JPH11302424A - Biodegradable foamed sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve shock absorbing performance, biodegradability, mildewproofness, moldability and flexibility by molding a polylactic acid resin composition comprising a polymer component containing polylactic acid and a biodegradable aliphatic polyester, and a biodegradable plasticizer. SOLUTION: A polylactic acid resin composition is obtained by blending 100 pts.wt. of a polymer component comprising 90-50 wt.% of a polylactic acid having a weight average molecular weight of 10,000-1,000,000 and 10-50 wt.% of a biodegradable aliphatic polyester having a weight average molecular weight of 10,000-1,000,000 and a melting point of 80-250 deg.C with 5-25 pts.wt. of a biodegradable plasticizer and optionally 0.1-10 pts.wt., based on 100 pts.wt. of the total of the polymer component and the plasticizer, of at least one inorganic filler selected from the group consisting of talc, magnesium silicate, calcium carbonate, aluminum powder, silica and kaolinite. This composition is molded into a film, softened by heating to 50-100 deg.C, and subjected to an embossing process to form a projection 1a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a foam sheet which is decomposable in a natural environment and is produced from a thermoplastic polymer composition containing polylactic acid or a polymer containing at least 50% by weight of a lactic acid component as a main component. And a composite sheet on which kraft paper and the like are bonded.

[0002]

2. Description of the Related Art [Technical Background] A bubble sheet in which a large number of bubbles are formed by laminating an embossed sheet having a large number of embosses and a base sheet, and kraft paper or the like is laminated on one or both sides of the bubble sheet. The composite sheet has been widely used as a buffer and a wrapping material when transporting articles such as electric parts, glass, pottery, food, and art. General-purpose resins such as polyethylene resin are generally used for the foam sheet and the composite sheet. However, foam sheets manufactured from such general-purpose resins include:
Some have excellent impact resistance, light weight, heat absorption resistance, and flexibility, but when discarded, they increase the amount of garbage and hardly decompose in the natural environment. Will remain in the ground. In addition, abandoned plastics cause problems such as degrading the landscape and destroying the living environment of marine life.

To solve such a problem, for example, Japanese Patent Laid-Open No.
JP-A-320654 and JP-A-7-16966 disclose that an extruder melt-mixes a plurality of resins composed of an ethylene / carbon monoxide copolymer resin, a high-density polyethylene resin, a polyamide resin, and an aliphatic polyester resin. A bubble sheet comprising a mixed resin composition is disclosed. This sheet has the following features 1) to 3). 1) It has an effective function as a packaging material, a heat insulating material, a sound absorbing material, a civil engineering building material, and an agricultural material. 2) Excellent gas barrier properties. 3) It is easily decomposable. In other words, it has the function of biodegrading when buried in the soil after disposal, and photodecomposes when exposed to sunlight to reduce the volume. However, this bubble sheet contains a general-purpose polymer having substantially no decomposability (high-density polyethylene resin, polyamide resin, etc.), and the decomposability is not always sufficient.

On the other hand, as a biodegradable polymer of a thermoplastic resin, polylactic acid, a copolymer of lactic acid and another aliphatic hydroxycarboxylic acid, an aliphatic polyhydric alcohol and an aliphatic polycarboxylic acid are used. Polyester and the like have been developed. Some of these polymers are 100% biodegradable within months to one year in animals or, when placed in soil or seawater, begin to degrade within weeks in a humid environment, with about 1 Some disappear in a few years. These decomposition products have the property of becoming lactic acid, carbon dioxide, and water that are harmless to the human body. In particular, polylactic acid has recently been produced in large quantities and inexpensively by fermentation of L-lactic acid as a raw material,
Due to its high decomposition rate in compost and excellent characteristics such as mold resistance, odor resistance to food, and coloration resistance, it is expected to expand its field of use.

Against this background, the present inventors have disclosed, in Japanese Patent Application Laid-Open No. 7-76628, a foam sheet made of a thermoplastic resin composition containing polylactic acid as a main component. This bubble sheet is excellent in scratch resistance, waterproofness, mold resistance, etc., and can be decomposed under natural environment,
It is suitable as a buffer material that also eliminates the problem of environmental pollution. Also,
A composite sheet made of a foam sheet and kraft paper is suitable as a material for transportation such as cardboard, envelopes and the like. However, polylactic acid has high rigidity, and it is hard to say that it is an appropriate resin for applications requiring flexibility such as films and packaging materials.Depending on the composition ratio and molding processing conditions of the resin composition used,
Requires advanced technology for forming. Further, the flexibility and flexibility of the obtained product is not always sufficient, and cracks may occur at the time of winding after the production of the bubble sheet, and bubbles may be removed or burst, which is not very practical. Therefore, in order to obtain a practical foam sheet containing polylactic acid as a main component, it is necessary to impart flexibility by some method.

On the other hand, in general, techniques for imparting flexibility to polylactic acid include 1) addition of a plasticizer, 2) formation of a copolymer,
3) Methods of blending soft polymers and the like are known. However, in the methods 1) and 2), even if sufficient flexibility can be imparted, the glass transition temperature of the resin composition decreases, and as a result, crystallization or
In the case of a method in which a property change such as hardening occurs, or a method in which a plasticizer is added, there are problems such as further bleeding of the plasticizer and blocking of the sheet. There's a problem.

In the method 3), considering biodegradability, which is one of the problems to be described later, the resin to be blended is limited to a biodegradable resin having flexibility. Examples of such a resin include polybutylene succinate, polyethylene succinate, polycaprolactone and the like, which have already been disclosed in JP-A-8-245866 and JP-A-9-111107. However, in this method, in order to impart sufficient flexibility (the elastic modulus is 1000 MPa or less) to the polylactic acid resin composition, it is necessary to add a large amount (for example, in the case of polybutylene succinate, 60% by weight or more). As a result, the above-mentioned characteristics of polylactic acid are impaired. As described above, it has been impossible to impart flexibility and heat resistance without deteriorating the characteristics of polylactic acid by using the conventional technology.

[0008]

The problems to be solved by the present invention are excellent in buffering performance, biodegradability and anti-mold property, and in the production thereof, the moldability and yield are remarkably improved. Moreover, an object of the present invention is to provide a foam sheet having significantly improved flexibility and flexibility. More specifically,
An object of the present invention is to provide a foam sheet made of a polylactic acid-based resin composition having both flexibility and heat resistance.
Furthermore, it has flexibility (elastic modulus of 100 to 1000 MPa) and heat resistance (blocking temperature of 60 ° C. or more), such as polypropylene, polyethylene and polyvinyl chloride used for garbage bags and packaging materials. An object of the present invention is to develop a foam sheet made of a biodegradable polylactic acid-based resin composition.

[0009]

As described above, the bubble sheet disclosed in Japanese Patent Application Laid-Open No. 7-76628 is extremely significant in that it has excellent decomposability. Since it is a relatively hard resin, depending on the composition ratio of the resin composition used and the molding processing conditions, advanced techniques are required for molding, and the flexibility and flexibility of the obtained product are not always sufficient. There were cases. Therefore, the present inventors have intensively studied to further develop the technical idea underlying the invention disclosed in JP-A-7-76628.

That is, the present inventors have disclosed in Japanese Patent Laid-Open No. 7-76.
When the thermoplastic polymer composition containing polylactic acid used in the invention disclosed in Japanese Patent No. 628 is formed into a foam sheet, in order to improve flexibility and flexibility,
Moreover, the screening of plasticizers that do not easily pollute the environment has been studied. As a result, to a mixture of polylactic acid and a specific soft biodegradable resin, by adding a specific plasticizer having good compatibility with the mixture, a polylactic acid-based resin capable of solving the above-mentioned problems It has been found that a foam sheet made of the composition can be obtained, and the present invention has been completed.

That is, the present invention is specified by the following items. 1) Consisting of a polylactic acid (al), a polymer component (A) containing a biodegradable aliphatic polyester (a2) having a melting point of 80 to 250 ° C., and a biodegradable plasticizer (B). A bubble sheet made of a polylactic acid-based resin composition. 2) The bubble sheet is a composite sheet formed by laminating an embossed sheet provided with a large number of uneven portions by embossing on at least one surface of a flat base sheet.
1) The bubble sheet according to the above. 3) The polymer component (A) is polylactic acid (al) 90-5
0% by weight and aliphatic polyester (a2) 10 to 5
The bubble sheet according to 1) or 2), comprising 0% by weight and containing 5 to 25 parts by weight of a plasticizer (B) based on 100 parts by weight of the polymer component (A). 4) The bubble sheet according to 3), wherein the aliphatic polyester (a2) is polybutylene succinate.

5) The plasticizer (B) is at least one selected from the group consisting of aliphatic polybasic acid esters, aliphatic polyhydric alcohol esters, and oxyacid esters.
The bubble sheet according to 3) or 4). 6) The plasticizer (B) is acetyl tributyl citric acid,
The bubble sheet according to 5), which is at least one selected from the group consisting of triacetin, dibutyl sebacate, and triethylene glycol diacetate. 7) The resin composition comprises a polymer component (A) and a plasticizer (B)
Contains at least one inorganic filler selected from the group consisting of talc, magnesium silicate, calcium carbonate, aluminum powder, silica and kaolinite in an amount of 0.1 to 10 parts by weight with respect to 100 parts by weight of the total amount of 1) ~
6) The bubble sheet according to the above.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. [Polylactic acid (al)] In the present invention, polylactic acid (a)
Specific examples of lactic acid as a raw material of l) include L-lactic acid and D-lactic acid.
-Lactic acid, DL-lactic acid or a mixture thereof, or lactide which is a cyclic dimer of lactic acid. However, when the obtained polylactic acid is used by mixing L-lactic acid and D-lactic acid, it is necessary that either L-lactic acid or D-lactic acid is 75% by weight or more.

The polylactic acid (a) used in the present invention
As a specific example of the production method 1), for example, a method in which lactic acid or a mixture of lactic acid and an aliphatic hydroxycarboxylic acid is used as a raw material and subjected to direct dehydration polycondensation (for example, USP 5,3
10,865), a ring-opening polymerization method in which a cyclic dimer of lactic acid (lactide) is melt-polymerized (for example, a production method disclosed in US Pat. No. 2,758,987), Cyclic 2 of lactic acid and aliphatic hydroxycarboxylic acid
Lactide or glycolide and ε-caprolactone in the presence of a catalyst in the presence of a catalyst in a ring-opening polymerization method (for example, the production method disclosed in US Pat. No. 4,057,537), lactic acid, and fat. For directly dehydrating and polycondensing a mixture of an aliphatic dihydric alcohol and an aliphatic dibasic acid (for example, the production method disclosed in US Pat. No. 5,428,126), A method of condensing a polymer with an aromatic dibasic acid in the presence of an organic solvent (for example, a production method disclosed in European Patent Publication No. 0712880 A2), and the like. Not limited. Further, a small amount of an aliphatic polyhydric alcohol such as glycerin, an aliphatic polybasic acid such as butanetetracarboxylic acid, and a polyhydric alcohol such as a polysaccharide may coexist and may be copolymerized. The molecular weight may be increased by using a binder (polymer chain extender) such as a diisocyanate compound.

[Aliphatic polyester (a2)] The aliphatic polyester (a2) in the present invention has a biodegradability which can be produced by variously combining an aliphatic hydroxycarboxylic acid, an aliphatic dihydric alcohol and an aliphatic dibasic acid. It is a polymer. As a method for producing the aliphatic polyester (a2), a method similar to the method for producing the polylactic acid (a1) can be used, but the method is not limited thereto.

[Aliphatic hydroxycarboxylic acid] Specific examples of the aliphatic hydroxycarboxylic acid include glycolic acid,
Examples thereof include 3-hydroxybutyric acid, 4-hydroxybutyric acid, 3-hydroxyvaleric acid, 4-hydroxyvaleric acid, and 6-hydroxycaproic acid. Further, cyclic esters of aliphatic hydroxycarboxylic acids, for example, glycolic acid Examples include glycolide which is a dimer and ε-caprolactone which is a cyclic ester of 6-hydroxycaproic acid. These can be used alone or in combination of two or more.

[Aliphatic dihydric alcohol] Specific examples of the aliphatic dihydric alcohol include ethylene glycol, diethylene glycol, triethylene glycol, and the like.
Polyethylene glycol, propylene glycol, dipropylene glycol, 1,3-butanediol, 1,4
-Butanediol, 3-methyl-1,5-pentanediol, l, 6-hexanediol, 1,9-nonanediol, neopentyl glycol, polytetramethylene glycol, 1,4-cyclohexanedimethanol, 1 ,
4-benzenedimethanol and the like. They are,
They can be used alone or in combination of two or more.

[Aliphatic dibasic acid] Specific examples of the aliphatic dibasic acid include succinic acid, oxalic acid, malonic acid, and the like.
Examples include glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanoic acid, dodecaneniic acid, phenylsuccinic acid, 1,4-phenylenediacetic acid, and the like. These can be used alone or in combination of two or more.

In the present invention, the aliphatic polyester (a
2) is a biodegradable aliphatic polyester having a melting point of 80 ° C to 250 ° C, which can be produced by variously combining the above-described aliphatic hydroxycarboxylic acid, aliphatic dihydric alcohol and aliphatic dibasic acid. There are no restrictions.
Particularly, a soft aliphatic polyester having crystallinity is preferable. When the melting point of the aliphatic polyester is lower than 80 ° C., the heat resistance of the resulting polylactic acid-based resin composition decreases,
Conversely, if the temperature is higher than 250 ° C., the melting temperature at the time of mixing and pelletizing with polylactic acid becomes high, so that the polylactic acid component tends to be deteriorated or colored, which is not preferable.

Preferred aliphatic polyesters include polyethylene oxalate, polybutylene oxalate,
Examples thereof include polyneopentyl glycol oxalate, polyethylene succinate, polybutylene succinate, polyhydroxybutyric acid, and a copolymer of β-hydroxybutyric acid and β-hydroxyvaleric acid, with polyethylene succinate and polybutylene succinate being particularly preferred.
Further, these aliphatic polyesters may have a polymer chain extended by a binder such as diisocyanate, a small amount of an aliphatic polyhydric alcohol such as glycerin, and a small amount of fatty acid such as butanetetracarboxylic acid. Copolymerization may be carried out in the presence of polyhydric alcohols such as group polybasic acids and polysaccharides.

The weight average molecular weight (Mw) and molecular weight distribution of the polylactic acid (al) and the aliphatic polyester (a2) are not particularly limited as long as they can be molded. The weight average molecular weight of the polylactic acid (al) and the aliphatic polyester (a2) used in the present invention is not particularly limited as long as it shows substantially sufficient mechanical properties, but generally, the weight average molecular weight ( Mw), preferably from 1 to 1,000,000, more preferably from 3 to 500,000, even more preferably from 50,000 to 300,000. In general, when the weight average molecular weight (Mw) is smaller than 10,000, mechanical properties are not sufficient. On the contrary, when the molecular weight exceeds 1,000,000, handling becomes difficult and production cost becomes uneconomical. Or may be.

[Polymer Component (A)] The polymer component (A) shown in the present invention is obtained by adding and mixing an aliphatic polyester (a2) to polylactic acid (al) for the purpose of imparting softness, particularly heat resistance. Things. The mixing ratio of the polymer component (A) 10
90 parts by weight of polylactic acid (al) / 0 parts by weight /
10 to 50 parts by weight of the aliphatic polyester (a2) is good,
Preferably it is 85 to 55 parts by weight / 15 to 45 parts by weight, more preferably 80 to 60 parts by weight / 20 to 40 parts by weight. If the polylactic acid component exceeds 90 parts by weight, the flexibility may be insufficient. On the other hand, even if a method of softening with a plasticizer described later is used, a large amount of a plasticizer is required, and as a result, the heat resistance of the composition is reduced, and bleeding of the plasticizer and blocking of films are prevented. Problems may occur. Conversely, if the polylactic acid component is 5
If less than 0 parts by weight, there is a tendency that easily decomposable and mold resistance in the compost having polylactic acid is reduced, for example,
It may not be used for applications that come into contact with food such as tableware packaging bags.

[Plasticizer (B)] In the present invention, it is necessary to further add a plasticizer for the purpose of imparting the desired flexibility (elastic modulus of 1000 MPa or less) to the polymer component (A). The plasticizer (B) used in the present invention needs to have biodegradability and have good compatibility with the polymer component (A). Examples of such a plasticizer include aliphatic polybasic acid esters, ethers and esters of aliphatic polyhydric alcohols, and oxyacid esters.

Examples of the aliphatic polybasic acid ester include dimethyl adipate, di-2-ethylhexyl adipate, diisobutyl adipate, dibutyl adipate, diisodecyl adipate, dibutyl diglycol adipate, di-2-ethylhexyl adipate, dibutyl sebacate and dibutyl sebacate. -2-ethylhexyl sebacate and the like.

Examples of the aliphatic polyhydric alcohol ethers and esters include diethylene glycol dibenzoate, diethylene glycol monomethyl ether, diethylene glycol dimethyl ether, diethylene glycol monoethyl ether, diethylene glycol diethyl ether, diethylene glycol monobutyl ether, diethylene glycol dibutyl ether, diethylene glycol monohexyl ether, Polydiethylene glycol monooleyl ether, triethylene glycol diacetate, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether,
Polydiethylene glycol monooleyl ether, triacetin, glycerin tripropionate and the like can be mentioned.

Examples of the oxyacid esters include methyl acetyl ricinoleate, butyl acetyl ricinoleate, and acetyl tributyl citric acid. In particular, triacetin, acetyl tributyl citric acid, dibutyl sebacate, and triethylene glycol diacetate are particularly excellent in compatibility with the polymer component (A) and are preferably used. These can be used as one kind or as a mixture of two or more kinds.

The amount of the plasticizer (B) to be added is 5 to 25 parts by weight, preferably 7 to 20 parts by weight, more preferably 10 to 18 parts by weight, based on 100 parts by weight of the polymer component (A). If the amount of the plasticizer is less than 5 parts by weight, the plasticizing effect may be insufficient and the desired flexibility may not be provided. Conversely, if the amount is more than 25 parts by weight, the heat resistance of the composition may be poor, or the plasticizer may be inferior. Bleed-out may occur.

The polylactic acid resin composition according to the present invention comprises:
Various additives (antioxidants, ultraviolet absorbers, heat stabilizers, flame retardants, internal mold release agents, inorganic additives, antistatic agents) depending on the purpose (for example, improvement in tensile strength, heat resistance, weather resistance, etc.) , A surface wetting improving agent, an incineration aid, a lubricant such as a pigment) and the like. For example, in inflation molding and T-die extrusion molding, it is recommended to add an inorganic additive or a lubricant (aliphatic carboxylic acid amide) in order to improve blocking prevention and slipperiness of a film, a sheet and a bubble sheet.

[Lubricants (aliphatic carboxylic acid amides)] Aliphatic carboxylic acid amides include "10889 chemical products (1
989, Kagaku Kogyo Nippo, Nihonbashi-hama-cho, Chuo-ku, Tokyo) on page 389, right column to page 391, left column. All the descriptions are incorporated as a part of the disclosure of the specification of the present application by explicitly citing the cited documents and the cited range, and by referring to the explicitly cited ranges, the matters or disclosures described in the specification of the present application are all Items that can be directly and unambiguously derived by the trader are disclosed.

Specific examples of the aliphatic carboxylic acid amide include, for example, oleic acid amide, stearic acid amide,
Erucamide, behenic amide, N-oleyl palmitamide, N-stearyl erucamide, N, N '
-Ethylene bis (stearamide), N, N'-methylene bis (stearamide), methylol stearamide, ethylene bisoleic acid amide, ethylene bisbehenic acid amide, ethylene bis stearic acid amide,
Ethylene bislaurate amide, hexamethylene bisoleate amide, hexamethylene bisstearate amide, butylene bisstearate amide, N,
N'-dioleyl sebacic amide, N, N'-dioleyl adipamide, N, N'-distearyl adipamide, N, N'-distearyl sebacamide, m-xylylene bis stearamide , N, N '
-Distearyl isophthalamide, N, N'-distearyl terephthalamide, N-oleyl oleamide, N-stearyl oleamide, N-stearyl erucamide, N-oleyl stearamide,
N-stearyl stearamide, N-butyl-N '
Stearyl urea, N-propyl-N ′ stearyl urea,
N-allyl-N 'stearyl urea, N-phenyl-N'
Examples include stearyl urea, N-stearyl-N 'stearyl urea, dimethitol oil amide, dimethyl laurate amide, dimethyl stearate amide and the like.
In particular, oleic acid amide, stearic acid amide, erucic acid amide, behenic acid amide, N-oleyl palmitamide, and N-stearyl erucic acid amide are preferably used. These may be one kind or a mixture of two or more kinds.

[Addition amount of lubricant (aliphatic carboxylic acid amide)] The addition amount of the aliphatic carboxylic acid amide is preferably 0.05 to 10.0 parts by weight, based on 100 parts by weight of the polymer component (A). Is 0.1 to 7.0 parts by weight, more preferably 0.3 to 5.0 parts by weight, most preferably 0.5 to 5.0 parts by weight.
3.0 parts by weight is preferred. As with the case of the inorganic additive, the amount of the additive is appropriately selected from the optimum amount that the moldability of the target film, the blocking resistance of the obtained film, sheet and bubble sheet, and the favorable slip property are good. You.

In the present invention, an inorganic filler having a controlled particle size can be added for the purpose of improving the blocking properties of the film, sheet and bubble sheet. Specific examples of the inorganic filler include, for example, talc, magnesium silicate, calcium carbonate, aluminum powder, silica, kaolinite and the like. The particle size of the agent is 50 μm
Or less, preferably 30 μm or less, more preferably 20 μm
m, more preferably 15 μm or less, and most preferably 10 μm or less. If the particle size is larger than 50 μm, defects may occur at the interface between the film and the additive, and bubbles in the resin sheet may be easily released. The amount of the inorganic filler to be added is 0.1 to 100 parts by weight of the polylactic acid-based resin composition.
The amount is from 1 to 10.0 parts by weight, preferably from 0.5 to 7.0 parts by weight, more preferably from 1.0 to 5.0 parts by weight, and an optimum amount for obtaining the desired effect is appropriately selected.

[Polylactic acid-based resin composition] As a method for producing a lactic acid-based resin composition, a polylactic acid (al), an aliphatic polyester, and a plasticizer (B), if necessary, other additives may be mixed with a high-speed stirrer or a low-speed mixer. After uniformly mixing using a stirrer or the like, a method of melting and kneading with a single-screw or multi-screw extruder having sufficient kneading ability can be adopted. Usually, the shape of the resin composition according to the present invention is preferably a pellet, a rod, a powder, or the like.

The bubble sheet of the present invention is a flexible sheet composed of the above-described resin composition and having a large number of protrusions or protrusions on one surface. The shape, size, number of projections per unit area, and the like are not particularly limited, and are appropriately selected according to the purpose. Usually, the height of the protrusions or protrusions is 1 to 18 mm, generally 3.3 to 1
About 3 mm, width or diameter is 2 to 45 mm, generally 3 to 37 mm, and the area occupied by the projections or protrusions is 20 to 90%, generally 60 to 85% per sheet surface Kong. The shape of the convex protrusions of the bubble sheet is not particularly limited, but is usually a semicircular shape, a columnar shape, an elliptical shape, or the like. Within the above-mentioned range, functions as a packaging material, a heat insulating material, a sound absorbing material, a material for civil engineering and construction, and a material for agricultural use can be sufficiently exhibited.

The base film thickness of the bubble sheet is not particularly limited, and is appropriately selected according to the purpose. The thickness of the projections or protrusions is not particularly limited, and is appropriately selected depending on the purpose. Usually, the thickness of the base sheet of the bubble sheet is 50 to 300 μm.
m, and the thickness of the projections or protrusions is 25 to 150 μm.

A typical embodiment of the bubble sheet of the present invention is a composite sheet having hollow projections or protrusions formed by laminating a base sheet and an embossed sheet provided with a large number of uneven portions by embossing.

The method for producing the bubble sheet of the present invention includes:
Polylactic acid shown above, aliphatic polyester, a specific plasticizer, in some cases other plasticizers, a resin composition mixed with an inorganic filler, mixed using a general mixer or extruder, pelletized After this, the desired resin sheet can be obtained with a usual molding machine and molding method, and there is no limitation on the molding machine or molding method. For example, as a specific method of forming a resin sheet, a resin composition is formed using a normal inflation molding machine or a T-die extruder, and then a flat sheet is formed and then a bubble sheet is formed. Method of forming a foam sheet (Japanese Patent Publication No. 54-36)
617).

In producing the foam sheet of the present invention, the base sheet used as a raw material is the same as the conventional polyethylene resin sheet at a temperature of approximately 100 to 120 ° C.
Embossing is possible in the temperature range of ~ 100 ° C, and the welding temperature of the molded embossed sheet and base sheet is 60-170 ° C, compared to 120-150 ° C for polyethylene resin. Excellent workability.

Also, when a composite sheet is manufactured by laminating kraft paper or the like on one or both sides of the bubble sheet,
In the case of polyethylene resin, extrude polyethylene from the T-die of the extruder at a temperature of 300 ° C or more and bond it to kraft paper, or lower the temperature of the embossing roll to 280 ° C or less and preheat the kraft paper at a temperature of about 60 ° C in advance. In general, the base sheet and the kraft paper of the raw materials are directly heated at a temperature of 180 to 250 ° C.
Welding is possible at a pressure of 0.1 to 0.5 kg / cm ² . As for the laminating conditions, the composite sheet can be easily bonded at a relatively low temperature and in a wide temperature range, so that a composite sheet having good workability and stable can be produced.

An embodiment of the method for producing a bubble sheet according to the present invention will be described below. 1) Production of Base Sheet A resin composition comprising polylactic acid, an aliphatic polyester, and a plasticizer is formed into a base sheet having a thickness of 15 to 300 μm. 2) Production of embossed sheet Just like the production of the base sheet, the thickness is 15 to 300 μm.
m sheets are manufactured. The sheet is held in a thermostat or heated and softened to a temperature of 50 to 100 ° C. by a hot roll. Next, the heat-softened sheet is wrapped around a temperature-controlled embossing roll, and a pressure reduction degree of 1
0 to 400 mmHg, preferably 20 to 100 mmHg
Then, an embossed sheet having a concave portion on the entire peripheral surface is formed by vacuum forming. Here, as the embossing roll, for example, a roll having a depth of 5 mm, a diameter of 9.5 mm, a number of holes of 9,720 / m ² , and each of which has a vacuum hole capable of being vacuum formed is used. used.

3) Manufacture of bubble sheet The embossed sheet is separately heated to 60 to 170 by a hot roll.
A base sheet having a thickness of 15 to 300 μm heated and softened to a temperature of ° C. is welded and cooled to produce a foam sheet.
In this case, it is general that the base sheet is continuously heat-welded to the flat portion of the embossed sheet in the process of “2) Production of embossed sheet”.

[0042]

The present invention will be described more specifically with reference to the following examples. The weight average molecular weight (Mw) in the examples was determined by gel permeation chromatography (GPC) (column temperature; 40 ° C., chloroform solvent) in comparison with a polystyrene standard sample. In Examples and Comparative Examples, the foam sheets were subjected to the following tests 1) to 5) and evaluated. 1) Degradability test A test piece was buried in soil at a temperature of 35 ° C and a water content of 30%.
The appearance and weight loss rate after a month were determined. 2) Mold resistance test A test piece was placed on an inorganic agar medium according to JIS Z-2911, and a spore suspension of five test bacteria was spray-inoculated.
After culturing at 30 ° C., the growth of mold with time was observed.

3) Compressive strength A foam sheet of 120 × 120 mm is compressed to half of the initial thickness and held in this state for 1 minute in accordance with the Defense Agency standard (draft) test method for foamed plastic film cushioning material for packaging. Then, the burst of the bubbles was observed. 4) Flexibility (Flexibility) The elastic modulus of the blown films obtained in Examples and Comparative Examples was determined according to JIS K6732.

5) Heat resistance The blown films obtained in Examples and Comparative Examples were subjected to 80 ° C./500 g load according to JIS Z0219.
The state of the film when it was kept under the conditions described above was observed. * Bleeding of plasticizer ○ ・ ・ ・ No bleed × ・ ・ ・ Bleed * Film blocking ○ ・ ・ ・ No blocking △ ・ ・ ・ Slightly blocking × ・ ・ ・ Blocking

Synthesis Example 1 In a 500 ml four-neck flask equipped with a stirrer and a thermometer, 104.3 g of 90% monolactic acid and diphenyl ether 2 were added.
25.0 g and 2.0 g of metallic tin were added, and 130 ° C./140
The mixture was heated and stirred at 7 mmHg for 7 hours while distilling the generated water out of the system. A Dean Stark Trap was attached thereto, and azeotropic dehydration was performed at 140 ° C./130 mmHg for 8 hours. Then, a drying tube filled with 40 g of molecular sieves 3A was attached, and the distilled solvent was returned to the reactor through the drying tube. At 130 ° C / 17 mmHg
Heated to reflux for an hour. After cooling, the reaction mass was dissolved in 600 ml of chloroform, added to 4 liters of acetone, reprecipitated, and the precipitated solid was filtered off. Next, 500 ml of an isopropyl alcohol (hereinafter, referred to as IPA) solution in which 5 g of hydrochloric acid is dissolved is added to the filter cake, and the mixture is stirred for 30 minutes. Further, 500 ml of IPA is added.
The wet cake obtained at 60 ° C / 100mmH
g for 15 hours. The obtained solid was polylactic acid in the form of a white powder, the yield was 69.1 g, the yield was 92.2%, and the weight average molecular weight (Mw) was 29.5 million.

Synthesis Example 2 In a 1000 ml four-neck flask equipped with a stirrer and a thermometer, 730.3 g of 90% monolactic acid and 5.0 g of zinc powder were added, and the produced water was distilled out of the system at 130 ° C./50 mmHg for 3 hours. After the mixture was heated and stirred while being discharged, the pressure was further reduced to 5 mmHg. At this time, lactide, which is a cyclic dimer of white lactic acid, was distilled off. The obtained lactide was recrystallized from ethyl acetate to obtain 420.0 g of purified ratatide. The yield was 80.0%. In a 500 ml reactor equipped with a thermometer, a stirring blade, a nitrogen inlet tube, and a reaction mass outlet at the bottom, 200 g of purified lactide and 0.02 tin otatanate were added.
g and lauryl alcohol (0.06 g) were heated and stirred at 200 ° C./10 mmHg for 2 hours under a nitrogen stream. After completion of the reaction, a melt of polylactic acid was extracted from the lower outlet, cooled, and cut with a pelletizer. The obtained polylactic acid had a yield of 164.0 g, a yield of 82.0%, and a weight average molecular weight (Mw) of 138,000.

Synthesis Example 3 In a reactor equipped with a Dien-Stark trap,
50.5 kg of 1,4-butanediol and succinic acid
After 5 kg of tin powder and 45 g of tin powder were charged, water was distilled off while stirring at 100 ° C. for 3 hours, and the mixture was further stirred at 150 ° C./50 mmHg for 2 hours to oligomerize. 385 kg of diphenyl ether is added to this oligomer,
An azeotropic dehydration reaction of 5 mmHg was performed, and the distilled water and the solvent were separated by a water separator, and only the solvent was returned to the reactor. Two hours later, the organic solvent to be returned to the reactor was passed through a column filled with 50 kg of molecular sheep 3A, and then returned to the reactor. The reaction was carried out at 130 ° C./17 mmHg for 15 hours, and the weight average molecular weight (Mw) was obtained. 14,000 polybutylene succinate (hereinafter abbreviated as PSB) solution was obtained. After 180 kg of dehydrated diphenyl ether was added to this solution for dilution, the solution was cooled to 40 ° C., and the precipitated crystals were filtered. 200 kg of 0.5N HCl and 200 kg of ethanol were added to this powder, stirred at 25 ° C. for 1 hour, filtered, dried at 60 ° C./50 mmHg, and dried with PSB 91.5%.
kg (94.8% yield). The weight average molecular weight (Mw) of this PSB was 138,000.

Example 1 80 kg of polylactic acid obtained in the same manner as in Synthesis Example 1 and PSB20 obtained in Synthesis Example 3 as an aliphatic polyester
kg, acetyltributyl citric acid 17k as plasticizer
g, 3.0 kg of silica as an inorganic filler and 1.0 kg of erucamide as a lubricant were mixed well with a Henschel mixer, and the resin temperature was 170 to 220 ° C. using a twin screw extruder.
And extruded into pellets. This pellet is heated at 70 ° C / 1
After drying for 5 hours, the extruder of 40mmΦ
And inflation molding was performed under the conditions of an extrusion temperature of 180 to 200 ° C. and an expansion ratio of 2, to obtain a sheet having a thickness of 40 μm. The sheet was heated and softened by a roll controlled at a temperature of 80 ° C., and further embossed roll (hole depth 5 mm, hole diameter 9.5 m) controlled at a reduced pressure of 50 mmHg.
m, number of holes 9720 / m ² ). At this time, 1
A base sheet having a thickness of 40 μm passed through a smooth roll heated to 20 ° C. is wound around the embossed sheet and welded to a flat portion of the embossed sheet, and a 5 mm-thick bubble sheet 1 of FIG. (About 70% per area).

1) Degradability test The shape collapsed and became loose. 2) Mold resistance test No mold growth was observed even after 3 months. 3) Compressive strength There was no burst of bubbles in the bubble sheet. 4) Flexibility Flexibility and flexibility (the elastic modulus of the sheet was 400 MPa) were superior to the foam sheet manufactured in Comparative Example 1. The winding of the bubble sheet was good without bursting the bubbles. 5) Heat resistance * Bleeding of plasticizer ... * * Blocking of film ... *

Example 2 70 kg of polylactic acid obtained in Synthesis Example 2, 30 kg of Bionole # 3001 (trade name, manufactured by Showa Kogyo KK) as an aliphatic polyester, and 15.0 kg of triethylene glycol diacetate as a plasticizer A bubble sheet was prepared in the same manner as in Example 1, except that 5.0 kg of silica and 1.0 kg of erucamide were used as the inorganic filler. 1) Degradability test The shape was disintegrated and it was broken apart. 2) Mold resistance test No mold growth was observed even after 3 months. 3) Compressive strength There was no burst of bubbles in the bubble sheet. 4) Flexibility Flexibility and flexibility (the elastic modulus of the sheet was 350 MPa) were superior to the foam sheet manufactured in Comparative Example 1. The winding of the bubble sheet was also good. 5) Heat resistance * Bleeding of plasticizer ... * * Blocking of film ... *

Example 3 60.0 kg of polylactic acid obtained in Synthesis Example 2 and Bionole # 3001 (trade name, manufactured by Showa High Polymer Co., Ltd.) 40 k
g, 13 kg of triacetin as a plasticizer and 2.0 kg of silica as an inorganic filler were used to prepare a foam sheet in the same manner as in Example 1. 1) Degradability test The shape was disintegrated and it was broken apart. 2) Mold resistance test No mold growth was observed even after 3 months. 3) Compressive strength There was no burst of bubbles in the bubble sheet. 4) Flexibility Flexibility and flexibility (the elastic modulus of the sheet was 350 MPa) were superior to the foam sheet manufactured in Comparative Example 1. The winding of the bubble sheet was also good. 5) Heat resistance * Bleeding of plasticizer ... * * Blocking of film ... *

Example 4 65.0 kg of polylactic acid obtained in Synthesis Example 2 and Bionole # 3001 [trade name, manufactured by Showa High Polymer Co., Ltd.] 35 k
g, 15 kg of dibutyl sebacate as a plasticizer, and 3.0 kg of silica as an inorganic filler, to prepare a foam sheet in the same manner as in Example 1. 1) Degradability test The shape was disintegrated and it was broken apart. 2) Mold resistance test No mold growth was observed even after 3 months. 3) Compressive strength There was no burst of bubbles in the bubble sheet. 4) Flexibility Flexibility and flexibility (the elastic modulus of the sheet was 350 MPa) were superior to the foam sheet manufactured in Comparative Example 1. The winding of the bubble sheet was also good. 5) Heat resistance * Bleeding of plasticizer ... * * Blocking of film ... *

Comparative Example 1 100 kg of the polylactic acid obtained in Synthesis Example 1 and 0.15 kg of silica as an inorganic filler were thoroughly mixed with a Henschel mixer, and the resin temperature was 170 to 220 ° C. using a twin screw extruder.
And extruded into pellets. A bubble sheet was obtained in the same manner as in Example 1. 1) Degradability test The shape was disintegrated and it was broken apart. 2) Mold resistance test No mold growth was observed even after 3 months. 3) Compressive strength Bubbles were ruptured. 4) Flexibility Compared with the foam sheet manufactured in Example 1, the flexibility and the flexibility (the elastic modulus of the sheet was 1950 MPa) were inferior, and the bubbles burst when the foam sheet was wound up. 5) Heat resistance * Bleeding of plasticizer ... * * Blocking of film ... x

Comparative Example 2 The procedure of Example 1 was repeated except that 80 kg of the polylactic acid obtained in Synthesis Example 2, 20 kg of acetyltributylcitric acid as a plasticizer, 3.0 kg of silica as an inorganic filler, and 1 kg of erucamide as a lubricant were used. To create a bubble sheet. 1) Degradability test The shape was disintegrated and it was broken apart. 2) Mold resistance test No mold growth was observed even after 3 months. 3) Compressive strength There was no burst of bubbles in the bubble sheet. 4) Flexibility Flexibility and flexibility (the elastic modulus of the sheet was 250 MPa) were superior to the foam sheet manufactured in Comparative Example 1. The winding of the bubble sheet was also good. 5) Heat resistance * Bleeding of plasticizer ... x * Blocking of film ... x

Comparative Example 3 85 kg of the polylactic acid obtained in Synthesis Example 2, 15 kg of PSB as an aliphatic polyester, 30 kg of acetyl tributyl citric acid as a plasticizer, and silica as an inorganic filler.
Using 0 kg and erucamide 1 kg as a lubricant, a bubble sheet was prepared in the same manner as in Example 1. 1) Degradability test The shape was disintegrated and it was broken apart. 2) Mold resistance test No mold growth was observed even after 3 months. 3) Compressive strength There was no burst of bubbles in the bubble sheet. 4) Flexibility Flexibility and flexibility (the elastic modulus of the sheet was 250 MPa) were superior to the foam sheet manufactured in Comparative Example 1. The winding of the bubble sheet was also good. 5) Heat resistance * Bleeding of plasticizer ... x * Blocking of film ... x

Comparative Example 4 Using 40 kg of the polylactic acid obtained in Synthesis Example 2, 60 kg of PSB as an aliphatic polyester, 1.0 kg of silica as an inorganic filler, and 1 kg of erucamide as a lubricant,
A bubble sheet was prepared in the same manner as in Example 1. 1) Degradability test The shape was disintegrated and it was broken apart. 2) Mold resistance test After 3 months, mold growth was observed. 3) Compressive strength There was no burst of bubbles in the bubble sheet. 4) Flexibility The flexibility and flexibility (the elastic modulus of the sheet was 900 MPa) were superior to the foam sheet manufactured in Comparative Example 1, but the winding of the foam sheet was slightly poor. 5) Heat resistance * Bleeding of plasticizer ... * * Blocking of film ... *

Comparative Example 5 Using 80 kg of polylactic acid obtained in Synthesis Example 2, 20 kg of PSB as an aliphatic polyester, 17 kg of liquid paraffin as a plasticizer, 3.0 kg of silica as an inorganic filler, and 1 kg of erucamide as a lubricant, As in Example 1, but the bleeding of the plasticizer was so severe that a bubble sheet could not be obtained.

Comparative Example 6 80 kg of polylactic acid obtained in Synthesis Example 2, 20 kg of PSB as an aliphatic polyester, and dioctyl phthalate 17
kg, 3.0 kg of silica as an inorganic filler and 1 kg of erucamide as a lubricant were used in the same manner as in Example 1, but the bleeding of the plasticizer was so severe that a bubble sheet could not be obtained.

Comparative Example 7 80 kg of polylactic acid obtained in Synthesis Example 2, 20 kg of PSB as an aliphatic polyester, 17 kg of trimellitic acid,
3.0 kg of silica was used as an inorganic filler and 1 kg of erucamide was used as a lubricant. The procedure was the same as in Example 1, but the bleeding of the plasticizer was so severe that a bubble sheet could not be obtained.

Comparative Example 8 80 kg of polylactic acid obtained in Synthesis Example 2, 20 kg of PSB as an aliphatic polyester, 17 k of ethyl stearate
g, 3.0 kg of silica as an inorganic filler and 1 kg of erucamide as a lubricant were used as in Example 1, but
The bleeding of the plasticizer was so severe that a bubble sheet could not be obtained.

Comparative Example 9 80 kg of polylactic acid obtained in Synthesis Example 2, 20 kg of PSB as an aliphatic polyester, 17 k of epoxidized soybean oil
g, 3.0 kg of silica as an inorganic filler and 1 kg of erucamide as a lubricant were used as in Example 1, but
The bleeding of the plasticizer was so severe that a bubble sheet could not be obtained.

Comparative Example 10 80 kg of polylactic acid obtained in Synthesis Example 2, 20 kg of PSB as aliphatic polyester, 17 kN of tributyl phosphate
g, 3.0 kg of silica as an inorganic filler and 1 kg of erucamide as a lubricant were used as in Example 1, but
The bleeding of the plasticizer was so severe that a bubble sheet could not be obtained.

Comparative Example 11 A low-density polyethylene 40 μm film was heated and softened with a roll whose temperature was controlled to 40 ° C., and the embossing roll depth was controlled to a degree of vacuum of 50 mmHg.
mm, hole diameter 9.5 mm, number of holes 9720 / m2). At this time, a base sheet having a thickness of 40 μm passed through a smooth roll heated to 150 ° C. was wound around the embossed sheet, and was welded to a flat portion of the embossed sheet. (The number is about 70% per unit area). 1) Degradability test Even after three months, the shape was maintained. 2) Mold resistance test No mold growth was observed even after 3 months. 3) Compressive strength There was no burst of bubbles in the bubble sheet. 4) Flexibility It was superior to the foam sheet manufactured in Comparative Example 1 in flexibility and flexibility (the elastic modulus of the sheet was 150 MPa). 5) Heat resistance * Bleeding of plasticizer ... * * Blocking of film ... *

[0064]

According to the present invention, the buffering performance, decomposability, and mold resistance are excellent, and in the production thereof, the moldability and yield are remarkably improved, and the flexibility and flexibility are remarkably improved. An improved foam sheet can be provided.
In addition, the foam sheet according to the present invention is a composite sheet composed of the foam sheet and kraft paper, which is suitable as a material for transportation such as a cardboard, an envelope and the like.

[Brief description of the drawings]

FIG. 1 is a perspective view of a bubble sheet as an example of the present invention.

[Explanation of symbols]

 1 ... bubble sheet 1a ... protrusion or protrusion (bubble)

Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI B65D 81/03 B65D 81/14 C // C08L 67:00 (72) Inventor Hisashi Aihara 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Mitsui Chemicals, Inc. (72) Inventor Ikuki Yoshida 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Prefecture Inside Mitsui Chemicals Co., Ltd. Masanobu 1190 Kasama-cho, Sakae-ku, Yokohama City, Kanagawa Prefecture Inside Mitsui Chemicals, Inc.

Claims (7)

[Claims] 1. A polylactic acid (al) having a melting point of 80 to 25.
A foam sheet composed of a polymer component (A) containing a biodegradable aliphatic polyester (a2) at 0 ° C. and a biodegradable plasticizer (B). 2. The foam sheet according to claim 1, wherein the foam sheet is a composite sheet formed by laminating an embossed sheet provided with a large number of uneven portions by embossing on at least one surface of a flat base sheet. 3. The polymer component (A) is polylactic acid (al).
90 to 50% by weight, and an aliphatic polyester (a2)
10 to 50% by weight, and the polymer component (A) 1
3. The foam sheet according to claim 1, wherein the plasticizer (B) is contained in an amount of 5 to 25 parts by weight based on 00 parts by weight. 4. The foam sheet according to claim 3, wherein the aliphatic polyester (a2) is polybutylene succinate. 5. The foam sheet according to claim 3, wherein the plasticizer (B) is at least one selected from the group consisting of an aliphatic polybasic acid ester, an aliphatic polyhydric alcohol ester, and an oxyacid ester. . 6. The foam sheet according to claim 5, wherein the plasticizer (B) is at least one selected from the group consisting of acetyl tributyl citric acid, triacetin, dibutyl sebacate, and triethylene glycol diacetate. 7. A resin composition comprising a group consisting of talc, magnesium silicate, calcium carbonate, aluminum powder, silica and kaolinite, based on 100 parts by weight of the total of the polymer component (A) and the plasticizer (B). The foam sheet according to claim 1, comprising 0.1 to 10 parts by weight of at least one inorganic filler selected from the group consisting of: