Stable slurry composition with enhanced barrier properties

Abstract

A stable slurry composition with enhanced barrier properties is provided. The slurry comprises materials with a density greater than 15 μm. 2 A composite material of pigments and microcrystalline cellulose with a surface area of ​​ / g BET and carboxymethyl cellulose. This slurry can be used to formulate barrier coatings, which are applied to the surface of paper or paperboard products to enhance and improve the barrier properties of the products.

Description

Technical Field

[0001] This invention provides a stabilized slurry comprising a high aspect ratio pigment. When this stabilized slurry is mixed with a suitable latex, a formulation with enhanced barrier properties is produced. This stabilized slurry includes minerals and pigments, such as talc, with a BET surface area greater than 15 m². 2 / g; Jennings and Parslow aspect ratio >30; and a composite of microcrystalline cellulose and carboxymethyl cellulose to form a microcrystalline cellulose gel. The formulated and stable pulp can be applied to the surface of paper or paperboard products to enhance and improve the barrier properties of the products and extend the shelf life of the final products. Background Technology

[0002] The present invention relates to stabilizing slurry compositions, such as talc slurries, used as components in papermaking processes, for example, in barrier coating formulations. For instance, a standard method for producing barrier coating formulations (e.g., coatings containing talc) involves mixing talc with latex under high shear conditions for 10 to 60 minutes. This is not a robust process and leads to significant product instability and variability. Key variables affecting barrier coatings include the hydrophilicity of the rheology modifier and formulation stratification due to density mismatch between the pigment and the latex binder. Other variables include latex aging, temperature, agitator speed, flow distribution (determined by reactor geometry and agitator position), and the talc addition rate.

[0003] Typically, stable coloring slurries are required in applications such as fracturing drilling fluids, coating development, and advancements in cement slurry technology. Efforts to stabilize slurries used in these industries involve the use of large amounts of thickeners and rheology modifiers. These modifiers form a physical network with low aspect ratio fillers or non-layered particles. However, when using these modifiers, slurries (e.g., talc slurries) can result in very high viscosity, making them more difficult to handle in production facilities. Furthermore, the effectiveness of these conventional rheology modifiers for high aspect ratio pigments (e.g., high aspect ratio talc) is reduced, leading to pigment compaction within days.

[0004] It is well known in this field that high aspect ratio talc provides significantly better barrier properties for paper or paperboard compared to low aspect ratio talc. Current methods for producing stable, high aspect ratio barrier coating formulations involve on-the-spot preparation to avoid settling. This process is performed on-site and often results in product inconsistencies. Other techniques exist, including the use of holding tanks where the formulation is continuously stirred.

[0005] Formulations have been described that utilize mixtures of talc, chelating agents, and multivalent ions, and stabilize the mixtures by adjusting the pH to between about 10.2 and about 11.8. Other methods include formulations containing microfibrillated cellulose and inorganic particulate materials, which exhibit enhanced viscosity and tensile strength properties suitable for paper or coated paper manufacturing.

[0006] However, there is still a need for a water-based talc slurry that has a reasonable shelf life and minimizes compaction and / or soft settling of high aspect ratio talc. Summary of the Invention

[0007] This overview is intended to introduce some concepts in a simplified form, which will be further described in the detailed description below. This overview is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

[0008] A slurry is provided, comprising a concentration of more than 15 m 2 A composite material consisting of talc with a surface area of ​​ / g BET, comprising approximately 50 wt.% to approximately 65 wt.% of the total slurry weight, and microcrystalline cellulose (MCC) and carboxymethyl cellulose (CMC), which forms a microcrystalline cellulose gel (MCG).

[0009] Talc must also contain Jennings and Parslow aspect ratios >30, where the median particle size measured by sedimentation diagrams and laser measurements, as well as the calculation methods for Jennings and Parslow aspect ratios, are as follows:

[0010] In addition, a method for producing paper or paperboard with improved barrier properties (e.g., liquid and vapor barrier properties) is provided. The pulp as described above is applied to the surface of the paper or paperboard. Attached Figure Description

[0011] This disclosure will be described in conjunction with the following figures, wherein the same numerals denote the same elements, and wherein: Figure 1 The results show that MCG exhibits better water barrier performance as measured by the standard 30-minute Cobb water absorption test (Tappi method T441), where it outperforms all standard rheology modifiers and thickeners used in coloring pastes.

[0012] Figure 2 The sedimentation behavior of the talc slurry was observed at a high solids content of 62% total solids, with a viscosity of approximately 1000 cP. This MCG rheology modifier significantly outperforms typical rheology modifiers and thickeners used in the industry.

[0013] Figure 3 The results show that, with a total solids content of 52%, the sedimentation behavior of talc slurry exhibits a viscosity of approximately 1000 cP. MCG rheology modifiers significantly outperform typical rheology modifiers and thickeners used in industry.

[0014] The following detailed descriptions are merely illustrative in nature and are not intended to limit the invention or its application and use. As used herein, the term "illustrative" means "as an example, instance, or illustration." Therefore, any embodiment described herein as "illustrative" should not be construed as preferred or superior to other embodiments. All embodiments described herein are exemplary embodiments intended to enable those skilled in the art to make or use the invention, and should not limit the scope of the invention, which is defined by the claims. Furthermore, there is no intention to be bound by any express or implied theory set forth in prior art, background art, summary of the invention, or the following detailed descriptions.

[0015] Unless otherwise specified or obvious from the context, the term "about" as used herein shall be understood to mean within the normal tolerance range in the field, such as within 2 standard deviations of the mean. "About" may be understood to mean within 10%, 5%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the value stated. "About" may also be understood to imply the exact value stated. All numerical values ​​provided herein are modified by the term "about" unless explicitly stated otherwise from the context.

[0016] As used in this article, the term "paper" refers to paper products including toilet paper, tissues, and cardboard.

[0017] A slurry is provided, comprising a concentration of more than 15 m 2 A talc solution with a surface area of ​​ / g BET, combined with a microcrystalline gel (MCG), which is a composite material composed of microcrystalline cellulose (MCC) and carboxymethyl cellulose (CMC). The microcrystalline cellulose and carboxymethyl cellulose (CMC) together form a microcrystalline cellulose gel (MCG). While not wishing to be theoretically limited, the MCG forms a three-dimensional elastic gel network, thereby preventing talc particle flocculation and reducing sedimentation. This ensures that the talc slurry remains stable over a longer period (at least 60 days) and minimizes the workload required for its use in production. Furthermore, the final coated product also remains more stable over a longer period, and the talc particles are better dispersed in the coating, ensuring optimal barrier properties of the coating, with the MCG producing optimal water retention when formulated and coated onto paper.

[0018] In some aspects of the slurry, the talc is flake talc, which accounts for about 40 wt.% to about 75 wt.% or about 50 wt.% to about 65 wt.% of the slurry.

[0019] In some aspects of the slurry, microcrystalline cellulose gels comprise microcrystalline cellulose and carboxymethyl cellulose in a molar ratio of about 1:1 to about 1:4.

[0020] In other aspects of the slurry composition, the slurry further includes other additives, such as xanthan gum, sodium alginate, acrylate, or the formulation may contain a combination of additives. The additives may comprise from about 0.5 wt.% to about 5 wt.% of the slurry by weight.

[0021] In other aspects of the slurry composition, the slurry may optionally include dispersants and wetting agents well known in the art, such as nonionic surfactants. In other aspects of the slurry, the pH value is approximately 6 to approximately 11.

[0022] In other aspects, the slurry is at 25 ο After being stored at temperature C for at least 60 days, the slurry remains in suspension as determined visually.

[0023] In addition, a method for producing paper or paperboard with improved barrier properties is provided.

[0024] The method includes providing a paper or paperboard barrier coating product, and applying a slurry composition comprising an aqueous coloring slurry, a microcrystalline cellulose gel, and a polymer binder emulsion to at least one surface of the paper or paperboard.

[0025] In some aspects of this method, the pigment is talc, such as layered talc, having a thickness greater than 15 μm. 2 BET surface area per g, and aspect ratios greater than 30 for Jennings and Parslow.

[0026] In some aspects of this method, the pigment accounts for about 40 wt.% to about 75 wt.% or about 50 wt.% to about 65 wt.% of the slurry composition.

[0027] In other aspects of the method, the microcrystalline gel in the slurry is a composition comprising microcrystalline cellulose and carboxymethyl cellulose.

[0028] In some aspects of this method, the molar ratio of microcrystalline cellulose to carboxymethyl cellulose is about 1:1 to about 1:4.

[0029] In some aspects of this method, the polymer adhesive emulsion may be selected from styrene-butadiene, styrene acrylate, polyethylene, polypropylene, polyethylene oxide, polyacrylate, polyvinyl alcohol, polyvinyl acetate, polyethyleneamine, and combinations thereof.

[0030] In other aspects of this method, the pigment can be selected from talc, kaolin, bentonite, calcium carbonate, mica, and combinations thereof.

[0031] In other aspects of the method, a barrier coating is applied to the surface of a substrate comprising about 30 wt.% to about 70 wt.% of a polymer content and about 30 wt.% to about 70 wt.% of a colorant content based on the total dry weight of the coating, or about 30 wt.% to 50% of a polymer content and about 50 wt.% to 70 wt.% of a colorant content based on the total dry weight of the coating, or about 30 wt.% to 40 wt.% of a polymer content and about 60 wt.% to 70% of a colorant content based on the total dry weight of the coating.

[0032] The range of rheology modifiers is from about 0.03% by weight to about 3% by weight based on the total dry weight of the solid talc present.

[0033] In other aspects of this method, the coloring paste includes pigments, water, polyacrylic acid, microcrystalline cellulose gel, rheology modifiers, and combinations thereof.

[0034] In other aspects of the method, the slurry further comprises other additives, such as those selected from xanthan gum, sodium alginate, acrylates, and combinations thereof.

[0035] In some aspects of this method, the slurry is sheared for about 20 minutes or longer, after which latex or latex combinations are added to form a water-based barrier coating formulation that can be applied to the surface of paper or paperboard. Example

[0036] The following studies were conducted using a wide range of rheology modifiers. These studies aimed to optimize inorganic talc dispersions, improve their shelf life, reduce talc sedimentation, and mitigate agglomeration.

[0037] Example 1 – Sedimentation Study of Talc / Alginate Formulation In this study, 303 g of talc, 2 g of sodium acrylate, 4.7 g of nonionic wetting agent (Hydropala™ WE3197, Dow Chemical Company), and 1 g of sodium alginate were added to a one-liter container / reactor containing 189 g of water and mixed / shuffled for 15 minutes. This formulation / mixture was then transferred to a storage container and left to stand for more than 60 days.

[0038] Example 2 – Sedimentation Study of Talc / Acrylamide-acrylate Formulation The method was the same as in Example 1, except that the alginate was replaced with an acrylamide-acrylate composition. As shown in Table 1, it contains Sterocoll... ™The formulations of FS and CHP701 (an aqueous anionic dispersion of a copolymer of acrylate and carboxylic acid) thickened continuously over time, causing the product to gel after prolonged storage. This resulted in the compaction of the talc layer at the bottom of the storage container, making it difficult to reincorporate into a homogeneous slurry mixture.

[0039] Example 3 – Sedimentation Study of Talc / Carbohydrate-Based (Hydrocarbon-Based) Formulations In this study, the same procedure as in the previous examples was used, except that alginate and acrylamide-acrylate compositions were replaced with carbohydrate-based thickeners (CMC, xanthan gum). However, as the results shown in Table 1 indicate, the talc / carbohydrate-containing formulations lacked shear stability, had a shortened shelf life, and functioned only within a limited range of talc solids content.

[0040] Example 4 - Sedimentation of formulations co-treated with talc / microcrystalline cellulose (MCC) and carboxymethyl cellulose (CMC) Research In this study, layered talc slurry and microcrystalline cellulose (MCC) co-treated with CMC were combined. The prepared talc slurry had a solids content of 52% by weight. Figure 2 ) to approximately 63% by weight ( Figure 3 The slurry has a BET surface area greater than 15 g / g. It is stabilized with microcrystalline cellulose gel (MCG). MCG is a composite material composed of microcrystalline cellulose (MCC) and sodium carboxymethyl cellulose (Na-CMC). The microcrystalline cellulose and carboxymethyl cellulose (CMC) together form the microcrystalline cellulose gel (MCG). While not wishing to be limited by theory, MCG forms a 3D elastic gel network that prevents talc particle flocculation, thereby reducing sedimentation. This ensures that the talc slurry remains stable for a longer period (>60 days) and minimizes the workload required to use it in production. Furthermore, the final coated product is also more stable over a longer period, and the talc particles are better dispersed in the coating, ensuring optimal barrier properties, with MCG producing the best water retention when formulated and coated onto paper.

[0041] Table 2 – Settling characteristics of talc slurry with 52% solids content

[0042] Table 3 – Settling characteristics of talc slurry with 62% solids content

[0043] The results shown in Tables 2 and 3 above indicate that adding MCG to talc slurry can reduce the settling tendency of talc slurry at both high (62%) and low talc solids content (52%), while maintaining a viscosity of approximately 1000 cP in both samples.

[0044] Compared to traditional carbohydrate-based thickeners (CMC, HEMC, xanthan gum), talc slurries exhibit enhanced stability with significantly reduced settling and agglomeration under the following conditions: increased talc solids content range: 50-65% vs. 60-65%. The novel compositions provide enhanced talc stability at higher manufacturing shear rates, and at >10 6 s -1 The stability loss is very small at the shear rate.

[0045] Example 5 – Applying a coating formulation containing stable pigments and latex to coated paper / paperboard substrates Waterborne research In this study, the slurry formulations of Examples 1-4 were each mixed with 319 g of styrene-butadiene emulsion (Tykote). ™ 1004) Mixing. The resulting coating formulation was applied to 80 GSM paper using a benchtop coater, with 10 GSM of coating applied. The paper and coating were dried in an oven at 95°C for 2 hours. The water absorption rate was measured using Tappi method T441.

[0046] Table 3 – Water Absorption Study of Coated Paper Using Emulsion and Talc Slurry with 62% Solids Content

[0047] As shown in Table 3, Cobb test results indicate that formulations containing MCG exhibit the best tolerance to water absorption, followed by formulations containing CMC. Other formulations show significant improvements in sedimentation behavior compared to formulations without thickeners, but perform poorly in terms of water absorption.

[0048] While at least one exemplary embodiment has been presented in the specific implementation of the subject matter of this invention, it should be understood that numerous variations exist. It should also be understood that the one or more exemplary embodiments are merely examples and are not intended to limit the scope, applicability, or configuration of the subject matter of this invention in any way. Rather, the detailed description above will provide those skilled in the art with a convenient roadmap for implementing the exemplary embodiments, and it should be understood that various changes can be made to the arrangement of functions and elements described in the exemplary embodiments without departing from the scope of the invention as defined in the appended claims and their legal equivalents.

Claims

1. A slurry composition comprising: pigments having a BET surface area greater than 15 m 2 / g and an aspect ratio greater than 30; Microcrystalline cellulose gel; and water.

2. The slurry composition according to claim 1, wherein the pigment comprises about 40% to about 75% by weight of the total weight of the slurry.

3. The slurry composition according to claim 1, wherein the pigment is selected from talc, kaolin, bentonite, calcium carbonate, mica, and combinations thereof.

4. The slurry composition according to claim 3, wherein the pigment is layered talc.

5. The slurry composition according to claim 1, wherein the microcrystalline cellulose gel comprises microcrystalline cellulose (MCC) and carboxymethyl cellulose.

6. The slurry composition according to claim 5, wherein the ratio of microcrystalline cellulose to carboxymethyl cellulose is from about 1:1 to about 1:

4.

7. The slurry composition according to claim 1, further comprising an additive selected from xanthan gum, sodium alginate, acrylates, and combinations thereof.

8. The slurry composition according to claim 7, wherein the additive is present in an amount of about 0.5% by weight to about 5% by weight of the total slurry weight.

9. The slurry composition according to any one of claims 1-8, wherein at 25°C... ο After being stored at a temperature of C for at least 60 days, approximately 40% to approximately 75% of the pigment solids were visually determined to remain in suspension.

10. The slurry composition of claim 9, comprising about 50% by weight pigment solids, wherein the slurry composition is prepared at 25°C. ο After being stored at temperature C for at least 60 days, it was visually confirmed to remain in suspension.

11. A method for producing paper or paperboard with improved barrier properties, the method comprising the steps of: Provide paper or paperboard products with a surface, and Apply a slurry composition, said slurry composition comprising a concentration greater than 15 m 2 Pigments with a BET surface area of ​​ / g and an aspect ratio greater than 30; microcrystalline cellulose gels; and polymer binder emulsions.

12. The method of claim 11, wherein the polymer adhesive emulsion is selected from styrene-butadiene, styrene-acrylate, polyethylene, polypropylene, polyethylene oxide, polyacrylate, polyvinyl alcohol, polyvinyl acetate, polyvinylamine, and combinations thereof.

13. The method of claim 11, wherein the pulp composition is sheared for at least 10 minutes before being applied to the surface of the paper or paperboard.

14. The method of claim 11, wherein the slurry composition is applied to the paper or paperboard by spraying, gravure printing, rod coating, doctor blade coating, and curtain coating.

15. The method according to any one of claims 11-14, wherein the paper or paperboard to which the pulp composition is applied has improved liquid and vapor barrier properties by about 13% when tested using a 30-minute Cobb absorbency test, compared to paper or paperboard without the pulp composition.

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