A method for decoloring polymeric light stabilizers

Abstract

The present application belongs to the technical field of hindered amine light stabilizers, and particularly relates to a decolorization method of a polymeric light stabilizer, which comprises the following steps: (1) mixing a laggard product with an organic solvent, a polymeric light stabilizer or a combination of the granular laggard product, to obtain a solution containing the laggard product; (2) feeding the solution containing the laggard product into a hydrogenation reactor loaded with a catalyst, and performing a hydrogenation reaction under the action of the catalyst; then filtering to obtain a polymeric light stabilizer reaction liquid after reduction and decolorization; (3) feeding the polymeric light stabilizer reaction liquid into a desolventizing kettle for treatment, and evaporating all the solvents to obtain a polymeric light stabilizer after reduction and decolorization; (4) feeding the polymeric light stabilizer after reduction and decolorization into a granulation process to form product granules, and optionally applying the evaporated solvents to a batching kettle of the next batch. The decolorization method has obvious decolorization effect, and the light transmittance of the obtained product after decolorization is significantly improved; the product quality is improved, and at the same time, cumbersome processes such as solid waste treatment are reduced, and the cost is reduced.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of hindered amine light stabilizers, and particularly relates to a decolorization method of a polymeric light stabilizer. BACKGROUND

[0002] Hindered amine light stabilizers (HALS) are a class of piperidine derivatives with steric hindrance effect. Different types of HALS are produced due to different types of auxiliary groups and substituents, thus resulting in different types of HALS with different numbers of piperidine groups and molecular weights.

[0003] Early industrialized HALS have low molecular weight and strong alkalinity, such as light stabilizer 770. During product processing and product use, the auxiliary agent is not resistant to extraction and is prone to migration to the surface of the product, thereby affecting the service life of the product.

[0004] Therefore, the research, development and application of high molecular weight and low alkaline light stabilizers have attracted the attention of many researchers. Through a large amount of data analysis, the molecular weight of polymeric light stabilizers is mostly 2000-5000 Da. The polymeric HALS is generally prepared by a granulation method. However, the granulation process inevitably causes the discoloration of the obtained granular product due to high temperature or contact with air. For example, light stabilizer 944, light stabilizer 119, light stabilizer 622 and their compositions are subjected to high-temperature desolventization, granulation and other processes. The obtained products are prone to yellowing, thereby reducing the light transmittance and affecting the use of downstream customers.

[0005] In order to well handle the stale products formed due to discoloration, the current reported decolorization technologies for polymeric light stabilizers mainly include the following:

[0006] 1. Adsorption decolorization method, which is based on the characteristics that an adsorbent with strong adsorption capacity can adsorb pigments and other impurities in a solution. The pigments and impurities adsorbed are removed by filtering the adsorbent, so as to achieve the purpose of decolorization and purification. Common adsorbents include the following: activated clay, activated carbon, attapulgite, silica gel and ion exchange resin.

[0007] 2. Reduction decolorization method, which uses aluminum isopropoxide, sodium borohydride and the like as a reducing agent to reduce the reducing agent to a low-valence ion through an oxidation-reduction reaction, so as to realize decolorization.

[0008] 3. Oxidation decolorization method, which uses an oxidizing decolorizing agent to realize decolorization. The oxidizing decolorizing agent uses oxidizing substances such as sodium hypochlorite, potassium permanganate, ozone and hydrogen peroxide to destroy the colored groups, so as to remove the color.

[0009] The adsorption decolorization method is not ideal for most polymeric light stabilizers, and a large amount of adsorbent needs to be recovered, which increases the pressure of solid waste treatment and the cost. The reduction decolorization method and the oxidation decolorization method are rarely used in industry due to the high price of reducing agents and oxidizing agents and the complex post-reaction treatment.

[0010] Therefore, it is worth studying to explore a decolorization method with low cost and simple process to improve the light transmittance and appearance of polymeric light stabilizers. SUMMARY

[0011] The present application provides a decolorization method for polymeric light stabilizers, which has obvious decolorization effect, significantly improves the light transmittance of the product after decolorization, breaks the traditional decolorization method of polymeric light stabilizers, improves the product quality, reduces the cumbersome procedures such as solid waste treatment, and reduces the cost. The method improves the light transmittance of polymeric light stabilizers while improving their appearance, and ultimately achieves the purpose of treating the sluggish products generated during the industrial production of polymeric light stabilizers.

[0012] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0013] A decolorization method for polymeric light stabilizers, comprising the following steps:

[0014] (1) In a batching kettle, organic solvent, polymeric light stabilizer or its composition particle sluggish product is contacted and mixed to obtain a solution containing sluggish product, which is ready for use;

[0015] (2) The solution containing the sluggish product obtained in step (1) enters a hydrogenation reactor loaded with a catalyst and undergoes hydrogenation reaction under the action of the catalyst; after the reaction is completed, a reduced and decolorized polymeric light stabilizer reaction liquid is obtained (for example, by filtration);

[0016] (3) The reduced and decolorized polymeric light stabilizer reaction liquid obtained in step (2) enters a desolventizing kettle for treatment, and all solvents are distilled out to obtain a reduced and decolorized polymeric light stabilizer;

[0017] (4) The reduced and decolorized polymeric light stabilizer obtained is subjected to a granulation process to produce product particles, and the solvent distilled out in step (3) is optionally used in the batching kettle of the next batch.

[0018] According to the decolorization method provided by the present application, in some embodiments, in step (1), the polymeric light stabilizer or its composition particle is selected from one or more of the granulated products of light stabilizer 944, light stabilizer 622, light stabilizer 119 and their compositions.

[0019] In some embodiments, in step (1), the organic solvent is selected from one or more of n-hexane, n-heptane, octane, nonane, decane, toluene, ethylbenzene, xylene and mesitylene, preferably n-heptane or toluene.

[0020] In some embodiments, in step (1), the ratio of the organic solvent to the sluggish product by weight is 1:1 to 7:1 (e.g., 1.5:1, 2.5:1, 3:1, 3.5:1, 4.5:1, 5:1, 6:1, 6.5:1), preferably 2:1 to 4:1.

[0021] In some embodiments, in step (2), the hydrogenation reactor is selected from one or more of a reaction kettle, a fixed bed reactor, a fluidized bed reactor and a microchannel reactor, preferably a microchannel reactor.

[0022] In some embodiments, the flow rate of the liquid inlet of the microchannel reactor is 2 to 10 mL / min (e.g., 2.5 mL / min, 3.5 mL / min, 4.0 mL / min, 5.0 mL / min, 6.0 mL / min, 8.0 mL / min, 9.0 mL / min), preferably 3 to 7 mL / min; the residence time of the material in the microchannel reactor is 10 to 50 s (e.g., 15 s, 20 s, 35 s, 40 s, 45 s, 48 s), preferably 30 to 50 s.

[0023] In some embodiments, the catalyst is a supported catalyst.

[0024] In some embodiments, the supported catalyst comprises a carrier and an active ingredient supported on the carrier; wherein the active ingredient is selected from at least one of Cu, Co, Ni, Mn, Fe, Ag, V, Pt, Pd, Rh, Au, Ir and oxides thereof; the carrier is selected from at least one of Al2O3, SiO2, ZrO2, TiO2, ZnO.

[0025] In some embodiments, in the hydrogenation reactor, the ratio of the amount of the catalyst to the sluggish product by weight is 1 wt% to 15 wt% (e.g., 2 wt%, 3 wt%, 4 wt%, 6 wt%, 7 wt%, 10 wt%, 12 wt%, 14 wt%), preferably 5 wt% to 8 wt%.

[0026] In some embodiments, in step (1), the process conditions for mixing are stirring at 70°C for more than 30 min (e.g., 40 min, 50 min, 60 min).

[0027] In some embodiments, in step (2), the reaction temperature is 70-200℃ (for example, 80℃, 90℃, 100℃, 105℃, 110℃, 120℃, 130℃, 140℃, 160℃, 180℃), preferably 100-150℃; the hydrogen pressure is 0.1-5.0 MPa (for example, 0.2 MPa, 0.5 MPa, 1.0 MPa, 1.5 MPa, 2.5 MPa, 3.5 MPa, 4.0 MPa, 4.5 MPa), preferably 2.0-3.0 MPa.

[0028] In step (3), the desolventizing kettle used can be a conventional device in the art; the operation and process conditions for removing the solvent can also be conventional choices in the art; and thus, no further elaboration is provided herein.

[0029] In step (4), the granulation procedure for the obtained reduced and decolored polymeric light stabilizer can also be a conventional choice in the art, and thus, no further elaboration is provided herein.

[0030] In the text, the “dull product” refers to a product with unqualified light transmittance. For example, a product with unqualified light transmittance produced in the industrial production of a polymeric light stabilizer.

[0031] In the art, the standard for the light transmittance of a light stabilizer product is generally that the light transmittance at 425 nm is also above 90%, and the higher the light transmittance, the better the product quality. Different product standards are different, for example:

[0032] The light transmittance of light stabilizer 944 (425 nm) is ≥98%;

[0033] The light transmittance of light stabilizer 119 (425 nm) is ≥97%;

[0034] The present application improves the light transmittance of the polymeric light stabilizer by hydrogen reduction decolorization of the dull product of the polymeric light stabilizer or its composition; and in the hydrogenation reaction, the mass transfer effect is high, which is conducive to the hydrogenation reaction; and the use of a supported catalyst in the hydrogenation reaction improves the intrinsic safety.

[0035] Compared with the prior art, the beneficial effects of the technical scheme of the present application are as follows:

[0036] (1) The present application uses hydrogen reduction method to decolorize the polymeric light stabilizer, and the recovery rate of the dull product reaches more than 99%, and the b value of the obtained product after decolorization is below 1.5, and the light transmittance (425 nm) can reach more than 98%;

[0037] (2) The decolorization method of the present application simplifies the process, reduces the energy consumption, and uses a supported catalyst to reduce the cumbersome procedures and wastewater generated in the treatment of the catalyst;

[0038] (3) The decolorization method of the present application can reduce pollution and cost, as no adsorbent is used, so there is no need to dispose of a large amount of solid waste adsorbent, and the cost is reduced by at least 30% to 50%. DETAILED DESCRIPTION

[0039] In order to enable a detailed understanding of the technical features and content of the present application, the preferred embodiments of the present application will be described in more detail below. Although the preferred embodiments of the present application are described in the examples, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments described herein. If no specific conditions are specified in the examples, the conditions are carried out according to the conventional conditions or the conditions recommended by the manufacturer.

[0040] <Raw material source>

[0041] In the following examples and comparative examples, the source of the reagents or raw materials used is not specified, and the reagents or raw materials that are not specified by the manufacturer are conventional products that can be obtained by purchase on the market.

[0042] Light stabilizer 944 dregs are products (such as head and tail) produced during the production of light stabilizer 944, which cannot meet the sales requirements in terms of transmittance and appearance.

[0043] Example 1

[0044] (1) Add 90 g of n-heptane and 30 g of light stabilizer 944 dregs to a batching kettle, and stir at 70°C for more than 30 min to obtain a solution containing dregs, which is ready for use;

[0045] (2) The n-heptane solution containing light stabilizer 944 dregs obtained is pumped into a hydrogenation micro-channel reactor at a pump flow rate of 5 mL / min, the reactor is loaded with Pb / TiO2 supported catalyst, and the loading amount is 7 wt% of the amount of dregs, and hydrogenation reaction is carried out under the action of the Pb / TiO2 supported catalyst, the residence time of the material in the hydrogenation micro-channel reactor is 30 s, the reaction temperature is 130°C, and the hydrogen pressure is 2.0 MPa; after the reaction is completed, filtration is carried out to obtain a reduced and decolorized light stabilizer 944 reaction liquid;

[0046] (3) The reduced and decolorized light stabilizer 944 reaction liquid is introduced into a desolventizing kettle, and all the solvents are distilled off to obtain reduced and decolorized light stabilizer 944;

[0047] (4) The solvents distilled off in step (3) are used in the next batch of batching kettle, and the reduced and decolorized polymeric light stabilizer is introduced into a granulation process to produce product particles, and the mass of the reduced and decolorized light stabilizer 944 is 29.8 g, and the yield is 99.33%; the b value of the product obtained is 1.0, the transmittance (425 nm) is 98.7%, the transmittance (450 nm) is 99.5%, and the transmittance (500 nm) is 99.7%.

[0048] Example 2

[0049] (1) Add n-heptane 90 g, light stabilizer 944 sludge 30 g into a batching kettle, and stir at 70 °C for more than 30 min to obtain a solution containing sludge, ready for use;

[0050] (2) The obtained n-heptane solution containing light stabilizer 944 sludge is pumped into a hydrogenation micro-channel reactor at a pump flow rate of 10 mL / min, the reactor is packed with Pb / TiO2 supported catalyst, and the packing amount is 5 wt% of the amount of sludge, hydrogenation reaction is carried out under the action of Pb / TiO2 supported catalyst, the residence time of the material in the hydrogenation micro-channel reactor is 20 s, the reaction temperature is 130 °C, and the hydrogen pressure is 2.0 MPa; after the reaction is completed, filtration is carried out to obtain the reaction solution of light stabilizer 944 after reduction and decolorization;

[0051] (3) The reaction solution of light stabilizer 944 after reduction and decolorization is introduced into a desolventizing kettle, and all the solvents are distilled to obtain light stabilizer 944 after reduction and decolorization;

[0052] (4) The distilled solvent of step (3) is used in the next batching kettle, and the light stabilizer 944 after reduction and decolorization is introduced into a granulation process to prepare product particles, and the mass of light stabilizer 944 after reduction and decolorization is 29.77 g, and the yield is 99.23%; the b value of the obtained product is 1.2, the light transmittance (425 nm) is 98.5%, the light transmittance (450 nm) is 99.4%, and the light transmittance (500 nm) is 99.7%.

[0053] Example 3

[0054] (1) Add n-heptane 90 g, light stabilizer 944 sludge 30 g into a batching kettle, and stir at 70 °C for more than 30 min to obtain a solution containing sludge, ready for use;

[0055] (2) The obtained n-heptane solution containing light stabilizer 944 sludge is pumped into a hydrogenation micro-channel reactor at a pump flow rate of 5 mL / min, the reactor is packed with Pb / TiO2 supported catalyst, and the packing amount is 7 wt% of the amount of sludge, hydrogenation reaction is carried out under the action of Pb / TiO2 supported catalyst, the residence time of the material in the hydrogenation micro-channel reactor is 30 s, the reaction temperature is 160 °C, and the hydrogen pressure is 1.5 MPa; after the reaction is completed, filtration is carried out to obtain the reaction solution of light stabilizer 944 after reduction and decolorization;

[0056] (3) The reaction solution of light stabilizer 944 after reduction and decolorization is introduced into a desolventizing kettle, and all the solvents are distilled to obtain light stabilizer 944 after reduction and decolorization;

[0057] (4) The solvent evaporated in step (3) is used for the next batch of the preparation kettle, and the reduced and decolorized polymeric light stabilizer enters the granulation process to produce product particles, and the mass of the reduced and decolorized light stabilizer 944 is 29.81 g, and the yield is 99.37%; the b value of the obtained product is 1.3, the light transmittance (425 nm) is 98.3%, the light transmittance (450 nm) is 99.2%, and the light transmittance (500 nm) is 99.6%.

[0058] Example 4

[0059] (1) Add n-heptane 180 g and light stabilizer 944 sludge 30 g to the preparation kettle, and stir at 70°C for more than 30 min to obtain a solution containing sludge, which is ready for use;

[0060] (2) The n-heptane solution containing light stabilizer 944 sludge obtained is pumped into the hydrogenation micro-channel reactor at a pump flow rate of 10 mL / min, the Pb / TiO2 supported catalyst is loaded in the reactor, and the loading amount is 3 wt% of the amount of sludge, and the hydrogenation reaction is carried out under the action of the Pb / TiO2 supported catalyst, the residence time of the material in the hydrogenation micro-channel reactor is 15 s, the reaction temperature is 170°C, and the hydrogen pressure is 1.0 MPa; after the reaction is completed, filtration is performed to obtain a reduced and decolorized light stabilizer 944 reaction liquid;

[0061] (3) The reduced and decolorized light stabilizer 944 reaction liquid enters the desolventizing kettle, and all the solvent is evaporated to obtain a reduced and decolorized light stabilizer 944;

[0062] (4) The solvent evaporated in step (3) is used for the next batch of the preparation kettle, and the reduced and decolorized polymeric light stabilizer enters the granulation process to produce product particles, and the mass of the reduced and decolorized light stabilizer 944 is 29.71 g, and the yield is 99.03%; the b value of the obtained product is 1.4, the light transmittance (425 nm) is 97.8%, the light transmittance (450 nm) is 99.2%, and the light transmittance (500 nm) is 99.6%.

[0063] Example 5

[0064] The decolorization method of the polymeric light stabilizer is the same as that in Example 1, except that in step (2), the n-heptane solution containing light stabilizer 944 sludge obtained is pumped into the hydrogenation micro-channel reactor at a pump flow rate of 2 mL / min, and the residence time of the material in the hydrogenation micro-channel reactor is 50 s; the remaining steps are the same as those in Example 1.

[0065] The mass of the light stabilizer 944 after reduction and decolorization is 29.90 g, and the yield is 99.67%; the b value of the obtained product is 1.3, the light transmittance (425 nm) is 98.2%, the light transmittance (450 nm) is 98.9%, and the light transmittance (500 nm) is 99.7%.

[0066] Example 6

[0067] The decolorization method of the polymeric light stabilizer refers to Example 1, except that the loading amount of the Pb / TiO2 supported catalyst in the reactor in step (2) is 15 wt% of the amount of the stale product; the other steps are the same as those in Example 1.

[0068] The mass of the light stabilizer 944 after reduction and decolorization is 29.90 g, and the yield is 99.67%; the b value of the obtained product is 1.3, the light transmittance (425 nm) is 98.2%, the light transmittance (450 nm) is 98.9%, and the light transmittance (500 nm) is 99.7%.

[0069] Example 7

[0070] The decolorization method of the polymeric light stabilizer refers to Example 1, except that the loading amount of the Pb / TiO2 supported catalyst in the reactor in step (2) is 15 wt% of the amount of the stale product; the other steps are the same as those in Example 1.

[0071] The mass of the light stabilizer 944 after reduction and decolorization is 29.90 g, and the yield is 99.67%; the b value of the obtained product is 1.3, the light transmittance (425 nm) is 98.2%, the light transmittance (450 nm) is 98.9%, and the light transmittance (500 nm) is 99.7%.

[0072] Comparative Example 1

[0073] The light stabilizer 944 stale product is treated by adsorption decolorization:

[0074] (1) 90 g of n-heptane and 30 g of the light stabilizer 944 stale product are added to a batching kettle, and stirred at 70°C for more than 30 min to obtain a solution containing the stale product, which is ready for use;

[0075] (2) 3 g of activated clay is added to the solution containing the stale product obtained in step (1), stirred for 1 h, and filtered to obtain the light stabilizer 944 filtrate after decolorization;

[0076] (3) The decolorized light stabilizer 944 filtrate obtained in step (2) was put into a desolventizing kettle, and all the solvent was evaporated to obtain 28.95 g of light stabilizer 944 with a yield of 96.5%. The b value of the obtained product was 2.5, the light transmittance (425 nm) was 96.6%, the light transmittance (450 nm) was 97.1%, and the light transmittance (500 nm) was 97.9%.

[0077] Comparative Example 2

[0078] The light stabilizer 944 stale product was treated by an oxidation decolorization method:

[0079] (1) 90 g of n-heptane and 30 g of light stabilizer 944 stale product were added into a batching kettle, and stirred at 70°C for more than 30 min to obtain a solution containing the stale product, which was used for the next step;

[0080] (2) 2 g of 35% hydrogen peroxide was slowly added into the solution containing the stale product obtained in step (1), and stirred for 1 h to obtain a decolorized light stabilizer 944 filtrate;

[0081] (3) The decolorized light stabilizer 944 filtrate obtained in step (2) was put into a desolventizing kettle, and all the solvent was evaporated to obtain 29.75 g of light stabilizer 944 with a yield of 99.17%. The b value of the obtained product was 2.8, the light transmittance (425 nm) was 95.9%, the light transmittance (450 nm) was 96.8%, and the light transmittance (500 nm) was 97.7%.

[0082] Comparative Example 3

[0083] The decolorization method of the polymeric light stabilizer was the same as that in Example 1, except that the reactor in step (2) was filled with Raney nickel catalyst; the other steps were the same as those in Example 1.

[0084] The reduced and decolorized light stabilizer 944 had a mass of 29.64 g with a yield of 98.8%. The b value of the obtained product was 2.5, the light transmittance (425 nm) was 96.9%, the light transmittance (450 nm) was 97.5%, and the light transmittance (500 nm) was 98.6%.

[0085] The above has described various embodiments of the present application, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes are obvious to those skilled in the art without departing from the spirit of the present application.

Claims

1. A method for decolorizing a polymeric light stabilizer, characterized in that, The decolorization method includes the following steps: (1) In a mixing tank, organic solvent, polymeric light stabilizer or their composition particles are mixed to obtain a solution containing the stagnant material for later use; The polymeric light stabilizer or its composition particles are selected from one or more of the granulated products of light stabilizer 944, light stabilizer 622, light stabilizer 119 and their compositions; (2) The solution containing stagnant material obtained in step (1) enters a hydrogenation reactor filled with catalyst and undergoes hydrogenation reaction under the action of catalyst; after the reaction is completed, a reduced and decolorized polymeric light stabilizer reaction solution is obtained. The catalyst is a supported catalyst; the supported catalyst includes a support and an active component supported on the support; wherein the active component is at least one of Pd and its oxides; (3) The reaction solution of the reduced and decolorized polymeric light stabilizer obtained in step (2) is put into the solvent removal vessel for treatment, and all the solvent is evaporated to obtain the reduced and decolorized polymeric light stabilizer. (4) The obtained polymeric light stabilizer after reduction and decolorization is put into the granulation process to make product granules. Optionally, the solvent distilled in step (3) can be reused in the next batch of batching tank.

2. The decolorization method according to claim 1, characterized in that, In step (1), the organic solvent is selected from one or more of n-hexane, n-heptane, octane, nonane, decane, toluene, ethylbenzene, xylene and trimethylbenzene.

3. The decolorization method according to claim 1, characterized in that, The organic solvent is n-heptane or toluene.

4. The decolorization method according to claim 1, characterized in that, In step (1), the ratio of organic solvent to stagnant product by weight is 1:1 to 7:

1.

5. The decolorization method according to claim 1, characterized in that, In step (1), the ratio of organic solvent to stagnant product by weight is 2:1 to 4:

1.

6. The decolorization method according to claim 1, characterized in that, In step (2), the hydrogenation reactor is selected from one or more of the following: reaction vessel, fixed bed reactor, fluidized bed reactor and microchannel reactor.

7. The decolorization method according to claim 1, characterized in that, In step (2), the hydrogenation reactor is a microchannel reactor.

8. The decolorization method according to claim 6, characterized in that, The inlet pump of the microchannel reactor has a flow rate of 2~10 mL / min; the retention time of the material in the microchannel reactor is 10~50 s.

9. The decolorization method according to claim 6, characterized in that, The inlet pump of the microchannel reactor has a flow rate of 3-7 mL / min; the retention time of the material in the microchannel reactor is 30-50 s.

10. The decolorization method according to claim 1, characterized in that, In the catalyst, the support is selected from at least one of Al2O3, SiO2, ZrO2, TiO2, and ZnO.

11. The decolorization method according to claim 1, characterized in that, In the hydrogenation reactor, the ratio of catalyst to stagnant material by weight is 1wt% to 15wt%.

12. The decolorization method according to claim 1, characterized in that, In the hydrogenation reactor, the ratio of catalyst to stagnant material by weight is 5wt% to 8wt%.

13. The decolorization method according to any one of claims 1-12, characterized in that, In step (1), the mixing process conditions are: stirring at 70°C for more than 30 minutes.

14. The decolorization method according to any one of claims 1-12, characterized in that, In step (2), the reaction temperature is 70~200℃; the hydrogen pressure is 0.1~5.0MPa.

15. The decolorization method according to claim 14, characterized in that, In step (2), the reaction temperature is 100~150℃ and the hydrogen pressure is 2.0~3.0MPa.