DD214847A1 - METHOD FOR THE PRODUCTION OF MODIFIED POLYISOCYANATES - Google Patents

Abstract

The invention relates to a process for the preparation of modified polyisocyanates for industrial use in the production of paints, coatings, adhesives and other polyurethane materials. The aim of the invention is to develop a simplified process for the preparation of modified polyisocyanates, in particular to facilitate the separation of monomeric diisocyanates, to reduce the viscosity of the solutions and to increase their storage stability. According to the invention, this object is achieved by modifying the conventional urethane group-containing polyisocyanates by polyisocyanates having a biuret, allophanate or acylurea structure.

Description

Title of the invention

Expired for the production of modified polyisocyanates

Field of application of the invention

The invention relates to a process for the preparation of modified polyisocyanates for industrial use in the production of paints, coatings, adhesives and other polyurethane materials.

Characteristic of the known technical solutions

The technical preparation of suitable polyisocyanates is generally carried out so that di- and trivalent hydroxy compounds are reacted with a relatively large excess of diisocyanates and then the unreacted diisocyanate is removed by extraction or thin film distillation · Technically important hydroxy compounds are trimethylolpropane, EutandiolC1.3) »Diglycol or mixtures thereof · They lead to polyisocyanates with relatively high ЫСО contents, thus guaranteeing a favorable application economy. According to their chemical structure, they contain urethane groups, isocyanate groups, arylene, alkylene or cycloalkylene groups and ether groups when using ether alcohols. A commercial product of this type has been prepared, for example, from tolylene diisocyanate, trimethylolpropane, diglycol. In the technical production process of the mentioned reaction products, a number of difficulties occur, which relate in particular to the stage of separation of the excess diisocyanates. Thus the high softening point, the crystals

- £ MAM933 * O88iü;

tion tendency and the high melt viscosities to a considerable mechanical stress of the thin-film distillation or extraction apparatuses, to deposits and blockages, and by the necessary thermal Uberbeanspruchung to decomposition and polymerization reactions. This not only makes the control of this process difficult, but also affects the properties of the final product or its appropriate solutions aas by significant viscosity increases, reducing the UCO content, difficulties in the dissolution process or lack of storage stability occur »products without the deficiencies mentioned are obtained when the separation of the diisocyanates is carried out at low temperatures in the presence of auxiliaries. Thus, a number of extraction methods have become known which operate at temperatures below 80 ⁰ C and in which the extraction process is carried out with solvent systems, such as hexane-ethyl acetate, petroleum ether-sulfur dioxide, gasoline-butyrolactone or heptane-acetonitrile · The significant amounts of auxiliary solvents required however, their separation, recovery and workup do not allow for an economical alternative to extraction processes on auxiliary solvents or distillation processes.

Object of the invention

The aim of the invention is to develop a simplified process for the preparation of modified polyisocyanates, in particular to facilitate the separation of monomeric diisocyanates, to reduce the viscosity of the solutions and to increase their storage stability.

Explanation of the essence of the invention

The object of the invention is to develop a process for the preparation of modified polyisocyanates having improved properties,

- According to the invention the object is achieved in that the modification of the usual urethane group-containing polyisocyanates ε polyisocyanates, the following biuret structure

ОСЖ-А-Ш

OCII-A-Ii

ОСШ-Α-Ή

CO-N-A-KCO

(CO-HX-A) n-! 7C0 or the following allophanate structure CCOR

(CO-KX-A) n-b "00 or the following acyl urea

structure CO-R

\ (C0-3X-A) n-NC0,

where A is a polyvalent radical of a di- or polyisocyanate, ζ, B. alkylene, cycloalkylene, arylene, u. a · X is H. or -CO-NH-ITCO and R is either the radical of a mono- or dialcohol or

Represent the remainder of a carboxylic acid "

The polyisocyanates having biuret structure, allophanate structure or acylurea structure which are suitable for the modification according to the invention can be prepared by processes known from the literature. For the modification by polyisocyanates with biuret structure, diisocyanates are preferably reacted with water, formic acid, tertiary butanol or mixtures thereof. One chooses a PolyisocyanatüberschuS of greater than 5 mole of polyisocyanate to 1 mole of biuretizing · m

In the use of polyisocyanates with allophanate structure, diisocyanates are preferably reacted with alcohols or polyalcohols and then reacted in the presence of catalytic amounts of strong acids, acid halides or alkyl esters of strong acids at elevated temperatures to allophanate polyisocyanates. An excess of 4 moles to 10 moles of diisocyanate per equivalent of hydroxyl group is chosen to obtain products of idealized structure.

Polyisocyanates with Acylharnstoffstruktur be obtained by reaction of diisocyanates with carboxylic acids or mixtures thereof at temperatures above 100 ⁰ C. This results after decar-

Boxylierung of intermediate products via the stage of aryl amides predominantly polyisocyanates with acyl urea structure. LiI selects an excess of greater than 5% diisocyanate to 1 mole of carboxylic acid.

The polyisocyanates prepared, which are obtained in excess diisocyanate at about 30% to 60%, are mixed with urethane polyisocyanates likewise dissolved in excess diisocyanate and then subjected to workup. The mixing ratio of biuret polyisocyanate or allophanate polyisocyanate to urethane polyisocyanate is from about 1: 1 to 1: 20 selectable, preferably the range of 1 i 2 to 1: 5.

The preparation of the urethane polyisocyanates is carried out according to the known methods of the prior art from diisocyanates and polyhydroxy compounds, either in batchwise manner, wherein the PolyhydroxyIverbindungen, optionally dissolved in a suitable solvent, an excess of diisocyanate in portions feeding, or by continuous mixing of the components by means of mixing nozzles, mixing chimneys or similar devices "Temperatures of 50 ⁰ G to 12C ⁰ G ensure a sufficient reaction rate, the 2JCO / CH ratio is chosen so that at least two IT C G Grup ρ en account for an OH group, but preferably 2.5-8, with an NCO / OH ratio of 3-4 gives the highest relative space-time AusbeUuten the desired polyisocyanates with idealized structure,

To avoid segregation, it is advisable to stabilize with 0.001 % to 1.0% of an organic or inorganic acid chloride of an acid with a pks value less than 2 or its alkyl esters. Compounds suitable for this purpose are, for example, hydrogen chloride, phosphoric acid, sulfuric acid, phosphorus trichloride, toluenesulfonyl chloride, benzoyl chloride, methyl tosylate or dimethyl sulfate. Isocyanates suitable for preparing the products of the invention are: tolylene diisocyanates, phenylene diisocyanates, 2-naphthyl diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, trimethylhexane diisocyanate, isophorone diisocyanate, xylylene diisocyanate, and others , Vorzugeweise are reaction products with toluene diisocyanates in the inventive

Products included.

The polyisocyanates which have been modified according to the invention have the same fields of application as the unmodified products and are therefore used for the production of paints, adhesives, coating and impregnating materials.

The separation of the excess diisocyanates is carried out according to the prior art via a thin-film distillation or by extraction with aliphatic hydrocarbons, which can be used because of the inventive properties of the modified polyisocyanates prepared much gentler conditions. The demonomerized products are dissolved in common solvents, preferably in ethyl acetate or ethyl glycol acetate / ZyloK1: 1).

The presence of the biuret, allophanate or acylurea polyisocyanates in polyisocyanates having an urethane structure brings about a reduction in the softening points, the melt viscosities, the tendency to crystallization and considerably facilitates the separation of the monomeric diisocyanates by extraction or thin-film distillation. The polyisocyanates of the invention are characterized by good solubility in esters, ethers, ketones and aromatic hydrocarbons and have improved storage stability.

A particular feature of the solutions prepared from the erfindungsgeaäß modified polyisocyanates, for example in the commonly used Lösungsmittel3ystemen, which is compared to unmodified polyisocyanate significantly reduced viscosity.

The polyisocyanates modified according to the invention have the same fields of application as the unmodified products and are therefore used for the production of paints, adhesives, coating and impregnating materials.

The invention will be explained in more detail below to 9 exemplary embodiments.

A) Preparation of a biuret polyisocyanate

1. Su 522 parts 2.4 / 2.6 Toluene diisocyanate is

drops of 100 ⁰ C in 0.5 h 25 parts of anhydrous formic acid and 3 h at a temperature of 130 ⁰ G ~ erührt. The resulting Eiuretpolyisocyanat is contained to about 50 % in the diisocyanate solution with a pesticide content of 51.5 % and a KGO value of 36.1 % .

2. 522 parts of 2.4 / 2.6 toluene diisocyanate are mixed with 37 parts of tertiary butanol and then heated for 6 hours to a temperature of 140 ⁰ C with 0.2 parts of phosphoric acid as a catalyst. The resulting solution has a solids content of 44.5% with a KCO value of 39 %.

3 · 9 parts of water, dissolved in 10 parts of 2-methoxyethanol are added dropwise to 522 parts of 2,4 / 2,6-toluene diisocyanate at a temperature of 90 ⁰ C to 100 ⁰ C in the course of 1 h and then to a temperature 2.5 h heated by 140 ⁰ C. The polyisocyanate solution obtained has a pesticide content of 50.6% and a L ^T CQ «Vert of 36.3 % ·

B) Preparation of allophanate polyisocyanate:

1. 696 parts of 2.4 / 2.6 toluene diisocyanate (80/20) are added at a temperature of 60 ⁰ C with 32 parts of methanol, 1 part of benzoyl chloride and 0.2 parts of 3,5-di-tert-butyl-4-methylphenol and stirred for 30 min. Subsequently, the temperature is increased to 130 ⁰ C and left for 10 h. The resulting allophanate polyisocyanate solution is obtained in excess toluene diisocyanate with the following values: pesticide content = 42 %.

NCO value = 37.6 %

2. 696 parts of 2,4 / 2,6-tolylene diisocyanate (80/20) at a temperature of 60 ⁰ C with 74 parts of n-butanol, 0.2 parts of 3 * 5-di-tert-butyl-4-methylphenol and 1 part treated concentrated hydrochloric acid (365aig The temperature is then slowly increased to a temperature ІЗО ⁰ C, leaving it for 8 hours to give a layer consisting essentially of allophanate polyisocyanate in excess of toluylene diisocyanate with the following V / Erten..:

Pesticide content = 44 % ITCO value = 34.6 %

3. A mixture of бЭб parts 2.4 / 2.6 toluene diisocyanate (80/20) and 80 parts triethylene glycol in 1 part of benzoyl chloride and 0.5 parts of 3> 5-di-tert-butyl-4-methylphenol for 4 h at a temperature heated by 150 ⁰ G. After cooling, an allophanate polyisocyanate solution is obtained in excess toluene diisocyanate having the following contents: pesticide content = 40 % KCO-iYert = 35 %

G) production; an acyl urea polyisocyanate:

1. In 522 parts of 2.4 / 2.6 toluene diisocyanate (80/20) is introduced at temperatures of 130 ⁰ C over the course of 1 hour, a mixture of 30 parts of acetic acid and 20 parts of lauryl alcohol. It is stirred until gas evolution ended, and then a further 2 hours at a temperature of 140 ⁰ C. The resulting polyisocyanate having acylurea is dissolved in excess toluene diisocyanate and has a Peststoff content of 44% and a ЖЮ-.Vert of 38.3% ·

2 · In 522 parts of 2.4 / 2.6-tolylene diisocyanate (80/20) is added dropwise at a temperature of 140 ⁰ C over the course of 1 h, a mixture of 72 parts of octanoic acid, 5 parts of ethoxylated 4-monylphenol and 0.5 parts of ezoyl chloride. The polyisocyanate solution has a pesticide content of 38 % and a KCO value of 36.1 %,

D) Solutions according to the invention

Comparative example

T of a trimethylolpropane-diglycol mixture (3: 1) dissolved in 100 parts of methyl glycol acetate are added to 553 parts of 2,4 / 2,6-tolylene diisocyanate (80/20) at ⁰ G over 1 hour. The reaction is allowed to proceed for a further 4 hours at this temperature and then worked up as follows:

a) 250 T of the resulting polyisocyanate are extracted at a temperature of 80 ⁰ G to 90 ⁰ C once with 400 T and three times with 250 T n-heptane to remove the unreacted diisocyanate, then the remaining resident polyisocyanate is taken up in ethyl glycol acetate containing n Heptane removed and brought to a Peststoffgehalt of 67 % with xylene and further Sthylglykolacetat (ethylene glycol acetate / xylene = 1: 1). The viscous polyisocyanate solution has the following characteristics:

JICO = 11.8%, TDI = 1.2 %, viscosity ^ o _Q = 2100 mPa.s.

b) 500 T of the polyisocyanate solution obtained are in a thin-film evaporator

at a temperature of 180 ⁰ C and 0.3 torr of the volatile components.

The resin emerging from the thin-film evaporator is prepared in 3-ethyl glycol acetate / XyloK1: 1) to give a 67% solution having the following characteristics: 11CÖ = 11.2 56, TDI = 0.6%, viscosity oO _Q = ЗбОО mPa.s.

Embodiment 1

300 parts of the polyisocyanate solution described in the Comparative Example are mixed with 100 parts of the biuret polyisocyanate solution A and then extracted at a temperature of 80 ⁰ G to 90 ⁰ C once with 500 parts of n-heptane and then three times with 250 parts of n-heptane. The remaining modified polyisocyanate is freed from the absorbed n-heptane and with ethyl glycol acetate / XyloK1: 1) to a 67%. Solution processed. The following characteristic values are obtained: 2IC0 value = 12.2 %, TDI = 0.8 %, viscosity ^ o _c = 410 mPa.s.

Example 2

300 parts of a urethane group-containing polyisocyanate (prepared from 1000 parts of 2,4 / 2,6-toluene diisocyanate and 1SO parts of a 6: 2: 2 Polyo! Mixture of trimethylolpropane, diglycol and Ädipinsäure-bis-diglycolester) and 100 parts of Biuretpolyisocyanatlcsung A 1 are mixed and then as in

Working up Example 1. A modified polyisocyanate solution in ethyl glycol acetate / xylene (1: 1) with a pesticide content of 67 % and the following data results: LiCO value = 11.9 %, TDI = 1.2 %, viscosity η _c = 320 mPa.s , The polyisocyanate yield in the extraction was 97.6 %,

Embodiment 3

300 parts of the urethane group-containing polyisocyanate solution of Example 2 are mixed with 100 parts of Biuretpolyisocyanatlösung A 2 and then freed by means of a thin film evaporator at a temperature of 170 ⁰ C and a pressure 0.2 torr of diisocyanate. The light emerging from the thin film evaporator resin was immediately in ethyl glycol acetate / xylene (1: 1) to a 67% solution processed with the following data: UCO-value = 11.8%, TDI = 0.5%, viscosity = 640 _c ^ o mPa.s.

Embodiment 4

300 parts of the polyisocyanate pre-adduct described in the comparative example are mixed with 1CO parts of Allophanatpolyisocyanatlcsung Б 1 and then extracted at a temperature of 80 ⁰ C to 90 ⁰ C once with 500 parts of n-heptane and three times with 250 parts of n-heptane. The remaining polyisocyanate is freed of n-heptane in vacuo and processed in ethyl glycol acetate / xylene (1: 1) to a 67% solution with the following characteristics: ЗГСО-iVert = 11.9 %, TDI = 1.2%, viscosity at 20 ⁰ C = 420 mPa.s.

Embodiment 5

300 parts of the polyisocyanate pre-adduct described in the comparative example are mixed with 100 parts of the allophanate polyisocyanate solution B 2 and extracted at a temperature of 80 ⁰ C to 90 ⁰ C as in Example 4 with n-heptane. The reclaimed 67% solution in ethyl glycol acetate / xylene (1: 1) has the following characteristics:

- 10 -

NCO-7 / ert = 11.8%, TDI = 1.3%, viscosity _2Q ο _σ = 480 mPa.s. Embodiment 6

300 parts of the polyisocyanate pre-adduct described in the comparative example are mixed with 100 parts of the allophanate polyisocyanate solution B 3 and then freed on a thin-film evaporator at a temperature of 180 ⁰ C and a pressure of 0.5 torr from DiisoC3, the contained. The resulting solvent-free modified polyisocyanate was taken up in ethyl glycol acetate / xylene (1: 1) in a 67% solution. 3s has the following characteristics: UCO value = 11.2%, TDI = 0.5 %, viscosity _2Q o _Q = 820 mPa.s.

embodiment ^{1 year}

300 parts of the Polyisocyanatvoradduktes described in Comparative Example are mixed with 100 parts of the Acylharnstoffpolyisocyanatlösung G 1 and then extracted at a temperature of 80 ⁰ C to 90 ⁰ C once with 500 parts of n-heptane and further three times with 250 parts of n-heptane. The residual polyisocyanate is freed from the absorbed n-heptane and processed with styrenyl acetate / xylene (1: 1) to a 67% reading. The following parameters are obtained: HCO value = 12.2%, TDI = 1.0%, viscosity ^ q ° q ⁼ 350 mPa.s.

Embodiment 8

300 parts of the polyisocyanate solution described in Comparative Example are mixed with 100 parts of the Acylharnstoffpolyisocyanatlösung C 2 and then extracted at an Temperstur from 80 ⁰ G to 90 ⁰ C with n-heptane, ie, in Example 7. After work-up, an o7% solution in 3-methyl-glycol acetate / 1-l-1-ylene is obtained with the following characteristics: ЯCO value = 11.6 %, TDI = 0.9%, viscosity _2Q o _Q = 460 mPa.s.

- 11 -

- 11 . Operation Example ft

Uan proceeds as in Embodiment 8, but carries out the separation of the toluene diisocyanate at a temperature of 170 ⁰ C and a pressure of 0.2 torr in a thin film evaporator. The escaping resin is collected in 3-methyl glycol acetate and processed with xylene to a 67% solution. Poling characteristics are obtained: NGO T / ert = 11.3%, TDI = 0.4 %, viscosity _{Q Q} o _c = 830 mPa.s.

Claims (3)

invention claims 1 «A process for the preparation of modified polyisocyanates having lowered softening points, melt and Lösungsvisko- properties and improved storage stability, characterized in that the modification of the usual urethane group-containing polyisocyanates with polyisocyanates, the following biuret structure CO-NA-NCO
OCN-AN _ч (CO-KX-A) n-NC0 or the following allophanate structure COOR
OCN-AN ^ (CO-NX-A) n-NCO or the following acyl urea structure, CO-R * (CO-NX-A) n-NCO, contain, where A is a polyvalent radical of a di- or polyisocyanate, ζ, B. alkylene, cycloalkylene, arylene, u. a. X is H or -CO-NH-NCO and R is either the radical of a mono- or dialcohol or Residue of a carboxylic acid
represent, takes place and the preparation and further processing of the urethane polyisocyanates in the presence of 0.001 % to 1 % of an inorganic or organic acid chloride, an acid having a pK value less than 2 or their alkyl esters, is performed. 2. The method according to item 1, characterized in that the polyisocyanates with biuret structure used for the modification are prepared by the reaction of aromatic diisocyanates with formic acid, water, tertiary butanol or mixtures thereof. - 13 - 3 · Procedure after. Item 1, characterized in that tolylene diisocyanates are used for the preparation of the polyisocyanates with allophanate or icy structure which are used for the modification.