WO2018114317A1

WO2018114317A1 - Methods of removing coatings from glass fibers

Info

Publication number: WO2018114317A1
Application number: PCT/EP2017/081472
Authority: WO
Inventors: Hans VAN LIMPT
Original assignee: Sibelco Nederland N.V.
Priority date: 2016-12-23
Filing date: 2017-12-05
Publication date: 2018-06-28
Also published as: GB201622089D0; GB2558254A

Abstract

The present invention relates to methods of removing coatings from glass fibers.

Description

Title: Methods of removing coatings from glass fibers

Description of Invention The present invention relates to methods of removing coatings from glass fibers.

Fiberglass comprises glass fibers coated (in whole or in part) with an organic coating, the organic coating providing bonding between the glass fibers. The glass fibers may be randomly arranged, flattened into a sheet or woven into a fabric, among other possibilities. Examples of organic coatings in fiberglass include a thermosetting plastic or a thermoplastic.

Fiberglass is a strong material used in the forming of composites and to manufacture a variety of products; non-limiting examples include components which make up: aircraft, boats, automobiles, baths, swimming pools, storage tanks, pipes, roofing and doors.

Common types of glass fibers and fiberglass, along with methods of forming glass fibers and fiberglass, are set out in the ASM Handbook, Volume 21 , "Composites", 2001 , Editors: Miracle et al., particularly the chapter entitled "Glass Fibers" authored by Wallenberger et al., pages 27-34 (the contents of which are hereby incorporated by reference). We discuss a general method of forming fiberglass below. The below method is not limiting. Other methods of forming fiberglass are known, some of which are described in detail in the ASM Handbook reference above.

A common method of manufacturing fiberglass is called pultrusion. During pultrusion, the glass fibers are formed by melting the components of the glass in a furnace. Common examples of components of the glass include silica sand, limestone, burned lime, kaolin clay, fluorspar, colemanite, boric acid and dolomite. The exact mixture of components depends on the type of glass desired for the glass fibers. The glass is then extruded through bushings, which are bundles of small orifices (typically from 5 to 25 μιτι in diameter for E- Glass; 9 μιτι plus or minus 10% for S-Glass).

The extruded glass fibers are then coated with a chemical solution (the solution is sometimes referred to as a sizing). The chemical solution (sizing) consists of several components, each of which is important for adhesion between the glass fibers, as well as adhesion and compatibility between the glass fibers and the composite produced. The chemical solution (sizing) affects the composite interface and thus the strength of the fiberglass (which is a composite). In one example, the chemical solution (sizing) includes a mixture of silane polymer chains and a film former (for example polyurethanes, polyvinyl acetates, polyesters, polyalkenes and epoxies). The coated glass fibers may then be bundled in large numbers to form a roving.

The diameter of the filaments, and the number of filaments in a roving, determine its weight which is expressed in units of yield (number of yards of fiber in one pound of roving (SI units: number of 0.9144 metres in 453.6 grams of roving); a smaller yield means a heavier roving) or tex (how many grams 1 km of roving weights, inverted from yield; a smaller number means a lighter roving). The ravings are then used in a composite application such as pultrusion, filament winding, gun roving, to manufacture fabrics such as a chopped strand mat, woven fabrics, knit fabrics or uni-directional fabrics, among other possibilities.

A coating or primer is sometimes applied to a roving to protect the glass fibers during processing and ensure proper bonding in the composite. During the production of fiberglass, it is common for at least 10% of the coated glass fibers to be rejected from further processing into ravings, and subsequently into fiberglass products. These coated glass fibers can include defects, such as incomplete coatings or erroneously shaped glass formations following extrusion through bushings.

Coated glass fibers which are rejected from further processing cannot be recycled in a glass furnace because of their organic coating. The organic coating, if added to a glass furnace, lowers the efficiency of the glass furnace by forming a foam on top of the glass melt and causing redox problems.

As a result, the at least 10% of the coated glass fibers to be rejected from further processing often end up as lower grade products, e.g. in aggregates, or end up in landfill. This results in the waste of high quality glass fibers.

It is known to use pyrolysis technologies and other heating technologies (for example combustion of fuel or electric heating) to remove coatings from coated glass fibers. At least one problem with these technologies is that they do not efficiently and consistently remove all of the glass fiber coatings. The coated glass fibers produced by these technologies still have some organic coating, and there can be different amounts of organic coating on the coated glass fibers. When these glass fibers are recycled in a glass furnace the redox state (the oxidation state of glass expressed as the ration between ferrous iron (Fe²⁺) and ferric iron (Fe³⁺)) of the produced glass will vary and foaming problems can be expected. Because of the variations in glass redox, the cooling rates of the produced glass filaments differ and more breakage can be expected during spinning processes and other glass processing steps.

In a conventional glass incinerator which is fired with fuel, large amounts of flue gases are generated; with only partial removal of the organic coatings the flue gases are contaminated with organic compounds. These organic compounds must be removed from the flue gases using expensive scrubber technologies. There is a need to remove coatings from glass fibers completely, efficiently and consistently.

According to a first aspect of the present invention, there is provided a method of removing coatings from glass fiber, the method comprising:

providing glass fiber coated with a glass fiber coating; and

applying a gyrotron beam to the glass fiber coated with a glass fiber coating, to remove some or all of the glass fiber coating. Preferably, wherein the glass fiber starting material is one or more glass fibers.

Further preferably, wherein the glass fiber starting material is coated in whole or in part with a glass fiber coating. Advantageously, wherein the gyrotron beam is electromagnetic radiation produced by a gyrotron.

Preferably, wherein the gyrotron beam has a frequency of from 20 to 250 GHz. Further preferably, wherein the gyrotron beam has a frequency of from 30 to 1 10 GHz; or from 50 to 100 GHz; or from 60 to 80 GHz.

Advantageously, wherein the glass fiber is formed of E-glass, A-glass, E-CR- glass, C-glass, D-glass, R-glass or S-glass.

Preferably, wherein the glass fiber coating is an organic coating.

Further preferably, wherein the glass fiber coating is an organic coating formed of synthetic or semi-synthetic organic compounds that are malleable. Advantageously, wherein the glass fiber coating is an organic coating, the organic coating being an organic polymer of high molecular mass (optionally greater than 700 kDa). Preferably, wherein the glass fiber coating comprises, or consists of, an organic coating, the organic coating comprising epoxy, polyester resin or vinylester; optionally, wherein the organic coating includes one or more silanes. Further preferably, wherein the method further comprises the step of:

before applying a gyrotron beam, grinding the glass fiber coated with a glass fiber coating.

Advantageously, wherein the method further comprises the step of:

during or after applying a gyrotron beam, removing the volatilised glass fiber coating as waste.

Preferably, wherein the method further comprises the step of:

after removing some or all of the glass fiber coating, introducing the produced glass fiber into a glass furnace.

Further preferably, wherein the gyrotron beam is applied for:

from 1 , 2, 3, 4, or 5 seconds to any one of 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55 or 60 seconds; or,

from 10, 20, 30, 40, 50 or 60 seconds to any one of 1 .5, 2, 3, 4, 5, 6, 7,

8, 9 or 10 minutes.

According to a further aspect of the present invention, there is provided a glass fiber obtained, or obtainable by, a method according to any one of the above methods. According to a further aspect of the present invention, there is provided a method of forming glass, the method comprising the steps of:

introducing the glass fiber produced by any one of above methods into a glass furnace.

According to a further aspect of the present invention, there is provided glass obtained, or obtainable by, a method according to the above method of forming glass. Embodiments of the invention are described below with reference to the accompanying drawings, in which:

Figure 1 is a schematic diagram of a mat of fiberglass fibers. Figure 2 is a schematic cross-section a fiberglass fiber.

Figure 3 is a schematic representation of a method of removing coatings from glass fibers. Some of the terms used to describe the present invention are set out below:

"Glass fiber" refers to generally elongate fibers formed of glass. There are many types of glass which can be formed into glass fiber. The common types of glass fiber used in fiberglass include, but are not limited to, E-glass (alumino-borosilicate glass with less than 1 % w/w alkali oxides), A-glass (alkali-lime glass with little or no boron oxide), E-CR-glass (Electrical/Chemical Resistance; alumino-lime silicate with less then 1 % w/w alkali oxides, with high acid resistance), C-glass (alkali-lime glass with high boron oxide content, used for glass staple fibers and insulation), D-glass (borosilicate glass, named for its low dielectric constant), R-glass (alumino-silicate glass without MgO and CaO with high mechanical requirements as reinforcement), and S-glass (alumino silicate glass without CaO but with MgO content with high tensile strength). Other types of glass fiber include any type of glass fiber described in the ASM Handbook, Volume 21 , "Composites", 2001 , Editors: Miracle et al., particularly the chapter entitled "Glass Fibers" authored by Wallenberger et al., pages 27- 34 (the contents of which are hereby incorporated by reference). In some examples, glass fibers have an aspect ratio (diameter to length) of: 1 :1 .1 or greater; or, 1 :2 or greater; or, 1 :3 or greater; or, 1 :5 or greater; or, 1 :10 or greater; or, 1 :20 or greater; or, 1 :30 or greater; or, 1 :40 or greater; or, 1 :50 or greater; or, 1 :100 or greater; or, 1 :200 or greater. "Glass fiber coating" refers to a coating on a glass fiber. In fiberglass, the glass fiber coating is an organic coating.

"Fiberglass" refers to glass fibers coated (in whole or in part) with an organic coating, the organic coating providing bonding between the glass fibers. The glass fiber may be randomly arranged, flattened into a sheet or woven into a fabric, among other possibilities. The glass fiber is coated (in whole or in part) by an organic coating, for example a thermosetting plastic or a thermoplastic. Table 1 , below, shows some common fiberglass types: Table 1 : fiberglass types (Source: Wikipedia™, "Fiberglass" page)

"Organic coating" refers to a material comprising synthetic or semi-synthetic organic compounds. The organic compounds can form organic plastics. Examples of organic plastics include a thermosetting plastic or a thermoplastic. Common organic compounds included as glass fiber coatings in fiberglass are: epoxy, polyester resin or vinylester. Organic coatings included as glass fiber coatings can include silanes.

A "gyrotron" refers to a high-power linear-beam vacuum tube which generates millimetre-wave electromagnetic waves by cyclotron resistance of electrons in a strong magnetic field. Gyrotron output powers range from 10 kilowatts to 2 megawatts. Gyrotrons can provide pulsed or continuous waves. An example of a gyrotron is a gyrotron as sold by Gyrotron Technology, Inc.™ (of Bensalem, PA, USA).

A "gyrotron beam" refers to a beam of electromagnetic radiation produced by a gyrotron. A gyrotron beam has output frequencies of from 20 to 250 GHz. Optionally, a gyrotron beam has output frequencies of from 30 to 1 10 GHz. Figure 1 is a schematic diagram of a non-limiting mat of fiberglass fiber. The fiberglass fibers are arranged in layers of generally parallel fibers, each layer being arranged perpendicular to the corresponding layers above and below. The fibers can be arranged in many other ways. For example, the fiberglass fibers can be arranged as a single mat of fibers, with multiple layers, with any angled relationship between layers or in a non-ordered fashion.

Figure 2 is a schematic cross-section of a fiberglass fiber 10. The fiberglass fiber 10 includes a glass fiber 1 1 and an organic coating 12. The fiberglass fiber 10 is generally elongate (not shown). The glass fiber 1 1 and the organic coating 12 are bonded along much of the interface between the glass fiber 1 1 and the organic coating 12.

As discussed above, during the production of fiberglass, it is common for at least 10% of the coated glass fibers to be rejected from further processing into rovings, and subsequently into fiberglass products. In order to recycle the glass fiber (for example 1 1 ) of a fiberglass fiber (for example 10), it is desirable to remove all of the organic coating (for example 12), before heating the glass fiber (for example 1 1 ) in a glass furnace (not shown).

In a method according to the present invention, a gyrotron beam (not shown) is applied to one or more glass fibers coated with a glass fiber coating. The glass fibers coated with a glass fiber coating are optionally derived from waste materials formed during the manufacture of fiberglass. The application of the gyrotron beam volatilises the glass fiber coating, leaving only the glass waste product. This glass waste product can be introduced into a glass furnace without the drawbacks of additionally including amounts of the glass fiber coating.

Example An E-glass epoxy composite fiberglass was formed using standard methods.

During the formation of the E-glass epoxy composite, waste materials were formed, the waste materials consisting of E-glass fibers coated by epoxy. In this non-limiting example, the glass fiber is E-glass and the glass fiber coating is epoxy (an organic coating).

The waste materials were ground so that the ground waste materials fitted through a 10mm sieve. In other examples, the waste materials are not ground, or are ground either finer or coarser.

The waste materials were subjected to a gyrotron beam of 60 Ghz, with a spectrum ±5 kHz and over 99% Gaussian distribution. The gyrotron beam volatilised the epoxy coating, leaving pure E-glass. The pure E-glass was subsequently used in a glass furnace to form a fresh E-glass batch. Without wishing to be bound by theory, it is believed that the difference in boiling points of the E-glass and the epoxy coating make the use of a gyrotron effective to remove the epoxy coating, in this example. The frequency of the gyrotron can be changed depending on the particular glass and its coating, to effect volatilisation of the coating.

Figure 3 is a schematic representation of a method 20 of removing coatings from one or more glass fibers. In Figure 3, coated glass fibers are provided in step 21 . The coated glass fibers are milled or ground in step 22. When the coated glass fibers are milled, they are milled in a ball mill. The ball mill can be any ball mill; for example a ball mill sold by Retsch™, a non-limiting example being the MM 200 sold by Retsch™. Other examples of ball mills, which could be used to mill the coated glass fibers, include those sold by DUTTO™ S.P.A. The milled or ground coated glass fibers are then placed in a gyrotron beam in step 23; the gyrotron beam is applied for: from 1 second to any one of 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55 or 60 seconds; or from 10, 20, 30, 40, 50 or 60 seconds to any one of 1 .5, 2, 3, 4, 5, 6, 7, 8, 9 or 10 minutes. The gyrotron beam volatilises the organic polymer coating; the volatilised organic polymer coating is removed and disposed of at step 25. The resulting glass fibers, provided at step 24, have their organic polymer coating removed. The resulting glass fibers (optionally in combination with other raw materials) can be placed in a glass furnace, and used to form glass, without any interference from organic molecules. When used in this specification and claims, the terms "comprises" and "comprising" and variations thereof mean that the specified features, steps or integers are included. The terms are not to be interpreted to exclude the presence of other features, steps or components. The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

1 . A method of removing coatings from glass fiber, the method comprising: providing glass fiber coated with a glass fiber coating; and

applying a gyrotron beam to the glass fiber coated with a glass fiber coating, to remove some or all of the glass fiber coating.

2. The method of claim 1 , wherein the glass fiber starting material is one or more glass fibers.

3. The method of claim 1 , wherein the glass fiber starting material is coated in whole or in part with a glass fiber coating.

4. The method of any one of claims 1 to 3, wherein the gyrotron beam is electromagnetic radiation produced by a gyrotron.

5. The method of any one of claims 1 to 4, wherein the gyrotron beam has a frequency of from 20 to 250 GHz.

6. The method of any one of claims 1 to 5, wherein the gyrotron beam has a frequency of from 30 to 1 10 GHz; or from 50 to 100 GHz; or from 60 to 80 GHz.

7. The method of any one of claims 1 to 6, wherein the glass fiber is formed of E-glass, A-glass, E-CR-glass, C-glass, D-glass, R-glass or S-glass.

8. The method of any one of claims 1 to 7, wherein the glass fiber coating is an organic coating.

9. The method of any one of claims 1 to 8, wherein the glass fiber coating is an organic coating formed of synthetic or semi-synthetic organic compounds that are malleable.

10. The method of any one of claims 1 to 9, wherein the glass fiber coating is an organic coating, the organic coating being an organic polymer of high molecular mass (optionally greater than 700 kDa).

1 1 . The method of any one of claims 1 to 10, wherein the glass fiber coating comprises, or consists of, an organic coating, the organic coating comprising epoxy, polyester resin or vinylester; optionally, wherein the organic coating includes one or more silanes.

12. The method of any one of claims 1 to 1 1 , wherein the method further comprises the step of:

13. The method of any one of claims 1 to 12, wherein the method further comprises the step of:

14. The method of any one of claims 1 to 13, wherein the method further comprises the step of:

15. The method of any one of claims 1 to 14, wherein the gyrotron beam is applied for:

from 10, 20, 30, 40, 50 or 60 seconds to any one of 1 .5, 2, 3, 4, 5, 6, 7,

8, 9 or 10 minutes.

16. A glass fiber obtained, or obtainable by, a method according to any one of claims 1 to 15.

17. A method of forming glass, the method comprising the steps of:

introducing the glass fiber produced by any one of claims 1 to 15 into a glass furnace.

18. Glass obtained, or obtainable by, a method according to claim 17.

19. A method as hereinbefore described, with reference to Figure 3.

20. Any novel feature or combination of features disclosed herein.