JP7675603B2 - Flame retardant granules - Google Patents

Description

The present invention relates to a flame retardant granule.

In order to impart flame retardancy to thermoplastic resins and elastomers, powdered flame retardants may be blended. Powdered flame retardants generally have a low bulk density and poor flowability during transportation, which means that there are many issues to be resolved in terms of handling, such as transportation, storage, packaging, and supply stability to processing machines, as well as issues to be resolved in terms of the working environment and safety for the human body. In particular, when blending powdered flame retardants with thermoplastic resins or elastomers using a melt kneading device (a representative example of which is an extruder), particularly when blending flame retardants at high concentrations, there is a problem that the supply of the powdered flame retardant to the melt kneading device becomes a bottleneck, resulting in a significant decrease in the production rate of melt kneading. Patent Document 1 proposes granulating the powdered flame retardant as one solution to this problem. However, Patent Document 1 suggests that the binding force may be insufficient when granulating powdered flame retardants with high melting points. Recently, the use of phosphorus-containing compound flame retardants, nitrogen-containing compound flame retardants, inorganic flame retardants, and metal salt flame retardants as non-bromine flame retardants has increased, and they are often in powder form. In addition, in flame retardancy standards such as the UL94 standard, there is an increasing demand for resin compositions that contain a high amount of flame retardant in order to stably achieve a high level of flame retardancy.

Japanese Unexamined Patent Publication No. 8-92562

The present invention has been made to solve the above problems, and its purpose is to provide a flame retardant granule that can improve the handleability, safety, and working environment improvement of a powdered flame retardant, and can contribute to improving the productivity of a resin composition or a resin molded product that contains a high concentration of flame retardant.

The flame retardant granules of the present invention contain a powdery flame retardant and a binder, and the content of the powdery flame retardant is 80 to 99.9 parts by weight per 100 parts by weight of the total amount of the powdery flame retardant and the binder.
In one embodiment, the powdery flame retardant is at least one selected from the group consisting of a halogen-containing compound-based flame retardant, a phosphorus-containing compound-based flame retardant, a nitrogen-containing compound-based flame retardant, an inorganic flame retardant, and a metal salt-based flame retardant.
In one embodiment, the binder is at least one selected from the group consisting of polyolefin-based resins, polyvinyl alcohol-based resins, polyvinylpyrrolidone-based resins, polyester-based resins, polyamide-based resins, acrylic-based resins, polyurethane-based resins, epoxy-based resins, polysaccharides, and swelling clay minerals.
In one embodiment, the binder is composed of at least one resin selected from the group consisting of polyvinylpyrrolidone-based resins, polyester-based resins, polyamide-based resins, polyurethane-based resins, and epoxy-based resins.
According to yet another aspect of the present invention, there is provided a method for producing the flame retardant granules, comprising a mixing step of mixing the powdered flame retardant with a binder, a granulation step of granulating the mixture obtained through the mixing step to obtain a granule precursor, and a drying step of drying the granule precursor.
In one embodiment, the binder is added as an aqueous liquid containing the binder.
In one embodiment, the production method includes granulation by a semi-wet granulation method in the granulation step.
In one embodiment, the production method includes performing granulation by a disk pelleter method in the granulation step.
According to yet another aspect of the present invention, there is provided use of the above-mentioned flame retardant granules as a raw material for a thermoplastic resin compound.

According to the present invention, by forming a flame retardant granule containing a powdered flame retardant and a binder, in which the content of the powdered flame retardant is 80 to 99.9 parts by weight per 100 parts by weight of the total of the powdered flame retardant and the binder, it is possible to improve the handleability, safety, and working environment improvement of the powdered flame retardant, and also to improve the productivity of a resin composition or a resin molded product containing a high concentration of the flame retardant.

FIG. 2 is a photograph showing the appearance of the flame retardant granules obtained in Example 1.

A. Overview of the flame retardant granules The flame retardant granules of the present invention contain a powdered flame retardant (hereinafter, simply referred to as a flame retardant) and a binder. The content of the powdered flame retardant is 80 parts by weight to 99.9 parts by weight per 100 parts by weight of the total amount of the powdered flame retardant and the binder. The flame retardant granules are formed by binding the flame retardant with the binder.

The flame retardant granules of the present invention can be added to a resin composition in various plasticizing melt processing, including melt compounding (melt kneading) of the resin composition. In the present invention, a flame retardant granule can be produced with excellent efficiency and has excellent quality stability (shape stability, uniformity of hardness, low fine powder mixing) by adding a binder and granulating the flame retardant granules. In addition, the productivity of the resin composition can be improved by using the flame retardant granules. Specifically, since the flame retardant granules are extremely stable when put into an extruder or other device, the productivity (compound processing speed per hour) of the flame retardant-containing resin composition can be dramatically improved by using the flame retardant granules. In addition, the working environment pollution caused by dust can be significantly improved, the occupational safety and health environment of the workers can be improved, and the time required for cleaning the equipment can be significantly reduced. Furthermore, the flame retardant granules of the present invention can be produced with excellent production efficiency even though they contain a large amount of flame retardant. Therefore, by using the flame retardant granules of the present invention, it is possible to improve the productivity of resin compositions or resin molded products containing high concentrations of flame retardant.

In one embodiment, the flame retardant granules can be obtained by processing a mixture (e.g., an aqueous solution or an aqueous dispersion) containing the flame retardant and the binder by any suitable method. In one embodiment, the flame retardant granules are produced by a semi-wet granulation method. The semi-wet granulation method makes the above effects more pronounced.

The flame retardant granules may be in any suitable shape. Typically, the flame retardant granules are cylindrical (pellet-shaped).

When the flame retardant granules are cylindrical, the diameter of the flame retardant granules is, for example, 2 mm to 5 mm. The length (height) of the flame retardant granules is, for example, 1 mm to 5 mm. Such a shape makes it possible to obtain flame retardant granules that are easy to handle. The diameter of the flame retardant granules can be adjusted by the diameter of the die hole of the disc plate during granulation, and the length can be adjusted by the distance between the disc plate and the cutter. By matching the flame retardant granules to the pellet size of the resin used in combination, handling properties are improved and the dispersion of the flame retardant in the molten compound is also improved.

The breaking stress of the flame retardant granules measured with a Kiya hardness tester is preferably 0.05 kg to 10 kg, more preferably 0.5 kg to 7 kg, and even more preferably 1.0 kg to 5 kg. Within these ranges, a flame retardant granule with excellent handling properties and melt processability can be obtained. Here, the breaking stress refers to the average disintegration stress measured for 20 or more granules (preferably 25 or more granules).

The moisture content of the flame retardant granules may be any appropriate moisture content. The moisture content of the flame retardant granules is preferably 10% by weight or less, more preferably 5% by weight or less, even more preferably 3% by weight or less, particularly preferably 1% by weight or less, and most preferably 0.5% by weight or less. The moisture content of the flame retardant granules is measured using an infrared moisture meter as described below.

The bulk density of the flame retardant granules is preferably 0.3 kg/L to 2.0 kg/L, and more preferably 0.5 kg/L to 2.0 kg/L. Increasing the bulk density increases the supply speed and supply stability of the flame retardant granules when melt-kneading. The bulk density is calculated by using a measuring cup, allowing the powder to fall naturally into the cup until it is filled to the brim, weighing out exactly 1 liter of volume, and measuring the weight (unit: kg/L).

A-1. Powdery flame retardant As the powdery flame retardant, any appropriate flame retardant can be used. In one embodiment, a flame retardant used in rubber, resin, etc. is used as the powdery flame retardant. In one embodiment, the powdery flame retardant is at least one selected from the group consisting of a halogen-containing compound-based flame retardant, a phosphorus-containing compound-based flame retardant, a nitrogen-containing compound-based flame retardant, an inorganic flame retardant, and a metal salt-based flame retardant. Among them, from the viewpoint of environmental compatibility, at least one selected from the group consisting of a phosphorus-containing compound-based flame retardant, a nitrogen-containing compound-based flame retardant (which may contain phosphorus as described later)-based flame retardant, and a metal salt-based flame retardant is particularly preferably used.

In one embodiment, a halogen-containing compound-based flame retardant is used as the powdered flame retardant. If a halogen-containing compound-based flame retardant is used, the effect of the flame retardant granule of the present invention can be preferably brought out. Examples of halogen-containing compound-based flame retardants include halides such as tetrabromobisphenol A, tetrabromobisphenol A-bis(2-hydroxyethyl ether), tetrabromobisphenol A-bis(2,3-dibromopropyl ether), hexabromodiphenyl ether, octabromodiphenyl ether, decabromodiphenyl ether, bis(tribromophenoxy)ethane, bis(pentabromophenoxy)ethane, bis(pentabromophenyl)ethane, and hexabromocyclodecane.

In addition, an oligomeric halogen compound may be used as the halogen-containing compound-based flame retardant. Examples of oligomeric halogen compounds include polymers of compounds such as monobromophenol, tribromophenol, pentabromophenol, tribromocresol, dibromopropylphenol, tetrabromobisphenol S, and cyanuric chloride, and copolymers of these compounds with the above-mentioned halides. In the copolymers, only one type of halide may be used, or two or more types may be used in combination.

Also, as the halogen-containing compound-based flame retardant, an oligomer of tetrabromobisphenol A, an oligomer of tetrabromobisphenol A and bisphenol A, an oligomer of tetrabromobisphenol S, an oligomer of tetrabromobisphenol S and bisphenol S, etc. may be used.

Also, a halogenated epoxy oligomer having an epoxy group in its structure may be used as the halogen-containing compound-based flame retardant.

In addition, chlorinated paraffin, chlorinated polyethylene, brominated polystyrene, ethylene bis tetrabromophthalimide, etc. may be used as the halogen-containing compound-based flame retardant.

In one embodiment, a phosphorus-containing compound-based flame retardant is used as the powdered flame retardant. By using a phosphorus-containing compound-based flame retardant, the flame retardant granule of the present invention can preferably exhibit its effect. Examples of phosphorus-containing compound-based flame retardants include phosphate esters and condensed phosphate esters, and preferred examples include triphenyl phosphate and 1,3-phenylene bis(dixylenyl) phosphate.

In one embodiment, a nitrogen-containing compound-based flame retardant is used as the powdery flame retardant. If a nitrogen-containing compound-based flame retardant is used, the effect of the flame retardant granule of the present invention can be preferably brought out. The nitrogen-containing compound-based flame retardant may contain phosphorus. Examples of the nitrogen-containing compound-based flame retardant include dialkylphosphinic acid and/or its salt, melamine condensation product, reaction product of melamine and phosphoric acid, reaction product of melamine condensation product and polyphosphoric acid, ammonium polyphosphate, benzoguanamine, tris(hydroxyethyl)isocyanurate, allantoin, glycouril, melamine, melamine cyanurate, dicyandiamide, and guanidine. Other examples include phosphazenes, and a specific example is phosphonitrilic acid phenyl ester.

In one embodiment, an inorganic flame retardant is used as the powdered flame retardant. If an inorganic flame retardant is used, the effect of the flame retardant granule of the present invention can be preferably brought out. Specific examples of inorganic flame retardants include magnesium oxide, calcium oxide, aluminum oxide, zinc oxide, manganese oxide, tin oxide, antimony oxide, boehmite, dihydrotalcite, hydrocalumite, magnesium hydroxide, calcium hydroxide, aluminum hydroxide, zinc hydroxide, tin oxide hydrate, manganese hydroxide, zinc borate, basic zinc silicate, zinc stannate, red phosphorus, etc.

In one embodiment, a metal salt-based flame retardant is used as the powdered flame retardant. If a metal salt-based flame retardant is used, the effect of the flame retardant granule of the present invention can be preferably brought out. Examples of metal salt-based flame retardants include organic phosphinic acid metal salts, organic sulfonic acid metal salts, and perfluoroalkanesulfonic acid metal salts. Specific examples include tris(diethylphosphinic acid)aluminum salt and perfluorobutanesulfonic acid potassium salt.

The size of the flame retardant may be any appropriate size. The number average particle size of the flame retardant is, for example, 10 nm to 100 μm. The size of the flame retardant may be determined by a laser diffraction method.

The bulk density of the flame retardant is preferably 0.01 kg/L to 1 kg/L, more preferably 0.05 kg/L to 0.8 kg/L, and even more preferably 0.1 kg/L to 0.5 kg/L. The flame retardant granules of the present invention are advantageous in that they can improve supply stability and supply accuracy while containing a powdered flame retardant with a low bulk density, and the use of the flame retardant granules makes it possible to stably obtain a flame retardant-containing resin composition with high productivity.

As described above, the content of the flame retardant is 80 parts by weight to 99.9 parts by weight per 100 parts by weight of the total amount of the flame retardant and the binder. Within this range, a flame retardant-containing resin composition to which flame retardancy is efficiently imparted can be obtained. The content of the flame retardant is preferably 80 parts by weight to 99 parts by weight, more preferably 85 parts by weight to 96 parts by weight, and even more preferably 88 parts by weight to 95 parts by weight per 100 parts by weight of the total amount of the flame retardant and the binder. In one embodiment, the content of the flame retardant is 89 parts by weight to 94 parts by weight per 100 parts by weight of the flame retardant granules.

A-2. Binder In one embodiment, the binder may be composed of any appropriate resin. Examples of resins constituting the binder include polyolefin resins, polyvinyl alcohol resins, polyalkylene glycol resins, polyvinylpyrrolidone resins, polyester resins, polyamide resins, acrylic resins, polyurethane resins, and epoxy resins. Among them, polyolefin resins, polyvinylpyrrolidone resins, polyester resins, polyamide resins, polyurethane resins, and epoxy resins are preferred, and polyvinylpyrrolidone resins, polyester resins, polyamide resins, polyurethane resins, and epoxy resins are particularly preferred, and polyvinylpyrrolidone resins are most preferred. Since polyvinylpyrrolidone resins are excellent in binding power, heat resistance, and compatibility with various resins, if polyvinylpyrrolidone resins are used, their effects can be preferably brought out as a binder for the flame retardant granules of the present invention. In another embodiment, polysaccharides are used as the binder. In yet another embodiment, the binder is a swelling clay mineral (e.g., smectite, vermiculite, etc.). The binder may be used alone or in combination of two or more.

In one embodiment, the binder is composed of at least one selected from the group consisting of polyolefin resins, polyvinyl alcohol resins, polyvinylpyrrolidone resins, polyester resins, polyamide resins, acrylic resins, polyurethane resins, epoxy resins, polysaccharides, and swelling clay minerals.

In one embodiment, the binder is composed of at least one resin selected from the group consisting of polyvinylpyrrolidone-based resins, polyester-based resins, polyamide-based resins, polyurethane-based resins, and epoxy-based resins.

In one embodiment, flame retardant granules are produced using a polymer liquid (polymer solution, polymer dispersion) containing a binder. The polymer liquid can efficiently and uniformly coat the flame retardant surface, resulting in flame retardant granules with less powder fall-off, high collapse hardness, and high bulk density. Furthermore, the dispersibility of the flame retardant in the flame retardant-containing resin composition can be greatly improved.

Commercially available products may be used as the binder. Examples of commercially available products include Chemipearl (registered trademark) manufactured by Mitsui Chemicals, HYPOD (registered trademark) manufactured by Dow Chemical Company, AQUACER (registered trademark) manufactured by BYK Japan, ZAIKXEN, SEPOLJON, and SEPOLEX (registered trademark) manufactured by Sumitomo Seika Chemicals, Michem (registered trademark) manufactured by Michaelman Japan, Bondic (registered trademark) manufactured by DIC Corporation, and Saibinol and Saiden Glue (registered trademark) manufactured by Saiden Chemical Industries, Ltd. Other preferred examples include ethylene-vinyl alcohol copolymer (EVOH; EVAL (registered trademark) manufactured by Kuraray Co., Ltd.), and butenediol-vinyl alcohol copolymer (BVOH; Nichigo G Polymer (registered trademark) manufactured by Mitsubishi Chemical Corporation). Further preferred examples include the aqueous sulfopolyester dispersion sold under the trademark Eastman AQ® by Eastman Chemical Company, and the salt of hexane-1,6-diamine and adipic acid (AH salt) sold by Ascend Performance, which is diluted with water to form an aqueous polymer dispersion.

The content of the binder may be any appropriate ratio depending on the size, shape, water absorption, oil absorption, bulk density, etc. of the flame retardant. The content of the binder is preferably 0.1 to 20 parts by weight, preferably 0.5 to 15 parts by weight, and more preferably 1 to 10 parts by weight, per 100 parts by weight of the total amount of the flame retardant and binder. Within such a range, the binding force to the flame retardant is preferably exerted, and a flame retardant granule with excellent handleability can be obtained.

A-3. Dispersant In one embodiment, the flame retardant granule further contains a dispersant. By adding a dispersant, a flame retardant granule that can be produced with excellent production efficiency while containing a large amount of flame retardant and has excellent quality stability (shape stability, uniformity of pellet hardness, low fine powder contamination) can be obtained. Although the flame retardant granule containing a dispersant contains a high concentration of flame retardant, the flame retardant-containing resin composition obtained by using the flame retardant granule has excellent flame retardant dispersibility.

As the dispersant, a surfactant is preferably used. The hydrophilic/hydrophobic balance in the dispersant (surfactant) can be controlled by adjusting the degree of esterification of the compound to be the dispersant, the type of fatty acid (presence or absence of hydroxyl groups, saturated or unsaturated fatty acid, alkyl chain length), and the degree of polymerization. By using a dispersant, the productivity (discharge speed) of the flame retardant granules can be improved, and the cleaning properties of the processing machine can be improved. In addition, when the thermoplastic resin and the flame retardant granules are plasticized and melt-kneaded, the dispersant acts to improve the dispersibility of the flame retardant in the resin composition and the processability of the resin composition.

Examples of the dispersing agent include fatty acids, fatty acid metal salts, fatty acid sulfonates, fatty acid amides, acrylamides, polyhydric alcohol fatty acid esters, polyglycerin fatty acid esters, etc. One type of dispersing agent may be used alone, or two or more types may be used in combination.

In one embodiment, the dispersant is at least one selected from the group consisting of polyhydric alcohol fatty acid esters, fatty acid amides, polyglycerin fatty acid esters, condensed hydroxy fatty acids, and alcohol esters of condensed hydroxy fatty acids.

The polyhydric alcohol fatty acid ester is an ester compound composed of a polyhydric alcohol and a fatty acid. Examples of polyhydric alcohol fatty acid esters include esters of polyhydric alcohols such as pentaerythritol and glycerin and fatty acids having 8 or more carbon atoms (preferably 8 to 24 carbon atoms, more preferably 10 to 22 carbon atoms).

The fatty acid amide is a compound having a structure formed by dehydration condensation of a fatty acid with ammonia or a primary or secondary amine. Examples of the fatty acid amide include saturated fatty acid monoamides such as lauric acid amide, palmitic acid amide, stearic acid amide, and behenic acid amide.

The polyglycerol fatty acid ester is an ester compound composed of polyglycerol and a fatty acid. Examples of polyglycerol fatty acid ester include diglycerol palmitate, diglycerol stearate, diglycerol oleate, decaglycerol palmitate, decaglycerol stearate, and decaglycerol oleate.

The content of the dispersant is preferably 0.1 to 10 parts by weight, more preferably 0.1 to 7 parts by weight, even more preferably 0.1 to 5 parts by weight, particularly preferably 0.5 to 3 parts by weight, and most preferably 0.5 to 2 parts by weight, relative to 100 parts by weight of the total amount of the flame retardant and binder. Within such a range, the productivity of the flame retardant granules, the flame retardancy of the resin composition, the dispersibility of the flame retardant, and the processability of the resin composition can be controlled in a well-balanced manner.

A-4. Other components The flame retardant granules may further contain any other appropriate components (additives) as necessary. Examples of the additives include antioxidants, light stabilizers, foaming agents, ultraviolet absorbers, antiblocking agents, heat stabilizers, impact modifiers, antibacterial agents, compatibilizers, processing aids, lubricants, coupling agents, flame retardant assistants, oxygen scavengers, colorants, etc.

If necessary, a flame retardant assistant may be added. Examples of the flame retardant assistant include aluminum phosphite, iron oxide, borax, zinc borate, barium metaborate, zirconium oxide, molybdenum oxide, and antimony compounds such as antimony trioxide, antimony tetraoxide, antimony pentoxide, sodium antimonate, and antimony phosphate. The flame retardant assistant may be used alone or in combination of two or more.

B. Method for Producing Flame Retardant Granules The flame retardant granules can be produced by any suitable method. For example, the flame retardant granules can be obtained by subjecting a mixture containing the flame retardant, the binder, and the dispersant added as necessary to a semi-wet granulation method.

In one embodiment, the method for producing the flame retardant granules includes a mixing step of mixing the powdered flame retardant with a binder, a granulation step of granulating the mixture obtained through the mixing step to obtain a granule precursor, and a drying step of drying the granule precursor. In one embodiment, in the mixing step, the binder is added as an aqueous liquid (aqueous solution or aqueous dispersion) containing the binder. In another embodiment, in the mixing step, a dispersant is further added.

When the aqueous liquid containing a binder is an aqueous solution (homogeneous system), the content of the binder in the aqueous liquid containing a binder is preferably 1 to 70 parts by weight, more preferably 3 to 50 parts by weight, and even more preferably 5 to 30 parts by weight, per 100 parts by weight of the aqueous liquid. Within such a range, the viscosity can be favorably adjusted when mixing the aqueous liquid and the flame retardant, and a mixed liquid with excellent dispersibility of the binder can be obtained. By using such a mixed liquid, a flame retardant granule in which the flame retardant is favorably bound can be stably obtained.

When the aqueous liquid containing a binder is an aqueous dispersion (heterogeneous system), the solids concentration of the binder in the aqueous liquid containing a binder is preferably 1% by weight to 70% by weight, more preferably 3% by weight to 60% by weight, and even more preferably 5% by weight to 50% by weight. Within these ranges, the viscosity can be favorably adjusted when mixing the aqueous liquid and the flame retardant, and a mixed liquid with excellent dispersibility of the binder can be obtained. By using such a mixed liquid, a flame retardant granule in which the flame retardant is favorably bound can be stably obtained.

The mixing ratio of the aqueous liquid containing the binder is preferably 1 to 30 parts by weight, more preferably 5 to 25 parts by weight, and even more preferably 10 to 20 parts by weight, per 100 parts by weight of the flame retardant.

In the mixing step, other components (e.g., the additives described above), a solvent (preferably, water or an alcohol aqueous solution), etc. may be further mixed. In one embodiment, the addition of these components optimizes the mixing of the aqueous liquid containing the binder and the flame retardant. The water to be added is not particularly limited, and may be, for example, tap water, distilled water, ion-exchanged water, hard water, soft water, etc. The alcohol concentration of the alcohol aqueous solution is preferably 20% by weight or more, more preferably 40% by weight or more, and even more preferably 50% by weight or more.

In the mixing process, it is preferable to mix the components at room temperature and homogenize them using any suitable mixer. Examples of mixers include a Henschel mixer, a powder kneader (KDH, KDA, CKD, CPM) (Dalton), a Spartan mixer (SPM) (Dalton), and a SP granulator (SPG) (Dalton).

The mixing time in the mixing step can be any appropriate time depending on the type of components, the type of mixer, the component blending ratio, etc. Preferably, the mixing time is set so that the surface of the flame retardant is sufficiently and uniformly covered with the binder. With a high-speed mixer such as a Henschel mixer or Spartan mixer, the processing time can be 1 to 10 minutes. On the other hand, with a powder kneader, a processing time of several minutes to 60 minutes may be required.

In the granulation process, a compression granulation method is preferably used. In addition, in the granulation process, a semi-wet granulation method can be preferably used. Examples of the compression granulation method/semi-wet granulation method include the disk pelleting method, the tableting method, and the briquetting method. From the viewpoint of the balance between productivity and the quality of the obtained flame retardant granules, the disk pelleting method is preferably used.

The basic structure of a disk pelletizer is one or two disks with many holes of 2 mm to 30 mm, and a roller for pressure-feeding the raw material into the holes of the disk. The raw material supplied between the disk and the roller, or between the two disks, is pressed into the holes of the disk as the roller rotates, forming a cylindrical extrudate. Here, the disk holes are tapered, and a compressive stress is applied from the outer periphery of the die hole as the mixture passes through the holes. The length of this tapered hole is called the effective length. The extruded granulated material precursor is cut by a cutter or the like on the back side of the disk to obtain a pellet-shaped flame retardant granulated material. The length of the granulated material precursor (resulting in a flame retardant granulated material) can be adjusted by the distance between the back side of the disk and the cutter and the number of rotations of the roller. The distance between the back side of the disk and the cutter is usually in the range of 1 mm to 30 mm, preferably in the range of 2 mm to 20 mm, and more preferably in the range of 3 mm to 10 mm.

Specific examples of the disc pelleter system include the roller disc die system, roller ring die system, double die system, and flat die system. An example of a commercially available disc pelleter system granulator is the Disc Pellet F Series manufactured by Dalton.

Any suitable method can be used as the drying method in the drying step. After the drying step, a flame retardant granule from which fine powder has been removed can be obtained by processing with a vibrating sieve or the like. Any suitable drying equipment can be used in the drying step. For example, a vibrating fluidized dryer is preferred because it can perform drying efficiently in a short time, and examples of such equipment include the VDF series vibrating fluidized dryers manufactured by Dalton.

C. Melt compound of resin and flame retardant In one embodiment, the flame retardant granules are used as a raw material for a thermoplastic resin compound. Any thermoplastic resin can be used as the thermoplastic resin.

Any suitable method may be used to produce the molten compound. For example, a kneader, a Banbury mixer, a roll, or a single-screw or multi-screw extruder having two or more screws may be used. A twin-screw extruder is preferably used. The composition obtained by melt kneading is pelletized.

Specific examples of the above-mentioned optional thermoplastic resins include, for example, high density polyethylene (HDPE), medium density polyethylene (MDPE), low density polyethylene (LDPE), polypropylene (PP), polyvinyl chloride (PVC), polyvinylidene chloride, polystyrene (PS), polyvinyl acetate (PVAc), polyurethane (PUR), fluorine-based resins, general-purpose resins such as ABS resin (acrylonitrile butadiene styrene resin), AS resin, and acrylic resin (PMMA), polyamide (PA), polyacetal (POM), polycarbonate (PC), polyphenylene ether, and modified polyphenylene ether (m- At least one selected from the group consisting of engineering plastics such as polyphenylene sulfide (PPS), polytetrafluoroethylene (PTFE), polysulfone (PSF), polyethersulfone (PES), amorphous polyarylate (PAR), liquid crystal polymer (LCP), polyetherimide (PEI), polyetheretherketone (PEEK), thermoplastic polyimide (TPI), polyamideimide (PAI), etc. Furthermore, as the optional thermoplastic resin, a biodegradable polymer may be used. Examples of biodegradable polymers include aliphatic polyester resins (e.g., homopolymers or copolymers of polycaprolactone, polylactic acid, polyethylene succinate, polybutylene succinate adipate, polyhydroxyvalerate, etc., and modified products of these homopolymers or copolymers), aliphatic/aromatic polyester resins (e.g., block polymers or random polymers of aliphatic carboxylic acids or hydroxy acids, aromatic dicarboxylic acids and 1,3-propanediol, etc.), polyvinyl alcohol resins (e.g., polyvinyl alcohol, polyvinyl acetate, polyvinyl butyrate, ethylene-vinyl alcohol copolymers, etc.), etc.

In the melt compound of the thermoplastic resin and the flame retardant granules, the flame retardant granules have excellent stability and can be easily fed into a melt kneading device such as an extruder, so the productivity of the resin composition can be dramatically improved and the flame retardant can be easily dispersed in the resin. This also contributes greatly to improving the working environment and the occupational safety and health environment for workers.

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. Note that parts and percentages are based on weight unless otherwise specified.

[Example 1]
A Henschel mixer (manufactured by Nippon Coke and Engineering Co., Ltd., product name "5FM5C/I"; processing volume: 5 L) was charged with 100 parts by weight of a powdered flame retardant (aluminum tris(diethylphosphinic acid) salt, manufactured by Clariant, product name "Exolit OP1230"; average particle size: 30 μm, bulk density: 0.5 kg/L; in the table, "A-1") and 20 parts by weight of a binder dispersion (polyolefin dispersion (aqueous PE dispersion); manufactured by Mitsui Chemicals, Inc., product name "Chemipearl A100"; polyolefin solids concentration: 40 wt %; average particle size of polyolefin particles: 4 μm; in the table, "B-1"), and the mixture was stirred and mixed at a rotation speed of 1,000 rpm for 2 minutes to obtain a mixture.
The mixture was fed into a disk pelleter (manufactured by Dalton, product name "Disc Pelleter F-5/11-175") to obtain a pellet-shaped granulated precursor. At this time, the hole diameter of the die was 3 mm, the thickness of the die plate was 15 mm, the effective length of the die hole was 10 mm, and the rotation speed of the roller of the disk pelleter was 108 rpm.
The obtained granule precursor was dried at 100° C. for 4 hours using a hot air circulation type dryer to obtain a flame retardant granule FRG-1. A photograph of the appearance of the obtained flame retardant granule (FRG-1) is shown in FIG.

[Examples 2 to 7, Comparative Examples 1 to 2]
A flame retardant granule was obtained in the same manner as in Example 1, except that the powdered flame retardant, binder, dispersant and other components (water, alcohol aqueous solution) shown in Table 1 were used in the amounts shown in Table 1. The contents of each component used are as shown in Table 2.

<Evaluation>
The flame retardant granules obtained in Examples 1 to 7 and Comparative Examples 1 and 2 were subjected to the following evaluations. The results are shown in Table 3.

(1) Granulation Property The granulation property of the obtained flame retardant granules was evaluated according to the following criteria.
Good: Granules with a diameter of 3 mm were obtained.
△: The flame retardant is in the form of granulated material, but the binding strength is insufficient and it easily falls apart.
×: The powdered flame retardant clogged the die or had no cohesiveness and did not become granular.

(2) Granulation rate The production rate (kg/h) of the flame retardant granules per hour was calculated.

(3) Bulk density The dried flame retardant granules were allowed to fall naturally into a 1-liter measure, and the measure was filled to the brim. The resultant measure had a volume of exactly 1 liter, and the weight was measured to calculate the bulk density (unit: kg/L) of the flame retardant granules.

(4) Pellet Size Twenty pellets of the flame retardant granules were taken out, and the average length and diameter of the pellets were calculated using a vernier caliper.

(5) Moisture Content The moisture content (unit: weight %) remaining in the flame retardant granules was measured using an infrared moisture meter (FD-660 manufactured by Kett Electric Laboratory).

(6) Measurement of collapse strength The collapse stress (unit: kg) of the dried flame retardant granules was measured using a Kiya hardness tester (manufactured by Shiro Sangyo Co., Ltd., product name "WPF1600-B"). The measured value was the average value of 25 granules.

(7) Measurement of Fine Powder Amount 1 kg of the flame retardant granules was weighed and sieved through a 12 mesh sieve to measure the mass percentage of the fine powder amount (unit: weight %).

As shown in Table 3, in Examples 1 to 7 (FRG-1 to FRG-7), pellet-shaped flame retardant granules with stable pellet shape, high granulation speed, and appropriate hardness can be obtained. On the other hand, in Comparative Example 1 (FRG-C1) and Comparative Example 2 (FRG-C2), since no binder is included, pellet-shaped flame retardant granules cannot be obtained, or the pellets easily crumble after drying.

[Example 8]
75 parts by weight of polyamide 6 resin (manufactured by Unitika Ltd., product name "Unitika Nylon 6 A1030BRL-1") and 25 parts by weight of flame retardant granules (FRG-1) were charged into a twin-screw extruder (manufactured by Toshiba Machine Co., Ltd., product name "TEM18SS", L/D = 48) and continuously melt-kneaded to produce pellets of a resin composition of nylon 6 resin and flame retardant ("A-1" in Table 1).
The polyamide 6 pellets and the flame retardant granules (FRG-1) were premixed in advance and quantitatively fed into the twin-screw extruder from the hopper position at the most upstream part of the extruder via a feeder. The cylinder temperature of the extruder was set to 230°C from the middle stage of the extruder onwards. The rotation speed of the main screw of the twin-screw extruder was set to 100 rpm, and the discharge speed was set to 5 kg/Hr. The melt-kneaded resin composition was extruded in the form of a strand, cooled in a water-cooled bath, and made into pellets with a length of about 3 mm.
The resulting resin composition exhibited excellent flame retardancy, with excellent supply stability of the flame retardant (A-1 in the table) to the extruder, excellent melt-kneading dispersion property, and excellent strand take-up stability.

[Examples 9 to 11]
Pellets of a resin composition were obtained in the same manner as in Example 8, except that the flame retardant granules shown in Table 4 were used in the amounts shown in Table 4.

[Comparative Example 3]
The nylon 6 was passed through the extruder alone and pelletized.

[Comparative Example 4]
Except for using a powdered flame retardant (A-1 in Table 2) instead of the flame retardant granules (FRG-1), melt kneading was performed in the same manner as in Example 8 to attempt pellet production. Because a bridge of the powdered flame retardant was formed at the chute opening, continuous production was not possible.

<Evaluation>
The pellets of the resin compositions obtained in Examples 8 to 11 and Comparative Examples 3 and 4 were subjected to the following evaluations. The results are shown in Table 4.
(a) Feeding Characteristics of Granulated Flame Retardant (or Powdered Flame Retardant) The state of continuous feeding into the inlet of the extruder was checked, and the granulation properties were evaluated according to the following criteria.
〇: Stable supply possible.
×: Bridging may occur when feeding powdered flame retardant, and feeding is unstable.

(b) Dispersibility The dispersibility of the resin and the flame retardant granules during melt kneading was evaluated based on the feel of the strand surface of the molten mixture according to the following criteria.
◯: The surface is smooth and dispersibility is good.
×: The surface is rough and dispersibility is poor.

(c) Granulation Stability of Resin Composition Pellets The take-up stability of the strand of the molten mixture of the flame retardant and the thermoplastic polymer extruded from the die was evaluated according to the following criteria.
◯: The resin composition can be granulated stably without breaking the strands.
×: The raw material supply is unstable, causing strand breakage.

(d) Evaluation of Flame Retardancy A strand of the molten mixture was cut into a length of about 10 cm, fixed vertically to a stand, and ignited at the bottom using a gas burner (flame height: 1 cm). The flame durability was evaluated according to the following criteria.
AA: Almost no ignition (excellent flame retardancy)
A: It will ignite but will self-extinguish (dripping may occur).
B: Does not extinguish inflammation

Claims (5)

A mixing step of mixing a powdered flame retardant and a binder;
a granulation step of granulating the mixture obtained through the mixing step to obtain a granulated product precursor;
A method for producing a flame retardant granule, comprising:
The flame retardant granules contain a powdered flame retardant and a binder,
the content of the powdery flame retardant is 80 parts by weight to 99.9 parts by weight per 100 parts by weight of the total amount of the powdery flame retardant and the binder;
The diameter of the flame retardant granules is 2 mm to 5 mm,
The flame retardant granules have a breaking stress of 1.0 kg to 5 kg as measured by a Kiya hardness tester;
The binder is added as an aqueous liquid containing a binder,
In the granulation step, granulation is performed by a disk pelleter method.
A method for producing flame retardant granules. The method for producing a flame retardant granule according to claim 1, wherein the powdery flame retardant is at least one selected from the group consisting of a halogen-containing compound-based flame retardant, a phosphorus-containing compound-based flame retardant, a nitrogen-containing compound-based flame retardant, an inorganic flame retardant, and a metal salt-based flame retardant . The method for producing a flame retardant granule according to claim 1 or 2, wherein the binder is at least one selected from the group consisting of polyolefin-based resins, polyvinyl alcohol-based resins, polyvinylpyrrolidone-based resins, polyester-based resins, polyamide-based resins, acrylic-based resins, polyurethane- based resins, epoxy-based resins, and polysaccharides. The method for producing a flame retardant granule according to claim 1 or 2, wherein the binder is at least one selected from the group consisting of polyvinylpyrrolidone-based resins, polyester-based resins, polyamide-based resins, polyurethane-based resins and epoxy -based resins. The method for producing a flame retardant granulated product according to claim 1 , further comprising the step of granulating the flame retardant by a semi-wet granulation method.