A nylon elastomer composition, its preparation method and use

Abstract

The application discloses a nylon elastomer composition and a preparation method and application thereof. The composition comprises the following components: 100 parts of nylon elastomer; 20-100 parts of polyolefin elastomer; 1-10 parts of amphiphilic branched copolymer; 0.1-0.5 parts of antioxidant; and 0.1-0.5 parts of lubricant. The composition has good overall compatibility, and has high elongation at break and melt strength.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of nylon elastomer compositions, especially a kind of nylon elastomer compositions and its preparation method and application. BACKGROUND

[0002] Nylon elastomer is the common name of thermoplastic polyamide elastomer, which refers to a kind of block copolymer composed of high melting point crystalline polyamide (nylon) hard segment and non-crystalline polyether or polyester soft segment. This material has excellent softness, elastomer recovery rate and fatigue resistance, and is widely used in the production of functional parts of mechanical and electrical precision instruments, automobile parts, sports goods, etc. It can also be used to make high-end running shoe soles, compressed air pipes, fire 2 hoses, etc. after foaming.

[0003] However, the market price of nylon elastomer is relatively high (about 100 yuan / kg), which is not conducive to product promotion. Blending modification of nylon elastomer with polyolefin elastomer (below 20,000 yuan / ton) with lower sales price is the main idea to reduce production cost. However, due to the large difference in polarity between them, the compatibility between them is poor. Therefore, how to improve the compatibility of the blended material is the main direction of current research work. On the other hand, there are few brands of commercially available nylon elastomer products, and the performance is single, which cannot meet the application fields of some high melt strength nylon elastomers, such as high foaming ratio shoe sole foaming material, high-end large diameter pipe, etc. SUMMARY

[0004] The present application aims to provide a kind of nylon elastomer composition with good compatibility and high melt strength, and its preparation method and application.

[0005] In order to solve the above technical problems, the present application first proposes a kind of nylon elastomer composition.

[0006] A kind of nylon elastomer composition comprises the following components by weight: 100 parts of nylon elastomer; 20-100 parts of polyolefin elastomer; 1-10 parts of amphiphilic branched copolymer; 0.1-0.5 parts of antioxidant, 0.1-0.5 parts of lubricant;

[0007] The amphiphilic branched copolymer is a copolymer with polyolefin elastomer as linear main chain and polyether polyol oligomer as branched side chain.

[0008] As some specific examples of the nylon elastomer composition in the present application, the melt index of the nylon elastomer under the test conditions of 235℃ and 2.16kg is 4-40g / 10min;

[0009] As some specific examples of the nylon elastomer composition in the present application, the melt index of the polyolefin elastomer under the test conditions of 235℃ and 2.16kg is 0.5-5g / 10min;

[0010] Preferably, the polyolefin elastomer is selected from one or more of POE (polyolefin elastomer), POP (polyolefin plastomer), SBS (styrene-butadiene-styrene block copolymer), SEBS (hydrogenated SBS).

[0011] As some specific examples of the nylon elastomer composition in the present application, the antioxidant is selected from one or more of a compound of antioxidant 1010, antioxidant 1098, antioxidant 168, antioxidant H10;

[0012] Preferably, the lubricant is selected from one or more of ethylene bis-stearamide, oleic acid amide, silicone oil, paraffin wax.

[0013] The present application also proposes a preparation method of the nylon elastomer composition as described above, comprising the following steps: high-speed mixing the nylon 12 elastomer, the polyolefin elastomer, the amphiphilic branched polymer, the lubricant, and the antioxidant for 10-20 min, melt extrusion, water cooling, granulation, drying, and obtaining the nylon elastomer composition.

[0014] As some specific examples of the preparation method of the nylon elastomer composition in the present application, the preparation method of the amphiphilic branched polymer is as follows:

[0015] S1, mixing the polyolefin elastomer, maleic anhydride, and initiator and then extruding to obtain a maleic anhydride grafted modified polyolefin elastomer;

[0016] S2, mixing the polyether polyol and monobasic acid, catalyst, heating to 200-240℃, then vacuumizing to 100-500 Pa absolute pressure, and reacting for 0.5-1 h; after stopping vacuumizing, adding nitrogen to 100-300 kPa, stopping stirring, and cooling to obtain a monohydroxyl-terminated polyether polyol oligomer;

[0017] S3, mixing the maleic anhydride grafted modified polyolefin elastomer obtained in step S1 and the monohydroxyl-terminated polyether polyol oligomer, heating to 200-240℃, vacuumizing to 100-500 Pa absolute pressure, and continuing to react for 0.5-1 h to obtain the amphiphilic branched polymer. The obtained amphiphilic branched copolymer is a copolymer with the polyolefin elastomer as a linear main chain and the polyether polyol oligomer as branched side chains. The amphiphilic branched copolymer can improve the interfacial strength of the nylon elastomer and the polyolefin elastomer, realize smaller phase size dispersion of the polyolefin elastomer in the nylon elastomer, avoid stress cracking at the interfacial phase during use, and improve the elongation at break of the material. In addition, the special dendritic structure is easy to form a network structure in the nylon elastomer and the polyolefin elastomer blending system, further improving the melt strength of the blending system.

[0018] As some specific examples of the preparation method of the nylon elastomer composition in the present application, in step S1, the maleic anhydride is added in an amount of 2-10% by mass of the polyolefin elastomer;

[0019] Preferably, the initiator is selected from at least one of benzoyl peroxide, azobisisobutyronitrile, dicumyl peroxide, more preferably the initiator is added in an amount of 0.2-0.5% by mass of the polyolefin elastomer;

[0020] Preferably, the extrusion temperature in step S1 is 150-250℃.

[0021] As some specific examples of the preparation method of the nylon elastomer composition in the present application, in step S2, the number average molecular weight of the polyether polyol is 500-3000;

[0022] Preferably, the monobasic acid is one or more of formic acid, acetic acid, propionic acid, n-butyric acid, more preferably the monobasic acid is added in an amount of (0.95-1.05):1 by molar ratio of carboxyl group to terminal hydroxyl group of the polyether polyol;

[0023] Preferably, the catalyst is selected from one or more of tetrabutyl titanate, ethylene glycol antimony, dioctyl tin oxide, zirconium n-propyl alcohol, more preferably the catalyst is added in an amount of 0.05-0.2% by mass of the polyether polyol.

[0024] As some specific examples of the preparation method of the nylon elastomer composition in the present application, in step S3, the mass ratio of the monohydroxyl-terminated polyether polyol oligomer and the maleic anhydride grafted modified polyolefin elastomer is 1:(2-10);

[0025] The present application also provides an application of the nylon elastomer composition as described above or prepared by the method as described above in shoe sole foaming material, large-diameter pipe material.

[0026] The present application improves the compatibility of the nylon elastomer and the polyolefin elastomer by the amphiphilic branched copolymer, and realizes the sub-micron size dispersion of the polyolefin elastomer in the nylon elastomer. At the same time, the presence of the amphiphilic branched copolymer can effectively improve the melt strength of the nylon elastomer and the polyolefin elastomer blending system, and is especially suitable for application occasions with high melt strength requirements, such as supercritical CO2 foaming, pipe material extrusion and other application fields. DETAILED DESCRIPTION

[0027] The present application is further described below by specific examples, which are only used to illustrate the present application and do not limit the scope of the present application.

[0028] The main test methods involved in the following examples of the present application are as follows:

[0029] (1) Polyolefin elastomer dispersed phase size measurement: The nylon elastomer / polyolefin elastomer blend strip was brittle fractured in liquid nitrogen, etched with 60°C n-heptane for 3 min, and then gold sprayed for cross-section observation with a scanning electron microscope (JSG-5900LV, Japan).

[0030] (2) Melt strength test: A Gottfert RHEOTENS 71.97 melt strength tester was used, and the test temperature was 180°C.

[0031] (3) Elongation at break: The test was performed according to the ISO 527 standard.

[0032] The raw materials and reagents involved in the following examples of the present application can be purchased through commercial channels unless otherwise specified.

[0033] Example 1

[0034] (1) A high-speed mixer was used to mix 5 kg of POE (Dow Engage 8150, MFR = 1.0 g / 10 min) and 100 g of maleic anhydride monomer (Beijing Inokai Technology Co., Ltd.), 10 g of benzoyl peroxide (Beijing Inokai Technology Co., Ltd.) initiator uniformly; a twin-screw extruder with a length-diameter ratio of 68 was used for extrusion, and the temperature of the feeding section to the die was set to 160°C, 210°C, 220°C, 220°C, 210°C, and 200°C, respectively, the screw speed was 100 rpm, and the extruded material was drawn, water-cooled, pelletized, and dried to obtain a maleic anhydride grafted modified polyolefin elastomer (TPE-MA-1).

[0035] (2) 1800 g of polyethylene glycol (Mn = 600, Beijing Inokai Technology Co., Ltd.), 138 g of formic acid (Beijing Inokai Technology Co., Ltd.), and 3.6 g of ethylene glycol antimony were added to a 10 L reaction kettle, nitrogen was replaced three times, heated to 240°C, then vacuumed to 100 Pa absolute pressure for 60 min to complete the esterification reaction; stop vacuuming, add nitrogen to 100 kpa, stop stirring and cool to 30°C to obtain a monohydroxyl-terminated polyether polyol oligomer CJW-001.

[0036] (3) 16 kg of TPE-MA-1 was added to the reaction kettle containing 1938 g of monohydroxyl-terminated polyether polyol oligomer CJW-001, nitrogen was replaced three times, then heated to 240°C, vacuumed to an absolute pressure of less than 100 Pa, and continued to react for 60 min, then drawn, water-cooled, and pelletized to obtain amphiphilic branched copolymer pellets (TPE-PA-1).

[0037] Example 2

[0038] (1) Using a high mixer to mix 5 kg SEBS (Baliny petrochemical YH-533, MFR = 5.0 g / 10 min) and 250 g maleic anhydride monomer (Beijing Inokai Technology Co., Ltd.), 15 g of azobisisobutyronitrile (Beijing Inokai Technology Co., Ltd.) initiator uniformly; using a double screw extruder with a length-diameter ratio of 68 to perform extrusion, the temperature of the feeding section to the die head is set to 160℃, 210℃, 220℃, 220℃, 210℃, 200℃ in turn, the screw rotation speed is 100 rpm, the extruded material is pulled, water cooled, granulated and dried to obtain a maleic anhydride grafted modified polyolefin elastomer (TPE-MA-2).

[0039] (2) Put 2000g polypropylene glycol (Mn = 1000, Beijing Inokai Technology Co., Ltd.), 120g acetic acid (Beijing Inokai Technology Co., Ltd.), 2.12g tetrabutyl titanate into a 10L reaction kettle, replace with nitrogen three times, heat to 230℃, then vacuum to 200Pa absolute pressure for 50min, complete the esterification reaction; stop vacuuming, add nitrogen to 200kpa, stop stirring and cool to 30℃, prepare a monohydroxyl-terminated polyether polyol oligomer CJW-002.

[0040] (3) Put 5kg TPE-MA-2 into the reaction kettle containing 2120g monohydroxyl-terminated polyether polyol oligomer CJW-002, replace with nitrogen three times, then heat to 230℃, vacuum to reduce the absolute pressure of the reaction system to below 200Pa, continue to react for 50min, then pull, water cooled, granulation to obtain amphiphilic branched copolymer particles (TPE-PA-2).

[0041]

Preparation Example 3

[0042] (1) Using a high mixer to mix 5 kg POP (Dow VERSIFY 2300, MFR = 0.50 g / 10 min) and 500 g maleic anhydride monomer (Beijing Inokai Technology Co., Ltd.), 25 g of azobisisobutyronitrile (Beijing Inokai Technology Co., Ltd.) initiator uniformly; using a double screw extruder with a length-diameter ratio of 68 to perform extrusion, the temperature of the feeding section to the die head is set to 160℃, 210℃, 220℃, 220℃, 210℃, 200℃ in turn, the screw rotation speed is 100 rpm, the extruded material is pulled, water cooled, granulated and dried to obtain a maleic anhydride grafted modified polyolefin elastomer (TPE-MA-3).

[0043] (2) Put 2000 g of polybutylene glycol (Mn = 2000, Beijing Inokai Technology Co., Ltd.), 70 g of propionic acid (Beijing Inokai Technology Co., Ltd.), 3.11 g of zirconium n-propyl alcohol into a 10 L reaction kettle, replace with nitrogen for three times, heat to 220℃, then vacuum to 300 Pa absolute pressure for 40 min, complete the esterification reaction; stop vacuum, add nitrogen to 300 kpa, stop stirring and cool to 30℃, prepare monohydroxyl terminated polyether polyol oligomer CJW-003.

[0044] (3) Put 3.2 kg of TPE-MA-3 into the reaction kettle containing 2070 g of monohydroxyl terminated polyether polyol oligomer CJW-003, replace with nitrogen for three times, heat to 220℃, vacuum to reduce the absolute pressure of the reaction system to below 300 Pa, continue to react for 40 min, then pull, water cooling, and pelletizing to obtain amphiphilic branched copolymer pellets (TPE-PA-3).

[0045]

Preparation Example 4

[0046] (1) Mix 5 kg of POE (Dow Engage 8150, MFR = 1.0 g / 10 min) and 100 g of maleic anhydride monomer (Beijing Inokai Technology Co., Ltd.), 10 g of benzoyl peroxide (Beijing Inokai Technology Co., Ltd.) initiator uniformly by using a high-speed mixer; use a double screw extruder with a length-diameter ratio of 68 to perform extrusion, and set the temperature of the feeding section to the die head as 160℃, 210℃, 220℃, 220℃, 210℃, 200℃ in turn, the screw rotation speed is 100 rpm, the extruded material is pulled, water cooled, pelletized, and dried to prepare maleic anhydride grafted modified polyolefin elastomer (TPE-MA-1).

[0047] (2) Put 3000 g of polybutylene glycol (Mn = 3000, Beijing Inokai Technology Co., Ltd.), 92 g of n-butyric acid (Beijing Inokai Technology Co., Ltd.), 1.54 g of dioctyl tin oxide into a 10 L reaction kettle, replace with nitrogen for three times, heat to 200℃, then vacuum to 500 Pa absolute pressure for 30 min, complete the esterification reaction; stop vacuum, add nitrogen to 300 kpa, stop stirring and cool to 30℃, prepare monohydroxyl terminated polyether polyol oligomer CJW-004.

[0048] (3) Put 12 kg of TPE-MA-1 into the reaction kettle containing 3092 g of monohydroxyl terminated polyether polyol oligomer CJW-004, replace with nitrogen for three times, heat to 200℃, vacuum to reduce the absolute pressure of the reaction system to below 500 Pa, continue to react for 30 min, then pull, water cooling, and pelletizing to obtain amphiphilic branched copolymer pellets (TPE-PA-4).

[0049] Example 1

[0050] The nylon 12 elastomer composition was prepared according to the following method:

[0051] 10 kg of nylon 12 elastomer (Arkema Pebax 4033, MFR = 40 g / 10 min), 10 kg of POE (Dow Engage 8150, MFR = 1.0 g / 10 min), 1000 g of amphiphilic branched copolymer (TPE-PA-1), 50 g of lubricant EBS (Kao Japan), 100 g of antioxidant 1010 and antioxidant 168 were mixed in a high-speed mixer for 20 min to obtain a compounded material. The compounded material was melt-extruded through a twin-screw extruder with a length-diameter ratio of 42, water-cooled, pelletized, dried, and a nylon elastomer composition was prepared. The screw rotation speed was 150 rpm, and the temperature from the feeding section to the die head was set to 180-220°C.

[0052] Example 2

[0053] The nylon 12 elastomer composition was prepared according to the following method:

[0054] 10 kg of nylon 12 elastomer (Arkema Pebax 4033, MFR = 40 g / 10 min), 5 kg of SEBS (Baling Pebax YH-533, MFR = 5.0 g / 10 min), 500 g of amphiphilic branched copolymer (TPE-PA-2), 30 g of lubricant EBS (Kao Japan), 20 g of antioxidant 1010 and antioxidant 168 were mixed in a high-speed mixer for 20 min to obtain a compounded material. The compounded material was melt-extruded through a twin-screw extruder with a length-diameter ratio of 42, water-cooled, pelletized, dried, and a nylon elastomer composition was prepared. The screw rotation speed was 150 rpm, and the temperature from the feeding section to the die head was set to 180-220°C.

[0055] Example 3

[0056] The nylon 12 elastomer composition was prepared according to the following method:

[0057] A blend was prepared by mixing 10 kg of nylon 12 elastomer (Arkema Pebax 2533, MFR = 10 g / 10 min), 7 kg of POP (Dow VERSIFY 2300, MFR = 0.50 g / 10 min), 700 g of the amphiphilic branched copolymer (TPE-PA-3), 30 g of lubricant EBS (Kao, Japan), 50 g of a 1 : 1 mixture of antioxidant 1010 and antioxidant 168 in a high-speed mixer for 20 min. The blend was melt-extruded through a twin-screw extruder with a length-diameter ratio of 42, water-cooled, pelletized, and dried to obtain a nylon elastomer composition. The screw rotation speed was 150 rpm, and the temperature was set to 180-220 °C from the feeding section to the die head.

[0058] Example 4

[0059] A nylon 12 elastomer composition was prepared according to the following method:

[0060] A blend was prepared by mixing 10 kg of nylon 12 elastomer (Arkema Pebax 7233, MFR = 4 g / 10 min), 1 kg of POE (Dow Engage 8150, MFR = 1.0 g / 10 min), 100 g of the amphiphilic branched copolymer (TPE-PA-4), 10 g of lubricant EBS (Kao, Japan), 10 g of a 1 : 1 mixture of antioxidant 1010 and antioxidant 168 in a high-speed mixer for 20 min. The blend was melt-extruded through a twin-screw extruder with a length-diameter ratio of 42, water-cooled, pelletized, and dried to obtain a nylon elastomer composition. The screw rotation speed was 150 rpm, and the temperature was set to 180-220 °C from the feeding section to the die head.

[0061] Comparative Example 1

[0062] A nylon 12 elastomer composition was prepared according to the same method as in Example 1, except that the amphiphilic branched copolymer (TPE-PA-1) was replaced by the same amount of maleic anhydride grafted POE (Dow N493).

[0063] Comparative Example 2

[0064] A nylon 12 elastomer composition was prepared according to the same method as in Example 1, except that the amphiphilic branched copolymer (TPE-PA-1) was replaced by a 1 : 8.3 mixture of monohydroxyl-terminated polyether polyol oligomer CJW-001 and maleic anhydride grafted modified polyolefin elastomer TPE-MA-1.

[0065] The nylon 12 elastomer compositions prepared in the examples and comparative examples were tested for the size of the polyolefin elastomer dispersed phase, elongation at break, and melt strength, and the results are shown in Table 1.

[0066] Table 1, performance test results

[0067]

[0068] From the data comparison in Table 1, it can be seen that the polyolefin elastomer dispersed phase size in the nylon 12 elastomer compositions prepared in Examples 1-4 of the present application is less than 2 μm, indicating that the system has good compatibility, and the improvement of compatibility is conducive to further improving the elongation at break of the composition. In addition, the nylon 12 elastomer composition added with the amphiphilic branched copolymer in the present application exhibits higher melt strength, indicating that the polymer melt has excellent resistance to extension and melt sagging.

[0069] The above only describes the preferred embodiments of the present application, and it should be noted that for those skilled in the art, without departing from the method of the present application, a number of improvements and supplements can also be made, which should also be considered as the protection scope of the present application.

Claims

1. A nylon elastomer composition, characterized in that, Based on parts by weight, it contains the following components: 100 parts nylon elastomer; 20-100 parts polyolefin elastomer; 1-10 parts amphiphilic branched copolymer; 0.1-0.5 parts antioxidant; and 0.1-0.5 parts lubricant. The amphiphilic branched copolymer is a copolymer with polyolefin elastomer as the linear main chain and polyether polyol oligomer as the branched side chain. The preparation method of the amphiphilic branched polymer is as follows: S1. After mixing polyolefin elastomer, maleic anhydride and initiator, the mixture is extruded to obtain maleic anhydride grafted modified polyolefin elastomer. S2. After mixing polyether polyol, monobasic acid and catalyst, heat to 200-240℃, then evacuate to absolute pressure of 100-500Pa and react for 0.5-1h. After stopping the evacuation, add nitrogen to 100-300kPa, stop stirring and cool down to obtain monohydroxy-terminated polyether polyol oligomer. S3. The maleic anhydride grafted modified polyolefin elastomer obtained in step S1 and the monohydroxy-terminated polyether polyol oligomer are mixed and heated to 200-240℃, vacuumed to an absolute pressure of 100-500Pa, and the reaction is continued for 0.5-1h to obtain the amphiphilic branched polymer.

2. The nylon elastomer composition according to claim 1, characterized in that, The melt index of the nylon elastomer under test conditions of 235℃ and 2.16kg is 4-40g / 10min.

3. The nylon elastomer composition according to claim 1, characterized in that, The polyolefin elastomer has a melt index of 0.5-5 g / 10 min under test conditions of 235°C and 2.16 kg.

4. The nylon elastomer composition according to claim 2, characterized in that, The polyolefin elastomer is selected from one or more of POE, POP, SBS, and SEBS.

5. The nylon elastomer composition according to any one of claims 1-4, characterized in that, The antioxidant is selected from one or more of antioxidant 1010, antioxidant 1098, antioxidant 168, and antioxidant H10, or a combination thereof.

6. The nylon elastomer composition according to claim 5, characterized in that, The lubricant is selected from one or more of ethylene bis-stearamide, oleamide, silicone oil, and paraffin wax.

7. A method for preparing a nylon elastomer composition according to any one of claims 1-6, characterized in that, Includes the following steps: Nylon elastomer, polyolefin elastomer, amphiphilic branched polymer, lubricant, and antioxidant are mixed at high speed for 10-20 minutes, melt-extruded, water-cooled, pelletized, and dried to obtain a nylon elastomer composition.

8. The method for preparing the nylon elastomer composition according to claim 7, characterized in that, The preparation method of the amphiphilic branched polymer is as follows: S1. After mixing polyolefin elastomer, maleic anhydride and initiator, the mixture is extruded to obtain maleic anhydride grafted modified polyolefin elastomer. S2. After mixing polyether polyol, monobasic acid and catalyst, heat to 200-240℃, then evacuate to absolute pressure of 100-500Pa and react for 0.5-1h. After stopping the evacuation, add nitrogen to 100-300kPa, stop stirring and cool down to obtain monohydroxy-terminated polyether polyol oligomer. S3. The maleic anhydride grafted modified polyolefin elastomer obtained in step S1 and the monohydroxy-terminated polyether polyol oligomer are mixed and heated to 200-240℃, vacuumed to an absolute pressure of 100-500Pa, and the reaction is continued for 0.5-1h to obtain the amphiphilic branched polymer.

9. The method for preparing the nylon elastomer composition according to claim 8, characterized in that, In step S1, the amount of maleic anhydride added is 2-10% of the mass of the polyolefin elastomer.

10. The method for preparing the nylon elastomer composition according to claim 9, characterized in that, The initiator is selected from at least one of benzoyl peroxide, azobisisobutyronitrile, and dicumyl peroxide.

11. The method for preparing the nylon elastomer composition according to claim 10, characterized in that, The amount of initiator added is 0.2-0.5% of the mass of the polyolefin elastomer.

12. The method for preparing the nylon elastomer composition according to claim 9, characterized in that, The extrusion temperature in step S1 is 150-250℃.

13. The method for preparing the nylon elastomer composition according to any one of claims 8-12, characterized in that, In step S2, the number average molecular weight of the polyether polyol is 500-3000.

14. The method for preparing the nylon elastomer composition according to claim 13, characterized in that, The monocarboxylic acid is one or more of formic acid, acetic acid, propionic acid, and butyric acid.

15. The method for preparing the nylon elastomer composition according to claim 14, characterized in that, The amount of monocarboxylic acid added, calculated as the molar ratio of carboxyl group to terminal hydroxyl group of polyether polyol, is (0.95-1.05):

1.

16. The method for preparing the nylon elastomer composition according to claim 14, characterized in that, The catalyst is selected from one or more of tetrabutyl titanate, antimony glycolate, dioctyltin oxide, and zirconium propoxide.

17. The method for preparing the nylon elastomer composition according to claim 15, characterized in that, The amount of catalyst added is 0.05-0.2% of the mass of the polyether polyol.

18. A method for preparing the nylon elastomer composition according to any one of claims 8-12, characterized in that, In step S3, the mass ratio of the monohydroxy-terminated polyether polyol oligomer to the maleic anhydride-grafted modified polyolefin elastomer is 1:(2-10).

19. The use of a nylon elastomer composition as described in any one of claims 1-6 or a nylon elastomer composition prepared by the method as described in any one of claims 7-18 in shoe sole foam materials and large-diameter pipes.

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