Complex, preparation method thereof and eye protection paper

Abstract

The invention provides a complex. The complex is formed by connecting lutein and rare earth metal ions through coordinate bonds. The invention also provides a preparation method of the complex and eye protection paper using the complex. The complex provided by the invention is formed by lutein and rare earth metal ions through coordinate bonds, the wavelength range of absorbed light covers 315-430nm ultraviolet-visible light wave bands, light of harmful wave bands in reflected light of paper can be remarkably reduced, visual fatigue can be relieved, and the prepared eye protection paper has a relatively good eye protection effect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of paper modification, and particularly relates to a complex, a preparation method thereof and eye-protecting paper. BACKGROUND

[0002] Blue light is a part of visible light. Among them, short-wave blue light with a wavelength of 380-445 nm has relatively high energy, is easy to cause visual fatigue and vision damage, affects the secretion of melatonin to cause poor sleep quality, and also damages the skin. In daily life, artificial light sources will produce harmful high-frequency blue light when in use, causing damage to human health.

[0003] At present, the eye protection of paper basically adopts the way of adding yellow dye, which reduces the reflection of blue light by using the blue light absorption of yellow dye. However, the main absorption band of yellow dye is between 430-720 nm, while the short-wave blue-violet light of 380-445 nm is more harmful to the eyes. The use of yellow dye cannot completely absorb it, and the eye protection effect is limited. SUMMARY

[0004] In view of the technical problems of the existing yellow dye that the absorption wavelength is not complete and the eye protection effect is limited, the present application provides a complex. The present application also provides a preparation method of the above-mentioned complex, and eye-protecting paper containing the above-mentioned complex. The complex provided by the present application is formed by coordination bond between lutein and rare earth metal ions, and the absorption wavelength range covers 315-430 nm ultraviolet-visible light band, which can significantly reduce the harmful waveband of light reflected by paper, relieve visual fatigue, and the eye-protecting paper produced has good eye-protecting effect.

[0005] A complex is formed by coordination bond between lutein and rare earth metal ions. The rare earth metal ion is at least one of La 3+ , Ce 3+ , Pr 3+ .

[0006] Preferably, the molar ratio of lutein to rare earth metal ion is 3:1.

[0007] The preparation method of the complex according to any one of the above, comprising the following steps: The lutein and the rare earth metal ion are added to a non-aqueous solvent, an organic base is used to adjust the pH to alkaline, a catalyst is added, and the reaction is heated under a protective gas to obtain the complex.

[0008] Preferably, the non-aqueous solvent is anhydrous ethanol and dimethyl sulfoxide in a volume ratio of (3-4):1; and / or, The pH is adjusted to 8.0-10.0; and / or, The protective gas is any one of nitrogen, helium and argon; and / or, The temperature of the heating reaction is 55-65℃, and the time of the heating reaction is 6-8h; and / or, The catalyst is pyridine.

[0009] Preferably, triethylamine is used to adjust the pH; and / or, The temperature of the heating reaction is 58-62℃; and / or, The catalyst accounts for 0.05-0.5% of the mass percentage of the used reaction raw materials.

[0010] Preferably, the purification step is further included: the reaction liquid after the heating reaction is cooled, ice ethyl ether is added, the precipitate is separated out, and the finished product powder is obtained through filtration, washing and drying.

[0011] Preferably, the reaction liquid is cooled to 2-6℃, ice ethyl ether is added in an equal volume of the reaction liquid, the precipitate separated out is vacuum filtered by using a 0.22μm filter membrane, anhydrous ethanol is washed for 2-4 times, and vacuum drying is performed at 35-45℃ for 10-20 hours.

[0012] An eye-protecting paper, wherein the coating on the surface of the eye-protecting paper contains the complex according to any one of the above-mentioned items or the complex prepared by the preparation method according to any one of the above-mentioned items.

[0013] Preferably, in the coating on the surface of the eye-protecting paper, the mass percentage of the complex is 0.5-1.0%.

[0014] Lutein is a natural carotenoid, which has a strong absorption peak at 425nm, but has the problems of poor photothermal stability, easy oxidation failure, poor water solubility and difficult uniform dispersion in the coating of paper. The complex provided by the application is formed by coordination between lutein and rare earth metal ions, and the complex can efficiently absorb blue-violet light of 380-430nm. Moreover, the complex can also absorb ultraviolet light (UVA) of 315-380nm, covering the ultraviolet-visible light band of 315-430nm, and can significantly reduce the light of harmful wave band in the reflected light of paper, thereby relieving visual fatigue.

[0015] Specifically, the complex prepared in the application has the following advantages: 1. Spectral expansion: the f-f electron transition of at least one of La 3+ , Ce 3+ , Pr 3+ is coupled with lutein to jump, and the absorption peak is red-shifted to 400-430nm; 2. Stability improvement: the light resistance of lutein is improved by 3 times due to the coordination bond; 3. Dispersion optimization: the hydrophilicity of the complex is enhanced, and the complex is suitable for water-based paper coating.

[0016] In the present application, the rare earth metal ion (RE 3+ ) is at least one of lanthanum La 3+ , cerium Ce 3+ , praseodymium Pr 3+ . One of them can be used to form a complex, or two or more of them can be used to form a complex.

[0017] The present application also provides a preparation method of the above-mentioned complex, comprising the following steps: adding lutein and a rare earth metal ion into a non-aqueous solvent, adjusting the pH to alkaline by using an organic base, adding a catalyst, and heating the reaction under a protective gas to obtain the complex.

[0018] The reaction principle is that the β-diketone structure (cyclohexene diketone group at the end of the molecule) of lutein (molecular formula C 40 H 56 O2) forms a six-coordinated chelate with a rare earth metal ion (RE 3+ ) under alkaline conditions. The reaction process can be divided into two steps, as follows: First, enolization and deprotonation of the β-diketone structure of lutein.

[0019] The β-diketone group (-CO-CH2-CO-) of lutein undergoes enol tautomerism in an alkaline environment to generate an enol structure (-C(OH)=C-CO-), which is further deprotonated to form a bidentate ligand anion ([H-1L] - ): C 40 H 56 O2 (lutein) + OH - → C 40 H 55 O2 (enol anion) + H2O.

[0020] The key condition of the above reaction is an alkaline environment to promote the deprotonation of the β-diketone, and a non-aqueous solvent to avoid hydrolysis.

[0021] The pH is preferably 8.0-10.0. Triethylamine is preferably used to adjust the pH.

[0022] The non-aqueous solvent is preferably a mixture of anhydrous ethanol and dimethyl sulfoxide to ensure the solubility of lutein and the ion dissociation. More preferably, the volume ratio of anhydrous ethanol and dimethyl sulfoxide is (3-4):1.

[0023] Pyridine is preferably added as a catalyst to stabilize the intermediate as a neutral ligand.

[0024] Second, the formation of a six-coordinated chelate Three lutein enol anions form a six-coordinated chelate with one RE3+ coordinated to form a neutral hexacoordinated chelate RE(C 40 H 55 O2)3: RE 3+ + 3 C 40 H 55 O2 (alkenol anion) → RE(C 40 H 55 O2)3 The above heating reaction is carried out under a protective gas to avoid oxidation.

[0025] Preferably, the molar ratio of lutein to rare earth metal ions is 3:1 to prevent precipitation caused by excess metal ions.

[0026] Preferably, the temperature of the heating reaction is 55-65°C (preferably 58-62°C) to accelerate coordination and prevent lutein decomposition. Preferably, the time of the heating reaction is 6-8 hours to ensure complete reaction.

[0027] Reaction end point determination: the solution changes from orange red to dark red brown, and the absorbance at 430 nm increases by ≥50%.

[0028] Preferably, the purification step is also included, in which the reaction solution after the heating reaction is cooled, ice ether is added, a precipitate is separated out, and the product powder is obtained by filtration, washing, and drying. More preferably, the solution is cooled to 2-6°C (preferably 4°C), an equal volume of ice ether is added to the reaction solution, the flocculent complex is separated out, vacuum suction filtration is performed using a 0.22 μm filter membrane, anhydrous ethanol is washed 2-4 times (preferably 3 times), vacuum drying is performed at 35-45°C (preferably 40-42°C) for 10-20 hours (preferably 12-15 hours), and the yield of the product powder is ≥85%. DETAILED DESCRIPTION

[0029] In order for those skilled in the art to better understand the technical solutions in the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0030] Raw material preparation Lutein raw material: lutein ester (purity ≥90%). Saponification treatment: NaOH-ethanol solution (concentration 1 mol / L), hydrolysis at 60°C for 2 hours to convert to free lutein.

[0031] Rare earth metal salts: lanthanum chloride (LaCl3), cerium chloride (CeCl3), praseodymium nitrate (Pr(NO3)3), purity ≥ 99.9%. Pretreatment: vacuum drying at 120-160°C for 4 hours to remove crystal water.

[0032] Example 1: Lutein-lanthanum complex Dissolve 2.85 g of lutein in 200 mL of anhydrous ethanol / dimethyl sulfoxide mixed solvent (volume ratio of anhydrous ethanol to dimethyl sulfoxide 4:1); add 0.61 g of anhydrous LaCl3 and stir to dissolve; add triethylamine dropwise to adjust the pH to 8.5, and add 0.02 g of pyridine; react at 60°C under nitrogen protection for 7 hours, then cool the reaction solution to ≤4°C, add an equal volume of ice ethyl ether to the reaction solution, and use a 0.22 μm filter membrane to vacuum filter the precipitate, wash with ethanol 3 times, and vacuum dry at 40°C for 12 hours to obtain 3.21 g of product.

[0033] Example 2: Lutein-cerium complex Replace 0.61 g of anhydrous LaCl3 with 0.62 g of anhydrous CeCl3, and the rest is the same as in Example 1. After purification, 3.09 g of product is obtained.

[0034] Example 3: Lutein-praseodymium complex Replace 0.61 g of anhydrous LaCl3 with 1.09 g of anhydrous Pr(NO3)3, and the rest is the same as in Example 1. After purification, 3.22 g of product is obtained.

[0035] Take the unreacted free lutein and the products obtained in Examples 1-3 to perform absorbance tests, and the results are shown in Table 1: Table 1

[0036] As can be seen from Table 1, compared with lutein, the absorbance of the complex in the target wavelength band is increased by more than 160%.

[0037] Similarly, after 200 hours of light exposure (sunlight simulator), the absorbance changes of the above samples are shown in Table 2: Table 2

[0038] As can be seen from Table 2, compared with lutein, the absorbance of the complex after 200 hours of light exposure is attenuated by less than 5%, and the light stability of the complex is good.

[0039] Example 4: Eye protection paper (formula one) Paper pulp ratio: 20% of kraft softwood chemical pulp, 40% of kraft hardwood chemical pulp, and 40% of poplar mechanical pulp; Pulp beating: the beating degree of kraft softwood chemical pulp was controlled at 42SR, the beating degree of kraft hardwood chemical pulp was controlled at 36SR, and the beating degree of poplar chemi-mechanical pulp was controlled at 48SR.

[0040] The pulp was prepared into pulp with a concentration of 3.2%, and then was screened, adjusted, and pulped, at this time the concentration was controlled at 0.92%, and then was desanded, degassed, and sized, and then was screened, flowed into a headbox, formed into a web in a wire section, pressed, pre-dried, surface coated, post-dried, calendered, wound, packaged, and finally made into an eye protection paper. The moisture of the paper sheet out of the pre-drying was 4.8%, the moisture of the paper sheet out of the post-drying was 6.5%, and the product basis weight was 55g / m 2 , which was used for book printing (offset printing).

[0041] The coating formula was as follows: The La-Lutein complex powder prepared in Example 1: 0.5% (mass percent); starch: 2% (mass percent); water was used as a solvent for dispersion, and the coating was prepared.

[0042] The coating process was as follows: the coating was coated on both surfaces of the base paper, and hot air drying was performed at 100°C, and the coating amount on both surfaces was controlled at 4-5g / m 2 , and the basis weight of the finished paper was controlled at about 55g / m 2 .

[0043] The uncoated ordinary paper and the commercially available eye protection paper were used for comparative tests, and the results were shown in Table 3. Table 3

[0044] As shown in Table 3, the present application precisely covered the blue-violet light of 400-430nm through coordination bond regulation of electronic transition energy level, and had high stability, and the complex had weather resistance on the surface of the paper for more than 12 months.

[0045] Example 5: eye protection paper (formula two) Pulp ratio: kraft softwood chemical pulp 25%, kraft hardwood chemical pulp 20%, and poplar chemi-mechanical pulp 55%. Pulp beating: the beating degree of kraft softwood chemical pulp was controlled at 43SR, the beating degree of kraft hardwood chemical pulp was controlled at 32SR, and the beating degree of poplar chemi-mechanical pulp was controlled at 51SR.

[0046] The pulp was prepared into pulp with a concentration of 3.1%, and then was screened, adjusted, and pulped, at this time the concentration was controlled at 0.90%, and then was desanded, degassed, and sized, and then was screened, flowed into a headbox, formed into a web in a wire section, pressed, pre-dried, surface coated, post-dried, calendered, wound, packaged, and finally made into an eye protection paper. The moisture of the paper sheet out of the pre-drying was 4.5%, the moisture of the paper sheet out of the post-drying was 6.3%, and the product basis weight was 70g / m2 , for making books.

[0047] The paint formula is as follows: The Ce-Lutein complex powder prepared in Example 2: 0.5% (mass percentage); starch: 2% (mass percentage); water is used as a solvent for dispersion to prepare the paint.

[0048] The coating process is as follows: the paint is coated on the double-sided surface of the base paper, hot air drying at 100°C, and the double-sided coating amount is controlled at 4-5 g / m 2 , and the paper product basis weight is controlled at about 70 g / m 2 . Comparative tests are conducted using uncoated ordinary paper and commercially available eye protection paper, and the results are shown in Table 4: Table 4

[0049] As can be seen from Table 4, the present application precisely covers the blue-violet light of 400-430 nm by regulating the electronic transition energy level through coordination bond; high stability: the complex has a weather resistance on the paper surface of >12 months.

[0050] Example 6: Eye protection paper (formula three) Paper pulp ratio: 15% of kraft softwood chemical pulp and 85% of poplar mechanical pulp; Pulp beating: the beating degree of the kraft softwood chemical pulp is controlled at 46SR, and the beating degree of the poplar mechanical pulp is controlled at 49SR.

[0051] The pulp is mixed into a pulp with a concentration of 3.0%, and then the pulp is screened, mixed, and washed, at this time the concentration is controlled at 0.93%, and then the sand and gas are removed, the pulp is sized, and then the paper machine screen, headbox, net section dewatering, pressing, pre-drying, surface coating, post-drying, calendering, winding, and packaging are performed to produce the eye protection paper. Among them, the water content of the paper sheet after pre-drying is 4.6%, the water content of the paper sheet after post-drying is 6.2%, and the product basis weight is 80 g / m 2 , for book printing (UV ink printing).

[0052] The paint formula is as follows: The Pr-Lutein complex powder prepared in Example 3: 0.5% (mass percentage); starch: 2% (mass percentage); water is used as a solvent for dispersion to prepare the paint.

[0053] The coating process is as follows: the paint is coated on the double-sided surface of the base paper, hot air drying at 100°C, and the double-sided coating amount is controlled at 4-5 g / m 2 , and the paper product basis weight is controlled at about 80 g / m 2 .

[0054] The comparative test was performed using uncoated ordinary paper and commercially available eye protection paper, and the results are shown in Table 5. Table 5

[0055] The paper prepared by using the pulp ratio of "15% sulfite softwood chemical pulp and 85% poplar mechanical pulp" in the examples has lower whiteness and light reflection. In order to compare the coating effect and reduce the interference of other factors, the commercially available eye protection paper selected for comparison is also prepared by using "15% sulfite softwood chemical pulp and 85% poplar mechanical pulp", and the paper is coated with yellow dye on both sides.

[0056] As can be seen from Table 5, compared with ordinary paper and commercially available eye protection paper, the paper prepared by the scheme of the application has better effect. Specifically, the application precisely covers the blue-violet light of 400-430 nm by regulating the electronic transition energy level through coordination bond; high stability: the complex has weather resistance on the surface of the paper for more than 12 months.

[0057] The above only describes the embodiments of the application, and it should be noted that those skilled in the art can make improvements without departing from the inventive concept, and these all belong to the protection scope of the application.

Claims

1. A complex characterized in that, Formed by coordination bond between lutein and rare earth metal ions; The rare earth metal ion is at least one of La 3+ , Ce 3+ , Pr 3+ .

2. The complex of claim 1, wherein, The molar ratio of lutein to rare earth metal ions is 3:

1.

3. A process for the preparation of a complex according to any one of claims 1-2, characterized in that, Comprising the following steps: Lutein and rare earth metal ions are added into non-aqueous solvent, pH is adjusted to alkaline using organic base, catalyst is added, and the reaction is heated under protective gas to obtain the product.

4. The production method according to claim 3, characterized by, The non-aqueous solvent is anhydrous ethanol and dimethyl sulfoxide in a volume ratio of (3-4):1; and / or, The pH is adjusted to 8.0-10.0; and / or, The protective gas is any one of nitrogen, helium and argon; and / or, The temperature for heating the reaction is 55-65℃, and the time for heating the reaction is 6-8h; and / or, The catalyst is pyridine.

5. The preparation method according to claim 4, characterized in that, The pH is adjusted using triethylamine; and / or, The temperature for heating the reaction is 58-62℃; and / or, The mass percentage of the catalyst in the reaction raw materials is 0.05-0.5%.

6. The preparation method according to claim 3, characterized in that, The reaction liquid after the heating reaction is cooled, and ice ethyl ether is added to precipitate, and the product powder is obtained by filtration, washing and drying.

7. The preparation method according to claim 6, characterized in that, The reaction liquid is cooled to 2-6℃, and ice ethyl ether is added in an equal volume to the reaction liquid, the precipitate is vacuum filtered using a 0.22μm filter membrane, washed with anhydrous ethanol for 2-4 times, and vacuum dried at 35-45℃ for 10-20 hours.

8. An eye-protecting paper, characterized by, The coating on the surface of the eye protection paper contains the complex of any one of claims 1-2, or the complex prepared by the preparation method of any one of claims 3-7.

9. The ophthalmic paper of claim 8, wherein, The mass percentage of the complex in the coating on the surface of the eye protection paper is 0.5-1.0%.

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