Phenolphthalein functionalized polyacrylonitrile fiber as well as preparation method and application thereof

Abstract

The invention discloses a preparation method of phenolphthalein functionalized polyacrylonitrile fiber, which belongs to the technical field of functional materials, and is prepared by the following preparation method: pretreatment of polyacrylonitrile fiber: putting polyacrylonitrile fiber into distilled water, refluxing under magnetic stirring, filtering, washing with distilled water, and drying the washed fiber for later use; amination reaction: carrying out addition reaction on the pretreated polyacrylonitrile fibers and triethylene tetramine, and grafting amido onto polypropylene fibers to prepare aminated polyacrylonitrile fibers; and preparation of the phenolphthalein functionalized polyacrylonitrile fiber: adding the aminated polyacrylonitrile fiber and phenolphthalein into a formaldehyde aqueous solution and ethanol, and carrying out a reflux reaction to obtain the phenolphthalein functionalized polyacrylonitrile fiber. The pH value range of color change of the phenolphthalein functional polyacrylonitrile fiber is 10-13, the phenolphthalein functional polyacrylonitrile fiber can rapidly change color when responding to organic alkali, and the phenolphthalein functional polyacrylonitrile fiber does not change color after being soaked in the organic alkali for 12 hours and is good in stability; the color-changing response time is short, and the color is changed within 1s.

Description

Technical Field

[0001] The invention relates to the technical field of functional materials, and in particular to a phenolphthalein functionalized polyacrylonitrile fiber and a preparation method and application thereof. Background Art

[0002] Color-changing fiber material is a special fiber that can automatically change color under the stimulation of external conditions such as light, heat, moisture or radiation. Color-changing fiber is a kind of smart fiber, which has great application value in special clothing, sensors and other fields. The manufacturing technology of color-changing fiber includes two parts: color-changing fiber and color-changing dye. The color-changing material is combined with the fiber by physical or chemical methods to make textiles with color-changing effect.

[0003] Acid-base color-changing fiber is a special smart fiber that can change color according to the change of environmental pH value. This fiber is usually made by embedding a chemical color-changing indicator into the fiber. When encountering liquids with different pH values, the indicator changes color, causing the fiber to show the corresponding color. Acid-base color-changing fiber has great application prospects in the preparation of packaging materials with automatic warning functions for chemical leakage or food spoilage, and protective equipment that automatically displays the acidity and alkalinity of contact objects.

[0004] Phenolphthalein is an organic compound often used as an acid-base indicator. Its characteristics are that it is colorless in acidic and neutral solutions and purple-red in alkaline solutions. Phenolphthalein is insoluble in water, but soluble in ethanol and alkaline solutions. It shows color when it encounters alkali because it generates phenolphthalein salt, which is highly soluble in water. However, phenolphthalein also has defects as an indicator. It is easily oxidized by oxidants, causing the color to disappear. In addition, overly concentrated sodium hydroxide can also cause phenolphthalein to fade, and the fading process is irreversible.

[0005] Existing fibers lack active functional groups that can be used to connect sensor molecules; in addition, the inevitable steric hindrance of fiber materials often makes those functional molecules that are sensitive to steric hindrance ineffective. At present, suitable functional groups that can be used to covalently connect functional molecules can be introduced into the fiber by using appropriate modification methods. Polyacrylonitrile fiber (PANF), commonly known as acrylic fiber, is one of the most widely used synthetic fibers. It has very good weather resistance, corrosion resistance and mildew resistance. There are a large number of cyanide groups on polyacrylonitrile fibers, which can be easily converted into carboxyl groups, amide groups, amidoxime groups and other groups. Therefore, acrylic fiber is a suitable raw material for preparing acid-base color-changing fibers. The most common amination reaction of polyacrylonitrile fiber is to convert cyano groups into acyl groups. The reaction formula is shown in the figure below:

[0006]

[0007] However, when the acid-base indicator made of the aminated polyacrylonitrile fiber responds to an organic base, the fiber can change color quickly at first, but the color will fade quickly. After the faded fiber is washed and re-immersed in an alkaline solution, the fiber no longer changes color. Based on the above reasons, the present invention is proposed. Summary of the invention

[0008] In view of this, the present invention provides a phenolphthalein functionalized polyacrylonitrile fiber and a preparation method and application thereof. The phenolphthalein functionalized polyacrylonitrile fiber prepared by the present invention can be used as a cyclic acid-base indicator and has a good organic base response.

[0009] In order to achieve the above technical purpose, the present invention provides a method for preparing phenolphthalein functionalized polyacrylonitrile fiber, which is prepared by the following preparation method:

[0010] (1) Pretreatment of polyacrylonitrile fiber: put the polyacrylonitrile fiber into distilled water, reflux under magnetic stirring, filter, wash with distilled water, and dry the washed fiber for later use;

[0011] (2) Amination reaction: The pretreated polyacrylonitrile fiber is subjected to an addition reaction with triethylenetetramine to graft the amine group onto the polypropylene fiber to obtain the aminated polyacrylonitrile fiber. The reaction formula of the amination reaction is as follows:

[0012]

[0013] (3) Preparation of phenolphthalein functionalized polyacrylonitrile fiber: Add aminated polyacrylonitrile fiber and phenolphthalein into formaldehyde aqueous solution and ethanol for reflux reaction to obtain the fiber. The reaction formula of phenolphthalein functionalized polyacrylonitrile fiber is as follows:

[0014]

[0015] Wherein, in step (1), the mass volume ratio of polyacrylonitrile fiber to distilled water during reflux is 1:50-80 g / ml, the reflux time is 8-12 h, and the temperature of the distilled water for washing is 50-70°C.

[0016] Wherein, in step (2), the bath ratio of the pretreated polyacrylonitrile fiber to triethylenetetramine is 1:30-80, and the soaking time in triethylenetetramine is 0.5-5h; the heating reaction temperature is 60-120°C, and the addition reaction time is 2-6h.

[0017] Wherein, in step (2), after the addition reaction, the step of washing and drying is also included, and the drying temperature is 40-80°C.

[0018] Wherein, in step (3), the reflux reaction is carried out under a N2 atmosphere, the mass ratio of the aminated polyacrylonitrile fiber to phenolphthalein is 1:1.5-2.5, the mass volume ratio of the aminated polyacrylonitrile fiber to the formaldehyde aqueous solution is 1:(8-15) g / ml, and the mass volume ratio of the aminated polyacrylonitrile fiber to ethanol is 1:(20-40) g / ml.

[0019] Wherein, the mass percentage concentration of the formaldehyde aqueous solution is 35-45%.

[0020] After the reflux reaction in step (3), the fiber is taken out by suction filtration, washed three times with ethanol, and vacuum dried at below 70° C. for 12 h to obtain the fiber.

[0021] The invention also provides phenolphthalein functionalized polyacrylonitrile fiber prepared by the preparation method.

[0022] The invention also provides application of the phenolphthalein functionalized polyacrylonitrile fiber as a circulatory acid-base indicator.

[0023] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0024] 1. The preparation of the phenolphthalein functionalized polyacrylonitrile fiber of the present invention adopts a two-step reaction. The first step is to use triethylenetetramine to perform an addition reaction with the polyacrylonitrile fiber to convert the cyano group of the polyacrylonitrile fiber into an amide group, and introduce a large number of amino functional groups on the polyacrylonitrile fiber; the second step is to use the Mannich reaction to connect the acid-base indicator molecules with active points such as phenolphthalein to the amino groups of the aminated acrylic fiber through covalent bonds. The preparation steps of this synthetic method are simple, the reaction conditions are mild, and the raw materials used are cheap and easy to obtain.

[0025] 2. The pH value range of the color change of the phenolphthalein functional polyacrylonitrile fiber prepared by the present invention is 10-13. When responding to organic base, it can change color quickly and does not change color after being immersed in the organic base for 12 hours, and has good stability; the color change response time is short, and the color change response time is short in an alkaline solution with a pH value range of 10-13, and the color changes within 1 second.

[0026] 3. The phenolphthalein functional polyacrylonitrile fiber prepared by the present invention has good reusability. After being recycled for 300 times, the fiber is basically unchanged. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The figure shows the discoloration of the phenolphthalein functionalized polyacrylonitrile fiber prepared in Example 1 in alkali.

[0028] Figure 2 The figure shows the discoloration of the phenolphthalein functionalized polyacrylonitrile fiber prepared in Example 1 in different concentrations of alkali.

[0029] Figure 3The color change of the phenolphthalein functionalized polyacrylonitrile fiber prepared in Example 1 after 300 cycles of color change in 0.1 mol / L alkali.

[0030] Figure 4 The color change of the phenolphthalein functionalized polyacrylonitrile fiber prepared in Example 1 in solutions of different pH values.

[0031] Figure 5 The strong acid and alkali stability of the phenolphthalein functionalized polyacrylonitrile fiber prepared in Example 1 was measured. DETAILED DESCRIPTION

[0032] The following embodiments are provided for a better understanding of the present invention, but are not limited to the best mode of implementation, and do not limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained under the inspiration of the present invention or by combining the features of the present invention with other prior arts shall fall within the protection scope of the present invention.

[0033] Example 1

[0034] This embodiment provides a method for preparing phenolphthalein functionalized polyacrylonitrile fiber, which is prepared by the following preparation method:

[0035] (1) Pretreatment of polyacrylonitrile fiber: put the polyacrylonitrile fiber into distilled water, reflux under magnetic stirring, the mass volume ratio of polyacrylonitrile fiber to distilled water is 1:65g / ml, and the reflux time is 10h; filter, wash with 60℃ distilled water, and dry the washed fiber for later use;

[0036] (2) Amination reaction: The pretreated polyacrylonitrile fiber was immersed in triethylenetetramine (bath ratio: 1:50, time: 2.5 h), and reacted in a round-bottom flask in a 90°C oil bath for 4 h to graft the amino group onto the fiber cloth; washed with water until neutral and then dried (drying temperature 60°C) to aminate the polyacrylonitrile fiber;

[0037] (3) Preparation of phenolphthalein functionalized polyacrylonitrile fiber: add aminated polyacrylonitrile fiber and phenolphthalein into a 40% formaldehyde aqueous solution and ethanol, wherein the mass ratio of aminated polyacrylonitrile fiber to phenolphthalein is 1:2, the mass volume ratio of aminated polyacrylonitrile fiber to formaldehyde aqueous solution is 1:12 g / ml, and the mass volume ratio of aminated polyacrylonitrile fiber to ethanol is 1:30 g / ml, and reflux reaction is carried out under a N2 atmosphere to obtain the obtained fiber.

[0038] Example 2

[0039] This embodiment provides a method for preparing phenolphthalein functionalized polyacrylonitrile fiber, which is prepared by the following preparation method:

[0040] (1) Pretreatment of polyacrylonitrile fiber: put the polyacrylonitrile fiber into distilled water, reflux under magnetic stirring, the mass volume ratio of polyacrylonitrile fiber to distilled water is 1:50g / ml, and the reflux time is 12h; filter, wash with 50℃ distilled water, and dry the washed fiber for later use;

[0041] (2) Amination reaction: The pretreated polyacrylonitrile fiber was immersed in triethylenetetramine (bath ratio: 1:30, time: 5 h), and reacted in a round-bottom flask in an oil bath at 60°C for 6 h to graft the amino group onto the fiber cloth; the fiber was washed with water until neutral and then dried (drying temperature 40°C) to aminate the polyacrylonitrile fiber;

[0042] (3) Preparation of phenolphthalein functionalized polyacrylonitrile fiber: add aminated polyacrylonitrile fiber and phenolphthalein into a 35% formaldehyde aqueous solution and ethanol, wherein the mass ratio of aminated polyacrylonitrile fiber to phenolphthalein is 1:2.5, the mass volume ratio of aminated polyacrylonitrile fiber to formaldehyde aqueous solution is 1:8 g / ml, and the mass volume ratio of aminated polyacrylonitrile fiber to ethanol is 1:40 g / ml, and reflux reaction is carried out under a N2 atmosphere to obtain the obtained fiber.

[0043] Example 3

[0044] This embodiment provides a method for preparing phenolphthalein functionalized polyacrylonitrile fiber, which is prepared by the following preparation method:

[0045] (1) Pretreatment of polyacrylonitrile fiber: put the polyacrylonitrile fiber into distilled water, reflux under magnetic stirring, the mass volume ratio of polyacrylonitrile fiber to distilled water is 1:80g / ml, and the reflux time is 8h; filter, wash with 70℃ distilled water, and dry the washed fiber for later use;

[0046] (2) Amination reaction: The pretreated polyacrylonitrile fiber was immersed in triethylenetetramine (bath ratio: 1:80, time: 0.5 h), and reacted in a round-bottom flask in an oil bath at 120°C for 2 h to graft the amino group onto the fiber cloth; the fiber was washed with water until neutral and then dried (drying temperature 80°C) to aminate the polyacrylonitrile fiber;

[0047] (3) Preparation of phenolphthalein functionalized polyacrylonitrile fiber: add aminated polyacrylonitrile fiber and phenolphthalein into a 45% formaldehyde aqueous solution and ethanol, wherein the mass ratio of aminated polyacrylonitrile fiber to phenolphthalein is 1:1.5, the mass volume ratio of aminated polyacrylonitrile fiber to formaldehyde aqueous solution is 1:15 g / ml, and the mass volume ratio of aminated polyacrylonitrile fiber to ethanol is 1:20 g / ml, and reflux reaction is carried out under a N2 atmosphere to obtain the obtained fiber.

[0048] Example 4

[0049] This embodiment provides a method for preparing phenolphthalein functionalized polyacrylonitrile fiber, which is prepared by the following preparation method:

[0050] (1) Pretreatment of polyacrylonitrile fiber: put the polyacrylonitrile fiber into distilled water, reflux under magnetic stirring, the mass volume ratio of polyacrylonitrile fiber to distilled water is 1:60g / ml, and the reflux time is 11h; filter, wash with 55℃ distilled water, and dry the washed fiber for later use;

[0051] (2) Amination reaction: The pretreated polyacrylonitrile fiber was immersed in triethylenetetramine (bath ratio: 1:40, time: 4 h), and reacted in a round-bottom flask in an oil bath at 70 °C for 5 h to graft the amino group onto the fiber cloth; the fiber was washed with water until neutral and then dried (drying temperature 50 °C) to aminate the polyacrylonitrile fiber;

[0052] (3) Preparation of phenolphthalein functionalized polyacrylonitrile fiber: add aminated polyacrylonitrile fiber and phenolphthalein into a 38% formaldehyde aqueous solution and ethanol, the mass ratio of aminated polyacrylonitrile fiber to phenolphthalein is 1:2.4, the mass volume ratio of aminated polyacrylonitrile fiber to formaldehyde aqueous solution is 1:10 g / ml, and the mass volume ratio of aminated polyacrylonitrile fiber to ethanol is 1:35 g / ml. Reflux reaction is carried out under N2 atmosphere to obtain the obtained fiber.

[0053] Example 5

[0054] This embodiment provides a method for preparing phenolphthalein functionalized polyacrylonitrile fiber, which is prepared by the following preparation method:

[0055] (1) Pretreatment of polyacrylonitrile fiber: put the polyacrylonitrile fiber into distilled water, reflux under magnetic stirring, the mass volume ratio of polyacrylonitrile fiber to distilled water is 1:70g / ml, and the reflux time is 9h; filter, wash with 60℃ distilled water, and dry the washed fiber for later use;

[0056] (2) Amination reaction: The pretreated polyacrylonitrile fiber was immersed in triethylenetetramine (bath ratio: 1:70, time: 2 h), and reacted in a round-bottom flask in an oil bath at 100 °C for 3 h to graft the amino group onto the fiber cloth; the fiber was washed with water until neutral and then dried (drying temperature 70 °C) to aminate the polyacrylonitrile fiber;

[0057] (3) Preparation of phenolphthalein functionalized polyacrylonitrile fiber: add aminated polyacrylonitrile fiber and phenolphthalein into a 42% formaldehyde aqueous solution and ethanol, wherein the mass ratio of aminated polyacrylonitrile fiber to phenolphthalein is 1:1.8, the mass volume ratio of aminated polyacrylonitrile fiber to formaldehyde aqueous solution is 1:12 g / ml, and the mass volume ratio of aminated polyacrylonitrile fiber to ethanol is 1:25 g / ml. Reflux reaction is carried out under N2 atmosphere to obtain the obtained fiber.

[0058] Comparative Example 1

[0059] This embodiment provides a method for preparing phenolphthalein functionalized polyacrylonitrile fiber, which is prepared by the following preparation method:

[0060] (1) Add 20 mL of triethylenetetramine and 40 mL of water to 1 g of dried polyacrylonitrile fiber, stir under electromagnetic stirring, and reflux for 3 h. Take out the fiber, filter it, and wash it repeatedly with warm water at 60-70°C until the water is neutral. After drying in the air, dry it in a vacuum at 70°C for 4 h, and weigh it for later use. The reaction formula of this step is as follows:

[0061]

[0062] (2) Amination reaction: The pretreated polyacrylonitrile fiber was immersed in triethylenetetramine (bath ratio: 1:50, time: 2.5 h), and reacted in a round-bottom flask in a 90°C oil bath for 4 h to graft the amino group onto the fiber cloth; washed with water until neutral and then dried (drying temperature 60°C) to aminate the polyacrylonitrile fiber;

[0063] (3) Preparation of phenolphthalein functionalized polyacrylonitrile fiber: add aminated polyacrylonitrile fiber and phenolphthalein into a 40% formaldehyde aqueous solution and ethanol, wherein the mass ratio of aminated polyacrylonitrile fiber to phenolphthalein is 1:2, the mass volume ratio of aminated polyacrylonitrile fiber to formaldehyde aqueous solution is 1:12 g / ml, and the mass volume ratio of aminated polyacrylonitrile fiber to ethanol is 1:30 g / ml, and reflux reaction is carried out under a N2 atmosphere to obtain the obtained fiber.

[0064] Performance Testing

[0065] 1. Color change test

[0066] 0.10 g of the phenolphthalein functionalized polyacrylonitrile fiber prepared in Example 1 was placed in 5 ml of a 1 mol / L dimethylamine aqueous solution, and the color change of the fiber was observed after 1 second.

[0067] The results are as follows Figure 1 As shown, the fiber immersed in the dimethylamine aqueous solution turns purple, and the color change response time is short, changing color within 1 s.

[0068] 2. Color change in different concentrations of alkali:

[0069] The phenolphthalein functionalized polyacrylonitrile fiber prepared in Example 1 was immersed in 5 mol / L, 2.5 mol / L, 1 mol / L, 0.5 mol / L, and 0.1 mol / L dimethylamine aqueous solutions, respectively. Figure 2 The color change of polyacrylonitrile fiber in different concentrations of alkali is shown in Figure 2. Figure 2 It can be seen that the fiber appears purple in different concentrations of organic alkali.

[0070] 3. Color change stability

[0071] Figure 3 The color change of the phenolphthalein functionalized polyacrylonitrile fiber prepared in Example 1 after 300 cycles of color change in a 0.1 mol / L dimethylamine aqueous solution is shown in FIG. Figure 3 It can be seen that after 300 cycles, the fiber can still change color rapidly in the alkaline solution, which is basically indistinguishable from the newly made fiber.

[0072] 4. Color change in different solutions

[0073] The phenolphthalein functionalized polyacrylonitrile fibers prepared in Example 1 were immersed in 1 mol / L aqueous dimethylamine solutions of KH2PO4, NaHCO3, Na2HPO4, Na2CO3, and KOH, respectively. Figure 4 The color change of phenolphthalein functionalized polyacrylonitrile fiber in different solutions is shown in Figure 2. Figure 4 It can be seen that the fiber did not change color in KH2PO4 solution and showed yellow; it showed orange in NaHCO3 and Na2HPO4 solutions, light purple in Na2CO3 solution, and dark purple in KOH solution. From the above content, it can be seen that phenolphthalein functionalized polyacrylonitrile fiber shows different colors in solutions with different pH values.

[0074] 5. Alkali resistance and stability

[0075] The phenolphthalein functionalized polyacrylonitrile fiber prepared in Example 1 was immersed in a 1 mol / L dimethylamine aqueous solution. Figure 5 To determine the alkali stability of phenolphthalein functionalized polyacrylonitrile fiber, Figure 5 It can be seen that the phenolphthalein functionalized polyacrylonitrile fiber of the present invention does not change color after being immersed in an organic base for 12 hours.

[0076] Although the embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and cannot be understood as limiting the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and purpose of the present invention. The protection scope of the present invention is defined by the claims and their equivalent technical solutions.

Claims

1. A method for preparing phenolphthalein functionalized polyacrylonitrile fiber, It is characterized by Made by the following preparation method: (1) Pretreatment of polyacrylonitrile fiber: put the polyacrylonitrile fiber into distilled water, reflux under magnetic stirring, filter, wash with distilled water, and dry the washed fiber for later use; (2) Amination reaction: The pretreated polyacrylonitrile fiber is subjected to an addition reaction with triethylenetetramine to graft the amine groups onto the polypropylene fiber to obtain aminated polyacrylonitrile fiber; (3) Preparation of phenolphthalein functionalized polyacrylonitrile fiber: Add aminated polyacrylonitrile fiber and phenolphthalein into formaldehyde aqueous solution and ethanol, and carry out reflux reaction to obtain the obtained fiber.

2. The method for preparing phenolphthalein functionalized polyacrylonitrile fiber according to claim 1, Features: In step (1), the mass volume ratio of polyacrylonitrile fiber to distilled water during reflux is 1:50-80 g / ml, the reflux time is 8-12 h, and the temperature of the distilled water for washing is 50-70°C.

3. The method for preparing phenolphthalein functionalized polyacrylonitrile fiber according to claim 1, Features: In step (2), the bath ratio of the pretreated polyacrylonitrile fiber to triethylenetetramine is 1:30-80, and the soaking time in triethylenetetramine is 0.5-5h; the heating reaction temperature is 60-120°C, and the addition reaction time is 2-6h.

4. The method for preparing phenolphthalein functionalized polyacrylonitrile fiber according to claim 1, Features: In step (2), after the addition reaction, the process further includes washing and drying steps, and the drying temperature is 40-80°C.

5. The method for preparing phenolphthalein functionalized polyacrylonitrile fiber according to claim 1, Features: In step (3), N 2 The reflux reaction is carried out in an atmosphere of , the mass ratio of the aminated polyacrylonitrile fiber to phenolphthalein is 1:1.5-2.5, the mass volume ratio of the aminated polyacrylonitrile fiber to the formaldehyde aqueous solution is 1:(8-15) g / ml, and the mass volume ratio of the aminated polyacrylonitrile fiber to ethanol is 1:(20-40) g / ml.

6. The method for preparing phenolphthalein functionalized polyacrylonitrile fiber according to claim 5, Features: The mass percentage concentration of the formaldehyde aqueous solution is 35-45%.

7. The method for preparing phenolphthalein functionalized polyacrylonitrile fiber according to claim 5, Features: After the reflux reaction in step (3), the fiber is taken out by suction filtration, washed three times with ethanol, and dried under vacuum at below 70° C. for 12 h.

8. A phenolphthalein functionalized polyacrylonitrile fiber prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the phenolphthalein functionalized polyacrylonitrile fiber according to any one of claims 1 to 7 as a recyclable acid-base indicator.

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