JPH0636092B2 - Method for producing support for photographic paper - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a support for photographic printing paper. More specifically, the present invention relates to a method for producing a photographic paper support having a water-resistant resin material coating layer in which pigments are finely and uniformly dispersed and having excellent resolution. is there.

[Conventional technology]

Conventionally, baryta paper has been used as a support for photographic printing paper, but in recent years, a water-resistant support in which a coating layer made of a polyolefin resin is provided on both surfaces of a base made of paper has come to be used. This water-resistant support shortens the washing and drying times during development of photographic paper produced from it, eliminates the need for ferrotypes, saves chemical consumption, maintains rigidity and various strengths at high levels, and It has advantages such as less contamination due to chemical penetration.

In order to coat a photographic emulsion on the surface of such a water-resistant support to obtain a photographic printing paper having excellent resolution, the water-resistant resin material coating layer on the surface side of the support on which the photographic emulsion is to be coated It is generally practiced to add a white pigment such as titanium dioxide to improve the hiding power of the resin material coating layer.

In order to uniformly contain a pigment such as titanium dioxide in the water-resistant resin, a Banbury mixer, a kneader, or a single-screw extruder for kneading is used, and in the water-resistant resin material, 20 ~
A pigment such as 60% by weight of titanium dioxide is melt-kneaded to prepare a masterbatch, and a water-resistant resin material is added to this masterbatch to adjust the pigment content of the resulting mixture to 5 to 5.
A method of adjusting to a desired value of 20% by weight has been used (Japanese Patent Publication No. 61-26649).

[Problems to be solved by the invention]

When a masterbatch is manufactured using a Banbury mixer or a kneader, the mixing effect of the resin material and the pigment is excellent, but the manufacturing process becomes a batch type batch, and thus the problem of poor productivity is encountered. is there.

Further, when a masterbatch is produced using a kneading single-screw extruder, there is an advantage that the process is continuously performed and the productivity is high, but fine dispersion of pigment particles and uniform dispersion in the resin material can be achieved. Insufficient, therefore, the hiding property of the resin material coating layer of the resulting photographic printing paper support becomes uneven and insufficient, and the photographic printing paper produced from such a support has a high resolution. Causes a problem of low.

As described above, the conventional support for photographic printing paper does not have a manufacturing method that is sufficiently satisfactory in both productivity and quality (fine and uniform dispersion of pigment) as described above, and its development is strongly desired. Was there.

That is, the present invention overcomes the drawbacks of the conventional batch-type mixing method, that is, low productivity and low work efficiency, and overcomes the drawbacks of the conventional continuous-type mixing method, that is, the low dispersion effect and low quality. It is intended to provide a method for producing a support for photographic printing paper, which can be carried out with high productivity and high work efficiency, and can obtain a high dispersion effect and high quality comparable to a batch type mixing method. is there.

[Means and Actions for Solving Problems]

The method for producing a support for photographic printing paper according to the present invention is a biaxial method for laminating a mixture containing a water-resistant thermoplastic synthetic resin and a pigment on at least one surface of a sheet-like substrate by a melt extrusion coating method. The biaxial meshing screw has a meshing screw, and the diameter D of each screw of the biaxial meshing screw and the length L thereof satisfy the following relationship: L ≧ 20D, and at least one position of the biaxial meshing screw is present. , At least one set of kneading discs is arranged, and the total thickness of the kneading discs is related to the diameter D of the screw by the following relation: 2D ≦ T ≦ 10D -The pigment mixture is prepared through at least one melt-kneading step.

In the method of the present invention, at least one surface of the sheet-like substrate,
In particular, a mixture containing a water resistant / thermoplastic synthetic resin and a pigment is laminated by a melt extrusion coating method on the surface to be coated with the photographic emulsion.

The sheet-like substrate used in the method of the present invention can be selected from base papers generally used for photographic printing paper supports,
Examples thereof include natural pulp paper, synthetic pulp paper, mixed paper of natural pulp and synthetic pulp, and various types of laminated paper. In general, natural pulp mainly composed of softwood pulp, hardwood pulp, softwood mixed hardwood pulp and the like is widely used. The base paper may contain additives such as a sizing agent, a fixing agent, a paper-strengthening agent, a filler, an antistatic agent, and a dye, which are generally used in papermaking, and a surface sizing agent and a surface paper-strengthening agent. Alternatively, the surface may be coated with an antistatic agent layer as appropriate.

The sheet-like substrate usually has a weight of 50 to 300 g / m ² and has a smooth surface.

The water resistant / thermoplastic resin used for coating both sides of the sheet-like substrate is preferably selected from polyolefin resins. The polyolefin resin can be selected from ethylene, α-olefins such as homopolymers of propylene, at least two copolymers of the above olefins, and a mixture of at least two of these various polymers. Particularly preferred polyolefin resins are low density polyethylene, high density polyethylene, and mixtures thereof. The molecular weight of the polyolefin resin is not particularly limited, but one having a range of 20,000 to 20,000 is usually used. Each coating layer is typically formed on a paper substrate at a weight of 10-50 g / m ² .

White pigments such as titanium dioxide are dispersed and mixed in the polyolefin resin used for the coating layer, but in addition, various additives such as colored pigments, fluorescent whitening agents, antioxidants, and / or dispersants are added. You may add.

In the method of the present invention, a water resistant / thermoplastic resin, a pigment such as titanium dioxide, and optionally other additives are melt-dispersed and mixed.

The titanium dioxide pigment used in the practice of the present invention,
Sulfuric acid method, chlorine method, rutile type,
Any of the anatase type may be used, but the anatase type is advantageous from the viewpoint of whiteness. Further, a titanium dioxide pigment which has not been surface-treated can also be used, or a surface of titanium dioxide to which an inorganic surface-treating agent such as hydrous aluminum oxide is applied, or, for example, organopolysiloxane,
It is also possible to use those to which an organic surface treating agent such as amine, alcohol, alkyl titanate, etc. has been applied, and further to appropriately combine an inorganic surface treating agent and an organic surface treating agent, but at least 0.2 to Al ₂ O ₃ content Those treated with 2.0% hydrous aluminum oxide are preferred.

In the method of the present invention, various conventionally used pigments and chemicals can be basically used. Also, coloring pigments,
For example, ultramarine, an antioxidant, a fatty acid metal salt, etc. are preferably added together with titanium dioxide.

As the ultramarine that can be used in the method of the present invention, any commercially available ultramarine can be used as long as it has no hindrance when applied to a photographic resin composition. The amount of ultramarine contained in 100 parts by weight of the resin composition is
It is preferably 0.05 to 10 parts by weight.

As the antioxidant that can be used in the method of the present invention,
Any commercially available antioxidant can be used as long as it does not cause any trouble when applied to a photographic resin composition, but in particular, a phenol-based, thioether-based or phosphite-based oxidation agent can be used. Inhibitors are preferred.

The content of the antioxidant in the resin composition is preferably, for example, 5 to 500 ppm with respect to 100 parts by weight of the resin composition.

Examples of the fatty acid metal salt that can be used in the method of the present invention include zinc stearate, calcium stearate, aluminum stearate, magnesium stearate, zirconium octylate, sodium palmitate, calcium palmitate, sodium laurate and the like. . Further, the addition amount thereof is preferably in the range of 0.01 to 5% by weight with respect to the resin mixture containing the titanium dioxide pigment.

If necessary, other white pigments such as zinc oxide, talc, calcium carbonate, aluminum hydroxide and barium sulfate may be added to the titanium dioxide-containing resin mixture in the present invention. For example, yellow lead,
Titanium yellow, red iron oxide, carbon black and the like may be added, and further, fibrous substances such as glass, asbestos and whiskers, and fluorescent whitening agents and the like may be contained.

In the method of the present invention, the mixture of the water resistant / thermoplastic resin and the pigment is prepared through at least one melt-kneading step using an extruder having a twin screw.

Regarding the structure and function of the biaxial meshing melt extruder, for example,
"Plastic Age" August 1985 page 75, "Chemical Engineering" December 1984 page 933, and "Engineering Materials" Volume 30,
No. 11, page 93, etc.

The twin-screw meshing melt extruder has a cylinder equipped with a heating means and two screws arranged in the cylinder and parallel to each other. The two screws rotate in the same direction or in opposite directions to melt the thermoplastic resin-pigment mixture charged in the cylinder and knead it into a sheet, string or beads. It is extruded into a shape. The shape and size of the groove formed in the screw are determined according to the rotation direction of the two screws. When both screws rotate in the same direction due to the engagement of the grooves, the grooves of both screws have the same shape, but when they rotate in the opposite directions, the grooves of both screws are symmetrical to each other. Take a shape.

In the example shown in FIG. 1, the twin-screw meshing melt extruder 1 includes a first feeding section 2, a second kneading section 3, a ring section 4, a second section.
It has a supply part 5, a second kneading part 6, a reverse screw ring part 7, a vent part 8 and a measuring part 9. The twin-shaft meshing screw 10 shown in FIG.
In addition, a screw portion 14 and a screw 12 formed on the screw 11 having a plurality of sets of kneading disks 13.
The threaded portions 15 formed on the first and second threaded portions have directions opposite to each other. Therefore, in this case, the screws 11 and 12 rotate in mutually opposite directions, and the kneading discs mounted on the respective screws also rotate in mutually opposite directions.

Of course, the screw parts formed on a pair of screws may have the same direction, in which case both screws rotate in the same direction, so that the kneading discs mounted on each screw also move in the same direction. Rotate.

According to the method of the present invention, when the resin-pigment mixture is kneaded by a twin-screw intermeshing melt extruder, a high position exchange effect and a strong shearing effect act on the mixture, the pigment is dispersed in fine particles, and the resin Evenly distributed in the base material. Here, the "position exchange effect" refers to the effect of macroscopically uniformly mixing the substance to be dispersed in the base material, and the "shear effect" refers to the substance to be dispersed microscopically. It has the effect of dividing to the level of primary particles and uniformly dispersing it in the base material.

The twin-screw intermeshing extruder preferred for the method of the present invention is, for example, as described in "Industrial Materials" Volume 30, No. 11, page 95,
A parallel shaft meshing type, generally a shallow groove type is preferable, and both screws may rotate in the same direction or may rotate in the opposite direction. In order to efficiently and highly disperse pigments and the like in the resin base material with such a twin-screw meshing extruder, generally,
The biaxial meshing screw, for the diameter D of each screw,
It is more preferable that the length L satisfies the following relationship: L ≧ 20D, and the following relationship: L ≧ 25D.

When the length L of the screw is less than 20 times the diameter D, the dispersion of the pigment in the heat resistant / thermoplastic synthetic resin becomes insufficient.

A single-thread screw to a triple-thread screw is used as a method of screwing the screw, but it is preferable to use a triple-thread screw.

In the method of the present invention, in order to give a higher shearing effect to the pigment or the like to be dispersed and obtain a higher dispersion, at least one portion of the twin screw is at least 1
Preferably, a set of kneading discs is provided.

The kneading discs are provided on each of the biaxial meshing screws so as to face each other.

The kneading disc may be flat plate-like bodies 21a and 21b having a three-lobed (triangular) flat shape as shown in FIG. 3 (A), for example. Alternatively, the kneading disk may be a flat disc 22 having a two-lobe (elliptical) plane shape as shown in FIG. 3 (B).
It may be a and 22b.

The major axis of these kneading discs is smaller than the inner diameter of the cylinder accommodating each screw, the kneading discs 7 do not contact each other, and the kneading disc and the inner wall surface of the cylinder also contact each other. Without rotating, it rotates in a predetermined direction. Then, the substance to be dispersed is finely divided by the strong shearing force between the lobe tips of the kneading disk or the inner wall surface of the cylinder, and is uniformly dispersed in the resin base material.

The kneading disc may be provided at one place for each screw, or at two or more places separated from each other, and one pair of kneading discs or two or more kneading discs may be provided for each screw. In each screw, the total thickness T of the kneading disk mounted on the screw satisfies the following relation with respect to the screw diameter D: 2D ≦ T ≦ 10D, and the following relation: 4D ≦ T ≦ 10D. More preferably.

When the value of the ratio T / D is less than 2, the uniformity of the pigment dispersion becomes insufficient when the resin and the pigment are mixed and kneaded, and
When the value of the ratio T / D is larger than 10, the discharge of the resin-pigment mixture becomes unstable and the production of the masterbatch becomes difficult.

When two or more kneading discs are installed in each screw, an angular phase difference may be given to the lobe positions of adjacent kneading discs installed in each screw, and this may have a screw function. , There may be no phase difference (straight). When giving a phase difference to the lobe position, the phase may be shifted in the forward direction of the screw direction of the screw or may be shifted in the reverse direction.

In the twin-screw meshing extruder used in the method of the present invention, a sealing disc may be arranged and provided immediately downstream of the kneading disc provided in each screw in the extrusion direction. This sealing disk is effective in preventing short pass of the resin-pigment mixture melt in the cylinder.

The following is an example of a twin-screw intermeshing extruder useful for the method of the present invention.

The relationship between the length L of the screw downstream of the feed section of the extruder cylinder and the diameter D of the screw is L = 28D, and at the position 3/7 (first position) from the feed section of the length of the cylinder. , Equipped with a plurality of 2-lobe or 3-lobe kneading discs with a total thickness of 2.5D (straight) without phase difference of the lobes, and 5/7 from the screw length feed Position (2nd position)
Is equipped with a kneading disc with a plurality of 2 lobes or 3 lobes with a total thickness of 2.5D. This second
The angle of the lobes of the kneading disc (lobe crest position) installed in the position may be arranged so as to be shifted by a predetermined angle, for example, 30 degrees in the forward direction and the winding direction of the screw of the screw in the extrusion direction. .

The twin-screw meshing extruder used in the method of the present invention preferably comprises a temperature control device for controlling the temperature of the resin-pigment mixture charged in the cylinder to a predetermined value.

Further, the twin screw may rotate in the same direction as each other, or may rotate in the opposite direction. However, in the case of reverse rotation, the amount of adjustment of the relationship between the feed amount of the charge and its compression ratio is small, and if too much feed is applied, the extruder will be overloaded. It is easy to cause problems such as the fact that it does not go away. Therefore, it is generally preferable to employ the same-direction rotation of the twin screw.

In the method of the present invention, the water resistance / thermoplastic resin is 5
-80% (by weight) of additives such as pigments can be uniformly mixed and extruded.

In the method of the present invention, using a twin screw intermeshing melt extruder,
Preparation of a masterbatch or compound of water-resistant / thermoplastic resin material containing 10 to 80% by weight of pigment, particularly titanium dioxide, with or without addition of resin material, pigment content May be adjusted to a predetermined value.

The twin-screw intermeshing melt extruder used in the method of the present invention is for performing continuous operation, and therefore it is necessary to supply the raw materials to be kneaded continuously and at an accurate supply amount. .

As such a supply device, a so-called fixed amount feeder can be used, and a gravity type feeder, a reciprocating type feeder, a vibrating type feeder, an endless belt type feeder, a screw type feeder, a table type feeder and the like can be used. As the quantitative feeder, for example,
Screw type feeders (for example, Auger type, live bin type, Accurate type, K-Tron type, Acrison type, Novadale type, biaxial weighing type, etc.) and table feeders (eg table type, groove type table type, stairs) Mold table type, auto feed type, etc. can be used. In these supply devices, the supply amount is
It is also possible to detect the differential weight loss by the flow balance method and feed back the required increase or decrease to stabilize the supply amount.

Each of the feedstocks may be supplied separately or by mixing them in advance in a predetermined ratio and supplying the mixture.

The titanium dioxide-containing polyolefin resin mixture produced by the twin-screw intermeshing kneading extruder of the present invention may be used as a high-concentration masterbatch and directly diluted with a diluting resin to be used in a melt extrusion coating process. Alternatively, it may be prepared into a secondary masterbatch or compound through a single-screw extruder before use. Alternatively, it may be directly used as a compound without going through a masterbatch.

In the method of the present invention, a resin mixture melt containing a pigment such as titanium dioxide is usually formed on a sheet-like substrate such as running paper or synthetic paper from a slit die of an extruder into a single-layer or multi-layer film form. It is melt extrusion coated.
Generally, the melt extrusion temperature is preferably 200 ° C to 350 ° C. Further, it is preferable to perform activation treatment such as corona discharge treatment or flame treatment on the substrate before melt extrusion coating the resin composition on the substrate. The thickness of the resin layer is not particularly limited, but it is generally advantageous that the resin layer is extrusion coated to a thickness of about 5 to 50 microns. In addition, in a usual support in which both surfaces of the substrate are coated with resin, the resin surface containing the titanium dioxide pigment has a glossy surface, a matte surface, a silky surface, etc. depending on the application, and the back surface on the opposite side. Is usually a matte surface, and activation treatment such as corona discharge treatment or flame treatment can be applied to the surface or both front and back surfaces as required. If necessary, a sub-coat layer for improving the adhesion to the photographic emulsion on the surface resin layer or a back cot layer for improving the writing property and antistatic property on the back surface resin layer is applied. You can

〔Example〕

 The present invention will be further described with reference to examples.

In the examples, the light scattering coefficient S on the surface of the support was measured and calculated as follows.

The resin coating layer was peeled from the support produced by the resin melt extrusion coating method, and the obtained resin film was subjected to the following light scattering test.

Apparatus: Hunter whiteness meter (using a blue filter) Measurement method: (i) A white plate having a reflectance Rg was applied to the back of the resin film to be tested, and the light reflectance R of the film to be tested was measured.

(Ii) A black plate having a reflectance of O was applied to the back surface of the test film to measure the reflectance R ₀ of the test film.

(Iii) The weight (g / m ² ) W of the test resin film was measured.

[Note: Rg value is 0.8 to 0.85] Calculation: The light scattering coefficient S (cm ² / g) of the test film is Kub.
It was calculated from the following modified equation of the elka-Munk equation.

[However, in the above formula The light scattering coefficient is a measure of the dispersion of titanium, and when the same kind of titanium is used and the titanium contents are equal, the light scattering coefficient can be used to evaluate the dispersibility as well as the resolution.

Example 1 0.18 parts of an antioxidant (manufactured by Ciba-Geigy, commercial method: Irganox 1010), 1.8 parts of zinc stearate to 60 parts of titanium dioxide (manufactured by Ishihara Sangyo Co., Ltd., trademark: A-220) in advance.
A 1: 1 (by weight) mixture of blue ultramarine and violet ultramarine (Daiichi Kasei Kogyo Co., Ltd., trademark: # 2000, and DV-1).
36 parts and high density polyethylene (Density = 0.94g / cm ² , MI
= 8) 40 parts was premixed with a tumbler.

This mixture was quantitatively supplied to the following twin-screw kneading extruder with an auger type quantitative feeder to produce a masterbatch. That is, as a twin-screw kneader, an extruder with L / D = 30 and a screw diameter of 65 mm, and one 3-lobe kneading disk (segment type, thickness: 2.5D, straight) from the supply side to the screw length Attach it to the position near 3/7,
Also, from the supply side to the thickness near the screw length 5/7
Nine 0.25D kneading discs (segment type) were mounted by sequentially shifting the lobe angle by 30 degrees in the forward direction. (T = 2.5D + 0.25D × 9 = 4.75D) Both screws were of the same rotation type, and this extruder was operated at a discharge rate of 50 kg / hour and a rotation speed of 200 rpm. The resin temperature is about 110 ℃ in the first half and about 150 ℃ in the second half.
Met. A pellet type masterbatch A was obtained.

This masterbatch A is divided into 4 parts, and each is made of high-density (HD) polyethylene resin (density ≈ 0.94 g / cm ³ , MI =
8) and / or diluted with a low density (LD) polyethylene resin (density = 0.918 g / cm ² , MI = 7) with the composition shown in Table 1 to bring the concentration of titanium dioxide to the level shown in Table 1. It was adjusted and made into pellets. Sample A2 of this diluted mixture was further diluted with polyethylene resin to adjust its titanium dioxide concentration to the value shown in Table 1, while Samples A1, A3 and A4 were left undiluted. It was subjected to a melt extrusion operation.

On the other hand, a sheet substrate was prepared as follows.

Canadian Standard Freeness (JIS P-8121-76)
Softwood bleached sulfite pulse (NBSP) 20% beaten to 250 ml
And 80% of bleached hardwood sulphate pulp (LBKP) beaten to a freeness of 280 ml are mixed and weighed 170 g / m ^{2 of} rice, with a tenacity of 1.
A paper substrate having 0 g / cm ³ and 8% water content was obtained. At this time, the following amount was used as an additive for papermaking with respect to the pulse absolute dry weight.

Cationized starch 2.0% Alkyl ketene dimer resin 0.4% Anionic polyacrylamide resin 0.1% Polyamide polyamine epichlorhydrin resin 0.
Adjusted to 7% caustic soda HP7.5 As a size press chemical, carboxyl-modified PVA and sodium chloride were mixed in a weight ratio of 2: 1 and dissolved in water to prepare 5% size liquid 25g on both sides of the paper. / M ^{2 was} applied. In this way, a paper substrate was obtained.

First, the back side of the paper substrate was subjected to corona discharge treatment, and high density polyethylene (density = 0.94 g / cm ³ , MI = 8.0) was applied to this side.
And low-grade polyethylene (density = 0.92 g / cm ³ , MI = 4.6) 1.1 mixture was melt-extruded at a resin temperature of 330 ° C and laminated, and cooled while matting with a cooling roll, and thickness
A 30 μm backside resin coating layer was formed.

Then, the corona discharge treatment is applied to the front surface of the paper base,
On this side, each of the resin-pigment mixtures was placed at a resin temperature of 320
The resin coating layer having a thickness of 30 μm was formed by melting and extruding at a temperature of 0 ° C. to form a glossy resin coating layer.

The light scattering coefficient of the surface layer of the obtained support was excellent as shown in Table 1.

Example 2 The same operation as in Example 1 was performed. However, the composition of the masterbatch is as shown in Table 1, and with respect to 30 parts of titanium dioxide, the same antioxidant as in Example 1 was 0.09 parts, zinc stearate was 0.9 parts, and the same ultramarine blue mixture as in Example 1 was 0.18. The parts were premixed with a Henschel mixer.

This powder mixture was fed to a twin-screw kneader with a table quantitative feeder, and at the same time, high density polyethylene (density = 0.94 g /
cm ³ , MI = 8.0) was supplied by an auger type feeder. However, the ratio of the supply amount of the powder mixture and the polyethylene resin is adjusted to be 30:70 by weight, and each supply amount is measured by a weight-reduction weighing machine and fed back to the feeder to determine the supply amount. It was automatically controlled to be stable.

The same biaxial kneader as in Example 1 was used to carry out dispersion kneading to produce a masterbatch. In this kneading, the discharge amount is 50 kg
The rotation speed was 180 rpm, and the resin temperature was 110 ° C in the first half and 150 ° C in the second half and the adapter. In this way, Masterbatch B was obtained.

Master batch B is divided into 3 parts, and sample B1 is included in each divided part.
B3 and B3 were diluted with high-density polyethylene to adjust the titanium dioxide concentration as shown in Table 1, and directly subjected to melt extrusion coating. Further, the sample B3 was diluted with high-density polyethylene in the melt extrusion coating step, and the coating operation was performed while adjusting the titanium dioxide concentration as shown in Table 1.

The light scattering coefficient of the surface of the obtained support was excellent as shown in Table 1.

Example 3 The same operation as in Example 2 was performed. However, the composition of the resin-pigment mixture obtained by using the twin-screw intermeshing kneading extruder is the first
It was as described in the table.

As this biaxial kneading apparatus, the one having the almost same arrangement as that described in Example 1 was used, but the rotating directions were the same and opposite steps.

Let C be the compound obtained by rotating in the same direction, and D be the compound obtained by rotating in the opposite direction. In the biaxial kneading, the discharge rate was 50 kg / hour, the rotation speed was 150 rpm, and the temperature was 110 ° C in the first half and 150 ° C in the second half and the adapter. Each of Compounds C and D was subjected to its as-is melt extrusion coating.

The light scattering coefficient of the surface layer of the obtained support was excellent as shown in Table 1.

Example 4 The same operation as in Example 2 was performed. However, in the biaxial kneading, the premixed pigment mixture was fed to the biaxial kneader with a biaxial quantitative feeder, and at the same time, high density polyethylene (density = 0.94 g / cm ³ , MI = 8.0) was applied with an auger type feeder. Supplied. However, automatic control operation was performed with the same device as in Example 2 such that the ratio of the amount of the powder mixture to the amount of the polyethylene mixture supplied was 15:85 by weight.

This twin-screw kneading machine used was one having almost the same arrangement as in Example 1, but did not use the 3-lobe kneading disc nearer to the supply side, and instead used a Banbury-like type with a length of 0.75. Use the rotor part of D inserted one by one in the forward and reverse directions, and use a 3-lobe kneading disc (thickness: 0.3D, segment system) at angles of 30 degrees farther from the supply side. 6 sheets were arranged in the forward direction and 6 sheets were arranged in the reverse direction, and they were operated in the same direction rotation system at a discharge rate of 50 kg / hour and a rotation speed of 200 rpm. (T = 0.3D
(* 6 + 0.3D * 6 = 3.6D) Temperature is 110 ℃ in the first half.
The temperature was 150 ° C before and after, the latter half and the adapter. In this way, Compound E was obtained.

This compound E was subjected to melt extrusion coating. The light scattering coefficient of the surface layer of the obtained support was excellent as shown in Table 1.

Example 5 The same operation as in Example 1 was performed. However, replacing the resin used with low density polyethylene (density = 0.918, MI = 7),
The dispersion temperature was 90 ° C in the first half and 130 ° C in the second half and the adapter. As a result, a masterbatch F having the composition shown in Table 1 was obtained.

This masterbatch F was divided into two parts, each was diluted with high-density ethylene or a high-density ethylene-low-density ethylene mixture (1: 1 by weight), the titanium dioxide concentration was adjusted as shown in Table 1, and this dilution was performed. The mixture was subjected to melt extrusion coating.

The light scattering coefficient of the surface layer of the obtained support was excellent as shown in Table 1.

Example 6 The same operation as in Example 1 was performed. However, as a twin-screw kneading device, an extruder with L / D = 24 and a screw diameter of 65 mm is used in a 3-lobe kneading disk (segment type, thickness:
2D, straight) 1 piece is installed from the supply side to a position of about 3/7 of the screw length, and a kneading disc with a thickness of 0.2D at a position of from the supply side to about 5/7 of the screw length. (Segment method) Nine sheets were mounted by sequentially shifting the lobe angle by 30 degrees in the forward direction and used (T = 2D + 0.2D × 9 = 3.8D).

The light scattering coefficient of the surface layer of the obtained support was excellent as shown in Table 1.

Comparative Example 1 The same operation as in Example 1 was performed. However, the masterbatch X was manufactured using a 1.7 Banbury mixer instead of the twin-screw extruder.

The filling volume ratio of the Banbury mixer was 0.7. The mixture was mixed for 15 minutes while controlling heating and water cooling so that the maximum temperature did not exceed 150 ° C.

The kneaded product was formed into a sheet with a sheeter, and further formed into square pellets with a square-cutting pelletizer (trade name: SGE-220, manufactured by Horai Iron Works Co., Ltd.) to produce a high-concentration masterbatch X.

This comparative masterbatch X was divided into 3 parts, and each was diluted with high-density polyethylene resin to adjust the titanium dioxide concentration to the first
The pellets were adjusted to the values shown in the table. Sample X2 was further diluted with high-density polyethylene, and melt extrusion coating was performed while adjusting the titanium dioxide concentration as shown in Table 1.

The samples X1 and X3 were subjected to the melt extrusion coating as they were.

The light scattering coefficient of the surface layer of the obtained comparative support was unsatisfactory as shown in Table 1.

Comparative Example 2 The same operation as in Example 4 was performed. However, in the biaxial kneading device, the part of the kneading disk farther from the supply side was removed and replaced with a normal screw. The composition of the masterbatch is the same as in Example 1, and the kneading is 50 kg.
It was carried out at a rotation speed of 20 ppm at a discharge rate of 1 hour / hour, and the temperature was 110 ° C in the first half and 150 ° C in the second half and the adapter. Thus, Masterbatch Y was obtained.

The masterbatch Y was divided into two, each was diluted with high-density polyethylene, and the titanium dioxide concentration was adjusted to the value shown in Table 1.

Sample Y1 was subjected to the as-is melt extrusion coating.
Further, the sample Y2 was further diluted with high-density polyethylene and subjected to melt extrusion coating while adjusting the titanium dioxide concentration thereof as shown in Table 1.

The light scattering coefficient of the surface layer of the obtained support was as shown in Table 1.

Comparative Example 3 The same operation as in Example 1 was performed. However, as a twin-screw kneading device, an extruder with L / D = 18 and a screw diameter of 65 mm is used in a 3-lobe kneading disk (segment type, thickness:
1.5D, straight) 1 piece is installed from the supply side to a position of about 3/7 of the screw length, and a 0.15D thick kneading from the supply side to a position of about 5/7 of the screw length. The surface of the obtained support was used by mounting 9 discs (segment type) with the lobe angles sequentially shifted by 30 degrees in the forward direction (T = 1.5D + 0.15D × 9 = 2.85D). The light scattering coefficient of the layer was unsatisfactory as shown in Table 1.

Comparative Example 4 The same operation as in Example 4 was performed. However, for a biaxial kneading kneading disk, six kneading disks (segment type) with a thickness of 0.25D are placed at positions near 5/7 of the screw length from the supply side, and the lobe angles are sequentially set at 30 degrees. I just put them on in the forward direction (T =
0.25D x 6 = 1.5D).

The light scattering coefficient of the surface layer of the obtained support was unsatisfactory as shown in Table 1.

Comparative Example 5 The same operation as in Example 1 was performed. However, the twin-screw kneading device has an L / D = 22, a screw diameter of 65 mm and a 3-lobe kneading disk (segment type, thickness: 2.5).
5 sheets (D, straight) were mounted at positions of about 3/7 from the supply side with the lobe angles sequentially shifted by 30 degrees in the forward direction (T = 2.5D × 5 = 12.5D). An attempt was made to produce a masterbatch having the same formulation as in Example 1 using this extruder, but stable discharge was not possible and the masterbatch could not be produced.

As is clear from Table 1, the method of the present invention was performed using the Banbury mixer shown in Comparative Example 1 and Comparative Example 2
The light scattering coefficient is higher and the titanium dioxide is higher than in the case of using the secondary kneader without the kneading disk shown in FIG. The dispersibility of is improved. Also, the combined thickness of the kneading disc is 2 with respect to the screw diameter D.
If it is less than D or exceeds 10D, the pigment dispersion is not uniform,
Or, the ejection failure of the resin-pigment mixture occurs.

〔The invention's effect〕

By using the twin-screw intermeshing kneading extruder in the method of the present invention, the pigment such as titanium dioxide is finely dispersed in the primary particles, and such fine pigment particles can be uniformly distributed in the resin base material. Moreover, this operation can be carried out continuously and with high efficiency, thus improving the productivity.

Further, the use of the twin-screw intermeshing kneading extruder in the method of the present invention reduces the contamination of the extruder, especially the microgrit and the lip, by the pigment during melt extrusion coating.

Furthermore, since a high degree of dispersion of the pigment is obtained, it is not necessary to use various surface treatment agents applied to the pigment, especially titanium dioxide particles, and / or additive chemicals, or it is possible to save the amount of use. At the same time, it is expected that the reduction of the amount of these additive chemicals will reduce the microgrit and lip stain during melt extrusion coating.

[Brief description of drawings]

FIG. 1 is a side view of a screw portion of a twin-screw intermeshing kneading extruder, and FIG. 2 is an enlarged explanatory view of a kneading disc portion.
FIGS. 3 (A) and 3 (B) are cross-sectional explanatory views of the 3-lobe and 2-lobe kneading disks. 2,5 ... Supply section, 3,6 ... Kneading section, 4,7 ... Ring section, 8 ... Vent section, 9 ... Measuring section, 10 ... Biaxial engagement screw, 11,12 ... Screws, 13, 21a, 21b, 22a, 22b ... Kneading disk, 14, 15 ... Screw part.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Katsuhiko Sakata 1850 Totaka, Nichinan City, Miyazaki Prefecture Inside Nichinan Mill, Oji Paper Co., Ltd. (72) Inventor Toshiho Inada 4-7-5 Ginza, Chuo-ku, Tokyo Within Oji Paper Co., Ltd. (72) Inventor Tatsumi Okada 4-7-5 Ginza, Chuo-ku, Tokyo Inside Oji Paper Co., Ltd. (56) Reference JP-A-59-164550 (JP, A) JP-A-62 -148945 (JP, A) JP-A-56-162626 (JP, A) JP-A-54-60358 (JP, A) JP-A-57-127430 (JP, A) JP-A-54-149068 (JP, A) ) "Plastic extrusion molding and its application" / Page 9 to 23 / Author Keiji Sawada / Published by Seibundo Shinkosha / (June 25, 1966)

Claims (6)

[Claims] 1. When laminating a mixture containing a water-resistant thermoplastic synthetic resin and a pigment on at least one surface of a sheet-like substrate by a melt extrusion coating method, a biaxial meshing screw is provided, and this biaxial meshing is used. The diameter D of each screw and the length L of each screw satisfy the following relationship: L ≧ 20D, and at least one set of kneading discs is arranged at at least one position of the biaxial meshing screw. And the total thickness T of the kneading disc
Is prepared by an extruder, which satisfies the following relationship with respect to the diameter D of the screw: 2D ≦ T ≦ 10D, through at least one melt-kneading step. A method for manufacturing a support for photographic paper. 2. The method according to claim 1, wherein the twin-screw meshing screw has a sealing disc located immediately downstream of the kneading disc with respect to its extrusion direction. 3. The method according to claim 1, wherein the sheet-like substrate is made of paper. 4. The method according to claim 1, wherein the water resistant and thermoplastic synthetic resin is selected from polyolefin resins. 5. The method according to claim 4, wherein the polyolefin resin is selected from polyethylene resins. 6. The method according to claim 1, wherein the pigment is mainly composed of titanium dioxide.