JP2000136255A - Polylactic acid-based foam and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polylactic acid-based foamable molded product in an unfoamed state, having an excellent expansion ratio in foaming molding in a mold and reproducibility of mold shape of molded product, etc., suitable for producing a foam useful for a disposable foam container, etc., comprising a specific foamable resin composition by making a degree of crystallization in a specific range. SOLUTION: This foamable molded product comprises (A) 100 pts.wt. of a polylactic acid-based resin such as poly(L-lactide), etc., and (B) 1-30 pts.wt. of a volatile blowing agent such as carbon dioxide, etc., and has 0-20% degree of crystallization. The molded product is obtained, for example, by completely melting the component A supplied to an injection molding machine, supplying the component B from another line to the machine and injection molding the melt. A mold is changed with 3-10 MPa nitrogen gas, etc. A foam obtained from the molded product has biodegradability in soil and is useful as a cushioning material, a material for industry of civil enginnering, a material for agriculture, fisheries, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an expandable molded article made of a polylactic acid resin. Further, the present invention relates to a foam molded article obtained by foaming a foamable molded article.

[0002]

2. Description of the Related Art Generally, foam materials are manufactured from resins such as polyethylene, polypropylene, and polystyrene.
It is used in various fields by making use of its performance 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.

In particular, polylactic acid has recently been used in a large amount and at low cost by fermentation as a raw material, and its decomposition rate in compost is high. 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, a foam obtained, and a laminate of the foam, and an aliphatic polyester and a dispersant which are the object of the present invention. At present, there is no technology relating to a technique for foaming an expandable molded product mainly composed of styrene in a mold.

[0006]

DISCLOSURE OF THE INVENTION The present inventors have developed a foamable molded article having good expansion ratio at the time of mold foam molding, reproducibility of the mold shape of the molded article, good adhesion between foamed particles, and the foamed molded article. It is an object of the present invention to develop a foam obtained by heating a heat-resistant molded article.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies on a foamed molded article containing a polylactic acid-based resin as a component. As a result, a foamable resin containing a volatile foaming agent was added to the polylactic acid-based resin. The composition is filled into a mold by an injection molding machine, cooled, crystallized in the range of 0 to 20%, and is taken out in an unfoamed state. And found a foam obtained by heating the molded article in a mold, thereby completing the present invention. That is, the present invention is specified by the following items [1] to [5].

[1] An unfoamed polylactic acid having a crystallinity of 0 to 20%, comprising a foamable resin composition containing 1 to 30 parts by weight of a volatile foaming agent with respect to 100 parts by weight of a polylactic acid-based resin. -Based foamed molded product.

[2] An unfoamed polylactic acid having a crystallinity of 0 to 20%, comprising a foamable resin composition containing 1 to 30 parts by weight of a volatile foaming agent with respect to 100 parts by weight of a polylactic acid-based resin. The polylactic acid-based foam is heated at a temperature equal to or higher than the glass transition temperature of the polylactic acid-based resin to foam a volatile foaming agent contained in the polylactic acid-based resin. Production method.

[3] A polylactic acid-based foam obtained by the production method described in [2].

[4] Forming a foamable resin composition containing 1 to 30 parts by weight of a volatile foaming agent with respect to 100 parts by weight of a polylactic acid resin in a crystallinity of 0 to 20% and in an unfoamed state. A method for producing a polylactic acid-based foamed molded article, characterized by comprising:

[5] A foamable resin composition containing 1 to 30 parts by weight of a volatile foaming agent with respect to 100 parts by weight of a polylactic acid-based resin is molded at a mold temperature of -40 to 50 ° C. and a crystallinity of 0 to 0. 2
A method for producing a polylactic acid-based expandable molded article, characterized in that the molded article is molded in an unfoamed state at 0%.

[0013]

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

[Polylactic acid-based resin] Here, the polylactic acid-based resin 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 foam molded article is required to be high (for example, 60 ° C. or higher), the obtained polylactic acid is preferably crystalline, and for that purpose, L-lactic acid and D-lactic acid are used. When lactic acid is used as a mixture, it is necessary that either L-lactic acid or D-lactic acid is 75% by weight or more.

[Aliphatic hydroxycarboxylic acid] Specific examples of the aliphatic hydroxycarboxylic acids which are the 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, dipropylene glycol, and the like. 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, the above-mentioned aliphatic hydroxycarboxylic acid, aliphatic polyhydric alcohol, or aliphatic polybasic acid may be used, and a publicly known method may be employed. Can be. 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). When a polyester polymer is produced by performing a dehydration polycondensation reaction, a method in which solid phase polymerization is performed in at least a part of the steps can be exemplified, but the production method is not particularly limited. Also, small amounts of aliphatic polyhydric alcohols such as glycerin,
Aliphatic polybasic acids such as butanetetracarboxylic acid, and polyhydric alcohols such as polysaccharides may coexist and be copolymerized, and a binder (polymer chain extender) such as a diisocyanate compound. May be used to increase the molecular weight. It may be crosslinked with a peroxide such as bis (t-butylperoxyisopropyl) benzene or dicumyl peroxide.

Weight average molecular weight (Mw) of polylactic acid resin
The molecular weight distribution is not particularly limited as long as it 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 exhibits substantially sufficient mechanical properties, but generally, the weight-average molecular weight (M
In w), it is preferably from 100,000 to 500,000, more preferably from 300,000 to 400,000, still more preferably from 50,000 to 300,000.

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. Decomposition type foaming agent used in the present invention,
Inert gas, hydrocarbon having 3 to 8 carbon atoms or chlorinated hydrocarbon, fluorocarbons, fluorocarbons, water, nitrogen, L
PG, LNG, low-boiling organic liquid, carbon dioxide, 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> inert compound foaming agent, <2> aliphatic hydrocarbon foaming agent, and <3> halogenated hydrocarbon foaming agent. 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 foaming agent Specific examples of the inert compound foaming 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, and more specifically, 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 to be added is not particularly limited as long as the object of the invention is not impaired. In the present invention, the amount of the volatile foaming agent to be added varies depending on the desired expansion ratio and foaming agent at the time of mold foaming molding, but is generally 1 to 100 parts by weight of the polylactic acid-based resin. 30 parts by weight is preferable, 3 to 27 parts by weight is more preferable, and 5 to 25 parts by weight is further preferable. In general, if the amount is less than 1 part by weight, foaming tends to become non-uniform or uneven, and if it exceeds 30 parts by weight, not only the effect of excessive addition but also the effect is not obtained.
Problems such as poor appearance and non-uniform cell diameter may occur.

[Injection Molding Method] In the present invention, a polylactic acid-based resin impregnated with a volatile foaming agent in advance is subjected to injection molding, or a separate line for supplying a foaming agent to an injection molding machine is provided. A volatile foaming agent may be fed from the line to perform injection molding. In this case, the volatile foaming agent is preferably in a supercritical state and is completely compatible with the molten resin.

[Temperature for Absorbing Volatile Foaming Agent in Aliphatic Polyester] In the present invention, if the volatile foaming agent is impregnated in the polylactic acid resin before molding (such as injection molding), the aliphatic polyester The temperature at which the volatile foaming agent is absorbed (Ta [° C.]) differs depending on the type of the aliphatic polyester, but is generally represented by the formula (1) [Equation 1] (Tg; glass transition temperature). ). [Equation 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 in the range of −40 to 50 ° C. is there. Preferably -30 to 40C, more preferably -20 to 30
C, more preferably -10 to 20C. If the temperature is lower than −40 ° C., handling becomes difficult when the foaming type volatile agent is absorbed. If it exceeds 50 ° C., the resin may be crystallized depending on the conditions. In addition, the adhesiveness between the foamed molded products may be poor, it may be difficult to obtain a molded product, or the strength of the obtained molded product may be reduced.

[Pressure for Absorbing Foaming Agent] In the present invention, when a polylactic acid resin is impregnated with a volatile foaming agent before molding (such as injection molding), the pressure for absorbing the volatile foaming agent is as follows. There is no particular limitation. Specifically, usually 0.1
The range is preferably from 10 to 10 MPa, preferably from 0.5 to 8 MPa, more preferably from 1 to 7 MPa. Even under a reduced pressure of less than 0.1 MPa, the effect of absorbing does not change so much. If it exceeds 10 MPa, the cost of the apparatus may increase.

[Back pressure in injection molding] When molding by injection molding, it is necessary to control the pressure in the system by applying a back pressure so that the resin melted in the cylinder does not foam. Usually, the back pressure is 3 to 15 MPa, preferably 5 to 13 MPa, and more preferably 7 to 10 MPa. When the back pressure is less than 3 MPa, the foaming is performed in the cylinder to obtain a desired foamable molded product, or even if the foamable molded product is obtained, the foaming agent is not uniformly dispersed, and then foamed. Also, problems such as poor appearance and uneven foaming may occur. The pressure at which the blowing agent is charged into the cylinder is usually 3 to 30 MPa, preferably 5 to 25 MPa,
More preferably 7 to 20 MPa, still more preferably 10 to 20 MPa
15MPa is good. If the pressure is lower than 3 MPa, the above-described problem may occur. If it exceeds 30 MPa, the cost of the apparatus may increase.

[Filling the Gas in the Die] The die immediately before injection is filled with a high-pressure gas supplied through a pressure control valve by a gas cylinder or a pressure pump under a predetermined pressure. preferable. For example, when using nitrogen or carbon dioxide as the high-pressure gas, the pressure is 0.5 to 1
The range is 5 MPa, preferably 1 to 13 MPa, more preferably 3 to 10 MPa. At less than 0.5 MPa,
In some cases, cells grow during the filling process, and an unfoamed foamed molded product cannot be obtained. If it exceeds 15 MPa, a problem may occur in filling the resin. After the injection, the polylactic acid-based expandable molded product filled in the mold without being foamed is released.

[Crystallinity of Expandable Molded Article]
The crystallinity of the foamable molded product 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%. When the degree of crystallinity exceeds 20%, the elastic modulus of the resin drops sharply near the melting point when heated and foamed in a mold, and the generated bubbles can be broken and a good foam can be obtained. Can not.

[Mold Temperature and Crystallinity] In the present invention, in order to obtain an expandable molded product having a crystallinity of 0 to 20%,
Molding is performed at a mold temperature of -40 to 50 ° C. Preferably, it is -30 to 40C, more preferably -20 to 30C, and still more preferably -10 to 20C. Even if the mold temperature is lower than −40 ° C., the effect does not change so much although it takes time and effort. When molding at a temperature exceeding 50 ° C., especially when an additive such as a nucleating agent is added, the degree of crystallinity may exceed 20%. By adding a volatile foaming agent to the polylactic acid-based resin, T
It is considered that g is decreased and crystallization easily occurs in the mold.

[Method for Producing Foam] After release, the unfoamed foamed molded article is placed in a desired foaming mold and heated with warm water or steam to obtain a polylactic acid-based foam. be able to. 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-Conc
is Encyclopedia of Polym
er Science and Engineerine
g (edited by Kroschwitz, edited by Tatsuta Mita, Maruzen, Tokyo, 1994) ”, pages 810 to 815, can be suitably employed. 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. Foam voids ("bubbles", "voids",
It also includes the concept of terms such as “microvoid”, “cavity”, and “cell”. ), Continuity, independence,
Characteristics such as size, shape, distribution, and size uniformity can be controlled by appropriately setting foaming conditions according to the purpose.

[Heating temperature] The heating temperature (Th
[° C.]) is generally represented by the formula (2) [Equation 2] (Tg; glass transition temperature, Tm; melting point). In general, it is preferable in the order of Expression (2) [Equation 2] to Expression (6) [Equation 6]. T
If the temperature is lower than g, foaming may not occur. On the other hand, if the temperature is higher than Tm, the foamed product may re-shrink or bubbles may be broken, which is not preferable. [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, an expandable molded article is used. Any method can be used without limitation as long as the energy required for heating and foaming is supplied by some method. For example, a mold containing foamed particles is put into a heat medium, exposed to a temperature-controlled atmosphere, or heated inert gas such as nitrogen, steam, or carbon dioxide gas is blown into a mold. Etc. can be used.

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

[Foam] The term "foam" used in the claims and specification of the present application includes many voids ("bubbles", "voids", "microvoids") inside a resin. , "Cavities", "cells" and the like are included.) In the continuous phase of the resin having a small apparent density, a void phase (a void is continuous,
(Including independent ones), a resin structure having a two-phase structure or a multi-phase structure, such as a polymer having a cellular structure, a foamed polymer, an expanded polymer, a polymer foam, and a polymer This includes general structures recognized as structures such as foams, and also includes soft and hard structures. When the foamed article obtained by subjecting the foamable molded article according to the present invention to foam molding is used in the form of a foam, it has excellent cushioning properties, impact resistance, heat insulation properties, etc. It is suitably used for insulation materials for furniture, furniture, cushioning materials for automobiles, 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. Foams range from 2-3 times low foaming to 10-20 times medium foaming, 30-50 times (30-100 times depending on the case)
High foaming. Specific examples of the use of so-called high foams, which are mainly composed of sheets and board-like foams, include, for example, packaging and packing, construction / civil engineering, vehicles /
For ships, for industrial insulation, for agriculture, forestry and fisheries, and for sports and miscellaneous goods.

[Synthetic Wood] In the present invention, the foamed molded article may be a low-foamed foam falling in the category of synthetic wood. Here, "synthetic wood ([Artifici
alwoods]) "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 [Structura
lfoam] "substantially corresponds to this. That is, a foaming ratio of 1.1 to 1.0 having a skin layer
It refers to a plastic low-foaming product of about 4 times. Synthetic wood is a highly promising material from the standpoint of global wood shortage and environmental protection. By selecting a molding method, it is possible to produce synthetic wood that is difficult to distinguish from natural wood in appearance, and can be applied to applications with high added value such as furniture. Specific examples of uses of synthetic wood include, for example, cutting boards, sawboards, container pallets, concrete panels, and the like.

[Use] The foam obtained from the expandable molded article of the present invention can also 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 difficult to collect or disposable foam container, buffer (packaging) material, material for civil engineering industry,
It can be suitably used as a substitute for a general-purpose resin foam used for materials for agriculture and fisheries and leisure goods.

General Purpose Applications Foams obtained from the foamable molded article of the present invention include, for example,
Lunch boxes, tableware, containers for lunches and prepared foods sold at convenience stores, cups for cup ramen, cups used for vending machines for beverages, foodstuffs such as fresh fish, meat, vegetables and fruits, tofu, prepared foods Containers and trays, torobaco (fish boxes for fisheries) used in the fresh fish market, containers for dairy products such as milk, yogurt, lactic acid bacteria drinks, carbonated drinks,
Containers for soft drinks, liquor drinks such as beer and whiskey, cosmetic containers, detergent containers, bleach containers, cool boxes, flower pots, tapes, buffers for use in transporting home appliances such as TVs and stereos Materials and packaging materials, cushioning materials for transportation of precision machines such as computers, printers, watches, etc., cushioning materials for transportation of optical machines such as cameras, glasses, microscopes, telescopes, etc., glass, ceramics, etc. Cushioning material used for transportation of ceramic products, loose cushioning material (easy packing material that can be packed on site), light shielding material, heat insulating material (extruded board etc.), soundproofing material / sound insulation material (extruded board etc.), Extruded foam sheet (polymer paper for food related applications, prepackaged. Mainly applied to packaging materials and containers for food), non-foamed film bonded to foam sheet Of sewage furnace over filter, a net-like foam, it can be suitably used as a foaming type and the like.

General Industrial Use and Recreational Use of the Foam The foam obtained from the expandable molded article of the present invention can be used for general industrial use and leisure, including agriculture, fishing, forestry, industry, construction and civil engineering, and transportation. It can be suitably used for recreational applications including sports. 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.

[0043]

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 (Tm) Differential scanning calorimeter (DSC-50, manufactured by Shimadzu Corporation)
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).

The degree of 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.

Shape Reproducibility The reproducibility of the mold shape of the foam 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%
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)> In a 100-liter reactor equipped with a Dien-Stark trap, 10 kg of 90% L-lactic acid was added at 150 ° C / 5.
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). Was. The weight average molecular weight Mw of this polymer is
It was 118,000. To 40.0 g of the obtained polybutylene succinate, 160.0 g of polylactic acid obtained by the same method as in Production Example 2 (weight-average molecular weight Mw is 2,000,000),
Diphenyl ether (800 g) and metal tin (0.7 g) were mixed, and a dehydration condensation reaction was performed again at 130 ° C./17 mmHg for 20 hours. After completion of the reaction, post-treatment was carried out in the same manner as in Production Example 2 to obtain 188 g of a copolymer of polybutylene succinate and polylactic acid (yield 94%). Copolymer of this polybutylene succinate and polylactic acid (copolymer C)
Had a weight average molecular weight Mw of 14,000.

[Production Example 4] <Production of copolymer D (polycaproic acid / polylactic acid copolymer)> The 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 of polycaproic acid and polylactic acid (copolymer D) was obtained. Yield is 92
%, And the weight average molecular weight Mw was 153,000. [Production Example 5] <Production of polymer E (blend of polylactic acid and polybutylene succinate)> Polylactic acid (weight average molecular weight Mw1) obtained in Production Example 1
160,000) and 40 g of the polybutylene succinate obtained in Production Example 3 (weight average molecular weight Mw: 14,000)
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)> Polylactic acid obtained in Production Example 1 (weight average molecular weight Mw1)
(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 A polylactic acid (polymer A) pellet was supplied as a polylactic acid-based resin from a hopper into a continuous plasticizing apparatus, and was heated and melted at 170 ° C. to obtain 100 parts by weight of the polylactic acid (polymer A) pellet. On the other hand, carbon dioxide is 18MP
a, and supplied when the resin was completely melted. After measuring the homogenized molten resin into the injection molding machine, 50
It was injected into a mold of mm × 50 mm (thickness 3.2 mm). At this time, the mold was previously filled with nitrogen gas at a pressure of 7 MPa. Mold temperature is 20 ° C, cooling time is 2
Performed at 0 seconds. After the injection is completed, remove the nitrogen gas from the mold,
After cooling, the foamable molded product was taken out. The obtained foamable molded article had a crystallinity of 0% and was not foamed. A mold (length × width × height = 100 mm × 100 mm × 20 m) made of the foamed molded product from a 2 mm-thick iron plate with an air hole.
m), the foam was blown through hot air at 110 ° C. from the air hole to fuse the particles together, and then cooled. The mold was opened, the obtained foam was taken out, and its shapeability and strength were evaluated. The results are shown in Table 1.

[Examples 2 to 12 and Comparative Examples 1 to 5] Examples 2 to 12 and Comparative Examples 1 to 5 were made of a polylactic acid resin, a foaming agent, a melting temperature, production conditions of a foamable molded product, and foam molding. The procedure was performed in the same manner as in Example 1 except that the molding conditions of the product were changed.
The results are shown in Table 1 [Table 1], Table 2 [Table 2], and Table-3 [Table 3].

[0055] [Legend] “←” means “same as left”. [Legend] “←” means “same as left”. [Legend] “←” means “same as left”.

[0056]

By forming and processing the expandable molded article 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. Thus, a foamed molded article of any shape can be obtained. The foamed molded article has biodegradability and is difficult to collect and reuse, and is a foamed (molded) article, a disposable foamed container, a cushioning material, a material for the civil engineering industry, a material for the agriculture and water industry, a leisure article. The foam molded article which can be suitably used as a substitute for the foam molded article used in (1) 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.

Continuing on the front page (72) Inventor Yasuhiro Kitahara 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Prefecture Inside Mitsui Chemicals Co., Ltd. In-house (72) Inventor Tomoyuki Nakata 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Mitsui Chemicals, Inc.

Claims (5)

[Claims] 1. An unfoamed polylactic acid having a crystallinity of 0 to 20%, comprising a foamable resin composition containing 1 to 30 parts by weight of a volatile foaming agent with respect to 100 parts by weight of a polylactic acid-based resin. Foamable molded product. 2. An unfoamed polylactic acid having a crystallinity of 0 to 20%, comprising a foamable resin composition containing 1 to 30 parts by weight of a volatile foaming agent with respect to 100 parts by weight of a polylactic acid based resin. Manufacturing a polylactic acid-based foam, comprising heating a foamable molded article at a temperature equal to or higher than the glass transition temperature of the polylactic acid-based resin to foam a volatile foaming agent contained in the polylactic acid-based resin. Method. 3. A polylactic acid-based foam obtained by the production method according to claim 2. 4. A method for molding a foamable resin composition containing 1 to 30 parts by weight of a volatile foaming agent with respect to 100 parts by weight of a polylactic acid-based resin in a non-foamed state with a crystallinity of 0 to 20%. A method for producing a polylactic acid-based foamable molded product, which is characterized by the following. 5. A foamable resin composition containing 1 to 30 parts by weight of a volatile foaming agent with respect to 100 parts by weight of a polylactic acid-based resin, a mold temperature of -40 to 50 ° C. and a crystallinity of 0 to 20. % And a method for producing a polylactic acid-based expandable molded article, characterized in that the molded article is molded in an unfoamed state.