Flame-retardant high-temperature-resistant fiber woven fabric and preparation process thereof

Abstract

The invention relates to a flame-retardant high-temperature-resistant fiber woven fabric and a preparation process thereof, and belongs to the technical field of textiles. The preparation method comprises the following steps: grafting and crosslinking a self-made grafting monomer and polyvinyl chloride, and then weaving to obtain the modified polyvinyl chloride fiber fabric; a phosphate group in the monomer can promote surface carbonization to form a protective carbon layer, silicate generated by decomposition of a siloxy group at a high temperature is combined with the carbon layer to improve the strength and melt viscosity of the carbon layer, and the phosphate group and the siloxy group synergistically enhance the flame retardance and the molten drop resistance of the fabric; a cyclic phosphate group and a pyridine ring are connected to form a rigid structure with relatively high thermal stability, chain segment movement is limited, a plurality of siloxy groups in a monomer are crosslinked to form a crosslinked network, molecular chain segments are difficult to move, and the combination of the rigid group and the crosslinked network improves the high temperature resistance of the fabric and effectively improves the mechanical properties of the fabric; in addition, the positively charged quaternary ammonium salt structure in the monomer improves the antistatic performance of the fabric, and cooperates with trifluoromethyl to destroy the structural integrity of bacterial cells, so that the fabric achieves efficient bacteriostasis.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of textiles, and in particular relates to a flame-retardant high-temperature-resistant fiber woven fabric and a preparation process. BACKGROUND

[0002] In modern industry and daily life, fire hazards have always been a major factor threatening life and property safety, which makes the research and application of flame-retardant high-temperature-resistant fiber woven fabric attract much attention.

[0003] As a common fiber fabric, chlorofiber has rich raw materials, simple process and low cost, and has certain flame-retardant basis due to the presence of chlorine element. However, its intrinsic thermal stability is poor, and it starts to shrink at 60-70 DEG C, which seriously limits its application in high-temperature environment. Even if an external agent is added for modification, the heat resistance will weaken with long-term use, and the chlorofiber may produce toxic smoke when burning, which cannot meet the flame-retardant requirements of relevant national standards.

[0004] Based on this, the present application provides a flame-retardant high-temperature-resistant fiber woven fabric and a preparation process. SUMMARY

[0005] The present application aims to provide a flame-retardant high-temperature-resistant fiber woven fabric and a preparation process to solve the problems mentioned in the background.

[0006] The object of the present application can be achieved by the following technical solutions:

[0007] The preparation process of the flame-retardant high-temperature-resistant fiber woven fabric comprises the following steps:

[0008] In the first step, 2,3-dihydroxy pyridine, S-trifluoromethyl diphenyl sulfide salt, organic base and N,N-dimethyl formamide are added to a three-necked flask under nitrogen protection, a condenser tube and a thermometer are installed, magnetic stirring is started, and after 16-24 hours of reaction at room temperature, the organic phase is extracted with ethyl acetate and reserved, and the organic phase is washed with saturated sodium chloride solution and water, dried, rotary evaporated and then eluted by column chromatography to obtain a bacteriostatic agent;

[0009] In the second step, the bacteriostatic agent, phosphorus oxychloride, an acid binding agent, aluminum chloride and acetonitrile are added to a three-necked flask, a condenser tube and a thermometer are installed, magnetic stirring is started, and after 2-3 hours of reaction at 60-70 DEG C, the temperature is raised to 75-85 DEG C, and after 18-22 hours of reaction at 75-85 DEG C, the reaction is cooled to room temperature, rotary evaporated and then eluted by column chromatography to obtain a flame retardant;

[0010] In the third step, the flame retardant, 3-aminopropyl triethoxysilane, an acid binding agent and tetrahydrofuran are added to a three-necked flask, a condenser tube and a thermometer are installed, magnetic stirring is started, and after 16-24 hours of reaction at 50-60 DEG C, the reaction is cooled to room temperature and dried to obtain a crosslinking agent.

[0011] The fourth step is to add the cross-linking agent, 6-chloro-1-hexene and acetonitrile into a three-necked flask, install a condenser and a thermometer, start magnetic stirring, react at 40-60℃ for 8-12h, filter and dry after cooling to room temperature to obtain the grafted monomer;

[0012] The fifth step is to add the grafted monomer, polyvinyl chloride, azobisisobutyronitrile and tetrahydrofuran into a reaction kettle under nitrogen protection, react at 60-70℃ for 4-6h, then add water and dibutyltin dilaurate, and react at 110-120℃ for 2-3h, filter after cooling to room temperature, wash the obtained solid with methanol, dry to constant weight to obtain the modified polyvinyl chloride, then mix the modified polyvinyl chloride with an antioxidant, melt extrude in a double-screw extruder, and then melt spin, cool, draw, and cut to obtain the modified chlorofiber fabric.

[0013] Further, the organic base in the first step is one of 1,8-diazabicyclo[5.4.0]undec-7-ene, 1,5,7-triazabicyclo[4.4.0]dec-5-ene and 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene.

[0014] Further, the mass fraction ratio of 2,3-dihydroxypyridine, S-trifluoromethyl dibenzothiophene salt, organic base and N,N-dimethylformamide in the first step is 11-13:48-60:21-23:160-240.

[0015] Further, the acid-binding agent is one of triethylamine, pyridine and diisopropyl ethylamine.

[0016] Further, the mass fraction ratio of the bacteriostatic agent, phosphorus oxychloride, acid-binding agent, aluminum chloride and acetonitrile in the second step is 15-18:4.8-5.6:20-23:0.76-0.95:200-220.

[0017] Further, the mass fraction ratio of the flame retardant, 3-aminopropyl triethoxysilane, acid-binding agent and tetrahydrofuran in the third step is 18-22:17-21:8-10:180-200.

[0018] Further, the mass fraction ratio of the cross-linking agent, 6-chloro-1-hexene and acetonitrile in the fourth step is 24-28:8.5-10:150-160.

[0019] Further, the antioxidant in the fifth step is at least one of antioxidant 1010, antioxidant 1076 and antioxidant 2246.

[0020] Furthermore, in step five, the mass ratio of graft monomer, polyvinyl chloride, azobisisobutyronitrile, tetrahydrofuran, water, dibutyltin dilaurate, and antioxidant is 23–28: 16–20: 0.3–0.4: 150–170: 1–1.2: 0.06–0.08: 0.06–0.08.

[0021] Furthermore, the melt extrusion temperature in the fifth step is 160–180°C.

[0022] Flame-retardant and high-temperature resistant fiber woven fabric and its preparation process: The flame-retardant and high-temperature resistant fiber woven fabric is prepared by any of the above preparation processes.

[0023] The beneficial effects of this invention are:

[0024] 1) This invention uses 2,3-dihydroxypyridine and S-trifluoromethyldibenzothiophene salt as raw materials to carry out a trifluoromethylation reaction to obtain an antibacterial agent; uses the antibacterial agent and phosphorus oxychloride as raw materials to carry out a phosphorylation reaction to obtain a flame retardant; then uses the flame retardant and 3-aminopropyltriethoxysilane as raw materials to carry out a nucleophilic substitution reaction to obtain a crosslinking agent; uses the crosslinking agent and 6-chloro-1-hexene as raw materials to carry out a quaternary ammonium salt reaction to obtain a grafted monomer; finally, the grafted monomer is used to modify polyvinyl chloride and then obtained modified chlorofiber fabric through melt spinning and weaving.

[0025] 2) The phosphate ester groups and siloxy groups in the grafted monomers of this invention can synergistically enhance the flame retardant properties of the fabric. At high temperatures, the phosphate ester groups decompose to generate phosphorus-containing free radicals. These free radicals can capture hydrogen free radicals and hydroxyl free radicals in the combustion reaction to inhibit gas-phase combustion. They can also dehydrate and carbonize the fabric surface to form a dense char protective layer, preventing the spread of flames. At the same time, the silicates generated by the decomposition of siloxy groups at high temperatures combine with the char layer to improve the strength and thermal stability of the char layer, further blocking combustion. Therefore, the synergistic effect of phosphate ester groups and siloxy groups can effectively improve the flame retardancy of the modified fabric. Meanwhile, due to the introduction of phosphate ester groups and siloxy groups, the char layer formed on the surface during combustion is firmly attached to the fabric surface, so that the fabric basically does not melt and drip.

[0026] 3) The grafted monomers of this invention contain multiple siloxy groups. After grafting onto polyvinyl chloride (PVC), they cross-link through silicon-oxygen-silicon covalent bonds, constructing a highly thermally stable three-dimensional network structure. This architecture restricts the thermal motion of the molecular chains, requiring higher temperatures for chain segment movement and increasing the difficulty of the material transitioning from a glassy state to a highly elastic state. The silicon-oxygen bonds themselves possess excellent resistance to heat and oxygen aging. Simultaneously, the cross-linked network can both restrict the overall slippage of the PVC chains through a rigid framework and adjust stress distribution through local bond angles, thereby reducing brittle fracture under high-temperature conditions. Furthermore, the rigid structures such as cyclic phosphate groups and pyridine rings in the grafted monomers, after being incorporated into the molecular chains, further enhance the rigidity of the entire polymer chain, restricting chain segment movement from another dimension. The synergistic effect of these multiple properties enhances the high-temperature resistance of the fabric while effectively improving its mechanical properties.

[0027] 4) The positively charged quaternary ammonium salt groups in the monomers grafted onto the polyvinyl chloride (PVC) chain segments in this invention readily bind to the negatively charged bacterial cell membranes, disrupting cell membrane integrity. They can also penetrate the cell interior through osmosis, interfering with intracellular enzyme activity, protein synthesis, and metabolic processes, leading to bacterial death or loss of reproductive capacity. Trifluoromethyl groups possess strong hydrophobicity, reducing the free energy of the fabric surface to resist bacterial cell membrane formation, and bacteria have difficulty adhering to hydrophobic surfaces. The hydrophobic environment created by trifluoromethyl groups also enhances the efficiency of the quaternary ammonium salt groups in disrupting bacterial cell membranes. Through synergistic effects, the modified fabric achieves highly efficient antibacterial activity. Simultaneously, the positively charged quaternary ammonium salt groups provide charge carriers for ionization, allowing for directional migration and charge conduction under an electric field, thus achieving the antistatic effect of the fabric. Detailed Implementation

[0028] The technical solutions of the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments in this application specification, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection claimed in this application.

[0029] The raw materials used in this invention are not particularly restricted in terms of their source; they can be purchased from the market or prepared using conventional methods known to those skilled in the art.

[0030] Example 1

[0031] The preparation process of flame-retardant and high-temperature resistant fiber woven fabric includes the following steps:

[0032] Step 1: Under nitrogen protection, 11g of 2,3-dihydroxypyridine, 48g of S-trifluoromethyldibenzothiophene salt, 21g of 1,8-diazabicyclo[5.4.0]undec-7-ene and 160g of N,N-dimethylformamide were added to a three-necked flask, fitted with a condenser and thermometer, and magnetic stirring was turned on. After reacting at room temperature for 16h, the mixture was extracted with ethyl acetate and the organic phase was retained. The organic phase was washed with sodium chloride solution and water, dried, rotary evaporated, and then eluted by column chromatography to obtain the antibacterial agent.

[0033] Step 2: Add 15g of antibacterial agent, 4.8g of phosphorus oxychloride, 20g of triethylamine, 0.76g of chlorine chloride and 200g of acetonitrile to a three-necked flask, attach a condenser and thermometer, turn on magnetic stirring, and react at 60℃ for 3h, then raise the temperature to 75℃ and react at 75℃ for 22h. After the reaction is completed, cool to room temperature, evaporate by rotary evaporation and then elute by column chromatography to obtain the flame retardant.

[0034] Step 3: Add 18g flame retardant, 17g 3-aminopropyltriethoxysilane, 8g pyridine and 180 tetrahydrofuran into a three-necked flask, attach a condenser and thermometer, turn on magnetic stirring, and react at 50℃ for 24h. After cooling to room temperature, wash with water and dry with anhydrous magnesium sulfate to obtain crosslinking agent.

[0035] Step 4: Add 24g of crosslinking agent, 8.5g of 6-chloro-1-hexene and 150g of acetonitrile to a three-necked flask, attach a condenser and a thermometer, turn on magnetic stirring, and react at 40℃ for 12h. After cooling to room temperature, filter and dry with anhydrous magnesium sulfate to obtain the grafted monomer.

[0036] Step 5: Under nitrogen protection, 23g of graft monomer, 16g of polyvinyl chloride, 0.3g of azobisisobutyronitrile and 160g of tetrahydrofuran were added to the reactor and reacted at 60℃ for 6 hours. Then, 1g of water and 0.06g of dibutyltin dilaurate were added and reacted at 110℃ for 3 hours. After cooling to room temperature, the mixture was filtered. The resulting solid was washed with methanol and dried to constant weight to obtain modified polyvinyl chloride. The modified polyvinyl chloride was then mixed with 0.06g of antioxidant 1010 and melt-extruded in a twin-screw extruder at 160℃. The modified chlorofiber fabric was then obtained through melt spinning, cooling, stretching, chopping and weaving.

[0037] Flame-retardant and high-temperature resistant fiber woven fabric is prepared by the above-mentioned preparation process.

[0038] Example 2

[0039] The preparation process of flame-retardant and high-temperature resistant fiber woven fabric includes the following steps:

[0040] Step 1: Under nitrogen protection, 12g of 2,3-dihydroxypyridine, 54g of S-trifluoromethyldibenzothiophene salt, 22g of 1,5,7-triazabicyclo[4.4.0]dec-5-ene and 200g of N,N-dimethylformamide were added to a three-necked flask, fitted with a condenser and thermometer, and magnetic stirring was turned on. After reacting at room temperature for 20h, the mixture was extracted with ethyl acetate and the organic phase was retained. The organic phase was washed with sodium chloride solution and water, dried, rotary evaporated, and then eluted by column chromatography to obtain the antibacterial agent.

[0041] The second step involves adding 16.5g of antibacterial agent, 5.2g of phosphorus oxychloride, 21.5g of pyridine, 0.86g of chlorine chloride, and 210g of acetonitrile to a three-necked flask, attaching a condenser and a thermometer, turning on the magnetic stirrer, and reacting at 65℃ for 2.5h. Then, the temperature is raised to 80℃ and reacted at 80℃ for 20h. After the reaction is completed, the mixture is cooled to room temperature, rotary evaporated, and then eluted by column chromatography to obtain the flame retardant.

[0042] Step 3: Add 20g flame retardant, 19g 3-aminopropyltriethoxysilane, 9g diisopropylethylamine and 190g tetrahydrofuran into a three-necked flask, attach a condenser and thermometer, turn on magnetic stirring, and react at 55℃ for 20h. After cooling to room temperature, wash with water and dry with anhydrous magnesium sulfate to obtain crosslinking agent.

[0043] Step 4: Add 26g of crosslinking agent, 9.75g of 6-chloro-1-hexene and 155g of acetonitrile to a three-necked flask, attach a condenser and a thermometer, turn on magnetic stirring, and react at 50℃ for 10h. After cooling to room temperature, filter and dry with anhydrous magnesium sulfate to obtain the grafted monomer.

[0044] Step 5: Under nitrogen protection, 25.5g of graft monomer, 18g of polyvinyl chloride, 0.35g of azobisisobutyronitrile and 170g of tetrahydrofuran were added to the reactor and reacted at 65℃ for 5h. Then, 1.1g of water and 0.07g of dibutyltin dilaurate were added and reacted at 115℃ for 2.5h. After cooling to room temperature, the mixture was filtered. The resulting solid was washed with methanol and dried to constant weight to obtain modified polyvinyl chloride. The modified polyvinyl chloride was then mixed with 0.07g of antioxidant 1076 and melt-extruded in a twin-screw extruder at 170℃. The modified chlorofiber fabric was then obtained through melt spinning, cooling, stretching, chopping and weaving.

[0045] Flame-retardant and high-temperature resistant fiber woven fabric is prepared by the above-mentioned preparation process.

[0046] Example 3

[0047] The preparation process of flame-retardant and high-temperature resistant fiber woven fabric includes the following steps:

[0048] Step 1: Under nitrogen protection, 13g of 2,3-dihydroxypyridine, 60g of S-trifluoromethyldibenzothiophene salt, 23g of 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene and 240g of N,N-dimethylformamide were added to a three-necked flask, fitted with a condenser and thermometer, and magnetic stirring was turned on. After reacting at room temperature for 24h, the mixture was extracted with ethyl acetate and the organic phase was retained. The organic phase was washed with sodium chloride solution and water, dried, rotary evaporated, and then eluted by column chromatography to obtain the antibacterial agent.

[0049] The second step involves adding 18g of antibacterial agent, 5.6g of phosphorus oxychloride, 23g of diisopropylethylamine, 0.95g of chlorine chloride, and 220g of acetonitrile to a three-necked flask, attaching a condenser and a thermometer, turning on the magnetic stirrer, and reacting at 70℃ for 2 hours. The temperature is then raised to 85℃ and reacted at 85℃ for 18 hours. After the reaction is completed and cooled to room temperature, the flame retardant is obtained by rotary evaporation followed by column chromatography.

[0050] Step 3: Add 22g flame retardant, 21g 3-aminopropyltriethoxysilane, 10g triethylamine and 200g tetrahydrofuran into a three-necked flask, attach a condenser and thermometer, turn on magnetic stirring, and react at 60℃ for 16h. After cooling to room temperature, wash with water and dry with anhydrous magnesium sulfate to obtain crosslinking agent.

[0051] Step 4: Add 28g of crosslinking agent, 10g of 6-chloro-1-hexene and 160g of acetonitrile to a three-necked flask, attach a condenser and a thermometer, turn on magnetic stirring, and react at 60℃ for 8 hours. After cooling to room temperature, filter and dry with anhydrous magnesium sulfate to obtain the grafted monomer.

[0052] Step 5: Under nitrogen protection, 28g of graft monomer, 20g of polyvinyl chloride, 0.4g of azobisisobutyronitrile and 170g of tetrahydrofuran were added to the reactor and reacted at 70℃ for 4h. Then, 1.2g of water and 0.08g of dibutyltin dilaurate were added and reacted at 120℃ for 2h. After cooling to room temperature, the mixture was filtered. The resulting solid was washed with methanol and dried to constant weight to obtain modified polyvinyl chloride. The modified polyvinyl chloride was then mixed with 0.08g of antioxidant 2246 and melt-extruded in a twin-screw extruder at 180℃. The modified chlorofiber fabric was then obtained through melt spinning, cooling, stretching, chopping and weaving.

[0053] Flame-retardant and high-temperature resistant fiber woven fabric is prepared by the above-mentioned preparation process.

[0054] Comparative Example 1

[0055] 18g of polyvinyl chloride and 0.07g of antioxidant 1076 are mixed evenly and then added to a twin-screw extruder for melt extrusion at 170℃. The resulting product is obtained by melt spinning, cooling, stretching, chopping, and weaving.

[0056] Experimental Example 1

[0057] The fabrics in Examples 1-3 and Comparative Example 1 were subjected to performance analysis. The dripping condition of each group of fabrics during combustion was tested according to GB8965.1-2020 "Flame-retardant Protective Clothing". The heat shrinkage rate of each group of fabrics was tested according to GB / T6505-2017 "Test Method for Heat Shrinkage Rate of Chemical Fiber Filaments". The resistivity of each group of fabrics was tested according to GB / T14342-2015 "Test Method for Specific Resistance of Chemical Fiber Short Fibers". The elongation at break of each group of fabrics was tested according to GB / Z32009-2015 "Mechanical Property Data Sheet for New Textile Materials". The antibacterial rate of each group of fabrics against Staphylococcus aureus and Escherichia coli was tested according to GB / T20944.3-2008 "Evaluation of Antibacterial Properties of Textiles". The fabric in Comparative Example 1 served as a blank control. The test results are shown in Table 1.

[0058] Table 1

[0059] Item Dripping condition Thermal shrinkage (%) Specific resistance (Ω·m) Elongation at break (%) Bacteriostatic rate (%) Example 1 No dripping 9.1 10 10 ]] 30.8 97.6 Example 1 No dripping 8.9 10 9 ]] 32.5 98.3 Example 1 No dripping 9.6 10 10 ]] 31.6 96.8 Comparative Example 1 Dripping 15.0 10 15 ]] 17.6 Blank control

[0060] As can be seen from Table 1, compared with Comparative Example 1, Examples 1-3 have higher elongation at break and antibacterial rate, lower heat shrinkage and resistivity, and do not melt and drip during combustion. This indicates that the anti-drip properties, heat resistance, antistatic properties, toughness, and antibacterial properties of Examples 1-3 are all better than those of Comparative Example 1. Combined with Comparative Example 1, it can be seen that grafting monomers can effectively improve the anti-drip properties, heat resistance, antistatic properties, toughness, and antibacterial properties of modified chlorofiber fabrics.

[0061] The above description of the embodiments is merely to aid in understanding the method and core ideas of the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A preparation process for flame-retardant and high-temperature resistant fiber woven fabric, characterized in that, Includes the following steps: Preparation of crosslinking agent: A bacteriostatic agent is obtained by trifluoromethylation reaction of 2,3-dihydroxypyridine, S-trifluoromethyldibenzothiophene salt and organic base. Then, a flame retardant is obtained by phosphorylation reaction of bacteriostatic agent, phosphorus oxychloride and acid binder. Finally, a crosslinking agent is obtained by substitution reaction of flame retardant and 3-aminopropyltriethoxysilane. Preparation of modified chlorofiber fabric: Graft monomers are obtained by reacting a crosslinking agent with 6-chloro-1-hexene to form a quaternary ammonium salt; the graft monomers are grafted onto polyvinyl chloride, and then crosslinked with water and dibutyltin dilaurate to obtain modified polyvinyl chloride; the modified polyvinyl chloride is mixed with antioxidants and then melt-extruded, spun, and woven by a twin-screw extruder to obtain modified chlorofiber fabric.

2. The preparation process of the flame-retardant and high-temperature resistant fiber woven fabric according to claim 1, characterized in that, The organic base is one of 1,8-diazabicyclo[5.4.0]undec-7-ene, 1,5,7-triazabicyclo[4.4.0]dec-5-ene, or 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene.

3. The preparation process of the flame-retardant and high-temperature resistant fiber woven fabric according to claim 1, characterized in that, The acid-binding agent is one of triethylamine, pyridine, or diisopropylethylamine.

4. The preparation process of the flame-retardant and high-temperature resistant fiber woven fabric according to claim 1, characterized in that, The mass ratio of 2,3-dihydroxypyridine, S-trifluoromethyldibenzothiophene salt, and organic base is 11–13:48–60:21–23; the mass ratio of antibacterial agent, phosphorus oxychloride, and acid-binding agent is 15–18:4.8–5.6:20–23; and the mass ratio of flame retardant and 3-aminopropyltriethoxysilane is 18–22:17–21.

5. The preparation process of the flame-retardant and high-temperature resistant fiber woven fabric according to claim 1, characterized in that, The antioxidant is at least one of antioxidant 1010, antioxidant 1076 and antioxidant 2246.

6. The preparation process of the flame-retardant and high-temperature resistant fiber woven fabric according to claim 1, characterized in that, The temperature conditions for grafting are 60–70℃, and the time conditions are 4–6 hours.

7. The preparation process of the flame-retardant and high-temperature resistant fiber woven fabric according to claim 1, characterized in that, The crosslinking temperature is 110–120℃ and the time is 2–3 h.

8. The preparation process of the flame-retardant and high-temperature resistant fiber woven fabric according to claim 1, characterized in that, The mass ratio of crosslinking agent, 6-chloro-1-hexene, graft monomer, polyvinyl chloride, water, dibutyltin dilaurate, and antioxidant is 24-28:8.5-10:23-28:16-20:1-1.2:0.06-0.08:0.06-0.

08.

9. The preparation process of the flame-retardant and high-temperature resistant fiber woven fabric according to claim 1, characterized in that, The melt extrusion temperature is 160–180℃.

10. A flame-retardant and high-temperature resistant woven fiber fabric, characterized in that, Flame-retardant and high-temperature resistant fiber woven fabric is prepared by the preparation process described in any one of claims 1 to 9.