Selection and application of characteristics of cooking-resistant plastic ink pigments (1)

Many kinds of foods need to be sterilized together with plastic packaging. If the retort resistance of the ink is poor, color change or fading will occur after cooking at high temperature; in order to keep the printed plastic bags normal after high-temperature cooking The color, the choice of high temperature cooking plastic ink is very important; and the key to high temperature cooking ink is the choice of pigment in the ink.

The high-temperature retortability of ink mainly refers to the heat resistance of the ink, that is, the degree of discoloration of the ink layer under heat. The heat resistance of plastic ink mainly refers to the heat resistance of the package in the process of cooking, heat sealing and compounding, and the poor heat resistance is mainly manifested in the fading, discoloration, and unclear graphics. The heat resistance of the ink is mainly determined by the pigment and the binder. The heat resistance of the binder is poor and it changes from white to brown after heating. Therefore, the heat resistance of the light ink depends on the binder and the heat resistance of the colored ink. It depends on the pigment. This article will use red organic pigment ink as an example to analyze the heat resistance of the ink and the choice of pigment.

Organic pigment heat resistance test

The cooking-resistant plastic ink consists of a binder, a colorant, and an auxiliary agent (for example, a filler, a wetting agent, a viscosity reducer, etc.) composed of different resins. Organic pigments are insoluble in water and organic solvents. They are highly dispersed particulate colorants with bright colors, high color strength, and have good light resistance, weather resistance, heat resistance, solvent resistance, migration resistance, and dispersibility.

In the course of this experiment, four kinds of red pigments were selected as the colorants of plastics resistant cooking inks, because red pigments are commonly used pigments for printing inks, and the red organic pigments in solvent inks are the most common; furthermore, the heat resistance of red pigments is general. In four grades, it is colorful, and even slight discoloration can be distinguished.

1. Experimental pigments and instruments

1) Experimental pigment

The four red pigments used in this experiment were:

1 Jin Guanghong C (Yellow Red) pigment, pigment index number: PR53:1, is a yellow powder, generally produced by CLT acid diazo coupling.

2 Permanent Red F4R (FR3560) pigment, pigment index number: PR8, is a bright red color powder, good alkali resistance, general light resistance, poor heat resistance, the case of concentrated nitric acid was blue and red, and concentrated sulfuric acid was yellow Everbright red, does not change color in case of sodium hydroxide.

3 Lisol Red BK (N53) pigment, pigment index number: PR57:1, is a dark red powder with blue light, bright color, high coloring power, insoluble in ethanol, golden red when dissolved in hot water, acid resistant Good alkalinity, general light fastness, heat resistance up to 150°C, concentrated sulfuric acid red, dilute to magenta precipitation, aqueous hydrochloric acid precipitation in the case of hydrochloric acid, the case of concentrated sodium hydroxide was brown.

4 Permanent red 2B (big red) pigment, pigment index number: PR48:2, purple-red powder, insoluble in water and ethanol, purple red in case of concentrated sulfuric acid, reddish blue precipitate after dilution, and brownish red in case of concentrated nitric acid. Concentrated sodium hydroxide is red and has good heat resistance.

2) The main instrument

KGZ-1A gloss meter; SM-II type sander; PB203-N type electronic balance; XXQG02 type steam sterilizer; XD type scraper fineness meter: DMDE450 optical coating machine; D-8401 multi-function speed regulation stirrer .

3) Experimental raw materials and drugs

Resin A solution, resin B solution, DCHP, low molecular wax, 4 pigments, toluene (analytical purity), butanone (analytical purity).

2. Preparation of experimental ink

First, the resin A liquid, low molecular wax, DCHP, toluene, butanone were mixed according to the formula, and after fully stirring for 10 minutes, it was used as the a part; then, an appropriate amount of the resin B liquid was further added and stirred for about 60 minutes as the b part to mix the components. Uniform.

1 The well-stirred ink is poured into a sand mill for grinding, so that the milled ink has various rheological properties and printability that the ink should have.

2 Place the prepared ink in a sample bottle, cap tightly, and label it for testing.

The formulation and the preparation process used in this test were performed according to the conventional method for industrial production of ink.

The inks prepared using the same quality of raw materials are gold red C and permanent red F4R in descending order of volume. Lisuerbao Red BK, Everlasting Red 2B. Among them, the volume of the Jinguanghong C ink is about 3 times that of the permanent red 2B ink. The formulated permanent red 2B ink is very thick and difficult to filter. Therefore, when testing, use a solvent to dilute the permanent red 2B ink to the appropriate concentration.

3. Test sample preparation and heat resistance test

1) Preparation of samples

The prepared ink was separately screen printed on PET film, BOPA film and ion bombarded BOPA film. The performance of the ink is tested according to the standard requirements. The heat resistance test refers to the heat resistance test standard for metallic inks. Several 20mm × 100mm PET films and BOPA films are cut for use.

2) Pigment heat resistance test content

1 Dry the pigments in 4 kinds of pigments at 100°C for 40 minutes. Compare them with the standard samples after cooling and observe the color changes.

2 Samples of 8 inks were dry-baked under 5 conditions at 100°C for 40 minutes. After cooling, they were compared with the standard samples to investigate their color changes.

3 Eight kinds of four kinds of inks were steamed and tapped in tap water under three conditions of 100°C and 40 minutes. After cooling, they were compared with the standard sample. The color change, fading, and water color of the sample were examined. Changes.

4. Experimental standard

This experiment was conducted in accordance with the national standards for gravure plastic ink inspection methods, glossiness test, fineness test, primary dryness test, adhesion fastness test, anti-blocking test, color inspection standard, and ink flow test standard.