JP2000136261A - Foaming particle and production of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain foaming particles of an aliphatic polyester excellent in foaming magnification in foaming in the mold, repeatability of formed articles on mold shape or the like useful for manufacturing foamed article used for a disposable foamed container in an easy operation by setting the degree of crystallization in a specific range and making a volatile foaming agent absorbed. SOLUTION: This prescribed foaming particle is obtained by making (B) a volatile foaming agent (e.g.; n-pentane or the like) absorbed to (A) an aliphatic polyester, preferably, a lactic acid based polymer (e.g.; poly L-lactide or the like) having 0 to 20% of crystallinity, in amount of 5 to 25 pts.wt. of the component (B) to 100 pts.wt. of the component (A), preferably at -40 to 50 deg.C, having 0 to 20% of crystallinity. This foaming particle is obtained in a process impregnating the component (B) in the component (A) in an autoclave or the like. The foamed article obtained from this foaming particle has biodegradable properties in soil and useful for buffer, civil engineering material or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to expandable particles made of an aliphatic polyester. Furthermore, the present invention relates to a foam molded article obtained by foaming expandable particles.

[0002]

2. Description of the Related Art Generally, foam materials are manufactured from resins such as polyethylene, polypropylene, and polystyrene.
It is used in many fields, taking advantage of its properties such as light weight, heat insulation, soundproofing, and cushioning. However, these foamed materials are difficult to recover and reuse after use, and are hardly decomposed in the natural environment, so they remain semi-permanently in the ground. In addition, abandoned plastics have caused problems such as spoiling the landscape and destroying the living environment of marine life.

On the other hand, lactic acid-based polymers such as polylactic acid and copolymers of lactic acid and other aliphatic hydroxycarboxylic acids, and aliphatic polyhydric alcohols and aliphatic polyhydric alcohols include thermoplastic resins having biodegradability. Aliphatic polyesters derived from carboxylic acids 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 It disappears in a few years from the year. Furthermore, the decomposition products have the property of becoming lactic acid, carbon dioxide, and water that are harmless to the human body.

[0004] In particular, polylactic acid has recently been used as a raw material in a large amount and at a low cost by fermentation, and has a high decomposition rate in compost. Expansion is expected.

The prior art relating to the foaming of aliphatic polyesters is disclosed, for example, in JP-A-4-304244, JP-A-5-140361, JP-A-5-170965, JP-A-5-170966, and JP-A-6-240037. ,
JP-A-6-287347, JP-A-6-287338
And Japanese Patent Application Laid-Open No. 9-263652. These techniques mainly disclose a method for producing a foam using an extruder, the obtained foam, and further a laminate of the foam. At present, there is substantially no technology relating to expandable particles containing a blowing agent as a main component, and further to a method for producing the particles.

[0006]

DISCLOSURE OF THE INVENTION The present inventors have developed a foamed molded article having good expansion ratio at the time of mold foam molding, reproducibility of the mold shape of the molded article, and good adhesion between foamed particles by a simple operation. An object of the present invention is to develop an expandable particle containing an aliphatic polyester, which is suitable for production by the method described above.

[0007]

Means for Solving the Problems The present inventors have conducted intensive studies on expanded particles containing an aliphatic polyester as a component. As a result, a volatile foaming agent was added to the aliphatic polyester in a crystallinity range of 0 to 20%. It has been found that the above problem is solved by the absorption, and the present invention has been completed. That is, the present invention is specified by the following items [1] to [9].

[1] The degree of crystallinity is 0 to 20%, and
Aliphatic polyester foamable particles characterized by absorbing a volatile foaming agent.

[2] The expandable particle according to [1], wherein the aliphatic polyester is a lactic acid-based polymer.

[3] A method for producing expandable aliphatic polyester particles, characterized in that a volatile foaming agent is absorbed in an aliphatic polyester having a crystallinity of 0 to 20%.

[4] A process for producing expandable aliphatic polyester particles, characterized in that a volatile foaming agent is absorbed in a temperature range such that the crystallinity of the aliphatic polyester is in the range of 0 to 20%.

[5] The method for producing expandable particles according to [3] or [4], wherein the aliphatic polyester is a lactic acid-based polymer.

[6] The temperature range in which the degree of crystallization of the aliphatic polyester is in the range of 0 to 20% is -40 to 5%.
The method for producing expandable particles according to [4] or [5], wherein the temperature is 0 ° C.

[7] Expandable particles produced by the production method according to any one of [3] to [6].

[8] The expandable particles described in [1], [2] or [7] are heated in a mold in a temperature range from the glass transition temperature (Tg) to the melting point (Tm) of the aliphatic polyester. Foamed article obtained by

[9] The expandable particles described in [1], [2] or [7] are heated in a mold in a temperature range from the glass transition temperature (Tg) to the melting point (Tm) of the aliphatic polyester. And / or a foamed sheet obtained by the above method.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

[Aliphatic polyester] In the present invention,
Aliphatic polyesters are homopolymers, copolymers (random copolymers, block copolymers) obtained by polymerizing in combination with aliphatic hydroxycarboxylic acids, aliphatic polyhydric alcohols, and aliphatic polybasic acids as monomers. , Alternating copolymers), and mixtures thereof. In the present invention, it is preferable that the aliphatic polyester is usually amorphous when extruded into pellets. When heat resistance is required for the foamed molded product, it is preferable that the material be amorphous when extruded into pellets and have a high glass transition temperature or a high melting point and be crystalline. Such polymers include lactic acid-based polymers.

[Lactic acid-based polymer] Here, the lactic acid-based polymer includes a polymer containing 50% by weight or more of a lactic acid component in terms of the weight of a monomer to be subjected to polymerization. Specific examples thereof include, for example, polylactic acid, a copolymer of lactic acid and another aliphatic hydroxycarboxylic acid, lactic acid, a copolymer of an aliphatic polyhydric alcohol and an aliphatic polybasic acid, a mixture of any combination of the following, And the like.

Specific examples of lactic acid which is a raw material of polylactic acid include L-lactic acid, D-lactic acid, DL-lactic acid or a mixture thereof, or lactide which is a cyclic dimer of lactic acid. As described above, when the heat resistance of the foamed molded product is required (for example, 60 ° C. or higher), the obtained polylactic acid is preferably crystalline.
When lactic acid and D-lactic acid are used in combination, L-lactic acid or D-lactic acid
-It is necessary that any one of lactic acid is 75% by weight or more.

[Aliphatic hydroxycarboxylic acid] Specific examples of the aliphatic hydroxycarboxylic acids as raw materials of the aliphatic polyester shown in the present invention include, for example, glycolic acid, lactic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid,
Examples thereof include 4-hydroxyvaleric acid, 5-hydroxyvaleric acid, and 6-hydroxycaproic acid, and a cyclic ester of an aliphatic hydroxycarboxylic acid, for example, glycolide or 6-hydroxyl which is a dimer of glycolic acid. Ε-caprolactone, which is a cyclic ester of caproic acid, can be mentioned. These can be used alone or in combination of two or more. Particularly, 6-hydroxycaproic acid or ε-caprolactone is preferably used.
These can be used alone or in combination of two or more.

[Aliphatic polyhydric alcohol] Specific examples of the aliphatic polyhydric alcohol which is a raw material of the aliphatic polyester shown in the present invention include, for example, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, Propylene glycol, 1,3-butanediol, 1,4-butanediol, 3-methyl-1,5-pentaneddiol, 1,
6-hexanediol, 1,9-nonanediol, neopentyl glycol, polytetramethylene glycol,
Examples thereof include 1,4-cyclohexanedimethanol and 1,4-benzenedimethanol. These can be used alone or in combination of two or more.

[Aliphatic polybasic acid] Specific examples of the aliphatic polybasic acid which is a raw material of the aliphatic polyester shown in the present invention include, for example, succinic acid, oxalic acid, malonic acid, glutaric acid, adipic acid, pimerine Acid, suberic acid, azelaic acid, sebacic acid, undecandioic acid, dodecandioic acid, phenylsuccinic acid, 1,4-phenylenediacetic acid and the like. These can be used alone or in combination of two or more. As a specific example of the method for producing the aliphatic polyester used in the present invention, a known and publicly-known method can be employed using the above-mentioned aliphatic hydroxycarboxylic acid, aliphatic polyhydric alcohol, and aliphatic polybasic acid.
For example, in the case of polylactic acid, a method in which lactic acid or a mixture of lactic acid and an aliphatic hydroxycarboxylic acid is used as a raw material and directly subjected to dehydration polycondensation (for example, a production method described in US Pat. No. 5,310,865), A ring-opening polymerization method for melt-polymerizing a cyclic dimer (lactide) (for example, a production method disclosed in US Pat. No. 2,758,987), a cyclic dimer of lactic acid and an aliphatic hydroxycarboxylic acid,
For example, a ring-opening polymerization method in which lactide or glycolide and ε-caprolactone are melt-polymerized in the presence of a catalyst (for example, a production method disclosed in US Pat. No. 4,057,537), lactic acid, aliphatic divalent A method of directly dehydrating and polycondensing a mixture of an alcohol and an aliphatic dibasic acid (for example, a production method disclosed in US Pat. No. 5,428,126);
A method of condensing a polymer of polylactic acid, an aliphatic dihydric alcohol and an aliphatic dibasic acid in the presence of an organic solvent (for example, a production method disclosed in European Patent Publication No. 0712880). In producing a polyester polymer by performing a dehydration polycondensation reaction, a method of performing solid-state polymerization in at least a part of the steps can be mentioned, but the production method is not particularly limited.
Also, a small amount of an aliphatic polyhydric alcohol such as glycerin, an aliphatic polybasic acid such as butanetetracarboxylic acid,
Polyhydric alcohols such as polysaccharides may coexist and be copolymerized, or the molecular weight may be increased by using a binder (polymer chain extender) such as a diisocyanate compound. It may be crosslinked with a peroxide such as bis (t-butylperoxyisopropyl) benzene or dicumyl peroxide.

The weight average molecular weight (M
The w) and the molecular weight distribution are not particularly limited as long as they can be substantially molded. The molecular weight of the lactic acid-based polymer used in the present invention is not particularly limited as long as it shows substantially sufficient mechanical properties. In general, the weight-average molecular weight (Mw) is preferably 1 to 500,000, 30,000 to 400,000 are more preferable, and 50,000 to 300,000 are still more preferable.

Generally, the weight average molecular weight (Mw) is 1
If the molecular weight is smaller than 10,000, the mechanical properties of the foamed foam obtained are insufficient, or if the molecular weight exceeds 500,000, handling may be difficult or uneconomical.

[Type of volatile foaming agent] In the present invention,
Known and publicly used foaming agents can be suitably used. For example, "MARUZEN High Polymer Dictionary-Co
nise Encyclopedia of Pol
ymer Science and Engineer
ing (edited by Kroschwitz, edited by Tatsumi Mita, Maruzen, Tokyo, 1994) ”, pages 811 to 815, can be suitably used. 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 Matters or disclosures that can be directly and uniquely derived by the trader.

The volatile foaming agent used in the present invention includes an inert gas, a hydrocarbon having 3 to 8 carbon atoms or a chlorinated hydrocarbon, fluorocarbons, fluorocarbons, water, nitrogen, LP
G, LNG, low boiling organic liquid, carbon dioxide gas, inert gas,
Ammonia and the like. Further, in accordance with the regulations of the Montreal Protocol concerning the regulation of chlorofluorocarbons for protecting the ozone layer, a new or known / publicly-used foaming agent which meets environmental regulation standards and a foaming technique using the same can be suitably used.

In the present invention, the volatile foaming agent has a function of causing a phase transition from a liquid phase to a gas phase when heated in a temperature range from the glass transition temperature (Tg) to the melting point (Tm) of the aliphatic polyester. And those having In the present invention, the volatile foaming agent is generally used at room temperature and normal pressure (2.
(5 ° C., 1 atm), it is in the liquid phase and undergoes a phase transition from the liquid phase to the gas phase when heated in a temperature range from the glass transition temperature (Tg) to the melting point (Tm) of the aliphatic polyester. Those having a function are preferred. In the present invention,
The volatile foaming agent, even in a gaseous phase at normal temperature and normal pressure (25 ° C., 1 atm), is compressed or simultaneously cooled to a liquid state, and is liquefied gas filled in a pressure-resistant container or an insulated container. Those having a low boiling point are also preferred. Specific examples of the volatile foaming agent include, for example, <1> inactive compound foaming agent, <2>
Aliphatic hydrocarbon-based blowing agents, <3> halogenated hydrocarbon-based blowing agents, and the like. In the present invention, as the volatile foaming agent, generally, carbon dioxide gas and water, which are volatile foaming agents having both safety and economy, are particularly preferable.

<1> Inert Compound Blowing Agent Specific examples of the inert compound blowing agent include nitrogen,
Examples include carbon dioxide gas, argon, and water.

<2> Aliphatic Hydrocarbon Blowing Agent Specific examples of the aliphatic hydrocarbon blowing agent include ethane, propane, butane, ethylene, propylene, petroleum ether, pentanes (n-pentane, 2, 2-dimethylpropane, 1-pentene, cyclopentane, etc.), hexanes (n-hexane, 2-methylpentane, 3-methylpentane, 2,2-dimethylbutane, cyclohexane, etc.), heptane (n-heptane, , 2-dimethylpentane, 2,4-dimethylpentane, 3-ethylpentane, 1-heptene, etc.), toluene, trichloromethane,
Examples thereof include tetrachloromethane, trichlorofluoromethane, methanol, 2-propanol, isopropyl ether, and methyl ethyl ketone.

<3> Halogenated Hydrocarbon Blowing Agent Preferred specific examples of the halogenated hydrocarbon-based blowing agent include, for example, halogenated hydrocarbons having 2 to 6 carbon atoms. Examples include methyl chloride, dichloroethane, chloroform, fluoromethane, difluoromethane, trifluoroethane, chlorotrifluoromethane, dichlorodifluoromethane, fluorochloroethane, dichlorotetrafluoroethane, and the like. Specific examples of fluorocarbons include, for example, Freon (R-11, R-12), and alternative Freon (R-134).
a), CFC-11, CFC-12, CFC-113,
CFC series Freon (Freon) such as CFC-114.

[Amount of Volatile Foaming Agent] In the present invention, the amount of the volatile foaming agent is not particularly limited as long as the object of the invention is not impaired. In the present invention, the addition amount of the volatile foaming agent varies depending on the desired expansion ratio and foaming agent at the time of mold foaming molding, but is generally 1 to 30 parts by weight based on 100 parts by weight of the aliphatic polyester. The weight is preferably 3 to 27 parts by weight, more preferably 5 to 25 parts by weight. In general, if the amount is less than 1 part by weight, foaming tends to be lost or uneven, and conversely 3
If the amount exceeds 0 parts by weight, not only the effect of excessive addition is not obtained, but also problems such as poor appearance and uneven cell diameter may occur.

[Expandable Particles] The shape of the expandable particles is not particularly limited, but the particle diameter (average particle diameter) is 0.001 to 0.3.
0 mm is good, 0.005-20 mm, 0.01-10
mm, 0.05 to 5 mm, and 0.1 to 3 mm in this order. The particle size is appropriately selected according to conditions such as a foaming method and a mold shape. For example, in the case of mold foaming, a relatively small particle size is preferable when foaming is performed in a small mold, and a relatively large particle size is preferable when foaming is performed in a large mold. The shape of the expandable particles is not particularly limited, but preferred specific examples include, for example, a spherical shape and a spheroidal shape. Here, the “particles” include, for example, polymer emulsion, latex, and microspheres constituting a polymer suspension.

[Crystallinity of Aliphatic Polyester] In the present invention, the volatile foaming agent is absorbed in a temperature range where the crystallinity of the aliphatic polyester is in the range of 0 to 20%.
Preferably it is in the range of 0-15%, more preferably 0-10%, most preferably 0-5%. 20% crystallinity
When the volatile foaming agent is absorbed in a range exceeding the above range, the elastic modulus of the resin rapidly decreases near the melting point when heated and foamed in the pre-foaming stage, and the generated foam breaks, resulting in a good foam. Can not get.

[Temperature for Absorbing Volatile Foaming Agent in Aliphatic Polyester] The temperature (Ta [° C.]) at which the aliphatic polyester absorbs the volatile foaming agent differs depending on the type of aliphatic polyester, but is generally used. Has the formula (1) [Equation 1]
(Tg; glass transition temperature).

[Formula 1] −40 [° C.] ≦ Ta [° C.] ≦ 50 ° C. (1) In the case of a lactic acid-based polymer, the temperature (Ta [° C.]) at which the volatile foaming agent is absorbed is −40 to 50 ° C. Range. Preferably -30 to 40C, more preferably -20 to 30
° C, more preferably in the range of -10 to 20 ° C. -4
If the temperature is lower than 0 ° C., handling becomes difficult when absorbing the foaming type volatile agent. If it exceeds 50 ° C., the resin may be crystallized depending on the conditions. In addition, the adhesion between the expandable particles may be poor, and it may be difficult to obtain a molded article, or the strength of the obtained molded article may be reduced.

[Pressure for Absorbing Foaming Agent] The pressure for absorbing the volatile foaming agent is not particularly limited. Specifically, the range is usually 0.1 to 10 MPa, preferably 0.5 to 8 MPa, more preferably 1 to 7 MPa. 0.1M
Even under a reduced pressure of less than Pa, the effect of absorbing is not significantly changed. If it exceeds 10 MPa, the cost of the apparatus may increase.

[Additives] In the present invention, the purpose of the present invention is to improve the foaming properties and the physical properties of the foam (for example, to improve the foaming properties, the flexibility of the foam, the tensile strength, the heat resistance, the weather resistance, etc.). Various additives (nucleating agent, plasticizer, antioxidant,
UV absorbers, heat stabilizers, flame retardants, internal mold release agents, inorganic additives, antistatic agents, surface wetting improvers, incineration aids, lubricants such as pigments, dispersants) and the like can be added. Specific examples of the nucleating agent include, for example, titanium oxide, talc, kaolin, clay, calcium silicate, silica, sodium citrate, calcium carbonate, diatomaceous earth, calcined perlite, zeolite, bentonite, glass, limestone, calcium sulfate, aluminum oxide, Examples include titanium oxide, magnesium carbonate, sodium carbonate, and ferric carbonate.

[Production Method of Expandable Particles] The production method of the expandable particles used in the present invention is a production method capable of controlling the crystallinity of the aliphatic polyester component contained in the expandable particles to 20% or less. There are no restrictions. For example, aliphatic polyester and various additives depending on the purpose are uniformly mixed using a high-speed stirrer or a low-speed stirrer, melt-kneaded in an extruder, and once again, pellets having a crystallinity of 20% or less are taken out in the same manner as described above. After that, a method of impregnating a foaming agent in a container such as an autoclave or the like can be given. The shape of the resin composition according to the present invention may be generally a pellet, a rod, or the like. Further, the expandable particles may be unexpanded particles or pre-expanded particles, but are not particularly limited, but those which can substantially satisfy the adhesion of the expanded particles when heated and expanded in a mold. Must. In the latter case, the foaming ability when heated and foamed is 1.2 times, preferably 1.5 times or more,
More preferably 2.0 times or more, further preferably 2.5 times or more, and most preferably 3.0 times or more of expandable particles.

[Method for Producing a Foam] In the present invention, a free foam can be obtained by heating the expandable particles. Further, by foaming in a specific mold, it is possible to obtain a foam molded product that reproduces the shape of the mold. The foam can be manufactured by a publicly-known / public method. For example, "MARUZEN High Polymer Dictionary-Concise
Encyclopedia of Polymer
Science and Engineering (K
Roschwitz, translated by Tatsuta Mita, Maruzen, Tokyo, 1
994) ", pp. 811 to 815. All the descriptions are
By explicitly citing the cited documents and the cited ranges, they become a part of the disclosure of the present specification, and by referring to the explicitly cited ranges, those skilled in the art can directly and in view of the matters or disclosures described in the present application specification. Matters or disclosures that can be uniquely derived. Continuity, independence, size, and shape of the voids of the foam (including the concepts of the terms "bubble", "void", "microvoid", "cavity", "cell", etc.) Characteristics such as distribution, size uniformity, etc. can be controlled by appropriately setting foaming conditions according to the purpose. For example, a method of injecting carbon dioxide or nitrogen gas into foamable particles in advance, imparting secondary foamability, filling the mold, blowing steam, heating and foaming, and then cooling to obtain a molded article, or foamable particles. Is directly filled in a mold, heated and foamed, and then cooled to obtain a molded article.

[Heating] Temperature for heating (Th [° C.])
Is generally represented by Expression (2) [Equation 2] (Tg;
Glass transition temperature, Tm; melting point). In general, the equations (3) [Equation 3] to (6) [Equation 6] are preferable in this order. If the temperature is lower than Tg, the foam may not be formed. On the other hand, if the temperature is higher than Tm, the foamed product may re-shrink or the cells may break.

[Equation 2] Tg [° C.] ≦ Th [° C.] ≦ Tm [° C.] (2)

[Equation 3] Tg [° C.] + 5 [° C.] ≦ Th [° C.] ≦ Tm [° C.] − 5 [° C.] (3)

[Equation 4] Tg [° C.] + 10 [° C.] ≦ Th [° C.] ≦ Tm [° C.] − 10 [° C.] (4)

[Equation 5] Tg [° C.] + 15 [° C.] ≦ Th [° C.] ≦ Tm [° C.] − 15 [° C.] (5)

[Equation 6] Tg [° C.] + 20 [° C.] ≦ Th [° C.] ≦ Tm [° C.] − 20 [° C.] (6) As a heating method, energy required for heating and expanding the expandable particles is used. Is given in some way,
It can be used without any restrictions. For example, the mold containing the expandable particles may be placed in a heat medium, exposed to a controlled temperature atmosphere, or heated inert gas such as nitrogen, water vapor, or carbon dioxide may be blown into the mold. And other methods can be used.

[Foam] The term "foam" used in the present specification includes many voids ("bubbles", "voids", "microvoids", "cavities", A void phase (including voids, both continuous and independent) is mixed in the continuous phase of the resin, in which the concept of the word “cell” etc. is present. Encompasses a resin structure having a two-phase structure or a multi-phase structure, and is recognized as a structure such as a polymer having a cellular structure, a foamed polymer, an expanded polymer, a polymer foam, and a polymer foam. General and also includes soft and hard ones. When the foamed molded article obtained by subjecting the foamable particles according to the present invention to foam molding is used in the form of a foam, the foamed article has excellent cushioning properties, impact resistance, heat insulation properties, etc. Insulation,
It is suitably used for furniture, automobile cushion materials, interior materials, living goods, sports goods, health goods, agricultural materials and the like. Depending on the application, it is desired that the vacuoles in the foam are in communication with adjacent vacuoles through pores (open cells), and when the individual vacuoles exist independently (closed cells). It may be desirable, and in some applications, either is acceptable. The foamed molded article can have a low foaming of 2-3 times, a medium foaming of 10-20 times, and a high foaming of 30-50 times (in some cases, 30-100 times). Specific examples of the use of so-called high foams, which are mainly made of sheets and board-like foams, include, for example, packaging and packing, construction and civil engineering, vehicles and ships, industrial insulation, agriculture, forestry and fisheries, sports and miscellaneous goods. And the like.

[Synthetic Wood] In the present invention, the expandable particles may be a low-expanded foam falling within the category of synthetic wood. Here, "synthetic wood ([Artificia
lwoods]) "is a common name among those skilled in the art, and a formal definition has not yet been defined.
In Europe and the United States, “Structural foam products [Structural
what is called "foam]" substantially corresponds to this. That is, it refers to a plastic low-foamed product having a skin layer and an expansion ratio of about 1.1 to 4 times. Synthetic wood is a highly promising material from the standpoint of global wood shortage and environmental protection. Depending on the choice of molding method,
In terms of appearance, synthetic wood can also be manufactured that is difficult to distinguish from natural wood, and can be applied to high value-added applications such as furniture. Specific examples of uses for synthetic wood include:
For example, a cutting board, a sawboard, a container pallet, a concrete panel and the like can be mentioned.

[Use] The foam obtained from the expandable particles of the present invention can be used as a substitute for the use of a publicly known foam before the application of the present invention. In particular, the foam of the present invention has biodegradability in soil, and is used for difficult-to-collect or disposable foam containers, cushioning (packaging) materials, materials for the civil engineering industry, materials for the agricultural and marine industries, and leisure goods. It can be suitably used as a substitute for a general-purpose resin foam.

General-purpose use The foam obtained from the expandable particles of the present invention can be used, for example, in a lunch box, tableware, a container for lunch boxes and side dishes, a cup for cup ramen, and a vending machine for beverages as sold in convenience stores. Used cups, containers and trays for foodstuffs such as fresh fish, meat, fruits and vegetables, tofu, prepared foods, torobaco (fish box for fisheries) used in the fresh fish market, milk, yogurt, lactic acid bacteria drinks, etc. Containers for dairy products, containers for carbonated drinks and soft drinks, containers for liquor drinks such as beer and whiskey, cosmetic containers, detergent containers, bleach containers, cool boxes, flower pots, tapes, home appliances such as TVs and stereos Cushioning materials and packaging materials for transportation of products, cushioning materials for transportation of precision machines such as computers, printers and watches, cameras, glasses, microscopes, and telescopes Cushioning material for transportation of optical machinery, cushioning material for transportation of ceramic products such as glass and ceramics, loose cushioning material (easy packing material that can be packed at the site), light shielding material, heat insulating material ( Extrusion board, etc.), soundproofing / sound insulation (extrusion board, etc.), extruded foam sheet (polymer paper for food related applications, prepackaged. Mainly applied to food packaging and containers), foaming It can also be suitably used as a sheet obtained by bonding a non-foamed film to a sheet, a filter for passing through a sewage furnace, a net-like foam, a foamed product, and the like.

General Industrial Use and Recreational Use of the Foam The foam obtained from the expandable particles of the present invention can be used for general industrial use including agriculture, fishing, forestry, industry, construction and civil engineering, transport and transportation, and leisure and sports. Can be suitably used for recreational purposes including: For example, agricultural cold gauze, oil absorbing material, soft ground reinforcement, artificial leather, floppy disk lining, sandbag bag, heat insulating material, soundproofing material, cushioning material, furniture cushioning material such as beds and chairs, floor cushioning material , Packaging materials, binding materials, muddy
It can be suitably used as a non-slip material for snowy roads and the like.

[0052]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the scope of the present invention.

[Evaluation of Physical Properties] Weight average molecular weight (Mw), glass transition temperature (Tg), melting point (Tm), crystallinity of expandable particles, and foam Shapeability and strength were measured by the following methods.

Weight Average Molecular Weight The weight average molecular weight of the aliphatic polyester was measured by gel permeation chromatography (GPC) using polystyrene as a standard under the following conditions. Apparatus: Shimadzu LC-IOAD Detector: Shimadzu RID-6A Column: Hitachi Chemical GL-S350DT-5, GL-S3
7ODT-5 Solvent: chloroform Concentration: 1% Injection volume: 20 μl Flow rate: 10 ml / min

Glass transition temperature (Tg), melting point (T
m) Differential scanning calorimeter (manufactured by Shimadzu Corporation, DSC-50)
The point at which the molded body changed to a rubbery state when the temperature of the molded body was raised at 10 ° C./min was defined as the glass transition point (Tg), and the peak of the melting peak was defined as the melting point (Tm).

Crystallinity The crystallinity was measured with an X-ray diffractometer (Rint 1500, manufactured by Rigaku Corporation), and the ratio of the crystal peak area to the total area of the obtained chart was determined.

Shapeability The reproducibility of the mold shape of the foamed molded article was visually observed. ○ ・ ・ ・ Good. △ ... Shape of corner part is not good. ×: defective.

Strength The following classification was performed for the strength of the foamed molded article.・ ・ ・: Strong. Δ: Slightly brittle. ×: brittle.

Examples and Comparative Examples [Production Example 1] <Production of Polymer A (Poly L-lactide)> 100 parts by weight of L-lactide and stannous octoate 0.1 part by weight.
01 parts and 0.03 parts of lauryl alcohol were sealed in a thick cylindrical stainless steel polymerization vessel equipped with a stirrer, degassed under vacuum for 2 hours, and then replaced with nitrogen gas. The mixture was heated at 200 ° C. for 3 hours with stirring under a nitrogen atmosphere. While maintaining the temperature as it was, the air was gradually degassed by a vacuum pump through an exhaust pipe and a glass receiver, and the pressure inside the reaction vessel was reduced to 3 mmHg. One hour after the start of degassing, the distillation of the monomer and low-molecular-weight volatiles disappeared. Therefore, the inside of the vessel was replaced with nitrogen, and the polymer was drawn out from the lower part of the vessel in the form of a strand, pelletized, and homopolymer of L-lactide (polymer A) was obtained. The yield was 78% and the weight average molecular weight Mw was 136,000.

[Production Example 2] <Production of Polymer B (Poly L-lactic acid)> 10 kg of 90% L-lactic acid was placed at 150 ° C / 5 in a 100-liter reactor equipped with a Dien-Stark trap.
After distilling water while stirring at 0 mmHg for 3 hours, 6.2 g of tin powder was added, and the mixture was further heated at 150 ° C / 30 mmHg for 2 hours.
The mixture was oligomerized by stirring for an hour. 28.8 g of tin powder and 21.1 kg of diphenyl ether were added to this oligomer,
An azeotropic dehydration reaction at 150 ° C./35 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 packed with 46 kg of molecular sieve 3A, and then returned to the reactor. A solution of polylactic acid was obtained. Diphenyl ether 44 dehydrated in this solution
After adding kg and diluting, the mixture was cooled to 40 ° C., and the precipitated crystals were filtered, washed three times with 10 kg of n-hexane, and dried at 60 ° C./50 mmHg. 0.5 N of this powder
-Add 12 kg of HCl and 12 kg of ethanol, and add 35
After stirring at 1 ° C. for 1 hour, the mixture was filtered, dried at 60 ° C./50 mmHg, and 6.1 kg of white polylactic acid was obtained (yield: 85%).
%). The weight average molecular weight Mw of this polylactic acid (Polymer B) was 145,000.

[Production Example 3] <Production of copolymer C (polybutylene succinate / polylactic acid copolymer)> 50.5 g of 1,4-butanediol and 66.5 of succinic acid
g to 293.0 g) Metal tin 2.02
g was added and heated and stirred at 130 ° C./140 mmHg for 7 hours while distilling water out of the system to oligomerize. to this,
Attach Dean-Stark trap, 140 ° C
After azeotropic dehydration for 8 hours at / 30 mmHg, a tube filled with 40 g of molecular sieve 3A was attached, and the distilled solvent was returned to the reactor through the molecular sieve tube, and stirred at 130 ° C / 17 mmHg for 49 hours. did. The reaction mass was dissolved in 600 ml of chloroform, added to 4 liters of acetone and reprecipitated, and then a solution of HCl in isopropyl alcohol (hereinafter abbreviated as IPA) (H
(CI concentration: 0.7 wt%) for 0.5 hour (three times), washed with IPA, and dried under reduced pressure at 60 ° C for 6 hours to obtain polybutylene succinate (hereinafter abbreviated as PSB). The weight average molecular weight Mw of this polymer is 1
It was 18,000. To 40.0 g of the obtained polybutylene succinate, 160.0 g of polylactic acid (weight average molecular weight Mw is 2,000,000), 800 g of diphenyl ether and 0.7 g of metal tin obtained by the same method as in Production Example 2 were mixed. And
The dehydration condensation reaction was performed again at 130 ° C./17 mmHg for 20 hours. After the reaction, post-treatment was performed in the same manner as in Production Example 2,
Copolymer of polybutylene succinate and polylactic acid 1
88 g (94% yield) were obtained. The weight average molecular weight Mw of this copolymer of polybutylene succinate and polylactic acid (copolymer C) was 14,000.

[Production Example 4] <Production of copolymer D (polycaproic acid / polylactic acid copolymer)> A reaction was carried out in the same manner as in Production Example 2 except that 6-hydroxycaproic acid was used instead of lactic acid. As a result, polycaproic acid (weight average molecular weight Mw was 150,000) was obtained. Next, 10.0 g of the obtained polycaproic acid and 19 of polylactic acid were obtained.
Using 0.0 g (weight average molecular weight Mw is 100,000) and in the same manner as in Production Example 3, a copolymer (copolymer D) of polycaproic acid and polylactic acid was obtained. The yield is 92%,
The weight average molecular weight Mw was 153,000.

[Production Example 5] <Production of polymer E (blend of polylactic acid and polybutylene succinate)> Production Example 1 Polylactic acid obtained (weight average molecular weight Mw is 1)
160,000 g of the polybutylene succinate obtained in Production Example 3 (weight average molecular weight Mw is 14,000) 40
g, and the mixture was melt-kneaded using a twin-screw extruder at a cylinder and die temperature of 160 to 200 ° C., and pelletized with a pelletizer. The weight average molecular weight Mw of the obtained pellet was 14,000.

Production Example 6 Production of Polymer F (Blend of Polylactic Acid and Polycaproic Acid) Production Example 1 Polylactic acid obtained (weight average molecular weight Mw is 1)
(36,000) 160 g and 40 g of the polycaproic acid (weight average molecular weight Mw is 150,000) obtained in Production Example 4 were mixed, and using a twin-screw extruder, the cylinder and die temperature were 160 to 200 ° C. The mixture was melt-kneaded in a temperature range and pelletized by a pelletizer. The weight average molecular weight Mw of the obtained pellet was 141,000.

Example 1 150 g of polylactic acid (polymer A) pellets as an aliphatic polyester, 30 g of n-pentane, and a 0.5 wt% PVA aqueous solution as a dispersant were charged into an autoclave (1 liter) equipped with a stirrer. . When the temperature is increased to 40 ° C. while stirring, the internal pressure is almost 0.1%.
MPa. After stirring for 20 hours, the pellets (expandable particles) were taken out. The crystallinity of the polylactic acid component of the expandable particles was 5%.

A mold (length × width × height = 100) made of a 2 mm-thick iron plate provided with the foamable particles and having air holes.
(mm × 50 mm × 20 mm), and foamed with hot air at 110 ° C. from the air holes to fuse the particles together and then cool. The mold was opened, and the obtained foamed molded product was taken out, and its shapeability and strength were evaluated. Table-Results
1 [Table 1].

Examples 2 to 6 Examples 2 to 6 were carried out in the same manner as in Example 1 except that the production conditions for the aliphatic polyester and the expandable particles and the molding conditions for the expanded molded article were changed. The results are shown in Table 1 [Table 1].

[Comparative Examples 1 to 4] Comparative Examples 1 to 4 were carried out in the same manner as in Example 1 except that the production conditions of the aliphatic polyester, the expandable particles, and the molding conditions of the expanded molded article were changed. The results are shown in Table 2 [Table 2].

[0069] [Legend] “←” means “same as left”.

[0070] [Legend] “←” means “same as left”.

Example 7 150 g of polylactic acid (polymer A) pellets as an aliphatic polyester were placed in an autoclave (1 l) directly connected to a carbon dioxide (CO 2) cylinder via a pressure regulating valve. After the temperature of the autoclave was reduced to 0 ° C., CO2 was charged and the pressure in the cylinder was increased to 4M.
It was set to Pa and left for 2 hours. Next, CO2 in the autoclave was extracted, and pellets (expandable particles) were extracted. The crystallinity of the expandable particles was 0%.

A mold (length × width × height = 100) made of the expandable particles made of a 2 mm-thick iron plate with an air hole.
(mm × 50 mm × 20 mm), foamed with hot air at 130 ° C. from the air hole, fused the particles to each other, and then cooled. The mold was opened, and the obtained foamed molded product was taken out, and its shapeability and strength were evaluated. Table-Results
3 [Table 3].

Examples 8 to 12 Examples 8 to 12 were carried out in the same manner as in Example 7 except that the production conditions for the aliphatic polyester and the expandable particles and the molding conditions for the foamed molded product were changed. The results are shown in Table 3 [Table 3].

[0074] [Legend] “←” means “same as left”.

Comparative Examples 5 to 10 Comparative Examples 5 to 10 were carried out in the same manner as in Example 7 except that the production conditions for the aliphatic polyester and the expandable particles and the molding conditions for the foamed molded product were changed. The results are shown in Table 4 [Table 4]. [Legend] “←” means “same as left”.

[0076]

By forming and processing the expandable particles according to the present invention, not only a polylactic acid-based foam, which was difficult to obtain with the conventional technique, but also a foam in a mold can be obtained. In this way, a foam molded article having an arbitrary shape can be obtained. The foam molded product has biodegradability and is difficult to collect and reuse, and is a foam (molded) body, a disposable foam container, a cushioning material, a material for the civil engineering industry, a material for the agriculture and fisheries industry, leisure. The foam molded article which can be suitably used as a substitute for the foam molded article used in the article has at least the following excellent properties <1> to <7>. <1> It can be soft or hard. <2> Low thermal conductivity and good heat insulation (energy saving effect). <3> Degradable. <4> Excellent heat resistance and oil resistance. <5> Even when incinerated, harmful substances are hardly generated. <6> Non-toxic and odorless. <7> Excellent workability.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court ゛ (Reference) B29L 7:00 (72) Inventor Yasuhiro Kitahara 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Mitsui Chemicals Co., Ltd. (72 Inventor Ikuki Yoshida, Mitsui Chemicals Co., Ltd., 1-2-1, Waki, Waki-cho, Kuga-gun, Yamaguchi Prefecture (72) Inventor Tomoyuki Nakata 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Prefecture Mitsui Chemicals, Inc.

Claims (9)

[Claims] An aliphatic polyester expandable particle having a crystallinity of 0 to 20% and absorbing a volatile foaming agent. 2. The expandable particle according to claim 1, wherein the aliphatic polyester is a lactic acid-based polymer. 3. A process for producing expandable aliphatic polyester particles, wherein a volatile foaming agent is absorbed in an aliphatic polyester having a crystallinity of 0 to 20%. 4. The crystallinity of the aliphatic polyester is from 0 to 2.
A method for producing expandable aliphatic polyester particles, characterized in that a volatile foaming agent is absorbed in a temperature range of 0%. 5. The method for producing expandable particles according to claim 3, wherein the aliphatic polyester is a lactic acid-based polymer. 6. An aliphatic polyester having a crystallinity of 0 to 2
The method for producing expandable particles according to claim 4 or 5, wherein the temperature range in which the range is 0% is -40 to 50 ° C. 7. Expandable particles produced by the production method according to claim 3. Description: 8. Foaming obtained by heating the expandable particles according to claim 1, 2 or 7 in a mold in a temperature range from the glass transition temperature (Tg) to the melting point (Tm) of the aliphatic polyester. Molded body. 9. Foaming obtained by heating the expandable particles according to claim 1, 2 or 7 in a mold in a temperature range from the glass transition temperature (Tg) to the melting point (Tm) of the aliphatic polyester. Film and / or foam sheet.