JPS6342997A - Production of paper, cardboard and thick paper having high dry strength - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a process for making paper, paperboard or cardboard having high dry strength.

In paper production, paper stock is added to the paper stock to purify it from anionic substances that interfere with the circulating water of the paper machine, as well as to promote the dewatering of the paper stock on screens and to increase the water retention of the fibrous material and filler. For example, an aqueous solution of high molecular weight polyethyleneimine is used as the additive. In addition to this effect, the addition of 0.1 to 2% by weight of polyethyleneimine relative to the dry fiber material also serves to improve the wet strength of the paper.

According to German Patent Application No. 2821830, an anionic synthetic sizing agent and a modified starch (starch, water-soluble cationic polymer or condensate) are mixed together in the presence of water at a temperature higher than the gelatinization temperature of the starch. A method for surface sizing of paper is known by using a sizing product which is a mixture of sizing products obtained by heating to .

According to U.S. Pat.
by heating to a temperature of 10°C for about 0.5 to 5 hours,
Methods for producing cationic starches are known. This mixture is polyalkyleneimine or polyalkylenepolyamine 0
．． It contains 5-40% by weight and starch 995-60% by weight. According to Example 1, polyethyleneimine having an average molecular weight of about 200,000 is heated with potato starch to 90'C for 2 hours in an aqueous solution. This modified potato starch can be precipitated in a mixture of methanol and diethylene ether. The reaction products of starch and polyethyleneimine or polyalkylene polyamines described in this patent specification are used as flocculants.

In addition, it is known to use natural starch, which has been rendered water-soluble by heating in water, as an internal additive in the manufacture of paper, in order to increase the dry strength of the paper. The holding power of starch dissolved in water to the paper fibers in the stock is extremely small).

The object of the invention was to improve the dry strength of paper when starch is added compared to known methods. In particular, the substantivity of the starch should be increased when adsorbed onto the fibers in the paper stock.

The present invention solves this problem by adding a drying strength agent to the paper stock, dehydrating the stock while forming paper sheets, and adding natural potato starch as the drying strength agent in an aqueous medium. This is a method for producing paper, paperboard or paperboard having high dry strength, which is characterized by using a mixture obtained by heating the starch to a temperature equal to or higher than the gelatinization temperature of the starch, together with polyethyleneimine.

The mixture used as dry strength agent in the present invention has good retention on paper fibers. Interfering substances present in the dry environment are unlikely to have any adverse effects. The activity of this mixture is particularly evident in the pH range from 3 to 10.

Mixtures used as dry strength agents are known (US Pat. No. 3,467,608 and German Patent Application No. 28,218
(Refer to each specification of No. 30). Although according to known techniques any starch is reacted with polyethyleneimine and the reaction product is used as a flocculant or to improve the surface sizing of paper, for the production of the paper dry strength agent according to the invention, natural Only potato starch is used. As in the known process, in order to render the natural potato starch water-soluble, it is mixed with polyethyleneimine in an aqueous suspension at a concentration of 70-110%.
Heat to 'C. Heating of the aqueous suspension of potato starch is carried out in the presence of polyethyleneimine; the aqueous suspension of natural potato starch is first heated from 7o to 110'CK to form a solution, and then the polyethyleneimine is heated at this temperature. An aqueous solution of may also be added.

Potato starch solubilized in an aqueous medium can also be reacted with polyethyleneimine by heating to 15-70'C. Solubilization of the starch requires about 6 minutes to 5 hours, preferably 5 to 30 minutes, at said temperature. It is important to heat the unbroken potato starch with polyethyleneimine in the presence of water to a temperature above the gelatinization temperature of natural potato starch.

Gelatinization temperature means the temperature at which the double refraction of starch grains is lost (see Ullmanns Entiklovedi Dertechnischen Hemie, Vol. 16, p. 322, 1965). For the modification of already destroyed natural potato starch, it is sufficient to react it with high molecular weight polyethyleneimine at a temperature of 15 DEG to 70 DEG C. Lower temperatures require longer contact times. It is also possible to carry out the reaction at temperatures up to 110° C. with shorter contact times. However, in each case the reaction is carried out in the absence of oxidizing agents and/or polymerization initiators as well as alkalis (commonly used for starch destruction).

Polyethyleneimines used to modify natural potato starch are known. i oooo ~ 33000 especially 20
Viscosity of Q OO to '5100 G mPas (measured at 20°C at 20 rpm with a Brookfield viscometer)
Preference is given to using high molecular weight polyethyleneimine as a 50% by weight aqueous solution with .

To produce the mixture used as dry strength agent according to the invention, preferably 100% natural potato starch
Based on the weight part, 1 to 20 parts by weight, especially 8 to 12 parts by weight, of high molecular weight polyethyleneimine is used.

In order to produce the mixture used as a dry strengthening agent according to the invention, one starts from an aqueous suspension of natural potato starch containing from o, i to 10 parts by weight of natural potato starch per 100 parts by weight of water. . Other types of starch do not achieve the advantageous effects according to the invention. The mixture used as a dry strengthening agent according to the invention has a 0.5
It is added to the stock in an amount of ~3.5% by weight, preferably 1.2-2.5% by weight. The pH value of the mixture is between 9 and 11, preferably between 95 and 10.5. The aqueous solution of dry strengthening agent is 2
．． At a solids concentration of 2% by weight, it has a viscosity (measured with a Brookfield viscometer at 'l Orpm and 20 DEG C.) of from 20 to 500 mPas, preferably from 50 to 200 mPas.

The dry strength agents used according to the invention can be used in the production of all types of paper, cardboard or paperboard, such as writing paper, printing paper or packaging paper. various fiber materials,
For example, bleached or unbleached sulphite valves or kraft valves, ground wood valves, waste paper, thermomechanical valves (TMP)
Or paper can be made from chemical thermomechanical pulp (CTMP). The pH value of the bulb suspension is 4.0-10, preferably 4.3-8. This dry strengthening agent is suitable for coarse grinding,
It can be used in the production of low basis weight paper (LWC paper) as well as cardboard. The basis weight of the paper is 30 to 200, preferably 65
~150.9/7F12, but for cardboard it is 600
It is less than 97m2. The paper products produced according to the invention have improved e.g. tear length, rupture degree, C
It has significantly improved strength, quantitatively understood by MT value and tear resistance.

Parts in the examples below are parts by weight and percentages are by weight.

Paper sheets were produced on a rapid Guten laboratory paper sheet former. The dry tear length is according to the first leaf of DIN 55112,
Dry rupture degree according to DIN 53141, CMT value D
according to IN53143 and tear resistance is DIN53
115.

Each test was conducted after conditioning the paper sheets at 23° C. and 50% relative humidity for 24 hours.

The value of the polymer is Ferrose-Hemi-13 Vol. 58-6
4 and 71-74 (1932) in a 5% saline solution at 20°C and 0.5
Measured in weight percent polymer concentration. In this case =
It means ni・103.

The following substances were used in the test.

Polymer 1: Polyethyleneimine having a viscosity of 28000 mPas in a 50% aqueous solution.

Polymer 2 Copolymer with a value of 205 from 70% niacrylamide and 60% dimethylamine ethyl acrylate-methchloride.

Strengthening agent 1: A 1050% polymer aqueous solution is added to a 6% suspension of natural potato starch (gelatinization temperature 90°C) in water, and this mixture has a weight of 10% based on the natural potato starch used. Contains union. This mixture was then stirred for 90 min.
Heat to a temperature of ~95°C for 15 minutes. After cooling to a temperature of 10 DEG to 40 DEG C., it can be used as a dry strength agent for paper according to the invention and is added to the paper stock before sheet formation.

Strengthening agent 2: 6% suspension of natural potato starch in water, heated with stirring to 90-95°C for 15 minutes.

The gelatinization temperature of natural potato starch is 90°C.

The clear solution obtained is cooled to 70° C. and an amount of Polymer 1 is added such that the resulting mixture contains 10% of polymer based on the natural potato starch used. 7 of the mixture
It is kept at 0° C. for 15 minutes and then cooled. After cooling to a temperature below 40° C., the inventive dry strength agent for papermaking is obtained. It is added to the pulp suspension before sheet formation.

Strengthening agent 3 (comparison): A 6% suspension of natural potato starch in water is added after cooling to an amount such that the resulting mixture contains 10% polymer relative to the natural potato starch used. is used as an additive in pulp suspensions.

Strengthening agent 4 (comparison): A 3% suspension of natural potato starch in water was heated to 90-95°C.
Heat for 15 minutes. The mixture is then cooled to 70° C. and an amount of Polymer 2 is added such that the resulting mixture contains 10% of Polymer 2 based on the natural potato starch used.

After further heating the mixture at 70° C. for 15 minutes and cooling to a temperature below 4000° C., the mixture can be used to make paper.

Example 1 Paper sheets having a basis weight of 1209/If were produced using a rapid Köten sheet former. The paper stock consisted of 80% mixed waste paper and 20% bleached beech sulfite pulp, and had a Schopper-Riegler freeness of 49° SR. Add to this an amount of reinforcing agent 1 such that the solid content of reinforcing agent 1 is 2.2% based on the dry paper stock.
was added. The pH value of the pulp suspension was Z7.

In order to investigate the influence of the reinforcing agent on the properties of the papers thus produced, the properties listed in Table 1 were measured.

Example 2 Consisting of 80% mixed waste paper and 20% bleached beech sulfite pulp, beaten to 49°SR and rated at 2.0% on dry stock.
A paper stock containing 2% of toughener 2 was spun and dewatered in a Koten sheet former. The pH value of the pulp suspension was 7.7. The paper sheet had a basis weight of 120 g/m2. The strength values of the paper measured in the test are shown in Table 1.

Comparative Example 1 The stock with a pH value of 17 as described in Example 1 was dewatered in a sheet former without any other additives. Obtained basis weight: 120g
Table 1 shows the strength values of the /7!2 paper sheets.

Comparative Example 2 The procedure was as in Example 1, but instead of the reinforcing agent 10,
A 2% natural potato starch aqueous solution (a 6% aqueous suspension of natural potato starch was added to the dry paper stock at 90-95°C for 15 minutes)
(obtained by heating for 1 minute) was added. The aqueous solution of natural potato starch heated above the gelatinization temperature of the starch had a temperature of 23°C at the time of use.

Comparative Example 3 Proceed as in Example 1, but instead of Strengthening Agent 1,
Strengthening agent 3 was also added in an amount of 2.2% based on the dry stock. The strength values of the obtained papers are shown in Table 1.

Comparative Example 4 Operate as in Example 1, but instead of reinforcing agent 10,
The same amount of reinforcement 4 was used. Obtained basis weight 120g/m
Table 1 shows the strength values for No. 2 paper sheets.

1st Table 2 167 166 3.227 1788 Comparative Example Example 3 Using an experimental paper machine, at a paper machine speed of 50 m/min,
Paper with a width of 68 cm and a basis weight of 120.9/m2 was produced. 80% mixed waste paper and 20% bleached beech sulfite pulp as paper stock
% (freeness level 50°SR), and add reinforcing agent 1 to it.
It was added in an amount such that the pulp suspension contained 1.65% of toughener 1 based on the dry stock. The pH value of bank water was ZO. The strength values of the obtained papers are shown in Table 2.

Comparative Example 5 The procedure was the same as in Example 6, except that the addition of Strengthening Agent 1 was omitted. The strength values of the obtained papers are shown in Table 2.

Comparative Example 6 Proceed as in Example 3, but as shown in Table 2 for Toughener 1.

Comparative Example 7 The procedure was as in Example 6, but instead of the reinforcing agent 10,
1.5% of natural potato starch (obtained by heating a 3% aqueous suspension of natural potato starch at 90-95°C for 15 minutes and cooling the solution) was added. The strength values of the obtained papers are shown in Table 2.

Table 2 Comparative Example Example 4 A laboratory paper machine was used to produce a basis weight of 50 g/r suitable as a base paper for LWC paper at a paper machine production speed of 60 m/min.
rL2 paper was made from the following raw materials. 40% bleached groundwood pulp, 60% bleached softwood sulfite pulp and 30% bleached Shirakaba kraft pulp (beating degree 65°SR). Then 20% china clay and 0.3% of a 7% aqueous solution of a commercially available weakly cationic polyacrylamide (K value 120) were added to the dry stock. In addition, 0.5% of alum and 2.2% of toughening agent 1, based on the dry stock, were added to the stock. The pH value of bank water was 6.0. The strength values of the obtained papers are shown in Table 6.

Comparative Example 8 The same procedure as in Example 4 was carried out, except that the addition of the reinforcing agent was omitted. The strength values of the obtained papers are shown in Table 3.

Comparative Example 9 The procedure was as in Example 4, except that an aqueous solution of natural potato starch at 2% of the dry stock was added to the stock. An aqueous solution of natural potato starch was prepared by heating a 3% aqueous suspension of natural potato starch to 90-95°C for 15 minutes and then cooling. The strength values of the obtained papers are shown in Table 6.

Table 3 Comparative example

Claims (1)

[Claims] 1. After adding a drying strength agent to the paper stock, the paper stock is dehydrated while forming paper sheets, and at this time, natural potato starch is added to polyethylene in an aqueous medium as a drying strengthing agent. A method for producing paper, paperboard or paperboard having high dry strength, characterized in that a mixture obtained by heating starch to a temperature equal to or higher than the gelatinization temperature of starch is used together with imine. 2. Claim 1, characterized in that a mixture obtained by reacting 1 to 20 parts by weight of polyethyleneimine with 100 parts by weight of natural potato starch is used as the dry strengthening agent. Method described. 3. 10,000 to 33,000 in 50% by weight aqueous solution
Viscosity in mPas (20 by Bruckfield viscometer)
3. Process according to claim 2, characterized in that polyethyleneimine is used, which has a temperature of 20 rpm (measured at 20 rpm).