CA2188308A1

CA2188308A1 - Method for making dual-glass fibers

Info

Publication number: CA2188308A1
Application number: CA002188308A
Authority: CA
Inventors: James E. Loftus; Carl R. Strauss; Robert L. Houston
Original assignee: Individual
Current assignee: Owens Corning
Priority date: 1994-05-02
Filing date: 1995-04-03
Publication date: 1995-11-09
Also published as: US5529596A; BR9507584A; TR28719A; DK0758305T3; DE69503372T2; KR100341648B1; EP0758305A1; ZA953460B; FI964361A; ATE168094T1; FI964361A0; CN1147240A; DE69503372D1; AU2237495A; KR970702219A; CZ321396A3; ES2117864T3; NO964643D0; EP0758305B1; WO1995029880A1

Abstract

A method for making dual-glass fibers includes supplying first and second molten glass to a rotating spinner having an orificed peripheral wall, where the first glass has a higher viscosity than that of the second glass, centrifuging the first and second glasses through the orifices as molten dualglass streams, maintaining the dual-glass streams at a temperature sufficient to enable the second glass to flow around the first glass, and cooling the dual-glass streams to make dual-glass fibers.

Description

-W095/29880 2 1188 3~8 r~l"J~ ~s ~
METHOD FOR MAKING DUA~GLASS FIBERS

TEs3T~IcAT FTFT.n This invention relates to the u~uL~,Lul e of dual-glass fibers having two 5 glasses of different ~....1..,~:l;~ ." More particularly, this invention pertains to the e of molten dual-glass streams under conditions in which one ofthe glasses reacts differently to the fiber forming CIIV;I I ' than the other glass.
I~ACK-~.R(-)UNn ART
Recent dci.,lv~ lll.,.-t~ in the art of,. ",r 1,..; .g glass fibers have resulted in 10 new methods for making irregululy shaped glass fibers comprising two distinct glass ,,,,,c with different coefflcients ofthermal expunsion. The difference in coefflcient of thermal expunsion between the two glasses enables the resulting glass fiba to have an irregular shape, thereby providing numerous attributes to the glass fiber which enhance the ,c. ''( of products made with those fibers. Some of those product ~ ' 15 include increased ~. .n ~&1 ~ among the fibers, increased recovery of insulation products made by the fibers, lower K values, lower irritability upon huldling, and a more uniform volume filling nature.
Dual-glass fibers disclosed m the ut so far were comprised of glasses that have generally similu viscosities und soflening points. For example, in U.S. patent 20 2,998,620, to Stalego, the differences in viscosities and softening points of the four glass r~ - disclosed are relatively minor. Since the viscosities and softening points of the two glasses of the dual-glass fibers of the prior art are relatively similar, the two glasses will react similarly to the fiber forming conditions ell~UUllttlCd by the dual-glass stream as it forms into a solid dual-glass fiber. It would be ~dv ~ to make a dual-glass fiber from 25 a molten dual-glass stream where there are differences in the viscosity und/or the softening point of the two glasses in order to enable the two glasses to exhibit differing reactions to the fiber forming c..~;.u~ ,.lL.
D~ .OSU~T~ OF INVF~TION
There has now been developed a method for producing dual-glass fibers in 30 which the first glass of the two glasses has a higher viscosity thun that of the second glass so that the two glasses can react differently to the fiber forming Cl..:.~ t, thereby affecting woss/29880 2 r~83~&' r~ s~
the shape of the dual-glass fiber, the internal ~ . .., ~ u 1, . n ~ . . of the dual-glass fiber, andlor th~
properties of the dual-glass fiber According to this invention, there is provided a method for making dual-glass fibers comprising supplying first and second molten glasses to a rotating spinner having an 5 orificed peripheral wall, where the first glass has a higher viscosity than that of the second glass, r ~ g the fi}st and second glasses through the orifices as molten dual-glass streams, ~, the dual-glass streams at a ltu"~ Lu~c; sufficient to enable the second glass to flow around the first glass, and cooling the dual-glass streams to make dual-glass fibers.
In a specific ~ ..lI,ou;....,.l~ ofthe invention, the viscosity ofthe first glass, at the It.l.lJ.,. ~Lul ~ of the spinner wall, is higher than that of the second glass by a factor within the range of from about 5 to about 1000. More preferably, the viscosities differ by a factor within the range of firom about 50 to about 500. For example, the second glass (glass B) might have a viscosity at the spinner wall t~,...l..,..~Lult: (1037~C) of 100 poise, while the first 15 glass (glass A) has a viscosity of 100,000 poise at the same L ~ .tu.t. It is to be understood that the viscosity u~,~u~ L~ as used in this ~ are to be taken at the Le...~ Lu. ~ of the spinner peripheral wall.
In a particular ' - ' of the invention, the lower viscosity second glass flows all the way around the first glass so that the second glass encloses the first glass to 20 forrn a cladding.
In yet another c...l" ' of the invention, the soflening point of the second g]ass is lower than the sofrening point of the first glass by at least 50~C. Preferably, the difference in sofltening point is at least 100~C.
The dual-glass fibers from glasses having differing soflening points can be 25 collected as a wool pack and subjected to a L~ Lu~; greater than the soflening point of the second glass but less than the soflening point of the first glass This will enable the second glass to soflen, thereby causing the dual-glass fibers to bond to each other upon cooling. The result will be that the second glass acts as a binder material for the first glass fibers in the wool pack By making a glass fiber insulation product from dual-glass fibers having glasses with different softening points and passing the product through an oven to heat the lower soflening point glass to act as a binder, the insulation product can be pro~uced wogs/29880 . ~ 383~
without using an organic binder. This method, then, enables the production of glass fiber insulation products while avoiding the ~llvhul~ ..al problems associated with organic binders. This may be particularly useful where one desires higher densities and the advantages of having the lower ttll~ ILulc glass to shape the pack into a rectangular ... .
5 1 . .
In yet another ' - ' of the invention, there is provided a method for making dual-glass fibers comprising supplying first and second molten glasses to a textile busbing, where the first glass has a viscosity higher than that of the second glass by a factor witbin the range of from about 50 to about SOO, drawing the first and second glasses from 10 the bushing as molten dual glass streams, ~ ~ ~ ~ the dual glass streams at a L~ ul c sufficient to enable the second glass to flow around the first glass, and cooling the dual-glass streams to make dual-glass fibers.
In another _ ~1 .o.l;, - 1 of the invention the flowing of the second glass around the first glass is effected by making the surface tension of the second glass higher 15 than that of the first glass. Then, as long as the t~ UI c is maintained bigh enough and long enough, the second glass will flow around the first glass. The use of two glasses having different surface tensions can be used alone or in ~ ; with the use of two glasses having different viscosities.
FiRlFF DEs(~RlpTloN OF VRAWINGS
Figure I is a schematic view in eclevation of apparatus for carrying out the method of making dual-glass fibers by the rotary process.
Figure 2 is a cross-sectional view in elevation of a rotary fiberizer by which dual-glass fibers can be produced according to the invention.
Figure 3 is a schematic view in p~ .Li ~ ., of a portion of the spinner of 25 Figure 2.
Figure 4 is a schematic view in elevation of the spinmer of Figure 2, taken along line 4-4.
Figure 5 is a schematic cross-sectional view of a dual-glass fiber comprised of two glasses having generally similar viscosities and softcning points.
Figure 6 is a schematic cross-sectional view of a dual-glass fiber ofthe invention in which differing glass viscosities of the two glasses enables the second glass to flow partially around the first glass.

W09~29880 j~ 7 ~ r~ ol .~
Figure 7 is a schematic cross-sectional view of a dual-glass fiber of the O
invention in which the differing glass viscosities enables the lower viscosity second glass to nearly enclose the higher viscosity glass.
Figure 8 is a schematic cross-sectional view of a dual-glass fiber of the 5 invention in which the lower viscosity glass flows all the way around the higher viscosity glass to enclose the higher viscosity glass and form a cladding.
Figure 9 is a schematic view in elevation of a textile bushing used in a method of making continuous dual-glass fibers according to the invention.
MQDF~ FOR CARRYING OUT T~F INVE~TION
As used in this ~ \ the term "glass" includes glassy forms of other mineral materials, such as rock, slag and basalt.
Referring to Figure 1, it can be seen that two distinct molten glass are supplied fi om furnaces 10 via forehearths 12 to fiberizers 14. Veils 18 of irregularly shaped glass fibers produced by the fiberizers are collected on conveyor 16 as 15 wool pack 20 by means of a partial vacuum positioned beneath the conveyor. As the fibers are blown downward by air or gases to the conveyor by means of blowers 22 in thefiberizers, they are attenuated and assume their irregular shape.
Where the method employs a second glass having a soRening point lower than the soRening point of the first glass so that the second glass can act as a binder or 20 solder material, the wool pack can be passed through an oven or other heating means, such as oven 24, to soRen the lower tu.~ ul~ glass and thereby bind the higher ~L...~ Lu~
glass. While passing through the oven, the wool pack is shaped by top conveyor 26 and bottom conveyor 28, and by edge guides, not shown. While in the oven, the glass fibers may be subjected to flows of hot gases to facilitate uniform heating. The wool pack then exits the 25 oven as insulation product 30.
As shown in Figure 2, spinner 32 is comprised of spinner bottom wall 34 and spinner peripheral wall 36. The rotation of the spinner centrifuges molten glass tbrough the spinner peripheral wall into primary fibers 40. In one; ~ ~ " of the invention, the primary fibers are maintained in a soR, attenuable condition by the heat of annular burner 42.
30 In another .l v ~ of the invention, an internal burner, not shown, provides heat to the interior of the spinner. The annular blower pulls the primary fibers and fiurther attenuates them into a veil of secondary fibers 48, suitable for use in wool insulating materials.

2 1 ~ 8 ~ ~ 8 ~ r~
Optionaily, a binder can be applied to the fibers. The secondary fibers, or dual-glass irregularly shaped glass fibers, are then collected for forrnation into a wool pack.
The interior of the spinner is supplied with two separate streams of molten glass, first stream 50 containing glass A amd second stream 52 containing glass B. The glass 5 in stream 50 drops directly onto the spinner bottom wail and flows outwardly by centrifiugai force toward the spinner peripheral wall to form a head of glass A. Glass B in molten giass stream 52 is positioned closer to the spinner peripherai wail than stream 50, and the glass in stream 52 is intercepted by horizontai flange 54 before reaching the spinner bottom wail.
Thus, a build-up or head of glass B is formed above the horizontai flange.
As shown in Figure 3, the spinner is adapted with verticai interior wail 56 which is generaily .,;.. '' .,..t;~,l and positioned radiaily inwardly from the spinner peripheral wall. A series of vertical baffies 58, positioned between the spinner peripherai wail and the vertical interior wall, divide that space into a series of ~.u.,.l.~ 60.
Aiternate . . i contain either glass A or glass B.
The spinner peripheral wall is adapted with orifices 62 which are positioned adjacent the radially outward end of the verticai baffle. The orifices have a width greater than the width of the verticai baffle, thereby enabling a flow of both glass A and glass B to emerge from the orifice as a single duai-giass nnolten stream of glass.
As can be seen in Figure 4, each ~ , 60 runs the entire height of 20 spinner peripheral wail 36 with orifices along the entire verticai baffle separating the Other spinner cc,..C~;u. al;ùns can be used to supply duai streams of glass to the spinner orifices. As shown in Figure 4, the orifices 62 are in the shape of slots, aithough other shapes of orifices can be used.
Where the A and B glasses have different viscosities at the t~.l~!~ CltU~ ci of the 25 spinner peripheral wall, an orifice perfectly centered about the verticai baflie 58 would be expected to emit a higher throughput of the lower viscosity glass than the throughput ofthe higher viscosity glass. In order to counteract this tendency and to balance the IhlUU~Sh~UIS
of the two glasses, the slot orifice can be positioned offset from the centerline of the verticai baflfle. In such a case, the orifice will have a snuiler end such as end 64 which will restrict 30 the flow of the lower viscosity materiai, amd larger end 66 which will enable a . ' ' -flow or throughput of the higher viscosity material. Another method to equaiize the flow of the low viscosity glass with the high viscosity glass is to restrict the flow of glass into the 21 8~30~
WO 95/29880 P~ S ~ IJ~
altemate ~,UUI~ UI~ t~ containing the low viscosity glass, thereby partially starving the ho!~
so that the throughputs of the A and B glass are roughly equivalent.
The irregularly shaped fibers ofthe present invention are dual-glass fibers, i.e.
each fiber is composed of two different glass ~ ;. - ., glass A and glass B. If one were 5 to make a cross-section of an ideal irregularly shaped glass fiber of the present invention, one half of the fiber would be glass A, with the other half glass B. Cross-section I .1.. ~l og"~ of fibers can be obtained by mounting a bundle of fibers in epoxy with the fibers oriented in parallel as much as possible. The epoxy plug is then cross-sectioned and is polished. The polished sample surface is then coated with a thin carbon layer to provide a conductive 10 sample for analysis by scanning electron UIl~lU ~ y (SEM~. The sample is then examined on the SEM using a b~l..k~dtlGIGd-electron detector, which displays variations in average atomic number as a variation in the gray scale. This analysis reveals the presence of two glasses by a darker and lighter region on the cross-section of the fiber, and shows the interface of the two glasses.
If the A/B ratio is 50:50, the interface 68 between the two glasses, glass A 70 and glass B 72, passes through the center 74 of the fiber cross-section, as shown in Figure 5.
As shown in Figure 6, where the B glass has a lower viscosity, the B glass can somewhat bend around or wrap around the higher viscosity A glass so that the interface 68 becomes curved. This requires that the dual-glass stream emanating from the spinner be maintained at 20 a t~ LU- G sufficient to enable the low viscosity B glass to flow around the higher viscosity A glass. Adjustments in the fiberizer operating parameters, such as burner gas pressure, blower pressure, and spinner t~ Lul G, may be necessary to achieve the desired wrap of the low viscosity glass.
As shown in Figure 7 the lower viscosity B glass has flowed almost all the 25 way around the higher viscosity A glass. One way to quantify the extent to which the lower viscosity glass flows around the higher viscosity glass is to measure the angle of wrap, such as the angle alpha shown in Figure 7. In some cases the lower viscosity glass flows around the higher viscosity glass to fomm an angle alpha of at least 270~, i.e., the lower viscosity glass flows around the higher viscosity glass to an extent that at least 270~ of the 30 C;l ~ r Gllfidl surface 76 of the dual-glass fiber is made up of the second glass.
As shown in Figure 8, under certain conditions the second glass can flow all the way around the first glass so that the second glass encloses the first glass to fomm a woss/2s880 ~ 3308 r~ cO IG99 cladding. In that case, the entire ~,;" r ~".L~ surface (360~) ofthe dual-glass fiber is the second glass or the lower viscosity glass.
As shown in Figure 9, the dual-glass fibers can be made according to the method of the present invention using a textile busbing such as bushing 80 and a mechanical 5 or pneumatic pulling force. First and second molten glasses are supplied to the textile bushing where the second glass has a viscosity lower than that of the first glass by a factor within the range of from about 5 to about 1000, and preferably about 50 to about 500. The first and second glasses are drawn from the bushing as molten dual-glass streams, which are maintained at a II,...~J~,.a~UI~; sufficient to enable the second glass to flow around the first 10 glass. The dual-glass stream is cooled to make dual-glass fibers 82. The fibers can be passed over size applicator 84 and gathered into strand 86 before being wound as package 88 on collet 90. These fibers can be used for any ,~ """""L or filler purpose.
The method of the invention is not necessarily limited to the use of just two glasses of different viscosities. For example, first, second and third molten glasses can be 15 supplied to a rotating spinner having an orificed peripheral wall. The first, second and third glasses can be centrifuged through the orifices as a molten tri-glass stream, and the tri-glass stream can be maintained at a i . ~ suffcient to enable one of the lower viscosity glasses to flow around at least one of the other glasses. Upon cooling of the tri-glass stream, a tri-glass fiber will be formed in a manner similar to that of the dual-glass fiber.
The use of two glasses having different surface tensions can also be used to cause the second glass to flow around the first glass. The driving force is the difference between the surface tension of the two glasses. A difference greater than about 20 dynes/cm should be effective to cause one glass to flow around another, assuming the glasses have the same viscosity and assuming the process is carried out under conditions allowing sufficient 25 heat for~sufficient duration for the one glass to flow around the other. The fiber forming conditions may enable the flow around effect with even smaller differences in surface tension, or may require greater differences. Surface tension can be measured by a dipping cylinder method, based on a calculation of the force required to pull a small platinum cylinder of known diameter and wall thickness from the surface of molten glass, as described 30 in "Mt~difir~tion of the Dipping Cylinder Method of Measuring Surface Tension", Ralph L.
Tiede, Ir~7e A~nerican Cerantic Socie~ Bulletin, Vol. 51, No. 6, June, 1972.

3~
WO 95~29880 ~ J.,,3,G 1099 lt will be evident from the foregoing that various ...~ can be mad~
to this invention. Suc4 however, are considered as being v.~ithin the scope of the invention.
INDIJSTRIAr. AP~LICARrr.rTY
This invention will be found to be useful in the r ' C of glass fibers for 5 use in insulation products.

Claims

1. A method for making dual-glass fibers (48) comprising supplying first and second molten glasses (A,B) to a rotating spinner (32) having an orificed peripheral wall (36), where the first glass (A) at the temperature of the peripheral wall (36) has a viscosity higher than that of the second glass (B), centrifuging the first and second glasses (A,B) through the orifices (62) as molten dual glass streams, maintaining the dual glass streams at a temperature sufficient to enable the second glass (B) to flow around the first glass (A), and cooling the dual-glass streams to make dual-glass fibers (48).

2. A method according to claim 1, wherein the rotating spinner (32) has a plurality of internal baffles (58) defining a series of compartments (60) positioned at the peripheral wall (36) and orifices (62) in the peripheral wall each having a width greater than the width of the baffles and wherein the first and second glasses (A,B) are directed into alternate compartments so that adjacent compartments contain different glasses, thereby enabling a flow of both the first and second glasses through the orifices (62), the orifices being positioned offset from the centerline of the baffles (58) with the smaller ends of the orifices in communication with the compartments containing the lower viscosity second glass (B).

3. A method according to claim 1 or claim 2, wherein the viscosity of the first glass (A) at the temperature of the peripheral wall is higher than that of the second glass (B) by a factor of 5 to 1000.

4. A method for making dual-glass fibers (48) comprising supplying first and second molten glasses (A,B) to a rotating spinner (32) having an orificed peripheral wall (36), where the softening point of the second glass is lower than the softening point of the first glass by at least 50°C, centrifuging the first and second glasses through the orifices (62) as molten dual-glass streams, maintaining the dual-glass streams at a temperature sufficient to enable the second glass (B) to flow around the first glass (A), and cooling the dual-glass stream to make dual-glass fibers (48).

5. A method according to any one of claims 1 to 4, wherein the viscosity of the first glass (A) at the temperature of the peripheral wall is higher than that of the second glass (B) by a factor of 50 to 500.

6. A method for making dual-glass fibers (82) comprising supplying first and second molten glasses (A,B) to a textile bushing (80), where the first glass (A) at the temperature of the bushing has a viscosity higher than that of the second glass (B) by a factor of 50 to 500, drawing the first and second glasses from the bushing as molten dual glass streams, maintaining the dual glass streams at a temperature sufficient to enable the second glass (B) to flow around the first glass (A) and cooling the dual-glass streams to make dual-glass fibers (82).

7. A method according to any one of claims 1 to 3, 5 and 6, wherein the softening point of the second glass (B) is lower than the softening point of the first glass (A) by at least 50°C.

8. A method according to any one of claims 1 to 7, wherein the softening point of the second glass (B) is lower than the softening point of the first glass (A) by at least 100°C.

9. A method according to any one of claims 1 to 8, wherein the second glass (B) flows around the first glass (A) to the extent that at least 270° of the circumference of the dual-glass fiber is constituted by the second glass.

10. A method according to claim 9, wherein the second glass (B) flows all the way around the first glass (A) so that the second glass (B) encloses the first glass (A) to form a cladding.

11. A method according to any one of claims 1 to 5 and 7 to 10, wherein the dual-glass fibers (48) are collected as a wool pack (20) and the wool pack is subjected to a temperature greater than the softening point of the second glass (B) but less than the softening point of the first glass (A).

12. A method for making dual-glass fibers (48) comprising supplying first and second molten glasses (A,B) to a rotating spinner (32) having an orificed peripheral wall (36) where the first glass (A) at the temperature of the peripheral wall has a surface tension lower than that of the second glass (B), centrifuging the first and second glasses (A,B) through the orifices (62) as molten dual-glass streams, maintaining the dual glass streams at a temperature sufficient to enable the second glass (B) to flow around the first glass (A), and cooling the dual-glass streams to make dual-glass fibers (48).
.13. A method for making tri-glass fibers comprising supplying first, second and third molten glasses to a rotating spinner having an orificed peripheral wall, where the first glass at the temperature of the peripheral wall has a viscosity higher than that of the second glass, centrifuging the first, second and third glasses through the orifices as molten tri-glass streams, maintaining the tri-glass streams at a temperature sufficient to enable the second glass to flow around at least the first glass, and cooling the tri-glass stream to make tri-glass fibers.