JPS60149487A - Printing method on molded resin product of polyolefin group - Google Patents

Abstract

PURPOSE:To produce printed matters with less runs, superior abrasion resistance and chemical resistance by roviding two stage heat treatment of heat drying and heating to a molded product of polyolefin group resin composite which was directly printed and by sublimating printed disperse dyestuff to infiltrate into the molded product. CONSTITUTION:Directly on the surface of a molded product made of polyolefin group resin composite a printing is performed with disperse dyestuff of pulverized powder in a paste form, using a bud printing machine or silk printing machine preferably with the etching depth of 10-20mum. Subsequently, the molded product is heat dried, preferably at 80-95 deg.C for 2-10min as a pretreatment and a heat treatment is provided, preferably at 120-160 deg.C for 2-10min and printed disperse dyestuff is sublimated from the surface of the molded product and infiltrated. Additionally, if chemical compounds of ester group and/or inorganic filler are mixed in the above stated resin composite, the infiltrating property of the dyestuff and security is improved, resulting in a satisfaction.

Description

Detailed Description of the Invention The present invention is a printing method that forms characters and marks that are not easily erased by friction or chemicals by impregnating and fixing dyes into molded products made from polyolefin resin compositions such as polyethylene and polypropylene. More specifically, the present invention relates to a printing method in which a molded article made of a polyolefin resin composition is printed with a disperse dye and then subjected to specific heat treatment and cooling treatment to infiltrate and fix the dye into the molded article.

Conventionally, methods such as hot stamping, transfer printing, silk screen printing, and dry offset printing have been used to print characters and marks on the surface of synthetic resin molded products. The letters and marks on the surface of the molded product have problems with wear resistance because the printing ink adheres to the surface and is raised up, so they cannot withstand long-term use. The disadvantage is that letters, marks, etc. are easily erased. Due to this, recently two-color molding methods have been developed in which two-color synthetic resins are used as raw materials to display characters and marks on the resin itself, and polyester-based heat-resistant resin molded products are printed with dispersible dyes and then subjected to high-temperature heat treatment. Sublimation printing is used to infuse the product with dye.

However, with the former two-color molding method, it is difficult to display minute characters and marks, and it is necessary to manufacture a precise mold for each character or symbol, which increases the cost of the mold.

Furthermore, it may be impossible to display characters or the like at an initial predetermined location due to limitations of the mold structure. Furthermore, since the latter method of sublimation printing for heat-resistant resin molded products involves high-temperature treatment, there is a tendency for letters and marks that have penetrated to bleed due to the influence of heating during the process. In particular, in the case of polyolefin resins, which have relatively low heat resistance, they are greatly affected by the heat treatment process, resulting in poor penetration and fixation of the dye between the molecules of the synthetic resin, poor finishing, and the dye gradually oozing into the resin. This often caused the outlines of letters, marks, etc. to become unclear.

The present inventors aimed to eliminate the drawbacks of these conventional printing methods and to improve the sublimation printing method for resin molded products such as polyolefins, which have relatively low heat resistance and poor printability. The present invention was completed by discovering a method for strongly fixing the dye that has sublimated and penetrated into the resin by using specific conditions for drying, heating, and cooling molded articles made from polyolefin resin compositions.

That is, the present invention directly prints a paste made of fine disperse dye powder on the surface of a molded product made from a polyolefin resin composition using a pad printing machine or a silk printing machine, and then heats the molded product. It is characterized by performing a two-step heat treatment of drying and heating to allow the printed disperse dye to sublime and penetrate.

Examples of the polyolefin resin used in the present invention include polymers and copolymers of ethylene, propylene, butene, and mixtures of these (co)polymers.

Penetration of the sublimation dye into the polyolefin resin of the present invention,
An ester compound and/or an inorganic filler may be mixed to improve adhesion. Ester compounds are compounds that have an ester group in the molecule, and examples of monomers include esters of aromatic dicarboxylic acids such as dimethyl isophthalate, and neopentyl-type polyhydric alkyl esters such as pentaerythritol stearate.
Examples include fatty acid esters, esters of neobentyl polyhydric alcohols such as trimethylolpropane-trimethacrylate and acrylic acid or methacrylic acid, and esters of glycols and acrylic acid or methacrylic acid such as triethylene glycol dimethacrylate. . Polymers include acrylic ester polymers,
Copolymer of ethylene and (meth)acrylic acid ester, copolymer of ethylene and glycidyl (meth)acrylate, (
Copolymer of methyl meth)acrylate and glycidyl (meth)acrylate, copolymer of styrene and glycidyl (meth)acrylate, methyl (meth)acrylate-ethyl acrylate-glycidyl (meth)acrylate copolymer Examples include acrylic resins such as and ethylene-vinyl acetate copolymers.

This ester compound is a polyolefin resin 50-9
It is preferable that the amount is 1 to 50% by weight per 9% by weight.

Inorganic fillers include calcium carbonate, titanium oxide,
Examples include talc, silica, clay, zinc oxide, white carbon, barium sulfate, zinc sulfide, and glass fiber. Among these, particularly preferred are calcium carbonate, talc, and the like, which are effective in improving the heat-resistant rigidity of polyolefins and fixing sublimation dyes. The particle size of the inorganic filler is preferably 102 to 20p in consideration of fixation of the sublimation dye and processability of the molded product. Moreover, it is preferable to use 1 to 240 parts by weight based on 100 parts by weight of the mixture of polyolefin and ester compound.

There are no particular restrictions on the method of blending the polyolefin, ester compound, and/or inorganic filler into the polyolefin, and any known blending method may be employed. Molded products made from such resin compositions include electronic devices and
It is used for parts, covers, name tags, etc. of A-equipment, and is especially used for key caps of button-type telephones, calculators, typewriters, word processors, personal computers, etc.

In addition, during molding, it is preferable to add ultraviolet absorbers and nucleating agents to improve the weather resistance and gloss of the molded product and the characters and marks that have penetrated into it. Antistatic agents, lubricants, pigments, etc. can also be used.

The disperse dye used in the present invention is preferably a heat-permeable dye, and a commonly used heat-sublimable dye is used. For example, Diacelliton F, Pink
R, Dianix F Violet 2R, Dian
iX FSky Blue B, etc. can be mentioned. It is preferable to perform printing using a finely powdered disperse dye made into a paste with a solvent.

Next, as a printing method to form images of characters and marks on polyolefin resin molded products, direct printing methods such as pad printing and silk screen printing, which can print not only on flat surfaces but also on uneven surfaces, are preferable. Pad printing is preferred because of its high printing accuracy.

Furthermore, in order to reduce the spread of printing due to bleeding of sublimated characters and marks, and at the same time to reduce the cleaning effort in the post-processing process, images representing the characters and marks are printed on the surface of the molded product. Preferably, the thickness of the ink is adjusted to the desired range by etching the printing plate to a depth of 10-20 microns.

In the present invention, after printing letters and marks on the surface of a polyolefin resin molded product, two steps are taken to allow the dye to penetrate.
It is necessary to carry out a staged heat treatment. Molded products printed with ink containing disperse dyes are heated for 2 to 10 minutes at 80 to 95°C.
Perform heat drying as a pretreatment for 120-16 min.
A heat treatment is performed at 0° C. for 2 to 10 minutes to sublime and permeate the disperse dye from the surface of the molded product. By performing two-step processing, it is possible to almost eliminate smudging. In this case, it is preferable to rapidly cool the molded product to room temperature or lower within 1 minute after the infiltration to firmly fix the infiltrated dye.

The dye penetrates into the molded product by 20μ or more from the surface of the molded product, and predetermined characters and marks are displayed. After cooling, unnecessary materials remaining on the surface of the molded product are removed using an organic solvent or the like to obtain a penetrant-printed molded product.

The characters and marks sublimated with disperse dyes, etc. on the polyolefin resin molded product obtained by the present invention penetrate approximately 20 to 50 μm into the molded product surface and are fixed, with little bleeding and good abrasion resistance. Provides chemical resistance.

The present invention will be explained below with reference to Examples.

Example 1 1 part by weight of antioxidant a, 13 parts by weight of weathering stabilizer and 3 parts by weight of nucleating agent α were added to 100 parts by weight of crystalline polypropylene (M-15), and key tops were produced by injection molding.

Next, fine powder of Diacelliton F Pink R was dispersed in an appropriate solvent to prepare a paste.
This paste-like material was used to directly print the letters rAJ on the surface of the key top using a Sakuratsudo printing machine (having a plate depth of 17 .mu.m).

Next, the printed key tops were heat-dried at 90°C for 4 minutes.
Subsequently, Diace-111ton F Pi
nkR was sublimated and permeated to display the letters rAJ. The surface of the obtained key top was cut with a microtome and the penetration depth of the characters was examined under a microscope and found to be 27μ. In addition, the boundaries between the letters were clear. Furthermore, the abrasion resistance, weather resistance, and solvent resistance of the letters were investigated, and the results are shown in the table.

Example 2 555 parts by weight of crystalline polypropylene (M Engineering 15) Methyl methacrylate-glycidyl methacrylate copolymer (G
MA polymer, glycidyl methacrylate content! IO%
) 5 parts by weight and 400 parts by weight of talc (average particle size 12 μm) was used, but in the same manner as in Example 1, the letters rAJ were directly printed on the key tops.

Next, the printed key tops were heat dried at 90°C for 5 minutes.
Next, heat treatment was performed at 150°C for 5 minutes to sublimate and penetrate the dye from the surface of the printed key top to display the letters rAJ. Immediately after that, the key top was cooled to below room temperature, and then unnecessary materials on the surface of the key top were removed. Removed. The penetration depth of the letters on the surface of the key top was 50 μm, and the boundaries of the letters were clear. The results of various physical property tests are shown in the table.

Comparative Example 1 A sublimation-printed key top was prepared in the same manner as in Example 1, except that the key top on which the character "Mu" was printed was not heat-dried, but was heat-treated at 160° C. for 5 minutes. Obtained.

The penetration depth of the characters on the surface of the obtained key top was 14 μm, and the boundaries of the characters were unclear.

The results of various physical property tests are shown in the table.

Example Comparative example *1) Abrasion resistance test No change No change Surface roughness weathering test <) O◎ △ Solvent resistance test) Toluene ○ ◎ △ Neutral detergent ◎ ◎ ◎ Artificial sweat liquid ◎ ◎ ◎ Lotion ◎ ◎ ◎ 1-thiosulfuric acid ◎ ◎ ◎ 1-chi caustic potassium ◎ ◎ ◎ 脣1) Abrasion resistance test: Sand eraser (Lion 5o) 50
0 times (one-way tension: 5 oy) (change in appearance) Tatami 2) Weather resistance test: 100 hours test at 63°C using a Sunshine Weather-Ometer (change in appearance).

◎Very good, ○Good, △Fading, bleeding 3) Solvent resistance test: Wiping test. Using gauze soaked in the chemical solution, pass through the test 100 times in one direction at a load of 500 t1 and a speed of 30 times/min (change in appearance).

◎Very good, ○Good, ΔFading, bleeding Among agents: 1) Akira Agent Ryo Hagi Hara -

Claims (3)

[Claims] (1) After directly printing a paste consisting of fine disperse dye powder on the surface of a molded product made from a polyolefin resin composition using a pad printing machine or silk printing machine, the molded product is subjected to two steps of thermal drying and heating. A method for printing polyolefin resin molded products, which is characterized by performing stepwise heat treatment to sublimate the printed disperse dye and allowing it to penetrate into the molded product. (2) The method according to claim 1, wherein the disperse dye is sublimated and permeated into the molded article by a two-step heat treatment, and then the molded article is rapidly cooled to room temperature or below within one minute. (3) When printing directly, set the etching depth of the printing plate to 10
-20μ, the method according to claim 1 or 2.