U.S. patent application number 10/334468 was filed with the patent office on 2004-11-18 for aqueous emulsification of high molecular weight functionalized polyolefins.
Invention is credited to Kashikar, Sanjay.
Application Number | 20040229985 10/334468 |
Document ID | / |
Family ID | 32069512 |
Filed Date | 2004-11-18 |
United States Patent
Application |
20040229985 |
Kind Code |
A1 |
Kashikar, Sanjay |
November 18, 2004 |
AQUEOUS EMULSIFICATION OF HIGH MOLECULAR WEIGHT FUNCTIONALIZED
POLYOLEFINS
Abstract
A one-step direct method of making a high molecular weight
functionalized polyolefin aqueous emulsion is provided. In this
one-step direct method, a functionalized polyolefin having a
molecular weight of at least 10,000, a fatty acid, a base, a
surfactant, and water are heated in a pressure reaction vessel to a
temperature above the emulsification temperature of the polyolefin
with agitation for a period of time sufficient to form an aqueous
emulsion. This high molecular weight functionalized polyolefin
aqueous emulsion can be added to a sizing composition and applied
directly onto glass fibers in the glass fiber manufacturing
process.
Inventors: |
Kashikar, Sanjay; (Kelmis,
BE) |
Correspondence
Address: |
OWENS CORNING
2790 COLUMBUS ROAD
GRANVILLE
OH
43023
US
|
Family ID: |
32069512 |
Appl. No.: |
10/334468 |
Filed: |
December 31, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60416687 |
Oct 7, 2002 |
|
|
|
Current U.S.
Class: |
524/247 ;
524/251; 524/322; 524/819; 524/836 |
Current CPC
Class: |
C03C 25/30 20130101;
C08F 255/02 20130101; C08J 3/05 20130101; C08J 3/03 20130101; C08L
51/06 20130101; C08J 2323/00 20130101; C08J 2323/02 20130101; C08L
51/06 20130101; C09D 151/06 20130101; C09D 151/06 20130101; C08L
2666/02 20130101; C08L 2666/02 20130101 |
Class at
Publication: |
524/247 ;
524/251; 524/322; 524/819; 524/836 |
International
Class: |
C08L 001/00 |
Claims
1. A one-step direct pressure method of forming an aqueous emulsion
of a high molecular weight polyolefin comprising the stop of:
heating a single mixture including a polyolefin having a molecular
weight of at least 10,000, a surfactant, a fatty acid, a base, and
water a single time to a temperature above an emulsification
temperature of said polyolefin in a pressure reaction vessel with
agitation at high pressure for a time period sufficient to form an
aqueous polyolefin emulsion.
2. The method of claim 1, wherein said period of time is from 30 to
60 minutes.
3. The method of claim 1, wherein said temperature is 10 to
20.degree. C. above said emulsification temperature of said
polyolefin.
4. The method of claim 1, wherein said polyolefin is a
functionalized polyolefin including at least one reactive chemical
functional group.
5. The method of claim 4, wherein said polyolefin is selected from
the group consisting of polyethylene, polypropylene, polybutene,
polyisobutylene and polyhexene.
6. The method of claim 5, wherein said polyolefin has a molecular
weight of about 100,000-120,000.
7. The method of claim 4, wherein said reactive chemical functional
group is selected from the group consisting of maleic acid, acrylic
acid, methacrylic acid, maleic anhydride, acrylic anhydride,
methacrylic anhydride, glycidyl acrylates and methacrylates.
8. The method of claim 4, wherein said fatty acid is selected from
the group consisting of at least one saturated fatty acid, at least
one unsaturated fatty acid and combinations thereof and is present
in an amount of from 5-25% by weight.
9. The method of claim 8, wherein said saturated fatty acid is
selected from the group consisting of stearic acid, palmitic acid,
lauric acid, myristic acid and behenic acid.
10. The method of claim 4, wherein said base is selected from the
group consisting of organic bases, inorganic bases and combinations
thereof and is present in an amount of from 1-10% by weight.
11. The method of claim 10, wherein said base is selected from the
group consisting of NaOH, KOH, Ca(OH).sub.2,
2-dimethylamino-1ethanol, 2-dimethylamino-1-propanol,
triethylamine, ammonia, 2-dimethylamino-2-methyl-1-propanol,
2-amino-2-methyl-1-propanol and combinations thereof.
12. The method of claim 10, wherein said base is a hydroxylamine
containing both amino and hydroxyl groups.
13. The method of claim 1, wherein said surfactant is selected from
the group consisting of ethoxylated alkyl alcohols and ethoxylated
alkyl acids and is present in an amount of from 5-20% by
weight.
14. The method of claim 1, wherein a solid content of the aqueous
emulsion in said pressure reaction vessel is from 10-45% by
weight.
15-34. (Canceled)
35. A one-step direct pressure method of forming an aqueous
emulsion of a high molecular weight polyolefin comprising the step
of heating 52-90% by weight of a polyolefin having a molecular
weight of at least 10,000,5-20% by weight of a surfactant, 5-25% by
weight of a fatty acid, 1-10% by weight of a base, and water to a
temperature above an emulsification temperature of said polyolefin
in a pressure reaction vessel with agitation at high pressure for a
time period sufficient to form an aqueous polyolefin emulsion.
36. The on-step method of claim 35, wherein said polyolefin is a
functionalized polyolefin including at least one reactive chemical
functional group.
37. The one-step method of claim 36, wherein said reactive chemical
functional group is selected from the group consisting of maleic
acid, acrylic acid, methacrylic acid, maleic anhydride, acrylic
anhydride, methacrylic anhydride, glycidyl acrylates and
methacrylates.
38. The one-step method of claim 35, wherein said polyolefin has a
molecular weight of about 100,000-120,000.
39. The one-step method of claim 38, wherein said polyolefin is
selected from the group consisting of polyethylene, polypropylene,
polybutene, polyisobutylene and polyhexene.
40. The one-step method of claim 35, wherein said temperature is 10
to 20.degree. C. above said emulsification temperature of said
polyolefin.
41. The one-step method of claim 40, wherein said period of time is
from 30 to 60 minutes.
42. The one-step method of claim 35, wherein a solid content of the
aqueous emulsion in said pressure reaction vessel is from 10-45% by
weight.
43. A one-step direct pressure method of forming an aqueous
emulsion of a high molecular weight polyolefin consisting
essentially of: heating a polyolefin having a molecular weight of
at least 10,000, a surfactant a fatty acid, a base, and water to a
temperature above an emulsification temperature of said polyolefin
in a pressure reaction vessel with agitation at high pressure for a
time period sufficient to form an aqueous polyolefin emulsion.
44. The one-step method of claim 43, wherein said polyolefin has a
molecular weight of about 100,000-120,000.
45. The one-step method of claim 44, wherein said polyolefin is a
functionalized polyolefin including at least one reactive chemical
functional group.
46. The one-step method of claim 45, wherein said reactive chemical
functional group is selected from the group consisting of maleic
acid, acrylic acid, methacrylic acid, maleic anhydride, acrylic
anhydride, methacrylic anhydride, glycidyl acrylates and
methacrylates.
47. The one-step method of claim 44 wherein said polyolefin is
selected from the group consisting of polyethylene, polypropylene,
polybutene, polyisobutylene and polybexene.
48. The one-step method of claim 43, wherein said temperature is 10
to 20.degree. C. above said emulsification temperature of said
polyolefin.
49. The one-step method of claim 43, wherein said period of time is
from 30 to 60 minutes.
50. The one-step method of claim 43, wherein a solid content of the
aqueous emulsion in said pressure reaction vessel is from 10-45% by
weight.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This non-provisional application claims priority under 35
U.S.C. .sctn.120 to U.S. Ser. No. 60/416,687, filed Oct. 7, 2002,
the contents of which are incorporated in its entirety.
TECHNICAL FIELD AND INDUSTRIAL APPLICABILITY OF THE INVENTION
[0002] The present invention relates generally to the aqueous
emulsification of high molecular weight polyolefins using a direct
pressure process. In particular, the present invention relates to
the aqueous emulsification of functionalized or chemically modified
polyolefins that have a molecular weight greater than 10,000 in a
one-step direct pressure process. The present invention also
relates to the direct application of these high molecular weight
functionalized polyolefin emulsions onto glass fibers, either
during the glass fiber manufacturing process or at a later stage,
to obtain reinforced polypropylene composites with a high
mechanical performance.
BACKGROUND OF THE INVENTION
[0003] It is known in the art that glass fiber reinforced polymer
composites possess higher mechanical properties compared to
unreinforced polymer composites, provided that the reinforcement
fiber surface is suitably modified by size chemical formulation.
Thus, better dimensional stability, tensile strength and modulus,
flexural strength and modulus, and impact resistance and creep
resistance can be achieved with glass fiber reinforced
composites.
[0004] Glass fiber reinforced polypropylene (PP) composites have
widespread applications in various market sectors such as
automotive, household, and other electrical appliances, that
require a combination of specific short- and long term mechanical,
physical, chemical, aging, and aesthetic properties. These
properties play an important role in designing the final composite
part. For example, stronger polypropylene composites permit the
formation of parts with thinner walls, which helps to improve
productivity with reduced cycle time, to reduce the weight of the
part, to reduce the materials used to make the part, and to reduce
the cost of the part. Improving the strength of composites also
helps extend the life of the final part. In view of emerging
application demands, the polypropylene composite industry is
constantly looking for ways to develop stronger "next generation"
polypropylene composites for new market applications and for
replacements of other more expensive engineering plastics currently
in use.
[0005] It is also known in the art that fiber-matrix interface
interactions influence many bulk mechanical properties of
reinforced composites. Thus, to effectively transfer the applied
load from a weaker matrix resin to stronger fibers, it is necessary
to improve fiber-matrix interactions, especially in glass fiber
reinforced thermoplastic composites. Fiber surface treatment by
applying chemical sizing formulations during glass fiber
manufacturing to modify the fiber surface and improve fiber-matrix
interactions, adhesion, and compatibility in composites has been
practiced in the industry.
[0006] Various aqueous sizing formulations have been used in the
glass fiber industry to maximize the fiber-matrix interactions for
polypropylene composites. These sizing formulations include
ingredients that collectively form an interphase between glass
fibers and the matrix resin. Typically, the sizing formulation
includes ingredients such as a film forming resin, a silane, a
lubricant, an antistatic agent, and other chemical ingredients.
Sizing formulations that include an aqueous emulsion of chemically
modified or functionalized polyolefins, such as maleic anhydride
grafted polypropylene, have been found to be beneficial.
[0007] The maleic anhydride grafted polypropylene ingredient
included in most conventional sizing formulations in the form of an
aqueous emulsion possesses a very low molecular weight (i.e., a
molecular weight 6,000-9,000) and high grafting functionality
levels (i.e., 5-10% by weight). The lower molecular weight (i.e., a
molecular weight less than 10,000), the lower melt viscosities, and
the higher maleic anhydride functionalization of these grafted
polypropylenes have enabled their emulsification, such as by
"indirect pressure" or "direct pressure" methods, without much
difficulty. For example, a low molecular weight polyolefin is
typically melted together and mixed with suitable emulsifying
agents. An emulsion is then obtained by adding the necessary amount
of water.
[0008] One example of a low molecular weight grafted polypropylene
that is readily available is Epolene E43, a homopolypropylene
grafted with maleic anhydride having a weight average molecular
weight of approximately 9100. An aqueous emulsion from this grafted
polypropylene has been useful in glass fiber sizing applications
when it is a major ingredient. However, it is believed that because
of the low molecular weight of the grafted polypropylenes, the
composites reinforced with glass fibers sized with such low
molecular weight grafted polypropylene formulations are not strong
enough to meet current application needs. To enhance the lower end
properties of such polypropylene composites, it has become common
practice to add a high molecular weight functionalized
polypropylene in solid form during the compounding stage of the
manufacturing process. However, high quantities in solid form must
be added to compensate for these lower end properties (e.g.,
between 2-15% by weight of the matrix resin must be added).
Moreover, during the compounding stage, the added high molecular
weight grafted polypropylene is dispersed throughout the composite
part and is only partially directed towards the fiber surface,
which results in a non-optimal use of this generally more expensive
grafted solid polypropylene additive.
[0009] The aqueous emulsification of such high molecular weight
grafted polypropylenes is difficult due to their higher molecular
weight, higher melt viscosity, lower melt flow rate (MFR) or melt
flow index (MFI), higher hydrophobicity, and relatively lower
polarity. The emulsification of isotactic, high molecular weight
grafted polypropylene becomes even more difficult due to their
higher tendency to crystallize. Thus, it is extremely difficult to
derive formulations to successfully achieve an aqueous
emulsification of high molecular weight grafted polypropylene.
[0010] Various techniques have been disclosed to emulsify high
molecular weight functionalized polyolefins. For example, French
Patent No. 2,588,263 describes a technique for emulsifying
isotactic polyolefins of high molecular weight by dissolving the
polymer with heat in an organic solvent that is immiscible in
water. Water is then added to dilute the mixture. This process
requires the subsequent elimination of the solvent by extraction or
by washing and drying. In addition to the burden of having
additional steps, the use of organic hydrocarbon solvents creates
safety concerns for the chemist emulsifying the polyolefins.
[0011] U.S. Pat. No. 4,240,944 describes the co-emulsification of a
mixture of a high molecular weight isotactic grafted polypropylene
together with a lower molecular weight amorphous grafted
polypropylene in a ratio of 1:1 to 1:4 parts by weight along with
the base and surfactant and subsequent addition of water to obtain
an emulsion. However, in this method, not more than 50% of the
isotactic high molecular weight grafted polypropylene can be
incorporated into the emulsion. Further, it is believed that fairly
large concentrations of lower molecular weight amorphous grafted
polypropylene may ultimately be detrimental for composite
properties at room temperature and, particularly, at elevated
temperature applications.
[0012] U.S. Pat. No. 5,242,969 and U.S. Pat. No. 5,389,440 describe
a two-step method of forming a high molecular weight polypropylene
aqueous emulsion. In the first step, fluidization, melt mixing, and
melt blending of a high molecular weight grafted polypropylene with
a sufficient quantity of fatty acid is accomplished in an extruder
at high shear and high temperature. The mixture is then cooled and
ground. In the second step, the mixture is combined with a base and
other ingredients in a pressure reactor. This method is
disadvantageous in that it requires two steps, is expensive, and
causes the polypropylene resin to experience two thermal cycles,
which leads to excessive degradation and deterioration of the
polypropylene structure. This degradation and deterioration of the
polypropylene affects its mechanical properties and color
performance in the composites formed.
[0013] U.S. Pat. No. 6,166,118 (and Great Britain Patent
Application 232616A) describes an "indirect pressure"
emulsification method, also called a "dilution method" or a
"pressure dilution method". In this method, the ingredients are
heated in a pressure vessel with agitation to form a pre-emulsion
concentrate. Hot water (or steam) is then slowly added with
pressure to the pressure reactor to dilute the contents. However,
the addition of water leads to cooling of the reactor and the
pre-emulsion concentrate must, therefore, be reheated and kept at
that elevated temperature for time sufficient to form an emulsion.
The mixture is then cooled to form an aqueous emulsion. This method
is disadvantageous in that it requires extra equipment or a
facility for hot water (or steam) handling, is time consuming due
to the necessity of having to re-heat the contents of the pressure
reactor after the water has been added, and is potentially
dangerous due the fact that hot water (or steam) must be added with
pressure during the course of the emulsification.
[0014] Therefore, it is desirable to provide an aqueous
emulsification of high molecular grafted polypropylene coupling
agents in a one-step direct pressure process to overcome the
disadvantages of the prior art. It is also desirable to provide an
efficient way of applying high molecular weight grafted
polypropylenes onto glass fiber surfaces during the glass fiber
manufacturing process.
SUMMARY OF THE INVENTION
[0015] Accordingly, an important object of the present invention is
to provide a method of emulsifying high molecular weight
functionalized polyolefins that overcomes the disadvantages of the
prior art.
[0016] It is another object of the present invention to provide an
aqueous emulsion of functionalized polyolefins that have a
molecular weight greater than 10,000.
[0017] It is yet another object of the present invention to provide
a one-step direct pressure process for the aqueous emulsification
of high molecular weight functionalized polyolefins.
[0018] It is a further object of the present invention to provide
stable, low discoloring, high molecular weight functionalized
polypropylene emulsion formulations.
[0019] It is another object of the present invention to provide
aqueous emulsions of high molecular weight functionalized
polyolefins suitable for direct application to a glass fiber
surface during the glass fiber manufacturing process.
[0020] It is another object of the present invention to deposit
high molecular weight grafted polyolefin directly on the glass
fiber surface during the glass fiber manufacturing process.
[0021] It is a feature of the present invention that the high
molecular weight functional polyolefin emulsion is free of alkyl
phenol based surfactants.
[0022] It yet another feature of the present invention that the
high molecular weight functionalized polyolefin emulsion is free of
solvents and volatile organic compounds.
[0023] It is an advantage of the present invention that the high
molecular weight functionalized polyolefin emulsion allows
efficient direct interaction with the glass fiber surface.
[0024] It is a further advantage of the present invention that the
high molecular weight emulsion is able to reduce oxidation and
discoloration of the composite part.
[0025] It is an advantage of the present invention that the high
molecular weight functional polyolefin emulsion is environmentally
friendly.
[0026] It is yet another advantage of the present invention that
little or no quantity of high molecular weight grafted
polypropylene coupling agents in solid form is required during the
subsequent compounding stage to obtain a high composite mechanical
performance.
[0027] It is a further advantage of the present invention that less
glass fibers are needed to achieve high performance in the
composite product.
[0028] These and other objects, features, and advantages are
accomplished according to the present invention by providing a
one-step direct method of making a high molecular weight
functionalized polyolefin aqueous emulsion. In this one-step direct
method, a functionalized polyolefin having a molecular weight of at
least 10,000, a fatty acid, a base, a surfactant, and water are
heated in a pressure reaction vessel to a temperature above the
emulsification temperature of the polyolefin with agitation for a
period of time sufficient to form an aqueous emulsion. This high
molecular weight polyolefin aqueous emulsion can be added to a
sizing composition and added directly to glass fibers in the glass
fiber manufacturing process.
[0029] The foregoing and other objects, features, and advantages of
the invention will appear more fully hereinafter from a
consideration of the detailed description that follows.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] The advantages of this invention will be apparent upon
consideration of the following detailed disclosure of the
invention, especially when taken in conjunction with the
accompanying drawings wherein:
[0031] FIG. 1 is a graphical illustration of tensile strengths for
composite parts based on high molecular weight aqueous emulsions
according to the present invention and a reference sample;
[0032] FIG. 2 is a graphical illustration of flexural strengths for
composite parts based on high molecular weight aqueous emulsions
according to the present invention and a reference sample;
[0033] FIG. 3 is a graphical illustration of charpy unnotched
impact strengths for composite parts based on high molecular weight
aqueous emulsions and reference sample; and
[0034] FIG. 4 is a graphical illustration of izod notched impact
strength for composite parts based on high molecular weight aqueous
emulsions according to the present invention and a reference
sample;
[0035] FIG. 5A is a graphical illustration of the mean particle
size and particle distribution of emulsion sample E25 of Table
2;
[0036] FIG. 5B is a graphical illustration of the mean particle
size and particle distribution of emulsion sample E13 of Table
2;
[0037] FIG. 5C is a graphical illustration of the mean particle
size and particle distribution of emulsion sample E20 of Table 2;
and
[0038] FIG. 5D is a graphical illustration of the mean particle
size and particle distribution of emulsion sample E18 of Table
2.
DETAILED DESCRIPTION AND PREFERRED EMBODIMENTS OF THE INVENTION
[0039] The present invention solves the aforementioned
disadvantages and problems of the prior art by providing an aqueous
emulsification of high molecular weight functionalized polyolefins
in a one-step direct pressure emulsification process that enables
the application of these emulsions directly, efficiently, and
evenly onto glass fibers during the sizing step in the
manufacturing process. The term "grafted" and "functionalized" are
used interchangeably herein. In addition, the term "polyolefin" and
"polypropylene" are used interchangeably herein.
[0040] The emulsion components include a high molecular weight
functionalized polyolefin, a surfactant or mixture of different
surfactants, a fatty acid or mixture of different fatty acids, a
base, and water. The functionalized polyolefins include polymers
that are based on monomers of olefins having 2 to about 6 carbon
atoms. Suitable examples of polymers based on these monomers,
called polyolefins, include polyethylene, polypropylene,
polybutene, polyisobutylene, and polyhexene. Preferred polymers
include homo- and copolymers of polyethylene that have a low,
medium, or high density, as well as homo- and co-polymers of
polypropylene that are crystalline, semi-crystalline, amorphous, or
rubbery and elastomeric.
[0041] Functionalized or grafted polyolefins used in the emulsion
include the above-described polyolefins that have reactive chemical
functional groups attached to them. Suitable examples of the
reactive groups include, but are not limited to, acids or
anhydrides such as maleic acid, acrylic acid, methacrylic acid,
maleic anhydride, acrylic anhydride, methacrylic anhydride, and
oxiranes such as glycidyl acrylates or methacrylates. Suitable
examples of high molecular weight maleic anhydride grafted
polypropylenes available as coupling agents in solid form include,
but are not limited to, Polybond PB3200, Polybond PB3000, Polybond
PB4000, Fusabond M613-05, Fusabond MD353D, Fusabond 411D, Exxcelor
P01020, Priex 20099, Priex 21099, Epolene 3015, and Epolene 3003,
and Orevac CA100. Functionalized polyolefin coupling agents are
generally characterized by their type, molecular weight, melt flow
index, degree of functionalization (given in weight percent), and
acid number. Table 1 set forth below indicates varying types,
degrees of functionalization, acid numbers, and molecular weights
for different suitable high molecular weight grafted polypropylene
coupling agents.
1TABLE 1 Examples of Maleic Anhydride Grafted Polypropylene
Coupling Agents Acid No Reference Polymer MA % Mg KOH/g
MeltFlowIndex Melting Names Type Mw range Mn by wt resin g/10 min
Point .degree. C. PP1 Homo 84000-120000 33000 0.67-1.1 7.7-12.64
90-140 157 (190.degree. C./2.16 kg) PP2 Homo 61000-84000 24000
0.9-1.12 10.35-12.87 380-430 157 (190.degree. C./2.16 kg) PP3 Homo
61000-84000 24000 0.9-1.12 10.25-12.87 380-430 157 (190.degree.
C./2.16 kg) PP4 RandomCopo 61400-71000 22900 1.3-1.7 14.94-19.54
450 136 (190.degree. C./2.16 kg) PP5 RandomCopo 73000 27900 >1
>11.49 290 136 (190.degree. C./2.16 kg) PP6 Impact Copo 79000
19000 0.65-0.85 7.47-9.77 102 160 (190.degree. C./2.16 kg) PP7 Homo
93000 25000 0.55 6.32 120 162 (190.degree. C./2.16 kg) PP8
RandomCopo 60000 24000 0.5 5.75 134 PP9 Homo 60000 20000 0.26 3 160
PP10 Homo 60000 25000 0.64-0.8 7.36-9.2 80-170 160 (190.degree.
C./1.2 kg) PP11 Homo 47000 24800 1.05-1.57 12-18.0 155 PP12 Homo
52000 27200 1-1.5 8 156 PP13 Homo 9100 3900 4-8.0 45 155 PP1-PP12 =
High mol wt maleic anhydride grafted Polypropylene coupling agents
PP13 = Low mol wt grafted Polypropylene shown as a reference in
this table Homo = Homopolymer based on propylene monomer RandomCopo
= Random copolymer of propylene and ethylene monomer ImpactCopo =
Impact copolymer or impact modifier based on Ethylene-Propylene
rubber Mw = Wt average mol wt Mn = Number average mol wt MA% = % by
wt of Maleic Anhydride grafted on Polypropylene
[0042] Grafted polypropylene coupling agents having as low as a
0.5% maleic anhydride grafting level and having an acid number as
low as 5.75 (e.g., PP8 in Table 1), and polypropylenes having a
molecular weight as high as 120,000 (e.g., PP1 in Table 1) have
been successfully emulsified using the one-step direct pressure
process method described herein. However, the maleic anhydride
grafting level is preferably greater than 0.5% and the molecular
weight is preferably from about 100,000 to about 120,000. The high
molecular weight grafted polypropylene coupling agents can be used
alone or as a mixture of different coupling agents in the
emulsification formulation. The amount of functionalized
polyolefins in the emulsion is typically between 52-90% by weight
of the total dry solids content, preferably between 60-80%, and
more preferably between 65-75%.
[0043] A second component of the emulsion is saturated or
unsaturated alkyl acids or fatty acids either in solid or liquid
form having either a linear or branched structure. Suitable fatty
acids include fatty compounds modified to contain acids,
anhydrides, or esters. Saturated alkyl or fatty acids are preferred
because they provide a better final color and are more stable to
thermo-oxidation. Examples of suitable saturated fatty acids
include stearic acid, palmitic acid, lauric acid, myristic acid,
caprylic acid, and behenic acid, and fatty acids that contain 4-36,
and preferably from 8-36, carbons. Typical examples of unsaturated
fatty acids include oleic acid, tall oil fatty acid, palmitoleic,
myristoleic, lauroleic, and linoleic acids. Fatty acids are
advantageously used in lowering the melt viscosity of the high
molecular weight polyolefin without degrading the polyolefin. In
addition, the fatty acids act as lubricating agents during the size
application process during glass fiber manufacturing. The fatty
acids provide a structure that is similar to the polyolefins which
improves the dispersion of the glass fibers in composites and
provides compatibility between the fibers and the matrix resin
during the cooling of the matrix resin. Because the fatty acids are
capable of undergoing varying degrees of neutralization and are
capable of producing varying HLB (Hydrophilic-Lypophilic Balance)
values required for emulsification formulating systems, they can
also be used as emulsifying agents. Therefore, the fatty acids are
useful as emulsifiers for various emulsification systems alone or
in combination with other emulsifying components. Typically, the
quantity of fatty acid(s) present in the high molecular weight
functionalized polypropylene emulsion is from 5-25%, more
preferably from 10-20%, and even more preferably from 13-17% by
weight of the of the total dry solids content.
[0044] A third component of the aqueous emulsion is a non-ionic
emulsifier or surfactant or a mixture of non-ionic emulsifiers or
surfactants. Although any non-ionic surfactant is suitable for use
in the aqueous emulsion, ethoxylated aliphatic alkyl alcohols,
ethoxylated fatty alcohols, ethoxylated aliphatic alkyl acids,
ethoxylated fatty acids, or any combination thereof are desirably
used. Suitable examples of such non-ionic emulsifiers include, but
are not limited to, Pegosperse 1500MS (HLB of 14) which is an
ethoxylated fatty acid, Brij 78 (HLB 15.3) which is an ethoxylated
fatty alcohol, Brij 35 (HLB 16.9), Lutensol ON60 (HLB 12.5) which
is an ethoxylated alkyl alcohol.
[0045] The number of carbon atoms in the alky- or fatty chain can
vary between 4 and 36 and the length of the ethoxylation in these
compounds may range from 2-50 ethoxy units, but is desirably in the
range of 3-35 ethoxy units. The number of carbon atoms in the alkyl
group chain is generally between 4-36 carbons. Other surfactant
types such as non-ionic surfactants and surfactants based on
alkylphenols or ethoxylated nonylphenol compounds are not preferred
for use in the aqueous emulsion because they are not
environmentally friendly and are thermally less stable, which can
cause yellowing in the composite part. The amount of surfactant or
mixture of surfactants present in the aqueous emulsion ranges from
5-20%, preferably from 8-15% and more preferably 10-13% by weight
of the total dry solid content.
[0046] Mixtures of emulsifiers having different HLB values have
been used to produce an HLB value that is suitable for
emulsification. The surfactants or emulsifiers in the aqueous
emulsion provide long-term storage stability and are used to ensure
good emulsion quality with fine particle size. Such emulsifiers
also retain the color of the emulsion upon heating and do not
produce discolored components.
[0047] A fourth component of the aqueous emulsion is a base. The
base can be either organic, inorganic, or a combination of organic
and inorganic bases. Although the base can be any known organic or
inorganic base, suitable examples include hydroxides of the
alkaline earth metals such as NaOH, KOH, and Ca(OH).sub.2, or
organic amines, such as, but not limited to,
2-dimethylamino-1-ethanol (DMAE), 2-dimethylamino-1-propanol
(DMAP), triethylamine (TEA), ammonia (NH3),
2-dimethylamino-2-methyl-1-propanol (DMAMP), and
2-amino-2-methyl-1-propanol (AMP). Preferably, the base is an
organic amine or combination of amines, which is used to neutralize
the carboxyl functions. The base is present in the aqueous emulsion
in an amount sufficient to provide neutralization of the acid
functions of the emulsion components. The base can be present in
the aqueous emulsion from about 1-10% by weight, preferably from
about 3-8% by weight, and even more preferably from 5-7% by weight
of the total dry solid content.
[0048] A hydroxylamine containing both amino and hydroxyl groups is
the most desirable base due to qualities such as better handling,
lower odor, lower volatility, and higher base strength. Such an
amine permits lower quantities to be used to achieve a stable
aqueous emulsion and provides improved stability to the aqueous
emulsions. In addition, such an amine has the ability to neutralize
higher molecular weight functionalized polyolefins (including
functionalized polyolefins that have a lower acid functionality),
to provide a solubilized system, and to facilitate the
emulsification of the high molecular weight polyolefins. In
addition, these amines can form water azeotrops so that excess
amine can be easily removed from the aqueous system during drying.
Moreover, the hydroxylamine provides improved water resistance to
the dried systems and does not cause undesirable color development
in the dried parts.
[0049] Optionally, the aqueous emulsion can include one or more
ingredients to improve the emulsion's physical characteristics
(e.g., color and stability) and the coating performance. Such
ingredients include bisulfites, sulfites, phosphites, phosphonites,
phosphinates, hypophosphites of either alkali metals, alkaline
earth metals, or ammonia. Suitable examples include sodium
metabisulfite, sodium sulfite, and sodium hypophosphite, which can
be used to improve the stability and color of the emulsion. The
aqueous emulsion may also include antioxidants based on hindered
phenols, diarylamines, thioethers, or metal
deactivator/antioxidants to protect the composite product from
degradation, which can ultimately result in better color. Color
enhancers such as zinc sulfide or a zinc sulfide pigment may also
be used in small quantities. Fluorescent ingredients, also known as
optical brighteners, may also be included during the emulsification
phase to improve the color of the emulsion and the final coating
resulting from the emulsion. Other oligomeric or polymeric
ingredients (e.g. oxidized polyethylene, low molecular weight
polyamides, and poly(maleic anhydride-alt-1-octadecene)) with
molecular weights ranging from 30,000-500,000 may be included to
improve other characteristics such as adhesion and surface tension.
The optional ingredients can range from 0.01 to 20% of the total
dry content of the emulsion. The optional components may be used as
alone or in combination with each other.
[0050] By including the optional ingredients during the
emulsification phase, they can be dispersed in the aqueous emulsion
and avoid any need to include these optional ingredients during
size chemical mixing, which is generally done at milder mixing
conditions which can lead to the settling of these ingredients.
Such settling can cause breaks in the glass fiber manufacturing or
can result in a poor coating onto the glass fiber. In addition,
because these ingredients are dispersed in the aqueous emulsion
when the emulsion is coated as sizing onto fiber surface, they can
protect the coating from degradation and discoloration.
[0051] To form a high molecular weight functionalized polyolefin
aqueous emulsion, all of the components of the aqueous emulsion
(e.g., a high molecular weight functionalized polyolefin, a
surfactant or mixture of different surfactants, a fatty acid or
mixture of different fatty acids, a base, and water) are added to a
pressure reaction vessel capable of performing at high temperature
and high pressure conditions. Any well-known conventional pressure
vessel is suitable for use in the emulsification of the high
molecular weight functionalized polyolefin. Typical pressures of
the emulsification range from 6-11 bars, but depend on the
particular polyolefin being used, the total dry content of the
emulsion, and the volume in the pressure vessel. Examples of
emulsion formulations and emulsification results are set forth in
Tables 2-2C below.
2TABLE 2 Emulsification Formulations Emulsion ingredients E1 E2 E3
E4 E5 E6 E7 E8 PP1 13.28 13.10 13.17 13.17 13.27 13.27 13.63 13.38
PP2 PP3 PP4 PP5 PP6 PP7 PP8 PP9 PP10 PP11 PP12 Stearic acid 3.72
4.58 3.69 3.69 3.19 3.19 1.36 1.34 Peg1500MS 1.59 1.57 1.58 1.59
Brij 78 1.58 1.59 1.64 3.01 Brij 72 Brij 35 0.79 0.79 0.80 0.80
0.82 1.27 DMAMP-80 1.63 2.03 1.61 1.61 1.39 1.39 0.61 0.60 AMP-95
NaMBS 0.13 0.13 0.13 0.13 0.13 0.13 0.14 0.13 (Na2S2O5) PA-18 ZnS
Water 79.65 78.59 79.03 79.03 79.63 79.63 81.80 80.27 Total 100.00
100.00 100.00 100.00 100.00 100.00 100.00 100.00 Actual Solids
19.10 20.20 19.90 20.00 19.40 19.30 * * content % Quality G G VG VG
VG VG NG NG Stability Stable Stable Stable Stable Stable Stable * *
Remarks* 1) All ingredients are given in parts per 100 parts of
total formulation. 2) NG = Not Good (either no emulsion formed or
poor emulsification yield) 3) G = Good (particle size <1 .mu.)
4) VG = Very Good (particle size <200 nm) 5) PP1-PP12 = high mol
wt grafted polypropylenes (see Table 1) 6) NaMBS = Sodium
metabisilfit 7) DMAMP-80 = 80% solution of
2-dimethylaminomethyl-1-propanol (from Angus Chemie) 8) AMP-95 =
95% solution of 2-amino-2-methyl-1-propanol (from Angus Chemie) 9)
Peg1500MS = POE-(15)-stearic acid (HLB = 14) (from Lonza Group) 10)
Brij 78 = POE-(20)-stearyl alcohol (HLB = 15.3) (from Uniqema, ICI)
11) Brij 72 = POE-(2)-stearyl alcohol (HLB = 4.9) (from Uniqema,
ICI) 12) Brij 35 = POE-(23)-lauryl alcohol (HLB = 16.9) (from
Uniqema, ICI) 13) Stearic acid = Radiacid 152 (95% pure stearic
acid) (from Fina Chemicals) 14) PA-18 = Poly (maleic
anhydride-alt-1-octadecene) 15) Zns = Zinc Sulphide (from Sachleben
Chemie) 16) E = emulsion *Remarks are applicable to Tables 2-2C
TABLE 2A (continuation of Table 2) Emulsion ingredients E9 E10 E11
E12 E13 E14 E15 E16 E17 PP1 13.34 13.30 13.27 20.97 20.97 20.94 PP2
20.58 PP3 PP4 PP5 PP6 PP7 13.27 13.27 PP8 PP9 PP10 PP11 PP12
Stearic acid 2.00 2.66 3.19 5.03 5.03 5.02 3.72 3.19 5.76 Peg1500MS
2.52 2.47 Brij 78 2.40 2.00 1.59 2.52 2.51 1.59 1.59 Brij 72 Brij
35 1.20 0.93 0.80 1.26 1.26 1.26 0.80 DMAMP-80 0.87 1.16 1.39 2.20
2.20 2.20 1.63 1.39 2.67 AMP-95 NaMBS 0.13 0.13 0.13 0.21 0.21 0.21
0.17 0.13 0.15 (Na2S2O5) PA-18 ZnS 0.17 Water 80.05 79.81 79.63
67.81 67.81 67.69 79.63 79.63 68.36 Total 100.00 100.00 100.00
100.00 100.00 100.00 100.00 100.00 100.00 Actual Solids * 19.20
19.60 30.00 30.10 30.10 19.30 19.40 29.90 content % Quality NG G G
VG VG VG G G VG Stability * Stable Stable Stable Stable Stable
Stable Stable Stable TABLE 2B (continuation of Table 2) Emulsion
ingredients E18 E19 E20 E21 E22 E23 E24 E25 E26 E27 PP1 PP2 20.97
PP3 20.54 20.97 PP4 21.06 20.70 20.95 20.84 20.97 PP5 PP6 PP7 PP8
20.97 PP9 PP10 20.97 PP11 PP12 Stearic acid 5.03 5.75 5.03 4.21
6.11 4.19 4.17 5.03 5.03 5.03 Peg1500MS 2.52 2.47 2.52 2.52 2.52
2.52 Brij 78 4.21 2.17 4.19 4.17 Brij 72 Brij 35 1.26 1.26 1.26
1.26 1.26 DMAMP- 2.20 2.67 2.20 1.90 2.54 1.89 1.88 2.20 2.20 2.20
80 AMP-95 NaMBS 0.21 0.15 0.21 0.16 0.16 0.16 0.16 0.21 0.21 0.21
(Na2S2O5) PA-18 0.52 1.04 ZnS 0.15 Water 67.81 68.26 67.81 68.46
68.32 68.10 67.74 67.81 67.81 67.81 Total 100.00 100.00 100.00
100.00 100.00 100.00 100.00 100.00 100.00 100.00 Actual 30.10 29.90
30.00 29.80 29.80 29.90 30.30 29.70 29.70 29.80 Solids content %
Quality VG VG VG VG VG VG VG VG VG VG Stability Stable Stable
Stable Stable Stable Stable Stable Stable Stable Stable TABLE 2C
(continuation of Table 2) Emulsion ingredients E28 E29 E30 E31 E32
E33 PP1 PP2 PP3 17.89 PP4 21.00 21.36 PP5 20.97 19.67 PP6 3.06 PP7
PP8 PP9 PP10 PP11 20.97 PP12 Stearic acid 5.03 5.51 5.03 5.03 5.04
Peg1500MS 2.52 2.36 2.52 2.52 2.52 Brij 78 4.27 Brij 72 4.27 Brij
35 1.26 1.18 1.26 1.26 1.26 DMAMP- 2.20 2.41 2.20 2.21 0.53 80
AMP-95 2.07 NaMBS 0.21 0.20 0.21 0.21 0.21 0.16 (Na2S2O5) PA-18 ZnS
Water 67.81 68.68 67.81 67.83 67.90 69.41 Total 100.00 100.00
100.00 100.00 100.00 100.00 Actual 29.80 29.70 30.00 * 29.60 *
Solids content % Quality G VG VG NG VG NG Stability Stable Stable
Stable * Stable *
[0052] The components of the aqueous emulsion are then heated with
agitation at high pressure to a temperature above the melting
temperature of the high molecular weight functionalized polyolefin
for a period of time sufficient to emulsify the high molecular
weight polyolefin. Typically, the components are heated to a
temperature 10-20.degree. C. above the melting temperature of the
high molecular weight functionalized polyolefin for approximately
30-60 minutes with stirring, e.g., such as with a propeller type of
stirrer or an anchor type of stirrer, or a combination of stirrers,
to produce an aqueous emulsion. The resultant emulsion is
subsequently cooled. Optimally, the cooling rate is as slow as
possible, and is preferred to be just below 1.degree. C. per
minute. Additional cooling can optionally be provided once the
temperature of the emulsion has cooled to approximately 95.degree.
C. The solid content of the aqueous emulsion in the reactor is
generally 10-45%, preferably from 15-40%, and most preferably from
25-35% by weight.
[0053] As a result of the one-step direct pressure method described
herein, very stable aqueous emulsions are formed which have a fine
particle size and a milky white appearance. Particle size
analytical results for representative inventive emulsions are set
forth in FIGS. 5A, 5B, 5C, and 5D. As seen in FIGS. 5A-5D, which
represent the particle size analysis for inventive aqueous
emulsions E25, E13, E20 and E18 as described in Tables 2A and 2B,
fine particle size and good quality aqueous emulsions are formed
with the particle size ranging from 0.081 .mu.m to 0.2 .mu.m in
diameter.
[0054] Unlike the conventional emulsification methods described
above, the inventive method is a one-step direct pressure process,
e.g., all the components are placed together in the reaction vessel
and heated. There is no dilution step necessary (as in an indirect
process), it does not require any extra equipment for hot water (or
steam) handling, and no extrusion or grinding is necessary.
[0055] Once the aqueous emulsion of the high molecular weight
functionalized polyolefin has been formed, the aqueous emulsion can
be used in numerous applications, such as a component in coatings
for floors, cars, metals, paper, textiles, as a component for
sizing fibers (inorganic, synthetic, organic, or natural), as
lubricants in paper calendaring, and as coatings for fruits. In one
application, the aqueous polyolefin emulsion is incorporated into
the sizing formulation that is deposited directly onto the surface
of the glass fibers during the manufacturing process. The aqueous
emulsion can be deposited onto the glass fibers by any means known
to one skilled in the art. Glass fibers deposited with a sizing
including the high molecular weight functionalized polyolefin
aqueous emulsion can then be used to reinforce polyolefin matrix
resins in a wide variety of forms, such as continuous strands,
chopped strands, fabrics, and mats made form continuous-, chopped-,
woven-, or non-woven fibers.
[0056] By applying the emulsified polyolefin emulsion to the glass
fiber during the sizing step, the high molecular weight
functionalized polyolefin is placed directly, evenly, and
efficiently on the glass fibers. Applying such a high molecular
weight polyolefin emulsion directly on the glass fiber surface
provides optimal use of the high molecular weight grafted
polyolefin for compatibilizing and coupling the glass fiber and the
matrix resin and results in improved mechanical properties. When
the high molecular weight grafted polyolefin is deposited directly
on the glass fibers, it participates in creating a strong
interphase between the glass fibers and the resin matrix and
provides better compatibility with the polypropylene matrix. Thus,
the high molecular weight grafted polyolefin emulsion not only
provides stronger protection to the glass fiber surface but also
improves the adhesion and compatibility of the glass fiber (an
inorganic material) to the polyolefin matrix resin (an organic
material). Moreover, since the high molecular weight grafted
polyolefin coupling agent, used conventionally in solid form during
the compounding stage, is now deposited on the fibers prior to the
compounding stage, there is little need of the addition of a very
high molecular weight grafted polyolefin coupling agent in solid
form during a subsequent compounding stage.
[0057] Having generally described this invention, a further
understanding can be obtained by reference to certain specific
examples illustrated below which are provided for purposes of
illustration only and are not intended to be all inclusive or
limiting unless otherwise specified.
EXAMPLE
[0058] Sizing compositions shown in Table 3 below were prepared and
applied to glass fibers during the glass fiber manufacturing
process. The wet fibers were subsequently chopped in-line and dried
in an oven according to standard manufacturing conditions. The
dried chopped strands were compounded with a matrix polymer resin
in a standard twin-screw extruder. The extruded compound was then
chopped in-line into pellets and then molded using a standard
injection molding machine to produce the composite parts and the
test pieces.
3TABLE 3 Examplary Formulations and the Chopped Glass Fiber Strands
Produced from Them Exemplary Sizing Ingredients Sizing Aque.
Chopped Formulation Emulsion Silane Lubricant* Antifoam* Fibers
SRef* ERef* RRef* RRef* RRef* FRef* S1 82.64 17.24 0.00 0.12 F1 S2
66.65 16.19 17.07 0.11 F2 S3 67.35 16.36 16.17 0.11 F3 S4 63.50
15.42 20.97 0.11 F4 S5 74.85 17.54 7.49 0.13 F5 S6 74.85 17.54 7.49
0.13 F6 S7 71.16 21.60 7.12 0.12 F7 S8 71.16 21.60 7.12 0.12 F8 S9
55.64 16.93 27.33 0.10 F9 Remarks 1) All values in % by wt base on
total dry content 2) Silane = Gamma aminopropyltriethoxysilane 3)
Lubricant* = Same lubricant is used for all the examples and is
given as proprietary information 4) Antifoam* = Same Antifoaming
agent is used for all the examples and is given as proprietary
information 5) ERef* = Reference aqueous emulsion based on low mol
wt grafted Polypropylene (mol wt < 10000) 6) FRef* and F1-F9 =
Dried, chopped fibers based on sizing SRef* and S1-S9 respectively
7) RRef* = Proprietary sizing raw ingredients 8) SRef* = Aqueous
sizing based on ERef* aqueous emulsion 9) S1, S2, S3, S4 = Aqueous
sizing based on E22, E25, E18, E20 aqueous emulsions of invention
respectively 10) S5-S9 = Aqueous sizings based on E13 aqueous
emulsions of invention 11) Chopped fibers F1-F6 and F9 have average
diameter of 14 .mu. 12) Chopped fibers F7 has 17 .mu. whereas F8
has diameter of 10 .mu.
[0059] In one example, 30 parts of chopped glass fibers (average 4
mm in length) which were dried after applying the sizing which
included the high molecular weight functionalized polyolefin
aqueous emulsion according to the present invention, were extrusion
compounded using a ZSK30/2 type extruder from Werner &
Pfleiderer with 70 parts of homopolymer polypropylene matrix resins
having a melt flow index of 10-12 g/10 min (236.degree. C./2.16 kg)
and 1.2 g/10 min (236.degree. C./2.16 kg). The extrusion
compounding formulations were blended with different concentrations
of high molecular weight grafted polypropylene coupling agent in
solid form (e.g., PB3200 from Uniroyal Chemicals, Crompton, U.S.)
as shown below in Table 4.
4TABLE 4 Exemplary Extrusion Compounding Formulations Compounding
PB3200 Formulation 0% 0.5% 1% 1.20% 2% CRef* X X X X X C1 X X X C2
X X X X X C3 X C4 X C5 X X X X C6 X X X X C7 X X C8 X X C9 X X X
Remarks 1) All formulations include 30 parts by wt of dried,
chopped glass fibers based on total formulation 2) 70 parts by wt
of total formulation comprises Polypropylene matrix resin, high mol
wt grafted coupling agent PB3200 in solid form and antioxidant
HP2215 3) PB3200 = High mol wt grafted Polypropylene coupling agent
added in solid form, from Uniroyal Chemicals, Crompton, US, in % by
wt based on polypropylene matrix resin 4) HP2215 = Antioxidant from
Ciba Chemicals 5) All formulations include 1% by wt of antioxidant
e.g. HP 2215 based on the Polypropylene matrix resin 6) All
formulation containing 0, 0.5, 1, and 2% by wt of PB3200 use
Polypropylene matrix resin with Melt Flow Rate of 10-12 g/10 min
(236.degree. C./2.16 kg). 7) All formulations containing 1.2% by wt
of PB3200 use Polypropylene matrix resin with Melt Flow Rate of 1.2
g/10 min (236.degree. C./2.16 kg). 8) CRef* = compounding
formulation based on dried, chopped fiber "FRef" 9) C1-C9 =
compounding formulation based on dried, chopped fibers "F1-F9"
respectively.
[0060] The extruded pellets were then injection molded using
standard injection molding techniques known to those of skill in
the art on a Demag D80 machine (Demag Hamilton Plastics, Ltd.) to
produce ISO molding pieces that were then subjected to mechanical
testing. Tensile strength was measured using a universal testing
machine from Zwick according to ISO method 527-4, and the results
were reported in MPa. Impact testing was carried out using a
testing machine from Zwick. Impact resistance, a measure of the
degree of impact force that the composite can withstand, measured
in KJ/m.sup.2 was measured according to ISO Method 179/ID in
un-notched specimens, and according to ISO Method 180 in notched
specimens (which were notched at 2 mm). Charpy impact strength is
also a measure of impact strength and was measured as resistance in
KJ/m.sup.2. The results of the mechanical testing in given in Table
5.
5TABLE 5 Tensile Strength Comparison PB3200 MRef* M1 M2 M3 M4 M5 M6
M7 M8 M9 (%) (MPa) (MPa) (MPa) (MPa) (MPa) (MPa) (MPa) (MPa) (MPa)
(MPa) A 0 71.4 * 70.4 * * 63 58.7 * * * B 0.5 74.7 * 91.06 * * 97.9
95 * * * C 1 78.7 93.6 93.4 95.4 97.1 99.7 96.9 88.65 106 97.6 D
1.2 97.7 99.6 101.1 * * * * * 112.9 106.9 E 2 88.4 94.3 94.4 * * 99
97.9 91.7 * 98.2 Remarks 1) PB3200 = Maleic Anhydride grafted high
mol wt Polypropylene coupling agent added in solid form 2) MRef* =
Molded test pieces based on CRef* compounding formulation 3) M1-M9
= Molding test pieces based on C1-C9 compounding formulations 4) A,
B, C and E = Based on Polypropylene resin matrix of 10 g/10 min
(236.degree. C./2.16 kg) 5) D = Based on Polypropylene resin matrix
of 1.2 g/10 min (236.degree. C./2.16 kg)
[0061] Tensile strength results were then compared for samples
having different concentrations of high molecular weight grafted
polypropylene coupling agents in solid form during the compounding
stage. From the results shown in Table 5, it is clear that the
mechanical properties are enhanced significantly for composites
that used reinforcement fibers sized with a coating that included
an aqueous emulsion of a high molecular weight grafted
polypropylene according to the present invention (samples M1-M9 in
Table 5) as compared to the reference (sample MRef in Table 5)
which used reinforcement glass fibers "FRef" coated with sizing
"SRef" comprising aqueous emulsion "ERef" of much lower molecular
weight grafted polypropylenes. Moreover, the samples according to
the invention (e.g., M1-M9) reached a maximum level of mechanical
strength at a much lower concentration of high molecular weight
grafted polypropylene coupling agent added in solid form during the
compounding stage, whereas the reference sample required about 2%
or more of a high molecular weight grafted polypropylene coupling
agent in solid form to be added during the compounding stage to
achieve an acceptable level of mechanical strength. Generally,
higher composite properties are obtained when the reinforcement
fiber diameter is reduced (i.e., the length to diameter ratio,
called "aspect ratio" is increased). Accordingly, lower diameter
reinforcement fibers provided higher mechanical properties for the
composite as can be seen by sample M8 (having a 10 .mu.m diameter)
compared to other higher diameter reinforcement fibers. However, as
can be seen from the results in Table 5, a higher diameter sample
(e.g., M7 having a 17 .mu.m diameter) showed higher level of
mechanical properties as compared the reference sample MRef (having
a 14 .mu.m diameter). Thus, this improvement in mechanical strength
is attributed to the sizing composition that includes a high
molecular weight grafted polypropylene aqueous emulsion.
[0062] Tensile strength results are also graphically represented in
FIG. 1 for inventive samples such as M2, M5, and M6 compared to
reference sample, MRef. Similarly, FIG. 2 illustrates a clear
enhancement in flexural strength properties for inventive samples
such as M2, M5, and M6 compared to reference sample, MRef. FIGS. 3
and 4 provide comparisons for Charpy Unnotched Impact resistance
and Izod Notched Impact resistance respectively. From FIGS. 1-4, it
can be seen that significant improvements in composite performance
have been achieved by the use of aqueous emulsions of high
molecular weight grafted polypropylenes according to the present
invention. Also, because a higher mechanical performance is
obtained at a lower level of addition of high molecular weight
grafted polypropylene coupling agents in solid form during the
compounding stage, optimal use is made of these coupling agents by
first emulsifying the high molecular weight functionalized
polypropylene in an aqueous phase and depositing it directly on the
glass fibers during sizing in the glass fiber manufacturing
process.
[0063] From the results illustrated in Tables 3-5 and in FIGS. 1-4,
it is apparent that using the high molecular weight grafted
polypropylene coupling agents in the form of aqueous emulsions
provides an unexpected and superior improvement in composite
mechanical properties at a reduced level of addition of the
coupling agent during the compounding stage in chemically coupled
polypropylene reinforcement by glass fibers.
[0064] The invention of this application has been described above
both generically and with regard to specific embodiments. Although
the invention has been set forth in what is believed to be the
preferred embodiments, a wide variety of alternatives known to
those of skill in the art can be selected within the generic
disclosure. The invention is not otherwise limited, except for the
recitation of the claims set forth below.
* * * * *