THERMOPLASTIC HOT MELT ADHESIVE COMPOSITION CONTAINING A FLAME RETARDANT - Patent application

Abstract

The present invention relates to a thermoplastic hot melt adhesive composition comprising a flame retardant mixture, a method for producing said composition, and its use in cold pressure molding.

Description

[Technical Field]

[0001] The present invention relates to a thermoplastic hot melt adhesive composition comprising a flame retardant mixture, a method for producing said composition, and its use in cold pressure molding. [Background technology]

[0002] Thermoplastic hot melt adhesives are widely used in various fields, including electrical and electronic products and communication equipment. In some applications, flame retardancy is required in thermoplastic hot melt adhesives to protect the internal components of equipment and devices from heat and fire. To achieve this flame retardancy, flame retardants are typically added. However, flame retardants are typically high-viscosity solids or compounds that adversely affect the viscosity of hot melt adhesives, making them unsuitable for low-temperature pressure molding techniques. Thermoplastic hot melt adhesives are also used to encapsulate electrical and electronic components such as printed circuit boards (PCBs), connectors, and sensors. Phosphorus-based flame retardants, in particular, are known for their potentially destructive corrosive behavior, which can affect sensitive encapsulation compounds.

[0003] EP 1104766 describes a crosslinked phenoxyphosphazene compound as a flame retardant and a flame-retardant resin composition containing the flame retardant.

[0004] EP 1975217 relates to a flame retardant adhesive or sealing composition containing 0.1 to 99% by weight of an adhesive or thermoplastic polymer and 0.1 to 99% by weight of a flame retardant comprising at least one dialkyl or diaryl phosphinic acid metal or organic base salt and / or alkylene or arylene diphosphinic acid metal or organic base salt.

[0005] CN 10340320 discloses a halogen-free flame-retardant polyamide hot melt adhesive containing 100 parts of a dimer acid type polyamide hot melt adhesive, 15-65 parts of a halogen-free flame retardant, and 0.3-3 parts of an antioxidant. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] European Patent Application Publication No. 1104766 [Patent Document 2] European Patent Application Publication No. 1975217 [Patent Document 3] Chinese Patent Application Publication No. 10340320 Summary of the Invention [Problem to be solved by the invention]

[0007] For applications in the manufacture of electrical or electronic composite materials, hot melt adhesive compositions should achieve a flame retardancy rating of V-0 in the UL-94 flame retardancy test (Test for Flammability of Plastic Materials Used in Equipment Components), a standard test for evaluating flame retardancy. To achieve a V-0 rating, flames must not persist for longer than the specified time, and dripping of molten resin must not occur, igniting the cotton located under the test specimen. It has been found that while some standard thermoplastic hot melt adhesive compositions can achieve a V-0 rating, they are unable to maintain this V-0 rating after aging and / or at different thicknesses. Therefore, an object of the present invention is to provide a thermoplastic hot melt adhesive composition that meets the requirements of the V-0 standard while also having low viscosity and good corrosion resistance, making it applicable to low-temperature pressure molding technology. [Means for solving the problem]

[0008] It has now surprisingly been found that this object is achieved by a polyamide-based thermoplastic hot melt composition comprising a mixture of a phosphorus-based flame retardant and a halogen-free flame retardant.

[0009] Therefore, the primary object of the present invention is to provide a composition comprising: a) at least one polyamide; b) at least one phosphorus-based flame retardant in an amount of 0.1 to 5% by weight; and c) at least one halogen-free flame retardant in an amount of 0.1 to 15% by weight wherein the at least one phosphorus-based flame retardant is different from the at least one halogen-free flame retardant.

[0010] It was found that the hot melt adhesive composition of the present invention has improved thermal stability and can be rated V-0 even after aging or at different thicknesses.

[0011] In a preferred embodiment, the at least one halogen-free flame retardant is selected from the group consisting of melamine cyanurate, melamine polyphosphate, ammonium phosphate, pentaerythritol and zinc oxide, in particular, the at least one halogen-free flame retardant is melamine cyanurate.

[0012] Polyamide hot melt adhesives are generally characterized by good adhesive properties and high chemical resistance. In particular, polyamides based on dimer fatty acids also exhibit excellent basic flame retardancy. Therefore, in a preferred embodiment, the at least one polyamide is a polyamide based on dimer fatty acids.

[0013] The dimer fatty acid or polymer fatty acid in the present invention is a fatty acid obtained by dimerization from natural raw materials by known methods. They are produced from unsaturated long-chain fatty acids and then purified by distillation. Industrial dimer fatty acids contain less than 5% of monobasic fatty acids (mainly C 1 acids such as linoleic acid or oleic acid) depending on the purity. 18 fatty acids), up to 98% by weight of C 36These include dibasic fatty acids (more narrowly defined as dimer fatty acids) and small amounts of higher polybasic fatty acids ("trimer acids"). The relative proportions of monomer, dimer, and trimer fatty acids in the polymeric fatty acid mixture depend on the nature of the starting compounds used, the polymerization, dimerization, or oligomerization conditions, and the extent of distillative separation. Distillatively purified dimer fatty acids contain up to 98% by weight of dimer fatty acids. In a separate processing step, these dimer fatty acids can also be hydrogenated. These hydrogenated dimer fatty acids can also be used in accordance with the present invention.

[0014] In a preferred embodiment, the at least one polyamide is a polyamide comprising at least one dimer fatty acid and at least one dicarboxylic acid, preferably C6-C8 24 The dicarboxylic acids are obtained from a reaction mixture containing a dicarboxylic acid selected from succinic acid, adipic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, glutaric acid, suberic acid, and pimelic acid. Aromatic dicarboxylic acid moieties, such as terephthalic acid, isophthalic acid, or mixtures of the aforementioned dicarboxylic acids, can also be used in the reaction mixture. However, longer chain aliphatic dicarboxylic acids, such as C 10 ~C 18 In this case, the water absorption of the resulting polyamide can be reduced.

[0015] The diamine component consists essentially of one or more aliphatic diamines, with the amino group at the end of the carbon chain. The aliphatic diamine can contain 2 to 20 carbon atoms, and the aliphatic chain can be linear or branched. Examples include ethylenediamine, diethylenetriamine, dipropylenetriamine, 1,4-diaminobutane, 1,3-pentanediamine, methylpentanediamine, hexamethylenediamine, trimethylhexamethylenediamine, 2-(2-aminomethoxy)ethanol, 2-methylpentamethylenediamine, C 11Examples of the primary alkylenediamine include neopentanediamine, diaminodipropylmethylamine, and 1,12-diaminododecane. Particularly preferred primary alkylenediamines include those having an even number of carbon atoms, such as C2 to C6. 12 It is a diamine.

[0016] The amino component can also include cyclic or heterocyclic diamines, such as, for example, 1,4-cyclohexanediamine, 4,4'-diaminodicyclohexylmethane, piperazine, cyclohexanebis(methylamine), isophoronediamine, dimethylpiperazine, dipiperidylpropane, norbornanediamine, or m-xylylenediamine. In certain embodiments, mixtures of alkylene diamines and cyclic diamines are used.

[0017] The thermoplastic hot melt adhesive composition of the present invention comprises at least one phosphorus-based flame retardant. The at least one phosphorus-based flame retardant is preferably selected from the group consisting of cyclic phosphonates and bridged phenoxyphosphazene compounds. In a particularly preferred embodiment, the at least one phosphorus-based flame retardant is a bridged phenoxyphosphazene compound comprising a cyclic phosphazene group and a linear or branched phosphazene chain bridged with at least one bridging group selected from the group consisting of a phenylene group and a bisphenylene group. Suitable bridged phenoxyphosphazene compounds are described in EP 1 104 766 A1. In a preferred embodiment, the phosphorus-based flame retardant has a solubility in water at 25°C of less than 0.05%, preferably less than 0.02%, and in particular less than 0.01%. Surprisingly, the use of such phosphorus-based flame retardants in the composition of the present invention improves corrosion resistance and thermal stability.

[0018] In a preferred embodiment of the thermoplastic hot melt adhesive composition of the present invention, the at least one polyamide is present in the composition in an amount of at least 80 wt. %, preferably at least 85 wt. %, each based on the total weight of the composition.

[0019] The thermoplastic hot melt adhesive composition is characterized by a low content of halogen-free flame retardants. Additionally, it has surprisingly been found that the amount of phosphorus-based flame retardants can be reduced without affecting the flame retardancy of the composition. Thus, in a preferred embodiment, the amount of at least one phosphorus-based flame retardant in the composition is 0.2 to 2 wt. % each, based on the total weight of the composition.

[0020] In a more preferred embodiment, the amount of each halogen-free flame retardant in the composition is 1.0 to 12 wt %, more preferably 5 to 9.5 wt %, based on the total weight of the composition.

[0021] In a particularly preferred embodiment, the thermoplastic hot melt adhesive composition comprises at least 80 wt. %, preferably at least 85 wt. %, of a polyamide based on dimer fatty acid, preferably 0.2 to 2 wt. % of a crosslinked phenoxyphosphazene compound, and 1.0 to 12 wt. %, more preferably 5 to 9.5 wt. % of melamine cyanurate.

[0022] One requirement for a hot melt adhesive to be suitable for low-temperature pressure molding technology is low viscosity. Thus, in a preferred embodiment, the thermoplastic hot melt adhesive composition of the present invention has a viscosity of 10,000 mPas or less, preferably less than 5000 mPas, at 200 to 230°C, measured according to ASTM D3236.

[0023] The thermoplastic hot melt adhesive composition of the present invention is further characterized by a high thermal stability that ensures a V-0 classification even after aging. Therefore, preferred embodiments of the thermoplastic hot melt adhesive composition are those in which the thermoplastic hot melt adhesive composition is thermally stable at temperatures up to 210°C. Thermal stability may be determined visually by comparing the color of the composition after heating with a standard color sheet.

[0024] The thermoplastic hot melt adhesive composition of the present invention has a corrosion resistance of 10% at 40°C and 90% relative humidity in accordance with J-STD-004 A. 8Due to this high corrosion resistance, the hot melt adhesive composition of the present invention is particularly suitable for the manufacture of electrical and electronic components.

[0025] A further object of the present invention is a process for producing the thermoplastic hot melt adhesive composition of the present invention, which comprises melting at least one polyamide and adding, under stirring, at least one phosphorus-based flame retardant and at least one halogen-free flame retardant.

[0026] The hot melt adhesive composition of the present invention is particularly designed for low-temperature pressure molding. Therefore, in a further aspect, the present invention relates to the use of the thermoplastic hot melt adhesive composition according to the present invention in low-temperature pressure molding techniques. Preferably, the composition is used for sealing electrical and / or electronic components.

[0027] Another object of the present invention are molded articles obtainable from the thermoplastic hot melt adhesive compositions of the present invention by cold pressure molding.

[0028] The present invention will be described in more detail based on the following examples, but these examples should not be construed as limiting the scope or spirit of the present invention. [Example]

[0029] Example Composition 1 89.5 wt. % of a polyamide based on dimer fatty acid with a softening point of 155°C was melted and 1.5 wt. % of a mixture of phosphorus-based flame retardants with a solubility in water of more than 0.05% at 25°C and 9 wt. % of melamine cyanurate were added under stirring.

[0030] The resulting hot melt adhesive composition met the V-0 classification of UL 94 V and had a viscosity of 2,500 mPas at 210° C. However, this composition slightly discolored at a temperature of 190° C.

[0031] Composition 2 90% by weight of a polyamide based on dimer fatty acid with a softening point of 155°C was melted and 1.0% by weight of a phosphorus-based flame retardant with a solubility in water at 25°C of less than 0.01% and 9% by weight of melamine cyanurate were added under stirring.

[0032] The resulting composition met the requirements of UL 94 V V-0 classification before and after aging at 70°C for 168 hours, and had a viscosity of 4,500 mPas at 210°C. 8.6 It has good corrosion resistance of ohmic and showed no corrosion on PCB after 168 hours at 40°C and 90% relative humidity according to J-STD-004 A. There was no discoloration when heated to 190°C, and only slight discoloration was detected at temperatures of 210°C.

[0033] Composition 3 90% by weight of a polyamide based on dimer fatty acid with a softening point of 175°C was melted and 1.0% by weight of a phosphorus-based flame retardant with a solubility in water at 25°C of less than 0.01% and 9% by weight of melamine cyanurate were added under stirring.

[0034] The resulting composition met the requirements of UL 94 V V-0 classification, and had a viscosity of 4,500 mPas at 225°C. 8.2 It has good corrosion resistance and showed no discoloration even when heated to temperatures up to 210°C. No corrosion was detected on the PCB after aging the composition for 168 hours at 40°C and 90°C relative humidity. No change in flame retardancy was observed after aging for 168 hours at 70°C.

Claims

1. Based on the total weight of the composition, a) at least one polyamide; b) at least one phosphorus-based flame retardant in an amount of 0.1 to 5 wt. %; and c) at least one halogen-free flame retardant in an amount of 0.1 to 15% by weight A thermoplastic hot melt adhesive composition comprising: The composition wherein the at least one phosphorus-based flame retardant is different from the at least one halogen-free flame retardant.

2. 2. The thermoplastic hot melt adhesive composition of claim 1, wherein the at least one halogen-free flame retardant is selected from the group consisting of melamine cyanurate, melamine polyphosphate, ammonium phosphate, pentaerythritol, and zinc oxide.

3. 3. The thermoplastic hot melt adhesive composition according to claim 1 or 2, characterized in that the at least one halogen-free flame retardant is melamine cyanurate.

4. 4. Thermoplastic hot melt adhesive composition according to claim 1, characterized in that the at least one polyamide is a polyamide based on dimer fatty acid.

5. 5. The thermoplastic hot melt adhesive composition of claim 4, wherein the at least one polyamide is obtained from a reaction mixture comprising at least one dimer fatty acid and at least one dicarboxylic acid.

6. 6. The thermoplastic hot melt adhesive composition according to claim 1, wherein the at least one phosphorus-based flame retardant is selected from the group consisting of cyclic phosphonates and bridged phenoxyphosphazene compounds.

7. 7. The thermoplastic hot melt adhesive composition according to claim 1, wherein said at least one polyamide is present in the composition in an amount of at least 80 wt.-%, preferably at least 85 wt.-%, based on the total weight of the composition.

8. 8. The thermoplastic hot melt adhesive composition according to claim 1, wherein the amount of said at least one phosphorus-based flame retardant in the composition is 0.2 to 2 wt.-%, each based on the total weight of the composition.

9. 9. The thermoplastic hot melt adhesive composition according to claim 1, wherein the amount of said halogen-free flame retardant in the composition is 1.0 to 12 wt.%, more preferably 5 to 9.5 wt.%, each based on the total weight of the composition.

10. 10. The thermoplastic hot melt adhesive composition according to any one of claims 1 to 9, characterized in that the viscosity of the composition at 200-230°C, measured according to ASTM D3236, is not more than 10,000 mPas, preferably less than 5000 mPas.

11. A thermoplastic hot melt adhesive composition according to any one of claims 1 to 10, characterized in that the composition is thermally stable at temperatures up to 210°C.

12. The corrosion resistance of the composition according to J-STD-004 A at 40°C and 90% relative humidity is 10 ８ The thermoplastic hot melt adhesive composition according to any one of claims 1 to 11, characterized in that it has a hardness of 0.1 ohm or more.

13. 13. A method for producing a thermoplastic hot melt adhesive composition according to any one of claims 1 to 12, characterized in that the at least one polyamide is melted and the at least one phosphorus-based flame retardant and the at least one halogen-free flame retardant are added with stirring.

14. Use of the thermoplastic hot melt adhesive composition according to any one of claims 1 to 12 in cold pressure moulding techniques.

15. A molded article obtained from the thermoplastic hot melt adhesive according to any one of claims 1 to 12.

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