GB1564783A - Disinfecting waste paper - Google Patents

Description

(54) DISINFECTING WASTE PAPER (71) We, INTERLOX, a Belgian Society' Anonyme organised under the Laws of Belgium, of Rue du Prince Albert 33, 1050 Brussels, Belgium, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates to a process for disinfecting waste paper.

Waste paper represents an important source of raw materials for the paper industry, particularly in the production of newspaper, toilet paper and packaging papers and boards. The waste paper is usually crushed in the aqueous phase and may or may not undergo a deinking treatment depending on its destination.

When the waste paper is entended for producing packaging papers or boards it is generally not subject to deinking. In this case the waste paper is crushed most frequently in a pulper in order to obtain a pulp which may afterwards be subjected to such operations as filtration, purification or washing prior to the actual manufacture of boards or papers for packaging.

Waste paper used industrially to date chiefly comes from collections of waste paper. In order to increase the recovery rate, the recovery of waste paper, which comes from ungraded materials in household refuse, has also been considered.

Nonetheless, paper recovered from household refuse is contaminated by various microorganisms such as microbes (bacteria or viruses) or moulds and this makes it somewhat dangerous to handle.

Furthermore, when pulps obtained by crushing this kind of waste paper are not subjected to any chemical treatment which may destroy these microorganisms to at least some extent, some part of these microorganisms can be found in the finished products. Papers and boards for packaging which are obtained in this way have a comparatively limited use for this reason.

The applicant has found a means of ameliorating this inconvenience.

According to the present invention there is provided a process for disinfecting waste paper comprising the step of crushing the waste paper in an aqueous medium containing hydrogen peroxide in the absence of added alkali, thereby producing pulp which is suitable for forming into sheets.

The process according to the present invention is particularly suitable for disinfecting waste paper which has not undergone deinking treatment prior to being formed into sheets of paper pulp, and is especially applicable to waste paper recovered from household refuse.

The amount of hydrogen peroxide used at the crushing stage is generally between 0.01 and 10% by weight based on the weight of the waste paper and preferably between 0.05 and 5% in weight. The hydrogen peroxide is generally introduced in the form of a solution in any known solvent for hydrogen peroxide which is miscible with water. In general an aqueous solution of hydrogen peroxide is used. The concentration of the solutions used is not critical. Most frequently it is between 5 and 40% in weight.

The temperature at which the disinfection takes place is most frequently between 10 and 140"C and preferably between 15 and 1200C. Other temperatures can also be.

used, if desired.

The duration of the crushing stage can vary within fairly broad limits. In general, it is greater than I min., preferably greater than 10 min. The crushed and disinfected liquid pulps obtained in this way can be directly formed into pulp sheets after one or more preliminary filtration, purification or washing stages. Alternatively they can also be stored for a period selected within a very wide range before they are formed into pulp sheets. This advance storage can prove to be very favourable to the process because it can enable the bacteria content to be further diminished. Advantageously the pulp is stored for between 10 min and I day, preferably between 30 min and 5 hours, before being subjected to a subsequent treatment.

The quality of the water used for crushing the waste paper is not important, both demineralised water and undemineralised water being usable with substantially equal success.

The consistency of the pulp obtained by crushing the waste paper is usually between 0.1 and 15% and preferably 0.5 and 10%.

The process in the invention offers the advantage of very greatly reducing the bacteria content of pulp obtained by crushing, and this is much less dangerous for the operators during subsequent treatments.

Furthermore, the degree of cleanliness of the board based on pulps of this kind is greatly improved.

Certain embodiments of the present invention are described more fully by way of example only. Examples 1, 5, 7 and 8 are present by way of comparison only.

Examples.

In each of the Examples, waste paper recovered from household refuse, together with demineralised water with a bacterial content of 0 to 3 per cm3 were introduced into a pulper of approximately 2 litre capacity so that a normal working consistency of 3.5% (Examples 2, 3, 4, 6 and 7R and 8R) or 5% (Examples IR and 5R) was obtained. On reaching the test temperature, additives as specified in the Table were added and the pulper treatment was continued for 20 min.

Any unconsumed hydrogen peroxide was decomposed by addition of sodium hydrosulphite, the solution diluted and the bacteria content was then measured by counting by filtration on a Satorius membrane.

In a first series of tests, carried out for comparative purposes (Examples 1 R and 5R), no reagent was added.

In a second series of tests, carried out in accordance with the invention (Examples 2, 3, 4 and 6) amounts of hydrogen peroxide specified in the Table were introduced.

In a third series of tests, also carried out for comparative purposes (Examples 7R and 8R), an alkaline aqueous solution of the type usually used for deinking was introduced into the pulper and aqueous hydrogen peroxide was introduced one minute later. Example 8R, the number of bacteria was measured directly at the outlet from the pulper. In Example 7R the mixture coming out of the pulper underwent flotation before the number of bacteria was measured.

The results obtained are summarised in the Table below.

THE TABLE

Example 1R 2 3 4 5R 6 7R 8R Crushing in the pulper Temperature C 25 25 25 25 50 50 50 50 Additives %by weight of waste paper H2O2 - 0.1 0.5 1 - 1 1 0.5 NaOH - - - - - 1 1 Sodium Silicate - - - - - - 5 5 Stearin - - - - - - 0.2 0.2 Oleic Acid - - - - - - 0.2 0.2 Na Tripolyphosphate - - - - - - 0.15 0.15 Foamer (PERATOM) - - - - - - 0.15 0.15 Bacteria No./g of waste 380 x 106 17.2 x 103 8.3 x 103 3.9 x 103 39.9 x 106 6.2 x 103 13.3 x 103 113 x 103 paper H2O2 Consumption % - 72 41 26 - 26 An examination of the results given in the Table above (Examples 1R, 2, 3, 4, 5R and 6) shows that the preliminary treatment with hydrogen peroxide alone is particularly effective for removing bacteria even when the hydrogen peroxide is in low concentration (see Example 2) under the conditions employed. On the other - hand, a comparison of Example 6 with Examples 7R and 8R shows that the treatment with hydrogen peroxide alone, as in the invention, is more effective under the conditions employed at removing bacteria than a normal deinking treatment employing an identical hydrogen peroxide content in the presence of added alkali, Example 7R and 8R.

WHAT WE CLAIM IS: 1. A process for disinfecting waste paper comprising the step of crushing the waste paper in an aqueous medium containing hydrogen peroxide in the absence of added alkali thereby producing pulp which is suitable for forming into sheets.

2. A process as claimed in claim 1 wherein the amount of H2O, used is between 0.01 and 10% by wt. based on the dry weight of the waste paper.

3. A process as claimed in either claim 1 or 2 wherein the crushing stage is carried out at a temperature between 10 and 140"C.

4. A process as claimed in claim 3, wherein the crushing stage is carried out at a temperature between 15 and 1200C.

5. A process as claimed in any preceding claim wherein the pulp obtained at the crushing stage is stored before being formed into sheets of paper pulp.

6. A process as claimed in claim 5 wherein the pulp is stored for a period between 10 min and 1 day.

7. A process for disinfecting waste paper substantially as described herein with respect to any of Examples 2, 3, 4 and 6.

8. Disinfected paper pulp whenever produced by a process claimed in any preceding claim.

9. Sheets of paper or board formed from disinfected pulp claimed in claim 8.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (9)

**WARNING** start of CLMS field may overlap end of DESC **. An examination of the results given in the Table above (Examples 1R, 2, 3, 4, 5R and 6) shows that the preliminary treatment with hydrogen peroxide alone is particularly effective for removing bacteria even when the hydrogen peroxide is in low concentration (see Example 2) under the conditions employed. On the other - hand, a comparison of Example 6 with Examples 7R and 8R shows that the treatment with hydrogen peroxide alone, as in the invention, is more effective under the conditions employed at removing bacteria than a normal deinking treatment employing an identical hydrogen peroxide content in the presence of added alkali, Example 7R and 8R. WHAT WE CLAIM IS:

1. A process for disinfecting waste paper comprising the step of crushing the waste paper in an aqueous medium containing hydrogen peroxide in the absence of added alkali thereby producing pulp which is suitable for forming into sheets.

2. A process as claimed in claim 1 wherein the amount of H2O, used is between 0.01 and 10% by wt. based on the dry weight of the waste paper.

3. A process as claimed in either claim 1 or 2 wherein the crushing stage is carried out at a temperature between 10 and 140"C.

4. A process as claimed in claim 3, wherein the crushing stage is carried out at a temperature between 15 and 1200C.

5. A process as claimed in any preceding claim wherein the pulp obtained at the crushing stage is stored before being formed into sheets of paper pulp.

6. A process as claimed in claim 5 wherein the pulp is stored for a period between 10 min and 1 day.

7. A process for disinfecting waste paper substantially as described herein with respect to any of Examples 2, 3, 4 and 6.

8. Disinfected paper pulp whenever produced by a process claimed in any preceding claim.

9. Sheets of paper or board formed from disinfected pulp claimed in claim 8.