Note: Descriptions are shown in the official language in which they were submitted.
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STORAGE STABLE POLYOLEFIN COMPATIBLE SIZE
FOR FIB~R GLASS STRANDS
Background of the Invention
l Field of the Invention
The present invention relates to glass fiber strand treatment
and particularly relates to treating glass fibers during or after forming
with an aqueous sizing which prepares the glass fibers for bonding to
polyolefins in the reinforcement of polyolefin materials and further has
long shelf life and can be used from forming packages.
2. Description of the Prior Art
It is known that glass fibers in the form of continuous strands,
chopped strands or mats can be used successfully to reinforce polyolefins.
And it is known that without effective coupling between the glass and the
polyolefin, the adhesion between the two will be weak and separation will
occur under shear or tensile stresses. It is further known that the
affinity of glass for water aggravates bond weakness when glass is inade-
quately bonded to polyolefins.
A workable method has been disclosed which permits bonding
glass to "lower" polyolefins which are essentially crystalline plastics
formed from monomers having three or more carbon atoms. As discloset
in U.S. Patent No. 3,013,915 at column 2, lines 38-46, glass bonding
to polyolefins may be improved by "cleaning the glass surface, apply-
ing a coupling agent to it, treating with a chemical agent which is a
source of dehydrogenating or oxidizing radicals, contacting the poly-
olefin with the glass, and fusing it by heating the polyolefin above
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its melting point to complete the interbonding." At column 4, lines
16-1~, the disclosure reveals a preference for radical sources having
low decomposition points below 180F. and at columr. 4, lines 69-71,
U.S. Patent No. 3,849,148 proposes the method of sizing
fiber glass strsnds with an aqueous sizing containing a coupling agent,
a heat stable organic peroxide, a non-ionic surfactant and a lubricant.
This process was successful in giving some storage capability to the
sized strands but did not result in long storage life and further remains
susceptible to degradation by high storage temperatures.
U.S. Patent No. 3,882,068 discloses the sizing composition
for glass fibers in several plastic resin systems wherein the size comprises
a coupling agent and a polyolefin emulsion.
U.S. Patent No. 3,437,550 discloses a method of increasing
the bonding of glass fibers to polyolefins by treating the fiber with a
crystalline polypropylene matrix polymer. The preferred modifiers disclosed
are maleic anhydride and acrylic acid.
U.S. Patent No. 3,883,333 discloses a method and apparatus
for forming a continuous glass fiber mat of sized fibers that are suitable
for bonting with polyolefins. The process and apparatus, although continuous,
tiscloses lay down of the fibers immediately after formation of strands.
While the above processes and compositions were useful, there
remains a need in the art for a sizing to promote the binding of polyolefins
to continuous glass fiber strands with increased adhesion. Further, there
remains a need for a sizing for glass fiber strands which will allow the
formation of the sized fiber into forming packages that may be stored
indefinitely prior to use. Effective sizings containing peroxides have
limited shelf-life since they are very sensitive to elevated temperature
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variations during drying of the fibers and high temperatures during ~torage
which can cause premature degradation of the peroxides thus reducing the
effectiveness of the sizlng in binding the glass fiber strands to th~
polypropylene matrix.
Summary of the Invention
It 18 an ob~ect of thls inventlon to overcome the dlsadvantages
of the prior processes and composltlons.
It is another ob~ect of this invention to provide a storage
stable polyolefin bonding sizing for contlnuous glass fibers.
It i8 another ob~ect of this invention to produce polyolefin
glass fiber composites using glass fibers from forming packages.
It is further additional ob~ect to produce storage stable forming
packages of polyolefln compatable glass fiber strands.
It 18 another ob~ect to create a polyolefln bonding sizing not
susceptible to thermal degradation during the drying operation.
These and other ob~ects of the invention are generally accom-
plished by applying a sizing comprising a cDupling agent, a stabllizer, a
maleonated or acrylic modified polypropylene lubricant, a non-crossllnking
film-former, a self-reactive crosslinking film former, and an aqueous
carrier to a glass fiber strand. The sized strand is then wound into a
forming package and dried for later use as a reinforcement for polypropylene
material.
In a preferred embodiment of the invention, an aqueous sizing
comprising a coupling agent of gamma-amino-propyltriethoxysilane, a stabilizer
comprising cis-butenedioic acid, a lubricant of an emulsion of maleonated
amorphous polypropylene, a non-crosslinking film former of vinyl acetate
homopolymer, and a self-reactive copolymer of vinyl acetate and N-methylol-
acrylamide are applied in an aqueous sizing to a glass fiber 80 as to
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impregnate the strand and improve its ability to reinforce polypropylene
articles. The strand after being wound as a forming package and drying to
remove the aqueous carrier may be withdrawn from the forming package and
laid down on a mat which is contacted with polypropylene sheet and under
heat and pressure formed into a fiber reinforced article.
Description of the Preferred Embodiments
The utilization of the sizing system of the instant invention
results in numerous advantages over the prior processes. The utili-
zation of a storage stable sizing with no shelf-life limitation improves
production capability because it allows the storing and distribution of
forming packages of sized glass fiber strand. Prior to the instant inventionJ
it was necessary that the sized fiber be used shortly after forming or be
immediately formed into a mat for forming composite articles. Further, the
drying of the sized fiber was difficult as the drying temperature conditions
were limited by a necessity to not decompose the peroxide, an important
ingretient of the siæing. With utilization of the instant system, it is
possible to form forming packages of sized glass fiber strands at a central
location. These may be then shipped without limitations as to temperature
or stmosphere during shipping to distant points for fabrication into
composite polyolefin glass-fiber-reinforced articles. This offers consid-
erable improvement since the forming of glass strands no longer must be
carried out at the same location that the polyolefin glass fiber reinforced
article is formed. Thus as can be seen that although the individual
ingredients had been used in other sizings, the instant combination of
ingredients allows the achievement of numerous advantages not present in
prior systems.
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Any glass suitable for reinforcing and for dra~ing in fiber form
may suitably be treated in accordance with the present invention. Soda-lime
glasses and borosilicate ("E") glasses are particularly suited for this
practice.
The glass fiber strands to be treated according to this invention
may be typically produced according to the teachings of U.S. Patent No.
2,133,238. The glass fiber strands are composed of a multitude of fine
glass filaments which are formed by being drawn at a high rate of speed
from molten cones of glass located at the tips of small orificeg in a
bushing. During formation, the filaments are coated with the aqueous
sizing prepared according to the description below. Coating of the fila-
ments takes place while they are moving at a speed of the order of 1,000
to 20,000 feet per minute. The coating is accomplished in the immediate
vicinity of the hot bushings and the glass furnace in which the glass is
melted, and after coating, the glass fiber strands move a short distance
onto collecting means. After the strands have been ~ized, they may be
dried to drive off residual moisture from the sized glass.
The aqueoufi sizing to contact, impregnate and coat the gla~s
fiber strand is composed of a coupling agent, a stabilizer, a maleonated
or acrylic modlfied polypropylene lubricant, a non-crosslinking film
former and a self-reactive crosslinking film former.
The coupling agent may be any interfacial boundary area adhesive
compound which acts to unite the surface of the glass fiber strand with the
polyolefin polymer. Among typical coupling agents for uniting glass fiber
strand and polymer~ are metal salts of the strong metal acids such as basic
chromium chloride, basic chromium sulfide having a trivalent metal ion
3elected from the group consisting of chromium, cobalt, nickel, copper, and
lead having at least one hydroxyl group attached to the metal and at least
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one anion of a strong mineral acid attached to the metal; ~erner type
complexes in which a trivalent nuclear atom such as chromium is coordinated
with an organic acid such as methacrylic acid, for instance, methacrylic
C
r ~¦ql~a acid complex of~Pe~c chloride, and other Werner type coupling agents,
having vinyl alkyl amino, epoxy, mercapto, thioalkyl, thioalkyl and phenol
groups. Suitable for the utilization in the instant invention are coupling
agents from the silane and siloxane groups. Typical of such coupling
agents are hydrolyzable, vinyl, allyl, beta-chloropropyl, phenyl, thio-alkyl,
thio-alkaryl, amino-alkyl, methacrylato, epoxy, and mercapto silanes their
hydrolysis products and polymers of hydrolysis products and mixtures of any
of these. A preferred coupling agent is gamma-aminopropyltriethoxysilane
as this material has been found to provide very good coupling between the
glass fiber strand and polyolefin polymers at low concentrations and with
good stability.
Any stabilizer may be selected which acts as a secondary coupler
to improve the stability of the sizing system, assists in crosslinking,
improves the coupling agent fiber innerface and assists the action of the
silane in coupling. Typical of stabilizers for sizes suitable for the
instant invention are ethylenically unsaturated mono or di-carboxylic
acids or anhydrides. Examples of such acids and anhydrides include
maleic acid, fumaric acid, itaconic acid, citrconic acid, acrylic acid,
methacrylic acid, crotonic acid, isocrotonic acid, mesaconic acid, himic
anhydride, maleic anhydride? itaconic anhydride and citraconic anhydride,
and mixtures thereof. A preferred stabilizer is maleic acid (cis-butenedioic
acid) that gives a stable system and improves the coupling action of the
silane coupling agent.
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The material that acts as a lubricant to aid film forming and
assist the coupling which may be used as the lubricant of the in~ention
are chemically modified propylenes. These are maleonated or acrylic
modified polypropylenes as they result in a sized flber with good storage
properties and ability to feed from the formlng package.
The polymer whlch forms the non-crosslinked film former material
of the sizing of the system of the instant invention may be any material
that provides strand integriey to aid in the process-ability of the glass
fiber strand allowing strand removal from a forming package. The non-
crosslinked polymer provides the desired level of plasticity to the sizesuch that the sized fiber of the instant system has an extended shelf-life
and also the processability to allow successful needling of a mat formed of
the sized fibers of the instant invention. The non-crosslinking polymer
generally is a homopolymer or mixtures of homopolymers that will not
crossllnk in the conditions of the sizing and molding operations to which
the sized fiber is sub~ected in the drying of the aqueous sizing from the
fiber and molding with an olefin homopolymer such as polypropylene.
Typical of non-crosslinked film-forming polymers suitable for the instant
invention are epoxies, polyesters, polyurethanes and acrylics. A preferred
non-crosslinked fllm-forming material is vinyl acetate ho polymer as vinyl
acetate homopolymer i8 low in cost, does not degrade at the instant forming
temperatures, and provide good strand integrity when used on a glass fiber
strand.
The self-reactive crosslinked polymer of the instant system may
be any polymer or copolymer that contributes to the formability, strand
integrity (hardness), strand lay, non-scroopy finish, and needleability
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and is capable of auto-co-reaction and cross-linking. These self-reactable
cro~slinking polymers may be definet as a polymer or copolymer capable of
becoming crosslinked without addition of further materials in the conditions
encountered during the drying of the sized gtrand forming package. Typical
of self-reactive crosslinking polymers are vinylacetate~ epoxies, polyesters,
polyurethanes and acrylic polymerg. A preferred polymer is a self-reactive
vinyl acetate-N-methylolacrylamide copolymer that has the advantage of
compatabllity with the polyolefin polymers particularly polypropylene, low
cost, and stability at the forming temperatures of polyolefins.
The sized glass fibers may be formed and the size applied by the
known methods of fiber formation and sizing application. Representative
of a method of fiber formation and sizlng application is the process illu-
strated in Figure 2 of U.S. Patent No. 3,849,148. Glass fiber filaments
emerge from orifices of an electrically heated bushing. These fibers are
attenuated and by means of a strand pulling device these filaments are
gathered to form a strand of glass fiber which may comprise numerous
individual fibers. The sizing 18 applied to the fibers by a conventional
size appllcator such as a kiss appllcator or a belt applicator devlce.
Detail of a slzing appllcator is shown in U.S. Patent No. 2,728,972. The
filaments after exiting the bushing are cooled by air or preferably water.
The filaments are gathered into bundles by a gathering shoe and are then
led to a strand pulling device such as illustrated in U.S. Patent No.
3,292,013 as well as in the above referenced, U.S. Patent No. 3,849,148.
The glass fiber strand or strands, if the filaments exiting from the
bushing have been separated into several strands, are then wound onto a
forming tube on a collet rotating at approximately 7,500 rpm to produce
a strand travel of approximately 12,000 to 15,000 feet per minute.
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The glass fiber strand forming packsges are then dried. This generally
is accompllshed by baking the packages of fiber at a tempersture and for
a length of time sufficient to remove ~ubstantislly all of the water.
Generally a curing time for the ingtant size is about ll hours at 270F.
After drying the forming tube may be removed resulting in a forming package
of sized gla~s fiber. These formlng packages may be stored virtually
indefinitely when sized with the instant sizing. When the forming package
is desired for use in forming a polyolefin composite article, a group of
the forming packages are arranged 80 that the strands may be drawn from
the packages and laid down to form a mat of fibers such as disclosed in
U.S. Patent No. 3,883,333 or U.S. Patent No. 3,664,909. The mat i~ then
needled and combined or impregnated with polyolefin resin or laminated
with polyolefin sheets to form relnforced polyolefin articles which are
heated at a temperature in the rsnge of 400F. to about 430F. at a pressure
of about 9250 pounds per square inch for about 5 to about 20 minutes to
bind the sized glass fibers of the invention to the polyolefin. The
laminated polyolefin glass fiber mat articles may then be stamped or molded
by a varlety of means, including that of U.S. Patent No. 3,664,909 to
produce reinforced polyolefin lamlnates suitable for use as contalner~ or
for other low-cost, hlgh strength and low temperature uses.
The coupling agent may be utilized in amounts which re~ults in
good interfacial boundary area adhesion between the glass fiber strand
and the polyolefin. A sllane coupling agent concentration of about .2
to about 18 percent by weight of the solids of the sizing concentration
has been found to be suitable. A preferred percent of silane has been
found to be about 6 percent by weight of the solids in the sizing of the
silane to give maximum adhesion with minimum cost.
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The maleonated or acrylic modified polypropylene lubricant may
be utilized in any amount which results in good stability of the sizing
system. A suitable amount has been found to be about 30 to about ~0 percent
by weight of solids in the sizing solution. A preferred amount of the
maleonated amorphous polypropylene for good forming and fabrication
processability has been found to be about 60 percent by weight of the
solid's in the sizing emulsion.
The stabilizer may be used in any amount which results in good
lnterface bonding of the film-forming materials to the glass fiber strand.
A suitable amount has been found to be about 1 to about 9 percent stabilizer
to the solids of the sizing emulsion, A preferred amount of stabllizer has
been found to be about one-half the amount of the silane coupling agent to
give good adhesion of the film formers to the coupling agent.
The non-crosslinking-fllm forming material and the self-reactive
crosslinking material are blended to give the desired handling properties
to the æized strand. The non-crosslinkable polymer, preferably vinyl
acetate h opolymer imparts plasticity to the fiber and its use is dependent
on the hardness of brittleness of the self-reactive crossllnking film
former. The self-reactive crosslinklng film former act~ to provide
integrity to the glass fiber strand 80 that it does not come apart into
filaments during processing or cutting operations. A normal range of the
non-crosslinkable polymer would be between about 5 and 40 percent by weight
of the solids in the sizing emulsion. A suitable amount of self-reactive
crosslinking material would be between about 10 and about 50 percent by
weight of the solids in the sizing emulsion. A preferred amount of the
self-reactive crosslin~ing material would be about 22 percent of the
solids in the sizing emulsion such that the fiber has good integrity.
A preferred amount of the non-crosslinking vinyl acetate homopolymer is
about 9 percent by weight of the solids in the sizing emulsion to give
optimum handability.
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~ e sizing emulsion generally contains between about 95 percent
and about 80 percent water. It is preferred in the use of a kiss roll
applicator to have between 83 and 93 parts by weight water in the sizing
solution. Thus, solids amount is greatly dependent on the applicator that
is used to size the fiber strand.
lhe sized fiber forming packages of the instant system may
be utilized to reinforce any polymeric resin article. However, the
instant fibers find greater functionality in the reinforcement of polyolefinic
resin polymers including polyethylene and 5-methyl pentene polymers. A
preferred polyolefinic polymer for utilization with the instant sized glass
fiber strand is polypropylene since this polymer binds very well with the
instant sizing, is relatively low cost and gives good strength properties
when glass reinforced. The ratio of polyolefinic polymer to glass may be
selected in any ratio that gives the desired properties to the finished
article. Generally a ratio of about 10 to about 60 percent glass by weight
is suitable. A preferred amount is about 35 to about 45 percent by weight
glass in a polypropylene molded article to give a good balance of cost,
properties and structural strength.
The amount of the sizings used on the glass may be any amount
which results in good structural strength of the finished polyolefin fiber
composite, good fiber integrity and handleability. A suitable amount of
sizing is about .02 to about 1 percent by weight sizing solids to total
weight of the sized strand of glass. A preferred range is about .6 percent
to give good fiber integrity and handleability.
The following Example is a preferred embodiments of the instant
invention. The parts and percentages are by weight unless otherwise
indicated.
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E~AMPLE I
-
Ingredient
Parts by Weight Percent of
Functional Identification Chemical Identification Of Sizing Size Solids
Coupling agent gamma-aminopropyltriethoxy- .7 6
silane
, B (Union Carbide A-1100)
Stabilizer cis-butenedioic acid .35 3
Lubricant emulsion of maleonated
amorphous polypropylene 7.3 60
22% active
10% surfactant and KOH
68% water
surfactant = alkoxylated
phenol
Non-crosslinking film vinylacetate homopolymer 1.1 9
former emulsion
54% solids
(National Starch Resyn 25-1031)
Self-reactive film emulsion of vinyl acetate-n- 2.6 22
methyolacrylamide
52% solids
(National Starch Resyn 25-2828 ~
Water 87.95
~ r~ad~ ~
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The glass fiber strand sizing is prepared by adding most of
the necessary deionized water to the mix tank and then slowly adding the
lubricant to the mix tank as it is agitated. The coupling agent is then
added to the mix tank followed by adding the maleic acid with continued
agitation. After the addition of the maleic acid, stirring is carried out
for about 20 minutes to dissolve the acid. Then the non-crosslinking
film-forming material is added to the tank followed by the addition of the
crosslinkable polymeric emulsion which is diluted with an equal quantity of
cold deionized water prior to addition. Additional make-up water necessary
is added and the batch is checked to determine that the specifications are
within the range of about a pH of about 6 and a solids of about 5 percent
solids.
In a preferred embodiment, the aqueous sizing mixture is applied
to fiber filaments that are formed from a 400-hole bushing. The filaments
are treated by a kiss roll applicator to coat about .6 percent solids by
weight of the glass onto the filaments. The filaments are gathered into
four strands or more then wound onto the collets to form packages of about
20 pounds or more each. The formed packages are cured for about 11 hours
st 270F. Following the curing the forming package can be stored indefinitely
at ambient conditions. The forming packages are then utilized to form a
mat of continuous fibers which is then needled and laminated with poly-
propylene polymer in the weight of about 60 parts by weight of polypropylene
polymer to 40 parts by weight of the needled mat. The polyolefin resin and
mat are combined via a temperature range of about 400F. at a pressure of
about 9C pounds per square inch for about 5 minutes to bond the reinforcing
glass fibers to the polyolefin. The heating is carried out between stainless
steel belts. The laminate of sized fiber matting and polypropylene is then
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stamped into test tubs such as described at column 6 through column 7 of
U.S. Patent No. 3,849,148 and tested for structural strength and structural
modulus. The flexural strength averages at least about 23,000 pounds
per square inch and the flexural modulus about 1 x 106 pounds per square
inch. This example shows that the polypropylene reinforcing sized glass
fiber strands of the instant invention provide satisfactory strong rein-
forced articles even after extended storage period of the forming packages.
While the invention has been described with reference to several
embodiments, those skilled in the art will recognize that variations may be
made to the described methods and devices without departing from the
substance of this invention. For instance, a pigment or dye could be added
to the sizing solution without interference with its effect.
As will be apparent to those skilled in the art, the present
system may be modified and equivalent elements or processes may be employed
in combination therewith without departing from the spirit of the invention.
For instance, an application device for the sizing could be utilized which
would not require as large an amount of water in the sizing emulsion.
Further, the fiber forming packages of the instant invention could be
utilized in the reinforcing of polymeric materials other than polyolefins.
Also, a combination of the sized fiber forming packages of this invention
could be utilized with fibers sized with a different material, with
unsized fibers or with chopped strand sized with the sizing of this invention.
Thus, the present disclosure of preferred embodiments is not
intended to limit the scope of the applicant's invention.
