JPS61162568A - Removal of film - Google Patents

Abstract

PURPOSE:To accomplish the titled removal by immersing into an aqueous alkali solution of specific concentration a base body having an its surface multifunctional acrylic cured film to perfectly eliminate said film without damaging the body, thus leading to giving coating film entirely similar to that of new article on coating again. CONSTITUTION:A base body having an its surface multifunctional acrylic cured film is immersed into an aqueous alkali solution of a concentration >=5wt% (pref. 10-30wt%) at, for example, 50-80 deg.C (e.g. derived from LiOH, NaOH, KOH, Mg(OH)2, or Ca(OH)2), thus accomplishing the separation of the film from the body.

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention is applicable to a substrate having a polyfunctional acrylic cured film on its surface, for example, when the formation of a beautiful cured film fails and it is desired to re-form the cured film. The present invention relates to a method for removing a cured film that can be applied when the cured film is removed from a substrate and the film is formed again. [Prior art] Generally, molded bodies of thermoplastic resin, thermosetting resin, etc.
Compared to metal products, glass products, etc., it is not only lightweight and has excellent impact resistance, but also has various advantages such as being cheaper and easier to mold. It is widely used in place of these materials in many fields such as household electrical appliances and daily necessities. However, molded bodies made of these resins have lower surface hardness than metals, glass, etc., and are weak against scratches and friction, so they have the disadvantage of being easily scratched on the surface.For example,
The use of these molded bodies is severely limited due to defects in their surface properties, such as susceptibility to surface damage due to contact, collision, scratching, etc., during installation or transportation of molded parts, or during use of the product. There is. Many proposals have been made to improve the above-mentioned drawbacks of the basic surface of molded products such as resins, and one example is a polyfunctional acrylic compound having two or more C meth)acryloyl groups in one molecule. There is a known method in which a hard film is formed by applying a material to a surface and then crosslinking it with heat or light. By the way, when the above method is actually applied on an industrial scale, when applying a polyfunctional acrylic compound to a molded body,
For example, dust floating in the air can get into the painted surface, causing minute holes and protrusions in the hardened film.

[So-called puttu] often occurs and the value of the product is lost. Furthermore, there is a strong demand from consumers to repair and restore the product to its original condition if the surface of the product is damaged by some force during use. Conventionally, methods for dealing with such cases include methods such as sanding and repainting the area where the paint has been replaced, methods of repainting directly on the scratched area, and methods of dissolving the film using a special solvent that dissolves the hardened film. There is a known method of repainting the removed part. However, the first
In this method, the film is much harder than that of ordinary paints, so it is difficult to polish uniformly, and the adhesion of the new film formed by applying it over the old film that remains is also poor. Second
As mentioned above, this method has problems in that the adhesion of the overcoated film is poor and the physical properties of the thick film deteriorate. The fifth method has a problem in that the basic synthetic resin itself is attacked by the solvent. [Problems to be Solved by the Invention] Based on one or more actual circumstances, the present inventors have developed a method that allows a polyfunctional acrylic hardened film to be completely removed without damaging the base, and that can be repainted after removal. We conducted repeated research to find a removal method that would yield a surface that would be no different from a newly painted surface. [Means for Solving the Problems] That is, the present invention provides a substrate having a polyfunctional acrylic cured coating on its surface in an alkaline aqueous solution with a concentration of 5% or more at a temperature range above room temperature but below the temperature at which the substrate deforms. The present invention relates to a method for removing a coating, which comprises separating the cured coating from the substrate by immersing the substrate in water. [Function] In the present invention, in order to remove the polyfunctional acrylic cured coating from the base, it is brought into contact with an alkaline aqueous solution of a specific concentration at a specific temperature by means such as impregnation. It is truly surprising that a polyfunctional acrylic cured film, which has traditionally been considered difficult to remove, can be removed cleanly. In other words, the polyfunctional acrylic cured coating to which the method of the present invention is applied is recognized to have excellent chemical resistance (alkali resistance), unlike silicone cured coatings that exhibit a similar surface protection effect. Various reports also emphasize this point. For example, the magazine "Painting and Paints" published by Paint Publishing Co., Ltd.
A357゜P59-48 contains a low concentration of hydroxide) I
There is a statement that there was no abnormality in the cured film even after partial contact with a Jium aqueous solution for 4 hours. Similar reports are also available in "Polymer Processing J @ Vol. 32 No. 5 P5-59, [JCIA Monthly Report J April 1983 issue pis-26 and "Industrial Materials" Vol. 50 No. 4 P68-72 Both of these studies support the fact that polyfunctional acrylic cured coatings have good chemical resistance. As described above, it is impossible for those skilled in the art to predict that a polyfunctional acrylic cured coating could be so easily dissolved and removed using an alkaline aqueous solution of a specific concentration at a specific temperature as in the present invention, and even more so. It was completely unexpected that a cured film as good as new could be formed again by recoating on the surface of the substrate. The coating material forming a polyfunctional acrylic cured film to which the method of the present invention can be applied may be any coating material as long as it is mainly composed of a compound having two or more (meth)acryloyl groups in one molecule. There are no restrictions. Examples of such paints include those described in the above-mentioned documents, as well as patent application publication No. 46-16091.51-286.
77.55-45553.54-1742.56-44
011. Patent application publication 49-”+0466.50-11
0477.52-126474.53-102936.
54-30466.54-62269.54-8398
5.54-134795.59-20515.59-2
5840.59-30810.59-53511.59
-16115.59-41566.59-56462.
59-58035.59-6641 Q, 59-664
62.59-68317.59-68375.59-7
1535.59-78242.59-78245.59
-80472.59-81563.5'? -8492
6, 59-84952, 59-86631, 59-86
666, 59-86667, 59-86661L 59
-89531.59-89332.59-89367.
59-93715.59-95755.59-9811
Examples include those disclosed in each publication of No. 5.59-124961. The substrate to which the polyfunctional acrylic paint is applied may be any inorganic material such as metal, glass, or ceramics, or a combed material such as a synthetic resin molding, as long as it is not attacked by an alkaline aqueous solution at room temperature or above. But that's fine. In particular, synthetic resin molded bodies such as thermoplastic resins and thermosetting resins, which have conventionally been considered difficult to peel and remove, can be easily removed by the method of the present invention. Examples of synthetic resins include polymethyl methacrylate, polycarbonate, polyethylene, polypropylene, poly-4-methylpentene-1, etc., but are not limited to these resins. The alkaline aqueous solution is an aqueous solution of an alkali metal or alkaline earth metal hydroxide, and examples thereof include aqueous solutions of lithium hydroxide, sodium hydroxide, potassium hydroxide, magnesium hydroxide, calcium hydroxide, and the like. The concentration of the aqueous solution is at least 5 (weight 2
% or more, from 5 to 30% in terms of workability and safety, and in particular 10% in terms of industrial continuous productivity.
~20% is preferred. If the concentration is less than 5%, especially less than 10%, it will take too long for the cured film to dissolve and peel off.
Productivity decreases. The temperature of the alkaline aqueous solution may be within a range of room temperature or higher and lower than the temperature at which the substrate deforms. However, if the temperature exceeds 100°C, the work must be carried out under pressure, so it is safe to operate preferably below 100'C, especially in the range of 50 to 80'C5, and even 60 to 75°C. Excellent and Basic - This is particularly preferred as it has no effect on synthetic resin substrates.If the temperature is lower than room temperature, it will take too long for the cured film to dissolve and peel off, which is practically the same as not dissolving at all.Basics To remove the polyfunctional acrylic cured coating, the substrate is immersed in the alkali aqueous solution mentioned above, and the temperature of the aqueous solution is adjusted to the above temperature range, preferably 50 to 80" C1, especially 6
The temperature is kept constant within the range of 0 to 75°C, and the basic polyfunctional acrylic cured coating is removed by dissolving and peeling. There is no particular restriction on the impregnation time, and it is until the film is completely removed, but if the temperature of the aqueous solution is 50"C or higher, most of the time can be removed within 2 hours, especially within 1 hour. The removed X wood may be repainted as necessary to re-form the hardened film15, and in this case, the re-formed hardened film has no performance improvement compared to the hardened film formed on the #r product. There is no difference. [Example] Preferred examples of the present invention are shown below as Examples, but the present invention is not limited to these examples in any way unless otherwise specified. Examples 1 to 5 and Comparative Examples 1 to 2 A UV-curable polyfunctional acrylic coating composition was prepared from tris(acroyloxyethyl)isocyanurate as the main component as a polyfunctional acrylic monomer, a photopolymerization initiator, an inorganic filler, and an organic solvent. On the other hand, polypropylene [manufactured by Mitsui Petrochemical Industries KK, trade name, Mitsui Petrochemical Polypro, R, 140r Gunjo] was mixed with 1.2
An injection square plate C (thickness: 2 mm) made from 1°1.1-trichloroethane vapor (hereinafter abbreviated as PP) was exposed to 1°1.1-trichloroethane vapor for 30 seconds, then dried for 1 minute at room temperature, and then coated with various coatings. The composition was applied by air spray (discharge pressure: 5 kg, 7 cm), and after setting for 5 minutes, it was dried at 80° C. for 5 minutes. Next, this test piece was placed under a 3KW high-pressure mercury lamp. The outer coating was cured by irradiating it with ultraviolet light for about 50 seconds at a distance of 151 mm. The injection molded square plate coated in this manner was immersed in the stripping solution shown in Table 1 for 50 minutes, and the peeling status of the coating layer was observed. The results are shown in Table 1. Note that Table 1 also shows the results of Examples 6 to 8, which will be described later. Example 6 Poly-4-methyl-1-pentene C manufactured by Mitsui Petrochemicals, product name: TPX MX-004 (hereinafter abbreviated as TPX)-2
A mm-thick injection-molded square plate was prepared with 15 g/1 of maleic anhydride-modified EPR (maleic anhydride content near, 7 + weight)%].
Primer treatment was performed by immersing it in a toluene solution at 28 degrees for 10 seconds. After standing at room temperature for 5 minutes, an outer coating layer was formed by the method described in Example 1. The injection molded square plate coated in this way was kept at 70°C.
When it was immersed in a 5% hydroxide aqueous solution for 50 minutes, the coating film was completely dissolved and removed. Examples 7-8 Polycarbonate c coated with a polyfunctional acrylic ultraviolet curable hard coat as a surface-coated polymer sheet
Hereinafter abbreviated as PC] Sheet (manufactured by Mitsubishi Rayon, product name:
Dialite ■AR) and polymethyl methacrylate c (hereinafter abbreviated as PMMA) sheet (manufactured by Mitsubishi Rayon,
Cut out a test piece from the product name Niacrylite ■AR).
When immersed in an aqueous sodium hydroxide solution using the method described in Example 1, all of the coating layers were completely dissolved and removed. Table 1 (Continued) Example 9 A cured film was again formed in the same manner as in Example 1 on the base material from which the film had been removed in Example 1. The physical properties of the resulting coating are shown in Table 2 in comparison with those of a cured coating formed on a new substrate. Table 2 *1 This was carried out in conjunction with the burrow test in JIS K 5400-1979. *1 Performed according to 60 degree specular gloss in JIS K 5400-1979. [Effects of the Invention] As described above, according to the method of the present invention, (1) it is possible to remove a polyfunctional acrylic cured film, which has conventionally been difficult to remove; (2) it is possible to remove the The cured film can be removed reliably and completely. (3) It does not affect the substrate at all. (4) It is easy to work as it only needs to be immersed in an alkaline aqueous solution. (5) The basic surface after removal of the cured film is clean, and therefore the performance of the cured film after repainting is also good. shows.

Claims (4)

[Claims] (1) Separate the cured film from the substrate by immersing the substrate with a polyfunctional acrylic cured coating on the surface in an alkaline aqueous solution with a concentration of 5% or more at a temperature range above room temperature but below the temperature at which the substrate deforms. A film removal method characterized by: (2) The method for removing a film according to claim 1, wherein the temperature of the alkaline aqueous solution is 50 to 80°C. (3) The method for removing a film according to claim 1 or 2, wherein the concentration of the alkaline aqueous solution is 10 to 30%. (4) Removal of the film according to any one of claims 1 to 5, wherein the alkaline aqueous solution is selected from aqueous solutions of lithium hydroxide, sodium hydroxide, potassium hydroxide, magnesium hydroxide, and calcium hydroxide. Method.