Modified halogen-free flame retardant resins for electronic devices

Abstract

Halogen-free phosphorus-containing flame retardant resins are disclosed. The halogen-free phosphorus-containing flame retardant resin is mixed with a metal oxide to form a modified halogen-free phosphorus-containing flame retardant. The modified halogen-free phosphorus-containing flame retardant composition can be used for electronic equipment.

Description

Technical Field

[0001] The present invention relates to a modified halogen-free flame retardant resin for electronic devices. In particular, the present invention relates to a halogen-free flame retardant resin having metal oxides added to a resin that can be used for electronic devices. The modified halogen-free flame retardant resin may optionally contain additional additives. Background Art

[0002] To meet fire safety requirements and reduce fire hazards, various flame retardants have been used. Flame retardants block the pyrolysis of the underlying polymer. Adding a flame retardant to a polymer can help prevent the final product made from such a polymer from burning. However, adding a flame retardant to a polymer may affect both the mechanical properties and the electrical properties of the polymer.

[0003] The UL 94 test is used to measure the burning rate and characteristics of polymer materials. One method for determining flame retardancy is UL94, a standard for the flammability testing of plastic materials for parts in devices and appliances (the Standard for Tests for Flammability of Plastic Materials for Parts in Devices and Appliances). The UL94 V-0 rating is based on a vertical burning test in which the afterflame time of the polymer is determined. A UL 94 V-0 rating for a polymer indicates that the polymer will self-extinguish within 10 seconds and will not drip (UL 94, approved as ANSI / UL 94-2001, April 11, 2001). Having such a rating is important in many applications.

[0004] Various flame retardants have been used to improve the flammability rating of base polymers to achieve the UL 94 rating. Generally, halogenated flame retardants have been used to improve the flammability rating of polymers. Halogenated flame retardants block the gas phase of polymer combustion by generating free radicals such as dioxins and furans. Many of these halogenated flame retardants have environmental problems, and the use of these halogenated flame retardants in polymers is being phased out.

[0005] As a result, halogen-free flame retardants are being used more and more to improve the flame retardancy of polymers. Halogen-free phosphorus-based flame retardants are considered viable alternatives to halogenated flame retardants. These halogen-free phosphorus-based flame retardants are widely used because of their low toxicity, high efficiency, multiple flame retardant mechanisms, and diverse molecular structures.

[0006] Unfortunately, for the use of halogen-free phosphorus-based flame retardants, phosphoric acid is released when the flame retardant composition is subjected to environmental conditions such as high temperature or high humidity and any combination of environmental conditions. If such a flame retardant is used in a polymer, the release of the acid may have an adverse effect on the surrounding components in the device.

[0007] In the literature "The Study on Flame Retardancy Synergistic Mechanism of Magnesium Oxide for PA66 / AlPi Composite" (Mater. Res. Express 6 (2019) 115317), the authors described the important role of flame retardants in polyamide 6,6. The authors described how magnesium oxide reacts with diethylphosphinic acid produced by the degradation of aluminum diethylphosphinate.

[0008] There is a need for a halogen-free flame retardant resin that does not have an adverse effect on the polymers used in the surrounding components of a device and can be used in multi-component electronic devices. Brief Description of the Drawings

[0009] The drawings incorporated herein and forming a part of the specification schematically illustrate one or more illustrative embodiments of the invention and, together with the general description given above and the detailed description given below, are used to explain the principles of the invention, and in which:

[0010] Figure 1 is a flow chart showing the Compression Set Test Procedure for the FRIANYL A3 GF 30 V0 resin (as defined in the examples) made in accordance with the invention and used in a device made of a silicone polymer composition.

[0011] Figure 2 is a graph showing the silicone tensile strain retention at 85 °C and 125 °C after 504 hours and 1008 hours when in contact with the modified FRIANYL A3 GF 30 V0 resin (as defined in the examples).

[0012] Figure 3 is a graph showing the aging effect on silicone compression set after 1008 hours at 85 °C and 125 °C when the silicone polymer composition is in contact with the modified FRIANYL A3 GF 30 V0 resin (as defined in the examples).

[0013] Figure 4It is a graph showing the silicone compression set after 0 hours and 504 hours at 125°C when the silicone polymer composition is in contact with two different modified flame retardant resins (as defined in the examples) of the present invention. SUMMARY OF THE INVENTION

[0014] One embodiment relates to a modified halogen-free phosphorus-containing flame retardant resin comprising a halogen-free phosphorus-containing flame retardant and a metal oxide.

[0015] Another embodiment relates to an electronic device comprising a component made of a silicone polymer composition and a component made of the modified halogen-free flame retardant resin of the present invention.

[0016] Other features and advantages of the present invention will be apparent from the following more detailed description of the preferred embodiments in conjunction with the accompanying drawings, which illustrate the principles of the present invention by way of example. DETAILED DESCRIPTION

[0017] The description of the illustrative embodiments in accordance with the principles of the present invention is intended to be read in relation to the accompanying drawings, which are to be considered as a part of the entire written description. In the description of the embodiments of the present invention disclosed herein, any reference to direction or orientation is for the purpose of convenience in description only and is not intended to limit the scope of the present invention in any way. Relative terms such as "lower", "higher", "horizontal", "vertical", "above", "below", "upper", "lower", "top" and "bottom" and their derivatives (e.g., "horizontally", "downwardly", "upwardly", etc.) should be construed to refer to the orientation as then described or as shown in the drawings under discussion. These relative terms are for convenience in description only and do not require the device to be constructed or operated in a particular orientation unless explicitly so stated. Unless otherwise explicitly described, terms such as "attached", "fixed", "connected", "coupled", "interconnected", etc. refer to a relationship in which structures are fastened or attached to each other directly or indirectly through an intermediate structure, and include both movable or rigid attachments or associations.

[0018] Furthermore, the features and benefits of the present invention are described with reference to the preferred embodiments. Accordingly, the present invention should be clearly not limited to such embodiments that illustrate some possible non-limiting combinations of features that may exist alone or in other combinations of features, and the scope of the present invention is defined by the appended claims.

[0019] The modified halogen-free flame retardant resin of the present invention comprises a halogen-free phosphorus-containing flame retardant resin mixed with a metal oxide. The modified halogen-free phosphorus-containing flame retardant resin should meet the UL 94 V-0 rating. An example of a commercially available halogen-free phosphorus-based flame retardant resin that can be used in the present invention is FRIANYL A3 GF 30 V0 available from Celanese, which is a halogen-free flame retardant composition based on polyamide containing 30% glass fiber.

[0020] Phosphorus-based flame retardants that can be used in the modified halogen-free flame retardant composition include, but are not limited to: phosphates, phosphonates, phosphinates, phosphinites, phosphonites, phosphites, phosphines, phosphine oxides, red phosphorus, and phosphonium compounds.

[0021] Alternatively, the phosphorus-based flame retardant resin can be a mixture of a polymer and a phosphorus-based flame retardant. The polymer used in the halogen-free flame retardant resin can be any desired polymer. Preferably, the polymer itself meets the UL 94 V-0 rating. Examples of such suitable polymers include, but are not limited to: polyethylene, polypropylene, acrylonitrile-butadiene-styrene resin, polystyrene, polyketone, polybutylene terephthalate, polyamide, polyester, polyphenylene ether, polycarbonate, polysulfone, polyaryl ether ketone, and polyethersulfone.

[0022] The halogen-free phosphorus-based flame retardant resin used in the present invention is mixed with a metal oxide. Metal oxides are crystalline solids containing metal cations and oxygen anions. They can react with water to form bases or with acids to form salts. Examples of metal oxides that can be used in the present invention include, but are not limited to: alumina, antimony oxide, bismuth(III) oxide, calcium oxide, gallium(III) oxide, magnesium oxide, barium oxide, strontium oxide, zinc oxide, titanium(II) oxide, titanium(IV) oxide, cerium oxide, copper oxide, iron oxide, nickel oxide, manganese oxide, chromium oxide, or lead oxide. Preferably, the metal oxide is magnesium oxide. The amount of the metal oxide used in the modified halogen-free phosphorus-based flame retardant resin ranges from about 0.5 wt% to about 10 wt% of the modified halogen-free phosphorus-based flame retardant resin.

[0023] Other conventional additives can be incorporated into the halogen-free flame retardant resin having a metal oxide. Examples of conventional additives include: pigments, dyes, voiding agents, antistatic agents, foaming agents, plasticizers, radical scavengers, antiblocking agents, dust-proofing agents, antifouling agents, surfactants, slip aids, optical brighteners, viscosity modifiers, gloss improvers, dispersion stabilizers, UV stabilizers, UV absorbers, antioxidants (such as phenolic antioxidants or amine antioxidants), lubricants, heat stabilizers, hydrolysis stabilizers, crosslinking activators, coupling agents, layered silicates, radiation opacifiers (such as, but not limited to, barium sulfate), tungsten metal, non-oxide bismuth salts, fillers, colorants, reinforcing agents, adhesion promoters (such as, but not limited to, 2-hydroxyethyl-methacrylate-phosphate), impact strength improvers, and any combination thereof. Such additives can be included in conventional amounts.

[0024] In another aspect, the present invention relates to the preparation of a halogen-free flame retardant resin having a metal oxide. First, a halogen-free phosphorus-containing flame retardant resin is mixed with a metal oxide to form a modified halogen-free phosphorus-containing flame retardant resin. Using any conventional process for mixing materials together, the modified halogen-free phosphorus-containing flame retardant resin and any other additional additives are mixed together in particulate form. The mixing equipment can be any suitable equipment used in the field of mixing concentrated solids. Examples of such equipment suitable for flame retardant resins include: batch mixers, such as Brabender mixers, Banbury mixers; single screw extruders, twin screw extruders, high-speed centrifugal mixers, Henschel mixers, belt blenders, vibrators, tube drums, etc. The polymer, modified halogen-free phosphorus-containing flame retardant, and any desired additives can be heated, melted, and compounded together using conventional processes.

[0025] Once the halogen-free flame retardant resin is mixed with the desired additives, it can be further processed. The halogen-free flame retardant resin can be extruded, injection molded, overmolded, compression molded, reaction injection molded, laminated, or 3D printed to form any desired object.

[0026] The modified halogen-free flame retardant resin of the present invention has a variety of uses. For example, the composition can be molded into seals, gaskets, connectors, wires, cables, printed circuit boards, or EMI shields, as well as other electronic or computer components. The composition can be used to fabricate electronic components meeting UL 94 standards, such as smartphones, General Motors parts, electric motors, e-powertrains, batteries and battery enclosures, chargers for electric vehicles, and other components of electric vehicles. Additionally, the composition of the present invention can be used to fabricate molded parts.

[0027] In addition, the modified halogen-free flame retardant resin of the present invention can be used as a component in combination with other components in a device. For example, the modified halogen-free flame retardant resin can be used as a component in an electronic device in combination with a seal or gasket made of a silicone polymer composition.

[0028] The silicone polymer composition that can be used in the components of a device that also contains the halogen-free flame retardant resin of the present invention can be any silicone elastomer or polymer containing a chain made of alternating silicon atoms and oxygen atoms. It can be liquid silicone rubber (LSR), high-consistency rubber (HCR), fluorosilicone, polyhedral oligomeric silsesquioxane (cage-like poly silsesquioxane, POSS), silicone polyamide, silicone polyurethane, silicone epoxy resin, and other silicones. Examples of suitable silicones are LSR 2660 and LSR7060 from GE Silicones. The type of silicone used depends on the final target application. Depending on the final desired target application, the silicone used in the silicone polymer composite can also contain other additives. Examples of suitable additives include fumed silica, antioxidants, fluxes, or catalysts. Suitable antioxidants include phenolic antioxidants or amine antioxidants. Examples of suitable fluxes include NH 4 F, NH 4 Cl, and Na 2 B 4 O 7。 Feasible catalysts that can be used include peroxides or platinum catalysts.

[0029] Silicone polymer compositions are particularly vulnerable to acidic environments. In particular, when used in combination with components made of the modified halogen-free flame retardant resin of the present invention, the silicone polymer composition is affected reactively. As shown below, in silicone polymer compositions, the hydrolysis of siloxane bonds under acidic conditions is a well-known process, especially in the presence of strong nucleophiles such as water.

[0030]

[0031] The resulting silanol groups can recombine with another silanol group, thereby forming a three-dimensional network. The formation of this three-dimensional network results in a reduction in the elasticity of the silicone polymer composition. Environmental conditions accelerate this process. For example, when the halogen-free flame retardant is subjected to environmental conditions such as temperature and humidity, phosphoric acid is released that attacks the device made of the silicone polymer composition. The use of the halogen-free flame retardant of the present invention prevents the formation of such an acidic environment and prevents the deterioration of the components made of silicone polymer in the device.

[0032] Examples

[0033] The flame retardant composition used in the examples is FRIANYL A3 GF 30 V0 resin. The silicone polymer composition used as part of the examples is a two-part liquid silicone rubber (LSR) containing 5% silicone oil and having a Shore A hardness of 30. The part A and part B of the LSR were mixed together using a FlackTek Speed Mixer DAC 150.1 FVZ mixer. After mixing, a compression molding process was used to prepare test specimens with dimensions of 13 mm in diameter and 6 mm in thickness. Compression molding was also used to prepare plates of 150 mm × 150 mm × 2 mm. After curing, the plates were then cut into dumbbells using an ISO-37-2 mold. The test specimens were then completely buried inside the FRIANYL A3 GF 30 V0 resin and aged for 504 and 1008 hours at both 125 °C and 85 °C / 85% relative humidity (“RH”).

[0034] After aging, the silicone compression set and tensile properties were evaluated. The compression set test was based on ASTM D395 Method B, using samples with dimensions of 13 mm in diameter and 6 mm in thickness. The test procedure is shown in Figure 1 . After completion of the test, the compression set can be calculated according to ASTM D395 Method B.

[0035] Tensile strain and tensile stress at break were measured using an Instron tester at a tensile speed of 100 mm / min.

[0036] As seen by Figure 2 , when the silicone polymer composition is in contact with the FRIANYL A3 GF 30 V0 resin, the silicone tensile strain retention rate decreases to approximately 50 - 60% of the original sample under both aging conditions (temperature and relative humidity (RH)). However, if not in contact with the FRIANYL A3 GF 30 V0 resin, the silicone polymer composition still retains more than 90% of the tensile strain under both aging conditions. This data shows that the acidic environment generated by the FRIANYL A3 GF 30 V0 resin accelerates the degradation of the silicone polymer composition and severely affects the silicone tensile strain.

[0037] As seen by Figure 3As seen from the results in [section], when the silicone polymer composition is not in contact with any flame retardant, the silicone compression set increases from the original 7% to approximately 15% under both aging conditions. However, when it is in contact with FRIANYL A3 GF 30V0 resin, the silicone compression set increases from the original 7% to approximately 22% under both aging conditions. This means that, compared with the case of not contacting any resin, when the silicone polymer composition is in contact with FRIANYL A3 GF 30 V0 resin, the additional increase in the compression set of the silicone polymer composition is 7%. The results show that the acidic environment generated by FRIANYL A3 GF 30 V0 resin during thermal aging accelerates the degradation of the silicone polymer composition and seriously affects the compression set.

[0038] In another series of experiments, three samples were prepared. The first sample contained the halogen-free phosphorus-containing flame retardant resin FRIANYL A3 GF 30 V0 resin available from Celanese. The second sample contained the halogen-free phosphorus-containing flame retardant FRIANYL A3GF 30 V0, accompanied by 5 wt% of magnesium oxide. The third sample contained FRIANYL A3 GF 30 V0 resin, accompanied by 10 wt% of magnesium oxide.

[0039] First, magnesium oxide was mixed with FRIANYL A3 GF 30 V0 resin to make a modified halogen-free phosphorus-based V-0 resin. Then, silicone test specimens were prepared. The test specimens were embedded inside the modified halogen-free phosphorus-containing flame retardant composition and then aged at 125 °C for 504 hours and 1008 hours. After aging the samples, the compression set test was carried out at 175 °C for 22 hours according to ASTM D395 as described above.

[0040] The results of the compression set test can be found in Figure 4 [section]. The results show that, compared with when using only the halogen-free phosphorus-containing flame retardant resin, the samples with the halogen-free phosphorus-containing flame retardant resin modified with metal oxide performed better after aging at 125 °C for 504 hours when in contact with the silicone specimens.

[0041] These test results show that when the halogen-free phosphorus-containing flame retardant resin is in contact with the silicone polymer composition and the silicone polymer composition is subjected to a thermal degradation environment, the metal oxide in the flame retardant resin acts as an acid scavenger. Adding the metal oxide to the flame retardant ensures that the silicone polymer composition does not lose its physical properties and deteriorate when subjected to aging or thermal degradation or other environmental conditions in the presence of the halogen-free phosphorus-containing flame retardant resin.

Claims

1. A halogen-free flame retardant composition, comprising a halogen-free flame retardant resin and a metal oxide, wherein the halogen-free flame retardant is mixed with the metal oxide. 2 . The composition according to claim 1 , wherein the halogen-free flame retardant resin is a halogen-free phosphorus-containing flame retardant resin.

3. The composition of claim 2, wherein the halogen-free phosphorus-containing flame retardant resin comprises a phosphorus-containing flame retardant selected from the group consisting of phosphates, phosphonates, hypophosphites, phosphinates, phosphites, phosphites, phosphites, phosphine oxides, red phosphorus, and phosphonium compounds.

4. The composition according to claim 3, wherein the halogen-free phosphorus-containing flame retardant resin comprises: Polyethylene, polypropylene, acrylonitrile butadiene styrene resin, polystyrene, polyketone, polybutylene terephthalate, polyamide, polyester, polyphenylene ether, polycarbonate, polysulfone, polyaryletherketone or polyethersulfone.

5. The composition of claim 1, wherein the metal oxide is selected from the group consisting of aluminum oxide, antimony oxide, bismuth (III) oxide, calcium oxide, gallium (III) oxide, magnesium oxide, barium oxide, strontium oxide, zinc oxide, titanium (II) oxide, titanium (IV) oxide, cerium oxide, copper oxide, iron oxide, nickel oxide, manganese oxide, chromium oxide, or lead oxide.

6. The composition of claim 5, wherein the metal oxide is magnesium oxide.

7. The composition of claim 6, wherein the magnesium oxide is at least 5% by weight of the composition.

8. The composition of claim 6, wherein the magnesium oxide is at least 10% by weight of the composition.

9. The composition of claim 6, wherein the magnesium oxide is in the range of about 0.5% to about 10% by weight of the composition.

10. The composition of claim 1, wherein the composition has a UL 94 V-0 rating.

11. An electronic device having a component made of a silicone polymer composition and a component made of a halogen-free flame retardant composition, the halogen-free flame retardant composition comprising a halogen-free flame retardant resin and a metal oxide, wherein the halogen-free flame retardant resin is mixed with the metal oxide. 12 . The electronic device according to claim 11 , wherein the halogen-free flame retardant resin is a halogen-free phosphorus-containing flame retardant resin.

13. The electronic device of claim 11, wherein the device has a UL 94 V-0 rating.

14. The electronic device of claim 11, wherein the metal oxide is magnesium oxide.

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