**1. Introduction**

Ecological awareness among the public has led to a renewed investigation of natural dyes derived from plants for dyeing and printing textiles. Natural dyes can be extracted from any part of the plant like roots, leaves, fruits, seeds, petals [1]. They have certain advantages over synthetic dyes such as non-toxicity, medicinal properties (e.g., antibacterial activity), UV protective effects, biodegradability, and natural renewability of the plant source [1,2]. Disadvantages of natural dyes are their low wash and light fastnesses and that they can only achieve limited hues, mainly yellow, reddish, and brown [2,3].

Natural dyes from various plant sources, such as alkanet [4–6], rhubarb [4,5,7], manjistha [6], turmeric [5,8–10], marigold [8], chrysanthemum seed [9], locust bean seed [11], madder, buckthorn, walnut bark [12], red poppy [1], *Butea monosperma* flower [13], golden dock, cutch [14], pomegranate peel [14,15], nutshell, orange tree leaves, dyer's chamomile [15], and annatto [6,14,16] have already been investigated for textile printing.

The aim of this study was to investigate the possible use of an extract from the flower of *Impatiens glandulifera* Royle for printing, which as a natural dye, has not previously been studied for textile dyeing or printing.

*Impatiens glandulifera* Royle (of the Balsaminaceae family), commonly known as Himalayan balsam, originally native to Southern Asia (Himalayas), also known as policeman's helmet because of its hat-shaped flower, is an invasive species that is spreading rapidly across Europe and North America, causing harmful effects on native plant species by competing for space, nutrients, and monopolizing pollinators [17].

Due to the harmful spread of invasive alien plants, their removal from the natural ecosystem should be planned, including finding their new beneficial uses. They can be a

**Citation:** Klanˇcnik, M. Printing with Natural Dye Extracted from *Impatiens glandulifera* Royle. *Coatings* **2021**, *11*, 445. https://doi.org/10.3390/ coatings11040445

Academic Editor: Philippe Evon

Received: 9 March 2021 Accepted: 9 April 2021 Published: 13 April 2021

**Publisher's Note:** MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

**Copyright:** © 2021 by the author. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

source for the production of paper [18] or the extraction of natural dyes used for wood coating [19] or textile dyeing and printing. A yellow dye from the rhizome of Japanese knotweed has been successfully used for dyeing plasma-pretreated cellulosic fabrics [20], and natural dyes from the leaves of Japanese knotweed [21] and the petals of Goldenrod [22] for dyeing cationic pretreated cotton fabrics in shades of brown and light yellow. The extract of the rhizome of Japanese knotweed has also been successfully used for screen printing on papers and fabrics, where an interesting phenomenon of darkening of the prints from yellow to orange-brown on exposure to light has been observed [23].

In the present study, an extract of the purple petals of *Impatiens glandulifera* Royle was used to prepare printing inks for screen printing on fabrics and various papers. Antipruritic, anti-anaphylactic, and anti-nociceptive effects of the flowers have already been reported [24]. The use of the flower extract as a dye for human contact products may be desirable due to its medicinal properties. For printing with the low-substantive natural dye, a pigment printing paste with a binder was used as a simple alternative to today's ecologically unacceptable and mostly toxic metal salt mordants [12,15]. In pigment printing, the molecules of the natural dye are held on the fabric surface in a film of polymeric binder that adheres to the fibers [25].

The ability to print was tested on different substrates, such as cotton and polyester fabrics, two commercial papers; one made from virgin cellulose fibers and the other from recycled cellulose fibers, and two innovative papers made from different contents of the stem fibers of the invasive alien plant Japanese knotweed. The violet extract from the petals of *Impatiens glandulifera* Royle is a mixture of different types of flavonoids [24], the color of which can be altered by changing the pH. Therefore, the influence of alkali and acid additives in the printing paste on the color change of the ink, prints, and their fastness properties on different substrates was also observed. The quality of prints was determined by color measurements and fastness tests to rubbing, light exposure, and on fabrics as well as to wet ironing and washing.

#### **2. Materials and Methods**

#### *2.1. Printing Materials*

The following materials were used for printing:


#### *2.2. Printing Ink Preparation*

The natural violet dye was prepared by the National Institute of Chemistry (Ljubljana, Slovenia) by extraction from the purple flowers of *Impatiens glandulifera* Royle with 1M HCl in methanol.

For the screen printing inks, the printing paste for pigment printing was prepared according to the following recipe with ingredients from AchitexMinerva Ltd. (Vaiano Cremasco, Italy); 150 g of a self-crosslinking acrylic binder Binder SECONC, 18 g of acrylic thickener Clear MCS, and up to 1000 g of demineralized water.

The violet dye was added in six different concentrations; 0.5, 1, 2, 3, 4, and 5 g per 100 g of the prepared printing paste with pH 7.43. The violet inks from light to dark shades were obtained. To prepare an alkaline printing paste, 1 g of Na2CO3 calc. (Sigma-Aldrich, St. Louis, MO, USA) was added to 100 g of the prepared printing paste, thus raising the pH value to 8.99. To this alkaline paste, 3 g of the violet dye was then added and a bluish-green printing ink was obtained. To prepare an acidic printing paste, 2 mL of CH3COOH 60% (Carl Roth, Karlsruhe, Germany) was added to 100 g of the originally prepared paste to obtain a pH of 5.38, and then 3 g of a violet dye was mixed into the paste and a lighter violet printing ink was obtained.
