CROSS REFERENCE TO THE RELATED APPLICATIONS

This application is the national phase entry of International Application No. PCT/CN2020/120739, filed on Oct. 14, 2020, which is based upon and claims priority to Chinese Patent Application No. 202010798857.8, filed on Aug. 11, 2020, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention belongs to the field of new materials, and particularly to a method for preparing a color masterbatch with a natural dye.

BACKGROUND

Natural dyes extracted from nature are environmentally friendly, non-toxic, harmless, biodegradable, and many of them have antibacterial, anti-inflammatory, anti-ultraviolet and other functions, which are widely used in the fields of textile, cosmetics, medicine and healthcare. In the field of textile and clothing, natural dyes can be used to dye synthetic fibers, but there is often a problem of poor color fastness. When natural dyes are made into a color masterbatch, which is then added in the spinning process, colored fibers with excellent color fastness can be obtained. However, its heat resistance has always been a bottleneck in the preparation of colored fibers by melt spinning.

SUMMARY

The technical problems to be solved by the present invention are to overcome the problem that the existing natural dyes have poor thermal stability and cannot be directly used for synthetic fiber melt spinning, and to provide a method for preparing a color masterbatch with a natural dye.

In order to solve the above technical problems, the technical solution adopted by the present invention is as follows. A method for preparing a color masterbatch with a natural dye, firstly, taking a mixed solution of a phase change material tetradecane and ethanol as a solvent to extract the natural dye, removing the ethanol by rotary evaporation, taking the ethanol-free mixture as a core material and polybutylene succinate as a wall material to prepare natural dye/tetradecane microcapsules by a solvent evaporation method; and taking the natural dye/tetradecane microcapsules as a dyeing component of the color masterbatch, melt-blending with a carrier resin, extruding and granulating.

The method for preparing the color masterbatch with the natural dye includes the following steps.

(1) Removing impurities of a natural plant raw material, cleaning, drying the raw material in the air, crushing into 80-200 mesh, and soaking in a mixed solvent of tetradecane and ethanol for 1-2 h, extracting under a reflux at 60-100° C. for 0.5-2 h and filtering, extracting 3-5 times repeatedly, combining the extracted solutions obtained from multiple times of extraction to obtain a natural dye stock solution; removing the ethanol by decompression distillation to obtain a natural dye/tetradecane solution.

The natural plant raw material is one selected from the group consisting of rhubarb, turmeric, red pepper, camphor leaves, madder, and vervain, and a volume ratio of the tetradecane to the ethanol is 1:5-2:5.

(2) Dissolving polybutylene succinate into 100 mL chloroform, adding the natural dye/tetradecane solution obtained in step (1), stirring at a high speed, and mixing uniformly to obtain a chloroform solution of polybutylene succinate containing natural dye.

A mass ratio of the natural dye/tetradecane solution to the polybutylene succinate is 3:1-5:1.

(3) Adding 100 mL deionized water, Arabic gum and sodium dodecylbenzene sulfonate into a 250 mL three-port flask, fully stirring and dissolving; adding the chloroform solution of polybutylene succinate containing natural dye obtained in step (2) into the three-port flask, slowly raising a temperature to 40-50° C., condensing and recovering steam, keeping at this temperature for 4-6 h, forming microcapsules by the gradual solidification of the polybutylene succinate caused by the evaporation of chloroform, collecting solids, fully cleaning with deionized water and drying to obtain natural dye/tetradecane microcapsules.

A mass ratio of the Arabic gum and the sodium dodecylbenzene sulfonate is 1:3-1:6, and a total mass of the Arabic gum and the sodium dodecylbenzene sulfonate accounts for 2%-4% of a total mass of the system.

(4) Adding 10-25 parts by weight of the natural dye/tetradecane microcapsules, 0.5-1.5 parts by weight of an antioxidant and 70-90 parts by weight of a carrier resin to a high-speed mixer with a rotation speed of 500-1,500 rpm, mixing at 1550-150° C. for 10-30 min, and adding the well-mixed material into a twin-screw extruder for melt blending, extrusion and granulation, in which screw temperatures are set as follows: 200-250° C. in a first zone, 230-255° C. in a second zone, 220-260° C. in a third zone, 220-260° C., in a fourth zone, 220-260° C. in a fifth zone and 220-260° C. in a sixth zone; after cooling with 25-30° C. water, pelletizing, and drying at 80-100° C.

The antioxidant is antioxidant 1010, and the carrier resin is ethylene terephthalate.

It can be seen from the above technical solution that: firstly, the fat-soluble pigment in the plant raw material is extracted by the mixed solvent of phase change material tetradecane and ethanol, and the ethanol in the extracted solution is removed by rotary evaporation; then, the tetradecane and natural pigment are coated with polybutylene succinate as the wall material to improve the heat resistance/thermal stability of natural pigment; the coating of the polyester material improves the compatibility of the core material and carrier resin. Additionally, the phase change material tetradecane is able to adjust the temperature intelligently according to the change of external temperature to further improve the heat resistance of natural pigment.

The advantages of the present invention are as follows.

(1) The natural pigment is microencapsulated with polybutylene succinate as a wall material to improve its thermal stability and compatibility with carrier resin.

(2) The natural dye containing tetradecane is used as a core material. When the external temperature changes, tetradecane will undergo phase transformation, thereby reducing the influence of external temperature on plant extracts. The thermal stability of natural pigment is further improved by the intelligent temperature regulation function of tetradecane.

