MXPA96002244A - Preparation of polyeter polyol that contains aromati compounds - Google Patents

Abstract

In a process for preparing polyether polyols containing aromatics by molecular addition of alkylene oxide to H-functional initiators at a temperature of 70øC to 135øC and pressures of 0.1 MPa to 1.0 MPa, the alkoxylation is carried out using at least one initiator comprising at least 95 weight percent of 2,3- and 3,4-isomers of tolylenediamine, from 0.5 percent to 4 weight percent of 2,4 and 2,6-isomers of tolylenediamine and of 0.1 by 100 to 1.5 percent by weight of more volatile fractions of tolylenediamine production. The polyether polyols prepared by this process to produce rigid polyurethane foams

Description

"PREPARATION OF POLYETER POLYOL CONTAINING AROMATIC COMPOUNDS" The invention relates to a process for preparing polyether polyols containing aromatic compounds by the molecular addition of alkylene oxide to the H-functional initiators, wherein the initiator used is a specific mixture of isomers of tolylenediamnine (TDA) and also the polyether polyols prepared by this process and its use as a component and a polyol mixture to produce rigid polyurethane foams. The preparation of polyetherols by alkoxylation of the H-functional substances has been known for a long time. The use of aromatic diamines such as mixtures of TDA isomer, specifically 2,4- and 2,6-TDA, 2,3- and 3,4-TDA (o-TDA) and blends with more molecular weight aromatic diamines elevated also has also been described. British Patent Number GB-A-972,772 describes the alkoxylation of 2,4- and 2,6-TDA and mixtures thereof. The use of o-TDA as an initiator for the preparation of polyetherols is disclosed in Patent Number DE-C-2017038.

It is also known that the propoxylation of the TDA isomers leads to products of high viscosity whose handling is very problematic. In contrast to this, the ethoxylation of the TDA isomers leads to low viscosity polyetherols but their content of exclusively primary OH groups leads to high reaction rates with the isocyanate. This makes them too active for most rigid foam applications. Well-suited polyetherols for the application of rigid foam are described in US Patent Number US-A-4, 209, 609. According to that patent, approximately 4 moles of ethylene oxide are added per mole of TDA and in addition is added propylene's OXID. The incorporation of an internal block of ethylene oxide reduces the viscosity. The catalyst is preferably added only after ethoxylation. This method leads, when KOH is used as the catalyst, at low viscosity but not to products capable of being prepared reproducibly having very high contents of free o-TDA (from 1 percent to 2 percent by weight). In DD-A-290, 201, use is made of an amine initiator which is obtained as the distillation product in the purification of TDA. It comprises from 20 percent to 50 percent by weight of TDA isomers, predominantly 2,4- and 2, 6-isomers, and from 50 percent to 80 percent by weight of a heavy product consisting essentially of weight compounds higher molecular weight such as aromatic hydrazine and cycloaromatic and derivatives of TDA. These initiator mixtures lead to very dark polyetherols. DD-A-290,202 describes the preparation of polyetherols based on initiators which are the higher distillation products containing amine. They comprise from 10 percent to 40 percent by weight of 2,3-TDA, from 20 percent to 50 percent by weight of 3,4-TDA, from 30 percent to 60 percent by weight of 2,4- and 2, 6-TDA and about 1 weight percent toluidines. The alkoxylation of this mixture of isomers sometimes also in combination with co-initiators and / or residual distillation products is carried out with the aid of basic catalysts, with nickel catalysts being present sometimes. This leads to increased contents of secondary amine groups. EP-A-0 318,784 describes the preparation of a polyetherol based on o-TDA. The synthesis of the polyether is carried out here with the aid of specific amine catalysts. The products prepared in this way are said to be exempt from all the inconveniences mentioned above, such as cracking and discolouration of the core in the foam. The preparation process leads to polyetherols based on o-TDA and having an OH number of 400-630, wherein from 5 percent to 20 percent by weight of the reactive groups towards the isocyanates are groups of secondary aminos and whose contents of free o-TDA are said to be less than 0.2 weight percent. The described preparation method results in a considerable part of the amino groups being only monoalkoxylated so that a relatively large proportion of secondary amino groups remains. This is evidently the cause of the low viscosity. Polyetherols prepared in this way have an increased initial activity during foam formation, leading to reduction in the amounts of the catalyst used. However, this reduction in the amount of the catalyst during foaming detrimentally affects the healing of many systems in some applications. Therefore, the rapid reaction of the secondary amino groups with the isocyanate groups gradually increases the molecular weights and viscosities and greatly deteriorates the flow properties of the systems, particularly in molded parts, so that complete filling can not be achieved. , particularly in the case of large molded parts such as refrigeration appliances. DE-A-4232970 describes a process for preparing polyetherols using the alkaline oxide-catalyzed molecular admixture to TDA. The ADT has an isomer content of 2,3- and 3,4-TDA of >; 50 percent by weight, based on the total amount of TDA, with the proportion of ethylene oxide being from 5 percent to 12 percent by weight of the total amount of the alkylene oxide. It is further claimed that with an increased content of the 2,3 and 3,4 isomers of TDA, the content of ethylene oxide in the alkylene oxide also increases. In addition, the TDA isomer mixture also contains aromatic monoamines in an amount of < 5 percent by weight based on the TDA, such as aniline and / or toluidines. Alkoxylation of this mixture of isomers with the aid of base catalysis provides low viscosity polyetherols having hydroxyl numbers, for example, from 410 to 435 milligrams of KOH per gram. Specifically, in Example 1 a product having a hydroxyl number of 435 milligrams of KOH per gram has a viscosity at 25 ° C of only 5100 Pas. This product contains 0.002 weight percent of primary and secondary amino groups.

The low viscosity of 5100 mPas (20 ° C) at a hydroxyl number of 435 milligrams of KOH per gram, however, can only be achieved by using base catalysis of the reaction with an aqueous potassium hydroxide solution whether the TDA as an initiator, it contains a significantly higher amount of aniline or toluidines or if the content of the primary and secondary amino groups is also significantly higher. The desired low viscosity is achieved, therefore, by means of a decreased functionality of the initiator mixture or in the polyol, as already described in EP 0318 784. The decrease in viscosity is also possible by means of a content increased ethylene oxide. However, in the example, the content of the ethylene oxide is only 2.8 weight percent, based on the amount of alkylene oxide. This amount, however, is not sufficient to decrease the viscosity to 5100 mPas at a hydroxyl number of 435 milligrams of KOH per gram. Increased the content of the primary and secondary amino groups, also increases the danger of residual contents of free ADT. U.S. Patent No. A-4,562,290 describes the preparation of polyetherols based on vicinal TDA. The isomer composition is about 90 weight percent 2,3- and 3,4-TDA and about 10 weight percent 2,4- and 2,6-TDA. The alkoxylation is carried out using an addition of 1 to 3 moles of ethylene oxide at 125 ° C and a propoxylation of 4 to 8 moles of propylene oxide at a temperature greater than 140 ° C. However, it has been found that alkoxylation of the local TDA at elevated temperatures, such as synthesis temperatures of more than 140 ° C, leads to dark or thermally damaged polyetherols. However, due to the changed requirement profiles, lighter colored polyetherols are desired. The forced synthesis by means of an elevated temperature allows propoxylation to occur predominantly in the OH groups formed by the above ethoxylation and causes an increased proportion of NH groups to remain. This decrease in functionality provides the reduced viscosity. However, for many applications, the functionality of at least 4 is absolutely necessary. An increased proportion of NH groups has a detrimental effect on the flow compartment during foam insulation of a refrigerator. The reaction of the NH groups with the isocyanate groups deteriorates the flow and prevents complete filling of the space. U.S. Patent Number A-4,391,728 describes only the propoxylation of the local TDA. Use is made of the same mixture of TDA isomers as in US Patent Number A-4,562,290 and of polyoxyalkylene polyethers having equivalent weights of 50 to 300 and functionalities of 2 to 6. Here also, the reaction temperature in propoxylation is greater than 140 ° C and, therefore, leads to the disadvantages already indicated in US Patent Number A-4,562,290. An object of the present invention is to develop an economically favorable process for preparing polyether polyols based on the TDA isomer mixture, if desired mixed with additional co-initiators, with the polyether polyols prepared in this way having a property profile advantageous for use in rigid polyurethane foams systems. It has been found that this object is achieved by the process for preparing polyether polyols containing aromatic compounds by the molecular addition of alkylene oxides to the H-functional initiators which is carried out in a customary manner with the initiator for the alkoxylation comprising at least 95 percent by weight of 2,3- and 3,4-isomers of TDA, from 0.5 percent to 4 percent by weight of 2,4- and 2,6-isomers of TDA and from 0.1 percent to 1.5 percent by weight of more volatile fractions of TDA production, with proportions adding up to 100 percent by weight. The invention accordingly provides a process for preparing polyether polyols containing aromatics by the molecular addition of alkylene oxides to the H-functional initiators at a temperature of 70 ° C to 135 ° C and pressures of 0.1 MPa to 1.0 MPa, where the alkoxylation is carried out using a primer comprising at least 95 percent by weight of 2,3- and 3,4-isomers of TDA, from 0.5 percent to 4 percent by weight of 2,4- and 2 , 6- TDA isomers and from 0.1 percent to 1.5 percent by weight of more volatile fractions of TDA production. The invention also provides the polyether polyols containing aromatics prepared by this process and provides means for their use as a component of a polyol blend to produce rigid polyurethane foams. The initiator mixture for the polyetherols of the invention contain at least 95 weight percent of 2,3- and 3,4-isomers of TDA, from 0.5 percent to 4 weight percent of 2,4- and 2 , 6-isomers of TDA, and from 0.1 percent to 1.5 percent by weight of more volatile fractions of TDA production, with proportions adding up to 100 percent by weight.

The most volatile fractions of the TDA production preferably contain toluidines and aniline. The TDA having the composition according to the invention is obtained, inter alia, as a by-product in the preparation of TDA containing 80 percent of 2,4-TDA and 20 percent of 2,6-TDA, the material of The starting material for the preparation of toluene diisocyanate 80/20, one of the most widely used industrial isocyanates and with its low content of 2,4- and 2,6-TDA in the total TDA, is appropriate to produce those structural differences in the polyetherols which result in the preferential use of the 2,3- and 3,4-isomers and provide excellent viscosity as well as excellent flow properties. In addition, the initiator mixture may contain customary H-functional additions generally alcoholic co-initiators and / or diamine, for example, diols, such as eg glycols, ethylene glycol, and / or propylene glycol and their homologs, triols, such as glycerol and / or lower aliphatic amines. The polyether polyols are prepared by the process of adding alkylene oxide catalyzed with a base known per se. The addition of alkylene oxide is carried out using lower alkylene oxides, such as ethylene oxide, propelene oxide and butylene oxide. Preference is given to the use of ethylene oxide and propylene oxide particularly in cases where a low viscosity of the prepared polyether polyols is desired. The process of the invention for preparing polyether polyols containing aromatic compounds is advantageously carried out in such a way that the first phase of the alkoxylation is an ethoxylation which is not catalyzed, with the molar ratio of TDA to ethylene oxide being of 1: 2.5 to 1: 4, preferably from 1: 2.6 to 1: 3, providing significantly lower contents of primary hydroxyl groups, and the second subsequent phase is a slightly catalyzed propoxylation at a KOH content of 0.03 percent a 0.15 percent by weight. The basic catalysts used are hydroxides and / or alkali metal and / or alkaline earth metal carbonates, in particular potassium hydroxide in an amount of 0.03 percent to 0.3 percent by weight based on the total reaction mixture. The hydroxyl numbers of the polyetherols prepared according to the invention are from 340 to 420 milligrams of KOH per gram when this method is used. The products synthesized in this way have viscosities at 25 ° C of 5000 to 20,000 mPas at the specified hydroxyl numbers and a functionality of 3.95 to 4.

The contents of the primary hydroxyl groups which are essential for the foaming reaction are <1. 10 percent, usually around 5 percent, and the contents of the secondary amino groups are < 0.05 per coento. The primary amino groups are not detectable. Polyol components particularly suitable for foam forming systems in the application of refrigerators are the polyetherols derived from a mixture of TDA isomers of the composition according to the invention and having average molecular weights of 500 to 700 grams per mole, but in particular from 540 to 570 grams per mole. A specific advantage of the polyetherols of the invention based on the mixture of TDA isomers is the very low content of the secondary amino groups providing the functionality of 3.95 to 4 for polyetherols initiated with TDA desired for the application of rigid foam. The TDA isomer mixture of the composition according to the invention leads, during the alkoxylation, to polyetherols whose reactivity towards the reagents containing isocyanate groups is at a low level. It is observed that this reactivity decreases with an increased content of 2,3- and 3,4-isomers of the initiator. Therefore, a very high content of 2,3- and 3,4-isomers of TDA in the initiator, as applied to the composition according to the invention, allows the reactivity of the polyetherol to be maintained at a low level. This advantageously provides a high degree of control of the foam system by means of catalysts and at the same time provides viscosities that are still low enough to allow processing without problems. The ethoxylation of TDA is carried out at a temperature of about 100 ° to 130 ° C, propoxylation with mild catalysis at a temperature of about 110 ° to 135 ° C with pressures that are capable of being 0.1 to 1.0 MPa. The alkoxylation is followed by the customary post-reaction until the conversion is complete. In the case of block polymers, the known separation by means of nitrogen follows. The crude polyether polyol formed in this manner is freed from unreacted alkylene oxide and the volatile compounds and dehydrated by distillation, preferably under reduced pressure, and the catalyst is removed by acid neutralization and subsequent filtration. The preferred neutralization is carried out using monobasic and / or polybasic organic acids, and / or inorganic acids, for example, phosphoric acid, hydrochloric acid or sulfuric acid, CO2 but also acid salts, ion exchangers or earths. The content of free ADT is at most 180 parts per million. The polyetherols obtained in this way can be used in particular as starting materials for producing polyurethane plastics, preferably rigid polyurethane foams. For this purpose, they are reacted and formed in foam with isocyanates and / or compounds containing isocyanate groups and, if desired, additional polyols in the presence of auxiliaries and / or additives, such as catalysts and initiating agents. The isocyanate components used are customary isocyanates such as toluene diisocyanate, diphenylmethane diisocyanate, polyphenylenepolymethylene polyisocyanate, but also isocyanate-containing prepolymers or isocyanates containing isocyanurate or uretdione groups. The rigid polyurethane foam is preferably produced using polyphenylenepolymethylene polyisocyanate. The swelling agents used are usually highly inert, particularly organic, volatile organic compounds, for example hydrocarbons, such as n-pentane, n-hexane, cyclopentane, cyclohexane and / or fully or partially halogenated hydrocarbons, particularly chlorinated and / or fluorinated, example, fluorotrichloromethane or difluorodichloromethane. The catalysts used are preferably the customary amine catalysts, eg, dimethylcyclohexylamine. The foams produced in this way have particularly when pentane or cyclopentane is used as the swelling agent, low thermal conductivities, excellent flow behavior, a regular foam structure, optimum cure and high service life and properties. The processing leads to crack-free foams. They have, therefore, an advantageous profile of properties, particularly for use in refrigerators and interleaves. The preparation of the polyetherols based on the TDA isomer mixture according to the invention is illustrated by the following examples.

Example 1 In a liter capacity autoclave equipped with a stirrer, regulated supply, heating and cooling and pressure measuring facilities, 122 grams of TDA containing 96.4 weight percent of 2,3- and 3,4-TDA , 3.45 weight percent of 2,4- and 2,6-TDA and 0.15 weight percent of volatile constituents, were treated with nitrogen and reacted with 110 grams of ethylene oxide (approximately 2.5 molar) at room temperature. 95 ° to 110 ° C at a pressure that decreased from 5.0 to 1.0 bar. and they were subjected to a post-reaction at 110 ° C for 1.5 hours. Subsequently, after purging with nitrogen, the reaction mixture was mixed with 1 gram of an aqueous solution of potassium hydroxide (concentration of 48 percent) and homogenized. Then 328 grams of propylene oxide were regularly supplied at a temperature of 100 ° to 120 ° C at a pressure that decreased from 6.0 to 1.0 bar. The post-reaction time was 2.5 hours at 115 ° C. The alkaline polyetherol was hydrolyzed with water and neutralized with phosphoric acid. Subsequently, it was vacuum distilled and filtered. The obtained polyetherol had the following properties: Hydroxyl number: 385 milligrams of KOH per gram Viscosity at 25 ° C: 5750 mPa Primary OH content: 5 weight percent Content of secondary amino groups: 0.02 weight percent Example 1 of comparison. 122 grams of TDA containing 88.2 weight percent of 2,3- and 3,4-TDA, 11.51 weight percent of 2,4- and 2,6-TDA and 0.29 weight percent of volatile constituents were placed in an autoclave of the type described in Example 1. 110 grams of ethylene oxide were reacted at a temperature of 125 ° C under a pressure that decreased from 5.0 to 1.0 bar, and the mixture was subjected to a reaction at 110 °. C for 1.5 hours. Subsequently, after purging with nitrogen, the reaction mixture was mixed with one gram of an aqueous solution of potassium hydroxide (concentration of 48 percent) and homogenized. 328 grams of propylene oxide were subsequently supplied in a regulated manner at 145 ° -150 ° C at a pressure which decreased from 6.0 to 1.0 bar. The post-reaction time was 2.5 hours at 115 ° C. The alkaline polyetherol was hydrolyzed with water and neutralized with phosphoric acid. Then it was vacuum distilled and filtered. The obtained polyetherol had the following properties: Hydroxyl number: 382 milligrams of KOH per gram Viscosity at 25 ° C: 4920 mPa. Primary OH content: 7 percent by weight. Content of secondary amino groups: 0.19 percent by weight.

In contrast to Example 1, the product was brown.

Example 2 In an autoclave similar to that of Example 1, 150 grams of TDA containing 97.6 weight percent of 2,3- and 3,4-TDA, 2.29 weight percent of 2,4- and 2,6-TDA and 0.11 weight percent of the volatile constituents were treated with nitrogen and reacted with 150 grams of ethylene oxide (about 3 moles) at a temperature of 100 ° to 115 ° C at a pressure which decreased from 6.0 to 2.0 bar and they underwent a post-reaction at 110 ° C for 1.5 hours. Subsequently, after purging with nitrogen, the reaction mixture was mixed with 0.8 gram of a potassium hydroxide solution and homogenized. Then 390 grams of propylene oxide were added regularly at a temperature of 105 ° C to 120 ° C at a pressure that decreased from 5.0 to 1.0 bar. The post-reaction time was 3.5 hours at 115 ° C. After purification of the polyetherol, the following values were obtained.

Hydroxyl number: 417 milligrams of KOH per gram Viscosity at 25 ° C: 16440 mPa. Primary OH content: 6.5 weight percent. Secondary amino group content: 0.011 percent by weight.

Comparison Example 2 150 grams of TDA containing 66.9 weight percent of 2,3- and 3,4-TDA, 31.26 weight percent of 2,4- and 2,6-TDA and 0.84 weight percent of volatile constituents were placed in an autoclave similar to that of Example 1, they were mixed with 2 grams of a potassium hydroxide solution and homogenized. At a temperature of about 120 ° C, 150 grams of ethylene oxide followed by 190 grams of propylene oxide were regulated. The post-reaction time was 3.5 hours at 115 ° C. After purification of the polyether, the following values were obtained: Hydroxyl number: 403 milligrams of KOH per gram Viscosity at 25 ° C: 13120 mPa. Primary OH content: 12.4 percent by weight. Content of secondary amino groups: 0.24 percent by weight.

Examples 3a and 3b In an autoclave similar to that of Example 1, 122 grams of ADT containing 97.1 weight percent (Example 3a) or 95.7 weight percent (Example 3b) of 2,3- and 3,4-TDA were treated with nitrogen and were reacted with 176 grams of ethylene oxide (about 4 moles) at a temperature of 95 ° C to 115 ° C, at a pressure that decreased from 6.0 to 1.0 bar and a post-reaction at 110 ° C. It was carried out for 1.5 hours. Subsequently, after purging with nitrogen, the reaction mixture was mixed with one gram of a potassium hydroxide solution and homogenized. 262 grams of propylene oxide were then supplied in a regulated manner at a temperature of 100 ° C to 120 ° C, at a pressure that decreased from 6.0 to 1.0 bar. The post-reaction time was 2.5 hours at 110 ° C. After purification of the polyetherol, the values shown in Table 1 were obtained.

Comparison Examples 3a and 3b The syntheses similar to those of the Examples 3a and 3b were carried out using TDA containing 88.2 weight percent (Comparative Example 3a) or 67.9 weight percent (Comparison Example 3b) of 2,3- and 3,4-TDA. After the polyetherol purification, the values shown in Table 1 were obtained. Table 1 Ex 3a Ex 3b Ex Ej of Comp 3a Co p 3b Content of 2,3- / 3,4-TDA% by weight 97.1 95.7 88.2 67.9 Content of 2,4- / 2,6-TDA% by weight 2.75 4.13 11.51 31.26 Volatile toluidines / aniline% by weight 0.15 0.17 0.29 0.84 Hydroxyl number mg KOH / gra or 344 350 346 351 Viscosity at 25 ° C mPa s 4400 4410 4410 4460 Primary OH content 8.1 8.2 8.4 8.2 Content of secondary amino groups% 0.010 0.009 0.007 0.011 Use of amine catalyst in foam parts 102 100 96 91 To obtain comparable reactive systems, increased amounts of amine catalysts with an increased content of 2, 3/3, 4-isomer must be used.

Claims (7)

1. A process for preparing polyether polyols containing aromatics by molecular addition of alkylene oxides to H-functional initiators at a temperature of 70 ° C to 135 ° C and pressures from 0.1 MPa to 1.0 MPa, wherein the alkoxylation is carried out using at least one initiator comprising at least 95 weight percent of 2,3-isomers and 3,4-isomers of tolylenediamine, from 0.5 to 4 weight percent of 2,4- and 2,6-isomers of tolylenediamine and 0.1 to 1.5 weight percent of more volatile fractions of tolylenediamine production, with proportions adding up to 100 weight percent.

2. A process for preparing polyether polyols containing aromatics according to claim 1, wherein the first phase of the alkoxylation is an ethoxylation that is not catalyzed and is carried out using a molar ratio of tolylenediamine to ethylene oxide from 1: 2.5 to 1: 4.

3. A process for preparing polyether polyols containing aromatic compounds according to claim 1, wherein the second phase of the alkoxylation is carried out in the presence of 0.03 percent to 0.15 percent by weight of potassium hydroxide, with the molecular masses of 500 to 700 grams per mole being synthesized.

4. A polyether polyol containing aromatic compounds which can be prepared by molecular addition of alkylene oxides to H-functional initiators at a temperature of 70 ° C to 135 ° C and pressures of 0.1 MPa to 1.0 MPa, wherein the alkoxylation is carried performed using at least one initiator comprising at least 95 weight percent of 2,3- and 3,4-isomers of tolylenediamine, and from 0.5 percent to 4 weight percent of 2,4- and 2 , 6-isomers of tolylendiamine and from 0.1 percent to 1.5 percent by weight of more volatile fractions of tolylenediamine production, with proportions adding up to 100 percent by weight.

5. A polyether polyol containing aromatic compounds according to claim 4, wherein the basic aromatic polyether polyol contains less than 0.05 weight percent retained non-tertiary nitrogen.

6. A polyether polyol containing aromatic compounds according to claim 4, wherein the basic aromatic polyester polyol contains from 2 percent to 10 weight percent of primary hydroxyl groups.

7. The use of a polyether polyol containing aromatic compounds according to claim 4, as a component of a polyol mixture to produce rigid polyurethane foams.