Heat-conducting flame-retardant PC composite material suitable for fireproof shell and preparation method and application thereof

Abstract

The invention discloses a heat-conducting flame-retardant PC (polycarbonate) composite material suitable for a fireproof shell as well as a preparation method and application of the heat-conducting flame-retardant PC composite material. The heat-conducting and flame-retardant PC composite material is prepared from the following raw materials in parts by mass: 65 to 70 parts of polycarbonate, 25 to 30 parts of a heat-conducting agent, 1 to 3 parts of a toughening agent, 1 to 3 parts of a whitening agent, 0.9 to 1 part of a sulfonate flame retardant, 0.36 to 0.4 part of an organic siloxane flame retardant, 0.27 to 0.3 part of an anti-dripping agent, 0.2 to 0.5 part of an antioxidant and 0.1 to 0.5 part of a lubricating agent, the total mass of the polycarbonate and the heat conducting agent is 100 parts; the heat conduction agent comprises aluminum oxide and boron nitride in a mass ratio of (4-6): 1; the anti-dripping agent is polytetrafluoroethylene; the mass ratio of the sulfonate flame retardant to the heat conducting agent is not less than 1: 30; the mass ratio of the organic siloxane flame retardant to the sulfonate flame retardant is 0.4: 1; the mass ratio of the anti-dripping agent to the sulfonate flame retardant is 0.3: 1.

Description

Technical Field

[0001] The present invention relates to the field of polymer materials, and in particular to a thermally conductive flame-retardant polycarbonate (PC) composite material suitable for fireproof housings, and a preparation method and application thereof. Background Art

[0002] Today's home appliances are becoming increasingly powerful and equipped with more functions. Consequently, the power consumption and heat generation of their PCB circuitry are rapidly increasing. If this heat isn't dissipated promptly, it can affect the operating accuracy and service life of functional components. It can also overheat and cause the plastic casing (supporting the PCB) to ignite, potentially leading to a fire.

[0003] PC is an engineering plastic with excellent overall performance, widely used in lighting fixture housings, power supply housings, and engine casings. However, with the development of these home appliances, conventional PC composite materials with low thermal conductivity (thermal conductivity coefficient K = 0.2 W / M / K) are increasingly unable to meet the heat dissipation requirements of home appliances. Furthermore, although PC resin has UL94 V-2 flame retardancy without the addition of flame retardants, the current higher flame retardancy requirements for plastic fireproof housings pose a new challenge to the flame retardancy of PC composite materials.

[0004] Therefore, based on the above-mentioned defects in the prior art, there is an urgent need to develop a thermally conductive flame-retardant PC composite material suitable for fireproof housings.

[0005] Patent specification CN118006105A discloses a needle-flame-resistant polycarbonate composition, its preparation method, and its application. The needle-flame-resistant polycarbonate composition comprises the following components by weight: 89.8% to 99.5% polycarbonate resin; 0.1% to 9% epoxy resin; 0.1% to 1% aromatic polyamine; and 0.1% to 1% sulfonate flame retardant. The addition of thermally conductive powdered fillers improves the thermal conductivity of the PC composite but reduces its flame retardancy. This patented technology eliminates the need for thermal conductivity and the addition of thermally conductive powdered fillers, making it easier to achieve good flame retardancy.

[0006] Patent specification CN102558821A discloses a thermally conductive, halogen-free, flame-retardant polycarbonate resin material comprising the following components: 70%-90% polycarbonate, 2%-20% flame retardant, 1%-5% thermal conductor, 2%-6% compatibilizer, 1%-3% coupling agent, and 0.3%-0.5% other additives. The flame retardant can be a silicon-based flame retardant combined with a fluorinated sulfonate. The silicon-based flame retardant is primarily composed of methylphenylsiloxane, potassium perfluorobutyl iodate, and a fluorinated anti-drip agent. The thermal conductor can be an inorganic filler such as Al2O3, AlN, SIC, or BN. This patented technology uses a single thermal conductor and does not investigate composite thermal conductors. Furthermore, its flame retardancy still requires further improvement, and the flame retardancy test does not involve needle flames. Summary of the Invention

[0007] In response to the technical problems introduced in the background technology and the shortcomings in the field, the present invention provides a thermally conductive flame-retardant PC composite material suitable for fireproof enclosures, as well as a preparation method and application thereof. On the one hand, a specific compound thermal conductive agent is used to achieve high thermal conductivity (thermal conductivity coefficient greater than 0.5 W / M / K) and high mechanical properties of the PC composite material while maintaining low cost, without affecting the flame retardant performance. On the other hand, by optimizing the flame retardant system formula, high flame retardant performance is achieved at a low flame retardant system addition amount, so that the PC composite material can not only pass the needle flame test, but also does not suffer from deterioration of other properties such as mechanical properties due to excessive addition of the flame retardant system.

[0008] The specific technical solutions are as follows: In a first aspect, the present invention provides a thermally conductive flame-retardant PC composite material suitable for a fireproof enclosure, wherein the raw material composition comprises, by weight: 65-70 parts of polycarbonate, 25-30 parts of a thermal conductor, 1-3 parts of a toughening agent (e.g., 2 parts), 1-3 parts of a brightener (e.g., 1.5 parts), 0.9-1 parts of a sulfonate flame retardant, 0.36-0.4 parts of an organosiloxane flame retardant, 0.27-0.3 parts of an anti-dripping agent, 0.2-0.5 parts of an antioxidant (e.g., 0.3 parts), and 0.1-0.5 parts of a lubricant (e.g., 0.3 parts). The total mass of polycarbonate and thermal conductive agent is 100 parts; The thermal conductor is aluminum oxide and boron nitride in a mass ratio of 4 to 6:1, preferably 5:1; The anti-drip agent is polytetrafluoroethylene; The mass ratio of sulfonate flame retardant to thermal conductor is not less than 1:30; The mass ratio of the organosiloxane flame retardant to the sulfonate flame retardant is 0.4:1; The mass ratio of the anti-dripping agent to the sulfonate flame retardant is 0.3:1.

[0009] To ensure that the PC composite material can be used in the production of fireproof enclosures, the thermal conductor used in the PC composite material of the present invention is relatively high, accounting for 25% to 30% of the total mass of the polycarbonate and thermal conductor. The inventors have found that at this thermal conductor dosage ratio, the use of other thermal conductors such as talc significantly reduces the mechanical and flame retardant properties of the PC composite material. Therefore, considering the raw material cost and the impact of the thermal conductor on the mechanical and flame retardant properties of the PC composite material, the thermal conductor of the present invention is primarily composed of low-cost aluminum oxide, supplemented by an appropriate amount of boron nitride. This significantly improves the thermal conductivity of the PC composite material at this thermal conductor dosage ratio while also maintaining both mechanical and flame retardant properties. However, excessive boron nitride usage increases raw material costs and reduces the mechanical properties of the PC composite material. Therefore, the thermal conductor of the present invention comprises aluminum oxide and boron nitride in a mass ratio of 4 to 6:1, preferably 5:1. In this design, the mass of boron nitride accounts for no more than 6%, preferably no more than 5%, of the total mass of the polycarbonate and thermal conductor, ensuring that the PC composite material exhibits excellent mechanical, flame retardant, and thermal conductivity properties.

[0010] Although thermal conductive powder can improve the thermal conductivity of PC composite materials, it will hinder the improvement of the flame retardant properties of PC composite materials. Since a relatively large amount of thermal conductive powder is added to the PC composite material of the present invention, it is a major technical difficulty for the flame retardant properties of the PC composite material to pass the needle flame test. To solve this technical problem, the present invention adopts a compound flame retardant system of sulfonate flame retardant, organosiloxane flame retardant and polytetrafluoroethylene anti-drip agent, and by limiting the dosage ratio between sulfonate flame retardant and thermal conductive agent, as well as the dosage ratio between sulfonate flame retardant, organosiloxane flame retardant and polytetrafluoroethylene anti-drip agent, the sulfonate flame retardant, organosiloxane flame retardant and polytetrafluoroethylene anti-drip agent play a synergistic role, and ultimately, when the total dosage of the compound flame retardant system is very low, the PC composite material can pass the needle flame test without affecting the mechanical properties and thermal conductivity of the PC composite material. Specifically, the total amount of the composite flame retardant system composed of a sulfonate flame retardant, an organosiloxane flame retardant, and a polytetrafluoroethylene anti-drip agent in the present invention is 1.53 to 1.7 parts by mass, which is only 1.53% to 1.7% of the total mass of the polycarbonate and the thermal conductor. The inventors have found that if the ratio of the amount of the sulfonate flame retardant to the thermal conductor or the ratio of the amount of the sulfonate flame retardant, the organosiloxane flame retardant, and the polytetrafluoroethylene anti-drip agent required by the present invention is not followed, the needle flame test cannot be passed under the above-mentioned total amount of the composite flame retardant system. If the needle flame test needs to be passed, the total amount of the composite flame retardant system needs to be increased, which will result in a significant decrease in the mechanical properties and thermal conductivity of the PC composite material.

[0011] This invention addresses the technical problem of common PC composite materials, which suffer from poor heat dissipation and flame retardancy, leading to the susceptibility of plastic fireproof enclosures to fire. It provides a thermally conductive, flame-retardant PC composite material with excellent thermal conductivity (thermal conductivity coefficient K>0.5 W / M / K), a flame retardancy rating of V0, and passing the new national standard S.2 needle flame test.

[0012] Preferably, the polycarbonate is a powder, which is compounded by polycarbonate A and polycarbonate B in a mass ratio of 1:1. The melt index of polycarbonate A at 300°C and 1.2 kg is 10 g / min, and the melt index of polycarbonate B at 300°C and 1.2 kg is 20 g / min.

[0013] Preferably, in the raw material composition, polycarbonate accounts for 70 parts by mass and thermal conductor accounts for 30 parts by mass.

[0014] Preferably, the toughening agent comprises an acrylate core-shell impact modifier.

[0015] Preferably, the whitening agent includes titanium dioxide.

[0016] Preferably, the antioxidant is a compound antioxidant, including a primary antioxidant and a secondary antioxidant, the primary antioxidant includes antioxidant 1076, and the secondary antioxidant includes antioxidant 168.

[0017] Preferably, the mass ratio of the primary antioxidant to the secondary antioxidant is 1:1.

[0018] Preferably, the lubricant comprises pentaerythritol stearate (PETS).

[0019] In a second aspect, the present invention provides a method for preparing the thermally conductive flame-retardant PC composite material suitable for fireproof shells described in the first aspect, comprising: feeding the raw materials into an extruder for melt extrusion, cooling and drying to obtain the thermally conductive flame-retardant PC composite material suitable for fireproof shells.

[0020] Preferably, the temperature of the melt extrusion is 240-260°C.

[0021] Preferably, the screw speed of the extruder is 300-400 rpm, such as 350 rpm.

[0022] In a third aspect, the present invention provides use of the thermally conductive flame-retardant PC composite material suitable for fireproof enclosures described in the first aspect in preparing fireproof enclosures.

[0023] Compared with the prior art, the present invention has the following beneficial effects: 1. Through the study of compounding different thermal conductive powders such as talc, alumina and boron nitride, it was found that the use of alumina and boron nitride in a specific amount and ratio can make the thermally conductive flame-retardant PC composite material have good thermal conductivity (thermal conductivity coefficient K>0.5 W / M / K) and maintain good comprehensive mechanical properties.

[0024] 2. Under the condition of high filling of thermal conductive powder (high proportion of filler will affect flame retardancy), the specific amount and proportion of organic silicone flame retardant, sulfonate flame retardant and polytetrafluoroethylene anti-drip agent are compounded to make the thermal conductive flame retardant PC composite material meet the flame retardant grade V-0 requirements and the new national standard S.2 needle flame test requirements. DETAILED DESCRIPTION

[0025] The present invention will be further described below in conjunction with specific examples. It should be understood that these examples are intended to illustrate the present invention and are not intended to limit the scope of the invention. The operating methods in the following examples where no specific conditions are specified are generally performed under conventional conditions or as recommended by the manufacturer.

[0026] In the following embodiments: Polycarbonate (PC) is a powder, which is compounded by polycarbonate A and polycarbonate B in a mass ratio of 1:1. The melt index of polycarbonate A at 300°C and 1.2 kg is 10 g / min, and the melt index of polycarbonate B at 300°C and 1.2 kg is 20 g / min. The toughening agent is M577 from Japan Kanebuchi; The sulfonate flame retardant was HES-2 from Arichem; The organosiloxane flame retardant is SIFR-870M from Quansheng Chemical; The anti-drip agent is polytetrafluoroethylene.

[0027] The preparation methods of the PC composite materials in the following examples are described as follows: the raw materials are mixed uniformly in a high-speed mixer, melt-extruded through an extruder at an extrusion temperature of 240-260°C and a screw speed of 350 rpm, and then cooled, dried, and diced into pellets to obtain the product PC composite material.

[0028] Table 1 and Table 2 show the raw material composition of each embodiment, unit: weight part.

[0029] Table 1 Table 2 Tables 3 and 4 show the mechanical properties, thermal conductivity, and flame retardancy of the PC composite materials prepared in each embodiment, wherein the needle flame test duration is 60 s and the product thickness is 2 mm.

[0030] Table 3 Table 4 The test results of Examples 1-2 show that, while the addition of low-cost talc improves the thermal conductivity of PC composites compared to alumina, it significantly degrades the material's flame retardancy and toughness. The test results of Examples 2-4 show that the addition of an appropriate amount of boron nitride can improve the thermal conductivity of PC composites. Excessive boron nitride, while improving thermal conductivity, also affects the material's mechanical properties and formulation cost (boron nitride is significantly more expensive on the market than alumina).

[0031] In addition, as can be seen from Examples 4 to 6, the proportion of the compounded flame retardant system needs to be increased to meet the requirements of the new national standard S.2 needle flame test, in addition to the flame retardant grade V-0 of the PC composite material. According to Examples 6 to 13, by optimizing the proportion of the sulfonate flame retardant, the organosiloxane flame retardant, and the polytetrafluoroethylene anti-drip agent, the total amount of the compounded flame retardant system can be appropriately reduced. The PC composite material can still meet the relevant flame retardant requirements such as the needle flame test, and the mechanical properties and thermal conductivity of Example 7 are also better than those of Example 6. In summary, from the perspective of comprehensive performance and cost reduction of PC composite, Example 7 is the best.

[0032] In addition, it should be understood that after reading the above description of the present invention, those skilled in the art may make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application.

Claims

1. A thermally conductive flame-retardant PC composite material suitable for fireproof housing, characterized in that: The raw material composition includes, by weight: 65-70 parts of polycarbonate, 25-30 parts of thermal conductive agent, 1-3 parts of toughening agent, 1-3 parts of brightening agent, 0.9-1 parts of sulfonate flame retardant, 0.36-0.4 parts of organosiloxane flame retardant, 0.27-0.3 parts of anti-dripping agent, 0.2-0.5 parts of antioxidant, and 0.1-0.5 parts of lubricant; The total mass of polycarbonate and thermal conductive agent is 100 parts; The thermal conductor is aluminum oxide and boron nitride in a mass ratio of 4 to 6:1, preferably 5:1; The anti-drip agent is polytetrafluoroethylene; The mass ratio of sulfonate flame retardant to thermal conductor is not less than 1:30; The mass ratio of the organosiloxane flame retardant to the sulfonate flame retardant is 0.4:1; The mass ratio of the anti-dripping agent to the sulfonate flame retardant is 0.3:

1.

2. The thermally conductive flame-retardant PC composite material suitable for fireproof housing according to claim 1, characterized in that: The polycarbonate is a powder, which is compounded by polycarbonate A and polycarbonate B in a mass ratio of 1:

1. The melt index of polycarbonate A at 300°C and 1.2 kg is 10 g / min, and the melt index of polycarbonate B at 300°C and 1.2 kg is 20 g / min.

3. The thermally conductive flame-retardant PC composite material suitable for fireproof housing according to claim 1, characterized in that: The toughening agent includes an acrylate core-shell impact modifier.

4. The thermally conductive flame-retardant PC composite material suitable for fireproof housing according to claim 1, characterized in that: The whitening agent includes titanium dioxide.

5. The thermally conductive flame-retardant PC composite material suitable for fireproof housing according to claim 1, characterized in that: The antioxidant is a compound antioxidant, including a primary antioxidant and a secondary antioxidant, wherein the primary antioxidant includes antioxidant 1076 and the secondary antioxidant includes antioxidant 168; The mass ratio of the primary antioxidant to the secondary antioxidant is 1:

1.

6. The thermally conductive flame-retardant PC composite material suitable for fireproof housing according to claim 1, characterized in that: The lubricant includes pentaerythritol stearate.

7. The method for preparing a thermally conductive flame-retardant PC composite material suitable for a fireproof enclosure according to any one of claims 1 to 6, characterized in that: include: The raw materials are put into an extruder for melt extrusion, and then cooled and dried to obtain the thermally conductive flame-retardant PC composite material suitable for fireproof housing.

8. The preparation method according to claim 7, characterized in that The temperature of the melt extrusion is 240-260°C; The screw speed of the extruder is 300-400 rpm.

9. Use of the thermally conductive flame-retardant PC composite material suitable for fireproof enclosures according to any one of claims 1 to 6 in the preparation of fireproof enclosures.

Images