CRYSTALLINE ALUMINUM PHOSPHITE, PREPARATION METHOD AND APPLICATION THEREOF

Abstract

The present invention discloses a crystalline aluminum phosphite, a preparation method thereof and an application thereof as or for the preparation of a flame retardant or a flame retardant synergist. The preparation method has the following processes: 1, reacting aluminum hydrogen phosphite with an aluminum-containing compound in water at 80-110° C. to obtain a precipitate in the presence of no strong acid or a small amount of strong acid; 2, washing and filtering the precipitate; 3, drying the precipitate at 100-130° C.; 4, continuously heating the dried solid step by step at a low speed, where the material temperature is increased to not exceeding 350° C. from room temperature at about 5-10 h, with a temperature rise rate not exceeding 5° C./min. Compared with amorphous aluminum hydrogen phosphite, the crystalline aluminum phosphite has a higher thermal decomposition temperature, lower water absorption and weaker acidity, and can be synergistic with diethyl aluminum hypophosphite to achieve better flame retardant property and thus, is used for a halogen-free flame retardant component of high polymer materials.

Claims

1. A preparation method of a crystalline aluminum phosphite, comprising the following steps: (1) preparing an aluminum-containing compound/water mixed solution containing a strong acid or free of a strong acid, then adding the mixed solution to an aluminum hydrogen phosphite solution at 80-110° C. for reaction, and controlling a pH value of a liquid phase to be less than 4 at the end of the reaction; wherein the aluminum-containing compound is at least one of aluminum sulfate, aluminum nitrate, aluminum chloride, aluminum hydroxide and aluminum oxide; (2) filtering the reacted mixture and washing a precipitate until washing effluent has a conductivity less than 50 μs/cm; (3) heating and drying the washed precipitate at 100-130° C., such that the precipitate has a water content below 0.3wt % below; (4) continuously heating the precipitate for dehydration reaction in an inert atmosphere or under vacuum conditions, with temperature rise not exceeding 350° C. within 5-10 h and temperature rise rate not exceeding 5° C./min, and finally cooling to obtain the crystalline aluminum phosphite.

2. The preparation method according to claim 1, wherein in the step (1), the strong acid comprises at least one of sulfuric acid, nitric acid, hydrochloric acid and phosphoric acid, and the strong acid is 2%-5% of the mass of the aluminum hydrogen phosphite; in a mixed solution obtained by dispersing the aluminum-containing compound into water, the aluminum-containing compound has a mass concentration of 15%-50%; in the aluminum hydrogen phosphite solution, the aluminum hydrogen phosphite has a mass concentration of 15%-50%; when the aluminum-containing compound is at least one of aluminum sulfate, aluminum nitrate and aluminum chloride, the aluminum-containing compound/water mixed solution containing a strong acid is prepared; when the aluminum-containing compound is at least one of aluminum hydroxide and aluminum oxide, the aluminum-containing compound/water mixed solution free of a strong acid is prepared; the aluminum-containing compound/water mixed solution is added dropwisely to the aluminum hydrogen phosphite solution, and total reaction time is 1-5 h; the pH value of the liquid phase is controlled to be less than 4 by addition of an alkali or a metal oxide at the end of the reaction.

3. A crystalline aluminum phosphite prepared by the preparation method according to claim 1.

4. The crystalline aluminum phosphite according to claim 3, wherein the crystalline aluminum phosphite has a particle size of 0.1-1000 μm, a water solubility of 0.01-10 g/L and a bulk density of 80-800 g/L.

5. A method for the preparation of a flame retardant or a flame retardant synergist comprising the step of utilizing the crystalline aluminum phosphite according to claim 3.

6. The method according to claim 5, wherein the flame retardant or the flame retardant synergist is used for the following uses, comprising: the inflaming retarding of a varnish or a foaming coat, the inflaming retarding of timber or a cellulose-containing product, and the preparation of a flame-retardant polymer molding material, a flame-retardant polymer film, and a flame-retardant polymer fiber.

7. The method according to claim 6, wherein the flame-retardant polymer molding material, the flame-retardant polymer film, and the flame-retardant polymer fiber comprise the following ingredients based on 100% by total weight: 55%-99.9% of polymer matrix; 0.1%-45% of crystalline aluminum phosphite; 0-44.9% of filler and/or reinforcing material; and 0-44.9% of additive.

8. The method according to claim 6, wherein the flame-retardant polymer molding material, the flame-retardant polymer film, and the flame-retardant polymer fiber comprise the following ingredients based on 100% by total weight: 55%-99.9% of polymer matrix; 0.1%-45% of flame-retardant system; 0-44.9% of filler and/or reinforcing material; and 0-44.9% of additive. the flame-retardant system comprises: 0.1%-50% of crystalline aluminum phosphite; and 50%-99.9% of flame retardant.

9. The method according to claim 8, wherein the flame retardant is a metal salt of diethyl hypophosphorous acid.

10. The method according to claim 7, wherein the polymer matrix is selected from at least one of nylon, polyester and POK.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0072] FIGS. 1 and 3 show an XRD pattern of a crystalline aluminum phosphite;

[0073] FIG. 2 shows an XRD pattern of an amorphous crystalline aluminumphosphite.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0074] The present invention will be further set forth in combination with the specific embodiments below. It should be understood that these embodiments are only used to illustrate the present invention, but not for the limitation of the scope of the present invention. The operating method not noted with specific conditions in the following examples is usually subjected to conventional conditions or the conditions recommended by a manufacturer.

Example 1 Preparation of a Crystalline Aluminum Phosphite

[0075] Preparation process was as follows: 270 g (1 mol) aluminum hydrogen phosphite ((H.sub.2PO.sub.3).sub.3Al) and 630 g water were added to a 2 L reaction still, and fully stirred to be dissolved to obtain an aluminum hydrogen phosphite solution. 75 g aluminum sulfate was dissolved into 175 g water in a 500 mL beaker, then 8.1 g concentrated phosphoric acid (H.sub.3PO.sub.4) having a concentration of 85.1 wt % were added to an aluminum sulfate solution to be stirred fully and mixed evenly, then transferred to a dropping funnel. The reaction still was heated up to 90° C., and the aluminum sulfate solution containing phosphoric acid was added dropwisely and added completely within 2 h, and an alkali was added to adjust the pH value to 2.2, then the solution was kept warm for continuous reaction for 1 h. The reacted mixture was filtered while it was hot and a precipitate was washed repeatedly until washing effluent had a conductivity less than 50 μs/cm. The materials were transferred to a drying oven, and heated up to 120° C. and dried for 60 min; solids had a water content of 0.1 wt %; the dried solids were heated up to 180° C. at a rate of 2° C./min, kept for 60 min, and then heated up to 240° C. at a rate of 1° C./min, and kept for 60 min, then heated up to 300° C. at a rate of 2° C./min, and kept for 60 min, and cooled to room temperature and discharged; the materials were crushed; the mean grain size D50 was 38 μm, and the yield was 98.2%; and the materials were subjected relevant tests and application.

[0076] Test items and methods:

[0077] a, the prepared compound was subjected to XRD analysis to determine whether the obtained compound is crystalline. If XRD pattern was close to FIG. 1, the obtained compound was considered to be crystalline; if XRD pattern was close to FIG. 2, the obtained compound was considered to be amorphous.

[0078] b, test on water absorption: 50 g materials were weighed and put in a constant temperature humidity chamber under conditions of 85% humidity at 85° C., kept for 7 d to test the weight increment of the material; and the percentage of the weight increment was, namely, the water absorption of the material.

[0079] c, test on the acidity of the prepared compound: 10 g powdered material was dispersed into 100 g water, and kept for 2 hr at a constant temperature of 25° C. to test a pH value of the solution.

[0080] d, TGA was tested, and the temperature of 2 wt % weight loss served as a thermal weight loss temperature.

[0081] FIG. 3 shows an XRD result of the prepared aluminum phosphite.

[0082] XRD result indicated that the prepared aluminum phosphite was a crystalline form. Thermal weight loss, water absorption and pH value were shown in Table 2.

Example 2 Preparation of a Crystalline Aluminum Phosphite

[0083] Preparation process was as follows: 270 g (1 mol) aluminum hydrogen phosphite ((H.sub.2PO.sub.3).sub.3Al) and 630 g water were added to a 2 L reaction still, and fully stirred to be dissolved to obtain an aluminum hydrogen phosphite solution. 78 g aluminum hydroxide was dispersed into 200 g water in a 500 mL beaker, then transferred to a dropping funnel. The reaction still was heated up to 90° C., and a suspension of aluminum hydroxide was added dropwisely and added completely within 2 h, and the pH value was adjusted to 2.6 by a solid aluminum hydroxide, then the solution was kept warm for continuous reaction for 1 h. The reacted mixture was filtered while it was hot and a precipitate was washed repeatedly until washing effluent had a conductivity less than 50 μs/cm. The materials were transferred to a drying oven, and heated up to 120° C. and dried for 60 min; solids had a water content of 0.1 wt %; the dried solids were heated up to 180° C. at a rate of 2° C./min, kept for 60 min, and then heated up to 240° C. at a rate of 1° C./min, and kept for 60 min, then heated up to 300° C. at a rate of 2° C./min, and kept for 60 min, and cooled to room temperature and discharged; the materials were crushed; the mean grain size D50 was 55 μm, and the yield was 99.3%; and the materials were subjected relevant tests and application. The thermal weight loss, water absorption and pH value were shown in Table 2.

Comparative Example 1

[0084] The preparation process of the Comparative Example 1 was the same as that in Example 1 except aluminum hydrogen phosphite was replaced with sodium phosphite to obtain the materials, XRD was tested, and the results indicated an amorphous structure. TGA, water absorption and pH value were tested and the results were shown in Table 2. The method is a preparation method of the existing crystalline aluminum phosphite.

Comparative Example 2

[0085] The preparation process of the Comparative Example 2 was the same as that in Example 1 except high temperature post-processing was not performed, materials were obtained, and XRD was tested, and the results indicated an amorphous structure. TGA, water absorption and pH value were tested and the results were shown in Table 2.

Comparative Example 3

[0086] The preparation process of the Comparative Example 3 was the same as that in Example 1 except high temperature post-processing was not performed, materials were obtained, and XRD was tested, and the results indicated an amorphous structure. TGA, water absorption and pH value were tested and the results were shown in Table 2.

TABLE-US-00002 TABLE 2 2 wt % weight Water Crystalline loss temp- absorption pH state erature (° C.) (%) value Example 1 Crystalline 442 0.12 3.0 Example 2 Crystalline 443 0.10 3.1 Comparative Amorphous 425 0.50 2.6 Example 1 Comparative Amorphous 280 0.80 2.3 Example 2 Comparative Amorphous 265 1.05 2.1 Example 3

[0087] It can be seen from the results of Table 2 that the aluminum phosphite prepared in the present invention is a crystalline aluminum phosphite, but an amorphous aluminum phosphite might be prepared only by the existing conventional process. Relative to amorphous aluminum hydrogen phosphite, the crystalline aluminum phosphite has a higher thermal decomposition temperature, lower water absorption and weaker acidity. These characteristics have obvious advantages for the amorphous aluminum hydrogen phosphite used as a flame retardant.

Application of a Flame Retardant

Example 3

[0088] 52 wt % nylon 66, 30 wt % glass fiber, 3.4 wt % crystalline aluminum phosphite in Example 1 and 14.6 wt % diethyl aluminum hypophosphite (LFR8003, Jiangsu LiSiDe New Material Co., Ltd.) were prepared into a fire-retardant glass fiber reinforced nylon 66 by conventional regulations, and a sample was prepared to test the flame retardant property, and the flame retardant property of the material was up to UL94 V0 (0.8 mm).

Comparative Example 4

[0089] 50 wt % nylon 66, 30 wt % glass fiber, 20 wt % diethyl aluminum hypophosphite (LFR8003, Jiangsu LiSiDe New Material Co., Ltd.) were prepared into a fire-retardant glass fiber reinforced nylon 66 by conventional regulations the same as those in Example 2, and a sample was prepared to test the flame retardant property, and the flame retardant property of the material was up to UL94 V2 (0.8 mm) (based on the flame-retardant grading standard of UL94, the flame retardant efficiency of grade V2 was inferior to that of grade V0).

Comparative Example 5

[0090] 52 wt % nylon 66, 30 wt % glass fiber, 3.4 wt % crystalline aluminum phosphite in Example 1 and 14.6 wt % diethyl aluminum hypophosphite (LFR8003, Jiangsu LiSiDe New Material Co., Ltd.) were prepared into a fire-retardant glass fiber reinforced nylon 66 by conventional regulations the same as those in Example 2, and a sample was prepared to test the flame retardant property, and the flame retardant property of the material was up to UL94 V1 (0.8 mm) (based on the flame-retardant grading standard of UL94, the flame retardant efficiency of grade V1 was inferior to that of grade V0).

Comparative Example 6

[0091] 52 wt % nylon 66, 30 wt % glass fiber, 3.4 wt % crystalline aluminum phosphite in Example 2 and 14.6 wt % diethyl aluminum hypophosphite (LFR8003, Jiangsu LiSiDe New Material Co., Ltd.) were prepared into a fire-retardant glass fiber reinforced nylon 66 by conventional regulations the same as those in Example 2, and a sample was prepared to test the flame retardant property, and the flame retardant property of the material was up to UL94 V2 (0.8 mm) (based on the flame-retardant grading standard of UL94, the flame retardant efficiency of grade V2 was inferior to that of grade VO and grade V1).

Comparative Example 7

[0092] 52 wt % nylon 66, 30 wt % glass fiber, 3.4 wt % crystalline aluminum phosphite in Example 3 and 14.6 wt % diethyl aluminum hypophosphite (LFR8003, Jiangsu LiSiDe New Material Co., Ltd.) were prepared into a fire-retardant glass fiber reinforced nylon 66 by conventional regulations the same as those in Example 2, and a sample was prepared to test the flame retardant property, and the flame retardant property of the material was up to UL94 V2 (0.8 mm) (based on the flame-retardant grading standard of UL94, the flame retardant efficiency of grade V2 was inferior to that of grade V0 and grade V1).

[0093] It can be seen from the application results that the crystalline aluminum phosphite of the present invention may be synergistic to diethyl aluminum hypophosphite to improve the flame retardant efficiency. Meanwhile, relative to the amorphous aluminum phosphite, the crystalline aluminum phosphite has better flame retardant efficiency when it is synergistic with diethyl aluminum hypophosphite, showing the advantages of the crystalline aluminum phosphite.

[0094] Moreover, it should be understood that a person skilled in the art may make various alterations or modifications to the present invention after reading the above description of the present invention, and these equivalent forms should fall within the scope of the claims of the present application.