JPS60149485A - Printing method on molded resin product of polyolefin group - Google Patents

Abstract

PURPOSE:To prevent disappearance of printed letters, etc. by using as a molding material a composite which has an improved heat resistance by combinin inorganic filler with polyolefin and by printing on the surface of the above molded product by a subimation printing method and subsequently, by strongly fixing the dye in the resin into which the dye is infiltrated by sublimation through the process of heat treatment. CONSTITUTION:The surface of a molded product which is obtained by molding a composite which is consisting of 30-99(wt)% of polyolefin and 1-70% of inorganic filler (preferably, 0.02-20mum of diameter of calcium carbonate, talc) is printe with a matter in a paste form consisting of pulverized powder of disperse dye. Subsequently, heat treatment (for instance, at 120-160 deg.C for 1-30min in case of PP resin base) is provided and the printed disperse dye is sublimated and infiltrated into the molded product to reveal specified letters, marks and etc. Additionally, a bud printing method is desirable for the above mentioned printing.

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 penetrating and fixing dye into polyolefin resin molded products such as polyethylene and polypropylene. In particular, the present invention relates to a printing method in which a molded article made of a polyolefin containing an inorganic filler is printed with a disperse dye ink and then heat treated to penetrate 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 are raised up with printing ink attached to the surface, so there are problems with wear resistance, and they cannot withstand long-term use, and are prone to wear and tear on the tabs. It had the disadvantage that letters, marks, etc. were easily erased by chemicals. 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 sublimation printing method for heat-resistant resin molded products involves high-temperature treatment, the resin is required to have a certain degree of heat resistance, and polyester resins, etc., which have functional groups that allow dyes to easily penetrate into the resin, are most preferred. It was said that Moreover, even with these relatively heat-resistant resins, characters and marks that have penetrated the resin tend to bleed due to the influence of heating during the process.

Furthermore, if polyolefin resin is used as it is, it will not have sufficient heat resistance, and the dye will have poor penetration and fixation into the synthetic resin molecules, resulting in a poor finish and the dye will gradually ooze out throughout the resin, making the outlines of letters and marks unclear. It was easy for this phenomenon to occur.

The present inventors have addressed the shortcomings of these conventional printing methods, and in order to improve the sublimation printing method for resin molded products such as polyolefins, which have relatively low heat resistance and poor printability, the present inventors added inorganic fillers to polyolefins. The present invention was completed by discovering a method of widening the temperature range in which heat treatment can be carried out by adding , and also strongly fixing the dye that has sublimated and penetrated into the resin.

That is, in the present invention, a paste consisting of fine powder of a disperse dye is applied to the surface of a molded article obtained by molding a composition consisting of a polyolefin of 50-99% by weight and an inorganic filler of 1 to 70% by weight. After printing, a heat treatment is performed to sublimate the printed disperse dye and allow it to penetrate into the surface of the molded product.

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

Examples of inorganic fillers used in the present invention include calcium carbonate, titanium oxide, talc, silica, clay, zinc oxide, white carbon, barium sulfate, zinc sulfide, and glass fiber. Among these, calcium carbonate, Merck, and the like are particularly preferred, as they are effective in improving the heat-resistant rigidity of polyolefins and fixing sublimation dyes. The particle size of the inorganic filler is preferably 0.02 to 20 μm in consideration of fixation of the sublimation dye and processability of the molded product. Further, the blending amount is preferably 30 to 99% by weight of polyolefin and 1 to 70% by weight. If it exceeds 70% by weight, the physical properties of the resulting molded product will deteriorate, and if it is less than 1% by weight, the print finish will be poor and bleeding will easily occur.

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

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 commonly used heat-sublimable dyes are used. For example, Diacθ1l-1ton F Pi
nk R, Dianix F Violet 2R, D
ianixF Sky Blue B and the like. It is preferable to print by using a fine powder of such a disperse dye, which is 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, especially for printing accuracy. High pad printing is preferred.

In the sublimation printing method of the present invention, after printing letters and marks on the surface of a polyolefin resin molded product, it is necessary to heat-treat it to allow the dye to penetrate.The heat treatment conditions are determined by the type of dye, Conditions vary depending on the type of olefin resin, the type of inorganic filler, etc., but when polypropylene resin is used as the base resin, it is 120 to 16
It is preferable to process at 0°C for 1 to 30 minutes. The disperse dye permeates into the molded product by 20 microns or more from the surface of the molded product to display predetermined characters and marks, and after the heat treatment, unnecessary substances remaining on the surface of the molded product are removed to obtain a permeation-printed molded product.

As described above, the text mark sublimated with disperse dye on the inorganic filler-containing polyolefin resin molded product penetrates approximately 20 to 50 μm into the molded product surface and is fixed, with little bleeding and good wear resistance. Provides chemical resistance.

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

Example 1 Mixture 1 consisting of 60% by weight of crystalline polypropylene (M-15) and 40% by weight of talc (average particle size 12μ)
00 parts by weight, 01 parts by weight of antioxidant, and 0.00 parts by weight of weathering stabilizer.
3 parts by weight and 0.3 parts by weight of the nucleating agent were mixed using a high-speed mixer, and the resulting mixture was granulated and then injection molded to form key tops. Next, Diacelliton F Pin
A paste was prepared by dispersing fine powder of kR in an appropriate solvent, and the letters rAJ were directly printed on the surface of the key top using this paste using a pad printer.

Next, the printed key tops are heat-treated at 160°C for 2 minutes to remove Diacell from the surface of the key tops with the printed characters.
iton F Pink R was sublimated and penetrated to display the letter (A).The depth of penetration of the letters into the key top surface thus obtained was investigated and found to be 30μ. The abrasion resistance, solvent resistance, and weather resistance of the letters were investigated and the results are shown in the table.

Examples 2 to 5 and Comparative Example 1 Printing was carried out on molded articles in the same manner as in Example 1 except that the type and amount of the inorganic filler in Example 1 were changed as shown in the table. For comparison, the results when no inorganic filler was added are also shown.

Examples Comparative example Polyolefin composition Polypropylene (parts by weight) 100 100 100
100 100 100 Talc (parts by weight) 411 2
0 1o---Calcium carbonate (parts by weight)---50
--Glass fiber (parts by weight)---20- Change Change Change Change Change Change Surface No No No No No Rough Weather Resistance Test "2) ○ ○ ○ ○ △ Δ Solvent Resistance Test" 6) Toluene ○ ○ ○ OOΔ Neutral detergent ◎ ◎ ◎ ◎ ◎ ◎ Artificial sweat liquid ◎ ◎ ◎ ◎ ◎ O Lotion ◎ ◎ ◎ ◎ ◎ 0 1% sulfuric acid ◎ ◎ ◎ ◎ ◎ 0 1% caustic Potash ◎ ◎ ◎ ◎ ◎ ・Ao1) Abrasion resistance test: Sand eraser 500 times (one-way tension 5oy) (
Appearance change) Screen 2) Weather resistance test: 66℃, 100 hour test using Sunshine Weatherometer (Appearance change) ○ Good, △ Fading, bleeding Ax 3) Solvent resistance test: Wiping test, gauze immersed in chemical solution Rub it 100 times one way under the conditions of a load of 5 oay and a speed of 3 DW min.

(Appearance change).

◎Very good, ○Good, △Discoloration, blurring agent: 1
) Akira agent Ryo Hagiwara −

Claims (1)

[Claims] 60-99% by weight polyolefin and 1-70% inorganic filler
After printing a paste made of fine disperse dye powder on the surface of a molded product obtained by molding a composition consisting of A method for printing polyolefin resin molded products, characterized by: