JP2007320977A - Chitosan powder and water-based coating agent - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a chitosan powder that, even when added to various kinds of water-based coating agents, does not cause the coating agent to gel and does not hinder functions of other functional agents contained in the coating agent. <P>SOLUTION: The chitosan powder to be added to the water-based coating agent has an average particle size of at most 100 μm and gives a pH of a dispersion obtained by dispersing it in pure water at a concentration of 1 mass% of at least 6.5. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a chitosan powder and an aqueous coating agent, and more specifically, a chitosan powder which can be added to various aqueous coating agents without causing the coating agent to gel, and an aqueous coating formed by adding the chitosan powder. It relates to the agent.

  In recent years, as social health orientation has become stronger, one of the issues to be noticed is the solution of the sick house problem, which is one of the issues that have to be solved as a problem of the impact on the human body and also as a social environmental problem. It is a big theme. Conventional coatings, adhesives, insect repellents, and fungicides used in various buildings include chemical substances called VOCs (Volatile Organic Compounds: formaldehyde, toluene, xylene, etc.) ing.

  By using the coating agent or the like, VOCs volatilize in the environment in the building, causing sick house syndrome and chemical sensitivity. In addition, it has been clarified that VOC has an action of exacerbating allergic symptoms caused by mold. The countermeasures that have been taken up to this point are merely providing adhesives and building materials that reduce the amount of materials used as the source of formaldehyde and the like, and are not sufficient countermeasures. Accordingly, development of a more effective method for suppressing the generation of VOCs and an effective method for removing VOCs once volatilized are required.

  As one of the developments of the above-mentioned new technology, the use of chitosan, which is a natural product material, can be used with peace of mind in terms of environmental safety and exhibits antibacterial and deodorizing functions, has attracted attention. Chitosan, known as a natural polysaccharide, is industrially produced by deacetylating chitin isolated from crustaceans such as shrimp and crabs. In addition, the properties unique to chitosan have functions such as film-forming properties, antibacterial properties, water retention and aggregating ability, and are practically used as functional polymers in various fields.

  Particularly recently, chitosan has been applied as a safe function-imparting agent capable of imparting the above functions to various articles. For example, as an antibacterial property-imparting coating agent for various films, nonwoven fabrics, and textile products, Then, as a wound dressing, in the cosmetics field, as a powder property improving agent, in the coating field, as a thickener, dispersant, or film-forming agent, in the design application field, imparting antibacterial properties, and pigmentation Attempts have been made to use it as a seed coloring agent.

  For example, Patent Documents 1 and 2 disclose a chitosan-containing coating agent having excellent coating strength, wherein chitosan is allowed to coexist in a solution state when a monomer is polymerized as a chitosan-containing emulsion aqueous coating agent composition. Is described.

  However, in any of the above-mentioned techniques, the chitosan contained in the coating agent is an aqueous solution at the time of polymerization, so that the amount of chitosan that can be contained is limited, and the chitosan content in the coating agent cannot be increased. Issues remain in terms.

  Conventionally, wall coating agents for homes and general buildings have many anti-bacterial functions such as the resolution and removal of indoor odors, the response to social issues such as VOC problems, and the prevention of germs and mold. It is required to have the following functions.

  For example, Patent Document 3 describes a wall coating agent containing white-baked bamboo charcoal as an additive. Further, Patent Document 4 describes a room deodorizer using zeolite or titanium oxide. Further, Patent Document 5 describes a deodorizing method using cyclodextrin or zeolite. Patent Document 6 describes an antibacterial deodorant and a heat generating agent using zeolite or chitosan.

  In each of the above methods, when various functional agents and chitosan are used in an aqueous coating agent, the aqueous chitosan aqueous solution and other functional agents may interact to cause the aqueous coating agent to gel. Therefore, we tried to add chitosan powder to the aqueous coating agent instead of the chitosan aqueous solution. However, when conventional chitosan powder was added to a commercially available aqueous coating agent, emulsion breakage occurred in the aqueous coating agent, and the stability including chitosan powder No aqueous coating agent was obtained.

JP 2005-272649 A JP 2004-175876 A JP 2003-336374 A JP 2003-116974 A JP 2002-291857 A JP-A-7-236504

  Accordingly, an object of the present invention is to provide a chitosan powder which does not cause gelation of the coating agent even when added to various aqueous coating agents, and does not hinder the function of other functional agents contained in the coating agent, It is an object of the present invention to provide a multifunctional environment-friendly aqueous coating agent containing the chitosan powder.

The above object is achieved by the present invention described below.
That is, the present invention provides an aqueous coating agent characterized in that the average particle size is 100 μm or less, and the pH of the dispersion when dispersed in pure water at a concentration of 1% by mass is 6.5 or more. Provide chitosan powder for adding.

  Moreover, this invention provides the aqueous coating agent characterized by adding the chitosan powder of the said invention. The aqueous coating agent preferably contains an adsorbent and / or a photocatalyst. The adsorbent is preferably at least one selected from bamboo charcoal, shiratake charcoal, zeolite, cyclodextrin, and shell fired product, and the photocatalyst is preferably titanium dioxide.

  When the chitosan powder having an average particle size of 100 μm or less, preferably 50 μm or less, more preferably 10 μm or less is dispersed in pure water at a concentration of 1% by mass, the pH of the dispersion is 6.5 or more. As a result of mixing the obtained chitosan powder into a commercially available aqueous coating agent, it was found that the chitosan powder can be stably dispersed in the aqueous coating agent without causing gelation, which may be caused by emulsion breakage that has occurred in the past.

  The chitosan powder can be directly added to various aqueous coating agents, and can coexist with various adsorbents and photocatalysts contained in the aqueous coating agent. Therefore, according to the present invention, a multifunctional environment-friendly chitosan powder-containing coating agent having adsorption ability, decomposability, deodorizing properties, and antimicrobial properties of harmful substances is simply provided.

Next, the present invention will be described more specifically with reference to the best mode for carrying out the invention.
Chitosan used in the present invention is a deacetylated product of chitin which is a kind of natural polymer contained in crab, shrimp, shells of insects, mushrooms, etc., and 2-amino-2-deoxy-D -A basic polysaccharide having glucose as one constituent unit. Chitosan, which is such a deacetylated chitin, has already been industrially produced and is available in various grades. There is no particular limitation on the origin and production method of chitosan used in the present invention. Any industrially produced chitosan can be used.

  Moreover, there is no special restriction | limiting in the deacetylation degree and polymerization degree of chitosan, What is necessary is just to select optimal conditions suitably according to a use. Usually, the degree of deacetylation is preferably 30% or more, more preferably from 70% to 100%, and still more preferably from 80% to 100%. In addition, the chitosan used in the present invention preferably has a viscosity of 1 mPa · s to 10,000 mPa · s of an aqueous solution containing 1% by mass of chitosan and 1% by mass of acetic acid.

(Deacetylation degree measuring method)
The degree of deacetylation of the chitosan is calculated from the titer measured by colloid titration. Specifically, a toluidine blue solution is used as an indicator and colloidal titration with an aqueous polyvinyl potassium sulfate solution to quantify the free amino groups in the chitosan molecule and determine the degree of deacetylation of chitosan. Hereinafter, sample preparation and titration tests were performed at room temperature of about 20 ° C.

-Sample preparation and titration test A predetermined amount of chitosan is added to a 0.5% by mass acetic acid aqueous solution, and the prepared solution with a pure chitosan concentration of 0.5% by mass is made exactly 100 g and dissolved by stirring. Next, 10 g of this prepared solution and 90 g of ion-exchanged water are accurately collected, and a 0.05 mass% chitosan solution is prepared by stirring and mixing. Further, 10 g is accurately weighed from this 0.05 mass% chitosan solution, and 50 ml of ion exchange water and about 0.2 ml of toluidine blue solution are added thereto, and titrated with a polyvinyl potassium sulfate solution (N / 400 PVSK). The titration rate is 2 ml / min to 5 ml / min, and the end point titration is the point at which the measurement solution is changed from blue to reddish purple and held for 30 seconds or more.

-Blank test The same titration test is performed using ion-exchanged water instead of the preparation solution used in the above titration test.

Calculation method X = 1/400 × 161 × f × (V−B) / 1000
= 0.4025 * f * (V-B) / 1000
Y = 0.5 / 100-X
X: free amino group mass in chitosan (equivalent to glucosamine residue mass)
Y: Mass of bound amino group in chitosan (corresponding to mass of N-acetylglucosamine residue)
f: titer of N / 400 PVSK V: titration of sample (ml)
B: Blank test titration (ml)
Deacetylation degree (%) = (free amino group) / {(free amino group) + (bound amino group)} × 100
= (X / 161) / (X / 161 + Y / 203) × 100
161 is the equivalent molecular weight of the glucosamine residue, and 203 is the equivalent molecular weight of the N-acetylglucosamine residue.

(Chitosan viscosity measurement method)
A predetermined amount of chitosan is added to a 1% by mass acetic acid aqueous solution to prepare a chitosan pure concentration of 1% by mass. After stirring and dissolving this prepared solution, the viscosity was measured using a B-type rotational viscometer while maintaining the temperature at 20 ° C. in a thermostatic bath.

  In addition, chitosan pure content means solid content conversion in a chitosan sample, and is specifically solid content mass calculated | required by drying a chitosan sample at 105 degreeC for 2 hours.

  When the degree of deacetylation of chitosan is less than 30%, the expected effect cannot be obtained due to the extreme decrease in the amino group content of chitosan. Moreover, when the viscosity is less than 1 mPa · s, the cost for reducing the molecular weight is high, which is disadvantageous in production cost.

  On the other hand, when the viscosity exceeds 10,000 mPa · s, it is extremely difficult to pulverize chitosan, and chitosan having the predetermined particle size cannot be obtained. That is, the chitosan used in the present invention is an aqueous solution having a degree of deacetylation of 80% to 100% and containing 1% by mass of chitosan and 1% by mass of acetic acid in terms of obtaining effective antibacterial properties. More preferably, the viscosity is 3 mPa · s to 1,000 mPa · s.

  Moreover, the average particle diameter of the chitosan powder of the present invention relates to the dispersibility of the chitosan powder in the aqueous coating agent, and is 100 μm or less, preferably 50 μm or less, more preferably 10 μm or less. When the average particle diameter exceeds 100 μm, defects tend to occur in the film formed from the aqueous coating agent containing chitosan powder having such particle diameter. The finer the particle size of the chitosan powder is, the better, but there is a drawback that the cost is drastically increased if the chitosan powder has an average particle size of 1 μm or less. Moreover, it is preferable that the addition amount with respect to the aqueous coating agent of chitosan powder is the quantity which occupies 0.1-20 mass% in the aqueous coating agent whole mass. If the addition amount is less than 0.1% by mass, sufficient effects of deodorant, antibacterial and antifungal properties of chitosan cannot be obtained. On the other hand, if the addition amount exceeds 20% by mass, chitosan is contained in the aqueous coating agent. The water-based coating agent loses fluidity and lacks coating suitability.

  The chitosan powder of the present invention needs to have a pH of 6.5 or higher when the dispersion is dispersed in pure water at a concentration of 1% by mass, or the pH is adjusted to 6.5 or higher. It is necessary to be a chitosan powder. Pure water here is distilled water in which reabsorption of carbon dioxide is suppressed as much as possible.

  When chitosan powder having a pH of less than 6.5 when chitosan is dispersed in pure water at a concentration of 1% by mass is mixed with an aqueous coating agent, the aqueous coating agent gels. , It will not function as a coating agent. In other words, by using the chitosan powder of the present invention, there is no limitation on the type of binder resin or emulsion of the target aqueous coating agent. It can also be used for water-soluble coating binders composed of water-soluble resin binders such as polyvinyl alcohol, general-purpose acrylic, acrylic silicon, urethane, and fluorine-based emulsions.

  The method for producing the chitosan powder of the present invention is not particularly limited, and chitosan powder can be obtained by dry pulverization or wet pulverization, isolation from chitosan acid solution, etc., for example, spray drying (for example, spray drying) or lyophilization. The production method may be selected according to the purpose, including the required particle size, production efficiency, and economic effects such as (freeze drying), and the chitosan powder of the present invention can be obtained by a known method. Preferably, chitosan having a molecular weight adjusted as necessary is used as a starting material, and thereafter dry pulverization or wet pulverization is performed using, for example, a hammer mill, a jet mill, a ball mill, or a vibration mill as a pulverizer. Furthermore, in order to obtain a required particle size, it is also one of the preferable forms to repeatedly grind by the same grinding method or different methods.

  In addition, classifying chitosan powder after pulverization to uniform the particle size of chitosan powder is also preferable in terms of removing chitosan having a particle size outside the preferred range simultaneously with uniform dispersion of chitosan powder. By using it, the characteristics as a coating agent can be drawn out more sufficiently.

  Further, the aqueous coating agent to which the chitosan powder of the present invention is added contains at least one selected from an adsorbent and a photocatalyst, thereby causing harmful substances, particularly odor components such as VOC, such as ammonia, trimethylamine, formaldehyde, It is possible to obtain an aqueous coating agent that has a multifunctional environment-compatible coating film that has adsorption ability such as toluene, resolution, deodorization property, and antimicrobial property and is excellent in chemical safety.

  Examples of the adsorbent to be used include bamboo charcoal, white bamboo charcoal, zeolite, cyclodextrin, and shell fired product, and examples of the photocatalyst include titanium dioxide. Details of each adsorbent and photocatalyst used are described below.

  Bamboo charcoal is known as a natural material having a deodorizing and sterilizing effect because of its ability to adsorb chemical substances to functional groups in a pore structure formed by baking bamboo at a high temperature. Also, the functional group changes due to the difference in firing temperature, and bamboo charcoal that is generally fired at around 500 ° C. shows weak acidity, and so-called white bamboo charcoal that is fired at around 1,000 ° C. becomes weakly alkaline.

  These properties are related to the adsorption ability of acidic and basic organic chemical substances. For example, basic ammonia is more easily adsorbed on bamboo charcoal and toluene is more easily adsorbed on white bamboo charcoal. That is, there is no restriction | limiting in particular in use of the bamboo charcoal or white bamboo charcoal in this invention, According to the intended purpose, you may use it individually or in mixture, The addition amount is 0.1-30 in the aqueous coating agent total mass. It is the amount occupying mass%.

  In addition, the porous zeolite is known to have excellent adsorption ability and antibacterial properties for ammonia and the like due to physical adsorption by metal cations present in the crystal and van der Waals force. Furthermore, there are natural and artificial zeolites, and artificial zeolites with a regular chemical structure are selected and used according to their economic effects and purpose of use because they have superior performance such as adsorption capacity compared to natural products. Is done.

  There is no restriction | limiting in particular in the usage-amount of the said artificial or natural zeolite, It selects according to a use purpose etc., The addition amount is the quantity which occupies 0.1-20 mass% in the total mass of an aqueous coating agent.

  Cyclodextrins are known to have excellent deodorizing ability by inclusion and adsorption, and are cyclic oligosaccharides that are hydrophilic on the outside of the molecular ring and hydrophobic on the inside, and include organic molecules on the inside. ing. Further, cyclodextrins generally have three types, α (6), β (7), and γ (8), depending on the number of glucose molecules constituting them, and there is no particular limitation on their use in the present invention. The three types may be used alone or in combination, and the amount added is an amount occupying 0.1 to 20% by mass in the total mass of the aqueous coating agent.

  Moreover, the said shell baked product is a natural oxidation obtained as a food additive (Ministry of Health, Labor and Welfare No. 120 Food Sanitation Law Food Additive 218) obtained by baking shell obtained from nature in a high temperature of 1,000 ° C. or higher. It is calcium. Already, antibacterial, bactericidal and deodorizing effects are recognized and used as adsorbents such as formaldehyde.

  The shell baked product having the above-mentioned alkali property is also used as an adsorbent, more preferably for adjusting the pH of the aqueous coating agent, and the amount added is 0.1 to 20% by mass in the total mass of the aqueous coating agent. It is.

  In addition, titanium dioxide as the photocatalyst excites electrons by ultraviolet rays, oxidizes adsorbed water on the catalyst surface with the generated holes, and oxidatively decomposes organic matter with hydroxy radicals having strong oxidizing power generated thereby. It is known. In general, it is used in various applications such as antibacterial, antifouling, antifungal, decomposition of pollutants and deodorization.

  In addition, there are three types of titanium dioxide, tetragonal low temperature type anatase type, tetragonal high temperature type rutile type, and orthorhombic type brookite type, although there are differences in the performance of each, Industrially, anatase type and rutile type are generally used. Particularly, the anatase type having a high photocatalytic activity is most frequently used because of the strong absorption near the ultraviolet region. The Brook Kite type has catalytic activity against particularly weak light and is used according to the purpose. These uses in the present invention are not particularly limited, and each of the three types may be used alone or in combination. Regarding the use of titanium dioxide in the present invention, the amount added is 0. 0 in the total mass of the aqueous coating agent. The amount occupying 1 to 20% by mass.

  For example, it is preferable to use titanium dioxide at the same time as silica or a silicone-based binder because cracks are unlikely to occur during the formation of the coating film, and the photocatalytic action of titanium dioxide is more effectively performed.

  Furthermore, including the action of the chitosan powder of the present invention, the physical adsorption of the adsorbent to the organic substance peculiar to the porous material is performed simultaneously with deodorization of the surrounding atmosphere, for example, when the coating film is formed, to the coating film itself. It also leads to residual odors. That is, it is more preferable to use the titanium dioxide at the same time as the adsorbent because it has the effect of decomposing the residual odorous substance simultaneously with the adsorption.

  Each of the adsorbents and titanium dioxide is preferably treated by ordinary pulverization classification for the purpose of effective use due to the expansion of the contact area with organic matter, which has little influence during dispersion processing and coating film formation during preparation of the aqueous coating agent. The particle size is not particularly limited, and the adsorbent is preferably used with an average particle size of 100 μm or less and titanium oxide of 10 μm or less. That is, when the average particle diameter in the adsorbent used exceeds 100 μm, and when the average particle diameter in titanium dioxide exceeds 10 μm, for example, the dispersion stability of the aqueous coating agent during long-term storage, the film during coating film formation This is not preferable because there is a limit to the thickness adjustment or an adverse effect on homogenization at the time of coating film formation, and the effect of VOC adsorption and decomposition is further reduced.

  The aqueous coating agent containing the adsorbent and / or photocatalyst can be used, for example, as a dispersion, paste, or solution, and the amount of adsorbent or photocatalyst used at that time is appropriately adjusted according to the purpose of use. In a more preferable form, other additives are also used as necessary, such as improvement of suitability for the application object. Other additives include surfactants, antifoaming agents, antiseptics, antifungal agents, algaeproofing agents, coloring agents, UV absorbers, antioxidants, plasticizers, slip agents, antistatic agents, thickeners , Adhesives, inorganic fillers, extender pigments (for example, calcium carbonate), and organic resins. It is also preferable to add calcium carbonate as an extender pigment or heavy calcium carbonate obtained by pulverizing natural limestone, and slaked lime that performs the same function, and it plays a role in improving the film-forming property of the aqueous coating agent and preventing cracks. Fulfill. From the above, a coating agent comprising at least one selected from other additives is also a preferred form.

  In the production of the chitosan powder-containing aqueous coating agent of the present invention, the mixing / dispersing or dissolving method of chitosan powder and various additives in the aqueous coating agent is not particularly limited, and is a general mixing / dispersing machine, fine dispersing machine, or atomizing machine. For example, a ball mill, a dyno mill, a sand mill, a roll mill, a glen mill, a dissolver, a disper, a paint shaker, and the like are more preferable if they can be refined simultaneously with mixing.

  Further, the aqueous coating agent of the present invention is sprayed, applied or impregnated on glass, ceramics, plastics, metals, fibers, nonwoven fabric products, and packaging materials (for example, plastic films, aluminum and resin composite films), and then coated. By evaporating the solvent therein, various articles with a coating attached can be obtained. Drying may be performed at a temperature equal to or higher than the boiling point of water under reduced pressure or normal pressure, and preferably heated at 100 to 150 ° C. Furthermore, additional addition of a crosslinking agent can be performed as appropriate.

  Next, the present invention will be described more specifically with reference to examples and comparative examples. Note that the present invention is not limited to these.

<Example 1>
Each of the following five types of aqueous coating agents contains chitosan powder (average particle size 5 μm, chitosan 1 mass% acetic acid 1 mass% aqueous solution viscosity at 20 ° C. 5 mPa · s, deacetylation degree 98%, pure water 1 mass% When the dispersion was dispersed at a concentration of 1 to 8% in an amount corresponding to 2% by mass of the aqueous coating agent, no aqueous coating agent was gelled and the chitosan powder could be mixed stably. . In contrast, when chitosan having a pH of 6 when dispersed in pure water at a concentration of 6% was added in an amount corresponding to 2% by mass of the same aqueous coating agent, only Dystender 3000 was gel. The chitosan powder could be stably mixed without conversion, but all other aqueous coating agents gelled.

・ Loan coat (acrylic emulsion coating agent)
・ Dystainer 2000 (acrylic silicone coating)
・ Dystainer 3000 (fluorine coating agent)
・ Dice coat (modified colloidal silica coating agent)
・ Shiratake Charcoal LC-1000 (acrylic emulsion coating agent)
All of the above are trade names of water-based coating agents of Dainichi Seika Kogyo Co., Ltd.

<Example 2>
8 parts of chitosan powder was added to 100 parts of “Shiratake Charcoal LC-1000” and dispersed with a paint shaker for 1 hour to obtain a chitosan powder-containing aqueous coating agent. In addition, "Shiratake Charcoal LC-1000" used above is an ion hybrid paint managed and registered as a formaldehyde-regulated product by the Japan Paint Industry Association. As main components, Shiratake Charcoal, photocatalyst (titanium dioxide), This is an emulsion paint that contains calcined shell calcium and tourmaline.

Next, the aqueous coating agent is applied to an aluminum plate (10 cm × 10 cm) with a bar coater so that the solid content is 40 g / m ^2, and then dried at 150 ° C. for 3 minutes to obtain a coating sheet containing chitosan powder. Obtained.
Also, for Examples 3 and 4, a chitosan powder-containing coating sheet was prepared in the same manner as in Example 2. In the comparative example, “Shiratake Charcoal LC-1000” used alone as a base was used, and each coating sheet was obtained.
The formulation composition of the prepared aqueous coating agent is described below (Table 1), and Examples 2, 3, 4 and Comparative Examples are shown.

  Furthermore, each coating sheet obtained above was used as a sample, and an evaluation test was performed as described below for deodorizing, antibacterial and antifungal properties of each sheet.

[Deodorization performance measurement test]: Formaldehyde deodorization test Each sample (5 cm square x 2) of the examples and comparative examples and formaldehyde were injected into the tetrabag (3 L) so that the initial concentration was 4 ppm, and every elapsed time. The formaldehyde concentration was measured using a detector tube. At the same time, a (60w) fluorescent lamp was used, and light illumination was performed at a light source / sample distance of 1.5 m. As the blank, an uncoated aluminum plate (5 cm square × 2 pieces) was used. The test results are shown below (Table 2).

[Antibacterial / antifungal test]
(Test method)
Each sample (5 cm square) after sterilization was subjected to an antibacterial test in accordance with JIS Z2801: 2000 (antibacterial processed product, antibacterial test method). Similarly, an antifungal test was conducted according to the wet method defined in JIS Z2911 (mold resistance test method).

(Used cells)
・ Antimicrobial test: Escherichia coli NBRC3972, Staphylococcus aureus subsp.aureus NBRC12732
-Antifungal test: Aspergillus niger, Penicillium citrinum

(Test results)
For each sample in Examples 2, 3, and 4, including a comparative example of “Shiratake Charcoal LC-1000” used alone as a base, no growth of the bacteria was observed, and all samples had antibacterial / antifungal performance. It was confirmed to be excellent.

According to the present invention as described above, even when added to various aqueous coating agents, the coating agent does not gel and does not inhibit the function of other functional agents contained in the coating agent. And a multifunctional environment-friendly aqueous coating agent containing the chitosan powder.

Claims (5)

  Chitosan powder for addition to an aqueous coating agent, characterized in that the average particle size is 100 μm or less and the pH of the dispersion when dispersed in pure water at a concentration of 1% by mass is 6.5 or more .   An aqueous coating agent, wherein the chitosan powder according to claim 1 is added.   The aqueous coating agent according to claim 2, wherein the aqueous coating agent contains an adsorbent and / or a photocatalyst.   The water-based coating agent according to claim 3, wherein the adsorbent is at least one selected from bamboo charcoal, white bamboo charcoal, zeolite, cyclodextrin, and fired shell. The aqueous coating agent according to claim 3, wherein the photocatalyst is titanium dioxide.