JP2006124481A - Method for producing (co)polyamide nano composite material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a polymer nano composite material composition that can give a (co)polyamide nano composite material in which the nano fillers are perfectly dissolved from each other. <P>SOLUTION: (a) A molten polyamide having an intrinsic viscosity of less than 1 and nanofillers are mixed and the nanofillers are dispersed in the polyamide and (b) the resultant mixture is polymerized under the polymerization condition to prepare the polymer nano composite material composition. The intrinsic viscosity of the polyamide is kept less than 0.9. The process step (a) is preferably selected from uniaxial or biaxial screw extruder. The process step (b) may be carried out in the molten state or in the solid state. The polymerization in the step (b) is carried out by using a catalyst and/or an extruder having vacuum zones. The catalyst may be a residue used in the production of polyamide. The nano filler is preferably laminated or layered silicate salts. The advantages of the production process is (1) to obtain the (co)polyamide nano composite material in which the nanofillers are perfectly dissolved from each other; (2) the viscosity can be selected; (3) the nanofillers can be dispersed well; (4) a common extruder or mixing machine can be used; and (5) the nano filler can perfectly be dissolved while the process is executed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a process for producing (co) polyamide composite materials, in particular (co) polyamides containing dispersed nanofillers.

The following literature describes a process for producing polyamide composites:
European Patent No. 1 405 874

  This polyamide composite material has a feed zone (a) having supply ports (a) meshed with each other, a kneading zone (b) having a high dispersion mixing capability having a supply port (b), and a high distribution mixing capability. Using a twin screw extruder having kneading zones (b) in this order, a diamine component containing 70 mol% or more of m-xylylenediamine and 50 mol% or more of C4 to C20 α, ω-aliphatic linear dicarboxylic acid It is made from polyamide A1 and polyamide A2 obtained by polycondensation with a dicarboxylic acid component containing, and organized clay B.

The patent features the following process:
(1) A step of sending polyamide A1 having a relative viscosity of 1.1 to 4.7 containing a phosphorus compound having an amount of phosphorus atoms of 500 ppm or less and organized clay B to zone (a) through feed port (a). ,
(2) a melt-kneading step of polyamide A1 and organized clay B to obtain a melt-kneaded product by dispersion kneading in zone (a),
(3) The obtained melt-kneaded material is sent from zone (a) to zone (b) and at the same time, polyamide A2 having a relative viscosity of 2.0 to 4.7 is fed to zone (b) via feed port (b). Process,
(4) Disperse and mix in the kneading zone (b) to melt-knead each of the melt-kneaded product and the polyamide A2 from the supply zone (b) to make a polyamide composite material.

  In the specification, it is described that the phosphorous compound concentration of the polyamides A1 and A2 is preferably 1 to 500 ppm, more preferably 350 ppm or less, further preferably 200 ppm or less in terms of phosphorus atoms. If it exceeds 500 ppm, the effect of preventing discoloration cannot be obtained, and the fogging of the film made from this polyamide composite material increases.

  In Example 1 of this patent, PA1 having a relative viscosity of 2.56 is fed to the twin-screw extruder at a feed rate of 6.12 kg / hr, and clay is fed to the twin-screw extruder at a feed rate of 2.04 kg / hr, and PA2 having a relative viscosity of 2.5 is 51.84. A polyamide composite material having a relative viscosity of 2.50 is obtained by feeding to a twin screw extruder at a feed rate of kg / hour. There is no increase in viscosity. That is, even when 500 ppm of a phosphorus compound is added to A1, there is no increase in viscosity. The purpose of adding the phosphorus compound is to improve the processing stability during melt molding and prevent discoloration of the polyamides A1 and A2.

The following literature describes a method for producing the polymer nanocomposite material.
International Patent No. WO 99-41060

  The method of this patent makes a fluid mixture of polyamide and silicate material, dissociates (but not all of) the silicate is dissociated (the meaning of dissociation is described in detail), and dissociated fluidity The polyamide in the mixture is polymerized in the solid state. All examples relate to PA 6.6. The polyamide mixed with the silicate material has an intrinsic viscosity of 1.33 to 1.38. For the polymerization in the solid state (mixture PA + silicate), in the examples, the intrinsic viscosity is increased from 1.67 to 2.5, from 1.67 to 2.73 and from 1.63 to 2.05.

  The inventor has found that in order to better disperse the nanofiller, the viscosity of the polyamide must be lowered, for example in the range of 1 to 0.4, after which the mixture of polyamide and nanofiller must be further polymerized. .

The present invention resides in a method for producing a polymer nanocomposite composition characterized by the following (a) and (b):
(A) Mixing a melted polyamide having an intrinsic viscosity of 1 or less and a nanofiller to disperse the nanofiller in the polyamide,
(B) The resulting mixture is subjected to polymerization conditions to polymerize the polyamide to produce a polymer nanocomposite composition.

The intrinsic viscosity of the polyamide is preferably 0.9 or less, and more preferably 0.4 to 0.8.
Step (a) is performed with an extruder or a mixer. A single or twin screw extruder is preferably used. Step (b) can be performed in a molten state or a solid state, but can be easily performed in the same apparatus as in step (a). For example, (a) is performed with an extruder and (b) is performed with the same extruder.
In the process of making).

The polymerization in step (b) uses a catalyst and / or operates the zone of the extruder in which step (b) takes place under vacuum. The catalyst can be introduced in step (a) or step (b). Since the catalyst used to make the polyamide remains, the catalyst may be originally contained in the polyamide.
The nanofiller is preferably a layered or laminated silicate.

The present invention has the following advantages:
(1) A (co) polyamide nanocomposite material in which nanofillers are completely dissociated can be obtained.
(2) The viscosity can be selected by adjusting in step (b).
(3) Nano filler is well dispersed.
(4) An ordinary extruder or mixer can be used, and no specific equipment is required.
(5) Nano filler can be completely dissociated during the process.

The catalyst is a polycondensation catalyst such as an inorganic or organic acid, such as phosphoric acid.
To avoid depolymerization, it is preferred to dry the polyamide thoroughly (preferably carefully controlling the moisture level). The amount of catalyst can be 5 ppm to 15000 ppm with respect to the polyamide. Phosphoric acid or hypophosphorous acid is preferred. The amount of catalyst is 3000 ppm or less, preferably 200 to 4500 ppm, more preferably 550 to 4500 ppm, based on the amount of polyamide. The proportion in the case of other catalysts, such as boric acid, is different from that described above, and the amount can be selected according to the usual techniques of polycondensation of polyamides.

Polyamide means the following condensation products:
1) Condensation of one or more amino acids such as aminocaproic acid, 7-aminoheptanoic acid, 11-aminoundecanoic acid and 12-aminododecanoic acid, or one or more lactams such as caprolactam, enanthractam and lauryllactam,
2) One or more diamines such as hexamethylene diamine, dodecamethylene diamine, meta-xylylene diamine, bis (p-aminocyclohexyl) methane, trimethylhexamethylene diamine salt or mixture and diacids such as isophthalic acid, terephthalic Condensation with acids, adipic acid, azelaic acid, suberic acid, sebacic acid, dodecanedicarboxylic acid.
Examples of polyamides include PA 6, PA 6-6, PA 11 and PA 12.

Copolyamides can also be used advantageously. Examples of copolyamides include at least two α, ω-amino carboxylic acids, or two lactams, or those obtained by condensation of one lactam with one α, ω-aminocarboxylic acid. .
It is also possible to use a copolyamide obtained by condensation of at least one α, ω-aminocarboxylic acid (or one lactam), at least one diamine and at least one dicarboxylic acid.

  Examples of lactams include those having 3 to 12 carbon atoms on the main ring, and the lactam may be substituted. Examples include β, β-dimethylpropiolactam, α, α-dimethylpropiolactam, amylolactam, caprolactam, capryllactam and lauryllactam.

Examples of α, ω-aminocarboxylic acid include aminoundecanoic acid and aminododecanoic acid. Examples of dicarboxylic acids include adipic acid, sebacic acid, isophthalic acid, butanedioic acid, 1,4-cyclohexanedicarboxylic acid, terephthalic acid, sodium salt or lithium salt of sulfoisophthalic acid, dimerized fatty acid (this dimerized fatty acid) And didecaneic acid (HOOC— (CH ₂ ) ₁₀ —COOH).

  The diamine can be an aliphatic diamine having 6 to 12 carbon atoms and may be of aryl and / or saturated ring type. Examples include hexamethylenediamine, piperazine, tetra-methylene-diamine, octa-methylene-diamine, deca-methylene-diamine, dodecamethylenediamine, 1,5-diamino-hexane, 2,2,4-tri-methyl-1. , 6-diaminohexane, diamine polyol, isophoronediamine (IPD), methylpentamethylenediamine (MPDM), bis (aminocyclohexyl) methane (BACM), bis (3-methyl-4-aminocyclohexyl) methane (BMACM) be able to.

  Examples of copolyamides include caprolactam and lauryl lactam copolymers (PA 6/12), caprolactam and adipic acid and hexamethylenediamine copolymers (PA 6 / 6-6), caprolactam, lauryl lactam, adipic acid and hexa Copolymers with methylenediamine (PA 6/12 / 6-6), caprolactam, lauryllactam, copolymers of 11-aminoundecanoic acid, azelaic acid and hexamethylenediamine (PA6 / 6-9 / 11/12), caprolactam, lauryl Examples include copolymers of lactam, 11-aminoundecanoic acid, adipic acid and hexa-methylenediamine (PA6 / 6-6 / 11/12), copolymers of lauryllactam, azelaic acid and hexamethylenediamine (PA 6-9 / 12) It is done. For convenience, the copolyamide is preferably selected from PA 6/12 and PA 6 / 6-6.

Polyamide blends can also be used.
Even if a part of the polyamide is replaced with a copolymer having a polyamide block and a polyether block, it does not depart from the present invention. That is, in the present invention, a mixture of the above polyamide and a copolymer having at least one polyamide block and at least one polyether block can be used.

A copolymer of a polyamide block and a polyether block is obtained by copolycondensation of a polyether block having a reactive end and a polyamide block having a reactive end, and examples thereof include the following. :
1) polycondensation of a polyamide block having a diamine chain end with a polyoxyalkylene block having a dicarboxylic acid chain end,
2) Polyamide having a diamine chain end obtained by cyanideation and hydrogenation of an aliphatic dihydroxylated α, ω-polyoxyalkylene block called polyether diol and a polyamide block having a dicarboxylic acid chain end Polycondensation with oxyalkylene blocks,
3) Polycondensation of a polyamide block having a dicarboxylic acid chain end and a polyether diol, and the compound obtained in this case is called a polyether ester amide. This copolymer is preferably used.

Polyamide blocks having dicarboxylic acid chain ends are obtained, for example, by condensation of α, ω-aminocarboxylic acids, lactams or dicarboxylic acids with diamines in the presence of the chain regulator dicarboxylic acid.
The polyether can be, for example, polyethylene glycol (PEG), polypropylene glycol (PPG) or polytetramethylene glycol (PTMG). The latter is also called polytetrahydrofuran (PTHF).

The number average molar mass of the polyamide block is 300-15000, preferably 600-5000. The number average molar mass of the polyether block is 100 to 6000, preferably 200 to 3000.
The polymer having a polyamide block and a polyether block may contain randomly dispersed units. These polymers can be prepared by simultaneous reaction of polyether and polyamide block precursors.

  For example, it is possible to react a polyether diol, a lactam (or α, ω-amino acid) and a chain regulator diacid in the presence of a small amount of water. The resulting polymer is primarily composed of various lengths of polyether blocks and polyamide blocks, but may also include various randomly reacted components randomly distributed along the polymer chain.

  Polymers having polyamide blocks and polyether blocks can be obtained by copolycondensation of pre-made polyamide and polyether blocks or can be made by a single stage reaction, for example, Shore D hardness 20-75, preferably Is 30 to 70 and has an intrinsic viscosity (measured at 250 ° C. at an initial concentration of 0.8 g / 100 ml in metacresol) of 0.8 to 2.5. MFI is 5-50 (235 ° C under 1kg load).

  The polyether diol block is used as it is and polycondensed with a polyamide block having a carboxylic acid end, or aminated and converted into a polyether diamine, and condensed with a polyamide block having a carboxylic acid end. Further, it is possible to make a polymer having a polyamide block and a polyether block having a unit in which a polyamide precursor and a chain regulator are brazed and randomly dispersed.

Polymers with polyamide and polyether blocks are described in the chemical and patent:
U.S. Pat.No. 4,331,786 U.S. Pat.No. 4,115,47 U.S. Pat.No. 4,195015 U.S. Pat.No. 4,839,441 US Patent 4864014 U.S. Pat.No. 4,230,838 U.S. Pat.No. 4,332,920

  The weight ratio of the copolymer of polyamide block and polyether block to the amount of polyamide is from 10/90 to 60/40. Examples include (i) PA 6 and (ii) blends of PA6 blocks and PTMG block copolymers, (i) PA 6 or PA 12 and (ii) blends of PA 12 blocks and PTMG block copolymers.

Also included are copolyamides of the formula: X / Y, Ar.
(here,
Y represents an aliphatic diamine residue having 8 to 20 carbon atoms;
Ar represents an aromatic dicarboxylic acid residue,
X is either amino undecanoic acid NH2- (CH _{2) 10} -COOH residues, represents a lactam -12 or its corresponding amino acid, further, X is aliphatic diacid having 8 to 20 carbon atoms and (x) a diamine Represents the unit Y, x of the residue obtained by condensation with X, or X represents the unit Y, I of the residue obtained by condensation with diamine and isophthalic acid)

The di X / Y, Ar preferably represents:
-11/10, T (condensation of aminoundecanoic acid, 1,10-decanediamine and terephthalic acid),
-12/12, T (Condensation of lactam-12, 1,12-dodecanediamine and terephthalic acid)
-10,10 / 10, T (condensation of sebacic acid, 1,10-decanediamine and terephthalic acid)
-10, I / 10, T (Condensation of isophthalic acid, 1,10-decanediamine and terephthalic acid)

Mention may also be made of polyamides of the formula: XY / Z or 6.Y2 / Z.
(here,
X represents an aliphatic diamine residue having 6 to 10 carbon atoms;
Y represents an aliphatic diacit residue having 10 to 14 carbon atoms;
Y2 represents an aliphatic diacid residue having 15 to 20 carbon atoms,
Z is also selected from among lactam residues, α, ω aminocarboxylic acid residues, units X1.Y1 (where X1 represents an aliphatic diamine residue and Y1 represents an aliphatic dicarboxylic acid residue) Represents one unit,
Weight ratio: Z / (X + Y + Z) and Z / (6 + Y2 + Z) are 0-15%)

Plasticizers are benzenesulfonamide derivatives such as N-butylbenzenesulfonamide (BBSA), ethyltoluene-sulfonamide or N-cyclohexyltoluenesulfonamide, esters of hydroxybenzoic acid such as 2-ethylhexyl-para-hydroxybenzoate and 2 -Decylhexyl-para-hydroxybenzoate, ester or ether of tetrahydrofurfuryl alcohol, such as oligoethyleneoxytetrahydrofurfuryl alcohol, succinate or hydroxymalonic acid, such as oligoethyleneoxymalonate. A particularly preferred plasticizer is N-butylbenzenesulfonamide (BBSA). The use of a mixture of plasticizers does not depart from the scope of the present invention. The plasticizer can be added to the polyamide during or after polycondensation.
Preferably, the polyamide is 72-92% based on the total amount of plasticizer of 28-8%.

  The nanofiller used in the present invention is preferably a laminated or layered silicate. This layered silicate has a structure composed of a negatively charged crystal layer (silicate layer) mainly composed of silicate and a cation having ion exchange ability interposed between the layers. The silicate layer is a basic unit constituting the layered silicate, and is a plate-like inorganic crystal obtained by breaking the layer structure of the layered silicate (hereinafter referred to as “cleavage”). The silicate layer in this invention means the lamination | stacking state of 1 or less of this layer one by one or an average five layers or less.

  In the present invention, “uniformly dispersed” refers to a state in which the silicate layer exists without forming a lump when dispersed in the resin matrix. Specifically, when the silicate layer is dispersed in the resin matrix, it means a state in which each layer maintains an interlayer distance of 2 nm or more on average and does not form a lump. Here, the interlayer distance is the distance between the centers of gravity of the silicate layers. This state can be confirmed from a transmission electron micrograph of a test piece of the obtained resin composition.

Layered silicates may be natural or artificial, such as smectites (montmorillonite, beidellite, hectorite, saconite, etc.), vermiculites (vermiculite, etc.), micas (fluorine mica, muscovite, paragonite, phlogopite, Repidolite, etc.), brittle mica family (margarite, clintnite, anandite, etc.), chlorite family (donbasite, sudoite, kukeite, clinochlore, chamosite, nimaiandite, etc.).
In the present invention, swellable fluorine mica and montmorillonite are particularly preferably used. In particular, the swellable fluorine mica is more preferable because it has excellent whiteness and a large effect of increasing rigidity.

Swellable fluoromica has the structural formula represented by the general formula:
M _a (Mg _b Li _c ) Si ₄ O ₁₀ F ₂
(here,
0 <a ≦ 1,
2.5 ≦ b ≦ 3,
0 ≦ c ≦ 0.5,
a + b + 2c = 6,
M represents an ion-exchangeable cation, specifically sodium or lithium)
This swellable fluorine mica can be obtained by a melting method or an intercalation method.

Montmorillonite has the structural formula shown below:
_{M a Si (Al 2-a} Mg) O 10 (OH) 2 · nH 2 O
(here,
0.25 ≦ a ≦ 0.6,
n is zero or a positive integer,
M represents an ion-exchangeable cation)
This montmorillonite can be obtained by refining a naturally produced product using a water treatment or the like.
In addition, montmorillonite is known to have the same type of ion substitution product such as magnesia montmorillonite, iron montmorillonite, iron magnesia montmorillonite, and these may be used.

The amount of the layered silicate is preferably 0.1 to 30% by weight, more preferably 1 to 10% by weight, as the amount of inorganic ash that is an incineration residue of the obtained polyamide resin composition. When the amount of inorganic ash is less than 0.1% by weight, high rigidity cannot be obtained, and when it exceeds 30% by weight, the specific gravity increases and the weight cannot be reduced, and the toughness is greatly reduced.
In the present invention, the layered silicate is preferably brought into contact with a swelling agent in advance to increase the interlayer distance in order to uniformly disperse the silicate layer in the resin matrix. The swelling agent is preferably an organic cation, and examples include organic ammonium ions and organic phosphonium ions.
Examples of organic ammonium ions include primary to quaternary ammonium ions. Examples of the primary ammonium ion include octyl ammonium, dodecyl ammonium, octadecyl ammonium and the like. Secondary ammonium ions include dioctyl ammonium, methyl octadecyl ammonium, dioctadecyl ammonium and the like. Examples of tertiary ammonium ions include trioctylammonium, dimethyldodecylammonium, didodecylmonomethylammonium and the like. Quaternary ammonium ions include tetraethylammonium, trioctylmethylammonium, octadecyltrimethylammonium, dioctadecyldimethylammonium, dodecyldihexylmethylammonium, dihydroxyethylmethyloctadecylammonium, methyldodecylbis (polyethylene glycol) ammonium, and methyldiethyl (polypropylene glycol) ammonium. Etc. Further, examples of the organic phosphonium ion include tetraethylphosphonium, tetrabutylphosphonium, tetrakis (hydroxymethyl) phosphonium, 2-hydroxyethyltriphenylphosphonium, and the like. These compounds may be used alone or in combination of two or more. Of these, ammonium ions are preferably used.

When the layered silicate is brought into contact with the organic cation, first, the layered silicate is dispersed in water or alcohol, and the organic cation is added thereto in the form of a salt, followed by stirring and mixing to form a layered structure. Ion exchange of inorganic ions of silicate with organic cations. Then filter, wash and dry.
The composition of the present invention may contain additives such as antioxidants, ultraviolet absorbers, pigments and other stabilizers. These additives per se are those used in ordinary polyamides and are known. The amount of the additive is 5 parts by weight or less, preferably 0.5 to 2 parts by weight with respect to 100 parts by weight of the polyamide resin composition. The composition according to the invention is generally in the form of granules.

The following materials were used in the examples:
Nanomer I.24TL: Montmorillonite clay modified with 12-aminododecanoic acid (provided by NANOCOR),
PA11-1: Nylon-11 obtained using a catalyst with a density of 1.030 g / cm ³ and an ISO intrinsic viscosity of 0.8 dl / g,
PA11-2: Nylon-11 obtained using a catalyst with a density of 1.030 g / cm ³ and an ISO intrinsic viscosity of 0.4 dl / g,
PA11-3: Nylon-11 obtained using a catalyst with a density of 1.030 g / cm ³ and an ISO intrinsic viscosity of 1.35 dl / g,
Stab: Stabilizing additive system for “heat and light”,
Equipment used:
Twin screw extruder (co-rotating HAAKE 16)
Characterization method:
Observation with a transmission electron microscope: A sample made by a low temperature ultra slice method was photographed with a ZEISS CEM 902.
In all examples, the intrinsic viscosity was measured at 20 ° C. in a solution of 5 × 10 ⁻³ g of polyamide in 1 cm ³ of metacresol. The ISO corrected value of intrinsic viscosity was determined using the following formula:
轗_{ISO correction value} =轗_measurement × 100 / [(100% -x %) × 1.034]
(Where x% is the extractables and mineral content)

Example 1
PA11-1 (94.8%), NANOMER I.24TL (4%) and Stab (1.2%) dry blend composition WERNER® 30 (D / L = 30) co-rotating twin screw extrusion Compounded on the machine. The feed zone was not heated. The other bands adopted a flat temperature profile of 270 ° C. The profile of the screw is divided into four main zones:
(1) Feed band composed of transport elements,
(2) Melting / intercalation zone composed of kneading block + backflow element,
(3) a degassing zone having a vacuum vent hole made up of only conveying elements;
(4) Final extrusion zone composed of mixing / distribution elements to reliably disperse the pieces. The viscosity of nylon PA1 obtained at the highest vacuum level is 1.6.
[Figure 1] shows a photograph of the peeled piece.
When the screw rotation speed was 300 rpm, the extrusion speed at the die outlet was 20 kg / hour. The obtained rod was cooled in a water tank to form granules, and the obtained granules were dried at 80 ° C. for 12 hours. After water content inspection (water% = 0.08%), they were packed in a sealed bag.

Example 2
A dry blend composition of 94.8% PA11-2, 4% NANOMER I.24TL and 1.2% Stab was compounded in a CLEXTRAL BC21 (D / L = 24) type co-rotating twin screw extruder. The feed zone was not heated. The other zone had a flat temperature profile of 230 ° C. The outline structure of the screw was the same as in Example 1. The obtained tablet was pulverized into a fine powder and then the viscosity was increased to a solid state. The viscosity of nylon 11 of this PA2 was 1.3. [Figure 2] shows a photograph of the peeled piece.

Example 3
A dry blend of PA11-2 (94.8%), NANOMER I.24TL (4%) and Stab (1.2%) was compounded as in Example 2. The resulting tablet was introduced into a WERNER (30 (D / L = 30) co-rotating twin screw extruder. The feed zone was not heated. The other zones were flat at 270 ° C. The profile of the screw and the compounding conditions were the same as in Example 1.
The viscosity of nylon PA3 obtained at the highest vacuum level was 1.4. [FIG. 3] shows a photograph of the peeled piece.

Example 4
A dry blend composition of PA11-3 (94.8%), NANOMER I.24TL (4%) and Stab (1.2%) was compounded under the same conditions as in Example 1.
[FIG. 4] is a photograph showing a partially peeled state (a state in which a laminated state remains).

4 is a transmission electron microscope photograph of the sample of Example 1. FIG. 4 is a transmission electron microscope photograph of the sample of Example 2. FIG. 6 is a transmission electron microscope photograph of the sample of Example 3. FIG. 6 is a transmission electron microscope photograph of the sample of Example 4. FIG.

Claims (8)

A method for producing a polymer nanocomposite comprising the following steps (a) and (b):
(A) Mixing a melted polyamide having an intrinsic viscosity of 1 or less and a nanofiller to disperse the nanofiller in the polyamide,
(B) The resulting mixture is subjected to polymerization conditions to polymerize the polyamide to produce a polymer nanocomposite composition.   2. The method according to claim 1, wherein the polyamide has an intrinsic viscosity of 0.9 or less.   The method according to claim 2, wherein the polyamide has an intrinsic viscosity of 0.4 to 0.8.   The method as described in any one of Claims 1-3 which performs the process of (a) with an extruder or a mixer.   The method as described in any one of Claims 1-4 which performs the process of (b) in a molten state.   The method as described in any one of Claims 1-5 which performs the process of (b) in a molten state in the same apparatus as the process of (a).   The method according to any one of claims 1 to 6, wherein the polymerization in the step (b) is performed using a catalyst and / or the extruder in which the step (b) is performed is operated under vacuum.   The method according to claim 1, wherein the nanofiller is a layered or laminated silicate.

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