JPS5817874A - Dip coating method for synthetic resin - Google Patents

Abstract

PURPOSE:To form a uniformly cured film on the surface of a synthetic resin by dip coating curable liq. of specific temp. on the surface of the synthetic resin base material of specific temp. in an atmosphere having specific temp. and dew point temp. CONSTITUTION:In the stage of dip coating UV curable (meth)acrylic curing liq. on the surface of a synthetic resin, the temp. of the curin liq. is kept in a 10- 30 deg.C range, the temp. of the atmosphere of the curing liq. tank in a 10-30 deg.C range, the dew point of the atmoshpere below (the temp. of the curing liq. -3 deg.C), and further the temp. of the synthetic resin base material prior to dipping in the curing tank above (the temp. of the curing liq. -10 deg.C) and below (the temp. of the curing liq. +20 deg.C). The substrate coated with the curing liq. under such conditions is suspended from a hanger, and is conveyed to a curing stage by a conveyor, whereby the substrate is subjected to UV irradiation with a metal hallide lamp or the like, whereby the paint on the surface is cured.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to dip coating of a synthetic resin when curing the surface of the synthetic resin.

It is well known that after coating the surface of a synthetic resin with an ultraviolet curable (meth)acrylic curing liquid by dip coating, the surface of the synthetic resin is cured by irradiation with ultraviolet rays. However, it has been pointed out that a problem with this curing method is that it is extremely difficult to uniformly form a cured film on the surface of the synthetic resin, and there is a strong demand for imparting smoothness.

The atmosphere throughout the surface hardening process is dust free.
It goes without saying that it is necessary to maintain a clean and dust-free condition, but the smoothness of the cured film also depends on the balance of the ambient temperature, the temperature of the ilm or curing liquid, the temperature of the synthetic resin being immersed, etc. Sexuality is damaged. As a countermeasure for this problem, the present inventors have taken measures such as abnormal evaporation rate of the cured coating film and dew condensation of moisture in the air on the coating film surface. While various studies are being conducted on the mechanisms by which paint film flakes (uneven thickness depending on location) and whitening occur, it has been discovered that the above-mentioned problems can be alleviated by using the zero-order method.

That is, 1. The gist of the present invention is 1. In a method of coating the surface of a synthetic resin with an ultraviolet curable (meth)acrylic curing liquid by dip coating, the temperature of the curing liquid is set to 1.
The range is 0 to 30"C, and the atmospheric temperature of the curing liquid tank is 10"C.
~30°C, and the dew point temperature of the armpit atmosphere is [curing liquid temperature -3°C] or less, and the temperature of the synthetic resin base material before being immersed in the curing liquid tank is [curing liquid temperature -10'C]. The present invention provides a dip coating method for a synthetic resin, characterized in that the temperature is below [hardening solution temperature +20''C].

If the temperature is outside this range, the viscosity of the curing liquid will increase and ocrogel-like substances will occur. It is also necessary to maintain the ambient temperature of the curing liquid tank at 10 to 3G"CK. If the temperature is outside this range and is less than 10℃, the paint film will sag or sag, and if it exceeds 30℃, evaporates too quickly, causing film thickness unevenness.Furthermore, in relation to the above-mentioned ambient temperature, it is necessary to keep the dew point temperature of the atmosphere below [curing liquid temperature - 3°C], and this dew point temperature If the temperature is high, water in the air will condense due to the drop in temperature when the solvent evaporates from the coating surface, resulting in a coating ff1K yuzu skin.Furthermore, in relation to the temperature of the curing liquid, the temperature of the immersed coating will decrease. The temperature of the synthetic resin base material under the processed material is set to [cured liquid temperature -10
℃] or higher than [curing liquid temperature + 20"C). If the temperature is outside this temperature range, the curing liquid may deteriorate, or it may adhere to the object to be treated and the thickness of the blade to be pulled up may vary. .

The dip coating method according to the present invention can be adapted to any ordinary dip coating method as appropriate;
The dip coating curing apparatus described in No. 30144, that is, the synthetic resin base material to be treated (hereinafter simply referred to as the treated object) is hung on a hanger and immersed in an aqueous solution containing a neutral detergent etc. by a conveyor for cleaning. After that, the material is immersed in hot water and then slowly pulled up to dry the moisture adhering to the surface of the workpiece, then immersed in a hardening liquid tank, pulled up, and then hardened. When carrying out the method of the present invention using a cleaning agent, in order to prevent foreign matter from adhering to the surface of the workpiece and forming spots on the cured film during the cleaning, drying, and immersion in the hardening solution, Hinoki, dried
, in either of the curing liquid baths, the sonic cleaning mat < ultra-high wave) intensity - o, g ~ s watts/'CIL''t and the capacity lO
~100 tat/J 11 degrees),
Also to prevent dirt and dust in the atmosphere.

In particular, regarding the atmosphere around the curing liquid tank, use a filter or the like to send air that has been sufficiently dusted and temperature-controlled, and the air flow rises from the curing liquid tank, passes through the hot water drying tank, and heads toward the grinding tank. The hardening Wl used in the method of the present invention is as follows.

If the method of the present invention can be implemented, it will not be used if it is d, but preferably 0 e.g.
An acrylic curing liquid that is cured by ultraviolet rays, such as that described in No. 633, is used.

Examples of the synthetic resins used in the method of the present invention include polystyrene, polycarbonate, polymethyl methacrylate F', methyl methacrylate comonomer, polydiethylene glycol diglycol carbonate such as polydiethylene glycol bisallyl carbonate, etc. , polyethylene terephthalate, nylon, etc. Among these, polymethacrylate, which has excellent transparency,
Can be applied to synthetic resins such as methyl methacrylate copolymer, polyallyl diglycol λ carbonate, -IJ It may also have the following.

Organic window glass, lighting equipment covers, reflectors, mirrors
Molded products such as lenses for sunglasses, lenses for sunglasses, and lenses for cows can be preferably applied as objects to be treated.

□The workpiece coated with the curing liquid by the dip coating method of the present invention as described above is suspended on a hanger and transported to the curing process by a conveyor.

The surface is cured by UV irradiation using a metal halide lamp, low pressure or high pressure mercury lamp.

Examples of suitable apparatuses for carrying out the dip coating method of the present invention are as follows:
! be. In the apparatus shown in FIGS. 1 to 3,
The first sprocket moves 9 times along (12)
Chain conveyor (1) Rotatable K primary hanger (4
) is imprinted on the object to be treated ((
They are arranged at intervals such that when the addition of the materials to be treated (22') and (r) is completed, the drying tank (7) containing warm water, etc., and the washing tank (8) are also completed with the addition of the materials to be treated (22') and (r). [There is, further I1
1 The movement of the chain conveyor is from the pulling start point M, N and! It moves at a low pulling speed up to the pulling completion point n point 1F and point V, and moves at a higher speed than the pulling speed at other places.

This speed change is performed by a wood clutch mechanism activated by a signal from the limit F switch of the first chain conveyor (1).

The primary hanger (4) K has one or more secondary hangers (
5) is installed, the secondary hanger (S) K is the object to be processed ((2) is attached. The primary hanger (4) is loaded on the right side of the loading rail (9) of the intermediate conveyor (2) When the secondary hanger (s) is installed, it is ejected from the 71st hanger (4) and placed on the loading rail (9) at 66.
′ Move to Zuo Confucianism. , -. ” On the other hand, the second chain conveyor (3) K rotating at a uniform speed along the sprocket (13) is suitably further conveyed one by one by the intermediate conveyor (2). Ultraviolet light--6 suspended on the hook (14) of the conveyor (3)
(15) K-Send.゛The primary hanger (4), which discharges the secondary hanger (5) from the intermediate conveyor (2) K, returns to point 0 and is transferred to the secondary hanger (4) where the object to be processed is suspended.
Ready for the next installation.
-゛-On the other hand, the treated products that have passed through the external ray irradiator (15) and been dried and hardened are sold individually at 9 points along with the secondary hudger.

” (i6) and (17) are the drive machines for the lid chain conveyor (1) and the second chain conveyor (3), respectively, and (18) is the drive machine for the first chain conveyor (1).
This is a speed change unit for moving at high speed, stopping, and moving at low speed. (19) is the drive machine that moves the chain conveyor (u) of the intermediate conveyor (2) and the primary hanger (
From 4), the unloading of 2 & hanger (5) is activated in response to the stop signal of the first chain conveyor (1), and the second chain conveyor (3)
When suspended on the second chain conveyor, the second chain conveyor operates in response to a signal from the second chain conveyor so that the objects to be processed do not interfere with each other on the second chain conveyor. A pair or several pairs of opposing ultraviolet lamps are used for the ultraviolet irradiation II (15).

Next, the method of the present invention will be explained in more detail with reference to Examples. The examples shown below were carried out using an apparatus as shown in FIGS. 1 to 3.

Example 1. Comparative Examples 1 to 3 Amount of 1 ton of acrylate added to dipentaerythritol
, dipentaerythritol pentaacrylate 15
Parts by weight, dipentaerythritol tetraacrylate 5
Parts by weight, 10 parts by weight of tetrahydrofurfuryl acrylate, 30 parts by weight of inpropyl alcohol, 30 parts by weight of toluene
A curing solution consisting of 1 part by weight and 2 parts by weight of benzoin ethyl ether was placed in a curing tank under the conditions shown in Table 1, and a K 0.3-neutral detergent aqueous solution was added to a washing tank at 40°C.
of hot water was charged into each hot water tank, and the liquid in all the tanks was circulated without letting the liquid exceed 7 μm.

A 5KW high-pressure mercury lamp was placed on one side as an ultraviolet irradiator so as to irradiate both sides of the object to be treated.

A methacrylic resin board with a thickness of 3 cranes is suspended on a conveyor,
After being sequentially immersed in a washing tank, a hot water drying tank, and a hardening liquid tank, the pulling speed was set to f 1.2 cga/s@c.

Ultraviolet rays from a high-pressure mercury lamp were applied for about 4.5 seconds at a moving speed of the conveyor of 2.1 m/ml. Table 1 shows the treatment conditions and the appearance of the surface-hardened plates obtained.

No. 1llI

[Brief explanation of drawings]

1 and 2H are a plan view and a sectional side view, respectively, schematically showing a dip coating curing apparatus suitable for carrying out the method of the present invention, and FIG. It is a perspective view showing an embodiment in which a hanger is attached, (l) is a first chain conveyor, (2) is an intermediate conveyor, (3) itllE2 chain conveyor, (4)
) is an Ic bunker. (5) is a secondary hanger, (6) is a curing liquid tank, and (7) is a drying tank. (8) is the washing tank, (9) is the loading rail, and (10) is the hook. (11) is a chain conveyor, (12) is a sprocket. (13) It is the sprocket F of the second chain conveyor. (14) is a hook, (15) is an ultraviolet irradiator,
(16) and (17) are the drive machines for the primary and secondary chain conveyors; (18) is the variable speed Ennin), (
1G) is the drive shaft, (20) and (21) are the tension devices,
(22) is the object to be processed, (23) is the cook, (
24) is anti-slip, and (25) is hardening liquid. (26) shows the drying liquid, and (27) shows the washing liquid.

Claims (1)

[Claims] In a method of coating the surface of a synthetic resin with an ultraviolet curable (meth)acrylic curing liquid by dip coating, the curing liquid temperature is set at 10 to 30°C for 1 ms, and the curing liquid bath is The ambient temperature is in the range of 10 to 30°C, and the dew point temperature of the atmosphere is [curing liquid temperature l! -3℃] or below, and
I. A method for dip coating a synthetic resin, characterized in that the temperature of the synthetic resin base material before being immersed in a chemical casing tank is between [curing liquid temperature - 10° C.] and [curing liquid IL degree + 20° C.] or less.