JPH0561263B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing guanidine sulfamate. More specifically, the present invention combines sulfamic acid and dicyandiamide into sulfamic acid,
The present invention relates to a production method in which ammonia and water are coexisting during the reaction by adding to a reaction mixture of ammonium sulfamate and dicyandiamide or one or more reaction media selected from ammonium sulfamate. The most commonly used method for producing guanidine sulfamate is to melt-react ammonium sulfamate and dicyandiamide and recover the liberated ammonia. As an improved method of this well-known method, JP-A No. 57-64663 discloses a method in which sulfamic acid and dicyandiamide are added to a small amount of a reaction medium in the presence of ammonia, and reacted directly. However, this improved method still has room for improvement in terms of the required amount of ammonia and the quality of the product, such as its thermal stability and crystallization rate. As a result of various studies to achieve these improvement objectives, the present inventors completed the present invention after learning that the above-mentioned improvement objectives can be achieved by allowing water to coexist with ammonia. As is clear from the above description, an object of the present invention is to provide a process improvement method for producing guanidine sulfamate directly from sulfamic acid and dicyandiamide.
Another object is to provide a method for producing guanidine sulfamate by which guanidine sulfamate can be stably obtained by a known direct method. The present invention has the following configurations (1) and (2). (1) Sulfamic acid and dicyandiamide are continuously supplied with ammonia and water vapor,
It is added to one or more reaction media selected from guanidine sulfamate, a reaction mixture of ammonium sulfamate and dicyandiamide, or ammonium sulfamate, and the reaction mixture is maintained at a temperature of 120 to 125°C and a pH of 7 or more to carry out the reaction. A method for producing guanidine sulfamate, which comprises passing ammonia gas through the reaction mixture after the addition of sulfamic acid and dicyandiamide to cause the reaction to occur at 140 to 170°C. (2) The production method according to item (1) above, wherein the reaction is carried out initially at 140 to 150°C and then at 160 to 170°C. In the present invention, sulfamic acid and dicyandiamide are added to a certain reaction medium described below and reacted in a molten state within a certain temperature range. The coexistence of ammonia and water is required during the reaction. Commercial products can be used for both sulfamic acid and dicyandiamide, and these can be charged individually or as a mixture into a reactor. The reaction may be carried out in a batch manner or in a continuous manner. The molar ratio of sulfamic acid to dicyandiamide is 1:1.4 to 2.0, preferably 1:1.7 to 1.95. Certain reaction media used in the present invention include guanidine sulfamate, a reaction mixture of ammonium sulfamate and dicyandiamide, or
One or more selected from ammonium sulfamate. These media are necessary as an initial medium for starting the reaction between the raw materials sulfamic acid and dicyandiamide.
It has the advantage that it does not need to be separated from the special product after the reaction is completed, either as it is or by converting it to guanidine sulfamate. Therefore, there is no need to replenish the medium mentioned above during the continuous reaction. The amount of the medium to be used is not limited, but it is sufficient to use about 1/20 to 1/2, preferably 1/10 to 1/3, of the capacity of the reactor or the total amount of raw materials to be charged. Instead of the above-mentioned guanidine sulfamate, a predetermined amount of ammonium sulfamate and dicyandiamide may be reacted in advance in a reactor and used as guanidine sulfamate. The same applies to the above. If the raw materials sulfamic acid and dicyandiamide are directly subjected to reaction conditions without using such a reaction medium, a product of good quality cannot be obtained even if ammonia, which will be described later, is present. In a typical method of carrying out the present invention, for example, sulfamic acid and dicyandiamide are added in the form of powder while blowing steam and ammonia gas into a reaction mixture of dicyandiamide and ammonium sulfamate heated to a molten state, and the reaction is carried out. The addition method may be any method, but preferably it is added sequentially into the reaction system. It is also possible to use a solvent (eg water). However, the use of water as a solvent and the small amount of water allowed to coexist during the reaction in the present invention have different meanings, and the manner in which they are used as specific constituent elements is also different. For example, the above-mentioned JP-A-57-64663 describes that the reaction is carried out by adding sulfamic acid and dicyandiamide while raising the temperature while blowing ammonia into an aqueous solution of ammonium sulfamate as a medium. The fundamental difference between this aspect of the known method and the present invention is that the former is i. During the raw material supply reaction, there is a period when a relatively large amount of water is present compared to ammonia, and b. There is a period during which there is no moisture and only ammonia is present during the raw material supply reaction. Furthermore, in the latter case, that is, the method of the present invention, c. The coexistence of ammonia and water throughout the raw material supply reaction brings about an effect unique to the present invention (see Comparative Example below). The method of the invention involves reacting sulfamic acid and dicyandiamide in the presence of ammonia and moisture. In a preferred embodiment, sufficient amounts of water vapor and ammonia are continuously supplied and circulated into the reaction system to maintain the pH within the reaction system at 7 or higher at all times. The ammonia used in the present invention is usually blown into the reaction system in a gaseous form. On the other hand, the water used in the present invention may be added dropwise, injected or sprayed into the reactor in liquid form, or water vapor may be blown into the reactor. In the method of the present invention, when using ammonia,
It is characterized by the fact that water always coexists in the reaction system. The ratio of the amount of water supplied per unit time to the sulfamic acid added is sulfamic acid/
Water = 0.005 to 3.00 is preferred. Even when the ratio is less than 0.005, the effect is observed, but the degree of effect is somewhat weak. It is also effective when the ratio exceeds 3.00, but in order to maintain the reaction temperature at 110 to 140°C, the supplied water must be evaporated, and when the ratio exceeds 3.00, the amount of water to be evaporated increases and energy is consumed. This makes it difficult to maximize production capacity for a given capacity reactor. The quality referred to in the present invention refers to one or more of guanidine content, whiteness, melting point crystallization rate, and water-insoluble content shown in Examples and Comparative Examples described below. In a preferred embodiment of the present invention, the pH within the reaction system is constantly maintained at 7 or higher during the reaction by continuously supplying ammonia. This means that the amount of ammonia present relative to unreacted sulfamic acid in the reaction system is more than the stoichiometric amount. The above-mentioned PH7 means that it is impossible to directly measure the PH of the reaction product (note
This refers to the value measured for a sample obtained by diluting the reaction mixture 10 times with water, taking into account the fact that the amount of water is insufficient. Maintaining the pH above 7 means constantly supplying ammonia and a small amount of water to keep the reaction system from becoming acidic. When sulfamic acid and dicyandiamide are added and reacted when ammonia and a small amount of water are insufficiently supplied and the pH is less than 7, there will be many side reactions in addition to the desired reaction, and the content of guanidine sulfamate in the product will decrease. The product has a slow solidification rate and a low melting point. When attempting to use this product as a flame retardant for cellulosic materials such as paper, it cannot be used as is because of its poor thermal stability. Of course, even if the PH is less than 7, the lower it is to 7 and the shorter the time it takes to be less than 7, the fewer side reactions will occur and usable products will be obtained, but it is preferable to
The reaction is carried out by supplying enough ammonia and water to maintain the value of 7 or more. In this way, as shown in the examples, the content of guanidine sulfamate in the product is high and the purity is 95% or more. can also be easily obtained. Even when the product obtained in this way is used as it is as a flame retardant for cellulose materials such as paper, it has the excellent thermal stability mentioned above, and when used after being dissolved in water, there is no generation of insoluble matter, making it a flame retardant. It is extremely excellent. In the reaction of the present invention, even if the amount of ammonia and a small amount of water supplied is sufficient, sulfamic acid is added as a solid. It is necessary to finely grind the ammonia and adjust the addition rate so that the supply of ammonia and water is not insufficient. The reaction temperature in the production method of the present invention is 110°C ~
The reaction proceeds without any problem in the range of 200℃, but at 110℃
Preferably, the reaction is carried out at ~170°C. When the reaction temperature is low, side reactions are less likely to occur, which is preferable in terms of quality, but the reaction rate becomes slow. Below 110°C, the added sulfamic acid and dicyandiamide exist in the form of a slurry, and the reaction hardly progresses. Furthermore, as the reaction temperature increases, the reaction rate becomes faster, but side reactions are promoted, and when the temperature exceeds 200°C, side reactions become more intense, producing products that are unfavorable in terms of quality. In the method for producing guanidine sulfamate according to the present invention, the starting stage of the reaction is such that the melting point of both the sulfamic acid and dicyandiamide to be added is 200°C.
Therefore, as mentioned above, a small amount of reaction medium is required to bring these into a molten state. The small amount of reaction medium required for this starting step may be a melt or aqueous solution of guanidine sulfamate that has already been prepared. Using an aqueous solution prepared by dissolving a small amount of ammonium sulfamate in water, or an aqueous ammonium sulfamate solution prepared by adding sulfamic acid while supplying ammonia to water, raise the temperature while blowing in ammonia and water, and dissolve the sulfamic acid. The reaction is carried out by adding dicyandiamide. After the addition of sulfamic acid and dicyandiamide is completed, the supply of water is stopped, the supply of water is switched to dry ammonia, and the reaction is carried out at an internal temperature of 140 to 150° C. for about 1 hour. Also preferably after that
If the reaction is carried out at 160 to 170°C for several hours (for example, 4 hours), the variation in quality between reaction lots can be further reduced. The effects of the present invention can be summarized as follows. In terms of quality, this is superior to a production method that does not supply water. (1) Excellent thermal stability when attached to paper. Conventional method Invention 200℃ 3 minutes Whiteness 50-68% 68-71% 220℃ 3 minutes 30-40% 50-60% Case (Meaning) Recently, high-temperature treatment is sometimes performed due to speeding up wallpaper production, etc., but in this case, thermal stability especially at high temperatures becomes a problem. If water is not supplied
Heat treatment at 220°C for 3 minutes significantly reduced the white field, but in the case of the present invention, the reduction was small. (2) Excellent crystallinity. mp. is slightly high Crystallization rate is fast Conventional example Invention mp 110-120℃ 115-125℃ Crystallization rate 60 minutes or more 30 minutes or less (Meaning) Guanidine sulfamate is produced by cooling and solidifying the molten material after the reaction is completed. In many cases, a steel belt cooler is used as a method of cooling and solidifying the product, and in this case, a high crystallization rate is extremely important. That is, when the crystallization rate is slow, the length of the belt must be increased, and it is necessary to reduce the processing capacity. The embodiment of the present invention is capable of cooling and solidifying guanidine sulfamate at a rate of 450 kg/hr using a steel belt cooler with an effective width of 1.0 m and a horizontal portion length of 6 m. The method for producing guanidine sulfamate of the present invention will be explained below using Examples and Comparative Examples. Tests on guanidine sulfamate obtained in Examples and Comparative Examples were conducted in the following manner. (1) Guanidine content The guanidine concentration was measured by the picrate method. (2) Insoluble matter in water A 40% aqueous solution was prepared and separated at room temperature, and the dry weight of the water-insoluble matter was measured. (3) Thermal stability (whiteness) Paper (Toyo Paper No. 2) was immersed in a 10% aqueous solution, and 20±3% of the dry weight was adhered to it, then dried.
This was heat-treated in a hot air circulation dryer at 200°C for 3 minutes, and the whiteness was measured with a Kett phototube whiteness meter.
However, when only the paper was heat treated at 200°C for 3 minutes, the whiteness was 77%. (4) Crystallization rate Γ apparatus; three-neck separable flask with stirrer and thermometer. Heating oil bath, cooling water bath thermometer recorder. Γ method: 250g sample in a 300ml separable flask
Heat and melt in an oil bath. When the melt becomes transparent and the temperature becomes constant at 165°C to 170°C, stop stirring the melt and turn the oil bath into a cooling water bath (50°C). Record these temperature changes separately for sample temperature and bath temperature using a recorder. The cooled sample crystallizes and releases crystal/heating, so record the time. Measurement results using this measurement method The time from the start of cooling until the exothermic temperature due to crystallization reaches its maximum value was measured and compared as the crystallization rate. Example 1 First, 38 g of dicyandiamide and 95 g of mammonium sulfamate were heated in an oil bath while blowing ammonia gas into a parallel flask equipped with a stirrer, and the mixture was reacted at 130 to 150°C for 30 minutes, and this was used as the reaction medium for the starting stage. 319.4 g of sulfamic acid and 149.6 g of dicyandiamide were continuously added and reacted at a reaction temperature of 120 to 125° C. while keeping the pH of the reaction system at 7 or higher while blowing ammonia gas and steam. In addition, the amount of ammonia gas used is 180
/hr, the amount of steam blown was 52.8g/hr, and the time required for addition was 75 minutes. After the addition is complete, stop the water vapor supply and reduce the ammonia supply amount to 60%.
The temperature was gradually increased to 150 to 170°C for an additional 4 hours to produce guanidine sulfamate. The results are shown in the table. Example 2 Guanidine sulfamate obtained in Example 1
133 g was used as the medium for the starting stage of the reaction, and sulfamic acid was added to it while supplying ammonia gas at 138/hr.
319.4g, dicyandiamide 149.6g and water vapor 105
A continuous addition reaction was carried out while keeping the pH at 7 or higher while blowing g/hr. The reaction temperature was 120 DEG -125 DEG C. and the addition time was 1 hour 35'. After the addition was completed, the same reaction as in Example 1 was carried out to produce guanidine sulfamate. The results are shown in the table below. Comparative Example A reaction was carried out in the same manner as in Example 2 except that water vapor was not blown into it. The results are shown in the table.

【table】

【table】 [Brief explanation of the drawing]

The figures are cooling curves for Examples 1 (Curve A), 2 (Curve B) and Comparative Example (Curve C) according to the crystallization rate measurement method described in the text.

Claims (1)

[Claims] 1. Sulfamic acid and dicyandiamide are mixed in one or more reaction media selected from guanidine sulfamate, a reaction mixture of ammonium sulfamate and dicyandiamide, or ammonium sulfamate while continuously supplying ammonia and steam. to bring the temperature of the reaction mixture to
The reaction was carried out at 120-125°C while maintaining the pH at 7 or higher, and after the addition of sulfamic acid and dicyandiamide was completed, ammonia gas was passed through the reaction mixture at 140-125°C.
A method for producing guanidine sulfamate, characterized by carrying out the reaction at 170°C. 2. The manufacturing method according to claim 1, wherein the reaction is initially carried out at 140-150°C and then at 160-170°C.