Introduction
As issues relating to global warming continue to take hold across the world, reducing CO 2 emissions has become a major concern due to the significant contribution such emissions make to the greenhouse effect. In particular, industrial waste disposal relating to plastic products has grown in significance with every passing year. Biomass-derived materials have a lower environmental impact than plastic during processes such as disposal, making them worthy of discussion when considering carbon neutrality in the face of this situation. While CO 2 may be generated when biomass-derived materials are incinerated, the carbon atoms in question were already contained in CO 2 that was then converted through photosynthesis. Consequently, the effect on atmospheric CO 2 levels can be considered neutral. 11 From this perspective, products made from biomass-derived materials can be considered to be environmentally friendly. Against this backdrop, ThreeBond has developed and launched various products made using biomass-derived materials. In this article, the authors describe a selection of ThreeBond's environmentally-friendly biomass-based products. Hereafter, ThreeBond is abbreviated as TB.

= Table of Contents =

Biomass-based Products
1.
The main components of adhesives and sealants generally include resin components, filler components and additives. TB is developing biomass-based products by using biomass-derived materials for these components. The Japan Organics Recycling Association (JORA) uses the following definitions in relation to biomass-based products. 21 (1) Products that contain biomass (renewable, organic, non-fossil material from living organisms, including shells and other inorganic materials directly produced by living organisms) (2) Products with a biomass content of at least 10% Based on these definitions, biomass-based products can be developed by replacing part of existing product formulations with biomass materials. However, TB has gone beyond simply developing biomass products. It is carrying out product development with the aim of increasing use of biomass-derived materials as much as possible, and making use of the characteristics of these materials to surpass the performance of existing products. Prominent examples of products that have been created include TB1539 series elastic adhesives, TB2209 single- component low temperature curing epoxy resin and TB3049 UV-curing resin. In the subsequent sections, the authors describe the biomass materials used in each product, their biomass content, and their performance characteristics.
TB1539 Series Elastic Adhesives
2i
The TB1539 series comprises single-component, low temperature curing, fast curing elastic adhesives that feature plant-derived material as a main component. The biomass material used in this series is a castor oil modified polymer, produced by chemically denaturing oil squeezed from castor beans.
Using this castor oil modified polymer as a main component has enabled a biomass content of at least 35% to be achieved (Table 1). The TB1539 series lineup includes TB1539 and TB1539B, which differ in terms of appearance, and TB1539K, which has been developed for improved adhesion on polycarbonate (PC). In addition to having high biomass content, TB1539 series products are REACH compliant and do not use halogen compounds or organic tin compounds, compounds which have a significant environmental impact.
2-1   Castor Oil
Castor oil is a type of natural oil obtained by squeezing and refining castor beans.3) Castor beans are grown in various regions, and countries with particularly significant production include India, China and Brazil. In terms of carbon neutrality, plant-derived biomass materials can be expected to have a greenhouse effect- mitigating impact through CO 2 absorption. Ricinoleic acid is the main component of castor oil, meaning it also boasts properties such as flexibility, low temperature performance, chemical stability and electrical properties that enable the addition of various functions when it is used as a main component in adhesives.
2-2. Curing Conditions
The TB1539 series of single-component elastic adhesives can be cured by heating for a short time (as little as 1 minute) at the relatively low temperature of approximately 60°C, overcoming the long curing times that are a disadvantage of other single-component elastic adhesives. Such characteristics can reduce energy required for heating, lower costs, and result in shorter takt times. In order to achieve curing at this low temperature, the formulation contains a thermally latent curing agent that activates at approximately 60°C. An example of this curing behavior is shown in Figure 1, which shows changes in viscosity measurements with a rheometer when TB1539 is heated at a rate of 5°C/min. As the temperature approaches approximately 60°C, which is the initial reaction temperature, the viscosity rises sharply before the behavior stabilizes a short time (about 1 minute) later. Figure 1 is an example of curing behavior. The curing time may vary depending on the heat capacity of the adherend.
2-3. Properties and Characteristics
The properties and basic performance characteristics of the TB1539 series of environmentally-friendly elastic adhesives are shown in Table 2.
AF: Adhesive fracture, CF: Cohesion failure
TB2209 Single-component Low
ど
Temperature Curing Epoxy Resin
TB2209 is a single-component epoxy resin containing scallop shell in its formulation and can be cured at low temperatures. With scallop shell as the biomass-derived material, it achieves a biomass content of at least 40%. It provides the same or greater adhesive strength compared to TB2202, TB's standard low temperature curing type epoxy resin, while also providing environmental benefits.
3-1. Scallop Shells
Scallops mainly feed on marine plants, which absorb atmospheric CO 2 through photosynthesis. As a result, as scallops grow based on this marine plant-based diet, this carbon is transferred from the plants to the scallops and stored. * Atmospheric carbon (CO 2 ) that is absorbed and stored in marine ecosystems is known as blue carbon. This is mainly produced through photosynthesis by organisms such as seaweed, seagrass and phytoplankton. 41 While CO 2 is released when the shells are incinerated, this can be considered the same atmospheric CO 2 that was absorbed during each shell's development. As such, there are no new CO 2 emissions from a carbon neutrality perspective.
3-2. Curing Conditions
Figure 2 shows the relationship between curing time and tensile shear bond strength for TB2209 at different temperatures. Curing can be performed at a low temperature of 80°C × 60 minutes and high temperatures of 100°C × 30 minutes or 120°C × 10 minutes. Even with adherends that are sensitive to heating, curing can be performed in a short time at 80°C.
3-3. Properties and Characteristics
Tensile shear bond strengths for various adherend materials are shown in Table 3. Properties and basic performance characteristics are shown in Table 4.
(TB2202) Testing method: 3TS-4100-011 * Material failure
* Curing conditions: 80°C × 60 min (TB2209), 70°C × 50 min (TB2202)
4.
TB3049 UV-curing Resin
TB3049 is a UV-curing resin that uses plant-derived raw materials as its main component. The biomass materials are derived from pine resin and soy beans, and the product has a biomass content of at least 45%.
4-1. Pine Resin and Soy Beans
Pine resin is natural resin discharged by plants in the genus Pinus of the family Pinaceae. It mainly comprises turpentine and rosin. Soybean oil is extracted from soybean seeds and is one of the most well-known plant oils. UV curable acrylic acid is added to compounds refined from these materials to create the base materials for the product.
4-2. Curing Conditions
TB3049 can be cured using UV-LEDs. UV-curable resins can be broadly divided into those cured with high- pressure mercury vapor lamps and those cured with UV- LEDs. TB's UV-curable resins are generally designed to be cured with high-pressure mercury vapor lamps. However, some products can be cured with UV-LEDs. Against this backdrop, demand for UV-LED curing has grown in recent years in consideration of energy saving and reducing running costs, and TB3049 is an environmentally-friendly product in terms of its design. Curing with UV-LEDs enables power consumption to be reduced compared to high-pressure mercury vapor lamps, meaning that customer-side processes also become more environmentally friendly.
*² Curing conditions: High-pressure mercury vapor lamp (30 kJ/m²) *³ Curing conditions: UV-LED (365 nm), 500 mW/cm² × 6 sec
4-3. Properties and Characteristics
The properties and physical characteristics of TB3049 are shown in Table 5. Data for TB's general-purpose UV- curing resin TB3042B is also shown as a comparison. TB3049 was developed with the aim of replicating the properties and physical characteristics of TB3042B. This makes TB3049 a versatile resin. In addition, while TB3042B does not support UV-LED curing, TB3049 can be cured to at least 2 mm with UV-LEDs.
4-4. Adhesive Strength of TB3049
The adhesive strength of TB3049 on various adherend materials when cured with a high-pressure mercury vapor lamps and UV-LEDs is shown in Figures 3 and 4. The adhesive strength of TB3042B when cured with a high-pressure mercury vapor lamp is also shown for comparison. Both TB3049 and TB3042B demonstrate good adhesive strength on various materials. TB3049 also exhibits higher adhesive strength than TB3042B for some materials. Even when TB3049 is cured with UV-LEDs, it demonstrates similar adhesive strength to curing with high-pressure mercury vapor lamps. It can be used for wide-ranging applications in various locations.
4-5. Expected Effects in Terms of Reduction of
Environmental Load
One of the effects that can be expected when using TB3049 is a reduction in CO2 emissions. Focusing on CO2 emissions during incineration, substantive CO2 emissions for products made using biomass materials are lower than for those made exclusively from petroleum-derived raw materials (Figure 5). TB3049 has a biomass content of 45%, meaning it is 45% naturally-derived material. Based on the aforementioned approach, a reduction of approximately 45% can therefore be expected. 51 This product can also be cured with UV-LEDs. Calculations showed that CO 2 emissions from the power consumption during UV-LED curing were about 1/10 those produced when using high-pressure mercury vapor lamps (Figure 6). As a result, a reduction in environmental impact can be expected. 69
Closing
In this article, the authors described TB's work on biomass-based products. TB is also reviewing the biomass content of materials used in its existing products to evaluate their environmental impact and is examining the use of biomass in manufacturing containers for products. TB aims to contribute to technological innovation in global industry and environmental conservation by focusing on product and technology development in line with market trends. It will also continue to ensure that it provides safety and peace of mind to all stakeholders through its business activities. <References> l) "Biomass Plastic", Japan Organics Recycling Association website: https://www.jora.jp/faq/questions/bioplastic-plastic/ 2) "Biomass Mark Business Standards", Japan Organics Recycling Association website: https://www.jora.jp/biomassmark/info/ 3) Abe, Y., ed. Fats and Oils Handbook , p.290, Saiwai Shobo 4) “Blue Carbon to ha” (lit. “What is Blue Carbon?”), Ministry of Land, Infrastructure, Transport and Tourism (Government of Japan): https://www.mlit.go.jp/kowan/kowan  tk6  000069.html 5) Ministry of the Environment website (Government of Japan): https://ghg-santeikohyo.env.go.jp/files/calc/itiran_2020_rev.pdf 6)Keisan Online Calculator website: https://keisan.casio.jp ThreeBond Co., Ltd.  R&D Group Electronics Market Department, Product Development Division Il Shotaro Mano Koki Mihashi Mitsuhiro Kaneta Industrial Market Department, Product Development Division III Haruka Hanochi Kuniyasu Asai ● ThreeBond is a trademark or registered trademark of ThreeBond Holdings Co., Ltd.