JPS63145318A - Preparation of polyurethane - Google Patents

Abstract

PURPOSE:To obtain polyurethane having excellent dyeability, water absorption, antistatic properties, heat resistance and adhesiveness and having a high sulfonate content, by reacting an isocyanate compound with an active hydrogen compound including a specified compound. CONSTITUTION:A mono(meth)allyl compound of a triol compound of formula I (where Z is formula II or III; X is a direct bond, -CH2-, or formula IV, provided that X is -CH2- when Z is formula II; R is H, CH3 or C2H5; R' is H or CH3) is reacted with a bisulfite of an alkali metal in a molar ratio of 1:1.05-1.20 in water or in an aqueous solution of alcohol at about 80 deg.C to give a compound (a) of formula V (where A is formula IV or VII; M is a cation). An isocyanate compound (e.g. phenyl isocyanate) is reacted with an active hydrogen compound consisting of 0.01-50equimolar% of the ingredient (a) and a high-molecular polyol (e.g. polyether polyol) to give a sulfonate-containing polyurethane having a molecular weight of 10,000 to 1mm and a sulfonate content of 0.1-20wt%.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing polyurethane containing sulfonic acid groups (salts).

[Conventional technology]

Conventionally, as a method for producing sulfonic acid (salt) group-containing saliurethane, there has been known a method in which an addition product of allyl alcohol and sodium bisulfite is used and reacted with preisocyanate (for example, Japanese Patent Publication No. 42-24192).
.

[Problem that the invention seeks to solve]

However, this compound has the problem that only a small amount of nosulfonic acid (salt) groups can be introduced into polyurethane.

[Means for solving problems]

The present inventors have intensively studied methods for producing urethane that can contain a larger amount of sulfonic acid (salt) groups, and as a result, have arrived at the present invention.

That is, the present invention provides a method for producing polyurethane by reacting an isocyanate compound (A) with an active hydrogen atom-containing compound β, in which at least a part of (1) is the general formula % (1) or -CH,-. A is -CH1CH,CH,-
or CH3 CL CHCHt. M is a cation. This is a method for producing a sulfonic acid (salt) group-containing 1e urethane, which is characterized by using the compound (B1) shown in ).

In general formula (1), the cations of M include H, alkali metals (lithium, sodium, potassium, etc.), ammonium, and amine cations [(mono, di-tri, or tetra)alkyl (the number of carbon atoms in the alkyl group is usually 1 to
18) Ammonium (methylammonium, diethylammonium, tributylammonium, tetraethylammonium.

(tetraethylammonium, tetra-n-butylammonium, trimethyllauryl ammonium, etc.), and alkanol ammonium (2-propanol ammonium, methyljetanol ammonium, triethanol ammonium, etc.).

The inner rod tt,< of M is sodium, potassium, ammonium, and tetraalkylammonium.

Specific examples of the compound (B1) represented by general formula (1) include the following compounds.

[1] Compounds represented by the general formula % (21) Compounds having the groups shown in Table 1 in the general formula (2) are mentioned.

Table-1 HOCH, -C-X-0-A-3o, M
(31) Compounds represented by Ho -CHt Compounds having the general formula (3) as shown in Table 2 are mentioned.

As a method for synthesizing the compound of general formula (1), general formula (1)
When M is an alkali metal, the general formula Z-X-OHf4)
[In the formula, Z and
=cH.

(In the formula, R' is H or CH3., Z and X have the same meanings as in the general formula (1).)

) and an alkali metal bisulfite salt in a molar ratio of usually 1:1.
05 to 1.20 and about 80 in water or alcohol aqueous solution
It can be synthesized by reacting at °C.

As another method, it can be synthesized by reacting the acetalized product of general formula (9) with an alkali metal bisulfite salt, and then hydrolyzing the acetal group.

When M in general formula (1) is an ammonium salt or an amine salt, the above alkali metal salt and the ammonium salt or amine salt of a mineral acid (hydrochloric acid, sulfuric acid, etc.) are reacted in alcohol (ethanol, isopropyl alcohol, etc.). can be synthesized by separating and removing precipitated alkali metal salts of mineral acids.

In the present invention, the compound (B,
) Other active hydrogen atom-containing compounds can be used. Examples of other active hydrogen atom-containing compounds include high-molecular f-liol (B,) and low-molecular active hydrogen atom-containing compounds (B3).

Examples of high-molecular polyols include yriether polyols and polyester polyols, both of which are commonly used as raw materials for polyurethane, and can be used alone or as a mixture.

Examples of polyether preols include those obtained by adding alkylene oxide to active hydrogen-containing compounds such as polyhydric alcohols, polyhydric phenols, amines, and phosphoric acid.

Examples of polyhydric alcohols include glycols (ethylene glycol, fluoropylene glycol, 1,3 butylene glycol, 1,4 butanediol, hexylene glycol, 1
．． 6-hexanediol), tri- to octavalent alcohols (glycerin, trimethylolpropane, hexanetriol, pentaerythritol, diglycerin, α-methylglucoside, dipentaerythritol, sorbitol, xylit, mannitol, glucose, fructose, sucrose, etc.).

Examples of polyhydric phenols include pyrogallol, hydroquinone, bisphenol A, bisphenol sulfone, and a condensate of phenol and formaldehyde.

Amines include ammonia and alkanolamines (
monoethanolamine, jetanolamine, triethanolamine, triisopropanolamine, etc. and other alkanolamines), aliphatic mono- or peramines (ethylenediamine, diethylenetriamine, hexamethylenediamine and other aliphatic amines) ), aromatic mono- or polyamines (such as aniline, phenylene diamine, diaminotoluene, xylylene diamine, methylene dianiline, diphenyl ether diamine and other aromatic amines), cycloaliphatic amines (such as isophorone diamine and other aromatic amines), cyclic amines, etc.), heterocyclic amines (aminoethylpiperazine and other heterocyclic amines described in Japanese Patent Publication No. 55-21044), and the like.

Examples of the alkylene oxide include ethylene oxide, propylene oxide, butylene oxide, epichlorohydrin, and styrene oxide. Preferred alkylene oxides are propylene oxide and combination systems of propylene oxide and ethylene oxide (random, block, and mixed systems). The addition reaction of alkylene oxide can be carried out in a conventional manner, and is carried out in one step or in multiple steps under normal pressure or increased pressure without a catalyst or in the presence of a catalyst (alkali catalyst, amine catalyst, acidic catalyst).

Alcohols of n2-3fH (ethylene glycol, propylene glycol, 1
．． 3-butylene glycol, 1,4-butanediol,
Neopentyl glycol, 1,6-hexanediol,
glycerin, trimethylolpropane, etc.) and/or the aforementioned preether polyols with aliphatic dicarboxylic acids, acid anhydrides, and ester-forming carboxylic acid derivatives (geltal acid, adipic acid, sebacic acid, maleic anhydride, phthalic anhydride) , dimethyl terephthalate, etc.); and vaccines (
Examples include those produced by ring-opening polymerization of caprovacton, etc.).

Among the polymer polyols, preferred are divalent polyether diols and polyester diols.

The equivalent weight of these polymeric polyols is usually 200 to 4.
000, preferably 400 to 3,000.

Furthermore, a low-molecular active hydrogen atom-containing compound (B3) can also be used.

The low-molecular active hydrogen-containing compound is usually referred to as a crosslinking agent or chain extender, and contains at least 2, preferably 2 to 5, active hydrogen equivalents of less than 200 (the molecular weight of the active hydrogen-containing group). Specific examples include di- to trihydric alcohols (ethylene glycol,
Propylene glycol, 1,3-butylene glycol,
1.4-butanediol, 1.6-hexanediol,
Glycerin, trimethylolpropane), amines (jetanolamine, triethanolamine, triisopropanolamine, ethylenediamine, diethylenetriamine, isophoronediamine, diaminotoluene,
diethyltoluenediamine, methylene dianiline, methylene binuorthochloroaniline, etc.) and the above 2 to 8
alcohols, tetrahydric to octahydric alcohols (pentaerythritol, methyl glucoside, sorbitol, succalone, etc.), polyhydric phenols (bisphenol A
1 hydroquinone, etc.), the above amines, other amines (aminoethyl bipewodine, aniline, etc.), etc., with a small amount of alkylene oxide such as ethylene oxide and/or propylene oxide added, and prehydroxy compounds with a molecular weight of less than 200, water. and dimethylolpropionic acid.

Among these, preferred are glycols, diamines,
water, dimethylolpropionic acid, etc.

Furthermore, the low-molecular active hydrogen-containing compound (B3) is commonly referred to as an end-blocking agent, and monoalcohols and monoamines can be used. Specific examples include monoalcohols (hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate,
Examples include hydroxypropyl methacrylate, trimethylolpropane diallyl ether, and amines (butylamine, diallylamine, etc.).

Preferred among these are hydroxyethyl acrylate and hydroxypropyl acrylate.

Among the active hydrogen atom-containing compounds, the amount of (B1) in (1) is usually 0.01 to 50 equivalents, preferably 0.5 to 20 equivalents. When the -desirability of (Bl) is less than 0.01 per cent @winter, the performance (dyeability, dispersibility, antistatic property, etc.) based on the sulfonic acid group is not expressed, and when it exceeds 50 p Ryu 4 (
B+) will not be sufficiently dissolved in the reaction system, and the urethanization reaction will not proceed sufficiently.

The amount of (B,) in (2) is usually 10 equivalents or more, preferably 80 to 40 equivalents. (If the amount of B is less than 10 equivalents, the resin physical properties of polyurethane (tensile strength, elongation, impact resistance, etc.) will not be expressed. The amount of (B, ) in (B) is usually 50 to 41 or less, preferably is in the range of 10 to 40%.When the amount of (B3) exceeds 50%, the physical properties of the polyurethane resin (tensile strength, elongation, impact resistance, etc.) are no longer expressed.

As the isocyanate compound used in the present invention, those conventionally used in the production of polyurethane can be used.
In this way, as an isocyanate compound, the number of carbon atoms (NG
Aromatic isocyanates (excluding the carbon in the O group) of 6 to 20 (e.g. phenyl isocyanate, 2,4- and/or 2,6-) lylene diisocyanate (TDI
), crude TDI, 2.4'-Oyohi/l 7'c is 4,
41-diphenylmethane diisocyanate (MDI),
Crude MDI (crude diaminophenylmethane (condensation product of formaldehyde with aromatic amine (Ani 117) or mixtures thereof)
For example, phosgenates of 5 to 20% by weight 4) of mixtures with octafunctional or higher polyamines: polyallyl polyisocyanate (PAPI)), etc.; aliphatic isocyanates having 2 to 18 carbon atoms (e.g. stearyl isocyanate, hexamethylene diisocyanate, lysine diisocyanate, etc.]: Alicyclic isocyanate having 4 to 15 carbon atoms [e.g., cyclohexyl inocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate]: Aroliphatic isocyanate having 8 to 15 carbon atoms [
For example, xylylene diisocyanate]: and modified products of these isocyanates (modified products containing urethane group, carbodiimide group, allophanate group, urea group, biuret group, uretdione group, uretonimine group, isocyanurate group, oxazolidone group, etc.): and Isocyanates other than those described in Japanese Patent Application No. 59-199160 and mixtures of two or more thereof may be mentioned.

Among these, aromatic, aliphatic, cyclic, and araliphatic diisocyanates are preferred.

In the present invention, the isocyanate index CNC0/St ratio of active hydrogen atom-containing group x lOO] is usually 80 to 140,
Preferably it is 96-110.

The polyurethane can be produced by a conventional polyurethane production method. Examples include a method in which (2) and (Bl) are divided and reacted in multiple stages (prepolymer method) and a method in which (A) and .

As an example of the preprimer method, after reacting a cyanocyanate compound, a high molecular weight diol, and a compound of general formula (1) (sulfonate-containing diol) in advance,
A method in which the reaction is completed by reacting with a low-molecular-weight diamine. Alternatively, the diisocyanate compound and the sulfonate-containing diol of general formula (1) are reacted in advance, and then a high-molecular-weight diol is reacted, and then a low-molecular-weight diamine is reacted to complete the reaction. Here are some ways to complete it.

In the present invention, the reaction can be carried out using a solvent that is inert to isocyanate groups. Examples of solvents include amide solvents (such as N-methylpyrrolidone, dimethylformamide, and dimethylacetamide), ketone solvents (acetone,
methyl ethyl ketone, methyl isophyl ketone, cyclohexanone, etc.), aromatic hydrocarbon solvents (toluene, xylene, etc.), ether solvents (ethyl acetate, cellosolve acetate), ether solvents (oxane, tetrahydrofuran, etc.), sulfoxide solvents (dimethyl sulfoxide, etc.) and mixed solvents of two or more of these.The amount of the solvent is usually 0 to 400 times the weight of the polyurethane.The reaction temperature is usually under mild conditions, for example, 20 to 150 °C, Preferably 20~
It is 10°C. Moreover, the reaction time is usually 3 to 20 hours. The reaction pressure is also usually carried out under normal pressure, but it may be carried out under increased pressure.

In addition, catalysts commonly used to accelerate the reaction, such as amine catalysts (triethylenediamine, N-methylmorpholine, triethylamine, etc.), tin catalysts (dibutyltin dilaurate, etc.), and lead catalysts (lead octylate, etc.), etc. May be used.

The molecular weight of the polyurethane obtained in the present invention is usually from 10 weights to 1t4. If the content of sulfonic acid (salt) groups is low, there will be no superiority in various performances (dying properties, dispersibility, antistatic properties, etc.) compared to urethane that does not contain sulfonic acid groups, and If the amount is too large, the molecular weight of the urethane flashes and decreases, making it impossible to obtain the physical properties (tensile strength, elongation, impact resistance, etc.) of the resin as a polyurethane.

When using the polyurethane obtained in the present invention, additives such as plasticizers, crosslinking agents, pigments, colorants, leveling agents, heat stabilizers, and ultraviolet absorbers may be added as necessary to improve the performance of the polyurethane. It's okay. Additives such as heat stabilizers and ultraviolet absorbers are preferably added during polyurethane mold making.

The polyurethane obtained in the present invention can be made into an aqueous polyurethane dispersion by a conventional method (for example, the method described in Japanese Patent Publication No. 42-24192). For example, water is added to a solution of polyurethane obtained in the present invention (concentration: 604) under stirring, and then niacetone is distilled off under heating to obtain a polyurethane resin aqueous dispersion (approximately 46
Excellent) can be obtained.

〔Example〕

The present invention will be further explained below with reference to Examples, but the present invention is not limited thereto.

The parts in the examples indicate heavy electrical parts.

Synthesis Example 1 8-(2,a-dihydroxyproboxy)-1-
Propanesulfonic acid sodium salt (compound a in Table 1)
Synthesis method of 8-(2,-propenyloxy)-1,2-propanediol (glycerin monoallyl ether) 182.9
(1,0 mol) and sodium sulfite 68. p(0,5
A solution of 109 g (1.05 mol) of sodium bisulfite in 15 QI of water was added dropwise to the solution over 1 hour while blowing air at 60°C. After reacting at the same temperature for 2 hours, water was distilled off under reduced pressure, so much isopropyl alcohol was added, insoluble matter was filtered, and the isopropyl alcohol was distilled off. Powdered target product 21 (g (yield: 90 or more)) was obtained.

Synthesis Example 2 8-(2,2-bis(hydroxymethyl)butoxy)-
Synthesis method of 2-methyl-1-propanesulfonic acid sodium salt (Compound ■ in Table 2) Trimethylolpropane monometallic acid Sodium IQ 9g (1.05 mol) dissolved in 15J9 water was added dropwise over 1 hour. did. The insoluble matter was heated at the same temperature for 2 hours in a v5 pot, and the isopropyl alcohol was distilled off. Powdered object 2δ4. ! i+ (yield 8
7 yen).

Synthesis example 8 8- (2,2-bis(hydroxymethyl)butoxy)
-2-Methyl-1-propanesulfonic acid tetraethylammonium salt (Compound ■ in Table 2) Obtained in Synthesis Example 2 (Compound ■) 146. lit (0,
5 mol), tetraethylammonium crophyte 88p
(0.5 mol) was dissolved in 200 g of isopropyl alcohol, stirred at 60°C for 1 hour, cooled to 20°C, undissolved matter was filtered, and the isopropyl alcohol was distilled off. 190.9 (95%) of the target product in powder form was obtained.

Practical Example 1 47 parts of compound a of Synthesis Example 1, 2000 parts of polytetramethylene glycol with a molecular weight of 2,000, and 1.4-
Butanediol 157 parts Dimethylformamide 690 parts
0 parts and uniformly dissolved. Add 737 parts of diphenylmethane-4,4-diisocyanate to this solution,
The reaction occurred at 0″O.

This polyurethane solution has a solid content of over 30 and a viscosity of 1000.
ps, and the sulfonic acid group-containing layer has a solid content of 0.7
It was excellent.

Example 2 24 parts of compound a of Synthesis Example 1, 1.4 with a molecular weight of 2000
-2000 parts of f-diester diol from butanediol adipic acid and 157 parts of 1,4-butanediol
1 part was mixed with 6800 parts of dimethylformamide and uniformly dissolved. 718 parts of diphenylmethane-4,41-diisocyanate was added to this solution and reacted at 70°C. This polyurethane solution has a solid content of 304 and a viscosity of 700 ps.
The sulfonic acid group content was 0.85% of the solid content.

Comparative Example 1 The same procedure as in Example 1 was repeated except that 12 parts of ethylene glycol was used in place of Compound a in Example 1. Comparative Example 2 The same procedure as in Example 2 was carried out except that 10 parts of 1,6-hexanediol was used instead of compound a of Example 2.

This terizurethane solution has a solid content of 804 and a viscosity of goo p
It was s.

Test Example 1 A wet porous film was prepared by the following method using the polyurethane solutions of Example 1.2 and Comparative Example 1.2, and a dyeing test was conducted on this film. The results are shown in Table 3.

Dyeing test (creation of wet porous film) Dimethylformamide was added to the stock solution to adjust the solid content to 20, then spread on a glass board to a thickness of IB, submerged in water at 40°C, solidified for 15 minutes, and formed a solidified film. peeled from a glass plate,
After washing with water for another 10 minutes, it was dried at 80°C. Thickness Q, g
A white porous film of myi was obtained.

(Dyeing method) gr+-gap soda 1.
54 Pour the film into a dye bath at a bath ratio of 1:20 and heat at 95°C.
Stain the valve for 140 minutes. After cooling to below 40''C, washing with water and drying Table 3 Example 8 027 parts of the compound of Synthesis Example 2, 1.
514 parts of polyester diol from 4-butanediol/adipic acid, 85 parts of tolylene diisocyanate, and 200 parts of acetone were reacted under pressure at 80°C for 8 hours.

The mixture was then cooled to 50° C., 440 parts of acetone and 17 parts of isophoronediamine were added, and the mixture was reacted at the same temperature for 2 hours.

1000 parts of the condensate was added, and acetone was distilled off under heating to obtain a polyurethane aqueous dispersion.

This dispersion has a solids content of 40% and a viscosity of 60 CpS,
The sulfonic acid group content was determined by the solid content of 1.871.

The results are shown in Table G.

Comparative example 8 Ivy.

Test Example 2 An adhesion (heat resistant creep) test was conducted on the dispersions of Example 8 and Comparative Example 8.

(1) Adhesive composition (2) Measurement method Apply this adhesive composition on plywood (12o/rrLs)
Then, a 0.2 mm semi-rigid PVC sheet was crimped and dried at room temperature for 5 days.1 Plywood/semi-rigid PVC board was cut into a width of 25 myi and a length of loo+qm, a load of 500 g was applied to the PVC sheet, and a 60" The sample was left in a constant temperature bath of C, and the peeled length (length) was measured.The measurement results are shown in Table 1.

Example 4 076 parts of the compound of Synthesis Example 8, molecule-Fi'12,000
200 parts of teripropylene glycol, 82 parts of dihydroxyethyl bisphenol A, and 95 parts of isophorone diisocyanate were reacted at 80° C. for 8 hours. Then, 400 parts of acetone and 5 parts of isophoronediamine were added, and the mixture was reacted at 80° C. for 8 hours under pressure. Then, 420 parts of water was added and acetone was distilled off at 80°C to obtain an almost translucent polyurethane solution. This polyurethane solution had a solids content of 404 cps and a viscosity of 2500 cps, and the sulfonate content was 5 parts solids. created a film. Further, a film was similarly prepared using the urethane emulsion prepared in Comparative Example 8.

Preparation of Volume Resistance Test Film 100 parts of polyurethane solution I and 2 parts of water-soluble glycidyl ether (our company's Glycidyl 5TE-250) were mixed uniformly, spread on a glass plate, and dried at room temperature to a thickness of 0.51.
Obtain a transparent film.

Measurement of volume resistance: Measurement is performed at 20°C and 1654RH using a Takeda Horken super insulation meter.

Surface measurement results Volume resistivity S/Fu -〇 Example 4 7X10 Comparative example 8 2X10-" Example 5 038 parts of the compound of Synthesis Example 8, 200 parts of holica prolactone with molecules tt and ooo, dicyclohexylmethane-4,
A magnetic paint was prepared from 79 parts of 4'-diisocyanate and a urethane resin of methyl isobu, and the dispersibility of the magnetic powder was evaluated as a magnetic tape binder. In addition, a magnetic paint was prepared in the same manner using a commercially available urethane resin and a 50% solution of Tuboran 5088) in methyl isobutyl ketone.

Dispersibility test of magnetic powder Preparation of magnetic paint r-Fe203 S property 100 parts Urethane solution of Example 5 50 parts Toluene
50 parts methyl ethyl ketone
100 parts nitrocellulose (Cell line manufactured by Daicel) 1 part The above mixture was heated in a ball mill for 40 minutes.
A magnetic paint was created by time mixing and dispersion.

Preparation of Magnetic Film The prepared paint was applied onto a 15 μm polyester film using a bar coater so that the coating thickness of the solid content was 5 to 6 μm, and it was immediately oriented in a parallel magnetic field of 6,000 oersteds. 0 then 70-80″C
The solvent was gradually removed by leaving it in a circulating air dryer for about 30 minutes. In this state, it was calendered to smooth the surface (1 to 6 times of calendering). Further, this was placed in a constant temperature bath at 40 to 50° C. for 40 hours to harden the magnetic layer and obtain a fin: film.

Evaluation of dispersibility The glossiness of the magnetic coating surface of the magnetic film was investigated.

It can be said that the higher the gloss, the better the dispersibility. The measuring device is Nippon Heavy Industries (Digital variable angle gloss meter VC-I)
Type D was used. The reflectance relative value of each sample when the specular reflectance at a measurement angle of 75° is set as 100 for the reflectance of a standard glass plate (indicated by a sword).

The evaluation results are shown in the table.

Table≦ 〔Effect of the invention〕 The present invention has the following effects.

(1) The solubility of the sulfonic acid (salt) group-containing compound in the reaction system during the production of urethane resin is sufficient. The conventional one (Japanese Patent Publication No. 42-24192) was not sufficient.

(2) Therefore, sulfonic acid group-containing polyurethanes having various compositions can be produced.

(3) It is also possible to produce polyurethane with a high content of sulfonic acid groups.

(4) The shape of polyurethane can also be in a resin state, an F8 liquid state, an aqueous dispersion state, or an aqueous solution state.

(5) Zaryurethane containing sulfonate groups has better performance such as dyeability, water absorption, antistatic property, steel resistance, adhesion, dispersibility, biocompatibility, etc. compared to polyurethane with a similar composition that does not contain sulfonate groups. is excellent.

Since the above effects are achieved, the polyurethane according to the present invention may be used alone or with a binder such as other synthetic or natural resin,
Gluing agent in the textile and paper industry.

Claims (1)

[Scope of Claims] 1. In a method for producing polyurethane by reacting an isocyanate compound (A) and an active hydrogen atom-containing compound (B), at least a part of (B) is a compound of the general formula Z-X-
O-A-SO_3M(1) (In the formula, Z is ▲a mathematical formula, chemical formula, table, etc.▼ or ▲
There are mathematical formulas, chemical formulas, tables, etc. ▼, where R is H, CH_3 or C_2H_3. X is a direct bond, ▲There are mathematical formulas, chemical formulas, tables, etc.▼ or -CH_2
When -Z is ▲There are mathematical formulas, chemical formulas, tables, etc.▼, it is ▲There are mathematical formulas, chemical formulas, tables, etc.▼ or -CH_2-. A is -CH_2CH_2CH_2- or ▲ formula,
There are chemical formulas, tables, etc.▼. M is a cation. ) A method for producing a sulfonic acid (salt) group-containing polyurethane, characterized by using the compound (B_1) shown below. 2. The content of sulfonic acid (salt) groups in the polyurethane is 0.01 to 20% based on the weight of the polyurethane resin.
A manufacturing method according to claim 1.