DD233388A5 - METHOD FOR PRODUCING FIBROUS MATERIAL FROM PRINTED COLOR-POLLUTED RECYCLED CELLULOSE MATERIAL AND PREPARING FOR IMPLEMENTING THE METHOD - Google Patents

Abstract

According to the invention, the material is macerated in an aqueous dispersion which contains sufficient amounts of a liquid non-fiber-forming resin precursor which can be hardened in the dispersion in order to facilitate the subsequent removal of printing ink and to leave the resin precursor during the process Macerierens harasses.

Description

Field of application of the invention :

The invention relates to a process for the production of pulp from recycled cellulose material contaminated by printing ink and to a preparation for carrying out the process.

Characteristic of the known technical solutions:

An increasing amount of cellulosic fibrous material for the paper industry is made from recycled waste cellulosic material, particularly virgin fiber rewoven newspaper paper and magazine paper. Fiber material containing one or other of these wastes is usually contaminated with pigments derived from the printing ink which must be removed to obtain a fiber material of adequate brightness.

Typically, pigment particles are removed by froth flotation using the surface active agents naturally present in the pulp to promote foaming or, less commonly, extraneous surfactants and / or foam promoters as additives. An alternative is to use various solvents and / or surfactants to wash out the pigment from the pulp. None of these methods has been found to be able to sufficiently remove ink to achieve maximum viable brightness of the pulp.

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In an attempt to improve the degree of separation of the ink, various proposals have been made to agglomerate or adsorb the ink onto relatively large particles that are more easily separated by flotation or even by centrifugation or sieving. However, all of these proposals had serious drawbacks that prevented their large-scale implementation despite the generally accepted inadequacy of conventional washing and flotation technology.

State of the art :

French Patent 1,379,252 and U.S. Patent 3,377,234 describe the addition of surfactants to the pulp liquor prior to making the pulp slurry. In this case, however, the ink is not completely separated. U.S. Patent Nos. 4,013,505 and 4,147,616 disclose the precipitation of calcium soap in the slurry C (pulper) vessel to adsorb the ink, after which the resulting island is separated by centrifugation. This procedure is only partially successful.

U.S. Patent Nos. 3,846,227 and 3,963,560 describe the use of N-cyclohexylpyrrolidone as a solvent in the slurry pulping stage to promote the removal of the ink. The process requires relatively high temperatures of about 73 C, which increases the energy cost of the process and causes unacceptable solvent losses.

In British Patent Specification 2,080,354 it has been proposed to add polymers to the pulp at temperatures above their softening point to remove sticky substances from the recycled pulp. High temperatures are needed and effective removal of the ink is not achievable.

Explanation of the essence of the invention :

Waste paper pulp is a chemically and physically complex system that is highly variable in unpredictable ways. Little is known about the mechanism by which known methods of ink removal work. The possible solutions to the technical problem have so far been mainly empirical.

It was therefore investigated to find reasons for insufficient work of the prior art methods.

By far the major amount is pigment which is present in the pulp recycled paper and the amount which has the greatest effect on the brightness of the finished pulp, carbon black, which is also one of the non-steerable fabrics in terms of ink removal methods. The following discussion of the problem speaks in particular of soot. However, the comments are generally applicable, including to other pigments.

It is believed, without it being understood that carbon black is present in the ink, and more particularly in newsprint, in the form of particles that are poorly trapped in an oily matrix. During pulp recovery, it is believed that this matrix disintegrates and peels off small particles that are incorporated into the fibril surface of the fibers. It is believed that the particles, once entrapped, are particularly difficult to remove by known ink removal technologies.

It has now been found that substantially improved ink removal can be achieved by pulping slurry of waste paper in an aqueous suspension of a non-fiber bulking room temperature vulcanizable resin and curing the resin in situ. It is believed that, according to the present invention, any pigment particles are rapidly coated with uncured or partially cured resin, which inhibits disintegration and subsequent re-incorporation into the cellulosic fibers, and which upon curing gives rise to the particles forming agglomerates which are relatively resistant to comminution and are separable from pulp by conventional means such as washing, flotation, centrifuging or sieving.

In one embodiment, the invention provides an aqueous dispersion of at least one liquid non-fiber reactive resin precursor which is curable in aqueous dispersion and a sufficient amount of a curing catalyst to effect curing of the formulation in the dispersion.

Preferably, the formulation contains a dispersant for the resin precursor. It was further found that the proportion of the curable. Resin needed can be significantly reduced by admixing an inert extender or diluent, which can increase the economics of the process.

According to a second embodiment, therefore, the invention provides a preparation consisting of 10 to 85% by weight of a liquid, non-fibering H-precursor which is curable in aqueous solution and at least 5% by weight, based on the preparation of an inert, non-fiber liquid diluent and an effective amount of a dispersant for the formulation.

In another embodiment, the invention provides a process for producing pulp from recycled cellulosic material contaminated with printing ink, characterized in that the material is macerated in an aqueous dispersion containing sufficient amounts of a third, non-fibering resin precursor which is curable in the dispersion to facilitate subsequent ink removal and to cure the resin precursor during maceration.

The resin precursor

The resin precursor according to the invention may be any non-fiber based liquid which is curable in aqueous suspension, preferably in aqueous alkaline suspension. In particular, it is desirable that the resin precursor is curable at temperatures below 50 ⁰ C and preferably at room temperature. The resin precursor is preferably a sufficiently hydrophobic material that is not readily adsorbed onto the cellulosic fibers, but is conveniently compatible with the ink. Typically, the resin precursor comprises a mixture of a liquid prepolymer having at least two reactive functional groups per molecule and a crosslinking agent capable of reacting with the functional groups, at least in the presence of a suitable catalyst. Where the polymer system is capable of curing in the pulper in the absence of a catalyst, the resin precursor is usually formed in situ, with the crosslinking agent being added to the prepolymer at or just prior to addition to the pulper.

Most preferred is a resin which is a room temperature vulcanizable organopolysiloxane. Particularly suitable are mixtures of a dihydroxy-poly (dialkylsiloxane) polymer with a poly (alkylhydrosiloxane) crosslinking agent. Preferably, the alkyl groups are in each case lower alkyl groups (e.g., alkyl groups of 1 to 4 carbon atoms), typically methyl groups. An alternative curable resin system for compounding according to the invention comprises an oligomeric hydroxyacrylate prepolymer crosslinked with a diisocyanate, e.g. a sthylacrylate resin mixed with 1,6-hexamethylene diisocyanate.

Typically, the prepolymer has an average molecular weight of from 100 to 70,000, preferably from 10,000 to 50,000, e.g. 30,000 to 40,000. Prepolymers having molecular weights in a wide range, e.g. a mixture of a short chain prepolymer having a molecular weight of 3,000 to 12,000 and a long chain prepolymer having an average molecular weight of 50,000 to 70,000.

The crosslinking agent typically has an average molecular weight of 1,000 to 5,000. Typically, the crosslinking agent is present in an amount of 1:10 to 10: 1, preferably 1: 2 to 2: 1, and most preferably 3: 4 to 4: 3, e.g. 1i1, based on the weight and on the difunctional polymer.

The dispersant

Any surfactant or dispersant which is water-soluble or miscible with it and which is also miscible with the relatively hydrophobic resin precursor can be used. Examples of organopolysiloxane resin precursor dispersants are nonionic surfactants such as polyalkoxylated organopolysiloxanes, e.g. a poly (dimethylsiloxane) -poly (ethylene glycol) ether and polyethoxylated sorbitan monoalkanoates, as well as cationic surfactants. Anionic surfactants are less preferred.

However, particularly preferred are film-forming dispersants and in particular polymeric protective colloids such as polyvinyl alcohol, carboxymethyl cellulose, polyvinylpyrrolidone or cellulose acetate.

The amount of dispersant is sufficient to form a stable dispersion for the resin precursor in water, amounts above the minimum needed to disperse the resin precursor are preferably avoided for economic reasons, typically the amount of dispersant is 0.1 to 20% by weight of the resin precursor is present, for example, in an amount of 3 to 7 % It does not preclude the possibility of dispersing the resin precursor without dispersant or the dispersant effect of normal components of the pulp which happen to be present in the pulper , to use.

The diluent

The diluent is optionally present in any proportion up to about 95 percent by weight of the formulation, preferably in an amount of from 5 to 90 percent by weight, e.g. 55 to 80 percent by weight, in particular 65 to 75 percent by weight.

The diluent may be any inert oil that is sufficiently hydrophobic not to grow on fibers and to be miscible with the resin precursor. Typical examples of diluents include methyl-terminated polydimethylsiloxanes and hydrocarbon oils. The diluent is preferably sufficiently liquid to render the formulation pourable, but sufficiently viscous to provide effective protection of the ink particles in the furnish to prevent comminution and / or entrapment in early stages of fiberizing and to ensure that the product is ready for use mechanically strongly hardened agglomerate is formed.

The catalyst

The catalyst may be any catalyst capable of catalyzing the curing of the resin precursor in aqueous suspension, preferably at room temperature.

Preferably, the two alkyl groups are lower alkyl groups with, for example, 2 to 4, preferably 4 carbon atoms and the two alkanoyl groups have 2 to 20 carbon atoms, preferably 8 to 14, eg dibutyltin bis (ethyl hexonate) or dibutyltindilaurate.

The activity and volatility of the catalyst increase with increasing carbon number of the alkanoyl groups. A catalyst is preferred which is sufficiently active to cure the resin prefler fully within the normal pulp production period, e.g. within 15 to 40 minutes. More active catalysts, e.g. Dibutyltin diacetate are less preferred, although they work as well.

The catalyst may be present as a solution in an organic solvent such as trichlorethylene, but it is preferred to use emulsions of the water-based catalyst which are commercially available and have been found to have better activity in the aqueous pulp liquor.

In general, it is believed that the brightness of the pulp reaches a maximum after completion of the curing period and may subsequently decrease as the pulping is continued. It is therefore preferred catalysts that give a curing time, which are approximately equal to the pulp production time, and not those that result in virtually complete curing in an early stage in Aufschlä mmungsprozeß.

A catalyst is preferably used, even in systems capable of curing in the absence of a catalyst at temperatures attained in the pulper, although this is not critical to the invention.

The pulp liquor

Preferably, the resin precursor is dispersed in water in the presence of the catalyst (or added crosslinking agent when no catalyst is needed) and allowed to cure for a short period of time, eg, 10 seconds to 5 minutes, preferably 0.5 to 1 minute and at a pH of 10 to 10 minutes. Value of preferably 8 to 12 before the waste cellulose is added. Typically, the pre-cure is 1 to 10% of the total cure time. Preferably, the resin precursor is used in an amount of 0.1 to 10 %, based on the weight of pulp solid, preferably in an amount of 1 to 5% eg 1.5 to 4%.

The catalyst may be present in an amount of 0.1 to 50 %, based on the weight of the resin precursor, preferably 0.5 to 20 %, eg 1 to 10 % .

The pulp liquor is preferably alkaline. Typically, the pulp content should be at a pH of 8 to 12.5, e.g. from 9 to 10 have. This can be achieved using e.g. of sodium hydroxide, sodium carbonate, sodium silicate or mixtures thereof. The resin precursor and the catalyst may be suspended directly in the pulp liquor or, alternatively, a more concentrated suspension may be prepared and added to the pulp liquor just prior to production.

The pulp production

The furnish for the pulp may consist of newsprint and / or magazine paper and / or other ink-contaminated cellulosic waste. The feed preferably comprises a mixture of newsprint and magazine paper, which may for example consist of 10 to 60% by weight of magazines. However, the process is feasible with 100 % newsprint, a feed that is particularly difficult to satisfactorily remove ink from available technology. The waste paper is macerated with the pulp liquor for a period of 10 to 60 minutes, preferably 15 to 40 minutes, at a temperature typically in the range of 5 to 60 C, preferably 20 to 50 ⁰ C, for example 35 ⁰ C. can. The pulp may contain 2 to 25 % solids and usually 5 to 15 % solids.

sequestering agents

It has been found that the brightness of the pulp, freed from ink according to the invention, can be substantially increased by the presence of a sequestering agent in the pulp liquor for alkaline earth metals and especially for calcium, e.g. by ethylenediaminetetraacetic acid or by phosphates, condensed phosphates or phosphonates, in particular sodium tripolyphosphate or by silicates. This is a preferred aspect of the invention. It is preferred that the sequestering agent should be in amounts up to the stoichiometric amount, based on total alkaline earth metal sequesterable ions present in the pulp.

Various accessories

It is desirable that the cured resin particles have such a physical form that they are easily separable from pulp. You can e.g. differ substantially in their density from the aqueous medium, preferably be substantially lighter to facilitate separation by centrifugation, or they can be of sufficient size to permit efficient screening. The former can e.g. by selecting a low density extender or by incorporating a blowing agent into the resin precursor. The latter can be achieved by a volatile liquid such as a fluorocarbon vaporized by the exothermic curing reaction to form expanded particles.

Alternatively, either size or density can be controlled by adding solid particles or granules of polymer. Preferably, the particles are made of a low density material such as expanded polystyrene and / or are of sufficient size to be separable by sieving. They preferably have a surface on which the resin precursor and the pigment readily coagulate.

In particular, it has been found that separated coarser particles, either of an added polymer having surface-agglomerated ink or the cured agglomerated resin itself, can be advantageously recycled to the pulper to achieve more complete separation of the agglomerated ink.

Thus, according to another embodiment of the invention, recycled cellulosic material contaminated with ink is reslurried in a pulper in the presence of a dispersed curable resin which does not wick to the cellulose but draws on the ink under conditions so controlled. curing of the resin and agglomeration of the ink are thereby effected. The pulp is withdrawn from the pulper and the hardened resin is separated from the pulp and part of the cured resin is returned to the pulp.

Surfactants, foam stabilizers or anti-foaming agents may be added to the pulper or subsequently to the promotion or control of the foaming.

Separation .

The coagulated ink can be separated from the pulp using the known procedures, depending on the physical form of the cured particles.

The particles can be separated using conventional foam flotation. If necessary, foam conveyors and / or inhibitors may be added to the pulp to adjust the degree of foaming. Alternatively, the agglomerated ink can be removed by washing e.g. can be removed by dewatering and wetting the pulp.

If the particles have sufficient density differences from the pulp, they can be separated by centrifuging, while sufficiently large particles can be separated by sieving.

Typically, the pulp is diluted to a solids content of less than 2% by weight and sieved to remove large particles. Any ink containing particles remaining in the pulp can then be separated by washing, centrifuging and / or flotation.

The invention is illustrated by the following examples:

Examples

Unless otherwise stated, the following conditions are used in the examples:

Resin precursor:

50% by weight of hydroxy-functional polydimethylsiloxane 45% by weight of Si-H functional polydimethylsiloxane prepolymer 5% by weight of polyethyleneoxy-2-polypropyleneoxy-functional polydimethylsiloxane.

Pulper consistency: 4 %

initial pH in the pulper: 10.5

initial pulper temperature: 30 ^° C.

Slurry time: 25 min.

Resin addition: 2% by weight, based on fibers

Addition Method: Resin mixture is added to water and dispersed prior to addition of the fiber, caustic soda and catalyst.

Feeding: 100% newsprint

example 1

Using 0.2% by weight, based on fibers, of sodium dibutyltin dilaurate as a catalyst in a laboratory experiment, a pulp brightness of 49 % was measured, compared to 41 % in the absence of the resin.

Example 2

Example 1 was repeated using 100% magazine paper instead of newsprint. The brightness of the pulp from the pulper was 57 % compared to 54 % in the absence of the resin.

Example 3

Example 1 was repeated using 50 % newsprint, 50 % magazines as feed. The brightness of the pulp from the pulper was 52 % as compared to 47 % in the absence of the resin.

Examples 4-6

Using 1.5% by weight, based on fibers, of different catalysts, the following results were obtained:

No resin - 45 % brightness

Example 4 - Dibutyltin diacetate: 55.5 % brightness Example 5 - Dibutyltin dilaurate: 56.5 % brightness Example 6 - Dibutyltin bis (2-ethylhexanoate) (in.

Ethanol) 58 % brightness

Example 7

Figure 1 illustrates the change in pulp brightness over time in a papermaking trial using dibutyltin diacetate as catalyst with 1 ton of newsprint at a consistency of up to 15 %. The lower curve is a comparative experiment without added resin. The middle curve was measured with 2 % resin and 0.25 % catalyst by weight of fiber, and the upper curve was made with 4 % resin and 0.5 % catalyst by weight of fiber.

Example 8

Figure 2 shows the effect of changing temperature of 6 runs using "4 % resin and 1.5% by weight dibutyltin diacetate, based on fiber weight.

Example 9

Figure 3 shows the effect of increasing resin concentration using 1.5% by weight dibutyltin diacetate, based on fiber weight.

Example 10

Example 1 was repeated with the addition of expanded polystyrene beads of 1 to 10 mm diameter to the dispersed resin precursor just prior to the addition of the fiber. The beads were easily separated from the pulp and provided a significant improvement in agglomeration and ink separation. Optimal results were obtained with 1 to 2 mm beads. The separated beads were returned to the pulper and the experiment repeated. The recycled beads gave a substantially equivalent improvement in the agglomeration of the ink as compared to that achieved by the original non-contaminated beads.

Example 1 "i

Example 1 was repeated. Particles of agglomerated ink were separated from the pulp and 50 % of the separated particles were returned to the pulp = and the example was repeated again. In the second run, improved agglomeration and easier separation were observed.

Example 12 and 15

An acrylic resin precursor was used in Examples 12 and 13 having the following composition:

% By weight of substance · function carrier name

65 % hydroxyethyl prepolymer 50 % in "DURASOL" acrylate-butyl acetate

30 Hexamethylene Crosslinker Xylene "DESMODUR" N75 1,6-diisocyanate

5 ethylene glycol / dispersing "GLYCOI / 'B"

Propylene glycol-hydroxymethylsiloxane copolymer

This was compared with the silicone resin precursor of Example 1 as follows:

Example 12

Feed 100 % Newspaper Catalyst Dibutyl Azide Dilaurate (1 % on fiber addition)

Brightness R 457 Only lye Ex-pulper final wash 3 % acrylate / lye 37 49 2 % silicone / lye 45 51 1/2 Example 13 47 55 1/2

Loading 50/50 newspaper / magazines

Catalyst Dibutyltin dilaurate (1 % on fiber addition)

Brightness R

457 Ex-pulper after flotation

Only lye 50 54 1/2

2 % Acrylate RTV / Lye 52 63 1/2

2 % silicone RTV / lye 56 62

Example 14

To illustrate the effects of including a non-functional extender in the resin, Example 1 was repeated with the addition of various amounts of methyl-functional polydimethylsiloxane to the reactive prepolymer, with the following results:

% By weight of reactive prepolymer Ex pulper brightness

95 51.5 45 51.8 25 51.9 10 50.0 Comparison ( no resin) 40.7 Example 15

A prepolymer emulsion was prepared as follows:

DihydroxypolyCydimethylsiloxane) η = 49-144

(average MW = 7566) -10g

Dihydroxypoly (dimethylsiloxane) η = 850

(average MW = 63066) 40 g

Poly (methyl hydrosiloxane) η = 40

(average MW = 2562) 45 g

5% aqueous solution of polyvinyl alcohol 165 g

A catalyst emulsion with 33 wt% solids was prepared separately:

Dibutyltin dilaurate 60 g

Polyvinyl alcohol 7 g

V / asser 133 g

There were added 1900 ml of water and 6 g of prepolymer emulsion (1% resin by weight of fiber) in a pulper with 13 ml of concentrated sodium hydroxide solution and 0.3 ml of catalyst emulsion (0.05 % by weight of fiber) at room temperature for 30 seconds stirred as a precure period. 2.36 g of newspaper waste was added and a pulp with a consistency of 11 % was produced.

After 25 minutes of slurrying, the pulp was washed and compared to a comparative run using only sodium hydroxide solution.

Ex pulper brightness brightness after

To wash

Comparison 36.5 42.8

Example 15 46.3 51

Claims (28)

-Ι, Λ - claims 1. Process for the production of pulp ·. reclaimed cellulosic material contaminated with printing inks, characterized in that the material is macerated in an aqueous dispersion containing sufficient amounts of a liquid, non-fibering resin precursor which is curable in the dispersion for subsequent removal of To facilitate printing ink and hardening the resin precursor during Macerierens. 2. The method according to item 1, characterized in that one prepares an aqueous dispersion according to item 1 and allowed to cure the dispersion for up to 20 minutes before the addition of the cellulosic material. 3. Process according to item 1 and item 2, characterized in that the resin precursor is used in an amount of 0.1 to 10% by weight, based on the weight of pulp solid. 4. Method according to items 1 to 3, characterized in that one uses a dispersion having a pH of 8 to 12.5 during Macerierung. 5. The method according to items 1 to 4, characterized in that the cellulose material in a pulp lye 10 to 16 minutes, at a temperature of 5 to 60 ⁰ C with a solids content of 2 to 25 % macerated. -Z 2. - 6. The method according to the items 1 to 5, characterized in that one uses a fiber pulp containing a sequestering agent for calcium ions. 7. The method according to points 1 to 6, characterized in that the pulp liquor contains a blowing agent. 8. The method according to points 1 to 7, characterized in that the pulp contains solid polymer particles. A process for the production of pulp using recycled cellulosic material contaminated with ink reslurried in a pulper in the presence of a dispersed hardenable resin which does not draw on the cellulose but draws on the ink under conditions which to effect curing of the resin and agglomeration of the ink, further pulp being withdrawn from the pulper, and hardened resin being separated from the pulp and part of the hardened resin returned to the pulper. A composition for use in the process of items 1 to 9 for facilitating the removal of ink from recycled waste cellulosic fibrous material, characterized in that it consists of an aqueous dispersion of at least one liquid, non-fibering resin precursor is curable in the aqueous dispersion, and contains sufficient amounts of a curing catalyst for effecting the curing of the preparation in the dispersion. 11. A preparation according to item 10, characterized in that it consists of a mixture of the resin precursor with an inert, non-fiber absorbable liquid diluent, the 10 to 85 wt .-% of the mixture of Harzvorläufers.- and at least 5 wt .-% the preparation constitutes. 12. A preparation according to items 10 or 11, characterized in that it additionally contains an effective amount of a dispersant for the preparation. 13. Preparation according to the preceding points, characterized in that the resin precursor is curable at temperatures below 50 ⁰ C. 14. Preparation according to item 13, characterized in that the resin precursor is curable at room temperature. 15. Preparation according to the preceding points, characterized in that the resin precursor. a liquid prepolymer having at least two reactive funktiohellen in the molecule. 16. A preparation according to item 15, characterized in that the resin precursor is mixed with a crosslinking agent which can react with the functional groups at least in the presence of a catalyst. 17. A preparation according to item 16, characterized in that it contains a mixture of a Dihydroxypoly (dialkylsiloxane) polymers with a poly (alkylhydroxisiloxan) crosslinking agent. -Ik - 18. Preparation according to item 17, characterized in that each alkyl group has 1 to 4 carbon atoms. 19. Preparation according to item 18, characterized in that the alkyl groups are methyl groups. 20. A preparation according to Item 16, characterized in that it consists of a mixture of an oligomeric hydroxy acrylate G _e prepolymer and a di-isocyanate crosslinking agent. 21. A preparation according to items 16 to 20, characterized in that the crosslinking agent in an amount of 1:10 to 10: 1, based on the prepolymer weight, is present. 22. A preparation according to items 12 to 21, characterized in that the dispersant is a polymeric protective colloid. 23.A preparation according to the preceding points, characterized in that the dispersant is present in an amount of 0.1 to 20 wt .-% of the resin precursor. 24. Preparation according to points 11 to 23, characterized in that the extender in an amount of 55 to 80 wt - . %, Based on the preparation, is present. , 25. A preparation according to items 11 Ms 24, characterized in that the extender is a methyl-terminated polydimethylsiloxane or a hydrocarbon oil. 26. Aqueous dispersion according to the preceding points, characterized in that the curing catalyst is a Dialkylζinndialkanaat. 27. A preparation according to item 26, characterized in that the catalyst is a Dibutylζinndialkanoat, each Alkanoatrest has 8 to 14 carbon atoms. 28. An aqueous dispersion according to the items 25 to 27, characterized in that the catalyst is present in an amount of 0.1 to 50 parts by weight 9ό, based on the weight of the resin precursor. For this 3 sheets of drawings