PROCESS FOR TREATING WOVEN GLASS CLOTH
A solvent wash employing a polar washing solvent is employed to effectively remove the sizing agent on a woven glass cloth, while retaining the tensile strength of the woven glass cloth. Loss of tensile strength of the woven glass cloth due to removal of a sizing agent from the woven glass cloth is compensated by simultaneous or subsequent deposition of a coupling agent on surfaces from which the sizing agent is removed. The concurrent removal of the sizing agent and deposition of the coupling agent provides an effective removal of the sizing agent while maintaining sufficient tensile strength to structurally support the woven glass cloth. Further, integration of the removal of the sizing agent and the simultaneous deposition of the coupling agent in the washing solvent in a same processing step can provide a cost-effective manufacturing method for forming a finished woven glass cloth.
The present disclosure generally relates to a manufacturing process, and particularly to a manufacturing process to clean a woven glass cloth.
“Glass cloth,” or “woven glass cloth” is a woven material that includes glass fibers. Glass cloth can be woven in various ways resulting in different patterns, for example, checked glass cloths for a plain weave.
Woven glass cloths are employed for various applications. One of the applications for woven glass cloths includes printed circuit boards (PCBs). A printed circuit board (PCB) is a structure that mechanically supports and electrically connects electronic components using conductive pathways formed on a non-conductive substrate. Dielectrics that can be employed for the non-conductive substrates include, for example, FR-4 (Woven glass and epoxy), FR-5 (Woven glass and epoxy), G-10 (Woven glass and epoxy), CEM-3 (Woven glass and epoxy), CEM-4 (Woven glass and epoxy), and CEM-5 (Woven glass and polyester). The conductive pathways are typically formed with copper. The board with copper on it is called a “copper-clad laminate.”
Conductive anodic filament (CAF) failure is an electrochemical failure of electronic substrates involving growth of a metal-containing filament subsurface along the polymer-glass interface, from anode to cathode. CAF failures are increasing as circuit density increases on printed circuit boards. Several conditions must be present in order for CAF formation to ensue. Foremost among those is a pathway between adjacent plated through holes (PTHs) of different voltages. This pathway is a result of interfacial delamination of the resin from the glass cloth or improper glass surface coverage during fabrication.
Glass cloth manufacturing processes known in the art leave an appreciable amount of organic residue on the glass surface. The organic residue subsequently interferes with the bonding between a coupling agent and the glass cloth surface containing silanols. This in turn results in poor interfacial adhesion and provides the pathway necessary for CAF formation. Woven glass cloth is currently processed in a roll-to-roll format utilizing several elevated temperature baking operations to remove the sizing agent from the cloth. Unfortunately, not all of the sizing is removed. This appears to be by design as the tensile strength of the glass cloth decreases significantly following elevated temperature exposure.
SUMMARYA solvent wash employing a polar washing solvent is employed to effectively remove the sizing agent on a woven glass cloth, while retaining the tensile strength of the woven glass cloth. Loss of tensile strength of the woven glass cloth due to removal of a sizing agent from the woven glass cloth is compensated by simultaneous or subsequent deposition of a coupling agent on surfaces from which the sizing agent is removed. The concurrent removal of the sizing agent and deposition of the coupling agent provides an effective removal of the sizing agent while maintaining sufficient tensile strength to structurally support the woven glass cloth. Further, integration of the removal of the sizing agent and the simultaneous deposition of the coupling agent in the washing solvent in a same processing step can provide a cost-effective manufacturing method for forming a finished woven glass cloth.
According to an aspect of the present disclosure, a method of treating a woven glass cloth is provided, which includes providing a solution including at least a solvent and a coupling agent; removing a sizing agent from surfaces of the woven glass cloth in a bath including the solution or another solution; and immersing the woven glass cloth in the solution, wherein a compound that is derived from the coupling agent is deposited on the surfaces of the woven glass cloth in the solution.
According to another aspect of the present disclosure, an apparatus for treating a woven glass cloth includes: at least one container including at least one solution, the at least one solution including a coupling-agent-including solution that includes a solvent and a coupling agent and having a chemistry that causes a compound that is derived from the coupling agent to be deposited on surfaces of a woven glass cloth introduced into the coupling-agent-including solution, the at least one solution includes a sizing-agent-dissolving solution for removing a sizing agent from the surfaces of the woven glass cloth, wherein the sizing-agent-dissolving solution is the same as, or different from, the coupling-agent-including solution; and means for immersing the woven glass cloth in, and for subsequently removing the woven glass cloth out of, the coupling-agent-including solution.
As stated above, the present disclosure relates to a manufacturing process to clean a woven glass cloth, which is now described in detail.
As used herein, a “sizing agent” or an “organic sizing” refers to a material that is at least temporarily incorporated into glass fibers standing alone or woven glass fibers to act as filler or glaze to provide structural support. Starch and starch-derivatives are typically employed as a sizing agent for a woven glass cloth.
As used herein, a “binding polymer material” refers to a polymer material that becomes embedded in a woven glass cloth and provides structural support to the glass fibers of the woven glass cloth.
As used herein, a “coupling agent” refers to a material that provides a permanent bond between glass fibers in a woven glass cloth and a binding polymer material.
As used herein, “coupling” of a woven glass cloth refers to a process of providing bonding between glass fibers in a woven glass and a binding polymer material.
A woven glass cloth that includes a sizing agent therein is provided. At this step, the sizing agent is in the same form and concentration as originally applied to glass fibers prior to weaving of the glass fibers. Thus, the woven glass cloth is not caramelized or heat treated at this step.
The woven glass cloth can be provided by weaving multiple glass fibers oriented in at least two different directions. As provided, the multiple glass fibers in the woven glass cloth have a coating of a sizing agent thereupon. Further, the woven glass cloth is not embedded in a matrix resin or any other binding polymer material as provided.
A woven glass cloth can be provided in any manner. A series of processing steps can be employed to convert molten glass into a woven glass cloth. An exemplary series of processing steps includes, for example, an extraction step, a warping step, a slashing step, an entering step, and a weaving step. For example, glass fibers can be extracted from molten glass through a set of holes in the bushing containing the molten glass. Water can be sprayed to cool the glass fibers during extraction before the glass fibers are rubbed against a surface containing a sizing agent. The sizing agent can be starch based as known in the art. The contact between the glass fibers and the surface containing the sizing agent is typically performed at a temperature lower than 100° C., and the duration of contact between the glass fibers and the surface containing the sizing agent can be less than 0.5 milliseconds for any point on the glass fibers. The surface containing the sizing agent can be provided by a roller including the sizing agent. The fiber glasses are pulled through past the surface containing the sizing agent at a pull rate, which can be greater than 1,000 m/min to form bobbins.
In the warping step, multiple bobbins of the glass fiber are pulled simultaneously to form a section beam, in which multiple glass fibers are aligned along the direction of the pull. Several section beams can be consolidated into a set.
In the slashing step, warp ends of the set's multiple section beams are combined into a single beam for weaving, which is called a warp or a loom beam. An additional sizing agent can be applied to a threadsheet during slashing. The additional sizing agent penetrates and encapsulates individual warp ends so as to minimize broken filaments and to avoid abrasion of individual strands. The organic sizing applied at the slashing step, i.e., the additional sizing agent, facilitates the subsequent steps of entering and weaving.
In the entering step, a warp is set up for installation in a loom. A warp can contain over 4,500 individual ends depending on the design and the style of the warp. Each warp end is drawn through a drop wire, heddles, and a reed, either by machine or hand. The drop wire, the heddles, and the reed work together to mechanically arrange and control a warp yarn spreadsheet on the loom during the entering step.
In the weaving step, a warp beam is installed in the loom. The filling yarns are interlaced at a 90 degree angle to the warp ends on the loom. Rapier technology or air jet technology can be employed to interlace the filling yarns. The interlaced fabric is called a greige or a loom state. The interlaced fabric is then wound on a roll, and the weaving step is complete. The interlaced fabric, either on a roll or as a cut-up piece, is a woven glass cloth that can be employed for subsequent processes of the present disclosure.
Once a woven glass cloth is provided, the woven glass cloth is treated in order to remove at least a substantial portion of the sizing agent and to deposit a coupling agent thereupon.
In a comparative exemplary processing scheme, a glass cloth manufacturing process can utilize several elevated temperature bakes to “clean” the glass cloth prior to deposition of a coupling agent. During the cleaning of the glass cloth, the sizing agent, which is applied during extraction of the glass fibers and/or the slashing step, is at least partially removed to expose at least some surfaces of the glass fibers in preparation for subsequent deposition of the coupling agent. However, as the sizing agent is removed during the exposure to elevated temperature performed to clean the glass cloth, the tensile strength of the glass cloth decreases dramatically. In some cases, the decrease in the tensile strength of the glass cloth due to exposure to elevated temperature can be by more than 50% of the original tensile strength of the glass cloth before cleaning. A decrease in the tensile strength by almost an order of magnitude has also been observed.
Since the glass cloth is processed in a roll-to-roll format for subsequent application of a coupling agent and a binding polymer material, adequate tensile strength is required to pull the cloth from a feed reel to a take up reel. In order to provide sufficient tensile strength to a woven glass cloth after the cleaning process, the temperature and the duration of the elevated temperature bakes are selected so that less than 100% of the sizing agent is removed in the elevated temperature bakes. A significant fraction, estimated to be more than 50% of the amount originally present in a newly woven glass cloth, of the sizing agent is present after the cleaning step. Since the sizing agent is starch-based, an organic residual material, or residual organic “contamination” material is present in the woven glass cloth after cleaning. From the perspective of mechanical strength, a low level of residual organic contamination enhances the tensile strength of the cleaned woven glass cloth. However, the residual organic contamination material is detrimental to the effectiveness of subsequent deposition of a coupling agent because a significant fraction of the surfaces of the glass fibers is covered by the residual organic contamination material, and the coupling agent cannot directly bond to the surfaces of the glass fibers wherever the residual organic contamination material is present.
The elevated temperature bakes can be effected, for example, by a series of processing steps that include a caramelization step and a heat cleaning step.
The caramelization step is a continuous heat treatment process designed to remove a significant portion of the sizing agent. During the caramelization step, a sheet of a woven glass cloth is continuously moved through a caramelizer or a coronizer. The caramelizer and the coronizer provide a high temperature process that oxidizes a significant portion of the sizing agent and any additional organic binders from the woven glass cloth, which is in the form of a greige or a loom state.
The caramelization step is followed by the heat cleaning step, during which the woven glass cloth in the form of the greige or the loom state is wound onto mandrels then subjected to another elevated temperature bake to drive off an additional amount of the sizing agent from the woven glass cloth. The mandrels are first placed on racks, and then loaded into a large oven, and then exposed to an elevated temperature to remove additional amount of the sizing agent and additional organic binders.
Once the woven glass cloth is cleaned employing the caramelization step and the heat cleaning step, a finishing step is performed to apply a coupling agent to the woven glass cloth. In one embodiment, the finishing step can be performed in an acidic bath having a pH from 4.0 to 5.0. A silicon-containing coupling agent can be subjected to pre-hydrolysis in a solvent prior to application to the woven glass cloth, for example, by immersion in the acidic bath.
For example, Dow Corning® Z-6032 Silane, which is a benzylamine coupling agent that is commercially available from Dow Corning®, may be applied to form dilute aqueous dispersions including 0.1% to 1.0% of active silicon-containing coupling agent by weight. Most silicious surfaces can be treated directly by first diluting one part of the silicon-including coupling agent with four parts of an ether alcohol solvent, such as propylene glycol methyl ether (PGME), and by blending in a high shear mixer. The coated woven glass cloth can be subsequently heated to promote condensation thereupon.
In an exemplary processing scheme according to an embodiment of the present disclosure, the set of steps including the caramelization step, the heat cleaning step, and the finishing step is replaced with a single wet processing step employing a solvent wash. The solvent wash can be performed in a wet bath. The solvent wash effectively removes the sizing agent while retaining the tensile strength. Moreover, a coupling agent is deposited simultaneously with the removal of the sizing agent. This can also be completed using subsequent baths, one to remove sizing and a second to deposit coupling agent.
The solution of the bath includes a non-aqueous solution including a polar solvent and a coupling agent. Thus, the solution is not water-based. The woven glass cloth is immersed in the solution, and removal of the sizing agent and deposition of a compound that is derived from the coupling agent occur simultaneously on the woven glass that is immersed in the solution.
In one embodiment, the coupling agent can have a formula of:
in which R represents an organofunctional group that can subsequently bind to a polymer, k is a positive integer, and each of X1, X2, and X3 represents a hydrolysable group that can be the same or different among themselves.
In another embodiment, the coupling agent can have a formula of:
in which R represents an organofunctional group that can subsequently bind to a polymer, k is a positive integer, l is another positive integer that is independent of k, and each of X1, X2, X3, Y1, Y2, and Y3 represents a hydrolysable group that can be the same or different among themselves.
In yet another embodiment, the coupling agent can have a formula of:
in which R represents an organofunctional group that can subsequently bind to a polymer, k is a positive integer, l is another positive integer that is independent of k, m is yet another integer that is independent of k and l, and each of X1, X2, X3, Y1, Y2, Y3, Z1, Z2, and Z3 represents a hydrolysable group that can be the same or different among themselves.
In one embodiment, the coupling agent includes a silicon atom and at least one hydrolysable group directly attached to the silicon atom. Each of the at least one hydrolysable group can include a hydrolysable group having a formula of OCpH2p+1, in which p is any positive integer. For example, each of the at least one hydrolysable group can be independently selected from OCH3, OC2H5, and OC3H7.
In one embodiment, the coupling agent includes three hydrolysable groups that are attached to a silicon atom and having a formula of OCpH2p+1, OCqH2q+1, and OCrH2r+1, respectively, wherein p, q, and r are independent positive integers.
The coupling agent also includes an organofunctional group that forms a bond with a polymer in a subsequent processing step in which a binding polymer material is applied.
Upon dissolving in the non-aqueous solution containing a hydrolysis catalyst, the coupling agent is hydrolyzed. A derivative of the coupling agent is thereby formed in the non-aqueous solution. The chemical formula for the derivative of the coupling agent can be
in which R represents an organofunctional group that can subsequently bind to a polymer, k is a positive integer, or can be
in which R represents an organofunctional group that can subsequently bind to a polymer, k is a positive integer, l is another positive integer that is independent of k, or can be
in which R represents an organofunctional group that can subsequently bind to a polymer, k is a positive integer, l is another positive integer that is independent of k, m is yet another integer that is independent of k and l.
The hydroxide groups in the hydrolyzed derivative of the coupling agent interact with dangling hydroxide groups that are bonded to silicon atoms on the surface of the glass fibers in the woven glass cloth. A water molecule can be formed from two hydroxide groups that come into contact with each other, thereby forming a —Si—O—Si— bond. Thus, a compound that is derived from the coupling agent by hydrolyzation and dehydration is bonded to the silicon atoms in the glass fibers in the woven glass cloth.
The polar solvent is a liquid that dissolves the sizing agent, which is an organic material. Polar solvents that can dissolve the sizing agent include acetone, tetrahydrofuran (THF), ethyl acetate, ethanol, and methanol. Non-polar solvents that can dissolve the sizing agent and be used for the purposes of the present disclosure include toluene. The range of the Hildebrand solubility parameter for suitable polar solvents for dissolving the sizing agent is from, and including, 17.4 MPa0.5 and to, and including, 21.7 MPa0.5. It is noted that the Hildebrand solubility parameters for ethanol and methanol are outside this range.
In one embodiment, the polar solvent is not only effective at removing the sizing, but also dissolves the coupling agent. Exemplary polar solvents that provide these dual functions include acetone, tetrahydrofuran (THF), and ethyl acetate.
In one embodiment, the solution can further include an acidic catalyst. The acidic catalyst can be, for example, acetic acid or formic acid. Further, additional catalysts conventionally employed in deposition of a coupling agent may also be added.
The exemplary processing scheme according to an embodiment of the present disclosure does not require any elevated temperature bake. Thus, the removal of the sizing agent does not need to employ an elevated temperature sufficient to remove the sizing agent by oxidation, i.e., burning. In one embodiment, the temperature of the woven glass cloth can be maintained below 100 degree Celsius between the weaving of the multiple glass fibers and the immersing of the woven glass cloth in the solution. In another embodiment, the temperature of the woven glass cloth can be maintained between 50 degrees Celsius between the weaving of the multiple glass fibers and the immersing of the woven glass cloth in the solution.
In one embodiment, the temperature of the bath including the polar solvent and the coupling agent as dissolved therein can be between 0 degrees Celsius and 100 degrees Celsius. In another embodiment, the temperature of the bath including the polar solvent and the coupling agent as dissolved therein can be between 10 degrees Celsius and 50 degrees Celsius.
Relative to the comparative exemplary processing scheme, the exemplary processing scheme according to an embodiment of the present disclosure provides a more thorough coating of the coupling agent, and can provide enhanced tensile strength in the woven glass cloth prior to application of a binding polymer material. The weight of the woven glass cloth processed with the methods of the comparative exemplary processing scheme loses weight by less than 0.1% during the processing steps of elevated temperature bakes. In contrast, a woven glass cloth treated with the solvent wash according to the exemplary processing scheme according to an embodiment of the present disclosure can lose weight by more than 0.2% during the immersing in the solution.
As a theoretical matter, the weight percentage of a coupling agent applied to a woven glass during the solvent wash can be estimated in the following manner. The radius of a typical glass fiber, as determined by measuring the cross-sectional profile of glass fibers, is about 0.1 mil, or 2.54×10−4 cm. Thus, the volume of a glass fiber having a length of 1 cm is about 2.03×10−7 cm3. Since the density of a glass fiber is about 2.55 g/cm3, the mass of the glass fiber having a length of 1 cm is about 5.17×10−7 g. 3-aminopropyl triethoxysilane (APS), which is a coupling agent employed in experiments that have led to the instant disclosure, forms a monolayer on the surface of glass fibers. The thickness of the monolayer of APS is about 0.9 nm, or 9×10−8 cm, which is less than 1×10−7 cm. If a coating of APS on the fiber glass surfaces is assumed to include up to three monolayers of APS, the volume of a cylindrical shell of APS around the sidewall of a 1 cm long glass fiber is less than 4.62×10−10 cm3. Since the density of APS is 0.949 g/cm3, the mass of the cylindrical shell of APS around the sidewall of the 1 cm long glass fiber is less than 4.38×10−10 g. Thus, if the cylindrical shell of APS around the sidewall of the 1 cm long glass fiber is removed, the weight percentage of the coupling agent on a glass fiber in general is on the order of 100%×(4.38×10−10 g)/(5.17×10−7 g+4.38×10−10 g)=0.085%. Thus, the order of magnitude for the weight percentage of a coupling agent on glass fibers should normally be on the order of 0.1%.
The above calculations show that the order of magnitude for the fractional weight of the sizing agent on glass fibers should also be on the order 0.1% if the amount of residual sizing agent on the glass fibers after preparation for application of a coupling agent (for example, at the end of the elevated temperature bakes) is to be maintained on par with the amount of the coupling agent to be applied.
In order to quantify the effectiveness in removal of the sizing agent in the exemplary processing scheme according to an embodiment of the present disclosure, different groups of experimental samples were prepared and measured in the course of experiments leading to the present disclosure. Specifically, a first group of experimental samples sampled immediately after the weaving step, i.e., before the elevated temperature bakes or the solvent wash. A second group of samples were prepared by providing samples of the same material as the first group of experimental samples and subsequently employing the comparative exemplary processing scheme thereupon in which elevated temperature bakes are employed. The temperature and duration of the elevated temperature bake was 500° C. and 60 minutes, respectively, for the second group. A third group of experimental samples were prepared by providing additional samples of the same material as the first group of experimental samples and subsequently employing the exemplary processing scheme thereupon according to an embodiment of the present disclosure. Acetone was employed as the solvent and APS was employed as the coupling agent for the third group. The duration of the solvent wash was 20 minutes.
Weight loss was measured on each group. The method employed for measuring the weight loss is an industry standard method based on ASTM D-4963-94, “Standard Test Method For Ignition Loss of Glass Strands and Fabrics.” Specifically, experimental samples were pre-dried at 105° C. for 60 minutes to drive off water. The experimental samples were then cooled to ambient temperature in a dessicator to prevent condensation of moisture. Then, the experimental samples were placed in a muffle furnace and baked at 625° C. for 30 minutes. By comparing the weight distribution of the first group, the second group, and the third group, the average and the standard distribution of weight loss were calculated for each of the comparative exemplary processing scheme and the exemplary processing scheme according to an embodiment of the present disclosure.
The average of weight loss for the comparative exemplary processing scheme was 0.1140%. The standard deviation of weight loss for the comparative exemplary processing scheme was 0.0555%. The average of weight loss for the exemplary processing scheme according to an embodiment of the present disclosure was 0.3698%. The standard deviation of weight loss for the exemplary processing scheme according to an embodiment of the present disclosure was 0.0919%.
The above data indicates that the method, i.e., the solvent wash, of the exemplary processing scheme according to an embodiment of the present disclosure can be at least three times more effective in removing sizing agents than the method of the comparative exemplary processing scheme. Further, the data above also indicates that at least 0.25% of the total weight of woven glass cloth prepared by employing elevated temperature bakes according to the comparative exemplary processing scheme is attributable to a residual sizing agent that is not removed even after the elevated temperature bakes.
The mechanical strength of woven glass cloths was also measured for the three groups of experimental samples. Table 1 below tabulates the result of the mechanical strength measurements performed on the three groups of experimental samples.
Load to break is measured from the experimental samples. Maximum tensile stress and maximum tensile strain are calculated at the extension (the incremental length in the stretched woven glass cloth relative to the original length of the woven glass cloth) that supports the maximum load. The maximum tensile stress is calculated by dividing the load to break by the cross-sectional area of each sample. Young's modulus was calculated from cursor-selected data points in the linear elastic region in a plot of an extension distance versus load.
As can be seen in the data in Table 1 and
The exemplary processing scheme according to an embodiment of the present disclosure cleans the glass fibers in a woven glass cloth and simultaneously deposits a silicon-including coupling agent on the glass fibers in the woven glass cloth. The exemplary processing scheme according to an embodiment of the present disclosure provides retention of tensile strength of the woven glass cloth, which is not possible in the comparative exemplary processing scheme that employs elevated temperature bakes (or any equivalent heat cleaning processes). Further, cleaner glass fiber surfaces with less residual sizing agent can be provided by the exemplary processing scheme according to an embodiment of the present disclosure relative to the comparative exemplary processing scheme that employs elevated temperature bakes. It is noted that the more thorough the cleaning is in the comparative exemplary processing scheme (for example, by increasing the temperature or the duration of the elevated temperature bakes), the more loss in a sizing agent occurs, and with the loss of the sizing agent, the tensile strength of the woven glass cloth decreases rapidly. Yet further, the exemplary processing scheme according to an embodiment of the present disclosure replaces multiple processing steps (two extended baking operations and a separate coupling agent application step) in the comparative exemplary processing scheme with a single solvent washing step.
In an alternate exemplary processing scheme according to another embodiment of the present disclosure, the glass fibers in a woven glass cloth can be cleaned in a first bath including a first polar solvent, and subsequently a silicon-including coupling agent can be deposited on the glass fibers in the woven glass cloth in a second bath including a second polar solvent. In this embodiment, the woven glass cloth is treated sequentially in two baths, in a first bath to remove the sizing agent, and the second bath to deposit a coupling upon the glass fibers in the woven glass cloth.
The solution in the first bath, which is herein referred to as a sizing-agent-dissolving solution, removes the sizing agent, and may, or may not, include a coupling agent. The solution in the second bath, which is herein referred to as a coupling-agent-including solution, includes a coupling agent, and may, or may not, remove the sizing agent. Thus, the sizing-agent-dissolving solution does not need to be able to deposit a coupling agent, but dissolves the sizing agent. Suitable polar solvents for the sizing-agent-dissolving solution include acetone, tetrahydrofuran (THF), and ethyl acetate. Suitable non-polar solvents for the sizing-agent-dissolving solution include toluene.
The coupling-agent-including solution may, but does not need to, dissolve the sizing agent. The coupling-agent-including solution deposits a coupling agent to the glass fibers in the woven glass cloth. Suitable polar solvents for the coupling-agent-including solution include acetone, tetrahydrofuran (THF), ethyl acetate, ethanol, and methanol. Suitable non-polar solvents for the coupling-agent-including solution include toluene.
In one embodiment, the coupling-agent-including solution can further include an acidic catalyst. The acidic catalyst can be, for example, acetic acid or formic acid. Further, additional catalysts conventionally employed in deposition of a coupling agent may also be added.
In one embodiment, the first bath and the second bath are prepared as two separate baths, and the woven glass cloth is sequentially immersed in the first bath, pulled out of the first bath, and then immersed in the second bath. In another embodiment, the woven glass cloth can remain in a same bath apparatus, and the bath apparatus can be filled with the liquid of the first bath, and then the liquid of the first bath is replaced with the liquid of the second bath. The replacement of the liquid of the first bath with the liquid of the second bath can be performed, for example, by draining the liquid of the first bath and then refilling the bath apparatus with the liquid of the second bath, by gradually adding the liquid of the second bath while draining the liquid of the second bath, or by adding a suitable additive such as the coupling agent if the first polar liquid is the same as the second polar liquid.
Once the surfaces of the glass fibers in the woven glass cloth are treated in the solvent washing step of the exemplary processing scheme according to an embodiment of the present disclosure, a binding polymer material is applied to the woven glass cloth. The woven glass cloth is embedded in the applied binding polymer material to provide a “finished” or “coupled” woven glass cloth, in which the voids between the glass fibers are filled with the binding polymer material. An organofunctional group (such as the organofunctional group R in the exemplary coupling agents discussed above) forms a chemical bond with the binding polymer material. Exemplary binding polymer materials include, but are not limited to, epoxy resin, phenolic resins, polyphenylene ether (PPO) resins, cyanate esters, cyanate ester/epoxy blends, PPO/epoxy blends, and vinyl-functionalized PPO resins.
Referring to
At least the first solution 112 is a sizing-agent-dissolving solution for removing a sizing agent from the surfaces of the roll of the woven glass cloth 40. In one embodiment, the sizing-agent-dissolving solution includes a coupling agent so that removal of a sizing agent and deposition of a coupling agent occur simultaneously in the sizing-agent-dissolving solution. In another embodiment, the sizing-agent-dissolving solution does not include a coupling agent so that removal of a sizing agent occurs in the sizing-agent-dissolving solution, and deposition of a coupling agent does not occur in the sizing-agent-dissolving solution.
At least the third solution 132 is a coupling-agent-including solution for depositing a coupling agent on the surfaces of the roll of the woven glass cloth 40. In one embodiment, the coupling-agent-including solution includes a solvent that removes a sizing agent so that removal of the sizing agent and deposition of the coupling agent occur simultaneously in the coupling-agent-including solution. In another embodiment, the coupling-agent-including solution does not remove a sizing agent so that, deposition of a coupling agent occurs in the coupling-agent-including solution, and removal of a sizing agent does not occur in the coupling-agent-including solution.
Each coupling-agent-including solution may, or may not, be a sizing-agent-dissolving solution Likewise, each sizing-agent-dissolving solution may, or may not, be a coupling-agent-including solution.
In one embodiment, each of the first solution 112, the second solution 122, and the third solution 132 is both a sizing-agent-dissolving solution and a coupling-agent-including solution.
In another embodiment, the first solution 112, the second solution 122, and the third solution 132 are sizing-agent-dissolving solutions, the second solution 122 and the third solution 132 are coupling-agent-including solutions, and the first solution 112 is not a coupling-agent-including solution.
In even another embodiment, the first solution 112, the second solution 122, and the third solution 132 are sizing-agent-dissolving solutions, the third solution 132 is a coupling-agent-including solution, and the first solution 112 and the second solution 122 are not coupling-agent-including solutions.
In yet another embodiment, the first solution 112 and the second solution 122 are sizing-agent-dissolving solutions, the third solution 132 is not a sizing-agent-dissolving solution, and the first solution 112, the second solution 122, and the third solution 132 are coupling-agent-including solutions.
In a still another embodiment, the first solution 112 and the second solution 122 are sizing-agent-dissolving solutions, the third solution 132 is not a sizing-agent-dissolving solution, and the first solution 112 is not a coupling-agent-including solution, and the second solution 122 and the third solution 132 are coupling-agent-including solutions.
In further another embodiment, the first solution 112 is a sizing-agent-dissolving solution, the second solution 122 and the third solution 132 are not sizing-agent-dissolving solutions, and the first solution 112, the second solution 122, and the third solution 132 are coupling-agent-including solutions.
In yet further another embodiment, the first solution 112 is a sizing-agent-dissolving solution, the second solution 122 and the third solution 132 are not sizing-agent-dissolving solutions, and the first solution 112 is not a coupling-agent-including solution, and the second solution 122 and the third solution 132 are coupling-agent-including solutions.
As discussed above, non-limiting examples for a polar solvent for a sizing-agent-dissolving solution include acetone, tetrahydrofuran (THF), and ethyl acetate, and non-limiting examples for a polar solvent for a coupling-agent-dissolving solution include acetone, tetrahydrofuran (THF), ethyl acetate, ethanol, and methanol.
Thus, the first exemplary apparatus 100 includes at least one coupling-agent-including solution (which includes at least the first solution 112) that includes a polar solvent and a coupling agent and having a chemistry that causes a compound that is derived from the coupling agent to be deposited on surfaces of a roll of woven glass cloth 40 introduced therein. Further, at least one sizing-agent-dissolving solution (which includes at least the third solution 132) for removing a sizing agent from the surfaces of the roll of woven glass cloth 40 is provided as well. Each of the at least one sizing-agent-dissolving solution can be the same as, or different from, one of the at least one coupling-agent-including solution.
Further, means are provided for immersing the roll of woven glass cloth 40 in, and for subsequently removing the roll of woven glass cloth 40 out of, the at least one sizing-agent-dissolving solution and the at least one coupling-agent-including solution. Such means may include a feed-in roller 5, in-solution rollers (9, 11, 19, 21, 29, 31), out-of-solution rollers (15, 25), and a pull-out roller 35, which turn in synchronization to continuously or intermittently move the roll of woven glass cloth 40 through the first exemplary apparatus. A chemical supply system 80 and a chemical pumping system 1 can be provided in the first exemplary apparatus 100 to supply, and/or to remove, chemicals including at least one polar solvent for each of the first solution 112, the second solution 122, and the third solution 132.
In one embodiment, the means for immersing the roll of woven glass cloth 40 in, and for subsequently removing the roll of woven glass cloth 40 out of, the at least one sizing-agent-dissolving solution and the at least one coupling-agent-including solution can be configured to move the roll of woven glass cloth 40 into a sizing-agent-dissolving solution, then to move the roll of woven glass cloth 40 out of the sizing-agent-dissolving solution, then to move the roll of woven glass cloth 40 into a coupling-agent-including solution that is different from the sizing-agent-dissolving solution, and then to move the roll of woven glass cloth out of the coupling-agent-including solution.
In a non-limiting exemplary implementation of the first exemplary apparatus 100, fresh solvent and a coupling agent can be added to the third solution 132 in the third container 20. The third solution 132 can overflow into the second container 20 through a counter current solvent flow indicated by an arrow with a label “CCSF.” The second solution 122 can overflow into the first container 10 through a counter current solvent flow indicated by another arrow with another label “CCSF.” The level of the first solution 112 is lower than the level of the second solution 122, and the level of the second solution 122 is lower than the level of the third solution 132. The first solution 112 and the second solution can be initially provided as solutions without any coupling agent therein. During operation, due to the counter current solvent flow, i.e., spillage, of solutions from the third solution 132 to the second solution 122, and from the second solution 122 to the first solution 112, the concentration of the coupling agent is the greatest in the third solution 132, and is the lowest in the first solution 112.
Initially, the first solution 112, the second solution 122, and the third solution 132 can be sizing-agent-dissolving solutions and the third solution 132 can be a coupling-agent-including solution. During operation of the first exemplary apparatus 100, the first solution 112, the second solution 122, and the third solution 132 become mixed solutions each of which is both a sizing-agent-dissolving solution and coupling-agent-including solution. The third solution 132 is the most effective as a coupling-agent-including solution because of fresh supply of the coupling agent, and the first solution is primarily employed for the function of a sizing-agent-dissolving solution. Thus, the roll of the woven glass cloth 40 is predominantly solvent-cleaned in the first solution 112, and is predominantly treated with the coupling agent in the third solution 132. Upon exiting the first exemplary apparatus 100, the roll of the woven glass cloth 40 is sent to a dryer (not shown) and wound onto a take up mandrel (not shown).
Referring to
Referring to
Instead of eliminating at least one container from the first exemplary apparatus 100, at least one additional container including an additional solution can be added between the first container 10 and the third container. Such embodiments are expressly contemplated herein.
While the disclosure has been described in terms of specific embodiments, it is evident in view of the foregoing description that numerous alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, the disclosure is intended to encompass all such alternatives, modifications and variations which fall within the scope and spirit of the disclosure and the following claims.
Claims
1. A method of treating a woven glass cloth comprising:
- providing a solution comprising a solvent and a coupling agent;
- removing a sizing agent from surfaces of said woven glass cloth in a bath including said solution or another solution; and
- immersing said woven glass cloth in said solution, wherein a compound that is derived from said coupling agent is deposited on said surfaces of said woven glass cloth in said solution.
2. The method of claim 1, wherein said compound is derived from said coupling agent and coupled to glass fibers of said woven glass cloth through at least one —Si—O—Si— bond.
3. The method of claim 1, wherein said coupling agent comprises a silicon atom.
4. The method of claim 3, wherein said coupling agent further comprises at least one hydrolysable group directly attached to said silicon atom.
5. The method of claim 4, wherein said at least one hydrolysable group includes a hydrolysable group having a formula of OCpH2p+1, wherein p is a positive integer.
6. The method of claim 5, wherein said at least one hydrolysable group is selected from OCH3 and OC2H5.
7. The method of claim 3, wherein said coupling agent includes three hydrolysable groups having a formula of OCpH2p+1, OCqH2q+1, and OCrH2r+1, respectively, wherein p, q, and r are independent positive integers.
8. The method of claim 4, wherein said coupling agent further includes an organofunctional group that forms a bond with a polymer.
9. The method of claim 1, further comprising applying a binding polymer material to said woven glass cloth after said immersing, wherein said woven glass cloth is embedded in said applied binding polymer material,
10. The method of claim 1, wherein said woven glass cloth is provided by weaving multiple glass fibers oriented in at least two different directions.
11. The method of claim 10, wherein temperature of said woven glass cloth is maintained below 100 degree Celsius between said weaving of said multiple glass fibers and said immersing of said woven glass cloth in said solution.
12. The method of claim 1, wherein said solvent is a polar solvent that includes at least one of acetone, tetrahydrofuran (THF), ethyl acetate, ethanol, and methanol.
13. The method of claim 1, wherein said woven glass cloth is not embedded in a matrix resin.
14. The method of claim 1, wherein said solution is not a water-based solution.
15. The method of claim 1, wherein said compound is derived from said coupling agent by hydrolyzation and dehydration upon coupling to surfaces of glass fibers in said woven glass cloth.
16. The method of claim 1, wherein said removal of said sizing agent and said deposition of said compound occur concurrently on said woven glass in said solution.
17. The method of claim 1, wherein said another solution is a different solution than said solution.
18. The method of claim 1, wherein said compound is deposited on said surfaces of said woven glass cloth after said removing of said sizing agent from said surfaces of said woven glass cloth.
19. The method of claim 1, wherein said bath includes said another solution, and said another solution includes a solvent that dissolves said sizing agent.
20. An apparatus for treating a woven glass cloth comprising:
- at least one container including at least one solution, said at least one solution including a coupling-agent-including solution that comprises a solvent and a coupling agent and having a chemistry that causes a compound that is derived from said coupling agent to be deposited on surfaces of a woven glass cloth introduced into said coupling-agent-including solution, said at least one solution includes a sizing-agent-dissolving solution for removing a sizing agent from said surfaces of said woven glass cloth, wherein said sizing-agent-dissolving solution is the same as, or different from, said coupling-agent-including solution; and
- means for immersing said woven glass cloth in, and for subsequently removing said woven glass cloth out of, said coupling-agent-including solution.
21. The apparatus of claim 20, wherein said sizing-agent-dissolving solution is the same as said coupling-agent-including solution.
22. The apparatus of claim 20, wherein said sizing-agent-dissolving solution is different from said coupling-agent-including solution, and said means is configured to move said woven glass cloth into said sizing-agent-dissolving solution, then to move said woven glass cloth out of said sizing-agent-dissolving solution, then to move said woven glass cloth into said coupling-agent-including solution, and then to move said woven glass cloth out of said coupling-agent-including solution.
23. The system of claim 20, wherein said coupling agent comprises silicon and at least one hydrolysable group directly attached to said silicon atom.
24. The system of claim 23, wherein said at least one hydrolysable group includes a hydrolysable group having a formula of OCpH2p+1, wherein p is a positive integer.
25. The system of claim 20, wherein said solvent is a polar solvent includes at least one of acetone, tetrahydrofuran (THF), ethyl acetate, ethanol, and methanol.
Type: Application
Filed: Sep 13, 2011
Publication Date: Mar 14, 2013
Applicants: PARK ELECTROCHEMICAL CORP. (Melville, NY), INTERNATIONAL BUSINESS MACHINES CORPORATION (Armonk, NY)
Inventors: Dylan J. Boday (Tucson, AZ), Michael Haag (Rodenbach), Ruediger Kellmann (Mainz), Joseph Kuczynski (Rochester, MN), Markus Schmidt (Seibersbach), Johannes Windeln (Bodenheim), Silvio Bertling (Mesa, AZ)
Application Number: 13/231,160
International Classification: D01F 11/00 (20060101); D06F 1/02 (20060101);
