JP2775798B2 - 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 in cushioning materials, heat insulating materials, building materials, and the like. ing.

[Conventional technology]

Among polyurethane foams, soft 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 exhibits acidity because it contains free sulfuric acid in addition to the sulfuric acid existing between the layers of the graphite, and thus, when forming a polyurethane foam, deactivates the catalyst and lowers the reactivity. 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 seeks 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 problem]

In order to solve the above-mentioned problems, the present inventors have solved the above-mentioned problems by using a specific heat-expandable graphite without any modification to a raw material system usually used for producing a polyurethane foam. It has been found that the invention can be performed.

That is, the present invention relates to a flame-retardant polyurethane foam containing heat-expandable graphite, 1) that the heat-expandable graphite contains an alkaline earth metal, and 2) a concentration of 1% by weight of the heat-expandable graphite. PH of the aqueous dispersion of
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.

Thermal 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 in the manufacture of

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 is prepared by, for example, mixing graphite pulverized to about 20 to 100 mesh in a mixture of 98% concentrated sulfuric acid and 60% hydrogen peroxide solution at a temperature of 45 ° C. or less.
It can be manufactured by contacting for 30 minutes, washing with water and drying.

The heat-expandable graphite used in the present invention contains Ca, Ba, and Mg as alkaline earth metals, and the alkaline earth metal reacts with free sulfuric acid contained in the heat-expandable graphite to form a salt. In addition, 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 is brought into contact with an alkaline earth metal hydroxide dissolved or dispersed in water or an alcohol such as methanol or ethanol after the acid treatment, after washing with water or in the washing step. Then, the mixture can be produced by filtering 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 catalyst 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, it will contain an excessive amount of alkaline earth metal, and when added to a polyurethane foam, it is expected that the physical properties thereof will be adversely affected. Therefore, it is usually 4.
5-8.0 is preferred.

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

As the alkaline earth metal, Ca, Ba, Mg 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. Of course, it is also 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, a reaction catalyst such as amines, freon gas for adjusting 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 alkaline earth metal,
It is added to the polyol so as to be contained in the polyurethane foam at a ratio of 5 to 30% by weight, and is reacted with the polyisocyanate 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.

〔Example〕

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 shown together in the margin of Table 1. Table 2 shows the alkaline earth metals contained in the thermally expandable graphite used and the pH of the aqueous 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.

On the other hand, in order to examine the stability over time of the polyol mixture to which the heat-expandable graphite was added, immediately after the production of the mixture, and after placing the mixture in a container and closing it at 5 ° C. and keeping it at 5 ° C. for 5 or 10 days, The volume of the foam obtained by reacting with the polyisocyanate was measured.

Table 1 shows the results of Examples 1 to 4 and Comparative Examples 1 to 3. As shown in Table 1, in Examples 1 to 4, the cream time and the rise time at the time of the reaction were not inferior to those of Comparative Example 1 in which no heat-expandable graphite was added, and the volume of the foam was almost the same. Met. In addition, even when the heat-expandable graphite containing an alkaline earth metal is added, there is almost no change in the polyol over time, and even after 10 days from the addition to the polyol, the reactivity is higher than that of the polyol without the heat-expandable graphite. There is almost no change in
Compared to the case of using thermally expandable graphite treated with ammonia,
Good stability over time and excellent reactivity.

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 3 shows the average value of the measurement results for n = 5. As shown in Table 3, 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, Comparative Examples 4 to 6 Production of rigid polyurethane foam Raw materials were reacted at the mixing ratios shown in Table 4. The details of the raw materials used are summarized in the margin of Table 4. In Examples 5 to 8, the thermally expandable graphite used in Examples 1 to 4 was used in correspondence with each other. In Comparative Examples 4 and 6, Comparative Examples 1 to 6 were used.
Corresponding to 3. (Comparative Example 4 did not contain any heat-expandable graphite.) The reaction method was as follows.

First, a polyol, a catalyst, a foam stabilizer and a foaming agent are mixed in a predetermined ratio in a polyethylene container, heat-expandable graphite is added thereto, and the mixture is sufficiently stirred and mixed. Then, the liquid temperature is maintained at 20 ± 1 ° C., and then foaming is performed. The mixture was added to obtain a mixed raw material. (In order to make the foam density the same, the amount of the foaming agent was reduced in Comparative Example 4.) Then, a predetermined amount of the mixed raw material was taken in one polyethylene beaker, a predetermined amount of the polyisocyanate was added thereto, and 5 After vigorous stirring for 2 seconds, the contents were quickly transferred to a 20 cm × 20 cm × 20 cm container and allowed to stand.
The results are shown in Table 4.

As shown in Table 4, the cream time, the gel time, and the rise time of Examples 5 to 8 are comparable to those of Comparative Example 4 to which no heat-expandable graphite is added.

Combustion test About Examples 5-8 and Comparative Examples 4-6, Examples 1
4. Combustibility test and JIS-K as in Comparative Examples 1-3
The oxygen index was measured in accordance with -7201. The results are shown in Table 5. As shown in Table 4, the polyurethane foam to which the heat-expandable graphite was added exhibited better flame resistance than that of Comparative Example 4 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 resistance, and the activity of the catalyst does not decrease in the urethane-forming reaction step.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08G 101: 00) (72) Inventor Satoshi Inaba, 34 Takayama, Onahama, Iwaki-shi, Fukushima Prefecture Within Nihon Kasei Co., Ltd. (72) Invention Person Shoichi Okubo 1000 M Kamoshida-cho, Midori-ku, Yokohama-shi, Kanagawa Prefecture Inside the M-D Kasei Co., Ltd. research institute (72) Inventor Hiroaki Katano 1000 M Kamoshida-cho, Midori-ku, Yokohama-shi, Kanagawa Prefecture M-D Kasei Co., Ltd. research institute (56) References JP-A-55-50035 (JP, A) JP-A-2-153967 (JP, A) JP-A-1-299870 (JP, A) JP-A-1-311137 (JP, A) JP-A-1 -311167 (JP, A) JP-A-2-105811 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C08G 18/00-18/87 C08L 75/00-75/16 C01B 31/04

Claims (1)

(57) [Claims] 1. A flame-retardant polyurethane foam containing heat-expandable graphite, comprising: 1) the heat-expandable graphite contains an alkaline earth metal; 2) a concentration of 1% by weight of the heat-expandable graphite. PH of the aqueous dispersion of
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.