WO2013092667A1

WO2013092667A1 - Liquid crystalline furandicarboxylic acid-based aromatic polyesters

Info

Publication number: WO2013092667A1
Application number: PCT/EP2012/076094
Authority: WO
Inventors: Carolus Henricus R. Maria WILSENS; Sanjay Rastogi; Martijn Arnoldus Johannes Veld; Enno Anton KLOP; Bart Adrianus Johannes Noordover
Original assignee: Teijin Aramid B.V.
Priority date: 2011-12-23
Filing date: 2012-12-19
Publication date: 2013-06-27

Abstract

The invention pertains to a fully aromatic liquid crystalline furandicarboxylic acid- based aromatic polyester obtainable from a mixture of monomers comprising 2,5- furandicarboxylic acid, p-hydroxybenzoic acid, an aromatic diol, and 5-40 mol% of an aromatic monocarboxylic acid selected from vanillic acid, ferulic acid, salicylic acid, and syringic acid, or mixtures thereof. In a preferred embodiment at least 90% of the 2,5-furandicarboxylic acid and aromatic monocarboxylic acid are bio-based monomers.

Description

LIQUID CRYSTALLINE FURANDICARBOXYLIC ACID-BASED AROMATIC POLYESTERS

The invention pertains to fully aromatic liquid crystalline furandicarboxylic acid-based polyesters and shaped products obtained thereof.

Thermotropic polyesters have been studied extensively over the last 30 years.

Numerous patents and articles have been published on the synthesis of novel aromatic polyesters that show liquid crystalline behavior in their molten state. Melt- processing of thermotropic liquid crystalline (LC) polymers is an interesting and relatively cheap and easy processing route for high performance fibers compared to the air-gap spinning process that is frequently required for the processing of other high-performance materials, such as Twaron^® and Kevlar^® p-aramids. The low viscosity of the pre-ordered melt ensures easy processing in combination with good fiber properties. The highly anisometric shape of these molecules combined with the rigidity of the backbone gives these polymers the ability to align along the flow direction while maintaining a low viscosity. The directional order is characterized by the tendency of these molecules to align along a common director giving rise to highly anisotropic properties, which results in fibers with superior properties compared to polymers that do not show liquid crystalline behavior. Especially some thermotropic polyesters, such as Vectran^® which is a copolymer mainly based on 6- hydroxy-2-naphthoic acid and p-hydroxybenzoic acid, have received considerable attention from industry in the last decennia because of their high thermal stability, low processing costs and excellent fiber properties.

Examples of 2,5-furandicarboxylic acid-based polyesters are known. In JP

2010254827 and US 2010174044 aliphatic polyester-ethers containing 2,5- furandicarboxylic acid which can be derived from a biomass, have been described. The present invention relates to aromatic rather than aliphatic polyesters. In US 2008081883 polyester polyols have been described which are provided by reaction of FDCA with polyepoxides. These polyesters also contain aliphatic instead of aromatic units, originating from the epoxides. In JP 2009-062465 a polyester resin having a structural unit derived from a 2,5- furandicarboxylic acid ester and an itaconic acid ester, and a method for producing the polyester resin by copolymerizing a 2,5-furandicarboxylic acid or its ester with itaconic acid or its ester in the presence of a polyhydric alcohol has been disclosed. Itaconic acid ester is an aliphatic ester.

In EP 0294863 a polyester has been described as obtained from polymerization of 2,5-furandicarboxylic acid and p-hydroxybenzoic acid, with the non-bio-based materials 2,6-dihydroxyanthraquinone, isophthalic acid, terephthalic acid, and p- phenylenediamine, or the non-bio-based materials 2,6-naphtalenedicarboxylic acid and naphthalic acid. This reference describes fully aromatic liquid crystalline 2,5- furandicarboxylic acid-based polyesters, however, derived from monomers that cannot be obtained from bio-based materials. The monomers of these polyesters are obtained from oil (petrol) or coal, which sources are not infinitive. There is an increasing demand to polyesters that, at least partially, can also be obtained from bio-based materials.

The first objective of this invention is to synthesize liquid crystalline polyesters that can be obtained from bio-based materials. The monomers are selected such that the melting temperature of the liquid crystalline polymer is low enough to be processed economically from its melt state. The invention is driven in the quest to reduce C0₂ emissions during the life cycle of the product, and to provide an alternative resource to fossil fuels for producing monomers for making high-strength high-modulus materials. To obtain high performance bio-based materials it is essential to design polymers that show liquid crystalline behavior in the melt or in the presence of solvent. US patent 4,230,817 discloses for the synthesis of a liquid crystalline polymer the use of ferulic acid for making thermotropic polyesters, optionally in combination with other monomers such as vanillic acid and p-hydroxybenzoic acid, which can be obtained from natural resources such as lignin. However, the polymer does not contain 2,5-furandicarboxylic acid-derived units and appears to be thermally unstable at temperatures higher than 300 °C. The present invention has as one of its objectives the issue of increasing thermal stability of furandicarboxylic acid-based polymers comprising both vanillic acid (or alternatively ferulic acid, salicylic acid, or syringic acid, or mixtures thereof) and hydroxybenzoic acid, which was not possible earlier, while maintaining the liquid crystalline nature of the polymer synthesized using monomers that can be obtained from bio-based resources, and in combination with an economically attractive processing window.

To this end the present invention pertains to a fully aromatic liquid crystalline 2,5- furandicarboxylic acid-based polyester obtainable from a mixture of monomers comprising 2,5-furandicarboxylic acid, p-hydroxybenzoic acid, an aromatic diol, and 5-40 mol% of an aromatic monocarboxylic acid selected from vanillic acid, ferulic acid, salicylic acid, and syringic acid, or mixtures thereof.

Although the fully aromatic liquid crystalline furandicarboxylic acid-based polyester can be made from monomers obtained from both bio-based and non-bio-based materials, for all polyesters of this invention it is preferred that at least 90% of the 2,5- furandicarboxylic acid and at least 90% of the aromatic monocarboxylic acid are bio- based.

It is more preferred when also the p-hydroxybenzoic acid for at least 90%, even more preferred for at least 95%, is bio-based. The term bio-based means that the monomers are obtained from sources such as agricultural materials, plants, plankton or microbiological products, in contrast to non-bio-based materials that have their origin in oil or coal. In the definitions of this invention the term "bio-based" does not include material obtained from oil, coal or other petro-chemical products. Most preferably these monomers are fully (i.e. 100%) bio-based and are not obtained from non-bio-based materials or mixed with the corresponding monomers from non-bio- based origin. In another preferred embodiment the polyester is obtained from 3-20 mol% of each of the monomers FDCA (2,5-furandicarboxylic acid) and aromatic diol. More preferably, these amounts are 5-15 mol%. The aromatic monocarboxylic acid is contained in the mixture of monomers for 5-40 mol%, preferably for 5-25 mol%, more preferably for 8- 20 mol%. The preferred amount of HBA (p-hydroxybenzoic acid) is 20-89 mol%, more preferably 30-70 mol%. Any combination of the above preferred amounts can be used, optionally in combination with amounts of other monomers to add to 100 mol%, provided that stoichiometric amounts of FDCA and aromatic diol are used.

2,5-Furandicarboxylic acid can be obtained from D-fructose. p-Hydroxybenzoic acid can be extracted from natural resources such as Cocos nucifera. Vanillic acid is found in the root of Angelica sinensis and ferulic acid can be found in the seeds of coffee, apple, artichoke, peanut, and orange, as well as in both seeds and cell walls of commelinid plants (such as rice, wheat, oats, and pineapple). Salicylic acid is biosynthesized from the amino acid phenylalanine, and syringic acid can be obtained from palm tree {Euterpe oleracea). Other vegetal sources of these monomers are also known. The aromatic diols are not necessarily obtained from bio-based materials, but preferably also these are partially (such as for at least 80%) or completely bio-based.

In another preferred embodiment the polyester is obtained from 40-89 mol% of HBA in combination with:

(a) 3-20 mol% of each of the monomers FDCA and aromatic diol. More preferably these amounts are 5-15 mol%. FDCA and the aromatic diol should be present in stoichiometric amounts, and

(b) 5-40 mol%, preferably for 5-25 mol%, more preferably for 8-20 mol% of the aromatic monocarboxylic acid selected from vanillic acid, ferulic acid, salicylic acid and syringic acid, or mixtures thereof. These amounts can be used with any amount of other monomers up to a total of 100 mol%. In another preferred embodiment the aromatic diol has the formula:

HO-Ar-(X-Ar)_m-OH, wherein Ar is a phenyl or naphthyl group which may be

substituted by a methyl or methoxy group, m is 0 or 1 , and X is selected from a bond, S, O, SO, SO₂, CO, CH₂ and C(CH₃)2- Positioning of the hydroxy groups is preferably para with respect to other functional groups, but may also be meta or ortho.

Exam les are aromatic diols of the formulae:

bis(4-hydroxyphenyl sulfone) dihydroxydiphenyl ether

O

dihydroxydiphenyl sulfide dihydroxybenzophenone

dihydroxynaphthalene

The aromatic phenyl or naphthyl groups may independently be substituted by one to four methyl or methoxy groups. The positions of the hydroxy groups may be meta or ortho, but the para position as depicted in the above examples is preferred.

In another preferred embodiment of this invention a polymer is claimed that is obtained by polymerizing 2,5-furandicarboxylic acid, p-hydroxybenzoic acid, and aromatic monocarboxylic acid, wherein at least 90% to a maximum of 100% of these monomers have been obtained from bio-based feedstock, with one or more aromatic diol monomers, which are not necessarily, but preferably for at least 80%, bio-based. Other preferred polymers comprise 2,5-furandicarboxylic acid (FDCA) , vanillic acid (VA), p-hydroxybenzoic acid (HBA), and an aromatic diol which preferably is a commercially available diol such as 4,4'-biphenol, 4-(4-hydroxyphenoxy)phenol, 4,4'- dihydroxybenzophenone. The melting temperature of these polymers can be tuned by varying the amount of the monomers of the composition resulting in a specific processing window.

A system is created where the melting temperature can be tuned to obtain a processing window without loss of thermal stability and without losing aromatic content by combining the four monomers as mentioned in claim 1 . The fully aromatic liquid crystalline 2,5-furandicarboxylic acid-based polyester of this invention can be used to make shaped products by common manners known in the art. For instance, the polymers can be made to a powder or can be molten followed by mixing or extrusion into shaped products or in shaped particles prior to the final shaping process. Particularly useful shaped products are fibers, fibrids, tapes, non- wovens, fabrics and films that can be obtained by spinning, casting or jet spinning the molten or dissolved polymer. Such methods are also well known in the art. Examples of fibers are continuous fiber, chopped fiber, staple fiber, pulp, fibrils, and the like.

The invention is illustrated by the following non-restrictive examples.

Example 1

Polyesters have been synthesized following known methods for transesterification, according to Bhowmik P.K., Lenz, R. Journal of Polymer Science: Part A: Polymer Chemistry Vol. 31 ,21 15-2122 (1993) and Dong, D., Jiang, S., Ni, Y., Jiang, B., European Polymer Journal, (2001 ), 37, 61 1 -617. Composition (ratio mol%) Tm °C Tm °C T99wt% Td

1 ^st heating 2^nd heating °C °C cycle cycle

FDCA-BP-HBA (15/15/70) 378 343 31 1 461 (comparison according to EP

0294863)

FDCA-BP-HBA- VA (15/15/60/10) 278 273 365 410

FDCA-BP-HBA- VA (15/15/50/20) 243 234 306 417

FA-HBA-VA (40/50/10) 300^a 300^a < 300 <300 (comparison according to US

4,230,817)

a published value of US 4,230,817 (unknown whet her value was measured in first or second heating cycle).

FDCA= 2,5-furandicarboxylic acid; BP = biphenol; HBA = p-hydroxybenzoic acid; VA = vanillic acid; FA = ferulic acid

Tm = peak melting temperature as observed on transition from crystal to liquid

crystalline phase during the first or second heating cycle in Differential

Scanning Calorimetry (DSC) at the heating rate of 10 °C/min in nitrogen rich atmosphere. The second heating cycle refers to sample heated again after cooling from its liquid crystalline phase.

T99wt% = highest temperature where 99 wt % of the original material remains while 1 wt% of the material is lost. This value is measured using Thermal Gravimetric Analysis while heating at 10 °C/min in nitrogen rich atmosphere.

Td = onset of the degradation temperature, which is measured as change in slope during Thermal Gravimetric Analysis while heating the sample at 10° C/min in nitrogen rich atmosphere.

The polyester FDCA-BP-HBA has only a small difference (32 °C) between the melt temperature Tm and T99wt%, whereas T99wt% is lower than Tm. This results in substantial decomposition during melt-processing. Also the polyester FA-HBA-VA, which is not furandicarboxylic acid-based, shows a greatly decreased thermal stability compared to the polyesters of this invention. The polyesters of this invention have a large difference between Tm and T99wt%, wherein T99wt% is higher than the melting temperature.

The polymer of example 1 which comprises FDCA-BP-HBA-VA (15/15/60/10) was melted and heated to 305 °C and melt-spun through a 300 μιτι aperture to obtain a monofilament.

This shows that the polymers according to this invention can be spun to obtain fibers. Such fiber, e.g. in the form of continuous fibers, can be further processed to yarn, cords, weaves, non-wovens, pulp, and the like and be used in various applications.

Example 2

The following polymers were prepared using a thin-film polymerization according to the method as described in Chung, T.S. (2001 ), Thermotropic Liquid Crystal

Polymers, Thin-film Polymerization, Characterization, Blends and Applications, Technomic Publishing Company. The polymerization was done at minimum

temperature (Tm) where a stable liquid crystalline melt, without its transformation into the crystalline domains, is observed via optical microscopy. These temperatures are listed in the table below.

a Complete degradation.

b Partial degradation.

c Also determined by DSC after the peak melting temperature on transition from crystal to liquid crystalline phase in the first heating cycle in Differential Scanning Calorimetry at the heating rate of 10 °C/min in nitrogen rich atmosphere. Data are similar to the Tm determined by the optical microscopy method.

d According to prior art (polyester without vanillic acid).

This experiment shows that the melting temperature of the mixture reaches a minimum value at about 20 mol% of vanillic acid for a polymer with 15 mol% FDCA and 15 mol% of BP. When the vanillic acid content is increased further the melting temperature increases again and the liquid crystallinity is lost above 40 mol% of vanillic acid.

Example 3

The following polymers were prepared using a thin-film polymerization as described in example 2. The polymerization was done at minimum temperature (Tm) where a stable liquid crystalline melt, without its transformation into the crystalline domains, is observed via optical microscopy. These temperatures are listed in the table below.

a Partial degradation.

SyA = syringic acid SA = salycilic acid

HPP = 4-(4-hydroxyphenoxy)phenol

HBP= 4,4'-dihydroxybenzophenone These experiments show that incorporation of aromatic monocarboxylic acid (entries 1 -4) in comparison with example 2, entry 7, leads to decrease of the melting temperature of the polymers resulting in a stable liquid crystalline. Further, these experiments show that the polymers containing various aromatic diols, such as 4-(4- hydroxyphenoxy)phenol or 4,4'-dihydroxybenzophenone, have similar lowered melting temperatures and stable liquid crystalline melts (compare entry 1 with entries 6 and 8). As in examples 1 and 2, deleting the aromatic monocarboxylic acid leads to higher melting temperatures (entries 5 vs. 6, and 7 vs. 8).

Claims

Claims:

1 . A fully aromatic liquid crystalline furandicarboxylic acid-based polyester

obtainable from a mixture of monomers comprising 2,5-furandicarboxylic acid, p-hydroxybenzoic acid, an aromatic diol, and 5-40 mol% of an aromatic monocarboxylic acid selected from vanillic acid, ferulic acid, salicylic acid, and syringic acid, or mixtures thereof.

2. The polyester of claim 1 , wherein at least 90% of the 2,5-furandicarboxylic acid and aromatic monocarboxylic acid are bio-based monomers.

3. The polyester of claim 2, wherein at least 90% of the 2,5-furandicarboxylic acid, p-hydroxybenzoic acid, and aromatic monocarboxylic acid are bio-based monomers.

4. The polyester of claim 2 or 3, wherein at least 80% of the aromatic diol is bio- based.

5. The polyester of any one of claims 1 -4, wherein the aromatic diol has the

formula:

HO-Ar-(X-Ar)_m-OH, wherein Ar is a phenyl or naphthyl group which may independently be substituted by a methyl or methoxy group, m is 0 or 1 , and X is selected from a bond, S, O, SO, SO₂, CO, CH₂,and C(CH₃)₂.

6. The polyester of any one of claims 1 -4 wherein the aromatic diol is biphenol and the aromatic monocarboxylic acid is vanillic acid.

7. A shaped product comprising the polyester of any one of claims 1 -6.

8. The shaped product of claim 7, which is a fiber, fibrid, tape, non-woven, fabric, or film.