Background of the Invention

This invention relates to methods for deinking paper products. Huge quantities of paper products are currently recycled. The methods employed to deink the paper products vary, but generally entail mixing the paper, usually in a pulping apparatus, in an aqueous solution containing one or more surfactants to thereby remove ink from the paper. Due to the heavy demand for recycled products, new and useful deinking processes are highly sought. Summary of the Invention

In one respect, this invention is a process useful for deinking paper, comprising (A) mixing an aqueous solution containing inked paper, the aqueous solution optionally containing an ethylene oxide and butylene oxide block polyol, to dissolve ink from the paper into aqueous solution and (B) subjecting the aqueous solution resulting from Step A to flotation, with the provision that the aqueous solution contains the ethylene oxide and butylene oxide block polyol during flotation, whereby the polyol and ink form a flotation mass on the aqueous solution.

In a another respect, this invention is a process useful for deinking paper, comprising (A) mixing an aqueous solution containing inked paper, the aqueous solution containing (1) an ethylene oxide and butylene oxide block polyol having an average molecular weight of ethylene oxide of from about 2,200 to about 3,100 and an average molecular weight of butylene oxide of rom about 2,100 to about 2,200; (2) hydrogen peroxide; (3) sodium silicate; (4) sodium hydroxide or potassium hydroxide and (5) diethylene triamine pentacetic acid or ethylenediaminetetraacetic acid, to dissolve ink from the paper into aqueous solution and (B) subjecting the aqueous solution resulting from Step A to flotation whereby the polyol and ink form a flotation mass on the aqueous solution.

This invention, in another respect, is a composition useful in deinking paper, comprising: (a) an ethylene oxide and butylene oxide block polyol; (b) a bleaching agent; (c) a bleach stabilizer; (d) a base and (e) and chelating agent. In another respect, this invention is a composition useful in deinking paper, comprising: (a) an ethylene oxide and butylene oxide block polyol having an average molecular weight of ethylene oxide of from about 2,200 to about 3,100 and an average molecular weight of butylene oxide of from about 2,100 to about 2,200; (b) hydrogen peroxide; (c) sodium silicate; (d) sodium hydroxide or potassium hydroxide and (e) diethylene triamine pentacetic acid or ethylenediaminetetraacetic acid. Detail Description of the Invention

Many types of inked paper can be deinked in the practice of this invention. The paper products as used herein take its ordinary meaning. Representative examples of suitable

paper products include single or multicolored paper, f lexographic (water-based ink) paper, and offset or letterpress (oil-base ink) paper, all of which can be newspapers and magazines.

In the practice of the process of this invention, the polyol is added to the aqueous solution prior to subjecting the admixture to flotation to thereby separate the ink which is in solution from the paper. It is preferred to incorporate the polyol into the aqueous solution prior to mixing of the admixture of inked paper and aqueous solution. Mixing is accomplished by immersing inked paper in the aqueous solution such that the solids content is from 0.1 to 50 weight percent, preferably from about 1 to about 15 weight percent. The admixture is then mixed to thereby facilitate dispersing the ink from the paper into the aqueous solution. Such mixing can be performed in conventional equipment designed for such purpose, such as a pulping apparatus. The paper can be shredded prior to immersion.

After mixing, the ink in solution can be separated from the paper by conventional methods such as by flotation. In flotation, air bubbles are introduced into the aqueous solution with mixing whereby flotation of the ink is effected and the ink can thus be skimmed away. Following flotation, the paper is separated from the solution by filtration or similar means. Alternatively, though less preferably, after mixing, the ink containing aqueous solution is simply filtered to leave the paper. Temperature during the deinking process is generally between 20°C and 50°C, with about 40°C being preferred. The process of this invention can be repeated to remove ink from the paper which was not removed initially. The process can be operated batchwise or continuously.

In the practice of this invention, an ethylene oxide and propylene oxide block polyol is employed in the aqueous solution. The polyois are also referred to as EO/BO or EO/BO/EO block copolymers. The polyois useful in this invention have an average molecular weight of from about 1,000 to about 10,000. Preferred polyois have an average molecular weight of from about 4,000 to about 7,000 and more preferably from about 4,000 to about 5,500. Polyois having an average molecular weight of ethylene oxide of from about 2,000 to about 3,500 are preferred, more preferably from about 2,200 to about 3, 100. Polyois having an average molecular weight of butylene oxide of from about 1 ,500 to about 2,500 are preferred, more preferably from about 2,100 to about 2,200. The polyol is generally present in the aqueous solution at a concentration greater than about 0.01 weight percent, preferably greater than about 0.1 weight percent; less than about 1 percent and preferably less than about 0.5 percent.

The polyois of this invention can be readily prepared by well-known techniques. Generally, the polyois are prepared by reaction of an initiator and butylene oxide, usually 1,2- butylene oxide, in the presence of a base such as potassium hydroxide at 100°C to 150°C. The initiator can be, for instance, 1,2-propylene glycol to form triblock copolymeric polyois or propanol to form diblock copolymeric polyois. Following reaction of the butylene oxide, ethylene oxide is next reacted in a similar way. Since butylene oxide and ethylene oxide are

gaseous at reaction temperatures, a sealed reaction vessel is generally used. Following reaction, the polyois can be isolated and purified by standard techniques such as filtration, distillation, washing and chromatography.

The aqueous solution can contain additional compounds to further facilitate the deinking process. Representative examples of such additional compounds include base to swell the paper fibers such as sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate and potassium carbonate with potassium hydroxide and sodium hydroxide being preferred, bleaching agents such as hydrogen peroxide and sodium percarbonate with hydrogen peroxide being preferred, bleach stabilizers such as sodium silicates and sodium o phosphonates with sodium silicates being preferred and chelating agents to trap metal ions to limit destruction of hydrogen peroxide from the metal ions such as diethylene triamine pentacetic acid and ethylenediamine-tetraacetic acid. Further, added anionic and nonionic surfactants can be included. Such of these additional additives are generally employed in concentrations of less than 3 weight percent per additive base on the total weight of the 5 aqueous solution. Typical ranges for base, less than 2 weight percent; for bleaching agent, less than 2 weight percent; chelating agent, less than 1 weight percent; bleach stabilizer, less than 3 weight percent; and added surfactants, less than 2 weight percent.

The following examples are provided to illustrate the invention and should not be construed to limit the scope of the invention or the claims. Unless otherwise specified, all 0 percentages are based on weight. Preparation of Polyois

Into a closed-system steel reaction vessel was charged 92 grams of 1,2-propylene glycol containing 6 percent (w/w) of KOH. The reactor was sealed and the temperature was increased to 130°C at which time 4193 grams of 1,2-butylene oxide was fed at such a rate to 5 maintain an internal pressure of below 70 pounds per square inch absolute ("PSIA") (483 kPa absolute). Following all the addition of 1 ,2-butylene oxide, the temperature of the reaction mixture was maintained at 130°C until the pressure drop over a one-hour period was less than 0.5 PSIA. After this butylene oxide digestion period was complete, the reactor contents were sampled and percent hydroxyl analysis performed to determine the molecular weight of the 0 product. The analysis showed the diol polymer to have a hydroxyl equivalent weight of 1770 (total molecular weight of 3540). In order to allow room for the feeding of the next oxide, 2000 grams of the intermediate diol were removed. This amount of material included small samples removed for hydroxyl analysis. The remaining contents of the reactor were then fed with 2104 grams of a 80/20 (w/w) mixture of ethylene oxide/ 1,2-butylene oxide to give the 5 final product which, after digestion of any residual oxide, was analyzed to have a hydroxyl equivalent weight of 3400 (total molecular weight of 6800). The resulting liquid polyether surfactant was then filtered through an agent suitable to remove the residual basicity of the KOH catalyst. In this procedure an ethylene oxide/butylene oxide, rather than ethylene oxide

only, was added as the final block to decrease crystallinity of the final polyol, thereby imparting liquidity at room temperature for ease of handling.

Using similar procedures, the polyois identified in Table I were prepared and which were used in the following examples. Polyol 5 represents the specific polyol of the procedure above. For polyois other than numbers 5 and 15, the final block did not contain butylene oxide.

TABLE

*EO% made up of an 80/20 BO random.

Deinking Procedure

The following procedure was used for all the succeeding examples. A large quantity of identical offset printed newspaper and magazine was obtained and stored in the dark at 3°C. The waste paper employed in the examples was a combination of 70 percent newspaper and 30 percent magazine.

Aqueous solutions for deinking were prepared by addition to the pulper of 1 percent sodium hydroxide, (reagent grade, Fisher Scientific), 1 percent hydrogen peroxide (reagent grade, Fisher Scientific), 2 percent sodium silicate (Anachemia), 0.45 percent diethylene triamine pentacetic acid (VERSENEX ^® 80, The Dow Chemical Company) and a percentage of EO/BO polyol as indicated in the tables throughout the examples. The percentages of these ingredients were calculated based on the oven dry weight of paper fed to the pulper as described below.

In the following examples, a laboratory helico pulper (Lamort) was used as the pulping equipment. The pulper was adapted to operate at rotor speeds of 0 to 1800 rpm. In the examples, 1 kg of paper was used in a pulping consistency of 8 percent (w/w). The paper to be deinked was soaked in tap water for at least 4 hours to facilitate tearing when charged to the pulper. The water used for soaking the paper was decanted and used as part of the water added to the pulper to form the aqueous deinking solution. The pulping water was heated to 40°C which was maintained during the pulping procedure. Next, the polyol was added, followed by the sodium silicate, hydrogen peroxide, sodium hydroxide, diethylene triamine pentacetic acid and polyol. The soaked paper was torn and added to the pulper while the rotor was rotating at 120 rpm. After all the paper was added to the pulper, the rotor speed was increased to 900 rpm. After 30 minutes, the rotor speed was reduced to 120 rpm for another 30 minutes. Next, the pulper was converted to a flotation cell by replacing the helico rotor with a high speed rotor (flat plate type), placing an aeration screen/air suction column on the rotor and installing an overflow weir for ink sludge collections. A portion of paper pulp was removed so that a consistency of 1 percent was employed during flotation. Flotation was performed for 10 minutes (1500 rpm) at a consistency of 1 percent and at 20°C. After flotation, the pulp was removed and promptly acidified to a pH of 5.5.

Next, 3.5 g handsheets were made from the deinked paper pulp using Canadian Pulp and Paper Association Standard C5 procedure. 457 nm wavelength light was used to measure brightness of the handsheets. In all the tables, handsheet brightness is described in "1S0" terms, which is a unit of measurement for reflectance from the handsheets, indicating brightness. Handsheets were prepared using both paper pulp removed before flotation and

pulp removed after flotation. In the tables, the columns termed "Before Flotation Brightness" designate data for handsheets made from paper pulp removed prior to flotation. Conversely, the columns termed "After Flotation Brightness" report data for handsheets made from paper pulp obtained after flotation.

Example 1 : In this Example 1 , the flotation pH was 9 for the results reported in Table II and a pH of 6 for the results reported in Table III.

TABLE II

TABLE III

Polyol/ Before After (% amount) RUN # Flotation Flotation Flotation

Brightness Brightness Losses %

18 (0.5%) 10 53.7 56.5 2.9

18 (0.3%) 11 54.4 56.6 2.2

Example 2: In this example, the flotation pH was 9 and the results are reported in Table IV. In run 22, the data represents the average of the five runs in Table VI.

TABLE IV

Example 4: In this example, the flotation pH was 6 and the results are reported in Table V. In run 39, the data represents the average of the five runs in Table VII.

TABLE V

Example 5: In this example, polyol 5 at a concentration of 0.3 percent was used. The results are reported in Tables VI and VII. In Table VI, flotation pH was 9 and in Table VII, pH was 6.

TABLE VI

1 Standard deviation expressed at 95% confidence level.

TABLE VII

1 Standard deviation expressed at 95% confidence level.

Example 6: In this example, letterpress paper was exchanged for offset paper. Polyol 5 was used at a 0.3 percent concentration. The results are shown in Table VIII.

TABLE VIII

Before After

Flotation pH RUN # Flotation Flotation Flotation

Brightness Brightness Losses %

9.00 54 51.6 59.9 8.7

6.00 55 53.0 60.1 8.1

Example 7: In this example, the paper sample was made up of 58 percent offset paper, 12 percent f lexographic paper and 30 percent magazine. Polyol 5 was used at a concentration of

0.3 percent. The results are set forth in Table IX.

TABLE IX