Polytrimethylene Terephthalate

Polytrimethylene terephthalate (PTT) is a newly commercialized aromatic polyester generally made by the melt polycondensation of 1,3-propanediol and terephthalic acid (figure 1). Bio-based polytrimethylene terephthalate is produced from the renewable sources such as sugarcane or corn rather than being derived from the petrochemical feedstocks. Bio-based polytrimethylene terephthalate has better environmental credentials as compared to the petroleum based polytrimethylene terephthalates because it does not generate carbon emissions, greenhouse gases or air pollutants during its production process.

Fig. 1 Chemical structure of polytrimethylene terephthalate

Synthesis of Bio-based Polytrimethylene Terephthalate

There are two main methods for the preparation of bio-based polytrimethylene terephthalate: transesterification and direct esterification, as shown in figure 2. The difference between the two methods mainly lies in the first step. As for former method, the oligomer intermediate is obtained by using the transesterification of dimethyl terephthalate (DMT) and with 1,3-propanediol. While in direct esterification, terephthalic acid (TPA) reacts with 1,3-propanediol to form the oligomer intermediate. Polytrimethylene terephthalate is then synthesized by polycondensation reaction of the oligomer intermediate. Due to the high cost of transesterification reactions (both the material and the production process), the direct esterification is absolutely dominant in industrial production. As a result, the bio-based terephthalic acid and 1,3-propanediol are of particular importance.

Fig. 2 Synthetic pathway of bio-based polytrimethylene terephthalate (bio-based PTT).
(a) transesterification and (b) direct esterification

• Synthesis of bio-based terephthalic acid

Bio-based terephthalic acid can be synthetized through different methods: the iso-butanol method, the muconic acid method, the limonene method or the furfural method. For instance, furfural is an ideal biomass resource, as it is traditionally produced from cellulosic and waste biomass such as corncob, corn stock and rice hull. Another advantage of using furfural is that it can be readily converted to other useful chemicals due to its high reactivity. Figure 3 represents the synthetic route to bio-based terephthalic acid from biomass-derived furfural ^[1].

Fig. 3 Synthetic route to bio-based terephthalic acid (bio-based TPA) from biomass-derived furfural

• Synthesis of bio-based 1,3-propanediol

The first description of the fermentation of glycerol to 1,3-propanediol dates back to the end of the 19th century. Essentially, there are two enzymatic activities directly involved in the conversion of glycerol to 1,3-propanediol: glycerol dehydratase and 1,3-propanediol oxidoreductase. The representation of the metabolic pathway from biomass to 1,3-propanediol is showed in figure 4.

Fig. 4 Representation of the metabolic pathway from biomass to 1,3-propanediol
A) Glycerol dehydratase, B) 1,3-propanediol oxidoreductase

Applications

Because of its lightweight and degradability, bio-based polyethylene terephthalate is used in the packaging of food products, soft drinks, alcoholic beverages, cosmetics, pharmaceutical products, and edible oils. Besides, it can be used in textile, automotive, film and coating, consumer goods, industrial electrical & electronics, etc.

Fig. 5 Typical applications of bio-based polytrimethylene terephthalate

Growing demand for bio-based and recyclable solutions in the packaging sector coupled with rising awareness among consumers regarding the benefits of bio-based products is anticipated to boost the growth of the polytrimethylene terephthalate market over the forecast period.

Our Bio-based Polytrimethylene Terephthalate

Our polytrimethylene terephthalate polymer is made using bio-based 1, 3-PDO as main raw material. The inherent 3D spiral-shaped molecular structure of polytrimethylene terephthalate endows the fiber with excellent elasticity. It can be used in i) filament fiber and short fiber, endowing fabric and garments with unique performance; ii) carpets for houses and businesses which are soft and resistant to abrasion and stains; iii) down-like fillings, the best choice for down jackets and beddings; iv) engineering plastics.

Alfa Chemistry is a professional supplier of bio-based polytrimethylene terephthalate. For high quality products, professional technical service, use suggestion and latest industry news, please feel free to contact us.

Reference

1. Tachibana, Y., Kimura, S., & Kasuya, K. Synthesis and Verification of Bio-based Terephthalic Acid from Furfural. Scientific Reports, 2015, 5(1).

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