EP2744841A2

EP2744841A2 - Method for producing rigid polyurethane foams

Info

Publication number: EP2744841A2
Application number: EP12748207.3A
Authority: EP
Inventors: Andreas Emge; Holger Seifert; Daniel Freidank
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2011-08-17
Filing date: 2012-08-14
Publication date: 2014-06-25
Also published as: AU2012296911A1; WO2013024101A2; JP2014524493A; BR112014003673A2; KR20140052022A; WO2013024101A3; RU2014109848A; IN2014CN01171A; MX2014001705A; CN104039858A

Abstract

The invention relates to polyurethane foams containing particles and characterised in that the particles are predominantly embedded in the cell walls.

Description

description

The invention relates to a process for the production of rigid polyurethane foams by reacting polyisocyanates with compounds having at least two isocyanate-reactive hydrogen atoms.

Polyurethane hard foams have been known for a long time and have been described many times in the literature. They are usually prepared by reacting polyisocyanates with compounds having at least two isocyanate-reactive hydrogen atoms, in particular polyfunctional alcohols. The rigid polyurethane foams are preferably used for insulation in refrigerators or for components. It is a constant task to improve the properties of rigid polyurethane foams. In particular, the thermal conductivity of the foams should be lowered and their mechanical properties, in particular the compressive strength, improved.

One way to achieve this goal is to use polyols containing fillers in the production of rigid foams. A frequently used group of fillers-containing polyols are those which are prepared by in-situ polymerization of olefinically unsaturated monomers, in particular styrene and / or acrylonitrile, in polyols, in particular polyether alcohols. Such products are well known and are referred to as polymer polyols or graft polyols.

Polyurethane rigid foams which are produced using graft polyols are described, for example, in WO2005 / 097863 and WO2004 / 035650. The rigid foams described there are characterized by a low demolding time, good mechanical properties and low thermal conductivity.

For the properties of the foams, a uniform distribution of the particles in the foam matrix is essential. A good distribution in the first step means that no aggregates of several particles form, but the filler evenly distributed in the polymer material. Only then can a filler be used economically sensible. Such a distribution of the particles is, for example, with graft polyols, as used, for example, in US Pat

WO2005 / 097863 and WO2004 / 035650 are described.

In addition to the avoidance of aggregates, a further point for the distribution of the particles in the foam material is essential: Normally, at least 80% of the polyurethane material is found in the cell webs of the rigid foam (see DW Reitz, MA Schütz, LR Glicksman "A basic study of aging of foam insulation, Journal of cellular plastics, 1984, 20 (2), 104-1. Thus, almost all particles are found in the cell stems, only a few filler particles are also found in the cell wall. If a foam of a large me- As a result of mechanical pressure or tensile stress, the failure of the material begins at the weak points, ie at the very thin cell walls, while the much more stable cell bridges initially remain intact. If, therefore, reinforcement of the foam with a filler is to be achieved, it is necessary for the largest possible proportion of the filler to be present in the cell walls, since only this proportion of the filler used overall has a reinforcing effect. According to the prior art, such a distribution of the filler with accumulation of the particles in the cell walls is not known.

The use of fillers to optimize the properties of rigid polyurethane foam materials requires extensive control of the distribution of the individual particles in the foam.

It was the object of the present invention to provide polyurethane foams, in particular rigid polyurethane foams, which are distinguished by good mechanical properties, low thermal conductivity, and good processing properties, for example a reduced demolding time. In particular, the compressive strength of the foams should be improved. As a result, the density of the foams can be lowered. Furthermore, a high compatibility of the starting components for the production of the polyurethanes, in particular the polyol component, with the blowing agents, and in particular with the non-polar hydrocarbons, should be achieved.

Surprisingly, the object could be achieved by storing the particles predominantly in the cell walls of the foams, the particles being polymers of olefinically unsaturated monomers or inorganic particles and the surface of the particles being modified by surface-active substances.

The invention therefore relates to particle-containing polyurethane foams, characterized in that the particles are incorporated predominantly in the cell walls, wherein the particles are polymers of olefinically unsaturated monomers or inorganic particles and the surface of the particles modified by surface-active substances has been.

The term "predominantly" here means that at least 50% by weight of the particles, based on their total weight, are incorporated in the cell walls.

The invention further provides a process for the production of rigid polyurethane foams by reacting a) polyisocyanates with b) compounds having at least two isocyanate-reactive hydrogen atoms in the presence of c) blowing agents, characterized in that at least one of the components a) or b) contains particles whose surface has been modified by surface-active substances.

The invention furthermore relates to particle-containing polyether alcohols which can be prepared by in-situ polymerization of olefinically unsaturated monomers in a polyether alcohol, characterized in that at least one of the olefinically unsaturated monomers has surface-active properties.

The invention further provides a process for preparing particle-containing polyether alcohols by in situ polymerization of olefinically unsaturated monomers in a polyether alcohol, characterized in that at least one of the olefinically unsaturated monomers has surface-active properties.

The term surface-active means that the compounds mediate between immiscible substances, in particular between immiscible liquids or immiscible liquids and gases. Such compounds have groups that are compatible with one substance and those that are compatible with the other substance. Therefore, the surface active compounds attach to the interfaces between the immiscible materials.

Preferably, the particles have a size of less than 50 μηη, in particular in the range between 0.5 to 10 μηη.

The particles are preferably selected from the group comprising organic particles, such as organic polymers or thermoplastic particles, and inorganic particles, in particular carbon-rich particles, such as carbon black or graphite, or oxides, in particular inorganic oxides.

As stated above, the surface of the particles has surface-active properties because it has been modified with surfactants. This can be effected in particular by applying surfactants to the surface of the particles. The attachment of the surfactants to the particles can be effected by non-covalent or preferably by covalent bonds.

In a preferred embodiment of the invention, the particles are inorganic particles. These are preferably the carbon-rich particles listed above, such as carbon black or graphite, or inorganic oxides, in particular metal oxides.

In the case of the inorganic particles, the surfactants are preferably brought into contact with the particles in such a way that they adhere to the surface of the particles. In a further preferred embodiment of the invention, the particles are polymers of olefinically unsaturated monomers.

On the one hand, these may be thermoplastic particles which are dispersed in components a) or preferably b). Such processes, also referred to as melt-emulsion processes, are known and are described, for example, in WO 2009/138379.

Again, as with the inorganic particles, the surfactants are preferably contacted with the particles so that they adhere to the surface of the particles.

In a particularly preferred embodiment of the invention, the particles are prepared by in situ polymerization of olefinically unsaturated monomers in a polyol, in particular a polyether alcohol. Polyols prepared by these processes are well known and are often referred to as graft polyols.

The synthesis of graft polyols by both methods is known and described in a number of examples. Thus, the synthesis of graft polyols according to the semi-batch process is described in the following patents: EP 439755 and US 4522976. A special form of the semi-batch process is the semi-batch seeding process, in which a graft polyol is additionally used as seed in the reaction template, for example described in EP 510533 and in EP 698628. The synthesis of graft polyols by a continuous process is also known and is described inter alia in WO 00/59971 and WO 99/31160. For organic particles prepared by polymerization, especially those prepared by in situ polymerization of olefinically unsaturated monomers in a polyether alcohol, the surfactants are preferably introduced into the particles, preferably by having at least one of the monomers surfactant groups and at least one has olefinic group.

Such monomers can be prepared by reacting a surfactant having at least one reactive group with a compound having a group reactive with this group and having an olefinically unsaturated group. Preferably used are surfactants which mediate between liquid and gases by non-covalent interactions. Such compounds are often used in the production of polyurethanes as foam stabilizers.

Preferred examples of such surfactants are polyether siloxanes which have at least one side chain with at least one hydroxyl group, for example polyether siloxanes of the following formula in which x, y, z, n and m are numbers and R is an alkyl group having 1 to 10 C atoms, M is a bivalent aliphatic, aromatic or araliphatic group having 2 to 10 C atoms, which via an ether, ester, Urethane, acetal group attached to the polyether chain mean. The sum of x, y, z is preferably chosen such that the molecular weight of the siloxane chain in these compounds is, for example, 2000 to 6000 g / mol, preferably 4000 to 5500 g / mol, z is preferably 1 or 0, on the average 0.9 , y is preferably in the range between 3 and 20. Thus, x is defined, n and m are inventively preferably chosen so that the side chain has a molecular weight of 400 to 2500 g / mol. The ratio n / (n + m) is preferably between 10 and 90%, values for m / (n + m) are preferably analog.

The present invention therefore preferably relates to the process according to the invention wherein polyether siloxanes which have at least one side chain with at least one hydroxyl group are used as surfactants.

Furthermore, the present invention preferably relates to the foam according to the invention, wherein the surface-active substances are polyether siloxanes which have at least one side chain with at least one hydroxyl group.

Furthermore, the present invention preferably relates to the particle-containing polyether alcohols according to the invention, preparable by in situ polymerization of olefinically unsaturated monomers in a polyether alcohol, wherein at least one of the olefinically unsaturated monomers by using polyether siloxanes having at least one side chain having at least one hydroxyl group, surface-active Features.

The present invention furthermore preferably relates to the process according to the invention for preparing particle-containing polyether alcohols by in-situ polymerization of olefinically unsaturated monomers in a polyether alcohol, wherein at least one of the olefinically unsaturated monomers is prepared by using polyethersiloxanes which have at least one side chain with at least one Have hydroxyl group, having surface-active properties. The molecular weight of the siloxane chain in these compounds is, for example, 2000 to 6000 g / mol, preferably 4000 to 5500 g / mol. The molecular weight of these compounds is, for example, 10 000 to 25 000 g / mol, preferably 1 1000 to 22 000 g / mol, particularly preferably 1 1000 to 20 000 g / mol.

The hydroxyl group can be reacted with an unsaturated compound having at least one isocyanate-reactive group. These groups may be an acid group or an acid anhydride group. Examples of such unsaturated acids and acid derivatives are maleic anhydride (MSA), fumaric acid, acrylate and methacrylate derivatives. Preferred is MSA. This group may preferably be an isocyanate group, since the resulting urethane group is more stable to hydrolysis than an ester group. Examples of unsaturated isocyanates are the 3-isopropenyl-1, 1-dimethylbenzyl isocyanate (TMI) and the isocyanatoethyl methacrylate, preferably the TMI. These compounds with olefinically unsaturated groups are often referred to as macromers or stabilizers.

Further macromers which can be used instead of or preferably in combination with the compounds described above are usually linear or branched polyether oils having molecular weights Mw 1000 g / mol which contain at least one mostly terminal, reactive olefinically unsaturated group. The ethylenically unsaturated group may be obtained by reaction with ethylenically unsaturated carboxylic acids and / or carboxylic acid anhydrides, such as maleic anhydride, fumaric acid, acrylate and methacrylate derivatives, and unsaturated isocyanate derivatives, such as 3-isopropenyl-1,1-dimethylbenzyl isocyanates, Isocyanatoethylmethacryl- ate be inserted into an existing polyol. Another approach is the preparation of a polyol by the alkoxylation of propylene oxide and ethylene oxide using starting molecules having hydroxyl groups and ethylenic unsaturation.

Examples of such macromers are described in US 4,390,645, US 5,364,906, and US 6013731.

The surfactants can be incorporated into the macromers.

In a further embodiment of the invention, the graft polyols are prepared by in situ polymerization of olefinically unsaturated monomers in a polyether alcohol, wherein the graft particles are modified after their preparation by reaction with a surface-active component.

In one embodiment of the invention, the surfactants contain no halogen atoms, in particular no fluorine atoms.

These monomers are attached to the surface of the particles in the preparation of the graft polyols. Thus, the particles behave like surface-active substances.

The surface-active particles used according to the invention may additionally carry functional groups, preferably those with which the particles can be chemically bound into the PU matrix. But it is also possible that the particles of the invention carry no reactive functional groups on the surface.

As already mentioned, the foams according to the invention are obtained by reacting a) polyisocyanates with b) compounds having at least two isocyanate-reactive hydrogen atoms, wherein at least one of components a) or b), preferably component b), contains particles.

The incorporation of the particles into component a) is less preferred, since due to the higher reactivity of the polyisocyanates may lead to disorders and undesirable side reactions.

It is therefore preferred that component b) contains the particles whose surface has been modified by surface-active substances. The particles-containing polyols, in particular polyether alcohols, can, as described, in a preferred embodiment, prepared by in situ polymerization of olefinically unsaturated monomers in polyether alcohols, often referred to as carrier polyols. These polyols are often referred to as graft polyols. The carrier polyols are preferably prepared by addition of alkylene oxides, in particular ethylene oxide and / or propylene oxide, to H-functional compounds, preferably those having hydroxyl or amino groups. The H-functional compounds may be alcohols having 2 to 4 hydroxy groups in the molecule. Preferred examples are glycerol, trimethylolpropane, and glycols, for example ethylene glycol, diethylene glycol, propylene glycol and dipropylene glycol. In a further embodiment of the invention, the H-functional compounds are primary or secondary amines having 2 to 4 reactive hydrogen atoms. Examples of aliphatic amines are ethylenediamine, propylenediamine and ethanolamine. Aromatic amines are preferably used, the toluenediamine, and in particular the ortho-isomers, being preferred.

The carrier polyols preferably have a hydroxyl number in the range between 40 and 250 mgKOH / g.

The solids content of the graft polyols is preferably in the range between 30 to 55% by weight, based on the weight of the graft polyol. The olefinically unsaturated monomers used are preferably styrene and / or acrylonitrile, more preferably mixtures of styrene and acrylonitrile. The content of acrylonitrile in these mixtures is particularly preferably in the range between 30 and 80% by weight, based on the mixture.

The graft polyols b1) preferably have a particle size of the polymers of 0.1 μηη to 8 μηη, preferably 0.2 μηη to 4 μηη with a maximum in the particle size at 0.2 to 3 μηη preferably at 0.2 to 2.0 μηη , In a further preferred embodiment of the graft polyols b1), the particle size distribution is bimodal, that is, the distribution curve of the particle size has two maxima. Such graft polyols can be prepared, for example, by mixing graft polyols having a monomodal particle size distribution and different particle size in the corresponding ratio but also by using a polyol as support polyol in the reaction template which already contains polymers of olefinically unsaturated monomers. The particle size is also in this embodiment in the range described above.

The graft polyols can be made continuously in one embodiment of the invention.

In a further preferred embodiment, the graft polyols are prepared in the semi-batch process.

For the production of polyurethane foams, in particular hard foams, the following can be said in detail.

Suitable organic polyisocyanates a) are preferably aromatic polyfunctional isocyanates. Specific examples are: 2,4- and 2,6-toluene diisocyanate (TDI) and the corresponding isomer mixtures, 4,4'-, 2,4'- and 2,2'-diphenylmethane diisocyanate (MDI) and the corresponding isomer mixtures, mixtures of 4,4'- and 2,4'-diphenylmethane diisocyanates, polyphenyl polymethylene polyisocyanates, mixtures of 4,4'-, 2,4'- and 2,2'-diphenylmethane diisocyanates and Polyphenyl polymethylene polyisocyanates (crude MDI) and mixtures of crude MDI and toluene diisocyanates. The organic di- and polyisocyanates can be used individually or in the form of mixtures.

Frequently, so-called modified polyfunctional isocyanates, ie products obtained by chemical reaction of organic di- and / or polyisocyanates are used. Examples include isocyanurate and / or urethane-containing di- and / or polyisocyanates. The modified polyisocyanates may optionally together or with unmodified organic polyisocyanates such as 2,4'-, 4,4'-diphenylmethane diisocyanate, crude MDI, 2,4- and / or 2,6-toluene diisocyanate are mixed.

In addition, reaction products of polyfunctional isocyanates with polyhydric polyols, as well as their mixtures with other di- and polyisocyanates can be used.

Has proven particularly useful as organic polyisocyanate crude MDI having an NCO content of 29 to 33 wt .-% and a viscosity at 25 ° C in the range of 150 to 1000 mPa-s. The particle-containing polyol bi1) can in principle be used as the only compound having at least two isocyanate-reactive hydrogen atoms b). However, it is preferred to use this compound b1) in admixture with other compounds having at least two isocyanate-reactive hydrogen atoms. For this purpose, the customary and known compounds having at least two isocyanate-reactive hydrogen atoms can preferably be used. Preferably in combination with the polyols b1) polyether alcohols and / or polyester alcohols are used.

The polyester alcohols used together with the polyols b1) are usually obtained by condensation of polyhydric alcohols, preferably diols, having 2 to 12 carbon atoms, preferably 2 to 6 carbon atoms, with polyfunctional carboxylic acids having 2 to 12 carbon atoms, for example succinic acid, glutaric acid, adipic acid, suberic acid, Azelaic acid, sebacic acid, decanedicarboxylic acid, maleic acid, fumaric acid and preferably phthalic acid, isophthalic acid, terephthalic acid and the isomeric naphthalenedicarboxylic acids.

The polyether alcohols used together with the polyols b1) usually have a functionality between 2 and 8, in particular 3 to 8. In particular, come polyether alcohols which are prepared by known methods, for example by anionic polymerization of alkylene oxides in the presence of catalysts, preferably alkali metal hydroxides to Commitment.

The alkylene oxides used are usually ethylene oxide and / or propylene oxide, preferably pure 1,2-propylene oxide.

In particular, compounds having at least 3, preferably 4 to 8, hydroxyl groups or having at least two primary amino groups in the molecule are used as starting molecules. As starting molecules having at least 3, preferably 4 to 8, hydroxyl groups in the molecule are preferably trimethylopropane, glycerol, pentaerythritol, sugar compounds such as glucose, sorbitol, mannitol and sucrose, polyhydric phenols, resoles, such as oligomers Condensation products of phenol and formaldehyde and Mannich condensates of phenols, formaldehyde and dialkanolamines and melamine used.

As starting molecules having at least two primary amino groups in the molecule it is preferred to use aromatic di- and / or polyamines, for example phenylenediamines, 2,3-, 2,4-, 3,4- and 2,6-toluenediamine (TDA), in particular 2 , 3- and 3,4-TDA, and 4,4'-, 2,4'- and 2,2'-diaminodiphenylmethane and aliphatic di- and polyamines, such as ethylenediamine used. The 2,3- and 3,4-isomers of TDA are also referred to as vicinal TDAs. The polyether alcohols have a functionality of preferably 3 to 8 and hydroxyl numbers of preferably 100 mg KOH / g to 1200 mg KOH / g and in particular 240 mg KOH / g to 570 mg KOH / g.

In a preferred embodiment of the process according to the invention, a mixture of the graft polyol bi1) and at least one aliphatic amine-initiated polyether alcohol bii2) is used as compounds having at least two isocyanate-reactive hydrogen atoms. This preferably has a hydroxyl number in the range between 375 and 525 mg KOH / g. In a further preferred embodiment of the method according to the invention is used as compounds having at least two isocyanate-reactive hydrogen atoms, a mixture of the graft polyol bi1) and at least one started with an aromatic amine polyether alcohol bii3). This preferably has a hydroxyl number in the range between 375 and 525 mgKOH / g. It is also possible to use polyether alcohols started with vicinal TDA having a hydroxyl number of 100 to 250 mgKOH / g as the polyol bii3).

In a further preferred embodiment of the process according to the invention is used as compounds having at least two isocyanate-reactive hydrogen atoms, a mixture of the graft polyol bi1) and at least one with a sugar, in particular sorbitol or sucrose, started polyether alcohol bii4). This preferably has a hydroxyl number in the range between 300 and 700 mgKOH / g.

In a further preferred embodiment of the process according to the invention is used as compounds having at least two isocyanate-reactive hydrogen atoms, a mixture of the graft polyol bi1) and at least one with a trihydric alcohol, in particular glycerol and / or trimethylolpropane started polyether alcohol bii5). This preferably has a hydroxyl number in the range between 100 and 250 mgKOH / g. In another preferred embodiment of the invention, polyol bi) or bii) contains a polyether alcohol bii6 started with a difunctional alcohol. In a further preferred embodiment of the invention, compound b) contains at least one polyol bii1), at least polyol bii4) and at least one polyol bii2) and / or bii3).

Preferred polyol components include polyol bii1 in a proportion of 10-30 wt .-%, Polyol bii2 of 0-15 wt .-%, bii3 of 15-40 wt .-%, bii4 of 25-60 wt .-% and bii5 of 0-15% by weight.

The compounds having at least two isocyanate-reactive hydrogen atoms b) also include the optionally used chain extenders and crosslinkers. The polyurethane rigid foams can be produced without or with the concomitant use of chain extenders and / or crosslinking agents. For the modification of the mechanical properties, the addition of difunctional chain extenders, trifunctional and higher functional crosslinking agents or possibly also mixtures thereof may prove to be advantageous. As chain extenders and / or crosslinking agents it is preferred to use alkanolamines and in particular diols and / or triols having molecular weights of less than 400, preferably 60 to 300.

Chain extenders, crosslinking agents or mixtures thereof are expediently used in an amount of 1 to 20% by weight, preferably 2 to 5% by weight, based on the compounds having at least two isocyanate-reactive hydrogen atoms b).

The reaction is usually carried out in the presence of catalysts, blowing agents and customary auxiliaries and / or additives.

The catalysts used are in particular compounds which greatly accelerate the reaction of the isocyanate groups with the groups reactive with isocyanate groups.

Such catalysts are strongly basic amines, such as. As secondary aliphatic amines, imidazoles, amidines, and alkanolamines or organic metal compounds, especially organic tin compounds.

If also isocyanurate groups are to be incorporated in the rigid polyurethane foam, special catalysts are required for this purpose. The isocyanurate catalysts used are usually metal carboxylates, in particular potassium acetate and its solutions.

The catalysts can, depending on requirements, be used alone or in any mixtures with one another. As propellant preferably water can be used which reacts with isocyanate groups with elimination of carbon dioxide. In combination with or instead of water, so-called physical blowing agents can also be used. These are compared to the feed components inert compounds, which are usually liquid at room temperature and evaporate at the conditions of the urethane reaction. Preferably, the boiling point of these compounds is below 50 ° C. The physical blowing agents also include compounds which are gaseous at room temperature and are introduced under pressure into or dissolved in the starting components, for example carbon dioxide, low-boiling alkanes and fluoroalkanes.

The compounds are usually selected from the group comprising alkanes and / or cycloalkanes having at least 4 carbon atoms, dialkyl ethers, esters, ketones, acetals, fluoroalkanes having 1 to 8 carbon atoms, and tetraalkylsilanes having 1 to 3 carbon atoms in the alkyl chain, in particular tetramethylsilane ,

Examples which may be mentioned are propane, n-butane, iso- and cyclobutane, n-, iso- and cyclopentane, cyclohexane, dimethyl ether, methyl ethyl ether, methyl butyl ether, methyl formate, acetone, as well as fluoroalkanes, which can be degraded in the troposphere and therefore for the ozone layer is harmless, such as trifluoromethane, difluoromethane, 1,1,1,3,3-pentafluorobutane, 1,1,1,3,3-pentafluoropropane, 1,1,1,2-tetrafluoroethane, difluoroethane and 1,1, 1, 2,3,3,3-heptafluoropropane, and perfluoroalkanes, such as: C3F8, C4F10, C5F12, CeF-u or C7F17. The said physical blowing agents can be used alone or in any combination with each other.

Most preferably, the propellant contains at least one aliphatic hydrocarbon, preferably containing at least 4 carbon atoms. In a preferred embodiment of the process according to the invention, a combination of water and an aliphatic hydrocarbon is used as blowing agent. Preferred hydrocarbons are n-pentane, isopentane and cyclopentane.

In particular, when using the hydrocarbons as propellant optimal incorporation of the particles can be made in the cell walls.

If necessary, the process according to the invention can be carried out in the presence of flame retardants and customary auxiliaries and / or additives auxiliaries and / or additives. As flame retardants, organic phosphoric acid and / or phosphonic acid esters can be used. Preference is given to using compounds which are not reactive toward isocyanate groups. Chlorine-containing phosphoric acid esters are also among the preferred compounds. Typical typical representatives of this group of flame retardants are triethyl phosphate, diphenyl cresyl phosphate, tris (chloropropyl) phosphate and diethyl ethane phosphonate. In addition, bromine-containing flame retardants can also be used. As bromine-containing flame retardants, it is preferable to use compounds having groups which are reactive toward the isocyanate group. Such compounds are, for example, esters of tetrabromophthalic acid with aliphatic diols and alkoxylation products of dibromobutenediol. Compounds derived from the brominated, OH group-containing neopentyl compounds may also be used.

Suitable auxiliaries and / or additives are the substances known per se for this purpose, for example surface-active substances, foam stabilizers, cell regulators, fillers, pigments, dyes, flameproofing agents, hydrolysis protection agents, antistatic agents, fungistatic and bacteriostatic agents.

Further details on the starting materials, blowing agents, catalysts and auxiliaries and / or additives used for carrying out the process according to the invention can be found, for example, in the Kunststoffhandbuch, Volume 7, "Polyurethane" Carl Hanser Verlag, Munich, 1st edition, 1966, 2 Edition, 1983 and 3rd edition, 1993.

To prepare the rigid polyurethane foams, the polyisocyanates a) and the compounds having at least two isocyanate-reactive hydrogen atoms b) are reacted in amounts such that the isocyanate index is in a range between 100 and 220, preferably between 15 and 195 , lies. The rigid polyurethane foams can be prepared batchwise or continuously by means of known mixing devices. In the production of polyisocyanurate foams, it is also possible to work with a higher index, preferably up to 350.

The rigid polyurethane foams according to the invention are usually prepared by the two-component process. In this process, the compounds are mixed with at least two isocyanate-reactive hydrogen atoms b), with the flame retardants, the catalysts c), the blowing agents d), and the other auxiliaries and / or additives to a so-called polyol component and these with the polyisocyanates or Mixtures of the polyisocyanates and optionally blowing agents, also referred to as isocyanate component, reacted.

The starting components are usually mixed at a temperature of 15 to 35 ° C, preferably from 20 to 30 ° C. The reaction mixture can be poured into closed support tools with high or low pressure metering machines. In addition, the reaction mixture can also be poured or sprayed freely on surfaces or in open cavities. Roofs or complicated containers can be insulated on site using this method. The reaction mixture can also be in one place or in several places be introduced simultaneously into a closed mold and complex geometry. The position of injection of the reaction mixture may be at various points in the mold. The mold may be differently oriented with respect to the spatial directions at the time of injection of the reaction mixture. Such methods are typical, for example, for the production of refrigeration appliances. Also, the reaction mixture can be poured into an open mold, which is closed after completion of the filling process. This procedure is typical for example for the production of doors for refrigerators.

Preparation of graft polyols

The graft polyols used in the following examples can be prepared in continuous processes and batch processes. The synthesis of graft polyols by both methods is known. The synthesis of graft polyols according to the semi-batch process is described for example in EP 439755. A special form of the semi-batch process is the semi-batch seeding method, in which a graft polyol is additionally used as seed in the reaction template, for example described in EP 510533. The synthesis of graft polyols having a bimodal particle size distribution is described in WO 03/078496. The synthesis of graft polyols according to a continuous process is also known and is described, for example, in: WO 00/59971.

Graftpolyols for the examples and comparative examples prepared in the semi-batch process

The preparation of the graft polyols for the examples and comparative examples by the semi-batch process was carried out in a 2 liter autoclave equipped with 2-stage agitator, internal cooling coils and electric heating jacket. Before starting the reaction, the reactor was charged with a mixture of carrier polyol and macromer, purged with nitrogen and heated to a synthesis temperature of 125 and 130 ° C, respectively. In some syntheses, a graft polyol was additionally added to the reaction template in addition to the carrier polyol and the macromer as a seed. In another group of experiments only a part of the macromer was presented in the reactor. The remaining amount was transferred to the reactor via an independent metering stream during the synthesis.

The remainder of the reaction mixture, consisting of further carrier polyol, initiator, the monomers and the reaction moderator, was initially introduced into at least two dosing containers. The graft polyols were synthesized by transferring the raw materials from the dosing containers at a constant metering rate via a static in-line mixer into the reactor. The metering time for the monomer-moderator mixture was 150 or 180 minutes while the polyol-initiator mixture was metered into the reactor for 165 or 195 minutes. After a further 10 to 30 minutes of reaction time at the reaction temperature, the crude graft polyol was transferred via the bottom drain valve into a glass flask. Subsequently, the product at a temperature of 135 ° C under vacuum (<0.1 mbar) of the unreacted th monomers and other volatile compounds. The final product was finally stabilized with antioxidants.

For the graft polyols 5-7 a special macromer was used. For this purpose, a poly ethersiloxan, according to the following formula

wherein x, y, z, n and m are numbers having the values given in the description and R is an alkyl group having 1 to 10 C atoms, M is a bivalent aliphatic, aromatic or araliphatic group having 2 to 10 carbon atoms, the an ether, ester, urethane, acetal group is attached to the polyether chain, mean, for. B. Tegostab B8462, reacted with dimethyl meta-isopropenylbenzylisocyanat (TMI) at 80 ° C, wherein a molecular deficit of TMI is used, so that statistically not more than one OH group per Polyethersiloxanmolekül is reacted.

Production of rigid foams (machine foaming)

The various polyols, stabilizers, catalysts are mixed with water and the blowing agent in the ratios given in Table 1. 100 parts by weight of the polyol component were mixed with the respective amount of a mixture of diphenylmethane diisocyanate and polyphenylene polymethylene polyisocyanate with an NCO content of 31.5% by weight and a viscosity of 200 mPa.s (in Table 1) ( 25 ° C) in a high-pressure foaming machine of the type Puromat® HD 30 (Elastogran GmbH). The reaction mixture was poured into a mold measuring 200 cm × 20 cm × 5 cm or

40 cm x 70 cm x 9 cm injected and allowed to foam there. The properties and characteristics of the resulting foams are given in Table 1.

The rigid polyurethane foams produced by the process according to the invention can be produced with a very short demolding time on the basis of a phase-stable polyol component, which allows significantly shorter cycle times. Despite the presence of the graft polyol, large amounts of physical blowing agents are soluble in the polyol component, so that fabric densities in the component of less than 30 g / l can be achieved. The foam properties in terms of pressure resistance, thermal conductivity and quality of the foam surfaces (formation of voids) are excellent. the polyurethane reaction mixture in a form of dimensions 200 x 20 x 5 cm ³ poured

(10% overfilling) and after a few hours a specimen of dimension 20 x 20 x 2 cm ^{3 cut} from the middle.

The compressive strength was determined according to DIN 53421 / DIN EN ISO 604.

The proportion of particles in the cell walls was determined by quantitative evaluation of SEM images of the foams.

Determination of the proportion of particles in the cell walls: SEM images, statistical evaluation of the particles.

The invention will be explained in more detail in the following examples. All data in parts by weight unless stated otherwise. Key figure and flow factor are dimensionless.

Comparative Comparison Example. 1 example. 2 example. 3 same example. 2

example. 1

Polyol 1 25 25 25 25 25

Polyol 2 52 52 52 52 52

Polyol 3 16 13 13 13 13

Polyol 4 - 3 - - -

Polyol 5 - - 3 - -

Polyol 6 - - - 3 -

Polyol 7 - - - - 3

Stabilizer 2 2 0.4 0.4 2

Water 2.3 2.3 2.3 2.3 2.3

Catalyst 1 .8 1 .8 1 .8 1 .8 1 .8

Cyclopentane 9.8 9.8 9.8 9.8 9.8

Isopentane 4.2 4.2 4.2 4.2 4.2

Formic acid - 2.3 - 2.3 -

Key figure 1 17 1 17 1 17 1 17 1 17

Setting time [s] 43 40 37 40 38

Cleared 23.8 24.5 23.9 24.3 24.5

Bulk density [g / l]

Minimum filling density31.9 32.1 29 31.6 31.8 te [g / l]

Flow factor (at least 1 .31 1 .31 1 .33 1 .30 1 .30

Filling density / free

bulk density)

Openness [%] 6 5 6 5 4

Thermal conductivity 18.8 19.6 18.8 19.8 19.5

[MW / mK]

Compressive strength 0.16 0.16 0.20 0.21 0.20

(RD 31) 20% OP,

[N / mm2]

Drive after 93.2 92.8 91.8 91.3 91.5

24h, 4 min. 20%

Overpack [mm]

Proportion of filler in 0% 10% 60% 70% 60% of the cell wall Polyol 1 - polyether alcohol of vicinal TDA and ethylene oxide and propylene oxide, hydroxyl number 390 mgKOH / g

Polyol 2 - polyether alcohol from sucrose, glycerine and propylene oxide, hydroxyl number 440 mgKOH / g

Polyol 3 - polyether alcohol from vicinal TDA and ethylene oxide and propylene oxide, hydroxyl number 160 mgKOH / g polyol 4 - graft polyol, hydroxyl number 19 mgKOH / g, prepared by in situ polymerization of styrene and acrylonitrile in a polyether alcohol of glycerol and propylene oxide, hydroxyl number 35 mgKOH / g. Macromer is a reaction product of sorbitol with ethylene oxide / propylene oxide and TMI, molecular weight 18,000 g / mol. Polyol 5 - graft polyol analogous to polyol 4, prepared in the presence of a polyethersiloxane surfactant, d. H. Macromers according to the above formula. The molecular weight of the siloxane chain in this compound is 4400 g / mol, in the side chain 81% of ethylene oxide and 19% of propylene oxide are present, the molecular weight of these compounds is 13000 g / mol. Polyol 6 graft polyol analogous to polyol 4, prepared in the presence of a polyether siloxane

Surfactants, d. H. Macromers according to the above formula. The molecular weight of the siloxane chain in this compound is 5050 g / mol, in the side chain are 60% ethylene oxide and 40% propylene oxide, the molecular weight of the compounds is 19,000 g / mol. Polyol 7 graft polyol analogous to polyol 4, prepared in the presence of a polyether siloxane

Surfactants, d. H. Macromers according to the above formula. The molecular weight of the siloxane chain in this compound is 5050 g / mol, in the side chain are 60% ethylene oxide and 40% propylene oxide, the molecular weight of these compounds is 16,000 g / mol. Stabilizer is Tegostab B8462

Catalyst is a mixture of N, N dimethylcyclohexylamine, N, N, N ', N ", N" - pentamethyldiethylenetriamine and Lupragen N600 (1, 3,5-tris (dimethylaminopropyl) -sym-hexahydrotriazine; S-triazine) in the ratio 53 : 26: 21.

The foams of the invention have an increased compressive strength. Thus, the bulk density of the foam according to the invention can be further lowered in future than with conventional foams. Another advantage is a good curing of the edge zone of the foam. After only a short demolding time, the foam is firm and less soft and deformable than in the comparative formulations. This brings advantages in the handling of the freshly produced foam.

Claims

claims

1 . Particles containing polyurethane foams, characterized in that the particles are incorporated predominantly in the cell walls, wherein the particles are polymers of olefinically unsaturated monomers or inorganic particles and the surface of the particles has been modified by surface-active substances.

2. Foam according to claim 1, characterized in that the surface-active substances polyether siloxanes, the at least one side chain with at least one

Have hydroxyl group are.

3. A process for the preparation of rigid polyurethane foams by reacting a) polyisocyanates with b) compounds having at least two isocyanate-reactive hydrogen atoms in the presence of c) blowing agents, characterized in that at least one of the components a) or b) contains particles whose Surface was modified by surface-active substances.

4. The method according to claim 3, characterized in that polyether siloxanes having at least one side chain with at least one hydroxyl group are used as surfactants.

5. The method according to claim 3 or 4, characterized in that the particles are contained in the component b).

6. The method according to any one of claims 3 to 5, characterized in that component b) contains at least one particle-containing polyether alcohol bi) having at least two isocyanate-reactive hydrogen atoms, which by in situ polymerization of olefinically unsaturated monomers in a polyether alcohol wherein at least one of the monomers contains an olefinically unsaturated bond and a surface-active group.

7. The method according to any one of claims 3 to 6, characterized in that the component b) contains at least one particle-containing polyether alcohol bi) having at least two isocyanate-reactive hydrogen atoms, by in situ polymerization of olefinically unsaturated monomers in a polyether alcohol manufactured was prepared, wherein the graft particles are modified after their preparation by reaction with a surface-active component.

Method according to one of claims 3 to 7, characterized in that component b) contains at least one further polyol bii).

Method according to one of claims 3 to 8, characterized in that the polyol bi) or bii) contains a aliphatic amine started polyether alcohol bii2).

Method according to one of claims 3 to 8, characterized in that the polyol bi) or bii) contains a starting with an aromatic amine polyether alcohol bii3).

Method according to one of claims 3 to 8, characterized in that the polyol bi) or bii) contains a started with a sugar polyether alcohol bii4).

Method according to one of claims 3 to 8, characterized in that the polyol bi) or bii) contains a trihydric alcohol started polyether alcohol bii5).

A process according to any one of claims 3 to 8, characterized in that the polyol bi) or bii) contains a polyether alcohol bii6) started with a difunctional alcohol.

Method according to one of claims 3 to 13, characterized in that compound b) contains at least one polyol bii4) and at least one polyol bi1) and / or bii2).

Particle-containing polyether alcohols, preparable by in situ polymerization of ole- finically unsaturated monomers in a polyether alcohol, characterized in that at least one of the olefinically unsaturated monomers has surface-active properties.

A process for preparing particle-containing polyether alcohols by in situ polymerization of olefinically unsaturated monomers in a polyether alcohol, characterized in that at least one of the olefinically unsaturated monomers has surface-active properties.

A process for the preparation of particle-containing polyether alcohols according to claim 15 by in situ polymerization of olefinically unsaturated monomers in a polyether alcohol, characterized in that the preparation is carried out in a semibatch process.