Method for producing flame-retardant polycarbonate resin composition pellets

Abstract

Provided is a method for producing a polycarbonate resin composition pellet with a twin-screw extruder, the polycarbonate resin composition pellet comprising: 30-95 mass% of (A) a resin pellet including more than 40 mass% of a polycarbonate resin in the pellet; 5-40 (exclusive of 40) mass% (B) a phosphate ester flame retardant that is liquid at room temperature; 0-50 mass% of (C) polycarbonate resin flakes; 0-30 mass% of (D) an ABS resin; and 0-15 mass% of (E) an additive other than (B). The method is characterized by including a first step for putting (A), (C), (D), and (E) into a twin-screw extruder and kneading with a first kneading unit, a second step for adding (B) to a downstream part in the first kneading unit and kneading with a second kneading unit, and a third step for decompressing a vent in the downstream part in the second kneading unit to devolatilize and extrude, wherein the first kneading unit has a specific screw configuration in which the length thereof is 2.4-6.0 D, and the second kneading unit has a specific screw configuration in which the length thereof is 1.3-4.0 D.

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 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, which are crushed, washed, separated, and recovered and then pelletized into pellets. In addition, by-products such as sprues and runners from 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 halogen-based flame retardant or a phosphorus-based flame retardant with the polycarbonate resin, and currently phosphorus-based flame retardants are 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 liquid phosphorus-based flame retardants, and unmelted polycarbonate resin is easily generated, vent-up occurs at the vent opening, discharge rate does not increase, strands cannot be taken up, and the flame retardancy of the obtained polycarbonate resin composition pellets is easily insufficient, and color tone is easily reduced. An object (object) of the present invention is to provide a method for producing a flame-retardant polycarbonate resin composition by using a liquid phosphorus-based flame retardant, thereby solving the above problems. [Means for solving the problem]

[0009] Means for Solving the Problems The present inventors have conducted extensive research in order to achieve the above object, and as a result have found that when a phosphate flame retardant that is liquid at room temperature is added to resin pellets containing a polycarbonate resin and produced in a twin-screw extruder, the liquid phosphate is added downstream of a first kneading section, and then the pellets are kneaded in a subsequent kneading section, and each kneading section has a specific screw configuration, thereby making it possible to produce polycarbonate resin composition pellets that are uniform, have excellent flame retardancy, and are excellent in hue, with a high discharge rate, in a stable and productive manner, and have 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, The first kneading section is configured to have a length of 2.5D to 6.0D (D is the screw diameter) by combining two or more of an R kneading disc, an N kneading disc, an L kneading disc, an L screw, a seal ring, a mixing screw, or a rotor screw, The second kneading section is configured to have a length of 1.3D to 4.0D by combining two or more of an R kneading disc, an N kneading disc, an L kneading disc, an L screw, a seal ring, a mixing screw, or a rotor screw. 1. A method for producing polycarbonate resin composition pellets, comprising the steps of: 2. The manufacturing method according to the above 1, wherein the polycarbonate resin pellets account for more than 50 mass% of the resin pellets (A). 3. The method according to 1 or 2 above, wherein the amount of the resin pellets (A) is 30 to 80% by mass, with the total of (A) to (E) being 100% by mass. 4. The method according to any one of 1 to 3 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, with the total of (A) to (E) being 100% by mass. 5. The method for producing polycarbonate resin composition pellets according to any one of the above 1 to 4, wherein the resin pellets (A) contain recycled resin pellets. 6. A method for producing polycarbonate resin composition pellets according to any one of 1 to 5 above, which contains, as resin components, 50 to 100 mass % of polycarbonate resin and 50 to 0 mass % of ABS resin and / or polyester resin (based on a total of 100 mass % of both). 7. The method for producing polycarbonate resin composition pellets according to any one of the above 1 to 6, 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. Effect of the Invention

[0011] According to the production method of the present invention, polycarbonate resin composition pellets which are uniform and have excellent flame retardancy and color can be produced stably and productively at a high discharge rate without generating unmelted materials or vent-up. [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. 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 are, based on a total of 100 mass% of (A) to (E), 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), where the total of (A) to (E) is 100 mass%.

[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. As the resin pellets (A), it is sufficient that the polycarbonate resin is contained in the resin pellets (A) in an amount of more than 40% by mass, and mixtures or alloys containing other resins than polycarbonate resin, such as ABS resin, thermoplastic polyester (polybutylene terephthalate resin, polyethylene terephthalate resin, etc.), can also be preferably used. In the resin pellets (A), it is preferable that the polycarbonate resin pellets are more than 50% by mass.

[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. Preferred examples of used products 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, building components such as corrugated sheets, etc. Also usable as recycled polycarbonate resins are crushed products obtained from non-conforming products, sprues, or runners during molding, or pellets obtained by melting these.

[0025] [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 being liquid at 23°C. Examples of the phosphate flame retardant include phosphate compounds and condensed phosphates, with condensed phosphates being preferred.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] [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.

[0032] 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.

[0033] Fig. 1 is a cross-sectional view showing one example of the screw configuration of an extruder used in the method of the present invention. The production method of the present invention will be described below with reference to Figs.

[0034] 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 of the extruder, and the resin pellets (A) are transported while being melted and kneaded toward a discharge port 9 on the right side in FIG. 1 by the heating of the extruder barrel and the rotation of the screws, and the strands discharged from the discharge port 9 are pelletized in a granulator.

[0035] 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.

[0036] Next, the resin pellets (A) are melted in the first kneading section 3, which is composed of a combination of two or more of an R kneading disc, an N kneading disc, an L kneading disc, an L screw, a seal ring, a mixing screw, or a rotor screw, and has a length of 2.5D to 6.0D (D is the screw diameter).

[0037] The first kneading section means a region where kneading is performed before the liquid phosphate ester flame retardant is introduced, and this first kneading section may be a continuous or divided section of two or more of the R kneading disc, N kneading disc, L kneading disc, L screw, seal ring, mixing screw, or rotor screw. The total length of the R kneading disc, N kneading disc, L kneading disc, L screw, seal ring, mixing screw, or rotor screw may be 2.5D to 6.0D (D is the screw diameter), and a normal feed flight that does not have a kneading function is not included in the length of the first kneading section. For example, as in the first kneading section 3 in FIG. 2, a normal feed flight-like element (an element with oblique hatching in 3 in FIG. 2) may be inserted between a plurality of kneading discs, and such a feed flight-like element is not included in the length of 2.5D to 6.0D.

[0038] The R kneading disc is also called the progressive kneading disc (hereinafter sometimes referred to as R), and usually has two or more blades with a twist angle Θ of 10 degrees to 75 degrees. By setting the blades at a specified angle in this way, it is possible to feed the resin and apply a strong shearing force. 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 the twist angle Θ of the blade being 75 degrees to 105 degrees. Because the blades are set at approximately 90 degrees offset from each other, there is almost no force to send the resin, but the kneading force is strong. The L kneading disc is also called the reverse kneading disc (hereinafter sometimes referred to as L), and usually has two or more blades with a twist angle Θ of -10 degrees to -75 degrees. The L kneading disc is an element with the ability to block incoming resin or to boost pressure by working in the direction of returning the resin that has been sent. By installing it downstream of the element that promotes kneading, it blocks the resin and exerts a strong kneading effect. The L screw, also known as the reverse feed screw, is a screw that spirals in the opposite direction to the 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, it blocks resin by being installed downstream of the element that promotes kneading, and exerts a strong kneading effect.

[0039] The above-mentioned blades are usually elliptical, with flat parts at the two vertices of the ellipse. These blades are also called disks, and each kneading disk is usually composed of 3 to 7 disks. These disks may be roughly triangular in shape and have 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. Among the kneading disks, there are also twist kneading disks, whose vertices are twisted in the screw axial direction, and similar kneading effects can be obtained.

[0040] The seal ring is a ring-shaped device that is fitted to the screw, and blocks about 70-90% of the flow path, retaining the resin flow and increasing the resin pressure. As with L kneading, by installing it downstream of the element that promotes kneading, the resin is blocked, providing a powerful kneading effect. A mixing screw is made by cutting the crest of a screw flight, and is a single- or double-start or reverse-start screw that has a strong shear dispersion force. There are forward-start notch type mixing screws and reverse-start notch type mixing screws. The rotor screw has elliptical (two-blade structure) or triangular rotor blades, and can generate strong shear force due to the gap (tip clearance) between the rotor and the inner wall surface of the barrel.

[0041] The first kneading section 3 is a combination of two or more of the above, but 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 RNNL, RNNNL, etc., is preferred.

[0042] Further, the disk configuration of the first kneading section 3 has a length of 2.5D to 6.0D, and preferably in the range of 3.5 to 5.5D.

[0043] The resin pellets (A) are sufficiently melted in the first kneading section 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.

[0044] 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 21% by mass or less.

[0045] 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.

[0046] The second kneading section 6 is configured to combine two or more of an R kneading disc, an N kneading disc, an L kneading disc, an L screw, a seal ring, a mixing screw, or a rotor screw, and has a length of 1.3D to 4.0D. 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), and it is possible to stably and productively produce polycarbonate resin composition pellets that are uniform, have excellent flame retardancy, and are also excellent in color.

[0047] The second kneading section means a region where the phosphate ester flame retardant enters and is kneaded until it reaches the vacuum vent, and this second kneading section may be continuous with two or more of the R kneading disc, N kneading disc, L kneading disc, L screw, seal ring, mixing screw, or rotor screw, or may be divided into a plurality of parts. The total length of the two or more of the R kneading disc, N kneading disc, L kneading disc, L screw, seal ring, mixing screw, or rotor screw may be 1.3D to 4.0D (D is the screw diameter), and a normal feed flight that does not have a kneading function is not included in the length of the second kneading section. For example, as in the second kneading section 6 in FIG. 2, a normal feed flight-like element (the diagonally hatched element in 6 in FIG. 2) may be inserted between a plurality of kneading discs to divide them, and such a feed flight-like element is not included in the length of 1.3D to 4.0D.

[0048] The second kneading section 6 is a combination of two or more of the above, 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, followed by an L, is preferable, and RNL, RNNL, RNNNL, RNNNNL, RNNNNNL, etc. are particularly preferable. Note that each R, N, and L in the configuration can be used in any combination of 0.5D or 1.0D.

[0049] Further, the disk configuration of the second kneading section 6 has a length of 1.3D to 4.0D, and preferably in the range of 2.0D to 4.0D.

[0050] 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, and particularly preferably 500 kg / hr or more, is possible.

[0051] 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 is preferably about 280 to 300°C, more preferably about 280 to 290°C.

[0052] 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 for polycarbonate resin flakes (C), 0-30% by mass for ABS resin (D), and 0-15% by mass for other additives (E) other than (B), based on the total of (A)-(E) being 100% by mass. 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.

[0053] 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.

[0054] 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.

[0055] 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. The amount of additives (E) other than (B) used 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.

[0056] 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 %].

[0057] 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.

[0058] 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

[0059] 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.

[0060] The screw configuration of the extruder used in the examples and comparative examples is as follows. <Configuration example of the first kneading section> Each of the configuration examples 1 to 4 has five kneading discs and a disc length of 1D. Configuration example 1: RL length 2D Configuration example 2: RNNL length 4D Configuration example 3: RNNNL length 5D Configuration example 4: RNNNNNL length 7D <Configuration example of the second kneading section> Configuration examples 1, 2, and 4 have five kneading discs with a disc length of 1D, while configuration example 3 has five kneading discs with a disc length of 0.5D. Configuration example 1: L length 1D Configuration example 2: RNL length 3D Configuration example 3: RNNNNNL length 3.5D Configuration example 4: RNNNL length 5D

[0061] The raw materials used in the examples and comparative examples are as follows. Resin pellets (A) (A-1) Polycarbonate resin recycled pellets "2010ANC" manufactured by SHANGHAI AUSELL MATERIAL 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 (manufactured by Mitsubishi Engineering Plastics Corporation, "S3000F", viscosity average molecular weight Mv = 22000) and 20% by mass of ABS resin pellets (manufactured by Nippon A&L Corporation, "SXH-330") in advance. Liquid phosphorus-based flame retardant (B) Bisphenol A bis-diphenyl phosphate ADEKA "ADEKA STAB FP-600" Polycarbonate resin flakes (C) Mitsubishi Engineering Plastics Corporation, "S3000F", Mv=22000 ·ABS resin (D) ABS resin pellets, manufactured by Nippon A&L Co., Ltd., "SXH-330" Additives other than (B) (E) PTFE Daikin Industries, Ltd., "FA500H"

[0062] <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 to a co-rotating twin-screw extruder ("TEX44αII", manufactured by Japan Steel Works, Ltd.), and mixed in the first kneading section of screw configuration example 3. Then, liquid phosphorus-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 2. 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 with transmitted light using a Spectrophotometer "SE6000" manufactured by Nippon Denshoku Co., Ltd. In addition, the total light transmittance (%) of this 3 mm plate was measured with a haze meter "NDH4000" manufactured by Nippon Denshoku Co., Ltd., using a light source of D65 / 10°, JIS K7361, and transmitted light. The results are shown in Table 1.

[0063] <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.

[0064] <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 3. However, unmelted raw 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 pellets were not completely melted.

[0065] <Comparative manufacturing examples A2~A8> Production Example A1 was carried out in the same manner, except that the screw configuration of the first kneading section and the second kneading section was the configuration example shown in Table 1. The results are shown in Table 1. In Comparative Production Examples A4, A5, and A6, liquid was observed in the vent and vent-up occurred. Strands were also frequently broken, making it difficult to sample the product pellets. This was thought to be due to the second kneading section being too short, which prevented the liquid phosphorus-based flame retardant from dispersing.

[0066] <Comparative manufacturing example A9> The compounding was carried out in the same manner as in Production Example A1, except that the liquid phosphorus-based flame retardant (B) was added from the same supply port at the base of the extruder as the other raw materials. However, there was strong venting up, some of the material was not melted, and it was impossible to take up the strands. It is believed that the liquid phosphorus-based 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 up and could not be compounded.

[0067] <Comparative manufacturing example A10> In the same condition as Comparative Production Example A9, the rates of all the raw materials were lowered at a constant rate until the discharge rate reached 300 kg / h, but the situation did not improve.

[0068] <Comparative manufacturing example A11> The feed rates were gradually reduced while keeping all raw material rates constant from the state of Comparative Production Example A10. As a result, in order to make it possible to take up strands without venting up, it was necessary to significantly reduce the total feed rate to 140 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 total light transmittance was low, and the YI also showed a high value. The above results are shown in Table 1-2.

[0069] [Table 1]

[0070] [Table 2]

[0071] <Production examples B1 to B6, comparative production examples B1 to B8> The compounding was carried out in the same manner as in Production Example A1, except that the polycarbonate resin recycled pellets (A-1) were fed at 200 kg / h (50 mass%), the polycarbonate flakes (C) were fed at 140 kg / h (35 mass%), the liquid phosphorus-based flame retardant (B) was fed at 60 kg / h (15 mass%), and the screw rotation speed was set to the rotation speed shown in the table. The results are shown in Table 3.

[0072] [Table 3]

[0073] <Production examples C1 to C6, comparative production examples C1 to C8> The compounding was carried out in the same manner as in Production Example A1, except that the polycarbonate resin recycled pellets (A-1) were fed at 320 kg / h (80 mass%), the polycarbonate flakes (C) were fed at 0 kg / h (0 mass%), the liquid phosphorus-based flame retardant (B) was fed at 80 kg / h (20 mass%), and the screw rotation speed was set to the rotation speed shown in the table. The results are shown in Table 4.

[0074] [Table 4]

[0075] <Manufacturing examples D1 to D6, comparative manufacturing examples D1 to D8> The compound was prepared in the same manner as in Production Example A1, except that the polycarbonate resin recycled pellets (A-1) were fed at 200 kg / h (50% by mass), the polycarbonate flakes (C) at 40 kg / h (10% by mass), the ABS resin pellets (D) at 80 kg / h (20% by mass), the liquid phosphorus-based flame retardant (B) at 80 kg / h (20% by mass), and the screw rotation speed was set to the rotation speed shown in the table. The color tone YI was measured by reflected light. The results are shown in Table 5.

[0076] [Table 5]

[0077] <Production examples E1 to E6, comparative production examples E1 to E8> The compound was prepared in the same manner as in Production Example A1, except that polycarbonate resin recycled pellets (A-1) were fed at 200 kg / h (50 mass%), polycarbonate flakes (C) at 40 kg / h (10 mass%), ABS resin pellets (D) at 78 kg / h (19.5 mass%), PTFE as other additives (E) at 2 kg / h (0.5 mass%), liquid phosphorus-based flame retardant (B) at 80 kg / h (20 mass%), and the screw rotation speed was set to the rotation speed shown in the table. The color tone YI was measured by reflected light. The results are shown in Table 6.

[0078] [Table 6]

[0079] <Manufacturing examples F1 to F6, comparative manufacturing examples F1 to F8> The compound was prepared in the same manner as in Production Example A1, except that the polycarbonate resin pellets "S000N" (A-2) were fed at 320 kg / h (80% by mass), the liquid flame retardant (B) was fed at 80 kg / h (20% by mass), and the screw rotation speed was set to the rotation speed shown in the table. The color tone YI was measured by transmitted light. The results are shown in Table 7.

[0080] [Table 7]

[0081] <Manufacturing examples G1 to G6, comparative manufacturing examples G1 to G8> The compound was prepared in the same manner as in Production Example A1, except that the polycarbonate resin / ABS resin pellets (A-3) were fed at 240 kg / h (60 mass%), the polycarbonate flakes (C) at 40 kg / h (10 mass%), the ABS resin pellets (D) at 40 kg / h (10 mass%), the liquid phosphorus-based flame retardant (B) at 80 kg / h (20 mass%), and the screw rotation speed was set to the rotation speed shown in the table. The color tone YI was measured by reflected light. The results are shown in Table 8.

[0082] [Table 8] [Industrial Applicability]

[0083] According to the method of the present invention, it is possible to produce polycarbonate resin composition pellets which are uniform, have excellent flame retardancy and hue, and are stable and productive at a high discharge rate without generating unmelted materials or vent-up. The obtained polycarbonate resin 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, architecture, 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 but less than 25 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%], 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 is configured to have a length of 3.5D to 5.5D (D is the screw diameter) by combining two or more of an R kneading disc, an N kneading disc, an L kneading disc, an L screw, a seal ring, a mixing screw, or a rotor screw; The second kneading section is configured to have a length of 2.0D to 4.0D by combining two or more of an R kneading disc, an N kneading disc, an L kneading disc, an L screw, a seal ring, a mixing screw, or a rotor screw.

1. A method for producing polycarbonate resin composition pellets, comprising the steps of:

2. The production method according to claim 1, wherein the resin pellets (A) contain polycarbonate resin pellets in an amount of more than 50 mass%.

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

4. The method for producing polycarbonate resin composition pellets according to any one of claims 1 to 3, wherein the resin pellets (A) contain recycled resin pellets.

5. 5. The method for producing polycarbonate resin composition pellets according to claim 1, 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 (based on a total of 100% by mass of both).

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