Sizing composition and sized strand useful as reinforcement for reinforced molded composites having improved physical properties

Sizing compositions having polyurethane latex, cationic silane having unsaturation and polyamino silane are provided. The compositions are used to treat glass fibers to produce sized glass fibers having improved physical properties such as integrity. The sized glass fibers when used with molding compounds yields molded articles with improved physical properties like tensile strength, flexural strength and articles with impact strength.

BACKGROUND OF THE INVENTION 
The present invention relates to a sizing composition and sized glass fiber 
strand useful in reinforcing polymers. 
More particularly the present invention relates to a sizing composition for 
glass fibers to produce sized glass fibers with improved performance in 
polymeric molding compounds. 
Reinforced thermosetting plastics can be reinforced with several forms of 
glass fibers including roving, continuous strand, chopped fibers, mat, 
woven fabrics and the like. The reinforced thermosetting plastic 
composites can be produced from thermosetting molding compounds like bulk 
molding compounds and sheet molding compounds, that typically have about 
15 to 25 and 25 to 45 percent glass content respectively. Two families of 
fiber glass reinforced molding sheets that have recently been 
commercialized are the XMC.RTM. composites and HMC.RTM. composites 
available from PPG Industries, Inc., Pittsburgh, Pa. These composites have 
high-strength for structural uses. The HMC.RTM. composite offers isotropic 
strength properties approaching twice those of conventional sheet molding 
compound by employing high glass fiber content with little or no filler. 
XMC.RTM. composite is a directionally oriented, moldable resin-glass fiber 
sheet containing 65 to 75 percent continuous reinforcement. 
The glass fibers used as reinforcement for the thermosetting molding sheets 
are formed by being drawn at a high rate of speed from molten cones of 
glass from tips of small orifices in a platinum device called a bushing. 
In order to protect the glass fibers from interfilament abrasion during 
formation and further processing and to make them compatible with 
polymeric materials like the thermosetting materials, a sizing composition 
is applied to the glass fibers during their formation. 
In order to form acceptable fiber glass reinforced molding composites, the 
glass fibers must have an acceptable sizing composition on their surface. 
The sizing compositions conventionally contain lubricants, film formers, 
coupling agents, wetting agents, emulsifiers, and the like. The solubility 
of the glass fiber sizing composition in ethylenically unsaturated organic 
solvents can affect the final properties of the molded product, because a 
myriad of applications of sized glass fibers in thermosetting molding 
composites utilize unsaturated polyesters or vinyl ester resins. In 
instances where severe shear is necessary to disperse the glass fibers 
through the polyester premix, it is desirable to have a sizing composition 
which is substantially insoluble or totally insoluble in the polyester 
resin premix to prevent filamentation of the strand, i.e., to keep the 
filaments in discreet bundles. For example, bulk molding compounds, which 
are chemically thickened premixed resins having a mixture of the resin and 
monomer with an inert filler, glass fiber reinforcement, a catalyst and 
possible other additives, are prepared by mixing the components in a high 
shear mixer. The unaged polyester monomer solution, having a thickening 
agent and other ingredients, have dispersed homogeneously throughout the 
resinous phase the chopped glass fiber strand or roving as glass fibers by 
the action of the high shear mixer. The bulk molding compound produced 
from the mixing after thickening on aging can be sliced into desired 
shapes such as cubes and the like and placed in a press to form articles 
of the desired design. 
When severe shear is not necessary to homogeneously disperse the glass 
fiber strand throughout the polyester or vinyl ester premixed during 
compounding and molding, increased solubility of the sizing composition on 
the strand can be tolerated. 
If the sizing composition on the glass fibers is not properly formulated, 
the fibers will not disperse uniformly throughout the resin premix. The 
characteristic of the molding compound formed from the polyester and glass 
fibers which describes the homogeneity of the premix composite is called 
"wet-through" or "flow-through". It is desirable to have a high degree of 
wet-through in a bulk molding compound, sheet molding compound, and the 
HMC.RTM. composites and the XMC.RTM. composites, in order that the final 
physical properties of the composites and the processibility thereof are 
at their maximum level. 
On the other hand, it is also desirable that the glass fiber strand be 
wet-out during compounding which means that the resin encapsulates the 
glass fiber strands and no bare glass is visible throughout the formed 
molded compound. Wet-out during compounding is a measure of the apparent 
intimacy of contact between the resin matrix and the glass fiber strand. 
If the glass fiber strands are not immediately wet-out following 
compounding it is not expected that they will wet-out on aging due to the 
increase in the viscosity of the compound. This leads to adverse effects 
on the processibility, molding characteristics, and surface properties of 
the final molded article or composite. 
It is the object of the present invention to provide a sizing composition 
to give glass fibers improved wet-through or flow-through properties and 
better or improved wet-out properties. 
It is an additional object of the invention to provide a sizing composition 
which yields improved physical properties such as integrity between the 
glass fibers and the resin of a thermosetting molding compound in the 
production of thermosetting molding sheet composites. 
It is a further additional object of the invention to provide a sizing 
composition which yields improved integrity between glass fibers and 
polyester, vinyl ester or epoxy resins where severe shear is necessary to 
disperse the glass fibers throughout the resin premix, for example, in the 
preparation of bulk molding compound. 
It is another further object of the invention to provide sized glass fibers 
in the form of continuous strand, chopped fibers, mat, or roving and woven 
fabrics that have improved integrity, wet-out and wet-through in use for 
the preparation of reinforced thermosetting molding composites. 
It is a further additional object of the invention to provide a sizing 
composition for glass fibers that yields sized glass fiber strands having 
improved integrity and reduced degradation in polyester resins, vinyl 
ester resins, and epoxy resins during the severe abuse experienced by the 
glass fibers during the injection process in the production of HMC.RTM. 
composites. 
It is a further additional object of the present invention to provide sized 
glass fiber strands that can be used in reinforced thermosetting molding 
composites that leads to improved physical properties of the composites. 
SUMMARY OF THE INVENTION 
According to the invention, there is provided an aqueous sizing composition 
having an aqueous emulsion of curable polyurethane polymer, one or more 
cationic methacrylate-functional silanes and one or more aminofunctional 
silanes. 
Also, in accordance with this invention glass fibers are provided that have 
at least a portion of their surface in contact with the residue produced 
by removing water from an aqueous sizing composition present on the fibers 
and having one or more curable polyurethane polymers, one or more cationic 
methacrylate functional silanes and one or more aminofunctional silanes. 
In addition, according to the present invention a method is provided for 
imparting to glass fibers improved integrity by treating the glass fibers 
at forming with an aqueous sizing composition having an aqueous emulsion 
of one or more curable polyurethane polymers, one or more cationic 
methacrylate-functional silanes and one or more amino-functional silanes. 
In the composition, sized glass fiber and method of the present invention 
additional ingredients can be used that are conventionally used with glass 
fiber sizing compositions. Also, the amounts of the polyurethane, and 
silanes generally used are respectively those amounts necessary to be 
effective in providing a partial or complete film on the glass fibers and 
in providing adhesion between the film former and glass fibers. 
DETAILED DESCRIPTION OF THE INVENTION 
The sizing composition and method of sizing glass fibers of the present 
invention provide sized glass fibers for use as reinforcement in polymeric 
molding compositions wherein the sized glass fiber strands have improved 
physical properties such as integrity and the reinforced polymeric molded 
composite has better physical properties. The sizing composition, sized 
glass fiber strands and method of sizing glass fibers of the present 
invention can be used for any reinforcement application, but it is 
preferred to use the composition, strands and method with bulk molding 
compounds to produce thermoset bulk molding composites. Examples of other 
reinforcement applications would include the use of the sizing 
composition, sized glass fibers and method of sizing of the present 
invention with sheet molding compounds or in the production of HMC.RTM. 
composites. The form of glass fiber that has the sizing composition of the 
present invention can be any conventional form, for example, chopped 
strand, roving, woven glass fiber strand and the like, but the preferred 
form is the chopped glass fiber strand. For the preferred glass fiber 
strand any conventional method of producing the chopped strand can be 
used. 
The aqueous sized composition has a solid content from about 1 to about 20 
weight percent, but can also have a high solids content of materials 
greater than 20 weight percent. In its preferred form the sizing 
composition will contain about 3 to about 10 weight percent solids 
content. 
Aqueous emulsions of curable, blocked or unblocked polyurethane resins that 
are useful in the present invention are aqueous solutions of polyurethane 
polymers formed by reaction of an organic isocyanate or polyisocyanate 
with an organic polyhydroxylated compound or hydroxyl terminated polyether 
or polyester polymer having present anionic and/or nonionic surfactant. 
Particularly suitable aqueous emulsions of polyurethane polymers are 
designated "Rucothane Latex 2010L, 2030L, 2040L, 2050L, and 2060L" 
available from Ruco Division of Hooker Chemical Corporation, New York. 
These materials are thermoplastic urethane latices having a varying 
particle size of a high molecular weight aliphatic isocyanate based 
thermoplastic elastomer in a water dispersion with an anionic or nonionic 
surfactant. The amount of the thermoplastic polyurethane latex present in 
the sizing composition can vary from about 2 to about 40 weight percent 
and preferably about 5 to 18 weight percent of the sizing composition. The 
Rucothane latexes are based on aliphatic components having an ester 
backbone and have polymer solids content of the stabile emulsions ranging 
from 55 to 65 percent by weight, although generally the polyurethane latex 
can have a total solids content of less than 70 percent. The Rucothane 
latexes have a Brookfield viscosity RVF 4 in centipoise at 2 RPM ranging 
from 7,000 for the 2060L and 2030L latexes up to 25,000 for the 2020L. 
In the sizing composition of the present invention the major amount of the 
solids in the sizing composition is composed of the polyurethane latex, 
while the cationic methacrylate functional silane and polyamino functional 
silane are used in minor amounts. 
It is also within the scope of the present invention to use more than one 
type of polyurethane polymer to make up the proper amount of polyurethane 
polymer in the sizing composition. Another type of polyurethane that is a 
non-exclusive example of polyurethane that can be used alone or in 
combination with the aforedescribed polyurethane latex produced from 
isocyanate monomer "Hylene W" available from E. I. Dupont de Nemours & 
Company. Also, other blocked or unblocked polyurethane latices can be used 
as long as the polyurethane latex can be cured by heat. 
Any suitable cationic silane containing unsaturation may be used in the 
sizing composition of the present invention. The cationic silane with 
unsaturation can be used in the form of the quaternary salt or of the 
amine or amide hydrochloride salt. Non-exclusive examples of cationic 
silanes with unsaturation include: cationic, methacrylate functional 
silane having a formula similar to the following: 
##STR1## 
where the latter is prepared by the mono-addition of ethylene 
dimethacrylate; and cationic styrene functional silane having formula 
similar to the following: 
##STR2## 
and cationic vinyl functional silane having a formula similar to the 
following: 
##STR3## 
A cationic methacrylate or styrene functional silane are more fully 
described in and can be prepared in accordance with the teachings of E. P. 
Pluddenmann in "Cationic Organo-functional Silane Coupling Agents," Soc. 
Plast. Inc. RPC Proc. 27, 21B (1972) hereby incorporated by reference. The 
quaternary salts or amine or amide hydrochloride salts can be prepared in 
accordance with methods common in the art like the quaternization of 
amines and amides. 
One cationic methacrylate functional silane particularly suitable in the 
sizing composition of the present invention is designated "Y-5823" 
available from Union Carbide Corporation. Other cationic silanes 
containing unsaturation that can be used include the methacrylate 
functional "Z-6031" silane and styrene functional "Z-6032", silane 
available from Dow Corning Corporation, and the styrene functional 
"Y-9014" silane available from Union Carbide Corporation. The amount of 
cationic silane with unsaturation, preferably methacrylate functionality, 
used in the sizing composition is in the range of about 0.05 to about 2 
weight percent based on the total sizing composition. 
In the sizing composition of the present invention, any polyamino 
functional silane is used. Such polyamino silanes have the formula: 
EQU [H--(NH--CH.sub.2 --CH.sub.2).sub.a --NH(CH.sub.2).sub.3 ].sub.n 
SiX.sub.4-n 
wherein n is an integer from 1 to 3, a is an integer from 1 to 5 and X is a 
readily hydrolyzable group such as an alkoxy with one to four carbon atoms 
or a halogen. Non-exclusive examples of polyamino silanes that can be used 
include: 
N-(beta-aminoethyl)-gammaaminopropyltrimethoxysilane 
N-(beta-dimethylaminoethyl)-gammaaminopropyltrimethoxysilane 
N-(beta-aminoethylaminoethyl)-gammaaminopropyltrimethoxysilane 
N-(gamma-aminopropyl)-gammaaminoisobutylmethyldiethoxysilane 
N-(beta-aminoethyl)-gammaaminopropyltrithoxysilane 
A particularly suitable polyamino functional silane is the preferred 
diamino silane available from Dow Corning Corporation that is 
N-(2-aminoethyl)-3-aminopropyltrimethoxysilane in a concentration of 40 
percent in methanol. Another diaminosilane like "Z-6020" silane available 
from Dow Corning Corporation can be used. The amount of polyamino silane 
used in the sizing composition is in the range of about 0.05 to about 2 
weight percent based on the total sizing composition. 
In addition to the polyurethane polymer, cationic silane with unsaturation, 
and polyamino silane components of the sizing composition, additional 
agents may be added to the sizing composition although it is preferred 
that the sizing composition contains only the polyurethane polymer, 
cationic methacrylate functional silane and polyamino silane. 
Non-exclusive examples of the additional agents that can be used in the 
sizing composition include coupling agents, such as 
gamma-aminopropytriethoxysilane, beta-(3, 
4-epoxycyclohexyl)-ethyltrimethoxysilane and vinyl tris 
(2-methoxyethoxy)silane; curing agents, such as Ruco Catalyst available 
from Hooker Corporation, cross-linking agents such as Cymel 370, available 
from American Cyanamid and other similar additives. In addition, melamine 
containing agents such as "Tybon A" and polyamide-containing agents such 
as "Tybon B" both available from Pacific Resins and Chemicals Co., 
Washington 98421 can be incorporated into the sizing composition of the 
present invention. 
In the preferred embodiment of the present invention, the sizing 
composition contains the polyurethane latex, cationic methacrylate 
functional silane, and diaminosilane and the method for preparing this 
preferred sizing composition involves the following steps. First, cationic 
silane with unsaturation and the polyamino silane are added respectively 
to a sufficient amount of water to adequately disperse the silanes and 
then they are combined. Second, the polyurethane latex emulsion is diluted 
in water and then added to the diluted silanes. Then the components are 
diluted to the final desired volumn. All of the aforementioned steps are 
accomplished in the presence of a sufficient amount of mixing of the 
components. 
After the sizing composition has been formed as stated above, it is pumped 
in a recirculating fashion to a binder applicator which applies the sizing 
to the glass filaments during formation. The glass fibers are formed in 
the conventional manner by applying the sizing composition by a belt-type 
applicator gathering the individual glass fibers into a strand, and 
collecting strand on a forming tube which is mounted on a winder. The 
forming package is removed from the winder and dried in a forced air oven 
or a dielectric oven until substantially all the water is removed 
therefrom usually at a temperature of around 270.degree. F. (132.degree. 
C.). Subsequent to drying the sized glass fibers can be unwound and used 
for reinforcement, fabricated into chopped strand, formed into roving or 
the like for use in molding compounds like bulk molding, sheet molding 
compounds, HMC.RTM. composites, XMC.RTM. composites and reaction injection 
molding, although the sized glass fibers are preferred for use in bulk 
molding compounds where the best improvement in physical properties is 
obtained. 
It is preferred in the treatment of the glass fibers in formation of strand 
with the sizing composition that the amount of composition placed on the 
strand is around 0.2 to about 3 weight percent.

The invention will be further elucidated by the following Examples. 
EXAMPLE I 
A sizing composition was prepared having the following formulation: 
______________________________________ 
Ingredient % by weight of total Size 
______________________________________ 
Polyurethane resin 
(Rucothane 2010L resin 
Hooker Chemical Co.) 
14.0 
Cationic methacrylate 
functional silane 
("Y-5823" Union 
Carbide Corp.) 0.5 
Diamino silane 
(Z-6026 silane 
Dow Corning Chemical Co.) 
0.8 
______________________________________ 
The formulation was prepared by adding the cationic methacrylate functional 
silane and the diaminosilane to a sufficient amount of water to disperse 
each silane. The diluted silanes are combined and to them there was added 
the diluted polyurethane resin. This diluted polyurethane resin is 
produced by adding the Rucothane 2010L resin to a sufficient amount of 
water to disperse the resin. The mixture in the main mix tank is then 
diluted to the desired volume. During the preparation of the formulation, 
adequate mixing is provided in the main mix tank where the silanes are 
combined and in mix tanks where dilution of the various components occur. 
This sizing composition was applied to glass fibers in forming K-37 glass 
fiber strands. The fibers were formed in the conventional manner as 
aforedescribed. The forming package of the K-37 glass fiber strands was 
dried for about 11 hours at about 270.degree. F. (132.degree. C.). The 
glass fiber strand was chopped into 1/8 inch (0.318 cm), 1/4 inch (0.635 
cm) and 1/2 inch (1.27 cm) chopped strand in a conventional process and 
apparatus. Forming was accomplished in an acceptable manner and chopping 
performance was excellent. The chopped strands were evaluated for 
filamentation, and LOI by methods well known to those skilled in the art. 
The results for this evaluation were: 
______________________________________ 
Chopped Strand 
Filamentation LOI 
______________________________________ 
1/4" 0.2/0.3 1.7% 
______________________________________ 
The chopped strand was combined with bulk molding compound for compression 
and injection molding. The molded article was evaluated for impact 
strength, tensile and flexural strength against molded articles prepared 
in the same manner with commercial chopped strand. The evaluation gave the 
following results: 
__________________________________________________________________________ 
Molded Physical Properties of Thermoset Polyester 
BMC 
Physical Properties 
Content Tensile 
Flexural 
Flexural 
Notched 
Base Type FG Resin 
Filler 
Strength 
Strength 
Modulus 
Izod 
Strand Compound 
% % % PSI (10).sup.3 
PSI (10).sup.3 
PSI (10).sup.6 
Ft-lbs/in 
__________________________________________________________________________ 
Commercial 
CM.sup.1 
22. 
33.6 
-- 2.9(22.1) 
11.1(34.9) 
1.20(13.1) 
5.63(43.8) 
1/2 inch 
IM.sup.2 4.2(20.7) 
8.4(22.2) 
1.21(8.25) 
3.54(26.6) 
PPG-3029 
R.sup.3 144 78 63 
Example 1 
CM 25.7 
32.9 
-- 4.7(23.0) 
12.0(41.1) 
1.28(12.4) 
6.62(57.3) 
1/2 inch 
IM 5.2(26.5) 
10.0(28.0) 
1.24(12.3) 
3.71(29.5) 
R 111 83 56 
__________________________________________________________________________ 
Notes: 
.sup.1 Data on First Line across represent testing of compression molded 
(CM) 9 .times. 16 inch panels. 
.sup.2 Data on Second Line across represent testing on injection molded 
(IM) 8 inch sq. panels. 
.sup.3 Data on the third line across represent testing of reaction 
injection molded samples. Data for each test type represent overall 
averages to account for fiber glass orientation effects. 
Values in () represent coefficient of variation percentages. 
The results shown above and other results obtained comparing molded samples 
using chopped strand made in accordance with the present invention with 
molded samples using commercially available chopped strand show the 
benefit of the present invention. These benefits are improved impact 
strength of the molded article while achieving similar or improved tensile 
strength and flexural strength and modulus. For example, the molded 
article using chopped strand in accordance with the present invention 
compared to molded articles with commercially available chopped strand 
gave: 
Tensile strength 10%&gt;commercial 
Flex strength 10%&gt;commercial 
Impact strength 10%&gt;commercial 
The foregoing has described a sizing composition having a polyurethane 
latex, cationic silane with unsaturation and polyamino silane. This sizing 
composition when applied to glass fibers during their formation yields 
sized glass fiber strands that have improved physical properties such as 
integrity. Glass fibers sized with the sizing composition of the present 
invention produced molded articles having improved physical properties 
such as impact strength, and flexible strength.