Note: Descriptions are shown in the official language in which they were submitted.
~20~586
WO 96/12759 PCT/US9~/13313
A PROCESS FOR PREPARING POLYURETHANE FOAM IN THE PRESENCE OFA HYDROCARBON
BLOWING AGENT
t This invention relates to a process for preparing a rigid, hydrocarbon blown,
polyurethane foam by reacting a polyisocyanate with a polyol composition comprising a
material which compatibilizes the hydrocarbon in the polyurethane formulation.
A recent trend in the manufacture of polyurethane foam, especially rigid
polyurethane foam, is the use of hydrocarbon blowing agents as substitute or replacement for
the traditionally employed blowing agents including trichlorofluoromethane. Such trend has
10 been motivated by the desire to eliminate the use of certain fully halogenated alkanes in an
effort to protect the environment including the ozone content of the atmosphere. The general
use of hydrocarbons as a blowing agent for polyurethane foam is widely reported in the
literature. For example, U.S. Patent 5,096,933 discloses the use of cyclopentane, cyclohexane or
mixtures thereof. U.S. Patent 5,182,309 discloses the use of pentane. U.S. Patent 5,001,164
15 discloses the use of pentane in combination with trichloroethane. U.S. Patent 5,286,759
discloses combinations of hydrocarbons containing at least 4 carbon atoms with
perfluoroalkanes as a blowing agent for polyurethane foam manufacture. U.S. Patent
4,263,412 discloses the preparation of polyurethane foam in the presence of butane. Of the
mentioned hydrocarbons, use of cyclopentane and pentane is presently favored due to
20 availability and general benefit to the physical properties of the foam.
However, to prepare polyurethane foam which exhibits attractive physical
properties, advantageously all reactants should be readily miscible with one another and/or
high efficiency mixing procedures be employed to ensure even distribution of all starting
materials. In the presence of poor miscibility or poor mixing, the resulting foam may exhibit
25 inferior, unattractive, physical properties. Hydrocarbon blowing agents, especially when used
in significant amounts as might be required to produce a low density foam, are generally not
noted for having attractive miscibility with the majority of polyesl:er or polyether polyols
commonly used to prepare polyurethane foam. Frequently separation results leading to poor
mixing and/or poor foam quality.
In the art when problems of miscibility are encountered, using the traditional
type of blowing agents, frequently they can be resolved by varying the amount of cell
stabilizing agent or surfactant present in the foaming process. In many instances, the problem
has been resolved by use of a surfactant in an amount of from 0.1 to 2 parts per 100 parts of
polyol. Use of greater amounts of surfactants, normally a mineral oil of the polysiloxane type,
35 can lead to a significant decline in the physical properties of the resulting foam. For closed-cell
rigid polyurethane foam, this can be a reduction of compressive strength, a loss of thermal
insulation potential as a consequence of an acquired open-cell content, or poor mold filling
(flow) characteristics. When preparing low density polyurethane foam in the presence of a
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WO 9~/12759 PCT/US95/13313
hydrocarbon blowing agent with elevated loadings of the conventional surfactants, the poor
miscibility problem is not satisfactorily resolved. Accordingly it would be desirable to provide
for an alternative foaming process permitting the manufacture of polyurethane foam,
especially low density foam, in the presence of a hydrocarbon blowing agent which does not t
sufferfrom the above-mentioned deficiencies.
For this purpose, the use of compatibilizing agents has been investigated.
In a first aspect, this invention relates to a process for preparing a closed-
celled polyurethane foam which includes reacting, in the presence of a hydrocarbon blowing
agent, a polyisocyanate with a polyol composition wherein the polyol composition comprises:
10 i) a polyether or polyester polyol having a hydroxyl number value of from 100 to
1200; and
ii) from 5 to 25 parts, per 100 parts by total weight of the polyol composition, o~ a
compatibilizing agent containing a compatibilizing radical of the formula
~(CnH2n+ 1)
wherein n is a number greater than or equal to 5, and wherein the
compatibilizing agent contains at least one active hydrogen atom, provided that
there is no more than one aromatic group per molecule, and further wherein the
compatibilizing agent is a fat, oil, monoglyceride, diglyceride, fatty acid, fatty
alcohol, fatty amide, fatty amine, fatty acid ester, alkoxylated adduct of any of
the foregoing, alkyl phenol or propoxylated adduct thereof, alkyl phenol or
adduct thereof with ethylene oxide or propylene oxide, alkyl phenol or adduct
thereof with less than an average of four molecules of ethylene oxide per
molecule of alkyl phenol, or a mixture thereof.
In a second aspect, this invention is a process for preparing a closed-celled
25 polyurethane foam which comprises reacting, in the presence of a hydrocarbon blowing agent,
a polyisocyanate with a polyol composition, wherein the polyol composition comprises:
i) a polyether or polyester polyol having a hydroxyl number value of from 100 to
1200; and includes:
ii) from 5 to 25 parts, per 100 parts bytotal weight of the polyol composition, of a
compatibilizing agent comprising a fat or oil having a hydroxyl number of from
100 to 550.
In a third aspect, this invention relates to a closed-celled polyurethane foam
obtained according to an above-mentioned process.
In a fourth aspect, this invention relates to a blend, suitable for use in the
inventive process as a polyurethane precursor composition, which comprises the above-
mentioned polyol composition containing a compatibilizing agent as defined herein and
further a blowing agentwhich is present in an amount of from 1 to 20 parts per 100 parts by
2 ~ 0 1 5 8 6
WO 96/12759 PCT/US95/13313
total weight of the composition and which is a C1 g hydrocarbon, and preferably butane,
n-pentane, i-pentane, hexane, cydopentane, methylcyclopentane, cyclohexane,
methylcyclohexane, isomer thereof, or a mixture of two or more thereof.
Surprisingly, it has been found that use of a compatibilizing agent as defined
5 enhances the miscibility of the hydrocarbon blowing agent and rninimizes the susceptibility to
i separation of the formulation. The presence of the compatibilizing agent allows for an
increased loading of the hydrocarbon blowing agent, thereby permitting the manufacture of
foam having a lower density while retaining overall attractive physical properties.
The present invention relates to a process for preparing a rigid, closed-celled
10 polyurethane foam by reacting, in the presence of a hydrocarbon blowing agent, a
polyisocyanate with a polyol composition comprising a certain compatibilizing agent.
Advantageously, the resulting foam is of a low free rise density of from 10 to 50, preferably
from 15 to 40, and more preferably from 15 to 35 kglm3.
The polyurethane precursor composition comprises: (a) an isocyanate-reactive
15 component, usually a polyether or polyester polyol, having a hydroxyl number value of from
100 to 1200, preferably from 100 to 800, more preferably from 200 to 800, and yet more
preferably from 200 to 600 and preferably being a polyester or polyether polyol; and (b) a
compatibilizing agent. The compatibilizing agent allows for attractive miscibility of the
hydrocarbon blowing agent with the polyol and is present in an amount of from 5 to 25,
20 preferably from 6, more preferably from 7, and preferably up to 18, more preferably up to 15
parts by total weight of the polyol composition including polyol and compatibilizing agent.
The compatibilizing agent is defined herein as containing a compatibilizing radical of the
formula
~(CnH2n+ 1)
25 wherein n is a number greater than or equal to 5, and wherein the compatibilizing agent
contains at least one active hydrogen atom, provided that there is no more than one aromatic
group per molecule, wherein the compatibilizing agent is a fat, oil, monoglyceride, diglyceride,
fatty acid, fatty alcohol, fatty amide, fatty amine, fatty acid ester, alkoxylated adduct of any of
the foregoing, alkyl phenol, or propoxylated adductthereof, alkyl phenol, or adductthereof
30 with ethylene oxide or propylene oxide, alkyl phenol, or adduct thereof with less than an
average of four molecules of ethylene oxide per molecule of alkyl phenol or a mixture thereof.
In preferred embodiments each molecule contains only one active hydrogen atom.
The active hydrogen atoms contained in these compatibilizing agents are such as
associated with hydroxyl, thiol, amine and carboxylic acid functionality. The presence of the
35 isocyanate reactive hydrogen atom is desired to permit reaction with the polyisocyanate,
thereby incorporating, to the advantage of the polymer physical properties, the
compatibilizing agent into the polyurethane polymer.
r 2 2 1) 1 5 8 6
WO 96/12759 PCT/US95/13313
Advantageously, the compatibilizing agent is a fat, oil, or alkoxylated adduct
thereof, with hydroxyl functionality and having a hydroxyl numbervalue of from 100,
preferablyfrom 130, more preferablyfrom 140, and up to 550, more preferably up to 300, still
more preferably up to 200, and yet more preferably up to 180.
When fats or oils are selected, they prer~rdbly comprise a hydroxyl-substituted
fattyacid constituent. Detailed descriptions of these materials and theirfatty acid constituents
are well known. See, for example, the entry "Fats and Fatty Oils" in Ullmann's Encyclopedia of
Indus~rial Chemistry, ISBN 0-89573-160-6, or alternatively Kirk-Othmer Encyclopedia of
Chemical Technology, ISBN 0-471-02062-1. For the present inven1:ion, suitable compatibilizing
10 agents contain, as a fatty acid constituent, for example, ricinoleic acid, dihydroxystearic acid,
palmitic acid, stearic acid, oleic acid, linoleic acid, eicosanoic acid, or mixtures of two or more
thereof. Preferred in one embodiment of the present invention is ricinoleic acid, which exhibits
excellent miscibility with polar substances, such as alcohols including polyols, and limited
miscibility with nonpolar substances such as hydrocarbons. A convenient and readily available
15 natural fatty oil source comprising a hydroxyl-substituted fatty acid constituent is castor oil
which is understood to comprise on average 90 weight percent of a glyceride of ricinoleic acid,
4 weight percent of a glyceride of linoleic acid, with the balance to 100 percent of glycerides of
dihydroxystearic acid, palmitic acid, stearic acid, oleic acid, linolenic acid and eicosanoic acid.
Castor oil, essentially independent of source, has a hydroxyl number of from 160 to 168.
Suitable polyols include polyester or polyether polyols such as are conventionally
used in the preparation of rigid polyurethane foam and having a hydroxyl number value within
the above-mentioned range. Additionally, such polyols will generally contain from 2 to 8,
preferably from 3 to 8, and more preferably from 3 to 6 hydroxyl groups per molecule.
Examples of suitable, and preferred, polyols are polyether polyols as described more fully in
U.S. Patent 4,394,491. Exemplary of such polyether polyols include those commercially
available under the trademark VORANOL, which include VORANOL 202, VORANOL 360,
VORANOL 370, VORANOL 446, VORANOL 490, VORANOL 575, VORANOL 640, VORANOL 800,
VORANOL CP1000, VORANOL CP260, VORANOL CP450, and VORANOL RN482, all available
from The Dow Chemical Company. Other preferred polyols include alkylene oxide derivatives
of Mannich condensate as taught in, for example, U.S. Patents 3,297,597; 4,137,265 and
4,383,102; and amino-alkylpiperazine-initiated polyether polyols as described in U.S. Patents
4,704,410 and 4,704,411.
As mentioned, the polyurethane foaming process of this invention requires the
presence of a hydrocarbon blowing agent which advantageously comprises a C1 8 aliphatic or
35 cycloaliphatic hydrocarbon, preferably C4 8, which is an alkane, alkene or alkyne. Such
hydrocarbons are selected as the blowing agent because they have a boiling point lower than
the reaction exotherm, generally more than 120C, and usually of from 150C to 200C,
encountered when preparing a polyurethane foam. Suitable hydrocarbons include those
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~ WO 96/12759 PCT/US95/13313
- having a boiling point of less than 120C, preferably less than 100C, and more preferably less
than 50C such as, for example, butane, n-pentane, i-pentane, cyclopentane, methyl-
cyclopentane, hexane, cyc1Ohexane, methylcyclohexane, isomers thereof, or mixtures of two or
more thereof. Preferred hydrocarbons, due to their ability to confer attractive thermal
5 insulation properties to the polyurethane foam, are n-pentane, i pentane and cyclopentane.
Especially p~er~rled is a mixture of isomers n-pentane and i-pentane wherein the ratio of n-
pentaneto i-pentane isfrom 5:95 to 50:50, preferablyfrom 10:90to35:65. Thisfraction of
i-pentane is found to be advantageous for optimum flow properl ies when preparing a
polyurethane foam and for confe" ing attractive thermal insulation properties to the resulting
10 foam Typically the hydrocarbon will be present in an amount of from 1 to 20, preferably from
5 to 20, and more preferably from 7 to 18 parts per 100 parts by total weight of the
composition comprising polyol and compatibilizing agent.
In addition to the hydrocarbon blowing agent, optionally a supplemental
blowing means can be provided by the presence of water. Water reacts with polyisocyanate
15 leading to the production of carbon dioxide which is able to confer a réduced density to the
polyurethane polymer. When present, the amount of water advantageously is from 0.5 to 10,
preferably from 1.5 to 3, and more preferably from 2 to 6 parts per 100 parts by weight of the
polyol composition including the fatty oil. In a highly prefer, ed embodiment of the invention,
polyurethane foam is prepared in the presence of water and hydrocarbon blowing agent
zo wherein, per 100 parts by weight of the polyol composition including the compatibilizing
agent, the water is present in an amount of from 2 to 6 parts, and the hydrocarbon blowing
agent being n-pentane, i-pentane, cyclopentane, or mixtures of at least two thereof is present
in an amount of from 1 to 20 parts. In a lesser preferred embodiment, it is also possible to use
conventional fluorocarbons or hydrogen-containing chlorofluorocarbons, as supplemental
25 physical blowing agent, including difluorochloromethane, difluoroethane,
difluorochloroethane, tetrafluoroethane dichlorotrifluoroethane and others such as those
taught, for example, in U.S. Patent4,945,119.
Suitable polyisocyanates include aromatic, aliphatic and cycloaliphatic
polyisocyanates and combinations thereof. A crude polyisocyanate may also be used in the
30 practice of this invention, such as the crude toluene diisocyanate obtained by the phosgenation
of a mixture of toluene diamines or the crude diphenylmethane diisocyanate obtained by the
phosgenation of crude methylene diphenylamine. Preferred are aromatic polyisocyanates
comprising a methylene diphenylisocyanate, polymethylene polyphenylisocyanate, or mixtures
thereof. Suitable mixtures include those containing, based on total weight of polyisocyanate,
35 from 10 to 50 weight percent of methylene diphenylisocyanate; and from 90 to 50 weight
percent of polymethylene polyphenylisocyanate. For the purpose of providing cross-linkages
in the end polymer, advantageously such an aromatic polyisocyanate has an average isocyanate
220 ~86
WO 96/12759 PCTIUS95/13313
functionality of at least 2.3, preferably from 2.5 to 3.5, and more preferably from 2.7 to 3.1.
Exemplary of commercially available aromatic polyisocyanates suitable for use in this invention
include crude methylene diphenylisocyanate mixtures supplied by The Dow Chemical Company
under the trademark VORANATE and designated as M220, M229, M269, M595 and M580.
The amount of polyisoyanate present when preparing the polyurethane foam is
such to provide for an isocyanate reaction index of typically from 60 to 550, preferably from 70,
more pl er~rdbly from 80, and preferably up to 300, more preferably up to 200, still more
preferably up to 160, and yet more preferdbly up to 140. An isocyanate reaction index of 100
corresponds to one isocyanate group per isocyanate reactive hydrogen atom present including
10 those from the polyol composition containing compatibilizing agent and, if present, any water.
Optionally other ingredients may be present when preparing the polyurethane
foam. Among these other ingredients are catalysts, surfactants, colorants, antioxidants,
reinforcing agents, fillers, anli~ldlic agents and flame retardants. Suitable flame retardants
include phosphorus containing substances such as tris(chloroalkyl)phosphate and
15 trisalkylphosphates, for example triethylphosphate; and nitrogen-containing substances such
as melamine.
One or more catalysts for the reaction of the active hydrogen-containing
compound with the polyisocyanate are advantageously present. Suitable catalysts include
tertiary amine compounds and organometallic compounds. Exemplary tertiary amine catalysts
20 include triethylenediamine, pentamethyldiethylenetriamine, N-ethylmorpholine,N-cocomorpholine, N-methylmorpholine, tetramethylethylenediamine, dimethylbenzylamine,
1 -methyl-4-dimethylaminoethylpiperazine,3-methoxy-N-dimethylpropylamine,
diethylethanolamine,N,N-dimethyl-N',N'-dimethylisopropylpropylenediamine and N,N-
-diethyl-3-diethylaminopropylamine. Exemplary organometallic catalysts include organo-
25 mercury, organolead, organoferric and organotin catalysts, with organotin catalysts beingprefer, ed among these. Suitable tin catalysts include stannous chloride, tin salts of carboxylic
acids such as dibutyltin di-2-ethyl hexanoate, as well as other organometallic compounds such
as are disclosed in U.S. Patent 2,846,408. A catalyst for the trimerization of polyisocyanates and
formation of polyisocyanurate polymers, such as an alkali metal alkoxide, alkali metal
30 carboxylate, or quaternary amine compound, may also optionally be employed herein. When
employed, the quantity of catalyst used is sufficient to increase the rate of polymerization
reaction. Precise quantities must be determined experimentally, but generally will range from
0.01 to 3.0 parts by weight per 100 parts polyol depending on the type and activity of the
catalyst.
It is generally highly preferred to employ a minor amount of a surfactant to
stabilize the foaming reaction mixture until it cures. Such surfactants, distinguished from the
compatibilizing agent, are generally manufactured mineral oils including liquid or solid
organosilicone surfactants. Other, less preferred surfactants, include amine salts of long chain
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WO 96/12759 2 2 ~ ~ 5 8 ~ PCT/US95/13313
alkyl acid sulfate esters, and alkyl sulfonate esters and alkyl arylsulfonic acids. Such surfactants
are employed in amounts sufficient to stabilize the foaming reaction mixture against collapse
and the formation of large, uneven cells. Typically, from 0.1 to 3 parts of the surfactant per 100
parts by weight polyol are sufficient for this purpose.
In making a polyurethane foam, the polyol(s), polyisocyanate and other
components are contacted, thoroughly mixed and permitted to expand and cure into a cellular
polymer. The particular mixing apparatus is not critical, and various types of mixing head and
spray apparatus are conveniently used. It is often convenient, but not necessary, to preblend
some of the raw materials prior to reacting the polyisocyanate and active hydrogen-containing
10 components. For example, it is often useful to blend the polyol(s), blowing agent, surfactants,
catalysts and other components except for polyisocyanates, and then contact this mixture with
the polyisocyanate. Alternatively, all components can be introduced individually to the mixing
zone where the polyisocyanate and polyol(s) are contacted. It is also possible to prereact all or
a portion of the polyol(s) with the polyisocyanate to form a prepolymer, although such is not
15 preferred. For optimum processing, it is found convenient to prepare the polyurethane by
mixing at an ambient temperature the reactants which themselves have a temperature of from
1 0C to 35C, and preferably from 1 5C to 25C.
The polyurethane foam obtained in accordance with this invention is of value forthe appliance and construction industry where its attractive compressive strength, dimensional
20 stability and thermal insulation is highly desirable. The invention may also be used to provide
polyurethane foam for semirigid applications such as for example sealant foam applications.
The invention is illustrated by way of the examples given hereinbelow. Unless
otherwise indicated all amounts given are parts by weight.
Example 1
The storage stability of various hydrocarbon/-polyol mixtures optionally
containing castor oil is reported in Table 1. The substances and relative amounts making up the
hydrocarbon and polyol mixtures are also given in Table 1. The storage stability is determined
in accordance with the following general procedure in which the hydrocarbon is blended into a
polyol mixture, replesenldlive of a formulation typically used forthe manufacture of rigid
30 polyurethane foam, and the resulting blend allowed to stand at room temperature for 7 days.
After this period, the stability of the resulting blend is visually rated according to the following
scheme:
"Separates" - blend separates into multiple layers.
"Turbid" - the turbid blend does not separate into multiple layers and
does not become clear on agitation.
"Limit" - the turbid blend does not separate into multiple layers and
on agitation becomes clear.
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WO 96/127S9 PCT/US95/13313
"Separates" - blend separates into multiple layers.
"Turbid" - the turbid blend does not separate into multiple layers and
does not become clear on agitation.
" Limit" - the turbid blend does not separate into multiple layers and on
agitation becomes clear.
''ClearU - the blend is clear and not separated into multiple layers.
Blends 1, 2 and 5 which separate are undesirable for the purposes of preparing a polyurethane
foam; Blends 3 and 4 are observed to have a "clear or "limit" sta1:us and are preferred as they
are more readily manipulated in a consistent manner to the benefit of the foaming process.
Table i
partsbyweight Blend1* Blend2* Blend3 Blend4 Blend5*
CastorOil 0 3 7 10 28.5
Polyol 1 51 51 51 52.3 51
Polyol 2 14.3 14.3 14.3 12 14.3
15Polyol 3 28.5 25.5 21.5 20
Surfactant 1 2 2 2 1.5 2
Catalyst 2.2 2.2 2.2 2.2 2.2
Water 2 2 2 2 2
i-pentane 10 10 10 10 10
20n-pentane 3 3 3 3 3
Blend Stability after
7 days at:
i) 20C / Turbid Limit ClearSeparates
ii) 5C Separates Separates Turbid Limit Separates
* Not an example of this invention.
Polyol 1: a sorbitol-initiated oxypropylene poiyether polyol having a hydroxyl
number of 480.
Polyol 2: an ethylenediamine-initiated oxypropylene polyether polyol having
hydroxyl number of 640.
Polyol 3: a glycerine-initiated oxypropylene polyether polyol having a hydroxyl
numberof 160.
Surfactant 1: TEGOSTAB B8462 a silicon-based surfactant from Th Goldschmidt AGCatalyst: a blend of urethane promoting catalysts containing 1.2 pbw
dimethylcyclohexylamine, 0.4 pbw pentamethyldiethylenetriamine;
and 0.6 pbw of CURITHANE 206 a proprietary urethane promoting
catalyst available from The Dow Chemical Company.
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WO 96/127S9 PCT/US9S/13313
- Example 2
Rigid polyurethane foam is machine-prepared in the presence of a hydrocarbon
blowing agent and castor oil using the formulation as given in Table ll. High pressure mixing
conditions with reactants being introd uced to the mixer head at a temperature of about 20C
5 are used. The results indicate that an improved blend stability is obtained while still
maintaining an acceptable overall foam physical performance.
Table ll
parts by weight Foam 1 * Foam ZFoam 3
Castor Oil 0 5 10
Polyol 1 O 50 48 50.5
Polyol 2 (~) 15 14 14
Polyol 3 ~3 28.5 27 18.5
Surfactant 1 (~) 2 1.5 1.5
Catalyst O Z.2 2.2 2.2
Water 2.3 2.3 2.3
i-pentane 9.5 10 10
n-pentane 3 3 3
Isocyanate (~) Index 115 115 115
Blend Stability after 7 days at 5Cseparates limit clear
20Free Rise Density (kg/m3) 22.6 21.7 22.4
Molded Foam properties, 34 3 32.6 32.9
Density (kg/m3)
CompressiveStrength(kPa) 154.9 119.6 137
(ASTM C-518) 23.1 23.5 23.2
25Demold post expansion at 3 9 5 4 3
4 minutes (mm)
Not an example of this invention.
(~) As given for Example 1.
(~) VORATEC SD100, a polymeric methylene diphenylisocyanate with an
NCO functionality of 2.7, available from The Dow Chemical Company.
30 Example 3
The storage stability of various hydrocarbon/polyol mixtures containing
compatibilizing agents other than castor oil i5 reported in Table ]Il. The alternative
compatibilizing agents and relative amounts making up the hydrocarbon and polyol mixtures
is also given in Table lll. The storage stability as reported is determined in accordance with the
35 general procedure described for Example 1.
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WO 96/127S9 PCT/US95/13313
Table lll
partsbyweight Blend6* Blend7 Blend8 Blend9 Blend 10
Polyol 4 100 90 90 75 80
Cyclopentane 20 20 20 25 25
Compatibilizing 0 10 0 0 0
Agent2 10 o o
Compatibilizing 0 0 0 25 0
Castor oil 0 0 0 0 20
Blend Stabilityat turbid clear clear clear clear
* Not an example of this invention.
15 Polyol 4: a sucrose/glycerine oxypropylene polyol having a hydroxyl number of 490.
Compatibilizing Agent 1: C1zHz5-(OCH2CH2)4-OH
Compatibilizing Agent 2: p(CgH19)-C6H4-(OCH2CH2)2-OH
Compatibilizing Agent 3: monoglyceride adduct of oleic acid
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