JPH0480838B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for dyeing and painting the surface of a plastic molded article, and uses an ink containing a sublimation dye or a heat-melting transferable dye to dye and decorate the surface of a plastic molded product.
Printing characters, figures, etc. on the surface of the molded product immediately after molding,
In the next step, this is heated to transfer the dye into the plastic, resulting in a painting with excellent abrasion resistance.

Generally speaking, the methods of painting on the surface of plastic molded products include screen printing using pigment-based ink,
There are tacho printing, transfer using adhesives, and label pasting, but these have drawbacks such as wear resistance, solvent resistance, weather resistance, etc., and the sharpness of patterns, letters, figures, etc. decreases with age. However, due to problems in terms of functionality and design, its practical use is currently extremely limited. As a method to solve these problems, that is, to obtain patterns, characters, figures, etc. with excellent wear resistance, solvent resistance, and weather resistance, there is a method using a multicolor injection molding machine, or a method described in Utility Model Application No. 186944 (1983). There is a method using sublimation transfer as described above.

A supplementary explanation of the above two methods is as follows.

In other words, the method using a multicolor injection molding machine involves preparing two sets: a mold for molding the pattern and a mold for molding other parts, molding the design in the first step, and then molding the other parts. The pattern is molded using a different colored resin.

However, in this case, there are disadvantages such as high mold cost, inability to express complicated patterns, characters, figures, etc., and considerable restrictions on the shape of the molded product.

In addition, the sublimation transfer method is a method in which after the molded product is formed, the molded product is set in a predetermined jig in a separate process, and a transfer machine is used to print on the surface of the molded product with ink containing a sublimable dye prepared in advance. By bringing them into close contact and pressing a heating plate from the back side of the transfer paper, the dye and the molded article are heated, and the dye sublimates and permeates into the molded article.

However, in this case, the process of setting the molded product on the transfer jig is complicated, it is difficult to obtain an accurate positional relationship between the pattern and characters printed on the transfer paper, and the molded product is difficult to transfer. There are drawbacks such as the need to raise the temperature of the molded product to a predetermined temperature, which lengthens the transfer cycle, and the possibility that the molded product may be deformed during heating.

The present invention provides wear resistance and abrasion resistance on the surface of plastic molded products.
The present invention relates to a molding/painting method which is a method for painting patterns, letters, figures, etc. with excellent solvent resistance and weather resistance, and which has a new concept that improves the drawbacks of the conventional methods described above.

The present invention will be explained in detail below.

The present invention is a method for painting plastic molded products, and the target products include, for example, computers,
These include key tops used in telephones, electrical and construction-related parts that require durability, and containers that are used under harsh conditions such as boiling, abrasion, and other conditions.
Thermoplastic materials used as plastic molding materials include polyester resins such as polyethylene terephthalate and polybutylene terephthalate, polyamide resins, cellulose-modified resins, acrylic resins, and ABS.
(acrylonitrile-butadiene-styrene copolymer) resin, AS (acrylonitrile-styrene) resin, polycarbonate resin, vinyl chloride resin, etc. are used. Further, as the thermosetting resin, epoxy resin, urethane resin, urea resin, phenol resin, polyester resin, melamine resin, etc. can be used.

The equipment constituting the present invention is basically an injection molding machine, a mold, a concave offset printing (hereinafter referred to as octopus printing) machine, or a screen printing machine. or,
The ink used to decorate molded products contains sublimable dyes, but dyes such as oil-based dyes, disperse dyes, and basic dyes can be used, and should be selected depending on the plastic molded product to be painted. I can do it.

For example, when dyeing polyester resin, disperse dyes are suitable, and dyes with heat transfer properties of CI Pisperse Red 60 can be used. For polyimide resins, disperse dyes or basic dyes can be used, such as CIPisperse Red 8 or CIBasic
Direct dyes and reactive dyes can be used for cellulose-modified resins such as Blve 5, and cationic dyes are preferred for acrylic resins, ABS resins, and AS resins. On the other hand, disperse dyes are generally suitable for thermosetting resins, and CIBasic Orange
You can use a dye like CIBasic Orange 7 or CIBasic Orange 8.

The dyeing elements constituting the present invention have been described above, and will be explained in detail below using specific examples based on the drawings.

This specific example is a method of molding and painting a key top made of polybutylene terephthalate resin and having letters on the top surface, which is the molded product 1 shown in FIG.
As shown in FIG. 2, first, a molded article 1 without any decoration is molded by a vertical injection molding machine 2. At this time, a mold consisting of a female mold 3 and a male mold 5 is set in the injection molding machine 2, and the female mold 3 is attached to the nozzle 4 side of the injection molding machine 2, and when resin is injected and cooled, it is placed downward. Then the male mold 5 was assembled. The male mold 5 is attached to a moving table 6, and is moved directly below the female mold 3 during resin injection and cooling, and to a printing station at other times. Molding conditions such as resin injection temperature, injection pressure, and molding cycle are general conditions for molding polybutylene terephthalate. When the cooling process during molding is completed, the female mold 3 opens upward, and at this time, the molded product 1 remains on the male mold 5 side. When the mold opening is completed, the male mold 5 on the moving table 6 is moved to the printing station with the molded product still attached. A tacho printing machine is set in the printing station 7. The octopus printing machine has a concave plate 8,
It is composed of a doctor 9, a pad 10 made of silicone, and a rod 11 for moving the pad.Here, first, ink 12 is placed on the intaglio plate, and the ink is applied by the doctor to the concave part of the concave plate 8 having a predetermined character shape. 13 is filled, and then the pad 10 is brought into close contact with the recess 13 to transfer the ink. These series of operations are linked to the operations of the injection molding machine 2,
At the same time as the male mold 5 stops at a predetermined position on the printing station, a pad 10 is moved and brought into close contact with a predetermined position on the top surface of the molded product on the male mold, and the ink on the pad 10 is transferred to the molded product. When the transfer is completed, the pad 10 moves to a predetermined position on the intaglio plate 8. On the other hand, the molded product after the transfer is removed from the male mold and sent to the next process. At the same time as the molded product 1 is discharged, the male die 5 moves directly below the female die 13, and the next cycle begins. The predetermined characters 14 are printed on the top surface of the molded product 1 after the transfer has been completed, but as the ink is not adhering sufficiently to the molded product 1, the molded product 1 is removed from the mold. After collecting it, it moves on to the drying process. Drying is performed at 100 to 250°C for about 10 to 100 seconds. During the drying process, the temperature of the molded product rises and at the same time the ink printed on the top surface is also heated, and the sublimable dye contained in the ink penetrates into the molded product, resulting in improved wear resistance and solvent resistance. , it is possible to obtain a molded product with a pattern that is excellent in weather resistance.

In addition to the injection molding machine shown in the specific example, the injection molding machine used in the present invention can also be a horizontal injection molding machine, but in this case, the male mold mounting plate rotates or moves, or the mold opening amount is sufficiently increased. A structure that can be used is preferable. When a horizontal injection molding machine is used, the printing process is naturally carried out within the platen of the injection molding machine. The mold for carrying out the present invention does not need to have a special structure, but in order to shorten the cycle of molding and painting, it is necessary to prepare two or more male molds for one female mold and perform injection molding. It is sufficient to adopt a process in which the painting or molded products are collected at another station at the same time as this is being performed. In addition to the movable table that performs reciprocating motion, it is also possible to use a movable table that performs rotary motion.

In addition to tacho printing, the printing machine may also use screen printing, dry offset printing, or inkjet printing.

In the above-mentioned specific example, the dye was permeated into the molded product during the drying process, but the resin of the molded product,
Depending on the type of dye and molding conditions, sublimation and penetration may be possible immediately after painting by utilizing the surface temperature of the molded product immediately after molding. Possible drying methods include hot air, infrared rays, microwaves, and the like.

Furthermore, even after drying, dyes that do not penetrate into the molded product or various binders in the ink may remain on the surface of the molded product, but this can be removed as necessary using a solvent suitable for the ink composition. I think it is appropriate to do so.

The above is the explanation of the present invention. By using the present invention, the cost is significantly lower than the method using a multicolor molding machine, which has been conventionally used as a method of painting plastic molded products that require durability. It is now possible to down-size the product, and it is now possible to decorate the molded product with no restrictions on the shape of the pattern. Also, compared to conventional methods and methods that use sublimation dyes, that is, methods in which molding and painting are done off-line, it is possible to utilize the heat of the molded product immediately after molding, and it is possible to repaint the molded product after molding. There is no need to reinsert the painting jig, the positional accuracy of painting is greatly improved, the painting jig is no longer necessary, or when heating the molded product after painting to sublimate the dye. This method is also considered to be a method of painting plastic molded products that has a number of advantages, such as being able to utilize preheating of the molded product.

(Example) 182×182× made of polybutylene terephthalate
10.5Hm/m key top with a vertical injection molding machine (Yamashiro Seiki SUS-100 type) with a slide table.
Molded using a cut-out mold. The mold structure is a cold runner method.The gate is a tunnel gate method.The molding conditions are cylinder temperature 200-260℃, mold temperature 80℃, molding cycle is 18 seconds, molding including the movement of the slide table, and the painting cycle is 20 seconds,
The male type uses type 2, the printing machine uses a modified pad-type automatic transfer machine (manufactured by Taihei Kogyo), the pads are made of silicone rubber, and the letters "A" and "B" are used for the pads.
Alphabetical characters such as "C", kana characters, and other various marks.

The ink composition is as follows.

Dye Sumikalon FB Conc (Sumitomo Chemical) 20 parts Ethyl cellulose 20 Isopropyl alcohol 30 Methyl cellosolve 30 Using the above ink, transfer the specified characters to the top surface of the key top using a pad. A transfer cycle of 3 to 4 seconds is sufficient. It is. 16 characters are transcribed at the same time, resulting in 16 different types of characters.

Immediately after painting the molded product molded and painted under the above conditions16
Collect each type separately and immediately put it into drying.
℃ for 10 seconds, collect, cool, and wash in a water bath.

Through the above process, clear characters with no stains, stains, or chips were printed on the molded product. In addition, in practical tests, it cleared various conditions such as a key touch test using 10 million finger pressures, a 1000hs weather resistance test using a weather meter, and a solvent resistance test against xylene, gasoline, etc., proving that it is sufficiently durable for practical use.

[Brief explanation of the drawing]

The drawing is an example of the painting method of the present invention,
Fig. 1 is a perspective view of a plastic molded product before painting, Fig. 2 is a perspective view of a plastic molded product after painting, and Fig. 3 is a molding machine for carrying out the painting method of the present invention. and an explanatory diagram of a painting device. 1... Plastic molded product, 2... Injection molding machine, 3... Female mold, 4... Nozzle, 5... Male mold, 6
...Moving table, 7...Printing station, 8
...Intaglio, 9...Doctor, 10...Patsudo, 1
1...Moving rod, 12...Ink, 13...
Concave part, 14...Pictured letters.

Claims (1)

[Claims] 1. An ink containing a sublimable dye or a heat-melt migration dye is applied to the surface of a plastic molded product molded by an injection molding machine before the molded product is ejected from the mold. A method for painting a plastic molded product, which is characterized by printing patterns, characters, figures, etc., and sublimating the dye in the ink by using preheating after molding to allow the dye to penetrate into the plastic molded product. 2. Claim No. 2, characterized in that the preheating of the molded product immediately after molding and the heat of the drying process after printing are used to sublimate the dye in the ink and allow the dye to penetrate into the plastic molded product. A method for painting a plastic molded product as described in item 1.