JP2005297291A - Laminated foamed polypropylene resin sheet, production method, and molding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laminated foamed polypropylene resin sheet which is excellent in lightweight properties, heat resistance, and rigidity and produces a decorative molding simply by heating and molding. <P>SOLUTION: The laminated sheet is obtained by laminating a non-foamed layer on an extruded foamed polypropylene resin sheet. A pattern allotted to each mold used when at least two moldings are obtained simultaneously in the heating/molding of the laminated sheet is applied to the non-foamed layer so that the laminated foamed polypropylene resin sheet having the above characteristics can be obtained. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a polypropylene-based resin laminated foam sheet. More specifically, the present invention relates to a polypropylene-based resin laminated foam sheet that is excellent in design properties and suitable for food container applications and the like because a molded body that is simply decorated by heat molding can be obtained.

  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.

  However, polystyrene-based resin foam sheets that are widely used in food containers and the like have the disadvantage of being inferior in heat resistance and oil resistance due to the nature of the polystyrene-based resin as a base material.

  On the other hand, polypropylene resin with excellent heat resistance and oil resistance has been considered difficult to obtain an extruded foam sheet because of its low viscosity and tensile strength at the time of melting, but in recent years by irradiating the polypropylene resin with radiation. A method using a resin in which long chain branching is introduced (for example, Patent Document 1) or a method using a resin obtained by modifying a polypropylene resin by reaction with a conjugated diene compound and a radical polymerization initiator (for example, Patent Document 1) 2) etc., it was found that a foam sheet can be produced.

  In addition, for the purpose of improving the rigidity immediately after heating of the polypropylene resin foam sheet, a laminated foam sheet in which biaxially stretched polypropylene resin films are laminated has also been proposed (for example, Patent Document 3).

However, the polypropylene-based resin film laminated to improve rigidity is colorless, or has been printed with a single color or endless wood grain pattern, and the molded product obtained by thermoforming becomes monotonous. In addition, when filling and selling contents such as sugar beet, it was not possible to sufficiently stimulate consumers' willingness to purchase.
Japanese Patent No. 2521388 JP-A-11-228726 JP-A-11-170455

  An object of the present invention is to provide a polypropylene-based resin laminated foam sheet that is excellent in light weight, heat resistance, and rigidity, and that can provide a molded body that is simply decorated by heat molding.

  As a result of intensive studies to solve such problems, the present inventor, as a result, positions allocated for each mold used when simultaneously obtaining a plurality of molded bodies by thermoforming the non-foamed layer of the polypropylene resin laminated foam sheet It has been found that by giving a pattern to the shape in advance, it is possible to easily obtain a molded article having excellent design properties, and the present invention has been achieved.

That is, the present invention
A polypropylene resin laminated foam sheet obtained by laminating a non-foamed layer on a polypropylene resin extruded foam sheet, and a pattern assigned to each mold used for heat molding of the polypropylene resin laminated foam sheet is applied to the non-foamed layer. A polypropylene-based resin laminated foam sheet (claim 1),
The polypropylene resin laminated foam sheet according to claim 1, wherein the polypropylene resin film printed with the pattern and a polypropylene resin extruded foam sheet are laminated.
The polypropylene resin laminated foam sheet according to claim 2, wherein when the polypropylene resin film on which the pattern is printed and the polypropylene resin extruded foam sheet are laminated, the tension of the polypropylene resin film is controlled. A manufacturing method (claim 3), and
A molded body obtained by thermoforming the polypropylene-based resin laminated foam sheet according to claim 1 (Claim 4).
About.

  The polypropylene resin laminated foam sheet of the present invention is excellent in light weight, heat resistance, and rigidity, and can be molded into a molded body that is easily decorated by heat molding. it can.

  A feature of the present invention is that a plurality of moldings are simultaneously performed by thermoforming by applying a pattern assigned to each mold used when simultaneously obtaining a plurality of molded bodies by thermoforming on a non-foamed layer of a polypropylene resin laminated foam sheet. When obtaining a body, the same pattern is formed on each molded body. Here, the pattern formed on each molded body is, for example, colored at the edge of the dish-shaped molded body, with a ceramic-like pattern, or colored at the bottom and sides of the container-shaped molded body. Different designs, such as different designs on the left and right sides of the molded product, exhibit high design characteristics by combining with the molded product shape, etc. Does not include patterns that do not need to be done.

  The pattern of the non-foamed layer is preferably arranged and designed in consideration of shrinkage or drawdown of the polypropylene-based resin laminated foam sheet under preheating conditions during thermoforming, and the pattern of the same shape is not necessarily required. They are not necessarily lined up at intervals. To match the shape of the pattern with the shape of the molded body, heat-mold a polypropylene resin laminated foam sheet with a pattern such as a lattice or concentric circles, and grasp the pattern shift and partial elongation due to drawdown. It is preferable to determine a pattern for designability.

  The polypropylene resin used in the non-foamed layer in the present invention is one or more of a propylene homopolymer, a block copolymer with a copolymerizable α-olefin, and a random copolymer, Examples thereof include crystalline polymers. As propylene copolymers, those containing propylene in an amount of 75% by weight or more, particularly 90% by weight or more, are retained in the crystallinity, rigidity, chemical resistance, etc., which are characteristic of polypropylene resins. preferable. Examples of copolymerizable α-olefins include ethylene, butene-1, isobutene, pentene-1, 3-methyl-butene-1, hexene-1, 4-methyl-pentene-1, 3,4-dimethyl-butene- 1, one or more of heptene-1, 3-methyl-hexene-1, octene-1, decene-1, and the like. Of these, ethylene and butene-1 are preferable in that they are inexpensive. Moreover, the polypropylene resin used for the non-foamed layer may contain a resin or rubber other than the polypropylene resin as necessary.

  There is no limitation on the method of forming a pattern assigned to each mold used when simultaneously obtaining a plurality of molded bodies by thermoforming on the non-foamed layer of the polypropylene resin laminated foam sheet, for example, a pattern is printed in advance. Examples include a method of laminating a polypropylene resin film and a polypropylene resin extruded foam sheet, and a method of printing a non-foamed layer after forming a plain non-foamed layer on a polypropylene resin extruded foam sheet by lamination or coextrusion. It is done. Among these, a method of laminating a polypropylene resin film preliminarily printed with a pattern and a polypropylene resin extruded foam sheet is preferable because of high productivity.

  Furthermore, when laminating a polypropylene resin film pre-printed with a polypropylene resin extruded foam sheet, controlling the tension of the polypropylene resin film makes it easier to stabilize the quality of the polypropylene resin laminated foam sheet. To preferred. Here, as a method for controlling the tension of the film, there is a method in which the tension is detected by a load cell or the like attached to a roll and the resistance of the film feeding portion is controlled from when the film is fed to when the film is laminated. It is done. The tension to be set may be appropriately set depending on the properties of the polypropylene resin film to be used and the laminating apparatus. However, it is preferable that the tension swing is ± 8% or less of the set value, and ± 5% or less. More preferred. Thereby, the local elongation of a film is suppressed, and when it is set as a polypropylene resin foaming laminated sheet, position shift with a metal mold | die can be eliminated. In addition, in the case of a film having a pattern like a whole-grain pattern that has been conventionally used, the film elongation does not matter as long as it does not affect the film width, and thus precise film tension control is unnecessary.

  In addition, there is no limitation on the method of laminating the polypropylene resin film and the polypropylene resin extruded foam sheet preprinted with the pattern, for example, the method of laminating with the polypropylene resin extruded foam sheet after preheating the polypropylene resin film, Examples include a method of laminating via an adhesive and a method of laminating via a polypropylene resin extruded from a T die. Among these, the method of laminating via a polypropylene resin extruded from a T die is preferable because the quality is easily stabilized. In addition, the polypropylene resin extruded from the T-die preferably has a melt flow rate of 5 to 15 g / 10 minutes because of good adhesion and less uneven thickness.

  The polypropylene-based resin film is preferably a biaxially-stretched polypropylene-based resin film because the pattern is easily stretched uniformly during the thermoforming of the polypropylene-based resin laminated foam sheet.

  In the present invention, the method for printing a pattern on the polypropylene resin film is not limited, and examples thereof include gravure printing and screen printing. Of these, gravure printing is preferred because of its high productivity.

  Gravure printing can be performed by using an ink whose main component is a mixture of a resin, a solvent and a pigment in the polypropylene resin film. Resins for printing inks include copolymers of vinyl chloride and vinyl acetate, chlorinated products of rubber, chlorinated products of polyvinyl acetate, chlorinated products of polypropylene, polymers of acrylic acid and its derivatives, condensation of dimer acid and polyamine Products, polyester or polyether and diisocyanate polymers, cell source nitrate ester compounds, and the like. Moreover, you may use those resin 1 type or in mixture of 2 or more types. In particular, from the viewpoint of adhesiveness to a polypropylene resin, a chlorinated product of polypropylene or a chlorinated product of polyvinyl acetate is preferable. Moreover, you may add an anchor coating agent, an antistatic agent, a stabilizer, antioxidant, a dispersing agent etc. to printing ink as needed.

  In the present invention, an anchor coating agent can be used in order to improve the adhesiveness between the printed polypropylene resin film and the polypropylene resin extruded foam 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 it is a solvent system or an aqueous system, the solvent and water are volatilized by coating and drying, and coating with a desired basis weight can be easily performed.

  In addition, when laminating the printed polypropylene resin film and the polypropylene resin extruded foam sheet, the printed surface of the polypropylene resin film is placed on the inner surface (polypropylene tree extruded foam sheet side) to provide gloss. A laminated foam sheet having excellent oil resistance can be obtained.

  As described above, the non-foamed layer can be formed.

  The thickness of the non-foamed layer in the present invention is preferably 20 to 200 [mu] m, more preferably 70 to 120 [mu] m, from the viewpoint that there are few printing omissions and is excellent in lightness and cost.

The density of the polypropylene resin extruded foam sheet in the present invention is preferably 100 to 500 kg / m ³ , and more preferably 110 to 200 kg / m ³ , since it is excellent in lightness and rigidity.

  The closed cell ratio of the polypropylene resin extruded foam sheet in the present invention is preferably 50% or more because of excellent heat moldability and rigidity.

  The thickness of the polypropylene resin extruded foam sheet in the present invention is preferably 1 to 5 mm, more preferably 1.3 to 2.5 mm, because of excellent heat moldability and rigidity.

The basis weight of the polypropylene resin extruded foam sheet in the present invention is preferably 0.20 to 0.35 kg / m ² because it is excellent in lightness, rigidity and cost.

  Although there is no restriction | limiting in particular in the polypropylene resin used for manufacture of the polypropylene resin extrusion foamed sheet in this invention, Since it becomes easy to control the density, closed cell ratio, and thickness of an extrusion foamed sheet, it is 230 of polypropylene resin. The melt tension measured at ° C is preferably 5 g or more, more preferably 7 g or more.

  The melt tension is measured as follows. Using a Toyo Seiki melt tension tester, a polypropylene resin heated to 230 ° C. was extruded at a speed of 1 m / min from an orifice having a diameter of 1 mm, a length of 10 mm and an inflow angle of 45 °, and the extrudate was subjected to tension detection. The product was wound up while passing through a pulley for accelerating from a speed of 1 m / min, and the tension value when the extrudate was cut was measured, and the value was taken as the melt tension.

In addition, the polypropylene resin used in the production of the polypropylene resin extruded foam sheet in the present invention has a smaller drawdown during the heat molding of the laminated foam sheet, and the pattern assigned to each mold used for the heat molding is designed. Therefore, the equilibrium compliance measured at 210 ° C. is preferably less than 1.2 × 10 ⁻² Pa ⁻¹ .

  The equilibrium compliance is measured using a rheometer SR-2000 manufactured by Rheometric Scientific by the following method. After sandwiching a molded product of polypropylene resin having a thickness of 3 mm between two parallel disks and maintaining the temperature at 210 ± 1 ° C. and sufficiently melting, the interval between the parallel disks is adjusted to 1.4 mm, Remove the resin protruding from the disc. Next, at time t = 0, one disk is rotated with respect to the other so that the stress σc applied to the sample is maintained at a constant value of 100 N / m 2, and the strain amount γ (t (t ) Is measured over time.

  Next, the creep compliance J (t) defined by the following equation (1) is plotted against the time t from the start of giving the stress σc.

  After sufficient time has elapsed, the creep compliance J (t) has a linear relationship with the time t, and the equilibrium compliance is a linear relationship between the creep compliance J (t) and the time t. Is given as an intercept when the extrapolated portion at time t = 0.

As a polypropylene resin whose equilibrium compliance measured at 210 ° C. is less than 1.2 × 10 ⁻² Pa ⁻¹ , for example, a linear polypropylene resin is irradiated with radiation, or a linear polypropylene resin is used. Examples thereof include polypropylene resins containing a branched structure or a high molecular weight component obtained by a method such as melt-mixing a radical polymerization initiator and a conjugated diene compound such as isoprene or butadiene. Among these, a modified polypropylene resin obtained by melt-mixing a linear polypropylene resin, a radical polymerization initiator and a conjugated diene compound is preferable because it can be produced at a low cost.

  There is no restriction | limiting in the shape and magnitude | size of the said polypropylene resin, A pellet form may be sufficient.

  Examples of the foaming agent used for producing the polypropylene resin extruded foam sheet in the present invention include aliphatic hydrocarbons such as propane, butane, isobutane, pentane, hexane, and heptane, and fats such as cyclobutane, cyclopentane, and cyclohexane. Cyclic hydrocarbons, chlorodifluoromethane, dichloromethane, dichlorofluoromethane, dichlorodifluoromethane, trichlorofluoromethane, chloroethane, dichlorotrifluoroethane, dichlorotetrafluoroethane, trichlorotrifluoroethane, tetrachlorodifluoroethane, perfluorocyclobutane, etc. Inorganic gases such as halogenated hydrocarbons, nitrogen, carbon dioxide, and air can be used. You may use these individually or in mixture of 2 or more types.

  The addition amount of the foaming agent in the present invention is selected depending on the type of foaming agent and the density of the foam sheet desired to be extruded, but is generally preferably 0.5 to 10 parts by weight with respect to 100 parts by weight of the resin mixture.

  Moreover, in order to control the bubble diameter of the extruded foam sheet to an appropriate size, for example, a chemical foaming agent such as a mixture of sodium bicarbonate and citric acid or a physical foam nucleating agent such as talc is used in combination. Also good. These addition amounts used as necessary are generally used in an amount of 0.01 to 5 parts by weight with respect to 100 parts by weight of the resin mixture.

  In the polypropylene resin used in the production of the polypropylene resin extruded foam sheet in the present invention, if necessary, an antioxidant, a metal deactivator, and a phosphorus-based processing are used as long as the effects of the present invention are not impaired. Stabilizers, UV absorbers, UV stabilizers, optical brighteners, metal soaps, antacid adsorbent stabilizers, crosslinking agents, chain transfer agents, nucleating agents, lubricants, plasticizers, fillers, reinforcing materials, pigments Additives such as dyes, flame retardants and antistatic agents may be used.

  Moreover, since the laminated foam sheet in this invention is excellent in secondary moldability, such as plug molding, vacuum molding, and pressure forming, it is possible to obtain a molded article having a small thickness unevenness and a beautiful appearance.

  Examples of secondary molding 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・ Methods such as AND ridge molding and ridge molding can be mentioned.

  In the examples and comparative examples, various evaluations were performed by the following methods.

(Extruded foam sheet thickness)
The thickness was measured at 10 points in the width direction of the obtained foamed sheet, and the average value was obtained.

(Extruded foam sheet density)
The density of the obtained foamed sheet was measured according to JIS-K6767.

(Closed cell ratio of extruded foam sheet)
The closed cell ratio of the obtained foam sheet was measured with an air pycnometer according to ASTM D-2856.

(Amount of extruded foam sheet)
It calculated from the area and weight of the strip cut out to the width of 100 mm in parallel with the width direction of the obtained foam sheet.

(Compatibility between the molded foam sheet and the molded product during heat molding)
Using a continuous molding machine (FLC415-PB4-C3-S, manufactured by Asano Laboratories), the upper heater set temperature is 400 ° C., the lower heater set temperature is 430 ° C., the upper die is female, and the lower die Was molded with a non-foamed layer as the bottom by matched molding using a male mold. The molding die has a round plate-shaped container having a flange with a width of 20 mm at the mouth, the container mouth having an outer diameter of 220 mm, an inner diameter of 200 mm, a bottom diameter of 160 mm, and a depth of 30 mm. A total of 16 pieces are arranged, with 4 pieces arranged at intervals of 250 mm in the width direction and 4 pieces arranged at intervals of 250 mm in the flow direction. . For all the molded articles molded at once, the conformity between the pattern and the molded article was evaluated according to the following criteria from the deviation of the flange portion of the molded article and the pattern.
(Double-circle): The pattern exists in the whole surface in the flange part of all the molded objects.
○: The width of the part deviated from the pattern is less than 1 mm in the flange portions of all the molded bodies.
X: In the flange part, there is a molded body having a width of 1 mm or more at a part removed from the pattern.

  The polypropylene resin used in the production of the extruded foam sheets of Examples and Comparative Examples is shown below.

  PP-1: propylene homopolymer having a melt tension of 13.7 g and an equilibrium compliance of 0.8 × 10 −2 Pa-1 (t-butyl peroxybenzoate 0.25 with respect to a propylene homopolymer having a melt flow rate of 3 g / 10 min) After stirring and mixing parts by weight with a blender, the mixture was supplied to a twin screw extruder, and 0.5 parts by weight of isoprene was press-fitted from the middle of the extruder using a liquid pump, and melt kneaded at 200 ° C. to produce. .

  PP-2: propylene homopolymer having a melt tension of 10.1 g and an equilibrium compliance of 1.1 × 10 −2 Pa−1 (0.4% of t-butyl peroxybenzoate with respect to a propylene homopolymer having a melt flow rate of 3 g / 10 min) After stirring and mixing parts by weight with a blender, the mixture was supplied to a twin-screw extruder, 0.3 parts by weight of isoprene was injected from the middle of the extruder using a liquid pump, and melt-kneaded at 200 ° C. to produce. .

(Example 1)
Tandem extrusion consisting of 115 mmφ uniaxial -150 mmφ uniaxially blended with 100-1 part by weight of PP-1 and 0.14 part by weight of bubble nucleating agent (Cermic 417, manufactured by Sankyo Kasei Co., Ltd.) with a ribbon blender And melted in a first stage extruder (115 mmφ) set at 200 ° C., and then, 1.7 parts by weight of isobutane as a foaming agent was pressed into and mixed with 100 parts by weight of the resin composition. It is cooled in the second stage extruder (150mmφ) set to, discharged from the circular die (225mm) under atmospheric pressure, blown while being molded in a cooling tube of 670mmφ, and stretched and cooled by blowing air inside. This was cut into two sheets with a cutter to obtain an extruded foam sheet having a width of 1050 mm. The density of the obtained extruded foamed sheet was 145 kg / m ³ , the closed cell ratio was 78%, the thickness was 1.9 mm, and the basis weight was 0.28 kg / m ² .
On a polypropylene resin biaxially stretched film (thickness 30 μm and width 1030 mm), four black rings having an outer diameter of 225 mm and an inner diameter of 195 mm are arranged at intervals of 250 mm in the width direction and 250 mm intervals in the flow direction. It was gravure printed.
Using extrusion laminating equipment, propylene homopolymer (melt flow rate 9 g / 10 min) is extruded into a film from a T-die, and the extruded foam sheet and printed biaxially stretched film are fed out and pressure-bonded between two rolls. The laminated foam sheet in which the thickness of the non-foamed layer composed of the printed biaxially stretched film and the extruded resin was 100 μm was obtained by taking out the film. Here, the tension control of the printed biaxially stretched film is performed by detecting the tension by passing a roll directly connected to the load cell, and adjusting the rotational resistance of the film feeding portion according to this tension. When the tension was set to 10 kg and the film tension was controlled by adjusting the resistance of the feeding shaft, the film tension shook in the range of 9.8 to 10.2 kg, and the deflection width was ± 2% or less of the set value. .
The obtained laminated foam sheet was heat-molded using a continuous molding machine (Asano Laboratory Co., Ltd., FLC415-PB4-C3-S), and the suitability of the laminate foam sheet pattern and the molded product was evaluated. As a result, the entire surface was a pattern in the flange portions of all 16 molded bodies molded at one time, and the evaluation was good. The evaluation results are shown in Table 1.

(Example 2)
Except that the polypropylene resin was changed to PP-2, an extruded foam sheet having a density of 153 kg / m ³ , a closed cell ratio of 84%, a thickness of 1.6 mm and a basis weight of 0.25 kg / m ^{2 was} obtained in the same manner as in Example 1. In addition, a laminated foam sheet having a non-foamed layer thickness of 80 μm was obtained using the printing film of Example 1 by extrusion lamination. The evaluation results are shown in Table 1.

(Comparative Example 1)
When extruding and laminating an extruded foam sheet and a printed film to obtain a laminated foam sheet, when the film tension was not controlled, the tension fluctuated in the range of 7 to 15 kg, and the obtained laminated foam sheet The pattern was displaced by a maximum of 12 mm in the flow direction due to stretching of the printing film. The evaluation results are shown in Table 1.

(Comparative Example 2)
A laminated foam sheet was obtained in the same manner as in Example 2 except that the film for printing the pattern was an unstretched polypropylene resin film (thickness 25 μm and width 1030 mm). The evaluation results are shown in Table 1.

(Example 3)
When printing a pattern on an unstretched polypropylene-based resin film, a laminated foamed sheet was obtained in the same manner as in Comparative Example 2, except that the pattern in the center two rows in the width direction was moved 7 mm outward. The evaluation results are shown in Table 1.

  From the laminated foamed sheet of the example, there was a pattern printed in advance on the flange portion, and a molded article excellent in design was obtained. On the other hand, the laminated foamed sheet of Comparative Example 1 in which tension control was not performed when laminating the print film had a pattern that was greatly displaced even when molded, and was poor in design. Further, in the laminated foam sheet of Comparative Example 2 in which the drawdown during heat molding is relatively large, it is unacceptable for the molded product formed from the two inner rows of the molding dies arranged in four rows parallel to the flow direction. There was a shift, and when the elongation due to drawdown was not taken into account, the pattern was shifted. On the other hand, when the position of the pattern was shifted in advance in consideration of the drawdown amount, the shift of the pattern in the flange portion was within an allowable range in all the molded bodies.

Claims (4)

  A polypropylene resin laminated foam sheet obtained by laminating a non-foamed layer on a polypropylene resin extruded foam sheet, and a pattern assigned to each mold used when simultaneously obtaining a plurality of molded bodies in the heat molding of the laminated foam sheet A polypropylene-based resin laminated foam sheet, characterized in that is applied to a non-foamed layer.   The polypropylene resin laminated foam sheet according to claim 1, wherein the polypropylene resin film on which the pattern is printed and a polypropylene resin extruded foam sheet are laminated.   The polypropylene resin laminated foam sheet according to claim 2, wherein when the polypropylene resin film on which the pattern is printed and the polypropylene resin extruded foam sheet are laminated, the tension of the polypropylene resin film is controlled. Manufacturing method.   The molded object obtained by heat-molding the polypropylene resin laminated foam sheet of Claim 1 or 2.