Three-dimensional molding clay cat litter

Abstract

The present invention is a process for preparing shaped three-dimensional clay particles with improved absorbency suitable for use in cat litter. The method is three-dimensionally printing a clay slurry into a desired particulate shape, where the printed clay particles (when printed at low temperature and when dried) provide improved absorbency compared to extruded clay particles. The particles are not pulverized and are not sintered at high temperatures.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of provisional patent application #63 / 486,750, filed February 24, 2023, which is incorporated herein by reference. Technical Field

[0003] The present invention relates to cat litter, and more particularly to three-dimensional shaped clay cat litter. Background Art

[0004] Natural clay, also known as earthy clay, has long been used as a liquid absorbent, particularly in animal litters. As more and more livestock are kept as domestic pets, there's a need for litters that facilitate the urination or excretion of liquid or solid waste in a controlled, indoor area. Many cat litters use clay as an absorbent. Typically, clay is mined, dried, and crushed into the desired particle size. While this method allows for control over the overall particle size, it doesn't allow for control over the particle shape. Therefore, there's a need for shaped clay particles with improved absorbency.

[0005] Extruding clay is a method of providing sand molding. Extruded animal litter is known in the art. U.S. Patent No. 3,923,005 discloses an animal litter comprising alfalfa and starch made using an extrusion process. U.S. Patent No. 4,206,718 discloses a method for producing lightweight animal litter from ground alfalfa and gelatinizable flour or starch. In one embodiment, the sand contains up to 10% bentonite as a binder. U.S. Patent No. 5,452,684 and U.S. Patent No. 5,577,463 disclose an animal litter comprising extruded montmorillonite clay, which forms a stronger agglomerate when moistened with animal urine. U.S. Patent No. 7,603,964 discloses a method of mixing a clay material with a lightweight material and forming the mixture into composite particles using various methods (e.g., agglomeration, compaction, and extrusion). WO2009133212A1 discloses a method for producing low-density agglomerated pet litter using a mineral having a attapulgite content greater than 50% and an extrusion process.

[0006] Generally speaking, these extruded litters perform well for their intended uses, such as absorbing liquid animal excreta like urine. However, extruded clay cat litters also have some disadvantages. Many extruded animal litters, particularly those made from clay and starch, have a "film" on the surface of the litter particles. While this film can be useful for various purposes, such as reducing dust generated during litter use, it often negatively impacts the litter's absorptivity. US Pat. No. 8,904,963 discloses extruded animal litter particles that have been crushed to expose the interior of the particles to the external environment. The interior of these extruded litter particles has the ability to absorb liquids, such as animal urine or water from animal feces or other excreta, at an increased rate compared to the extruded surface portion of the particles. Therefore, extruded animal litters with increased absorptivity contain these crushed litter particles because the extruded particles have expanded pores within them, resulting in greater absorbency. Furthermore, the crushed particles have a greater surface area to volume ratio, resulting in increased absorbency. Disadvantages of crushed extrudates include increased dust formation and the irregular shape of the crushed particles.

[0007] 3D printing has been used to create porous ceramics, such as specialized filters. However, most 3D-printed objects require sintering (heating to high temperatures) to enhance their strength and create a non-porous surface. No inventions have yet been proposed for 3D-printing porous clay products for use as cat litter. US2017 / 0251713 discloses a method for 3D-printing an open container and then 3D-printing food into it. Clay is mentioned as one of many materials that can be used to print a second material for the container. Clay is also mentioned as a removable support material. However, there is no mention of clay being suitable for absorbing cat urine. US2021 / 0212352 discloses a 3D-printed container that can be filled with various substances to be delivered via 3D printing. Of over 70 proposed applications for 3D-printed delivery systems, only one is for cat litter. However, these containers do not mention the use of natural clay, but rather water-soluble or porous polymers. There is no suggestion that these containers are suitable for absorbing cat urine. On the contrary, the containers are proposed to be made from water-soluble or porous polymer films (such as polyvinyl alcohol), which are completely unsuitable for use as absorbent cat litter.

[0008] The present invention provides shaped absorbent clay particles and a method for making cat litter without crushing. The absorbent material is formed into particles using a three-dimensional (3D) printing process (also known as additive manufacturing). Although extruded clay litter uses starch to bind the extrudate, because the surface of the extruded clay is heated during the extrusion process, the starch forms a film on the surface, which has poor water absorption. In the present invention, the 3D printing process does not provide cat litter particles with such a film, because the 3D printing process is preferably carried out at a temperature below 52 degrees Celsius, or at room temperature. Optionally, the wet print is annealed after printing. In addition, performance-enhancing additives are optionally included in the absorbent material during the 3D printing process, either uniformly mixed or added in layers. Exemplary additives include antimicrobial agents, odor absorbers / inhibitors, fragrances, health indicator materials, non-stick release agents, and mixtures thereof. Many additives are not heat-resistant. The 3D process can provide a method for making cat litter containing additives, wherein the additives are not damaged by the heating step.

[0009] In a preferred embodiment, the absorbent particles do not contain starch additives.In a more preferred embodiment, the absorbent particles do not have an absorbency-impeding film on their surface.

[0010] In a preferred embodiment, the composite absorbent particles may comprise a core material fully or partially surrounded by a natural clay.

[0011] The preferred properties of sand products such as odor control, additive optimization, low density, low tracking, low dust, strong agglomeration, etc. can be optimized to provide the specific properties desired. Another aspect of the present invention is the use of encapsulated additives, that is, the additives are made into the particles themselves and can enter through pores or discontinuities in the particles. The encapsulation of the additives provides a slow release mechanism, allowing the additives to be effective for a longer period of time. Another aspect of the present invention provides control over the strength of the particles, thereby controlling the degradation and / or disintegration characteristics. Controlling the rate at which the particles degrade (for example, when the particles disintegrate due to urine deposition) provides another mechanism for slowly releasing additives from the interior and surface of the particles, thereby optimizing performance.

[0012] Another advantage of 3D-printed cat litter is the ability to control the packing density of the litter, thereby reducing the overall weight of the litter and improving the convenience of picking up and scooping the litter for consumers. On the other hand, if the packing density is increased, cats are less likely to remove the litter from the litter box or have the litter stick to their paws.

[0013] Other aspects and advantages of the invention will become apparent from the following detailed description which illustrates, by way of example, the principles of the invention. Summary of the Invention

[0014] The present invention discloses a method for preparing shaped three-dimensional natural clay particles with improved absorbency suitable for cat litter. The method prints a natural clay slurry into a desired particle shape, wherein the printed natural clay particles (when printed at low temperatures and when dried) have improved absorbency compared to extruded clay particles. The particles are not crushed, and the particles are not sintered at high temperatures.

[0015] Further areas of applicability of the present invention will become apparent from the detailed description below.It should be understood that the detailed description and specific examples, while indicating preferred embodiments of the present invention, are for illustrative purposes only and are not intended to limit the scope of the present invention. DETAILED DESCRIPTION

[0016] The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.

[0017] The shaped clay cat litter of the present invention is made from natural clay or a mixture of natural clays. The most commonly used natural clay in cat litter is bentonite, such as sodium bentonite or calcium bentonite, which swells to 15 times its original volume when exposed to water. Other clays commonly added to cat litter mixtures include sepiolite, montmorillonite, kaolinite, and combinations thereof. In a preferred embodiment, the clay does not contain any additives such as gelatinizable flour or starch, or other similar additives that would form a skin on the outer surface of the particles.

[0018] Suitable shapes for cat litter include, but are not limited to, cubes, parallelograms, spheres (solid and hollow), cups, boxes, open boxes, and other shapes. Shapes with openings are suitable for increasing absorbency by increasing surface area. A preferred shape is a parallelogram with right angles and at least two rectangular surfaces.

[0019] The size of the cat litter particles can vary from about 0.065 inches to about 0.50 inches. Preferably, the size is from about 0.20 inches to about 0.40 inches. More preferably, the size is from about 0.25 inches to about 0.37 inches. In a preferred embodiment, the particles are three-dimensional polygonal.

[0020] Preferably, the polygon is approximately rectangular. This shape allows the litter to align neatly when poured into the litter box. Compared to shredded (irregularly shaped) cat litter, the polygon provides better support for the cat's paws when entering the litter box. Preferably, the polygon is less than 0.5 inches in size. More preferably, it is less than about 0.37 inches. Most preferably, the rectangular polygon is about 0.37 inches to about 0.10 inches in size.

[0021] The use of 3D printing (also known as additive manufacturing) includes direct deposition of ceramic materials, namely fused deposition of ceramics (FDC), paste deposition modeling (PDM), extrusion freeform fabrication (EFF), direct ink writing (DIW), and WASP liquid deposition modeling (LDM). The present invention covers all of the above methods as well as methods not listed.

[0022] Used in Front.Mater., 21 April 2021, Sec.Structural Materials, Volume 8-2021 https: / / doi.org / 10.3389 / fmats.2021.582885 In the paper entitled “3D-Extrusion Manufacturing of a Kaolinite Dough Takenin Its Pristine State”, Boyer, AE et al., Direct Ink Writing (DIW), which is hereby incorporated by reference. The study used the most popular aluminosilicate material, kaolinite clay, which has the molecular formula: 2SiO2·Al2O3·2H2O. Kaolinite is a popular material because it is the most abundant in the Earth’s crust. DIW (the most common type of 3D printing) builds complex geometries by extruding a slurry of material at room temperature, with the ability to print ceramic-type slurries so that they retain their shape during the extrusion process. Layers of material are printed one after another through an extrusion nozzle, and the printed geometry is created using a common computer-aided design program such as AutoCAD-3D. Once printing is successfully completed via DIW, the sample must be sintered, a process in which the sample is heated at extremely high temperatures to cure the binder used in the slurry, which helps the material retain its shape. The binder component used in DIW is typically an organic or polymer-based binder fluid.

[0023] In a first preferred embodiment, the first step in DIW is to create an AutoCAD drawing of the desired shape. This drawing is converted into software compatible with the 3D printer. Second, the software is loaded onto the printer. Third, a clay material is selected and a slurry is made of clay and water. Kaolinite clay is selected so that the water content of the clay / water mixture is approximately greater than 23 wt.% and less than 27 wt.%, although kaolinite has been used with up to 30 wt.% water. Fourth, the optimal flow rate is set, and the article is printed as a green (wet) article at room temperature. The fifth and final step is drying and sintering.

[0024] Typically, the drying and sintering steps for ceramics begin after air drying at room temperature for about 24 hours.

[0025] Step 1: Start from room temperature and increase the temperature at a rate of 10°C / min for about 48 minutes.

[0026] Step 2: Annealing at 500°C (or 700°C) for about 1 hour to induce the following reaction: Al2(OH)4Si2O→Al2O32SiO2+2H2O(hydrated kaolin)(metakaolin)(water, elimination).

[0027] Step 3: Heating at 350-750°C at a rate of 10°C / min causes the following reaction: Al2O3 2SiO2→Al2O3+SiO2(metakaolin)(alumina)(silicon dioxide) 950-1050°C, Al2O3 2SiO2→MgAl2O4+SiO2(metakaolin)(spinel)(amorphous silica).

[0028] Step 4: sintering at 1200°C for 1 h, causing the following reaction: Al2O3 2SiO2→2(3Al2O3 2SiO2)+5SiO2(metakaolin)(mullite)(amorphous silica).

[0029] Step 5: Cooling rate 10°C / min.

[0030] The present invention relates to the preparation of absorbent cat litter. To this end, the drying and sintering processes are not carried out to the end, as sintering eliminates porosity and densifies the material. The method for preparing the absorbent cat litter is completed at the end of the annealing step, when the evaporated water has formed open pores. The clay product at this point has been freed of molecular water and is porous. The preferred annealing temperature range is about 200 to 1000°C. A more preferred annealing temperature range is about 250 to 750°C. Heating above 1000°C, and more specifically, heating to 1200°C, is avoided.

[0031] In a second preferred embodiment, printed cat litter can be completed by low temperature (less than 52 degrees Celsius) or room temperature drying. This process is most suitable for "fast drying" clay. One type of fast drying clay is paper clay. Paper clay is a natural clay combined with fibers. Natural fibers are cellulose fibers, such as provided by pulp, cotton, hemp, flax, linen and wood. The advantage of paper clay is that the product is light in weight and dries quickly. Typically, paper clay contains 1 to 25 wt.% cellulose fibers. More preferably, the clay contains 2 to 20 wt.% cellulose fibers. When recycled materials (such as newsprint or cardboard) are used, cat litter has the preferred characteristic of reusable recycled materials. In a preferred embodiment, paper clay is combined with natural clay to form cat litter particles.

[0032] Another preferred type of epoxy clay is fast-drying epoxy clay. Epoxy clay is a clay that combines two separate epoxy adhesives. After separation, the two-part epoxy clay is stable for storage. When used, the two parts are combined, preferably in equal amounts, and the combined clay hardens at room temperature in about 4 to 24 hours. Commercially available epoxy clays include Sculpt, Magic TM Sculpt and Milliput TM Putty.

[0033] The absorbent cat litter of the present invention absorbs at least 50 wt.% of its weight in water. Preferably, the absorbent cat litter absorbs 50 wt.% to 200 wt.% of its weight in water. Most preferably, the absorbent cat litter absorbs 100 wt.% to 200 wt.% of its weight in water.

[0034] In a preferred embodiment, clay is combined with other ingredients such as silica, ceramic powder, wood ash, etc. Kaolinite has been mixed with lime, talc and fly ash at concentrations of 3 wt.%, 5 wt.% and 7 wt.% with varying results. The addition of steel dust waste from an electric arc furnace (EAFD) was studied and the optimal addition level was determined to be 20%. In addition, a study was conducted to add hydroxyapatite to clay and the results showed that print quality was better when the weight ratio of clay to hydroxyapatite was 80:20 wt.%. In addition, it has been reported that adding waste ceramic dust to clay can improve strength and water absorption.

[0035] Additives are used to improve the flow properties of kaolinite, such as sodium silicate and sodium polyacrylate in concentrations ranging from 0.2 to 0.8 wt.%.

[0036] 3D printing cat litter can be combined with other types of litter, including extruded clay litter, crushed clay litter, cellulose litter, etc. However, preferred combinations contain about 1 to 100 wt.% 3D printing litter. In more preferred combinations, the amount of 3D printing litter is less than 50 wt.%. In another embodiment of the present invention, the combination contains less than 10 wt.% 3D printing litter. In another embodiment of the present invention, the combination contains about 1 to 10 wt.% 3D printing litter.

[0037] These embodiments were chosen and described in order to best explain the principles of the invention and its practical application to those skilled in the art. Since various modifications may be made to the exemplary embodiments described above with reference to the corresponding drawings without departing from the scope of the present invention, it is intended that all matter contained in the foregoing description and shown in the accompanying drawings be interpreted as illustrative and not restrictive. Therefore, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the appended claims and their equivalents.

Claims

1. A method for making shaped cat litter particles, comprising three-dimensional printing to make particles, The particles contain natural clay; wherein the particles are not extruded; wherein the particles are absorbent; and The 3D printing particles are not crushed.

2. The method of claim 1, wherein the three-dimensional printing method is selected from the group consisting of ceramic fused deposition, paste deposition modeling, extrusion freeform fabrication, direct ink writing, and liquid deposition modeling.

3. The method of claim 2, wherein the cat litter absorbs 50 to 200 wt. % of its weight of water.

4. The method of claim 3, wherein the method further comprises direct ink writing, wherein the method further comprises the steps of: forming a natural clay slurry from clay; 3D printing wet-molded pellets; as well as The wet shaped pellets are dried to form shaped cat litter pellets.

5. The method of claim 4, wherein the wet-formed article is dried by annealing at about 200 degrees Celsius to 1000 degrees Celsius.

6. The method of claim 1, wherein the granules are free of starch.

7. The method of claim 6, wherein the particles do not have a starch film on their surface that would hinder absorption.

8. The method of claim 4, wherein the wet formed granules are air-dried at a temperature below 52 degrees Celsius.

9. The method of claim 8, wherein the natural clay is selected from the group consisting of paper clay and epoxy clay.

10. A pellet for cat litter, made by a method comprising three-dimensional printing to make the pellet, The particles contain natural clay; wherein the particles are not extruded; The particles are absorbents; wherein the 3D printing particles are not crushed; and The particles have a three-dimensional shape.

11. According to claim 10, wherein the three-dimensional printing process is selected from the group consisting of ceramic fused deposition, paste deposition modeling, extrusion freeform fabrication, direct ink writing and liquid deposition modeling.

12. The particle according to claim 11, wherein the particle absorbs 50 to 200 wt.% of its weight of water.

13. The particle of claim 12, wherein the particle further comprises liquid deposition modeling, wherein the method further comprises the steps of: forming a natural clay slurry from clay; 3D printing wet-molded pellets; as well as The wet shaped particles are dried to form shaped cat litter particles.

14. The pellets of claim 13, wherein the wet-formed article is dried by annealing at about 200 degrees Celsius to 1000 degrees Celsius.

15. The granule of claim 10, wherein the granule is free of starch.

16. The particle according to claim 15, wherein the particle does not have a starch film on its surface that hinders absorption.

17. The granules of claim 13, wherein the wet formed granules are air dried at a temperature below 52 degrees Celsius.

18. The particle of claim 8, wherein the natural clay is selected from the group consisting of paper clay and epoxy clay.

19. The particle of claim 1, wherein the three-dimensional shape is selected from the group consisting of a cube, a parallelogram, a sphere (solid or hollow), a cup, a closed box, and an open box.

20. The particle of claim 19, wherein the three-dimensional shape is selected from the group consisting of a parallelogram having right angles and at least two rectangular surfaces.