JPH08198992A - Foam of lactic acid copolyester - Google Patents

Abstract

PURPOSE: To obtain lactic acid copolyester foam which comprises the units obtained by dehydrative polycondensation of lactic acid and the units obtained by dehydrative polycondensation of a dicarboxylic acid and a diol, and is useful as table ware, vessels or industrial material because it is high macromolecular, biodegradable, flexible, shock-resistant and readily moldable. CONSTITUTION: A lactic acid type copolyester comprising the structural units obtained by dehydrative polycondensation of lactic acid and the structural units obtained by dehydrative polycondensation of a dicarboxylic acid such as sebacic acid and a diol such as 1,4-butanediol, a nucleating agent such as talc, a volative foaming agent such as butane and a decomposition type foaming agent such as azodicarbonamide are used in combination, kneaded in an extruder and foamed at 140-170 deg.C to give this foamed lactic acid copolyester which has a weight-average molecular weight of 20,000-400,000, biodegradability, sufficient flexibility and impact resistance and excellent moldability, thus is useful in a wide variety of applications.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention uses a lactic acid-based copolyester having a structure in which lactic acid, a dicarboxylic acid and a diol are dehydrated and condensed to provide sufficient flexibility, impact resistance, and excellent moldability and biodegradability. The present invention relates to a foam having the same.

The foam of the lactic acid-based copolyester of the present invention can be easily molded by a method such as match molding type vacuum molding and is useful as a food container, an industrial material, an industrial article and the like.

[Prior art]

Lactic acid-based polymers are highly safe, biodegradable, have a low calorific value when burned, and have been actively researched and developed in recent years as environmentally friendly polymers. Examples of the foam using a lactic acid-based polymer include JP-A-4-304244 and WO92 / 01.
737, Japanese Patent Publication No. 5-508669, Japanese Patent Publication No. 5
No. 5,140,361 is known.

They relate to polylactic acid itself or a foamed product of a copolymer of lactic acid and ε-caprolactone.
Polylactic acid foams have the drawbacks of poor elasticity and resilience, and brittleness against impact.The copolymer of lactic acid and ε-caprolactone is inferior in heat resistance. It was difficult to obtain, and there was a problem that it could only be used for limited purposes.

[0005]

The problem to be solved by the present invention is that it retains biodegradability, has sufficient flexibility, impact resistance and excellent moldability, and is suitable for various applications. It is to provide a useful lactic acid-based polymer foam.

[0006]

Means for Solving the Problems As a result of intensive investigations by the present inventors, by using a lactic acid-based copolyester having a weight average molecular weight of 20,000 to 400,000 including a structural unit obtained by dehydration condensation of dicarboxylic acid and diol, The present invention has been completed by obtaining a foam having flexibility and impact resistance while maintaining biodegradability and having excellent moldability.

[0007]

[Structure] That is, the present invention is to foam a lactic acid-based copolymer polyester having a weight average molecular weight of 20,000 to 400,000, which comprises a structural unit obtained by dehydration condensation of lactic acid and a structural unit obtained by dehydration condensation of dicarboxylic acid and diol. It is the body.

In the present invention, a lactic acid-based copolyester comprising a structural unit obtained by dehydration condensation of lactic acid, a structural unit obtained by dehydration condensation of dicarboxylic acid and a diol, a nucleating agent and a foaming agent are kneaded in an extruder. A method for producing a foam comprising a lactic acid-based copolyester, the method comprising foam-molding.

More specifically, the present invention uses a volatile foaming agent as a foaming agent, and a method for producing a foam made of a lactic acid-based copolymer polyester, and a volatile foaming agent as a foaming agent and a decomposition-type foaming agent. A method for producing a foam comprising a lactic acid-based copolymer polyester, which is characterized by being used in combination with an agent.

Further, the present invention is a method for producing a foam comprising a lactic acid type copolymer polyester, which is characterized in that a hydrocarbon is used as a volatile type foaming agent. The present invention also includes a method for producing a foam made of a lactic acid-based copolymer polyester, which is characterized in that azodicarbonamide is used as a decomposition-type foaming agent.

The present invention comprises a structural unit obtained by dehydration condensation of lactic acid and a structural unit obtained by dehydration condensation of dicarboxylic acid and diol, which is produced by the production method of the present invention, and has a weight average molecular weight of 20,000 to 400,000. It includes a foam made of a lactic acid-based copolymer polyester.

The resins used in the present invention will be described below in order. The lactic acid-based copolymer polyester having a weight average molecular weight of 20,000 to 400,000, which is composed of a structural unit obtained by dehydration condensation of lactic acid and a structural unit obtained by dehydration condensation of dicarboxylic acid and diol, used in the present invention is a cyclic lactic acid. Lactic acid-based product obtained by ring-opening copolymerization and transesterification of 25-99 parts of dimer lactide and 75-1 part of polyester composed of dicarboxylic acid component and diol component in the presence of a ring-opening polymerization catalyst. Copolymers,

A lactic acid copolymer obtained by transesterification of 25 to 99 parts of polylactic acid with 75 to 1 part of polyester composed of a dicarboxylic acid component and a diol component, and a total of equimolar amounts of dicarboxylic acid and diol. 75 to 1 part,
A lactic acid copolymer obtained by directly copolymerizing 25 to 99 parts of lactic acid with a weight average molecular weight of 20,000 to
It is a lactic acid-based copolyester of 400,000.

The lactide referred to in the present invention is a cyclic compound in which two lactic acid molecules are dehydrated and condensed, and the two lactic acid units constituting the lactide are L-lactide only and D-lactide only when D-only. , D- and L-forms are referred to as meso-lactide, and L-lactide and D-lactide are equivalent to DL-lactide.

In the present invention, in order to express particularly high thermophysical properties, the lactide is 7% of the total lactide.
The content of 5% or more is preferable, and the expression of higher thermophysical properties is preferably such that the lactide contains 90% or more of L-lactide in the total lactide.

The polyester as the raw material of the resin used in the present invention will be described. The production method is not particularly limited, but it is a polyester having a structure obtained by dehydration condensation of dicarboxylic acid and diol, and can be produced by dehydration / deglycol condensation or transesterification reaction.

The method for producing the lactic acid-based copolyester is not particularly limited, but specifically, lactide is added to polyester obtained by dehydration condensation of dicarboxylic acid and diol.
In the presence of a ring-opening polymerization catalyst, there are a method of carrying out a ring-opening copolymerization and a transesterification reaction, and a method of carrying out a transesterification reaction of a polyester obtained by dehydration condensation of a dicarboxylic acid and a diol and a polylactic acid.

Next, constituent components of the lactic acid-based copolymer will be sequentially described. The dicarboxylic acid component in the lactic acid-based copolyester is not particularly limited, but specifically, succinic acid, methylsuccinic acid, 2-methyladipic acid, methylglutaric acid, adipic acid, azelaic acid, sebacic acid,
Brassylic acid, dodecanedicarboxylic acid, cyclohexanedicarboxylic acid, phthalic acid, isophthalic acid, terephthalic acid,
Examples thereof include naphthalenedicarboxylic acid, dimer acid, maleic anhydride and fumaric acid.

The diol component in the lactic acid-based copolyester is not particularly limited as long as it is a diol, and specifically, ethylene glycol, propylene glycol, 1,2-butylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, 1,4-pentanediol, 1,5-pentanediol, 2,4-
Pentanediol, hexamethylene glycol, octanediol, neopentyl glycol, cyclohexanedimethanol, xylene glycol,

Diethylene glycol, triethylene glycol, polyethylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, dibutanediol, polytetramethylene glycol, 3-hydroxypivalyl pivalate ethylene glycol, hydrogenated bisphenol A and the like can be mentioned. .

Hexamethylene diisocyanate,
2,4-tolylene diisocyanate, 2,5-tolylene diisocyanate, toluene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, 1,5-naphthylene diisocyanate, isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, diisocyanate-modified polyether, diisocyanate modification Polyester, a compound obtained by modifying a polyhydric alcohol with a bifunctional isocyanate,

Polyurethane modified with polyvalent isocyanate, polyester modified with polyvalent isocyanate, or a urethane bond formed by a mixture thereof, trifunctional or higher functional (anhydrous) trimellitic acid, (anhydrous) pyromellitic acid,
A polyvalent carboxylic acid such as epicuron, a polyhydric alcohol such as trimethylolpropane and pentaerythritol may be contained as a constituent component.

Further, as a copolymerization component, a cyclic dimer of hydroxy acid such as glycolide or an intramolecular lactide, particularly ε-caprolactone, γ-valerolactone, γ-undecalactone, β-methyl-δ-valerolactone, etc. It may include a structure using the cyclic ester or the α-hydroxycarboxylic acid.

The lactic acid-based copolyester preferably has a molecular weight of a certain level or more, specifically, a weight average molecular weight of 20,000 to 400,000, more preferably 50,000 to 350,000. less than,
The foam of the present invention will be described.

In the method for producing the foam of the present invention, a volatile foaming agent or a decomposing foaming agent may be used. The volatile foaming agent here is a foaming agent that is foamed by volatilizing a foaming agent mixed and impregnated with resin.
The decomposable foaming agent refers to an agent that decomposes a foaming agent dispersed in a resin to generate and foam gas.

Specific volatile foaming agents used in the present invention include hydrocarbons (butane, pentane, etc.), freons (R-11, R-12), alternative freons (R-134a).
Etc. The hydrocarbon used in the present invention is preferably one having a low boiling point, specifically, a hydrocarbon having up to 6 carbon atoms.

The decomposable foaming agent used in the present invention is a decomposable foaming agent such as azozylbonamide, 4,4'-oxybisbenzenesulfonylhydrazide, azobisisobutyronitrile. Examples include a foaming agent and an inorganic foaming agent such as sodium bicarbonate and ammonium bicarbonate. In the present invention, any decomposable foaming agent may be used. Further, in the foam of the present invention, by using the volatile foaming agent and the decomposition foaming agent together, a foam having a higher expansion ratio and excellent flexibility can be obtained.

Further, an inert gas such as carbon dioxide gas, nitrogen, helium or argon may be impregnated and used as a volatile foaming agent, or may be mixed and dispersed in a resin in a gas state. These foaming agents may be used alone or in combination of two or more. Furthermore, a plasticizer, a solvent such as toluene, ethylbenzene, or xylene may be added as a foaming aid.

In the production of the foamed product of the present invention, a nucleating agent which serves as a core for foaming and is used for the purpose of controlling the foam diameter, a lubricant for suppressing shearing heat in a die during extrusion foaming, and coloring for coloring. Any additive such as an agent may be used. Specific examples of the nucleating agent include talc and sodium citrate, and examples of the lubricating agent include magnesium stearate, aluminum stearate, calcium stearate and the like.

As a specific method for producing the foam of the present invention, a bead-shaped resin impregnated with gas is heated and foamed in a mold, or is extruded by an extruder to foam, or decomposed with the resin. A method of heating and foaming a mixture of mold foaming agents in a press, in which a volatile foaming agent is press-fitted into the molten resin in an extruder, and the resin in which the foaming agent has melted is foamed when it exits the die. There is a method of obtaining a foam.

It is also possible to produce a laminate with a non-foamed material by a method such as lamination. In this case, the non-foam used may be the same resin as the foam or a different resin, but it is preferable to use a biodegradable resin.

As an extrusion foaming device used when forming a foamed sheet by extrusion foaming, a single-screw foaming extrusion device or two single-screw extruders are connected to each other to melt the resin and to blow the foaming agent in the first stage. There is a tandem type foam extruding device that press-fits and mixes and cools in a temperature range that does not solidify uniformly in the second stage.

The foam extruding apparatus used for producing the foam of the present invention may be a single-screw foam extruding apparatus, but a tandem type foam extruding apparatus is particularly preferable. With a single-screw foam extruder,
It is desirable that one screw has the function of two tandem-type foam extrusion machines, that is, a shape in which resin supply, melting, gas injection, mixing, and cooling are efficiently performed.

Further, as a specific shape, a ring for preventing gas leakage to the hopper side and a ring for preventing resin backflow from the die side are installed before and after the gas injection portion, and the ring is uniformly mixed. Installation of pins between both rings to
It is preferable to use a notch for flight in the mixing zone, or a dullage for the purpose of thorough mixing near the final part of the screw.

As the die, any one such as a circular die, a capillary die, a T die or the like may be used depending on the purpose. The heating method of the cylinder and die is an electric heater,
Either method of oil heating may be used, but it is desirable to heat the oil by providing a jacket on the die and the cylinder near the die so that the temperature can be precisely controlled.

In order to obtain a high-quality foam with a high expansion ratio, the foaming agent is vaporized in the mixture of the resin extruded from the die and the foaming agent, and rapidly formed into a foam. It is generally desirable to prevent the escape of the blowing agent by cooling it rapidly. For this reason, it is desirable to install a cooling device after the extruder, and there are a method of spraying a gas such as air and a method of passing or spraying through a liquid such as water.

When a circular die is used, it can be wound into a roll by installing a mandrel, a cutter, a take-up machine and a take-up machine. Further, in the production of the foam of the present invention, it is desirable to use a dried lactic acid-based copolyester, and in order to prevent the dried resin from absorbing moisture again, the feeder and the hopper are dried with nitrogen or the like. It is desirable to use a dry gas atmosphere.

It is still more preferable to connect a dryer to the extruder and supply the dried raw material resin without touching the outside air. The appropriate extrusion temperature varies depending on the molecular weight of the lactic acid-based copolyester used, the amount of residual lactide, and the type and amount of the volatile foaming agent, but is preferably a temperature at which it can flow.

The sheet-like foam of the present invention or a laminate of the non-foamed product can be molded into a food tray, a lunch box or the like by vacuum pressure molding or the like. It can also be used as a cushioning material or a fish box.

The lactic acid-based copolyester foam of the present invention is a packaging material, daily sundries, toys, food containers, industrial materials,
It is useful for a wide range of applications such as industrial products, and is particularly promising for food packaging materials because of its excellent biodegradability, flexibility, and moldability.

The lactic acid-based copolyester foam obtained in the present invention has a good biodegradability, and when it is discarded in the soil or dumped in the sea, it is hydrolyzed and decomposed by microorganisms. Decomposition in seawater also deteriorates the strength of the resin within a few months, and if it takes more time, it can be decomposed without maintaining its outer shape.

[0042]

EXAMPLES The present invention will be described in more detail below with reference to examples and comparative examples. All parts in the examples are on a weight basis unless otherwise specified.

The moldability test will be described. Lunch box mold (upper 225m)
m, width 165 mm, depth 35 mm) using a single-shot vacuum forming machine manufactured by Sanwa Kogyo Co., Ltd., to form a lunch box container under the conditions of a mold temperature of 35 ° C, an upper table heater of 400 ° C and a lower table heater not used. did. The molded product was evaluated according to the following four grades.

⊚: Good. ◯: Molding defects such as slight deformation and distortion are present. ●: There is some deformation such as deformation and distortion. X: There is a molding defect such as obvious deformation or distortion.

The biodegradability test was carried out by Shinki Gosei Co., Ltd., Composting container Tombo Miracle Component 10 with a capacity of 100 liters.
Type 0 is used, 50kg of garbage is put in it and 10cm
A sample of a foamed sheet having a size of 10 cm was placed, and further garbage was put into a thickness of about 5 cm. On top of this, 500 g of Nyxaminone, a fermentation accelerator manufactured by Aron Kasei Co., was sprinkled, and the apparatus was installed outdoors.

One month after the start of the test, the test piece was taken out and evaluated in the following four stages. ⊚: Tattered to a state where the original shape was not retained. ○: The original shape was retained, but it became brittle. Δ: Changes were observed, but decomposition did not proceed to the point of disintegration. X: No change at all.

In the drop strength test, a foamed sheet was molded into a lunch box (length 225 mm, width 165 mm, depth 35 mm),
The contents were put in this and dropped on the tile from a height of 1.5 m to examine the damage condition, and evaluated in the following 5 stages.

⊚: No damage occurred. ◯: Almost no damage. ●: Minor damage. Δ: Some damage. X: Large damage.

Reference Example 1 Aliphatic polyester (sebacic acid component: 50 mol%, 1,4-butanediol component: 50)
Molar%, weight average molecular weight 20,000 (polystyrene conversion) 5 parts, L-lactide 95 parts and toluene 15 parts as a solvent were added, and an inert gas atmosphere was added.
Both were melted and mixed at 1 ° C. for 1 hour, 0.03 parts of tin octanoate was added as a catalyst and reacted for 5 hours, taken out, cooled and pelletized, and volatile components were removed at 130 ° C. and 1 mmHg. The weight average molecular weight was 180,000 (in terms of polystyrene) (Resin A).

Reference Example 2 5 parts of an aliphatic polyester (50 mol% of succinic acid component, 25 mol% of ethylene glycol component, 25 mol% of propylene glycol component, weight average molecular weight of 20,000 (in terms of polystyrene)) was added with L-
Lactide 48 parts and DL-lactide 47 parts, and toluene 15 parts as a solvent were added, and both were melted and mixed at 170 ° C. for 1 hour under an inert gas atmosphere, and 0.03 part of tin octoate was added as a catalyst. And reacted for 5 hours.
After taking out, cooling and pelletizing, 130 ℃, 1mmHg
The volatile components were removed with. Weight average molecular weight is 170,000
It was 0 (polystyrene conversion) (resin B).

Reference Example 3 0.15 parts of pyromellitic dianhydride was added to 20 parts of aliphatic polyester (50 mol% sebacic acid component, 50 mol% propylene glycol component, weight average molecular weight 20,000 (in terms of polystyrene)). And agitate at 200 ° C. for 3 hours to react to give a weight average molecular weight of 1
A polymer of 0,000 (in terms of polystyrene) was produced, to which 64 parts of L-lactide and 16 parts of DL-lactide, and 15 parts of toluene as a solvent were added,
Melt both at 170 ° C for 1 hour in an inert gas atmosphere.
After mixing, adding 0.03 parts of tin octoate as a catalyst and reacting for 6 hours, taking out, cooling and pelletizing,
Volatile components were removed at 1 ° C and 1 mmHg. The weight average molecular weight was 110,000 (converted to polystyrene) (Resin C).

Reference Example 4 Aliphatic polyester (50 mol% azelaic acid component, 10 mol% ethylene glycol component, polypropylene glycol (weight average molecular weight 10
00) component 40 mol%, weight average molecular weight 20,000
(Polystyrene conversion) 20 parts, L-lactide 80
Parts and 15 parts of toluene as a solvent, and both were melted and mixed at 170 ° C. for 1 hour in an inert gas atmosphere, 0.03 parts of tin octoate was added as a catalyst, reacted for 5 hours, and taken out. After cooling and pelletizing, 130 ℃, 1
Volatile components were removed with mmHg. Weight average molecular weight is 17
It was 50,000 (polystyrene conversion) (resin D).

(Reference Example 5) 80 parts of poly L-lactide manufactured by Purac and 20 parts of poly DL-lactide manufactured by Purac were mixed with a twin-screw extruder manufactured by Toyo Seiki Seisakusho Ltd. (model: Labo Plastomill 2D25WS, screw: Diameter 26m
m, L / D = 25), melted and kneaded, and pelletized. The weight average molecular weight was 120,000 (converted to polystyrene) (Resin E).

(Example 1) To 100 parts of the resin A of Reference Example 1 which had been dried, 2 parts of talc (high filler) and 0.2 part of magnesium stearate were mixed in a vinyl bag under a nitrogen atmosphere. As the extruder, a 40 mm extruder manufactured by NAS Engineering Co., Ltd. with a foaming device and manufactured by Kasamatsu Kako Kenkyusho Co., Ltd. was used. An oil jacket was installed in the cooling zone and the die to control the temperature.

For the screw, L / D = 45, compression ratio = 2.
87, with a ring for preventing gas leakage was used.
At a resin discharge rate of 15 kg / hr, a high pressure micro pump manufactured by Kyowa Seimitsu Co., Ltd. was used from the middle of the extruder, and Freon 12 was pressed into the resin at a flow rate of 1 to 3% by weight. Resin temperature is 140-170 ℃, die temperature is 100-140
° C.

The resin discharged from the die in a cylindrical shape is blown with compressed air from the surroundings by a cooling air ring to cool the surface of the foamed sheet, cover the mandrel and inflate with compressed air from the inside (blow ratio = 2.83), After being continuously cut in the extrusion direction with a cutter under the mandrel to form one sheet, which was passed through a take-up machine and wound up, a moldability test, a biodegradability test, and a drop strength test were performed.

Example 2 Using the resin B of Reference Example 2,
The same operation as in Example 1 was performed.

Example 3 Using resin C of Reference Example 3,
The same operation as in Example 1 was performed.

(Example 4) Using resin D of Reference Example 4,
The same operation as in Example 1 was performed.

Example 5 The same operation as in Example 1 was carried out by adding 1 part of azodicarbonamide (Vinihol DW # 6) manufactured by Eiwa Chemical Co., Ltd. before mixing talc.

Example 6 The same operation as in Example 1 was carried out using Resin B of Reference Example 2 and butane as the volatile foaming agent.

Example 7 The same operation as in Example 4 was carried out using Resin B of Reference Example 2 and pentane as a volatile foaming agent. The appearance of the foams obtained in Examples 1 to 7 was good.

Comparative Example 1 The same operation as in Example 1 was carried out using the resin E of Reference Example 5 as the resin. The results obtained are shown in Table 1.

[0064]

[Table 1]

[0065]

INDUSTRIAL APPLICABILITY The present invention can provide a foam of a lactic acid-based polymer which is biodegradable, has sufficient flexibility, impact resistance and excellent moldability and is useful for various purposes.

Claims (7)

[Claims] 1. A foam of a lactic acid-based copolymer polyester having a weight average molecular weight of 20,000 to 400,000, comprising a structural unit obtained by dehydration condensation of lactic acid and a structural unit obtained by dehydration condensation of dicarboxylic acid and diol. 2. A lactic acid-based copolyester comprising a structural unit obtained by dehydration condensation of lactic acid and a structural unit obtained by dehydration condensation of dicarboxylic acid and diol, a nucleating agent and a foaming agent are kneaded in an extruder, and then foamed and molded. A method for producing a foam comprising a lactic acid-based copolyester. 3. The method for producing a foam made of a lactic acid-based copolymer polyester according to claim 2, wherein a volatile foaming agent is used as the foaming agent. 4. The method for producing a foam made of a lactic acid-based copolymer polyester according to claim 2, wherein a volatile foaming agent and a decomposing foaming agent are used together as the foaming agent. 5. The method for producing a foam made of a lactic acid-based copolymer polyester according to claim 3, wherein the volatile foaming agent is a hydrocarbon. 6. The method for producing a foam comprising a lactic acid-based copolymer polyester according to claim 4, wherein the decomposable foaming agent is azodicarbonamide. 7. A weight-average molecular weight, which is produced by the production method according to claim 2 and comprises a structural unit obtained by dehydration condensation of lactic acid and a structural unit obtained by dehydration condensation of dicarboxylic acid and diol. A foam made of a lactic acid-based copolymer polyester having a viscosity of 20,000 to 400,000.