SE442171B - PROCEDURE FOR DISPERSING OF TALK FOR USE IN PAPERING OF PAPER WHERE THE TALK IS DISPERSED IN THE WATER USING AN ORGANIC POLYELECTROLYT DISPERSERY AND ANIONIC OR NONMONIC - Google Patents

Description

f; b * - 25 ll J) 79003753-7 Percent on dispersion on talc As dispersant: disodium salt of F 'copolymer of maleic anhydride and diisobutylene 0.68 2 l As thickener: carboxymethylcellulose 0.685 l For pH control: 1M NaOH solution 0.78 l.13 However, for coating paper, a talc is required, for which the majority of the particles are less than 2.5 .mu.m. Known dispersants do not allow dispersion of more than about 60% by weight of such particles.

According to the present invention it is possible to obtain a satisfactory dispersion of coating grade talc, if the following constituents are incorporated in the dispersion system: (i) an organic polyelectrolyte dispersant (ii) a non-ionic or anionic wetting agent, said system giving a pH of 7- ll and dispersion.

The dispersant can e.g. be an alkali metal salt of a polycarboxylic acid, e.g. a copolymer of maleic anhydride and diisobutylene or preferably a homo- or copolymer of acrylic acids. Other dispersants include carboxymethylcellulose and naphthalene sulfonate / formaldehyde condensate.

The dispersant preferably has a weight average molecular weight of less than 100,000 and a number average molecular weight above 1000, e.g. from 1,000 to 10,000.

The wetting agent may be any of the known anionic or non-ionic surfactants, e.g. nonionic substances such as oxyethylated and / or oxypropylated fatty alcohols, fatty acids, alkylphenols or fatty amines, or anionic substances such as alkyl ether sulphates, olefin sulphonates, alkyl benzene sulphonates, alkylphenol ether sulphates, alkyl sulphates or amine sulphates.

Particularly preferred are the dialkyl sulfosuccinates.

Preferably the wetting agent has one or two alkyl groups having from 6 to 1 carbon atoms, e.g. from 8 to 10 carbon atoms. A typical example is dioctyl sulfosuccinate having either straight or branched alkyl groups.

The composition may optionally contain inorganic dispersants, such as sodium or potassium polyphosphates, silicates or hexametaphosphates.

It is desirable to avoid or reduce foaming, and according to preferred embodiments of the invention, this can be accomplished in one of three ways: 1. By selecting a wetting agent (eg a dialkyl sulfosuccinate) which has a relatively low foaming character . By incorporating an anti-foaming agent, such as a fatty alcohol or a silicone antifoaming agent. 5. By using mixing techniques that do not involve any appreciable liquid / gas interface.

According to an embodiment of the present invention, there is provided a stable, pumpable dispersion in water of at least 60% by weight based on the dispersion of talc having a major part of particles less than 2.5 .mu.m, the dispersion containing from 0.1 to 2%. , based on the weight of the talc, of an organic polyelectrolyte dispersant having a number average molecular weight greater than 10000 and a weight average molecular weight less than 100,000, and from 0.1 to 2.5%, based on the weight of the talc, of a non-ionic or anionic wetting agent and having a pH between 7 and 11.

Preferably the dispersion contains at least 65% by weight of the talc, e.g. 65-75%. agent is 0.3-1% based on the weight of the talc.

The preferred concentration of dispersant is The preferred concentration of wetting agent is 0.5-2%, based on the weight of the talc. The preferred pH is 8-10.5. The dispersant system according to the invention can be prepared as an aqueous concentrate containing a total of 20-80% of dispersant and wetting agent. The purchaser of this concentrate can add a base for adjusting the final pH and then water to the required dilution before mixing with the talc.

The invention is illustrated by the following examples: EXAMPLE 1 The talc to be dispersed, which goes under the trade name "Lohjatalc PV10", had the following composition: 99.9% less than 20 .mu.m 99% "" 10 .mu.m 7903755-7 The dispersion had the following composition: "Lonjatalc Pv1oÉ 65% (dry weight)" Empicryl APD "(sodium salt of diisobutylic anhydride copolymer , 25% solids content); 0, H9% (0.75% on talc) "Empilan KA10 / 80", a mixture of C10-12 fatty alcohol, 10 mol ethoxylate, 80%; water 20%; 0.81% ( 1.25% on talc).

Molar sodium hydroxide solution; 0.73% (1.5% on talc).

Water; the remainder up to l00%.

The dispersion was prepared by dissolving all the water-soluble components of the composition in the required residual water and then adding the talc to the solution using a high speed mixer for a period of H5 / 50 minutes - maleic acids.

The viscosity of the dispersion was measured using a Brookfield viscometer at room temperature immediately after preparation and after 3 days of storage. The slurry tended to thicken and sediment when left to stand but could be easily regenerated by gentle agitation.

Result Time Viscosity 0 days H80 cP 3 days 160 cP EXAMPLE 2 A dispersion was prepared as described in Example 1. The composition of the dispersion was as follows: "Lohjatalç PV l0Û; _65% (dry weight) 'Dispex NÄO", (sodium polyacrylate, 30% solids content); 0.325% (0.5% on talc) VEmpimin OT "(60% active dioctyl sulfosuccinate); 0.975% (1.5% on talc). 1 molar sodium hydroxide solution; 0.75% (1.55% on talc ).

Water; the remainder up to 100%.

The viscosity was measured as in Example 1 with the following result: Result Time Viscosity 0 days 1,200 cP 3 days 800 cP .wr- U? EXAMPLE 5 A dispersion prepared in the manner described in Example 1.

The composition of the dispersion was as follows: "Lønjataic Pv1o"; 65% (dry weight) "Dispex NUO"; 0.20 (0.5% on talc) "Empimin KSN70" (sodium C12-18 alkyl, 5 moles of ether sulphate); 1.8% (1.8% on talc). 1 molar sodium hydroxide solution; 0.75% (1.5% on talc) Water; the remainder up to l00%.

The viscosity was measured as in Example 1 with the following result: Tid Results Time X-viscosity 0 days 2,500 cP 5 days 800 cP EXAMPLE U A dispersion was prepared in the manner described in Example 1 except that instead of "Lohjatalc PV10" - turned a talc known as "Finntalc C10" and having the following composition: 99% less than 12 / um H / um 50% less than 2,5 / um 25% less than 1,2 / um 75% less than Sodium tripolyphosphate was used as a defloeculant.

The dispersion had the following composition: "Finntalc C10"; 65% (dry weight) "Empicryl APD"; 0.09% (0.75% on talc) "smilan KA10 / 80" 0.81% (1.25% on talc) Sodium tripolyphosphate; 0.065% (0.1% on talc) 1 molar sodium hydroxide solution and 0.73% (1.3% on talc) Water; the rest up to 100%.

Result Time Viscosity 0 days 960 cP 3 days 280 cP EXAMPLE 5 A dispersion was prepared as in Example U except that "Empicryl APD" was replaced with equal weight by "Dispex NHO".

Result Time Viscosity 0 days 500 cP 5 days 5,500 cP.

POOR- QUÄLITY 7903753-7 Lä) * O EXAMPLE 6 A dispersion was prepared in the manner described in Example 1. The talc used in the dispersion was "Finntalc C10".

Sodium silicate, marketed under the tradename WPyramid Grade No.8U "(Crosfields), was used as an optional ingredient.

The dispersion had the following composition: "Finntalc C10"; 65% (dry weight) "Empißryl APD"; 0,9 H9% (0,75% on talc) "smpiian kAio / Sr fl; 0.81% (1.25% on talc) Sodium silicate; 0.35% (0.5% on talc) 1 molar sodium hydroxide solution; 0.75% (1.3% on talc) Water; the remainder up to 100%.

Result Time Viscosity 0 days SKIN cP 3 days 400 cP EXAMPLE 7 The following comparative experiments were performed using the dispersion system described above on page. l. This means the following composition for a talc dispersion with a solids content of 65%: Polyelectrolyte dispersant; 0.65% (1% on talc) 0.65% (1% on talc) 1 molar sodium hydroxide solution; 0.75% (1.3% on talc) This dispersion system was used in an attempt to produce a 65% talc dispersion of both "Finntalc C10" and "Lohjatalc".

PV10 "using" Empicryl APD "as the polyelectrolyte dis- Carboxymethylcellulose;

In both of these experiments it was impossible to disperse all the talc.

EXAMPLE 8 The experiment of Example 7 was repeated using "Lohjatalc PV10" with "Dispex NHO" as the polyelectrolyte dispersant. It was not possible to disperse all the talk.

Claims (6)

7 7903753-7 QATENTKRQX A process for dispersing talc for use in coating paper, characterized in that the talc is dispersed in an aqueous solution containing 0.1 to 2%, by weight of the talc, of a polyacrylic acid dispersant having a weight average molecular weight of less than 100,000 and a nonionic or anionic wetting agent selected from oxyethylated and / or oxypropylated fatty alcohols, oxyethylated and / or oxypropylated fatty acids, oxyethylated and / or oxypropylated alkylphenols, oxyethylated and / or oxypropylated fatty amines, alkyl ether sulfates, olefin sulfonates, alkyl benzene sulphates, alkyl benzene sulphates, alkyl benzene sulphates and dialkyl sulfosuccinates, the wetting agent being present in an amount of 0.1 - 2.5%, based on the weight of the talc, and optionally an effective amount of an antifoaming agent, the solution having a pH of 7-11. Process according to claim 1, characterized in that the dispersant has a number average molecular weight which is greater than 1,000 and preferably less than 10,000. Process according to either of Claims 1 and 2, characterized in that the wetting agent has 1 or Z alkyl groups having 8 to 10 carbon atoms, e.g. dioctyl sulfosuccinate. Process according to any one of the preceding claims, characterized in that the antifoaming agent is a fatty alcohol or a silicone. Process according to one of the preceding claims, characterized in that the talc has a main part of particles smaller than 2.5 μm. Process according to one of the preceding claims, characterized in that the talc is dispersed in an amount of at least 60% by weight. pøon QUaL; -fri_