JP2017105963A - Paint composition and coated article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic solvent-type paint composition that can form a coating film including cellulose fiber uniformly dispersed in a paint, and having an improved elastic modulus and being resistant to a decrease in elongation.SOLUTION: The present invention provides a paint composition comprising cellulose fiber (A), film-formative resin (B) and organic solvent (C), where the cellulose fiber (A) has an acetyl group and a carboxy group, and the organic solvent (C) has a solubility parameter value of 8.5 or more.SELECTED DRAWING: None

Description

  The present invention relates to a coating composition capable of forming a highly elastic coating film, and a coated article formed by forming a coating film from the coating composition.

  In recent years, the development of materials using biomass has been activated due to increasing resource and environmental problems. In particular, cellulose, which is a representative polysaccharide, has the largest reserves of biomass existing on the earth. Therefore, research on its effective use has been actively conducted, and composite materials using fine fibers of cellulose have been studied. (Patent Literature 1, Patent Literature 2, Patent Literature 3, etc.). It is known that cellulose exhibits a low linear expansion coefficient, a high elastic modulus, and a high strength because of its extended chain crystal. In addition, it has been attracting attention as a material exhibiting high transparency when made into a composite material by miniaturization.

On the other hand, the hydrophilicity is high, and when refining cellulose, it is generally performed in water. Therefore, in order to apply fine cellulose fibers in the paint field, it has been proposed to use a water-based paint (Patent Documents 4 and 5). Even if an aqueous dispersion of cellulose fiber is added to an organic solvent-type paint, it is aggregated and cannot be dispersed uniformly. Therefore, attempts have been made to replace the aqueous dispersion with a solvent, but some paints can be dispersed uniformly. However, there was a problem that the expected highly elastic coating film could not be formed.
In addition, as a method of increasing the elastic modulus of the coating film, a method of adding an inorganic filler to the coating material is known. Although this method increases the elastic modulus of the coating film, the elongation of the coating film decreases, and the coating is reduced. There has been a problem that the processability of the article may be reduced (Patent Document 6).

No. 2012/066713 JP 2014-152290 A JP 2012-188654 A Japanese Patent Application Laid-Open No. 2011-057549 JP 2013-181168 A JP 2007-501886 A

  Accordingly, an object of the present invention is to provide an organic solvent-type coating composition capable of forming a coating film in which cellulose fibers are uniformly dispersed in the coating, have a higher elastic modulus, and suppress a decrease in elongation. There is to do.

  As a result of studying to solve the above-mentioned problems, by using a specific cellulose fiber, a film-forming resin, and a specific organic solvent, the cellulose fiber can be uniformly dispersed in the paint and has a higher elastic modulus. And it discovered that the coating film by which the fall of elongation was suppressed can be formed.

That is, this invention is a coating composition containing a cellulose fiber (A), a film-forming resin (B), and an organic solvent (C), and the cellulose fiber (A) has an acetyl group and a carboxy group. A coating composition comprising an organic solvent (C) having a solubility parameter value of 8.5 (cal / cm ³ ) ^1/2 or more, and a coating film comprising a cured product of the coating composition; It relates to the coated article which has.

  According to the present invention, it is possible to form a coating film in which cellulose fibers are uniformly dispersed in a coating material, have a higher elastic modulus, and suppress a decrease in elongation.

Hereinafter, embodiments of the present invention will be described in detail.
[Cellulose fiber (A)]
The cellulose fiber (A) used in the present invention has an acetyl group and a carboxy group. Preferably, the substitution degree of the acetyl group is 0.5 or more and 1.0 or less. More preferably, the amount of carboxy group is 0.10 mmol / g or more and 0.60 mmol / g or less. More preferably, the number average fiber diameter of the cellulose fibers is preferably 2 nm or more and 400 nm or less.

<Cellulose fiber raw material>
In the present invention, the cellulose fiber raw material is obtained by removing impurities from a cellulose-containing material as shown below through a general purification process.

(Cellulose-containing material)
Examples of cellulose-containing materials include woods such as conifers and hardwoods, cotton such as cotton linter and cotton lint, pomace such as sugar cane and sugar radish, bast fibers such as flax, ramie, jute and kenaf, sisal and pineapple, etc. Examples include leaf vein fibers, petiole fibers such as abaca and banana, fruit fibers such as coconut palm, stem stem fibers such as bamboo, bacterial cellulose produced by bacteria, natural celluloses such as seaweeds such as valonia and falcons, or squirt sac. . These natural celluloses are preferable because of their high crystallinity and high elasticity.

As the cellulose-containing material, wood such as conifers and hardwoods is particularly preferable. Since wood of conifers and hardwoods has a fine fiber diameter, and is the largest biological resource on the earth, it is a sustainable resource that produces about 70 billion tons per year. The contribution to the reduction of carbon dioxide, which affects global warming, is also significant, which is advantageous from an economic point of view.
Such a cellulose-containing material is made into a cellulose fiber raw material of the present invention through a general purification process.

The cellulose fiber raw material used in the present invention is obtained by purifying the cellulose-containing material derived from the above by an ordinary method.
Although there is no restriction | limiting in particular in the refinement | purification degree of the cellulose fiber raw material obtained by refine | purifying a cellulose containing material, The direction with little content of fats and oils and lignin and a high content rate of a cellulose component has few coloring of a cellulose fiber raw material, and is preferable. The content of the cellulose component of the cellulose fiber raw material obtained by refining the cellulose-containing material is preferably 80% by weight or more, more preferably 90% by weight or more, and still more preferably 95% by weight or more.

  The cellulose component can be classified into a crystalline α-cellulose component and an amorphous hemicellulose component. A higher ratio of crystalline α-cellulose is preferable because a low linear expansion coefficient, high elastic modulus, and high strength can be easily obtained when a cellulose fiber composite material is obtained. The ratio of α-cellulose and amorphous hemicellulose of the cellulose fiber raw material obtained by refining the cellulose-containing material is preferably 90 to 10 or more, more preferably 95 to 5 or more, more preferably 97 to 3 or more. A high ratio of cellulose is preferred.

(Fiber diameter of cellulose fiber raw material)
The fiber diameter of the cellulose fiber raw material used in the present invention is not particularly limited, and the number average fiber diameter is 1 μm to 1 mm. What has undergone general purification is about 50 μm. For example, when a chip or the like having a size of several centimeters is refined, it is preferable to perform a mechanical treatment with a disintegrator such as a refiner or a beater to make it about 50 μm.

<Oxidation treatment>
By subjecting the cellulose fiber raw material to an oxidation treatment, it is preferable to substitute a part of cellulose hydroxyl groups with 0.10 mmol / g or more of carboxy groups based on the weight of the cellulose fibers. Usually, in the cellulose fiber raw material that has been subjected to the purification treatment, the hydroxyl group of cellulose is substituted with some carboxy groups, but does not exceed 0.10 mmol / g.
When some hydroxyl groups in cellulose are oxidized to carboxy groups, the surface of the cellulose fibers is covered with the negative charge of the carboxy groups and a repulsive force is generated between the cellulose fibers. It is presumed that the effect of improving and improving the defibration property can be obtained.

  Further, the carboxy group in the cellulose fiber may be 0.10 mmol / g or more, preferably 0.15 mmol / g or more, more preferably 0.20 mmol / g or more. Moreover, the carboxy group in a cellulose fiber is 0.60 mmol / g or less normally, Preferably it is 0.55 mmol / g or less, More preferably, it is 0.50 mmol / g or less.

  When the substitution ratio of the carboxy group is not less than the above lower limit value, the effect of improving the defibration property due to the introduction of the carboxy group into the cellulose fiber can be sufficiently obtained. The coloring at the time of heating is remarkably strong, and if it is not more than the above upper limit, it is considered that coloring can be suppressed by introducing an acetyl group.

  Although there is no restriction | limiting in particular as a specific method of an oxidation process, For example, a method which makes a cellulose fiber raw material contact an oxidizing gas (henceforth oxidizing gas), a cellulose fiber raw material to the solution containing an oxidizing chemical species Examples include oxidation treatment performed by suspending or immersing.

(Method of contacting oxidizing gas and cellulose fiber raw material)
The method of contacting the oxidizing gas and the cellulose fiber raw material is as follows:
(1) Hold the cellulose fiber raw material in an atmosphere containing an oxidizing gas for a predetermined time, or
(2) This can be done by exposing the cellulose fiber raw material to an oxidizing gas stream.
In the contact between the cellulose fiber raw material and the oxidizing gas, various conditions such as the amount of the oxidizing gas added, the processing temperature, and the processing time can be appropriately determined according to the desired amount of carboxy groups introduced into the cellulose fiber.
In the case of a method of holding for a predetermined time in an atmosphere in which an oxidizing gas is present (above (1)), the atmosphere in which the oxidizing gas is present is usually 10 ppm or more, preferably 100 ppm or more, more preferably oxidizing gas in the atmosphere. May be present at 1000 ppm or more, and a gas other than the oxidizing gas may coexist.
The predetermined time is usually 30 seconds or longer, preferably 1 minute or longer, and usually 10 hours or shorter.

When the cellulose fiber raw material is exposed to an oxidizing gas stream (above (2)), the oxidizing gas is usually present in the gas stream in an amount of usually 10 ppm or more, preferably 100 ppm or more, more preferably 1000 ppm or more. In addition, a gas other than the oxidizing gas may coexist.
When the cellulose fiber raw material is exposed to an oxidizing gas stream, it is preferably exposed for a predetermined time, as in the case of holding the oxidizing gas in an atmosphere where the oxidizing gas exists, and the time is usually 30 seconds or more. , Preferably 1 minute or longer, and usually 10 hours or shorter.

  Although it does not specifically limit as oxidizing gas, For example, ozone, chlorine gas, fluorine gas, chlorine dioxide, nitrous oxide etc. are mentioned, Even if these are individual, they contain 2 or more types. There may be. In particular, ozone can be generated in a timely and required place by supplying oxygen-containing gas such as air, oxygen gas, oxygen-added air, etc. to the ozone generator, and the ozone generator is commercially available. It is preferable because it can be used easily.

  When a gas other than the oxidizing gas coexists in the atmosphere where the oxidizing gas exists or in the air flow of the oxidizing gas, the coexisting gas may be any one that does not inhibit the oxidation of the hydroxyl group of cellulose, For example, air, oxygen gas, nitrogen gas, carbon dioxide, argon gas etc. are mentioned, These may be individual or 2 or more types may be contained.

Hereinafter, preferable conditions when ozone is used as the oxidizing gas will be described.
The amount of ozone added is preferably 0.1 to 1000% by weight, more preferably 1 to 100% by weight, and even more preferably 5 to 50% by weight with respect to the dry mass of the cellulose fiber raw material.
The added amount of ozone corresponds to the total mass of ozone used for the cellulose fiber raw material in the following ozone treatment.
The cellulose fiber raw material to be brought into contact with ozone (hereinafter sometimes referred to as ozone treatment) may be in a completely dried state or may be in a wet state with a dispersion medium such as water. It may be in the state of a dispersion liquid (cellulose fiber dispersion liquid) in which is dispersed in a dispersion medium such as water. When the contact area between ozone and the cellulose fiber raw material is larger, the oxidation efficiency becomes higher. Therefore, when a cellulose fiber dispersion is used, it is more preferable to bubble ozone gas into the dispersion.

Even if the cellulose fiber raw material is wet with a dispersion medium or a cellulose fiber dispersion, the higher the solid content concentration of the cellulose fiber raw material, the higher the oxidation efficiency. The solid content concentration of the wet cellulose fiber raw material or the cellulose fiber raw material in the cellulose fiber dispersion to be used is preferably 5% by weight or more, more preferably 20% by weight or more, and even more preferably 40% by weight or more.
The temperature of the ozone treatment is preferably in an atmosphere of 0 ° C. to 100 ° C., more preferably 20 ° C. to 50 ° C. If the treatment temperature is lower than the lower limit, it becomes difficult to handle the sample, for example, the water-wet cellulose fiber raw material or cellulose fiber dispersion freezes, and if the upper limit is exceeded, the self-decomposition reaction of ozone accelerates and the oxidation efficiency is increased. May decrease.
It is preferable that the cellulose fiber raw material after the oxidation treatment such as ozone treatment is sufficiently suspended and washed with water.

(Method of suspending or immersing cellulose fiber raw material in a solution containing oxidizing chemical species)
Moreover, you may oxidize by suspending or immersing a cellulose fiber raw material in the solution containing an oxidizing chemical species.
As the oxidizing chemical species, a reagent that can oxidize alcohol to an aldehyde or carboxylic acid can be generally used, and is not particularly limited. For example, a hexavalent chromic acid sulfuric acid mixture, Jones reagent (chromium anhydride) Acid sulfuric acid solution), chromic acid oxidizing reagent such as pyridilinium chlorochromate (PCC reagent), activated dimethyl sulfoxide reagent used for Swern oxidation, and tetrapropylammonium tellurate (TPAP) that causes catalytic oxidation And N-oxyl compounds such as 2,2,6,6, -tetramethylpiperidine-1-oxyl (TEMPO). In particular, it is known that the oxidation of cellulose fibers by TEMPO is known to proceed under mild conditions in an aqueous dispersion.

When the cellulose fiber raw material is suspended or immersed in a solution containing an oxidizing chemical species, it may be added to the solution containing the oxidizing chemical species using the cellulose fiber raw material in a completely dried state. Oxidizing chemical species may be added to the dispersion. The solvent or dispersion medium of the solution containing the oxidizing chemical species or the cellulose fiber dispersion is usually water, but may contain other solvents.
The cellulose fiber after the oxidation treatment is preferably sufficiently suspended and washed with water and / or an organic solvent.

(Additional oxidation treatment)
It is preferable to add an additional oxidation treatment step after the method in which the cellulose fiber raw material is brought into contact with the oxidizing gas or the oxidation treatment performed by suspending or immersing the cellulose fiber raw material in a solution containing an oxidizing chemical species. Oxidation treatment). By adding the oxidation treatment, the formyl group in the cellulose fiber is oxidized to the carboxy group, so that the defibration property is further improved and the effect of suppressing coloring during heating is obtained, which is more preferable.

Although it does not specifically limit as a chemical species used for an additional oxidation process, For example, chlorites, such as sodium chlorite, are mentioned. Specifically, the cellulose fiber raw material after the oxidation treatment is suspended in a solution prepared by adding an acid such as hydrochloric acid or acetic acid to an aqueous solution of 1 to 5% by weight of sodium chlorite to pH 4 to 5. The additional oxidation treatment can be performed by holding for a certain time, for example, 1 to 100 hours. The temperature during this additional oxidation treatment is usually 0 ° C. to 100 ° C., preferably 20 ° C. to 50 ° C., for the same reason as in the ozone treatment.
It is preferable that the cellulose fiber raw material after the additional oxidation treatment is sufficiently suspended and washed with water. When the cellulose fiber raw material is stored in a strongly acidic or strongly basic state, the crystallinity of the cellulose is lowered, and when it is made into a cellulose fiber composite material, a low linear expansion coefficient may not be obtained. Is preferably repeated until the pH of the washed water is in the range of 4-9.

(Quantitative determination method of carboxy group and formyl group in cellulose fiber)
In this invention, the quantity (mmol / g) of the carboxy group in the cellulose fiber with respect to the weight of a cellulose fiber and a formyl group was quantified with the following method.
The amount of the carboxy group was determined according to the method of “Test Method T237 cm-08 (2008): Carboxyl Content of Pull” of TAPPI, USA. At this time, the absolutely dry cellulose fiber used as a measurement sample was obtained by freeze-drying in order to avoid the alteration of cellulose due to heating that may occur in heat drying.
The amount of formyl group is substantially zero because the formyl group is oxidized to a carboxy group when the above-described additional oxidation treatment is performed. By quantifying the amount of carboxy group before and after the additional oxidation treatment, the difference can be regarded as the amount of formyl group before the additional oxidation treatment.
Further, the amount of carboxy groups in the cellulose fiber increases in mass as the acetyl group is added to the cellulose when the acetylation treatment described later is performed, and therefore the numerical value per 1 g of dry cellulose changes. Therefore, the amount of carboxy groups in the cellulose fiber of the present invention needs to be determined as a value after substitution with acetyl groups.

<Acetylation treatment>
The cellulose fiber of the present invention is characterized in that a part of the hydroxyl group of cellulose is substituted with an acetyl group and a carboxy group.
The acetyl group is preferably introduced by acetylation treatment described in detail below.
In addition, although it described that it was preferable that a carboxy group is substituted by the said oxidation process, you may introduce | transduce similarly to the process explained in full detail below.
The acetylation treatment may be performed before the step of oxidizing the cellulose fiber raw material, or after the step of oxidizing the cellulose fiber raw material. In order to avoid detachment of the chemical modification group due to oxidation treatment, the chemical modification treatment is more preferably performed after the step of oxidizing the cellulose fiber raw material.

(Acetylation method)
The acetylation method is not particularly limited, and for example, there is a method of reacting a cellulose fiber raw material with the following acetylating agent. Although there are no particular limitations on the reaction conditions, a solvent, a catalyst, or the like may be used, or heating, decompression, or the like may be performed as necessary.
Examples of the acetylating agent include one or more selected from the group consisting of acetic acid, acetic anhydride, and acetyl halide.

(Degree of substitution)
The degree of substitution as used herein refers to the number of substituents introduced per unit structure (glucopyranose ring) constituting cellulose. In other words, it is defined as “the number of moles of the introduced substituent divided by the total number of moles of the glucopyranose ring”. Since pure cellulose has three substitutable hydroxyl groups per unit structure (glucopyranose ring), the theoretical maximum value of the degree of substitution of the cellulose fiber of the present invention is 3 (minimum value is 0).

The degree of substitution of the chemical modifying group can be measured and determined by the following titration method.
0.05 g of dry cellulose is precisely weighed, and 1.5 ml of ethanol and 0.5 ml of distilled water are added thereto. This is left to stand in a hot water bath at 60 to 70 ° C. for 30 minutes, and then 2 ml of 0.5 M aqueous sodium hydroxide solution is added. After leaving this in a 60-70 degreeC hot water bath for 3 hours, it ultrasonically shakes for 30 minutes with an ultrasonic cleaner. This is titrated with 0.1 M aqueous hydrochloric acid using phenolphthalein as an indicator.

Here, from the amount Z (ml) of 0.1 M hydrochloric acid aqueous solution required for titration and the amount Z ₀ (ml) of 0.1 N hydrochloric acid aqueous solution required for titration of the blank sample (= sample without dry cellulose), The total amount Q (mol) of the carboxy group and the acetyl group is determined by the formula.
Q (mol) = (Z ₀ −Z) × 0.1 / 1000

The mass of dry cellulose (= 0.05 g of the exact balance, denoted as A) is substituted with an unmodified glucopyranose ring structure (C ₆ H ₁₀ O ₅ , Mw = 162), a carboxy group It can be considered as a sum of masses of the glucopyranose structure (C ₆ H ₈ O _6, Mw = 176) and the acetylated glucopyranose structure (Mw = 204). If the number of moles of each structure is x, y, z (mol),
A (g) = 162 × x + 176 × y + 204 × z Equation 1

Further, the following relationship is established for Q (mol) previously obtained by titration.
Q (mol) = y + z Formula 2

In addition, the amount of carboxy groups in the cellulose fibers (mmol / g, denoted by B as a symbol) determined by the method described in the above section (Method for quantifying carboxy groups in cellulose fibers) can be converted to y. .
y (mol) = B (mmol / g) × A (g) / 1000 Formula 3

Here, the degree of substitution is defined as “a value obtained by dividing the number of moles of the introduced substituent by the total number of moles of the glucopyranose ring”, and the degree of substitution of the acetyl group can be expressed as the following formula. it can.
Degree of substitution of acetyl group (dimensionless number) = z / (x + y + z)

  When formulas 1 to 4 are used to arrange A, B, Q, and T, the degree of substitution of the chemical modification group can be obtained by formula 5 below.

式５

Formula 5

In the present invention, the degree of substitution of cellulose fibers is usually 0.50 or more, preferably 0.55 or more, more preferably 0.6 or more. The degree of substitution of cellulose fibers is preferably 1.0 or less, more preferably 0.95 or less, and still more preferably 0.90 or less.
By introducing an acetyl group other than a carboxy group by performing an acetylation treatment, the compatibility with the resin is improved. However, if the degree of substitution is too high, the cellulose structure is destroyed and the crystallinity is lowered, so that the cellulose obtained There is a problem that the elastic modulus of the fiber composite material is lowered, which is not preferable.

<Defibration processing>
Cellulose fiber raw material is defibrated cellulose fiber by defibrating treatment. Hereinafter, the manufacturing method of a defibrated cellulose fiber is demonstrated. As described above, in the present invention, there is no particular limitation on the procedure of oxidation treatment, chemical modification treatment, and defibration treatment of the above-described cellulose fiber raw material. Preferably, the defibration treatment is performed after the oxidation treatment and the chemical modification treatment. Applied to fiber raw materials.

In addition, the defibrated cellulose fiber is usually obtained in the state of a dispersion in which the defibrated cellulose fiber is dispersed. That is, in this case, the defibrated cellulose fiber is referred to as a defibrated cellulose fiber including a dispersion in which the defibrated cellulose fiber is dispersed.
A specific method of the defibrating treatment is not particularly limited. For example, ceramic beads having a diameter of about 1 mm are dispersed in a cellulose fiber raw material concentration of 0.1 to 10% by weight, for example, about 1% by weight. Examples thereof include a method of defibrating cellulose by putting it in a liquid (hereinafter sometimes referred to as “cellulose fiber dispersion”) and applying vibration using a paint shaker or a bead mill.

In addition, it is preferable to use the organic solvent (C) mentioned later as a dispersion medium of a cellulose fiber dispersion liquid. However, it is also possible to replace with the organic solvent (C) after defibration using another organic solvent, water, or a mixture of an organic solvent and water. Further, a resin solution in which a film-forming resin (B) described later in advance is dissolved in an organic solvent (C) may be used as a dispersion medium.
Other defibrating methods include a blender type disperser and a method of using a cellulose fiber dispersion to apply shear force between slits rotating at high speed (using a high-speed rotating homogenizer), or from high pressure to abruptly. A method of using a high-pressure homogenizer method to generate a shearing force between cellulose fibers by depressurizing the fiber (a method using a high-pressure homogenizer method), an opposing collision type disperser, etc. The method etc. are mentioned. In particular, the efficiency of defibration is improved by adopting a treatment using a high-speed rotation type homogenizer or a high-pressure homogenizer.

In the case of defibration by these treatments, the solid content concentration as the cellulose fiber raw material is 0.1% by weight or more, preferably 0.2% by weight or more, particularly 0.3% by weight or more, and 10% by weight or less, particularly A defibrating treatment is performed on 6% by weight or less of the cellulose fiber dispersion. If the solid content concentration in the cellulose fiber dispersion to be subjected to the defibrating process is too low, the amount of liquid will be excessive with respect to the amount of cellulose fiber raw material to be processed, and the efficiency will be poor, and if the solid content concentration is too high, the fluidity will be poor. Therefore, the concentration of the cellulose fiber dispersion used for the defibrating treatment is adjusted by adding water as appropriate.
In addition, you may perform the refinement | miniaturization process which combined the ultrasonic process after the process by such a high voltage | pressure homogenizer and the process by a high-speed rotation type homogenizer.

(Number average fiber diameter of fibrillated cellulose fiber raw material)
The fiber diameter of the cellulose fiber (defibrated cellulose fiber) in the cellulose fiber dispersion defibrated or further refined by the above method should be observed with SEM, TEM, etc. after the dispersion medium in the dispersion is removed by drying. Can be measured and determined.
The number average fiber diameter of the fibrillated cellulose fibers is preferably 400 nm or less, and preferably 350 nm or less in order to obtain a coating film with good surface properties, high elastic modulus, and suppressed decrease in elongation. More preferably, it is particularly preferably 300 nm or less. Further, the number average fiber diameter is preferably as small as possible. However, in order to develop a high elastic modulus, it is important to maintain the crystallinity of cellulose, and the fiber diameter of the cellulose crystal unit is substantially 2 nm or more. It is.

[Film-forming resin (B)]
As the film-forming resin (B) used in the present invention, a resin known per se that has been conventionally used in paints can be used. Examples of the resin include acrylic resin, polyester resin, alkyd resin, polyurethane resin, and epoxy resin.
The film-forming resin (B) preferably has a crosslinkable functional group in order to react with the crosslinking agent (D) described later to form a crosslinked coating film. Examples of the crosslinkable functional group include a hydroxyl group, an epoxy group, a carboxy group, and the like.
In particular, as a film-forming resin (B), from the viewpoint of compatibility with the above-described cellulose fiber (A), a hydroxyl group-containing resin having a measured solubility parameter value of 9.5 or more, preferably 9.7 to 12.0 ( B-1) is preferred

Here, the actually measured solubility parameter value of the resin is a value measured by a cloud point titration method. W. SUH, J. et al. M.M. Calculated according to the CORBETT equation (see the description of Journal of Applied Polymer Science, VOL. 12, 2359-2370 (1968)).
Measured solubility parameter value = (√Vml · δH + √Vmh · δD) / (√Vml + √Vmh)

Vml, Vmh, δH, and δD are No. 4 of newspapers in which n-hexane was added to 0.5 g of resin (solid content) dissolved in 10 mL of acetone at a measurement temperature of 20 ° C. and placed under the bottom. The limit at which the type can be seen through the top of the beaker is defined as the turbid point, and the titration amount H (mL) at the turbid point and the resin 0.5 g (solid content) dissolved in 10 mL of acetone at a measurement temperature of 20 ° C. It is a value calculated by applying the titer D (mL) at the cloud point when water is added to the following formula.
Vml = 74.4 × 130.3 / {(1−VH) × 130.3 + VH × 74.4}
Vmh = 74.4 × 18 / {(1−VD) × 18 + VD × 74.4}
VH = H / (10 + H)
VD = D / (10 + D)
δH = 9.75 × 10 / (10 + H) + 7.24 × H / (10 + H)
δD = 9.75 × 10 / (10 + D) + 23.43 × D / (10 + D)
The molecular volume (mL / mol) of each solvent is acetone: 74.4, n-hexane: 130.3, deionized water: 18, and the SP value of each solvent is acetone: 9.75, n -Hexane: 7.24, deionized water: 23.43.

  Examples of the hydroxyl group-containing resin (B-1) include a hydroxyl group-containing acrylic resin, a hydroxyl group-containing polyester resin, a hydroxyl group-containing alkyd resin, a hydroxyl group-containing polyurethane resin, and a hydroxyl group-containing epoxy resin. These can be used in combination. Among these, from the viewpoint of the modulus of elasticity and elongation of the resulting coating film, the hydroxyl group-containing resin (B-1) is at least one selected from the group consisting of a hydroxyl group-containing acrylic resin, a hydroxyl group-containing polyester resin, and a hydroxyl group-containing alkyd resin. It is preferable that

The hydroxyl group-containing resin (B-1) also has a hydroxyl value of 50 to 200 mgKOH / g, preferably 100 to 150 mgKOH / g, and a weight average molecular weight of 1, from the viewpoint of elasticity and elongation of the resulting coating film. It is preferable to be in the range of 000 to 100,000, preferably 3,000 to 50,000.
In addition, the weight average molecular weight here is a conversion value using polystyrene having a known molecular weight as a standard substance, measured using tetrahydrofuran as a solvent using a gel permeation chromatograph.

The hydroxyl group-containing acrylic resin can be produced by copolymerizing a hydroxyl group-containing polymerizable unsaturated monomer and other polymerizable unsaturated monomers by a conventional method such as a solution polymerization method.
Examples of the hydroxyl group-containing polymerizable unsaturated monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and the like. Monoesterified product of (meth) acrylic acid and dihydric alcohol having 2 to 8 carbon atoms; ε-caprolactone modified product of monoesterified product of (meth) acrylic acid and dihydric alcohol having 2 to 8 carbon atoms; allyl Examples of the alcohol include (meth) acrylates having a polyoxyethylene chain having a hydroxyl group at the molecular end, and these monomers can be used alone or in combination of two or more.

  Examples of the other polymerizable unsaturated monomers include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, i-propyl (meth) acrylate, n-butyl (meth) acrylate, i -Butyl (meth) acrylate, tert-butyl (meth) acrylate, n-hexyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, tridecyl (meth) acrylate, lauryl (Meth) acrylate, stearyl (meth) acrylate, “isostearyl acrylate” (trade name, manufactured by Osaka Organic Chemical Industry Co., Ltd.), cyclohexyl (meth) acrylate, methylcyclohexyl (meth) acrylate, t-butylcyclohexyl Alkyl or cycloalkyl (meth) acrylate such as (meth) acrylate, cyclododecyl (meth) acrylate; unsaturated monomer having an isobornyl group such as isobornyl (meth) acrylate; adamantyl group such as adamantyl (meth) acrylate Unsaturated monomers having an aromatic ring; unsaturated monomers containing aromatic rings such as styrene, α-methylstyrene, vinyltoluene, phenyl (meth) acrylate; vinyltrimethoxysilane, vinyltriethoxysilane, γ- (meth) acryloyloxypropyltrimethoxy Unsaturated monomers having an alkoxysilyl group such as silane and γ- (meth) acryloyloxypropyltriethoxysilane; (meth) acrylic acid, maleic acid, crotonic acid, and β-carboxyethyl acrylate Boxyl group-containing unsaturated monomers; nitrogen-containing products such as (meth) acrylonitrile, (meth) acrylamide, dimethylaminopropyl (meth) acrylamide, dimethylaminoethyl (meth) acrylate, adducts of glycidyl (meth) acrylate and amines Saturated monomer: Epoxy group-containing unsaturated monomer such as glycidyl (meth) acrylate, 3,4-epoxycyclohexylethyl (meth) acrylate, and allyl glycidyl ether; (meth) acrylate having a polyoxyethylene chain whose molecular terminal is an alkoxy group An unsaturated monomer having a carbonyl group such as acrolein, diacetone acrylamide, diacetone methacrylamide, acetoacetoxyethyl methacrylate, etc. Combinations of two or more can be used.

  The hydroxyl group-containing polyester resin can be produced by a conventional method, for example, by an esterification reaction between a polybasic acid and a polyhydric alcohol. The polybasic acid is a compound having two or more carboxyl groups in one molecule. For example, phthalic acid, isophthalic acid, terephthalic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, tetrahydrophthalic acid, hexa And hydrophthalic acid, maleic acid, fumaric acid, itaconic acid, trimellitic acid, pyromellitic acid and their anhydrides. The polyhydric alcohol contains two or more hydroxyl groups in one molecule. For example, ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2,2-diethyl-1,3 -Propanediol, neopentyl glycol, 1,9-nonanediol, 1,4-cyclohexanediol, hydroxy Diols such as valinic acid neopentyl glycol ester, 2-butyl-2-ethyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2,2,4-trimethylpentanediol, hydrogenated bisphenol A, etc. , And trivalent or higher polyol components such as trimethylolpropane, trimethylolethane, glycerin, pentaerythritol, and the like, and 2,2-dimethylolpropionic acid, 2,2-dimethylolbutanoic acid, 2,2-dimethylol Examples thereof include hydroxycarboxylic acids such as pentanoic acid, 2,2-dimethylolhexanoic acid, and 2,2-dimethyloloctanoic acid.

In addition, a monoepoxy compound such as α-olefin epoxide such as propylene oxide and butylene oxide, Cardura E10 (manufactured by Momentive Specialty Chemicals, trade name, glycidyl ester of synthetic hyperbranched saturated fatty acid) and the like are reacted with an acid, The compound may be introduced into the polyester resin.
When introducing a carboxyl group into a polyester resin, for example, it can be introduced by adding an acid anhydride to a hydroxyl group-containing polyester and half-esterifying it.
Examples of the hydroxyl group-containing alkyd resin include those obtained by modifying an esterified product of the above-mentioned polybasic acid and polyhydric alcohol with a higher fatty acid.

[Organic solvent (C)]
The organic solvent (C) used in the present invention has a solubility parameter value of 8.5 or more, preferably 8.7 to 14.5. If the solubility parameter value is less than 8.5, the cellulose fiber (A) and the film-forming resin (B) may not be uniformly dispersed.
Here, the solubility parameter value [unit (cal / cm ³ ) ^1/2 ] of the organic solvent is a value calculated from the basic structure of the compound by the method proposed by Fedors. Specifically, from the evaporation energy Δe (cal) of each atom or atomic group at 25 ° C. and the molar volume Δv (cm ³ ) of each atom or atomic group at the same temperature, the solubility parameter according to the following formula: A value (SP value) is calculated. The SP value in the case of the mixed solvent system is a value obtained by multiplying the SP value of each organic solvent constituting the system by the respective component ratio (molar fraction) and adding them up.
SP value (δ) = (ΣΔe / ΣΔv) ^1/2
(Reference: Shinji Mukai, Noriyuki Kaneshiro, Kodansha, “Practical polymers for engineers”, published in October 1981, P71-77).

The organic solvent (C) is not particularly limited as long as it satisfies the above SP value. For example, the organic solvent (C) can be appropriately selected from ester solvents, alcohol solvents, ether solvents, ketone solvents and the like. Specifically, ester solvents such as ethyl acetate, propyl acetate, and butyl acetate; alcohol solvents such as methanol, ethanol, n-propanol, isopropanol, and n-butanol; propylene glycol monomethyl ether, ethylene glycol monobutyl ether, propylene glycol Examples include ether solvents such as monomethyl ether acetate; ketone solvents such as acetone, methyl ethyl ketone, and cyclohexanone. These can be used alone or in combination of two or more.
Organic solvents other than those described above may be used in combination as long as the uniformity of the paint is not impaired.

[Crosslinking agent (D)]
The crosslinking agent (D) is a compound capable of curing the coating composition of the present invention by reacting with a functional group such as a hydroxyl group, a carboxyl group, or an epoxy group in the cellulose fiber (A) or the film-forming resin (B). is there. Examples of the crosslinking agent (D) include polyisocyanate compounds, blocked polyisocyanate compounds, amino resins, epoxy group-containing compounds, carbodiimide group-containing compounds, and the like. Of these, polyisocyanate compounds and amino resins are preferred. A crosslinking agent (D) can be used individually or in combination of 2 or more types.

The polyisocyanate compound is a compound having at least two isocyanate groups in one molecule, such as aliphatic polyisocyanate, alicyclic polyisocyanate, araliphatic polyisocyanate, aromatic polyisocyanate, Derivatives and the like can be mentioned.
Moreover, the said polyisocyanate compound can also use the blocked polyisocyanate compound which is a compound which blocked the isocyanate group in the said polyisocyanate and its derivative with the blocking agent.

As the amino resin, a partially methylolated amino resin or a completely methylolated amino resin obtained by a reaction between an amino component and an aldehyde component can be used. Examples of the amino component include melamine, urea, benzoguanamine, acetoguanamine, steroguanamine, spiroguanamine, dicyandiamide and the like. Examples of the aldehyde component include formaldehyde, paraformaldehyde, acetaldehyde, benzaldehyde and the like.
Moreover, what methylated the methylol group of the said methylolated amino resin partially or completely with suitable alcohol can also be used. Examples of the alcohol used for etherification include methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, 2-ethylbutanol, and 2-ethylhexanol.

[Coating composition]
In the present invention, the blending amount (solid content) of the cellulose fiber (A) is based on the solid content of 100 parts by mass of the film-forming resin (B) (crosslinking agent (D) from the viewpoint of forming a highly elastic coating film. When used, based on 100 parts by mass of the total solid content of the resin (B) and the crosslinking agent (D)), 0.1 to 10 parts by mass, preferably 0.3 to 8 parts by mass, preferably 0.5 to A range of 5 parts by weight is preferred.
The blending ratio of the film-forming resin (B) and the crosslinking agent (D) is 50 to 95 parts by weight, preferably 60 to 90, based on 100 parts by weight of the total solid content of both. The mass part and the crosslinking agent (D) are 5 to 50 parts by mass, preferably 10 to 40 parts by mass.

The coating composition of the present invention may further be used as required for ordinary coatings such as dryers, curing catalysts, pigments, pigment dispersants, thickeners, leveling agents, ultraviolet absorbers, light stabilizers, plasticizers, and the like. It can contain paint additives used in the field.
The coating composition of the present invention preferably has a coating solid content in the range of 20 to 80% by mass, particularly 30 to 70% by mass.

The coating composition of the present invention can be applied by a known coating method such as an air spray, an airless spray, electrostatic coating or the like so as to obtain a desired film thickness on various substrate surfaces. Moreover, the coated article which has a coating film which consists of a hardened | cured material of a coating composition is obtained by hardening the coating composition coated on the base-material surface.
Examples of the substrate include metal materials such as iron, aluminum, brass, copper, stainless steel, tinplate, galvanized steel, alloyed zinc (Zn-Al, Zn-Ni, Zn-Fe, etc.) plated steel; polyethylene Resin, polypropylene resin, acrylonitrile-butadiene-styrene (ABS) resin, polyamide resin, acrylic resin, vinylidene chloride resin, polycarbonate resin, polyurethane resin, epoxy resin, and various plastic materials such as FRP; glass, cement, concrete Inorganic materials such as these may be used, and these may be subjected to surface treatment or the like.

  Hereinafter, the present invention will be described more specifically with reference to production examples, examples and comparative examples. However, the present invention is not limited to these. In each example, “parts” and “%” are based on mass unless otherwise specified. Moreover, the film thickness of a coating film is based on a cured coating film.

Production of Cellulose Fiber (A) Production Example 1
Cellulose fiber 3% dispersion (A-1)
After adding hardwood bleached kraft pulp (LBKP, manufactured by Oji Holdings Co., Ltd .: moisture 30%, freeness 600 mLcsf) as pulp fiber weight to the container, 20 g of pulp dry weight and 2 L of air were added, followed by ozone / oxygen mixing with an ozone concentration of 200 g / m ³ After 15 L of gas was added, shaken at 25 ° C. for 2 minutes, and allowed to stand for 6 hours in order, ozone and air in the container were removed to perform ozone treatment. This operation was performed twice to obtain a cellulose fiber which was sufficiently washed / dehydrated with ion-exchanged water and subjected to ozone treatment.
200 g of 0.2 wt% sodium chlorite aqueous solution whose pH was adjusted to 4 to 5 with hydrochloric acid was added to the obtained cellulose fiber after ozone treatment (solid content concentration: 20 wt%). 3% by weight as sodium chlorite was added to the dry weight) and treated at 70 ° C. for 3 hours to obtain carboxy group-containing cellulose fibers. The amount of carboxy group of the obtained carboxy group-containing cellulose fiber was 0.37 mmol / g.
580 g of acetic anhydride was added to 20 g of this carboxy group-containing cellulose fiber as an absolute dry weight, and reacted at 60 ° C. for 1 hour and 115 ° C. for 3 hours while stirring. After cooling, the reaction mixture was filtered and washed with methanol followed by water until neutral. The degree of substitution of acetylation was 0.78.

This cellulose fiber having an acetyl group and a carboxy group is dispersed in isopropanol and filtered, and then dispersed in butyl acetate (ester solvent, solubility parameter value 8.7) and filtered twice to perform solvent replacement. It was.
Next, to the resin solution obtained by diluting 75% AC-800 manufactured by Kansai Paint Co., Ltd. 5 times with butyl acetate, the cellulose fiber having the acetyl group and the carboxy group is added so that the cellulose fiber concentration becomes 3% by weight, and the homogenizer is used. After pre-dispersion, the cellulose fiber was defibrated by 10 passes in a bead mill (Ultra Apex Mill UAM-015 manufactured by Kotobuki Industries Co., Ltd.) at a bead diameter of 0.3 mm and a peripheral speed of 11.4 m / sec. A 3% fiber dispersion (A-1) was obtained. The number average fiber diameter of the obtained cellulose fibers was 40 nm.

Production Example 2
Cellulose fiber 3% dispersion (A-2)
In the same manner as in Production Example 1, acetyl group- and carboxy group-containing cellulose fibers were obtained. The degree of substitution for acetylation was 0.67.
This cellulose fiber having an acetyl group and a carboxy group is mixed with a resin solution so as to have a concentration of 3% by weight in the same manner as in Production Example 1, and the cellulose fiber is defibrated to obtain a 3% cellulose fiber dispersion. (A-2) was obtained. The number average fiber diameter of the obtained cellulose fibers was 40 nm.

Production Example 3
Cellulose fiber 3% dispersion (A-3)
In the same manner as in Production Example 1, a carboxy group-containing cellulose fiber was obtained. An acetylation treatment was performed in the same manner as in Production Example 1 except that the carboxy group-containing cellulose fiber was reacted at 115 ° C. for 2 hours. The degree of substitution for acetylation was 0.50.
This cellulose fiber having an acetyl group and a carboxy group is mixed with a resin solution so as to have a concentration of 3% by weight in the same manner as in Production Example 1, and the cellulose fiber is defibrated to obtain a 3% cellulose fiber dispersion. (A-3) was obtained. The number average fiber diameter of the obtained cellulose fibers was 40 nm.

Production of film-forming resin (B) Production of acrylic resin Production Example 4
Hydroxyl group-containing acrylic resin (B-1)
A reactor equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen introduction tube was charged with 70 parts by mass of butyl acetate and heated to 90 ° C. in a nitrogen atmosphere, and then 10 parts by mass of styrene and 20 parts by mass of methyl methacrylate. , 30 parts by mass of n-butyl acrylate, 35 parts by mass of hydroxyethyl methacrylate, 5 parts by mass of methacrylic acid, 1 part by mass of 2,2′-azobis (2-methylbutyronitrile) and an organic solvent (C-1) (butyl acetate , Ester solvent, solubility parameter value 8.7) A mixture of 5 parts by mass was added dropwise over 4 hours. After completion of dropping, the mixture was held at 90 ° C. for 2 hours, and then the nonvolatile content was adjusted to 65% with an organic solvent (C-1) to obtain a hydroxyl group-containing acrylic resin (B-1) solution. The obtained hydroxyl group-containing acrylic resin (B-1) had a measured solubility parameter value of 10.6, a hydroxyl value of 150 mgKOH / g, and a weight average molecular weight of 20,000.

Production Example 5
Hydroxyl group-containing acrylic resin (B-2)
A reactor equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen introduction tube was charged with 70 parts by mass of butyl acetate and heated to 90 ° C. in a nitrogen atmosphere, and then 10 parts by mass of styrene and 20 parts by mass of methyl methacrylate. , 55 parts by mass of n-butyl acrylate, 10 parts by mass of hydroxyethyl methacrylate, 5 parts by mass of methacrylic acid, 1 part by mass of 2,2′-azobis (2-methylbutyronitrile) and organic solvent (C-1) (butyl acetate , Ester solvent, solubility parameter value 8.7) was added dropwise over 4 hours. After completion of dropping, the mixture was held at 90 ° C. for 2 hours, and then the nonvolatile content was adjusted to 65% with an organic solvent (C-1) to obtain a hydroxyl group-containing acrylic resin (B-2) solution. The obtained hydroxyl group-containing acrylic resin (B-2) had a measured solubility parameter value of 9.2, a hydroxyl value of 43 mgKOH / g, and a weight average molecular weight of 22,000.

Production Example 6
Hydroxyl group-containing acrylic resin (B-3)
A reactor equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen introduction tube was charged with 70 parts by mass of butyl acetate and heated to 90 ° C. in a nitrogen atmosphere, and then 10 parts by mass of styrene and 20 parts by mass of methyl methacrylate. , 55 parts by mass of n-butyl acrylate, 10 parts by mass of hydroxyethyl methacrylate, 5 parts by mass of methacrylic acid, 1 part by mass of 2,2′-azobis (2-methylbutyronitrile) and organic solvent (C-1) (butyl acetate , Ester solvent, solubility parameter value 8.7) A mixture of 5 parts by mass was added dropwise over 4 hours. After completion of the dropwise addition, the mixture was kept at 90 ° C. for 2 hours, and then the organic solvent (C-5) (2,2,4-trimethyl-1,3-pentanediol 1-isobutyrate, common name: texanol, alcohol solvent, solubility The non-volatile content was adjusted to 65% with a parameter value of 8.2) to obtain a hydroxyl group-containing acrylic resin (B-3) solution. The measured solubility parameter value of the obtained hydroxyl group-containing acrylic resin (B-3) was 9.2, the hydroxyl value was 42 mgKOH / g, and the weight average molecular weight was 22,000.

Production of polyester resin Production Example 7
Hydroxyl-containing polyester resin (B-4)
In a 2 L glass flask equipped with a nitrogen gas inlet tube, a reflux condenser, and a stirrer, 758.2 parts of diethylene glycol (7.14 mol, charged molar ratio 0.53), 652.6 parts of adipic acid (4.47 mol, charged) Molar ratio 0.33) and 278.2 parts of phthalic anhydride (1.88 mol, charged molar ratio 0.14) were charged, and heating was started under a nitrogen stream. A dehydration condensation reaction was carried out at an internal temperature of 200 ° C. by a conventional method. When the acid value reached 13 KOH mg / g, the nonvolatile content was adjusted to 65% with an organic solvent (C-4) (cyclohexanone, ketone solvent, solubility parameter value 10.4), and a hydroxyl group-containing polyester resin (B-4 ) A solution was obtained. The measured solubility parameter value of the obtained hydroxyl group-containing polyester resin (B-4) was 9.9, the hydroxyl value was 110 mgKOH / g, and the weight average molecular weight was 5,000.

Production of alkyd resin Production Example 8
Hydroxyl-containing alkyd resin (B-5)
A four-necked flask equipped with a stirrer, thermometer, reflux condenser with dehydration trap and nitrogen gas introduction device was charged with 505 parts of soybean oil, 0.13 parts of lithium hydroxide and 152 parts of pentaerythritol, and alcohol at 250 ° C. for 1 hour. After performing the exchange reaction, it was cooled to 180 ° C. Next, after adding 46 parts of ethylene glycol, 255 parts of phthalic anhydride and 31 parts of xylene (solubility parameter value: 8.9), the temperature was gradually raised to 220 ° C. over 3 hours, and further at 220 ° C. The dehydration reaction was performed for 8 hours, and then the nonvolatile content was adjusted to 65% with xylene to obtain a hydroxyl group-containing alkyd resin (B-5) solution. The measured solubility parameter value of the obtained hydroxyl group-containing alkyd resin (B-5) was 9.5, the hydroxyl value was 100 mgKOH / g, and the weight average molecular weight was 28,000.

Production of coating composition Example 1
33 parts of cellulose fiber (A-1) dispersion obtained in Production Example 1 (solid part of cellulose fiber), 107 parts of hydroxyl group-containing acrylic resin (B-1) solution (solid part of 70 parts) and organic solvent (C) -1) 29 parts of (butyl acetate, ester solvent, solubility parameter value 8.7) was placed in a wide-mouth glass bottle, sealed with glass beads having a diameter of about 1 mmφ as a dispersion medium, and dispersed with a paint shaker for 3 hours. Thereafter, the glass beads were removed to obtain a fiber dispersion.
Next, 169 parts of the obtained fiber dispersion (solid part 75 parts) and “Sumidule N3300” (trade name, manufactured by Sumika Bayer Urethane Co., Ltd., isocyanurate of hexamethylene diisocyanate, solid content 100%, isocyanate group content 21.8%) 30 parts (solid content 30 parts) were mixed and stirred, and the coating composition No. 1 was obtained. The coating composition No. The solubility parameter value of the organic solvent (C) in 1 is 8.7.

Examples 2-10, Comparative Examples 1-2
In Example 1, except that the formulation is as shown in Table 1, the coating composition No. 2-12 were obtained.

(Note) in Tables 1 and 2 means the following.
(Note 1) “Cymel 350”: trade name, manufactured by Daicel Ornex, melamine resin, solid content 100%.
(Note 2) “SURFACE STRAND REV1”: trade name, manufactured by Owens Corning, glass fiber, solid content 100%.
(Note 3) Organic solvent (C-2): methanol, alcohol solvent, solubility parameter value 14.5.
(Note 4) Organic solvent (C-3): propylene glycol monomethyl ether, ether solvent, solubility parameter value 10.4.
(Note 5) Organic solvent (C-4): cyclohexanone, ketone solvent, solubility parameter value 10.4.
(Note 6) Organic solvent (C-5): 2,2,4-trimethyl-1,3-pentanediol 1-isobutyrate, common name: texanol, alcohol solvent, solubility parameter value 8.2.
(Note 7) “DICATE 3111”: trade name, manufactured by DIC, dryer, solid content 31%.

Preparation of test plates Examples 11 to 16, 18 to 20, Comparative Examples 3 to 4
On the polypropylene plate, the coating composition Nos. Obtained in Examples 1-6, 8-10 and Comparative Examples 1-2. 1-6, no. 8-12 were each coated using an applicator so that the dry film thickness would be 30 μm. Next, after leaving at room temperature for 7 minutes, it heated at 140 degreeC for 30 minutes, and the test board with which the cured coating film was formed on the polypropylene board was obtained.

Example 17
On the polypropylene plate, the coating composition No. obtained in Example 7 above. 7 was coated with an applicator so that the dry film thickness was 30 μm. Next, it was left to stand at 23 ° C. and 65% RH for 7 days to obtain a test plate having a cured coating film formed on a polypropylene plate.

Evaluation of test plate Each test plate obtained was subjected to various tests. The evaluation results are shown in Table 3.

Test method Dispersibility: The following cured coating film was evaluated for formability and transparency.
Formability of coating film: The coated surface appearance of each test plate was visually evaluated.
○: A uniform coating film is formed. ×: At least one of the roughness of the coating film surface and a partial decrease in transparency is observed, and a uniform coating film is not formed.
Transparency: In each test plate, the cured coating film was peeled from the polypropylene plate, and the transmission haze of the cured coating film was measured using a haze meter “COH300A” manufactured by Nippon Denshoku Industries Co., Ltd. The smaller the transmission haze, the higher the transparency of the cured coating film.

Elastic modulus:
The elastic modulus of the coating film was evaluated using Young's modulus. In addition, the evaluation of the elastic modulus is based on each coating composition No. Each coating composition No. of the elasticity modulus of the coating film obtained from 1-12. About 1-12, the cellulose fiber (A-1)-(A-3) or the glass fiber evaluated by the ratio with respect to the elasticity modulus of the coating film obtained from the coating composition which is not added. Specifically, the evaluation was made based on the following change rate (%) of Young's modulus.
Ratio of change in Young's modulus (%) = (Young's modulus of a coating obtained from a coating composition containing a fiber component−Young's modulus of a coating obtained from a coating composition not containing a fiber component) / (Fiber component (Young's modulus of a coating film obtained from a coating composition not containing) × 100.

More specifically, for example, in the case of Example 11,
Ratio of change in Young's modulus (%) = (Young's modulus of the coating film obtained from coating composition No. 1−cellulosic fiber (A-1) is obtained from the coating composition without addition of coating composition No. 1) Young's modulus of the coating film) / (Young's modulus of the coating film obtained from the coating composition in which the cellulose fiber (A-1) is not added for coating composition No. 1) × 100
It becomes.

It shows that the coating film which has a high elasticity modulus by the mixing | blending of a fiber component can be formed, so that the ratio of the said change of Young's modulus is large on the plus side.
The Young's modulus was measured by the following method. First, in each of the test plates, the cured coating film was peeled from the polypropylene plate and cut into a strip shape having a length of 20 mm and a width of 5 mm to obtain a test piece. Next, "Tensilon UTM-II-20" (trade name, manufactured by Orientec Co., Ltd., tensile tester) was used, and the test was performed under the conditions of measurement temperature: 20 ° C, pulling speed: 4 mm / min, and distance between chucks: 20 mm. A stress-strain curve was obtained by pulling in the longitudinal direction until the piece broke. Subsequently, the Young's modulus was calculated from the tangent of the rising portion of the obtained stress strain curve.

Elongation:
The elongation of the coating film was evaluated using the elongation rate (breaking elongation rate) when the test piece was broken in the measurement of the elastic modulus. In addition, the evaluation of the elongation was carried out according to each of the coating composition Nos. Each coating composition No. of the elongation at break of the coating film obtained from 1-12. 1 to 12 were evaluated by the rate of change with respect to the elongation at break of the coating film obtained from the coating composition to which cellulose fibers (A-1) to (A-3) or glass fibers were not added. Specifically, the evaluation was made based on the following change rate (%) of elongation at break.
Ratio of change in elongation at break (%) = (Elongation at break of coating film obtained from coating composition containing fiber component−Elongation at break of coating film obtained from coating composition not containing fiber component) / ( (Elongation at break of coating film obtained from coating composition not containing fiber component) × 100.

More specifically, for example, in the case of Example 11,
Ratio of change in elongation at break (%) = (Elongation at break of coating film obtained from coating composition No. 1−From coating composition in which cellulose fiber (A-1) is not added for coating composition No. 1 Elongation at break of coating film obtained) / (Elongation at break of coating film obtained from coating composition to which cellulose fiber (A-1) is not added with respect to coating composition No. 1) × 100
It becomes.

It shows that the coating film which has high elongation can be formed by the mixing | blending of a fiber component, so that the ratio of the change of the said breaking elongation rate is large on the plus side.
The elongation at break can be determined from the following formula.
Elongation at break (%) = (Distance between chucks at break−Distance between chucks before test) / (Distance between chucks before test) × 100.

In the said evaluation result, in Examples 11-20, the coating film excellent in the formability and transparency of a coating film is formed, and the fiber component is disperse | distributed uniformly. In addition, since both the modulus of elasticity and the elongation of the coating film are positive, the coating film has an excellent physical property that the elasticity modulus is improved and the elongation of the coating film does not decrease as compared with the case where no fiber component is contained. Have.
On the other hand, in Comparative Examples 3 and 4, since the formability and transparency of the coating film are inferior, the fiber component is not uniformly dispersed. In addition, the elastic modulus of the coating film is positive, while the elongation is negative. Therefore, although the elastic modulus is improved compared to the case where the coating film does not contain a fiber component, the elongation of the coating film is decreased. Has the disadvantages.

Claims (9)

  A coating composition containing cellulose fiber (A), film-forming resin (B) and organic solvent (C), wherein the cellulose fiber (A) has an acetyl group and a carboxy group, and an organic solvent ( C) has a solubility parameter value of 8.5 or more.   The coating composition according to claim 1, wherein the cellulose fiber (A) has an acetyl group substitution degree of 0.5 to 1.0.   The coating composition according to claim 1 or 2, wherein the amount of carboxy groups in the cellulose fiber relative to the mass of the cellulose fiber of the cellulose fiber (A) is 0.10 to 0.60 mmol / g.   The coating composition according to any one of claims 1 to 3, wherein the cellulose fiber (A) has a number average fiber diameter of 2 to 400 nm.   The coating composition according to any one of claims 1 to 4, wherein the film-forming resin (B) is a hydroxyl group-containing resin (B-1) having a measured solubility parameter value of 9.5 or more.   The coating composition according to claim 5, wherein the hydroxyl group-containing resin (B-1) is at least one selected from the group consisting of a hydroxyl group-containing acrylic resin, a hydroxyl group-containing polyester resin, and a hydroxyl group-containing alkyd resin.   The coating composition according to any one of claims 1 to 6, wherein the organic solvent (C) contains at least one selected from the group consisting of an ester solvent, an alcohol solvent, an ether solvent, and a ketone solvent.   Furthermore, the coating composition of any one of Claims 1-7 containing a crosslinking agent (D).   The coated article which has a coating film which consists of a hardened | cured material of the coating composition of any one of Claims 1-8 on a base-material surface.