RU2848185C1 - Thermal insulation protective coating - Google Patents

Abstract

FIELD: materials science.

SUBSTANCE: invention relates to materials science, specifically to polymeric thermal insulation and fire-resistant materials in the form of coatings on thermally insulated surfaces. A polyurethane thermal insulation composition is proposed, consisting of a two-component polyurethane binder and hollow glass microspheres, and additionally containing chopped glass fibre, wollastonite, ground mica, organophosphorus flame retardant and pigments in the following proportions: polyurethane binder A+B 65-70 wt.%; hollow glass microspheres 20-18 wt.%; chopped glass fibre up to 150 μm in length 3-2 wt.%; wollastonite 1-0.5 wt.%; ground mica 3-2.5 wt.%; trichloropropyl phosphate 5-4.5 wt.%; green, black or white pigment paste 3.0-2.5 wt.%. In this case, the polyurethane binder used is a material with the following composition by weight (wt%) per 100 wt% of mixture A+B: component A: oligopropylene oxide diol 2000Da 29.5 wt%; castor oil 30.2 wt%; 1,4-butanediol 4.8 wt.%; diethyltoluene diamine 2.5 wt.%; component B: polyisocyanate brand "Vannat 200" 33.0 vol.

EFFECT: thermal insulation of special equipment, including in field conditions, by applying a curable thermal insulation polyurethane mastic to its surface.

2 cl, 2 tbl, 7 ex

Description

Field of technology

The invention relates to materials science, specifically to polymeric heat-insulating and fire-resistant materials in the form of coatings on heat-insulated surfaces.

State of the art

It is known that among polymer thermal insulation materials, mastic compounds, such as those based on polyurethane, epoxy, polyester, and siloxane resins, are of significant practical importance. They can be applied to insulated surfaces using a variety of methods, including manual application with spatulas and brushes, mechanized pumping, and spraying. The use of such compounds, filled with air bubbles, foamed mineral particles (perlite, expanded clay, vermiculite), or foam plastic particles, allows for the thermal insulation of complex structures, including in field conditions, which is important, for example, for the thermal insulation of pipelines and special equipment. However, low-strength and relatively coarse-grained (0.3-2.0 mm) fillers reduce the strength properties of composites.

Polyurethane binders for creating thermal insulation mastic materials have a number of advantages over epoxy, polyester, or silicone resins. In particular, they are distinguished by high wear resistance, impact resistance, vibration resistance, frost resistance, adhesion to various substrates, and tensile and tear strength [Zonnenshain M.F. Polyurethanes. Composition, Properties, Production, Application. Translated from English. – St. Petersburg: TsOP "Profession", 2018. – 576 p.].

However, like most polymeric materials, polyurethanes are not fire-resistant and, moreover, when burned, they emit highly toxic combustion products, so the use of thermal insulation coatings based on them is limited.

Syntactic closed-cell foams are known to be gas-filled composite materials in which the fillers are hollow spherical particles, most often referred to as hollow microspheres [Aristova E. Yu., Denisova V. A., Drozhzhin V. S. et al. Composite Materials Using Hollow Microspheres. - Aviation Materials and Technologies, 2018, No. 1 (50), pp. 52-57]. Among the hollow microspheres, a distinction is made between aluminosilicate (ash), glass, ceramic, metal, polymer, and carbon microspheres. The presence of hollow particles with a strong shell, such as glass microspheres, in a composite material provides it with low density, reduced thermal conductivity and sound permeability, a high Young's modulus, compared to conventional foam plastics, a low coefficient of thermal expansion, and, in some cases, radio transparency. Due to this, syntactic foams, or spheroplasts, are used in aircraft construction and spacecraft designs as thermal insulation coatings (for example, in the form of ablative thermal protection), shipbuilding (buoyancy blocks, hulls of floating craft, elements of deep-sea stationary systems, submersibles, buoy devices), insulation of industrial equipment and pipelines, etc.

Rigid polyurethane foams filled with glass microspheres for the purpose of increasing the strength properties of the material are known [U.S. Pat. 3,993,608. 1976. IPC C08G 18/14; B32B 27/40; C09K 3/00]. According to the invention, strong, non-friable polyurethane-isocyanurate foam plastics are provided that contain hollow glass spheres and that are particularly useful in structural applications where impact resistance or energy absorption properties are required, for example, as a means of reinforcement in structural panels such as automobile doors, or as building sandwich panels.

However, such polyurethane foams are flammable and are not intended for outdoor use.

Known [Patent RF 2,226,202. 2004. IPC C08L75/04; C08J9/32)] are polyurethane thermal insulation compositions based on rigid polyurethane foam, containing 70-95 wt.% polyurethane and 5-30 wt.% glass microspheres. Fractions of glass microspheres with sizes of 30-50 μm, 60-140 μm, as well as mixtures of the specified fractions are used. The invention makes it possible to reduce the flammability of the foam, increase lightfastness, compressive and bending strength, and improve processability during pouring and spraying. The claimed products are recommended for the manufacture of protective coatings for building structures and pipelines for the purpose of their thermal insulation and complex insulation.

However, rigid polyurethane foams of the specified composition are not strong enough and are not classified as non-flammable.

The closest in composition to the material we are claiming is a polymer heat-insulating paint and varnish composition (prototype), consisting of a polymer binder of various chemical natures, including polyurethane (example 5 from the prototype), hollow microspheres (including glass) and mineral pigment fillers, which predominantly reflect the infrared region of the solar spectrum [US Patent 8,287,998 B2. 2016. B32B5/16; B32B 8/00].

The use of these fillers results in a thermal conductivity of less than 0.3 W/(m⋅deg.), which is not a high value for thermal insulation coatings. Furthermore, the patent description lacks information on the strength characteristics, crack resistance, adhesion to substrates, or fire resistance of the thermal insulation paint coatings. It can be assumed that these values are low, as the proposed materials are not designed for use under high mechanical loads and possible fire exposure.

Disclosure of invention

The proposed invention solves the problem of thermal insulation of special equipment, including in field conditions, by applying to its surface a curable thermal insulation polyurethane mastic, conditionally named by the authors as "Teplosfera", filled with a fine-grained filler in the form of hollow glass microspheres and other functional additives.

This problem is solved by using a newly developed composition of polyurethane, which is cured under normal weather conditions, as a polymer binder. It has a short gelation time, high strength, frost resistance, heat resistance, and adhesion to metal, paint, and other surfaces.

The polyurethane thermal insulation composition consists of a two-component polyurethane binder and hollow glass microspheres. To enhance the strength and fire resistance of the thermal insulation coating for special equipment, it additionally contains chopped fiberglass, wollastonite, ground mica, an organophosphorus flame retardant, and pigments. It additionally contains chopped fiberglass, wollastonite, ground mica, an organophosphorus flame retardant, and pigments in the following proportions (wt%):

polyurethane binder A+B 65…70;

glass hollow microspheres 20…18;

chopped glass fiber up to 150 µm long 3…2;

wollastonite 1…0.5;

ground mica 3...2.5;

trichloropropylphosphate 5...4.5.

The following material parts by weight (w.p.) were used as a polyurethane binder per 100 w.p. of mixture A+B:

component A:

oligopropylene oxide diol 2000 Da -29.5;

castor oil – 30.2;

1,4-butanediol 4,8;

diethyltoluenediamine 2.5;

component B:

polyisocyanate brand "Vannat 200" 33.0,

and also contains pigment pastes of green, black and white colors in the amount of 2.5...3 wt.%.

To reduce viscosity and for application by spraying, the composition may additionally contain a mixed solvent of grade P4 in an amount of 20...30 wt.% relative to the weight of the cured thermal insulation polyurethane mastic.

Implementation of the invention

Relatively accessible raw materials listed in Table 1 were used as starting components for obtaining the polyurethane binder.

Table 1

No. Product name Supplier Note 1 Oligopropylene oxide glycol with a molecular weight of 2000 Da, brand "Sintepol 2000" LLC "Sintez OKA", Dzerzhinsk 2 1,4-Butanediol Platmass-Group LLC, Moscow 3 Castor oil Nortex LLC, Noginsk 4 Diethyltoluenediamine Nortex LLC, Noginsk 5 Dibutyltin dilaurate (reaction catalyst) Nortex LLC, Noginsk If you need to speed up the reaction 6 Polyisocyanate brand "Vannat 200" Ross-Polymer LLC, Moscow

The presence of polypropylene oxide blocks and castor oil units in the polyurethane provides the material with sufficient flexibility, elasticity (elongation at break up to 50%), impact and vibration resistance, and frost resistance down to -50°C. The introduction of 1,4-butanediol units linked to an aromatic polyisocyanate into the polymer structure gives the material increased tensile strength (10 MPa) and elastic modulus (30 MPa). The use of diethyltoluenediamine as an active chain extender provides the polyurethane with a rapid gain in thixotropy and strength. Chemical crosslinking of the binder through the use of trifunctional castor oil and polyisocyanate gives the material additional strength and resistance to swelling in liquid fuels and oils (3 wt%).

Glass microspheres (30-50 µm), ground mica, wollastonite, and ground chopped glass fiber (150 µm) were used as fillers in the syntactic thermal insulation material. The glass microspheres, produced by NPO Stekloplastik (Solnechnogorsk, Moscow Region), provide the material with a low density (0.6 g/ ^cm³ ) and thermal conductivity, while increasing mechanical strength and elastic modulus. The microspheres also make the filled material fireproof and self-extinguishing (instantly extinguished when removed from the flame of a gas burner).

To enhance the fire resistance of polyurethane spheroplast, 2-4% by weight of ground Muscovite SMM mica (VitaReaktiv LLC, Moscow) is added to the composite. Its flakes reduce the rate of oxygen diffusion into the material. Trichloropropyl phosphate (Nortex LLC, Noginsk) is also added to the composite, forming a dense barrier crust of chlorinated polyphosphoric acids with low oxygen permeability on the surface. After the addition of these additives, the thermal insulation composite becomes coated with a dark brown crust in a burner flame and becomes non-flammable.

To increase the strength properties, resistance to tearing and cracking, elongated particles were introduced into the composite material: wollastonite grade "Casiflux FG20" (OOO Nortex, Noginsk) and chopped glass fiber (microfiber) with an average fiber length of 150 μm and an elementary thread diameter of 10 μm (OOO ExpressKhim, Chelyabinsk), obtained by grinding dispersed glass fiber 12 mm long in a fine grinder.

To create a camouflage effect, polyurethane tinting pastes are added to the thermal insulation mastic. These pastes typically consist of a 20% pigment dispersion in glycol (Polyanet. Fiberglass Technologies, Moscow). These pastes can be green, black, or white. Mixing green and black pigments allows for the adjustment of the brightness and shades of the green.

Component A of the two-component filled thermal insulation mastic is prepared as follows: oligopropylene oxide diol, castor oil, 1,4-butanediol, and diethyltoluenediamine are mixed in a container with a stirrer. The catalyst dibutyl tin dilaurate (if necessary in winter), trichloropropyl phosphate, ground mica, wollastonite, glass microfiber, hollow glass microspheres, and coloring pastes are added to the resulting liquid mixture sequentially and while stirring. The result is a viscous and thixotropic mastic with a long shelf life (3 months in tightly sealed metal buckets). Component B is liquid polyisocyanate grade "Vannat 200" and is stored in containers securely sealed to prevent exposure to water vapor.

After mixing components A and B, a thixotropic mastic is formed, which is applied to clean and dry surfaces using spatulas. The layer thickness should be 4-6 mm. To mechanize the application of mastic thermal insulation, the material is diluted with a mixed solvent for polyurethanes of the "P4" type; for this, 20-30% by weight of solvent is added, depending on the ambient temperature. Spray the thermal insulation mastic onto the surfaces to be insulated in 2-3 steps using airless spray equipment with a nozzle diameter of 3 mm. The interval between coats is 15-20 minutes. The mastic hardens to a tack-free state in 60-120 minutes for concentrated mastic and in 4-24 hours for mastic diluted with solvent, depending on the ambient temperature.

Preparing insulated surfaces, including in the field, involves removing dust and dirt with water and wiping off excess water from the structures with a clean cloth. Work should be carried out in dry weather or under cover.

After curing, the Teplosfera heat-insulating mastic turns into a durable composite material containing 18...20 wt.% (60...65% of the composite volume (vol.%)) of glass microspheres, with the properties given in Table 2.

Table 2.

No. Coating property, dimension Example, number 2 3 4 5 1 Density, g/ ^cm3 0.6 0.6 0.7 0.7 2 Hardness, Shore A 74 75 70 71 3 Thermal conductivity, W/m•deg 0.120 0.120 0.125 0.125 4 Tensile strength, kgf/ ^cm2 35 37 31 33 5 Modulus of elasticity at break, kgf/ ^cm2 1650 1700 1600 1630 6 Relative elongation at break, % 18 19 30 35 7 Adhesion to steel-3, kgf/ ^cm2 30 30 31 32

From a practical standpoint, increasing the glass microsphere content in the spheroplast above 65% by volume (more than 20% by weight) is impractical, as the mastic's viscosity becomes too high and difficult to apply to surfaces. Furthermore, its elasticity decreases, making the composite brittle. Reducing the glass microsphere content in the spheroplast below 60% by volume (less than 18% by weight) is also impractical, as this increases its density and, most importantly, thermal conductivity.

The fire resistance of the composite coating is achieved through a high degree of filling with microspheres, lamellar filler (ground mica) and the addition of an organophosphorus fire retardant.

The light resistance of the thermal insulation coating is ensured by fillers that absorb light energy in the surface layer of the cured material.

Frost resistance of spheroplast down to minus 50 degrees is achieved due to the elastic part of the polyurethane binder, which contains elastic blocks of polypropylene oxide with a molecular weight of 2000 and flexible links of castor oil.

The high strength properties of the thermal insulation gas-filled composite, compared to rigid foam plastics, are associated with the presence of strong intermolecular physical bonds between polar urethane groups, a three-dimensional chemical network formed through the use of trifunctional castor oil and polyisocyanate, the use of elongated fillers and durable glass microspheres.

The developed polyurethane thermal insulation material is repairable; damage to coatings based on it can be easily repaired by mechanically cleaning the defect and applying a new layer of mastic, while ensuring a high cohesive bond between the old and new layers.

Below are examples of the invention implementation.

Example 1. Preparation of 67 kg of component A of polyurethane binder under production conditions.

To prepare 67.0 kg of component A of the polyurethane binder, 29.5 kg of Sintepol 2000 oligomer, 30.2 kg of castor oil, 4.8 kg of 1,4-butanediol, and 2.5 kg of diethyltoluenediamine are added to a 100-liter stainless steel container equipped with a low-speed (100-300 rpm) frame stirrer to avoid introducing air bubbles. After mixing, the mixture produces a homogeneous solution of hydroxyl- and amine-containing compounds.

This amount of component A must react with 33.0 kg of component B (hardener), which is a polyisocyanate of the Vannat 200 brand.

Example 2. Preparation of filled component A of the two-component polyurethane heat-insulating composition "Teplosfera" of dark green color under production conditions.

To the obtained liquid component A (e.g. 1.67 kg, or 43.55% in the composite) of polyurethane binder (after mixing with 33 kg of hardener it will make up 65% in the composite) 7.69 kg (which will make up 5% in the cured composite) of trichloropropyl phosphate, 4.62 kg of ground mica (3% in the composite), 1.54 kg of wollastonite (1% in the composite), 4.62 kg of glass microfiber (3% in the composite), 30.77 kg of glass hollow microspheres (20% in the composite), 3.08 kg of RAL 6009 “Fir green” tinting paste (2% in the composite), 1.54 kg of RAL 9005 “Deep black” tinting paste (1% in the composite) are successively added with stirring.

The finished filled composite mastic, made from component A of the polyurethane binder, is packaged in quantities of 120.86 kg each in 20-liter metal buckets with sealed lids fitted with a hoop. This quantity of filled component A (15.10 kg), dark green in color, is accompanied by component B (4.12 kg), packaged in a sealed 5-liter metal bucket.

Example 3. Preparation of filled polyurethane heat-insulating composition "Teplosfera" of white color in production conditions.

To the obtained liquid component A (example 1, 67 kg, or 43.55 wt.% in the composite) of polyurethane binder (after mixing with 33 kg of hardener A + B will make 65 wt.% in the composite) 7.69 kg (which will make 5 wt.% in the cured composite) of trichloropropyl phosphate, 4.62 kg of ground mica (3 wt.% in the composite), 1.54 kg of wollastonite (1 wt.% in the composite), 4.62 kg of glass microfiber (3 wt.% in the composite), 30.77 kg of glass hollow microspheres (20 wt.% in the composite), 4.62 kg of white tinting paste RAL 9010 "Pure White" (3 wt.% in the composite) are successively added with stirring.

The finished filled composite mastic, made from component A of the polyurethane binder, is packaged in quantities of 120.86 kg each in 20-liter metal buckets with sealed lids fitted with a hoop. This quantity of filled component A (15.10 kg), white in color, is supplemented with 4.12 kg of component B, packaged in a sealed 5-liter metal bucket.

Example 4. Preparation of a filled polyurethane heat-insulating composition "Teplosfera" of dark green color with greater elasticity under production conditions.

To the obtained liquid component A (example 1.67 kg, or 46.90 wt.% in the composite) of polyurethane binder (after mixing with 33 kg of hardener A + B will be 70 wt.% in the composite) sequentially with stirring add 6.43 kg (which will amount to 4.5 wt.% in the cured composite) of trichloropropyl phosphate, 3.57 kg of ground mica (2.5 wt.% in the composite), 0.71 kg of wollastonite (0.5 wt.% in the composite), 2.86 kg of glass microfiber (2 wt.% in the composite), 25.71 kg of glass hollow microspheres (18 wt.% in the composite), 2.38 kg of tinting paste RAL 6009 "Fir green" (1.67 wt.% in the composite), 1.19 kg of tinting paste RAL 9005 "Deep black" (0.83 wt.% in composite).

The finished filled composite mastic, made from component A of the polyurethane binder, is packaged in 15.69 kg portions in 20-liter metal buckets with sealed lids fitted with a hoop. This quantity of filled component A (15.69 kg), dark green in color, is accompanied by component B (4.71 kg), packaged in a sealed 5-liter metal bucket.

Example 5. Preparation of a filled polyurethane heat-insulating composition "Teplosfera" of white color with greater elasticity under production conditions.

To the obtained liquid component A (for example 1.67 kg, or 46.90 wt.% in the composite) of polyurethane binder (after mixing with 33 kg of hardener A + B it will make 70 wt.% in the composite) 6.43 kg (which will make 4.5 wt.% in the cured composite) of trichloropropyl phosphate, 3.57 kg of ground mica (2.5 wt.% in the composite), 0.71 kg of wollastonite (0.5 wt.% in the composite), 2.86 kg of glass microfiber (2 wt.% in the composite), 25.71 kg of glass hollow microspheres (18 wt.% in the composite), 4.57 kg of white tinting paste RAL 9010 "Pure White" (2.5 wt.% in the composite) are successively added with stirring. The finished filled composite mastic, made from component A of the polyurethane binder, is packaged in quantities of 109.85 kg each in 20-liter metal buckets with sealed lids fitted with a hoop. This quantity of filled component A (15.69 kg), white in color, is accompanied by 4.71 kg of component B, packaged in a sealed 5-liter metal bucket.

Example 6. Manual application of the curable thermal insulation mastic "Teplosfera" to a painted metal surface in the field.

Fill a 20-liter bucket with 15.10 kg of component A, a viscous, dark-green, colored mastic (example 2), thoroughly mixed using a corded (or corded) electric drill with a screw attachment at low speeds, pressing the stirrer against the sides and bottom of the container. After mixing the filled mastic, add 4.12 kg of liquid, low-viscosity component B (hardener) to the 20-liter bucket and mix thoroughly. This yields 19.22 kg of thixotropic mastic, which is poured into 3-liter polypropylene buckets (3-6 buckets for 3-6 workers) and applied manually with spatulas, first to horizontal and inclined surfaces, and then to vertical ones. During this time, the viscosity and thixotropy of the mastic increase, and it runs off vertical surfaces less. The open time for applying mastic is 30-60 minutes depending on the ambient temperature.

Example 7. Mechanized application of the curable thermal insulation mastic "Teplosfera" onto a painted metal surface in the field in the presence of an electrical network.

Filled component A in a 20-liter bucket in the amount of 15.10 kg in the form of a viscous, colored white mastic (example 3) is mixed using an electric drill with a screw attachment at low speeds, pressing the stirrer against the walls and bottom of the container. After mixing the filled mastic, liquid low-viscosity component B (hardener) in the amount of 4.12 kg is added to the 20-liter bucket and the mixture is thoroughly mixed. This produces 19.22 kg of thixotropic mastic, which is diluted with a mixed solvent of grade "P4" in an amount of 20-30 wt.% of the mastic weight (3.8-5.7 kg of solvent is added to the bucket) depending on the ambient temperature (from 3 to 40°C) and the power of the spraying equipment. The diluted mastic is used for application to the surfaces of structures using airless spray equipment equipped with a gun with a nozzle diameter of 3 mm. The time interval between applications of 2 mm thick mastic layers in a single pass is 15-30 minutes, depending on the ambient temperature. To achieve good thermal insulation properties, especially on the hottest areas of the surface, the applied mastic thickness should be at least 4 mm, preferably 6 mm. The open time for applying diluted mastic is 1.5-2 hours, depending on the ambient temperature.

Claims (17)

1. A polyurethane thermal insulation composition consisting of a two-component polyurethane binder and glass hollow microspheres, characterized in that it additionally contains chopped glass fiber, wollastonite, ground mica, an organophosphorus fire retardant and pigments in the following proportions, wt.%: polyurethane binder A+B 65-70; glass hollow microspheres 20-18; chopped glass fiber up to 150 µm long 3-2; wollastonite 1-0.5; ground mica 3-2.5; trichloropropylphosphate 5-4.5; pigment paste of green, black or white colors 3.0-2.5; in this case, the material used as a polyurethane binder was the following: parts by weight (w.p.) per 100 w.p. of mixture A+B: component A, wt.: oligopropylene oxide diol 2000 Da 29.5; castor oil 30.2; 1,4-butanediol 4,8; diethyltoluenediamine 2.5, component B, w.c.: polyisocyanate brand “Vannat 200” 33.0. 2. A polyurethane composition according to claim 1, characterized in that additionally contains a mixed solvent of grade P4 in an amount of 20-30% by weight relative to the weight of the cured thermal insulation polyurethane mastic.