DD210170A3 - RECOVERY OF THE DEFICIENCY OF 4,4'-DIPHENYLMETHANDIISOCYNATE DISTILLATION IN POLYURETHANOUS FUEL SYSTEMS - Google Patents

Abstract

The invention is used in the manufacture of multilayer elements. The aim and object of the invention are to fully utilize the residue of the 4.4'-Diphenylmethandiisocyanatdestillation economically, is used as the isocyanate bottom product of the backbone for the production of rigid polyurethane foam systems with a wide range of applications in particular for the production of multilayer elements.The object is achieved by acting as isocyanate a mixture is used, consisting of the resulting bottom product of the residue and of crude 4.4'-diphenylmethane diisocyanate in ratio 1 to at least 1.5. The mixture has an initial viscosity at 25 degrees C less than 1200 mPas, a relative content of 4,4'-diphenylmethane diisocyanate greater than 40%, and a relative content of APA structures less than 22%. The bottoms product has a viscosity at 25 degrees C less than 10000mPas, a relative content of 4.4'-diphenylmethane diisocyanate greater than 35% and a relative content of APA structures less than 55%.

Description

Title of the invention

Recovery of the residue of the 4J4 ^f -Diphenylmethandiisocyanatdestillation in rigid polyurethane foam systems

Field of application of the invention

The invention relates to the utilization of the residue of the 4,4-diphenylmethane diisocyanate distillation in rigid polyurethane foam systems which are suitable for the production of multilayer elements with rigid or flexible cover layers and a core of rigid polyurethane foam.

Characteristic of the known technical solutions

The polyisocyanate mixture obtainable by phosgenation of the condensation products of aniline W and formaldehyde, referred to below as crude MDI in the following polyisocyanate, contains, in addition to the 4,4'-diphenylmethane diisocyanate, also higher condensed compounds. Since pure 4o4'-diphenylmethane diisocyanate is necessary for certain types of polyurethane, the crude polyisocyanate based MDI is subjected to a distillation process · Usually, the distillation is carried out in vacuo with temperatures of more than 250 ⁰ G are ultimately used in the course of this distillation Polyisocyanate based on crude MDI distilled off as much 4 »4'-diphenylmethane diisocyanate as is technically possible and economically justifiable · The bottom product resulting from the distillation process becomes solid during cooling because on the one hand the high molecular weight compounds accumulate on the other

12J0M932 * O2i9Sl

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Effect of the relatively high temperatures, further high molecular weight compounds are formed. This solid residue is usually burned.

A number of papers deal with the economic use of this distillation printing stock. In principle, as described in DE-OS 2 532 384, the HCO-Gruppenhaluge residue can be dissolved in suitable solvents. These solutions can be used as crosslinking component for the preparation of rigid polyurethane foams. According to the invention, the distillation of 4-octoxy-2-olefluorocarbons which are used in the preparation of polyurethane foams as blowing agents is also achieved by distillation of ICO group-containing distillation residues "4 ^{I" -} diphenylmethane diisocyanate residue can be used, in the Ausführungsbe! Play only the use of the residue of toluene diisocyanate distillation described '' A reworking of the invention shows a much poorer solubility of the residue of 4 * 4 '* diphenylmethane diisocyanate distillation in the relatively low-boiling halogeno-fluorohydrocarbons. Using trichlorofluoromethane only a small part of the residue can be dissolved. The use of these solutions as isocyanate component in rigid polyurethane foam systems leads to extremely brittle foams. The adhesive strength of these foams to cover layers is low. Therefore, such foams can only be used as low-stressed insulating material.

laughing DE-OS 2,544,567 is digested the residue of 4 »4 ¹ -Biphenylaiethandiisocyanat distillation at elevated temperature with alkaline reacting substances. The resulting amino group-containing product is alkoxylated in a further process step. The polyether alcohols obtained are used as polyol components in rigid foam systems. The process, however, requires a series of time-consuming stages. Owing to the complexity of this process, the polyether alcohols obtained are As a result, the polyether alcohols produced with this polyether alcohols are also economically unfavorable

Hard foam systems negatively affected in their economics

 Furthermore, polyether alcohols having a very high content of aliphatically bonded nitrogen atoms are obtained by the use of monoethanolamine as a disintegrating agent. Such polyethers have a high catalytic activity on the ITCO-OH reaction. In the course of the reaction, however, the catalytic activity decreases considerably, since the nitrogen atoms are no longer freely mobile as catalytically active centers. As a result, the reaction rate of the rigid polyurethane foam systems produced with these polyether alcohols drops sharply toward the end of polymer formation. These systems have poor curing, ie fresh foams are soft and plastic for a long time. In the continuous production of multi-layer elements only low production speeds are possible and in the discontinuous products long molding residence times are necessary. The production processes become ineffective ·

In DE-OS 2,105,193 a special process for the distillation of 4 »4 ^{t-diphenylmethane} diisocyanate will be described. By a short path distillation at pressures of 10 to 0.1 Pa, a residue is obtained, the viscosity at 25 ⁰ C in the range of 10,000 to 130,000 m, Pas has, so in principle remains liquid "Due to the shorter temperature load in a lower TJmpfang higher molecular weight Compounds The content of residual 4,4'-diphenylmethane diisocyanate is less than 15 %. This product can be used directly as an isocyanate component for the production of rigid polyurethane foam systems. However, the residue produced according to the invention has too high a viscosity to be processed on the usual Verschäummaschinen can Uach an information document from the applicant of DE-OS 2,105,193, the residue of 4,4'-diphenylmethane diisocyanate distillation with a residual content of 15 to 25% 4 "4'-diphenylmethane diisocyanate are supplied to a technical use by dilution with trichlorofluoromethane, by processing at temperatures above 50 ⁰ C, or by admixing üblichea base polyisocyanate of crude MDI,

However, the use of the residue as sole isocyanate component for the production of rigid polyurethane foam systems also leads to very brittle foams. The brittleness is pronounced particularly in the edge zone, so that between the rigid polyurethane foam and foamed cover layers only a small or "no liability exists" The linsatz of mixtures of your DE-OS 2,105,193 prepared residue and conventional Polyisöcyanat base Raw MDI causes a number of problems and thus reduces the possibilities of use. According to the inventors of DB-OS 2,105,193, rigid foam systems produced with a residue-containing isocyanate component have a less favorable flow behavior, and this causes an increase in the foam bulk density of 60%. If similar bulk densities are set, such rigid foams have lower compressive and flexural strength than the conventional rigid foams produced with residue-free polyisocyanate based on crude MDI. In addition, mixtures of the described residue and polyisocyanate base give crude MDI even at relatively low levels Proportions of residue Significant worsening of the minimum Veri zil time of moldings in tools and the adhesion of the foams to cover layers. Another disadvantage of the DE-OS 2,105,193 residues of 4 * 4'-diphenylmethane diisocyanate distillation is their unfavorable behavior during storage · The viscosity of the residue increases within 8 weeks by 100 to 200 % · The mixtures of Residues with polyisocyanates based on crude MDI significantly change their viscosity in accordance with the residue content, so that the limit of processability is exceeded even after a short storage period. Processes for using the residue of the 4.4 ^r- diphenylmethane diisocyanate distillation are known in the prior art.

However, the use of the residue-containing isocyanates prepared by the known processes in rigid foam systems is only limited possible, since the use of these isocyanates always leads to foam systems or rigid foams with reduced utility level · In particular

The use of the residue in the very special polyurethane rigid foam systems for the production of multi-layer elements with a core of rigid polyurethane foam has not hitherto been possible. Multi-layer elements with a core made of rigid polyurethane foam and rigid or flexible cover layers are manufactured on highly productive systems, which have a high level of efficiency In addition, good adhesion between the foam and the cover layer is required to ensure the sandwich character of the multilayer elements. In addition, to ensure the effectiveness of the production, a good hardening of the rigid foam systems is necessary to realize the necessary production speeds. This prerequisite for the production is not guaranteed when the residue is digested and converted to a polyether alcohol ·

The residue of 4.4 ^t * diphenylmethane-distillation can only be found for the production of rigid polyurethane foam systems use who only meet supply functions "This represented technical solutions of the invention does not lead to complete recovery of the residue of 4 _# 4 ^I -Diphenylmethandiisocyanatdestillation according to the prior art , These produced polyurethane foams show insufficient pressure and adhesion, they are not dimensionally stable at 80 ⁰ G and are not suitable for the production of multi-layer element eggu

Object of the invention

The aim of the invention is to utilize the residue of the 4.4'-diphenylmethane diisocyanate distillation completely economically.

Essence of the invention

The object of the invention is to achieve the object, as isocyanate, of the residue obtained in the distillation of 4'-diphene / ^1- methanediisocyanate as bottom product for rigid polyurethane foam systems with great application *

** 6

particular for the production of multilayer elements «

According to the invention the object is achieved in that as isocyanate a mixture is used, consisting of the obtained in the distillative removal of pure 4 »4 ^t -Diphenylmethandiiso- cyanate bottom product and from crude 4» 4'-diphenylmethane diisocyanate in a ratio of 1 to at least 1, It is surprisingly found that the residue of the 4,4'-diphenylmethane diisocyanate distillation is used completely economically if it is used for the production of rigid polyurethane foam systems for the production of multilayer elements only those bottom products are used, the viscosity is at 25 ⁰ C is less 10000 * in.Pas their relative content of 4 »4'-Diphenylmethandiisoeyanat greater than 35%, and their relative content of APA structures does not exceed 55% * The data having these characteristics obtained sump product is 30, while maintaining the mixing ratio according to the invention mixed with conventional polyisocyanate based raw diphenylmethane diisocyanate that the viscosity of the mixture at 25 ^{0 is} less than 1200 m.Pas, the relative content of 4.4'-diphenylmethane diisocyanate greater than 40 % and the relative content of APA structures is less than 22%. The viscosity of the mixture is preferably less than 700 m.Pas at 25 ⁰ G and the relative content of 4 »4 * -Diphenylmethandiisocyanat is preferably in the range of 45 to 55 % ·

When the isocyanate according to the invention is used in polyurethane rigid foam systems for the production of rigid polyurethane foams for multilayer elements, it is possible for the first time to utilize the residue of 4 * 4'-diphenylmethane diisocyanate distillation completely economically. These polyurethane foams harden good, are dimensionally stable at 80 ⁰ G, have good adhesive strength and good compressive strength. They have an insulating and supporting effect ·

The invention will be explained in more detail with the following examples.

embodiments

The content of 4 · 4 ^! -Dlphenylmethandiisocyanat in the bottom product of 4 · 4'-diphenylmethane diisocyanate distillation or »in a mixture. Bottom product polyisocyanate Easily crude biphenylmethane diisocyanate is determined by high pressure liquid chromatography. ♦ The evaluation is made by comparing the area attributed to 4'4 ^f diphenylmethane diisocyanate with the total area

The relative content of APA structures is determined by IR spectroscopy according to the Upjohn test method ITr * 5-68. · APA structures are formed by reaction of a carbodiimide and an isocyanate group with ring closure.

The curing of the systems is determined according to the method described in DD-ViP C 08G / 220.

Embodiment 1

A bottom product of the distillation of 4'4'-D.iphenylmethandiisocyanat with the viscosity of 3.3OG m-Pas at 25 ⁰ C, a relative content of 4 »4 ^f -Diphenylmethandiisocyanat of 44 % and a relative content of APA structures of 41 % is mixed in the ratio of 1 to 3 with raw polyisocyanate based · diisocyanate · Ss result is a polyisocyanate mixture having a viscosity of 550 m.Pas at 25 ⁰ C, a relative content of 4 »4'-diphenylmethane diisocyanate of 48% and a relative APA content of 18% x 60 parts of a polyether alcohol base sucrose / glycerol, OH number 470, 12.4 parts of a polyether alcohol base diethylenetriamine, OH number 470, 8.0 parts of tris-2-chloroethyl phosphate, 0.5 part of a Si-containing cell stabilizer, 1.6 parts of dimethylcyclohexylamine, Q5 parts of water and 17 parts of trichlorofluoromethane are thoroughly mixed together »40 g of this mixture, component A, are weighed into a paper cup, volume of 500 cm. For this purpose, as isocyanate 40 g of the described mixture of the bottom product

and polyisocyanate, based on crude diphenylmethane diisocyanate ,. Component B, given These two mixtures are thoroughly mixed for 10 seconds. It can be determined following reaction data at 20 ⁰ C component temperature: start time: see 19, setting time: 59 see, bulk density of the rigid polyurethane foam in the cup 46 kg / m, Aashärtung measured from 170 lake: 4.2 em »400 g component A and 400 g Component B are mixed thoroughly with one another. The reaction mixture is poured into a tool measuring 400 mm χ 200 mm χ 80 mm, where it is foamed and cured. The following characteristic values are determined on the shaped body obtained:

In a tool measuring 500 mm χ 200 mm χ 40 mm, 10 aluminum sheets measuring 50 mm χ 50 mm are fastened. The mold is heated to 35 ^° C. »180 g of component A and 180 g of component B are thoroughly mixed. The reaction mixture is poured into the open mold and the tool is closed. This results in a shaped body with a Ge · *

• 5

velvet density of 60 kg / m. From this molded article 10 test specimens for the determination of the adhesive strength are announced. After the test of the adhesion the fracture pattern is evaluated.

Gross density, total: 78 kg / irr

Bulk density, core: 56 kg / m

Compressive strength

in the foaming direction. : 0.50 MPa

senkr, z * of foaming:: 0.47 MPa dimensional stability at 80 ⁰ G

Max. Linear expansion: 0.6 % Thermal conductivity: 0.020 W / mK Fire behavior according to TGL 26 247/06: self-extinguishing Adhesive strength in aluminum cover layers with bonding agent: 0.45 ifiuPa

100 % breakage in the foam core

On a double belt machine with a support belt length of 12 m, using the described components A and B in a ratio of 1.0 to 1.0 multi-layer elements with a core

_ Q ".

Made of rigid polyurethane foam and cover layers made of aluminum, 50.mm thick elements can be manufactured at a speed of 4.0 to 4.2 m / min. Elements with the following properties are obtained

Bulk density, core: 44 kg / nr

Compressive strength

perpendicular to the plane of the board: 0.22 MPa Adhesive strength of the foam to the primer coated / coated aluminum facings: 0.20 MPa

Dimensional stability at 80 ^° C.: max. linear expansion 0.5%

Embodiment 2

48.2 parts of a polyether alcohol based on sucrose / glycerol OH number 470, 8.0 parts of a polyether alcohol based on diethylenetriamine OH number 470, 8.0 parts of tris-2-chloroethyl phosphate, 0.5 part of a si-containing cell stabilizer, 1.1 parts Dime thylcyclohexylamin, 0.6 parts of water and 29 parts of trichlorofluoromethane are mixed thoroughly. 40 g of this mixture, component A, are weighed into a paper cup, volume 500 cm, V_j. For this purpose, 40 g of the isocyanate according to the invention described in working example 1, consisting of the bottom product and polyisocyanate based on crude MDI, component B, are added.

Both components are thoroughly mixed for 10 seconds. At component temperatures of 20 ^° C., the following reaction data are determined: starting time 21 sec, setting time 75 sec, gross density of the rigid polyurethane foam in the cup 33 kg / m · curing measured from 240 sec .: 5.7 cm.

300 g of component A and 300 g of component B are mixed thoroughly with one another. The reaction mixture is poured into a tool of dimensions 400 mm × 300 mm × 80 mm, where it foams up and hardens. The following properties are determined on the resulting shaped article:

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Total density: 53 kg / nr

Raw core density: 42 kg / nr

compressive strength

in the foaming direction: 0.27 MPa

perpendicular to the foaming direction: 0.25 MPa

Dimensional stability at 90 ^° C: max. Linear expansion 1,8%

Thermal conductivity: 0.019 W / mK

Fire behavior according to TGL 28 247/06: self-extinguishing

In.ein Stützv / ool the dimensions of 2000 mm χ 1000 mm χ 50 mm aluminum surface layers coated with bonding agent, inserted · The mold temperature is 35 ⁰ C. With a Hiederdruckverschäummaschine the component A and B are metered to 1 in the ratio 1, mixed and into the tool, which is tilted at 15 ° from the horizontal, cast after a 3-second-continuous-time of 25 minutes, the meixr-shell element is removed from the tool.

The following characteristic values are determined on the multilayer elements:

Mean value ¹ ^ range ² ^ gross density, total: 55 kg / nr

Bulk density, core: 45 kg / m ³ 43-48 kg / m ³

compressive strength

vertical z. Plate plane: 0.29 MPa. 0.27-0.31 MPa

in plate plane ·: 0.29 MPa 0.26-0.31 MPa

Adhesive strength: 0.26 MPa 0.21-0.36 MPa

Dimensional stability at 90 ^° C .; max, linear expansion 3.1 %

1) Average of the individual values from different sampling areas

2) Scattering of the individual values from different sampling

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Embodiment 3

The bottom product of the distillation of 4 »4 ^f -Diphenylinethan- diisocyanate according to Embodiment 1 will in 1 ratio. 2 polyisocyanate-based crude 4 * 4'-diphenyl diisocyanate mixed thiisocyanate · The result is a polyisocyanate mixture having a viscosity of 700 m.Pas at 25 ⁰ C, a relative content of 4 · 4'-diphenylmethane diisocyanate of 47 % and a relative Content of APA structures of 20%

 Analogously to exemplary embodiment 1, the reaction data are determined using the written component A and the body is manufactured to determine the foam properties. The following characteristic values are determined:

start time

setting time

Bulk density, cup

curing

Bulk density, shaped body total

19 see 61 see 47 kg / m ³ 3.2 cm 81 kg / m ³

Compressive strength

in the foaming direction;

· senkr to the foaming dimensional stability at 90 ⁰ C;

Thermal conductivity:

Fire behavior according to TGL 28 247/06: Adhesion to aluminum cover layers with adhesion promoter;

0.53 MPa Q> 48 MPa mas. Linear expansion 0.3% 0.020 W / mK self-extinguishing

0.45 MPa 100% break in the foam core

Exemplary embodiment 4

The bottom product of the distillation of 4 · 4'-diphenylmethane diisocyanate according to Example 1 is mixed in the ratio 1: 5 with polyisocyanate, based on crude 4 * 4'-diphenylmethane

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diisocyanate, mixed. The result is a polyisocyanate mixture having a viscosity of 370 nuPas at 25 ⁰ G, a relative content of 4,4'-Dipheny! Methandiisocyanat of 49 % and a relative content of APA structures of 15 % · Analogously to Example 1 using the described Component A determines the reaction data and prepared the IJOrmkörper to determine the polyurethane foam material properties. The following characteristics are determined:

start time

setting time

Bulk density, cup

curing

Bulk density, shaped body total

Bulk density, foam core

Compressive strength

in the foaming direction:

vertical, foaming direction:

Dimensional stability at 90 ^° C.:

Thermal conductivity:

Fire behavior according to TGL 28 247/06:

Adhesive strength on aluminum cover layers with adhesion promoter:

18 seconds 57 seconds 47 kg / m ³ 4.4 cm 81 kg / m ³ 62 kg / m ³

0.50 MPa 0.45 MPa max. linear expansion 0.8 % 0.020 W / mK self-extinguishing

0.38 MPa 100 % break in the foam core

Embodiment 5

Sin bottom product of the distillation of 4 »4 ⁱ -Diphenylmethandiisocyanat with a viscosity 5500 m.Pas at 25 ⁰ C, a relative content of 4» 4 ^f -Diphenylmethandiisocyanat of 39 % and a relative APA content of 52%, is in the ratio 1 to 4.0 with polyisocyanate, based on crude 4.4 ¹ -Diphenylmethandiisooyanat mixed. The resulting isocyanate mixture has a viscosity of 950 nwPas at 25 ⁰ C, a relative content of 4 »4 ^t -2iphenylmethandiisocyanat of 47 % and a relative content of APA structures of 20 % ₉

~ 13 -

Analogously to Example 1, the reaction data are determined using the described component A, as well as the moldings for determining the foam characteristics produced. The following characteristic values are determined:

Start time i ί 20 sec r Setting time; ί 59 sec Bulk density, cup: , 49 kg / m ³ curing : 4.5 cm Bulk density, shaped body total 82 kg / m ³ Bulk density, core: ί 60 kg / m ³ Compressive strength in the foaming direction ; 0.57 MPa Vert. z · foaming direction : 0.53 MPa Diinensionsstabilität at 90 ⁰ C , max, linear exp 1.2% thermal conductivity ί 0.020 W / mK Fire behavior according to TGI 28 247 / 06j ί self-extinguishing Adhesion to aluminum Cover layers with adhesion promoter : 34 m.Pa Break-70 % foam core 30 % border zone

Embodiment 6

The bottom product of the distillation of 4 »4 ^I diphenylmethane diisocyanate having a viscosity of 1,200 m.Pas at 25 ⁰ C ,. a relative content of 4,4'-diphenylmethane diisocyanate of 50 % and a relative content of APA structures of 37% is mixed in a ratio of 1 to 3 with a polyisocyanate, based on crude 4,4'-diphenylmethane diisocyanate. The resulting isocyanate-mixture has a viscosity of 270 m.Pas at 25 ⁰ C, a relative content of 4,4'-Dipheny! Diisocyanate of 50% and a relative content of APA structures of 13% · Analog Embodiment 1, by using the described component A, the reaction data and the

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Formed body for determining the polyurethane hard material properties, the following characteristics are determined:

start time

setting time

Bulk density, cup

curing

Bulk density, moldings total raw material, Sc ha ums t off core compressive strength

in foaming:

senkr, z, foaming direction

Dimensional stability at 90 ^° C.:

Thermal conductivity:

Fire behavior according to TGL 28 247/06: Adhesion to aluminum cover layers with adhesion promoter:

18 see

56 see 46 kg / m ³ 3,7 cm 82 kg / m ³ 61 kg / m ³

0.53 MPa 0.50 MPa max »linear expansion 0.7 % 0.020 W / mK self-extinguishing

0.48 MPa 100% break in the foam core

Comparative Example 1

The bottom product of the distillation of 4o4 ^r -Diphenylmethandiisocyanat according to embodiment 1 is mixed in a ratio of 1 to 1 with polyisocyanate-based crude 4 * 4 * -Diphenylmethandiisocyanat. The result is a polyisocyanate mixture having a viscosity of 1700 m.Pas at 25 ⁰ G, a relative content of 4 "4 * -Diphenylmethandiisocyanat of 46 % and a relative content of APA structures of 23 % * Analog embodiment 1 are using described the reaction data of the described component A and the shaped bodies for determining the foam properties produced · Bs the following characteristics are determined:

Start time setting time

density

: 21 see: 59 see: 50 kg / in ³

- 15 -

Curing: 6,6 cm

Bulk density, total body: 83 kg / nr

• 3

Bulk density, foam core: 62 kg / m compressive strength

in the foaming direction: 0.57 MPa

vertical to the foaming direction: 0.42 MPa

Dimensional stability at 90 ^° C: max. linear expansion 2.2 %

Thermal conductivity: 0.020 W / mK

Fire behavior according to TGI 28 247/06: self-extinguishing Adhesion to aluminum coatings with adhesion promoter: 0.07 MPa

Break 100% edge zone

When processing the polyurethane rigid foam system on the usual Hiederdrtickverschäummaschinen problems arise in the 'dosing and' mixing of the components · The resulting foam is large-celled and shows significant mixing errors.

Comparative Example 2

Am sump product of the distillation of 4 «4. ^{t-diphenylmethane} diisocyanate having a viscosity of 12, 000 Nupas at 25 ⁰ C, a relative content of 4 · 4'-diphenylmethane diisocyanate of 36% and a relative content of APA structures of 56% is in the ratio 1 za 2 with a polyisocyanate based on mixed crude 4 · 4'-diphenylmethane diisocyanate · The resulting isocyanate mixture has a viscosity of 3200 Nupas, a relative content of 4 * 4 ^f diphenylmethane diisocyanate of 46% and a relative content of APA structures of 25% · analog embodiment 1 the seaction data are determined using the component A which has been described and the shaped bodies are produced to determine the foam characteristic values. The following characteristic values are determined:

Start time 21 see

Setting time 57 see

»16«

Bulk density, cup : 50 kg / m ³ curing : 5.2 cm Bulk density, shaped body total : 82 kg / m ³ Bulk density, foam core : 58 kg / m ³ Compressive strength in the foaming direction : 0.50 MPa vertical, to the viewing direction : 0.41 MPa Dimensional stability at 90 ^° C. : max, linear off elongation 2.7 % thermal conductivity : 0.019 W / mK

Fire behavior according to TGI ₁ 28 247/06: self-extinguishing ν adhesion to aluminum ·

topcoats with primer: no adhesion, cover *

layers dissolve with a brittle foaming hair *

The system can not be processed with the usual polyurethane spreader because the problems with the metering and mixing of the components are unmanageable. The isocyanate component is not stable in storage. Its viscosity is doubled within 3 weeks.

Comparative Example 3

"j Sin bottom product, which solidifies at room temperature, is in the ratio of 1 to S at elevated temperature with polyisocyanate, crude base 4 x 4 * diphenylmethane diisocyanate mixed. The mixture has a viscosity of 350 m.Pas, a relative content of 4 · 4 * -Diphenylmethandiisocyanat of 48% and a relative content of APA structures of 14 % * Analogously to Example 1 using the described component A, the reaction data are determined and the moldings for determining the foam characteristics produced · The following characteristics are determined:

Start time 17 see

Setting time 54 see

Bulk density, cup 48 kg / m ³

- 17 -

Curing:

Bulk density, shaped body:

Bulk density, foam core: compressive strength

in the foaming direction:

vertical z · foaming direction:

Dimensional stability at 90 ^° C.:

Thermal conductivity: Fire behavior according to TGL 28 247/06: Adhesion to aluminum «-

Cover layers with adhesion promoter:

5.1 cm 84 kg / m ³ 66 kg / m ³

0.59 MPa 0.55 MPa max · linear elongation 3 »5 % 0.020 W / mK self-extinguishing

0.09 MPa fraction 100% marginal zone

Comparative Example 4

A commercial polyisocyanate based crude 4 "4 ^{t-diphenylmethane} diisocyanate, having a viscosity of 210 m.Pas at 25 a relative content of 4 * 4 ^f -Diphenylmethandiisoeyanat of 44% and a relative content of APA structures of 8.5% ₉ is implemented according to Embodiment 1 with the described component A. The following reaction data and the foam characteristics are determined in an analogous manner:

start time

setting time

Bulk density, cup

curing

Bulk density, shaped body total

Raw density foam core

Compressive strength

in the foaming direction

Vert. to the foaming dimensional stability at 90 ⁰ C

thermal conductivity

see lake

kg / m ³ 4,7 cm kg / m ³ kg / m ³

0.50 MPa 0.45 MPa max. linear expansion 1.2 % 0.020 W / mK

Fire behavior according to TGL 26247/06: self-extinguishing

- 18 -

- * 18 -

Adhesion to aluminum

Cover layers with adhesion promoter: 0.35 MPa

100 % breakage in the scarf core

Analogously to exemplary embodiment 1, the system is processed on the double belt system for the production of multilayer elements with aluminum cover layers. The operating speed of the plant is 50 mm thick elements in the range of 3.8 to 4.0 m / min ·· ^ί 1ϋϋerer elements obtained with the following properties:

Bulk density, core: 43 kg / nr

Compressive strength

perpendicular to the plate plane: 0.22 MPa Adhesive strength of the foam: on the outer layers: 0.18 MPa

Dimensional stability at 80 ^° C.: max. linear expansion 0.7 %

Claims (2)

~ 19 - Brfind claims 1. utilization of the residue of the 4 · 4'-Biphenylmethandiisocyanatdestillation in rigid polyurethane foam systems, characterized in that the isocyanate for Polyurethanhartscha taustoffsysteme for the production of multilayer elements, a mixture is used, consisting of the obtained in the distillative separation of pure 4a4 ^t wDiphenylmethandiisocyanat bottom product and of crude 4 '4 ^{I-diphenylmethane} diisocyanate in a ratio of 1 to at least 1.5, wherein the mixture has an initial viscosity at 25 ⁰ C is less rruPas 1200, a relative content of 4J4 ^{t-diphenylmethane} diisocyanate of more than 40%, and a * rela tive content of APA · Structures of less than 22 % and the bottom product has a viscosity at 25 ⁰ G smaller than 10000 m. Pas, a relative content of 4 ^»f 4-diphenylmethane diisocyanate of more than 35% and a relative content of APA structures smaller than 55% having" 2 * utilization of the residue of the 4 · 4'-Diphenylmethandiisocyanatdestillation in rigid polyurethane foam systems according to item 1, characterized in that the bottom product and the crude 4o4'-diphenylmethane diisocyanate is preferably mixed in the range of 1 to 2 to 1 to 10, the vis- viscosity of Mixture is preferably less than 700 m.Pas at 25 ⁰ G and the relative content of 4,4'-diphenylmethane diisocyanate is preferably in the range of 45 % to 55 % »