Sulfonated polyborosiloxane flame retardant for transparent flame-retardant polycarbonate and preparation method thereof

Abstract

The invention relates to the field of transparent flame-retardant modification of polycarbonate, in particular to a sulfonated polyborosiloxane flame retardant for transparent flame-retardant polycarbonate and a preparation method of the sulfonated polyborosiloxane flame retardant. The preparation method comprises the following steps: adding octamethylcyclotetrasiloxane, tetraethyl silicate, boric acid and a sulfonate compound into an organic solvent, adjusting the pH value to 2-5, and reacting to obtain the sulfonated polyborosiloxane flame retardant. The sulfonated polyborosiloxane provided by the invention is simple in preparation process and safe in process, and does not involve the use of halogen compounds. The sulfonated polyborosiloxane prepared by the method has the characteristics of good thermal stability, high carbon residue, self-extinguishing property and the like, and has an excellent effect of expanding to form carbon.

Description

Technical Field

[0001] The invention relates to the field of transparent flame-retardant modification of polycarbonate, in particular to a sulfonated polyborosiloxane flame retardant for transparent flame-retardant polycarbonate and a preparation method thereof. Background Art

[0002] Polycarbonate (PC) has been widely used in the fields of construction, transportation, optical lighting, electrical and automotive, medical equipment, etc. due to its good thermal stability, chemical resistance, transparency and impact resistance. Although pure PC shows certain flame retardancy in the UL-94 vertical test, with LOI of 24%, reaching V-2 level, with the increasing attention to fire safety, problems such as severe burning dripping and large smoke release have greatly hindered its further application in the fields of aerospace and electronics. Therefore, the preparation of PC with excellent flame retardant properties is of great significance and has broad application prospects.

[0003] So far, a wide range of flame retardant additives have been developed, including halogen flame retardants, phosphorus flame retardants, sulfonate flame retardants, silicon flame retardants, boron flame retardants and carbon-based nanomaterials, etc., to give PC higher fire resistance. These different types of flame retardants have their own advantages and disadvantages. With the gradual improvement of people's environmental awareness and the introduction of various laws and regulations, the development of halogen flame retardants has been greatly restricted. Although some areas continue to use them due to their low price and high efficiency and stable flame retardant performance, their research value is inconsistent with the development trend of society, and the development of environmentally friendly halogen-free flame retardants is more in line with the development needs of future society. Phosphorus flame retardants have been deeply studied and widely used due to their advantages such as environmental friendliness and low smoke emission. At present, phosphorus flame retardants are mainly organic phosphorus, and the organic phosphorus flame retardants used more in PC are mainly phosphates, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and phosphazenes. Among them, phosphate flame retardants have the advantages of low toxicity, long-lasting flame retardant performance, and low economic cost, and are widely used in PC. At present, the phosphate flame retardants used for PC flame retardancy in industry mainly include triphenyl phosphate, resorcinol and diphenyl phosphate. However, phosphate flame retardants cannot effectively improve the dripping phenomenon of PC, so a certain amount of anti-drip agent (such as polytetrafluoroethylene, etc.) is required to achieve better flame retardant effect. However, anti-drip agents will greatly affect transparency. Silicon-based flame retardants are more environmentally friendly. Silicone flame retardants mainly include polysiloxane flame retardants, which can significantly reduce the heat release rate, but the synthesis process is complicated and difficult to mass produce. Silicate inorganic silicon materials with layered structures, such as mica, have a significant effect on smoke suppression and flame retardancy. Recently, a study designed and synthesized a phosphorus-containing polyhedral oligomer silsesquioxane (DPOP-POSS). It was found that when 6wt% of DPOP-POSS was added to PC, the LOI value would be as high as 30.1%, but the transmittance was reduced by 10. Sulfonate flame retardants have a high flame retardant effect due to their sulfur content, but their effect on reducing the heat release rate is not significant because they catalyze PC degradation and cause structural fragility. It is worth mentioning that the concentration of the flame retardant, that is, the amount added, is closely related to the flame retardant effect, and a high concentration does not necessarily lead to high flame retardant properties. Lai et al. prepared a synergistic flame retardant polyborosiloxane (PBSil) containing boron and silicon by the condensation reaction of boric acid and siloxane. On this basis, Zhu et al. introduced tetraethyl silicate (TEOS) as a branch into the polyborosiloxane chain to synthesize branched polyborosiloxane (PBS-X) for use as a flame retardant for PC. PC / PBS-X composites containing 2wt% PBS-X exhibit excellent flame retardancy without affecting mechanical properties. However, highly branched polyborosiloxane materials cause PC to lose its excellent transparency.Zhou et al. studied the effect of polyborosiloxane chain structure on the flame retardancy of PC and found that linear polyborosiloxane can avoid the problem of PC transparency decreasing with the addition of flame retardants, but the flame retardant can only reach the UL 94V-0 level when added at a dosage of about 3wt%, and the LOI value is about 30%.

[0004] In summary, for PC, developing flame retardants with excellent flame retardancy and low addition amount without affecting the transparency of polycarbonate is still a difficult challenge. In addition, sulfonated polyborosiloxane flame retardants have not been reported yet. Summary of the invention

[0005] Based on the above content, the present invention provides a sulfonated polyborosiloxane flame retardant for transparent flame retardant polycarbonate and a preparation method thereof.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] One of the technical solutions of the present invention is a sulfonated polyborosiloxane flame retardant, the structural formula of which is shown in Formula I;

[0008]

[0009] In formula I, n=3-10; R is methyl or hydroxyl, and R1 is C5-C16 alkyl.

[0010] The second technical solution of the present invention is a method for preparing the above-mentioned sulfonated polyborosiloxane flame retardant, comprising the following steps:

[0011] Octamethylcyclotetrasiloxane, tetraethyl silicate, boric acid and sulfonate compounds are added to an organic solvent, and the pH is adjusted to 2 for reaction to obtain the sulfonated polyborosiloxane flame retardant.

[0012] The present invention incorporates a small amount of boric acid into a polysiloxane chain. Boric acid with three functional groups tends to form a branched polysiloxane derivative, which is easier to cross-link into carbon than a straight-chain polysiloxane. Sulfonate compounds with surfactant properties are used to participate in the polymerization reaction of polyborosiloxane to induce phase separation or form an uneven network structure, so as to prepare a powdered polyborosiloxane with a high cross-linking density.

[0013] The main chain of the sulfonated polyborosiloxane flame retardant of the present invention is composed of silicon and oxygen elements, wherein a small amount of boric acid and tetraethyl orthosilicate allow the polysiloxane to form a branched structure, and the sulfonic acid compound is combined with the polyborosiloxane Si-OH or B-OH through covalent or non-covalent action, or forms a highly cross-linked network structure when the polyborosiloxane is formed through the catalytic properties of the sulfonic acid compound itself. The sulfonated polyborosiloxane flame retardant prepared by the present invention has the characteristics of good thermal stability and high residual carbon content, and can significantly improve the flame retardant properties of polycarbonate; the prepared modified polycarbonate composite material has high flame retardant efficiency, and the extremely low flame retardant addition amount of 0.2wt% can make the polycarbonate composite material pass the UL-94V0 flame retardant level, and the transparency is maintained at 70% to 78%.

[0014] The third technical solution of the present invention is a polycarbonate composite material, the raw materials of which include the above-mentioned sulfonated polyborosiloxane flame retardant; the content of the sulfonated polyborosiloxane flame retardant in the polycarbonate composite material is 0.1% to 0.3wt%.

[0015] A fourth technical solution of the present invention is a method for preparing the above-mentioned polycarbonate composite material, comprising the following steps:

[0016] The sulfonated polyborosiloxane flame retardant and polycarbonate are heated, melted and blended, and then hot-pressed to obtain the polycarbonate composite material.

[0017] The present invention provides a novel sulfonated polyborosiloxane and a transparent flame-retardant polycarbonate prepared using the same, which broadens the application of polycarbonate. The sulfonated polyborosiloxane prepared by the present invention has the characteristics of good thermal stability, high carbon residue, self-extinguishing property, etc., and has an excellent effect of expanding into carbon.

[0018] The present invention discloses the following technical effects:

[0019] The preparation process of the sulfonated polyborosiloxane provided by the present invention is simple and safe, and does not involve the use of halogen compounds.

[0020] The present invention introduces sulfonic acid compounds on the surface of branched polyborosiloxane through molecular structure design. The specific effect is: boric acid with three functional groups tends to form branched polysiloxane derivatives, which are easier to cross-link into carbon than straight-chain polysiloxane, and will present an expanded charred layer, which will expand violently during the combustion process. However, the excessive branching structure will affect the transparency of PC. The sulfonate structure will promote the decomposition of PC in advance, accelerate the Fries rearrangement and isomerization of PC, and will also promote cross-linking into carbon. In addition, sulfonic acid compounds can support flame retardancy in the gas phase. The synergistic flame retardancy of the two makes the addition amount of flame retardant extremely low. The polycarbonate composite material with a flame retardant addition of 0.2wt% reaches the UL94 V0 level and the transparency is 70%. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 This is the infrared spectrum of the sulfonated polyborosiloxane flame retardant prepared in Example 1.

[0023] Figure 2 This is the XPS analysis result of the sulfonated polyborosiloxane flame retardant prepared in Example 1.

[0024] Figure 3 This is the TGA spectrum of the sulfonated polyborosiloxane flame retardant prepared in Example 1.

[0025] Figure 4 These are the transparency results of pure polylactic acid material and polycarbonate composite material (the amount of sulfonated polyborosiloxane flame retardant added is 0.2wt% of PC mass).

[0026] Figure 5 These are the vertical combustion test results of pure polylactic acid material and polycarbonate composite material (the amount of sulfonated polyborosiloxane flame retardant added is 0.2wt% of the PC mass). DETAILED DESCRIPTION

[0027] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0028] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0029] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0030] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0031] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0032] The first aspect of the present invention provides a sulfonated polyborosiloxane flame retardant, the structural formula of which is shown in Formula I;

[0033]

[0034] In formula I, n=3-10; R is methyl or hydroxyl, and R1 is C5-C16 alkyl.

[0035] The second aspect of the present invention provides a method for preparing the above-mentioned sulfonated polyborosiloxane flame retardant, comprising the following steps:

[0036] Octamethylcyclotetrasiloxane, tetraethyl silicate, boric acid and sulfonate compounds are added to an organic solvent, and the pH is adjusted to 2 for reaction to obtain the sulfonated polyborosiloxane flame retardant.

[0037] In a preferred embodiment of the present invention, the molar ratio of tetraethyl silicate, boric acid, sulfonate compound and octamethylcyclotetrasiloxane is 5:6:1:50.

[0038] In a preferred embodiment of the present invention, the reaction is divided into two stages; wherein, the first reaction stage is carried out at 70°C for 2 hours, and the boric acid and sulfonate are completely dissolved by uniform stirring; the second reaction stage is carried out at 120°C for 4 hours to ensure sufficient reaction of the borohydroxyl group and the silanol group.

[0039] In a preferred embodiment of the present invention, the sulfonate compound is a sulfonic acid compound with an amino group or a sulfonate having surfactant properties.

[0040] In a preferred embodiment of the present invention, the surface active sulfonic acid compound may be sodium dodecyl sulfonate, sodium dodecylbenzene sulfonate or secondary alkyl sulfonate.

[0041] In a preferred embodiment of the present invention, the organic solvent is diethylene glycol dimethyl ether.

[0042] The present invention does not impose any particular limitation on the amount of organic solvent added, as long as the amount can allow the raw materials to react fully.

[0043] In a preferred embodiment of the present invention, after the reaction is completed, the steps of filtering, washing and vacuum drying are further included. The purpose of washing is to remove salt byproducts.

[0044] The third aspect of the present invention provides a polycarbonate composite material, the raw materials of which include the above-mentioned sulfonated polyborosiloxane flame retardant; the content of the sulfonated polyborosiloxane flame retardant in the polycarbonate composite material is 0.1% to 0.3wt%.

[0045] A fourth aspect of the present invention provides a method for preparing the above-mentioned polycarbonate composite material, comprising the following steps:

[0046] The sulfonated polyborosiloxane flame retardant and polycarbonate are heated, melted and blended, and then hot-pressed to obtain the polycarbonate composite material.

[0047] In a preferred embodiment of the present invention, the heating melt blending is carried out by a torque rheometer, the processing temperature is 260°C, the processing time is 10 to 20 minutes, and the rotation speed is 50r / min; the hot pressing molding is carried out using a flat plate vulcanizer, the hot pressing temperature is 240°C, and the pressure is 5MPa.

[0048] The technical solutions described in the present invention, unless otherwise specified, are all conventional solutions in the art, and the reagents or raw materials used, unless otherwise specified, are purchased from commercial channels or have been disclosed.

[0049] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0050] Example 1

[0051] At room temperature, in a dry three-mouth reactor, 1.04g TEOS, 0.361g boric acid, 0.361g sodium dodecylsulfonate, and 14.83g octamethylcyclotetrasiloxane were first dissolved in 40ml diethylene glycol dimethyl ether solvent, and 1ml hydrochloric acid was added. After stirring and reacting at 70°C for 2 hours, the reaction was then continued at 120°C for 4 hours. The obtained reaction product was filtered, rinsed, and then vacuum dried to obtain a sulfonic acid compound modified polyborosiloxane, i.e., a sulfonated polyborosiloxane flame retardant (abbreviated as: flame retardant).

[0052] The sulfonated polyborosiloxane flame retardant prepared in Example 1 has a relatively high silicon and oxygen content, and expands violently into char during combustion, achieving a condensed phase flame retardant effect.

[0053] The infrared spectrum of the sulfonated polyborosiloxane flame retardant prepared in Example 1 is as follows: Figure 1 As shown, 2925cm -1 The absorption peak is the absorption peak of CH, 1004cm -1 The absorption peak at 1349 cm corresponds to the characteristic absorption peak of Si-O-Side. -1 The absorption peak at 1660cm corresponds to the vibration peak of BOB. -1 The absorption peak at may be the newly generated C=O stretching vibration.

[0054] The sulfonated polyborosiloxane flame retardant prepared in Example 1 was analyzed by XPS. The results are as follows: Figure 2 As shown, Figure 2 This indicates that the flame retardant contains Si, B, and S related main elements.

[0055] The TGA spectrum of the sulfonated polyborosiloxane flame retardant prepared in Example 1 is as follows: Figure 3 As shown, the thermogravimetric analysis test results show that the initial (mass loss reaches 5%) thermal decomposition temperature of the prepared sulfonated polyborosiloxane flame retardant is 150°C, but the residual carbon content at 800°C is 79wt%.

[0056] Thermogravimetric analysis test results show that the sulfonated polyborosiloxane prepared in Example 1 has excellent thermal stability and carbon-forming ability.

[0057] The sulfonated polyborosiloxane flame retardant prepared in Example 1 was applied to PC to prepare a polycarbonate composite material (PC / FR), specifically as follows: PC and the sulfonated polyborosiloxane flame retardant were vacuum dried at 80°C for 6 hours, 0.3wt% of the sulfonated polyborosiloxane flame retardant was added to PC, and then heated and melt-blended using a torque rheometer (processing temperature was 260°C, processing time was 15min, and rotation speed was 50r / min); then, hot pressing molding was performed using a flat plate vulcanizer (hot pressing temperature was 240°C, pressure was 5MPa).

[0058] The transparency and flame retardancy of the composites were tested. Figure 4 As shown, the transparency is only slightly reduced. And compared with blank PC (i.e. without flame retardant), PC with flame retardant passed UL-94V-0 combustion grade (such as Figure 5 As shown, Figure 5 PC / 2 means PC / FR).

[0059] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A sulfonated polyborosiloxane flame retardant, characterized in that: The structural formula is shown in Formula Ⅰ; In formula I, n=3-10; R is methyl or hydroxyl, and R1 is C5-C16 alkyl.

2. A method for preparing the sulfonated polyborosiloxane flame retardant according to claim 1, characterized in that: The following steps are involved: Octamethylcyclotetrasiloxane, tetraethyl silicate, boric acid and sulfonate compounds are added to an organic solvent, and the pH is adjusted to 2-5 for reaction to obtain the sulfonated polyborosiloxane flame retardant.

3. The method for preparing the sulfonated polyborosiloxane flame retardant according to claim 2, characterized in that: The molar ratio of tetraethyl silicate, boric acid, sulfonate compound and octamethylcyclotetrasiloxane is 5:6:1:

50.

4. The method for preparing the sulfonated polyborosiloxane flame retardant according to claim 2, characterized in that: The reaction is divided into two stages; the first reaction stage is at 70° C. for 2 hours; the second reaction stage is at 120° C. for 4 hours.

5. The method for preparing the sulfonated polyborosiloxane flame retardant according to claim 2, characterized in that: The sulfonate compound is a sulfonate having surfactant properties.

6. The method for preparing the sulfonated polyborosiloxane flame retardant according to claim 2, characterized in that: The organic solvent is diethylene glycol dimethyl ether; after the reaction is completed, the steps of filtering, washing and vacuum drying are also included.

7. A polycarbonate composite material, characterized in that: The raw materials include the sulfonated polyborosiloxane flame retardant according to claim 1; the content of the sulfonated polyborosiloxane flame retardant in the polycarbonate composite material is 0.1% to 0.3wt%.

8. The method for preparing a polycarbonate composite material according to claim 7, characterized in that: The following steps are involved: The sulfonated polyborosiloxane flame retardant and polycarbonate are heated, melted and blended, and then hot-pressed to obtain the polycarbonate composite material.

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