Abstract:
A spinner adapted to produce a dual glass fibre component and a single straight fibreglass insulation product; said spinner including a plurality of horizontal baffles adjacent to a spinner peripheral wall; said baffles separating two molten glasses of differing coefficients of thermal expansion and also separating a single molten glass which creates a straight glass fibre and providing mechanical strength and resistance to reduce deformation of said spinner.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The general field of this invention is a method and apparatus for a simultaneous, rotary process, high throughput capacity manufacturing of single-component and dual-component fibres from thermoplastic materials, and thermal and acoustical insulation products formed from a certain mixture of such fibres. More particularly, this invention relates to a method and apparatus for the combined centrifuging single-component, straight and dual-component, curly glass fibres, and products formed from these straight and curly glass wool type fibres.  
           [0002]    A typical glass fibre thermal or acoustical insulation product is made of rather short, single glass and basically straight glass fibres. A common method of manufacturing these glass wool type fibres is a rotary fiberizing process, where a single molten glass composition is forced by a high speed rotation through the orifices in the peripheral wall of a centrifuge, usually referred to as a spinner, and is further subjected to the combined action of a high temperature flame and low temperature/high velocity compressed air blasts.  
           [0003]    It has been recognized that virtually straight fibre geometry, offered by a conventional rotary fiberizing process, certainly is not the best one for forming some high performance thermal and acoustical insulation product. It became apparent that adding an element of curvature to the basic fibre shape should, in principle, offer some highly desired and sought for features and product attributes, including a substantially higher allowable product compression ratio, therefor offering quite substantial cost savings in product storage, transportation (distribution) and also in packaging materials. Other advantages are a better volume filling ability, lower dust level, less itch, and potential for much lower organic binder level required to assure product integrity. This is due to the improved curly fibre self-cohesion, interlocking and intertwining properties. The result is lower binder cost, and reduced organic emissions. It is also reasonable to expect a slightly higher product thermal resistance, i.e., a possibility of increased earnings due to consequential density reductions.  
           [0004]    The very first attempts to make curly glass fibre were based on a differential cooling, quenching or the like of a textile-type single glass composition fibre (U.S. Pat. No. 2,927,621). Both the fibre and process were not suitable for insulation products. Tiede in U.S. Pat. No. 3,073,005 discloses a non-rotary fiberizing process for making bi-component curly glass fibre. Two glasses with differing thermal expansion coefficients are put into side by side contact. This bi-component curly fibre was not meant to be used for insulation products. Some other patents disclosing methods of making curly or kinky glas fibres are disclosed in U.S. Pat. Nos. 3,236,616 and 4,145,199, but sill these methods would not be that practical for making an insulation product.  
           [0005]    It is generally accepted that a non-rotary fibre-forming process cannot effectively compete with the rotary one for the economic manufacture of a typical glass fibre-insulating product. The issues are a substantially lower throughput capacity and too coarse fibre to make a good glass wool. As a consequence, some methods of imparting kink by pulling fibre from a textile bushing and mechanically crimping it by passing fibre, while still in a hot state, through a series of opposed intermeshing gears are not a viable option.  
           [0006]    In the early 1960&#39;s, Stalego (U.S. Pat. No. 2,998,620) disclosed a rotary method for making a bi-component curly glass fibre, where two glass compositions differ in their thermal expansion coefficients, however, there is no mention of using these curly fibres for insulation products. In the mid 1990&#39;s, Owens-Corning obtained the first patents for protecting a newly developed technology for manufacturing bi-component curly glass fibre by a rotary fiberizing technique, with the clear objective of using this non-straight or irregular dual-glass fibre for thermal and acoustical insulation products. The scope of patenting is wide, including both processes, apparatus and product. By 2002, other major or global manufacturers of fibre glass insulation, namely Isover Saint Gobain and Johns-Manville, were granted patents for manufacturing dual-glass curly wool type fibres.  
           [0007]    A typical approach to manufacture curly bi-component glass fibre by rotary fiberizing, is to use two glass formulations with widely different coefficients of thermal expansion and feed these two glasses as separate glass streams, in a radially displaced configuration, into some sort of integrated glass distributor inside a spinner assembly and force first and second glasses into alternate vertical compartments circumferentially spaced around the interior of the spinner peripheral wall. Finally, one centrifuges these two glasses through orifices drilled in the spinner peripheral wall along the adjacent compartments dividing line in such a way that the two glasses join each other in a side-to-side contact before emerging from a single orifice as a bi-component fibre.  
           [0008]    Some spinner designs for making dual-glass curly fibres are disclosed in U.S. Pat. Nos. 5,468,275; 5,474,590; 5,595,766; and 5,987,928. Clearly, a throughput capacity offered by these dual-glass spinners cannot be reasonably high, making the whole operation rather costly.  
           [0009]    A binderless, plastic sleeve encapsulated, extremely high compression ratio insulation product, entirely formed from rotary process which made dual-glass curly fibre, became commercially available in the early 1990&#39;s. Since the product had no binder, an irregularly-shaped glass fibre, after being collected at approximately 600 degrees Celsius temperature on opposed, downwardly converging collection conveyors, were passed through a heat-setting oven to shape the individual fibres into a cohesive insulation product at temperatures from approximately 400 to 600 degrees Celsius.  
           [0010]    There are numerous patents disclosing both the method of manufacturing (process) and dual-glass fibre insulation products, for example, the following U.S. Pat. Nos.: 5,431,992; 5,536,550; 5,618,327; 5,629,089; 5,672,429; and 5,723,216. Insulation products comprised of irregularly-shaped glass fibres exhibit a substantially uniform volume filling nature, and provide improved thickness recovery and thermal insulating abilities.  
           [0011]    Irregularly-shaped dual-glass fibres for pourable or blowable loose-fill insulation products (blowing wool) are disclosed in U.S. Pat. Nos. 5,624,742; 5,683,810; and 5,786,082. Some benefits include improved coverage (lower product densities), higher thermal efficiency and less dust upon blowing or pouring. A loose-fill insulation product can entirely be made of irregularly-shaped dual-glass fibres, or be some blend of single-glass and dual-glass fibres.  
           [0012]    A need exists for an improved glass wool insulating material. Of particular importance is a substantially higher product thickness recovery (allowable compression ratio) and reduced thermal conductivity. The product should be made in a cost effective way, meaning production rates closely matching the existing ones, and the overall process changes kept to the absolute minimum. It is believed that insulation material made as some mixture or blend of single-glass straight, and dual-glass curly fibres, simultaneously fiberized by the same spinner, mixed right during the fibre-forming stage, bonded by a 20 percent to 50 percent reduced amount of standard, phenol-formaldehyde binder, and further processed in a standard or conventional way, should in principle meet expectations. No use of an encapsulating plastic sleeve should be necessary. The insulation product should be suitable for all typical applications. Skin irritation and material dustiness, factors particularly important to product end users or installers, should be reduced.  
           [0013]    U.S. Pat. No. 5,968,645 discloses an insulation product made as a mixture of single-component and multi-component inorganic fibres, where the material cohesion and shape is ensured, at least partially, by using some sort of organic or inorganic binder. Such product exhibits a remarkable recovery of thickness after decompression. Being compressed to {fraction (1/20)}th of its initial thickness for 72 hours, the product bounces back to 110 percent to 120 percent of its nominal thickness, the thickness required during product installation after unpacking. This 20:1 compression ratio favourably compares with a typical 10:1, allowable ratio for a standard, single-component light density fibreglass insulation products. For a given product density, its thermal insulation performance is slightly better as well. Unlike a binderless, plastic sleeve enclosed or encapsulated insulating material, consisting only of bi-component irregularly-shaped glass fibres, this product lends itself to thermal or acoustical insulation of vertical walls in buildings.  
           [0014]    Canadian Patent Application CA 2202208 describes a method and device for producing mineral wool products being in principle a mixture of four distinct types of glass fibres, namely a straight single-glass fibres of glasses A and B, curly dual-glass fibre where there is a mutual side-to-side contact along the entire fibre length, and a composite or compound curly fibre where two single-glass fibres are joined at separate points only along the compound fibre length, resulting in a twisted or curled rope ladder fibre structure. The spinner design is based on having separate and alternate vertical glass compartments and two chambers for glasses A and B along the spinner circumferential wall. By adding single-glass orifices to a dual-glass spinner structure, a substantial increase in productivity can be achieved. This modified spinner follows the basic design explained in U.S. Pat. No. 5,987,928.  
           [0015]    Thermal and mechanical properties of such insulation product can be controlled and optimized. There is a wide field of possible combinations and/or mixtures of pure mono-composition straight fibres, composite curly fibres and bi-component irregularly-shaped fibres to choose from. Softer glass will work as a binder, at least in certain cases. There is no direct mention of using standard organic binder for this mixed fibre insulation product made by a rotary fiberizing technique.  
           [0016]    European Patent Application EPO 994079 discloses a method and apparatus for manufacturing an insulation product consisting of single-glass straight and dual-glass curly fibres. It discloses a dual-glass spinner with separate vertical glass compartments for glasses A and B, arranged in an alternate fashion along the inner side of the spinner circumferential wall, is additionally equipped with a multiplicity of single-glass bores drilled in the spinner peripheral wall in the central area of any vertical glass compartment. A substantial spinner throughput capacity increase will result. The thermal and/or acoustical insulation product is a mixture of straight single-glass fibres of glass A, glass B and dual-glass curly fibres. It is claimed to be a binderless product. Thermal, and particularly mechanical properties of the insulation product are expected to be substantially improved.  
         SUMMARY OF INVENTION  
         [0017]    The object of the present invention is to provide an integrated or hybrid dual-glass/single-glass spinner and a method to produce a mixed straight/curly fibre insulation product with improved thermal and mechanical properties, particularly with respect to the allowable compression ratio or thickness recovery.  
           [0018]    The essence of the invention is a multiple, horizontal and alternate layering of glasses A and B along the height of inner surface of the spinner peripheral wall, combined with extruding these glasses through a unique geometry of bores drilled in the spinner peripheral wall in such a way as to result in a high density exit hole pattern with the required distribution of single-glass and dual-glass orifices on the peripheral wall surface.  
           [0019]    There are two basic approaches to implement this process concept. One could use a specialized spinner casting, where the separate, vertically displaced fiberizing zones for making either a dual-glass or single-glass fibre are already built in into the spinner geometry or structure. Many particular configurations are possible. Some examples will be given below. The second approach is to use the present invention dual-glass spinner casting, and only vary the orifice configurations drilled in the spinner peripheral wall. Again, a variety of possibilities or options exist.  
           [0020]    In order to produce the straight/curly glass fibre insulation product using the spinner of the present invention, modifications are nominal. For example, the baffles on the lower periphery of the spinner can be eliminated and glass A can pass directly outwardly through a series of radially extending channels from orifices on the inside of the peripheral wall of the spinner. With regard to the dual glass fibre output these continue to be passed through the upper part of the peripheral wall through channels for glass A and glass B whereupon inner orifices in the peripheral wall extend into numerous channels connected to orifices on the outer peripheral wall where the two glasses meet to form a curly fibre.  
           [0021]    In a second configuration, dual glass fibre are created in the upper peripheral wall of the spinner and straight glass fibres are created there below. Another plurality of dual glass fibres are created with straight glass fibres below that, and finally, dual-glass fibres are created at the bottom of the spinner.  
           [0022]    In a third configuration, dual-glass fibres A and B are created in the upper portion of the spinner. Straight glass fibres A are created there below, followed there below by dual-glass fibres followed there below by glass B straight fibres and finally at the bottom of the spinner dual glass fibres A and B are again formed. It is to be understood that such configurations can be varied with little changes other than the positioning of the horizontal baffles and the position of the inner orifices in the inner portion of the peripheral wall.  
           [0023]    The inventors have produced a spinner for use in producing a bi-component fibre glass insulation product, including an interior slinger cup; said slinger cup being circumferentially secured in a fixed manner to a bottom of said spinner inwardly of said spinner periphery; said slinger cup having a bottom portion extending inwardly and being adapted to receive a first molten glass A which, through centrifugal movement, forces said glass A in an outward direction; said slinger cup further comprising a vertically extending circumferential wall and an upper horizontally extending flange adapted to receive a second stream of molten glass B with a different coefficient of thermal expansion than said first glass A; said glass B being forced outwardly through centrifugal movement; said spinner having a plurality of vertical baffles creating vertical chambers inwardly of a spinner peripheral wall; said slinger cup having a plurality of openings on an outwardly facing wall, such that glass A emerges into first of said vertical chambers and glass B emerges above said slinger cup horizontal flange into second alternative vertical chambers; said chambers being greater than 2 in number and lesser than or equal to 32 in number; said spinner further comprising a plurality of horizontal baffles disposed between said vertical chambers such that glass A and glass B enter separately from said vertical chambers between said baffles; said baffles creating alternate vertically disposed horizontal chambers; said spinner on its inner periphery wall having a plurality of apertures adapted to receive glass A from one horizontal chamber and glass B from an alternative upper or lower horizontal chamber; said apertures opening into either glass A or glass B channels; whereupon in operation, each one of glass A channels and each one of glass B channels connects to a single common orifice through the spinner exterior peripheral wall; said spinner wall having a large number of orderly placed, said single common orifices; thereby creating a bi-component primary glass fibre, which after further attenuation by a combined action of rotating spinner, external main burner and compressed air blower, create curly, irregularly-shaped glass fibres, due to glass A and B having different coefficients of thermal expansion; said spinner further including portions of the inner peripheral wall containing a number of orifices or inlet holes accepting only glass A or glass B; said orifices communicating directly with the outer peripheral wall of said spinner through radial channels to outlets thereby producing through said orifices, channels and outlets straight glass fibres which, in operation, once fiberized, will mix with said curly dual glass fibres to form a mixed straight and curly fibre wool pack there below for further processing. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]    The invention will be more clearly described in conjunction with the accompanying drawings wherein:  
         [0025]    [0025]FIG. 1A is a transverse cross section of a spinner used in the present invention;  
         [0026]    [0026]FIG. 1B is a top view of the spinner showing one half of the total circumference;  
         [0027]    [0027]FIG. 2 is an expanded view of a transverse cross section of one side of the spinner;  
         [0028]    [0028]FIG. 3 is a transverse cross section of approximately one half of the spinner with other components;  
         [0029]    [0029]FIG. 4 is similar to FIG. 2 with different components shown;  
         [0030]    [0030]FIGS. 5 and 6 are expanded views of the transverse cross section of the spinner&#39;s interior and exterior peripheral walls;  
         [0031]    [0031]FIG. 7 is a perspective view from the inside of the spinner peripheral wall showing a hole drilling pattern;  
         [0032]    [0032]FIGS. 8A, 8B and  8 C show various sections the channels through which the glass passes at various angles;  
         [0033]    [0033]FIGS. 9A, 9B and  9 C are similar types of drawings as FIG. 8 showing the channels and hole drilling patterns;  
         [0034]    FIGS.  10  to  12  show different configurations of the peripheral wall of the spinner; and  
         [0035]    FIGS.  13  to  20  show different hole drilling patterns.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0036]    [0036]FIG. 1A is a transverse cross section of a spinner used to produce glass fibres through centrifugal force, heat, and aerodynamic pressure. The spinner  1  is basically a round dish having a peripheral circumference with holes drilled therein. The spinner has an upper top side flange but otherwise has an open top which permits molten glass to enter into the spinner and be forced to the circumference. In FIG. 1A there is mounted within the spinner a slinger cup  2 . The slinger cup is fixedly mounted within the spinner. It has a peripheral wall or rim  3 , a slinger cup middle flange  4 , and a middle flange upturned member  4 A. The slinger cup also has a top flange  5 . The purpose of the slinger cup is to separate two molten glasses A and B. Molten glass B is directed into the slinger cup on top of the middle flange  4  whereas molten glass A falls inside the spinner  1  inwardly of the slinger cup middle flange upturned member  4 A.  
         [0037]    On examination of FIG. 2, one views that a molten stream of glass B descends upon the slinger cup middle flange  4  while glass A falls to the bottom of slinger cup  2  and exits through glass A slots  6 . Glass B, on the other hand, exits through glass B slots  7 .  
         [0038]    As can be seen in FIG. 1B, which is a cross section A-A of FIG. 1A, the periphery of the spinner on the exterior side of the slinger cup  2  is divided into a number of chambers separated from one another by vertical baffles  9 . In a preferred embodiment, eight circumferential compartments are used, four for glass A and four for glass B. Hence, around the circumference of the slinger cup, glass B, directed through holes  7 , is directed to vertical chambers  8   b  and glass A is directed to alternate vertical chambers  8   a . From chambers  8   a  and  8   b , the molten glass is permitted to pass towards the periphery of spinner  1  by means of slots  12   a  for glass A, and  12   b  for glass B. Only those chambers marked as  8   a  permit the passage of glass A glass towards the periphery and only those chambers marked as  8   b , i.e. the alternate circumferential chambers, permit glass B to pass towards the periphery. Before proceeding further, it is noteworthy in FIG. 4 that the spinner bottom is marked as  11  and the spinner top as  10 . Slots  12   a  and  12   b , which are shown in FIG. 5 and which are directed radially outwardly, are separated by ring-shaped internal horizontal flanges. Thus, glass A has access only to those slots  12   a  and glass B has access only to those slots  12   b . Within the peripheral wall, however, glass A slots pass towards circumferential cavities  14   a  and glass B passes through to circumferential cavities  14   b.    
         [0039]    Before proceeding with the essence of the invention, i.e. the peripheral hole formation, one must understand in FIG. 3 the basic components of the spinner mechanism. The spinner  1  turns at approximately 2400 r.p.m. In order to keep the molten glass at a sufficiently high temperature, there is an inner burner  20  and an inner burner deflector ring  21 . Spinner  1  is attached to a mounting hub  26  having a mounting cap  27 . Mounting hub  26  has a number of peripheral grooves or slots  22  and the spinner  1  has a bottom radiation shield  25  to contain the heat upwards.  
         [0040]    Separating the slotted bottom radiation shield  25  from the spinner  1  is a slotted spacer ring  23 . Spinner  1  is also equipped with a number of spinner elevation adjustment spacers for adjusting the spinner in relation to the mounting hub  26 . Between the slotted bottom radiation shield  25  and the spinner bottom  11  are a number of bottom radiation shield exit slots  28 . Mounting cap  27  mounts the spinner  1  to the mounting hub  26  by means of bolts.  
         [0041]    In FIG. 4, the spinner  1  has an inner peripheral wall  13  and an outer peripheral wall  16 . As previously mentioned, glasses A and B enter the peripheral wall through slots  12   a  and  12   b , which are separated by horizontal flanges  15 . Within the circumferential wall are glass A circumferential rings  14   a  and glass B circumferential rings  14   b . Thus, as shown more clearly in FIG. 5, glass B and glass A are alternately permitted to enter through the circumferential wall bounded by inner peripheral wall  13  and outer peripheral wall  16 .  
         [0042]    [0042]FIG. 6 shows more closely the inner peripheral wall  13  and the outer peripheral wall  16  of the spinner. Slots  12   a  and  12   b  enter through the inner peripheral wall  13  and then become ring-shaped cavities for glass A and glass B shown as  14   a  and  14   b , respectively. Separating these horizontally radially outwardly projecting cavities are horizontal flanges  15 .  
         [0043]    As glass A progresses outwardly through ring-shaped cavity  14   a , it enters an inlet hole  17  on the inside of the outer peripheral spinner wall  16 . Similarly, as glass B progresses outwardly through ring-shaped cavitity  14   b , it also enters an inlet hole  17 . From common inlet holes  17 , in a preferred embodiment, a plurality of channels emerge, some lead outwards radially and some are angularly slanted and lead outwards.  
         [0044]    In a preferred embodiment there are four such channels generally labeled, as is shown in FIGS. 6, 7,  8  and  9  as  18   a ,  18   b ,  18   c  and  18   d . The outer side of peripheral wall  16  is equipped with a plurality of highly structured patterned holes  19   a  for outlet hole type A and  19   b  for outlet hole type B. Through this innovative configuration of slanted and radially outward channels, both glasses A and glasses B join in each one of holes  19   a  and  19   b . Thus, the two glasses emerge from outer peripheral wall  16  through orifices  19   a  and  19   b , together side by side. Because of their different coefficients of thermal expansion, the two glasses shrink upon cooling to a different degree thus forming curly or irregularly-shaped fibres which are then directed downwardly and collected on a foraminous belt conveyor, equipped with bottom suction.  
         [0045]    Drawings  8 A,  8 B and  8 C and  9 A,  9 B and  9 C show various configurations through different views, wherein glass A and glass B are lead through inlet holes  17  and move in the unique configuration of slanted and radially drilled channels into outlet holes  19   a  and  19   b.    
         [0046]    The essence of the invention is to create a dual-glass fibre of twisted or curly nature along with straight fibres in high capacity output through the manipulation of vertical and horizontal flanges and through the use of a unique geometry or configuration for drilling fiberizing orifices in the spinner peripheral wall.  
         [0047]    [0047]FIG. 10 is a modified version of the dual-glass spinner which will produce both straight and curly glass fibres. As noticed, glass B still descends upon the upper portion of the slinger cup and glass A is directed towards the lower portion of the slinger cup. These through-spaced orifices move through centrifugal force glass B into glass B vertical baffle chambers and glass A into glass A vertical baffle chambers. Glass B, however, is not permitted to enter the lower portion of the peripheral wall, but simply the upper portion along with glass A thereby creating a dual glass fibre. Glass A, on the other hand, can continue directly outward in the lower portion of the spinner through a plurality of orifices radially and thus, as shown in FIG. 10, move outwardly through orifices  28  through  38 , thereby producing a straight fibre outwardly of the outer peripheral wall of the spinner.  
         [0048]    In FIG. 11, glass A is permitted to emerge from its vertical chambers, generally four in number, outwardly either, through channels A, which direct it through both slanted and radially aligned channels to outer orifices, or directly through the portions marked A through straight radial channels thereby producing glass A straight fibres. These portions have been marked by having them cross-hatched in the spinner area.  
         [0049]    Glass B is permitted only to emerge through orifices on the inner walls between the horizontal baffles outwardly to the inner peripheral wall and then is directed to a number of slanted or radial channels to come together in a common outer peripheral wall orifice having both glasses A and B joined and through the difference in their coefficients of thermal expansion, produce a curly fibre.  
         [0050]    In a third embodiment of the present invention shown in FIG. 12, glasses A and B are permitted, through orifices and channels, to both produce two different straight fibres of glasses A and B and curly fibres at three different positions on the spinner outer peripheral wall.  
         [0051]    As an aside, one may also use different (actually somewhat simplified) spinner casting and mix fibre in horizontal layers or zones.  
         [0052]    A simplified casting is lighter, probably easier to heat up and less expensive, using lesser amount of highly priced cobalt-based or nickel-based super alloy.  
         [0053]    It is possible to make a mixture of single-glass and dual-glass fibres by using a dual-glass spinner in its modified (simplified form already described, or by utilizing a full dual-glass spinner casting, only with the adjusted hole drilling pattern to suit one&#39;s needs. A full dual-glass spinner casting gives a freedom of choice as to the single-glass to the dual-glass mass ratio after tne spinner is cast with different drilling.  
         [0054]    Drawings beginning with FIG. 13, as a general introduction, show the top sketch always gives an entry hole pattern, section A-A in FIG. 13. The bottom sketch shows the appearance of the resulting exit holes, section B-B of FIG. 13. The type of glass for the entry, and fibre composition at the exit is clearly marked (A, B, A+B).  
         [0055]    FIGS.  14  to  20  show some of the possible hole drilling operations.  
         [0056]    [0056]FIG. 14 shows A+B fibre only, that is to say, four channels per single entry hole which is a typical dual-glass fibre hole drilling pattern. FIG. 15 shows (A+B), A and B fibre; (A+B):(A,B)=1:1 mass Ratio of Dual-component (A+B) glass fibre, to single-component glass fibre made both of glasses A and B. Different fibre types are formed in horizontal layers (1-Dimensional mixing). There are three channels per entry hole. Horizontal and vertical channels of different diameters deliver the same amount of molten glass per unit of time, re a 1:1 mass ratio dual-glass to single-glass (combined glass A and glass B fibres) in the insulation product. By varying mass flow rate per channel, also other dual-glass to single-glass mass ratios can be achieved in a fibre mixture.  
         [0057]    [0057]FIG. 16 shows (A+B) and A Fibre; (A+B):A=1:1 Ratio Only glass A will be used to form single-component glass fibre. There will be no single-component glass B fibre in the product. Four channels for entry holes supply glass A, and two channels for entry holes supplying glass B. Channel diameter is adjusted to have the same mass flow rate, and therefore a 1:1 dual-glass (A+B) to single-glass A mass ratio in the insulation product.  
         [0058]    A practical way of achieving a high difference in thermal expansion coefficients of glasses A and B, needed for making curly fibre this way, and still maintaining other glass properties at the desired level is to use two alternate glass compositions, namely high soda-low boron versus high boron-low soda glass composition. Boron is the most expensive component of a glass batch. Soda is the second most expensive component, its price being more or less half of boron. Other batch components are relatively inexpensive, for example, nepheline syenite costs about $33.00 Cdn per ton. Basically, it is boron and soda interaction which make a batch price difference.  
         [0059]    [0059]FIG. 17 shows a hole pattern for (A+B) fibre and A fibre, i.e. (A+B):A=3:1 Ratio. There is a large percentage (75% by mass) of bi-component glass fibre in (A+B) and A fibre mixture. Four channels per hole receive glass A, one channel per hole receives glass B. All channels, in principle, are not the same diameter. Glass A fibre is sandwiched between horizontal layers of (A+B) fibres, that is to say, 1-D mixing.  
         [0060]    [0060]FIG. 18 shows a hole pattern for (A+B) fibre and B Fibre; i.e. (A+B):B=1:1 Ratio. There are two channels per glass A entry hole and four channels per glass B entry hole.  
         [0061]    Not all channels are the same diameter if (A+B):B mass ratio must be 1:1. There is horizontal layering of fibre types.  
         [0062]    [0062]FIG. 19 shows a hole configuration for (A+B) fibre and A and B Fibre; i.e. (A+B):(A,B)=1:1. There is a 2-D Mixing Entry hole for glass A equipped alternately with two or four channels. Similarly, entry holes for glass B communicate alternately with two or four channels. In principle, channels are not of the same diameter. For a given row, neighbouring fibres are always of opposite types, i.e., dual-glass and single-glass fibres. There is a two-dimensional fibre mixing pattern; not only row to row (vertical) but also within a given row (horizontal). Neighbouring rows have single-glass fibres made from different glasses. Dual-glass fibre to the combined glass A and glass B single-glass fibre mass ratio in a fibre mix is basically 1:1, i.e., with the same pull rate per exit hole.  
         [0063]    [0063]FIG. 20 shows a hole configuration for (A+B) fibre and A fibre; (A+B):A=1:1. That is a 2-D Mixing Entry hole for glass A is connected with four channels. An entry hole for glass B also has four channels. The number of glass B entry holes per row is half of that for glass A. If one is having the same mass flow rate per exit hole, the diameter of inclined channels starting at the entry point for glass A and reaching the zone internally prescribed for glass B, varies, depending whether this channel merges with the channel starting at glass B entry point or not. For the same mass flow rate per exit hole the mass ratio of dual-glass (A+B) fibre to single-glass, glass A only, fibre is 1:1. Fibres are well intermingled since the mixing process is 2-D (two-dimensional). In a given row, the neighbouring fibres are alternately of dual-glass and single-glass types (glass A).