Preparation method of asymmetric citrate and PVC composite material thereof

Abstract

The invention discloses preparation methods of asymmetric citrate and a PVC composite material thereof, and relates to the technical field of chemical synthesis. The asymmetric citrate is obtained by carrying out esterification reaction on citric acid powder, p-toluene sulfonic acid and fatty alcohol under the action of an acid catalyst and then washing and distilling; the fatty alcohol is a mixture of octanol and decanol in a molar fraction ratio of (1-2): (1-2). The preparation method of the asymmetric citrate / PVC composite material comprises the following steps: mixing PVC powder, asymmetric citrate and tetrahydrofuran, and stirring for dissolving; pouring the mixture into a mold, placing the mold in a ventilated manner for a whole night, and drying the mold in a drying oven to obtain the asymmetric citrate / PVC composite material. According to the preparation method, the mixture of octanol and decanol and a certain amount of citric acid are subjected to esterification reaction to synthesize the novel asymmetric citrate plasticizer, and the synthesized asymmetric citrate product is regular in molecular structure and high in stability.

Description

Technical Field

[0001] The invention relates to the technical field of chemical synthesis, in particular to a method for preparing an asymmetric citrate ester and a PVC composite material thereof. Background Art

[0002] The Qarhan Salt Lake is a chloride-type deposit. With the development and utilization of metal elements such as magnesium and lithium in the salt lake, the chlorine balance problem has become increasingly prominent and has become one of the main bottlenecks restricting the sustainable development of the salt lake industry. Among the many ways to balance chlorine, converting chlorine into polyvinyl chloride (PVC) is one of the most effective ways to solve the chlorine balance problem. Pure PVC resin is rigid due to the presence of C-Cl polar bonds on the molecular chain, and plasticizers need to be added to enhance flexibility. There are many industrial plasticizers at present, among which phthalate plasticizers represented by dioctyl phthalate (DOP) have become the preferred plasticizers for PVC because of their excellent plasticizing efficiency and good product transparency. However, studies have found that DOP has a very high mobility in PVC and has a carcinogenic risk. Therefore, the design and development of environmentally friendly plasticizers is crucial to the development of PVC materials.

[0003] In recent years, there has been an endless stream of research on environmentally friendly plasticizers at home and abroad, mainly including citrates, trimellitate esters, epoxies, etc. Among them, biocompatible citrate esters have the most outstanding plasticizing properties. Sawada, Abdollahi and others found that tributyl citrate (TBC), acetyl tributyl citrate (ATBC) and others can greatly increase the elongation at break and cross-sectional shrinkage of PVC resin. Dang Xiyun, Zhou Guomao and others systematically studied the toxic effects of ATBC and TBC as medical PVC plasticizers on the human body and found that citrate esters have low toxicity to the human body. The above research results fully demonstrate that citrate esters have broad application prospects in the field of environmentally friendly PVC materials. Summary of the invention

[0004] The object of the present invention is to overcome the shortcomings of the prior art and provide a method for preparing an asymmetric citrate ester and a PVC composite material thereof. A mixture of octanol and decanol is selected to carry out an esterification reaction with a certain amount of citric acid to synthesize a new type of asymmetric citrate ester plasticizer with a regular molecular structure, and then the asymmetric citrate ester plasticizer is mixed with a PVC resin to prepare a composite material with high tensile strength and high elongation at break.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] An asymmetric citric acid ester is obtained by esterification reaction of citric acid powder, p-toluenesulfonic acid and fatty alcohol under the action of an acid catalyst, followed by washing and distillation; the fatty alcohol is a mixture of octanol and decanol in a molar ratio of 1-2:1-2.

[0007] Furthermore, the added mass ratio of citric acid powder and p-toluenesulfonic acid is 50:0.5, and the added amount of the acid catalyst is 1-2% of the mass of the citric acid powder, and the added amount of the fatty alcohol is 3.2-3.5 times the molar fraction of citric acid.

[0008] Furthermore, the acidic catalyst is p-toluenesulfonic acid monohydrate.

[0009] Furthermore, during the esterification reaction, the temperature is 150-155° C., and the reaction is completed when no more water condenses in the water separator.

[0010] Furthermore, after the esterification reaction, the mixture is washed with Na2CO3 solution and deionized water, and the washing temperature is controlled at 65-75°C. After each washing, the pH value of the aqueous phase is measured using pH test paper. When the aqueous phase is neutral, the washing is stopped, and a separatory funnel is used to separate the liquid to obtain an organic phase solution.

[0011] Furthermore, the washed organic phase solution was distilled by reduced pressure distillation at a distillation temperature of 150°C.

[0012] The method for preparing the asymmetric citrate / PVC composite material as described in any one of the above items comprises:

[0013] S1: Mix PVC powder, asymmetric citrate and tetrahydrofuran, stir and dissolve, and let stand until all bubbles disappear to obtain a mixed solution;

[0014] S2: Pour the mixture into a mold and leave it in a ventilated place overnight;

[0015] S3: placing the mold in an oven for drying to form a PVC composite film, i.e., an asymmetric citrate ester / PVC composite material.

[0016] Furthermore, in step S1, after the PVC powder, the asymmetric citrate and tetrahydrofuran are mixed, the solid content is controlled at 0.1 g / ml, and the added mass ratio of the PVC powder and the asymmetric citrate is 1:1.

[0017] Furthermore, in step S3, during drying, the temperature of the oven is 60° C. and the drying time is 30 minutes.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The invention uses a mixture of octanol and decanol and a certain amount of citric acid for esterification reaction, synthesizes an environmentally friendly asymmetric citric acid ester novel plasticizer, can replace the preparation of traditional DOP plasticizer, and greatly reduces the harm of plasticizer to human body during use. The asymmetric citric acid ester product synthesized by the invention has a regular molecular structure and strong stability. The synthesized novel plasticizer is added to PVC resin to prepare an asymmetric citric acid ester / PVC composite material. The tensile strength and elongation at break of the composite material are better than those of the symmetric citric acid ester / PVC composite material. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is the H NMR spectrum of symmetrical citrate CA0 / 3;

[0021] Figure 2 is the H NMR spectrum of asymmetric citrate CA1 / 2;

[0022] Figure 3 is the H NMR spectrum of asymmetric citrate CA 1 / 1;

[0023] Figure 4 is the H NMR spectrum of the asymmetric citrate CA 2 / 1;

[0024] Figure 5 is the H NMR spectrum of the symmetrical citrate CA 3 / 0;

[0025] Figure 6 This is a graph showing the tensile strength test results of citrate / PVC composite materials at different citrate contents;

[0026] Figure 7 This is the test result of elongation at break of citrate / PVC composite materials at different citrate contents. DETAILED DESCRIPTION

[0027] The present invention is further described below in conjunction with the accompanying drawings and embodiments. The embodiments of the present invention include but are not limited to the following embodiments.

[0028] The present invention provides a method for synthesizing an asymmetric citrate ester, comprising the following steps:

[0029] (1) Add 50.00g of anhydrous citric acid powder, a certain amount of fatty alcohol and 0.50g of p-toluenesulfonic acid to a 250mL three-necked flask. Since the citric acid molecule contains three carboxyl groups, it can react with alcohol at a molar ratio of 1:3. In order to complete the esterification reaction, the amount of reactant alcohol added is controlled to 3.2-3.5 times the molar fraction of anhydrous citric acid, and p-toluenesulfonic acid monohydrate is selected as the reaction catalyst (the amount added is 1wt%-2wt% of the amount of anhydrous citric acid added). The fatty alcohol used in this embodiment is a mixture of octanol and decanol, and the molar ratio of octanol to decanol is 1:2, 1:1 or 2:1.

[0030] (2) Use an oil bath to heat the reaction and control the reaction temperature to 150-155°C. The reaction is complete when no more water condenses in the water separator.

[0031] (3) Pour the obtained oily liquid into a beaker and wash the oily liquid with a 1% Na2CO3 solution and deionized water respectively. The washing temperature is controlled at 65-75°C. After each washing, the pH value of the aqueous phase is measured with a pH test paper. When the aqueous phase is neutral, the washing is stopped and the liquid is separated using a separatory funnel to obtain an organic phase solution.

[0032] (4) The organic phase solution is distilled using a vacuum distillation apparatus, and the distillation temperature is controlled to be 150° C. to distill out the water and unreacted alcohol in the organic phase. A colorless and transparent asymmetric citrate ester is obtained.

[0033] Example 1

[0034] This embodiment provides a method for synthesizing an asymmetric citrate ester, comprising:

[0035] (1) Add 50.00 g of anhydrous citric acid powder, a certain amount of fatty alcohol and 0.50 g of p-toluenesulfonic acid to a 250 mL three-necked flask. The amount of the reactant alcohol added is controlled to be 3.2 times the molar fraction of the anhydrous citric acid, and p-toluenesulfonic acid monohydrate is selected as the reaction catalyst (the amount added is 1 wt% of the amount of anhydrous citric acid added). The fatty alcohol used in this example is a mixture of octanol and decanol (CA 1 / 2) with a molar fraction ratio of 1:2.

[0036] (2) Oil bath, reaction temperature controlled at 150°C, the reaction is complete when no more water condenses in the water separator.

[0037] (3) Pour the obtained oily liquid into a beaker and wash the oily liquid with a 1% Na2CO3 solution and deionized water respectively. The washing temperature is controlled at 70°C. After each washing, the pH value of the aqueous phase is measured with a pH test paper. When the aqueous phase is neutral, the washing is stopped and the liquid is separated with a separatory funnel to obtain an organic phase solution.

[0038] (4) The organic phase solution is distilled using a vacuum distillation apparatus, and the distillation temperature is controlled to be 150° C. to distill out the water and unreacted alcohol in the organic phase. A colorless and transparent asymmetric citrate ester is obtained.

[0039] This embodiment also provides a method for preparing an asymmetric citrate ester / PVC composite material, comprising:

[0040] (1) Weigh 15 g of a mixture of PVC powder and asymmetric citrate (the mass proportion of citrate is 50%, that is, 7.5 g of PVC powder and asymmetric citrate) and place it in a clean beaker. Add 150 ml of tetrahydrofuran to make the solid content in the beaker 0.1 g / ml. Then stir and dissolve on a magnetic stirrer. Stop stirring when there are no transparent small particles in the beaker. Let it stand for a while and wait for all the bubbles in the beaker to disappear.

[0041] (2) Pour the stirred solution into a glass mold and place the glass mold in a fume hood overnight to allow the solvent to evaporate as completely as possible. Try not to create disturbances during the evaporation process to avoid bubbles or wrinkles during the film formation process.

[0042] (3) The mold is placed in a 60°C oven and dried for 30 minutes to completely remove the remaining small amount of solvent and form a PVC composite film.

[0043] Example 2

[0044] On the basis of Example 1, the fatty alcohol is a mixture of octanol and decanol in a molar ratio of 1:1 (CA 1 / 1), and the remaining steps are the same as those in Example 1.

[0045] Example 3

[0046] On the basis of Example 1, the fatty alcohol is a mixture of octanol and decanol in a molar ratio of 2:1 (CA 2 / 1), and the remaining steps are the same as those in Example 1.

[0047] Example 4

[0048] On the basis of Example 1, the addition amount of the reactant alcohol is controlled to be 3.5 times the molar fraction of the anhydrous citric acid, the addition amount of the catalyst toluenesulfonic acid monohydrate is 2wt% of the anhydrous citric acid addition amount, the anhydrous citric acid powder, a certain amount of fatty alcohol and p-toluenesulfonic acid are mixed, the temperature of the oil bath is 155°C, and the remaining steps are the same as in Example 1.

[0049] Comparative Example 1

[0050] On the basis of Example 1, octanol was selected as the fatty alcohol to synthesize trioctyl citrate (CA 3 / 0).

[0051] Comparative Example 2

[0052] On the basis of Example 1, decyl alcohol was selected as the fatty alcohol to synthesize tridecyl citrate (CA 0 / 3).

[0053] The citrates synthesized in Examples 1-4 are all asymmetric citrates, and their molecular structures are regular. Comparative Examples 1 and 2 synthesize symmetric citrates. The nuclear magnetic resonance hydrogen spectra of the citrates synthesized in Examples 1, 2, 3 and Comparative Examples 1 and 2 are as follows: Figure 1-5 As shown, the peak with a chemical shift of 1.18 ppm comes from the common methylene group on the hydrophobic alkyl chain. CA0 / 3 is tridecyl citrate, and the number of its common methylene groups is 30, while the number of methylene groups on CA 1 / 2, CA 1 / 1, CA 2 / 1 and CA 3 / 0 are 34, 36, 38 and 42, respectively, which further confirms that the product has a regular structure. During the preparation process of CA 1 / 1, there are three main grafted parts, and the grafting ratio is 1:1, one grafted with 2, and one grafted with 1, so that CA 1 / 1 has two possible structures and there are isomers.

[0054] The tensile strength of the citrate / PVC composite materials prepared in Examples 1, 2, 3 and Comparative Examples 1 and 2 was tested. The test results are as follows: Figure 6 The horizontal axis represents the content of citrate. The tensile strength of asymmetric citrate / PVC composites is better than that of single trioctyl citrate (CA 3 / 0) / PVC and tridecyl citrate (CA 0 / 3) / PVC composite films. The tensile strength of CA 1 / 2 (50wt%) is increased by 11.21% and 6.7% compared with CA 3 / 0 and CA 0 / 3.

[0055] The elongation at break of the citrate / PVC composite materials prepared in Examples 1, 2, 3 and Comparative Examples 1 and 2 was tested. The test results are as follows: Figure 7 The tensile strength of asymmetric citrate (CA 1 / 2) / PVC composite materials is better than that of single trioctyl citrate (CA 3 / 0) / PVC and tridecyl citrate (CA 0 / 3) / PVC composite films, among which the elongation at break of CA1 / 2 (50wt%) is increased by 1.2% and 8.0% compared with CA 3 / 0 and CA 0 / 3.

[0056] The above embodiment is only one of the preferred implementation modes of the present invention and should not be used to limit the protection scope of the present invention. Any changes or modifications that are made to the main design concept and spirit of the present invention and have no substantive significance, and the technical problems they solve are still consistent with the present invention, should be included in the protection scope of the present invention.

Claims

1. An asymmetric citrate ester, characterized in that: It is obtained by esterification reaction of citric acid powder, p-toluenesulfonic acid and fatty alcohol under the action of acid catalyst, followed by washing and distillation; The fatty alcohol is a mixture of octanol and decanol in a molar ratio of 1-2:1-2.

2. An asymmetric citrate according to claim 1, characterized in that: The added mass ratio of citric acid powder and p-toluenesulfonic acid is 50:0.5, and the added amount of the acid catalyst is 1-2% of the mass of the citric acid powder, and the added amount of the fatty alcohol is 3.2-3.5 times the molar fraction of the citric acid.

3. An asymmetric citrate according to claim 2, characterized in that: The acid catalyst is p-toluenesulfonic acid monohydrate.

4. An asymmetric citrate according to claim 1 or 3, characterized in that: During the esterification reaction, the temperature is 150-155°C, and the reaction is completed when no more water condenses in the water separator.

5. An asymmetric citrate according to claim 4, characterized in that: After the esterification reaction, the mixture is washed with Na2CO3 solution and deionized water. The washing temperature is controlled at 65-75°C. After each washing, the pH value of the aqueous phase is measured with pH test paper. When the aqueous phase is neutral, the washing is stopped and the liquid is separated using a separatory funnel to obtain an organic phase solution.

6. An asymmetric citrate according to claim 5, characterized in that: The washed organic phase solution was distilled by reduced pressure distillation at a distillation temperature of 150°C.

7. The method for preparing the asymmetric citrate / PVC composite material according to any one of claims 1 to 6, characterized in that: include: S1: Mix PVC powder, asymmetric citrate and tetrahydrofuran, stir and dissolve, and let stand until all bubbles disappear to obtain a mixed solution; S2: Pour the mixture into a mold and leave it in a ventilated place overnight; S3: placing the mold in an oven for drying to form a PVC composite film, i.e., an asymmetric citrate ester / PVC composite material.

8. The method for preparing an asymmetric citrate ester / PVC composite material according to claim 7, characterized in that: In step S1, after PVC powder, asymmetric citrate and tetrahydrofuran are mixed, the solid content is controlled at 0.1 g / ml, and the added mass ratio of PVC powder and asymmetric citrate is 1:

1.

9. The method for preparing an asymmetric citrate ester / PVC composite material according to claim 8, characterized in that: In step S3, during drying, the temperature of the oven is 60° C. and the drying time is 30 minutes.

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