Note: Descriptions are shown in the official language in which they were submitted.
2~81079
Preparation of polyols containing isocyanurate groups
The invention relates to a process f or preparing polyols contain-
ing isocyanurate groups by reacting polyi~ yeu-uL.ltes (PIR) with
short-chain, hydroxyl-containing , '- in the presence of
carrier polyols. The invention further relates to the use o~ the
polyols thus obtained for producing polyurethanes (PUR) and PIR.
10 PIR are produced as cellular or cell-free plastics by the poly-
addition process, in which c~talysts which allow isocyanate
groups to trimerize into isocyanurate groups are added to a mix-
ture of isocyanates, in particular one based on polymethylene
diisocyanate, and polyols, in which mixture the isocyanates are ==
present in a large excess. Catalyst9 of this type are specifi-
cally phosphines, phospholin derivatives, amines, alkali metal
salts, metal compounds and Mannich bases. The process i8 de-
scribed in detail in Becker/Braun, Kunststoffhandbuch, Volume 7,
Polyurethane, Carl-Hanser-Verlag, 3rd Edition, Munich, Vienna
20 1993. The ob~ect of the PIR ~ormation is the development of
particular properties such as, for example, high hardness, flame
resistance and an increase in the thermal stability. For this
purpo6e, isocyanates are incorporated into the system comprising
polyol component and isocyanate in an amount ~oLL__p~JIlding to an
i~ocyanate index of at least 1,0, but usually from 200 to 800.
This excess of isocyanate groups reacts virtually quantitatively
and irreversibly to form isocyanurate.
In the patent and specialist literature, processes for the chemi-
30 cal recycling of PIR are mentioned rather rarely in comparison
with PUR and PUR/polyureas. In most cases, PIR is mentioned in
addition to PUR, but no concrete examples are given. An example
of this is DE-A-29 02 509 in which catalysts based on titanium
and ~irconium are claimed for the glycolysis of PUR and PIR, but
only PUR is used in the examples.
H. Ulrich et al. in Polymer Engineering and Science lB (1978) 11,
pp. 844 to B4B and in SPE Tech. Papers 35, Conf., Montreal, Vol-
ume 23, 1977, pp. 41 to 43, describQ a process for the glycolysis
of PIR ~o~ms which was patented in 1973 by US-A-3 70B 440. If the
40 procedure of this process is repeated, the result is not the ex-
pected homogeneous glycolysate which can be used for new PUR and/
or PIR syntheses. It instead gives black, coke-like lumps which
make further processing impossible.
218107~
Ei. Ulrich discusses a reaction -hsln; ~`m according to which the
glycolysis glycol cleaves the isocyanurate ring to form short-
chain urethane and aromatic amine.
The glycolysis processes frequently described in the literature
are also unsuccessful in the case of PIR. In each case, the PIR
are not converted into a liguid, but c'~ ~ to form coke-like
lumps. Examples of such glycolysi~ processes which can be used
for PUR but not for PIR are described in the patents
US-A-4 110 266,
EP-A-0 601 596,
EP-Ei-0 542 806,
DB-A-43 24 156,
DE--A-42 15 014,
DE-A-41 40 967 and
DE--A--41 28 588.
This list is far from complete.
The glycolysis described in DE-A-42 34 335 also does not lead to
the objective in the case of PIR~ Although it gives liquid prod-
ucts, these contain a high level of black, crumbly impurities.
It is an object of the present invention to develop a simple and
economical process for the glycolysis of PIR which leads to a re-
cycled poly~1 whose amine content is below the characteristic
value of 0.1 ~ by weight and which can immediately be used as
such for producing PUR and PIR.
We have found that this object i8 achieved by the preparation of
polyols containing isocyanurate groups being carried out by
reacting PIR with short-chain, hydroxyl-containing compounds in
the presence of carrier polyols having an OH number of at most
500 mg KOH/g and a molecular mass of at least 450 g/mol.
The invention accordingly provides a process for preparing poly-
ols containing isocyanurate groups by reacting PIR with short-
chain, hydroxyl-containing, ~ r wherein the reaction of the
40 PIR is carried out in the presence of carrier polyols having an
OH number of at most 500 mg XOH/g and a molecular mass of at
least 450 g/mol.
The invention further provides the po1yols containing isocyanu-
rate groups which are prepared by this process, and also provides
~or their use for producing PUR and PIR.
218107~
To carry out the process of the inver~tion, the PIR, usually in
comminuted form, 18 reacted with a mixture of short-chain, hy-
droxyl-containing ~- ' used znd carrier polyol.
According to a particularly advantageous embodiment, the process
of the invention is carried out in such a way that the mixture of
short-chain, hydroxyl-containing c. '- used and carrier poly-
ol is heated to from 190 to 240 C, preferably from 210 to 230 C,
before addition of the PIR and the temperature is lowered by from
10 10 to 40 C after addition of the PIR. At thiD temperature, the
reaction iB carried out over a period of from 1.5 to 3 hour6,
preferably from 2 to 2.5 hours, with continual stirriDg. After
the reaction is complete, the reaction mixture is cooled to from
50 to 150 C, preferably from 80 to 130 C, and a hydroxide of an
alkali metal or an alkaline earth metal is added to the reaction
mixture in an amount of at most 5 ~ by weiqht, based on the total
mixture. The mixture i8 stirred for from 0.5 to 1.5 hours at this
t. , clLUL~:.
20 Preference is given to using sodium hydroxide or potassium hy-
droxide f or this purpose .
According to a further advantagéous embodiment, the reaction mix-
ture is, after the reaction is complete, cooled to from 100 to
160 C, a glycidyl ether is added to the reaction mixture in an
amount of at most 10 ~ by weight, based on the total mixture, and
the mixture is st~rred for ~rom 0.5 to 1.5 hours at this tempera-
ture .
30 The glycidyl ether used is preferably a monofunctional glycidyl
ether, particularly preferably 2-ethylhexyl glycidyl ether.
If desired, this can be followed by a work-up of the recycled
polyol, for example by filtration.
The ratio of the short-chain, hydroxyl-containing compounds used
to the carrier polyol is generally ~5-20) :1, the ratio of the
mixture of short-chain, hydroxyl-containing compounds used and
carrier polyol to the PIR is ( 1-5 ) :1.
The reaction of PIR with 3hort--chain, hydroxyl-containing com-
pounds is, according to the invention, carried out usin~ carrier
polyols having an O~ number of at most 500 mg ~COE~g and a molecu-
lar mass of at least 450 g/mol. Suitable carrier polyols are, for
example, polyols prepared by polyaddition of propylene oxide to
2181079
trihydric alcohols. Preference is given to using polyols based on
glycerol and/or trimethylolpropane.
The short-chain, hydroxyl-containing compounds can in principle
be any dihydric or higher-functional alcohols.
Dihydric alcohol3 are particularly advantageous ~or the process
of the invention. The alcohols can be u3ed individually or a6 a
mixture .
Preference is given to using ethylene glycol and lta higher homo-
logs, in particular diethylene glycol, snd propylene glycol and
it3 higher homologs, in particular dipropylene glycol, individu-
ally or in admixture with one another.
The process can be carried out in the presence of customary poly-
urethane catalysts. Preference i8 given to u3ing organic tin and
titanium compounds for this purpose.
20 The PIR used can be scrap, for example from the production of PIR
block foams, PIR moldings or sandwich elements.
It was surprising that the glycolysis to give liquid products
leads to no significant content of solid products if it is
carried out according to the invention using a carrier polyol.
It was also surprising that the glycolysis polyols prepared by
this process have an aromatic amine content of below 0.1 ~, which
dispenses with the need for complicated deamination. It would
30 have been expected that amines would have been formed to a
greater extent by hydrolysis and urea cleavage during the glyco-
lysi3 .
It was also surprising that the IR spectra 3how the i30cyanurate
structure3 virtually unchanged in the glycolysate, thus refuting
the abovementioned theory of H . Ulrich ( attack on and breaking up
of the isocyanurate rings ) .
The glycolysis polyols prepared by this process can, without fur-
40 ther treatment, be again ~L~:es6ed to give PU~ or PIR.
For this purpose, they are reacted alone, but preferably in ad-
mixture with other hydroxyl-containing '~, with polyiso-
cyanates in the presence of customary blowing agents, catalyst3,
auxiliaries and additives.
.
, ~. 2181079
Since the glycolysis polyols of the invention have very low vis-
cosities, they can also be advantageously used for CFC-free rigid
foam systems.
The invention is illustrated by the following examples.
Example 1 (comparison)
120 g of diethylene glycol were admixed with 0.15 9~ by weight,
10 based on the total mixture, of titanium tetrabutoxide and heated
to 220 C. 50 g of PI}~ foam (NCO index 350) were then added at such
a rate that the mass remained stirrable. The mixture was stirred
for 3 hours. The product contained black pieces which still
showed the foam ~lu.1 u~.
The product was unusable.
Example 2 ( comparison )
20 ~he ~ e.lU~ was as in Example 1, but 20 e by weight, based on
the total mixture, of 2-ethylhexyl glycidyl ether were added
dropwise over the reaction time~ similar to the method described
in DE-A 42 34 335. Here too the product was; nhl j~ne.u~ and un-
usable .
Example 3
55 g of a PIR foam (NCO index 350 ) were introduced at from 215 to
225 C into a mixture of 100 g of diethylene glycol, 15.5 g of a
30 polyol based on glycerol and propylene oxide (PO) (1 mol of glyc-
erol: 8.5 mol of PO, Lupranol 3300 from BASF Aktiengesellschaft)
and 0.15 ~ by weight, based on the total mixture, of titanium
tetrabutoxide in such a way that the contents of the flask re-
mained stirrable. After the addition was complete, the tempera-
ture was lowered to from 190 to 200 C and the mixture was left
stirring for 2 hours. The temperature was then lowered further to
100 C, 2 g of solid NaO~ were added and the mixture was stirred
for a further hour. This gave a homogeneous black-brown liquid
having the following properties:
OE~ number : 638 mg ROH/g
Acid number : O . 22 mg ROE~/g
Viscosity at 25 C : 3520 mPa- s
MDA content : O . 089 ~ by weigh
2~81079
Example 4
The procedure was as in Example 3, but the NaOE~ treatment was not
carried out. The glycolysate had the following properties:
OH number : 625 mg }COH/g
Acid number : 11. 4 mg ICOH/g
Visco~ity at 25-C : 3844 mPa-s
MDA content : 0 . 071 % by weight
lo
Examplo S
The ~ e~uL~ wa~ as in Example 3, but a PIR foam having an NCO
index of 600 was used. The glycolysate had the following proper-
ties:
OH number : 734 mg ~OH/g
Acid number : 0 . 05 mg KO~/g
Viscosity at 25 C : 3174 mPa s
20 MDA content : 0 . 030 ~ by weight
Example 6
80 g of a PIR foam based on a polyethylene terephthalate polyol
(NCO index 450) and containing ~bout 20 ~ by weight of glass
fibres were added at from 215 to 225 C to a mixture of 100 g of
diethylene diglycol and 32 g of Lupranol 3300 and 0.1 % by
weight, based on the total mixture, of tin(II) octoate in such a
way that the contents of the flask remained stirrable. The tem-
30 perature was then lowered to from 190 to 200 C and maintained for2 hours while stirring. The mixture was then cooled further to
150 C and 9 g of 2-ethylhexyl glycidyl ether were added and the
mixture was stirred for a further hour at this temperature. This
gave a homogeneous dark brown liquid having the following proper-
ties:
OH number : 610 mg KOH/g
Acid number : 0 . 6 mg ~OH/g
Vi6cosity at 25-C : 3180 mPa-s
40 MDA content : 0 . 042 % by weight
