JPS6036823B2 - How to dry a lacquer-based paint film - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for drying a lacquer-based paint film.

Traditionally, lacquer-based paints such as refined urushi or paints made from the reaction product of cashew nut shell liquid and formaldehyde (hereinafter referred to as cashew paints) have excellent film performance and have been widely used for arts and crafts, everyday practical items, etc. ing. However, since these lacquer-based paints dry slowly, dirt may adhere to them during the drying process, and the paint film may smudge or run.

Furthermore, when the coating film was thick, the coating surface was wrinkled and had dust particles that spoiled its aesthetic appearance. The purpose of the present invention is to provide a method for drying a lacquer-based paint film that eliminates the drawbacks of the conventional methods, significantly shortens the drying time of a lacquer-based paint film, and that enables mass production of painted objects. This will be explained in detail below.

The present inventors have conducted various studies to solve the problems that occur in conventional drying processes, and found that by irradiating ultraviolet rays for a very short period of time at the beginning of the drying process of purified lacquer and cashew paints,
It was discovered that the drying time of conventional coatings could be significantly shortened. The sap used in the present invention is an emulsion of water and lacquer called raw lacquer.
It is refined by heating the raw lacquer while kneading it for a long time to evaporate the moisture contained in the raw lacquer.During the heating process, this refined lacquer is mixed with drying oil such as linseed oil and the moisture is evaporated. It includes so-called vermilion lacquer.

Furthermore, the cashew paint used in the present invention is prepared by adding 7 parts by weight of hexamethylenetetramine, which is a condensation product of formaldehyde and ammonia, and a reaction catalyst to 10 parts by weight of cashew nut shell liquid.
0 for 3 to 4 hours, and a diluting solvent and a small amount of a metal salt such as naphthenic acid or octenoic acid as a drying accelerator for the coating film were added thereto to form a paint.

The gist of the present invention is to accelerate the drying of the coating by irradiating ultraviolet rays for a short period of time onto a coating film formed by applying the purified lacquer and lacquer-based coatings such as cashew coatings.

As a light source for irradiating ultraviolet rays, a commercially available mercury lamp, which is practically simple, can be used, and the characteristic is that the ultraviolet wavelength range is 200 to 67 m (a light source containing a large amount of 200 to 365 nm is more effective). Commercially available mercury lamps have an output per tube length of 0.36 to 16 skins/skin, but the optimum range for the present invention is 20 to 4 skins/skin.

Air drying of conventional oil-based paints begins with the paint film absorbing atmospheric oxygen.

In other words, this absorption is caused by the double bonds contained in the oil-based paint.
In the case of non-conjugation, it is added to the adjacent methylene group (1C ratio -) as a hydroperoxide (100H), and in the case of conjugation, it is known that it is mainly a direct addition to the double bond [Mihara, Color Materials, 40 451 (1973)]. The dryer (organic acid salt of center-position metal) commonly used at this time is a redox catalyst that acts as a promoter for the decomposition of the oxygen compound as described above and the action of abstracting hydrogen from the methylene group. In any case, the main factor behind the slow drying of these oil-based paints is the long conversion period for atmospheric oxygen to turn into hydroperoxides or oxygen adducts.
Therefore, many studies have been conducted for a long time regarding shortening this induction period.

In other words, D. A. There is a study by Perry et al. on the effects of light energy.
[oHic. Dig. ,32(NO.422)340(
1990)]. This means that in the presence of a cobalt dryer, blue light promotes oxygen absorption by 3.7 times compared to clear-colored light, and a similar fact is also reported by Funke. [Deut. Farbe side. , 21 (5) 233 (
1967)] OR. It was found that inclusion of ozonated oxygen during drying also promoted cloze [lnd, Loo et al.
kinBemeh, 36(3) 234 (1968)] Furthermore, the ability to promote ozone production under ultraviolet irradiation has also been reported. [Nagakura, Painting Technology, 1970, (9)9
0: Paint Pig. Vernis, 46.155
(1970)] However, all of these are oil-based paints and have not been put into practical use due to practical problems. Furthermore, special paints such as purified lacquer and cashew paint, which were the object of the present inventors, were completely unknown and unclear. In other words, in purified lacquer, the main component urushiol is cured and dried by the action of oxygen in the air called urushilacase, while in cashew paint, a formaldehyde condensation resin of alkyl (C, 5days 27) cardanol and cardol is cured and dried. By air oxygen in the presence of a normal metal dryer
It is cured and dried.

Next, the present invention will be explained in more detail with reference to Examples.

Example 1 Refined lacquer was applied to a glass plate using a Dr. Plaid trowel of 76 mm, and immediately heated under 20 arcs of a high-pressure mercury lamp (output: 3 skin/low, wavelength range: 200 to 67 meters). Interstitial layer,
Next, when the humidity was 80% and the temperature was 20°C, it was allowed to settle down in a constant temperature room, and it was dry in 2 hours (no fingerprints were left even when touched with a finger), and hardened and dried in 10 hours.

Comparative Example 1 Refined lacquer was applied in the same manner as in Example 1, and immediately placed in a constant temperature and humidity room and left to stand. It was dry to the touch in 5 hours, and cured and dried in 2 hours.

Example 2 Cashew black (a paint containing a black colorant in the reaction product of 10 parts by weight of cashew nut shell liquid and 7 parts by weight of hexamethylenetetramen) was applied in the same manner as in Example 1, and immediately exposed to a high-pressure mercury lamp. The sample was irradiated with ultraviolet rays between acids at step 3, and then left in a Jinongaki humidity room.

Dry to the touch took 1 hour and 3 cycles, and dry to the touch took 4 hours. Comparative Example 2 Cashew black was applied in the same manner as in Example 1, and immediately placed in a thermostatic chamber and left to stand.

Dry to the touch took 3 hours and 30 minutes, and drying took 8 hours. Example 3 Cashew transparency (a paint made from the reaction product of 10 parts by weight of cashew nut shell liquid and 5 parts by weight of hexamethylenetetramine) was applied to the same machine as in Example 1, and immediately irradiated with tritopic sand ultraviolet rays using a high-pressure mercury lamp. Then, it was placed in a room with constant temperature and humidity.

It took 4 hours and 30 minutes to dry to the touch, and 9 hours to cure. Comparative Example 3 Cashew translucent was applied in the same manner as in Example 1, and immediately placed in a constant temperature room and allowed to stand.

It took 1 hour to dry to the touch and 1 hour to harden.
The appearance of the coating films of Examples 1 to 3 and Comparative Examples 1 to 3 were as shown in Table 1 below.

Table 1 Note that the pencil hardness was measured after being left in a constant temperature and humidity room for an additional 7 days.

According to the present invention, the drying time of the lacquer-based paint film can be significantly shortened, the film performance is comparable to conventional ones, and the lacquer-based paint can be mass-produced. A method for drying a paint film can be obtained.

Claims (1)

[Claims] 1. Application of a lacquer-based paint characterized by irradiating ultraviolet rays for a short period of time to accelerate drying of the coating film of the lacquer-based paint, such as refined lacquer or Kashiyu paint made of a reaction product of Kashiyu-Nutssiel liquid and formaldehyde. Membrane drying method.