JPH0334764B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for producing a paper filler comprising crosslinked aminoaldehyde polymer particles. The present invention provides fillers useful for improving paper blank opacity, ink receptivity during offset printing, and post-print opacity. [Prior art] A BET specific surface area obtained by mixing and solidifying an initial condensate consisting of 1.0 mole part of urea and 1.0 to 2.0 mole parts of formaldehyde and an acidic aqueous solution has a BET specific surface area of 5 to 100 m ² /g.
It is already known that crosslinked urea formaldehyde polymer particles are useful as fillers for improving paper whiteness and white paper opacity. (Tokuko Showa 51
-23601, JP 54-135893) [Problems to be solved by the invention] Printing paper, including newspaper rolls, tends to be lighter in weight in order to save resources and streamline transportation, and weight reduction means making the paper thinner. This can be accomplished by doing things, but through-through is a hindrance. Show-through is caused by a decrease in the opacity of the paper itself (hereinafter referred to as white paper opacity), and
Printed ink permeates the paper and becomes visible from the back side (hereinafter, the degree to which this is prevented is referred to as post-print opacity), which causes bleeding. Both physical properties are important physical properties for printing paper, as the printed image on the back side is visible from the front side, making the front side difficult to read. In offset printing, ink receptivity is also an important physical property in order to obtain a uniform printing surface without printing unevenness. The above-mentioned known crosslinked urea formaldehyde polymer particles are not necessarily sufficient in these effects. In particular, the effects of improving post-print opacity and ink receptivity are insufficient. Reducing the weight of newspaper rolls is an important issue, and the current basis weight is 46.0 g/m ^{2 compared to the conventional 49.0 g/m 2 ,} and a further 43.0 g/m ² is being considered.
In this case, the performance required for paper is whiteness,
The main factors are blank paper opacity, printing opacity, and ink receptivity, and especially for the first three, the basis weight is 43.0.
When it comes to about g/m ² , it becomes extremely difficult to improve it by 1%. Newspaper roll paper with a basis weight of 46.0 g/m ² is possible by using the above-mentioned crosslinked urea formaldehyde polymer particles as a filler, but with a basis weight of 43.0 g/m 2 .
m ² , it is no longer possible to use such a filler because the above-mentioned performance becomes insufficient. Therefore, it is desired to develop a paper filler with even better performance. In view of these circumstances, the present invention provides a filler for paper manufacturing that improves the blank opacity, post-printing opacity, and ink receptivity of paper, thereby making it possible to produce 43.0 g/m ² newspaper roll paper. The purpose is to [Means for Solving the Problems] As a result of intensive research to obtain lightweight printing paper, the present inventors have found that a part of the urea component in the crosslinked urea-formaldehyde polymer particles is replaced with cyanamide or a dicyanamide derivative, or formaldehyde Cross-linked aminoaldehyde polymer particles of a specific particle size obtained by substituting a part of the component with an alkyl aldehyde or alkenyl aldehyde significantly improve the white paper opacity of paper, ink receptivity during offset printing, and opacity after printing. The present invention was completed based on the discovery that the present invention has the following properties. That is, the present invention consists of 1.0 mole part of urea and 1.0 to 2.0 mole parts of formaldehyde, and 50 mole% of the urea.
The following are substituted with cyanamide or dicyanamide derivatives, and 50 mol% or less of the formaldehyde is substituted with an alkyl aldehyde or alkenyl aldehyde, or either the urea or the formaldehyde is substituted with the above-mentioned This is a method for producing a paper filler having an average primary particle size of 0.15 to 0.50μ, which is characterized by mixing an aminoaldehyde initial condensate and an acid catalyst and solidifying the mixture at a pH of 3.0 or less. The filler produced according to the present invention has an average primary particle size of
0.15-0.5μ, usually 0.17-0.35μ. If the average primary particle size is less than 0.15μ, the effect of improving white paper opacity is insufficient, and if it exceeds 0.5μ, the effect of improving opacity after printing is insufficient. Here, the average primary particle size and average secondary particle size have the following meanings. That is, the filler in the present invention is an agglomeration of individual fine particles. Therefore, the average diameter of individual particles is called the average primary particle diameter, and the average diameter of aggregated particles is called the average secondary particle diameter. usually,
The former is measured using an electron micrograph, and the latter is measured using a Coulter counter. In the present invention, the crosslinkable aminoaldehyde polymer particles are obtained by substituting a part of the urea component of crosslinked urea-formaldehyde polymer particles with a cyanamide or dicyanamide derivative, or by replacing a part of the formaldehyde with an alkyl aldehyde or an alkenyl aldehyde. The main idea is to obtain it by substitution. Here, cyanamide or dicyanamide derivatives include dicyandiamide, thiourea, guanidine, acetoguanamine, benzoguanamine, spiroguanamine, phenylacetoguanamine, melamine, melam, melem, amelide, amerin, etc.
The reason for limiting it to mol% or less is that the substitution amount is 50 mol%.
This is because the whiteness of the paper decreases if it exceeds this. The preferred amount of substitution is 5 to 40 mol%, and preferred derivatives are dicyandiamide, guanidine, acetoguanidine, melamine, thiourea and the like. Further, the alkyl aldehyde or alkenyl aldehyde includes acetaldehyde, isobutyraldehyde, n-butyraldehyde, acrolein, crotonaldehyde and the like. The reason why the formaldehyde substitution amount is limited to 50 mol % or less is that if the substitution amount exceeds 50 mol %, the whiteness of the paper similar to the above decreases. The preferred amount of substitution is 5 to 40 mol%, and isobutyraldehyde,
Preferred aldehydes include n-butyraldehyde and the like. The reason for limiting the amount to 1.0 to 2.0 mole parts of the alkyl aldehyde or alkenyl aldehyde partially substituted group of formaldehyde (hereinafter referred to as the total aldehyde compound) per 1.0 mole part of the cyanamide or dicyanamide derivative partially substituted group of urea (hereinafter referred to as the total amino compound) is If the total amount of aldehyde compounds is less than 1.0 mole part, the average primary particle size of the crosslinked aminoaldehyde polymer particles obtained will be larger than 0.5μ, and the printing opacity of the printing paper containing this will be reduced. Furthermore, if the total amount of aldehyde compounds exceeds 2.0 mol, the yield of crosslinkable aminoaldehyde polymer particles (hereinafter referred to as yield) becomes small based on the total weight of all amino compounds and all aldehyde compounds. The reaction to obtain an aminoaldehyde initial condensate (hereinafter referred to as initial condensate) from all amino compounds and all aldehyde compounds is carried out at a pH of 3 to 10 and a reaction temperature of 20 to 100.
Under conditions of ℃, the liquid viscosity at 25℃ measured by a Burckfield viscometer is 10 to 60% by weight for an aqueous solution with a concentration of 20 to 60% by weight.
Performed up to 200 centipoise. For long-term storage of the initial condensate, adjust the pH to a range of 6 to 8 using an acid such as hydrochloric acid, nitric acid, sulfuric acid, formic acid, acetic acid, or an alkali such as caustic soda, caustic potash, ammonia, ethanolamine, isopropanolamine, etc. You can also do it. As a step after obtaining the initial condensate, the initial condensate is mixed with an acid catalyst for the purpose of reaction solidification while stirring. Acid catalysts suitable for this purpose include mineral acids such as sulfuric acid, phosphoric acid, hydrochloric acid, nitric acid, organic acids such as formic acid, oxalic acid, maleic acid, succinic acid and chloric acid, sulfamic acid, ammonium hydrogen sulfate,
Examples include acids such as methylammonium hydrogen sulfate, ethyl ammonium hydrogen sulfate, and hydroxyethylammonium hydrogen sulfate. In the present invention, the pH of the mixture of the initial condensate and the acid catalyst is
It needs to be 3.0 or less, preferably 2.0 or less. If the pH exceeds 3.0, the condensation reaction will not proceed sufficiently and the average primary particle size of the resulting product will exceed 0.50μ, making it impossible to achieve the object of the present invention. The amount of acid used to adjust the pH to 3.0 or lower is generally from 1 to 30% by weight, particularly from 3 to 20% by weight, based on the solid weight of the initial condensate. Acid catalysts are usually used in aqueous solutions and are usually 1 to 10
Used in a concentration range of % by weight. Further, the solid content concentration range of the initial condensate at this time is 10 to 40% by weight, and the temperature of the aqueous solution of the initial condensate is controlled within the range of 5 to 95°C. When the initial condensate is reacted and solidified with an acid catalyst, more preferable results can be obtained by adding a water-soluble organic polymer substance having a protective colloid effect to the initial condensate in advance. In this case, preferred water-soluble organic substances having a protective colloid effect (hereinafter referred to as protective colloid agents) include starch, methyl cellulose,
Examples include natural products such as ethylcellulose and beta-hydroxyethylcellulose, and synthetic polymers such as polyvinyl alcohol and polyvinylpyrrolidone. The amount of the protective colloid used is generally 0.1 to 8% by weight, particularly 0.2 to 5% by weight, based on the weight of the reaction product of all amino compounds and all aldehyde compounds. The protective colloid agent can be added at any stage before, during or after the formation of the initial condensate. An acid catalyst is added and mixed in order to react and solidify the initial condensate aqueous solution with stirring. In this case, preferably, the temperature of the initial condensate aqueous solution and the acid catalyst is adjusted to 20°C so that the initial condensate aqueous solution and the acid catalyst solidify within 50 seconds after addition and mixing.
Adjust to a range of ~90℃. Industrially, the initial condensate aqueous solution and the acid catalyst are mixed using an in-line mixer or the like, and just before solidification of the mixture proceeds, the mixture is fed onto an extruder or a rotating endless belt to proceed with the reaction and solidification. The thus obtained coagulate is dispersed into a slurry with stirring according to a conventional method, washed with water to reduce residual formaldehyde, neutralized, and milled to reduce the average secondary particle size to 1 to 30μ, preferably 2 to 30μ. crushed to 10μ,
A paper filler consisting of crosslinked aminoaldehyde polymer particles is obtained. However, water washing to reduce residual formaldehyde is performed by repeating dispersion of the solidified material in water and filtration or centrifugation, but this operation removes residual formaldehyde, that is, unreacted formaldehyde, and water-soluble The aminoaldehyde reactant is removed. Therefore, removal of residual formaldehyde by washing with water is not preferred from the viewpoint of improving the yield of the desired crosslinked aminoaldehyde polymer particles, and furthermore, drainage of the liquid requires treatment, which requires a large amount of cost. Therefore, as a method for reducing residual formaldehyde, after adding urea, ammonium or an ammonium salt, sulfite or sulfite and reacting with the residual formaldehyde, a dispersion containing 90 to 95% water is usually prepared for transportation and storage. Because of its advantages, it is concentrated by filtration, and the liquid generated in this overconcentration process still contains a relatively small amount of unreacted substances such as water-soluble urea, amino compounds, formaldehyde, and other aldehyde compounds, or these and ammonia or Since the ammonium salt, sulfite, or a reactant with the sulfite is included, a method of returning the reaction system to the reaction system before the solidified product of aminoaldehyde polymer particles is produced can be adopted as a preferable method. When the aforementioned method for reducing residual formaldehyde is carried out by adding urea, urea can be added in solid form or as an aqueous solution, and the pH of the dispersion at this time is usually 4.0 or less. The amount of urea added is equal to or more than the mole of residual formaldehyde present in the aqueous phase of the dispersion, the reaction temperature is 10 to 70°C, and the reaction time is sufficient to be in the range of 5 to 30 minutes. In addition, when reducing the residual formaldehyde described above with ammonia or ammonium salt, add ammonia or ammonium salt in a range of 0.5 to 4.0 mol per 1 mol of residual formaldehyde.
A reaction time of 5 to 100 minutes at a temperature of 10 to 90°C is sufficient. When reducing residual formaldehyde using sulfite or sulfite, add sulfite or its salt to 1 mole of residual formaldehyde.
It is sufficient to add 0.5 to 1.5 mol and react for several minutes at 10 to 90°C. As mentioned above, after reducing the residual formaldehyde with urea, ammonia or an ammonium salt, sulfite or sulfite, the pH of the liquid is adjusted to 5 to 10, preferably 6 to 10, with a caustic soda aqueous solution or a sulfuric acid aqueous solution.
The mixture is further stirred at 10 to 90°C for 5 to 100 minutes while adjusting the particle diameter to a particle size of 1 to 90°C, and then ground to an average secondary particle size of 1 to 30 μm using a pulverizer. It is then filtered to obtain a cake of liquid and crosslinked aminoaldehyde polymer particles. The liquid is returned to the reaction system before solidification of crosslinked aminoaldehyde polymer particles is produced. That is, it is used as concentration-adjusting water when obtaining an initial condensate and/or as concentration-adjusting water for an acidic aqueous solution. The thus obtained cross-linked aminoaldehyde polymer particle filler cake is mixed with water and stirred to form a dispersion of 4 to 10% by weight of polymer particles, which is then added to a pulp slurry for printing paper to form a uniform pulp slurry. The paper is made using a twin wire or fourdrinier paper machine under stirring to obtain the following properties. In this context, printing paper is uncoated paper, and refers to paper and newspaper rolls printed by general printing companies. Paper printed by general printing companies includes regular printing paper A, B, C, D, gravure paper, printing paper, securities paper, check paper, dictionary paper, book paper, telephone directory paper, etc. It is a printing paper made according to the paper, and includes lightweight printing paper. The raw material pulp used for newspaper rolls and printing paper is kraft pulp (KP), sulfite pulp (SP), semi-chemical pulp (SCP), CGP, TMP, RGP, which is obtained from softwood (N) and hardwood (L).
These include semi-mechanical pulp such as GP, mechanical pulp, and deinked wastepaper pulp (DIP), and these are bleached to different degrees depending on the whiteness of the paper type being made, and various blends are used. The crosslinked aminoaldehyde polymer particle filler is added to the pulp slurry after the pulp is blended or at any step between the refiner step and the fan pump. It is usually preferable to add it by machine chiest. Sizing agents, fillers such as aluminum sulfate or clay, talc, kaolin, calcium carbonate, etc. can also be added to the machine chest at the same time for use or in combination. Printed papers obtained by adding cross-linked aminoaldehyde polymer particles are particularly useful for lightweight newspaper rolls, telephone directory paper, and other lightweight printing papers, and are suitable for offset printing due to their good receptivity to printing inks. Useful as paper. [Example] The present invention will be explained below using Examples, but the present invention is not limited thereto. The conditions for producing the crosslinked aminoaldehyde polymer particles, the measurement methods for physical quantities, and the tests on the processed paper were conducted in the following manner. The number of seconds for solidification after mixing the aminoaldehyde initial condensate and the acidic aqueous solution was determined by mixing within 5 seconds and then measuring the number of seconds until solidification. The yield and yield of crosslinked aminoaldehyde polymer particles are determined by first measuring the weight of the white cake-like material obtained, then measuring the non-volatile content, that is, the concentration of polymer particles according to JIS K-6801, and calculating the weight of the cake-like material x polymer particles. The yield of polymer particles is calculated from the concentration equation. The yield of polymer particles is calculated by (number of yielded parts of polymer particles/number of parts of raw materials used) x 100. The number of raw materials used is the total of the protective colloid agent, all amino compounds, and all aldehyde compounds, but the molecular weight of all aldehyde compounds is based on the assumption of the chemical structure after addition reaction and dehydration reaction for all amino compounds. did. The average primary particle size was calculated from electron micrographs. The basis weight was measured and calculated according to JIS (P-8111). The stiffness was calculated by measuring the thickness of the paper according to JIS (P-8118) and using the formula (basis weight/thickness) x 1000. The whiteness was measured using a Hunter whiteness meter using a blue filter. White paper opacity was measured according to JIS (P-8138). The opacity after printing was determined according to the method described in the literature (Paper Technology Times, September issue, 1978, pages 1 to 13). Using an offset ink receptivity RI tester (manufactured by Mei Seisakusho), apply water to the test piece using a Molton roll, and under conditions that do not cause picking, perform a solid printing with black ink for offset printing to check the ink receptivity ( The ink density was determined visually. Evaluation was made on a 5-point scale, with 5 points being the most excellent and 1 point being the least acceptable. In addition, all parts and % are based on weight (excluding %, which is a unit of whiteness, white paper opacity, and post-print opacity). Example 1 In a flask, 20.0 parts of water and 0.33 parts of sodium salt of carboxymethylcellulose (trade name: Celogen F-3H, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) were added and dissolved, and then 24.60 parts of a 37% formaldehyde aqueous solution and n-butyl were added. Add 0.79 parts of aldehyde and adjust the pH to 7.5 with aqueous caustic soda solution. Then urea 11.38
0.49 parts of dicyandiamide and 5.71 parts of water were added, the temperature was raised to 70°C with stirring, and a condensation reaction was carried out for 2.0 hours. The concentration of parts of the raw materials used was 27.0%, and the molar ratio of amino compound to aldehyde compound was 1:1.15. An aminoaldehyde initial condensate containing 3 mol % of dicyandiamide in the amino compound and 3 mol % of n-butyraldehyde in the aldehyde compound was obtained. This initial condensate is cooled to 45℃ and
Add the amount of sulfuric acid equivalent to 6.98%, i.e. 1.26 parts of 95% sulfuric acid, to water.
Immediately mix uniformly with a 4.0% aqueous solution diluted with 28.57 parts. It solidifies after about 46 seconds, at which time the temperature of the mixture rises to 59°C. It is then held at about 59°C for 1 hour. Next, this solidified material is processed using a cutter granulator for 1~
Coarsely divide into particles with a particle association size of 2 mm, add 100 parts of water to make a slurry, and neutralize the pH to 7.5 with a 20% aqueous solution of caustic soda. The obtained slurry was finely ground in a grinder, and then dispersed in 1000 parts of water.
After excessive dehydration, 76.93 parts of a white cake-like material of cross-linked aminoaldehyde polymer particle filler was obtained. The nonvolatile content of this cake is 21.5%, so the yield is
Since the total amount of raw materials used is 16.54 parts and 17.09 parts, the yield is 96.8%. Also, the average primary particle size is
It was 0.25μ. Examples 2 to 13 and Comparative Examples 1 to 4 In Example 1, by changing the amounts of urea, dicyandiamino, formaldehyde aqueous solution, and n-butyraldehyde used, the mol% of dicyandiamino in the total amino compounds and A white cake-like material of crosslinked aminoaldehyde polymer particle filler was obtained in the same manner as in Example 1 except that the mole % of n-butyraldehyde in all aldehyde compounds was shown in Table 1. The solidification reaction time, yield, and average primary particle size were as shown in Table 1. Examples 14 to 15 and Comparative Example 5 A white cake-like material of crosslinked aminoaldehyde polymer particle filler was prepared in the same manner as in Example 2 except that the solidification reaction pH was changed as shown in Table 1 by changing the amount of sulfuric acid. I got it. Table 1 shows the solidification time, yield, and average primary particle size. Comparative example 5 with PH of 4.0
Because the solidification reaction rate is slow, the solidification time is
It was long at 180 seconds, and the average primary particle size was large at 0.9μ. Examples 16 to 18 and Comparative Examples 6 to 7 In Example 2, the molar ratio of all amino compounds to all aldehyde compounds was changed by changing the amounts of urea, dicyandiamino, formaldehyde aqueous solution, and n-butyraldehyde used. A white cake-like material of crosslinked aminoaldehyde polymer particle filler was obtained in the same manner as in Example 2 except for the above. The solidification reaction number, yield, and average primary particle size were as shown in Table 1. Comparative Example 6 with a molar ratio of 1:0.8 had a large average primary particle size of 0.7μ, and Comparative Example 7 with a molar ratio of 1:2.3 had a low yield.

[Table] Application example 1 Beating degree (Hereinafter, the beating degree is Canadian Standard.
Indicated by Freeness. ) 300ml N.BKP25%, freeness
190ml RGP, freeness 180ml TMP, freeness 170
ml of blended pulp consisting of 25% DIP at bone dry weight of 20.0
1 part and 2000 parts of water were put into a disintegrator and dispersed for 2 minutes, and then the filler cake of Example 1 was added to 1 part dry weight and water was added to make 20 parts, and the concentration of parts of the raw material used was 5%. This is added as a dispersion into a disintegrator and stirred for 1 minute. Paper was made using a square sheet machine using the blended pulp slurry containing the filler of Example 1, and after pressing at 3 kg/cm ² for 15 minutes, it was dried by passing through a drum dryer with a surface temperature of 115 ± 5°C for 3 minutes. After that, 2 calenders of 7Kg/cm
Passed twice in a constant temperature and humidity room with a humidity of 65% and a room temperature of 21℃.
After 24 hours of sheathing, a printing paper containing the filler of Example 1 with a basis weight of 43.1 g/m ² was obtained. Thereafter, printing papers containing fillers of Examples 1 to 18 and Comparative Examples 1 to 7 were obtained in the same manner. These printing papers have different tension,
Smoothness, whiteness, blank opacity, post-print opacity and offset ink acceptability were measured. These results are shown in Table-2. As is clear from Table 2, the amount of dicyandiamide in all amino compounds and the amount of n-butyraldehyde in all aldehyde compounds are within the range of the present invention, and the performance of processed paper using the fillers of Examples 1 to 13 All are excellent, especially Examples 2 and 5 to 7
and those using 10 to 12 fillers have excellent performance. On the other hand, Comparative Example 1 which is outside the scope of the present invention
Those using the filler of Comparative Examples 2 and 3 were particularly poor in opacity and ink receptivity after printing, and those using the fillers of Comparative Examples 2 and 3 were particularly poor in whiteness. Regarding the solidification reaction PH, all the fillers using the fillers of Examples 14 and 15, which are within the scope of the present invention, have excellent performance, but Comparative Example 5, in which the solidification reaction was performed at PH4,
Those using fillers have particularly poor opacity after printing. Regarding the molar ratio of all amino compounds to all aldehyde compounds, the fillers of Examples 16 to 18, which are within the scope of the present invention, had excellent performance, but the comparative examples, which were outside the scope of the present invention. As can be seen from Table 1, the paper containing filler No. 6 had poor opacity after printing, and the paper containing filler No. 7 was not so inferior in paper performance. The yield of filler is extremely low.

【table】

[Table] Example 19 20.0 parts by weight of water and Celogen F- in a flask.
After 0.33 part of 3H was added and dissolved, 17.33 parts of a 37% formaldehyde aqueous solution and 0.81 part of n-butyraldehyde, which is an alkyl aldehyde, were added, and the pH was adjusted to 7.5 with a caustic soda aqueous solution. Then urea
4.26 parts of melamine, 5.97 parts of melamine, and 3.92 parts of water were added, and the temperature was raised to 70°C with stirring to conduct a condensation reaction for 2.0 hours.The concentration of the raw materials used was 27.0%, and the molar ratio of amino compound to aldehyde compound was 1: 1.9, an aminoaldehyde initial condensate containing 40 mol% of melamine in the amino compound and 5 mol% of n-butyraldehyde in the aldehyde compound was obtained. This initial condensate is 45
The mixture is cooled to ℃ and immediately mixed uniformly with a 4.0 aqueous solution prepared by diluting 1.03 parts of 95% sulfuric acid with 23.40 parts of water, which corresponds to 6.89% of the raw material used. about
After 15 seconds, the mixture solidifies and the temperature of the mixture rises to 60°C. Then, hold at about 60°C for 1 hour. Next, this solidified material is coarsely divided into particle association sizes of 1 to 2 mm using a cutter granulator, 100 parts of water is added to form a slurry, and the pH is neutralized to 7.5 with a 20% aqueous solution of caustic soda. The obtained slurry was ground in a grinder, dispersed in 1000 parts of water, and then super-dehydrated to obtain a white cake-like substance. Further to wash this with water
A white cake of cross-linked aminoaldehyde polymer particle filler is obtained by dispersing 1000 parts of water and then dehydrating it.
Obtained 63.54 copies. The nonvolatile content of this cake-like substance is
21.2%, so the yield is 13.47 parts,
Since the total raw material used is 14.18 parts, the yield is 95.00%.
becomes. The average primary particle size was 0.17μ. Example 20 According to the procedure of Example 19, n in Example 19
- Using isobutyraldehyde instead of butyraldehyde and using guanidine instead of melamine, the molar ratio of amino compound to aldehyde compound is 1:1.5, guanidine in the amino compound is 10 mol %, isobutyraldehyde in the aldehyde compound The conditions for obtaining the initial condensate, such as the concentration of the raw materials used and the condensation conditions, were completely the same, except that the amount was changed to 10 mol%, and the solidification conditions and until the cake was obtained, except that the solidification time was 37 seconds. The conditions and operations were exactly the same as in Example 16 to obtain 60.69 parts of a white cake-like material of crosslinked aminoaldehyde polymer particle filler. The nonvolatile content of this cake is 20.8%, so the yield is 12.62 parts, and since the total raw material used is 13.40 parts, the yield is 94.2%. The average primary particle size was 0.23μ. Example 21 According to the procedure of Example 19, 10% of thiourea was used instead of melamine as the amino compound in Example 19.
There were no conditions for obtaining the initial condensate, such as the concentration of the raw materials used and the condensation conditions, except that 10 mol% of n-butyraldehyde was used as the aldehyde compound and the molar ratio of the amino compound to the aldehyde compound was 1:1.7. A white cake-like product of the cross-linked aminoaldehyde polymer particle filler of Example 21 was prepared using the same solidification conditions and the same operations and conditions until the cake was obtained, except that the solidification time was 19 seconds.
Obtained 84.79 copies. The nonvolatile content of this cake-like substance is
20.4%, so the yield is 17.30 parts,
Since the total raw material used is 18.42 parts, the yield is 93.9%.
becomes. The average primary particle size was 0.35μ. Example 22 In Example 19, 7 mol% of acetoguanidine was used instead of melamine as the amino compound, 7 mol% of isobutyraldehyde was used as the aldehyde compound, and the molar ratio of the amino compound to the aldehyde compound was 1: Except that it is 1.6.
The conditions for obtaining the initial condensate, such as the concentration of the raw materials used and the condensation conditions, were exactly the same, and the solidification conditions and operations and conditions until obtaining the cake were the same, except that the solidification time was 14 seconds. 87.24 parts of a white cake of crosslinked aminoaldehyde polymer particle filler of Example 22 was obtained. The nonvolatile content of this cake-like substance is
20.8%, so the yield is 18.15 parts,
Since the total raw material used is 19.04 parts, the yield is 95.3%.
becomes. The average primary particle size was 0.21μ. The above Examples 19 to 22 are summarized in Table 3.

[Table] Application Example 2 Printing papers containing the fillers of Examples 19 to 22 were obtained in the same manner as in Application Example 1. The performance of these printing papers was excellent as shown in Table 4.

〔Effect of the invention〕

As is clear from the above, the printing paper containing the filler produced according to the present invention has excellent whiteness, white paper opacity, post-print opacity, and ink receptivity, and even with a basis weight of 43 g/m ² Paper containing this filler has sufficient performance as printing paper. Therefore, the present invention has great significance also from the point of view of reducing the weight of paper.

Claims (1)

[Claims] 1 Consisting of 1.0 mol part of urea and 1.0 to 2.0 mol parts of formaldehyde, 50 mol% or less of the urea is substituted with cyanamide or a dicyanamide derivative, and 50 mol% or less of the formaldehyde is substituted with an alkyl aldehyde or alkenyl aldehyde. or in which either the urea or the formaldehyde is substituted with the above-mentioned aminoaldehyde initial condensate and an acid catalyst, and the mixture is solidified at a pH of 3.0 or less. A method for producing paper filler with a primary particle size of 0.15 to 0.50μ.