WO2010022895A1

WO2010022895A1 - Viscoelastic rigid polyurethane and polyisocyanurate foams

Info

Publication number: WO2010022895A1
Application number: PCT/EP2009/006061
Authority: WO
Inventors: Stephanie Vogel; Klaus Gerke
Original assignee: Bayer Materialscience Ag
Priority date: 2008-08-27
Filing date: 2009-08-17
Publication date: 2010-03-04

Abstract

The present invention relates to rigid polyurethane and polyisocyanurate foams comprising 5.0 to 20.0% by weight of hollow microbeads based on the total weight of the foam, to methods of producing them, and to their use for producing elements of wind turbines, motor vehicles and sports equipment, for insulating appliances, especially household appliances, for producing insulating boards and for use as modelling foam.

Description

Viscoelastic polyurethane and Polyisocvanurat rigid foams

The present invention relates to rigid polyurethane and polyisocyanurate foams comprising from 5.0 to 20.0% by weight of hollow microspheres based on the total weight of the foam, to processes for their preparation, and to their use for producing elements of wind turbines, automobiles and sports equipment, for the insulation of equipment, in particular household appliances, for the production of insulation boards and for use as a model building foam.

Rigid foams are known in the art and find their application in heat insulation materials, as sound insulation and insulation. The steady and not inconsiderable increase in the cost of starting materials for the production of rigid foams has contributed to the development and use of filling materials, which serve to reduce the deficiencies of the raw materials used. In this context, proposed filler materials are, for example, hollow microspheres.

Polyurethane and Polyisocyanuratschaumstoffe have a relatively high brittleness. Therefore, their use in the field of wind turbines is critical, since very good dynamic mechanical properties such as shear, tensile, bending and compressive strength and thus a certain toughness and viscoelasticity is imperative for these purposes.

Therefore, it is an object of the present invention to provide rigid polyurethane and polyisocyanurate foams which have the usual advantageous mechanical properties and at the same time do not become brittle at a certain load but have increased toughness and viscoelasticity.

Another object of the present invention is to provide rigid polyurethane and polyisocyanurate foams having good heat insulating properties. In particular, these foams exhibit a k-factor in the range 20 to 25 mWm ^'K' ".

Another object of the present invention is to provide rigid polyurethane and polyisocyanurate foams whose heat-insulating properties remain unchanged over an extended period of time.

It is also an object of the present invention to provide rigid polyurethane and polyisocyanurate foams having high compressive strength while retaining the usual advantageous mechanical properties of polyurethane and polyisocyanurate foams. The foregoing objects have been achieved by providing a rigid polyurethane and polyisocyanurate foam having a bimodal cell size distribution comprising 5.0 to 20.0 weight percent microballoons based on the total weight of the foam.

The polyurethane and polyisocyanurate foams according to the invention show improved heat-insulating properties and a considerably increased dimensional stability. In addition, the foams according to the invention have viscoelastic properties.

According to DIN 53423, the foams preferably have a modulus of elasticity of 1.5 to 3.5 MPa in the foaming direction and a modulus of elasticity of 7.0 to 10.0 MPa perpendicular to the foaming direction.

The foams in the foaming direction according to DEST 53423 particularly preferably have a modulus of elasticity of from 2.0 to 3.0 MPa. Particularly preferably, the foams perpendicular to the foaming direction according to DIN 53423 have a modulus of elasticity of 8.0 to 9.0 MPa.

The foam according to the invention preferably comprises 6.0 to 10.0% by weight of hollow microspheres, based on the total weight of the foam. The proportion of hollow microspheres used depends on the desired properties such as heat-insulating properties, viscoelastic properties and compressive strength. The hollow microspheres can be added directly to a foam formulation as a solid additive.

The hard polyurethane and polyisocyanurate foams according to the invention exhibit a bimodal cell size distribution in which the mean diameter of the hollow microspheres present in the finished foam differs by at least one to two orders of magnitude from that of the foamed matrix. Preferably, the hollow microspheres have an average diameter in the range of 6 to 45 microns, more preferably in the range of 8 to 20 microns. Preferably, the cells of the foam have an average diameter in the range of 80 to 350 microns, preferably in the range of 110 to 250 microns.

The hollow microspheres are preferably selected from the group consisting of hollow thermoplastic microspheres, hollow glass microspheres and glass ceramic microspheres.

Examples of glass or glass-ceramic microspheres are the commercially available Z-Lite W-1000 hollow microspheres from Zeelan Industries and Scotchlite from 3M and CEL 300 and 650 from PQ Corporation.

Preference is given to the use of thermoplastic hollow microspheres. The thermoplastic hollow microspheres used herein are known to those skilled in the art and commercially available under the product name Expancel (Akzo Nobel) from Schönox GmbH (Essen Germany). These are hollow microspheres whose shell is based on a copolymer consists of acrylonitrile and the cavity is filled with a propellant gas. As a rule, the unexpanded hollow microspheres have a diameter of 6 to 45 μm and a density of 1000 to 1300 kg / m ³ . The propellants are typically volatile hydrocarbons such as butane, pentane, hexane, heptane, isobutene, isopentane, neopentane, cyclobutane, cyclobutane and cyclopropane. If necessary, these hollow spheres can be made and filled with any other low-boiling solvents. If the hollow microspheres are heated, the gas increases the internal pressure, the polymer layer softens and the expansion process begins. Upon complete expansion, the hollow microsphere has increased its diameter three to four times its original diameter and increased its volume by more than forty times its original volume. The density is <30 kg / m ³ after the expansion process. The expansion temperatures are generally in the range between 80 and 190 ^° C. After cooling, the thermoplastic material solidifies again, so that the expanded volume is retained.

The polyurethane and polyisocyanurate foam according to the invention is advantageously closed-cell. Particularly preferred is a proportion of <10% open cells, since this can improve the heat insulating properties. The proportion of open and closed cells is determined using a pycnometer (AccuPyc 1330, Micromeritics GmbH, Mönchengladbach, Germany) according to the principle of gas phase displacement.

Preferably, a foam according to the present invention directly after its production, a by 0.3 to 1.0 mWm ^'' K ^'' has reduced, more preferably is reduced by 0.4 to 0.8 mWm 'K ^"1 thermal conductivity. After 30 days, has an inventive foam relative to a foam without hollow microspheres preferably by 0.8 to 2.0 HiWm reduced ^-1 K ^"1, more preferably reduced to 1.0 to 1.4 mWm ^{'K' 1} thermal conductivity.

The cells of the foam preferably have an average diameter in the range from 80 to 350 μm, particularly preferably in the range from 110 to 250 μm. This was determined by means of digital image analysis of five light microscopic images on thin sections of the various rigid foam samples. Only those cells were counted manually, which were clearly defined as such. For each sample at least 500 cells were evaluated according to their diameter.

Preferably, the foam of the present invention exhibits a bimodal cell size distribution in that the average diameter of the hollow microspheres embedded as a filler is smaller by 1 to 2 orders of magnitude than that of the foam matrix (Figure 1). In contrast, Fig. 2 shows the cell size distribution of a classic rigid polyurethane foam in a light micrograph. The production of rigid foams of the present invention is known and has been described, for example, in German Offenlegungsschriften DE 1,694,142, DE 1,694,215 and DE 1,720,768 as well as in Kunststoff-Handbuch, Volume VII, Polyurethane, Vieweg and Hochtlen (ed.), Carl Hanser Verlag, Munich (1966) and in the more recent edition of this volume, edited by G. Oertel, Carl Hanser Verlag, Munich, Vienna (1983).

These foams are mainly those which contain urethane and / or isocyanurate and / or allophanate and / or uretdione and / or urea and / or carbodiimide groups. The following may be used to prepare the isocyanate-based bimodal foams using the hollow microspheres of the present invention:

As starting components are aliphatic, cycloaliphatic, araliphatic, aromatic and heterocyclic polyisocyanates, such as those described by W. Siefken in Justus Liebigs Annalen der Chemie 562, pp. 75-136, e.g. those of the formula

Q (NCO) _n

wherein n = 2-4, preferably 2-3 and Q is an aliphatic hydrocarbon radical having 2-18, preferably 6-10 carbon atoms, a cycloaliphatic hydrocarbon radical having 4-15, preferably 5-10 carbon atoms, an aromatic hydrocarbon radical having 6-15 , preferably 6-13 carbon atoms or an araliphatic hydrocarbon radical having 8-15, preferably 8-13 carbon atoms, such as polyisocyanates, which are described in DE-OS 2,832,253, p 10-11, suitable.

Particularly preferred are usually those polyisocyanates which are technically readily available, such as 2,4- and 2,6-toluene diisocyanate (TDI) and mixtures of these isomers. Polyphenyl polymethylene polyisocyanates, such as e.g. those obtained by aniline-formaldehyde condensation and subsequent treatment with phosgene (crude MDI) and polyisocyanates containing carbodiimide, urethane, allophanate, isocyanurate, urea or biuret groups (modified polyisocyanates), in particular those modified polyisocyanates derived from 2,4- and / or 2,6-toluene diisocyanate and from 4,4'- and / or 2,4'-diphenylmethane diisocyanate.

The starting components may also be compounds having a molecular weight of usually 400 to 10,000, which contain at least two hydrogen atoms and are reactive towards isocyanates. In addition to compounds having amino, thio or carboxyl groups, this preferably comprises compounds having hydroxyl groups, especially those containing one Molecular weight of 1000 to 6000 g / mol, preferably 2000 to 6000 g / mol such as polyether and polyester and polycarbonates and polyester amides having at least 2, usually 2 to 8, preferably 2 to 6 hydroxyl groups. The use of these compounds for the preparation of homogeneous and cellular polyurethanes is known per se and disclosed for example in DE-OS 2,832,253, pp. 11-18.

In some cases, compounds having at least two isocyanate-reactive hydrogen atoms and having a molecular weight of from 32 to 399 can also be used as further starting components. In this case, compounds having hydroxyl groups and / or amino groups and / or thiol groups and / or carboxyl groups, preferably compounds having hydroxyl groups and / or amino groups, are understood to mean those which are used as chain extenders or crosslinkers. These compounds usually have 2 to 8, preferably 2 to 4, hydrogen atoms which are reactive toward isocyanates. Suitable examples are disclosed in DEG-OS 2,832,253, pages 19-20.

The blowing agents used in connection with the present invention may include both chemical blowing agents such as water and / or physical blowing agents in the form of volatile organic or inorganic substances and other volatile blowing agents typically used to foam PUR / PIR. Foams are used. Organic leavening agents include acetone, ethyl acetate, halo-substituted alkanes such as methylene chloride, chloroform, ethylene chloride, vinylidene chloride, monofluorotrichloromethane, chlorodifluoromethane, dichlorodifluoromethane, dichlorodifluoroethane, dichlorotrifluoroethane; also butane, pentane, hexane, heptane or diethyl ether. Specific examples of such blowing agents include: 1,1,1,4,4,4-hexafluorobutane (HFC-356); Tetrafluoroethanes such as 1,1,1,2-tetrafluoroethane (HFC-134a); 1,1,2,3,3-pentafluoropropane (HFC-245ea); 1,1,1,2,3-pentafluoropropane (HFC-245ca) and 1,1,2,2,3,3-hexafluoropropane (HFC-236ca); Nexafluoropropanes such as 1,1,2,2,3,3-hexafluoropropane (HFC-236ca); 1,1,1,2,2,3-hexafluoropropane (HFC-236cb); 1,1,1,2,3,3-hexafluoropropane (HFC-236ea); 1,1,1,3,3,3-hexafluoropropane (HFC-236fa); Pentafluorobutanes such as 1,1,1,3,3-pentafluorobutane (HFC-365) and difluoroethanes such as 1,1-dufluoroethane (HFC-152a). Examples of inorganic blowing agents are air, CO ₂ and N ₂ O. A blowing effect can also be achieved by adding compounds which decompose at temperatures above room temperature and release gases such as azodicarbonamide or azoisobutyronitrile. Further examples of blowing agents can be found in the Plastics Handbook, Volume VE, Polyurethane, Vieweg and Hochtlen (ed.), Carl Hanser Verlag, Munich (1966) on pages 108-109, 453-455 and 507-510. In some cases, other auxiliaries and additives may also be used simultaneously, for example well-known catalysts in amounts of up to 10% by weight, surface-active additives such as emulsifiers and foam stabilizers and reaction retardants such as acidic substances such as hydrochloric acid or halides of organic acids, as well as well-known Cell regulators such as paraffins, fatty alcohols or dimethylpolysiloxanes and pigments or dyes and / or other well-known flame retardants such as Trikre- sylphosphat, stabilizers against aging and weathering, plasticizers, fungicides, bactericides and fillers such as barium sulfate, diatomaceous earth, carbon black or whiting.

Further examples of surface-active additives, foam stabilizers, cell regulators, reaction retarders, stabilizers, flame retardants, plasticizers, dyes, fillers, fungicides and bactericides, which can be used simultaneously in some cases, as well as details regarding the use and effect of these additives are for example on S 103-113 of the Plastics Handbook, Volume VII, Polyurethane, Vieweg and Hochtlen (ed.), Carl Hanser Verlag, Munich (1966).

The proportion of the blowing agent in relation to the weight of the entire foam formulation is preferably in the range from 0.1 to 5.0% by weight, more preferably in the range from 1.0 to 5.0% by weight, most preferably in the range from 2.0 to 4.0% by weight.

The density of the hard polyurethane / polyisocyanurate foams according to the invention is preferably in the range between 20 and 80 kg / m ³ , particularly preferably in the range between 25 and 65 kg / m ³ , very particularly preferably in the range between 28 and 35 kg / m ³ .

The foams according to the invention can be prepared by methods known to the person skilled in the art. For example, the reactants are reacted by a well-known one step process, the prepolymer or semi-prepolymer process, often using engineering equipment disclosed in US Patent 2,764,565. Details relating to the processing plant, which are also relevant with respect to the invention, can be found on pages 121-205 of the Plastics Handbook, Volume VE, Polyurethane, Vieweg and Hochtlen / hrsg), Carl Hanser Verlag, Munich 1966) , The hollow microspheres are hereby fed to the polyol formulation immediately prior to the addition of the isocyanate component as a solid filler. This processing method offers the advantage that the processability of the microballoon-containing formulations is easier compared to the prior art due to the low filler content required and the fact that only unexpanded material is used, and in contrast, no adaptation or modification of generally conventional formulations. Chen plants for the production of hard polyurethane and Polyisocyanuratschäumen is required.

The hollow microspheres used for the purposes of the invention are used as a free-flowing solid in completely unexpanded form (DE quality of the manufacturer, DE being "dry unexpanded") In this context, "completely unexpanded" means that the hollow microspheres are used without further work-up step without having previously been dispersed in a polyurethane raw material and / or expanded.

Thermoplastic hollow microspheres consist of a shell of a thermoplastic polymer which includes a blowing agent. It has now surprisingly been found that the exothermic nature of a polyurethane or a combined polyurethane and polyisocyanurate reaction is sufficient to cause expansion of the hollow thermoplastic microspheres in situ during the foaming process. Neither does the expansion of the hollow microspheres due to the rapid setting of the PUR-ZPIR matrix nor the PUR / PIR reactions adversely affect the expansion of the blowing agent-containing thermoplastic hollow microspheres.

The polyurethane-Polyisocyanuratschäume invention are suitable for the production of elements of wind turbines, automobiles and sports equipment, for the isolation of equipment, in particular household appliances, for the production of insulation boards and for use as a model foam.

Description of the drawings

Fig. 1 REM-Aufhahmen a rigid polyurethane foam, embedded in the matrix thermoplastic microspheres.

Fig. 2 light micrographs of a standard rigid polyurethane foam.

Examples Example 1:

A hard polyurethane product having a bulk density of 32 kg / m ^{3 and} serving as a comparison was obtained by mixing the following substances: a) 100 parts by weight. Polyol / b) 2.4 parts by weight. Stabilizer, ² c) 1.4 parts by weight. Water, d) 18 parts by weight. Tris (2-chloroisopropyl) phosphate, e) 2.5 parts by weight. Cyclohexyldimethylamine, f) 16 parts by weight. n-pentane g) 195 parts by weight. polymeric MDI /

'Baymer VP.PU 29HB40 (Bayer MaterialScience AG, Leverkusen, Germany)

² Tegostab B8421 (Evonik Goldschmidt GmbH, Essen, Germany)

³ Desmodur ^® 44V40L (Bayer MaterialScience AG, Leverkusen, Germany)

Example 2:

A hard polyurethane product according to the present invention having a bulk density of 32 kg / m ³ and containing 8.2% by weight thermoplastic hollow microspheres was obtained by mixing the following substances: a) 30 parts by weight. thermoplastic hollow microspheres ⁷ , b) 100 parts by weight. Polyol, ² c) 2.4 parts by weight. Stabilizer, ⁵ d) 1.5 parts by weight. Water, e) 18 parts by weight. Tris- (2-chloroisopropyl) phosphate, f) 2.7 parts by weight. Cyclohexyldimethylamine, g) 12 parts by weight. n-pentane h) 198 parts by weight. polymeric MDI /

'Expancel 053 DU 40 (Schönox GmbH, Essen, Germany) ^ Baymer VP.PU 29HB40 (Bayer MaterialScience AG, Leverkusen, Germany)

³ Tegostab B8421 (Evonik Goldschmidt GmbH, Essen, Germany)

⁴ Desmodur ^® 44V40L (Bayer MaterialScience AG, Leverkusen, Germany)

Example micro hollow sphere bulk density k-factor E _B3 ^α E _d ^fc E, ^c

[kg / m ³ ] [mW m ^~ 1K ^"1 ] [MPa] [MPa] [MPa]

in the foaming direction: 1 32 20.2 2.5 7.9 2.6 2 053 DU 40 32 19.5 2.8 5.6 3.1

perpendicular to the foaming direction:

1 - 32 4.0 3.3 15.7

2 053 DU 40 32 2.3 19.4

a) E-module DIN 53 423 from three-point bending test. b) E-module DIN EN 826 from compression test. c) E-modulus DIN 53 430 from tensile test. d) not determined.

Claims

claims

1. Hard polyurethane and Polyisocyanuratschäume with a bimodal cell size distribution comprising 5.0 to 20.0 wt .-% hollow microspheres based on the total weight of the foam.

2. Hard polyurethane and Polyisocyanuratschäume according to claim 1, characterized in that the foam comprises 6.0 to 10.0 wt .-% hollow microspheres based on the total weight of the foam.

3. Hard polyurethane and Polyisocyanuratschäume according to claim 1 or 2, characterized in that the hollow microspheres are selected from the group consisting of thermoplastic hollow microspheres, hollow microspheres of glass and hollow microspheres of glass ceramic.

4. Hard polyurethane and Polyisocyanuratschäume according to claim 3, characterized in that the hollow microspheres are thermoplastic hollow microspheres.

5. Hard polyurethane and Polyisocyanuratschäume according to claim 3 or 4, characterized in that the softening temperature of the shell of the thermoplastic hollow microspheres in the range of 80 to 190 ⁰ C, preferably in the range of 80 to 135 ⁰ C.

6. Hard polyurethane and Polyisocyanuratschäume according to one or more of claims 1 to 5, characterized in that the hollow microspheres have an average diameter in the range of 6 to 45 microns, preferably in the range of 8 to 20 microns.

7. Hard polyurethane and Polyisocyanuratschäume according to one or more of claims 1 to 6, characterized in that the foam is closed cell.

8. Hard polyurethane and polyisocyanurate foams according to one or more of claims 1 to 7, characterized in that the cells of the foam have a mean throughput knife in the range of 80 to 350 microns, preferably in the range of 120 to 250 microns have.

9. A process for the preparation of rigid polyurethane and Polyisocyanuratschäume according to one or more of claims 1 to 8, characterized in that the hollow microspheres of the foam formulation are added immediately before the PUR reaction.

10. Use of hard polyurethane and Polyisocyanuratschäume according to one or more of claims 1 to 8 for the production of elements of wind turbines, automobiles and sports equipment, for the isolation of equipment, in particular household appliances, for the production of insulation boards and for use as a model foam.