Ligno-novolak resins, either in the form of physical blends of lignin and novolak resins or as synthetically derived from the reaction of lignin, phenol and an aldehyde in the presence of an acidic catalyst, are provided. The resins, including the physical blends, are curable to thermoset, substantially completely cross-linked resins in which the lignin is interreacted and cross linked through the action of a curing agent such as hexamethylenetetramine. The resins are useful in the production of molding compounds that exhibit properties that are at least comparable to those of compounds derived from novolak resins. Moreover, excellent heat deflection temperatures and superior electrical properties are exhibited by such molding compounds.

BACKGROUND OF THE INVENTION 
1. Prior Art 
The prior art is believed to be best exemplified by the following patents 
and literature references: 
Hochwalt et al, U.S. Pat. No. 2,168,160, July 1939, and Hochwalt et al., 
U.S. Pat. No. 2,282,518, May, 1942, relate to production of 
phenol-aldehyde-lignin resins that are useful in molding compounds and in 
which lignin containing about 80% by weight water or a desulfonated 
lignosulfonate is dissolved in phenol, admixed with aldehyde and heated to 
effect condensation in the presence of either an acid or alkaline 
catalyst. The references appear to involve condensations of the resole 
type. 
Ball, U.S. Pat. No. 3,185,654, May, 1965, relates to reaction of lignin 
with phenol-formaldehyde A-stage resin to produce resole type resins. 
Salimsakov et al., Plast, Massy, 12, 61-3 (1973) [Chemical Abstracts, 78, 
112897a, 1973], relates to the use of hydrolysis lignin as a filter for 
phenol-formaldehyde resins in the production of molding powders. 
Doi et al., Japan No. 70/20,308, July (1970) [Chemical Abstracts 74, 64926s 
(1971)], relates to rapid curing phenolic varnishes produced by reaction 
of phenol, formaldehyde, toluenesulfonamide and lignin in the presence of 
a basic catalyst followed by incorporation of hexamethylenetetramine in 
the resin thus obtained. 
Kalnins et al., Akad. Nauk. Lalv., SSR, 24, 65-70 (1962) [Chemical 
Abstracts, 58, 5880b (1963)], prepared molding powders by precipitation of 
lignin from spent hydrotropic liquor and reaction of the lignin with 
phenol to form a condensate followed by reaction of the condensate with 
formaldehyde to form novolak resins. 
Apel et al., U.S. Pat. No. 2,956,033, November, 1960, relates to 
phenol-aldehyde-lignin resins of the novolak type suitable for molding 
prepared from "low temperature" lignin obtained as a waste product in a 
saccharification process. A phenol-formaldehyde condensate is first 
produced which is then reacted with phenol, sulfuric acid and hydrolysis 
lignin. The particular hydrolysis lignin is disclosed to be critical and 
other hydrolysis lignins are said to be unsuitable in the process. 
Clark, U.S. Pat. No. 2,520,913, September/1950, relates to production of a 
resin from reaction of cresylic acid, phenol and formaldehyde and, 
optionally, hydrolysis lignin, obtained by the saccharification of corn 
cobs, in the presence of sulfuric acid. The resultant resin is 
neutralized, washed with water, and compounded with hydrolysis lignin and 
hexamethylenetetramine to produce a molding material. 
Donahue et al., Plastics, 1, No. 2,45,101 (1944) discloses hydrolysis 
lignin as a filler in phenol-formaldehyde molding compounds. 
Mori et al., Hokkaidoritsu Rinsan Shikenjo Kenkyu Hokoku 1969, No. 53, 
45-81 (Japan) [Chemical Abstracts 74, 127848r, (1971)] relates to 
production of foamable lignin resins by resole type condensation of alkali 
lignin with formaldehyde and phenol. 
Popova et al., Tezisy Dokl.--Vses. Konf. Khim. Ispol'z Lignina, 6th, 1975 
(Pub. 1976), 160-3 (Russia) [Chemical Abstracts 86, 173343t (1977)], 
discloses compression molding compositions derived from a powdered 
composition of sawdust, phenol, formaldehyde and HCl. 
Grigor'ev et al., Tr. Leningrad. Tecknol. Inst. Tsellyul.--Bum. Prom. No. 
21, 199 (1968) [Chemical Abstracts, 71, 72120c (1969)], relates to studies 
of condensation products of lignin and ammonium lignosulfonate with phenol 
and formaldehyde. 
2. Field of the Invention 
This invention relates to ligno-novolak resin blends and synthetic 
ligno-novolak resins; to molding compositions derived from such resins and 
resin blends; and to cured, crosslinked derivatives of such resins and 
resin blends. 
Lignin is derived from wood as a by-product in the pulping process and, as 
an abundant, natural and renewable product, it has tremendous potential 
for many industrial uses as a replacement for increasingly scarce and 
expensive petroleum based materials. Lignin has found limited utilization 
commerically, however, because it is complex chemically and physically and 
its characteristics have been found to vary considerably, depending on 
many factors including variation in pulping conditions, the kind of wood 
being pulped, the conditions under which it is recovered, etc. 
It is known that lignin obtained as a by-product in alkaline pulping 
processes contains both aliphatic and aromatic hydroxyl groups that are 
attractive sites for chemical modifications. Indeed, because of the well 
known guaiacyl moiety present in lignin and its derivatives, lignin has 
been proposed as a replacement for phenol in the production of phenolic 
resins. In view of the ever-rising cost of phenols and potential shortages 
due to diminishing resources, the use of such lignin substitutes from 
renewable and natural sources becomes increasingly more attractie. 
One technological area in which lignin has been proposed as a phenol 
substitute has been in the production of phenol-formaldehyde type resins. 
These resins have generally been categorized as "resoles", i.e., resins 
produced from reaction of a molar excess of formaldehyde with phenol, 
normally in the presence of alkaline catalysts and curable without the 
necessity of a curing agent, or "novolaks", i.e. resins produced from 
reaction of a molar excess of phenol with formaldehyde generally in the 
presence of an acid catalyst, and curable in the presence of a substantial 
quantity of a curing agent such as hexamethylenetetramine. 
Where lignin has been proposed in the production of novolak resins for 
molding compounds, it has in general been viewed as a filler or it has 
been employed as a reactant, replacing a portion of the phenol being 
reacted with formaldehyde. Many of such prior proposals employ hydrolysis 
lignin for such purposes. Such hydrolysis lignin is a highly purified 
material derived from acid hydrolyzates which are in turn derived by 
digestion of lignocellulosic materials with dilute aqueous acid at 
temperatures ranging from about 190.degree. to 225.degree. C. and 
pressures of about 200 to 400 psi, normally under the action of injected 
steam. The acid hydrolyzates will contain sugars such as xylose or 
glucose, furfural, humins, lignin decomposition products such as vanillin 
or other aromatic compounds. Hydrolysis lignin is the solid left in the 
hydrolyzate after separation of the sugars and other components. In other 
words, hydrolysis lignin is a highly purified, chemically altered lignin 
material. Alkali or Kraft lignin, on the other hand, is obtained as a 
by-product of alkaline pulping using either the soda process in which the 
pulping liquor contains sodium hydroxide or the sulfate process, wherein 
the pulping liquor contains both sodium hydroxide and sodium sulfide. 
During the pulping process, the lignin becomes dissolved in the pulping 
liquor as a salt of lignin and is conventionally recovered by acid 
precipitation as either free lignin or as a lignin salt depending upon the 
specific conditions under which the lignin is obtained. The two types of 
lignin materials, i.e., alkali lignin and hydrolysis lignin, are quite 
different as is well recognized in the art. 
Heretofore, whether the phenol replacement has been proposed in the 
synthesis of resole or novolak resins employing hydrolysis lignin or 
otherwise, there has been little or no commercial use of lignin in the 
production of such resins. This has primarily been the result of 
processing difficulties that have been encountered, such as slow cure, 
high water absorptivity, plating out in the molding process, etc., as well 
as adverse effects upon the properties as compared with the properties of 
the resins produced without phenol replacement. 
It would, of course, be desirable to optimize and, indeed, improve the 
properties of novolak type resinous products while also realizing the cost 
savings that are possible through utilization of a less expensive 
substitute. Moreover, it would be most advantageous to achieve such 
optimization and savings in a manner that is versatile, convenient and 
straightforward, and that requires no special or expensive equipment or 
procedures to carry out. 
Accordingly, a primary object of the present invention is to provide a 
novel formulation for producing a thermoset lignin/phenol/aldehyde resin 
of the novolak type that exhibits desirable properties and in which lignin 
is interreacted and crosslinked. 
Another objective of the present invention is to provide novel 
lignin/phenol/aldehyde resins suitable for use in the production of 
molding compounds. 
Another object of the invention is to provide novel novolak molding 
compounds comprised of such ligno-novolak resins, which compounds exhibit 
properties that are at least equivalent, and in some respects superior, to 
those of conventional novolak molding compounds. 
It is also an object of the invention to provide such formulations and 
molding compounds which exhibit desirable processing and molding 
characteristics. 
Yet another object of the invention is to provide such formulations and 
molding compounds which can be produced in a manner that is both versatile 
and convenient and also relatively inexpensive. 
SUMMARY OF THE INVENTION 
It has been discovered that ligno-novolak resins can be employed to produce 
molding compounds suitable for compression molding and possessing 
acceptable water absorptivity and mechanical strength, higher heat 
deflection temperatures and superior electrical properties compared to 
those of commercial novolak molding compounds. Moreover, it has been found 
that such compounds may be produced from ligno-novolak resins derived 
either through substitution of lignin for a portion of the phenolic 
component in the conventional novolak synthesis or by replacement of a 
portion of the novolak resin with lignin by physically blending the two 
materials. 
To our knowledge, no ligno-novolak molding compounds have heretofore been 
produced wherein the overall properties are at least comparable and the 
electrical properties are superior to those obtained with commercial 
novolak resins. 
It was particularly unexpected to discover that ligno-novolak resins 
possessing such attributes could be prepared by physically blending a 
lignin material, a novolak resin and a curing agent resulting in a 
cross-linked, coreacted material in which lignin is present, not as a 
filler, but as a coreacted thermoset matrix with the novolak resin in the 
molded product. 
In its most preferred embodiments, the invention comprises: 
A. Ligno-novolak resin blend formulations (and the cured, coreacted, 
cross-linked products thereof) comprising a physical admixture of from (a) 
about 5 to about 50 weight percent of alkali lignin, preferably 10 to 40 
percent; (b) about 50 to about 95 weight percent, preferably 60 to 90 
percent, of a novolak resin; and (c) a curing agent. 
B. Ligno-novolak resins (and the cured, cross-linked products thereof) 
comprising (a) the reaction product of alkali lignin, a molar excess of 
phenol, and formaldehyde in the presence of an acid catalyst, the lignin 
replacing from about 5 to 50 weight percent of the phenol and preferably 
from about 10 to 40 weight percent of the phenol; and (b) a curing agent. 
C. Molding compounds derived from such ligno-novolak resins and resin 
blends and especially wood flour filled general purpose compression 
molding compounds, i.e., ASTM Type II molding compounds. 
In the blends, the lignin and novolak components are capable of 
polymerization and/or cross-linking to higher molecular weights upon 
activation with the curing agent. Similarly, the synthetic resins are 
capable of further polymerization and/or crosslinking to higher molecular 
weights in the presence of a curing agent. In both embodiments, the curing 
agent is present in an amount sufficient to effect substantially complete 
cross-linking of the resultant ligno-novolak resin and preferably is 
present in an amount of about 5 to 20 percent based on the weight of the 
ligno-novolak resin or resin blend. 
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Lignin suitable for use in this invention is alkali or Kraft lignin 
recovered from sulfate or soda pulping processes and preferably recovered 
from such processes by acid precipitation at a pH varying from as high as 
about 9 to as low as about 2 or lower depending on the desired end use of 
the resultant molding compound. Such acid precipitation may be 
accomplished by the introduction of acids, such as CO.sub.2, H.sub.2 
SO.sub.4, HCl and other conventional mineral acids as well as organic 
acids such as acetic and formic, to the black liquor to effect the 
precipitation of the lignin followed by washing the lignin with neutral or 
acid water thereby providing lignin containing a suitable ach content. Ash 
is present mainly in the form of hydrophilic salts, e.g., principally as 
sodium phenate when the lignin is precipitated at pH 8-9 and principally 
as sodium sulfate when the precipitation is at pH 3-4. Such hydrophilic 
salts convey a degree of water absorptivity which may in turn increase the 
softening point of the lignin and result in poor processability of molding 
compounds. 
Softening points indicate the minimum temperature at which the resins can 
be processed. As used herein, the closer the softening point to that of 
commercial novolak resins, the better the processability of the resins is 
deemed to be. The control resin, Durez 19896 for example, exhibits a 
softening point of about 85-90.degree. C. In general, the softening points 
of the ligno-novolak resins of the invention depend on the level of lignin 
present, the aldehyde to phenol mole ratio for the synthetic resins and 
the softening point of the novolak present in the blend as well as the ash 
content of the total lignin. Thus the ash content of the lignin is a 
relevant consideration in the successful practice of the invention. The 
ash content can be controlled through selection of the pH at which the 
lignin is precipitated. Precipitation at higher pH will produce higher ash 
contents while lower pH precipitation will produce lower ash contents. The 
ash content may also be controlled by subjecting the lignin to acid 
washings. For example, the precipitated lignin may be washed as thoroughly 
as may be practical so as to ensure the removal of salts. Additionally, 
the ash content of the resins employed to produce the molding compounds 
will be related to the amount of lignin present in the total resin and may 
also be kept within tolerable limits through adjustment of the relative 
proportions of the components in the blend or of the reacting components 
in synthesizing the resins. In the preferred embodiments, the lignin will 
be precipitated at sufficiently low pH and/or will be subjected to 
sufficient acid washings to have an ash content that does not exceed about 
1 to 7 percent based on the weight of the total lignin. 
Lignosulfonates have inherently high water absorptivity and softening 
points and are therefore not useful per se as lignin materials in this 
invention. However, such lignosulfonates that have been substantially 
desulfonated may be employed, if desired. Alkali lignin is the preferred 
lignin material. 
The novolak resins utilized in forming the ligno-novolak blends are well 
known in the art and may be produced by known methods. In general, such 
resins will be produced by an acid catalyzed condensation of a 
stoichiometric excess of a phenolic material with an aldehyde. Suitable 
phenolic materials may be selected, for example, from the group of phenol, 
cresol, cresylic acid and xylenols with phenol being the preferred 
reactant. The aldehyde components may be desirably selected, for example, 
from the group of formaldehyde, furfural, paraformaldehydes, etc. with 
formaldehyde being the preferred reactant. In general, molar ratios of 
formaldehyde to phenol of about 0.5 to 0.9 and preferably about 0.75 will 
be employed. The preferred novolak resins will be those produced through 
reaction of phenol and formaldehyde. The condensation may be permitted to 
proceed to any molecular weight from which the resultant novolak resin is 
curable or capable of further polymerization or cross-linking in the 
presence of a curing agent. Preferably, such novolak resins will have 
molecular weights within the range of about 500 to about 2,000 and 
especially from about 700 to about 1,500. 
Ligno-novolak resins of the invention may be produced from blends of lignin 
and the novolak by any convenient means permitting thorough and intimate 
mixing. In the preferred embodiment, the resins are ground together, for 
example, ball-milled, for the time necessary to provide a suitable 
intimate admixture. Alternatively, the resins may be milled together, 
melted at a suitable temperature, cooled and remilled to insure intimate 
mixing. 
The synthetically produced ligno-novolak resins of the invention may be 
produced in substantially the same way as the novolak resins discussed 
above except that lignin will be substituted for a portion of the phenol 
reactant. Molar ratios of formaldehyde to phenol of about 0.5 to 0.9 and 
preferably about 0.7 will be employed. Since Kraft lignins possess much 
higher softening points than commercial novolaks, ligno-novolaks 
synthetically produced are desirably obtained at lower formaldehyde to 
phenol molar ratios to minimize differences in processability of the blend 
resins and the commercial novolak resins. Preferably such resins are also 
ground (ball milled) or reduced in size prior to being combined with the 
curing agent. 
It is also preferred that both the ligno-novolak resin blends and the 
synthetically derived resins be adequately dried to keep the moisture 
content of the molding compounds derived therefrom at a preferred level. 
Molding compounds may be produced from the ligno-novolak resins or resin 
blends by means well known in the art. Preferably, the ligno-novolak 
resins or resin blends, in powder form, are mixed with desirable 
lubricants, fillers, curing agents and other conventional molding compound 
additives in a suitable blender or mixing device with griding, if desired. 
In the preferred embodiment, a 7.times.16 inch rubber mill, set for 
270.degree. F./132.degree. C. (both rolls) was employed. A 500 gram charge 
of formulation was poured onto rotating rolls, worked for 45 seconds and 
removed from the roll as a sheet. The sheet was cooled and chopped to pass 
through a 10 mesh screen. 
Compression molding was used for all tests herein. Mold temperature was 
170.degree. C.; molding time was 5 minutes; and mold pressure was 2,500 
psi. Specimens were molded from preforms in a 4.times.6 inch shallow, 
positive pressure mold. Preforms were made by compressing pellets of the 
molding compounds in a 4.times.6 inch mold at 70.degree. C. 
Any curing agent known in the art to be effective for curing novolak resins 
may be employed herein to cure the ligno-novolak resins of the invention. 
Such compounds may advantageously be selected from the group of 
hexamethylenetetramine, paraformaldehyde, or any other compounds that are 
capable of generating formaldehyde at molding temperatures. Hexamethylene 
tetramine is the preferred curing agent. 
Exemplary of the efficacy of the present invention are the following 
examples, wherein all parts specified are on a weight basis, unless 
expressly stated to the contrary. The lignins utilized therein are 
prepared as follows: 
To provide a suitable softwood lignin, a 5-kilogram sample of softwood 
lignin having a moisture content of 47 percent and an ash content of 7 
percent is charged into a 10-gallon reactor containing 20 liters of water 
at 70.degree. C. Sodium hydroxide is added, with stirring, in the amount 
of 150 grams, and the resultant solution is maintained at 75.degree. to 
80.degree. C. while a 50 percent sulfuric acid solution is added to adjust 
the pH to a value between 2 and 3, and to thereby effect precipitation of 
the lignin product. Upon filtering, washing with hot water (to remove 
substantially all uncombined sulfate), and drying in a circulating oven at 
40.degree. C., a yield of 2440 grams of lignin is obtained. The softening 
point of the product is 230.degree. to 250.degree. C., and its ash content 
is less than 1 percent. 
A suitable hardwood lignin product is prepared by charging approximately 20 
gallons of hardwood black liquor (16.5 weight percent solids) to a 
30-gallon reactor. The liquor is heated with steam, through a stainless 
steel coil, to about 70.degree. C., and is vigorously stirred while 
concentrated sulfuric acid is added to produce a pH value just under 4. 
Lignin is recovered from the resultant slurry by hot filtration, and the 
product is thereafter washed with hot water until determined to be free of 
uncombined sulfate. After drying in a circulating air oven at 40.degree. 
C., the yield of lignin is found to be 3142 grams; the material has a 
softening point of approximately 160.degree. C. and an ash content of less 
than 1 percent.

EXAMPLE ONE 
A. Blends 
Two ligno-novolak blends are prepared, each containing 25 weight percent of 
one of the foregoing lignins. Specifically, 795 grams of the selected 
lignin is charged into a large ball mill with 2384 grams of DUREZ 19896 
(all DUREZ products referred to herein are commercial novolak resins 
available from the Hooker Chemical Company) and suitable grinding media 
such as, for example, steel balls. After 20 hours of milling, the balls 
are removed and the resultant blend is dried for 20 hours in a circulating 
air oven at 40.degree. C. A sample of the blend is fused in a small beaker 
and is thereafter cooled and crushed; softening point and gel time 
determinations are made with the samples. The softwood lignin blend is 
found to have a softening point of 114.degree. and 118.degree. C., and the 
hardwood lignin blend is found to have a softening point of 107.degree. to 
109.degree. C. Mixing the hardwood blend with 15 percent of 
hexamethylenetetramine to cause cross-linking results in gel times of 187 
and 59 seconds at 135.degree. and 165.degree. C., respectively; the 
softwood blend containing the same amount of the curing agent exhibits a 
gel time of 57 seconds at 165.degree. C. 
B. Synthetic Resins 
To produce a 25 weight percent sythetic softwood ligno-novolak product, 900 
grams of phenol is introduced into a three-liter kettle equipped with a 
stirrer, two reflux condensers, a thermometer, and an oil heating bath. 
The reactor is brought to a temperature of about 55.degree. to 65.degree. 
C., following which 334 grams of a softwood Kraft lignin, precipitated at 
a pH of 8 to 9 and ground and dried, is added; the lignin has an ash 
content of 7 percent and a water content of 3.5 percent, thus providing 
300 grams of lignin on a dry, ash-free basis. A solution consisting of 40 
grams of 96 percent sulfuric acid and 672 grams of 37 percent formaldehyde 
is then added to the phenol and lignin in the reaction kettle. The 
reaction mixture is then heated to a temperature of about 100.degree. C., 
and maintained at approximately that temperature, under refluxing 
conditions, for a total period of approximately 1.5 to 1.6 hours, 
following which the sulfuric acid is neutralized with calcium hydroxide. 
Thereafter, the contents of the kettle are heated to strip the volatiles, 
the latter phases of the stripping operation being effected under vacuum. 
After the pressure over the reaction mixture has been reduced to 100 
millimeters and the temperature has risen to 120.degree. C., the reaction 
is deemed to be essentially complete; the total period of the reaction is 
approximately five hours. The contents of the reactor are finally cooled 
in a stainless steel tray, and the cooled product is ground in a ball mill 
and air dried at 40.degree. C. 
A hardwood synthetic ligno-novolak is prepared in much the same manner, 
utilizing 900 grams of phenol, 306 grams of hardwood Kraft lignin (300 
grams on a dry basis), 626 grams of 37 percent formaldehyde and 12 grams 
of 98 percent sulfuric acid. Although slight variations are made in the 
specific conditions of reaction, ultimately the product recovered is 
ground and dried, and is utilized in evaluations. 
The softwood ligno-novolak resin is found to have a softening point of 
98.degree. to 101.degree. C. and the hardwood ligno-novolak resin is found 
to have a softening point of 92.degree. to 95.degree. C. Mixing the 
hardwood resin with 15 percent of hexamethylenetetramine results in gel 
times of 190 and 58 seconds at 135 and 165.degree. C., respectively. 
Gel times of the resin are significant indicators of processability and 
moldability. Since phenolic resins are thermosetting resins, the resin 
must be reasonably stable with respect to cross-linking at the processing 
temperature but rapidly cross-linked at the higher temperature of molding. 
The lower temperature gel time is a measure of the "barrel life" and the 
longer this time, the better the processability of the resin. The higher 
temperature gel time is a measure of how fast an article can be molded and 
is desirably as fast as possible. 
In these examples, the gel times at 165.degree. are an indication that 
moldability of the ligno-novolak resins, whether derived synthetically or 
by blending, is superior to that of the commercial novolak Durez 19896 
which has a gel time at 165.degree. C. of 70 seconds. 
It was found that at the processability gel times, e.g., 190 seconds at 
135.degree. C., the presence of moisture decreases the gel time of both 
the ligno-novolak resins and the commercial novolak. Therefore, it is 
preferred that the ligno-novolak resins be dried prior to processing to 
ensure the processing times that are desirable. Gel times at 165.degree. 
were not affected by moisture. 
Processability of the two resin blends and of the two synthetic resins is 
evaluated by first compounding each of them on a 7 inch by 16 inch rubber 
mill, with both rolls heated to 132.degree. C. Each of the resin blends 
and resins is mixed with an equal weight of wood flour, curing agent and 
other compounding additives; a half-kilogram charge of the filled mixture 
is deposited upon the rotating rolls, and the charge is worked for a 
period of approximately 45 seconds after banding of the material is first 
observed (normally about 7 seconds after milling is commenced). The 
product is removed as a sheet, which is then cooled and chopped to a 
10-mesh particle size. The ability of the material to form a well-fused 
and smooth band around the mill roll in a reasonably short period of time 
and without excessive cross-linking is indicative of good processability. 
Each of the filled molding compounds perform well in this regard, with the 
millability of the softwood blend being particularly excellent. 
Processability is further evaluated utilizing a Brabender blender fitted 
with No. 6 "roller" mixing blades and a 60 milliliter bowl preheated with 
oil at a temperature of 125.degree. C. After charging 50 grams of the 
filled blend or resin into the Brabender bowl, and commencing rotation of 
the blades at 15 revolutions per minute, the associated timing chart is 
started. The periods which elapse before curing is complete (crumble time) 
are taken as indicative of the barrel or pot life of the compound, with 
longer periods being desirable to afford more time for processing. The 
minimum torque value is also noted, with the lower torques indicating 
greater ease of processing, and hence being the more desirable since less 
energy input is required. 
Moldability of material is determined using a Molding Index, or cup flow 
test, carried out in accordance with the procedure of ASTM D731. 
Specifically, the cup mold is heated to 165 degrees Centigrade, the 
selected maximum pressure point is set, 38 grams of the filled molding 
compound is charged into the unit, and closing of the mold is effected. 
After four minutes, the molded cup is removed, and the thickness of the 
flash along the upper lip is measured. If the flash is more than 8-mils 
thick, progressively higher pressures are utilized for subsequent runs 
until the minimum pressure capable of producing an 8-mils thick flash has 
been determined. 
A short closing time is indicative of a faster, and hence more desirable, 
molding cycle, and the benefits of minimizing the pressure required to 
effect molding are obvious. 
For purposes of comparison, a molding compound based on the same commercial 
novolak and processed in the manner described but formulated without any 
lignin was evaluated in the same way. The results were as set forth in 
Table I which follows. 
TABLE I 
__________________________________________________________________________ 
PROCESSABILITY AND MOLDABILITY OF 
LIGNO-NOVOLAK RESINS 
Brabender Test at 125.degree. C. 
Cup Flow Tests at 170.degree. C. 
Cure 
Minimum 
Crumble 
Time To 
Minimum 
Start, 
Torque, 
Time, 
Close Press, 
Mold Press 
Surface 
Resins (min.) 
(M-g) 
(Min.) 
(Sec.) (p.s.i) 
Gloss 
__________________________________________________________________________ 
Durez 19,896 
(Control) 
5.2 3850 7.2 24 7,000 Good 
A. Blends 
Softwood Lignin- 
4.5 3400 10.4 35 10,000 Excellent 
Durez 19896 
Hardwood 
Lignin-Durez 
4.8 1575 14.7 32 7,800 Fair to Good 
19896 
B. Synthetics 
Softwood Ligno- 
4.2 1375 15.7 24 7,500 Fair 
Novolak 
Hardwood 
Ligno-Novolak 
2.2 2000 13.0 26 7,000 Fair to Good 
__________________________________________________________________________ 
It will be seen from Table I that the ligno-novolak molding compounds made 
in accordance with the invention perform as well as the control in the 
molding tests, within the range of allowance recognized in the evaluation 
process, and satisfy minimum industry standard for materials of this sort. 
Moreover, the appearance of the molded articles is very desirable, with 
the samples made from the softwood lignin blend showing particularly 
excellent gloss. 
EXAMPLE TWO 
A number of test specimens are produced by utilizing preforms made by 
pressing pellets of the molding compound into a 4 inch by 6 inch mold at a 
temperature of 70 degrees Centigrade. The molding composition comprises a 
physical blend of 75 parts by weight of DUREZ 19896 and 25 parts by weight 
of either a hardwood or a softwood lignin prepared in the manner 
hereinabove described or 100 parts of a 25% replacement level softwood or 
hardwood ligno-novolak resin prepared in the manner described above. In 
addition to the resinous components, the molding compounds contain 15 
percent, based upon the weight of the ligno-novolak resin or resin blend, 
of the hexamethylenetetramine crosslinking agent, and are filled with wood 
flour in an amount equal to the weight of novolak resin or resin blend. 
Specimens measuring 4 inches by 6 inches by 1/4inch are produced by 
compression molding of the preforms at a temperature of 170 degrees 
Centigrade and a pressure of 2,500 psi for a period of five minutes; in 
accordance with the prescribed ASTM conditions, the mold is unvented. 
Utilizing the foregoing samples, the ligno-novolak molding compounds 
embodying the present invention are evaluated to determine certain of 
their properties using ASTM test procedures and specifications for Type II 
molding compounds. The results were as listed in Table II below. 
TABLE II 
__________________________________________________________________________ 
PROPERTIES OF LIGNO-NOVOLAK MOLDING COMPOUNDS 
25% Softwood 
25% Hardwood 
Lignin-75% 
Lignin*-75% Control 
ASTM Test 
ASTM Type-II 
Durez Blend 
Durez Blend 
25% Synthetic 
25% Synthetic 
Durez 
Property No. Specification 
19896 19896 Softwood Resin 
Hardwood 
19896 
__________________________________________________________________________ 
Specific Gravity 
D-792 1.40 MAX. 
1.37 1.37 1.39 1.38 1.36 
Mold Shrinkage, 
(%) D-955 0.8 MAX. 
0.68 0.63 0.70 0.66 0.70 
Izod Impact, 
(ft.-lb.) D-256 -- 0.34 0.34 0.38 0.35 0.42 
Flexural Modulus 
(psi .times. 10.sup.6) 
D-790 1.0-1.2 1.11 1.14 1.16 1.12 1.10 
Flexural Strength 
(psi .times. 10.sup.3) 
D-790 9.00 MIN. 
8.70 9.90 9.59 11.30 9.62 
Heat Deflection 
Temperature, (.degree.C.) 
D-648 -- 319 320 323 303 307 
Water Absorption, 
% Gain, 24 hrs. 
D-570 0.8 MAX. 
0.65 0.67 0.75 0.65 0.52 
Water Absorption, 
% Gain, 7 weeks 
D-570 -- 8.84 9.25 10.0 8.58 8.15 
__________________________________________________________________________ 
*Recovered by acid precipitation at pH 3-4 
It will be seen from Table II that the compounds produced in accordance 
with the present invention are at least equivalent and in some instances 
superior in basic properties when compared to compounds produced from 
commercial novolak resin in meeting ASTM Type II-molding compound 
specifications. For example, it can be concluded from the heat deflection 
temperature results that the molded compounds produced in accordance with 
the invention are suitable for uses in which the temperature demands are 
somewhat greater (10.degree.-15.degree. F.) than those in which the 
commercial novolak resin may be used. 
The water absorption data indicated that the ligno-novolaks appear to 
absorb more water than the control initially. However, all samples 
including the control exhibited about the same weight gain and still 
maintained physical integrity after 7 weeks. 
Resistance to boiling solvents is tested in accordance with ASTM D-543 
using acetone, 95 percent ethanol, ethyl acetate, and toluene as solvents. 
All the ligno-novolak based samples, as well as the lignin-free control, 
were found to be similarly resistant to the solvents as measured by weight 
loss or gain. In addition, the dimensional changes are found to be 
insignificant for all samples tested. 
EXAMPLE THREE 
In view of the fact that novolak molding compounds find their major 
application in the electric and appliance industries, the electrical 
properties of the compounds are of primary importance. Filled resins 
produced in accordance with the procedure of Example Two and the filled 
Durez control were evaluated for electrical properties according to ASTM 
tests and specifications for Type-II molding compounds. The results were 
as reported in Table III which follows. 
TABLE III 
__________________________________________________________________________ 
ELECTRICAL PROPERTIES OF LIGNO-NOVOLAK MOLDING COMPOUNDS 
25% Softwood 
25% Hardwood 
Lignin - 75% 
Lignin - 75% Control 
ASTM Test 
ASTM Type II 
Durez 19896 
Durez 19896 
25% Softwood 
25% Hardwood 
Durez 
Property No. Specification 
Blend Blend Synthetic Resin 
Synthetic 
19896 
__________________________________________________________________________ 
Insulation Resistance 
(500V) ohms .times. 10.sup.-10 
D-257 0.1 MIN. 
4.8 6.2 6.2 1.2 0.7 
Dielectric Constant 
100 cps 7.0 MAX. 
5.8 5.3 5.9 6.3 7.2 
1000 cps D-150 -- 5.3 4.9 5.4 5.3 6.0 
10.sup.6 cps 5.0 MAX. 
4.5 4.2 4.5 4.4 4.8 
Dissipation Factor 
100 cps 0.15 MAX. 
0.09 0.08 0.10 0.15 0.14 
1000 cps D-150 -- 0.05 0.05 0.05 0.08 0.09 
10.sup.6 cps 0.05 MAX. 
0.04 0.03 0.04 0.04 0.04 
Arc Resistance, Sec. 
D-495 -- 124 125 89 80 124 
Dielectric Strength, 
(V/Mil.) 
Short Time D-149 -- 360 370 390 400 421 
Step-By-Step 250 MIN. 
300 300 320 300 340 
Moisture Content, % 
Karl Fisher Method 
1.4 1.8 3.5 1.9 3.1 
__________________________________________________________________________ 
It will be seen from Table III that the ligno-novolak molding compounds 
produced in accordance with the present invention are not only 
satisfactory in general in their electrical properties but, in some 
respects, they are dramatically and surprisingly superior. For example, 
the insulation resistance measures surface and internal electrical 
resistance at 500 volts. The ligno-novolak resins of the invention exhibit 
insulation resistance at a level of 12 to 62 times the minimum specified 
ASTM value and about 2 to 9 times greater than that of the control 
compound. Additionally, it can be seen that the ligno-novolaks are 
significantly superior to the novolaks in terms of the dielectric 
constant. Dissipation factor, arc resistance, and dielectric strength are 
found to be at least comparable and, in some instances, superior to those 
exhibited by the control novolak molding compounds. Within the moisture 
content range illustrated in the Table, there is no apparent effect on 
electrical properties. 
EXAMPLE FOUR 
The degree of crosslinking that is produced in molding compositions of the 
present sort has a profound effect upon many of the properties of the 
article produced, including its glass transition temperature, thermal 
stability, chemical resistance, etc., all of which characteristics improve 
with increasing levels of crosslinking. To maximize and optimize the 
properties of the ultimate product, it is therefore desirable that 
crosslinking occur to the greatest extent possible, and that all resins 
present in the molding compound be reacted; specifically, to achieve 
ultimate benefits it is necessary that the lignin react chemically with 
the phenol and the formaldehyde, and be crosslinked by the curing agent in 
the molding process. A most surprising aspect of the ligno-novolak blend 
formulations provided in accordance with the present invention resides in 
the fact that, notwithstanding that they are only physically blended with 
the novolak resin and are not reacted therewith prior to the curing 
process, a remarkably high level of crosslinking is exhibited in the cured 
product. 
To demonstrate the foregoing, a 50:50 blend of the resin to be tested and 
wood flour is mixed with 15 weight percent of the hexamethylenetetramine 
curing agent, and cured by compression molding at 160.degree. C. in a 
2-inch disk mold. The chips produced are then ground to a fine powder, and 
digested in para-dioxane for a period of seven days, with occasional 
shaking of the container. At the end of the digestion period, each of the 
samples is filtered, dried, and weighed to determine the fraction that is 
insoluble in the para-dioxane solvent. The amount over 50% that is 
insoluble is indicative of the degree of crosslinking that has been 
attained in the resin since values up to 50% may be attributable to the 
insoluble wood flour fillers. 
For purposes of comparison, parallel tests are conducted with products made 
from the ligno-novolak resins of the invention, with samples made from 
DUREZ 19896 alone (the same conventional novolak used in the lignin 
blends); and also with samples made from a synthetic ligno-novolak resin 
of the invention prepared as in Example One. 
Utilizing the foregoing samples and extraction procedure, the percentages 
of crosslinking are determined, with the results set forth below: 
______________________________________ 
Percent 
Filled Cross- 
Sample No. 
Molding Compound linking 
______________________________________ 
(1) 25% Hardwood lignin (synthetic) 
98.21 
(2) 25% Hardwood lignin (blend) 
98.15 
(3) DUREZ (control) 98.12 
(4) 25% Softwood lignin (blend 
98.09 
(5) 25% Softwood lignin (synthetic) 
97.96 
(6) 100% Hardwood lignin (without curing 
agent) 51.6 
(7) 25% Hardwood (blend) 
(without curing agent) 64.0 
(8) Kraft lignins (100% Softwood; 
100% Hardwood; without curing agent; 
without filler) 0.0 
(9) Uncured Novolak (without curing agent; 
without filler) 0.0 
______________________________________ 
The data indicate that neither lignin nor novolak resin in the blends 
crosslinks to any significant extent in the absence of the curing agent 
(Samples 6, 7, 8 and 9). The ligno-novolak resins, both synthetic and 
blend derived, are highly crosslinked in the presence of curing agent. 
The degree of crosslinking was also determined on the unfilled 
ligno-novolak resins using the same procedure as described hereinabove but 
substituting Durez-22091 for Durez-19896. The results were as follows: 
______________________________________ 
Unfilled Molding 
Sample No. 
Compound Insoluble (%) 
______________________________________ 
(1) 25% Hardwood Lignin (synthetic) 
91 
(2) 25% hardwood lignin (blend) 
92 
(3) Durez 22091 Control (cured) 
78 
(4) Durez 22091 Control (uncured) 
0 
(5) 25% Softwood Lignin (blend) 
91 
(6) 25% Softwood Lignin (synthetic) 
94 
(7) Softwood Kraft Lignin (without 
curing agent) 0 
(8) Hardwood Kraft Lignin (without 
curing agent) 5 
______________________________________ 
All ligno-novolaks were found to be highly crosslinked. 
The data also indicate that the low molecular weight Durez novolak resin 
cures more readily with the lignin than by itself, whether the lignin is 
in the form of chemically bound interpolymer or a physical blend. 
As can be seen from the foregoing data, the thermoset resins produced 
utilizing the blended novolaks of the present invention are crosslinked to 
substantially the same level as are the resins produced utilizing both the 
commercial novolak and also the synthetically produced ligno-novolak 
resins. Thus, it is evident that the lignin of the blended resins is not 
acting as a filler but is an integral part of the crosslinked structure. 
It is also evident that substantially the same result is obtained 
regardless of whether the lignin is initially present in the novolak as a 
chemically bound constituent, or in physically blended form. This 
indicates a surprising, and especially beneficial aspect of the present 
invention. 
The ability to produce such products by blending, rather than by chemical 
synthesis, greatly facilitates resin manufacture. Thus, the ligno-novolaks 
are readily used in standard manufacturing operations, and neither 
reactors nor other special equipment need be provided. 
As has been suggested hereinabove, phenol/formaldehyde thermoset resins of 
the present sort are normally filled to either enhance, or to provide, 
certain properties to the molding compound and the ultimate product. 
Typical fillers are wood flour, cotton linters, canvas, asbestos, mica, 
and the like. The nature of the filler will often dictate, or be dictated 
by, the application for which the resin is to be utilized; these factors 
are well known by those skilled in the art; and need not be discussed in 
detail. 
Thus, it can be seen that the present invention provides novel formulations 
for producing thermoset ligno-novolak resins exhibiting desirable 
properties, and molding compounds utilizing the same, in which either a 
portion of the phenol content or the novolak resin content is provided by 
lignin. The formulations exhibit desirable processing and molding 
characteristics, and can be produced in a manner that is both convenient 
and also relatively inexpensive. While cost savings are normally realized 
by the practice of the invention, the ligno-novolaks are not "cheapened" 
as a result; their properties are generally comparable to those of 
conventional products and, indeed, they are superior in many respects.