JPH02215857A - Flame-retardant polyurethane foam - Google Patents

Abstract

PURPOSE:To remarkably improve the flame retardancy by compounding, as flame retardants, a specific nitrogen compd. and a thermally expandable graphite into a polyurethane foam. CONSTITUTION:A polyurethane foam contg. a thermally expandable graphite and at least one nitrogen compd. selected from the group consisting of melamine, a derivative thereof, urea, thiourea, and isocyanuric acid. The graphite suitable for this purpose is one obtd. by treating a graphite such as natural graphite, a thermally decomposed graphite, or a kish graphite with a mixture of conc. sulfuric acid and a strong oxidizing agent, washing the treated graphite with water, and drying it. Such an expandable graphite, when quickly heated to about 500 deg.C or higher, expands by a factor of several tens to several hunders in the direction of C axis. An esp. pref. expandable graphite has such an expansion ratio that the specific volume after expansion by rapid heating an 1000 deg.C for 10sec is 50-250cc/g, contains a sulfate of an alkali or alkaline earth metal, and gives a 1wt.% aq. dispersion thereof with a pH of 4.5 or higher.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to flame-retardant polyurethane foams, and particularly to flame-retardant polyurethane foams having extremely high flame retardancy.

[Prior Art] Foam materials such as rigid polyurethane foam have been used in various fields by taking advantage of their excellent properties, for example, as heat insulating materials for electric refrigerators and building materials such as heat insulating panels. However, various problems have been pointed out with this foam material, and in particular, from the perspective of preventing disasters caused by fire in recent years, there has been a demand for improvement, especially in terms of resistance to combustion. form was developed.

Since flame-retardant polyurethane foam has excellent flame retardancy and heat resistance, it has been widely used in fields that require fire protection properties and high-temperature properties. In particular, in the field of building materials, organic flame-retardant polyurethane foam, which is a superior heat insulating material compared to conventional inorganic materials, is showing steady growth.

Flame-retardant polyurethane foam is produced by mixing and stirring an organic polyisocyanur and a polyhydroxy compound with a catalyst, a flame retardant, a blowing agent, a foam stabilizer, etc. Conventional flame-retardant polyurethane foams produced in this manner cannot be said to be fully satisfactory in terms of flame retardancy and combustion resistance, and there is much room for improvement. In particular, in recent years, there has been a demand for insulation materials to have a high degree of flame resistance in order to prevent disasters caused by fire, so it is important to improve the flame retardancy and flame resistance of flame-retardant polyurethane foam. This is considered an issue.

Various attempts and proposals have been made to improve the flame resistance of flame-retardant polyurethane foam6.
For example, foam-molded polyurethane is mixed with a phosphoric acid compound,
A method of impregnating and drying a halogen compound, aluminum hydroxide, etc. in an aqueous solution or emulsion, a method of adding a phosphoric acid compound, a halogen compound, aluminum hydroxide, and an inorganic compound such as borax, perlite to polyurethane foam, one of the raw materials. Methods of using phosphorus-containing polyols, halogen-containing polyols, and silicone-based polyols (Japanese Patent Publication No. 57-42086) as the polyols are known. Also known are methods in which melamine, melamine derivatives, urea, nitrogen-containing compounds such as isocyanuric acid, and nitrogen-containing polyols such as amine polyols are used alone. Furthermore, a method is also known in which a heat-resistant structure such as an isocyanurate group, which is a trimer of isocyanur, is formed in the foam.

In addition, as another means, a method of increasing flame retardance by adding thermally expandable graphite to urethane products has been proposed (tlsP 3,514,844, ll5P4
．． 689,369, Special Publication No. 6l-29374).

[Problems to be Solved by the Invention] However, by any of the above conventional methods, it is not possible to obtain a flame-retardant polyurethane foam that can fully satisfy the flame-retardant requirements that have become increasingly strict in recent years. In order to obtain this property, it is necessary to incorporate a large amount of additives for improving flame retardancy, which has disadvantages such as deterioration of foam properties and high raw material cost.

The present invention aims to provide an improved flame retardant polyurethane foam.

[Means for Solving the Problem] The flame-retardant polyurethane foam of claim (1) contains at least one flame retardant selected from the group consisting of melamine, melamine derivatives, urea, thiourea, and isocyanuric acid.
The flame-retardant polyurethane foam of claim (2), characterized in that it contains a nitrogen-containing compound and thermally expandable graphite, is the flame-retardant polyurethane foam of claim (1), characterized in that it contains a nitrogen-containing compound and thermally expandable graphite. It is characterized in that it contains a metal sulfate and has a pH of 4.5 or higher in an aqueous dispersion with a concentration of 1% by weight.

That is, as a result of intensive studies to improve the flame retardancy of the foam, the present inventors have found that by using a specific nitrogen-containing compound and thermally expandable graphite together as a flame retardant, the conventional thermally expandable graphite can be improved. The present invention was completed based on the discovery that a synergistic effect is more pronounced when exposed to flame than when used alone, and a significantly higher wind-burning prevention effect can be obtained.

The present invention will be explained in detail below.

In a broad sense, the thermally expandable graphite used in the present invention can include various compositions manufactured by various methods.
In the present invention, thermally expandable graphite obtained by treating natural graphite, pyrolytic graphite, quiche graphite, etc. with a mixture of concentrated sulfuric acid and a strong oxidizing agent, washing with water, and drying is used. preferable. This is usually the industrial thermally expandable graphite used in the manufacture of graphite sheets, etc. Such thermally expandable graphite is heated rapidly to about 500 degrees Celsius or higher, resulting in tens to several tens of degrees of thermal expansion in the C-axis direction. It has the property of expanding 100 times. In particular, the thermally expandable graphite used in the present invention has an expansion degree of 50 to 250 c/c when rapidly heated at 1000°C for 10 seconds.
g, and such thermally expandable graphite is prepared, for example, in a mixture of 93 to 99% by weight, especially 98% by weight of concentrated sulfuric acid and 30 to 60% by weight, especially 60% by weight of hydrogen peroxide solution. It is produced by contacting graphite crushed into approximately 20 to 100 meshes at 45° C. or below for 10 to 30 minutes, followed by washing with water and drying.

In the present invention, particularly preferred thermally expandable graphite further includes:
Alkali metals such as Na or Ni and/or Ca, Ba%M
containing alkaline earth metals such as It is preferable that the thermally expandable graphite has a pH of 4.5 or more in an aqueous dispersion thereof at a concentration of 1% by weight.

Such thermally expandable graphite can be prepared after acid treatment with the above-mentioned mixture of concentrated sulfuric acid and hydrogen peroxide solution, after washing with water, or after washing with water.
It can be produced by contacting with an aqueous solution of an alkali metal and/or alkaline earth metal hydroxide in a water washing step, followed by filtering and drying.

The thermally expandable graphite used in the present invention preferably has a pH of 465 or higher in an aqueous dispersion of thermally expandable graphite at a concentration of 1% by weight, but if the pH is lower than 4.5, foam is generated. This may reduce the effectiveness of the catalyst, which may impede production at the desired reaction rate.

Although there is no particular upper limit to this pH, for example, if the pH exceeds 8, it will contain excessive alkali or alkaline earth metals, which may have an adverse effect on the physical properties when added to the foam. As expected, the normal pH
A value of 4.5 to 8 is preferable.

In the present invention, the pH of an aqueous dispersion of thermally expandable graphite with a concentration of 1% by weight is determined by adding 1 g of thermally expandable graphite to be measured into 99 g of deionized water, stirring for 10 minutes, and then measuring the pH using a pH electrode. Ru. The deionized water used in this measurement must have a pH within the range of 5.5 to 7.0.

Further, in the thermally expandable graphite used in the present invention, it is preferable that the alkali metal and/or alkaline earth metal be contained in the form of sulfate, but some of the alkali metal and/or alkaline earth metal may be present in the form of excess hydroxide or carbonate. It may exist in

The particle size of such thermally expandable graphite is preferably 30 to 100 mesh from the viewpoint of flame retardant effect and dispersibility into foam. That is, the particle size of thermally expandable graphite is approximately 8
If the mesh is finer than 0, the thermal expansivity tends to decrease, and if the mesh is finer than 150, the thermal expandability is extremely reduced, and as a result, the flame retardant effect of the foam is reduced. On the other hand, if the particle size is large, for example 20 to 3
When the mesh size is about 0, the thermal expansion property is sufficiently high, but the dispersibility into the foam raw material is not good, resulting in a decrease in work efficiency. Therefore, the particle size of the thermally expandable graphite used in the present invention is preferably 30 to 100 mesh, and more preferably 40 to 100 mesh.
It is most preferable to use particles sized to about 80 mesh.

The particle size of thermally expandable graphite usually depends on the particle size of the raw graphite used to produce it. Therefore, the particle size can be easily adjusted by pulverizing the raw graphite or the obtained thermally expandable graphite.

On the other hand, as the nitrogen-containing compound, one or more selected from the group consisting of melamine, melamine derivatives, urea, thiourea, and incyanuric acid is used. Among these, melamine can be industrially produced materials that are usually used as raw materials for adhesives or as raw materials for melamine-formaldehyde resins, but they are generally difficult to dissolve in foam manufacturing raw materials, so they have poor dispersibility. It is advantageous to be as detailed as possible in order to increase

The ratio of the nitrogen-containing compound to the thermally expandable graphite is such that the weight ratio of thermally expandable graphite/nitrogen-containing compound is 110.
It is preferably in the range of 02 to 115, particularly 110.
It is preferable to use the ratio in the range of 1 to 1/1.2. Even if this ratio exceeds 110.02 or less than 115, the excellent synergistic effect between the thermally expandable graphite and the nitrogen-containing compound according to the present invention You may not be able to obtain it.

In particular, when using melamine as the nitrogen-containing compound, the ratio of thermally expandable graphite to melamine is 98:2 to 98:2 by weight.
25 near 5, particularly preferably 90:10 to 45:55. When adding melamine to foam raw materials, melamine tends to reduce the reactivity of foam formation, so the blending ratio of melamine should be designed to be as low as possible within the range that allows the desired flame retardancy to be obtained. is desirable.

In addition, as for the content, the total amount of both is 5 to 5 of the form.
Preferably, the amount is 0% by weight. If the total weight of thermally expandable graphite and nitrogen-containing compound is less than 5% of the foam weight, flame retardation will be insufficient, and if it exceeds 50%, the properties of the foam will deteriorate. This is not desirable because it causes

Among the polyurethane foam raw materials used in the present invention, the polyisocyanur includes organic polyisocyanur having two or more isocyanur groups in the molecule, including aliphatic and aromatic polyisocyanur compounds, Further included are modifications thereof. Examples of aliphatic polyisocyanur include hexamethylene diisocyanur, isophorone diisocyanur, dicyclohexylmethane diisocyanur, methylcyclohexane diisocyanur, and examples of aromatic polyisocyanur include toluene. Examples include diisocyanur, diphenylmethane diisocyanur, polymeric diphenylmethane diisocyanur, and the like. Examples of these modified products include carbodiimide modified products and prepolymer modified products. Preferred polyisocyanurs in the present invention are aromatic polyisocyanurs or modified products of aromatic polyisocyanurs, and particularly preferred are diphenylmethane diisocyanur, polymeric diphenylmethane diisocyanurs, and modified products thereof. These isocyanurs are specifically shown below.

Diphenylmethane diisocyanur has the structure shown below.

Polymeric diphenylmethane diisocyanur is a polymer of the above diphenylmethane diisocyanur,
NCO content is 29-35%, viscosity 2500cp
s (25°C) or lower.

Examples of these modified products include carbodiimide modified products and prepolymer modified products. The carbodiimide-modified product is one in which a carbodiimide bond is introduced using a known phosphorus-based catalyst. The prepolymer modified product is obtained by reacting isocyanur with a polyol to leave an incyanate group at the end. As the polyol for this prepolymer, all polyols for polyurethane resins can be used.

On the other hand, the polyhydroxy compound used in the present invention may be any compound having two or more active hydrogen atoms in the molecule, and specifically, the compounds shown in (1) to (4) below are mentioned.

■ Alcohols, amines; For example, ethylene glycol, propylene glycol,
Butylene glycol, glycerin, trimethylolpropane, pentaerythritol, methylamine, ethylamine, ethylenediamine, toluenediamine, etc.

(2) Polyether polyol, a compound obtained by adding alkylene oxide such as ethylene oxide or propylene oxide to the compound of (2); For example, diethylene glycol, triethylene glycol, polyethylene glycol, dipropylene glycol, etc.

■ Polyester polyol, polycarboxylic acid and compound (■ or ■) subjected to esterification reaction, or polycarboxylic acid to which alkylene oxide is added; Examples of polycarboxylic acids include maleic acid, succinic acid, and adipic acid. , sebacic acid, phthalic acid, trimellitic acid, pyromellitic acid, etc. are used.

■Other polyols, broadly included in the above polyols, include halogen-based polyols containing halogen elements as special polyols for flame retardancy and low flammability;
Phosphate ester polyols containing one or more active hydrogens, octarophosphate polyols containing a halogen element to phosphoric ester polyols, silicate polyols containing St elements, and the like.

These polyols may be used alone or in combination of two or more.

In the present invention, preferred polyols that can improve the low smoke emission, heat resistance, flame retardance, and low brittleness of the flame-retardant polyurethane foam obtained are polyols with low organic content and polyols using alkylene oxide. So, polyols with a high proportion of ethylene oxide,
These include polyols containing ester bonds, and especially polyols such as those listed in ①. In addition, aromatic polyester polyol itself is effective in improving flame retardancy,
It is also effective in improving mechanical strength.

As the blowing agent used in the present invention, all blowing agents used in the production of urethane foam can be used. For example, trichlorofluoromethane as a low boiling inert solvent,
Fluorocarbon compounds such as dichlorodifluoromethane, etc., which generate gas by methylene chloride reaction, include water, acid amides, nitroalkanes, etc., and compounds which generate gas by thermal decomposition, such as sodium bicarbonate, ammonium carbonate, etc. Among these, preferable blowing agents include fluorocarbon blowing agents, particularly preferably trichlorofluoromethane.

As the catalyst used in the present invention, all catalysts commonly used in the production of urethane foam can be used. Examples include tin-based catalysts such as dibutyltin dilaurate and stannath octoate, and tertiary amines such as triethylamine and tetramethylhexamethylene diamine.

In the present invention, a surfactant, a flame retardant, and other auxiliary agents may be further mixed and used as necessary. As the surfactant, a silicone surfactant is usually used. Examples of flame retardants include conventionally known flame retardants such as tris(2-chloroethyl) phosphate and tris(2゜3-dibupropyl) phosphate, as well as organic powders such as urea and thiourea, or metals. Inorganic powders such as hydroxide and antimony trioxide can be used. For example, λ,
10% by weight of aluminum hydroxide based on the foam weight
Below, it can be added in particular at most 8rIL amount %, particularly at most 6 to 2% by weight. Examples of other auxiliary agents include colored powders such as pigments and dyes, powders such as talc and graphite, short glass fibers, other inorganic fillers, and organic solvents.

The flame-retardant polyurethane foam of the present invention is produced by using the above-mentioned thermally expandable graphite and nitrogen-containing compound together as a flame retardant when producing the foam using the above-mentioned polyisocyanur, polyhydroxy compound, blowing agent, catalyst, etc. It can be manufactured in the same manner as conventional foams except for blending.

In general, when manufacturing foam, it is customary to add all raw materials other than polyisocyanur to the polyhydroxy compound side and mix them together. Although there are no particular restrictions on the method of adding the carbonaceous graphite and the nitrogen-containing compound, it is usually preferable to add them to the polyhydroxy compound and carry out the reaction. In this case, depending on the type of polyhydroxy compound used, workability may decrease if the amount added is such that the total weight of thermally expandable graphite and nitrogen-containing compound is 501i% or more based on the foam weight. . In either case, the thermally expandable graphite and the nitrogen-containing compound are in a dispersed state during the reaction, so if they are left added to the polyhydroxy compound, they may settle and deposit in the lower layer of the mixture. It is desirable to stir well just before use.

In addition, in this invention, foam raw material NCO10H equivalent ratio is normally manufactured with NCOloH equivalent ratio of 0.9-1.3.

[Function] Thermally expandable graphite rapidly expands when it comes into contact with flame, suppresses foam combustion, and has an excellent effect of improving flame retardancy in that it prevents the spread of fire. Therefore, by using thermally expandable graphite and a nitrogen-containing compound in combination, an extremely excellent synergistic effect that cannot be obtained by using each alone can be produced, and a flame-retardant polyurethane foam having extremely good flame retardancy can be obtained.

In particular, by using thermally expandable graphite that contains an alkali or alkaline earth metal sulfate and has a pH of 4.5 or more in an aqueous dispersion with a concentration of 1% by weight,
Flame retardancy is further improved.

[Examples] The present invention will be described in more detail with reference to Examples and Comparative Examples below, but the present invention is not limited to the following Examples unless it exceeds the gist thereof. In addition, in Examples and Comparative Examples, details of the raw materials used are as follows.

i1 supreme polyisocyanur: polymethylene polyphenylene polyisocyanate (trade name rPAPI-135J NCO equivalent; 138 (M)
Polyol: Polyether polyol (propylene oxide adduct of sucrose) (trade name rH3-209J OH equivalent: 12
5 (manufactured by Sanyo Chemical Co., Ltd.)) Surfactant: Silicone surfactant (trade name r, 1.-5340)
J (manufactured by Nippon Unicar) Catalyst: Amine type (product name rKao-No, IJ (manufactured by Kao)) Flame retardant: Phosphorus, halogen type (product name "Fyrol")
CEF” (manufactured by Kashima Industries)) thermally expandable graphite 1(N)f
3IA buried product) (manufactured by Nippon Kasei Co., Ltd.) Thermal expandable graphite IT (KOH treated product) (manufactured by Nippon Kasei Co., Ltd.) Melamine powder (1st grade reagent) (manufactured by Nissan Chemical Co., Ltd.) Urea (reagent) Thiourea (reagent) Isocyanur Acid (manufactured by Nissan Chemical Co., Ltd.) Foaming agent: Freon type (product name: rR-11E J (manufactured by Shio Glass Co., Ltd.)) H2O (desalinated water) In addition, the physical properties of the obtained flame-retardant polyurethane foam were evaluated using the following evaluation test method. It was measured.

11-way flame retardancy: JIS K Fu 201 (performed based on combustion test of polymer materials (oxygen index)) JIS A 9514 (combustion test of rigid urethane foam) Mechanical strength: JIS A 9514 compressive strength heat conduction Rate: ASTM C-177 Example 1 Polymeric isocyanur (trade name rPAP1-13
5j) and sucrose-based polyether polyol (trade name rH
3-209J), silicone surfactant (trade name r
L-53404), catalyst (product name "niao-No.1"
), Freon-based blowing agent (trade name rR-tlEJ), and demineralized water are reacted at the ratio shown in Table 1, using thermally expandable graphite (KOH treated product,
A flame-retardant foam was produced by adding 1% by weight aqueous dispersion with a pH of 7) and melamine powder in the amount shown in Table 1, raising the liquid temperature to 20°C, mixing with a stirrer, and foaming. The time required for foaming was as shown in Table 1.

Table 1 shows the physical properties of the obtained flame-retardant polyurethane foam.

Examples 2 to 8, Comparative Examples 1 to 7 Flame-retardant polyurethane foams were produced in the same manner as in Example 1, except that the raw materials were blended as shown in Table 1. Table 1 shows the physical properties of the obtained flame-retardant polyurethane foam.

Table 1 shows that the flame-retardant polyurethane foam of the present invention, in which thermally expandable graphite and a nitrogen-containing compound such as melamine are added in combination, has a markedly improved oxygen index in the JIS K 7201 test, and has also improved in the JIS A9514 combustion test. It is clear that the flame retardance is significantly improved due to the excellent barrier effect during combustion due to the thermally expandable graphite and nitrogen-containing compound, such as shortening the combustion distance and combustion time and improving flammability.

Examples 9 to 14, Comparative Example 8.9 The raw materials were reacted at the blending ratios shown in Table 2.

First, in a polyethylene container, polyisocyanur, blowing agent rR-11EJ, and raw materials other than thermally expandable graphite are mixed at a predetermined ratio, then thermally expandable graphite is added at a predetermined ratio, and thoroughly stirred and mixed. A predetermined amount of blowing agent was added to obtain a mixed raw material while keeping the liquid temperature at 20 ± 1°C. A predetermined amount of the mixed raw material was taken into polyethylene beakers 0 and 11, and a predetermined amount of polyisocyanur was added thereto. Immediately stir vigorously for 5 seconds, then quickly transfer the contents to <20cm x 20cm
Transfer it to a container with a size of m x 20 cm and leave it as it is 3
The foamed molded product was taken out after 0 minutes.

The thermally expandable graphite has a particle size distribution of 35 to 80 mesh and an expansion degree of 200 m at 1000°C for 10 seconds.
JL/g and contains 0.2% by weight of Na element,
A 1% by weight aqueous dispersion having a pH of 7.2 was used.

For the obtained foam molded product, JIS-720
1, the oxygen index was measured and the results are shown in Table 2 and FIG.

From Table 2 and FIG. 1, it is clear that there is a synergistic effect due to the combined use of thermally expandable graphite and melamine, and it is clear that superior flame retardance can be obtained.

[Effects of the Invention] As detailed above, according to the flame-retardant polyurethane foam of the present invention, the flame retardance is higher than that of conventional products due to the extremely excellent synergistic effect of the combination of thermally expandable graphite and nitrogen-containing compound. A polyurethane foam with significantly improved flame retardant properties is provided.

In particular, it contains an alkali or alkaline earth metal sulfate as thermally expandable graphite, and 1! When using an aqueous dispersion having a pH of 4.5 or more at a concentration of i%, flame retardance is further improved.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the measurement results of the oxygen index of Examples 9 to 14 and Comparative Examples 8.9. Agent Patent Attorney Tsuyoshi Shigeno

Claims (2)

[Claims] (1) Melamine, melamine derivatives, urea as flame retardants,
A flame-retardant polyurethane foam characterized by containing at least one nitrogen-containing compound selected from the group consisting of thiourea and isocyanuric acid and thermally expandable graphite. (2) A patent characterized in that the thermally expandable graphite contains an alkali metal and/or alkaline earth metal sulfate and has a pH of 4.5 or more in an aqueous dispersion with a concentration of 1% by weight. The flame-retardant polyurethane foam according to claim 1.