JPS6017387B2 - Method for improving filler dispersion - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a method for improving dispersions of crosslinked urea formaldehyde polymer particles useful as paper fillers.

It is known that fine crosslinked urea formaldehyde polymer particles having a particle size of 0.1 to 1.0 m are added to paper as a so-called filler for the purpose of improving the paper's performance such as opacity.

Generally, the filler is added to the pulp slurry in the papermaking process as an aqueous dispersion or a cake obtained by dehydrating the aqueous dispersion in a furnace.

However, in the cross-linked urea-formaldehyde polymer particle filler mentioned above, free formaldehyde from the hexalysis reaction remains, which not only causes problems in the working environment during the papermaking process, but also formaldehyde in paper containing these particles. Because of this, its use is limited. On the other hand, about 9% of the crosslinked urea formaldehyde polymer single particle dispersion
% by weight is water, which requires a great deal of cost to transport and store as it is; therefore, the liquid dispersion is usually dehydrated in a furnace to form a cake (usually with a dry solids content of about 25%.Hereafter, this A cake like this is abbreviated as "approximately 25% cake."
). When such a cake is used, it is necessary to redisperse the cake with a large amount of water during papermaking, but in this case, fine particles, such as aggregates that pass through a 100 mesh sieve, remain, and these particles remain after papermaking. This caused the surface of the paper to become sticky, significantly lowering the commercial value of paper products.
Conventionally, it has been considered to wash these particles with water to remove free formaldehyde, but this is difficult to carry out on an industrial scale due to the small size of the particles.

Therefore, for example, as described in Tokuka Sho 53-109135, free formaldehyde and urea in an equivalent molar amount or more are added to a dispersion of cross-linked urea-formaldehyde polymer particles with a pH of 4 or less and allowed to react for 3 to 6 minutes. It had been removed. However, in this conventional method, urea is added under acidic conditions with a pH of 4 or less, so the cross-linked urea-formaldehyde polymer particles obtained by urea treatment have a high performance as a filler for paper, that is, a filler content in paper. Retention rate (referring to the rate at which the added filler remains in the paper)
Also, the redispersibility of the cake-like filler was still unsatisfactory. The objects of the present invention are to provide an aqueous dispersion of a crosslinked urea-formaldehyde polymer particle filler by: (i) removing formaldehyde odor; (ii) improving the filler's permeability in paper;
(iii) Improving the redispersibility of the cake-like material produced from the dispersion is simultaneously achieved.

The present inventors completed the present invention by considering selectively removing only free formaldehyde in the aqueous phase while retaining the methylol groups that are thought to exist on the surface of cross-linked urea formaldehyde polymer particles. .

That is, in the present invention, 0.5 to 4.0 equivalents of ammonia or ammonium salt are added to 1.0 mol of free formaldehyde dissolved in a filler dispersion consisting of one particle of crosslinked urea formaldehyde polymer, and the axis is 4. The content is to adjust it to ~10. A typical embodiment of the method of the present invention will be explained below in order of steps.

First, crosslinked urea formaldehyde polymer particles are produced by a known method, for example, the method of Hakama Kaisho 54-135893. That is, after mixing formaldehyde aqueous solution, urea, carboxymethyl cellulose and water, the - is adjusted to 7 with caustic soda water and reacted to obtain an initial condensate. The liquid of this initial condensate is continuously mixed with an aqueous solution of several percent sulfuric acid using an in-line mixer and is supplied onto an inorganic belt made of acid-resistant rubber before the condensate begins to solidify. The liquid mixture solidifies on the belt. The solid material thus obtained is collected in a container, water is added thereto, and the slurry is made into a slurry, which is then finely pulverized in a colloid mill to obtain a dispersion of crosslinked urea formaldehyde polymer particles (filler dispersion). Next, according to the method of the present invention, a predetermined amount of ammonia or ammonium salt was added to the filler dispersion, and the mixture was concentrated at 0 to 90°C for 5 to 12 minutes, and then the pH was adjusted to 4 to 1 with aqueous caustic soda or sulfuric acid solution.
Female agency preferably adjusts to 6-9 and then further adjusts to 0-9 pi 0 to 5-5
After 120 minutes, an improved dispersion of crosslinked urea formaldehyde polymer single particle filler is obtained. The liquid dispersion to which the present invention is applied is one in which cross-linked urea formaldehyde polymer particles are dispersed in water, and it is applicable to any type of dispersion produced by any known method, not just those produced by the above-mentioned method. Ammonia may be in any form, including ammonia gas, liquefied ammonia, and aqueous ammonia. The ammonia water may be commercially available as a 29% aqueous solution, or may be one in which water is added to further reduce the concentration. As the ammonium salt, any of ammonium chloride, ammonium nitrate, ammonium sulfate, ammonium phosphate, other inorganic ammonium salts, ammonium formate, ammonium acetate, ammonium tate, and other organic ammonium salts can be used. Although ammonium salts are usually obtained as solids, they may be added to the filler dispersion as a solid, or they may be added to the filler dispersion as an aqueous solution that has been previously dissolved in water.
One feature of the present invention is that ammonia or ammonium salts are used among many amino compounds.
Amino compounds other than ammonia and ammonium salts,
For example, since the effects of the present invention cannot be obtained with ethylenediamine, diethylenetriamine, triethylenetetramine, urea, melamine, etc., it can be said that ammonia acts specifically. In the present invention, the amount of ammonia added is equal to the amount of free formaldehyde dissolved in the filler dispersion.
．． It should be 0.5 to 4.0 equivalents per 0 mole.

If the amount added is less than 0.5 equivalent, remove formaldehyde odor (reduce the amount of free formaldehyde in the aqueous phase by approximately 150
This corresponds to lowering the wind. ) becomes insufficient. If the amount added exceeds 4.0 equivalents, the formaldehyde odor, the retention rate of the loss material in paper, and the redispersibility of the cake-like loss material will reach their limits, and no significant difference will be seen even if the amount added is increased. Note that adding 0.5 equivalent of an ammonium salt means adding 0.5 mol of a monovalent ammonium salt, such as ammonium chloride or ammonium formate, and also adding 0.5 mole of a monovalent ammonium salt, such as ammonium chloride or ammonium formate, or adding a divalent ammonium salt such as ammonium sulfate or ammonium monohydrogen phosphate. 0.25 mol of trivalent ammonium compounds such as ammonium phosphate.
．． 17 moles may be added.

In order to achieve the purpose of the present invention, the pH of the filler dispersion must be 4 to 4.
Must be adjusted to 10.

The preferred pH is 6-9. pH adjustment can be carried out by adding caustic soda water or sulfuric acid aqueous solution while checking with a normal glass electrode fence filter. If the pH after addition of ammonia or ammonium salt is lower than 4, the retention rate of the filler in the paper will be low and the redispersibility of the caked waste will also be poor. If the pH is higher than 10, the ammonia odor of the filler becomes so pronounced that it is not practical. There is no particular restriction on the order of addition of ammonia or ammonium salt and pH adjustment with caustic soda water or sulfuric acid aqueous solution, etc., and either can be done first, but after adding ammonia first, the pH is adjusted.
It is preferable to adjust.

According to the method of the present invention, the formaldehyde odor was removed and the filler retention rate in the paper was significantly improved, and surprisingly, the redispersibility of the caked filler was also significantly improved.

Another advantage of the method of the invention is that it can be applied not only to batch processes, but also to continuous processes, making it extremely suitable for industrial production.

That is, in the conventional method of removing free formaldehyde by adding an aqueous urea solution to the filler dispersion, the reaction is carried out at a certain temperature for a certain period of time (urea treatment) at a pH of ~4, and then immediately treated with caustic soda water, etc. It is necessary to neutralize it to effectively stop the reaction. In this case, for example, if the urea treatment time varies by ±5 minutes, it will significantly affect the performance of the final product. Therefore, when applied to a continuous process that inevitably produces a residence time distribution in the urea treatment time, the performance of the final product will be inconsistent.

However, according to the method of the present invention, ammonia addition and p
Since there are no strict restrictions on the processing temperature and processing time in the H adjustment operation, it is suitable for continuous processing. As a continuous process device, filler dispersion liquid, ammonia aqueous solution, and pH adjustment liquid may be continuously supplied to a single tank or multiple stages of rope tanks, or a tubular reactor may be used.・In-line A mixer may also be used. Examples are shown below. Example 1 37% of formaldehyde (hereinafter all percentages are by weight).

) 38.4 parts of aqueous solution (all parts hereinafter are by weight)
, urea 18. $ parts, carboxyme, chill cellulose 0.
7 parts, water 42. The two parts were mixed, the pH was adjusted to 7 with 20% caustic soda water, and the mixture was reacted at 70°C for 2 hours to obtain a urea formaldehyde initial condensate. 10 sparse parts of this initial condensate
180 parts of this 2.7% sulfuric acid aqueous solution was added, mixed, and left for 1 hour. The obtained gel-like material was coarsely ground and slurried (the pH of the dispersion was 1.5 at this time) to obtain a dispersion (filler dispersion) consisting of cross-linked urea formaldehyde polymer particles. Obtained. The free formaldehyde force in the aqueous phase of this filler dispersion was 550 kg, and the pungent formaldehyde odor was extremely strong. After adding 2.8 parts of 20% aqueous ammonia to 100 parts of the filler dispersion (the molar ratio of ammonia to free formaldehyde at this time was 2:1, this was then added to the NH3/C base 0=
Shown as 2.0. ), and concentrated at 40 qo for 1 hour while adjusting the pH to 7.0 with 20% caustic soda water. The mixture was then pulverized in a colloid mill and further dehydrated in a separate furnace to obtain a cake and furnace liquid with a solid content of about 25%. As shown in experiment number 1 in the table, the amount of free formaldehyde in the furnace liquid was similar to that of 25Q, and no formaldehyde odor was detected. Solid content approximately 25%
After storing the cake at 4,000 °C for 3 weeks, double the amount of water was added to prepare a redispersion (at this time, the content of cross-linked urea formaldehyde polymer particles in the redispersion was approximately 8%). ), the mixture was heated for 3 minutes at a rotational speed of 200 pm, filtered through a 100-mesh metal mesh, washed with water, dried with hot air, and the weight of the filter residue was determined. The ratio of the weight of the furnace residue to the weight of the crosslinked urea formaldehyde polymer particles in the redispersion liquid is calculated (hereinafter, the value obtained by this procedure will be expressed as the cake redispersibility defective rate): 0.01% Met. This value is experiment number 7
This is 1/6 of the defective cake redispersibility rate of the sample obtained by the conventional urea treatment method shown in . When paper is made by adding these polymer particles at a ratio of 1 part to 1 part to 10 parts of dry pulp, the filler retention rate in paper (the filler added during paper making remains in the paper after paper making) Table 1 shows the ratio) and the opacity of the paper. A remarkable improvement effect is seen compared to the conventional urea treatment method (Experiment No. 7). The opacity of the paper that did not contain monkey material was 81.5%. Example 1 Ten volumes of the same filler dispersion as in Example 1 were added to 8.7 g of a 20% aqueous ammonium chloride solution (the molar ratio was N
H40/CQO=2.0.

), and the mixture was stirred for 1 hour at 40 qo while adjusting the pH to 7.0 with 20% caustic soda water. The mixture was then pulverized in a colloid mill and further dehydrated in a separate furnace to obtain a cake and furnace liquid with a solid content of approximately 25%. The amount of free formaldehyde in the furnace liquid was 252 capes, as shown in Experiment No. 2 in Table 1, and no formaldehyde odor was detected. The above cake was redispersed using the same machine as in Example 1, and the cake redispersibility failure rate was determined to be 0.01%.

At this time, paper was made in exactly the same manner as in Example 1, and
The results shown in Experiment No. 2 in Table 1 were obtained for the gradation rate of the filler and the opacity of the paper.

Example 3 Same filler dispersion as in Example 1 20$ Mariko 2
Add 1.54 parts of 0% ammonia water (at this time,
C ratio 0 = 0.55), after 3 stages, this dispersion was divided into two parts, and the pH of each part was adjusted to 4.5% with 20% caustic soda water.
While adjusting the temperature to 5 (experiment number 3) and 9.5 (experiment number 4), I lit the light for an hour at 40oo.

The mixture was then finely pulverized in a colloid mill and further dehydrated in a separate furnace to obtain a cake and a furnace liquid each having a solid content of approximately 25%. The amount of free formaldehyde in the furnace liquid was 120Q and 110, respectively, and both had a slight formaldehyde odor. This cake was redispersed in exactly the same manner as in Example 1, and the cake redispersibility failure rate was determined to be 0.04% (Experiment No. 3).
) and 0.02% (experiment number 4). When paper was made from these materials in exactly the same manner as in Example 1, the results shown in Table 11 were obtained for the filler weight in paper and the paper opacity. Actual example 4 The same filler dispersion as in Example 1 was added with 11.06 parts of 20% ammonia water (NH3/C yen = 3.95 at this time), and After pouring this dispersion into
Divide the food into 4 pieces and adjust each bait to 4.5 (experiment number 5) and 9.5 (experiment number 6) with 20% caustic soda water.
We stayed together for an hour.

The mixture was then finely pulverized in a colloid mill, and further dehydrated in a furnace to obtain a cake and a furnace liquor each having a solid content of about 25%. The amount of free formaldehyde in the furnace liquid was 350 kaze and 27 kamisaki, respectively.
No formaldehyde odor was detected in either case. This cake was redispersed in exactly the same manner as in Example 1, and the cake redispersibility failure rate was determined to be 0.03% (Experiment No. 5).
and 0.01% (experiment number 6). Experiment number 5 and 6
When paper was made from the filler obtained in Example 1 in exactly the same manner as described in Example 1, the results shown in the table were obtained as the paper weight loss rate and paper opacity. Comparative Example 1 20 parts of the same liquid dispersion as in Example 1 were added to 12 parts of the 30% urea aqueous solution.
After adding 4 parts (at this time, the dispersion was divided into two parts, and each part was divided into two parts with 20% caustic soda water.
After heating at 40°C for 30 minutes while adjusting H to 2.5 (experiment number 7) and 8.0 (experiment number 8), only the sample of experiment number 7 was immediately neutralized with 20% caustic soda water to pH 7.
~8 The methylenation reaction between urea and methylol group was virtually stopped.

The mixture was then finely pulverized in a colloid mill and further dehydrated in a separate furnace to obtain a cake and a furnace liquid each having a solid content of about 25%. The amount of free formaldehyde in the furnace liquid was 32Q in Experiment No. 7, and 180Q in Experiment No. 8. The formaldehyde odor of the latter was quite strong. This cake was redispersed in exactly the same manner as in Example 1, and the cake redispersibility failure rate was determined to be 0.06% (experiment number 7) and 0.05% (
Experiment number 8). When paper was made using these fillers in exactly the same machine as in Example 1, the results shown in Table 11 were obtained for the filler weight in paper and paper opacity.

Table-1

Claims (1)

[Claims] 1.0 free formaldehyde dissolved in a dispersion of filler consisting of cross-linked urea-formaldehyde polymer particles.
0.5 of ammonia or ammonium salt per mole
A method for improving a filler dispersion, characterized by adding ~4.0 equivalents and adjusting the pH to 4 to 10.