Paper making and fiber liberation – Processes and products – Non-fiber additive
Reexamination Certificate
2000-12-19
2003-05-20
Chin, Peter (Department: 1731)
Paper making and fiber liberation
Processes and products
Non-fiber additive
C162S072000, C162S168100, C162S005000
Reexamination Certificate
active
06565708
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a paper quality improver composition for papermaking, which can improve bulky value and optical properties such as brightness and opacity of a sheet obtained from a pulp feedstock by papermaking as well as which can improve a paper-strength.
PRIOR ART
From the viewpoint of conservation of the environment in earth, a reduction in the used amount of pulp is demanded. As a result, it has been demanded to make paper light and to increase the blending amount of deinked pulp. However, paper obtained by merely reducing the amount of pulp in the paper becomes thin so that its opacity becomes low. Thus, its quality becomes poor. According to the lightening of paper based on reducing the amount of pulp, about paper for which stiffness in proportion to cube of thickness is required, such as paperboard, its stiffness is unfavorably lowered. On the other hand, if the blending ratio of deinked pulp is raised, brightness is lowered by remaining ink or the like in the deinked pulp. Moreover, the pulp itself becomes skinny in recycle process so that the thickness of the resultant paper is lowered. Thus, its opacity becomes low. Accordingly, if amount of the pulp in paper is reduced as well as the blending ratio of deinked pulp is raised, the opacity and the brightness of the obtainable paper are lowered still more. Further, it is not preferable that opacity of obtained paper is reduced still more, if brightness of deinked pulp which makes brightness low is raised by deinking and/or bleaching.
In order to prevent the thickness of paper from being lowered by lightening the paper, hitherto various bulky value improving methods have been attempted. For example, about a producing method of making press pressure low, there arises a problem that smoothness is lowered so that printability becomes poor. Examples of the attempts also include methods in which a crosslinked pulp is used (JP-A 4-185792, etc), in which a mixture of pulp with synthetic fibers is used as a feedstock for papermaking (JP-A 3-269199, etc), in which spaces among pulp fibers are filled with a filler such as an inorganic substance (JP-A 3-124895, etc), and in which spaces are formed (JP-A 5-230798, etc). However, pulp cannot be recycled or smoothness of paper is damaged. Although there is known a paper bulking promoter disclosed in WO99/63156 (corresponding to EP-A 1001082 A1 and JP-B 2971447), a paper-strength performance is insufficient.
On the other hand, in order to improve opacity and brightness, a method of adding a large amount (e.g., 5 to 20% by weight) of an inorganic filler, such as calcium carbonate, kaolin and white carbon has been carried out in the present industry. However, only if the inorganic filler is added in a large amount, the weight of paper increases remarkably. Even if the amount of pulp is reduced and the inorganic filler is added, it is impossible to make the paper light. In the case that the inorganic filler is added in particular to deinked pulp, a large amount of the inorganic filler is necessary. The lightening of the paper becomes increasingly difficult.
DISCLOSURE OF INVENTION
An object of the present invention is to solve the above-mentioned various problems associated with the lightening of paper and the increase in the amount of deinked pulp. Specifically, it is to provide a paper quality improver composition for papermaking, which can attain at least two of improvements in bulky value, brightness and opacity due to modifying a surface of pulp as well as which can improve a paper-strength.
The present invention provides a paper quality improver composition for papermaking; which comprises (A) a compound having a lyotropic degree, defined below, of not less than 4% and meeting at least two efficiencies selected from the following paper quality improving efficiencies (i) to (iii) and (B) a water-soluble polymer satisfying at least one selected from an average molecular weight of 1000 to 10000000 and a viscosity of 1 to 4000 mPa•s at 25° C. in a 1% aqueous solution thereof; which is internally added before or in papermaking step;
(i) standard improved bulky value of not less than 0.02 g/cm
3
,
(ii) standard improved brightness of not less than 0.5 point, and
(iii) standard improved opacity of not less than 0.5 point; and lyotropic degree (%)=(&agr;
0
−&agr;)/&agr;
0
×100
wherein
&agr;: the water content in a wet sheet obtained by adding 5 parts by weight of the compound which becomes the paper quality improver composition for the papermaking to 100 parts by weight of pulp and subjecting the resultant to the papermaking, and
&agr;
0
: the water content in a wet sheet obtained by subjecting pulp to the papermaking without adding the compound which becomes the paper quality improver composition for papermaking to the pulp.
The water-soluble polymer is a polymer compound from which an aqueous solution having a concentration of 0.1% or more by weight at 40° C. can be obtained. It includes a polymer compound from which an aqueous solution having a concentration of 0.1% or more by weight can be obtained by dissolving it in water at a temperature of higher than 40° C. and then cooling the solution.
The present invention provides also a process for producing a pulp sheet, which comprises adding the composition as defined above anytime before or in papermaking step. Further, the present invention provides a pulp sheet produced by adding the composition as defined above at anytime before or in papermaking step.
The following will describe methods for measuring the lyotropic degree, the standard improved bulky value, the standard improved brightness and the standard improved opacity according to the present invention, in detail.
[Method for Measuring the Lyotropic Degree]
(A) Pulp for Use
There is used a bleached hardwood pulp which is derived from a beech and whose Hunter's brightness (JIS P 8123) of a hand-made pulp sheet, prepared by the method for preparing hand-made paper for a pulp test according to JIS P 8209, is 80±5%. (This pulp is referred to as an LBKP hereinafter.)
(B) Measurement of the Lyotropic Degree
{circle around (1)} A predetermined amount of an LBKP is disintegrated (brushed out) with a beater at 25±3° C. and then beaten into a Canadian standard freeness (JIS P 8121) of 460±10 ml so as to obtain an LBKP slurry whose pulp concentration is 1.0% by weight.
This pulp slurry is weighed out so that the basis weight of the LBKP of a sheet to be prepared by papermaking becomes 80±2 g/m
2
. The pH thereof is then adjusted into 4.5 with aluminum sulfate, and subsequently 5 parts (net) by weight of an ethanol-solution of 1.0% by weight of a paper quality improver composition for papermaking is added as compared with 100 parts by weight of the pulp. The resultant is subjected to papermaking using a 150-mesh wire (area: 200 cm
2
) in a circular TAPPI papermaking machine to obtain a wet sheet. Two filter papers having a basis weight of 320±20 g/m
2
(diameter: 185 mm) are stacked on the wet sheet, and further a coach plate is stacked thereon to perform coaching. Thereafter, the wet sheet is taken out. Next, the wet sheet is put between the above-mentioned two filter papers at upper-face and bottom-face therefrom and then is pressed at a pressure of 340±10 kPa for 5 minutes. After the press, the weight W (g) of the wet sheet is promptly measured.
Next, the wet sheet is dried at 105±3° C. for 60 minutes. A basis weight W
d
(g) of obtained dry sheet is measured.
{circle around (2)} From the W and W
d
obtained as above, the water content &agr; (%) is obtained by the formula (1):
&agr;(%)=(
W−W
d
)/
W×
100 (1).
Without adding any compound which becomes a paper quality improver composition for papermaking, a sheet is prepared in the same manner. The water content obtained in the same manner is represented by &agr;
0
.
{circle around (3)} From the water contents &agr; and &agr;
0
obtained as above, the lyotropic degree is obta
Ikeda Yasushi
Tadokoro Takaaki
Takahashi Hiromichi
Chin Peter
Hug Eric
Kao Corporation
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