JPH0629310B2 - Filler manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to a method for industrially producing a paper filler comprising urea formaldehyde crosslinked resin particles having improved performance.

The paper filler comprising urea formaldehyde cross-linked resin particles obtained according to the present invention can improve the optical properties of the paper product such as whiteness, opacity, and opacity after printing when filled in the paper product. It can be used to advantage.

<Prior Art> In the fields of newsprint, telephone directory paper, coated base paper, and the like, weight reduction has been remarkably advanced in recent years. Generally, the weight saving of paper is achieved by reducing the amount of pulp material used, that is, the basis weight, but for that reason, the strength such as stiffness (rigidity) decreases, the optical characteristics decrease, the printability decreases, etc. Various problems arise. On the other hand, for the purpose of improving optical properties such as whiteness of paper, opacity and opacity after printing,
Fine particles of inorganic substances such as kaolin, talc, and white carbon, and fine particles of urea-formaldehyde resin crosslinked body are blended as a filler.

Various methods have been known so far regarding the method for producing fine particles of crosslinked urea-formaldehyde resin for a filler. For example, an initial condensate of urea and formaldehyde is reacted in the presence of a protective colloid agent at room temperature to 100 ° C. with sulfamic acid or the like as a catalyst to form a gel, which is roughly pulverized, neutralized, and dried. The method of crushing is known (Japanese Patent Publication No. 46-28087).

When the initial condensate of urea and formaldehyde and the acidic catalyst aqueous solution are mixed, the reaction mixture first becomes a soft gel-like solid, and then the reaction proceeds to form a hard crosslinked resin.
If the reaction mixture is stirred during this period, the physical properties of the finally obtained filler are unfavorably affected. As an industrial continuous method for producing a crosslinked urea-formaldehyde resin without stirring, an initial condensate and an acidic catalyst aqueous solution are continuously mixed in an in-pipe mixer, and gelation is performed in an extrusion screw to obtain a product. A method of post-curing the obtained gel-like solid for another 30 minutes has been proposed (Japanese Patent Publication No. 49-2350). Further, a method has also been proposed in which the initial condensate and the acidic aqueous solution are continuously mixed, the mixture is supplied onto a rotating endless belt, and the mixture is solidified on the belt (Japanese Patent Publication No. 57-26686).

<Problems to be Solved by the Invention> As described above, various methods for producing a urea-formaldehyde cross-linked resin by mixing and reacting an initial condensate of urea and formaldehyde with an aqueous acidic catalyst solution are known. In the process of advancing the reaction by mixing the initial condensate of and formaldehyde with the acidic catalyst aqueous solution, the reaction product forms a hydrogel and becomes a solid, so let's carry out this reaction without stirring in the tank. Then, the inside of the tank is solidified as one body, a large amount of solid is generated and stirring cannot be performed after the reaction is completed, or it is difficult to efficiently discharge the reaction product from the reaction tank.

<Means for Solving Problems> As a result of various studies to solve the conventional problems, the present inventors filled a filler composed of urea formaldehyde crosslinked resin particles having high linseed oil absorption. It was found that the optical properties of the paper obtained by papermaking, especially the opacity of the paper after printing, are greatly improved, and a patent application was filed therefor (filed on April 1, 1987).

The inventors of the present invention have conducted various studies on a production method of urea formaldehyde crosslinked resin particles having such a high linseed oil absorption amount that can be industrially advantageously carried out, and as a result, use both non-stirring and stirring in a reaction tank. It was found that the above was extremely effective, and the present invention was reached.

That is, according to the present invention, an initial condensate and an acidic catalyst obtained by reacting urea and formaldehyde at a charging ratio of 1: 1.9 to 1: 2.4 (molar ratio) are used, and
When reacting at 35 to 65 ° C. in the presence of ˜20 weight times of water and carboxymethyl cellulose or a salt thereof,
After the reaction raw materials are mixed, the mixture is kept under non-stirring state for 3.5 to 20 minutes, then stirred for a short time, and then held again under non-stirring state to proceed the reaction to obtain a linseed oil absorption amount suitable as a filler. A high urea-formaldehyde cross-linked resin can be easily manufactured.

Hereinafter, the present invention will be described in detail.

In the present specification, “%” and “part” represent “% by weight” and “part by weight” unless otherwise specified.

Urea in the present invention is produced by a known method, and as the formaldehyde in the present invention, an aqueous formaldehyde solution having a formaldehyde concentration of 30 to 55% is usually used, but other formaldehyde is paraformaldehyde. Water-soluble formaldehyde polymers such as

The initial condensate of urea and formaldehyde in the present invention is a mixture of urea and formaldehyde in a ratio of 1: 1.9 to 1: 2.4 (molar ratio), and the reaction is neutral to weakly alkaline at 60 to 90 ° C. for 30 to 120 minutes. It is a water-soluble urea-formaldehyde resin obtained by
It is about the concentration. The preferred charging ratio of urea and formaldehyde when producing the initial condensate is 1: 2.0 to
It is 1: 2.2 (molar ratio). When the amount of formaldehyde is less than 1: 1.9, the urea-formaldehyde crosslinked resin particles obtained have a small oil absorption, and the effect of improving the optical properties of paper is not sufficient. If the amount is large, the reaction yield is lowered, which is not economical, and the oil absorption amount is also small, and the effect of improving the optical characteristics of the paper is not sufficient. The weight of the initial condensate is equal to the total weight of urea and formaldehyde used in the reaction, excluding those that have escaped to the outside of the system.

The urea-formaldehyde cross-linked resin obtained by the method of the present invention is an aggregate substantially composed of primary particles having a particle diameter of 1 μm or less. In the production method of the present invention, it is necessary to allow carboxymethyl cellulose or a salt thereof to coexist as a protective colloid agent during the reaction in order to generate uniform and fine primary particles of the urea-formaldehyde cross-linked resin. Examples of the carboxymethyl cellulose salt include carboxymethyl cellulose sodium salt and carboxymethyl cellulose potassium salt, and those produced by a known method having an etherification degree (DS) of 0.4 to 0.7 can be used. The amount of these carboxymethyl cellulose or its alkali metal salt used is usually about 0.1 to 10%, preferably 0.5 to 2%, based on the initial condensate. In addition, the addition method is not particularly limited, carboxymethyl cellulose alkali metal salt is previously dissolved in water and mixed with either urea or formalin, and added to the reaction system when the initial condensate is produced. Is advantageous.

Examples of the acidic catalyst in the present invention include mineral acids such as sulfuric acid and hydrochloric acid, organic acids such as formic acid, acetic acid, sulfamic acid and paratoluenesulfonic acid. Further, since these acidic catalysts improve the mixing, it is advantageous to add them after diluting them with water to about 5 to 20%. PH during the reaction is 3
It is necessary to keep below, preferably 2 or less.

In the present invention, when the precondensate of urea and formaldehyde and the acidic catalyst are mixed and reacted, 5 to 20 parts of water must be made to coexist with 1 part of the precondensate. When the amount of coexisting water is less than 5 parts or more than 20 parts, the urea-formaldehyde cross-linking resin obtained has a small oil absorption and the effect of improving the optical properties of the paper is not sufficient.

As a mode for carrying out the present invention, first, when the aqueous solution of the initial condensate and the aqueous solution of the acidic catalyst are mixed, 5 to 20 parts of water is contained with respect to 1 part of the initial condensate. prepare. Then, both solutions are introduced into an in-line mixer and continuously mixed, and the mixture discharged from the in-line mixer is immediately introduced into the reaction tank, or one of the solutions is put into the reaction tank first, and then the inside of the tank is closed. Stir in cooperation and prepare the other. At this time, it is advantageous to first pour the solution having a large volume into the reaction tank. It is preferable that the charging is completed in the shortest possible time, within 1 minute at the longest, and the stirring is stopped at the same time. That is, once the inside of the reaction tank has reached the condensation reaction condition, the stirring is stopped as soon as possible, preferably before the inside of the tank becomes cloudy. Then, the inside of the reaction tank is maintained for 3.5 minutes to 20 minutes, preferably 4 to 10 minutes, that is, it is kept under non-stirring conditions.

Further, the temperature of the contents in the reaction tank is set so as to fall within the range of 35 to 65 ° C, preferably 45 to 60 ° C. In addition,
It is not always necessary to maintain this temperature range at the end of the reaction.

If the unstirred state is maintained for a predetermined time, the inside of the reaction tank is stirred for a short time, and then the unstirred state is maintained again. Repeat this operation if necessary and continue the reaction for at least 30 minutes for a total reaction time. The stirring in the course of the reaction in the method of the present invention is for facilitating the reaction operation. That is, according to the studies by the present inventors, the physical properties of the obtained urea-formaldehyde crosslinked resin as a filler are the best when the reaction is completed without stirring.
However, if the reaction is consistently completed without stirring, the inside of the tank will solidify or large lumps will be generated, so even if you try to crush the product into small lumps by stirring after the reaction, the stirrer Sometimes the load is too high to stir. Even if a powerful stirrer is installed and stirred, the product adhered to the tank wall may remain as it is, or it may be difficult to form small particles. Have difficulty.

The present invention has been made from the viewpoint of improving the operability during the reaction without impairing the physical properties of the finally obtained filler. It is kept for 3.5 to 20 minutes in the non-stirred state and then stirred for a short time, and then, It is based on the finding that the operability of the reaction can be improved without impairing the physical properties of the finally obtained filler if it is maintained under the non-stirred state again. In the present invention, at the time of the first stirring, the reaction product is not hardened so much, so that the stirring is easy. The stirring is preferably carried out in the shortest possible time as long as the reaction product is separated from the tank wall and crushed into small pieces, and mild stirring within 1 minute is usually sufficient. When the mixture is stirred for a long time, the physical properties of the finally obtained filler deteriorate. When the first stirring is completed, the reaction is allowed to proceed again without stirring. Usually, stirring is carried out again after 5 to 20 minutes. Since the reaction considerably progresses between the first and second stirring, the conditions of the second stirring do not affect the physical properties of the filler so much in the first stirring, and the stirring of the third and subsequent stirring is further improved. The effect is small. Therefore, once the reaction has proceeded to a certain point, it is possible to continue stirring thereafter so as to reduce the size of the agglomerates formed. In a preferred embodiment of the present invention, a cycle consisting of holding for 4 to 10 minutes in a non-stirred state and subsequent stirring within 1 minute is repeated twice or more, preferably three times or more.

When the reaction temperature is lower than 35 ° C, the oil absorption of the obtained urea-formaldehyde cross-linked resin particles is small, while the temperature of 65 ° C is low.
If it is higher, the reaction yield decreases.

Usually, it is desirable to set the reaction temperature higher when the ratio of water to the initial condensate is high, and lower when the ratio is higher.

Stopping the reaction reduces the temperature of the contents, or
This is done by adding an alkaline substance and neutralizing it.
As the alkaline substance used to stop the reaction, a commonly used alkaline substance, for example, caustic soda, sodium carbonate, ammonia and the like can be mentioned, and pH
It is preferable to neutralize it to about 4.5 to 7. When neutralizing,
The efficiency can be increased by adding water, or by adding water and then stirring with a stirrer.

After neutralization, the reaction product is separated by filtration, washed with water if necessary, pulverized, adjusted to a desired particle size, and filled into paper.

The paper filler comprising the urea-formaldehyde cross-linked resin particles of the present invention usually has an average particle size of 2 to 9 μm, preferably 3 μm.
Adjust the particle size to be ~ 6μ.

When the paper is filled with the urea-formaldehyde cross-linked resin particles obtained by the method of the present invention, it can be made into paper by an ordinary method, and as a pulp raw material for producing paper, it is usually used as a raw material for paper. GP and RG used
P, SP, KP, DIP, etc. can be used.

<Examples> Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples unless it exceeds the gist. The particle size, the linseed oil absorption, and the filler yield were measured by the following methods.

Measurement of linseed oil absorption (JIS K5101) Slurry obtained by neutralization (about 50 g as cross-linked resin)
Is suction-filtered with a glass filter (G4), the residue is again put into 2 liters of water, and after stirring well, again,
Suction filtration was performed to obtain a water-containing cake (solid content: about 20%). To 30 g of this cake, add 70 ml of water to prepare a slurry of about 6%, and use a home-use juice mixer to prepare 2
After crushing for minutes, suction filtration was performed again with a glass filter to obtain a water-containing cake (solid content: about 20%). 20 g of this cake-like substance was put into 200 ml of methanol, and the mixture was stirred at room temperature for 30 minutes, and then, a glass filter (G
Suction filtration was performed in 4). Then, the filtration residue was vacuum dried at 40 ° C. for 8 hours to obtain a white powder.

1 g of this white powder is taken on a glass plate, linseed oil is dripped little by little, kneaded with a spatula on the glass plate, and the titer amount of linseed oil when the sample is in a fluidized state is read. The linseed oil absorption was determined.

Here G: linseed oil absorption (%) H: linseed oil amount (ml) S: sample mass (g) Measurement of average particle size of urea formaldehyde crosslinked resin particles Measured by light transmission method using Stokes' law did.
That is, the crosslinked resin particles are dispersed in distilled water, the change in turbidity due to the sedimentation of the particles is measured as the change in light transmittance, and the weight cumulative distribution curve (one logarithm) is determined from the measured values.
The% particle size is defined as the average particle size. When calculating the weight cumulative distribution curve, the true specific gravity of the sample: 1.45, distilled water (20 ° C)
The specific gravity of 0.998 and the viscosity of 1.005 were used. The maximum particle size was 50 μm.

To prepare the sample, put 50 ml of distilled water and 100 mg of the paper quality evaluation sample (solid) in a beaker, and use an ultrasonic disperser (output 2
Dispersion treatment was carried out for 5 minutes at 0 W and a frequency of 40 kHz, and when this was placed in a measurement cell, the absorbance [-log (Io
/ I)] was diluted to 1.3 to 1.4 with distilled water to obtain a measurement sample.

As the measuring device, Micron Fort Sizer (SKC-2000S) manufactured by Seishin Co., Ltd. was used.

Filler yield The filler yield was calculated by the following formula by measuring the nitrogen content in the paper and papermaking slurry by the Kjeldahl method.

Example 1 (1) Preparation of initial condensate 37% concentration of formalin 51.8 parts (0.638 kg-mol) water 54.4
Parts into a flask equipped with a water bath and a stirrer, 0.84 parts of sodium carboxymethylcellulose sodium salt [“CMC Daicel 1193” manufactured by Daisen Co., Ltd.] is dissolved with stirring, the pH is adjusted to 7.5 with caustic soda, and then urea is added. 19.2
Part (0.32 kg-mol) was charged and the temperature was raised. After the temperature was raised to 70 ° C., the reaction was carried out for 1.5 hours, and then the flask was transferred to a water bath and cooled to obtain an aqueous solution of an initial condensate (a molar ratio of urea and formaldehyde of 1: 2.0). This had a total concentration of urea and formaldehyde of 30%, and had a pH of 7.3 according to BTB test paper.

This initial condensate was diluted with water to prepare a liquid A having a concentration of 18%. Further, 10% diluted sulfuric acid was prepared and used as solution B.

(2) Production of Urea-Formaldehyde Cross-Linked Resin As a reaction tank, a 20-liter type "Double Planetary Mixer" manufactured by Tokushu Kika Kogyo Co., Ltd. equipped with a stirrer for planetary motion was used. In this stirring device, the stirring blade revolves around its axis while rotating, and the inside of the tank can be efficiently stirred.

To the reaction tank that had been preheated with warm water and warmed,
000 g was charged and the mixture was heated to 48 ° C. with stirring. 900g of solution B heated to 45 ° C was added thereto in about 5 seconds,
Rotation speed 80 rpm, revolution speed 4 for 15 seconds
After continuing stirring at 0 rpm, stirring was stopped. The temperature of the liquid at that time was 47 ° C. Shortly after the stirring was stopped, the liquid in the reaction tank began to become cloudy, and at the same time, the liquid flow stopped. After holding for 5 minutes, the rotation speed is 80rp for 5 seconds.
The mixture was stirred at m and revolution speed of 40 rpm.

Then, after holding the stirring for 5 minutes again,
The mixture was stirred for 5 seconds at a rotation speed of 80 rpm and a revolution speed of 40 rpm. The same operation was repeated 6 times in total (total stirring stop time of 30 minutes). The contents were a mass of agglomerated solids of maximum about 20 mm and the temperature was 51 ° C. After the final stirring, 1000 g of water was added, and the number of revolutions of the stirrer was increased to 110 rpm for rotation and 55 rpm for revolution.
Stir for minutes. At this point, the contents are a slurry that contains a solid matter of up to about 5 mm and is easy to flow.
580 g of 0% caustic soda aqueous solution was gradually added to neutralize to pH 7. After neutralization, the discharge port provided at the bottom of the reaction tank was opened and the contents were discharged to the receiver to obtain 6470 g of slurry (corresponding to 99.8% of the total charged amount), but the discharge situation is extremely easy. there were.

(3) Preparation of sample for paper quality evaluation 600 g of the slurry obtained by neutralization was suction-filtered with a glass filter (G4), the residue was again put into 2 liters of water, and the mixture was stirred well, and then suction-filtered again. And then
A wet cake (solid content about 20%) was obtained. 70 cc of water was added to 30 g of this cake to prepare a slurry of about 6%, which was crushed with a household juice mixer for 2 minutes. The average particle size of the crushed particles is 5μ, and this is 5.0%.
A paper was prepared by adjusting the concentration and using it as a filler.

(4) Preparation of paper Using the above sample for paper quality evaluation as a filler, paper was prepared as follows. As pulp formulation, 15 parts of NBKP,
1000% 1% pulp slurry with a beating degree of 280 ml (CSF) consisting of 25 parts of TMP, 30 parts of DIP and 30 parts of RGP
To 10 parts, 10 parts of an aqueous dispersion of the filler adjusted to a concentration of 5.0% in advance is added and stirred for 2 minutes, then 3 parts of 10% aluminum sulfate aqueous solution is added, and further stirred for 2 minutes to obtain a prepared slurry. It was Then, paper was made with a 25 cm × 25 cm TAPPI square sheet machine, press dehydrated at 35 kg / cm ² , and then dried for 3 minutes with a rotary dryer having a surface temperature of 105 to 110 ° C. Then line pressure 40kg / cm
After calendering at 65% relative humidity, temperature 2
Seasoning was carried out for 24 hours in a constant temperature and humidity room at 0 ° C. to obtain a paper for paper quality evaluation.

(5) Evaluation of paper quality Regarding the paper obtained as described above, the whiteness is JIS P812.
3, opacity is JIS P-8138, opacity after printing is J.TAPPIN
The measurement was performed according to o.45-84. The results are shown in Table 1.

Example 2 Using the liquids A and B prepared in Example 1, a 100-liter type "Combimix" manufactured by Tokushu Kika Kogyo Co., Ltd. equipped with a composite stirrer was used as a reaction tank. This reactor has one low-speed rotating anchor type stirring blade and two dispersers independently rotating at high speed.

To the reaction tank that had been preheated with warm water and warmed,
0 kg was charged and the mixture was heated to 50 ° C. with stirring with an anchor blade. 9 kg of solution B heated to 48 ° C. was added thereto in about 15 seconds, and the mixture was stirred for 5 seconds at a rotation speed of 40 rpm,
The stirring was stopped. The temperature of the liquid at that time was 48 ° C.
Shortly after the stirring was stopped, the liquid in the reaction tank began to become cloudy, and at the same time, the liquid flow stopped. After holding it for 5 minutes,
The mixture was stirred for 5 seconds at an anchor blade rotation speed of 20 rpm. Then, after the stirring was again held for 5 minutes while the stirring was stopped, the stirring was carried out for 5 seconds at a rotation speed of the anchor blade of 20 rpm. The same operation was repeated 6 times in total (total stirring stop time was 30 times).
Minutes). The contents were a mass of lumpy solids of up to about 50 mm and its temperature was 53 ° C. After the final stirring, 20 kg of water was added and the speed of the stirrer was set to 80 rpm.
It was raised to m and stirred for 10 minutes. Then, 5.8 kg of a 10% caustic soda aqueous solution was gradually added to neutralize the pH to 7, and then the two dispersers were rotated at 1000 rpm and held for 10 minutes while keeping the rotation speed of the anchor blade at 80 rpm. The discharge port provided at the bottom of the reaction tank was opened and the contents were discharged to the receiver.
%, But the situation of emissions was extremely easy.

Table 1 shows the results of the measurement of the oil absorption amount and the particle size, and the evaluation when the paper was filled in the same manner as in Example 1.

Comparative Example 1 The procedure of Example 1 was repeated, except that the solutions A and B prepared in Example 1 were used and the stirring method was changed as follows.

Stirring stop time; 2 minutes Stirring first time; rotation 80 rpm, revolution 40 rpm 2 minutes Stirring stop time; 2 minutes Stirring second time; rotation 80 rpm, revolution 40 rpm 2 minutes Stirring stop time; 6 minutes Stirring 3rd time; rotation 80 rpm, revolution 40 rpm 2 After that, the operation of stirring for 5 minutes, stirring; rotation of 80 rpm and revolution of 40 rpm for 2 minutes was repeated 4 times. Eventually the contents become a slurry containing up to about 5 mm of solids,
After neutralization, the amount of slurry discharged to the receiver was 6465 g (corresponding to 99.8% of the total amount charged).

Table 1 shows the results of the measurement of the oil absorption amount and the particle size, and the evaluation when the paper was filled in the same manner as in Example 1.

Comparative Example 2 The liquids A and B prepared in Example 1 were first reacted for 30 minutes without stirring, and then stirred for 30 seconds (rotational speed 80
rpm, revolution speed 40 rpm), and then again 30 without stirring
The reaction was carried out in the same manner as in Example 1 except that the reaction was carried out for a minute. After stirring for 10 minutes, the content became a slurry containing a maximum of about 50 mm of solid matter. However, the amount of slurry discharged from the discharge port at the bottom of the reaction tank was 4350 g (equivalent to 67.1% of the total amount charged), and large lumps and deposits on the tank wall were not discharged and remained in the tank. .

Table 1 shows the results of the measurement of the oil absorption amount and the particle size and the evaluation when the paper was filled in the same manner as in Example 1.

<Effects of the Invention> According to the examples and the comparative examples, the paper filler produced by the production method of the present invention has a well-balanced improvement in optical properties such as whiteness, opacity, and opacity after printing. It can be seen that the yield on paper is high and that it is excellent.

Claims (4)

[Claims] 1. A charging ratio of urea and formaldehyde of 1:
The initial condensate and acidic catalyst obtained by reacting at 1.9 to 1: 2.4 (molar ratio) are added in the presence of 5 to 20 times by weight of water and carboxymethyl cellulose or a salt thereof at 35 to 65 ° C. with respect to the initial condensate. In the reaction, a mixture of reaction raw materials is kept for 3.5 to 20 minutes under non-stirring state, then stirred for a short time, and then again held under non-stirring state to proceed the reaction, thereby producing a filler. Method. 2. The method for producing a filler according to claim 1, characterized in that it is held for 4 to 10 minutes under non-stirred state, stirred for 1 minute or less, and then held under non-stirred state again. And how to. 3. A method for producing a filler according to claim 1 or 2, characterized in that a cycle consisting of holding in a non-stirring state and then stirring for a short time is repeated. . 4. A method for producing a filler according to any one of claims 1 to 3, wherein an initial condensate obtained by reacting urea with formaldehyde in the presence of carboxymethyl cellulose or a salt thereof is used. A method characterized by the use.