JP2597101B2 - Method for manufacturing surface cured resin molded body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention provides a method for improving adhesion when applying a surface scratch preventing coating to a synthetic resin molded article.

<Conventional technology> Synthetic resin molded products manufactured from polymethyl methacrylate resin, polycarbonate resin, polyallyl diglycol carbonate resin, etc. are lighter and have higher impact strength than glass products. Building materials such as partitions, counters, sky domes, sunroofs, carports, lighting applications such as lighting fixture covers, decorative applications such as signboards, display boards, interiors and displays, and vehicle parts applications such as meter covers, panels, and lamp covers Applications for industrial parts such as nameplates and covers, as well as miscellaneous goods and their uses are also diverse.

Since these synthetic resin molded products have insufficient abrasion resistance on the surface, their appearance is impaired due to the effects of contact, impact, scratching, etc. during transportation and use, and improvement thereof is strongly desired. ing. Various methods for improving the drawbacks of such a synthetic resin molded product have been conventionally studied, and a method of coating a synthetic resin molded product with a scratch-resistant coating film is most commonly used. As such a method, an organosiloxane-based, epoxy-based, urethane-based, melamine-based paint or the like is used, and after application, heat curing is performed. An active energy ray-curable type cross-linking coating method of using a polyfunctional acrylate or methacrylate having two or more unsaturated unsaturated groups, applying, and then irradiating an active energy ray such as an ultraviolet ray or an electron beam to obtain a cross-linked coating. There is.

In the latter method, a crosslinked film can be obtained at room temperature in a short time of the order of minutes or seconds, and is far superior in productivity to the thermosetting type.

It also shows excellent properties in terms of the storage stability of the paint, so-called pot life, and does not deteriorate during storage as in the thermosetting type.

Above all, the method using ultraviolet light has attracted attention as a new method for curing a coating film because the ultraviolet irradiation device is also relatively simple.

Ultraviolet-curing paints cure instantaneously at room temperature and provide high-strength coating films.On the other hand, due to large volume shrinkage during curing, the adhesion between the resulting coating film and the substrate is insufficient. Have a problem.

In order to solve this problem, coating compositions have been improved (for example, Japanese Patent Application Laid-Open Nos.
-82173, JP-A-52-105936, JP-A-55-1
No. 42003, JP-A-60-32859) Those using a primer (for example, JP-A-48-67330) and those defining the molding conditions of a molded product (for example, JP-A-51-20260)
JP, JP-A-51-20967), a method in which ultrasonic waves are applied during dip coating to enhance the solvent immersion effect (eg, JP-A-57-15871), or a method of pre-irradiating a substrate with ultraviolet rays Various methods have been tried, for example, Japanese Patent Application Laid-Open No. 53-9876.

<Problems to be Solved by the Invention> In the method disclosed in JP-A-48-39594, etc., in which the coating composition is improved, it is difficult to achieve both the hardness and the adhesion of the coating film. If it does, the hardness of the coating film decreases.

The method using the primer disclosed in JP-A-48-67336 or the like complicates the working process and lowers the productivity, and the molding conditions of the molded product disclosed in JP-A-51-20260 and the like Is problematic in that it is difficult to apply it to a wide variety of general injection molded products.

The method disclosed in JP-A-57-15871 for applying ultrasonic waves during dip coating is applicable to dip coating, but is difficult to apply to spray coating.

In the method disclosed in JP-A-53-9876, in which the substrate is irradiated with ultraviolet rays before coating, sufficient effects are not necessarily obtained as exemplified in Comparative Examples.

<Means for Solving the Problems> In view of these facts, the present inventor has conducted intensive studies.
It has been found that the use of a low-pressure mercury lamp irradiator significantly improves the adhesion strength, and the present invention has been achieved.

The present invention provides a surface hardening method comprising: applying an ultraviolet-curable surface-curing material to a resin molded body and performing ultraviolet-curing, after performing ultraviolet irradiation using a low-pressure mercury lamp, and then performing ultraviolet irradiation using a high-pressure mercury lamp. The present invention relates to a method for manufacturing a resin molded body.

The ultraviolet-curable surface curing agent used in the present invention can be used without any particular limitation as long as it can be cured by ultraviolet rays. Among them, a crosslinkable resin material having two or more acryloyl groups or methacryloyl groups in one molecule is suitably used. Examples of such crosslinkable resin materials include (1) trimethylolpropane triacrylate or trimethacrylate, trimethylolethane triacrylate or trimethacrylate, pentaglycerol triacrylate or trimethacrylate, pentaerythritol triacrylate or trimethacrylate, pentaerythritol tetraacrylate or tetramethacrylate. Methacrylate, glycerin triacrylate or trimethacrylate, dipentaerythritol triacrylate or trimethacrylate,
Dipentaerythritol tetraacrylate or tetramethacrylate, dipentaerythritol pentaacrylate or pentamethacrylate, dipentaerythritol hexaacrylate or hexamethacrylate, tripentaerythritol tetraacrylate or tetramethacrylate, tripentaerythritol pentaacrylate or pentamethacrylate, 2,2-bis (4-acryloxydiethoxyphenyl) propane, 2,2-bis (4-methacryloxyethoxyphenyl) propane, diethylene glycol di (meth) acrylate, triethylene glycol di (meth)
Polyacrylates or polymethacrylates of polyhydric alcohols such as acrylate, tetraethylene glycol dimethacrylate, tripentaerythritol hexaacrylate or hexamethacrylate, tripentaerythritol heptaacrylate or heptamethacrylate; (2) malonic acid / trimethylolethane / acrylic acid Or methacrylic acid, malonic acid / trimethylolpropane / acrylic acid or methacrylic acid, malonic acid / glycerin / acrylic acid or methacrylic acid, malonic acid / pentaerythritol / acrylic acid or methacrylic acid, succinic acid /
Trimethylolethane / acrylic or methacrylic acid,
Succinic acid / trimethylolpropane / acrylic acid or methacrylic acid, succinic acid / glycerin / acrylic acid or methacrylic acid, succinic acid / pentaerythritol / acrylic acid or methacrylic acid, adipic acid / trimethylolethane / acrylic acid or methacrylic acid, adipine Acid / trimethylolpropane / acrylic acid or methacrylic acid, adipic acid / pentaerythritol / acrylic acid or methacrylic acid, adipic acid / glycerin / acrylic acid or methacrylic acid, glutaric acid / trimethylolethane / acrylic acid or methacrylic acid, glutaric acid / Trimethylolpropane / acrylic or methacrylic acid, glutaric acid /
Glycerin / acrylic acid or methacrylic acid, glutaric acid / pentaerythritol / acrylic acid or methacrylic acid, sebacic acid / trimethylolethane / acrylic acid or methacrylic acid, sebacic acid / trimethylolpropane / acrylic acid or methacrylic acid, sebacic acid / glycerin / Acrylic acid or methacrylic acid, sebacic acid / pentaerythritol / acrylic acid or methacrylic acid, fumaric acid / trimethylolethane / acrylic acid or methacrylic acid, fumaric acid / trimethylolpropane / acrylic acid or methacrylic acid, fumaric acid / glycerin / Acrylic acid or methacrylic acid, fumaric acid / pentaerythritol / acrylic acid or methacrylic acid, itaconic acid / trimethylolethane / acrylic acid or methacrylic acid, itaconic acid /
Trimethylolpropane / acrylic acid or methacrylic acid, itaconic acid / pentaerythritol / acrylic acid or methacrylic acid, maleic anhydride / trimethylolethane / acrylic acid or methacrylic acid, maleic anhydride / glycerin / acrylic acid or methacrylic acid, phthalic anhydride Acid / dipentaerythritol / acrylic acid or methacrylic acid, hexahydrophthalic acid / dipentaerythritol /
(3) Tolylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, dicyclohexyl methane diisocyanate, or these diisocyanates Diisocyanate compounds obtained by hydrogenating aromatic isocyanates among the compounds (for example, diisocyanate compounds such as hydrogenated xylylene diisocyanate and hydrogenated diphenylmethane diisocyanate) triphenylmethane triisocyanate, dimethylene triphenyl triisocyanate There are divalent or trivalent polyisocyanate compounds such as isocyanates Acrylic monomers, such as 2-hydroxyethyl acrylate or methacrylate with an isocyanate-containing compound with an active hydrogen polyisocyanate compounds obtained by multimerization of diisocyanate compound, 2-
Hydroxypropyl acrylate or methacrylate, 2-hydroxy-3-methoxypropyl acrylate or methacrylate, N-methylolacrylamide or methacrylamide, N-hydroxyacrylamide or methacrylamide, etc., are reacted in a conventional manner at 2 mol or more per isocyanate molecule. (4) Tris 2-hydroxyethyl isocyanuric acid triacrylate or methacrylate. The above compounds can be used in various combinations.

The UV-curable surface curing agent used in the present invention may optionally contain additives such as an antistatic agent, an ultraviolet absorber, a light stabilizer, an antioxidant, a smoothness-imparting agent, and a storage stabilizer. Can be used.

As a raw material resin of the resin molded article of the present invention, a thermoplastic resin, a thermosetting resin is used without distinction, for example, polymethyl methacrylate, polycarbonate, polyallyl diglycol carbonate resin, ABS resin, polystyrene, PVC, polyester resin , Acetate resin and the like are used. In addition to general molded articles, sheets, films, and the like are also objects of the resin molded article of the present invention.

The UV-curable surface curing agent can be used in combination with a solvent, and is advantageous for forming a uniform and thin coating film.

Examples of the solvent include alcohols such as ethanol, propanol, isopropanol and butanol, benzene, aromatic hydrocarbons such as toluene, acetates such as ethyl acetate and butyl acetate, ketones such as acetone and methyl ethyl ketone, and 2- (2-ethoxy). (Ethoxy) Ethers such as ethanol, glycol monomethyl ether, glycol monoethyl ether and dioxane are used alone or in combination. The amount of the solvent used is appropriately selected within the range of 0 to 250 parts by weight based on 100 parts by weight of the ultraviolet curable surface curing agent.

In order to obtain a crosslinked cured film according to the present invention, it is necessary to add a photosensitizer capable of initiating a polymerization initiation reaction by ultraviolet irradiation to an ultraviolet curable surface curing agent.

Examples of the photosensitizer include benzoin, benzoin ethyl ether, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexylphenyl ketone, azobisisobutyronitrile, benzoyl peroxide and the like. It can be used alone or in combination of two or more.

The photosensitizer is used in an amount of 1 to 10 parts by weight, preferably 2 to 5 parts by weight, per 100 parts by weight of the ultraviolet curable surface curing agent. If the amount of the photosensitizer is more than 10 parts by weight, the cured film will be colored, while if less than 1 part by weight, the curing will be insufficient. As a method of applying the surface hardening agent, a known method such as brush coating, spray coating, roll coating, flow coating, and dipping may be appropriately used. In short, the desired uniform thickness,
Any method can be used as long as a smooth surface can be obtained, and it is preferable to select an appropriate method according to the shape of the object to be coated.

When the adherend is an injection-molded product, spray coating and dip coating are advantageous methods in view of production.

When applying the surface hardening resin composition to the synthetic resin molded body, the synthetic resin molded body can be used as it is, but if necessary, used after performing pretreatment such as washing, etching, dyeing, printing, annealing, etc. Is also good.

In particular, when the synthetic resin molded product is an injection molded product, it is desirable to perform annealing.

The thickness of the coating film is 1 to 30 μm, preferably 2 to 20 μm
If it is less than 1 μm, sufficient hardness cannot be obtained,
If it exceeds 30 μm, cracks and the like are likely to occur. After applying the surface-curing resin composition, the solvent is evaporated at 15 ° C. to 100 ° C., preferably 20 ° C. to 60 ° C., and then ultraviolet irradiation is performed to form a cured film.

The low-pressure mercury lamp used in the present invention has a sealed mercury pressure of 0.
It has a maximum energy in the wavelength range of 2540 ° and 1840 ° near 001 to 0.1 mmHg. When the low-pressure mercury lamp is used, the energy intensity around the wavelength range of 3650Å where the so-called high-pressure mercury lamp shows the maximum energy is 2540Å and
It is smaller than the energy around 1840Å.

The UV irradiation methods include: 1) a method of obtaining a crosslinked cured film by irradiating a low-pressure mercury lamp alone 2) a method of irradiating with a low-pressure mercury lamp and then irradiating a post-pressure mercury lamp to obtain a crosslinked film 3) a low-pressure mercury lamp / high-pressure Irradiation using a mercury lamp together can be used to obtain a crosslinked film, etc., but in the present invention, 2) irradiation with a low-pressure mercury lamp followed by irradiation with a high-pressure mercury lamp is performed based on the adhesion and hardness of the resulting surface cured film. A method of obtaining a crosslinked film by the above method is employed.

The irradiation time depends on the type of surface-cured resin composition, product shape,
It is to be determined according to the type and output of the low-pressure mercury lamp and the high-pressure mercury lamp, the irradiation distance, and the like.

In the method 1) using only a low-pressure mercury lamp, it is desirable to lengthen the irradiation time in consideration of the irradiation energy of the ultraviolet irradiation device.

When a low-pressure mercury lamp with an output of 100 W / cm is used, the irradiation time is preferably 3 seconds to 10 minutes, and more preferably 5 seconds to 4 minutes.

In the method of irradiating the high-pressure mercury lamp after irradiating the low-pressure mercury lamp in the above 2), when a device having an output of 100 W / cm is used as the low-pressure mercury lamp and a device having an output of 80 W / cm is used as the high-pressure mercury lamp,
The irradiation time of the low-pressure mercury lamp is preferably 1 second to 2 minutes, preferably 1 second to 30 seconds, and the irradiation time of the high-pressure mercury lamp is preferably 1 second to 1 minute, preferably 3 seconds to 30 seconds.

In the method 3) of irradiating with a combination of a low-pressure mercury lamp and a high-pressure mercury lamp, the irradiation time is 1 second when a device with an output of 100 W / cm is used as the low-pressure mercury lamp and a device with an output of 80 W / cm is used as the high-pressure mercury lamp. From 2 minutes, preferably from 1 second
Preferably between 30 seconds.

When a cross-linking curing reaction is performed using a high-pressure mercury lamp, a coating film with high coating strength can be obtained, but the problem of insufficient adhesion between the coating film and the base material occurs. Shows a particularly marked tendency when obtained by

On the other hand, it is an unexpected result that the adhesion is greatly improved by irradiation with a low-pressure mercury lamp. The reason why such a result is obtained is not clear, but the low-pressure mercury lamp has a lower total irradiation energy than the high-pressure mercury lamp, so the cross-linking curing reaction speed is slow, and therefore, the shrinkage distortion generated in the cross-linked cured film is small. It is considered as the cause.

Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited thereto.

<Examples> Synthesis of crosslinkable resin material (1) Synthesis example of urethane acrylate Synthesis Example 1 2.5 kg of trimethylolpropane diacrylate and 2 g of hydroquinone monomethyl ether were placed in the autoclave of Example 10 while stirring at a temperature of 60 ° C. 850 g of 2,4-tolylene diisocyanate were fed into the autoclave by a pump over 1 hour. After the feed, the mixture was further stirred at 60 ° C. for 1 hour, and then dibutyltin diacetate 0.5 g
Was fed and reacted for 2 hours to obtain 3.3 kg of a polyfunctional urethane acrylate.

Synthesis Examples 2 to 6 In a similar manner, urethane acrylate was synthesized from another type of active hydrogen acrylic monomer and an isocyanate compound. Examples of the synthesis of these various urethane acrylates are described in the first.
It is described in the table.

(2) Synthesis Example of Polyester Acrylate (Synthesis Example 7) 180 g (1.5 mol) of trimethylolethane, 98 g (0.83 mol) of succinic acid, and acrylic acid were placed in a glass flask equipped with a stirrer, a thermometer, and a water cooler. 240 g (3.3 mol), toluene 1500 g, CuCl ₂ 5 g, and p-trienesulfonic acid 20 g were charged.

The mixture was stirred while blowing air, and the reaction was carried out under reflux, and 70 cc of water was removed with an azeotropic mixture of toluene and water.

After the reaction, the oil layer was separated, and the oil layer was further washed with 0.5% aqueous sulfuric acid solution and pure water three times each.

After washing, the oil is dried with anhydrous sodium sulfate, then 50-60
The toluene was removed under reduced pressure at a temperature of 0 ° C. to obtain a pale yellow polyester acrylate as a residue.

(Synthesis Examples 8 to 11) Table 2 shows synthesis examples of other polyester acrylates obtained from polyhydric alcohols, polycarboxylic acids and acrylic acid.

(Example 1) 0.3 kg of dipentaerythritol hexaacrylate,
The urethane acrylate obtained in urethane acrylate synthesis example 1
0.3 kg of xylate, 0.56 kg of xylene, 0.2 ethylcellosolve
8 kg, butyl acetate 0.35 kg, diacetone alcohol 0.21 k
g, 1-hydroxycyclohexyl phenyl ketone 30 g
The mixture was sufficiently mixed to prepare an ultraviolet-curable surface curing agent. The hard
Methyl methacrylate resin injection molded plate (Sumipet
Cousin MHO, manufactured by Sumitomo Chemical Co., Ltd. Length 150mm, width 90m
m, thickness 3mm) to form a coating film, and room temperature for 20 minutes
After standing, it was irradiated with ultraviolet light under the conditions shown in Table 3 to
An oxide film was obtained. UV irradiation is a low-pressure mercury lamp (Sen special light source)
UVB110-2A) and a high-pressure mercury lamp (eye graph
CUIS Corporation, Eye Cure UE021-403C 500V, H02-L41
(2)).

Table 3 shows the results obtained when the ultraviolet irradiation was performed by three different methods.

Here, the UV irradiation method 1 is a case where only the low-pressure mercury lamp is irradiated, the UV irradiation method 2 is a case where the low-pressure mercury lamp is irradiated and then the high-pressure mercury lamp is irradiated, and the UV irradiation method 3 is a case where the low-pressure mercury lamp and the high-pressure mercury lamp are irradiated simultaneously. Is shown.

 The physical property evaluation method of the surface cured film is as follows.

(1) Abrasion test using steel wool hardness of # 000 steel wool A: no damage even if rubbed hard B: slightly scratched if rubbed hard C: slightly scratched if rubbed lightly D: even if rubbed lightly (2) Taper abrasion (100 times) Change in haze value (Haze value%) Measured according to ASTM D1044 (3) Adhesion Cross cut cellophane tape peeling test, 1 mm on coating
A film cutting lines reaching the substrate in spacing put vertically and horizontally 11 present, the number of eye 1 mm ² 100 pieces making, abruptly peeled off adhered cellophane tape thereon. This cellophane tape operation is repeated three times at the same location, and is expressed by the number of stitches that have not been peeled off.

(Examples 2 to 4, Comparative Examples 1 to 5) A surface hardening treatment was performed in the same manner as in Example 1 except that the ultraviolet irradiation method and the conditions were changed, to obtain a surface hardened film. The results are shown in Table 3.

(Examples 5 to 8, Comparative Example 6) A surface-cured film was obtained in the same manner as in Example 1 except that the arethane acrylate compound and the ultraviolet irradiation method and conditions were changed. The evaluation results are shown in Table 4 together.

(Examples 9 to 11, Comparative Examples 7 to 8) Using a polyester acrylate compound (Synthesis Examples 7 to 11), surface cured films were obtained under the same conditions as in Example 1 except that the irradiation method and conditions were changed. The evaluation results are shown in Table 4 together.

Comparative Example 9 The irradiation distance was 10 cm and the irradiation time was 10
A surface cured film was obtained in the same manner as in Example 1 except that the time was changed to seconds. The steel wool hardness was A, but the adhesion was 80/100, which was poor.

Comparative Example 10 A surface cured film was obtained in the same manner as in Comparative Example 9 except that the urethane acrylate of Example 10 was used. The steel wool hardness was A, but the adhesion was 15/100, which was poor.

Comparative Example 11 A surface hardening treatment was performed in the same manner as in Comparative Example 9 except that a high-pressure mercury lamp was irradiated for 5 seconds at an irradiation distance of 10 cm before applying the ultraviolet-curable surface hardener to the resin molded product. The adhesiveness of the obtained cured film was 25/100, indicating poor adhesion.

Comparative Example 12 A surface hardening treatment was performed in the same manner as in Comparative Example 11 except that irradiation with a high-pressure mercury lamp was performed at an irradiation distance of 10 cm for 40 seconds before applying the ultraviolet-curable surface curing agent to the resin molded product. The adhesiveness of the obtained cured film was 10/100, and the adhesiveness was poor.

Comparative Example 13 A surface hardening treatment was performed in the same manner as in Example 9 except that only a high-pressure mercury lamp was used without using a low-pressure mercury lamp. The cured film obtained showed good results of steel wool hardness of A, but poor adhesion of 5/100.

Comparative Example 14 A surface hardening treatment was performed in the same manner as in Comparative Example 13 except that the polyester acrylate was changed to Synthetic Example 11. Although the steel wool hardness of the obtained cured film was A, the adhesion was 10/100, which was poor.

Continuation of the front page (56) References JP-A-59-22934 (JP, A) JP-A-46-7185 (JP, A) JP-B-51-27466 (JP, B2)

Claims (1)

(57) [Claims] 1. A method of applying an ultraviolet-curable surface curing agent to a resin molded article and curing the resin-molded body by performing ultraviolet irradiation using a low-pressure mercury lamp and then performing ultraviolet irradiation using a high-pressure mercury lamp. A method for producing a surface-cured resin molded product.