JP7083313B2 - Manufacturing method of polystyrene resin multilayer foam sheet and polystyrene resin multilayer foam sheet - Google Patents

Description

The present invention relates to a method for producing a polystyrene-based resin multilayer foamed sheet and a polystyrene-based resin multilayer foamed sheet. Specifically, the present invention is a method for producing a polystyrene-based resin multilayer foamed sheet having excellent thermoformability, and a polystyrene-based resin multilayer foaming having excellent thermoforming property. Regarding the sheet.

Conventionally, a polystyrene-based resin multilayer foamed sheet (hereinafter, also simply referred to as a multilayer foamed sheet) in which a resin layer made of an impact-resistant polystyrene-based resin is laminated on a polystyrene-based resin foamed sheet has been widely used. As a method of laminating the impact-resistant polystyrene-based resin layer on the polystyrene-based resin foamed sheet, a method of laminating the molten resin of the impact-resistant polystyrene-based resin on the foamed sheet by extrusion laminating to form a resin layer, or a method prepared in advance. A method of laminating an impact-resistant polystyrene-based resin film on a foam sheet by thermal laminating to form a resin layer has been carried out. Further, there is also a method of manufacturing a multilayer foamed sheet in which a resin layer is laminated on a foamed sheet by co-extruding a molten resin for forming a resin layer and a molten resin for forming a foamed sheet layer.

The multilayer foamed sheet is a material having excellent thermoformability, and a molded product obtained by thermoforming from the multilayer foamed sheet has features such as excellent heat insulating properties and a beautiful appearance. Further, since the impact-resistant polystyrene-based resin layer is laminated, the multi-layer foamed sheet has a wide heating time range in which thermoforming is possible, so that a food container having a relatively deep bottom such as a bowl is particularly formed. In recent years, it has been used in large quantities as a material for thermoforming. The multilayer foamed sheet has improved rigidity and impact resistance as compared with the single-layer polystyrene-based resin foamed sheet.

In recent years, the multi-layer foam sheet is used to thermoform a food container having a shape deeper than a bowl or the like, specifically, a container such as a vertical cup having a large expansion ratio (for example, 2.5 times or more). Became. In the prior art, when thermoforming a container having a large unfolding ratio, a multi-layer foam sheet having a large basis weight has been used. This is because when trying to obtain a container having a large unfolding ratio by using a multi-layer foam sheet having a small basis weight, there arises a problem that molding defects such as pear and medium cracking are likely to occur. In order to solve this problem, attempts have been made to improve the thermoformability of the resin layer by increasing the melt tension and uniaxial extensional viscosity of the impact-resistant polystyrene-based resin constituting the resin layer.

For example, in Patent Document ¹ , as a resin layer, rubber having a maximum elongational viscosity of 7.0 × 105 Poise or more and an extensional viscosity strain hardening index of 1.1 or more in an extensional viscosity measurement at 130 ° C. A foamed laminated sheet in which a modified polystyrene non-expanded film (resin layer) is laminated, and a styrene-based resin foamed laminated sheet capable of forming a deep container by deep drawing without causing appearance defects such as yaki and naki. Is disclosed.

Further, Patent Document 2 describes a rubber-modified styrene-based resin obtained by blending a styrene-based resin (a) and a rubber-modified polystyrene (b) at a mass ratio of (a) / (b) = 5/95 to 95/5. It is disclosed that a non-foaming sheet is produced using a resin composition, and the rubber-modified styrene-based resin composition is rubber-modified in which rubber-like polymer particles are dispersed in a styrene-based resin forming a matrix phase. In a styrene-based resin composition, the Z average molecular weight (Mz) of the matrix phase is 500,000 or more, the branching ratio of the matrix phase at a molecular weight of 1.5 million or more is gM1, and the branching ratio at a molecular weight of 1 million to 1.5 million is gM2. Then, gM1 is 0.70 to 0.20, the value of (gM2-gM1) is 0.05 or more, and the styrene resin (a) is one molecule with respect to the styrene monomer. It is disclosed that the resin is obtained by adding 50 ppm to 1000 ppm of a solvent-soluble polyfunctional vinyl copolymer having a plurality of double bonds and having a branched structure on a mass basis and polymerizing the polymer. Further, in Patent Document 2, the obtained rubber-modified styrene resin sheet has an excellent balance between rigidity and impact resistance, and since there is little uneven thickness due to molding, it has excellent compressive strength and drop strength of the container, and the container has excellent compressive strength and drop strength. It is disclosed that it is possible to make the shape complicated and to reduce the thickness and weight.

Japanese Unexamined Patent Publication No. 9-99507 Japanese Unexamined Patent Publication No. 2016-222751

However, even though the styrene-based resin foam laminated sheet described in Patent Document 1 does not cause appearance defects such as yaki and naki, the molding conditions are such that a deep-drawn container without appearance defects can be formed. The range was narrow and unsuitable for continuous production.
Further, the rubber-modified styrene resin sheet described in Patent Document 2 can be deep-drawn and molded only by a non-foamed sheet. Since cracks occur on the side surfaces, the deep drawability is still insufficient.

An object of the present invention is to provide a method for producing a polystyrene-based resin multilayer foamed sheet having excellent deep drawability, and a polystyrene-based resin multilayer foamed sheet having excellent deep drawability obtained by the manufacturing method.

According to the present invention, the following method for manufacturing a polystyrene-based resin multilayer foamed sheet and a polystyrene-based resin multilayer foamed sheet are provided.
[1] In a method for manufacturing a multilayer foamed sheet by laminating a polystyrene-based resin layer on at least one surface of a polystyrene-based resin foamed sheet.
The polystyrene-based resin layer is composed of a mixed resin of an impact-resistant polystyrene-based resin in which a granular rubber-like polymer is dispersed in a polystyrene-based resin matrix and a branched polystyrene-based resin having a branched chain.
The absolute weight average molecular weight measured by the GPC-MALS method of the branched polystyrene resin is 1 million to 5 million, and the average value of the shrinkage factor measured by the GPC-MALS method of the branched polystyrene resin is 0. It is 80 or less, and the content of the isocyanate insoluble content of the branched polystyrene resin is 0.1% by weight or less (including 0).
A method for producing a polystyrene-based resin multilayer foamed sheet, wherein the weight ratio of the branched polystyrene-based resin in the mixed resin is 5% by weight or more and less than 30% by weight.
[2] The method for producing a polystyrene-based resin multilayer foamed sheet according to 1 above, wherein the branched polystyrene-based resin does not contain a component derived from a polyfunctional monomer in the molecular chain.
[3] The polystyrene-based resin according to 1 or 2 above, wherein the weight ratio of the molecule having an absolute molecular weight of 1 million or more measured by the GPC-MALS method in the branched polystyrene-based resin is 20% by weight or more. A method for manufacturing a multilayer foam sheet.
[4] The absolute weight average molecular weight of the impact-resistant polystyrene resin matrix measured by the GPC-MALS method is 100,000 to 350,000, and the average shrinkage factor measured by the GPC-MALS method of the matrix. The method for producing a polystyrene-based resin multilayer foamed sheet according to any one of 1 to 3 above, wherein the value is 0.95 or more.
[5] The method for producing a polystyrene-based resin multilayer foamed sheet according to any one of 1 to 4, wherein the laminated amount of the resin layer is 50 to 150 g / m ² .
[6] In a multilayer foamed sheet in which a polystyrene-based resin layer is laminated on at least one side of the polystyrene-based resin foamed sheet.
The polystyrene-based resin layer is composed of a mixed resin of an impact-resistant polystyrene-based resin in which a granular rubber-like polymer is dispersed in a polystyrene-based resin matrix and a branched polystyrene resin having a branched chain.
The absolute weight average molecular weight measured by the GPC-MALS method of the branched polystyrene resin is 1 million to 5 million, and the average value of the shrinkage factor measured by the GPC-MALS method of the branched polystyrene resin is 0. It is 80 or less, and the content of the isocyanate insoluble content of the branched polystyrene resin is 0.1% by weight or less (including 0).
A polystyrene-based resin multilayer foamed sheet, wherein the weight ratio of the branched polystyrene-based resin in the mixed resin is 5% by weight or more and less than 30% by weight.

The polystyrene-based resin multilayer foamed sheet obtained by the production method of the present invention is a resin formed by using a mixed resin of a branched polystyrene-based resin having a large molecular weight and a highly branched branched structure and an impact-resistant polystyrene-based resin. Since it was obtained by laminating the layer on a polystyrene-based resin foam sheet, it is possible to perform thermal molding in a wide molding temperature range even in the thermal molding of deep-drawing molded products with a large expansion ratio, and it is stable and continuous. Production is possible.

This is an example of a Debye plot obtained when the molecular weight of a polystyrene resin is measured by the GPC-MALS method.

Hereinafter, the method for producing the polystyrene-based resin multilayer foamed sheet of the present invention and the polystyrene-based resin multilayer foamed sheet obtained by the manufacturing method will be described in detail.
In the method for producing a polystyrene-based resin multilayer foamed sheet (hereinafter, also simply referred to as a multilayer foamed sheet) of the present invention, a polystyrene-based resin resin is used on one or both sides of a polystyrene-based resin foamed sheet (hereinafter, also simply referred to as a foamed sheet). A multilayer foamed sheet is manufactured by laminating layers (hereinafter, also simply referred to as resin layers).

The laminating of the resin layer on the foamed sheet can be performed by manufacturing the foamed sheet and laminating the resin layer on the obtained foamed sheet by extrusion laminating. In this case, a conventionally known device can be used for the device used for manufacturing the foamed sheet, a conventionally known method can be used for the manufacturing method, and a conventionally known device can be used for the extrusion laminating. It can be used, and a conventionally known method can be used as the extrusion laminating method.
Further, in the method of the present invention, a thermal laminating method in which a prefabricated impact-resistant polystyrene resin film is laminated and adhered to a foamed sheet to form a resin layer, or a foamable molten resin for forming a foamed sheet and a resin layer are formed. It is also possible to adopt a coextrusion foaming method in which the molten resin is laminated using a coextrusion die and coextruded and foamed. As the device and method in this case, conventionally known devices and methods can be used.

In the method of the present invention, the resin layer is formed using a specific mixed resin.
The mixed resin is composed of a mixed resin of an impact-resistant polystyrene-based resin in which a granular rubber-like polymer is dispersed in a polystyrene-based resin matrix and a branched polystyrene-based resin having a branched chain.

Next, the impact-resistant polystyrene-based resin constituting the mixed resin will be described.
The impact-resistant polystyrene-based resin is a resin in which a granular rubber-like polymer is dispersed in a polystyrene-based resin matrix. That is, the impact-resistant polystyrene-based resin is obtained by forming a matrix of polystyrene-based resins and dispersing granular rubber-like polymers (rubber-like polymer particles) in the matrix, and the rubber-like weight. The impact resistance of the polystyrene-based resin is improved by the coalesced particles.

Examples of the styrene-based monomer which is a constituent element of the polystyrene-based resin forming the matrix include styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene and the like alone or in admixture, and styrene is particularly preferable. be. Further, as other vinyl-based monomers copolymerizable with the styrene-based monomer, acrylic acid, methacrylic acid, acrylonitrile, methacrylic acid, butyl acrylate, methyl methacrylate, maleic anhydride and the like can be used to achieve the effects of the present invention. It can also be copolymerized to the extent that it is not impaired.

The rubber-like polymer particles dispersed in the matrix are obtained by graft-polymerizing a styrene-based monomer on the rubber-like polymer. Examples of the rubber-like polymer include polybutadiene, styrene-butadiene copolymer, ethylene-propylene-non-conjugated diene copolymer, polyisoprene, styrene-isoprene copolymer and hydrogenated products thereof. The rubber-like polymer is used alone or in combination of two or more.

When the rubber-like polymer in the impact-resistant polystyrene-based resin is polybutadiene, the content of polybutadiene is usually preferably 3 to 20% by weight, more preferably 5 to 15% by weight. When the content is within this range, the resin has an excellent balance between impact resistance and rigidity.

In the present specification, the content of butadiene in the impact-resistant polystyrene-based resin is measured as follows.
Weigh 0.3 to 1.0 g of impact-resistant polystyrene-based resin to be measured, add 50 mL of chloroform to it to dissolve the impact-resistant polystyrene-based resin, and then use the Wiiss reagent (acetic acid solution of iodine monochloride). Add 25 mL, stir lightly, seal tightly, and leave in a dark place at room temperature. Next, 20 mL of 100 g / L potassium iodide aqueous solution and 100 mL of purified water were added to this, and after stirring, a 0.1 mol / L sodium thiosulfate solution was used as a titration solution, and titration was performed using a potential difference titrator. Is used to calculate the butadiene content.

Butadiene content (%) = ({(V ₀ -V ₁ ) x f x 1.269}) / S x 54.09 / 253.8
S: Mass of collected sample (g)
V ₀ : Amount of titrant required in the blank test (mL)
V ₁ : Amount of titrant required in this test (mL)
f: Titration solution factor (1.000)

For the matrix of the impact-resistant polystyrene-based resin, the absolute weight average molecular weight measured by the GPC-MALS method is preferably 100,000 to 350,000, more preferably 150,000 to 300,000. Impact-resistant polystyrene-based resins having an absolute weight average molecular weight in the above range show good fluidity, so that they can be easily extruded and also have good impact resistance. The average value of the shrinkage factor measured by the GPC-MALS method of a matrix of impact-resistant polystyrene which is usually commercially available is 0.95 or more.

Next, the branched polystyrene-based resin constituting the mixed resin will be described.
The branched polystyrene-based resin is a polystyrene-based resin having a branched chain. In the present invention, among the branched polystyrene-based resins, a branched polystyrene-based resin having a higher molecular weight and being more highly branched is used. Specifically, the absolute weight average molecular weight measured by the GPC-MALS method of the branched polystyrene resin is 1 million to 5 million, and the shrinkage factor measured by the GPC-MALS method of the branched polystyrene resin. The average value is 0.80 or less, and the content of the isocyanate insoluble content of the branched polystyrene-based resin is 0.1% by weight or less (including 0).

Examples of the styrene-based monomer that is a constituent element of the branched polystyrene-based resin include styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene and the like alone or in admixture, and styrene is particularly preferable. Further, as other vinyl-based monomers copolymerizable with the styrene-based monomer, acrylic acid, methacrylic acid, acrylonitrile, methacrylic acid, butyl acrylate, methyl methacrylate, maleic anhydride and the like can be used to achieve the effects of the present invention. It can also be copolymerized to the extent that it is not impaired.

The absolute weight average molecular weight of the branched polystyrene-based resin used in the present invention is 1 million to 5 million as measured by the GPC-MALS method. If the absolute weight average molecular weight is too low, it may not be possible to improve the deep drawability of the multilayer foamed sheet. From this point of view, the absolute weight average molecular weight is preferably 1.2 million or more, more preferably 1.55 million or more, and even more preferably 1.8 million or more. On the other hand, if the absolute weight average molecular weight of the polystyrene-based resin is too high, it may not be sufficiently compatible with the impact-resistant polystyrene-based resin. From this point of view, the absolute weight average molecular weight is preferably 4 million or less.

From the viewpoint of further improving the deep drawability of the multilayer foamed sheet, the weight ratio of the molecule having an absolute molecular weight of 1 million or more as measured by the GPC-MALS method is 20% by weight or more in the branched polystyrene-based resin. Is preferable, more preferably 25% by weight or more, still more preferably 30% by weight or more. The upper limit of the weight ratio is preferably about 80% by weight, more preferably 70% by weight.

The average value of the shrinkage factor measured by the GPC-MALS method of the branched polystyrene resin is 0.80 or less. If the shrinkage factor is too large, the degree of branching of the molecular chain becomes too small, and there is a possibility that the deep drawing formability of the multilayer foamed sheet cannot be improved. From this point of view, the average value of the contractile factors is more preferably 0.75 or less, and further preferably 0.70 or less. The lower limit is about 0.4.

In the present invention, the content of the isocyanate insoluble content of the branched polystyrene resin is 0.1% by weight or less (including 0), preferably 0.05% by weight or less, and preferably 0.01% by weight or less. It is more preferable to have. When the content is 0.1% by weight or less, it means that the resin contains substantially no gelled product.
The branched polystyrene-based resin used in the present invention does not substantially contain a gelled product even when the absolute weight average molecular weight exceeds 1 million and the average value of the shrinkage factor is 0.80 or less. Such a branched polystyrene-based resin can be obtained, for example, by forming a branched chain by graft polymerization. In the polystyrene-based resin having such a branched structure, it is considered that the branched chains are not locally concentrated and bonded to the main chain, and the branched chains are uniformly bonded to the entire main chain. It is considered that this structure suppresses the formation of gelled products even if the molecular weight is high and the cells are highly branched.

Tetrahydrofuran insoluble (THF insoluble) can be determined as follows.
1 g of the branched polystyrene resin is precisely weighed, 30 ml of tetrahydrofuran is added thereto, the mixture is immersed at 23 ° C. for 24 hours, shaken for 5 hours, and allowed to stand. The supernatant is then removed by decantation, 10 ml of tetrahydrofuran is added again and allowed to stand, the supernatant is removed by decantation, and the mixture is dried at 23 ° C. for 24 hours. The weight after drying is determined, and the tetrahydrofuran insoluble content is determined by the following formula.
Tetrahydrofuran insoluble content (%) = [weight of insoluble matter after drying / weight of sample] x 100

Next, the blending amount of the branched polystyrene-based resin in the mixed resin used in the present invention will be described.
In the mixed resin, the weight ratio of the branched polystyrene-based resin in the mixed resin is 5% by weight or more and less than 30% by weight. If the blending amount of the branched polystyrene-based resin is too small, the effect of improving moldability may not be sufficiently exhibited. On the other hand, if the blending amount is too large, the impact resistance of the resin layer is too low, and the obtained molded product may be easily cracked. From this point of view, the lower limit of the weight ratio of the branched polystyrene resin is preferably 10% by weight, and the upper limit thereof is preferably 20% by weight.

As described above, the branched polystyrene-based resin used in the present invention has (1) an absolute weight average molecular weight measured by the GPC-MALS method of 1 million to 5 million (2) measured by the GPC-MALS method. It is characterized by satisfying that the average value of the shrinkage factor to be obtained is 0.80 or less, and (3) the content of the tetrahydrofuran insoluble content of the branched polystyrene resin is 0.1% by weight or less (including 0). Such a branched polystyrene-based resin can be produced by the following polymerization method.

(1) Polystyrene-based resin nuclei particles are dispersed in an aqueous medium, and (2) a polymerization initiator containing an organic peroxide and a styrene monomer are then added to the aqueous medium to substantially styrene. The nuclei particles are impregnated with the polymerization initiator and the styrene monomer at a temperature at which the polymerization of the monomer does not proceed, and (3) the temperature of the aqueous medium is then raised to polymerize the styrene monomer. (4) Next, a styrene monomer is additionally added to the aqueous medium, and the styrene monomer is impregnated into the nuclei particles while the styrene monomer is impregnated into the nuclei particles. The branched polystyrene-based resin used in the present invention can be obtained by graft-polymerizing a styrene monomer to a polystyrene-based resin while keeping the concentration of styrene in a specific range.

Conventional branched polystyrene-based resins have been produced by polymerizing styrene monomers in the presence of a large amount of polyfunctional monomers (branching agents). However, in such a polymerization method, the polymerized portion of the polyfunctional monomer becomes excessively high in molecular weight. When the amount of the polyfunctional monomer added is increased in order to produce a more highly branched branched polystyrene-based resin, the branching points are further concentrated in the portion where the polyfunctional monomer is polymerized, and gelation occurs. There was a problem that it was easy to occur. Therefore, in the polymerization method using the polyfunctional monomer, it was not possible to produce a branched polystyrene-based resin having a high molecular weight, highly branched, and substantially free of gelled products.

In the above production method, in the step (4), the number of branching points is increased by keeping the styrene monomer in the nuclear particles serving as the reaction field of the polymerization at a specific concentration or less and polymerizing the styrene monomer. It is considered that the molecular weight can be increased while (high degree of branching), and the branching points can be separated from each other. When the concentration of the styrene monomer in the reaction field is low, not only the polymerization reaction between the initiator radical or the growing terminal radical of the polymer chain and the styrene monomer but also the hydrogen extraction reaction of the polymer chain by the initiator radical is likely to occur. Conceivable. As a result, when the styrene monomer is graft-polymerized to the radical on the polymer chain generated by the hydrogen abstraction reaction, or the growing terminal radical of the polymer chain is recombined, a branched chain is generated in the polymer chain. Conceivable. Furthermore, since the position where the branched chain is generated in the polymer chain is in a sterically crowded state, further branched chains are unlikely to occur near the generated branch point, and on the polymer chain away from the branch point. It is considered that the hydrogen abstraction reaction occurs again and a branched chain is formed. Therefore, it is considered that a branched polystyrene-based resin having many branched chains and having a high molecular weight can be obtained without gelation because the branched chains are generated while the branched points are appropriately separated from each other.

In the step (4), the amount of the styrene monomer added is preferably 50 to 700 parts by weight with respect to 100 parts by weight of the nuclear particles, and the content of the styrene monomer in the nuclear particles is adjusted. It is preferably maintained at 10% by weight or less.

The "temperature at which the polymerization of the styrene monomer does not substantially proceed" in the step (2) is a temperature at which the organic peroxide does not substantially decompose. From the viewpoint of suppressing the decomposition of the organic peroxide, when the 10-hour half-life temperature of the organic peroxide is T _1/2 , the temperature of the aqueous medium in the step is (T _{1 /} 2-15) ° C. or less. Is preferable. On the other hand, from the viewpoint of the impregnation property of the styrene monomer into the nuclear particles, the temperature of the aqueous medium in the impregnation step is preferably 70 ° C. or higher.

In the step (2), the amount of the styrene monomer added is preferably 10 to 200 parts by weight with respect to 100 parts by weight of the nuclear particles. When the amount of the styrene monomer added is within the above range, the nuclear particles can be sufficiently plasticized, the polymerization initiator can be sufficiently impregnated into the nuclear particles, and the styrene monomer can be sufficiently impregnated outside the nuclear particles. It is possible to suppress the generation of fine particles due to polymerization.

In the step (3), it is preferable to initiate the polymerization of the styrene monomer by setting the temperature of the aqueous medium to a temperature at which the organic peroxide is substantially decomposed. From the viewpoint of productivity, it is preferable that the temperature of the aqueous medium is (T _{1 / 2-10} ) ° C. or higher.

By the steps (1) to (4) above, a high molecular weight and high degree of branching polystyrene resin can be obtained without using a polyfunctional monomer (branching agent). However, the polyfunctional monomer may be added to the aqueous medium as long as gelation does not occur during polymerization. The amount of the polyfunctional monomer added to the aqueous medium is preferably 0.1 part by weight or less, preferably 0.05 part by weight, based on 100 parts by weight of the total of the nuclear particles and the styrene-based monomer. Is more preferable. However, it is particularly preferable that the polyfunctional monomer is not used, that is, the branched polystyrene-based resin does not contain a component derived from the polyfunctional monomer in the molecular chain.

Next, a molecular analysis method by the GPC-MALS method will be described.
By the GPC-MALS method, the absolute molecular weight and turning radius of the polystyrene-based resin (branched polystyrene-based resin, matrix portion of the impact-resistant polystyrene-based resin) are measured. Specifically, when a measurement sample such as polystyrene resin is dissolved in a solvent such as tetrahydrofuran to prepare a polystyrene resin solution and subjected to GPC measurement, the polymer having a larger molecular size elutes first. The polystyrene solution can be divided according to the molecular size. Subsequently, in the MALS measurement, the polystyrene-based resin solution divided by the molecular size in the GPC measurement is irradiated with laser light, and the scattered light intensity generated from the styrene-based resin solution by Rayleigh scattering is measured. From the obtained measured values, the weight average molecular weight Mw'and the root mean square turning radius <R _g ² > are calculated using the following formula (1) and the Debye plot shown in FIG.

K ^* : Optical parameters (4π ² _{n 0} ² (dn / dc) ² / [λ ₀ ⁴ NA])
_{n 0} : Refractive index of solvent dn / dc: Increment of refractive index concentration λ ₀ : Wavelength of incident light in vacuum NA: Avogadro's number c: Sample concentration (g / mL)
R (θ): Rayleigh ratio of overscattering Mw': Weight average molecular weight (g / mole)
P (θ): Interference factor P (θ) = (1-2 {(4π / λ) sin (θ / 2)} ² <R _g ² > / 3! + ...)
λ: Wavelength in the measurement system λ ₀ / n ₀
<R _g ² >: Root mean square radius of gyration A ₂ : Second virial coefficient

In FIG. 1, styrene-based resin solutions having different resin concentrations are measured by the GPC-MALS method, and the vertical axis (Y axis) is “K ^* c / R (θ)” and the horizontal axis (X axis) is “sin”. This is an example of a Debye plot plotted as " ² (θ / 2)".
From the section between the regression line and the vertical axis obtained by the Debye plot (Y-axis section), the weight average molecular weight Mw'of the polystyrene-based resin divided by the molecular size by GPC measurement, and the initial gradient of the regression line, the polystyrene-based resin. The squared average turning radius <R _g ² > of is obtained.
In the GPC measurement, the sample concentration at each elution time is very dilute, so when the term 2A 2c is analyzed as ₀ , the weight average molecular weight Mw'and the square average of the polystyrene resin divided by the molecular size in the GPC measurement. The turning radius <R _g ² > is obtained by the following equations (2) and (3), respectively.

K ^* c / R ₀ : K ^* c / R (θ) at an angle θ = 0 °
dy / dx: Initial gradient of regression line

As a specific example of the measurement method by the GPC-MALS method, for example, a Prominence LC-20AD (2HGE) / WS system manufactured by Shimadzu Corporation and a multi-angle light scattering detector DAWN HELEOS II manufactured by Wyatt Technology are used by Wyatt. There is a method of performing analysis by the analysis software ASTRA of. In this method, the absolute weight average molecular weight (Mw') and the absolute number average molecular weight (Mn) of the polystyrene resin are obtained from the absolute weight average molecular weight Mw'and the squared average turning radius <R _g ² > of the polystyrene resin of each molecular size. '), Absolute Z average molecular weight (Mz'), and the degree of long-chain branching per 1000 units of styrene are obtained.
The weight average molecular weight Mw'obtained by this analysis is the "absolute weight average molecular weight determined by the GPC-MALS method" in the present invention, and the number average molecular weight Mn'is determined by the "GPC-MALS method" in the present invention. "Absolute number average molecular weight", and Z average molecular weight Mz'is "absolute Z average molecular weight obtained by the GPC-MALS method" in the present invention.
On the other hand, using linear polystyrene as a standard material, the weight average molecular weight Mw, the number average molecular weight Mn, and the Z average molecular weight Mz obtained by the GPC method are relative molecular weights of the polystyrene-based resin.

Further, the shrinkage factor g of the polystyrene-based resin is obtained as follows.
The ratio of the mean square turning radius <R _g ² > _B of the polystyrene resin and the mean square turning radius <R _g ² > _L of the linear polystyrene is used as the shrinkage factor g, and shrinkage is based on the following formulas (4) to (6). The factor g can be obtained.

In the above equation, gi is the contraction factor in the section _{i and c i is} the sample concentration in the section i.

When measuring the absolute weight average molecular weight, shrinkage factor, etc. of the impact-resistant polystyrene resin matrix by the GPC-MALS method, the rubber component is removed and the matrix portion (polystyrene resin component) is isolated from the sample. It shall be. The rubber component can be removed as follows.
The sample to be measured is dissolved in a mixed solvent of methyl ethyl ketone / methanol (mass ratio 10/1), and the sample is centrifuged with a centrifuge. The supernatant liquid after separation is added dropwise to methanol little by little to precipitate the polystyrene-based resin component, and then suction filtration is performed using a paper filter to separate the styrene-based resin which is the matrix phase. This is dried by vacuum drying or the like to prepare a measurement sample.

The ratio of the number average molecular weight Mn', the Z average molecular weight Mz', the Z average molecular weight Mz'to the number average molecular weight Mn' measured by the GPC-MALS method of the branched polystyrene resin used in the present invention (Mz'/. Mn'), the ratio of the weight average molecular weight Mw'to the number average molecular weight Mw'(Mw'/ Mn'), and the ratio of the Z average molecular weight Mz'to the weight average molecular weight Mw'(Mz'/ Mw') are as follows. It is preferably within the range.

The number average molecular weight Mn'of the branched polystyrene resin is preferably 300,000 or more, and more preferably 500,000 or more.
Further, from the viewpoint of fluidity at the time of melting, the number average molecular weight Mn'is preferably 3 million or less, more preferably 1 million or less, and further preferably 900,000 or less.

The Z average molecular weight Mz'of the branched polystyrene resin is preferably 3 million or more, more preferably 3.5 million or more, further preferably 5 million or more, and particularly preferably 8 million or more. preferable.
Further, from the viewpoint of fluidity at the time of melting, the Z average molecular weight Mz'is preferably 15 million or less, and more preferably 12 million or less.

The ratio (Mz'/ Mn') of the Z average molecular weight Mz'and the number average molecular weight Mn'of the branched polystyrene resin is preferably 4 or more, more preferably 7 or more, and 8 or more. It is more preferable, and it is particularly preferable that it is 10 or more. The upper limit of Mz'/ Mn'is preferably 25, more preferably 20.

Next, the melt properties (melt tension, melt viscosity, melt flow rate) of the branched polystyrene-based resin used in the present invention will be described.
The melt tension of the branched polystyrene-based resin used in the present invention at 200 ° C. is preferably 500 mN or more.
Further, the upper limit of the melt tension is not particularly limited as long as it is possible to achieve the intended object of the present invention, but it is preferably about 1500 mN.

The melt tension can be measured by, for example, Capillograph 1D manufactured by Toyo Seiki Seisakusho Co., Ltd. Specifically, a cylinder having a cylinder diameter of 9.55 mm and a length of 350 mm and an orifice having a nozzle diameter of 2.095 mm and a length of 8.0 mm are used, and the set temperature of the cylinder and the orifice is set to 200 ° C. Put the required amount in the cylinder, leave it for 4 minutes, then extrude the molten resin from the orifice in a string shape at a piston speed of 10 mm / min, and hang this string on a tension detection pulley with a diameter of 45 mm. The string-like object is picked up by the pick-up roller while increasing the pick-up speed at a constant speed so that the pick-up speed reaches from 0.2 m / min to 200 m / min in minutes. The maximum value of the tension observed until the winding speed reaches 200 m / min is defined as the melt tension. If the string-like material breaks before the winding speed reaches 200 m / min, the maximum value of the tension observed up to that point is taken as the melt tension.

The melt viscosity of the branched polystyrene resin at 200 ° C. and a shear rate of 100 sec ^-1 is preferably 2100 Pa · s or less, and more preferably 2000 Pa · s or less. The lower limit of the melt viscosity is not particularly limited, but is preferably 1000 Pa · s or more.

The melt viscosity can be measured by, for example, a capillograph 1D manufactured by Toyo Seiki Seisakusho Co., Ltd. in the same manner as the melt tension. Specifically, a cylinder having a cylinder diameter of 9.55 mm and a length of 350 mm and an orifice having a nozzle diameter of 1.0 mm and a length of 10.0 mm are used, and the set temperature of the cylinder and the orifice is set to 200 ° C. After putting the required amount in the cylinder and leaving it for 4 minutes, the piston speed is changed to a shear speed of 10, 50, 100, 200, 300 sec ^-1 , and the molten resin is extruded from the orifice in a string shape to generate it. Record the stress applied in the load cell. As for the melt viscosity at each shear rate, the acquisition of the melt viscosity data is started 30 seconds after the piston speed reaches the specified value, and the data acquisition is finished 30 seconds later. The melt viscosity is calculated from the stress obtained during this 30 seconds.

The melt flow rate (MFR) of the branched polystyrene-based resin is preferably 0.2 to 5 g / 10 minutes from the viewpoint of ease of extrusion processing.
The MFR is a value measured at 200 ° C. and a load of 5 kg based on JIS K7210-1: 2014.

Next, a polystyrene-based resin foamed sheet (hereinafter, also simply referred to as a foamed sheet) constituting the multilayer foamed sheet obtained by the present invention will be described.
As the foamed sheet, a sheet manufactured by a conventionally known extrusion foaming method can be used. The resins, physical foaming agents, additives and the like used in the production of the foamed sheet are as follows.

Examples of the polystyrene-based resin used for producing the foamed sheet include polystyrene, styrene-acrylonitrile copolymer, styrene-methacrylic acid copolymer, styrene-methyl methacrylate copolymer, and styrene-acrylic acid copolymer. Examples thereof include styrene-butyl acrylate copolymer, styrene-maleic anhydride copolymer, polymethylstyrene, polystyrene-polyphenylene ether copolymer, a mixture of polystyrene and polyphenylene ether, and a mixture of two or more of these. The content of the styrene component in the polystyrene-based resin is preferably 50% by mass or more, more preferably 70% by mass or more. Further, in order to improve the impact resistance of the foamed sheet, a styrene-based thermoplastic elastomer can be blended with the polystyrene-based resin. In this case, the blending amount of the elastomer is preferably 3 to 20% by weight with respect to 100 parts by weight of the polystyrene-based resin.

Examples of the physical foaming agent used for producing the foamed sheet include aliphatic hydrocarbons such as propane, normal butane, isobutane, normal pentane, isopentane, normal hexane and isohexane, and alicyclic hydrocarbons such as cyclopentane and cyclohexane. , Hydrocarbons such as methyl chloride and ethyl chloride, organic physical foaming agents such as fluorinated hydrocarbons such as 1,1,1,2-tetrafluoroethane and 1,1-difluoroethane, nitrogen, carbon dioxide, air, Examples thereof include inorganic physical foaming agents such as water. Two or more of the above-mentioned physical foaming agents can be used in combination. Of these, organic physical foaming agents are particularly preferable from the viewpoint of compatibility with polystyrene-based resins and foamability, and among them, those containing normal butane, isobutane, or a mixture thereof as a main component are preferable.

The amount of the physical foaming agent added is adjusted according to the type of foaming agent and the desired apparent density. The amount of the bubble adjusting agent added is adjusted according to the target bubble diameter.

A bubble adjusting agent is mentioned as a main additive used in the production of the foamed sheet. As the bubble adjusting agent, either an organic type or an inorganic type can be used. Examples of the inorganic bubble adjusting agent include boric acid metal salts such as zinc borate, magnesium borate, and borosand, sodium chloride, aluminum hydroxide, talc, zeolite, silica, calcium carbonate, and sodium bicarbonate. Examples of the organic bubble adjusting agent include sodium phosphate-2,2-methylenebis (4,6-tert-butylphenyl), sodium benzoate, calcium benzoate, aluminum benzoate, sodium stearate and the like. Further, a combination of citric acid and sodium bicarbonate, an alkaline salt of citric acid and sodium bicarbonate and the like can also be used as the bubble adjusting agent. Two or more of these bubble adjusting agents can be used in combination.
The amount of the bubble adjusting agent added is preferably 0.01 to 3 parts by weight, more preferably 0.03 to 1 part by weight per 100 parts by weight of the base resin.

Next, the multilayer foamed sheet obtained by the present invention will be described.
The multilayer foamed sheet is obtained by laminating the resin layer on one side or both sides of the polystyrene-based resin foamed sheet. Examples of the method for laminating the resin layer include extrusion laminating, thermal laminating, and coextrusion method, and in order to carry out these, conventionally known devices and methods can be used. Among these methods, it is preferable to laminate the resin layer on the foamed sheet by extrusion laminating.

From the viewpoint of achieving both the effect of improving rigidity and impact resistance, the effect of improving thermoforming property, and the lightness, the laminated amount of the resin layer is preferably 50 to 150 g / m ² , preferably 70 to 140 g / m 2. It is more preferably m ² . In the present invention, by laminating a specific resin layer on a foamed sheet, it is possible to improve the deep drawing formability of the multilayer sheet without excessively increasing the laminating amount of the resin layer.

From the viewpoint of the balance between lightness and strength, the apparent density of the multilayer foamed sheet is preferably 0.05 to 0.30 g / cm ³ , and more preferably 0.07 to 0.25 g / cm ³ . , 0.09 to 0.21 g / cm ³ , more preferably.

From the viewpoint of the balance between thermoformability and strength, the thickness of the multilayer foamed sheet is preferably 1 to 3 mm, more preferably 1.4 to 2.8 mm, and 1.8 to 2.4 mm. It is more preferable to have.

From the viewpoint of thermoforming property, cost, light weight, and strength of the obtained molded product, the basis weight of the entire multilayer foamed sheet is preferably about 150 to 550 g / m ² , more preferably 200 to 450 g / m. It is ² , more preferably 220 to 400 g / m ² .

Next, the polystyrene-based resin multilayer foamed sheet of the present invention will be described. The multilayer foamed sheet can be obtained by the method for producing the multilayer foamed sheet.
The multilayer foamed sheet has a resin layer laminated on one side or both sides of the foamed sheet, and the resin layer has the resistance to which a granular rubber-like polymer is dispersed in a polystyrene-based resin matrix. It is made of a mixed resin of an impact-resistant polystyrene-based resin and the branched polystyrene resin having a branched chain.
As described above, the branched polystyrene resin has an absolute weight average molecular weight of 1 million to 5 million measured by the GPC-MALS method, and an average value of shrinkage factors measured by the GPC-MALS method is 0.80. It is a resin having the following content and having a tetrahydrofuran insoluble content of 0.1% by weight or less of the branched polystyrene-based resin. The weight ratio of the branched polystyrene-based resin in the mixed resin is 5% by weight or more and less than 30% by weight.

The multilayer foamed sheet of the present invention can be molded by a conventionally known molding method, and is particularly excellent in deep drawing formability. Molding methods include vacuum forming, pneumatic forming, and as applications thereof, free drawing forming, plug and ridge forming, ridge forming, matched molding, straight forming, drape forming, reverse drawing forming, air slip forming, etc. Plug-assist molding, plug-assist reverse load molding, etc., and a method combining these are adopted.

The unfolding ratio of the molded product obtained by thermoforming the multilayer foam sheet of the present invention is not particularly limited, but is generally preferably 2 to 5 times, preferably 3 to 5 times, from the viewpoint of enabling deep drawing. Is more preferable, and 3.5 to 5 times is further preferable. The expansion ratio of the molded body is the ratio of the surface area of the surface of the molded body to the opening area of the molded body. At this time, the surface area of the inner surface of the molded body can be obtained by a method of directly measuring from the molded body, a method of measuring with a 3D shape measuring machine, or the like.

Examples of the molded body molded by using the multilayer foamed sheet of the present invention include deep-drawn bowls, cups and the like. However, it can also be used for molding shallow trays, lunch boxes, and the like.

Next, the method for producing the multilayer foamed sheet of the present invention will be described in detail with reference to Examples. However, the present invention is not limited to the examples.

The following resin was used as the impact resistant polystyrene for forming the resin layer.
(1) Abbreviation "HIPS1": Impact-resistant polystyrene "475D" manufactured by PS Japan Corporation (MFR = 4 g / 10 min, butadiene amount 6.3%)
(2) Abbreviation "HIPS2": Impact-resistant polystyrene "H450" manufactured by Toyo Styrene Co., Ltd. (MFR = 5.5 g / 10 min, butadiene amount 5.1%)
(3) Abbreviation "HIPS3": Impact-resistant polystyrene "408" manufactured by PS Japan Corporation (MFR = 7 g / 10 min, butadiene amount 5.0%)
(4) Abbreviation "HIPS4": Impact-resistant polystyrene "AGI02" manufactured by PS Japan Corporation (MFR = 15 g / 10 min, butadiene amount 5.3%)
Table 1 shows various physical characteristics of the impact-resistant polystyrene-based resin.

The following resins were used as the branched polystyrene-based resin for forming the resin layer.
(1) Abbreviation "multi-branch PS1"
(Preparation of nuclear particles)
In an autoclave with an internal volume of 1 m ³ equipped with a stirrer, 350 kg of deionized water, 2.1 kg of tricalcium phosphate (20.5% slurry manufactured by Taihei Kagaku Sangyo Co., Ltd.) as a suspending agent, and dodecylbenzene as a surfactant. Sodium sulfonate (manufactured by Tokyo Kasei Kogyo Co., Ltd., 10% aqueous solution) 0.158 kg, dodecyldiphenyl ether disodium sulfonate (manufactured by Kao Co., Ltd., Perex SSH, 10% aqueous solution) 0.053 kg, sodium acetate 0.535 kg as an electrolyte I put it in.
Next, as a polymerization initiator, 0.975 kg of t-butylperoxy-2-ethylhexanoate (PerbutylO manufactured by Nichiyu Co., Ltd.) and 0.284 kg of t-butylperoxy-2-ethylhexyl monocarbonate (Nippon Oil Co., Ltd.) 15.4 g of 4-tert-butylcatecol as a polymerization inhibitor of Perbutyl E) manufactured by the company was dissolved in 390 kg of styrene and supplied into an autoclave while stirring at 110 rpm. After the inside of the autoclave was replaced with nitrogen, the temperature was started to be raised to 90 ° C. over 1 hour and 15 minutes.
After reaching 90 ° C., the temperature was raised to 100 ° C. over 5 hours. After reaching 100 ° C., the temperature was raised to 115 ° C. over 1 hour and 30 minutes. It was kept at 115 ° C. for 2 hours and 40 minutes, and then cooled to 40 ° C. over 2 hours. During the temperature rise to 90 ° C., when the temperature reached 60 ° C., 1.95 g of potassium persulfate was put into the autoclave as a suspension aid.
After cooling, the contents were taken out, the tertiary calcium phosphate adhering to the surface of the polymerized polystyrene resin particles was dissolved with nitric acid, washed with water, and dehydrated with a centrifuge.
The obtained particles were sieved, and particles having a diameter of 0.5 to 1.3 mm (average particle diameter of 0.8 mm) were taken out and used as nuclear particles.

410 kg of deionized water, 2.56 kg of sodium pyrophosphate and 6.39 kg of magnesium nitrate were supplied to an autoclave having an internal volume of 1.5 m ³ equipped with a stirrer, and pyrophosphate as a suspending agent in the autoclave by salt exchange. Magnesium was synthesized. After supplying 0.128 kg of sodium alkylsulfonate (manufactured by Kao Co., Ltd., Latemul PS, 40% aqueous solution) as a surfactant and 78.2 kg of nuclear particles obtained by the above method to the autoclave, the gas phase portion in the autoclave. Was replaced with nitrogen.

Then, the temperature was raised to 80 ° C. with stirring at 50 rpm. After reaching 80 ° C, 82 kg of deionized water, 0.166 kg of sodium alkylsulfonate (Latemuru PS, 40% aqueous solution), 27.6 kg of styrene (styrene monomer), t-butyl as a polymerization initiator Peroxy-2-ethylhexyl monocarbonate (manufactured by Nichiyu Co., Ltd., perbutyl E, 10-hour half-life temperature T _1/2 : 99.0 ° C) 3.06 kg, α-methylstyrene polymer as a chain transfer agent (Nippon Oil Co., Ltd.) A mixture of 1.15 kg of Nohmer MSD (manufactured by the company) was prepared into an emulsion by a homogenizer, and the emulsion was supplied into an autoclave. Then, the inside of the autoclave was pressurized with nitrogen until it reached 0.1 MPa (G), and kept at 80 ° C. for 15 minutes.

Then, the temperature was raised to 105 ° C. over 1 hour. After the temperature in the autoclave reached 105 ° C., 354.3 kg of styrene (styrene monomer) was continuously added into the autoclave at a rate of 0.87 kg / min while maintaining the temperature for 7 hours and 30 minutes.
When adding styrene, the content of styrene in the nuclear particles with respect to the elapsed time by simulation based on the above addition conditions, the chemical properties of the polymerization initiator used for polymerization, and the polymerization rate of styrene calculated from the polymerization temperature. The amount change and the temperature change were confirmed, and based on the simulation, styrene was additionally added so that the styrene content in the core particles during the addition of styrene was 10% by weight or less.
When the styrene content in the polystyrene-based resin particles was measured at the start of the additional addition of styrene, 2.5 hours after the start of the addition, and at the end of the additional addition, the styrene content in the nuclei particles was 3 weight each. %, 5% by weight, and 4% by weight.
Then, the aqueous medium was heated to 120 ° C. over 2 hours and kept at 120 ° C. for 3 hours to polymerize the unreacted styrene monomer.
After cooling the inside of the autoclave, the polystyrene resin particles taken out from the autoclave are washed with dilute nitric acid to dissolve and remove the suspending agent adhering to the particle surface, then washed with water, further dehydrated with a centrifuge, and multi-branched. Obtained PS1.

(2) Abbreviation "multi-branch PS2"
The multi-branched PS2 was produced in the same manner as the production conditions of the multi-branched PS1 except that the amount of the polymerization initiator was changed from 3.06 kg to 1.54 kg and the amount of the chain transfer agent was changed from 1.15 kg to 0.22 kg. .. The styrene content in the styrene-based resin particles was measured at the start of the additional addition of styrene, 2.5 hours after the start of the addition, and at the end of the additional addition. It was 7% by weight, 7% by weight, and 6% by weight.
(3) Abbreviation "Multi-branch PS3": "High branch HP780AN" manufactured by DIC Corporation
Table 2 shows various physical characteristics of the branched polystyrene resin. In addition, in the measurement of the melt tension in Table 2, for the purpose of homogenizing the measurement sample, the above-mentioned branched polystyrene resin was used in a biaxial extruder (screw diameter: 26 mm) at 200 ° C. and the rotation speed: 80 rpm. , Discharge: A sample obtained by melt-kneading and repelletizing under the condition of 15 kg / hr was used as a measurement sample.

The absolute molecular weights of the polystyrene-based resin, the number average molecular weight Mn', the weight average molecular weight Mw', the Z average molecular weight Mz', and the shrinkage factor g were measured by the following methods. Using "Prominence LC-20AD (2HGE) / WS system" manufactured by Shimadzu Corporation and DAWN HELEOS II multi-angle light scattering detector manufactured by Waitt Technology, eluent: Tetrahydrofuran (THF), flow rate 1.0 ml / min. The measurement was performed under the conditions. As the column, TSKgel GMHR × 2 manufactured by Tosoh Corporation and TSKgel HHR-H × 1 manufactured by Tosoh Corporation were connected in series and used. The number average molecular weight Mn', the weight average molecular weight Mw', and the Z average molecular weight Mz' of the polystyrene-based resin were determined by the analysis software ASTRA of Wyatt Technology. The shrinkage factor g is the ratio of the square of the radius of gyration <R _b ² > of the polystyrene resin to be measured to the square of the radius of gyration <R _l ² > of the linear styrene resin (the above formula (4)). I asked for it. As the linear styrene resin, the data of the polystyrene resin produced as the nuclear particles was used. Further, from the above formula (5), the average value _gw of the contractile factor was obtained for the range of the absolute molecular weight of 1 million or more.

As a polystyrene resin foam sheet for laminating a resin layer, a polystyrene resin foam sheet B220MRN manufactured by JSP Co., Ltd. (thickness 1.85 mm, basis weight 220 g / m ² , apparent density 0.119 g / m ³ , closed cell ratio 90%) is used. used.

Examples 1 to 4, Comparative Examples 1 to 6
Impact-resistant polystyrene and branched polystyrene resin of the types and weight ratios shown in Table 3 are supplied to a twin-screw extruder in the same direction (screw diameter: 26 mm, rotation speed: 80 rpm, discharge: 15 kg / hr) at 200 ° C. The mixture was melted and mixed to obtain mixed resin pellets. The mixed resin pellets are put into an extruder equipped with a T-die, melted to a resin temperature of 240 ° C., and extruded and laminated so that the basis weight is 120 g / m ² on one surface of the foamed sheet. Laminated (take-up speed: 10.0 m / min).
The apparent density of the multilayer foam sheets obtained in Examples and Comparative Examples was 0.17 g / cm ³ , the thickness was 2.0 mm, and the basis weight was 340 g / m ² .
Table 3 shows the thermoformability evaluation of the multilayer foamed sheets obtained in Examples and Comparative Examples. Table 3 shows the results of measuring the melt viscosity and melt tension of the mixed resin used to form the resin layer.

For the obtained polystyrene-based resin foamed multilayer sheet, a thermoforming apparatus (“FKS-0631-10” manufactured by Asano Laboratories Co., Ltd.) was used so that the surface on which the resin layers were laminated was located on the outside of the container. After heating the sheet for a predetermined number of seconds, thermoforming was performed using a circular cup-shaped mold (expansion magnification 4.1 times) having an opening having a diameter of 94 mm, a height of 94 mm, and a bottom surface having a diameter of 70 mm. The heater temperature was 340 ° C. on the resin layer laminated surface side and 250 ° C. on the opposite surface side. The evaluation of thermoformability is shown in Table 3. The obtained molded product was subjected to an impact resistance test. The results are shown in Table 3.

In Table 3, each measurement and evaluation was performed as follows.

The melt tension was measured by the above method.

The melt viscosity was measured by the above method.

Thermoformability evaluation criteria (moldable heating time)
◯: The range of heating time from which a good molded product can be obtained is 5 seconds or more.
X: The range of heating time from which a good molded product can be obtained is less than 5 seconds.
If the heating time range in which a good molded product can be obtained is 5 seconds or more, stable molding is possible even in continuous molding.

Evaluation Criteria for Impact Resistance (Buckling / Cracking of Flange) of Molded Body Using Tensilon manufactured by Orientec Co., Ltd .: RTC-1250A, the flange part formed on the peripheral edge of the opening of the molded body was attached to the container opening. It was compressed in the horizontal direction at a speed of 100 mm / min, and the displacement when a crack occurred in the flange portion was measured and evaluated according to the following criteria.
◯: The amount of displacement in which the flange is cracked is 30% or more.
X: The amount of displacement in which the flange is cracked is less than 30%.

Claims (6)

In a method for manufacturing a multilayer foamed sheet by laminating a polystyrene-based resin layer on at least one surface of a polystyrene-based resin foamed sheet.
The polystyrene-based resin layer is composed of a mixed resin of an impact-resistant polystyrene-based resin in which a granular rubber-like polymer is dispersed in a polystyrene-based resin matrix and a branched polystyrene-based resin having a branched chain.
The absolute weight average molecular weight measured by the GPC-MALS method of the branched polystyrene resin is 1 million to 5 million, and the average value of the shrinkage factor measured by the GPC-MALS method of the branched polystyrene resin is 0. It is 80 or less, and the content of the isocyanate insoluble content of the branched polystyrene resin is 0.1% by weight or less (including 0).
A method for producing a polystyrene-based resin multilayer foamed sheet, wherein the weight ratio of the branched polystyrene-based resin in the mixed resin is 5% by weight or more and less than 30% by weight.
The method for producing a polystyrene-based resin multilayer foamed sheet according to claim 1, wherein the branched polystyrene-based resin does not contain a component derived from a polyfunctional monomer in the molecular chain.
The polystyrene-based resin multilayer foam according to claim 1 or 2, wherein the weight ratio of the molecule having an absolute molecular weight of 1 million or more measured by the GPC-MALS method in the branched polystyrene-based resin is 20% by weight or more. Sheet manufacturing method.
The absolute weight average molecular weight of the impact-resistant polystyrene resin matrix measured by the GPC-MALS method is 100,000 to 350,000, and the average value of the shrinkage factor measured by the GPC-MALS method of the matrix is 0. The method for producing a polystyrene-based resin multilayer foamed sheet according to any one of claims 1 to 3, wherein the content is .95 or more.
The method for producing a polystyrene-based resin multilayer foamed sheet according to any one of claims 1 to 4, wherein the laminated amount of the resin layer is 50 to 150 g / m ² .
In a multilayer foamed sheet in which a polystyrene-based resin layer is laminated on at least one side of a polystyrene-based resin foamed sheet.
The polystyrene-based resin layer is composed of a mixed resin of an impact-resistant polystyrene-based resin in which a granular rubber-like polymer is dispersed in a polystyrene-based resin matrix and a branched polystyrene resin having a branched chain.
The absolute weight average molecular weight measured by the GPC-MALS method of the branched polystyrene resin is 1 million to 5 million, and the average value of the shrinkage factor measured by the GPC-MALS method of the branched polystyrene resin is 0. It is 80 or less, and the content of the isocyanate insoluble content of the branched polystyrene resin is 0.1% by weight or less (including 0).
A polystyrene-based resin multilayer foamed sheet, wherein the weight ratio of the branched polystyrene-based resin in the mixed resin is 5% by weight or more and less than 30% by weight.

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