POLYISOCYANATE COMPOSITION, PREPARATION METHOD THEREFOR AND APPLICATION THEREOF

Abstract

A polyisocyanate composition, a preparation method therefor and an application thereof. The value of the mass content of alkaline hydrolyzed chlorine minus the mass content of water hydrolyzed chlorine in the polyisocyanate composition is 0.1 ppm-100 ppm. The mass content of the alkaline hydrolyzed chlorine is the mass content obtained by calculating halogen dissociated under alkaline conditions and/or halogen dissociated under a temperature condition of 100° C. or more as the relative atomic mass of a chlorine atom. In the polyisocyanate composition containing a specific amount of alkaline hydrolyzed chlorine, when a reaction locally becomes out of control causing causes a local severe exotherm, chlorine in alkaline hydrolyzed chlorine will be dissociated and be toxic to catalysts, thereby reducing the reactivity in local overreactive areas to thereby avoid the turbidity of a polyurethane synthetic emulsion, such that the light transmittance and yellowing resistance of polyurethane products are further improved.

Claims

1.-10.

11. A polyisocyanate composition, wherein a mass content of alkaline-dissociated chlorine minus a mass content of hydrolyzed chlorine has a value of 0.1 ppm-100 ppm; the mass content of the alkaline-dissociated chlorine is a mass content obtained by calculation based on halogen dissociated under alkaline condition and/or halogen dissociated at more than or equal to 100° C. with the relative atomic mass of chlorine atom.

12. The polyisocyanate composition according to claim 11, wherein the mass content of alkaline-dissociated chlorine minus the mass content of hydrolyzed chlorine has a value of 0.2 ppm-60 ppm, preferably 0.4 ppm-40 ppm.

13. The polyisocyanate composition according to claim 11, wherein the polyisocyanate composition comprises a combination of polyisocyanate, an alkaline-dissociated chlorine impurity and a hydrolyzed chlorine impurity; preferably, the polyisocyanate is diisocyanate; preferably, the polyisocyanate comprises any one or a combination of at least two of alicyclic diisocyanate, aromatic diisocyanate or chain diisocyanate; preferably, the polyisocyanate comprises any one or a combination of at least two of dicyclohexylmethane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, m-xylylene diisocyanate, p-xylylene diisocyanate, 1,3-dimethyl isocyanate cyclohexane, 1,4-dimethyl isocyanate cyclohexane, tetramethylene diisocyanate, pentamethylene diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, benzene diisocyanate, naphthalene diisocyanate or cyclohexyl diisocyanate.

14. The polyisocyanate composition according to claim 11, wherein a raw material for preparation comprises a combination of polyamine and a phosgene raw material; preferably, impurities having an olefin structure, a secondary amine structure or a hydroxyl structure in the polyamine have a total mass content of 0.1 ppm-400 ppm.

15. A preparation method of the polyisocyanate composition according to claim 11, comprising: subjecting polyamine and a phosgene raw material to a phosgenation reaction to obtain the polyisocyanate composition.

16. The preparation method according to claim 15, wherein the phosgenation reaction comprises a gas-phase phosgenation reaction, a liquid-phase phosgenation reaction or a salt-forming phosgenation reaction; preferably, the gas-phase phosgenation reaction comprises: subjecting a polyamine gas stream and the phosgene raw material to a gas-phase phosgenation reaction, and mixing a reaction product with a liquid inert medium and cooling to less than or equal to 150° C., or, mixing a reaction product with a liquid inert medium and a target isocyanate product mixture and cooling to less than or equal to 150° C., preferably 100-140° C.; preferably, the liquid-phase phosgenation reaction comprises: subjecting a polyamine solution and the phosgene raw material to a cold reaction at 0-100° C. and then to a hot reaction at 60-180° C., wherein the cold reaction and the hot reaction have a total retention time of less than or equal to 7 h; preferably, the salt-forming phosgenation reaction comprises: subjecting the polyamine, hydrogen chloride and/or carbon dioxide to a salt-forming reaction in an inert solvent, and then subjecting the system and the phosgene raw material to a phosgenation reaction; the salt-forming reaction and the phosgenation reaction have a total retention time of less than or equal to 7 h.

17. A polyurethane resin, wherein a raw material to prepare the polyurethane resin comprises a combination of the polyisocyanate composition according to claim 11 and a compound containing a reactive hydrogen group.

18. The polyurethane resin according to claim 17, wherein the compound containing a reactive hydrogen group comprises a polyol compound and/or an amine compound; preferably, the polyol compound has a molecular mass of 400-20000; preferably, the polyol compound has a hydroxyl value of 10 mg KOH/g-1500 mg KOH/g; preferably, the polyol compound has a functionality of 2-8.

19. The polyurethane resin according to claim 17, wherein the raw material to prepare the polyurethane resin further comprises a catalyst and/or a chain extender.

20. A method for preparing polyurethane elastomers, polyurethane optical materials, polyurethane coating materials or polyurethane foams by using the polyurethane resin according to claim 17; preferably in preparing polyurethane elastomers.

Description

DETAILED DESCRIPTION

[0119] The technical solutions of the present application are further described below through embodiments. It should be apparent to those skilled in the art that the embodiments are only used for a better understanding of the present application and should not be construed as a specific limitation of the present application.

Example 1

[0120] This example provides a polyisocyanate composition, and its preparation method is as follows. [0121] a) Hexanediamine (HDA) was gasified and heated to 355° C. using the heater disclosed in Example 1 of application CN105214568A, and under the protection of nitrogen, and HAD and gaseous phosgene that was heated to 355° C. were continuously added to a reactor via their respective feed pipes for a phosgenation reaction; the reaction was performed at 0.05 MPa (absolute pressure) and at 360° C.; HDA was fed at 800 Kg/h and gaseous phosgene was fed at 3000 Kg/h; the gas mixture obtained from the reaction was cooled rapidly (with a contact time of about 10 s) to 100° C. using an o-dichlorobenzene solution via a gas injection absorption device to obtain a crude product containing HDI, phosgene and the o-dichlorobenzene solution; [0122] the reaction tail gas was fed in a tail gas absorption tower and then absorbed with an o-dichlorobenzene solution at −35° C. to obtain an o-dichlorobenzene solution containing phosgene. [0123] b) The crude product obtained from step a) was subjected to a treatment of removing phosgene and the o-dichlorobenzene solution, and the o-dichlorobenzene solution and excess phosgene in the crude product were removed at 168° C. and 0.1 MPa (absolute pressure) to obtain an HDI crude product without phosgene and an o-dichlorobenzene solution containing phosgene. [0124] c) The o-dichlorobenzene solution containing phosgene obtained from the reaction tail gas absorption in step a) and the o-dichlorobenzene solution containing phosgene obtained from the removal process in step b) were fed in a distillation column for a separation of phosgene and o-dichlorobenzene solution; the separation process was performed at 0.125 MPa (absolute pressure), a column-bottom temperature of 155° C. and a column-top temperature of 15° C. to obtain phosgene with 98% purity and an o-dichlorobenzene solution with a phosgene content of less than 0.001%, and the separated phosgene and the o-dichlorobenzene solution were all subjected back to step a) for recycling. [0125] d) The HDI crude product without phosgene obtained from step b) was purified by distillation at 0.5 KPa (absolute pressure) and a distillation range of 135-140° C. to obtain an HDI (hexamethylene diisocyanate) product.

[0126] An olefin structure, a secondary amine structure and a hydroxyl structure in the hexanediamine used had a total content of 200 ppm.

[0127] The yield of the HDI product obtained is 97% and the product purity is 99.75%. The product obtained contains 25 ppm of hydrolyzed chlorine and 30 ppm of alkaline-dissociated chlorine, and a difference between the alkaline-dissociated chlorine and the hydrolyzed chlorine is 5 ppm.

[0128] This example also provides a polyurethane resin, and its preparation method is as follows.

(1) Preparation of Polyurethane Prepolymer

[0129] 100 parts of polyoxypropylene glycol were weighed out, which had a relative molecular mass of 1000, a hydroxyl value of 110 mg KOH/g, a functionality of 2 (Shanghai Gaoqiao Petrochemical Company, polyether polyol GE-210), heated to 110° C. with stirring, subjected to pressure reduction to 200 Pa (absolute pressure) to remove water for 2.5 hours, and cooled to 60° C., and 168 parts of the HDI produced during the above synthesis of the isocyanate were added. The system was heated to 80° C. and reacted for 120 min to obtain a blue transparent polyurethane prepolymer emulsion.

[0130] The turbidity test result for the prepolymer emulsion is 0.42 NTU.

[0131] (2) The polyurethane prepolymer obtained from step (1), 82 parts of 1,4-butanediol (BASF Corporation, after a water removal treatment at 102° C. and 200 Pa (absolute pressure) for 2.5 hours) and 0.1 part of dibutyltin dilaurate (Dabco T-12, Air Chemicals, USA) were added in a casting machine, heated to 45° C., respectively, subjected to pressure reduction to 1 Kpa (absolute pressure) and de-bubbled for 0.5 hours, mixed evenly, poured into a mold which had been preheated to 75° C., heated and cured for 4 h to obtain the polyurethane resin.

[0132] The obtained polyurethane product was tested for light transmittance according to the method provided by GB/T 2410-2008, and the result is 97.5%.

[0133] The obtained polyurethane resin was put into an oven at 80° C. and baked for 12 h to obtain a dried polyurethane product. The color value b of the polyurethane product was tested with a colorimeter (X-Rite 528), and then the polyurethane film was baked in an oven at 150° C. for 0.5 h. The color value b of the resin film after baking was tested with a colorimeter and the color difference ΔE was 0.45 (the lower the value, the better the performance), which showed that the polyurethane resin provided in this example has good yellowing resistance.

Example 2

[0134] This example provides a polyisocyanate composition, and its preparation method is as follows.

[0135] The phosgenation reaction in step a) is a liquid-phase phosgenation reaction, which is performed by the following steps in a tank reactor with reference to the disclosed application CN103319372A.

[0136] 1) Cold reaction: 4,4′-diaminodicyclohexylmethane (H.sub.12MDA) was prepared into a solution of 15% mass content with o-dichlorobenzene as the solvent and preheated to 40° C., and the prepared solution and liquid phosgene at −5° C. were simultaneously introduced into a tank reactor containing an o-dichlorobenzene solution for a liquid-phase phosgenation reaction; H.sub.12MDA was fed at 400 Kg/h, the phosgene for the cold reaction was fed at 1500 Kg/h, and a temperature of the cold reaction was controlled at 60° C. and a retention time was 5 min.

[0137] 2) Hot reaction: a temperature of the hot reaction was controlled at 155° C. and a retention time was 6 h, and the hot reaction was performed in the presence of an o-dichlorobenzene solution and excess phosgene to obtain a reaction liquid (crude product) containing the product H.sub.12MDI, phosgene and the o-dichlorobenzene solution.

[0138] The cold and hot phosgenation reaction stages had a total retention time of six hours and five minutes.

[0139] The reaction tail gas was fed in a tail gas absorption tower and then absorbed with an o-dichlorobenzene solution at −35° C. to obtain an o-dichlorobenzene solution containing phosgene. [0140] b) The reaction liquid obtained from step a) was subjected to a treatment of removing phosgene and the o-dichlorobenzene solution, and the o-dichlorobenzene solution and excess phosgene in the reaction liquid were removed at 155° C. and 0.05 MPa (absolute pressure) to obtain an H.sub.12MDI crude product without phosgene and an o-dichlorobenzene solution containing phosgene.

[0141] During the removal process, the o-dichlorobenzene solution containing phosgene was controlled at 155° C. for a retention time of 1 h. [0142] c) The o-dichlorobenzene solution containing phosgene obtained from the reaction tail gas absorption in step a) and the o-dichlorobenzene solution containing phosgene obtained from the removal process in step b) were fed in a distillation column for a separation of phosgene and o-dichlorobenzene; the separation process was performed at 0.125 MPa (absolute pressure), a column-bottom temperature of 145° C. and a column-top temperature of 15° C. to obtain phosgene with 98% purity and an o-dichlorobenzene solution with a phosgene content of less than 0.001%, and the separated phosgene and the o-dichlorobenzene solution were all subjected back to step a) for recycling. [0143] d) The H.sub.12MDI crude product without phosgene obtained from step b) was purified by distillation at 0.5 KPa (absolute pressure) and a distillation range of 150-160° C. to obtain an H.sub.12MDI (dicyclohexylmethane diisocyanate) product.

[0144] An olefin structure, a secondary amine structure and a hydroxyl structure in the H.sub.12MDA used had a total content of 270 ppm.

[0145] The yield of the H.sub.12MDI product obtained is 96% and the product purity is 99.8%. The product obtained contains 5 ppm of hydrolyzed chlorine and 7 ppm of alkaline-dissociated chlorine, and a difference between the alkaline-dissociated chlorine and the hydrolyzed chlorine is 2 ppm.

[0146] This example also provides a polyurethane resin, and its preparation method is as follows.

(1) Preparation of Polyurethane Prepolymer

[0147] 100 parts of polyoxypropylene glycol were weighed out, which had a relative molecular mass of 1000, a hydroxyl value of 110 mg KOH/g, a functionality of 2 (Shanghai Gaoqiao Petrochemical Company, polyether polyol GE-210), heated to 110° C. with stirring, subjected to pressure reduction to 200 Pa (absolute pressure) to remove water for 2.5 hours, and cooled to 60° C., and 262 parts of the H.sub.12MDI produced during the above synthesis of the isocyanate were added. The system was heated to 85° C. and reacted for 100 min to obtain a blue transparent polyurethane prepolymer emulsion.

[0148] The turbidity test result for the prepolymer emulsion is 0.25 NTU.

[0149] (2) The polyurethane prepolymer obtained from step (1) was prepared into the polyurethane resin and tested for color difference LE according to Example 1, and the result is 0.31. It is shown by the data that the polyurethane resin provided by this example has good yellowing resistance.

[0150] The obtained polyurethane product was tested for light transmittance according to the method provided by GB/T 2410-2008, and the result is 95.5%.

Example 3

[0151] This example provides a polyisocyanate composition, and its preparation method is as follows.

[0152] The phosgenation reaction in step a) is a salt-forming phosgenation reaction, which is performed by the following steps in a tank reactor with reference to the disclosed Example 1 in application CN05218422A.

[0153] 1) 1000 Kg of o-dichlorobenzene was added in a salt-forming tank reactor as a reaction solvent in advance, a circulation pump and agitation were operated, compressed hydrogen chloride gas was introduced in the reactor at 50 mol/min via a premixer, and stirred for 15 min, and a mixed liquid of isophorone diamine (IPDA) and o-dichlorobenzene was heated to 30° C. through a raw material preheater, and fully contacted with hydrogen chloride gas at a flow rate of 335 Kg/h to generate a salt; the system was cooled by external circulating cooling water to remove part of the reaction heat, in which the circulating liquid had a flow rate of about 5 m.sup.3/h, and the reaction liquid was maintained at 30-45° C., and after feeding for 1 h, the feeding of the mixed liquid of IPDA and o-dichlorobenzene was stopped, and HCl gas was continuously introduced for 30 min.

[0154] 2) The IPDA hydrochloride slurry obtained from step 1) was transferred to a phosgenation tank reactor, and the phosgenation tank reactor had a phosgene inlet pipe, gas-phase condensation reflux and agitation; the phosgenation tank reactor was heated and the agitation was simultaneously operated, and when the temperature reached 60° C., phosgene was introduced, in which a phosgene feeding speed was 50 mol/min, and a reaction temperature was 145° C.; when the reaction liquid was clarified, the feeding was stopped, and a salt-forming phosgenation reaction liquid (crude product) containing the product IPDI, phosgene and o-dichlorobenzene was obtained; [0155] the salt-forming reaction was performed for 0.5 h, the phosgenation reaction was performed for 6 h, and the salt-forming reaction and the phosgenation reaction had a total retention time of 6.5 h; [0156] the reaction tail gas was fed in a tail gas absorption tower and then absorbed with an o-dichlorobenzene solution at −30° C. to obtain an o-dichlorobenzene solution containing phosgene. [0157] b) The reaction liquid obtained from step a) was subjected to a treatment of removing phosgene and the o-dichlorobenzene solution, and the o-dichlorobenzene solution and excess phosgene in the reaction liquid were removed at 145° C. and 0.04 MPa (absolute pressure) to obtain an IPDI crude product without phosgene and an o-dichlorobenzene solution containing phosgene. [0158] c) The o-dichlorobenzene solution containing phosgene obtained from the reaction tail gas absorption in step a) and the o-dichlorobenzene solution containing phosgene obtained from the removal process in step b) were fed in a distillation column for a separation of phosgene and o-dichlorobenzene; the separation process was performed at 0.125 MPa (absolute pressure), a column-bottom temperature of 165° C. and a column-top temperature of 15° C. to obtain phosgene with 98% purity and an o-dichlorobenzene solution with a phosgene content of less than 0.001%, and the separated phosgene and the o-dichlorobenzene solution were all subjected back to step a) for recycling. [0159] d) The IPDI crude product without phosgene obtained from step b) was purified by distillation at 0.5 KPa (absolute pressure) and a distillation range of 140-150° C. to obtain an IPDI (isophorone diisocyanate) product.

[0160] An olefin structure, a secondary amine structure and a hydroxyl structure in the IPDA used had a total content of 170 ppm.

[0161] The yield of the IPDI product obtained is 97.6% and the product purity is 99.85%. The product obtained contains 35 ppm of hydrolyzed chlorine and 41 ppm of alkaline-dissociated chlorine, and a difference between the alkaline-dissociated chlorine and the hydrolyzed chlorine is 6 ppm.

[0162] This example also provides a polyurethane resin, and its preparation method is as follows.

(1) Preparation of Polyurethane Prepolymer

[0163] The 100 parts of polyoxypropylene glycol were weighed out, which had a relative molecular mass of 1000, a hydroxyl value of 110 mg KOH/g, a functionality of 2 (Shanghai Gaoqiao Petrochemical Company, polyether polyol GE-210), heated to 110° C. with stirring, subjected to pressure reduction to 200 Pa (absolute pressure) to remove water for 2.5 hours, and cooled to 60° C., and 222 parts of the H.sub.12MDI produced during the above synthesis of the isocyanate were added. The system was heated to 85° C. and reacted for 150 min to obtain a blue transparent polyurethane prepolymer emulsion.

[0164] The turbidity test result for the prepolymer emulsion is 0.32 NTU.

[0165] (2) The polyurethane prepolymer obtained from step (1) was prepared into the polyurethane resin and tested for color difference LE according to Example 1, and the result is 0.22. It is shown by the data that the polyurethane resin provided by this example has good yellowing resistance.

[0166] The obtained polyurethane product was tested for light transmittance according to the method provided by GB/T 2410-2008, and the result is 96.7%.

Example 4

[0167] This example provides a polyisocyanate composition, and its preparation method is as follows. [0168] a) diamine IPDA was gasified and heated to 355° C. using the heater disclosed in Example 1 of application CN105214568A, and under the protection of nitrogen, and IPDA and gaseous phosgene that was heated to 355° C. were continuously added to a reactor via their respective feed pipes for a phosgenation reaction; the reaction was performed at 0.05 MPa (absolute pressure) and at 360° C.; IPDA was fed at 800 Kg/h and gaseous phosgene was fed at 3000 Kg/h; the gas mixture obtained from the reaction was cooled rapidly (with a contact time of about 10 s) to 105° C. using a dichlorobenzene solution via a gas injection absorption device to obtain a crude product containing IPDI, phosgene and the dichlorobenzene solution; [0169] the reaction tail gas was fed in a tail gas absorption tower and then absorbed with a dichlorobenzene solution at −25° C. to obtain a dichlorobenzene solution containing phosgene. [0170] b) The crude product obtained from step a) was subjected to a treatment of removing phosgene and dichlorobenzene solvent, and the dichlorobenzene and excess phosgene in the crude product were removed at 168° C. and 0.1 MPa (absolute pressure) to obtain an IPDI crude product without phosgene and a dichlorobenzene solution containing phosgene. [0171] c) The dichlorobenzene solution containing phosgene obtained from the reaction tail gas absorption in step a) and the dichlorobenzene solution containing phosgene obtained from the removal process in step b) were fed in a distillation column for a separation of phosgene and the dichlorobenzene solution; the separation process was performed at 0.125 MPa (absolute pressure), a column-bottom temperature of 155° C. and a column-top temperature of 15° C. to obtain phosgene with 98% purity and a dichlorobenzene solution with a phosgene content of less than 0.001%, and the separated phosgene and the dichlorobenzene solution were all subjected back to step a) for recycling. [0172] d) The IPDI crude product without phosgene obtained from step b) was purified by distillation to obtain an IPDI (isophorone diisocyanate) product at 0.5 KPa (absolute pressure) and a distillation range of 140-150° C.

[0173] An olefin structure, a secondary amine structure and a hydroxyl structure in the IPDA used had a total content of 170 ppm.

[0174] The yield of the IPDI product obtained is 97.5% and the product purity is 99.85%. The product obtained contains 17 ppm of hydrolyzed chlorine and 22 ppm of alkaline-dissociated chlorine, and a difference between the alkaline-dissociated chlorine and the hydrolyzed chlorine is 5 ppm.

[0175] This example also provides a polyurethane resin, and its preparation method is as follows.

(1) Preparation of Polyurethane Prepolymer

[0176] 100 parts of polyoxypropylene glycol were weighed out, which had a relative molecular mass of 1000, a hydroxyl value of 110 mg KOH/g, a functionality of 2 (Shanghai Gaoqiao Petrochemical Company, polyether polyol GE-210), heated to 110° C. with stirring, subjected to pressure reduction to 200 Pa (absolute pressure) to remove water for 2.5 hours, and cooled to 60° C., and 222 parts of the IPDI produced during the above synthesis of the isocyanate were added. The system was heated to 85° C. and reacted for 150 min to obtain a blue transparent polyurethane prepolymer emulsion.

[0177] The turbidity test result for the prepolymer emulsion is 0.19 NTU.

[0178] (2) The polyurethane prepolymer obtained from step (1) was prepared into the polyurethane resin and tested for color difference LE according to Example 1, and the result is 0.21. It is shown by the data that the polyurethane resin provided by this example has good yellowing resistance.

[0179] The obtained polyurethane product was tested for light transmittance according to the method provided by GB/T 2410-2008, and the result is 94.9%.

Example 5

[0180] This example provides a polyisocyanate composition, and its preparation method differs from Example 1 only in that an olefin structure, a secondary amine structure and a hydroxyl structure in the HDA used had a total content of 50 ppm; other operation steps and conditions were the same as in Example 1.

[0181] The yield of the HDI product obtained is 97% and the product purity is 99.75%. The product obtained contains 25 ppm of hydrolyzed chlorine and 25.4 ppm of alkaline-dissociated chlorine, and a difference between the alkaline-dissociated chlorine and the hydrolyzed chlorine is 0.4 ppm.

[0182] This example also provides a polyurethane resin, and its preparation method is the same as in Example 1.

[0183] The turbidity of the synthesized emulsion of polyurethane prepolymer is 0.10 NTU; the prepared polyurethane resin was tested for color difference LE and the result is 0.09.

[0184] The obtained polyurethane product was tested for light transmittance according to the method provided by GB/T 2410-2008, and the result is 98.5%.

Example 6

[0185] This example provides a polyisocyanate composition, and its preparation method differs from Example 1 only in that, in step (a), the gas mixture obtained from the reaction was cooled rapidly (with a contact time of about 10 s) to 120° C. using an o-dichlorobenzene solution via a gas injection absorption device; other operation steps and conditions were the same as in Example 1.

[0186] The yield of the HDI product obtained is 97% and the product purity is 99.8%. The product obtained contains 23 ppm of hydrolyzed chlorine and 63 ppm of alkaline-dissociated chlorine, and a difference between the alkaline-dissociated chlorine and the hydrolyzed chlorine is 40 ppm.

[0187] This example also provides a polyurethane resin, and its preparation method is the same as in Example 1.

[0188] The turbidity of the synthesized emulsion of polyurethane prepolymer is 0.11 NTU; the prepared polyurethane resin was tested for color difference LE and the result is 0.10.

[0189] The obtained polyurethane product was tested for light transmittance according to the method provided by GB/T 2410-2008, and the result is 98.4%.

Example 7

[0190] This example provides a polyisocyanate composition, and its preparation method differs from Example 2 only in that an olefin structure, a secondary amine structure and a hydroxyl structure in the H.sub.12MDA used had a total content of 120 ppm; other operation steps and conditions were the same as in Example 2.

[0191] The yield of the HDI product obtained is 96.2% and the product purity is 99.8%. The product obtained contains 4.1 ppm of hydrolyzed chlorine and 4.3 ppm of alkaline-dissociated chlorine, and a difference between the alkaline-dissociated chlorine and the hydrolyzed chlorine is 0.2 ppm.

[0192] This example also provides a polyurethane resin, and its preparation method is the same as in Example 2.

[0193] The turbidity of the synthesized emulsion of polyurethane prepolymer is 0.14 NTU; the prepared polyurethane resin was tested for color difference LE and the result is 0.15.

[0194] The obtained polyurethane product was tested for light transmittance according to the method provided by GB/T 2410-2008, and the result is 96.2%.

Example 8

[0195] This example provides a polyisocyanate composition, and its preparation method differs from Example 2 only in that the cold and hot phosgenation reaction stages had a total retention time of six hours, wherein the cold reaction was 5 min, and the hot reaction was 5 hours and 55 minutes; other operation steps and conditions were the same as in Example 2.

[0196] The yield of the H.sub.12MDI product obtained is 96% and the product purity is 99.8%. The product obtained contains 5 ppm of hydrolyzed chlorine and 65 ppm of alkaline-dissociated chlorine, and a difference between the alkaline-dissociated chlorine and the hydrolyzed chlorine is 60 ppm.

[0197] This example also provides a polyurethane resin, and its preparation method is the same as in Example 2.

[0198] The turbidity of the synthesized emulsion of polyurethane prepolymer is 0.15 NTU; the prepared polyurethane resin was tested for color difference LE and the result is 0.15.

[0199] The obtained polyurethane product was tested for light transmittance according to the method provided by GB/T 2410-2008, and the result is 96.0%.

Example 9

[0200] This example provides a polyisocyanate composition, and its preparation method differs from Example 3 only in that an olefin structure, a secondary amine structure and a hydroxyl structure in the IPDA used had a total content of 180 ppm; other operation steps and conditions were the same as in Example 3.

[0201] The yield of the IPDI product obtained is 97.5% and the product purity is 99.85%. The product obtained contains 17 ppm of hydrolyzed chlorine and 22 ppm of alkaline-dissociated chlorine, and a difference between the alkaline-dissociated chlorine and the hydrolyzed chlorine is 5 ppm.

[0202] The yield of the IPDA product obtained is 97.6% and the product purity is 99.87%. The product obtained contains 17.4 ppm of hydrolyzed chlorine and 17.5 ppm of alkaline-dissociated chlorine, and a difference between the alkaline-dissociated chlorine and the hydrolyzed chlorine is 0.1 ppm.

[0203] This example also provides a polyurethane resin, and its preparation method is the same as in Example 3.

[0204] The turbidity of the synthesized emulsion of polyurethane prepolymer is 0.19 NTU; the prepared polyurethane resin was tested for color difference LE and the result is 0.18.

[0205] The obtained polyurethane product was tested for light transmittance according to the method provided by GB/T 2410-2008, and the result is 94.0%.

Example 10

[0206] This example provides a polyisocyanate composition, and its preparation method differs from Example 3 only in that the salt-forming reaction and the phosgenation reaction had a total retention time of 6 h, in which the salt-forming reaction was 0.5 h, and the phosgenation reaction was 5.5 h; other operation steps and conditions were the same as in Example 3.

[0207] The yield of the HDI product obtained is 97.5% and the product purity is 99.88%. The product obtained contains 17 ppm of hydrolyzed chlorine and 117 ppm of alkaline-dissociated chlorine, and a difference between the alkaline-dissociated chlorine and the hydrolyzed chlorine is 100 ppm.

[0208] This example also provides a polyurethane resin, and its preparation method is the same as in Example 3.

[0209] The turbidity of the synthesized emulsion of polyurethane prepolymer is 0.19 NTU; the prepared polyurethane resin was tested for color difference LE and the result is 0.20.

[0210] The obtained polyurethane product was tested for light transmittance according to the method provided by GB/T 2410-2008, and the result is 94.8%.

Comparative Example 1

[0211] This comparative example provides a polyisocyanate composition, and its preparation method differs from Example 1 only in that, in step (a), the gas mixture obtained from the reaction was cooled rapidly (with a contact time of about 10 s) to 175° C. using an o-dichlorobenzene solution via a gas injection absorption device; other operation steps and conditions were the same as in Example 1.

[0212] The yield of the HDI product obtained is 97% and the product purity is 99.74%. The product obtained contains 23 ppm of hydrolyzed chlorine and 170 ppm of alkaline-dissociated chlorine, and a difference between the alkaline-dissociated chlorine and the hydrolyzed chlorine is 147 ppm.

[0213] This example also provides a polyurethane resin, and its preparation method is the same as in Example 1.

[0214] The turbidity of the synthesized emulsion of polyurethane prepolymer is 1.7 NTU; the prepared polyurethane resin was tested for color difference LE and the result is 1.5.

[0215] The obtained polyurethane product was tested for light transmittance according to the method provided by GB/T 2410-2008, and the result is 81.5%.

Comparative Example 2

[0216] This comparative example provides a polyisocyanate composition, and its preparation method differs from Example 2 only in that the cold reaction had a retention time of 30 min, and the hot reaction had a retention time of 8 h, and the cold and hot phosgenation reaction stages had a total retention time of 8.5 h; other operation steps and conditions were the same as in Example 2.

[0217] The yield of the H.sub.12MDI product obtained is 96.2% and the product purity is 99.81%. The product obtained contains 3 ppm of hydrolyzed chlorine and 170 ppm of alkaline-dissociated chlorine, and a difference between the alkaline-dissociated chlorine and the hydrolyzed chlorine is 167 ppm.

[0218] This example also provides a polyurethane resin, and its preparation method is the same as in Example 2.

[0219] The turbidity of the synthesized emulsion of polyurethane prepolymer is 1.9 NTU; the prepared polyurethane resin was tested for color difference LE and the result is 1.7.

[0220] The obtained polyurethane product was tested for light transmittance according to the method provided by GB/T 2410-2008, and the result is 79.1%.

Comparative Example 3

[0221] This comparative example provides a polyisocyanate composition, and its preparation method differs from Example 3 only in that, in step a), the salt-forming reaction and the phosgenation reaction had a total retention time of 9.5 h; other operation steps and conditions were the same as in Example 3.

[0222] The yield of the IPDI product obtained is 97.4% and the product purity is 99.86%. The product obtained contains 25 ppm of hydrolyzed chlorine and 131 ppm of alkaline-dissociated chlorine, and a difference between the alkaline-dissociated chlorine and the hydrolyzed chlorine is 106 ppm.

[0223] This example also provides a polyurethane resin, and its preparation method is the same as in Example 3.

[0224] The turbidity of the synthesized emulsion of polyurethane prepolymer is 0.67 NTU; the prepared polyurethane resin was tested for color difference LE and the result is 1.9.

[0225] The obtained polyurethane product was tested for light transmittance according to the method provided by GB/T 2410-2008, and the result is 85.5%.

Comparative Example 4

[0226] This comparative example provides a polyisocyanate composition, and its preparation method differs from Example 4 only in that an olefin structure, a secondary amine structure and a hydroxyl structure in the IPDA used had a total content of 0.2 ppm; other operation steps and conditions were the same as in Example 4.

[0227] The yield of the IPDI product obtained is 97.4% and the product purity is 99.85%. The product obtained contains 21 ppm of hydrolyzed chlorine and 21 ppm of alkaline-dissociated chlorine, and a difference between the alkaline-dissociated chlorine and the hydrolyzed chlorine is 0 ppm.

[0228] This example also provides a polyurethane resin, and its preparation method is the same as in Example 4.

[0229] The turbidity of the synthesized emulsion of polyurethane prepolymer is 0.75 NTU; the prepared polyurethane resin was tested for color difference LE and the result is 0.27.

[0230] The obtained polyurethane product was tested for light transmittance according to the method provided by GB/T 2410-2008, and the result is 73.2%.

[0231] By comparing Example 1 and Comparative Example 1, Example 2 and Comparative Example 2, Example 3 and Comparative Example 3, and Example 4 and Comparative Example 4, it can be seen that the polyisocyanate composition provided by the present application which contains a specific amount (0.1 ppm-100 ppm difference from hydrolyzed chlorine) of alkaline-dissociated chlorine can effectively prevent the polyurethane synthetic emulsion from becoming turbid, thus improving the light transmittance and yellowing resistance of polyurethane products.

[0232] By comparing Examples 1 and 5-10, it can be seen that in the case where a mass content of alkaline-dissociated chlorine minus a mass content of hydrolyzed chlorine has a value of 0.2 ppm-60 ppm in the polyisocyanate composition (Examples 1 and 5-8), the turbidity problem of the polyurethane synthetic emulsion can be further relieved, improving the light transmittance and yellowing resistance of the products, and the result is better when the difference is within 4 ppm-40 ppm (Examples 1 and 5-6).