DE102022106913A1 - Process for liquefying polyurethanes - Google Patents

Abstract

The subject of the present invention is a process for the liquefaction of polyurethanes by aminolysis and the products produced by the process as well as the use of the liquefaction products in the direct cycle for new flexible foams.

Description

The present invention relates to a process for the liquefaction of polyurethanes by aminolysis and the products produced by the process as well as the use of the liquefaction products in the direct cycle for new flexible foams.

The liquefaction of polyurethanes for the purpose of recycling the raw materials from which they were manufactured is known. In particular, glycolysis using various glycols and/or polyols including polyether or polyester alcohols, hydrolysis by splitting using water at high temperature (up to 500 ° C) and high pressure, acidolysis using carboxylic acids, inorganic acids or carboxylic anhydrides, and aminolysis have been used so far , especially used in combination with water or glycols.

Polyurethanes are generally made up of at least one polyol, at least one di- or polyisocyanate, catalysts and possibly additives. In the case of foams, at least one blowing agent is used during production. If water is used as a blowing agent, it preferentially reacts with the isocyanate component and forms urea phases in the polymer structure, which determine the hardness and strength of the “polyurethanes” produced in this way (which are actually poly(urethane-ureas)). The phase sizes and the distribution of the oligoureas according to molecular size are determined by the molar ratio of hydroxyl groups from the polyols to those of the water. In the following, the term oligoureas is used for all ureas formed in this reaction, even if they are often polymers with more than 10 repeating structural units. The oligoureas can therefore have two recurring structural units (e.g. in elastomers) and up to 10,000 recurring structural units (e.g. in flexible block foams).

During hydrolysis, the ureas are generally not split and are separated from the polyol phase in the known processes in order to be used separately, e.g. B. as starter molecules for alkoxylation or for regenerating the diamines originally used to produce the isocyanates.

oder durch eine nucleophile Substitutionsreaktion in Gegenwart der als Nucleophile wirkenden Hydroxylgruppen der Glykole aus den Harnstoffen nach $$\sim \sim {\text{R}}^{\text{1}}\text{NH}-\text{C}\left(\text{O}\right)-\text{NH}-{\text{R}}^1\sim \sim \stackrel{\text{R}-\text{OH}}{\to }2{\text{ NH}}_2-{\text{R}}^1+{\text{CO}}_2$$

During glycolysis, which is usually carried out at temperatures between 200 and 260 ° C, two side reactions take place through which primary aromatic amines are formed from the urethanes and ureas: from the urethanes by thermal cleavage of the urethane group into amine and olefin after $$\sim \sim \text{O}-{\text{Ch}}_2-{\text{Ch}}_2-\text{O}-\text{C}\left(\text{O}\right)-\text{NH}-{\text{R}}^1\stackrel{\Delta }{\to }{\text{CO}}_2+\sim \sim \text{O}-\text{Ch}={\text{Ch}}_2+{\text{NH}}_2-{\text{R}}^1$$

or by a nucleophilic substitution reaction in the presence of the hydroxyl groups of the glycols from the ureas, which act as nucleophiles $$\sim \sim {\text{R}}^{\text{1}}\text{NH}-\text{C}\left(\text{O}\right)-\text{NH}-{\text{R}}^1\sim \sim \stackrel{\text{R}-\text{OH}}{\to }2{\text{NH}}_2-{\text{R}}^1+{\text{CO}}_2$$

During aminolysis, these reactions do not take place due to the lower temperatures possible during the reaction and therefore no additional aromatic amines are formed.

Aminolysis is described in the patent literature. So will after the DE 102006034613 A1 With a weight and stoichiometric amine deficit, two phases are obtained during polyurethane cleavage, which can be separated from each other and then processed into new polyurethane products. Oligopropylenamines with primary and secondary amino groups are used as the cleavage reagent, which are reacted at temperatures between 120 and 200 ° C, with this reaction forming two phases containing polyol and oligo- or polyureas. Homogeneous reaction products are not described.

According to the teachings of EP 1142945 A2 polyurethanes are reacted into a liquid containing the polyol, a urea compound soluble in the polyol, and a urea compound insoluble in the polyol in the presence of a polyamine compound at 120 to 250°C; The solids are then separated off and the residue is hydrolyzed with water at 200 to 300 ° C under high pressure.

The DE 4128588A1 teaches the production of disperse liquids containing hydroxy- and/or amino-functional compounds by reacting polyurethane, polyurethane/polyurea, polyurea waste with at least one diamine compound.

For this purpose, the polyurethane is converted into a mixture of a long-chain polyether alcohol and a diamine, e.g. B. N,N'-diethyl-tolylenediamine, and additional organometallic catalyst and reacted at 160 to 180 ° C with a reaction time of 30 to 120 min. This results in reaction products that can be used again to produce polyurethanes or poly(urethane-ureas).

In the US 3,117,940 A process for the liquefaction of polyurethanes is described in which the reaction medium is exclusively a primary amine, e.g. B. aniline, 2,4-toluenediamine, 1-naphthylamine, o-phenylenediamine etc. and is implemented at temperatures above 70 ° C.

There are no known processes for recycling polyurethanes that produce homogeneous reaction products through aminolysis with a high proportion of polymer material, i.e. H. over 50% by weight of the reaction mixture can be produced. In addition, the previously known processes are carried out at temperatures above 200 ° C with reaction times of up to 10 hours, which corresponds to a high amount of energy, and generally lead to products that are only available in small quantities (5% by weight or less). can be used for the same products, often with deterioration in properties.

The object of the invention is the liquefaction of polyurethanes or polyurethane ureas) by aminolysis, through which homogeneous reaction products with a very low proportion of aromatic diamines are produced in a shorter time when the amine mixture is heavily loaded with the polyurethane products at comparatively low temperatures and are converted back into new, identical or Similar polyurethane or poly(urethane-urea) products as the products originally used are reacted with di- and/or polyisocyanates.

According to the invention, the object is achieved in that the polyurethanes or poly(urethane-ureas) are reacted at a temperature between 40 and 180 ° C in a mixture of amines within a short time in such a way that a homogeneous reaction product is formed, which leads to new identical or Similar polyurethane or poly(urethane-urea) products to the products originally used are reacted with di- and/or polyisocyanates.

1. a) nur sekundären Amin-Gruppen und keinen tertiären Amin-Gruppen;
2. b) einer primären und zumindest einer sekundären Amin-Gruppe und keinen tertiären Amin-Gruppen;
3. c) zwei und mehr primären Amin-Gruppen und zumindest einer sekundären Amin-Gruppe und keine tertiären Amin-Gruppen; und
4. d) zumindest einer tertiäre Amin-Gruppe.

The amine mixture used for this purpose comprises at least two amines, which are selected from: aliphatic, cycloaliphatic or araliphatic

1. a) only secondary amine groups and no tertiary amine groups;
2. b) a primary and at least one secondary amine group and no tertiary amine groups;
3. c) two or more primary amine groups and at least one secondary amine group and no tertiary amine groups; and
4. d) at least one tertiary amine group.

The tertiary amine is in particular a tertiary amine with the tertiary amine group as part of a cycle, or tetra-methylguanidine (TMG). Amine d) is preferably used.

The reaction is carried out in such a way that the polyurethane or poly(urethane urea) product is introduced into the amine mixture and is degraded within 10 minutes to one hour, resulting in a homogeneous reaction mixture with polyols dissolved in the polyurethane forming or dispersed as nanoscale particles Oligoureas are formed.

Furthermore, the reaction is carried out in such a way that the polyurethane or poly(urethane-urea) product, which is based on a so-called polymer polyol, is introduced into the amine mixture at a temperature of 80 to 165 ° C and within 10 minutes up to an hour, forming a homogeneous reaction mixture with oligoureas dissolved in the polyols forming the polyurethane or dispersed as nanoscale particles, the SAN, styrene or polyurea particles used as the polymer in the polymer polyol remaining in their original size and shape remain.

• - für die Temperatur, die zur Umsetzung erforderlich ist,
• - für die Geschwindigkeit der Umsetzung,
• - für die Viskosität des Umsetzungsprodukts,
• - für die Teilchengröße der Oligoharnstoffteilchen und damit ihrer Dispergierbarkeit im Polyol des Polyurethans,
• - für die Teilchengröße der Polymerteilchen und damit ihrer Dispersion im Polyol des Polyurethans,
• - für die Eigenschaften der aus den Dispersionspolyolen hergestellten Poly(urethan-harnstoffe).

It was found that when polyurethanes, polyurethaneureas) or polymer-polyol-based polyurethanes or polyurethaneureas) are reacted in very specific amine mixtures, this reaction leads to dispersion polyols with predeterminable properties. The ratio and type of amines are crucial

• - for the temperature required for implementation,
• - for the speed of implementation,
• - for the viscosity of the reaction product,
• - for the particle size of the oligourea particles and thus their dispersibility in the polyol of the polyurethane,
• - for the particle size of the polymer particles and thus their dispersion in the polyol of the polyurethane,
• - for the properties of the poly(urethane-ureas) produced from the dispersion polyols.

The weight ratio of the amines of the four groups is determined by the polyurethane foam used.

Suitable aliphatic groups are linear or branched C2-C20 groups, suitable cycloaliphatic groups are substituted or unsubstituted cyclohexyl groups or dicyclohexyl or methylenebis(cyclohexyl) groups, suitable araliphatic groups are e.g. B. xylylene, tetramethylxylylene, toluene or mesityl groups.

Suitable amines include, among others
to a) di-n-butylamine, N,N'-diethyl-toluene-2,4/2,6-diamine, N-ethyl-cyclohexylamine, to b) N-ethyl-dicyclohexylmethane-4,4'-diamine, N-propyl-cyclohexane-1,4-diamine, N-ethyl-1,3-xylylenediamine, N-ethyl-1,4-xylylenediamine,
to c) dipropylene triamine, tripropylene tetramine, diethylene triamine, triethylene tetramine, 4-(N-ethylaminomethyl)-octane-1,8-diamine,
to d) triethylenediamine, 1,8-diazabicyclo[5.4.0]undec-7-ene, dimorpholinodiethyl ether, dimethylcyclohexylamine, N,N,N',N'-tetramethylguanidine, bis(2-dimethylaminoethyl)ether, 1,3, 5-Tris-[3-(dimethylamino)propyl]-hexahydro-1,3,5-triazine, N-methyldicyclohexylamine, tris-[3-(dimethylamino)propyl]amine, tetramethyldipropylenetriamine, N,N-bis(2-aminoethyl )methylamine.

The reaction takes place in stirred reactors with heatable and coolable walls at temperatures between 40 and 200 ° C, preferably between 75 and 180 ° C. After the reaction has ended, the reaction products do not require any workup. Essentially no aromatic amines are formed from the polyurethanes during the reaction; any small excess of amine contained therein does not have a detrimental effect on the further reaction.

The dispersion polyols according to the invention are clear to milky, viscous liquids whose viscosity is between 1000 and 20,000 mPas (25 ° C), depending on the amount of foam added. Due to the polyols originally used in the polyurethane or poly(urethane-urea) used, they have hydroxyl numbers between 30 and 500 mg KOH/g. The amine numbers are usually between 5 and 200 mg KOH/g. The particle size of the oligourea particles is determined on the one hand by the preformed oligoureas and on the other hand by the amines used in the amine mixture. For polyurethane cold-formed flexible foams, e.g. B. the maximum particle size was 12 nm (LLD); for flexible polyurethane block foams, several particle size maxima were usually measured, e.g. B. at approx. 45, 160 and 800 nm. The particle size of the polymer particles when using polymer-polyol-based flexible polyurethane foams is between 2000 and 20,000 nm (according to LDD measurement).

By selecting the amines from the respective groups and their relationship to one another, the implementation and properties of the end products as well as the poly(urethane-ureas) produced from them can be controlled within wide limits. By using certain amines, additional properties can also be achieved, e.g. B. Corrosion protection, antifouling, adhesion to substrates, thermal resistance or UV protection. The use of long-chain secondary amines, e.g. B. N-ethyl-N-dodecylamine or N-methyl-N-octadecalamine, the hydrophobicity of the poly(urethane-ureas) produced from them is improved, the use of isophoronediamine increases the UV resistance and in combination with diethylenetriamine and/or N ,N-Bis(3-aminopropyl)methylamine reduces or prevents the formation of biofilms on surfaces.

By selecting the specific amines and their combination, the reactions are generally carried out at temperatures of 150 to 175 ° C and with reaction times of less than one hour. This is not possible given the current state of technology.

The process according to the invention therefore makes it possible for the first time that polyurethanes or poly(urethane-ureas) based on polymer polyols can be implemented in the form of flexible foams in such a way that the polymer particles (usually SAN with melting points around 170 ° C) in their original form and not agglomerated, fused or preserved as a molten phase and can therefore be used again directly.

By reacting with suitable di- and/or polyisocyanates, the reaction products according to the invention are converted directly or after formulation with suitable components into poly(urethane-ureas) as compact materials, as semi-hard, hard or soft foams or cellular elastomers in the Shore A hardness range produced between 45 and 90.

The invention is explained below using examples. These serve only to explain the essence of the invention and do not limit in any way the scope of the invention.

Examples

example 1

Production of an oligourea dispersion polyol from polyurethane cold-molded foam
90.3 g of di-n-butylamine, 6.18 g of diethylenetriamine and 23.58 g of N-ethylcyclohexylamine were added to a 3L glass reactor with a high-speed mechanical stirrer, thermocouple, nitrogen blanket and reflux condenser. The amine mixture was heated to 120°C. While stirring and slowly increasing the temperature to 175 ° C, 650 g of PUR cold molded foam in the form of flakes were added within 3 hours. The mixture was then stirred at 180°C for another 30 minutes. The mixture was cooled to ambient temperature, remaining clear, with a viscosity of 18900 mPas (25°C), a hydroxyl number of 71 mg KOH/g and an amine number of 55 mg KOH/g.

Example 2

Production of an oligourea dispersion polyol from polyurethane cold-molded foam
75 g of di-n-butylamine, 35 g of diethylenetriamine and 15 g of 4-(N-ethylaminomethyl)-1,8-octanediamine were added to a 3L glass reactor with a high-speed mechanical stirrer, thermocouple, nitrogen blanket and reflux condenser. The amine mixture was heated to 120°C. While stirring and slowly increasing the temperature to 175 ° C, 750 g of PUR cold molded foam were added in the form of flakes within 3 hours. The mixture was then stirred at 180°C for another 30 minutes. The mixture was cooled to ambient temperature, remained clear, had a viscosity of 15,400 mPas (25°C), a hydroxyl number of 83 mg KOH/g and an amine number of 61 mg KOH/g.

Example 3

Production of an oligourea dispersion polyol from polyurethane cold-molded foam
23.5 g of 2,2,4-trimethyl-1,6-hexanediamine, 9.3 g of N,N'-dimethylpentane-1, 5-diamine, 16.5 g of N-ethyl-cyclohexylamine and 12.0 g of N,N'-diethylhexane-1,6-diamine were added. The amine mixture was heated to 120°C. While stirring and slowly increasing the temperature to 165 ° C, 750 g of PUR cold molded foam were added in the form of flakes within 3 hours. The mixture was then stirred at 180°C for another 30 minutes. The mixture was cooled to ambient temperature and is a milky, highly viscous liquid.

Example 4

75 g of di-n-butylamine, 18 g of hexatrane (4-(aminomethyl)-octane-1,8-diamine), and 35 g of N were placed in a 3L glass reactor with a high-speed mechanical stirrer, thermocouple, nitrogen blanket and reflux condenser -Ethylcyclohexylamine given. The amine mixture was heated to 120°C. While stirring and slowly increasing the temperature to 165 ° C, 350 g of PUR block flexible foam in the form of Flakes entered within 1.5 hours. The mixture was then stirred at 180°C for another 30 minutes. The mixture was cooled to ambient temperature and was a milky, highly viscous liquid.

Example 5

5 g of di-n-butylamine, 90 g of diethylenetriamine, 1 g of tetramethylguanidine and 25 g of N-ethyl-cyclohexylamine were added to a 3L glass reactor with a high-speed mechanical stirrer, thermocouple, nitrogen blanket and reflux condenser. The amine mixture was heated to 130°C. While stirring and slowly increasing the temperature to 165 ° C, 790 g of viscoelastic PUR soft foam were added in the form of flakes within 1.5 hours. The mixture was then stirred at 170°C for another 30 minutes. The mixture was cooled to ambient temperature and was a milky, highly viscous liquid.

Example 6

5 g of di-n-butylamine, 80 g of diethylenetriamine, 1 g of tetramethylguanidine and 25 g of N-ethyl-cyclohexylamine were added to a 3L glass reactor with a high-speed mechanical stirrer, thermocouple, nitrogen blanket and reflux condenser. The amine mixture was heated to 130°C. The amine mixture was heated to 125°C. While stirring and slowly increasing the temperature to 150 ° C, 650 g of PUR soft foam based on polymer polyol were added in the form of flakes within 1.5 hours. The mixture was then stirred at 165°C for a further 30 minutes. The mixture was cooled to ambient temperature and was a milky, highly viscous liquid. Using laser light scattering, two peaks were determined at 355 nm (oligoureas) and 3700 nm (SAN particles); the viscosity of the reaction mixture was 9810 mPas (25 ° C).

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102006034613 A1 [0007]
• EP 1142945 A2 [0008]
• DE 4128588 A1 [0009]
• US 3117940 [0011]

Claims (12)

Process for the liquefaction of polyurethanes or polyurethane ureas) to obtain liquefied polyurethane products by aminolysis, the polyurethanes or poly(urethane ureas) being degraded at a temperature between 40 and 220 ° C in an amine mixture within 10 minutes to three hours, wherein a homogeneous dispersion, in particular a homogeneous suspension, is formed. Procedure according to Claim 1 , characterized in that amine mixtures comprising at least two amines which are selected from: aliphatic, cycloaliphatic or araliphatic with a) only secondary amine groups and no tertiary amine groups; b) a primary and at least one secondary amine group and no tertiary amine groups; c) two or more primary amine groups and at least one secondary amine group and no tertiary amine groups; and d) at least one tertiary amine group is used and these are introduced into the polyurethanes or poly(urethane-ureas) and break them down within 10 minutes to three hours at temperatures of 80 to 200 ° C, forming a homogeneous dispersion with in Oligoureas dissolved in the polyols forming the polyurethane or dispersed as nanoscale particles are formed. Method according to at least one of the preceding claims, wherein the polyurethanes or poly(urethane-ureas) are added to the amine mixture at a temperature between 40 and 200°C Claim 2 entered and broken down within 10 minutes to three hours. Method according to at least one of the preceding claims, wherein the liquefaction of the polyurethanes and / or polyureas with a mixture of di-n-butylamine as amine a) N,N-Bis(2-aminoethyl)methylamine as amine d) and Diethylenetriamine as amine c) and Tetramethylguanidine as amine d) is carried out at 120 to 180°C. Method according to at least one of the preceding claims, wherein the liquefaction of the polyurethanes and / or polyureas with a mixture of N-ethyl-cyclohexylamine as amine a) and N,N-Bis(3-aminopropyl)methylamine as amine d) and Triethylenetetramine as amine c) at 120 to 180 ° C within 20 minutes to 2 hours. Method according to at least one of the preceding claims, wherein the weight ratio of the amines of the three groups is between a: b: c such as 2.5: 7.5: 5 to 25: 2.5: 10. Method according to at least one of the preceding claims, wherein polyurethanes and/or polyureas based on polymer polyols are reacted in an amine mixture at temperatures of 80 to 175°C within 10 minutes to 3 hours and, after cooling, homogeneous polyols are used for further conversion to polyurethanes and/or or poly(urethane-ureas). Method according to at least one of the preceding claims, wherein the weight ratio of the amines of the three groups is between a: b: c 10 to 20: 3 to 9: 1 to 4. Liquefied polyurethane products obtainable by the process according to at least one of the preceding claims, wherein the polyurethane products are liquid and homogeneous with at least 50% by weight of polymer content, the polymer content being obtained by washing with methanol and drying the solid content. Liquefied polyurethane products Claim 9 , characterized in that the polyurethane products contain less than 0.2% by weight of aromatic amines, in particular without further reactions or process steps. Polyurethanes or poly(urethane-ureas) obtainable by reacting the liquefaction products according to at least one of the preceding claims with at least di- and/or polyisocyanates. Polyurethanes or poly(urethane-ureas). Claim 11 , whereby compact materials, semi-hard, hard or soft foams or cellular elastomers are produced by reacting the liquefaction products with the di- and/or polyisocyanates and other auxiliary materials.