Technical Area

The invention relates to poly (vinylphosphonic acid-co-vinyl imidazole) copolymers developed for the production of flame retardant materials to be used in areas such as textile, building -construction, cable and wire production, electrical and electronic equipment, transportation and automotive.

State of the Art

Today, many sectors are trying to take measures to protect themselves from the effects of flame and heat. One of the most important developments for this purpose is to produce flame retardant materials. By using various additives in the technical field, it is aimed to provide flame retardant (FR) properties to the final product.

The documents identified in the patent and literature search for the state of the art are summarized below.

The international patent application with the publication number WO 2021151493 A1 relates to chemical compositions used in textiles, furniture and construction to provide flame retardant properties. According to the document, the said chemical composition comprises a flame-retardant compound, surfactant, binder and organic salt. However, the document does not specifically mention the use of poly(vinylphosphonic acid-co- vinyl imidazole) copolymers. At the same time, the reaction conditions and chemicals also differ.

The Chinese patent application with publication number CN111423771 A discloses a polymer with flame retardant properties and a method of manufacturing the coating provided thereby. The document does not specifically mention the use of poly(vinylphosphonic acid-co-vinyl imidazole) copolymers.

Consequently, due to the above-mentioned problems and the inadequacy of the existing solutions, it has become necessary to make an improvement in the relevant technical field.

Brief Description of the Invention

The present invention relates to poly(vinylphosphonic acid-co-vinyl imidazole) copolymers suitable for the production of flame retardant materials, which meet the above-mentioned requirements, eliminate all disadvantages and bring some additional advantages.

The invention is inspired by the current state of the art and aims to solve the above- mentioned problems.

The main purpose of the invention is to develop a copolymer suitable for flame retardant materials the production to be used in areas such as textile, buildingconstruction, cable and wire production, electrical-electronic devices, transportation and automotive. Thanks to the invention, poly(vinylphosphonic acid-co-vinyl imidazole) copolymer can be used directly or indirectly as an additive in the production of materials in the aforementioned fields and provides a flame retardant effect.

The structural and characteristic features and all advantages of the invention will be more clearly understood with the detailed description given below, and therefore the evaluation should be made by taking this detailed description into consideration.

Figures to Help Understand the Invention

Figure 1 shows the Fourier transform infrared spectra (FT-IR) of the structure of the synthesized product.

Figure 2 shows the SEM image impregnated on the fabric. Figure 3 shows the SEM image of the polymer after it was impregnated on cotton fabric and burned.

Figure 4 shows the SEM image of the fiber analyzed from the fabric sample.

Figure 5 shows the radicalization mechanism of halogen-free phosphorus-containing flame retardants.

Figure 6 shows a schematic representation of a polymer combustion cycle.

Detailed Description of the Invention

In this detailed description, the preferred embodiments of the poly(vinylphosphonic acid-co-vinyl imidazole) copolymers suitable for the production of flame retardant materials, which are the subject matter of the invention, are described only for a better understanding of the subject matter.

The invention relates to poly(vinylphosphonic acid-co-vinyl imidazole) copolymers for the production of flame retardant materials to be used in areas such as textile, building and construction, cable and wire production, electrical and electronic equipment, transportation and automotive applications. These poly(vinylphosphonic acid-co-vinyl imidazole) copolymers can be used directly or indirectly as additives. In this way, flame retardant properties are added to the final product. In the production process, values such as temperature, time and pressure are determined separately in order to impart flame retardancy.

In the invention, poly(vinylphosphonic acid-co-vinyl imidazole) copolymer is added to textile material, building - construction material, cable and wire material, electrical- electronic material, transportation material, automotive material in order to provide flame retardancy. The products in which poly(vinylphosphonic acid-co-vinyl imidazole) copolymer is used are not limited to those listed above. The preferred poly(vinylphosphonic acid-co-vinyl imidazole) copolymer by weight for the mentioned areas of use is 10%. The poly(vinylphosphonic acid-co-vinyl imidazole) copolymer can be in the range of 1-20 wt%. The production temperature is between 20 and 180 ID and the production time can vary between 1 minute and 2 hours. Synthesis and Characterization of PolvfVinylphosphonic Acid-Co-Vinyl Imidazole)

Vinylimidazole (VI) and vinylphosphonic acid (VPA) in the same monomer ratios (1 :1) were placed in a hot water jacketed glass reactor, dibenzyl peroxide was added as an initiator and the reaction was continued at 70 ID f or 3 hours. As a result of the reaction, a dark yellow coloured flame retardant product was obtained.

Poly(Vinylphosphonic Acid-Co-Vinyl Imidazole) can be synthesized both in solvent (toulene, water, benzene, methanol, etc.) and in solvent-free environment.

The same results were obtained by changing the monomer ratios. These ratios are in the range of VI/VPA 1 :99, 99:1 in moles.

The structure analysis of the synthesized copolymer was elucidated by FT-IR and SEM. The structure of the product was characterized using Fourier transform infrared spectra (FT-IR) (Figure 1).

After combustion, there are charring residues on the fabric and fiber breaks as shown in Figure 3. The SEM image of the fiber analyzed from the fabric sample is given in Figure 4.

The LOI test results of the fabric impregnated with FR are given below:

Test Name : LOI (Limit Oxygen Index)

Related Standard: TS 11162-2 EN ISO 4589-2:2001

Conditions: 20±2 O, 65±4%RH

The LOI test of 30 fabric samples showed a value of 31.4 (+/- 3 margin of error). Selfextinguishing was observed in the fabric sample. When the articles in the literature are examined; Zhang et. al. (2020) synthesized a new aminoethylpiperazine spirocyclic pentaerythritol bisphosphonate functional heptamethyltrisiloxane (ASPBH) for modified flame retardant cotton fabrics and applied it to the fabric and examined its combustion behaviour. The LOI value was found to be 27.2% in 100% cotton fabrics.

Rao et. al. (2021) synthesized an environmentally friendly halogen and formaldehyde- free structure consisting of ammonium polyphosphate (APP), sodium alginate (SA) and tetraethoxysilane (TEOS) for fabrics using sol-gel method. In the resulting cotton fabric, a high LOI value of 31% was obtained in the vertical combustion test.

Xie et. al. (2013) treated cotton fabric using chemicals containing boric acid and 2,4,6- tri[(2-hydroxy-3-trimethyl-ammonium)propyl]-1 ,3,5-triazine chloride (Tri-HTAC) as nitrogen source. The flame retardant properties of the treated cotton fabrics and the synergistic effects of boron and nitrogen elements were determined as 27.5 by LOI measurement.

Most materials are highly flammable due to their chemical structure and organic composition. Due to the presence of nitrogen and phosphorus in the structure of the monomers (vinyl imidazole and vinyl phosphonic acid) used in the synthesized copolymer, char formation occurs during combustion and the flame is dampened. With the synthesized flame retardant polymeric material, it is provide self-extinguishing by preventing ignition by reducing the amount of limit oxygen. Combustion is a complex physical and chemical process and therefore several mechanistic principles act simultaneously and consequently it is difficult to identify one dominant mechanism. In general, the gas phase and the solid, where charring occurs, have been recognized as the primarily effective mechanism of flame retardancy.

The self-sustaining combustion cycle takes place in two phases: condensed and gaseous phases. Fire retardants reduce the rate of chemical and/or physical processes occurring in one or both phases, leading to flame extinction.

The flame retardancy of phosphate occurs in two different ways. It either forms a carbon layer in the solid phase or it occurs in the gas phase, dampening the flame. The first step takes place in the gas phase. The basic condition of the reaction mechanism in the gas phase is that phosphorus-containing compounds react with oxygen in the structure of polymers in the solid phase to form the pyrolysis reaction. The first step takes place in the gas phase. Flame retardants (FR) show their activity by releasing non-flammable gases into the flame zone area to reduce the heat and oxygen levels responsible for flame spread. When polymers containing mineral fillers as FRs are exposed to heat or flame, the mineral fillers begin to decompose and release nonflammable gases such as CO ₂ , water, SO ₂ and some acids, resulting in a reduction of oxygen content and cooling of the flame zone.

In the last step of the pyrolysis reaction of phosphate, pyrophosphate structures are converted into phosphoric acids, releasing water molecules. These water molecules dampen the flame and inhibit the gas. The second step takes place in the solid phase. The phosphoric acids formed in the first step act as catalysts and attack the phosphoric acids in order to prevent the flame from advancing. The radicalization reaction is given in Figure 5.

REFERENCES

● Rao, W., Shi, J., Yu, C., Zhao, H. B., & Wang, Y. Z. (2021). Highly efficient, transparent, and environment-friendly flame-retardant coating for cotton fabric. Chemical Engineering Journal, 424, 130556.

● Xie, K., Gao, A., & Zhang, Y. (2013). Flame retardant finishing of cotton fabric based on synergistic compounds containing boron and nitrogen. Carbohydrate polymers, 98(1), 706-710.