gilsonite is unique natural resin

Gilsonite is a Unique Natural Resin

ABSTRACT

GILSONITE has been used successfully for many years in sealant and adhesive products. These applications were restricted to products that could utilize the inherent variability of GILSONITE. Now with new production technology and quality control, this unique natural resin can be considered as a substitute for synthetic resins at a fraction of the raw material cost. Example formulations are presented which use GILSONITE to provide cost effective products. Included in the examples presented are GILSONITE/heat reactive systems and water based products. These suggested formulas are given to show trends and are not intended to represent final products. Cost and performance data are also presented. Information for the use of GILSONITE in the formulations as a substitute for synthetic resins is presented. The effective use of this unique natural resin in high performance applications is based on the consistent high quality of GILSONITE.

INTRODUCTION

GILSONITE is a natural resin which is one of the asphaltites, a mineral class of natural asphaltlike substances. These materials are characterized by high softening points (above 110°C). Other members of this class include glance pitch and grahamite (1). The origin of GILSONITE is still in question; however, there is a strong relationship between the alkyl porphyrins found in GILSONITE and those present in many petroleum compounds found in the Green River Formation (Eocene, Uinta Basin, Utah). These studies suggest that the porphyrins present in GILSONITE were formed as a result of mild thermal reductive degradation of naturally occurring chlorophylls (2,3,4).

The only commercial sources are found in northeastern Utah. GILSONITE in these deposits occurs in vertical veins up to 1500 feet in depth and 15 to 20 miles in length. These veins range in thickness from a few inches to approximately 20 ft. The GILSONITE ore is 98 to 99.9% pure, with only a small amount of inherent ash. Selectively mined ore is brought to the surface and processed to remove ash, reduce the moisture level, and produce the required particle size. Much effort has been devoted to the production of a consistently pure product with reproducible properties. This was made possible in part by design and construction of a processing plant and large scale segregated storage which is unique to the industry .

PROPERTIES

The data presented is somewhat contrary to existing information; however, these data are based on current state of the art analytical instrumentation and methods. The physical and chemical characteristics of GILSONITE are important to anyone wishing to formulate products that utilize its resinous properties. Recently these characteristics have been examined to obtain a better understanding of the chemical nature of GILSONITE. Several grades of GILSONITE are produced but the general chemical properties do not vary significantly between grades.General properties of GILSONITE resins are given in Table I, where the characteristics of typical resins are listed.

The data presented in Tables II through V were based on GILSONITE 350 grade. GILSONITE is graded by its ring and ball softening point value. This information is presented to provide a better understanding of the chemical nature of GILSONITE. This could be of particular importance when considering reactive formulations.

Table II shows the elemental composition of GILSONITE. It is important to note that there is a significant amount of nitrogen present in GILSONITE. This is higher than the amount normally found in asphaltic type compounds and is possibly one of the reasons for the difference in behavior between GILSONITE and asphaltic compounds.

Data given in Tables II and III, where the H/C atomic ratio and the carbon-13 NMR data are presented, support the idea that there is a significant aromatic fraction present in GILSONITE. Previously it was thought that GILSONITE had a very low aromatic content and little conjugation. The NMR data also indicates that there are a number of linear side chains with lengths up to 5 carbons. These conjugated ring systems could account for the stability of GILSONITE products under normal conditions of manufacturing and use.

The molecular weight of GILSONITE is given in Table IV as determined by vapor pressure osometry (VPO). Two different solvents; toluene and pyridine were used. These solvents were selected to measure the degree of association of GILSONITE in solution. Pyridine would tend to inhibit this association
while toluene would not. Since this is a number average method, then dissociation into a larger number of units would give a lower molecular weight, which is the case.

When the data in Tables II, III, and IV are combined, then the average number of atoms per molecule can be calculated. The results of these calculations are given in Table V. There are several nitrogen and oxygen atoms per molecule which when used with the results of the FTIR analysis could give a better understanding of the structure of GILSONITE.

Functional group analysis by FTIR of GILSONITE dissolved in methylene chloride showed the presence of pyrrolic (>NH), phenolic (-OH), and carbonyl (>C=0) groups. The carbonyl absorption is characteristic of the type found in amides. This is supported by the presence of the pyrrolic groupings. Since the oxygen content is lower than the nitrogen and there are phenolic groups present which also uses oxygen, then there would be a significant portion of the nitrogen available to form basic compounds. This is supported by the fact that GILSONITE reacts with HCl to form a toluene insoluble fraction. Typically this precipitate weighs 50 to 60% of the GILSONITE sample weight, which would indicate a large basic nitrogen fraction. In addition, if the acid number is used to calculate the number of acid sites there would be a 0.12 per molecule. Thus only a small portion of the oxygen would be required to produce the phenolic groups. Therefore the three oxygens could be associated with amide type groups, which would also use three nitrogens. Geochemical characterization of GILSONITE showed the presence of porphyrin type structures, which would require four nitrogens per unit. Mass spectrographic data indicated that the molecular weights of these units were around 460 (3). On the average, this indicates there would be one porphyrin structure with three amide groups per GILSONITE molecule. The remainder of the structure would consist of aromatic and aliphatic hydrocarbons with few olefinic groups, as indicated by the iodine number.

Another consideration is the potential for GILSONITE to enter into crosslinking or additional type reactions. It is known that GILSONITE will react with formaldehyde in the presence of H2S04 to produce a formolite resin. Reactions of GILSONITE with phenol and formaldehyde have also been studied. These reactions can be quite rapid depending upon the reaction conditions.

The melt viscosity vs. temperature is shown in Table VI for two grades of GILSONITE with softening points of 300° and 350° F. These softening points were measured in a Brookfield viscometer equipped with a Thermosel.

Another important parameter is the solution viscosity, which is shown in Table VII. Here the viscosity was measured in toluene at 30 percent solids and 25° C for two grades of GILSONITE.

Data in Tables VI and VII illustrate the usefulness of 300 grade GILSONITE in products. For any grade of GILSONITE it has been found that when used in combination with other resins there is a synergistic effect, which lowers the melt and solution viscosity more than predicted.

Applications

Recently there is increased emphasis on cost reduction in adhesive and sealant products. This has led to reexamination of materials where cost savings can be realized without loss in quality of the product. The availability of new and more uniform grades of GILSONITE, for example 300 grade, now makes GILSONITE a viable substitute for more expensive resins.

In adhesive and sealant applications GILSONITE can be used as a tackifying resin, film former, or other modifier where color is not an overriding factor. GILSONITE is also used to modify the performance of other polymers for example: polyethylene; polyamides; polyvinylacetate; poly (ethylene vinylacetate) copolymer; and a variety of rubbers.

Our current development work is focused on the use of GILSONITE in solvent based, water based, and heat reactive systems. Typical formulations are presented along with measured physical properties and relative costs. These examples are given in Tables VIII through XIII.

Contact Adhesives

Contact adhesives were prepared that contained GILSONITE as a substitute for a phenolic tackifying resin. The suggested starting formulas and the test results are given in Table VIII. The data suggest that when GILSONITE is substituted for the phenolic component there is an opportunity for improved performance. Increasing the concentration of GILSONITE may provide even greater cost performance benefits.

Construction Mastics

Construction mastics were prepared with GILSONITE as a substitute for a midblock, Pentalyn H, and an endblock, Cumar LX509, resin in formulations with Kraton D1101. GILSONITE was a satisfactory substitute for the midblock resin, but not an adequate substitute for both resins. This suggests that GILSONITE behaves more like a midblock resin in Kraton systems. The formulations, shear strength, and comparisons are compiled in Table IX. Again it must be pointed out that an increased level of GILSONITE could provide a greater benefit.

Hot Melts

Hot melt adhesives were prepared based on Elvax 210 where GILSONITE was compared with Piccolyte A115, a polyterpene. The data indicated that the peel strength were similar for all formulations. The formulations, test data and cost comparisons are given in Table X.

Of particular interest are two new types of GILSONITE adhesive technologies that offer exciting potential while responding to environmental and health safety interests. These technologies use reactive resin systems and water based systems.

Heat Reactive

Two examples of this new approach are shown in the heat reactive resin system in Tables XI and XII. These formulas show how GILSONITE can be used to produce products that can be cured at temperatures as low as 250° F in 30 minutes. The basic difference in the data is the method of mixing, where either the GILSONITE is fluxed into the resin (Table XI) or dispersed into the resin (Table XII). These data were selected to show trends and do not emphasize the high performance that can be achieved with these systems.

Two uses of this new technology would be auto seam sealers and corrosion resistant pipe coatings.

Water Based

In addition to these studies it has been possible to develop water based products for applications such as carpet and tile adhesives. These new water based systems hold great potential in application where flammable solvents cannot be used. An example of a GILSONITE water based formula is shown in Table XIII.

Other examples of water based formulas have been shown to produce materials similar to current commercial products.

These examples in this paper indicate that GILSONITE can be used not only in the traditional way as a filler or extender but has good potential as a resin for many types of adhesive and sealant products.

LITERATURE CITED

1. K.R. Neel, Encyclopedia Chem. Tech., 11, 3rd. Ed., pp 802-806, (1980).
2. J.M. Sugihara and L.R. McGee, J. Org. Chem. 22, 795 (1957).
3. J.M.E. Quirke, J.M. Maxwell, and G. Eglinton, Tetrahedron 36, 3453 (1980).
4. S.K. Hajibrahim, J.M.E. Quirke, and G. Eglinton, Chem. Geology, 32, 173 (1981).