GB2141751A

GB2141751A - Sizing compositions

Info

Publication number: GB2141751A
Application number: GB08315307A
Authority: GB
Inventors: Brian Tormey; Peter Christopher Rober Street
Original assignee: Roe Lee Paper Chemicals Co Ltd
Current assignee: Ciba Specialty Chemicals RC GB Ltd
Priority date: 1983-06-03
Filing date: 1983-06-03
Publication date: 1985-01-03
Also published as: GB2141751B; GB8315307D0

Abstract

A method of sizing paper, or the fibres from which paper is produced, comprises treating said paper or said fibres with a rosin and a polyelectrolyte (preferably a polydi (lower alkayl) diallyl quaternary ammonium chloride). The rosin and the polyelectrolyte may be premixed to form a stable aqueous dispersion which is used as 'one-shot' sizing composition.

Description

SPECIFICATION Sizing compositions This invention relates to sizing compositions useful particularly, but not exclusively, for the sizing of paper which term as used herein is generic to paper, paperboard and likeprod- cuts which may or may not be of a cellulosic nature.

The standard method of sizing paper is to treat either the fibres from which the paper is to be produced or the finished paper with a dispersion of a rosin size and alum. These two components are generally added separately to the bath in which the fibres or finished paperare immersed. The alum acts to break down the rosin dispersion so that the rosin may be deposited on the fibres or paper to effect sizing.

The amounts in which the rosin and alum are used are of course well known in the art and are not further discussed here.

It is also known from published U.K. Specification No. 2 050 453 A to produce a "oneshot" sizing composition by mixing together alum and a rosin dispersion. On mixing, the rosin dispersion is initially broken down (as would be expected from the previously known effect of alum on rosin) but is subsequently re-established on further mixing to produce a stable product which may be used as the "oneshot" sizing composition.

The above compositions do however suffer from a number of disadvantages in the case where chalk (used as a filler) is used in the sizing stage. Chalk may also be present in recycled waste paper which is to be sized.

Chalk adversely affects the rosin dispersion so that satisfactory sizing of chalk loaded papers may not be in achieved by use of either the standard method or "oneshot composition" referred to above.

It is an object of this invention to obviate or mitigate the abovementioned disadvantage.

According to a first aspect of the present invention there is provided a method of sizing paper, or the fibre from which paper is prepared, comprising effecting the sizing with a rosin dispersion and a polyelectrolyte.

The rosin dispersion and polyelectrolyte may be introduced separately, and preferably at high dilution, into the vessel is which sizing is to be effected. We have however found that a stable "one-shot" composition may be prepared from the rosin dispersion and polyelectrolyte by mixing the two components together and continuing mixing until a stable dispersion is established.

Therefore according to a second aspect of the present invention there is provided a sizing composition comprising a stable aqueous dispersion obtained by admixing a rosin dispersion and a polyelectrolyte.

The invention will be further described with specific reference to ('r,e "one-shot" composition but it should be appreciated that the types of polymer and rosin dispersion hereinafter described may also be used in the first aspect of the invention.

The mixing of the polymer with the rosin initially causes the rosin dispersion to break and a floc-like precipitate is formed. However, continued mixing causes a stable dispersion may settle slightly with time but may be reestablished by gentle shaking.

Preferably the polyelectrolyte is an organic polymer with positive charges along the chain, most preferably a water solubly quaternary ammonium polymer, preferably a homopolymer. More preferably the quaternary ammonium polymer is one obtained by free radical polymerisation of a quaternary ammonium salt (particularly the chloride) having two substituted or unsubstituted alkyl groups bonded to the nitrogen atom. Such polymers are described in U.S. Patent No 3 288 770, the disclosure of which is incorporated herein by reference. This patent gives more details of the structure of the polymers, but briefly the polymers comprise a linear chain of 6 membered rings incorporating the quaternary nitrogen atom and linked by methylene groups.

The preferred polymer for use in this invention is a polydi (lower alkyl) diallyl ammonium chloride, most preferably polydimethyldiallyl ammonium chloride.

Quaternary ammonium polymers suitable for use in the invention are available under the name CATFLOC. In particular, we have found CATFLOC T-1 to be eminently suitable.

Other polyelectrolytes which may be used are, for example, cationic polyamides, eg the products designated 1780, 1190, 11 95 and Polyethylan amide available from Betz Ltd of Winsford- Cheshire.

The rosin may be any rosin size dispersion as normally used in the sizing of paper, and may include fortified rosins obtained by reacting rosin with unsaturated carboxylic acids or anhydrides. Preferably, however the rosin is as described in our copending U.K. Patent Application No 82 36483.

The polyelectrolyte may be used in a wide weight range relative to the rosin proper (i.e.

excluding water in the rosin dispersion). The polymer may be used in the form of an aqueous solution or dispersion containing 1 5 to 30% (e.g. 20%) by weight of polymer whereas the rosin dispersion will generally contain 20-40% (e.g. 30%) of rosin. Usually the volume ratio of rosin emulsion to polymer solution or dispersion will be from 10:1 to 2:1, more preferably 6:1 to 4:1, most preferably about 5:1.

The composition is preferably produced as a "concentrate" which may be diluted with water before being used in the sizing process.

Such a concentrate may contain, for example, 1 5 to 40% by weight of solids as determined by evaporation and drying the concentrate to constant weight, e.g. at 100-105"C. More preferably the concentrate contains 1 5 to 30% by weight of solids on the same basis, and most preferably about 20% by weight.

The composition of the invention may be prepared by mixing together the rosin dispersion and the polyelectrolyte in the requisite proportions and amounts. Mixing may be effected in a standard high speed mixer. Initially the rosin dispersion breaks but upon further mixing a dispersion is re-established which is stable over comparatively long periods of storage, e.g. a few weeks. Even when phase separation occurs, the dispersion may readily be re-established simply by shaking.

To effect sizing, the composition of the invention may be used as a "one-shot" composition under the same conditions as employed in the standard method of sizing described above (save that, of course, the separate additions of rosin dispersion and alum are replaced by an addition of the one-shot composition). The amount of the composition used will be such as to give amounts of rosin similar to those utilized in the standard process.

In the sizing process, the fibres of the paper act to destabilise the dispersion so that rosin may be deposited thereon.

Papers which contain chalk may be sized with the composition of the invention which although possibly slightly adversely affected by the chalk nevertheless is not so badly affected that sizing will not occur.

The invention is further illustrated by reference to the following non-limiting Example.

Example 10 mls of CATFLOC T-1 was added to 50 mls of RL-E30 emulsion (a 30% solids rosin emulsion available from Roe Lee Paper Chemicals Co. Ltd.) using high speed mixer. The expected precipitation occurred, which became smoother with continued mixing. The mixture was not perfectly homogeneous (some particles present in the resulting emulsion). 1 ml of this emulsion was diluted to 30mls to give approximately a 1 % dry basis solids content.

20 g of presoaked hardwood pulp was disintegrated in 500 mls of water and the mixture was made up to 600 mls.

200 mls of the paper-making stock thus obtained (6.6 g pulp approx) was treated with 3.3 mls of the diluted emulsion, i.e. 0.5% dry solids cationic size/ fibre.

The above sized stock was diluted to 3 litres in the laboratory sink prior to sheetmaking.

The pH of the diluted stock has 5.5-6.0.

Handsheets were then prepared as follows:(a) Handsheet made from the above sized stock. (b) A further 1.5 mls of diluted size was added to the stock in the sink to bring the rosin/fibre ratio to approx. 0.75%.

Two handsheets made from this stock. (c) 5% chalk added to the sized stock in the sink and pH checked again. The pH was approx. 6.0 using pH papers. Two handsheets made from this stock (i.e. 0.75% rosin/fibre + 5% chalk). (d) The stock in the sink was made up to 1 % sized (dry basis). Two handsheets made from this stock (i.e. 1% rosin/fibre + 5% chalk).

All handsheets were oven dried at 110"C and all proved to be hard sized when tested by pen and ink.

Since handsheet (c) contained added chalk, it would appear that the Cationic sizing product has some degree of tolerance to chalk loading.

Claims

1. A method of sizing paper or the fibre from which paper is prepared, comprising effecting the sizing with a rosin dispersion and a polyelectrolyte.

2. A method as claimed in claim 1 wherein the polyelectrolyte is an organic polymer with positive charges along the chain.

3. A method as claimed in claim 2 wherein the polymer is a water soluble quaternary ammonium polymer.

4. A method as claimed in claim 3 wherein the polymer is a polydi (lower alkayl) diallyl ammonium chloride.

5. A method as claimed in claim 4 wherein the polymer is polydimethyldiallyl ammonium chloride.

6. A sizing composition comprising a stable aqueous dispersion obtained by admixing a rosin dispersion and a polyelectrolyte.

7. A composition as claimed in claim 6 wherein the polyelectrolyte is an organic polymer with positive charges along the chain.

8. A composition as claimed in claim 7 wherein the polymer is a water soluble quaternary ammonium polymer.

9. A composition as claimed in claim 8 wherein the polymer is a polydi (lower alkayl) diallyl ammonium chloride.

10. A composition as claimed in claim 9 wherein the polymer is a polydimethyldiallyl ammonium chloride.

11. A composition as claimed in claim 6 which has been prepared by admixture of 2 to 10 parts by volume of a 1 5 to 30% by weight solution or dispersion of the polymer and 1 part by volume of a 20-40% by weight rosin dispersion.

1 2. A method of sizing paper or the fibres from which paper is prepared substantially as hereinbefore described with reference to the Example.

13. A sizing composition substantially as hereinbefore described with reference to the Example.