Production of high molecular weight polyisoprene latex is enhanced by administering to plants, particularly Guayule Plants, an amine containing at least one two-carbon chain substituent and preferably substituted trialkylamine of the general structure: ##STR1## where R.sub.4, R.sub.5 and R.sub.6 are alkyl, preferably ethyl and at least one of R.sub.4, R.sub.5 and R.sub.6 is preferably an electron withdrawing group substituted aryloxy or arylthio ethyl group

Bauman, Albert J.

NASA Technical Reports Server

United States Patent 1191 11 13 4,159,903 
Bauman [451 Jul. 3,1979 
[54] ENHANCEMENT OF POLYISOPRENE 
[75] Inventor: Albert J. Bauman, Sierra hfatlre, 
Calif. 
[73] Assignee: California Institute of Technology, 
Pasadena, Calif. 
[21] Appl. No.: 819,263 
[22] Filed: Jul. 27, 1977 
[51] h t .  ( 3 . 2  ......................... AOlN 9/12; AOlN 9/22; 
AOlN 9/24; AOlN 9/20 
[52] U.S. c1. ........................................... 71/98; 71/86; 
71/92; 71/94; 71/106,71/111; 71/121 
[58] Field of Search ................... 71/121, 86, 106, 111, 
71/98 
[561 References Cited 
LATEX PRODUCTION 
U.S. PATENT DOCUMENTS 
3,544,304 12/1970 Soper ................................. 71/121 X 
3,833,350 9/1974 C a k e  et al. ...................... 71/121 X 
3,898,257 8/1975 Gregory ............................ 71/121 X 
3,991,515 11/1976 Drew ................................. 71/121 X 
Primary Examiner-Joseph Paul Brust 
Attorney, Agent, or Firm-Marvin E. Jacobs 
[571 ABSTRACT 
Production of high molecular weight polyisoprene latex 
is enhanced by administering to plants, particularly 
Guayule Plants, an amine containing at least one two- 
carbon chain substituent and preferably substituted 
trialkylamine of the general structure: 
&-N--Rs 
I 
R6 
where %, R5 and R6 are alkyl, preferably ethyl and at 
least one of R4, R5 and R6 is preferably an electron 
withdrawing group substituted aryloxy or arylthio 
ethyl group. 
10 Claims, No Drawings 
https://ntrs.nasa.gov/search.jsp?R=20080012269 2019-08-30T03:53:31+00:00Z
4,159,903 
1 
ENHANCEMENT OF POLYISOPRENE LATEX 
SRODUCI'ION 
ORIGIN OF THE INVENTION 
The invention described herein was made in the per- 
formance of work under a NASA contract and is sub- 
ject to the provisions of Section 305 of the National 
Aeronautics and Space Act of 1958, Public Law 83-568 
BACKGROUND OF THE INVENTION 
5 
(72 Stat. 435; 42 USC 2457); 10 
1. Field of the Invention 
The present invention relates to plant growth regula- 
tors, and more particularly, to the enhancement of pro- 15 
duction of polyisoprene rubber. 
2. Description of the Prior Art 
Guayule is a desert shrub native to the southwestern 
United States and northern Mexico that produces poly- 
meric isoprene essentially identical to that made by 20 
Hevea rubber trees in Southeast Asia. As recently as 
1910 it was the source of half of the natural rubber used 
in the U.S. Since 1946, however, its use as a source of 
rubber has been all but abandoned in favor of cheaper 
Hevea rubber and synthetic rubbers. However, demand 25 
for natural rubber is expected to produce shortages of 
that material as early as 1980 and rubber prices are 
expected to double by 1985. Natural rubber having 
lower heat hysteresis is required for many kinds of tires 
and amounts to about 35% of US. rubber use. 
It is technically possible to satisfy projected demand 
with synthetics, but the rise in world petroleum prices 
has prompted the rubber industry to look for alternative 
sources of natural rubber. The principal, if not the only 
such, source is Guayule. It is conceivable that Guayule 35 
eventually could replace Hevea trees because of the 
susceptibility of the Hevea tree to a number of devastat- 
ing diseases. 
To minimize dependence on dwindling supplies of 
fossil fuel, attention is being directed to the production 40 
of hydrocarbons in plants such as Hevea and Guayule. 
Guayule plants thrive on the dry, sandy mil of south- 
western U.S. and Mexico. During World War 11, exten- 
sive plantings of Guayule were carried out in Califor- 
nia. near Indio and Salinas. Guavule normallv vields 45 
30 
one half ton of rubber per acre in chivation whk; after 
two years, the entire plant is harvested and processed. 
Various known Hevea tree latex modifiers, such as 
Etherill (2-ethyl phosphonic acid), which boost latex 
yield in Hevea trees by preventing clotting of flowing 
latex will not work with Guayule plants. In Guayule the 
latex is present as tiny inclusions in the bark, which are 
not interconnected. The literature suggests that no 
known plant regulator mechanism was applicable to 
Guayule, or that if any growth enhancement ever were 
to be achieved, it would have to come by way of a 
biochemical modification of the membrane process 
ivhich produces the polyisoprenic latex. 
SUMMARY OF THE INVENTION 
The yield of high molecular, weight polyisoprene is 
significantly increased by use of the bioinduction agent 
according to the present invention. Though the agent 
does not initiate rubber accumulation, it markedly influ- 
ences the magnitude of plant response to latex produc- 
tion in the cells. After about a month of growth, plants 
sprayed with dilute solution of the agent exhibited at 
least about 20% increase in rubber production, some 
50 
55 
60 
65 
2 
agents demonstrating increase in yield of up to 400% to 
500%. 
The bioinduction agents of the invention are selected 
from amines of the formula: 
where at least one of R1, R2 and R3. is a hydrocarbon 
chain containing at least two carbon atoms. R1, R2 and 
R3 may be hydrogen, alkyl of from 1 to 10 carbon 
atoms, aryl such as phenyl or R1 may be a carbon-car- 
bon bond and R2 and R3 may be combined into a cyclic 
structure containing 1 to 10 carbon atoms and hetero 
atoms such as oxygen, nitrogen, or sulfur such as pyri- 
dine, P-ethyl pyridine, 2,4,dichloropyridine or imidaz- 
ole. 
Preferred polyisoprene bioinducing agents of the 
invention are trialkyl amines of the formula: 
R4-N-Q 
I 
Rs 
where % and R5 are alkyl of 1 to 10 carbon atoms 
preferably ethyl and at least one of %, R5 and R6 are 
substituted with an electron withdrawing group such as 
halogen, preferably chloro, iodo or bromo, nitro, car- 
bonyl, aldehyde, alkoxy, aryloxy and thio analogs 
thereof. At least one of &, R5 and R6 has the structure 
-CH2-(CH&R7 where q is an integer from 1 to 6 and 
R7 is hydrogen, an electron withdrawing group, aryl 
such as phenyl, substituted phenl such as R9Ph- where 
R9 is alkyl of 1 to 6 carbon atoms or an electron with- 
drawing group and Ph is phenyl, (CH2)pO-R8 and 
(CH2)pS-Rs where p is an integer from 1 to 6 and 
Rs is hydrogen, alkyl of 1 to 4 carbon atoms, aryl such 
as phenyl or -Ph-R9. R4, R5 or R6 may be substituted 
with various groups which do not interfere with sys- 
temic transport into the plant nor with the bioinduction 
activity such as phosphoric, sulfuric groups or esters 
thereof. The compounds. can be ' administered to the 
plant as the free base, salt, hydroxide or acid addition 
salt of hydrochloric or phosphoric acid. 
Representative compounds are presented in the fol- 
lowing table: 
Compounds 
1 2-(khlorophenyIthio) triethylamine 
hydrochloride (CFTA) 
EtzN(CH&Ph, where Ph is phenyl and 
q = KO, 2(3, 3(4), 4(5), 5(6) 
phenylene and R6 = H(7), p-Me(8), p-ET(9), 
p-iso-Pr(l0) and p-tert-Bu(l1) 
12-14 EtzNCHzCH2O-CgHqOCOR7 where C6H4 is 
phenylene and R7 is H(12), Me(13) or C,5H5(14) 
2-6 
7-11 EtzNCHzCHzOCgHq-Rg where W is 
15 Choline 
16 N,Ndiacetylethanolamine phosphate 
17 H 
EtzN-C-H 
c=o I 
4,159,903 
3 4 
synthesis. Guayule rubber is an isoprene molecule of 
molecular weight of about 2 million. 
A group of compounds of the tertiary alkyl amine 
type, and particularly triethylamine. have been utilized 
5 as citrus color-change regulators by causing an in- 
creased production of carotenoid pigments in the citrus 
by inducing accumulation of lycopene. Lycopene has a 
low molecular weight polyisoprene structure. It is be- 
lieved that enhancement of lycopene production in 
10 cirtrus and polyisoprene latex in Guayule proceeds by 
similar membrane involved mechanisms. This hypothe- 
sis was confirmed since it has been demonstrated that 
the trialkyl amines useful for citrus-color change are 
also applicable to enhancing production of high molec- 
In a commercial scheme for production of latex from 
Guayule, a dilute solution of the agent is sprayed topi- 
cally on the young plants shortly after planting. Spray- 
ing is repeated at regular intervals until the plants are 
2o ready for harvest in 2 to 3 years. The plant is readily 
adaptable to commercial harvesting. 
The natural rubber latex in Guayule is found in all 
parts of the plant except the leaves. It is contained in 
plants in dilute aqueous media by spraying the prepara- plant, except the leaves, must be POeessed to extract 
tion onto the plant or feeding the preparation to the the latex* 
roots of the plant. 0.1 to 5% of an organic solvent such over the Years, Procedures have been develo@ that 
as alkanol suitably ethanol or isopropanol can be pres- Can r ~ ~ ~ e r  as much as 95% of the available natural 
ent to assist in dissolving some of the more water insolu- 31) rubber. The first step is Parboiling, which COa&ates 
-continued 
Compounds 
20 
21 
N(CH2CH2--S-@Clh 
Et2N-CHZCH2-O-@-CI 
22-24 EtzNCHzCH2-0-X 
0 
l5 ular weight polyisoprene in Guayule. 
=@CHO, @O-CHl 
25 Et2N. HCI 
26 Bu3N. HCI 
21 
EtZNCHzCHz-0 
The agents of the invention can be applied to the 25 micro~coPic that are unconnected. The entire 
_ _  
ble agents. The comp&ition typically contains from 
0.05% to 5% by weight of the agent, the remainder 
being water and optionally a minor amount of from 0.1 
to 3% of a surfactant, suitably a nonionic alkylene oxide 
surfactant such as Tween to assist in penetration of the 35 
wax coating on the surface of the plant for topically 
applied formulations 
The bioinducers of the invention are generally appli- 
cable to increasing the production of polyisoprene hav- 
ing a molecular weight above 300,000 typically about 
2,000,000 in plants such as Guayule (Parthenium argen- 
tatum Gray), Hevea (Hevea brasiliensis Muell), Euphor- 
bia tirucalli and Russian dandelion (Taraxacum kox 
saghz Rodin). 
growth enhancement involves a biochemical modifica- 
tion of the membrane process which produces the poly- 
isoprene latex. There is a considerable literature on the 
biochemical mechanisms of membrane processes. It is 
known, for example, that lecithin which is a phospho- 
lipid or phosphatide which includes the tertiary alkyl 50 
amine group, -Cz&-N(CH3)2, actively participates 
in membrane-bound enzymatic systems. Similarly, the 
phosphatide phosphatyl ethanolamine is also membrane 
active and is a direct analog of the bioinducer structure: 
It is believed that the mechanism responsible for 45 
55 
R 
I 
F=O 
0 6 0  
II 
I 
0 0 
II I 
I 
H2N-CH2-CH2-O-P-O-CH2-CH-CH2-0-C-R 
-0 
where R and R are fatty acids and the NW2 moiety, if 65 
substituted with N-(Et)2 is an analog. It was hypothe- 
sized that the formation of polyisoprenic rubber in 
Guayule occurs through a membrane-bound enzgmatic 
- -  
the latex in the cells, removes dirt from the roots, and 
removes the leaves from the stems. Rubber is releasd 
from the cells by milling in a caustic solution. The 
milled bagasse sinks to the bottom of the processing 
vessel. Latex combined with dissolved resins agglomer- 
ate into “worms resin” and float to the surface, where 
they are skimmed off and washed to remove the caustic. 
The worms contain up to 25% natural resins. Accetone 
extraction removes the resins and some residual water 
in a fluid-bed extractor. Acetone is recovered by distil- 
lation and the resins are valuable chemical intermediates 
(such as terpineols) which are recovered separately. 
The deresinated rubber is then dried and sent on to 
further processing. 
In a gel permeation chromatogram it is all but impos- 
sible to distinguish between the molecular weight dis- 
persion of rubber from the Guayule plant and that from 
the Heavea tree. Similarly, mechanical tests for tacki- 
ness, plasticity, and the like show little difference be- 
tween the two. Tests do show, however, that the 
amount of curing chemicals needed for processing 
Guayule rubber into tires is slightly different from that 
required for Hevea rubber and a modified molding 
procedure is required. 
The production economics of Guayule may be much 
better than for Hevea. Natural rubber from Hevea trees 
is extremely labor intensive, but Guayule can probably 
be harvested mechanically and processed entirely with- 
out resorting to hand operations. There also is the prob- 
ability of some significant by-product credits with 
Guayule. The natural wax on Guayule leaves can be 
easily extracted as a clear, white material with a boiling 
point exceeding that of carnauba wax, which is highly 
prized and currently sells for more than $2.00 per lb. 
The bagasse may have some value as a papermaking 
material. The resins from the Guayule plant have not 
been fully characterized but appear to contain signifi- 
cant quantities af terpenes similar to those obtained 
5 
4,159,903 
6 
from pine trees. These are used in the paper, paint and 
essential oils industries. 
DESCRIPTION of the Preferred Embodiments 
Hoagland's solution containing about 0.05% CPTA and 
subjected to light. Growth rate was observed as corn- 
pared to an adjacent Guayule branch immersed in Hoa- 
gland's solution. After about one month, it was found 
that the control plant for a fmed weight of material 10 
yielded mg. of rubber upon extraction, and the 
treated plant yielded about 59 mg. of rubber; and hence 
a 50% increase in rubber production occurred in a 
month. 
Rooted young plants of Guayule, about four months 
control, of about 150%. The choline phosphate was less 
effective, causing an increase of about 20%. 
Lower molecular weight trialkyl amine derivatives 
such as (C2Hs)2NSCH2CH2Br appear to provide even 
A branch of a Guayule plant was Cut, immersed in 5 higher yields of polyisoprene. Bioinduction of latex of 2 
to 6 fold with C n A  as compared to control has been 
achieved in stem and root tissues of greenhouse grown 
4 month old Guayule seedlings and in 8 month old field 
grown Guayule plants* 
It is to be understood that only preferred embodi- 
ments of the invention have been described and that 
numerous substitutions, modifications and alterations 
are permissible without departing from the spirit and 
scope of the invention as defined in the following 
15 claims. 
What is claimed is: Old and lo cm* high, Obtained from the 
County Arboretum were transplanted 
1. A method of stimulating the production of polyiso- 
prene latex having a molecular weight above 3~,m in a field plot. 
After allowing the plants to get accustomed to their 
new enviroment, they were sprayed 13 days later with 20 
Mixtures 1 and 2 (see Table 1) and again 30 days later. 
Four plants were treated with each mixture, "drench- 
ing" all the leaves and stems with a hand sprayer during 
the warm part of the day, at an ambient temperature of 
a ~~~l~ plant comprising the step of: 
to the plant an amount effective to 
increase production of polyisoprene by at least 
20% of a bioinducing agent of the formula: 
R5 
I about 70" F. The plants were harvested about 4 weeks 25 
after treatment, as described earlier in the text. R4-N-Ra 
TABLE 1 where Rs and R6 are selected from phenyl, 
-CHz(CH2)& where q is an integer from 1 to 6, R7 is 
phosphate, 5000 ppm isopropyl alcohol and about 50 30 hydrogen; Phenyl; an electron Withdrawing POUP; R9 
ppm of Tween 80 surfactant. phenyl- where R9 is alkyl of 1 to 6 carbon atoms or an 
Mixture 2: loo0 ppm of choline phosphate, 5 0 0  ppm electron withdrawing P O U P ;  -(CHZ)pGR8 Or 
hydrogen, alkyl of 1 to 4 carbon atoms, phenyl or 
period was one with occa- 35 phenyl R9, and &is hydrogen or R5, and at least one of 
%, Rs and R6 has the structure: -CHz-(CH&-R7. 
2. A method according to claim in which R4 and Rs 
are ethyl. 
is dispersed in an aqueous carrier. 
to claim in which the agent 
dispemion is fed to the roots of the plant. 
dispersion is sprayed onto he plants. 
is present in the dkpe&,n in an amount from 0.05% to 
5% by weight. 
7. A method according to claim 6 in which the agent 
dispersion further includes a minor amount of a water- 
8. A method according to claim 7 in which the disper- 
sion further includes a minor amount of a surfactant. 
9. A method according to claim 3 in which the agent 
is 2-(4chlorophenylthio) triethyl amine hydrochloride. 
10. A method according to claim 1 in which the elec- 
tron withdrawing group is a halogen. 
Mixture 1: loo0 ppm N,N-diacetylethanolamine 
isopropyl alcohol and about 50 ppm of Tween 80 sur- --(CH2)$-R8 where P is an integer from 2 to 6, R8 is 
factant. 
sional heavy rains during which the plants grew vigor- 
ously. The plants (four experimental for each com- 
dried at 60" C., ground to a fine powder under liquid 
nitrogen in a mortar/pestle, and extracted sequentially 
in a Soxhlet extractor within a microporous Teflon 
methylene chloride. The latter contained the rubber 
metric aliquot under nitrogen and weighing the residue 
on a microbalance. The yields are listed in Table 2 in 
mg. of rubbedgm. dry weight of plant. 
TABLE 2 
ne climate during 
pound spray) and (four) were harvested and 3. A method according to claim 1 in which the agent 
4. A method 
thimble with (a) water, then (b) acetone and finally (c) 5. A method according to claim.3 in which the agent 
which was dete-ed by evaporating a known V O h -  45 6. A method according to claim 3 in which the agent 
50 miscible, organic solvent for the agent. 
. Control Treated Gain, % 
150 Mixture 1 22.0 53.0 
Mixture 2 16.5 19.4 17.6 
Briefly, the use of N,N-diacetylethanolamine phos- 55 
phate in the mixture and proportions listed caused an 
increase in rubber yield, in comparison to that of the * * * * *  
60 
65 


Enhancement of polyisoprene latex production

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