JP4697861B2 - Polylactic acid-based resin foamed particles and polylactic acid-based resin in-mold foam molding - Google Patents

Description

  The present invention relates to a polylactic acid-based resin expanded particle and a polylactic acid-based resin in-mold foam molded body.

  Conventionally, in-mold foam molded products made of general-purpose resins such as polyethylene resins, polypropylene resins, and polystyrene resins have been widely used as cushioning materials for packaging, agricultural boxes, fish boxes, automobile parts, building materials, civil engineering materials, etc. I came. However, in-mold foam molded articles made of these general-purpose resins, when left in a natural environment after use, are hardly decomposed by microorganisms in the soil, which may cause a problem of environmental pollution.

  In order to solve the environmental problems, biodegradable resins that are decomposed by microorganisms in the soil have been developed. One of them is a biodegradable polylactic acid resin. The polylactic acid-based resin has microbial degradability and is excellent in safety to the human body, and thus has been put into practical use as, for example, a surgical suture and has a long track record. Moreover, in recent years, lactic acid, which is a raw material for polylactic acid-based resins, has been produced in large quantities and at low cost by fermentation methods that use corn or the like as a raw material. Has been done.

  Prior arts related to foams made of polylactic acid-based resins include JP-A-5-508669, JP-A-4-304244, JP-A-5-139435, JP-A-5-140361, JP-A-9. Examples relating to extruded foams such as -263651, and those relating to expanded particles such as JP-A-5-170965, JP-A-5-170966, and JP-A 2000-136261 (Patent Document 1).

  Among the prior arts related to the polylactic acid-based resin foam, those related to the foamed particles can obtain a foam having a desired shape without being relatively restricted in shape, such as lightness, shock-absorbing property, and heat insulation. Since it is easy to design physical properties according to the purpose, it is particularly promising as a practical one.

  However, the in-mold foam molded article made of a polylactic acid-based resin described in Patent Document 1 and the like fills the mold with foamable non-foamed resin particles and simultaneously foams the resin particles with hot air. Because it was fused, the density variation of the portion of the in-mold foamed molded product was large, and the fusion properties and dimensional stability between the foamed particles were insufficient, resulting in poor mechanical properties. .

  To solve the problems of the in-mold foam-molded article described in Patent Document 1 and the like, and to provide a polylactic acid in-mold foam-molded article having excellent fusion properties between foam particles, dimensional stability, and mechanical properties. As an object, the present inventors first produced foamed particles in a state where the polylactic acid-based resin is not crystallized using a crystalline polylactic acid-based resin, and in-mold foam molding using the foamed particles. An attempt was made to obtain a body (Patent Document 2). Specifically, polylactic acid-based resin expanded particles having a difference between an endothermic amount and a calorific value of 0 to 30 J / g and a calorific value of 15 J / g or more were developed. As a result, the obtained expanded particles were far superior in terms of the fusibility between the expanded particles and the secondary expandability at the time of in-mold molding as compared with those described in Patent Document 1.

JP 2000-136261 A JP 2004-83890 A

However, even though the polylactic acid-based resin expanded particles of Patent Document 2 have improved fusibility, when they are heated in a high-temperature steam pressure in order to further improve the fusibility during molding in the mold, the obtained mold is obtained. The surface of the inner molded body was melted by heating. Therefore, there is a demand for foamed particles that can be molded with a low-temperature steam pressure while satisfying the fusibility between the foamed particles.
The present invention relates to a polylactic acid-based resin foamed particle that is excellent in fusion property between foamed particles and can be molded in a mold at a low temperature (low-pressure steam), and a polylactic acid-based resin in-mold foamed product obtained by using the foamed particle The issue is to provide

As a result of intensive studies by the present inventors, it has been found that by incorporating a fusibility improver into the expanded particles, molding can be performed at a low steam pressure while satisfying the fusibility, and the present invention has been achieved.
That is, according to the present invention, the following polylactic acid-based resin expanded particles and polylactic acid-based in-mold expanded molded articles are provided.
[1] A foamed particle having a polylactic acid resin as a base resin,
The endothermic amount (Rendo) in differential scanning calorimetry at a heating rate of 2 ° C./min of the base resin is 5 J / g or more,
The ratio (Bexo / Bendo) of the calorific value (Bexo) and the endothermic amount (Bendo) in differential scanning calorimetry at a heating rate of 2 ° C./min of the foamed particles exceeds 0.2, and the endothermic amount (Bendo) Is 5 J / g or more,
A polylactic acid characterized in that the relationship between the calorific value (Bs: J / g ) of the surface layer of the expanded particles and the calorific value (Bi: J / g ) inside the expanded particles satisfies the following formula (1) Resin foam particles.
(Bi−Bs) / (Bi) ≦ 0.6 (1)
[2] The polylactic acid according to claim 1, wherein the base resin contains a fusing property improving agent comprising a single or plural mixture selected from the following i) to vii). Resin foam particles.

i) Fatty acid composed of at least one saturated fatty acid selected from caprylic acid having 8 carbon atoms, capric acid having 10 carbon atoms, lauric acid having 12 carbon atoms, myristic acid having 14 carbon atoms, and palmitic acid having 16 carbon atoms. A glycerin derivative comprising a glycerin fatty acid ester containing at least 75% by mass of monoglyceride and / or acetylated product thereof.
ii) an ether ester derivative comprising a compound represented by the following chemical formula (1)
R (OR ') nOOC-R "-COO (R'O) mR (1)
(In the formula, R represents an alkyl group, R ′ represents an alkylene group, R ″ represents a divalent organic group containing an alkylene group, and m and n each independently represents 1 to 500.)
iii) Glycolic acid derivative consisting of triethylene glycol diacetate
iv) a citric acid derivative consisting of tributyl acetylcitrate
v) Adipic acid derivative comprising dimethyl adipate, diethyl adipate, dibutyl adipate, dioctyl adipate
vi) A rosin derivative comprising a compound represented by the following chemical formula (2)
_{Ro-COO - ((CHR 1} ) l (CHR 2) m -O) n ((CHR 3) l '(CHR 4) m' -O) n '-R 5 (2)
(In the formula, Ro is a rosin residue, R ₁ , R ₂ , R ₃ , R ₄ are hydrogen atoms or methyl groups, R ₅ is a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an acyl group, l, l 'Is an integer of 0 to 6, m and m' are integers of 0 to 6 (where 1 ≦ l + m ≦ 6, 1 ≦ l ′ + m ′ ≦ 6), n and n ′ are integers of 0 to 7 (however, 1 ≦ n + n ′ ≦ 7))
vii) Tetrahydrofurfuryl alcohol derivative comprising a compound represented by the following chemical formula (3)
Th-OOC-R (3)
(In the formula, Th is a tetrahydrofurfuryl alcohol residue, R is an alkyl group, an alkenyl group, an aryl group, an aryl group in which at least one hydrogen is replaced by a hydroxyl group, a rosin residue, a general formula (4): —COOTh or Formula (5): -X- (COOY) n (where X is an aryl group, an aryl group in which at least one hydrogen is replaced by a hydroxyl group, a cycloalkyl group, a cycloalkenyl group, or at least one hydrogen is replaced by an acylated hydroxyl group) An optionally substituted alkylene group or alkenylene group, Y represents an alkyl group or a tetrahydrofurfuryl alcohol residue, and n represents an integer of 1 to 4).

[3] It is composed of at least one saturated fatty acid selected from C8 caprylic acid, C10 capric acid, C12 lauric acid, C14 myristic acid, and C16 palmitic acid. It contains a fusibility improver comprising a single or plural mixture selected from glycerin derivatives comprising a fatty acid monoglyceride and / or a glycerin fatty acid ester containing 75% by mass or more of an acetylated product thereof. The polylactic acid-based resin expanded particles according to claim 1.

[4] A polylactic acid resin in-mold foam molded product obtained by fusing the polylactic acid resin foamed particles according to any one of [1] to [3] to each other.

The foamed particles according to claim 1 of the present invention have a specific relationship between the calorific value (Bs: J / g ) of the surface layer of the foamed particles and the calorific value (Bi: J / g ) therein. In-molding can be performed at a low steam pressure regardless of the presence or absence of crystal components and the progress of crystallization.
Foamed particles according to claim 1 of the present invention, heat absorption amount of the substrate resin (Rendo) is excellent in heat resistance since it is 5 J / g or more, excellent in-mold expansion molded article obtained heat resistance Can be granted.
Foamed particles according to claim 1 of the present invention can be a low temperature steam pressure to fuse the expanded beads mutual because crystallization is not advanced.
Since the in-mold foam-molded article according to claim 4 of the present invention is obtained by fusing the polylactic acid-based resin foam particles having good secondary foam properties to each other, there are few gaps between the foam particles, Appearance is good, and shows excellent biodegradability in soil after use.

Hereinafter, the polylactic acid-based resin expanded particles and the polylactic acid-based resin in-mold foam molded body of the present invention will be described in detail.
The base resin of the polylactic acid-based resin expanded particles (hereinafter also simply referred to as “expanded particles”) of the present invention is a polylactic acid-based resin. The polylactic acid resin refers to a polymer containing 50 mol% or more of lactic acid component units. This includes, for example, (1) a polymer of lactic acid, (2) a copolymer of lactic acid and another aliphatic hydroxycarboxylic acid, and (3) a lactic acid, an aliphatic polyhydric alcohol and an aliphatic polycarboxylic acid. Copolymer, (4) Copolymer of lactic acid and other aliphatic polyhydric carboxylic acid, (5) Copolymer of lactic acid and aliphatic polyhydric alcohol, (6) According to any combination of (1) to (5) Mixtures and the like are included. Specific examples of the lactic acid include L-lactic acid, D-lactic acid, DL-lactic acid or their cyclic dimer L-lactide, D-lactide, DL-lactide or a mixture thereof. .

  Examples of other aliphatic hydroxycarboxylic acids in the above (2) include glycolic acid, hydroxybutyric acid, hydroxyvaleric acid, hydroxycaproic acid, hydroxyheptanoic acid and the like. In addition, as the aliphatic polyhydric alcohol in the above (3) and (5), ethylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, decamethylene glycol Glycerin, trimethylolpropane, pentaerythritol and the like. In addition, as the aliphatic polyvalent carboxylic acid in (3) and (4), succinic acid, adipic acid, suberic acid, sebacic acid, dodecanedicarboxylic acid, succinic anhydride, adipic anhydride, trimesic acid, propanetricarboxylic acid, Examples include pyromellitic acid and pyromellitic anhydride.

Further, the base resin in the present invention includes a crystalline polylactic acid resin (i) of 10 to 90 parts by weight, and an amorphous polylactic acid resin (ii) of 10 to 90 parts by weight. (However, the sum of (i) and (ii) is 100 parts by weight).
When the proportion of the crystalline polylactic acid resin (i) is less than 10 parts by weight, the resulting in-mold foam molded product may have insufficient heat resistance, and the crystalline polylactic acid resin (i) When the ratio exceeds 90 parts by weight, high-temperature steam may be required to ensure sufficient fusion between the foamed particles during molding. From this viewpoint, the lower limit of the crystalline polylactic acid resin (i) is preferably 20 parts by weight or more, and more preferably 30 parts by weight or more. On the other hand, the upper limit is preferably 80 parts by weight or less, and more preferably less than 70 parts by weight. However, the total of the crystalline polylactic acid resin (i) and the noncrystalline polylactic acid resin (ii) is 100 parts by weight.

The polylactic acid resin, which is the base resin for the expanded particles of the present invention, has a heat absorption (Rendo) of 5 J / g or more in the differential scanning calorimetry at a heating rate of 2 ° C./min among the polylactic acid resins described above . There is .
When the endothermic amount is less than 5 J / g, there is a possibility that an in-mold foam-molded product having heat resistance, rigidity and the like such that the crystal component is too small to be easily deformed in a heated atmosphere may not be obtained. . In this respect, the heat absorption is preferably 10 J / g or more, more preferably 15 J / g or more, and even more preferably 20 J / g or more. On the other hand, the upper limit is that if there are many crystal components, it may be difficult to handle because it takes time and time to crystallize, and the foamed particles that have crystallized may be fused with each other unless the steam is hot. In addition, the surface of the obtained in-mold foam molded product may be uneven. In this respect, the heat absorption is preferably 50 J / g or less, more preferably 40 J / g or less, and particularly preferably less than 30 J / g. In general, the endothermic amount is displayed as a negative value, but the endothermic amount in the present specification means an absolute value.

In the present specification, the endothermic amount (Rendo) in the differential scanning calorimetry of the polylactic acid-based resin is a value obtained by heat flux differential scanning calorimetry described in JIS K7122 (1987) for the polylactic acid-based resin. However, 1 to 4 mg of a polylactic acid resin is used as a test piece, and the condition adjustment of the test piece and the measurement of the DSC curve are performed according to the following procedure. The test piece was put in a container of a DSC apparatus, heated and melted to 200 ° C., kept at that temperature for 10 minutes, then cooled to 110 ° C. at a cooling rate of 2 ° C./min, kept at that temperature for 120 minutes, A DSC curve is obtained when heat-melting to a temperature about 30 ° C. higher than the end of the melting peak at a heating rate of 2 ° C./min after the heat treatment cooling to 40 ° C. at a cooling rate of 2 ° C./min. The endothermic amount (Rendo) of the polylactic acid resin, as shown in FIG. 1, is a point a where the endothermic peak departs from the low-temperature base line of the endothermic peak of the DSC curve, and the endothermic peak is on the high-temperature side. A point returning to the base line is a point b, and a value obtained from a straight line connecting the point a and the point b and an area of a portion surrounded by the DSC curve. Also, the apparatus should be adjusted so that the baseline is as straight as possible. If the baseline is inevitably curved as shown in FIG. 2, the curved baseline on the low temperature side of the endothermic peak is curved. Maintaining the state and drawing to the high temperature side, the point where the endothermic peak departs from the curved low temperature side baseline is point a, and the curved base line on the high temperature side of the endothermic peak is maintained in the curved state of the curve Then, a drawing extending to the low temperature side is performed, and a point where the endothermic peak returns to the curved high temperature side baseline is defined as a point b.
In the measurement of the endothermic amount (Rendo), the condition of the test piece and the measurement conditions of the DSC curve were as follows: holding at 110 ° C. for 120 minutes, cooling rate of 2 ° C./min, and heating rate of 2 ° C./min. The reason for adopting it is to obtain the endotherm (Rendo) of the polylactic acid test piece that has been adjusted to a fully crystallized state or a state close to it by crystallization as much as possible. Because it is. As described above, the case where the polylactic acid-based resin is used as the test piece has been described. However, the endothermic amount can also be measured using the resin from which the foamed particles are removed as a test piece.

  In addition, the crystalline polylactic acid in this specification shall have an endothermic peak exceeding 2 J / g in the DSC curve obtained by the above-described procedure for measuring the endothermic amount (Rendo) of polylactic acid. The endothermic amount (Rendo) of the crystalline polylactic acid is usually 20 to 80 J / g. In addition, the non-crystalline polylactic acid in the present specification refers to a case where an endothermic peak of 2 J / g or less appears in the DSC curve obtained by the above-described procedure for measuring the endothermic amount (Rendo) of polylactic acid or an endothermic peak does not appear. It is.

  Specific examples of the method for producing the polylactic acid resin used in the present invention include, for example, a method of direct dehydration polycondensation using lactic acid or a mixture of lactic acid and aliphatic hydroxycarboxylic acid as a raw material (for example, US Pat. No. 5,310). , 865), a ring-opening polymerization method for polymerizing a cyclic dimer (lactide) of lactic acid (for example, the production method disclosed in US Pat. No. 2,758,987), lactic acid and A ring-opening polymerization method in which a cyclic dimer of an aliphatic hydroxycarboxylic acid, for example, lactide or glycolide and ε-caprolactone is polymerized in the presence of a catalyst (for example, production disclosed in US Pat. No. 4,057,537) Method), a method of directly dehydrating polycondensation of a mixture of lactic acid, an aliphatic dihydric alcohol and an aliphatic dibasic acid (for example, the production method disclosed in US Pat. No. 5,428,126). ), A method of condensing lactic acid, an aliphatic dihydric alcohol, an aliphatic dibasic acid and a polymer in the presence of an organic solvent (for example, a production method disclosed in European Patent Publication No. 071880 A2), a lactic acid polymer In producing a polyester polymer by performing a dehydration polycondensation reaction in the presence of a catalyst, a method of performing solid phase polymerization in at least a part of the steps can be exemplified, but the production method is particularly limited. Not. In addition, a small amount of an aliphatic polyhydric alcohol such as glycerin, an aliphatic polybasic acid such as butanetetracarboxylic acid, a polyhydric alcohol such as a polysaccharide may be coexisted and copolymerized. The molecular weight may be increased by using a binder (polymer chain extender) such as a polyisocyanate compound. Further, it may be branched by a branching agent typified by a polyhydric aliphatic alcohol such as pentaerythlit.

Moreover, other resin can be added to the base resin which comprises the expanded particle of this invention in the range which does not inhibit the objective and effect of this invention. The mixed resin of polylactic acid and other resin preferably contains 50% by weight or more of polylactic acid, more preferably 70% by weight or more, and still more preferably 90% by weight or more.
Examples of other resins that can be mixed with polylactic acid include polyethylene-based resins, polypropylene-based resins, polystyrene-based resins, polyester-based resins, and the like. Among them, biodegradable aliphatic compounds that contain at least 35 mol% of aliphatic ester component units. Polyester resins are preferred. Examples of the aliphatic polyester resin in this case include hydroxy acid polycondensates other than the polylactic acid resin, ring-opening polymerization products of lactones such as polycaprolactone, polybutylene succinate, polybutylene adipate, polybutylene succinate adipate , Polycondensates of aliphatic polyhydric alcohols such as poly (butylene adipate / terephthalate) and aliphatic polycarboxylic acids.

In the polylactic acid-based resin expanded particles of the present invention, the relationship between the calorific value (Bs: J / g ) of the surface layer of the expanded particles and the calorific value (Bi: J / g ) inside the expanded particles is expressed by the following formula (1 ) Must be satisfied.
(Bi−Bs) / (Bi) ≦ 0.6 (1)

When the present inventors examined paying attention to the relationship between the calorific value (Bi) inside the foamed particles and the calorific value (Bs) of the surface layer, (Bi−Bs) / (Bi) ≦ 0.6. In this case, it was found that molding can be performed with a low steam pressure.
The fact that the internal heat generation amount (Bi) and the surface heat generation amount (Bs) satisfy the relationship of (Bi−Bs) / (Bi) ≦ 0.6 is, for example, that the foam particles contain a fusing improver. In addition, when foaming the resin particles, it can be achieved by rapidly cooling the surface of the resin particles to a non-crystalline state by a method of releasing into water or a method of blowing cold air.
In addition, although the mechanism which can be shape | molded with a low temperature steam pressure is not certain, it is thought that it is because the emitted-heat amount of the surface layer does not fall. In other words, it is considered that if the crystallization of the surface layer of the expanded particle does not proceed, molding can be performed with a low-temperature steam pressure. Thus, the heating value of the surface layer in the foamed particles (Bs) is large, if Kere sufficiently smaller than the interior of the heating value (Bi) and the surface layer of the heating value heat value difference is inside the (Bs) (Bi), a surface layer This indicates that the crystallization is not progressing, so that molding can be performed at a lower steam pressure.

From the above viewpoint, the relationship between the calorific value (Bs) of the foamed particle surface layer and the internal calorific value (Bi) preferably satisfies the following formula (2), and more preferably satisfies the following formula (3).
(Bi-Bs) / (Bi) ≦ 0.55 (2)
(Bi-Bs) / (Bi) ≦ 0.5 (3)

  The surface layer of the expanded particles refers to a portion where the entire surface layer portion of the expanded particles is deleted and the deleted portion is 1/5 or less of the weight of the original expanded particles. On the other hand, the internal foamed layer refers to a portion obtained by deleting the entire surface layer portion, further cutting out, and cutting out so as to be not more than a quarter of the particle weight of the original foamed particles.

  The expanded particles of the present invention preferably contain the fusibility improver. Foamed particles containing a fusibility improver can be molded with low-temperature steam compared to expanded particles that do not contain a fusibility improver, regardless of the presence or absence of crystal components and expanded crystallization. it can. The resulting polylactic acid-based resin-in-mold foamed molded product has excellent heat resistance, has little deformation under high-temperature atmosphere, and has little decrease in compressive strength. It is more preferable that the content is larger than the content inside the particles, and it is still more preferable that the fusing property improving agent exists only in the surface layer.

As a sample of the surface layer portion of the foamed particles, the surface layer portion including the surface may be cut using a cutter knife, a microtome, etc., and the surface layer portion may be collected and used for measurement. However, it should be noted that the entire surface layer of one foamed particle must be excised and the weight of the surface layer part excised from one foamed particle is not more than one-fifth of the original foamed particle weight. Is cut so as to be 1/5 to 1/7 of the particle weight of the original expanded particles. When the weight of the excised surface layer part exceeds 1/5 of the original foam particle weight, the internal foam layer is contained in a large amount, and there is a possibility that the calorific value of the surface layer part cannot be measured accurately. Furthermore, when the surface layer part obtained from one expanded particle is less than 2-4 mg, it is necessary to repeat the said operation about several expanded particle.
On the other hand, as a method for preparing the sample of the internal foam layer, it is necessary to perform a cutting process with a cutter knife or the like for the purpose of cutting out the internal foam layer not including the surface layer portion. When preparing a sample of the internal foam layer, the entire foam surface is cut out so that the entire surface portion of one foam particle is cut out, and the internal foam layer is cut out so as to have the same center of gravity as possible. At this time, it is necessary that the cut out internal foamed layer is not more than a quarter of the particle weight of the original foamed particles (preferably a quarter to a sixth), and the shape of the original foamed particles. It is preferable that the relationship is as similar as possible. Furthermore, when the internal foamed layer obtained from one foamed particle is less than 2 to 4 mg, it is necessary to repeat the above operation and use a plurality of foamed particles.
In addition, the measuring method of the calorific value (Bi) of the inside and the calorific value (Bs) of the surface layer is the same measuring method as the calorific value (Bexo) of the expanded particles described later.

Hereinafter, the fusing property improving agent will be described.
As used herein, the term “fusibility improver” refers to an agent having a function of lowering the midpoint glass transition temperature of a polylactic acid resin when added. Specifically, although depending on the type and amount of the fusibility improver to be used, those that lower the midpoint glass transition temperature by 0.5 to 20 ° C are preferred, and those that lower the 1 to 15 ° C are more preferred. In addition, the said intermediate point glass transition temperature is measured with the measuring method mentioned later.

  Examples of the fusion improver used in the present invention include those used as plasticizers for thermoplastic resins. From the viewpoint of compatibility with polylactic acid, glycerin derivatives, ether ester derivatives, glycolic acid derivatives. Preferred examples include single or plural mixtures selected from citric acid derivatives, adipic acid derivatives, rosin derivatives, and tetrahydrofurfuryl alcohol derivatives.

As said glycerol derivative, glycerol fatty acid ester etc. are mentioned, for example.
The glycerin fatty acid ester is a glycerin fatty acid ester containing 75% by mass or more of diacetyl monoacylglycerol having a saturated fatty acid having 8 to 16 carbon atoms. Fatty acid monoglycerides composed of unsaturated fatty acids, fatty acid diglycerides composed of saturated fatty acids, and fatty acid triglycerides are inferior in compatibility with polylactic acid, and thus the effects of the present invention may not be obtained. Preferred glycerin fatty acid esters include at least one saturated fatty acid selected from C8 caprylic acid, C10 capric acid, C12 lauric acid, C14 myristic acid, and C16 palmitic acid. Glycerin fatty acid ester containing 75% by mass or more of fatty acid monoglyceride and / or acetylated product thereof. More preferable examples include acetylated products of saturated fatty acid monoglycerides having 8 to 10 carbon atoms, which have particularly good compatibility with polylactic acid. Monolaurate, glycerin triacetate, glycerin tributyrate, glycerin tripropionate, and the like are mentioned, and among these, glycerin derivatives with high safety such as little influence on the human body even when bleeding out from expanded particles Among them, glycerol diacetomonocaprylate is preferably used. Specifically, “trade name Riquemar PL-019” manufactured by Riken Vitamin Co., Ltd. is commercially available.

As said ether ester derivative, what is shown by following Chemical formula (1) is mentioned.
R (OR ') nOOC-R "-COO (R'O) mR (1)
In the formula (1), R represents an alkyl group, R ′ represents an alkylene group, R ″ represents a divalent organic group containing an alkylene group, and m and n each independently represent 1 to 500.
(1) Examples of the alkyl group represented by R in the formula include methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, tert-butyl, isobutyl, amyl, hexyl, heptyl, octyl, isooctyl, and 2-ethyl. Examples include those having 1 to 20 carbon atoms such as xylyl, nonyl, decyl, isodecyl, dodecyl, tetradecyl, hexadecyl, octadecyl and the like.
Examples of the alkylene represented by R ′ include those having 2 to 8 carbon atoms such as ethylene, 1,2-propylene, 1,2-butylene and 1,4-butylene.

As the glycolic acid derivative, triethylene glycol diacetate and the like can be used.
As the citric acid derivative, in addition to tributyl acetyl citrate, similar ones can be used.
Examples of the adipic acid derivative include dimethyl adipate, diethyl adipate, dibutyl adipate, dioctyl adipate and the like.

Examples of the rosin derivative include compounds represented by the following chemical formula (2).
_{Ro-COO - ((CHR 1} ) l (CHR 2) m -O) n ((CHR 3) l '(CHR 4) m' -O) n '-R 5 (2)
(In the formula, Ro is a rosin residue, R ₁ , R ₂ , R ₃ , R ₄ are hydrogen atoms or methyl groups, R ₅ is a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an acyl group, l, l 'Is an integer of 0 to 6, m and m' are integers of 0 to 6 (where 1 ≦ l + m ≦ 6, 1 ≦ l ′ + m ′ ≦ 6), n and n ′ are integers of 0 to 7 (however, 1 ≦ n + n ′ ≦ 7))
Specific examples include diethylene glycol rosin ester, diethylene glycol rosin ester acetate, triethylene glycol rosin ester, tetraethylene glycol rosin ester, triethylene glycol monomethyl ether rosin ester, and triethylene glycol monoethyl ether rosin ester.

Examples of the tetrahydrofurfuryl alcohol derivative include compounds represented by the following chemical formula (3).
Th-OOC-R (3)
(In the formula, Th is a tetrahydrofurfuryl alcohol residue, R is an alkyl group, an alkenyl group, an aryl group, an aryl group in which at least one hydrogen is replaced by a hydroxyl group, a rosin residue, a general formula (4): —COOTh or Formula (5): -X- (COOY) n (where X is an aryl group, an aryl group in which at least one hydrogen is replaced by a hydroxyl group, a cycloalkyl group, a cycloalkenyl group, or at least one hydrogen is replaced by an acylated hydroxyl group) An optionally substituted alkylene group or alkenylene group, Y represents an alkyl group or a tetrahydrofurfuryl alcohol residue, and n represents an integer of 1 to 4).
Specifically, for example, succinic acid ditetrahydrofurfuryl alcohol ester, adipic acid ditetrahydrofurfuryl alcohol ester, sebacic acid ditetrahydrofurfuryl alcohol ester, dodecanedioic acid ditetrahydrofurfuryl alcohol ester, ditetrahydrofurfuryl phthalate Examples include alcohol esters.

In the expanded particles of the present invention, the ratio (Bexo / Bendo) between the calorific value (Bexo) and the endothermic amount (Bendo) in differential scanning calorimetry at a heating rate of 2 ° C./min exceeds 0.2, and the amount of heat (Bendo) is Ru der more than 5J / g. When the ratio (Bexo / Bendo) is less than 0.2, special molding with high clamping force so that the mold does not open because high temperature steam is required when heating because of advanced crystallization. There is a possibility that a machine must be used, or partial melting occurs due to the high-temperature steam, which causes shrinkage, and there is a possibility that the molding range for obtaining an in-mold foam molded article having no surface irregularities may be narrowed. In addition, the amount of steam required for in-mold molding is large, and productivity may be poor. From the above viewpoint, the ratio (Bexo / Bendo) is preferably 0.25 or more, more preferably 0.3 or more, and the upper limit is usually 1.

  The difference (Bendo-Bexo) between the endothermic amount (Bendo) and the calorific value (Bexo) is preferably 0 J / g or more and less than 30 J / g, and the endothermic amount (Bendo) is preferably 5 J / g or more. . The difference (Bendo-Bexo) is an endothermic amount (Bendo) that is absorbed when the crystal part of the expanded particle melts at the time of temperature rise, and the foamed particle is crystallized prior to melting of the crystal part at the time of temperature increase. This represents the difference in calorific value (Bexo), which is the energy released by crystallization of the non-exposed portion, and the smaller the difference, the less the crystallization of the expanded particles, the larger the difference, the expanded particles This means that the crystallization is progressing. If the difference (Bendo-Bexo) is 30 J / g or more, the secondary foaming of the foamed particles deteriorates during molding in the mold, and there is a risk of forming an in-mold foam molded product with poor fusion between the foamed particles. There is a possibility that the surface of the in-mold foam molded product obtained by excessively raising the pressure melts. On the other hand, when the difference (Bendo-Bexo) is in the above range, molding is easy and the surface smoothness of the in-mold foam molded article is excellent. From the above viewpoint, it is preferably 25 J / g or less, more preferably 20 J / g or less. The difference (Bendo-Bexo) may be 0 J / g. The smaller the difference (Bendo-Bexo) value, the lower the heating temperature during molding of the expanded particles in the mold, but if it is too low, it becomes difficult to adjust the temperature during molding in the mold, and the shrinkage of the resulting in-mold foam molded product The rate may be non-uniform.

In the expanded beads of the present invention, heat absorption amount in the differential scanning calorimetry at a heating rate of 2 ℃ / min (Bendo) is Ru Der least 5 J / g. The larger the endothermic amount (Bendo), the more the crystalline component of the expanded particles, and the ability to increase the degree of crystallization, which may lead to excellent heat resistance. When the endothermic amount (Bendo) is less than 5 J / g, the crystal component is too small, and an in-mold foam molded article having desired heat resistance, rigidity, etc. cannot be obtained. From this viewpoint, the endothermic amount (Bendo) is preferably 10 J / g or more, more preferably 15 J / g or more, and further preferably 20 J / g or more. On the other hand, the upper limit is, if crystalline component is large, when molding a mold, since there is no Banara such only Re using a special molding machine is required high-temperature steam, the endothermic amount (Bendo) is preferably at most 50 J / g, 40 J / g or less is more preferable, and less than 30 J / g is particularly preferable.

  Although it depends on the endothermic amount (Bendo) of the expanded particles, the calorific value (Bexo) in differential scanning calorimetry at a heating rate of 2 ° C./min is preferably 5 J / g or more. A larger calorific value (Bexo) means that even the crystalline expanded particles are not crystallized. When the calorific value (Bexo) is less than 5 J / g, the crystalline component is small or the crystallization is too advanced, and when the crystalline component is small, the heat resistance such as being easily deformed in a high-temperature atmosphere is poor. It will be a thing. Also, if crystallization has progressed too much, high temperature steam may be required to improve the fusion between the foamed particles during in-mold molding, or partial melting may occur due to the high temperature steam. There exists a possibility that the shaping | molding range which shrinks | contracts and obtains the in-mold foaming molding without surface unevenness | corrugation may become narrow. From this viewpoint, the calorific value (Bexo) is preferably 8 J / g or more, and more preferably 10 J / g or more. On the other hand, since the energy required for crystallization may increase and the time for crystallization may increase, the calorific value (Bexo) is preferably 50 J / g or less, and 40 J / g or less. More preferred is less than 30 J / g.

In the present specification, the exothermic amount (Bexo) and endothermic amount (Bendo) of the expanded particles are values obtained by heat flux differential scanning calorimetry described in JIS K7122 (1987). However, the test piece is 1 to 4 mg of expanded particles, and the condition adjustment and DSC curve measurement of the test piece are performed according to the following procedure.
A test piece is put into a container of a DSC apparatus, and a DSC curve is obtained when the temperature is raised from 40 ° C. to 200 ° C. at a heating rate of 2 ° C./min without heat treatment. The exothermic amount (Bexo) of the expanded particles is defined as a point c where the exothermic peak is separated from the low temperature side baseline of the DSC curve, and a point d where the exothermic peak returns to the high temperature side baseline. A value obtained from a straight line connecting the points c and d and the area of the portion surrounded by the DSC curve. Further, the endothermic amount (Bendo) of the expanded particles is defined as a point e where the endothermic peak is separated from the low-temperature base line of the endothermic peak of the DSC curve, and a point f where the endothermic peak returns to the high-temperature base line. , And a value obtained from a straight line connecting the points e and f and the area of the portion surrounded by the DSC curve.
However, the apparatus is adjusted so that the baseline in the DSC curve is as straight as possible. If the baseline is inevitably curved, the curved baseline on the low temperature side of the exothermic peak is extended to the high temperature side while maintaining the curved state of the curve. The point at which the exothermic peak deviates from the point c, and the curved base line on the high temperature side of the exothermic peak is extended to the low temperature side while maintaining the curved state of the curve, and the exothermic peak appears on the curved high temperature side baseline Let the point to return be a point d. Further, the base line curved at the low temperature side of the endothermic peak is extended to the high temperature side while maintaining the curved state of the curve, and the point at which the endothermic peak moves away from the curved base line at the low temperature side is the endothermic point. Drawing is performed to extend the curved base line on the high temperature side of the peak to the low temperature side while maintaining the curved state of the curve, and the point where the endothermic peak returns to the curved high temperature side baseline is defined as a point f.

For example, in the case shown in FIG. 3, the heat generation amount (Bexo) of the expanded particles is obtained from the area surrounded by the straight line connecting the points c and d and the DSC curve determined as described above, and determined as described above. The endothermic amount (Bendo) of the expanded particles is obtained from the area surrounded by the straight line connecting the points e and f and the DSC curve. In the case shown in FIG. 4, since it is difficult to determine the points d and e as described above, the intersection of the straight line connecting the points c and f determined as described above and the DSC curve. Is determined as a point d (point e) to determine the heat generation amount (Bexo) and the heat absorption amount (Bendo) of the expanded particles. In addition, as shown in FIG. 5, when a small exothermic peak occurs on the low temperature side of the endothermic beak, the exothermic amount (Bexo) of the expanded particles is equal to the area A of the first exothermic peak in FIG. It is determined from the sum of the area B of the second exothermic peak. That is, the area A is defined as a point c where the exothermic peak moves away from the low temperature side baseline of the first exothermic peak, and a point d where the first exothermic peak returns to the high temperature side baseline. It is assumed that the area A is a portion surrounded by a straight line connecting the point d and the DSC curve. The area B is defined as a point g where the second exothermic peak is separated from the low temperature side baseline of the second exothermic peak, a point f where the endothermic peak returns to the high temperature side baseline, and a point g. The intersection of the straight line connecting the point f and the DSC curve is defined as a point e, and the area B of the portion surrounded by the straight line connecting the point g and the point e and the DSC curve is defined. On the other hand, in FIG. 5, the endothermic amount (Bendo) of the expanded particles is a value obtained from the area surrounded by the straight line connecting the point e and the point f and the DSC curve.
In the measurement of the exothermic amount (Bexo) and endothermic amount (Bendo), the reason for adopting the heating rate of 2 ° C./min as the measurement condition of the DSC curve is that the exothermic peak and the endothermic beak are separated as much as possible. This is based on the inventor's knowledge that a heating rate of 2 ° C./min is suitable when obtaining a high endothermic amount (Bendo) and (Bendo-Bexo) by heat flux differential scanning calorimetry.

  In the present invention, as described above, it is preferable to use a base resin having a calorific value (Rexo) within a specific range. Furthermore, the ratio of the exothermic amount (Bexo) to the endothermic amount (Bendo) (Bexo / Bendo) and the difference (Bendo-Bexo) of the foamed particles used as the base resin are adjusted within a specific range. Is preferred. Since the ratio (Bexo / Bendo) and the difference (Bendo-Bexo) depend on the degree of crystallization of the base resin as described above, the crystalline polylactic acid resin constituting the base resin is crystalline polycrystal. When a material containing a lactic acid resin is used, the expanded particles used in the method of the present invention can be suitably configured. Specifically, (a) those consisting only of a crystalline polylactic acid resin, and (b) those consisting of a crystalline polylactic acid resin and an amorphous polylactic acid resin can be mentioned. In addition, as a method for adjusting (Rendo), (c) a method of selecting a crystalline polylactic acid resin having an endothermic amount (Rendo) of the base resin specified in the present invention, and (d) a crystalline property. Method of blending two or more different types of crystalline polylactic acid resins, (e) one or more crystalline polylactic acid resins and one or more amorphous polylactic acids And a method of blending a resin.

  In the method for obtaining the expanded particles of the present invention, among the polylactic acid resins (i) and (b) above, in terms of ease of adjustment of the endothermic amount (Bendo) and exothermic amount (Bexo) of the expanded particles ( It is preferable to use as the base resin a material comprising a crystalline polylactic acid resin and an amorphous polylactic acid resin. Since the base resin contains an amorphous polylactic acid-based resin, when foamed particles are molded in the mold, the fusion property between the foamed particles and the secondary foamability are improved, and the surface smoothness is improved. An excellent in-mold foam molded article can be obtained.

On the other hand, the calorific value (Bexo) of the expanded particles varies depending on the heat history until the expanded particles are obtained. The heating value (Bexo) of the expanded particles depends on the rapid cooling conditions of the resin particles used to obtain the expanded particles, the impregnation conditions of the foaming agent of the resin particles, the expansion conditions of the resin particles, or the curing conditions of the expanded particles. Since they differ, the calorific value (Bexo) of the expanded particles can be adjusted by controlling each condition. Specifically, by rapidly cooling the resin particles, the calorific value (Bexo) of the expanded particles is increased, and the atmosphere temperature when the resin particles are impregnated with the foaming agent is made higher than the glass transition temperature, The heating value (Bexo) of the foamed particles is reduced by lengthening the heating time for heating and foaming. Moreover, the calorific value (Bexo) of a foamed particle becomes small also by curing a foamed particle on high temperature conditions. The calorific value (Bexo) of the expanded particles can be adjusted by combining these methods and other methods as necessary.
Therefore, adjustment of the difference (Bendo-Bexo) for the above-mentioned expanded particles is made by adjusting the crystallinity of the polylactic acid resin to be used and the resin particle preparation conditions, the conditions for impregnating the resin particles with the blowing agent, the heating time conditions for the resin particles, It can be performed according to the curing conditions of the particles.

The apparent density of the expanded particles in the present invention is preferably from 0.016 g / cm ³ or more from the viewpoint of shrinkage there is a possibility that increase in post-mold molding, 0.021 g / cm ³ or more is more preferable. On the other hand, the upper limit of the density tends to increase the density variation of the expanded particles, and there is a risk of the physical properties of the in-mold expanded molded product being deteriorated, which may lead to the expansion, fusing property, and variation of the expanded particles during heat molding in the mold. From such a viewpoint, 0.630 g / cm ³ or less is preferable, and 0.420 g / cm ³ or less is more preferable.

  When the foamed particles of the present invention pay attention to the relationship between the internal heat generation amount (Bi) and the surface heat generation amount (Bs) in the foamed particles, the above relationship is a low temperature steam of 0.01 to 0.2 MPaG. Can be molded.

The apparent density of the expanded particles in this specification is measured as follows.
Prepare a graduated cylinder containing ethanol at 23 ° C, and wire over 500 expanded foam particles (weight W1 of the expanded particle group) left in the graduated cylinder for 2 days at a relative humidity of 50%, 23 ° C and 1 atm. Is obtained by dividing the weight W1 (g) of the expanded particle group placed in the graduated cylinder by the volume V1 (cm ³ ) of the expanded particle group that is read from the rise in the ethanol water level (W1). / V1).

Next, the manufacturing method which obtains the polylactic acid-type resin expanded particle of this invention is demonstrated.
The foamed particles of the present invention can be obtained by foaming resin particles. The foamed particles are excellent in mutual fusion at the time of molding because the relationship between the calorific value (Bs) of the surface layer and the calorific value (Bi) inside the foamed particles satisfies the formula (1), In-mold molding is possible at low temperature (low pressure steam).
The production method for obtaining the expanded particles of the present invention includes, for example, 1) a resin particle preparation step in which a resin particle is prepared by melt-kneading a polylactic acid resin and a desired additive, and 2) impregnating the resin particles with a foaming agent. A foaming agent impregnation step, 3) a foaming step of foaming resin particles impregnated with the foaming agent, and 4) melt-kneading a polylactic acid resin combined with the above 1) and 2), a desired additive and a foaming agent. Examples include a combination of foamable resin particle production steps for producing resin particles impregnated with a foaming agent.

  The relationship between the calorific value (Bs) of the surface layer and the calorific value (Bi) inside the foamed particles satisfies the above formula (1) is that the surface layer of the resin particles is at least one of the steps 1) to 4). When a fusion improving agent is contained and the resin particles are further foamed, it can be achieved by rapidly cooling to a non-crystalline state by a method of releasing into water or a method of blowing cold air.

As a method for incorporating the fusion improver into the resin particles, for example, in the resin particle preparation step 1), a polylactic acid resin and a desired additive, and further a fusion improver are added and melt-kneaded to obtain a resin. A method for producing particles may be mentioned. The resin particle preparation process will be described in detail later.
Moreover, the method of making a resin particle contain a fusion improving agent in the foaming agent impregnation process of said 2), or before or after that is mentioned.
Further, in the foaming step of 3), when foaming resin particles are foamed with a heating medium using a pre-foaming machine, for example, a mist-like shape is applied so that the pre-foaming machine adheres the fusibility improver to the surface of the resin particles. While spraying or spraying in the form of a mist, the heating medium is injected into a pre-foaming machine and foamed, or the heating medium added with a fusing property improving agent is injected into the pre-foaming machine and foamed, The method of spraying a fusion improving agent on the surface of the resin particle is mentioned. In addition, the resin particles are impregnated with a foaming agent in an aqueous medium using an airtight container, and the resin particles impregnated with the foaming agent are discharged together with the aqueous medium into a low-pressure region (foaming method using a dispersion medium). In the case where the resin particles are foamed, there is a method in which a fusion improving agent is added to the aqueous medium and the fusion improving agent is contained on at least the surface of the resin particles.
Also, in the foaming step of 4), a polylactic acid resin composition, to which a polylactic acid resin, a foaming agent, a desired additive, and further a fusing improver are added, is melt-kneaded using an extruder and the foaming agent. And a method of producing resin particles impregnated with.

  Alternatively, foamed particles may be prepared in advance, and at least a surface layer of the foamed particles may contain a fusibility improver. For example, a method of melting the surface of the expanded particles with a pressure kneader and spraying a fusion improver in the form of a mist to include the adhesion improver on at least the surface of the expanded particles, or the surface of the expanded particles with a pressure kneader And a method of adding a fusibility improver to at least the surface layer of the foamed particles by sprinkling fine particles of a polylactic acid resin previously containing a fusibility improver. However, this method has the disadvantages that a special apparatus must be used and the number of steps increases. In consideration of productivity, it is preferable to include a fusing property improving agent in at least the surface layer of the resin particles in the above-described steps 1) to 4).

  That is, among the above-described foamed particles of the present invention, a foaming agent impregnation step of impregnating polylactic acid resin particles with a foaming agent in an aqueous medium, and a foaming step of foaming polylactic acid resin particles impregnated with the foaming agent. It is preferable to manufacture by the method of making a foaming particle contain a fusing property improving agent by adding a fusing property improving agent in the aqueous medium used by this foaming agent impregnation process.

  In the resin particle manufacturing step, resin particles are manufactured using a base resin composed of a polylactic acid resin including a crystalline polylactic acid resin as a raw material. Specifically, the raw material is charged into an extruder, the base resin is heated and melt-kneaded, extruded into a strand, cooled by submerging the strand-shaped extrudate, It can be obtained by cutting the extruded strand or cooling the extruded strand to an appropriate length after cooling or simultaneously with the cutting. In addition, as a method for producing resin particles from the base resin, the base resin is heated and melt-kneaded using an extruder, then extruded into a plate shape or a lump shape, and the extrudate is cooled by a cooling press or the like. The cooling resin can also be obtained by crushing or breaking in a lattice shape. In addition, the cooling at the time of producing the resin particles described above is easy to adjust the difference (Bendo-Bexo) between the heat generation amount (Bexo) of the foamed particles and the heat absorption amount (Bendo) of the foamed particles obtained in the subsequent steps. From this point, it is preferable to quench by submerging.

  The weight per resin particle is 0.05 to 10 mg, preferably 0.1 to 4 mg. When the particle weight is smaller than this range, it becomes difficult to produce the resin particles. On the other hand, when the particle weight is larger than this range, uniform impregnation of the foaming agent becomes difficult, and the density of the center part of the obtained foamed particles may be increased. The shape of the resin particles is not particularly limited, and can be various shapes such as a columnar shape (pellet shape), a spherical shape, and a rod shape.

  In the step of melt-kneading the base resin with an extruder as described above and extruding the base resin into a strand or the like, when the base resin is hygroscopic, it is preferable to dry the base resin in advance. When a resin containing a large amount of moisture is introduced into the extruder, bubbles that adversely affect the uniformity of the foamed foam bubbles when mixed with the resin particles, or melt-kneaded with an extruder There is a risk that the physical properties of the base resin will deteriorate and the melt flow rate (MFR) will become extremely large.

In order to suppress deterioration of the base resin, a method of removing moisture from the base resin by vacuum suction using an extruder with a vent port can be employed.
Further, the upper limit temperature of the extrusion temperature condition is set so that the MFR of the base resin does not become extremely large.

For example, the base resin of the present invention may be colored by adding a coloring pigment or dye such as black, gray, brown, blue, or green. If colored resin particles obtained from a colored base resin are used, colored foamed particles and molded bodies can be obtained.
Examples of the colorant include organic and inorganic pigments and dyes. As such pigments and dyes, various conventionally known pigments can be used.

  In addition, inorganic substances such as talc, calcium carbonate, borax, zinc borate, aluminum hydroxide, calcium stearate, and the like can be added to the base resin in advance as a bubble regulator. When an additive such as a color pigment, dye or inorganic substance is added to the base resin, the additive can be kneaded into the base resin as it is, but usually an additive master batch in consideration of dispersibility and the like. It is preferable to make and knead it with the base resin. Although the addition amount of the color pigment or dye varies depending on the color of the color, it is usually preferably 0.001 to 5 parts by weight with respect to 100 parts by weight of the base resin. Moreover, it is preferable that the addition amount of an inorganic substance shall be 0.001-5 weight part with respect to 100 weight part of base resin, and also 0.02-1 weight part. By adding an inorganic substance to the base resin, an effect of improving the expansion ratio can be obtained.

  In the above method, additives such as a flame retardant, an antistatic agent, a weathering agent and a thickener can be mixed. Assuming that the product is discarded after use, it is not preferable to add a high concentration of additives such as pigments and bubble regulators.

  The obtained resin particles are preferably stored in an environment where hydrolysis does not proceed by avoiding high temperature and high humidity conditions.

  Next, a foaming agent impregnation step for impregnating the resin particles with a foaming agent will be described. In the foaming agent impregnation step, the polylactic acid resin particles are impregnated with the foaming agent in an aqueous medium. That is, an aqueous medium is put in an airtight container, and resin particles and a foaming agent are added thereto and stirred to impregnate the resin particles with the foaming agent.

  As the aqueous medium, water is preferably used, and more preferably ion-exchanged water. However, it is not limited to water, and the polylactic acid resin is not dissolved, and the resin particles can be dispersed. Any solvent or liquid that does not impair the effect can be used. Examples of the aqueous medium other than water include ethylene glycol, glycerin, methanol, ethanol, and the like. The aqueous medium includes a mixed solution of water and an organic solvent such as the alcohol.

  Examples of the blowing agent include conventionally known propane, isobutane, normal butane, isohexane, normal hexane, cyclobutane, cyclohexane, isopentane, normal pentane, cyclopentane, trichlorofluoromethane, dichlorodifluoromethane, chlorofluoromethane, and trifluoro. Organic physics such as methane, 1,1,1,2-tetrafluoroethane, 1-chloro-1,1-difluoroethane, 1,1-difluoroethane, 1-chloro-1,2,2,2-tetrafluoroethane Examples include foaming agents and inorganic physical foaming agents such as nitrogen, carbon dioxide, argon, and air. Among them, inorganic physical foaming agents that do not destroy the ozone layer and are inexpensive are preferable, particularly nitrogen, air, and carbon dioxide. Is preferred. In the present invention, carbon dioxide is more preferable from the viewpoint of obtaining expanded particles having a smaller apparent density with respect to the amount of the foaming agent used. Two or more blowing agents such as carbon dioxide and isobutane can also be used.

In order to obtain the expanded particles of the present invention, it is preferable to add a fusibility improver to the aqueous medium used in the foaming agent impregnation step.
Specifically, a fusing agent is dispersed in a dispersion medium in an aqueous medium together with resin particles in the presence of a foaming agent in a closed container, and the aqueous medium is stirred while adjusting the temperature to foam into the resin particles. An impregnation agent is impregnated and at the same time an impregnation agent is impregnated. According to this method, at least the surface layer of the foamed particles can contain the fusibility improver uniformly, and even foamed particles having a uniform cell shape can be obtained.
In the case of this method, the fusibility improver is preferably a liquid because it can be easily dispersed in the aqueous medium used in the foaming agent impregnation step.

The amount of the plasticizer added is preferably 0.2 to 3 parts by weight with respect to 100 parts by weight of the resin particles. If it is less than 0.2 parts by weight, it may be difficult to contribute to an improvement in magnification when foaming. In this respect, 0.3 part by weight or more is preferable, and 0.4 part by weight or more is more preferable. On the other hand, if the amount exceeds 3 parts by weight, the foamed particles obtained may stick to dust, and the in-mold foam molded product obtained from the foamed particles may have a reduced compressive strength in a high-temperature atmosphere. . From this viewpoint, 2.5 parts by weight or less is preferable, and 2 parts by weight or less is more preferable.

Hereinafter, the case where carbon dioxide is used as the foaming agent will be described.
The impregnation amount of carbon dioxide is usually 2.5 to 30% by weight, preferably 3 to 20% by weight, and more preferably 3.5 to 15% by weight. If the amount of impregnation is too small, the resin particles may not be sufficiently foamed. On the other hand, if the amount of impregnation is too large, the expandability and fusion properties of the obtained foamed particles during molding in the mold will be poor. May be sufficient. This is presumably because the crystallization of the resin particles easily proceeds.

  The impregnation temperature of carbon dioxide is preferably 10 to 50 ° C, more preferably 20 to 40 ° C. In particular, when carbon dioxide is used as the foaming agent, the impregnation temperature is preferably (−0.6X + 50) or less when the amount of carbon dioxide impregnation is (X wt%). When (−0.6X + 50) is exceeded, particularly in a polylactic acid resin having high crystallinity, an improvement in the expansion ratio may not be expected due to the extreme progress of crystallization. In addition, when the obtained expanded particles are molded in the mold, the expandability of the expanded particles and the possibility of fusion between the expanded particles must be reduced or the surface must be molded with high temperature steam. There is a possibility that it becomes an in-mold foam molded article.

  The pressure of carbon dioxide in the resin particle atmosphere in the carbon dioxide impregnation step for the resin particles also varies depending on the apparent density (expansion ratio) of the target expanded particles, but is usually 0.05 to 0.50 MPaG. Yes, the impregnation time is 0.2 to 7 hours.

The impregnation amount (% by weight) of carbon dioxide in the resin particles of the present specification is obtained by the following equation (4).
Carbon dioxide impregnation (wt%)
= {Weight of carbon dioxide impregnated in resin particles (g) x 100} /
{Weight of resin particles before carbon dioxide impregnation (g) + weight of carbon dioxide impregnated into resin particles (g)} (4)
The weight of the carbon dioxide impregnated in the resin particles in the formula (4) is obtained from the difference in weight of the resin particles before and after the carbon dioxide impregnation, and the weight measurement of the resin particles is measured to the order of 0.0001 g.

Next, a foaming process for foaming resin particles impregnated with a foaming agent will be described.
In the foaming process, there are roughly two methods. One is (a) dispersing resin particles in a dispersion medium in a closed container in the presence of a foaming agent, stirring the contents while adjusting the temperature, and impregnating the foaming agent in the resin particles; A so-called dispersion medium discharge foaming method in which a foaming agent impregnation step and a foaming step in which the contents are released into a region lower than the pressure of the sealed container and foamed is continuously performed, and (b) heating the expandable resin particles. And foaming. Among them, the method (b) in which the foamable particles are heated and foamed is preferable because substantially spherical foamed particles can be obtained efficiently.
As a method for heating and foaming the expandable particles, a conventionally known method can be employed. However, it is usually preferable to fill the expandable particles in a sealed container and introduce water vapor to foam. If the airtight container is provided with an opening valve that slightly exhausts the internal heating medium, the atmospheric temperature in the airtight container can be easily maintained constant, and foam particles having a uniform density can be easily obtained. This is preferable.

  In the method (b), the atmospheric temperature at which the foamable particles impregnated with the foaming agent are heated, that is, the foaming temperature is usually (Tg-50) ° C. to (Tg + 50) ° C. of the base resin, preferably It is (Tg-40) degreeC-(Tg + 40) degreeC. When the foaming temperature is lower than the above range, sufficient foaming hardly occurs, and when the foaming temperature is higher than the above range, the closed cell ratio of the foamed particles is lowered and it is difficult to obtain foamed particles exhibiting good moldability. . When the foaming agent is carbon dioxide, it is foamed even at a temperature lower than the midpoint glass transition temperature by impregnation. In this case, the foaming temperature is (Tg-30) ° C. to (Tg + 30) ° C., preferably (Tg−20) ° C. to (Tg + 20) ° C. of the base resin. The Tg is the midpoint glass transition temperature.

  In this specification, the midpoint glass transition temperature (Tg) is a value determined as the midpoint glass transition temperature of a DSC curve obtained by heat flux differential scanning calorimetry according to JIS K 7121 (1987). Note that the measurement conditions for determining the midpoint glass transition temperature are those described in JIS K7121 (1987) 3. Condition of test piece According to “When measuring glass transition temperature after performing a certain heat treatment” described in (3), put the test piece into a container of DSC apparatus and heating rate from 0 ° C. to 200 ° C. 10 The temperature was raised at 0 ° C./min and dissolved by heating. The temperature was immediately adjusted to 0 ° C. at a cooling rate of 10 ° C./min. Next, the temperature was raised from 0 ° C. to 200 ° C. at a heating rate of 10 ° C./min. It is calculated | required from the DSC curve obtained when doing.

  In addition, it is preferable to preserve | save the obtained expanded particle on the conditions which avoid high temperature and a humid condition, and do not hydrolyze.

  Further, the foamed particles obtained by the above operation may be subjected to gelation by the method described in JP-A No. 2003-64213. However, the foamed particles of the present invention are preferably non-crosslinked foamed particles that are not subjected to gelation treatment from the viewpoint of productivity, recyclability, etc., and the uncrosslinked foamed particles are in-mold foam molding. In the body, the above-mentioned remarkable effects are further exhibited. The term “non-crosslinked” as used herein refers to the case where the insoluble content is 5% by weight or less of the sample, and the insoluble content is preferably 3% by weight or less, preferably 0% by weight. Most preferably it is. The smaller the insoluble content, the easier it is to reuse.

The ratio of insolubles in the resin particles and foamed particles in the present specification is measured as follows. Using about 1 g of resin particles or expanded particles as a sample, the sample weight W3 is weighed. Next, a weighed sample and 100 ml of chloroform are placed in a 150 ml flask and heated and refluxed at 62 ° C. for 10 hours under atmospheric pressure. Filtration is performed using a suction filtration device having a 200 mesh wire net. The obtained filtered product on the wire mesh is dried in an oven at 80 ° C. under a condition of 30 to 40 Torr for 8 hours. The dry matter weight W2 obtained at this time is measured. The percentage of the weight ratio of the weight W2 to the sample weight W3 (W2 / W3) × 100% is defined as insoluble.
In the case of an in-mold foam molded product obtained using foamed particles, the insoluble fraction was measured by cutting out a plurality of rectangular parallelepipeds of 5 mm in length, 5 mm in width, and 5 mm in height so as not to include the surface of the in-mold foam molded product. The measurement is performed in the same manner as in the case of the expanded particles except that the sample is used as a sample.

Next, a method for forming an in-mold foam molded body using the foamed particles of the present invention will be described.
In the method, in-mold foam molding is performed by a process including a molding step for obtaining an in-mold foam molded product by fusing the foam particles to each other and a curing step for curing the in-mold foam molded product obtained in the molding step. It is preferred to produce a body.

  In the molding step, it is preferable that after the foam particles are filled in the mold, the foam particles are fused to each other by heating the foam particles with a heating medium such as steam or hot air. Thus, when heat-molding, the foamed particles are fused to each other, and an integrated in-mold foam-molded product is obtained. As a mold for molding in this case, a conventional mold or a steel belt used in a continuous molding apparatus described in JP-A No. 2000-15708 is used. As the heating means, steam is usually used, and the heating rate may be set to a temperature at which the surface of the expanded particles melts.

  The foamed particles containing the fusibility improver of the present invention can be molded with steam at a pressure of 0.01 to 0.2 MPaG lower than the steam pressure of the conventional foam particles (not containing the fusibility improver).

In the case of producing an in-mold foam molded article, it is preferable to previously give a gas to the foam particles provided in the mold using an inorganic gas such as air, nitrogen, carbon dioxide or the like. An organic gas such as butane can also be used. Of these, carbon dioxide is preferable because it requires less time to apply the internal pressure. By using foamed particles with gas as foaming particles for molding, secondary foaming properties such as less gaps between the foaming particles during molding, moldability such as the same shape as the mold, The resilience of the in-mold foam molded product is improved. The gas is preferably applied in the range of 0.3 to 4 mol / (1000 g expanded particles), more preferably 0.7 to 4 mol / (1000 g expanded particles).
In the present specification, the amount of gas in the expanded particles (mol / 1000 g expanded particles) is determined by the following equation (5).

Gas amount in expanded particles (mol / 1000 g expanded particles) =
{Gas increase (g) × 1000} / {Gas molecular weight (g / mol) × Expanded particle weight (g)} (5)

The gas increase amount (g) in the equation (5) is obtained as follows.
Take out 500 or more foamed particles filled in the molding machine whose internal pressure is increased by applying gas, and move to a constant temperature and humidity chamber under atmospheric pressure at 23% and 50% relative humidity within 60 seconds. Then, place it on a balance in the constant temperature and humidity chamber, take out the foamed particles, and read the weight after 120 seconds. The weight at this time is defined as Q (g). Next, the foamed particles are allowed to stand for 240 hours in the same constant temperature and humidity room at 50% relative humidity and 23 ° C. atmospheric pressure. Since the high-pressure gas in the expanded particles permeates the bubble membrane and escapes to the outside as time passes, the weight of the expanded particles decreases accordingly, and after 240 hours, the weight has reached equilibrium. stable. The weight of the expanded particles after 240 hours is measured in the same constant temperature and humidity chamber, and the weight at this time is defined as S (g). Any of the above weights shall be read up to 0.0001 g. The difference between Q (g) and S (g) obtained by this measurement is defined as the amount of gas increase (g) in equation (5).

The in-mold foam molded body obtained in the molding step is preferably maintained in an atmosphere at a temperature of [Tg + 5] to [Tg + 30] ° C. in the curing step.
When the temperature of the curing process is lower than [Tg + 5] ° C., it is necessary for a long time to crystallize the polylactic acid-based resin, and there is no effect of improving the heat resistance of the in-mold foam molded product, resulting in poor heat resistance. In-mold foam molded product. In this respect, the curing temperature is preferably [Tg + 8] ° C. or higher, and more preferably [Tg + 10] ° C. or higher. On the other hand, when the temperature is higher than [Tg + 30] ° C., the in-mold foam molded product is deformed, and it is difficult to obtain a good in-mold foam molded product. From this viewpoint, [Tg + 25] ° C. or lower is preferable, and [Tg + 20] ° C. or lower is more preferable.

  Moreover, as time to hold | maintain under a specific atmosphere at a curing process, 1 hour or more is preferable from a viewpoint of a heat resistant improvement, 3 hours or more are preferable, and especially 5 hours or more are preferable. On the other hand, the upper limit is usually 36 hours or less from the viewpoint of preventing the in-mold foam molded product from being deformed or discolored. From the above viewpoint and productivity balance, 24 hours or shorter is more preferable, and 12 hours or shorter is particularly preferable.

Further, the relative humidity in the curing process is 40% RH or less because there is a possibility that the in-mold foamed molded body is easily hydrolyzed when the relative humidity is high, and the in-mold foam molded body inferior in mechanical properties may be formed. preferable. From the above viewpoint, 30% RH or less is more preferable, and 20% RH or less is more preferable. On the other hand, the lower limit of 0% RH is preferably 5% RH or more because there is a possibility that a special apparatus may be required to satisfy the condition.
Moreover, when the time of the whole curing process is 100%, from the above viewpoint, the time when the relative humidity exceeds 40 RH% is preferably 50% or less, and more preferably 25% or less.

  When curing, the in-mold foam molded body may be in the form as it is, but if the temperature is high, the in-mold foam molded body may be deformed. In such a case, it is preferable to fix the in-mold foam molded body with a jig or the like for fixing the shape.

  According to the curing step, crystallization can be performed based on the midpoint glass transition temperature of the base resin, so that an in-mold foam-molded article with improved heat resistance can be obtained efficiently. The heating medium in the curing process is usually performed with hot air.

In the in-mold foam-molded product obtained by the curing process, the ratio (bFexo) between the calorific value (bFexo) and the endothermic amount (bFendo) of the in-mold foam-molded product in differential scanning calorimetry at a heating rate of 2 ° C./min. / BFendo) is preferably 0 to 0.2, and an in-mold foam molded article having a difference (bFendo-bFexo) between the endothermic amount (bFendo) and the exothermic amount (bFexo) of 10 J / g or more is obtained. Is preferred.
With such a structure, crystallization proceeds and an in-mold foam molded article having excellent heat resistance is obtained.

When the ratio (bFexo / bFendo) exceeds 0.2, crystallization does not proceed, so that an in-mold foam molded product with low heat resistance is obtained. From the viewpoint of improving the heat resistance, 0.18 or less is preferable, 0.16 or less is more preferable, 0.14 or less is more preferable, and 0 is particularly preferable. On the other hand, the lower limit is 0 when the amount of heat generation (bFexo) in the ratio is completely accelerated, and thus the lower limit of the ratio is usually 0.
Further, the difference (bFendo-bFexo) between the endothermic amount (bFendo) and the exothermic amount (bFexo) of the in-mold foam molded article obtained is more preferably 10 J / g or more from the viewpoint of improving practical heat resistance. 15 J / g or more is more preferable. On the other hand, the upper limit depends on the endothermic amount of the base resin, but is preferably 50 J / g or less, more preferably 40 J / g or less, and particularly preferably less than 30 J / g.

In the curing process, when curing the in-mold foam molded product in which the calorific value (aFexo) of the in-mold foam molded product in differential scanning calorimetry at a heating rate of 2 ° C./min is 5 J / g or more, the heating rate 2 The ratio (bFexo / aFexo) between the calorific value (bFexo) of the in-mold foam molded product and the calorific value (aFexo) in differential scanning calorimetry at ° C / min is preferably 0 to 0.7.
Mold obtained when the ratio (bFexo / aFexo) of the calorific value (aFexo) of the in-mold foam molded body before the curing process and the calorific value (bFexo) of the in-mold foam molded body after the curing process exceeds 0.7 The inner foamed molded article has insufficient heat resistance improvement. The lower limit of the ratio is preferably 0.65 or less, more preferably 0.6 or less, because crystallization proceeds and heat resistance is improved as the calorific value (bFexo) of the in-mold foam molded product is closer to 0 after the curing process. 0.55 or less is more preferable, and 0 is particularly preferable.

  In addition, the measuring method of calorific value (aFexo) and endothermic amount (aFendo), and the measuring method of calorific value (bFexo) and endothermic amount (bFendo) are the above-mentioned exothermic except using the sample extract | collected from the in-mold foaming molding. It is the same as the measuring method of quantity (Bexo) and endothermic quantity (Bendo).

Hereinafter, the polylactic acid-based resin in-mold foam-molded product obtained using the foamed particles of the present invention will be described.
The in-mold foam-molded article obtained using the foamed particles of the present invention is an in-mold foam-molded article having a good appearance because there are few gaps between the foam particles because it is obtained from the foam particles having good secondary foamability. After use, it is an in-mold foam molded article that exhibits excellent biodegradability in soil.
Furthermore, it is preferable that the crystallization of the in-mold foam molding is promoted because the heat resistance is improved, and the method of performing the curing process as described above efficiently increases the crystallization without increasing the number of processes, and the heat resistance. Can be improved.

  The shape of the in-mold foam molded product obtained from the foamed particles of the present invention is not particularly limited, and the shape can be various shapes such as a container shape, a plate shape, a cylindrical shape, a column shape, a sheet shape, and a block shape. can do. Moreover, it is excellent in dimensional stability and surface smoothness.

Further, the apparent density of the expanded obtained from the particle-mold expansion molded article of the present invention is preferably 0.023 g / cm ³ or more, 0.030 g / cm ³ or more is more preferable. On the other hand, the upper limit is preferably 0.900 g / cm ³ or less, and more preferably 0.600 g / cm ³ or less.
In the present specification, the apparent density of the in-mold foam molded product is obtained by dividing the weight WM (g) of the in-mold foam molded product by the volume VM (cm ³ ) determined from the external dimensions of the in-mold foam molded product (WM / g). VM).

Further, the porosity of the in-mold foam molded product obtained from the expanded particles of the present invention is preferably 3% or less, more preferably 1% or less, and most preferably 0%, although depending on the purpose. When it is normally used as the porosity, it is a polylactic acid resin-in-mold foam-molded product that is inhibited from hydrolysis and exhibits excellent biodegradability in soil after use.
In addition, the value calculated | required by the following Formula is employ | adopted for the porosity.
The porosity (%) of the in-mold foam molded product is a (cm ³ ) based on the outer dimensions (25 mm × 25 mm × 100 mm) of the test piece cut out from the in-mold foam molded product, and the sample is charged with alcohol. The true volume of the sample obtained from the increment of the scale when submerged in alcohol in a graduated container was defined as b (cm ³ ), and obtained from the following formula (6).
Porosity (%) = {1- (b / a)} × 100 (6)

  The in-mold foam molded body obtained from the foamed particles of the present invention is excellent in heat resistance by performing the curing process described above. The specific heat resistance is preferably within 4%, more preferably within 3%, and more preferably within 2% of the absolute value of the heating dimensional change rate in 22 hours in an atmosphere of 90 ° C. preferable. If the absolute value of the heating dimensional change rate exceeds 4%, the use range may be narrowed, such as being difficult to use in the field used near 90 ° C.

  The in-mold foam molded article is preferably used for, for example, fish boxes, packaging materials, automobile interior materials, and the like, and is biodegradable, so even if it is left in a natural environment after use, Since it is decomposed by microorganisms, it does not cause environmental pollution problems.

  Next, the present invention will be described in more detail with reference to examples.

Examples 1-4, Comparative Examples 1-4
<Manufacture of resin particles>
Crystalline polylactic acid having an endotherm (iendo) of 49 J / g (Mitsui Chemicals Co., Ltd., Lacia H-100: expressed as crystalline resin in Table 1) and non-crystallinity of endotherm (iendo) of 0 J / g Polylactic acid (Mitsui Chemicals Co., Ltd., Lacia H-280: described as non-crystalline resin in Table 1) was blended with the formulation shown in Table 1, and this blend had a calcium stearate content of 1000 ppm. Then, both were melt-kneaded with an extruder and extruded into a strand. Next, the strand was quenched and solidified in water at about 25 ° C., and then cut to obtain uncrosslinked resin particles having a length (L) / diameter (D) of 1.5 and about 2 mg per piece. The midpoint glass transition temperatures of the base resins of Examples 1, 2, 4 and Comparative Examples 1, 2, and 4 were 57 ° C., and the midpoint glass transition temperatures of Example 3 and Comparative Example 3 were 55 ° C. .

The endothermic amount (Rendo) (J / g) of the obtained resin particles was measured by the measurement method described above. The product name “DSC-50” manufactured by Shimadzu Corporation was used as the measuring device, and the “partial area analysis program version 1.52 for Shimadzu Thermal Analysis Workstation TA-60WS” was used as the analysis software.
As a result of measuring the endothermic amount (Rendo) of the resin particles, a DSC curve as shown in FIG. 1 was obtained by the measurement method described above. The endothermic amount (Rendo) is defined as a point a where the endothermic peak moves away from the low temperature side baseline of the DSC curve and a point b where the endothermic peak returns to the high temperature side baseline. The value obtained from the straight line connecting b and the area of the portion surrounded by the DSC curve was used. Table 1 shows the measured endotherm (Rendo).

<Manufacture of expanded particles>
Next, 3000 ml of water and 1000 g of resin particles are charged into an autoclave having an internal volume of 5 L, and glycerol diacetomonocaprylate “trade name” manufactured by Riken Vitamin Co., Ltd. is used as a fusion improver for 100 parts by weight of the resin particles. Riquemar PL-019 "was added in parts by weight as shown in Table 1.

Next, after adjusting to the impregnation temperature shown in the column of impregnation conditions in Table 1, carbon dioxide (CO ₂ ) is injected into the autoclave through the pressure regulating valve, and the pressure is shown in the column of impregnation conditions in Table 1. The impregnation pressure was adjusted so that the time shown in the column of impregnation conditions in Table 1 was maintained (retention time). Next, after removing carbon dioxide from the autoclave, the expandable resin particles were taken out. Table 1 shows the carbon dioxide (CO ₂ ) impregnation amount of the expandable resin particles.

  After filling the expandable resin particles impregnated with carbon dioxide into a sealed container equipped with a pressure control valve, steam of 0.05 MPaG (65 ° C.) is introduced for 5 seconds and heated to expand and foam uncrosslinked foam. Expanded particles were obtained. Table 1 shows the apparent density, calorific value (Bexo), endothermic amount (Bendo), ratio (Bexo / Bendo) and difference (Bendo-Bexo) of the expanded particles.

The exothermic amount (Bexo) and endothermic amount (Bendo) of the expanded particles were measured by the measurement method described above. As a measuring apparatus, a product name “DSC-50” manufactured by Shimadzu Corporation was used, and “analysis software was a partial area analysis program version 1.52 for Shimadzu Thermal Analysis Workstation TA-60WS”.
The DSC curve as shown in FIG. 3 was obtained by the measurement method described above. The exothermic amount (Bexo) of the expanded particles is defined as a point c where the exothermic peak moves away from the low-temperature base line of the DSC curve, and a point d where the exothermic peak returns to the high-temperature base line. A value obtained from the straight line connecting c and point d and the area of the portion surrounded by the DSC curve was used. Further, the endothermic amount (Bendo) of the expanded particles is defined as a point e where the endothermic peak is separated from the low-temperature base line of the endothermic peak of the DSC curve, and a point f where the endothermic peak returns to the high-temperature base line. , And a value obtained from a straight line connecting the points e and f and the area of the portion surrounded by the DSC curve.
The apparatus was adjusted so that the baseline in the DSC curve was as straight as possible.

For the carbon dioxide (CO ₂ ) content in Table 1, the value obtained by dividing the amount of gas increase in the above-described formula (5) by the weight of the expanded particle group used for the measurement and adopting a fraction of 100 was adopted. Also, apparent density, calorific value (Bexo), endothermic amount (Bendo), ratio (Bexo / Bendo), difference (Bendo-Bexo), internal calorific value (Bi), surface calorific value (Bs), and internal and surface As the difference (Bi-Bs), the value obtained by the measurement method described above was adopted.

<In-mold molding>
Using the obtained expanded particles, in-mold molding was performed as follows.
The foamed particles are filled in a sealed container, pressurized with carbon dioxide, and applied to the foamed particles so that the impregnation amount of carbon dioxide is 1.3 mol / 1000 g), and then 200 (mm) × 250 (mm) × 10. (Mm) compression ratio 50% (bulk volume before compression (cm ³ ) −mold inner volume after mold clamping (cm ³ )) × 100 / mold inner volume after mold clamping ( cm ³ )) [%], and molded in-mold at the molding pressure (steam pressure) shown in Table 1.

The molding pressure (steam pressure) is changed for each steam pressure by changing the steam pressure (steam temperature) by 0.01 MPa (G) from 0.05 MPa (G) to 0.30 MPa (G). The lowest steam with a wear rate of 0.8 was adopted.
The specific measurement of the fusion rate is as follows. First, the obtained in-mold foam molded article was cut with a cutter knife in the thickness direction of the in-mold foam molded article by about 3 mm, and then hand-cut from the cut section. The inner foamed molded body was broken. Next, the number of expanded particles (n) present on the fracture surface and the number of expanded particles (b) with material destruction were measured, and the ratio (b / n) of (n) and (b) was fused. Rate. The porosity of the in-mold foam molded articles obtained in the examples and comparative examples was 3%.

When Examples 1 and 2 were compared with Comparative Example 1, the resin particles of Examples 1 and 2 containing a fusion improver had a lower apparent density than that of Comparative Example 1, and the foaming ratio was easily obtained. . The foamed particles obtained in Examples 1 and 2 were able to be molded with low temperature steam as compared with Comparative Example 1.
Moreover, the in-mold foam molded bodies obtained in Examples 1 and 2 were excellent in secondary foaming and had few gaps between the foamed particles. In contrast, the in-mold foam molded bodies obtained in Comparative Examples 1 and 2 were damaged by heating, the surface melted, voids were generated, and the appearance was poor.
Comparing Example 3 and Comparative Example 3, it can be seen that the expanded particles of Example 3 containing a fusion improver can be molded with low temperature steam.
Since the in-mold foam molded body obtained in Example 3 and Comparative Example 3 has a low endothermic amount (Rendo) of the base resin, crystallization is not improved even if crystallization is promoted in the curing process. The heat shrinkage was severe and the heat resistance was low before and after curing.
When Example 4 and Comparative Example 4 are compared, it can be seen that the expanded particles of Example 4 containing a fusion improver can be molded with low-temperature steam.

<Secondary foamability>
The secondary foamability shown in Table 1 was evaluated by the following method.
○: There are no gaps between the foamed particles on the surface of the in-mold foam molded body, and the corner shape is the same as the mold shape.
Δ: There are few gaps between the foamed particles on the surface of the in-mold foam molded product, and the corner shape is slightly rounder than the mold shape.
X: There are many gaps between the foamed particles on the surface of the in-mold foam molded body, and the corner shape is rounder than the mold shape.

<Mold shrinkage>
The following formula (7) is used by using the mold dimensions of 200 (mm) × 250 (mm) × 10 (mm) used in the mold and the dimensions of each in-mold foam molding corresponding to the mold dimensions. It calculated | required more, the value which carried out the arithmetic mean of each 100 fraction was employ | adopted, and it evaluated as follows.
(Die size-In-mold foam molding size) / Die size x 100 = Mold shrinkage (7)
◎: 1% or less ○: 1% to 2% or less △: 2% to 3% or less

<Curing process>
The obtained in-mold foam molded product was cured in a thermostat under the curing conditions shown in Table 1. After curing, the heating was stopped and the mixture was left in an incubator for 3 hours and lowered to 23 ° C. At this time, the relative humidity was 30% RH or less. Table 1 shows the heat generation amount (bFexo), the heat absorption amount (bFendo), the ratio (bFexo / bFendo), and the heating dimensional change rate of the expanded particles collected from the in-mold foam molding.
In addition, the value obtained by the same measurement as the said emitted-heat amount (aFexo) and the endothermic amount (aFendo) was employ | adopted for the value of the emitted-heat amount (bFexo) and endothermic amount (bFendo) of Table 1.

The heating dimensional change rate was measured as follows.
A test piece (thickness 10 mm × 150 mm × 150 mm) was cut out from the in-mold foam molded bodies obtained in the examples and comparative examples, and the test piece was compliant with the 5.7 heating dimension change of JIS K6767 (1976). (Former name Tabai Espec Co., Ltd.), product name “Perfect Oven Original” model PH-401 was heated at 90 ° C. for 22 hours, then immediately removed and left at 23 ° C. for 1 hour. The dimensional change rate of the test piece was calculated by the following equation (8).

Heating dimensional change rate (%) = [(X−Y) / X] × 100 (8)
However, X is the length (mm) of the test piece shown in the evaluation of the heating dimensional stability, and represents the dimension of the in-mold foam molded product before heating. Y represents the length (mm) after heating of the portion corresponding to X.

The example of the DSC curve which shows the endothermic amount (Rendo) of the base resin calculated | required with a heat flux differential scanning calorimeter. The example of the DSC curve which shows the endothermic amount (Rendo) of the base resin calculated | required with a heat flux differential scanning calorimeter. The example of the DSC curve which shows the emitted-heat amount (Bexo) of a foamed particle calculated | required with a heat flux differential scanning calorimeter, and an endothermic amount (Bendo). The example of the DSC curve which shows the emitted-heat amount (Bexo) of a foamed particle calculated | required with a heat flux differential scanning calorimeter, and an endothermic amount (Bendo). The example of the DSC curve which shows the emitted-heat amount (Bexo) of a foamed particle calculated | required with a heat flux differential scanning calorimeter, and an endothermic amount (Bendo).

Claims (4)

Expanded particles having a polylactic acid resin as a base resin,
The endothermic amount (Rendo) in differential scanning calorimetry at a heating rate of 2 ° C./min of the base resin is 5 J / g or more,
The ratio (Bexo / Bendo) of the calorific value (Bexo) and the endothermic amount (Bendo) in differential scanning calorimetry at a heating rate of 2 ° C./min of the foamed particles exceeds 0.2, and the endothermic amount (Bendo) Is 5 J / g or more,
A polylactic acid characterized in that the relationship between the calorific value (Bs: J / g ) of the surface layer of the expanded particles and the calorific value (Bi: J / g ) inside the expanded particles satisfies the following formula (1) Resin foam particles.
(Bi−Bs) / (Bi) ≦ 0.6 (1)
2. The polylactic acid resin foam according to claim 1, wherein the base resin contains a fusing property improving agent comprising a single or plural mixture selected from the following i) to vii). particle.

i) Fatty acid composed of at least one saturated fatty acid selected from caprylic acid having 8 carbon atoms, capric acid having 10 carbon atoms, lauric acid having 12 carbon atoms, myristic acid having 14 carbon atoms, and palmitic acid having 16 carbon atoms. A glycerin derivative comprising a glycerin fatty acid ester containing at least 75% by mass of monoglyceride and / or acetylated product thereof.
ii) an ether ester derivative comprising a compound represented by the following chemical formula (1)
R (OR ') nOOC-R "-COO (R'O) mR (1)
(In the formula, R represents an alkyl group, R ′ represents an alkylene group, R ″ represents a divalent organic group containing an alkylene group, and m and n each independently represents 1 to 500.)
iii) Glycolic acid derivative consisting of triethylene glycol diacetate
iv) a citric acid derivative consisting of tributyl acetylcitrate
v) Adipic acid derivative comprising dimethyl adipate, diethyl adipate, dibutyl adipate, dioctyl adipate
vi) A rosin derivative comprising a compound represented by the following chemical formula (2)
_{Ro-COO - ((CHR 1} ) l (CHR 2) m -O) n ((CHR 3) l '(CHR 4) m' -O) n '-R 5 (2)
(In the formula, Ro is a rosin residue, R ₁ , R ₂ , R ₃ , R ₄ are hydrogen atoms or methyl groups, R ₅ is a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an acyl group, l, l 'Is an integer of 0 to 6, m and m' are integers of 0 to 6 (where 1 ≦ l + m ≦ 6, 1 ≦ l ′ + m ′ ≦ 6), n and n ′ are integers of 0 to 7 (however, 1 ≦ n + n ′ ≦ 7))
vii) Tetrahydrofurfuryl alcohol derivative comprising a compound represented by the following chemical formula (3)
Th-OOC-R (3)
(In the formula, Th is a tetrahydrofurfuryl alcohol residue, R is an alkyl group, an alkenyl group, an aryl group, an aryl group in which at least one hydrogen is replaced by a hydroxyl group, a rosin residue, a general formula (4): —COOTh or Formula (5): -X- (COOY) n (where X is an aryl group, an aryl group in which at least one hydrogen is replaced by a hydroxyl group, a cycloalkyl group, a cycloalkenyl group, or at least one hydrogen is replaced by an acylated hydroxyl group) An optionally substituted alkylene group or alkenylene group, Y represents an alkyl group or a tetrahydrofurfuryl alcohol residue, and n represents an integer of 1 to 4).
The fusing property improver is at least one kind of saturation selected from C8 caprylic acid, C10 capric acid, C12 lauric acid, C14 myristic acid, and C16 palmitic acid. 3. The mixture according to claim 2, wherein the mixture is a single or a plurality of mixtures selected from glycerin derivatives comprising fatty acid monoglyceride composed of fatty acid and / or glycerin fatty acid ester containing 75% by mass or more of acetylated product thereof. Polylactic acid resin foam particles.
A polylactic acid resin in-mold foam-molded product obtained by fusing the polylactic acid resin foamed particles according to any one of claims 1 to 3 to each other.

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