D E S C R I P T I O N
SIZING COMPOSITION FOR GLASS FIBERS-
TECHNICAL FIELD This invention relates to the field of size coatings for glass fibers for use as reinforcement in resinous articles and includes aqueous sizing compositions by means of which the size coating is applied t.o the glass fibers, glass fibers lightly coated, i.e. sized, with a dried residue of such sizing compositions, and resinous articles reinforced with such sized glass fibers, particularly wound continuous filament reinforced pipes and tanks.
BACKGROUND ART It has long been recognized that it is advantageous to provide a v ery light coating, known as a size or size coating, of suitable composition on glass fibers which are to be employed as reinforcing elements in resinous articles in order to enhance the mechanical reinforcing properties of the glass fibers when they are embedded in the matrix resin of the article to be reinforced. It has also long been recognized that it is advantageous to apply such size coatings to glass fibers by wetting the fibers as soon as practicable after forming with a liquid, frequently aqueous, sizing composition w ich, when dried in situ, deposits the desired size as a residue lighly coating the surface of the glass fiber, since the application of a suitable sizing composition at an early stage serves also to help protect the fibers from
damage during the handling which they subsequently undergo much of which may be at high speeds or high stress, such a being gathered into multi-filament strands, collected into suitable packages, heated to dry and/or cure the size coating, shipped to the point of use, depackaged, incorporated into the matrix resin which they are to reinforce and shaped with that resin into the desired articles. The size also tends to act as an adhesive to hold the individual filaments together in multi-filament strand.
Such sizing compositions typically contain a - film-forming polymer, a lubricant and a coupling agent, all dispersed or dissolved in a liquid medium which is frequently an aqueous medium. The film-forming polymer is usually selected to be reasonably compatible with the matrix resin or resins in which " the glass fiber.s will be embedded as reinforcement. A broad range of oils, waxes, surfactants, etc. have been employed as lubricants. Among the most frequently used coupling agents are organosi 1 anes. Other components, such as surfactants, anti-static agents, colorants, biocides, anti-foam agents, pH regulators, etc., are also frequently included in such sizing compositions. DISCLOSURE OF THE INVENTION AND
THE BEST MODE FOR CARRYING " IT OUT
In one of its aspects, the present invention is an aqueous sizing composition for glass fibers which comprises a film-forming polymer, a lubricant and a coupling agent " / said coupling agent comprising (i) a first organosilane having an epoxy group non-hydrolyzably linked to a silicon atom and at least two groups each of which is joined by a readily hydrolyzable bond to a silicon atom, or a hydrolysis product thereof, and (ii) a second organosilane having * an acrylyl or methacrylyl group non-hydrolyzably linked to a silicon atom and at least two groups each of which is joined by a readily hydrolyzable bond to a silicon atom, or a hydrolysis product thereof,
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where each of said organosi1 anes is substantially devoid of halogen substitution in its non-hydrolyzabl e portion.
In another of its aspects, the present invention is a glass fiber having a size coating comprising the dried residue of an aqueous sizing co psoition of the invention. In yet another of its aspects, the present invention is a cured resinous article having sized glass fiber of the invention embedded in the matrix resin thereof. . In a further aspect, the present invention is a cured resinous article in the form of a shell having the configuration of a pipe or tank and having the sized glass fiber of the invention embedded in. the matrix resin as ^ong, essentially continuous, multi-filament strand circu wiπding the hollow portion of the article.
In a still further aspect, the presen.t invention is a reinforced cured resinous article as described in which the matrix resin comprises a vinyl ester of an epoxy resin. The film-forming polymer component of the aqueous sizing composition can be any suitable polymer which can be dispersed or dissolved in aqueous medium and which will coalesce to form a film when the sizing composition which has been applied to the glass fiber is dried. To achieve the most satisfactory reinforcing effects the film-forming polymer component should be selected additionally for compatibility with the matrix resin in which the sized glass fibers wil ^ be embedded as reinforcing elements. Thus for the sizing of glass fiber to be used as reinforcement for epoxy resins or vinyl esters of epoxy resins, epoxy resins are particularly suitable as the fiber-forming polymer component of the aqueous sizing composition of the * ιnveπtion. Epoxy resins a re also suitable as the film-forming polymer in sizing compositions for glass fiber for reinforcing other curable matrix resins such as unsaturated polyester resins, but such other film-forming polymers as suitable unsaturated polyesters,
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particularly for glass fibers for reinforcing unsaturated polyester matrix resin, can also be employed as the film-forming polymer of the sizing composition.
Where an epoxy resin is employed as the film-forming polymer in the aqueous sizing composition of the invention, diglycidyl ethers of substantially linear epichl orohydri n-bi sphenol A condensates are particularly suitable, especially where the matrix resin in which the sized glass fibers are to be embedded as reinforcement comprises a vinyl ester of an epoxy resin. Such epoxy resins can advantageously be admixed with minor proportion of a solvent such as diacetone alcohol and/or xylene and this mixture dispersed in the aqueous medium of the sizing composition using a non-ionic surfactant such as a polyal kyl eneglycol .
The lubricant component of the aqueou.s sizing composition of this invention can be any normally liquid o solid lubricating material suitable for the purpose. Such materials include vegetable and mi neral. oi 1 s, waxes of various types and certain materials which also have utilit as surfactants, such as fatty acid monoesters of polyal kyl eneglycol s. In the context of the present invention, it has been found advantageous to employ a normally liquid lubricant material as at " least part of the lubricant component of the sizing composition. It has bee found particularly advantageous to employ as the normally liquid portion of the lubricant an isostearate monoester o a. polyethyl ene " gl col , and, if a normally solid lubricant material is to be used therewith, to employ a normally solid stearate monoester of a polyethyl eneglycol . The normally liquid lubricant material should preferably constitute at least about 50% by weight of the total
__ lubricant in order that a fairly uniformly deposited size coating on the glass fibers can be more easily and consistently achieved in commercial production.
The coupling agent component of the aqueous sizing composition of the invention comprises two
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non-hal ogenated organosil anes , each of which has at least two groups joined by a readily hydrolyzable bond to a silicon atom of the silane, or hydrolysis products thereof. The first of these organosi 1 anes also has an epoxy, i.e., oxirane, group linked through only non-hydrolyzabl e bonds to a silicon atom of such first silane. The second organosilane has, in addition to its hydrolyzable groups, an acrylyl or methacrylyl group linked through only non-hydrolyzable bonds to a'silicon atom of such second silane; preferably the acrylyl or methacrylyl group is a acrylyloxy or methacrylyl oxy group. By the terms "non-hydrolyzable" and "non-hydrolyably" are meant bonds or functional groups which are at least as resintant to hydrolysis as aliphatic organic carboxylic esters. Suitable hydrolyzable organosi 1 anes include monosilanes containing the structure >SE(0R) 2 -* where the R 's can be virtually any organic group, b'ut lower alky! groups such as methyl or ethyl are particularly convenient and satisfactory. As the first organosilane, a glycidoxy poly ethyl enetri al koxysi 1 ane, suc as
3-glycidoxy-l-propyltrimethoxysi 1 ane is particularly suitable. As the second organosilane, an acryloxy- or methacrylyloxypolymethyl enetri al koxyl sil ane such as 3-methacrylyloxy-l-propyltrimethoxysil ane is particularly suitable. Preferably the first and second organosil anes should be present in weight ratios from about 1:5 to about 1:1 respectively.
The " proportions of the various components and the mixing procedure for the aqueous sizing compositions of the invention are not critical. The proportions and procedures of the Examples given below are representative, but are not intended to be limiting. The aqueous sizing compositions will preferably have the various non-volatile components present within the following approximate ranges, given as percent by weight of the total composition: 1-10% film-forming polymer, 0.2-5% lubricant and 0.2-5% coupling agent. The total solids content will prefereably be from
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1.about 1 to about 25% and more preferably from about 3 to about 10%, by weight.
The aqueous sizing composition can be applied to the glass fibers by drawing the fibers over a roll, pad or 5 other suitable surface wet or flooded with the aqueous sizing composition, by spraying, by dipping, or by any other suitable means. The overall concentration of the non-volatile components in the aqueous sizing composition can be adjusted over a wide'range according to the means o application to be employed, the character of the glass fibers to be sized, e.g. their diameter and composition, and the weight of dried size coating desired for the intended use of the sized fibers. Preferably the sized fibers wilf have a loading of about 0.1 to about 5 percent by weight of dried size.
The sized glass fibers of the invention can be incorporated into the curable matrix resin which is to be reinforced thereby in the final cured resinous article as either moπofi 1 ament or multi-filament strand, the latter being more usual and preferred, and as either long, essentially continuous, elements or short chopped pieces, depending upon the shape and method of fabrication of the article to be formed. The sized glass fibers of this invention are particularly adapted for use in the form of long, essentially continuous, multi-filament strand in reinforcing cured resinous articles such as pipes or tanks fabricated by filament winding, whereby the sized glass fibers are embedded in the liquid matrix resin by winding them about a suitable form while simultaneously applying the liquid matrix resin to that form, as by loading the glass fiber strand therewith as it approaches the winding form upon which the article is being constructed. The matrix resin is subsequently cured to provide the final reinforced resinous article. The sized glass fibers of th invention in the form of long multi -fi 1 ament strand are also particularly adapted for use in reinforcing cured resinous articles formed by so-called pultrusion processes
wherein the strand of sized fibers is drawn through a zone where it is immersed in the liquid matrix resin and then pulled through a shaping die whereby excess liquid resin is removed and the remaining resin having the glass fiber strand embedded therein is shaped into the desired cross-sectional form and then_ cured.
Example 1 A preferred aqueous sizing composition has the following formulation: * Component Wt. %
Epoxy resin 2.63
Diacetone alcohol 0.58
Xylene 0.29
Poly(ethyl eneglycol/propyl eneglycol ) copolymer 0.58 3-Methacryl oxypropyl trimethoxysi 1 ane 0.56
3-Glycidoxypropyltrimethoxysi 1 ane , 0.30
Polyethyleneglycolmonostearate (solid) 0.44 Polyethy-1 eneglycolmonoi so ' stearate (liquid) 0.66 Polyvinylpyrolidone (90,000 MW) 0.08 Glacial acetic acid 0.03
Water Balance
The epoxy resin is a diglycidyl ether of an epichl orohydri n/bisphenol A condensate and has an epoxy equivalent weight of about 250. It is codissolved with the xylene and diacetone alcohol and that mixture then dispersed in part of the water with the poly(ethyl eneglycol /propyl eneglycol ) as surfactant. The raethacryl oxysi 1 a-ne is premixed with part of the water and acidified with the acetic acid before adding to the epoxy dispersion. The epoxysilane is also premixed with part of the water and then added to the main mixture. Finally, the two polyεthyl eneglycol monoesters and the polyvinyl yroli¬ done are premixed together with part of the water and added to the main mixture. The total solids are about 5.35% and the pH about 4-4.5. This sizinig composition is particularly adapted for use on glass fibers gathered together to form multi-filament strand and then embedded as
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continuous reinforcement in the epoxy resin or vinyl ester of epoxy resin matrix of pipes or tanks formed by filament winding.
Example 2 Another preferred aqueous sizing composition has the same formulation as that of Example 1 except that the epoxy resin has an epoxy equivalent weight of about 625 an the proportion of polyvinyl pyrol idone is increased to . 0.15%. This sizing composiUion is particularly adapted fo use on glass fibers gathered together into multi-fi Tament strand and then embedded as reinforcement in epoxy resin o unsaturated polyester resin products formed by pultrusion.
INDUSTRIAL APPLICABILITY The aqueous sizing compositions of this inventio provide a means for producing glass fiber reinforced resinous articles having improved tensile and f.lexural strengths while simultaneously reducing the undesirable presence of fuzz during fabrication operations, as compared •to prior sizing compositions. Numerous variations and modificati ons ' of this invention will be apparent to those skilled in the art and are contemplated as being within the scope of this invention.
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