JPH07148737A - Method for collecting paper stock from resin-covered paper - Google Patents

Abstract

PURPOSE:To weaken the bonding strength between paper stock and resin covering layer and consequently facilitate the separation of the resin covering layer so as to facilitate the recovery and reuse of resin-covered paper by a method wherein the resin-covered paper is bought into contact with the steam of organic solvent under the condition that holes are bored in the resin covering layer so as to pass through the layer in order to reach the paper stock. CONSTITUTION:Resin-covered paper is used for waterproofing milk pack or the like by coveringly coating thermoplastic resin onto both the sides of paper stock. At the recovery and reuse of resin-covered paper, the separation between the paper stock and resin covering layer is necessary. In this case, firstly, the resin-covered paper 1.4 is fed between a vertically sliding type punching roll 10 so as to bore holes, which pass through the resin covering layer and reach the paper stock, in the resin covering layer. Next, by introducing the resin-covered paper 14 in an organic solvent tank 18, the steam 20 of organic solvent is brought into contact with the resin-covered paper 14 so as to weaken the bonding strength between the paper stock and the resin covering layer. In succession, by feeding the resin-covered paper 14 between a pair of separating blades 12 and 13 both the front and rear resin covering layers 17 and 15 are respectively separated from the paper stock 16.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for peeling a thermoplastic resin layer from a paper base of a resin-coated paper whose both sides are coated with the thermoplastic resin layer.

[0002]

2. Description of the Related Art Generally, milk, fruit juice, liquor packs, photographic printing paper and the like are coated with a thermoplastic resin for the purpose of waterproofing. These are produced by melting and extruding a thermoplastic resin on both sides of a paper base material, but from the viewpoint of waterproofness, a resin coating layer and a paper base material are used at the time of pack molding processing and development processing of photographic printing paper. Is required to have particularly good adhesiveness. For this reason, the paper base material has been subjected to activation treatment such as corona treatment or flame treatment to improve the adhesive strength with the thermoplastic resin.

[0003]

However, if the adhesive strength between the paper base material and the resin coating layer is high, this recovers the used resin coated paper or the resin coated paper that does not become a product generated in the production process. However, it is difficult to separate the paper base material and the resin coating layer when trying to reuse them, and therefore, they are usually discarded and incinerated, which is extremely uneconomical.

In recent years, resin-coated paper has been separated and separated from the resin-coated paper in the form of a paper substrate because of its easy handling.
There is a demand for effective reuse of the paper base material and the resin coating layer. Therefore, a method of separating the resin coating layer from the paper base material and adopting the paper base material has been put to practical use.For example, the milk carton is immersed in an alkaline solution for several hours to float and remove the resin coating layer. , A method of collecting and collecting pulp dispersed in a solution has been developed (for example, Japanese Patent Laid-Open No. Sho 6).
No. 2-156378).

This is because the resin coating layer and the paper base material are separated by permeation of the liquid into the paper base material from the periphery of the resin-coated paper, and therefore the time required for the liquid to permeate the paper base material. It is not efficient. In addition, in order to eliminate the contamination between the resin coating layer and the paper layer, the floating separation operation in the solution is performed for 2 to 3 times.
It needs to be repeated twice and is not efficient. Also, rather than being recovered in the form of a paper base material, it is recovered in a pulp state in which the solution is sufficiently absorbed, so a large amount of dry heat energy is required when reused as dry pulp, which is not economical. Further, when it is reused as wet pulp, it is necessary to arrange a system connected to the paper making process, and there is a disadvantage that the separation treatment place is limited.

The present applicant has previously proposed that a water-soluble organic solvent such as methanol, ethanol or propanol, or benzene,
A liquid such as an organic solvent such as toluene, xylene, or acetone is permeated into the paper base material to reduce the adhesive strength between the paper base material and the resin coating layer, and to separate and separate the paper base material and the resin coating layer. However, in order to reduce the adhesive strength between the paper base material and the resin coating layer, it was found that there is a problem that the resin coated paper needs to be immersed in a liquid for a long time. .

An object of the present invention is to solve these problems and provide a method for easily peeling a paper base material and a resin coating layer in a short time.

[0008]

DISCLOSURE OF THE INVENTION The present invention has been found as a result of diligent studies for easily peeling and separating a paper base material and a resin coating layer in a double-sided resin-coated paper. It was found that the paper base material and the resin coating layer can be easily peeled and separated by forming a hole penetrating at least one of the resin coating layers and bringing them into contact with the vapor of the organic solvent prior to the peeling of the layer.

The resin-coated paper to which the present invention is applied is not limited to a milk pack or the like, but is particularly suitable for separating the paper base material and the resin layer in the photographic resin-coated paper.

As the coating resin, polyolefin such as polyethylene, polypropylene, polyethylene copolymer, etc., and particularly preferably polyethylene is used. As the polyethylene, high density polyethylene, low density polyethylene, linear low density polyethylene and blends of these polyethylenes can be used. The melt flow rate (hereinafter referred to as MFR) of polyolefin resin before processing is JIS
1.2 g as measured under condition 4 of Table 1 of K 7210
/ 10 minutes to 30 g / 10 minutes.

The titanium dioxide (TiO ₂ ) which is a white pigment contained in the resin layer may be either anatase type or rutile type, but when priority is given to whiteness, anatase type TiO ₂ is used, and sharpness is increased. When giving priority, rutile TiO ₂ is preferable. TiO ₂ was kneaded into the resin with a kneader such as a two-roll, three-roll, kneader or Banbury mixer using metal salt of higher fatty acid, higher fatty acid ethyl, higher fatty acid amide, higher fatty acid, etc. as a dispersion aid. Use one. The TiO ₂ concentration in the pellets is generally about 30% by weight to 75% by weight. An antioxidant may be contained in the resin layer, and the content may be 50 ppm to 1000 ppm with respect to the amount of the water resistant resin.

The resin layer is obtained by diluting pellets containing titanium dioxide or the like with a heat-resistant resin on a paper or synthetic paper which is a running base, if necessary, and melting the pellets, or by a sequential laminating method or a foot block type, It is applied and formed by any one of a laminating method using a multi-manifold type or a multi-slot type multilayer extrusion die.
The shape of the multilayer extrusion die is generally a T die, a coat hanger die, etc., and is not particularly limited. The outlet temperature at the time of melt-extrusion of the resin is usually 280 ° C to 350 ° C,
Particularly preferably, it is 310 ° C to 330 ° C. Before the resin is coated on the substrate, the substrate is subjected to activation treatment such as corona discharge treatment, flame treatment and glow discharge treatment.

The surface of the outermost layer of the resin on which the emulsion is coated is
A glossy surface or a fine surface, a matte surface or a silk surface as described in JP-A-55-26507 is imprinted, and the back surface is matte. An activation treatment such as corona discharge treatment or fire treatment can be applied to the surface after the molding, and after the activation treatment, an undercoating treatment as described in JP-A-61-84643 is performed.

The total thickness of the resin layer is generally 10 μm to 70 μm.
μm, and in the case of a multi-layered structure, each layer is 2 μm to
It is 30 μm.

As the paper base material, a normal pulp paper containing natural pulp as a main component, a mixed paper consisting of natural pulp and synthetic fibers, a synthetic fiber paper containing synthetic fibers as a main component, polystyrene, polypropylene and the like are synthesized. Although any of so-called synthetic papers obtained by converting a resin film into a pseudo paper may be used, a natural pulp paper (hereinafter simply referred to as a base paper) is particularly preferably and advantageously used as a substrate of a polyolefin resin-coated paper for photographic printing paper. As additive chemicals, in addition to alkyl ketene dimer, fillers such as clay, talc, calcium carbonate, urea resin fine particles, rosin, higher fatty acid salt, paraffin wax, sizing agents such as alkenyl succinic acid, paper strengthening agents such as polyacrylamide The one to which a fixing agent such as sulfuric acid band is added is used. In addition, dye,
A fluorescent dye, a slime control agent, an antifoaming agent, etc. are added. Further, a softening agent is added if necessary.

The surface of the pulp can be surface-sized with a film-forming polymer such as gelatin, starch, carboxymethyl cellulose, polyacrylamide, polyvinyl alcohol, and a modified product of polyvinyl alcohol. In this case, as the polyvinyl alcohol modified product,
Examples thereof include carboxyl group-modified products, silanol-modified products and copolymers with acrylamide. Further, the coating amount of the film-forming polymer when the surface size is treated with the film-forming polymer is 0.1 g / m ^{2 to} 5.0 g / m ² , preferably 0.5 g / m ^{2 to} 2.0 g / m ^2. Adjusted to.
Furthermore, an antistatic agent, a fluorescent whitening agent, a pigment, an antifoaming agent, etc. can be added to the film-forming polymer at this time, if necessary.

The raw paper is prepared by pulp pulp slurry containing the above-mentioned pulp and additives such as fillers, sizing agents, paper-strengthening agents, and fixing agents, which are optionally added, by a paper machine such as a Fourdrinier paper machine. Manufactured by paper making, drying and winding. The surface size treatment is performed before or after the drying, and the calender treatment is performed between the drying and the winding. When the surface sizing treatment is performed after drying, this calendering treatment can be carried out either before or after the surface sizing treatment, but it is preferable to carry out the calendering treatment in the final finishing step after various treatments have been carried out. . In the calendering process, known metal rolls and elastic rolls that are commonly used in the production of paper are used. The base paper is calendered as described above and finally adjusted to a film thickness of 50 μm to 250 μm. The density of the base paper ^{0.8g / cm 3 ~1.3g / cm 3} , preferably from ^{1.0g / cm 3 ~1.2g / cm 3} .

The photographic resin-coated paper also has antistatic,
Various back coat layers are applied to prevent curling. Also, the back coat layer is Japanese Patent Publication No. 52-1802.
No. 0, JP-B-57-9059, JP-B-57-5394
No. 0, JP-B-58-56859 and JP-A-59-214.
No. 849, JP-A No. 58-184144 and the like, or an inorganic antistatic agent, an organic antistatic agent, a hydrophilic binder, a latex, a curing agent, a pigment, a surfactant, etc., which are described or exemplified, may be contained in an appropriate combination. be able to.

As the photographic resin-coated paper, various photographic constituent layers are coated and used for color photographic printing paper, black-and-white photographic printing paper, typesetting photographic paper, photographic printing paper, reverse photographic material, silver Salt diffusion transfer method It is used for various purposes such as negative and positive, printing materials, silver chloride, silver bromide, silver chlorobromide,
A silver iodobromide and silver chloroiodobromide emulsion layer is provided, and the silver halide photographic emulsion layer contains a color coupler to form a multilayer silver halide color photographic constituent layer.
Further, the silver salt diffusion transfer image-receiving layer is provided by containing a physical phenomenon nucleus.

According to the present invention, in such double-sided resin-coated paper, a through hole that penetrates the resin coating layer to reach the paper base material layer is punched by a punching jig or the like having sharp needle-shaped pins, and after that, Provided is a method of peeling and separating a paper base material and a resin coating layer by contacting with vapor of an organic solvent.

The size of the holes penetrating the resin coating layer and the number of holes per unit area are important factors because they are involved in reducing the adhesive strength between the paper base material and the thermoplastic resin coating layer. This factor depends on the pulp type of the paper base material, the sizing degree, the density, and the like, and is greatly influenced by the size of the holes and the number per unit area.

On the other hand, the size of the hole also depends on the type of thermoplastic resin, viscoelasticity, Young's modulus and the like. Moreover, when a hole is formed in the resin coating layer, the resin piece corresponding to the hole peels off,
There may be a defect of contamination such as peeling off of the resin coating layer and mixing of the peeled resin pieces on the side of the separated paper substrate. Therefore, since the perforation diameter and the perforation speed depend on the type and physical properties of the paper base material and the thermoplastic resin used for the peeling treatment, the perforation speed, and the like, it is desirable to determine it by an experiment under the conditions of implementation.

The punching jig may be of a die shape and punched by vertical movement, or may be a roll-shaped rotary punching type, and in any case, continuous punching is possible. With respect to the through holes of the resin-coated paper, holes may be penetrated to the front and back resin coating layers, or holes may be drilled through the paper base layer or the resin coating layer on the opposite side separately. The number of through holes and the hole diameter are
It seems that there is an appropriate relationship to the ease of peeling between the paper base material and the resin coating layer, depending on the permeation rate and permeation amount of the organic solvent vapor into the paper base material. That is, since the paper base material and the resin coating layer are separated and separated from each other by a tensile force with respect to the respective release surfaces, the paper base material is wet or the peeling of the resin coating layer is caused by the through hole of the resin coating layer. This is because there is a problem that cutting is performed without being able to withstand the pulling force. Therefore, it depends on the thickness, wettability, permeability, etc. of the resin-coated paper to be treated, and it is desirable to determine the way of forming the through-holes by experiments under the conditions to be carried out. Although depending on the type and thickness of the resin coating layer, the through holes can also be generated by corona discharge treatment of the resin coating layer.

Further, an organic solvent that penetrates through the through holes of the resin coating layer and reduces the adhesive strength between the paper substrate and the resin coating layer is
Depending on the type, the permeation rate affects the peeling treatment rate, which greatly affects the wetting properties of the resin coating layer and the paper substrate. It has been found that a water-soluble organic solvent such as methanol, ethanol, propanol and acetone or an organic solvent such as benzene, toluene and xylene is particularly preferable as a material for weakening the anchoring effect between the base material layer and the resin coating layer.

Considered from another point of view, as an organic solvent, a resin coating layer is easily wetted and penetrates into a paper base material through a through hole. Required. Further, from another point of view, it is necessary that the paper base material that has penetrated into the paper base material, separated from the resin coating layer, and separated and then easily evaporates and dries, and that the environment surrounding the treatment process is not affected. There is no need to consider economy.

As a method of supplying the organic solvent vapor to the perforated resin-coated paper, the resin-coated paper perforated with the through-hole is vaporized into the organic solvent vapor for a certain period of time in a container filled with the organic solvent vapor. Good to contact.

The resin-coated paper to be treated in the present invention may be in the form of a sheet or a roll, and can be handled continuously. For sheet-shaped ones, use one by one, for example, the same type of thermoplastic resin tape as the resin coating layer, and join the resin-coated surfaces together by heat pressure fusion or ultrasonic fusion. It can be handled as a continuous sheet, and it is possible to continuously perforate, infiltrate steam, and peel off, including the seam. According to this, it is possible to collect the resin coating layer without peeling or separation, and without mixing of foreign materials and contamination.

[0028]

In the present invention, the detailed mechanism by which the separation of the paper base material and the resin coating layer is facilitated by contacting with the organic solvent vapor is not clarified, but compared with the case of dipping in an organic solvent. The permeation rate and permeation amount of the organic solvent can be increased. This is because by contacting with an organic solvent vapor, a significant decrease in the adhesive strength due to the breakage of hydrogen bonds between the paper base layer and the resin coating layer, and a decrease in the anchorage adhesive strength due to the wet expansion deformation of the paper base, It is considered that the paper base material and the resin coating layer are easily separated.

The present invention will be described in detail below with reference to examples. The gas concentration of the organic solvent in the organic solvent tank described in each of the examples and comparative examples is the same as that of a syringe-like sample in the organic solvent tank. Insert a container to suck and collect the organic solvent gas, then dilute it with air at the ratio shown in Table 1, measure the gas concentration using a direct-reading gas detector tube manufactured by Gastec Co., Ltd., and measure it. The gas concentration was obtained by multiplying the value by the dilution rate with air. Table 1 shows the dilution ratio of the organic solvent and the usage detector tube.

[0030]

[Table 1]

[0031]

Example 1 The resin-coated paper used for separating the paper base material and the resin-coated layer was a resin-coated paper for roll-shaped photographic printing paper having a width of 35.6 cm before the application of a photosensitive emulsion. Show.

[0032]

[Table 2]

In the table, LDPE in the surface layer is low density polyethylene having a melt flow rate of 3.5 (density of 0.
920 g / cm ³ ), white pigment is titanium dioxide [Ishihara Sangyo Co., Ltd., trade name A-220)], containing 15% by weight of white pigment, LBSP is hardwood beaten sulfite pulp, LBKP is hardwood. Beaten kraft pulp with paper base mixed with LBSP 60% and LBKP 40%. HDPE in the back layer is a high density polyethylene with a melt flow rate of 15 (density 0.970 g / c
m ³ ), and LDPE / HDPE = 2: 3 (weight ratio)
belongs to.

This resin-coated paper was separated into its paper base material and resin coating layer using the peeling / separating apparatus shown in FIG. In the figure, 1, 3 to 9 are transport rolls, 2 are drive rolls, 1
0 is a perforating roll, 11 is its pedestal, 12 to 13 are stripping blades, 14 is double-sided resin coated paper, 15 and 17 are resin coated layers, 16 is a paper substrate, 18 is an organic solvent tank, 19 is an organic solvent. Reference numeral 20 indicates a high-concentration gas of an organic solvent, and reference numeral 21 indicates a heat retaining tank.

First, the resin-coated paper 14 is a vertical sliding type perforation roll 10 whose speed is interlocked with the drive roll 2 and its pedestal 11.
And a hole penetrating from the resin coating layer on the back surface to the resin coating layer on the front surface is opened. Next, the perforated resin-coated paper passes through the transport roll 4 and is guided into the organic solvent tank 18.

Ethanol was put in the organic solvent tank 18 and hot water (70 ° C.) was put in the heat insulating tank 21 to make the organic solvent tank 18 have an atmosphere of ethanol gas concentration of 50%. Here, the organic solvent tank 1 between the transport rolls 4 and 5
The high-concentration ethanol gas 20 comes into contact with the resin-coated paper in 8 and penetrates through the resin-coated layer through the through-holes into the paper substrate,
It diffuses and the adhesive strength between the front and back resin coating layers and the paper base material is significantly weakened, and the state becomes easy to peel.

Then, the back resin coating layer 15, the paper base material 16,
The surface resin coating layer 17 is separated from the peeling blades 12 and 13 as starting points, and is continuously guided to the transport rolls 6 to 9, respectively. In this case, the peeling / separating speed was 70 m / min, but the resin coating layer was free from paper, and the peeling / separating treatment could be performed efficiently.

[0038]

COMPARATIVE EXAMPLE In Example 1, the organic solvent tank 18 was filled with ethanol (about 25 ° C.) instead of ethanol gas, and the other steps were carried out in the same manner as in Example 1 to peel the resin-coated paper. As a result, in order to completely separate the resin coating layer and the paper base material layer, it was necessary to set the separation and separation speed to 40 m / min.

[0039]

Example 2 The procedure of Example 1 was repeated except that the ethanol gas concentration in the organic solvent tank 18 was 100% and the hot water temperature in the heat retaining tank 21 was 80 ° C. Tried to peel. As a result, at the peeling / separating speed of 70 m / min, the resin coating layer could be peeled off and separated without paper.

[0040]

Example 3 The same procedure as in Example 1 was repeated except that the ethanol gas concentration in the organic solvent tank 18 was 30% and the hot water temperature in the heat retaining tank 21 was 60 ° C. I tried. As a result, the separation and peeling speed, 45
The resin coating layer and the paper substrate layer could be completely separated at m / min.

[0041]

Fourth Embodiment In the first embodiment, acetone is put in the organic solvent tank 18 instead of ethanol, and the acetone gas concentration is 50%.
% Atmosphere and the hot water temperature in the heat insulation tank 21 is 45 ° C.
Except for the above, the peeling of the resin-coated paper was tried in the same manner as in Example 1. As a result, the resin coating layer could be peeled and separated at a peeling and separating speed of 70 m / min.

[0042]

Example 5 In Example 1, toluene was put in the organic solvent tank 18 instead of ethanol, and the toluene gas concentration was 50%.
%, And the hot water temperature in the heat insulation tank 21 is 95 ° C.
Except for the above, the peeling of the resin-coated paper was tried in the same manner as in Example 1. As a result, the resin coating layer could be peeled and separated at a peeling and separating speed of 70 m / min.

[0043]

INDUSTRIAL APPLICABILITY According to the present invention, a double-sided resin-coated paper which has not been economically and effectively reused so far can be peeled efficiently, continuously and easily, and the resin-coated layer and the paper base are respectively Since it can be recovered independently, its industrial value is extremely high.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an apparatus used for separating and separating a resin-coated paper into a paper base material and a resin-coated layer.

[Explanation of symbols]

1, 3 to 9 are conveying rolls, 2 are driving rolls, 10 is a perforating roll, 11 is a perforating roll holder, 12 to 13 are peeling blades, 14 is double-sided resin coated paper, 15 and 17 are resin coated layers, and 16 is A paper base material, 18 is an organic solvent tank, 19 is an organic solvent, 20 is a high-concentration organic solvent gas, and 21 is a heat retaining tank.

Claims (1)

[Claims] 1. A resin-coated paper in which a thermoplastic resin is coated on both sides of a paper substrate, after at least one resin-coated layer has a hole penetrating to the paper substrate and then contacted with vapor of an organic solvent. A method for collecting a paper base material from a resin-coated paper, which comprises peeling the resin coating layer from the paper base material layer.