POSS-based polyphosphazene and PET / POSS-based polyphosphazene composite materials and their preparation methods

Abstract

The present invention relates to the technical field of PET flame retardant materials, and more particularly to a kind of POSS-based polyphosphazene and PET / POSS-based polyphosphazene composite materials and their preparation methods. The present invention uses hexachlorocyclotriphosphazene as a cross-linking agent, utilizes similar compatibility principle to introduce 3,4-dihydroxybenzoic acid to improve the compatibility of flame retardant and PET matrix, simultaneously introduces amino POSS to build phosphorus nitrogen silicon collaborative flame retardant system, and finally synthesizes a kind of POSS-based polyphosphazene flame retardant. The addition of this flame retardant plays the role of condensed phase and gas phase flame retardancy, better improves the flame retardant properties of PET material.

Description

Technical Field

[0001] The invention relates to the technical field of PET flame retardant materials, in particular to a POSS-based polyphosphazene and a PET / POSS-based polyphosphazene composite material and preparation methods thereof. Background Art

[0002] Polyethylene terephthalate (PET) is a thermoplastic with excellent overall performance and low price. It is widely used in many fields, including synthetic fibers, engineering plastics, and packaging materials. However, PET is easily flammable and is accompanied by severe melt dripping during combustion, which can easily ignite surrounding flammable materials, posing many potential risks to people's lives and property. Therefore, PET materials need to be flame-retardant modified. POSS has the characteristics of an organic-inorganic hybrid structure and is environmentally friendly, and has great development prospects in flame-retardant material applications. However, its mostly crystalline structure has poor compatibility with the polymer matrix, and it also has disadvantages such as difficult synthesis processes and high costs. Therefore, it needs to be used in combination with traditional flame retardants to achieve the goal of reducing costs while maintaining good flame retardancy and mechanical properties. Hexachlorocyclotriphosphazene (HCCP) is often used to prepare engineering materials with high flame retardancy. Its molecular structure contains Cl, P, and N elements, which can form a PN synergistic flame retardant system. However, using it directly as a flame retardant can generate large amounts of hydrogen chloride gas, which can easily cause secondary pollution. Furthermore, hexachlorocyclotriphosphazene readily hydrolyzes, and the acid produced by hydrolysis significantly degrades the mechanical properties of the polymer matrix. Therefore, appropriate modification of HCCP is crucial for practical production applications. Summary of the Invention

[0003] The technical problems to be solved in the present invention are: POSS is a crystalline structure and has poor compatibility with a polymer matrix, and it is costly to use only POSS as a flame retardant; hexachlorocyclotriphosphazene is directly added to a PET matrix as a flame retardant, has poor compatibility with the polymer matrix, releases a large amount of toxic gases when burned, and is easily hydrolyzed, and the acid generated by the hydrolysis significantly reduces the mechanical properties of the polymer matrix. To this end, the present invention provides a POSS-based polyphosphazene and a PET / POSS-based polyphosphazene composite material and a preparation method thereof.

[0004] The technical solution adopted by the present invention to solve the technical problem is: a POSS-based polyphosphazene is used to compound with PET and reduce the flammability of PET, and the structural formula is:

[0005]

[0006] The formula contains a group derived from 3,4-dihydroxybenzoic acid and a group derived from aminoPOSS, wherein R1 and R2 at different positions are groups derived from 3,4-dihydroxybenzoic acid or groups derived from aminoPOSS; the structural formula of aminoPOSS is:

[0007] The present invention also provides a method for preparing the above-mentioned POSS-based polyphosphazene, comprising the steps of:

[0008] (1) Preparation of amino POSS: amino POSS was prepared by hydrolysis and condensation reaction of 3-aminopropyltriethoxysilane;

[0009] (2) Preparation of POSS-based polyphosphazene: POSS-based polyphosphazene was prepared by nucleophilic substitution using 3,4-dihydroxybenzoic acid and amino POSS as monomers, hexachlorocyclotriphosphazene as a cross-linking agent, triethylamine as an acid-binding agent, and tetrahydrofuran as a solvent.

[0010] Furthermore, step (1) is specifically performed according to the following steps:

[0011] A set amount of 3-aminopropyltriethoxysilane is added dropwise to a mixed solution of deionized water, acetonitrile, propanol and tetraethylammonium hydroxide, and the mixture is reacted for a period of time. After the reaction is completed, the mixed solution is precipitated in an ice bath, and the obtained product is centrifuged and washed to obtain amino POSS.

[0012] Furthermore, step (2) is specifically performed according to the following steps:

[0013] A set amount of 3,4-dihydroxybenzoic acid is weighed into a reaction container and dissolved in tetrahydrofuran. An appropriate amount of triethylamine is added dropwise, and ultrasonication is performed to uniformly mix the mixture. Then, a tetrahydrofuran solution of hexachlorocyclotriphosphazene and a tetrahydrofuran solution of aminoPOSS are added dropwise. After the addition is completed, the mixed system is allowed to continue to react. The obtained product is centrifuged, washed, and vacuum dried to obtain POSS-based polyphosphazene.

[0014] The present invention is based on the flame retardant modification of PET by the above-mentioned POSS-based polyphosphazene, and specifically provides a PET / POSS-based polyphosphazene composite material, which comprises the following components in percentage by weight:

[0015] The POSS-based polyphosphazene 0.25-3%,

[0016] PET remainder.

[0017] The present invention also provides a method for preparing the PET / POSS-based polyphosphazene composite material, comprising the following steps: drying PET pellets in an oven, then adding a set proportion of POSS-based polyphosphazene to the PET according to a formula, and blending the mixture using an internal mixer to prepare the PET / POSS-based polyphosphazene composite material.

[0018] Furthermore, the temperature of the internal mixer is set to 260-270° C., and the speed is set to 40-60 r / min.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The present invention provides a POSS-based polyphosphazene with a novel structure, and uses the POSS-based polyphosphazene for flame-retardant modification of PET. When POSS or hexachlorocyclotriphosphazene is directly used as a flame retardant for a PET polymer, both have poor compatibility with a PET matrix and are very likely to agglomerate, thereby affecting the flame retardant performance of the PET polymer. The hexachlorocyclotriphosphazene is also easily hydrolyzed, resulting in a significant decrease in the mechanical properties of the PET polymer. The present invention utilizes the principle of like dissolves like to improve the compatibility of the flame retardant with the polymer matrix by introducing 3,4-dihydroxybenzoic acid. At the same time, amino POSS is introduced into the phosphazene to construct a phosphorus-nitrogen-silicon synergistic flame retardant system. The flame retardant generates a dense silicon dioxide ceramic phase during combustion, promotes dehydration and carbonization of PET, and achieves a good insulation effect. In addition, the flame retardant generates nitrogen-containing non-combustible gas, further enhancing the flame retardant effect and better improving the flame retardant performance of the PET material without significantly reducing the mechanical properties of the PET polymer. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 : Infrared spectrogram of POSS-based polyphosphazene prepared by the present invention. DETAILED DESCRIPTION

[0022] The present invention is further described in detail below in conjunction with the embodiments:

[0023] Example 1

[0024] (1) Preparation of amino POSS

[0025] 18 mL of deionized water, 2 mL of acetonitrile, 8 mL of propanol, and 1 mL of tetraethylammonium hydroxide were added to a three-necked flask with mechanical stirring. After the temperature was raised to 50°C, 44.2 mL of KH-550 was added dropwise to the mixed solution and allowed to react for 24 hours. After the reaction was complete, approximately 3 volumes of tetrahydrofuran were added and the mixture was precipitated in an ice bath. Filtration afforded a white product, which was then dried under vacuum at 80°C to yield octaaminopropylsilsesquioxane.

[0026] (2) Preparation of POSS-based polyphosphazene

[0027] In a 250 mL three-necked flask, add 50 mL of tetrahydrofuran, weigh 0.08 g (0.5 mmol) of 3,4-dihydroxybenzoic acid (PCA) and dissolve it in the THF solution. Then, dropwise add 3.34 mL of triethylamine (TEA) and mix thoroughly. Place the mixture in an ultrasonic reactor and sonicate for 10 minutes. After sonication, transfer the mixture to an oil pan. Dissolve 0.35 g (1 mmol) of hexachlorocyclotriphosphazene (HCCP) and 0.5 g of QapPOSS in 50 mL of THF, then slowly add the mixture dropwise to the solution. After the additions, the mixture is allowed to react for 3 hours at 50°C. The centrifuged product is washed with THF and then dried under vacuum at 80°C for 24 hours to constant weight, yielding a white powder.

[0028] Figure 1 This is the infrared spectrum of POSS-based polyphosphazene. As can be seen from the figure, at 1734cm -1 and 1675cm -1 A large characteristic peak appears at 1166 cm, which is the C=O stretching vibration peak of 3,4-dihydroxybenzoic acid and the C=O stretching vibration peak of amide. -1 is the PN vibration absorption peak of hexachlorocyclotriphosphazene, 1110 cm -1 is the Si-O-Si stretching vibration peak, 1055 cm -1 The appearance of the POC group vibration absorption peak at 1123 cm -1 Compared with the Si-O-Si stretching vibration peak at 1110 cm -1 )The stretching vibration peak has a blue shift, which just proves that the reaction has occurred and the product has been successfully prepared.

[0029] (2) Preparation of PET / POSS-based polyphosphazene composites

[0030] The PET pellets were dried in an oven at 120°C for more than 12 hours, and then a certain proportion of POSS-based polyphosphazene was added to the PET and blended using an internal mixer at a temperature of 260-270°C and a speed of 40-60 r / min.

[0031] A PET / POSS-based polyphosphazene composite material with a POSS-based polyphosphazene content of 0.25 wt% was prepared.

[0032] Example 2

[0033] (1) The preparation of amino POSS is the same as in Example 1.

[0034] (2) The preparation of POSS-based polyphosphazene was the same as in Example 1.

[0035] (3) Preparation of PET / POSS-based polyphosphazene composites

[0036] The PET pellets were placed in a 120° C. oven and dried for more than 12 h. A certain proportion of POSS-based polyphosphazene was then added to the PET, and the mixture was blended using an internal mixer at a temperature of 260-270° C. and a rotation speed of 40-60 r / min to prepare a PET / POSS-based polyphosphazene composite material having a POSS-based polyphosphazene content of 0.5 wt%.

[0037] Example 3

[0038] (1) The preparation of amino POSS is the same as in Example 1.

[0039] (2) The preparation of POSS-based polyphosphazene was the same as in Example 1.

[0040] (3) Preparation of PET / POSS-based polyphosphazene composites

[0041] The PET pellets were dried in an oven at 120° C. for more than 12 h, and then a certain proportion of POSS-based polyphosphazene was added to the PET. The mixture was blended using an internal mixer at a temperature of 260-270° C. and a rotation speed of 40-60 r / min to prepare a PET / POSS-based polyphosphazene composite material having a POSS-based polyphosphazene content of 1 wt%.

[0042] Example 4

[0043] (1) The preparation of amino POSS is the same as in Example 1.

[0044] (2) The preparation of POSS-based polyphosphazene was the same as in Example 1.

[0045] (3) Preparation of PET / POSS-based polyphosphazene composites

[0046] The PET pellets were dried in an oven at 120° C. for more than 12 h, and then POSS-based polyphosphazene was added to the PET, and the mixture was blended using an internal mixer at a temperature of 260-270° C. and a rotation speed of 40-60 r / min to prepare a PET / POSS-based polyphosphazene composite material having a POSS-based polyphosphazene content of 1.5 wt%.

[0047] Example 5

[0048] (1) The preparation of amino POSS is the same as in Example 1.

[0049] (2) The preparation of POSS-based polyphosphazene was the same as in Example 1.

[0050] (3) Preparation of PET / POSS-based polyphosphazene composites

[0051] The PET pellets were dried in an oven at 120° C. for more than 12 h, and then POSS-based polyphosphazene was added to the PET and blended using an internal mixer at a temperature of 260-270° C. and a rotation speed of 40-60 r / min to prepare a PET / POSS-based polyphosphazene composite material having a POSS-based polyphosphazene content of 2 wt%.

[0052] Example 6

[0053] (1) The preparation of amino POSS is the same as in Example 1.

[0054] (2) The preparation of POSS-based polyphosphazene was the same as in Example 1.

[0055] (3) Preparation of PET / POSS-based polyphosphazene composites

[0056] The PET pellets were dried in an oven at 120° C. for more than 12 h, and then POSS-based polyphosphazene was added to the PET, and the mixture was blended using an internal mixer at a temperature of 260-270° C. and a rotation speed of 40-60 r / min to prepare a PET / POSS-based polyphosphazene composite material having a POSS-based polyphosphazene content of 3 wt%.

[0057] Comparative Example 1

[0058] (1) Preparation of PET materials

[0059] The PET pellets were placed in an oven at 120°C and dried for more than 12 hours, and then passed through an internal mixer to obtain pure PET material.

[0060] Comparative Example 1 is the same as Example 1, except that no POSS-based polyphosphazene is added in Comparative Example 1.

[0061] Comparative Example 2

[0062] (1) Preparation of PET / hexachlorocyclotriphosphazene composite materials

[0063] The PET pellets were dried in a 120°C oven for at least 12 hours and then passed through an internal mixer to produce a pure PET material. A certain proportion of hexachlorocyclotriphosphazene was then added to the PET and blended using an internal mixer set at 270°C and 40 rpm to produce a PET / hexachlorocyclotriphosphazene composite material containing 1 wt% hexachlorocyclotriphosphazene.

[0064] Comparative Example 2 is the same as Example 3, except that hexachlorocyclotriphosphazene is directly used in Comparative Example 2 to replace the homemade POSS-based polyphosphazene of the present invention.

[0065] Comparative Example 3

[0066] (1) Preparation of PET / amino POSS composites

[0067] The PET pellets were dried in an oven at 120°C for more than 12 hours and then passed through an internal mixer to prepare a pure PET material. Amino POSS was then added to the PET and blended using an internal mixer at 270°C and 40 rpm to prepare a PET / amino POSS composite material with an amino POSS content of 1 wt%.

[0068] Comparative Example 3 is the same as Example 3, except that amino POSS is used in place of the homemade POSS-based polyphosphazene of the present invention.

[0069] Comparative Example 4

[0070] (1) Preparation of PET / hexachlorocyclotriphosphazene / amino POSS composites

[0071] PET pellets were dried in an oven at 120°C for more than 12 hours and then passed through an internal mixer to prepare a pure PET material. A certain proportion of hexachlorocyclotriphosphazene and aminoPOSS were then added to the PET and blended using an internal mixer at a temperature of 260-270°C and a speed of 40-60 rpm to prepare a PET / hexachlorocyclotriphosphazene / aminoPOSS composite material having a hexachlorocyclotriphosphazene content of 0.5 wt% and an aminoPOSS content of 0.5 wt%.

[0072] Comparative Example 4 is the same as Example 3, except that, Comparative Example 4 directly uses hexachlorocyclotriphosphazene and amino POSS to replace the homemade POSS-based polyphosphazene of the present invention.

[0073] Performance testing:

[0074] The flame retardant properties and mechanical properties of the PET composite materials obtained in Examples 1-6 and Comparative Examples 1-4 were tested according to relevant testing standards.

[0075] Flame retardancy: Limiting oxygen index: tested according to ASTM D 2863-97 standard using TM606 digital oxygen index tester; Vertical burning: tested according to UL 94-2013 standard using vertical burning tester.

[0076] Tensile strength: According to GB / T 1040 standard, the test was carried out using an electronic universal material testing machine.

[0077] The test results of each embodiment and comparative example are shown in the table below:

[0078] Table 1 Limiting oxygen index and vertical combustion data of samples

[0079]

[0080] As shown in Table 1, the limiting oxygen index value of pure PET is 22.5%; when the POSS-based polyphosphazene content is 0.25wt%, the limiting oxygen index of the composite material is 25.8%; when the POSS-based polyphosphazene content is 3wt%, the limiting oxygen index of the composite material is 29.7%, which is greatly improved compared to the limiting oxygen index of 22.5% of pure PET. The flaming combustion time t1 of each sample is only 0.8s, and t2 is only 0.78s. The total flaming combustion time t1+t2 of each group of samples is only 1.58s. After the second flame application, the flaming and flameless combustion time t2+t3 of each sample is only 0.88s.

[0081] When the homemade POSS-based polyphosphazene of the present invention is added to the PET matrix, the t1 and t2 of the composite materials obtained in Examples 1-6 are both less than 10s, the values ​​of t1+t2 are also less than 50s, and t2+t3 are also less than 30s. These conditions all meet the requirements of V-0 flame retardancy. However, since the drippings generated by the composite materials obtained in Examples 1-3 ignite the absorbent cotton, the flame retardancy level only reaches the V-2 level. The composite materials obtained in Examples 4, 5 and 6 are not completely burned and the drippings generated do not ignite the absorbent cotton, indicating that their flame retardancy level reaches the V-0 level.

[0082] Table 2 Tensile strength data of PET composite materials

[0083]

[0084] As can be seen from Table 2, with the increase of the POSS-based polyphosphazene content, the tensile strength of the PET composite material shows a downward trend, but the tensile strength of the embodiment is higher than that of the comparative example 2, and the tensile strength of the embodiment 3 is higher than that of the comparative examples 1-4.

[0085] With the above-described preferred embodiments of the present invention as a guide, and with reference to the above description, relevant personnel are fully capable of making various changes and modifications without departing from the technical scope of this invention. The technical scope of this invention is not limited to the contents of the specification and must be determined according to the scope of the claims.

Claims

1. A POSS-based polyphosphazene for compounding with PET and reducing the combustibility of PET, characterized in that: The POSS-based polyphosphazene structural formula is: ； The formula contains a group derived from 3,4-dihydroxybenzoic acid and a group derived from aminoPOSS, wherein R1 and R2 at different positions are groups derived from 3,4-dihydroxybenzoic acid or groups derived from aminoPOSS; the structural formula of aminoPOSS is: ； The preparation method of the POSS-based polyphosphazene comprises the following steps: (1) Preparation of amino POSS: amino POSS was prepared by the hydrolysis condensation reaction of 3-aminopropyltriethoxysilane; (2) Preparation of POSS-based polyphosphazene: POSS-based polyphosphazene was prepared by nucleophilic substitution using 3,4-dihydroxybenzoic acid and amino POSS as monomers, hexachlorocyclotriphosphazene as a cross-linking agent, triethylamine as an acid-binding agent, and tetrahydrofuran as a solvent.

2. A preparation method for a POSS-based polyphosphazene according to claim 1, characterized in that: The steps include: (1) Preparation of amino POSS: amino POSS was prepared by the hydrolysis condensation reaction of 3-aminopropyltriethoxysilane; (2) Preparation of POSS-based polyphosphazene: POSS-based polyphosphazene was prepared by nucleophilic substitution using 3,4-dihydroxybenzoic acid and amino POSS as monomers, hexachlorocyclotriphosphazene as a cross-linking agent, triethylamine as an acid-binding agent, and tetrahydrofuran as a solvent.

3. the preparation method of POSS base polyphosphazene according to claim 2, is characterized in that: Step (1) is specifically carried out as follows: A set amount of 3-aminopropyltriethoxysilane is added dropwise to a mixed solution of deionized water, acetonitrile, propanol and tetraethylammonium hydroxide, and the mixture is reacted for a period of time. After the reaction is completed, the mixed solution is precipitated in an ice bath, and the obtained product is centrifuged and washed to obtain amino POSS.

4. the preparation method of POSS base polyphosphazene according to claim 2, is characterized in that: Step (2) is specifically carried out as follows: A set amount of 3,4-dihydroxybenzoic acid is weighed into a reaction container and dissolved in tetrahydrofuran. An appropriate amount of triethylamine is added dropwise, and ultrasonication is performed to uniformly mix the mixture. Then, a tetrahydrofuran solution of hexachlorocyclotriphosphazene and a tetrahydrofuran solution of aminoPOSS are added dropwise. After the addition is completed, the mixed system is allowed to continue to react. The obtained product is centrifuged, washed, and vacuum dried to obtain POSS-based polyphosphazene.

5. A PET / POSS-based polyphosphazene composite material, characterized in that: In terms of percentage by weight, Includes the following ingredients: 0.25-3% of the POSS-based polyphosphazene according to any one of claims 1 to 4, PET remainder.

6. A method for preparing a PET / POSS-based polyphosphazene composite material according to claim 5, characterized in that: The method comprises the following steps: placing PET pellets in an oven to dry, then adding POSS-based polyphosphazene in a set proportion into the PET according to a formula, and blending the mixture in an internal mixer to prepare a PET / POSS-based polyphosphazene composite material.

7. The preparation method of PET / POSS based polyphosphazene composite material according to claim 6, wherein: The mixer temperature was set at 260-270°C and the speed was set at 40-60 r / min.

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