JP2013082861A - Anti-fogging resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an anti-fogging resin composition that can exert excellent anti-fogging properties and water resistance, and can form a coating film with high pick.SOLUTION: The anti-fogging resin composition includes a water-soluble polyvinyl acetal resin and water, wherein the average polymerization degree is 1,000-3,500, the degree of acetalization is 21-40 mol%, the amount of a hydroxyl group is 45-64 mol%, and the proportion of a structural unit acetalized by an aromatic aldehyde is at least 90% of all structural units that have been acetalized.

Description

The present invention relates to an antifogging resin composition that can exhibit excellent antifogging properties and water resistance and can form a coating film having high surface strength.

Houses and tunnels for crop cultivation use agricultural films such as polyethylene and polyvinyl chloride, various types of glass, mirrors, etc., but with these members, water vapor condenses and adheres to the surface. As a result, there has been a problem of preventing the transmission of light. In addition, the windshield, rear glass, and the like of automobiles also have problems such as a reduction in visibility due to cloudiness.
As an anti-fogging technique for automobile window glass and the like, a method of increasing the glass surface temperature is most commonly used. That is, if it is a windshield, warm air is blown on the glass surface, and if it is a rear glass, the glass is heated by a heater embedded in the glass. On the other hand, in summer when the temperature and humidity are high, a method of cooling the interior of the vehicle to lower the humidity in the air and lowering the dew point is used.
However, it is difficult to constantly control the temperature and humidity in the vehicle interior by opening and closing doors for opening and exiting, opening and closing windows, and taking in outside air. In particular, if a vehicle that has been left when the outside air temperature is low or the humidity is high and the vehicle is started without sufficiently warming up, a large amount of cloudiness is likely to occur at the start of operation.

On the other hand, Patent Document 1 discloses an antifogging coated synthetic resin window material in which a silicone hard coat layer is formed on an exothermic pattern layer. In such a technology, the surface temperature of the optical article is increased, and the moisture in the air is prevented from condensing on the surface to provide antifogging properties. However, the heater part and the energy source are indispensable. There was a problem that became too complicated.

In recent years, therefore, attempts have been made to form various antifogging films on the surface of the window glass of a vehicle. Examples of the antifogging film include hydrophilic antifogging films. By forming a hydrophilic anti-fogging film, moisture generated near the glass surface first spreads quickly on the hydrophilic coating and prevents water droplets. As such a hydrophilic type anti-fogging film, an organic hydrophilic film such as a surfactant, polyvinyl alcohol, or polyethylene glycol is used. However, these are water-soluble or not wear-resistant. And it could not be a permanent measure.

On the other hand, a water absorption type antifogging agent has also been developed. As a water absorption type antifogging agent, for example, Patent Document 2 discloses the use of a silica fine particle porous film and a water absorbent resin.
However, these water-absorbing membranes do not have sufficient water-absorbing ability, and further improvement is necessary for the development of anti-fogging properties due to water absorption. In addition, since the generation of cloudiness is suppressed by storing moisture in the film, it is inferior in terms of water resistance, and there is a problem that the film expands or dissolves due to long-term use. . Furthermore, due to a decrease in the water resistance of the formed film, the film strength (hardness) becomes low. As a result, scratches such as nails or wiping when a window is wiped enter, and the antifogging property is reduced. There was also the problem of a drop.
In addition, there is a problem that the transparency of the film is lowered due to the scratches.

Japanese Patent No. 3844255 JP 2000-239045 A

An object of this invention is to provide the anti-fogging resin composition which can exhibit the outstanding anti-fogging property and water resistance, and can form a coating film with high surface strength.

The present invention is an antifogging resin composition containing a water-soluble polyvinyl acetal resin and water, having an average polymerization degree of 1000 to 3500, an acetalization degree of 21 to 40 mol%, and a hydroxyl group amount of 45 to 64 mol%. And the ratio of the structural unit acetalized by the aromatic aldehyde among all the structural units acetalized is 90% or more of the antifogging resin composition.
The present invention is described in detail below.

The present inventor uses a water-soluble polyvinyl acetal resin having a predetermined structure as a constituent resin of the antifogging resin composition, and sets the average degree of polymerization, the amount of hydroxyl groups, and the degree of acetalization within a predetermined range. The present inventors have found that an antifogging resin composition capable of realizing excellent water resistance while maintaining antifogging properties and capable of forming a coating film with high surface strength is obtained, and the present invention is completed. It came to.

The antifogging resin composition of the present invention has an average degree of polymerization of 1000 to 3500, an acetalization degree of 21 to 40 mol%, a hydroxyl group amount of 45 to 64 mol%, and all acetalized structural units. Among them, a water-soluble polyvinyl acetal resin containing 90% or more of a structural unit acetalized with an aromatic aldehyde is contained.

In the water-soluble polyvinyl acetal resin of the present invention, the lower limit of the average degree of polymerization is 1000 and the upper limit is 3500. When the average degree of polymerization is less than 1000, the viscosity of the antifogging resin composition containing the water-soluble polyvinyl acetal resin is decreased, dripping occurs during coating, or the surface smoothness of the coating film is decreased. To do. Moreover, the water resistance of the antifogging resin composition is lowered, and the coating film swells and dissolves.
When the average degree of polymerization exceeds 3500, leveling properties at the time of coating decrease, and the unevenness of the surface of the coating film increases. The preferable lower limit of the average degree of polymerization of the water-soluble polyvinyl acetal resin of the present invention is 1700, and the preferable upper limit is 3300.
In addition, in this specification, the average degree of polymerization of water-soluble polyvinyl acetal resin can be calculated | required from the average degree of polymerization of modified polyvinyl alcohol which is a raw material. Moreover, in this specification, the average degree of polymerization of modified polyvinyl alcohol means the average value calculated | required from the polymerization degree of each modified polyvinyl alcohol in the modified polyvinyl alcohol which is a mixture.

In the water-soluble polyvinyl acetal resin, the lower limit of the amount of hydroxyl groups is 45 mol%, and the upper limit is 64 mol%. When the amount of the hydroxyl group is less than 45 mol%, the water absorption of the water-soluble polyvinyl acetal resin is lowered, or the viscosity stability of the antifogging resin composition is lowered. When the amount of the hydroxyl group exceeds 64 mol%, the water-absorbing property of the water-soluble polyvinyl acetal resin is increased and the stability is lowered. The preferable lower limit of the amount of the hydroxyl group is 50 mol%, and the preferable upper limit is 64 mol%.

In the water-soluble polyvinyl acetal resin, the lower limit of the degree of acetalization is 21 mol%, and the upper limit is 40 mol%. When the degree of acetalization is less than 21 mol%, the water absorption is good, but the coating film hardness is lowered. If it exceeds 40 mol%, the adhesion of the antifogging resin composition to a substrate such as glass is lowered.
The preferable lower limit of the degree of acetalization is 25 mol%, and the preferable upper limit is 35 mol%.

In the water-soluble polyvinyl acetal resin, the proportion of structural units acetalized with an aromatic aldehyde is 90% or more of all acetalized structural units (total degree of acetalization). Thereby, even when the degree of acetalization is low, an antifogging resin composition having good water absorption, water resistance and transparency can be obtained.
When the proportion of the structural unit acetalized by the aromatic aldehyde is less than 90%, the water resistance is deteriorated and sufficient antifogging properties cannot be obtained.
A preferred lower limit of the proportion of structural units acetalized with the aromatic aldehyde is 90%, and a preferred upper limit is 100%.

Examples of the aromatic aldehyde include benzaldehyde, 2-methylbenzaldehyde, 3-methylbenzaldehyde, 4-methylbenzaldehyde, other alkyl-substituted benzaldehydes, chlorbenzaldehyde, and other halogen-substituted benzaldehydes.
An aromatic aldehyde having a substituent such as a hydroxy group, an alkoxy group, an amino group, or a cyano group on the aromatic ring may be used. Of these, benzaldehyde, 2-methylbenzaldehyde, 3-methylbenzaldehyde, and 4-methylbenzaldehyde are preferable.

The water-soluble polyvinyl acetal resin can be obtained by acetalizing polyvinyl alcohol in water with an aldehyde containing an aromatic aldehyde.

Aldehydes other than the aromatic aldehyde described above are not particularly limited, and examples include formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, amylaldehyde, hexylaldehyde, heptylaldehyde, 2-ethylhexylaldehyde, cyclohexylaldehyde, furfural, glyoxal, glutaraldehyde, and the like. Is mentioned. Among them, it is preferable to use acetaldehyde or butyraldehyde alone or use acetaldehyde and butyraldehyde in combination.

The minimum with preferable content of the said water-soluble polyvinyl acetal resin in the anti-fogging resin composition of this invention is 3 weight%, and a preferable upper limit is 20 weight%. By setting it within the above range, there is no unevenness during coating, and antifogging properties can be exhibited.

The antifogging resin composition of the present invention contains water in addition to the water-soluble polyvinyl acetal resin.
Although it does not specifically limit as said water, Pure water etc. can be used.

In the antifogging resin composition of the present invention, various known additives may be blended within a range not impeding the effects of the present invention. As the above additives, glycerin, ethylene glycol, polyethylene glycol, various other surfactants, antioxidants, anti-aging agents, ultraviolet absorbers, silane coupling agents, titanium coupling agents for improving water absorption performance, Leveling agents, thixotropic agents, anti-skinning agents, plasticizers, thickeners, diluents, reactive diluents, crosslinking agents, fillers, pigments (pigments, dyes), antiseptics, fungicides, and the like.

As the surfactant, any one of anionic, cationic and nonionic may be used. Examples of the antioxidant include phenol-based, aromatic amine-based, sulfur-based, phosphorus-based and the like. Examples of the antiaging agent include amines and phenols.

The antifogging resin composition of the present invention uses a water-soluble polyvinyl acetal resin having a predetermined structure as a constituent resin, and by setting the average degree of polymerization, the amount of hydroxyl groups, and the degree of acetalization within a predetermined range, While maintaining anti-fogging properties, it is possible to achieve excellent water resistance and to form a coating film with high surface strength.
The use of the antifogging resin composition of the present invention is not particularly limited. For example, antifogging agents used for various types of glass such as automobile rear glass, side glass, windshield, sunroof, and room mirror, plastic bottles, labels thereof, etc. Etc. Moreover, the antifogging resin composition of this invention can be used also for the antifogging coating | covering material of various glass.

When using the antifogging resin composition of this invention as an antifogging coating material of glass, it does not specifically limit as glass used, The transparent glass generally used can be used. Specific examples include inorganic glass such as float glass, polished glass, template glass, netted glass, lined glass, colored glass, heat ray absorbing glass, heat ray reflecting glass, and green glass.
When the antifogging coating layer is formed by coating the antifogging resin composition of the present invention, the thickness of the antifogging coating layer to be formed is not particularly limited, but effectively exhibits the antifogging performance. Therefore, 3-100 micrometers is preferable and 5-50 micrometers is more preferable.

ADVANTAGE OF THE INVENTION According to this invention, the antifogging resin composition which can exhibit the outstanding antifogging property and water resistance, and can form a coating film with high surface strength can be provided.

Examples of the present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Example 1
To 3000 g of an aqueous solution containing 350 g of polyvinyl alcohol (average polymerization degree 1700, saponification degree 88 mol%), 170 g of 35 wt% hydrochloric acid and 120 g of benzaldehyde are added, and the acetalization reaction is carried out for 5 hours while maintaining the liquid temperature at 10 ° C. And a sponge-like reaction precipitate slurry was obtained. The slurry was washed and neutralized with water to remove the hydrochloric acid catalyst and unreacted aldehyde, and then dried to obtain a resin precipitate. This resin was dissolved in a 60/40 mixed solvent of water / isopropyl alcohol (alcohol solvent) to obtain a water-soluble acetal resin solution having a concentration of 10%.
The water-soluble polyvinyl acetal resin in the obtained solution has a hydroxyl group amount of 63 mol%, an acetalization degree (total acetalization degree) of 22 mol%, and a proportion of structural units acetalized with an aromatic aldehyde is 100. %Met.

(Example 2)
To 3000 g of an aqueous solution containing 350 g of polyvinyl alcohol (average polymerization degree 2200, saponification degree 88 mol%), 165 g of aldehyde total consisting of 170 g of 35 wt% hydrochloric acid, 163 g of benzaldehyde and 2 g of butyraldehyde was added, and the liquid temperature was adjusted to 10 ° C. The acetalization reaction was carried out for 5 hours while being retained to obtain a sponge-like reaction precipitate slurry. The slurry was washed and neutralized with water to remove the hydrochloric acid catalyst and unreacted aldehyde, and then dried to obtain a resin precipitate. This resin was dissolved in a 60/40 mixed solvent of water / isopropyl alcohol (alcohol solvent) to obtain a water-soluble acetal resin solution having a concentration of 9%.
The water-soluble polyvinyl acetal resin in the obtained solution has a hydroxyl group amount of 58 mol%, an acetalization degree (total acetalization degree) of 30 mol%, and a ratio of structural units acetalized by an aromatic aldehyde of 99 mol%. %Met.

(Example 3)
To 3000 g of an aqueous solution containing 350 g of polyvinyl alcohol (average polymerization degree 3300, saponification degree 88 mol%), 200 g of aldehyde total consisting of 170 g of 35 wt% hydrochloric acid, 198 g of 2-methylbenzaldehyde and 2 g of butyraldehyde was added, and the liquid temperature was adjusted. While maintaining at 10 ° C., acetalization reaction was performed for 5 hours to obtain a sponge-like reaction precipitate slurry. The slurry was washed and neutralized with water to remove the hydrochloric acid catalyst and unreacted aldehyde, and then dried to obtain a resin precipitate. This resin was dissolved in a 60/40 mixed solvent of water / isopropyl alcohol (alcohol solvent) to obtain a water-soluble acetal resin solution having a concentration of 9%.
The water-soluble polyvinyl acetal resin in the obtained solution had a hydroxyl group amount of 52 mol%, an acetalization degree (total acetalization degree) of 35 mol%, and a ratio of structural units acetalized with an aromatic aldehyde of 99 mol%. %Met.

(Comparative Example 1)
To 3000 g of an aqueous solution containing 350 g of polyvinyl alcohol (average polymerization degree 800, saponification degree 88 mol%), 35 g of hydrochloric acid 170 g, benzaldehyde 31 g and butyraldehyde 4 g were added to 35 g of aldehyde, and the liquid temperature was adjusted to 10 ° C. The acetalization reaction was carried out for 5 hours while being retained to obtain a sponge-like reaction precipitate slurry. The slurry was washed and neutralized with water to remove the hydrochloric acid catalyst and unreacted aldehyde, and then dried to obtain a resin precipitate. This resin was dissolved in a 60/40 mixed solvent of water / isopropyl alcohol (alcohol solvent) to obtain a water-soluble acetal resin solution having a concentration of 9%.
The water-soluble polyvinyl acetal resin in the obtained solution has a hydroxyl group amount of 82 mol%, an acetalization degree (total acetalization degree) of 6 mol%, and a proportion of structural units acetalized by an aromatic aldehyde of 88 mol%. %Met.

(Comparative Example 2)
To 3000 g of an aqueous solution containing 350 g of polyvinyl alcohol (average polymerization degree 2200, saponification degree 87 mol%), 170 g of 35 wt% hydrochloric acid and 30 g of benzaldehyde were added, and the acetalization reaction was carried out for 5 hours while maintaining the liquid temperature at 10 ° C. And a sponge-like reaction precipitate slurry was obtained. The slurry was washed and neutralized with water to remove the hydrochloric acid catalyst and unreacted aldehyde, and then dried to obtain a resin precipitate. This resin was dissolved in a 60/40 mixed solvent of water / isopropyl alcohol (alcohol solvent) to obtain a water-soluble acetal resin solution having a concentration of 7%.
The water-soluble polyvinyl acetal resin in the resulting solution has a hydroxyl group amount of 83 mol%, an acetalization degree (total acetalization degree) of 5 mol%, and a proportion of structural units acetalized with an aromatic aldehyde of 100 mol%. %Met.

(Comparative Example 3)
To 3000 g of an aqueous solution containing 350 g of polyvinyl alcohol (average polymerization degree 3300, saponification degree 86 mol%), 35 g of hydrochloric acid 170 g and 4-methylbenzaldehyde 35 g are added, and the liquid temperature is kept at 10 ° C. for 5 hours while acetal is maintained. The reaction was carried out to obtain a sponge-like reaction precipitate slurry. The slurry was washed and neutralized with water to remove the hydrochloric acid catalyst and unreacted aldehyde, and then dried to obtain a resin precipitate. This resin was dissolved in a 60/40 mixed solvent of water / isopropyl alcohol (alcohol solvent) to obtain a water-soluble acetal resin solution having a concentration of 8%.
The water-soluble polyvinyl acetal resin in the obtained solution has a hydroxyl group amount of 83 mol%, an acetalization degree (total acetalization degree) of 6 mol%, and a proportion of structural units acetalized with an aromatic aldehyde is 100. %Met.

(Comparative Example 4)
To 3000 g of an aqueous solution containing 350 g of polyvinyl alcohol (average degree of polymerization 1700, saponification degree 89 mol%), 170 g of 35% by weight hydrochloric acid, 29 g of 2-methylbenzaldehyde and 30 g of aldehyde total consisting of 1 g of butyraldehyde were added, and the liquid temperature was adjusted. While maintaining at 10 ° C., acetalization reaction was performed for 5 hours to obtain a sponge-like reaction precipitate slurry. The slurry was washed and neutralized with water to remove the hydrochloric acid catalyst and unreacted aldehyde, and then dried to obtain a resin precipitate. This resin was dissolved in a 60/40 mixed solvent of water / isopropyl alcohol (alcohol solvent) to obtain a water-soluble acetal resin solution having a concentration of 9%.
The water-soluble polyvinyl acetal resin in the obtained solution has a hydroxyl group content of 84 mol%, an acetalization degree (total acetalization degree) of 5 mol%, and a ratio of structural units acetalized with an aromatic aldehyde of 98 mol%. %Met.

(Comparative Example 5)
To 3000 g of an aqueous solution containing 350 g of polyvinyl alcohol (average polymerization degree 2000, saponification degree 88 mol%), an aldehyde total 42 g consisting of 170 g of 35 wt% hydrochloric acid, 39 g of benzaldehyde and 3 g of butyraldehyde was added, and the liquid temperature was adjusted to 10 ° C. The acetalization reaction was carried out for 5 hours while being retained to obtain a sponge-like reaction precipitate slurry. The slurry was washed and neutralized with water to remove the hydrochloric acid catalyst and unreacted aldehyde, and then dried to obtain a resin precipitate. This resin was dissolved in a 60/40 mixed solvent of water / isopropyl alcohol (alcohol solvent) to obtain a water-soluble acetal resin solution having a concentration of 10%.
The water-soluble polyvinyl acetal resin in the obtained solution had a hydroxyl group content of 79 mol%, an acetalization degree (total acetalization degree) of 8 mol%, and a proportion of structural units acetalized by aromatic aldehydes of 92 mol%. %Met.

<Evaluation>
The following evaluation was performed about the water-soluble polyvinyl acetal resin aqueous solution obtained by the Example and the comparative example. The results are shown in Table 1.

(1) Hygroscopic (1-1) Resin sheet Water-soluble polyvinyl acetal resin aqueous solution is coated on a PET film that has been subjected to a release treatment so that the thickness after drying becomes 20 μm using a coater, and then dried for 3 hours. By doing so, a resin sheet was obtained.
The obtained resin sheet was peeled from the PET film, and the state after immersing the sample obtained by cutting the peeled sheet into 5 × 10 cm in 1 L of water for 5 minutes was visually observed, and judged according to the following criteria.

(1-2) Resin layer forming glass Water-soluble polyvinyl acetal resin aqueous solution on a float glass (JIS R 3202, thickness 2.5 mm, 15 cm × 15 cm) so that the thickness after drying using a coater is 5 μm After coating, a resin layer forming glass having a polyvinyl acetal resin layer formed thereon was obtained by drying for 3 hours.
The state of the polyvinyl acetal resin layer after the obtained resin layer-formed glass was immersed in 1 L of water for 5 minutes as it was was visually observed and judged according to the following criteria.
Moreover, the resin layer forming glass in which the thickness of the polyvinyl acetal resin layer was 20 μm and the resin layer forming glass in which the thickness of the polyvinyl acetal resin layer was 30 μm were similarly evaluated.

◎ There was no change.
〇 It was swollen.
Δ Partially dissolved (difficult to maintain sheet shape or layer shape).
X It was dissolved.

(2) Coating film strength The surface strength of the resin sheet obtained by “(1) Hygroscopicity” and the three types of resin layer-forming glasses was measured based on the pencil hardness test of JIS K 5600-6-4. Note that “◯” indicates no flaw and “×” indicates flaw.

(3) After putting 450 g of water at 30 ° C. into a container (500 cc) having an antifogging opening, cover the opening so that the resin sheet obtained in “(1) Hygroscopicity” is on the inside and seal it. After leaving in a room set at room temperature (20 ° C.), it was set at a low temperature (0 ° C.) and left for 5 seconds. And the cloudiness state of the resin sheet was evaluated visually according to the following criteria.
Moreover, it replaced with the resin sheet obtained by "(1) hygroscopicity", and the same evaluation was performed also about the case where three types of resin layer formation glass obtained by "(1) hygroscopicity" was used.

◎ Cloudiness and water droplets were not seen.
〇 A few large drops of water were seen.
△ Many small water droplets were seen.
× The entire surface was clouded.

ADVANTAGE OF THE INVENTION According to this invention, the antifogging resin composition which can exhibit the outstanding antifogging property and water resistance, and can form a coating film with high surface strength can be provided.

Claims (2)

An antifogging resin composition containing a water-soluble polyvinyl acetal resin and water,
An average polymerization degree of 1000 to 3500, an acetalization degree of 21 to 40 mol% and a hydroxyl group amount of 45 to 64 mol%, and among all the acetalized structural units, a structure acetalized with an aromatic aldehyde An antifogging resin composition having a unit ratio of 90% or more. An anti-fogging coating material comprising the anti-fogging resin composition according to claim 1.