There seems to be an astounding amount of development activity related to bio-based chemical building blocks. But they have not made a significant commercial impact in the adhesive market yet.
- One reason for this is that the price of petroleum has decreased. This has lessen one of the more striking value prospects behind the overall development of bio-products – lower cost and less price volatility.
- Another reason is the lower volume of polymers used in adhesives when compared to amount of plastics used in:
- Building, and
- Consumer products sectors
The adhesive industry generally follows these other industries in the development of bio-based products.
Even so, the adhesive industry is taking reasonable, controlled steps to develop adhesive systems based on renewable sources. This calls for innovation and collaboration between the new material developers and the adhesive formulators. Commercial bio-based materials now have a place in the formulator’s toolbox along with traditional petrochemical based products.
The relationship between bio- and petrol-based products is less adversarial. This is because, the formulators see advantages to increasing the bio-content of their formulation. The development of an entirely bio-based adhesive formulation may be an attractive goal. But may not be necessary for coexistence of bio-based products with synthetic products.
This article will help you understand the value of bio-products as an alternative to more traditional petrol-based products in a clearer manner. Also, it provides with examples of fully developed bio-based products that are now commercially available. And being used in the development of practical adhesive formulations. These can be chemical building blocks or finished products such as a surfactant.
A long-view of these products will generally provide an impressive outlook on both the many types and numbers of products available. For example, the SpecialChem Adhesive selector database currently has 576 monomers, 157 polymers, and 1369 additives that are bio-based.
Biobased Monomers, Polymers, and Additives in SpecialChem Adhesive Selector Database
Bio-based products, as defined by the US Secretary of Agriculture, are commercial or industrial products that are composed in whole, or in significant part, of biological products or renewable agricultural or forestry materials. There is value in providing:
- An adhesive product that is derived from 100% renewable matter, and
- An adhesive product that is not 100% renewable but has a high bio-content
Standardized tests, such as ASTM D6866, have been developed to quantify the bio-content of a product or material.
The process by which renewable agricultural feedstock is converted into useful fractions, chemicals, and polymers have become known as “bio-refining”. Bio-refinery technologies vary depending on differences in composition and structure from one feedstock to another. They encompass physical, chemical, as well as microorganism conversion technologies.
Many building block chemicals have been identified that can be produced from vegetable oils or sugars via biological or chemical conversions. These can be further converted to secondary chemicals or families of derivatives to obtain bio-monomers. These bio-monomers produce polymers and then further formulated into adhesive compositions.
It should be noted that the modern bio-refinery is not only capable of producing the base polymers for use in adhesives and sealants, but it can also produce additives and modifiers. This will allow the adhesive formulator to create products that are significantly bio-based 100% renewable”. Developments of such “platform” chemicals for new polymers include those listed in the table below:
|Carbon Number||Chemical Building Block||Company||Potential|
|Formic acid||Maine BioProducts||Pipeline|
|2||Ethylene||Braskem, Dow/Mitsui, Songyuan, Ji’an Biochemical||Growth|
|3||Lactic acid||Purac, NatureWorks, Galactic, Henan Jindan, BBCA||Growth|
|Acrylic acid||Cargill, Perstorp, OPXBio, Dow, Arkema||Pipeline|
|Ethyl lactate||Vertec BioSolvents||Growth|
|Isopropanol||Genomatica, Mitsui Chemicals||Pipeline|
|4||n-Butanol||Cathay Industrial Biotech, Butamax, Bualco, Cobalt/Rhodia||Growth|
|Methyl methacrylate||Lucite/Mitsubishi Rayton, Evonik/Arkema||Pipeline|
|Succinic acid||BioAmber, Myriant, BASF/Purac, Reverdia (DSM/Roquette), PTT Chem / Mitsubishi CC||Growth|
|Isoprene / farnesene||Goodyear / Genencor, GlycosBio, Amyris||Pipeline|
|Glutamic acid||Global Biotec, Meihua, Fufeng, Juhua||Growth|
|Adipic acid||Verdezyne, Rennovia, BioAmber, Genomatica||Pipeline|
|Citric acid||Cargill, DSM, BBCA, Ensighn, TTCA, RZBC||Growth|
|n||PHA||Metex, Meridian Plastics, Tianjin, Green Bioscience||Growth|
|Para-xylene||Gevo, Amyris, UOP, Annellotech, Virent||Pipeline|
|Dicarboxylic acids||Cathay Biotech, Evonik||Growth|
|Fatty acid derivatives||Croda, Elevance||Growth|
Selected Example of Chemical Building Blocks from Renewable Feedstock, Suppliers, and Market Potential1
In several cases these compounds are also end-products (e.g., methanol, ethanol). But they also provide perspective as to the bio-based building blocks available for adhesive monomers, polymers, and additives.
Value Proposition for Products with High Bio-Content
Bio-based chemical building blocks are being developed and commercialized based primarily on three value propositions:
- A method of disconnecting from reliance on petroleum
- Environmental benefit not only in their manufacture but also in their disposal
- Certain bio-products exhibit improved properties over their conventional counterparts
Although oil prices have stabilized a bit in recent years, they are still well above historic norms. Also, experts believe that they will regain a strong upward trend as global demand increases and political events disrupt the market. Adoption of bio-products will also help to preserve the finite supply of oil for future generations.
- Bio-products represent an environmental benefit not only in their manufacture but also in their disposal.
- There are reduced energy consumption and greenhouse gas emissions during the manufacture of bio-polymers.
- Also, physical recycling of conventional plastics soiled by food and other biological substances is often impractical and undesirable. So reuse and recycling become problematic. Landfill for the disposal of municipal waste is limited. Bio-materials may suppress these problems by virtue of their biodegradability.
New materials including bio-products often represent a disruptive technology. They initially are high priced and can only be justified in niche markets and applications – at least until their volumes develop. Often their performance properties are viewed as being inferior to conventional products. Surprisingly, certain bio-polymers exhibit improved properties over their conventional counterparts. For example, castor oil based polyurethanes have improved hydrophobicity and provide the formulator with reduced viscosity and lower toxicity.
Conventional chemical building blocks are expected to maintain their dominant position. However, bio-based materials will likely play an increasingly important role in a society moving towards sustainable and environmentally responsible materials.
It is extremely unlikely that bio-materials will make a significant impact in displacing petrochemical based raw materials in adhesive formulations. However, a more plausible scenario foresees renewable plant resources supplementing hydrocarbon resources. Even materials that are only partly based on renewable feedstock can be a useful approach. This is especially useful if the value proposition is not degraded by high cost or inferior properties.
Consumers are also finding value in the bio-based label, which states the bio-contents of a particular product. Purchases made by government organizations and large companies are beginning to be based in part on the bio-content represented by this label.
Barriers to Bio-Products also Exist
There are also many challenges to the full-scale commercialization of bio-polymers. The most severe market barriers include the following:
- Competition with inexpensive commodity materials familiar to the consumer
- Expectation of poorer performance of bio-materials in functional products (at least in the case of early developed products)
- Recycling of certain, new bio-products may require an infrastructure and capital investment. As incorporation with currently recycled petroleum-based materials is difficult
Even with these disadvantages, there is an increased incentive to use and produce materials obtained from renewable resources. Bio-based chemical building blocks are currently a fast developing for two main reasons:
- The relatively high and variable cost of petroleum feedstock, and
- The environmental consequences of using petrochemical feedstock
However, these are both defensive positions. If the economic and environmental problems associated with petroleum-based feedstock would go away (a highly unlikely event), there would be little demand for bio-based chemical products. The recent drop in oil prices from their 2008 highs and the use of renewable feedstock for gasoline substitutes has somewhat dampened the enthusiasm for bio-materials in adhesives and sealants.
The Formulator’s Modern Day Toolbox
Modern-day adhesives are often fairly complex formulations of components that perform specialty functions. Very few polymers are used without the addition of some modifying substance such as plasticizer, tackifier, or inert filler. The selection of the actual ingredients will depend on:
- End-properties required
- Application and processing requirements, and
- Overall cost target of the adhesive
The various components that can constitute an adhesive formulation include those shown in the table below:
Commonly Used Compounds in the Adhesives Industry
Although substitution of the base polymer or binder with a material based on renewable sources will improve environmental impact, there are many other components in an adhesive system that can still detract from it being ultimately “environmentally friendly”. Many of these additives are low molecular weight petroleum-based compounds. These could migrate out of the adhesive during its service life.
Plasticizers, flame retardants, biocides, etc. have now come under considerable scrutiny. As they have been found in water sources and possibly could be detrimental to human health. As a result, there is significant effort going into the development of adhesives that have environmentally friendly additives as well as base polymers.
In an age of increasing environmental concerns, many of the tools that formulators had utilized in the past are no longer acceptable. Use of solvents has drastically been curtailed. Plasticizers must often be used in limited amounts. Regional regulations place demands that total VOC emission be kept to a minimum. Certain catalysts and additives are discouraged because of safety or health issues.
Monomers, Oligomers, and Polymers
Tables below provide examples of bio-based monomers / oligomers and polymers that are included in the SpecialChem adhesives selector database.
|Acrylates / Methacrylates Monomers||Sarbio 5000 Series||Arkema||Functional acrylates|
|Ecomer||Eccosynthetix||Sugar-based acrylic monomer|
|Photomer||IGM Resins||Lauryl acrylate based monomer|
|Acrylates / Methacrylates Oligomers||Sarbio 7000 Series||Arkema||Functional polyester-, epoxy-, and urethane- acrylates|
|EBecryl 5849||Allnex||Multi-functional, polyester acrylate|
|Diacids||Succinic acid||BioAmber||Biobased succinic acid|
|Biosuccinium||Reverdia||Biobased succinic acid|
|Diamines||Priamine 1071||Croda||Biobased, low viscosity dimer diamine|
|Diols||MEG||India Glycol||Monoethylene glycol|
|Polycard XFN 100||Composite Technical Services||Aromatic specialty polyol with primary and secondary hydroxyl groups|
|Emerox Series||Emery Oleochemicals||Aliphatic ethylene glycol azelate diols|
|Susterra||DuPont Tate and Lyle||1,3, propanediol|
|Monoacids||Levulinic ketals||GF Biochemicals||Derivatives of levulinic acid esters|
|Olefins / unsaturated||Butadiene||Glycos Biotechnologies||Olefinic butadiene monomer|
|Bio-SIM||Glycos Biotechnologies||Biologically produced synthetic isoprene monomer|
|Polyester polyol||Stepanpol BC-180||Stepan||Modified aromatic polyester polyol|
|Dynacoll Terra EP||Evonik||Range of saturated polyester polyols|
|Polyether polyol||Velvetol Series||Weylchem||Range of polyether polyols made with 1, 3-propanediol|
|Sovermol 830||BASF||Polyether-ester polyol|
|Triols||Emerox 14060||Emery Oleochemicals||Aliphatic 2900 MW ethylene glycol azelate triol|
Bio-based Monomers and Oligomers
|Epoxy||Super SAP Series||Entropy Resins||Range of epoxy systems made of liquid epoxy resin mixed with hardener|
|Vegetable based||Cardolite LITE 2100||Cardolite||Cashew nutshell liquid modified hydrocarbon resins used as an epoxy modifier|
|Dextrin||Sanstar Bio-Polymers||Polymer prepared by roasting starch in the presence of acid|
|Polyurethane||Pearlthane ECO Series||Lubrizol||Thermoplastic polyurethanes (TPUs)|
|Pearlbond ECO Series||Merqunisa (Lubrizol Group)||Series of linear, aromatic bio-polyurethane based on specialty polyols|
|Polyvinyl acetate emulsions and derivatives||Axilat HP 8538||Momentive||Biobased vinyl acetate / versatate|
The bio-content of these products ranges from about 30 percent to 100 percent. Much of the bio-based chemical building blocks are going into the high volume plastic markets for obvious commercial reasons. However, the products listed in these tables have found acceptance in the adhesive markets.
Today, bio-based polymers for adhesive formulations include primarily those based on soy and other vegetable products. However, this landscape is likely to change considerably in the future due to the customer’s desire for bio-based adhesives. Even for those having less than 100% bio-content.
Previously, the following have been described:
The development and use of bio-based polyols are, in fact, not a recent occurrence. In sealants, especially, castor oil polyols have been used to provide good hydrophobicity and low moisture vapor transmission rate. The major barriers to the widespread acceptance of these raw materials are their availability and the cost to produce them.
- Polyols made from soybean oil are beginning to be used as partial substitutes for petroleum-based polyols. It has been noted that soy-based polyols do not have the high functionality and other properties to compete head-on as direct substitutes. However, they are increasingly becoming economically competitive as costs for competing petrochemical polyols rise.
- The use of soybean protein in water dispersed adhesives. Principally to replace formaldehyde adhesives in wood composites and panels2
These applications make up the majority of the current opportunities for soy in bio-based adhesives.
Both the triglycerides and the free fatty acids in vegetable oil such as soy can be epoxidized. These can find application in higher value products such as:
- Adhesives, and
The major feedstock for this conversion is vegetable oil. Epoxidized oil is used mainly as a biodegradable plasticizer for adhesives and plastics. But, it also can be made part of a flexible epoxy resin molecule.
Bio-based Polyamides in Adhesives
- Textile interlining
- Technical textiles
- Building and construction
- Electronics, and
Following is the list of bio-based products by top Suppliers:
- Evonik Industries (Germany) has added a group of biobased polyamides to its Vestamid product line. These are based on monomers produced partly or entirely from fatty acids. The most important source is currently castor oil.
- Evonik is also forging ahead with the development of semi-crystalline polyamides . These are distinguished by high mechanical strength and good resistance to chemicals and stress cracking.
- Another new bio-based product is Platamid Renew from Arkema. This is a high performance thermoplastic hot melt adhesive. It is produced from 100% vegetable oil developed for highly demanding and durable applications. The product can be processed into web, film, and filament using standard conditions and equipment.
Development in Green Additives
There is significant effort going into the development of green adhesives. These have environmentally friendly additives as well as base polymers. The major “green” adhesive additives are the subject of this section. The focus will be on the higher volume additives that are used in adhesive formulations. Replacement of lesser used hazardous materials such as flame retardants, biocides, etc. is well covered in the scientific literature. This relates to more specialty adhesive products.3,4
Table below provides examples of bio-based adhesive additives that are included in the SpecialChem adhesives selector database. The biocontent of these products ranges from about 30 percent to 100 percent.
|Coalescing agents||ADM CA118||ADM||Low-VOC, biobased coalescent|
|Vistinol INB||Evonik||Benzoic acid isononyl ester acts as a plasticizer/ coalescing agent.|
|Crosslinking / curing agent||Desmodur eco N7300||Covestro||Biobased polyisocyanate based on pentamethylene diisocyanate (PDI)|
|Defoamers||Toynol LS-101||Tianjin Surfychem||Modified fatty amide surfactants|
|Dispersing agents||Toynol LS-101||Tianjin Surfychem||Modified fatty amide surfactants|
|Itaconix DSP 2K||Itaconix||Low molecular weight linear polytaconic acid partially neutralized with sodium salt|
|Flame retardant||Polycard XFN 53||Composite Technical Services||Renewable aromatic
|Plasticizers||Reflex Series||PolyOne||Bioderived, non-phthalate|
|Paraplex Series||Hallstar||Epoxidized soybean oil|
|Plasthall PR-A610||Hallstar||Renewable ester|
|Plasthall ELO||Hallstar||Epoxidized linseed oil|
|Vestinol INB||Evonik||Benzoic acid isononyl
|Oxiblue DOSX||Oxea||Dioctyl succinate|
|Dow Ecolibrium Series||Dow Chemical||Range of phthalate free
and lead free plasticizers
|Biocides||Dowicil QK-20||Dow Chemical||2,2-dibromo-3-nitrilopropionamide biocide|
|Reactive Diluents||Araldite DY-CNO||Huntsman||Monofunctional, aromatic
monoglycidylether of cardanol
|Araldite DY-S||Huntsman||Multiglycidylether of
polyglycerol; acts as a polyfunctional, aliphatic, epoxy resin
|Rheology modifiers||Rheolate 212||Elementis||Polyether polyurethane
resin solution in water: acts as an associative flow modifier
|Tylose H Series||SE Tylose||Range of hydroxyethyl
|Tylose MH Series||SE Tylose||Range of
methylhydroxyethyl cellulose modifiers
|Solvents||Vertec Bio ELpine||Vertec Biosolvents||Biobased, plant-derived
biodegradable green alternative solvent
|VertecBio Gold #1, #2, #3||Vertec Biosolvents||Patented blends of
vegetable esters made with soybean and corn derived ingredients
|VertecBio Gold #4||Vertec Biosolvents||Methyl soyate|
|VertecBio ELSOL Series||Vertec Biosolvents||Broad range of solvent
blends designed to replace specific petroleum based solvents
|Surfactants||Toynol LS-101 and LS-101E||Tianjin Surfychem||Modified fatty amide
|Tackifiers||KA-1000||Keeneyes Industrial||Aromatic modified terpene
|Sylvalite Endura 99||Kraton||Stabilized tall oil resin|
|Wetting agents||Toynol LS-101 and LS-101E||Tianjin Surfychem||Modified fatty amide
In recent years, environmentally safe or “green” solvents have appeared on the market. They can provide alternatives for conventional solvents when regulatory, environmental, or safety and health pressures are exerted. Many of these solvents are based on agricultural or “bio-based” feedstock. As such, they not only provide environmental benefit from their use, but they also avoid the more costly petroleum based route to production. Several of the more common green solvents that have recently been commercialized include ethyl lactate, d-limonene, and methyl soyate.
There is an increasing desire to develop plasticizers based on renewable raw materials. Compared to current petroleum derived polymers, these new products are expected to eventually offer:
- Reduced price
- Less price volatility, and
- A more favorable environmental footprint
They may also have certain application or performance properties discovered. This may further improve their commercial value.
Certain reports are coming to light that indicate that the bio-plasticizers may have functional attributes. These are of value and not available from current petroleum based products. It has been shown, for example, that one of the new bio-plasticizers (Reflex 100 from PolyOne having 94% bio-content) has significantly better performance properties compared to past industry standards, like:
- Thermal stability
- Lower plasticizer migration, and
- Improved plasticizer efficiency
Typical bio-polymers derived today from renewable sources generally lack elastomeric character. For example, renewable polymers such as polyhydroxyalkanoate or polylactic acids are not considered to have elastic characteristics and are noted for their:
- High degree of crystallinity
- High glass transition temperature, and
- Low elongation
As a result, most bio-polymers that are used in adhesive formulations require toughening agents or plasticizers to achieve greater flexibility.
Examples of natural product tackifiers are:
- Rosin acid derivatives and other esters.
- Another natural product is that based on a class of materials known as the terpenes. These tackifiers are extracted from pine trees and the paper production processes and then converted into resins. This is done with the help of distillation and further processing.
- Other, more modern bio-based tackifiers are based on citrus resources.
The adhesives industry represents a significant opportunity for the developing bio-polymers market. However, many obstacles must be overcome on the way to commercialization. To gain acceptance and supplant adhesive products derived from petroleum, industrial bio-polymers will need to be able to compete in terms of both cost and performance.
Advances in biotechnology and adhesive formulation will play a key role in surmounting these economic and technical barriers. By replacing conventional base polymer and property additives with bio-based products, formulators will project a “green” image to companies. As they are increasingly interested in promoting their use of bio-based materials.
- IEA Bioenergy, Task 42 Biorefinery, Bio-Based Chemicals from Value Added Products from Biorefineries, February, 2012.
- Petrie, E.M., “Adhesives from Renewable Resources”, SpecialChem, July 2009.
- Petrie, E.M., “Soybean Adhesives” SpecialChem4Adhesives, December 2009.
- Martin, J., “Biocides”, Adhesives & Sealants Industry, July / August 2004.
- Weil, E.D. and Levchik, S., “A Review of Current Flame Retardant Systems for Epoxy Resins”, Journal of Fire Sciences, vol. 22, January, 2004, pp. 25-40.