DE4007074A1 - Organic esp. aromatic poly:isocyanate stabilisation, for paint mfr. - Google Patents

Abstract

3,5-Dialkyl-3-hydroxyphenylpropionic acid cpds. of formula (I) are used as stabilisers for organic polyisocyanates (II), esp. aromatic polyisocyanates: R1 and R2 independently = 1-8C alkyl. The prepn. of (I) (not claimed) is described in DE2120285.

Description

The present invention relates to the use of 3,5-di-tert-butyl-4-hydroxy-phenylpropionic acid to Sta stabilization of polyisocyanates.

The organic isocyanates have for the production of Polyurethane plastics acquired great importance. So who the z. As the organic polyisocyanates with polyols (Polyether and polyester) for the foam, fiber, Film, elastomers and paint production used.

However, the organic polyisocyanates tend to be in position even at low temperatures, discoloration. This property is particularly pronounced when the Storage at higher temperatures must be done, for. For example the solid polyisocyanates for a homogeneous Reaktionsfüh tion with reaction partners, such as B. polyether polyols, Polyester polyols or glycols to polyurethanes vice should be set. Also in prepolymer production must the NCO-OH reaction at higher temperatures be guided. It is observed that the isocyanates  discolour quickly if no stabilization was made.

It has already been suggested various stabilisato ren organic polyisocyanates to the Ver tendency to color the organic polyisocyanates to verrin gladly. Known stabilizers are sterically hindered Phenols, dialkyldiphenylamines, phenothiazines, phosphites or mixtures of representatives from these classes of substances (See, for example, US-PS 37 15 301, US-PS 40 64 157, DT-OS 16 68 275, DT-AS 16 18 845).

Most commonly found is 2,6-di-tert-butyl-4-methylphenol (BHT) alone or in combination with other compounds of the listed stabilizer classes Stabilization of organic polyisocyanates.

The disadvantage of BHT is the relatively high volatility and migration tendency in polyurethanes enveloping substrates and the resulting strong yellowing of the substrates in NO _x -belasteter atmosphere. Stabilizers without these disadvantages are therefore of interest, and it was an object of the present invention to provide such materials already.

Metal salts of 3,5-di-tert-butyl-4-hydroxyphenylpro pionsäure be in DE-OS 22 09 102 for stabilization described by organic material, wherein the substrate Dependent effectiveness decisively of the Me used depends on tallatom.

The subject of the present invention is the use of 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid (BHP) as a stabilizer for organic polyisocyanates, esp aromatic polyisocyanates.

Although free carboxyl groups are more normal as substituents do not lead to stabilizers of particular effectiveness and therefore usually derivatives of carboxylic acids, such as esters, amides, hydrazides, etc., were used DE now surprisingly found that 3,5-di- tert-butyl-4-hydroxyphenylpropionic acid as stabilizing antioxidant for organic polyiso cyanate is suitable.

Depending on the basic structure of the polyisocyanate are also combi effective with conventional antioxidants, wherein generally 3,5-di-tert-butyl-4-hydroxyphenyl propionic acid amounts of 0.003-1.0 wt .-%, preferably 0.003-0.5 wt .-%, and combination stabilizers from 0.003-0.5 wt .-%, based on the polyisocyanate, can be used.

BHP, the z. B. by basic catalyzed addition of Acrylic acid methyl ester of 2,6-di-tert-butylphenol and on closing saponification (see DE 21 20 285) produced and commercially available, is suitable for all ge common polyisocyanates, including aliphati rule, aromatic and cycloaliphatic Polyisocyana Examples are: ethylene diisocyanate, Tetramethylene diisocyanate, hexamethylene diisocyanate, cyclo hexyl diisocyanate, 4,4'-methylene-bis- (cyclohexylisocya  nat), m-phenylene diisocyanate, p-phenylene diisocyanate, toluene ylen-2,4-diisocyanate, toluylene-2,6-diisocyanate, 4,4'-Me thylene bis (phenyl isocyanate), 2,2'-methylene bis (phe nylisocyanate), 2,3-methylene bis (phenyl isocyanate), toluene ylene-2,4,6-triisocyanate.

The thus stabilized organic polyisocyanates show a very much reduced tendency to discoloration Storage at elevated temperatures and can with advantage used for the production of polyurethanes. The polyurethanes are in turn used for the foaming, Film, paint or Elastomersherstellung used.

The object of the present invention is based on the following examples are explained in more detail (% -Anga in each case,% by weight and all temperature data mean ° C).  

example 1

From this compilation shows that 30 ppm BHP additive shows a similar stabilizing effect as 100 ppm addition of BHT.  

example 2 Desmodur 44 M® (diphenylmethane diisocyanate

Sample A 44M® 500 g + 50 mg BHT
Sample B 44M® 500 g + 50 mg BHP
Sample C 44M® without additive

The samples were subjected to a UV irradiation test, to investigate the yellowing behavior. After 70 hours The exposure of these samples was reduced by color numbers APHA measured.

FC (APHA) Sample A 100 Sample B 60 Sample C 250 before the irradiation 0-5

Example 3

The isocyanate was heated 5 times to 60 ° C and again cooled.

Claims (2)

1. Use of 3,5-di-tert-butyl-4-hydroxyphenyl Propionic acid (BHP) as a stabilizer for organic Polyisocyanates. 2. Use according to claim 1, together with in itself known stabilizers for polyisocyanates.