. Within the outer container is an inner, coaxial, cylindrical container having a metering bar or t:h~nn~ol The plurality of orifices on the outer container are disposed such that they will cyclicly align with the metering bar or channel on the inner col-L~ er when the outer container is rotated.
Typically, molten polyester is ~ relled to the inner container ofthe pa.~ti11~tor and, under pressure, is dispensed onto a surface such as a conveyor belt in uniform amounts, forming droplets or unsolidified pellets, as each of the plurality of orifices on the outer container align with the metering bar on the inner container. Pastillators are COI~ .,;ally available, e.g., the ROTOFORMER~) pastillator m~n11f~rtl1red by Sandvik Process Systems (Totowa, NJ). For more details on ~llllhlg polyester particles by p~eti11~tion, see copending, commonly~ n~d and copending application Serial ~o. 08/376,599.
The 3GT, as droplets, can be conveniently cooled by cont~ting them with a metal surface, preferably in a controlled tt--~ Lul t; en /i- on~ .L, such as a conveyor belt or moving table held at the proper temperature to achieve the desired crystalline morphology. It is p~ t:r~l -ed if the 3 GT initially contacts this metal while still largely molten, since a liquid will usually provide better heat transfer than a solid of the same material. A re~1l~ted flow of an inert gas may be passed over the particles to increase the overall rate of cooling.
The temperature to which the 3GT mass (or pellet) is brought, l~ÇG,led to above, is the bulk average temperature, defined as the average temperature of the mass (or pellet) or the average of the telll~ Lul~ in every location of the mass (or pellet). To determine the bulk average temperature of pellets, for example, the measurement of bulk average can proceed as follows. Quickly collect a sample of the pellets from the solid surface or gas, whichever is used to thermally shock the pellets. Immf~ t~1y place the pellets in an in~l]1~tecl container, preferably evacu~ted. Preferably, the pellets nearly fill the container. Insert a thermocouple.
Allow the container to come to an equilibrium temperature and record it as the bulk average temperature.

CA 0223990~ l998-06-08 W O 97/23543 PCTrUS96/19647 Alternately, a bulk average temperature of pellets being processed can be calculated as follows. Collect a sample of the pellets. Tm mç~ tely place the pellets in a preweighed amount of distilled water, at a known temperature, in a preweighed in~ ted container. Reweigh the the total mass. Observe the equilibrium temperature. Calculate the bulk average temperature of the pellets based on the following equation:
(mw) X (cpw) X (Te - Tu,) = (mp) X (cpp) X (Tp - Te) wherein mw is the mass of the water, CpW is the heat capacity of the water, mp is the mass of the pellets, cpp is the heat capacity of the pellets, Tp is the equilibrium temperature, and T~y is the initial temperature of the water, and X represents multiplication. This equation can be solved to determine Tp, the bulk temperature of the pellets.
As will be appreciated by one of ordinary skill in the art, the bulk average temperature of the pellets, under various conditions, can be estim~te(l with a reasonable degree of accuracy and precision based on standard heat transfer equations. The skilled artisan will be familiar with such c~lr~ tions~ inr.l~lcling numerical and/or computer techniques for improved efficiency and accuracy.
For example, if one knows the heat transfer coefficient of the ellvi, ul~nent and the process conditions, then an estim~te of the change in bulk average temperature of the particle with time can be obtained from the equations:

Q = mpcp ~= hA(Te-Tp) ~= hA (T~-Tp) dT
dt = kTe-kTp hA
where k = m c ~ t Tpo 0 -Ln (~0) = kt CA 0223990~ 1998-06-08 W O 97~3543 PCTrUS96/19647 Te-Tp = (Te-Tpo)(e~kt) Tp = Tp0(e~kt) + Te( 1 -e~kt) This equation in~ic~tçs that if the heat transfer constant, k, is known for a given system as well as the initial temperature of the particle and the temperature of the environment, then the bulk average temperature of the particle as a function of time can be ~lc~ ted wherein mp is the mass of the pellet, cp is the heat capacity of the pellet, t is time, h is the heat transfer coefficient of the surface or gas to which the pellet is subjected, Te is the temperature of the surface or gas to which the pellet is subjected, and ~ is the area which is contacted or subjected to the heat source, whether a solid surface or a gas. For example, a hemispherical particle dropped on a steel belt may have a flat area A in touch with the belt, which area can be readily estim~ted as (7~)(radius)2. Alternatively, an average value A of a sample of pellets can be physically measured for use in the above e~uations.
These e~uations can be solved for Tp, the bulk average temperature of the pellet.
As mentioned above, thermal shock can be imposed on 3GT pellets so that the temperature gradient experienced by the pellets occurs in either direction, that is as a result of either heating or cooling. However, it is preferable that the pellets be cryst~lli7ed by cooling from the melt. This avoids the need to reheat cooled particles and is thus more energy ~fl~ nt In an integrated process for producing high molecular weight 3GT, the low mnlec~ r weight 3GT having the morphology described above may be further polymerized to higher molecular weight. The 3GT may be melted and melt polymerized, but the crystalline 3GT described herein is especially suitable for use in solid-state poly"le~ Lion. Solid-state polymerization in general is well known to the artisan. See, for in~t~nce, F. Pilati in G. Allen, et al., Ed., Comprehensive Poly-ner Science. Vol. 5, p. 201-216 (Pergamon Press, Oxford 1989). In general, solid-state polymerization involves heating particles of a polymer to a temperature below the melting point and passing a dry gas, usually nitrogen, usually concurrently in continuous operation, around and over the particles. At the elevated temperature, tran~st~rification and polyconrlPn~tion reactions proceed,and the gas can be employed to carry away the volatile products (similar other methods, such as employing a vacuum, may be used for this purpose), thereby 3 5 driving higher the molecular weight of the polymer. Some embodiments employ both an inert gas flow and a vacuum.
In the past, a number of problems or difficulties have been associated with the solid-state polymerization of some polyesters such as PET. In particular, the particles to be polymerized usually have had to undergo an anne~linf~ or CA 0223990~ 1998-06-08 crystallization process~ so that when they are heated during solid-state polymerization, they do not undergo partial melting and stick together. If, alternatively, the polymerization occurs at a relatively lower tt;ll,pel dL-Ire to avoid sticking, this would increase the polymerization time, since the reactions which5 drive the molecular weight up proceed faster at higher telll,~)t;l~Lul~s. In either event, these (liffic ~lties or problems tend to make the solid-state pol~ eli~aLion process more expensive to run.
Advantageously and surprisingly, the 3GT polymer with the crystalline morphology disclosed herein does not need additional prolonged crystallization 10 steps after the initial cryst~lli7~tion, and may be more directly polym~ ed (preferably without prolonged ann~lin~). In addition, particles produced acco~ g to the present process may, in some cases at least, be more resistant toattrition. This would usually be advantageous where polymer particles, in solid-state pol~ e~ Lion ~u~al~ s, tend to wear against each other or the apparatus 1 5 itself.
In any pol~..leliGaLion of low molecular weight 3GT to higher molecular weight 3 GT, normal additives, such as polymerization catalysts, may be present.These may have been added when the low molecular weight 3GT was formed.
Catalysts cont~inin~ tit~nillm, antimony, or l~nth~nllm are commonly used in 20 tr~n~est~qrification and polycon~1~n~fion of polyesters.
In the following Examples, certain analytical procedures are used. Aside from X-ray diffraction, which is described in detail above, these procedures aredescribed below. References herein to these types of analyses, or their results,correspond to these exemplary procedures.
25 Intrinsic Viscositv (I.V.) A solvent is made by mixing one weight portion trifluoroacetic acid and one weight portion methylene chloride. The 3GT polymer, in the amount of applo~ lely 0.01 g, is weighed into a clean 30 ml vial. Appropriate ~uantity of solvent is added to make a 0.4% by weight solution. The vial is sealed (to prevent 30 evaporation of the solvent) and shaken for 2 hours or until polymer dissolves. The solutions are measured in duplicate on a Viscotek~3 Y501B force flow viscometer at 19~C with a pure methylene chloride reference stream. A three point calibration scheme with blank correction is used to c~lc -l~te single point intrinsic viscosity (I.V.) using the standard Viscotek~) ETA 4.10 software package.
35 Meltin~ Point Melting point was determined by Dirrel~llLial Scanning Calorimetry (DSC) and all samples were analyzed using a TA Instruments DSC 910. The instrument was calibrated with indium consistent with the system doc lm~nt~ion. The CA 0223990~ 1998-06-08 samples were analyzed as received, no pre-grinding, using 5-10 mg ~0.005 mg.
The samples were sealed in ~ mimlm pans then heated from room temperature to 300~C at 10~~/min. in a nitrogen purged environment. Glass transition temperature, melting point temperature and heat of fusion c~lcl-l~tions were done 5 with the TA Inst~ument software. The reported DSC peak melting temperature is the corresponding temperature of the peak in the main melting endotherm.
In the Examples that follow, SSP means solid-state polymerization.
EXA~lPL:ES 1-5 These Examples 1-5 illustrate cryst~lli7~tion of 3GT from molten droplets 10 according to one embodiment ofthe present invention. The polymer 3GT was polymerized in the melt from dimethyl terephth~l~te (DMT) and 1,3-propanediol (3G) to the intrinsic viscosity listed in Table 1 below. This low molecular weight polymer was heated in a melt indexer at 270~C until the polymer dripped out of its orifice (1 mm in d;~lwLel) under its own weight onto a programmable hot plate a~,u~ll~a~ely 20 cm below. The hot plate was set to 135~~. Cryst~iliz~tion was monitored by observing the clear amorphous drop turn into an opaque solid. Once it was opaque, the surface was tipped at an angle to ho,i~o-~Lal so the particlewould slide off and cool to room tt~ L~lre. The particles were shaped like p~nc~k~s,a~lo~ll~a~ely 5 mm in ~i~m~t~.r and 2.5 mm thick. DSC analysis ofthe 20 cryst~lli7ed samples in~lic.~te~l no pre-melting endotherms. The intrinsic viscosities and the average app&-el-L crystallite sizes determined from the 010 reflection are shown in Table 1 below.
Table 1 ACSol0 (nm) ASColo (nm) Ex.No. I.V. (Wg)Pearson VII DeconvolutionGaussian Deconvolution*
1 0.16 21.6 2 0.18 19.7 3 0.35 19.7 4 0.50 20.9 20.5 0.70 20.5 19.5 6 0.89 23.2 21.5 *Numbers obtained using Gaussi~n dc~ul.vul.~Lion rnay vary (usually within about s%) firom what would be obtained using Pearson VII deconvolution.

This Example shows that the novel crystalline morphology created by the 25 therrnal shock cryst~li7~tion was preserved when the low molecular weight prepolymer was solid-state polymerized to higher molecular weight. Particles from Example 2 above, with an I V. of 0.18 dl/g, were solid-state polymerized for 24 hr -~_,h~ . ~ .. - CA 0 2 2 3 9 9 0 5 19 9 X - l! ( - 11 X~ .- . c at ~05~C The SSP batch unit consisted of:1 m~.aiYtut ~ ~ .., ."*-c r~ C:-long) with a mesh screen on the botton. Ni~ ec;rT,'.,'~iJ~-~'~lUa t~, t~C.SCt temperature. heated the outside of the tube an(l ~ ~.i~hQ~ou~g.P'tn'~'~sc~ ting the particles. The SSP'd particles had an r.v. 'ofO 9~Pd./~. .n~.~,i,cso;~ r~:' S ~1.5 nm using Gaussian deconvolution. ~:~.t ' - COMPARATIVE EXf~ f.. r E'~ ;4 e~
The polymer 3GT was made by a convcrltional m~ r~ma,cin~
(PET) in order to show that this material does not !l.;.i, ~th~,crv's 2ilinc 'orrn shown in Examples 1-6 The samples listed in T.lblc 2 b~,;low'w~er~è poly;T.cri~:d in 10 the melt from DMT and 1,3-propanediol to an l.~i. or'abo~t O :7~,dl/',~. Thc polymer was extruded under slight pressure, round strands,~ 7A~ ter~ into a quenching water bath and cut into lengths about~ L/8 inc~ er chips were shaKered, then crystallized for 6 hr in a vacuum o~ r soc. The ,~ crystAIli7ed chips were solid-state polymerized in a fl~ i7e(i~y inert gas 15 (nitrogen). The temperature was ramped from 190~C to 210~C ~n 10~C steps and kept at 210~C untiI the desired molecular weight was obtained. Sam~p e 8 also contained 0.3% TiO2. The intrinsic viscosities and the average. appaL~L crystallite sizes determined from the 010 reflection are shown in Table 2 below;
Table 2 ACSolo (nm) Ex. No. I.V. (Wg)Pearson VII D~uuvuluLi~
7 1.06 16. 1 8 1 . 14 16.9 9 1.39 15.7 ~ , .

Claims (24)

What is claimed is:

1. A composition, comprising modified or unmodified poly(trimethylene terephthalate) having an average apparent crystallite size of about 18.0 nm or more, determined from 010 reflection.

2. The composition as recited in Claim 1 wherein said average apparent crystallite size is about 19.0 nm or more.

3. The composition as recited in Claim 1 wherein said average apparent crystallite size is about 20.0 nm or more.

4. The composition as recited in Claim 1 wherein the composition has an intrinsic viscosity of 0.05 to 2.0 dl/g.

5. The composition as recited in Claim 1 wherein said modified poly(trimethylene terephthalate) comprises up to 5 percent of repeat units otherthan trimethylene terephthalate repeat units.

6. The composition as recited in Claim 1 wherein said modified poly(trimethylene terephthalate) comprises repeat units derived from comonomers selected from the group consisting of isophthalic acid, triethylene glycol, 1,4-cyclohexane dimethanol, 2,6-napthalene dicarboxylic acid, adipic acid, esters of the foregoing, diethylene glycol, and mixtures thereof.

7. Particles of the composition of Claim 1.

8. The particles as in Claim 7 having an average diameter of 0.05 cm to 2 cm.

9. The particles as recited in Claim 7 or 8 wherein said average apparent crystallite size is about 19.0 nm or more.

10. The particles as recited in Claim 7 or 8 wherein said average apparent crystallite size is about 20.0 nm or more.

11. The particles as recited in Claim 7 or 8 comprised of poly(trimethylene terephthalate) having an intrinsic viscosity of 0.5 to 2 dl/g.

12. The particles as recited in Claim 11 wherein the intrinsic viscosity is 0.7 to 2 dl/g.

13. The particles as recited in Claim 7 or 8, wherein the particles are spherical, hemi-spherical, cyclindrical, or pancake-like in shape.

14. The particles of Claim 13 wherein the particles are spherical with a diameter of 0.05 cm to 0.3 cm.

15. The particles of Claim 13 wherein the particles are hemispherical with a maximum cross section of 0.1 cm to 0.6 cm.

16. The particles of Claim 13 wherein the particles are right circular cylinders with a diameter of 0.05 cm to 0.3 cm and a length of 0.1 cm to 0.6 cm.

17. A process for crystallizing poly(trimethylene terephthalate), comprising cooling at a rate sufficient to cool a molten poly(trimethylene terephthalate), or heating at a sufficient rate to heat a glassy poly(trimethylene terephthalate), to a temperature of about 60°C to about 190°C, to produce a crystalline poly(trimethylene terephthalate) having an average apparent cristallite size of about 18.0 nm or more as determined from 010 reflection, wherein said crystallizing is carried out in about 5 minutes or less.

18. The process as recited in Claim 17 wherein said temperature is about 80°C
to about 170°C.

19. The process as recited in Claim 17 wherein said average apparent crystalline size is about 19.0 nm or more as determined from 010 reflection, and said crystalline poly(trimethylene terephthalate) produced has an intrinsic viscosity of about 0.05 to 0.9 dl/g.

20. The process as recited in Claim 17 wherain said poly(trimethylene terephthalate) produced is in the form a particle.

21. The process as recited in Claim 17 comprising the additional step of solid-state polymerization of said crystalline poly(trimethylene terephthalate).

22. A process for the solid-state polymerization of poly(trimethylene terephthalate) comprising heating particle of poly(trimethylene terephthalate) in an inert gas flow or vacuum or an inert gas flow and vacuum to above their Tg but below their melting point, the improvement comprising starting with poly(trimethylene terephthalate) particles having an average apparent crystallite size of about 18.0 nm or more and an intrinsic viscosity of about 0.05 to 0.9 dl/g.

23. The process as recited in Claim 22 wherein said average apparent crystallite size is about 19.0 nm or more.

24. The process as recited in Claim 22 wherein said average apparent crystallite size is about 20.0 nm or more.