JP5288535B2 - Resin composition and method for producing resin molded body - Google Patents

Description

  The present invention relates to a resin composition containing a polylactic acid resin and a method for producing a resin molded body using the resin composition, and more specifically, a resin capable of providing a molded body excellent in impact resistance and heat resistance. The present invention relates to a composition and a method for producing a resin molded body.

  In recent years, biodegradable resins that are decomposed by the action of microorganisms in a natural environment have attracted attention. It is known that biodegradable resins are gradually degraded by hydrolysis and biodegradation in soil and water, and finally become harmless degradation products.

  Of these, polylactic acid is particularly attracting attention. Polylactic acid is synthesized from plants such as corn and sugar millet, and since it does not use petroleum resources as raw materials, it is expected to be used as a carbon neutral material, and petroleum-derived resins were used. Utilization is gradually progressing as an alternative material for applications.

However, polylactic acid has problems in that it is inferior in mechanical elongation and flexibility and has low impact resistance compared to conventional petroleum-derived general-purpose resins. In addition, polylactic acid has a problem of low heat resistance, such as being easily deformed under a high temperature environment of 60 ° C. or higher.
Therefore, conventionally, in order to improve the physical properties of polylactic acid, polylactic acid resin compositions in which other components are added to polylactic acid are known (Patent Documents 1 to 6).

For example, a polylactic acid resin composition containing polylactic acid containing an aliphatic polyester other than polylactic acid, an aromatic aliphatic polyester, and a spherical filler is disclosed (Patent Document 1). Also disclosed is a polylactic acid resin composition containing an inorganic filler selected from natural rubber, talc and the like in polylactic acid (Patent Document 2). Furthermore, a resin composition containing a plasticizer and hydrophilic silica particles in an aliphatic polyester such as polylactic acid is described (Patent Document 3). Furthermore, a resin composition containing inorganic particles whose surfaces are coated with an acrylic resin on a polylactic acid resin is described (Patent Document 4). Furthermore, a resin composition containing a polylactic acid resin whose ends are blocked with carbodiimide, a crystal nucleating agent, surface-treated reinforcing fibers, and surface-treated inorganic particles is described (Patent Document 5). Furthermore, a resin composition containing a metal phosphate (crystal nucleating agent) and an inorganic filler in a polylactic acid resin is described (Patent Document 6).
JP 2006-52342 A JP 2004-143315 A JP 2004-189991 A JP 2007-197521 A JP 2007-154002 A JP 2004-224990 A

  Incidentally, resins are used in various fields, and some of them require high impact resistance and heat resistance. In order to be used in such a field, the biodegradable resin needs to have excellent impact resistance and heat resistance. Therefore, it is desired to develop a polylactic acid resin composition in which impact resistance and heat resistance, which are disadvantages of polylactic acid, are simultaneously improved.

  This invention makes it the subject which should be solved to provide the resin composition which can obtain the polylactic acid resin molded object in which impact resistance and heat resistance were improved simultaneously, and the manufacturing method of such a resin molded object.

  The feature of the resin composition according to claim 1 that solves the above problems is that a polylactic acid resin mainly composed of polylactic acid, a crystal nucleating agent that promotes crystallization of the polylactic acid resin, an active hydrogen group, or an epoxy group It is to have a surface-modified inorganic filler made of a spherical inorganic filler introduced on the surface, and a crosslinking agent that causes a reaction between the polylactic acid and the inorganic filler.

  The feature of the resin composition according to claim 2 that solves the above-mentioned problem is that, in claim 1, the surface-modified inorganic filler is obtained by reacting an organosilane having an active hydrogen group or an epoxy group with an inorganic filler. It is in.

  The feature of the resin composition according to claim 3 that solves the above-mentioned problem is that, in claim 1 or 2, the inorganic filler is silica.

  The feature of the resin composition according to claim 4 that solves the above problem is that in any one of claims 1 to 3, the circularity of the inorganic filler is 0.8 or more.

  The feature of the resin composition according to claim 5 for solving the above-mentioned problem is that, in any one of claims 1 to 4, the volume average particle diameter of the inorganic filler is 0.1 μm to 10 μm.

  The feature of the resin composition according to claim 6 that solves the above-mentioned problem is that in any one of claims 1 to 5, the inorganic filler is spherical silica obtained by oxidizing metal silicon.

  The characteristic of the resin composition which concerns on Claim 7 which solves the said subject is that the said inorganic filler is spherical silica obtained by heat-melting crushing silica in any one of Claims 1-5.

  The characteristic of the resin composition which concerns on Claim 8 which solves the said subject is one or more in which the said active hydrogen group is selected from a hydroxyl group, an amino group, a mercapto group, and a carboxyl group in any one of Claims 1-7. It is in the functional group.

  The characteristic of the resin composition which concerns on Claim 9 which solves the said subject is that the said crosslinking agent in any one of Claims 1-8 is a compound which has two or more isocyanate groups.

  The feature of the resin composition according to claim 10 for solving the above-mentioned problem is that, in any one of claims 1 to 9, the crystal nucleating agent is phenylphosphonate metal salt, talc, phosphate metal salt, dibenzylidene From sorbitol compounds, aliphatic carboxylic acid metal salts, trimesic acid triamide compounds, boron nitride, basic inorganic aluminum compounds, melamine compound salts, and / or amide compounds (including aromatic hydroxymonocarboxylic acids and amine compounds (including hydrazine)) To be configured).

  The feature of the resin composition according to claim 11 for solving the above problem is that in any one of claims 1 to 10, the surface-modified inorganic filler is 5 to 50 parts by mass with respect to 100 parts by mass of the polylactic acid resin. The crystal nucleating agent has a mixing ratio of 0.1 to 5 parts by mass.

  The feature of the resin composition according to claim 12 that solves the above-described problem is that, in any one of claims 1 to 11, the inorganic filler does not substantially include a form other than a spherical shape.

  The characteristic of the manufacturing method of the resin molding which concerns on Claim 13 which solves the said subject exists in having the shaping | molding process which shape | molds the resin composition which concerns on Claims 1-12, and obtains a molded object.

  A feature of the method for producing a resin molded body according to claim 14 for solving the above-described problem is that, in claim 13, heat treatment is performed simultaneously with the molding of the molded body in the molding step, or the molded body is formed after the molding step. A heat treatment step for performing a heat treatment.

  The characteristic of the manufacturing method of the resin molding which concerns on the said 15th which solves the said subject is the differential scanning calorimetry (DSC measuring method) of the said polylactic acid resin in the heating process and heating time in the said heat processing process in Claim 13 The degree of crystallinity obtained by the above is to be combined so that it becomes 20% or more.

  In this specification, the DSC measurement method for determining the degree of crystallinity is specifically based on the following method. That is, first, a sample (5 to 10 mg) was collected from a test piece that is a molded body made of a resin composition, placed in an aluminum pan, and a nitrogen atmosphere using a DSC (Differential Scanning Calorimeter, manufactured by Shimadzu Corporation, DSC-60). The following amounts of heat are measured while changing the temperature as follows.

  -30 ° C. → 200 ° C., temperature rising rate 10 ° C./min: Measure the heat generation amount (ΔHc) due to crystallization appearing in the middle and the heat absorption amount (ΔHm) due to crystal melting.

Based on ΔHc and ΔHm thus measured, the following formula:
Crystallinity (%) = {(ΔHm−ΔHc) / 135} × 100
(In the above formula, “135” means the heat of crystal fusion (135 J / g) when polylactic acid shown in known literature is crystallized 100%. ΔHc and ΔHm are absolute values. The unit is J / g.) The degree of crystallinity (%) is calculated.

  Although it can be predicted that the heat resistance is improved by including an inorganic filler in the resin composition, the impact resistance is usually lowered as it is. In the invention according to claim 1, by adopting these combinations, the impact resistance can be remarkably improved while maintaining the high heat resistance.

  In the invention which concerns on Claim 2, as a method of obtaining a surface modification inorganic filler, it is advantageous at the point which can employ | adopt the simple method of making the organosilane which has an active hydrogen group or an epoxy group react with an inorganic filler.

  In the invention according to claim 3, by adopting silica having excellent mechanical properties and relatively small specific gravity as an inorganic filler, a resin molded product having high mechanical properties while minimizing an increase in mass. The resin composition which makes | forms can be provided.

  In the invention which concerns on Claim 4, the resin composition which shows the outstanding moldability can be provided by making circularity of the said inorganic filler into 0.8 or more. And as disclosed in claim 5, when the volume average particle diameter of the inorganic filler is 0.1 μm to 10 μm, it is possible to provide a resin composition capable of forming a resin molded article exhibiting excellent impact resistance. For example, when silica is employed as the inorganic filler, examples of the inorganic filler having a high degree of circularity and / or a volume average particle diameter falling within the above-described range are those described in claim 6 or 7.

  In the invention according to claim 8, the active hydrogen group is one or more functional groups selected from a hydroxyl group, an amino group, a mercapto group, and a carboxyl group, so that the resin molding can exhibit more excellent impact resistance. A body-forming resin composition can be provided.

  In the invention which concerns on Claim 9, when the crosslinking agent is a compound which has two or more isocyanate groups, the resin composition which makes the resin molding which can exhibit the more outstanding impact resistance can be provided.

  In the invention which concerns on Claim 10, the resin composition which makes the resin molding which can exhibit the more outstanding impact resistance can be provided by comprising from the above-mentioned material, a compound, etc. as a crystal nucleating agent.

  In the invention which concerns on Claim 11, the resin composition which makes the resin molding which can exhibit the more outstanding impact resistance by employ | adopting the said mixing ratio can be provided.

  The invention according to claim 12 is a resin excellent in fluidity that becomes a problem at the time of injection molding, the surface form of the resin molded body, etc., by not containing substantially non-spherical forms as the inorganic filler. A composition can be provided.

  In the invention which concerns on Claim 13, the above-mentioned outstanding resin composition can be manufactured. In the invention according to claim 14, by performing the heat treatment, the crystallinity of the lactic acid resin can be improved, and more excellent impact resistance can be exhibited. As for the heat treatment conditions, particularly as in the invention according to claim 15, it is necessary and sufficient that the combination of the heating temperature and the heating time is such that the crystallinity obtained by the DSC measurement method of the polylactic acid resin is 20% or more. Any amount of heating conditions can be employed.

  The resin composition and the method for producing a resin molded body of the present invention will be described in detail based on the following embodiments. Although the resin composition of the present invention has excellent impact resistance and heat resistance even when it is molded as it is, a resin molded body that can exhibit further excellent impact resistance by heating / molding or molding / heating is obtained. It can be provided. The use of the obtained resin molded body is not particularly limited, and it can be employed for applications that require excellent mechanical properties.

(Resin composition)
The resin composition of this embodiment has a polylactic acid resin, a crystal nucleating agent, a surface-modified inorganic filler, a crosslinking agent, and other necessary members.

  The polylactic acid resin is a resin mainly composed of lactic acid. Here, the main component means that it is contained in an amount of 50% by mass or more based on the polylactic acid resin, and preferably 70% by mass or more, 90% by mass or more, and 100% by mass if possible. Here, lactic acid and other resin (monomer) may be copolymerized. The polylactic acid resin also includes a polymer alloy mixed with other resins. Examples of the copolymer include a polylactic acid-polycaprolactone copolymer, a polylactic acid-succinate copolymer, and a polylactic acid-succinate adipate copolymer. Other resins suitable for forming a mixture such as alloy include polycarbonate and other biodegradable resins. Specific examples of biodegradable resins include, for example, biodegradable resins produced by microorganisms (polyhydroxybutyrate, etc.), biodegradable resins obtained by chemical synthesis (polylactic acid, polyglycolic acid, polycaprolactone, polybutylene succin) And aliphatic polyester resins such as polyethylene succinate, polyvinyl alcohol and polyamino acid), and biodegradable resins derived from natural products (chitosan, starch, cellulose acetate, etc.). In addition, said other resin may be used individually by 1 type, and may be used together 2 or more types.

  Polylactic acid includes polylactic acid composed of D-lactic acid, polylactic acid composed of L-lactic acid, block copolymer including both DL, alternating copolymer, random copolymer, and D-lactic acid and L-lactic acid. Any form such as a stereocomplex type polylactic acid in which both polylactic acids are mixed may be adopted.

  The molecular weight of the polylactic acid resin is not particularly limited, and those having a necessary molecular weight can be employed depending on the application. In the present invention, polylactic acid resins having various average molecular weights can be used as necessary. The weight average molecular weight of the polylactic acid resin is usually 50,000 to 500,000, more preferably 80,000 to 300,000, and more preferably 100,000 to 250,000. It is preferable that the weight average molecular weight of the polylactic acid resin is in the above range since the impact resistance and workability of the resulting resin composition can be improved.

  There are both crystalline and non-crystalline polylactic acid resins, and any of them can be adopted. The above range of weight average molecular weight is applicable to both crystalline polylactic acid resins and noncrystalline polylactic acid resins.

  There is no particular limitation on the method for obtaining the polylactic acid resin. Examples thereof include ring-opening polymerization of lactide (low molecular weight polylactic acid), which is a cyclic diester, and direct dehydration condensation polymerization from lactic acid. In these polymerizations, a polylactic acid resin containing lactic acid and other monomers can be obtained by adding other monomers as necessary.

  In the polycondensation method, for example, at least one of L-lactic acid, D-lactic acid and other monomers is selected and mixed so as to have a composition of each structural unit of the target polylactic acid resin, and this mixture A lactic acid resin is obtained by dehydrating and polymerizing each monomer. In the ring-opening polymerization method, for example, L-lactide, which is a cyclic dimer of L-lactic acid, and cyclic dimer of D-lactic acid, so as to have a composition of each structural unit of the target polylactic acid resin. At least one of D-lactide, DL-lactide, which is a cyclic dimer composed of L-lactic acid and D-lactic acid, and other monomers is selected and mixed, and if necessary, a polymerization regulator or the like The polylactic acid resin is obtained by ring-opening lactide in the presence of a predetermined catalyst and a polymerization reaction (copolymerization reaction) under a predetermined condition. Further, in such a polymerization method, in order to improve the heat resistance of the obtained polylactic acid resin, an aromatic dicarboxylic acid such as terephthalic acid or an ethylene oxide adduct of bisphenol A is used as a small amount of a copolymer component. Aromatic diols or both aromatic dicarboxylic acids and aromatic diols may be used. In such a polymerization method, a small amount of chain extender may be used in order to increase the molecular weight of the resulting polylactic acid resin. Examples of the chain extender include diisocyanate compounds such as hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, and diphenylmethane diisocyanate, epoxy compounds, and acid anhydrides.

  Lactic acid can be obtained from plants such as corn, sugar radish, and sugar millet, as well as from old rice. It can also be obtained from raw garbage etc. by lactic acid fermentation. Lactic acid may be either L-lactic acid or D-lactic acid, or both. For example, when the polymerization is carried out by direct dehydration condensation, any lactic acid of L-lactic acid, D-lactic acid, DL-lactic acid, or a mixture thereof may be used. The constituent molar ratio L / D of L-lactic acid and D-lactic acid contained in lactic acid is usually 100/0 to 0/100, preferably 100/0 to 60/40, more preferably 100/0 to 80/20. is there.

  Lactide can usually be synthesized by depolymerizing low molecular weight polylactic acid. As the lactide, any of L-lactide, D-lactide, DL-lactide, meso-lactide or a mixture thereof may be used.

  As long as the other monomer to be copolymerized is a monomer copolymerizable with lactic acid or lactide, the type and structure thereof are not particularly limited. For example, dicarboxylic acid having two or more ester bond-forming functional groups, polyhydric alcohol, hydroxycarboxylic acid, and lactone, and derivatives (esters, etc.) thereof can be mentioned. The other monomers may be used alone or in combination of two or more.

  Examples of the dicarboxylic acid include one or more of aliphatic dicarboxylic acids such as succinic acid, adipic acid, and fumaric acid, and aromatic dicarboxylic acids such as terephthalic acid and isophthalic acid.

  Examples of the polyhydric alcohol include one or more of aliphatic polyhydric alcohol, ether glycol, and aromatic polyhydric alcohol. More specifically, examples of the aliphatic polyhydric alcohol include one or more of ethylene glycol, propylene glycol, 1,2-butylene glycol, 1,3-butylene glycol, glycerin, sorbitan, and the like. More specific examples of the ether glycol include one or more of diethylene glycol, triethylene glycol, polyethylene glycol, and polypropylene glycol.

  Examples of the hydroxycarboxylic acid include one or more of glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 3-hydroxyvaleric acid, 4-hydroxyvaleric acid, and 6-hydroxycaproic acid. .

  Examples of the lactone include one or more of glycolide, ε-caprolactone glycolide, ε-caprolactone, β-propiolactone, δ-butyrolactone, β- or γ-butyrolactone, pivalolactone, and δ-valerolactone. Can be mentioned.

  Such a polylactic acid resin may be a commercially available product, for example, the Lacia (registered trademark) series manufactured by Mitsui Chemicals, and the Nature Works (registered trademark) series manufactured by Nature Works LLC. It is done.

  The crystal nucleating agent is not particularly limited as long as it exhibits an action of promoting crystallization of the polylactic acid resin. Crystal nucleating agents are classified into inorganic nucleating agents and organic nucleating agents. Specific examples of the inorganic nucleating agent include, for example, talc, montmorillonite, clay (kaolin clay, etc.), mica, calcium carbonate, titanium oxide, magnesium oxide, barium sulfate, boron nitride, basic inorganic aluminum compound or layered silicate. , Kaolin, kaolinite, barium sulfate, silica and the like. Specific examples of the organic nucleating agent include, for example, phenylphosphonic acid metal salts, aliphatic carboxylic acid metal salts, aromatic carboxylic acid metal salts, aromatic phosphate esters, aromatic amides and esters, fatty acid amides, Organic sulfonates, rosin acid derivatives, sorbitol derivatives (benzylidene sorbitol compounds, etc.), amide compounds composed of aromatic hydroxymonocarboxylic acids and amine compounds (including hydrazine), plant waxes, (meth) acrylic acid copolymers More specifically, trimesic acid tricycloamide compounds, diketopyrrolopyrrole compounds, isoindolinone compounds, melamine compounds such as melamine cyanurate and polymelate melamine, sebacic acid dibenzoic acid bidrazide , Calcium lactate, sodium benzoate It can be illustrated. In addition, as the organic nucleating agent, for example, an organized clay obtained by organizing a layered clay mineral having a cation exchange ability with an organic ammonium salt compound may be used. These crystal nucleating agents may be used alone or in combination of two or more. Among these, in the present embodiment, since the crystallinity (crystallization rate) of the lactic acid resin composition at the time of molding can be easily increased, phenylphosphonate metal salt, talc, phosphate ester metal salt, diester Amide compounds composed of benzylidene sorbitol compounds, aliphatic carboxylic acid metal salts, trimesic acid triamide compounds, boron nitride, basic inorganic aluminum compounds, melamine compound salts, aromatic hydroxymonocarboxylic acids and amine compounds (including hydrazine) Preferred are phenylphosphonic acid metal salts and talc.

  The addition amount of the crystal nucleating agent is not particularly limited, but the crystal nucleating agent is preferably 0.1 to 5 parts by mass, and 0.5 to 3 parts by mass with respect to 100 parts by mass of the polylactic acid resin described above. Is more preferably 0.5 to 2 parts by mass. When the content of the crystal nucleating agent is within this range, the crystallinity (crystallization rate) of the lactic acid resin is sufficiently increased, and saturation of the crystallization rate is hardly observed. Moreover, when these crystal nucleating agents are used, the heat resistance of a polylactic acid-type resin composition can be improved. Furthermore, these crystal nucleating agents may be used alone or in combination of two or more.

  The material that acts without being dissolved in polylactic acid such as talc is not limited in particle size, but preferably has a volume average particle size of 0.05 to 20 μm, and a material having a size of about 0.1 to 10 μm is adopted. It is more desirable. The metal contained in the phenylphosphonic acid metal salt is divalent, for example, zinc (Zn), calcium (Ca), magnesium (Mg), or the like.

  The surface-modified inorganic filler is an inorganic filler in which active hydrogen groups or epoxy groups are introduced on the surface. Although the addition amount of a surface modification inorganic filler is not specifically limited, Content of a surface modification inorganic filler is 5-100 mass parts, 5-70 mass parts, 5-50 with respect to 100 mass parts of the above-mentioned polylactic acid resin. It is desirable in the order of 10 parts by mass, 10 to 45 parts by mass, and 20 to 30 parts by mass.

  As the active hydrogen group, any functional group having a releasable hydrogen in its structure is sufficient, and one or more functional groups selected from a hydroxyl group, an amino group, a mercapto group, and a carboxyl group are desirable.

  The form of the inorganic filler is not particularly limited, but is preferably spherical. In this specification, the form is spherical when the circularity is 0.8 or more. In particular, the circularity is desirably 0.9 or more. This is because the high circularity increases the fluidity during molding and improves the moldability. The inorganic filler is preferably substantially spherical.

In this specification, the degree of circularity is calculated by (circularity) = {4π × (area) ÷ (perimeter length) ² } based on the area and perimeter of the observed particle taken by SEM. Calculate as a value. The closer to 1, the closer to a true sphere. Specifically, an average value measured for 100 particles using an image processing apparatus is employed. The inorganic filler is preferably a metal oxide. For example, silica, alumina, zirconia, titania and the like. In particular, it is desirable to employ silica.

  The particle size of the inorganic filler is not particularly limited, but the volume average particle size is preferably 0.1 μm to 10 μm, more preferably 0.3 μm or more and less than 4.7 μm, and 0.5 μm to 1.5 μm. More desirable is.

  The method for producing the spherical inorganic filler is not particularly limited. When a metal oxide is used as the inorganic filler, a deflagration method (VMC method) in which a metal powder corresponding to the metal oxide is burned in an oxidizing atmosphere, or a metal oxide powder is charged into the flame and melted. For example, a melting method that spheroidizes can be used. In particular, the VMC method is desirable because particles that are simple and have high circularity can be obtained.

  Although it does not specifically limit as a method of introduce | transducing the above-mentioned functional group into the surface of the above-mentioned inorganic filler, The method of making the organosilane which has the active hydrogen group or epoxy group which is a functional group to introduce | transduce is mentioned. This reaction can also be carried out in a suitable solvent. The amount of these functional groups to be introduced is not particularly limited, but it is desirable that the amount of the inorganic filler be substantially covered. Specific examples of the organosilane coupling agent include epoxy silanes such as γ-glycidoxypropyltriethoxysilane and β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, aminopropyltriethoxysilane, and ureidopropyltriethoxy. Examples include silane, aminosilane such as N-phenylaminopropyltrimethoxysilane, and mercaptosilane such as γ-mercaptotrimethoxysilane.

  The crosslinking agent is a compound that reacts between the polylactic acid resin and the surface-modified inorganic filler. For example, a polyfunctional isocyanate compound (diisocyanate, triisocyanate, etc.) having two or more isocyanate groups can be exemplified. Examples of the polyfunctional isocyanate compound include aliphatic isocyanates, alicyclic isocyanates, and aromatic isocyanates. These may be used alone or in combination of two or more.

  Specific examples of the aliphatic isocyanates include hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 3-isocyanate methyl-3,5,5-trimethylcyclohexyl isocyanate, dicyclohexylmethane-4,4′-. Diisocyanate, 2,6-diisocyanatohexanoic acid methyl ester, 2-isocyanatoethyl-2,6-diisocyanate caproate (LTI: lysine triisocyanate), 3-isocyanatopropyl-2,6-diisocyanate caproate, 1, 3,6-hexamethylene triisocyanate, 1,8-diisocyanate-4-isocyanate methyloctane, 1,6,11-undecane triisocyanate and the like can be mentioned.

  Specific examples of the alicyclic isocyanates include isophorone diisocyanate and bicycloheptane triisocyanate.

  Specific examples of aromatic isocyanates include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, mixed isocyanate of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate, 4, Examples thereof include 4′-diphenylmethane isocyanate, hydrogenated jephenylmethane diisocyanate, diphenylmethylmethane diisocyanate, 1,3-phenylene diisocyanate, 1,5-naphthylene diisocyanate, xylylene diisocyanate, and tolidine diisocyanate.

  In addition, triisocyanates such as an adduct of trimethylolpropane and toluylene diisocyanate, an adduct of trimethylolpropane and 1,6-hexamethylene diisocyanate can be used as the polyfunctional isocyanate compound.

  There is no particular limitation on the ratio of the crosslinking agent. For example, it is 0.1-5 mass parts normally with respect to 100 mass parts of said polylactic acid resin, Preferably it can be set as 0.5-3 mass parts.

  The resin composition of the present invention may contain other necessary members as long as the effects thereof are not significantly impaired. For example, hydrolysis inhibitors, lubricants, stabilizers, flame retardants, coupling agents, antibacterial agents, antifungal agents, antioxidants, antiblocking agents, ultraviolet absorbers, weathering (light resistance) agents, plasticizers, colorants ( Pigments, dyes), antistatic agents, foaming agents, antifogging agents, foaming agents, fillers, anti-drip agents, release agents and the like. These may be used alone or in combination of two or more.

  There is no limitation in particular in the use of the resin composition of this embodiment. The resin composition of the present embodiment maintains excellent heat resistance and is also excellent in impact resistance as compared with a conventional resin composition containing polylactic acid. Therefore, it can be widely used for packaging materials, agricultural materials, civil engineering and building materials, automobile parts, OA equipment, home appliances, and sunday goods such as toys and stationery.

(Production method of resin molding)
The manufacturing method of the resin molding of this embodiment has a shaping | molding process, and also has a heat treatment process as needed.

  The molding step is a step of molding the above-described resin composition of the present embodiment into a target shape, and the molding method is not limited. For example, a thermoplastic molding method such as an injection method, a casting method, a compression method, or an extrusion method can be suitably employed. Specifically, various molded products can be formed by known molding methods such as sheet / film molding, injection molding, sheet extrusion, vacuum molding, profile forming, foam molding, injection press, press molding, and blow molding. .

  The heat treatment step is a step in which heat treatment is performed simultaneously with molding of the molded body in the molding step as necessary, or heat treatment is performed on the molded body after the molding step. That is, it is possible to employ either a method of performing a heat treatment by heating at the same time when forming, or a method of performing a heat treatment separately from the forming step on the formed body. By performing a heat treatment step, the polylactic acid resin contained in the resin composition is crystallized to improve impact resistance.

  The conditions for the heat treatment are not particularly limited, but as a combination of the heating temperature and the heating time, a combination in which the degree of crystallinity obtained by the differential scanning calorimetry (DSC measurement method) of the polylactic acid resin is 20% or more may be adopted. desirable. For example, a process of heating at 110 ° C. for 2 hours can be employed.

Test 1: Content dependency of inorganic filler, evaluation of effect of crystal nucleating agent and cross-linking agent-Polylactic acid resin at the blending ratio shown in Table 1 (% represents mass%. The same applies to Tables 2 and 3) (PLA: polylactic acid homopolymer: trade name U'z S-32, manufactured by Toyota Motor Corporation) and surface modified silica particles as surface modified inorganic filler (surface treated with epoxy silane (SEJ) ), Surface treated with epoxy silane (alicyclic) (GRJ), volume average particle size of about 0.5 μm), and silica particles as inorganic filler not subjected to surface treatment (C2: volume average particle) The diameter is about 0.5 μm) and a crystal nucleating agent (phenylphosphonic acid zinc salt: PPA-Zn: Eco Promote, manufactured by Nissan Chemical Industries, Ltd.) and a crosslinking agent (LTI, manufactured by Kyowa Hakko Chemical Co., Ltd.) are mixed. The mixture Obtained. The obtained mixture was melt-kneaded (190 ° C. to 200 ° C.) using a twin-screw extruder (manufactured by Technovel: diameter 20 mm, L / D30) and pelletized. In addition, the silica particle made from Admatechs Co., Ltd., and Admafine was used and the surface was modified as needed.

Using the resulting pellets, press molding was carried out at 190 ° C. for 15 minutes with a compression molding machine (Kamito Metal Industry Co., Ltd .: clamping force 10 tons) to prepare test pieces (molding process).
-The obtained test piece was evaluated based on an Izod impact test (JIS K7110, with a notch) and a deflection temperature under load (JIS K7191-2, 0.45 MPa, edgewise). The results are shown in Table 1. The circularity of the silica particles (C2, SEJ and GRJ) in Table 1 was all 0.99.

  As is clear from Table 1, sample 2 to which only the crystal nucleating agent is added and sample 3 to which the crystal nucleating agent and the crosslinking agent are added are compared with sample 1 to which the silica particles, the crystal nucleating agent and the crosslinking agent are not added. It was found that the deflection temperature under load increases and only the heat resistance is improved.

  Compared to Sample 1, Sample 4 to which only surface-modified silica particles were added and Sample 5 to which surface-modified silica particles and a crosslinking agent were added had slightly improved Izod impact strength and improved impact resistance. Although the effect is slightly seen, no change can be confirmed in the deflection temperature under load, and it can be seen that the effect of improving the heat resistance is not seen.

  Samples 6 to 10 and 12 to which surface-modified silica particles, a crystal nucleating agent and a cross-linking agent are added have remarkably improved both Izod impact strength and deflection temperature under load, improving both impact resistance and heat resistance. It turns out that it is excellent in effect. Here, the addition amount of the surface-modified silica particles is sufficient in the range of 10% by mass (11.1 parts by mass with 100 parts by mass of PLA) to 50% by mass (100 parts by mass with 100 parts by mass of PLA). It was revealed that the impact and heat resistance can be improved. In particular, it has been clarified that a high effect is exhibited in the range of more than 10% by mass and less than 50% by mass, and further in the range of 20% by mass to 40% by mass (66.7 parts by mass with PLA as 100 parts by mass). .

  Further, the sample 12 having a different type of functional group (epoxy group: alicyclic) introduced to the surface as the surface-modified silica particles is more resistant to impact than the sample 7 (epoxy group) having the same configuration except for the functional group. Although heat resistance decreased, heat resistance improved.

  And the sample 11 which employ | adopted the silica particle which has not surface-modified the surface-modified silica particle is compared with the sample 7 which has the same structure except for the surface-modified silica particle, both in impact resistance and heat resistance. It became clear that it did not show sufficient values. It can be seen from this that the surface modification of the silica particles is a necessary treatment for improving the impact resistance.

Test 2: Dependence of particle size of silica particles as inorganic filler ・ PLA, surface-modified silica particles, crystal nucleating agent (phenyl phosphonate zinc salt: PPA-Zn), and cross-linking agent at the compounding ratio shown in Table 2 (LTI) was mixed to obtain a mixture. Silica particles with a particle size of 0.3 to 1.9 μm are obtained by oxidizing spherical silicon, and silica particles with a particle size of 4.7 to 35.2 μm are obtained by heating and melting crushed silica. The obtained spherical silica was used, and each having a modified epoxy silane surface was used. The obtained mixture was melt-kneaded (190 ° C. to 200 ° C.) using a twin-screw extruder (manufactured by Technovel: diameter 20 mm, L / D30) and pelletized.

Using the resulting pellets, press molding was carried out at 190 ° C. for 15 minutes with a compression molding machine (Kamito Metal Industry Co., Ltd .: clamping force 10 tons) to prepare test pieces (molding process).
-The obtained test piece was evaluated based on an Izod impact test (JIS K7110, with a notch) and a deflection temperature under load (JIS K7191-2, 0.45 MPa, edgewise). The results are shown in Table 2. The circularity of the silica particles was 0.99 when the particle size was 0.3 to 9.7 μm, and 0.98 when the particle size was 35.2 μm.

  As apparent from Table 2, not only the sample 1 lacking both the crystal nucleating agent and the crosslinking agent, but also the sample 2 to which only the crystal nucleating agent is added, the surface nucleating agent and the crosslinking agent being added, but the surface-modified silica particles are added. As compared with Sample 3 to which no surface was added, Samples 7 and 13 to 18 to which surface-modified silica particles were added were all found to have a high deflection temperature under load and excellent heat resistance. Izod impact strength is when surface-modified silica particles are 0.3 μm, 0.5 μm, 1.5 μm, 1.9 μm, 4.7 μm, and 9.7 μm and no surface-modified silica particles are added. The value was higher than that of, and it was revealed that it had excellent impact resistance. Sample 18 having a particle size of 35.2 μm exhibits excellent heat resistance, but the impact resistance is comparable to Samples 1 to 3 not containing surface-modified silica particles, and the effect of improving impact resistance is improved. I found that there was no.

Test 3: Examination of Heat Treatment Sample 7 in Test 1 was heat-treated at 110 ° C. for 2 hours to give an Izod impact strength of 9.1 KJ / m ² (7.8 KJ / m ² ) and a deflection temperature under load of 136.5. ° C (125.7 ° C). Both values were superior to the values before the heat treatment step shown in parentheses, and it was revealed that the heat resistance and the heat resistance were further improved by the heat treatment.

Claims (14)

A polylactic acid resin mainly composed of polylactic acid;
A crystal nucleating agent for promoting crystallization of the polylactic acid resin;
A surface-modified inorganic filler comprising a spherical inorganic filler having an epoxy group introduced on its surface;
A crosslinking agent that causes a reaction between the polylactic acid and the inorganic filler,
The crystal nucleating agent is 0.1 to 5 parts by mass, the surface-modified inorganic filler is 5 to 100 parts by mass, and the crosslinking agent is 0.1 to 5 parts by mass with respect to 100 parts by mass of the polylactic acid resin. A resin composition characterized by the above. The resin composition according to claim 1, wherein the surface-modified inorganic filler is obtained by reacting an organosilane having an epoxy group with an inorganic filler.   The resin composition according to claim 1, wherein the inorganic filler is silica.   The resin composition according to claim 1, wherein the inorganic filler has a circularity of 0.8 or more.   The resin composition according to any one of claims 1 to 4, wherein the inorganic filler has a volume average particle size of 0.1 µm to 10 µm.   The resin composition according to claim 1, wherein the inorganic filler is spherical silica obtained by oxidizing metal silicon.   The resin composition according to claim 1, wherein the inorganic filler is spherical silica obtained by heating and melting crushed silica. The resin composition according to any one of claims 1 to 7 , wherein the crosslinking agent is a compound having two or more isocyanate groups. The crystal nucleating agent includes phenylphosphonate metal salt, hydrous magnesium silicate (talc), phosphate ester metal salt, dibenzylidene sorbitol compound, aliphatic carboxylic acid metal salt, trimesic acid triamide compound, boron nitride, basic inorganic aluminum The resin composition according to any one of claims 1 to 8 , which is a compound, a melamine compound salt, and / or an amide compound (consisting of an aromatic hydroxymonocarboxylic acid and an amine compound (including hydrazine)). The resin composition according to any one of claims 1 to 9 , wherein the surface-modified inorganic filler is 5 to 50 parts by mass with respect to 100 parts by mass of the polylactic acid resin. The resin composition according to any one of claims 1 to 10, wherein the inorganic filler does not contain a circularity of less than 0.8. A method for producing a resin molded body, comprising a molding step of molding the resin composition according to any one of claims 1 to 11 to obtain a molded body. The manufacturing method of the resin molding of Claim 12 which has a heat processing process which heat-processes simultaneously with shaping | molding of the said molded object in the said shaping | molding process, or heat-treats the said molded object after the said shaping | molding process. The method for producing a resin molded body according to claim 13 , wherein the combination of the heating temperature and the heating time in the heat treatment step is a combination in which the crystallinity obtained by the differential scanning calorimetry of the polylactic acid resin is 20% or more.