JP2002069887A - Method for producing kraft paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a kraft paper having excellent high tensile strength, burst strength and tear strength. SOLUTION: An amphoteric starch is added to a pulp slurry, which is subjected to papermaking. The amphoteric starch is an ordinary starch containing a cationic group and an anionic group in the molecule.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing kraft paper, and more particularly, to a method for producing kraft paper in which a decrease in tear strength is alleviated in addition to an improvement in tensile strength and burst strength.

[0002]

2. Description of the Related Art Kraft paper has high paper strength and is often used for heavy paper bags, but is also used for light packaging such as envelopes and shopping bags. Conventionally, such kraft paper is made only of unbleached softwood kraft pulp for heavy bags, but for light packaging, unbleached kraft pulp made of hardwood, bleached kraft pulp and softwood kraft pulp are used in combination. Sometimes used.

[0003] Since it is used for packaging, it protects the contents,
Paper strength is required to obtain durability in transportation and carrying, and excellent printability is also required as an advertising, advertising and decoration media.To improve printability, unbleached kraft pulp made of hardwood, bleached The use of kraft pulp tends to increase. However, hardwood pulp has problems such as poor paper strength and poor drainage in papermaking.

[0004]

In order to prevent such a decrease in paper strength and improve productivity, and to further enhance paper strength, a method of adding a paper strength enhancer to a pulp slurry has been generally adopted. ing. However, kraft papers manufactured by adding currently available paper-strengthening agents (polyacrylamide, starch derivatives, CMC, synthetic polymers such as polyamide epichlorohydrin resin, etc.) have low tensile strength and burst strength. Although an improvement is observed, the tear strength tends to decrease.

An object of the present invention is to provide a method for producing kraft paper in which the tensile strength, burst strength, and the like are improved and the decrease in tear strength is alleviated. Another object of the present invention is to improve drainage in order to increase papermaking speed together with paper strength.

[0006]

Means for Solving the Problems The present inventors have studied and studied from various angles in order to achieve the above-mentioned object. As a result, the amphoteric starch effectively acts as a paper strength enhancer and has a tensile strength. -It has been found that kraft paper can be produced which not only improves the burst strength but also reduces the decrease in the tear strength. The present invention has been made based on this.

Therefore, the method for producing kraft paper of the present invention is characterized in that amphoteric starch is added to pulp slurry to make paper.

[0008] The amphoteric starch used here preferably has a degree of substitution of 0.1 to 0.3 for cationic groups and 0.1 to 0.3 for anionic groups. The amount of the amphoteric starch added to the pulp slurry is preferably 0.1 to 1.0% by weight based on the dry weight of the pulp.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail.

[0010] The amphoteric starch used in the present invention is a raw material starch such as potato starch, tapioca starch, corn starch, a hydrolyzed starch thereof, etc., which has a cation group and an anion group in the starch molecule. Is defined as That is, in order to introduce both functional groups, it is necessary to chemically introduce each group.

The cationization can be carried out by a usual method using a cationizing agent containing a tertiary amino group or a quaternary amino group as a modifier, for example, a wet method, a dry method or the like. The anionization modification method can be carried out by using an anionizing agent containing a phosphoric acid group, a sulfonic acid group, a carboxyl group, or the like, and performing the same treatment as the above-mentioned cationization.

[0012] Some of the raw starches obtained from the rhizome have anionic groups in advance, but such starches can be easily converted to amphoteric starch simply by a cationization reaction.

[0013] The amphoteric starch is one in which a cationic group and an anionic group are introduced into a starch molecule by successively reacting these modifying agents with starch. The degree is generally represented by the degree of substitution, which is defined by the number of substituents introduced relative to the number of glucose units of the starch molecule. The preferred degree of substitution of the amphoteric starch used in the present invention is 0.1 to 0.3, preferably 0.15 to 0.25 for the cationic group, and 0.1 to 0.3, preferably 0.1 to 0.2 for the anionic group.

When the degree of substitution of the cationic group is less than 0.1, the effect of increasing the paper strength is poor, and when it exceeds 0.3, the effect corresponding to the degree of starch modification cannot be obtained.

When the degree of substitution of the anion group is less than 0.1, there is a disadvantage that it is difficult to obtain a fixing effect via aluminum ions. It is not preferable.

The amount of the amphoteric starch to be added is 0.1 to 1.0% by weight, preferably 0.2 to 0.7% by weight, based on the dry weight of the pulp. If the amount is less than 0.2% by weight, the strength of the paper, especially the tensile strength, is poor.

No attempt has been made to produce kraft paper using the amphoteric starch described above. In the method for producing kraft paper of the present invention, when the amphoteric starch is added to the pulp slurry to make paper, how the amphoteric starch acts to improve the burst strength, improve the tensile strength and alleviate the decrease in the tear strength. Although the mechanism of this is not fully understood, the amphoteric starch is fixed to the fibers and the internal strength is improved by reinforcing the hydrogen bonds between the fibers, while the bonding between the fibers is higher than that of polyacrylamide etc. It is considered that since the degree of freedom of the crosslinked portion contributing to the reinforcement is high, a decrease in the tear strength is alleviated.

When a zwitterionic starch polyion complex comprising a mixture of a cationic starch and an anionic starch is used instead of the amphoteric starch of the present invention,
The fixing rate to pulp is low, and the effect as high as the amphoteric starch of the present invention cannot be expected.

When the amphoteric starch of the present invention is used, if necessary, clay, sulfate band, sizing agent, dry paper strength improver, wet paper strength improver, fixing agent, drainage improver, dye Commonly used chemicals for paper making such as are added,
A kraft paper according to the invention is produced.

[0020]

EXAMPLES Next, the present invention will be described more specifically with reference to examples, but it is needless to say that the present invention is not limited to these examples. The parts here are based on weight.

Example 1 Softwood unbleached kraft pulp (freeness: 600 ml) 97.4 parts, commercial sizing agent 0.2 part,
2.0 parts of sulfate band, amphoteric starch (degree of substitution: quaternary amino group)
A kraft paper having a basis weight of 75 g / m ² was produced using a fourdrinier paper machine using a papermaking material consisting of 0.2 and 0.15) and 0.4 part of a phosphate group.

Example 2 Kraft paper was prepared in the same manner as in Example 1, except that the amount of the amphoteric starch was changed to 0.6 part.

Comparative Example 1 Kraft paper was prepared in the same manner as in Example 1, except that an amphoteric starch polyion complex comprising a mixture of a cationic starch and an anionic starch was used instead of the amphoteric starch. .

Comparative Example 2 Kraft paper was prepared in the same manner as in Example 1, except that 0.35 parts of a commercially available paper strength enhancer (copolymeric amphoteric PAM) was used in place of the amphoteric starch.

The kraft paper thus produced is described by JI
The specific tear strength was measured based on SP8116, the specific burst strength was measured based on JIS P8112, and the tensile strength was measured based on JIS P8113. Table 1 shows the results.

[0026]

[Table 1]

[0027]

As is evident from the results in Table 1, the kraft paper produced by using the amphoteric starch of the present invention as a paper-strengthening agent is as follows.
Because both tensile strength and tear strength are good,
Suitable for use in clupaks. When kraft paper is made by incorporating the amphoteric starch of the present invention, the reduction in tear strength is small and the drainage is improved, so that the paper making speed can be increased.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Akira Takeda 5-1 Kamiyacho, Iyo Mishima City, Ehime Prefecture Daio Paper Co., Ltd. F-term (reference) 4L055 AA02 AC06 AG48 AH16 BD10 EA29 EA32 FA13 GA05

Claims (3)

[Claims] 1. A method for producing kraft paper, comprising adding amphoteric starch to a pulp slurry to form a paper. 2. The degree of substitution of the amphoteric starch is 0.1 to 0.1.
The method for producing kraft paper according to claim 1, wherein the number of the kraft papers is 0.3 and the number of the anionic groups is 0.1 to 0.3. 3. The amount of the amphoteric starch added to the pulp slurry is as follows:
3. The method for producing kraft paper according to claim 1, wherein the amount is 0.1 to 1.0% by weight based on the dry weight of the pulp.