JPH0596689A - Laminated paper - Google Patents

Abstract

PURPOSE:To facilitate regeneration of used papers in producing the laminated papers for shopping bag, etc., by forming on the paper the plastic layer consisting mainly of the acrylic ester copolymer containing, beta-unsaturated carboxylic acid and/or vinyl group-containing acid anhydride as a copolymerizing component and soluble in an alkaline solution. CONSTITUTION:Alpha, beta-unsaturated carboxylic acid and/or vinyl group- containing acid anhydride, e.g. acrylic acid, the acrylic ester of acrylic acid and/or methacrylic acid, e.g. the acrylic ester of a mono-hydric alcohol having C1-C18 and, as required, a copolymerizable vinylcontaining monomer is copolymerized to form the acrylic ester copolymer soluble in an alkaline solution at a glass-transition temperature of 40-120 deg.C and an acid value of 50-300. This copolymer is formed by a uniaxial extruder into a stretched film, which is then layered on the paper to form a laminated paper.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated paper which can be easily recycled as waste paper pulp, that is, a laminated paper in which plastic and paper are laminated.

[0002]

2. Description of the Related Art For the purpose of protecting the surface of paper packaging materials such as shopping bags and box-shaped cases, and printed paper products such as book covers, calendars, and labels, or for providing a good appearance such as high gloss. The one in which a plastic film is laminated on paper is widely used. As a plastic film used for this purpose, conventionally, films of polyvinyl chloride, polyethylene, polypropylene, polyester and the like have been preferably used.

On the other hand, used waste paper is generally recycled as waste paper pulp. The use of waste paper pulp is generally more advantageous than that made from wood in terms of yield and manufacturing cost, and in particular, in recent years, depletion of forest resources and the environmental damage caused by it have become a problem, and regeneration is an increasingly important issue. Is becoming However, the laminated paper having the above-mentioned plastic film has a problem that a large amount of foreign matter is generated during pulping of waste paper, which makes it extremely difficult to remove it or, in some cases, completely impossible.

[0004]

The present invention has been studied to solve such problems, and as a result, by using a plastic material which is easily dissolved in the cooking process of waste paper, it can be easily recycled as waste paper pulp. It has been found that it is possible, and the main component is an acrylic acid ester-based copolymer containing α, β-unsaturated carboxylic acid and / or a vinyl group-containing acid anhydride as a copolymerization component, and it can be used in an alkaline solution. It is characterized in that a layer of molten plastic is laminated on the paper.

The present invention will be described in detail below. The acrylic ester-based copolymer, which is the main component of the plastic layer in the present invention, comprises (A) an α, β-unsaturated carboxylic acid and / or vinyl group-containing acid anhydride (B) acrylic acid and / or methacrylic acid Two components of an alkyl ester are essential components, and (C) a copolymerizable vinyl group-containing monomer other than the above (A) and (B) is copolymerized if necessary.

Examples of the monomer (A) include acrylic acid, methacrylic acid, maleic acid, itaconic acid, maleic anhydride and itaconic anhydride. As the monomer (B), acrylic acid or methacrylic acid ester of C _{1 to} C ₁₈ monohydric alcohol, specifically, methyl acrylate, ethyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, 2 -Ethylhexyl methacrylate and the like can be mentioned.

Further, if necessary, a monomer (C) other than the above (A) and (B) is copolymerized for the purpose of adjusting the glass transition temperature, improving the film strength, improving the gloss and the like. You can also Examples of the monomer (C) include styrene, vinyl chloride, vinyl acetate, and C _{1 to} C ₁₈ vinyl ethers.

Further, since the copolymer is put to practical use for laminated paper, it preferably has a glass transition temperature (Tg) in the range of 40 ° C to 120 ° C, and particularly preferably in the range of 50 ° C to 100 ° C. Is. If the Tg is less than 40 ° C., problems such as fusion at room temperature occur, and if it exceeds 120 ° C., problems such as difficulty in forming a film occur and are not suitable for practical use. Here, Tg means a temperature at which a loss tangent peak corresponding to main dispersion when dynamic viscoelasticity is measured at a frequency of 1 Hz is shown. In the present invention, it was measured with a viscoelasticity spectrometer VES F-III type manufactured by Iwamoto Seisakusho.

Further, in the present invention, the acrylic acid ester-based copolymer needs to be easily dissolved in the alkaline solution, and therefore, the acid value thereof is preferably 50 or more. Fifty
If it is less than the above range, it will not be dissolved in a short time, which is inconvenient. On the other hand, when the acid value of the polymer exceeds 300, the water absorption of the polymer becomes excessively high, resulting in inconveniences such as tackiness and poor water resistance. Here, the Tg of the acrylic acid ester-based copolymer can be adjusted by the copolymerization ratio of the components (A), (B) and (C), and the acid value is mainly determined by that of the component (A). Depends on quantity.

The method for producing such a copolymer is not particularly limited, and solution polymerization, emulsion polymerization,
It can be easily obtained by a known production method such as suspension polymerization and bulk polymerization.
A solid copolymer can be obtained.

The plastic layer in the present invention is, for example,
The copolymerized solid may be melt-extruded with an extruder and formed into a flat or tubular film by a T-type die or an annular die. The extrusion temperature depends on the degree of polymerization of the copolymer and Tg, but is usually 150 ° C to 280.
It is preferably in the range of 0 ° C., particularly preferably 1
It is 70 ° C to 230 ° C.

Although the plastic film can withstand practical use even in a substantially unstretched state, it is used as a thin film or for the purpose of improving productivity and film strength (particularly folding endurance). In addition, it can be stretched in one direction or two directions. As a stretching method, in the case of a T-die, stretching may be performed uniaxially in the extrusion direction using a roll or the like, or may be performed in a direction orthogonal to the extrusion direction with a tenter or the like. It is also possible to stretch biaxially with a combination thereof. The annular die may be uniaxially stretched in the axial direction or the circumferential direction, or may be biaxially stretched individually or simultaneously in the axial direction and the circumferential direction.

The stretching temperature depends on the Tg of the copolymer,
It is in the range of 40 to 140 ° C, preferably 70 to 110 ° C. The stretching ratio is not particularly limited, but it is preferably adjusted within the range of 1.05 to 4.0 times according to the purpose. Although the thickness of the film varies depending on its purpose, it is usually 5 to 150 μm, preferably 10 to 120 μm for practical use.

Further, the plastic film may be mixed with a polymer component other than the acrylic acid ester-based copolymer for the purpose of adjusting its physical properties. For example, addition of a known impact modifier for the purpose of improving impact resistance, and addition of an acrylic acid ester-based copolymer that does not substantially contain a carboxyl group for the purpose of adjusting the glass transition temperature may be mentioned. Be done.

The amount of the polymer component added is preferably in the range of not more than 30 parts by weight with respect to 100 parts by weight of the acrylic ester copolymer, and when it is more than 30 parts by weight, the pulp of the waste paper is In the polymerizing step, a large amount of insoluble polymer is generated, which tends to cause inconvenience.

The plastic film thus obtained is laminated by a usual laminating machine for paper processing. For example, it is carried out by applying an adhesive having an appropriate adhesive force to paper or a plastic film and then pressure-bonding it with a heated laminating roll.

Adhesives applicable to the plastic film of the present invention include vinyl acetate type, acrylic type,
Solvent-based or emulsion-based adhesives having good transparency such as urethane-based adhesives are suitable, but are not particularly limited and may be natural rubber-based or synthetic rubber-based adhesives depending on the purpose. Alternatively, a hot melt type adhesive may be used.

The above-mentioned plastic film has excellent solubility in an alkaline aqueous solution as described above, but is insoluble in a neutral medium or an acidic medium. Therefore, the plastic film of the present invention can have practically sufficient water resistance and does not cause any inconvenience even if it is used for the purpose of protecting articles.

The laminated paper laminated with the plastic layer of the present invention can be easily recycled as waste paper pulp. Generally, in order to pulp waste paper, a method is used in which the fibers of the paper are disintegrated in water using a kneader, pulper, etc., and then steamed in an alkaline solution in order to remove the sizing agent, printing ink, etc. Has been. The conditions for steaming are to steam at a temperature of 90 ° C. or higher in a 2-5% caustic soda aqueous solution containing a surfactant and other auxiliaries and steam for several hours.

The laminated paper of the present invention has the property that the plastic layer can be easily dissolved in a dilute alkaline aqueous solution even at room temperature. Therefore, in this cooking step, the dissolution is completed in a very short time, and the sizing agent and the printing agent are printed. Has no adverse effect on the removal of ink, etc.

Further, in the laminated paper of the present invention, it is possible to easily dissolve and remove the plastic by immersing it in a dilute aqueous alkaline solution before pulping the waste paper. If it is dipped in an aqueous solution, it also has the effect that the disaggregation of the fibers becomes very easy. Hereinafter, detailed description will be made in Examples.

[0022]

EXAMPLE An acrylic copolymer having a weight average molecular weight of 160,000, in which the monomer composition of the copolymer was 1 mol of methacrylic acid 2 mol of methyl acrylate 0.4 mol of tridecyl methacrylate,
The film having a thickness of 50 μm was extruded with a T-die at a temperature of 190 ° C. into a uniaxial extruder. After cooling this, in a tenter adjusted to 80 ° C., 1.
The film was stretched 5 times and 2.0 times in the direction orthogonal to the extrusion direction to obtain a stretched film having a thickness of 17 μm.

When the dynamic viscoelasticity of the film before stretching was measured, the temperature showing a peak of loss tangent corresponding to the main dispersion at 1 Hz was 55 ° C. The acid value of this acrylic copolymer was 150.

Polyurethane solvent-based adhesive (Takelac A-970 / Takenate A-19 =
15/1, manufactured by Takeda Pharmaceutical Co., Ltd.) with a film thickness of 1.5 after drying.
The coating was uniformly applied so as to have a thickness of μm, and dried in an oven at 80 ° C. for 1 minute. Next, they were laminated with a pressure roll and aged at 40 ° C. for 24 hours to obtain a laminated paper. The obtained laminated paper has sufficient gloss, and the appearance of the printed matter is sufficiently improved.

When 100 g of this laminated paper was placed in a 5% caustic soda aqueous solution and vigorously stirred at 95 ° C. for 2 hours, the plastic film was completely dissolved and the disintegration state of the paper fibers was also good. As a comparative example, a test in which hard vinyl chloride (a biaxially stretched film having a film thickness of 15 μm) was laminated was subjected to a dissolution test in an alkaline aqueous solution, but the film only yellowed and the shape did not change. Further, the disaggregated state of the paper fibers was not good because the plastic film was insoluble.

[0026]

INDUSTRIAL APPLICABILITY As described above, the laminated paper of the present invention has an effect that pulping of waste paper becomes extremely easy as compared with the conventional paper, and the original purpose thereof is to protect the surface of paper.
It does not impair the quality of aesthetics.

Claims (2)

[Claims] 1. A layer of a plastic which is mainly composed of an acrylate copolymer containing an α, β-unsaturated carboxylic acid and / or a vinyl group-containing acid anhydride as a copolymerization component and which is soluble in an alkaline solution. A laminated paper characterized by being laminated on paper. 2. The glass transition temperature of the acrylate copolymer is 40 to 120 ° C., and the acid value is 50 to 300.
The laminated paper according to claim 1, which is in the range of.