JP3388052B2 - Degradable laminate material - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminate material which decomposes in a natural environment, and more particularly to a laminate of a polylactic acid polymer film and a paper material. [0002] Paper is widely used as a packaging material. Paper can easily be incinerated after use and can be decomposed even if left in the natural environment, so it can be said that it is an excellent material from the viewpoint of environmental protection. However, coated paper is used depending on the application because paper has low water resistance, oil and fat resistance, tear strength and the like, and has insufficient gas barrier properties and moisture-proof properties. In order to further improve the performance, it is sometimes used in combination with a plastic material such as polyethylene, polypropylene, or polyvinyl chloride. However, since the plastic material generally remains without being decomposed in the natural environment, the composite material often does not have spontaneous disintegration. Also, it is difficult to separate paper and plastic materials for processing. On the other hand, so-called biodegradable plastics, which can be decomposed even when left in a natural environment as a plastic material, have received attention in recent years. Practical use of a polylactic acid-based film that can produce a thin film among biodegradable plastics and that can compensate for the above-described drawbacks of paper has been desired. Therefore, Japanese Patent Application Laid-Open No. 4-334448 discloses a biodegradable composite material in which a substrate containing vegetable fibers is coated with polylactic acid or a derivative thereof.
No. 336246 discloses a thermoplastic decomposable polymer mainly composed of polylactic acid or a copolymer of lactic acid and oxycarboxylic acid, and a decomposable laminated paper made of paper. Further, Japanese Patent Application Laid-Open No. 5-38784 discloses polylactic acid or lactic acid. A decomposable laminate composition comprising a thermoplastic decomposable polymer having a copolymer of oxycarboxylic acid as a main component and a regenerated cellulose film is disclosed. However, in the above-mentioned biodegradable composite material, degradable laminate paper and degradable laminate composition, a substrate or paper containing vegetable fibers is bonded to a polylactic acid film. At the time of bonding, the polylactic acid film may be broken due to its own brittleness, and if left at high temperature after bonding, a change in appearance such as devitrification of the polylactic acid film is likely to occur. Further, when the obtained laminate material is bent, whitening and cracks are easily generated in the fold. Furthermore, even if it performs glazing, sufficient luster cannot be obtained. That is, although the techniques disclosed in the above publications have compensated for the drawbacks of paper, they have created new problems as composite materials. [0008] The present invention solves the above-mentioned problems and, after use or disposal, hydrolyzes naturally in soil or water and leaves no intact form in the soil to form harmless decomposition products. The present invention provides a decomposable laminate material comprising a polymer film. The gist of the present invention is that the degree of plane orientation ΔP is not less than 3.0 × 10 ⁻³ , the heat of crystal fusion ΔHm when the temperature of the film is raised, and the temperature rise. (ΔHm−ΔH) from the heat of crystallization ΔHc generated by crystallization
c) is 20 J / g or more and {(ΔHm−ΔHc) / ΔH
m} is I der 0.75 or more, the L- lactic acid and D- lactic acid
A degradable laminate material characterized by laminating a oriented polylactic acid-based film made of a copolymer having a ratio in the range of 98: 2 to 94: 6 and paper. Hereinafter, the present invention will be described in detail. The oriented polylactic acid-based film used in the decomposable laminate material of the present invention contains polylactic acid or a copolymer of lactic acid and another hydroxycarboxylic acid as a main component, and other polymers as long as the effects of the present invention are not impaired. Materials may be mixed. In addition, plasticizers, lubricants for the purpose of adjusting moldability and film properties,
It is also possible to add additives such as inorganic fillers and ultraviolet absorbers, and modifiers. Lactic acid includes L-lactic acid and D-lactic acid, and hydroxycarboxylic acid includes glycolic acid and 3-lactic acid.
Examples include hydroxybutyric acid, 4-hydroxybutyric acid, 3-hydroxyvaleric acid, 4-hydroxyvaleric acid, and 6-hydroxycaproic acid. As the polymerization method, any known method such as a condensation polymerization method or a ring-opening polymerization method can be employed. Further, a small amount of a chain extender such as a diisocyanate compound or an epoxy compound is used for the purpose of increasing the molecular weight. Compounds, acid anhydrides and the like may be used. The weight average molecular weight of the polymer is preferably from 50,000 to 1,000,000. If the weight average molecular weight is lower than the above range, practical physical properties are hardly exhibited. The conditions for forming the unstretched sheet will be described. The polylactic acid-based polymer is sufficiently dried to remove water, and then melted by an extruder. Since the melting temperature varies depending on the composition, it is preferable to appropriately select the melting temperature accordingly.
In practice, a temperature range of 140 ° C. to 250 ° C. is usually selected. It is preferable that the polymer melt-formed into a sheet is rapidly cooled by contact with a rotating casting drum (cooling drum). The temperature of the casting drum is suitably 50 ° C. or less. Above this, the polymer sticks to the casting drum and cannot be pulled off. In addition, since crystallization is promoted and spherulites develop and cannot be stretched, it is preferable to set the temperature below the glass transition point and quench to make them substantially amorphous. The stretching method may be any of uniaxial stretching, sequential biaxial stretching, and simultaneous biaxial stretching. However, for the purpose of use, it is necessary to improve the physical properties in both the vertical and horizontal directions. In the present invention, the stretching ratio of the unstretched sheet is 1.5 in each of the longitudinal (longitudinal) direction and the transverse (width) direction.
In the non-oriented sheet or film, the plane orientation degree ΔP of 1.0 × 10 ⁻³ or less is specified by the present invention by appropriately selecting the stretching temperature in the range of 50 ° C. to 90 ° C. To 3.0 × 10 ⁻³ or more to obtain a thin, tough oriented film. ΔP indicates the degree of orientation in the plane direction with respect to the thickness direction of the film, and is usually calculated by the following formula by measuring the refractive index in the direction of three orthogonal axes. [0017] ΔP = {(γ + β) / 2} -α (α <β <γ) where, gamma, beta refractive index parallel Cartesian biaxial the film surface, alpha is the refractive index of the film thickness direction It is. ΔP also depends on the degree of crystallinity and crystal orientation, but largely depends on the molecular orientation in the film plane. That increase in ΔP is in the film plane, with respect to particular direction the flow direction and / or the Cartesian film, increasing the molecular orientation to enhance the strength of the film, leading to improving the brittleness. As a method for increasing ΔP, a molecular orientation method using an electric field or a magnetic field can be employed in addition to any known film stretching method. Note that the upper limit of ΔP is practically about 30 × 10 ⁻³ , and if ΔP is further increased, disadvantageously, stretching becomes unstable or impossible. By setting ΔP to 3.0 × 10 ⁻³ or more, the strength is remarkably improved, and at the same time, embrittlement and whitening mainly caused by spherulite growth observed in the case of a non-oriented sheet are obtained. Can be prevented. However, on the other hand, the thermal dimensional stability of the film becomes poor. Specifically, the film shrinks during the hot summer months. Alternatively, the film may be naturally shrunk during storage in a roll state, causing the film to sag or undulate. For this reason, lamination with paper is difficult. Also, the film shrinks due to the heat applied during lamination,
There is a problem of curling. Therefore, it is important that the polylactic acid-based film does not shrink at a temperature slightly higher than room temperature, that is, at a temperature of about 50 ° C. or more, that is, it has thermal dimensional stability. Therefore, in the case of a polylactic acid-based film having a ΔP of 3.0 × 10 ⁻³ or more, (ΔHm−ΔHc) of the film is set to 20 J / h in order to obtain practical thermal dimensional stability.
g and {(ΔHm−ΔHc) / ΔHm} is 0.7
It is important to control to 5 or more. In other words, if these conditions are not satisfied,
The film has poor thermal dimensional stability, and tends to cause problems such as shrinkage at a temperature applied by lamination, drying, aging, etc., and is not practical. If the condition is exceeded, the thermal dimensional stability becomes good and there is no problem in practical use. ΔHm and ΔHc are determined by differential scanning calorimetry (DSC) of the film sample.
Hm is the amount of heat required to melt all the crystals when the temperature is raised at a rate of 10 ° C./min, and is determined from the area of the endothermic peak due to crystal melting which appears near the crystal melting point of the polymer. ΔHc is determined from the area of the exothermic peak generated during crystallization that occurs during the temperature rise process. ΔHm mainly depends on the crystallinity of the polymer itself, and takes a large value for a polymer having high crystallinity. Incidentally, in the case of a complete homopolymer of L-lactic acid or D-lactic acid without a copolymer, it is 60 J / g or more, and in a copolymer of these two types of lactic acid, ΔHm changes depending on the composition ratio. ΔHc is an index relating to the crystallinity of the film at that time with respect to the crystallinity of the polymer. When ΔHc is large, the crystallization of the film proceeds in the process of raising the temperature. That is, it indicates that the crystallinity of the film was relatively low based on the crystallinity of the polymer. Conversely, when ΔHc is small, it indicates that the crystallinity of the film was relatively high based on the crystallinity of the polymer. 1 for increasing (ΔHm−ΔHc)
One direction is to produce a film having a relatively high crystallinity from a polymer having a high crystallinity. The degree of crystallinity of the film depends not less on the composition of the polymer, and the composition ratio of L-lactic acid and D-lactic acid is in the range of 98: 2 to 94: 6 in order to make ΔHm of the polymer itself 20 J / g or more. It is important to Further, in order to reduce ΔHc, that is, to increase the crystallinity of the film, it is necessary to select film forming conditions. In order to increase the crystallinity of the film in the forming step, particularly in the biaxial stretching by the tenter method, it is useful to increase the stretching ratio to promote oriented crystallization, or to heat-treat after stretching in an atmosphere at a temperature higher than the crystallization temperature. It is. The crystallization temperature tends to decrease as ΔP increases, and in the case of the present invention, as a result of intensive studies, heat treatment is performed at least at 70 ° C. or more, preferably at 90 ° C. to 170 ° C. for 3 seconds or more. Thermal dimensional stability can be imparted. Within this range, the higher the heat treatment temperature and the longer the heat treatment time, the better the thermal dimensional stability. The film thus obtained does not break or distort due to the tension and heat applied in a laminating process such as dry lamination, wet lamination, and hot melt lamination, and performs extremely stable laminate production. be able to. Also, since the film is molecularly oriented and crystallized, spherulites do not grow even after aging, so there is no whitening, devitrification or embrittlement due to spherulites, and appearance and mechanical and protective properties. Maintain excellent performance. Further, by stretching the polylactic acid-based polymer film so as to give the properties in the above-mentioned specified range, the uniformity of the thickness of the film is enhanced, and the transparency and gloss are also improved. Further, the impact resistance is improved, and the same or better effect can be obtained even with a thin film as compared with a case where a single piece of paper or an unstretched film is laminated.
The paper to be bonded to the oriented polylactic acid-based film is not particularly limited, and for example, printing paper, kraft paper, imitation paper, paperboard, and the like can be used. Further, a polylactic acid-based polymer film may be further bonded to coated paper such as art paper or coated paper. The oriented polylactic acid-based film is bonded to paper with an adhesive or a pressure-sensitive adhesive. Existing synthetic adhesives and pressure-sensitive adhesives include vinyl-based, acrylic-based, polyamide-based, polyester-based, rubber-based, and urethane-based adhesives. From the viewpoint of the laminate material, the amount of the adhesive or pressure-sensitive adhesive is small, but it is originally preferable that these are also biodegradable.For example, carbohydrates such as starch, proteins such as glue, gelatin, casein, and uncured There are natural materials such as sulfur natural rubber. The constitution of the decomposition laminate material of the present invention is, for example, a two-layer constitution of oriented polylactic acid-based polymer film / paper, a three-layer constitution of oriented polylactic acid-based polymer film / paper / oriented polylactic acid-based polymer film, etc. However, there is no particular limitation. The decomposition laminate material of the present invention comprises a bag, a box,
It can be suitably used in the field of packaging materials such as trays, cups and lids. A "window" may be formed by partially punching out a piece of paper, and an oriented polylactic acid-based polymer film may be attached thereto to form a container for seeing through the contents. Moreover,
It is also suitable for applications requiring beautiful appearance such as calendars, posters and book covers; display materials such as labels and stickers; packing and wrapping tapes; and process paper used in the manufacture of various products. EXAMPLES Examples will be shown below, but the present invention is not limited to these examples. The measured values shown in the examples were calculated by measuring under the following conditions. [0036] (1) Cartesian three axial directions of a refractive index by ΔP Abbe refractometer (alpha, beta,
γ) was measured and calculated by the following equation. [0037] ΔP = {(γ + β) / 2} -α (α <β <γ) γ: maximum refractive index of the film plane beta: And the refractive index of the film in-plane direction Cartesian alpha: film thickness direction of the Refractive index (2) ΔHm−ΔHc and (ΔHm−ΔHc) / ΔHm Using DSC-7 manufactured by PerkinElmer, when 10 mg of a film sample is heated at a rate of 10 ° C./min based on JIS-K7122. The heat of crystal fusion ΔHm and the heat of crystallization ΔHc were determined and calculated from the thermogram. (3) Suitability for laminating The adhesive was uniformly applied to a polylactic acid film cut to 100 mm × 100 mm, dried in an oven at 60 ° C. for 3 minutes, and the shape change of the polylactic acid film was observed. If the dimensional change is large, it is not suitable for bonding to paper. (4) Heat resistance 100 mm × 100 mm laminate sample was
The change after standing for 3 hours in a thermostat at 0 ° C. was examined. (5) Impact resistance Hydro shot high-speed impact tester HTM-1 (trade name)
The impact resistance was measured using Shimadzu Corporation. 100m
Paper, film, and their laminated body samples cut out to mx 100 mm were fixed with a clamp, a weight was dropped at the center of the film to give an impact, and the breaking energy when the sample was broken was read. The measurement temperature is 23 ° C., and the falling speed of the drop is 3 m / sec. The lower the maximum load and the energy at the time of breaking the film, the lower the impact resistance and the more brittle. Example 1 The ratio of the structural unit composed of L-lactic acid to the structural unit composed of D-lactic acid was about 98: 2, the glass transition point was 58 ° C., the melting point was 175 ° C., and the weight average molecular weight was 18.
Ten thousand polylactic acid with 30mmφ single axis extruder
It was extruded from a T-die at 200 ° C. to prepare a 150 μm-thick unstretched sheet. The unstretched sheet is roll-stretched twice in the longitudinal direction, then stretched three times in the width direction by a tenter, and then heat-treated in the tenter at 100 ° C. for about 30 seconds to prepare an oriented polylactic acid-based film. did. The oriented polylactic acid-based film is 100 mm
× 100 mm, and a polyurethane solvent-based adhesive (Takelac A-970 / Takenate A-19 = 15 /
1, Takeda Pharmaceutical Co., Ltd.) was uniformly applied to a thickness of 1 μm and dried in an oven at 60 ° C. for 3 minutes. At this time, there was no change in the appearance and dimensions of the film. Next, high quality paper cut out to the same size,
The above-mentioned oriented polylactic acid-based film was adhered while being pressed with a roller, and aged at 40 ° C. for 24 hours to obtain a decomposition laminate material. Used fine paper (thickness 60μ)
m, the mass per 1 m ² area was 51 g), and the maximum impact load was 2 kgf and the breaking energy was 4 kgf · mm. The ΔP,
(ΔHm−ΔHc), ｛(ΔHm−ΔHc) / ΔH
m｝ and lamination suitability of the decomposition lamination material,
Table 1 shows the heat resistance and impact resistance. ΔP, (ΔHm−Δ
Hc), {(ΔHm−ΔHc) / ΔHm} is within the scope of the present invention. (Example 2) [0046] Except that the conditions for forming an oriented polylactic acid-based film from an unstretched sheet were as follows:
A decomposition laminate material was obtained in the same manner as in Example 1. Roll stretching in the longitudinal direction by 2.5 times, then stretching in the width direction by 2.5 times with a tenter, and subsequently 100 ° C in the tenter,
Heat treatment was performed for about 25 seconds to prepare an oriented polylactic acid-based film. Table 1 shows the properties of the obtained oriented polylactic acid-based film and the decomposition laminate material. Δ
P, (ΔHm−ΔHc), ｛(ΔHm−ΔHc) / ΔH
m｝ is within the scope of the present invention. Example 3 Polylactic acid having a ratio of a structural unit composed of L-lactic acid to a structural unit composed of D-lactic acid of about 96: 4, a glass transition point of 57 ° C., a melting point of 152 ° C. and a weight average molecular weight of 140,000 was prepared. Using the same apparatus as in Example 1,
The sheet was extruded at 190 ° C. to form an unstretched sheet having a thickness of 220 μm. The unstretched sheet is roll-stretched 2.5 times in the longitudinal direction and then stretched 3 times in the width direction by a tenter.
Subsequently, heat treatment was performed at 120 ° C. for about 25 seconds in a tenter to prepare an oriented polylactic acid-based film. Using the oriented polylactic acid-based film, a decomposition laminate material was prepared in the same manner as in Example 1. Table 1 shows the properties of the obtained oriented polylactic acid-based film and the decomposition laminate material. ΔP, (ΔHm−ΔH
c), {(ΔHm−ΔHc) / ΔHm} is within the scope of the present invention. Example 4 Polylactic acid having a ratio of a structural unit composed of L-lactic acid to a structural unit composed of D-lactic acid of approximately 95: 5, a glass transition point of 57 ° C., a melting point of 147 ° C. and a weight average molecular weight of 110,000 was prepared. Using the same apparatus as in Example 1,
The sheet was extruded at 190 ° C. to prepare an unstretched sheet having a thickness of about 250 μm. The unstretched sheet is roll-stretched 1.5 times in the longitudinal direction, then stretched 1.5 times in the width direction by a tenter, and then heat-treated in a tenter at 120 ° C. for about 40 seconds to give oriented polylactic acid. A system film was created. Using the oriented polylactic acid-based film, a decomposition laminate material was prepared in the same manner as in Example 1. Table 1 shows the properties of the obtained oriented polylactic acid-based film and the decomposition laminate material. ΔP, (ΔHm−ΔH
c), {(ΔHm−ΔHc) / ΔHm} is within the scope of the present invention. (Comparative Example 1) Poly-L- used in Example 1
Lactic acid at 200 ° C with 30mmφ single axis extruder
While being quenched with a nip roll while quenching with a casting roll. The thickness of the polylactic acid sheet of the obtained laminate was 100 μm. Table 1 shows the properties of the obtained oriented polylactic acid-based film and the decomposition laminate material. (Comparative Example 2) The unstretched sheet used in Example 1 was roll-stretched 1.2 times in the longitudinal direction, then stretched 1.5 times in the width direction by a tenter, and subsequently at 100 ° C in a tenter. Heat treatment was performed for about 30 seconds to prepare an oriented polylactic acid-based film. Using the oriented polylactic acid-based film, a decomposition laminate material was prepared in the same manner as in Example 1. Table 1 shows the properties of the obtained oriented polylactic acid-based film and the decomposition laminate material. (ΔHm−ΔHc) and {(ΔHm−ΔHc) / ΔHm} are within the range of the present invention, but the plane orientation degree ΔP of the film is less than 3.0 × 10−3, which is outside the range of the present invention. . Comparative Example 3 An unstretched sheet having a thickness of 310 μm was prepared in the same manner as in Example 1. The unstretched sheet was stretched twice in the longitudinal direction, and then stretched three times in the width direction by a tenter to prepare an oriented polylactic acid-based film. Using the above oriented polylactic acid-based film, a decomposition laminate material was prepared in the same manner as in Example 1. Table 1 shows the properties of the obtained oriented polylactic acid-based film and the decomposition laminate material. ΔP and (ΔHm−Δ
Hc) is within the scope of the claims, but ｛(ΔHm−ΔH)
c) / ΔHm｝ is less than 0.75, which is outside the scope of the present invention. Comparative Example 4 Polylactic acid having a ratio of a structural unit composed of L-lactic acid to a structural unit composed of D-lactic acid of approximately 93: 7, a glass transition point of 57 ° C., a melting point of 125 ° C. and a weight average molecular weight of 110,000 was prepared. Using the same apparatus as in Example 1,
It was extruded at 180 ° C. to produce a 170 μm-thick unstretched sheet. The unstretched sheet was roll-stretched 1.5 times in the longitudinal direction, then stretched 2 times in the width direction by a tenter, and subsequently heat-treated in the tenter at 80 ° C. for about 40 seconds to prepare an oriented polylactic acid-based film. Using the oriented polylactic acid-based film, a decomposition laminate material was prepared in the same manner as in Example 1. Table 1 shows the properties of the obtained oriented polylactic acid-based film and the decomposition laminate material. ΔP and ｛(ΔHm−
ΔHc) / ΔHm} is within the scope of the present invention,
Hm-ΔHc) is less than 20 J / g, which is outside the scope of the present invention. [Table 1] ◎: Laminate material having particularly excellent characteristics ：: Laminate material having excellent characteristics △: Laminate material having characteristics of practical level ×: Laminate material having characteristics of practical level or less As shown in Table 1. , ΔP, (ΔHm−ΔHc),
In Examples 1 to 4 where {(ΔHm−ΔHc) / ΔHm} is within the range of the present invention, the lamination suitability, heat resistance, and impact resistance are all within the range required as a laminate material, and the overall evaluation is ◎ to △. It is. By performing lamination,
The impact resistance is greater than the maximum load of 2 kgf and the breaking energy of 4 kgf · mm of the high quality paper used. However, Comparative Examples 1 to 4 lacked the range in which various properties were required as a laminate material, and the overall evaluation was x. That is, when a stretched oriented polylactic acid-based film within the scope of the present invention is used, an excellent decomposable laminate material can be obtained. As described above, the present invention can provide a decomposable laminate material which does not compensate for the drawbacks of paper and has excellent properties as a composite material.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-256480 (JP, A) JP-A-6-23836 (JP, A) JP-A-4-334448 (JP, A) JP-A-4-334 336246 (JP, A) JP-A-7-308961 (JP, A) JP-A-8-22618 (JP, A) JP-A-8-52171 (JP, A) JP-A-7-205278 (JP, A) JP-A-8-198955 (JP, A) JP-A-7-207041 (JP, A) JP-A-7-275653 (JP, A) JP-A-9-25345 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B32B 1/00-35/00 C08J 5/18 B29C 55/00-55/30

Claims (1)

(57) [Claims] 1. The degree of plane orientation ΔP is 3.0 × 10 ⁻³ or more, and the heat of crystal fusion ΔH when the film is heated.
m and the amount of heat of crystallization ΔHc generated by crystallization during temperature rise (ΔHm−ΔHc) is 20 J / g or more and {(ΔHm
-ΔHc) / ΔHm} it is 0.75 or more der, L- milk
When the ratio of acid to D-lactic acid is in the range of 98: 2 to 94: 6,
A degradable laminating material comprising a laminate of an oriented polylactic acid-based film made of a polymer and paper.