Composite fiber and method for producing same

Abstract

A method of making the composite fibers can include combining calcium hydroxide slake and a carbon dioxide containing gas with an aqueous slurry containing the fibers, the addition of the slake being controlled to maintain the conductivity below saturation, thereby producing composite fibers with improved bulk and stiffness properties when used as a filler in papermaking.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS Benefit of priority to U.S. Provisional Patent Application No. 63 / 326,240, filed March 31, 2022, is claimed herein, the disclosure of which is incorporated by reference in its entirety.

[0002] The present disclosure relates to composite fibers and methods for making composite fibers, and more specifically to mineralized nanocellulose comprising calcium carbonate, and methods for precipitating calcium carbonate for attachment to nanocellulose. [Background technology]

[0003] Various techniques for the precipitation of calcium carbonate are known in the art. Precipitated calcium carbonate (PCC) is used in various paper industries for fine papers such as copy paper, mechanical grade papers such as SC, containers, carton boards. Various forms of precipitated calcium carbonate and cellulose-calcium composites have been used in the paper industry as filler materials. Traditional cellulose-calcium carbonate materials incorporate calcium carbonate in such a way that the essential fibrous nature of the cellulose component is maintained. The fibrous nature of the composite has been generally recognized in the art as necessary to better incorporate the composite into the fibrous matrix of the paper.

[0004] U.S. Patent No. 9,150,738 teaches a reverse carbonation process for forming various crystal morphologies of precipitated calcium carbonate. The reverse carbonate process has been found to be particularly useful for targeting the scalenohedral morphology. The '738 patent teaches that an important feature is the initial addition of carbon dioxide to the reaction vessel until a controlled pH of 5-7 is obtained. After such pH control, calcium hydroxide slurry is added at a rate such that the target conductivity is achieved, thereby precipitating calcium carbonate.

[0005] WO 97 / 01670 teaches porous aggregates of calcium carbonate particles precipitated on the surface of cellulose fibers. EP 0930345 and EP 0935020 teach similar fillers, but the calcium carbonate is not precipitated on the surface of the fibers, but rather mixed with them. US Patent No. 10,683,616 teaches a method of producing a composite material in which microfibrillated cellulose is introduced during the calcium carbonate precipitation process after a portion of the calcium hydroxide has reacted with carbon dioxide.

[0006] Surface mineralized fibers are also known, as disclosed in WO2021 / 252572. Such fibers are generally produced using sodium carbonate for carbonation and have low fiber pick-up. Summary of the Invention

[0007] There remains a need in the art for improved filler materials. The fibers produced according to the methods of the present disclosure have a significant improvement in mineral attachment. For various applications, minerals can be beneficially provided as long chains of scalenohedral PCC attached to nanocellulose fibers for improved properties.

[0008] Fillers according to the present disclosure may include bicomponent fibers, each bicomponent fiber comprising a mineral attached to the fiber, the mineral being at least about 90% by weight based on the total weight of the bicomponent fiber, the uncoated fibers having an average length of less than 300 μm, and the bicomponent fibers having a Horiba d of at least 10 μm. 90 For example, the fiber can be nanocellulose and the mineral can be calcium carbonate.

[0009] A method of making composite fibers according to the present disclosure includes preparing calcium hydroxide slake by diluting lime in water, combining the aqueous fiber slurry with dilution water in a reactor, and reacting the calcium hydroxide slake and CO. 2A contained gas is added to a reactor containing an aqueous fiber slurry mixed with dilution water to precipitate calcium carbonate onto the fibers, and CO is added to the mixture after the calcium hydroxide slake addition is started until the pH reaches 7.0. 2 and continuing the flow of the containing gas. The calcium hydroxide slake is added at a rate to maintain a target conductivity that is 50%-80% of saturation, the target conductivity being maintained until addition of the calcium hydroxide slake is completed, the fiber slurry includes fibers having a length of 300 μm or less, and the fiber slurry includes fibers in an amount such that the fiber content in the composite fiber is 10% by weight or less based on the total weight of the composite fiber. The calcium hydroxide slake is added at a rate to maintain a target conductivity that is 50%-80% of saturation, the target conductivity being maintained until addition of the calcium hydroxide slake is completed, 2 They may be added simultaneously before or after the start of the addition. [Brief description of the drawings]

[0010] [Figure 1A-1B] 1 is a scanning electron microscopy (SEM) image of a composite fiber according to the present disclosure. [Diagram 2] 1 is a graph showing pH, conductivity, temperature, and gas flow rate as a function of time for a process according to the present disclosure. [Figure 3A-3B] 1 is a SEM image of a conventional fiber-containing precipitated calcium carbonate (PCC). [Figure 4A] FIG. 1 is a graph showing the comparative bulk properties of handsheets made with a composite fiber filler according to the present disclosure, precipitated calcium carbonate without nanocellulose, or PCC with nanocellulose added to the furnish. [Figure 4B] FIG. 1 is a graph showing the comparative break length of handsheets made with a composite fiber filler according to the present disclosure, a precipitated calcium carbonate without nanocellulose, and a PCC with nanocellulose added to the furnish. [Figure 4C] FIG. 1 is a graph showing the comparative flex resistance index of handsheets made with a composite fiber filler according to the present disclosure, a precipitated calcium carbonate without nanocellulose, or a PCC with nanocellulose added to the furnish. [Figure 5A-5B] 1 is a SEM image of a composite fiber according to the present disclosure. [Fig. 5C-5D] FIG. 1 is an SEM image of calcium carbonate precipitated using the inverse carbonation process with 50% saturation but no fibers present. [Figure 6] FIG. 13 is an SEM image of fiber-free precipitated calcium carbonate produced at 50% saturation with a starting carbonation temperature of 42° C. [Figure 7] 1 is an SEM image of a composite fiber according to the present disclosure produced using 50% saturation, with 0.5% by weight fiber and an onset carbonation temperature of 39° C. [Figure 8] 1 is an SEM image of a composite fiber according to the present disclosure produced using 50% saturation, with 0.5% by weight fiber and an onset carbonation temperature of 11° C. [Figure 9] 1 is an SEM image of a composite fiber according to the present disclosure produced using 50% saturation, with 0.5% by weight fiber and an onset carbonation temperature of 26.5° C. [Figure 10] 1 is an SEM image of a composite fiber produced using 70% saturation with 0.5 wt % fiber and an onset carbonation temperature of 26.5° C. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The composite fibers and methods of the present disclosure unexpectedly and advantageously provide improved bulk and strength properties when used as fillers in making paper products. Typically, it was expected that high strength fillers would densify paper sheets and adversely affect the stiffness of the sheets. Surprisingly, it was found that the composite fibers of the present disclosure can improve both bulk and strength resulting in improved stiffness. In addition, the methods of the present disclosure can advantageously provide a significant improvement in the percentage of attached minerals. Furthermore, the methods of the present disclosure can allow for control of mineral morphology, and can advantageously provide composite fibers in which all or substantially all of the minerals are present in a desired morphology, such as scalenohedral morphology.

[0012] For example, the composite fibers of the present disclosure may have long chains of scalenohedral minerals, such as scalenohedral calcium carbonate, attached to the fiber template, which may advantageously result in the composite fibers maintaining fiber-like qualities when used as a filler in papermaking.

[0013] The bicomponent fibers of the present disclosure, when used as fillers in papermaking, can provide high loft and stiffness, good natural water retention and drainage, and impart increased physical strength. The process of the present disclosure results in significantly greater surface coverage on the fibers, with all or substantially all of the precipitated minerals attached to the fibers.

[0014] Composite fibers according to the present disclosure include fibers and minerals attached thereto. For example, the minerals may be in the form of long chains that are attached to the fibers and surround the fibers, thereby coating the fibers, as shown in FIG. 1. The composite fibers have at least 90% by weight of the minerals based on the total weight of the fibers. For example, the composite fibers may have about 0.5% to about 10% by weight of the fibers based on the total weight of the composite fibers. There should be a sufficient amount of fibers to direct all or substantially all of the sediment of the minerals onto the fibers. It has been found that amounts of fibers less than 0.5% by weight result in excess unattached minerals. However, it has been found that amounts of fibers greater than 10% by weight negatively affect the ability of the minerals to grow into scalenohedral, instead resulting in rhomboidal or cubic morphology.

[0015] Bicomponent fibers according to the present disclosure advantageously exhibit fibrous properties when included as a filler. Bicomponent fibers according to the present disclosure have a Horiba d of at least about 10 μm, at least about 20 μm, at least about 25 μm, at least about 30 μm, at least about 40 μm, or at least about 50 μm. 90 has.

[0016] The fibers can be nanocellulose. Nanocellulose is a cellulose material having at least one dimension, such as a fibril particle diameter or width, on the order of nanometers, for example, 100 nm or less. The fibers have a length of 300 μm or less. For example, the fibers before coating with minerals can have a length of about 100 μm to about 300 μm. For example, the fibers can have a length of about 200 μm. Any nanostructured cellulose can be used as the fibers.

[0017] A method of forming a composite fiber according to the present disclosure includes forming an aqueous slurry containing the fibers. The amount of fibers in the aqueous slurry is selected such that the fibers are present in the composite fiber in an amount of from about 0.1% to about 10%, from about 0.25% to about 5%, from about 0.5% to about 8%, or from about 0.25% to about 1% by weight based on the total weight of the composite fiber. For example, the fibers can be present in an amount of about 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10 weight percent based on the total weight of the composite fibers, or any range defined by such values. The slurry can have a solids content of about 0.1% to about 3%, about 0.1% to about 1%, about 0.5% to about 1.5%, or about 0.1% to about 6%. Other suitable solids contents include 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.2, 1.4, 1.6, 1.8, 2, 2.2, 2.4, 2.6, 2.8, 3, or any range defined by these values. The aqueous fiber slurry is added to the reactor as a heel.

[0018] The mineral slake may be prepared by mixing a suitable mineral-containing material with water. For example, the mineral slake may be calcium hydroxide slake. The calcium hydroxide slake is prepared by mixing lime with water. The ratio of water to lime may be about 4:1 to about 15:1, about 5:1 to about 10:1, or about 5:1 to about 7:1. For example, the ratio of water to lime may be 7:1. The lime and water may be mixed to form the slake. In various embodiments, control of the initial temperature of the water is not required and may depend on the process water in the plant. For example, the initial water temperature may be 32° C. Once mixed, the slake may optionally be screened to remove larger grit particles. For example, the slake may be screened through a 30 mesh screen, a 60 mesh screen, or a 200 mesh screen.

[0019] The heel can be mixed in the reactor, then the slake and CO 2 A gas containing may be added to precipitate the minerals onto the fibers present in the heel. The initial reactor temperature may be from about 1° C. to about 50° C., from about 11° C. to about 45° C., or from about 35° C. to about 50° C., but does not need to be controlled during the process.

[0020] For example, slake can be added and then CO 2 Alternatively, CO 2 The containing gas can be flowed and then the slake added immediately thereafter. For example, the two components can be added in either order within a few seconds of each other, for example within 10 seconds.

[0021] The disclosed method utilizes reverse addition, where calcium hydroxide slake is metered into the aqueous fiber containing heel at a controlled rate of addition to limit the conductivity to about 50%-80% of saturation. The rate of calcium hydroxide slake addition is controlled throughout the settling process to maintain the target conductivity. As used herein, "saturated" refers to a conductivity of the starting calcium hydroxide slurry in a fully saturated form. A conductivity of about 70% of saturation refers to a conductivity that is less than 70% of the conductivity of the starting calcium hydroxide slurry. Control of the conductivity can be achieved to within about 1% until the reaction is nearly complete. The target conductivity can be, for example, 50% of saturation, 60% of saturation, 70% of saturation, or 80% of saturation. For example, the target conductivity can be 50% of saturation. The actual conductivity value can vary depending on the conductivity of the starting slake and the reactor. However, the actual conductivity value to control the reaction to 70% of saturation can be easily determined by measuring the conductivity of the slake prior to addition and setting the conductivity to less than 70% of the measured value. For example, 50% of saturation can be maintained at conductivity values ​​of about 3000 μs / cm to 5500 μs / cm, depending on the starting conductivity of the slake, as illustrated in the various examples.

[0022] It was found that the pH did not need to be tightly controlled during the precipitation process. Once all the slake had been added, CO was added until the pH reached 7.0. 2 The flow of the contained gas may be continued.

[0023] CO 2 The contained gas is, for example, CO 2 For example, the gas or gas mixture may be a blend of about 5% CO 2 ~ Approximately 100% CO 2 may include.

[0024] The process of the present disclosure results in bicomponent fibers in a slurry. Due to the fibrous nature of the resulting bicomponent fibers, the slurry cannot be screened. The slurry can be used directly, for example, as a filler in papermaking. Alternatively, the bicomponent fiber slurry can be dried to provide a dry product that can be used in other applications. EXAMPLES

[0025] Example 1 Mineralized nanocellulose fibers were prepared according to the method of the present disclosure. Calcium hydroxide slake was prepared by mixing water and lime in a 7:1 mass ratio. Specifically, 357 g of lime was mixed with 2500 ml of water. The water had a starting temperature of 32°C. The lime was added to the water while mixing at 750 rpm and mixing was continued for 15 minutes. The resulting slurry was screened through a No. 200 mesh screen and the +200 mesh grid was removed.

[0026] 147.48g of nanocellulose with 0.5% solids content was diluted in 800ml water to form a slurry with a solids content of 0.5% 8% solids. The target PCC% in the PCC / fiber composition was 99. The addition of nanocellulose template was calculated to be 1 wt% of the final product weight. Nanocellulose was added to the reactor first as a carbonator heel and mixed at 1250 rpm. The initial temperature was 40.8°C. CO 2 Gas, 0.76 slm CO 2 The reactor was then flushed with air at a flow set point of 3.1 slm and 3.2 slm. Then, within 10 seconds, calcium hydroxide slake was added to the carbonator heel pump at a rate of 14 ml / min for 120 minutes. The slake addition rate was adjusted to maintain a conductivity of 4.5-5.0 ms / cm, which was 50% of the starting slake conductivity. After all the slake had been added, CO was pumped until the end point reaction of pH 7.0. 2 The addition of was continued. The resulting product could not be screened through a 325 mesh due to its fibrous nature. Figure 1 is an SEM image of the resulting composite fiber.

[0027] The resulting product was characterized for Horiba particle size and BET surface area. The characterization is shown in Table 1: [Table 1]

[0028] Figure 2 is a graph of the pH, conductivity, and temperature trends in the reaction. The pH at saturation was found to be an unimportant parameter for controlling the process.

[0029] Example 2 After starting the calcium hydroxide slake addition, 2 Composite fibers were produced according to the method described in Example 1, except that the addition of CO 2 It was found that the addition of calcium hydroxide and the order of addition of the slake did not affect the composite fiber characteristics, and importantly, control of the pH before the calcium hydroxide slake was not necessary to obtain good fiber properties. The following table shows the results for Example 1 (CO before slake) 2 (addition of CO after slake addition) and this Example 2 (addition of CO after slake addition) 2 1 provides a comparison of fiber properties made according to the addition of 100% saturation in the heel within 1% of the total reaction time. [Table 2]

[0030] Example 3 The bicomponent fibers produced according to Example 1 were tested in the production of copy paper handsheets. The bicomponent fibers of the present disclosure were compared to standard precipitated calcium carbonate and methods of adding nanocellulose to the furnish.

[0031] Conventional nanocellulose containing precipitated calcium carbonate was treated with CO to precipitate calcium carbonate at 100% saturation. 2The nanocellulose was formed by adding nanocellulose as a precursor additive to the calcium hydroxide slurry before passing the gas. Referring to FIG. 3, the conventional nanocellulose containing PCC showed less adhesion and a very different morphology compared to the composite fiber of the present disclosure. As shown in the table below, there is a significant difference in the particle size distribution of the conventional nanocellulose PCC and the composite of the present disclosure, especially in the d90 and d50, indicating that the conventional nanocellulose PCC had less fibrous material. The conventional nanocellulose PCC exhibited a single scalenohedral morphology with loosely connected particles. In FIG. 4, nanocellulose 1 and nanocellulose 2 refer to samples prepared using the same method of the present disclosure but with different fiber types with similar particle size. This morphology was found to be more sensitive to the shear forces of the paper machine. [Table 3]

[0032] Copy paper handsheets were prepared with eucalyptus pulp refined to a Canadian Standard Freeness of 400. Handsheets were produced at a target basis weight of 80 gsm. Filler levels were adjusted to achieve target levels of 15, 25, 35, or 50%. Additives were added as follows: 3 kg cationic starch (Stalok 310) per tonne of paper, target levels of filler, 0.01 kg retention aid (Percol 175) per tonne of paper. All chemicals were added on a dry-to-dry basis. Handsheets were formed on a Formax (Nobel and Wood) sheet former. With the sheet still on the forming wire and sandwiched between paper machine felt material, it was pressed at 4 psi. The handsheet was then removed from the forming wire, sandwiched between two sheets of unsized blotter paper, and pressed at 25 psi. The handsheet was then dried on a drum dryer at 125° C. for 1 minute. Finally, the handsheets were conditioned at 23° C. and 50% relative humidity.

[0033] The composite fibers of the present disclosure demonstrated unexpected improvements in both bulk properties and strength. With reference to Figure 4A, hand sheets produced with the composite fibers of the present disclosure demonstrated significant improvements in bulk compared to those produced using conventional nanocellulose (nanocellulose 1 and nanocellulose 2 in Figure 4A). With reference to Figures 4B and 4C, hand sheets produced using the composite fibers also demonstrated improved strength compared to those produced with standard PCC, as well as improved flex resistance compared to hand sheets produced with either standard PCC or conventional nanocellulose.

[0034] Example 4 To analyze the performance benefits imparted by the presence of fiber, composite fibers were made according to the method described in Example 1 (maintaining 50% saturation) and compared to precipitated calcium carbonate produced using the same method, except that no fiber was present in the heel. The properties of the resulting calcium carbonate produced with and without fiber are shown in the table below. [Table 4]

[0035] In the absence of nanocellulose, the precipitated calcium carbonate was found to be in the form of non-fibrous, large calcium carbonate structures, as shown in Figures 5C and 5D. In comparison, the fibrous nature of the composite fibers of the present disclosure can be seen in Figures 5A and 5B. The calcium carbonate produced without fibers also had no light scattering, given the large structures. Without wishing to be bound by theory, it is believed that the calcium carbonate produced without fibers densifies the paper sheet, resulting in reduced bulk and stiffness. Furthermore, without wishing to be bound by theory, it is believed that the non-fibrous calcium carbonate is not well retained within the sheet due to its low specific surface area, non-acicular nature.

[0036] Example 5 Large scale production of a composite according to the present disclosure was produced using nanocellulose produced at the University of Maine. The nanocellulose had an average fiber length of 224 μm and a fiber width of 21.9 μm. The product had 74.7% fines, a twist index of 1.2, a twist angle of 13.96, and an average curl of 0.114.

[0037] The slake was prepared by diluting the lime to a target slake solids of 15-17%, screening through a 60 mesh screen, and then discharging into a 470 gallon tank. The slake was held at approximately 50-55°C using heating coils in the slake holding tank.

[0038] Water was added to the reactor and heated as needed to the target start temperature. The start temperatures were 11° C., 25° C., or 40° C. Once the target start temperature was reached, the water was drained to 202 gallons as the target start volume. The water was stirred at half speed and aqueous nanocellulose was added at a loading of 0.5 wt. % dry nanocellulose based on slake volume and slake concentration (MO) based on the total dry end product weight. The stirring was then increased to full speed and the aqueous fiber containing heel was mixed for 5 minutes.

[0039] CO 2 The contained gas is CO 2 and air blend was flowed into the reactor at the target flow rates specified in the table below. Once the gas reached full flow rate, the slake additive was pumped from the slake holding tank into the reactor using a Moyno pump. The slake was added at a rate to maintain approximately 50% saturation (conductivity value of 3.0-3.5 ms / cm) or approximately 70% saturation (conductivity value of 4.0-4.5 ms / cm). Once all the slake was added, the reaction mixture was gassed until a pH of 7.0 was reached. One liter and five gallon samples were collected for characterization.

[0040] A comparative sample with no added fiber was also produced using the same procedure, except no fiber was added to the aqueous heel. The conditions tested and the resulting calcium carbonate properties are shown in the table below. [Table 5-1] [Table 5-2] [Table 5-3]

[0041] Figure 6 is an SEM image of precipitated calcium carbonate without fibers. Figures 7-9 include SEM images of composite fibers produced according to the present disclosure using 50% saturation at different starting hydrothermal temperatures. The resulting composite fibers had a precipitated calcium carbonate morphology that was primarily a mixture of scalenohedral and prismatic calcite. A starting temperature of 11°C resulted in smaller, narrower particle size distribution and slightly higher surface area compared to using a higher heel starting temperature.

[0042] Figure 10 includes SEM images of composite fibers produced at 70% saturation. The resulting composite fibers have a much narrower particle size distribution, higher surface area, and more scalenohedral morphology compared to the product made at 50% saturation.

[0043] Aspects Aspect 1. A filler comprising composite fibers, each composite fiber comprising a mineral attached to the fiber, the mineral being at least about 90% by weight based on the total weight of the composite fibers, the uncoated fibers having an average length of less than 300 μm, and the composite fibers having a Horiba d 90 A filler having the formula: Example 2. The filler of example 1, wherein the mineral is calcium carbonate and the fiber is nanocellulose. Aspect 3. The composite fiber has a Horiba d 90 3. The filler of claim 1 or 2, having the following structure: Embodiment 4. The filler of any one of embodiments 1-3, wherein the fiber is present in an amount of about 0.1% by weight to about 10% by weight, based on the total weight of the composite fiber. Aspect 5. The filler of any one of aspects 1 to 4, wherein the fibers have an average length of from 100 μm to less than 300 μm. Embodiment 6. The filling material of embodiment 5, wherein the fibers have an average length of about 200 μm. Embodiment 7. The filling material of any one of embodiments 1 to 6, wherein the fiber is nanocellulose. Aspect 8. The filler of any one of aspects 1-7, wherein the mineral has a scalenohedral morphology. Embodiment 9. A method of making a composite fiber, comprising: preparing calcium hydroxide slake by diluting lime in water; combining the aqueous fiber slurry with dilution water in a reactor; Calcium hydroxide slake and CO 2 adding contained gas to a reactor containing an aqueous fiber slurry mixed with dilution water to precipitate calcium carbonate onto the fibers; After calcium hydroxide slake addition is started, CO is added to the admixture until the pH reaches 7.0. 2 and continuing the flow of the contained gas; calcium hydroxide slake is added at a rate to maintain a target conductivity of 50% to 80% of saturation, and the target conductivity is maintained until addition of the calcium hydroxide slake is completed; The fiber slurry comprises fibers having a length of 300 μm or less; The method, wherein the fiber slurry comprises an amount of fibers such that the fiber content in the bicomponent fiber is 10% by weight or less, based on the total weight of the bicomponent fiber. Embodiment 10. The method of embodiment 9, wherein the calcium carbonate has a scalenohedral morphology. Aspect 11. The method of aspect 9 or 10, wherein the addition of calcium hydroxide slake is started before starting the addition of the gas comprising carbon dioxide. Aspect 12. The method of aspect 9 or 10, wherein the addition of calcium hydroxide slake is started after the addition of the gas comprising carbon dioxide is started. Aspect 13. The method of any one of aspects 9 to 12, wherein the aqueous fiber slurry is mixed while adding calcium hydroxide slakes and a gas comprising carbon dioxide. Example 14. The method of any one of Examples 9 to 13, wherein the aqueous fiber slurry has a solids content of about 0.1% to 3% solids. Example 15. The method of example 14, wherein the aqueous fiber slurry has a solids content of less than about 1%. Aspect 16. The method of any one of aspects 9 to 15, wherein the calcium hydroxide slake comprises water and lime in a mass ratio of about 4:1 to about 15:1. Example 17. The method of any one of Examples 9 to 16, wherein the calcium hydroxide slake is screened through a mesh screen having a mesh size of 40 mesh to 200 mesh prior to addition to the aqueous fiber slurry. Embodiment 18. The method of any one of embodiments 9 to 17, wherein calcium hydroxide is added at a rate to maintain a conductivity that is about 50% to about 70% of saturation. Embodiment 19. The method of any one of embodiments 9 to 18, wherein the target conductivity is achieved and maintained after 1% or less of the reaction is complete. Aspect 20. The method of any one of aspects 9 to 19, wherein the carbon dioxide-containing gas comprises about 5% to about 100% carbon dioxide. Embodiment 21 The method of any one of embodiments 9 to 20, wherein the fiber is nanocellulose.

[0044] Modifications and other embodiments disclosed herein will come to mind to one skilled in the art to which the disclosed compositions and methods pertain having the benefit of the teachings presented in the foregoing description. It is understood, therefore, that the disclosure is not limited to the specific embodiments disclosed, but that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

[0045] It should also be understood that the terms used herein are merely for the purpose of describing certain embodiments and are not intended to be limiting. When used in this specification and claims, the term "comprises" can include the embodiment "consisting of". Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the disclosed compositions and methods belong. In this specification and the following claims, reference is made to some terms defined herein.

[0046] As will be apparent to one of ordinary skill in the art upon reading this disclosure, each of the individual embodiments described and illustrated herein has distinct components and features which may be readily separated from or combined with the features of any of the other several embodiments without departing from the scope or spirit of the present disclosure. Any recited method may be carried out in the order of events recited or in any other order which is logically possible.

[0047] In the context of the disclosure herein (especially in the context of the claims), the use of the terms "a," "an," "the," and similar referents should be construed to encompass both the singular and the plural, unless otherwise indicated. The recitation of ranges of values ​​herein is intended to merely serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated herein as if it were individually recited herein. Any and all examples provided herein, or the use of exemplary language (e.g., "etc."), are intended to better illustrate the disclosure herein, and do not limit the scope of the disclosure herein, unless otherwise indicated. No language in the specification should be construed as indicating any element not claimed as essential to the practice of the disclosure herein.

Claims

1. 1. A filler comprising bicomponent fibers, each bicomponent fiber comprising a mineral attached thereto, said mineral being at least about 90% by weight based on the total weight of said bicomponent fibers, said uncoated fibers having an average length of less than 300 μm, and said bicomponent fibers having a Horiba d ratio of at least 10 μm. ９０ A filler having the formula:

2. 2. The filler of claim 1, wherein the mineral is calcium carbonate and the fiber is nanocellulose.

3. The composite fiber has a Horiba d ９０ The filler according to claim 1 or 2, having the formula:

4. 10. The filler of claim 1, wherein the fiber is present in an amount of about 0.1% to about 10% by weight based on the total weight of the bicomponent fiber.

5. 2. The filler of claim 1, wherein the fibers have an average length of from 100 μm to less than 300 μm.

6. 6. The filler of claim 5, wherein the fibers have an average length of about 200 μm.

7. 2. The filler of claim 1, wherein the fiber is nanocellulose.

8. 2. The filler of claim 1, wherein the mineral has a scalenohedral morphology.

9. 1. A method of making a bicomponent fiber, comprising the steps of: preparing calcium hydroxide slake by diluting lime in water; combining the aqueous fiber slurry with dilution water in a reactor; The calcium hydroxide slake and CO ２ adding a contained gas to the reactor containing the aqueous fiber slurry mixed with the dilution water to precipitate calcium carbonate onto the fibers; After the calcium hydroxide slake addition is started, the CO 2 is added to the admixture until the pH reaches 7.

0. ２ and continuing the flow of the contained gas; the calcium hydroxide slake is added at a rate to maintain a target conductivity that is between 50% and 80% of saturation, and the target conductivity is maintained until the addition of the calcium hydroxide slake is completed; The fiber slurry comprises fibers having a length of 300 μm or less; The method, wherein the fiber slurry comprises an amount of fibers such that the fiber content in the bicomponent fiber is 10 wt% or less, based on the total weight of the bicomponent fiber.

10. 10. The method of claim 9, wherein the calcium carbonate has a scalenohedral morphology.

11. 11. The method according to claim 9 or 10, wherein the addition of calcium hydroxide slake is started before starting the addition of the gas comprising carbon dioxide.

12. 11. The method according to claim 9 or 10, wherein the addition of calcium hydroxide slake is started after starting the addition of the gas comprising carbon dioxide.

13. 10. The method of claim 9, wherein the aqueous fiber slurry is mixed while adding the calcium hydroxide slakes and the gas comprising carbon dioxide.

14. The method of claim 9, wherein the aqueous fiber slurry has a solids content of about 0.1% to 3% solids.

15. The method of claim 14, wherein the aqueous fiber slurry has a solids content of less than about 1%.

16. 10. The method of claim 9, wherein the calcium hydroxide slake comprises water and lime in a weight ratio of about 4:1 to about 15:

1.

17. 10. The method of claim 9, wherein the calcium hydroxide slake is screened through a mesh screen having a mesh size of 40 mesh to 200 mesh prior to addition to the aqueous fiber slurry.

18. 10. The method of claim 9, wherein the calcium hydroxide is added at a rate to maintain a conductivity that is about 50% to about 70% of saturation.

19. 10. The method of claim 9, wherein the target conductivity is achieved and maintained after 1% or less of the reaction is complete.

20. The method of claim 9, wherein the carbon dioxide containing gas comprises from about 5% to about 100% carbon dioxide.

21. 10. The method of claim 9, wherein the fiber is nanocellulose.

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