HK1168367B - Polyester polyols from terephthalic acid and oligoalkyl oxides - Google Patents

Description

Polyester polyols derived from terephthalic acid and oligoalkylene oxides

The invention relates to polyester polyols derived from terephthalic acid and oligoalkylene oxides, to a method for the production thereof and to the use thereof for producing rigid PUR/PIR foams.

Nowadays, rigid PUR/PIR foams are predominantly produced on the basis of polyester polyols, since these polyester polyols have a positive influence on the flame retardancy of rigid PUR/PIR foams and on their thermal conductivity. The raw materials mainly used for the preparation of polyester polyols are succinic acid, glutaric acid, adipic acid, phthalic acid/phthalic anhydride, terephthalic acid and isophthalic acid. In addition to polyester polyols, polyether polyols are sometimes added to increase the pentane solubility or to reduce the brittleness of isocyanurate-containing PUR/PIR rigid foams relative to polyester polyols.

In this respect, US 4,039,487 describes polyester polyols obtainable from polyethylene glycol and aromatic polycarboxylic acids having an equivalent weight of 75 to 225 g/mol. The use of a part of the aliphatic polycarboxylic acid together is not considered.

EP-A1834974 is similarly restricted to aromatic polycarboxylic acids, and furthermore US 5,003,027 is restricted to processing polyester polyols in the RIM process.

Although WO-A99/54380 also discloses the use of aliphatic dicarboxylic acids for the preparation of polyester polyols, polyethylene terephthalate (PET) is always used as a source of aromatic dicarboxylic acids. However, a general disadvantage of this process based on recycled materials is that it is potentially contaminated with foreign materials, which in some cases must be removed at great expense.

US 4,469,824 is also based on recycled PET, adipic acid being proposed as one of the further reaction components.

However, the use of aromatic acids in the preparation of polyester polyols, in particular terephthalic acid, leads to polyester polyols which are solid at room temperature and thus to technical processing difficulties.

However, no specific processing guidelines are disclosed in the prior art by which polyester polyols can be prepared that meet all of the important processing parameters in the PUR/PIR rigid foam art.

In addition, many conventional PUR/PIR rigid foams based on polyester polyols do not exhibit sufficient flame retardancy, since they generally only comply with the flame class (Brandshuttzklas) B3 as defined in DIN 4102-1.

It was therefore an object of the present invention to provide polyester polyols which, when used in PUR/PIR rigid foams, lead to improved flame retardancy, in particular to PUR/PIR rigid foams which comply with the flame class B2 and/or the SBI test according to DIN 4102-1 (DIN EN 13823).

It is a further object of the present invention to provide polyester polyols which are easy to process technically in the preparation of PUR/PIR rigid foams and at the same time improve the flame retardancy of PUR/PIR rigid foams.

The object according to the invention is achieved by providing a polyester polyol, which is prepared from a mixture comprising:

(A) optionally with C₁-C₄Terephthalic acid in one of the alkyl ester forms,

(B) oligo (ethylene glycol) of the formula H- (OCH₂CH₂)_n-OH wherein the number average number n of oxyethylene groups is from 3.0 to 9.0, and

(C) at least one aliphatic dicarboxylic acid selected from succinic acid, glutaric acid, adipic acid, sebacic acid, suberic acid, azelaic acid, decanedicarboxylic acid, tetradecanedioic acidAnd omega-hydroxycaproic acid, and,

characterized in that the prepared polyester polyol has an ether group concentration of 9.0mol/kg polyester polyol to 16mol/kg polyester polyol.

Terephthalic acid C₁-C₄The alkyl ester is preferably an ester selected from the group consisting of dimethyl terephthalate, diethyl terephthalate, di-n-butyl terephthalate and diisobutyl terephthalate.

Within the scope of the present invention, the general formula H- (OCH)₂CH₂)_nThe compounds of-OH have:

n = 1, having one oxyethylene group and no ether group;

n = 2, having two oxyethylene groups and one ether group;

n = 3, having three oxyethylene groups and two ether groups;

n = 4, having four oxyethylene groups and three ether groups;

n = 5, having five oxyethylene groups and four ether groups;

n = 6, having six oxyethylene groups and five ether groups;

n = 7, having seven oxyethylene groups and six ether groups;

n = 8, having eight oxyethylene groups and seven ether groups; and

n = 9, having nine oxyethylene groups and eight ether groups.

Component (B) is preferably a mixture of various oligoethylene glycols, where the value of n denotes the average number of oxyethylene groups in component (B). Component (B) particularly preferably comprises less than 8% by weight of oligomers with n = 2, very particularly preferably less than 3% by weight. The value of n given can therefore be a non-integer, for example 3.1, 3.2 or 3.24.

The oligoethylene glycol (B) preferably has a number average molecular weight of 145-450 g/mol, particularly preferably of 150-250 g/mol.

The polyester polyols prepared preferably have an ether group content of from 9.1 mol/kg of polyester polyol to 13 mol/kg of polyester polyol.

The mixture comprises at least one aliphatic dicarboxylic acid (C) selected from succinic acid, glutaric acid, adipic acid, sebacic acid, suberic acid, azelaic acid, decanedicarboxylic acid, tetradecanedioic acid and omega-hydroxycaproic acid. The mixture particularly preferably comprises at least one aliphatic dicarboxylic acid (C) selected from succinic acid, glutaric acid and adipic acid.

Component (A) is preferably present in an amount of from 10 to 40% by weight, particularly preferably in an amount of from 15 to 35% by weight, relative to the total amount of the mixture for preparing the polyester polyol according to the invention.

Component (B) is preferably present in an amount of from 60 to 90% by weight, particularly preferably from 55 to 85% by weight, relative to the total amount of the mixture for preparing the polyester polyol according to the invention.

Component (C) is preferably present in an amount of from 0 to 20% by weight, particularly preferably from 2 to 20% by weight, very particularly preferably from 3 to 15% by weight, very particularly preferably from 5 to 14% by weight, relative to the total amount of the mixture for preparing the polyester polyol according to the invention.

It has surprisingly been found that the use of component (C) together, which is otherwise identical in formulation and does not alter the hydroxyl number of the polyester polyol, advantageously reduces the viscosity of the polyester polyol.

The polyester polyols preferably have a hydroxyl number of from 100mg KOH/g to 400mg KOH/g, particularly preferably from 110 mg KOH/g to 220 mg KOH/g, very particularly preferably from 150 mg KOH/g to 200 mg KOH/g.

The OH number is determined by: the terminal hydroxyl groups in the polyester polyol sample are first reacted with a defined excess of anhydride, for example acetic anhydride, which is hydrolyzed and the free carboxyl content is determined by direct titration with a strong base, for example sodium hydroxide. The difference between the carboxyl groups introduced in the form of anhydrides and the carboxyl groups determined experimentally is a measure of the number of hydroxyl groups in the sample. If this value is corrected with the number of carboxyl groups contained in the original sample due to incomplete esterification, i.e.the acid number, the OH value is obtained. The titration with sodium hydroxide is mainly carried out in terms of equivalent potassium hydroxide, so that the acid value and the hydroxyl value have dimensions of g KOH/kg. Here, there is a calculation relationship between the hydroxyl value (OH #) and the number average molecular weight (M) in which M = (56100. multidot.F)/OH #. Where F denotes the number average functionality and can be deduced well approximated from the formulation. Methods for determining the OH number are described, for example, in Houben Weyl, methods of organic chemistry (Methoden der Organischen Chemie), volume XIV/2 Makromolekulare Stoffe, page 17, Georg Thieme Verlag, Stuttgart 1963.

The molar mass of the polyester polyols according to the invention is preferably 280-1120 Da, particularly preferably 510-1020 Da, very particularly preferably 560-750 Da.

The acid number of the polyester polyols according to the invention is preferably from 0.1 KOH/g to 4 mg KOH/g, particularly preferably from 0.2 KOH/g to 2.8 KOH/g.

Methods for determining the acid number are described, for example, in Houben Weyl, method of organic chemistry (Methoden der Organischen Chemie), volume XIV/2 Makromolekulare Stoffe, from page 17, Georg Thieme Verlag, Stuttgart 1963.

The polyester polyols according to the invention preferably have a viscosity of 800mPas to 4500mPas, particularly preferably 1000 mPas to 3000 mPas, at 25 ℃ determined according to DIN 53019.

The oligoethylene glycol (B) preferably has a number average vinyl oxide number n of from 3.1 to 9, particularly preferably from 3.5 to 8.

The polyester polyols preferably have a melting point of from-40 ℃ to 25 ℃ and particularly preferably from-20 ℃ to 23 ℃.

The polyester polyols according to the invention are preferably prepared from a mixture comprising terephthalic acid (A) and a compound of the formula H- (OCH₂CH₂)_n-an oligoethylene glycol (B) having OH and an average number n of ethylene oxide groups ranging from 3.0 to 9.0, and at least one aliphatic dicarboxylic acid (C) selected from succinic acid, glutaric acid and adipic acid.

The present invention also provides a process for preparing the polyester polyols according to the invention, wherein components (A) and (B) are reacted for 7 to 100 hours, preferably in the presence of a catalyst selected from tin (II) salts and titanium tetraalkoxides, at temperatures of from 160 ℃ to 240 ℃ and pressures of from 1 to 1013 mbar.

All catalysts known to the person skilled in the art can be used for preparing the polyester polyols according to the invention. Tin (II) chloride and titanium tetraalkoxide are preferably used. Tin dichloride dihydrate is particularly preferably used in a proportion of from 20 to 200 ppm, very particularly preferably from 45 to 80 ppm, relative to all components used.

The components are preferably reacted in bulk to prepare the polyester polyols according to the invention.

The invention also provides a process for preparing a PUR or PUR/PIR foam, comprising the steps of:

a) at least one polyester polyol according to the invention is reacted with

b) At least one polyisocyanate-containing component,

c) at least one kind of foaming agent,

d) at least one or more catalysts selected from the group consisting of,

e) optionally at least one flame retardant and/or further auxiliary substances and additives,

optionally at least one compound having at least two groups reactive with isocyanates.

Conventional aliphatic, cycloaliphatic and in particular aromatic diisocyanates and/or polyisocyanates are suitable as polyisocyanate-containing components. Toluene Diisocyanate (TDI), diphenylmethane diisocyanate (MDI) and especially mixtures of diphenylmethane diisocyanate and polyphenylene polymethylene polyisocyanate (polymeric MDI) are preferably used. Isocyanates can also be modified, for example, by introducing uretdione, urethane, isocyanurate, carbodiimide, allophanate and in particular urethane groups. Polymeric MDI is particularly useful for making rigid polyurethane foams. In the prior art, isocyanurate formation takes place almost exclusively during the foaming reaction and gives flame-retardant PUR/PIR foams which are preferably used in industrial rigid foams, for example in the building industry as insulation panels, sandwich elements and truck bodies.

As compounds having at least two groups which react with isocyanates, i.e.compounds having at least two hydrogen atoms which react with isocyanate groups, it is generally possible to use the compounds described generally below.

Suitable compounds having at least two groups which react with isocyanates are compounds which bear two or more groups selected from OH, SH, NH in the molecule₂Radicals and CH-acidic groups, for example reactive groups of beta-diketones. Compounds having 2 to 8 OH groups are used in particular for the preparation of the compositions according to the inventionThe process of the invention preferably produces rigid polyurethane foams. Preference is given to using polyether polyols and/or polyester polyols. In the production of polyurethane rigid foams, the polyether polyols and/or polyester polyols used preferably have a hydroxyl number of from 25 to 850 mg KOH/g, particularly preferably from 25 to 450 mg KOH/g; the molecular weight is preferably greater than 400 g/mol. Component (f) preferably comprises polyether polyols which are prepared by known methods, for example by anionic polymerization using alkali metal hydroxides such as sodium hydroxide or potassium hydroxide, or alkali metal alkoxides such as sodium methoxide, sodium ethoxide or potassium isopropoxide as catalysts and with addition of at least one initiator molecule which has from 2 to 8, preferably from 2 to 6, active hydrogen atoms, or by cationic polymerization using Lewis acids as catalysts, for example in particular antimony pentachloride, boron fluoride etherate or fuller's earth, from one or more alkylene oxides having from 2 to 4 carbon atoms in the alkylene radical. In addition, the polyether polyols can be prepared by means of double metal cyanide catalysts, continuous operating modes also being possible.

Suitable alkylene oxides are, for example, tetrahydrofuran, 1, 3-propylene oxide, 1, 2-or 2, 3-butylene oxide, styrene oxide and preferably ethylene oxide and 1, 2-propylene oxide. The alkylene oxides can be used individually, alternating with one another or as mixtures. Suitable initiator molecules are, for example, glycerol, trimethylolpropane, pentaerythritol, sucrose, sorbitol, methylamine, ethylamine, isopropylamine, butylamine, benzylamine, aniline, toluidine, naphthylamine, ethylenediamine, diethylenetriamine, 4' -methylenedianiline, 1, 3-propanediamine, 1, 6-hexanediamine, ethanolamine, diethanolamine, triethanolamine and other di-or polyhydric alcohols, which may themselves also be oligoether polyols or mono-or polyvalent amines.

Component (f) may also optionally comprise polyester polyols, chain extenders and/or crosslinkers. Difunctional or trifunctional amines and alcohols are particularly useful as chain extenders and/or crosslinkers, in particular diols and/or triols having molecular weights of less than 400 g/mol, preferably from 60 to 300 g/mol. Polyether polyols and/or polyester polyols having a hydroxyl number of greater than 160, particularly preferably greater than 200 mg KOH/g, and particularly preferably a functionality of from 2.9 to 8, are preferably used as compound (f). Polyether polyols having an equivalent weight, i.e.molecular weight divided by functionality, of less than 400 g/mol, preferably less than 200 g/mol, are particularly preferably used as compound (f) which is reacted with isocyanates. Compound (f) is typically in liquid form.

Hydrocarbons are preferably used as blowing agent component (c). These may be used in admixture with water and/or other physical blowing agents. These are understood to be compounds which dissolve or emulsify in the substances used for the polyurethane preparation and evaporate under the polyurethane-forming conditions. Among them are, for example, hydrocarbons, halogenated hydrocarbons and other compounds, for example perfluorinated alkanes, such as perfluorohexane, chlorofluorocarbons, and ethers, esters, ketones and/or acetals.

The blowing agent component (c) is preferably used in an amount of from 2 to 45% by weight, preferably from 4 to 30% by weight, particularly preferably from 5 to 20% by weight, relative to the total weight of components (b) to (f). In a preferred embodiment, the blowing agent mixture (c) comprises a hydrocarbon, in particular n-pentane and/or cyclopentane, and water. Particularly preferred hydrocarbons are n-pentane, cyclopentane, isopentane and/or isomer mixtures. Cyclopentane and/or n-pentane are particularly used as blowing agents (c).

Conventional and known polyurethane-or polyisocyanurate-forming catalysts are used as catalyst (d) for preparing the polyurethane or polyisocyanurate foams according to the invention, for example organotin compounds, such as tin diacetate, tin dioctoate, dibutyltin dilaurate, and/or strongly basic amines, such as 2,2, 2-diazabicyclooctane, triethylamine or preferably triethylenediamine, N, N-dimethylcyclohexylamine or bis (N, N-dimethylaminoethyl) ether, and also potassium acetate, potassium octoate and aliphatic quaternary ammonium salts for catalyzing the PIR reaction.

The catalyst is preferably used in an amount of 0.05 to 3% by weight, preferably 0.06 to 2% by weight, relative to the total weight of all components.

The reaction of the above components is optionally carried out in the presence of (e) additives, such as flame retardants, fillers, cell regulators, foam stabilizers, surface-active compounds and/or stabilizers, to prevent oxidative, thermal or bacterial decomposition or ageing, preferably flame retardants and/or foam stabilizers. Substances which promote the formation of a regular pore structure in the foam formation are referred to as foam stabilizers. The following are exemplified: silicone-containing foam stabilizers, for example siloxane-oxyalkylene mixed polymers and other organopolysiloxanes, also fatty alcohols, oxo alcohols (Oxoalkohol), fatty amines, alkylphenols, dialkylphenols, alkylcresols, alkylresorcinols, naphthols, alkylnaphthols, naphthylamines, anilines, alkylanilines, toluidines, bisphenol a, alkylated bisphenol a, alkoxylation products of polyvinyl alcohols, and also alkoxylation products of formaldehyde and alkylphenols, formaldehyde and dialkylphenols, formaldehyde and alkylcresols, formaldehyde and alkylresorcinols, formaldehyde and anilines, formaldehyde and toluidines, formaldehyde and naphthols, formaldehyde and alkylnaphthols and condensation products of formaldehyde and bisphenol a. For example, ethylene oxide, propylene oxide, poly-THF and higher homologues may be used as alkoxylating agents.

Flame retardants known from the prior art can generally be used as flame retardants. Suitable flame retardants are, for example, brominated ethers (e.g. Ixol)^®B251) Brominated alcohols such as dibromoneopentyl alcohol, tribromoneopentyl alcohol and PHT-4-diol, and chlorinated phosphates such as tris- (2-chloroethyl) phosphate, tris- (2-chloroisopropyl) phosphate (TCPP), tris (1, 3-dichloroisopropyl) phosphate, tris- (2, 3-dibromopropyl) phosphate and tetrakis- (2-chloroethyl) ethylene diphosphate. In addition to the halogen-substituted phosphoric acid esters already mentioned, inorganic flame retardants, for example red phosphorus, red phosphorus-containing preparations, hydrated aluminum oxide, antimony trioxide, ammonium polyphosphate and calcium sulfate or cyanuric acid derivatives, for example melamine, or mixtures of at least two flame retardants, for example mixtures of ammonium polyphosphate and melamine and optionally starch, can also be used for flame-retarding the PUR or PUR/PIR rigid foams prepared according to the invention. Diethyl ethane phosphonate (DEEP), triethyl phosphate (TEP), dimethylpropyl phosphonate (DMPP), cresyl Diphenyl Phosphate (DPK) and others can be used as additional liquid halogen-free flame retardants. Within the scope of the present invention, the flame retardants are preferably used in amounts of from 0 to 30% by weight, particularly preferably from 2 to 25% by weight, in particular from 2.5 to 3.5% by weight, based on the total weight of the components (b) to (e).

Further details of the above and other materials can be found in the specialist literature, for example in Kunststoffhandbuch, volume VII, Polyurethane, Carl Hanser Verlag munich, vienna, first, second and third edition, 1966, 1983 and 1993.

For the preparation of polyurethane rigid foams, the polyisocyanate (b) and the component (a) and optionally (f) are reacted in amounts such that the foam has an isocyanate value of from 90 to 600, preferably from 150 to 500, particularly preferably from 180 to 450.

The rigid polyurethane foam can be produced discontinuously or continuously by means of known processes. The person skilled in the art is aware of the use, inter alia, of the preparation of slabstock foams (continuous and discontinuous), in one-component systems (discontinuous) and in the moulding of insulating foams (discontinuous). The invention described herein relates to all processes, but preferably a continuous two-belt process, wherein flexible and/or rigid materials can be used as outer layers.

The rigid polyurethane foam according to the invention preferably has a closed cell content of more than 90%, particularly preferably more than 95%.

The PUR or PUR/PIR foams according to the invention preferably have a weight of 28 g/m³－300 g/m³Particularly preferably 30 g/m³－50 g/m³The density of (c).

The rigid polyurethane foam according to the invention is particularly useful for example for refrigerators, containers or buildings, for example for thermal insulation in the form of thermal insulation pipes (gel ä mmt Rohr), sandwich elements, insulation panels or refrigerators.

Polyurethanes within the meaning of the present application are also understood to include polymeric isocyanate adducts which, in addition to urethane groups, also contain further groups, which are formed, for example, by reaction of isocyanate groups with themselves, for example isocyanurate groups, or by reaction of isocyanate groups with groups other than hydroxyl groups, the listed groups being present in the polymer predominantly together with urethane groups.

The invention further provides for the use of the polyester polyols prepared by the above-described process for preparing polyurethanes. Polyurethanes are versatile materials used in many fields. Due to the wide variety of raw materials that can be used, products with a wide variety of properties can be prepared, such as rigid foams for insulation, flexible slabstock foams for mattresses, flexible molded foams for automobile seats and seat cushions, acoustic foams for sound insulation, thermoplastic foams, shoe foams or microcellular foams, as well as compact casting systems and thermoplastic polyurethanes.

The invention is illustrated below with the aid of examples.

Examples

Composition of the raw materials used in the examples

Industrial Lanxess glutarate; molar mass about 134 Da

Interquisa terephthalic acid

Phthalic anhydride (PSA) Industrial PSA from Lanxess

PEG 200 BASF

PEG 180 Ineos

Ethylene Glycol (EG) EG from Ineos

Tin (II) dichloride dihydrate Aldrich

Titanium tetrabutoxide Aldrich

The apparatus used was:

viscometer MCR 51 from Anton Paar

The analytical method used was:

hydroxyl number according to Houben Weyl, method of organic chemistry (Methoden der Organischen Chemie), volume XIV/2 Makromolekulare Stoffe, page 17, Georg Thieme Verlag; Stuttgart 1963.

Acid number according to Houben Weyl, method of organic chemistry (Methoden der Organischen Chemie), volume XIV/2 Makromolekulare Stoffe, from page 17, Georg Thieme Verlag, Stuttgart 1963.

A) Preparation of polyester polyols

Example 1 (according to the invention):

2280 g (11.4 mol) of PEG 200 are placed at 100 ℃ under a nitrogen blanket in a 4 l four-necked flask equipped with a heating mantle, a mechanical stirrer, an internal thermometer, a 40cm packed column, a distillation head, a descending forced cooler (Intensivkuhler) and a diaphragm vacuum pump. 732 g (4.41 mol) of terephthalic acid are added with stirring over about 5 minutes, and 83 mg of tin dichloride dihydrate are added. The mixture was heated at 230 ℃ for 2 hours, during which time water distilled off and the turbidity of the reaction mixture disappeared. 314 g (2.34 mol) of technical glutaric acid were then added and the mixture was heated for a further 90 minutes at 230 ℃. Then an additional 83 mg of tin dichloride dihydrate were added and vacuum was applied, finally 30 mbar. The mixture was concentrated under these conditions for an additional 5.5 hours. The mixture was cooled and the following properties were measured:

analysis of the polyester:

hydroxyl value 160 mg KOH/g

Acid value of 2.0 mg KOH/g

Viscosity 1620 mPas (25 ℃ C.), 310 mPas (50 ℃ C.), 110 mPas (75 ℃ C.).

Example 3(V) is not according to the invention, since component (C) (in the case of these examples commercial glutaric acid) is not used in its preparation. Example 4(V) is not according to the invention, since the fraction of ether groups from the oligoethylene glycol is less than 9 mol/kg of ester and since the fraction of components other than (A), (B) or (C) is greater than 10% by weight; in this particular case 14.1 wt% ethylene glycol was used. The same applies to examples 5(V), 6(V) and 7 (V). Table 1 further shows that the polyester polyols 4(V), 5(V), 6(V) and 7(V) which are not according to the invention are disadvantageously solid at room temperature, whereas the polyester polyols 1,2, 3 and 8 according to the invention are advantageously liquid. Example 9(V) meets this criterion but does not contain terephthalic acid, which, moreover, proves to be disadvantageous in terms of combustion properties.

Raw materials for PUR/PIR rigid foams:

a.) polyesters from examples 1,2, 3, 8, 9(V)

A foam additive consisting of b.) to d.):

b.) crosslinking agent from Evonik

c.) Tegostab, stabilizer from Evonik

d.) DMCHA, N-dimethylcyclohexylamine from Rheinchemie

e.) TCPP, tris (1-chloro-2-propyl) phosphate from Lanxess

f.) n-pentane, Kraemer & Martin

g.) water, softened

h.) activator Desmorapid VP.PU 1792, Bayer MaterialScience

i.) Desmodur VP. PU 44V40L, polyisocyanate from Bayer MaterialScience.

TABLE 2 composition and Properties of PUR/PIR foams based on polyester polyols according to and not according to the invention

The index refers to the molar ratio of all isocyanate groups to zerewitinoff-active hydrogen atoms.

On a laboratory scale, all the raw materials of the rigid foam formulation, except for the polyisocyanate component, were weighed into a cardboard beaker, the temperature was adjusted to 23 ℃, mixed with a Pendra ulik laboratory mixer (for example type LM-34 from Pendra ulik), and optionally a volatile blowing agent (pentane) was added. The polyisocyanate component (likewise adjusted to a temperature of 23 ℃) was then added to the polyol mixture with stirring, this was mixed intensively and the reaction mixture was poured into paper-lined wood moulds. The set time and tack-free time were measured during the foaming process. After 24 hours, a cube-shaped sample having a side length of 9cm was cut from the foam blank.

The following properties were measured:

dimensional stability was determined by measuring the dimensional change of the cube-shaped samples after 24 hours of storage at-22 ℃ and +80 ℃ respectively. In each spatial direction, the foams according to the invention exhibit a relative length change of at most 1% (absolute).

Core coarse density is determined by the volume and weight of the cut cube shaped sample.

KBT-Small flame Source test is defined in DIN 4102-1. The rigid foam according to the present invention meets the combustion rating B2.

Adhesion was determined by slowly pulling the foamed liner paper from the foam by hand. The adhesion rating is from 1 (very good) to 6 (unsatisfactory), where a rating of 1 means that the paper cannot be pulled out of the foam and tears, and 6 is the lack of any adhesion between the paper and the foam.

Setting time was determined by dipping a wooden stick into the reacted polymer melt and removing it again. The time at which the polymer melt solidified was characterized.

Tack-free time-characterizing the surface properties of the foam. It was determined by whipping the foam with a wooden stick no longer rising. The time at which bonding is stopped is called the tack-free time.

Table 2 shows that all foams according to the invention reached a fire grade B2, whereas foam 16(V) failed, despite containing the same amount of flame retardant TCPP.

Claims (13)

1. A polyester polyol having an ether group concentration of from 9.0mol/kg polyester polyol to 16mol/kg polyester polyol prepared from a mixture comprising:

(A) the amount of terephthalic acid is such that,

(B) a number average number n of oxyethylene groups of 3.0-9.0 of the formula H- (OCH)₂CH₂)_n-OH of an oligoethylene glycol, and

(C) at least one acid selected from the group consisting of: aliphatic dicarboxylic acids selected from succinic acid, glutaric acid, adipic acid, sebacic acid, suberic acid, azelaic acid, decanedicarboxylic acid and tetradecanedioic acid, and omega-hydroxycaproic acid.

2. Polyester polyol according to claim 1, characterized in that component (a) is present in an amount of 10 to 40% by weight relative to the total amount of the mixture.

3. Polyester polyol according to claim 1, characterized in that component (B) is present in an amount of 90 to 60% by weight relative to the total amount of the mixture.

4. Polyester polyol according to claim 1, characterized in that component (C) is present in an amount of 2 to 20% by weight relative to the total amount of the mixture.

5. Polyester polyol according to any of claims 1 to 4, characterized in that the polyester polyol has a hydroxyl value of from 100mg KOH/g to 400mg KOH/g.

6. A polyester polyol according to any of claims 1 to 4, characterized in that the polyester polyol has a viscosity of 800mPas to 4500mPas at 25 ℃ measured according to DIN 53019.

7. Polyester polyol according to any of claims 1 to 4, characterized in that the oligoethylene glycol (B) has a number n of average number of ethylene oxide groups of from 3.1 to 9.

8. Polyester polyol according to any of claims 1 to 4, characterized in that the polyester polyol has a melting point of-40 ℃ to 25 ℃.

9. Process for the preparation of a polyester polyol according to any of claims 1 to 8, characterized in that components (A), (B) and (C) are reacted in the presence of a catalyst selected from tin (II) salts and titanium tetraalkoxides at a temperature of 160 ℃ to 240 ℃ and a pressure of 1 to 1013 mbar for 7 to 100 hours.

10. Use of a polyester polyol according to any of claims 1 to 8 for the preparation of PUR or PUR/PIR foams.

11. A process for preparing a PUR or PUR/PIR foam, comprising the steps of:

a) at least one polyester polyol according to any of claims 1 to 8 reacted with:

b) at least one polyisocyanate-containing component,

c) at least one kind of foaming agent,

d) at least one or more catalysts selected from the group consisting of,

e) optionally at least one flame retardant and/or further auxiliary substances and additives,

f) optionally at least one compound having at least two groups reactive with isocyanates.

12. PUR or PUR/PIR foam obtainable by a process according to claim 11.

13. Use of a PUR or PUR/PIR foam obtainable by the process according to claim 11 for the manufacture of a thermally insulated pipe, a sandwich element, an insulation board or a freezer.