Method for preparing pentaerythritol maleate and preparing heat stabilizer from pentaerythritol maleate
Technical Field
The invention relates to a method for preparing pentaerythritol maleate and a heat stabilizer from the pentaerythritol maleate, belonging to the technical field of application of plastic additives.
Background
Polyvinyl chloride (PVC) products are widely applied to various fields of electronics, packaging, new materials and the like due to the advantages of excellent mechanical property, wide raw material sources, strong corrosion resistance, low price, good plasticity and the like. The PVC product has poor thermal stability due to the structural defects, so a certain amount of heat stabilizer needs to be added in the PVC processing process to improve the thermal stability. Guided by the way of replacing wood with plastic and replacing steel with plastic, the PVC industry is rapidly and sustainably developed. The traditional lead salt heat stabilizer belongs to heavy metal salt, and is eliminated in the market at present under increasingly perfect environmental protection laws. Therefore, the demand of PVC heat stabilizer will increase, and the demand is moving towards diversification, environmental protection, compound type and multiple functions. At present, the calcium/zinc type composite heat stabilizer with the advantages of low price, greenness, no toxicity, wide raw materials and the like gradually becomes the key point of domestic and foreign research.
The molecular structure of the maleic anhydride has carbon-carbon double bonds, and the cyclic structure of the maleic anhydride has very easy reactivity and can generate Diels-Alder addition reaction with a conjugated polyene chain in a PVC chain, so that the growth of the conjugated bonds is effectively inhibited, and the coloring of the conjugated polyene chain is inhibited and relieved. The polyhydric alcohol is used as an auxiliary heat stabilizer, and inhibits the catalytic degradation of metal chloride to PVC molecular chains through a complexation reaction, so that the long-term stability of the main heat stabilizer is improved. Meanwhile, the polyalcohol can also absorb HCl generated by PVC molecular chain degradation under the catalysis of metal chloride to achieve a stabilizing effect. Therefore, the polyhydric alcohol is usually compounded with main heat stabilizers such as zinc salt, cadmium salt and the like to obtain an ideal composite PVC heat stabilizer. The synergistic effect of a polyol on a heat stabilizer such as a zinc salt or a cadmium salt is related to the molecular structure of the polyol and the number of hydroxyl groups contained in the molecule. The effect of improving the long-term thermal stability is positively correlated with the number of hydroxyl groups contained in the polyol. Pentaerythritol is used as the most commonly used polyol auxiliary heat stabilizer, has four hydroxyl groups in the structure, and has excellent auxiliary heat stability.
Therefore, the auxiliary heat stabilizer and the main heat stabilizer are prepared by taking maleic anhydride and pentaerythritol as raw materials, and the heat stability of the auxiliary heat stabilizer and the main heat stabilizer is improved in the aspects of a plurality of heat stability mechanisms.
Disclosure of Invention
The invention aims to provide a method for preparing pentaerythritol maleate and a heat stabilizer thereof, which designs the characteristics of a product from the aspect of molecular structure and overcomes some defects of the existing heat stabilizer.
The technical scheme of the invention is that the preparation method of the maleic acid pentaerythritol ester comprises the following steps: putting maleic anhydride into a reaction container, moving the reaction container to an oil bath pan, and heating the reaction container until the maleic anhydride is completely dissolved; adding the pentaerythritol which is ground into powder into a reaction container, stirring for reaction, testing the acid value of reactants at intervals, and stopping the reaction after the theoretical acid value is reached to obtain the pentaerythritol maleate.
Further, four different intermediates are prepared according to the reaction process according to different molar ratios of maleic anhydride and pentaerythritol: monopentaerythritol maleate, dipentaerythritol maleate, tripentaerythritol maleate and tetrapentaerythritol maleate.
Further, the specific steps are as follows: putting maleic anhydride into a reaction container, moving the reaction container to an oil bath, heating the reaction container to 90 ℃, after the maleic anhydride is completely dissolved, proportionally adding powdered pentaerythritol into the reaction container, stirring the mixture at the speed of 250-350r/min for reaction, sampling every 10min to test the acid value of the reaction system, stopping the reaction when the theoretical acid value is reached, and obtaining the pentaerythritol maleate.
Further, the maleic anhydride and pentaerythritol are sequentially prepared according to different molar ratios of 1:1, 2:1, 3:1 and 4: 1 to obtain monopentaerythritol maleate, dipentaerythritol maleate, tripentaerythritol maleate and tetrapentaerythritol maleate.
The pentaerythritol maleate is used for preparing a heat stabilizer, and the heat stabilizer is specifically a calcium/zinc pentaerythritol maleate heat stabilizer or a calcium/zinc pentaerythritol maleate stearate heat auxiliary stabilizer.
Further, the calcium/zinc pentaerythritol maleate thermal stabilizer is specifically a calcium pentaerythritol maleate thermal stabilizer and/or a zinc pentaerythritol maleate thermal stabilizer; the two can be used independently or in combination.
The preparation method of the calcium/zinc heat stabilizer of pentaerythritol maleate comprises the steps of putting pentaerythritol maleate into a four-neck flask, moving the flask into an oil bath pot for heating, slowly dripping a calcium acetate/zinc solution, and continuing to react for a period of time after all dripping is finished; after the reaction is finished, moving the mixture into a drying oven for drying, removing water and acetic acid in the reaction system, and finally preparing a maleic acid pentaerythritol ester calcium/zinc heat stabilizer;
according to different pentaerythritol maleates, a monopentaerythritol maleate calcium/zinc heat stabilizer, a dipentaerythritol maleate calcium/zinc heat stabilizer, a tripentaerythritol maleate calcium/zinc heat stabilizer and a tetrapentaerythritol maleate calcium/zinc heat stabilizer are correspondingly prepared.
Further, the method comprises the following specific steps: putting pentaerythritol maleate into a four-neck flask, moving the flask into an oil bath pot, heating the flask to 90 ℃, slowly dripping calcium acetate/zinc acetate solutions with different proportions at the speed of 1d/s, and continuously reacting for 1-3h after all the dripping is finished; after the reaction is finished, moving the mixture into a drying oven with the temperature of 100 ℃ for drying for 6-10h, removing water and acetic acid in a reaction system, and finally preparing a calcium/zinc heat stabilizer of pentaerythritol maleate;
the ratio of the calcium acetate/zinc acetate solution to different pentaerythritol maleate esters is 1:2, 1:1, 1.5:1 and 2:1 in sequence; and correspondingly preparing a monopentaerythritol maleate calcium/zinc heat stabilizer, a dipentaerythritol maleate calcium/zinc heat stabilizer, a tripentaerythritol maleate calcium/zinc heat stabilizer and a tetrapentaerythritol maleate calcium/zinc heat stabilizer.
The reaction equation is as follows:
the preparation method of the thermal auxiliary calcium stearate/zinc maleate stabilizer comprises the steps of compounding calcium stearate and zinc stearate with the prepared thermal auxiliary pentaerythritol maleate stabilizer; wherein the weight ratio of calcium stearate: zinc stearate: the ratio of pentaerythritol maleate was 0.32:0.16: 0.1.
The specific reaction equation is as follows:
the invention relates to a calcium/zinc heat stabilizer of pentaerythritol maleate, which is prepared by taking pentaerythritol maleate as an intermediate. The raw materials and the product are wide in source, non-toxic and environment-friendly, a toxic solvent is not needed in the reaction process, the thermal decomposition of PVC is inhibited by a plurality of thermal stability mechanisms, and the PVC has excellent thermal stability.
In the invention, the used raw materials of maleic anhydride and pentaerythritol have wide sources and extremely high yield, and are nontoxic and environment-friendly. The intermediate pentaerythritol maleate is synthesized by adopting a one-step method, and the reaction condition is mild. In the preparation of the calcium pentaerythritol maleate/zinc heat stabilizer, a calcium acetate/zinc aqueous solution is used as a solvent, so that the reaction is sufficient, and an organic reagent is not needed. The synthesis method has the advantages of simple process, energy conservation and low consumption in the reaction process, and non-toxic and environment-friendly reactants and products.
In the invention, different intermediate products of pentaerythritol maleate are prepared according to different ratios of the raw material maleic anhydride and pentaerythritol.
In the invention, different compounding ratios of calcium maleate and zinc maleate are prepared to achieve the optimal thermal stability effect.
The invention has the beneficial effects that: the raw materials used in the invention are cheap, are byproducts of phthalic anhydride production and are utilized, and the raw materials have wide sources, are nontoxic and environment-friendly. The preparation process is simple, the reaction condition is mild, and no organic solvent is used, so that the whole production process is green and environment-friendly, and the production cost is greatly reduced.
The intermediate product and the final product prepared by the method can be used as an environment-friendly heat stabilizer, the product in each step is fully utilized, and the value of the whole process is greatly improved.
The calcium/zinc maleate pentaerythritol ester heat stabilizer prepared by the invention improves the heat stability of PVC by multiple heat stability mechanisms, such as: neutralizing and absorbing hydrogen chloride; Diels-Alder addition to a conjugated polyene chain; complex metal chlorides, and the like. Thereby greatly improving the thermal stability of the product.
Drawings
FIG. 1 is an infrared spectrum of pentaerythritol maleate prepared in examples 1 to 4.
FIG. 2 is an infrared spectrum of calcium/zinc monopentaerythritol maleate prepared in accordance with the present invention.
Detailed Description
The present invention is further described with reference to the following examples, but the scope of the present invention is not limited to the examples, and those skilled in the art can make modifications to the technical patent of the present invention within the scope of the present invention.
EXAMPLE 1 preparation of monopentaerythritol maleate
9.806g of maleic anhydride (0.1 mol) was placed in a 250mL four-necked flask, the flask was transferred to a 90 ℃ oil bath, and 13.615g of pulverized pentaerythritol (0.1 mol) was added after the maleic anhydride was completely dissolved. The reaction was further stirred, and the acid value of the reaction system was measured at regular intervals, and the reaction was stopped when the acid value approached or reached the theoretical acid value (theoretical acid value =4.23 × 10)-3mol/g) to obtain the product maleic acid monopentaerythritol ester, and an infrared spectrum is shown in figure 1.
EXAMPLE 2 preparation of dipentaerythritol maleate
19.612g of maleic anhydride (0.2 mol) was placed in a 250mL four-necked flask, the flask was transferred to a 90 ℃ oil bath, and 13.615g of pulverized pentaerythritol (0.1 mol) was added after the maleic anhydride was completely dissolved. The reaction was further stirred, and the acid value of the reaction system was measured at regular intervals, and the reaction was stopped when the acid value approached or reached the theoretical acid value (theoretical acid value =6.02 × 10)-3mol/g) to obtain the product maleic acid dipentaerythritol ester, and an infrared spectrum is shown in figure 1.
EXAMPLE 3 preparation of Tripentaerythritol maleate
29.406g of maleic anhydride (0.3 mol) was placed in a 250mL four-neck flask, transferred to a 90 ℃ oil bath, and when the maleic anhydride was completely dissolved, powdered pentaerythritol was addedTetraol 13.615g (0.1 mol). The reaction was further stirred, and the acid value of the reaction system was measured at regular intervals, and the reaction was stopped when the acid value approached or reached the theoretical acid value (theoretical acid value =6.97 × 10)-3mol/g) to obtain the product of the maleic acid tripentaerythritol ester, and an infrared spectrum is shown in figure 1.
EXAMPLE 4 preparation of pentaerythritol maleate
39.224g of maleic anhydride (0.4 mol) was placed in a 250ml four-necked flask, which was then transferred to a 90 ℃ oil bath and 13.615g of pulverized pentaerythritol (0.1 mol) was added after the maleic anhydride had completely dissolved. The reaction was further stirred, and the acid value of the reaction system was measured at regular intervals, and the reaction was stopped when the acid value approached or reached the theoretical acid value (theoretical acid value =7.57 × 10)-3mol/g) to obtain the product of pentaerythritol maleate, and an infrared spectrum is shown in figure 1.
1705 cm-1Is the characteristic peak of carbonyl groups attached to the conjugated double bond, 1632cm-1Characteristic absorption peaks of carbon-carbon double bonds are shown on the left and the right, and the appearance of the two characteristic peaks indicates that the maleic anhydride ring is opened; 1163cm-1The left and the right are C-O-C characteristic peaks; the above peaks indicate an efficient synthesis of pentaerythritol maleate.
EXAMPLE 5 calcium monopentaerythritol maleate thermal stabilizers
23.421g of monopentaerythritol maleate (0.1 mol) is added into a 250mL four-neck flask, the flask is moved into an oil bath pot and heated to 90 ℃, calcium acetate solution (1 mol/L, 50 mL) is slowly added dropwise, and the stirring reaction is continued for 2 hours after all the calcium acetate solution is added dropwise. After the reaction is finished, the mixture is moved to a 100 ℃ oven to be dried for 8h, water and acetic acid in the reaction system are removed, and the monopentaerythritol maleate calcium heat stabilizer is finally prepared, wherein an infrared spectrogram is shown in figure 2.
EXAMPLE 6 Monopentaerythritol maleate Zinc Heat stabilizer
23.421g of monopentaerythritol maleate (0.1 mol) is added into a 250mL four-neck flask, the flask is moved into an oil bath pot and heated to 90 ℃, a zinc acetate solution (1 mol/L, 50 mL) is slowly added dropwise, and the stirring reaction is continued for 2 hours after all the zinc acetate solution is added dropwise. After the reaction is finished, the mixture is moved to a 100 ℃ oven to be dried for 8h, water and acetic acid in the reaction system are removed, and the zinc heat stabilizer of the maleic acid monopentaerythritol ester is finally prepared, wherein an infrared spectrogram is shown in figure 2.
1575 cm-1The characteristic peaks of the metal carboxylate are shown on the left and the right, and the synthesis of the calcium/zinc monopentaerythritol maleate is proved.
EXAMPLE 7 preparation of pentaerythritol maleate calcium stearate/Zinc thermal Assistant stabilizer
The commercially available calcium stearate/zinc and the prepared pentaerythritol maleate ester auxiliary heat stabilizer are compounded for use, and the specific proportion is as follows: zinc stearate: pentaerythritol maleate =0.32:0.16: 0.1.
Application example 1 use of pentaerythritol maleate stearate calcium/Zinc thermal auxiliary stabilizer
The pentaerythritol maleate prepared in the embodiments 1-4 of the present invention and calcium stearate/zinc stearate are compounded to form a heat stabilizer system, so as to obtain a heat stabilizer, and the heat stabilizer is added into a PVC sample to perform a heat aging experiment: the prepared pentaerythritol maleate is compounded with commercially available calcium stearate/zinc stearate for use. The total amount of PVC resin is 16g, DOP is 8g, CaSt2And ZnSt2Total 3% of CaSt2/ZnSt2And =2: 1. PVC resin, DOP and a heat stabilizer are mixed and stirred uniformly and are spread on a smooth glass plate. Moving to a 120 ℃ oven for plasticizing for 20min, cooling and then cutting into small square pieces with the size of 1 multiplied by 1 mm. The PVC square sheets were placed in aluminum foil sheets on an enamel tray, placed in a 180 ℃ oven, sampled every 10min, and the color change of the PVC pattern was observed. The test results are shown in table 1.
TABLE 1 Heat aging oven test CaSt2/ZnSt2Color change of PVC test specimens with PAM System
Pentaerythritol maleate-R; dipentaerythritol maleate-2R;
pentaerythritol maleate-3R; pentaerythritol maleate-4R;
pentaerythritol-PE.
As can be seen from the test results in Table 1, the PVC samples added with pure calcium stearate/zinc stearate have certain thermal stability but poor effect, and the yellowing phenomenon appears already at 20min and the severe blackening phenomenon appears at 50 min. The thermal stability of the PVC sample of the compound system added with the pentaerythritol maleate is obviously improved, wherein the PVC sample added with the monopentaerythritol maleate has the best effect, the initial whiteness is maintained for 30min, the blackening phenomenon occurs only in 60min, and the blackening is completely performed in 80 min.
Application example 2 application of calcium/Zinc bis-pentaerythritol maleate thermal stabilizer
The calcium/zinc heat stabilizer of the monopentaerythritol maleate prepared in the embodiment 5 or 6 of the invention is added into a PVC sample for a heat aging experiment: the prepared pentaerythritol maleate calcium/zinc ester is used as a PVC main heat stabilizer. The total amount of the PVC resin is 16g, the DOP is 8g, and the calcium/zinc monopentaerythritol maleate is compounded according to different proportions and accounts for 3 percent of the total mass of the PVC. PVC resin, DOP and a heat stabilizer are mixed and stirred uniformly and are spread on a smooth glass plate. Moving to a 120 ℃ oven for plasticizing for 20min, cooling and then cutting into small square pieces with the size of 1 multiplied by 1 mm. The PVC square sheets were placed in aluminum foil sheets on an enamel tray, placed in a 180 ℃ oven, sampled every 10min, and the color change of the PVC pattern was observed. Specific results are shown in table 2.
TABLE 2 color change of PVC samples tested for PAM-Ca/Zn system by heat aging oven method
Calcium monopentaerythritol maleate-PAM-Ca; maleic acid monopentaerythritol ester zinc-PAM-Zn.
As can be seen from the test results in Table 2, the thermal stability of the PVC samples added with the calcium/zinc monopentaerythritol maleate thermal stabilizer is improved. The long-term thermal stability of the PVC sample which is separately added with the calcium monopentaerythritol maleate and thermally stable is obviously improved, and blackening does not occur until 60 min. PVC samples with the addition of the zinc monopentaerythritol maleate heat stabilizer alone maintained initial whiteness, but were susceptible to "zinc burn". By compounding in different proportions, the effect is best when the calcium/zinc ratio is =2:1, the initial whiteness is maintained for 50min, and the complete blackening is not carried out until 90 min.