US3540980A

US3540980A - Process of rosin sizing paper

Info

Publication number: US3540980A
Application number: US772474A
Authority: US
Inventors: Harold L Jones
Original assignee: International Paper Co
Current assignee: International Paper Co
Priority date: 1968-10-30
Filing date: 1968-10-30
Publication date: 1970-11-17
Anticipated expiration: 1987-11-17

Description

United States Patent US. Cl. 162180 6 Claims ABSTRACT OF THE DISCLOSURE A process of sizing paper in which a water-soluble aluminate is added to aqueous 'wood pulp until its pH is at least 9, a material yielding hydrogen ions and nonaluminum-containing polyvalent anions is added to bring the pH down to not less than about 4.5, and rosin size is applied to the surface of paper made from the pulp.

This invention relates to the sizing of paper and to a novel method of increasing the resistance of paper to water penetration and otherwise enhancing the quality of the sizing of the paper.

This application is a continuation of SN. 716,001, filed Mar. 26, 1968 now abandoned and a continuationin-part of co-pending U.S. Ser. No. 549,819, filed May 13, 1966, now abandoned.

US. Pat. No. 3,074,843 issued to Lagally et al. shows a process of producing paper having high dry strength and good wet strength wherein aluminum hydroxide is precipitated by mixing an aluminum-containing compound and an acid, a base, or an aluminum salt in the absence of nonaluminum-containing polyvalent anions (e.g., the sulfate ion). Optimum results were achieved at a pH within the range of 6 to 9. See, particularly, column 6, lines 29 to 32, and column 2, lines 61 to 63, of the Lagally et al. patent. Lagally et al. stress their need to be free of nonaluminum-containing polyvalent anions by calling it essential to their invention. See column 2, lines 27 and 28, of the Lagally et al. patent.

It has now been found, however, that the stated need of Lagally et al. for the attainment of strength when wet can be obviated, and that remarkable levels of sizing can be obtained concurrently with the development of strength. It has been found that, if a water-soluble aluminate is added to an aqueous wood pulp slurry until its pH is at least 9, i.e., 9 or above and if a material yielding hydrogen ions such as sulfuric acid or papermakers alum is then added to the pulp and aluminate mixture to bring the overall pH down, i.e., to bring the pH down to not less than about 4.5, aluminum hydroxide will precipitate in such a manner and to such a degree as to assure excellent levels of sizing once rosin size or the like is added to complete the process. In short, then, it has been found that, if the pH of the wood pulp is attended to correctly, the presence of the nonaluminumcontaining polyvalent anions of papermakers alum Al (SO .14H Oor sulfuric acid is of little or no deleterious effect. The following examples, which describe a standard sizing method ,(Example 1) and variations of the method of present invention (Examples 2 to 18), and tables, which compile data of tests made on products of the examples, confirm this finding:

EXAMPLE 1 A mixture of 60% and 40% hardwood kraft pulp, bleached to 85% GE. brightness, was refined in an Patented Nov. 17, 1970 experimental beater, at 1.75% consistency, to 509 CS. freeness. Forty grams (ovendry basis) of the refined pulp were suspended in distilled water at 3% consistency. Fortified size (commercially available Paper Product 2409) was added to the slurry at a rate of 42.8 pounds of size solids per ton of pulp. A mechanical stirrer was used to keep the slurry thoroughly mixed during the addition. Stirring was continued, and after five minutes papermakers alum 'was added at the rate of 53.5 pounds Al (SO .14H O per ton of pulp. Stirring was continued for 10 minutes. pH of the slurry after the addition of alum was 4.0. A solution of half normal sodium hydroxide was added to pH 5.0. Stirring was continued for one minute. Consistency was adjusted to 0.375% with water containing enough hydrochloric acid to give pH 5.0. Handsheets were formed on a British sheet mold, pressed between a polished metal plate and blotters, clamped in rings, and dried in a forced-draft oven at 150 C. for 30 minutes. Basis weight and caliper averaged pounds and 7.0 mils, respectively. Before testing, sheets were brought into equilibrium with the atmosphere of a room maintained at 50% relative humidity and 73 F.

EXAMPLE 2 Thirty grams (ovendry basis) of the refined pulp used in Experiment 1 were adjusted to 3% consistency with distilled water. A solution of sodium aluminate (commercially available Nalco 680) was slowly added to the slurry at the rate of 90 pounds per ton of pulp. Stirring was rapid during this addition. After five minutes of continuous stirring, the slurry was transferred to a TAPPI standard disintegrator. The disintegrator was started, and as violent agitation began pH was adjusted to 5.5 by the addition of a normal solution of sulfuric acid. At this point, flocculation occurred. Cf., Curtman, L. J.; Qualitative Chemical Analysis; The MacMillan Company; New York, 1938; p. 181 and Kolthoff et al.; Textbook of Quantitative Inorganic Analysis (3rd ed.); The MacMillan Company; New York, 1952, p. 318. The slurry was returned to a beaker and stirring was continued for 25 minutes, during which period a solution of fortified rosin size (Paper Product 2409) was delivered into the mixture at the rate of 3.4 pounds of size solids per ton of pulp. The slurry was diluted to 0.375% consistency, and handsheets were prepared, pressed, and conditioned as in Experiment 1.

Each dried sheet was weighed, dipped in a solution of fortified rosin size (Paper Product 2409), blotted lightly, weighed, and heated to incipient dryness at C. between a polished metal plate and blotters on a Carver press. The sized sheets were clamped in rings and dried in a forced-draft oven at 105 C. for 30 minutes. Size solids pickup was equivalent to 3.4 pounds per ton of pulp.

EXAMPLE 3 Example 2 was repeated, except that the slurry of pulp and sodium aluminate was adjusted to pH 5 .5 by the addition of a solution of papermakers alum.

EXAMPLE 4 Thirty grams (ovendry basis) of the pulp used in Experiment 1 were suspended in distilled water at 3% consistency. A solution of sodium aluminate was slowly added to the slurry at the rate of 90 pounds Na Al O .3H O per ton of pulp. Stirring was rapid during this addition. The mixture was transferred to a TAPPI standard disintegrator, and as violent agitation began, a normal solution of sulfuric acid was rapidly added to the slurry in such volume as to lower pH to 5.5 and flocculation of the variety discussed in the Curtman and Kolthofl et a1. texts, supra, occurred. Agitation was continued for 30 seconds. The treated pulp was returned to a beaker and stirred at a moderate rate for 20 minutes. Handsheets were prepared, pressed, and dried as in Experiment 1. Each dried sheet was weighed, dipped in a fresh solution of fortified rosin size (Paper Product 2409), blotted ligthly, weighed, and heated to incipient dryness at 105 C. between a polished metal plate and blotters on a Carver press. The sized sheets were clamped in rings and dried in a forced-draft oven at 105 C. for 30 minutes. Basis weight and caliper averaged 100 pounds and 7.0 mils, respectively. Size solid pickup was equivalent to 6.8 pounds per ton of pulp.

EXAMPLE Example 4 Was repeated, except that pH of the slurry of pulp and sodium aluminate was adjusted to 5.5 by the addition of a solution of papermakers alum.

EXAMPLE 6 Thirty grams (ovendry basis) of the pulp used in Experiment l were suspended in distilled water at 3% consistency. A solution of sodium aluminate was slowly added to the slurry at the rate of 90 pounds Na Al O -3H O per ton of pulp. Stirring was rapid during this addition. While stirring continued, 0.5 N sulfuric acid was slowly added in such volume as to lower pH to 5.5 and flocculation of the variety discussed in the Curtman and Kolthoif et a1. texts, supra, occurred. Agitation was continued for 20 minutes. Handsheets were prepared, pressed, and dried as in Experiment 1. Each dried sheet was weighed, dipped in a fresh solution of fortified rosin size (Paper Product 2409), blotted lightly, weighed, and heated to incipient dryness at 105 C. between polished metal plates and blotters on a Carver press. The sized sheets were clamped in rings and dried in a forced-draft oven at 105 C. for 30 minutes. Basis Weight and caliper averaged 100 pounds and 7.0 mils, respectively. Size solids pickup was equivalent to 6.8 pounds per ton of pulp.

EXAMPLE 7 Example 6 was repeated, except that pH of the slurry of pulp and sodium aluminate was adjusted to 5.5 by the addition of a solution of papermakers alum.

EXAMPLE 8 Example 6 was repeated, except that sodium aluminate was used at the rate of 60 pounds per ton of pulp, and that size solids pickup was equivalent to pounds per ton of pulp.

EXAMPLE 9 Example 8 was repeated, except that pH of the slurry of pulp and sodium aluminate was adjusted to 5 .5 by the addition of a solution of papermakers alum.

EXAMPLE l0 and Koltholf et al. texts, supra, occurred. Violent agita tion was continued for 30 seconds; the treated pulp was returned to a beaker and stirred at a moderate rate for minutes. Handsheets were prepared, pressed, and dried as in Experiment 1. Each dried sheet was weighed, dipped in a fresh solution of pale rosin size (Paper Product 2408A), blotted lightly, weighed, and heated to incipient 4 dryness at 105 C. between a polished metal plate and blotters on a Carver press. The sized sheets were clamped in rings and dried in a forced-draft oven at 105 C. for 30 minutes. Basis weight and caliper averaged 100 pounds and 7.0 mils respectively. Size solids pickup was equivalent to 5.7 pounds per ton of pulp.

EXAMPLE 11 Example 10 was repeated, except that pH of the slurry of pulp and sodium aluminate was adjusted to 5.5 by the addition of a solution of papermakers alum.

EXAMPLE 12 Example 4 was repeated, except that the pulp was unbleached pine kraft, and that pH of the slurry of pulp and sodium aluminate was adjusted to 5.5 by the addition of 0.5 N sulfuric acid.

EXAMPLE 13 Example 12 was repeated, except that pH of the slurry of pulp and sodium aluminate was adjusted to 5.5 by th addition of a solution of papermakers alum.

EXAMPLE 14 Four hundred thirty grams of pulp (ovendry basis) similar to that used in Experiment 1 were Weighed into a Valley beater and diluted to 1.75% consistency with demineralized water. A solution of sodium aluminate containing the equivalent of pounds Na Al O -3H O per ton of pulp was added to the slurry during mixing. A 0.5 N solution of sulfuric acid was added to adjust pH to 5.5. Here, flocculation as discussed in the Curtman and Kolthoff et al. texts, supra, occurred. Mixing was continued for 20 minutes after the addition of acid before refining was begun. With a 5-kilogram weight in place, the pulp was beaten for 21 minutes to 509 CS. freeness. The refined pulp was transferred to a large container and diluted with demineralized Water (at pH 5.5) to s'heetmaking consistency. Handsheets were prepared, pressed, dried, sized, and conditioned as in Experiment 4.

EXAMPLE 15 Example 8 was repeated, except that a solution of sodium aluminate containing the equivalent of 40' pounds Na Al O -3H O per ton of pulp was added to the slurry during mixing.

EXAMPLE 16 Example 15 was repeated, except that pH of the slurry of pulp and sodium aluminate was adjusted to 5 .5 by the addition of a solution of papermakers alum.

EXAMPLE 17 Example 15 was repeated, except that pH of the slurry of pulp and sodium aluminate was adjusted to 6.5 by the addition of a 0.5 N solution of sulfuric acid.

EXAMPLE 18 Example 17 was repeated, except that pH of the slurry of pulp and sodium aluminate was adjusted to 4.5 by the addition of a 0.5 N solution of sulfuric acid.

EXAMPLE l9 Thirty grams (ovendry basis) of bleached kraft pulp at C8. freeness 500 were suspended in distilled Water at 3% consistency. A solution of sodium aluminate was slowly added to the slurry at the rate of 90 pounds Na Al O 3H O per ton of pulp. Stirring was rapid during this addition. While stirring continued, a normal solution of orthophosphoric acid was slowly added in such volume as to lower pH to 5.4 and flocculation of the variety discussed in the Curtman and Kolthofi et al. texts, supra, occurred. Agitation was continued for 20 minutes. Handsheets Were prepared, pressed, and dried as in Experiment 1. Each dried sheet was weighed, dipped in a fresh solution of fortified rosin size (Paper Product 2409), blotted lightly, weighed, and heated to incipient dryness at 105 C. between polished metal plates and blotters on a Carver press. The sized sheets were clamped in rings and dried in a forced-draft oven at 105 C. for 30 minutes. Basis weight and caliper averaged 100 pounds and 7.0 mils, respectively. Size solids pickup was equivalent to 6.8 pounds per ton of pulp.

EXAMPLE 20 Forty grams (ovendry basis) of refined pulp similar to that used in Example 1 were suspended in distilled water at 3% consistency. Slurry pH was adjusted to 1.9 by the slow addition of a normal solution of sulfuric acid. Stirring was rapid during this addition. After five minutes of continuous stirring, the slurry was transferred to a TAPPI standard disintegrator. The disintegrator was started, and as violent agitation began pH was adjusted to 5.5 by the addition of a solution of sodium aluminate at the rate of 90 pounds per ton of pulp. Flocculation occurred.

The slurry was returned to a beaker and stirring was continued for 25 minutes, during which period a solution of fortified rosin size was delivered into the mixture at the rate of 3.4 pounds of size solids per ton of pulp. The slurry was diluted to 0.375% consistency, and handsheets were prepared, pressed, and conditioned as in Example 1.

Each dried sheet was weighed, dipped in a solution of fortified rosin size, blotted lightly, weighed, and heated to incipient dryness at 105 C. between a polished metal plate and blotters on a Pasadena press. The sized sheets were clamped in rings and dried in a forced-draft oven at 105 C. for 30 minutes. Size solids pickup was equivalent to 3.4 pounds per ton of pulp.

EXAMPLE 21 Forty grams (ovendry basis) of pulp similar to that used in Example 1 were suspended in distilled water at 3% consistency. Slurry pH was adjusted to 1.9 by the addition of a normal solution of sulfuric acid. Stirring was rapid after this addition. The mixture was trans ferred to a TAPPI standard disintegrator and as violent agitation began a solution of sodium aluminate was added in such volume as to lower pH to 5.5. Flocculation occurred.

Agitation was continued for 30 seconds. The treated pulp was returned to a beaker and stirred at a moderate rate for 20 minutes. Handsheets were prepared, pressed, and dried as in Example 1. Each dried sheet was weighed, dipped in a fresh solution of fortified rosin size, blotted lightly, weighed, and heated to incipient dryness at 105 C. between a polished metal plate and blotters on a Pasadena press. The sized sheets were clamped in rings and dried in a forced-draft oven at 105 C. for 30 minutes. Basis weight and caliper averaged 100 pounds and 7.0 mils, respectively. Size solids pickup was equivalent to 6.8 pounds per ton of pulp.

EXAMPLE 22 Example 21 was repeated, except that pH of the pulp slurry was adjusted to 3.7 by the addition of a solution of papermakers alum before adding a solution of sodium aluminate to flocculation pH 5.5.

EXAMPLE 23 Forty grams (ovendry basis) of pulp similar to that used in Example 1 were suspended in distilled water at 3% consistency. While the slurry was slowly stirred, pH was adjusted to 1.9 by the slow addition of half normal sulfuric acid. After 5 minutes pH was adjusted to 5.5 by the addition of a solution of sodium aluminate containing the equivalent of 90 pounds Na Al O .3H O per ton of pulp. Agitation was continued for 20 minutes. Handsheets were prepared, pressed, and dried as in Example 1. Each dried sheet was weighed, dipped in a fresh solution of fortified rosin size, blotted lightly, weighed, and heated to incipient dryness at C. between polished metal plates and blotters on a Pasadena press. The sized sheets were clamped in rings and dried in a forced-draft oven at 105 C. for 30 minutes. Basis weight and caliper average 100 pounds and 7.0 mils, respectively. Size solids pickup was equivalent to 6.8 pounds per ton of pulp.

EXAMPLE 24 Example 23 was repeated, except that sulfuric acid was added to the pulp slurry in such amount that flocculation pH 5.5 was attained by the addition of the equivalent of 60 pounds Na Al O 3H O per ton of pulp.

EXAMPLE 25 Example 24 was repeated, except that the volume of sulfuric acid used to adjust slurry pH was such as to require only 40 pounds Na Al O .3H O per ton of pulp to give flocculation pH 5.5.

TABLE 1 Lactic acid Cofiee Dry Water penepeneindi- Cobb absorpscope, scope, cator, size, g./ tion, minutes minutes seconds sq. m. percent The data set forth in Table I, supra, suggest that a unique and remarkably effective method of sizing paper has been developed. Sizing by the present flocculated aluminate-rosin size procedure has produced handsheets superior in the characteristics evaluated to similar sheets prepared by orthodox means.

The following additional observations are worthy of note:

Variations in flocculation pH between 4.5 and 6.5 have little influence on sizing (Examples 15, 17, and 18, Table I);

Violent agitation during and immediately after flocculation does not appear to affect sizing (Examples 4 and 6, Table I); and

Both fortified rosin size and regular pale rosin size are compatible with the flocculated aluminate system (Examples 2 and 10, Table I).

What is claimed is:

1. A process for sizing paper made from wood pulp comprising a step of adding a water-soluble aluminate to an aqueous slurry of wood pulp in an amount sufficient to bring the pH of the aqueous slurry of the wood pulp to about 9 and above, a step of adding a material yielding hydrogen ions and non-aluminum-containing polyvalent anions to the aqueous slurry of wood pulp in an amount sufficient to flocculate the aluminate without lowering the pH of the aqueous slurry of the wood pulp beyond about 4.5, and a step of adding a rosin size to the wood pulp after it is transformed from the aqueous slurry into a web of paper.

2. A process for sizing paper made from wood pulp comprising a first step of adding a water-soluble aluminate to an aqueous slurry of wood pulp in an amount sufficient to bring the pH of the aqueous slurry of wood pulp to about 9 and above, a second step of adding a material yielding hydrogen ions and non-aluminum-containing polyvalent anions to the aqueous slurry of wood pulp in an amount suflicient to flocculate the aluminate without lowering the pH of the aqueous slurry of the wood pulp beyond about 4.5, and a third step of adding a rosin size to the wood pulp after it is transformed from the aqueuos slurry into a web of paper.

3. The process of claim 1 wherein the Water-soluble aluminate is sodium aluminate.

4. The process of claim 1 wherein the material is sulfuric acid.

5. The process of claim 1 wherein the material is paper- 15 makers alum.

References Cited UNITED STATES PATENTS 4/1919 De Cew 16218O 1/1969 Jones 162185 S. LEON BASHORE, Primary Examiner R. H. ANDERSON, Assistant Examiner US. Cl. X.R.