JP3366738B2 - Degradability information recording card - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to various plastic cards such as credit cards, cash cards, and ID cards.
Cards, telephone cards (registered trademark) and various prepaid cards that use decomposable plastics to prevent pollution of discarded cards, and have a particularly practical practical strength degradable information recording card. Is provided.

[0002]

2. Description of the Related Art In recent years, a large amount of various plastic cards have been used in various fields of social life. For example, a credit card using a vinyl chloride sheet as a base material, a cash card or an ID card, or a polyethylene terephthalate sheet. Telephone cards (registered trademark) and various prepaid cards using are widely used. After use, these cards, especially telephone cards (registered trademark) and prepaid cards, are left in the telephone box or in recreation areas such as ski resorts and amusement parks to cause pollution, or are collected and landfilled. Since it is not decomposed and remains as it is, the ground of the landfill is not stable, and it has caused problems such as shortening the life of the landfill.

In order to solve this problem, a card in which the card base material is made of a degradable (biodegradable) polymer has also been proposed (JP-A-5-42786, JP-A-5-85).
088). However, even if they have degradable characteristics, they are not strong enough as the essential card. Therefore, at present, there is no information recording card that has practical strength and is disintegratable. That is, all the cards proposed above have low strength and bending strength, and are too soft to be practically used as cards.

As a biodegradable card material that does not cause these problems, polylactic acid, which is a so-called elastic material having high tensile elastic modulus and bending elastic modulus, can be mentioned as a candidate. Polylactic acid is also preferable in that it can impart transparency by devising a processing method. However, polylactic acid is fragile as it is, and is a material that is weak against impact and bending, and it is still difficult to satisfy as a base material of a card that is repeatedly used.

[0005]

DISCLOSURE OF THE INVENTION The present invention provides a polylactic acid which, after being used / discarded, undergoes spontaneous hydrolysis in soil or water to leave no original shape in the soil, and then becomes a harmless decomposed product by microorganisms. Disclosed is a degradable information recording card which is made of a system polymer, has excellent transparency, and has strength that does not hinder normal use.

[0006]

Means for Solving the Problems As a result of intensive investigations by the present inventors, a sheet-like material made of a polylactic acid-based polymer having a degree of plane orientation ΔP of 3.0 × 10 ⁻³ or more and a sheet When the difference (ΔHm-ΔHc) between the heat of crystal fusion ΔHm when the temperature was raised and the amount of heat of crystallization ΔHc generated by crystallization during the temperature rise was 20 J / g or more, practical strength and thermal dimensional stability were excellent. It has been found that it can be used as a base material for information recording cards. Further, it has been found that the information recording portion is provided on the base material and the thickness is 0.05 mm or more and 1 mm or less, which is particularly suitable as a degradable information recording card.

The present invention will be described in detail below. The polylactic acid-based polymer used in the present invention is polylactic acid or a copolymer of lactic acid and another hydroxycarboxylic acid, or a mixture thereof, and other polymer materials within a range that does not impair the effects of the present invention. May be mixed. In addition, additives such as plasticizers, lubricants, inorganic fillers, and ultraviolet absorbers, and modifiers may be added for the purpose of adjusting moldability and sheet properties.

Lactic acid includes L-lactic acid and D-lactic acid, and other hydroxycarboxylic acids include glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 3-hydroxyvaleric acid and 4-hydroxyvaleric acid. Typical examples include 6-hydroxycaproic acid and the like.

As these polymerization methods, any known method such as condensation polymerization method and ring-opening polymerization method can be adopted, and further, a small amount of a chain extender such as diisocyanate compound for the purpose of increasing the molecular weight. , Epoxy compounds, acid anhydrides, etc. may be used. The weight average molecular weight of the polymer is preferably 50,000 to 1,000,000, and practical physical properties are hardly expressed below this range.
If it exceeds, the melt viscosity becomes too high and the moldability becomes poor.

To obtain a base material for an information recording card from the polylactic acid polymer, the polylactic acid polymer is melt-formed into a sheet and rapidly cooled to obtain an unstretched sheet, which is subjected to a stretching treatment and a heat treatment. It is practical to apply.

The film forming conditions for the unstretched sheet will be described. The polylactic acid-based polymer is sufficiently dried to remove water, and then melted in an extruder. Since the melting temperature changes depending on the composition, it is preferable to appropriately select the melting temperature. In practice, a temperature range of 140 to 230 ° C. is usually chosen.

The polymer melt-formed into a sheet is preferably brought into contact with a rotating casting drum (cooling drum) to be rapidly cooled. The temperature of the casting drum is preferably 50 ° C. or lower. If it is higher than this, the polymer sticks to the casting drum and cannot be removed. In addition, crystallization is promoted, spherulites develop, and stretching becomes difficult. Therefore, it is preferable to set the temperature within the above temperature range and quench the material to make it substantially amorphous.

The stretching method may be uniaxial stretching, sequential biaxial stretching or simultaneous biaxial stretching, but it is desirable to perform biaxial stretching because it is necessary to improve physical properties in both longitudinal and transverse directions for the purpose of use. The stretching ratio of the sheet in the present invention is in the range of 1.5 to 5 times in each of the longitudinal direction and the transverse direction,
The stretching temperature is appropriately selected in the range of 50 ° C. to 90 ° C., and the plane orientation degree ΔP, which is 1.0 × 10 ⁻³ or less in the non-oriented sheet, is increased to 3.0 × 10 ⁻³ or more specified in the present invention. be able to.

ΔP represents the degree of orientation in the plane direction with respect to the thickness direction of the sheet, and is usually calculated by the following formula by measuring the refractive index in the directions of three orthogonal axes. ΔP = {(γ + β) / 2} -α (α <β <γ) where γ and β are biaxial refractive indices parallel to the sheet surface,
α is the refractive index in the sheet thickness direction.

ΔP depends on the crystallinity and the crystal orientation, but largely depends on the molecular orientation in the sheet plane. That is, the increase in ΔP is achieved by increasing the molecular orientation in the plane of the sheet, particularly in the sheet flow direction and / or the direction orthogonal thereto, thereby increasing the strength of the sheet and improving the brittleness. As a method for increasing ΔP, in addition to any known sheet stretching method, a molecular orientation method using an electric field or a magnetic field can be adopted.
The upper limit of ΔP is about 30 × 10 ⁻³ , and if ΔP is attempted to be higher than this, there is a disadvantage that stretching becomes unstable or impossible.

By thus setting ΔP to be 3.0 × 10 ⁻³ or more, the strength can be remarkably improved and the embrittlement due to the structural change with time which is observed in the case of the non-oriented sheet can be prevented. it can.

On the other hand, however, the thermal dimensional stability of the sheet becomes poor, and the sheet shrinks during the hot summer months, making it unusable as a base material for cards. Therefore, it is important to be able to return to its original shape without shrinking in an atmosphere at a temperature slightly higher than room temperature, that is, at a temperature of about 50 ° C. or higher.

In order to obtain practical thermal dimensional stability in a polylactic acid type sheet having a ΔP of 3.0 × 10 ^-3 or more,
It is important to control the (ΔHm−ΔHc) of the sheet to 20 J / g or more. That is, when (ΔHm-ΔHc) is less than 20 J / g, the thermal dimensional stability of the sheet is poor and it is not suitable for practical use at a temperature slightly higher than room temperature, but if it is 20 J / g or more, The thermal dimensional stability is good and there is no practical problem.

ΔHm and ΔHc are obtained by differential scanning calorimetry (DSC) of a sheet sample, and ΔHm
m is the amount of heat required to melt all the crystals when the temperature is raised at a temperature rising rate of 10 ° C./min, and is determined from the area of the endothermic peak due to crystal melting that appears near the crystal melting point of the polymer. Further, ΔHc is obtained from the area of the exothermic peak generated during crystallization that occurs during the temperature rising process.

ΔHm mainly depends on the crystallinity of the polymer itself, and takes a large value in a polymer having high crystallinity. By the way, for homo-L-lactic acid polymer without copolymer,
It becomes 0 J / g. ΔHc is an index relating to the crystallinity of the sheet at that time with respect to the crystallinity of the polymer, and ΔHc is
When Hc is large, it means that the crystallization of the sheet proceeds in the temperature rising process, that is, the crystallinity of the sheet was relatively low based on the crystallinity of the polymer. Conversely, ΔHc
Is small, it means that the crystallinity of the sheet was relatively high based on the crystallinity of the polymer.

That is, one direction for increasing (ΔHm-ΔHc) is to use a polymer having high crystallinity as a raw material.
To make a sheet with a relatively high degree of crystallinity. Although the crystallinity of the sheet depends to a large extent on the composition of the polymer, it is also greatly influenced by the molding processing conditions of the sheet. In order to increase the crystallinity of the sheet in the molding process step, particularly in the tenter method biaxial stretching, it is useful to increase the stretching ratio to promote oriented crystallization, and to perform heat treatment after stretching in an atmosphere at a crystallization temperature or higher.

It is effective that the heat treatment temperature is higher than the crystallization temperature of the sheet, but the crystallization temperature of the sheet is Δ.
The larger P is, the more it tends to decrease. In the case of the present invention, thermal dimensional stability can be imparted by performing heat treatment in the range of 90 ° C to 160 ° C for 5 seconds or more.

An information recording card is obtained by providing an information recording section on the sheet thus obtained. The information recording portion can be formed by a method known per se, for example, by applying a magnetic ink in which a known magnetic ferrite is dispersed in a resin binder, or by forming a magnetic layer by transfer from a magnetic transfer foil. It is preferable that the information recording card has a thickness of 0.05 mm or more and 1 mm or less from the viewpoint of strength, waist strength, economical efficiency, etc. It can be favorably used within a thickness range of 0.1 to 0.3 mm.

Examples will be shown below, but the present invention is not limited thereto. The measured values shown in the examples were measured and calculated under the following conditions.

(1) ΔP Using an Abbe refractometer, the refractive indices (α, β,
γ) was measured and calculated by the following formula. ΔP = {(γ + β) / 2} -α (α <β <γ) γ: Maximum refractive index β in the sheet surface β: Refractive index in the sheet in-plane direction orthogonal thereto α: Refractive index in the sheet thickness direction (2 ) ΔHm-ΔHc Using DSC-7 manufactured by Perkin Elmer, a sheet sample 10 mg was heated at a heating rate of 1 based on JIS-K7122.
The heat of fusion of crystal ΔHm and the heat of crystallization ΔHc were calculated from the thermogram when the temperature was raised at 0 ° C./min.

(3) Tensile strength and brittleness Tensileon type II machine of Toyo Seiki Co., Ltd.
It measured based on S-K7127. Tensile speed is 10
It is 0 mm / min. Further, the brittleness was judged by touch. M
D indicates the flow direction of the film, and TD indicates the direction orthogonal to the flow of the film.

(4) Tensile Elastic Modulus Tensile elastic modulus was measured to show the rigidity of the card. The sheet is 360 mm long and 5 mm wide, with scratches, wrinkles,
The sample was collected without creases, the distance between the balance lines was set to 300 mm, and the tensile speed was measured at 5 mm / min using a Toyo Seiki Tensilon II machine. MD is the flow direction of the film,
TD indicates the direction orthogonal to the film flow.

(5) Thermal dimensional stability A sheet sample was cut into 100 mm × 100 mm,
After dipping in a hot water bath at 80 ° C. for 10 seconds, the vertical and horizontal dimensions were measured, and the values were expressed as (vertical × horizontal), which was used as an index of thermal dimensional stability.

(6) A water resistant sheet sample was cut into 50 mm × 50 mm and
The weight change, appearance (transparency) and tactile sensation after standing in water at ℃ for 48 hours were examined. The weight retention rate was expressed by% by dividing (sample weight before immersion)-(sample weight after immersion) by sample weight before immersion.

(7) Immersion in water degradability test A test was conducted according to the immersion method in water in the field test of the biodegradable plastics research group. That is,
The sheet was cut into 120 mm × 30 mm, and it was sandwiched in the center of the three stainless steel sample holders. A window with the same shape as the sheet sample is opened in the center of the sample holder, two stainless steel wire nets (40 mesh) are bitten, the sheet does not flow out as it is, and the contact with water is good I chose

After soaking in fresh water for 3 months in winter, the weight average molecular weight retention, appearance and touch of the sheet were examined. Weight average molecular weight is Shimadzu Chromatopack C-R4A type G
A sheet sample was dissolved in chloroform with a PC to prepare a concentration of about 0.5 (w / v)%, and a flow rate was 1.0 m / min.
It was measured at a column temperature of 40 ° C. and converted into polystyrene. The weight average molecular weight retention rate was expressed as% by dividing (sample weight average molecular weight before immersion)-(sample weight average molecular weight after immersion) by the sample weight average molecular weight before immersion.

Comparative Example 1 Biopol D61 which is a copolymer of 3-hydroxybutyric acid and 3-hydroxyvaleric acid
0G (manufactured by Zeneca) was extruded with a 30 mm single-screw extruder at a T-die temperature of 180 ° C. and quenched with a casting roll to obtain a sheet having a thickness of 210 μm. No additives were added to this sheet. The resulting sheet was opaque.

Comparative Example 2 Starch blend type Matterby AT05H (sold by Nippon Gohsei Co., Ltd.) was extruded at a T-die temperature of 160 ° C. with a 30 mm single screw extruder, and rapidly cooled with a casting roll to a thickness of 180 μm. Got the sheet. No additives were added to this sheet. The resulting sheet was slightly transparent.

(Comparative Example 3) Poly-L-lactic acid having a weight average molecular weight of 100,000 was added to a T-die temperature of 18 using a 30 mm single screw extruder.
It was extruded at 0 ° C. and quenched with a casting roll to obtain a sheet having a thickness of 210 μm.

(Comparative Example 4) Poly-L-lactic acid having a weight average molecular weight of 100,000 was extruded under the same conditions as in Comparative Example 3, and subsequently roll-stretched 2.6 times in the length direction and then 3 in the width direction. After being stretched by 3 times the tenter, heat treatment was performed in the tenter at a temperature of 35 ° C. to obtain a sheet having a thickness of 120 μm. The flow rate of the sheet was 3 m / min, and the passing time through each stretching / heat treatment zone was about 20 seconds.

(Examples 1 and 2) Melt extrusion and stretching were carried out in the same manner as in Comparative Example 4, and then the temperature was 100 ° C or 140 ° C.
Was heat treated in order to obtain a sheet having a thickness of 120 μm.

Example 3 After being extruded in the same manner as in Comparative Example 3, roll stretching was carried out 2.5 times in the length direction and then tenter stretching was carried out 2.0 times in the width direction. Heat treatment was performed in a tenter to obtain a sheet having a thickness of 210 μm.
Tables 1 and 2 show the results of measurement and evaluation of each of the above sheets.

[0038]

[Table 1]

[Table 2]

As shown in Tables 1 and 2, the sheet of Comparative Example 1 has excellent decomposability, but has low strength and elastic modulus.
At least it could not be put to practical use as it is.
Further, the sheet of Comparative Example 2 had low strength and elastic modulus, and also low water resistance, so that it could not be put to practical use as it is.

The sheet of Comparative Example 3 was made of polylactic acid, but was not stretched and had a low strength and was a brittle material. Further, the sheet of Comparative Example 4 has a degree of plane orientation ΔP of 3.0 × 10 ⁻³ or more by stretching and has high strength and improved brittleness, but lacks thermal dimensional stability and is not practical.
On the other hand, the sheets of Examples 1 to 3 in which ΔP and (ΔHm−ΔHc) were within the specified range of the present invention were excellent in strength and thermal dimensional stability, and also had good decomposability.

[0041]

According to the present invention, a base material for information recording cards and an information recording card having excellent practical strength can be obtained from degradable polylactic acid.

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Claims (2)

(57) [Claims] 1. A sheet-like material made of a polylactic acid-based polymer, having a degree of plane orientation ΔP of 3.0 × 10 ⁻³ or more, and a heat of crystal fusion ΔHm when the sheet is heated and Difference from the heat of crystallization ΔHc generated by crystallization (ΔHm−
ΔHc) is 20 J / g or more, a base material for information recording cards. 2. A degradable information recording card having a thickness of 0.05 mm or more and 1 mm or less, comprising an information recording portion provided on the base material according to claim 1.