JP2012077180A - Cushioning material for packaging - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cushioning material for packaging which is a renewable resource derived from a biodegradable plant and is excellent in heat resistance.SOLUTION: The cushioning material for packaging is a biodegradable resin foam molded body including a biodegradable resin having carboxy group terminals, wherein a part of the carboxy group terminals is blocked by a strength deterioration inhibitor included at the rate of more than 2.5 pts.wt. and not more than 5.0 pts.wt. relative to 100 pts.wt. of the biodegradable resin, and the biodegradable resin foam molded body satisfies the following formula (I) 0≤(F-F)/F≤0.40, wherein Fis 5% compressive strength of the biodegradable resin foam molded body based on JIS K 7220:1999 after the biodegradable resin foam molded body is left in an atmosphere having the temperature of 80°C and the relative humidity of 95% for 800 hours, and Fis 5% compressive strength of the biodegradable resin foam molded body before left.

Description

  The present invention relates to a cushioning material for packaging. More specifically, the present invention relates to a packaging buffer material that is a biodegradable plant-derived renewable resource and excellent in heat resistance.

  2. Description of the Related Art Conventionally, foam molded articles obtained from expandable thermoplastic resin particles containing a polystyrene-based resin are widely used as packaging cushioning materials for home appliances and the like because of excellent moldability and heat insulation.

  However, imports and exports of home appliances and the like are usually performed by transportation by ship using containers. In this case, the inside of the container becomes high temperature and high humidity, and the foamed molded product is placed in a severe wet heat atmosphere for a long time. In such a case, the foamed molded article may cause a decrease in strength, dimensional change, weight change, etc. over time due to insufficient heat resistance, and may not be able to obtain desired effects such as moldability and heat insulation. . In addition, the dimensional change may cause poor appearance of the foamed molded product.

  For this reason, in view of the above-mentioned problems, Patent Document 1 proposes a foamed molded article obtained from foamable thermoplastic resin particles as a foamed molded article having excellent heat resistance. Further, as a foam molded article having excellent heat resistance and biodegradability, Patent Document 2 proposes a polylactic acid foam molded article obtained by blocking a part of a carboxy group terminal of a polylactic acid resin with a carbodiimide compound. Yes.

JP 2007-262345 A JP 2006-111735 A

  However, although the foam molded article proposed in Patent Document 1 has excellent heat resistance, it uses petroleum resources as a raw material, and if these are used as they are, there is a problem that the petroleum resources are exhausted. is there. These problems are not appropriate from an environmental point of view.

  On the other hand, the polylactic acid-based foam molded article proposed in Patent Document 2 is a foam-molded article excellent in heat resistance and biodegradability because it contains a lactic acid monomer as a constituent monomer component. However, the polylactic acid-based foamed molded article is not satisfactory from the viewpoint of heat resistance required as a cushioning material for packaging, that is, heat resistance under extremely severe and long-time humid heat atmosphere.

  Accordingly, in view of these problems, it is desired to provide a packaging cushioning material that is a biodegradable plant-derived renewable resource and that is superior in heat resistance.

Thus, according to the present invention, there is provided a biodegradable resin foam molded article containing a biodegradable resin having a carboxy group end,
A part of the carboxy group terminal is blocked with a strength-reducing inhibitor contained in a proportion of more than 2.5 parts by weight and less than 5.0 parts by weight with respect to 100 parts by weight of the biodegradable resin,
The biodegradable resin foam molded article has the following formula (I):
0 ≦ (F ₀ −F ₈₀₀ ) / F ₀ ≦ 0.40 Formula (I)
(In the formula, F ₈₀₀ represents the biodegradable resin foam molded article in accordance with JIS K 7220: 1999 after the biodegradable resin foam molded article is allowed to stand for 800 hours in an atmosphere at a temperature of 80 ° C. and a relative humidity of 95%. 5% compressive strength of the body, and F ₀ is the 5% compressive strength of the biodegradable resin foam molded body before leaving)
The cushioning material for packaging characterized by satisfy | filling is provided.

  ADVANTAGE OF THE INVENTION According to this invention, it is a biodegradable plant-derived renewable resource and can obtain the packaging buffer material excellent in heat resistance.

According to the present invention, the biodegradable resin foam molded article has the following formula (II):
0 ≦ (F ₀ −F ₁₄₀₀ ) / F ₀ ≦ 0.40 Formula (II)
(In the formula, F ₁₄₀₀ is a biodegradable resin foam molded article conforming to JIS K 7220: 1999 after leaving the biodegradable resin foam molded article in an atmosphere of 80 ° C. and 95% relative humidity for 1400 hours. 5% compressive strength, F ₀ is the 5% compressive strength of the biodegradable resin foam before standing)
When satisfy | filling, the buffer material for packaging excellent in heat resistance for a further long time can be obtained.

  Further, according to the present invention, when the biodegradable resin is a polylactic acid-based resin, it is possible to obtain a packaging buffer material that is superior in heat resistance.

  Further, according to the present invention, the biodegradable resin contains both D isomer and L isomer as constituent monomer components, and the content of the smaller of the D isomer and L isomer. Is less than 5 mol%, or if it contains a polylactic acid resin containing only one optical isomer of either D-form or L-form as a constituent monomer component, it is even more excellent in heat resistance A cushioning material for packaging can be obtained.

  Further, according to the present invention, when the strength reduction inhibitor is a carbodiimide compound, it is possible to obtain a cushioning material for packaging which is excellent in hydrolysis resistance and as a result further excellent in heat resistance.

Further, according to the present invention, when the biodegradable resin foam molded article has a unity of 0.02 to 0.08 g / cm ³ , it is possible to obtain a packaging cushioning material excellent in moldability, heat insulation and the like. it can.

According to the present invention, the biodegradable resin foam molded article
Supplying the biodegradable resin and the strength reduction inhibitor to an extruder and melt-kneading under a foaming agent;
While extruding the biodegradable resin extrudate from the nozzle mold attached to the front end of the extruder and foaming the biodegradable resin extrudate, at the temperature of the nozzle mold of 180 to 235 ° C., the front end surface of the nozzle mold A step of producing biodegradable resin foamed particles by cutting with a rotary blade rotating at a rotational speed of 2000 to 10,000 rpm while contacting, and scattering the biodegradable resin foamed particles by cutting stress;
A step of cooling the biodegradable resin foam particles by colliding with a cooling member disposed in front of the nozzle mold,
A step of impregnating the obtained biodegradable resin expanded particles with an inert gas,
Heating and foaming biodegradable resin foam particles impregnated with inert gas;
When obtained by a production method including a step of re-impregnating a biodegradable resin foam particle that has been heated and foamed with an inert gas and a step of molding the biodegradable resin foam particle in a mold, a desired cushioning material for packaging can be more easily obtained. Obtainable.

It is the schematic cross section which showed an example of the manufacturing apparatus of biodegradable resin expanded particle. It is the schematic diagram which looked at the nozzle metal mold from the front. It is a graph which shows the 5% compressive strength of an Example and a comparative example.

The feature of the present invention consists of a biodegradable resin foamed molded article containing a biodegradable resin having a carboxy group end,
A part of the carboxy group terminal is blocked with a strength-reducing inhibitor contained in a proportion of more than 2.5 parts by weight and less than 5.0 parts by weight with respect to 100 parts by weight of the biodegradable resin,
The biodegradable resin foam molded article has the following formula (I):
0 ≦ (F ₀ −F ₈₀₀ ) / F ₀ ≦ 0.40 Formula (I)
(In the formula, F ₈₀₀ represents the biodegradable resin foam molded article in accordance with JIS K 7220: 1999 after the biodegradable resin foam molded article is allowed to stand for 800 hours in an atmosphere at a temperature of 80 ° C. and a relative humidity of 95%. 5% compressive strength of the body, and F ₀ is the 5% compressive strength of the biodegradable resin foam molded body before leaving)
It is a cushioning material for packaging that satisfies the above.

  Specifically, since the packaging cushioning material of the present invention contains a biodegradable resin, it is a biodegradable plant-derived renewable resource and is a packaging cushioning material that is extremely excellent from the environmental viewpoint. In the present invention, the biodegradable resin means a resin whose resin component can be metabolized and decomposed by microorganisms or the like.

  Moreover, in this invention, a part of carboxy-group terminal of biodegradable resin is blocked with the intensity | strength fall prevention agent by the predetermined ratio. Therefore, the packaging cushioning material of the present invention is a packaging cushioning material that is excellent in heat resistance, as a result of which hydrolysis of the resin component due to the carboxy group terminal is suppressed. In the present invention, the strength reduction inhibitor means a compound capable of forming a chemical bond with a carboxy group terminal. Moreover, blockage means the said chemical bond.

  Furthermore, since the cushioning material for packaging of the present invention satisfies the above formula (I), it has excellent heat resistance without causing a great change in strength even under extremely severe and long-time humid heat atmosphere.

(Biodegradable resin having a carboxy group terminal)
In the present invention, any biodegradable resin having a carboxy group terminal can be used as long as the desired heat resistance is not affected. Specific examples include resins such as polyester resins, polyvinyl alcohol resins, polysaccharide resins, and polyhydroxyalkanoate resins that are biodegradable and have a carboxy group terminal. Moreover, the said biodegradable resin may be used independently and may use 2 or more types together.

(Polylactic acid resin)
In the present invention, polylactic acid resin is preferred as the biodegradable resin because it is biodegradable, has a carboxy group end in the resin, and is easily commercially available. The polylactic acid-based resin is hydrolyzed to have a low molecular weight due to hydrolysis of ester bonds by moisture contained in the environment, and can finally be decomposed into carbon dioxide and water by microorganisms. Specifically, it may be decomposed in about 1 week in compost.

  In the present invention, a resin obtained by polymerizing lactic acid by an ester bond can be used as the polylactic acid resin. In addition, from the viewpoint of commercial availability and imparting foamability to polylactic acid-based resin expanded particles, a copolymer of D-lactic acid and L-lactic acid, D-lactic acid (D-form) or L-lactic acid (L-form) And a ring-opening polymer of one or more lactides selected from the group consisting of D-lactide, L-lactide and DL-lactide. Moreover, since lactic acid has a carboxy group, the polylactic acid resin which is a polymer thereof has a carboxy group terminal.

Polylactic acid resin is a fatty acid such as glycolic acid, hydroxybutyric acid, hydroxyvaleric acid, hydroxycaproic acid, hydroxyheptanoic acid, etc., as a monomer component other than lactic acid, as long as it does not affect the foam molding process or desired physical properties. Group hydroxycarboxylic acids;
Aliphatic polycarboxylic acids such as succinic acid, adipic acid, suberic acid, sebacic acid, dodecanedicarboxylic acid, succinic anhydride, adipic anhydride, trimesic acid, propanetricarboxylic acid, pyromellitic acid, pyromellitic anhydride;
Aliphatic polyhydric alcohols such as ethylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, decamethylene glycol, glycerin, trimethylolpropane, pentaerythritol, etc. May optionally be included.

  In addition, the polylactic acid resin used in the present invention may be an alkyl group, vinyl group, aromatic group, ester group, ether group, aldehyde group, amino group, as long as it does not affect the foam molding process and desired physical properties. Other functional groups such as a group, a nitrile group, and a nitro group may be included. Moreover, it may be bridge | crosslinked with the isocyanate type crosslinking agent etc., and you may couple | bond together with bonds other than an ester bond. Furthermore, a polylactic acid-type resin may be used independently and 2 or more types may be used together.

  On the other hand, since good extrudability at the time of molding may be obtained, the polylactic acid resin used in the present invention is obtained from the extrusion amount per unit time of 190 ° C., load 20 kg, orifice diameter 2 mm. The melt viscosity is preferably 2000 to 5000 Pa · s.

  When manufacturing a polylactic acid-type resin, it does not specifically limit as the manufacturing method, All can use a well-known method. Specifically, a lactide method in which lactide is polymerized in the presence of a catalyst such as tin (II) octoate; a direct polymerization method in which a lactic acid compound is heated under reduced pressure in a solvent such as diphenyl ether to perform polymerization while removing water; Examples of the polymerization method include a melting method in which polymerization is performed while melting a lactic acid compound.

  In addition, the polylactic acid resin can be easily impregnated with a desired amount of foaming agent. Furthermore, the polylactic acid resin has a high gas barrier property against the foaming agent. For this reason, in this invention, the polylactic acid-type resin expanded particle which has a high open cell ratio can be obtained, As a result, the foaming molding which has a high porosity can also be obtained easily.

  Here, a copolymer of D-form and L-form in which the proportion of the lesser optical isomer of D-form or L-form is less than 5 mol%, and the single weight of either D-form or L-form The coalescence tends to increase in crystallinity and melting point as the smaller optical isomer decreases. On the other hand, a copolymer of D-form and L-form in which the ratio of the smaller optical isomer of D-form or L-form is 5 mol% or more increases the crystallinity as the smaller optical isomer increases. Tends to be low and eventually become amorphous. Thus, for example, the former polylactic acid-based resin can be used in applications where high heat resistance is desired, and the latter polylactic acid-based resin can be used in applications where improvement in filling properties in complicated spaces is desired.

  Moreover, the latter polylactic acid-type resin can improve the heat resistance of the foaming molding obtained. Further, the foamed molded product can maintain its form even at a high temperature. Therefore, it becomes possible to take out the foamed molded product from the mold at a high temperature, the cooling time in the mold of the foamed molded product is shortened, and the production efficiency of the foamed molded product may be improved.

  Therefore, from the above viewpoint, the copolymer of the D-form and the L-form preferably has a ratio of the lesser of the D-form and the L-form of the optical isomer of less than 5 mol%, and 4 mol More preferably, it is less than%.

  The storage elastic modulus obtained by dynamic viscoelasticity measurement is an index indicating elastic properties in viscoelasticity, and is an index indicating the elasticity of the bubble film in the foaming process. It is an index indicating the magnitude of the foaming pressure required to expand the bubbles against the contraction force of the.

  That is, when the storage elastic modulus obtained by the dynamic viscoelasticity measurement of the polylactic acid-based resin is low, when the cell membrane is stretched, the force with which the cell membrane attempts to contract against the stretching force is small. For this reason, as a result of a foaming film | membrane expanding easily with the foaming pressure required for manufacture of polylactic acid-type resin expanded particles, a bubble film | membrane may extend | expand excessively and a bubble breakage may be produced. On the other hand, when the storage elastic modulus obtained by the dynamic viscoelasticity measurement of the polylactic acid-based resin is high, when the expansion force is applied to the cell membrane, the contraction force of the cell membrane resists the expansion. Therefore, even if the bubbles expand once at the foaming pressure required for the production of the polylactic acid-based resin expanded particles, the bubbles may shrink as the foaming pressure decreases over time due to a temperature drop or the like. is there.

  Moreover, the loss elastic modulus obtained by the dynamic viscoelasticity measurement is an index indicating a viscous property in viscoelasticity. Specifically, it is an index indicating the viscosity of the bubble film in the foaming process. In particular, in the foaming process, it is an index indicating an allowable range of how much the bubble membrane can be stretched without being broken. At the same time, after the bubbles are expanded to a desired size by the foaming pressure, the expanded bubbles are expanded in size. It is also an indicator that shows the ability to maintain the same.

  That is, if the loss elastic modulus obtained by the dynamic viscoelasticity measurement of the polylactic acid-based resin is low, when the cell membrane is expanded by the foaming pressure required for the production of the polylactic acid-based resin expanded particles, It can easily be torn. On the other hand, if the loss elastic modulus obtained by dynamic viscoelasticity measurement of polylactic acid resin is high, the foaming force is converted into thermal energy by the foam film, and the foam film is smoothed during the production of polylactic acid resin foam particles. It may be difficult to expand the air bubbles, and it may be difficult to expand the bubbles.

  Thus, in producing polylactic acid resin foamed particles by foaming polylactic acid resin, in the foaming process, the elastic force to stretch appropriately without breaking the cell membrane due to foaming pressure, that is, storage elasticity It is preferable to have a rate. In addition, the foam force smoothly expands without breaking the bubble film, and the viscous force to maintain the expanded bubble to the desired size regardless of the decrease in the foam pressure over time, that is, It is preferable to have a loss elastic modulus.

That is, in the extrusion foaming process, it is preferable that both the storage elastic modulus and loss elastic modulus of the polylactic acid-based resin have values suitable for extrusion foaming, and the storage elastic modulus and loss suitable for such extrusion foaming. In order to impart an elastic modulus to the polylactic acid resin in the extrusion foaming process, the temperature T (below) at the intersection of the storage elastic modulus curve and the loss elastic modulus curve obtained by dynamic viscoelasticity measurement in the polylactic acid resin. (Referred to as “temperature T”) and the melting point (mp) of the polylactic acid-based resin are preferably adjusted to satisfy the following formula (1), more preferably to satisfy the following formula (2). This adjustment makes it possible to improve the extrusion foamability while balancing the storage elastic modulus and loss elastic modulus, and stably produce the polylactic acid-based resin expanded particles.
[Melting point of polylactic acid resin (mp) −40 ° C.]
≦ Temperature at the intersection T ≦ Melting point of polylactic acid resin (mp) Expression (1)
[Melting point of polylactic acid resin (mp) -35 ° C.]
≦ Temperature at the intersection T ≦ [Melting point of polylactic acid resin (mp) −10 ° C.] Expression (2)

  Furthermore, the reason why it is preferable to adjust the temperature T and the melting point (mp) of the polylactic acid resin so as to satisfy the formula (1) will be described in detail below.

  First, when the temperature T is lower than the melting point (mp) of the polylactic acid resin by more than 40 ° C., the loss elastic modulus of the polylactic acid resin at the time of extrusion foaming is too large compared to the storage elastic modulus. The balance between the loss elastic modulus and the storage elastic modulus is lost.

  Therefore, if the foaming force suitable for the loss elastic modulus of the polylactic acid-based resin, that is, the foaming force matched to the viscosity, the foaming force with respect to the elastic force is too large, and the bubble film is broken to cause bubble breakage and good polylactic acid -Based resin expanded particles may not be obtained. Conversely, if the foaming force suitable for the storage elastic modulus of the polylactic acid-based resin, that is, the foaming force matched to the elasticity, the foaming force with respect to the viscous force is small, and the polylactic acid-based resin is difficult to foam, and good polylactic acid -Based resin expanded particles may not be obtained.

  If the temperature T is higher than the melting point (mp) of the polylactic acid resin, the storage elastic modulus of the polylactic acid resin at the time of extrusion foaming is too large compared to the loss elastic modulus. For this reason, the balance between the loss elastic modulus and the storage elastic modulus may be lost as described above.

  Therefore, if the foaming force suitable for the storage elastic modulus of the polylactic acid-based resin, that is, the foaming force matched to the elasticity, the foaming force with respect to the viscous force is too large, and the bubble film is broken to cause bubble breakage and good polylactic acid-based Resin foam particles may not be obtained. On the contrary, if the foaming force suitable for the loss elastic modulus of the polylactic acid-based resin, that is, the foaming force matched to the viscosity, the foaming force with respect to the elastic force is small. As the foaming power decreases, the air bubbles contract, and good polylactic acid resin expanded particles may not be obtained.

  As the weight average molecular weight of the polylactic acid resin increases, the temperature T increases. Therefore, in order to adjust the temperature T and the melting point (mp) of the polylactic acid-based resin to satisfy the above formula (1), it can be obtained by adjusting the reaction time or reaction temperature during the polymerization of the polylactic acid-based resin. The method of adjusting the weight average molecular weight of the polylactic acid-type resin obtained, and the method of adjusting the weight average molecular weight of a polylactic acid-type resin before extrusion foaming or at the time of extrusion foaming using a thickener or a crosslinking agent are mentioned.

In addition, a part of the carboxy group terminal of the polylactic acid resin is blocked with a strength lowering inhibitor to suppress hydrolysis of the resin component by the carboxy group terminal, but the higher the molecular weight of the polylactic acid resin, the higher the carboxy group terminal. And the addition amount of the strength reduction inhibitor can be reduced. Therefore, the molecular weight of the polylactic acid resin suitable for the present invention is in a range where extrusion foaming is possible, and it is desirable that the molecular weight is high within that range.
From such a viewpoint, the weight average molecular weight of the polylactic acid-based resin is preferably adjusted to 100,000 to 300,000, more preferably 120,000 to 290,000, and particularly preferably 140,000 to 280,000. preferable.

(Strength reduction preventing agent)
In the present invention, a part of the carboxy group terminal of the biodegradable resin is blocked with the strength reduction inhibitor. In general, a biodegradable resin, particularly a polylactic acid resin, has a property that an ester bond contained in its main chain is gradually hydrolyzed by water in water or in the atmosphere, that is, biodegradable. Degradability can affect long-term quality stability and cause changes in physical properties. However, according to the present invention, the hydrolysis of the biodegradable resin is highly enhanced by blocking the carboxy group at the end of the molecular chain with a strength-reducing inhibitor, that is, suppressing the acid-catalytic effect at the carboxy end. Can be controlled. Moreover, as long as the desired hydrolysis inhibitory effect can be acquired, a part of carboxy-group terminal may be blocked with the intensity | strength fall prevention agent, and all may be blocked.

  In the present invention, any strength reduction inhibitor can be used as long as it forms a chemical bond with the carboxy group terminal and does not affect the desired physical properties such as heat resistance and biodegradability. Specifically, as a strength reduction inhibitor, a carbodiimide compound having a functional group represented by -N = C = N-, which can form a chemical bond with a carboxy group terminal, an alcohol compound having a hydroxy group, isocyanate Examples thereof include an isocyanate compound having a group and an amino compound having an amino group. Moreover, the said strength reduction inhibitor may be used independently and may use 2 or more types together.

  In the present invention, a carbodiimide-based compound is preferable because it can be easily obtained commercially and the hydrolysis rate can be easily adjusted as the strength reduction inhibitor. In addition, the carbodiimide-based compound may easily form a chemical bond with a carboxy group terminal in the biodegradable resin by a dehydration condensation reaction. In the present invention, this is also preferable from this viewpoint.

  Furthermore, since the dehydration condensation reaction can be promoted and side reactions can be suppressed, it is more preferable to use a condensation accelerator such as 1-hydroxytriazole or N-hydroxysuccinamide in combination. In the present invention, the carbodiimide compound means a compound having a functional group represented by -N = C = N- in the molecule.

  Examples of the carbodiimide compound include a polycarbodiimide compound having a plurality of functional groups in a polymer chain and a monocarbodiimide compound having one functional group.

  Specifically, as a monocarbodiimide compound, dimethylcarbodiimide, diethylcarbodiimide, diisopropylcarbodiimide, diisobutylcarbodiimide, dioctylcarbodiimide, t-butylisopropylcarbodiimide, di-t-butylcarbodiimide, dicyclohexylcarbodiimide, diphenylcarbodiimide, 2,2,6, 6-tetraethyldiphenylcarbodiimide, 2,2,6,6-tetramethyldiphenylcarbodiimide, 2,2,6,6-tetraisopropyldiphenylcarbodiimide, di-β-naphthylcarbodiimide, 1-ethyl-3- (3-dimethylamino Propyl) carbodiimide hydrochloride and the like.

  On the other hand, as the polycarbodiimide compound, the polycarbodiimide compound may have two or more carbodiimide groups represented by (—N═C═N—) in the molecule, and the polyvalent carbodiimide compound has two or more carbodiimide groups. For example, poly (4,4′-dicyclohexylmethanecarbodiimide), poly (4,4′-biphenylmethanecarbodiimide), poly (1,6-hexamethylenecarbodiimide), poly (1,3-cyclohexylenecarbodiimide), Poly (1,4-cyclohexylenecarbodiimide), poly (3,3′-dimethyl-4,4′-diphenylmethanecarbodiimide), poly (naphthylenecarbodiimide), poly (p-phenylenecarbodiimide), poly (m-phenylenecarbodiimide) ), Poly (1,3,5-triisopropylbenzene carbodi) Examples thereof include polycarbodiimide compounds such as (imide), poly (tolylcarbodiimide), and poly (diisopropylcarbodiimide). In the present invention, a polycarbodiimide compound is preferable from the viewpoint of the hydrolysis inhibiting effect. The polycarbodiimide compound is commercially available from Nisshinbo under the trade name “Carbodilite LA-1” (poly (4,4′-dicyclohexylmethanecarbodiimide)), for example.

  In addition, since a biodegradable resin foamed molded article having superior hydrolysis resistance can be obtained, the strength reduction preventing agent exceeds 2.5 parts by weight with respect to 100 parts by weight of the biodegradable resin. It is preferably contained in a proportion of not more than parts by weight, more preferably not less than 3.0 parts by weight and not more than 5.0 parts by weight.

  The biodegradable resin of the present invention may contain other resin components such as a polystyrene resin and a polyolefin resin as long as the desired physical properties and molding process are not affected. In addition, the biodegradable resin of the present invention includes talc, calcium silicate, calcium stearate, synthetically or naturally produced silicon dioxide, ethylene bis-stearic acid amide, methacrylate ester copolymer, polytetrafluoroethylene. A flame retardant such as triallyl isocyanurate hexabromide; a colorant such as carbon black, iron oxide, and graphite; and a surfactant.

(Manufacture of biodegradable resin foam moldings)
In the present invention, the biodegradable resin expanded particles can be produced by a known method. Specifically, using a commercially available extruder, the biodegradable resin and the strength reduction inhibitor are melt-extruded in the presence of a foaming agent and granulated by underwater cutting, strand cutting, etc. Resin foam particles can be produced. Subsequently, a biodegradable resin foam molded article can be produced by molding the biodegradable resin foam particles in a mold.

In addition, according to the present invention, since a desired biodegradable resin foam molded article can be obtained more easily,
Biodegradable resin foam moldings
Supplying the biodegradable resin and the strength reduction inhibitor to an extruder and melt-kneading under a foaming agent;
While extruding the biodegradable resin extrudate from the nozzle mold attached to the front end of the extruder and foaming the biodegradable resin extrudate, at the temperature of the nozzle mold of 180 to 235 ° C., the front end surface of the nozzle mold A step of producing biodegradable resin foamed particles by cutting with a rotary blade rotating at a rotational speed of 2000 to 10,000 rpm while contacting, and scattering the biodegradable resin foamed particles by cutting stress;
A step of cooling the biodegradable resin foam particles by colliding with a cooling member disposed in front of the nozzle mold,
A step of impregnating the obtained biodegradable resin expanded particles with an inert gas,
Heating and foaming biodegradable resin foam particles impregnated with inert gas;
It is preferably obtained by a production method including a step of impregnating an inert gas into biodegradable resin foam particles that have been heated and foamed and a step of molding the biodegradable resin foam particles in a mold.

  Hereinafter, although the manufacturing method of a biodegradable resin foaming molding using polylactic acid system resin as a biodegradable resin which has a carboxy group end is illustrated, the present invention is not limited to the following manufacturing methods.

  First, the polylactic acid resin and the strength reduction preventing agent are supplied to the extruder shown in FIGS. 1 and 2 and melt kneaded in the presence of a foaming agent. At the time of the melt-kneading, a part of the carboxy terminus is blocked with a strength reduction preventing agent by a dehydration condensation reaction or the like. Thereafter, the polylactic acid resin extrudate is extruded from a nozzle mold attached to the front end of the extruder, and the polylactic acid resin extrudate is foamed, while the nozzle mold is at a temperature of 180 to 235 ° C. The polylactic acid resin foamed particles are produced by cutting with a rotary blade rotating at a rotational speed of 2000 to 10,000 rpm while being in contact with the front end surface of the resin, and the polylactic acid resin foamed particles are scattered by cutting stress. The extruder is not particularly limited as long as it is a conventionally used extruder. Examples thereof include a single-screw extruder, a twin-screw extruder, and a tandem type extruder in which a plurality of extruders are connected.

  As the foaming agent, those conventionally used are used. For example, chemical blowing agents such as azodicarbonamide, dinitrosopentamethylenetetramine, hydrazoyl dicarbonamide, sodium bicarbonate; saturated aliphatic hydrocarbons such as propane, normal butane, isobutane, normal pentane, isopentane, hexane, dimethyl ether, etc. Examples include ethers, chlorofluorocarbons such as methyl chloride, 1,1,1,2-tetrafluoroethane, 1,1-difluoroethane, monochlorodifluoromethane, and physical foaming agents such as carbon dioxide and nitrogen. Among these, from the viewpoint of imparting high foamability to the polylactic acid-based resin expanded particles, a physical foaming agent is preferable, and normal butane and isobutane are more preferable. A foaming agent may be used alone or two or more kinds may be used in combination as long as the foam molding process and desired physical properties are not affected.

  Here, if the amount of the foaming agent contained in the polylactic acid resin expanded particles is small after production, the polylactic acid resin expanded particles may not be expanded to a desired expansion ratio. On the other hand, if the amount is too large, the foaming agent acts as a plasticizer, so that the viscoelasticity of the molten polylactic acid-based resin is too low, and the foamability is lowered, making it impossible to obtain good polylactic acid-based resin expanded particles. is there. In addition, the expansion ratio of the polylactic acid-based resin expanded particles may be too high to control the crystallinity. Therefore, the amount of the foaming agent is preferably 1.5 to 3.8 parts by weight and more preferably 1.6 to 3.0 parts by weight with respect to 100 parts by weight of the polylactic acid resin foamed particles.

  In addition, it is preferable that a bubble regulator is added to the extruder, but since many of the bubble regulators act as crystal nucleating agents for the polylactic acid resin foamed particles, crystallization of the polylactic acid resin is not promoted. It is preferable to use a bubble regulator, and as such a bubble regulator, polytetrafluoroethylene powder or polytetrafluoroethylene powder modified with an acrylic resin is preferred.

  On the other hand, when the amount of the air conditioner supplied to the extruder is small, the air bubbles of the polylactic acid-based resin expanded particles become coarse, and the appearance of the obtained foamed molded product may be deteriorated. On the other hand, when the polylactic acid-based resin is extruded and foamed, foam breakage may occur, and the closed cell ratio of the polylactic acid-based resin expanded particles may decrease. Therefore, the amount of the air conditioner is preferably 0.01 to 3 parts by weight, more preferably 0.05 to 2 parts by weight, and particularly preferably 0.1 to 1 part by weight with respect to 100 parts by weight of the polylactic acid resin. preferable.

  And the polylactic acid-type resin extrudate extruded from the nozzle metal mold | die 1 continues to a cutting process. The polylactic acid resin extrudate is cut by rotating the rotary shaft 2 with a motor 3 and rotating the rotary blade 5 disposed on the front end surface 1a of the nozzle mold 1 at a constant rotational speed of 2000 to 10000 rpm. It is preferable.

  All the rotary blades 5 are always rotating in contact with the front end face 1a of the nozzle mold 1. The polylactic acid-based resin extrudate extruded and foamed from the nozzle mold 1 is in the atmosphere at regular intervals due to shear stress generated between the rotary blade 5 and the edge of the nozzle outlet 11 in the nozzle mold 1. Is cut into polylactic acid-based resin expanded particles. At this time, water may be sprayed onto the polylactic acid resin extrudate in a range where the cooling of the polylactic acid resin extrudate does not become excessive.

  It is preferable that the polylactic acid resin does not foam in the nozzle of the nozzle mold 1. Therefore, immediately after the polylactic acid-based resin is discharged from the nozzle outlet portion 11 of the nozzle mold 1, the polylactic acid-based resin has not yet been foamed, and starts to foam after a short time has elapsed since being discharged. Therefore, the polylactic acid-based resin extrudate is in the process of foaming extruded before the unfoamed portion, which continues from the unfoamed portion immediately after being discharged from the nozzle outlet portion 11 of the nozzle mold 1 and the unfoamed portion. The foamed part.

  The non-foamed portion maintains its state from when it is projected from the outlet 11 of the nozzle of the nozzle mold 1 until foaming is started. The time for which the unfoamed part is maintained can be adjusted by the resin pressure at the nozzle outlet 11 of the nozzle mold 1, the amount of foaming agent, and the like. When the resin pressure at the nozzle outlet 11 of the nozzle mold 1 is high, the polylactic acid resin extrudate does not foam immediately after being extruded from the nozzle mold 1 and maintains an unfoamed state. The adjustment of the resin pressure at the nozzle outlet 11 of the nozzle mold 1 can be adjusted by the nozzle diameter, the extrusion amount, the melt viscosity and the melt tension of the polylactic acid resin. By adjusting the amount of the foaming agent to an appropriate amount, the polylactic acid resin can be prevented from foaming inside the mold, and the unfoamed portion can be reliably formed.

  In the present invention, the polylactic acid resin foamed particles are foamed at a nozzle mold temperature of preferably 180 to 235 ° C., more preferably 190 to 230 ° C. When the temperature of the nozzle mold is lower than 180 ° C., the nozzle may be clogged with resin, and stable production may not be possible. On the other hand, when the temperature is higher than 235 ° C., the polylactic acid-based resin may be thermally decomposed and the melt tension necessary for foaming may not be obtained, and a good foam may not be obtained. Here, the temperature of the nozzle mold means a temperature at a position of 7 mm from the flow path closest to the mold.

  Since all the rotary blades 5 cut the polylactic acid-based resin extrudate while being always in contact with the front end surface 1 a of the nozzle mold 1, the polylactic acid-based resin extrudate is used as the nozzle of the nozzle mold 1. Polylactic acid-based resin expanded particles are produced by cutting at the unfoamed portion immediately after being discharged from the outlet portion 11.

  Since the obtained polylactic acid-based resin expanded particles cut the polylactic acid-based resin extrudate at the unfoamed portion, there is no cell cross section on the surface of the cut portion. The entire surface of the polylactic acid-based resin expanded particles is covered with a skin layer having no cell cross section.

  Moreover, it is preferable that the rotary blade 5 is rotating at a constant rotational speed. The rotational speed of the rotary blade 5 is preferably 2000 to 10000 rpm, more preferably 3000 to 9000 rpm, and further preferably 4000 to 8000 rpm.

  When this is less than 2000 rpm, it becomes difficult to reliably cut the polylactic acid resin extrudate with the rotary blade 5. Therefore, the polylactic acid-based resin expanded particles may be united with each other, and the shape of the polylactic acid-based resin expanded particles may be nonuniform.

  On the other hand, if it exceeds 10,000 rpm, the following problems may occur. The first problem is that when the cutting stress due to the rotary blade is increased and the polylactic acid resin foam particles are scattered from the nozzle outlet toward the cooling member, the initial speed of the polylactic acid resin foam particles is high. Become. As a result, the time from when the polylactic acid resin extrudate is cut until the polylactic acid resin expanded particles collide with the cooling member is shortened, and the foaming of the polylactic acid resin expanded particles becomes insufficient. . The second problem is that the wear of the rotary blade and the rotary shaft is increased and the life of the rotary blade and the rotary shaft is shortened.

Furthermore, the discharge amount and the rotation speed of the extruder are expressed by the following formula (3):
(Where
Dn: Mold nozzle diameter (cm)
Q: Discharge amount per hole (g / hr)
R: Cutter blade rotation speed (rpm)
N: Number of cutter blades (sheets)
X: Multiple of the obtained foamed particles (g / cm ³ )
It is preferable to satisfy. If the relationship of the above formula (3) is not satisfied, similarly, desired spherical or substantially spherical polylactic acid resin expanded particles cannot be produced, which may affect moldability and the like.

  The polylactic acid-based resin foam particles are scattered outward or forward simultaneously with the cutting by the cutting stress of the rotary blade 5 and immediately collide with the inner peripheral surface of the peripheral wall portion 41 b of the cooling drum 41. The polylactic acid-based resin foamed particles continue to foam until they collide with the cooling drum 41, and grow into a spherical or substantially spherical shape by foaming.

  Subsequently, the obtained polylactic acid-based resin expanded particles are cooled by colliding with a cooling member disposed in front of the nozzle mold. Specifically, the inner peripheral surface of the peripheral wall portion 41b of the cooling drum 41 is entirely covered with the cooling liquid 42, and the polylactic acid-based resin foam particles that collide with the inner peripheral surface of the peripheral wall portion 41b of the cooling drum 41 are It cools immediately and the foaming stops. In this way, after the polylactic acid resin extrudate is cut by the rotary blade 5, the polylactic acid resin foam particles are immediately cooled by the cooling liquid 42, thereby forming the polylactic acid resin foam particles. The crystallinity of the lactic acid resin can be prevented from increasing, and the polylactic acid resin foamed particles can be prevented from excessively foaming.

  Therefore, the polylactic acid resin foamed particles exhibit excellent foamability and heat-fusibility during in-mold molding. The crystallinity of the polylactic acid-based resin expanded particles can be increased during in-mold molding to improve the heat resistance of the polylactic acid-based resin, and the resulting foamed molded article has excellent heat resistance.

  If the temperature of the cooling liquid 42 is low, the nozzle mold located in the vicinity of the cooling drum 41 is excessively cooled, which may adversely affect the extrusion foaming of the polylactic acid resin. On the other hand, if it is high, the degree of crystallinity of the polylactic acid-based resin constituting the polylactic acid-based resin expanded particles becomes high, and the heat-fusibility of the polylactic acid-based resin expanded particles may be lowered. Therefore, the temperature is preferably 0 to 45 ° C, more preferably 5 to 40 ° C, and particularly preferably 10 to 35 ° C.

  In order to use the said manufacturing method, the polylactic acid-type resin expanded particle of this invention is shapes, such as spherical shape or substantially spherical shape, columnar shape, cylindrical shape, needle shape, flake shape. Here, the shape of the polylactic acid-based resin expanded particles is preferably spherical or substantially spherical. In the case of having a spherical or substantially spherical shape, the polylactic acid resin foamed particles are superior in fluidity and expanded in comparison with the polylactic acid resin foamed particles having a columnar shape, cylindrical shape, needle shape, or flake shape. It is excellent in filling properties to a molding machine, and as a result, it is excellent in moldability. Furthermore, a foamed molded article having a desired complicated shape can be easily produced. Spherical or substantially spherical means that the projected view of the polylactic acid-based resin expanded particles includes from spherical particles to elliptical particles.

  Further, the ratio (minor axis / major axis) of the longest diameter (major axis) to the shortest diameter (minor axis) of the polylactic acid resin expanded particles is preferably in the range of 1 to 1.3 by measurement using calipers. More preferably, it is the range of 1-1.2. When the minor axis / major axis is not included in the range of 1 to 1.3, there may be a problem in terms of filling into the foam molding machine. Formability may not be obtained. The minor axis / major axis = 1 means a true sphere.

  The polylactic acid-based resin expanded particles have an open cell ratio. When the open cell ratio of the polylactic acid-based resin expanded particles is high, the polylactic acid-based resin expanded particles hardly foam at the time of in-mold foam molding, resulting in low fusion between the polylactic acid-based resin expanded particles. Since the mechanical strength of the polylactic acid resin foamed molded article may be lowered, it is preferably less than 20%, more preferably 10% or less, and particularly preferably 5% or less. The open cell ratio of the polylactic acid-based resin expanded particles can also be adjusted by adjusting the extrusion foaming temperature of the polylactic acid-based resin from the extruder, the supply amount of the foaming agent to the extruder, and the like.

Here, the open cell ratio of the polylactic acid-based resin expanded particles is measured in the following manner. First, a sample cup of a volumetric air comparison type hydrometer is prepared, and the total weight A (g) of polylactic acid resin expanded particles in an amount satisfying about 80% of the sample cup is measured. Next, the volume B (cm ³ ) of the whole polylactic acid-based resin expanded particles is measured by a 1-1 / 2-1 atmospheric pressure method using a hydrometer. The volumetric air comparison type hydrometer is commercially available, for example, from Tokyo Science Co. under the trade name “1000 type”.

  Subsequently, a wire mesh container is prepared, the wire mesh container is immersed in water, and the weight C (g) of the wire mesh container in the state immersed in the water is measured. Next, after all the polylactic acid-based resin expanded particles are put in the wire mesh container, the wire mesh container is immersed in water, and the wire mesh container and the wire mesh container are immersed in water. The weight D (g) of the total amount of the polylactic acid-based resin expanded particles put in the container is measured.

Then, the apparent volume E (cm ³ ) of the polylactic acid-based resin expanded particles is calculated based on the following formula, and the following formula is calculated based on this apparent volume E and the volume B (cm ³ ) of the entire polylactic acid-based resin expanded particles. Thus, the open cell ratio of the polylactic acid-based resin expanded particles can be calculated. The volume of 1 g of water was 1 cm ³ .
E = A + (CD)
Open cell ratio (%) = 100 × (EB) / E

The polylactic acid-based resin expanded particles are preferably unified 0.06 to 0.5 g / cm ³ (bulk factor 2.5 to 21 times), more preferably unified 0.08 to 0.4 g / cm ³ (bulk factor 3). .1 to 16 times). If the unification is greater than 0.5 g / cm ³ , the resulting foamed molded article will have a high weight and may lack practicality. On the other hand, when the bulk density is less than 0.06 g / cm ³ , the strength of the obtained foamed molded product is lowered, and it may be difficult to use it for a structural member or the like.

  The average particle diameter of the polylactic acid-based resin expanded particles is preferably 1.0 to 5.0 mm, and more preferably 1.5 to 4.0 mm. When the average particle diameter is larger than 5.0 mm, the filling property of the polylactic acid-based resin foam particles into the foam molding machine may be lowered, and the strength of the obtained foam molded body may be lowered. Moreover, when smaller than 1.0 mm, the bulk specific gravity of a foaming molding may be affected.

The degree of crystallinity of the polylactic acid-based resin expanded particles is preferably less than 30%, more preferably less than 25%. When the degree of crystallinity is 30% or more, foamability may be affected. The degree of crystallinity of the polylactic acid-based resin expanded particles depends on the time from when the polylactic acid-based resin extrudate is extruded from the nozzle mold 1 until the polylactic acid-based resin expanded particles collide with the cooling liquid 42, It can also be adjusted by temperature. Next, the obtained biodegradable resin foam particles are filled in a cavity of a mold and heated to foam the polylactic acid resin foam particles, so that the polylactic acid resin foam particles are brought together by their foam pressure. A polylactic acid-based resin foam molded body having a desired shape can be obtained by fusing together.
The heating medium for the expanded polylactic acid-based resin particles filled in the mold is not particularly limited, and includes hot air, hot water, etc. in addition to water vapor, but it is preferable to use water at 60 to 100 ° C.

  Furthermore, before the in-mold foam molding, the foamed polylactic acid resin particles may be further impregnated with an inert gas to improve the foaming power of the polylactic acid resin foam particles. Thus, by improving the foaming power of the polylactic acid-based resin expanded particles, the fusion property between the polylactic acid-based resin foamed particles is improved at the time of in-mold foam molding, and the resulting polylactic acid-based resin foam molded product is even more excellent Has high mechanical strength. Examples of the inert gas include carbon dioxide, nitrogen, helium, and argon, and carbon dioxide is preferable.

  As a method for impregnating the polylactic acid-based resin expanded particles with an inert gas, for example, by placing the polylactic acid-based resin expanded particles in an inert gas atmosphere having a pressure higher than normal pressure, A method of impregnating with an inert gas can be mentioned. In such a case, an inert gas may be impregnated before filling the polylactic acid resin expanded particles into the mold, but the entire mold is inactive after the polylactic acid resin expanded particles are filled into the mold. It may be placed in a gas atmosphere and the polylactic acid resin expanded particles may be impregnated with an inert gas.

  And the temperature at the time of making an inert gas impregnate polylactic acid-type resin expanded particle has preferable -40-25 degreeC, and its -10-20 degreeC is more preferable. This is because when the temperature is low, the polylactic acid-based resin expanded particles are cooled too much, and the polylactic acid-based resin expanded particles cannot be sufficiently heated at the time of in-mold foam molding. This is because the heat-sealing property is lowered, and the mechanical strength of the obtained polylactic acid resin foamed molded product may be lowered. On the other hand, if the temperature is high, the amount of impregnation of the inert gas into the polylactic acid resin expanded particles becomes low, and sufficient foamability may not be imparted to the polylactic acid resin expanded particles. This is because crystallization of the resin foam particles is promoted, the heat-fusibility of the polylactic acid resin foam particles is lowered, and the mechanical strength of the resulting polylactic acid resin foam molding may be lowered.

  The pressure when impregnating the polylactic acid resin expanded particles with an inert gas is preferably 0.2 to 1.6 MPa, and more preferably 0.28 to 1.2 MPa. When the inert gas is carbon dioxide, 0.2 to 1.5 MPa is preferable, and 0.25 to 1.2 MPa is more preferable. This is because, when the pressure is low, the impregnation amount of the inert gas into the polylactic acid resin foamed particles becomes low, and sufficient foamability cannot be imparted to the polylactic acid resin foamed particles. This is because the mechanical strength of the resin foam molding may be lowered.

  On the other hand, when the pressure is high, the degree of crystallinity of the polylactic acid-based resin expanded particles increases, the heat-fusibility of the polylactic acid-based resin expanded particles decreases, and the mechanical strength of the resulting polylactic acid-based resin foamed molded product increases. It is because it may fall.

  Furthermore, the time for impregnating the polylactic acid-based resin expanded particles with the inert gas is preferably 20 minutes to 24 hours, more preferably 1 to 18 hours, and particularly preferably 3 to 8 hours. When the inert gas is carbon dioxide, 20 minutes to 24 hours are preferable. This is because if the impregnation time is short, the polylactic acid resin expanded particles cannot be sufficiently impregnated with the inert gas. On the other hand, if the impregnation time is long, the production efficiency of the polylactic acid-based resin foamed molded product is lowered.

  Thus, by impregnating the polylactic acid resin expanded particles with an inert gas at −40 to 25 ° C. and a pressure of 0.2 to 1.6 MPa, the degree of crystallinity of the polylactic acid resin expanded particles can be improved. While suppressing the rise, foamability can be improved, and therefore, during the in-mold foam molding, the polylactic acid resin foam particles can be firmly heat-sealed and integrated with sufficient foaming force, and the mechanical strength In particular, it is possible to obtain a polylactic acid resin foam molded article having excellent impact strength.

  As described above, when the polylactic acid resin foam particles are impregnated with an inert gas, the polylactic acid resin foam particles may be heated and foamed in a mold as they are. Before the foamed particles are filled into the mold, they may be heated and subjected to secondary foaming, and further formed into highly foamed secondary foamed particles, then filled into the mold and heated and foamed. By using such secondary expanded particles, it is possible to obtain a polylactic acid resin foamed molded article having a high expansion ratio. In addition, as a heating medium for heating the polylactic acid-based resin expanded particles, dry air is preferable.

  As the temperature when foaming the polylactic acid-based resin expanded particles to obtain secondary expanded particles, if the temperature is high, the crystallization of the polylactic acid-based resin increases and the heat-fusibility between the secondary expanded particles decreases. Since the mechanical strength and appearance of the obtained polylactic acid resin foamed molded article are lowered, the temperature is preferably less than 70 ° C.

If the unification of the secondary foamed particles is small, the open cell ratio of the secondary foamed particles may increase, and the foaming force necessary for the secondary foamed particles may not be imparted during foaming in the in-mold foam molding. . On the other hand, if the size is large, the foamed secondary foamed particles are uneven, and the foamability of the secondary foamed particles during in-mold foam molding may be insufficient. / Cm ³ (bulk multiple of 6.3 to 63 times) is preferable, and 0.03 to 0.1 g / cm ³ (bulk multiple of 6.9 to 42 times) is more preferable.

  And if the open cell ratio of the secondary foamed particles is high, the secondary foamed particles hardly foam at the time of in-mold foam molding, and the fusion property between the secondary foamed particles becomes low, and the resulting polylactic acid resin Since the mechanical strength of the foamed molded product may be lowered, it is preferably less than 20%, more preferably 10% or less, and particularly preferably 5% or less. The adjustment of the open cell ratio of the secondary expanded particles is performed by adjusting the open cell ratio of the polylactic acid-based resin expanded particles and adjusting the secondary expansion conditions. The open cell ratio of the secondary expanded particles can be measured in the same manner as the method for measuring the open cell ratio of the polylactic acid resin expanded particles.

  The degree of crystallinity of the secondary expanded particles is preferably less than 30%, and more preferably less than 25%. When the degree of crystallinity is 30% or more, foamability may be affected.

  Even when the secondary foamed particles are filled in a mold and molded, the secondary foamed particles are not treated under the same conditions and in the same manner as when the polylactic acid resin foamed particles are impregnated with an inert gas. It is preferable to impregnate the active gas to improve the foamability of the secondary foamed particles.

(Biodegradable resin foam molding)
In the present invention, the biodegradable resin foam molded article obtained is a biodegradable resin foam molded article excellent in heat resistance because a part of the carboxy group terminal of the biodegradable resin is blocked with a strength reduction preventing agent. It is.

Specifically, the biodegradable resin foam molded article of the present invention has the following formula (I):
0 ≦ (F ₀ −F ₈₀₀ ) / F ₀ ≦ 0.40 Formula (I)
(In the formula, F ₈₀₀ is a biodegradable resin foam-molded product in accordance with JIS K 7220: 1999 after leaving the biodegradable resin foam-molded product in an atmosphere of 80 ° C. and 95% relative humidity for 800 hours. 5% compressive strength, F ₀ is the 5% compressive strength of the biodegradable resin foam before standing)
In order to satisfy the above, a biodegradable resin foam molded article having a very small change in compressive strength even when placed in a humid heat atmosphere for a long time, that is, a biodegradable resin foam molded article excellent in heat resistance It is.

From the same viewpoint, it is preferable that 0 ≦ (F ₀ −F ₈₀₀ ) / F ₀ ≦ 0.30, and more preferably 0 ≦ (F ₀ −F ₈₀₀ ) / F ₀ ≦ 0.20. preferable.

Furthermore, the biodegradable resin foam molded article has the following formula (II):
0 ≦ (F ₀ −F ₁₄₀₀ ) / F ₀ ≦ 0.40 Formula (II)
(In the formula, F ₁₄₀₀ is a biodegradable resin foam molded article conforming to JIS K 7220: 1999 after leaving the biodegradable resin foam molded article in an atmosphere of 80 ° C. and 95% relative humidity for 1400 hours. 5% compressive strength, F ₀ is the 5% compressive strength of the biodegradable resin foam before standing)
When satisfy | filling, the biodegradable resin foaming molded object which was excellent by heat resistance over a further long time can be obtained.

From the same viewpoint, it is more preferable to satisfy 0 ≦ (F ₀ −F ₁₄₀₀ ) / F ₀ ≦ 0.35.

In the present invention, good heat resistance and the like can be imparted to the biodegradable resin foam molded article, but F ₀ , F ₈₀₀ and F ₁₄₀₀ are determined by unification of the biodegradable resin foam molded article. , F ₀ is preferably 0.09 to 0.55 MPa, more preferably 0.10 to 0.47 MPa. Similarly, F ₈₀₀ and F ₁₄₀₀ are preferably 0.06 to 0.35 MPa, and more preferably 0.07 to 0.32 MPa.

On the other hand, since a biodegradable resin foam molded article excellent in moldability, heat insulation and the like can be obtained, the biodegradable resin foam molded article may have a unity of 0.02 to 0.08 g / cm ^3. Preferably, it has a unity of 0.02 to 0.07 g / cm ³ .

  Since the biodegradable resin foam molded article of the present invention is excellent in heat resistance, it can be suitably used as a cushioning material for packaging.

EXAMPLES Hereinafter, although an Example is given and further demonstrated, this invention is not limited by these Examples.
<Lactic acid content of D-form or L-form of polylactic acid-based resin expanded particles>
The lactic acid content of D-form or L-form in the polylactic acid resin can be measured by the following method.
The polylactic acid resin is freeze-pulverized and 200 mg of the polylactic acid resin powder is supplied into the Erlenmeyer flask, and then 30 ml of 1N sodium hydroxide aqueous solution is added to the Erlenmeyer flask. Then, the polylactic acid resin is completely dissolved by heating to 65 ° C. while shaking the Erlenmeyer flask. Thereafter, 1N hydrochloric acid is supplied into the Erlenmeyer flask to neutralize it, a decomposition solution having a pH of 4 to 7 is prepared, and a predetermined volume is obtained using a volumetric flask. Next, the decomposition solution is filtered through a 0.45 μm membrane filter and then analyzed using liquid chromatography. Based on the obtained chart, the area ratio is determined from the peak area derived from the D-form and the L-form as the abundance ratio. The amount and L body mass are calculated. Then, the same procedure as described above is repeated 5 times, and the obtained D-form amount and L-form amount are arithmetically averaged to obtain the D-form amount and L-form amount of the polylactic acid resin.

Measurement conditions for liquid chromatography HPLC apparatus (liquid chromatography): manufactured by JASCO Corporation, product name PU-2085 Plus system column: manufactured by Sumitomo Analysis Center, Inc., product name SUMICHILAR OA5000 (4.6 mmφ × 250 mm)
Column temperature: 25 ° C
Mobile phase: Mixed solution of 2 mM CuSO ₄ aqueous solution and 2-propanol (CuSO ₄ aqueous solution: 2-propanol (volume ratio) = 95: 5)
Mobile phase flow rate: 1.0 ml / min Detector: UV 254 nm
Injection volume: 20 μl

<Weight average molecular weight of polylactic acid resin>
In each Example and Comparative Example, polylactic acid resin particles were prepared in the same manner except that no foaming agent was used, and about 30 mg of the obtained polylactic acid resin particles were dissolved in 10 ml of chloroform. After filtration through a 45 μm chromatographic disk, the weight average molecular weight in terms of polystyrene is measured using an HPLC apparatus (liquid chromatograph) (trade name “Detector 484, Pump 510” manufactured by Water).
As measurement conditions,
Column: Showa Denko Co., Ltd. Trade name “Shodex GPC K-806L” (φ8.0 mm × 300 mm) Two column temperature: 40 ° C.
Mobile phase: Chloroform mobile phase Flow rate: 1.2 ml / min Injection / pump temperature: Room temperature Detection: UV254 nm
Injection volume: Standard polystyrene for 50 ml calibration curve:
Product name "Shodex" manufactured by Showa Denko KK Weight average molecular weight 1030000
Weight average molecular weight 5480000,3840000,355000,102000,37900,9100,2630,495 manufactured by Tosoh Corporation

<Unification of biodegradable resin foam particles>
The unification of biodegradable resin expanded particles refers to those measured in accordance with JIS K6911: 1995 “General Test Method for Thermosetting Plastics”. That is, it measures using the apparent density measuring device based on JISK6911, and unity of a biodegradable resin expanded particle is measured based on a following formula.
Unified biodegradable resin foam particles (g / cm ³ )
= [Mass of measuring cylinder with sample (g) -Mass of measuring cylinder (g)]
/ [Capacity of measuring cylinder (cm ³ )]

<Foaming agent content of biodegradable resin foam particles>
5-20 mg of biodegradable resin foam particles are precisely weighed and used as a measurement sample. This measurement sample is set in a pyrolysis furnace (manufactured by Shimadzu Corporation: PYR-1A) maintained at 180 to 200 ° C., and the measurement sample is sealed and heated for 120 seconds to release the foaming agent component. Using this released foaming agent component, a chart of the blowing agent component is obtained under the following conditions using a gas chromatograph (manufactured by Shimadzu Corporation: GC-14B, detector: FID). Based on the calibration curve of the foaming agent component measured in advance, the foaming agent content of the biodegradable resin foamed particles is calculated from the obtained chart.
Measurement condition column for gas chromatography: “Shimalite 60/80 NAW” (φ3 mm × 3 m) manufactured by Shinwa Kako Co., Ltd. Column temperature: 70 ° C.
Detector temperature: 110 ° C
Inlet temperature: 110 ° C
Carrier gas: Nitrogen carrier gas Flow rate: 60 ml / min

<Measurement of foam particle size of biodegradable resin foam particles>
The particle size of the biodegradable resin expanded particles is measured by measuring the longest diameter (major axis) and the shortest diameter (minor axis) at the cut surface of each biodegradable resin expanded particle with a caliper. The length of the expandable resin foam particles in the direction perpendicular to the cut surface is measured, and the arithmetic average value of the major axis, the minor axis and the length of the biodegradable resin foam particles is defined as the particle size of the biodegradable resin foam particles.

<Unification of biodegradable resin foam moldings>
The unification of a biodegradable resin foam molded article refers to that measured according to JIS K6911: 1995 “General Test Method for Thermosetting Plastics”. That is, it measures using the apparent density measuring device based on JISK6911, and unity of a biodegradable resin foaming molding is measured based on a following formula.
Unified biodegradable resin foam (g / cm ³ )
= [Mass of measuring cylinder with sample (g) -Mass of measuring cylinder (g)]
/ [Capacity of measuring cylinder (cm ³ )]

<5% compressive strength of biodegradable resin foam molding>
The 5% compressive strength of a biodegradable resin foam molded article refers to that measured in accordance with JIS K7220: 1999 “Foamed plastics—Compression test of hard material”.
That is, using a Tensilon universal tester (Orientec Co., Ltd., product name UCT-10T), the specimen size is 50 × 50 × 20 mm, the temperature is 80 ° C., and the relative humidity is 95% for a predetermined time ( The compression strength at 5% compression (F ₈₀₀ and F ₁₄₀₀ ) is measured at a compression rate of 10 mm / min.
Further, the 5% compressive strength of the biodegradable resin foam molded body before heating is defined as F ₀ .
The 5% compressive strength of the biodegradable resin foam molding is evaluated according to the following criteria.
When 1.0 ≦ (F ₀ −F ₈₀₀ ) / F ₀ ≦ 0.40: ○ (pass)
2. In the case of 0.40 <(F ₀ −F ₈₀₀ ) / F ₀ : × (failed)

Example 1
The polylactic acid resin expanded particles for in-mold molding were manufactured using the manufacturing apparatus shown in FIGS. First, a crystalline polylactic acid resin (manufactured by Unitika, trade name “TERRAMAC HV-6250H”, melting point (mp): 169.1 ° C., D-form ratio: 1.2 mol%, L-form ratio: 9
8.8 mol%, obtained by dynamic viscoelasticity measurement, temperature T: 138.8 ° C. at the intersection of storage elastic modulus curve and loss elastic modulus curve) 100 parts by weight and polytetrafluoroethylene as a bubble regulator 0.1 part by weight of powder (trade name “Fluon L169J”, manufactured by Asahi Glass Co., Ltd.) and 2.6 parts by weight of carbodiimide compound (trade name “Carbodilite LA-1”, manufactured by Nisshinbo Co., Ltd.) having an aperture of 65 mm. In the single-screw extruder, the polylactic acid resin was first melt-kneaded at 180 ° C., then melt-kneaded while raising the temperature to 210 ° C., and the resin temperature was set to 180 ° C. Extrusion was carried out at a temperature adjusted to ° C.

Subsequently, in the middle of the single screw extruder, a polylactic acid-based polylactic acid in a molten state so that butane composed of 35% by weight of isobutane and 65% by weight of normal butane is 1.0 part by weight with respect to 100 parts by weight of the polylactic acid-based resin. It was press-fitted into the resin and uniformly dispersed in the polylactic acid resin. Thereafter, after the molten polylactic acid resin was cooled, the polylactic acid resin was extruded and foamed from each nozzle of the multi-nozzle mold 1 attached to the front end of the single screw extruder at a shear rate of 18118 sec ⁻¹ . The multi-nozzle mold 1 has 20 nozzles having a diameter of the outlet portion 11 of 0.5 mm, and all the outlet portions 11 of the nozzle are assumed to be on the front end face 1a of the multi-nozzle die 1. Are arranged at equal intervals on a virtual circle A of 139.5 mm. The multi-nozzle mold 1 was held at 220 ° C.

Then, four rotary blades 5 are integrally provided at equal intervals in the circumferential direction of the rotary shaft 2 on the outer peripheral surface of the rear end portion of the rotary shaft 2, and each rotary blade 5 is a multi-nozzle mold 1. It is configured to move on the virtual circle A while always in contact with the front end face 1a. Further, the cooling member 4 includes a cooling drum 41 including a front circular front part 41a and a cylindrical peripheral wall part 41b extending rearward from the other peripheral edge of the front part 41a and having an inner diameter of 315 mm. It was. The cooling water 42 is supplied into the cooling drum 41 through the supply pipe 41d and the supply port 41c of the drum 41, and the cooling water 42 at 20 ° C. is forwarded along the inner surface of the peripheral wall portion 41b. It was flowing in a spiral.

  The rotary blade 5 disposed on the front end face 1a of the multi-nozzle mold 1 is rotated at a rotational speed of 4800 rpm, and the polylactic acid resin extruded and foamed from the outlet 11 of each nozzle of the multi-nozzle mold 1 The extrudate was cut with a rotary blade 5 to produce substantially spherical polylactic acid-based resin expanded particles. The polylactic acid-based resin extrudate was composed of an unfoamed portion immediately after being extruded from the nozzle of the multi-nozzle mold 1 and a foamed portion in the course of foaming continuous with the unfoamed portion. And the polylactic acid-type resin extrudate was cut | disconnected in the opening end of the exit part 11 of a nozzle, and the cutting | disconnection of the polylactic acid-type resin extrudate was performed in the unfoamed part. In the production of the polylactic acid-based resin expanded particles described above, first, the rotating shaft 2 was not attached to the multi-nozzle mold 1 and the cooling member 4 was retracted from the multi-nozzle mold 1. In this state, the polylactic acid-based resin extrudate is extruded and foamed from an extruder, and the polylactic acid-based resin extrudate is continuous with the unfoamed portion immediately after being extruded from the nozzle of the multi-nozzle mold 1. It confirmed that it consists of a foaming part in the process of foaming. Next, after attaching the rotating shaft 2 to the multi-nozzle mold 1 and disposing the cooling member 4 at a predetermined position, the rotating shaft 2 is rotated, and the polylactic acid resin extrudate is placed at the opening end of the outlet portion 11 of the nozzle. Polylactic acid resin foamed particles were produced by cutting with a rotary blade 5.

The polylactic acid-based resin foamed particles are blown outward or forward by the cutting stress of the rotary blade 5, collide with the cooling water 42 flowing along the inner surface of the cooling drum 41 of the cooling member 4 and immediately cool down. It was done. The cooled polylactic acid resin foamed particles were discharged together with the cooling water 42 through the discharge port 41e of the cooling drum 41, and then separated from the cooling water 42 by a dehydrator. The obtained polylactic acid-based resin expanded particles had a particle size of 1.0 to 2.2 mm and a unity of 0.20 g / cm ³ .

Next, the polylactic acid-based resin expanded particles are supplied into a 10-liter pressure vessel and sealed, and carbon dioxide is injected into the pressure vessel at a pressure of 1.0 MPa (G) at 25 ° C. for 6 hours. The polylactic acid resin expanded particles were impregnated with carbon dioxide. The polylactic acid-based resin expanded particles are taken out from the pressure vessel, and the polylactic acid-based resin expanded particles are immediately supplied to a hot air dryer equipped with a stirrer, and the polylactic acid-based resin expanded particles are stirred with 54 ° C dry hot air. It was heated and foamed for 3 minutes to obtain polylactic acid resin foamed particles having a particle size of 2.8 to 3.5 mm and a unity of 0.047 g / cm ³ .

  Next, the obtained polylactic acid-based resin expanded particles having a high expansion ratio are supplied into a sealed container, and carbon dioxide is press-fitted into the sealed container at a pressure of 0.65 MPa (G). The polylactic acid resin foamed particles were impregnated with carbon dioxide by being left for a period of time. Subsequently, the polylactic acid-based resin expanded particles were filled in a cavity of an aluminum mold. In addition, the internal dimension of the cavity of a metal mold | die was a rectangular parallelepiped shape of length 30mm x width 300mm x height 300mm. In addition, a total of 252 circular supply ports having a diameter of 8 mm were formed at intervals of 20 mm in order to allow the inside of the mold cavity to communicate with the outside of the mold. Each supply port is provided with a lattice portion having an opening width of 0.4 mm so that the polylactic acid resin foam particles filled in the mold do not flow out of the mold through the supply port. On the other hand, the water can be smoothly supplied from the outside of the mold into the cavity through the supply port of the mold.

Then, water maintained at 90 ° C. is stored in a heated water tank, and a mold filled with polylactic acid-based resin foam particles is completely immersed in the water in the heated water tank for 1 minute to supply the mold. Water was supplied to the polylactic acid-based resin expanded particles in the cavity of the mold through the mouth, and the polylactic acid-based resin expanded particles were heated and expanded to integrate the polylactic acid-based resin expanded particles by heat fusion. Next, the mold was taken out from the heated water tank. And the water maintained at 20 degreeC was stored in another cooling water tank, and the metal mold | die was completely immersed in this cooling water tank over 5 minutes, and the polylactic acid-type resin foaming molding in a metal mold | die was cooled. . The mold was taken out from the cooling water tank, and the mold was opened to obtain a rectangular parallelepiped polylactic acid resin foam molded product. The obtained polylactic acid resin foamed molded article had a very excellent appearance.

The resulting polylactic acid-based resin expanded particles are
The weight average molecular weight is 252.8 × 10 ³ ;
The average particle size is 1.6 mm,
Unification is 0.20 g / cm ² ,
0.8 parts by weight of a foaming agent was contained with respect to 100 parts by weight of the expanded polylactic acid resin particles.
The resulting polylactic acid resin foamed molded article is
The unity is 0.047 g / cm ³ ,
F ₀ and F ₈₀₀ were 0.230 and 0.140 MPa, respectively.
With F ₁₄₀₀ , the strength of the polylactic acid resin foamed molded article was significantly reduced, and the test was stopped.

(Example 2)
A rectangular parallelepiped polylactic acid resin foam molded article was obtained in the same manner as in Example 1 except that 4.0 parts by weight of the strength lowering inhibitor was added.

The resulting polylactic acid-based resin expanded particles are
The weight average molecular weight is 253.0 × 10 ³ ;
The average particle size is 1.6 mm,
Unification is 0.20 g / cm ² ,
0.8 parts by weight of a foaming agent was contained with respect to 100 parts by weight of the expanded polylactic acid resin particles.
The resulting polylactic acid resin foamed molded article is
Unification is 0.046 g / cm ³ ,
F ₀ and F ₈₀₀ and F ₁₄₀₀ were 0.241, 0.229 and 0.149 MPa, respectively.

(Example 3)
A rectangular parallelepiped polylactic acid resin foam molded article was obtained in the same manner as in Example 1 except that 5.0 parts by weight of the strength lowering inhibitor was added.

The resulting polylactic acid-based resin expanded particles are
The weight average molecular weight is 259.8 × 10 ³ ;
The average particle size is 1.6 mm,
The unity is 0.020 g / cm ²
0.8 parts by weight of a foaming agent was contained with respect to 100 parts by weight of the expanded polylactic acid resin particles.
The resulting polylactic acid resin foamed molded article is
The unity is 0.048 g / cm ³ ,
F ₀ , F ₈₀₀ and F ₁₄₀₀ were 0.235, 0.219 and 0.166 MPa, respectively.

(Comparative Example 1)
A rectangular parallelepiped polylactic acid resin foam molded article was obtained in the same manner as in Example 1 except that the strength reduction inhibitor was not added.

The resulting polylactic acid-based resin expanded particles are
The weight average molecular weight is 201.2 × 10 ³ ;
The average particle size is 0.16 mm,
Unification is 0.20 g / cm ² ,
0.8 parts by weight of a foaming agent was contained with respect to 100 parts by weight of the expanded polylactic acid resin particles.
The unification of the polylactic acid resin foamed molded product was 0.047 g / cm ³ .
Although the 5% compressive strength of the polylactic acid-based resin foamed molded article was evaluated, the strength of the polylactic acid-based resin foamed molded article was remarkably reduced, and further investigation was stopped.

(Comparative Example 2)
A rectangular parallelepiped-shaped polylactic acid resin foam in the same manner as in Example 1 except that the addition amount of a carbodiimide compound (trade name “Carbodilite LA-1” manufactured by Nisshinbo Co., Ltd.), which is a strength reduction inhibitor, was 1.0 part. A molded body was obtained.

The resulting polylactic acid-based resin expanded particles are
The weight average molecular weight is 249.1 × 10 ³ ;
The average particle size is 0.16 mm,
Unification is 0.20 g / cm ² ,
0.8 parts by weight of a foaming agent was contained with respect to 100 parts by weight of the expanded polylactic acid resin particles.
The unification of the polylactic acid resin foamed molded product was 0.046 g / cm ³ .
Although the 5% compressive strength of the polylactic acid-based resin foamed molded article was evaluated, the strength of the polylactic acid-based resin foamed molded article was remarkably reduced, and further investigation was stopped.

(Comparative Example 3)
Extrusion was carried out in the same manner as in Example 1 except that the addition amount of the carbodiimide compound (trade name “Carbodilite LA-1” manufactured by Nisshinbo Co., Ltd.), which is a strength lowering inhibitor, was 6.0 parts. The pressure of was high, and expanded particles could not be obtained.
For this reason, further examination was discontinued.

In Table 1, the raw material seed | species of an Example and a comparative example, the evaluation result of a polylactic acid-type resin foaming molding, etc. are shown.
FIG. 3 shows the 5% compressive strength of Examples and Comparative Examples.

From Table 1 and FIG. 3, the polylactic acid-type resin moldings of Examples 1 to 3 show biodegradability and a low strength reduction rate under high temperature and high humidity, that is, excellent heat resistance.
Therefore, the polylactic acid resin molded product of the present invention can be suitably used as a cushioning material for packaging.

1 Nozzle mold 1a Front end face 2 of nozzle mold 1 Rotating shaft 3 Drive member (motor)
4 Cooling member 5 Rotating blade 11 Nozzle outlet 41 Cooling drum 41a Cooling drum front 41b Cooling drum peripheral wall 41c Cooling drum supply port 41d Cooling drum supply pipe 41e Cooling drum discharge port 41f Cooling drum discharge pipe 42 Cooling drum coolant A Rotary blade folder

Claims (7)

A biodegradable resin foam molded article comprising a biodegradable resin having a carboxy group terminal;
A part of the carboxy group terminal is blocked with a strength-reducing inhibitor contained in a proportion of more than 2.5 parts by weight and less than 5.0 parts by weight with respect to 100 parts by weight of the biodegradable resin,
The biodegradable resin foam molded article has the following formula (I):
0 ≦ (F ₀ −F ₈₀₀ ) / F ₀ ≦ 0.40 Formula (I)
(In the formula, F ₈₀₀ represents the biodegradable resin foam molded article in accordance with JIS K 7220: 1999 after the biodegradable resin foam molded article is allowed to stand for 800 hours in an atmosphere at a temperature of 80 ° C. and a relative humidity of 95%. 5% compressive strength of the body, and F ₀ is the 5% compressive strength of the biodegradable resin foam molded body before leaving)
The cushioning material for packaging characterized by satisfy | filling. The biodegradable resin foam molded article has the following formula (II):
0 ≦ (F ₀ −F ₁₄₀₀ ) / F ₀ ≦ 0.40 Formula (II)
(In the formula, F ₁₄₀₀ represents the biodegradable resin foam molded article in accordance with JIS K 7220: 1999 after the biodegradable resin foam molded article is left for 1400 hours in an atmosphere at a temperature of 80 ° C. and a relative humidity of 95%. 5% compressive strength of the body, and F ₀ is the 5% compressive strength of the biodegradable resin foam molded body before leaving)
The cushioning material for packaging according to claim 1, wherein   The cushioning material for packaging according to claim 1 or 2, wherein the biodegradable resin is a polylactic acid resin.   The biodegradable resin contains both D-form and L-form optical isomers as constituent monomer components, and the content of the smaller of the D-form and L-form is less than 5 mol%. The packaging according to any one of claims 1 to 3, comprising a polylactic acid resin containing only one optical isomer of either D-form or L-form as a constituent monomer component. Cushioning material.   The packaging buffer material according to any one of claims 1 to 4, wherein the strength reduction inhibitor is a carbodiimide compound. The biodegradable resin foam molded article, cushioning material for packaging according to any one of claims 1-5 having a bulk density of 0.02 to 0.08 g / cm ^3. The biodegradable resin foam molded article is
Supplying the biodegradable resin and the strength reduction inhibitor to an extruder and melt-kneading under a foaming agent;
While extruding a biodegradable resin extrudate from a nozzle mold attached to the front end of the extruder and foaming the biodegradable resin extrudate, at a temperature of the nozzle mold of 180 to 235 ° C., A step of producing biodegradable resin foam particles by cutting with a rotating blade rotating at a rotational speed of 2000 to 10000 rpm while contacting the front end surface, and scattering the biodegradable resin foam particles by cutting stress,
Cooling the biodegradable resin foam particles by colliding with a cooling member disposed in front of the nozzle mold,
Impregnating an inert gas into the obtained biodegradable resin foam particles,
Heating and foaming biodegradable resin foam particles impregnated with inert gas;
Any one of Claims 1-6 obtained by the manufacturing method including the process of re-impregnating the biodegradable resin foam particle which carried out heat foaming again with inert gas, and the process of shape-molding the biodegradable resin foam particle. The cushioning material for packaging according to 1.