Preparation method of modified polyvinyl alcohol, modified polyvinyl alcohol and application of modified polyvinyl alcohol

Abstract

The invention relates to modified polyvinyl alcohol, in particular to a preparation method of modified polyvinyl alcohol, modified polyvinyl alcohol and application thereof. The preparation method comprises the following steps: S1, mixing a vinyl acetate monomer, methanol, a modifier and an initiator, carrying out a polymerization reaction to obtain a polyvinyl acetate methanol solution, and carrying out purification, alcoholysis and separation to obtain particles; s2, drying the particles to obtain the modified polyvinyl alcohol, wherein the modifying agent is straight chain aldehyde of C2-C3; wherein the drying comprises first-stage drying, second-stage drying and third-stage drying; the temperature of the first-stage drying is 65-80 DEG C; the temperature of the second-stage drying is 85-100 DEG C; and the temperature of the third-stage drying is 110-140 DEG C. Specific modified polyvinyl alcohol is prepared by adopting a synergistic effect of a specific modifier and a drying mode, the variety of the modified polyvinyl alcohol is enriched, and the method can be applied to the field of emulsion polymerization.

Description

Technical Field

[0001] The present invention relates to modified polyvinyl alcohol, and particularly to a preparation method of modified polyvinyl alcohol, modified polyvinyl alcohol and its application. Background Art

[0002] Polyvinyl alcohol can be used to produce fibers and can also be used as sizing agents for chemical fiber fabrics, coatings, adhesives, emulsifiers, paper processing aids, etc. With the continuous development of technology, the demand for functional polyvinyl alcohol with different degrees of polymerization and different degrees of alcoholysis is becoming increasingly urgent. Summary of the Invention

[0003] The purpose of the present invention is to overcome the problem of the single variety of modified polyvinyl alcohol existing in the prior art, and to provide a modified polyvinyl alcohol, its preparation method and application. The modified polyvinyl alcohol includes: polyvinyl alcohol with reactive functional groups, high degree of polymerization and high degree of alcoholysis, so that the modified polyvinyl alcohol can be used as a variety of reaction precursors.

[0004] To achieve the above purpose, the first aspect of the present invention provides a preparation method of modified polyvinyl alcohol, wherein the preparation method includes the following steps:

[0005] S1. Mix vinyl acetate monomer, methanol, modifier and initiator for polymerization reaction to obtain a polyvinyl acetate methanol solution, and then purify, alcoholize and separate to obtain particles;

[0006] S2. Dry the particles to obtain the modified polyvinyl alcohol;

[0007] Wherein, the modifier is a straight-chain aldehyde with C2-C3;

[0008] Wherein, the drying includes primary drying, secondary drying and tertiary drying;

[0009] The conditions of the primary drying include: the temperature of the primary drying is 65-80 °C;

[0010] The conditions of the secondary drying include: the temperature of the secondary drying is 85-100 °C;

[0011] The conditions of the tertiary drying include: the temperature of the tertiary drying is 110-140 °C.

[0012] The second aspect of the present invention provides a modified polyvinyl alcohol prepared by the aforementioned preparation method.

[0013] The third aspect of the present invention provides an application of the aforementioned modified polyvinyl alcohol in emulsion polymerization.

[0014] By the above technical solutions, the following beneficial effects are achieved:

[0015] (1) In the preparation method of the present invention, a specific modifier and a drying method act synergistically to obtain a specific modified polyvinyl alcohol, enriching the types of modified polyvinyl alcohols.

[0016] (2) In the present invention, the modified polyvinyl alcohol can be used as a protective emulsifier system for the polymerization of unsaturated monomers, with a more stable reaction and a more stable system during the polymerization process. Description of the Drawings

[0017] Figure 1 It is the infrared spectrum of the modified polyvinyl alcohol in Example 1 of the present invention. Detailed Embodiments

[0018] 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, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they 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.

[0019] The first aspect of the present invention protects a preparation method of a modified polyvinyl alcohol, wherein the preparation method includes the following steps:

[0020] S1. Mix vinyl acetate monomer, methanol, a modifier, and an initiator for a polymerization reaction to obtain a polyvinyl acetate methanol solution, and then purify, alcoholize, and separate to obtain particles;

[0021] S2. Perform a drying treatment on the particles to obtain the modified polyvinyl alcohol;

[0022] Wherein, the modifier is a straight-chain aldehyde with C2-C3;

[0023] Wherein, the drying includes primary drying, secondary drying, and tertiary drying;

[0024] The conditions for the primary drying include: the temperature of the primary drying is 65-80 °C;

[0025] The conditions for the secondary drying include: the temperature of the secondary drying is 85-100 °C;

[0026] The conditions for the tertiary drying include: the temperature of the tertiary drying is 110-140 °C.

[0027] In the present invention, a specific modifier and a drying method act synergistically, so that the obtained modified polyvinyl alcohol has a higher content of conjugated double bonds, better resin solubility, and less foam during the dissolution process. The appearance of this polyvinyl alcohol resin enriches the types of modified polyvinyl alcohols and provides a reliable guarantee for the stability of the unsaturated monomer copolymerization system.

[0028] In the present invention, during the purification process: adding methanol to the polyvinyl acetate methanol solution multiple times can remove the unreacted vinyl acetate monomer more thoroughly. As a result, the polyvinyl alcohol particles obtained in the subsequent alcoholysis reaction process have a whiter color, consume less lye, and have a lower sodium acetate content in the product. It is preferably added 5 - 10 times, and the unreacted vinyl acetate monomer is blown out by heating to 70 - 80°C. In a particularly preferred embodiment, the weight ratio of the methanol to the polyvinyl acetate methanol solution is 2 - 3:1.

[0029] In the present invention, during the alcoholysis process: adjusting the concentration of the purified polyvinyl acetate solution with methanol; in the new polyvinyl acetate methanol solution, after adjusting the concentration of polyvinyl acetate to 10 - 20 wt%, a water bath treatment is carried out. The conditions of the water bath treatment are that the temperature of the water bath is 30 - 50°C and the time of the water bath is 30 - 60 min; adding sodium hydroxide methanol solution to the solution after the water bath treatment for alcoholysis. The conditions of the alcoholysis are that the temperature of the alcoholysis is 30 - 50°C and the time of the alcoholysis is 10 - 60 min. Among them, in the sodium hydroxide methanol solution, the content of sodium hydroxide is 2.5 - 6.2 wt%.

[0030] In a particularly preferred embodiment of the present invention, azobisisobutyronitrile is added to initiate the polymerization reaction of vinyl acetate; a linear aldehyde is used as a chain transfer agent for end group capping to terminate the polymerization reaction of vinyl acetate; the macromolecular chain is subjected to alcoholysis, and the structure contains an R-CO end group is converted into drying is carried out to cause the elimination of -OH, and finally C=C structure, C=C-C=C structure, and C=C-C=C-C=C structure are obtained.

[0031] In the present invention, a specific drying method can obtain more C=C-C=C structure and C=C-C=C-C=C structure, making the conjugated double bond content in the finally prepared modified polyvinyl alcohol higher, and obtaining a more stable polymerization protection system.

[0032] Furthermore, the conditions of the primary drying include: the temperature of the primary drying is 70 - 75°C, and the time of the primary drying is 0.3 - 1.2 h, preferably 0.5 - 1 h.

[0033] Furthermore, the conditions of the secondary drying include: the temperature of the secondary drying is 90 - 95°C, and the time of the secondary drying is 0.3 - 1.2 h, preferably 0.5 - 1 h.

[0034] Furthermore, the conditions of the tertiary drying include: the temperature of the tertiary drying is 120 - 130°C, and the time of the tertiary drying is 1 - 3.5 h, preferably 1.5 - 3 h.

[0035] According to the present invention, in S1, relative to 100 parts by weight of vinyl acetate monomer, the methanol is 3-19 parts by weight, the modifier is 1-2.4 parts by weight, and the initiator is 0.005-0.014 parts by weight.

[0036] In the present invention, when the amounts of vinyl acetate monomer, methanol, modifier and initiator meet the above ranges, a polyvinyl alcohol resin containing conjugated double bonds can be obtained, so that the reaction system is more stable and controllable when used for the polymerization of unsaturated monomers, and a more stable polymerization protection system is obtained.

[0037] Furthermore, relative to 100 parts by weight of vinyl acetate monomer, the methanol is 5-18 parts by weight, the modifier is 1.2-2.2 parts by weight, and the initiator is 0.008-0.012 parts by weight.

[0038] In the present invention, in S1, the polymerization reaction is carried out in a reactor.

[0039] According to the present invention, the conditions of the polymerization reaction include: the polymerization reaction temperature is 60-64° C., and the polymerization reaction time is 4-8 hours.

[0040] In the present invention, when the polymerization reaction conditions can meet the above range, a polyvinyl alcohol resin containing conjugated double bonds can be obtained; when it is used for the polymerization of unsaturated monomers, the reaction system is more stable and controllable, and a more stable polymerization protection system is obtained.

[0041] Furthermore, the conditions of the polymerization reaction include: the polymerization reaction temperature is 61-63° C.; the polymerization reaction time is 5-7 hours.

[0042] The second aspect of the present invention provides a modified polyvinyl alcohol prepared by the above-mentioned preparation method.

[0043] According to the present invention, the macromolecular main chain of the modified polyvinyl alcohol contains C=C structure, C=CC=C structure and C=CC=CC=C structure.

[0044] In the present invention, the polyvinyl alcohol in the modified polyvinyl alcohol includes a specific content of reactive functional groups, thereby enriching the types of modified polyvinyl alcohol.

[0045] According to the present invention, the degree of polymerization of the modified polyvinyl alcohol is 1000-2500, preferably 1100-2400.

[0046] According to the present invention, the end-capping group of the main chain of the macromolecule is R-CO-; wherein R is selected from -CH 2 CH 3 or -CH 3 .

[0047] According to the present invention, the degree of alcoholysis of the polyvinyl alcohol is 85-99.9%, preferably 86-99%.

[0048] According to the present invention, for the polyvinyl alcohol, the ultraviolet absorption value at 215 nm is 0.05-0.25, the ultraviolet absorption value at 280 nm is 0.1-0.4, and the ultraviolet absorption value at 320 nm is 0.08-0.35.

[0049] Furthermore, for the polyvinyl alcohol, the ultraviolet absorption value at 215 nm is 0.06-0.22, the ultraviolet absorption value at 280 nm is 0.12-0.36, and the ultraviolet absorption value at 320 nm is 0.1-0.32.

[0050] According to the present invention, at 90 °C, the modified polyvinyl alcohol is formulated into an aqueous polyvinyl alcohol solution with a concentration of 4 wt%, and the viscosity of the 4 wt% aqueous polyvinyl alcohol solution is 10-60 mPa·s, preferably 12-58 mPa·s.

[0051] The third aspect of the present invention provides an application of the aforementioned modified polyvinyl alcohol in emulsion polymerization.

[0052] The present invention will be described in detail below through examples.

[0053] Test method for the degree of polymerization of polyvinyl alcohol: The test is carried out in accordance with the provisions of GB / T12010.5-2010.

[0054] Test method for the degree of alcoholysis of polyvinyl alcohol: The test is carried out in accordance with the provisions in Appendix D of GB / T12010.2-2010.

[0055] Test method for the ultraviolet absorption value of polyvinyl alcohol: Using an ultraviolet / visible spectrometer UV-3700 (Shimadzu, Japan), with a solution concentration of 0.1%, ultraviolet absorption tests are carried out, and the ultraviolet absorption values at 215 nm, 280 nm, and 320 nm are respectively measured.

[0056] Test method for the viscosity of polyvinyl alcohol: The test is carried out using a Brookfield viscometer in accordance with the provisions in Appendix E of GB / T12010.2-2010, and the test temperature is 20 °C.

[0057] Vinyl acetate, methanol, acetaldehyde, and azobisisobutyronitrile (AIBN) are all commercially available products.

[0058] Example 1

[0059] S1. Polymerization reaction

[0060] Add 100 parts by weight of vinyl acetate, 5 parts by weight of methanol, 2.2 parts by weight of acetaldehyde, and 0.008 parts by weight of azobisisobutyronitrile to a reaction kettle for polymerization reaction. The temperature of the polymerization reaction is 64 °C, and the time of the polymerization reaction is 8 h;

[0061] Purification:

[0062] Add 300 parts by weight of methanol to the polyvinyl acetate methanol solution in 5 portions, heat up to 70 °C to blow out the unreacted vinyl acetate for purification;

[0063] Alcoholysis:

[0064] Add methanol to the partially purified polyvinyl acetate solution to prepare a new polyvinyl acetate methanol solution. In the new polyvinyl acetate methanol solution, the concentration of polyvinyl acetate is 10 wt%, perform a water bath treatment. The temperature of the water bath is 50 °C, and the time of the water bath is 30 min. Add 0.46 parts by weight of sodium hydroxide methanol solution (the content of sodium hydroxide is 6.2 wt%) to the solution after the water bath treatment for alcoholysis. The temperature of the alcoholysis is 50 °C, and the time of the alcoholysis is 60 min; add 0.035 parts by weight of acetic acid to terminate the reaction;

[0065] Separation:

[0066] Use a centrifuge to separate the polyvinyl alcohol after alcoholysis to obtain polyvinyl alcohol pretreatment particles;

[0067] S2. Drying treatment

[0068] Dry the obtained polyvinyl alcohol pretreatment particles. The temperature of the first-stage drying is 70 °C, and the time of the first-stage drying is 0.5 h; the temperature of the second-stage drying is 85 °C, and the time of the second-stage drying is 1 h; the temperature of the third-stage drying is 130 °C, and the time of the third-stage drying is 3 h to obtain modified polyvinyl alcohol A1;

[0069] Figure 1 is the infrared spectrum of the modified polyvinyl alcohol prepared in Example 1. It can be seen from the figure that: at 3228 cm -1 is the stretching vibration peak of -OH, and at 2922 cm -1 is the stretching vibration peak of -CH, and at 2854 cm -1 is the stretching vibration peak of -CH=CH, and at 1731 cm -1 is the stretching vibration peak of -OOCCH 3 ; Figure 1 It can prove that the synthesized product is polyvinyl alcohol.

[0070] Example 2

[0071] In the same manner as in Example 1, except that in S1, "1.6 parts by weight of acetaldehyde" is used to replace "2.2 parts by weight of acetaldehyde", to obtain modified polyvinyl alcohol A2.

[0072] Example 3

[0073] In the same manner as in Example 1, except that in S1, "1 part by weight of propionaldehyde" is used to replace "2.2 parts by weight of acetaldehyde", to obtain modified polyvinyl alcohol A3.

[0074] Example 4

[0075] In the same manner as in Example 1, except that in S2, "the temperature of the first-stage drying is 65°C and the time of the first-stage drying is 0.5 h" is used to replace "the temperature of the first-stage drying is 70°C and the time of the first-stage drying is 0.5 h", to obtain modified polyvinyl alcohol A4.

[0076] Example 5

[0077] In the same manner as in Example 1, except that in S2, "the temperature of the second-stage drying is 80°C and the time of the second-stage drying is 1 h" is used to replace "the temperature of the second-stage drying is 85°C and the time of the second-stage drying is 1 h", to obtain modified polyvinyl alcohol A5.

[0078] Example 6

[0079] In the same manner as in Example 1, except that in S2, "the temperature of the third-stage drying is 110°C and the time of the third-stage drying is 3.5 h" is used to replace "the temperature of the third-stage drying is 130°C and the time of the third-stage drying is 3 h", to obtain modified polyvinyl alcohol A6.

[0080] Example 7

[0081] In the same manner as in Example 1, except that "1.0 part by weight of acetaldehyde" is used to replace "2.2 parts by weight of acetaldehyde" and "the temperature of the first-stage drying is 80°C and the time of the first-stage drying is 1 h" is used to replace "the temperature of the first-stage drying is 70°C and the time of the first-stage drying is 0.5 h", to obtain modified polyvinyl alcohol A7.

[0082] Example 8

[0083] In the same manner as in Example 1, except that "the temperature of drying is 130°C and the time of drying is 3.5 h" is used to replace "the third-stage drying", to obtain modified polyvinyl alcohol A8.

[0084] Comparative Example 1

[0085] In the same manner as in Example 1, except that no modifier is added, to obtain modified polyvinyl alcohol D1.

[0086] Comparative Example 2

[0087] In the same manner as in Example 1, except that the three-stage drying is not carried out, modified polyvinyl alcohol D2 is obtained.

[0088] The modified polyvinyl alcohols obtained in the examples and comparative examples were tested, and the results are shown in Table 1.

[0089] Table 1

[0090]

[0091] It can be seen from the results in Table 1 that the modified polyvinyl alcohol in the present invention includes a specific content of reactive functional groups and has a relatively high degree of polymerization.

[0092] Comparing Example 1, Example 2, and Example 3, it can be known that different types of linear aldehydes result in different structures in the structure shown in formula (1), enriching the types of modified polyvinyl alcohols and affecting their viscosities, further affecting their applications in emulsion polymerization.

[0093] Comparing Example 1, Example 4, Example 5, and Example 6, it can be concluded that the change in three-stage drying will affect the content of double bonds in the final modified polyvinyl alcohol, which can be ensured by the value of ultraviolet absorption.

[0094] Comparing Example 1 with Comparative Example 1, it can be known that in the modified polyvinyl alcohol modified by the modifier, the degree of polymerization is smaller, the viscosity is lower, and the ultraviolet absorption value is larger.

[0095] Comparing Example 1 with Example 7, it can be known that the modifier and the drying conditions act synergistically to jointly affect the degree of polymerization, degree of alcoholysis, viscosity, and ultraviolet absorption of polyvinyl alcohol.

[0096] 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 preparation method of modified polyvinyl alcohol, characterized in that, the preparation method comprises the following steps: S1. Mix vinyl acetate monomer, methanol, modifier and initiator for polymerization reaction to obtain a polyvinyl acetate methanol solution, then purify, alcoholize and separate to obtain particles; S2. Dry the particles to obtain the modified polyvinyl alcohol; Among them, the modifier is C 2 -C 3 linear aldehyde; wherein, the drying includes primary drying, secondary drying and tertiary drying; the conditions of the primary drying include: the temperature of the primary drying is 65 - 80 °C; the conditions of the secondary drying include: the temperature of the secondary drying is 85 - 100 °C; the conditions of the tertiary drying include: the temperature of the tertiary drying is 110 - 140 °C.

2. The preparation method according to claim 1, wherein, the conditions of the primary drying include: the temperature of the primary drying is 70 - 75 °C; the time of the primary drying is 0.3 - 1.2 h, preferably 0.5 - 1 h; preferably, the conditions of the secondary drying include: the temperature of the secondary drying is 90 - 95 °C; the time of the secondary drying is 0.3 - 1.2 h, preferably 0.5 - 1 h; preferably, the conditions of the tertiary drying include: the temperature of the tertiary drying is 120 - 130 °C; the time of the tertiary drying is 1 - 3.5 h, preferably 1.5 - 3 h.

3. The preparation method according to claim 1 or 2, wherein, in S1, relative to 100 parts by weight of vinyl acetate monomer, the methanol is 3 - 19 parts by weight, the modifier is 1 - 2.4 parts by weight, and the initiator is 0.005 - 0.014 parts by weight; preferably, relative to 100 parts by weight of vinyl acetate monomer, the methanol is 5 - 18 parts by weight, the modifier is 1.2 - 2.2 parts by weight, and the initiator is 0.008 - 0.012 parts by weight.

4. The preparation method according to any one of claims 1 - 3, wherein, the conditions of the polymerization reaction include: the temperature of the polymerization reaction is 60 - 64 °C, preferably 61 - 63 °C; the time of the polymerization reaction is 4 - 8 h, preferably 5 - 7 h.

5. Modified polyvinyl alcohol prepared by the preparation method according to any one of claims 1 - 4.

6. The modified polyvinyl alcohol according to claim 5, wherein, in the macromolecular main chain of the modified polyvinyl alcohol, there are C=C structures, C=C - C=C structures and C=C - C=C - C=C structures; preferably, the degree of polymerization of the modified polyvinyl alcohol is 1000 - 2500, preferably 1100 - 2400.

7. The modified polyvinyl alcohol according to claim 5 or 6, wherein, The end group of the macromolecular main chain is R-CO-; wherein, R is selected from -CH 2 CH 3 or -CH 3 ; preferably, the degree of alcoholysis of the polyvinyl alcohol is 85 - 99.9%, preferably 6 - 99%.

8. The modified polyvinyl alcohol according to any one of claims 5 - 7, wherein, for the polyvinyl alcohol, the ultraviolet absorption value at 215 nm is 0.05 - 0.25, the ultraviolet absorption value at 280 nm is 0.1 - 0.4, and the ultraviolet absorption value at 320 nm is 0.08 - 0.35; Preferably, the ultraviolet absorption value of the polyvinyl alcohol at 215 nm is 0.06 - 0.22, the ultraviolet absorption value at 280 nm is 0.12 - 0.36, and the ultraviolet absorption value at 320 nm is 0.1 - 0.

32.

9. The modified polyvinyl alcohol according to any one of claims 5 - 8, at 90 °C, the modified polyvinyl alcohol is configured into an aqueous polyvinyl alcohol solution with a concentration of 4 wt%, and the viscosity of the 4 wt% aqueous polyvinyl alcohol solution is 10 - 60 mPa·s, preferably 12 - 58 mPa·s.

10. Application of the modified polyvinyl alcohol according to any one of claims 5 - 9 in emulsion polymerization.

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