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.

1. 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.
2. Another reason is the lower volume of polymers used in adhesives when compared to amount of plastics used in:

• Packaging
• 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.

Monomers	Polymers	Additives
Acrylates / methacrylates monomers Acrylates / methacrylates oligomers Diacids Diamines Diols Monoacids Olefins / unsaturated Polyols Triols	Acrylates / methacrylates monomers Acrylates / methacrylates oligomers Diacids Diamines Diols Monoacids Olefins / unsaturated Polyols Triols	Coalescing agents Crosslinking / curing / vulcanizing agents Defoamers / antifoamers Dispersing agents Flame retardants / fire retardants Plasticizers Preservatives / biocides / fungicides Reactive diluents Rheology modifiers / viscosity modifiers / thickeners Solvents Surfactants Tackifiers Wetting agents

Biobased Monomers, Polymers, and Additives in SpecialChem Adhesive Selector Database

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“Bio-Based” Products

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
1	Methanol	BioMCN, Chemrec	Growth
	Formic acid	Maine BioProducts	Pipeline
2	Ethylene	Braskem, Dow/Mitsui, Songyuan, Ji’an Biochemical	Growth
	Ethyl acetate	Zeachem	Pipeline
	Ethanol	Many	Growth
	Acetic acid	Wacker	Growth
3	Lactic acid	Purac, NatureWorks, Galactic, Henan Jindan, BBCA	Growth
	Acrylic acid	Cargill, Perstorp, OPXBio, Dow, Arkema	Pipeline
	Glycerol	Many	Growth
	Epichlorohydrin	Solvay, Dow	Growth
	n-Propanol	Braskem	Pipeline
	Ethyl lactate	Vertec BioSolvents	Growth
	Isopropanol	Genomatica, Mitsui Chemicals	Pipeline
	Propylene glycol	ADM	Growth
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
5	Furfural	Many	Growth
	Isoprene / farnesene	Goodyear / Genencor, GlycosBio, Amyris	Pipeline
	Glutamic acid	Global Biotec, Meihua, Fufeng, Juhua	Growth
6	Sorbitol	Roquette, ADM	Growth
	Adipic acid	Verdezyne, Rennovia, BioAmber, Genomatica	Pipeline
	Isosorbide	Roquette	Growth
	Citric acid	Cargill, DSM, BBCA, Ensighn, TTCA, RZBC	Growth
	Caprolactam	DSM	Pipeline
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.

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Value Proposition for Products with High Bio-Content

Bio-based chemical building blocks are being developed and commercialized based primarily on three value propositions:

1. A method of disconnecting from reliance on petroleum
2. Environmental benefit not only in their manufacture but also in their disposal
3. 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.

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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.

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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:

Base resin or binder Catalysts or hardeners Catalysts Accelerators, inhibitors, and retarders Solvents Thickeners and thixotropic agents Diluents Extenders Fillers

Carriers and reinforcement Plasticizers Flexibilizers and tougheners Tackifiers Film formers Antioxidants, antihydrolysis and antifungal agents, and stabilizers Soaps, surfactants and wetting agents

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.

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Monomers, Oligomers, and Polymers

Tables below provide examples of bio-based monomers / oligomers and polymers that are included in the SpecialChem adhesives selector database.

Type	Trade Name	Supplier	Description
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

 

Type	Trade Name	Supplier	Description
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

Bio-based Polymers

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:

• Composites
• Adhesives, and
• Plasticizers

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
• Automotive

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.

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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.

Type	Trade Name	Supplier	Description
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 multifunctional polyol
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 ester
	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 cellulose modifiers
	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 surfactant
Tackifiers	KA-1000	Keeneyes Industrial	Aromatic modified terpene resin
	Sylvalite Endura 99	Kraton	Stabilized tall oil resin
Wetting agents	Toynol LS-101 and LS-101E	Tianjin Surfychem	Modified fatty amide surfactant

Biobased Additives

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.

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Conclusions

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.

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References

1. IEA Bioenergy, Task 42 Biorefinery, Bio-Based Chemicals from Value Added Products from Biorefineries, February, 2012.
2. Petrie, E.M., “Adhesives from Renewable Resources”, SpecialChem, July 2009.
3. Petrie, E.M., “Soybean Adhesives” SpecialChem4Adhesives, December 2009.
4. Martin, J., “Biocides”, Adhesives & Sealants Industry, July / August 2004.
5. 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.