THE SIGNIFICANCE OF NATURAL PIGMENTS USAGE TO PRODUCE INDUSTRIAL PAINTS: A SYSTEMATIC REVIEW

: Paints have been known since ancient times and have developed over time. They are evolving and are no longer used only for aesthetic purposes and can be used for protection. With globalization, there has been considerable growth in this sector, bringing the need for new products and technologies. Due to this evolution, products that harm the environment, the population health and generate harmful waste show up. So, there has been the need to produce raw materials that do not harm the environment and do not jeopardize the well-being of humans. This study conducts a systemic review on pigments for automotive paints and natural dyes extracted from animals, also addressing the impact on the environment.


INTRODUCTION
Paint is a liquid or powder product that, when applied on a substrate, forms an opaque film with decorative protective characteristics or techniques [1]. Known since the ancient times they have developed over time. In the 19th century, organic coatings emerged, considered the greatest diffusion, but it was only in the last century that the great technological development of coating compositions and raw materials occurred, and paints started to be used also for protection, especially in places where climatic conditions were more severe [2;3].
The Brazilian paint market is already consolidated. Although they often go unnoticed, paints are essential products wherever you go or in any manufactured item, e.g.: vehicles, bicycles, toys, home appliances, clothing, equipment, crafts, printing, serigraphy and construction, thus surpassing the mark of one billion liters of paints produced annually [4].
The main applications of paints are in the architectural paints market, also called decorative or real estate line, which is one of the most important segments for the paint industry. Also, the market for automotive painting and refinishing, coating for plastics and industrial maintenance [2].
Environmental protection need has also become an essential theme in the paint development sector. Processes are being studied and used that can allow and considerably reduce aggression to the environment and those who handle it. Among the main developments there is a reduction or elimination of products considered toxic in the composition of the paints.

Paints Composition
Regards coating concept perspective that meets all application requirements, different materials are used in a combined manner, in different quantity and presentation. Each of these components has specific functions and behaviors that assigns specific characteristics to the paints [4]. These materials that compose the paint can be grouped into four categories as shown in Table 1

Dye
Dyes are substances or a mix of substances that has the property of conferring or intensifying the products colors [11]. Colors are added to products for leastways three reasons: 1) to restore original appearance of the product after production storage and packaging process steps; 2) to make the product visually more attractive and 3) reinforce the colors already existing. The main types of existing dyes are shown in the table 3. There are several natural dyes types, among them we can highlight cochineal dye, produced from the bodies of Dactylopiidae female insects of the cochineal. There is evidence of its use since the tenth century. Various studies have shown that tunics and gowns were dyed with cochineal at the pre-Columbian time [10].
Currently, there is a wide cochineal application due to miscellaneous range of the red and other colors replacing synthetic dyes. This dye is stable to light, heat and the presence of oxidizing agents, it has the property of linking itself with proteins, which makes it useful in coloring milk-based products, such as yogurt, ice cream, milk drinks, meat products and biscuits, jellies and beverages, as well as pharmaceutical and textile coatings [11].

Characteristics Pig. Organic Pig. Inorganic
Thermal Resistance Medium to Low High

Dyeing Power
High Low

Density
Low High

Variety of Colors
High Limited

Type of Dye Obtainment
Organic Natural From vegetable, or possibly from animal, whose coloring principle has been isolated using an appropriate technological process.

Synthetic organic
By organic synthesis using a process appropriate technological: 1 -Artificial dye -synthetic organic dye not found in natural products; 2 -Synthetic organic dye identical to natural -whose chemical structure is similar to that of the active ingredient isolated from natural organic dye.

Inorganic
From mineral substances and submitted to elaboration and purification processes appropriate for its application.
The first stage of this systematic review is to systematize questions that will guide the survey of top publications. This study was guided by the following guiding questions: P1) How important is cochineal for use as a natural dye? P2) What are the most used types of pigments in automotive paints? P3) Is there any study about the pigment obtained from natural extraction to use in the industrial paints? After questions definition, the second stage began, which was the search process in the Google Scholar and Science Direct repositories, during the months of September 2019 to June 2020. Descriptors and combination used were: "Cochineal", "Pigment types", "Carminic acid"; "Automotive paints"; Industrial Paints. Criteria to study inclusion were: Portuguese, English and Spanish language without a defined period. Publications without a focus on complex projects, reviews, training materials were not considered.
In the stage 3 is compose of evaluation through qualifying questions with their respective weights of the publications resulting from stage 2. The question and respective weights were: P1) Foundations about cochineal / pigments? (weight 2); P2) Discuss about innovation and new applications of the pigments? (weight 1); P3) Discuss about development of new markets for cochineal / pigments? (weight 1); P4) Production process of the cochineal dye and pigment for automotive paints? (weight 1). Each question was answered according to notes: 1(meet), 0.5(meet partially) and 0(do not meet). Thus, papers with a total score greater or equal than 4 or whose P1 score is equal to 1 were selected as relevant.
The overview of the systematic review is showed in the Figure 1.  Table 4 shows the results found by stages 1 and 2 defined in the methodology: 381 publications were found associated with the descriptors from September 2019 to June 2020. Step 1 of the table consists of applying the inclusion and exclusion criteria (Portuguese, English and Spanish language published without a defined period), step 2, the terms of identification were sought in the title and summary, resulting in 37 publications and in step 3, only materials whose methodology and analysis were related to the proposed theme were considered, culminating in 24 publications. ISSN: 2357-7592  Table 5 shows the results of the publications after the answers to the qualifying questions and in table 6 the publications that obtained satisfactory notes are presented. Table 5. Qualification of publications selected by step 3. Source: The Author Table 6. Validation of publication quality. Source: The Author

RESULTS AND DISCUSSION
In the selected materials, it was understood the clear difference between dyes and pigments. Pigments is insoluble in the medium in which it's applied and dispersed as solid particles or crystals, whereas the dyes are soluble in the applied medium forming a molecular solution [6]. The classification according to chemical aspect between dye and pigment is shown in Table 7. In summary, in addition to color,

Repositories
Step 1 Step 2 Step pigments, when used properly in paints, provide opacity, coverage and dyeing, while the dye only gives the color. Dyes is used in the most varied segments of the industry, such as textiles, leather goods, paper, food, cosmetics, commercial paints and plastics. Pigments is mainly used in the paint, plastics, ceramics, automotive, marine, cosmetics and other industries. It was not found in the analyzed publications the direct application of a dye from animal extraction or from plant, being used as a pigment for automotive or industrial paint to coat metallic and plastic substrates. However, all the publications expressed a need for studies about this development in general since the need for more sustainable products that least harm the environment is being requested. There is a publication with a proposal to study the physical-chemical and biological properties of a bacterial pigment [12]. In another, the prospecting of pigments produced by cochineals in food, pharmaceutical, cosmetic and textile segments is demonstrated massively, ceasing to be only a red dye and being able to have other tones of red and even other colors changing only the pH [13].
The largest cochineal centers production is found in the semi-arid areas of Peru, Bolivia, Chile, the Canary Islands (Spain) and Mexico. Peru leads the world production with 85% of that market. Regarding cochineal carmine, the main importer is Germany, with 19%, followed by Brazil with 10% [14]. Also, it was found a publication showing the tinting power of carminic acid. Due to this, in the last 10 years, the use of this type of dye has increased the demand by almost 150% [14]. Studies have advanced in order to innovate processes to increase production capacity and market for cochineal dye [10].
In pigments publications, it has shown that the strong trend towards natural and more sustainable products contributes to the increase of organic pigments in the composition of paints. This is because in addition to being low toxicity raw materials, it has several benefits in its use in the paints formulation, such as high tinting power, color diversity, high chromaticity, brighter, pure, intense and transparent colors, good weather resistance, excellent saturation, chemical and thermal resistance, durability, among others when compared to inorganic pigments [3] [5]. Organic pigments publications cite as the most important yellow, orange and red azo pigments, blue and green copper phthalocyanines, quinacridones, indanthrones, flavantrones, quinophthalones, pyazo-quinazolones and perylenes. Perylenes from the polycyclic group pigments have wide application in the automotive industry for painting metals and plastics due to the excellent fastness to light, weather, solvents and temperature [6].

CONCLUSION
The analyzed publications pointed out a lack of studies on the extension of use of the natural colorant cochineal in industrial paints. The research related to this dye has basically focused on three areas: formulation and processing technology and alternative sources of pigments. They have proven to be successful and have contributed to the increase in the use of natural dyes in the food and beverage industry that already uses it. However, due to the demand for sustainable products, there is an increase in the use of organic pigments as it is non-polluting materials, also aiming to overcome some limitations of natural pigments in industrial paints. Scientific advances in chemical synthesis allowed the industrial production of many paints with that pigment in its structure.