FI123480B - A method for improving wet strength and a paper product having improved wet strength - Google Patents

Description

A METHOD FOR IMPROVING wet strength and a paper product with improved wet strength

FIELD OF THE INVENTION

The invention relates to a method for improving wet strength as defined in the preamble of claim 1 and to a paper product as defined in the preamble of claim 5 having improved wet strength.

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BACKGROUND OF THE INVENTION

In the papermaking industry, the use of mainly inorganic chemicals as fillers in paper is known in the art. Pigments 15 used as fillers are added to the pulp. Pigments include, for example, precipitated calcium carbonate or PCC, marble, kaolin, talc, special pigments, etc. Pigments of the order of 1 to 10 µm are commonly used. Fillers are used to improve the optical properties of the paper 20 and to reduce the amount of fiber used, thereby reducing the cost of papermaking.

The problem with adding fillers is that the fillers weaken the paper's strength properties, such as wet strength, as a function of the filler content. 25 The strength of paper made from pure fibers is always ^ better than that of paper doped with filler, δ It is generally recognized in the art that

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the poor wet strength of the paper containing the substance is due to 1 inhibition of hydrogen bonding. Further, it is known that the strength of the wet web increases due to surface tension and friction. On the other hand, if the surface of the fiber is coated, then hydrogen bonds cannot be formed.

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SUMMARY OF THE INVENTION

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The object of the invention is to eliminate the above disadvantages. In particular, it is an object of the invention to provide a novel method for improving the wet strength of paper and a novel type of paper-5 product having improved wet strength.

SUMMARY OF THE INVENTION

The process and product of the invention are characterized by what is disclosed in the claims of patent 10.

The invention is based on a method for improving the wet strength of a paper product. According to the invention, a nano-PCC pigment having particles of less than 200 nm in size class 15 is used as at least part of the paper filler.

In one embodiment of the invention, pigments having a particle size of about 150 nm are used.

In one embodiment, the filler may be nano-grade pigments alone, or alternatively other pigments in addition to the nano-grade pigments. In one embodiment, the amount of nano-grade pigment used is preferably <50 wt% of the total amount of filler. In an alternative embodiment, the amount of nano-class 25 pigment is greater than 50 wt% of the total amount of filler.

In one embodiment of the invention, the nano-class pigment is a nano-PCC pigment, i. nano class tL of precipitated calcium carbonate pigment either alone or in combination with other pigments. In an alternative embodiment, the process of the invention can use any nano-class pigment or pigments known per se and suitable.

In one embodiment of the invention, the nanoparticulate pig ...

g 35 cents are added to the pulp, preferably just before the paper is made. The paper pulp may be any paper pulp, e.g. chemical or mechanical pulp or recycled pulp.

When the pigment particles are small in diameter, less than 200 nm, they interfere less with the wet-5 strength of the paper. In addition, in the process of the invention, nano-class pigments adhere to the fiber surface, increasing friction. This increases the wet strength with the use of nano-class pigments.

Further, the invention is based on a paper product 10 made of a fiber-based material. According to the invention, the paper product has improved wet strength and contains less than 200 nm size of nano-PCC pigment as at least part of a filler.

As used herein, a paper product is any fiber product, such as paper, paperboard or the like.

The invention provides improved wet strength on paper. The invention provides better fiber-to-fiber bond formation and reduces steric barriers. Thanks to the invention, it is possible to increase the running speeds on a paper machine.

DETAILED DESCRIPTION OF THE INVENTION

The invention will now be described with reference to the detailed exemplary embodiments, with reference to the accompanying Figures 1-8, which show experimental results obtained by the method according to the invention.

δ c \ j i märk Example 1 cd 30 x The wet strength of paper crepe was tested in a series of experiments in this example.

S For the test series, 80 g / m2 fine paper sheets of the invention were prepared using nano-PCC in combination with conventional SPCC and 80 g / m2 reference sheets using a conventional PCC blend. with 65% SPCC and 35% RPCC. Nano-PCC had a particle size of about 150 nm, and SPCC and RPCC had a particle size of about 2-3 µm.

The wet strength properties of the various sheets were tested and the results obtained from the sheets according to the invention were compared with those of the reference sheets.

Table 1 shows the experimental data.

Table 1

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In coniferous wood,% 30 30__30

Birch pulp,% 70 70 70 Starch, kg / tonne of paper 880 PCC filler,% (65% SPCC, 23.6 34.6 35% RPCC) ____ SPCC filler,% __19.8 n-PCC,% ___ 10

Percol 47, standardized, was used as a retention agent at points in the test series. Roquette [Hi-Cat 5163 AM] starch was used as starch.

In the test 1 according to the invention, starch was not used. In the experiment of the invention, conventional RPCC was replaced by nano-PCC.

In the test series, several wet strength measurements of reference sizes 20, tests 1 and 2 and experiment 1 were performed at various dry solids concentrations. The results are shown in Figures 1-4. Figures 1-4 show the tensile index (Figure 1), the tensile stiffness index (Figure 2), the fracture index (Figure 3), and the elongation (Figure 4) in relation to the dry solids content. The results give information about the paper

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g of wet strength.

o From the figures it can be seen that the tensile index,

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The tensile stiffness index, fracture index, and elongation are significantly increased when nano-PCC is used to replace conventional fillers. These strength improvements are achieved without starch.

Experiments show that the use of nano-grade PCC as a filler significantly improves the wet strength properties of the paper.

In the 0 tests shown in the figures, no substantially fillers were added to the pulp.

Example 2 In this series of tests, the wet strength of a paper sheet according to the invention with respect to reference sheets was investigated.

In the test series, substantially the same amount of pigment by weight as in the reference pulp was used in the pulp of the present invention. Fine paper sheets and reference sheets of Example 1 were prepared in a test series.

The wet strength properties of the various sheets were tested and the results of the sheets according to the invention were compared with those of the reference sheets.

Table 2 shows the experimental data.

Table 2 25

Ref 1 Ref 2 Koel Experiment2 Experiment 3 Experiment 4 c \ j ^ Coniferous Wood,% 30 30 30 30 30 30 c \ j i Birch Wood,% 70 70 70 70 70 70 V Starch, kg / t of paper 8 8 8 8 15 8

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ria_______ g Filler content, 22.8 31.7 25.6 32.2 32.4 30,% of which 4

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CD S-PCC filler,% 65 65 65 65 65 0 o R-PCC filler,% 35 35 o ^ n-PCC filler,% 35 35 35 100 6

Percol 47, standardized, was used as a retention agent at points in the test series. Roquette [Hi-Cat 5163 AM] starch was used as starch.

In tests 1-3 of the invention, conventional RPCC was replaced by nano-PCC and in experiment 4, both SPCC and RPCC were replaced by nano-PCC.

In the test series, several wet hair measurements according to reference tests 1 and 2 as well as tests 1-4 were performed with different dry matter contents. Results 10 are shown in Figures 5-8. Figures 5-8 show tensile index (figure 5), tensile stiffness index (figure 6), fracture index (figure 7) and elongation (figure 8) in relation to dry solids content.

From the figures it can be seen that the tensile index, tensile stiffness index, tensile index and elongation are significantly increased when using nano-PCC to replace conventional fillers. In this series of tests, even wet wet strengths of paper-20 made from the pulp of the invention were achieved as compared to the reference.

When nanoparticulate pigments alone were used as filler in the pulp (Experiment 4), the wet strength continued to increase relative to the reference sheets. However, it is not necessary to use nanoscale pigments alone to achieve optimum wet-wet hair and other properties of paper.

In the 0 tests shown in the figures, the paper pulp c ...

No substantial fillers were added.

From the tests it can be seen that the use of V 30 nano-grade PCC as part of the filler or as a filler completely improves the wet strength properties of the paper.

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The process according to the invention is suitable for use in different applications for the production of different paper production from different paper pulps.

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The embodiments of the invention are not limited to the examples shown, but may vary within the scope of the appended claims.

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Claims (6)

A method of improving the hydrogen pour strength of a paper product, characterized in that a nano-PCC pigment of an order of magnitude below 200 nm is used at least as part of the paper filler. Process according to claim 1, characterized in that pigments of an order of magnitude below 150 nm are used as fillers in the paper. 3. A method according to claim 1 or 2, characterized in that the nanostore pigment is applied to the pulp. Process according to any one of claims 1 to 3, characterized in that the nanostore pigment is applied to the pulp just before the paper is produced. 5. Paper product, made of a fiber-based material, characterized in that the paper product contains nano-PCC pigments of an order of magnitude below 200 nm at least as part of the filler, and the paper product has an improved hydrogen strength. Product according to claim 5, characterized in that the paper product contains pigments of an order of magnitude below 150 nm. c \ j δ c \ j i CD X cc CL 't co CD O CD O O C \ l