JP7566510B2 - Polyurea resin composition, noncombustible powder, and method for forming polyurea resin layer - Google Patents

Description

The present invention relates to a polyurea resin composition, a noncombustible powder, and a method for forming a polyurea resin layer, and in particular to a polyurea resin composition, a noncombustible powder, and a method for forming a polyurea resin layer that are useful for forming a polyurea resin layer that is excellent in corrosion resistance, abrasion resistance, waterproofness, impact resistance, elasticity, and noncombustibility.

Polyurea resins with excellent waterproofing, impact resistance, corrosion resistance, etc. have been proposed. Among these polyurea resins, particularly high-purity polyurea resins (pure polyurea resins) formed using only polyisocyanate and polyamine as organic polymer compounds can have improved corrosion resistance, abrasion resistance, waterproofing, impact resistance, UV protection, and elasticity by adding various fillers (the inherent properties of polyurea resins).

Polyurea resin can be applied to the surface of a concrete block wall to form a resin layer (approximately 1.5 mm to 3 mm) to reinforce the wall, or can be injected into cracks in a concrete wall to repair/reinforce the wall.

However, like other organic polymeric compounds (e.g., polyurethane resins), polyurea resins have the disadvantage that, in the event of a fire, they break down into smaller molecules due to an increase in temperature, producing flammable gases and therefore easily combust.

For this reason, when polyurethane resin is actually used to repair cracks in block walls or concrete walls installed outdoors, or even when it is attempted to be laid on the rooftops of houses with an eye on its waterproofing properties, its flammability prevents the building from achieving flame retardancy (semi-fire resistance), making it unsuitable for use in these structures.

It has been conventional to impart flame retardancy to other general organic polymer compounds (e.g., polyurethane) other than polyurea resins by using ammonium polyphosphate, borax, expandable graphite, or the like as a filler for these other organic polymer compounds.
Regarding polyurea resins, it has been proposed in, for example, the following patent documents and non-patent documents that the addition of various fillers used in other organic polymer compounds to the resins can impart flame retardancy.

JP 2017-082229 A CN-A-102559022

"Further study on the flame retardancy of polyurea: Effects of coatings and flame retardant additions" J-GLOBAL ID No.: 11A1320776

In particular, the above-mentioned Non-Patent Document 1 discloses that in order to impart flame retardancy to a polyurea resin, it is possible to include a flame retardant additive (ammonium polyphosphate, expandable graphite, zinc borate, etc.) that has conventionally been used in other organic polymer compounds.
However, there is no specific disclosure or suggestion as to what fillers should actually be added to the polyurea resin and in what ratio, and further, whether the polyurea resin to which these fillers have been added still has its inherent properties (corrosion resistance, abrasion resistance, waterproofness, impact resistance, UV protection, elasticity), etc.

By the way, polyurea resin is generally sprayed onto an object (block walls, concrete cracks, etc.) to form a layer of a desired thickness on the surface of the object (spraying method), but none of the above patent and non-patent documents discloses or suggests at all whether or not polyurea resin containing the above-mentioned flame retardant additive (filler) can actually be sprayed using the conventional spraying method.

The present invention has been made in view of the above circumstances, and aims to provide a polyurea resin composition suitable for forming a flame-retardant and non-combustible (preferably semi-fire-resistant) polyurea resin layer on an object by a conventional method (spraying method) without impairing the inherent properties of the polyurea resin (corrosion resistance, abrasion resistance, waterproofing, impact resistance, elasticity, etc.), a non-combustible powder, and a method for forming a polyurea resin layer using the polyurea resin composition.

In a first invention, a polyurea resin composition contains 100 parts by mass of polyamine, 100 to 160 parts by mass of polyisocyanate, and 15 to 30 parts by mass of expandable graphite, and the particle size of the expandable graphite is 100 mesh or smaller.

In addition, the second invention is a method for forming a polyurea resin layer of a desired thickness by spraying a polyurea resin composition containing 100 parts by mass of polyamine, 100 to 160 parts by mass of polyisocyanate, and 15 to 30 parts by mass of expandable graphite (having a particle size of 100 mesh or smaller) onto an object, the method comprising the steps of: adding the expandable graphite to at least one of the polyamine and the polyisocyanate; heating the polyamine and the polyisocyanate so that the temperature of the polyurea resin produced by mixing and stirring the polyamine and the polyisocyanate is between 60 degrees Celsius and 80 degrees Celsius; pressurizing the polyamine and the polyisocyanate so that the pressure of the polyurea resin produced by mixing and stirring the polyamine and the polyisocyanate is a predetermined pressure; and spraying the polyurea resin heated to 60 degrees Celsius to 80 degrees Celsius and pressurized to the predetermined pressure onto the object.

The third invention is the second invention, further comprising, in the step of heating the polyamine and the polyisocyanate, heating the polyisocyanate to 70 to 80 degrees Celsius when the expanded graphite is added to the polyisocyanate, and heating the polyamine to 70 to 80 degrees Celsius when the expanded graphite is added to the polyamine.

The fourth invention includes a first tank for storing polyisocyanate, a second tank for storing polyamine, a first heating means for adjusting the temperature of the polyisocyanate supplied from the first tank, a second heating means for adjusting the temperature of the polyamine supplied from the second tank, a first pressurizing means for pressurizing the polyisocyanate supplied from the first tank, a second pressurizing means for pressurizing the polyamine supplied from the second tank, a compression means for compressing gas, a generation means for mixing and stirring the polyisocyanate and the polyamine to generate a polyurea resin, and a jet nozzle. When the polyurea resin composition according to the first invention is sprayed onto an object to form a polyurea resin layer using a polyurea spraying device equipped with a spraying means for spraying the generated polyurea resin from the spray nozzle, the temperature of the polyurea resin in the spraying means is maintained at 60 to 80 degrees Celsius by the first heating means and the second heating means, the pressure of the polyurea resin in the spraying means is pressurized to a predetermined pressure by the first pressurizing means and the second pressurizing means, and the pressurized polyurea resin is sprayed onto the object from the spray nozzle to form a polyurea resin layer.

The fifth invention is the fourth invention in which the nozzle diameter of the polyurethane spraying device is 1.5 mm, and the predetermined pressure adjusted by the first pressure means and the second pressure means is 23.5 MPa to 24.0 MPa.

The sixth invention is the fourth or fifth invention, in which when the expanded graphite is added to the polyisocyanate, the first heating means heats the polyisocyanate to 70 to 80 degrees Celsius, and when the expanded graphite is added to the polyamine, the second heating means heats the polyamine to 70 to 80 degrees Celsius.

According to the first invention, 15 to 30 parts by mass of expanded graphite having a particle size of 100 mesh or smaller is added to a polyurea resin produced by mixing and stirring 100 parts by mass of polyamine and 100 to 160 parts by mass of polyisocyanate. This makes it possible to spray the polyurea resin onto an object using a conventionally used polyurea spraying device, and to form a polyurea resin layer of a desired thickness on the surface of the object.
In this case, no clogging due to expanded graphite occurs in the polyurea spraying device (particularly inside the spray gun device). The polyurea resin layer formed in this case can be imparted with excellent flame retardancy (quasi-fire resistance) without impairing the inherent properties of the polyurea resin.

In addition, according to the second invention, even if the expanded graphite is added to at least one of the polyamine and the polyisocyanate in a spraying method using a conventional polyurea spraying device, the temperature of the polyurea resin generated by mixing and stirring the polyamine and the polyisocyanate is adjusted to between 60°C and 80°C, and the generated polyurea resin is pressurized to a predetermined pressure, so that the generated polyurea resin can be sprayed onto an object without causing clogging inside the polyurea spraying device, and a polyurea resin layer of the desired thickness can be formed.

According to the third invention, when the expanded graphite is added to the polyisocyanate in the second invention, the polyisocyanate is heated to 70 to 80 degrees Celsius, and when the expanded graphite is added to the polyamine, the polyamine is heated to 70 to 80 degrees Celsius, so that the polyurea resin can be sprayed from the nozzle of the polyurea spraying device.

In addition, according to the fourth invention, when the polyurea resin composition of the first invention is sprayed onto an object, the temperature of the polyurea resin in the spray section is maintained at 60 to 80 degrees Celsius by the first heating means and the second heating means, and the pressure of the polyurea resin in the spray section is pressurized to a predetermined pressure by the first pressurizing means and the second pressurizing means, so that the heated/pressurized polyurea resin can be sprayed onto the object from the spray nozzle to form a polyurea resin layer of the desired thickness.

In addition, according to the fifth invention, the polyurethane resin composition of the first invention can be sprayed onto an object using a conventional polyurethane spraying device having a nozzle diameter of 1.5 mm and a pressure capacity of 23.5 MPa to 24.0 MPa.

According to the sixth invention, when the expanded graphite is added to the polyisocyanate, the polyisocyanate is heated to 70 to 80 degrees Celsius, and when the expanded graphite is added to the polyamine, the polyamine is heated to 70 to 80 degrees Celsius. In this way, the polyurea resin composition can be sprayed onto an object to form a polyurea resin layer of the desired thickness.

When expanded graphite is added to both the polyisocyanate and the polyamine, the temperatures of both the polyisocyanate and the polyamine can be adjusted to 70 to 80 degrees Celsius, and the polyurea resin composition can be sprayed onto an object to form a polyurea resin layer of the desired thickness.

FIG. 1 is a diagram showing a schematic configuration of a polyurea spraying device (spraying device) 100. FIG. 2 is a photograph showing a combustion experiment in which the noncombustible powder of the second embodiment is not added to the polyurea resin. FIG. 3 is a photograph showing a combustion experiment in which 15 parts by mass of noncombustible powder was added to 100 parts by mass of a base material of a polyurea resin. FIG. 4 is a photograph showing a combustion experiment in which 20 parts by mass of noncombustible powder was added to 100 parts by mass of a base material of a polyurea resin. FIG. 2 is a photograph showing a combustion experiment in which 25 parts by mass of noncombustible powder was added to 100 parts by mass of a base material of a polyurea resin. FIG. 2 is a photograph showing a combustion experiment in which 30 parts by mass of noncombustible powder was added to 100 parts by mass of a base material of a polyurea resin. FIG. 2 is a photograph showing a combustion experiment in which 40 parts by mass of noncombustible powder was added to 100 parts by mass of a base material of a polyurea resin.

(First embodiment)
Hereinafter, a description will be given of a polyurea resin having excellent flame retardancy (preferably having semi-fire resistance) according to a first embodiment, and a method for forming a polyurea resin layer using the same.
The base material of the polyurea resin used in the first embodiment is made of only polyisocyanate and polyamine as organic polymer compounds (pure polyurea resin).
Pure polyurea resin, which uses only polyisocyanate and polyamine as organic polymer compounds, can exhibit excellent corrosion resistance, abrasion resistance, waterproofing, impact resistance, and elasticity by adding various fillers.

First, the "intrinsic properties" of pure polyurea resin will be described.
The following "Table 1" shows the properties of the polyurea resin "Qtech-406" provided by Qingdao Shaku New Materials Co., Ltd. This "Qtech-406" has particularly high "waterproofing" properties due to the ingenuity of the filler added.

The following "Table 2" shows the properties of the polyurea resin "Qtech-417" provided by Qingdao Shaku New Materials Co., Ltd. This "Qtech-417" has particularly high "elasticity" due to the ingenuity of the filler added.

The following "Table 3" shows the properties of the polyurea resin "Qtech-420" provided by Qingdao Shaku New Materials Co., Ltd. This "Qtech-420" has particularly high "impact resistance" due to the ingenuity of the filler added.

However, like other organic polymer compounds, these polyurea resins undergo thermal decomposition as the temperature rises, resulting in low molecular weights and generating combustible gaseous products, which means that they are prone to combustion in the event of a fire. Therefore, they are particularly unsuitable for use in places where there is open flames.

To impart flame retardancy to polyurea resin, it is conceivable to use as a filler a flame retardant (e.g., ammonium polyphosphate, borax, expandable graphite, etc.) that has been used conventionally in other organic polymer compounds (e.g., polyurethane) (e.g., Non-Patent Document 1), but it is necessary to specifically consider what kind of filler should be added and how it should be added in order to achieve flame retardancy without impairing the inherent properties of the polyurea resin.

In addition, since it is planned that the polyurea resin will be applied to cracks in block walls and concrete walls, and to waterproof sheets on the roofs of buildings, it is necessary to specifically examine whether a flame-retardant (semi-fireproof) polyurea resin layer can be formed to the desired thickness (1.5 to 3 mm) on these block walls and other objects using a simple method (spraying method) that uses a conventionally used polyurea spraying device.

In this embodiment, the polyurea resin composition to which flame retardancy (preferably semi-fire resistance) is added is a composition (pure polyurea resin) that uses only polyisocyanate (A-ingredient) and polyamine (B-ingredient) as organic polymer compounds, and contains 100 to 160 parts by mass of polyisocyanate per 100 parts by mass of polyamine.
It will be obvious to those skilled in the art that the optimum ratio of polyurea resin is 110 parts by mass of polyisocyanate per 100 parts by mass of polyamine.

The present inventors have confirmed that the inherent properties expected of a polyurea resin (determined by the presence or absence of elasticity, which is a representative property) can be exhibited when the polyisocyanate is in the range of 100 to 160 parts by mass per 100 parts by mass of polyamine.

If the polyisocyanate is used in an amount of 90 parts by mass per 100 parts by mass of polyamine, the desired elasticity cannot be obtained, and the inherent properties of the polyurea resin cannot be expected.
Furthermore, even when 170 parts by mass of polyisocyanate is used per 100 parts by mass of polyamine, the desired elasticity is not obtained, and the inherent properties of the polyurea resin cannot be expected.

The required elasticity of polyurea resin (such as the breaking elongation in Tables 1 to 3 above) varies depending on the intended use. In other words, the allowable elasticity varies depending on the intended use (such as sprayed concrete block walls, cracks in poured concrete, building rooftops, etc.) and the specifications required by the customer.

For this reason, the present inventors considered that, in light of common general technical knowledge, sufficient elasticity, etc. would be obtained for the above-mentioned exemplary uses, etc., if the polyurea resin (base material) is 100 to 160 parts by mass of polyisocyanate per 100 parts by mass of polyamine, as described above.
With regard to waterproofness, no problems occurred with any of No. 1 to No. 5 in Table 4.

In order to study how to impart flame retardancy (quasi-fire resistance) to this polyurea resin, the present inventor prepared a conventional filler (ammonium polyphosphate, borax, and expanded graphite (80 mesh: 175 to 177 microns)) that has been proposed in the past, and added it to a composition with an optimal mixture ratio of 100 parts by mass of polyamine and 110 parts by mass of polyisocyanate.
(1) Whether or not a polyurethane resin layer can be easily formed on an object by a conventional method was examined. (2) Whether or not the formed polyurethane resin layer exhibits flame retardancy (quasi-fire resistance) was examined.

The results are shown in Table 5 below.

As is clear from Table 5 above, a polyurea resin composition containing 20 parts by mass of ammonium polyphosphate as a filler can provide flame retardancy compared to a non-added composition, but it quickly dissolves when burned, so the flame retardant (quasi-fireproof) effect quickly disappears. However, it is possible to form a polyurea resin layer using a spraying method with a conventional polyurea spraying device.

Although the polyurea resin composition to which 20 parts by mass of borax (powder) is added as a filler can be made more flame-retardant than that to which no borax is added, the effect of flame retardancy (quasi-fire resistance) is quickly lost because the composition dissolves immediately upon combustion. However, it is possible to form a polyurea resin layer by a spraying method using a conventional polyurea spraying device.
A polyurea resin composition to which 15 parts by mass of conventionally widely used expanded graphite (equivalent to 175 to 177 microns in terms of 80 mesh) was added as a filler was able to achieve extremely excellent flame retardancy (semi-flame retardancy) compared to a composition to which the graphite was not added (confirmed by hand application here).

However, when attempting to form a polyurea resin layer containing added expanded graphite (80 mesh) by spraying it onto an object using a conventional polyurea spraying device, the polyurea resin generated inside the polyurea spraying device becomes highly pressurized, causing a problem in that expanded graphite with a large particle size adheres to the inside of the spray gun and the nozzle (approximately 1.5 mm) of the polyurea spraying device, resulting in clogging.
This is because the particle size of the expanded graphite itself is large (80 mesh) and the viscosity of the polyurea resin increases due to the addition of expanded graphite.

Based on the above results ("Table 5"), the present inventors have determined that expandable graphite is the most preferable filler for imparting flame retardancy (quasi-fire resistance) to polyurea resin.
The inventors then investigated how to prevent the problem that occurs when using expanded graphite, i.e., clogging that can occur inside the polyurethane spraying equipment (particularly the spray gun part), and to develop a polyurethane resin composition that enables spraying work to be performed using conventional polyurethane spraying equipment as is.

Here, a polyurea spraying device that has been conventionally used for forming a polyurea resin layer will be described.
A known example of a conventional polyurea spraying device is the "Polyurea Sprayer" manufactured by Sham.
The following "Table 6" shows the performance of the polyurea spraying equipment listed in the specifications for the Siamese Polyurea Sprayer (PHX-3).

FIG. 1 is a schematic diagram showing the configuration of a typical polyurethane spraying device 100 that has been used conventionally.
The polyurea spraying device 100 includes a first tank 10 for storing polyisocyanate (agent A), a second tank 20 for storing polyamine (agent B), a compressor 40, and a spray gun device 50 for spraying a polyurea resin (polyurea resin composition) produced by mixing and stirring the polyisocyanate and the polyamine onto an object.

The first tank 10 is connected to the spray gun device 50 by a first pipe 11, and the second tank 20 is connected to the inside of the spray gun device 50 by a second pipe 21.

A first pump 12 is provided in the first piping 11 between the first tank 10 and the spray gun device 50. In addition, a second pump 22 is provided in the second piping 21 between the second tank 20 and the spray gun device 50.
The first pump 12 adjusts the pressure of the polyisocyanate supplied from the first tank 10 to the spray gun device 50 in response to a control signal from a compression adjustment mechanism 30. The second pump 22 adjusts the pressure of the polyamine supplied from the second tank 20 to the spray gun device 50 in response to a control signal from the compression adjustment mechanism 30.
The compression adjustment mechanism 30 receives a command from the control unit 60 and outputs the control signal to each of the first pump 12 and the second pump 22 .
By using the first pump 12 and the second pump 22, the maximum pressure within the spray gun device 50 can be adjusted to approximately 24 MPa (see Table 6).

The polyisocyanate and polyamine pressurized by the first pump 12 and the second pump 22, respectively, are mixed and stirred inside the spray gun device 50, and a polyurea resin is produced.
The compressor 40 is in communication with the inside of the spray gun device 50 through a third pipe 41. Air compressed by the compressor 40 is supplied to the inside of the spray gun device 50.

A first heater 13 is disposed in the first pipe 11, and the temperature of the polyisocyanate supplied from the first tank 10 to the inside of the spray gun device 50 can be adjusted to a desired temperature (at least 60 degrees Celsius to 80 degrees Celsius). The temperature of the polyisocyanate heated by the first heater 13 is maintained by a hose heater 14 (maximum heating value is 88 degrees Celsius: see Table 6).

In addition, a second heater 23 is provided in the second pipe 21, and the temperature of the polyamine supplied from the second tank 20 to the inside of the spray gun device 50 can be adjusted to a desired temperature (60 degrees Celsius to 80 degrees Celsius). The temperature of the polyamine heated by the second heater 23 is maintained by a hose heater 24 (maximum heating value is 88 degrees Celsius: see Table 6).

Based on the switching state of the switch SW, the control unit 60 recognizes whether or not expanded graphite has been added to the isocyanate (agent A), whether or not expanded graphite has been added to the polyamine (agent B), the amount of expanded graphite added, etc., and based on this information, appropriately controls the pressure of the polyurea resin by the first pump 12 and the second pump 22, and the temperature of the polyurea resin by the first heater 13 and the second heater 23.

In this embodiment, expanded graphite (filler) with a particle size of 100 mesh is added to the polyisocyanate (Part A).
For this reason, the temperature of the polyisocyanate is adjusted to 70° C. to 80° C. by the first heater 13. The polyamine to which no expanded graphite is added is adjusted to a lower temperature than the polyisocyanate (60° C. to 70° C.) by the second heater 23.

The reason for adjusting the temperature of the polyisocyanate with added expanded graphite to be higher than that of the polyamine without added expanded graphite is to suppress the increase in viscosity caused by the addition of expanded graphite by increasing the temperature. At this time, the polyurea resin produced inside the spray gun device 50 is generally at a temperature between 60 degrees Celsius and 80 degrees Celsius.

If expanded graphite with a particle size of 100 mesh is added only to polyamine, the temperature of the polyamine may be set to 70° C. to 80° C., and the temperature of the polyisocyanate may be set to 60° C. to 70° C. In this case, the polyurea resin generated inside the spray gun device 50 will be generally between 60° C. and 80° C.
In this way, by increasing only the temperature of the solvent (agent A in this case) whose viscosity increases due to the addition of expanded graphite having a particle size of 100 mesh, the power required for heating can be reduced.

In addition, if expanded graphite is added to both the polyisocyanate (agent A) and the polyamine (agent B), the viscosity of both can be kept low by setting the temperatures of both the polyisocyanate and the polyamine to 70 to 80 degrees Celsius. In this case, the polyurea resin produced inside the spray gun device 50 will be at a temperature of approximately 70 to 80 degrees Celsius.

The polyisocyanate (A agent) pressurized by the first pump 12 and heated by the first heater 13, and the polyamine (B agent) pressurized by the second pump 22 and heated by the second heater 23 are both fed into the spray gun device 50, where they are mixed and stirred (impingement mixing), and a polyurea resin is produced by a chemical reaction.

The polyurethane resin produced by mixing and stirring inside the spray gun device 50 is mixed with compressed air supplied from the compressor 40, and by pulling the trigger 52B of the gun part 52, it is released from the nozzle 52A and sprayed in a mist.

At this time, the polyurethane resin produced by mixing and stirring inside the spray gun device 50 is kept at a predetermined temperature (60 to 80 degrees Celsius) and has low viscosity, so that when the nozzle 52A (diameter 1.5 mm) is opened, it is sprayed at the desired flow rate (10 L/min in the first embodiment) (the polyurethane resin is at 23.5 to 24.0 MPa inside the spray gun device 50).
The expanded graphite added at this time has a small particle size, and the viscosity of the polyurea resin is low, so that clogging does not occur inside the spray gun device 50 (particularly the nozzle 52A).

In this way, in the polyurea spraying device 100, the polyisocyanate (agent A) and polyamine (agent B) can be heated and adjusted to the desired temperature inside the spray gun device 50, so the reaction conditions (resin reaction) between the polyisocyanate (agent A) and polyamine (agent B) can be stabilized, and by adjusting the temperature of the polyisocyanate (agent A) or polyamine (agent B) to which the expanded graphite has been added to a high temperature, the increase in viscosity caused by the addition of the expanded graphite can be suppressed.

Incidentally, if the ratio of expanded graphite added to polyisocyanate is the same, it is believed that the flame retardancy decreases in proportion to the reduction in particle size (particle size of 100 mesh or smaller).
Therefore, in order to realize flame retardancy (quasi-fire resistance) equivalent to that achieved when conventional expanded graphite having a relatively large particle size (particle size of 80 mesh or more) is added (15 parts by mass of expanded graphite per 100 parts by mass of polyamine and 100 to 160 parts by mass of polyisocyanate = "Table 5"), it is necessary to increase the amount of expanded graphite added by the amount corresponding to the smaller particle size (30 parts by mass of expanded graphite per 100 parts by mass of polyamine and 100 to 160 parts by mass of polyisocyanate).

Increasing the amount of expanded graphite added in this way increases the viscosity of the polyurea resin produced by mixing and stirring, but in this embodiment, the polyurea resin produced by mixing and stirring is adjusted to a high temperature (60 degrees Celsius to 80 degrees Celsius), so the viscosity can be kept low and it can be sprayed from the spray gun device 50 of the polyurea spraying device 100.

In addition, if it is acceptable to weaken the flame retardant (quasi-fireproof) effect of the expanded graphite somewhat, the amount of expanded graphite added can be the same as when conventional expanded graphite with a larger particle size is used (15 parts by mass of expanded graphite for 100 parts by mass of polyamine and 100 to 160 parts by mass of polyisocyanate).

When 15 parts by mass of conventionally used 80 mesh particle size expanded graphite is added to 100 parts by mass of polyamine and 100 to 160 parts by mass of polyisocyanate, the time until the polyurea resin carbonizes without generating a flame is 60 seconds (see Table 5), but when the same amount of 100 mesh expanded graphite (15 parts by mass) is used, the time until the polyurea resin carbonizes without generating a flame is slightly shorter at about 30 seconds (see Table 7 below).

As described above, in this first embodiment, in order to enable the use of a conventional polyurea spraying device (injection port diameter 1.5 mm, pressure capacity 23.5 to 24.0 MPa, temperature adjustment possible up to 88 degrees Celsius = "Table 6") as is, the particle size of the expanded graphite added to the polyurea resin is made small (particle size 100 mesh), and the amount added is set to 15 to 30 parts by mass relative to 100 parts by mass of polyamine and 100 to 160 parts by mass of polyisocyanate.
The polyurea resin produced by mixing and stirring the polyisocyanate and polyamine is heated and maintained at 60° C. to 80° C. inside the spray gun device, whereby the polyurea resin can be sprayed onto an object to form a polyurea resin layer of a desired thickness. At this time, clogging does not occur in the polyurea spray device 100 (particularly, inside the spray gun device 50).

The present inventors confirmed the flame retardancy (quasi-fire resistance) of a polyurea resin layer having a predetermined thickness (here, 2 mm) formed on an object using a polyurea resin (polyurea resin composition) to which expanded graphite having a particle size of 100 mesh was added (combustion experiment).
The experimental results are shown in Table 7 below.

As described above, the ratio of polyamine to polyisocyanate at which the inherent properties (elasticity) of polyurea are fully exhibited is 100 parts by mass of polyamine to 100 to 160 parts by mass of polyisocyanate, so a polyurea resin composition having the following ratio was prepared.
(1) 100 parts by mass of polyamine, 100 parts by mass of polyisocyanate, 15 parts by mass of expanded graphite = (Sample 1)
(2) 100 parts by mass of polyamine, 100 parts by mass of polyisocyanate, 30 parts by mass of expanded graphite = (Sample 2)
(3) 100 parts by mass of polyamine, 160 parts by mass of polyisocyanate, 15 parts by mass of expanded graphite = (Sample 3)
(4) 100 parts by mass of polyamine, 160 parts by mass of polyisocyanate, 30 parts by mass of expanded graphite = (Sample 4)

Each of the above-mentioned polyurethane resin compositions (samples 1 to 4) was formed on a target object (a concrete plate of 20 cm x 20 cm) to a film thickness of about 2 mm, and this was left at room temperature (about 20°C) for 6 hours to be thoroughly dried.
In this combustion experiment, since it is sufficient to confirm the flame retardancy (quasi-fire resistance) of the polyurea resin when expanded graphite having a particle size of 100 mesh is added at a certain ratio (15 to 30 parts by mass of expanded graphite per 100 parts by mass of polyamine and 10 to 160 parts by mass of polyisocyanate), for convenience, a polyurea resin layer was formed by so-called "hand painting" and its flame retardancy (quasi-fire resistance) was confirmed.

Concrete plates 1 to 4, each having a polyurethane resin layer (thickness: 2 mm) with different composition ratios (samples 1 to 4), were placed vertically, and their surfaces were burned with a commercially available torch burner. The tip of the flame of the torch burner was placed so as to be in contact with the concrete plate.
The combustion time and the combustion results of each of the concrete panels 1 to 4 are as shown in Table 7 below.

In order to confirm the flame retardancy (quasi-fire resistance) obtained in the first embodiment, a concrete plate 5 of 20 cm x 20 cm was prepared by forming a polyurethane resin layer (sample 5) containing 80 mesh expanded graphite to a thickness of 2 mm on the surface thereof.

As is clear from the experimental results in "Table 7," in both cases where the polyurea resin layer was formed using Sample 1 and Sample 2, in which 15 parts by mass and 30 parts by mass of expanded graphite (100 mesh) were added to the base material of the polyurea resin consisting of 100 parts by mass of polyamine and 100 parts by mass of polyisocyanate, respectively, no fire occurred until 30 to 60 seconds had elapsed. This was almost the same result as the experimental result (60 seconds) of Sample 5, which used 30 parts by mass of expanded graphite (80 mesh) as a filler.

In addition, in both cases where the polyurea resin layer was formed using Sample 3 and Sample 4, in which 15 parts by mass and 30 parts by mass of expanded graphite (100 mesh) were added to a base material of polyurea resin consisting of 100 parts by mass of polyamine and 160 parts by mass of polyisocyanate, respectively, no fire occurred until 30 to 60 seconds had elapsed. This was almost the same as the experimental result (60 seconds) of Sample 5, which used 30 parts by mass of expanded graphite (80 mesh) as a filler.

Furthermore, there was no visible difference in the state of the sample surfaces after a certain period of combustion among Samples 1 to 4 and Sample 5.
From these findings, it was found that even if the particle size of the expanded graphite was changed from the conventional 80 mesh (175 to 177 microns) to 100 mesh (147 to 149 microns), a polyurea resin layer with a thickness of about 2 mm could adequately withstand combustion for 30 to 60 seconds.

As described above, even when 15 to 30 parts by mass of 100 mesh expanded graphite as a filler was added to a polyurea resin base material of 100 to 160 parts by mass of polyisocyanate per 100 parts by mass of polyamine (polyurea resin composition) and this was sprayed to form a polyurea resin layer, excellent flame retardancy (quasi-fire resistance) equivalent to that obtained when expanded graphite with a large particle size (particle size of 80 mesh or more) was used as a filler was obtained.

A polyurea resin (base material) containing 100 parts by mass of polyamine and 100 to 160 parts by mass of polyisocyanate to which 15 to 30 parts by mass of expanded graphite has been added is produced by mixing and stirring in a conventionally used polyurea spraying device 100.
The produced polyurethane resin is heated and adjusted to 60-80 degrees Celsius within the spray gun device 50 of the polyurethane spraying device 100, thereby keeping its viscosity low and enabling it to be sprayed sufficiently onto the target object from the nozzle (diameter 1.5 mm).
At this time, by adjusting the pressure of the polyurethane resin inside the spray gun device 50 to 23.5 to 24.0 MPa, the amount of the resin sprayed from the nozzle 52A can be set to 10 L/min.

The less expanded graphite is added, the less likely it is that the inherent properties of the formed polyurea resin layer will be impaired, and the less expanded graphite required, the lower the production costs. Therefore, depending on the intended use, by using 15 parts by mass of expanded graphite for 100 parts by mass of polyamine and 100 to 160 parts by mass of polyisocyanate, it is possible to reduce production costs while imparting non-flammability (semi-fire resistance) to the formed polyurea resin layer.

In the first embodiment, the particle size of the expanded graphite is described as 100 mesh, but even if the particle size is smaller than 100 mesh, it is fully possible to spray the polyurethane resin using the conventional polyurethane spraying device 100.
This is because if the particle size becomes smaller, there will be no risk of clogging in the polyurea spraying device 100 (particularly the inside of the spray gun device 50).
If the viscosity increases due to the addition of expanded graphite, the temperature of the solution (A or B) to which the expanded graphite has been added can be adjusted to a higher temperature (for example, to nearly 88° C. in the case of the polyurea spraying device in Table 6).

When the particle size of the expanded graphite is made smaller in this way, it is possible to increase the amount added to achieve sufficient flame retardancy (quasi-fire resistance), but in that case, by further increasing the adjustment temperature of the polyurea resin produced by mixing and stirring, it is possible to spray from the spray gun device 50 while keeping the viscosity low.

In the above embodiment, the example of adding expanded graphite with a particle size of 100 mesh to isocyanate has been mainly described, but it goes without saying that expanded graphite may be added only to polyamine, or to both polyisocyanate and polyamine.

Second Embodiment
Next, a second embodiment of the present invention will be described with reference to FIGS.
In this second embodiment, the non-combustible powder added to the base material consisting of polyamine and polyisocyanate (the base material having a high purity similar to that in the first embodiment is used in this second embodiment) contains at least the following:
(A) Expanded graphite (particle size 100 mesh)
(B) Brominated flame retardant (C) Melamine polyphosphate (D) Silica powder

The particle size of the expanded graphite is set to be smaller than 100 mesh so that a polyurea resin layer can be formed using the polyurea spraying device 100 of the first embodiment. Incidentally, by appropriately modifying the design of the spraying pressure, temperature adjustment, and size of the opening of the polyurea spraying device 100, it is also possible to make the particle size of the expanded graphite approximately 80 mesh.

The optimum ratios of the components (A) to (D) in the noncombustible powder are as follows:
(A) Expanded graphite: 40 parts by weight (B) Brominated flame retardant: 80 parts by weight (C) Melamine polyphosphate: 80 parts by weight (D) Silica powder: 100 parts by weight

The amount (percentage) of such a "non-flammable powder" to be added to the base material (base material composition) of a polyurea resin consisting of polyamine and polyisocyanate depends on the level of "non-flammability (quasi-fire resistance)" to be achieved in the polyurea resin layer actually formed by the spraying method.

Therefore, the inventor changed the ratio of the "non-combustible powder" added to the base material of the polyurea resin (polyamine and polyisocyanate) as shown below in (2) to (6), and conducted combustion experiments to confirm the degree to which "non-combustible property (quasi-fire resistance)" could be achieved at each ratio.
In the following combustion experiments, (A) the expanded graphite was "9510045 (-100 mesh)" manufactured by Ito Graphite Industries, (B) the brominated flame retardant was "Fireguard (FG8500)" manufactured by Teijin Limited ("Fireguard" is a registered trademark of Teijin Limited), and (C) the melamine polyphosphate was "EXOLIT AP462" manufactured by Clariant Chemicals Japan Co., Ltd. ("EXOLIT" is a registered trademark of Clariant Produkte (Deutschland) Gesellschaft mit Beschlenkter Haftung).
As for (D) the silica powder, a commercially available general silica powder (fine silica dioxide, low melting point glass powder) was used.
(1) 0% (Figure 2)
(2) 15% (Figure 3)
(3) 20% (Figure 4)
(4) 25% (Figure 5)
(5) 30% (Figure 6)
(6) 40% (Figure 7)

For the combustion experiment, samples were prepared by forming a polyurethane resin layer of about 3 mm thickness on the surface of a 300 mm x 300 mm, 9 mm thick plywood board using polyurea resin (1) without the addition of non-combustible powder, and polyurea resins (2) to (6) with the addition of non-combustible powder (Figures 2 to 7). Note that, for the combustion experiment, samples were prepared by so-called "hand painting", but the polyurethane resin layer formed by the "spraying method" using the polyurethane spraying device 100 has better uniformity of film quality than the polyurethane resin layer formed by "hand painting", which can cause unevenness, and has better main properties of the polyurethane resin layer and non-combustibility (quasi-fire resistance) according to the present invention.

The results of a combustion experiment conducted for 120 seconds (2 minutes) using each of the samples (1) to (6) prepared above are shown in Figs. 2 to 7.
In the combustion experiment, each of the samples (1) to (6) was set upright and a flame from a torch burner was applied vertically from a position 150 mm away from the combustion surface for 2 minutes (the burner temperature was approximately 1200°C).

In the case of (1) where the "non-combustible powder" according to the second embodiment is not added (0%), as shown in FIG. 2, discoloration begins in the area where the burner flame hits after 15 seconds, and after 30 seconds, smoke begins to rise and dripping begins. After 60 seconds, the dripping becomes more noticeable and there is more smoke. After 1 minute 30 seconds, the dripping becomes more intense, the base of the plywood becomes visible, and after 1 minute 50 seconds, the fire begins to spread.

In the case of (2), in which 15% "non-combustible powder" was added, as shown in Figure 3, 10 seconds after the start of combustion, the area where the burner flame hit began to swell, and at 30 seconds, the swelling increased and carbonization progressed, and dripping began due to melting of the resin (during this time, a flame appeared momentarily, but it quickly went out and did not spread). At 60 seconds, the dripping became noticeable and the flame grew larger (again, the fire did not spread). At 1 minute 20 seconds, the dripping became even more intense, and the base of the plywood began to become visible, and at 1 minute 30 seconds, the resin where the burner flame hit melted off and part of the plywood burned, but the polyurethane resin layer itself did not spread to the fire.

In the case of (3), in which 20% of the "non-combustible powder" was added, as shown in Figure 4, 10 seconds after the start of combustion, carbonization began at the point where the burner flame hit, and at 20 seconds, carbonization had progressed around that point, causing it to swell more (a flame appeared momentarily at this point, but quickly went out). Dripping began at 30 seconds, and at 60 seconds, the dripping became noticeable. At 1 minute 30 seconds, the dripping became even more noticeable, and occasional flames became noticeable (even in this case, the flames did not spread to the polyurethane resin). At 2 minutes, the dripping became intense, and the expansion due to carbonization of the burning surface also became intense (the flames still did not spread). Sufficient non-combustibility (semi-fire resistance) was achieved throughout.

In the case of (4), which contained 25% "non-combustible powder," as shown in Figure 5, 10 seconds after the start of combustion, the area where the burner flame hit changed color (carbonization had barely begun), and 30 seconds after the start of combustion, carbonization became noticeable (a flame appeared for a moment but quickly disappeared, and there was no dripping). The condition remained almost the same between 30 and 60 seconds. Although dripping became noticeable at 1 minute 30 seconds, there was no significant change in the burning surface (the area where the burner flame hit). There was no significant change between 1 minute 30 seconds and 2 minutes, with the burning surface merely expanding. Although dripping of the resin occurred throughout the experiment, sufficient non-combustibility (semi-fire resistance) was obtained, even compared to the case of (3).

In the case of (5), in which 30% "non-combustible powder" was added, as shown in Figure 6, 10 seconds after the start of combustion, slight discoloration occurred mainly in the area where the burner flame hit (carbonization barely started). Up until 30 seconds, there was almost no change, and carbonization only progressed slightly. At 60 seconds, carbonization became noticeable (a flame appeared for a moment, but quickly went out, and no dripping occurred). At 1 minute 30 seconds, a large flame appeared for a moment, but quickly went out and did not spread. After 1 minute 30 seconds, even after 2 minutes, there was no dripping, and there was almost no change in the burning surface (the area where the burner flame hit).

In the case of (6), in which 40% of the “noncombustible powder” was added, the results were almost the same as when 30% was added as described above, except that the discoloration of the burning surface and the spread of carbonization were slightly narrower than when 30% was added.
In this way, in both cases where the non-combustible powder was used at 30% or 40% to the base material (base material composition) of the polyurea resin made of polyisocyanate and polyamine, no noticeable flame or smoke was generated during the combustion experiment lasting at least two minutes, and extremely excellent non-combustibility (quasi-fire resistance) was realized. Moreover, the area discolored and carbonized by the burner flame did not expand over time, and no resin dripping occurred.

In view of the above, if the objective is simply to prevent the combustion of the polyurea resin itself during combustion, the amount of "non-combustible powder" added may be approximately 15 parts by mass (15%) per 100 parts by mass of the polyurea resin base material.
Furthermore, if one wishes to achieve non-combustibility (semi-fire resistance) sufficient to prevent the spread of flames in the polyurethane resin layer for a certain period of time or longer, it is understood that the amount of "non-combustible powder" added should be approximately 20 parts by mass (20%) per 100 parts by mass of the polyurethane resin base material.
Furthermore, if one wishes to achieve non-combustibility (semi-fire resistance) that not only prevents the "spread of flames" but also suppresses carbonization and expansion of the burning surface and also suppresses dripping, the amount of "non-combustible powder" to be added will be approximately 25 parts by mass (25%) per 100 parts by mass of the polyurea resin (base material).

Furthermore, if you want to prevent the "spread of flames," suppress carbonization and expansion of the burning surface, and achieve non-flammability (quasi-fire resistance) to the extent that dripping does not occur, the amount of "non-flammable powder" added should be 30 parts by mass (30%) per 100 parts by mass of polyurea resin (base material). In this case, throughout a two-minute combustion experiment, the polyurea resin layer shows almost no deformation during combustion. Furthermore, when 40% non-flammable powder is added, there is no difference in non-flammability (quasi-fire resistance) between when 30% is added and when impurities are reduced as much as possible in order to maintain the inherent properties of the polyurea resin, and furthermore, considering the need to reduce the cost of forming the polyurea resin layer, adding 30% non-flammable powder is sufficient.

When actually spraying the non-flammable (semi-fireproof) polyurethane resin described above onto an object, the polyurethane spraying device 100 of the first embodiment can be used (FIG. 1).
This is because the "expanded graphite" added to the "noncombustible powder" in the second embodiment is 100 mesh.

The following method is used to spray a polyurea resin (polyurea resin composition) containing a "noncombustible powder" onto an object using the polyurea spraying device (spraying device) 100. Note that since the configuration and operation of the polyurea spraying device 100 are explained in the first embodiment, detailed explanations thereof will be omitted in this second embodiment.
(1) First, a desired amount of fireproof powder (15% to 40% in this embodiment) is added to at least one of polyamine and polyisocyanate.
(2) The polyamine and polyisocyanate are mixed and stirred to produce a polyurea resin, which is then heated to a temperature between 60°C and 80°C.
(3) The polyamine and the polyisocyanate are mixed and stirred to produce a polyurea resin, which is then pressurized to a predetermined pressure.
(4) The polyurethane resin, which has been heated to 60 to 80 degrees Celsius and pressurized to a predetermined pressure, is sprayed onto an object.

At this time, when the polyamine and polyisocyanate are heated, if a non-flammable powder is added to the polyisocyanate, the polyisocyanate is heated to 70 to 80 degrees Celsius.
On the other hand, when noncombustible powder is added to the polyamine, the polyamine is heated to 70° C. to 80° C. The heating is performed by heaters 13 and 23 provided in the polyurea spraying device 100.

As described above, this polyurethane spraying device 100 has a nozzle diameter of 1.5 mm and the specified pressure is 23.5 MPa to 24.0 MPa, so even if non-combustible powder containing expanded graphite with a particle size of 100 mesh (or smaller) is added to the polyurethane resin base material (base material composition), the polyurethane spraying device 100 can be used to form a uniform polyurethane resin layer on the target object.

In addition, according to the polyurea spraying device 100, when a non-combustible powder is added to a polyisocyanate, the viscosity of the polyisocyanate can be kept low by heating the polyisocyanate to 70 to 80 degrees Celsius, and when a non-combustible powder is added to a polyamine, the viscosity of the polyamine can be kept low by heating the polyamine to 70 to 80 degrees Celsius. This makes it possible to reduce the overall viscosity of the polyurea resin (polyurea resin composition). Even if a "non-combustible powder" containing expanded graphite with a particle size of 100 mesh (or a particle size smaller than this) is added to the base material of the polyurea resin, the polyurea resin (polyurea resin composition) can be uniformly sprayed onto the target object to form the polyurea resin (polyurea resin composition). The polyurea resin layer formed by uniform spraying achieves excellent non-combustibility (quasi-fire resistance) without impairing the inherent properties of the polyurea resin.

In addition, the spraying method using this polyurethane spraying device 100 can efficiently form a polyurethane resin layer as needed at the work site where the target object is located, dramatically improving the efficiency of the work of forming/installing non-flammable (semi-fireproof) polyurethane resin layers.

10: First tank 11: First pipe 12: First pump (first pressurizing means)
13 First heater (first heater)
14, 24 Hose heater 20 Second tank 21 Second piping 22 Second pump (second pressurizing means)
23 Second heater (second heater means)
30 Compression adjustment mechanism 40 Compressor (compression means)
41 Third piping 50 Spray gun device (generation means, spraying means)
52 Gun part 52A Injection nozzle 52B Trigger 60 Control part SW Switch

Claims (6)

A polyurea resin composition comprising 100 parts by mass of polyamine, 100 to 160 parts by mass of polyisocyanate, and 15 to 30 parts by mass of expanded graphite, wherein the particle size of the expanded graphite is 100 mesh or smaller. A method for forming a polyurea resin layer by spraying the polyurea resin composition according to claim 1 onto an object to form a polyurea resin layer having a desired thickness, comprising the steps of:
adding the expanded graphite to at least one of a polyamine and a polyisocyanate;
a step of heating the polyamine and the polyisocyanate so that the temperature of the polyurea resin produced by mixing and stirring the polyamine and the polyisocyanate is between 60 degrees Celsius and 80 degrees Celsius;
a step of pressurizing the polyamine and the polyisocyanate so that a pressure of a polyurea resin produced by mixing and stirring the polyamine and the polyisocyanate becomes a predetermined pressure;
A method for forming a polyurea resin layer, comprising the steps of: heating the polyurea resin to 60 degrees Celsius to 80 degrees Celsius and pressurizing it to the predetermined pressure, and spraying the polyurea resin onto an object. The method for forming a polyurea resin layer according to claim 2, characterized in that in the step of heating the polyamine and the polyisocyanate, when the expanded graphite is added to the polyisocyanate, the polyisocyanate is heated to 70 to 80 degrees Celsius, and when the expanded graphite is added to the polyamine, the polyamine is heated to 70 to 80 degrees Celsius. 2. A method for forming a polyurea resin layer by spraying the polyurea resin composition according to claim 1 onto an object using a polyurea spraying device including: a first tank for storing a polyisocyanate; a second tank for storing a polyamine; a first heating means for adjusting the temperature of the polyisocyanate supplied from the first tank; a second heating means for adjusting the temperature of the polyamine supplied from the second tank; a first pressurizing means for pressurizing the polyisocyanate supplied from the first tank; a second pressurizing means for pressurizing the polyamine supplied from the second tank; a compression means for compressing a gas; a generating means for mixing and stirring the polyisocyanate and the polyamine to generate a polyurea resin; and a spraying means having a spray nozzle and spraying the generated polyurea resin from the spray nozzle,
The temperature of the polyurethane resin in the injection means is maintained at 60° C. to 80° C. by the first heating means and the second heating means;
The pressure of the polyurethane resin in the injection means is increased to a predetermined pressure by the first pressurizing means and the second pressurizing means;
The method for forming a polyurea resin layer comprises spraying the pressurized polyurea resin from the nozzle onto an object to form a polyurea resin layer. The method for forming a polyurea resin layer according to claim 4, characterized in that the diameter of the injection nozzle is 1.5 mm, and the predetermined pressure is 23.5 MPa to 24.0 MPa. the first heating means heats the polyisocyanate to 70° C. to 80° C. when the expanded graphite is added to the polyisocyanate;
The method for forming a polyurea resin layer according to claim 4 or claim 5, characterized in that the second heating means heats the polyamine to 70 to 80 degrees Celsius when the expanded graphite is added to the polyamine.