Method for producing flame-retardant polycarbonate resin composition pellets

Abstract

To provide a manufacturing method for the stable production of polycarbonate resin composition pellets with excellent hue, uniformity, and superior flame retardancy at high discharge rates.SOLUTION: There is provided a manufacturing method of polycarbonate resin composition pellets, in which a polycarbonate resin composition is placed in a twin-screw extruder, a first kneading section 3 uses a 3-row eccentric kneading disk as a kneading disk and has a length of 2.5D to 6.5D (D is the cylinder inner diameter), and a second kneading section 6 uses a 3-row eccentric kneading disk as a kneading disk and has a length of 1.5D to 4.5D.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for producing flame-retardant polycarbonate resin composition pellets. [Background technology]

[0002] Polycarbonate resins are resins with excellent heat resistance and mechanical properties, and are therefore widely used in, for example, electrical equipment, electronic equipment, vehicles such as automobiles, office automation equipment such as printers and copiers, housing, construction, and materials for manufacturing parts in other industrial fields. These products are required to be flame retardant from a safety standpoint in order to prevent fires caused by high temperatures. In particular, flame-retardant polycarbonate resin compositions are suitably used for housings for office automation equipment such as printers and copiers, personal computers, various mobile terminals, batteries, etc.

[0003] On the other hand, in recent years, there has been a strong social demand for recycling resins due to growing awareness of environmental protection, and regulations are being strengthened under various legal systems. For example, there is a particular demand for the use of recycled resins for the exteriors and housings of office automation equipment and electronic devices, and there are an increasing number of cases in which polycarbonate resin compositions containing a specified amount of recycled resin are required.

[0004] To regenerate thermoplastics from used products, for example as described in Patent Document 1, thermoplastic components recovered from equipment parts are crushed, washed with a cleaning solution, and the crushed thermoplastic material is separated from the crushed mixture.

[0005] Examples of raw materials for recycled (regenerated) polycarbonate resin include optical disks such as CDs and DVDs, light guide plates, automobile headlamp lenses, transparent vehicle components such as automobile window glass and windshields, containers such as water bottles, eyeglass lenses, soundproof walls and glass windows, building components such as corrugated sheets, sheets, etc. These are crushed, washed, separated and recovered, and pelletized into pellets. In addition, by-products such as sprues and runners during molding are also repelletized and used.

[0006] In order to use such recycled materials in office equipment, in particular, they need to be highly flame-retardant. Conventionally, as a means for imparting flame retardancy to polycarbonate resin, a method of blending a halogen-based flame retardant such as an organic bromine compound with the polycarbonate resin has been widely known. In recent years, however, it has been proposed to blend a phosphorus-based flame retardant with the polycarbonate resin, and phosphorus-based flame retardants are now becoming the predominant flame retardant. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent Publication No. 2000-198116 Summary of the Invention [Problem to be solved by the invention]

[0008] Phosphorus-based flame retardants, for example, phosphoric ester-based flame retardants, are either solid or liquid at room temperature, and liquid flame retardants require liquid addition to an extruder.However, when using an extruder to melt-knead liquid phosphorus-based flame retardants and pellet-shaped polycarbonate resin such as the above-mentioned recycled material, they are difficult to mix with the liquid phosphorus-based flame retardants, and unmelted polycarbonate resin is easily generated, vent-up occurs at the vent opening, the discharge amount does not increase, strands cannot be taken up, and the color of the obtained polycarbonate resin composition pellets is easily reduced, and the flame retardancy is also easily insufficient. An object (object) of the present invention is to provide a production method for producing, at a high output, a flame-retardant polycarbonate resin composition (pellets) that exhibits good hue and physical properties, using a liquid phosphate ester-based flame retardant. [Means for solving the problem]

[0009] As a result of extensive research conducted by the present inventors in order to achieve the above object, they have found that when a phosphate flame retardant that is liquid at room temperature is added to resin pellets containing polycarbonate resin and produced in a twin-screw extruder, the liquid phosphate is added downstream of the first kneading section, and then the mixture is kneaded in the next kneading section, and the screw configuration of each kneading section is a triple-lobe eccentric kneading disk with a specific configuration and length, which has a strong pellet cutting (distribution) effect, promotes melting by heat transfer, prevents the generation of unmelted material or vent-up, and enables the production of polycarbonate resin composition pellets that are excellent in hue, uniform, and excellent flame retardancy at a high discharge rate with good productivity, and thus completed the present invention. The present invention relates to the following method for producing polycarbonate resin composition pellets.

[0010] 1. A method for producing polycarbonate resin composition pellets comprising 30 to 95 mass% of resin pellets (A) containing more than 40 mass% of polycarbonate resin in the pellets, 5 mass% or more but less than 40 mass% of a phosphate ester flame retardant (B) that is liquid at room temperature, 0 to 50 mass% of polycarbonate resin flakes (C), 0 to 30 mass% of ABS resin (D), and 0 to 15 mass% of other additives (E) other than (B) [with the proviso that the total of (A) to (E) is 100 mass%], using a twin-screw extruder, The components (A), (C), (D) and (E) are placed in a twin-screw extruder, The method includes a first step of kneading in a first kneading section, a second step of adding the (B) to a downstream portion of the first kneading section and kneading the mixture in a second kneading section, and a third step of degassing and extruding the mixture by reducing the pressure of a vent downstream of the second kneading section, A method for producing polycarbonate resin composition pellets, characterized in that the first kneading section uses three-lobe eccentric kneading discs as kneading discs and has a length of 2.5D to 6.5D (D is the cylinder inner diameter), and the second kneading section uses three-lobe eccentric kneading discs as kneading discs and has a length of 1.5D to 4.5D. 2. The production method according to 1 above, wherein the amount of resin pellets (A) is 30 to 80% by mass in a total of 100% by mass of (A) to (E). 3. The method according to 1 or 2 above, wherein the amount of the phosphate ester flame retardant (B) which is liquid at room temperature is 5% by mass or more and less than 25% by mass, based on 100% by mass of the total of (A) to (E). 4. The method according to any one of 1 to 3 above, wherein the resin pellets (A) contain recycled resin pellets. 5. The method according to any one of 1 to 4 above, wherein the resin components comprise 50 to 100% by mass of polycarbonate resin and 50 to 0% by mass of ABS resin and / or polyester resin (the total of these being 100% by mass). 6. The method according to any one of 1 to 5 above, wherein the length of the first kneading zone is in the range of 3.5 to 5.5D, and the length of the second kneading zone is in the range of 2.0D to 4.0D. 7. The manufacturing method according to any one of 1 to 6 above, wherein the three-row eccentric kneading disc is a roughly triangular disc with bulging centers on each side, and is mounted on the screw shaft so as to rotate eccentrically. 8. The method for producing a cylinder according to any one of 1 to 7 above, wherein the eccentricity is 0.01D to 0.07D (D is the inner diameter of the cylinder) and the cylinder is attached to a screw. 9. The manufacturing method according to any one of 1 to 8 above, wherein the three-row eccentric kneading disc has three apexes with an angular interval θ of 110° to 130°, the radius at the apexes is 0.4D to 0.5D, and the radius at the center between the apexes is in the range of 0.25D to 0.38D (D is the inner diameter of the cylinder). Effect of the Invention

[0011] According to the production method of the present invention, it is possible to produce polycarbonate resin composition pellets that are free from unmelted matter or vent-up, have a high discharge rate, are stable and highly productive, are free from breakage of extruded strands, have an extremely good hue, and are uniform and have excellent flame retardancy. In particular, when recycled materials are used or combined as polycarbonate resin raw materials, the recycled materials have been subjected to thermal history and are therefore prone to discoloration at high temperatures due to heat, so it is necessary to lower the resin temperature more than in the case of virgin raw materials. However, the manufacturing method of the present invention has good melting characteristics, promotes melting at high discharge rates, and can suppress increases in resin temperature, making it particularly suitable for use in cases where recycled materials are used or combined. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a cross-sectional view showing an example of a screw configuration of an extruder used in the method of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view showing another example of the screw configuration of the extruder used in the method of the present invention. [Diagram 3] FIG. 2 is a cross-sectional view showing the cross-sectional shapes of a cylinder of a twin-screw extruder and an eccentric kneading disk attached to the screw. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, the present invention will be described in detail with reference to embodiments and examples, but the present invention should not be construed as being limited to the embodiments and examples.

[0014] The raw materials used in the method for producing polycarbonate resin composition pellets of the present invention, based on a total of 100 mass% of (A) to (E), are 30 to 95 mass% of resin pellets (A) containing more than 40 mass% of polycarbonate resin in the pellets, 5 mass% or more and less than 40 mass% of a phosphate ester flame retardant (B) that is liquid at room temperature, 0 to 50 mass% of polycarbonate resin flakes (C), 0 to 30 mass% of ABS resin (D), and 0 to 15 mass% of other additives (E) other than (B).

[0015] [Resin pellets (A)] The method for producing polycarbonate resin composition pellets of the present invention uses resin pellets (A) containing more than 40% by mass of polycarbonate resin in the pellets. The resin pellets (A) may contain more than 40% by mass of polycarbonate resin, and mixtures or alloys containing resins other than polycarbonate resin, such as ABS resin, thermoplastic polyester (polybutylene terephthalate resin, polyethylene terephthalate resin, etc.), can also be preferably used.

[0016] The resin pellets (A) may be unused so-called virgin pellets, recycled material (regenerated material) pellets, or pellets containing recycled material pellets. Examples of raw materials for recycled material pellets include optical disks such as CDs and DVDs, light guide plates, automobile window glass, automobile headlamp lenses, vehicle transparent parts such as windshields, containers such as water bottles, eyeglass lenses, soundproof walls, glass windows, corrugated sheets, and other building parts. In addition, crushed products obtained from non-conforming products, sprues, or runners during molding, or crushed, washed, separated, and collected to be repelletized may be used. Hereinafter, these recycled materials, regenerated materials, repellets, etc. are collectively referred to as recycled materials or recycled pellets.

[0017] In the method for producing polycarbonate resin composition pellets of the present invention, it is particularly preferable to use pellets of recycled materials, since the use of pellets of recycled materials results in a low LCA (Life Cycle Assessment). Recycled materials often contain other resins than polycarbonate resin and various additives, but any can be used as long as the polycarbonate resin is more than 40 mass% as resin pellets (A). Recycled polycarbonate resin pellets can also be purchased from recycled material manufacturers.

[0018] [Polycarbonate resin] Examples of the polycarbonate resin include aromatic polycarbonate resins, aliphatic polycarbonate resins, and aromatic-aliphatic polycarbonate resins. Of these, aromatic polycarbonate resins are preferred. Specifically, aromatic polycarbonate polymers or copolymers obtained by reacting an aromatic dihydroxy compound with phosgene or a diester of carbonic acid are used.

[0019] Examples of aromatic dihydroxy compounds include 2,2-bis(4-hydroxyphenyl)propane (i.e., bisphenol A), 2,2-bis(3-methyl-4-hydroxyphenyl)propane (i.e., bisphenol C), tetramethylbisphenol A, α,α'-bis(4-hydroxyphenyl)-p-diisopropylbenzene, hydroquinone, resorcinol, and 4,4'-dihydroxydiphenyl.

[0020] Preferred examples of polycarbonate resins include polycarbonate resins using bisphenol A as a dihydroxy compound or a combination of bisphenol A and other aromatic dihydroxy compounds, and polycarbonate resins using bisphenol C or a combination of bisphenol C and other aromatic dihydroxy compounds (particularly bisphenol A).

[0021] The polycarbonate resin may be a homopolymer consisting of one type of repeating unit, or a copolymer having two or more types of repeating units, in which case the copolymer may be selected from various copolymer forms such as a random copolymer, a block copolymer, etc. The method for producing the aromatic polycarbonate resin is not particularly limited, and may be a conventional method such as a phosgene method (interfacial polymerization method) or a melting method (ester exchange method).

[0022] The molecular weight of the polycarbonate resin is not limited, but the viscosity average molecular weight (Mv) is usually about 10,000 to 100,000, and preferably about 12,000 to 35,000. By making the viscosity average molecular weight equal to or greater than the lower limit of the above range, the mechanical strength of the polycarbonate resin composition can be further improved, and it is more preferable when used in applications requiring high mechanical strength. On the other hand, by making the viscosity average molecular weight equal to or less than the upper limit of the above range, the decrease in the flowability of the polycarbonate resin composition can be suppressed and improved, and the molding processability can be improved, making it easy to perform thin-wall molding. Two or more kinds of polycarbonate resins having different viscosity average molecular weights may be mixed and used. In this case, polycarbonate resins having a viscosity average molecular weight outside the above-mentioned preferable range may be mixed.

[0023] In the present invention, the viscosity average molecular weight (Mv) of a polycarbonate resin is a value calculated from the intrinsic viscosity ([η]) obtained by measuring the viscosity of a methylene chloride solution of the polycarbonate resin at 25° C. using an Ubbelohde viscometer, and then using the following Schnell viscosity formula: [η]=1.23×10 -4 Mv 0.83

[0024] The method for producing the polycarbonate resin is not particularly limited, and polycarbonate resins produced by either the phosgene method (interfacial polymerization method) or the melting method (ester exchange method) can be used. In addition, polycarbonate resins produced by the melting method and then subjected to post-treatment to adjust the amount of OH groups at the terminals are also preferred.

[0025] Preferred examples of products that can be used as recycled polycarbonate resin materials include optical recording media such as optical disks (CDs, DVDs), light guide plates, automobile window glass, automobile headlamp lenses, transparent vehicle components such as windshields, containers such as water bottles, eyeglass lenses, soundproof walls, glass windows, corrugated sheets, and other building components. In addition, examples of recycled polycarbonate resin materials that can be used include crushed products obtained from non-conforming products, sprues, or runners during molding, or pellets obtained by melting these products.

[0026] [Phosphate ester flame retardants (B)] The phosphate ester flame retardant used in the present invention is a phosphate ester flame retardant that is liquid at room temperature. Here, "liquid at room temperature" means that the material is liquid at a temperature of 23°C. Examples of the phosphate flame retardant include phosphate compounds and condensed phosphates, with condensed phosphates being preferred.

[0027] As the condensed phosphate ester, a phosphate ester compound represented by the following general formula (1) which is liquid at room temperature is particularly preferred. [ka] (In the formula, R 1 , R 2 , R 3 and R 4 represents an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 20 carbon atoms which may be substituted with an alkyl group; p, q, r, and s each represent 0 or 1; k represents an integer of 1 to 5; X 1 represents an arylene group.

[0028] The phosphate compound represented by the general formula (1) may be a mixture of compounds having different k numbers, and in the case of such a mixture of phosphate esters having different k numbers, k is the average value of the mixture. In the case of a mixture of compounds having different k numbers, the average k number is preferably in the range of 1 to 2, more preferably 1 to 1.5, even more preferably 1 to 1.2, and particularly preferably 1 to 1.15.

[0029] Also, X 1 represents a divalent arylene group, for example, a divalent group derived from a dihydroxy compound such as resorcinol, hydroquinone, bisphenol A, 2,2'-dihydroxybiphenyl, 2,3'-dihydroxybiphenyl, 2,4'-dihydroxybiphenyl, 3,3'-dihydroxybiphenyl, 3,4'-dihydroxybiphenyl, 4,4'-dihydroxybiphenyl, 1,2-dihydroxynaphthalene, 1,3-dihydroxynaphthalene, 1,4-dihydroxynaphthalene, 1,5-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 1,7-dihydroxynaphthalene, 1,8-dihydroxynaphthalene, 2,3-dihydroxynaphthalene, 2,6-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, etc. Among these, divalent groups derived from bisphenol A and 3,3'-dihydroxybiphenyl are particularly preferred.

[0030] In addition, p, q, r and s in the general formula (1) each represent 0 or 1, with 1 being preferred. Also, R 1 , R 2 , R 3 and R 4 respectively represent an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 20 carbon atoms which may be substituted with an alkyl group. Examples of such an aryl group include a phenyl group, a cresyl group, a xylyl group, an isopropylphenyl group, a butylphenyl group, a tert-butylphenyl group, a di-tert-butylphenyl group, and a p-cumylphenyl group, with the phenyl group, the cresyl group, and the xylyl group being more preferred.

[0031] Of the condensed phosphate esters represented by the general formula (1), specific examples that are liquid at room temperature include bisphenol A bis-diphenyl phosphate, etc. Commercially available products include "FP-600" manufactured by ADEKA Corporation and "CR-741" manufactured by Daihachi Chemical Industry Co., Ltd.

[0032] [Production of polycarbonate resin composition pellets] The manufacturing method of the present invention includes a first step of feeding the above-mentioned resin pellets (A) and other components into a twin-screw extruder and kneading them in a first kneading section, a second step of adding the above-mentioned (B) downstream of the first kneading section and kneading them in a second kneading section, and a third step of reducing the pressure of a vent downstream of the second kneading section to remove volatile components and extrude the mixture.

[0033] In the manufacturing method of the present invention, a twin-screw extruder is used. Various types of twin-screw extruders can be used, and the screw rotation method may be either co-rotating or counter-rotating, but a co-intermeshing twin-screw extruder is preferred. The twin-screw extruder is provided with a vent port that is open to reduced pressure or the atmosphere.

[0034] The production method of the present invention will be described below with reference to FIGS. 1 and 2 are cross-sectional views showing examples of the screw configuration of an extruder used in the method of the present invention. As shown in FIGS. 1 and 2, for the sake of explanation, the cylinders are labeled C1 to C11 from the upstream supply port 1 side of the extruder to the downstream discharge port 9 side.

[0035] The raw material resin pellets (A) and other components (C) to (E) are fed into the twin-screw extruder from a feed port 1 at the base C1 of the extruder. The resin pellets (A) are transported while being melted and kneaded toward a discharge port 9 on the right side in Figs. 1 and 2 by the heating of the extruder barrel and the rotation of the screws. The strands discharged from the discharge port 9 are pelletized in a granulator.

[0036] Resin pellets (A) etc. supplied from a supply port 1 are supplied, conveyed and preheated in the supply / conveying / preheating section 2. The conveying screw is preferably composed of a normal flight-type screw element.

[0037] Next, the resin pellets (A) are melted in the first kneading section 3, which is composed of a three-lobe eccentric kneading disc as a kneading disc and has a length of 2.5D to 6.5D (D is the cylinder inner diameter).

[0038] The first kneading section means a kneading area where kneading is performed before the liquid phosphate ester flame retardant is introduced, and the first kneading section may have a continuous three-lobe eccentric kneading disk or may be divided into several. The total length of the three-lobe eccentric kneading disks may be 2.5D to 6.5D (D is the cylinder inner diameter), and normal feed flights that do not have a kneading function are not included in the length of the first kneading section. For example, as in the first kneading section 3 in Fig. 2, normal feed flight-like elements (diagonally hatched elements in 3 in Fig. 2) may be inserted between several kneading disks, and such feed flight-like elements are not included in the length of 2.5D to 6.5D.

[0039] FIG. 3 is a cross-sectional view for explaining the cross-sectional shapes of the cylinder of a twin-screw extruder and a triple-blade eccentric kneading disk attached to the screw. The twin-screw extruder is equipped with a cylinder 1 having two cylindrical parts in which a pair of screws 2, 2' are arranged side by side. The cross section of the cylindrical part in the cylinder 1 taken along the axis perpendicular to the axis is formed so that two circles overlap.

[0040] The two screws 2, 2' are equipped with a driving device (not shown) such as a motor for rotating them without contacting each other, and the screws 2, 2' rotate inside the cylindrical part of the cylinder 1, and the axis x of the screw shafts of the screws 2, 2' coincides with the circular center of the cylindrical part of the cylinder 1. The screw shafts may rotate in either the same or opposite directions, but rotation in the same direction is preferred.

[0041] The screws 2, 2' are fitted with three-tooth kneading discs 3, 3'. The three-lobe eccentric kneading discs 3, 3' are substantially triangular with three apexes (tips) T1, T2, T3 as shown in Fig. 3. The angular interval θ between the three apexes (tips) T1, T2, T3 is preferably 110° to 130°, more preferably 115° to 125°, and particularly preferably a substantially triangular shape with equiangular intervals of θ of approximately 120°. It is preferable that each of the three-lobe eccentric kneading discs 3, 3' has a substantially triangular shape in which each side (flank) connecting the three apexes T1, T2, T3 draws an outward arc and the center bulges outward.

[0042] The three-row eccentric kneading discs 3, 3' preferably have a radius Da at the apex (the distance from the geometric center y of the three-row kneading disc to the apex T) in the range of 0.4D to 0.5D (D is the inner diameter of the cylinder), and preferably have a radius Dk at the center k of the flank between each apex T1, T2, T3 (the distance from the geometric center y of the three-row eccentric kneading disc to the center k; the shortest distance from y) in the range of 0.25D to 0.38D. The tip width dT of the top portion (tip) T is preferably 0.02D to 0.08D.

[0043] The three-lobe kneading discs 3, 3' are mounted on the screw shafts of the screws 2, 2' so as to rotate eccentrically. The amount of eccentricity e (the distance from the rotation center x of the screw to the geometric center y of the kneading disc) is preferably 0.01D to 0.07D (D is the cylinder inner diameter). It is preferable that the three-lobe eccentric kneading discs 3 and 3' are eccentric in the same direction as the direction connecting the two screw shafts.

[0044] In the three-lobe eccentric kneading disc, a kneading zone is usually formed by mounting a plurality of paddles along the axial direction. The number of paddles is preferably 3 to 15, more preferably 5 to 11, and particularly preferably 7 to 9. It is preferable to provide a gap between adjacent paddles, and the gap is preferably 0.2 mm to 2 mm.

[0045] It is preferable that the thickness of the three-lobe eccentric kneading disc is 0.1D or less per disc (hereinafter also referred to as a paddle) in the axial direction.

[0046] The triple-lobe eccentric kneading disc is used as an N disc, in which multiple paddles are overlapped without shifting, an R disc, in which multiple paddles are shifted to the right and overlap to create a flow in the forward direction, and an L disc, in which multiple paddles are shifted to the left and overlap to create a flow in the reverse direction, and a combination of these is used as a screw configuration.

[0047] The manufacturing method of the present invention uses a three-blade eccentric kneading disk, and only one (or two) of the vertices are close to the cylinder inner surface due to eccentricity. By using such a three-blade eccentric kneading disk, the resin can be melted at a low temperature, the discharge amount can be increased, and the resin pellets (A) of the cylinder raw material can be cut into small pieces, so that the melting characteristics of the resin are excellent under high discharge conditions, and the raw resin pellets can be melted quickly due to rapid heat conduction, and the resin temperature can be further reduced.

[0048] The first kneading section 3 is combined with the above-mentioned three-lobe eccentric kneading discs, preferably a combination of an R kneading disc, an N kneading disc, and an L kneading disc. For example, a configuration in which multiple Ns are placed after an R to form an L, particularly RNL, RRNL, RNNL, RRNNL, RNNNL, RNNNL, RRNNNL, etc., is preferred.

[0049] Further, the disk configuration of the first kneading section 3 has a length of 2.5D to 6.5D, and it is particularly preferable that the length is in the range of 3.5 to 5.5D.

[0050] The resin pellets (A) are sufficiently melted in the first kneading section 3 configured as described above, and then transported to the second kneading section 6 by the transport section 4. At that time, a liquid phosphate ester flame retardant (B) is added by a liquid addition device 5 (such as a liquid supply pump) provided downstream of the first kneading section.

[0051] The amount of liquid phosphoric acid ester flame retardant (B) added is 5% by mass or more and less than 40% by mass relative to 100% by mass of the resulting polycarbonate resin composition pellets, and by adding such an amount, high flame retardancy and heat resistance can be achieved at the same time. If it is 40% by mass or more, the heat resistance decreases. The amount added is preferably 7% by mass or more, more preferably 10% by mass or more, preferably less than 35% by mass, more preferably less than 30% by mass, among which less than 25% by mass, 23% by mass or less, and particularly preferably 22% by mass or less.

[0052] In the second kneading section 6, the molten resin pellets (A) and the like and the liquid phosphate ester flame retardant (B) are melt-kneaded.

[0053] The second kneading section 6 is configured with a three-lobe eccentric kneading disk having a length of 1.5D to 4.5D (D is the cylinder inner diameter). By configuring the screw of the second kneading section 6 as described above, in combination with the screw configuration of the first kneading section 3, it is possible to uniformly melt-knead the resin pellets (A) and the liquid phosphate ester flame retardant (B) at a low resin temperature and with high discharge rate, and it is possible to stably produce polycarbonate resin composition pellets with excellent color and flame retardancy with good productivity.

[0054] The second kneading section means a kneading region where the phosphate ester flame retardant (B) enters and is kneaded before reaching the vacuum vent 7, and the total length of the three-lobe eccentric kneading discs in this second kneading section is 1.5D to 4.5D (D is the cylinder inner diameter), and normal feed flights that do not have a kneading function are not included in the length of the second kneading section. For example, as in the second kneading section 6 in Fig. 2, normal feed flight-like elements (diagonally hatched elements in 6 in Fig. 2) may be inserted between multiple kneading discs to divide them, and such feed flight-like elements are not included in the length of 1.5D to 4.5D.

[0055] The second kneading section 6 is a combination of the above-mentioned components, but preferably a combination of an R kneading disc, an N kneading disc, and an L kneading disc. For example, it is preferable to arrange multiple Ns after an R, followed by an L, and in particular, RNL, RRNL, RNNL, etc. are preferred.

[0056] Further, the disk configuration of the second kneading section 6 has a length of 1.5D to 4.5D, and preferably in the range of 2.0D to 4.0D.

[0057] After the second kneading section 6, the pressure is reduced through a vent 7 downstream of the second kneading section to remove volatile matter, and the polycarbonate resin composition is extruded in the form of strands from an extrusion die at a discharge section 9 at the tip of the extruder by an extrusion section 8. The screw speed of the twin-screw extruder is preferably about 500 to 900 rpm. In the method of the present invention, it is possible to achieve a discharge rate of preferably 350 kg / hr or more, more preferably 380 kg / hr or more, even more preferably 400 kg / hr or more, of which 450 kg / hr or more, 500 kg / hr or more, and particularly preferably 550 kg / hr or more.

[0058] The extruded strand-like molten polycarbonate resin composition is then cooled in water and cut into pellets. The shape of the extrusion die is not particularly limited, and a known one can be used. The diameter of the die of the discharge nozzle is usually about 2 to 5 mm, depending on the extrusion pressure and the desired size of the pellets. The temperature of the polycarbonate resin immediately after extrusion can be lower than usual, preferably about 270 to 300°C, more preferably about 270 to 290°C.

[0059] In the method of the present invention, it is also preferable to blend polycarbonate resin flakes (C), ABS resin (D), and other additives (E) other than (B) in addition to the resin pellets (A) and liquid phosphate ester flame retardant (B). The blending amounts of each component are 0-50% by mass of polycarbonate resin flakes (C), 0-30% by mass of ABS resin (D), and 0-15% by mass of other additives (E) other than (B), based on 100% by mass of the total of (A) to (E). Except when side feeding is particularly preferred, these components (C) to (E) are fed together with the resin pellets (A) or separately from them through a feed port 1 at the base of a twin-screw extruder.

[0060] The polycarbonate resin flakes (C) preferably have an average particle size of 2 mm or less, more preferably 1.5 mm or less. By supplying flaky polycarbonate resin, the generation of unmelted matter and aggregation of additives can be suppressed, and homogeneous polycarbonate resin composition pellets can be easily obtained. When the polycarbonate resin flakes (C) are used, the blending amount is preferably 5 to 45% by mass.

[0061] The ABS resin (D) is preferably composed of an aromatic vinyl monomer component, a vinyl cyanide monomer component, and a diene rubber polymer component, and is preferably an acrylonitrile-butadiene-styrene copolymer. The ABS resin (D) is preferably in the form of pellets and fed from the feed port 1 at the base of the twin-screw extruder together with the resin pellets (A). When the ABS resin (D) is used, the blending amount is preferably 5 to 25% by mass.

[0062] Preferred examples of the additives (E) other than the liquid phosphate ester flame retardant (B) include flame retardant assistants such as fluororesins (PTFE), various elastomers (impact resistance modifiers), release agents, stabilizers, fillers, reinforcing agents, other resin components, other flame retardants, colorants (dyes and pigments), UV absorbers, antistatic agents, antifogging agents, antiblocking agents, flow improvers, plasticizers, dispersants, antibacterial agents, etc. When additives (E) other than (B) are used, the amount of the additives is 15% by mass or less, preferably 13% by mass or less, more preferably 12% by mass or less, of which 11% by mass or less, and particularly preferably 10% by mass or less.

[0063] The polycarbonate resin composition pellets obtained by the production method of the present invention consist of 30 to 95 mass %, and preferably 30 to 80 mass %, of resin derived from resin pellets (A), 5 to less than 40 mass %, and preferably 5 to less than 25 mass %, of a phosphate ester flame retardant (B), 0 to 50 mass % of a polycarbonate resin derived from polycarbonate resin flakes (C), 0 to 30 mass % of an ABS resin (D), and 0 to 15 mass % of other additives (E) other than (B) [with the proviso that the total of (A) to (E) is 100 mass %].

[0064] The method for producing a molded article from the obtained polycarbonate resin composition pellets is not particularly limited, and molding methods generally used for polycarbonate resins, such as general injection molding, ultra-high speed injection molding, injection compression molding, multi-color injection molding, gas-assisted injection molding, molding using an insulated mold, molding using a rapid heating and cooling mold, foam molding (including supercritical fluids), insert molding, IMC (in-mold coating molding) molding, extrusion molding, sheet molding, thermoforming, rotational molding, lamination molding, press molding, etc. can be used.

[0065] The obtained molded article can be suitably used as parts for office automation equipment such as printers and copiers, electrical equipment, electronic equipment, vehicles such as automobiles, office automation equipment such as printers and copiers, housing, architecture, and the like, and can be particularly suitably used as housings for office automation equipment such as printers and copiers, computers, personal computers, various mobile terminals, batteries, and the like. EXAMPLES

[0066] The present invention will be described in more detail below with reference to examples, but the present invention should not be construed as being limited to the following examples.

[0067] The screw configuration of the extruder used in the examples and comparative examples is as follows. <Configuration example of the first kneading section> The three-row eccentric kneading discs of the following configuration examples 1 to 4 each have nine kneading discs, and the disc length is 1D. As each paddle of the kneading disc, a three-row paddle was used in which three apexes (tips) T were arranged at an equal angle θ of 120° from the geometric eccentricity y of the disc. The radius Da at the apex (tips) T is 21.0 mm (0.447 D), and between the apexes T there is a flank k that draws an outward arc, and the radius Dk at the center k is 15.5 mm (0.330 D). The eccentricity e of the paddle is 1.8 mm = 0.038 D, and the paddles on the left and right screws 2 and 2' are eccentric in the same direction. The tip width dT of the apex (tip part) T is 2.2 mm (0.047 D), and the radius of the arc of the tip part is 21 mm (0.447 D). The thickness of each paddle is 4.1 mm (0.087D), and there is a gap of 0.5 mm between adjacent paddles to prevent contact between the left and right kneading discs. The three-lobe eccentric kneading disc R is composed of nine paddles with the paddles facing downward and offset 45° clockwise from the center x of the screw shaft. The three-lobe eccentric kneading disc N is composed of nine paddles with the paddles offset 180° from the center x of the screw shaft. The three-lobe eccentric kneading disc L used is composed of nine paddles with the paddles facing downward and offset 45° counterclockwise from the center x of the screw shaft. The cylinder inner diameter D of the extruder is 47.0 mm, and the screw center distance A is 38.7 mm (0.823D). Configuration example 1: 3-groove eccentric RL, length 2D Configuration example 2: 3-groove eccentric RRNL, length 4D Configuration example 3: 3-groove eccentric RRNNL, length 5D Configuration example 4: 3-groove eccentric RRNNNNL length 7D

[0068] The kneading discs in the following configuration examples 5 to 6 are normal two-row kneading discs. Each two-row kneading disc screw has five paddles, and the thickness of each paddle is 8.0 mm (0.170 D). The angle between the two tips is 180°, the radius Da at the tip is 46.1 mm (0.981 D), and the radius Dk at the center k (closest distance from y) of the flank that draws an outward arc between the two tips is 28.8 mm (0.613 D). There is no eccentricity of the paddle, and the eccentricity e is 0 mm. The tip width dT of the tip (tip part) T is 5.2 mm (0.11 D), and the radius of the tip part arc (flank) is 46.1 mm (0.981 D). The two-row kneading disc R is composed of five paddles with the paddles facing downward and shifted 45° clockwise with respect to the center x of the screw shaft. The N double-lobe kneading disc is composed of five paddles that are offset by 90° from the screw shaft center x. The L double-lobe kneading disc is composed of five paddles that are downward and offset by 45° counterclockwise from the screw shaft center x. The paddles used had a gap of 0.5 mm between them. Configuration example 5: Normal 2-row RRNL, length 4D Configuration example 6: Normal 2-row RRNNL length 5D

[0069] <Configuration example of the second kneading section> The three-lobe eccentric kneading discs of the following configuration examples 1 to 4 each have nine kneading discs and a disc length of 1D. The specifications of the R, N, and L three-lobe eccentric kneading discs are the same as those described for the three-lobe eccentric kneading discs of the first kneading section. Configuration example 1: 3-row eccentric L length 1D Configuration example 2: 3-groove eccentric RNL, length 3D Configuration example 3: 3-groove eccentric RRNL, length 4D Configuration example 4: 3-groove eccentric RRNNNL length 6D

[0070] The kneading discs of the following configuration examples 5 to 6 are normal two-row kneading discs, each of which has five kneading discs and a disc length of 1 D. The specifications of the normal two-row kneading discs R, N, and L are the same as those described for the two-row kneading discs of the first kneading section. Configuration example 5: Normal 2-row RNL, length 3D Configuration example 6: Normal 2-row RRNL, length 4D

[0071] The raw materials used in the examples and comparative examples are as follows. Resin pellets (A) (A-1) Polycarbonate resin recycled pellets "PC-15NP" manufactured by OS TECH MFR=14g / 10min (300℃, 1.2kg load) (A-2) Polycarbonate resin pellets Mitsubishi Engineering Plastics Corporation, "S3000N" Viscosity average molecular weight Mv=22000 (A-3) Polycarbonate resin / ABS resin pellets A pellet made by compounding 80% by mass of polycarbonate resin flakes ("S3000F" manufactured by Mitsubishi Engineering Plastics Corporation, viscosity average molecular weight Mv = 22000) and 20% by mass of ABS resin pellets ("SXH-330" manufactured by Nippon A&L Co., Ltd.) Liquid phosphate ester flame retardant (B) Bisphenol A bis-diphenyl phosphate ADEKA "ADEKA STAB FP-600" Polycarbonate resin flakes (C) Mitsubishi Engineering Plastics "7022PJ", Mv=22000 ·ABS resin (D) ABS resin pellets, "SXH-330" manufactured by Nippon A&L Co., Ltd. Additives other than (B) (E) PTFE Daikin Industries "FA500H"

[0072] <Production Example A1> Polycarbonate resin recycled pellets (A-1) were fed at 240 kg / h (60% by mass) and polycarbonate resin flakes (C) at 80 kg / h (20% by mass) from a feed port 1 into a co-rotating twin-screw extruder (manufactured by Japan Steel Works, Ltd., "TEX44αIII"), and mixed in the first kneading section of screw configuration example 3. Then, liquid phosphate ester-based flame retardant (B) was added at 80 kg / h (20% by mass) from a liquid feed pump 5, and mixed in the second kneading section of screw configuration example 3. Then, the mixture was vented to reduce pressure, extruded from a discharge port to form strands, and cooled in a water tank, followed by pelletizing to obtain polycarbonate resin composition pellets. The screw rotation speed was 700 rpm, and the cylinder set temperature was 260°C. The resulting pellets were injection molded into a plate having a thickness of 3 mm. The YI was measured using transmitted light using a Nippon Denshoku Corporation spectrophotometer "SE6000." The results are shown in Table 1. In Table 1 and Table 2 below, the "resin temperature" refers to the temperature of the strand coming out of the discharge port. It was measured using a commercially available thermometer for resins.

[0073] <Manufacturing examples A2~A6> Production Example A1 was carried out in the same manner, except that the screw configurations of the first kneading section and the second kneading section were the configuration examples shown in Table 1, and the screw rotation speeds were the discharge rates and rotation speeds shown in Table 1.

[0074] <Comparative manufacturing example A1> Compounding was performed in the same manner as in Production Example A1, except that the screw configuration of the first kneading section was changed to Configuration Example 1 and the second kneading section was changed to Configuration Example 2. However, unmelted raw material polycarbonate resin recycled pellets (A-1) were produced, strands were broken and could not be taken up, and vent-up also occurred. Sampling of the product pellets was difficult. It was thought that the screw configuration of the first kneading section was too short, and the raw material pellets were not completely melted.

[0075] <Comparative manufacturing examples A2~A4> Production Example A1 was carried out in the same manner, except that the screw configurations of the first kneading section and the second kneading section were the configuration examples shown in Table 2, and the discharge rate and screw rotation speed were changed as shown in Table 2. The results are shown in Table 2. In Comparative Example A3, liquid was observed in the vent and vent-up occurred. Strands were frequently broken, and sampling of the product pellets was difficult. This was thought to be due to the second kneading section being too short, which prevented the liquid phosphate ester flame retardant from dispersing.

[0076] <Comparative manufacturing examples A5~A8> The same procedure was carried out as in Production Example A1, except that the screw configuration of the first kneading section and the second kneading section was the example of the double-kneading disk configuration shown in Table 2, and the discharge amount and the screw rotation speed were changed as shown in Table 2. The results are shown in Table 2. In Comparative Production Examples A5 and A6, the resin temperature was higher than in Production Examples A4 and A5, and the YI was also higher than in Production Examples A4 and A5. In Comparative Production Example A7, the raw material polycarbonate resin recycled pellets (A-1) were left unmelted, the strands were broken and could not be taken up, and vent-up also occurred. Sampling of the product pellets was difficult. The cause was thought to be that, compared to Production Example A6, the pellets were not melted sufficiently in the first kneading section when the discharge rate was increased.

[0077] <Comparative manufacturing example A9> The same procedure as in Production Example A4 was followed, except that the liquid phosphate ester flame retardant (B) was added from the same feed port 1 at the base of the extruder as the other raw materials. However, there was violent venting, some parts were not melted, and it was impossible to take up the strands. It is believed that the liquid phosphate ester flame retardant acted as a lubricant, and the polycarbonate resin pellets (A-1) were not melted because they were not sheared in the first kneading section, and they were not completely melted in the second kneading section, so they vented and could not be compounded.

[0078] <Comparative manufacturing example A10> In the same condition as Comparative Production Example A9, the rates of all the raw materials were decreased at a constant rate, and the output was increased to 300 kg / h, but the situation did not improve.

[0079] <Comparative manufacturing example A11> The feed rates were gradually reduced from the state of Comparative Production Example A10 while keeping the rates of all raw materials constant. As a result, in order to enable strand withdrawal without venting up, it was necessary to significantly reduce the total feed rate to 150 kg / h. It is believed that the reduced feed rate resulted in a longer residence time, sufficient shearing was applied, and the polycarbonate resin pellets (A-1) melted. However, the YI showed a high value. The above results are shown in Table 1-2.

[0080] [Table 1]

[0081] [Table 2]

[0082] <Production examples B1 to B6, comparative production examples B1 to B8> The same procedure as in Production Example A1 was repeated except that the polycarbonate resin recycled pellets (A-1) were 50% by mass (e.g., 200 kg / h in Production Example B1), the polycarbonate resin flakes (C) were 35% by mass (e.g., 140 kg / h in Production Example B1), and the liquid phosphate ester-based flame retardant (B) was 15% by mass (e.g., 60 kg / h in Production Example B1), and the screw configuration, discharge rate, and screw rotation speed were as shown in Table 3. The results are shown in Table 3.

[0083] [Table 3]

[0084] <Production examples C1 to C6, comparative production examples C1 to C8> The polycarbonate resin recycled pellets (A-1) were 80% by mass (e.g., 320 kg / h in Production Example C1), the polycarbonate resin flakes (C) were 0% by mass (e.g., 0 kg / h in Production Example C1), the liquid phosphate ester-based flame retardant (B) was 20% by mass (e.g., 80 kg / h in Production Example C1), and the screw configuration, discharge rate, and screw rotation speed were as shown in Table 4. The same procedure as in Production Example A1 was repeated. The results are shown in Table 4.

[0085] [Table 4]

[0086] <Production examples D1 to D6, comparative production examples D1 to D8> The same procedure as in Production Example A1 was repeated except that the polycarbonate resin recycled pellets (A-1) were 50% by mass (e.g., 200 kg / h in Production Example D1), the polycarbonate resin flakes (C) were 10% by mass (e.g., 40 kg / h in Production Example D1), the liquid phosphate ester-based flame retardant (B) was 20% by mass (e.g., 80 kg / h in Production Example D1), and the ABS resin pellets (D) were 20% by mass (e.g., 80 kg / h in Production Example D1), and the screw configuration, discharge rate, and screw rotation speed were as shown in Table 5. The color tone YI was measured using reflected light. The results are shown in Table 5.

[0087] [Table 5]

[0088] <Production examples E1 to E6, comparative production examples E1 to E8> The polycarbonate resin recycled pellets (A-1) were fed at 50% by mass (e.g., 200 kg / h in Production Example E1), polycarbonate resin flakes (C) at 10% by mass (e.g., 40 kg / h in Production Example E1), ABS resin pellets (D) at 19.5% by mass (e.g., 78 kg / h in Production Example E1), PTFE at 0.5% by mass (2 kg / h) as other additives (E), and liquid phosphate ester flame retardant (B) at 20% by mass (e.g., 80 kg / h in Production Example E1). The screw configuration, discharge rate, and screw rotation speed were as shown in Table 6. The same procedure as in Production Example A1 was performed. The color tone YI was measured using reflected light. The results are shown in Table 6.

[0089] [Table 6]

[0090] <Manufacturing examples F1 to F6, comparative manufacturing examples F1 to F8> The same procedure as in Production Example A1 was repeated except that the polycarbonate resin pellets "S3000N" (A-2) were used at 80 mass% (e.g., 320 kg / h in Production Example F1), the liquid phosphate ester-based flame retardant (B) was used at 20 mass% (e.g., 80 kg / h in Production Example F1), and the screw configuration, discharge rate, and screw rotation speed were as shown in Table 7. The color tone YI was measured by transmitted light, and the results are shown in Table 7.

[0091] [Table 7]

[0092] <Manufacturing examples G1 to G6, comparative manufacturing examples G1 to G8> The same procedure as in Production Example A1 was repeated except that the polycarbonate resin / ABS resin pellets (A-3) were 60% by mass (e.g., 240 kg / h in Production Example G1), the polycarbonate resin flakes (C) were 10% by mass (e.g., 40 kg / h in Production Example G1), the ABS resin pellets (D) were 10% by mass (e.g., 40 kg / h in Production Example G1), and the liquid phosphate ester-based flame retardant (B) was 20% by mass (e.g., 80 kg / h in Production Example G1), and the screw configuration, discharge rate, and screw rotation speed were as shown in Table 8. The color tone YI was measured in reflected light, and the results are shown in Table 8.

[0093] [Table 8] [Industrial Applicability]

[0094] According to the method of the present invention, polycarbonate resin composition pellets having an extremely good hue and uniform and excellent flame retardancy can be produced. The obtained pellets can be widely used as materials for manufacturing parts in office automation equipment such as printers and copiers, electrical equipment, electronic equipment, vehicles such as automobiles, housing, construction, and other industrial fields, and have extremely high industrial applicability.

Claims

1. A method for producing polycarbonate resin composition pellets using a twin-screw extruder, the method comprising: 30 to 95 mass% of resin pellets (A) containing more than 40 mass% of polycarbonate resin in the pellets; 5 mass% or more and less than 40 mass% of a phosphoric acid ester flame retardant (B) that is liquid at room temperature; 0 to 50 mass% of polycarbonate resin flakes (C); 0 to 30 mass% of ABS resin (D); and 0 to 15 mass% of other additives (E) other than (B) [with the proviso that the total of (A) to (E) is 100 mass%], the method comprising the steps of: The (A), (C), (D) and (E) are placed in a twin-screw extruder, The method includes a first step of kneading in a first kneading section, a second step of adding the (B) to a downstream portion of the first kneading section and kneading the mixture in a second kneading section, and a third step of degassing and extruding the mixture by reducing the pressure of a vent downstream of the second kneading section, The first kneading section uses a three-row eccentric kneading disc as a kneading disc, and the combination of the three-row eccentric kneading discs is an R kneading disc followed by an N kneading disc, followed by an L kneading disc, with a length of 2.5D to 6.5D (D is the cylinder inner diameter); The second kneading section uses a three-row eccentric kneading disc as a kneading disc, and the combination of the three-row eccentric kneading discs is configured such that an N kneading disc is arranged after an R kneading disc, and an L kneading disc is arranged after the R kneading disc, and the length is 1.5D to 4.5D. A method for producing polycarbonate resin composition pellets, characterized in that the rotation speed of the screws of the twin-screw extruder is 500 to 900 rpm.

2. The method according to claim 1, wherein the amount of the resin pellets (A) is 30 to 80% by mass in 100% by mass of the total of (A) to (E).

3. 3. The method according to claim 1, wherein the amount of the phosphate ester flame retardant (B) that is liquid at room temperature is 5% by mass or more and less than 25% by mass, based on 100% by mass of the total of (A) to (E).

4. The method according to any one of claims 1 to 3, comprising, as resin components, 50 to 100% by mass of a polycarbonate resin, and 50 to 0% by mass of an ABS resin and / or a polyester resin (the total of these being 100% by mass).

5. The method according to any one of claims 1 to 4, wherein the length of the first kneading section is in the range of 3.5 to 5.5D, and the length of the second kneading section is in the range of 2.0D to 4.0D.

6. 6. The method according to claim 1, wherein the three-lobe eccentric kneading disc is a substantially triangular disc with bulging central portions of each side, and is mounted on the screw shaft so as to rotate eccentrically.

7. The method according to any one of claims 1 to 6, wherein the eccentricity is 0.01D to 0.07D (D is the inner diameter of the cylinder) and the screw is attached.

8. The manufacturing method according to any one of claims 1 to 7, wherein the three-lobe eccentric kneading disc has three apexes with an angular interval θ of 110° to 130°, the radius at the apexes is in the range of 0.4D to 0.5D, and the radius at the center between the apexes is in the range of 0.25D to 0.38D (D is the inner diameter of the cylinder).

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