JP2006104422A - Polypropylene-based resin foamed sheet or polypropylene-based resin laminated foamed sheet and molded product of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polypropylene-based resin foamed sheet or a polypropylene-based resin laminated foamed sheet which can be molded with little drawdown and excellent elongation and can be molded into partitioned containers, deep containers and containers each having a periodical pattern, and also to provide molded products prepared from the same. <P>SOLUTION: The polypropylene-based resin laminated foamed sheet and the polypropylene-based laminated foamed sheet having the above characteristics is prepared by setting heat shrinkage rates to 0-5.0% in the both winding and width directions of the polypropylene-based resin foamed sheet kept for 1 minute in the atmosphere of 190°C. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a polypropylene resin foam sheet or a polypropylene resin laminate foam sheet, and a molded body thereof.

  Foamed sheets made of thermoplastic resins are generally lightweight, have good heat insulation and buffering properties against external stress, and can be easily obtained by heat secondary molding such as vacuum molding. It is widely used in applications such as cushioning materials, food containers, heat insulating materials, and automotive parts, mainly based on polyethylene resins and polyethylene resins.

  Among them, a foam sheet using a polypropylene resin as a base resin is superior in heat resistance and oil resistance compared to a conventional polystyrene resin foam sheet due to the characteristics of the base resin, and has attracted attention in recent years. Collecting.

  On the other hand, polypropylene resins with excellent heat resistance and oil resistance have been considered difficult to obtain extruded foam sheets due to low viscosity and tension at the time of melting. Thus, a method using a resin into which a long chain branch is introduced (for example, Patent Document 1) or a method using a resin obtained by modifying a polypropylene resin by a reaction with a conjugated diene compound and a radical polymerization initiator (for example, a patent) It has been found from literature 2) that a foam sheet can be produced.

  However, foamed sheets obtained from these polypropylene resins have problems such as draw-down during molding, and poor molding elongation of the polypropylene resin laminated foam sheets.

Here, a method (see Patent Document 3) that solves the above problem by defining the bubble diameter of the foam sheet and the shrinkage ratio of the foam sheet under a specific heating atmosphere is disclosed. Although this method tends to improve drawdown and mold reproducibility during molding, a heat-stretching process may be required in addition to the foam sheeting process in order to produce a foam sheet with a specified shrinkage rate. , The specified shrinkage rate is too large, the elongation at the time of molding is poor, the sheet is torn in the molding of a deep container or a container with a partition part, or in the molding of what has a periodic pattern for each container, There was a problem that the pattern shifted from the mold.
Japanese Patent No. 2521388 JP-A-11-228726 JP 2001-287262 A

  The purpose of the present invention is that there is little drawdown during molding, good elongation during molding, container molding with a deep container or partition part, and container molding with a periodic pattern for each container. An object of the present invention is to provide a polypropylene-based resin foam sheet or a polypropylene-based resin laminated foam sheet, and a molded body obtained by thermoforming them.

  As a result of intensive studies to solve such problems, the present inventors have prescribed the heat shrinkage rate of a foamed sheet using a polypropylene resin having a specific melt viscosity as a base resin. The present inventors have found that a polypropylene resin foam sheet and a polypropylene resin laminated foam sheet having excellent workability and a beautiful appearance can be provided, and the present invention has been achieved.

That is, the present invention
It is a polypropylene resin foam sheet, and the heat shrinkage rate in the winding direction and width direction of the polypropylene resin foam sheet when left in an atmosphere of 190 ° C. for 1 minute is both 0 to 5.0%. A polypropylene resin foam sheet characterized in that (Claim 1),
The polypropylene resin foam sheet according to claim 1, wherein the base resin of the polypropylene resin foam sheet has a melt viscosity of 1200 to 2500 Pa · s at 200 ° C and 122 sec ^-1 (claim 2),
Foamed polypropylene resin sheet, wherein the basis weight ^{200g / m 2 ~400g / m 2} , at a density 0.08~0.5g / cc, 60% or more closed cell ratio and the thickness direction cell having 5 or more The polypropylene resin foam sheet according to claim 1 or 2 (claim 3),
A polypropylene resin laminate foam sheet in which a polypropylene resin film is laminated via a non-foamed polypropylene resin layer obtained by extrusion laminating a polypropylene resin to the polypropylene resin foam sheet according to claim 2 (claim 4). ,
The polypropylene-based resin laminated foam sheet (claim 5), wherein the non-foamed polypropylene-based resin layer has a thickness of 20 to 150 µm.
The polypropylene-based resin laminated foam sheet according to claim 4 or 5, wherein the polypropylene-based resin laminated film has a thickness of 15 to 50 µm (Claim 6),
The molded object obtained by heat-molding the polypropylene resin foam sheet according to any one of claims 1 to 3 or the polypropylene resin laminate foam sheet according to any one of claims 4 to 6 (claim 7).
About.

  The polypropylene resin foam sheet or polypropylene resin laminate foam sheet according to the present invention has little drawdown during molding and good elongation during molding. It becomes possible to form a container having a periodic pattern for each container.

  Hereinafter, the present invention will be described in detail.

  In the polypropylene resin foam sheet of the present invention, the shrinkage in the winding direction (MD direction) and the width direction (TD direction) when heated for 1 minute in an atmosphere of 190 ° C. is preferably 0 to 5%. 0 to 4% is more preferable. In the present invention, when the shrinkage rate in the winding direction or the width direction of the polypropylene resin foam sheet is less than 0%, the drawdown property at the time of thermoforming increases, and molding of a pattern with a periodic pattern for each container Then, the pattern tends to shift from the mold. In addition, when the shrinkage rate in the winding direction or the width direction exceeds 5%, the drawdown property at the time of thermoforming is improved, but the forming elongation of the foam sheet is deteriorated, and the container forming with a deep container or a partition part is performed. Then, molding defects such as tearing of the sheet tend to occur.

In addition, the measurement of the heat shrinkage rate in this invention uses "Fine oven DH62" by Yamato Co., Ltd. The measurement is to determine the heat shrinkage in the MD direction and the TD direction when the foamed sheet cut to a size of 100 mm in the MD direction × 100 mm in the TD direction is left in an oven set at 190 ° C. for 1 minute. In addition, the heat shrinkage rate employs a value calculated by the following equation after measuring the dimensions of the foam sheet before heating and the dimensions after heating with a caliper.
Heat shrinkage rate (%) = [(dimension before heating−dimension after heating) / (dimension before heating)] × 100

  As the polypropylene resin of the base resin used in the polypropylene resin foam sheet of the present invention, a linear polypropylene resin (hereinafter, this polypropylene resin may be referred to as “raw polypropylene resin”) is an electron. A modified polypropylene resin obtained by melting and kneading raw material polypropylene resin, an isoprene monomer and a radical polymerization initiator, which are introduced with long-chain branching by irradiation with a line (for example, HMS-PP manufactured by Basel) From the viewpoint of excellent foamability. In particular, a modified polypropylene resin obtained by melt-kneading a raw material polypropylene resin, an isoprene monomer and a radical polymerization initiator is preferable because it can be easily produced and the melt viscosity can be easily manipulated.

  In the present invention, by controlling the melt viscosity of the base resin used in the polypropylene resin foam sheet, the winding direction (MD direction) and the width direction (TD direction) when heated at 190 ° C. for 1 minute. ) Shrinkage rate can be controlled.

  The melt viscosity of the base resin used in the polypropylene resin foam sheet of the present invention is preferably 1200 to 2500 Pa · s, and more preferably 1300 to 2000 Pa · s. When the melt viscosity is less than 1200 Pa · s, the drawdown property at the time of thermoforming increases, and it becomes difficult to obtain a container having a uniform thickness, and it is difficult to control the heat shrinkage rate of the polypropylene resin foam sheet. Tend to be. On the other hand, when the melt viscosity exceeds 2500 Pa · s, the surface property of the polypropylene resin foam sheet tends to deteriorate.

In addition, the following method is employ | adopted as a method of measuring the melt viscosity in this invention. Using a piston type shear viscometer having a cylinder with a diameter of 10 mm and a length of 350 mm, equipped with an orifice having a diameter of 1 mm, a length of 10 mm and an inflow angle of 45 degrees at the tip, a polypropylene resin composition is applied to the cylinder heated to 200 ° C. About 15 g of product is charged. After preheating for 5 minutes after filling, a piston having the same diameter as the cylinder was lowered at a speed at which the shear rate was 122 sec ⁻¹ (piston descending speed was 10 mm / min). And As a measuring instrument, a Capillograph manufactured by Toyo Seiki Co., Ltd. can be used.

  The polypropylene resin foam sheet according to the present invention is prepared by, for example, melt-kneading a polypropylene resin and a foaming agent in an extruder, adjusting the foaming temperature in the extruder, and using a circular die having an annular lip, from the lip of the die. Easily obtained by extruding into atmospheric pressure to obtain a cylindrical foam, then drawing and cooling the cylindrical foam with a cooling cylinder (mandrel), and then cutting it into a sheet. Manufactured. When the modified polypropylene resin composition is used as a raw material, extrusion foaming may be performed continuously with the production of the modified polypropylene resin composition.

  Examples of the blowing agent include aliphatic hydrocarbons, alicyclic hydrocarbons, halogenated hydrocarbons, inorganic gases, water, and the like. Moreover, you may use combining those 1 type (s) or 2 or more types.

  The addition amount (kneading amount) of the foaming agent varies depending on the type of foaming agent and the target foaming ratio, but may be in the range of 0.5 to 10 parts by weight with respect to 100 parts by weight of the polypropylene resin composition. preferable.

  In the present invention, a nucleating agent such as sodium bicarbonate-citric acid mixture or talc may be used in combination as needed in order to control the bubble diameter of the foam sheet to an appropriate size. Although there is no restriction | limiting in particular in the addition amount of this nucleating agent used as needed, Usually, it is preferable that it is 0.01-3 weight part with respect to 100 weight part of polypropylene resin compositions.

  In the present invention, in the production of the foam sheet, a thermoplastic resin may be mixed as long as the foamability of the polypropylene resin is not impaired.

  If necessary, the polypropylene resin of the present invention includes an antioxidant, a metal deactivator, a phosphorus processing stabilizer, an ultraviolet absorber, an ultraviolet stabilizer, a fluorescent brightener, a metal soap, an antacid adsorbent, etc. Stabilizers or additives such as crosslinking agents, chain transfer agents, nucleating agents, lubricants, plasticizers, fillers, reinforcing materials, pigments, dyes, flame retardants and antistatic agents may be added.

  In the present invention, the polypropylene resin foam sheet according to the present invention may be used for the purpose of obtaining a desired cell structure, for example, by promoting air cooling after extrusion foaming or by stretching at the time of taking up to a mandrel. Good.

Basis weight of the polypropylene-based resin foam sheet of the present invention is preferably ^{200~400g / m 2, 220~360g / m} 2 is more preferable. When the basis weight of the polypropylene resin foam sheet is less than 200 g / m ² , the molded product obtained by heating tends to be inferior in rigidity. When the basis weight is greater than 400 g / m ² , the polypropylene resin foam sheet is heated. There is a tendency that the shrinkage rate tends to be small, and drawdown property is increased at the time of heat molding, and it may be difficult to obtain a molded body having a uniform thickness.

  The density of the polypropylene resin foam sheet in the present invention is preferably 0.08 to 0.5 g / cc, and more preferably 0.1 to 0.4 g / cc. When the density of the polypropylene resin foamed sheet is smaller than 0.08 g / cc, the rigidity of the molded product obtained by heating tends to be inferior, and when the density is larger than 0.5 g / cc, it is obtained by heating. There exists a tendency for the heat insulation of a molded object to be inferior.

  The closed cell ratio of the polypropylene resin foam sheet of the present invention is preferably 60% or more, more preferably 70% or more, and further preferably 80% or more. When the closed cell ratio of the polypropylene resin foam sheet is less than 60%, the molded article obtained by heating may be inferior in rigidity.

  The number of cells of the polypropylene resin foam sheet of the present invention is preferably 5 or more, more preferably 6 or more, and even more preferably 7 or more. When the number of cells of the polypropylene resin foam sheet is smaller than 5, the heat insulation property and surface property of the foam sheet tend to be inferior.

  1-5 mm is preferable and, as for the thickness of the polypropylene resin foam sheet in this invention, 1-3 mm is more preferable. When the thickness of the polypropylene resin foam sheet is less than 1 mm, the heat insulating property, rigidity and buffering property tend to be inferior, and when it exceeds 5 mm, the moldability tends to be inferior.

  The polypropylene resin laminated foam sheet in the present invention is produced via a non-foamed polypropylene resin layer extruded by extrusion lamination between the polypropylene resin foam sheet of the present invention and a polypropylene resin film. By adopting the extrusion laminating method, there is no complexity of the process of applying an adhesive to the film required by the dry laminating process, the process of thermocompression bonding, etc. The adhesive strength of can also be improved.

  Examples of the polypropylene resin used for the non-foamed polypropylene resin layer in the present invention include propylene homopolymer, block copolymer with propylene and other monomers, and random copolymerization with propylene and other monomers. Polypropylene homopolymers are preferable from the viewpoint of high rigidity and low cost, and block copolymers with propylene and other monomers from the viewpoint of improving low-temperature brittleness. Is preferred.

  In the present invention, when the polypropylene resin is a block copolymer of propylene and another monomer, or a random copolymer of propylene and another monomer, a high crystal characteristic of the polypropylene resin The propylene monomer component contained is preferably 75% by weight or more, more preferably 90% by weight or more, from the viewpoint of maintaining the properties, high rigidity, and good chemical resistance.

  In the non-foamed polypropylene resin layer in the present invention, not only a polypropylene resin but also two or more kinds can be mixed and used. Furthermore, what mixed the high density polyethylene, the low density polyethylene, the linear low density polyethylene, the ethylene-propylene copolymer, the ethylene-butene copolymer, the butene resin etc. can be used for a polypropylene resin.

  The melt flow rate (hereinafter referred to as “MFR”) of the polypropylene-based resin used in the non-foamed polypropylene-based resin layer in the present invention under the conditions of a temperature of 230 ° C. and a load of 21.18 N is high in workability and secondary moldability. From the point, it is desirable that it is 4 to 20 g / 10 minutes. If the MFR under the above conditions is less than 4 g / 10 minutes, the non-foamed resin layer tends to have uneven thickness, and the appearance of the molded body is impaired. At the same time, the rigidity of the molded body is partially reduced. Even when heated and softened at the time of the next molding, it does not soften to the extent that it is suitable for mold shaping, and there is a tendency that partial elongation occurs in the side wall of the molded body, the partition-shaped part, etc., and the rigidity of the molded body tends to be lowered. On the other hand, if the MFR exceeds 20 g / 10 minutes, it is difficult to handle the non-foamed resin layer during lamination processing, and the phenomenon of neck-in that the non-foamed resin layer extruded from the T die contracts in the T die width direction becomes large. This tends to make it difficult to control the width of the non-foamed resin layer.

  In addition, MFR of the polypropylene resin in this specification is measured according to JIS K7210.

  The melt tension (melt tension) at a temperature of 270 ° C. of the polypropylene resin used for the non-foamed polypropylene resin layer in the present invention is desirably less than 0.6 cN. When the melt tension of the polypropylene resin used for the non-foamed polypropylene resin layer is 0.6 cN or more, the thickness of the non-foamed polypropylene resin layer is uneven when the non-foamed polypropylene resin layer is laminated on the foamed sheet. There is a tendency to deteriorate the appearance and rigidity of the molded body due to the unevenness of the thickness.

  In addition, the melt tension (melt tension) of the polypropylene resin in this specification can be measured by the following method. That is, using a melt tension tester (manufactured by Toyo Seiki Co., Ltd.), a polypropylene resin heated to 270 ° C. was extruded into a strand shape from an orifice having a diameter of 2.095 mm and a length of 8 mm at a speed of 10 mm / min. The sample is passed through a tension detection pulley and wound up while gradually increasing the winding speed at a rate of about 5 rpm / second, and the tension value when the strand is cut is measured.

  The thickness of the non-foamed polypropylene resin layer of the present invention is preferably 20 μm to 150 μm, more preferably 30 μm to 120 μm, and even more preferably 50 μm to 100 μm from the viewpoints of adhesiveness, lightness, and rigidity. When the thickness of the non-foamed polypropylene resin layer is less than 20 μm, the adhesiveness (peeling strength) between the polypropylene resin foam sheet and the polypropylene resin film at a high temperature is lowered, or the rigidity of the foam sheet is reinforced. There is a tendency to be less effective. If the thickness of the non-foamed polypropylene resin layer exceeds 150 μm, the rigidity of the foamed sheet is improved, but there is a tendency to be inferior in terms of light weight and cost.

  The polypropylene resin film used in the present invention is a non-stretched or biaxially stretched polypropylene resin film mainly composed of a polypropylene resin such as a polypropylene homopolymer or a polypropylene copolymer. Moreover, you may use a multilayer film of two or more layers as a polypropylene resin film.

  In the present invention, examples of the polypropylene resin particularly suitable for forming a polypropylene resin film include propylene homopolymer, propylene-ethylene random copolymer, propylene-ethylene block copolymer, and the like. Further, the polypropylene resin forming the film may be mixed with other resins as long as the effects of the present invention are not impaired. As other resins, for example, homopolymers or copolymers such as ethylene and α-olefin, and olefin resins such as polyolefin elastomers are used singly or in combination of two or more.

  In the present invention, various additives such as an antifogging agent, an antiblocking agent, an antioxidant, a lubricant, and a filler are added to the polypropylene resin forming the polypropylene resin film, if necessary. You may add suitably in the range which is not impaired.

  The thickness of the polypropylene resin film is preferably 15 to 50 μm, more preferably 20 to 45 μm, and further preferably 25 to 40 μm. When the thickness of the polypropylene-based film is less than 15 μm, the film may be broken by stretching at the time of heat molding of the obtained laminated foamed sheet, and the moldability tends to be inferior. When the thickness exceeds 50 μm, the rigidity is improved, but the lightweight property of the laminated foam sheet tends to be insufficient.

Polypropylene having a basis weight of resin laminated foam sheet manufactured in the present invention is preferably ^{230g / m 2 ~500g / m 2} , 270g / m 2 ~450g / m 2 is more preferable. If the basis weight of the laminated sheet is smaller than 230 g / m ² , there is a tendency that sufficient rigidity cannot be obtained. If the basis weight exceeds 500 g / m ² , sufficient rigidity can be obtained, but lightness is lost and it is not preferable from the viewpoint of cost.

  The polypropylene resin laminated foam sheet of the present invention can be laminated by forming a printed layer on the surface of the polypropylene resin laminated film that adheres to the non-foamed resin layer in order to impart design properties.

  The printing layer in the present invention is formed by printing with an ink whose main component is a mixture of resin, solvent and pigment. Resins for printing ink include vinyl chloride and vinyl acetate copolymers, rubber chlorinated products, ethylene and vinyl acetate copolymer chlorinated products, polypropylene chlorinated products, acrylic acid and its derivatives, dimer acid And a polyamine condensate, a polyester or polyether-diisocyanate polymer, and a cell source nitrate ester compound. Moreover, you may use those resin 1 type or in mixture of 2 or more types. In particular, chlorinated polypropylene is preferable from the viewpoint of adhesiveness with a polypropylene resin. Moreover, you may add an anchor coating agent, an antistatic agent, a stabilizer, antioxidant, a dispersing agent etc. to printing ink as needed. However, the printing layer is not limited to those described above as long as the object of the present invention can be achieved.

  In the present invention, an anchor coating agent can be used to improve the adhesion between the printed layer and the foamed sheet. As the anchor coating agent, an anchor coating agent (for example, XGL-1200 manufactured by Sakata Inx Co., Ltd.) or an adhesive / primer treatment agent used for improving the printability and adhesiveness of a polypropylene resin that is generally used can be used. Among them, solvent-based and aqueous-based ones that are easy to apply are preferable from the viewpoint of applying a small basis weight. Since the anchor coating agent is solvent-based or water-based, it is possible to volatilize the solvent and water by coating and drying, and to easily apply a desired basis weight.

  The printing layer in the present invention is formed by a known method such as gravure printing. There is no particular limitation on the pattern of printing. By arranging the printed layer on the inner surface (the foamed layer side of the polypropylene resin layer film), it is possible to obtain a laminated foam sheet and a laminated foam having gloss and excellent design. Can do.

  The polypropylene resin foam sheet and the polypropylene resin laminated film used in the present invention are laminated via a non-foamed polypropylene resin layer formed by extrusion laminating a polypropylene resin. A typical method of extrusion lamination will be described with reference to FIG.

  As a method for producing a laminated foamed sheet 10 composed of the foamed sheet 1, the non-foamed resin layer 7 and the film 8, the foamed sheet 1 is fed between the nip roll 2 and the cooling roll 3 along the nip roll 2, and T The non-foamed resin layer 7 is extruded into a film form from the die 4, and the film 8 is further fed through an expander roll (roll for removing film wrinkles) 9 into the gap 6 between the nip roll 2 and the cooling roll 3, and cooled with the nip roll 2. The film 8, the non-foamed resin layer 7, and the foamed sheet 1 are pressed and taken with the roll 3 to obtain a laminated foamed sheet 10 composed of the foamed sheet, the non-foamed resin layer, and the film. At this time, the protrusion of the non-foamed resin layer from the foamed sheet is adjusted by changing the air gap 5 (distance until the non-foamed resin layer 8 coming out of the T-die 4 is pressure-bonded to the foamed sheet 1). In addition, the adhesive strength at the interface between the foamed sheet and the non-foamed resin layer and at the interface between the non-foamed resin layer and the film can be improved.

  Examples of thermoforming include plug molding, matched mold molding, straight molding, drape molding, plug assist molding, plug assist / reverse draw molding, air slip molding, snapback molding, reverse draw molding, free drawing molding, plug Examples include AND ridge molding and ridge molding.

  EXAMPLES Next, although this invention is demonstrated in detail based on an Example, this invention is not limited to this Example.

(Measurement of density of foam sheet)
Measurement was performed in accordance with JIS-K6767.

(Measurement of closed cell ratio of foam sheet)
In accordance with the method described in ASTM D2856, measurement was performed with an air pycnometer.

(Measurement of the number of cells in the thickness direction of the foam sheet)
Ten measurement points were provided at equal intervals in the width direction of the foamed sheet, and the number of cells in the thickness direction at the measurement points was measured using a loupe (peacock, pocket micro × 10). Then, the average of the measured value of each point was made into the number of cells of the thickness direction.

(Measurement of heat shrinkage)
The shrinkage rate was measured using “Fine Oven DH62” manufactured by Yamato Co., Ltd. as described above. For measurement, the foamed sheet cut into a size of 100 mm in the MD direction × 100 mm in the TD direction is left in an oven set at 190 ° C. for 1 minute, and the dimensions of the foamed sheet before and after heating are measured. Measured with calipers. The heating shrinkage in the MD direction and the TD direction at this time was obtained from the following formula.
Heat shrinkage rate (%) = [(dimension before heating−dimension after heating) / (dimension before heating)] × 100

(Drawdown evaluation)
The obtained foamed sheet or laminated foamed sheet was cut into a 540 × 540 mm square and fixed to a frame having an inner size of 500 × 500 mm using a single molding machine (VAS-66-45T manufactured by SENBA System Co., Ltd.), and then the atmosphere It was inserted into a heating furnace adjusted to a temperature of 200 ° C. for 50 seconds. The amount of sag at the center at this time was evaluated as drawdown according to the following criteria.
○: The amount of sag at the center of the foam sheet or laminated foam sheet is less than 20 mm. Δ: The amount of sag at the center of the foam sheet or laminate foam sheet is 20 to 40 mm.
X: The amount of sag at the center of the foam sheet or laminated foam sheet is 40 mm or more

(Formability evaluation of molded products)
Immediately after performing the drawdown evaluation, the heated foamed sheet or laminated foamed sheet has a square shape with an opening of 175 mm × 175 mm, a partition part having a width of 5 mm exists at the center of each side, and a depth of 30 mm. Were used for 50 seconds in a heating furnace adjusted to an atmospheric temperature of 200 ° C., and 10 pieces were formed by a matched mold forming method. The state of the molded body at this time was evaluated according to the following criteria.
○: The wall thickness of the partition part and the bottom part is uniform in any of the molded bodies, and there is no tearing.
X: The thickness of the partition part or the bottom part is not uniform in any of the molded bodies, and tearing is observed.

(Appearance evaluation of molded body)
Using the molded body for which the moldability was evaluated, the appearance was evaluated according to the following criteria.
○: None of the molded bodies have blurring or wrinkles on the side or bottom. Moreover, in the molded object obtained from the laminated foam sheet, there is no film shift and it is glossy.
X: There is blurring or wrinkles on the side or bottom of any of the molded articles, and when the molded body is obtained from a laminated foamed sheet, there is further film misalignment or no gloss.

  Below, the manufacturing method of the foam sheet used for the Example and the comparative example is shown.

(Method for producing polypropylene resin foam sheets A-1 to A-4)
A compound obtained by stirring and mixing a polypropylene homopolymer and a radical polymerization initiator (t-butylperoxybenzoate) with a ribbon blender according to the compounding shown in Table 1 is supplied to a twin-screw extruder using a metering feeder, and liquid-added. Isoprene was supplied from the middle of the extruder using a pump, and melt-kneaded in the twin-screw extruder to obtain pellets of a modified polypropylene resin composition. The melt viscosity of the modified polypropylene resin composition was the value shown in Table 1.
The twin-screw extruder was the same-direction twin-screw type, the screw diameter was 44 mmφ, and the maximum screw effective length (L / D) was 38. The set temperature of the cylinder part of the twin-screw extruder was 180 ° C. up to the isoprene press-in position, 200 ° C. after the isoprene press-in position, and the screw rotation speed was set at 150 rpm.

100 parts by weight of the modified polypropylene resin composition, 0.05 parts by weight of blend oil, and 0.5 parts by weight of a cell nucleation agent (manufactured by Eiwa Kasei Kogyo Co., Ltd., Cellbon SC / K) are mixed by stirring with a ribbon blender. The product is supplied to a 90-125 mmφ tandem type extruder and melted in a first stage extruder (90 mmφ) set at a cylinder temperature of 200 ° C., and then isobutane is used as the blowing agent in the modified polypropylene resin composition. 1.7 parts by weight of 100 parts by weight was mixed by press-fitting and cooled in a second stage extruder (125 mmφ) set at 160 ° C. (measured by a temperature sensor installed at the resin inflow part of the die), and a circular die (127 mmφ) ) Discharge at 4.4 m / min while discharging from the atmospheric pressure and forming with a cooling cylinder having an outer diameter of 335 mmφ and a body length of 800 mm Stretched and cooled to obtain a cylindrical foam, which was cut open with a cutter to obtain a foam sheet having a width of 1035 mm.
The physical properties of the obtained foam sheet were as shown in Table 1.

(Production method of polypropylene resin foam sheet A-5)
100 parts by weight of a polypropylene resin (manufactured by Sun Allomer, PF-814), 0.05 part by weight of blended oil, and 0.7 parts by weight of a cell nucleating agent (Selfon SC / K by Eiwa Kasei Kogyo Co., Ltd.) are stirred with a ribbon blender The mixed compound is supplied to a 90-125 mmφ tandem type extruder, melted in a first stage extruder (90 mmφ) set at 200 ° C., and then isobutane is used as the blowing agent in the modified polypropylene resin composition. 1.5 parts by weight of 100 parts by weight is injected and mixed, cooled in a second-stage extruder (125 mmφ) set at 165 ° C., and discharged from a circular die (127 mmφ) under atmospheric pressure. Stretching and cooling while forming at a speed of 4.6 m / min while forming with a 800 mm long cooling cylinder to obtain a cylindrical foam, which is opened with a cutter To obtain a foamed sheet of 1035mm wide by as. The physical properties of the obtained foam sheet were as shown in Table 1.

(Polypropylene resin non-foamed resin layer B-1)
A polypropylene homopolymer (manufactured by Mitsui Chemicals, J105G) with MFR = 9 g / 10 min was used as the non-foamed resin layer.

(Polypropylene resin biaxially stretched film C-1)
A biaxially stretched polypropylene film (manufactured by Santox Co., Ltd., MF20 # 30) having a thickness of 30 μm was used as the film.

(Polypropylene resin biaxially stretched film C-2)
A biaxially stretched polypropylene film (manufactured by Santox Co., Ltd., MF20 # 25) having a thickness of 25 μm was used as the film.

(Polypropylene resin unstretched film C-3)
An unstretched polypropylene film (manufactured by Santox Co., Ltd., KT # 25) having a thickness of 25 μm was used as the film.

(Examples 1-6 and Comparative Examples 1-4)
A laminated foamed sheet was obtained by combining the polypropylene resin foamed sheet, the non-foamed laminated resin and the polypropylene resin film as shown in Table 2. As a method for obtaining a laminated foam sheet, Examples 3 to 5 and Comparative Example 4 were performed by the extrusion laminating method shown in FIG. In extrusion lamination, the temperature of the non-foamed resin layer coming out of the T-die is adjusted to 230 to 240 ° C., and the distance (air gap 5) until the foamed resin layer coming out of the T-die 4 is pressed onto the foamed sheet is 15 cm. The width of the non-foamed resin layer 7 was 1030 mm. Table 2 shows the evaluation results of the laminated foam sheets in Examples and Comparative Examples.

As described above, it can be seen that the laminated foamed sheet in the combination of the foamed sheet, the non-foamed resin layer and the film as in Examples 1 to 5 has no drawdown and has good elongation during molding. Further, it can be seen that the obtained deep molded article also has a good appearance.
On the other hand, about the comparative example 1, since the shrinkage | contraction rate of MD and TD direction of a foam sheet and a laminated foam sheet is large, it turns out that the elongation at the time of heat molding is bad, and a moldability and the external appearance of a molded object are bad. In Comparative Examples 2 and 3, the shrinkage rate tends to be small, and it is easy to draw down at the time of thermoforming. In Comparative Example 3, it is difficult to maintain the heating balance between the foamed sheet surface side and the laminated film surface side, and the appearance is You can see that it tends to get worse.

  The polypropylene resin foam sheet and the polypropylene resin laminate foam sheet produced in the present invention are superior in heat resistance and oil resistance since the base resin is a polypropylene resin, and heat insulation is achieved by providing a foam layer. Excellent in lightness and lightness.

  From the above, the polypropylene resin foam sheet and the laminated foam sheet of the present invention are beautiful in appearance, excellent in heat resistance, oil resistance, light weight, and heat insulation, and cooked using a microwave oven or reheated. Suitable as a food container for range heating.

Diagram showing an example of extrusion lamination method

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Foam sheet 2 Nip roll 3 Cooling roll 4 T die 5 Air gap (Distance until the non-foamed resin layer 7 which came out of T die 4 is crimped | bonded to the foam sheet 1)
6 Gap formed by nip roll 2 and cooling roll 3 7 Non-foamed resin layer 8 Film 9 Expander roll (roll for removing wrinkles of film 8)
10 Laminated foam sheet

Claims (7)

  It is a polypropylene resin foam sheet, and the heat shrinkage rate in the winding direction and width direction of the polypropylene resin foam sheet when left in an atmosphere of 190 ° C. for 1 minute is both 0 to 5.0%. A polypropylene resin foam sheet characterized by 2. The polypropylene resin foam sheet according to claim 1, wherein the base resin of the polypropylene resin foam sheet has a melt viscosity of 1200 to 2500 Pa · s at 200 ° C. and 122 sec ⁻¹ . The polypropylene-based resin foam sheet has a basis weight of 200 to 400 g / m ² , a density of 0.08 to 0.5 g / cc, a closed cell ratio of 60% or more, and a thickness direction cell number of 5 or more. The polypropylene resin foam sheet according to 1 or 2.   A polypropylene resin laminated foam sheet in which a polypropylene resin film is laminated via a non-foamed polypropylene resin layer obtained by extrusion laminating a polypropylene resin to the polypropylene resin foam sheet according to claim 2.   5. The polypropylene resin laminated foam sheet according to claim 4, wherein the non-foamed polypropylene resin layer has a thickness of 20 to 150 [mu] m.   The polypropylene resin laminated foam sheet according to claim 4 or 5, wherein the thickness of the polypropylene resin laminated film is 15 to 50 µm.   The molded object obtained by heat-molding the polypropylene resin foam sheet in any one of Claims 1-3 or the polypropylene resin laminated foam sheet in any one of Claims 4-6.

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