Laminate comprising a composite membrane containing lignins and polyethyleneimine

Abstract

To provide a laminate with high gas barrier properties. [Solution] This laminate comprises a PET substrate and a composite film provided on the substrate containing lignins and polyethyleneimine. The lignins are one or more of the following: low-modified lignin, a salt of low-modified lignin, a sulfonic acid-substituted low-modified lignin, and a salt of a sulfonic acid-substituted low-modified lignin, with a yield of 15% or more of aromatic compound monomers produced by an alkaline nitrobenzene oxidation reaction. The lignin content / (lignin content + polyethyleneimine content) is 10% by mass or more and 67% by mass or less. The He transmittance of this laminate is 340 mL / m². 2 It is less than or equal to / bar / day.

Description

[Technical Field]

[0001] This application relates to a laminate having high gas barrier properties, wherein a composite film containing lignins and polyethyleneimine is formed on a substrate. [Background technology]

[0002] Towards the realization of a decarbonized society, the use of plants, which are biomass, as useful chemical products is being explored worldwide. Specifically, while about 10% of plants can be used as food, research is being conducted on utilizing the remaining inedible parts, specifically the approximately 60-70% polysaccharides and 20-30% lignin, as functional materials. In particular, since lignin has mainly been used as fuel, there is a need to develop functional materials that take advantage of its properties. For example, Patent Document 1 describes a polymer material for absorbing ultraviolet rays composed of low-modified lignin and PVA. Thus, the development of new materials using low-modified lignin is highly anticipated. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-204005 [Overview of the project] [Problems that the invention aims to solve]

[0004] The objective of this application is to provide a material with high gas barrier properties. [Means for solving the problem]

[0005] The precursor solution of this application is a precursor solution for a composite membrane containing lignins and polyethyleneimine. This precursor solution contains lignins, polyethyleneimine, and a liquid. The lignins are one or more of the following: low-modified lignin, a salt of low-modified lignin, a sulfonic acid-substituted low-modified lignin, and a salt of a sulfonic acid-substituted low-modified lignin, with a yield of 15% or more of aromatic compound monomers produced by an alkaline nitrobenzene oxidation reaction. The lignin content / (lignin content + polyethyleneimine content) is 10% by mass or more and 67% by mass or less.

[0006] The composite film of this application contains lignins and polyethyleneimine. The lignins are one or more of the following: low-modified lignin, a salt of low-modified lignin, a sulfonic acid-substituted product of low-modified lignin, and a salt of a sulfonic acid-substituted product of low-modified lignin, with a yield of 15% or more of aromatic compound monomers produced by an alkaline nitrobenzene oxidation reaction. The lignin content / (lignin content + polyethyleneimine content) is 10% by mass or more and 67% by mass or less.

[0007] The laminate of the present invention comprises a substrate and a composite film provided on the substrate, containing lignins and polyethyleneimine. The lignins are one or more of the following: low-modified lignin, a salt of low-modified lignin, a sulfonic acid-substituted low-modified lignin, and a salt of a sulfonic acid-substituted low-modified lignin, with a yield of 15% or more of aromatic compound monomers produced by an alkaline nitrobenzene oxidation reaction. The lignin content / (lignin content + polyethyleneimine content) is 10% by mass or more and 67% by mass or less. [Effects of the Invention]

[0008] The precursor solution for the composite film of the present invention contains lignins of a predetermined type and in predetermined amounts, polyethyleneimine, and a liquid. Therefore, the precursor solution of the present invention can be used to form a film. The composite film obtained from this precursor solution has high gas barrier properties. The composite film of the present invention contains lignins of a predetermined type and in predetermined amounts, and polyethyleneimine. Therefore, the composite film of the present invention has high gas barrier properties. The laminate of the present invention has a substrate and the composite film of the present invention provided on the substrate. Therefore, the laminate of the present invention has high gas barrier properties. [Brief explanation of the drawing]

[0009] [Figure 1] Top view image of the laminate of Example 1, in which a composite film of lignin and polyethyleneimine is formed on a PET film with the AIST logo printed on paper as the background. [Modes for carrying out the invention]

[0010] The precursor liquid, composite film, and laminate of this application will be described based on embodiments and examples. The composite film will be described as a component of the laminate. Repetitive explanations will be omitted as appropriate. The laminate of the embodiment of this application comprises a substrate and a composite film of the embodiment provided on this substrate. As the substrate, polymer substrates such as PET (polyethylene terephthalate), PVC (polyvinyl chloride), PP (polypropylene), PE (polyethylene), and PC (polycarbonate) are preferred. This is because the physical properties of the substrate can be largely maintained even when a composite film containing polymer components is formed on the substrate.

[0011] Note that the "on top" of the substrate does not necessarily mean direct contact. That is, one or more intermediate layers may be provided between the substrate and the composite film. Examples of intermediate layers include a layer to improve adhesion between the substrate and the composite film, an ultraviolet shielding layer, a layer to further improve gas barrier properties, a layer to further improve moisture resistance, and a layer to which decoration is applied. The composite film of the embodiment contains lignins and polyethyleneimine. The lignins are one or more of low-modified lignin, salts of low-modified lignin, sulfonic acid-substituted low-modified lignin, and salts of sulfonic acid-substituted low-modified lignin.

[0012] Lignin is a high-molecular-weight compound found in the cell walls or cell membranes of plants. Lignin is composed of hydroxyphenylpropane as its basic unit. The types and composition of substituted aromatic compounds that make up lignin vary depending on the plant species, such as conifers, broad-leaved trees, or grasses. When lignin is decomposed by alkali nitrobenzene oxidation, aromatic compound monomers such as vanillin, vanillic acid, and syringaldehyde are produced. In the low-modification lignin of this embodiment, the yield of these aromatic compound monomers is 15% or more.

[0013] In other words, if the total mass of these aromatic compound monomers is 15% or more of the total lignin mass in the plant material before decomposition by alkali nitrobenzene oxidation, then this plant material is the low-modified lignin of the embodiment. The low-modified lignin of the embodiment is a high-molecular-weight compound produced by condensation using hydroxyphenylpropane as the basic unit. For a method of quantifying the total lignin mass in the plant material, a specific method of the alkali nitrobenzene oxidation reaction, and qualitative and quantitative methods of aromatic compounds after decomposition by alkali nitrobenzene oxidation, please refer to Patent Document 1.

[0014] There are no particular limitations on the method for preparing the low-denatured lignin of the embodiment, but the low-denatured lignin of the embodiment can be obtained, for example, from solid components obtained by saccharifying cellulose and hemicellulose contained in the cell walls of plant raw materials with a saccharifying enzyme. This preparation method is called the Simultaneous Enzymatic Saccharification and Cominution method, and the low-denatured lignin obtained by this preparation method is called SESC lignin.

[0015] Simultaneous enzymatic saccharification and pulverization is carried out, for example, as follows: First, the plant material is coarsely pulverized to a size of 5 mm or less using a known pulverizer. Next, the coarsely pulverized plant material is wet-pulverized in a buffer solution in the presence of one or more saccharifying enzymes such as cellulase and hemicellulase to obtain a pulverized product containing a liquid component containing sugars and a solid component containing low-denatured lignin. Then, this pulverized product is centrifuged to separate the supernatant and the residue, and SESC lignin, which is low-denatured lignin, is obtained as the residue.

[0016] Examples of salts of low-denatured lignin include soda lignin, a compound in which some or more of the H atoms in the OH group bonded to the aromatic ring of low-denatured lignin are replaced with metals such as Na or K. Examples of sulfonic acid substitutions of low-denatured lignin include lignosulfonic acid, a compound in which some or more of the OR (where R is an alkyl group) bonded to the aromatic ring of low-denatured lignin are replaced with SO3H. Examples of salts of sulfonic acid substitutions of low-denatured lignin include compounds in which some or more of the H atoms in the SO3H of the sulfonic acid substitution of low-denatured lignin are replaced with metals such as Na or K.

[0017] Polyethyleneimine (PEI) may be linear or branched. Preferably, the molecular weight of the polyethyleneimine is between 600 and 70,000. This molecular weight is the weight-average molecular weight. The composite film of the embodiment may optionally contain additives other than lignins and polyethyleneimine. Examples of such additives include antioxidants, light stabilizers, processing stabilizers, compatibilizers, and colorants.

[0018] The ratio of the content of lignins to the sum of the content of lignins and the content of polyethyleneimine in the composite membrane (content of lignins / (content of lignins + content of polyethyleneimine)) is 10% by mass or more and 67% by mass or less. If the content of lignins is too high, the precursor solution of the composite membrane will phase-separate and film formation will not be possible. If the content of polyethyleneimine is too high, liquid components will remain in the precursor solution of the composite membrane and film formation will not be possible. This ratio is preferably 17% by mass or more and 50% by mass or less.

[0019] The UVA transmittance of the laminate of the embodiment shows a lower value compared to the UVA transmittance of only the substrate. The method for measuring the UVA transmittance will be described in the examples. When the substrate of the laminate of the embodiment is made of PET, the He transmittance of the laminate is 340 mL / m ,

[0021] , , , , , / bar / day or less, showing a lower value compared to the He transmittance of only the PET substrate. When the substrate of the laminate of the embodiment is made of PVC, the He transmittance of the laminate is 1440 mL / m 2 / bar / day or less, showing a lower value compared to the He transmittance of only the PVC substrate. The method for measuring the He transmittance will be described in the examples.

[0020] The precursor solution of the embodiment of the present application is a precursor solution of a composite membrane containing lignins and polyethyleneimine. The precursor solution of the embodiment contains lignins, polyethyleneimine, and a liquid. The types and contents of lignins and the molecular weight and content of polyethyleneimine are the same as those of the lignins and polyethyleneimine contained in the composite membrane of the embodiment. There are no particular restrictions on the liquid as long as lignins and polyethyleneimine can be dispersed therein. Examples of the liquid include water, ethanol, and methanol. The precursor solution of the embodiment may contain additives other than lignins and polyethyleneimine, if necessary. Examples of such additives include antioxidants, light stabilizers, processing stabilizers, compatibilizers, and colorants.

Examples

[0021] Production Example <Preparation of lignin dispersion> Cedar wood was crushed to a size of approximately 0.02-5 mm using a cutter mill or jet mill to obtain plant powder. 500 g of this plant powder was soaked overnight in 4.5 L of 100 mM phosphate buffer (pH 4-6) (the same applies hereafter), and then placed into a wet milling apparatus (Ashizawa Finetech, LMZ4). A cellulase-hemicellulase mixture (the same applies hereafter), prepared by mixing 50 mL of cellulase solution (DuPont Genencore, Optimash XL) and 50 mL of hemicellulase solution (DuPont Genencore, Optimash BG), was further added to the wet milling apparatus, and wet milling was performed at 50°C using 0.5 mm diameter zirconia beads.

[0022] During this wet grinding process, the average particle size of the plant powder was measured periodically. When the average particle size reached 10 μm, the 0.5 mm diameter beads were replaced with 0.1 mm diameter zirconia beads, and the wet grinding was continued. As the wet grinding progressed, the viscosity of the mixture decreased. The wet grinding was completed after a total of 4 hours to obtain a plant powder suspension. The average primary particle size of the plant powder in this suspension was 30-40 nm. This plant powder suspension was centrifuged to separate the supernatant from the residue.

[0023] After washing the residue with water, a cellulase-hemicellulase mixture and 1 L of phosphate buffer were added to the residue, and the saccharification reaction was carried out by stirring at 50°C for 12 hours. After the saccharification reaction was complete, the supernatant and residue were separated by centrifugation, and brown SESC lignin (hereinafter, "SESC lignin" may be simply referred to as "lignin") was obtained as the residue. This SESC lignin is a low-denatured lignin in which the yield of aromatic compound monomers produced by the alkaline nitrobenzene oxidation reaction is 15% or more (see Patent Document 1). After measuring the water concentration of this lignin with a water meter (A&D, MS-70), ultrapure water was added dropwise to this lignin to prepare a lignin dispersion of the production example, which is an aqueous dispersion containing lignin at a concentration of 2% by mass.

[0024] Example 1 <Formation of a composite membrane of lignin and polyethyleneimine> 5 mL of the lignin dispersion from the production example, 0.1 g of polyethyleneimine (Wako Pure Chemical Industries, molecular weight 10000) in an amount equal to the mass of lignin, and 3.23 mL of ultrapure water were mixed to obtain a lignin-polyethyleneimine mixture. Using a nanodisperser (Thinky, PR-1), this mixture was processed at 600 rpm for 30 minutes, and then degassed using a mixer (Thinky, Awatori Rentaro) at 2200 rpm for 5 minutes to obtain the lignin-polyethyleneimine composite membrane precursor liquid of Example 1 (hereinafter, "lignin-polyethyleneimine composite membrane precursor liquid" may be simply referred to as "precursor liquid"). This precursor liquid was dropped onto a PET film with a thickness of 100 μm and dried in a fume hood to obtain a laminate of Example 1 in which a disc-shaped composite membrane of Example 1 was formed on the PET film substrate. The thickness of the composite membrane of Example 1 was 12 μm. Figure 1 shows a top view image of the laminate of Example 1 placed on paper with a pattern printed on it.

[0025] <Evaluation of laminates> The laminate of Example 1 possessed flexibility and handling properties. That is, coating the PET film with a composite film did not impair the flexibility and handling properties of the PET film. The ultraviolet-visible absorption spectrum of the laminate of Example 1 was measured using a spectrophotometer (HITACHI, U-2910), and the transmittance at each wavelength was evaluated (the same procedure was followed for other examples and reference examples). The transmittance of the laminate of Example 1 in the UVA region (wavelengths 315-400 nm (hereinafter the same)) was 15%, and the transmittance in the UVB-UVC region (wavelengths 200-315 nm (hereinafter the same)) was 5% or less.

[0026] Furthermore, the transmittance of the PET film itself (Reference Example 1) in the UVA region was 75%. Coating the PET film with the composite film of Example 1 improved its ultraviolet shielding properties. In other words, it was found that the composite film of Example 1 itself has ultraviolet shielding properties. This is thought to be because the π-conjugation derived from the aromatic network structure of lignin contained in the composite film absorbs light in the ultraviolet region.

[0027] The helium permeability of the laminate in Example 1 was evaluated using a helium permeability measuring device (Canon Anelva, M-222LD) (the same procedure was followed for the other examples and reference examples). The helium permeability of the laminate in Example 1 was 332 mL / m². 2 The helium permeability was / bar / day. The helium permeability of the PET film itself was 1912 mL / m². 2 The gas barrier properties were / bar / day. Coating the PET film with the composite film of Example 1 improved the gas barrier properties. In other words, it was found that the composite film of Example 1 itself has gas barrier properties.

[0028] Furthermore, the moisture resistance of the laminate from Example 1 was evaluated by leaving it undisturbed for 24 hours in an environment with a temperature of 40°C and a relative humidity of 90% (the same procedure was followed for the other examples). As a result, no swelling of the composite film or laminate was observed. In other words, the composite film and laminate from Example 1 possess moisture resistance. This is thought to be because lignin settles in the composite film as the precursor liquid dries, and the lignin does not redisperse in water.

[0029] Example 2 The precursor solution of Example 2 was obtained in the same manner as in Example 1, except that the mixed mass of polyethyleneimine was changed so that the mass ratio of lignin to polyethyleneimine was 10:90. The precursor solution of Example 2 was dropped onto the same PET film as in Example 1 and dried, and the composite film of Example 2 was obtained. It was found that a composite film can be formed even when polyethyleneimine is present at 90% by mass.

[0030] Example 3 A laminate of Example 3 was obtained by coating a PET film with the composite film of Example 3 in the same manner as in Example 1, except that the mixed mass of polyethyleneimine was changed so that the mass ratio of lignin to polyethyleneimine was 17:83. The thickness of the composite film of Example 3 was 6 μm. The helium permeability of the laminate of Example 3 was 315 mL / m². 2 The result was / bar / day. Furthermore, when the moisture resistance of the laminate of Example 3 was evaluated, no swelling of the laminate or composite film was observed.

[0031] Example 4 The precursor solution of Example 4 was obtained in the same manner as in Example 1, except that the mixed mass of polyethyleneimine was changed so that the mass ratio of lignin to polyethyleneimine was 25:75. The precursor solution of Example 4 was dropped onto the same PET film as in Example 1 and dried to obtain the composite film of Example 4.

[0032] Example 5 The precursor solution of Example 5 was obtained in the same manner as in Example 1, except that the mixed mass of polyethyleneimine was changed so that the mass ratio of lignin to polyethyleneimine was 33:67. The precursor solution of Example 5 was dropped onto the same PET film as in Example 1 and dried to obtain the composite film of Example 5.

[0033] Example 6 The precursor solution of Example 6 was obtained in the same manner as in Example 1, except that the mixed mass of polyethyleneimine was changed so that the mass ratio of lignin to polyethyleneimine was 67:33. The precursor solution of Example 6 was dropped onto the same PET film as in Example 1 and dried to obtain the composite film of Example 6.

[0034] Example 7 The precursor solution of Example 7 was obtained in the same manner as in Example 1, except that the molecular weight of polyethyleneimine was changed to 600 (Wako Pure Chemical Industries). The precursor solution of Example 7 was dropped onto the same PET film as in Example 1 and dried to obtain the composite film of Example 7.

[0035] Example 8 The precursor solution of Example 8 was obtained in the same manner as in Example 1, except that the molecular weight of polyethyleneimine was changed to 1800 (Wako Pure Chemical Industries). The precursor solution of Example 8 was dropped onto the same PET film as in Example 1 and dried to obtain the composite film of Example 8.

[0036] Example 9 A laminate of Example 9 was obtained by coating a PET film with the composite film of Example 9 in the same manner as in Example 1, except that the molecular weight of polyethyleneimine was changed to 70,000 (Sigma-Aldrich). The thickness of the composite film of Example 9 was 14 μm. The transmittance of the laminate of Example 9 in the UVA region was 12%, and the transmittance in the UVB-UVC region was 5% or less. The helium transmittance of the laminate of Example 9 was 161 mL / m². 2 The result was / bar / day. Furthermore, when the moisture resistance of the laminate of Example 9 was evaluated, no swelling of the laminate or composite film was observed.

[0037] Comparative Example 1 An aqueous polyethyleneimine aqueous solution, which is the precursor solution for Comparative Example 1, was obtained in the same manner as in Example 1, except that lignin was not mixed in. The precursor solution for Comparative Example 1 was dropped onto the same PET film as in Example 1 and drying was attempted, but the polyethyleneimine film could not be formed as it remained in liquid form.

[0038] Comparative Example 2 In Comparative Example 2, the precursor solution was prepared in the same manner as in Example 1, except that the mixing mass of polyethyleneimine was changed so that the mass ratio of lignin to polyethyleneimine was 75:25. However, lignin precipitated, and the precursor solution was not homogeneous. As a result, a composite film of lignin and polyethyleneimine could not be formed on the PET film. The same result was observed in a precursor solution containing lignin and polyethyleneimine with a mass ratio of lignin to polyethyleneimine of 80:20. From the above, it was found that a composite film cannot be formed if the precursor solution contains less than 25% by mass of polyethyleneimine and more than 75% by mass of lignin as the film components.

[0039] The results for Examples 1 to 8 and Comparative Examples 1 to 2 are shown in Table 1 below.

[0040] [Table 1]

[0041] Example 10 A laminate of Example 10 was obtained by coating a PET film with the composite film of Example 10 in the same manner as in Example 1, except that the thickness of the PET film was changed to 188 μm. The thickness of the composite film of Example 10 was 13 μm. The transmittance of the laminate of Example 10 in the UVA region was 20%, and the transmittance in the UVB and UVC regions was 5% or less. The transmittance of the PET film itself in the UVA region was 71%. The helium permeability of the laminate of Example 10 was 252 mL / m 2 / bar / day. The helium permeability of the PET film itself (Reference Example 2) was 365 mL / m 2 / bar / day. Also, when the moisture resistance of the laminate of Example 10 was evaluated, no swelling of the laminate and the composite film was observed.

[0042] Example 11 A laminate of Example 11 was obtained by coating a PET film with the composite film of Example 11 in the same manner as in Example 1, except that the thickness of the PET film was changed to 188 μm and the mixing mass of polyethyleneimine was changed so that the mass ratio of lignin to polyethyleneimine was 17:83. The thickness of the composite film of Example 11 was 12 μm. The helium permeability of the laminate of Example 11 was 161 mL / m 2 / bar / day. Also, when the moisture resistance of the laminate of Example 11 was evaluated, no swelling of the laminate and the composite film was observed.

[0043] Example 12 A laminate of Example 12 was obtained by coating a PVC film with the composite film of Example 12 in the same manner as in Example 1, except that the PET film was changed to a PVC film with a thickness of 300 μm. The thickness of the composite film of Example 12 was 10 μm. It was found that in addition to PET, PVC can be used as the substrate of the laminate. The transmittance of the laminate of Example 12 in the UVA region was 10%, and the transmittance in the UVB and UVC regions was 5% or less. The transmittance of the PVC film itself (Reference Example 3) in the UVA region was 24%. The helium permeability of the laminate of Example 12 was 1435 mL / m 2 / bar / day. The helium permeability of the PVC film itself was 2316 mL / m2 The result was / bar / day. Furthermore, when the moisture resistance of the laminate of Example 12 was evaluated, no swelling of the laminate or composite film was observed.

[0044] Example 13 Except for changing lignin to ligninsulfonic acid (Tokyo Chemical Industries), a laminate of Example 13 was obtained by coating a PET film with the composite film of Example 13, which is a composite film of ligninsulfonic acid and polyethyleneimine, in the same manner as in Example 1. The thickness of the composite film of Example 13 was 9 μm. It was found that not only SESC lignin but also ligninsulfonic acid can be used as lignins to form the composite film. The transmittance of the laminate of Example 13 in the UVA region was 29%, and the transmittance in the UVB-UVC region was 5% or less. The helium transmittance of the laminate of Example 13 was 235 mL / m². 2 It was / bar / day.

[0045] Example 14 Except for changing lignin to lignin sulfonic acid (Tokyo Chemical Industries) and changing the thickness of the PET film to 188 μm, a laminate of Example 14 was obtained by coating a PET film with the composite film of Example 14 in the same manner as in Example 1. The thickness of the composite film of Example 14 was 14 μm. The transmittance of the laminate of Example 14 in the UVA region was 18%, and the transmittance in the UVB-UVC region was 5% or less. The helium transmittance of the laminate of Example 14 was 186 mL / m². 2 It was / bar / day.

[0046] The results for Example 1, Examples 10 to 14, and Reference Examples 1 to 3 are shown in Table 2 below.

[0047] [Table 2]

[0048] Example 15 The precursor solution of Example 15 was obtained in the same manner as in Example 1, except that lignin was replaced with lignin sulfonic acid (Tokyo Chemical Industries) and the molecular weight of polyethyleneimine was changed to 600 (Wako Pure Chemical Industries). The precursor solution of Example 15 was dropped onto the same PET film as in Example 1 and dried to obtain the composite film of Example 15.

[0049] Example 16 The precursor solution of Example 16 was obtained in the same manner as in Example 1, except that lignin was replaced with lignin sulfonic acid (Tokyo Chemical Industries) and the molecular weight of polyethyleneimine was changed to 1800 (Wako Pure Chemical Industries). The precursor solution of Example 16 was dropped onto the same PET film as in Example 1 and dried to obtain the composite film of Example 16.

[0050] Example 17 The precursor solution of Example 17 was obtained in the same manner as in Example 1, except that lignin was replaced with lignin sulfonic acid (Tokyo Chemical Industries) and the molecular weight of polyethyleneimine was changed to 70,000 (Sigma-Aldrich). The precursor solution of Example 17 was dropped onto the same PET film as in Example 1 and dried to obtain the composite film of Example 17.

[0051] Example 18 The precursor solution of Example 17 was obtained in the same manner as in Example 1, except that lignin was replaced with soda lignin and the molecular weight of polyethyleneimine was changed to 70,000 (Sigma-Aldrich). The soda lignin was extracted from cedar by alkaline pulping catalyzed with anthraquinone. The precursor solution of Example 17 was dropped onto the same PET film as in Example 1 and dried to obtain the composite film of Example 17. It was found that, in addition to SESC lignin and ligninsulfonic acid, soda lignin can also be used to form composite films.

[0052] The results of Examples 15 to 18 are shown in Table 3 below.

[0053] [Table 3]

Claims

1. A precursor liquid for a composite membrane containing lignins and polyethyleneimine, The above-mentioned lignins, polyethyleneimine, and a liquid are contained, The lignins are one or more of the following: low-modified lignin having a yield of 15% or more of aromatic compound monomers produced by an alkaline nitrobenzene oxidation reaction; a salt of the low-modified lignin; a sulfonic acid substituted product of the low-modified lignin; and a salt of the sulfonic acid substituted product of the low-modified lignin. A precursor solution having a lignin content / (lignin content + polyethyleneimine content) of 10% by mass or more and 67% by mass or less.

2. In claim 1, A precursor solution in which the polyethyleneimine has a molecular weight of 600 or more and 70,000 or less.

3. A composite membrane containing lignins and polyethyleneimine, The lignins are one or more of the following: low-modified lignin having a yield of 15% or more of aromatic compound monomers produced by an alkaline nitrobenzene oxidation reaction; a salt of the low-modified lignin; a sulfonic acid substituted product of the low-modified lignin; and a salt of the sulfonic acid substituted product of the low-modified lignin. A composite membrane having a lignin content / (lignin content + polyethyleneimine content) of 10% by mass or more and 67% by mass or less.

4. In claim 3, A composite membrane in which the polyethyleneimine has a molecular weight of 600 or more and 70,000 or less.

5. A laminate comprising a substrate and a composite film provided on the substrate containing lignins and polyethyleneimine, The lignins are one or more of the following: low-modified lignin having a yield of 15% or more of aromatic compound monomers produced by an alkaline nitrobenzene oxidation reaction; a salt of the low-modified lignin; a sulfonic acid substituted product of the low-modified lignin; and a salt of the sulfonic acid substituted product of the low-modified lignin. A laminate in which the content of lignins / (content of lignins + content of polyethyleneimine) is 10% by mass or more and 67% by mass or less.

6. In claim 5, A laminate in which the polyethyleneimine has a molecular weight of 600 or more and 70,000 or less.

7. In claim 5 or 6, The aforementioned substrate is a laminate made of PET.

8. In claim 7, He transmittance is 340 mL / m² ２ A laminate that is less than or equal to / bar / day.

9. In claim 5 or 6, The aforementioned substrate is a laminate made of PVC.

10. In claim 9, He transmittance is 1440 mL / m³ ２ A laminate that is less than or equal to / bar / day.

Images