Note: Descriptions are shown in the official language in which they were submitted.
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DESCRIPTION
POLYETHYLENE NAPHTHALATE POLYESTER POLYOL AND RIGID POLYURETHANE FOAMS
OBTAINED THEREFROM
This invention relates to the preparation of poly(alkylene polyaromatic
dicarboxylate) ester based polyester
polyols and the use thereof in the preparation of rigid polyurethane and
polyisocyanurate foams.
The invention more specifically relates to polyester polyols produced from
reacting polyethylene naphthalate.
l0 The preparation of a rigid polyurethane (PUR) and polyisocyanurate (PIR)
foam by the reaction of a
polyisocyanate, a polyol and a blowing agent in the presence of a catalyst is
well known. A wide variety of
polyols have been used as one of the components in the preparation of rigid
polyurethane foams, including
polyols from different waste streams.
The polyols are usually polyether alcohols or polyester alcohols, or a mixture
of the two. Both aliphatic and
f 5 aromatic polyester polyalcohols are in use. They are the reaction products
of an esterification of a
dicarboxylic acid or an anhydride with glycols (primary/secondary). More often
a transesterification process
is used. Aromatic polyester polyols used in rigid PUR/PIR foams are typically
based on production waste
streams of dimethyl terephtalate (DMT;>. Polyethylene terephtalate (PET) scrap
is also a source of aromatic
carboxylates. Depolymerization of production waste streams or post consumer
waste from e.g. PET bottles is
20 a known method in the preparation of a polyester polyol.
Presently available polyols made from scrap PET or DMT process residue suffer
from a variety of
disadvantages such as the lack of compatibility with blowing agents commonly
used in the manufacture of
rigid PUR/PIR foams. Foams prepared from these polyols are sometimes deficient
in compressive strength
and/or thermal insulation capacity and/or flame resistance.
:! 5
It has now been found that poly(ethyiene naphthalate) (PEN) can easily be
depolymerized and that a
polyester polyol with high aromatic content can be made based on this
depolymerization product. Rigid
polyurethane or polyisocyanurate foams made using this polyester polyol show
excellent mechanical
stability, good fire performance and low smoke generation together with a low
thermal conductivity.
?~0
The poly(alkylene polyaromatic dicarboxylate) ester preferably used in the
present invention is polyethylene
2,6-naphthalate). Other isomers of this polymer, or copolymers with e.g.
poly(ethylene terephtalate) (PET),
poly(butylene terephthalate) (PBT) or poly(butylene naphthalate) can also be
employed, as well as the
polyesters based on dicarboxylates with a multi ring structure (e.g.
anthracene, phenantrene) and their
? 5 copolymers.
The polyester polyol is prepared by a two step process.
In a first step. the polyester is depolymerised in the presence of a glycol.
This can be, for example, 1,4-
butanediol, diethyleneglycol (DEG) or dipropyleneglycol (DPG). Most suitable
as the diol is DEG and it is
40 preferably used in an amount in excess of that required for digestion.
Although the reaction takes place in the
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absence of catalysts, the reaction times are significantly shortened by use of
the appropriate catalysts. The
preferred catalyst is tetra-N-butyltitanatc; (TBT). Zinc oxide or mangane
acetate can also be employed.
The depolymerization is carried out at such temperature that the polyester
dissociates and the core units are
obtained. This is typically in the temperature range of 150 to 350°C,
preferably about 240°C. The process is
typically carried out at atmospheric pressure. However, it will be obvious
that pressures higher than
atmospheric can be used. At higher prcasures the reaction temperature can be
increased significantly, thus
shortening the reaction time. The obtained reaction mixture contains the
esterification product from the
polyaromatic dicarboxylate and the used glycol, together with the diol of the
alkylene chain between the
aromatic rings. Very often, excess glycols are present. When starting with
PEN, the product from this first
l0 step contains naphthalate polyols, unreacted glycols and ethylene glycol
from the PEN. During the
depolymerisation and esterification, removal of the formed ethylene glycol by
vacuum distillation is possible.
This normally results in a lower OH value of the final polyester polyol,
together with a reduction of fhe
aliphatic content, which is reflected in the fire performance of the obtained
foam. In the present invention the
ethylene glycol was not removed, with no detrimental effects on the final
rigid foam properties.
In a second step, the mixture is further transesterified by addition of other
polycarboxylic acids, anhydrides
or esters and a polyhydric alcohol. This further esterification brings the
final polyester polyol in the desired
viscosity range. The total content of polyester polymer used in the synthesis
of the polyester polyol is
typically in the range 5 to 50 wt%, prE;ferably 10 to 40 wt%. The
polycarboxylic acid and the polyhydric
2.0 alcohol are added at a temperature in the range of 80 to 240°C,
preferably 100 to 180°C.
Suitable examples of the polycarboxylic; acid component or its derivatives are
adipic acid, glutaric acid and
anhydride, succinic acid, oxalic acid, malonic acid, suberic acid, azelaic
acid, sebacic acid, phtalic acid,
phtalic anhydride, pyromellitic anhydride. As polyfunetional alcohol, glycols
are preferred. They can be a
simple glycol of general formula CnH2n(OH)2 or polyglycols with intervening
ether linkages, as represented
in the general formula CnH2nOx(OH)2. They also may contain heteroatoms.
The polycarboxylic component and polyhydric alcohol may include substituents
which are inert in the
reaction, e.g. chlorine and bromine substituents, and/or may be unsaturated.
Examples of suitable polyhydric
alcohols are alkylene glycols and oxyalkylene glycols, such as ethylene
glycol, diethylene glycol and higher
polyethylene glycols, propylene glycol, dipropyleneglycol and higher propylene
glycols, glycerol,
pentaerythritol, trimethylolpropane, sorb~itol and mannitol.
The two steps described above can also be carried out in a single step
process. The depolymerisation of the
polyester polymer is more complete and faster when using a two step process.
The final polyo) mixture for use in the present invention has an average
functionality of 1.5 to 8, preferably 2
to 3. The hydroxyl number is generally between 200 and 550 mg KOH/g polyol.
The molecular weight ofthe
polyesters is generally in the range 200 to 3000, preferably 200 to 1000, most
preferably 200 to 800.
The term polyester polyol as used herein includes. any minor amounts of
unreacted polyol remaining after the
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preparation of the polyester polyol and/or unesterified polyol.
The polyester polyol according to the present invention is used to make
polyurethane-based rigid foam. In the
processing of polyurethane and polyisocyanurate foams, the polyisocyanates and
the mixture of isocyanate-
reactive components are generally mixed in a one-shot method. Both high and
low-pressure techniques can
be employed in the mixing step. The ratio of the NCO/OH groups generally falls
within the range 0.85 to
1.40, preferably 0.95 to 1.2 for polyurethane foam, and within the range 50 to
1, preferably 8 to 1 for
polyisocyanurate foam.
Besides the PEN based polyester polyol of the present invention other
isocyanate-reactive compounds can be
used in the process for making rigid polyurethane or urethane-modified
polyisocyanurate foams. Suitable
isocyanate-reactive compounds include any of that known in the art for the
production of rigid polyurethane
foam, especially polyether polyols and other types of polyester polyols.
In general the PEN based polyester polyol of the present invention constitutes
between 60 and 100 % by
weight of total isocyanate-reactive compounds.
IS
The isocyanate-reactive mixture generally contains the polyhydric alcohols and
other optional additives such
as blowing agents, fire retardants, fillers, stabilizers, catalysts and
surfactants. Preferred catalysts for the
polyurethane formation are amines, most preferably tertiary amines. Dibutyl
tin dilaurate is an example of a
non-amine based polyurethane catalyst. Preferred polyisocyanurate catalysts
are alkali metal carboxylates
and quaternary ammonium carboxylat:es.
Any of the blowing agents known in the art for the preparation of rigid
polyurethane or urethane-modified
polyisocyanurate foams can be used in the process of the present invention.
Both physical and chemical
blowing agents can be used, singly or in mixtures.
Z~ Suitable physical blowing agents are. for example, hydrocarbons, dialkyl
ethers, alkyl alkanoates, aliphatic
and cycloaliphatic hydrofluorocarbons, hydrochlorofluorocarbons,
chlorofluorocarbons, hydrochlorocarbons,
fluorine-containing ethers and carbon dioxide. Examples of preferred blowing
agents are isomers of pentane
such as cyclopentane, n-pentane and isopentane, and mixtures thereof, 1,1-
dichloro-2-fluoroethane (HCFC
141b), I,1,1-trifluoro-2-fluoroethane (HFC 134a), chlorodifluoromethane (HCFC
22), I,1-difluoro-3,3,3-
trifluoropropane (HFC 245fa).
Carbon dioxide releasing products can be used as chemical blowing agent.
Water, which releases carbon
dioxide upon reaction with isocyanate, .is widely known as a chemical blowing
agent.
The total quantity of blowing agent is typically from 0.1 to 25% by weight
based on the total reaction system.
Both aliphatic and aromatic poiyisocyanates can be used. Preferred are the
aromatic polyisocyanates such as
diphenylmethane diisocyanate (MDI) and toluene diisocyanate (TDI) or
prepolymers thereof. Mixtures of
isomers and oligomers can be employed. Most preferred is the polymeric form of
MDI.
The polyisocyanate can be uretonimine or carbodiimide modified.
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The invention is illustrated by, but not limited to. the following examples.
Example 1-3: Synthesis of the polyester.
s In a two-liter flask equipped with an efficient agitator, thermocouple and
distillation set-up, diethylene glycol
and polyethylene 2,6-naphthalate was charged. 10 ppm of TBT was added. The
content was heated to 240°C
under efficient stirring and a nitrogen atmosphere. After 2 to 3 hours, the
temperature was towered to 160°C
and adipic acid and glycerol were charged (quantities see table 1 ), together
with 10 ppm TBT . The mixture
was heated slowly to 180°C and water was removed by distillation. To
complete the esterification, the
I 0 temperature was further increased to 200°C until the theoretical
stoichiometric amount of water was removed
by distillation under vacuum. When the distillation rate flattened out, an
acid value titration was performed.
Acid values of 2 mg KOHlgram are acceptable.
The specifications of the obtained polyesters are shown in Table I .
15 Table 1
Example 1: Example 2: Example 3:
polyol A polyol B polyol C
PEN (gram) 311.00 420.00 532.00
DEG (gram) 583.00 538.00 492.00
glycerol (gram) 133.00 134.00 136.00
adipic acid (gram)473.00 407.00 340.00
OH value 351.00 357.00 363.00
(mg KOH/gram)
Viscosity (cPs 2100.00 4100.00 12900.00
at 25C)
Free glycois
MEG (%) 1.10 1.60 1.90
DEG (%) 8.30 7.30 6.30
glycerol (%) 3.30 6.60 3.50
Example 4-7
Rigid urethane-modified polyisocyanurate foams were prepared from the
polyesters made according to
examples 1 to 3 above. The formulation components (400 gram) were mixed at
5000 rpm with a small-scale
iab mixing unit and poured into a 20x20x30 cm open mould. HCFC 141b was used
as blowing agent. After
standing at room temperature for at least 24 hours, physical properties of the
foams were tested. Ingredients
?~ amounts in parts by weight) and foam physical properties obtained with
polyols A. B and C and a
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comparative example based on a PET polyol are listed in Table 2.
PET polyol: polyester polyol based on scrap PET, OH value 350 mg KOH/gram.
Tegostab B 8406: silicone based surfactant available from Goldschmidt.
5 TEP: triethylphosphate fire retardant.
DMEA: dimethylethanolamine catalyst.
Niax A I : bis(dimethylamino ethylether) catalyst.
Dabco KIS: potassium octoate cataly;~t.
SUPRASEC 2085: polymeric MDl available from Huntsman Polyurethanes (SUPRASEC
is a trademark of
Huntsman ICI Chemicals LLC}.
CT: cream time, which is the time from mixing to the change of appearance of
the mixed chemicals, which
indicates the onset of the expansion.
ST: string time, which is the time from mixing to the instant at which it is
possible to pull a string of polymer
from the reacting mixture using a spatula.
ER: end-of rise time, which is the time from mixing to the end of expansion of
the foam.
TF: tack-free time which is the time; from mixing to when the surface of the
foam no longer sticks to a
spatula when light pressure is applied.
Density was measured according to standard DIN 53420.
Thermal conductivity was measured according to standard ISO 2581.
Compression strength was measured according to standard DIN 53421.
Kieinbrenner values were determined according to standard D1N 4102.
Limited 02 index was determined according to standard ASTM 2863.
NBS Smoke values were determined according to standard ASTM E 662.
Example 8-11
Rigid wethane-modified polyisocyatturate foams were prepared from the
polyesters made according to
examples 1 to 3 above. The formulation components (400 gram) were mixed at
5000 rpm and poured into a
20x20x30 cm open mould. lsopentane was used as blowing agent. After standing
at room temperature for at
least 24 hours, the physical properties of the obtained foams were tested.
Ingredients (amounts in parts by
weight) and foam physical properties obtained using polyols A, B and C and a
comparative PET based polyol
are listed in Table 3.
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Table 2
Example Exam le Exam Exam
4 S le 6 le 7
PET of of 100.00
of of A 100.00
of of B 100.00
of of C 100.00
Teeostab B 8406 2.00 2.00 2.00 2.00
TEP I 5.00 15.00 15.00 15.00
DMEA 2.40 2.50 2.50 2.50
Niax A 1 U.13 0.13 0.13 0.13
Dabco K 15 1.80 I .90 1.90 1.90
water 2.30 2.30 2.30 2.30
HCFC 141 b 21.00 25.00 25.00 25.00
SUPRASEC 2085 312.00 312.00 312.00 312.00
Index (%) 250.00 25(1.00 250.00 250.00
Reaction rofile
CT (sec) 14.00 14.00 14.00 14.00
ST (sec) 35.00 40.00 40.00 40.00
ER (sec) 50.00 75.00 75.00 75.00
TF (sec) 60.00 75.00 75.00 75.00
Densi k m3) 35,00 33.00 33.00 34.00
Thermal conductivi
(mW/m K
initiall 22.70 22.10 21.40 21.20
1 week 28.70 27.80 27.10 26.70
3 weeks 29.80 29.40 28.40 28.50
weeks 29:70 29:80 29.30 28.70
Com ression stren
th (kPa)
arallel to rise 312.00 270.00 270.00 299.00
a endicular to rise 97.00 87.60 82.70 94.30
Isotro is 33 k m3 130..00 127.00 122.00 131.00
Kleinbrenner
_
Ext. time (s) 15.00 15.00 15.00 15.00
Flame Hei ht (cm) 9.00 8.00 7.00 7.00
Limited 02 index (%) 28.0 28.1 28.1 28.1
NBS Smoke
mass loss (%) ___ 49.00 44.00 44.00 43.00
~
optical densitV~ 126.00 106.00 93.00 119.00
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Table 3
Exam le Exam Exam le Exam le
8 le 9 10 11
PET 7 of 10_0.00
~
of of A 100.00
_ _
of of B 100.00
of of C _ 100.00
Te ostab B 8406 2.00 2.00 2.00 2.00
TEP 15.00 15.00 15.00 15.00
__
DMEA 2.40 2.40 2.40 2.40
Niax A1 0.13 0.13 0.13 0.13
Dabco K 15 1.80 _ 1.80 1.80 1.80
water 2.30 2.30 2.30 2.30
i- entane 15.00 15.00 15.00 15.00
SUPRASEC 2085 312.00 312.00 312.00 312.00
lndex (% 250.00 250.00 250.00 250.00
Reaction rofile _
CT (sec) 10.00 11.00 10.00 10.00
~
ST (sec) 42.00 40.00 42.00 40.00
Densi (k m3) 32.00 31.00 32.50 33.00
Thermal conductivity
(mWlm K
initiall 24.00 23.60 24.30 23.60
1 week 27.10 26.50 27.50 26.50
3 weeks 29.00 28.60 28.40 28.40
_
weeks 28.30 27.70 28.60 28.30
Com ression Stren
h (kPa
arallel to rise 241.00 270.00 269.00 309.00
a endicular to 74.50_ 79.90 91.40 96.10
rise
Isotro is 33 k 116.70 132.00 134.00 142.00
m3
Limited 02 index 25.6 26.2 26.2 26.2
(%)
Kleinbrenner
Ext. time (sec) 15.00 15.00 15.00 15.00
Flame Hei ht (cm 11.00 11.00 12.00 11.00
NBS Smoke
_
mass loss (% 49.00 44.00 44.00 43.00
o tical densi __ 63.00 57.00 71.00
71.00
