JPS58197400A - Increasing of paper strength - Google Patents

Abstract

(57) [Summary] 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 method for increasing paper strength, and more particularly to a method for increasing paper strength by adding microfibrillated cellulose to a pre-paper slurry and forming paper.

In recent years, there has been a worldwide shortage of softwood pulp, and it has become necessary to use hardwood pulp as a raw material for paper. Reinforcement is a major issue in the paper industry.

Several methods have been used to improve the strength of paper.
1) Promote viscous beating, (2) Increase paper density, (3
) There are methods such as adding a binder.

Although they are effective in some cases, no effective method has yet been found in the field of impregnated paper.

That is, in the method (1) of proceeding with viscous beating, the entanglement of fibers increases and the strength is certainly improved, but the impregnation property is significantly reduced, so it is not suitable for increasing the paper strength of impregnated paper. (
Method 2) of increasing density has its limits due to mechanical constraints during manufacturing, and does not contribute much to improving strength (・.

The method (3) using a binder increases the strength, for example, by adding a cationic resin, but there is a problem with electrical properties.
For example, starch) does not have a large strength improvement effect.

As a result of various studies, we added microfibrillated cellulose (hereinafter abbreviated as MFC), which is made by suspending pulp fibers in water and applying a special beating method in which they are repeatedly passed through a homogenizer under high pressure, to the raw material slurry. We have discovered that paper with high dry strength can be obtained by papermaking. The manufacturing method and physical properties of MFC are disclosed in Japanese Patent Application Laid-open No. 1983.
-100801 Bow Specification, and is defined in the same specification as ``11 microscopic horizontally textured cellulose''.

The 39 papers that are commonly used as base materials for electrical insulating boards include linter paper and kraft paper, and the effect of adding MFC to both of them is very large.
%, 2 to 3 times more dry anus can be obtained.

MFC can also be used as a binder for making paper from fibers that cannot be made into paper by themselves, such as glass fibers and cellulose acetate fibers. in this case,
An addition of 5 to 10 units υ [1 for the fiber nail needle is practical.

The present invention will be explained below with reference to Examples.

4 cases A 2% dispersion of MFC was prepared by the method described in F.

Purified sulfide valve (α-cellulose containing + l 2
93%, polymerization degree 1050-1070) to make a 2% slurry, and using a Mont-Gaulin homogenizer, approximately 50()lcg was prepared according to the method disclosed in JP-A-56-100801. The slurry was circulated 40 times under high pressure of /ca. The water holding power of the obtained MFC at 100OG gravity'F- was about 7 times that of the raw material valve.

The obtained 2% dispersion of MFC was used in the examples, and the MFC addition ridge in the examples is a solid content equivalent value.

Example 1 and Comparative Example 1 Using a linter with a freeness of 22-23'SR, a dispersion of MFC was added to the linter slurry, and the density was 0.3 g.
/ rt and made a handmade paper.

Comparative examples include one using the same linter but without adding MFC, one with increased density, and one with increased beating degree.
A paper with an SR of ~28° was also made.

The dry strength (tensile strength) and oil permeability of the obtained paper were measured, and the results are shown in Table 1.

Incidentally, the degree of oil impregnation is a measure of impregnability, and a value of 20 seconds or less can be evaluated as having good impregnation. The measurement method is as follows.

Method for measuring oil penetration degree: 20±
A paper sample that has been left in an air-conditioned room at 1℃ and 65% relative humidity for more than 24 hours is cut into a 25-inch circle and placed with the wire side facing down, and visually inspected to see if any of the pieces of paper are white due to oil penetration. Measure the time until it becomes transparent.

Example 2 and Comparative Example 2 Using kraft valve as a raw material for kraft paper for laminates, MF and C were added in the same manner as in Example 1, and the paper properties were measured. The results are shown in Table 2.

Example 3 and Comparative Example 3 Kraft bulb, a raw material for producing cellulose derivatives, was subjected to fibrous acetylation to obtain cellulose acetate with a degree of acetylation of 48%.

This material was used in place of a valve to make paper, but only a product with low strength was obtained. When paper was made with the addition of MFC, a paper with sufficient strength for practical use was obtained. Example 1.2
The same measurements as above were carried out and the results are shown in Table 3.

Example 4 and Comparative Example 4 Papers made from glass fiber were prepared, and the same measurements as in Examples 1 to 3 were performed. The raw material glass fibers used have an average fiber length of 1 and a diameter of approximately 07z'' (A) and an average fiber length of 3.
mm, diameter to μm (B) σ) 2 types.

The linter used for paper mixing was the same as that used in Example 1. The results are shown in Table 4.

Claims (1)

[Claims] A method for increasing paper strength characterized by adding microfibrillated cellulose to a raw material slurry before paper making.