Method for manufacturing flame-retardant thermoplastic resin composition pellet

Abstract

To stably produce a thermoplastic resin composition pellet which is excellent in flame retardancy, has no fisheyes and has high quality.SOLUTION: A method for manufacturing a flame-retardant thermoplastic resin composition pellet includes a step (step 1) of melt-kneading 0.5 to 3 pts.mass of an unsaturated acid carboxylic acid or its anhydride (B), 20 to 60 pts.mass of a phosphorus-based flame retardant (C), and 30 to 100 pts.mass of zinc borate (D) by a twin screw extruder, with respect to 100 pts.mass of a polyphenylene ether resin (A) and manufacturing a master batch (F), and a step (step 2) of melt-kneading 70 to 30 mass% of the master batch (F) obtained in the step 1 and 30 to 70 mass% of a polyamide resin (G), based on 100 mass% of the total of (F) and (G) and pelletizing the mixture, wherein the resin temperature in the step 1 is 320°C or lower, the resin temperature in the step 2 is 320°C or lower, the cylinder set temperature in the kneading part on the most downstream side in the step 1 is 250°C or lower, and the cylinder set temperature in the kneading part on the most downstream side in the step 2 is 250°C or lower.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing flame-retardant thermoplastic resin composition pellets, and more particularly to a method for producing a flame-retardant thermoplastic resin composition containing a polyphenylene ether resin, a polyamide resin, and a flame retardant, as good pellets free from the generation of particles such as degradation products of the polyphenylene ether resin and foreign matter derived from the raw materials. [Background technology]

[0002] Polyphenylene ether resins are used in a wide range of applications due to their excellent mechanical properties, electrical properties, and heat resistance, as well as their excellent dimensional stability. However, they have poor moldability when used alone, and to improve this, they are blended with polyamide resins, and are widely used in vehicle parts, machine parts, electrical and electronic equipment parts, etc. However, since polyphenylene ether resins and polyamide resins have poor compatibility, resin compositions obtained by simply blending the two have poor mechanical properties. For this reason, it has been proposed to use modified polyphenylene ether resins obtained by modifying polyphenylene ether resins with acid anhydrides or the like.

[0003] In recent years, the above-mentioned products have been required to have a high level of flame retardancy. Patent Document 1 proposes a method for producing a flame-retardant resin composition, which avoids the problem of foaming of the phosphazene compound around the die of an extruder, by melt-kneading a powder of unmodified polyphenylene ether resin with an acid anhydride of an unsaturated aliphatic carboxylic acid and a phosphazene compound to obtain a resin composition, and then melt-kneading this resin composition with a polyamide resin.

[0004] The method of Patent Document 1 is effective in avoiding the foaming problem of phosphazene compounds. However, when the polyphenylene ether resin is melt-kneaded in an extruder to produce a resin composition, a polymer chain rearrangement reaction occurs in the polyphenylene ether resin under high temperature conditions, which causes a crosslinking reaction, which easily generates burnt foreign matter (also called "pimples"). This reaction is particularly likely to proceed in an oxygen atmosphere, which makes the generation of burnt foreign matter (pimples) more pronounced. These foreign matter (also called "pimples") exist in the resin composition and significantly impair the appearance of the molded product and cause a decrease in mechanical properties such as toughness. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-217756 Summary of the Invention [Problem to be solved by the invention]

[0006] Under normal production conditions, the amount of particles mentioned above is very small, on the order of a few grams per ton of resin, but in recent years, the required specifications for particles have become increasingly stringent, and even such a small amount can be fatal, especially for products such as films and sheets. Furthermore, when manufacturing using an extruder, a screen mesh is often installed downstream of the extruder screw, but foreign matter and agglomerated particles can clog the screen mesh in a short period of time, causing the resin pressure to rise and vent up, significantly reducing productivity. The object (purpose) of the present invention is to solve the above-mentioned problems and to provide a method for producing a flame-retardant polyphenylene ether resin / polyamide resin alloy (pellet) that suppresses the generation of particles to an extremely high level, and that enables stable, continuous production with high productivity. [Means for solving the problem]

[0007] As a result of extensive investigations into solving the above-mentioned problems, the present inventors have found that the glass transition temperature of polyphenylene ether resin is as high as about 210°C and that a higher temperature is required to melt it. However, because such a high-temperature environment promotes burning and the generation of particles, it is important to keep the resin temperature at 320°C or lower during melt-kneading in the extruder and to set the cylinder temperature in the kneading section to 250°C or lower. They have also found that the above-mentioned problems can be solved by blending specific amounts of an unsaturated acid carboxylic acid or its anhydride, a phosphorus-based flame retardant, and zinc borate with polyphenylene ether resin, melt-kneading them in a twin-screw extruder to produce a masterbatch, and melt-kneading and pelletizing the obtained masterbatch with a polyamide resin, thereby arriving at the present invention. The present invention relates to the following method for producing flame-retardant thermoplastic resin composition pellets and the pellets.

[0008] 1. A method comprising: a step (step 1) of melt-kneading 100 parts by mass of a polyphenylene ether resin (A) with a twin-screw extruder to produce a masterbatch (F); and a step (step 2) of melt-kneading the masterbatch (F) obtained in step 1 and a polyamide resin (G) at 70 to 30 mass% of the masterbatch (F) and 30 to 70 mass% of the polyamide resin (G), based on 100 mass% of the total of (F) and (G), and pelletizing the masterbatch (F) and polyamide resin (G), The resin temperature in step 1 is 320°C or less, and the resin temperature in step 2 is 320°C or less, A method for producing flame-retardant thermoplastic resin composition pellets, characterized in that the cylinder set temperature in the most downstream kneading section in step 1 is 250°C or less, and the cylinder set temperature in the most downstream kneading section in step 2 is 250°C or less. 2. The method according to the above item 1, wherein the twin-screw extruder is a fully intermeshing co-rotating twin-screw extruder, and the total length of the kneading section is 5D to 12D (D is the cylinder diameter). 3. The method according to 1 or 2 above, wherein the phosphorus-based flame retardant (C) is a phosphazene compound. 4. The method according to 1 or 2 above, wherein the particle size of the zinc borate (D) is 0.1 to 10 μm in terms of median diameter (D50) determined by a wet light scattering method. 5. Flame-retardant thermoplastic resin composition pellets obtained by the production method described in 1 to 4 above. [Effects of the Invention]

[0009] According to the manufacturing method of the present invention, it is possible to produce highly flame-retardant thermoplastic resin composition pellets with very few particles, enabling stable continuous production with high productivity. The resulting pellets can be used to produce molded articles with excellent flame retardancy, even if they are very small, with almost no particles. They can also be formed into sheets, films, etc., and even sheets and films with very few particles can be molded. Furthermore, because the generation of particles is very low, venting during production is less likely to occur, nozzle clogging during molding is less likely, and molded articles can be produced continuously and stably. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a conceptual diagram of a screw configuration of an extruder used in Examples or Comparative Examples. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention will be described in detail below with reference to embodiments and examples, but the present invention is not limited to the embodiments and examples shown below and can be implemented with any modifications within the scope of the present invention. In this specification, the symbol "to" is used to mean that the numerical values ​​before and after it are included as the lower limit and upper limit.

[0012] The production method of the present invention comprises the steps of: a step 1 of melt-kneading 100 parts by mass of polyphenylene ether resin (A) with a twin-screw extruder to produce a masterbatch (F); and a step 2 of melt-kneading the masterbatch (F) obtained in step 1 and polyamide resin (G) in an amount of 70 to 30% by mass of masterbatch (F) and 30 to 70% by mass of polyamide resin (G), based on 100% by mass of the total of (F) and (G), and pelletizing the masterbatch (F) and polyamide resin (G), The resin temperature in step 1 is 320°C or less, and the resin temperature in step 2 is 320°C or less, The cylinder temperature setting in the most downstream kneading section in process 1 is 250°C or less, and the cylinder temperature setting in the most downstream kneading section in process 2 is 250°C or less. The resin temperature in processes 1 and 2 refers to the temperature of the strand emerging from the nozzle closest to the geometric center of the die, measured with a contact thermocouple thermometer immediately after it leaves the die. Typically, in flat dies (dies with long horizontal nozzles arranged horizontally), the temperature of the strand emerging from the nozzle closest to the (geometric) center of the die tends to be higher than the other strands (the temperature of the strands at both ends tends to be lower due to the influence of the die holder temperature). The temperature of the strand closest to the (geometric) center of the die best reflects the resin temperature from the tip of the extruder screw to the die holder. Therefore, the resin temperature is the temperature of the strand emerging from the nozzle closest to the (geometric) center of the die. If there are an even number of nozzles, the resin temperature is the average temperature of the two strands emerging from the two nozzles closest to the (geometric) center of the die. Some dies are also circular (nozzles arranged circumferentially). In this case, the temperature of the topmost strand is the resin temperature.

[0013] Each component used in the present invention will be explained below.

[0014] [Polyphenylene ether resin (A)] The polyphenylene ether resin (A) is a polymer having a structural unit represented by the following formula in the main chain, and may be either a homopolymer or a copolymer.

[0015] [ka] (wherein two R a each independently represents a hydrogen atom, a halogen atom, a primary or secondary alkyl group, an aryl group, an aminoalkyl group, a haloalkyl group, a hydrocarbonoxy group, or a halohydrocarbonoxy group; b each independently represents a hydrogen atom, a halogen atom, a primary or secondary alkyl group, an aryl group, a haloalkyl group, a hydrocarbonoxy group, or a halohydrocarbonoxy group, provided that two R a cannot both become hydrogen atoms.)

[0016] R a and R b is preferably a hydrogen atom, a primary or secondary alkyl group, or an aryl group. Suitable examples of the primary alkyl group include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-amyl group, an isoamyl group, a 2-methylbutyl group, a 2,3-dimethylbutyl group, a 2-, 3-, or 4-methylpentyl group, or a heptyl group. Suitable examples of the secondary alkyl group include an isopropyl group, a sec-butyl group, or a 1-ethylpropyl group. In particular, Ra is preferably a primary or secondary alkyl group having 1 to 4 carbon atoms or a phenyl group. Rb is preferably a hydrogen atom.

[0017] Suitable homopolymers of polyphenylene ether resins include, for example, polymers of 2,6-dialkylphenylene ethers such as poly(2,6-dimethyl-1,4-phenylene ether), poly(2,6-diethyl-1,4-phenylene ether), poly(2,6-dipropyl-1,4-phenylene ether), poly(2-ethyl-6-methyl-1,4-phenylene ether), and poly(2-methyl-6-propyl-1,4-phenylene ether). Examples of the copolymer include 2,6-dialkylphenol / 2,3,6-trialkylphenol copolymers such as 2,6-dimethylphenol / 2,3,6-trimethylphenol copolymer, 2,6-dimethylphenol / 2,3,6-triethylphenol copolymer, 2,6-diethylphenol / 2,3,6-trimethylphenol copolymer, and 2,6-dipropylphenol / 2,3,6-trimethylphenol copolymer; graft copolymers in which styrene is graft polymerized onto poly(2,6-dimethyl-1,4-phenylene ether); and graft copolymers in which styrene is graft polymerized onto 2,6-dimethylphenol / 2,3,6-trimethylphenol copolymer.

[0018] As the polyphenylene ether resin in the present invention, poly(2,6-dimethyl-1,4-phenylene ether) and 2,6-dimethylphenol / 2,3,6-trimethylphenol random copolymer are particularly preferred.

[0019] The molecular weight of the polyphenylene ether resin is preferably such that the intrinsic viscosity measured in chloroform at 30°C is 0.2 to 0.8 dL / g, more preferably 0.3 to 0.6 dL / g. By setting the intrinsic viscosity to 0.2 dL / g or more, the mechanical strength of the resin composition tends to be further improved, while by setting it to 0.8 dL / g or less, the fluidity tends to be further improved and molding processability tends to be easier. Furthermore, two or more polyphenylene ether resins with different intrinsic viscosities may be used in combination to achieve an intrinsic viscosity within this range.

[0020] The method for producing polyphenylene ether resins is not particularly limited, and known methods can be used, such as oxidative polymerization of a monomer such as 2,6-dimethylphenol in the presence of an amine copper catalyst. The intrinsic viscosity can be controlled within a desired range by selecting the reaction conditions. The intrinsic viscosity can be controlled by selecting conditions such as polymerization temperature, polymerization time, and catalyst amount. Polyphenylene ether resins produced by these methods are usually in powder form.

[0021] The polyphenylene ether resin used in the present invention preferably has a median diameter (D50) of 1000 μm or less as measured by the dry light scattering method. This is because a smaller particle diameter makes it less likely for zinc borate particles to form when kneaded with zinc borate (D), makes it easier to mix with the phosphorus-based flame retardant (C), and makes it easier to react with the unsaturated carboxylic acid or its anhydride (B). It is more preferably 900 μm or less, even more preferably 800 μm or less, and particularly preferably 750 μm or less. A particle diameter of 100 μm or more is preferable. If it is less than 100 μm, flashing and aggregation tend to occur.

[0022] In the present invention, one type of polyphenylene ether resin may be used alone, or two or more types may be used in combination.

[0023] [Unsaturated carboxylic acid or its anhydride (B)] Examples of the unsaturated carboxylic acid or anhydride (B) include fumaric acid, maleic anhydride, itaconic anhydride, chloromaleic anhydride, citraconic anhydride, butenyl succinic anhydride, tetrahydrophthalic anhydride, and the acids. These unsaturated carboxylic acid anhydrides and / or unsaturated carboxylic acids may be used alone or in combination. Among the above, maleic anhydride and / or maleic acid are preferred, and maleic anhydride is most preferred. Maleic anhydride has high reactivity with polyphenylene ether resins and polyamide resins, and easily forms a crosslinked structure between the polyphenylene ether resin and the polyamide resin, making it possible to significantly improve the dispersibility of both resins.

[0024] [Phosphorus-based flame retardants (C)] The phosphorus-based flame retardant (C) is not particularly limited as long as it improves the flame retardancy of the resin composition, but a phosphoric acid ester compound is preferred. The phosphorus-based flame retardant may be used alone or in combination of two or more different compositions.

[0025] An example of the phosphorus-based flame retardant (C) is one represented by the following formula (1). [ka] (In the formula, R 1 , R 2 , R 3 , R 4 are each independently an aryl group which may be substituted, X is a divalent aromatic group which may have other substituents, and n is a number from 0 to 5.

[0026] In the above formula, R 1 ~R 4 Examples of the aryl group represented by X include a phenyl group and a naphthyl group. Examples of the divalent aromatic group represented by X include a phenylene group, a naphthylene group, and a group derived from a bisphenol. Examples of the substituents on these groups include an alkyl group, an alkoxy group, and a hydroxy group. When n is 0, the group is a phosphate ester, and when n is greater than 0, the group is a condensed phosphate ester (which may be a mixture).

[0027] Specific examples of such phosphate ester compounds include bisphenol A bisphosphate, hydroquinone bisphosphate, resorcinol bisphosphate, and substitution products and condensation products thereof. Commercially available condensed phosphate ester compounds that can be suitably used as such components are sold by Daihachi Chemical Industry Co., Ltd. under the trade names "CR733S" (resorcinol bis(diphenyl phosphate)), "CR741" (bisphenol A bis(diphenyl phosphate)), and "PX200" (resorcinol bis(dixylenyl phosphate)), and are readily available.

[0028] Phosphazene compounds can also be used as the phosphorus-based flame retardant (C). In particular, it is desirable to use phosphazene compounds with a high phosphorus concentration in order to achieve high flame retardancy. Compared to organic phosphate ester compounds, the use of phosphazene compounds can effectively increase the flame retardancy of polyphenylene ether resins, and can also improve mechanical properties and heat resistance.

[0029] <Phosphazene compounds> The phosphazene compound is an organic compound having a -P=N- bond in the molecule, and is preferably at least one compound selected from the group consisting of a cyclic phosphazene compound represented by the following general formula (2), a chain phosphazene compound represented by the following general formula (3), and a crosslinked phosphazene compound obtained by crosslinking at least one phosphazene compound selected from the group consisting of the following general formulas (2) and (3) via a crosslinking group.

[0030] [ka] In formula (2), a is an integer of 3 to 25, and R 5 and R 6 may be the same or different and represent an alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryloxy group, an amino group, a hydroxy group, an aryl group, or an alkylaryl group.

[0031] [ka] In the formula, R 7 , R 8may be the same or different and represent an alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, an aryloxy group, an amino group, a hydroxy group, an aryl group, or an alkylaryl group. R 9 is -N=P(OR 7 ) 3 Group, -N=P(OR 8 ) 3 Group, -N=P(O)OR 7 Group, -N=P(O)OR 8 R represents at least one selected from the group 10 is -P(OR 7 ) 4 groups, -P(OR 8 ) 4 groups, -P(O)(OR 7 ) 2 groups, -P(O)(OR 8 ) represents at least one selected from the following two groups.

[0032] In the above formulas (2) and (3), examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a t-butyl group, a pentyl group, a hexyl group, an octyl group, a decyl group, and a dodecyl group. In general, an alkyl group having 1 to 6 carbon atoms, such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a t-butyl group, a pentyl group, or a hexyl group, is preferred, and an alkyl group having 1 to 4 carbon atoms, such as a methyl group, an ethyl group, or a propyl group, is particularly preferred.

[0033] Examples of the cycloalkyl group include cycloalkyl groups having 5 to 14 carbon atoms, such as a cyclopentyl group and a cyclohexyl group, and among these, cycloalkyl groups having 5 to 8 carbon atoms are preferred. Examples of the alkenyl group include alkenyl groups having 2 to 8 carbon atoms, such as vinyl and allyl groups, and examples of the cycloalkenyl group include cycloalkenyl groups having 5 to 12 carbon atoms, such as cyclopentyl and cyclohexyl groups. Examples of the alkynyl group include alkynyl groups having 2 to 8 carbon atoms, such as ethynyl and propynyl groups, and aryl groups, such as ethynylbenzene groups.

[0034] Examples of the aryl group include aryl groups having 6 to 20 carbon atoms, such as a phenyl group, a methylphenyl (i.e., tolyl) group, a dimethylphenyl (i.e., xylyl) group, a trimethylphenyl group, and a naphthyl group. Among these, aryl groups having 6 to 10 carbon atoms are preferred, and a phenyl group is particularly preferred. Examples of the alkylaryl group include aralkyl groups having 6 to 20 carbon atoms, such as benzyl, phenethyl, and phenylpropyl groups. Of these, aralkyl groups having 7 to 10 carbon atoms are preferred, with benzyl being particularly preferred.

[0035] Among them, R in the above general formula (2) 5 and R 6 , R in the above general formula (3) 7 and R 8 Preferably, R is an aryl group or an arylalkyl group. By using such an aromatic phosphazene, the thermal stability of the thermoplastic resin composition can be effectively improved. From this viewpoint, 5 , R 6 , R 7 and R 8 is more preferably an aryl group, and particularly preferably a phenyl group.

[0036] Examples of the cyclic and / or chain phosphazene compounds represented by the general formulas (2) and (3) include (poly)tolyloxyphosphazenes such as phenoxyphosphazene, o-tolyloxyphosphazene, m-tolyloxyphosphazene, and p-tolyloxyphosphazene, (poly)xylyloxyphosphazenes such as o,m-xylyloxyphosphazene, o,p-xylyloxyphosphazene, and m,p-xylyloxyphosphazene, o,m,p-trimethylphenyloxyphosphazene, and phenoxy-o-tolyloxyphosphazene, Examples include (poly)phenoxytolyloxyphosphazenes such as phenoxy o,m-xylyloxyphosphazene, phenoxy o,p-xylyloxyphosphazene, phenoxy m-tolyloxyphosphazene and phenoxy p-tolyloxyphosphazene, (poly)phenoxytolyloxyxylyloxyphosphazenes such as phenoxy o,m-xylyloxyphosphazene, phenoxy o,p-xylyloxyphosphazene and phenoxy m,p-xylyloxyphosphazene, and phenoxy o,m,p-trimethylphenyloxyphosphazene, and preferred are cyclic and / or chain phenoxyphosphazenes.

[0037] The cyclic phosphazene compound represented by the general formula (2) includes R 5 and R 6 is a phenyl group. Examples of such cyclic phenoxyphosphazene compounds include compounds such as phenoxycyclotriphosphazene, octaphenoxycyclotetraphosphazene, and decafenoxycyclopentaphosphazene, which are obtained by isolating cyclic chlorophosphazenes such as hexachlorocyclotriphosphazene, octachlorocyclotetraphosphazene, and decachlorocyclopentaphosphazene from a mixture of cyclic and linear chlorophosphazenes obtained by reacting ammonium chloride and phosphorus pentachloride at a temperature of 120 to 130°C, and then substituting them with a phenoxy group. Furthermore, the cyclic phenoxyphosphazene compound is preferably a compound represented by general formula (2) in which a is an integer of 3 to 8, and may be a mixture of compounds with different a's.

[0038] The average of the above a is preferably 3 to 5, and more preferably 3 to 4. Among these, a mixture of compounds in which those in which a=3 are 50% by mass or more, those in which a=4 are 10 to 40% by mass, and those in which a=5 or more are 30% by mass or less in total is preferred.

[0039] The chain phosphazene compound represented by the general formula (3) includes R 7 and R 8 is a phenyl group. Examples of such chain phenoxyphosphazene compounds include compounds obtained by ring-opening polymerizing hexachlorocyclotriphosphazene obtained by the above method at a temperature of 220 to 250°C and substituting the resulting linear dichlorophosphazene having a degree of polymerization of 3 to 10,000 with a phenoxy group. In the linear phenoxyphosphazene compound, b in general formula (3) is preferably 3 to 1,000, more preferably 3 to 100, and even more preferably 3 to 25.

[0040] Examples of the crosslinked phosphazene compound include compounds having a crosslinked structure of a 4,4'-diphenylene group, such as a compound having a crosslinked structure of 4,4'-sulfonyldiphenylene (i.e., a bisphenol S residue), a compound having a crosslinked structure of a 2,2-(4,4'-diphenylene)isopropylidene group, a compound having a crosslinked structure of a 4,4'-oxydiphenylene group, and a compound having a crosslinked structure of a 4,4'-thiodiphenylene group.

[0041] The crosslinked phosphazene compound is a compound represented by the general formula (2) in which R 5 , R 6 a bridged phenoxyphosphazene compound obtained by crosslinking a cyclic phenoxyphosphazene compound in which R is a phenyl group with the above-mentioned crosslinking group, or 7 , R 8 is a phenyl group, is crosslinked by the above crosslinking group, is preferred from the viewpoint of flame retardancy, and a bridged phenoxyphosphazene compound is more preferred in which a cyclic phenoxyphosphazene compound is crosslinked by the above crosslinking group.

[0042] The content of phenylene groups in the bridged phenoxyphosphazene compound is usually 50 to 99.9%, preferably 70 to 90%, based on the total number of phenyl groups and phenylene groups in the cyclic phosphazene compound represented by general formula (2) and / or the chain phenoxyphosphazene compound represented by general formula (3). It is particularly preferred that the bridged phenoxyphosphazene compound is a compound having no free hydroxyl groups in its molecule. In the present invention, the phosphazene compound is preferably at least one selected from the group consisting of cyclic phenoxyphosphazene compounds represented by the above general formula (2) and crosslinked phenoxyphosphazene compounds obtained by crosslinking the cyclic phenoxyphosphazene compound represented by the above general formula (2) with a crosslinking group, from the viewpoint of flame retardancy and mechanical properties of the thermoplastic resin composition.

[0043] [Zinc borate (D)] Zinc borate (D) includes zinc borate (2ZnO·3B2O3) and zinc borate 3.5hydrate (2ZnO·3B2O3·3.5H2O). The zinc borate (D) preferably has a median diameter (D50) of 0.1 to 10 μm, more preferably 0.5 to 6 μm, as measured by a wet light scattering method. By using zinc borate with a median diameter of 0.1 to 10 μm, clogging of the screen mesh in the extruder does not occur even when used alone, and agglomerates tend not to form.

[0044] Each step of the production method of the present invention will be described in detail below.

[0045] [Process 1] In the present invention, first, in step 1, a polyphenylene ether resin (A), an unsaturated carboxylic acid or its anhydride (B), a phosphorus-based flame retardant (C), and zinc borate (D) are charged into a twin-screw extruder and melt-kneaded to produce a masterbatch (F).

[0046] The amount of each component in step 1 is 0.5 to 3 parts by mass of the unsaturated carboxylic acid or its anhydride (B) relative to 100 parts by mass of the polyphenylene ether resin (A), preferably 0.8 parts by mass or more, more preferably 1 part by mass or more, and preferably 2.5 parts by mass or less, more preferably 2 parts by mass or less. The phosphorus-based flame retardant (C) is 20 to 60 parts by mass, preferably 25 parts by mass or more, more preferably 30 parts by mass or more, and preferably 50 parts by mass or less, more preferably 45 parts by mass or less. The amount of zinc borate (D) is 30 to 100 parts by mass, preferably 40 parts by mass or more, more preferably 50 parts by mass or more, and preferably 90 parts by mass or less, more preferably 80 parts by mass or less, and even more preferably 70 parts by mass or less.

[0047] The twin-screw extruder used in step 1 is preferably a fully intermeshing co-rotating twin-screw extruder having two screws rotating in the same direction inside the barrel, with a kneading section consisting of multiple kneading disks intermeshing midway between the screws. The kneading section is a region that applies high shear while suppressing the molten resin's progression in the extrusion direction so that kneading is carried out effectively. There may be one kneading section, but it is also preferable to provide two kneading sections to achieve more effective kneading, or three or more kneading sections may be provided. The twin-screw extruder is preferably a vent type having a vent portion.

[0048] The twin-screw extruder used in step 2 described below is preferably configured similarly to the above, and the screw configuration and the disk configuration of the kneading section are preferably configured similarly to those described below.

[0049] A twin-screw extruder has a main raw material hopper, a cylinder equipped with a vent, and a die holder attached to the tip via a flange. The screw inside the cylinder is rotated by a motor via a screw connection and a gearbox.

[0050] Preferred kneading discs and the like used in the kneading section include an R kneading disc, an N kneading disc, an L kneading disc, an L screw, a seal ring and the like.

[0051] The R kneading disc is also called a progressive kneading disc (hereinafter sometimes referred to as R), and usually has two or more blades with a twist angle Θ of 10 to 75 degrees. By setting the blades at a predetermined angle in this way, it is possible to feed the resin and apply a strong shear force.

[0052] The N kneading disc is also called the orthogonal kneading disc (hereinafter sometimes referred to as N), and usually has two or more blades with a blade twist angle Θ of 75 to 105 degrees. Because the blades are installed at approximately 90 degrees offset, there is almost no force to feed the resin, but the kneading power is strong.

[0053] The L kneading disc is also called a reverse feed kneading disc (hereinafter sometimes referred to as L), and usually has two or more blades with a twist angle Θ of -10 to -75 degrees. The L kneading disc is an element with the ability to block incoming resin and increase pressure by working in the direction of returning the resin that has been fed. By installing it downstream of the element that promotes kneading, it blocks the resin and exerts a powerful kneading effect.

[0054] The L screw, also known as a reverse feed screw, is a screw that spirals in the opposite direction to a normal feed screw, and is an element that has the ability to block resin and increase pressure in the direction that returns the fed resin. Like the L kneading disc, by installing it downstream of the element that promotes kneading, it blocks resin and exerts a powerful kneading effect.

[0055] The blades mentioned above are usually elliptical, with flats at the two vertices of the ellipse. These blades are also called disks, and each kneading disk is usually made up of 3 to 7 disks. These disks may also be roughly triangular with three vertices, and are also called three-row kneading disks. Similarly, there are R, N, and L types. These can also be used in the same way. Some kneading disks have their vertices twisted in the direction of the screw axis, and similar kneading effects can be obtained.

[0056] The seal ring is a ring-shaped device fitted to the screw, blocking approximately 70-90% of the flow path and causing the resin flow to stagnate, thereby increasing the resin pressure.Like the kneading disc, by installing it downstream of the element that promotes kneading, it can block the resin and exert a powerful kneading effect.

[0057] Usually, the kneading section is composed of the above-mentioned kneading disks and seal rings, but in other cases, a mixing screw, a rotor screw, or a reverse full-flight screw may also be used.

[0058] Mixing screws are made by cutting off the crests of screw flights, and are single-, double-, or triple-start or reverse-start screws that have strong shear dispersion forces. There are forward-start notched mixing screws and reverse-start notched mixing screws.

[0059] The rotor screw has elliptical (two-blade structure) or triangular rotor blades, and the gap (tip clearance) between the rotor and the inner wall surface of the barrel allows for powerful shearing force to be generated. The reverse full-flight screw is a screw that runs in the opposite direction to the feed screw and has a strong resin rising force.

[0060] The kneading section is a combination of these screws and kneading discs, with devices for blocking or pressurizing the resin, L discs, reverse feed screws, etc. placed downstream, and devices for promoting kneading such as N kneading placed in front of them, and R kneading with feeding capabilities placed further in front of that. These allow the resin to accumulate and demonstrate a strong kneading function. The kneading section is the area where the resin fills and accumulates using these devices, and when it is composed of only kneading discs, it is preferable to arrange them in the order R, N, L.

[0061] The kneading section may be integrated into one location, or may be divided into two or more. It is preferable to divide the kneading section into two or more locations so as not to raise the resin temperature too much. For example, a normal feeding flight-like element may be inserted between multiple kneading discs, and the length of such a feeding flight-like element is not included in the kneading section length, which is defined as the preferred length of each kneading section as described below. When composed of kneading discs, it is preferable that they are arranged in the order R, N, and L from downstream. When the kneading section is divided into two or more sections, the most downstream kneading section refers to the most downstream kneading section as seen from the base of the screw, and when there is only one kneading section, that kneading section becomes the most downstream kneading section.

[0062] In order to react the polyphenylene ether resin with the unsaturated carboxylic acid or its anhydride in step 1, strong kneading is required. Therefore, the total length of the kneading section is preferably 5D or more (D means the cylinder diameter of the extruder). Furthermore, to prevent the polyphenylene ether resin from burning, it is necessary that the kneading is not too strong. Therefore, 12D or less is preferable. A more preferable range is 6D to 11D, and even more preferably 7D to 10D.

[0063] In the present invention, the cylinder temperature in the most downstream kneading section in step 1 is set to 250°C or lower, and the resin temperature in step 1 is set to 320°C or lower, which are lower than usual conditions. The cylinder temperature in the most downstream kneading section is preferably set to 240°C or lower, more preferably 235°C or lower, and even more preferably 230°C or lower, and is preferably 210°C or higher, and more preferably 220°C or higher. The resin temperature is preferably 310°C or lower, more preferably 305°C or lower, and even more preferably 300°C or lower, and is preferably 270°C or higher, and more preferably 280°C or higher. Since the resin temperature is highest in the most downstream kneading section, it is possible to effectively lower the resin temperature by lowering the cylinder temperature set there. The high resin temperature can be cooled by the cylinder of the most downstream kneading section, making it possible to lower the resin temperature. As mentioned above, the cylinder temperature set in the most downstream kneading section is preferably 240°C or lower, more preferably 230°C or lower. The temperature setting of the die holder is higher than this, preferably 250°C or higher, in order to stabilize the strands emerging from the die.

[0064] As mentioned above, polyphenylene ether resin is susceptible to crosslinking reactions due to heat, which can cause polymer chain transitions. This can lead to the formation of lumps. This reaction is particularly prevalent in oxygen-rich environments, resulting in significant lumping. Polyphenylene ether resin has a high glass transition temperature of approximately 210°C, requiring temperatures even higher to melt. This high temperature environment promotes burning and the formation of lumps. To prevent the formation of burnt particles, the melt-kneading temperature must be kept below 320°C. The polymerization product of polyphenylene ether resin is typically obtained as a fine powder, with a median diameter often below 2000 μm. To form a polymer alloy of polyphenylene ether resin and polyamide resin, an unsaturated carboxylic acid or its anhydride is used as a crosslinking agent. The reaction between a polyphenylene ether resin and an unsaturated carboxylic acid or its anhydride is usually slower than the reaction between a polyamide resin and an unsaturated carboxylic acid or its anhydride. Therefore, it is effective to carry out a two-step reactive kneading process (steps 1 and 2) in which, in step 1, a polyphenylene ether resin is first reacted with an unsaturated carboxylic acid or its anhydride, and then, in step 2, a polyamide resin is reacted with the polyphenylene ether resin.

[0065] The zinc borate used in the present invention is also a powder. Zinc borate has strong coagulation properties and is easily coagulated and tends to become coarse and form particles due to the force (compression force) applied during melt-kneading. In particular, since the raw material polyamide resin is in the form of pellets, when zinc borate and polyamide resin are kneaded together, the force applied during melting of the pellets acts as a compressive force on the other components, causing the zinc borate to easily coagulate and become coarse and form particles. For this reason, zinc borate must be blended and kneaded during the reactive kneading of the polyphenylene ether resin and the unsaturated acid carboxylic acid or its anhydride, i.e., in step 1. For this reason, the polyphenylene ether resin is preferably in powder form, and its median diameter is preferably 1000 μm or less, more preferably 900 μm or less.

[0066] Phosphorus-based flame retardants have a high affinity and are compatible with polyphenylene ether resins. Furthermore, because the melting point of phosphorus-based flame retardants is low, they lower the glass transition temperature and viscosity of the polyphenylene ether resin, making it possible to reduce the resin temperature during kneading. In other words, in step 1, it is necessary to add and knead the polyphenylene ether resin, the unsaturated carboxylic acid or its anhydride, zinc borate, and the phosphorus-based flame retardant. This allows the reaction between the polyphenylene ether resin and the unsaturated carboxylic acid or its anhydride to proceed, suppresses the resin temperature, reduces burnt foreign matter derived from the polyphenylene ether resin, and further suppresses the aggregation and coarsening of zinc borate.

[0067] The resin composition (masterbatch) thus produced in step 1, i.e., the masterbatch consisting of a reaction product of polyphenylene ether and unsaturated carboxylic acid or its anhydride, a phosphorus-based flame retardant, and zinc borate, contains very little burnt foreign matter of polyphenylene ether resin and very little zinc borate aggregates.

[0068] By melt-kneading this masterbatch and polyamide resin in step 2, a crosslinking reaction occurs between the polyphenylene ether resin in the masterbatch and the reaction product of the unsaturated acid carboxylic acid or its anhydride, and the polyamide resin, forming a polymer alloy with a fine structure with very little burnt foreign matter or zinc borate aggregates, and a uniform, highly flame-retardant resin composition is formed.

[0069] [Process 2] In step 2, the masterbatch obtained in step 1 is melt-kneaded with a polyamide resin and pelletized.

[0070] The twin-screw extruder used in step 2 is preferably configured similarly to that described in step 1, and the screw configuration, disk configuration of the kneading section, etc. are also preferably configured similarly to that described in step 1.

[0071] When the masterbatch obtained in step 1 and the polyamide resin are melt-kneaded in step 2, the cylinder temperature in the most downstream kneading section is set to 250°C or lower, and the resin temperature in step 1 is set to 320°C or lower, so that temperatures lower than usual are applied. The cylinder temperature in the most downstream kneading section is preferably set to 240°C or lower, more preferably 235°C or lower, and even more preferably 230°C or lower, and is preferably 210°C or higher, and more preferably 220°C or higher. The resin temperature is preferably 310°C or lower, more preferably 305°C or lower, and even more preferably 300°C or lower, and is preferably 270°C or higher, and more preferably 280°C or higher. In the above steps 1 and 2, since polyphenylene ether resins tend to burn at high temperatures and generate foreign matter, the resin temperatures must both be 320°C or lower, more preferably 310°C or lower, and even more preferably 300°C or lower. A lower resin temperature can reduce the amount of particles resulting from polyphenylene ether burning, but the cylinder temperature setting for the most downstream kneading section in both Process 1 and Process 2 must be 250°C or lower. In step 2, the resin temperature is also highest in the most downstream kneading section. By lowering the cylinder temperature there, it is possible to effectively lower the resin temperature. The high resin temperature can be cooled by the cylinder of the most downstream kneading section, making it possible to lower the resin temperature. The cylinder temperature of the most downstream kneading section is more preferably 240°C or lower, and even more preferably 230°C or lower. The temperature setting of the die holder is higher than this, preferably 250°C or higher, in order to stabilize the strands emerging from the die.

[0072] In order to react the masterbatch with the polyamide resin in step 2, strong kneading is required. Therefore, the total length of the kneading section is preferably 5D or more. Furthermore, to prevent the polyphenylene ether resin from burning, the kneading must not be too strong. Therefore, 12D or less is preferable. The more preferable range is 6D to 11D, and even more preferably 7D to 10D.

[0073] [Polyamide resin (G)] The polyamide resin (G) is not particularly limited, and examples thereof include polycaproamide (polyamide 6), polytetramethylene adipamide (polyamide 46), polyhexamethylene adipamide (polyamide 66), polyundecamethylene adipamide (polyamide 116), polymetaxylylene adipamide (polyamide MXD6), polyparaxylylene adipamide (polyamide PXD6), polyxylylene sebamide (polyamide 116), and the like. Polyamide (Polyamide XD10), Polytetramethylene sebacamide (Polyamide 410), Polyhexamethylene sebacamide (Polyamide 610), Polydecamethylene adipamide (Polyamide 106), Polydecamethylene sebacamide (Polyamide 1010), Polyhexamethylene dodecamide (Polyamide 612), Polydecamethylene dodecamide (Polyamide 1012), Polyhexamethylene isoflurane Examples of the polyamide include polytetramethylene terephthalamide (polyamide 6I), polytetramethylene terephthalamide (polyamide 4T), polypentamethylene terephthalamide (polyamide 5T), poly-2-methylpentamethylene terephthalamide (polyamide M-5T), polyhexamethylene terephthalamide (polyamide 6T), polyhexamethylene hexahydroterephthalamide (polyamide 6T(H)), polynonamethylene terephthalamide (polyamide 9T), polydecamethylene terephthalamide (polyamide 10T), polyundecamethylene terephthalamide (polyamide 11T), polydodecamethylene terephthalamide (polyamide 12T), polylauryllactam (polyamide 12), poly-11-aminoundecanoic acid (polyamide 11), and copolymers containing these structural units.

[0074] The polyamide resin (G) may be used alone or in combination of several kinds. Among these, polycaproamide (polyamide 6), polyhexamethylene adipamide (polyamide 66), polymetaxylylene adipamide (polyamide MXD6), and polyhexamethylene terephthalamide (polyamide 6T) are preferred as the polyamide resin (G) in terms of heat resistance and versatility. Among these, polyamide 6, which has a low melting point, is particularly preferred. This is because when a polyamide resin with a high melting point is used, the kneading temperature in step 2 becomes high, which makes it easy for particles to form in the polyphenylene ether resin due to crosslinking. Polyamide resins are usually in pellet form (like granules or rice grains), and pellet-shaped polyamide resin pellets are usually used. Polyamide resin pellets usually have a diameter of 2 to 5 mm and a length of 2 to 5 mm.

[0075] The blending ratio of the masterbatch (F) obtained in step 1 and the polyamide resin (G) is 70 to 30 mass% of the masterbatch (F) and 30 to 70 mass% of the polyamide resin (G), based on 100 mass% of the total of (F) and (G), and preferably 60 to 40 mass% of the masterbatch (F) and 40 to 60 mass% of the polyamide resin (G).

[0076] To further reduce the amount of burnt foreign matter and agglomerated particles in the resin composition obtained in step 2, it is desirable to insert a screen mesh downstream of the extruder screw in step 2. The opening of the screen mesh is preferably about 50 μm, and in terms of mesh number, about 300 mesh is appropriate. If it is finer than this, the mesh will be clogged with burnt foreign matter and agglomerated particles in a short time, increasing the resin pressure and making it more likely to vent up. When using 300 mesh, from an industrial productivity perspective, it is necessary to be able to produce continuously for 2 hours without venting up. A preferred continuous production time is 3 hours or more, more preferably 6 hours or more. When using 300 mesh with a small opening, it is usually preferable to sandwich the 300 mesh between multiple coarser meshes placed upstream and downstream for reinforcement.

[0077] [Other ingredients (E) in Step 1] In step 1, other components (E) than the polyphenylene ether resin (A), unsaturated carboxylic acid or its anhydride (B), phosphorus-based flame retardant (C), and zinc borate (D) may be blended as needed, as long as the desired physical properties are not significantly impaired. Examples of the other component (E) include a resin X other than the polyphenylene ether resin (A), a flame retardant, an elastomer, various resin additives, etc. When the other component (E) is blended in step 1, the amount thereof is preferably 0 to 20 parts by mass, more preferably 0 to 10 parts by mass, and even more preferably 0 to 5 parts by mass, per 100 parts by mass of the polyphenylene ether resin (A).

[0078] <Other Resin X> Examples of other resins X include thermoplastic polyester resins other than polyphenylene ether resins, such as polyethylene terephthalate resin, polytrimethylene terephthalate, and polybutylene terephthalate resin; styrene-based resins such as polystyrene resin, high impact polystyrene resin (HIPS), acrylonitrile-styrene copolymer (AS resin), acrylonitrile-styrene-acrylic rubber copolymer (ASA resin), and acrylonitrile-ethylene propylene rubber-styrene copolymer (AES resin); polyolefin resins such as polyethylene resin and polypropylene resin; polyimide resin; polyetherimide resin; polyurethane resin; polyphenylene sulfide resin; polysulfone resin; and polymethacrylate resin. Although the polyamide resin can be blended in step 1, it is preferable to blend the entire amount in step 2 in terms of suppressing the generation of lumps and the mechanical properties of the resulting resin composition. When added in step 1, the amount is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, per 100 parts by mass of the polyphenylene ether resin (A).

[0079] <Flame retardant> Examples of the flame retardant include flame retardants other than phosphorus-based flame retardants and zinc borate. Specific examples include nitrogen-containing compounds (e.g., aminotriazine compounds (melamine; guanamine; melamine condensates such as melam and melem), salts of aminotriazine compounds, organic acid or inorganic acid salts of the aminotriazine compounds (specifically, cyanurates such as melamine cyanurate, phosphates such as melamine polyphosphate), metal hydroxides (e.g., aluminum hydroxide, magnesium hydroxide, zirconium hydroxide, alumina hydrate (boehmite), etc.), halogen-containing organic compound-based flame retardants, inorganic flame retardants such as antimony oxide-based flame retardants, and fluororesin-based flame retardant assistants.

[0080] <Elastomer> The elastomer is preferably a graft copolymer obtained by graft copolymerizing a rubber component with a monomer component copolymerizable therewith. The rubber component usually has a glass transition temperature of 0° C. or lower, preferably −20° C. or lower, and more preferably −30° C. or lower. Specific examples of the rubber component include polybutadiene rubber, polyisoprene rubber, polyalkyl acrylate rubbers such as polybutyl acrylate, poly(2-ethylhexyl acrylate), and butyl acrylate-2-ethylhexyl acrylate copolymers, silicone rubbers such as polyorganosiloxane rubber, butadiene-acrylic composite rubber, IPN (Interpenetrating Polymer Network) composite rubbers consisting of polyorganosiloxane rubber and polyalkyl acrylate rubber, styrene-butadiene rubber, ethylene-α-olefin rubbers such as ethylene-propylene rubber, ethylene-butene rubber, and ethylene-octene rubber, ethylene-acrylic rubber, and fluororubber.

[0081] <Resin additives> Examples of resin additives include heat stabilizers, antioxidants, catalyst deactivators, release agents, dyes and pigments, antistatic agents, antifogging agents, lubricants, antiblocking agents, flow improvers, plasticizers, dispersants, antibacterial agents, and weather resistance agents (HALS).

[0082] [Other ingredients (H) in step 2] In step 2, other components (H) may be added as needed, as long as the desired physical properties are not significantly impaired. Examples of the other component (H) include a resin Y other than the polyamide resin (G), a flame retardant, an elastomer, various resin additives, etc. When the other component (H) is blended in step 2, the amount thereof is preferably 0 to 10 parts by mass, more preferably 0 to 7 parts by mass, and even more preferably 0 to 5 parts by mass, relative to 100 parts by mass of the masterbatch (F).

[0083] <Other Resin Y> Examples of other resins Y include thermoplastic polyester resins other than polyamide resins, such as polyethylene terephthalate resin, polytrimethylene terephthalate, and polybutylene terephthalate resin; styrene-based resins such as polystyrene resin, high-impact polystyrene resin (HIPS), acrylonitrile-styrene copolymer (AS resin), acrylonitrile-styrene-acrylic rubber copolymer (ASA resin), and acrylonitrile-ethylene propylene rubber-styrene copolymer (AES resin); polyolefin resins such as polyethylene resin and polypropylene resin; polyimide resin; polyetherimide resin; polyurethane resin; polyphenylene sulfide resin; polysulfone resin; and polymethacrylate resin. Although the polyphenylene ether resin can be blended in step 2, it is preferable to blend the entire amount in step 1 in order to prevent the occurrence of lumps. When added in step 2, the amount is preferably 5 parts by mass or less, and more preferably 3 parts by mass or less, per 100 parts by mass of the total of (F) and (G).

[0084] Examples of the flame retardant, elastomer, and various resin additives that may be blended in step 2 include the same ones as those exemplified in step 1 above.

[0085] The flame-retardant thermoplastic resin composition pellets produced by the method of the present invention can be molded into molded articles by various molding methods, such as injection molding, extrusion molding, sheet molding, blow molding, gas injection molding, vacuum molding, compression molding, etc. There are no particular restrictions on the type, shape, or size of the molded article. Molded articles made from the flame-retardant resin composition pellets of the present invention can be widely and suitably used as parts for electric and electronic devices, interior and exterior parts for vehicles, precision instrument parts, parts for computers and office automation equipment, etc., as well as sheets and films. [Example]

[0086] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the following examples and can be practiced with any modifications within the scope of the present invention.

[0087] The raw materials used are as follows: <Polyphenylene ether resin (A)> Polyxylenol Singapore Pte Ltd., "PX100L" It is in powder form and measured by the dry light scattering method using the following equipment and conditions: Median diameter (D50): 650 μm Equipment used: LMS-3000 (Malvern (manufactured by Panalytical) Injection type dry measurement, compressed air pressure 0.1MPa Measurement range: 0.10 to 3500 μm <Unsaturated Carboxylic Acid or Anhydride thereof (B)> NOF Corporation, Maleic Anhydride "Crystalman AB" <Phosphorus-based flame retardants (C)> Phosphazene flame retardants: Phenoxyphosphazene compound, Fushimi Pharmaceutical Co., Ltd., "Ravitor FP-110" <Zinc borate (D)> "Firebreak ZB Fine" manufactured by Borax Japan Median diameter (D50) measured using the wet light scattering method under the following conditions: 3.1 μm Equipment used: LMS-2000e (Seishin Enterprise Co., Ltd.) Dispersion medium used: ion-exchanged water, measured after 10 minutes of ultrasonic dispersion Measurement range: 0.020 to 2000.00 μm <Other ingredients (E)> SEBS elastomer TSRC (Nantong) Industries, "SEBS6151" <Polyamide resin (G)> Toray Industries, Inc. Polyamide 6, "Amilan CM1017" Pellet shape with a diameter of 3 mm and a length of 3 mm

[0088] [Example 1] The twin-screw extruder used in both steps 1 and 2 was the "TEX44αIII" (fully intermeshing co-rotating twin-screw extruder, cylinder diameter D=47 mm) manufactured by The Japan Steel Works, Ltd. The screw configuration used is shown in Figure 1. There were two kneading sections: the first kneading section with a kneading disc configuration of five paddles (RRNNL) was located near cylinder position C6, and the second kneading section (the most downstream kneading section) with a kneading disc configuration of four paddles (RNNL) was located near cylinder position C9. The length of each kneading disc was 0.936D. The total length of the kneading section was 8.42D. A flat die (with 11 nozzles arranged horizontally) was used. The resin temperature was measured with a contact thermocouple thermometer immediately after the strands formed from the central nozzles (the sixth from both ends) emerged from the nozzles.

[0089] <Process 1> 50 kg / h (100 parts by mass) of polyphenylene ether resin, 0.6 kg / h (1.2 parts by mass) of maleic anhydride, 18 kg / h (36 parts by mass) of phosphazene, and 31.4 kg / h (62.8 parts by mass) of zinc borate were fed into the hopper of the extruder "TEX44αIII" (total 100 kg / h). The screw rotation was 250 rpm, the cylinder temperature setting for cylinder positions C2 to C6 was 260 °C, and the cylinder temperature setting for C7 to C11, including the most downstream kneading section, was 225 °C. The die holder temperature was 250 °C, and the strand temperature upon exiting the die was 298 °C (resin temperature). The extruded strand was formed, cooled in a water bath, and cut to obtain pellets, which were the masterbatch. A breaker plate was used in step 1, but no screen mesh was used.

[0090] <Process 2> Next, 45 kg / h of this masterbatch and 55 kg / h of polyamide resin pellets were fed into the hopper of the same twin-screw extruder "TEX44αIII" (total 100 kg / h). The screw rotation was 200 rpm, the cylinder temperature was set to 260 °C for C2 to C6, and 225 °C for C7 to C11, including the most downstream kneading section. The die holder temperature was 250 °C, and the breaker plate was equipped with a screen mesh consisting of one 16 mesh, one 120 mesh, one 300 mesh, and one 60 mesh mesh from the downstream side. The resin that passed through the screen mesh was extruded through the die, and the strand temperature upon exiting the die was 292 °C (resin temperature). The extruded strand was cooled in a water bath to obtain pellets of a flame-retardant thermoplastic composition.

[0091] The initial resin pressure was 2.0 MPa and was running smoothly, but after 6 hours it rose to 8.0 MPa, and venting occurred 6 hours and 10 minutes later. Checking the screen mesh revealed black foreign matter (lumps), and examining the composition revealed that the main component was polyphenylene ether resin. In particular, when examining the surface of the 300-mesh screen, approximately 70% of the area was covered with black polyphenylene ether resin particles. It is believed that the polyphenylene ether resin crosslinked and formed particles at resin temperatures approaching 300°C during the kneading processes in Steps 1 and 2. Furthermore, maleic anhydride appears to promote crosslinking. As mentioned above, the preferred continuous production time is 3 hours or more, more preferably 6 hours or more. In this invention, it is important to delay crosslinking, suppress particle formation, delay screen mesh clogging, and extend the continuous production time. In other words, the longer the time until venting, the slower the rate of particle formation; and the shorter the time until venting, the faster the rate of particle formation. When the resin pressure reaches approximately 8 MPa, resin accumulates at the tip of the screw, reaches the vent, and venting can be determined to have occurred.

[0092] [Example 2] Extrusion was carried out in the same manner as in Example 1, except that the cylinder temperature setting for C2 to C6 in steps 1 and 2 was 260°C, and the cylinder temperature setting for C7 to C11 was 245°C. The resin temperature in step 1 was 310°C, and the resin temperature in step 2 was 303°C. The initial resin pressure in step 2 was 1.5 MPa, but after 3 hours it rose to 6.0 MPa, and venting occurred after 3 hours and 15 minutes. When the screen mesh was inspected, black foreign matter (lumps) was found, and when the composition was examined it was found that the main component was polyphenylene ether resin.

[0093] [Example 3] An experiment was conducted in the same manner as in Example 1, except that of the 50 kg / h (100 parts by mass) of polyphenylene ether resin (A) in step 1 of Example 1, 5 kg / h (11.1 parts by mass) was replaced with the other component (E), elastomer "SEBS6151." The resin temperature in step 1 was 299°C, and the resin temperature in step 2 was 295°C. The initial resin pressure in step 2 was 2.2 MPa, but rose to 8.0 MPa after 5 hours and 20 minutes, and venting occurred after 5 hours and 40 minutes. When the screen mesh was inspected, black foreign matter (lumps) was found, and when the composition was examined, it was found that the main component was polyphenylene ether resin.

[0094] [Comparative Example 1 (direct kneading without step 1)] 22.5 kg / h (100 parts by mass) of polyphenylene ether resin, 0.27 kg / h (1.2 parts by mass) of maleic anhydride, 8.1 kg / h (36 parts by mass) of phosphazene, 14.13 kg / h (62.8 parts by mass) of zinc borate, and 55 kg / h (244.4 parts by mass) of polyamide resin pellets were fed into the hopper of the extruder "TEX44αIII" (total 100 kg / h), the screw rotation was 200 rpm, the cylinder temperature was set to 260 ° C for C2 to C6, 225 ° C for C7 to C11, the die holder temperature was 250 ° C, and the breaker plate was equipped with a screen mesh with a mesh configuration of 16 mesh, 120 mesh, 1 300 mesh, and 1 60 mesh from downstream. The resin that passed through the screen mesh was extruded from the die and stranded, cooled in a water bath, and pellets of a flame-retardant thermoplastic composition were obtained. The resin temperature was 305°C. The initial resin pressure was 2.1 MPa, but it rose rapidly, reaching 6.0 MPa after 15 minutes, and venting occurred after 17 minutes. When the screen mesh was checked, numerous agglomerates of zinc borate were found on the 60 mesh and 300 mesh from upstream. Because polyamide resin pellets and zinc borate were fed into the C1 hopper at the same time, it is believed that a strong force was applied to the zinc borate when the pellets were sheared and kneaded, promoting the agglomeration (agglomeration) of zinc borate. This method was not feasible for practical production.

[0095] Comparative Example 2 In step 1, 98.81 g / h (100 parts by mass) of polyphenylene ether resin and 1.19 kg / h (1.2 parts by mass) of maleic anhydride were fed into the hopper of the "TEX44αIII" (total 100 kg / h), and the extrusion was performed with a screw rotation of 250 rpm and cylinder temperatures set at 260°C for C2 to C6 and C7 to C11. No screen mesh was used during this process. A masterbatch was obtained. The resin temperature was 356°C. When the die was opened, black burns were found on the wall of the die holder. Next, in step 2, 22.77 kg / h of this masterbatch, 8.1 kg / h of phosphazene, 14.13 kg / h of zinc borate, and 55 kg / h of polyamide resin pellets (total 100 kg / h: the final composition ratio was the same as the resin composition obtained in Example 1) were fed into the hopper of the TEX44αIII and extruded in the same manner as step 2 in Example 1. The resin temperature was 293°C. In step 2, the initial resin pressure was 1.7 MPa, but reached 5.0 MPa after 15 minutes, and venting occurred after 21 minutes. Checking the screen mesh revealed black foreign matter (lumps), and examination of the composition revealed that the main component was polyphenylene ether resin. Since a large amount of polyphenylene ether resin was burned, it was determined that the resin temperature in process 1 was high at 356°C, causing the polyphenylene ether resin to burn and turn into particles inside the extruder, which then clogged the screen mesh in process 2, causing it to vent. In particular, when the surface of the 300 mesh was examined, about 80% of the area was covered with black polyphenylene ether resin particles. This shows that the cross-linking reaction of the polyphenylene ether resin was very rapid due to the high temperature in process 1.

[0096] Comparative Example 3 Extrusion was carried out in the same manner as in Example 2, except that the screw rotation speed in process 1 was 350 rpm and the screw rotation speed in process 2 was 300 rpm. The resin temperature in process 1 was 328°C, and the resin temperature in process 2 was 323°C. In process 2, the initial resin pressure was 1.3 MPa, but reached 6.0 MPa after 1 hour, and venting occurred after 1 hour and 8 minutes. When the screen mesh was inspected, black foreign matter (lumps) were found, and when the composition was examined, it was found that the main component was polyphenylene ether resin.

[0097] Comparative Example 4 Extrusion was carried out in the same manner as in Example 1, except that the set temperatures for C2 to C6 in processes 1 and 2 were 260°C, and those for C7 to C11 were 270°C. The resin temperature in process 1 was 321°C, and the resin temperature in process 2 was 316°C. The initial resin pressure in process 2 was 1.5 MPa, but after 1 hour it rose to 6.0 MPa, and venting occurred after 1 hour and 15 minutes. When the screen mesh was inspected, black foreign matter (lumps) was found, and when the composition was examined it was found that the main component was polyphenylene ether resin.

[0098] Comparative Example 5 Extrusion was performed in the same manner as in Example 1, except that in step 1, the cylinder temperatures for C2 to C6 were set to 260°C, and for C7 to C11 to 270°C, and in step 2, the cylinder temperatures for C2 to C6 were set to 260°C, and for C7 to C11 to 245°C. The resin temperature in step 1 was 322°C, and the resin temperature in step 2 was 306°C. The initial resin pressure in step 2 was 1.6 MPa, but after one hour it rose to 6.0 MPa, and venting occurred after one hour and 32 minutes. When the screen mesh was inspected, black foreign matter (lumps) was found, and when the composition was examined, it was found to be primarily polyphenylene ether resin.

[0099] Comparative Example 6 Extrusion was performed in the same manner as in Example 1, except that in step 1, the cylinder temperatures for C2 to C6 were set to 260°C and for C7 to C11 to 245°C, and in step 2, the cylinder temperatures for C2 to C6 were set to 260°C and for C7 to C11 to 270°C. The resin temperature in step 1 was 312°C, and in step 2, the resin temperature was 318°C. The initial resin pressure in step 2 was 1.4 MPa, but after one hour it rose to 6.0 MPa, and venting occurred after one hour and 48 minutes. Checking the screen mesh revealed black foreign matter (lumps), and examining the composition revealed that the main component was polyphenylene ether resin. [Industrial Applicability]

[0100] According to the production method of the present invention, it is possible to stably produce high-quality pellets of a flame-retardant thermoplastic resin composition.

Claims

1. The method comprises the steps of: a step 1 of melt-kneading 100 parts by mass of polyphenylene ether resin (A) with a twin-screw extruder to produce a masterbatch (F); and a step 2 of melt-kneading the masterbatch (F) obtained in step 1 and polyamide resin (G) in an amount of 70 to 30% by mass of masterbatch (F) and 30 to 70% by mass of polyamide resin (G), based on 100% by mass of the total of (F) and (G), to form pellets. The resin temperature in step 1 is 320°C or less, and the resin temperature in step 2 is 320°C or less, A method for producing flame-retardant thermoplastic resin composition pellets, characterized in that the cylinder set temperature in the most downstream kneading section in step 1 is 250°C or less, and the cylinder set temperature in the most downstream kneading section in step 2 is 250°C or less.

2. 2. The method according to claim 1, wherein the twin-screw extruder is a fully intermeshing co-rotating twin-screw extruder, and the total length of the kneading section is 5D to 12D (D is the cylinder diameter).

3. 3. The method according to claim 1, wherein the phosphorus-based flame retardant (C) is a phosphazene compound.

4. 3. The method according to claim 1, wherein the particle size of the zinc borate (D) is 0.1 to 10 μm in terms of median diameter (D50) determined by a wet light scattering method.

5. Flame-retardant thermoplastic resin composition pellets obtained by the method according to any one of claims 1 to 4.

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