RU2522427C1 - Liquid hydroxylamine curing agent for isocyanate prepolymers for producing sprayed polyurea-urethane coatings - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to formulations of liquid "hybrid" hydroxylamine curing agents for urethane prepolymers with terminal isocyanate groups, used in producing sprayed thick-layer polyurea-urethane coatings designed for corrosion protection of metal pipes, moulded coupling components, stop valves of compressor and pump stations, mounting assemblies main and field oil and gas pipelines, reservoirs for underground storage of liquefied gas and oil storages in factory or route coating conditions during construction, reconstruction and overhaul repairs. The composition of the curing agent includes the following components: 3,3'-dichloro-4,4'-diaminodiphenylmethane as an aromatic diamine, polyoxypropylenetriol with molecular weight of 5000 units as oligoether polyol, polydiethylene glycol adipate with molecular weight of 800 units as oligoester polyol, N,N'-tetraoxypropylene ethylenediamine with hydroxyl number of 640-800 mgKOH/g as oxypropylated ethylenediamine, black dye Nigrosin as a fat-soluble pigment.

EFFECT: invention enables to obtain a liquid curing agent with active hydrogen atoms, obtain a non-primer anticorrosion polyurea-urethane, having metal adhesion and cathodic disbonding resistance higher than GOST R51164-98 requirements for coatings with a primer undercoating.

2 tbl, 7 ex

Description

The invention relates to the formulations of liquid "hybrid" hydroxylamine hardeners, including crystalline aromatic diamine, dissolved in a mixture of non-volatile solvents - hydroxyl-terminated oligoester polyols, and intended, in particular, for the curing of isocyanate prepolymers in the preparation of polyurea thick-walled pipe insulation and protective coatings for oil and gas pipelines obtained by the method of "hot" airless spraying using 2-K spraying plants high pressure with a separate supply of a liquid polymer isocyanate base (prepolymer) and a liquid hardener, heated to a temperature of 40-70 ° C, with their mixing directly in the spray device.

One of the requirements for the technological process for producing sprayable polymer coatings by the method of airless deposition is the consistency of the components used - they must be liquid and have better viscosity characteristics at the application temperature for better mixing. The second requirement for the method of airless spraying of coatings is that after mixing the components, the resulting mixture should be thixotropic, and its viability optimal (50-150 s) to ensure the required thickness (1-4 mm) of the protective layer that does not flow from inclined and vertical surfaces .

In the interaction of NCO groups of the isocyanate base with hydroxyl (OH) groups of the hardener, polyurethane coatings (I) are formed, in the reaction of NCO groups with amine (NH ₂ ) groups of the hardener, polyureas (II) are formed, and in the interaction of the NCO base with " a hybrid "mixture of hydroxyl and amino compounds form polyureaurethane coatings (III):

Polyurea coatings have higher adhesion and physicomechanical characteristics due to the greater polarity of macromolecules, and the rate of interaction of NCO groups with NH ₂ groups is several orders of magnitude higher than the rate of reaction of NCO groups with OH groups. Therefore, by varying the molar ratio between OH and NH ₂ groups in the hardener, the necessary viability of the reaction mixture and the required adhesive and physico-mechanical properties of the coating are achieved.

In most cases, aromatic diamines such as diaminodiphenylmethane, metaphenylene diamine or 3,3'-dichloro-4,4'-diaminodiphenylmethane (the latter's trade name is Kuamine-K, Diametr-X, or MOSA) are used as the amine-containing component of the hardener. "), which are crystalline substances at ordinary temperature (their melting point> 100 ° C).

To obtain liquid hardeners for polyurethane sprayed systems, such powdered diamines are usually dissolved in organic solvents that do not contain active hydrogen atoms in the molecule, such as butyl acetate, methyl ethyl ketone, cyclohexanone, etc. [1]. However, such liquid hardeners are volatile, toxic and fire hazard. Their use leads to significant internal stresses due to shrinkage of the resulting polymer coatings up to cracking.

A known composition of a liquid hardener for producing polyurethane products based on 3,3'-dichloro-4,4'-diaminodiphenylmethane dissolved in non-volatile plasticizers is a mixture of di- (2-ethylhexyl) -phthalate with tributyl phosphate, with a mass ratio between them of 0.5 -0.7: 0.5-0.3 [2].

The use of the known hardener in the compositions of sprayed mastics is difficult due to the great viability of the reaction mixture, which prevents the formation of thick non-draining coatings. In addition, such plasticizers that do not contain reactive groups in the molecule are capable of further migration and exudation from the finished coatings, which can lead to embrittlement of the latter.

Polyurea-urethane coatings are formed when a solution of diamine in polyether polyols with terminal hydroxyl groups and a molecular weight of 400-5000 cu is used as a hardener. Thus, the composition of a liquid hardener based on 3,3'-dichloro-4,4'-diaminodiphenylmethane dissolved in a simple oligoester polyol - polyoxytetramethylene glycol (polyfurite) with a molecular weight of 1000 cu is known. with a molar ratio between them of 0.67: 0.33 and intended in combination with a mixture of isocyanate prepolymers for the manufacture of large-sized elastic products [3].

Along with the high elasticity and strength of the obtained polyureaurethane products, their high resistance to cyclic loading, the known hardener significantly increases the viability of the reaction mixture, which makes it possible to produce large-sized products weighing up to several hundred kilograms (membranes, diaphragms, dies, etc.), but do not provide thixostropy and fast curing speed in the case of coating on the substrate, which leads to their runoff from inclined and vertical surfaces.

Also known is a liquid hardener used for the manufacture of polyurethane products operating under cyclic loading conditions, which along with 3,3'-dichloro-4,4'-diaminodiphenylmethane includes a mixture of simple oligoester polyol - polyoxytetramethylene glycol with a molecular weight of 1000 cu and a complex oligoester polyol - polyethylene glycol adipate with a molecular weight of 800 cu when their molar ratio of 1: 1 and the following ratio between the components of the liquid hardener (wt.%): [4]

3,3'-dichloro-4,4'-diaminodiphenylmethane 38-42 a mixture of polyoxytetramethylene glycol with polydiethylene glycol adipate 58-62

However, such a hardener has the same disadvantages as the previous one. When used in polyurethane systems designed to produce sprayed thick-layer polyureaurethane coatings, it has great viability and does not allow to obtain a thixotropic mastic after mixing with an isocyanate prepolymer that does not flow down from vertical and inclined surfaces.

To reduce the viability of the reaction mass after mixing with an isocyanate prepolymer, a liquid hardener composition is proposed that includes, along with 3,3'-dichloro-4,4'-diaminodiphenylmethane, a simple oligoester polyol - polyoxytetramethylene glycol with a molecular weight of 1000 cu or complex oligopoliol - polyethylene butylene glycol adipate with a molecular weight of 2000 cu and hydroxypropylated ethylene diamine-N, N'-tetraoxypropylene ethylenediamine with a molecular weight of 290 cu ("Laprol-294"), in the following ratio between the components of the liquid hardener (parts by weight): [5]

3,3'-dichloro-4,4'-diaminodiphenylmethane 3.2-13.2 N, N'-tetraoxypropylene ethylenediamine 0.7-2.9 simple or complex oligoester polyol with a molecular weight of 1000-2000 cu 84.8-95.9

N, N'-Tetraoxypropylene-ethylenediamine not only ensures the formation of a defect-free polyureaurethane network, but also accelerates the process of its formation due to the content of two tertiary nitrogen atoms in the molecule that catalyze the urethane formation reaction.

However, the hardener of the above composition provides elastomers with a reduced level of hardness of 50-65 conventional units on the Shore-A scale, which is unacceptable for external anti-corrosion coatings of pipes and pipe parts of oil and gas pipelines: the required level of hardness in this case, at least, should be at least 95 conventional units on Shore-A.

The closest to the claimed technical essence and formulation is a liquid hardener for isocyanate prepolymers based on 3,3'-dichloro-4,4'-diaminodiphenylmethane, which is part of the Forpol-Oil complex anticorrosive polyurea coating, which ensures optimal mastic life ( 60-120 s at a temperature of 50-70 ° C) and the necessary level of adhesive and physico-mechanical characteristics of the obtained protective thick-layer coatings, regulated by the relevant technical industry requirements the knowledge of OAO Gazprom, OAO AK Transneft and GOST R51164-98 [6 - prototype].

Known hardener with active hydrogen atoms (the sum of NH ₂ + OH groups) with a hydroxyl (OH) number of 95-105 mgKOH / g and a mass fraction of total titratable nitrogen (NH ₂ ) of 4.2-4.5 wt.% Along with the specified above diamine contains, as an active non-volatile solvent, a mixture of simple or complex oligoester polyol with a molecular weight of 800-1000 cu and oxyproline ethylenediamine with a hydroxyl number of 640-800 mgKOH / g, and additionally an organo (fat) soluble pigment, in the following ratio between hardener ingredients (wt.%):

aromatic spatially hindered diamine with an amine number of 12-16.7 wt.% (3,3'-dichloro-4,4'-diaminodiphenylmethane) 35-40 simple or complex polyetherdiol with a molecular weight of 800-1000 cu 55-60 N, N'-tetraoxypropylated ethylenediamine with a hydroxyl number of 640-800 mgKOH / g 3-4 organo (fat) soluble pigments the rest is up to 100

The liquid hardener of the above composition allows to obtain a thick-layer anticorrosive coating of an insulating type that meets the technical requirements of OAO Gazprom, OAO Transneft and GOST R51164-98, in particular, to protect metal pipes, shaped pipe fittings (fittings) from corrosion , shutoff valves and assembly units of the main and field oil and gas pipelines of underground and underwater laying, pipelines and valves of compressor and pump stations, underground storage tanks liquefied gas storage tanks with operating temperatures range from minus 30 ° C to plus 60 ° C in a factory and trass (field) applying during their construction, reconstruction and repair.

However, such a coating meets the requirements only if it is used together with a primer sublayer obtained on the basis of 1-K moisture-curing isocyanate primer with a mass fraction of isocyanate (NCO) groups of 6-8%. Without the use of a primer, the values of two basic quality indicators that determine the long-term protective properties of coatings operating in corrosive environments when exposed to electric protective potential and stray currents do not correspond to regulated values. Namely:

- the value of the initial adhesion of the coating to the metal (A) is less than the required norm of 7.0 MPa, and the decrease in its level (ΔA) after holding the metal samples coated in water at a temperature of (60 ± 3) ° C for 1000 h is more than the permissible norm (40%);

- the resistance of the coating to cathodic exfoliation, determined by the size of the area of the exfoliated area after exposure of the samples in a 3% aqueous NaCl solution at a polarization potential of 1.5 V, at a temperature of (20 ± 3) ° C for 30 days, the area is much worse exfoliating coatings more regulated 5 cm ² .

The technical problem to be solved within the framework of the present invention is the development of a liquid hardener based on crystalline aromatic diamine - 3,3'-dichloro-4,4'-diaminodiphenylmethane and a mixture of liquid complex and simple oligoester polyols with hydroxypropylated ethylene diamine, the spraying of which together with isocyanate prepolymers a polyurea-urethane thick-layer primerless coating is formed, which has increased adhesion to the metal (initial and after aging in water) and resistance to cathodic peeling with the long-term preservation of the basic physical and mechanical characteristics and other regulated protective properties.

The solution to the above goal is achieved due to the fact that, in contrast to the known mixed composition with active hydrogen atoms of the prototype, the proposed composition of the liquid hardener has a hydroxyl number of 85-95 mgKOH / g, a mass fraction of the total titrated nitrogen of 3.5-4.0% and along with 3,3'-dichloro-4,4'-diaminodiphenylmethane contains a mixture of a simple oligoester polyol - polyoxypropylene triol with a molecular weight of 5000 cu and a complex oligoester polyol - polyethylene glycol adipate with a molecular weight of 800 cu together with N, N'-tetraoxypropylene ethylenediamine having a hydroxyl number of 640-800 mgKOH / g, and a fat-soluble pigment - dye black 9315 "Nigrosine", in the following ratio between hardener components (wt.%):

3,3'-dichloro-4,4'-diaminodiphenylmethane 30-35 polyoxypropylene triol with molecular weighing 5000 cu 12-15 polyethylene glycol adipate with molecular weighing 800 cu 42-52 N, N'-tetraoxypropylene ethylenediamine with hydroxyl number 640-800 mgKOH / g 2-4 fat-soluble black dye 9315 "Nigrosin" the rest is up to 100

Due to the content of secondary amine groups in the Nigrosin dye, it acts not only as a pigment, but also as a cocatalyst of urethane formation reactions together with tertiary nitrogen atoms of hydroxypropylated ethylenediamine.

The proposed liquid hardener, mixing with isocyanate prepolymers containing 13-17% NCO groups directly in the spray device, is applied by the method of "hot" (temperature of components 40-70 ° C) airless spraying using 2-K high-pressure apparatuses (up to 25 MPa) firms "WIWA" (Germany) or "GRACO" (USA).

The recommended molar ratio between the components of the sprayed polyureaurethane mastic (isocyanate prepolymer: hydroxylamine hardener) 0.9-1.0 / 1 (NCO / OH + NH ₂ ) depending on the required physical and mechanical characteristics of the coating, which determines the ratio between the components of the mastic as 1 , 3-1.4 / 1 (by volume) or 1.2-1.3 / 1 (by weight).

The above limits of the ratios between components with active hydrogen atoms in the composition of the inventive liquid hardener are determined experimentally and are optimal in terms of achieving the declared positive effect. The reduction in the proportion of reactive groups (the sum of NH ₂ + OH) in the composition of the proposed “hybrid” hydroxylamine hardener compared to the prototype composition not only led to a correction of the survivability of the reaction mass after mixing the components of polyureaurethane mastic while maintaining its thixotropic properties, but also eliminated the use of primers to obtain the required level of adhesion characteristics of the obtained thick-layer coatings due to better wetting of the metal surface and spreading of the mastic.

As a polydiethylene glycol adipate with a molecular weight of 800 cu use the brand "PDA-800" according to TU 38.103287-80 or its imported equivalent. As a polyoxypropylene triol with a molecular weight of 5,000 cu use Laprol-5003-2-15 (Vladpol-5) according to TU 2226-006-10488057-94; TU 2226-023-10488057-95 or their imported analogues "Voranol SR4711"; "CP4702". Black fat-soluble dye 9315 "Nigrosin" import.

As the 3,3'-dichloro-4,4'-diaminodiphenylmethane, a domestic-produced diamine Diametr-X (TU 6-14-980-84) or its imported analogues, Kuamine-K or MOSA, are used.

As hydroxypropylated ethylenediamine with a hydroxyl number of 640-800 mgKOH / g, aminotetrols of the brands "Voranol RA-640", "Voranol RA-800" or the domestic analogue "Lapromol-294" according to TU 6-05-1681-80 are used.

The proposed liquid hardener is manufactured on standard chemical equipment by dissolving crystalline diamine in a mixture of oligoester polyols with hydroxypropylated ethylene diamine at a temperature of 90-110 ° C until a homogeneous solution is obtained.

This hardener can be used in conjunction with industrially produced isocinate prepolymers based on diphenylmethadiisocyanate with a mass fraction of NCO groups of 13-17% and a dynamic viscosity of 3-15 Pa · s at a temperature of (20 ± 3) ° C, for example, for curing the Forpol prepolymer -NCO "grades A and B according to TU 2458-104-20504464-2006 or the Surel-ML prepolymer TU 51-31323949-80-2004.

The developed hardener formulation is focused on the use of ingredients of both domestic and foreign production, manufactured on an industrial scale, using standard chemical equipment for its production. Polyureaurethane mastic with its content can be applied to the protected surfaces by existing machine spraying methods. All this allows us to make a reasonable conclusion about the conformity of the claimed technical solution to the inventive criterion of "Industrial applicability".

Comparison of the formulation of the proposed liquid hardener with known compositions of a similar purpose allows us to conclude that it meets the criterion of "Novelty", since in this case a new set of hardener ingredients is compiled, where for the first time as a non-volatile solvent of aromatic diamine, both complex and simple oligoester polyols are used together with liquid alkanolamine - hydroxypropylated ethylenediamine in the claimed amounts.

This innovation led to a non-obvious effect that could not be expected - obtaining an uncoated thick-layer polyurea-urethane coating with a high level of initial adhesion to the metal and an acceptable value of the drop in adhesion after prolonged aging of the coating in hot water, while maintaining technological, dielectric and other regulated physical, mechanical and operational characteristics. In addition, a high level of adhesive properties of the resulting coating ensures its resistance to cathodic peeling in accordance with existing technical requirements. The above indicates that the proposed technical solution meets the criterion of "Inventive step".

Samples of coatings for testing on metal plates of steel grade St.3 measuring 150 × 150 × 5-6 mm were prepared as follows. The plates were preliminarily subjected to abrasive blasting using cuproslag with a grain size of 1.5-3.0 mm as an abrasive to obtain a surface roughness (R _z ) of 50-120 μm, after which the treated plates were dedusted and degreased with solvent. Then, using a DIOMIX-230 high-pressure apparatus (WIWA), polyurea-urethane mastic consisting of the proposed hardener and the Forpol-NCO isocyanate prepolymer of grades A and B was applied onto prepared plates 2.5-3.0 mm thick. Temperature the hardener was 40-50 ° C, and the prepolymer was heated to 65-75 ° C. At such temperature conditions, the viscosities of both components of the mastic are close, which improves the uniformity of their mixing.

A free film of polyureaurethane coating for determining the physicomechanical and other characteristics was obtained by spraying mastic on fluoroplastic sheets.

All tests were carried out 5 days after coating in accordance with the methods set out in the appendices to GOST R51164-98 "Steel main pipelines. General requirements for corrosion protection".

The technical essence and advantages of the proposed liquid hardener in the composition of polyureaurethane mastic are illustrated by the following experimental data.

EXAMPLES 1-7

Table 1 shows the formulations and characteristics of the hardener of the prototype and the proposed liquid composition with active hydrogen atoms, as well as the characteristics of isocyanate prepolymers used to obtain polyurea coatings, and table 2 shows the results of their tests. The mass ratio between the isocyanate prepolymer and hardener in the composition of the mastic in all examples was 1.25: 1.0.

Thus, as can be seen from the above data, the proposed liquid hardener due to the combination of the properties of the liquid complex and simple oligoetherpolyols and N, N'-teraoxypropylene ethylene diamine with the properties of 3,3'-dichloro-4,4'-diaminodiphenylmethane dissolved in them allowed the isocyanate prepolymers to be cured based on diphenylmethanediisocyanate to obtain, without using a primer, a thick-layer anticorrosive polyurea-urethane coating having the same adhesive characteristics and resistance to cathodic peeling when stored injury to physico-mechanical and other quality indicators, as well as known coatings of a similar purpose, but used in conjunction with a primer sublayer. This reduces the range of unused materials, simplifies and speeds up the process of applying a protective polymer coating to oil and gas pipelines and their corresponding component parts and products. In addition, the absence of primers based on volatile organic solvents increases the environmental friendliness and reduces the fire hazard of the insulation works, which is especially relevant when they are carried out in closed production rooms.

Information sources

1. Labutin A.L., Shitov B.C. Protective coatings based on urethane elastomers. Series: "Synthetic Rubber Industry". - M .: TsNIITEneftekhim, 1977, S.12-13.

2. Patent No. 2292358 (RF). IPC ⁶ C08G 18/32; C08L 75/04. Liquid hardener for polyurethane systems. Claim 08/01/2005. Publ. 08/27/2007.

3. Patent No. 2155781 (RF). IPC ⁶ C08L 75/04. Polyurethane composition. Claim 10/07/1998. Publ. 09/10/2000.

4. Patent No. 2043369 (RF). IPC ⁶ C08G 18/32. Liquid hardener for polyurethane systems. Claim 12/02/1992. Publ. 09/10/1995.

5. Patent No. 2299216 (RF). IPC ⁶ C08G 18/32; C08L 75/04. Liquid hardener of prepolymers with terminal isocyanate groups. Claim 06/16/2005. Publ. 05/20/2007.

6. Patent No. 2428443 (RF). IPC ⁷ C09D 5/08; C09D 175/02; C09D 175/04. Integrated anti-corrosion polyurea coating. Claim 03/16/2010. Publ. 09/10/2011 - a prototype.

Claims (1)

A liquid hydroxylamine hardener of isocyanate prepolymers for producing sprayable polyureaurethane coatings containing crystalline aromatic diamine dissolved in a simple or complex oligoester polyol and hydroxypropylated ethylene diamine in the presence of a fat-soluble pigment, characterized in that the proposed composition with active OH atoms is 95 mg mass fraction of total titratable nitrogen is 3.5-4.0% and includes, as aromatic diamine, 3,3′-dichloro-4,4′-diaminodiphenylmethane, in as a simple oligoetherpolyol - polyoxypropylene triol with a molecular weight of 5000 cu, as a complex oligoetherpolyol - polyethylene glycol adipate with a molecular weight of 800 cu, as hydroxypropylated ethylene diamine - N, N′-tetraoxypropylene ethylene diamine with a hydroxyl number of 640-800 mg and also has a fat-soluble pigment - dye black "Nigrosine" in the following ratio between the specified ingredients of the hardener (wt.%):
3,3′-dichloro-4,4′-diaminodiphenylmethane 30-35 polyoxypropylene triol 12-15 polydiethylene glycol adipate 47-52 N, N′-tetraoxypropylene ethylenediamine 2-4 fat soluble dye the rest is up to 100