DE920808C - Clamping varnish, e.g. B. for aircraft - Google Patents

Description

Clamping varnish, e.g. B. for aircraft As a tensioning varnish, z. B. for aircraft, lacquers based on nitrocellulose, acetylcellulose and cellulose butyric acid are or cellulose propionic acid esters and the corresponding mixed esters or ester mixtures used. A number of other high molecular weight film formers, such as. B. polyvinyl chlorides and the post-halogenated polyvinyl chlorides and the vinyl chloride copolymers, furthermore the various chlorinated rubbers, which are particularly special because of their non-flammability Valuable have been used for these purposes as they do not have sufficient resilience have been found to be unusable.

It has now been found that as a tension varnish with excellent success Varnishes made from high molecular weight film formers, if appropriate, can be used along with plasticizers and pigments can be obtained when looking at the paint base small proportions, e.g. B. about $ ° / a finely divided solid particles, such as. Bi. Metal or metalloid oxides with an elementary particle size of less than 0.05, preferably o, oi, u, add. Such highly disperse oxides cannot be claimed here Way by decomposition of volatile metal or metalloid compounds in gaseous form State in the presence of combustible and / or non-combustible, preferably of Oxygen-containing gases are produced in a flame. In doing so, the volatile Compounds together with flammable, especially hydrogen-containing or hydrogen forming and possibly oxygen-containing gases of the flame continually over burners at temperatures below the melting point of the oxides to be formed and fed in at high flow rates, with flame temperature and Flow velocities are coordinated so that by a short residence time undesired surface changes of the oxides formed in the reaction zone, z. B. recrystallization, to be avoided on the oxide particles. The reaction products are rapidly removed from the flame zone and while maintaining temperatures above the dew point of the easily condensable, cooled vaporous reaction products. The aerosols are formed Oxides converted into the airgel form by coagulation and known per se Devices such as filters, cyclones or electrical separators obtained. the Deposition can also be advantageous on cooled, possibly moving surfaces on rollers, in which case it is expedient to use suitable bracing devices Care is taken that the once deposited oxide particles from renewed Exposure to the flame.

By adding metal or metalloid oxides with a particle size from o, o5, it. the elasticity of high molecular weight film formers becomes significant increased. Also, the tension of making tensioning varnish per se already suitable known film formers increased. With other film formers who already have a certain tension, but their tension without further ado is not yet sufficient, the additives according to the invention provide a better, now sufficient tension achieved.

A substance that is excellently suited for the purposes of the invention is caused by thermal cleavage of volatile silicon compounds such as silicon tetrachloride, available colloidal silica. Analog products are those in a similar way Extracted highly dispersed aluminum and titanium oxides.

By adding a few percent, about 1 to 5%, of these substances to solutions of high molecular weight film formers, as to the usual tension varnishes their resilience increased. Since the element particles of the above-mentioned highly dispersed Oxides are often weakly agglomerated to form coarser particles it is necessary to ensure a good distribution when rubbing these varnishes or the corresponding concentrates in the color grinding mill or on the roller mill respect, think highly of. Tensioning varnishes produced in this way are depending on their content of the named Additions more or less thixotropic. It is possible through these additions under Preservation of the clamping capacity in clamping varnishes that have been common since then, e.g. B. in nitrocellulose clamping varnishes, the plasticizer parts, especially the proportions of flame-retardant plasticizers, such as Tricresyl phosphate, triphenyl phosphate, trichlorophenyl phosphate, or chlorinated ones To increase the low volatility of hydrocarbons considerably and thus the sensitivity to fire to push back these paint films. In the case of acetyl cellulose clamping varnishes, similar Way the content of water-repellent plasticizers, such as triphenyl phosphate or tributyl phthalate, increased and thereby - the well-known moisture sensitivity of acetyl cellulose clamping varnishes be decreased.

It turned out to be a surprising moment that these additions even certain film formers who have so far had no or only insufficient elasticity possessed, can be processed into excellent tension varnishes. So it is B. possible with polyvinyl chlorides or post-halogenated polyvinyl chlorides or Vinyl chloride copolymers due to the addition of the type mentioned stretching varnishes with excellent Generate resilience. Even with chlorinated rubber, these additives create a generates a certain elasticity.

Such tension varnishes can contain the usual plasticizers, natural or Resin, pigments and fillers can be added.

In addition, solvents or mixtures can be used in the new paint compositions which, in addition to the usual proportions of solvents, also contain larger proportions of non-solvents, such as gasoline or hydrocarbons. Examples i. A lacquer of the following composition was applied to a tenter frame, which was covered with aircraft chipboard: 15010 post- chlorinated polyvinyl chloride, 67% mixture of ester solvents, 18% mixture of aromatic hydrocarbons, 0.3% plasticizer, 1.5% pigment.

The amount applied was 18 g / ni2. After 1/2 year of weathering, the indentation depth observed with a tension device was 6.1 mm for a load of 1 kg and = .4 mm for a load of 0.5 kg.

In a parallel test using practically the same paint composition, but with the addition of i o / o highly dispersed silicic acid obtained as an aerosol with a particle size of 0.004 to 0.025, u it was also after 1/2 year Ventilation with the tension device, observed depth of indentation with a load of i kg = 3.5 mm, with a load of 0.5 kg = 2 mm.

2. On a frame that is covered with an aircraft fabric was, a varnish of the following composition was applied: 13% spray-moist nitrocellulose, 3i'0 / 0 ester solvent mixture, 36% alcohol mixture, 1.2% Weichinachergemsch, i,% highly dispersed silica obtained as an aerosol.

After one year of ventilation, the indentation depth was 1 kg = 3.2 mm, with a load of 0.5 kg = 2 mm.

3. On a tenter frame that is covered with aircraft tension material a varnish of the following composition was applied: 7.5% medium-viscosity acetyl cellulose, 23% ester solvent mixture, 26% alcohol mixture, i i% toluene, i, i% plasticizer mixture, 0.75% highly dispersed silica obtained as _ ', erosol. The depth of the impression after 1/2 year of exposure to a load of i kg = 3.7 mm, with a load of 0.5 kg = 2.2 mm.

Claims (1)

PATENT CLAIM: Use of a varnish made from high molecular weight, flammable or non-flammable film formers, optionally with pigments, and optionally a very high content of particularly difficult to burn or water-repellent plasticizers with a small addition, about 5%, of highly disperse solid particles, e.g. B. metal or Metalloidoicyden, with an elementary particle size of below 0, o5, preferably below o, oi, u, as z. B. by thermal cleavage of corresponding volatile compounds, e.g. B. silicon compounds are to be obtained as a tension varnish, e.g. B. for aircraft.