JPH06250333A - Production of photographic printing paper substrate - Google Patents

Abstract

PURPOSE:To produce a photographic printing paper substrate having high whiteness and being hardly faded. CONSTITUTION:Both sides of a base paper are coated with polyolefin resin to produce a photographic printing paper substrate. In the process, the pulp bleaching sequence includes >=1 continuous sequence of the hypochlorite stage and chlorine dioxide stage, and the pulp is bleached at a high temp. of >=60 deg.C in an alkaline medium contg. >=1wt.% alkali (per absolute dry pulp weight) in at least one hypochlorite stage in the continuous sequence. The base paper is produced from the pulp thus bleached.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a support for photographic printing paper. More specifically,
The present invention relates to a method for producing a support for photographic printing paper, which has high whiteness and little discoloration.

[0002]

2. Description of the Related Art In recent years, with the speeding up of photo processing,
Instead of the conventionally used baryta paper, a water resistant photographic printing paper support in which both sides of a base paper are coated with a polyolefin resin has been used.

The properties required of a support for photographic printing paper are that they are excellent in dimensional stability, moisture resistance, adhesiveness and smoothness, and that they do not adversely affect the photographic emulsion layer. Especially, the hue is important. The surface hue of the photographic emulsion coated surface of the support for photographic printing paper is preferably pure white, and when this hue tends to yellow or red,
The image formed on the photographic paper has a dull or dull appearance. Therefore, various methods for improving the whiteness of the support have been studied so far. As an example, the following method has been proposed.

(1) A method of incorporating a white pigment in the polyolefin coating layer (for example, JP-A-55-108658).
(2) A method of applying a white pigment to the surface of the polyolefin coating layer (for example, JP-A-59-177542) (3) A method of dyeing pulp with a blue dye to improve the apparent whiteness of the base paper ( (For example, JP-A-58-105228) (4) Method of increasing the whiteness of base paper by using pulp with high whiteness Among these methods, (4) is the most effective method,
This method is usually used.

The bleached pulp used for the support is required to have not only high whiteness but also stability of whiteness, that is, a pulp property that is resistant to fading. Whiteness stability is measured by measuring the whiteness of pulp after exposing it to heat for a certain period of time, and calculating the difference in the whiteness before and after that (The Bleachin
g of Pulp, P358, TAPPI PRESS 1979), that is, the PC value (post color number), the stability of whiteness is greatly influenced by the bleaching sequence or bleaching conditions.

Japanese Patent Publication No. 58-43732 describes a method for producing a bleached pulp for a support which is alkaline and uses a peroxide. When hydrogen peroxide is used as the peroxide, the literature (The Bleaching of Pulp,
P382, P384, TAPPI PRESS (1979), N.Hartler, TAPPI
43 (11) 903 (1960)), the higher the addition rate and the longer the time, the better the fading property at high temperature. However, peroxides are expensive and explosive, requiring careful handling. Hydrogen peroxide, which is the most commonly used peroxide for bleaching, is corrosive, so there are problems such as the need to select the material of the reaction vessel, and it is inexpensive and has good workability. A bleach for a paper support is desired.

Hypochlorite is inexpensive, has a bleaching property similar to hydrogen peroxide, and is easier to handle than hydrogen peroxide. However, hypochlorite adversely affects the color fading property, and the higher the addition rate, the higher the temperature, and the longer the time, the worse the color fading property. (The Bleaching of Pulp, P38
3, TAPPI PRESS (1979). This is said to be due to the introduction of a carbonyl group at the end of the cellulose chain of bleached pulp by exposure to hypochlorite (WHRapson, CB Anderson,
GFKing, TAPPI 41 (8) 442 (1958)). Further, the bleaching property is improved as the temperature of the hypochlorite exposure increases, but there is a problem that the decrease in pulp viscosity becomes large at a high temperature. As described above, the exposure to hypochlorite is effective in improving the whiteness, but it has been considered that it has only a negative effect on the fading property and quality of bleached pulp.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a photographic printing paper support having high whiteness and less fading, and the whiteness usable for the support is The purpose of the present invention is to provide a base paper which is high and has little discoloration, and in particular, a pulp having a high degree of whiteness, which does not cause deterioration of discoloration property and deterioration of pulp viscosity by effectively utilizing hypochlorite exposure. The purpose of the present invention is to produce a support for photographic printing paper by using a base paper produced by using.

[0009]

DISCLOSURE OF THE INVENTION The inventors of the present invention have made various studies on pulp for base paper which can be used as a support having the above-mentioned characteristics. After hypochlorite exposure under conditions that are added in excess of bleaching, subsequent chlorine dioxide exposure causes less viscosity reduction and whiteness, despite hypochlorite exposure at high temperature. It was learned that a high pulp can be obtained. And, when the strong alkali hypochlorite exposure and chlorine dioxide exposure are performed at the high temperature, not only the whiteness is further improved,
The present invention has been completed based on the discovery of a surprising effect that the color fading property can be greatly improved.

The present invention relates to a method for producing a support for photographic printing paper by coating both sides of a base paper with a polyolefin resin. In the base paper, the pulp bleaching sequence is a continuous hypochlorite stage and a chlorine dioxide stage. At least one of the hypochlorite stages in the continuous sequence is alkaline with an alkali addition rate (based on dry pulp weight) of 1.0% by weight or more, and
The present invention relates to a method for producing a support for photographic printing paper, which comprises using a base paper produced from pulp produced according to a bleaching sequence which is a step of bleaching at a high temperature of 0 ° C or higher.

Further, the present invention relates to a bleaching sequence of pulp used for base paper, which comprises one or more continuous sequences (H- and H-) of a strong alkaline hypochlorite stage (H) and a chlorine dioxide stage (D) at high temperature. By combining D) with a chlorine stage (C), an alkaline stage (E), an ordinary hypochlorite stage (H), and a chlorine dioxide stage (D), the whiteness is high and the fading property is excellent. The present invention relates to a method which makes it possible to inexpensively manufacture a support for photographic printing paper.

In the method of the present invention, the hypochlorite used in the strong alkaline hypochlorite stage at high temperature is substantially calcium hypochlorite or sodium hypochlorite. , Considering workability, sodium hypochlorite (hypo) is good. The addition rate of hypo to the dry pulp weight is between 0.1% and 3% by weight, preferably between 0.5% and 1.5% by weight.

The alkali used as an auxiliary chemical can be selected from many alkaline compounds known to those skilled in the art, but caustic soda is the most convenient to use. The addition rate of NaOH per unit dry pulp weight is abnormally higher than that of normal hypo bleaching and is between 1% and 4% by weight, preferably between 1.5% and 2.5% by weight. . The reaction temperature is also between 60 ° C and 120 ° C, preferably between 70 ° C and 100 ° C, which is higher than that of normal hypo bleaching.

The pulp concentration is the same as in ordinary hypo bleaching,
Between 5 and 20% with a reaction time of 30 to 150
Between minutes, the final pH is between 8 and 12.5.
After the H-th step, as in the other steps, the washing or compression step is continuously performed.

The ClO ₂ used in the subsequent chlorine dioxide stage is C ₂ obtained from many ClO ₂ generation methods known to those skilled in the art.
You can choose from lO ₂ . Per dry pulp weight
The ClO ₂ addition rate is between 0.2% and 3% by weight in terms of ClO ₂ , the reaction temperature is between 40 ° C and 100 ° C, and the pulp concentration during the reaction time is between 5% and 15%. And the reaction time is between 15 and 300 minutes and the final pH is between 2 and 6.

The bleaching method of the pulp used for the base paper for the photographic printing paper of the present invention is not only chemical pulp such as kraft pulp (KP), alkaline pulp (AP) and sulfite pulp (SP) but also modified continuous steaming. Solution (Modified Continuous Coo
king) pulp, after cooking with normal crafting method,
Pulp that has been bleached with oxygen, and after cooking with a modified continuous cooking method,
It is also applicable to oxygen-bleached chemical pulp. Needless to say, it can be applied to both wood pulp and non-wood pulp.

[0017]

EXAMPLES Examples of the present invention will be described below.
The present invention is not limited to these examples. In the examples given below, bleaching conditions in a continuous sequence of high temperature, strong alkaline hypo and chlorine dioxide stages, photographic paper support production, bleached pulp and photographic paper support whiteness measurements and tests. Was based on the following operation means.

Strong alkaline hypo-stage and chlorine dioxide at high temperature
Continuous sequence of steps ( HD) Pulp was taken in a plastic bag, 2.5 wt% alkali and 1 wt% hypo were added to the dry pulp weight, and ion-exchanged water was added to adjust the concentration to 10%. After adjusting
The mixture was thoroughly stirred and kept at 90 ° C for 3 hours. After the reaction was completed, the sample was taken out of the bag, washed, and then dehydrated by centrifugation. Centrifuge dehydrated pulp is put in a plastic bag again and 1.0 wt%
ClO ₂ (in terms of ClO ₂ ) was added, ion-exchanged water was added to adjust the concentration, and the mixture was sufficiently stirred and kept at 90 ° C. for 3 hours.

Production of Support for Photographic Paper A bleached pulp was beaten to a Canadian freeness of 300 ml to prepare a pulp slurry. Alkyl ketene dimer resin as a sizing agent is 0.4% by weight per absolute dry pulp weight, anionic polyacrylamide resin as a strength agent is 0.1% by weight per absolute dry pulp weight, and cationized starch is absolute dry. 2.0 wt% per pulp weight and 0.7 wt% polyamide polyamine epichlorhydrin resin per absolute dry pulp weight were added, diluted with water and made into a 1% slurry. Paper was made from this slurry and passed through a dryer, size press, and machine calender to produce a base paper for photographic printing paper having a rice basis weight of 170 g / m ² , a tenacity of 1.0 g / m ³ , and a moisture content of 8%. As the size press chemicals, carboxyl-modified PVA and sodium chloride were mixed at a ratio of 2: 1 and dissolved in water to be applied as a 5% size liquid on both sides of the paper at a coating amount of 25 g / m ² .

High density polyethylene (density 0.951 g / cm ³ , melt index = 9 g / 1
0 minutes) and low density polyethylene (density 0.918g / c
A 1: 1 mixture of m ³ and melt index = 4 g / 10 min) was extrusion coated at a resin temperature of 330 ° C. and matted with a cooling roll to form a resin coating layer having a thickness of 30 μm. On the other surface, a polyethylene resin containing 10% by weight of anatase type titanium dioxide (density = 0.
50 parts by weight of linear low-density polyethylene of 926 g / cm ³ , melt index = 16 g / 10 min, and density = 0.
A mixture of 918 g / cm ³ and 50 parts by weight of low-density polyethylene (melt index = 4 g / 10 min) was extruded at a resin temperature of 320 ° C. to form a resin coating layer having a thickness of 30 μm. Formed to produce a photographic paper support.

Measurement of Whiteness of Pulp and Fading Test The whiteness of pulp was measured according to JIS P 8123. The fading test is performed by bleaching the bleached pulp for 2 hours in an air circulation type constant temperature bath at 105 ° C, and the whiteness after the fading is measured according to JIS P 81.
The value was measured according to 23, and the PC value was calculated from the following formula and displayed. [(1-after photobleaching whiteness) ^2/2 × after photobleaching whiteness - (1-
Fading before whiteness) ^2/2 × fade before whiteness] × 100

Measurement of Whiteness of Photographic Paper Support and Fading Test The whiteness of the photographic paper support was measured according to JIS P 8123. The fading test was carried out by enclosing the support for photographic printing paper immediately after production in a 100 μm black low-density polyethylene bag,
It was stored for 4 weeks in a constant temperature and humidity of 40 ° C. and 80% RH.

Example 1 Unbleached hardwood pulp (mixed material of domestic hardwood; whiteness 26.
2%, Kα value 18.3) Absolutely dry 50 g was put in a plastic bag, 2.8 wt% chlorine was added to the weight of pulp, and ion-exchanged water was added to adjust the concentration to 10%.
The mixture was thoroughly stirred and kept at 45 ° C for 30 minutes. After completion of the reaction, the washed and centrifugally dehydrated pulp is placed in a plastic bag, 1.0% by weight of alkali is added, ion-exchanged water is added to adjust the concentration to 10%, and the mixture is sufficiently stirred,
Hold at 1 ° C for 1 hour. After completion of the reaction, wash and spin-dry.
Continuous sequence exposure (HD) of a hypo alkali stage and a chlorine dioxide stage at high temperature was performed.

After the reaction was completed, the washed and centrifugally dehydrated pulp was put in a plastic bag, 0.3% by weight of hypo was added, and ion-exchanged water was added to adjust the concentration to 10%.
The mixture was thoroughly stirred and kept at 45 ° C for 1.5 hours. After the reaction was completed, the washed and centrifugally dehydrated pulp was placed in a plastic bag, 0.3 wt% of chlorine dioxide (ClO ₂ conversion) was added, ion water was added to adjust the concentration to 10%, and the mixture was thoroughly stirred. And kept at 70 ° C. for 2.5 hours. After the reaction,
Bleached pulp washed and centrifuged (C-E- (H-D) -H
-D sequence) was used as the base photographic paper support for photographic printing paper.
The results are shown in Table 1.

Example 2 The same unbleached hardwood pulp as in Example 1 was CEHD-
It was bleached in the (HD) sequence and used as a support base paper for photographic printing paper. The results are shown in Table 1.

Example 3 The same unbleached hardwood pulp as in Example 1 was CE- (H-
D)-(HD) sequence was bleached and used as a support base paper for photographic printing paper. The results are shown in Table 1.

Example 4 The same dry bleached hardwood pulp (50 g) as in Example 1 was placed in an autoclave, and 2.6% by weight of alkali and 1.5% by weight of oxygen were added to the pulp, and ion-exchanged water was added. After adjusting the concentration to 10%, stir well and mix at 90 ° C.
For 40 minutes. After the reaction was completed, the washed and centrifugally dehydrated pulp was placed in a plastic bag, 1.4% by weight of chlorine was added, ion-exchanged water was added to adjust the concentration to 10%, and the mixture was sufficiently stirred at 45 ° C. Hold for 30 minutes. After completion of the reaction, the washed and centrifugally dehydrated pulp is placed in a plastic bag, 0.5% by weight of alkali is added, ion-exchanged water is added to adjust the concentration to 10%, and then the mixture is sufficiently stirred, and then 50
Hold at 1 ° C for 1 hour.

After the completion of the reaction, washing and centrifugal dehydration were carried out, and a continuous sequence exposure (HD) of a strong alkaline hypo stage and a chlorine dioxide stage was carried out at a high temperature. After the reaction was completed, the washed and centrifugally dehydrated pulp was placed in a plastic bag, 0.3% by weight of hypo was added, ion-exchanged water was added to adjust the concentration to 10%, and the mixture was sufficiently stirred at 45 ° C. Hold for 1.5 hours. After the reaction was completed, the washed and centrifugally dehydrated pulp was placed in a plastic bag, 0.3% by weight of chlorine dioxide (as ClO ₂ ) was added, ion-exchanged water was added to adjust the concentration to 10%, and Stir and hold at 70 ° C. for 2.5 hours. After the reaction, washed and centrifugally dehydrated bleached pulp (O-C-E-
(H-D) -H-D sequence) was used as a support base paper for photographic printing paper. The results are shown in Table 1.

Example 5 The same unbleached hardwood pulp as in Example 1 was used as O-C-E-H-
It was bleached in the D- (HD) sequence and used as a support base paper for photographic printing paper. The results are shown in Table 1.

Example 6 The same unbleached hardwood pulp as in Example 1 was mixed with OCE- (H
It was bleached in the sequence -D)-(HD) and used as a support base paper for photographic printing paper. The results are shown in Table 1.

Comparative Example 1 The same unbleached hardwood pulp as used in Example 1 was CEHD-
It was bleached by an HD sequence and used as a base paper for a photographic printing paper support. The results are shown in Table 1.

Comparative Example 2 The same unbleached hardwood pulp as in Example 1 was used as O-C-E-H-.
It was bleached in the D-H-D sequence and used as a support base paper for photographic printing paper. The results are shown in Table 1.

[0033]

[Table 1]

[0034]

From Table 1 above, a support for photographic printing paper produced by using as a base paper bleached pulp in a sequence containing one or more consecutive sequences of a high alkali hypo stage and a chlorine dioxide stage at high temperature, It is clear that the whiteness is high and the fading property is remarkably improved. The high whiteness of the photographic printing paper support and the fading of the photographic printing paper make the photographic printing paper look crisp and maintain that dignity for a long time.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsuaki Onishi 1850 Todaka, Niinan City, Miyazaki Prefecture Oji Paper Co., Ltd. Nichinan Mill

Claims (2)

[Claims] 1. A method for producing a support for photographic printing paper by coating both sides of a base paper with a polyolefin resin, wherein as the base paper, a bleaching sequence of pulp is a continuous sequence of a hypochlorite stage and a chlorine dioxide stage. At least one of the hypochlorite stages in the continuous sequence is alkaline with an alkali addition rate (based on dry pulp weight) of 1.0 wt% or more and a high temperature of 60 ° C. or more. A method for producing a support for photographic printing paper, which comprises using a base paper produced from pulp produced according to a bleaching sequence which is a step of bleaching under. 2. The bleaching sequence of pulp used for base paper is chlorine stage, alkali stage, hypochlorite stage, chlorine dioxide stage,
The method for producing a support for photographic printing paper according to claim 1, which comprises a continuous sequence of a hypochlorite stage and a chlorine dioxide stage.