JP2014198404A - Method for manufacturing a polystyrenic resin foam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a simple and inexpensive method for manufacturing a novel and practical polystyrenic resin foam having an attractive streaky pattern of a polystyrenic resin layer and excellent in terms also of surface smoothness.SOLUTION: A resin having a peculiar melt viscosity (melt viscosity of 600-1400 Pa s at a shear rate of 100 secat 200°C) used as a polystyrenic resin for forming a resin layer 3 and a coloring agent and a volatile plasticizer are included within the polystyrenic resin while the respective addition ratios of both are being set within specified ranges. A polystyrenic resin foam 1 in which a streaky pattern of a polystyrenic resin layer 3 is formed on the surface thereof is manufactured in a single step by laminating, in a streaky fashion on the outer circumferential surface of a molten polystyrenic resin 2 for forming a foam layer, a molten polystyrenic resin 3 for forming the resin layer and co-extruding both.

Description

  The present invention relates to a method for producing a sheet-like or plate-like polystyrene-based resin foam having a large number of streaks on its surface.

  Sheet-like or plate-like polystyrene resin foam is excellent in light weight, heat insulation, moldability, etc., as a food container processed by thermoforming, or a box container assembled into a box shape after cutting into a strip shape, Furthermore, it is widely used as a display plate or the like.

  Among them, a sheet-like or plate-like polystyrene-based resin foam having an appearance with a pattern is excellent in appearance and has a high-class feeling, so that consumers' needs have increased and are currently used in large quantities. .

  Conventionally, as a method for producing a sheet-like or plate-like polystyrene resin foam having such a pattern, for example, the following (1) to (3) are known.

(1) A method of printing a pattern directly on the surface of a polystyrene-based resin foam sheet (Patent Document 1).
(2) A method of laminating a film on which a pattern is printed on the surface of a polystyrene-based resin foam sheet containing a colorant with an adhesive or the like (Patent Document 2).
(3) A method of laminating colored or strip-shaped polystyrene resin foam layers on the surface of a polystyrene resin foam sheet by coextrusion (Patent Document 3).

JP 2007-007966 A JP 05-38752 A JP 2003-94896 A

  However, the method of directly printing a pattern on the surface of the foam sheet of (1) requires two steps, namely, a process for producing a foam sheet as a raw fabric and a process for printing a pattern on this. The problem was left in the point. Moreover, since there exists a possibility that printing ink and a to-be-packaged object may contact, the use is limited and the device, such as laminating | stacking a film further on a printing surface, was required.

  The method of laminating a film with a pattern printed on the surface of the foamed sheet in (2) with an adhesive is a process for producing a foam sheet as a raw fabric, a process for producing a film on the surface, and a process for printing a pattern on the surface film. In addition, four steps such as a step of bonding the foam sheet and the film on which the pattern is printed are required, and the problem remains in terms of productivity as in the case (1).

  In addition, the foamed sheet having a streak pattern obtained by this method is difficult to recycle although the ink used for providing the streak pattern is on the inner surface side of the film, so that the ink does not directly touch food. In some cases, there was room for further improvement.

  In the method (3) of coextrusion of a streaky or strip-shaped foam layer on the outer peripheral surface of the foam core layer, a plurality of strip-shaped foam layers having different widths and intervals are laminated on the outer peripheral surface of the foam core layer. Is. Therefore, the polystyrene-based resin foam sheet obtained by this method has a structure in which a foam layer is laminated on the foam core layer, and has a drawback that it cannot form a streak pattern having poor surface smoothness and excellent appearance. .

  As described above, the conventional method for producing a polystyrene-based resin foam having a streak pattern leaves problems in production such as the need for multiple steps and a problem in the obtained foam. For this reason, there has been a strong demand for the development of a practical polystyrene-based resin foam having excellent productivity and a streak pattern with an excellent appearance. However, there has not yet been a satisfactory proposal. .

  The present invention has been made to overcome the above-mentioned problems, and can provide a beautiful streak pattern on the surface of the foam in one step and has an excellent appearance. It aims at providing the manufacturing method of a body.

  In order to solve the above-mentioned problems, the present inventors have completed the present invention as a result of intensive studies on polystyrene resins, plasticizers, colorants, co-extrusion methods, etc. constituting the resin melt for forming a resin layer. It came to do.

  That is, according to this invention, the manufacturing method of the sheet-like or plate-like polystyrene-type resin foam as described in the following <1>-<4> is provided.

<1> A polystyrene resin melt for forming a foam layer is formed by kneading the polystyrene resin (A) and a physical foaming agent, and the outer periphery of the polystyrene resin melt for forming the foam layer in an annular die. A polystyrene resin melt for forming a resin layer is streaked on the surface and coextruded, and the polystyrene resin melt for forming a foam layer is foamed, and the surface of the foam layer is formed by a resin layer. A method for producing a sheet-like or plate-like polystyrene-based resin foam in which a pattern is formed,
The polystyrene resin melt for forming the resin layer is obtained by kneading a polystyrene resin (B), a colorant, and a volatile plasticizer. The polystyrene resin (B) has a 200 ° C. shear rate of 100 sec ⁻¹ . The melt viscosity (ηB) under the conditions is 600 to 1400 Pa · s, and the ratio of the melt viscosity (ηB) to the melt viscosity (ηA) under the conditions of 200 ° C. and a shear rate of 100 sec ⁻¹ of the polystyrene resin (A). (ΗB / ηA) is less than 1.0, and the addition amount of the volatile plasticizer is 0.15 to 1.4 mol per kg of the polystyrene resin (B). Manufacturing method.

<2> The polystyrene resin foam according to <1>, wherein an average lamination amount per resin layer per 1 m in the extrusion direction of the polystyrene resin foam is 0.01 to 0.6 g. Body manufacturing method.

<3> The volatile plasticizer is selected from an aliphatic hydrocarbon having 2 to 7 carbon atoms, an aliphatic alcohol having 1 to 4 carbon atoms, and an aliphatic ether having 2 to 8 carbon atoms, or 2 The method for producing a polystyrene-based resin foam according to any one of <1> or <2>, wherein the polystyrene-based resin foam is one or more species.

<4> The method for producing a polystyrene resin foam according to any one of <1> to <3>, wherein an apparent density of the polystyrene resin foam is 0.35 g / cm ³ or less.

  According to the method for producing a polystyrene resin foam according to the present invention, the melt viscosity (ηB) of the polystyrene resin (B) constituting the polystyrene resin melt for forming the resin layer is 600 to 1400 Pa · s. The ratio (ηB / ηA) of the melt viscosity (ηB) to the melt viscosity (ηA) of the polystyrene resin (A) constituting the polystyrene resin melt for forming the foamed layer is less than 1.0, and the resin layer By using a specific amount of volatile plasticizer as a plasticizer to be included in the forming resin melt, it is possible to produce a polystyrene resin foam having a beautiful streak pattern by the resin layer on the surface of the foam layer. it can.

  In addition, the manufacturing process is extremely simple, only one process, so that the manufacturing cost can be greatly reduced, which is an industrially extremely advantageous manufacturing method.

It is explanatory drawing of the typical polystyrene-type resin foam of this invention. It is explanatory drawing of the manufacturing method of the typical polystyrene-type resin foam of this invention. It is explanatory drawing of the typical cyclic | annular die | dye used by this invention.

  Hereinafter, a typical method for producing a polystyrene-based resin foam (hereinafter simply referred to as a foam) provided with a streak pattern of the present invention will be described with reference to the drawings.

(Method for producing a polystyrene resin foam having a streak pattern on the surface)
FIG. 1 is an explanatory view of a polystyrene resin foam obtained by the production method of the present invention and having a streak pattern formed on a typical surface. 1 is a polystyrene resin having a streak pattern formed on the surface. Foam, 2 is a polystyrene resin foam layer (foam layer), and 3 is a polystyrene resin layer (resin layer). FIG. 2 is an explanatory view of a typical manufacturing method.

  As shown in FIG. 2, using an extruder 12 for forming a foam layer, polystyrene-based resin (A) 8, foaming agent 9, and other additives added as necessary are heated and kneaded to form a foam layer. Polystyrene resin melt (resin melt for forming a foam layer) 10 for use. On the other hand, using an extruder 11 for forming a resin layer, the polystyrene resin (B) 4, the colorant 5, the volatile plasticizer 6, and other additives that are added as necessary are heated and kneaded to obtain a resin layer. A forming polystyrene-based resin melt (resin melt for forming a resin layer) 7 is used.

  Thereafter, the resin melt 7 for resin layer formation is joined to the outer peripheral surface of the resin melt 10 for foam layer formation in a ring die, and is co-extruded to form a resin layer having a streak pattern on the surface of the foam layer. The tubular laminated foam is produced, and the tubular laminated foam is formed into a sheet or plate shape by a method known per se, whereby the resin layer 3 having a streak pattern is laminated on the surface of the foamed layer 2. In addition, the polystyrene foam 1 of the present invention can be produced.

  The method of making the cylindrical laminated foam into a sheet shape or a plate shape is not particularly limited. For example, a method in which one end of the cylindrical laminated foam is cut into a sheet shape, and the sheet-like foam is heated to form a plate shape. And a method of forming a plate by heating a sheet-like foam and molding it with a mold.

  Moreover, the foamed board by which the resin layer 3 of the streaky pattern was laminated | stacked on both surfaces of the foamed layer 2 is obtained by joining the inner surfaces of the foamed layer 2 with a pinch roll, and making it plate shape. You can also

  Here, the streaks mean, for example, linear or belt-like streaks stacked in the extrusion direction as shown in FIG.

  Hereinafter, the production method of the present invention will be described in more detail.

(Polystyrene resin melt for resin layer formation (resin melt for resin layer formation) 7)
In the present invention, a polystyrene resin (B) 4 and a colorant 5, a volatile plasticizer 6, and other additives that are added as necessary are kneaded as a polystyrene resin melt 7 for forming a resin layer. Is used.

(Polystyrene resin (B) 4)
In the present invention, it is important that the resin layer 3 is laminated on the outer peripheral surface of the foam layer 2 so as to have a streak pattern. Therefore, it is necessary to use a polystyrene resin (B) 4 having a melt viscosity ηB of 600 to 1400 Pa · s. If it is within the above range, by using a specific amount of volatile plasticizer described later, the resin layer has sufficient viscosity to form a streak pattern, and the resin layer may spread too much on the foam layer. The foam having a beautiful streak pattern is obtained by following the elongation of the foam layer forming resin melt.
From the viewpoint of more reliably preventing the resin layer from spreading, the lower limit of the melt viscosity of the polystyrene resin (B) is preferably 700 Pa · s, and more preferably 800 Pa · s. On the other hand, since the polystyrene resin melt for forming the resin layer is extruded through a narrow channel, the lower the melt viscosity of the polystyrene resin (B), the more the streaky pattern can be formed, and the upper limit is 1300 Pa · s is preferable, and 1200 Pa · s is more preferable.

  Such polystyrene resins (B) include styrene homopolymers and copolymers, and the styrene component content contained in the polymer is preferably 50% by mass or more, more preferably 80% by mass. That's it.

  Examples of the polystyrene resin include polystyrene, impact polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene-acrylonitrile copolymer, styrene-methacrylic acid copolymer, and styrene-methyl methacrylate copolymer. Examples include polymers, styrene-ethyl methacrylate copolymers, styrene-acrylic acid copolymers, styrene-methyl acrylate copolymers, styrene-ethyl acrylate copolymers, styrene-maleic anhydride copolymers, and the like. The

  In addition to polystyrene resin (B), polypropylene resin such as propylene homopolymer and ethylene-propylene copolymer, high-density polyethylene, low-density resin melt for resin layer formation Polyethylene resins such as polyethylene, polystyrene-polyphenylene ether copolymers, mixtures of polystyrene and polyphenylene ether, thermoplastic elastomers such as styrene-conjugated diene block copolymers and hydrogenated products, ethylene-propylene rubber, butadiene rubber, etc. The polymer can be blended. These polymers can be used in the resin layer forming resin melt at a ratio of 40% by mass or less, preferably 20% by mass or less, more preferably 15% by mass or less, and further preferably 10% by mass or less. .

(Volatile plasticizer 6)
In the present invention, the volatile plasticizer 6 is added to the polystyrene resin (B) to form a resin melt 7 for forming a resin layer.

  The volatile plasticizer 6 can reduce the melt viscosity of the polystyrene resin (B) in the state where it is present in the resin melt 7 for resin layer formation.

  In addition, by adding the volatile plasticizer 6, the resin melt 7 for resin layer formation at an appropriate foaming temperature when the resin melt 7 for resin layer formation and the resin melt 10 for foam layer formation are coextruded. Can be made to correspond to the elongation of the foamed layer forming resin melt 10 plasticized with a physical foaming agent.

  Further, after the co-extrusion, the volatile plasticizer 6 is a resin of the polystyrene-based resin foam 1 to which a streak pattern is imparted by heat immediately after the co-extrusion or gas permeation of the volatile plasticizer 6 thereafter. The volatile plasticizer 6 can be removed from the resin layer 3 by volatilizing naturally from the layer 3.

  Therefore, the volatile plasticizer 6 preferably has a boiling point of 120 ° C. or less, more preferably a boiling point of 80 ° C. or less from the viewpoint that it easily volatilizes from the resin layer 3. In addition, about the lower limit of the said boiling point, it is -50 degreeC in general.

  Examples of the volatile plasticizer 6 include aliphatic hydrocarbons having 2 to 7 carbon atoms, halogenated aliphatic hydrocarbons having 1 to 3 carbon atoms, aliphatic alcohols having 1 to 4 carbon atoms, or 2 or more carbon atoms. Those composed of one or two or more selected from 8 or less aliphatic ethers are preferably used.

  Examples of the aliphatic hydrocarbon having 2 to 7 carbon atoms exemplified in the volatile plasticizer 6 include ethane, propane, normal butane, isobutane, normal pentane, isopentane, isohexane, cyclohexane, and heptane.

  Examples of the halogenated aliphatic hydrocarbon having 1 to 3 carbon atoms include methyl chloride, ethyl chloride, 1,1,1,2-tetrafluoroethane, 1,1-difluoroethane, and the like. Examples of the aliphatic alcohol having 1 to 4 carbon atoms include methanol, ethanol, propanol, butanol, isopropyl alcohol, isobutyl alcohol, sec-butyl alcohol, tert-butyl alcohol, and the like.

  Examples of the aliphatic ether having 2 to 8 carbon atoms include methyl ether, ethyl ether, propyl ether, isopropyl ether, methyl ethyl ether, methyl propyl ether, methyl isopropyl ether, methyl butyl ether, methyl isobutyl ether, and methyl amyl ether. , Methyl isoamyl ether, ethyl propyl ether, ethyl isopropyl ether, ethyl butyl ether, ethyl isobutyl ether, ethyl amyl ether, ethyl isoamyl ether, vinyl ether, allyl ether, methyl vinyl ether, methyl allyl ether, ethyl vinyl ether, ethyl allyl ether, etc. .

(Addition amount of volatile plasticizer 6)
In the present invention, the volatile plasticizer 6 is used, and at the same time, the addition amount of the volatile plasticizer 6 is 0.15 mol / kg to 1.4 mol / kg per 1 kg of the polystyrene resin (B).

When the polystyrene resin (B) having the specific melt viscosity range described above is used and the addition amount of the volatile plasticizer 6 is 0.15 mol / kg or more, the resin layer is formed when the resin melt for resin layer formation is coextruded. Since the cooling adjustment to lower the resin temperature of the resin melt 7 for forming to a temperature that does not hinder the foaming of the resin melt 10 for forming the foamed layer is possible, the bubbles in the foamed layer 2 are not broken and desired. The foamed layer 2 having an apparent density can be obtained. Furthermore, since the resin melt for forming a resin layer is excellent in elongation at this temperature, a thin and beautiful streak pattern can be formed.
From the above viewpoint, the addition amount of the volatile plasticizer 6 is preferably 0.25 mol / kg or more, and more preferably 0.35 mol / kg or more.

  On the other hand, when the addition amount of the volatile plasticizer 6 is 1.4 mol or less per 1 kg of the polystyrene resin (B), a foam having a clear streak pattern without foaming the resin melt for forming the resin layer. Is obtained. From such a viewpoint, the amount of the volatile plasticizer 6 added is preferably 1.2 mol or less, more preferably 1.0 mol or less, per 1 kg of the polystyrene resin (B).

While making the addition amount of the volatile plasticizer 6 into the said range, and making the viscosity of a polystyrene-type resin (B) 600-1400 Pa.s, the temperature fall effect of the resin melt 7 for resin layer formation at the time of co-extrusion In addition, a thin and beautiful streak pattern can be formed due to the stretch improvement effect.

(Timing of addition of volatile plasticizer)
The timing of addition of the volatile plasticizer 6 is not particularly limited, but is preferably added after the polystyrene resin (B) constituting the resin layer 3 and the colorant 5 are kneaded.

  When the volatile plasticizer 6 is added at the above timing, the resin layer forming resin melt is more reliably plasticized when the resin layer forming resin melt and the foam layer forming resin melt are coextruded. be able to.

Such is to adopt the timing of the addition of the volatile plasticizer 6, in particular the foam layer 2, having a small apparent density, especially the apparent density 0.13 g / cm ³ or less, further 0.10 g / cm ³ or less When the average lamination amount per resin layer per 1 m in the extrusion direction of the resin layer 3 is small, especially when the average lamination amount is 0.25 g / m or less, and further 0.18 g / m or less. The polystyrene-based foamed sheet 1 to which a thin and beautiful streak pattern is imparted can be produced.

The volatile plasticizer 6 added to the polystyrene resin (B) is extruded at the time of extrusion depending on the type of the polystyrene resin (B) and the volatile plasticizer 6 constituting the resin layer 3 after coextrusion. There is a case where it is volatilized to the outside of the resin layer 3 by the heat of the heat and a case where it remains in the resin layer 3. The volatile plasticizer remaining in the resin layer 3 is volatilized out of the resin layer 3 over time after extrusion.

  By using a volatile plasticizer, it volatilizes from the resin layer, so that physical properties such as rigidity of the resin layer are hardly lowered. On the other hand, general non-volatile plasticizers such as liquid paraffin and fatty acid esters tend to remain in the resin layer even after extrusion, and may deteriorate physical properties such as rigidity of the resin layer. However, a non-volatile plasticizer may be added as long as the physical properties of the foam do not deteriorate. As specific addition amount, 3 mass parts or less are preferable with respect to 100 mass parts of polystyrene-type resin (B), and it is more preferable that it is 2 mass parts or less.

  In order to obtain a foam having excellent surface smoothness, the amount of the volatile plasticizer added to the polystyrene resin (B) is more than the amount of the physical foaming agent added to the polystyrene resin (A). It is preferable to keep it small.

(About colorants)
Examples of the colorant used in the present invention include organic pigments or dyes, inorganic pigments, and the like. Specific examples of the inorganic pigment as the colorant used in the present invention include iron oxide, carbon black, titanium oxide, titanium yellow, ultramarine, cobalt blue, calcined pigment, metallic pigment, mica, pearl pigment, zinc white, Examples include sinking silica and cadmium red. Examples of organic pigments include, for example, condensed azo series such as monoazo series and chromoftal red, anthraquinone series, isoindolinone series, heterocyclic series, perinone series, quinacridone series, perylene series, thioindigo series, and dioxazine series. Phthalocyanine, nitroso, phthalocyanine pigments, organic fluorescent pigments, and the like. Examples of organic dyes include anthraquinone, heterocyclic, perinone, basic dyes, acid dyes, and mordant dyes. Moreover, a coloring agent can also be used in mixture of 2 or more types.

Although the addition amount of a coloring agent is suitably adjusted according to various conditions, such as a requested | required color tone, 0.05-3.0 mass parts is preferable with respect to 100 mass parts of polystyrene-type resin (B). Moreover, More preferably, it is 0.05-2.5 mass parts, More preferably, it is 0.1-2.0 mass parts. Within the above range, it is easy to form a streak pattern with a beautiful appearance.
In addition, when used as a food container, it is necessary to determine the physical properties and addition amount of the colorant according to the values of the voluntary standards set by the Sanitation Council for Polyolefins.
When a brown colorant such as iron oxide is used as the colorant, the streaky pattern of the obtained foam has a wood grain tone, and a polystyrene resin foam with a particularly high-class feeling is obtained.
As a method for adding the colorant, a method in which a colorant master batch is prepared and supplied to the extruder can be employed.

  The average lamination amount per resin layer of the resin layer 3 used in the present invention is preferably 0.01 to 0.60 g per 1 m in the extrusion direction. If it is in the above-mentioned range, a good aesthetic streak pattern can be imparted to the surface layer. From the above viewpoint, the average lamination amount per resin layer of the resin melt for forming a resin layer is more preferably 0.02 g to 0.50 g or less per 1 m in the extrusion direction.

The average lamination amount per resin layer per 1 m in the extrusion direction can be obtained by dividing the discharge amount by the take-up speed and the sheet width and converting the unit.
Specifically, when a cylindrical laminated foam is cut open to form a sheet, the discharge amount of the resin layer is X (kg / hr), the take-up speed of the foam is Y (m / min), and the entire width of the foam The number of the resin layers is determined by the following formula (1), where Z is Z.
(1000 × X) / (60 × Y × Z) (1)
Moreover, when joining the inner surface of a foam layer with a pinch roll and making a plate shape into a plate shape, sheet-like foaming is carried out by making the width | variety of a plate-like foam in Formula (1) twice. It can be obtained in the same manner as the body.

(Other additives)
Various additives may be added to the resin layer forming resin melt 7 as long as the object of the present invention is not impaired.
Examples of the various additives include an antistatic agent, an antioxidant, a heat stabilizer, a weathering agent, an ultraviolet absorber, a flame retardant, a filler, and an antibacterial agent. In that case, the addition amount is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and particularly preferably 3 parts by mass or less with respect to 100 parts by mass of the polystyrene-based resin (B). The lower limit is approximately 0.01 parts by mass.

(Polystyrene resin melt for forming foam layer (resin melt for forming foam layer) 10)
In the present invention, a polystyrene resin melt 10 for forming a foam layer is formed by kneading the polystyrene resin (A) and the physical foaming agent 9 and other additives added as necessary.

(Polystyrene resin (A))
The melt viscosity (ηA) of the polystyrene-based resin (A) at 200 ° C. and a shear rate of 100 sec ⁻¹ of the melt viscosity (ηA).
It is necessary that the ratio (ηB / ηA) of the melt viscosity to the melt viscosity (ηB) is less than 1.0.

  If the ratio of melt viscosity (ηB / ηA) is less than 1.0, the resin layer forming resin melt 7 follows the flow of the foam layer forming resin melt 10 during coextrusion, and a uniform streaky pattern A foam with good appearance is formed. From the above viewpoint, the melt viscosity ratio (ηB / ηA) is preferably 0.5 or more and 0.9 or less, more preferably 0.6 or more and 0.8 or less.

  From the viewpoint of obtaining a polystyrene resin foam having a low apparent density, the melt viscosity (ηA) is preferably 800 Pa · s to 2000 Pa · s, more preferably 1000 Pa · s to 1700 Pa · s, and 1200 Pa · s to 1500 Pa. -S is more preferable.

  In addition, there is no restriction | limiting in particular as polystyrene-type resin (A), For example, resin similar to the polystyrene-type resin illustrated about the polystyrene-type resin (B) which comprises the resin layer 3 can be used.

(Physical foaming agent 9)
In the present invention, it is necessary to use the physical foaming agent 9 as a foaming agent from the viewpoint of stably obtaining a foam having a low apparent density.

  Examples of the physical blowing agent 9 include aliphatic hydrocarbons having 3 to 7 carbon atoms, such as propane, normal butane, isobutane, normal pentane, isopentane, cyclopentane, normal hexane, isohexane, cyclohexane, heptane, and chloride. Organic physical blowing agents such as halogenated aliphatic hydrocarbons having 1 to 3 carbon atoms such as methyl, ethyl chloride, 1,1,1,2-tetrafluoroethane, 1,1-difluoroethane, carbon dioxide, water, Examples thereof include inorganic physical foaming agents such as nitrogen.

  The physical foaming agent 9 described above can be used in combination of two or more. Among the above, the physical foaming agent 9 is preferably an organic physical foaming agent because it is excellent in foaming properties, and among them, those mainly composed of normal butane, isobutane, or a mixture thereof are suitable.

(Addition amount of physical foaming agent 9)
In the present invention, the amount of the physical foaming agent 9 added to the foamed layer forming resin melt 10 is appropriately adjusted according to various conditions such as the type of physical foaming agent and the apparent density required for the foaming layer 2. Moreover, 0.15-1.8 mol is preferable with respect to 1 kg of polystyrene-type resin (A), More preferably, it is 0.15-1.4 mol, More preferably, it is 0.35-1.2 mol. If it is the said range, a favorable polystyrene-type resin foam with a favorable external appearance and a low apparent density is obtained.

(Bubble conditioner)
For the foamed resin melt 10 for forming a foam layer, it is preferable to add a cell regulator. As the bubble adjusting agent, either an organic type or an inorganic type can be used.
Examples of the inorganic foam regulator include boric acid metal salts such as zinc borate, magnesium borate, and borax, sodium chloride, aluminum hydroxide, talc, zeolite, silica, calcium carbonate, sodium bicarbonate, and the like.

Examples of the organic air conditioner include sodium phosphate-2,2-methylenebis (4,6-tert-butylphenyl), sodium benzoate, calcium benzoate, aluminum benzoate, and sodium stearate. A combination of citric acid and sodium bicarbonate, an alkali salt of citric acid and sodium bicarbonate, or the like can also be used as the bubble regulator. These bubble regulators can be used in combination of two or more.
Moreover, the addition amount of the bubble regulator in the resin melt 10 for forming a foam layer is 0.05 parts by mass or more and 10 parts by mass or less, preferably 0.2 parts by mass or more and 5 parts by mass or less per 100 parts by mass of the polystyrene resin. It is.

(Coloring agent)
In the present invention, coloring can also be applied to the foamed layer. As the colorant added to the foam layer, the same colorant as the colorant added to the resin layer can be used. In consideration of the appearance as a foam, the colorant used in the foamed layer is preferably added in a smaller amount than the resin layer when the same colorant as the resin layer is used. When the same amount is used, it is preferable to use a colorant having a higher whiteness than the colorant used in the resin layer as the colorant used in the foam layer.

(Other additives)
Various additives may be added to the foamed layer forming resin melt 10 as long as the object of the present invention is not impaired.
Examples of the various additives include antioxidants, heat stabilizers, weathering agents, ultraviolet absorbers, flame retardants, inorganic fillers, antibacterial agents, and shrinkage inhibitors. In this case, the addition amount is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and particularly preferably 3 parts by mass or less with respect to 100 parts by mass of the resin. The lower limit is approximately 0.01 parts by mass.

(Coextrusion of resin melt 10 for forming foam layer and resin melt 7 for forming resin layer)
In the present invention, as described above, the foam layer-forming resin melt 10 and the resin layer-forming resin melt 7 are adjusted to the appropriate temperatures in each extruder, as shown in FIG. It is introduced into an annular die 13 for co-extrusion.

  Here, the appropriate temperature of the foamed layer forming resin melt 10 is a temperature at which the foamed layer forming melt 10 exhibits optimum viscoelasticity for forming the foamed layer 2.

  Moreover, the appropriate temperature of the resin melt 7 for resin layer formation means that the melt 7 for resin layer formation exhibits good extensibility for forming the resin layer 3 having a streak-like or band-like pattern and is a foamed layer. The temperature at which the formation of 2 is not inhibited.

  The appropriate temperature of the foamed layer forming resin melt 10 is preferably in the range of 130 ° C. or higher and 160 ° C. or lower, although the appropriate range varies depending on the melt viscosity of the main raw material and the amount of blowing agent injected.

  In consideration of these points, specifically, the suitable temperature of the resin layer forming melt 7 is preferably in the range of approximately 130 ° C. or more and 170 ° C. or less.

  By bringing the resin temperatures of the foam layer forming resin melt 10 and the resin layer forming resin melt 7 close to each other, a foam having a high closed cell ratio can be obtained.

  In the present invention, the resin melt 7 for forming a polystyrene-based resin layer prepared at an appropriate temperature as described above is used, and the melt 7 for forming a resin layer is formed on the outer peripheral surface of the resin melt 10 for forming a polystyrene-based resin foam layer. A cylindrical laminated foam having a streaky-patterned resin layer 3 on the surface of the foamed layer 2 by coextrusion after laminating so as to form a streak through the through hole and foaming the foam layer forming resin 10. Get the body.

  Although there is no particular limitation on the annular die, it is preferable to use a structure in which the resin melt for forming the resin layer can be laminated in a streak pattern on the outer peripheral surface of the resin melt for forming the foam layer, as shown in FIG. It is preferable to have a structure in which a large number of through-holes are formed as the resin flow path of the resin melt for forming the resin layer on the outer peripheral surface of the flow path of the resin melt for forming the foam layer.

The through hole processed in the annular die is not particularly limited as long as the streaky pattern of the resin layer is formed on the surface of the foam layer, but the cross-sectional shape of the through hole is A rectangular shape is preferable from the viewpoint of workability of the die.
Incidentally, the cross area per one through-hole is preferably in a range of 0.3～8Mm ^2, and more preferably a 0.4~6mm ^2.

  Moreover, about the width | variety of a through-hole, it is preferable to make the width | variety in the circumferential direction of a through-hole into the range of 0.4-4.0 mm, It is more preferable to set it as 0.4-3.0 mm, 0.4 More preferably, it is set to -2.0 mm. In addition, the width | variety of this through-hole measures the part which becomes the maximum in the circumferential direction.

The distance between the centers of the through holes is preferably in the range of 0.5 to 12 mm, and more preferably 1 to 10 mm.
The distance between the centers of the through holes is a circumferential distance between the center portion of the width of one through hole and the center portion of the width of the adjacent through hole in the annular die.

Further, the average distance between the centers of the through holes is preferably 1.5 to 6 mm from the viewpoint of forming a thin and beautiful streak pattern, more preferably 1.5 to 5 mm, and more preferably 1.5 to 4 mm. Further preferred.
The average distance between the centers of the through holes can be obtained by dividing the circumferential distance of the through holes of the annular die by the number of through holes.

  The number of through holes in the annular die is not particularly limited, but from the viewpoint that a streaky pattern of a resin layer having a good appearance is formed on the surface of the foam layer, the width of the polystyrene resin foam It is preferable to arrange 50 to 250 per 1 m in the direction. Within the above range, a polystyrene resin foam excellent in extrusion moldability and particularly excellent in appearance can be obtained.

(Polystyrene resin foam 1 with streaks on the surface)
As shown in FIG. 1, a polystyrene resin foam 1 having a streak pattern formed on the surface, obtained by the method of the present invention, has a streak pattern polystyrene on at least one side of a polystyrene resin foam layer (foam layer). A system resin layer (resin layer) is laminated.

The resin layer is required to be a non-foamed layer (non-foamed layer) from the viewpoint of expression of various characteristics such as surface smoothness and product strength. In addition, as long as expression of each of the above characteristics is not hindered, for example, a part of the resin layer in the vicinity of the interface with the foam layer may be locally present.
In order to make the resin layer non-foamed, it is necessary to keep the volatile plasticizer within a specific range. In addition, the resin melt for forming the resin layer and the resin melt for forming the foam layer are used together. Immediately after extrusion, by using a method of cooling by blowing air to the resin layer, a method of not adding as much as possible a cell core other than the colorant to the resin layer, a method of reducing the basis weight of the resin layer, etc. Thus, the resin layer can be brought into a non-foamed state more reliably.

(Appearance density and thickness of polystyrene resin foam 1 provided with a streak pattern)
The apparent density of the polystyrene resin foam is not particularly limited, but is preferably 0.35 g / cm ³ or less. If it is desired to obtain a molded article having excellent appearance and strength, and more preferably ^{0.04g / cm 3 ~0.21g / cm 3} , most preferably 0.05g ^/ cm ³ ~0.15g ^/ cm 3 are preferred.
In addition, the apparent density of the whole polystyrene resin foam can be calculated | required by dividing the mass of a foam by the volume of a foam, and converting into a unit to [g / cm < ³ >]. In addition, what is necessary is just to obtain | require the volume of a foam from the submerging method or an external dimension.

The thickness of the polystyrene resin foam produced by the method of the present invention is not particularly limited, but is preferably 0.5 to 10 mm.
A foam (sheet-like foam) having a thickness of 0.5 to 3 mm is filled with a high-class feeling that is thermoformed and has a streak pattern, such as a tray container, instant noodle container, lunch box container, natto container, frozen container, rice cake, etc. It is mainly used as a food container.
A foam (plate-like foam) having a thickness of 3 to 10 mm is mainly used as a folded box, a display core, or the like.

  In addition, the thickness of a polystyrene-type resin foam can be calculated | required with the following method. The thickness [mm] of the foam is measured at 10 points in the width direction at equal intervals, and the arithmetic average value of the thickness [mm] of the foam at each measured point is defined as the thickness [mm] of the foam.

  The former sheet-like foam is obtained by cutting the above-mentioned cylindrical laminated foam, and the latter plate-like foam (board) is formed by sandwiching the cylindrical laminated foam between pinch rolls and the inner surface of the polystyrene foam layer. It can be easily formed by bonding them together.

(Advantages of the production method of the present invention)
In the production method of the present invention, as described above, the polystyrene resin melt for forming a resin layer is obtained by kneading a polystyrene resin (B), a colorant and a volatile plasticizer, and the polystyrene resin (B ) At 200 ° C. and a shear rate of 100 sec ⁻¹ is 600 to 1400 Pa · s, and the polystyrene resin (A) has a melt viscosity (at 200 ° C. and a shear rate of 100 sec ⁻¹ ). The ratio (ηB / ηA) of the melt viscosity to ηA) is less than 1.0, and the addition amount of the volatile plasticizer is 0.15 to 1.4 mol per kg of the polystyrene resin (B). It is a manufacturing method which obtains the polystyrene-type foam which has the streak pattern excellent in the external appearance by combining manufacturing conditions.

In addition, the production method of the present invention is a very simple production method with only one step, and thus the production cost can be greatly reduced, which is an industrially extremely advantageous production method.
Furthermore, unlike the conventional product, the polystyrene foam obtained by the production method of the present invention has a streaky pattern of a polystyrene resin layer by coextrusion on its surface, It is also excellent in food safety and surface smoothness. Therefore, as described above, the demand is widely expected as a high-quality food container provided with a streak pattern, and further as a folding box or a display plate.

  Next, the present invention will be described in more detail with reference to examples.

[Raw material PS resin]
The following materials were used as the raw material PS resin.
PS resin (1): PS Japan 680: Melt viscosity: 930 Pa · s
PS resin (2): PS Japan 679: Melt viscosity: 650 Pa · s
PS resin (3): GX251 manufactured by PS Japan Co., Ltd .: Melt viscosity: 1230 Pa · s
PS resin (4): G100C manufactured by Toyo Styrene Co., Ltd .: Melt viscosity: 570 Pa · s
PS resin (5): GX154 manufactured by PS Japan Co., Ltd .: Melt viscosity: 1430 Pa · s
PS resin (6): PS Japan G0002: Melt viscosity: 1400 Pa · s

Example 1
First, the raw material polystyrene resin (B) (PS resin (1)) and the colorant (PS-M-SSCA11N7470BR manufactured by Dainichi Seika Kogyo Co., Ltd.) for the resin layer constitution at the ratio shown in Table 1 are set to the inner diameter (D ) After supplying to a 65 mm extruder, heating and melting and kneading, a volatile plasticizer was added and melt kneading to obtain a polystyrene resin melt for resin layer formation (resin melt for resin layer formation). At the same time, PS resin (5) as the raw polystyrene resin (A) for forming the foam layer at the ratio shown in Table 1 and an air conditioner were extruded with an inner diameter (D) of 90 mm and an inner diameter (D) of 120 mm. Supply to a tandem extruder consisting of two extruders with a machine, heat kneading, press-fitting a physical foaming agent, and further kneading to form a polystyrene resin melt for forming a foam layer (resin melt for forming a foam layer) ).

  Next, the foamed layer-forming resin melt and the resin layer-forming resin melt were set at 151 ° C. and 155 ° C., respectively, and introduced into the coextrusion annular die. As the annular die, one having a structure in which a through hole is arranged as a flow path of the resin melt for forming the resin layer on the outer peripheral surface of the flow path of the resin melt for forming the foam layer is formed. Randomly spaced the distance between the individual through holes in the range of 1.3 to 2.8 mm so that the average distance between the centers of the through holes is 2.0 mm. 163 were provided. Under the conditions described in Table 1, the resin melt for forming the resin layer is laminated in the die so as to form a streak in the extrusion direction on the outer peripheral surface of the resin melt for forming the foam layer, and then co-extrusion is performed. The resin melt for forming a foam layer was foamed to produce a cylindrical laminated foam having a streaky pattern resin layer formed on the surface of the foam layer.

Then, from the outside of the cylindrical laminated foam, it is cooled by blowing air at a temperature of 20 ° C. and a flow rate of 1.7 g / min, and while taking this cylindrical laminated foam along the outer surface of the cylindrical cooling device,
One end was cut open to form a sheet, and a polystyrene resin foam having a resin layer formed in a streak shape on one side of the foam layer was obtained. The blow-up ratio at this time was 4.0 times. The results of evaluating the appearance of this laminated foam are shown in Table 1. As shown in Table 1, this laminated foam sheet was a good extruded foam having a particularly beautiful streak pattern formed by a resin layer and excellent surface smoothness.

Example 2
The resin layer discharge amount is 15.4 kg / hr, the amount of resin layer forming resin melt is 20 g / m ^2, and the other production conditions are as described in Table 1, and the polystyrene type is the same as in Example 1. A resin foam was produced. The results of evaluating the appearance of this laminated foam are shown in Table 1. This laminated foam was a good extruded foam having a surface streak color tone darker than that of Example 1 and having a particularly beautiful streak and excellent surface smoothness.

Example 3
PS resin (6) is used as the raw polystyrene resin (A) for forming the foam layer, the resin layer discharge rate is 5.4 kg / hr, and normal butane and isobutane are used as the foaming agent for the resin melt for forming the foam layer. A polystyrene-based resin foam was prepared in the same manner as in Example 1, using a foam layer with a basis weight of 200 g / m ² , a foam sheet overall thickness of 2.1 mm, and other production conditions described in Table 1. .
The results of evaluating the appearance of this laminated foam are shown in Table 1. As shown in Table 1, this laminated foam was a good extruded foam with a surface linear or strip-like streak pattern having a particularly beautiful streak and excellent surface smoothness.

Example 4
As the raw material polystyrene resin (B) for the resin layer constitution, the PS resin (2) having a lower melt viscosity than the PS resin (1) used in Example 1 is used, and other production conditions are described in Table 1. As in Example 1, a polystyrene resin foam was produced in the same manner as in Example 1.
The results of evaluating the appearance of this laminated foam are shown in Table 1. As shown in Table 1, the laminated foam has a fine line-like or strip-like streak pattern on the surface even when the amount of the volatile plasticizer is reduced, and has excellent surface smoothness. It was an extruded foam.

Example 5
As the raw material polystyrene resin (B) for forming the resin layer, the PS resin (3) having a higher melt viscosity than the PS resin (1) used in Example 1 is used, and other production conditions are described in Table 1. As in Example 1, a polystyrene resin foam was produced in the same manner as in Example 1.
The results of evaluating the appearance of this laminated foam are shown in Table 1. As shown in Table 1, the laminated foam has a fine line-like or strip-like streak pattern on the surface even when the amount of the volatile plasticizer is increased, and has excellent surface smoothness. It was an extruded foam.

Example 6
As the raw material polystyrene resin (A) for forming the foam layer, the PS resin (3) is used, the discharge of the resin layer and the foam layer is set to the discharge amount shown in Table 2, and the blow-up ratio is set to 2.5. Other production conditions were as described in Table 2, and a cylindrical laminated foam was produced in the same manner as in Example 1. By passing the cylindrical laminated foam between pressing rolls and crushing to fuse the inner surface of the foam layer, a plate-like polystyrene resin foam having a streak pattern formed by the resin layer on both surfaces was obtained. .
The appearance of this laminated foam was evaluated. The results are shown in Table 2. As shown in Table 2, this laminated foam was a good extruded foam having a particularly fine streak with a linear or belt-like streak pattern on the surface and excellent surface smoothness.

Example 7
The resin layer discharge rate is 12.4 kg / hr, and the average lamination per resin layer in the extrusion direction of the resin layer through the through holes having different numbers, widths, average distances between the centers, and distances between the centers shown in Table 2. A cylindrical laminated foam was produced with an amount of 0.38 g / m and a basis weight of the foam layer of 450 g / m ² . By passing the cylindrical laminated foam between pressing rolls and crushing to fuse the inner surface of the foam layer, a plate-like polystyrene resin foam having a streak pattern formed by the resin layer on both surfaces was obtained. .
The appearance of this laminated foam was evaluated. The results are shown in Table 2. As shown in Table 2, this laminated foam was an extruded foam having a surface linear or belt-like streak pattern having a particularly beautiful streak and good surface smoothness.

Comparative Example 1
As a raw material polystyrene resin (B) for resin layer constitution, PS resin (4) is used, and other production conditions are as shown in Table 3, and a polystyrene resin foam is obtained in the same manner as in Example 1. It was. The results are shown in Table 3. In this case, since the melt viscosity of the polystyrene resin (B) for forming the resin layer was too low, the resin layer spread on the foamed layer, and a polystyrene resin foam having a beautiful streak pattern could not be obtained. .

Comparative Example 2
The PS resin (5) having a high melt viscosity is used as the raw material polystyrene resin (B) for constituting the resin layer, and the other production conditions are as shown in Table 3, and the polystyrene resin as in Example 1. A foam was obtained. The results are shown in Table 3. In this case, since the melt viscosity of the polystyrene resin (B) for forming the resin layer is too high, the resin layer is poorly stretched, cracks and tears occur, and a polystyrene resin foam having a beautiful streak pattern is obtained. It was not obtained. Moreover, the surface smoothness also deteriorated with the crack and tear of the resin layer.

Comparative Example 3
A polystyrene-based resin foam was produced in the same manner as in Example 1 except that the amount of the volatile plasticizer in the resin layer was 0.13 mol / kg, and the other production conditions were as shown in Table 3. The results are shown in Table 3. In this case, since the amount of the volatile plasticizer was too small, the elongation of the polystyrene resin for resin layer formation was poor, cracks and tears were generated, and a polystyrene resin foam having a beautiful streak pattern could not be obtained. Moreover, it became the polystyrene-type resin foam which is inferior to surface smoothness by a crack and a tear.

Comparative Example 4
A polystyrene-based resin foam was produced in the same manner as in Example 1, assuming that the amount of volatile plasticizer in the resin layer was 1.50 mol / kg, and other production conditions were as shown in Table 3. The results are shown in Table 3. Since the amount of the volatile plasticizer was too large, the resin layer foamed, the outline of the streak pattern was not clear, and a polystyrene resin foam having a beautiful streak pattern could not be obtained. Moreover, it became a polystyrene-type resin foam which is inferior also in surface smoothness because the resin layer foamed.

(Melt viscosity)
The melt viscosity of the polystyrene-based resin used for the resin layer and the foamed layer is a value measured using Capillograph 1D (manufactured by Toyo Seiki Seisakusyo Co., Ltd.) in accordance with JIS K 7199 (1999). Specifically, a cylinder with a cylinder diameter of 9.55 mm and a length of 350 mm and an orifice with a nozzle diameter of 1.0 mm and a length of 10 mm were used. The melted resin was extruded from the orifice in a string shape at a shear rate of 100 sec ⁻¹ and the melt viscosity at that time was measured.

(Apparent density)
The overall apparent density [g / cm ³ ] of the polystyrene resin foam was determined by dividing the mass [g] of the test piece by the volume [cm ³ ] determined from the outer dimensions of the test piece.

(Overall thickness)
The total thickness of the foam was measured by measuring the thickness [mm] of the foam at 10 points in the width direction at equal intervals, and calculating the arithmetic average value of the thickness [mm] of the foam at each measured point. ].

(Stacking amount)
The average lamination amount of the resin layer was calculated | required by the said Formula (1).

(Basis weight)
The basis weight of the foam layer was determined by dividing the discharge amount of the foam layer by the take-up speed and the sheet width.

  The appearance of the foam was evaluated according to the following criteria.

[Foam appearance criteria]
(Surface smoothness)
A: No irregularities due to the resin layer were observed on the foam surface. B: No irregularities due to the resin layer were observed on the foam surface. Δ: Foam due to cracks or tearing of the resin layer. Slight irregularities on the surface ×: Cracks or tears in the resin layer on the foam surface or foamed resin layer with irregularities on the foam surface

(Striated pattern)
A: A linear or strip-like streaky pattern on the surface of the foam is a particularly beautiful streak and a good extruded foam is obtained. B: A linear or strip-like streaky pattern on the surface of the foam is beautiful. *: When the resin melt for forming a resin layer is laminated on the resin melt for forming a foam layer, the width of the streaks of the resin layer is disturbed and stabilized. That could not form a streak pattern

DESCRIPTION OF SYMBOLS 1 Polystyrene-type resin foam in which the streaky pattern was formed on the surface 2 Polystyrene-type resin foam layer 3 Polystyrene-type resin layer 4 Polystyrene-type resin which comprises the resin layer 5 Colorant 6 Volatile plasticizer 7 Polystyrene for resin layer formation Resin melt 8 Polystyrene resin constituting the foam layer 9 Physical foaming agent 10 Polystyrene resin melt for foam layer formation 11 First extruder (for resin layer formation)
12 Second extruder (for forming foam layer)
13 Circular die

Claims (4)

A polystyrene resin (A) and a physical foaming agent are kneaded to form a polystyrene resin melt for forming a foam layer, and in a die, the polystyrene resin melt for forming the foam layer is formed into a resin layer formation The polystyrene resin melt was joined in a streak and co-extruded, and the polystyrene resin melt for forming the foamed layer was foamed to form a streak pattern composed of a resin layer on the surface of the foam layer. A method for producing a sheet-like or plate-like polystyrene-based resin foam,
The polystyrene resin melt for forming the resin layer is obtained by kneading a polystyrene resin (B), a colorant, and a volatile plasticizer. The polystyrene resin (B) has a 200 ° C. shear rate of 100 sec ⁻¹ . The melt viscosity (ηB) under the conditions is 600 to 1400 Pa · s, and the ratio of the melt viscosity (ηB) to the melt viscosity (ηA) under the conditions of 200 ° C. and a shear rate of 100 sec ⁻¹ of the polystyrene resin (A). (ΗB / ηA) is less than 1.0, and the addition amount of the volatile plasticizer is 0.15 to 1.4 mol per kg of the polystyrene resin (B). Manufacturing method.   2. The polystyrene-based resin foam according to claim 1, wherein an average lamination amount per one resin layer per 1 m in the extrusion direction of the polystyrene-based resin foam is 0.01 to 0.6 g. Production method.   The volatile plasticizer is one or two or more selected from an aliphatic hydrocarbon having 2 to 7 carbon atoms, an aliphatic alcohol having 1 to 4 carbon atoms, and an aliphatic ether having 2 to 8 carbon atoms. The method for producing a polystyrene-based resin foam according to claim 1 or 2, wherein the foam is a thing. The method for producing a polystyrene resin foam according to any one of claims 1 to 3, wherein an apparent density of the polystyrene resin foam is 0.35 g / cm ³ or less.