Eco-friendly Alkyd Resins Based on Vegetable Oil: Review

The alkyd resin industry currently needs environmentally friendly raw materials, which emphasized the aspect of sustainability. Alkyd resin is a polymer product with oil as raw material which is widely used in the paint, coating, and other industries. The abundant demand for alkyd resin has led to a diversification of the raw material for alkyd resin from vegetable oils. The advantages of vegetable oil include being a renewable energy source for industry, sustainability, biodegradability, and being environmentally friendly as important considerations for the industry in recent times. This paper examines alkyd resins derived from several vegetable oils that are environmentally friendly. Alkyd resin is prepared by alcoholysis and esterification. Based on several studies of alkyd resins, there have been many modifications to the raw materials, technology, and catalysts used which can refer to an environmentally friendly and affordable industry.


Alkyd Resin Raw Material
Alkyd resin production using vegetable oil as raw material results in a product that matches its utilization. Alkyd resins are divided into 3 types, namely Long Oil Alkyd (LOA) containing 56% fatty acids, Medium Oil Alkyd (MOA) containing 46-55% fatty acids, and Short Oil Alkyd (SOA) containing less than 35-45% fatty acids (Ploeger and Chiantore, 2012). Table 1 shows the process of making alkyd resin from different raw materials.

Alkyd Resin from Linseed Oil
Linseed oil is produced from the hemp plant and belongs to the drying oil group.
Linseed oil is often used in the coating industry to increase flexibility and speed up varnish drying (Sutanti et al., 2013). Linseed oil contains a lot of linoleic acids which has properties of unsaturated acid and cannot be reacted with acids unless preceded by alcoholysis first (Wibowo, 2013). Studies of alkyd resins with linseed oil have also been carried out by Godfrey et al. (2019).
In the initial stage, the oil was reacted with glycerol at a temperature range of     Soybean oil used by Kyenge et al. ( 2012) in their experiment has specific gravity of 0    The use of vegetable oils in the alkyd resin industry is as a drying agent. Oils that are suitable for drying are the highly unsaturated ones that will undergo oligomerization or polymerization when exposed to oxygen in the air, generally with the addition of a catalyst. (Derksen et al., 1996). Alkyd resins from vegetable oils have been the focus of many research to develop. The production of alkyd resins with vegetable materials has met the eco-friendly aspect because without the formation of chemical by-products, waste can be processed, and the exploitation of nonrenewable resources can be avoided. So, in principle, oil production has proven to be technologically feasible and able to replace fossil raw materials (Lligadas et al., 2013). analyze the process stages in situ to streamline the process of making alkyd resins.
Another approach to the alkyd resin development process could be to use drying or non-drying oil in layers as paint.
In situ transesterification or alcoholysis are a technology for the oil extraction process and the esterification or transesterification reaction which is carried out simultaneously where the oil extraction process and the esterification or transesterification reaction are carried out in one reactor. (Haas et al., 2004). The in situ process begins with the contact between the alcohol and an acid or alkaline catalyst. Then the alcohol enters the cell and destroys the parts of the cell and then dissolves the oil contained in the raw material.
The extracted oil reacts with alcohol to produce alkyl esters with the help of an acid or base catalyst. So that the production process can shorten production time, be efficient, save energy and produce high quality biodiesel (El-Enin et al., 2013).

Conclusions
Vegetable oils are abundant and environmentally friendly, so they are suitable to be used as raw material for alkyd resins.
Vegetable oils can generally be used as raw material for polymers because they contain lots of triglycerides, drying oil and non-drying oil. To streamline the process of making alkyd resin, it is necessary to study the raw materials that are not used simultaneously with the food industry, technology and catalysts used which can refer to industries that are environmentally friendly and affordable.