Whitening nylon as well as preparation method and application thereof

Abstract

The invention relates to the field of preparation of high polymer materials, in particular to whitening nylon as well as a preparation method and application thereof. According to the whitening nylon provided by the invention, a comonomer is added in the process of generating a nylon polymer by adopting a nylon monomer polymerization reaction, and the comonomer is connected to a main chain of the nylon polymer through a covalent bond, so that the nylon polymer containing a structural unit derived from the nylon monomer and the comonomer is generated. The whiteness of the whitening nylon provided by the invention is obviously improved, and the whitening effect is uniform. The preparation method of the whitening nylon provided by the invention is an in-situ polymerization method, does not need a complex bleaching process, simplifies the production steps of the existing whitening nylon, shortens the production cycle, and can greatly reduce the production cost.

Description

Technical Field

[0001] This invention relates to the field of polymer material preparation, and more specifically, to a whitening nylon, its preparation method, and its application. Background Technology

[0002] Whitening nylon is a nylon material that has undergone special treatment to improve its whiteness. Due to its high whiteness and good gloss, whitening nylon is widely used in the textile industry; it is often used to make various textiles, such as clothing and home textiles, to meet people's demands for product appearance and quality.

[0003] Whitening nylon is typically achieved through dyeing and printing. Fluorescent whitening agents are added to the dye bath to absorb invisible ultraviolet light and emit visible blue-violet fluorescence. This fluorescence complements the yellow light emitted by the fabric, increasing its whiteness and enhancing the fabric's whiteness. This treatment results in a whiter appearance and better luster for the nylon.

[0004] Currently, the conventional whitening printing process includes the following steps: weaving, degreasing, high-temperature setting, pre-dyeing fabric preparation, dyeing, loosening the fabric, pre-printing setting, printing, washing, and final setting. Before adding fluorescent whitening agents to the dyeing vat, the agents must be fully dissolved, requiring the use of auxiliaries to aid dissolution; different fluorescent whitening agents may require different auxiliaries to help them dissolve. Adding fluorescent whitening agents to the dyeing vat results in significant waste of the whitening agent and requires a huge amount of water for post-dyeing rinsing. To ensure uniformity and consistency in dyeing, the dyeing vat must be effectively cleaned, such as with high-pressure water jet cleaning, to ensure thorough cleaning. The process of cleaning the dyeing vat is very cumbersome.

[0005] In summary, the overall dyeing process of conventional whitening printing technology is complex. Summary of the Invention

[0006] To address the technical problem of complex processes involved in using fluorescent whitening agents to react with nylon to improve its whiteness, this invention provides a whitening nylon that does not require dyeing, its preparation method, and its applications.

[0007] The whitening nylon provided by this invention is prepared using an in-situ preparation method. Specifically, a comonomer is added during the polymerization reaction of monomeric raw materials (nylon monomers) to generate the nylon polymer. The comonomer is covalently bonded to the nylon polymer backbone, thereby generating a nylon polymer containing structural units derived from both the nylon monomers and the comonomer. Testing shows that the prepared nylon polymer exhibits significantly improved whiteness and a uniform whitening effect.

[0008] One of the objectives of this invention is to provide a whitening nylon.

[0009] The whitening nylon comprises structural units derived from nylon monomers and structural units derived from comonomers. The whitening nylon is a random copolymer.

[0010] The comonomer includes comonomer A; that is, the whitening nylon contains structural units derived from comonomer A. The carboxyl group in comonomer A reacts with the amino group in the nylon monomer to form an amide bond.

[0011] The structure of the comonomer A is shown in Formula I;

[0012]

[0013] In Formula I, R is independently selected from H, phenyl, alkyl chain, or sulfonic acid group, preferably from H. The phenyl group can be a substituted phenyl or an unsubstituted phenyl. The alkyl chain can be an alkyl chain with any number of carbon atoms. The alkyl chain can be a straight chain, can include branches, or can be a cycloalkyl group; the two Rs in Formula I can be the same or different.

[0014] The weight ratio of the structural unit derived from comonomer A to the structural unit derived from nylon monomer is 0.001-10:100, preferably 0.01-1:100, and more preferably 0.05-0.2:100.

[0015] To enhance the whitening properties of the whitening nylon, at least one of 1-pyrene, 2-pyrene, hexaaminotriphenylene, and o-phenylenediamine can be added as a comonomer during the polymerization process to participate in the copolymerization. Therefore, as a preferred embodiment of the whitening nylon of the present invention, the whitening nylon may further comprise structural units derived from comonomer B, that is, the comonomer further includes comonomer B, which is selected from one or more of 1-pyrene, 2-pyrene, hexaaminotriphenylene, and o-phenylenediamine. The amino group in the comonomer B reacts with the carboxyl group in the nylon monomer to form an amide bond.

[0016] The weight ratio of the structural unit derived from comonomer B to the structural unit derived from nylon monomer is 0.001-1:100, preferably 0.005-0.5:100, and more preferably 0.01-0.1:100.

[0017] To further adjust the molecular weight, fluorescence properties, mechanical properties, and thermal properties of the whitening nylon, one or more of maleic anhydride copolymers and imidazolic anhydride copolymers can be added as comonomers during the polymerization reaction to prepare the whitening nylon. The addition of maleic anhydride copolymers and imidazolic anhydride copolymers significantly improves the molecular weight and fluorescence properties of the obtained whitening nylon. Therefore, as a preferred embodiment of the whitening nylon of the present invention, the whitening nylon may further contain structural units derived from comonomer C, that is, the comonomer may further include comonomer C, which is selected from one or more of maleic anhydride copolymers and imidazolic anhydride copolymers; preferably, maleic anhydride copolymers, more preferably copolymers of maleic anhydride and olefins, such as maleic anhydride-styrene copolymers, maleic anhydride-1-hexene copolymers, etc. The carboxyl group in the comonomer C reacts with the amino group in the nylon monomer to form an amide bond.

[0018] The weight ratio of the structural unit derived from the comonomer C to the structural unit derived from the nylon monomer is 0.001-10:100, preferably 0.1-5:100, and more preferably 0.2-1:100.

[0019] The comonomer must contain comonomer A, and optionally comonomer B and / or comonomer C. For example, the comonomer can be just polymonomer A, the comonomer can be composed of polymonomer A and comonomer B, the comonomer can be composed of polymonomer A and comonomer C, or the comonomer can be composed of polymonomer A, comonomer B and comonomer C.

[0020] The nylon monomer can be any existing monomer capable of independently polymerizing to produce nylon. The nylon can be any existing nylon or nylon copolymer, including nylon 6, nylon 11, nylon 12, nylon 66, nylon 610, nylon 612, etc. Specifically, the nylon monomer can be selected from one or more of lactam, aminocaproic acid, and nylon 66 salt (polyhexamethylene adipamide salt).

[0021] One of the structures of the structural unit derived from nylon monomers is shown in Formula II;

[0022]

[0023] In Formula II, R1-R4 are independently selected from C4-C18 aromatic hydrocarbon groups, C4-C18 straight-chain hydrocarbon groups, or C4-C18 branched alkane groups; R3 and R4 cannot have the same structure at the same time; x+y+z=1, and x, y, and z can be 0.

[0024] As a preferred embodiment of the whitening nylon described in this invention, in Formula II, R1 is -(CH2)4-, -(CH2)6-, or -(CH2).10 -

[0025] As a preferred embodiment of the whitening nylon of the present invention, in Formula II, R2 is -(CH2)2-, -(CH2)4- or -(CH2)8-.

[0026] As a preferred embodiment of the whitening nylon described in this invention, in Formula II, R3 is -(CH2)5- or -(CH2). 10 -

[0027] As a preferred embodiment of the whitening nylon described in this invention, in Formula II, R4 is -(CH2)5- or -(CH2). 10 -

[0028] The whitening nylon provided by the present invention has a molecular weight characterized by relative viscosity testing, and its relative viscosity is 1.6-4.0, preferably 2.2-3.

[0029] According to the embodiments disclosed in this invention, the whitening nylon comprises structural units derived from autolactam and aminocaproic acid and structural units derived from stilbene dicarboxylic acid; or, the whitening nylon comprises structural units derived from autolactam and aminocaproic acid, structural units derived from stilbene dicarboxylic acid, and structural units derived from hexaaminotriphenylene; or, the whitening nylon comprises structural units derived from autolactam, aminocaproic acid, and nylon 66 salt and structural units derived from stilbene dicarboxylic acid; or, the whitening nylon comprises structural units derived from autolactam and aminocaproic acid, structural units derived from stilbene dicarboxylic acid, and structural units derived from styrene-maleic anhydride copolymer.

[0030] The whitening nylon provided by this invention can effectively convert ultraviolet light into blue-violet visible fluorescence (wavelength between 400-500 nanometers), which complements the yellow color produced by the yellowing of nylon, thus achieving the purpose of whitening. Furthermore, the whitening nylon provided by this invention has a total photoluminescence yield (quantum conversion efficiency) of over 62% for converting ultraviolet light to blue-violet visible fluorescence, resulting in excellent whitening effect.

[0031] The whitening nylon provided by this invention has a comonomer with whitening effect that is covalently linked to the polymer backbone, and has the effects of water resistance and abrasion resistance.

[0032] The second objective of this invention is to provide a method for preparing the whitening nylon described in the first objective of this invention.

[0033] The method for preparing the whitening nylon includes: polymerizing raw materials, including the nylon monomer and comonomer, to obtain the whitening nylon.

[0034] The polymerization can be any nylon polymerization method known in the art, such as at least one of condensation polymerization (including hydrolytic ring-opening polymerization), anionic polymerization, etc.; the polymerization reaction can be solution polymerization, bulk polymerization, or interfacial polymerization, etc. The polymerization process of the present invention can be carried out continuously or intermittently.

[0035] The polymerization reaction can be carried out under the typical reaction conditions for nylon polymerization. For example, the polymerization reaction is carried out under a protective gas atmosphere; the protective gas is a conventional protective gas, preferably nitrogen. The polymerization reaction temperature is 180-260°C. The polymerization reaction pressure is 0.1-20 atmospheres. The polymerization reaction time is 0.5-7 hours.

[0036] One specific embodiment of the whitening nylon preparation method of the present invention involves water-initiated ring-opening polymerization of nylon 6, comprising: reacting nylon 6 monomer and comonomer at 180-260°C and 1-20 atmospheres for 0.5-6 hours under a protective gas atmosphere; maintaining the reaction temperature at 180-260°C, reducing the pressure to below 200 Pa, and continuing the reaction for approximately 0.5 hours to obtain the whitening nylon.

[0037] The method for preparing whitening nylon provided by this invention is an in-situ polymerization method. Specifically, a comonomer with whitening properties is added during the polymerization reaction of the nylon monomers, allowing the comonomer to be covalently bonded to the nylon polymer backbone. Essentially, the whitening agent is covalently bonded to the nylon polymer backbone. Therefore, a complex bleaching process is eliminated, simplifying the existing production steps for whitening nylon, shortening the production cycle, and significantly reducing water and energy consumption, indirectly reducing carbon emissions and greatly lowering production costs. It also eliminates the need for handling and stretching in the dyeing vat, greatly reducing the risk of creases, and provides excellent bleaching results.

[0038] A third objective of this invention is to provide an application of the whitening nylon described in one of the objectives. Specifically, the whitening nylon is used in the textile industry, particularly in the apparel industry.

[0039] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0040] The whitening nylon provided by this invention can effectively convert ultraviolet light into blue-violet visible fluorescence (wavelength between 400-500 nanometers), which complements the yellow color caused by the yellowing of nylon, thus achieving the purpose of whitening.

[0041] The whitening nylon provided by this invention has a total photoluminescence yield (quantum conversion efficiency) of over 62% in the ultraviolet to blue-violet visible fluorescence range, resulting in a good whitening effect.

[0042] The whitening nylon provided by this invention has a uniform whitening effect and is also resistant to washing and abrasion.

[0043] The method for preparing whitening nylon provided by this invention is an in-situ polymerization method that does not require a complex bleaching process, simplifies the existing production steps of whitening nylon, shortens the production cycle, and greatly reduces water consumption, energy consumption, and indirectly reduces carbon emissions, thereby significantly reducing production costs. It also eliminates the need for handling and stretching in the dyeing vat, greatly reducing the risk of creases, and provides a good bleaching effect. Detailed Implementation

[0044] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0045] The raw materials used in the following examples and comparative examples are all commercially available products.

[0046] Relative viscosity tests of the whitening nylon product prepared in the examples and the fluorescent nylon product prepared in the comparative examples: Weigh 0.25g of polymer sample and place it in a 25ml volumetric flask. Add concentrated sulfuric acid (until the mark). After the sample is completely dissolved, add concentrated sulfuric acid to the mark in the volumetric flask and then shake well for measurement. Measure 10ml of the prepared solution into an Ubbelohde viscometer (4-1.0~1.1). Vertically install the viscometer in a constant temperature water bath at 25±0.5℃ for 20min. The time it takes for the solution to flow through both marks on the viscometer is the flow time. Measure each sample three times (with an error not exceeding ±0.2s) and take the average value.

[0047] The optical properties of the whitened nylon products prepared in the examples and the fluorescent nylon products prepared in the comparative examples were tested using an FLS 980 steady-state and transient fluorescence spectrometer from Edinburgh, UK. The excitation source for steady-state fluorescence spectroscopy was a xenon lamp; for fluorescence lifetime testing, an LED laser or supercontinuum laser was used; and for phosphorescence steady-state and transient spectroscopy testing, a microsecond lamp was used with gated operation. All detectors used were P928P PMT detectors. The total photoluminescence quantum yield and phosphorescence quantum yield were measured using the FLS 980 with an integrating sphere attachment. The excitation wavelength for steady-state fluorescence / phosphorescence spectroscopy, phosphorescence lifetime, and total / phosphorescence quantum yield tests was 365 nm.

[0048] Example 1

[0049] 130g of caprolactam and 20g of aminocaproic acid were added to a 500mL three-necked flask. Nitrogen gas was introduced to remove oxygen for 30 minutes. Then, 0.3g of stilbene dicarboxylic acid was added. The reactor was heated to 260℃ to carry out the hydrolysis ring-opening reaction. After stirring for about 3 hours, a vacuum was slowly drawn to maintain the reaction temperature at about 230℃. The low vacuum reaction was carried out for about 1 hour. After the excess water was removed, a high vacuum was drawn and the vacuum degree was further reduced to below 200Pa. The polycondensation reaction was carried out for 0.5 hours. The high quantum yield whitening nylon product A1 was obtained by discharging the product.

[0050] The product was tested and found to have a relative viscosity of 2.6, fluorescence emission at 440 nm, and a total photoluminescence yield of 66.98%.

[0051] Example 2

[0052] 130g of caprolactam and 20g of aminocaproic acid were added to a 500mL three-necked flask. Nitrogen gas was introduced to remove oxygen for 30 minutes. 0.4g of stilbene dicarboxylic acid was added. The reactor was heated to 260℃ to carry out the hydrolysis ring-opening reaction. After stirring for about 3 hours, a vacuum was slowly drawn to maintain the reaction temperature at about 230℃. The low vacuum reaction was carried out for about 1 hour. After the excess water was removed, a high vacuum was drawn and the vacuum degree was further reduced to below 200Pa. The polycondensation reaction was carried out for 0.5 hours. The high quantum yield whitening nylon product A2 was obtained by discharging the product.

[0053] The product was tested and found to have a relative viscosity of 2.8, fluorescence emission at 438 nm, and a total photoluminescence yield of 62.46%.

[0054] Example 3

[0055] Add 130g caprolactam and 20g aminocaproic acid to a 500mL three-necked flask, purge with nitrogen to remove oxygen for 30 minutes, add 0.75g stilbene dicarboxylic acid, heat the reactor to 260℃ to carry out the hydrolysis ring-opening reaction, stir the reaction for about 3 hours, then slowly evacuate the vacuum to maintain the reaction temperature at about 230℃, and react under low vacuum for about 1 hour. After the excess water is removed, start evacuating under high vacuum, further reduce the vacuum degree to below 200Pa, and carry out the polycondensation reaction for 0.5 hours. The high quantum yield whitening nylon product A3 is then discharged.

[0056] The product was tested and found to have a relative viscosity of 2.5, fluorescence emission at 438 nm, and a total photoluminescence yield of 62.46%.

[0057] Example 4

[0058] 130g of caprolactam and 20g of aminocaproic acid were added to a 500mL three-necked flask. Nitrogen gas was introduced to remove oxygen for 30 minutes. Then, 0.003g of stilbene dicarboxylic acid and 0.015g of 2-pyrene ammonia were added. The reactor was heated to 260℃ to carry out the hydrolysis ring-opening reaction. After stirring for about 3 hours, a vacuum was slowly drawn to maintain the reaction temperature at about 230℃. The low vacuum reaction was carried out for about 1 hour. After the excess water was removed, a high vacuum was drawn and the vacuum degree was further reduced to below 200Pa. The polycondensation reaction was carried out for 0.5 hours. The high quantum yield whitening nylon product A4 was obtained by discharging the product.

[0059] The product was tested and found to have a relative viscosity of 2.3, fluorescence emission at 442nm and 456nm, and a total photoluminescence yield of 72.71%.

[0060] Example 5

[0061] 130g of caprolactam and 20g of aminocaproic acid were added to a 500mL three-necked flask. Nitrogen gas was introduced to remove oxygen for 30 minutes. 0.003g of stilbene dicarboxylic acid and 0.03g of hexaaminotriphenylene were added. The reactor was heated to 260℃ to carry out the hydrolysis ring-opening reaction. After stirring for about 3 hours, a vacuum was slowly drawn to maintain the reaction temperature at about 230℃. The low vacuum reaction was carried out for about 1 hour. After the excess water was removed, a high vacuum was drawn and the vacuum degree was further reduced to below 200Pa. The polycondensation reaction was carried out for 0.5 hours. The high quantum yield whitening nylon product A5 was then discharged.

[0062] The product was tested and found to have a relative viscosity of 2.6, fluorescence emission at 438 nm, and a total photoluminescence yield of 70.32%.

[0063] Example 6

[0064] 100g caprolactam, 30g nylon 66 salt, and 20g aminocaproic acid were added to a 500mL three-necked flask. Nitrogen gas was introduced to remove oxygen for 30 minutes. Then, 0.4g stilbene dicarboxylic acid was added. The reactor was heated to 260℃ to carry out a hydrolysis ring-opening reaction. After stirring for about 3 hours, a vacuum was slowly drawn to maintain the reaction temperature at around 230℃. The low-vacuum reaction was carried out for about 1 hour. After the excess water was removed, a high vacuum was drawn and the vacuum degree was further reduced to below 200Pa. The polycondensation reaction was carried out for 0.5 hours. The high quantum yield whitening nylon product A6 was obtained by discharging the product.

[0065] The product was tested and found to have a relative viscosity of 3.1, fluorescence emission at 432 nm, and a total photoluminescence yield of 64.55%.

[0066] Example 7

[0067] Add 145g caprolactam and 5g water to a 500mL pressure reactor, purge with nitrogen to remove oxygen for 30 minutes, then add 0.4g stilbene dicarboxylic acid and 0.3g styrene-maleic anhydride copolymer. Heat the reactor to 260℃ and maintain pressure at 5 atmospheres to carry out the hydrolysis ring-opening reaction. After stirring for about 3 hours, slowly evacuate the reactor and maintain the reaction temperature at around 230℃. Continue the low-vacuum reaction for about 1 hour. Once excess water is removed, begin high-vacuum evacuation and further reduce the vacuum to below 200Pa to carry out the polycondensation reaction for 0.5 hours. The high quantum yield whitening nylon product A7 is then discharged.

[0068] The product was tested and found to have a relative viscosity of 3.3, fluorescence emission at 434 nm, and a total photoluminescence yield of 64.20%.

[0069] Comparative Example 1

[0070] Add 130g caprolactam and 20g aminocaproic acid to a 500mL three-necked flask, purge with nitrogen to remove oxygen for 30 minutes, heat the reactor to 260℃, and carry out the hydrolysis ring-opening reaction. After stirring for about 3 hours, start slowly drawing a vacuum to maintain the reaction temperature at about 230℃. The low vacuum reaction is carried out for about 1 hour. After the excess water is removed, start drawing a high vacuum and further reduce the vacuum degree to below 200Pa to carry out the polycondensation reaction for 0.5 hours. The nylon product B1 is then discharged.

[0071] The fluorescence emission was measured at 420 nm, and the total photoluminescence yield was 2.1%.

[0072] Performance testing

[0073] The relative viscosity and optical properties at room temperature of the nylon products prepared in Examples 1-7 and Comparative Example 1 were tested; the test results are shown in Table 1.

[0074] Table 1

[0075]

[0076] As shown in Table 1, the whitening nylon of this invention can absorb ultraviolet light and then re-emit blue-violet visible fluorescence (wavelength between 400-500 nanometers). The blue-violet light emitted by the whitening nylon mixes with the reflected light to mask the yellow or dull hues of the whitening nylon, thereby achieving a whitening and brightening effect from an optical perspective, making the whitening nylon appear whiter and brighter.

[0077] The higher the quantum efficiency (total photoluminescence yield) of the ultraviolet-to-blue light conversion, the better the whitening effect. The total photoluminescence yield of the whitening nylon of this invention can reach over 62%, indicating that the whitening nylon of this invention has excellent whitening effect.

[0078] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various modifications can be made to the technical solution of the present invention, all of which fall within the protection scope of the present invention.

[0079] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0080] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A whitened nylon characterized in that, The whitening nylon comprises structural units derived from nylon monomers and structural units derived from comonomers; The comonomers comprise comonomer A; The structure of the comonomer A is shown in formula I; In formula I, R is independently selected from H, phenyl, alkyl chain or sulfonic acid group.

2. The whitened nylon of claim 1 wherein, The weight ratio of the structural units derived from the comonomer A to the structural units derived from the nylon monomers is 0.001-10:100, preferably 0.01-1:100, and more preferably 0.05-0.2:

100.

3. The whitened nylon of claim 1 wherein, The comonomers comprise comonomer B; the comonomer B is selected from one or more of 1-pyrene amine, 2-pyrene amine, hexamino triphenylamine, and o-phenylenediamine.

4. The whitened nylon of claim 3 wherein, The weight ratio of the structural units derived from the comonomer B to the structural units derived from the nylon monomers is 0.001-1:100, preferably 0.005-0.5:100, and more preferably 0.01-0.1:

100.

5. The whitened nylon of claim 1 wherein, The comonomers comprise comonomer C; the comonomer C is selected from one or more of maleic anhydride copolymer and isosorbide anhydride copolymer, and is preferably a copolymer of maleic anhydride and olefin.

6. The whitened nylon of claim 5 wherein, The weight ratio of the structural units derived from the comonomer C to the structural units derived from the nylon monomers is 0.001-10:100, preferably 0.1-5:100, and more preferably 0.2-1:

100.

7. The whitened nylon of claim 1 wherein, The nylon monomers are selected from one or more of caprolactam, aminocaproic acid, and nylon 66 salt.

8. The whitened nylon of claim 1 wherein, The structural units derived from the nylon monomers are shown in formula II; In formula II, R1-R4 are independently selected from C4-C18 aromatic hydrocarbon group, straight-chain alkyl group, or branched alkyl group; R3 and R4 cannot have the same structure at the same time; x+y+z=1, and x, y, and z can be 0; Preferably, R1is -(CH2)4-, -(CH2)6- or -(CH2) 10 -; or / and, R2 is -(CH2)2-, -(CH2)4-, or -(CH2)8-; or / and, R3 is -(CH2)5- or -(CH2) 10 -; or / and, R4 is -(CH2)5- or -(CH2) 10 - 9. The whitened nylon of claim 1 wherein, The relative viscosity thereof is 1.6-4.0, and preferably 2.2-3.

10. A process for the production of the whitened nylon according to any one of claims 1 to 9, characterized in that, The preparation method comprises polymerizing raw materials comprising the nylon monomers and comonomers to obtain the whitening nylon.

11. The preparation method of claim 10, wherein, The polymerization reaction is carried out under the protection of a protective gas, and the protective gas is preferably nitrogen; or / and, The polymerization reaction temperature is 180-260°C; or / and, The polymerization reaction pressure is 0.1-20 atm; or / and, The polymerization reaction time is 0.5-7 h.

12. Use of the whitening nylon of any one of claims 1-9 in the field of textiles.

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