Preparation method of polyvinyl alcohol

Abstract

The invention relates to the technical field of polyvinyl alcohol preparation, and discloses a preparation method of polyvinyl alcohol. The method comprises the following steps: (1) in the presence of an initiator and a first solvent, carrying out polymerization reaction on vinyl ester to obtain polyvinyl ester; (2) in the presence of alkali and a second solvent, performing alcoholysis on polyvinyl ester to obtain polyvinyl alcohol; wherein the molar ratio of the alkali to the polyvinyl ester is (0.004-0.01): 1; the alcoholysis time is less than or equal to 20 minutes; the alcoholysis degree of the polyvinyl alcohol is less than or equal to 60 mol%; in the alcoholysis process, the alcoholysis degree of the polyvinyl alcohol is controlled by adjusting the alcoholysis time by utilizing a function relational expression K = aT + b. The alcoholysis degree of the product can be rapidly and accurately obtained, the alcoholysis process can be accurately controlled by adjusting the alcoholysis time, the production efficiency is improved, and the qualified rate and the quality stability of the product are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of polyvinyl alcohol preparation, and particularly relates to a method for preparing polyvinyl alcohol. Background Art

[0002] Polyvinyl alcohol (PVA) dispersant is a fine chemical product, which is a liquid product produced mainly from vinyl acetate and methanol. This product can not only increase the porosity of polyvinyl chloride, but also make the particle distribution more uniform, and is an important part of the polyvinyl chloride suspension polymerization system in recent years.

[0003] In the production process of polyvinyl alcohol dispersant, first, a polymerization solution is obtained through solution polymerization. Then, at an appropriate temperature, an appropriate amount of lye is added to the polymerization solution for alcoholysis. When the alcoholysis degree of the polymerization solution reaches the requirement, a certain amount of terminator is added to terminate the reaction, and a polyvinyl alcohol dispersant product is obtained. Currently, sampling and observation are one of the important methods to obtain and control the alcoholysis degree of polyvinyl alcohol dispersant. However, the method of relying on human eyes for observation, due to the instability of daily light and the differences in personnel's subjective feelings, leads to inaccurate judgment of the alcoholysis degree of polyvinyl alcohol dispersant products, easily resulting in unqualified products and large fluctuations in product quality.

[0004] Therefore, there is an urgent need to provide a method for preparing polyvinyl alcohol that can accurately judge the alcoholysis degree of the product. Summary of the Invention

[0005] In view of the problem in the existing polyvinyl alcohol preparation process that it is difficult to accurately judge the alcoholysis degree of the product, which in turn easily leads to unqualified products, an increase in waste and defective products, and large fluctuations in product quality, the present invention provides a method for preparing polyvinyl alcohol.

[0006] To achieve the above object, the present invention provides a method for preparing polyvinyl alcohol, comprising:

[0007] (1) In the presence of an initiator and a first solvent, polymerize vinyl ester to obtain polyvinyl ester;

[0008] (2) In the presence of an alkali and a second solvent, carry out alcoholysis on the polyvinyl ester to obtain polyvinyl alcohol;

[0009] Wherein, the molar ratio of the alkali to the polyvinyl ester is (0.004 - 0.01):1; the time of alcoholysis ≤ 20 min; the alcoholysis degree of the polyvinyl alcohol ≤ 60 mol%;

[0010] During the alcoholysis process, use the functional relationship K = aT + b to control the alcoholysis degree of polyvinyl alcohol by adjusting the alcoholysis time;

[0011] In the said functional relationship, K represents the degree of alcoholysis of polyvinyl alcohol, with the unit of mol%; T represents the alcoholysis time, with the unit of min; 0 < a ≤ 2; 40 ≤ b ≤ 50.

[0012] Through the above technical solution, in the preparation method of polyvinyl alcohol provided by the present invention, during the alcoholysis process, when the ratio of polyvinyl ester to alkali is fixed, by using the specific functional relationship between the degree of alcoholysis of the obtained polyvinyl alcohol and the alcoholysis time, it is possible to quickly determine the degree of alcoholysis of the product, and the alcoholysis process can be flexibly and precisely controlled by adjusting the alcoholysis time, so as to prepare various specifications of polyvinyl alcohol products with different degrees of alcoholysis. Compared with the preparation process using the sampling observation method, it can more accurately judge the degree of alcoholysis of the product, better provide a basis for process adjustment on the production site, improve production efficiency, and improve the qualified rate and quality stability of the product. Specific Embodiments

[0013] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0014] The following details the specific embodiments of the present invention. It should be understood that the specific embodiments described herein are only for explaining and illustrating the present invention, and are not used to limit the present invention.

[0015] The present invention provides a preparation method of polyvinyl alcohol, comprising:

[0016] (1) In the presence of an initiator and a first solvent, polymerize vinyl ester to obtain polyvinyl ester;

[0017] (2) In the presence of an alkali and a second solvent, alcoholize the polyvinyl ester to obtain polyvinyl alcohol;

[0018] Wherein, the molar ratio of the alkali to the polyvinyl ester is (0.004 - 0.01):1; the alcoholysis time ≤ 20 min; the degree of alcoholysis of the polyvinyl alcohol ≤ 60 mol%;

[0019] During the alcoholysis process, use the functional relationship formula K = aT + b to control the degree of alcoholysis of polyvinyl alcohol by adjusting the alcoholysis time;

[0020] In the said functional relationship, K represents the degree of alcoholysis of polyvinyl alcohol; T represents the alcoholysis time; 0 < a ≤ 2, with the unit of mol%; 40 ≤ b ≤ 50, with the unit of min.

[0021] In the existing polyvinyl alcohol preparation process, the degree of alcoholysis of polyvinyl alcohol products is often obtained by sampling and observation. This method has poor accuracy, resulting in inaccurate judgment of the degree of alcoholysis of the products. The alcoholysis reaction of vinyl esters (such as polyvinyl acetate) is a complex process involving multiple chemical reactions. The inventors of the present invention found through research that the alcoholysis process can be divided into two time periods. In the initial stage (0 - 6 min), the change rate of the degree of alcoholysis is relatively fast, and the degree of alcoholysis increases rapidly with the increase of alcoholysis time (but not in a linear relationship); in the later stage (after 6 min of alcoholysis), the change rate of the degree of alcoholysis is slower. When the ratio of vinyl ester to base is constant, the degree of alcoholysis of polyvinyl alcohol and the alcoholysis time basically satisfy the functional relationship K = aT + b (where K represents the degree of alcoholysis of polyvinyl alcohol, in mol%; T represents the alcoholysis time, in min; 0 < a ≤ 2; 40 ≤ b ≤ 50), until the base in the reaction system is exhausted and the reaction terminates. The present invention utilizes the above specific functional relationship between the degree of alcoholysis of polyvinyl alcohol obtained by alcoholysis and the alcoholysis time, and can quickly and accurately obtain the degree of alcoholysis of polyvinyl alcohol products, and can flexibly prepare various specifications of polyvinyl alcohol products with different degrees of alcoholysis by adjusting the alcoholysis time.

[0022] According to the present invention, in the said functional relationship, preferably, 0.5 ≤ a ≤ 1.5; 40 ≤ b ≤ 48.

[0023] According to the present invention, in the said functional relationship, preferably, when the alcoholysis time T is in the range of 6 - 10 min, 1 ≤ a ≤ 1.5; 40 ≤ b ≤ 45; when the alcoholysis time T is in the range of 10 - 20 min (excluding 10), 0.5 ≤ a ≤ 0.7; 46 ≤ b ≤ 48, which can make the calculated degree of alcoholysis of polyvinyl alcohol closer to the actual degree of alcoholysis.

[0024] According to the present invention, in the preparation method of the said polyvinyl alcohol, in step (1), the vinyl ester can be selected from at least one of vinyl formate, vinyl acetate, vinyl laurate, vinyl propionate, vinyl butyrate, trimethylvinyl acetate, vinyl versatate, vinyl stearate, and vinyl benzoate, and preferably vinyl acetate.

[0025] According to the present invention, in the preparation method of the said polyvinyl alcohol, in step (1), the initiator can be any initiator in the art that can initiate the solution polymerization reaction of vinyl esters to obtain polyvinyl esters. Preferably, the initiator can be selected from peroxide initiators and / or azo initiators. For example, the initiator can be selected from at least one of tert-butyl peroxyneodecanoate, tert-butyl peroxyneopentanoate, benzoyl peroxide, azobisisobutyronitrile, and azobisisoheptonitrile.

[0026] According to the present invention, in the preparation method of the polyvinyl alcohol, in step (1), the first solvent may be selected from at least one of methanol, ethanol, and methyl acetate, and is preferably methanol.

[0027] According to the present invention, in the preparation method of the polyvinyl alcohol, in step (1), preferably, the weight ratio of the initiator to the vinyl ester may be (0.008 - 0.23):100, and more preferably (0.01 - 0.2):100.

[0028] According to the present invention, in the preparation method of the polyvinyl alcohol, in step (1), the feeding mode of each raw material and the process of the polymerization reaction may be carried out in a conventional manner in the art, and the present invention has no special limitation on this. Preferably, the conditions of the polymerization reaction include: the temperature is 50 - 70 °C, and the time is 3 - 6 h.

[0029] According to the present invention, in the preparation method of the polyvinyl alcohol, step (1) further includes: separating the product system obtained from the polymerization reaction to separate the unreacted vinyl ester monomer, and obtaining a mixture of polyvinyl ester and the first solvent. In some embodiments of the present invention, the mixture of polyvinyl ester and the first solvent may be further separated to obtain polyvinyl ester and carry out subsequent alcoholysis, or it may not be separated, and the mixture of polyvinyl ester and the first solvent may be directly subjected to the subsequent alcoholysis step.

[0030] In the present invention, there is no special limitation on the method and conditions of the separation treatment, as long as the unreacted vinyl ester monomer can be separated, for example, the rectification method can be used.

[0031] According to the present invention, in the preparation method of the polyvinyl alcohol, in step (2), preferably, the base is selected from at least one of NaOH, KOH, and CH 3 ONa, and is preferably NaOH.

[0032] According to the present invention, in the preparation method of the polyvinyl alcohol, in step (2), preferably, the second solvent is selected from at least one of methanol, ethanol, and methyl acetate, and is preferably methanol.

[0033] According to the present invention, in the preparation method of the polyvinyl alcohol, in step (2), preferably, the polyvinyl ester is fed in the form of a polymer solution. The polymer solution is preferably a solution in which the polyvinyl ester and the second solvent together form a polyvinyl ester concentration of 40 - 50 wt%.

[0034] According to the present invention, in the method for preparing polyvinyl alcohol, in step (2), preferably, the base is fed in the form of an alkali solution. The alkali solution is preferably a solution with an alkali concentration of 30 - 50 g / L formed by the base and the second solvent.

[0035] According to the present invention, in the method for preparing polyvinyl alcohol, in step (2), preferably, the molar ratio of the base to the polyvinyl ester is (0.005 - 0.009):1.

[0036] According to the present invention, in the method for preparing polyvinyl alcohol, in step (2), the conditions for alcoholysis include: the temperature is 20 - 40°C, and the time is 6 - 20 min.

[0037] In the method for preparing polyvinyl alcohol provided by the present invention, in the alcoholysis stage, when the ratio of polyvinyl ester to base is fixed, by using the specific functional relationship between the degree of alcoholysis of the polyvinyl alcohol obtained by alcoholysis and the alcoholysis time, the degree of alcoholysis of the product can be quickly judged, and the deviation rate between the calculated degree of alcoholysis and the actual degree of alcoholysis is less than 2% (deviation rate = (|calculated degree of alcoholysis - degree of alcoholysis measured by chemical analysis method| / degree of alcoholysis measured by chemical analysis method × 100%), preferably less than 1%, with high accuracy. The obtained degree of alcoholysis data can better guide the process adjustment in the production site, thereby improving production efficiency and product qualification rate. In addition, the preparation method provided by the present invention can precisely control the degree of alcoholysis of the polyvinyl alcohol product by adjusting the alcoholysis time. Therefore, the product can be flexibly adjusted according to actual needs to obtain products with different degrees of alcoholysis.

[0038] The present invention will be described in detail below through examples. In the following examples and comparative examples,

[0039] Without special instructions, the materials used are all ordinary commercially available products.

[0040] Example 1

[0041] (1) Preheat a methanol solution of vinyl acetate with a concentration of 30 wt% to 60°C, and carry out a polymerization reaction in the presence of 0.2% (by weight percentage of vinyl acetate) of azobisisobutyronitrile (the reaction temperature gradually rises from 60°C to 70°C, and the reaction time is 6 h), and the polymerization rate of vinyl acetate is 90%;

[0042] (2) Rectify the polyvinyl acetate - methanol solution obtained after the above polymerization reaction to distill out the azeotropic liquid of unreacted vinyl acetate and methanol, obtaining a polyvinyl acetate - methanol solution with a concentration of 50 wt%; convey the above polyvinyl acetate - methanol solution to an alcoholysis machine, mix it with a 30 g / L NaOH - methanol solution in the alcoholysis machine (the molar ratio of NaOH to polyvinyl acetate is 0.007:1), the alcoholysis temperature is 30 °C, the alcoholysis time is 6 min, and after the alcoholysis is completed, add acetic acid with an equal molar amount to NaOH to terminate the reaction, obtaining polyvinyl alcohol;

[0043] Using the formula K = 1.4T + 42 (where K represents the alcoholysis degree of polyvinyl alcohol, in mol%; T represents the alcoholysis time, in min), the calculated alcoholysis degree of the polyvinyl alcohol obtained with an alcoholysis time of 6 min is 50.4 mol%, while when the alcoholysis reaches 6 min, by sampling and using chemical analysis method, the measured alcoholysis degree of polyvinyl alcohol is 50.8 mol%, and the deviation rate is 0.78%.

[0044] Example 2

[0045] (1) Preheat a methanol solution of vinyl acetate with a concentration of 30 wt% to 60 °C, and carry out a polymerization reaction in the presence of 0.2% (by weight percentage of vinyl acetate) azobisisobutyronitrile (the reaction temperature gradually rises from 60 °C to 70 °C, and the reaction time is 6 h), and the polymerization rate of vinyl acetate is 90%;

[0046] (2) Rectify the polyvinyl acetate - methanol solution obtained after the above polymerization reaction to distill out the azeotropic liquid of unreacted vinyl acetate and methanol, obtaining a polyvinyl acetate - methanol solution with a concentration of 50 wt%; convey the above polyvinyl acetate - methanol solution to an alcoholysis machine, mix it with a 30 g / L NaOH - methanol solution in the alcoholysis machine (the molar ratio of NaOH to polyvinyl acetate is 0.007:1), the alcoholysis temperature is 30 °C, the alcoholysis time is 8 min, and after the alcoholysis is completed, add acetic acid with an equal molar amount to NaOH to terminate the reaction, obtaining polyvinyl alcohol;

[0047] Using the formula K = 1.4T + 42 (where K represents the alcoholysis degree of polyvinyl alcohol, in mol%; T represents the alcoholysis time, in min), the calculated alcoholysis degree of the polyvinyl alcohol obtained with an alcoholysis time of 8 min is 53.2 mol%, while when the alcoholysis reaches 8 min, by sampling and using chemical analysis method, the measured alcoholysis degree of polyvinyl alcohol is 53.4 mol%, and the deviation rate is 0.37%.

[0048] Example 3

[0049] (1) Preheat a methanol solution of vinyl acetate with a concentration of 30 wt% to 60 °C and carry out a polymerization reaction in the presence of 0.2% (by weight percentage of vinyl acetate) of azobisisobutyronitrile (the reaction temperature gradually rises from 60 °C to 70 °C, and the reaction time is 6 h), and the polymerization rate of vinyl acetate is 90%;

[0050] (2) Rectify the polyvinyl acetate - methanol solution obtained after the above polymerization reaction to distill out the unreacted vinyl acetate as an azeotropic liquid with methanol to obtain a polyvinyl acetate - methanol solution with a concentration of 50 wt%; convey the above polyvinyl acetate - methanol solution to an alcoholysis machine, mix it with a 30 g / L NaOH - methanol solution in the alcoholysis machine (the molar ratio of NaOH to polyvinyl acetate is 0.007:1), the alcoholysis temperature is 30 °C, the alcoholysis time is 10 min, and after the alcoholysis is completed, add acetic acid with an equimolar amount to NaOH to terminate the reaction to obtain polyvinyl alcohol;

[0051] Using the formula K = 1.4T + 42 (K represents the degree of alcoholysis of polyvinyl alcohol, unit: mol%; T represents the alcoholysis time, unit: min), calculate that the degree of alcoholysis of polyvinyl alcohol obtained with an alcoholysis time of 10 min is 56 mol%, and when the alcoholysis reaches 10 min, the degree of alcoholysis of polyvinyl alcohol measured by sampling and using chemical analysis method is 55.8 mol%, and the deviation rate is 0.36%.

[0052] Example 4

[0053] (1) Preheat a methanol solution of vinyl acetate with a concentration of 30 wt% to 60 °C and carry out a polymerization reaction in the presence of 0.2% (by weight percentage of vinyl acetate) of azobisisobutyronitrile (the reaction temperature gradually rises from 60 °C to 70 °C, and the reaction time is 6 h), and the polymerization rate of vinyl acetate is 90%;

[0054] (2) Rectify the polyvinyl acetate - methanol solution obtained after the above polymerization reaction to distill out the unreacted vinyl acetate as an azeotropic liquid with methanol to obtain a polyvinyl acetate - methanol solution with a concentration of 50 wt%; convey the above polyvinyl acetate - methanol solution to an alcoholysis machine, mix it with a 30 g / L NaOH - methanol solution in the alcoholysis machine (the molar ratio of NaOH to polyvinyl acetate is 0.007:1), the alcoholysis temperature is 30 °C, the alcoholysis time is 14 min, and after the alcoholysis is completed, add acetic acid with an equimolar amount to NaOH to terminate the reaction to obtain polyvinyl alcohol;

[0055] Using the formula K = 0.57T + 48 (where K represents the degree of alcoholysis of polyvinyl alcohol in mol%, and T represents the alcoholysis time in min), the calculated degree of alcoholysis of polyvinyl alcohol obtained at an alcoholysis time of 14 min is 55.98 mol%. When sampling at the 14th minute of alcoholysis and measuring the degree of alcoholysis of polyvinyl alcohol using chemical analysis, it is 56.3 mol%, and the deviation rate is 0.57%.

[0056] Example 5

[0057] (1) Preheat a methanol solution of vinyl acetate with a concentration of 30 wt% to 60 °C, and carry out a polymerization reaction in the presence of 0.2% (by weight percentage of vinyl acetate) of azobisisobutyronitrile (the reaction temperature gradually rises from 60 °C to 70 °C, and the reaction time is 6 h). The polymerization rate of vinyl acetate is 90%;

[0058] (2) Rectify the polyvinyl acetate - methanol solution obtained after the above polymerization reaction to distill out the unreacted vinyl acetate as an azeotropic liquid with methanol, and obtain a polyvinyl acetate - methanol solution with a concentration of 50 wt%. Transport the above polyvinyl acetate - methanol solution to an alcoholysis machine, mix it with a 30 g / L NaOH - methanol solution in the alcoholysis machine (the molar ratio of NaOH to polyvinyl acetate is 0.007:1), the alcoholysis temperature is 30 °C, the alcoholysis time is 18 min, and after the alcoholysis is completed, add acetic acid with an equimolar amount to NaOH to terminate the reaction, obtaining polyvinyl alcohol;

[0059] Using the formula K = 0.57T + 48 (where K represents the degree of alcoholysis of polyvinyl alcohol in mol%, and T represents the alcoholysis time in min), the calculated degree of alcoholysis of polyvinyl alcohol obtained at an alcoholysis time of 18 min is 58.26 mol%. When sampling at the 18th minute of alcoholysis and measuring the degree of alcoholysis of polyvinyl alcohol using chemical analysis, it is 57.7 mol%, and the deviation rate is 0.97%.

[0060] Comparative Example 1

[0061] (1) Preheat a methanol solution of vinyl acetate with a concentration of 30 wt% to 60 °C, and carry out a polymerization reaction in the presence of 0.2% (by weight percentage of vinyl acetate) of an azo initiator (the reaction temperature gradually rises from 60 °C to 70 °C, and the reaction time is 6 h). The polymerization rate of vinyl acetate is 90%;

[0062] (2) The polyvinyl acetate - methanol solution obtained after the above polymerization reaction is rectified to distill out the unreacted vinyl acetate as an azeotropic liquid with methanol, obtaining a polyvinyl acetate - methanol solution with a concentration of 50 wt%. The above polyvinyl acetate - methanol solution is transported to an alcoholysis machine and mixed with a 30 g / L NaOH - methanol solution in the alcoholysis machine (the molar ratio of NaOH to polyvinyl acetate is 0.007:1). The alcoholysis temperature is 30 °C, the alcoholysis time is 22 min. After the alcoholysis is completed, acetic acid with an equimolar amount to NaOH is added to terminate the reaction, obtaining polyvinyl alcohol;

[0063] Using the formula K = 0.57T + 48 (K represents the alcoholysis degree of polyvinyl alcohol, in mol%; T represents the alcoholysis time, in min), the calculated alcoholysis degree of the polyvinyl alcohol obtained with an alcoholysis time of 22 min is 60.54 mol%. When sampling at the 22 - minute mark of alcoholysis and measuring the alcoholysis degree of polyvinyl alcohol by chemical analysis method, the measured value is 59.2 mol%, and the deviation rate is 2.3%.

[0064] The above examples and comparative examples show that the preparation method of polyvinyl alcohol provided by the present invention, by using the specific functional relationship between the alcoholysis degree and the alcoholysis time during the alcoholysis process, can quickly and accurately judge the alcoholysis degree of the product. The deviation rate between the calculated alcoholysis degree and the actual alcoholysis degree is less than 2%, preferably less than 1%, with high accuracy, which is conducive to better on - site quality control, improving production efficiency and product qualification rate, and can prepare products with different alcoholysis degrees.

[0065] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A method for preparing polyvinyl alcohol, comprising: (1) Polymerizing a vinyl ester in the presence of an initiator and a first solvent to obtain a polyvinyl ester; (2) Alcoholyzing the polyvinyl ester in the presence of a base and a second solvent to obtain polyvinyl alcohol; wherein, the molar ratio of the base to the polyvinyl ester is (0.004 - 0.01):1; the alcoholysis time ≤ 20 min; the degree of alcoholysis of the polyvinyl alcohol ≤ 60 mol%; During the alcoholysis process, the function relation K = aT + b is used to control the degree of alcoholysis of polyvinyl alcohol by adjusting the alcoholysis time; In the function relation, K represents the degree of alcoholysis of polyvinyl alcohol, with the unit of mol%; T represents the alcoholysis time, with the unit of min; 0 < a ≤ 2; 40 ≤ b ≤ 50.

2. The preparation method according to claim 1, wherein, 0.5 ≤ a ≤ 1.5; 40 ≤ b ≤ 48.

3. The preparation method according to claim 1 or 2, wherein, In step (1), the initiator is selected from peroxide initiators and / or azo initiators.

4. The preparation method according to any one of claims 1 - 3, wherein, In step (1), the first solvent is selected from at least one of methanol, ethanol, and methyl acetate, preferably methanol.

5. The preparation method according to any one of claims 1 - 4, wherein, In step (1), the weight ratio of the initiator to the vinyl ester is (0.008 - 0.23):100, preferably (0.01 - 0.2):

100.

6. The preparation method according to any one of claims 1 - 5, wherein, In step (1), the conditions of the polymerization reaction include: temperature is 50 - 70 °C, and time is 3 - 6 h.

7. The preparation method according to any one of claims 1 - 6, wherein, In step (2), the base is selected from at least one of NaOH, KOH and CH 3 ONa, preferably NaOH.

8. The preparation method according to any one of claims 1 - 7, wherein, In step (2), the second solvent is selected from at least one of methanol, ethanol, and methyl acetate, preferably methanol.

9. The alcoholysis method according to any one of claims 1 - 8, wherein, The molar ratio of the base to the polyvinyl ester is (0.005 - 0.009):

1.

10. The alcoholysis method according to any one of claims 1 - 9, wherein, The conditions of the alcoholysis include: temperature is 20 - 40 °C, and time is 6 - 20 min.