GB2125838A

GB2125838A - Inorganic filling agent composition

Info

Publication number: GB2125838A
Application number: GB08316514A
Authority: GB
Inventors: Jozsef Erdelyi; Tamas Kutasi; Gyula Balint; Gyozo Varga; Bela Bozsits; Zsolt Almasi
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-02-11
Filing date: 1983-06-17
Publication date: 1984-03-14
Also published as: FI68104C; GB2109428B; HU192063B; DE3231609C2; FI823128L; AT377295B; GB8316514D0; WO1982002730A1; GB2125838B; GB2109428A; DE3243904A1; DE3231609T1; AT382656B; FI823128A0; FI68104B; ATA425482A; ATA37782A

Description

SPECIFICATION

Inorganic filling agent composition The invention relates to an inorganic filling agent composition for the paper industry.

5 The invention aims at providing a composition by which the loss of filling agent can be reduced considerably in the paper industry. The improvement of the retention of the filling agent and fine fibres involves significant economic advantages.

The following inorganic mineral substances are 65 used as filling agents in the paper industry:

- silicates (such as kaolin, talc, etc.), - sulfates (such as BaS04, CaS04, etc.), 15 - carbonates (such as MgC031 CaC03, etc.), 70 - oxides (such as Ti021 ZnO, etc.), - sulfides (such as ZnS, etc.).

Of the above filling agents kaolin and talc, and, for specific purposes, barium sulfate and titanium 75 20 dioxide are utilized in the highest amounts in the industrial practice.

When using these agents in paper industry, an aqueous suspension of the agent is prepared, and this suspension is added to the cellulose fibre 25 suspension.

A considerable loss of filling agent occurs during paper production. The actual loss varies with the type and amount of the agent added, and with the process conditions of paper production.

30 The losses of filling agents can be attributed primarily to the fact that the agent and industrial cellulose fibre types have negative surface charges (zeta potential) in aqueous suspension. The zeta potentials of cellulose and some typical filling 90 agents are listed below:

Cellulose fibre Hungarian kaolin (mined at Szeg) -13 to -27 mV -28 to -32 mV 95 Austrian kaolin (AspengerA-2) -16to-2OmV Czechoslovakian kaolin Titanium dioxide Austrian talc Zeolex 113 (a synthetic silicate-type filling agent produced by Zeofinn Oy, Finland) -15to-25mV100 -40 to -50 mV -30 to -40 mV -35 to -40 mV.

Owing to their strong negative surface charges, cellulose fibres and particles of filling agent mutually repel one another in aqueous 50 suspensions, with the result that a considerable proportion of the filling agent particles is washed away with the process water through the paperproducing sieve together with the short cellulose GB 2 125 838 A 1 fibres (broken fibres and fines).

Now it has been found, unexpectedly, that when applying the composition according to the invention, the filling agent adheres to the cellulose fibres, suppressing thereby the loss to the minimum. The composition also increases the 60 strength of the paper.

According to the present invention there is provided a filling agent composition comprising an inorganic filling agent of a type conventionally used in the paper industry, together with an aluminium salt, a cationic polyelectrolye and, optionally, an aluminate.

When suspending the composition according to the invention in water, a suspension containing particles with positive surface charges (zeta potential) is obtained.

The filling agent composition according to the invention is prepared so that the polyelectrolyte and one or more air-dry compound(s) releasing aluminium ions, preferably aluminium sulfate and sodium aluminate, are added in a predetermined amount or composition to the filling agent in the last step of the conventional technology of filling agent production, i.e. when powdering the dried filling agent.

80 The preferred composition comprises 65 to 98% by weight of an inorganic filling agent, 2 to 35% by weight of an additive comprising an aluminium salt and, optionally, an aluminate and 0. 1 -6% by weight of a cationic polyelectrolyte 85 (preferably polyacrylamide). The amount of the aluminium salt in the said additive is preferably from 50 to 100% by weight.

When this air-dry mixture of appropriate composition is suspended under the conditions applied in paper industry, the surfaces of the filling agent particles will bear positive charge (i.e. they have positive zeta potential). Therefore, when added to the cellulose fibre suspension with negative surface charge, the filling agent particles adhere to the surface of the cellulose fibres due to electrostatic attraction, simultaneously increasing the hetero- or homocoaguiation of broken and fine fibres. These effects considerably increase the retention of filling agent and fine fibres in the sheet structure.

A filling agent suspension with positive surface charge can be obtained even when the ratio of the components is not within the optimum ranges. The positive surface charge appearing during the preparation of the suspension does not depend on the dilution of the suspension. By varying the ratio of aluminium sulfate and sodium aluminate, a filling agent suspension with positive surface charge can be obtained over a wide pH range (pH 110 2.0 to 10.0). This always enables one to adjust the pH of the suspension to the desired value, which is favourable with respect to the sizing of paper.

The retention achieved with the composition according to the invention is far superior to the 115 retention of known filling agents and of fine fibres that has been achieved hitherto. The compositions according to the invention have the further GB 2 125 838 A 2 advantage that with their application there is no need for conventional retention aids (these retention aids are expensive, they should be admixed separately, and are less effective than the 5 compositions according to the invention), furthermore, upon adjusting the pH of the filling agent suspension to the appropriate value, any desired sizing technology can be performed.

The invention is elucidated in more detail by the 10 aid of the following non-limiting Example.

A filling agent mixture of the following composition was prepared:

kaolin 940 kg crystalline aluminium sulfate 40 kg 15 sodium aluminate cationic polyacrylamide kg 40 kg total: 1000 kg We have found that use of the polyelectrolyte mentioned in the Example improves the retention 20 of small fibres and cellulose fibres and, in addition, the paper strength is improved without increasing loss of the filling agent.

Claims

1. An inorganic filling agent composition 25 comprising an inorganic filling agent of a type conventionally used in the paper industry, together with an aluminium salt, a cationic polyelectrolyte and, optionally, an aluminate.

2. An inorganic filling agent composition of 30 high retention for paper industry, characterised by containing 65 to 98% by weight of an inorganic filling agent for paper industry, 2 to 35% by weight of an additive comprising an aluminium salt optionally together with an aluminate in 35 addition 0.1-6% by weight of a cationic polyelectrolyte. 11

3. A composition as claimed in claim 1 or claim 2, wherein the amount of the aluminium salt in the I' additive is 50-100%.

4. A composition as claimed in any one of claims 1 to 3, wherein the aluminium salt is one or more of aluminium sulfate, potassium aluminium sulfate or aluminium chloride.

5. A composition as claimed in any one of claims 1 to 4, wherein the aluminate is sodium aluminate.

6. A composition as claimed in any one of claims 1 to 5, wherein the cationic polyelectrolyte is polyacrylamide.

50

7. A composition substantially as hereinbefore described in the accompanying Example.

Printed for Her Majesty's Stationery Office by the Courier Press, Leamington Spa, 1984. Published by the Patent Office, Southampton Buildings, London, WC2A 1AY, from which copies may be obtained.

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