JP2804629B2 - Polysilicate microgels as retention / drainage aids in papermaking - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Cross Reference to Related Application This application is a continuation-in-part of application 07 / 245,184, filed on September 16, 1988, filed on 07 / 388,9, filed on August 7, 1989.
No. 67 is a continuation-in-part application.

FIELD OF THE INVENTION The present invention relates to papermaking, and in particular, to a method of spraying a suspension of pulp and mineral filler in water on a wire or net and removing water to form a web or sheet of fibers. More particularly, the present invention relates to a method for removing pulp and fines in a water removal process such that water removal is easier and fines retention is further enhanced, thereby increasing both the productivity and yield of the papermaking process. It involves the addition of anionic polysilicate microgels along with the organic polymer to agglomerate.

Background and Summary of the Invention Many additive systems for improving wet-end draining and fines retention have been described in the prior art. In this system, polymers, combinations of polymers and polymers combined with colloidal silica are used. Although the last-named systems are the most efficient of the systems currently used, there is a continuing need to provide additives with lower cost and improved performance.

The present invention is formed by the partial gelling of an alkali metal silicate or a polysilicate such as sodium polysilicate, having 3.3 parts by weight of SiO _{2 and} 1 part by weight of Na ₂ O in the most common form. The polysilicate microgel is used as a retention and drainage aid. Microgels, referred to as "active" silicas, in contrast to commercially available colloidal silicas, are arranged in a three-dimensional network and chains, very fine, e.g. from an aggregate of 1 nm particles. Become. This microgel generally has a very large surface area, usually 100 m ² / g, and is used in the papermaking process with cationic polymers derived from natural or synthetic sources.

Polysilicate microgels can be most easily formed by adding an initiator to a solution of sodium polysilicate. The initiator initiates the gelation process, which will be allowed to proceed to completion and will result in complete solidification of the solution. The solidification time of the gel, the time required for complete solidification once it has begun, can range from seconds to months and depends on a variety of factors including pH, silica concentration, temperature and the presence of neutral salts. Dependent. For industrial applications, short gel setting times are preferred. Once initiated, the gelling process proceeds to about 5 to 95% of the gel set time before being stopped by diluting the polysilicate solution to desirably about 1% by weight or less.

The solution of the polysilicate microgel thus formed is an excellent retention and drainage aid when combined with a water-soluble cationic polymer, preferably cationic starch, cationic guar or cationic polyacrylamide. Is known.

Prior Art U.S. Pat. No. 2,217,466 describes that polysilicic acid or activated silica has been used early as a coagulation aid in the treatment of raw water. Chem.Eng.Progress Volume 1 (1
947) Merrill and Bolton on page 27, Ac
The tivated Sillica, a New Engineering Tool uses the use of activated silica as a coagulant for white water in paper mills and as a retention aid for fiber and filler fines when added to paper machine headboxes. Suggests. No mention is made of the use of anionic active silica together with the cationic polymer.

U.S. Pat. Nos. 3,224,927 and 3,253,978 disclose the use of colloidal silica and cationic starch as binders for inorganic fibers when applied for bonding heat resistant fibers. The amount of colloidal particles used is considerably higher than that used in papermaking applications.
That is, about 1% per product related to papermaking applications
On the other hand, for applications for bonding fibers, it is 10-20% by weight per product. In the bonding of the fibers, conditions leading to agglomeration should be avoided, but in papermaking agglomeration is the desired result for addition.

U.S. Pat.No. 4,388,150 is directed to adding to papermaking stock to improve the retention of components of the stock, or to reducing contamination problems and to recover the value of stock components. A binder composition comprising colloidal silica and cationic starch is disclosed. U.S. Patent No. 4,388,
No. 150 teaches that colloidal silica may take a variety of forms, including polysilicic acid, but the use of colloidal form of silica provides the best results. This patent teaches that polysilicic acid itself is undesirable and will degrade upon storage if not stabilized.

It has now been found that it is preferable to preserve or age polysilicic acid to some extent. Once the polysilicic acid gels, there is little benefit in using the solution as a retention and drainage aid, so complete gelation of the aqueous solution of polysilicic acid should be avoided. Storage or aging of the polysilicic acid results in the formation of silica microgels, which, when used in combination with various cationic polymers, are at least compatible with the retention and drainage systems provided by prior art colloidal silica / cationic starch combinations. Gives an equal and often superior system.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a photomicrograph of silicate cationic starch made by the method of Example 14.

FIG. 2 is a photomicrograph of a silicate cationic starch made by the method of Example 15.

FIG. 3 is a photomicrograph of silicate cationic starch made by the method of Example 16.

DETAILED DESCRIPTION OF THE INVENTION RKIler has published 174- of his book "The Chemistry of Silica," published by John Wiley & Sons of New York.
Pages 176 and 225-234 describe the polymerization of polysilicic acid and the formation of microgels consisting of three-dimensional aggregates of very fine particles of polysilicic acid. Such microgels are also referred to as "active silicas" and are distinguished from the parent, non-crosslinked polysilicic acid, and from the commercially common colloidal silica or colloidal silicic acid solutions. Is done. Microgels in sols cannot be easily detected by techniques commonly used to detect colloids in sols, for example by light dispersion. Similarly, microgels cannot be easily separated from sols by centrifugation. As described on page 231 of the book cited above, according to RKIler, the concentration of silica particles in the microgel's three-dimensional network, the refractive index of the microgel, and the density of the microgel are the same as in the surrounding sol. is there.

Another method for producing activated silica and its use in water purification is described in Reinhold Publishin, New York.
g Co., published in 1960 by James G. Vail, `` Sol
uble Silicates ". Reading this book and generally reading the published literature suggests that polysilicate microgels can be formed as follows.

(1) Aqueous solutions of alkali metal silicates can be acidified with acid exchange resins and inorganic and organic acids such as sulfuric acid and acetic acid. To enable the formation of polysilicate microgels, it is usually necessary to acidify the silicate to a pH of about 2-10.5 and then store or age the solution to some extent. The aging time mainly depends on the pH and concentration of the silica. Very short (about a few minutes) for solutions containing 4-5% by weight of silica at a pH of 3-4
After a good ripening time, the silica is reduced to about 1 to stabilize the solution by inhibiting further growth of the microgel.
The solution is diluted to weight percent or less.

(2) The aqueous solution of the alkali metal silicate is an acidic salt and gas such as sodium orthoborate (Bolux),
It can be acidified by sodium bisulfite, potassium dichromate, sodium bicarbonate, sodium dihydrogen phosphate, carbon dioxide, sulfur dioxide and chlorine. Acid salts of weak acids with strong acids, such as ammonium sulfate, aluminum sulfate, ferric chloride and ferrous chloride, can also be used.

(3) An alkali metal salt of an amphoteric metal acid may be added to the aqueous solution of an alkali metal silicate. Examples of such salts are sodium aluminate, sodium stannate, sodium zincate, potassium chromate and potassium vanadate. These salts initiate the process of gelation and formation of silica microgels, while not reducing the alkalinity of the silicate solution.

(4) Certain organic compounds may be added to the aqueous solution of the alkali metal silicate. Preferably, the organic compound is water-soluble and is capable of at least partially acidifying the silicate solution as a result of its hydrolysis,
Not necessarily essential. Examples of such compounds are organic anhydrides, amides, esters, lactones, nitriles and sultones. More particularly, these are succinic anhydride, acetamide, ethyl acetate, butyrolactone, propionitrile and propane sultone, respectively. In the case of more stable organic compounds, some heating of the mixture may be necessary to effect hydrolysis and consequent formation of a polysilicate microgel.

All the methods described above are applicable in principle to the formation of polysilicate microgels useful in papermaking. However, many of these have very poor commercial success when considering cost, safety and environmental standards. For example, vanadium salts are expensive and dangerous chlorine is best avoided from use. Similarly, the emission of toxic chromium salts into the white water of a paper mill is not preferred.

From an industrial point of view, the simplest and most economical method for producing the polysilicate microgels used according to the invention is the acidification of sodium polysilicate solutions with common mineral acids or sodium polysilicate. Addition of a gel initiator to the solution, such as alum, sodium borate or sodium aluminate.

To practice the present invention, Na ₂ O and S in a weight ratio of 1: 3.3
it is best to use commercially available solution of poly silicate sodium containing a iO _2. Such a solution
It is commonly supplied as containing silica at a concentration of 28-30% by weight. To produce polysilicate microgels, such commercially available solutions are diluted to concentrations suitable for both the particular preparation method selected to initiate microgel formation and the concentration of initiator used. I have to. For example, silica concentrations of about 0.1-6% by weight have been found to be most useful for forming microgels by acidification with mineral acids, while RKIler states in pages 288 of the above mentioned book that up to 12% by weight. It teaches that sodium polysilicate solutions containing SiO ₂ can be successfully acidified using sulfuric acid. However, if non-acidic substances such as sodium borate are to be used as initiators, in order to dilute and stabilize the polysilicate microgel before complete gel solidification occurs,
Any concentration of silicate can be used as long as the gel set time of the mixture is long enough. Stabilization of the polysilicate microgel can be achieved by diluting the SiO ₂ desirably to about 1% by weight or less.

In the production of polysilicate microgels, it is important to emphasize that chains of particles and three-dimensional networks should be given enough time to stabilize the gel by dilution. . This time, which varies according to the particular embodiment of the operation, should be about 5 to 95%, preferably 10 to 90%, of the time when a solid insoluble in water is formed (gel set time). Increasing the viscosity of the polysilicate solution itself is not a particular limitation as long as a homogeneous aqueous solution can be obtained upon subsequent dilution. In practice, the gel set time should be as short as possible. It is most convenient to mix the silicate solution with the initiator, which is also preferably a solution, and then dilute the mixture in as short a time as necessary to form a sufficient microgel.

The polysilicate microgels produced in this way generally have activity in retention / draining applications similar to colloidal silica currently used in industrial applications as well, and in many cases the combination of polysilicate microgels is It is accompanied by significantly improved performance at lower loading rates, which is an industrially desirable objective. This polysilicate microgel would also be a cost advantage over commercially available colloidal silica because it can be easily manufactured on paper mill premises and thus minimizes product shipping costs.

In the papermaking process, the polysilicate microgels of the invention are used with cationic polymers derived from natural or synthetic sources. The most useful of these polymers are cationic starch, cationic guar and cationic polyacrylamide, all of which have been described in the prior art for their application to papermaking. Other cationic polymers are also used alone or in combination with the polysilicate microgel, in addition to cationic starch, cationic guar and cationic acrylamide. Examples of such cationic polymers include polyethyleneimine, copolymers of polydiallyldimethylammonium chloride acrylamide with 2-methylacryloxyethyltrimethylammonium chloride, amine-epichlorohydrin condensation products, and condensation of polyamines with dicarboxylic acids. Then, the prepolymer is further reacted with epichlorohydrin to obtain a cationic wet strength resin. Cationic starches are particularly useful because of their advantages of low cost and of providing dry strength to the paper. Where paper strength is not a major requirement, the use of other polymers may be advantageous.

The cationic starch used can be obtained from any of the common starch-producing materials such as corn starch, potato starch, wheat starch and tapioca starch, but usually potato starch is used to practice the present invention. Provides the most preferred cationic product. Cationization is carried out when the degree of substitution of nitrogen is about 0.001-0.2 (ie about 0.01-2.0% by weight).
[Nitrogen / wt% of starch]) is carried out by a commercial manufacturer with a reactant such as 3-chloro-2-hydroxypropyltrimethylammonium chloride to obtain a cationic starch varying in the range of Any of these cationic starches can be used in combination with the polysilicate microgel of the present invention. Cationic starches with a degree of nitrogen substitution of about 0.03 (ie, 0.25% by weight) have been most frequently used.

Practically, the polysilicate microgel is present in an amount of about 0.001 to 3.0% by dry weight of the furnish with an amount of ionic polymer varying from about 0.001 to 3.0% by weight (0.02 to 60 lb / ton) of the dry weight of the furnish. Used in amounts varying from 1.0% by weight (0.02 to 20 pounds / ton). Higher amounts of either ingredient may be used, but usually without the beneficial effects, with the disadvantage of increased costs. The preferred loading is from about 0.05 to 1.0 weight percent (10 to 20 pounds / ton) of cationic silicate microgel with about 0.05 to 1.0 weight percent of cationic starch.
0.4% by weight (1-8 lb / ton) or, for cationic guar and cationic polyacrylamide, 0.001-1.0% by weight (0.02-20 lb / ton).

The combination of polysilicate microgel / polymer is
Although a wide pH range of about 4 to 10 may be used in the furnish, more neutral and alkaline furnishes are preferred for best results. The furnish may consist of various wood pulp and inorganic fillers. Thus, bleached kraft pulp, thermomechanical pulp, chemical thermomechanical pulp and groundwood pulp may all be used with clay as inorganic filler and precipitated or ground calcium carbonate and titanium dioxide. The following examples illustrate how to prepare and use the polysilicate microgels of the present invention.

Examples Illustrate the effect of polysilicate microgels in papermaking
The main measurement we performed was the Canadian Standard Freeness Test
(Canadian Standard Freeness Test)
It was a measure of performance. Of turbidity of white water from freeness test
The degree of retention of pulp and filler fines in the system is determined by measurement.
Ancillary measures of security are provided. Britt Dyna
Measurement of fines retention in the mic drainage jar was also performed. Approximation
BMA- to illustrate the utility compared to the prior art
Comparison with a commercially available colloidal silica sample called O
Adopted. This product is available from Marietta, Georgia, Proc
Sold in the United States by omp Inc. and in papermaking
Used retention / drainage aid system, Compozilt one of
It is a component of. About 5.5 nanometers of colloidal silica
(Nm) particle diameter and retention using colloidal silica /
U.S. Pat.
500-550m described in 4,388,150^Two/ g surface area
And

In each example, the same conditions were maintained for the order of mixing and addition of the components. The preferred method has been found to be to add the cationic polymer to the furnish first, followed by the addition of the polysilicate microgel. It has been found that this order generally gives better performance than the reverse addition method, but this reverse method (adding the polysilicate microgel first) may be used, or the respective materials may be separated and added. May be done. All mixing was performed in the Britt Jar with the stirrer set at 800 rpm according to the following chronological order.

(1) place the furnish in Britt Jar and stir for 15 seconds; (2) then add the cationic polymer and stir for 15 seconds; (3) then add the polysilicate microgel or colloidal silica Then agitate for 15 seconds, and (4) then drain the Britt Jar for fines retention measurement or place the Britt Jar contents in the Canadian Freeness Tester storage cup for drainage measurement. I was moved.

Reference Example 1 This example compares the performance of a simple polysilicic acid to the performance of a polysilicate microgel. A comparison of the performance of commercial colloidal silica with BMA-O is also included.

 The simple polysilicic acid used in this example is an excess of Do
wex 50W-X8 (H⁺] Polystyrene sulfonic acid resin
1% by weight of SiO_TwoSodium polysilicate solution containing
(Na_TwoO: SiO_TwoIs 1: 3.3) quickly by the batch method
Manufactured by deionization. Lower pH to 3.5
After allowing the resin to pass, the resin was removed by filtration and the solution_Two
 Diluted to 0.125% by weight.

Poly silicate microgels used were partial acidification of poly sodium silicate containing 4 wt% of SiO _2, and was prepared by aging. That is, 19 ml of 1.98 molar sulfuric acid was added to 300 g of sodium polysilicate solution under good stirring over 15 seconds. The pH of the solution dropped to 10.01. The solution was set aside and aged for 1 hour, after which the solution was stabilized by diluting it to 0.125% by weight of SiO ₂ .

For comparative testing, Canadian standard freeness was measured using an alkaline fine furnish having a consistency of 0.3% by weight. The suspended solids contained 70% by weight bleached kraft pulp (70% hardwood / 30% softwood) and 30% by weight precipitated calcium carbonate. pH was 8.0.

 All tests on various silica products are done on a furnish basis.
20 lb / ton on a dry weight basis
Performed in combination with cationic starch added at loading
Was. Cationic starch is available from Procomp for its Compozil When
The nitrogen substitution degree, which is sold for use with
BMB-S1960, which was 0.03 potato starch.
Table 1 shows the measured values of drainage.

From Table 1, it can be seen that simple, uncrosslinked polysilicic acid had little effect on improving the freeness of the furnish. However, microgelled polysilicic acid shows at least as good overall performance as commercially available colloidal silica and is industrially preferred
Even showed work that is somewhat enhanced in the low amount of SiO ₂ 1 to 4 lb / ton.

Reference Example 2 This example illustrates the use of alum used by papermakers as an initiator to form a polysilicate microgel.

In a 300 g sodium polysilicate solution containing 4 wt% SiO ₂ , which is put in a Waring mixer and stirred vigorously, 10 wt% alum [aluminum sulfate, Al
₂ (SO ₄ ) ₃ .14H ₂ O] 75 ml was added from a pipette. The mixture was stirred for 1 minute to give a milky solution of pH 9.8 containing a fine white precipitate. A portion was immediately diluted to 0.125% by weight of SiO ₂ (Microgel 2A). Another portion was left for 20 minutes and then diluted to 0.125% by weight of SiO ₂ (Microgel 2B). The remaining stock solution gelled completely after 30 minutes. These two dilute solutions of the polysilicate microgel were tested for drainage performance in a manner similar to that described in Example 1. Table 2 shows the results.

The freeness values in Table 2 indicate that the drainage achieved by both microgels was at least comparable to commercial samples of colloidal silica, especially in the normal usage range of 4-8 lb / ton. Is shown.

Reference Example 3 This example illustrates the use of borax (decahydrate ortho sodium _{borate, Na 2 B 4 O 7 ·} 10H 2 O) as an initiator to form the polysilicate microgel.

 60 g of borax solution of 5% by weight with good stirring
3.75 wt% SiO in liquid_TwoSodium polysilicate containing
40 g of the solution was added. After mixing, leave the mixture as it is
And aged. After 8 minutes, part of the SiO_Two 0.125% by weight
Diluted until. During the solidification of the remaining undiluted gel
The time was 23 minutes. Alkaline finished paper similar to Reference Example 1
Drain measurement for diluted microgels
Was. However, the cationic starch used was from DeI, Illinois.
Cationic diuretic obtained from A.E.Staley Mfg.Co.
Stalok, potato starch There were 400 samples. starch
Loading rate is also 20 lb / ton for all tests
there were. Table 3 shows the results of the test.

In SiO ₂ is industrially preferably lower loading rate of 1-4 lbs / ton, the performance of polysilicate microgel is outperformed the performance of the colloidal silica sol. For polysilicate microgels, optimal performance was observed at a loading of 4 lb / ton, whereas colloidal silica was 8 lb / ton.

Reference Example 4 This example illustrates two methods using sodium stannate (Na ₂ SnO ₄ ) as an initiator to produce a polysilicate microgel.

Microgel 4A: a solution containing 5.2% by weight of sodium stannate in 50g of sodium polysilicate containing 5% by weight of SiO ₂
50 g was added over about 15 seconds with good stirring.
The mixture was set aside. After 4 hours, the mixture had become somewhat viscous. It was then diluted to 0.125% by weight SiO _{2 to} evaluate as a drainer.

Microgel 4B: To 64 g of a sodium polysilicate solution containing 5.5% by weight of SiO ₂ , 46 g of a solution containing 10% by weight of sodium stannate were added over about 15 seconds with good stirring. The mixture was set aside. After about 3.5 hours, the mixture set to a very loose gel. The loose gel was transferred to a Waring mixer containing 350 g of water and high speed mixed for about 2 minutes to obtain a clear solution. Next, this solution was used to evaluate drainage performance.
It was further diluted to SiO ₂ 0.125% by weight.

The Canadian standard freeness was measured using both microgels at various loading rates in the alkaline finished sample similar to that used in Reference Example 1. All tests have loading rates
Performed with 20 lb / ton BMB S-190 cationic potato starch.

It can be seen that both microgels show significantly enhanced drainage performance.

Reference Example 5 This example utilizes sodium aluminate (NaAlO ₂ ) as an initiator in forming a polysilicate microgel.

Poly sodium silicate solution 7 containing 10 wt% of SiO _2.
5 g was diluted to 30 g with water. 1.0% by weight of Al ₂ O ₃
20 g of a sodium aluminate solution containing was slowly added with good stirring. The sodium aluminate used was from Vinings Industries, Atlanta, Georgia.
A diluent of VSA-45, a commercially available liquid concentrate obtained from. The mixture was aged for 5 minutes without stirring and a sample was taken. It was diluted sample to SiO ₂ 0.125 wt% for evaluation. The undiluted part gelled after 14 minutes. Using an alkaline stock similar to that used in Reference Example 1, a polysilicate microgel and 20 lb / ton BM
The freeness of several combinations with BS-190 cationic starch was measured. Table 5 shows the results.

Polysilicate microgels showed significantly improved performance over colloidal silica.

Reference Example 6 This example illustrates the use of potassium dichromate (K ₂ CrO ₇ ) as an initiator to form a polysilicate microgel.

25g of sodium polysilicate containing 10% by weight of SiO ₂
Potassium dichromate solution (71.6 g of 5% by weight K ₂ CrO ₇ ) was added with good stirring and pre-diluted to 94.4 g. The mixture was aged and aged.
It gelled in 3.5 minutes. 2.5 minutes after mixing, the second preparation was sampled and diluted to 0.125% by weight SiO ₂ . The drainage test was performed again under conditions similar to those outlined in Reference Example 1. The results are shown in Table 6.

The polysilicate microgel showed performance comparable to colloidal silica.

Example 7 This example illustrates the use of polysilicate microgels in combination with cationic guar in an acidic furnish having a pH of 4.5 and 6.0.

 6% by weight SiO_Two-Containing sodium polysilicate solution
By deionizing, a 6% by weight solution of polysilicic acid
I made it first. Polysilicate solution, Dowex 50W-X8
[H⁺Approximately 14 a of polystyrene sulfonic acid ion exchange resin
Through a 1.5 inch diameter glass cylinder
Was. Adjust the flow rate to keep the pH of the polysilicic acid effluent at about 2.6.
Adjusted to about 30 ml / min. After collecting about 300 ml of product,
SiO_TwoIs partially diluted to contain 1% by weight of
I left it. The rest of the product gels in just one day
It has become.

 After standing for one week, one is at pH 6 and the other is at pH 4.5
To evaluate drainage performance in two acidic furnishes
1% by weight of SiO_TwoPart of the solution is SiO_Two Up to 0.125% by weight
Diluted further. Surface area of aged polysilicate microgels
Is G.W.Se on Anal.Chem. 28 (1956) 1981 page
Using ars titration method, 1076m^Two/ g. Draining
The consistency of the furnish used in the retest was 0.3
Wt% and 70% by weight bleached kraft pulp (70%
Hardwood, 30% softwood) and 30% by weight Klondyke From clay
Had been adjusted to the appropriate pH. Klondyke Sticky
Soil is Engelhard Corporat, Edison, NJ
It is a product of ion. Polysilicic acid microgels
Obtained from Stein, Hall and Co. Inc. in New York, New York
Jaguar Used with C13 cationic guar gum. Trial
All tests were conducted with a guar loading rate of 4 lb / ton
did. Table 7 shows the results.

If SiO ₂ of loading rate is 8 lb / ton, the combination of poly silicate microgels / sun Iongua can know that the draining is significantly improved over the combination of the BMA-O / sun Iongua. This improvement is seen for both pH 4.5 and pH 6.0 furnishes.

Reference Example 8 This example reports the measurement of fineness retention along with the measurement of freeness and turbidity of white water using a sample of polysilicic acid microgel.

 Dowex 50W-X8 (H⁺] 4 layers using ion exchange resin
Amount% SiO_Two300 g of sodium polysilicate solution containing
Polysilicic acid micro
A stock gel solution was prepared. Dilute polysilicic acid to 1% by weight
And aged as it was. Prepared
The surface area of the microgel at the time of
1187m when measured using s titration method^Two/ g. About 1
After standing for 8 hours, the surface area is 1151m^Two/ g slightly reduced to
Was. Next, the Canadian Standard Freeness Test and Britt Jar Fines
In both retention tests, the performance of the microgel was tested.
Was.

For this test, a furnish similar to that used in Reference Example 1 was used. The furnish consistency was 0.3% by weight for the freeness test and 0.5% by weight for the fines retention test. In the freeness test, the turbidity of the drained white water was also measured as an additional indication of fines retention. All tests were performed in the presence of 20 lb / ton BMB S-190 cationic starch. The results are shown in Tables 8 and 8A.

From Table 8, it can be seen that the polysilicate microgel was comparable to the optimal performance of commercially available colloidal silica in both draining and fines retention, as judged by the near turbidity values. In addition, and most desirable from an industrial point of view, microgels reduce this optimum to a lower loading of 4 lb / ton, only half the loading of 8 lb / ton required by commercial silica. Achieved at a rate.

The results in Table 8A confirm that the results in Table 8, that is, the optimum value of fines retention when using microgels, is achieved at only half the loading required for commercial colloidal silica.

Example 9 This example compares the fines retention values obtained with the additional two polysilicate microgels with the retention values obtained with colloidal silica.

The polysilicate microgels used were made as in the case of the stannate-initiated microgel 4A of Example 4 and the aluminate-initiated microgel of Example 5. The colloidal silica compared was BMA-O and the polymer used was BMB S-190 cationic starch with a loading of 20 lb / ton in all cases. All tests were performed using a standard Britt Jar apparatus and the method described previously. The furnish used was alkaline with a pH of 8.0 and had a composition similar to that of Example 1.

The improved performance of the two polysilicate microgels over colloidal silica can easily be seen from the above data.

Reference Example 10 This example illustrates the improvement obtained by using polysilicic acid microgel in combination with cationic polyacrylamide. Broken wood
100% furnish was used.

 100% groundwood pulp (50% hardwood / 50% softwood)
A furnish with a 0.5% strength by weight was made. electrolytic
To simulate the quality, 0.66 g of anhydrous sodium sulfate
Thorium was added. pH was 5.7. First of all
Was diluted to 0.3% by weight, and Hyper
floc CP-905H cationic polyacrylamide
To some furnish parts after adding
The Canadian standard freeness was then measured. This cation
Polyacrylamide from Hychem In of Jampa, Florida
c., which has an average molecular weight of 13 million and is positive
The ionicity was 20-30% by weight. Cation polyacryl
Luamide loadings 0, 1, 2, 4, and 6 lb / ton
The values of the freeness measured in 390, 420, 43, respectively
0, 430 and 485 ml.

 Performance of polysilicate microgel compared to colloidal silica
To do, Hyperfloc CP-905H loading rate 4 pounds
Per ton. Polysilicic acid microgel has a pH of 3.5
Deionized and 4% by weight SiO_TwoPolysilicon containing
6 days before diluting the sodium acid solution
SiO_Two It was a 1% by weight solution. Colloidal silicon
Mosquito was BMA-O. Table 10 shows the obtained results. This
The results of turbidity for the drained white water from the freeness test
Degree measurements are included.

It can be seen that the combination of polysilicic acid microgel / cationic polyacrylamide improves both freeness and fines retention (reduces turbidity of white water).

Reference Example 11 This example illustrates the use of some organic compounds in forming a polysilicate microgel.

Microgel 11A (gamma-butyrolactone as initiator): 300 g of sodium polysilicate containing 4% by weight of SiO ₂
To this was added 6 ml (6.72 g) of gamma-butyrolactone under stirring. The mixture was found to form a solid gel in about 70 minutes on standing. The pH at that time is 1
It was 0.67. The above preparation was then repeated and samples were taken and diluted after 65 minutes of standing to form a very loose gel. This loose gel is easily broken by stirring, resulting in a polysilicate microgel containing 0.125% by weight of SiO ₂ .

Microgel 11B (ethyl acetoacetate as initiator): 200 g of sodium polysilicate containing 4% by weight of SiO ₂
To this was added 10 ml (10.2 g) of ethyl acetoacetate under stirring. The mixture became cloudy at first, but cleared within 1 minute. The pH dropped from 11.22 to 10.61. The mixture was set aside and found to form a solid gel in about 18 minutes. After a similar second preparation was allowed to stand for 12 minutes, it was diluted to 0.125% by weight of SiO ₂ to give a polysilicate microgel for evaluation.

Microgel 11C (succinic anhydride as initiator): sodium polysilicate solution 20 containing 4% by weight of SiO ₂
While stirring 0 g, succinic anhydride (2.5 g) was added. About 5
After stirring for a minute, the anhydride dissolved and the pH dropped to 10.22. Upon standing still, the mixture formed a solid gel in about 75 minutes. After standing the _second preparation for 45 minutes, the SiO ₂
After dilution to 0.125% by weight, a polysilicate microgel solution was obtained.

The drainage and retention performance of solutions of microgels 11A, 11B and 11C in an alkaline furnish similar to that described in Reference Example 1 was evaluated by measuring the turbidity of white water. All evaluations were performed in the presence of 20 lb / ton BMBS-190 cationic starch. The reference sample for comparison with the commercial product was the previously described colloidal silica BMA-O.

From the results in Table 11, the polysilicate microgel was colloidal, as evidenced by higher freeness (improved draining) and lower turbidity values of the drained white water (improved fines retention). It will be appreciated that silica has generally provided improved optimal results.

Reference Example 12 This example reports on some surface areas of the polysilicate microgels exemplified in the above examples.

The polysilicate microgels described in the above examples were remade and the surface area of the microgels was determined using a modification of the Sears titration method cited above. Each polysilicate microgel, after preparation, SiO ₂ about
It was diluted to a concentration corresponding to 0.75% by weight. The 200 g portion was then deionized batchwise at room temperature to pH 3.5, excess resin was removed by filtration and 150 g of filtrate was titrated for surface area according to the method of Sears. For polysilicate microgels formed with initiators such as borates and chromates that generate acid by themselves and deionize to pH 3.5, by performing a blank measurement on the initiator only, It is necessary to correct for the acid generated from the initiator.

 Table 12 shows the obtained surface areas.

As already mentioned, the combination of polysilicate microgels, when compared to the drainage / retention performance observed when using colloidal silica at higher loadings,
It has been found to provide improved performance at low loading rates. In another embodiment of the present invention, where the preferred cationic polymer for use with the polysilicate microgel for draining and retention is cationic starch,
One-component products can be made in which silica microgels are deposited on starch granules. This new composition is suitably referred to as a "silicated cationic starch composition". This microgel is usually formed as a deposit which is observed to be somewhat irregularly distributed on the surface of the individual starch granules. This can be seen more clearly in FIGS. In addition, one-component compositions will usually also include other agglomerates, all microgels, which are incorporated into the composition. The dry solid offers convenience and economy as compared to the combination of colloidal silica, as the product of this component system is a dry solid and avoids the transport of large amounts of water.

The silicated starch composition according to this aspect of the invention comprises:
Although it can be prepared to contain about 1 to 25% by weight silica, the most consistently satisfactory results are obtained when the composition contains about 5 to 20% by weight silica. In fact, the solid starch compositions of the present invention require about 0.2 to about 0.2 to use.
An aqueous solution containing 2.0% by weight of starch is added to at least about 5
By heating to a temperature in the range of about 80 ° to 100 ° C. for up to about 20 minutes or more, i.e., until the starch granules swell and rupture while the silica microgel is dispersed in the aqueous medium. , Can be manufactured.
Although the heated solution is somewhat viscous and slightly opaque, the solution may be added directly to the papermaking stock or furnish as a single component retention and drainage aid. The amount of this heated solution added to the furnish may vary from about 0.05 to 5% by weight (1 to 100 pounds / ton based on dry stock). The silicated cationic starch according to the present invention exhibits improved drainage and retention performance in both alkaline and acidic furnishes, wherein the pH varies within a relatively wide range of 4-11. May be. In addition, satisfactory results have been observed when using silicated starch compositions in acidic furnishes that also contain alum.

Infrared analysis of silicated cationic starch, unlike non-silicated cationic starch, showed 1050 and 1800
A significant increase in light absorption was shown at a wavelength of cm ^-1 . These light absorption wavelengths correspond to the light absorption wavelengths of the main absorption band of orthosilicate, thus indicating that some orthosilicate bonding can be expected in the silicate starch compositions of the present invention. The orthosilicate linkages impart additional amphoteric properties to the silicated cationic starch, and it is believed that this is involved in improving the performance of the alum-containing furnish.

Silicated cationic starch of the present invention, for example, wheat,
Made from starches derived from various sources such as oats, corn, tapioca and potatoes. Potato starch is generally preferred due to its general properties.

The deposition of silica on a substrate has been extensively described in U.S. Pat. No. 2,885,366, the teachings of which are incorporated herein by reference. The method involves controlled acidification of a solution of an alkali metal silicate containing a suspension of a solid substrate. Depending on the pH, the rate of acidification, and the temperature of use, the silica deposited on the substrate can be a perfect crust of amorphous particles, porous gel particles, or impermeable silica.

In practicing the present invention, it is preferred to deposit as much microgel as possible on each granule of starch. Thereby, when the starch is subsequently heated in water just before use,
Optimal redispersion of the microgel will be achieved. Good redispersion has been observed when the starch is dispersed in water and heated, even when the composition additionally comprises a microgel agglomerate.

Silica microgels can be deposited using pre-cationized starch, but to maximize microgel deposition, an additional step in the cationization process is to deposit silica microgels on the cationized starch granules. Is preferred. In each case, about 5 to 50% by weight of cationic starch and 0.1 to 10% as alkali metal silicate.
An aqueous suspension containing SiO _{2 by} weight is formed. The individual starch granules in the suspension will generally have a size of about 5-100 microns. Microgels are formed and deposited by subsequent acidification under stirring. The alkali metal silicate used is sodium metasilicate, Na ₂ O
· SiO ₂ or may be one of the plain water glass such as Na ₂ O · 3.3SiO _2. Acidification of the well-stirred mixture of starch and silicate is carried out by slow addition of a suitable acid, acid gas, or salt, such as hydrochloric acid, carbon dioxide, or sodium bisulfate, respectively. The preferred pH range for silica microgel deposition is about 1
0.4 to 10.8, but within this range silica deposition is somewhat slow and incomplete. However, in practice, the separation of silica is faster and more complete
It is even more convenient to carry out the acidification in the acidic range where the pH is lower than 6.5. However, in this case, agglomerates of silica microgel are separately formed.

The acidification may be carried out in the operating temperature range from 10 ° C. to 70 ° C., but room temperature is sufficient for most purposes. In order to minimize the swelling of starch granules and possible rupture that is observed during microgel deposition,
Neutral salts such as, for example, sodium or potassium sulfate or sodium or potassium chloride can be added in amounts up to about 15% by weight. Higher temperatures are more important than the presence of neutral salts and also help to deposit silica microgels.

Silica microgels in amounts of 0.1 to 25% by weight or more can be deposited on starch granules by using the general methods described above, with amounts of 5 to 20% by weight being preferred as described above. The product gives a silica / starch ratio of 1/5 to 1/20, which covers the optimal performance range for this type of drainage and retention aid.

The following examples illustrate a method for depositing silica microgels on cationic granules of starch.

Example 1 This example describes the cationization of potato starch first followed by the deposition of silica microgel. The resulting product contained 6.23% by weight of SiO ₂ and 0.2% by weight of N.

Methods of starch cationization are described in U.S. Patent Nos. 2,813,093 and 2,867,217, the teachings of which are incorporated herein by reference. Such cationization involves the reaction of starch hydroxy groups with an epoxy etherifying agent containing a tertiary or quaternary nitrogen group.

Preparation A three-necked 500 ml flask equipped with a stirrer, water condenser and dropping funnel and immersed in a 50 ° C water bath was charged with 100 ml of water.
g, sodium chloride 20g and potato starch (humidity 23.8
%, Sigma Chem. Co.) was added. In this mixture,
70g water, aqueous sodium polysilicate (Na ₂ O ・ 3.3SiO ₂ , Si
O ₂ 28.4% by weight) 30 g, sodium hydroxide 1.65 g and 50
An alkaline etherification mixture containing 16.7 g by weight of QUat 188 (Dow Chem. Co.) was added dropwise over about 10 minutes. Heating and stirring at 50 ° C. was continued for 5 hours. The reaction mixture was then diluted to 1.2 with water and acidified to pH 6.3 with hydrochloric acid. The mixture was filtered and the product was washed on the filter three consecutive times with 1 water. After drying overnight in a vacuum oven at 80 ° C., the product of the silicated cationic starch is 0.2% by weight N and 6.23% by weight.
Of SiO ₂ .

In this demonstration of service performance, the properties of the product compared to the above
Noh and the Marrietta Procomp Company in Georgia
Special grade cationic starch and colloidal
A commercial two-component draining and retaining system containing Rica
A Compozil A comparison was made between the performance of these
The ingredients are added separately to the papermaking furnish. The comparison is
Equal weight of all components (sum of cationic starch and silica)
And performed under the standard. Compozil Cationic starch and
And the silicate cationic starch of the present invention are both solid starch.
Made by cooking powder in water at 100 ° C for 20 minutes
The solution was added to the papermaking stock as a 0.5% by weight solution. Use
The papermaking paper used was 0.21% by weight bleached kraft pulp.
(70% hardwood, 30% softwood), 0.09 wt% Kl as filler
ondyke Clay and 0.040% by weight alum [Al_Two(SO
_Four) ・ 18H_TwoO]
Was. The test was carried out by sequentially adjusting the pH of the stock with caustic soda.
Adjusted to 5 and 6.5. At each pH, paper stock
Measurement of Canadian standard freeness using 1 liter (TAPPI
Standard method). Freeness is direct about draining
Volumetric scale (larger numbers are best)
On the other hand, the turbidity of drained water (white water) is a measure of fine powder retention.
(Low turbidity is best). Is typically used in industry
Total loading of 1% by weight (based on dry stock)
The comparison was made at the level of addition of the substance. The results are shown in Table 13.
You.

Example 2 This example describes the deposition of silica microgel on starch granules following cationization of potato starch. The average value of the products obtained was 16.8% by weight of SiO ₂ and 0.38% by weight of N.

Adjustment In the same apparatus as used in Example 1, 170 g of water, 20 g of sodium chloride, 3.7 g of a 45% aqueous sodium hydroxide solution,
Aqueous sodium polysilicate (Na ₂ O • 3.3SiO ₂ , SiO ₂ 28.2
% By weight) and potato starch (Sigma Chem. Co.) 9
I put 0g. The mixture was heated to 50 ° C. with stirring, then 23 ml of 65% by weight Quat 188 (Dow Chem. Co.) were added dropwise. Continued heating and stirring, and withdrawing a 100 g sample from the flask at 2.5 and 5.5 hours yielded products with different cationization levels (wt% N). The samples were diluted with water so that the SiO _{2 corresponded} to 3% by weight (based on the original silicate). Each sample was acidified to pH 6.5 with hydrochloric acid, stirred for 10 minutes, and then filtered. The solid product was redispersed in water 1, the pH was adjusted to 6, and then filtered again. This wash was repeated once more, after which the solid product was dried in a vacuum oven at 80 ° C. overnight. The analytical values of the dried samples can be found in Table 14.

Further, an electron micrograph of the sample 5.5 hours later was taken. This can be seen in FIG. The product mainly consists of granules of cationic starch with silica microgel.

Use An evaluation of the use of the product of this example was made again with Example 1.
By Canadian standard freeness measurements made on the same samples.
pH was 4.5. The test was 20 pounds of silicate starch /
Ton loading rate (based on 1% by weight of dry paper)
And 16.61 pounds / ton of cationic starch and
Loading of 3.4 lb / ton combination of id silica
Rate (17 wt% SiO_TwoOf silicate starch containing sucrose
Rate equivalent to 1% by weight). Ingredient gender
The comparison was performed using the ability as a control. Table 15 shows the results.

One can see the improved performance (higher freeness and lower turbidity values) of the silicated starch sample in both draining and fines retention.

Example 3 This example illustrates another method for depositing silica microgels into cationic starch. This method is suitable for producing silicated cationic starch compositions of the type described herein from preformed cationic starch.

350 g of water and 35 g of sodium sulfate in a 1 liter flask
g, aqueous sodium silicate (Na ₂ O · 3.3SiO ₂ , 28.4% by weight) 156 g and cationized potato starch (Sigma Che
m.Co.) 165 g. The mixture is stirred at room temperature 22 ° C.
Then 1M sulfuric acid was added dropwise until the pH dropped to 10.7. The pH is adjusted by stirring for 2 hours while adding a small amount of acid.
Was kept at this value. The mixture was then filtered and the filter cake was resuspended in one piece of water, stirred and filtered again. This second resuspension of the cake in water 1 has a pH of 10.28
Gave. The pH was adjusted to pH 4.7 with hydrochloric acid and filtered. The solid was resuspended in water 1 and filtered again. A final wash of the filtrate was performed. The solid was dried in a vacuum oven at 80 ° C. overnight. Ignition analysis
by sis), solid was found to contain SiO ₂ of 8.5 wt%. Electron micrographs reproduced as FIG. 2 showed that the microgels were deposited substantially all on the starch granules.

Example 4 This example illustrates another method for depositing silica microgels. This method is also suitable for producing silicated cationic starch from preformed cationic starch.

500 g of water, 50 g of sodium sulfate and aqueous sodium polysilicate (Na ₂ O ·
3.3 SiO ₂ , 28.2% by weight) were charged under stirring, followed by 235 g of potato starch (Sigma Chem. Co.). After stirring for about 5 minutes, a gradual addition of 1 M sulfuric acid at a rate of 1 ml per minute was started by a small pump. The addition of 116 ml of acid was continued over 2 hours until the pH of the mixture dropped to 4. Then the mixture was filtered. The filter cake was resuspended in water 1, stirred and filtered again. This is 2 more
The wet cake was placed in a vacuum oven at 80 ° C. and dried. 9.6% by weight of cake by ignition analysis
Of SiO ₂ . Electron micrographs of the product, reproduced as FIG. 3, show that in addition to the microgel deposited on the starch granules, there is a separate agglomeration of silica microgel.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) D21H 17 / 28,17 / 67 C08L 3/04 C08K 3/36

Claims (4)

(57) [Claims] 1. A dry solid containing from about 1 to 25% by weight of silica and consisting essentially of granules of cationized starch deposited on the surface in the form of a water-soluble polysilicate microgel. An improved drainage and retention aid for papermaking which is comprised of a silicated cationic starch composition which is added to an aqueous furnish containing pulp. 2. The improved drainage and retention aid according to claim 1, wherein the cationized starch is a cationized potato starch. 3. The improved drainage and retention aid according to claim 1, wherein the polysilicate microgel is randomly deposited around the surface of the starch granules. 4. A dry solid containing about 1 to 25% by weight of silica and consisting essentially of granules of cationized starch deposited on the surface in the form of a water-soluble polysilicate microgel. An improved papermaking drainage and retention aid for pulp-containing aqueous furnish comprising silicated cationic starch and another silica microgel agglomerate.