Polyvinyl alcohol derivative with ultraviolet protection performance and high transparency and polyvinyl alcohol film

Abstract

The invention relates to a polyvinyl alcohol derivative with ultraviolet protection performance and high transparency and a polyvinyl alcohol-based film. The invention also relates to a preparation method of the polyvinyl alcohol derivative and the polyvinyl alcohol film. The polyvinyl alcohol is modified and endowed with intrinsic ultraviolet protection performance, so that the polyvinyl alcohol derivative with the intrinsic ultraviolet protection performance is obtained, and the polyvinyl alcohol film obtained by utilizing the polyvinyl alcohol derivative has the ultraviolet protection performance and high transparency.

Description

Technical Field

[0001] The invention relates to polyvinyl alcohol derivatives and polyvinyl alcohol films with ultraviolet protection performance and high transparency, belonging to the field of polymer materials. Background Art

[0002] Film materials with UV protection properties play an important role in many key areas, including polymer aging protection and human health. Polyvinyl alcohol (PVA) is a hydrophilic and environmentally friendly polymer that is widely used as a base material for transparent films due to its excellent film-forming properties. However, PVA itself does not have UV protection properties, which limits its wide application in aerospace, food packaging, building and home furnishing, car film and other fields.

[0003] In order to enhance the ultraviolet protection performance of PVA film, a known method is to add ultraviolet absorbers. For example, Patent Document 1 (CN1222442A) discloses a polyvinyl alcohol film containing a water-soluble ultraviolet absorber having a solubility of 0.01 to 10 parts by weight in 100 parts by weight of water at 25°C.

[0004] In addition, methods of adding inorganic nanomaterials are also known. For example, Patent Document 2 (CN102504454A) discloses an anti-ultraviolet polyvinyl alcohol fruit bag film, which contains inorganic ultraviolet shielding agents such as nano titanium dioxide and nano zinc dioxide.

[0005] References:

[0006] Patent document 1: CN1222442A

[0007] Patent document 2: CN102504454A. Summary of the invention

[0008] Problem that the invention aims to solve

[0009] The polyvinyl alcohol film obtained by adding a water-soluble ultraviolet absorber in Patent Document 1 still has the problem of ultraviolet absorber precipitation when kept for a long time. The method of adding inorganic nanomaterials in Patent Document 2 has the problem of not being able to take into account both high light transmittance and high ultraviolet protection performance, and the compatibility of inorganic nanomaterials with polymer substrates is poor, and there are also potential health and environmental risks.

[0010] Therefore, the applicability of the existing technical solutions is limited to a certain extent, especially for UV protection scenarios that require high light transmittance. Therefore, there is still an urgent need to develop a polyvinyl alcohol film that has both high light transmittance and intrinsic UV protection performance.

[0011] Solutions for solving problems

[0012] In view of the above problems in the prior art, the present inventors have conducted long-term and in-depth research, and proposed to modify and modify PVA to endow it with intrinsic ultraviolet protection performance, so as to obtain a polyvinyl alcohol derivative with intrinsic ultraviolet protection performance. Using this polyvinyl alcohol derivative, a polyvinyl alcohol-based film with both ultraviolet protection performance and high light transmittance can be obtained.

[0013] Specifically, the present invention solves the problems of the present invention through the following solutions.

[0014] [1] A polyvinyl alcohol derivative, which comprises a structural unit A represented by formula I, a structural unit B represented by formula II, and a structural unit C represented by formula III,

[0015]

[0016] In formula III, R1 is a hydrogen atom or NR 0 R 00 , where R 0 and R 00 each independently selected from methyl, ethyl, propyl, isopropyl, butyl, phenyl, methylphenyl; R2 and R3 are each independently selected from a hydrogen atom, methyl, ethyl, propyl, isopropyl, butyl, phenyl;

[0017] The molar ratio of the structural unit A, the structural unit B to the structural unit C is (1-98):(1-12):(1-98); preferably (58-98):(1-12):(1-30); more preferably (78-98):(1-12):(1-10).

[0018] [2] The polyvinyl alcohol derivative according to [1], wherein R1 in formula III is a hydrogen atom, N,N-dimethyl, N-methyl-N-phenyl or N,N-diphenyl; R2 and R3 are each independently selected from a hydrogen atom, methyl, ethyl, propyl, preferably R2 and R3 are each independently selected from methyl and ethyl.

[0019] [3] A method for preparing the polyvinyl alcohol derivative according to [1] or [2], which comprises the following steps:

[0020] (1) Reacting polyvinyl alcohol with diketene to obtain an intermediate product-I containing a β-diketone structure;

[0021] (2) Performing a Hantzsch reaction on the intermediate product-I, an aldehyde compound, an ammonia source compound and a 1,3-diketone compound; wherein, the aldehyde compound is an aromatic aldehyde, the 1,3-diketone compound is a compound containing a 1,3-diketone structure, preferably a compound containing a 1,3-cyclohexanedione structure, and the ammonia source compound is an ammonium salt or ammonia, preferably one or more selected from ammonium acetate, ammonium carbonate and ammonia.

[0022] [4] According to the preparation method described in [3], wherein step (1) is carried out in an organic solvent, and the organic solvent is preferably a polar aprotic solvent, preferably one or more selected from N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), and N,N-dimethylformamide (DMF);

[0023] Preferably, the degree of polymerization of the polyvinyl alcohol is 300 to 3000, and the degree of alcoholysis is 88 to 99 mol%;

[0024] Preferably, the molar ratio of the hydroxyl group in the polyvinyl alcohol to diketene is 1:(0.01 to 1), preferably 1:(0.03 to 0.3);

[0025] Preferably, the reaction temperature of step (1) is 20 to 40°C, preferably 25 to 35°C; the reaction time is 1 to 3 hours, preferably 1 to 2.5 hours.

[0026] [5] According to the preparation method described in [3], wherein in step (2), the molar ratio of the aldehyde compound, the ammonia source compound to the 1,3-diketone compound is 1:(1 to 2):1, preferably 1:(1.1 to 1.6):1; the molar ratio of the aldehyde compound to the diketene in step (1) is (1 to 2):1, preferably (1.1 to 1.6):1;

[0027] Preferably, the Hantzsch reaction is carried out in the presence of a catalyst, and the catalyst is preferably an acid, more preferably one or more selected from amino acids and phenylboronic acid, and the amino acid is preferably glycine and / or proline; preferably, the molar ratio of the catalyst to the aldehyde compound is (0.05 to 0.2):1, preferably (0.09 to 0.16):1;

[0028] Preferably, the reaction temperature of the Hantzsch reaction is 70 to 85°C, preferably 70 to 80°C; the reaction time is 2 to 5 hours, preferably 2 to 4 hours.

[0029] [6] A polyvinyl alcohol-based membrane, which comprises the polyvinyl alcohol derivative described in claim 1 or 2.

[0030] [7] According to the polyvinyl alcohol-based membrane described in [6], wherein the ultraviolet shielding rate is more than 95%, and the visible light transmittance is more than 70%.

[0031] [8] A method for preparing a polyvinyl alcohol-based membrane, which comprises the following steps:

[0032] (a) Spreading a film-forming solution containing the polyvinyl alcohol derivative described in [1] or [2] on a film-forming substrate to obtain a coating film;

[0033] (b) Dry the coating film.

[0034] [9] The preparation method according to [8], wherein, in step (a), the content of the polyvinyl alcohol derivative in the film-forming solution is 1 to 30% by mass, preferably 5 to 10% by mass; the film-forming solution contains water and optionally contains an organic solvent. Preferably, the volume ratio of the organic solvent to water is (0 to 75):(25 to 100), and more preferably the film-forming solution does not contain an organic solvent.

[0035]

[10] The use of the polyvinyl alcohol derivative according to [1] or [2] or the polyvinyl alcohol-based film according to [6] or [7] for ultraviolet protection, especially for packaging materials, glass films, coatings.

[0036] Effects of the invention

[0037] The polyvinyl alcohol derivative of the present invention has intrinsic ultraviolet protection performance, does not have the problem of precipitation of ultraviolet absorbers, and does not have an adverse effect on the light transmittance of the film.

[0038] Using the polyvinyl alcohol derivative of the present invention, it is possible to greenly and environmentally construct a polyvinyl alcohol-based film material with both high light transmittance and intrinsic ultraviolet protection performance without adding other ultraviolet absorbers, which is of great significance for promoting the development of fields such as the food packaging industry, cultural relic protection, building and home furnishing, automotive films, and aerospace.

[0039] The preparation method of the polyvinyl alcohol derivative of the present invention utilizes the multi-component characteristics of the Hantzsch reaction to quickly and efficiently introduce ultraviolet absorption groups into the PVA polymer structure, and combines the property of the Hantzsch product itself absorbing ultraviolet rays to endow the PVA derivative with the ability to absorb ultraviolet rays in the full wavelength range, and a PVA derivative with intrinsic ultraviolet protection ability is prepared. The preparation method of the polyvinyl alcohol derivative of the present invention has a simple and efficient process and is suitable for large-scale preparation. Description of the drawings

[0040] Figure 1 1H-NMR spectrum of the PVA derivative P1 obtained in Example 1; 1 1H-NMR spectrum;

[0041] Figure 2 1H-NMR spectrum of the PVA derivative P2 obtained in Example 2; 1 1H-NMR spectrum;

[0042] Figure 3 1H-NMR spectrum of the PVA derivative P3 obtained in Example 3; 1 1H-NMR spectrum;

[0043] Figure 4For the PVA derivative P4 obtained in Example 4 1 1H-NMR spectrum;

[0044] Figure 5 For the photos in the visual observation evaluation;

[0045] Figure 6 For the infrared spectra of the polyvinyl alcohol membranes - I and polyvinyl alcohol membranes - C obtained in Example 5;

[0046] Figures 7 - 9 For the ultraviolet - visible absorption spectra of the aqueous solutions of the PVA derivatives P1 - P4 obtained in Examples 1 - 4 respectively;

[0047] Figure 10 For the ultraviolet - visible absorption spectra of the polyvinyl alcohol membranes - I and polyvinyl alcohol membranes - C obtained in Example 5, and four commercial ultraviolet protection films. Detailed implementation manners

[0048] Hereinafter, the content of the present invention will be described in detail. The description of the technical features recorded below is based on the representative embodiments and specific examples of the present invention, but the present invention is not limited to these embodiments and specific examples.

[0049] <Terms and definitions>

[0050] In this specification, the "ultraviolet protection" performance refers to the performance of protecting the object to be protected from ultraviolet damage, where ultraviolet rays refer to the radiation with wavelengths below 400 nm (such as 10 - 400 nm or 290 - 400 nm) in the wavelength electromagnetic spectrum.

[0051] In this specification, the numerical range expressed by "numerical value A - numerical value B" refers to the range including the end - point numerical values A and B.

[0052] In this specification, the numerical range expressed by "above" or "below" refers to the numerical range including this number.

[0053] In this specification, the meaning expressed by "can" includes both the meaning of performing a certain treatment and the meaning of not performing a certain treatment.

[0054] In this specification, the use of "optionally" or "optional" means that certain substances, components, execution steps, applied conditions, etc. are used or not used.

[0055] In this specification, the unit names used are all international standard unit names, and unless otherwise specified, the "%" used represents weight or mass percentage.

[0056] In this specification, "preferred embodiments", "embodiments", etc. refer to the specific elements (e.g., features, structures, properties, and / or characteristics) described in connection with such embodiments, which are included in at least one of the embodiments described herein and may or may not be present in other embodiments. Additionally, it should be understood that the elements may be combined in any suitable manner in various embodiments.

[0057] <Polyvinyl alcohol derivative>

[0058] An object of the present invention is to provide a polyvinyl alcohol derivative, which comprises a structural unit A represented by Formula I, a structural unit B represented by Formula II, and a structural unit C represented by Formula III.

[0059]

[0060] The structural unit A represented by Formula I is a vinyl alcohol structural unit. Based on the total molar number of the structural units of the polyvinyl alcohol derivative, the content of the structural unit A is 1 to 98 mol%, preferably 58 to 98 mol%, more preferably 78 to 98 mol%.

[0061] The structural unit B represented by Formula II is a vinyl acetate structural unit. Based on the total molar number of the structural units of the polyvinyl alcohol derivative, the content of the structural unit B is 1 to 12 mol%, preferably 1 to 10 mol%, more preferably 1 to 5 mol%.

[0062] The structural unit C represented by Formula III is a modified unit having a 1,4-dihydropyridine structure, and the structural unit C imparts ultraviolet protection performance to the polyvinyl alcohol derivative of the present invention. Based on the total molar number of the structural units of the polyvinyl alcohol derivative, the content of the structural unit C is 1 to 98 mol%, preferably 1 to 30 mol%, more preferably 1 to 10 mol%.

[0063] In Formula III, R1 is a hydrogen atom or NR 0 R 00 , where R 0 and R 00 are each independently selected from methyl, ethyl, propyl, isopropyl, butyl, phenyl, methylphenyl; preferably, R1 is a hydrogen atom, N,N-dimethyl, N-methyl-N-phenyl, or N,N-diphenyl.

[0064] In Formula III, R2 and R3 are each independently selected from a hydrogen atom, methyl, ethyl, propyl, isopropyl, butyl, phenyl; preferably, R2 and R3 are each independently selected from a hydrogen atom, methyl, ethyl, propyl; more preferably, R2 and R3 are each independently selected from methyl and ethyl; most preferably, both R2 and R3 are methyl.

[0065] In one embodiment, the molar ratio of structural unit A, structural unit B and structural unit C is (1-98):(1-12):(1-98); preferably (58-98):(1-12):(1-30); more preferably (78-98):(1-12):(1-10).

[0066] In one embodiment, the degree of polymerization of the polyvinyl alcohol derivative is 300-3000, preferably 400-2000, more preferably 500-1700.

[0067] In one embodiment, the polyvinyl alcohol derivative further has other structural units, such as structural units having a 1,2-diol structure. The molar content of other structures is 2% or less, preferably 1% or less, more preferably 0.5% or less.

[0068] <Preparation method of polyvinyl alcohol derivative>

[0069] An object of the present invention is to provide a preparation method of the polyvinyl alcohol derivative of the present invention, which comprises the following steps:

[0070] (1) React polyvinyl alcohol with diketene to obtain intermediate-I containing a β-diketone structure;

[0071] (2) Perform a Hantzsch reaction on intermediate-I, an aldehyde compound, an ammonia source compound and a 1,3-diketone compound; wherein, the aldehyde compound is an aromatic aldehyde, the 1,3-diketone compound is a compound containing a 1,3-diketone structure, preferably a compound containing a 1,3-cyclohexanedione structure, and the ammonia source compound is an ammonium salt or ammonia, preferably one or more selected from ammonium acetate (CH3COONH4), ammonium carbonate ((NH4)2CO3) and ammonia (NH3).

[0072] In one embodiment, the preparation method of the polyvinyl alcohol derivative of the present invention further comprises the following steps:

[0073] (3) Separate the polyvinyl alcohol derivative of the present invention from the reaction system obtained in step (2).

[0074] The preparation method of the present invention utilizes the multi-component characteristics of the Hantzsch reaction to quickly and efficiently introduce ultraviolet absorption groups into the PVA polymer structure, and combines the property of the Hantzsch product itself absorbing ultraviolet rays to endow the PVA derivative with the ability to absorb ultraviolet rays in the whole wavelength range, thereby obtaining a PVA derivative with intrinsic ultraviolet protection performance.

[0075] The following separately describes in detail each step of the preparation method of the polyvinyl alcohol derivative of the present invention.

[0076] Step (1)

[0077] In step (1), the hydroxyl group in the vinyl alcohol structural unit of polyvinyl alcohol reacts with diketene, converting the hydroxyl group into a β-diketone structure, thereby obtaining intermediate-I having a β-diketone structure in the side chain.

[0078] In step (1), there is no particular limitation on the polyvinyl alcohol used. It generally contains vinyl alcohol structural units and vinyl acetate structural units, and optionally other structural units such as structural units having a 1,2-diol structure.

[0079] Preferably, the degree of polymerization of the polyvinyl alcohol is 300 to 3000, preferably 400 to 2000, and more preferably 500 to 1700.

[0080] Preferably, the degree of alcoholysis of the polyvinyl alcohol is 88 to 99 mol%.

[0081] In one embodiment, commercially available polyvinyl alcohol can be used, such as PVA0588, PVA1788, PVA1799, etc.

[0082] Preferably, the molar ratio of the hydroxyl group in polyvinyl alcohol to diketene is 1:(0.01 to 1), preferably 1:(0.03 to 0.3).

[0083] In one embodiment, the reaction of step (1) is as follows:

[0084]

[0085] wherein i is the mole fraction of vinyl alcohol structural units in polyvinyl alcohol, and j is the mole fraction of structural units having a β-diketone structure in intermediate-I.

[0086] In one embodiment, the reaction of step (1) is carried out in an organic solvent. More specifically, the reaction of step (1) is carried out by adding diketene to a polyvinyl alcohol solution, wherein the polyvinyl alcohol solution contains an organic solvent.

[0087] Preferably, the above organic solvent is a polar aprotic solvent, preferably one or more selected from N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), and N,N-dimethylformamide (DMF).

[0088] Preferably, the reaction temperature of step (1) is 20 to 40 °C, preferably 25 to 35 °C.

[0089] Preferably, the reaction time of step (1) is 1 to 3 hours, preferably 1 to 2.5 hours.

[0090] Step (2)

[0091] In step (2), the intermediate - I, an aldehyde compound, an ammonia source compound and a 1,3 - diketone compound are subjected to a Hantzsch reaction, so that the structural unit containing a β - diketone structure in the intermediate - I is converted into a structural unit containing a 1,4 - dihydropyridine structure.

[0092] The aldehyde compound is an aromatic aldehyde, preferably having the structure shown by the following formula (1),

[0093]

[0094] wherein R1 has one of the meanings given by the context.

[0095] In one embodiment, the aldehyde compound is one or more selected from benzaldehyde, p - dimethylaminobenzaldehyde, 4 - [methyl(phenyl)amino]benzaldehyde, 4 - diphenylaminobenzaldehyde, 4 - methylbenzaldehyde, 4 - ethylbenzaldehyde, 4 - hydroxybenzaldehyde, 3,4 - dimethoxybenzaldehyde.

[0096] The 1,3 - diketone compound is a compound containing a 1,3 - diketone structure, and the 1,3 - diketone structure is preferably a 1,3 - cyclohexanedione structure. More preferably, the 1,3 - diketone compound has the structure shown by the following formula (2),

[0097]

[0098] wherein R2 and R3 have one of the meanings given by the context.

[0099] In a specific embodiment, the 1,3 - diketone compound is one or more selected from 5,5 - dimethyl - 1,3 - cyclohexanedione, 5,5 - diethyl - 1,3 - cyclohexanedione, 5 - methyl - 5 - ethyl - 1,3 - cyclohexanedione, 5 - methyl - 1,3 - cyclohexanedione, 1,3 - cyclohexanedione, 5 - phenyl - 1,3 - cyclohexanedione.

[0100] The ammonia source compound is an ammonium salt or ammonia, preferably one or more selected from ammonium acetate (CH3COONH4), ammonium carbonate ((NH4)2CO3) and ammonia (NH3).

[0101] In one embodiment, in step (2), the molar ratio of the aldehyde compound, the ammonia source compound to the 1,3 - diketone compound is 1:(1 - 2):1, preferably 1:(1.1 - 1.6):1.

[0102] In one embodiment, the molar ratio of the aldehyde compound to diketene in step (1) is (1 - 2):1, preferably (1.1 - 1.6):1.

[0103] In one embodiment, step (2) is carried out by adding an aldehyde compound, an ammonia source compound, and a 1,3-diketone compound to the reaction system obtained in step (1). That is, after step (1), no operations such as separation and purification of the reaction system are carried out, but instead an aldehyde compound, an ammonia source compound, and a 1,3-diketone compound are directly added to carry out the Hantzsch reaction. Therefore, the two-step reaction in the preparation method of the present invention can be carried out in one pot without an intermediate purification step, thus simplifying the preparation method.

[0104] Preferably, the Hantzsch reaction is carried out in the presence of a catalyst, and the catalyst is preferably an acidic catalyst, such as a weakly acidic catalyst, and more preferably one or more selected from amino acids and phenylboronic acid. The amino acid is preferably glycine and / or proline.

[0105] Preferably, the molar ratio of the catalyst to the aldehyde compound in the feed is (0.05 - 0.2):1, preferably (0.09 - 0.16):1.

[0106] In one embodiment, the reaction temperature of the Hantzsch reaction is 70 - 85 °C, preferably 70 - 80 °C.

[0107] In one embodiment, the reaction time of the Hantzsch reaction is 2 - 5 hours, preferably 2 - 4 hours.

[0108] In a specific embodiment, the preparation method of the polyvinyl alcohol derivative of the present invention is carried out according to the following reaction formula:

[0109]

[0110] Wherein i and j have the meanings given above.

[0111] Step (3)

[0112] In step (3), the polyvinyl alcohol derivative of the present invention is separated from the reaction system obtained in step (2).

[0113] In one embodiment, by mixing the reaction system obtained in step (2) with a poor solvent of the polyvinyl alcohol derivative, the polyvinyl alcohol derivative is precipitated, and then it is separated by filtration. The poor solvent of the polyvinyl alcohol derivative is, for example, one or more selected from acetone, methanol, ethanol, and / or acetonitrile.

[0114] In one embodiment, step (3) further includes drying the separated polyvinyl alcohol derivative. Preferably, the drying temperature is 25 to 80 °C, more preferably 40 to 80 °C. Preferably, the drying time is 12 to 48 hours, more preferably 12 to 36 hours.

[0115] <Polyvinyl alcohol-based film>

[0116] One object of the present invention is to provide a polyvinyl alcohol-based film containing the polyvinyl alcohol derivative of the present invention.

[0117] In one embodiment, based on the mass of the polyvinyl alcohol-based film, the content of the polyvinyl alcohol derivative of the present invention is 50% or more, preferably 60% or more, more preferably 70% or more, particularly preferably 80% or more, further preferably 90% or more, and most preferably 95% or more.

[0118] In one embodiment, the polyvinyl alcohol-based film of the present invention may further contain one or more selected from polyvinyl alcohol and other polyvinyl alcohol derivatives.

[0119] In one embodiment, the polyvinyl alcohol-based film may further contain common additives in the art, such as plasticizers, surfactants, pigments, dyes, antioxidants, etc.

[0120] Based on the total mass of the polyvinyl alcohol-based film, the content of the additive is 10% or less, preferably 5% or less, more preferably 3% or less, further preferably 2% or less, and most preferably 1% or less.

[0121] The polyvinyl alcohol-based film of the present invention has excellent ultraviolet protection performance and transparency.

[0122] In one embodiment, the ultraviolet shielding rate of the polyvinyl alcohol-based film of the present invention is 95% or more, preferably 96% or more, more preferably 97% or more, further preferably 98% or more, and most preferably 98.5% or more.

[0123] Among them, the ultraviolet shielding rate can be calculated according to the following formula based on the ultraviolet-visible absorption spectrum of the polyvinyl alcohol-based film:

[0124]

[0125] Among them, T is the ultraviolet-visible light transmittance, and λ is the wavelength.

[0126] In one embodiment, the visible light transmittance of the polyvinyl alcohol-based film of the present invention is 70% or more, preferably 75% or more, more preferably 80% or more, further preferably 83% or more, and most preferably 85% or more.

[0127] Among them, the visible light transmittance can be calculated based on the ultraviolet-visible absorption spectrum of the polyvinyl alcohol-based film according to the following formula:

[0128]

[0129] Among them, T is the ultraviolet-visible light transmittance, and λ is the wavelength.

[0130] <Preparation method of polyvinyl alcohol-based film>

[0131] An object of the present invention is to provide a preparation method of a polyvinyl alcohol-based film, which includes the following steps:

[0132] (a) Spreading a film-forming solution containing the polyvinyl alcohol derivative of the present invention on a film-forming substrate to obtain a coated film;

[0133] (b) Drying the coated film to obtain the polyvinyl alcohol-based film of the present invention.

[0134] Step (a)

[0135] Step (a) is a film-forming step, in which the film-forming solution is spread on the film-forming substrate to obtain a coated film.

[0136] In step (a), known film-forming methods in the art, such as casting, spin coating, knife coating, printing and other methods, can be used to spread the film-forming solution on the film-forming substrate.

[0137] In one embodiment, the film-forming solution is spread on the film-forming substrate by a continuous casting method.

[0138] The present invention has no particular limitation on the film-forming substrate, and those skilled in the art can specifically select according to needs. For example, it can be a glass substrate, a plastic (such as PET, etc.) substrate, a metal (such as stainless steel, etc.) substrate, etc. In addition, it can also be various casting drums or endless belts, etc.

[0139] In one embodiment, the content of the polyethanol derivative of the present invention in the film-forming solution is 1 to 30% by mass, preferably 5 to 10% by mass.

[0140] In one embodiment, the film-forming solution contains water and optionally contains an organic solvent. Preferably, the volume ratio of the organic solvent to water is (0 to 75):(25 to 100).

[0141] Preferably, the film-forming solution does not contain an organic solvent, that is, the film-forming solution is an aqueous solution of a polyvinyl alcohol derivative.

[0142] In one embodiment, step (a) is carried out at a temperature in the range of 10 to 100 °C. For example, it can be carried out at room temperature of 10 to 40 °C, or at a high temperature of 40 to 70 °C or even 70 to 100 °C.

[0143] Step (b)

[0144] In step (b), the coating film obtained in step (a) is dried. The drying can be carried out by methods known in the art, such as heating the coating film and the like.

[0145] In one embodiment, the drying temperature is 30 to 150 °C, preferably 40 to 130 °C.

[0146] In one embodiment, the method for preparing the polyvinyl alcohol-based membrane of the present invention may further include steps such as peeling the coating film from the film-forming substrate before or after drying, stretching and / or winding the obtained polyvinyl alcohol-based membrane.

[0147] The present invention also correspondingly relates to a polyvinyl alcohol-based membrane obtained by the method for preparing the polyvinyl alcohol-based membrane of the present invention.

[0148] <Use>

[0149] The present invention also correspondingly relates to the use of the polyvinyl alcohol derivative of the present invention or the polyvinyl alcohol-based membrane of the present invention for ultraviolet protection, particularly for use in packaging materials, glass films, and coatings.

[0150] Examples of packaging materials include food and health product packaging, pharmaceutical packaging, precision instrument packaging, etc.

[0151] The glass in the glass film includes various inorganic glasses and organic glasses, as well as various plastic plates used in place of glass. Specifically, examples include window glass films for buildings, window and windshield films for transportation vehicles (such as motor vehicle window films, motor vehicle windshield films), display screen films, lens films, etc.

[0152] Examples of coatings include coatings for building exterior walls, transportation vehicle exteriors (such as motor vehicle bodies, ship hulls), spacecraft exteriors, cultural relics, etc.

[0153] Examples

[0154] The present invention will be described in detail below through examples and comparative examples, and the raw material reagents used can be obtained commercially.

[0155] The polyvinyl alcohol raw material polyvinyl alcohol 0588 used in the following examples was purchased from Anhui Wanwei Group Co., Ltd., and the alcoholysis degree was 88%;

[0156] Example 1: Preparation of PVA derivative P1

[0157] Prepare PVA derivative P1 according to the following synthetic route:

[0158]

[0159] Dissolve polyvinyl alcohol 0588 (1.1 g, hydroxyl molar amount about 22 mmol) in anhydrous N-methylpyrrolidone (10 mL) to form a clear and transparent solution. Add diketene (92.5 mg, 1.1 mmol), and stir at 25 °C for 1 hour. Then add benzaldehyde (128.4 mg, 1.21 mmol), 5,5-dimethyl-1,3-cyclohexanedione (169.6 mg, 1.21 mmol), ammonium acetate (139.9 mg, 1.82 mmol), and glycine (9.1 mg, 0.12 mmol) to the reaction solution system. Heat the reaction solution system to 80 °C and react for 3.5 hours. After the reaction is completed, precipitate the reaction solution in acetone solution, then filter and dry to obtain 1.2 g of PVA derivative P1.

[0160] The 1 1H-NMR spectrum of PVA derivative P1 is as Figure 1 shown. Figure 1 In it, characteristic peaks of the benzene ring appear at a chemical shift of 6.90 - 7.18 ppm, and characteristic peaks of the nitrogen-hydrogen on the 1,4-dihydropyridine ring appear at about a chemical shift of 8.95 ppm, indicating the successful synthesis of PVA derivative P1.

[0161] Example 2: Preparation of PVA derivative P2

[0162] Prepare PVA derivative P2 according to the following synthetic route:

[0163]

[0164] Dissolve polyvinyl alcohol 0588 (1.1 g, hydroxyl molar amount about 22 mmol) in anhydrous N-methylpyrrolidone (10 mL) to form a clear and transparent solution. Add diketene (92.5 mg, 1.1 mmol), and stir at 25 °C for 1 hour. Then add p-dimethylaminobenzaldehyde (180.5 mg, 1.21 mmol), 5,5-dimethyl-1,3-cyclohexanedione (169.6 mg, 1.21 mmol), ammonium acetate (139.9 mg, 1.82 mmol), and glycine (9.1 mg, 0.12 mmol) to the reaction solution system. Heat the reaction solution system to 80 °C and react for 3.5 hours. After the reaction is completed, precipitate the reaction solution in acetone solution, then filter and dry to obtain 1.3 g of PVA derivative P2.

[0165] The 1 1H-NMR spectrum of PVA derivative P2 is as Figure 2 shown. Figure 2In it, characteristic peaks of the benzene ring appeared at chemical shifts of 6.43 - 7.05 ppm, and characteristic peaks of the nitrogen-hydrogen on the 1,4-dihydropyridine ring appeared at around chemical shift of 8.87 ppm, indicating the successful synthesis of the PVA derivative P2.

[0166] Example 3: Preparation of PVA derivative P3

[0167] The PVA derivative P3 was prepared according to the following synthetic route:

[0168]

[0169] Polyvinyl alcohol 0588 (1.1 g, hydroxyl molar amount about 22 mmol) was dissolved in anhydrous N-methylpyrrolidone (10 mL) to form a clear and transparent solution. Divinyl ketone (92.5 mg, 1.1 mmol) was added, and the mixture was stirred at 25 °C for 1 hour. Then, 4-[methyl(phenyl)amino]benzaldehyde (255.6 mg, 1.21 mmol), 5,5-dimethyl-1,3-cyclohexanedione (169.6 mg, 1.21 mmol), ammonium acetate (139.9 mg, 1.82 mmol), and glycine (9.1 mg, 0.12 mmol) were added to the reaction solution system. The reaction solution system was heated to 80 °C and reacted for 3.5 hours. After the reaction was completed, the reaction solution was precipitated in an acetone solution, then filtered and dried to obtain 1.3 g of PVA derivative P3.

[0170] The 1 1H-NMR spectrum of PVA derivative P3 is as Figure 3 shown. Figure 3 In it, characteristic peaks of the benzene ring appeared at chemical shifts of 6.71 - 7.21 ppm, and characteristic peaks of the nitrogen-hydrogen on the 1,4-dihydropyridine ring appeared at around chemical shift of 8.93 ppm, indicating the successful synthesis of the PVA derivative P3.

[0171] Example 4: Preparation of PVA derivative P4

[0172] The PVA derivative P4 was prepared according to the following synthetic route:

[0173]

[0174] Polyvinyl alcohol 0588 (1.1 g, hydroxyl molar amount about 22 mmol) was dissolved in anhydrous N-methylpyrrolidone (10 mL) to form a clear and transparent solution. Divinyl ketone (92.5 mg, 1.1 mmol) was added, and the mixture was stirred at 25 °C for 1 hour. Then, 4-diphenylaminobenzaldehyde (330.7 mg, 1.21 mmol), 5,5-dimethyl-1,3-cyclohexanedione (169.6 mg, 1.21 mmol), ammonium acetate (139.9 mg, 1.82 mmol), and glycine (9.1 mg, 0.12 mmol) were added to the reaction solution system. The reaction solution system was heated to 80 °C and reacted for 3.5 hours. After the reaction was completed, the reaction solution was precipitated in an acetone solution, then filtered and dried to obtain 1.4 g of PVA derivative P4.

[0175] The 1 1H-NMR spectrum of PVA derivative P4 is as Figure 4 shown. Figure 4 In it, characteristic peaks of the benzene ring appeared at a chemical shift of 6.72 - 7.34 ppm, and characteristic peaks of the nitrogen-hydrogen on the 1,4-dihydropyridine ring appeared at about a chemical shift of 8.96 ppm, indicating that PVA derivative P4 was successfully synthesized.

[0176] Example 5: Preparation of polyvinyl alcohol membrane

[0177] Polyvinyl alcohol membrane-I:

[0178] 5 g of PVA derivative P4 prepared in Example 4 was dissolved in a certain amount of water to prepare a casting solution with a mass fraction of 10%. The casting solution was used to prepare a wet film by scraping on a PET plate at a scraping speed of 10 mm / s. After heating to 40 °C and waiting for the solvent to evaporate, polyvinyl alcohol membrane-I was obtained.

[0179] Polyvinyl alcohol membrane-C

[0180] 5 g of polyvinyl alcohol 0588 was dissolved in a certain amount of water to prepare a casting solution with a mass fraction of 10%. The casting solution was used to prepare a wet film by scraping on a PET plate at a scraping speed of 10 mm / s. After heating to 40 °C and waiting for the solvent to evaporate, polyvinyl alcohol membrane-C was obtained.

[0181] <Evaluation>

[0182] a. Visual observation

[0183] The polyvinyl alcohol membrane-I, polyvinyl alcohol membrane-C obtained in Example 5, and four commercial ultraviolet protection films were covered on the cardboard printed with patterns, and then visual observation was carried out and photos were taken. The photos are as Figure 5 shown. Among them Figure 5 a has no film covered; Figure 5The polyvinyl alcohol-based membrane-I is covered in b; Figure 5 The polyvinyl alcohol-based membrane-C is covered in c; Figure 5 The 3M Optically Clear Protect UV protection film is covered in d; Figure 5 The 3M Prestige UV protection film is covered in e; Figure 5 The LLumar Oasis 15 UV protection film is covered in f; Figure 5 The LLumar Oasis 50 UV protection film is covered in g.

[0184] The above four commercial UV protection films used in the experiment were all purchased from the official JD.com flagship store.

[0185] It can be seen from Figure 5 that under visual observation, the pattern covered with the polyvinyl alcohol-based membrane-I ( Figure 5 b) has no obvious difference from the pattern without film ( Figure 5 a) and the pattern covered with the polyvinyl alcohol-based membrane-C ( Figure 5 c), but is significantly higher in fidelity than the patterns covered with commercial UV protection films ( Figure 5 d to Figure 5 g).

[0186] b. Infrared characterization

[0187] The polyvinyl alcohol-based membrane-I and the polyvinyl alcohol-based membrane-C obtained in Example 5 were subjected to infrared characterization, and the infrared spectra are as Figure 6 shown. Characteristic peaks located at around 1590 cm -1 and 1500 cm -1 were observed in the infrared curve of the polyvinyl alcohol-based membrane-I, which belong to the benzene ring in the P4 structure of the PVA derivative, and the characteristic peak at around 1170 cm -1 belongs to the C-N bond in the P4 structure of the PVA derivative. However, the above characteristic peaks were not observed in the infrared curve of the polyvinyl alcohol-based membrane-C, indicating that the structure of the PVA derivative P4 was not damaged during the film-forming process of Example 5.

[0188] c. UV protection and visible light transmittance performance test

[0189] c-1. Solution test

[0190] The PVA derivatives P1-P4 were respectively formulated into aqueous solutions with concentrations of 10 mg / mL, 5 mg / mL, and 2 mg / mL. An appropriate amount of the aqueous solution was placed in a cuvette, and a UV-visible spectrometer (Perkin-Elmer Lambda 750) was used to measure the UV-visible light transmittance of the aqueous solution. The test wavelength was 290-800 nm, and the UV-visible absorption spectra are as Figures 7 - 9 shown.

[0191] Among them, the ultraviolet shielding rate and visible light transmittance are calculated by the following formulas respectively:

[0192]

[0193]

[0194] T is the ultraviolet-visible light transmittance, and λ is the wavelength.

[0195] From Figure 7 it can be seen that at a solution concentration of 10 mg / mL, the solutions of PVA derivatives P1 - P4 all exhibit excellent ultraviolet protection ability, among which P2 - P4 can almost completely shield the entire ultraviolet band (ultraviolet shielding rates are: P1: 99.5%; P2: 99.9%; P3: 99.9%; P4: 100%).

[0196] As Figure 8 shown, at a solution concentration of 5 mg / mL, P3 and P4 can still completely shield the entire ultraviolet band. The ultraviolet protection ability of P1 and P2 decreases slightly compared to the solution concentration of 10 mg / mL, but still maintains an ultraviolet shielding rate of more than 96% (ultraviolet shielding rates are: P1: 96.1%; P2: 96.3%; P3: 99.7%; P4: 99.9%).

[0197] As Figure 9 shown, at a solution concentration of 2 mg / mL, the solutions of P1 - P4 all show a certain degree of decline in ultraviolet protection ability compared to the solution concentration of 5 mg / mL, but the solution of P4 can still maintain an ultraviolet shielding rate of more than 97%. Among them, the ultraviolet shielding rates of the solutions of P1, P2, and P3 also all exceed 74%, showing excellent ultraviolet protection ability. (Ultraviolet shielding rates are: P1: 81.5%; P2: 74.1%; P3: 91.9%; P4: 97.4%).

[0198] c-2. Film testing

[0199] The ultraviolet-visible light transmittance of the polyvinyl alcohol-based membranes - I and polyvinyl alcohol-based membranes - C obtained in Example 5, as well as four commercial ultraviolet protection membranes, was tested. The test wavelength was 290 - 800 nm, and the results are as Figure 10 shown.

[0200] From Figure 10It can be seen that the polyvinyl alcohol-based membrane-C has good light transmittance but hardly has ultraviolet protection ability (ultraviolet shielding rate: 6.0%; visible light transmittance: 93.9%). The polyvinyl alcohol-based membrane-I and four commercial ultraviolet protection membranes can all shield more than 95% of ultraviolet rays (ultraviolet shielding rate: polyvinyl alcohol-based membrane-I: 98.8%; LLumar Oasis 15: 98.4%; 3M Crystalline: 98.3%; 3M Prestige: 96.2%; LLumar Oasis 50: 95.9%), and even the ultraviolet protection ability of the polyvinyl alcohol-based membrane-I is slightly better than that of the four commercial ultraviolet protection membranes. Moreover, compared with the commercial ultraviolet protection membranes, the polyvinyl alcohol-based membrane-I exhibits significantly excellent light transmittance (visible light transmittance: polyvinyl alcohol-based membrane-I: 85.9%; 3M Crystalline: 58.8%; LLumar Oasis 50: 51.2%; 3M Prestige: 39.0%; LLumar Oasis 15: 14.2%). This indicates that the polyvinyl alcohol-based membrane-I not only has excellent ultraviolet protection performance but also maintains a high visible light transmittance.

[0201] Industrial applicability

[0202] The polyvinyl alcohol derivative, polyvinyl alcohol-based membrane, and their preparation methods of the present invention can be used for ultraviolet protection purposes, especially for packaging materials, glass films, and coatings.

Claims

1. A polyvinyl alcohol derivative, characterized in that, The structural unit A shown in Formula I, the structural unit B shown in Formula II, and the structural unit C shown in Formula III In formula III, R1 is a hydrogen atom or NR 0 R 00 , where R 0 and R 00 are each independently selected from methyl, ethyl, propyl, isopropyl, butyl, phenyl, methylphenyl; R2 and R3 are each independently selected from a hydrogen atom, methyl, ethyl, propyl, isopropyl, butyl, phenyl; The molar ratio of the structural unit A, the structural unit B, and the structural unit C is (1-98):(1-12):(1-98); preferably (58-98):(1-12):(1-30); more preferably (78-98):(1-12):(1-10).

2. The polyvinyl alcohol derivative according to claim 1, wherein R1 in Formula III is a hydrogen atom, N,N-dimethyl, N-methyl-N-phenyl, or N,N-diphenyl; R2 and R3 are each independently selected from a hydrogen atom, methyl, ethyl, propyl, and preferably R2 and R3 are each independently selected from methyl and ethyl.

3. The method for preparing a polyvinyl alcohol derivative according to claim 1 or 2, characterized in that, Comprising the following steps: (1) Reacting polyvinyl alcohol with diketene to obtain an intermediate product-I containing a β-diketone structure; (2) Performing a Hantzsch reaction on the intermediate product-I, an aldehyde compound, an ammonia source compound, and a 1,3-diketone compound; wherein, the aldehyde compound is an aromatic aldehyde, the 1,3-diketone compound is a compound containing a 1,3-diketone structure, preferably a compound containing a 1,3-cyclohexanedione structure, and the ammonia source compound is an ammonium salt or ammonia, preferably one or more selected from ammonium acetate, ammonium carbonate, and ammonia.

4. The preparation method according to claim 3, characterized in that, The step (1) is carried out in an organic solvent, and the organic solvent is preferably a polar aprotic solvent, preferably one or more selected from N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), and N,N-dimethylformamide (DMF); Preferably, the degree of polymerization of the polyvinyl alcohol is 300-3000, and the degree of alcoholysis is 88-99 mol%; Preferably, the molar ratio of the hydroxyl group in polyvinyl alcohol to diketene is 1:(0.01-1), preferably 1:(0.03-0.3); Preferably, the reaction temperature of the step (1) is 20-40 °C, preferably 25-35 °C; the reaction time is 1-3 hours, preferably 1-2.5 hours.

5. The preparation method according to claim 3, characterized in that, In the step (2), the molar ratio of the aldehyde compound, the ammonia source compound, and the 1,3-diketone compound is 1:(1-2):1, preferably 1:(1.1-1.6):1; the molar ratio of the aldehyde compound to the diketene in the step (1) is (1-2):1, preferably (1.1-1.6):1; Preferably, the Hantzsch reaction is carried out in the presence of a catalyst, and the catalyst is preferably an acid, more preferably one or more selected from amino acids and phenylboronic acid, and the amino acid is preferably glycine and / or proline; preferably, the molar ratio of the catalyst to the aldehyde compound is (0.05-0.2):1, preferably (0.09-0.16):1; Preferably, the reaction temperature of the Hantzsch reaction is 70-85 °C, preferably 70-80 °C; the reaction time is 2-5 hours, preferably 2-4 hours.

6. A polyvinyl alcohol-based membrane, characterized in that, Comprising the polyvinyl alcohol derivative described in claim 1 or 2.

7. The polyvinyl alcohol-based membrane according to claim 6, wherein The ultraviolet shielding rate is more than 95%, and the visible light transmittance is more than 70%.

8. A method for preparing a polyvinyl alcohol-based membrane, characterized in that, Comprising the following steps: (a) Spread the film-forming solution containing the polyvinyl alcohol derivative described in claim 1 or 2 on a film-forming substrate to obtain a coated film; (b) Dry the coated film.

9. The preparation method according to claim 8, characterized in that, In step (a), the content of the polyvinyl alcohol derivative in the film-forming solution is 1 to 30% by mass, preferably 5 to 10% by mass; the film-forming solution contains water and optionally contains an organic solvent. Preferably, the volume ratio of the organic solvent to water is (0 to 75):(25 to 100), and more preferably the film-forming solution does not contain an organic solvent.

10. Use of the polyvinyl alcohol derivative described in claim 1 or 2 or the polyvinyl alcohol-based film described in claim 6 or 7 for ultraviolet protection, particularly for use in packaging materials, glass films, and coatings.

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