DD154485A1 - PROCESS FOR PREPARING ISOCYANATE ADDUCTS - Google Patents

Abstract

The invention relates to a process for the continuous production of polyisocyanates. The aim of the invention is to develop an economic process for the continuous production of polyisocyanates having a high product content with ideal structure. The invention has for its object to develop a process for the continuous production of adducts of difunctional isocyanates and polyfunctional alcohols with a high product content with ideal structure, which is obtained in the optionally subsequent work-up a free of solvents and monomeric diisocyanates resin with excellent properties. The process is characterized in that the reaction is initiated in a first reaction zone under the conditions of an ideal backmixing, but is conducted only so far that the reaction mixture forms a homogeneous solution and the following reaction zones are designed so that, while largely avoiding backmixing a mixing is carried out perpendicular to the flow direction, while the reaction is carried out and terminated.

Description

22 0 7 53

Tite l the invention

Process for the preparation of isocyanate adducts.

Application Field of the fin-making

The invention relates to a process for the preparation of isocyanates, dduk th, which are mainly suitable for the production of paints, lacquers, adhesives, textile coating compositions and other special polyurethane systems _o

Characteristic of the known technical solutions

Isocyanate vapors are extremely toxic, so that a direct use of the low molecular weight, high volatility polyisocyanates in formulations for paints, coatings, adhesives, textile coating compounds and other special polyurethane B3? -St one not possible. Is _e

The implementation 'of difunctional isocyanates of the general formula R- (WCO) ρ with polyfunctional alcohols of the general formula X- (OH), .. in one. Although the ratio of KGO equivalents to 0H ~ equivalents of about 2 t 1 should theoretically on a higher molecular weight and therefore less volatile polyisocyanate of the general formula

T ("Π." Η Λ "ΐ \ ϊfr ό Tv r < ρ, \

However, the practice, however, proves that at called NCO-OH ratio in the final product compounds having a higher molecular weight than the theoretical, which is characterized by

        - H -

? 0 αΡΗ, Ι980 * 0 ÖÜ IK-

_S are the reaction of an ECO-group of the diisocyanate are used is also formed, when diisocyanates are used with different reactivity HCO-groups *, significant unreacted Moreover remain in the final product amounts of volatile, difunctional monomeric isocyanate back, the use of the allow such reaction products only to a limited extent taking into account special protective measures at the user.

In order to obtain the highest possible proportion of low-viscosity and free of monomeric diisocyanates ideal adducts, is carried out such that first a pre-adduct under such conditions, which excludes the formation of high molecular weight, preferably by polymerization and other lifting reactions resulting compounds as far as possible, is prepared, and in a second process step, the excess monomeric diisocyanate is separated off.

In general, with a KCO-OH ratio greater than 2 and worked at temperatures below 100 C. The excess diisocyanate is reacted in some processes by targeted chemical reaction with OH and / or UEL group-containing compounds, the monomeric rice products relatively are highly viscous and low in E'CO group content. "Preferably, physical separation processes such as distillation and extraction are used, since these methods ensure the almost complete removal of the monomeric diisocyanate with maximum yield of low molecular weight reaction products.

While the preparation of the pre-adduct used for the extraction is carried out as a batch process, a continuous process for Voradduktherstellung has been described in particular for the separation of monomers by means of distillation ^

The preheated isocyanate and polyol components are premixed in a mixing device and then heated in a pipe system _β By relaxing in a heated separator, most of the diisocyanate is removed * Ira downstream thin-film evaporator takes the Peindestillation,

~ 3 ~ 220753

The decisive disadvantage of this process is that the degree of conversion of the components is already relatively high even at the stage of ideal backmixing, which means that even when using a very high isocyanate excess at high temperatures of 60 to 70 C, higher molecular weight compounds must be formed , However, these in turn influence less the resulting isocyanate content in this case than the viscosity of the products after monomer separation. The same disadvantages occur when, to reduce the heat of reaction liberated per unit of time, part of the reacted product is recirculated and with fresh, fed starting products In addition, there is the need for relatively high temperatures, long residence times are necessary for the removal by distillation of the diisocyanate which simultaneously serves as the solvent, and further viscosity-increasing, relatively high molecular weight products are formed

 Object of the invention

The aim of the invention is a continuous process for the preparation of adducts of diisocyanates and polyhydric alcohols with high space / time yields, which under mild reaction conditions leads to a maximum adduct content with ideal structure, provides a consistent good product quality and is characterized by a low susceptibility , simple equipment and great flexibility of the process distinguished

The object of the invention is to find a process which can be carried out continuously and which allows the preparation of adducts of diisocyanates and polyhydric alcohols under such gentle reaction conditions, that undesired life reactions are largely suppressed, a high space / time yield is possible and in its techno

- 4 ~ 220753

logical sequence is so variable that also starting materials of different types can be processed to the respective desired Endproduktzusammen-settlements at a consistently high quality _e

It has been found that the preparation of adducts of diisocyanates and polyhydric alcohols can be carried out continuously in a multi-stage reactor, wherein in the first. Reaction zone, the reaction partners are thoroughly mixed and reacted so far that a homogeneous solution is formed and this is brought in the subsequent reaction zones while largely avoiding backmixing, but mixing perpendicular to the flow direction for further reaction «

According to the invention, this object is achieved in that the diisocyanates used as starting materials, and polyhydric alcohols optionally with the concomitant use of an inert solvent continuously fed to a multi-stage reactor, wherein in the first reaction zone under the conditions of an ideal backmixing the reaction at temperatures below 100 ⁰ G only as far as it is carried out that the reaction mixture forms a homogeneous solution and the following reaction zones are designed so that under extensive Verraeidung backmixing is a mixing perpendicular to the flow direction and the reaction at temperatures below 120 ⁰ C, preferably at 70 ⁰ O to 100 ⁰ C. The core of this process is a multistage reactor in which the formation of the adducts of diisocyanates and polyhydric alcohols takes place continuously. A feature of the invention is that the starting materials in the ers th reaction zone are reacted with intensive mixing to the extent that a homogeneous solution is formed. Diisocyanates have a poor miscibility in comparison to polyhydric alcohols, so that even with the addition of inert solvents, unlimited miscibility can not be achieved. "In contrast, the reaction in step 1 has the reaction of an NGO group with an OH"

29 π 7 4 U /

Group resulting urethanes, which in addition to a free NCO group in the molecule still have one or more OH groups, an excellent compatibility with the starting materials and act as a solubilizer. Therefore, it is particularly important in the process according to the invention that the residence time in the first reaction zone is chosen such that a sufficient amount of these occurring as an intermediate urethanes is formed and a completely homogeneous solution is formed, this feature is ignored and no sufficient residence time adhered to in the reaction zone, it comes in the subsequent reaction zones for partial separation of the reactants and darn-it in addition to low-quality or unusable end products to the formation of gel-like deposits which eventually lead to dislocation of the reactor. If, on the other hand, the residence time in the U reaction zone is chosen to be too large, the reaction proceeds further in the direction of the end products and the possibility of further reaction of the end products formed with starting materials to form undesired higher molecular weight compounds under the conditions of ideal backmixing increases in the 1st reaction zone is dependent on the type and concentration of the starting materials and the temperature and can be determined experimentally relatively quickly "It is on the order of a few seconds to about 5 minutes _o In the interest of gentle reaction, the temperature should be in this the first reaction zone preferably C are selected in the range of 30 to 50 ⁰ but not exceeding 100 ⁰ G, "as suitable for this first technical embodiment Reaktionsaone a small stirred tank can be used, which is provided with an intensive mixing device acting u nd the possibility to comply with the required temperatures offers »For this purpose, it is expedient, the reaction partners · - to preheat to the desired temperature and dissipate the released heat of reaction by means of cooling. When mixing fast-running agitators come with propeller, turbo or centrifugal pumps into consideration

6 * 220753

The latter are arranged outside the reaction vessel and continuously circulate the starting components metered into the suction line of the pump with simultaneous intensive mixing. In principle, however, any device is suitable as a reaction zone which, under the conditions of ideal backmixing, ensures rapid homogenization of the added starting materials. ensured the required residence time and the dissipation of the released heat of reaction

Another feature of this method essential to the invention is the fact that the following reaction zones are designed so that a Rüekvermischung is largely excluded, but nevertheless a good Durchmisehung is guaranteed perpendicular to the flow direction, "A suitable, this conditions corresponding embodiment of the reactor consists for example a vertically arranged double-walled tube, which is divided into segments and on a continuous central agitator shaft per segment contains a stirring unit "the stirring devices may be, for _o B realized ₀ by attached to the agitator discs, turbines, blades, propellers u" similar means ,, also the turntable extractors and similar designs, which are widely used in industry, can be advantageously used to carry out the process according to the invention as a reactor. The stirring speed is to be selected so that in each segment ment a uniform temperature distribution of the reaction product is detected.

The double jacket is flowed through by a heat transfer medium, which dissipates the released heat of reaction or «transfers the energy required to heat the reaction mixture. , , ,

The temperature of the Reaktionagemisches in Zo reaction zone can be equal to or above the temperature of 1 _O reaction zone are _e are preferred temperatures between 70 and 100 C "Never temperatures of 12 NC ⁰ C may -Will exceeded because undesirable side reactions occur to a considerable extent"

22075

It is possible. Nachzuschalten further reaction zones, wherein the reaction mixture can continue to react at different temperatures "is a temperature graduation in the sense of increasing reaction temperatures, because thus a shortening of the reaction time or« further increase the space / time yield realized with consistently good quality of the reaction product can be. Also in'diesem Pail shall not be exceeded 120 ⁰ G as the upper limit temperature _β The dimensioning of the reaction zones must be done so that the desired residence time j be realized, which can be of the order of a few minutes up to about 1 Std® "

They depend on the concentration and the reactivity of the starting materials as well as on the Reactcs temperature and the desired degree of conversion

In general, each reaction zone will be designed as a separate reactor unit. However, it is also possible to construct the reactor so that it contains several reaction zones at the same time. For example, it is possible to provide one of the conventional rotary disk reactors on the head with intensively operating stirring blades or propellers , which are attached to the continuous centric stirrer shaft © In such a reactor, the starting materials can be fed directly, with the additional stirring elements must ensure the rapid homogenization and ideal backmixing "The other hub reactor part is _$ as already described, as 2 · reaction zone» Es is also possible to divide the double jacket of a reactor, · so that a plurality of reaction temperatures can be realized in a reactor. The most expedient embodiment will be primarily dependent on the local conditions and is left to the user. "As diisocyanates for the preparation of the adducts all alkyl, aryl, cycloalkyl and Arylcycloalkyldiisocyanate come into consideration, for example be mentioned? Toluene diisocyanate, phenylene diisocyanate, laphthylene diisocyanate _? Hexamethylene diisocyanate _s trimethylhexamethylenediococranate, isophorone diisocyanate, xylylene

~ 8 »

~ 8 - 22Ö7SS

diisocyanates diphenylmethane diisocyanate "Suitable polyhydric alcohols include aliphatic diols, such as ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, 1,3-butanediol, 1,4-butanediol, hexanediol, octanediol, etc., triols, such as glycerine, trimethylolpropyl, irinethylolethane, butanetriol, Use hexane triol USW ₀ s. Also, polyethers and polyesters having two or more free OH groups per molecule are to be understood as polyhydric alcohols in the context of this invention. These compounds, referred to as starting materials, can be added to the multistage reactor both as individual components (a diisocyanate and a polyhydric alcohol) and in a mixture (several diisocyanates and / or several polyhydric alcohols). "In principle, however, diisocyanates may only be combined with polyhydric alcohols in the reactor." The amount of diisocyanate to polyhydric alcohol to be used depends entirely on the intended properties of the final product * such as IiCO- or "OH group content, polyaddition" and depends on the functionality and molecular weight of the starting materials. "Such calculations are familiar to the person skilled in the art and therefore not explained in more detail »In many cases, it makes sense to use an inert solvent and to carry out the adduct formation in the solvent.« The use of inert solvents generally allows lower reaction temperatures, especially in the first reaction phases and improves the solubility of the reactants ₀ Suitable inert solvents are for example esters, * nitrile ketones, alkyl carbonates, aromatics, halogenated hydrocarbons, cyclic ethers, etc. _o suitable - '- The inventive method is highly variable and allows the production unterschiedlichster products · Preferred is It is used for the preparation of Isocyanataddukteiiy which are freed from unreacted starting isocyanate in a subsequent stage and thus high quality as hardener components for paints _f adhesives, coating compositions u «a» suitable applications represent products «. Especially after the distillative Monoraerenabtrennung, which represents an additional thermal load leads

    - 9 -

~ 9 <* 22 0 753

the process of the invention to better end products, as they are obtainable from isocyanate adducts prepared in another way «, · ·.

The invention will be explained in more detail below with reference to some embodiments:

 Embodiment 1

A jacketed 500 ral glass reactor with a fast-running agitator is continuously filled with 1 _? 773 kg / h tolylene diisocyanate with an isomer ratio of 80 % 2,4- and 20 % 2,6-tolylene diisocyanate (TDI 80/20), 0.075 kg / h diethylene glycol (DÄG) _? 0.285 kg / h of trimethylol propane (TMP) and 0 _{s of} 861 kg / h of ethyl glycol acetate (EGA)

By means of a heat carrier which flows through the double jacket is _ώ in the reaction mixture maintained a temperature of 50 G a ~ The anreagierte homogeneous reaction mixture is continuously drawn off again and the upper part of a vertically arranged, divided into segments cylindrical double-jacketed tube supplied, in which in a perpendicular durchgeh led stirrer shaft a number of segments corresponding number of discs rotated

The subdivided jacket provides for three separately heatable reaction spaces _s wherein the upper reaction space and the two same lower reaction chambers each account for a quarter of the total reactor volume. "The reaction tube was previously filled with product of the same composition

The total length of the reaction tube is 125 cm and the inner diameter is 6 cm, so that a residence time of 80 min _e results. "The temperature is kept constant at 70 ° C. by means of a liquid flowing through the jacket." The lower end The finished product exiting the reaction tube is led up again in a riser and runs into a collecting vessel

It is almost colorless and clear and is characterized by a very low. Viscosity out within a lifetime

~ 10 ~

~ 10 ~ 22 0 753

from 24 hours unchanged from 150 to 200 cP. The NGO content is 18% * The content of free TDI is ca _o 14 % _o The product is ideal for distillation in a thin-film evaporator at 150 to 180 ⁰ C and 0.5 Torr, whereby a pale yellowish resin is obtained, their NGO content is 18.9 % and TDI content is about 0 _s 6 % . It is very soluble in aliphatic monocarboxylic acid esters and ketones,

Embodiment 2

The reaction tube described in Example 1 is modified by additional attachment of propeller blades at the upper end of the stirring shaft so that a reaction zone of about 10 cm long with ideal mixing is formed (which is separated by a sieve plate from the following reaction zone) and in which directly Starting materials are metered in The triple partitioned double jacket is charged with 60 C heat transfer medium in the upper part and 80 CY / carrier in the two lower parts «

The starting materials are fed in the same ratio over twice the amount as in Example 1 ", in the collecting vessel a slightly yellowish clear product is obtained, which is characterized by a very low viscosity of 150 to 180 cP» The isocyanate content is 17.8 %. The content of free TDI is about 14 %. After distillation in the thin-film evaporator, the same product parameters as in example 1 are obtained

Application example, el "}

Y / ie described in Example 1 is continuously at 50 ⁰ C, a reaction mixture from 3 _s 546 kg / h TDI (80/20), 0.150 kg / h DAG; 0.570 kg / h of TMP and 1.722 kg / h of EGA produced and continuously fed to the heated to 70 ⁰ C reaction tube, the product is already taken after a residence time of 20 min _o 1o reaction zone and analyzed The viscosity is at 20 ⁰ C ca _e 100 cP, the NCO content is found at 19.4 % and the TDI content at 18.0 % "

* 11 -

- 11 - 22 0 753

After a service life of 48 h, the viscosity is about ₀ 150 to 200 cP, the NCO content 17.9 % and the TDI content 14.5 % *

A clock etc. ung sbe I_SP ie I _- J;

As described in Example 1 is continuously at 50 ⁰ C, an anreacted product of 7.092 kg / h TDI (80/20), 0.300 kgVh DÄG; 1.140 kg / h TMP and 3.444 kg / h EGA produced and fed continuously to the reaction tube, the upper reaction zone to 70 ⁰ C and the two lower reaction zones are heated to 90 ⁰ C.

The product collected in the collecting vessel has a viscosity of 200 cP _s, an NCO value of 18.0 % and a TDI content of 17.9%. After a service life of 48 h, the viscosity is measured at 220 cP, the NCO Salary of 17.8 % and the TDI content of 17.3%

Version 1 5,

As Embodiment 4 but using toluylene diisocyanate with an isomer content of 65 % 2,4 and 35 % 2,6 Toluylendiisoeyanat (TDI 65/35) «.

The product obtained has a viscosity of 180 cP, an NCO content of 18 _? 9 % and a TDI content of 15.0 % *

After a service life of 48 h, a viscosity of 200 cP, an isocyanate content of 18 _? 2 % and a free TDI content of 14 _S 5 % received "

Ajasfiehrb e is pie I _- . 6

As Example 5 but using 70 C in the pre-reaction stage, 90 ⁰ C in the first reaction zone, 105 ⁰ C in the second reaction zone and 120 ⁰ C in the third reaction zone ο

A product yellow color is obtained whose analytical values are viscosity 300 cP, NCO content 17.6 % and TDI content 13.5% ",

_ 12 ~

" _{12 w} .'22 0 7 53

This product can also be demonomerized in the thin film evaporator with the demonomerized resin down to 0.7 % having an NCO content of 18.2 % .

As Embodiment 6 but using 2.4 TDI and DAG as a polyol component, 30 ⁰ C in the pre-reaction stage, 50 ⁰ C in the first reaction zone and 70 ⁰ C in the second and third reaction zone »

The isocyanate content is 18.8 % and the viscosity is determined to be 130 cP.

The product gives after distillation in Dünnschichtver ^

damper at ca _e 150 to 180 C a nearly colorless Harz.vom

Melting point 75 to 80 ⁰ C and an isocyanate content of 18.8 % »

Like embodiment 7 but using TDI 80/20 and TMP as polyol component _s 50 ⁰ C in the pre-reaction stage, 70 ⁰ C in the 1 "and 90 ⁰ C in the 2 * and 3ο reaction zone" The isocyanate content is 18.8 and the viscosity is determined to be 450 cP ·

The 75% strength solution produced in the thin-film evaporator after the distillation of the product in EGA / xylene has an iso cyanate content of 11.8% _t a monomer content of 0.4% and a viscosity of 6500 cP "

For example füh approximately 9

As Example 8 but · using TDI 65/35 and TMP butanediol 1.3 in the ratio 3 ' 1 * The temperature of the pre-reaction stage is 50 ⁰ C, the 1st reaction stage 70 ⁰ C, the 2 _e reaction stage 90 ⁰ C and the temperature of the third reaction stage is 110 ° C _e

The achieved isocyanate content is 18.8 % * The viscosity was determined to be 250 to 300 cP

^ ₁₃ - 220753

The product demmonomerized in a thin film evaporator has a melting point of 80 to 85 ° C and at 100 ⁰ C a viscosity of about ο 3000 to 4000 cP _e

Embodiment 10

B ^ TTCTI ¹ IT-H IJ HlWfIi ι. IJiEBi II "Ί Hf I" Φ 11 11! -Ι Γι | HeHBB tm * H ι n || l .1 I ll | ll pill mn "IH ^ lT"!>> In - <- tj JuKt

Y / ie is described in A & sführungs in game 1 .for 40 ⁰ C continuously an already partly reacted product of 10.195 kg / h TDI 80/20, 1.427 kg / h produced TMP and 0.376 kg / h DAG and continuously fed to the reaction tube, where upper reaction zone heated to 55 ⁰ C and the two lower reaction zones to 70 ⁰ C ·

It is a yellowish product with an isocyanate content of about 40 % and a viscosity of 5000 to 6000 cP receive, after distillation in a thin film evaporator at about 200 to 210 ⁰ C, a resin with an NCO content of ca, 18 _S 7 and a content of monomeric diisocyanate of ca, 0.8 % of _o

A u s t io s i ig ie I IJ _-

As described in Example 1, in the stirred reactor heated to 80 ° C., 4 × 0 kg / h of a reaction mixture consisting of 100 parts of a weakly branched polyester alcohol having the OH number of 56; 2.3 parts of butanediol ~ 1.4; 2j, 4 parts hexanediol-1 _f 6; ca "23 parts of diphenylmethane diisocyanate and 60 parts Athylglykolacetat produced continuously and then the equally in all reaction zones' extent to 120 0 heated reaction tube fed" In collecting a slightly yellowish product is obtained, which after distillative separation of the high boiling solvent, very good in low-boiling solvents ₅ , z, B ₁ acetone, is soluble and therefore z _e B »can be used as an adhesive component ο

XZ

As described in Example 11 are in the-on 60 ⁰ C.

~ H ~ 22 0 7 53

heated stirred reactor 4.0 kg / h of a reaction mixture, consisting of 0, y40 parts of a weakly branched polyester alcohols having the OH number 56; .0.080 parts TDI (80/20); 0.001 part of dibutyltin dilaurate and 1.531 parts of methyl ethyl ketone continuously prepared and then fed to the same in all reaction zones heated to 70 C reaction tube. A slightly yellowish product with a viscosity of about 600 to 800 cP at 20 ^° C., which is α "a, is produced in the collecting container. can be used as an adhesive component ο

- 15

Claims (1)

~ 15 ~ 220 753 claims Continuous process for the preparation of adducts of diisocyanates and polyhydric alcohols, in continuous. Feed of the starting materials, if appropriate with the use of an inert solvent, in a multistage reactor under mild reaction conditions, characterized in that in the first reaction zone under the conditions of an ideal backmixing the reaction at temperatures below 80 ⁰ C _5, preferably at 30 ⁰ C to 50 ⁰ C, introduced, but only to the extent that the reaction mixture forms a homogeneous solution and the following reaction zones are designed so that, while largely avoiding back mixing a mixing perpendicular to the flow direction and the reaction at temperatures below 120 ⁰ G, preferably at 70 ⁰ C to 100 ⁰ C, carried out and terminated _e 2 * method according to item 1, characterized in that the individual reaction stages have different reaction temperatures, which are rising between 30 ⁰ C and 120 ⁰ C _s 3e procedure after point. 1 and 2 characterized in that are used as 2 _Φ and the following reaction zones turntable reactors « 4e method according to item 1 to 3 characterized in that several or all reaction zones are housed in a reactor ₀ 5 «method according to item 1 to 4, characterized in that a centrifugal pump is used as a mixing device, which homogenizes the metered into the intake line starting materials and circulating a 'heat exchanger and intermediate container so that this arrangement served as the first reaction zone - 16 ·· • - 16. * -2 2.0 7 53 6. Process according to item 1 to 5, characterized in that the reaction of the diisocyanates with polyhydric alcohols was carried out in an inert solvent Process according to items 1 to 6, characterized in that the inert solvents used are esters, ketones, nitriles, alkyl carbonates, aromatics, halogenated hydrocarbons, cyclic ethers, but preferably ethyl glycol acetate. 8 «process according to item 1 to 7, characterized in that all alkyl, aryl, cycloalkyl and Arylcycloalkyldiisocyanate are used as the isocyanate * 9β Process according to items 1 to 8, characterized in that polyhydric alcohols, aliphatic diols, triols, polyethers and polyesters having two or more free OH groups are used. 10, process according to item 1 to 9, characterized in that the products thus obtained are freed in a subsequent stage of the unreacted portion of the starting isocyanate by distillation z »B., by means of thin-film evaporator, to a proportion below 0.7 % *.