JP3162165B2 - Surface negative charge measurement method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring the amount of negative charge on the surface of a substance, which can be used in the general industrial field.

[0002]

2. Description of the Related Art In the industrial field and the scientific field, methods for measuring the surface negative charge amount include, for example, neutralization titration with acid-alkali, reverse titration, redox titration, measurement by zeta potential, NMR, infrared absorbance measurement and the like. Is known as a known method. In a titration using a solution, in the solid state, the charge amount depends on the affinity of the sample for the solvent, and it is often difficult to measure, and a high value cannot be obtained with high accuracy. Fiber, woven,
In the case of shapes such as paper and nonwoven fabric, when measuring a minute amount of surface negative charge, there are many errors and a clear value cannot be obtained in many cases. Methods using optical instruments such as NMR and infrared absorbance measurement require an expensive measuring device, and many operations and the like require skill and cannot be said to be a simple method.

[0003] In the field of medical materials, it is known that a minute amount of negative charge, particularly on the surface, has a significant effect in vivo.

[0004] On the surface of a material having a negative charge on the surface, activation of blood coagulation factor XII occurs, and kallikrein is generated from prekallikrein by the activated blood coagulation factor XII. Kallikrein is known to limit the decomposition of high-molecular-weight kininogen in blood and to release a part thereof, namely blood kinin. It is also known that this blood kinin is one of the causative substances of anaphylactic shock such as lowering of blood pressure, flushing of the face, conjunctival hyperemia, contraction of smooth muscle, and pain. However, since there is no simple method for measuring the negative charge on the surface of the material, no study has been made on the surface negative charge of a clinically available material with low production of blood kinin.

[0005]

SUMMARY OF THE INVENTION The inventors of the present invention have studied for the practical use of a biocompatible material and found that there is a correlation between the surface negative charge and the biocompatibility. A detailed examination of the materials that have been put into practical use revealed that a large amount of blood kinin was generated when blood came into contact with the materials. However, in the case of fibrous or macroporous leukocyte separation materials, the amount of surface charge on the surface of the material cannot be measured accurately, so that the production of blood kinin has not been studied in terms of the surface negative charge. . Therefore, a simple and highly accurate measurement method of the surface charge amount of a material or the like, which has been difficult to measure, has been required.

[0006]

Means for Solving the Problems The present inventors have conducted intensive studies to develop a method for measuring the amount of negative charge present on the surface of a material, and as a result, have accomplished the present invention. That is, the present invention
This is a method of measuring the surface charge of a substance having a negative charge on the surface by measuring the absorbance of a triiodide complex ion produced by reacting iodine and iodide ions in an alcoholic solvent using a substance having a negative charge on the surface as a catalyst.

[0007] The amount of negative charge that can be measured in the present invention is not particularly limited, but may be 0.1 µeq / g or more and 100 meq / g or less, and more preferably 1 µeq / g.
g to 10 meq / g, most preferably 10 μe
Good measurement is possible in the range of q / g to 1 meq / g.

In the present invention, the term "negative charge" refers to a charge obtained by any acidic functional group such as a carboxyl group, a phosphoric acid group, a sulfonic acid group, and a phenol group. Achieved.

The negative charge includes a negative functional group of the polymer constituting the filter material itself, a negative charge generated by hydrolysis in a manufacturing process of the filter material by heat or the like, and a filter material which does not originally have a negative functional group. Introduced by immobilizing a low molecular weight substance having a negative group, a high molecular weight substance, etc. using any known method such as covalent bonding, ionic bonding, physical adsorption, embedding, or a material comprising an ester compound or All negative charges are included, such as those in which a negative group is generated by immobilizing an ester compound by alkali hydrolysis or radiolysis, and those in which a monomer having a negative group is graft-polymerized by radiation grafting or plasma grafting. However, the negative charge measured according to the present invention exists on the surface of the material, the negative functional group of the polymer constituting the material itself or the negative functional group generated by hydrolysis by heat or the like in the manufacturing process of the material. Among the negative functional groups generated and / or provided by the surface treatment or the like, the functional groups inside the material are not measured.

That is, the surface referred to in the present invention is a surface that can come into contact with a liquid, and does not include the inside of a material that cannot be brought into contact with the liquid.

Hereinafter, the method of the present invention will be described in more detail. The material whose surface negative charge is to be measured is thoroughly washed with an alcoholic solvent such as ethanol or methanol and / or a solvent having a high oligomer elution until the elution of the oligomer is eliminated. And react the iodine and iodide ions to measure the absorbance at a wavelength around 359 nm. Prior to this, a similar operation was performed using a control material having a known amount of negative charge such as a carboxyl group fixed on the surface.
A calibration curve between the absorbance around 59 nm and the negative charge amount is prepared, and the negative charge amount on the surface of the material can be obtained using the calibration curve.

As the substance giving iodide ions in the present invention, all iodide salts can be used.
Preferred examples include iodine that is easily dissolved in alcoholic solvents such as potassium iodide, sodium iodide, magnesium iodide, calcium iodide, zinc iodide, manganese iodide, iron (I) iodide, and lithium iodide. With chloride salts
In particular, iodide salts such as potassium iodide and sodium iodide are used more favorably than the solubility in alcoholic solvents, the availability, and the ease of storage. Further, as iodine, a trace amount of iodine contained in the iodide salt may be used, or good measurement can be carried out by further adding iodine thereto.
When measuring a minute amount of negative charge, it can be measured favorably only with a minute amount of iodine contained in the iodide salt.

The alcoholic solvent referred to in the present invention refers to water containing an alcohol such as methanol, ethanol, n-propanol, isopropyl alcohol, t-butanol and / or an organic solvent having no absorption around 359 nm. A solvent that does not dissolve the material itself and dissolves the iodide salt. The measurement can be performed with all the above-mentioned alcoholic solvents, but preferably 50% by weight aqueous alcohol or an alcohol containing 50% by weight organic solvent is preferable, and more preferably 70% by weight aqueous alcohol or 70% by weight. % Alcohol, most preferably 100% alcohol. In particular, when measuring the surface charge of a non-woven fabric such as polyester,
The best alcoholic solvent is 100% methanol because of the good affinity between the solvent and the material and the solubility of the iodide salt. In addition, alcoholic solvents include 200
Solvents that do not absorb in the visible and ultraviolet regions between nm and 500 nm are suitable, preferably between 250 nm and 450 n.
m, more preferably from 300 nm to 400
Preferably, it has no absorption at wavelengths between nm.

In the present invention, the concentration of iodine and iodide ions in the alcoholic solvent is not particularly limited,
The concentration must be such that it dissolves in the alcoholic solvent at the reaction temperature.

The absorption at around 359 nm indicates the absorption of triiodide complex ions generated from iodine and iodide ions in an alcoholic solvent catalyzed by surface negative charge in water or an alcoholic solvent. . Therefore, the absorption around 359 nm by the triiodide complex ion increases proportionally as the surface negative charge increases. The amount of increase in absorbance over a certain period of time corresponds to the amount of increase in the triiodide complex ion, and this is determined as the surface negative charge of the substance to be measured. As a result, the measurement can be performed if the surface negative charge exists in an amount of several μeq / g, and the measurement can be performed even for a minute amount of the negative charge. Furthermore, the amount of triiodide complex ion generated can be converted to ultraviolet absorbance for measurement, so that clear numerical values can be obtained, and the difference in negative charge amount can be amplified by replacing the surface negative charge amount with triiodide complex ion increase. This results in a large difference in absorbance, which enables highly accurate measurement.

In the measuring method of the present invention, it is ideal that no eluting oligomer is observed. Since the oligomers are uniformly present in the solution, the acidic functional groups exhibit higher catalytic properties than the acidic functional groups in the solid layer.
It may show a negative charge higher than the true charge, which may cause errors and, if the oligomer has the ability to chelate anions, complex the formed triiodide complex ion to reduce the absorption measurement wavelength. This is because the true negative charge cannot be measured by shifting. However, in the weight ratio of the alcoholic solution and the material to be measured under the measurement conditions, the absorbance in the ultraviolet absorption region of the eluate in the reaction time for the measurement at the temperature used for the measurement is 0.1 or less. In this case, the influence on the measurement result is small. Further, when the absorbance is 0.01 or less, and most preferably 0.001 or less, optimal high-precision measurement can be performed.

In the measuring method of the present invention, containers, plates, films, sheets, thin films, films such as hollow fibers, amorphous solids such as gels, beads, pieces, granules, powders, porous fibers, cotton, Woven fabrics, non-woven fabrics, meshes, substances in any form of known materials such as paper can be measured, but particularly suitable for non-woven fabrics obtained by melt blow method, flash spinning method, papermaking method, etc. It is a measuring method. Here, the nonwoven fabric refers to a cloth-like material in which an aggregate of fibers or yarns is chemically, thermally, or mechanically connected irrespective of knitting or weaving. When the fiber and the fiber maintain a certain shape due to contact with each other, it is included in being mechanically bonded.

Examples of the substance whose surface charge can be measured according to the present invention include polyesters such as polyethylene terephthalate, polybutylene terephthalate and polyoxyethylene terephthalate, polyamides such as polyacrylonitrile, nylon 6, nylon 6,6 and the like, aromatic polyamides, and the like. Polyethylene, polypropylene, polybutene-1,
Polyolefins such as polyisobutene, trans-1,
Polydienes such as 4-polybutadiene, cis-1,4-polyisoprene, trans-1,4-polyisoprene, polystyrene derivatives such as polystyrene, poly-o-methylstyrene, poly-α-methylstyrene, methyl methacrylate, ethyl Polymer compounds obtained by polymerizing methacrylate derivatives such as methacrylate and n-butyl methacrylate; polymer compounds obtained by polymerizing acrylate derivatives such as methyl acrylate and ethyl acrylate; polyacrylonitrile, polyvinyl formal, polysulfone Chlorine and / or fluorine polymers such as polyurethane, polycarbonate, phenoxy resin, polyvinyl chloride, polyvinylidene chloride, polytrifluorochloroethylene, polyvinyl fluoride, polyvinylidene fluoride, etc. Synthetic polymer compounds such as polyvinyl acetal, including homopolymers, copolymers, block polymers and polymer compounds of monomers and oligomers of the polymer compounds, including those blended and alloyed, Blends with regenerated fibers such as cellulose and / or derivatives thereof and the above-mentioned synthetic polymer compounds, and those containing alloyed ones are also included.

Surface modification by a known method such as graft polymerization of a polymer compound or a monomer thereof using radiation or plasma, or covalent bonding (Japanese Patent Laid-Open No. 1-2).
49063, JP-A-3-502094) can also be measured. Examples of monomers and polymer compounds used for surface modification include methacrylic acid, acrylic acid,
2-methacryloyloxyethyl succinic acid, mono (2-
(Methacryloyloxyethyl) acid phosphate, mono (2-acryloyloxyethyl) acid phosphate, 2-sulfoethyl methacrylate, 2-
Acrylic or methacrylic acid derivatives such as methacryloyloxyethylphthalic acid, etc .; styrene derivatives such as p-styrenesulfonic acid and p-vinylbenzoic acid; phenol derivatives such as vinylphenol; and allyl compounds such as sodium allylsulfonate. Vinyl monomer, acetylene derivative, a polymer compound obtained by polymerizing a monomer having a negative group such as a trioxane derivative, or a monomer having a polymerizable functional group, preferably having a vinyl group or an acetylene group, for example, , 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, 1,2
-Dihydroxyethyl methacrylate, methoxytriethylene glycol methacrylate, methoxy nonaethylene glycol methacrylate, methyl methacrylate,
Ethyl methacrylate, methyl acrylate, acrylate and methacrylate derivatives such as ethyl acrylate, neutral monomers such as styrene and its derivatives, N, N-diethylaminoethyl methacrylate,
N, N-dimethylaminoethyl methacrylate, N, N
A copolymer with a cationic monomer such as -diethylaminoethyl acrylate or N, N-dimethylaminoethyl acrylate, or a synthetic compound such as a polymer compound or an oligomer obtained as a block polymer. Further, a polymer compound obtained by polymerizing a vinyl monomer is preferable because of high polymerizability and easy availability. Furthermore, sugar chains such as dextran derivatives and heparin,
There are also natural polymer compounds having a negative group such as a polypeptide.

Among them, a polyester nonwoven fabric having a trace amount of carboxyl groups generated by hydrolysis by heat or the like in a manufacturing process, which is widely used as a leukocyte separation material such as polyethylene terephthalate, polybutylene terephthalate, and polyoxyethylene terephthalate. The measurement method of the present invention is suitable.

The present invention relates to all known methods such as covalent bonding, ionic bonding, radiation or plasma grafting of various low molecular weight and high molecular weight compounds on the material surface, physical adsorption, embedding, or precipitation insolubilization on the material surface. Although it is possible to measure the amount of negative charge fixed using, preferably, the fixed negative charge is insoluble in the alcoholic solvent used for measurement, most preferably, using a covalent bond, radiation or a grafting method using plasma or the like A fixed negative charge can be measured particularly preferably. It is also preferable to measure the amount of carboxyl groups generated by hydrolysis of monomers and polymer compounds during graft polymerization using radiation, plasma, or the like, sterilization, or the like.

[0022]

Next, the present invention will be described in more detail with reference to examples.

[0023]

Embodiment 1 A method for cleaning a material to be measured is described below. The materials and the alcoholic solvent are placed in a glass sealable container at the same weight ratio, and shaken at a set temperature for a set time. However,
The above operation is repeated by changing the alcoholic solvent until the difference in absorbance in the ultraviolet absorption region before and after shaking the alcoholic solution becomes 0.01 or less. After the difference in absorbance becomes 0.01 or less, vacuum-dry until the weight of the material becomes a constant weight,
Measure the surface negative charge.

5.3 g of a nonwoven fabric having a composition of polyethylene / polypropylene (1: 1) having an average fiber diameter of 1.53 μm is immersed in 390 ml of a methanol solution containing 0.5% by weight of methacrylic acid, and degassed by passing nitrogen through. I noticed. This solution was irradiated with γ-rays at 27.3 kGy (1.2 kGy / hour) to cause graft polymerization. Part of this non-woven fabric 40.8m
g, weigh 100 g with a glass sealable stopper
Then, 50 ml of a solution obtained by adding potassium iodide to 100% methanol to a concentration of 5% (% by weight) was added, sealed, placed in a 30 ° C. water bath and shaken for 24 hours. As a control, a sample bottle in which no material was inserted was prepared, and the same operation was performed except that no filtration material was inserted. The solution was taken out, and the absorbance at a wavelength of 359 nm was measured with an ultraviolet absorbance meter. At the same time, a known gel having a carboxyl group immobilized at the terminal (carboxyl group equivalent: 32 μeq / ml) was used as a sample having a known carboxyl group equivalent for a calibration curve, in an amount of 0.5 ml and 1.0 ml, respectively.
ml and 1.5 ml were precisely weighed, and the same operation as above was performed except that the gel was put without putting the filtration material into, and the wavelength was 359 n.
The absorbance at m was measured and used as the change in absorbance for the calibration curve. The amount of change in absorbance at 359 nm of each sample and the sample for the calibration curve was a value obtained by subtracting the absorbance value of the control from the absorbance value of the sample. 3 of this calibration curve sample
From the change in absorbance at 59 nm, a calibration curve of the change in absorbance with respect to the negative charge was prepared. As a result, a first-order linear relationship is observed between the negative charge amount and the absorbance change amount, and n
The number was 50 and the correlation coefficient was 0.915.

When the surface charge of the material was measured using a calibration curve, a value of 1162 μeq / g was obtained. This value was consistent with the terminal carboxyl group equivalent of 1162 μeq / g calculated from the weight change due to the grafting of methacrylic acid.

The amount of terminal acidic groups calculated from the weight change due to the graft was determined by dividing the weight change per unit weight by the molecular weight of the monomer used for the graft. The weight change means an amount obtained by subtracting the weight of the monomer before grafting from the weight of the material after grafting the monomer.

[0027]

Example 2 21.5 mg of the same nonwoven fabric as in Example 1 was used.
The same operation as in Example 1 was performed except that the weight was changed to 42.9 mg, 64.4 mg, and 85.5 mg, and the surface charge amount was measured. The surface negative charge is 25 μeq /
g, 50 μeq / g, 75 μeq / g and 100 μeq
/ G, indicating a positive first-order correlation.

Therefore, the same nonwoven fabric as in Example 2 can be used as a sample for a calibration curve instead of the gel having a known carboxyl equivalent for the calibration curve used in Example 1. In the following examples, a sample for a calibration curve was used.
The material whose surface charge was confirmed in Example 2 was used.

[0029]

EXAMPLE 3 Polyethylene terephthalate (water content: 45 pp) without any adjustment of the chip moisture content by a known method
The nonwoven fabric was spun using the chips of m). The surface charge of this nonwoven fabric was measured by the same operation as in Example 1 except that the weight of the nonwoven fabric used for measurement was 1 g, and it was 35 μeq / g.

Further, the above-mentioned polyethylene terephthalate nonwoven fabric was subjected to the same operation as described above 100 times to measure the surface charge, and the value of the surface charge was 35 ± 2 μeq /
g showed a constant value.

[0031]

To determine the surface charge amount of the same nonwoven fabric as Comparative Example 1] Example 3, was conducted using an automatic titrator the neutralization titration with 0.01N chlorine, a value between 0 and 70μeq / g It was not possible to obtain a clear quantification in terms of accuracy.

[0032]

Comparative Example 2 In order to determine the surface charge amount of the nonwoven fabric in the same manner as in Example 3, the nonwoven fabric was put into a 10% aqueous sodium chloride solution, ion-exchanged, and neutralized with 0.01 N sodium hydroxide. When the titration was performed using a titrator, a value was obtained between 10 and 50 μeq / g, but the dispersion was large and a clear quantitative determination could not be made in terms of accuracy.

[0033]

Example 4 In the same manner as in Example 3 , no adjustment of the moisture content of the chips was performed at all, and the nonwoven fabric was spun using chips of polyethylene terephthalate (water content: 52 ppm) left in the air. The surface charge of this nonwoven fabric was measured by the same operation as in Example 1, and was found to be 45 μeq / g.

[0034]

Example 5 A nonwoven fabric was spun using chips of polyethylene terephthalate (moisture: 2359 ppm) left in the air and having a high water content. The amount of surface charge of this nonwoven fabric was measured by the same operation as in Example 1.
μeq / g.

[0035]

Example 6 A polyethylene terephthalate chip was sufficiently dried using a dryer (water content: 25 ppm), and spinning was performed under drying so as not to absorb moisture, under conditions for reducing the surface charge. Made a nonwoven. When the surface charge amount of this nonwoven fabric was measured by the same operation as in Example 1 , a value of 29 μeq / g was obtained.

[0036]

Example 7 A polybutylene terephthalate non-woven fabric contains 0.43% by weight of 2-hydroxyethyl methacrylate and 0.082% by weight of methacrylic acid and 0.4% by weight of t-butanol by a known radiation grafting method. Grafting was performed using an aqueous solution. When the surface charge amount of this nonwoven fabric was measured by the same operation as in Example 1 , 13
A value of 2 μeq / g was obtained.

[0037]

Example 8 0.4% by weight of 2-hydroxyethyl methacrylate and 0.012% by weight of N, N-dimethyl were applied to a polyethylene terephthalate nonwoven fabric similar to the nonwoven fabric used in Example 3 by a known radiation grafting method. Grafting was performed using an aqueous solution containing 0.4% by weight of t-butanol together with aminoethyl methacrylate. When the surface charge of this nonwoven fabric was measured by the same operation as in Example 1, a value of 23 μeq / g was obtained.

[0038]

EXAMPLES 9 Similar polyethylene terephthalate nonwoven fabric and the nonwoven fabric used in Example 3, by a known plasma irradiation grafting method, 10 wt% of methoxy nano ethylene glycol dimethacrylate 0.5% by weight of N, N-dimethylamino Grafting was performed using a methanol solution with ethyl methacrylate. When the surface charge of this nonwoven fabric was measured by the same operation as in Example 1, a value of 19 μeq / g was obtained.

[0039]

Example 10 A nonwoven fabric having a composition of polyethylene / polypropylene (1: 1) having an average fiber diameter of 1.53 μm was immersed in a methanol solution of 2.5% by weight of p-styrenesulfonic acid by a known radiation grafting method. And vented with nitrogen to degas. Γ-ray was added to this solution at 27.3 kGy.
(1.2 kGy / hr) for graft polymerization.
When the surface charge amount of this nonwoven fabric was measured by the same operation as in Example 1 , a value of 123 μeq / g was obtained.

[0040]

Example 11 Polystyrene-divinylbenzene (2% by weight) copolymer beads were grafted with a methanol solution containing 2% by weight of mono (2-methacryloyloxyethyl) acid phosphate. The surface negative charge was measured by the same operation as in Example 1 except that the weight of the beads was changed to 50 mg and the alcoholic solvent was changed to 50% by weight of ethanol containing water.
A value of g was obtained. This value is consistent with <br/> molar number of terminal carboxyl groups is calculated from the weight change due to grafting of mono (2-methacryloyloxyethyl) acid phosphate.

[0041]

Example 12 Polyethylene film (100 μm thick)
m) into an aqueous solution containing 50% by weight acrylic acid,
4.8 kGy was irradiated and radiation grafted. The same operation as in Example 1 was performed except that the weight of the film was changed to 10 mg, and the surface charge amount of this film was measured. As a result, a value of 4.22 mmol / g was obtained. This value was consistent with the number of moles of terminal carboxyl groups calculated from the weight change due to the grafting of acrylic acid.

[0042]

Comparative Example 3 A film similar to the film used in Example 12 was subjected to the same operation as in Comparative Example 2 except that the material to be measured was a film, and the surface negative charge was measured by neutralization titration. Of 4.2 mmol / g, which were in excellent agreement with Example 12.

[0043]

The Example 13 polyvinyl known plasma irradiation grafting sponge Mar, 10 wt% of methoxy nano ethylene glycol dimethacrylate 0.5% by weight of N, after impregnated with a methanol solution with N- dimethylaminoethyl methacrylate, Take out of the solution,
After evaporating the solvent with a vacuum dryer, grafting was performed. When the surface charge amount of this sponge was measured by performing the same operation as in Example 1 , a value of 23 μeq / g was obtained.

[0044]

By using the method for measuring surface negative charge according to the present invention, the amount of negative charge on the surface of a material can be measured simply and with high accuracy. In particular, it is possible to measure a minute amount of surface negative charge in a solid state such as a nonwoven fabric. This is an effective index for developing a biocompatible material that does not cause activation of biological components due to negative charge of the material.

Claims (1)

(57) [Claims] The surface charge of said substance is measured by measuring the absorbance of a triiodide complex ion produced by reacting iodine and iodide ions in an alcoholic solvent using a substance having a negative charge on the surface as a catalyst. How to measure.