JP2717177B2 - Manufacturing method of lightweight cast coated paper - Google Patents

Description

The present invention relates to a lightweight cast-coated paper. (Prior art) Conventionally, cast-coated paper has a wet coating method in which the wet coating layer is pressed against the heating drum surface to produce a glossy finish. The wet coating layer is made into a gel state and pressed against the heating drum surface to produce a glossy finish. It is manufactured by a gel casting method, a wet coating method in which a wet coating layer is once dried or semi-dried, and then re-wet to plasticize and press against a heating drum surface. Also, a method has been proposed in which after forming an undercoat layer mainly composed of a pigment and a binder on a base paper, a top coat layer is formed, and while this overcoat layer is in a wet state, is pressed against a heating drum surface to perform a gloss finish. I have. (Problems to be Solved by the Invention) These casting methods are common in that a coating layer mainly containing a pigment and a binder in a wet state is peeled off after being pressed against a heating drum surface and dried. the coating amount is generally 15 to 35 g / m ^2, coating speed is 50 m / min before and after the low-speed when using the drum dryer with a diameter of 3.6 m, when the present inventors or the like is confirmed, and dried in a high speed casting It was found that pinholes and the like occurred on the surface, resulting in an unsatisfactory surface. (Means for Solving the Problems) The present inventors have made intensive studies to produce cast-coated paper having good surface properties at high speed, and as a result, have completed the present invention. That is, the present invention provides: 1. an undercoat layer containing 10 to 80% by weight of a pigment having a pigment and a binder as main components and an oil absorption (JIS K5101) of 50 m1 / 100 g or more, on a paper support; Air permeability (JIS P811
7) A method for producing a lightweight cast-coated paper, comprising providing a cast coat layer containing pigment, a heat-fusible substance and a binder as main components on a base paper of 300 seconds or less. 2. The method for producing a lightweight cast-coated paper according to the above item 1, wherein the coating amount of the cast coat layer is 0.5 to 10 g / m ² . 3. The main component of the cast coat layer is pigment 20 ~ 60% by weight,
3. The method for producing a lightweight cast-coated paper according to the above item 1 or 2, wherein the content is 10 to 50% by weight of a heat-fusible substance and 10 to 40% by weight of a binder. It is. Examples of pigments used in the undercoat layer include inorganic pigments such as kaolin, clay, calcium carbonate, magnesium carbonate, magnesium oxide, titanium oxide, zinc oxide, aluminum hydroxide, barium sulfate, talc, satin white, calcium sulfate, and silica. Organic pigments such as polystyrene, urea, formaldehyde resin, starch granules, etc. are used. In order to keep the air permeability of the base paper with an undercoat layer below 300 seconds, the oil absorption (JIS K5101) must be 50 ml / 100.
g or more of the pigment is preferable, and the oil absorption is 50 ml / 10.
The content of the pigment of 0 g or more is desirably 10 to 80% by weight based on the weight of the undercoat layer. If it is less than 10% by weight, the air permeability decreases, the evaporation of water slows down during casting, the operating speed decreases, and pinhole-like defects occur on the cast coat surface. If it exceeds 80% by weight, the adhesiveness becomes poor, the peeling off from the drum dryer during cast coating becomes poor, and scum adheres to the drum dryer. When a pigment having an oil absorption of 50 ml / mg or more is not used, the air permeability becomes non-uniform, and in areas where the air permeability is poor, swelling or defects such as pinholes occur due to evaporation of the cast coat coating solution water. Oil absorption 50ml / mg or more, preferably 80ml / mg
By using the above pigment, the uniformity of air permeability is maintained, and the surface property of the cast coat surface can be improved. Preferred pigments having an oil absorption of 50 ml / mg or more include, for example, the following. However, the values in parentheses indicate the oil absorption (ml / 100g). Diatomaceous earth (110-210), calcined diatomaceous earth (130-140), flux calcined diatomaceous earth (120-16
0), calcined clay (50-57), natural graphite fine powder (50-10
0), natural earth graphite (50-120), carbon black (50
~ 150), white carbon (50 ~ 300), fine anhydrous silica (100 ~ 300), fine anhydrous aluminum oxide (100 ~ 250), fine titanium oxide (50 ~ 120), magnesium carbonate (50 ~ 150) , Magnesium aluminate silicate (300-340), pigment is physically or chemically treated
Those having an oil absorption of 50 ml / 100 g or more, for example, those having needle-column-shaped calcium carbonate particles three-dimensionally combined to form a sea urchin shape and having an oil absorption of 60 ml / 100 g or more. Examples of the binder used in the undercoat layer include starch, modified starch, casein, protein, gelatin, celluloses, polyvinyl alcohol, modified polyvinyl alcohol, styrene, butadiene copolymer, styrene / acrylonitrile copolymer, and styrene. -Various natural and synthetic binders such as acrylic copolymer and polyacrylamide are used in the form of an aqueous solution, latex or emulsion. Since the adhesive strength varies depending on the type of the binder, the amount of the binder is not uniform. However, usually about 5 to 30% by weight of the solid content of the coating liquid is used. Alternatively, it is preferable to use a minimum amount necessary for adhesion to the cast coat layer. The undercoat coating liquid may contain a dispersant, a water-proofing agent, an antifoaming agent, a preservative, a dye, a heat-fusible substance, and the like, as necessary, and may include an air knife coater, a blade coater, and a bar coater. , A roll coater, a brush coater, a gravure coater, etc., coated on a paper support to a dry coating amount of 3 to 10 g / m ² , and if necessary, a machine calender, a super calender, etc. Is performed. Undercoat coating amount is poor surface properties of the cast-coated paper is less than 3 g / m ^2, also effect exceeds 10 g / m ² was decreased productivity without improvement, also cost economical, Not preferred. Air permeability of base paper with undercoat layer (JIS P811
It is important that 7) is 300 seconds or less, preferably 200 seconds or less, and if the air permeability exceeds 300 seconds, the coating speed cannot be reduced unless the coating speed is reduced. Defects and surface properties are impaired. As the pigment / binder used in the cast coat layer, the same pigments and binders as those described above for the undercoat layer can be used. Examples of the heat-fusible material include metal soaps such as zinc stearate and calcium stearate, carnapa wax, beeswax,
Natural waxes such as montan wax, petroleum waxes such as paraffin wax and micro wax, polyethylene waxes, and synthetic compounds such as fatty acid amides and fatty acid esters can be used. The amount of the pigment, the heat-fusible substance, and the binder is not uniform because the properties vary depending on the type of the chemical used. %, The heat-fusible substance is 10 to 50% by weight, and the binder is 10 to 40% by weight. The type and amount of the pigment are determined in consideration of ink acceptability, glossiness, etc.
If the amount is less than 50% by weight, ink receptivity becomes poor,
If the amount is too large, the surface properties deteriorate. The heat-fusible substance increases the plasticity of the cast coat layer when pressed and dried on the surface of the heating drum in a wet state, and a sufficiently good cast surface can be obtained even with a low coating amount. If the content of the heat-fusible substance is less than 10% by weight, the effect is insufficient and the surface property is deteriorated, and 50% by weight.
If the amount is too large, ink acceptability and the like deteriorate. The binder is a residue of the pigment and the heat-fusible substance, and is used in an amount sufficient to adhere the components to each other and adhere to the undercoat layer. The coating liquid of the cast coat may contain a dispersing agent, a defoaming agent, various surfactants, a water-proofing agent, a preservative, a dye, a fluorescent pigment, a fluorescent brightener, etc. as necessary. It is applied to a dry coating amount of 0.5 to 10 g / m ² by a casting method such as a wet casting method, a rewetting casting method, and a gelling casting method. 0.5 g / m ^{2 of} cast coat
If less than 10 g / m ² , drying takes a long time and the coating speed is reduced. (Function and Effect) As in the present invention, the air permeability of a base paper having an undercoat layer containing a pigment and a binder as main components on a paper support is set to 300 seconds or less, and the pigment, By providing a cast coat layer containing a heat-fusible substance and a binder as main components, it is possible to obtain a lightweight cast-coated paper with good surface properties with a coating amount of 15 g / m ² or less. Speed can be significantly increased. That is, the present invention is to improve the cast coat surface by providing an undercoat layer, in which case the moisture of the cast coat coating solution passes through the base paper by setting the air permeability of the base paper to 300 seconds or less. It promotes evaporation from the back side to enhance the drying property, and further achieves a low coating amount of the cast coat layer by the plasticity increasing effect of the heat fusible substance contained in the cast coat layer, Thus, it is possible to provide a lightweight cast-coated paper having good drying properties. The lightweight cast-coated paper of the present invention is used not only for printing paper, but also for thermal transfer receiving sheets, pressure-sensitive receiving sheets, heat-sensitive recording sheets, and inkjet recording paper magnetic recording by devising chemicals used for undercoat layers or cast layers. It can be applied to information-related paper such as sheet base paper, decorative sheets, etc., and is considered to be a very useful technology. (Examples) Next, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the description of these examples. Parts in the examples indicate parts by weight of the solid content. Example 1 Diatomaceous earth (Celite Supercross Oil Absorption 125: manufactured by Johns Manville Co.) 40 parts, light calcium carbonate (Sonex E oil absorption 40: manufactured by Shiraishi Industry Co., Ltd.) 30 parts, oxidized starch (M
15 parts of S.3800 Nippon Shokuhin Co., Ltd., modified acrylic resin emulsion (Movinyl L-8010: Hoechst Gosei Co., Ltd.)
Co., Ltd.) and an undercoat coating solution having a solid content concentration of 35% was prepared. A cast coat coating liquid having a solid content concentration of 30%, comprising 40 parts of kaolin, 20 parts of light calcium carbonate, 15 parts of zinc stearate, 10 parts of polyvinyl alcohol, and 15 parts of a modified acrylic resin emulsion, was prepared. Using the apparatus shown in FIG. 1, after coating and drying in air knife coater so that an undercoat coating solution and a dry coating amount of 6 g / m ² base paper of 50 g / m ^2, dry coating and cast coating a coating liquid The composition was applied so as to have an amount of 3 g / m ^2, and was cast-finished by a cast drum heated to 90 ° C. The surface of the light-weight cast-coated paper thus obtained was good without defects, and the maximum coating speed was 150 m / min. The air permeability of the undercoated base paper was 80 seconds. Example 2 The diatomaceous earth of the undercoat coating liquid of Example 1 was applied to three-dimensional needle-shaped calcium carbonate urchin-like particles (callite SA oil absorption 60: manufactured by Shiraishi Industry Co., Ltd.) with zinc stearate of the cast coating liquid. A lightweight cast-coated paper was obtained in the same manner as in Example 1 except that paraffin wax was used. The surface of the light-weight cast coated paper thus obtained was good without defects, and the maximum coating speed was 130 m / min.
The air permeability of the undercoated base paper was 200 seconds. Comparative Example 1 A lightweight cast-coated paper was prepared in the same manner as in Example 1 except that diatomaceous earth in the undercoat coating solution was changed to kaolin (Astrabright oil absorption 40: manufactured by Georgia Kaolin Co.). Drying of the coating solution was slow and the maximum coating speed was 90 m / min, and pinholes were conspicuous on the surface of the cast coat, resulting in poor surface properties. To improve surface properties, the dry coating amount of the cast coat layer should be 10
g / m ² or more was required, and the maximum coating speed became 60 m / min or less. The air permeability of the undercoated base paper is 500
Seconds. Comparative Example 2 45 parts of kaolin (Astrabright oil absorption 40), 20 parts of heavy calcium carbonate (Escalon # 1500 oil absorption 28: manufactured by Sankyo Seiko Co., Ltd.), polyvinyl alcohol (Kosenol N-300 Nippon Synthetic Chemical Co., Ltd.) 15 parts, styrene-butadiene latex (JSR 0561, Japan Synthetic Rubber Co., Ltd.) 20
An undercoat coating liquid having a solid content concentration of 45% was prepared. Using this undercoat coating solution and the cast coating solution of Example 1, a lightweight cast-coated paper was produced in the same manner as in Example 1. At this time, the air permeability of the undercoated base paper is 1000 seconds or more, the drying of the cast coat coating solution is slow, and the maximum coating speed is 40 m / min. And the surface of the cast coat had remarkable defects and poor surface properties. Comparative Example 3 A light-weight cast-coated paper was produced in the same manner as in Example 1 except that zinc stearate in the cast coat coating liquid was removed. The maximum coating speed at this time is 150m
/ min, and defects such as pinholes and uneven coating were noticeable on the surface of the cast coat. In order to improve the cast coat surface, the dry coating amount of the cast coat layer was required to be 10 g / m ² or more, and the maximum coating speed became 80 m / min or less.

[Brief description of the drawings] FIG. 1 is a schematic view of a coater used in the embodiment.

   ────────────────────────────────────────────────── ─── Continuation of front page    (56) References JP-A-55-76198 (JP, A)                 JP-A-49-118906 (JP, A)                 JP-A-57-117694 (JP, A)                 JP-A-62-95285 (JP, A)                 JP-A-54-23545 (JP, A)                 JP-A-62-173293 (JP, A)

Claims (1)

(57) [Claims] An undercoat layer containing a pigment and a binder as main components and containing 10 to 80% by weight of a pigment having an oil absorption (JIS K5101) of 50 m1 / 100 g or more is provided on a paper support.
7) A method for producing a lightweight cast-coated paper, comprising providing a cast coat layer containing pigment, a heat-fusible substance and a binder as main components on a base paper of 300 seconds or less. 2. ^{2. The} method for producing a lightweight cast-coated paper according to claim 1, wherein the coating amount of the cast coat layer is 0.5 to 10 g / m < ² >. 3. The main component of the cast coat layer is pigment 20 to 60% by weight,
3. The method for producing a lightweight cast-coated paper according to claim 1, wherein the content is 10 to 50% by weight of a heat-fusible substance and 10 to 40% by weight of a binder.