JP2006248187A - Polypropylene resin-laminated foamed sheet, its manufacturing method and its molding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide polypropylene resin-laminated foamed sheets suitable for obtaining moldings having a deep shape, which are lightweight, excellent in thermal insulation and the rigidity when used at a high temperature, and to provide their manufacturing methods and moldings obtained by heating and shaping the laminated foamed sheets. <P>SOLUTION: The polypropylene resin-laminated foamed sheet is formed by laminating a non-foamed polypropylene resin layer on at least one side of a polypropylene resin foamed sheet by extrusion lamination. After lamination, the polypropylene resin-laminated foamed sheet has a ratio of closed cells of 50% or higher, and thickness of 2.5-5.0 mm. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a polypropylene resin laminated foam sheet, a method for producing the same, and a molded body obtained from the polypropylene resin laminated foam sheet.

  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 resins and polyethylene resins.

  In recent years, foamed sheets using polypropylene resin as the base resin have attracted attention as food container applications because of their superior heat resistance and oil resistance compared to conventional polystyrene resin foam sheets due to the characteristics of the base resin. ing.

  However, when a polypropylene resin foam sheet is used as a food container, the container rigidity is insufficient, and these improvements are required. In order to solve the lack of rigidity of the container, it has been proposed to use a polypropylene resin foam sheet that specifies the density, thickness, closed cell rate, and cell shape (Patent Document 1 or Patent Document 2). However, the lack of rigidity of the container affected by the characteristics of the base resin has not been greatly improved.

A method of laminating a polypropylene resin foam sheet and a non-foamed resin layer by extrusion lamination (Patent Document 3) has been proposed. By laminating the non-foamed resin layer, the rigidity of the container when used at room temperature was greatly improved. However, if the pressure bonding and laminating conditions are selected with emphasis on the adhesion between the foamed sheet and the non-foamed resin layer during extrusion lamination, the closed cells of the foamed sheet are broken and become open-celled. When the container is exposed to a high temperature, such as when hot water is put into the container, the rigidity may be greatly reduced. In particular, as the thickness of the polypropylene-based resin foam sheet increases, the foam sheet and non-foamed resin layer are bonded and the closed cells are retained in the foam sheet after lamination due to the uneven thickness of the foam sheet and the influence of the cell shape. It was more difficult to achieve both.
Japanese Patent No. 3351967 JP 2001-226509 A JP 2001-310429 A

  An object of the present invention is to provide a polypropylene-based resin laminated foam sheet that can be suitably used to obtain a deep molded article having excellent lightness, heat insulation, and rigidity at high temperature use.

  As a result of intensive studies to solve such problems, the present inventors have reached the present invention.

That is, the present invention
1. A polypropylene resin laminated foam sheet in which a non-foamed polypropylene resin layer is laminated on at least one surface of a polypropylene resin foam sheet by extrusion lamination, and the foamed sheet after lamination has a closed cell ratio of 50% or more and a thickness of 2. A polypropylene resin laminated foam sheet (claim 1), characterized in that it is 5 to 5.0 mm;
A polypropylene resin laminated foam sheet in which a polypropylene resin film is laminated on a polypropylene resin foam sheet via a non-foamed polypropylene resin layer formed by extrusion lamination on at least one side of the polypropylene resin foam sheet, after lamination A polypropylene-based resin laminated foam sheet, wherein the foamed sheet has a closed cell ratio of 50% or more and a thickness of 2.5 to 5.0 mm (claim 2),
The polypropylene resin laminated foam sheet according to claim 1 or 2, wherein the polypropylene resin foam sheet has a density of 60 to 150 kg / m ³ , a closed cell ratio of 60% or more, and a thickness direction cell number of 7 or more. (Claim 3),
It is a manufacturing method of the polypropylene resin laminated foam sheet in any one of Claims 1-3, Comprising: In extrusion lamination, the clearance gap (the nip roll and the cooling roll for crimping | bonding a polypropylene resin foam sheet and a non-foamed resin layer ( T1) satisfies the following formula (1) with respect to the thickness (T2) of the polypropylene resin foam sheet: 0.2 ≦ T1 / T2 ≦ 0. 6 Form (1) (Claim 4) and a molded body obtained by thermoforming the polypropylene-based resin laminated foam sheet according to any one of Claims 1 to 3 (Claim 5)
About.

  Like the present invention, by defining the closed cell ratio and thickness of the polypropylene resin laminated foam sheet after lamination, and the density of the polypropylene resin foam sheet before lamination, etc., it is excellent in rigidity and heat insulation at high temperature use. A polypropylene resin fat-laminated foam sheet capable of obtaining a molded product can be obtained. In particular, the polypropylene-based resin laminated foam sheet of the present invention can be suitably used for molding a molded product having a deep shape.

  Hereinafter, the present invention will be described in detail.

  In the present invention, in addition to the closed cell ratio and thickness of the polypropylene resin laminated foam sheet after lamination, by defining the density, closed cell ratio and number of cells of the polypropylene resin foam sheet before lamination, rigidity and heat insulation The present invention provides a polypropylene-based resin laminated foam sheet suitable for obtaining a deep foam molded article having a high height.

  The closed cell ratio of the polypropylene resin laminated foam sheet after lamination in the present invention is 50% or more, preferably 60% or more, more preferably 70% or more. When the closed cell ratio of the laminated foamed sheet is less than 50%, rigidity and heat insulating properties may be inferior when used at a high temperature when formed into a deep mold.

The measurement of the closed cell ratio is a value calculated by the following equation (2) after measuring the closed space volume Va of the laminated foam sheet with an air pycnometer based on the method described in ASTM D2856.
Closed cell ratio (%) = [((Va × ρ / W) −1) / ((ρ × Vb / W) −1)] Formula (2)
However,
Va: closed space volume (cm ³ )
Vb: Submerged volume of the laminated foam sheet sample measured using a graduated cylinder (cm ³ )
W: Weight of laminated foam sheet sample (g)
ρ: Density of base resin (g / cm ³ )
At this time, twelve sheet samples were cut into a shape of 35 mm long × 20 mm wide and used as measurement samples. As a result, the ratio of the closed bubble space to the total bubble space excluding the stacked portion and the bubble wall portion is calculated.

  As a lower limit of the thickness of the polypropylene resin laminated foam sheet after lamination in the present invention, 2.5 mm is preferable, 2.7 mm is more preferable, and more than 3.0 mm is more preferable. When the thickness of the laminated polypropylene-based foamed sheet is less than 2.5 mm, it may be impossible to ensure the thickness of the molded body necessary to have high rigidity in the deep molded body. On the other hand, the upper limit value of the thickness of the polypropylene resin laminated foam sheet after lamination is preferably 5.0 mm, more preferably 4.8 mm, and even more preferably 4.2 mm. When the thickness exceeds 5.0 mm, the mold clamping force of the mold is insufficient at the time of thermoforming, and the appearance of the resulting molded body tends to be damaged.

  In addition, regarding the average thickness of the polypropylene-based resin laminated foam sheet, 10 points randomly selected in the width direction of the foam sheet were taken as measurement points, and the thickness of each measurement point was measured with a thickness gauge (for example, manufactured by Teclock Corporation, Thickness). The average value of the measured values at each point is taken as the thickness of the laminated foamed sheet.

  Although the manufacturing method of the polypropylene resin laminated foam sheet by the extrusion laminating method in this invention is demonstrated based on FIG. 1, implementation of this invention is not limited to this.

  As a method for producing a non-foamed foam sheet comprising a polypropylene resin foam sheet and a non-foamed polypropylene resin layer, first, the foam sheet 1 is placed along the nip roll 2 while the gap 6 between the nip roll 2 and the cooling roll 3 is set. Pull out and take along the cooling roll 3. At this time, after melting the non-foamed polypropylene resin in the extruder, the non-foamed resin layer 7 is extruded from the T die 4 into a film shape, and the non-foamed resin layer 7 and the foamed sheet 1 are pressure-bonded by the nip roll 2 and the cooling roll 3. The laminated foamed sheet 10 is obtained by taking out.

  As a method for producing a laminated foam sheet comprising a foam sheet, a non-foamed resin layer, and a film, as described above, the foam sheet 1 is fed between the nip roll 2 and the cooling roll 3 along the nip roll 2, The non-foamed resin layer 7 is extruded from the T-die 4 into a film shape, and further, the film 8 is fed into the gap 6 between the nip roll 2 and the cooling roll 3 through the expander roll 9. A laminated foamed sheet 10 composed of the foamed sheet 1, the non-foamed resin layer 7, and the film 8 is obtained by pressure-bonding and taking up the foamed resin layer 7 and the foamed sheet 1.

In the present invention, a nip roll 2 and a cooling roll 3 for pressure-bonding the polypropylene resin foam sheet 1 and the non-foam resin layer 7 or the polypropylene resin foam sheet 1, the non-foam resin layer 7 and the film 8 at the time of extrusion lamination. The gap (T1) satisfies the following formula (1) with respect to the thickness (T2) of the polypropylene resin foam sheet before lamination.
0.2 ≦ T1 / T2 ≦ 0.6 Formula (1)

  In the present invention, by setting the T1 / T2 condition within the above range, both the adhesiveness between the foamed sheet and the non-foamed resin layer and the retention of closed cells in the foamed sheet after lamination can be achieved.

  When T1 / T2 is less than 0.2, the gap (T1) between the nip roll and the cooling roll is too narrow with respect to the thickness (T2) of the polypropylene resin foam sheet before lamination, and the polypropylene resin laminate foam sheet after lamination has The closed cell ratio may be reduced. On the other hand, when T1 / T2 exceeds 0.6, the gap (T1) between the nip roll and the cooling roll is too wide with respect to the thickness (T2) of the foam sheet, and the foam sheet and the non-foam resin layer or the non-foam resin layer There may be a case where the adhesion with the film becomes weak or an unbonded portion occurs.

  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.

  The polypropylene resin constituting the non-foamed polypropylene resin layer in the present invention includes a propylene homopolymer, a block copolymer of propylene and another monomer, or a random weight of propylene and another monomer. The polypropylene homopolymer is preferable from the viewpoint of high rigidity and low cost, and it is a block copolymer of the propylene and other monomers from the viewpoint of low temperature brittleness. preferable. When the polypropylene resin is a block copolymer of propylene and another monomer, or a random polymer of propylene and another monomer, high crystallinity, high rigidity and From the viewpoint of maintaining good chemical resistance, the propylene monomer component contained is preferably 75% by weight or more, and more preferably 90% by weight or more.

  In the non-foamed polypropylene resin layer, not only the polypropylene resin is used alone, 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 resin used in the non-foamed polypropylene resin layer of the present invention under the conditions of a temperature of 230 ° C. and a load of 21.18 N is the point of workability and secondary moldability. From 4 to 20 g / 10 min. 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.

  In addition, the melt tension (melt tension) at a temperature of 270 ° C. of the polypropylene resin constituting 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 constituting 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 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 in 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 in the present invention is preferably 20 to 150 μm, more preferably 30 to 140 μm, and still more preferably 50 to 120 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 effect of reinforcing the rigidity of the foamed sheet tends to be thin. When the thickness of the non-foamed polypropylene resin layer exceeds 150 μm, the rigidity of the foamed sheet is improved, but the weight and cost may be inferior.

  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 the multilayer film of 2 or more layers as a polypropylene resin laminated | multilayer film.

  Examples of particularly suitable polypropylene resins for forming a polypropylene resin film include propylene homopolymers, propylene-ethylene random copolymers, propylene-ethylene block copolymers, 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 addition, various additives such as an antifogging agent, an antiblocking agent, an antioxidant, a lubricant, and a filler are appropriately added to the polypropylene resin as necessary within a range not impairing the effects of the present invention. May be.

  15-50 micrometers is preferable, as for the thickness of the polypropylene resin film used for this invention, 20-45 micrometers is more preferable, and 25-40 micrometers is more preferable. 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.

0.23-0.53 kg / m < ² > is preferable and, as for the basic weight of the polypropylene resin laminated foam sheet manufactured in this invention, 0.26-0.50 kg / m < ² > is more preferable. If the basis weight of the polypropylene resin laminated foam sheet is less than 0.23 kg / m ² , there is a tendency that sufficient rigidity cannot be obtained. If the basis weight exceeds 0.53 kg / m ² , sufficient rigidity can be obtained, but lightness is lost, and this is not preferable from the viewpoint of cost.

The density of the polypropylene-based resin foam sheet prior to lamination to be used in the present invention is preferably ^{60~150kg / m 3, 75~130kg / m} 3 and more preferably. If the density of the polypropylene-based resin foam sheet before lamination is less than 60 kg / m ³ , it may be inferior to the mold shape transfer when the deep mold is thermoformed and the appearance of the mold may be insufficient. If it exceeds 150 kg / m ³ , the molded body may have insufficient rigidity, and the lightness and economy may be impaired.

  The closed cell ratio of the polypropylene resin foam sheet before lamination used in the present invention is preferably 60% or more, more preferably 70% or more, and further preferably 80% or more. If the closed cell ratio of the polypropylene resin foam sheet before lamination is less than 60%, it may be difficult to secure the closed cell ratio of the polypropylene resin laminate foam sheet after lamination, and the rigidity of the molded body may be insufficient. . In addition, the closed cell rate of a polypropylene resin foam sheet is calculated | required by the method similar to the measuring method of the above-mentioned closed cell rate of a polypropylene resin laminated foam sheet.

  The number of cells of the polypropylene resin foam sheet before lamination used in the present invention is preferably 7 or more, and more preferably 8 or more. When the number of cells of the polypropylene resin foam sheet is smaller than 7, the heat insulation and surface properties of the polypropylene resin foam sheet before lamination tend to be inferior.

The basis weight of the polypropylene-based resin foam sheet prior to lamination of the present invention is preferably ^{0.2~0.4kg / m 2, 0.22~0.38kg / m} 2 is more preferable. If the basis weight of the foamed polypropylene resin sheet before lamination 0.2 kg / m ² less than, there tends to be inferior in the rigidity of the molded article obtained by heating, is greater than 0.4 kg / m ² is In addition, the heat shrinkage rate of the polypropylene resin laminated foam sheet after lamination becomes small, and the drawdown property becomes large at the time of thermoforming, and it tends to be difficult to obtain a molded product having a uniform thickness.

  As a lower limit of the thickness of the polypropylene resin foam sheet before lamination in the present invention, 2.5 mm is preferable, 2.7 mm is more preferable, and more than 3.0 mm is more preferable. If the thickness of the polypropylene resin foam sheet before lamination is less than 2.5 mm, the heat insulation, rigidity, and buffering properties tend to be inferior. On the other hand, the lower limit of the thickness of the polypropylene resin foam sheet before lamination is preferably 5.0 mm, more preferably 4.8 mm, and still more preferably 4.2 mm. If the thickness is greater than 5.0 mm, the formability tends to be inferior.

  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. And a modified polypropylene resin obtained by melt-kneading a raw material polypropylene resin, an isoprene monomer, and a radical polymerization initiator. Is preferable 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 manufactured and the melt viscosity can be easily adjusted.

In addition, the following method is employ | adopted as a method of measuring the said melt viscosity. Using a piston-type shear viscometer having a 10 mm diameter and 350 mm long cylinder fitted with an orifice with a 1 mm diameter, 10 mm length and 45 ° inflow angle at the tip, a polypropylene resin composition on a cylinder heated to 200 ° C. Fill about 15 g. 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). To do. As a measuring instrument, a Capillograph manufactured by Toyo Seiki Co., Ltd. can be used.

  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 tends to be difficult to obtain a container having a uniform thickness. On the other hand, when the melt viscosity exceeds 2500 Pa · s, the surface property of the polypropylene resin foam sheet tends to deteriorate.

  The polypropylene resin foam sheet in the present invention is, for example, after 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. By extruding into the atmospheric pressure from the lip to obtain a cylindrical foam, and then pulling out the cylindrical foam, forming by a cooling cylinder (mandrel), drawing and cooling, and then cutting it into a sheet Easy to manufacture. 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.

  Moreover, in order to control the bubble diameter of a foam sheet to a suitable magnitude | size, you may use together nucleating agents, such as a sodium bicarbonate-citric acid mixture or a talc, as needed. 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.

  Further, in the production of the foamed sheet, a thermoplastic resin may be mixed as long as the foamability of the polypropylene resin is not impaired.

  In addition, the polypropylene resin foam sheet in the present invention may be accelerated at the time of taking up to a mandrel, for example, by extruding and foaming to promote cooling for the purpose of obtaining a desired cell structure.

  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.

  The polypropylene resin laminated foam sheet of the present invention can be laminated by forming a printing layer on the surface to be pressure-bonded to the non-foamed resin layer of the polypropylene resin laminated film 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.

  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)
The density was measured according to JIS-K6767.

(Measurement of closed cell ratio of foam sheet)
The closed cell ratio is based on the method described in ASTM D2856, and the closed space volume Va (cm ³ ) of the polypropylene resin laminated foam sheet after lamination and the polypropylene resin foam sheet before lamination is measured by an air pycnometer, It is a value calculated by the following equation (2).
Closed cell ratio (%) = [((Va × ρ / W) −1) / ((ρ × Vb / W) −1)] Formula (2)
However,
Vb: Volume of the laminated foam sheet sample measured with a graduated cylinder (cm ³ )
W: Weight of laminated foam sheet sample (g)
ρ: Density of base resin (g / cm ³ )

(Measurement of thickness of foam sheet)
Ten points randomly selected in the width direction of the polypropylene resin foam sheets before lamination obtained in Examples and Comparative Examples were used as measurement points, and the thickness of each measurement point was measured using a thickness gauge manufactured by teclock. Then, the average of the measured value of each point was made into the average thickness (T1) of the foamed sheet before a heating. In addition, it measured by the same method also about the thickness of the polypropylene resin laminated foam sheet after lamination | stacking.

(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.

(Formability evaluation of molded products)
The laminated foam sheet is cut into 540 × 540 mm squares, fixed to a frame with an inner size of 500 × 500 mm using a single molding machine (manufactured by SENBA System Co., Ltd., VAS-66-45T), and then heated to an atmospheric temperature of 200 ° C. It was inserted into a controlled heating furnace for 50 seconds. The heated laminated foamed sheet is heated for 50 seconds in a heating furnace adjusted to an atmospheric temperature of 200 ° C. using a round mold having an opening of 160 mmφ, a bottom of 80 mmφ and a depth of 67 mm, and then subjected to a matched mold forming method. 10 pieces were molded. The state of the molded body at this time was evaluated according to the following criteria.
○: The thickness of the side portion and the bottom portion is uniform and there is no tearing in any of the molded bodies.
(Triangle | delta): The thickness of a side part or a bottom part is nonuniform in any one of a molded object, or a tear is seen.
X: The thickness of the side part or the bottom part is not uniform or broken in two or more of the molded bodies.

(Rigidity evaluation of molded body)
The rigidity evaluation of the molded body is shown in FIG. 2 by using a bowl-shaped molded body similar to the evaluation of the moldability described above, using IMADA Corporation DIGITAL FORCE GAUGE (MODEL No. MD-2000 (SV-2)). As shown, the lip of the opening of the molded body is fixed, and the molded body opening is compressed at a compression rate of 10 mm / second, and the load when compressed by 10 mm is measured. ) Divided by the basis weight (kg / m ² ) of the laminated foam sheet was taken as the rigidity value of the molded body.
A: The rigidity value of the molded body is 7.0 N · m ² / kg or more.
(Triangle | delta): The rigidity value of a molded object is 5.0 N * m < ² > / kg or more and less than 7.0 N * m < ² > / kg.
X: The rigidity value of the molded product is less than 5.0 N · m ² / kg.

(Evaluation of high-temperature rigidity of molded products)
350 g of hot water at 90 ° C. is filled in a bowl-shaped molded body similar to the rigidity evaluation of the molded body, and a value obtained by performing the same measurement as the rigidity evaluation of the molded body in a state where hot water is filled Value.
A: The rigidity value of the molded body is 6.0 N · m ² / kg or more.
△: rigidity of the molded body is 4.0N · m ² / kg or more, 6.0N · m ² / less than kg.
X: The rigidity value of the molded product is less than 4.0 N · m ² / kg.

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

[Method for producing polypropylene resin foam sheets A-1 to A-4]
A blended mixture of polypropylene homopolymer and radical polymerization initiator (t-butylperoxybenzoate) mixed in a ribbon blender with the composition shown in Table 1 is fed to a twin screw extruder with a metering feeder, and a liquid addition pump is used. Then, isoprene was supplied from the middle of the extruder, melt-kneaded in the twin-screw extruder, and melt-extruded to obtain pellets of the 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 this twin-screw extruder was 180 ° C. until the isoprene monomer injection, 200 ° C. after the isoprene injection, and the screw rotation speed was set to 150 rpm.
65-90 mmφ tandem was obtained by stirring and mixing 100 parts by weight of the resulting modified polypropylene resin composition and 0.6 parts by weight of a cell nucleus forming agent (manufactured by Eiwa Kasei Kogyo Co., Ltd., Cellbon SC / K) with a ribbon blender. After being supplied to a mold extruder and melted in a first stage extruder (65 mmφ) set at a cylinder temperature of 220 ° C., 2. as an blowing agent, isobutane is used in an amount of 2. parts by weight based on 100 parts by weight of the modified polypropylene resin composition. 1 part by weight is injected and mixed, cooled in a second stage extruder (90 mmφ) set at 160 ° C. (measured by a temperature sensor installed at the resin inflow part of the die), and discharged from the circular die (127 mmφ) under atmospheric pressure. Extruding at an amount of 75 kg / h, forming in a cooling cylinder with an outer diameter of 335 mm and a body length of 800 mm, and drawing and cooling while taking up to a predetermined basis weight Give the cylindrical foam, and which give a foamed sheet of 1040mm width by cutting open with a cutter. The physical properties of the obtained foam sheet were as shown in Table 1.

[Method for Producing Polypropylene Resin Foam Sheet A-5-6]
65- A blend of 100 parts by weight of a polypropylene resin (manufactured by Basel, PF-814) and 0.5 part by weight of a cell nucleating agent (manufactured by Eiwa Kasei Kogyo Co., Ltd., Cellbon SC / K) with stirring by a ribbon blender After supplying to a 90 mmφ tandem type extruder and melting in a first stage extruder (65 mmφ) set at 220 ° C., 1. as an blowing agent, isobutane is used in an amount of 1. with respect to 100 parts by weight of the modified polypropylene resin composition. 5 parts by weight is injected and mixed, cooled in a second stage extruder (90 mmφ) set at 165 ° C., and extruded from a circular die (127 mmφ) at a discharge rate of 75 kg / h under atmospheric pressure. While forming with an 800 mm cooling cylinder, drawing and cooling while taking up to a predetermined basis weight, a cylindrical foam is obtained, and this is opened by cutting with a cutter. To obtain a foamed sheet of 40mm width. 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 having a MFR = 7 g / 10 min (F107DV, manufactured by Mitsui Chemicals, Inc.) 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 unstretched film C-2]
An unstretched polypropylene film (manufactured by Santox Co., Ltd., KT # 25) having a thickness of 25 μm was used as the film.

(Examples 1-10 and Comparative Examples 1-6)
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 1 to 10 and Comparative Examples 1 to 6 were performed by the extrusion laminating method shown in FIG. In the extrusion lamination, the temperature of the non-foamed resin layer coming out from the T-die was adjusted to 230 to 240 ° C., and the width of the non-foamed resin layer 7 was set to 1030 mm.

  Table 2 shows the evaluation results of the laminated foam sheets in Examples and Comparative Examples.

  As described above, the laminated foam sheet in the combination of the foam sheet, the non-foamed resin layer and the film as in Examples 1 to 10 has a high closed cell ratio, and sufficient rigidity can be obtained even in a bowl-shaped container. Recognize. On the other hand, in Comparative Examples 1, 3, and 4, it can be seen that sufficient rigidity cannot be obtained in a bowl-shaped container because the closed cell ratio of the laminated foam sheet is low. In Comparative Examples 2 and 5, it can be seen that a laminated foam sheet cannot be obtained. In Comparative Example 6, it can be seen that although the closed cell ratio in the laminated foam sheet is sufficiently high, the laminated foam sheet is thin, so that sufficient rigidity cannot be obtained in the bowl-shaped container.

  The polypropylene resin laminated foam sheet produced by the present invention is superior in heat resistance and oil resistance by using a polypropylene resin as a base resin, and also has rigidity and heat insulation by regulating the closed cell ratio and thickness. Excellent in lightness and lightness.

  From the above, the polypropylene resin laminated foam sheet of the present invention is excellent in heat resistance, oil resistance, light weight, and heat insulation, and is suitable as a food container for microwave heating that is cooked or reheated using a microwave oven. It is. Furthermore, it can also be suitably used as a deep container of soup such as ramen, udon and soba.

Diagram showing an example of extrusion lamination method Diagram showing the method for evaluating the rigidity of a molded product

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 11 Molded body for evaluation 12 DIGITAL FORCE GAUGE
13 Lip fixing jig

Claims (5)

  A polypropylene resin laminated foam sheet in which a non-foamed polypropylene resin layer is laminated by extrusion lamination on at least one surface of a polypropylene resin foam sheet, and the closed cell ratio of the laminated polypropylene resin laminate foam sheet is 50%. A polypropylene-based resin laminated foam sheet having the above and a thickness of 2.5 to 5.0 mm.   A polypropylene resin laminated foam sheet in which a polypropylene resin film is laminated on a non-foamed polypropylene resin layer formed by extrusion laminating a polypropylene resin on at least one side of a polypropylene resin foam sheet, after lamination A polypropylene resin laminated foam sheet, wherein the foamed sheet has a closed cell ratio of 50% or more and a thickness of 2.5 to 5.0 mm. The polypropylene resin foam sheet according to claim 1 or 2, wherein the polypropylene resin foam sheet before lamination has a density of 60 to 150 kg / m ³ , a closed cell ratio of 60% or more, and 7 or more cells in the thickness direction. Laminated foam sheet. It is a manufacturing method of the polypropylene resin laminated foam sheet in any one of Claims 1-3, Comprising: In extrusion lamination, the clearance gap (the nip roll and the cooling roll for crimping | bonding a polypropylene resin foam sheet and a non-foamed resin layer ( T1) satisfies the following formula (1) with respect to the thickness (T2) of a polypropylene resin foam sheet, The manufacturing method of a polypropylene resin laminated foam sheet characterized by the above-mentioned.
0.2 ≦ T1 / T2 ≦ 0.6 Formula (1)   The molded object obtained by heat-molding the polypropylene resin laminated foam sheet in any one of Claims 1-3.

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