JP6014814B2 - Coating composition, method for producing the same, and coating method - Google Patents

Description

  The present invention relates to a coating composition that can be suitably used to improve the water resistance, weather resistance, and aesthetics of so-called green plastics made of woody materials such as beech and bamboo, a method for producing the same, and a method for coating the same. .

  In recent years, sustainable “manufacturing” in consideration of the environment has become an important issue in all industries regardless of the field. For this reason, technical development of so-called green plastics in which woody materials such as beech and bamboo are molded as plastic substitute materials has been vigorously performed (for example, Patent Document 1 and Patent Document 2).

JP 2009-107331 A JP 2008-37022 A JP 2007-284745 A

  However, the above-mentioned green plastic usually has a blackish brown color, and has problems such as a peculiar odor and poor water resistance due to easy water absorption. In order to solve these problems, it is conceivable to enhance the aesthetics, prevent odors, and improve water resistance by painting the surface. However, if an organic coating film mainly composed of petroleum-based raw materials is applied on the surface of green plastic, the significance of using wood-based materials in consideration of the environment will be diminished. For this reason, there has been a demand for a silicon-based coating agent that can exhibit water resistance, weather resistance and deodorization when coated on the surface of a green plastic.

  The present invention has been made in view of the above problems, and can provide a silicon-based coating composition that can improve water resistance, weather resistance and deodorization even when coated on the surface of a green plastic, and It is an object of the present invention to provide a manufacturing method and a coating method.

  As an alternative to a chromate film for improving the corrosion resistance of a galvanized film, the present inventors have already hydrolyzed a mixture of tetraalkoxysilane and methyltrialkoxysilane with an acid, and further subjected to dehydration polymerization (hereinafter referred to as a polymer). (Referred to as “hydrolyzed polymer”) (Patent Document 3). Further, the present inventors have considered the use of a hydrolyzed polymer of an alkoxysilane compound in order to solve the above-described problems related to green plastics. However, compared with the surface of the galvanized film, the surface of the wood-based molded product has irregularities and is porous, so that a film with good adhesion could not be obtained. For this reason, among the hydrolyzed polymers of many alkoxysilane compounds, those that easily penetrate into the inside of the green plastic were selected, and further intensive research was conducted. As a result, it has been found that a hydrolysis polymer of trimethoxyvinylsilane can solve the above-mentioned problems, and the present invention has been completed.

  That is, the coating composition of the present invention is a coating composition containing a hydrolysis polymer of trimethoxyvinylsilane, and the hydrolysis polymer is 2 to 10 times the number of moles of the trimethoxyvinylsilane. It is characterized by being hydrolyzed with an acid containing the following number of moles of water.

  The coating composition of the present invention contains a hydrolysis polymer of trimethoxyvinylsilane. Trimethoxyvinylsilane is hydrolyzed by acid to give three methyl alcohol molecules and one vinyltrihydroxysilane molecule. Further, silanol groups present in the vinyltrihydroxysilane molecules are dehydrated and condensed by the action of an acid to form a polymer having a network structure of silicon oxide, thereby forming a film.

  Here, the hydrolyzed polymer is hydrolyzed with an acid containing 2 to 10 times the number of moles of trimethoxyvinylsilane, so that it becomes a viscous and uniform transparent solution. It becomes a liquid that can be easily applied uniformly. And the film | membrane obtained by drying an application layer can exhibit water resistance, a weather resistance, and deodorizing property, when it coats on the surface of a green plastic.

  When water is less than twice the number of moles of trimethoxyvinylsilane, the methoxy group may remain without being hydrolyzed. Moreover, when water exceeds 10 times with respect to the number of moles of trimethoxyvinylsilane, a hydrolyzed polymer precipitates and it does not become a uniform transparent solution. Preferable is the range of 3.5 times or more and 4.5 times or less of water relative to the number of moles of trimethoxyvinylsilane, and more preferable range is 3.7 times or more and 4.3 times or less.

  As an acid for converting trimethoxyvinylsilane into a hydrolysis polymer, any acid can be used as long as it can hydrolyze a methoxy group into a silanol group and further dehydrate-condense the silanol group. . Examples of such an acid include nitric acid, carboxylic acid, orthophosphoric acid, pyrophosphoric acid, tripolyphosphoric acid, sulfonic acid, hydrochloric acid, sulfuric acid and the like. You may mix and use these. Among these, nitric acid and / or carboxylic acid having 4 or less carbon atoms are particularly preferable. This is because nitric acid and carboxylic acids having 4 or less carbon atoms are likely to volatilize and volatilize from the film after coating, so that there is little possibility of causing deterioration of the base material and corrosion of surrounding metals by the acid.

The acid concentration in the hydrolyzed polymer is preferably 10 ⁻⁵ mol / L or more and 10 ⁻¹ mol / L or less. If the acid concentration in the hydrolyzed polymer is less than 10 ⁻⁵ mol / L, the hydrolysis may be insufficient or the dehydration condensation may be insufficient. Weather resistance may be reduced. On the other hand, when the acid concentration exceeds 10 ⁻¹ mol / L, polymerization proceeds and white turbidity tends to occur in the coating composition, and the life of the liquid is shortened. More preferred is 10 ⁻⁴ mol / L or more and 10 ⁻³ mol / L or less.

  The coating composition of the present invention preferably further contains polyvinyl acetal and an alcohol having 4 or less carbon atoms. This is because the water resistance of the coating can be further improved by adding polyvinyl acetal. However, it is necessary to add an alcohol having 4 or less carbon atoms so that polyvinyl acetal does not precipitate. The inventors have confirmed that the water resistance is further improved when the polyvinyl acetal is polyvinyl butyral.

In the case of adding polyvinyl butyral, the content of polyvinyl butyral is the mass when the trimethoxyvinylsilane is hydrolyzed and further completely dehydrated and polymerized (in other words, trimethoxyvinylsilane is (CH ₂ = CHSiO _{3 / 2} ) It is preferable that it is 4 mass% or more and 15 mass% or less with respect to the sum total of the mass of _n and the polyvinyl butyral. If it is less than 4% by mass, the degree of improving the water resistance of the coating will be small. Moreover, when it exceeds 15 mass%, polyvinyl butyral will become difficult to melt | dissolve and the uniform application | coating to a base material will become difficult by generation | occurrence | production of an insoluble matter. Moreover, since polyvinyl butyral is a petroleum-based raw material component, its role as a coating composition considering the environment is reduced.

  The coating composition of the present invention preferably further contains a titania sol. Since titania sol has high reactivity of dehydration condensation reaction, it can accelerate the curing rate of the film, and can form a film with excellent water resistance even at a low temperature of 110 ° C. or less after coating. it can.

  The addition ratio in the case of adding the titania sol is preferably such that the value of (number of moles of titania sol) / (number of moles of trimethoxyvinylsilane + number of moles of the titania sol) is 0.002 or more and 0.04 or less. . If the value of (number of moles of titania sol) / (number of moles of trimethoxyvinylsilane + number of moles of the titania sol) is less than 0.002, the effect of improving weather resistance may be reduced. On the other hand, when the value of (number of moles of titania sol) / (number of moles of trimethoxyvinylsilane + number of moles of the titania sol) exceeds 0.04, solidification of the solution is accelerated and the life of the liquid is shortened.

The coating composition of the present invention can be easily produced by hydrolyzing trimethoxyvinylsilane with an acid containing water having a mole number of 2 to 10 times the mole number of the trimethoxyvinylsilane. it can. The acid concentration in the hydrolyzed polymer is preferably 10 ⁻⁵ mol / L or more and 10 ⁻¹ mol / L or less. If the acid concentration in the hydrolyzed polymer is less than 10 ⁻⁵ mol / L, the hydrolysis may be insufficient or the dehydration condensation may be insufficient. The weather resistance may be insufficient. On the other hand, when the acid concentration exceeds 10 ⁻¹ mol / L, polymerization proceeds and white turbidity tends to occur in the coating composition, and the life of the liquid is shortened. More preferred is 10 ⁻⁴ mol / L or more and 10 ⁻³ mol / L or less.

  Various substrates can be coated with the coating composition of the present invention. That is, the coating method of the present invention includes an adhesion step of attaching the coating composition of the present invention to a substrate, a drying step of drying the substrate on which the coating composition is adhered after the adhesion step, and the drying And a heating step of performing a heat treatment after the step.

  This coating method can be suitably used when the substrate is a wood-based molded body containing 50% by mass or more of a wood-based material such as beech wood powder or bamboo powder. Such wood-based materials tend to have disadvantages such as poor water resistance and weather resistance and bad odor, so that the coating method of the present invention can be used as a means for overcoming these disadvantages. Further preferable is a wood-based molded body containing 80% by mass or more of a wood-based material in which such a drawback is remarkable.

FIG. 2 is a drawing-substituting photograph before and after a water resistance test of a plate-like molded body made of beech using the coating composition of Example 1 three times. It is a drawing substitute photograph before and after the weather resistance test of what coated the plate-shaped molded object which consists of beech using the coating composition of Example 1. FIG. It is the drawing substitute photograph before and after the water resistance test of what applied the coating to the plate-shaped molded object which consists of 孟宗竹 using the coating composition of Example 1 twice, and what has not been coated. It is a drawing substitute photograph before and after the weather resistance test of what applied the coating to the plate-shaped molded object which consists of 孟宗竹 using the coating composition of Example 1 twice, and what has not been coated. Example 6-3 of a plate-shaped molded article made of Munetake bamboo coated with a polyvinyl butyral-containing coating composition of Example 6-3 (PVB solid content ratio 15 mass%) and Example 6-4 (PVB solid content ratio 20 mass%) It is a drawing substitute photograph before and after the water resistance test of a coating sample. FIG. 5 is a drawing-substituting photograph before and after a weathering test of a coating sample of a plate-shaped molded article made of Miso bamboo coated with a polyvinyl butyral-containing coating composition of Example 6-3 (solid content ratio of PVB: 15% by mass). It is a drawing substitute photograph of the vermilion case which coated the composition for polyvinyl butyral containing coating of Example 6-3 (solid content ratio of 15 mass% of PVB), and the vermilion case before coating. Example 6-3 (PVB solid content ratio 15% by mass) of a vermicelli case coated with a polyvinyl butyral-containing coating composition, after adhesion test by tape peeling (cross-cut method) (left side), and water resistance It is a drawing substitute photograph after a test (right side). FIG. 5 is a drawing-substituting photograph after a water resistance test on vermilion cases coated with the coating compositions of Examples 2-2, 7-3 and Example 6-3. It is a drawing typical photograph before and after the weather resistance test of Example 7-3 (twice coating) and the vermilion case which coated three times on the same conditions.

  Conventionally, as a coating agent using a sol-gel method, an inexpensive silane compound such as tetraethoxysilane or methyltriethoxylane is often used (for example, for improving the corrosion resistance of a galvanized film described in Patent Document 3). Coating composition as a substitute for chromate film). If these silane compounds are hydrolyzed with water, it is possible to produce a transparent and uniform coating composition. However, when coated on the surface of a green plastic such that the blending ratio of the wood-based material exceeds 90% by mass, the water resistance, weather resistance and deodorization could not be improved.

  In contrast, the coating composition of the present invention uses trimethoxyvinylsilane as an alkoxysilane compound, and dehydrates and condenses it with an acid, whereby a green plastic having a wood material content of more than 90% by mass. When coated on the surface, water resistance, weather resistance and deodorization can be improved.

  In the present invention, trimethoxyvinylsilane is preferably hydrolyzed with an acid containing as little water as possible to obtain a hydrolyzed polymer. However, if there is too little water, the hydrolysis will be insufficient, the development of the network structure of silanol bonds will be insufficient, and the film may be soft, and the weather resistance and deodorizing properties may be insufficient. For this reason, it is necessary to hydrolyze with an acid containing water having a mole number of 2 to 10 times the mole number of trimethoxyvinylsilane. Preferable is the range of 3.5 times or more and 4.5 times or less of water relative to the number of moles of trimethoxyvinylsilane, and more preferable range is 3.7 times or more and 4.3 times or less.

(Method for producing coating composition)
If the specific manufacturing method of the composition for coating is shown, it will be as follows, for example.
That is, the following liquid is prepared.
Trimethoxyvinylsilane ... Xmol
Acid (nitric acid, acetic acid, etc.)
Solution containing 2X to 10X mol of water Next, the liquid is stirred and mixed. In this case, the hydrolysis reaction is an exothermic reaction, and it is preferable to cool the reaction solution so that the temperature of the reaction solution is kept at a normal temperature. In this case, the acid concentration is preferably adjusted so that the acid concentration after hydrolysis is 10 ⁻⁵ mol / L or more and 10 ⁻¹ mol / L or less. In this way, the coating composition of the present invention which is transparent, viscous and uniform is obtained. More preferably, the acid concentration after hydrolysis is adjusted to be 10 ⁻⁴ mol / L or more and 10 ⁻³ mol / L or less.

  In the case of obtaining the coating composition of the present invention to which polyvinyl butyral is added, the transparent solution obtained as described above is a solution of polyvinyl butyral dissolved in an alcohol having 4 or less carbon atoms such as ethanol and methanol. It is sufficient to add to the coating composition of the present invention that is viscous and uniform and stir. Alternatively, after adding and stirring the alcohol having 4 or less carbon atoms such as ethanol and methanol to the transparent, viscous and uniform coating composition of the present invention obtained as described above, polyvinyl butyral is used. Further, it may be produced by adding and dissolving.

Further, when producing the coating composition of the present invention containing a titania sol, the titania sol is further added to the coating composition of the present invention containing polyvinyl butyral produced as described above, and mixed and stirred. do it. In addition, after adding titania sol, polyvinyl butyral and alcohol may be added.
The titania sol can be obtained by adding an aqueous nitric acid solution containing an equimolar amount of water to titanium isopropoxide to an ethanol solution of alkoxytitanium (for example, titanium isopropoxide) and stirring at room temperature.

  The number of coatings can be appropriately selected as necessary, but is usually preferably twice.

  The coating composition of the present invention can be diluted with an ethanol solvent, and polyvinyl butyral can be dissolved in the diluted solution. In the case of adding polyvinyl butyral, the solution is cooled to room temperature, diluted with a predetermined amount of ethanol, completely dissolved in polyvinyl butyral, and then heated and concentrated to a predetermined concentration. Polyvinyl butyral cannot be uniformly dissolved at a high solution concentration. By adding polyvinyl butyral, the liquid life is increased and the storage stability of the solution is improved.

  Examples of the trimethoxyvinylsilane used as a raw material include trimethoxyvinylsilane sold by Shin-Etsu Chemical Co., Tokyo Chemical Industry, etc.

<Preparation of coating composition>
(Examples 1-5)
37.05 g of trimethoxyvinylsilane (manufactured by Shin-Etsu Chemical Co., Ltd.) was weighed out, and the molar amount of 18 mL of water containing 0.1 mL of nitric acid (concentration 0.1 mol / L) (trimethoxyvinylsilane (hereinafter abbreviated as “TMBS”)) 4 times the molar amount) was added and stirred and mixed to obtain 51.75 g of the coating composition of Example 1 as a uniform transparent solution. The amount of TMBS was such that the final concentration was 5 mol / L, and the concentration of added nitric acid was adjusted to be 2 × 10 ⁻⁴ mol / L at the final concentration. (Similarly, in place of nitric acid, formic acid was used in Example 2, acetic acid was used in Example 3, propionic acid was used in Example 4, and butyric acid was used in Example 5. 1 and is not described in detail.)

  Addition of water containing an acid is necessary to hydrolyze the three methoxy groups of trimethoxyvinylsilane. From a stoichiometric viewpoint, the amount of water required to hydrolyze 1 mol of trimethoxyvinylsilane is 3 mol. However, in order to complete the hydrolysis, it is desirable to add 3 mol or more of water.

  When 1 mol amount of water is added to 1 mol of trimethoxyvinylsilane, a uniform transparent solution is obtained. However, since the hydrolysis of trimethoxyvinylsilane is insufficient, the solution is used on the glass plate. The produced film could not be cured sufficiently by heat treatment at 90 ° C.

  When 11 mole amount of water was added to 1 mole of trimethoxyvinylsilane, it seemed to be transparent, but many insoluble transparent precipitates were formed, resulting in a non-uniform solution. Moreover, a uniform film could not be produced on the glass plate.

  From the above results, in order to prevent the precipitation of solids from the coating composition and to provide a uniform coating, the amount of water added to 1 mole of trimethoxyvinylsilane is 10 times or more in molar ratio. It turned out that less than double is necessary.

(Comparative Example 1)
In Comparative Example 1, a solution in which tetraethoxysilane and methyltriethoxysilane were mixed at various ratios as an alkoxysilane compound was used. Other conditions are the same as those in the first embodiment, and detailed description thereof is omitted.

  When tetraethoxysilane and methyltriethoxysilane were mixed at a molar ratio of 20:80, 30:70, 40:60, 60:40, 80:20, the same uniformity as in Examples 1-5 A clear solution could be prepared.

  In addition, when a film was formed on a slide glass using a transparent solution prepared by mixing tetraethoxysilane and methyltriethoxysilane in a molar ratio of 60:40 and 80:20, the prepared film was Peeled during the drying process. In addition, in a transparent solution prepared by mixing tetraethoxysilane and methyltriethoxysilane in a molar ratio of 40:60, a film was prepared using a solution that had passed three days after preparation, and the prepared film was dried. Peeled inside.

From the above results, in the coating composition of Comparative Example 1 in which tetraethoxysilane and methyltriethoxysilane were mixed in various proportions, when the content of tetraethoxysilane is high, the flexibility of the film is lowered, and the drying process It was found that peeling occurred.
Moreover, when the content of methyltriethoxysilane is 70 mol% or more, a film without cracks or peeling can be produced on the slide glass. However, as will be described later, when a coating was applied to a wood-based molded body, a coating sample with a transparent film could be prepared. However, since the film became cloudy and peeled off in the water resistance test, it was used for coating. Was found to be unsuitable.

(Comparative Example 2)
In Comparative Example 2, only triethoxyvinylsilane was used, and water containing an acid was added under the same conditions as in Example 1, followed by stirring and mixing to obtain a coating composition. However, with this coating composition, precipitation occurred during stirring and mixing, and a uniform transparent solution was not obtained.

(Comparative Example 3)
In Comparative Example 3, a solution in which triethoxyvinylsilane and trimethoxyvinylxysilane were mixed at various ratios as an alkoxysilane compound was used. Other conditions are the same as those in the first embodiment, and detailed description thereof is omitted.
As a result, even when triethoxyvinylsilane and trimethoxyvinylsilane were mixed at a molar ratio of 15:85, a small amount of precipitation occurred, and a uniform transparent solution could not be prepared.

  Moreover, the film produced on the glass plate using the solution of Comparative Example 3 did not cure even when heated at 90 ° C.

  About the coating compositions of Examples 1 to 5 and Comparative Examples 2 and 3 obtained as described above, when the appearance was visually observed, the coating compositions of Examples 1 to 5 and Comparative Example 1 were In contrast to the viscous and colorless liquid, the coating compositions of Comparative Examples 2 and 3 cause white precipitates and do not form a uniform transparent solution, making it difficult to uniformly coat the substrate. Due to the fact that the film could not be cured by heating at 90 ° C., the coating on the wood-based molded body described later was abandoned.

<Coating on wood-based moldings>
Using the coating compositions of Example 1 and Comparative Example 1, the wood-based molded body was coated. As the wood-based molded body, a plate-shaped molded body pressure-molded using heated steam was used. There are two types of wood-based materials: beech and Miso bamboo.
-Coating to plate-shaped molded object The composition for coating was put into the beaker, the plate-shaped molded object was immersed in it, and it put into the vacuum bell. Then, suction was performed at −0.055 MPa for 1.5 hours with a vacuum pump. Thereafter, the vacuum bell was removed, the plate-shaped molded body was pulled up, and naturally dried for 12 hours, followed by heat treatment at 80 ° C. for 1 hour to prepare a once-coated plate-shaped molded body. Furthermore, in the same manner, when preparing a two-coated plate-like molded product obtained by repeating the coating treatment twice and a three-coated plate-shaped molded product obtained by repeating the coating three times, vacuuming is not performed in the second and subsequent coatings. In addition, only the immersion in the coating composition was performed, followed by drying and heat treatment.

<Evaluation>
The following evaluation was performed about the coated sample of the plate-shaped molded object which consists of a beech (or Miso bamboo) obtained as mentioned above.
1) Film hardness: Measured according to JIS K 5600-5-4, scratch hardness (pencil method).
2) Glossiness: The reflectance under a geometric condition of 60 ° in JIS K 5600-4-7 and specular glossiness was measured.
3) Water resistance: The whole sample was put in boiling water, boiled for 1 hour, taken out and dried for 5 minutes, and then the presence or absence of peeling of the film was examined to determine the water absorption rate by the weight increase rate of the sample.
4) Weather resistance: It was performed under the following conditions using a sunshine weather meter (Suga Test Instruments WEL-SUN-HCH · B).
・ Irradiation time: 70 hours ・ Black panel temperature: 63 ± 3 ℃
・ Rainfall conditions: Water spray for 12 minutes every 60 minutes 5) Film forming property: Visual inspection based on appearance of coating film

(result)
Table 1 shows the evaluation results of the coated samples of the plate-shaped molded body made of beech using the coating composition of Example 1. On the other hand, in the case where the wood-based molded body was coated using the coating composition of Comparative Example 1, a coating sample with a transparent film could be produced, but the film was not clouded or peeled off in the water resistance test. Since it happened, it turned out to be unsuitable for use in coating.

  As shown in Table 1, a sample in which the coating composition of Example 1 was used to coat a plate-shaped molded body made of beech three times showed a gloss of 70 and a pencil hardness of 5H. It was. Moreover, in the water resistance test, the weight increase rate after the test was 12%, and it was found that the water resistance was improved as compared to the weight increase rate of 15% in the absence of coating. As shown in FIG. 1, the sample coated three times showed almost no decolorization after boiling for 1 hour.

  Similarly, FIG. 2 shows a photograph substituted for a drawing before and after the weather resistance test of a wood-based molded body using beech wood flour that was coated twice or three times using the coating composition of Example 1. . Before the test, both had glossiness of 70 and pencil hardness of 5H, and both did not show any change after 20 hours of irradiation, but both were decolorized after 70 hours of irradiation. In addition, the degree of decolorization was less in the case of coating twice.

  On the other hand, the evaluation result about the sample which performed the coating 1-3 times to the plate-shaped molded object which consists only of Miso bamboo is shown in Table 2. From this table, it can be seen that the glossiness is 74 or more, the pencil hardness is as hard as 6H, and the weight increase after the water resistance test is 9.0% or less. Moreover, there was little decoloration by boiling and clear improvement of water resistance was recognized (refer FIG. 3). On the other hand, when the coating was not performed, the weight increase in the water resistance test was 13.5%.

  In addition, FIG. 4 shows a photograph substituted for a drawing before and after a weather resistance test on a sample obtained by coating a plate-shaped molded body made only of Miso bamboo. From this figure, it can be seen that significant decolorization occurs after 70 hours of irradiation.

(Examples 2 to 5)
In the coating composition of Example 2, formic acid was used in place of nitric acid in the coating composition of Example 1. Similarly, Example 3 used acetic acid, Example 4 used propionic acid, and Example 5 used butyric acid. The carboxylic acid concentration in the coating composition was 3 × 10 ⁻³ mol / L (however, 6.4 × 10 ⁻³ mol / L for acetic acid). Other conditions are the same as those in the first embodiment, and detailed description thereof is omitted.

  Using the coating compositions of Examples 2 to 5 obtained as described above, a plate-like molded body composed only of Munetake bamboo was coated twice, and a water resistance test was conducted. The method of coating and the method of water resistance test are the same as in Example 1.

  The results are shown in Table 3. From this table, it was found that when propionic acid was used as the carboxylic acid for hydrolysis, the weight increase rate was the lowest and the water resistance was improved by about 40%. However, when carboxylic acid is used as the acid for hydrolysis, there is a problem that the coating composition emits a odor peculiar to carboxylic acid. When nitric acid is used as the acid for hydrolysis, there is no such problem of odor, so it can be said that nitric acid is preferable to carboxylic acid as the acid.

(Examples 6-1, 6-2, 6-3, 6-4)
In Examples 6-1 to 6-4, a coating composition containing polyvinyl butyral was prepared.
That is, 100 mL of ethanol was added to 51.75 g of the coating composition prepared in Example 1 and mixed with stirring. Further, polyvinyl butyral (polyvinyl butyral 2000 average degree of polymerization 1900-2100 manufactured by Wako Pure Chemical Industries, Ltd.) (hereinafter “ PVB ”is a predetermined solid content ratio (4 mass% in Example 6-1; 13 mass% in Example 6-2; 15 mass% in Example 6-3; 20 mass in Example 6-4). %). Here, the solid content ratio is a value obtained by expressing the mass of PVB / (mass when TMBS is hydrolyzed and further completely dehydrated and polymerized + mass of PVB) as a percentage (the same applies hereinafter). And after stirring and making it heat-dissolve completely, it concentrated by heating until the total volume became 100 mL, and the polyvinyl butyral containing coating composition of Examples 6-1 to 6-4 was obtained.

<Coating on plate-like wood-based molded products>
Using the polyvinyl butyral-containing coating compositions of Examples 6-1, 6-2, and 6-3 prepared as described above, the above-described wood-based molded body composed of Munetake bamboo was coated once. The immersion time was 10 minutes for the polyvinyl butyral-containing coating composition of Example 6-1 and 35 minutes for the polyvinyl butyral-containing coating compositions of Example 6-2 and Example 6-3. Other coating conditions are the same as those described above, and a description thereof will be omitted.

<Evaluation>
The following evaluations were performed on the coated samples of the plate-like molded body made of Somune bamboo obtained as described above. In addition, about the film forming property, what was apply | coated to the glass surface was also evaluated.
1) Film hardness: Measured according to JIS K 5600-5-4, scratch hardness (pencil method).
2) Glossiness: The reflectance under a geometric condition of 60 ° in JIS K 5600-4-7 and specular glossiness was measured.
3) Water resistance: The whole sample was put in boiling water, boiled for 1 hour, taken out and dried for 5 minutes, and then the presence or absence of peeling of the film was examined to determine the water absorption rate by the weight increase rate of the sample.
4) Weather resistance: It was performed under the following conditions using a sunshine weather meter (Suga Test Instruments WEL-SUN-HCH · B).
・ Irradiation time: 70 hours ・ Black panel temperature: 63 ± 3 ℃
・ Rainfall conditions: Water spray for 12 minutes every 60 minutes 5) Film forming property: Visual inspection based on appearance of coating film

As a result, as shown in Table 4, when PVB having a solid content ratio of 15% by mass or more was added to the coating composition of Example 1 containing the hydrolysis polymer of TMBS, it was uniform on the glass plate. It was found that a film having no defects can be prepared.
In addition, the coating sample of the plate-like molded body made of Miso bamboo coated with the polyvinyl butyral-containing coating composition of Examples 6-1 6-2, and 6-3 has a glossiness of 75 or more and a film hardness of 4H or more. 11.4% in Example 6-1 and 6.8% in 6-2 compared with the value (13.5%) in the case where water resistance is uncoated despite one coating. In 6.7%, it was found that it improved significantly.

FIG. 5 shows a plate-like shape made of Munetake bamboo coated with a polyvinyl butyral-containing coating composition of Example 6-3 (solid content ratio of PVB 15% by mass) and Example 6-4 (solid content ratio of PVB 20% by mass). The photograph substituted for drawing before and after the water resistance test of the coating sample of a molded object is shown. From this figure, it can be seen that almost no decolorization by boiling for 1 hour is seen.
Also, in the weather resistance test, as shown in FIG. 6, a coating of a plate-like molded body made of Munetake bamboo coated with a polyvinyl butyral-containing coating composition of Example 6-3 (PVB solid content ratio 15% by mass) In the sample, although there was peeling of the film, the fading property was improved.
From the above results, it was found that the addition of PVB is very effective for preventing crack peeling and water resistance of the film, and also improves the weather resistance. Moreover, the preferable addition amount of PVB is 5-20 mass% in solid content ratio, The better thing is about 7-15 mass%, The best was 13-15 mass%.

  Further, the coating composition of Example 1 solidifies within a few weeks after preparation, whereas Examples 6-1 to 6-4 to which PVB was added did not solidify within a few weeks and the liquid life was long. It turns out to be long.

<Coating on vermilion case>
Using the coating composition of Example 6-3 (PVB solid content ratio: 15% by mass), coating on vermilion made of a wood-based molded body was performed. This vermilion case is made of 90% by mass of a wood-based material, and 10% by mass of a binder resin is added.
When trying to immerse the vermilion container into the coating composition of Example 6-3 (PVB solid content ratio 15% by mass) under reduced pressure, the components of the vermilion container eluted and the coating composition colored. For this reason, only immersion was carried out without reducing the pressure, and after lifting and natural drying, heating was performed at 60 ° C. for 30 minutes. The number of coatings was 2 times.

<Evaluation>
The coated vermilion case obtained as described above was evaluated as follows.
1) Adhesiveness: Performed according to JIS K 5600-5-6, adhesion (cross-cut method).
2) Film hardness: Measured according to JIS K 5600-5-4, scratch hardness (pencil method).
3) Water resistance: The whole sample was put in boiling water, boiled for 1 hour, taken out and dried for 5 minutes, and then the presence or absence of peeling of the film was examined to determine the water absorption rate by the weight increase rate of the sample.

FIG. 7 shows a photograph substituted for a drawing before and after the coating of vermilion. From this photograph, it can be seen that there is no significant deformation after coating and heat treatment. When the wood-based molded body constituting the vermilion case itself is heated at a temperature exceeding 60 ° C., swelling and foaming often occur, so the heating temperature at the time of coating was lowered to 60 ° C.
Moreover, in the adhesiveness test by tape peeling (cross-cut method), as shown in FIG. 8 (left), 50% of the film was peeled off. Further, the film hardness was a pencil hardness HB or less. Furthermore, in the water resistance test, as shown in FIG. 8 (right), the shape of the vermilion case was destroyed by boiling, but peeling of the coating film was not recognized.

  From the above results, the coating composition of Example 6-3 (PVB solid content ratio 15% by mass) can prevent crack peeling of the coating film in the 90% wood-based injection molded body (red meat case). I understood. Moreover, water resistance was able to be improved. Furthermore, the coating composition of Example 1 solidifies within a few weeks after preparation, whereas Examples 6-1 to 6-4 to which PVB was added did not solidify within a few weeks, and the liquid life Was found to be longer.

(Examples 7-1 to 7-4)
In Examples 7-1 to 7-4, a coating composition containing a titania sol in addition to polyvinyl butyral was prepared. Below, the preparation method is explained in full detail.
-Preparation of titania sol An aqueous nitric acid solution containing titanium isopropoxide and an equimolar amount of water was added to an ethanol solution of titanium isopropoxide (15.2% by mass) diluted 10-fold with an ethanol solvent. Here, the concentration of nitric acid was adjusted to 10 ⁻⁴ mol / L after preparation. Then, the mixture was stirred and dehydrated at room temperature to obtain 0.4 mol / L titania sol.
-Preparation of coating composition The coating composition of Example 6-3 (that is, the coating composition obtained by mixing PVB in the coating composition of Example 1 at a solid content ratio of 15% by mass) as described above. The titania sol thus prepared had a predetermined amount ((number of moles of titania sol) / (number of moles of TMBS + number of moles of titania sol)) of 0.04 in Example 7-1, Example 2-2 and Example 7- 3 was added to 0.01 and 0.002 in Example 7-4) and mixed to obtain coating compositions of Examples 7-1 to 7-4. The concentration of the hydrolysis polymer of trimethoxyvinylsilane was 1.4 mol / L in Example 7-1, 2 mol / L in Example 6-2 and Example 7-3 in terms of TMBS, and 2 in Example 7-4. 0.5 mol / L.

<Coating on vermilion case>
Using the polyvinyl butyral and titania sol-containing coating compositions of Examples 7-1 to 7-4 prepared as described above, coating to vermilion was performed. This vermilion case is made of 90% by mass of a wood-based material, and 10% by mass of a binder resin is added. As a coating method, the vermilion case was dipped in the coating compositions of Examples 7-1 to 7-4, pulled up and dried naturally, and then heated at 60 ° C. or 110 ° C. for 30 minutes. In addition, the coating frequency was 1 time or 3 times.
For comparison, a vermilion container coated with the coating composition of Example 6-3 (that is, a coating composition in which PVB is mixed with the coating composition of Example 1 at a solid content ratio of 15% by mass) is also used. Prepared.

<Evaluation>
The coated vermilion case obtained as described above was evaluated as follows.
1) Adhesiveness: Performed according to JIS K 5600-5-6, adhesion (cross-cut method).
2) Film hardness: Measured according to JIS K 5600-5-4, scratch hardness (pencil method).
3) Glossiness: The reflectance under a geometric condition of 60 ° in JIS K 5600-4-7 and specular glossiness was measured.
4) Water resistance: The entire sample was placed in boiling water, boiled for 1 hour, taken out and dried for 5 minutes, and then the presence or absence of peeling of the film was examined to determine the water absorption rate by the weight increase rate of the sample.
5) Weather resistance: It was performed under the following conditions using a sunshine weather meter (Suga Test Instruments WEL-SUN-HCH · B).
・ Irradiation time: 70 hours ・ Black panel temperature: 63 ± 3 ℃
・ Rainfall conditions: Water spray for 12 minutes every 60 minutes 6) Film forming property: Visual inspection based on appearance of coating film

The results are shown in Table 5.

  As a result, in the sample coated with the coating composition of Example 6-3 to which no titania sol was added and heat-treated at 60 ° C. for 30 minutes, as shown in Table 5, after the water resistance test, decoloration and film The sample was destroyed due to peeling. On the other hand, in the samples coated with Examples 7-1 to 7-4 to which titania sol was added, although a slight weight increase was observed in the water resistance test, it was not yet destroyed. Further, in Example 7-3, there was no white turbidity observed in Examples 7-1, 7-2, and 7-4, transparency was maintained, and the film hardness was most excellent. From the above results, the value of (number of moles of titania sol) / (number of moles of trimethoxyvinylsilane + number of moles of titania sol) is preferably 0.002 or more and 0.04 or less, and more preferably 0.01 or more and 0.0. It was found that 04 or less is preferable.

  FIG. 9 shows a drawing-substituting photograph of the sample after the water resistance test for Examples 2-2, 7-3, and Example 6-3. FIG. 10 shows representative photographs before and after the weather resistance test of Example 7-3 (twice coating) and a vermicelli case that was coated three times under the same conditions. From this figure, it was found that no deterioration such as fading or peeling of the film was observed after 70 hours of irradiation. From this, the coating composition used in Example 7-3 was coated twice or more in vermilion and heat-treated at 110 ° C. for 30 minutes, so that the most excellent adhesion, water resistance and weather resistance were obtained. It became clear that a coated vermilion can be prepared.

  The present invention is not limited to the description of the embodiments and examples of the invention described above. Various modifications are also included in the present invention as long as those skilled in the art can easily conceive without departing from the scope of the claims.

  The present invention can be suitably used as a coating composition for improving the water resistance, weather resistance and aesthetics of a green plastic made of a wood-based material.

Claims (12)

To coat a wood-based molded article containing a hydrolysis product of trimethoxyvinylsilane represented by the following chemical formula, polyvinyl acetal, and alcohol having 4 or less carbon atoms and containing 50% by mass or more of wood powder or bamboo powder. A coating composition comprising:
The coating composition according to claim 1, wherein the hydrolyzed polymer is hydrolyzed with an acid containing water having a mole number of 2 to 10 times the mole number of the trimethoxyvinylsilane.
  The coating composition according to claim 1, wherein the acid is nitric acid and / or a carboxylic acid having 4 or less carbon atoms. The coating composition according to claim 1 or 2, wherein the concentration of the acid in the hydrolyzed polymer is 10 ^-5 mol / L or more and 10 ^-1 mol / L or less.   The coating composition according to claim 1, wherein the polyvinyl acetal is polyvinyl butyral.   The content of the polyvinyl butyral is 4% by mass or more and 15% by mass or less with respect to the total mass of the mass when the trimethoxyvinylsilane is hydrolyzed and further completely dehydrated and the mass of the polyvinyl butyral is assumed. The coating composition according to claim 4.   The coating composition according to any one of claims 1 to 5, further comprising a titania sol.   The coating composition according to claim 6, wherein a value of (number of moles of the titania sol) / (number of moles of the trimethoxyvinylsilane + number of moles of the titania sol) is 0.002 or more and 0.04 or less. object. A step of hydrolyzing trimethoxyvinylsilane represented by the following chemical formula with an acid containing water having a mole number of 3 to 6 times the mole number of the trimethoxyvinylsilane;
A step of adding polyvinyl acetal and an alcohol having 4 or less carbon atoms after the hydrolysis step;
The method for producing a coating composition according to any one of claims 1 to 7, further comprising:
The method for producing a coating composition according to claim 8, wherein the concentration of the acid in the hydrolyzed polymer is 10 ⁻⁵ mol / L or more and 10 ⁻¹ mol / L or less. An adhesion step of adhering the coating composition according to any one of claims 1 to 7 to a wood-based molded body containing 50% by mass or more of wood powder or bamboo powder ;
A drying step of drying the wood-based molded body to which the coating composition is attached after the attaching step;
A heating step of performing a heat treatment after the drying step;
A coating method comprising: The coating method according to claim 10, wherein the wood-based molded body contains 50% by mass or more of wood powder . A coated woody molded body, wherein the woody molded body containing 50% by mass or more of wood powder or bamboo powder is coated with the coating composition according to any one of claims 1 to 7 .