Patent Description:
A thermal gravimetric analysis peak temperature is an important indicator of a flame retardant, which refers to a temperature when the gravity is fastest in thermal gravimetric analysis testing, and at this time, the flame retardant is decomposed in a fastest manner. This indicator involves many aspects of flame-retardant properties, processing and use of the flame retardant.

The flame retardant has a flame-retardant effect, and needs to be rapidly decomposed to release chemical components that inhibit combustion to extinguish flames. Therefore, as the flame retardant, it must have a suitable rapid decomposition temperature, that is, a decomposition peak temperature. If the peak temperature is close to an ignition and combustion temperature of a polymer material, both flame retarding and processing are taken into account. If the peak temperature is too high, the flame retardant will not work without rapid decomposition when the material is combusted, thereby losing the flame-retardant effect. From the perspective of the flame retarding, the lower the decomposition peak temperature is, the better the flame-retardant effect occurs in an early stage of material ignition, which is beneficial to the flame retarding. However, if the decomposition temperature of the flame retardant is too low, the flame retardant will be decomposed and loses the flame-retardant effect as it is subjected to a high temperature during the processing and molding of the material. Therefore, flame retardants all have a decomposition peak temperature that matches with the ignition temperature of the flame-retarded polymer material.

Usually, a flame-retardant compound has only a thermal gravimetric analysis peak temperature. According to actual conditions of a fire and a thermal decomposition mechanism of the flame retardant, it is hoped that the flame retardant may have multiple thermal gravimetric analysis peak temperatures. The flame retardant acts in multiple stages, thereby providing flame-retardant protection for a polymer at multiple temperature stages, effectively improving the flame-retardant property, reducing its dosage, and adapting to a wider range of processing temperature conditions. In addition, in some cases, there is still smoldering combustion without the flames after the flames are extinguished. At this time, the material is subjected to a high temperature, a secondary flame-retardant protection effect of the flame retardant at the high temperature is required, and the flame retardant is also required to be rapidly decomposed at a higher temperature in addition to a lower temperature.

At present, aluminum phosphite, because of its good flame-retardant synergy with aluminum diethylphosphinate and its lower water solubility and acidity, is widely used as a flame-retardant synergist in glass fiber reinforced engineering plastics, such as polyamide, polyester and other systems, and has better flame retardancy. However, the aluminum phosphite reported so far, with a thermal gravimetric analysis shown in <FIG>, only has a single-peak thermal gravimetric analysis temperature characteristic, so there are still problems of a slight shortage of the flame-retardant property in use, slightly long delayed combustion time during the secondary ignition in UL testing, and a large addition amount. This limits the application range of a flame retardant system. Aluminum hydrogen phosphite is similar in structure to the aluminum phosphite, is a water-soluble compound although it can produce the flame-retardant effect, and may not be used as the flame retardant due to a lower decomposition temperature.

To improve the flame-retardant property of the aluminum phosphite, the present disclosure provides an aluminum phosphite-based complex with dual-peak upon thermal gravimetric analysis, and will provide a synthesis method for preparing the complex and a use of the complex as the flame-retardant synergist in flame retarding of the polymer material.

<CIT> relates to flame retardant mixtures containing flame retardants and aluminum phasphites, processes for their production and their use.

<CIT> discloses thermoplastic moulding compounds containing A) <NUM> - <NUM> wt. % of a thermoplastic polyamide, B) <NUM> - <NUM> wt. % of red phosphorus, C) <NUM> - <NUM> wt. % of an aluminium salt of phosphoric acid, D) <NUM> - <NUM> wt. % of a fibre or particle-shaped filler or mixtures thereof, and E) <NUM> - <NUM> wt. % of additional additives, wherein the sum of A) to E) amounts to <NUM> wt.

In view of the above-mentioned technical problems and deficiencies in the art, the present disclosure provides an aluminum phosphite-based complex. The complex has the dual-peaks by thermal gravimetric analysis, which is beneficial to flame-retardant protection of a material after ignition and prevention of secondary combustion and smoldering combustion without open flames, may also serve as a flame-retardant synergist to cooperate with aluminum diethylphosphinate, has better flame-retardant property, is used for a halogen-free flame-retardant component of the polymer material, and is used as a flame-retardant system of glass fiber reinforced engineering plastics.

An aluminum phosphite-based complex with dual-peak upon thermal gravimetric analysis, a structural formula being as follows:.

()HPO<NUM>)<NUM>Al<NUM>) • ((H<NUM>PO<NUM>)<NUM>Al)x,.

The complex of the present disclosure has the dual-peaks as seen from a thermal gravimetric analysis (TGA). However, the aluminum phosphite ((HPO<NUM>)<NUM>Al<NUM>) currently used in the field of flame retardants has a typical TGA curve as shown in <FIG>. There is only a single-peak by thermal gravimetric analysis on the curve. Except for the existence of a low-temperature TGP peak similar to a first peak of the complex of the present disclosure, there is no high-temperature decomposition peak of the complex of the present disclosure. In the complex of the aluminum phosphite and aluminum hydrogen phosphite obtained by the present disclosure, dual peaks of its thermal gravimetric analysis are not a superposition of respective thermal decomposition peaks of the aluminum phosphite and the aluminum hydrogen phosphite. The aluminum hydrogen phosphite ((H<NUM>PO<NUM>)<NUM>Al), with a thermal gravimetric analysis curve as shown in <FIG>, has only a decomposition peak temperature of about <NUM>. Meanwhile, the aluminum phosphite and the aluminum hydrogen phosphite are simply mixed, and a measured thermal gravimetric analysis curve is as shown in <FIG>, which shows a superposition of respective thermal gravimetric analysis characteristics of the aluminum phosphite and the aluminum hydrogen phosphite. In the complex of the present disclosure, the low peak temperature of about <NUM> disappears. Apparently, a substance obtained by the present disclosure is a new complex of the aluminum phosphite and the aluminum hydrogen phosphite, which is not a simple mixture of the two, with a new structure.

Through experimental research by the inventor, to obtain the complex with the dual-peaks by thermal gravimetric analysis, the molar ratio of the aluminum phosphite to the aluminum hydrogen phosphite is <NUM>:(<NUM>-<NUM>). An excessively high proportion of the aluminum phosphite will obtain a single-peak upon thermal gravimetric analysis close to that of the aluminum phosphite. An excessively low proportion of the aluminum phosphite will obtain a single-peak upon thermal gravimetric analysis close to that of the aluminum hydrogen phosphite or present dual-peak upon thermal gravimetric analysis of the simple mixture of the aluminum phosphite and the aluminum hydrogen phosphite. But there are no high-temperature thermal gravimetric analysis peaks of <NUM>-<NUM> in the present disclosure. Therefore, the dual-peak thermal gravimetric analysis characteristics of the present disclosure may not be realized.

In addition to having a first peak temperature close to that of the aluminum phosphite, the complex with the dual-peaks by thermal gravimetric analysis in the present disclosure also has a higher second peak temperature, but does not have a lower characteristic peak temperature of the aluminum hydrogen phosphite. Unlike simple mixing of the aluminum phosphite and the aluminum hydrogen phosphite, the new complex has dual-peak decomposition temperatures, which is beneficial for use as a flame retardant. Moreover, the complex is obviously superior to the aluminum phosphite, the aluminum hydrogen phosphite and the simple mixture of the two in performances such as a water absorption rate and a pH value, which indicates that the substance obtained by the present disclosure is the new complex of the two, instead of the mixture of the aluminum phosphite and the aluminum hydrogen phosphite. Through testing and use, the aluminum phosphite-based complex with the dual-peak decomposition characteristics still has a synergistic flame-retardant effect with the aluminum diethylphosphinate, with the flame-retardant efficiency improved to a certain extent compared with the aluminum phosphite.

In the aluminum phosphite-based complex with the dual-peak upon thermal gravimetric analysis, pH is not lower than <NUM>, a particle size is <NUM>-<NUM>, the solubility in water is <NUM>-<NUM>/L, the bulk density is <NUM>-<NUM>/L, and the residual moisture is <NUM>-<NUM> wt%.

The present disclosure further provides a preferred preparation method of the aluminum phosphite-based complex with the dual-peak upon thermal gravimetric analysis, including: uniformly mixing the aluminum phosphite and the aluminum hydrogen phosphite according to the ratio in the structural formula, and then performing stepwise heating at a rate of <NUM>/min to raise the temperature of the mixture from the normal temperature to no more than <NUM> within <NUM>-<NUM> hours, so as to obtain the aluminum phosphite-based complex with the dual-peak thermal gravimetric analysis characteristics.

The complex of the present disclosure is obtained from the aluminum phosphite and the aluminum hydrogen phosphite in a certain proportion through a special high-temperature treatment process. The materials subjected to high-temperature treatment may be further pulverized to the required particle size.

From the result, it may be seen that the aluminum phosphite and the aluminum hydrogen phosphite may have a chemical interaction at a high temperature, thereby forming the new complex; and thermal decomposition shows respective characteristic decomposition of the two different substances subjected to compounding. In principle, there is no chemical reaction between the two compounds, but a new result appears in thermal gravimetric analysis, and some coordination bonds and hydrogen bonds may be formed between the two substances, thereby forming the new complex, and changing the thermal decomposition characteristics.

Preferably, three heat preservation platforms, being <NUM>, <NUM> and <NUM> respectively, are set during the stepwise heating, and heat preservation time is independently <NUM>-<NUM>.

The present disclosure further provides a use of the aluminum phosphite-based complex with the dual-peak upon thermal gravimetric analysis. The complex may be used as a flame retardant for a varnish and a foam coating, a flame retardant for wood and other cellulose-containing products and a nonreactive flame retardant for a polymer, is configured to prepare a flame-retardant polymeric molding material, a flame-retardant polymer molded body and/or endow polyester and cellulose pure and hybrid fabrics with flame retardancy by impregnation, and serves as a flame retardant mixture and a flame-retardant synergist.

The complex serves as or is configured to prepare the flame retardant or the flame-retardant synergist, and is configured to:.

Preferably, the flame-retardant polymeric molding material, the flame-retardant polymer film, and the flame-retardant polymer fiber, based on the total weight of <NUM>%, each comprises:.

The flame retardant may be dialkyl hypophosphorous acid and/or salt thereof; a condensation product of melamine and/or a reaction product of the melamine and phosphoric acid and/or a reaction product of the condensation product of the melamine and polyphosphoric acid or a mixture thereof; nitrogen-containing phosphate; benzoguanamine, tris (hydroxyethyl) isocyanurate, allantoin, glycoluril, melamine, melamine cyanurate, dicyandiamide and/or guanidine; and magnesium oxide, calcium oxide, aluminum oxide, zinc oxide, manganese oxide, tin oxide, aluminum hydroxide, boehmite, dihydrotalcite, hydrocalumite, magnesium hydroxide, calcium hydroxide, zinc hydroxide, tin oxide hydrate, manganese hydroxide, zinc borate, alkaline zinc silicate and/or zinc stannate.

The flame retardant may also be melam, melem, melon, dimelamine pyrophosphate, melamine polyphosphate, melam polyphosphate, melon polyphosphate and/or melem polyphosphate and/or mixed polysalt thereof and/or ammonium hydrogen phosphate, ammonium dihydrogen phosphate and/or ammonium polyphosphate.

The flame retardant further may be aluminum hypophosphite, zinc hypophosphite, calcium hypophosphite, sodium phosphite, monophenyl hypophosphorous acid and salt thereof, a mixture of dialkyl hypophosphorous acid and salt thereof and monoalkyl hypophosphorous acid and salt thereof, <NUM>-carboxyethyl alkyl hypophosphorous acid and salt thereof, <NUM>-carboxyethyl methyl hypophosphorous acid and salt thereof, <NUM>-carboxyethyl aryl hypophosphorous acid and salt thereof, <NUM>-carboxyethyl phenyl hypophosphorous acid and salt thereof, DOPO and salt thereof and an adduct on p-benzoquinone.

The flame retardant is preferably the aluminum diethylphosphinate.

The polymer matrix is selected from at least one of polyamide, polyester, and polyketone (POK).

When the flame-retardant system obtained by compounding the complex and the aluminum diethylphosphinate is used in the glass fiber reinforced engineering plastics, high-temperature melting by a twin-screw extruder, mixing and dispersion need to be performed.

Compared with the prior art, the present disclosure has the following main advantages: the aluminum phosphite-based complex with the dual-peak upon thermal gravimetric analysis is provided. The preparation method is simple. The complex has the dual-peak thermal decomposition temperature characteristics, and compared with amorphous aluminum phosphite, has one more high-temperature peak and a higher thermal decomposition temperature, which is beneficial to flame-retardant protection of the material after ignition and prevention of secondary combustion and smoldering combustion without open flames. Moreover, the complex may also serve as the flame-retardant synergist to cooperate with the aluminum diethylphosphinate, has the better flame-retardant property, is used for the halogen-free flame-retardant component of the polymer material, and is used as the flame-retardant system of the glass fiber reinforced engineering plastics.

The present disclosure is further described below with reference to the accompanying drawings and specific examples. It should be understood that these examples are merely used to illustrate the present disclosure and not to limit the scope of the present disclosure. In the following examples, operation methods without specific conditions are usually in accordance with conventional conditions or conditions suggested by the manufacturer.

A preparation method was as follows: <NUM> (<NUM> mol) of aluminum phosphite and <NUM> (<NUM> mol) of aluminum hydrogen phosphite were weighed respectively and mixed uniformly in a crucible. The crucible was put into an oven, the temperature was raised to <NUM> at a rate of <NUM>/min and held for <NUM>, the temperature was raised to <NUM> at a rate of <NUM>/min and held for <NUM>, the temperature was raised to <NUM> at a rate of <NUM>/min and held for <NUM>, the temperature was reduced to the room temperature, the materials were discharged and pulverized according to an average particle size D50 being <NUM>, and relevant testing and use were performed.

<FIG> illustrated a TGA result of the dual-peak upon thermal gravimetric analysis complex prepared in this example. The thermal gravimetric analysis, the water absorption rate and the pH value were as shown in a table <NUM>.

It was the same as the example <NUM>. Except that aluminum hydrogen phosphite was not used, other preparation processes were the same. Materials were obtained, and TGA was tested. A result was as shown in <FIG> and showed a single peak. A water absorption rate and a pH value were tested, and a result was as shown in a table <NUM>.

It was the same as the example <NUM>. Except that a molar ratio of aluminum hydrogen phosphite to aluminum phosphite was <NUM>:<NUM>, other preparation processes were the same. Materials were obtained, and TGA was tested. A result showed dual peaks. A water absorption rate and a pH value were tested, and a result was as shown in a table <NUM>.

Aluminum phosphite and aluminum hydrogen phosphite were mixed according to a ratio in the example <NUM>, high-temperature post-treatment was not performed, and TGA was directly tested. A result was as shown in <FIG> and showed dual peaks. A water absorption rate and a pH value were tested, and a result was as shown in a table <NUM>.

From the result in the Table <NUM>, it may be seen that the prepared complex of the present disclosure has dual-peak upon thermal gravimetric analysis, differing from single-peak upon thermal gravimetric analysis of aluminum phosphite and aluminum hydrogen phosphite; and for a higher proportion of the aluminum hydrogen phosphite in mixing of the aluminum phosphite and the aluminum hydrogen phosphite as well as simple mixing of the aluminum phosphite and the aluminum hydrogen phosphite, the dual-peak upon thermal gravimetric analysis characteristics are also showed, but a superposition of thermal decomposition characteristic peaks of two kinds of mixtures is showed, and there are no high-temperature upon thermal gravimetric analysis peaks (namely, decomposition peaks of <NUM>-<NUM>). Compared with the samples in the comparative examples, the complex has different thermal gravimetric analysis characteristics as well as a higher thermal gravimetric analysis temperature, a lower water absorption rate and weaker acidity, indicating that the complex is one with a new structure; and meanwhile, these characteristics are obviously advantageous for use as a flame retardant.

<NUM> wt% of polyamide <NUM>, <NUM> wt% of glass fiber, <NUM> wt% of a dual-peak upon thermal gravimetric analysis complex prepared according to the example <NUM> and <NUM> wt% of aluminum diethylphosphinate (LFR8003, Jiangsu Liside New Materials Co. ) were used to prepare flame-retardant glass fiber reinforced polyamide <NUM> according to general processes, and the flame-retardant properties were tested by sample preparation. A test result was as shown in a table <NUM>.

<NUM> wt% of polyamide <NUM>, <NUM> wt% of glass fiber and <NUM> wt% of aluminum diethylphosphinate (LFR8003, Jiangsu Liside New Materials Co. ) were used to prepare flame-retardant glass fiber reinforced polyamide <NUM> according to general processes, and the flame-retardant properties were tested by sample preparation. A test result was as shown in a table <NUM>.

<NUM> wt% of polyamide <NUM>, <NUM> wt% of glass fiber, <NUM> wt% of a single-peak upon thermal gravimetric analysis sample prepared according to the comparative example <NUM> and <NUM> wt% of aluminum diethylphosphinate (LFR8003, Jiangsu Liside New Materials Co. ) were used to prepare flame-retardant glass fiber reinforced polyamide <NUM> according to general processes, and the flame-retardant properties were tested by sample preparation. A test result was as shown in a table <NUM>.

<NUM> wt% of polyamide <NUM>, <NUM> wt% of glass fiber, <NUM> wt% of a sample prepared according to the comparative example <NUM> and <NUM> wt% of aluminum diethylphosphinate (LFR8003, Jiangsu Liside New Materials Co. ) were used to prepare flame-retardant glass fiber reinforced polyamide <NUM> according to general processes, and the flame-retardant properties were tested by sample preparation. A test result was as shown in a table <NUM>.

Claim 1:
An aluminum phosphite-based complex exhibiting a dual-peak upon thermal gravimetric analysis, a structural formula being as follows:

        ((HPO<NUM>)<NUM>Al<NUM>) • ((H<NUM>PO<NUM>)<NUM>Al )x,

wherein x is <NUM>-<NUM> and represents a molar ratio of (H<NUM>PO<NUM>)<NUM>Al to (HPO<NUM>)<NUM>Al<NUM>.
wherein the dual-peaks are as follows: a first peak temperature is <NUM>-<NUM>, and a second peak temperature is <NUM>-<NUM>.