KR100554275B1 - Intumescent fire-retardant composition for high temperature and long duration protection - Google Patents

Abstract

Flame retardant coating materials include a foamable base material with a foaming agent, a blowing agent, a carbonizing agent, a binder, a solvent, and a pigment. The coating material is a flame spreading reducing agent; Refractory fibers dispersed in the fluid foamable base material; Oxygen reducer; Heat conduction reducing agents; Stabilizers and volatile organic matter reducing ingredients; Mechanical enhancer components for adhesion and resistance to physical impact; Waterproofing agent; And an elastomer that increases resistance to cracking and shrinkage and facilitates spraying.

Description

Intumescent fire-retardant composition for high temperature and long duration protection

The present invention relates to flame retardant coatings which are applied to many organic and inorganic substrates to provide protection from fire by reducing flame spread and reducing thermal conduction. More specifically, it is new and used for harsh applications for the protection of substrates exposed to high temperatures or prolonged fire, or for use in substrates such as plastics and composites with relatively low melting or flash points. Improved flame retardant coating compositions are devised.

Intumescent materials have long been known and have been used as coatings to provide thermal protection up to about 2,000 ° F. Substrates such as wood, metals such as iron, aluminum and the like, and various kinds of plastics such as PVC, thermoplastics, and epoxides are coated to make them more flame retardant.

However, foam coatings applied to the aforementioned substrates are impractical when subjected to harsh physical and environmental conditions. In addition, with the increasing use of wood and wood by-products, and the proliferation of new types of wood composites used in the construction of homes and offices, as well as plastics and other organic composites, current foamed and flame-retardant coating compositions have long been burned with It does not provide adequate protection from them. At present, no single foamed flame retardant coating material has all of the following characteristics:

1. Reduce available oxygen in confined spaces, such as rooms, to extinguish a fire and delay the fire during flashover.

2. The coating provides low thermal conductivity to protect various substrates, especially where low weight and low cost are important, such as airplanes and ships.

3. Provides effective foamed flame retardant coatings for low density wood by-products, composite wood and plastic materials that require no flame spread for prolonged exposure in the event of fire.

4. Sufficient mechanical properties and durability to resist friction, shock and harsh weather.

5. Nontoxic before exposure to heat, and the amount of combustion products released upon exposure to heat is below the gas level emissions required by today's traffic standards.

In addition, in many cases where foamy flame retardant coatings are applied to substrates such as wood, PVC, thermoplastics, aluminum and epoxides, coatings are impractical for reasons other than protection from fire, which are not wear resistant, impact resistant, waterproof, And lack of resistance to other environmental factors. Because of these factors, current coatings do not provide protection from fire and heat for a sufficient time in a fire and are not durable enough to last long enough to be cost effective.

There is a need for new and improved foamed flame retardant coating materials that will provide substantial protection from fire and heat for a long time in a fire. The coating material can be applied to various substrates such as iron, steel, stainless steel, aluminum, and other nonferrous metals, wood, plywood, particle boards, and other wood by-products, plastics, PVC, thermoplastics, epoxides, and composites. Should be available for

Description of the Prior Art

Expandable flame retardant coating materials of various compositions for use in various substrates have been disclosed in the prior art. See, for example, US Pat. No. 4,380,593; 4,740,527; 4,879,320; 4,965,296; And 5,401,793 all disclose foamable flame retardant coating materials of different chemical compositions used in various substrates. None of the prior art patents discloses the chemical composition of the present invention.

It is therefore an object of the present invention to provide a foamable flame retardant coating composition that is effective at temperatures such as 2500 ° F. that are continuously maintained for a long time under severe environmental conditions while at the same time reducing the mechanical properties of the original material coated.

It is another object of the present invention to provide a thin, lightweight foamable flame retardant coating that provides low thermal conductivity.

Another object of the present invention is to provide a foamed flame retardant coating composition which reduces oxygen (O ₂ ) available in a limited area, in order to reduce the combustion time in case of fire or explosion and to delay the arrival of flashover. .

It is another object of the present invention to provide a foamed flame retardant coating composition for various low density wood and wood composite products that require zero flame spread upon prolonged exposure to fire.

Another object of the present invention is to provide a foamed flame retardant coating composition that does not emit harmful vapors in the surroundings in case of fire.

Another object of the present invention is to provide a foamed flame-retardant coating composition with improved adhesion to the substrate, wear resistance and impact resistance.

Another object of the present invention is to provide a foamed flame retardant coating composition which is waterproof and reduces the hygroscopicity of the coating material.

It is another object of the present invention to provide a foamed flame retardant coating composition in which a coating material on a given substrate is improved by reducing hygroscopicity in a coating material and having a longer life and exhibiting better performance in a fire.

Other objects of the present invention are iron, steel, stainless steel, aluminum, and other nonferrous metals, wood, plywood, cardboard, particle board, plastics, PVC, thermoplastics, epoxides, neoprene, rubber, and It is to provide a foamable flame retardant coating composition suitable for a variety of substrates, such as composites.

Another object of the present invention is to provide a foamed flame retardant coating composition that can be used in many industries such as construction, transportation, telecommunications, utilities, marine, chemical, petroleum, manufacturing, and military applications.

Another object of the present invention is to prevent corrosion due to chemicals, corrosive vapors, water, and brine when coated on a substrate; It is also to provide a foamed flame retardant coating composition that can withstand physical shock, high pressure, and / or mechanical vibration without peeling the coating material from the substrate.

Another object of the present invention is to form an intumescent base material, a flame spread reduction agent, an oxygen reduction agent, a thermal transmission reduction agent, a refractory fiber new combinations of fibers, stabilizers, volatile organic (VOC) reduction components, mechanical enhancer components for adhesion to the substrate and resistance to physical impact. It is to provide a foamed flame retardant coating composition comprising.

Another object of the present invention is to provide a foamed flame retardant coating composition comprising an elastomer that is acceptable for substrate durability and to coat the foam film thicker on substrates with little or no mud cracking.

It is a further object of the present invention to provide a foamable flame retardant coating composition comprising the new additives described above but which does not affect or degrade the overall thermal performance of the main foamable base material.

Another object of the present invention is to provide a foamable flame retardant coating composition which can be easily applied and mass produced in an automated and economical manner and which is cost effective for various applications by the user.

Summary of the Invention

In the present invention, the expandable base material, flame spreading agent, oxygen reducing agent, heat conduction reducing agent, refractory fibers dispersed therein, stabilizer, volatile organic substance reducing component, mechanical enhancer for resistance to physical impact and adhesion to the substrate Foamed flame retardant coating materials are provided that include components, waterproofing agents and elastomers that increase resistance to cracking and shirinking. This coating material can be used for most substrates, and for flame-retardant standards (for houses and roofs, factories, commercial buildings, airplanes, vehicles, ships, boats, sailboats, etc.) for related structures, including houses. It can be used in harsh climatic and environmental conditions where heat, cold and humidity are important factors in fire-retardant standards. When used in such harsh weather conditions or when used in water, a top coat such as coal tar or polyurethane is required on the coating material of the present invention. Such flame retardant coating material is a marine firewall; And cabins, bottoms, etc .; Airport loading bridges; Offshore oil rig; Cable and conduit sheaths; Storage tank; Filing cabinets and safes; It can also be used for firewall obstructions for cars, buses and trucks.

The foamed flame retardant coating composition of the present invention is iron, steel, stainless steel, aluminum, nonferrous metals, wood, plywood, cardboard, particleboard, composite board, plastic, PVC, thermoplastic, epoxide, neoprene, rubber, etc. Suitable for various material substrates.

Detailed description of the preferred embodiment

In the present invention, preferred embodiments of the foamable flame retardant coating composition include the following.

Component compound Content (% by weight) Effervescent base materials, including foaming agents, blowing agents, charring agents, binders, solvents and pigments 20 to 60 Ammonium orthophosphate, aluminum trihydrate (Al ₂ O ₃ ㆍ 3H ₂ O), zinc oxide (ZnO), zinc borate (3ZnO.2B ₂ O ₃ ), sodium silicate (Na ₂ SiO ₃ ), calcium silicate (Ca ₂ SiO ₄ ), flame spreading reducing agents such as antimony oxide, zinc metaphosphate and potassium metaphosphate 2 to 12 Oxygen reducing agents such as urea (CON ₂ H ₄ ), urea formaldehyde, dicyandiamide and melamine 1 to 5 Thermal conductivity reducing agents such as zirconium dioxide (ZrO ₂ ), chromium oxide (CrO), yttrium oxide (Y ₂ O ₃ ), and potassium oxide (K ₂ O) 2 to 6 Aluminum oxide (Al ₂ O ₃ ), silicon dioxide (SiO ₂ ), iron oxide (Fe ₂ O ₃ ), sodium oxide (Na ₂ O), zirconium oxide (ZrO ₂ ), beryllium oxide (BeO), manganese oxide (MnO) Refractory fibers such as zinc oxide (ZnO), titanium oxide (TiO ₂ ) and tantalum oxide (TaO ₂ ) 8 to 18 Stabilizers such as erythritol and paraffin and volatile organic substance (VOC) reducing agents 6 to 12 Mechanical enhancer components for adhesion to substrates and resistance to physical impacts such as calcium carbonate (CaCO ₃ ), ceramic oxides, calcium silicates, sodium silicates 1 to 4 Carboxymethyl cellulose, ethylhydroxyethyl cellulose, ammonium polyphosphate (NH ₄ H ₂ PO ₄ ), melamine-formaldehyde coatings, and other low solubility coatings and acrylics, silicones, diethylene glycol, and mono Waterproofing and efflorescence reducing agents such as ethyl ether acetate 4 to 8 Elastomeric agents that increase resistance to cracking and shrinkage and are well sprayed, such as vermiculite, perlite, elastomers and acrylics 0 to 20

As mentioned above, the fluidic foamable base material of the preferred embodiment includes a foaming agent, a blowing agent, a carbonizing agent, a binder, a solvent and a pigment. The foaming agent may be a chemical or coated compound having low solubility in water, such as ammonium phosphate or potassium tripolyphosphate. The blowing agent may be a compound such as melamine, urea, dicyandiamide, guanidine, or glycine. Carbonizing agents include dipentaerythritol (DPE), paraffin chloride, pentaerythritol, polyurethane, resorcinol, inositol, polyalcohol, sorbitol, or dextrin and It may be the same compound. The binder may be a compound such as calcium carbonate or butoxyethoxy ethanol. The solvent can be water, oil, toluene, or propylene glycol. The pigment may be a compound such as titanium oxide, lamp black or oxalate.

Examples of use for foamed flame retardant coating materials

Example 1

Five gallons of effervescent material of the present invention are mixed with 1.5 pounds of aluminum trihydrate, 2.2 pounds of milled refractory fiber, and 1.2 pounds of ammonium polyphosphate. The composition is applied to a Tl-11 siding comprising three walls of the room in accordance with the specifications of Uniform Building Code (UCC) 42-2. The coating is applied to a thickness of 0.012 inches. The test is performed according to UBC 42-2 with 40 kW corner exposure for 5 minutes and 150 kW corner exposure for the next 10 minutes. In radiant heat release, the maximum instantaneous increase (above the applied heat) is less than 20 kW.

Example 2

The same composition as used in Example 1 is applied to three walls consisting of cedar shakes and installed in a room similar to that of Example 1. Soffets and facia sections are similarly installed in the typical exterior configuration of the house. The coating is applied to a thickness of 0.012 inches and top coated with a common exterior grade acrylic latex paint suitable for painting houses. The entire system is exposed to the fire and thermal conditions of UBC 42-2 as in Example 1. The maximum instantaneous increase in radiant heat release is less than 50kW.

Example 3

The same composition as used in Example 1 is applied 0.012 inch thick to the surface of a 5/8 inch thick medium density (about 40 lbs./cu.ft.) Particle board. A propane torch rated at 2000 Btu / hour and having a flame temperature above 2100 ° F. is used to heat the surface. After 30 minutes, the particle board's backside temperature is less than 300 ° F.

Example 4

Five gallons of effervescent material of the present invention are mixed with 1.8 pounds of aluminum trihydrate, 3.5 pounds of milled refractory fiber, 2.8 pounds of pearlite, and 1.6 pounds of vermiculite. The composition is applied to a 30 inch section of a W10 x 49 steel column at a thickness of 0.060 inch. The column is fire tested in an oven configuration according to the specifications of Underwriters Laboratories Canada (ULS) S101. The average column temperature does not exceed the maximum average allowable temperature for more than 100 minutes.

Example 5

The same composition as used in Example 1 is applied 0.008 inches thick to a type 6061 0.140 inch thick aluminum 12 "x 24" plate surface. Samples are tested with propane burners, which are F.A.R. 25.855 Appendix F The temperature and heat requirements of Part III are exceeded. Aluminum does not bend, discolor, or burn for more than 15 minutes, which exceeds the requirements of the F.A.R standard.

Example 6

The same composition as used in Example 1 is used to coat the sheaths of five typical communication cables having various diameters and sheath materials. Cable diameters range from 0.5 to 2 inches. Sheath materials are various standard materials used in communication cables. The coating is twice and about 0.010 inches thick. The cable is tested in an oven configuration similar to the requirements of IEEE 383. The external cable temperature for small diameter cables does not exceed 200 ° F after 90 minutes. The temperature of large diameter cables does not exceed 125 ° F after 90 minutes.

Example 7

The same composition as used in Example 1 is applied to a portion of the plastic vehicle gas tank. The sample is about 6 "x 6" in size and coated 0.010 inches thick. The sample is exposed to a 2000 BTU / hour torch at 1600 ° F. for 7 minutes. The maximum backside temperature is lower than 300 ° F. after 5 minutes and lower than 420 ° F. after 7 minutes.

Example 8

The same composition as used in Example 4 is coated 0.018 inches thick on a 6 x 6 x 1/8 inch portion of cold rolled steel. The back of the steel sheet is insulated. The front face is exposed to a 2000 BTU / hour torch at 2100 ° F for 5 minutes. The back temperature of the steel sheet is lower than 450 ° F. after 5 minutes.

Example 9

The same composition as used in Example 1 is applied to one side of a door core made of particleboard 15/8 inch thick, density 34 lbs / cu.ft. The coating thickness is 0.008 inches. Coated door cores are tested in an oven similar to the requirements of ASTM E152. After 60 minutes, the temperature of the backside of the door core does not exceed 210 ° F anywhere in the door.

Example 10

The same composition as used in Example 1 is applied to one side of an Auratone ceiling tile made of American plaster. The coating thickness is 0.002 inches. Ceiling tiles are installed in a sealing grid assembly in a full scale room furnace and tested according to the requirements of FC 708. The sealing grid did not reach thermal transmission failure for 125 minutes. The ceiling tile did not fall from the assembly after 180 minutes.

Applications and Uses of the Invention

The foamable flame retardant coating material of the present invention is characterized in that the top coating material such as coal tar is subjected to severe climatic and environmental conditions in which heat, cold, humidity, and corrosion act as important factors for the flame retardant standard of the structure, object, or product being coated. top coat). For example, the harsh climatic and environmental applications of the present invention would be oil rigs located in the North Atlantic. These devices are made of steel and are subject to cold brine, chemical corrosion, and temperature changes. The coating material of the present invention is sprayed or painted onto a steel foundation and steel plant structure, followed by a protective top coating such as coal tar. The coating material of the present invention is combined with steel prior to placing the oil rigs at sea and will not peel off from the steel structure of these devices in use. This results in less damage from these fires in the event of an oil explosion or fire.

Another more typical application would be the coating of construction wood, wood by-products, composite boards, particle boards, plywood, and the like. Coating materials may be applied to exterior wallboards, internal structures, roofs, garages, ceilings, penetration barriers, PVC sheaths, and the like. Coating materials can also be applied to homes, hotels and lodgings, including wallpaper, ceiling tiles, kitchen cabinets, kitchen hoods, carpet backing, barriers, doors, filing cabinets, safes, PVC sheaths, wall fences ( wall barriers).

Other examples of typical applications include structural steel, columns, beams, steel decking, bar joists, hung sealing for the construction of commercial buildings, high-rise office buildings, high-rise apartments, bridges, tunnels, etc. hung ceilings).

Another example of application would be in the field of transportation where flame retardant coating materials are used in automobiles, buses, trucks, cargo ships, and airplanes. There are coated vehicular undercarriages, exhaust systems, gas tanks, firewalls, engine parts, catalytic converters, bonnets, cargo ship patches, airport loading bridges and the like.

Another example of application would be in the offshore industry where coating materials are used in firewalls, breakwaters, cabinet penetration barriers, cables, conduits, cargo areas, and offshore oil well drilling platforms.

Other examples of applications include coatings with cable sheaths and coatings, conduit sheaths, telecommunication towers, fire penetration barriers, seals, pipeline sheaths, storage tanks, reactors, ovens, distillation columns, It may be in the telecommunications, utilities, petroleum, and chemical industries used in furnaces and the like.

Advantage of the present invention

It is therefore an advantage of the present invention that the present invention provides a foamable flame retardant coating composition that is effective at temperatures such as 2500 ° F. continuously maintained for a long time under severe environmental conditions, while reducing the mechanical properties of the original material coated. will be.

Another advantage of the present invention is that the present invention provides a thin foamed flame retardant coating that provides low thermal conductivity.

Another advantage of the present invention is that the present invention provides a foamed flame retardant coating composition that reduces oxygen (O ₂ ) available in limited areas in order to reduce combustion time during fire or explosion and to delay flashover. Is to provide.

Another advantage of the present invention is that the present invention provides a foamed flame retardant coating composition for various low density wood and wood composite products that require zero flame spread upon prolonged exposure to fire.

Another advantage of the present invention is that the present invention provides a foamed flame retardant coating composition that does not emit harmful vapors to the occupants in the event of fire.

Another advantage of the present invention is that the present invention provides a foamed flame retardant coating composition with improved adhesion, abrasion resistance and impact resistance to many surfaces.

Another advantage of the present invention is that the present invention provides a foamed flame retardant coating composition that is waterproof and reduces the hygroscopicity of the coating material.

Another advantage of the present invention is that the present invention provides a foamed flame retardant coating composition that reduces the hygroscopicity in a coating material such that the coating material on a given substrate can be improved and has a longer life and better performance in fire.

Another advantage of the present invention is that the present invention provides iron, steel, stainless steel, aluminum, and nonferrous metals, wood, plywood, cardboard, particle board, plastic, PVC, thermoplastics, epoxides, neoprene, rubber It is to provide a foamable flame retardant coating composition suitable for a variety of substrates, such as.

Another advantage of the present invention is that the present invention provides a foamable flame retardant coating composition that can be used in many industries such as construction, transportation, telecommunications, utilities, marine, chemical, petroleum, manufacturing, and military applications.

Another advantage of the present invention is that the present invention can prevent corrosion due to chemicals, corrosive vapors, water, and brine when coating on a substrate; It is also to provide a foamable flame retardant coating composition that can withstand physical shock, high pressure, and / or mechanical vibrations without the coating material peeling off the substrate.

Another advantage of the present invention is that the present invention provides a foam base material, a flame spreading agent, an oxygen reducing agent, a thermal conductivity reducing agent, a refractory fiber, a stabilizer, a volatile organic substance reducing component, a resistance to physical impact and a mechanical property for adhesion to a substrate. It is to provide a foamable flame retardant coating composition comprising a novel combination of enhancer components, waterproofing agents and elastomeric agents.

Another advantage of the present invention is that the present invention provides a foamed flame retardant coating composition comprising an elastomer that is acceptable for substrate durability and to coat the foam film thicker on substrates with little or no mud cracking. .

Another advantage of the present invention is that the present invention provides a foamed flame retardant coating composition that includes the new additives described above but does not affect or degrade the overall thermal performance of the main foamable base material.

Another advantage of the present invention is that the present invention can be easily applied and mass produced in an automated and economical manner and provides a cost effective foamable flame retardant coating composition for various applications by the user.

A range of modifications, variations, and substitutions are possible with respect to the foregoing disclosure, and in some cases only some of the features of the invention may be used. Accordingly, the appended claims should be construed broadly and in accordance with the spirit and scope of the invention.

Claims (34)

a) a fluid foamable base material having a foaming agent, a blowing agent, a carbonizing agent, a binder, a solvent, and a pigment; b) flame spreading agents; c) refractory fibers dispersed in the fluid foamable base material; d) oxygen reducing agents; e) heat conduction reducing agents; f) stabilizers and volatile organic matter reducing components; g) mechanical enhancer components for resistance to physical impact and adhesion to the substrate; h) waterproofing agent; And i) Flame retardant coating material comprising an elastomer that increases resistance to cracking and shrinkage and allows for good spraying. The flame retardant according to claim 1, wherein the foaming agent in the fluid foamable base material is ammonium phosphate or potassium tripolyphosphate. A flame retardant as claimed in claim 1 wherein said blowing agent in said fluidic foamable base material is melamine, urea, dicyandiamide, guanidine or glycine. The method of claim 1, wherein the carbonizing agent in the fluid foamable base material is dipentaerythritol (DPE), paraffin chloride, alcohol, polyol, pentaerythritol (PE), polyurethane, resorcinol, inositol, Flame retardant material, characterized in that the poly alcohol, sorbitol, or dextrin. The flame retardant material according to claim 1, wherein the binder in the fluid foamable base material is calcium carbonate or butoxyethoxy ethanol. The flame retardant material as claimed in claim 1, wherein the solvent in the fluid foamable base material is water, oil, toluene or propylene glycol. The flame retardant material as claimed in claim 1, wherein the pigment in the fluid foamable base material is titanium oxide, lamp black, or oxalate. The method of claim 1, wherein the fluid foamable base material comprises titanium dioxide, ammonium orthophosphate, melamine, dipentaerythritol (DPE), calcium carbonate, vinyl acetate, acrylic resin, and propylene glycol Flame retardant. The flame retardant of claim 1, wherein the flame spreading agent is aluminum trihydrate, ammonium orthophosphate, zinc oxide, zinc borate, sodium silicate, calcium silicate, antimony oxide, zinc metaphosphate, or potassium metaphosphate. . The flame retardant material according to claim 1, wherein the refractory fiber is made of aluminum oxide and / or silicon dioxide. The method of claim 1, wherein the refractory fiber is aluminum oxide and / or silicon dioxide in combination with at least one or more of sodium oxide, iron oxide, zirconium oxide, beryllium oxide, manganese oxide, zinc oxide, titanium oxide and tantalum oxide. Flame retardant material, characterized in that made. The flame retardant material according to claim 1, wherein the refractory fiber is a ground fiber. The flame retardant of claim 1, wherein the oxygen reducing agent is urea, urea formaldehyde, or dicyanidiamide. The flame retardant of claim 1, wherein the heat conduction reducing agent is zirconium oxide, chromium oxide, yttrium oxide, or potassium oxide. The flame retardant according to claim 1, wherein the stabilizer and the volatile organic substance reducing component are erythritol or paraffin. The flame retardant of claim 1, wherein the mechanical enhancer component is calcium carbonate, ceramic oxide, calcium silicate, sodium silicate, or dibufilphthalate. The flame retardant according to claim 1, wherein the waterproofing agent is ethyl hydroxyethyl cellulose, carboxymethyl cellulose, ammonium polyphosphate, melamine-formaldehyde coating, acrylic, silicone, diethylene glycol, or monoethyl ether acetate. The flame retardant according to claim 1, wherein the elastic agent is vermiculite, pearlite, elastomer, or acrylic. The flame retardant material according to claim 1, wherein the content of the fluid foamable base material is 20 to 60% by weight. The flame retardant of claim 1, wherein the flame spreading agent is contained in an amount of 2 to 12 wt%. The flame retardant material as claimed in claim 1, wherein the content of the refractory fiber is preferably 4 to 28 ounces per gallon of foamable material. The flame retardant material as claimed in claim 1, wherein the content of the refractory fiber is generally 1 to 20 ounces per gallon of foamable material. According to claim 1, wherein the content of the refractory fiber is a flame retardant material, characterized in that 8 to 18% by weight. According to claim 1, wherein the content of the oxygen reducing agent is a flame retardant, characterized in that 1 to 5% by weight. The flame retardant of claim 1, wherein the content of the heat conduction reducing agent is 2 to 6% by weight. The flame retardant of claim 1, wherein the amount of the stabilizer and the volatile organic substance reducing component is 6 to 12 wt%. The flame retardant material according to claim 1, wherein the content of the mechanical enhancer component is 1 to 4% by weight. According to claim 1, wherein the content of the waterproofing agent is a flame retardant, characterized in that 4 to 8% by weight. According to claim 1, wherein the content of the elastic agent is a flame retardant, characterized in that 1 to 20% by weight. The method of claim 1, wherein the flame retardant material is iron, steel, stainless steel, aluminum, non-ferrous metals, wood, plywood, cardboard, particleboard, orientation strand board, composite board, plastic, PVC, thermoplastic, epoxy Flame retardant material, characterized in that applied to the side, neoprene, or rubber substrate. delete delete delete delete