DE1720710C3 - Process for the production of polyurethanes - Google Patents

Description

The polyurethanes produced for a wide variety of uses in practice are in obtained essentially by reacting polyhydroxyl compounds with polyisocyanates. The polyurethanes contain a large number of urethane groups, but can also be obtained from isocyanate polyaddition have derived urea, biuret or allophanate groups. As long as the polyurethanes still contain free NCO groups, they are sensitive to water in any form. The ones in these Moisture containing polyurethanes or their starting materials reacts with the Isocvanate groups, whereby carbon dioxide is released, which is noticeable by the formation of bubbles. These occurs especially when the polyurethanes are used in thick layers or when in solvent-poor or solvent-free systems are used, so that the carbon dioxide is no longer can diffuse out. Activated alkali aluminosilicates are already used to bind the disturbing moisture used with zeolite structure. F.s are synthetically produced alkali aluminosilicates, as they have come to be known as molecular sieves.

Despite the use of molecular sieve zeolites, it occurs particularly when processing at high levels Humidity to disturbing foam formation, which is based on the fact that the production of the polyurethanes The polyhydroxyl components used absorb moisture from the air the case with polyether alcohols. the /. B. by attachment of ethylene oxide and or propylene oxide multifunctional alcohols are produced.

In the production of polyurethanes using the transesterification products of castor oil and propoxylated sorbitol described ^{in US Pat. No. 2 0 () 4,674, there are considerable application deficiencies.} The transesterification product described in the above-mentioned USA patent is unsuitable in combination with polyisocyanates, for example for coating measures) because the processing time of a combination of the transesterification product with polyisocyanates is too short, the mechanical properties of the corresponding polyurethanes do not meet the requirements of practice, and in particular there the fabrics produced using the Umesferungsprodukles have strong surface defects due to the formation of bubbles.

Surprisingly, it has now been found that the troublesome bubble formation can be avoided if the polyhydroxyl component is one by transesterification Polyhydroxyl compound made from castor oil with cyclohexanone-formaldehyde condensates begins.

The invention thus provides a process for the production of polyurethanes by reaction of polyisocyanates with transesterification products from castor oil and polyvalent hydroxyl compounds.

ίο The method is characterized in that one as a transesterification product from castor oil and polyvalent hydroxyl compounds a transesterification product used from castor oil and cyclohexanone-formaldehyde condensates.

The castor oil used to produce the transesterification products used according to the invention can be natural oil made by pressing or extracting castor beans. Is preferred a quality first pressing used.

Ais condensate may be mentioned z. B. a cyclohexanone-formaldehyde condensate produced under alkaline catalysis, synthesized using one mole of cyclohexanone and 1.5 moles of formaldehyde has been. For the production of cyclohexanones formaldehyde condensates, see Ullmann's Encyclopedia der Technische Chemie, Vol. 8, Munich 1957, p. 444.

The transesterification of castor oil with the cyclohexanone-formaldehyde condensate takes place at temperatures: - temperatures above the melting point of the resin component, preferably at 120 C. The duration of the transesterification depends on the desired viscosity setting and can take several hours. A lower viscosity is usually desired for casting resins; in this case the transesterification canceled after 2 hours.

The quantitative ratio of castor oil to cyclohexanone-formaldehyde condensate can be varied from 10:10 to 10: 0.5. Particularly favorable in terms of quality the desired viscosity of the transesterification product to be used according to the invention and the mechanical Properties of the process products is z. B. a weight ratio of 75 parts by weight Castor oil and 25 parts by weight of cyclohexanone-formaldehyde condensate.

Suitable polyisocyanates are aliphatic, cycloaliphatic or aromatic polyisocyanates, e.g. B. 1.6-Hcxamethylene diisocyanate, Γ i- and 2,6-toluene diisocyanate and mixtures of these isomers and diphenylmethane ^^ '- diisocyanate. Fs can also pre-adducts of monomeric polyisocyanates to 1. B. polyhydric alcohols such as trimethylolpropane, further isocyanurate polyisocyanates or biuret polyisocyanates are used. A polyphenylpolymethylene polyisocyanate which is liquid at room temperature is preferred. which is produced by aniline-formaldehyde condensation and subsequent phosgenation.

The reaction of the transesterification products with the visocyanates can be carried out in the presence or absence done by solvents. Possible solvents are, for example, toluene, xylene, allyl acetate and Methyl isobutyl kelon. Furthermore, the reaction can be carried out in the presence of catalysts, which accelerates the reaction of the isocyanate groups with the active hydrogen atoms of the transesterification product cause. Possible catalysts are, for example, dibutyltin dilaurate and tin (II) octoate or amine catalysts such as dimethylbenzyU

amine. The polyurethanes produced according to the invention are found primarily as coating compounds and casting resins with excellent mechanical properties use.

As can be seen from the examples, there is chemical resistance as compared to polyurethanes made from castor oil alone clearly improved.

The polyurethanes produced according to the invention can also be used together with solvents such as ζ. Β. ίο Toluene, xylene, ethyl acetate and methyl isobutyl ketone can be processed. Additions of plasticizers, such as dibutyl phthalate, trioctyl phosphate and chlorinated paraffins are possible. For processing on In the casting resin and coating sector, fillers such as calcium carbonate, quartz powder, Asbestos flour, wood flour, rubber and cork flour are added.

The products of the process can be used for anti-corrosive coatings on iron. Furthermore, floor coatings on concrete and linings of containers can be carried out. In the cast resin sector, potting compounds such. B. for capacitors and cable locks. It is also possible to use the polyurethanes produced according to the invention in mold and gauge construction to use.

example 1
a) Production of the transesterification product

250 parts by weight of a condensation product from 1 mole of cyclohexanone and 1.5 moles of formaldehyde (manufacturing instructions: Ulimanns Encyklupadie der technischen Chemie, 8th volume, Munich 1957, p. 444) are ^{boiled with 750 parts by weight of first-pressed castor oil in a stream of nitrogen at 120 °} C. for 2 hours . After cooling, the following key figures result for the reaction product:

40

Hydroxyl content 5.0 ° "

Acid number 1.2

Viscosity 20 C 4950 cP

(Continuation)

b) Method according to the invention

45

1000 parts by weight of the transesterification product prepared according to a) are mixed with 420 parts by weight a polyphenyl-5 "obtained by aniline-formaldehyde condensation and subsequent phosgenation polymethylene polyisocyanate iNCO content 32.0 ° ") mixed. Poured into molds, the mixture solidifies to a solid resin within 4 to 6 hours, which will get its final strength after a further 48 hours.

For comparison, 1000 parts by weight become castor oil and 420 parts by weight of the same polyisocyanate prepared the corresponding Ri / inusölpolyurelhan. The superiority of the process product over castor oil polyurethane results from the following summary herd:

Stress at break, kp / cm ²
Elongation at break,%

Procedure '
product

145

85

Castor oil-

polyurethane

Ver Castor oil- fphrens- poly- product urethqn Shore hardness A 99 ? 0 Shore hardness D. 61 18th Tear strength according to Graves, kp / cm 59 4.5 Abrasion in milligrams after Taber - Abrase r, CS 10/1000 rev / 100 g ... IS - Adhesion strength to iron, kp / cm ² 169 39

The chemical resistance test also shows clear advantages for the process product:

Change in weight of standard bars (10-15-120 mm) in 10% potassium hydroxide solution at 100 C.

Process product

Castor oil poly
urethane

after 1 day 0 5.0

after 2 days 1.5 16.1

after 5 days 7.7 60.7

Example 2

530 parts by weight of the transesterification product prepared according to Example la) are mixed with 340 parts by weight Barium sulfate, 90 parts by weight of titanium dioxide and 120 parts by weight of a 50% dispersion Molecular sieve zeolite (Na-aluminosilicate) on a Distribution roller intimately mixed. To '.00 g of this mixture 23 g of a liquid polyisocyanate according to Example 1 (NCO content 31.5%) are added. This Approach is applied as a solvent-free varnish in a layer thickness of 0.25 mm on glass plates. The layer dries within 4 to 6 hours and forms a tough, glossy film without Blistering disorders.

In the same way as described above, a polyurethane is produced by the transesterification product by polypropylene glycol with an OH gel is replaced by 5.0%. The paint film obtained in this way is technical because of strong foaming not usable.

Comparison attempt using a
Transesterification product according to U.S. Patent 2,994,674

A mixture of 1053 parts by weight of castor oil, 457 parts by weight of propoxylated oil. Was sorbitol (hydroxyl content 9.5 ",,) and 15 parts by weight cal / iumnaphihenat first for 1 hour at 190 to 210 Q thin for 2 hours at 240 to 260 ⁰ C overcooked After cooling, a product is obtained having the following characteristics.:

21 53

έ. Viscose
⁰⁵ at 20 ⁰ C Hydroxyl
salary Acid number Water content 1920cP 6.1%. 1.2. 0.03%

5 6

According to Example J, 1000 parts by weight of a paint prepared with the reaction mixture

this transesterification product with 470 parts by weight up / down shows a multitude of bubbles on the upper

one by aniline-formaldehyde condensation and (laugh, which is due to the hydrophilic character of the

subsequent phosgenation obtained polyphenyl transesterification product used are conditioned,

polymethylene polyisocyanate (NCO content 32%) 5 In summary it can be said that a change

Nothing. The amount of polyisocyanate corresponds to the disorder product according to US Pat. No. 2,994,674

ehiometric amount. The mixture already solidifies. Production of coating compounds according to the pre-

Within 10 minutes to a solid polyurethane, the present invention is unsuitable because
which has the following characteristics:

¹⁰ 1. the processing time is too short,

Stress at break, kp / cm ² 68. ,,. . ,. ,

Bruchdehnungr ⁿ _o 55 · ^{2, the} mechanical properties unsatisfactory

Shore hardness a ' . "..' .. '.'. ........... 79 ^{are and}

Shore hardness D 30 3. the surface severely disturbed by the formation of bubbles

Tear strength, kp / cm 10.5 15 = _S 1.

Claims (1)

Claim: Process for the production of polyurethanes by reacting polyisocyanates with transesterification products made of castor oil and polyvalent hydroxy compounds, characterized in that that one is ais transesterification product from castor oil and polyvalent hydroxyl compounds a transesterification product made from castor oil and cyclohexanone-formaldehyde condensates used.