JP5654880B2 - Biodegradable laminated paper - Google Patents

Description

  The present invention relates to a biodegradable laminated paper, and in particular, can be easily heat-sealed at the time of assembling a food packaging container, and further, biodegradable that can be easily peelable as required. Regarding laminated paper.

  Conventionally, polyethylene, polypropylene, polyethylene terephthalate, nylon 6 and the like are used as plastics used for laminated paper for various containers and packaging including food. Laminated paper for packaging materials using these plastics will remain undecomposed when discarded in the natural environment after use, damage the landscape, and contaminate living environments such as fish and wild birds. Causes various problems. Under these circumstances, in recent years, with the increasing social awareness of environmental protection, when plastic processing in general is disposed of in the natural environment, it decomposes and disappears over time and does not place a burden on the natural environment. There is a need for plastic laminated paper.

  Polylactic acid is being used as an environmentally sustainable plastic because it is easily decomposed by microorganisms even if it is discarded in the natural environment and it can be produced from natural products. However, polylactic acid is hard and brittle, and there are many difficulties in laminating, resulting in significant restrictions on processing conditions.

In order to improve the problem that polylactic acid is hard and brittle, first, an attempt is made to add a plasticizer.
For example, a degradable polymer composition (PTL 1) containing a plasticizer for ordinary general-purpose resins such as a flutaric acid ester and a fatty acid dibasic acid ester, and a polylactic acid composition containing a polyalkylene ether which is a polymer plasticizer (Patent Document 2), a polylactic acid composition (Patent Document 3) containing a fatty acid dicarboxylic acid and an aliphatic polyester plasticizer has been proposed.

  Further, a biodegradable plastic film or sheet containing an aliphatic polyester having a low glass transition point (Patent Document 4), an impact imparting agent for polyhydroxycarboxylic acid comprising a lactic acid-based polyester comprising a lactic acid unit and a polyester unit ( Patent Document 5), a polylactic acid film (Patent Document 6) containing a specific polyester resin and a reactive acrylic resin, and a polylactic acid provided with a film made of paper and a biodegradable material such as a polylactic acid material and starch Paper and food containers made of the same (Patent Document 7) have been proposed.

JP-A-4-335060 JP-A-8-199052 JP-A-8-283557 JP-A-9-111107 JP 2001-335623 A JP 2010-189536 A JP 2010-189828 A

  However, in the composition of Patent Document 1, if the hardness and brittleness are sufficiently improved, it is difficult to avoid the problems of heat resistance, a decrease in the molecular weight of polylactic acid during processing, and a bleed-out problem. . The compositions of Patent Documents 2 and 3 also have the same problem.

  In Patent Documents 4, 5 and 6, a packaging material is mentioned as an application, but the packaging characteristics are not always sufficient. Furthermore, it cannot be said that the food container of Patent Document 7 necessarily has sufficient performance.

  In view of such circumstances, the problem to be solved by the present invention is to provide a biodegradable laminated paper that can satisfy various properties as a laminated paper for packaging using a biodegradable polylactic acid. is there. As various characteristics for packaging, it can satisfy a wide workability at the time of laminating, satisfy a sufficient heat seal property at the time of processing a container, etc., and if necessary, can be easily peelable so that the heat seal part can be easily peeled off, Furthermore, the waterproof property of the laminated paper, in particular, the waterproof property is not damaged when folded, and the present invention intends to provide a laminated paper that can satisfy these requirements with the polylactic acid-based composition.

  The first of the features of the present invention for solving the above-mentioned problems comprises polylactic acid (A) and lactic acid-based aliphatic polyester (B) containing 0.7 to 10% by weight of lactic acid. The resin composition having a content of 20 to 80 parts by weight with respect to 100 parts by weight of the (A) is laminated to a thickness of 20 to 50 μm on at least one surface of the paper substrate. It is a biodegradable laminated paper.

  The second feature of the present invention is a biodegradable laminated paper characterized in that the lactic acid-based aliphatic polyester (B) contains 0.8 to 8% by weight of lactic acid.

  A third feature of the present invention is a biodegradable laminated paper, wherein the lactic acid-based aliphatic polyester (B) containing lactic acid contains lactic acid, succinic acid, and 1,4-butanediol. It is.

The fourth feature of the present invention is that the lactic acid-based aliphatic polyester (B) containing lactic acid has 2 to 20 mol units of lactic acid with respect to 100 mol units of succinic acid and 1,4-butanediol. This is a biodegradable laminated paper.

A fifth feature of the present invention is a biodegradable laminated paper obtained by melt-extruding a resin composition onto a paper substrate.

  The biodegradable laminated paper of the present invention is a mixture of polylactic acid and a lactic acid-based aliphatic polyester containing a specific amount of lactic acid, so that the processing stability at the time of lamination is remarkably improved and the heat sealability is also improved. A good, easy-to-use biodegradable laminate paper is provided as needed. Further, the waterproof property of the laminated paper, in particular, the waterproof property is not impaired at the time of folding, and it is suitable for packaging.

  The polylactic acid (A) used in the present invention is D-polylactic acid, L-polylactic acid, DL-polylactic acid mainly composed of a D-lactic acid unit, an L-lactic acid unit, and a DL-polylactic acid unit. Are used alone or in admixture of two or more. Among the polymer components, D-polylactic acid and L-polylactic acid exhibit the properties of a component having a large content, and the crystallinity increases when the content is 80 mol% or more. When the D-lactic acid unit and the L-lactic acid unit are mixed in an amount of nearly 50 mol%, it approaches amorphous. In terms of stretchability, it is preferable that polylactic acid having high crystallinity and polylactic acid having low crystallinity are appropriately mixed.

  The molecular weight of the polylactic acid (A) is preferably 50,000 to 500,000 in terms of appropriate film forming properties and mechanical properties. The polylactic acid (A) of the present invention may contain other monomer units in addition to the lactic acid unit. Examples of other monomers include diols such as ethylene glycol, polymers such as polyethylene glycol, dibasic acids such as oxalic acid and adipic acid, and lactones. These copolymerization amounts are preferably 10 mol% or less.

The lactic acid-based aliphatic polyester (B) containing lactic acid mixed with the polylactic acid (A) is an aliphatic polyester composed of other dibasic acid and diol as a lactic acid unit (hereinafter sometimes simply referred to as polyester). The content of 0.7 to 10% by weight, preferably 0.8 to 8% by weight, based on the weight of is preferred.
Examples of the lactic acid component include lactide and polylactic acid in which two molecules of lactic acid are cyclized, and lactic acid or lactide is preferable.
The polyester component consists of a dibasic acid and a diol. Examples of the dibasic acid component include aliphatic dicarboxylic acids such as succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, and cyclohexanedicarboxylic acid. More than one species may be used in combination. Of these, the preferred dibasic acid is succinic acid.
Examples of the diol include ethylene glycol, propylene glycol, 1,4-butylene glycol, 1,3-butylene glycol and the like. Among these, a preferred diol is 1,4-butylene glycol.

The ratio between the polyester component and the lactic acid component, since dibasic acid and diol easily polymeric resin obtained in equimolar proportions a polyester component, lactic acid 2 relative to diacid, diol each 100 moles unit A lactic acid-based aliphatic polyester having 20 mol units is preferably used.
For example, in the case of a lactic acid-based aliphatic polyester composed of succinic acid, 1,4-butanediol, and lactic acid, a polybutylene succinate resin in which lactic acid is 2 mol units (2 mol%: 0.86 wt%) is a polyolefin or the like It is convenient because it has been confirmed that it complies with the voluntary standards (PL) for food containers and packaging made of synthetic resin. On the other hand, the upper limit of lactic acid is preferably 20 mol units (20 mol%: 7.96 wt%).
Moreover, the dibasic acid and the diol are known as lactic acid-based polyesters having an equimolar ratio to about 1.5 molar equivalents of excess diol. When this is applied to a lactic acid-based aliphatic polyester comprising succinic acid, 1,4-butanediol and lactic acid, the amount of lactic acid based on the unit of dibasic acid or diol is preferably about 0.7 to 10% by weight, About 8 to 8% by weight is more preferable. If the content of lactic acid in the lactic acid-based aliphatic polyester (B) is outside the above range, the mixing effect with the polylactic acid (A) is reduced, which is not preferable.
In order to produce lactic acid-based polyester, dibasic acid, diol, lactic acid or lactide are mixed in a required amount and heated to distill off the water produced while refluxing the lactic acid component. In a more preferred method, dibasic acid and glycol are heated and mixed under a nitrogen stream, and water formed is distilled off to obtain an aliphatic polyester. A method for obtaining a lactic acid-based polyester by distilling off water obtained by heating the obtained polyester and the required lactide in the presence of toluene is preferred. Heating should be increased stepwise to promote water distillation and finally stirred under reduced pressure. At this time, a small amount of lead acetate, titanium tetraisopropoxide, titanium tetrabutoxide, tin octoate, zinc octoate or the like can be added as a transesterification catalyst. However, magnesium, titanium, and germanium compounds are used to meet the aforementioned PL standard. The obtained lactic acid-based polyester is a polymer having a weight-average molecular weight converted to polystyrene using GPC, preferably 5000 or more, more preferably 10,000 or more, and still more preferably 100,000 or more.

  The polylactic acid (A) and the lactic acid-based aliphatic polyester (B) are 20 to 80 parts by weight, preferably 20 to 70 parts by weight, based on 100 parts by weight of the polylactic acid (A). Are mixed. If the amount of the lactic acid-based aliphatic polyester (B) is less than 20 parts by weight, the processability and heat sealability at the time of lamination described later are inferior, and if it exceeds 80 parts by weight, the heat resistance is inferior and the processability becomes slightly unstable. The mixed composition is preferably kneaded under melting. In the melt-kneading, it is extruded and pelletized from a nozzle at a temperature of 250 ° C. or less with a single-screw or twin-screw heat extruder, or directly extruded into a curtain shape from a slit and laminated on a paper substrate.

The curtain-like melt extruded from the slit-shaped T-die is laminated by being sandwiched by a rubber touch roll on a cooling roll maintained at a constant temperature, together with the paper substrate fed from the feed roll. . At this time, with polylactic acid alone or a composition close thereto, it is difficult to secure a constant flow rate at both end portions of the T die, and if this portion is heated excessively, it is difficult to perform stable processing that is easy to burn.
Antioxidants such as 2,6-di-t-butyl-4-methylphenol and butylhydroxyanisole, and heat stabilizers such as phosphate esters, isocyanates, and carbodiimides can be added to the resin composition of the present invention. In addition, processing aids such as metal soaps such as zinc stearate, magnesium stearate, calcium stearate, liquid paraffin, and lubricants such as ethylene bisstearyl amide can be used. Again, the food applications it is necessary to consider the so that be compatible with PL standards.
The paper used as the base material is not particularly limited, and for example, craft paper, coated paper, thin paper, glassine paper, paperboard and the like can be used as the base material.

Laminated paper is often used for packaging, such as trays, cups, various paper containers, and diapers. Of these, containers are often assembled by heat sealing, and it is also an important property that they can be easily peeled (easy peelable) when opened once opened.
Heat sealability is measured by the peel strength of two samples that are pressed and bonded to two metal plates (hot plates) at a certain pressure for a certain period of time. Packaging performance can be estimated.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated further more concretely, this invention is not limited only to these Examples.

Example 1
(Manufacture of laminated paper)
A high-quality paper of 104.7 g / m ^{2 was} fed from a paper base feeding machine. On the other hand, polylactic acid (A) with respect to (Unitika Ltd., Te Ramakku (R) TE-2000C) 100 parts by weight, lactic acid 2 mol% for each 100 mol% and succinic acid 1,4-butanediol A resin composition obtained by mixing 25 parts by weight of lactic acid aliphatic polyester (B) (GSPla (registered trademark) FZ81PD, manufactured by Mitsubishi Chemical Corporation) co-condensed with a 40 mm extruder, a die width of 400 mm, and a slit Melt extrusion was performed with a T die having a spacing of 0.8 mm. The extrusion temperature is set to 250 ° C., and the paper composition is sandwiched between a cooling roll having a temperature of 30 ° C. and a rubber touch roll, and the thickness of the resin composition layer (lamination layer) is 30 μm at a processing speed of 20 m / min. Laminated paper was obtained.

(Evaluation of processing characteristics)
The fluctuations in the end of the melt from the both ends of the die during processing, the width of lamination, and the width of fluctuation in thickness (thickness variation) were observed and measured. In addition, the thickness fluctuation width measured the machine direction and the width direction, and showed it by the difference of the highest and the lowest. The results are shown in Table 1.
The adhesion between the lamination layer and the paper substrate was evaluated in three stages: good, slightly bad, and bad.

(Heat sealability)
A tester that can apply two strips of 10mm width laminated paper facing each other with the lamination layers facing each other and apply a constant pressure of 3kg / cm ² for two seconds to two hot plates maintained at a constant temperature (Shiga The sample which heat-bonded the lamination layers was created by the packaging machine company). In this case, one end of each of the two laminated papers protrudes from the hot platen to form a non-adhesive portion, and both ends are subjected to a tensile tester to measure the peel strength when pulled in the direction of 90 ° C. with respect to the adhesive surface. . The tensile speed was 300 mm / min. The results are shown in Table 1.

Example 2
A laminated paper was prepared in the same manner as in Example 1 except that lactic acid-based aliphatic polyester (B) (GSPla (registered trademark) FZ81PD) was changed to 60 parts by weight, and its processing characteristics and heat sealability were observed and measured. did. The results are shown in Table 1.

Example 3
A laminated paper was prepared with the resin composition layer (lamination layer) thickness of 40 μm by adjusting the processing speed and extrusion discharge amount by the same method as in Example 1, and the workability and heat sealability were observed and measured. . The results are shown in Table 1.

Comparative Example 1
Laminated paper was prepared by the same method as in Example 1 using only polylactic acid (A) without mixing lactic acid-based aliphatic polyester (B) (GSPla (registered trademark) FZ81PD), and its processing characteristics and heat The sealing property was observed and measured. The results are shown in Table 1.

Comparative Example 2
A laminated paper was prepared in the same manner as in Example 1 except that the lactic acid-based aliphatic polyester (B) (GSPla (registered trademark) FZ81PD) was changed to 10 parts by weight, and its processing characteristics and heat sealability were observed and measured. did. The results are shown in Table 1.

Comparative Example 3
A laminated paper was prepared in the same manner as in Example 1 except that lactic acid-based aliphatic polyester (B) (GSPla (registered trademark) FZ81PD) was changed to 100 parts by weight, and its processing characteristics and heat sealability were observed and measured. did. The results are shown in Table 1.

Comparative Example 4
A laminated paper having a resin composition layer (lamination layer) thickness of 10 μm was prepared by adjusting the processing speed and extrusion discharge amount in the same manner as in Example 1, and the processing characteristics and heat sealability were observed and measured. . The results are shown in Table 1.

As is apparent from the results in Table 1, the processing stability during lamination can be remarkably improved by using polylactic acid and a lactic acid-based aliphatic polyester containing a specific amount of lactic acid. If the amount of the lactic acid-based aliphatic polyester is less than 20 parts by weight, the processing stability becomes insufficient (Comparative Example 2), and it becomes stable to rub more than 20 parts by weight. I understand. Moreover, when there is too much lactic acid-type aliphatic polyester, it will become a little unstable (Comparative Example 3). It can be seen that the adhesion to the paper substrate is also improved and the adhesion to the paper substrate is poor when the lamination thickness is less than 20 μm (Comparative Example 4).
Heat sealability useful for packaging can be measured by adding a lactic acid-based aliphatic polyester containing a specific amount of lactic acid to polylactic acid to increase the peel strength between lamination layers when the heat seal temperature is above a certain temperature, that is, It becomes a pseudo-adhesive state, and an easy and wearable state can appear. Thereafter, sufficient adhesive strength is obtained, leading to destruction of the paper layer. Furthermore, the waterproofness of the laminated paper and the waterproofness when folded were sufficient. However, when the blending amount of the lactic acid-based aliphatic polyester is too large, the heat seal temperature is lowered, but the temperature range in the pseudo-adhesion state is reduced, and the paper layer is destroyed (Comparative Example 3).
As described above, by using a suitable amount of lactic acid-based aliphatic polyester containing a specific amount of lactic acid in polylactic acid and setting the lamination thickness in an appropriate range, the processing stability during lamination can be significantly improved. The heat sealability is also good, and an easy-to-peel state can be produced as necessary.

  As described above, according to the present invention, the processing stability during lamination is remarkably improved, the heat sealability is also good, and a biodegradable laminated paper that can be easily peelable if necessary. Provided and its usefulness is enormous.

Claims (5)

  It comprises polylactic acid (A) and lactic acid-based aliphatic polyester (B) containing 0.7 to 10% by weight of lactic acid, and the content of (B) is 20 to 100 parts by weight of (A). A biodegradable laminated paper obtained by laminating a resin composition of 80 parts by weight on at least one surface of a paper substrate to a thickness of 20 to 50 μm.   The biodegradable laminated paper according to claim 1, wherein the lactic acid-based aliphatic polyester (B) contains 0.8 to 8% by weight of lactic acid.   The biodegradable laminated paper according to claim 1 or 2, wherein the lactic acid-based aliphatic polyester (B) containing lactic acid contains lactic acid, succinic acid, and 1,4-butanediol. The lactic acid-based aliphatic polyester (B) containing lactic acid has 2 to 20 mol units of lactic acid with respect to each 100 mol units of succinic acid and 1,4-butanediol. 4. The biodegradable laminated paper according to any one of 3 above. The biodegradable laminated paper according to any one of claims 1 to 4 , wherein the resin composition is melt-extruded on a paper substrate.