# US 5,707,489 A · Processing wastepaper containing waxes, hot melts and adhesives

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 5,707,489 A
- Document ID: US5707489A
- Status: Granted
- Kind: A
- Application number: 08/788,358
- Filed: 1997-01-24
- Granted: 1998-01-13
- Earliest claimed: 1993-05-26
- Assignees: J.M. Voith GmbH
- Inventors: Michael Von Grumbkow; Helmut Konecsny
- Web page: https://patentgrep.com/patent/US5707489A

## CPC

- D21B 1/32: of waste paper
- D21C 5/02: Working-up waste paper (mechanical part D21B1/08, D21B1/32)
- D21C 9/08: Removal of fats, resins, pitch or waxes; {Chemical or physical purification, i.e. refining, of crude cellulose by removing non-cellulosic contaminants, optionally combined with bleaching (fats, waxes C11B; natural resins C09F1/00; hemicellulose C08B37/14; purification by mechanical means D21D5/00)}
- Y02W 30/64: Paper recycling
- D21B: FIBROUS RAW MATERIALS OR THEIR MECHANICAL TREATMENT
- D21C: PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
- Y02W: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT

## Abstract

A method of processing recycled paper which contains such a high amount of wax, hot melts or stickies that they would be expected to cause a stoppage of the paper-manufacturing machine. The paper to be recycled is pulped in a pulper and passed on to respective subsequent stages which include a despecker, grader and hydrocyclone. Pulping takes place at a temperature of at least 60.degree. C., and at the same time subjects the paper to a high shear action. The processing line includes a pulp-thickening stage, preferably after the processing stages mentioned, in order to separate off a very high proportion of the wax, hot melts and stickies finely dispersed in the pulper.

## Claims

### Claim 1

A method for processing waste paper, said waste paper including impurities selected from the group consisting of waxes, hot melts and adhesives, said impurities being present in said waste paper in a range of from about 0.1 to about 8 wt. %, the method comprising the steps of:
(a) pulping the waste paper into a slurry in a pulper, said pulping step occurring at a temperature of at least 60.degree. C., and with a high shear effect upon the waste paper in the pulper, whereby the impurities disperse greatly and finely in said slurry;
(b) treating the slurry in further processing stages using a deflaker, a grader and a hydrocyclone, respectively;
(c) thickening the slurry from step (b) in a thickener at a temperature of maximally 50.degree. C., thereby leaving the impurities with a firmness suitable for passage through a filter in said thickener, and filtering said thickened slurry through the filter such that a thickener filtrate is produced, wherein said filtrate includes about 80% of said impurities; and
(d) cleaning said filtrate containing said impurities by at least one of microflotation, filtration or selective flotation.

### Claim 2 (depends on 1)

The method of claim 1, wherein the consistency of waste paper in the pulper is at least about 8%.

### Claim 3

A method for processing waste paper, said waste paper including impurities selected from the group consisting of waxes, hot melts and adhesives, said impurities being present in said waste paper in a range of from about 0.1 to about 8 wt. %, the method comprising the steps of:
(a) pulping the waste paper into a slurry in a pulper, said pulping step occurring at a temperature of at least 60.degree. C., and with a high shear effect upon the waste paper in the pulper, said shear effect being sufficient to finely divide said impurities and to disperse said freely-divided impurities in said slurry, said waste paper in the pulper having a consistency of at least about 8%;
(b) treating the slurry in further processing stages, said further processing stages comprising a deflaker, a grader and a hydrocyclone;
(c) thickening the slurry from step (b) in a thickener at a temperature of maximally 50.degree. C. such that the impurities maintain firmness suitable for passage through a filter in said thickener, and filtering said thickened slurry through the filter such that a thickener filtrate is produced, said filtrate including about 80% of said impurities; and
(d) cleaning said filtrate containing said impurities by at least one of microflotation, filtration or selective flotation.

### Claim 4 (depends on 3)

The method of claim 3, wherein the consistency of waste paper in the pulper is about 8%.