CS204487B1 - Polyurethane sealing material - Google Patents

Description

BACKGROUND OF THE INVENTION The present invention relates to a sealable polyurethane sealable diisocyanate composition suitable for sealing automotive headlight lenses, for sealing components in the electrical industry, for sealing expansion joints and for bonding and sealing in the construction industry, road and rail vehicles and wherever fast seal gaps and cavities at room temperature.

The prior art liquid sealants are applied either in the molten state, such as asphalt and bituminous materials or thermoplastic polymers, and then, like plastisols, are only suitable for thermally stable substrates or are polymer solutions or dispersions which solidify by the release of organic solvents or water. The dispersion and solution types of sealants solidify at normal temperature, but the cure rate is low, especially at high thicknesses. Both groups exhibit low resistance to fats, lubricants, fuels and organic solvents. Of the two-component sealants, polysulphides, polychlorobutadienes, polychlorosulphonethylene, polyacrylate and butyl rubber sealants and sealants are of minor importance due to the limited raw material base. The polyesters of the inhibited type exhibit surface tack, which is unacceptable for many applications, non-inhibited types are generally of low resistance to temperature variations. The epoxides either cure by a polyaddition mechanism with primary or secondary amines, or polymerized ionically, for example in the presence of boron trifluoride or tertiary amines. Both reactions

204 487

204 487 are relatively slow at normal temperature, amines act aggressively on most plastics and cause serious respiratory diseases and eczema. Silicone sealants have excellent resistance to temperature changes, their mechanical properties change only slightly in the temperature range of 230 to 420 ° K, but require a long time to cure air humidity into the mass to cure, or contain acid catalysts that compromise the corrosion resistance of sealants materials.

The above drawbacks are overcome by the diisocyanate curable polyurethane sealant according to the invention, which contains 10 to 35 wt. parts of refined castor oil, 50 to 70 wt. 0.1 to 15 wt. parts by weight of inorganic or organic powder pigment, 1 to 7 wt. parts of molecular sieve type 4A - synthetic crystalline zeolite of formula Na ^ / CAlOg) ₁₂ (SiO _{2) 12/27} · HgO 0.1 Etz 1 wt. a portion of dimethylformamide or 0.01 to 0.2 tin ( _II) Sn (OCOR ') ₂ , wherein R is alkyl of 2 to 8 C atoms, R * is alkyl of 2 to 18 C atoms, and 0.01 to 0.5 wt. parts by weight of adipic acid ester with diethylaminoethanol or 0.01 to 0.5 wt. parts

N, N'-dimethylbenzylamine.

The reaction of the secondary hydroxyl groups of castor oil 8 with diisocyanates is normally slow, but a synergistic catalytic mixture of a tertiary amine and an organotin compound in the sealant of the invention accelerates the reaction to the extent necessary. The ricinoleic chains of the cured polyurethane according to the invention improve the wettability of the substrate so that good adhesives are achieved on a number of substrate materials. The adhesion to the glass can be further improved by silanizing the glass. The optimum filling of the thermosetting plastics according to the invention with pigments and substrates improves the mechanical properties and reduces the flowability so that the mass does not tend to flow through the narrow slots outside the sealed spaces. The molecular sieve absorbs the moisture introduced into the system by pigments and castor oil, thus preventing the reaction leading to foaming:

RN = C = O + HgO-? R-NH ₂ + CO ₂ .

The cured polyurethane composition according to the invention is permanently flexible, resistant to gasoline and water, stable in the temperature range from 250 to 350 [deg.] K.

Example 1

5.5 wt. parts of molecular sieve type 4A dispersed in 7.5 wt. parts by weight of refined castor oil to a particle size below 0.02 mm, 18 wt. parts by weight of refined castor oil, 6.6 wt. rutile type titanium dioxide, 0.1 wt. part of black iron oxide, 64 wt. chisel parts with oil consumption according to ČSN 67 0531 9 to 12,

0.5 wt. 0.1 parts by weight of dimethylformamide; A portion of the adipic acid ester with diethanolaminoethanol is thoroughly mixed and dispersed on a three-roll friction machine to a particle size of up to 0.04 mm. The formed polyurethane mass, cured in a volume ratio of 5 parts by volume of the material with 1 part by volume of technical Ν, Ν'-diphenylmethane diisocyanate, is suitable for sealing optical inserts of automotive headlamps on a special extruder with a mixing chamber. The polyurethane compound mixed perfectly with the hardener loses stickiness at room temperature

204 46 surface in about 300 seconds and within 900 seconds is rigid. The cured polyurethane material of light gray color is homogeneous, glossy on the surface, resembles hard rubber by mechanical properties. It resists well the effects of water, fuel and atmospheric influences and shows sufficient adhesion to the glass and to the baking varnishes used as a base for optical inserts for vacuum steaming of aluminum.

Example 2 wt. parts of molecular sieve type 4A, 60 wt. parts of the chisel, 6 wt. parts of black iron oxide, 22 wt. parts by weight of refined castor oil, 0.5 wt. 0.08 parts by weight of dimethylformamide; parts by weight of dibutyltin diacetate and 0.1 wt. A portion of dimethylbenzylamine is dispersed in a bead mill to a particle size below 0.04 mm. The mass formed is cured in a ratio of 7 wt. parts by weight per 1 wt. part of technical diphenylmethane diisocyanate. The formed polyurethane mass at normal temperature gels for 2000 seconds in a permanently elastic, glossy black mass with good electroinsulating properties. The material is suitable for sealing of electronic elements by watering.

Claims (1)

SUBJECT OF THE INVENTION A diisocyanate curable polyurethane sealant comprising 10 to 35 wt. parts of refined castor oil, 50 to 70 wt. 0.1 parts by weight of mineral filler; parts by weight of inorganic or organic powder pigment, 1 to 7 wt. parts of molecular sieve type 4A - synthetic crystalline zeolite of formula Na ₁₂ / (A10 ₂ ) ₁₂ (SiO ₂ ) ₁₂ /. 27 H ₂ O, 0.1 to 1 wt. 0.01 to 0.2 parts of a tin (II ₎ Sn (OCOR ') ₂ compound, wherein R is alkyl of 2 to 8 C-atoms, R' is alkyl and 2 to 18 C-atoms, and 0.01 to 0.5 wt. % of the adipic acid ester with diethylaminoethan or 0.01 to 0.5 wt. % of N, N'-dimethylbenzylamine.