JP5545797B2 - Antistatic agent - Google Patents

Description

  The present invention relates to an antistatic agent capable of forming a transparent layer having antistatic properties and an antistatic molded article having a layer comprising the antistatic agent.

  Cellulose is a useful component as an antistatic agent, and a molded body having a layer having an antistatic effect can be obtained by means such as coating or spraying on the molded body.

  Patent Document 1 is an invention relating to a composition containing cellulose as an antistatic agent. However, since the average particle diameter of cellulose is 1 to 10 μm, the film obtained by coating by scattering of light is used. It is cloudy. Such a cloudy film has a problem of low transparency.

  Patent Document 2 is an invention relating to a coating agent containing microcrystalline cellulose and a laminated material in which the coating agent is applied to a substrate. It is described that the microcrystalline cellulose powder as a raw material preferably has an average particle size of 100 μm or less, and in the examples, only those having an average particle size of 3 μm and 100 μm are used. There was no description about the refinement treatment, and the transparency of the applied coating agent layer was insufficient.

  Patent Document 3 discloses an invention relating to fine cellulose fibers and describes the possibility of being used as a coating material, but does not describe the use for which a specific effect is shown.

JP 2000-327837 A JP 2002-348522 A JP 2008-1728 A

  An object of the present invention is to provide an antistatic agent capable of forming a transparent layer having antistatic properties, and an antistatic molded article using the antistatic agent.

  The present invention provides an antistatic material comprising a cellulose fiber having an average fiber diameter of 200 nm or less and a cellulose carboxyl group content of 0.1 to 2 mmol / g as a means for solving the problem. An antistatic agent having a haze value (JIS K7105) of a layer made of the antistatic agent of 3.8% or less is provided.

  As a means for solving another problem, the present invention provides an antistatic molded article having a layer made of the above-mentioned antistatic agent on a molded article serving as a base material.

  By using the antistatic agent of the present invention, a transparent layer having antistatic properties can be formed on the molded body serving as the substrate. For this reason, by selecting a molded body to be a base material, a transparent antistatic molded body can be obtained, and the color, pattern, etc. of the molded body surface can be utilized with the naked eye. A molded body having antistatic properties can be obtained in a state where it can be confirmed.

<Antistatic agent>
The antistatic agent of this invention contains the specific cellulose fiber demonstrated below.

  The cellulose fiber used in the present invention has an average fiber diameter of 200 nm or less, preferably 1 to 200 nm, more preferably 1 to 100 nm, still more preferably 1 to 50 nm, and particularly preferably 1 to 20 nm. An average fiber diameter is calculated | required by the measuring method as described in an Example.

  The carboxyl group content of the cellulose constituting the cellulose fiber used in the present invention is 0.1 to 2 mmol / g, preferably 0.4 to 2 mmol / g, from the viewpoint of obtaining high antistatic properties. Preferably it is 0.4-1.8 mmol / g. Carboxyl group content is calculated | required by the measuring method as described in an Example. By setting the carboxyl group content to 0.1 mmol / g or more, the average fiber diameter of the cellulose fibers can be refined to 200 nm or less by the fiber refinement process described below.

  The cellulose fiber used in the present invention has a content of carboxyl group of cellulose constituting the cellulose fiber in the above range, but depending on the control state such as oxidation treatment in the actual production process, the cellulose fiber after oxidation treatment What exceeds the said range may be contained in it as an impurity.

  The cellulose fibers used in the present invention have an average aspect ratio of 10 to 1,000, more preferably 10 to 500, and still more preferably 100 to 350. An average aspect ratio is calculated | required by the measuring method as described in an Example.

  The cellulose fiber used by this invention can be manufactured by the following method, for example. First, about 10 to 1000 times the amount (mass basis) of water is added to the raw natural fiber (absolute dry basis), and processed with a mixer or the like to form a slurry.

  Examples of the natural fiber used as a raw material include refined pulp subjected to delignification treatment such as wood, pulp, linter pulp, bamboo pulp, bagasse pulp, cellulosic natural fiber such as cotton fiber, cotton linter, hemp fiber, and grain. Or dietary fiber derived from fruits (eg wheat bran, oat bran, corn hulls, rice bran, beer lees, soybean meal, pea fiber, okara, apple fiber, etc.), ligno such as wood and rice straw Cellulose materials and the like can be used.

  Next, the natural fiber is oxidized using 2,2,6,6, -tetramethyl-1-piperidine-N-oxyl (TEMPO) as a catalyst. In addition, 4-acetamido-TEMPO, 4-carboxy-TEMPO, 4-phosphonooxy-TEMPO and the like, which are derivatives of TEMPO, can be used as the catalyst.

  The amount of TEMPO used is in a range of 0.1 to 10% by mass with respect to natural fibers (absolute dry standard) used as a raw material.

  During the oxidation treatment, an oxidant such as sodium hypochlorite and a bromide such as sodium bromide are used in combination with TEMPO as a co-oxidant.

  As the oxidizing agent, hypohalous acid or a salt thereof, hypohalous acid or a salt thereof, perhalogenic acid or a salt thereof, hydrogen peroxide, a perorganic acid, or the like can be used. Alkali metal hypohalites such as sodium bromite. The amount of the oxidizing agent used is in a range of about 1 to 100% by mass with respect to the natural fiber (absolute dry standard) used as a raw material.

  As a co-oxidant, it is preferable to use an alkali metal bromide such as sodium bromide. The usage-amount of a co-oxidant is the range used as about 1-30 mass% with respect to the natural fiber (absolute dry standard) used as a raw material.

  The pH of the slurry is desirably maintained in the range of 9 to 12 from the viewpoint of allowing the oxidation reaction to proceed efficiently.

  The temperature of the oxidation treatment (temperature of the slurry) is arbitrary at 1 to 50 ° C., but the reaction is possible at room temperature, and temperature control is not particularly required. The reaction time is preferably 1 to 240 minutes.

  After the oxidation treatment, the used catalyst or the like is removed by washing with water or the like. At this stage, since the reaction fiber is not refined, it can be performed by a purification method in which washing and filtration are repeated. An intermediate of an antistatic agent in the form of a fiber or powder that has been subjected to a drying treatment as necessary (an antistatic agent before the miniaturization treatment described later) can be obtained.

  Thereafter, the intermediate is dispersed in a solvent such as water and refined. Refinement treatment is performed by a disaggregator, a beater, a low-pressure homogenizer, a high-pressure homogenizer, a grinder, a cutter mill, a ball mill, a jet mill, a short-axis extruder, a twin-screw extruder, an ultrasonic stirrer, and a domestic juicer mixer. And can be adjusted to length. The solid concentration in this step is preferably 50% by mass or less. By setting it as the range, it is preferable at the point which can suppress the energy required at the time of dispersion | distribution.

  By such refinement treatment, cellulose fibers having an average fiber diameter of 200 nm or less can be obtained, and the average aspect ratio is 10 to 1,000, more preferably 10 to 500, and still more preferably 100 to 350. A certain cellulose fiber can be obtained.

  Thereafter, the suspension is adjusted to a solid content concentration as necessary, or is dried as necessary. However, it is a powdered material in which cellulose fibers are aggregated, and does not mean cellulose particles. be able to. In addition, when making into suspension, what used only water may be used, and the mixed solvent of water, other organic solvents (for example, alcohol, such as ethanol), surfactant, an acid, a base, etc. was used. It may be a thing.

  By such oxidation treatment and refinement treatment, the hydroxyl group at the C6 position of the cellulose structural unit is selectively oxidized to a carboxyl group via an aldehyde group, and the carboxyl group content is 0.1 to 2 mmol / g. Highly crystalline cellulose fibers that are made of cellulose and have an average fiber diameter of 200 nm or less can be obtained. This highly crystalline cellulose fiber has a cellulose I-type crystal structure. This means that the cellulose fiber is a fiber that is refined by surface oxidation of a naturally-derived cellulose solid raw material having an I-type crystal structure. In other words, natural cellulose fibers have a high-order solid structure built up by bundling fine fibers called microfibrils produced in the process of biosynthesis. The fine cellulose fiber is obtained by weakening the hydrogen bond) by introducing an aldehyde group or a carboxyl group, and further through a refinement treatment.

  Then, by adjusting the oxidation treatment conditions, the carboxyl group content is increased or decreased within a predetermined range, the polarity is changed, the electrostatic repulsion of the carboxyl group or the above-mentioned fine processing is performed. Thus, the average fiber diameter, average fiber length, average aspect ratio and the like of the cellulose fiber can be controlled.

  The antistatic agent of the present invention can be made into a suspension or a dried product containing the specific cellulose fiber described above. When the antistatic agent of the present invention is made into a suspension, the solid content concentration may be adjusted so that it can be molded according to the purpose. For example, the solid content concentration is in the range of 0.05 to 30% by mass. Can do.

  The antistatic agent of the present invention includes known fillers, colorants such as pigments, ultraviolet absorbers, water-resistant agents (silane coupling agents, etc.) within the range of types and amounts that can solve the problems of the present invention. ), Clay minerals (such as montmorillonite), crosslinking agents (additives having reactive functional groups such as epoxy groups and isocyanate groups), metal salts, colloidal silica, alumina sol, titanium oxide, and the like.

  The antistatic agent of the present invention preferably has a haze value of 3.8% or less, more preferably 3%, still more preferably 2% or less. In addition, the said haze value is calculated | required by the measuring method as described in an Example.

<Antistatic molding>
The antistatic molded article of the present invention has a layer (antistatic layer) made of the above-described antistatic agent on a molded article serving as a base material.

The antistatic molded article of the present invention can be produced by the following production method when a suspension-like antistatic agent is used.
First, an antistatic agent is attached to one surface or both surfaces of a molded body as a base material by a known method such as a coating method, a spraying method, or a dipping method, preferably by a coating method or a spraying method. Form. Then, it dries by methods, such as natural drying and ventilation drying.

  The thickness of the antistatic layer is preferably 20 to 5000 nm, more preferably 50 to 2000 nm, and still more preferably 100 to 1500 nm.

  As the molded body serving as the base material, a thin film such as a film, a sheet, a woven fabric, and a non-woven fabric having a desired shape and size, and a three-dimensional container such as a box or bottle having various shapes and sizes can be used. These molded products may be made of paper, paperboard, plastic, metal (a material having a large number of holes or a wire mesh, which is mainly used as a reinforcing material), or a composite of these. it can. The molded body serving as the base material can have a multilayer structure made of a combination of the same or different materials (for example, adhesiveness and wettability improver).

  The molded body serving as the substrate may be transparent, opaque, or colored, or may be a pattern, character, figure or the like displayed.

  The plastic used as the base material can be appropriately selected according to the application, but polyolefins such as polyethylene and polypropylene, polyamides such as nylon 6, 66, 6/10, and 6/12, polyethylene terephthalate (PET), and polybutylene. One or more selected from polyesters such as terephthalate, aliphatic polyester, polylactic acid (PLA), polycaprolactone, and polybutylene succinate, and cellulose such as cellophane and cellulose triacetate (TAC) can be used.

  The thickness of the molded body serving as the base material is not particularly limited, and may be appropriately selected so that strength according to the application can be obtained. For example, the thickness can be in the range of 1 to 1000 μm.

The antistatic molded article of the present invention preferably has a surface resistivity of 1.0 × 10 ¹⁰ Ω / □ or less, more preferably 1.0 × 10 ^{5 to} 5. The range is 0 × 10 ⁹ Ω / □.

  By using the antistatic agent of the present invention to form a transparent antistatic layer on a molded body serving as a substrate, it is possible to easily impart antistatic properties. For this reason, the antistatic molded article of the present invention does not impair the transparency when the substrate is transparent, the substrate is colored, a pattern is formed, characters, figures, etc. Even when displayed, the antistatic property is imparted without impairing the external appearance.

  The measuring method of each item shown in Table 1 is as follows.

(1) Cellulose fiber (1-1) Average fiber diameter, average fiber length and average aspect ratio The average fiber diameter of the cellulose fiber was observed by dropping a suspension diluted to 0.0001% by mass onto mica and drying it. As a sample, the fiber height was measured with an atomic force microscope (Nanoscope III Tapping mode AFM, manufactured by Digital Instrument Co., Ltd., probe using Point Probe (NCH) manufactured by Nano Sensors). In an image in which cellulose fibers can be confirmed, five or more were extracted, and the average fiber diameter was determined from the fiber height.

（The Theory of Polymer Dynamics, Ｍ.DOI and D.F.EDWARDS， CLARENDON PRESS・OXFORD,1986,P312に記載の剛直棒状分子の粘度式（８．１３８）を利用した（ここでは、剛直棒状分子＝セルロース繊維とした）。（８．１３８）式とＬｂ²×ρ₀＝M/N_Aの関係から数式１が導出される。ここで、η_spは比粘度、πは円周率、lnは自然対数、Pはアスペクト比（L/ｂ）、γ＝0.8、ρ_sは分散媒の密度（ｋｇ/ｍ³）、ρ₀はセルロース結晶の密度（ｋｇ/ｍ³）、Cはセルロースの質量濃度（C＝ρ/ρ_s）、Lは繊維長、ｂは繊維幅（セルロース繊維断面は正方形とする）、ρはセルロース繊維の濃度（ｋｇ/ｍ³）、Ｍは分子量、N_Aはアボガドロ数を表す。） The average aspect ratio was calculated from the viscosity of a diluted suspension (0.005 to 0.04% by mass) obtained by diluting cellulose fibers with water. The viscosity was measured at 20 ° C. using a rheometer (MCR300, DG42 (double cylinder), manufactured by PHYSICA). From the relationship between the mass concentration of the cellulose fiber and the specific viscosity of the cellulose fiber suspension with respect to water, the aspect ratio of the cellulose fiber was calculated by the following formula to obtain the average aspect ratio of the cellulose fiber.

(The theory of Polymer Dynamics, M.DOI and DFEDWARDS, CLARENDON PRESS / OXFORD, 1986, P312) The viscosity formula (8.138) of a rigid rod-like molecule was used (here, rigid rod-like molecule = cellulose fiber) ). (8.138) equation and _{^{Lb 2 × ρ 0 = M /}} N equation 1 from the relation of _a is derived. here, eta _sp is specific viscosity, [pi is circle ratio, ln is natural logarithm, P Is the aspect ratio (L / b), γ = 0.8, ρ _s is the density of the dispersion medium (kg / m ³ ), ρ ₀ is the density of cellulose crystals (kg / m ³ ), and C is the mass concentration of cellulose (C = ρ / ρ _s ), L is the fiber length, b is the fiber width (the cross section of the cellulose fiber is square), ρ is the concentration of the cellulose fiber (kg / m ³ ), M is the molecular weight, and N _A is the Avogadro number. )

  The average fiber length was calculated from the fiber diameter and aspect ratio measured by the above method.

(1-2) Carboxyl group content (mmol / g)
About 0.5 g of the dry weight of oxidized pulp is put in a 100 ml beaker, and ion exchange water is added to make a total of 55 ml. Then, 5 ml of 0.01 M sodium chloride aqueous solution is added to prepare a pulp suspension. Stir with a stirrer until dispersed. Then, 0.1M hydrochloric acid is added to adjust the pH to 2.5 to 3.0, and then 0.05M sodium hydroxide aqueous solution is injected under the condition of a waiting time of 60 seconds using an automatic titrator (AUT-501, manufactured by Toa DK Corporation). Then, the electric conductivity and the pH value of the pulp suspension every minute were measured, and the measurement was continued until the pH became about pH11. And the sodium hydroxide titration amount was calculated | required from the obtained electrical conductivity curve, and carboxyl group content was computed.
Natural cellulose fibers exist as aggregates of highly crystalline microfibrils formed by collecting about 20 to 1500 cellulose molecules. In the TEMPO oxidation reaction employed in the present invention, a carboxyl group can be selectively introduced onto the surface of the crystalline microfibril. Therefore, in reality, carboxyl groups are introduced only on the crystal surface, but the carboxyl group content defined by the measurement method is an average value per cellulose weight.

(2) Antistatic molding (2-1) Surface resistivity (Ω / □)
The antistatic film is stored in a constant temperature and humidity room at 25 ° C. and 50% RH, and after one day, the surface resistivity is measured according to the test method of ASTM D 257 using Yokogawa Hewlett Packard's model 4329A high resistance meter. Was measured (measurement voltage 100 V). The results are shown in Table 1.

(2-2) Haze value (%)
The haze value was measured according to the test method of JIS K7105 using a haze meter (HM-150 model, manufactured by Murakami Color Research Laboratory Co., Ltd.). The results are shown in Table 1. In addition, the haze value shown in Table 1 is the haze value of the antistatic layer, and the haze value of a polyethylene terephthalate (PET) sheet (trade name: Lumirror, manufactured by Toray Industries, Inc., sheet thickness: 7 μm) used as the base sheet. This is a value obtained by subtracting 7% from the measured value. The smaller the number, the better the transparency.
(2-3) Antistatic layer thickness (nm)
The thickness of the antistatic layer is a value calculated from the wet film thickness and the solid content with the specific gravity of the cellulose fiber being 1.5. This value was in good agreement with the film thickness measured with an atomic force microscope.

Production Example 1 [Production of Specific Cellulose Fiber Used as Antistatic Agent]
(1) Raw material, catalyst, oxidizing agent, co-oxidizing agent Natural fiber: Bleached kraft pulp of conifers (Manufacturer: Fletcher Challenge Canada, trade name “Machenzie”, CSF 650 ml)
TEMPO: Commercial product (Manufacturer: ALDRICH, Free radical, 98%)
Sodium hypochlorite: Commercial product (Manufacturer: Wako Pure Chemical Industries, Ltd. Cl: 5%)
Sodium bromide: Commercial product (manufacturer: Wako Pure Chemical Industries, Ltd.).

(2) Production procedure First, 100 g of bleached kraft pulp fiber of the above-mentioned coniferous tree was sufficiently stirred with 9900 g of ion-exchanged water, and then TEMPO 1.25% by mass, sodium bromide 28.4% by mass, hypoxia with respect to 100 g of pulp mass. Sodium chlorate (14.2% by mass) was added in this order, and a pH stud was used to maintain the pH at 10.5 by dropwise addition of 0.5M sodium hydroxide to carry out an oxidation reaction.

  Next, dripping was stopped at an oxidation time of 120 minutes to obtain oxidized pulp. The oxidized pulp was sufficiently washed with ion exchange water and dehydrated. Thereafter, 10 g of oxidized pulp and 990 g of ion-exchanged water are agitated for 10 minutes with a mixer (Vita-Mix-Blender ABSOLUTE, manufactured by Osaka Chemical Co., Ltd.) (refining time is 10 minutes), so that the fiber is refined. To obtain a suspension of specific cellulose fibers used as an antistatic agent. Solid content concentration (namely, specific cellulose fiber concentration) in the obtained suspension was 1.5 mass%.

Example 1
An antistatic agent comprising the cellulose fiber obtained in Production Example 1 on one side of a polyethylene terephthalate (PET) sheet (trade name: Lumirror, manufactured by Toray Industries, Inc., sheet thickness 7 μm, haze value 2.7%) as a base sheet (Suspension with a solid content of 1.5% by mass) was applied with a bar coater (# 50) and then dried at 23 ° C. for 120 minutes or more to obtain an antistatic film.

Example 2
An antistatic film was obtained in the same manner as in Example 1 except that the antistatic agent made of cellulose fiber obtained in Production Example 1 (however, the suspension having a solid content adjusted to 0.75% by mass) was used. .

Example 3
An antistatic film was obtained in the same manner as in Example 1 except that the antistatic agent made of cellulose fiber obtained in Production Example 1 (however, a suspension whose solid content was adjusted to 0.3% by mass) was used. .

Example 4
In Production Example 1, the same procedure as in Example 1 was used, except that an antistatic agent made of cellulose fibers produced with a micronization treatment time of 300 minutes (however, a suspension in which the solid content was adjusted to 0.3% by mass) was used. An antistatic film was obtained by this method.

Example 5
In Production Example 1, an antistatic agent comprising cellulose fibers produced with sodium bromide at 12.5% by mass, oxidation time of 10 minutes, and refinement treatment time of 60 minutes (however, the solid content was adjusted to 0.3% by mass) A suspension was prepared in the same manner as in Example 1 except that the suspension was used to obtain an antistatic film.

Comparative Example 1
A polyethylene terephthalate (PET) sheet (trade name: Lumirror, manufactured by Toray Industries Inc., sheet thickness: 7 μm) was used.

Comparative Example 2
Production Example 1 except that microcrystalline cellulose (MCC) (KC-Flock 300G, manufactured by Nippon Paper Chemicals Co., Ltd.) was used as a raw material, sodium hypochlorite was 56.8% by mass, and the refinement was not performed. A suspension was prepared in the same manner as described above. Thereafter, an antistatic film was prepared in the same manner as in Example 1, except that an antistatic agent comprising cellulose fibers obtained by this method (however, a suspension in which the solid content was adjusted to 0.3% by mass) was used. Obtained.

Comparative Example 3
Instead of the antistatic agent consisting of the cellulose fiber obtained in Production Example 1, an aqueous solution (solid content concentration 0.3 mass%) of carboxymethyl cellulose Na salt (substitution degree 0.47, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) An antistatic film was obtained in the same manner as in Example 1 except that it was used.

実施例１〜５と比較例３、４との対比から明らかなとおり、本発明の帯電防止剤を用いた成形体は、周知の水溶性ポリマー水溶液を用いたものと同程度の透明性（ヘイズ値）を示していた。
そして、実施例１〜５と比較例１〜４との対比から明らかなとおり、本発明の帯電防止剤を用いた成形体は表面抵抗値が小さく、高い帯電防止性を有していた。 Comparative Example 4
Instead of the antistatic agent made of cellulose fiber obtained in Production Example 1, Example 1 was used except that an aqueous solution of polyvinyl alcohol (PVA103, manufactured by Kuraray Co., Ltd.) (solid content concentration: 0.3% by mass) was used. An antistatic film was obtained in the same manner.

As is clear from the comparison between Examples 1 to 5 and Comparative Examples 3 and 4, the molded body using the antistatic agent of the present invention has the same degree of transparency (haze) as that using a well-known water-soluble polymer aqueous solution. Value).
As is clear from the comparison between Examples 1 to 5 and Comparative Examples 1 to 4, the molded body using the antistatic agent of the present invention had a small surface resistance and high antistatic properties.

Claims (4)

Cellulose fiber having an average fiber diameter of 200 nm or less and an average aspect ratio of 10 to 1,000 , and a cellulose fiber having a carboxyl group content of 0.1 to 2 mmol / g of cellulose constituting the cellulose fiber An antistatic agent comprising:
The antistatic agent whose haze value (JIS K7105) of the layer which consists of said antistatic agent is 3.8% or less. The antistatic agent of Claim 1 whose average aspect-ratio of the said cellulose fiber is 100-350 .   The antistatic molding which has the layer which consists of an antistatic agent of Claim 1 or 2 in the molded object used as a base material.   The antistatic molded article according to claim 3, wherein the layer made of the antistatic agent has a thickness of 5000 nm or less.