A method of obtaining a polyurethane prepolymer for protective coatings

 

(57) Abstract:

The invention relates to methods of producing polyurethane prepolymers, which are designed to produce coatings to protect metal, concrete, wood, glass surfaces from the effects of various atmospheric and corrosive environments, corrosion, static electricity, abrasive wear and can be used as a protective internal and external coating of pipes, vessels and tanks, engineering and hydraulic structures, power plants, port facilities, roofing and shingles, as well as decorative coatings. The method is carried out by mixing hydroxyl-containing component with a hydroxyl number 32-37 mg KOH/g Laprol 5003 or Laprol 4503 with white spirit, then butyl acetate or a mixture of butyl acetate with white spirit and the resulting mixture was added a polyisocyanate based on 4,4-diphenylmethanediisocyanate with a content of NCO-groups of at least 29,5 g/100 g and synthesis is carried out under stirring until the mass fraction of isocyanate NCO groups in the prepolymer 7,5-11,5%. The technical result of the invention is the obtaining of the prepolymer with stable characteristics (at least the year of the prepolymers, which are designed to protect metal, concrete, wood, glass surfaces from the effects of various atmospheric and corrosive environments, corrosion, static electricity, abrasive wear and can be used as a protective internal and external coating of pipelines, tanks, and cistern, engineering, and waterworks, power plants, port facilities, roofing and shingles, as well as a decorative coating.

Known methods for producing a one-component polyurethane coatings, curing moisture of the air, (O. C. Orlov, I. N. Fomicheva. Technology varnishes and paints. Moscow: Khimiya, 1990, page 139 [1]) by mixing the starting components. The final film-forming agent coating is isocyanatomethyl prepolymer (prepolymer), obtained by the reaction of hydroxyl-containing compound is a polyol with an excess of isocyanate. The prepolymers contain at least three free isocyanate groups, which provide crosslinking in the process of film formation. Curing and cross-linking of these polymers is done directly on the substrate by the interaction of the isocyanate groups with moisture wonder with moisture of the air with formation of amino groups is described in [1], p. 140. In the interaction of the amino groups with isocyanate groups of the prepolymer is formed polymer reticulate structure, ie, the curing of the coating. Known coatings (A. M. Tartakovsky, A. A. Blagonravov, one-component polyurethane coating materials, curing air moisture (literature review). Paint and varnish materials, 1976, No. 2, pages 19-21 [2], I. N. Bakirova, C. I. Mulukov, I., Demchenko, L. A., Seitova, N. A. Rosenthal. Varnishes on the basis of waste polyurethane production. Materials and intermediates, page 3-4 [3]), in ways which can be obtained by mixing the starting components polyisocyanates component and hydroxyl-containing component as polyisocyanates component used a mixture of aromatic isocyanates: isomers of 2,4-TDI, 2,6-TDI=65:36 and 80:20, and diphenylmethanediisocyanate (PIZ on MDI), xylylenediisocyanate [2], the reaction product of a terminal trimerization of isocyanate groups of 2,4-toluylene diisocyanate (TDI) in the presence of catalytic amounts of phenolic bases of manniche in the solvent environment [3]; know the use of pre-destructively polyurethane waste from industrial injection molding of polyurethanes based on polyester SKU-OHM, MCS-6, MCS-7, etc. [e polyesters and other [2].

A significant problem in some of the above polyurethane systems, curing moisture of the air is the lack of stability during storage, long drying time, which can be reduced only by the use of additional catalysts. Instability during storage due to the fact that during storage, the formation of urea and allophanate groups, decreases the content of isocyanate groups and increases the viscosity of prepolymer. The retention of such coverage in a tightly closed container does not exceed one month. The disadvantages of these methods is also constructive complexity of the equipment used for the preparation of the prepolymer, for example, a reactor that requires a water jacket, nipples for connection with vacuum equipment, thermometers for temperature control; requires vacuum equipment, heater, which complicates both the equipment itself and increases the energy production of the prepolymer.

The closest analogue is the way to obtain a protective coating comprising a mixture of initial components: a simple polyester with a tertiary nitrogen atom in a molecule containing three or more orites, for example white spirit, the ratio between ishodniki polyisocyanate and polyester, in which the final product still contains free isocyanate groups, providing atmospheric moisture curing [2, page 20]. Varnishes based on such products otverzhdajutsja much faster, does not require curing accelerators; they are of satisfactory storage stability, their performance does not change for several months up to six months.

The disadvantage of this method of obtaining coverage is still limited stability of the coatings during storage, the formation of urea and allophanate groups, decreases the content of isocyanate groups and increases the viscosity of the prepolymer.

The objective of the invention is to increase the stability of the coating, increasing the time of storage, expanding Arsenal of relatively cheap protective coatings.

The problem is solved using the method of producing polyurethane prepolymer for protective coatings, representing the prepolymer is a single component system, curing moisture of the air, including the mix of products source: polyisocyanate component in the form of MDI n the Ira, containing three hydroxyl groups, having a molecular weight of ~500-5000, in the presence of an inert solvent such as white spirit, the ratio between ishodniki polyisocyanate and polyester, in which the final product still contains free isocyanate groups, ensuring the consolidation of atmospheric moisture, which use a polyisocyanate component on MDI 4,4’-diphenylmethanediisocyanate with a content of NCO-groups of at least 29,5 g/100 g, as polyether use Laprol with gidroksilnym number 32-37 mg KOH/g, for example, Laprol 5003 or Laprol 4503, optionally add butyl acetate in the following starting components, wt.h.:

The polyisocyanate 26-32,5

Laprol 5003 or Laprol 4503 30-32,5

Butyl acetate 8,79-10,36

White spirit 22,9-26

in this first mix hydroxyl-containing component with the solvent white spirit, add butyl acetate or hydroxyl-containing component is mixed with a mixture of butyl acetate with white spirit, and then the mixture is added to the polyisocyanate, synthesis is carried out under stirring until the mass fraction of isocyanate NCO groups in the prepolymer 7,5-11,5%.

Used original products

The polyisocyanate on MDI 4,4’-diphenylmethanediisocyanate grades (a, B) TU 113-03-375-75. As MDI can be used product In 227 production BASF, Germany, which also represents the CRPS at DHS, with a content of NCO-groups to 31.2 g/100 g Product In 227 produced this firm in accordance with ISO 9001 called Diphenylmethan-4,4’-diisocyanat.

The prepolymer of LATEX obtained as follows. In the reactor according to the calculation load Laprol 5003 or 4503; pre optionally Laprol can be drained to the content of the mass fraction of water is not more than 0.1%. In Laprol add sequentially or as a mixture of the estimated amount of butyl acetate with white spirit, stirred for about 30 minutes, then portions 2-3 times with an interval of 20 minutes in the reactor with a mixture serves a polyisocyanate. After uploading the entire raw material mass in a closed reactor is stirred for 3,0-6,0 hours at ambient temperature, for example, not more than 30°C. In the mixing, the synthesis of the prepolymer, which is carried out until the content of the mass fraction polyisocyanate groups of up to 7,5-11,5%. Synthesis of the prepolymer with free isocyanate groups is made according to the scheme, known, for example, from [2]:

The way to get coverage is to apply the obtained prepolymer of LATEX any of the following methods: brush, roller, pneumatic or airless spray, a method of dipping on cleansed and fat protected surface at a temperature of from minus 10 to plus 70°C and with relative humidity 30-98%; after applying the prepolymer last begins to be vulcanized in the presence of moisture in the air with the formation of the polymer coating. Curing and cross-linking of prepolymer occurs directly on the substrate according to the scheme described in [2]. If necessary, the prepolymer can be applied in multiple layers, forming a protective surface with high mechanical strength.

The table below shows examples of the quantitative composition of the coatings and their characteristics compared to the characteristics of the prototype.

Using the described method of obtaining allows you to get prepolymer with stable characteristics that are stable over a long storage time (at least one year). As a result of additional use of butyl acetate, days total weight of the components of the prepolymer, decreased the possibility of its thick and precipitation. As a result of use of the invention expanded the range of relatively cheap polyurethane coatings.

A method of obtaining a polyurethane prepolymer for protective coating comprising a mixture of products source: polyisocyanate component in the form of MDI-based diphenylmethanediisocyanate and hydroxyl-containing component in the form of a polyether containing three hydroxyl groups, in the presence of an inert solvent white spirit, characterized in that used as a polyisocyanate component, a polyisocyanate based on 4,4'-diphenylmethanediisocyanate with a content of NCO-groups of at least 29,5 g/100 g, as polyether use Laprol with a hydroxyl number 32-37 mg KOH/g - Laprol 5003 or Laprol 4503, in addition use butyl acetate, when the next original content, wt.h.:

The polyisocyanate 26-32,5

Laprol 5003 or Laprol 4503 30-32,5

Butyl acetate 8,79-10,36

White spirit 22,9-26

in this first mix hydroxyl-containing component with solvent white spirit, add butyl acetate or geobased the polyisocyanate, synthesis is carried out under stirring until the mass fraction of isocyanate NCO groups in the prepolymer 7,5-11,5%.

 

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FIELD: organic chemistry, polymer materials.

SUBSTANCE: polyester-polyols are obtained by double metalcyanide catalyzed polyaddition of alkylenoxide to starting material containing active hydrogen atoms. Alkylenoxide is continuously fed into reactor during induction period while maintaining constant pressure in reactor.

EFFECT: method for polyester-polyol production with decreased induction time.

2 ex, 1 dwg

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