JP2710368B2 - Flame retardant polyurethane foam - Google Patents

Description

The present invention relates to a polyurethane foam having improved flame retardancy, and the polyurethane foam of the present invention is suitable for use as a cushioning material, a heat insulating material, a building material, and the like. ing.

[Prior Art] Among polyurethane foams, flexible foams are used as various cushioning materials such as sofas, mattresses, automobile seats, and rigid foams include, for example,
It has been used in various fields as a building material such as a heat insulating material and a heat insulating panel of an electric refrigerator, taking advantage of its excellent characteristics.

However, various problems have been pointed out with this foam material, and from the viewpoint of preventing disasters caused by fires in recent years, improvement in resistance to combustion has been demanded.

Various attempts have been made and proposed to meet the demand for enhancing the flame retardancy. For example, a method of impregnating and drying a foamed polyurethane in an aqueous solution or emulsion of a phosphoric acid compound, a halogen compound, aluminum hydroxide or the like.

Halogen compound, halogenated phosphate compound, metal hydroxide, metal oxide,
Physical method of containing antimony trioxide, etc., Use of phosphorus-containing polyols and halogen-containing polyols as polyols as one of the raw materials, and heat-resistant structures such as isocyanurate groups which are trimers of isocyanate in the foam Chemical methods such as the formation of are known.

Further, as another means for achieving such an object, U.S. Pat.No. 3,574,644 proposes a method of increasing flame retardancy by adding thermally expandable graphite to urethane products, and U.S. Pat. Similar proposals have been made.

The present inventors have conducted various studies on a polyurethane foam having excellent flame retardancy, and as a result, the method of adding the thermally expandable graphite, which is conventionally known, causes the thermally expandable graphite to rapidly increase upon contact with a flame. It was confirmed that a polyurethane foam product having excellent flame retardancy, which expands to suppress the burning of the polyurethane foam and prevent the spread of fire, can be obtained.

However, it has been found that the heat-expandable graphite obtained by a conventionally known and used method has the following problems when producing a urethane product, although an excellent flame retarding effect on a urethane product is recognized.

That is, the heat-expandable graphite usually shows acidity because it contains free sulfuric acid in addition to the sulfuric acid existing between the layers of the graphite, which deactivates the catalyst and reduces the reactivity when molding the polyurethane foam. As a result, the reaction does not proceed in the desired reaction time, or the properties of the obtained foam,
For example, mechanical strength such as the degree of formation of bubbles and compressive strength is reduced.

This problem can be solved to some extent by adding a new catalyst corresponding to the amount of deactivated catalyst. Also, in the above-mentioned U.S. Pat. No. 3,574,644, the addition of acidic heat-expandable graphite to a film-forming latex or emulsion degrades stability, so that the mixed system is neutralized with ammonia or heated. It is described that the expandable graphite is used after being brought into contact with ammonia in advance, and it is suggested that the acidity of the thermally expandable graphite is neutralized with a basic substance.

However, the former method of adding the catalyst is not preferable because the composition of the urethane foaming system is changed and the number of working steps is increased. According to the experimental results of the present inventors, the latter method of neutralization can prevent catalyst deactivation to some extent by neutralization with ammonia, but is not sufficient. It was found that the degree of catalyst deactivation increased, and it was evident that the operation was extremely inconvenient.

This is thought to be because ammonium sulfate, which is expected to be generated by neutralization, is decomposed by the heat of reaction generated during the urethanization reaction, and the generated sulfuric acid causes deactivation of the catalyst.

[Problems to be Solved by the Invention] The present invention aims to provide a polyurethane foam having excellent flame retardancy, and furthermore, such as deactivation of a catalyst.
An object of the present invention is to provide a polyurethane foam containing a flame retardant that does not inhibit a urethanization reaction.

[Means for Solving the Problems] In order to solve the above problems, the present inventors use a specific heat-expandable graphite to obtain a raw material system which is usually used for polyurethane foam production. The present inventors have found that the above-mentioned problems can be solved without adding them, and have reached the invention.

That is, the present invention relates to a flame-retardant polyurethane foam containing heat-expandable graphite; 1) the heat-expandable graphite contains an alkali metal; 2) water having a concentration of 1% by weight of the heat-expandable graphite. The pH of the dispersion
The flame retardant polyurethane foam is characterized in that it is 4.5 or more; and 3) the content of the thermally expandable graphite in the polyurethane foam is 5 to 30% by weight.

The heat-expandable graphite is obtained by treating graphite such as natural graphite, pyrolytic graphite, and quiche graphite with a mixture of concentrated sulfuric acid and a strong oxidizing agent, followed by washing with water and drying.
Used for manufacturing graphite sheets and the like.

This heat-expandable graphite has the property of expanding several tens to several hundreds times in the C-axis direction when rapidly heated to about 500 ° C. or more.

The raw graphite of the heat-expandable graphite used in the present invention, the production method is not particularly limited, but as its characteristics, at 1000 ℃
The degree of swelling when heated rapidly for 10 seconds is 50-250cm ³ / gr
It is desirable that Such a heat-expandable graphite can be obtained, for example, by mixing graphite ground to about 20 to 100 mesh in a mixture of 98% concentrated sulfuric acid and 60% aqueous hydrogen peroxide at 45 ° C. or lower.
It can be manufactured by contacting for 0 to 30 minutes, washing with water and drying.

The heat-expandable graphite used in the present invention contains Na and K as alkali metals, and the alkali metal reacts with free sulfuric acid contained in the heat-expandable graphite to form a salt, and It is necessary that the pH of the 1% by weight aqueous dispersion of the heat-expandable graphite is 4.5 or more.

Such heat-expandable graphite can be produced by contacting with an aqueous solution of an alkali metal hydroxide after acid treatment, washing with water or a washing step, followed by filtration and drying.

The heat-expandable graphite of the present invention requires that the pH of a 1% by weight aqueous dispersion of the heat-expandable graphite be 4.5 or more,
If the pH is lower than 4.5, the effect of improving contact deactivation is low, and the desired effect cannot be achieved.

There is no particular upper limit to the pH. However, for example, when the pH exceeds 8, an excessive amount of an alkali metal is contained, and when added to a polyurethane foam, its physical properties are expected to be adversely affected. , Usually 4.5 ~
8.0 is preferred.

Further, it is necessary that the alkali metal is contained as a sulfate, but a part of the alkali metal may be present and contained in the form of an excess of a hydroxide or a carbonate.

As the alkali metal, Na and K may be used alone or both may be appropriately mixed.

PH of 1% by weight aqueous dispersion of thermally expandable graphite of the present invention
Is measured by using a pH electrode after adding 1 gr of the heat-expandable graphite to be measured to 99 gr of deionized water and stirring for 10 minutes.
The pH of the deionized water used in this measurement must be in the range of 5.5 to 7.0.

The particle size of the heat-expandable graphite is usually influenced by the particle size of the raw material graphite at the time of producing the same, and has a certain range of particle size distribution according to the particle size of the raw material. It is of course possible to adjust the particle size by a method such as pulverizing raw graphite or thermally expandable graphite. The particle size distribution of the heat-expandable graphite used in the present invention is desirably within a certain range for the purpose of relating to the flame-retardant effect and for the purpose of being added to polyurethane products.

That is, when the particle size is smaller than about 80 mesh, the expandability tends to be small, and when the particle size is smaller than 150 mesh, the expandability is extremely reduced, and as a result, the flame retardant effect of the polyurethane product is significantly reduced. I do.

On the other hand, when the particle size is large, for example, in the case of about 20 to 30 mesh, the swelling property is sufficiently high, but when it is used in a urethane-forming reaction, uniform dispersion becomes difficult, and the desired flame retardancy is not obtained, and at the same time, polyurethane is used. The work efficiency is reduced due to poor dispersibility in the raw material system.

Therefore, the particle size of the thermally expandable graphite of the present invention is 30 to 10
A mesh of 0 mesh is desirable, and a mesh of about 40 to 80 mesh is most preferred.

The addition ratio of the heat-expandable graphite to the polyurethane foam is 5 to 30%, and if it is 5% or less, the flame retardancy is insufficient, and if it is 30% or more, the characteristics as the polyurethane foam are undesirably deteriorated.

This ratio can be appropriately selected according to the degree of flame retardancy required for the polyurethane foam, but when added to the polyol side, which is one of the raw materials, according to a conventional method, 25% may be used depending on the raw material polyol. % Or more may lower the workability.

The polyurethane foam raw material used in the present invention may be any of a flexible foam and a rigid foam,
Generally, as the polyol, polyoxypropylene glycol, polyethers such as polyoxyethylene glycol, polyethylene adipate, polyesters such as polyhexamethylene adipate can be mentioned as typical examples, but aromatic polyester polyols Itself is effective in improving the flame retardancy and is also effective in improving the mechanical strength.

Examples of the polyisocyanate include diisocyanates such as TDI and MDI.

In addition to these raw materials, reaction catalysts such as amines. Freon gas for arranging bubbles and adjusting foam density,
Water, silicone-based surfactants and the like are usually used.

Further, the polyurethane foam of the present invention includes tris (2-chloroethyl) phosphate and tris (2,3-
In addition to conventionally known flame retardants such as dibromopropyl) phosphate, organic powders such as urea, thiourea and melamine or inorganic powders such as metal hydroxides and antimony trioxide are added as flame retardants and used in combination. Is also good.

To produce the flame-retardant polyurethane foam of the present invention, a heat-expandable graphite containing an alkali metal is added to a polyol so that the polyurethane foam contains 5 to 30% by weight of the polyurethane foam. React with compound.

Note that additives other than the flame retardant are usually added to the polyol side. There is no particular limitation on the method of adding the heat-expandable graphite, and the heat-expandable graphite of the present invention has very little change with time and hardly loses its reactivity even when left to be added to the polyol. Although it is extremely advantageous from the viewpoint of properties, it may be settled and deposited in the lower layer of the polyol mixture in some cases, and in this case, it is used by stirring well immediately before use.

[Examples] Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples as long as the gist is not exceeded.

The numerical values indicating the amounts of the components described in the examples and the like are all parts by weight.

Examples 1 to 4 and Comparative Examples 1 to 3 Production of Flexible Polyurethane Foam Raw materials were reacted at the compounding ratios shown in Table 1. The details of the raw materials used are summarized in the margin of Table 1. Table 2 shows the alkali metals contained in the thermally expandable graphite used and the pH of the flake dispersion of the graphite.

 The reaction was carried out as follows.

First, a raw material other than polyisocyanate and heat-expandable graphite is added and mixed in a polyethylene container at a predetermined ratio, and then a heat-expandable graphite of a predetermined ratio is added, sufficiently stirred and mixed to obtain a mixed material. . Then, a predetermined amount of the mixed raw material was placed in one polyethylene beaker, a predetermined amount of the polyisocyanate was added thereto, and the mixture was immediately vigorously stirred for 5 seconds, the stirrer was removed, and the mixture was allowed to stand.

In the above operation, the liquid temperature was adjusted to 20 ± 1 ° C.

After performing the reaction operation, the cream time and rise time were measured. Furthermore, for the reactants left at room temperature,
After 5 hours, the volume of the product was measured.

In the same manner, an example (blank) in which the thermally expandable graphite of the present invention was not added was performed as Comparative Example 1. In addition, an example using thermally expandable graphite treated with ammonia is referred to as Comparative Example 2,
The reaction was carried out in the same manner as described above, using Comparative Example 3 as an example using a thermally expandable graphite having a pH of the aqueous dispersion of less than 4.5.

Table 3 shows the results of Examples 1-4 and Comparative Examples 1-3. As shown in Table 3, in Examples 1 to 4, the cream time and the rise time during the reaction were not inferior to those of Comparative Example 1 in which no additives were added, and the foam volumes were almost the same.

Combustion Test The polyurethane foams of Examples 1 to 4 and Comparative Examples 1 to 3 were subjected to a flammability test according to 6.9 of JIS-A-9514 (combustion test).

The test piece was 150 mm long, 50 mm wide, and 13 mm thick. Take five test pieces, apply the flame of a Bunsen burner with a fish tail light to one end for 60 seconds, and then move the Bunsen burner away from the test piece . After the flame was applied to the test piece, the time (sec) until the fire of the test piece extinguished and the length (mm) of the burned portion of the burned portion of the test piece were measured.

Table 4 shows the average value of the measurement results for n = 5. As shown in Table 4, the polyurethane foam of the present invention exhibited extremely excellent combustion resistance as compared with that of Comparative Example 1 to which no heat-expandable graphite was added.

Examples 5 to 8 and Comparative Examples 4 to 6 Production of Flexible Polyurethane Foam In the same manner as in Examples 1 to 4 and Comparative Examples 1 to 3, a polyol-based mixed raw material was produced, and a lid was placed on the container to examine changes over time. The mixture was kept at 5 ° C. and reacted with polyisocyanate in the same mixing ratio as shown in Table 1. The details of the used raw materials are the same as those used in Examples 1 to 4.

Immediately after the production of the mixed raw material, after 2 days, after 5 days, after 10 days, the production of the flexible polyurethane foam was performed,
The volume of the foam was measured.

Test Results Table 5 shows the results of Examples 5 to 8 and Comparative Examples 4 and 6. From these results, the polyurethane foam of the present invention was obtained by adding the heat-expandable graphite treated with ammonia of Comparative Example 5 because the time-dependent change of the polyol-based mixed raw material to which the heat-expandable graphite subjected to the specific treatment was added was small. Comparative Example 4 in which the change in volume was smaller than that of the polyurethane foam using the polyol-based mixed raw material, and the polyol-based mixed raw material to which the heat-expandable graphite was not added even when the polyol-based mixed raw material was used 10 days after mixing. Compared to the polyurethane foam, the change in volume is comparable.

Examples 9 to 12 and Comparative Examples 7 to 9 Production of Rigid Polyurethane Foam Raw materials were reacted in the proportions shown in Table 6. The details of the raw materials used are summarized in the margin of Table 6. The thermally expandable graphite used was the same as that shown in Table 2 above in Example 1.
４4 and Comparative Examples 1１〜３3, respectively.

Test results Table 7 shows the results of Examples 9 to 12 and Comparative Examples 7 to 9. As shown in Table 7, in Examples 9 to 12, the cream time, gel time, and rise time during the reaction were comparable to those of Comparative Example 7 in which no heat-expandable graphite was added.

Combustion Test For Examples 9 to 12 and Comparative Examples 7 to 9, IS-A-95
A flammability test was performed in accordance with Section 14 6.9 (flammability test).

The test piece was 150 mm long, 50 mm wide, and 13 mm thick. Take five test pieces, apply the flame of a Bunsen burner with a fish tail light to one end for 60 seconds, and then move the Bunsen burner away from the test piece . After the flame was applied to the test piece, the time (sec) until the fire of the test piece extinguished and the length (mm) of the burned portion of the burned portion of the test piece were measured.

 The oxygen index was measured based on JIS-K-7201.

Table 8 shows the results. As shown in Table 8, the polyurethane foam to which the heat-expandable graphite was added exhibited better flame resistance than that of Comparative Example 7 to which no heat-expandable graphite was added.

[Effects of the Invention] As described above, the polyurethane foam of the present invention has excellent flame retardancy (combustion resistance), and the activity of the catalyst does not decrease in the urethane-forming reaction step.

Continuation of the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location C08G 101: 00) (72) Inventor Satoshi Inaba 34-Nakayama, Onahama, Iwaki-shi, Fukushima Nihon Kasei Co., Ltd. (72) Inventor Shoichi Okubo 1000 M Kamoshida-cho, Midori-ku, Yokohama-shi, Kanagawa Pref. Inside the M-D Kasei Co., Ltd. In-house (56) References JP-A-2-153811 (JP, A) JP-A-1-3111137 (JP, A) JP-A-1-299870 (JP, A) JP-A-55-50035 (JP, A) JP-A-2-105811 (JP, A) JP-A-1-311167 (JP, A)

Claims (1)

(57) [Claims] 1. A flame-retardant polyurethane foam containing heat-expandable graphite, comprising: 1) the heat-expandable graphite contains an alkali metal; 2) water having a concentration of 1% by weight of the heat-expandable graphite. The pH of the dispersion
3) The flame-retardant polyurethane foam, characterized in that the content of the heat-expandable graphite in the polyurethane foam is 5 to 30% by weight.