JPS61127720A - Production of loading material of urea resin - Google Patents

Abstract

PURPOSE:To obtain the titled loading material having proper average secondary particle diameter, by reacting urea-formaldehyde precondensate with an acidic aqueous solution to give crosslinked urea-formaldehyde polymer dispersion, filtering the dispersion by a continuous vacuum filter, and slurrying it, and grinding it by an impact type grinder. CONSTITUTION:A urea-formaldehyde precondensate is reacted with an acidic aqueous solution (e.g., sulfuric acid, etc.), to give slurried crosslinked urea-formaldehyde polymer dispersion, which is filtered by a continuous vacuum filter (preferably Oliver filter), caked, slurried again, crushed by an impact grinder (preferably free crusher), to give the aimed filler having 1-30mu average secondary particle diameter suitable as loading material for paper. EFFECT:The cake has high solid content, so it is convenient for transportation and storage. Providing processed paper having improved white transparency free from occurrence of hard spot.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for producing crosslinked urea formaldehyde polymer particles useful as paper fillers.

[Conventional technology]

It is known that fine cross-linked urea-formaldehyde polymer particles are added to paper as a so-called filler for the purpose of improving paper properties such as opacity. Methods for producing such particles are also known. For example, the special public service in 1977-
26686 involves mixing a specific urea formaldehyde initial condensate and an acidic aqueous solution under specific conditions, continuously feeding the mixed solution onto a rotating endless belt, performing reaction solidification on the belt, and then taking out the produced polymer. A method for producing cross-linked urea-formaldehyde polymer particles is disclosed, which is characterized in that the particles produced in this way are further deagglomerated, for example, by post-mortem slurry neutralization and deagglomeration in a pulverizer to produce fillers for paper. It is stated that it can be used as

[Problem 3 to be solved by the invention: The crosslinked urea formaldehyde polymer particles used as paper filler are individual particles (
(hereinafter abbreviated as secondary particles) aggregated to an average size of 1 to 30 μm (hereinafter abbreviated as secondary particles).

It is disclosed in the above-mentioned Japanese Patent Publication No. 57-26686 that the average primary particle diameter is 0.1 to 1.0μ, but at the same time, the average secondary particle diameter is 1 to 30μ, preferably 1
It must be thrown within a range of ~10μ. That is, if the average secondary particle diameter is less than 1 μm, the retention rate in paper during paper making will decrease, making it impossible to obtain the desired paper performance. On the other hand, if the average secondary particle diameter exceeds 30 μ, the yield rate is high, but the dispersion in the paper is insufficient, and as a result, the desired paper performance cannot be obtained. This is extremely important, as the average primary particle size is 0.
．． Even if the average secondary particle diameter is in the range of 1 to 1.0μ,
If the particle size is outside the range of ~30μ, the performance of the crosslinked urea formaldehyde polymer particles as a paper filler will be reduced.

On the other hand, the crosslinked urea formaldehyde polymer particles thus obtained are an aqueous dispersion. However, aqueous dispersions are inconvenient to transport and store, and require a large amount of cost. This is particularly disadvantageous when the manufacturing plant for such filler and the paper mill that uses it are located far apart. For this reason, the dispersion liquid is filtered to form a cake that is convenient for transportation and storage, and the cake is redispersed and used during paper making. It goes without saying that such a cake preferably has as low a moisture content as possible, ie, a high solids content.

Especially when it is used as a filler for mass-produced paper such as newspaper rolls, the amount of filler used is enormous.
An increase in the solids content of the cake, even on the order of % by weight, is extremely significant. The solid content of the cake obtained by filtering a conventional crosslinked urea formaldehyde polymer particle dispersion is approximately 25% by weight, but due to the above-mentioned circumstances, there was a desire to further increase this content. be.

As a result of various studies, the present inventor found that the cake obtained by slurrying the polymer produced by reaction solidification and filtering it before pulverization has a higher solids content than the cake obtained by filtering it after pulverization. I found out. In other words, it is stored and transported in the form of a cake.

It has been found that significant benefits can be obtained by redispersing and grinding immediately before use. However, such a cake was very hard and difficult to form into a slurry, and the average secondary particle size of the pulverized product was larger than 30 μm, making it unsuitable for use as a filler for paper. The present inventor conducted further studies and found that the solid content of the cake is high, it is easy to form into a slurry, and the average secondary particle size of the product obtained after pulverization is 1.
The present invention was achieved by finding the conditions under which the thickness becomes ~30μ.

[Means for solving problems]

In the present invention, an initial condensate of urea and formaldehyde is reacted with an acidic aqueous solution, then slurried to form a dispersion, and then filtered and pulverized to produce a urea resin filler consisting of fine crosslinked urea-formaldehyde polymer particles. A process for producing a urea resin filler, characterized in that a cross-linked urea formaldehyde polymer dispersion is turned into a cake by blowing in a continuous vacuum P and A vessel, then slurried again, and then pulverized in an impact pulverizer. It's a method.

Filters generally include pressure filters and vacuum filters, but in order to achieve the object of the present invention, a vacuum filter is required. When using a pressure filter, the resulting cake is extremely hard and difficult to slurry. Even if this is forcibly slurried and crushed, the average secondary particle size of the resulting crosslinked urea formaldehyde polymer particles is 30 μm. Not only does it exceed the
The product value of the paper is significantly reduced. Furthermore, the vacuum filter needs to be of a continuous type, and a batch type would complicate the cake-forming operation and would be unsuitable for industrial scale production. The continuous vacuum filter may be either a cylindrical type, a single disk type, or a horizontal filter such as a table, pan, or belt type, and an Oliver type filter, which is a type of cylindrical type, is preferred.

In addition, as a crusher, ball mills, mobile ball mills, special ball mills, impact crushers, roller mills, jet crushers, colloid mills, etc. are generally used industrially. Even if only the impact type crusher is used and other crushers are used, it is not possible to obtain a filler having an average secondary particle size suitable for paper filler.

Impact type crushers include screen type, axial flow type, rotary type, etc., and any of them are acceptable (though a free crusher, which is a type of rotary type, is particularly desirable).

Both the filter and the grinder must be as described above; if only one is as described above, the object of the present invention will not be achieved.

The cross-linked urea-formaldehyde polymer dispersion in the present invention is prepared by reacting an initial condensate of urea and formaldehyde with an acidic aqueous solution, and turning this into a slurry.

The initial condensate is usually prepared at a ratio of 1 to 2.5 moles of formaldehyde to 1 mole of urea, at a pH of 4 to 9, and at a temperature of 40 to 40.
The reaction was carried out at 10°C. Examples of acidic aqueous solutions include sulfuric acid and hydrochloric acid.

Aqueous solutions of mineral acids such as nitric acid, organic acids such as uric acid, chloroacetic acid, and maleinoic acid, sulfamic acid, and ammonium hydrogen sulfate are used. The precondensate is reacted by mixing with an acidic aqueous solution to obtain an aggregate of crosslinked urea formaldehyde polymer particles, which is crushed and water added if necessary.

A dispersion of crosslinked urea formaldehyde polymer particles is obtained. This is usually neutralized with an alkali such as caustic soda.

[Effect]

This dispersion is dehydrated using a continuous vacuum filter to form a cake. The solids content of the cake obtained is approximately 27% by weight. The slurry is then made into a slurry again and pulverized using an impact pulverizer, but if storage or transportation is required, it is preferable to carry out this process in the form of a cake with a solid content of 27 weight width. Of course, if you want to use it immediately as a paper filler without requiring storage or transportation.

After dehydration, it is immediately subjected to a slurry process.

Slurrying can be easily carried out by adding blood water and stirring. This is because dehydration is performed using a continuous vacuum filter in the previous step, and if other filters are used, it is difficult to form a slurry.

The resulting slurry is pulverized by an impact pulverizer to form a filler of crosslinked urea formaldehyde polymer particles having an average secondary particle size of 1 to 30 microns, preferably 1 to 10 microns.

〔Example〕

This will be explained below using examples.

Production example: 38.4 parts of a 37% formaldehyde aqueous solution (all parts hereinafter referred to as parts by weight)
, urea 18.9 parts, carboxymethyl cellulose 0,
7 parts and 42.0 parts of water were mixed, the pH was adjusted to 7 with 20 ml of caustic soda water, and the reaction was carried out at 70°C for 2 hours to obtain a urea formaldehyde initial condensate.

180 parts of a 2.7-thiosulfuric acid aqueous solution was added to 100 parts of this initial condensate, and after mixing, the mixture was allowed to stand for 1 hour. The resulting gel was crushed, water was added, stirred, and then neutralized with a caustic Noda solution to obtain a crosslinked urea formaldehyde polymer particle dispersion.

This dispersion liquid was used in all subsequent Examples and Comparative Examples.

Example 1 A cake was obtained by filtering the dispersion of the production example using an Oriper type e-filter. Approximately 3 g of this cage was taken clockwise and treated in a hot air dryer at 105°C for 60 minutes, and the ratio of the weight after treatment to the amount of mold before treatment (hereinafter referred to as solid content content) was 27.3%. It was made.

Water was added to this cake again and stirred to form a slurry. Making slurry was extremely easy.

This slurry was pulverized using a free pulverizer to obtain a dispersion of crosslinked urea formaldehyde polymer particle filler.

The average secondary particle diameter was measured using a Coulter counter and was found to be 4.9μ. This filler is hereinafter referred to as Example-1 filler.

Comparative Example 1 A cake-like urea resin filler was obtained in the same manner as in FIG. 11 except that a ball mill was used as the pulverizer.

The average secondary particle diameter of this filler was measured in Example 1 and 1 and found to be 39μ. This filler is used as a comparative example below.
It is called the 1st class.

Comparative Example 2 A urea resin filler was obtained in the same manner as in Example 1 except that a colloid mill was used as the pulverizer. The average secondary particle diameter of this filler was measured in the same manner as in Example 1, and was found to be 0.85.
It was μ. This filler is hereinafter referred to as Comparative Example-2 filler.

Comparative Example 3 A cake was obtained by filtering the dispersion of the production example using a filter press as a filter. The solid content of this cake was measured and found to be 27.8%.

An attempt was made to form a slurry by adding water to the cake and stirring it again, but forming a slurry was extremely difficult and took a long time, and the resulting slurry contained many large lumps. Grind this slurry using a free grinder.

A dispersion of crosslinked urea formaldehyde particle filler was obtained. The average secondary particle size of this filler was 45μ.

Comparative Example 4 The dispersion of the production example was crushed using a free crusher, and then filtered using an Oliver type filter to obtain a cake. The solid content of this cake was 24.51, which was 2.8% compared to Example 1.
It was low.

Application Examples Table 1 shows the results of paper making using the Example 1 filler and Comparative Examples 1 to 3 fillers.

The paper was made as follows. That is, N.

Beating 1i (C8F) 330. A12 (804) 3, 18H20 for 2000 copies of A/'s 1st section, ζ Lupus Rally
Add 2 parts of 20.0% aluminum sulfate aqueous solution and wait for 2 minutes! Spend. Subsequently, 1 part of each urea resin filler was added on a dry weight basis and stirred for 5 minutes to obtain a prepared slurry. Next, paper was made using a TAPPI square paper machine, and the wet paper obtained by press dehydration was dried using a drum dryer with a surface temperature of 110°C.
Pass through the calendar twice at rL, humidity 65%, temperature 2
Seasoned for 24 hours in a constant humidity and constant room at 0°C.
I got processed paper.

The physical properties of these processed papers were measured and shown in Table 1.

Note that the physical properties were measured by the following method.

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-stts) and using the formula (basis weight/thickness) x 1000.

The white paper opacity was measured according to the method described in the literature (Paper (Technical Times, September 1977 issue, pages 1 to 13).

Table 1 [Effects] As is clear from Table 1, in Example 1 according to the method of the present invention, a urea resin filler having an average secondary particle size suitable as a paper filler was obtained, and this was used for paper making. The processed paper produced by this process has excellent white paper opacity, but in comparison examples 1 to 3 which are not based on the present invention, the average secondary particle size of the obtained filler is in an inappropriate range as a filler for paper. The white paper opacity of the paper made using this was poor, and in the processed paper using Comparative Example 3 filler, spots occurred on the surface of the paper.

From the above, the effects of the filler produced by the method of the present invention are clear, and the present invention has great significance.

Claims (1)

[Claims] An initial condensate of urea and formaldehyde is reacted with an acidic aqueous solution, and then slurried to form a dispersion.
In the method of producing a urea resin filler consisting of fine cross-linked urea-formaldehyde polymer particles by pulverizing after filtration, the cross-linked urea-formaldehyde polymer dispersion is filtered through a continuous vacuum filter to form a cake, and then slurried again, and then A method for producing a urea resin filler, which comprises pulverizing it using a post-impact type pulverizer.