FI123642B - Process for forming a pigment product of a cellulose derivative, pigment product and its use - Google Patents

Abstract

The invention relates to a process for producing a pigment product from a cellulose derivative. According to the invention, a selected cellulose derivative containing at least one OH group is crosslinked by using a hydroxyl-active crosslinker to form a substantially insoluble pigment product. Further, the invention relates to the corresponding product and to the use of the product.

Description

METHOD FOR FORMING A PIGMENT PRODUCT

SE LULOSE DERIVATIVES, PIGMENT PRODUCTS AND ITS USES

FIELD OF THE INVENTION

The invention relates to a process for forming a pigment product from a cellulose derivative as defined in the preamble of claim 1, to a pigment product as defined in the preamble of claim 14 and to the use of 10 pigment products as defined in the preamble of claim 15.

BACKGROUND OF THE INVENTION

Various cellulose derivatives and methods for their preparation are known in the art.

In addition, various pigments and fillers of mineral and organic origin and methods for their preparation are known in the art. It is known in the art to form organic pigments from starch based materials and from 20 pure cellulose. In this case, the pigment will usually be in admixture with another substance or dispersion. In addition, it is already known to make organic pigments from oil-based materials.

By replacing mineral fillers and prj coating pigments with substances of organic origin, either partially or completely, the environmental load can be reduced. By using q fillers of organic origin or pigment

C/O

For example, in paper making, paper recycling is more efficient and the de-inking sludge is easier to recycle or to dispose of. This makes it possible to use the spent fire, for example in the production of biofuels. In addition, in typical cases, organic

C \ J

35, and organic pigments can improve the smoothness of the paper surface during calendering.

The problem with oil-based organic pigments is the price that follows oil price developments, and the high cost of production.

Known organic pigments based on starch and made from pure cellulose often have the problem of their complexity due to the many manufacturing steps involved and hence the low level of industrial production.

PURPOSE OF THE INVENTION

It is an object of the invention to provide a novel process for the preparation of a pigment product from a cellulose derivative. A further object of the invention is to provide an industrially usable manufacturing process for the industrial production of a cellulose-based pigment product.

SUMMARY OF THE INVENTION

The process of the invention and the Pigment product are characterized by what is claimed.

The invention is based on a process for preparing an organic pigment product from a cellulose derivative. According to the invention, a selected cellulosic acid derivative containing at least one OH group is crosslinked by means of a hydroxylactive crosslinking amine to form a pigment 30 having a substantially insoluble porous structure. The pigment product may be in the form of particles, a cluster of particles, a dispersion or a foam

DC

in terms of.

cS The invention is specifically based on cellulose and its

LO

o, for further processing of the derivative to a higher processing grade.

C \ l 3

As used herein, a pigment product is a material or substance that imparts a color or other optical property to a substrate or surface. The pigment may be translucent or opaque.

In one embodiment of the invention, the pigment product formed is ground to microparticles. Microparticles as used herein refer to particles of the micro- and nanoscale size, preferably less than 50 µm, more preferably less than 10 µm. Par-10 blocks may be of any shape, e.g. spherical.

In one embodiment, microparticles are formed substantially during the manufacture of the pigment product. In one embodiment, the micro-particles are formed substantially after the preparation of the pigment product.

By grinding, as used herein, is meant any grinding, comminution, crushing or disintegration of material to a desired particle size. The operation of the grinding devices, preferably of the mills, is typically based on applying pressure, cutting, rubbing, compressing and / or impacting the blow caused by the blow or the like. Most of the mills work in combination with the use-25 principle.

The milling may be carried out by any suitable method known per se. In one embodiment, the pigment product is milled by air jet milling, preferably by air jet mill.

\ l S5 30 In one embodiment, the milling is done by Cryo oo milling. Grinding can be done wet or

Er dry and ground.

CL

In one embodiment of the invention, the cellulose derivative is a cellulose ether. In one embodiment, the cellulose derivative of m 35 is hydroxypropyl cellulose or HP (HPC). In one embodiment, the cellulose derivative is selected from hydroxyethylcellulose and carboxymethylcellulose. In a preferred embodiment, the cellulose derivative is selected to be water soluble. In one embodiment, the cellulose derivative has a substantially high molecular weight. The cellulose derivative may be a mixture of several cellulose compounds. The cellulose derivative may contain small amounts of non-cellulose-based compounds.

In one embodiment of the invention, the crosslinking agent is selected from divinylsulfones, dianhydrides, dialdehydes, formaldehydes, glyoxal, diisocyanates, ethylene glycol diglycidyl ether, oxalic and citric acids, and inorganic salts, e.g. The solubility of the cellulose derivative can be adjusted by means of crosslinking agents. The crosslinking agents are preferably selected so as to provide a substantially insoluble, preferably water-insoluble, pigment product with the cellulose derivative.

In one embodiment of the invention, the crosslinking agent is used in an amount of 4 to 15% by weight based on the amount of cellulose derivative 20.

In one embodiment of the invention, the crosslinking reaction is activated by at least one activator selected from heat, pH, catalyst, drying and radiation. In one embodiment, catalyst 25 is an aluminum sulfate catalyst. In one embodiment, metal catalysts such as inorganic co-salts of aluminum, magnesium and zinc may be used as the catalyst. In an alternative embodiment, as a catalyst

CM

, acid catalysts can be used, especially diald-? 30 for hydraulic and glyoxal crosslinkers.

In one embodiment of the invention, my cellulose derivative is dissolved in the selected solvent before crosslinking, in a preferred embodiment water.

S) Any suitable solvent may be used as the solvent. The combination of cellulose derivative and solvent is in the form of a solution, slurry, suspension or dispersion. In one embodiment, the solution of cellulose derivative 5 or the like has a solids content of less than 10% by weight.

In one embodiment, the crosslinking agent may be in liquid form and may be dissolved in a suitable solvent, e.g. water or ethanol.

In one embodiment of the invention, the cellulose is added to the derivative before crosslinking. The surfactant may be selected from the group consisting of dispersants, nonionic and anionic surfactants. In another embodiment, another suitable and required additive is added to the cellulose derivative.

In one embodiment of the invention, the foam structure of the porous pigment product, preferably light scattering, is formed by foaming, e.g., by vigorous mixing. In a preferred embodiment, the foam structure formed is stabilized, e.g., by cross-linking. In one embodiment, the crosslinking agent is added during the foaming step of the cellulose derivative. In one embodiment, the crosslinking agent is added during the structure stabilization step. In one embodiment, the crosslinking agent is added to the cellulose derivative prior to foaming. In one embodiment, the cellulose derivative is heated to provide a foam. The flotation 25 may be chemically and / or mechanically performed.

In one embodiment of the invention, the pigment product formed is dried. In one embodiment, the drying is carried out at a temperature of 70-100 ° C, more preferably at a temperature of about 80-90 ° C. Final cross-linking? 30 may occur during drying. At the latest during the drying of the pigment product, the crosslinking produces water-insoluble bonds between the polymer chains.

CD

S) In a preferred embodiment, grinding is carried out after drying, o cvj In one embodiment of the invention, a pigment product formed by heat curing.

6

Furthermore, the invention is based on a pigment product formed in one of the above-described ways and its use. The resulting pigment product may be used for surface treatment, such as coating and coating, of a substrate, such as paper, and / or as a filler for a substrate, such as paper.

The pigment product of the invention and the process for its manufacture can be used in the paper industry, e.g. fine papers, newsprint, printing papers and tissue papers, cosmetics industry, e.g.

As used herein, "paper" means any fiber-based paper or fiber product, or the like. The paper may be formed from pulp, mechanical pulp, chemimechanical pulp, recycled pulp and / or mixtures thereof, or the like. The paper may contain suitable fillers and additives, as well as various surface treatment and coating agents. The paper may be in the form of a sheet or sheet or other suitable form.

The pigment product formed according to the invention can be used either alone or in admixture with other substances in various pigments, pigment precursors, mixtures, compounds or the like.

9 * 30 The pigment product formed according to the invention or its particles can be modified, e.g. g by crosslinking and functionalization as required for the intended use. The product is provided with various functional properties. The properties of the product can be tailored, for example, to opacity, brightness, printing properties and oil absorption. The product can also be used as an additive or excipient for a variety of applications.

The invention provides an excellent industrially applicable way of producing an organic pigment-5 product.

The process of the invention provides a porous pigment product having a specific gravity lower than the previously known mineral based pigments.

A further advantage of the pigment product according to the invention is its recyclability. Thus, waste problems can be reduced.

The pigment product of the invention can be used in novel types of paper applications where the low specific gravity of the raw materials imparts new functional properties to the end product, such as paper, and improves cost-effectiveness in the product supply chain from manufacturer to customer.

DETAILED DESCRIPTION OF THE INVENTION

The invention will be described in more detail by the following example.

Example 1 This example investigated the cross-linking of commercial hydroxypropyl cellulose (HPC) and the preparation of the pigment product of the invention.

g Two commercial hydroxy-30 cipropyl cellulose 50/50 mixtures were used in the experiments; a) Klucel H (Mw 00 = 1150000, solution = 1% in water, viscosity = 1275 - x 3500 mPas) and b) Klucel M (Mw = 850000, solution = 2% in water, viscosity = 3500-7500 mPas).

to Hydroxypropyl celluloses were crosslinked in νέο 35 silica solution with glyoxal. Samples Prepared-

C \ J

in doses of 10-50 g. The aqueous solution was prepared by first mixing 50 g of the HPC powder mixture with hot water at a temperature of about 50-60 ° C at a solids content of 8 wt%. The homogenized dispersion was diluted in cold water (about 5-10 ° C, pH 4-5) under constant-5 mixing to give a final solids content of the resulting aqueous solution of 5% by weight. To the solution was added glyoxal solution (40 wt% in water), a few drops of surfactant (TISKO, Farmos) and aluminum sulphate catalyst at room temperature under vigorous mixing in a 10 wing type mixer to ensure sufficient air supply to the product formed. Glyoxal was added in an amount of 10% by weight of HPC and a catalyst was added in an amount of 5% by weight of HPC. The resulting product was in foam-like form.

The resulting foam product was dried in an oven at 90 ° C to remove water and provide a water insoluble foam structure. The short residence time of the product in contact with the leaving aqueous phase reduced the formation of the film 20 and the softening of the structure of the foam product, which improved the quality properties of the product.

Highly substituted, high molecular weight hydroxypropyl cellulose is a nonionic, cold water soluble derivative that forms a gel-like medium at elevated solution temperature and is reconstitutable during cooling. In the reaction, a hydroxyl-active glyoxal crosslinker

C/O

g produces a water-insoluble stable foam structure.

The dried HPC glyoxal foam structures were ground into microparticles in an air jet mill at a classifier speed of 10,000 rpm. The microparticles had 0-particle sizes in the range of 2 to 100 µm, and an average of 5 to 25 µm.

LO,, g 35 It was found that with lower amounts of cellulose derivative, 4-5% by weight of crosslinker could be used based on the amount of HPC. The relatively high solution viscosity of the cellulose derivative positively influenced the foaming.

In the experiments it was found that the pigment product formed serves both pigment and filler application purposes.

Example 2 This example investigated the cross-linking of commercial hydroxypropyl cellulose (HPC) and the preparation of the pigment product of the invention.

Commercial hydroxypropyl cellulose Klucel G (Mw = 370000, solution = 2% in water, viscosity = 125-450 mPas) was used in the experiments.

Hydroxypropylcellulose was crosslinked in aqueous solutions with methyldiphenyl diisocyanate (MDI) using different concentrations of crosslinker. Samples were prepared in portions of 5 to 10 g. The aqueous solution was prepared by first mixing 5/10 g HPC powder with hot 20 water at about 50-60 ° C, with a solids content of 8 wt%. The homogenized dispersion was diluted in cold water (about 5-10 ° C, pH 7) under constant stirring to give a final solids concentration of 6% by weight in the resulting aqueous solution.

To the solution was added MDI solution (about 30 wt% in ethanol) with either 50, 30 or 10 wt% of HPC and a few drops of surfactant (TISKO, Farmos) at room temperature in a snip type under vigorous agitation to ensure sufficient air supply to the resulting product. The resulting product was in a foamy form, ί The foam formed was dried in an oven.

CL

at 90 ° C, whereby the water was removed and a S) water insoluble foam structure was obtained. The reaction of MDI in the presence of cos § 35 caused active bubble formation during drying which retained its fine porosity in the dried foam structure. At all the concentrations used in MDI 10, the dried foam structures were opaque white, very brittle and porous, thus improving the quality of the product. Reaction of HPC with the hydroxyl active-5 diisocyanate crosslinker produces a water-insoluble stable foam structure which is comminutable to particles.

By the immersion liquid method, the refractive index of the particles of the HPC-MDI foam structure was estimated to be between 1.50 and 1.55, and thus higher than that of the corresponding untreated HPC (1.45 to 1.50).

The process according to the invention is suitable for use in various applications for the manufacture of a wide variety of pigment products.

The invention is not limited to the above example only, but many modifications are possible within the scope of the inventive idea defined by the claims.

20

C/O

δ c \ j cp o

C/O

X

DC

CL

CD

C \ 1

LO

LO

C/O

O

O

C \ 1

Claims (15)

A process for preparing a pigment product from a cellulose derivative, characterized in that the selected cellulose derivative containing at least one OH group is crosslinked to form a pigment product having a substantially insoluble porous structure by means of a hydroxyl active crosslinking agent. Process according to claim 1, characterized in that the pigment product formed is milled to microparticles. Process according to claim 1 or 2, characterized in that the cellulose derivative is a cellulose ether. Process according to one of Claims 1 to 3, characterized in that the cellulose derivative is hydroxypropyl cellulose (HPC). Process according to one of Claims 1 to 4, characterized in that the cellulose derivative is selected from hydroxyethylcellulose and carboxymethylcellulose. Process according to one of Claims 1 to 5, characterized in that the crosslinking agent is selected from divinylsulfones, dianhydrides, dialdehydes, formaldehydes, glyoxal, diisocyanates, ethylene glycol diglycidyl ether, oxalic and citric acids. Process according to any one of claims 1 to 6, characterized in that the crosslinking agent is 4 to 15% by weight of the cellulose derivative. x A process according to any one of claims 1 to 7, characterized in that the crosslinking reaction is activated by at least one activator selected from heat, pH, catalyst, drying and radiation. Process according to one of Claims 1 to 8, characterized in that the cellulose derivative is dissolved in the selected solvent before crosslinking. Process according to one of Claims 1 to 9, characterized in that a surfactant is added to the cellulose derivative before crosslinking. A process according to any one of claims 1 to 10, characterized in that the pigment product formed is dried. Process according to one of Claims 1 to 11, characterized in that the pigment product formed is heat-cured. A process according to any one of claims 1 to 12, characterized in that the selected cellulose derivative is crosslinked with an hydroxyl active crosslinking agent in an aqueous solution under vigorous mixing and the resulting product is dried to form a pigment product having a porous foamy structure. 14. Cellulose-based pigment product, characterized in that it is formed by a process according to any one of claims 1 to 13. Use of a pigment product formed by the process according to any one of claims 1 to 13, characterized in that the pigment product formed is used in the surface treatment of the substrate and / or in the fillers. 9 30 o co x IX Q. CO C \ J m m co o o C \ J PATE N TKRAV