JP4764171B2 - Resin foam and resin composition for foam molding - Google Patents

Description

  The present invention relates to a resin foam useful as a packaging material and the like, and a foam molding resin composition for forming the foam.

  Resin foams are widely used in various applications such as packaging materials, heat insulating materials, cushioning materials, and containers by utilizing properties such as elasticity, flexibility, and heat insulating properties. In recent years, a foam using a biodegradable polymer or the like is also known for environmental considerations.

For example, regarding a foam using a starch-based resin, Japanese Patent Application Laid-Open No. 2004-123945 (Patent Document 1) includes an ester-modified starch-based resin as a main component of a base resin and an apparent density of 30 to 600 kg / m ^3. An ester-modified starch-based resin foam sheet having a thickness of 0.2 to 10 mm and an open cell ratio of 45% or less is disclosed. Japanese Patent Application Laid-Open No. 2004-262217 (Patent Document 2) and Japanese Patent Application Laid-Open No. 2004-306507 (Patent Document 3) disclose an ester-modified starch-based resin and an aliphatic group on at least one surface of the ester-modified starch-based resin foam layer. There is disclosed a composite foamed plate made of a polyester resin or a mixture thereof, having a film layer made of a resin composition having a tensile elastic modulus at 23 ° C. of 400 MPa or more and having an open cell ratio of 45% or less. However, when a starch-based resin is used, the open cell ratio tends to be high, and depending on the application, the rigidity is insufficient, and it becomes necessary to form a multilayer structure as in Patent Documents 2 and 3 above.

Japanese Patent Application Laid-Open No. 2001-200084 (Patent Document 4) is manufactured by extruding a foamable resin composition containing a cellulose-acetate resin as a main component and simultaneously foaming it by the evaporation expansion force of moisture. In the cellulose / acetate-based resin foam, the foamable resin composition is 10 to 100 parts by weight with respect to 100 parts by weight of the cellulose / acetate-based resin, and biodegradability-imparting materials such as corn starch, rice flour, and starch ( A cellulose-acetate-based resin foam containing A), which is biodegradable and excellent in mechanical properties and heat formability is disclosed. In such a resin foam, variation in bubble size is large, it is difficult to stably form bubbles, and the open cell ratio tends to be high.
JP 2004-123945 A (Claim 1) JP 2004-262217 A (Claim 1) JP 2004-306507 A (Claim 1) JP 2001-200084 A (Claim 1)

  Accordingly, an object of the present invention is to provide a foam having a high closed cell ratio, moderate rigidity and biodegradability, and a foam molding resin composition for forming the foam. .

  Another object of the present invention is to provide a foam containing many closed cells with small variation in cell size, and a resin composition for foam molding for forming the foam.

  As a result of intensive studies to achieve the above-mentioned problems, the present inventor conducted foam molding of a resin composition composed of an olefin resin and starches using an organic physical foaming agent containing at least isobutane. The inventors have found that a foam having a high closed cell ratio can be formed, and completed the present invention.

That is, the foam of the present invention is a foam obtained by foam-molding a resin composition composed of an olefin resin and starches using an organic physical foaming agent containing at least isobutane. The boiling point of the organic physical foaming agent may be about −40 ° C. to + 15 ° C. as an average of the whole foaming agent. The organic physical foaming agent may be a foaming agent composed of isobutane alone or a mixed foaming agent composed of isobutane and at least one selected from n-butane, n-pentane and isopentane, Usually, you may contain isobutane in the ratio of 40 weight% or more. The olefin resin may be a polyethylene resin. The starches may be at least one selected from, for example, starch, etherified starch and esterified starch. The ratio (weight ratio) between the starches and the olefin resin may be about starch / olefin resin = 1/99 to 60/40. The foam may have a foaming ratio of about 18 to 90 times and a density of about 0.01 to 0.05 g / cm ³ . The closed cell ratio of the foam may be 80% or more. In the foam, the resin composition may further contain a fatty acid amide.

  The present invention also includes a foam molding resin composition used to form the foam. Further, the present invention provides a method for producing a foam by foam-molding a resin composition composed of an olefin resin and starches using an organic physical foaming agent containing at least isobutane, and A method for improving the closed cell ratio of the foam is also included.

  In the present invention, the resin composition composed of an olefin resin and a biodegradable component such as starch is foam-molded using an organic physical foaming agent containing at least isobutane. The rate can be improved and the rigidity can be improved. Further, when the proportion of isobutane in the foaming agent is increased, variation in the size of closed cells in the foam can be reduced.

  The resin composition for foam molding of the present invention is a resin composition used for forming the foam of the present invention, which is composed of an olefinic resin and starches, and contains at least isobutane. The foam can be formed by foam molding using a system physical foaming agent.

Examples of the olefin resins include chain olefin resins [for example, α-C _2-20 olefins such as ethylene, propylene, 1-butene, isobutene, 4-methyl-1-pentene (preferably α-C _{2 -6} olefin) homopolymer or copolymer, the α-C _2-20 olefin and other copolymerizable monomers ((meth) acrylic monomers such as (meth) acrylic acid and alkyl (meth) acrylate) Copolymers with unsaturated carboxylic acids such as maleic acid and maleic anhydride or anhydrides; vinyl esters such as vinyl acetate; cyclic olefins such as cyclopentene and norbornene; dienes such as butadiene; Ethylene- (meth) acrylic acid copolymer, ionomer, ethylene-alkyl (meth) acrylate copolymer, ethylene- Acid vinyl copolymer), etc.], cycloolefin resin [cyclic olefins (e.g., such as cycloalkenes (C _4-10 cycloalkene such as cyclopentene); cycloalkadiene such as cyclopentadiene (cyclo C _4-10 alkadiene such as ); Bicycloalkene or bicycloalkadiene such as norbornene and norbornadiene (such as C _8-20 bicycloalkene or bicycloalkadiene); tricycloalkene or tricycloalkadiene such as dihydrodicyclopentadiene and dicyclopentadiene (C _10-25 ); Tricycloalkene or tricycloalkadiene etc.)) or homopolymers; the cyclic olefin and another copolymerizable monomer (in addition to the copolymerizable monomer, the α-C _2-20 olefin) Etc.) ] And the like. Olefin resins can be used alone or in combination of two or more.

Among these olefin resins, polyethylene resins (polyethylene; copolymers of ethylene such as ethylene-propylene copolymer and other α-C _2-6 olefins), polypropylene resins (polypropylene, propylene and others) Of α-C _2-6 olefin copolymers, etc.), and particularly polyethylene resins [eg, low density polyethylene (LDPE), linear low density polyethylene (LLDPE), medium density polyethylene, high density polyethylene]. (HDPE) etc.] is preferred. The polyethylene also includes polyethylene polymerized using a metallocene catalyst.

The weight average molecular weight of the olefin resin is about 1 × 10 ⁴ to 50 × 10 ⁴ , preferably about 2 × 10 ⁴ to 10 × 10 ⁴ , and more preferably about 3 × 10 ^{4 to} 7 × 10 ⁴ .

  As the starches, it is sufficient that they can be decomposed by microorganisms, for example, starch (for example, various raw starches such as corn starch, potato starch, sweet potato starch, tapioca starch), physically modified starch (pregelatinized starch, amylose, etc.), Chemically modified starch (oxidized starch, esterified starch, etherified starch, cationized starch, crosslinked starch, etc.) and the like can be mentioned. Starches can be used alone or in combination of two or more. Among the above starches, starch, esterified starch (starch obtained by esterifying at least a part of starch hydroxyl group with organic acid and / or inorganic acid, for example, carboxylic acid-modified starch such as acetyl starch and allyl starch; nitrate ester Modified starch, inorganic acid-modified starch such as phosphate esterified starch, etc.), etherified starch (starch in which at least a part of the hydroxyl group of starch is etherified, for example, alkyl starch such as methyl starch; carboxymethyl starch, etc. Carboxyalkyl starch; hydroxyalkyl starch such as hydroxyethyl starch) is often used.

  In the foam molding resin composition and the foam of the present invention, the ratio (weight ratio) of starches to olefinic resins is starches / olefinic resins = 0.5 / 99.5-60 / 40 (for example, 1/99 to 60/40), preferably 1.5 / 98.5 to 50/50 (for example, 2/98 to 40/60), more preferably about 2.5 / 97.5 to 30/70. is there.

The resin composition and the foam may further contain a fatty acid amide. Examples of fatty acid amides include acid amides of mono- or divalent long-chain fatty acids (such as _C10-30 saturated or unsaturated fatty acids) and amines, such as capric acid amide, palmitic acid amide, stearic acid amide, and behenic acid. Acid amides of saturated fatty acids such as amides; Acid amides of unsaturated fatty acids such as oleic acid amides; Bisamides of C _1-6 alkylene diamines (especially C _1-2 alkylene diamines) and fatty acids (eg, ethylene bisstearyl amide, Hexamethylenediamine-distearic acid amide, etc.). These fatty acid amides can be used alone or in combination of two or more.

  In the present invention, the fatty acid amide may be used as an anti-shrinkage agent for preventing bubble shrinkage. The ratio of the fatty acid amide is, for example, 0.01 to 30 parts by weight, preferably 0.05 to 20 parts by weight, and more preferably about 0.1 to 10 parts by weight with respect to 100 parts by weight of the olefin resin. is there.

  The resin composition and foam of the present invention may further contain a cell regulator. Examples of the air conditioner include inorganic particles (clay minerals such as talc; metal oxides such as magnesium oxide, aluminum oxide, silicon and titanium oxide; metal hydroxides such as magnesium hydroxide; metal carbonates such as calcium carbonate. Salt), organic particles (cellulose powder, chitin, chitosan, wood powder, metal stearate, etc.) and the like. These bubble regulators can be used alone or in combination of two or more. Of these air conditioners, inorganic particles, particularly talc, metal hydroxides, metal carbonates, and the like are often used.

  The ratio of the cell regulator is, for example, 0.01 to 15 parts by weight, preferably 0.05 to 10 parts by weight, and more preferably about 0.1 to 5 parts by weight with respect to 100 parts by weight of the polyolefin resin. May be.

  The resin composition and the foam of the present invention may further contain other resins such as styrene resin, acrylic resin (polymethyl methacrylate, methyl methacrylate-styrene copolymer (MS resin), methyl methacrylate-acrylic acid. Ester copolymers), polyester resins (aromatic polyester resins, etc.), polyamide resins, polycarbonate resins, polyacetal resins, polyphenylene ether resins, polyphenylene sulfide resins, polysulfone resins, polyether sulfone resins. , Polyetherimide resins, polyether ketone resins, polyether ether ketone resins, thermoplastic elastomers (styrene, olefin, polyester, polyamide elastomers, etc.), thermoplastic polymers such as rubber polymers, etc. Contains It may be. These resins may be used alone or in combination of two or more. In addition, content of other resin is 0.1-50 weight part with respect to 100 weight part of polyolefin-type resin, for example, Preferably it is 1-30 weight part, More preferably, it is about 5-15 weight part. There may be.

The foam molding resin composition and the foam are optionally provided with a surfactant, for example, a nonionic surfactant [for example, ether type, ester ether type, ester type, nitrogen-containing type surfactant, etc.], anionic interface An activator, a cationic surfactant, an amphoteric surfactant and the like may be contained. Among these surfactants, nonionic surfactants, particularly ester type nonionic surfactants such as polyhydric alcohol fatty acid esters, such as (poly) glycerin, trimethylolpropane, propylene glycol, pentaerythritol, sorbitan, Esters of polyhydric alcohols such as sorbitol, glycerin, sucrose and higher fatty acids [for example, glycerin C _8-24 fatty acid esters such as glyceryl monostearate, glyceryl distearate, glyceryl _monobenzoate , sucrose monostearate, etc. sucrose C _8-24 fatty acid esters, sorbitan monooleate, sorbitan dioleate, and sorbitan C _8-24 fatty acid esters, such as sorbitan trioleate] is often used. These surfactants may be used alone or in combination of two or more.

  The addition amount (ratio) of the surfactant is, for example, 0.3 to 50 parts by weight, preferably 0.5 to 20 parts by weight, and more preferably about 1 to 10 parts by weight with respect to 100 parts by weight of the polyolefin resin. It may be.

  The resin composition for foam molding and the foam may be prepared by using conventional additives such as fillers (fiber fillers such as glass fibers and carbon fibers) and stabilizers (hindered phenol antioxidants, etc.) as necessary. Antioxidants; UV absorbers, heat stabilizers, weathering stabilizers, etc.), foaming aids, flame retardants, colorants (dyes, pigments, etc.), dispersants, mold release agents, antifogging agents, nucleating agents, lubricants , Lubricants, impact modifiers, plasticizers, shrinkage inhibitors, antistatic agents, antiblocking agents, antibacterial agents, antiseptics, antifungal agents, photocatalysts (such as titanium oxide), biodegradable ingredients Decomposition components, for example, polysaccharides such as celluloses, chitin and chitosan, peptides, proteins, etc.) may be contained. These additives can be used alone or in combination of two or more.

  In the present invention, the foam is formed by foam-molding the resin composition using an organic physical foaming agent containing at least isobutane. When such an isobutane-containing organic physical foaming agent is used, the foaming agent in the resin composition can be reduced in the ratio of being replaced with air, or the variation in the size of the formed bubbles can be reduced, and the closed cells can be reduced. In addition to being able to be formed stably, closed cells having a relatively large size can also be formed.

  The organic physical foaming agent may contain at least isobutane, may be isobutane alone, or may be a combination of isobutane and another organic physical foaming agent. Other organic physical blowing agents include propane, n-butane, pentane (n-pentane, isopentane, etc.), aliphatic hydrocarbons such as hexane (n-hexane, etc.); aromatic hydrocarbons such as toluene; Halogenated hydrocarbons such as trifluorochloromethane; ethers such as dimethyl ether and petroleum ether; ketones such as acetone. These other organic physical foaming agents can be used alone or in combination of two or more.

  Of the organic physical blowing agents, isobutane alone, a combination of isobutane and aliphatic hydrocarbons (particularly, at least one selected from n-butane, n-pentane, and isopentane) and the like are preferable.

  The proportion of isobutane in the organic physical foaming agent is, for example, 40% by weight or more (about 40 to 100% by weight), preferably 50% by weight or more (about 50 to 100% by weight), and more preferably 60% by weight or more (60 ˜100% by weight).

  The boiling point (boiling point at normal pressure) of the organic physical foaming agent is, for example, about −40 ° C. to + 15 ° C., preferably about −35 ° C. to + 10 ° C., more preferably about −30 ° C. to + 10 ° C. It may be. For example, when propane having a boiling point of −42 ° C. is used alone as a foaming agent, bubbles are easily broken, and the open cell ratio in the foam increases. The average value of the boiling points is the product of the boiling point (° C.) of each organic physical foaming agent and the ratio (weight ratio) of each organic physical foaming agent when the whole organic physical foaming agent is 1. Expressed as a sum.

  The proportion of the organic physical foaming agent is, for example, 0.01 to 30 parts by weight, preferably 0.1 to 25 parts by weight, and more preferably about 1 to 20 parts by weight with respect to 100 parts by weight of the polyolefin resin. .

  Along with the organic physical foaming agent, if necessary, other foaming agents (for example, gas such as nitrogen and carbon dioxide gas, volatile foaming agent such as water; sodium bicarbonate, citric acid, azodicarboxylic amide, benzenesulfonyl hydrazide, N, N'-dinitrosopentamethylenetetramine (DNPT) or the like may be used in combination.

  In addition, the said organic type physical foaming agent and / or other foaming agent may be contained in the resin composition for foam molding.

  The resin composition for foam molding of the present invention is prepared by using conventional methods such as (i) mixers (tumblers, V-type blenders, Henschel mixers, Nauta mixers, ribbon mixers, mechanochemical devices, extrusion mixers, etc.). And (ii) a master batch (for example, starch) of a desired component by premixing and melt-kneading with a melt-kneader (single screw or bent twin-screw extruder, etc.) and pelletizing with a pelletizing means (pelletizer, etc.) (Poly) masterbatch containing a high concentration of polymers, etc., and mixing with polyolefin, if necessary, with other components and melt-kneading in a melt-kneader to pelletize, (iii) melt-kneading each component (Iv) Adding predetermined components (for example, starches, bubble regulators, additives, etc.) in the middle of the melt kneader And kneading. The resin composition includes a molten mixture in addition to a pellet-like composition.

  The foam of the present invention can be produced by foam-molding the resin composition by a conventional method using the specific organic physical foaming agent. In addition, a foaming agent such as an organic physical foaming agent may be used by mixing with the resin composition, or may be added or press-fitted into the melt-kneaded resin composition. As the foam molding method, various methods such as an extrusion molding method (for example, a T-die method, an inflation method, etc.), an injection molding method, and the like can be used.

  The melt kneading temperature in the extruder can be appropriately selected depending on the material, and may be, for example, 120 to 300 ° C, preferably 140 to 280 ° C, and more preferably about 150 to 260 ° C.

  The shape of the foam is not particularly limited. For example, a one-dimensional shape such as a rod shape or a string shape, a sheet shape, a film shape, a two-dimensional shape such as a two-dimensional network (net) shape, a block shape, a plate shape, It may be a three-dimensional shape such as a three-dimensional mesh shape or a pipe shape. The surface of a molded body (such as a sheet-shaped molded body) may be smooth or may have irregularities. In addition to a sheet having both surfaces smooth, the sheet-like molded article also includes a sheet having one surface having irregularities such as undulations, the other surface being smooth, and both surfaces having undulations such as undulations. . The thickness of the sheet-like molded body may be, for example, about 0.5 to 3 mm, preferably 1 to 2 mm, and more preferably about 1 to 1.5 mm.

  In the foam, the expansion ratio can be selected from a range of, for example, about 5 to 100 times, preferably 10 to 90 times, and more preferably about 20 to 80 times. In the present invention, since foam molding is performed using an organic physical foaming agent containing isobutane, the expansion ratio can be increased. The expansion ratio may be 18 to 90 times (for example, 30 to 90 times), preferably 35 to 80 times, and more preferably about 40 to 70 times.

The density (apparent density) of the foam is, for example, 0.005 to 0.2 g / cm ³ , preferably 0.01 to 0.1 g / cm ³ (for example, 0.01 to 0.05 g / cm ³ ), More preferably, it is about 0.01-0.04 g / cm < ³ >.

  The foam of the present invention contains many closed cells. The closed cell ratio of the foam is 80% or more (for example, 80 to 100%), preferably 90% or more (for example, about 90 to 99.9%), and more preferably 95% or more (for example, 95 to 99.99). 7%), particularly 98% or more (for example, about 98-99.5%).

  In this invention, the closed cell rate of the foam obtained can be improved by foam-molding the said resin composition using the said specific organic type physical foaming agent. Such a method for improving or improving the closed cell ratio is also included in the present invention.

  Since the foam of the present invention has appropriate rigidity, it is filled in various packaging applications, packaging applications such as industrial products (such as cushioning materials for precision machine parts), and building materials (for example, heat insulating materials, gaps or joints). Useful for applications such as fillers for combined septic tanks. The buffer material may be in various forms such as a sheet shape, a net shape, a bag shape, and a cap shape.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

Examples 1 to 5 and Comparative Examples Low density polyethylene (LDPE) (manufactured by Nippon Polyethylene Co., Ltd., JF414A), starch-containing polyethylene (PE) (manufactured by Hitachi Chemical Filtech Co., Ltd., 813PE, starch content 20% by weight) , Stearamide, and talc in the proportions shown in Table 1, using an extruder (50φ (first stage) / 60φ (second stage)) while kneading and melting in the first stage, Table 1 The blowing agent in the ratio shown in FIG. Furthermore, in the second stage, the mixture was further uniformly kneaded and cooled, the mixture was extruded from a die into a rod-like 25φ, and taken up with a mandrel to obtain a foam.

  In Example 5, instead of the starch-containing polyethylene, a foam was obtained in the same manner as above except that starch (manufactured by Nippon Corn Starch Co., Ltd., Corn Pole CPR-EX1) was used in the ratio shown in Table 1.

  The results are shown in Table 1. In the example using starch-containing polyethylene, the starch content (parts by weight) calculated based on the starch content was shown in parentheses.

  As is apparent from the table, in the example of foam molding using isobutane, a foam having a high closed cell ratio and expansion ratio was obtained, whereas in the comparative example using a foaming agent other than isobutane, closed cells were used. A foam with very low both rate and expansion ratio was obtained.

Claims (12)

  A foam in which a resin composition composed of an olefin resin and starches is foam-molded using an organic physical foaming agent containing at least isobutane.   The foam according to claim 1, wherein the boiling point of the organic physical foaming agent is -40 ° C to + 15 ° C as an average of the whole foaming agent.   The organic physical foaming agent is a foaming agent composed of isobutane alone or a mixed foaming agent composed of isobutane and at least one selected from n-butane, n-pentane and isopentane. The foam according to claim 1, which is contained at a ratio of at least%.   The foam according to claim 1, wherein the olefin resin is a polyethylene resin.   The foam according to claim 1, wherein the starch is at least one selected from starch, etherified starch and esterified starch.   The foam according to claim 1, wherein the ratio (weight ratio) between the starch and the olefin resin is starch / olefin resin = 1/99 to 60/40. The foam according to claim 1, wherein the foaming ratio is 18 to 90 times, and the density is 0.01 to 0.05 g / cm ³ .   The foam according to claim 1, wherein the closed cell ratio is 80% or more.   The foam according to claim 1, wherein the resin composition further contains a fatty acid amide.   A resin composition for foam molding which is composed of an olefin resin and starches and is used for forming the foam according to claim 1 by foam molding using an organic physical foaming agent containing at least isobutane. object.   The method for producing a foam according to claim 1, wherein a foam molding resin composition comprising an olefin resin and starches is foam-molded using an organic physical foaming agent containing at least isobutane.   A method of improving the closed cell ratio of a foam by foam-molding a resin composition composed of an olefin resin and starches using an organic physical foaming agent containing at least isobutane.