TW201527375A - Process for producing a high solids pigment suspension comprising carboxymethylcellulose-based dispersant - Google Patents

Abstract

The present invention relates to a process for preparing an aqueous suspension comprising a mineral pigment material and a depolymerized carboxymethylcellulose having a degree of carboxylation in the range from 0.2 to 2.2, a molecular weight in the range from 5000 to 40000 g/mol, and a polydispersity index in the range from 2 to 10.

Description

Method for producing a high solid pigment suspension comprising a carboxymethyl cellulose based dispersant

This invention relates to aqueous suspensions of mineral pigment materials. In particular, the invention relates to mineral pigment suspensions containing additives based on renewable sources and to methods for preparing such suspensions. The invention also relates to high solids mineral pigment suspensions containing additives based on renewable sources and to processes for preparing such suspensions.

Mineral materials are the main components in paints, plastics, cosmetics, paper or paper coating dyes. Mineral materials such as calcium carbonate may provide improvements, for example, in paper and paint quality and agricultural properties or toothpaste, particularly with respect to their physical properties such as optical and/or abrasive properties.

Mineral materials in the form of high solids suspensions (i.e., a small amount of a suspension of water relative to the total weight of the suspension) are particularly suitable for reasons of suitability, aspiration, transport, storage and drying costs. Such high solids suspensions typically require the addition of dispersing or grinding aids to maintain the suspension stable, easy to pump and allow the mineral particles to be separated by grinding the suspensions.

Commonly used dispersants or grinding aids for the production and stabilization of such high solid mineral pigment material suspensions are mainly petrochemical based polymers such as salts of polycarboxylates such as sodium polyacrylate. However, from an environmental perspective, the use of products of such petroleum sources is undesirable. In particular, in order to comply with the Kyoto protocol and to reduce atmospheric fossil CO ₂ pollution during the combustion of the final product, it is intended to convert a petrochemical-based polymer into a polymer with a lower carbon dioxide footprint, for example into A polymer derived from natural or renewable resources.

FR 2 939 055 describes dispersants based on acrylic acid homopolymers or copolymers and/or Or a grinding aid, wherein the acrylic acid is obtained from glycerol. FR 2 932 804 describes polymers based on acrolein and acrolein/acrylic acid copolymers in which acrolein is obtained from glycerol. However, the process for producing acrolein and acrylic acid from glycerol is extremely complicated and expensive. In addition, hazardous intermediates and by-products may be produced during the preparation of such bio-based unsaturated monomers. The storage of monomers such as acrylic acid unsaturated monomers is also well known, and in particular the acrolein storage and polymerization process requires significant safety precautions because the monomers are highly reactive and uncontrolled polymerization can lead to serious human and installation events.

For completeness, the applicant will mention the unclaimed application number 12 167 664.7 European Patent Application is directed to an aqueous suspension comprising a modified polysaccharide.

Therefore, the need can be derived from renewable low toxicity resources, and its starting materials and raw Dispersing agents and grinding aids with less safety issues.

Accordingly, it is an object of the present invention to provide dispersants and grinding aids that are at least partially derived from renewable natural polymer resources. In addition, it would be desirable to provide educts and final polymeric dispersants and grinding aids that can be stored without any safety precautions and that do not require complicated manufacturing methods. It would also be desirable to provide dispersants and grinding aids that can be produced without the production of harmful by-products or intermediates. It would also be desirable to provide a step that can be produced in a high solids concentration to avoid energy intensive concentration steps. Dispersing agents and grinding aids such as heat concentration.

It is also an object of the present invention to provide a high solids aqueous suspension of mineral pigment materials. A float, which is a liquid, but contains only a relatively low amount of a petrochemical-based dispersant or abrasive or is completely free of petrochemical-based dispersants or abrasives.

It is also an object of the present invention to provide a method for preparing an aqueous suspension which The medium dispersant or grinding aid is produced directly in the form of a highly concentrated solution in order to avoid energy consumption concentration steps, such as heat concentration.

Another object of the present invention to reduce or remove the dispersant or fossil-based abrasive is preferably intended to follow during the final combustion products of atmospheric CO ₂ fossil reduce contamination of the Kyoto Protocol. The Kyoto Protocol is an international agreement related to the United Nations Framework Convention on Climate Change. The main feature of the Kyoto Protocol is its joint goal of reducing greenhouse gas (GHG) emissions for 37 industrialized countries and the European Community. This means that emissions in the five-year period from 2008 to 2012 averaged 5% of the 1990 level. The Kyoto Protocol was adopted in Kyoto, Japan on December 11, 1997 and entered into force on February 16, 2005.

The foregoing is achieved by the subject matter as defined in the scope of the independent patent application herein And other goals.

According to one aspect of the invention, there is provided a method for preparing an aqueous suspension comprising the following steps

a) providing a mineral pigment material, b) providing a depolymerized carboxymethyl cellulose having a degree of carboxylation in the range of 0.2 to 2.2, a molecular weight in the range of 5000 g/mol to 40,000 g/mol and a polydispersity index in the range of 2 to 10. Internally, by depolymerizing high molecular weight carboxymethyl cellulose in a process comprising the following steps Preparing the depolymerized carboxymethylcellulose: i) providing a high molecular weight carboxymethylcellulose having a molecular weight greater than 40,000 g/mol and a degree of carboxylation in the range of 0.2 to 2.0, ii) providing a hydrogen peroxide and/or a base thereof a peroxide of a metal salt, iii) providing a catalyst, iv) mixing at least a portion of the high molecular weight carboxymethylcellulose of step i) and/or at least a portion of step ii) in any order at a reaction temperature of from 50 ° C to 85 ° C a peroxide and/or at least a portion of the catalyst of step iii) and water, and v) adding the remainder of the high molecular weight carboxymethylcellulose to the mixture obtained in step iv) in one or more steps and/or Or the remainder of the peroxide and/or the remainder of the catalyst up to the mixture of step v) containing from 10% to 60% by weight, based on the total weight of the mixture of step v), of depolymerized carboxymethylcellulose, and up to the same time The Brookfield viscosity of the mixture of step v) is between 30 mPa at 20 °C. s with 10000mPa. Between s, wherein during the step v), the Brookfield viscosity of the mixture measured at the reaction temperature is maintained at 200 mPa. s with 1500mPa. Between s, and c) mixing the polymerized carboxymethylcellulose of step b), the mineral pigment material of step a) and water to form an aqueous suspension, wherein 10% to 80% by weight, based on the total weight of the suspension Adding the mineral pigment material in an amount of 0.05% by weight to 5.0% by weight based on the total weight of the mineral pigment material in the suspension The amount of the depolymerized carboxymethyl cellulose is added, and the Brookel viscosity of the aqueous suspension is 40 mPa at 20 ° C. s with 2000mPa. Between s.

According to another aspect of the invention, there is provided an aqueous pigment particle suspension obtainable by the process according to the invention.

According to a further aspect of the invention, there is provided the use of an aqueous suspension according to the invention for paper, plastic, paint, food, feed, pharmaceutical, drinking water and/or agricultural applications.

According to a further aspect of the invention, pigment particles are provided which can be obtained by drying an aqueous suspension according to the invention and optionally treating the dried granules.

According to a further aspect of the invention there is provided a use of a pigment granule according to the invention for use in plastics, paints and/or sealants.

Advantageous embodiments of the method of the invention are defined in the scope of the corresponding sub-application patent.

According to a specific example, the mineral pigment material is a calcium carbonate containing material, preferably selected from the group consisting of calcium carbonate, calcium carbonate containing minerals, mixed carbonate based fillers or mixtures thereof. According to another embodiment, the mineral pigment material is kaolin, talc, gypsum, lime, magnesia, titania, satin white, trialumina, tris(a), cerium oxide, mica or mixtures thereof . According to a further embodiment, the mineral pigment material is in the form of particles having a weight median particle size d _{50 of} from 0.1 μm to 100 μm, from 0.25 μm to 50 μm or from 0.3 μm to 5 μm, preferably from 0.4 μm to 3.0 μm.

According to a specific example, the degree of carboxylation of the depolymerized carboxymethylcellulose is in the range of 0.5 to 1.8, and preferably 0.6 to 1.4. According to another embodiment, the solution is added in an amount of from 0.05% by weight to 3.0% by weight, preferably from 0.1% by weight to 2.0% by weight, and more preferably from 0.2% by weight to 1.0% by weight, based on the total weight of the mineral pigment material of the suspension. Polymerized carboxymethyl cellulose. According to still another embodiment, the polydispersity index of the depolymerized carboxymethylcellulose is from 2 to 5, preferably from 2.5 to 4.5, and more preferably from 3 to 4. According to yet another embodiment, the molecular weight of the depolymerized carboxymethylcellulose is in the range of from 8,000 g/mol to 35,000 g/mol, and most preferably from 10,000 g/mol to 20,000 g/mol.

According to a specific example, the solids content of the suspension obtained in step c) is adjusted such that it is from 45 wt% to 80 wt%, preferably from 50 wt% to 78 wt%, and more preferably from 60 wt%, based on the total weight of the suspension. 75 wt%. According to another embodiment, the catalyst is selected from the group consisting of iron sulfate, sodium hypophosphite, iron sulphate, sodium tungstate or mixtures thereof. According to a further embodiment, the step ii) is provided in an amount of from 0.1% by weight to 50% by weight, preferably from 0.2% by weight to 40% by weight, and more preferably from 1% by weight to 30% by weight, based on the total of the high molecular weight CMC of the step i) peroxide.

According to a specific example, after step iv) and before step v), the viscosity of the mixture obtained in step iv) measured at the reaction temperature is adjusted to a Brookfield viscosity of 200 mPa. s with 1500mPa. Between s, preferably by adding to the mixture obtained in step iv) one or more steps the remainder of the other portion of the high molecular weight carboxymethylcellulose and/or the remainder of the other portion of the peroxide and / or the remainder of the other part of the catalyst. According to another embodiment, in step v), the remainder of the high molecular weight carboxymethylcellulose and/or the remainder of the peroxide are added to the mixture obtained in step iv) in one or more steps and / or the remainder of the catalyst until the mixture of step v) contains from 25 wt% to 45 wt%, preferably from 30 wt% to 40 wt% of the depolymerized carboxymethylcellulose, based on the total weight of the mixture of step v), and / or until the mixture of step v) has a Brookfield viscosity of 50 mPa at 20 ° C. s with 5000mPa. Between s, preferably at 1000 ° C at 20 ° C. s with 3000mPa. Between s, and the best at 20 ° C between 1500mPa. s with 2500mPa. Between s.

It should be understood that for the purposes of the present invention, the following terms have the following meanings.

In the literature of the present invention, "degree of carboxylation" is specified as the total amount of hydroxyl groups per unmodified monomer unit of the initial polysaccharide. The "carboxylation degree" of 1 means that one of the three hydroxyl groups in the unmodified monomer unit of the initial polysaccharide is carboxylated.

The term "depolymerized carboxymethylcellulose" (depolymerized CMC) refers to a carboxy group having a molecular weight _Mw greater than 40,000 g/mol (measured by gel permeation chromatography (GPC)). Carboxymethylcellulose (CMC) obtained by depolymerization or decomposition of methylcellulose.

In the meaning of the present invention, "ground calcium carbonate (GCC)" is obtained from natural sources (such as limestone, marble, calcite or chalk) and is wet and/or by, for example, a cyclone or classifier. Dry processing methods such as grinding, sieving and/or grading to process the calcium carbonate.

In the meaning of the present invention, "precipitated calcium carbonate (PCC)" is a synthetic material which is precipitated by reacting carbon dioxide with lime in an aqueous environment or precipitated from water by calcium and carbonate ions. obtain. PCC can be hexagonal calcite, calcite or aragonite.

In the meaning of the present invention, "Modified calcium carbonate (MCC)" may be characterized by naturally ground or precipitated calcium carbonate having internal structural modifications or surface reaction products.

For the purposes of the present invention, "mineral pigment" encompasses inorganic materials which are solid at room temperature (i.e., at a temperature of 20 ° C ± 2 ° C) and are insoluble in water (i.e., less than 1 wt% of the substance in the chamber). It is soluble in water at temperatures, and has a defined chemical composition and may be crystalline or amorphous or a mixture thereof.

In the meaning of the present application, "mineral pigment material" may cover, for example, calcium carbonate (such as calcite, aragonite, marble, limestone and chalk), talc, dolomite, mica, titanium dioxide, aluminum hydroxide ( Materials such as Gibbsit, Bayerit, magnesium hydroxide (such as brucite, hydromagnesite).

Throughout the literature of the present invention, the "particle size" of a mineral pigment material or calcium carbonate product is described by its particle size distribution. The value d _x indicates that the diameter of the x weight% of the particles is smaller than d _x with respect to the diameter. This means that all particles having a d ₂₀ value of 20% by weight are smaller than the particle size of the value, and all particles having a d ₇₅ value of 75 wt% are smaller than the particle size of the value. Thus, the d ₅₀ value is the weight median particle size, i.e., 50% by weight of all grains are larger or smaller than this particle size. For purposes of this invention, unless otherwise indicated, the particle size is specified as weight median particle size d _50. For the determination of the weight median particle size d ₅₀ of particles having a d ₅₀ value between 0.2 μm and 5 μm , a Sedigraph 5100 device from Micromeritics, Inc., USA can be used.

The term "polydispersity index" as used in the context of the present invention is a measure of the molecular weight distribution in a given polymer sample. When the polydispersity index is 1, the molecular weight distribution of all the polymers in the sample is monodisperse, that is, all polymers have the same chain length and thus the same molecular weight. However, for practical polymer, a polydispersity index greater than 1 and is generally represented by M _w / M _n ratio of the average molecular weight divided by the number average molecular weight for the polymer.

For the purposes of the present invention, the term "viscosity" or "Brinell viscosity" (Brookfield viscosity) means the Brookfield viscosity. For this purpose, the Brookfield viscosity is measured using a suitable Brookt (Typ RVT) viscometer at 20 ° C ± 2 ° C (unless indicated as "at the reaction temperature") at 100 rpm using a suitable spindle, and in mPa. s is specified for the unit.

In the meaning of the present invention, "suspension" or "slurry" includes insoluble solids and water, and optionally other additives, and usually contains a large amount of solids, and thus is more viscous than the liquid from which it is formed and The density may be higher.

When the term "comprising" is used in the specification and claims of the present invention, it does not exclude other elements. For the purposes of the present invention, the term "consisting of" is taken to mean a preferred embodiment of the term "comprising of". If a group is hereinafter limited to include at least a certain number of specific examples, it is also understood to disclose a group that is preferably only composed of such specific examples.

The use of an indefinite or definite article, such as "a/an" or "the", when referring to the singular noun, includes the plural of the noun, unless otherwise stated.

Terms such as "obtainable" or "definable" and "obtained" or "defined" are used interchangeably. This means, for example, that the term "obtaining" does not mean that, for example, a particular instance must be obtained by, for example, the sequence of steps after the term "obtaining", unless the context dictates otherwise, although the terms "acquired" or "defined" always include such restrictions. Sexual understanding is a preferred embodiment.

The process of the invention for preparing an aqueous suspension comprises the steps of (a) providing a mineral pigment material, (b) providing a degree of carboxylation in the range of from 0.2 to 2.2, a molecular weight in the range of from 5000 g/mol to 40,000 g/mol and being polydisperse. Depolymerized carboxymethyl fibers with a sex index in the range of 2 to 10. And (c) mixing the polymerized carboxymethylcellulose of step (b), the mineral pigment material of step (a) and water to form an aqueous suspension. The mineral pigment material is added in an amount of 10% by weight to 80% by weight based on the total weight of the suspension, and the depolymerized carboxymethyl fiber is added in an amount of 0.05% by weight to 5.0% by weight based on the total weight of the mineral pigment material in the suspension. And make the aqueous suspension have a Brookfield viscosity of 40mPa at 20 °C. s with 2000mPa. Between s. Depolymerized carboxymethylcellulose is prepared by depolymerizing high molecular weight carboxymethylcellulose in a process comprising the steps of: (i) providing a molecular weight greater than 40,000 g/mol and a degree of carboxylation in the range of 0.2 to 2.0. a molecular weight carboxymethylcellulose, (ii) a peroxide selected from hydrogen peroxide and/or an alkali metal salt thereof, (iii) a catalyst, (iv) a reaction temperature of from 50 ° C to 85 ° C, in any order Mixing at least a portion of the high molecular weight carboxymethylcellulose of step i) and/or at least a portion of the peroxide of step ii) and/or at least a portion of the catalyst of step iii) and water, and (v) in one or more steps Adding to the mixture obtained in step (iv) the remainder of the high molecular weight carboxymethylcellulose and/or the remainder of the peroxide and/or the remainder of the catalyst until the mixture of step (v) contains The total weight of the mixture of step (v) is from 10% by weight to 60% by weight of the depolymerized carboxymethyl cellulose, and until the mixture of the step (v) has a Brookfield viscosity of 30 mPa at 20 ° C. s with 10000mPa. Between s, wherein during the step (v), the Brookfield viscosity of the mixture measured at the reaction temperature is maintained at 200 mPa. s with 1500mPa. Between s.

The details and preferred embodiments of the method of the present invention are set forth in more detail below. It should be understood that these technical details and specific examples are also applicable to the suspensions of the present invention and their uses.

Step a)

According to step a) of the process of the invention, a mineral pigment material is provided. The mineral pigment material is added in an amount of from 10% by weight to 80% by weight based on the total weight of the suspension.

Examples of suitable mineral pigment materials are calcium carbonate (such as calcite, marble, limestone and chalk), talc, dolomite, mica or titanium dioxide, aluminum hydroxide and magnesium hydroxide.

According to a specific example, the mineral pigment material is a calcium carbonate containing material, preferably selected from the group consisting of calcium carbonate, calcium carbonate containing minerals, mixed carbonate based fillers or mixtures thereof.

According to another embodiment, the mineral pigment material is kaolin, talc, gypsum, lime, magnesia, titania, satin white, trialumina, tris(aluminum hydroxide), cerium oxide, mica or mixtures thereof.

According to a preferred embodiment of the invention, the mineral pigment material is calcium carbonate. The calcium carbonate may be selected from the group consisting of ground calcium carbonate (also known as heavy calcium carbonate), precipitated calcium carbonate (also known as light calcium carbonate), modified calcium carbonate or mixtures thereof.

Grinded (or natural) calcium carbonate (GCC) is understood to be a naturally occurring form of calcium carbonate that is extracted from sedimentary rocks such as limestone or chalk or metamorphic marble. Calcium carbonate is known to exist in three types of crystal polymorphs: calcite, aragonite and hexagonal calcite. Calcite (the most common crystalline polymorph) is considered to be the most stable crystalline form of calcium carbonate. Less common is aragonite, which has a dispersed or clustered acicular orthorhombic crystal structure. Hexagonal calcite is the rarest calcium carbonate polymorph and is generally unstable. The ground calcium carbonate is almost entirely a calcite polymorph, which is said to be a trigonal rhombohedron and represents the most stable calcium carbonate polymorph. In the meaning of the present application, the term "source" of calcium carbonate refers to a naturally occurring mineral material from which calcium carbonate is obtained. The source of calcium carbonate may comprise other naturally occurring components such as magnesium carbonate, aluminum citrate, and the like.

According to one embodiment of the invention, the source of ground calcium carbonate (GCC) is selected from the group consisting of marble, chalk, calcite, dolomite, limestone or mixtures thereof. Preferably, The source of ground calcium carbonate is selected from marble and dolomitic marble.

According to one embodiment of the invention, GCC is obtained by dry milling. According to another embodiment of the invention, GCC is obtained by wet milling and, optionally, subsequent drying.

In general, the grinding step can be carried out using any conventional grinding apparatus, for example, under conditions such that the pulverization is mainly caused by the impact of the secondary object, that is, in one or more of the following: a ball mill, a rod mill, a vibration mill Machines, roller crushers, centrifugal impact mills, vertical bead mills, mills, pin mills, hammer mills, mills, shredders, shredders, knife cutters or those skilled in the art have Know other such devices. In the case where the calcium carbonate-containing mineral material comprises a mineral material comprising wet-milled calcium carbonate, it may be subjected to conditions such that auto-grinding occurs and/or by horizontal ball milling and/or other familiar to those skilled in the art. Such methods are used to perform the grinding step. The thus obtained mineral material containing the wet-processed ground calcium carbonate can be washed and dehydrated by well-known methods, such as by flocculation, filtration or forced evaporation, before drying. Subsequent steps of drying can be carried out in a single step, such as spray drying, or in at least two steps. It is also common for such mineral materials to undergo a beneficiation step (such as a flotation, bleaching or magnetization separation step) to remove impurities.

According to a specific example, the calcium carbonate containing material comprises a ground calcium carbonate. According to another embodiment of the invention, the calcium carbonate-containing material comprises a mixture of two or more ground calcium carbonates selected from ground calcium carbonate from different sources. For example, the at least one ground calcium carbonate may comprise a GCC selected from the group consisting of dolomite and a GCC selected from the group consisting of marble.

According to another embodiment, the calcium carbonate containing material consists of only one milled calcium carbonate. According to another embodiment of the invention, the calcium carbonate-containing material consists of a mixture of two or more ground calcium carbonates selected from ground calcium carbonate of various sources.

According to a specific example, the calcium carbonate-containing material comprises at least one precipitated carbonic acid At least one ground calcium carbonate in combination with calcium.

In the meaning of the present invention, "precipitated calcium carbonate (PCC)" is a synthetic material which is generally precipitated by reacting carbon dioxide with lime in an aqueous environment or precipitated from water by calcium and carbonate ions or by calcium. And carbonate ions (for example, CaCl ₂ and Na ₂ CO ₃ ) are obtained by precipitation from a solution. Other possible ways of producing PCC are the lime base process, or the Solvay process, in which PCC is a by-product of ammonia production. Precipitated calcium carbonate exists in three primary forms: calcite, aragonite and hexagonal calcite, and each of these crystalline forms has many different polymorphs (crystal habits). Calcite has a three-way structure, and its typical crystal habits are such as scalenohedral (S-PCC), rhombohedron (R-PCC), hexagonal prism, axial, colloidal (C-PCC), cubic and prismatic. (P-PCC). The aragonite is an orthorhombic structure, and its typical crystal habit is a double-crystal hexagonal prismatic crystal, as well as different types of elongated prismatic, curved blade-like, steep-cone, braid-shaped crystals, branched dendrites and corals or Worm-like form. The hexagonal calcite belongs to the hexagonal crystal system. The obtained PCC slurry can be mechanically dehydrated and dried.

According to a specific embodiment of the invention, the calcium carbonate containing material comprises a precipitated calcium carbonate. According to another embodiment of the invention, the calcium carbonate-containing material comprises a mixture of two or more precipitated calcium carbonates selected from different crystalline forms of precipitated calcium carbonate and different polymorphs. For example, the at least one precipitated calcium carbonate can comprise a PCC selected from the group consisting of S-PCC and a PCC selected from the group consisting of R-PCC.

According to another embodiment, the calcium carbonate containing material consists of only one precipitated calcium carbonate. According to another embodiment of the invention, the calcium carbonate-containing material consists of a mixture of two or more precipitated calcium carbonates selected from the group consisting of different crystalline forms of precipitated calcium carbonate and different polymorphs.

The modified calcium carbonate may be modified with surface and/or internal structure (for example, Naturally ground or precipitated calcium carbonate is characterized by phosphoric acid).

According to one embodiment of the invention, the calcium carbonate containing material comprises a modified calcium carbonate. According to another embodiment of the invention, the calcium carbonate-containing material comprises a mixture of two or more modified calcium carbonates having different surface and/or internal structural modifications.

According to one embodiment of the invention, the calcium carbonate containing material consists of a modified calcium carbonate. According to another embodiment of the invention, the calcium carbonate-containing material consists of a mixture of two or more modified calcium carbonates having different surface and/or internal structural modifications.

According to another embodiment, the calcium carbonate-containing material is a mixture of ground calcium carbonate and/or precipitated calcium carbonate and/or modified calcium carbonate.

According to a specific embodiment of the invention, the calcium carbonate-containing mineral comprises dolomite.

According to a preferred embodiment, the mixed carbonate-based filler is selected from the group consisting of calcium and analogs or derivatives associated with magnesium, various materials such as clay or talc or the like or derivatives, and mixtures of such fillers (such as Talc-calcium carbonate or calcium carbonate-kaolin mixture), or natural calcium carbonate with aluminum hydroxide, mica or with synthetic or natural fiber or mineral common structure (such as talc-calcium carbonate or talc-titanium dioxide or calcium carbonate-titanium dioxide) a mixture.

According to a specific embodiment of the present invention, the mineral pigment material is in the form of particles having a weight median particle size d _{50 of} from 0.1 μm to 100 μm, preferably from 0.25 μm to 50 μm, more preferably from 0.3 μm to 5 μm, and most preferably from 0.4 μm to 3.0 μm.

According to a specific embodiment of the present invention, the mineral is added in an amount of 40% by weight to 80% by weight, preferably 45% by weight to 80% by weight, more preferably 50% by weight to 78% by weight, and most preferably 60% by weight to 75% by weight based on the total weight of the suspension. Pigment material.

Step b)

According to step b) of the process according to the invention, a depolymerized carboxymethylcellulose having a degree of carboxylation in the range from 0.2 to 2.2, a molecular weight in the range from 5000 g/mol to 40,000 g/mol and a polydispersity index in the range from 2 to 10 is provided. . The depolymerized carboxymethyl cellulose is added in an amount of 0.05% by weight to 5% by weight based on the total weight of the mineral pigment material in the suspension, and the Brookel viscosity of the aqueous suspension is 40 mPa at 20 ° C. s with 2000mPa. Between s.

Carboxymethylcellulose (CMC) can be prepared by reacting cellulose with monochloroacetic acid in the presence of caustic soda to form the sodium salt of carboxymethylcellulose. Each repeating D-monosaccharide unit contains three hydroxyl groups which can theoretically be etherified to give a theoretical maximum charge density of three carboxyl groups per monomer unit (i.e., a theoretical degree of substitution of three hydroxyl groups).

According to one embodiment of the invention, the degree of carboxylation of the depolymerized carboxymethylcellulose is in the range of from 0.5 to 1.8, and preferably from 0.6 to 1.4, such as 1.2. According to another embodiment of the invention, the degree of carboxylation of the depolymerized carboxymethylcellulose is about 0.8 or about 1.2. According to yet another embodiment of the invention, the depolymerized carboxymethylcellulose comprises a blend of two degrees of carboxylation, such as a blend having a degree of carboxylation of from about 0.8 to about 1.2.

The molecular weight of the carboxymethyl cellulose can be adjusted by treatment with hydrogen peroxide (H ₂ O ₂ ). Reference is made to DE 1 543 116 A1 for the preparation of low-viscosity water-soluble CMC by oxidative decomposition of H ₂ O ₂ (hydrogen peroxide), and to describe the dependence of the decomposition and treatment of the oxidizing agent on the amount, temperature and duration of the oxidizing agent. DE 44 11 681 A1. However, conventional methods of using hydrogen peroxide do not allow for the preparation of highly concentrated carboxymethylcellulose solutions using depolymerization or decomposition processes.

According to the process of the present invention, depolymerized carboxymethylcellulose is obtained by depolymerizing high molecular weight carboxymethylcellulose in a process comprising the steps of: i) providing a molecular weight of greater than 40,000 g/mol and a degree of carboxylation of 0.2 to Polymer in the range of 2.0 a quantity of carboxymethylcellulose, ii) providing a peroxide selected from hydrogen peroxide and/or an alkali metal salt thereof, iii) providing a catalyst, iv) mixing at least a portion in any order at a reaction temperature of 50 ° C to 85 ° C The high molecular weight carboxymethylcellulose of step i) and/or at least a portion of the peroxide of step ii) and/or at least a portion of the catalyst of step iii) and water, and v) in one or more steps to step iv) Adding to the mixture obtained in the remainder of the high molecular weight carboxymethylcellulose and/or the remainder of the peroxide and/or the remainder of the catalyst until the mixture of step v) contains the mixture according to step v) The total weight is from 10% by weight to 60% by weight of the depolymerized carboxymethyl cellulose, and until the mixture of the step v) has a Brookfield viscosity of 30 mPa at 20 ° C. s with 10000mPa. Between s, wherein during the step v), the Brookfield viscosity of the mixture measured at the reaction temperature is maintained at 200 mPa. s with 1500mPa. Between s.

The high molecular weight carboxymethylcellulose may have a molecular weight of from 50,000 g/mol to 700,000 g/mol, preferably from 100,000 g/mol to 500,000 g/mol, and more preferably from 200,000 g/mol to 400,000 g/mol. The degree of carboxylation of the high molecular weight CMC may be the same as the degree of carboxylation of the depolymerized CMC of process step b), or its degree of carboxylation may be less than the degree of carboxylation of the depolymerized CMC.

According to one embodiment of the invention, the peroxide is hydrogen peroxide. According to another embodiment, the peroxide is an alkali metal peroxide, preferably sodium peroxide. According to yet another embodiment, the peroxide is a mixture of hydrogen peroxide and one or more alkali metal salts thereof.

According to one embodiment of the invention, the catalyst is selected from the group consisting of iron sulphate, sodium hypophosphite, iron phthalocyanine, sodium tungstate or mixtures thereof.

The high molecular weight CMC of step i), the peroxide of step ii) and the catalyst of step iii) are selected such that a molecular weight in the range of from 5000 g/mol to 40,000 g/mol and a polydispersity index in the range of from 2 to 10 are obtained. Depolymerize CMC.

According to a specific example of the present invention, step ii is provided in an amount of from 0.1% by weight to 50% by weight, preferably from 0.2% by weight to 40% by weight, and more preferably from 1% by weight to 30% by weight, based on the total of the high molecular weight CMC of the step i) ) peroxide. The peroxide may be provided in the form of an aqueous solution having a concentration of from 3 wt% to 50 wt%, preferably from 25 wt% to 40 wt%, based on the total amount of the aqueous solution.

According to another embodiment of the invention, from 0.001 wt% to 0.020 wt%, preferably from 0.002 wt% to 0.015 wt%, and most preferably from 0.004 wt% to 0.010 wt%, based on the total of the high molecular weight CMC of step i) The amount of catalyst provided in step iii).

According to a specific embodiment of the invention, at least a portion of the high molecular weight CMC and at least a portion of the peroxide and at least a portion of the catalyst and water are mixed in any order in method step iv). For example, at least a portion of the high molecular weight CMC can be mixed with water in a first step, and a mixture of at least a portion of the peroxide and at least a portion of the catalyst can be added to the CMC/water mixture in a second step. At least a portion of the peroxide and at least a portion of the catalyst may be co-added to the CMC/water mixture, or the at least a portion of the catalyst may be added to the CMC/water mixture in a first step, and may be added to the mixture in a second step The at least a portion of the peroxide. Alternatively, at least a portion of the peroxide and at least a portion of the catalyst may be mixed with water in the first step. And in the second step, at least a portion of the high molecular weight CMC can be added to the peroxide/catalyst/water mixture. Alternatively, at least a portion of the high molecular weight CMC, at least a portion of the peroxide, and at least a portion of the catalyst can be combined with water in one step.

According to another embodiment of the invention, in method step iv), press any number of times At least a portion of the peroxide and at least a portion of the catalyst and water are mixed. According to yet another embodiment, at least a portion of the high molecular weight CMC and at least a portion of the peroxide and water are mixed in any order in method step iv). According to yet another embodiment, at least a portion of the high molecular weight CMC and at least a portion of the catalyst and water are combined in any order in method step iv). According to a further embodiment, at least a portion of the catalyst and water are mixed in process step iv).

In accordance with the present invention, the expression "at least one part" means adding a portion of the provided compound or providing all of the provided compound. Thus, the expression "remaining part" refers to the portion remaining after at least a portion of the provided compound has been added. In the case where part of the compound is not added in method step iv), the remainder is the total of the provided compound.

According to a specific example, all of the peroxide provided is added in method step iv). According to an alternative embodiment, 5%, 10%, 20%, 30%, 40% or 50% of the peroxide provided is added in process step iv). According to yet another alternative embodiment, all of the peroxide provided is added in method step v).

According to a specific example, all of the provided catalyst is added in process step iv). According to an alternative embodiment, 5%, 10%, 20%, 30%, 40% or 50% of the provided catalyst is added in process step iv). According to yet another alternative embodiment, all of the provided catalyst is added in process step v).

According to a specific example, 5%, 10%, 20%, 30%, 40% or 50% of the provided high molecular weight CMC is added in process step iv). According to an alternative embodiment, all of the provided high molecular weight CMC is added in process step v). Where at least a portion of the high molecular weight CMC is added in method step iv), the at least a portion of the high molecular weight CMC may be selected This makes it possible to stir the mixture obtained in step iv). For example, at least a portion of the high molecular weight CMC can be selected such that the mixture obtained in step iv) has a Brookfield viscosity of 200 mPa measured at the reaction temperature. s with 1500mPa. Between s.

According to a specific embodiment of the present invention, in step v), the remainder of the high molecular weight CMC and/or the remainder of the peroxide and/or the addition of the high molecular weight CMC are added to the mixture obtained in step iv) in one or more steps The remainder of the catalyst up to the mixture of step v) contains from 25 wt% to 45 wt%, preferably from 30 wt% to 40 wt% of the depolymerized CMC, based on the total weight of the mixture of step v), and/or up to the mixture of step v) The Brookfield viscosity is between 50mPa at 20 °C. s with 5000mPa. Between s, preferably at 1000 ° C at 20 ° C. s with 3000mPa. Between s, and the best at 20 ° C between 1500mPa. s with 2500mPa. Between s.

According to a specific embodiment of the present invention, in 1 to 20 steps, preferably 1 to 15 steps, more preferably 2 to 12 steps, for example, 3 to 5 steps or 10 to 12 steps The remainder of the high molecular weight CMC and/or the remainder of the peroxide and/or the remainder of the catalyst are added to the mixture obtained in step v).

According to a particular embodiment of the invention, the remainder of the high molecular weight CMC and/or the remainder of the peroxide and/or the remainder of the catalyst are continuously added to the mixture obtained in step v). In other words, the remainder of the high molecular weight CMC and/or peroxide and/or the remainder of the catalyst is added to the mixture obtained in step v) over a period of time in small increments.

According to an exemplary embodiment of the invention, the remainder of the high molecular weight CMC is added in 2 to 12 steps and the remainder of the peroxide is continuously added.

Method step v) can be carried out in a batch or continuous process. The continuous process can preferably be carried out in a cascade mode of at least 2 vessels, preferably in a cascade mode of 2 to 10 vessels.

According to the invention, during the method step v), the Brookfield viscosity measured by the mixture at the reaction temperature is maintained at 200 mPa. s with 1500mPa. Between s. Those skilled in the art will recognize that the Brookfield viscosity of the mixture can be controlled by the amount of polymeric CMC added. For example, if a certain amount of high molecular weight CMC is mixed with a peroxide, a catalyst, and water, the Brookfield viscosity of the mixture will decrease because the depolymerization will be carried out in the presence of a peroxide and a catalyst. To maintain the Brookfield viscosity of the mixture within the desired range, a high molecular weight CMC can be added which will increase the viscosity of the mixture. Additionally, additional peroxide and, if desired, a catalyst may be added to the mixture to depolymerize the newly added high molecular weight CMC. In the case where a mixture of peroxide, catalyst and water is provided, high molecular weight CMC can be added to the mixture until the Brookfield viscosity of the mixture is within the desired range. Additionally, additional high molecular weight CMC, peroxide, and (if necessary) catalyst may be added to the mixture in a ratio such that the Brookfield viscosity of the mixture is maintained within the desired range.

According to a specific example of the present invention, after step iv) and before step v), the viscosity of the mixture obtained in step iv) at the reaction temperature is adjusted to a Brookfield viscosity of 200 mPa. . s with 1500mPa. Between s, preferably by adding to the mixture obtained in step iv) one or more steps the remainder of the other portion of the high molecular weight carboxymethylcellulose and/or the remainder of the other portion of the peroxide and / or the remainder of the other part of the catalyst. According to a specific example, the remainder of the high molecular weight carboxymethylcellulose and/or the remainder of the peroxide and/or the remainder of the catalyst are added to the mixture obtained in step iv) in one or more steps. 5%, 10%, 20%, 30%, 40% or 50%.

According to another embodiment of the invention, the mixture obtained in step v) is cooled to a temperature below 75 °C.

According to a particular embodiment of the invention, the final mixture obtained in step v) comprises the depolymerized CMC of process step b), ie the degree of carboxylation is in the range from 0.2 to 2.2 and the molecular weight is in the range from 5000 g/mol to 40,000 g/mol. And the polydispersity index is in the range of 2 to 10 to depolymerize CMC.

The depolymerized CMC mixture obtained in process step v) can be used in the aqueous suspension of the invention without any further purification. The depolymerized carboxymethylcellulose mixture obtained in process step v) is purified according to a specific example selected as appropriate. Alternatively or additionally, the depolymerized carboxymethylcellulose mixture obtained in process step v) can be diluted or concentrated.

According to a particular embodiment of the invention, the molecular weight of the depolymerized carboxymethylcellulose is in the range from 8000 g/mol to 35000 g/mol, and most preferably in the range from 10,000 g/mol to 20,000 g/mol.

According to a specific embodiment of the present invention, the polydispersity index of the depolymerized carboxymethylcellulose is from 2 to 5, preferably from 2.5 to 4.5, and more preferably from 3 to 4.

According to the invention, the expression "a" depolymerized carboxymethylcellulose means that one or more types of depolymerized carboxymethylcellulose are provided in process step b). According to a specific example, only one type of depolymerized carboxymethylcellulose is provided in process step b). According to another embodiment, a mixture of at least two types of depolymerized carboxymethylcellulose is provided in process step b).

Surprisingly, the inventors have found that the aforementioned depolymerization process of high molecular weight of CMC allows the direct preparation of a depolymerized carboxymethylcellulose solution having a high concentration of carboxymethylcellulose. Thus, an energy depletion concentration step (such as heat concentration or ultrafiltration) can be avoided to allow the solids of the mineral pigment material suspension to be increased without further concentration. In addition, the inventors discovered The highly concentrated depolymerized CMC solution can be used directly as a dispersant or grinding aid in aqueous mineral pigment suspensions. Surprisingly, the inventors have also discovered that the depolymerized carboxymethylcellulose as defined above controls and modulates the viscosity of the suspension of the high solids pigment material and/or can improve or facilitate the grinding of such suspensions. Furthermore, the depolymerized carboxymethyl cellulose of the present invention can be easily prepared and stored without any special safety precautions.

The depolymerized carboxymethyl cellulose can be provided in the form of a solution or a dry material. For example, the depolymerized carboxymethylcellulose may have an aqueous solution having a carboxymethylcellulose concentration of from 10% by weight to 60% by weight, preferably from 25% by weight to 45% by weight, and more preferably from 30% by weight to 40% by weight, based on the total weight of the aqueous solution. form.

According to a specific embodiment of the present invention, in step b), 10% by weight to 60% by weight, preferably 25% by weight to 45% by weight, and more preferably 30% by weight to 40% by weight, based on the total weight of the mixture, of the polymerized CMC, and the cloth is contained. The viscosity is 30mPa at 20 °C. s with 10000mPa. Between s, preferably at 50 ° C at 20 ° C. s with 5000mPa. Between s, better at 1000 °C at 20 ° C. s with 3000mPa. Between s, and the best at 20 ° C between 1500mPa. s with 2500mPa. The mixture between s provides depolymerized carboxymethylcellulose.

According to a specific example of the present invention, 0.05% by weight to 3.0% by weight, preferably 0.1% by weight to 2.0% by weight, and more preferably 0.2% by weight to 1.0% by weight, based on the total weight of the mineral pigment material in the suspension. The depolymerized carboxymethyl cellulose was added in an amount. According to a specific example of the present invention, the Brookfield viscosity of the aqueous suspension is between 60 mPa at 20 ° C. s with 2000mPa. Between s, and preferably at 80 ° C at 20 ° C. s with 700mPa. Add the depolymerized CMC to the amount between s.

According to a specific embodiment of the present invention, the pH of the depolymerized carboxymethylcellulose of the present invention is from 4.5 to 12, preferably from 7 to 11, and more preferably from 8.0 to 10.5.

According to a specific example of the invention, the mixture obtained in step v) of the process is neutralized.

According to a particular embodiment of the invention, the carboxyl group of the depolymerized carboxymethylcellulose is at least partially neutralized by one or more monovalent and/or multivalent cations. According to a preferred embodiment, the monovalent cation is selected from the group consisting of Li ⁺ , Na ⁺ , K ⁺ or mixtures thereof. Preferably, the polyvalent cation is selected from the group consisting of Sr ²⁺ , Ca ²⁺ , Mg ²⁺ or mixtures thereof, and Ca ^{2+ in the} form of Ca(OH) ₂ is preferably added to the suspension and/or solution. According to a preferred embodiment, the carboxyl group of the depolymerized carboxymethylcellulose is at least partially neutralized by a Ca ²⁺ cation, and the Ca ^{2+ is} produced on the spot by adding a partially neutralized polysaccharide and/or an added acid. Additionally or alternatively, the carboxyl group of the depolymerized carboxymethylcellulose is at least partially neutralized by one or more trivalent cations, preferably selected from Al ³⁺ and/or Fe ³⁺ .

Monovalent cations and/or multivalent cations may also be added during the preparation of the depolymerized carboxymethylcellulose. For example, the monovalent cation can be added in the form of a base such as NaOH or KOH, as appropriate, during the depolymerization of the carboxymethylcellulose.

The monovalent cation can be added in the form of a saline solution, a suspension or a powder, and preferably in the form of a solution. The polyvalent cation can be added in the form of a saline solution, a suspension or a powder, and preferably in the form of a suspension.

Multivalent cations can also be produced on the spot, for example, by the addition of an acid and/or an acidic reactive salt and/or a partially neutralized polysaccharide. Multivalent cations can be added in place of monovalent cations or in combination with monovalent cations.

According to a preferred embodiment selected as appropriate, at least partially neutralize the depolymerized carboxymethyl fibers by adding one or more multivalent cations before and/or during and/or after method steps i) to v) The carboxyl group of the element, the one or more multivalent cations are formed in situ by the addition of an acid (preferably H ₃ PO ₄ ) or an acidic reactive salt (for example, NaH ₂ PO ₄ , preferably CaHPO ₄ ).

The acid or acidic reactive salt may be added in an amount of from 50 ppm to 500 ppm, preferably from 200 ppm to 400 ppm, based on the total weight of the solids in the suspension, preferably in the form of an aqueous solution or suspension.

The inventors have found that the addition of monovalent cations in suspension and in particular the addition of multivalent cations provides further advantages and in particular provides improved adsorption characteristics of the depolymerized carboxymethylcellulose for mineral surfaces. This enhances the utility of the depolymerized carboxymethylcellulose of the present invention as a dispersing agent and/or grinding aid. The inventors of the present invention have also found that the combination of the addition of a monovalent cation and a multivalent cation enhances the effectiveness of the modified polysaccharide as a dispersing agent and/or grinding aid.

According to a specific example, one or more monovalent cations and/or one or more are added in an amount of from 0.1% by weight to 5% by weight, preferably from 2% by weight to 3% by weight, based on the total weight of the dry or partially neutralized salt of the depolymerized CMC. A variety of multivalent cations. Ca(OH) ₂ may be added in an amount of from 50 ppm to 500 ppm, preferably from 200 ppm to 300 ppm, based on the total weight of the mineral pigment material in the aqueous suspension.

Step c)

According to method step c), the carboxymethylcellulose, the mineral pigment material of step a) and water are polymerized in step b) to form an aqueous suspension.

According to a specific example, in step c), the depolymerized carboxymethylcellulose is mixed with water in a first step and the mineral pigment material is added to the carboxymethylcellulose/water mixture in a second step. According to another specific example, in step c), the mineral pigment material is mixed with water in a first step and the depolymerized carboxymethylcellulose is added to the mineral pigment material/water mixture in a second step. According to yet another embodiment, in step c), depolymerized carboxymethylcellulose and a mineral pigment material are simultaneously added to the water.

Those skilled in the art will adapt the mixing conditions such as mixing speed and temperature according to their method equipment. For example, mixing can be carried out by means of a ploughshare mixer. The ploughshare mixer functions by a mechanically generated fluidized bed principle. The ploughshare blade rotates near the inner wall of the horizontal cylindrical drum and conveys the mixture components from the product bed to the open mixing space. The mechanically produced fluidized bed ensures even strong mixing of large materials in a very short time. A shredder and/or disperser is used to disperse agglomerates in dry operation. Equipment which can be used in the process of the invention is for example commercially available from Gebrüder Lödige Maschinenbau GmbH, Germany.

According to a specific example of the invention, method step c) is carried out using a ploughshare mixer.

Process step c) can be carried out at room temperature (i.e., at a temperature of 20 ° C ± 2 ° C) or at other temperatures. According to a particular embodiment of the invention, method step c) is carried out for at least 1 s, preferably at least 1 min, for example at least 2 min.

According to another aspect of the invention, there is provided an aqueous pigment particle suspension obtainable by the process according to the invention.

The aqueous suspension of the present invention may have a pH of from 7 to 12, preferably from 8 to 11, and more preferably from 8.5 to 10.5. The pH of the suspension can be adjusted, if necessary, by all methods known in the art.

According to a preferred embodiment, the aqueous suspension of the present invention does not include additional dispersants and/or grinding aids. According to another preferred embodiment, the aqueous suspension of the present invention does not comprise a petroleum chemical-based dispersant and/or a grinding aid, such as a petrochemical based homopolymer or based on, for example, acrylic acid, methacrylic acid, cis a copolymer of a polycarboxylate of butenedioic acid, fumaric acid or itaconic acid and acrylamide or a mixture thereof.

The aqueous suspension according to the invention can be used for paper, plastic, paint, food, Feed, pharmaceutical, drinking water and/or agricultural applications. According to a preferred embodiment, the aqueous suspension according to the invention is used as a carrier for web gravure and/or lithographic and/or ink jet printing and/or flexographic printing and/or electrophotography and/or decorative surfaces, Used in paper machine wet end processes, cigarette paper and/or coating applications.

According to one aspect of the invention, pigment particles are provided which can be obtained by drying an aqueous suspension of the invention and optionally treating the dried granules. For example, the aqueous suspension can be dried by spray drying, evaporation, nanofiltration or centrifugation. Preferably, the aqueous suspension of the present invention is dried by spray drying, whereby pigment particles can be obtained. The term "dry product" is understood to mean a pigment particle having a total surface moisture content of less than 0.5% by weight, preferably less than 0.2% by weight, and more preferably less than 0.1% by weight, based on the total weight of the pigment particles.

The surface treatment of the pigment particles can be carried out, for example, by treating or coating the particles with a hydrophobic surface treating agent such as an aliphatic carboxylic acid or a decane. Pigment particles may also be treated or coated with, for example, sodium polyacrylate or polydiallyldimethylammonium chloride (polyDADMAC) to become cationic or anionic.

According to one aspect of the invention, the pigment particles of the invention are used in plastic, paint and/or sealant applications.

Other method steps selected as appropriate

The mixing step c) is carried out under particle division conditions according to a specific example selected as appropriate. The term "dividing" as used in the present invention means dividing the particles into smaller particles. This can be achieved, for example, by using a ball mill, a hammer mill, a rod mill, a vibration mill, a roller mill, a centrifugal impact mill, a vertical bead mill, a mill, a pin mill, a hammer mill, a mill, Grinding, pulverizer, or knife cutter grinding. However, can be used to be able to be in method step c) Any other device in which the pigment particles formed during the period are divided into smaller particles. Those skilled in the art will adapt the particle segmentation conditions according to their method equipment.

According to a further embodiment selected as appropriate, the process according to the invention further comprises a step d) of grinding the suspension obtained in step c).

The polishing process can be carried out by all techniques and grinders known to those skilled in the art for wet milling. The grinding step can be carried out using any conventional grinding device, for example, under conditions such that the optimization is mainly caused by the impact of the secondary object, that is, in one or more of the following: ball mill, rod mill, vibrating mill, centrifugal shock Mills, vertical bead mills, mills or other such equipment known to those skilled in the art. The grinding step d) can be carried out batchwise or continuously (preferably continuously).

According to a specific example selected as appropriate, at least partially by adding one or more monovalent cations and/or one or more multivalent cations as defined above before and/or during and/or after the grinding step d) The carboxyl group of the polymerized carboxymethyl cellulose is depolymerized.

According to a specific example of the present invention, the grinding step d) is carried out at a temperature of from 30 ° C to 110 ° C, preferably from 40 ° C to 100 ° C.

In a preferred embodiment of the invention, the grinding step d) is carried out until the fraction of pigment particles having a particle size of less than 1 μm is greater than 10% by weight, preferably more than 20% by weight based on the total weight of the pigment particles, as measured by Sedigraph 5100 %, more preferably more than 30% by weight, and most preferably more than 50% by weight.

Additionally or alternatively, the grinding step d) is carried out until the fraction of pigment particles having a particle size of less than 2 μm is greater than 20% by weight, preferably more than 40% by weight, based on the total weight of the pigment particles, as measured by Sedigraph 5100, more preferably More than 60% by weight, and most preferably more than 90% by weight.

Additionally or alternatively, the grinding step d) is carried out until the fraction of pigment particles having a particle size of less than 0.2 μm is greater than 1% by weight, preferably more than 5% by weight, based on the total weight of the pigment particles, as measured by Sedigraph 5100, It is preferably greater than 10% by weight, and most preferably greater than 15% by weight.

The weight median particle diameter d ₅₀ of the mineral pigment particles obtained by the grinding step d) can be from 0.1 μm to 10 μm, preferably from 0.5 μm to 8 μm, and most preferably from 0.8 μm to 6 μm, as measured according to the deposition method, for example. It is in the range of 1.0 μm to 5.5 μm. Additionally or alternatively, the mineral pigment particles obtained in step d) may have a d _{98 of} less than 25 μm, preferably less than 20 μm, more preferably less than 15 μm, and most preferably less than 10 μm. Most preferably, less than 3 ppm of the mineral pigment particles obtained by grinding step d) have a particle size between 1 micron and 2 microns on a 45 micron screen.

According to a particular embodiment of the invention, the mixing step c) and/or the method according to the invention further comprises the step d) of grinding the suspension obtained in step c).

The solids content of the aqueous suspension obtained by the process according to the invention can be adjusted, as the case may be. The solids content of the aqueous suspension can be adjusted by methods known to those skilled in the art. To adjust the solids content of the aqueous suspension comprising the mineral material, the suspension may be partially or completely dehydrated by filtration, centrifugation or thermal separation. For example, the suspension may be partially or completely dehydrated by filtration such as nanofiltration or thermal separation such as evaporation. Alternatively, water can be added to the solid mineral material until the desired solids content is obtained. Additionally or alternatively, a suspension having a suitably lower solids content can be added to the granules of the mixed suspension until the desired solids content is obtained. The solids content of the aqueous suspension obtained by the process of the invention can also be adjusted by a concentration method known to those skilled in the art. It can be by means of a thermal process, for example in an evaporator at ambient, atmospheric or decompression, or by means of, for example, a filter press (such as nanometer). Filtration and/or mechanical processes in the centrifuge to achieve concentration of the aqueous suspension.

The method according to the invention further comprises the step of adjusting the solids content of the suspension obtained in step c), according to a specific example selected as appropriate. According to a particular embodiment of the invention, the solids content of the suspension obtained in step c) is adjusted such that it is from 45 wt% to 80 wt%, preferably from 50 wt% to 78 wt%, and more preferably 60 wt%, based on the total weight of the suspension. % to 75 wt%.

The solids content of the aqueous suspension obtained by process step c) is concentrated by a hot process according to a preferred embodiment selected as appropriate, such that it is from 45 wt% to 80 wt%, based on the total weight of the aqueous suspension. Preferably, it is 50% by weight to 78% by weight, and more preferably 60% by weight to 75% by weight. According to a preferred embodiment, the thermal process is thermally dried and/or performed under reduced pressure.

The scope and concerns of the present invention will be better understood on the basis of the following embodiments which are intended to illustrate particular embodiments of the invention and are non-limiting.

Example

Measurement method

The measurement method implemented in the examples is described below.

Brookfield viscosity

Measurement of pigment particle suspension after 1 hour of production and after stirring for 1 minute at 20 °C ± 2 °C using a Brookfield viscometer type RVT equipped with a suitable disk rotor (for example, rotors 2 to 5) The Brookfield viscosity of the liquid.

During the depolymerization, the Brookfield viscosity of the CMC solution was measured at a reaction temperature and at 100 rpm by using a Brookfield viscometer type RVT equipped with a disk rotor 5.

After depolymerization, at 100 ° C at 20 ° C ± 2 ° C, equipped with The Brookfield viscometer type RVT of the disk rotor 5 or 6 measures the Brookfield viscosity of the polymerized CMC solution.

Particle size distribution

The particle size distribution of the pigment particles was measured using Sedigraph 5100 from Micromeritics, USA. Methods and apparatus are known to those skilled in the art and are commonly used to determine the grain size of fillers and pigments. The measurement was carried out in an aqueous solution containing 0.1 wt% of Na ₄ P ₂ O ₇ . Disperse the sample using a high speed agitator and ultrasonic. For the measurement of the dispersed sample, no further dispersing agent was added.

Solid content of aqueous suspension

The suspension solids content (also known as "dry weight") was determined using the moisture analyzer MJ33 from Mettler-Toledo, Switzerland, using the following settings: 160 ° C drying temperature; if the cake was in a 30 second period After not changing more than 1 mg, it is automatically disconnected; standard drying 5g to 20g suspension.

Using GPC (SEC) with a molecular weight M _w, M _n and polydispersity index

The test portion of the polymer solution corresponding to 90 mg of dry matter was introduced into a 10 ml flask. A mobile phase with an additional 0.04 wt% dimethylformamide was added until a total mass of 10 g was reached. At pH 9, the composition of the mobile phase was as follows: 0.05 mol/l NaHCO ₃ , 0.1 mol/l NaNO ₃ , 0.02 mol/l triethanolamine and 0.03 wt% NaN ₃ .

SEC equipment from Waters ^TM 515 type isocratic pump (the flow rate is set at 0.8ml / min); Waters ^TM 717+ converter samples; containing "protected Ultrahydrogel Waters ^TM column" type of pre-column (its length and 6cm The inner diameter is 40 mm), followed by a large oven of "Ultrahydrogel Waters ^TM " type linear column (the length of which is 30 cm and the inner diameter is 7.8 mm).

By means of a Waters ^TM 410 type differential refractometer detection achieved. The large oven was heated to a temperature of 60 ° C and the refractometer was heated to a temperature of 45 ° C.

A series of sodium polyacrylate standards supplied by Polymer Standard Service with a maximum molecular weight between 2000 g/mol and 1.10 ⁶ g/mol and a polydispersity index between 1.4 and 1.7, and also an average weight molecular weight SEC was calibrated for sodium polyacrylate at 5600 g/mol and polydispersity index equal to 2.4.

The calibration curve is straight and takes into account the calibration obtained using the flow rate label (dimethylformamide).

The acquisition and processing of chromatograms is achieved by using the PSS WinGPC Scientific version 4.02 application. The chromatogram obtained was integrated in a region corresponding to a molecular weight higher than 65 g/mol.

Degree of carboxylation

The degree of carboxylation is determined by conductometric titration according to Katz et al. "The determination of strong and weak acidic groups in sulfite pulps" (Svensk Paperstidn., 1984, 6, pp. 48-53).

Wet grinding

In the absence of any specific instructions, use zirconium silicate beads with a diameter of 0.6mm to 1.2mm, in a tap water machine with a volume of 1.4 liters in tap water (15°dH) (Dynomill ^® , KDL-Pilot type) Wet grinding in a recirculation mode in Bachofen, Switzerland).

2. Examples

Example 1 - Comparative Example

Preparation of carboxymethyl cellulose (CMC) dispersant 1

7 kg of CMC (commercially available from ACROS Organics) having a M _w of 250,000 g/mol and a degree of carboxylation of 1.2 was dissolved in 180 kg of water to form a 8.0 wt% solid solution, and stirred at 80 ° C for 12 h (due to the high viscosity of the CMC solution, It is impossible to increase the solids by more than 8.0 wt%. Subsequently, the solution was maintained at 80 ° C, and 400 ml of a 30 wt% aqueous solution of H ₂ O _{2 was} added dropwise over a period of 8 h. Finally, the solution was stirred at 80 ° C for another 12 h. The pH of the solution was adjusted to 5 with 10% NaOH. Subsequently, the pH was further increased to 9 with a 10% calcium hydroxide solution.

CMC dispersing agent obtained the polydispersity index of 1 to 3.2 (M _w: 9335g / mol and M _n: 2880g / mol) and a pH of 9.0.

Preparation of mineral material suspension using CMC Dispersant 1

An Italian marble powder having a d ₅₀ value of 10 μm was used as the mineral pigment material. A slurry having a solid content of 60% by weight was prepared by mixing 2% by weight of the prepared CMC Dispersant 1 as a 7.8 wt% aqueous solution based on the total weight of the solid in the slurry with a mineral pigment material and water. Subsequently, the obtained mixture was wet-milled at 55 °C. Grinding was carried out for 25 min until the particle size distribution measured on Sedigraph 5100 showed a fraction of 60 wt% less than 2 μm and 36.7 wt% less than 1 μm.

The obtained mineral material suspension has a solid content of 70.9 wt%, a pH of 8.6, and a Brookfield viscosity of 88 mPa. s.

Example 2 - Example of the invention

Preparation of carboxymethyl cellulose (CMC) dispersant 2

285.7 g of water was heated to 80 ° C and 0.009 g of iron sulfate heptahydrate was added. The following chemicals were added over a period of about 165 minutes with stirring at 80 ° C: 12 parts, 12.5 g per part, added every 15 minutes to add 150 g of high molecular weight carboxymethyl cellulose (Aqualon ^® CMC- 12M8P, commercially available from Ashland, USA); at a rate of 0.086 g / min continuous infusion of an aqueous solution of 14.26g 35wt% H ₂ O _2. After the addition was completed, the reaction mixture was maintained at 80 ° C for an additional 4 hours with stirring. Subsequently, the reaction mixture was cooled to 70 ° C, and neutralized to pH 8.6 with an aqueous solution containing 50 wt% of sodium hydroxide and 10 wt% of calcium hydroxide.

The obtained dispersant CMC M _w 2 is 11035g / mol, M _n of 3025g / mol, a polydispersity index of 3.6, and a concentration of the total weight of the solution of 34.5wt% and a Brookfield viscosity meter at 20 ℃ It is 1450mPa. s (100 rpm, rotor 5) and 405 mPa at 60 °C. Solution form of s (100 rpm, rotor 5).

Preparation of mineral material suspension using CMC dispersant 2

Norwegian marble powder having a d ₅₀ of 45 μm was used as the mineral pigment material.

A slurry having a solid content of 70% by weight was prepared by mixing 0.27 wt% of CMC Dispersant 2, which is in the form of a solution prepared by 34.5 wt%, of the solid in the slurry with a mineral pigment material and water. Subsequently, the obtained mixture was wet-milled until the particle size distribution measured on Sedigraph 5100 showed a fraction of 60.5 wt% of less than 2 μm, 35.3 wt% of less than 1 μm and 8.1 wt% of less than 0.2 μm.

The solid content of the pigment particle suspension obtained was 70.9% by weight. The Brookfield viscosity of the suspension obtained after 1 hour of production measured at 100 rpm was 84 mPa. s (rotor N° 2), pH 9.0, and conductivity 567 μS/cm.

After storage for 14 days at room temperature, the Brookfield viscosity before handling was 986 mPa. s, pH 8.6 and conductivity 470 μS/cm. After handling, the viscosity at 3,000 rpm is 509 mPa. s.

Example 3 - Example of the invention

Preparation of carboxymethyl cellulose (CMC) dispersant 3

1421 water was heated to 80 ° C and 0.004 kg of iron sulfate heptahydrate was added. The following chemicals were added over a period of approximately 165 minutes with stirring at 80 ° C: a total of 11 parts, 6.8 kg each, added every 15 minutes to add 74.5 kg of carboxymethylcellulose (Aqualon ^® CMC-12M8P) It is available from Ashland, USA; continuously injects 7.08 kg of a 35 wt% H ₂ O ₂ aqueous solution at a rate of 42.9 g/min. After the addition was completed, the reaction solution was maintained at 80 ° C for an additional 6 hours with stirring. Subsequently, the reaction mixture was cooled to 63 ° C and neutralized to pH 8.1 with an aqueous solution containing 50 wt% of sodium hydroxide and 10 wt% of calcium hydroxide.

CMC dispersing agent obtained by the M _w 3 is 13260g / mol, M _n of 7095g / mol, a polydispersity index of 4.2, and a concentration of the total weight of the solution to 32.2wt% and a Brookfield 100rpm using a rotor 5 of The viscosity is 2000mPa. s and the rotor 6 is 2040 mPa. The solution form of s.

When the CMC concentration is 10wt% based on the total weight of the solution, the Brookfield viscosity of the CMC dispersant 3 solution is 35mPa at 20 °C. s (100 rpm, rotor 2), when the CMC concentration is 25 wt%, the Brookfield viscosity of the CMC dispersant 3 solution is 228 mPa at 20 °C. s (100 rpm, rotor 5) and 245 mPa at 20 °C. s (100 rpm, rotor 3), and at a CMC concentration of 32.5 wt%, the Brookfield viscosity of the CMC Dispersant 3 solution is 610 mPa at 65 °C. s (100 rpm, rotor 5).

Preparation of mineral material suspension using CMC dispersant 3

A Finnish marble powder having a d ₅₀ of 15 μm was used as the mineral pigment material.

The solid content was 70% by weight by mixing 0.26 wt% of CMC Dispersant 3 (which is in the form of a solution prepared by 32.5 wt%) and 0.02 wt% of phosphoric acid with the mineral pigment material and water, based on the total weight of the solids in the slurry. Slurry. Subsequently, the obtained mixture is wet-milled until The particle size distribution measured on Sedigraph 5100 showed a 50 wt% fraction of less than 2 μm and 20.7 wt% less than 1 μm.

The pigment particle suspension obtained had a solid content of 70.4% by weight and a specific surface area (BET) of 4.1 m ² /g. The Brookfield viscosity of the suspension obtained after 1 hour of production measured at 100 rpm was 120 mPa. s (rotor N ° 2; room temperature), pH 9.1.

Example 4 - Example of the Invention

A Finnish marble powder having a d ₅₀ of 15 μm was used as the mineral pigment material, and Dispersant 3 as defined in the above Example 3 was used as the CMC dispersant.

A solid content of 70% by weight was prepared by mixing 0.43 wt% of CMC Dispersant 3 (which is in the form of a solution prepared by 32.5 wt%) and 0.02 wt% of phosphoric acid with a mineral pigment material and water, based on the total weight of the solids in the slurry. Slurry. Subsequently, the obtained mixture was wet-milled until the particle size distribution measured on Sedigraph 5100 showed a fraction of 69 wt% of less than 2 μm and 35 wt% of less than 1 μm.

The pigment particle suspension obtained had a solid content of 70.6% by weight and a specific surface area (BET) of 6.5 m ² /g. The Brookfield viscosity of the suspension obtained after 1 hour of production measured at 100 rpm was 140 mPa. s and pH is 9.2.

Claims (17)

A process for the preparation of an aqueous suspension comprising the steps of a) providing a mineral pigment material, b) providing a depolymerized carboxymethylcellulose having a degree of carboxylation in the range of from 0.2 to 2.2 and a molecular weight in the range of from 5000 g/mol to 40,000 g In the range of /mol and the polydispersity index is in the range of 2 to 10, wherein the depolymerized carboxymethylcellulose is prepared by depolymerizing high molecular weight carboxymethylcellulose in a process comprising the following steps: i) providing a high molecular weight carboxymethylcellulose having a molecular weight greater than 40,000 g/mol and a degree of carboxylation in the range of 0.2 to 2.0, ii) a peroxide selected from hydrogen peroxide and/or an alkali metal salt thereof, iii) a catalyst, iv Mixing at least a portion of the high molecular weight carboxymethylcellulose of step i) and/or at least a portion of the peroxide of step ii) and/or at least a portion of step iii) in any order at a reaction temperature of from 50 ° C to 85 ° C. The catalyst and water, and v) the remainder of the high molecular weight carboxymethylcellulose and/or the remainder of the peroxide and/or the mixture obtained in step iv) in one or more steps Or the remainder of the catalyst until the step The mixture of v) contains from 10% by weight to 60% by weight, based on the total weight of the mixture of step v), of the depolymerized carboxymethylcellulose, and until the Brookfield viscosity of the mixture of the step v) is simultaneously carried out at 20 ° C At 30mPa. s with 10000mPa. Between s, wherein during the step v), the Brookfield viscosity of the mixture measured at the reaction temperature is maintained at 200 mPa. s with 1500mPa. Between s, And c) mixing the depolymerized carboxymethylcellulose of step b), the mineral pigment material of step a) and water to form an aqueous suspension, wherein the amount is from 10% by weight to 80% by weight based on the total weight of the suspension. Adding the mineral pigment material, and adding the depolymerized carboxymethyl cellulose in an amount of 0.05% by weight to 5.0% by weight based on the total weight of the mineral pigment material in the suspension, and allowing the aqueous suspension to be clothed The viscosity is 40mPa at 20 °C. s with 2000mPa. Between s. The method of claim 1, wherein the mineral pigment material is a calcium carbonate-containing material, preferably selected from the group consisting of calcium carbonate, calcium carbonate-containing minerals, mixed carbonate-based fillers, or mixtures thereof. The method of claim 1, wherein the mineral pigment material is kaolin, talc, gypsum, lime, magnesia, titania, satin white, trialumina, tris(a), oxidation Helium, mica or a mixture thereof. The method of any one of claims 1 to 3, wherein the mineral pigment material has a weight median particle size d _{50 of} from 0.1 μm to 100 μm, from 0.25 μm to 50 μm or from 0.3 μm to 5 μm, preferably 0.4 μm. In the form of particles up to 3.0 μm. The method of any one of claims 1 to 3, wherein the degree of carboxylation of the depolymerized carboxymethylcellulose is in the range of 0.5 to 1.8, and preferably 0.6 to 1.4. The method of any one of claims 1 to 3, wherein from 0.05 wt% to 3.0 wt%, preferably from 0.1 wt% to 2.0 wt%, based on the total weight of the mineral pigment material of the suspension. The depolymerized carboxymethylcellulose is added in an amount of preferably from 0.2 wt% to 1.0 wt%. The method of any one of claims 1 to 3, wherein the depolymerized carboxymethyl group The polydispersity index of the base cellulose is from 2 to 5, preferably from 2.5 to 4.5, and more preferably from 3 to 4. The method of any one of claims 1 to 3, wherein the molecular weight of the depolymerized carboxymethylcellulose is in the range of from 8,000 g/mol to 35,000 g/mol, and most preferably from 10,000 g/mol to 20,000 g/ Within the range of mol. The method of any one of clauses 1 to 3, wherein the solid content of the suspension obtained in step c) is adjusted such that it is from 45 wt% to 80 wt% based on the total weight of the suspension. Preferably, it is 50% by weight to 78% by weight, and more preferably 60% by weight to 75% by weight. The method of any one of claims 1 to 3, wherein the catalyst is selected from the group consisting of iron sulfate, sodium hypophosphite, iron phthalocyanine, sodium tungstate or mixtures thereof. The method of any one of claims 1 to 3, wherein 0.1 to 50% by weight, preferably 0.2, of the high molecular weight carboxymethylcellulose (CMC) according to step i) The peroxide of step ii) is provided in an amount of from wt% to 40% by weight, and more preferably from 1% by weight to 30% by weight. The method of any one of clauses 1 to 3, wherein after the step iv) and before the step v), the mixture obtained in the step iv) is measured at the reaction temperature. The viscosity is adjusted to a Brookfield viscosity of 200mPa. s with 1500mPa. Between s, preferably the remaining portion of the high molecular weight carboxymethylcellulose and/or another portion of the peroxide is added to the mixture obtained in step iv) in one or more steps. This remaining portion and/or another portion of the remainder of the catalyst is carried out. The method of any one of clauses 1 to 3, wherein in step v), the high molecular weight carboxymethyl group is added to the mixture obtained in step iv) in one or more steps The remainder of the cellulose and/or the remainder of the peroxide and/or the reminder The remainder of the agent up to step v) comprises from 25 wt% to 45 wt%, preferably from 30 wt% to 40 wt% of the depolymerized carboxymethylcellulose, and/or up to the total weight of the mixture of step v) The mixture of step v) has a Brookfield viscosity of 50 mPa at 20 ° C. s with 5000mPa. Between s, preferably at 1000 ° C at 20 ° C. s with 3000mPa. Between s, and the best at 20 ° C between 1500mPa. s with 2500mPa. Between s. An aqueous pigment particle suspension obtainable by the method of any one of claims 1 to 13. A pigment granule obtainable by drying the aqueous pigment particle suspension as in claim 14 of the patent application and optionally treating the dried granules. A use of the aqueous pigment particle suspension of claim 14 in paper, plastic, paint, food, feed, pharmaceutical, drinking water and/or agricultural applications. A use of pigment granules as claimed in claim 15 for use in plastics, paints and/or sealants.