JP2010235835A - Thick aliphatic polyester-based resin foam molding and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thick aliphatic polyester-based resin foam molding and a method for producing the same. <P>SOLUTION: In the aliphatic polyester-based resin foam molding, a content of a chloroform-insoluble component is 25% or more and a thickness is more than 60 mm and equal to or less than 200 mm. A heating process preferably comprises a preheating process and a main heating process. The aliphatic polyester-based resin foam molding is obtained by performing in-mold expansion molding when a molding space center temperature during the preheating process is more than Tg+30 (°C) and equal to or less than Tg+60 (°C), and the molding space center temperature during the main heating process is equal to or more than Tg+30 (°C) and equal to or less than Tg+60 (°C), assuming that a glass transition temperature of the aliphatic polyester-based resin is Tg. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a thick aliphatic polyester resin foam molded article and a method for producing the same.

In general, foam molded articles are widely used as civil engineering materials, building materials, distribution materials, automobile materials and the like by taking advantage of lightness, heat insulation, buffering properties and the like. For example, a polystyrene foam molded body having a thickness like a block shape is suitably used for civil engineering applications, building materials, and automobile applications, taking advantage of its light weight and increased volume. On the other hand, a resin having biodegradability has been applied as such a foamed molded article. For example, Patent Document 1 discloses foaming of an aliphatic polyester resin having a thickness of 60 mm and having a chloroform-insoluble content of 5% by weight or more. It is disclosed that the particle compact was molded at a molding temperature of 125 ° C. In Patent Document 2, foamed particles mainly composed of non-crystalline polylactic acid composed of L-form and D-form are treated for 10 to 30 seconds with a steam pressure of 0.5 kgf / cm ³ (about 110 ° C.) and molded. However, it is disclosed that a foamed molded product having a thickness of 60 mm was obtained.

Patent Document 3 discloses a tatami mat using a polylactic acid resin foam having a density of 0.02 to 0.30 g / cm ³ and a thickness of 5 mm or more. However, specifically, in the examples, a foam having a thickness of 50 mm is disclosed by filling foamed particles in a closed mold and molding with a steam molding machine by heating at a water vapor pressure of 0.1 MPa (about 120 ° C.) for 20 seconds. It has only been done. In Patent Document 4, non-crosslinked high foaming ratio is obtained by bringing expanded particles made of a non-crosslinked polylactic acid resin composition into contact with a gas heated to specific conditions based on the glass transition temperature of polylactic acid. It is disclosed that a polylactic acid-based resin foam molded article was obtained.

  As described above, in the aliphatic polyester resin foam molded article that is a typical biodegradable resin, a foam molded article having a thickness exceeding 60 mm has not been specifically reported so far.

JP 2001-49021 A JP 2001-98104 A JP 2004-156372 A JP 2006-111704 A

  An object of the present invention is to provide a thick aliphatic polyester resin foam molded article and a method for producing the same.

  As a result of intensive studies, the present inventor has found that a thick aliphatic polyester resin foamed molded article can be obtained by using a crosslinked aliphatic polyester resin, and the present invention has been completed.

That is, the present invention has the following configuration.
[1] An aliphatic polyester resin foam molded article having a chloroform insoluble content of 20% or more and a thickness of more than 60 mm and 200 mm or less.
[2] The maximum tensile stress of the surface layer portion and the center portion of the aliphatic polyester resin foam molded article is 0.35 MPa or more and 2.0 MPa or less, respectively, and the maximum tensile stress of the surface layer portion and the maximum tensile stress of the center portion. The aliphatic polyester-based resin foam molded article according to [1], wherein the ratio is from 0.80 to 1.20.
[3] The aliphatic polyester resin foam molded article according to [1] or [2], wherein the apparent density is 0.014 g / cm ³ or more and 0.050 g / cm ³ or less.
[4] The aliphatic polyester resin foam molded article according to any one of [1] to [3], wherein the aliphatic polyester resin is a polylactic acid resin.
[5] The foamed aliphatic polyester resin particles containing the aliphatic polyester resin are filled into a molding space composed of a mold that can be closed but cannot be sealed, and obtained through a heating process. [1] to [4] A method for producing an aliphatic polyester resin foam molded article according to any one of [1] to [4].
[6] The heating process includes a preheating process and a main heating process. When the glass transition temperature (Tg) of the aliphatic polyester resin is used, the center temperature of the molding space during the preheating process is Tg + 30 (° C.). Exceeding Tg + 60 (° C.) or less, and the molding space center temperature during the heating step is Tg + 30 (° C.) or more and Tg + 60 (° C.) or less, The production of an aliphatic polyester resin foam molded article according to [5] Method.
[7] The method for producing an aliphatic polyester resin foam molded article according to [6], wherein a mixture of water vapor and air is used as a heat medium used in the heating step.

  Since the aliphatic polyester-based resin foam molded article of the present invention has a thickness, it can be suitably used for civil engineering applications, architectural applications, automobile applications, and the like.

  According to the production method of the present invention, a thick aliphatic polyester resin foam molded article can be produced easily.

  The aliphatic polyester resin used in the present invention refers to an aliphatic polyester as a main component (50% by weight or more). For example, a polylactic acid resin including polylactic acid as a main component, poly-3- (hydroxy Butyrate), poly-3- (hydroxybutyrate-covalerate), poly-3- (hydroxybutyrate-cohexanoate) and other hydroxy acid polycondensates, and ring-opening polymers of lactones such as polycaprolactone And polycondensates of aliphatic polyhydric alcohols such as polybutylene succinate, polybutylene adipate, polybutylene succinate adipate, poly (butylene adipate / terephthalate) and aliphatic carboxylic acid, etc., selected from these groups Can be used.

  In addition, two or more aliphatic polyester resins can be mixed and used, and, as long as the effects of the present invention are not impaired, other resins are added to the aliphatic polyester resin to form a base resin. I can do things. At that time, the base resin preferably contains 50% by weight or more of an aliphatic polyester resin, more preferably 70% by weight or more, and still more preferably 90% by weight or more. Examples of the other resins include polyethylene resins, polypropylene resins, polystyrene resins, polyester resins, acrylic resins, and vinyl resins.

  Among these, in order to obtain the effects of the present invention, as the aliphatic polyester-based resin, a polylactic acid-based resin or a hydroxy acid polycondensate is preferable, and a polylactic acid-based resin is particularly preferable from the viewpoint of environmental friendliness.

  The polylactic acid-based resin is not particularly limited, but it is preferable that the main component is polylactic acid whose isomer ratio of the lactic acid component is 5% or more, preferably 8% or more. If it is the said range, since polylactic acid is amorphous, it is preferable from the point of foamability and moldability.

  The melt viscosity of the polylactic acid resin preferably has a melt index (MI) value in accordance with JIS K 7210 (load 2.16 kg) of 0.1 g / 10 min or more and 10 g / 10 min or less. If the MI value is within this range, it tends to be easy to obtain a foamed molded article having excellent productivity and a high foaming ratio, and the objects and effects of the present invention are easily exhibited.

  The weight average molecular weight of the aliphatic polyester of the present invention is preferably from 150,000 to 400,000. If the weight average molecular weight is within this range, expanded particles having good moldability and expanded molded articles having good appearance tend to be obtained.

  The aliphatic polyester resin foam molded article of the present invention has a chloroform insoluble content of 20% by weight or more, preferably 25% or more, and more preferably 30% or more. When the insoluble content of chloroform is within the above range, the viscosity decrease due to heat becomes moderate, the balance between the foaming force and the fusion force of the foamed particles is easy to be achieved, and the aliphatic polyester having a thickness of more than 60 mm and not more than 200 mm sufficiently fused internally. -Based resin foam molding is obtained.

In the present invention, the chloroform-insoluble matter is precisely weighed about 0.3 g of the foamed molded product, measured as follows, to obtain a weight W ₁ . Next, the weight of the mesh (mesh 200) into which the molded body was put was measured. Next, the foamed molded product is wrapped in a mesh (W ₂ (g)), placed in a flask containing 95 ml of chloroform, and heated to reflux for 8 hours. Thereafter, the foam-molded mesh was dried overnight in a vacuum dryer at 60 ° C., and then the weight (W ₃ (g)) of the foam-molded mesh was measured. It was.
Chloroform insoluble content (%) = (W ₃ −W ₂ ) / W ₁ × 100

  In order for the chloroform-insoluble matter of the aliphatic polyester resin foamed molded article to be 20% by weight or more, it is preferable to add a crosslinking agent to the aliphatic polyester resin to cause crosslinking.

  Examples of the crosslinking agent that can be used include general crosslinking agents such as polyisocyanate compounds, peroxides, acid anhydrides, and epoxy compounds.

  As the polyisocyanate compound, aromatic polyisocyanate, alicyclic polyisocyanate, aliphatic polyisocyanate, and the like can be used. An isocyanate compound is mentioned. Examples of the alicyclic polyisocyanate include polyisocyanate compounds having isophorone and diphenylmethane hydroxide as a skeleton, and examples of the aliphatic polyisocyanate include polyisocyanate compounds having hexamethylene and lysine as a skeleton.

  Examples of the peroxide include benzoyl peroxide, bis (butylperoxy) trimethylcyclohexane, bis (butylperoxy) cyclododecane, butylbis (butylperoxy) valerate, dicumyl peroxide, butylperoxybenzoate, and dibutyl peroxide. And organic peroxides such as bis (butylperoxy) diisopropylbenzene, dimethyldi (butylperoxy) hexane, dimethyldi (butylperoxy) hexyne, and butylperoxycumene.

  Examples of the acid anhydride include trimellitic anhydride, pyromellitic anhydride, ethylene-maleic anhydride copolymer, methyl vinyl ether-maleic anhydride copolymer, styrene-maleic anhydride copolymer, and the like.

  Examples of the epoxy compound include glycidyl methacrylate-methyl methacrylate copolymer, glycidyl methacrylate-styrene copolymer, glycidyl methacrylate-styrene-butyl acrylate copolymer, polyethylene glycol diglycidyl ether, trimethylolpropane polyglycidyl ether, coconut fatty acid glycidyl. Examples thereof include various glycidyl ethers such as esters, epoxidized soybean oil, and epoxidized linseed oil, and various glycidyl esters.

  Of these crosslinking agents, polyisocyanate compounds are preferably used. The reason is that if a polyisocyanate compound is used, torque increase due to cross-linking and thickening during kneading is small, and post-thickening due to urea bond, urethane bond, allophanate bond, etc. is possible by heating in the presence of moisture after kneading. It is. Among the polyisocyanate compounds, it is preferable to use a polyisocyanate compound having a tolylene or diphenylmethane skeleton, particularly a polyisocyanate of diphenylmethane, from the viewpoints of versatility, handleability, weather resistance, and the like.

  The addition amount of the crosslinking agent can be adjusted and determined for each crosslinking agent so as to obtain desired melting characteristics. The amount varies depending on the kind of the crosslinking agent and the amount of the functional group, but is preferably 0.1 parts by weight or more and 6.0 parts by weight or less, more preferably 0, with respect to 100 parts by weight of the aliphatic polyester resin. 2 parts by weight or more and 5.0 parts by weight or less, more preferably 0.5 parts by weight or more and 4.0 parts by weight or less.

  For example, a polylactic acid resin having a weight average molecular weight of about 200,000 and a polydispersity of about 2 to 2.5 is used as the aliphatic polyester resin, whereas an aromatic having a functional group of 2 to 3 is used as a crosslinking agent. When the polyisocyanate compound is used, the content is preferably 0.1 part by weight or more and 5 parts by weight or less, more preferably 0.2 part by weight or more and 4 parts by weight or less with respect to 100 parts by weight of the polylactic acid resin. The amount is more preferably 1.5 parts by weight or more and 3.5 parts by weight or less.

  Additives such as a bubble regulator and a colorant can be added to the aliphatic polyester resin. For example, examples of the air conditioner include inorganic substances such as talc, calcium carbonate, borax, zinc borate, aluminum hydroxide, and calcium stearate, and these can be added to the aliphatic polyester resin in advance. The addition amount of the cell regulator is preferably 0.001 to 10 parts by weight with respect to 100 parts by weight of the aliphatic polyester resin.

  Examples of the colorant include pigments such as black, gray, brown, blue and green pigments or dyes. Examples of the colorant include organic and inorganic pigments and dyes. Conventionally known pigments and dyes can be used.

  The addition amount of the colorant varies depending on the color of the color, but is usually preferably 0.001 part by weight or more and 5 parts by weight or less, and 0.02 part by weight or more and 3 parts by weight or less with respect to 100 parts by weight of the aliphatic polyester resin More preferably, it is as follows.

  In addition, additives such as a flame retardant, an antistatic agent, and a weathering agent may be added to the aliphatic polyester resin as long as the effects of the present invention are not impaired.

  When adding additives such as cell regulators and colorants to aliphatic polyester resins, the additives can be kneaded into the aliphatic polyester resins as they are, but usually the additives are taken into account dispersibility and the like It is preferable to make a masterbatch and knead it with an aliphatic polyester resin.

  The aliphatic polyester resin foam molded article of the present invention fills a molding space composed of a mold that can be closed but cannot be sealed with aliphatic polyester resin foam particles containing an aliphatic polyester resin. It is preferably obtained by a so-called bead method in-mold foam molding method obtained through a heating step.

In order to produce an aliphatic polyester resin expanded particle comprising an aliphatic polyester resin,
(A) impregnating a particulate aliphatic polyester resin with a foaming agent to form expandable aliphatic polyester resin particles, and heating and foaming the expandable aliphatic polyester resin particles to form expanded particles;
(B) A method of impregnating an aliphatic polyester resin in the form of particles in a pressure-resistant container with a foaming agent and releasing the foamed particles under a low-pressure atmosphere,
(C) a method of melt-kneading an aliphatic polyester-based resin together with a foaming agent in an extruder, and extruding, foaming or cutting into a foamed particle shape after completion of foaming,
(D) The aliphatic polyester resin is melt-kneaded in an extruder together with a foaming agent, cut into a particle shape while being extruded without being foamed, to obtain expandable aliphatic polyester resin particles, and the expandable aliphatic polyester A method of heating and foaming resin-based resin particles to form expanded particles,
And the like.

  The blowing agent that can be used in the present invention is not particularly limited and conventionally known blowing agents can be used, and hydrocarbons such as propane, isobutane, normal butane, isohexane, normal hexane, cyclobutane, cyclohexane, isopentane, normal pentane, cyclopentane, etc. -Based foaming agents; halogenated hydrocarbon foaming agents such as methyl chloride, methylene chloride, dichlorodifluoromethane; ether-based foaming agents such as dimethyl ether and methyl ethyl ether; inorganic foaming agents such as nitrogen, carbon dioxide, argon, air, etc. 1 type or 2 or more types can be used in combination.

  When producing foamed molded products by the in-mold foam molding method using beads, hydrocarbon-based foaming is possible because there is little gas dissipation with respect to aliphatic polyester-based resin, foamable particle transport is possible, and desired foamability is obtained. It is preferable to use an agent.

  The amount of foaming agent can be adjusted depending on the type of foaming agent and the desired expansion ratio, but it is preferably 2 parts by weight or more and 20 parts by weight or less with respect to 100 parts by weight of the aliphatic polyester resin. For example, in order to obtain expanded particles having an expansion ratio of 30 times or more, the amount of the foaming agent is preferably 4 parts by weight or more with respect to 100 parts by weight of the aliphatic polyester resin constituting the expandable particles.

The bulk density of the expanded aliphatic polyester resin particles is preferably from 0.014 g / cm ³ or more 0.050 g / cm ³ or less, 0.016 g / cm ³ or more 0.048 g / cm ³ and more preferably less, 0.018 g / Cm ³ or more and 0.046 g / cm ³ or less is more preferable. If the foamed particles have a bulk density within the above range, a lightweight and thick aliphatic polyester resin foamed molded product tends to be obtained. In addition, the bulk density of the aliphatic polyester-based resin expanded particles is measured based on JIS K6911, and the bulk density of the aliphatic polyester-based resin expanded particles is calculated based on the following formula.
Bulk density of aliphatic polyester resin expanded particles (g / cm ³ ) = [mass cylinder mass (g) -mass cylinder mass (g)] / [meas cylinder capacity (cm ³ )]

  The aliphatic polyester resin expanded particles obtained as described above are preferably filled with a molding space after relaxation of the pressure difference between the inside and outside of the expanded particles (also referred to as curing), and then subjected to a heating process. A resin-based in-mold foam molding is obtained. When the secondary foaming power of the aliphatic polyester resin foamed particles is poor, in addition to the pressure filling and compression filling methods used in general in-mold foam molding, inorganic gases such as air, nitrogen and carbon dioxide are used as fat. After imparting to the polyester resin foam particles, they may be subjected to in-mold foam molding.

  Here, an example of a method for producing polylactic acid resin expanded particles using a polylactic acid resin as a base resin will be described.

  First, polylactic acid resin particles are prepared from a polylactic acid resin. These polylactic acid resin particles can be produced by a conventionally known method. For example, after polylactic acid resin and, if necessary, a crosslinking agent and other additives are melt-kneaded with an extruder, an underwater cutter or a strand cutter is used. It can obtain by carrying out extrusion cutting by the above. The weight per polylactic acid resin particle is preferably 0.05 mg or more and 10 mg or less, more preferably 0.1 mg or more and 4 mg or less. When the particle weight is in the above range, the productivity of the resin particles is good and the filling property into the molding space tends to be good.

  Next, the polylactic acid resin particles are impregnated with a foaming agent to obtain expandable polylactic acid resin particles. The method for impregnating the polylactic acid resin particles with the foaming agent is not particularly limited as long as sufficient pressure is applied in the presence of the foaming agent that provides the desired foamability. For example, it is possible to impregnate a resin particle with a foaming agent by placing an aqueous medium or a non-aqueous medium in an airtight container, adding resin particles and a foaming agent thereto, and stirring at an appropriate temperature and time. is there. When impregnating with an aqueous medium, it is preferable that the polylactic acid-based resin is easily subjected to a hydrolysis reaction, and it is preferable to end the impregnation in a short time with a device for suppressing hydrolysis.

  In the impregnation with the foaming agent, an impregnation aid, a dispersing agent or the like may be used in order to obtain stable impregnation properties and foamability. Examples of the impregnation aid include proton solvents such as methanol, ethanol and propanol, ketones such as acetone and methyl ethyl ketone, esters such as ethyl acetate, butyl acetate and normal propyl acetate, toluene and xylene. Examples include aprotic solvents such as aromatic hydrocarbons. When impregnated with an aqueous medium, it is preferable to use an aprotic solvent that does not promote hydrolysis of the polylactic acid resin. Examples of the dispersant include a cationic surfactant, an anionic surfactant, and a nonionic surfactant. In the case of impregnation with an aqueous medium, monovalent metal salts such as sodium chloride, sodium sulfate, sodium carbonate, potassium chloride, potassium sulfate, potassium carbonate, and chloride are used for the purpose of suppressing water penetration into the resin particles. It is preferable to add water-soluble salts such as divalent metal salts such as magnesium and magnesium sulfate, and trivalent metal salts such as aluminum sulfate. The amount of water-soluble salts added for the purpose of suppressing water penetration into the resin particles is preferably 5 parts by weight or more and 20 parts by weight or less, and 7.5 parts by weight or more and 20 parts by weight or less with respect to 100 parts by weight of water. More preferred are parts by weight or less. When the amount is less than 5 parts by weight, the foaming agent may not be sufficiently impregnated, and when the amount is more than 20 parts by weight, the foaming agent may be difficult to enter.

  Alternatively, when obtaining expandable polylactic acid-based resin particles, the polylactic acid-based resin can be impregnated with a foaming agent using an extruder. In that case, the polylactic acid-based resin and, if necessary, a crosslinking agent, Other additives are put into an extruder, and after adding a foaming agent and melt-kneading, the kneaded product is extruded, and the extruded kneaded product is cut to obtain expandable particles.

  Next, the foamable polylactic acid resin particles are expanded to obtain polylactic acid resin foam particles. As such a method, for example, a method in which foamable polylactic acid resin particles are heated and foamed with steam, hot air, high frequency, etc., and the resin particles are dispersed in a dispersion medium in the presence of a foaming agent in a sealed container, Heat the contents to soften the resin particles, impregnate the particles with the foaming agent, then open one end of the container and disperse with the resin particles while maintaining the pressure inside the container at a pressure higher than the vapor pressure of the foaming agent. Simultaneously releasing the foam into a low-pressure atmosphere (usually under atmospheric pressure) from the container and foaming it, melting the polylactic acid resin and, if necessary, the crosslinking agent and other additives in an extruder It is foamed by kneading with a foaming agent to form a foamable melt-kneaded product, then extruding into a strand shape and foaming, and cutting it to an appropriate length after cooling, or cutting the strand to an appropriate length and then cooling. Method of making a child, and the like. Among these, from the viewpoint that the expandable particles can be transported and the operation is simple, a method of heating and foaming the expandable polylactic acid resin particles with steam, hot air, high frequency, or the like is preferable.

  As described above, the aliphatic polyester resin expanded particles that can be used in the present invention can be produced.

  It is preferable to obtain a thick aliphatic polyester resin foamed molded article by foaming the aliphatic polyester resin foamed particles in-mold. However, aliphatic polyester-based resins typified by polylactic acid-based resins tend to rapidly soften near the glass transition temperature (hereinafter sometimes referred to as Tg) and decrease with melt tension. If the temperature rise overlaps with the rise in internal pressure accompanying rapid expansion of the internal gas, it expands all at once and tends to cause poor internal fusion because it prevents the heat medium such as water vapor from entering the molding space. Therefore, for example, by performing the following heating step, it is possible to obtain an aliphatic polyester resin foam molded article having a thickness exceeding 60 mm that is sufficiently fused to the inside of the aliphatic polyester resin foam molded article. it can.

For example,
(1) Aliphatic polyester resin foaming in a molding space composed of a mold that can be closed but cannot be sealed in a molding machine usually used for molding polystyrene foam or a molding machine used for molding polyolefin resin foam particles Filling the particles and bringing a heat medium having a relatively low temperature into contact with the foamed aliphatic polyester resin particles,
(2) The mold filled with the aliphatic polyester resin expanded particles is immersed in water adjusted to a temperature of 100 ° C. or lower.
(3) Pour warm water adjusted to a temperature of 100 ° C. or lower through a mold filled with expanded foam of aliphatic polyester resin,
And the like, such as a heating step. Among these, the method (1) is preferable because an existing molding machine can be used.

  The heating process in the in-mold foam molding method of expanded polystyrene or polyolefin resin foamed particles generally includes a preheating process and a main heating process. The preheating process is a process in which the air in the space formed when the foam particles are filled in the mold is replaced with steam to raise the temperature of the foam particles, and in this heating process, the foam particles are melted by continuously applying steam. This is the process of wearing. When such a heating step is employed in the present invention, the molding space center temperature during the preheating step is preferably more than Tg + 30 (° C.) and not more than Tg + 60 (° C.), and more preferably Tg + 33 (° C.) or more and Tg + 60 (° C.) or less. More preferably, Tg + 33 (° C.) or higher and Tg + 55 (° C.) or lower is more preferable.

  Moreover, it is preferable that the molding space center temperature at the time of this heating process is Tg + 30 (degreeC) or more and Tg + 60 (degreeC) or less, Tg + 33 (degreeC) or more and Tg + 60 (degreeC) or less are more preferable, Tg + 33 (degreeC) or more and Tg + 55. (° C.) or less is more preferable. The molding space center temperature can be measured using a thermocouple or the like.

  In order to achieve such a molding space center temperature, an air line is connected to a steam line of a molding machine usually used for molding foamed polystyrene or a molding machine used for molding polyolefin-based resin foamed particles, so that steam and air are supplied. It is preferable to adjust by mixing or mixing steam and air in a buffer tank or the like.

  The heating process time is preferably 20 seconds or longer and 400 seconds or shorter, more preferably 20 seconds or longer and 380 seconds or shorter, and further preferably 20 seconds or longer and 360 seconds or shorter. When the molding space center temperature and the contact time are within the above ranges, an aliphatic polyester-based resin foam molded article having a thickness exceeding 60 mm that is sufficiently fused internally can be obtained.

  In addition, when the secondary foaming power of the aliphatic polyester resin foam particles is poor, in addition to the pressure filling and compression filling methods used for general in-mold foam molding, inorganic gases such as air, nitrogen, carbon dioxide, etc. May be imparted to the aliphatic polyester resin expanded particles.

The bulk density of the thus obtained aliphatic polyester resin expansion molding is preferably 0.014 g / cm ³ or more 0.050 g / cm ³ or less, 0.016 g / cm ³ or more 0.048 g / cm ^3, more preferably less, more preferably 0.018 g / cm ³ or more 0.046 g / cm ³ or less. If it is the said range, since it is lightweight, it is preferable.

  The thickness of the aliphatic polyester resin foam molded article of the present invention is more than 60 mm and 200 mm or less, and preferably 60 mm or more and 180 mm or less. Here, the thickness is a direction perpendicular to the spreading plane direction of the aliphatic polyester-based resin foam molding. However, in the case of an aliphatic polyester resin foam molded article produced by a bead method in-mold foam molding method, it means the maximum length of the foam molded article in the mold opening direction.

  The aliphatic polyester-based resin foam molded article of the present invention has a thickness of 30% from the surface with respect to the thickness direction of the foam molded article as “surface layer part” and a thickness from 30% to 70% as “center part”. The maximum tensile stress at the center part with the surface layer part is preferably 0.35 MPa or more and 2.0 MPa or less, more preferably 0.35 MPa or more and 1.8 MPa or less, and further preferably 0.35 MPa or more and 1. It is preferable that it is 6 MPa or less, and the ratio of the maximum tensile stress of the surface layer part to the maximum tensile stress of the center part is 0.80 or more and 1.20 or less.

  When the maximum tensile stress of the surface layer portion and the central portion is within the above range, it can be said that the aliphatic polyester-based resin foam molded body is sufficiently fused internally.

  Hereinafter, although the aliphatic polyester-type resin foaming molding of this invention is demonstrated in detail by a specific Example, this invention is not limited only to this Example. Unless otherwise specified, “part” and “%” are based on weight.

<Glass transition temperature measurement>
About 5 mg of aliphatic polyester resin particles are weighed, and the glass transition temperature (° C.) is raised by raising the temperature from 0 ° C. to 200 ° C. at a rate of temperature rise of 10 ° C./min with a differential scanning calorimeter (Seiko Instruments Inc.). It was measured.

<Measurement of chloroform insoluble matter>
About 0.3 g of the foam molded product is precisely weighed to obtain a weight W ₁ . Next, to measure the weight of the mesh (Mego 200) to put the molded body was W _2. Next, the molded body was wrapped in a mesh, placed in a flask containing 95 ml of chloroform, and heated to reflux for 8 hours. The molded mesh containing the heated reflux was dried overnight in a vacuum dryer at 60 ° C. The weight of the dried molded body containing mesh was measured and the W _3. The chloroform insoluble content was calculated from the following formula.
Chloroform insoluble content (%) = (W ₃ −W ₂ ) / W ₁ × 100

<Maximum tensile stress measurement>
From the surface layer part up to 30% in the thickness direction of the aliphatic polyester resin foam molded article and the center part of 30% or more and 70% or less, a test piece was cut out to a size according to JIS K-6767, and the test piece was pulled. Using a compression tester (TG-20kN, manufactured by Minebea), a tensile test was performed according to JIS-K6767, and the maximum tensile stress was determined from the obtained stress-strain curve.

<Fusability evaluation>
When the maximum tensile stress of the surface layer portion and the central portion is 0.35 MPa or more and 2.0 MPa or less, respectively, and the ratio of the maximum tensile stress of the surface layer portion and the maximum tensile stress of the central portion is 0.80 or more and 1.20 or less Was determined to be “good”. In other cases, the fusing property was “bad”.

Example 1
100 parts by weight of a polylactic acid resin having a D-form ratio of 10% and an MI value of 3.7 g / 10 minutes and 2.0 parts by weight of a polyisocyanate compound (manufactured by Nippon Polyurethane Co., Ltd., MR-200) Using a TEM 35B) manufactured by Kikai, it was melt-kneaded at a cylinder temperature of 185 ° C., and about 1 mmφ (about 1.5 mg) bead-shaped polylactic acid resin particles were obtained using an underwater cutter. It was 60 degreeC as a result of measuring the glass transition temperature (Tg) of the obtained polylactic acid-type resin particle.

  With respect to 100 parts by weight of the polylactic acid-based resin particles, 100 parts by weight of water, 12 parts by weight of deodorized butane (normal butane / isobutane weight ratio = 7/3) as a foaming agent, 10 parts by weight of sodium chloride, and polyoxy as a dispersion aid 0.3 parts by weight of ethylene oleyl ether was charged into an autoclave and maintained at 84 ° C. for 90 minutes. After sufficiently cooling, it was taken out and dried to obtain polylactic acid resin foamable particles. The resulting polylactic acid-based resin expandable particles had a blowing agent impregnation rate of 5.5%.

The polylactic acid-based resin expandable particles were put into a pre-foaming machine (BHP-300, manufactured by Daisen Kogyo Co., Ltd.) and kept in a 90 ° C. vapor for 40 to 60 seconds to obtain polylactic acid-based resin expanded particles. The obtained polylactic acid-based resin foamed particles were air-dried, and then the fused particles were separated using a sieve. The bulk magnification of the separated polylactic acid-based resin expanded particles was 0.025 g / cm ³ .

Using a molding machine in which a foam molding machine (made by Daisen Kogyo Co., Ltd., KR-57) is partially improved so that a mixture of steam and air can be introduced, a 300 × 520 × 100 mm thick mold is installed, In-mold foam molding was performed so that the molding space internal temperature was 95 ° C. during the preheating step and 95 ° C. during the main heating step, to obtain a polylactic acid resin foam molding having a density of 0.025 g / cm ³ . The obtained foamed molded product was cut into a surface layer portion and a center portion, subjected to a tensile test, and evaluated for fusing property. The results are shown in Table 1.

(Example 2)
Fusing property evaluation of the obtained foamed molding was performed in the same manner as in Example 1 except that the molding space internal temperature was 98 ° C. during the preheating step and 100 ° C. during the main heating step. . The results are shown in Table 1.

Example 3
Fusing property evaluation of the obtained foamed molded product was performed in the same manner as in Example 1 except that in-mold foam molding was performed with a 300 × 450 × 150 mm thick mold. The results are shown in Table 1.

Example 4
Fusing property evaluation of the obtained foamed molding was performed in the same manner as in Example 1 except that the molding space internal temperature was 82 ° C. during the preheating step and 85 ° C. during the main heating step. . The results are shown in Table 1.

(Example 5)
Fusing property evaluation of the obtained foamed molding was performed in the same manner as in Example 1 except that the molding space internal temperature was 90 ° C. during the preheating step and 92 ° C. during the main heating step. . The results are shown in Table 1.

(Example 6)
Obtained in the same manner as in Example 1 except that a 300 × 450 × 150 mm thick mold was used only with steam, and the molding space internal temperature was 80 ° C. during the preheating step and 83 ° C. during the main heating step. Evaluation of the fusing property of the foamed molded product was performed. The results are shown in Table 1.

(Comparative Example 1)
The mold was 300 x 520 x 100 mm thick using only steam and heated for 60 seconds at a vapor pressure of 0.1 MPaG, but the resin was large during the preheating process (the molding space internal temperature was 122 ° C at that time). Shrinkage did not yield a molded product.

(Comparative Example 2)
Except that the polyisocyanate compound was not kneaded with the polylactic acid resin, the same procedure as in Example 1 was carried out.

(Comparative Example 3)
The internal temperature of the molding space was the same as in Example 1 except that the temperature was 75 ° C. (introduction steam temperature was 90 ° C.) during the preheating process and 85 ° C. (introduction steam temperature was 100 ° C.) during the main heating process. Cracks occurred and no molded product was obtained.

  Aliphatic polyester resin foam molded products having a chloroform insoluble content of 20% or more and a thickness of more than 60 mm and not more than 200 mm can be used in various fields where the thickness of the foam is required.

Claims (7)

  An aliphatic polyester resin foamed molded article having a chloroform insoluble content of 20% or more and a thickness of more than 60 mm and not more than 200 mm.   The maximum tensile stress of the surface layer portion and the center portion of the aliphatic polyester resin foam molded article is 0.35 MPa or more and 2.0 MPa or less, respectively, and the ratio of the maximum tensile stress of the surface layer portion and the maximum tensile stress of the center portion is The aliphatic polyester resin foam molded article according to claim 1, which is 0.80 or more and 1.20 or less. The aliphatic polyester resin foam molded article according to claim 1 or 2, wherein the apparent density is 0.014 g / cm ³ or more and 0.050 g / cm ³ or less.   The aliphatic polyester resin foam molded article according to any one of claims 1 to 3, wherein the aliphatic polyester resin is a polylactic acid resin.   Claims characterized in that the aliphatic polyester-based resin foam particles containing the aliphatic polyester-based resin are filled in a molding space constituted by a mold that can be closed but cannot be sealed, and obtained through a heating step. Item 5. A method for producing an aliphatic polyester resin foam molded article according to any one of Items 1 to 4.   When the heating step includes a preheating step and a main heating step, and the glass transition temperature (Tg) of the aliphatic polyester resin is determined, the molding space center temperature during the preheating step exceeds Tg + 30 (° C.) and Tg + 60 ( 6) The method for producing an aliphatic polyester resin foam molded article according to claim 5, wherein the molding space center temperature during the heating step is Tg + 30 (° C.) or more and Tg + 60 (° C.) or less.   The method for producing an aliphatic polyester resin foam molded article according to claim 6, wherein a mixture of water vapor and air is used as a heat medium used in the heating step.