JPS6021191B2 - Method of using monoisocyanates as additives for increasing the storage stability of polyurethane compositions containing free isocyanate groups - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION It has been found that sulfonylisocyanates, particularly tosyl isocyanate, can be used as water binders in polyurethane compositions containing coagents to consume water and prevent reaction of water with the isocyanate groups of the polyurethane. (DT
-See PS1245590).

The use of these reactive monoisocyanates in lacquer systems makes it possible to advantageously prevent undesired secondary reactions involving water present in additives, such as solvents or pigments. In fact, there are also disadvantages to using tosyl isocyanates as additives in lacquer compositions. For example, common commercial grade tosyl isocyanate occasionally contains traces of tosyl chloride formed during its manufacture.

This means that noxious odors are generated when tosyl isocyanates are used. Moreover, the tosylamide formed during the reaction of tosyl isocyanate and water is
Due to its obvious crystallization phase, 4-gold stains will occur in the lacquer. Furthermore, tosylamides sometimes exhibit a reaction-inhibiting effect in polyurethane lacquer compositions. It is therefore an object of the present invention to provide an additive which increases the storage stability of polyurethane lacquer compositions based on prepolymers containing free isocyanate groups and auxiliaries, which for its stabilizing effect It is at least equivalent to cyanate and does not have the drawbacks mentioned above.

It has been found that by using certain cycloaliphatic or aliphatic oxycarponylisocyanates as additives, the aforementioned object can be achieved.

The suitability of tosyl isocyanate as a desiccant is due to its extremely high reactivity with water. It has been demonstrated that alkoxycarbonyl isocyanates are suitable for removing trace amounts of moisture components from plastic compositions.
Although described in the T-OSI 7 Madara Haishi issue, due to its relatively low water reactivity, alkoxycarbonyl lysocyanate is a free isocyanate group-containing prepolysocyanate.
As additives for increasing the storage stability of polyurethane lacquer compositions based on J-mers and auxiliaries, they cannot be expected to have a good effect.

However, surprisingly, although alkoxycarbonyl isocyanates have relatively low reactivity with water,
It has been found that it is superior in certain respects to tosyl isocyanate as an additive for increasing the storage stability of prepolymers and auxiliary-based polyurethane lacquer compositions containing free isocyanate groups. 1 Colored moisture curing (
To obtain a formulation with a stable viscosity of a one-component lacquer (moisture-hardening), iso-octoxycarbonyl isocyanate is used instead of tosyl isocyanate, the amount of which is required is much smaller (approximately 50%). be.

2. When diisooctoxycarbonyl isocyanate is used instead of tosyl isocyanate for long-term stability, even if stored at room temperature (2000C), it can be stored at high temperature (500C).
Even when stored at 500 ml, the liquid sample showed fairly good viscosity stability, as determined by the Dumpling 4-cup test according to DIN 53211.

3 Alkoxycarbonyl isocyanates hydrolyze to form readily soluble, low melting products which do not have an undesirable effect on the lacquer (spot formation).

4. Hydrolyzed compositions of alkoxycarbonyl isocyanates have a weak inhibitory effect on the reactions that occur during curing of lacquer compositions.

5. Both the oxycarbonyl isocyanate used according to the invention and its hydrolysis products are odorless under the conditions of practical use.

The invention therefore relates to a prepolymer containing free isocyanate groups obtained from a polyisocyanate and an insufficient amount of polyhydroxyl compound with respect to the addition reaction that takes place between isocyanate groups and hydroxyl groups, and a liquid or paste based prepolymer based on additives. In the process of using monoisocyanates as additives for increasing the storage stability of clear or pigmented polyurethane lacquer compositions, cyclohexyloxycarponylisocyanate or having 4 to 18 carbon atoms in the alkyl group is used. The invention relates to a method characterized in that it uses an alkoxycarbonyl isocyanate.

The term "auxiliary agents" refers to all components in the lacquer other than the binder (ie, prepolymer) and includes solvents, pigments, catalysts, etc. According to the invention, cyclohexyloxycarbonyl isocyanates or alkoxycarbonyl isocyanates having 4 to 18 carbon atoms are used as additives.

Preferred alkoxycarbonyl isocyanates are those having 6 to 12 carbon atoms in the alkyl group. 2-Ethylhexyloxycarbonyl isocyanate is particularly preferred.

Other examples of alkoxycarbonyl isocyanates corresponding to those mentioned above are n-butoxycarbonyl isocyanate, n-hexyloxycarbonyl isocyanate,
These are n-dodecyloxycarbonyl isocyanate, n-octadecyloxycarbonyl isocyanate, and isomers of these compounds having an alkyl group in a side chain.
The polyurethane lacquer compositions stabilized according to the invention are moisture-curable systems based on reaction products containing free isocyanate groups (prepolymers) of polyisocyanates and insufficient amounts of polyhydroxyl compounds.

Such prepo IJ-mers containing free isocyanate groups and their preparation are described, for example, in German Patent Specification No. 12 455
No. 9 or US Pat. No. 3,479,325. The additives used in this invention can be added to the polyurethane lacquer composition containing free isocyanate groups from 0.1 to 5.
% by weight, preferably from 0.5 to 2% by weight (based on the polyurethane lacquer composition prepared for use). The invention is utilized to increase the viscosity stability and storage stability of clear or pigmented polyurethane compositions containing free isocyanate groups in liquid or pasty form.

Solvent-containing one-component polyurethane lacquers are known per se and are described, for example, in DT-PS No. 124559 and U.
S-PS3479325, which is preferably stabilized by the present invention. The advantages obtained using this invention will be clear from the following test examples.

In the following Test Example IA ~ ship, the effects of 2-ethylhexyloxycarbonyl isocyanate (m) and tosyl isocyanate (0) as stabilizers were compared. The amounts stated in the prescription formulations are expressed in parts by weight. In addition to the additives 0 and m already mentioned, the following substances were used in the test examples: 1: NCO obtained by reacting a mixture of 1.8 mol of trimethylolpropane, 0.9 mol of diethylene glycol, and 0.9 mol of polypropylene glycol with a molecular weight of 1000 with 7.0 mol of 2,4-diisocyanatotoluene. - N content of 5.4% by weight (based on solution)
60% solution of CO-bre polymer.

W: Standard commercial grade defoamer with a 10% solution of polyacrylate in ethylene glycol monoethyl ether acetate.

V: Anti-settling agent (aluminum silicate of montmorillonite type), 10% suspension in xylene.

W: Commercial grade potassium zinc chromate. W: Commercial grade chromium oxide green.

W: Barium sulfate.

Illusion: Talc.

X: 5 moles of phthalic anhydride and 1 part of trimethylolpropane
Ethylene glycol monoethyl ether of the reaction product of 25 parts by weight of polyester with 5 moles of hexamethylene glycol and 75 parts by weight of biuretted hexamethylene diisocyanate containing 2% by weight of NCC. 60% solution in acetate noxylene (1:1).

The reaction product is obtained from the starting material by heating to 8000 °C for 2 hours. It has an NCO content of 9.5%. Phantom: Commercial grade cellulose acetobutyrate.

Fox: 10% solution of dibutyltin dilaurate in ethyl glycol monoethyl ether acetate. Xm: Commercial grade titanium dioxide pigment (goldenstone).

XW: A mixture of equal parts of ethylene glycol monoethyl ether acetate and the solvent xylene. Test Example IA~, summarized in Table 1, concerns the stabilization of NCO-prepolymers with isocyanate groups attached to aromatic nuclei.

The listed starting materials were mixed in a high speed concentrator for 18 minutes. The temperature of the mixture rose to about 50oC. After cooling to 20 qC (approximately 2 hours after the end of the fly frame), the first viscosity measurements were taken. Furthermore, the viscosity was measured after storage at 20qo for 30 days.
This was done after 14 days of storage at 50°C and 30 days of storage at 50qo. The results are shown in Table 1. Table 1 Characteristics regarding the viscosity of liquid lacquer → DIN 53211K (according to DIN 53211K) Effluent charge from DIN-4 cuff (seconds) Immediately at 20°C 40
21 39 21 39
After storage for 30 days at 2120℃ 71
32 75 30 65
After 14 days storage at 2650℃ 261
40 279 112 90
After storage for 30 days at 2850℃ Gelation 70 Kelization 90 10
Test Example 4A summarized in Table 2 concerns the stabilization of solvent-containing lacquers based on NCO-prepolymers with isocyanate groups attached to aliphatic groups.

The lacquer was prepared by removing the catalytic converter and mixing the components in a high-speed lacquer machine in the same manner as described above. After cooling, the catalyst was mixed and the first viscosity measurements were taken immediately. The results of viscosity measurement are shown in Table 2. Table 2 Characteristics of liquid lacquers according to DIN 53211 DIN-4 - Outflow from the cup (seconds)

Claims (1)

[Scope of Claims] 1. A prepolymer containing free isocyanate groups obtained from a polyisocyanate and an insufficient amount of a polyhydroxyl compound with respect to the addition reaction that occurs between the isocyanate group and the hydroxyl group, and 2. A liquid or auxiliary-based prepolymer. Cyclohexyloxycarbonyl isocyanate or having from 4 to 18 carbon atoms in the alkyl group, in the process of using monoisocyanates as additives for increasing the storage stability of pasty, clear or pigmented polyurethane lacquer compositions. A method characterized in that it uses an alkoxycarbonyl isocyanate. 2. Process according to claim 1, characterized in that an alkoxycarbonyl isocyanate having 6 to 12 carbon atoms in the alkyl group is used.