WO2014065205A1 - オレフィン系樹脂製発泡延伸成形体 - Google Patents
オレフィン系樹脂製発泡延伸成形体 Download PDFInfo
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- WO2014065205A1 WO2014065205A1 PCT/JP2013/078286 JP2013078286W WO2014065205A1 WO 2014065205 A1 WO2014065205 A1 WO 2014065205A1 JP 2013078286 W JP2013078286 W JP 2013078286W WO 2014065205 A1 WO2014065205 A1 WO 2014065205A1
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
- B29C44/34—Auxiliary operations
- B29C44/56—After-treatment of articles, e.g. for altering the shape
- B29C44/5627—After-treatment of articles, e.g. for altering the shape by mechanical deformation, e.g. crushing, embossing, stretching
- B29C44/5636—After-treatment of articles, e.g. for altering the shape by mechanical deformation, e.g. crushing, embossing, stretching with the addition of heat
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
- B29C44/34—Auxiliary operations
- B29C44/56—After-treatment of articles, e.g. for altering the shape
- B29C44/5627—After-treatment of articles, e.g. for altering the shape by mechanical deformation, e.g. crushing, embossing, stretching
- B29C44/5672—After-treatment of articles, e.g. for altering the shape by mechanical deformation, e.g. crushing, embossing, stretching by stretching the foam, e.g. to open the cells
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
- C08J9/0061—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof characterized by the use of several polymeric components
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
- C08J9/04—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent
- C08J9/12—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent by a physical blowing agent
- C08J9/122—Hydrogen, oxygen, CO2, nitrogen or noble gases
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
- C08J9/34—Chemical features in the manufacture of articles consisting of a foamed macromolecular core and a macromolecular surface layer having a higher density than the core
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
- B29B11/00—Making preforms
- B29B11/06—Making preforms by moulding the material
- B29B11/08—Injection moulding
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B29C2949/00—Indexing scheme relating to blow-moulding
- B29C2949/07—Preforms or parisons characterised by their configuration
- B29C2949/0715—Preforms or parisons characterised by their configuration the preform having one end closed
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- B29C2949/00—Indexing scheme relating to blow-moulding
- B29C2949/07—Preforms or parisons characterised by their configuration
- B29C2949/072—Preforms or parisons characterised by their configuration having variable wall thickness
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B29C2949/00—Indexing scheme relating to blow-moulding
- B29C2949/07—Preforms or parisons characterised by their configuration
- B29C2949/076—Preforms or parisons characterised by their configuration characterised by the shape
- B29C2949/0768—Preforms or parisons characterised by their configuration characterised by the shape characterised by the shape of specific parts of preform
- B29C2949/077—Preforms or parisons characterised by their configuration characterised by the shape characterised by the shape of specific parts of preform characterised by the neck
- B29C2949/0772—Closure retaining means
- B29C2949/0773—Threads
- B29C2949/0774—Interrupted threads
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
- B29C44/34—Auxiliary operations
- B29C44/3484—Stopping the foaming reaction until the material is heated or re-heated
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
- B29C44/34—Auxiliary operations
- B29C44/35—Component parts; Details or accessories
- B29C44/352—Means for giving the foam different characteristics in different directions
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C49/00—Blow-moulding, i.e. blowing a preform or parison to a desired shape within a mould; Apparatus therefor
- B29C49/02—Combined blow-moulding and manufacture of the preform or the parison
- B29C49/06—Injection blow-moulding
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
- B29K2023/00—Use of polyalkenes or derivatives thereof as moulding material
- B29K2023/10—Polymers of propylene
- B29K2023/12—PP, i.e. polypropylene
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
- B29K2105/00—Condition, form or state of moulded material or of the material to be shaped
- B29K2105/04—Condition, form or state of moulded material or of the material to be shaped cellular or porous
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
- B29K2105/00—Condition, form or state of moulded material or of the material to be shaped
- B29K2105/24—Condition, form or state of moulded material or of the material to be shaped crosslinked or vulcanised
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
- B29L2031/00—Other particular articles
- B29L2031/712—Containers; Packaging elements or accessories, Packages
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2203/00—Foams characterized by the expanding agent
- C08J2203/06—CO2, N2 or noble gases
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2205/00—Foams characterised by their properties
- C08J2205/04—Foams characterised by their properties characterised by the foam pores
- C08J2205/044—Micropores, i.e. average diameter being between 0,1 micrometer and 0,1 millimeter
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2205/00—Foams characterised by their properties
- C08J2205/04—Foams characterised by their properties characterised by the foam pores
- C08J2205/052—Closed cells, i.e. more than 50% of the pores are closed
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- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2207/00—Foams characterised by their intended use
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
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- C08J2323/04—Homopolymers or copolymers of ethene
- C08J2323/06—Polyethene
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- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
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- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
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- Y10T428/13—Hollow or container type article [e.g., tube, vase, etc.]
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Definitions
- the present invention relates to a foam stretch-molded body formed of an olefin resin.
- plastic foam moldings are excellent in light weight and heat insulation, and have improved mechanical properties such as rigidity, and are used in various applications.
- foaming by so-called microcellular technology foaming by so-called microcellular technology
- areas such as a packaging container (refer patent document 1).
- so-called chemical foaming using sodium carbonate or azo compound as a foaming agent and foaming to carbon dioxide gas or nitrogen gas generated by thermal decomposition of the foaming agent results in a large foam cell.
- the gas barrier property, the appearance characteristics, and the strength are significantly lowered due to foaming, it is difficult to use in the field of packaging containers.
- physical foaming can be applied to the field of packaging containers because the size of the foamed cells can be reduced or the size of the foamed cells can be distributed.
- thermoplastic resins can be used, what is actually studied and used is polyethylene terephthalate.
- an olefin resin such as polypropylene
- forming a foamed preform according to Patent Document 1 and stretching the foamed preform to produce a foamed stretched molded product made of olefinic resin
- the foamed cells are extremely coarsened, the light shielding property is lowered, or the appearance characteristics are remarkably deteriorated, so that a product that can be put to practical use cannot be obtained at all.
- Patent Document 6 discloses a foamed injection molded product of a propylene-based resin.
- the foaming agent used in the examples is a so-called chemical foaming agent, such as carbon dioxide gas or nitrogen gas. No specific study has been made on physical foaming using an inert gas.
- Patent Document 7 discloses an injection-foamed molded product of polypropylene by physical foaming using an inert gas, but no consideration is given to stretch molding.
- Patent Document 8 discloses a hollow foam molded body (blow molded body) of polypropylene, and discloses that polypropylene having a specific MFR and molecular weight distribution is used.
- an inert gas such as nitrogen gas can be used as a foaming agent
- all of the foaming agents actually used in the examples are inorganic foaming agents ( Polyslenes), and so-called physical foaming has not been studied at all.
- a non-foamed layer is formed on the surface by co-extrusion of a non-foaming thermoplastic resin on one or both sides of the hollow foam molded body in order to ensure surface smoothness. is doing.
- the present invention is a foam stretch-molded product comprising a single layer structure of an olefin resin, which is obtained by physical foaming using an inert gas as a foaming agent, and is effective for poor appearance or reduced light shielding due to foaming.
- Another object of the present invention is to provide a foamed stretch-molded product comprising a single-layer structure of a propylene-based resin having a shape of a container, particularly a bottle.
- the present inventors have introduced a foam structure by physical foaming (so-called micro-cellular foaming) using an inert gas as a foaming agent when producing an olefin resin stretch-molded body (for example, blow-molded body).
- foaming stretching with excellent surface smoothness was achieved by controlling the physical properties of the olefin resin, the amount of impregnation of inert gas, foaming conditions, etc., and suppressing foam cell coarsening.
- the molded body it is completely different from the physical foaming of the polyester resin, a foam cell having a unique shape is generated, and the finding that a high light-shielding property can be obtained even when the foaming ratio is low is found. It came to complete.
- a foamed stretch-molded product formed by physical foaming having a foaming ratio of 1.01 to 2.0 times, which is formed from a single-layer structure of an olefin-based resin, in which foamed cells are distributed inside.
- An olefin resin foamed stretch-molded article is provided, wherein the surface roughness Ra (JIS-B-0601-1994) in the region is 10 ⁇ m or less.
- the foam stretch molded article of the present invention (1) Seen in a cross section along the stretching direction, the foamed cells form a cell cluster continuous in the stretching direction with a number of 10 or more, (2)
- the olefin resin has an MFR (230 ° C.) of 1 to 80 g / 10 min. (3)
- the olefin-based resin has the following conditions (A) and (B): (A) containing 70% by weight or more of random polypropylene, (B) In the melting curve obtained by DSC measurement, the maximum intensity peak temperature is 1
- the difference (Ti ⁇ Tf) between the melting start temperature (Ti) and the melting end temperature (Tf) of the melting peak including the highest intensity peak is less than 50 ° C.
- this expanded foam molded article is (4) having a foaming ratio of 1.5 times or less and having a light transmittance of 25% or less in visible light; (5) having the form of a container; Is preferred.
- the cell cluster means an aggregate in which the foamed cells are in close contact with each other in the shape of a bunch of grapes, and the foamed cells in the cell cluster may have their internal spaces communicating with each other. A cell cluster that exists in the form of such an aggregate is different from a closed type cell that exists as a single independent bubble.
- the above-described expanded foam molded article of the present invention has the following steps: Preparing a resin melt in which an olefin resin is impregnated with an inert gas; The resin melt is injection filled by injection filling into an injection mold so that foaming does not occur; Removing the molded unfoamed preform from the injection mold; Releasing inert gas from the surface of the resulting unfoamed preform; Heating and foaming the unfoamed preform; Then stretching the foamed preform; It is manufactured through.
- the expanded foam molded article of the present invention is a single layer structure of an olefin resin such as polypropylene, the expansion of the expanded cells is effectively suppressed, and the expansion ratio is 2.0 times or less, particularly 1.5. It has a feature that it is suppressed to twice or less and is excellent in surface smoothness.
- the surface roughness Ra in the region where the foam cells are distributed inside is 10 ⁇ m or less, particularly 5 ⁇ m or less, and the surface smoothness is extremely high.
- a cell cluster in which 10 or more foamed cells are connected in the stretching direction can be formed.
- Such cell clusters are peculiar to physical foaming of an olefin resin, and cannot be formed by physical foaming of a polyester resin.
- the formation of such cell clusters is advantageous for improving the light shielding property at a low expansion ratio. For example, even at an expansion ratio of 1.5 times or less, a high light shielding property is obtained, and the light transmittance in visible light. Is 25% or less.
- rigidity can be imparted to the stretched molded body such as a container, and the bending strength is improved to 1.5 times or more at an expansion ratio of 1.5 times or less.
- the expansion ratio is a ratio of the volume when foamed to the volume when not foamed (the volume when foamed / the volume when not foamed) in a region where foamed cells are distributed.
- the foamed stretch-molded article made of an olefin resin of the present invention has a high light-shielding property although it is not blended with a color pigment. There is.
- generation with an olefin resin The figure for demonstrating the principle of the cell cluster production
- FIG. 1 The figure which shows the melting curve by DSC measurement of the olefin resin used in Experimental example 1 and Experimental example 6.
- FIG. The cross-sectional photograph along the maximum extending
- FIG. The figure which shows the relationship between the amount of residual gas and the skin layer temperature at the time of heat foaming (stretching molding temperature) about the foaming state in the surface layer part of the foam preform after foaming.
- a polyester represented by polyethylene terephthalate (PET) can be solidified in an amorphous state by quickly cooling from a molten state to a glass transition temperature (Tg) or lower.
- this polyester is impregnated with an inert gas (FIG. 1 (a1)), and the polyester solidified in an amorphous state is heated (above the glass transition temperature), the impregnated gas expands and has a spherical shape or a shape close to a spherical shape. Bubbles (foamed cells) are generated and grow, but when they grow to a certain size, the resin (polyester) around the bubbles is cured by the stress associated with the growth of the bubbles and the growth is suppressed.
- an olefin resin has characteristics that the glass transition point (Tg) is extremely low (for example, about ⁇ 10 ° C. for polypropylene) and the crystallization speed is extremely fast, so that it cannot be solidified in an amorphous state.
- Tg glass transition point
- the degree of crystallinity varies depending on the resin type, but is approximately 30 to 70%.
- FOG. 1 (b1) inert gas
- the resin In an olefin-based resin such as polypropylene, the resin is softened when heated to a temperature higher than the melting start temperature (Ti) of the crystal, and spherical bubbles grow.
- Ti melting start temperature
- the olefin resin has a very high gas diffusion rate as compared with the polyester resin, and further, stretch hardening does not work like the polyester resin. For this reason, when the olefin resin impregnated with the gas is heated, the bubbles grow greatly in a short time due to an increase in the gas pressure in the foam cell. This is because there is no element that suppresses the growth of bubbles like polyester.
- a foamed cell (bubble) at the time of foaming is used for a foamed stretch-molded product having a single layer structure of an olefin resin without adopting a laminated structure by coextrusion or the like in order to avoid poor appearance due to foaming It is indispensable to suppress the coarsening.
- the olefin-based resin is crystallized when it is cooled and solidified, and gradually softens with heating. When the temperature exceeds the crystal melting temperature of the resin, the crystal structure collapses and remarkably softens.
- the stretching step that is subsequently performed after the olefin resin is heated to a temperature higher than the crystal melting temperature, the craze is stretched in the stretching direction, and the craze is partially omnidirectional by the pressure of the inert gas that flows into the craze. It grows to a large number and forms a large number of foamed cells, forming a large number of foamed cells.
- the foam cells are in close contact with each other in the shape of a bunch of grapes, and a cell cluster is formed in which foam cells having a shape other than a spherical shape such as a prismatic shape are gathered.
- a cell cluster it is observed that a part of the walls of adjacent cells communicate with each other, which is derived from the fact that they were connected at the Craze stage.
- the foaming condition (foaming temperature) is set in an appropriate range according to the amount of impregnation of the gas, for example, by allowing foaming in a state where crystals are partially present, At the same time, a foam structure in which cell clusters are generated can be obtained.
- the expanded foam molded article of the present invention is obtained by first impregnating an olefin resin with an inert gas and then by injection molding using an olefin resin melt impregnated with the inert gas.
- an inert gas that is a foaming agent is impregnated but an unfoamed preform is obtained, a predetermined amount of gas is released from the surface of the unfoamed preform, and then heated to a predetermined temperature to perform foaming.
- the foamed preform is produced by stretch molding.
- a blow bottle is taken as an example of the stretch-molded product, as shown in FIG. 5, in the present invention, injection molding, foaming and remaining using an olefin resin impregnated with an inert gas are used.
- a foamed preform 50 for a container is produced by releasing the gas, and the foamed preform 50 is stretch-molded (blow-molded) to obtain a bottle 60 that is a stretch-molded body.
- the foamed preform 50 has a test tube shape as a whole, and includes a mouth part 51 and a molding part 53 (a part to be stretch-molded), and the lower end of the molding part 53 is closed to form a bottom part 55. is doing.
- the mouth portion 51 is a portion that is not stretched, and is formed with a screw portion 51a that is screw-engaged with the cap, and a support ring 51b for conveyance or the like (depending on the type of container to be molded) Some may not have a support ring 51b).
- the bottle 60 obtained by blow molding the foamed preform 50 has a mouth portion 61 corresponding to the mouth portion of the preform 50 and a body portion 63 corresponding to the preform forming portion 53.
- the end portion of the body portion 63 is closed to form a bottom portion 65.
- the mouth portion 61 has a screw portion 51 a and a support ring 51 b screw portion, like the mouth portion 51 of the preform 50.
- Olefin resins In the present invention, an olefin resin is used as the resin used for manufacturing the container. Olefin resins have a very high gas diffusion rate compared to other resins, for example, polyester resins, and do not work by stretching like polyester resins, so olefin resins impregnated with gas. As described above, when the is heated, the bubbles grow greatly in a short time due to an increase in the gas pressure in the foam cell.
- the MFR (ASTM-D-1238, 230 ° C.) of the olefin resin used is in the range of 1 to 80 g / 10 minutes, particularly 5 to 50 g / 10 minutes, most preferably 10 to 50 g / 10 minutes. It is necessary to be in As will be described later, when an unfoamed preform impregnated with an inert gas is produced by injection molding, if the MFR is outside the above range, foaming at the time of injection molding is performed without impairing the injection moldability. This is because it is difficult to avoid. There is also a problem that stretch moldability is impaired.
- the olefin resin used preferably has an MFR within the above range and satisfies the following conditions (A) and (B).
- A) It contains 70% by weight or more, preferably 80% by weight or more of random polypropylene.
- B) In the melting curve obtained by DSC measurement, the maximum intensity peak temperature (Tm) is less than 150 ° C., particularly 145 ° C. or less, and the melting start temperature (Ti) and melting end temperature ( The difference between (Tf) and (Ti ⁇ Tf) is 50 ° C. or higher, particularly 60 ° C. or higher.
- the random polypropylene is propylene and an ⁇ -olefin other than propylene (for example, ethylene, butene-1,4-methyl-1-pentene, etc.) or a cyclic olefin.
- polypropylene with high crystallinity for example, propylene homopolymer or propylene block copolymer
- foaming is performed by heating a polypropylene preform (cooled solidified product) impregnated with gas. This is because the peak is sharp, so that the crystals are melted and softened with heating, and as a result, the foamed cells are coarsened at once.
- polypropylene with high crystallinity has poor moldability.
- polypropylene having a large crystal size and a uniform crystal melting temperature is used, the proportion of amorphous resin is small, glaze formation becomes prominent at the crystal grain boundary, and breakage from the crystal grain boundary is likely to occur. End up.
- random polypropylene is contained in the above ratio. If the random polypropylene content is within the above range and satisfies other conditions, other olefin resins such as homopolypropylene, block copolymer of propylene and other ⁇ -olefins or cyclic olefins may be used. Those in which a polymer, polyethylene or the like is blended can also be suitably used.
- FIG. 8 is a diagram showing a melting curve by DSC measurement of the propylene-based resin used in Experimental Example 1 and Experimental Example 6 to be described later. As in Experimental Example 6, the maximum peak temperature of the melting curve is more than the above range.
- Impregnation with inert gas In the present invention, the melt of the olefin resin is impregnated with an inert gas which is a foaming agent. However, such an inert gas does not react with the olefin resin used. In addition, any inert gas can be used as long as it does not adversely affect the environment and the like. In general, nitrogen gas, carbon dioxide gas, or the like is used from the viewpoints of availability, environmental impact, safety, cost, and the like.
- an olefin-based resin that is held in a heated and melted state in a resin kneading part (or plasticizing part) of the injection molding machine is used in an injection molding process of the next process.
- an inert gas By supplying an inert gas at a predetermined pressure.
- the gas can be impregnated in the injection molding machine, and the inert gas can be efficiently impregnated in the process of molding the preform to be subjected to stretch molding.
- the temperature and gas pressure of the olefin-based resin melt are set so that a sufficient amount of gas is dissolved to form a desired number of foamed cells (bubbles).
- the higher the temperature the smaller the amount of gas dissolved, but the faster the impregnation rate.
- the lower the temperature the larger the amount of gas dissolved, but the longer the impregnation takes, and the higher the gas pressure, The amount of dissolution increases and therefore the number of foam cells also increases.
- a preform which is a precursor of the stretched molded body, is molded using a melt of a propylene-based resin impregnated with the above-described inert gas.
- the shape of this preform may be a test tube shape (in the case of producing a bottle by blow molding) or a sheet shape (a cup-shaped container by plug-assist molding) depending on the shape of the intended stretch molding. When manufacturing).
- injection molding is a closed system, and a gas-impregnated resin melt is injected and filled in the cavity (closed space) of the injection mold. This is because, even in a molten state, it is possible to effectively avoid the foaming by keeping the inside of the system at a high pressure.
- injection molding process it is important to inject and fill the resin melt impregnated with the inert gas into the cavity of the molding die while holding the pressure.
- foaming in the molding die is suppressed, and the size of the foamed cell generated by the subsequent foaming step can be controlled.
- Injection filling with holding pressure is performed by filling a predetermined amount of resin melt into the mold cavity and then continuing the injection to compensate for the volume shrinkage due to thermal shrinkage or resin crystallization.
- the resin melt in the molding die is pressurized, and foaming can be effectively suppressed.
- an olefin resin having an MFR in the range of 1 to 80 g / 10 minutes, particularly 5 to 50 g / 10 minutes, most preferably 10 to 50 g / 10 minutes. It will be understood that it is necessary.
- the inside of the mold cavity is kept at a high pressure (called counter pressure), and in this state, the gas-impregnated resin melt is subjected to holding pressure. Then, it is injected and filled into the cavity of the molding die and cooled and solidified in the cavity to form a preform having a predetermined shape. That is, such counter pressure and holding pressure effectively suppress foaming during injection molding, which is basically the same as the technique proposed by the present applicant for polyester.
- the resin melt filled in the cavity of the molding die can be prevented from foaming by applying pressure.
- the expansion of the inert gas in which the resin pressure is dissolved is suppressed, thereby preventing foaming.
- foaming when the resin melt flows in the mold cavity cannot be prevented by holding pressure.
- a gas-impregnated resin melt is filled in a mold maintained at atmospheric pressure
- the gas impregnated in the resin melt at the tip of the resin melt flowing in the mold Expands due to a pressure difference from the mold inner space, and bubbles are broken. That is, since the resin melt flows in the mold with the tip part broken, this state is transferred to the mold surface, and the broken foam is formed in the molded body by cooling and solidifying on the mold surface.
- swirl mark It is fixed to the surface of a certain preform, and this is generally called a swirl mark.
- Such swirl marks are reflected as surface roughness on the surface of a molded body obtained by stretch molding described later.
- the occurrence of such swirl marks is effectively prevented by injecting the gas-impregnated resin melt into a mold held in a pressurized state. This is because the bubble breakage during the flow of the resin melt in the mold is effectively suppressed by the pressure in the mold.
- an injection mold indicated by 20 as a whole has a shell mold 23 and a core mold 25 which are cooled and held, and these molds.
- a cavity 27 is formed by 23 and 25, and the cavity 27 is filled with a resin melt from an injection nozzle 29.
- a gas port 30 communicates with the cavity 27 via a gas vent.
- Such a cavity 27 corresponds to the shape of the preform to be molded, and in the example shown in the figure, corresponds to the container preform 50 shown in FIG.
- an olefin resin melt impregnated with an inert gas is injected into the cavity 27 from the injection nozzle 29, and the resin melt in the cavity 27 is cooled and solidified, whereby the resin melt is formed by the cavity 27. Shaped into the shape to be made.
- nitrogen gas, carbon dioxide gas, air, or the like is supplied from the gas port 30 into the cavity 27 to keep the cavity 27 at a high pressure.
- the surface of the mold cavity 27 is a surface having high smoothness due to mirror finishing or the like.
- a portion where smoothness is not particularly required for example, a portion corresponding to the bottom portion of the container
- sand blasting is performed as necessary. It may be partially roughened in advance using a method such as processing.
- the gas in the cavity 27 is discharged from the gas port 30 as the resin melt is injected and filled. Even after the gas is discharged, the resin melt is continuously injected to add a holding pressure. It is done. By this holding pressure, foaming in the cavity 27 is effectively prevented.
- the preform obtained by the above method has high transparency while being impregnated with a gas having a function as a foaming agent because foaming after injection filling is effectively suppressed by holding pressure.
- a gas having a function as a foaming agent because foaming after injection filling is effectively suppressed by holding pressure.
- the light transmittance for visible light having a wavelength of 500 nm is 50% or more.
- the degree of pressure retention (pressure retention time and time) is appropriately set according to the amount of inert gas impregnation, resin temperature, etc. so that foaming can be effectively suppressed.
- the weight reduction rate may be set to 3% or less.
- the weight reduction rate of the preform can be experimentally obtained by the following formula.
- Weight reduction rate [(M 0 ⁇ M 1 ) / M 0 ] ⁇ 100
- M 0 represents the weight of the preform obtained by injecting under the condition setting so that there is no molding defect such as sink without impregnation with inert gas
- M 1 represents the weight of the resulting gas-impregnated preform is impregnated with an inert gas. That is, the weight reduction rate decreases as the holding pressure increases, and the weight reduction rate decreases as the holding time increases.
- the pressure in the cavity 27 is not particularly limited, but is generally maintained in a range of 1.0 MPa or more, and a resin melt is injected and filled into the cavity 27 held at such pressure. It is preferable. If this pressure is small, foam breakage during the flow of the resin melt cannot be effectively suppressed, swirl marks are generated, and the surface smoothness is low.
- Gas release In the present invention, an inert gas produced as described above is impregnated, but an unfoamed preform is taken out from the cavity 27 and foamed, and this preform is impregnated prior to foaming. Part of the gas that is being discharged is released from the surface. By releasing such gas, it is possible to form a skin layer having no foam cells on the surface. Moreover, due to the release of gas, a concentration distribution is formed in which the gas concentration is high in the central portion of the preform and the gas concentration is low in the portion close to the surface.
- the bubble nucleation temperature is low, and crazes, which are the cause of cell cluster formation, are formed, and in the vicinity of the preform surface where the gas concentration is low, the bubble nucleation temperature is high.
- the bubble nuclei grow in a spherical shape, and spherical foam cells that become flat closed cells are formed by stretching, which will be described later, and the surface portion where no gas is present does not generate bubble nuclei, and the non-foamed skin layer become.
- Such a gas release from the preform can be performed by leaving the preform taken out from the cavity 27 under atmospheric pressure for an appropriate period of time. Is maintained at the upper limit of the temperature at which the production starts.
- Foaming The preform in which the skin layer having no gas on the surface is formed by the gas release as described above is subjected to a foaming process.
- foaming is performed by heating the non-foamed preform using an oil bath or an infrared heater.
- heating for foaming is performed from the inside of the preform using high-frequency heating with an iron core or the like inserted therein. It can be carried out.
- the molding part 53 is selectively heated. Of course, it is also possible to selectively heat a part of the molding part 53 to make a part of the molding part 53 a foamed region.
- foaming occurs inside the preform in which the inert gas remains, and as shown in FIG. 7, along with the fine foamed cells having a spherical shape or a shape close to a spherical shape, the thickness direction of the preform. In the center portion, a craze that is a factor of the cell cluster is generated.
- the thickness of the preform skin layer can be adjusted by the time until the heat foaming and the heat foaming time. That is, the longer the time until the start of heating foaming, the more gas is released from the surface of the preform, and the thicker the non-foamed preform skin layer is, the longer the heating foaming time is, Since the cell grows greatly, the thickness of the preform skin layer is reduced.
- the heating time for foaming is considerably short, and is generally about 20 seconds to 2 minutes, although it depends on the size (thickness) of the preform and the amount of gas impregnation.
- the heating temperature for foaming needs to be not higher than the melting point of the olefin resin (the maximum intensity peak temperature in the DSC melting curve). It differs depending on the type of olefin resin used, the amount of inert gas (residual gas amount) impregnated in the preform, the desired foamed form, and the like.
- the temperature is lower than the crystal melting start temperature of the olefin resin (cell nuclei are generated while the crystal structure is maintained). In this state, the stretching step described later is performed.
- the closed cell and the cell cluster can coexist in an appropriate balance.
- the surface side has the highest temperature and the thickness direction central portion has the lowest temperature.
- Spherical foam cell that is a factor of closed cell in the part near the skin layer by heating the preform skin layer to a temperature close to the crystal melting start temperature, but using the temperature distribution And crazes, which are factors of cell clusters, can be generated in the core. That is, even if the skin layer is heated to a temperature higher than the crystal melting start temperature, the temperature of the core is lower than that, so that crystals remain and it is possible to generate craze that is a factor of cell clusters.
- the foaming ratio of the foamed preform formed as described above is 1.05 to 2.0 times, particularly 1.05 to 1.5 times, and more preferably 1.1 to 1.3 times. It is preferable to adjust the foaming conditions (heating time for foaming) in accordance with the gas concentration in the preform so that the foaming range is within the range. Can be adjusted. That is, if the expansion ratio becomes higher than necessary, spherical foam cells or crazes grow to the preform skin layer, and a preform skin layer without foam cells (and crazes) is formed. Therefore, the appearance of the finally obtained expanded foam container will be deteriorated.
- the foaming ratio of the preform is preferably set within the above range.
- the average diameter (equivalent circle diameter) of the spherical foamed cells is about 5 to 200 ⁇ m
- the cell density of the spherical foamed cells is 10 4 to 10 10 cells. / Cm 3 or so.
- the maximum intensity peak temperature of the melting curve is low (less than 150 ° C.) and the difference between the melting start temperature (Ti) and the melting end temperature (Tf) is large (50 ° C. or more), and therefore the adjustment of the heating foaming temperature and foaming time described above is easy.
- the heating foaming temperature is between the melting start temperature (Ti) and the melting end temperature (Tf) (for example, 110 ° C. to 140 ° C.), and the closer to the melting start temperature (Ti), the generation amount of craze is reduced.
- Increasing the distance from the melting start temperature (Ti) can increase the amount of independent spherical foam cells generated.
- This stretch molding is performed by heating the preform to a temperature not lower than the melting start temperature (Ti) of the used olefin resin and lower than the maximum intensity peak temperature (Tm) of the melting point. That is, when the melting start temperature (Ti) or higher is reached, the resin begins to soften and stretch blow molding becomes possible, but when the crystal melting proceeds and exceeds the melting point peak (Tm), the resin becomes viscous and unsuitable for stretching. The resin becomes brittle.
- the present invention when an olefin resin satisfying the above-mentioned conditions (A) and (B) is used, there is an advantage that it becomes possible to perform stretch molding in the foaming temperature range of the preform. That is, if the melting peak width (Tf-Ti) of the olefin resin is small, the foaming temperature and the stretching temperature do not match, and the preform must be further heated for stretching. For this reason, the foam cell of the preform grows excessively, and at the time of stretch molding, a foam cell exceeding the thickness of the skin layer in which spherical foam cells or crazes do not exist may be formed. The appearance of the body may be impaired, but such inconvenience can be effectively avoided when stretch molding is performed in the foaming temperature range.
- the preform heated to the above-mentioned foaming temperature can be stretch-molded as it is, which is extremely in terms of productivity. It is advantageous.
- the spherical foam cells or crazes are stretched together with the foam preform wall, and the outer wall surface is stretched by contacting the molding die.
- the molded body is cooled and solidified, and the flat closed cells and cell clusters generated by stretching in the plane direction are fixed as they are.
- Such stretch molding can be performed by a method known per se, and is performed by blow molding, plug assist molding, or the like, depending on the shape of the target stretch molded body, for example, as shown in FIG.
- a flat foam cell having a long cell diameter in the stretching direction is formed on the surface side, and a cell cluster in which 10 or more foam cells are continuous in the stretching direction is formed in the center in the thickness direction.
- a non-foamed skin layer in which neither flat foam cells nor cell clusters exist is formed.
- the molding part 53 of the foamed preform 50 has a draw ratio in the axial direction (height direction) and the circumferential biaxial direction by blow molding by blowing air or the like.
- the film is stretched so as to be about 2 to 4 times, and blow molding is performed so that the thickness of the body part 63 is about 150 to 400 ⁇ m, and the surface of the body part 63 has 5 non-foamed skin layers. It is formed with a thickness of about 100 ⁇ m.
- the generation amount of the cell cluster can be adjusted by the above-described heating foaming temperature.
- the lower the heating foaming temperature the more the cell cluster generation rate, and the heating foaming temperature becomes the crystal.
- the lower the melting start temperature is, the smaller the number of flat closed cells that are mainly composed of cell clusters, and conversely, the higher the heating foaming temperature is than the crystal melting start temperature, the more the generation amount of cell clusters can be suppressed.
- the foaming ratio is 1.01 to 2.0 times, particularly 1.
- the range is 01 to 1.5 times, and further about 1.05 to 1.5 times. If the expansion ratio is too large, it is impossible to avoid a decrease in appearance characteristics due to the coarsening of the expanded cells, and if the expansion ratio is too small, the advantage of foaming is impaired.
- the foamed structure as described above exhibits high light shielding properties even at a low foaming ratio.
- the shading rate with respect to visible light at the body portion is 30% or less.
- the light shielding rate for visible light is 25% or less at a foaming ratio of 1.5 times or less.
- the foam structure in which many cell clusters are generated contributes to the improvement of rigidity. For example, in the bottle body, the bending strength is increased to 1.5 times or more even when the foaming ratio is 1.5 times or less, and 1500 Pa. This can be done.
- a foamed stretch-molded article having a single-layer structure of an olefin-based resin through the steps of impregnation with an inert gas, injection molding, foaming, release of residual gas, and stretch molding.
- Such a foamed stretch-molded body has a single layer structure of an olefin resin, but the foaming cell is effectively limited in its coarsening. For example, it has an appropriate foaming ratio and at the same time has a high surface smoothness. It effectively prevents deterioration of the appearance due to foaming, and exhibits advantages such as weight reduction, heat insulation, light shielding, and rigidity by foaming.
- Such a stretched stretch-molded article of the present invention is extremely useful as a field of containers, particularly as a bottle, because it effectively prevents deterioration in appearance due to foaming, for example, has excellent surface smoothness and high printability. .
- This resin melt was injected into a mold whose pressure was increased to 5 MPa by a counter pressure device, and the degree of holding pressure was adjusted so as not to foam (holding pressure 60 MPa, injection holding time 19 seconds) and solidified by cooling. .
- a test tube-shaped container preform which was impregnated with a gas having a weight of 12.3 g but was substantially non-foamed was obtained.
- the obtained preform had a weight reduction rate of 0% compared to the case where no foaming gas was added.
- the DSC curve of the random polypropylene used is as shown in FIG. 8, and the melting start temperature, maximum strength peak temperature, and melting end temperature in the measurement are 94 ° C., 140 ° C., and 163 ° C., respectively, and the melting peak width ( Tf—Ti) was 61 ° C.
- the obtained preform was stored at 20 ° C. for 6 hours.
- the weight of the preform before and after storage was measured, and the nitrogen gas remaining in the preform was calculated to be 0.22% by weight.
- the preform body part excluding the mouth part was foamed by adjusting the heating so that the surface temperature of the preform body part was 115 ° C. with an infrared heater, and immediately blow-molded.
- a cylindrical foaming bottle having an internal volume of about 400 ml, a height of 195 mm (cylindrical part 135 mm), and a maximum diameter (cylindrical part) of 60 mm was obtained.
- the series of foamed cells in the cell cluster along the stretching direction estimated from the image was 100 or more, the outer skin layer thickness was 70 ⁇ m, and the total light transmission amount at a wavelength of 500 nm was 14%.
- the compression specific strength was 2.0, indicating good strength characteristics.
- Bottle molding was performed in the same manner as in Experimental Example 1 except that the nitrogen gas supplied from the heating cylinder of the injection molding machine was 0.50% by weight.
- the nitrogen gas remaining in the preform before blowing was 0.28 wt%, and the body surface temperature of the preform heated by the infrared heater was 117 ° C.
- the obtained bottle had a non-foamed mouth portion, and bubbles were dispersed throughout the bottle body.
- the surface roughness (Ra) of the bottle was 1.9 ⁇ m, and the expansion ratio of the bottle body was 1.29 times.
- Bottle molding was performed in the same manner as in Experimental Example 2 except that the storage time of the preform obtained by injection molding was 24 hours.
- the nitrogen gas remaining in the preform before blowing was 0.09 wt%, and the body surface temperature of the preform heated by the infrared heater was 115 ° C.
- the obtained bottle maintained a non-foamed state at the mouth, and air bubbles were dispersed throughout the bottle body.
- the surface roughness (Ra) of the bottle was 0.39 ⁇ m, and the expansion ratio of the bottle body was 1.19 times. From the bottle body section SEM image, the cells were arranged almost independently, and 10 or more cell clusters were not observed.
- the outer skin layer thickness was 75 ⁇ m, the total light transmission amount at a wavelength of 500 nm was 30%, and the compression specific strength was 1.2.
- Bottle molding was carried out in the same manner as in Experimental Example 1 except that the nitrogen gas supplied from the heating cylinder of the injection molding machine was 0.30% by weight and the storage time of the preform was 4 hours.
- the nitrogen gas remaining in the preform before blowing was 0.19 wt%, and the body surface temperature of the preform heated by the infrared heater was 117 ° C.
- the obtained bottle maintained a non-foamed state at the mouth, and air bubbles were dispersed throughout the bottle body.
- the surface roughness (Ra) of the bottle was 2.3 ⁇ m, and the expansion ratio of the bottle body was 1.6 times.
- the thickness of the outer skin layer was 80 ⁇ m, and the total light transmittance at a wavelength of 500 nm was 25%.
- the preform body except the mouth was heated and foamed by an infrared heater, and immediately blow-molded.
- an infrared heater In order to mold without rupturing the bottle, when the temperature of the preform is heated up to 128 ° C on the surface of the body, it becomes coarser to 1 mm or more so that bubbles in the skin layer can be blown, and a foamed bottle with a good appearance is obtained. I could not.
- the resin In order to suppress foaming of the skin layer, when the body surface temperature of the preform is lowered to 120 ° C., the resin is insufficiently softened and cannot be molded into a bottle shape. No foaming bottle could be obtained.
- the preform body except the mouth was heated and foamed with an infrared heater and immediately blow-molded to obtain a foaming bottle having an internal volume of about 400 ml.
- the heating temperature of the preform was 113 ° C. on the body surface.
- the obtained bottle maintained a non-foamed mouth portion, and air bubbles were dispersed throughout the bottle body.
- the bottle surface maintained smoothness, the surface roughness (Ra) was 4.4 ⁇ m, and the foaming ratio of the bottle body was 1.14 times.
- the melting start temperature, maximum strength peak temperature, and melting end temperature in DSC measurement of this olefin resin were 113 ° C., 147 ° C., and 157 ° C., respectively, and the melting peak width (Tf—Ti) was 44 ° C.
- the weight reduction rate of the obtained preform was 0%.
- the preform body portion except the mouth portion was heated and foamed by an infrared heater and immediately blow-molded to obtain a foaming bottle having an internal volume of about 400 ml.
- the heating temperature of the preform was 120 ° C. on the body surface.
- the obtained bottle maintained a non-foamed mouth portion, and air bubbles were dispersed throughout the bottle body.
- the bottle surface maintained smoothness, the surface roughness (Ra) was 7.3 ⁇ m, and the expansion ratio of the bottle body was 1.20 times.
- the preform body except the mouth was heated and foamed by an infrared heater, and foamed bottle molding was attempted.
- the temperature of the preform was 135 on the body surface. When heated to 0 ° C., it became coarser to 1 mm or more so that bubbles in the skin layer could be repelled, and a foam bottle with a good appearance could not be obtained.
- the resin is insufficiently softened and cannot be molded into a bottle shape, and the heating conditions are adjusted. As a result, a good foaming bottle could not be obtained.
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Abstract
Description
また、特許文献7には、不活性ガスを用いての物理発泡によるポリプロピレンの射出発泡成形体が開示されているが、延伸成形に関しては何ら検討されていない。
本発明の他の目的は、容器、特にボトルの形態を有するプロピレン系樹脂の単層構造体からなる発泡延伸成形体を提供することにある。
(1)延伸方向に沿った断面で見て、前記発泡セルが10以上の数で延伸方向に連なったセルクラスタを形成していること、
(2)前記オレフィン系樹脂が1~80g/10分のMFR(230℃)を有していること、
(3)前記オレフィン系樹脂が、下記条件(A)及び(B):
(A)ランダムポリプロピレンを70重量%以上含んでいること、
(B)DSC測定で得られる溶融曲線において、最高強度ピーク温度が1
50℃未満であって、最高強度ピークを含む溶融ピークの溶融開始温度
(Ti)と溶融終了温度(Tf)との差(Ti-Tf)が50℃以上であ
ること、
を満足していること、
が好ましい。
さらに、この発泡延伸成形体は、
(4)1.5倍以下の発泡倍率を有しており、且つ可視光での光線透過率が25%以下の遮光性を示すこと、
(5)容器の形態を有していること、
が好適である。
尚、セルクラスタとは、発泡セルがブドウの房状に互いに密接した集合体を意味し、セルクラスタ内での発泡セル同士は、その内部空間が互いに連通しているものもある。このような集合体の形で存在しているセルクラスタは、全体独立した一個の気泡として存在しているクローズドタイプのセルと異なっている。
オレフィン系樹脂に不活性ガスが含浸された樹脂溶融物を調製し;
前記樹脂溶融物を、発泡が生じないように、射出金型内に射出充填して射出成形を行い;
成形された未発泡プリフォームを前記射出金型内から取り出し;
得られた未発泡プリフォームの表面から不活性ガスを放出し;
前記未発泡プリフォームを加熱して発泡させ;
次いで、該発泡プリフォームを延伸成形すること;
を経て製造される。
このようなセルクラスタは、オレフィン系樹脂の物理発泡に特有のものであり、ポリエステル樹脂の物理発泡では形成することができない。
しかも、このようなセルクラスタの形成は、低発泡倍率での遮光性の向上に有利であり、例えば1.5倍以下の発泡倍率でも、高い遮光性が得られ、可視光での光線透過率は25%以下である。さらに、容器等の延伸成形体に剛性を付与することができ、1.5倍以下の発泡倍率で曲げ強度は1.5倍以上に向上する。
尚、発泡倍率とは、発泡セルが分布している領域において、発泡時の容積と未発泡時の容積との比率(発泡時容積/未発泡時容積)である。
一般に、発泡セル(気泡)の生成は溶融状態の樹脂に発泡ガスを含浸させ、成形機内を高圧に保ち、これをダイから押し出す際に大気圧に解放することによって行われる押出発泡に代表されるように、溶融樹脂の圧力解放によってなされる。一方で、本発明者らは、特許文献1に示すように、発泡ガスが含浸されている樹脂を非発泡のまま冷却固化し、加熱しながら発泡させることで発泡セルを微細化できることを報告している。
ポリプロピレン等のオレフィン系樹脂では、結晶の溶融開始温度(Ti)以上に加熱されることにより樹脂が軟化し、球形状の気泡が成長する。しかしながら、オレフィン系樹脂はポリエステル系樹脂に比べ非常に高いガス拡散速度を有しており、さらにポリエステル系樹脂のような延伸硬化が作用しない。このため、ガスが含浸されているオレフィン系樹脂を加熱すると、発泡セル内のガス圧の高まりにより短時間で気泡が大きく成長していくこととなる。ポリエステルのように気泡の成長を抑制する要素がないからである。
即ち、本発明では、共押出等による積層構造を採用せず、オレフィン系樹脂の単層構造を有する発泡延伸成形体について、発泡による外観不良を回避するために、発泡に際しての発泡セル(気泡)の粗大化を抑制することが必須不可欠となる。
従って、発泡条件を適宜コントロールすることにより、セルの粗大化を回避すると同時に、セルクラスタの割合を多くしたり、或いはクローズドセルを主体とし、セルクラスタがほとんど生成していないような発泡構造を形成することが可能となる。
図4のフローチャートを参照して、本発明の発泡延伸成形体は、先ずオレフィン系樹脂に不活性ガスを含浸させ、次いで不活性ガスが含浸されたオレフィン系樹脂溶融物を用いての射出成形により、発泡剤である不活性ガスは含浸されているが未発泡のプリフォームを得、この未発泡プリフォームの表面から所定量のガスを放出し、次いで所定温度に加熱することにより発泡を行い、得られた発泡プリフォームを延伸成形することにより製造される。
かかる発泡プリフォーム50において、口部51は、延伸されない部分であり、キャップと螺子係合する螺子部51a及び搬送等のためのサポートリング51bが形成されている(成形される容器のタイプによってはサポートリング51bが無いものもある)。従って、このような発泡プリフォーム50をブロー成形して得られるボトル60は、プリフォーム50の口部に対応する口部61、プリフォームの成形部53に対応する胴部63を有しており、胴部63の端部は閉じられて底部65を形成している。また、口部61は、プリフォーム50の口部51と同様、螺子部51a及びサポートリング51b螺子部を有している。
従って、上記の発泡プリフォーム50においては、成形部53が発泡領域となっており、その内部には発泡セル(気泡)が分布しており、口部51は、非発泡領域となっており、その内部には、発泡セルは存在していない。また、ボトル60においては、胴部63(底部65を含む)が発泡領域となっており、その内部には、発泡セルが延伸方向に引き伸ばされ或いは延伸方向に連なった発泡セルが分布しており、口部61は、非発泡領域となっており、その内部には、発泡セルは存在していないこととなる。
本発明において、容器の製造に用いる樹脂としては、オレフィン系樹脂が用いられる。オレフィン系樹脂は、他の樹脂、例えばポリエステル系樹脂に比べ非常に高いガス拡散速度を有しており、さらにポリエステル系樹脂のような延伸硬化が作用しないため、ガスが含浸されているオレフィン系樹脂を加熱すると、発泡セル内のガス圧の高まりにより短時間で気泡が大きく成長するという性質を有していることは、先にも述べたとおりである。
(A)ランダムポリプロピレンを70重量%以上、好ましくは80重
量%以上含んでいること。
(B)DSC測定で得られる溶融曲線において、最高強度ピーク温度
(Tm)が150℃未満、特に145℃以下であり、最高強度ピーク
を含む溶融ピークの溶融開始温度(Ti)と溶融終了温度(Tf)と
の差(Ti-Tf)が50℃以上、特に60℃以上であること。
また延伸成形においても、結晶性の高いポリプロピレンは成形性が悪くなる。即ち、結晶サイズが大きく、結晶溶融温度の揃ったポリプロピレンを用いると、非晶状態の樹脂の割合が少なく、結晶粒界でのグレイズの生成が顕著となり、結晶粒界からの破断が生じ易くなってしまう。
従って、発泡セルの粗大化を防止するという観点から、上記の割合でランダムポリプロピレンを含有していることが好ましいわけである。尚、ランダムポリプロピレン含量が上述した範囲内にあり且つ他の条件を満足しているのであれば、他のオレフィン系樹脂、例えばホモポリプロピレンや、プロピレンと他のα-オレフィンもしくは環状オレフィンとのブロック共重合体、ポリエチレンなどがブレンドされているものも好適に使用することができる。
本発明においては、上記のオレフィン系樹脂の溶融物に、発泡剤である不活性ガスを含浸させるわけであるが、このような不活性ガスとしては、用いるオレフィン系樹脂に対して反応を示さず、且つ環境等に悪影響を与えないものであれば、特に制限されず、任意の不活性ガスを使用することができる。一般的には、入手の容易さ、環境への影響、安全性、コスト等の観点から、窒素ガスや炭酸ガスなどが使用される。
この方法によれば、射出成形機中でガスの含浸を行うことができ、延伸成形に供するプリフォームを成形する過程で効率よく不活性ガスを含浸させることができる。この場合、オレフィン系樹脂溶融物の温度やガス圧力は、所望の個数の発泡セル(気泡)が形成されるに十分な量のガスが溶解するように設定される。例えば、この温度が高いほど、ガスの溶解量は少ないが含浸速度は速く、温度が低いほどガスの溶解量は多いが、含浸には時間がかかることとなり、また、ガス圧が高いほど、ガス溶解量は多くなり、従って、発泡セルの個数も多くなる。
本発明においては、延伸成形体の前駆体であるプリフォームを、上述した不活性ガスが含浸されたプロピレン系樹脂の溶融物を用いて成形する。このプリフォームの形状は、目的とする延伸成形の形態に応じて、試験管形状であったり(ブロー成形によりボトルを製造する場合)、或いはシート状であったりする(プラグアシスト成形によりカップ状容器を製造する場合)。
尚、保圧をしながらの射出充填は、所定量の樹脂溶融物を成形型のキャビティ内に射出した後、熱収縮や樹脂の結晶化によって体積が収縮する分をさらに射出を継続して補填するというものであり、これにより、成形金型内の樹脂溶融物が加圧され、発泡を有効に抑制することができるわけである。
一方、金型キャビティ内を樹脂溶融物が流れているときの発泡は、保圧では防止することができない。例えば、大気圧に保持されている金型内にガス含浸樹脂溶融物を充填していくと、金型内を流れていく樹脂溶融物の先端部分において、樹脂溶融物内に含浸されているガスが金型内空間との圧力差のために膨張し、破泡を生じる。即ち、樹脂溶融物は、先端部が破泡した状態で金型内を流れていくため、この状態が金型表面に転写され、金型表面での冷却固化により、この破泡が成形体であるプリフォーム表面に固定されてしまい、これは、一般にスワールマークと呼ばれている。このようなスワールマークは、後述する延伸成形により得られる成形体の表面に、表面荒れとなって反映されてしまう。
しかるに、このようなスワールマークの発生は、加圧状態に保持された金型内にガス含浸樹脂溶融物を射出することにより、有効に防止される。金型内での樹脂溶融物の流動中の破泡が金型内圧力によって有効に抑制されるからである。
このようなキャビティ27が成形されるプリフォームの形状に対応しており、図に示す例では、図5に示されている容器用のプリフォーム50に対応している。
軽量化率=[(M0-M1)/M0]×100
式中、M0は、不活性ガスを含浸させずにヒケ等の成形不良がないように
条件設定して射出することにより得られたプリフォームの重量を示し、
M1は、不活性ガスを含浸させて得られたガス含浸プリフォームの
重量を示す。
即ち、保圧圧力を大きくするほど軽量化率は低下し、また、保圧時間を長くするほど、軽量化率は低くなる。本発明において、最も好適には軽量化率が0%となるように、保圧条件を設定するのがよい。
本発明においては、上記のようにして作製された不活性ガスを含浸しているが未発泡のプリフォームをキャビティ27から取り出し、これを発泡せしめるが、この発泡に先立って、該プリフォームに含浸されているガスの一部を、その表面から放出させる。このようなガスの放出により、表面に発泡セルの存在していない表皮層を形成させることができる。しかも、ガスの放出により、プリフォームの厚み中心部分はガス濃度が高く、表面に近い部分はガス濃度が低いという濃度分布が形成される。即ち、ガス濃度の最も高いプリフォーム厚み中心部分は、気泡核生成温度が低く、セルクラスタの発生要因であるクレイズが形成し、ガス濃度の低いプリフォーム表面近傍部分は、気泡核生成温度が高く、気泡核は球状に成長し、後述する延伸により偏平したクローズドセルとなる球状の発泡セルが生成し、ガスが存在していない表面部分は、気泡核が生成せず、非発泡の表皮層となる。
上記のようなガスの放出により、表面にガスが存在していない表皮層が形成されたプリフォームは、発泡工程に供される。
この発泡工程では、上記の非発泡プリフォームを、オイルバスや赤外線ヒータなどを用いて加熱することにより発泡が行われる。また、プリフォームが試験管状のように、中空形状を有している場合には、例えば、内部に鉄心などを挿入しての高周波加熱を利用してプリフォームの内部から発泡のための加熱を行うことができる。
また、図5に示されているような容器プリフォーム50の場合には、口部51を非発泡とするために、成形部53を選択的に加熱することとなる。勿論、成形部53の一部を選択的に加熱して成形部53の一部を発泡領域とすることも可能である。
例えば、非発泡のプリフォーム表皮層の厚みは、少なくとも5μm以上、特に10μm以上となるように、加熱発泡までの時間や加熱発泡時間を調整することが好適である。即ち、プリフォーム表皮層の厚みをこのような範囲に設定しておくことにより、本発明の発泡延伸成形体の非発泡表皮層の厚みが適当な範囲となるように設定することができる。
例えば、クレイズを多く生成させ、セルクラスタを主体とする発泡構造を得るためには、該オレフィン系樹脂の結晶融解開始温度よりも低い温度とし(結晶構造が維持されている状態で気泡核を生成させる)、この状態で後述する延伸工程を実施する。一方、クローズドセルを主体とする発泡構造を得るためには、結晶融解開始温度以上とし(結晶構造が崩壊した状態で気泡核を生成せしめる)、球形状の発泡セルを多く生成させ、この状態で後述する延伸工程を実施する。
尚、上記のような発泡倍率での発泡プリフォームでは、球形状の発泡セルの平均径(円相当径)は、5~200μm程度とし、球形状発泡セルのセル密度は104~1010cells/cm3程度とすることができる。
本発明では、加熱により軟化し、球状発泡セル或いはクレイズが形成された発泡プリフォームを延伸成形工程に供することにより目的とする発泡延伸成形体(例えば、前述したボトル60)を得ることができる。この場合、加熱により発泡させたプリフォームをそのまま延伸成形工程に供することにより目的とする発泡延伸成形体を得ることが好ましい。即ち、発泡させるために加えた熱を用いてそのまま延伸成形することにより、工程を増やさずに発泡延伸成形体を得ることができ、コスト面で有利となる。
このように、条件(A)及び(B)を満足するオレフィン系樹脂を使用することにより、前述の発泡温度に加熱したプリフォームをそのまま延伸成形することができ、これは生産性の点で極めて有利である。
y<-33x+132
式中、xは、残存ガス濃度(重量%)である、
を満足していることが好ましい。即ち、延伸成形温度yが高く、上記の条件を満足していない場合には、延伸により、得られる延伸成形体の外観が損なわれてしまう傾向がある。
また、前述した加熱発泡温度により、セルクラスタの生成量を調整することができることは先に述べたとおりであり、例えば、加熱発泡温度が低いほどセルクラスタの生成割合が多く、加熱発泡温度が結晶融解開始温度より低くなるほど、セルクラスタを主体とし、偏平形状のクローズドセルをかなり少なくすることができ、逆に、加熱発泡温度が結晶融解開始温度より高くなるほど、セルクラスタの生成量を抑制できる。
このようにして得られる発泡延伸成形体(例えば図5のボトル60)においては、前述した発泡プリフォームの発泡倍率に応じて、その発泡倍率は、1.01~2.0倍、特に1.01~1.5倍、さらには1.05~1.5倍程度の範囲となる。この発泡倍率が大きすぎると、発泡セルの粗大化による外観特性の低下を回避することができず、また、発泡倍率が小さすぎると、発泡による利点が損なわれてしまうこととなる。
さらに、セルクラスタが多く生成している発泡構造は、剛性の向上にも寄与し、例えばボトルの胴部では、発泡倍率が1.5倍以下でも曲げ強度を1.5倍以上に高め、1500Pa以上とすることができる。
尚、以下の実験で行った各種の測定は、以下の方法で行った。
測定装置としてPerkinElmer製Diamond DSCを使用し、樹脂ペレットを用いて昇温速度10℃/minの条件で測定した。
表面粗さ;
粗さ測定計としてサーフコム2000SD3(東京精密製)を用い、JIS B-0601-1994に準拠して行った。
ボトルの剛性;
剛性は、圧縮比強度により評価した。
圧縮比強度とは、同重量、同型状の非発泡ボトル圧縮強度に対する発泡ボトルの圧縮強度の比である。
ボトル胴部の円筒部中央を万能試験機を用いて圧縮し、1mm押し込んだ際の荷重を測定して計算した。
オレフィン系樹脂として、ランダムポリプロピレンJ246M(プライムポリマー製、MFR=30)を用意した。
上記のランダムポリプロピレン(MFR=30)を射出成形機に供給し、加熱筒の途中から窒素ガスを0.40重量%供給してランダムポリプロピレンと混練して溶解させた。
この樹脂溶融物を、カウンタープレッシャー装置にて5MPaに昇圧されている金型内に射出し、発泡しないよう保圧の程度を調整(保圧力60MPa、射出保圧時間19秒)して冷却固化した。
この結果、重量12.3gのガスは含浸しているが実質非発泡状態の試験管形状の容器用プリフォームを得た。
得られたプリフォームは、発泡ガスを添加しない場合と比べると軽量化率は0%であった。
また、用いたランダムポリプロピレンのDSC曲線は、図8に示すとおりであり、測定における溶融開始温度、最高強度ピーク温度、溶融終了温度はそれぞれ94℃、140℃、163℃であり、溶融ピーク幅(Tf-Ti)は61℃であった。
このプリフォームについて、口部を除くプリフォーム胴部を赤外線ヒータによりプリフォームの胴部表面温度で115℃となるように加熱を調整し発泡させ、ただちにブロー成形した。この結果、内容量が約400ml、ハイト195mm(円筒部135mm)、最大直径(円筒部)60mmの円筒形発泡ボトルを得た。
得られたボトルは口部が非発泡状態を維持しており、ボトル胴部全体に気泡が分散していた。ボトルの表面は平滑性を維持しており、表面粗さ(Ra)は1.7μm、ボトル胴部の発泡倍率は1.25倍であった。
また、ボトル胴部断面をSEMを用いて観察した結果を図3に示す。ボトル胴部断面には角柱状などのセルが集合したセルクラスタが周方向に横断的に形成されており、セルクラスタと同時に偏平状のクローズドセルが表層部側に生成していることが判る。画像から見積もられる延伸方向に沿ったセルクラスタでの発泡セルの連なりは100以上であり、外面側の表皮層厚みは70μmであり、波長500nmにおける全光線透過量は14%であった。圧縮比強度は2.0であり、良好な強度特性を示した。
射出成形機の加熱筒から供給する窒素ガスを0.50重量%とする以外は、実験例1と同様にボトル成形を行った。
ブロー前のプリフォームに残存していた窒素ガスは0.28重量%であり、赤外線ヒータにより熱せられたプリフォームの胴部表面温度は117℃であった。
また、得られたボトルは、口部が非発泡状態を維持しており、ボトル胴部全体に気泡が分散していた。ボトルの表面粗さ(Ra)は1.9μm、ボトル胴部の発泡倍率は1.29倍であった。
ボトル胴部断面SEM像から、角柱状などのセルが集合したセルクラスタが周方向に横断的に形成されており、同時に偏平状のクローズドセルが表層部側に生成していることが認められた。画像から見積もられる延伸方向に沿ったクラスタセルでの発泡セルの連なりは100以上であり、外面側の表皮層厚みは12μmであり、波長500nmにおける全光線透過量は12%であった。圧縮比強度は2.0であり、良好な強度特性を示した。
射出成形で得たプリフォームの保管時間を24時間とした以外は、実験例2と同様にボトル成形を行った。
ブロー前のプリフォームに残存していた窒素ガスは0.09重量%であり、赤外線ヒータにより熱せられたプリフォームの胴部表面温度は115℃であった。得られたボトルは、口部が非発泡状態を維持しており、ボトル胴部全体に気泡が分散していた。ボトルの表面粗さ(Ra)は0.39μm、ボトル胴部の発泡倍率は1.19倍であった。
ボトル胴部断面SEM像から、セルはほぼ独立して配されており、10以上の連なりとなるセルクラスタは観察されなかった。外面側の表皮層厚みは75μmであり、波長500nmにおける全光線透過量は30%、圧縮比強度は1.2であった。
射出成形機の加熱筒から供給する窒素ガスを0.30重量%、プリフォームの保管時間を4時間とした以外は、実験例1と同様にボトル成形を行った。
ブロー前のプリフォームに残存していた窒素ガスは0.19重量%であり、赤外線ヒータにより熱せられたプリフォームの胴部表面温度は117℃であった。
得られたボトルは、口部が非発泡状態を維持しており、ボトル胴部全体に気泡が分散していた。ボトルの表面粗さ(Ra)は2.3μm、ボトル胴部の発泡倍率は1.6倍であった。
ボトル胴部断面SEM像から、粗大なセルはほぼ独立して配されており、発泡セルの10以上の連なりとなるセルクラスタは観察されなかった。外面側の表皮層厚みは80μmであり、波長500nmにおける全光線透過量は25%であった。
射出成形機の加熱筒から供給する窒素ガスを1.1重量%、プリフォームの保管時間を10時間とした以外は、実験例1と同様にボトル成形を行った。
ブロー前のプリフォームに残存していた窒素ガスは0.41重量%であり、赤外線ヒータにより熱せられたプリフォームの胴部表面温度は112℃であった。
得られたボトルは、口部が非発泡状態を維持しており、ボトル胴部全体に気泡が分散していた。ボトルの表面粗さ(Ra)は0.35μm、ボトル胴部の発泡倍率は1.26倍であった。
ボトル胴部断面SEM像を図9に示す。図9から、発泡セルの10以上の連なりとなるセルクラスタが多数観察された。
外面側の表皮層厚みは40μmであり、波長500nmにおける全光線透過量は8%であった。
実験例1で用いたランダムポリプロピレンを射出成形機に供給し、加熱筒の途中から窒素ガスを供給し、このランダムポリプロピレンと混練して溶解させ、該ポリプロピレンの溶融物を、カウンタープレッシャー装置にて5MPaに昇圧された金型内に射出し、厚み1.5mmのプレートを得た。
このプレートを、ただちに予め加熱してあるホットプレートに挟み込み、15秒加熱して発泡が始まる温度および発泡セルの形状を観察した。窒素ガスの供給量を変えて試験した結果を表1に示す。窒素ガス量を増やすと、発泡温度が低下し、樹脂の溶融開始温度(94℃)を境に、セルの形状が球状からクレイズに変化する様子が観察された。
オレフィン系樹脂を、ポリプロピレンMG03B(日本ポリプロ製、MFR=30)に変えた以外は実験例1と同様にプリフォーム成形を行った。
このオレフィン系樹脂のDSC測定は、図8に示す通りであり、溶融開始温度、最高強度ピーク温度、溶融終了温度はそれぞれ113℃、152℃、161℃であり、溶融ピーク幅(Tf-Ti)は48℃であった。
また、得られたプリフォームの軽量化率は0%であった。
オレフィン系樹脂を、ポリプロピレンPM940M(サンアロマー製、MFR=30)に変えた以外は実験例1と同様にプリフォーム成形を行った。
このオレフィン系樹脂のDSC測定における溶融開始温度、最高強度ピーク温度、溶融終了温度はそれぞれ45℃、131℃、154℃であり、溶融ピーク幅(Tf-Ti)は109℃であった。
また、得られたプリフォームの軽量化率は0%であった。
得られたボトルは口部が非発泡状態を維持しており、ボトル胴部全体に気泡が分散していた。ボトルの表面は平滑性を維持し、表面粗さ(Ra)は4.4μm、ボトル胴部の発泡倍率は1.14倍であった。
オレフィン系樹脂を、ポリオレフィンJ-71GR(プライムポリマー製、MFR=11)に変え、射出保圧力を70MPaとした以外は実験例1と同様にプリフォーム成形を行った。
このオレフィン系樹脂のDSC測定における溶融開始温度、最高強度ピーク温度、溶融終了温度はそれぞれ113℃、147℃、157℃であり、溶融ピーク幅(Tf-Ti)は44℃であった。
得られたプリフォームの軽量化率は0%であった。
ボトルの表面は平滑性を維持し、表面荒さ(Ra)は9.0μm、ボトル胴部の発泡倍率は1.27倍であった。
オレフィン系樹脂を、ポリプロピレンB241(プライムポリマー製、MFR=0.5)に変え、実験例1と同様に加熱筒の途中から窒素ガスを0.40重量%供給し、射出成形を行ったところ、保圧力を100MPa、射出保圧時間22秒としてもプリフォーム中の発泡を抑えることができず、得られたプリフォームの軽量化率は4%であり、プリフォームの胴部全体が白化しており、次ぐブロー工程に用いることはできなかった。
オレフィン系樹脂を、ポリプロピレンPM20V(サンアロマー製、MFR=45)に変え、射出保圧力を70MPaとした以外は実験例1と同様にプリフォーム成形を行った。
このポリプロピレンのDSC測定における溶融開始温度、最高強度ピーク温度、溶融終了温度はそれぞれ90℃、146℃、159℃であり、溶融ピーク幅(Tf-Ti)は69℃であった。
得られたプリフォームの軽量化率は0%であった。
得られたボトルは口部が非発泡状態を維持しており、ボトル胴部全体に気泡が分散していた。ボトルの表面は平滑性を維持し、表面荒さ(Ra)は7.1μm、ボトル胴部の発泡倍率は1.21倍であった。
ランダムポリプロピレンJ246M(プライムポリマー製、MFR=30)80重量部に対し、ホモポリプロピレンPM900A(サンアロマー製、MFR=30)20重量部をドライブレンドした。
このポリプロピレンブレンド物をオレフィン系樹脂として用いた以外は実験例1と同様にプリフォーム成形を行った。
このブレンド物のDSC測定における溶融開始温度、最高強度ピーク温度、溶融終了温度はそれぞれ94℃、141℃、174℃であり、溶融ピーク幅(Tf-Ti)は71℃であり、MFR(230℃)は30であった。
得られたプリフォームの軽量化率は0%であった。
得られたボトルは口部が非発泡状態を維持しており、ボトル胴部全体に気泡が分散していた。ボトルの表面は平滑性を維持し、表面粗さ(Ra)は7.3μm、ボトル胴部の発泡倍率は1.20倍であった。
ランダムポリプロピレンJ246M(プライムポリマー製、MFR=30)50重量部に対しホモポリプロピレンPM900A(サンアロマー製、MFR=30)50重量部をドライブレンドした。
このポリプロピレンブレンド物を用いた以外は実験例1と同様にプリフォーム成形を行った。
このブレンド物のDSC測定における溶融開始温度、最高強度ピーク温度、溶融終了温度はそれぞれ94℃、165℃、174℃であり、溶融ピーク幅(Tf-Ti)は71℃であり、MFR(230℃)は30であった。
得られたプリフォームの軽量化率は0%であった。
また、表皮層の発泡を抑制するために、プリフォームの胴部表面温度を135℃以下で延伸すると、樹脂の軟化が不足しボトル形状に賦型することが不可能であり、加熱条件の調整によって良好な発泡ボトルを得ることはできなかった。
ランダムポリプロピレンJ246M(プライムポリマー製、MFR=30)を用い、供給する窒素ガス量を0.80重量%とする以外は実験例1と同様にプリフォーム成形を行った。
得られたプリフォームの軽量化率は0%であった。得られたプリフォームを25℃の室内で保管し、プリフォームの重量測定から含有させた窒素ガスの残存量を測定し、さらに加熱により表皮が著しく発泡を開始する際の表面温度の関係を調べた結果を表2および図10に示す。
この結果より、図10の点線部より下となる条件で延伸することにより、良好な外観の発泡ボトルを得ることができる。
60:ボトル
Claims (9)
- オレフィン系樹脂の単層構造体から形成されており且つ発泡倍率が1.01~2.0倍の物理発泡による発泡延伸成形品であって、発泡セルが内部に分布している領域での表面粗さRa(JIS-B-0601-1994)が10μm以下であることを特徴とするオレフィン系樹脂製発泡延伸成形体。
- 延伸方向に沿った断面で見て、前記発泡セルが10以上の数で延伸方向に連なったセルクラスタを形成している請求項1に記載の発泡延伸成形体。
- 前記オレフィン系樹脂が、1~80g/10分のMFR(230℃)を有している請求項1に記載の発泡延伸成形体。
- 前記オレフィン系樹脂が、下記条件(A)及び(B):
(A)ランダムポリプロピレンを70重量%以上含んでいること、
(B)DSC測定で得られる溶融曲線において、最高強度ピーク温
度が150℃未満であって、最高強度ピークを含む溶融ピークの溶
融開始温度(Ti)と溶融終了温度(Tf)との差(Ti-Tf)
が50℃以上であること、
を満足している請求項3に記載の発泡延伸成形体。 - 1.5倍以下の発泡倍率を有しており、且つ可視光での光線透過率が25%以下の遮光性を示す請求項1に記載の発泡延伸成形体。
- 容器の形態を有している請求項1に記載の発泡延伸成形体。
- オレフィン系樹脂に不活性ガスが含浸された樹脂溶融物を調製し;
前記樹脂溶融物を、発泡が生じないように保圧をかけながら射出金型内に射出充填して射出成形を行い;
成形された未発泡プリフォームを前記射出金型内から取り出し;
得られた未発泡プリフォームの表面から不活性ガスを放出し;
前記未発泡プリフォームを加熱して発泡させ;
次いで、該発泡プリフォームを延伸成形すること;
を特徴とする発泡延伸成形体の製造方法。 - 前記オレフィン系樹脂として、MFR(230℃)が1~80g/10分の範囲にあるものを使用する請求項7に記載の製造方法。
- 前記オレフィン系樹脂として、下記条件(A)及び(B):
(A)ランダムポリプロピレンを70重量%以上含んでいるこ
と、
(B)DSC測定で得られる溶融曲線において、最高強度ピー
ク温度(Tm)が150℃未満であり、最高強度ピークを含む
溶融ピークの溶融開始温度(Ti)と溶融終了温度(Tf)と
の差(Ti-Tf)が50℃以上であること、
を満足するものを使用する請求項8に記載の製造方法。
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EP13849236.8A EP2910598B1 (en) | 2012-10-22 | 2013-10-18 | Olefin resin foam stretch molded body |
CA2887993A CA2887993C (en) | 2012-10-22 | 2013-10-18 | Foamed stretch-formed polyolefin resin body |
KR1020157012268A KR101731417B1 (ko) | 2012-10-22 | 2013-10-18 | 올레핀계 수지제 발포 연신 성형체 |
CN201380055212.3A CN104755541B (zh) | 2012-10-22 | 2013-10-18 | 烯烃系树脂制发泡拉伸成形体 |
US14/433,812 US20150267019A1 (en) | 2012-10-22 | 2013-10-18 | Foamed stretch- formed polyolefin resin body |
MX2015005011A MX362971B (es) | 2012-10-22 | 2013-10-18 | Cuerpo de resina espumada de poliolefina, formado por estiramiento. |
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JP2012-232739 | 2012-10-22 | ||
JP2013-008668 | 2013-01-21 | ||
JP2013008668A JP5971131B2 (ja) | 2013-01-21 | 2013-01-21 | ポリオレフィン樹脂製発泡延伸容器 |
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JP2014132073A (ja) * | 2012-12-07 | 2014-07-17 | Japan Polypropylene Corp | 繊維強化ポリプロピレン系樹脂組成物及びその成形体 |
JP2016078292A (ja) * | 2014-10-15 | 2016-05-16 | 株式会社ジェイエスピー | 表皮材被覆発泡粒子成形体 |
JP2016083816A (ja) * | 2014-10-24 | 2016-05-19 | 株式会社吉野工業所 | ポリプロピレン製プリフォーム |
CN114196099A (zh) * | 2022-02-18 | 2022-03-18 | 苏州贝斯珂胶粘科技有限公司 | 一种聚烯烃系树脂发泡片材及其制备方法 |
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CN110167738B (zh) * | 2016-12-28 | 2022-06-14 | 坂东化学株式会社 | 食品用容器的制造方法 |
JP7132487B2 (ja) * | 2018-03-29 | 2022-09-07 | キョーラク株式会社 | 発泡成形体の製造方法 |
US20230365772A1 (en) * | 2020-09-30 | 2023-11-16 | Basf Se | A process for the production of a moulded article |
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Cited By (8)
Publication number | Priority date | Publication date | Assignee | Title |
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JP2014132073A (ja) * | 2012-12-07 | 2014-07-17 | Japan Polypropylene Corp | 繊維強化ポリプロピレン系樹脂組成物及びその成形体 |
JP2016078292A (ja) * | 2014-10-15 | 2016-05-16 | 株式会社ジェイエスピー | 表皮材被覆発泡粒子成形体 |
JP2016083816A (ja) * | 2014-10-24 | 2016-05-19 | 株式会社吉野工業所 | ポリプロピレン製プリフォーム |
CN107000303A (zh) * | 2014-10-24 | 2017-08-01 | 帝斯克玛股份有限公司 | 聚丙烯预制件 |
EP3210751A4 (en) * | 2014-10-24 | 2018-03-07 | Discma AG | Polypropylene preform |
CN114407228A (zh) * | 2014-10-24 | 2022-04-29 | 帝斯克玛股份有限公司 | 聚丙烯预制件 |
CN114932673A (zh) * | 2014-10-24 | 2022-08-23 | 帝斯克玛股份有限公司 | 聚丙烯预制件 |
CN114196099A (zh) * | 2022-02-18 | 2022-03-18 | 苏州贝斯珂胶粘科技有限公司 | 一种聚烯烃系树脂发泡片材及其制备方法 |
Also Published As
Publication number | Publication date |
---|---|
KR101731417B1 (ko) | 2017-04-28 |
MX2015005011A (es) | 2015-07-17 |
EP2910598A1 (en) | 2015-08-26 |
EP2910598A4 (en) | 2016-05-25 |
CA2887993C (en) | 2017-01-03 |
CN104755541B (zh) | 2017-07-18 |
EP2910598B1 (en) | 2021-03-10 |
CN104755541A (zh) | 2015-07-01 |
CA2887993A1 (en) | 2014-05-01 |
MX362971B (es) | 2019-02-28 |
US20150267019A1 (en) | 2015-09-24 |
KR20150070259A (ko) | 2015-06-24 |
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