JP2007276219A - Polypropylene resin laminated foamed sheet and its molded object - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polypropylene resin laminated foamed sheet capable of being molded into a molded object having proper slip properties suitable for a container in a case that the automatic filling of content especially such as precooked Chinese noodles or the like is performed. <P>SOLUTION: The polypropylene resin laminated foamed sheet capable of being molded into the molded object having proper slip properties can be obtained by coating at least one side of the polypropylene resin laminated foamed sheet with a silicone oil emulsion in an amount of 0.001-0.2 g/m<SP>2</SP>in terms of base oil. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a polypropylene resin laminated foam sheet having an appropriate slip property 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 easily obtain molded products by thermoforming such as vacuum forming. At the center, it is widely used in food container applications. And for instant noodle containers, molding obtained by thermoforming a polystyrene resin laminated foam sheet in which a polystyrene resin non-foamed film is laminated on the surface of the polystyrene resin foam sheet from the viewpoint of lightness, heat insulation, mechanical strength, etc. The product is widely used. However, the molded product of the polystyrene-based resin laminated foamed sheet can be suitably used when cooking by pouring hot water, but when it is heated using a microwave oven due to insufficient heat resistance, deformation, etc. It sometimes caused problems.

  On the other hand, polypropylene-based resin foam sheets are excellent in heat resistance and oil resistance, and can be applied to microwave oven heating. Therefore, they are used in pasta containers for convenience stores. However, when filling the molded body by hand such as pasta, the slipperiness of the molded body has not been a problem, but when automatic filling is performed by a machine such as instant noodles, the slipperiness is important. In other words, if the sliding property is poor, the molded products cannot be stacked straight due to catching, it is difficult to supply the stacked molded products one by one to the line, or the molded products stay between belt conveyors. On the other hand, if it is too slippery, there may be a problem in conveying the molded product on the line.

For the purpose of improving the slipperiness of such a molded product, a conventional method of applying a silicone oil to the surface of 0.10 to 0.20 g / m ² for a polystyrene resin laminated foam sheet (for example, Patent Documents 1 and 2). ) Has been proposed, but even when applied to a polypropylene-based resin laminated foam sheet, the failure in conveying the molded body has not been resolved.

In addition, since the polypropylene resin is highly charged by static electricity, it sometimes causes problems such as dust and dust adhering to the surface of the molded body.
JP-A-6-335988 JP 2004-330650 A

  An object of this invention is to provide the polypropylene-type resin laminated foam sheet which can obtain the molded object which has moderate slipperiness.

  As a result of earnestly studying the container formed by molding a polypropylene resin laminated foam sheet so that it can be suitably used in a line for automatically filling contents, a method of applying an appropriate amount of silicone oil to the laminated foam sheet And found the present invention.

That is, the present invention
A polypropylene resin laminated foam sheet obtained by laminating a non-foamed layer made of polypropylene resin on at least one surface of a polypropylene resin foam sheet, and a silicone oil emulsion is applied to at least one surface of the laminated foam sheet. In addition, a polypropylene-based resin laminated foam sheet (Claim 1) that is applied in an amount of 0.001 to 0.2 g / m ^{2 in} terms of base oil.
The polypropylene-based resin laminated foam sheet according to claim 1, wherein the silicone oil emulsion contains an antistatic agent (claim 2), and the polypropylene-based resin laminated foam sheet according to claim 1 or 2, are thermoformed. Formed body (Claim 3)
About.

  The molded product obtained by molding the polypropylene-based resin laminated foam sheet according to the present invention has an appropriate slipperiness without causing problems in stacking and belt conveyor transportation in the molding process and the subsequent content filling process. Is.

  In the polypropylene resin laminated foam sheet of the present invention, a small amount of silicone oil emulsion is applied to a polypropylene resin laminated foam sheet obtained by laminating a polypropylene resin non-foamed layer on at least one surface of the polypropylene resin foam sheet. Thus, the slipperiness of the molded body obtained by heat molding is improved.

  The type of silicone oil used in the present invention is generally widely used as a silicone release agent, that is, dimethyl silicone oil, methylphenyl silicone oil, etc. can be used, but the stability of the coating film, surface tension, From the viewpoint of surface energy, dimethyl silicone oil is preferred. Silicone oils may be emulsion type, oil type, spray type, etc., depending on the supply form, but the emulsion type silicone oil that can be used after diluting with water is environmental impact and safety. Furthermore, it is preferable in that a very small amount of application as in the present invention is uniformly and stably performed.

The coating amount of the polypropylene-based resin foam sheet surface of the silicone oil in the present invention is preferably 0.001-0.2 grams / m ^2, and more preferably 0.005~0.05g / m ² . If the application amount of the silicone oil is less than 0.001 g / m ² , the slip may be poor, and if the application amount exceeds 0.2 g / m ² , the slip may be excessive and economical efficiency will be impaired.

  Application | coating of the silicone oil emulsion to the polypropylene resin laminated foam sheet in this invention can be performed by the well-known roll coater method or the spraying method. Among them, the gravure coater method is preferable from the viewpoint of the uniformity of the coating film, and the method of spraying droplets from a rotor that rotates at high speed (for example, WEKO rotor dampening manufactured by Nikka Corporation) is preferable in terms of easy process control.

  When applying using the above-described application method, the amount of silicone oil applied in the present invention is very small, so it is necessary to dilute the silicone oil emulsion with ion-exchanged water. In some cases, the wettability of the diluted solution to the surface of the resin-based resin laminated foam sheet is extremely deteriorated, resulting in coating unevenness and drying unevenness. The dilution ratio of the silicone oil emulsion is preferably 5 to 50 times, more preferably 10 to 40 times.

  In the polypropylene resin laminated foam sheet of the present invention, the surface on which the silicone oil is applied may be either one or both surfaces of the polypropylene resin laminated foam sheet, but the lid is heat sealed like an instant noodle container or the like. In some cases, it is preferable to apply silicone oil only to the outer surface of the container.

  Furthermore, the addition of an antistatic agent to the silicone oil emulsion used in the present invention reduces the surface resistivity of the laminated foamed sheet and causes problems due to electrostatic charging such as surrounding dust and dust adhering to the surface of the molded product. Can be easily eliminated.

  Antistatic agents used in the present invention include poly (oxyethylene) alkylamine, poly (oxyethylene) alkylamide, poly (oxyethylene) alkyl ether, poly (oxyethylene) alkylphenyl ether, glycerin fatty acid ester, sorbitan fatty acid ester Nonionic systems such as alkyl sulfonates, alkylbenzene sulfonates, alkyl sulfates, alkyl phosphates, etc .; cationic systems such as hydroxyalkylethanolamines, quaternary ammonium chlorides, quaternary ammonium sulfates, quaternary ammonium nitrates, etc. Surfactants such as amphoteric systems such as alkylbetaines, alkylimidazolines, and alkylalanines. Of these, anionic surfactants and cationic surfactants are preferred because they are easy to use in combination with silicone oil emulsions and have a high effect of reducing surface resistivity.

The amount of the antistatic agent applied to the polypropylene resin foam sheet surface in the present invention is preferably 0.001 to 0.05 g / m ² , although it depends on the type of the antistatic agent used. More preferably, it is -0.04g / m < ² >. When the coating amount of the antistatic agent is less than 0.001 g / m ^2, insufficient improvement of the surface resistivity, sometimes dirt and dust may adhere, is applied beyond 0.05 g / m ² However, the antistatic effect is saturated and the economic efficiency is impaired.

  The polypropylene-based resin foam sheet in the present invention is obtained by extrusion-foaming a polypropylene-based resin. However, as a polypropylene-based resin as a base material, a linear sheet is used because a foam sheet is easily obtained because of high melt tension. A polypropylene resin (hereinafter also referred to as “raw polypropylene resin”) that is irradiated with an electron beam to introduce long chain branching (for example, HMS-PP manufactured by Sun Allomer Co., Ltd.), or raw polypropylene It is preferable to employ a modified polypropylene resin obtained by melt-kneading an isoprene monomer and a radical polymerization initiator with respect to a resin. In particular, a modified polypropylene resin obtained by melting and kneading a raw material polypropylene resin, an isoprene monomer and a radical polymerization initiator is preferable from the viewpoint that it can be produced at low cost.

Furthermore, the polypropylene resin used in the production of the polypropylene resin foam sheet in the present invention has an equilibrium compliance Jeo measured at 210 ° C. of 1.2 × 10 −2 because the drawdown during molding of the laminated foam sheet is small. It is preferably less than ³ Pa- ¹ .

The equilibrium compliance Jeo in the present specification is measured by the following method using a rheometer SR-2000 manufactured by Rheometric Scientific. 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 relative 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 at that time is over 300 seconds. (T) is measured over time. Next, the creep compliance J (t) defined by the following formula is plotted against the time t from the start of giving the stress σc.

After sufficient time has passed, the creep compliance J (t) has a linear relationship with the time t, and the equilibrium compliance Jeo is a straight line in the plot of the creep compliance J (t) and the time t. It is given as an intercept when extrapolating the part giving the relationship at time t = 0.

  As the raw material polypropylene resin in the present invention, a copolymer obtained by copolymerizing another monomer that can be copolymerized with propylene may be used. Examples of other monomers that can be copolymerized with propylene include ethylene, butene-1, α-olefin, cyclic olefin, diene monomer, and vinyl monomer. Of these monomers, ethylene or butene-1 is preferred because it is inexpensive.

  If necessary, other resins or rubbers may be added to the polypropylene resin as the base resin in the present invention as long as the effects of the present invention are not impaired. The amount of other resin or rubber added to the polypropylene resin as the base resin varies depending on the type of this resin or the type of rubber, as long as it is within the range not impairing the effects of the present invention as described above. Usually, it is preferably about 25 parts by weight or less.

  In the polypropylene resin as the base resin in the present invention, if necessary, an antioxidant, a metal deactivator, a phosphorus processing stabilizer, an ultraviolet absorber, an ultraviolet stabilizer, a fluorescent brightening agent, Effects of the present invention include stabilizers such as metal soaps and antacid adsorbents, or additives such as crosslinking agents, chain transfer agents, nucleating agents, lubricants, plasticizers, fillers, reinforcing materials, pigments, dyes, and flame retardants. You may add in the range which does not impair.

  The polypropylene-based resin foam sheet in the present invention is obtained by, for example, melting and kneading a polypropylene-based resin, a nucleating agent, and a resin and additives blended as necessary in an extruder, press-fitting a foaming agent, and then resin in the extruder After cooling and adjusting the temperature to a suitable foaming temperature, a circular die having an annular lip is used and extruded from the lip of the die into atmospheric pressure (that is, foaming is performed by releasing the pressure) to obtain a cylindrical foam. Then, after stretching and cooling with a cylindrical cooling cylinder (mandrel) installed inside the cylindrical foam so as to cool from the inner surface side of the cylindrical foam, a sheet shape obtained by cutting open and obtaining a foam sheet It is easily manufactured by the method of making. Further, if necessary, air may be blown from the inside and outside of the cylindrical foam before the cooling cylinder or at the position of the cooling cylinder.

  Examples of the blowing agent in the present invention include aliphatic hydrocarbons, alicyclic hydrocarbons, halogenated hydrocarbons, inorganic gases, water, and the like, and one or more of them are used in combination. Also good. Although the addition amount of a foaming agent changes with kinds of foaming agent and the density of the target foam sheet, 0.5-10 weight part is preferable with respect to 100 weight part of polypropylene resin, and 1-5 weight part is more. preferable.

  Examples of the nucleating agent in the present invention include sodium bicarbonate-citric acid mixture, organic acid metal salt, talc and the like, and one or more of them may be used in combination. The addition amount of the nucleating agent varies depending on the type of the nucleating agent and the number of cells in the target foam sheet, but is usually preferably 0.01 to 3 parts by weight with respect to 100 parts by weight of the polypropylene resin. .

The density of the polypropylene resin foam sheet in the present invention is preferably 75 to 300 kg / m ³ , more preferably 90 to 150 kg / m ^3, since the thickness of the molded body is easy to ensure and the rigidity of the molded body is high.

The basis weight of the polypropylene-based resin foam sheet in the present invention is preferably 0.23 to 0.50 kg / m ² because it is lightweight and economically advantageous, and the molded article has high rigidity. .45 kg / m ² is more preferred.

  Since the polypropylene resin foam sheet in the present invention has good heat insulation and excellent surface properties, the number of cells in the thickness direction is preferably 5 or more, and more preferably 7 or more.

  The closed cell ratio of the polypropylene resin foam sheet used in the present invention is preferably 60% or more, more preferably 70% or more, and further preferably 80% or more. When the closed cell ratio is less than 60%, it is difficult to secure the range of thickness increase of the present invention, and the resulting molded article may have poor rigidity.

  The polypropylene resin non-foamed layer in the present invention is composed of a polypropylene resin film, a resin layer extruded from a polypropylene resin from a T-die, a polypropylene resin film and a polypropylene resin extruded to laminate the resin film. Examples of the lamination method include a heat laminating method, an extrusion laminating method, and a coextrusion method.

  The polypropylene resin film used in the present invention is an unstretched or biaxially stretched polypropylene resin film made of a polypropylene resin such as polypropylene homopolymer or polypropylene copolymer. The laminated film may be a multilayer film having two or more layers. Furthermore, characters and patterns may be printed for the purpose of imparting design properties.

  Examples of the polypropylene resin constituting the polypropylene-based extruded resin layer include a propylene homopolymer, a block copolymer of propylene and another monomer, or a random polymer of propylene and another monomer. However, the polypropylene homopolymer is preferable from the viewpoint of high rigidity and low cost, and a block copolymer of the propylene and another monomer is preferable from the viewpoint of low temperature brittleness. 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 standpoint of maintaining good chemical resistance, the propylene monomer component contained is preferably 75 parts by weight or more, and more preferably 90 parts by weight or more.

  Moreover, in a polypropylene resin non-foamed layer, not only a polypropylene resin can be 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 thickness of the polypropylene resin non-foamed layer laminated in the present invention is preferably 20 μm to 300 μm, more preferably 50 μm to 200 μm, from the viewpoint of adhesiveness, lightness, or rigidity. When the thickness of the non-foamed polypropylene resin layer is less than 20 μm, the effect of increasing the rigidity of the foamed sheet of the present invention tends to be small. When the thickness of the non-foamed polypropylene resin layer exceeds 300 μm, the rigidity of the foamed sheet is improved, but the lightness is impaired and the cost tends to increase.

  Examples of thermoforming of the polypropylene resin laminated foam sheet in the present invention include plug molding, matched molding, straight molding, drape molding, plug assist molding, plug assist reverse draw molding, air slip molding, snapback molding, Examples include reverse draw molding, free drawing molding, plug and ridge molding, and ridge molding. Matched mold molding is preferred because of its excellent mold shape transferability, good appearance, and high rigidity. preferable.

  Examples of the present invention and comparative examples are shown below, but the present invention is not limited to such examples.

  In the examples and comparative examples, the polypropylene foam sheet and the method for producing the laminated foam sheet, the method for applying silicone oil, the production of the molded article for evaluation, and the method for evaluating the molded article are as follows.

[Method for producing foam sheet]
As a base resin for the foamed sheet, 100 parts by weight of homopolypropylene (G103 Polymer, J103WB) having a melt flow rate of 3.8 g / 10 min at 230 ° C., 0.25 radical polymerization initiator (t-butylperoxybenzoate) The pellets of modified polypropylene resin were obtained by melt-kneading 0.5 parts by weight of isoprene and 0.5 parts by weight of isoprene at a resin temperature of 200 ° C. with a twin screw extruder. The modified polypropylene resin had an equilibrium compliance of 0.8 × 10 ⁻³ Pa ⁻¹ .

A blend of 100 parts by weight of the modified polypropylene resin and 0.6 parts by weight of a cell nucleating agent master batch (manufactured by Eiwa Kasei Kogyo Co., Ltd., EE275F) with stirring by a ribbon blender is supplied to a 90-125 mmφ tandem extruder. And melted in a first-stage extruder (90 mmφ) set at 200 ° C., and then, isorich butane (isobutane / normal butane = 85/15) as a foaming agent was added to 100 parts by weight of the foamed sheet base resin. On the other hand, 4.0 parts by weight was press-fitted and mixed, cooled in a second-stage extruder (125 mmφ) set at 160 ° C., and extruded from a circular die (caliber 127 mmφ) at a discharge rate of 80 kg / hour under atmospheric pressure. The cylindrical foam to be discharged is molded from the periphery with a mandrel while being molded with a cylindrical cooling cylinder (mandrel) having an outer diameter of 335 mmφ and a main body length of 800 mm (external portion is 338 mmφ, with an enlarged portion of 40 mm in length). While blowing with air at 3 m ³ / min and drawing and cooling at a take-up speed of 3.9 m / min, a cylindrical foam is obtained by stretching and cooling, and by opening this with a cutter, the width is 1035 mm, the density is 89 kg / m ³ , A polypropylene resin foam sheet having a closed cell ratio of 80%, a basis weight of 0.33 kg / m ² , and 11 cells / thickness was obtained.

[Method for producing laminated foam sheet]
Homopolypropylene with a melt flow rate of 10 g / 10 min at 230 ° C. (CS3230, manufactured by Chisso Corporation) is melt-extruded from a T-die at a resin temperature of 230 ° C., and is pressure-bonded and laminated to the foamed sheet to obtain a thickness of 70 μm and a width of 1030 mm. A polypropylene resin laminated foam sheet having a non-foamed layer was obtained.

[How to apply silicone oil]
A diluted solution of a predetermined silicone oil emulsion was applied to the non-foamed layer side of the laminated foamed sheet using a gravure coater lattice type 400 mesh roll, and a predetermined amount of silicone oil was applied.

[Preparation of molded article for evaluation]
For the laminated foamed sheet coated with the silicone oil, using a m-width continuous vacuum forming machine (FLC415 model manufactured by Asano Laboratories), a mold having the shape shown in FIG. 2 (molded body size: opening 167 mmφ, bottom portion 82 mmφ, Matched mold double-sided vacuum forming was performed at a height of 68 mm, mold clearance: 2.2 mm, number of picks: 25 / shot, and a molded article for evaluation was obtained. The upper heater set temperature is 430 ° C., the lower heater set temperature is 400 ° C., the upper mold is a female mold, the lower mold is a male mold, and the non-foamed layer of the polypropylene resin laminated foam sheet is outside the container (non- Molding was performed so that the foam layer was on the upper surface. After molding, five continuous stacks of five molded bodies were obtained by sequentially punching five times (for one shot) with a continuous puncher attached to the continuous molding machine (five punches in the width direction at the same time).

[Method for evaluating molded article]
(Stackability of molded products)
The stacked state of the five molded bodies was visually observed for five peaks and evaluated according to the following criteria.
○: There is no disturbance in the stack in any mountain ×: There is a mountain in which the stack is disturbed, such as the end being caught

(Evaluation of slipperiness of molded products)
The longitudinal end of the plate 1 having a length of 200 mm and a width of 150 mm is connected to the autograph 2, and the other end is mounted on the autograph using the apparatus (FIG. 1) that slides on a horizontal plane. Then, it is pulled up at a speed of 300 mm / min, an angle when the molded body starts to move is obtained, and an average value of five molded bodies is calculated. Measurement was performed when the surface material of the plate 1 was polypropylene or polytetrafluoroethylene, and the evaluation was made according to the following criteria.
○: The surface material is polypropylene with an angle of less than 30 °, and the surface material is polytetrafluoroethylene with an angle of 10 ° or more. X: The surface material is polypropylene with an angle of 30 ° or more, or the surface material is poly. The angle with tetrafluoroethylene is less than 10 °

(Evaluation of surface resistivity of laminated foam sheet)
Cut out 5 sheets of 10cm square laminated foam sheet after application of silicone oil and leave it for 24 hours or more in an environment of temperature 23 ° C and humidity 50%, then the silicone oil application surface of the laminated foam sheet is 4319A made by Yokogawa Hewlett-Packard. Using a resistance meter, the surface resistivity was measured at an applied voltage of 1000 V and evaluated according to the following criteria.
○: Surface resistivity is less than 1.0 × 10 ⁻¹³ Ω / sq ×: Surface resistivity is 1.0 × 10 ⁻¹³ Ω / sq or more

Example 1
On the non-foamed layer side of the laminated foam sheet, a liquid obtained by diluting a silicone oil emulsion (manufactured by GE Toshiba Silicone, TSM6343, active ingredient 30%) 20 times with ion-exchanged water is used with a gravure coater type 400 mesh roll. 2.0 cc / m ^{2 was} applied, and 0.030 g / m ² of silicone oil was applied in terms of base oil. Table 1 shows the evaluation results of the molded body obtained from the silicone oil-coated laminated foam sheet.

(Example 2)
An anti-static agent (manufactured by Maruhishi Oil Chemical Co., Ltd., Denon 1895, 30% aqueous solution of alkyl sulfonate) added to the silicone oil emulsion used in Example 1 in the same amount as the silicone oil emulsion is 20 Except for using the double diluted solution, 0.029 g / m ² of silicone oil and 0.029 g / m ² of antistatic agent in terms of base oil were applied to the laminated foam sheet in the same manner as in Example 1. Table 1 shows the evaluation results of the molded body obtained from the silicone oil-coated laminated foam sheet.

(Example 3)
0.015 g / in terms of base oil in the same manner as in Example 2 except that the mixture obtained by changing the silicone oil emulsion to Shin-Etsu Silicone (KM9738, active ingredient 30%) was diluted 40 times with ion-exchanged water. m ² silicone oil and 0.015 g / m ² antistatic agent were applied to the laminated foam sheet. Table 1 shows the evaluation results of the molded body obtained from the silicone oil-coated laminated foam sheet.

(Comparative Example 1)
The dilution ratio of the silicone oil emulsion is 100 times, and more, except that the coating amount of 0.3 cc / m ^2, in the same manner as in Example 1, was coated with a silicone oil 0.0009 g / m ² in the base oil in terms . The evaluation results are shown in Table 1.

(Comparative Example 2)
A silicone oil of 0.3 g / m ^{2 in} terms of base oil was applied in the same manner as in Example 1 except that the dilution ratio of the silicone oil emulsion was doubled. The evaluation results are shown in Table 1.

  While the molded product obtained by molding the polypropylene resin laminated foam sheet of the present invention has moderate slipperiness, the molded product in Comparative Example 1 is insufficiently slipped. It can be seen that the molded body is too slippery. It can also be seen that the surface resistivity can be easily lowered by using an antistatic agent in combination.

It is a figure explaining the evaluation method of the slidability of a molded object.

Explanation of symbols

1 board (surface material: polypropylene or polytetrafluoroethylene)
2 Autograph 3 Molded body

Claims (3)

A polypropylene resin laminated foam sheet obtained by laminating a non-foamed layer made of polypropylene resin on at least one surface of a polypropylene resin foam sheet,
A polypropylene resin laminated foam sheet obtained by applying 0.001 to 0.2 g / m ² of a silicone oil emulsion to at least one surface of the laminated foam sheet in terms of base oil.   The polypropylene resin laminated foam sheet according to claim 1, wherein the silicone oil emulsion contains an antistatic agent.   The molded object formed by thermoforming the polypropylene resin laminated foam sheet of Claim 1 or 2.

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