阅读说明：本技术 层叠发泡片 (Laminated foam sheet ) 是由 远藤翔太 福山英司 森彩乃 于 2020-03-25 设计创作，主要内容包括：本发明提供一种强度和成形性优异的层叠发泡片。更具体而言,本发明涉及一种层叠发泡片,其层叠有树脂发泡层和树脂非发泡层,在最表层具备前述树脂发泡层,所述层叠发泡片具有5MPa以上的弯曲强度,由前述树脂发泡层构成的表面的算术平均粗糙度为3μm以上且10μm以下。(The invention provides a laminated foam sheet having excellent strength and moldability. More specifically, the present invention relates to a laminated foam sheet comprising a resin foam layer and a resin non-foam layer laminated thereon, the resin foam layer being provided on an outermost layer, the laminated foam sheet having a flexural strength of 5MPa or more, and the arithmetic mean roughness of the surface of the resin foam layer being 3 μm or more and 10 μm or less.)

1. A laminated foam sheet comprising a resin foam layer and a resin non-foam layer laminated thereon, the resin foam layer being provided on the outermost layer,

the laminated foam sheet has a bending strength of 5MPa or more,

the arithmetic average roughness of the surface of the resin foamed layer is 3 [ mu ] m or more and 10 [ mu ] m or less.

2. The laminated foam sheet according to claim 1, wherein the resin foam layer contains a polyester resin.

3. The laminated foam sheet according to claim 2, wherein the polyester-based resin is an aliphatic polyester-based resin.

4. The laminated foam sheet according to claim 3, wherein the aliphatic polyester-based resin is polybutylene succinate.

Technical Field

The present invention relates to a laminated foam sheet, and more particularly to a laminated foam sheet in which a resin foamed layer and a resin non-foamed layer are laminated.

The present application claims priority based on japanese patent application No. 2019-064179, filed on 28/3/2019, and the contents thereof are incorporated herein by reference.

Background

Conventionally, molded articles obtained by thermoforming resin foamed sheets to give three-dimensional shapes have been used in various applications because of their excellent lightweight properties and heat insulating properties.

Further, a laminated foamed sheet obtained by laminating a resin film on one surface or both surfaces of a resin foamed sheet has a resin foamed layer made of the resin foamed sheet and a resin non-foamed layer made of the resin film on the surface thereof, and therefore, is widely used as a material for forming a molded article having higher strength than a molded article made of the resin foamed sheet.

For example, trays and cups obtained by thermoforming a laminated foamed sheet are widely used as food containers for merchandise display in supermarkets and convenience stores.

Documents of the prior art

Patent document

Patent document 1: japanese re-listing 2017/069127

Disclosure of Invention

Problems to be solved by the invention

Such a laminated foam sheet is required to have not only excellent strength but also excellent thermoformability, but at present, such a requirement has not been sufficiently satisfied.

Accordingly, an object of the present invention is to provide a laminated foam sheet having excellent moldability.

Means for solving the problems

The present inventors have intensively studied to solve the above problems and found that: the above problems can be solved by forming the laminated foam sheet to have a predetermined surface roughness, and the present invention has been completed.

That is, the present invention for solving the above problems provides a laminated foam sheet,

which comprises a resin foamed layer and a resin non-foamed layer laminated on each other, and which is provided on the outermost layer with the resin foamed layer,

the laminated foam sheet has a bending strength of 5MPa or more,

the arithmetic average roughness of the surface of the resin foamed layer is 3 μm or more and 10 μm or less.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, a laminated foam sheet having excellent strength and moldability can be provided.

Drawings

Fig. 1 is a schematic view showing the configuration of an apparatus for producing a biodegradable laminated foamed sheet.

Fig. 2 is a schematic end view showing a portion shown by a broken line a in fig. 1.

Detailed Description

Hereinafter, embodiments of the present invention will be described.

First, an extrusion apparatus used in the method for producing a laminated foam sheet according to the present embodiment will be described.

In the following, a biodegradable laminated foam sheet containing a biodegradable resin as a main component is exemplified as the laminated foam sheet of the present invention.

The biodegradable laminated foam sheet of the present embodiment has a two-layer structure of a biodegradable resin foamed layer and a biodegradable resin non-foamed layer, and is produced by a co-extrusion method.

In the production of the biodegradable laminated foamed sheet of the present embodiment, a facility including a first extrusion line 6 (no reference numeral shown) for forming a non-foamed layer of a biodegradable resin and a second extrusion line 7 (no reference numeral shown) for forming a foamed layer of a biodegradable resin is used.

The first extrusion line 6 is provided with a separate extruder 60 for melt-kneading a non-foamable resin composition for forming a non-foamed layer of a biodegradable resin.

The second extrusion line 7 includes a tandem extruder 70 as an extruder for melt-kneading a foamable resin composition containing a biodegradable resin and a foaming agent.

The extruder 60 of the first extrusion line 6 has a hopper 61 for charging the material for forming the non-foamed layer of the biodegradable resin (non-foamable resin composition), and is configured to melt-knead the non-foamable resin composition therein and to discharge a melt-kneaded product obtained by the melt-kneading.

The tandem extruder 70 is connected to two extruders, an upstream side extruder 70a and a downstream side extruder 70b, and the upstream side extruder 70a is provided with a hopper 71 for charging a material for forming a biodegradable resin foam layer and a gas introduction portion 72 for supplying a foaming agent such as hydrocarbon into the cylinder from a gas supply device 73.

The downstream side extruder 70b is configured to discharge a molten kneaded product obtained by further melt-kneading the foamable resin composition in a molten state formed in the upstream side extruder 70 a.

The front end of the tandem extruder 70 is provided with: a confluence die 80 for merging the foamable resin composition melt-kneaded by the tandem extruder 70 and the non-foamable resin composition melt-kneaded by the extruder 60 of the first extrusion line 6, and an annular die 100 having an annular discharge port (hereinafter also referred to as a "die slit 111") for forming a cylindrical foamed sheet FB by extrusion-foaming the merged resin composition in a molten state into the atmosphere.

The confluence mold 80 is configured such that the foamable resin composition and the non-foamable resin composition are allowed to flow in a predetermined state through the annular mold 100 having a cylindrical resin passage 101 extending in the extrusion direction.

Specifically, the confluence mold 80 is configured to form a cylindrical passage having an inner side of the foamable resin composition and an outer side of the non-foamable resin composition in the resin passage 101.

The extrusion apparatus includes a cooling plug 200 for cooling the cylindrical foam sheet FB, which is discharged in a cylindrical shape from the annular die slit 111 opened in the front surface of the annular die 100, from the inner surface side.

The extrusion apparatus further includes a cooling device CR for cooling the foamed sheet (cylindrical foamed sheet) from the outside by blowing air from the outside to the foamed sheet before being cooled by the cooling plug 200.

A cutting blade CT for cutting a pair of left and right cuts into the tubular foamed sheet FB is attached to the downstream side of the cooling plug 200.

The extrusion apparatus of the present embodiment includes: a roller 91 for spreading the tubular foam sheet FB divided into two halves in the direction of extrusion by the cutting blade CT and a take-up roller 92 for taking up the spread biodegradable laminated foam sheet 1 in two blank rolls of an upper roll UR and a lower roll LR.

In the present embodiment, the cooling device CR for cooling the cylindrical foamed sheet FB from the outside from the ring die 100 to the cooling plug 200 has a cooling ring CR1 which is a flat ring-shaped hollow plate.

The cooling ring CR1 has a circular shape with an inner periphery slightly larger than the diameter of the die gap 111, and an air outlet 301 for blowing out air is formed in the inner periphery, and the air outlet 301 is formed in an annular shape along the inner edge of the cooling ring CR 1.

As described above, since the outlet 301 is opened along the inner periphery of the cooling ring CR1, the outlet 301 is opened at a slight distance from the outside of the die gap 111, and the cooling mechanism is configured to blow the cylindrical foam sheet FB immediately after extrusion.

The biodegradable laminated foamed sheet of the present embodiment is produced by a coextrusion method in which a biodegradable resin foamed layer and a biodegradable resin non-foamed layer are simultaneously extruded from the die slit 111, using the above-described apparatus.

The biodegradable laminated foam sheet of the present embodiment is not limited to the coextrusion method, and can be produced as follows: a biodegradable resin foamed sheet having a single resin foamed layer is produced by an extrusion foaming method, and then a biodegradable resin film is laminated on the biodegradable resin foamed sheet, and the resin foamed layer is formed from the biodegradable resin foamed sheet, and the resin non-foamed layer is formed from the biodegradable resin film.

The biodegradable laminated foam sheet has a two-layer structure in which a biodegradable resin foam layer and a biodegradable resin non-foam layer are laminated.

That is, the biodegradable laminated foam sheet of the present embodiment includes the biodegradable resin non-foamed layer on one outermost layer and the biodegradable resin foamed layer on the other outermost layer.

The biodegradable laminated foam sheet of the present embodiment may have a laminated structure of three or more layers including one or more intermediate layers between outermost layers.

The biodegradable laminated foamed sheet of the present embodiment has not only a biodegradable resin foamed layer but also a biodegradable resin non-foamed layer, and therefore can have excellent strength.

The biodegradable laminated foam sheet produced in the above manner preferably has a flexural strength of 5MPa or more in addition to exhibiting excellent strength to a molded article.

The flexural strength of the biodegradable laminated foam sheet is preferably 10MPa or less, more preferably 8MPa or less.

The flexural modulus of the biodegradable laminated foam sheet of the present embodiment is preferably 120MPa or more, more preferably 150MPa or more, and still more preferably 180MPa or more.

The flexural modulus of the biodegradable laminated foam sheet is preferably 500MPa or less, more preferably 350MPa or less, and still more preferably 270MPa or less.

The flexural strength and flexural modulus of the biodegradable laminated foam sheet can be determined, for example, as follows.

< measurement of flexural Strength >

Data were processed using a "TENSILON UCT-10T" universal tester manufactured by ORIENTEC, and a "UTPS-458X" universal tester manufactured by Soft Brain, and the test piece was measured with a test piece size of 50mm wide × 150mm long, a compression rate of 200mm/min, a pressure wedge of 3.2R, a support table of 3.2R, and a distance between supporting points of 100 mm.

The number of test pieces was set to 5, and the flexural modulus was determined by averaging the 5 test results.

The bending strength and the bending modulus were obtained with the origin of the displacement as an inflection point.

(bending Strength)

The bending strength R (MPa) is calculated by the following formula.

R＝(1.5F_R×L/bd²)×10³

·F_R: maximum load (kN)

L: distance between pivots (mm)

B: width of test piece (mm)

D: thickness of test piece (mm)

(flexural modulus of elasticity)

The flexural modulus of elasticity E (MPa) is calculated by the following formula.

E＝αL³/(4bd³)

α: elastic modulus slope (N/mm)

In the above bending strength measurement, a test performed such that the pressure wedge is brought into contact with one surface side (for example, the resin foam layer side) of the laminated foam sheet and a test performed such that the pressure wedge is brought into contact with the other surface side (for example, the resin non-foam layer side) of the laminated foam sheet are each performed 5 times, and an arithmetic average of the obtained 10-point measurement results is obtained.

That is, the bending strength and the bending modulus are obtained as an arithmetic average of 10-point measurement values.

The biodegradable laminated foam sheet of the present embodiment has a high flexural modulus of elasticity, and therefore, if heating is not performed so as to exhibit a sufficiently softened state during thermoforming, the shape of the forming mold may not be reflected with sufficiently good accuracy on the formed product.

However, when the biodegradable laminated foam sheet is sufficiently softened, the biodegradable laminated foam sheet may adhere to the molding surface of the molding die during thermoforming, and appropriate "slip" may not occur between the molding surface and the biodegradable laminated foam sheet, which may adversely decrease the moldability of the molded article.

The biodegradable laminated foamed sheet of the present embodiment is provided with the biodegradable resin foamed layer in a predetermined state on the outermost layer, and is an important condition for the biodegradable laminated foamed sheet to exhibit good moldability.

Specifically, the biodegradable laminated foam sheet described above is important: the arithmetic average roughness (hereinafter also referred to as "surface roughness (Ra)") of the surface of the biodegradable resin foamed layer is 3 μm or more and 10 μm or less.

This can prevent the biodegradable laminated foam sheet from being excessively adhered to the molding surface during thermoforming.

Further, the surface roughness is preferably not excessively rough, and the surface roughness is preferably 6 μm or less, more preferably 5 μm or less.

The surface roughness (arithmetic average roughness: Ra) of the biodegradable laminated foam sheet was measured in accordance with JIS B0601 "definition and expression of surface roughness".

That is, the biodegradable laminated foam sheet was conditioned under the standard atmosphere of class 2 represented by "23/50" (temperature 23 ℃ C., relative humidity 50%) in JIS K7100:1999 for 16 hours, and then measured under the following apparatus and measurement conditions.

(measurement conditions)

An apparatus: handysurf E-35A manufactured by Tokyo precision Co

Cutoff (λ c): 0.80mm

Evaluation length (L): 4.0mm

The measurement was performed in the TD direction (direction perpendicular to the extrusion direction, width direction) of the biodegradable laminated foam sheet, and was performed at 5 randomly selected positions.

The arithmetic average roughness Ra of the biodegradable laminated foam sheet was set to the average value of these arithmetic average roughness Ra.

In order to form the surface roughness of the biodegradable resin foamed layer as described above, the cell film constituting the surface of the biodegradable resin foamed layer may be expanded for each cell.

In order to achieve such a state, it is preferable to mix a blowing agent in advance when melt-kneading is performed by the tandem extruder 70.

In order to form the surface roughness of the biodegradable resin foamed layer as described above, it is also effective to enhance cooling of the side (outside) of the tubular foamed sheet FB on which the biodegradable resin non-foamed layer is provided and to suppress dissipation of the blowing agent gas from the side of the biodegradable resin non-foamed layer.

The thickness of the biodegradable laminated foam sheet is preferably 0.2mm or more, more preferably 0.5mm or more, and still more preferably 1.0mm or more.

The thickness of the biodegradable laminated foam sheet is preferably 6mm or less, more preferably 5mm or less, and still more preferably 4mm or less.

The thickness of the biodegradable laminated foam sheet can be determined as an average value of the thicknesses measured at, for example, 10 or more randomly selected measurement points.

The thickness of the non-foamed layer of the biodegradable resin of the biodegradable laminated foamed sheet may be set to a thickness of 1 μm or more and 200 μm or less.

The thickness of the non-foamed layer of the biodegradable resin can be determined as follows: a photomicrograph of a cross section of the non-foamed layer of the biodegradable resin (a cross section in a plane orthogonal to the planar direction of the biodegradable laminated foamed sheet) is taken, the thickness of the non-foamed layer of the biodegradable resin is measured at a plurality of randomly selected sites (for example, 10 sites) in the photomicrograph, and the arithmetic average of the measured values is calculated.

The basis weight of the biodegradable laminated foam sheet is preferably 200g/m²More preferably 250g/m or more²Above, more preferably 300g/m²The above.

The basis weight of the biodegradable laminated foam sheet is preferably 800g/m²Hereinafter, more preferably 700g/m²The following.

The basis weight of the biodegradable laminated foam sheet is determined by, for example, cutting a plurality of sheets (e.g., 10 sheets) of 100cm²The mass and area of each of the above samples were measured and determined from the following formulas.

Basis weight (g/m)²)10,000 test piece mass (g)/test piece area (cm)²)

The density (apparent density) of the biodegradable laminated foam sheet is not particularly limited, but is preferably 200kg/m³Above, more preferably 300kg/m³The above.

The apparent density is preferably 1,000kg/m³Hereinafter, more preferably 900kg/m³The concentration is preferably 800kg/m or less³The following.

The apparent density of the biodegradable laminated foam sheet can be determined by the method described in JIS K7222:1999 "measurement of foamed plastics and rubber-apparent density", specifically, the following method was used.

(method of measuring apparent Density)

Cutting 100cm from biodegradable laminated foam sheet without changing original foam cell structure³In the above-mentioned sample, the sample was conditioned under a standard atmosphere of class 2 designated by "23/50" (temperature 23 ℃ C., relative humidity 50%) in JIS K7100:1999 for 16 hours, and then the dimensions and mass thereof were measured to calculate the density from the following formula.

Apparent density (kg/m)³) Mass of sample (kg)/volume of sample (m)³)

For the measurement of the size of the sample, for example, model "DIGIMATIC" CD-15 manufactured by MITUTOYO may be used.

In order to exhibit good moldability, the biodegradable laminated foam sheet preferably has an open cell ratio of 25% or less, more preferably 20% or less, and still more preferably 15% or less.

The continuous bubble rate is usually 1% or more.

The open cell ratio of the biodegradable laminated foam sheet was measured as follows.

< interconnected cell ratio of biodegradable laminated foam sheet >

A plurality of sheet-like samples having a length of 25mm and a width of 25mm were cut from a biodegradable laminated foam sheet, the cut samples were superposed on each other without any gap to prepare a measurement sample having a thickness of 25mm, and the external dimensions of the measurement sample were measured to 1/100mm using "DIGIMATIC CALIPER" manufactured by MITUTOYO, Inc., to obtain an apparent volume (cm)³)。

Next, the volume (cm) of the sample for measurement was determined by 1-1/2-1 air pressure method using an air comparison type densitometer 1000 (manufactured by Tokyo scientific Co., Ltd.)³)。

The continuous bubble percentage (%) was calculated from the values obtained above and the following formula, and the average value of 5 test numbers was obtained.

The measurement was carried out in a standard atmosphere of class 2, which was prepared under the symbol "23/50" (temperature 23 ℃ C., relative humidity 50%) of JIS K7100-1999 for 16 hours, and then in the same standard atmosphere.

The air comparison type densitometer was calibrated with standard balls (28.9 cc larger and 8.5cc smaller).

Percent ratio of continuous bubbles (%) (apparent volume-measured volume based on air-comparison type densitometer)/apparent volume × 100

The average cell diameter of the biodegradable laminated foam sheet is preferably 0.7mm or less, and more preferably 0.6mm or less.

The average cell diameter is usually 0.1mm or more.

The average cell diameter of the biodegradable laminated foam sheet was measured as follows.

< average cell diameter of biodegradable laminated foam sheet >

A cross section cut perpendicularly to the surface of the biodegradable laminated foam sheet along the MD direction (extrusion direction) and the TD direction (width direction) from the center portion in the width direction of the biodegradable laminated foam sheet was enlarged to 100 times using a scanning electron microscope "SU 1510" manufactured by hitachi high-tech co.

At this time, the microscope image was captured so that 2 images (4 images in total) were printed in parallel on 1 sheet of a4 paper in the horizontal direction, and the image was at a predetermined magnification.

Specifically, when an arbitrary 60mm straight line parallel to each direction of MD and TD is drawn on the image printed as described above and a 60mm straight line is drawn along a direction orthogonal to each direction (also referred to as thickness direction and VD direction), the imaging magnification of the electron microscope is adjusted so that the number of bubbles present on the straight line is about 3 to 10.

Microscope images of 2 fields each and a total of 4 fields were taken for each of a cross section cut along the MD direction (hereinafter referred to as "MD cross section") and a cross section cut along the TD direction (hereinafter referred to as "TD cross section"), and printed on a sheet of a4 paper as described above.

3 arbitrary straight lines (length 60mm) parallel to the MD direction were drawn for 2 images of the MD cross section, and 3 arbitrary straight lines (length 60mm) parallel to the TD direction were drawn for 2 images of the TD cross section.

Further, 3 straight lines (60mm) parallel to the VD direction were drawn for 1 image of the MD cross section and 1 image of the TD cross section, and 6 arbitrary straight lines of 60mm parallel to the MD direction, TD direction, and VD direction were drawn for each direction.

In the case of contact, the bubble is also added as the number of bubbles.

The number of air bubbles D counted for 6 arbitrary straight lines in each of the MD direction, TD direction, and VD direction is arithmetically averaged to be the number of air bubbles in each direction.

The average chord length t of the bubble is calculated from the image magnification for counting the number of bubbles and the number of bubbles by the following equation.

Average chord length t (mm) 60/(bubble number × image magnification)

The image magnification was measured to 1/100mm by measuring the scale on the image with "DIGIMATICCALIPER" manufactured by MITUTOYO, and was determined from the following equation

Image magnification (mm) scale actual measurement value (mm)/scale index value (mm)

Then, the bubble diameter in each direction is calculated by the following equation.

Diameter of bubble D (mm) ═ t/0.616

Further, the cubic root of the product of these was taken as the average bubble diameter.

Average bubble diameter (mm) — (D)_MD×D_TD×D_VD)^1/3

·D_MD: diameter of bubble in MD (mm)

·D_TD: diameter of bubble in TD direction (mm)

·D_VD: bubble diameter (mm) in VD direction

The biodegradable laminated foam sheet of the present embodiment can be formed from a resin composition containing a biodegradable resin as a main component as described above.

The resin composition for forming the resin foaming agent layer will be described below.

The resin composition constituting the resin non-foamed layer may be the same as the resin composition exemplified below, except that the foaming agent is not contained.

The resin composition of the present embodiment may contain, for example, only a biodegradable resin, or may contain a biodegradable resin, an additive, and the like.

Examples of the biodegradable resin according to the present embodiment include biodegradable polyester resins.

Examples of the biodegradable polyester resin include aliphatic polyester resins obtained by polycondensation of a diol and an aliphatic dicarboxylic acid, and dicarboxylic acid and diol are suitable as constituent units.

Examples of the aliphatic polyester-based resin include polyethylene succinate, polybutylene succinate, 1, 6-hexanediol polysuccinate, polyethylene adipate, 1, 6-hexanediol polysuccinate, polybutylene adipate, polyethylene oxalate, polybutylene oxalate, neopentyl oxalate, polyethylene sebacate, polybutylene sebacate, 1, 6-hexanediol polysebacate, polybutylene succinate adipate, and polybutylene succinate carbonate.

The biodegradable polyester resin according to the present embodiment may be, for example, poly (α -hydroxy acid) such as polyglycolic acid or polylactic acid, or a copolymer thereof; poly (. omega. -hydroxyalkanoates) such as poly (. epsilon. -caprolactone) and poly (. beta. -propiolactone), poly (3-hydroxybutyrate), poly (3-hydroxyvalerate), poly (3-hydroxyhexanoate), poly (3-hydroxyheptanoate), poly (3-hydroxyoctanoate), and the like; and aliphatic polyester resins such as poly (4-hydroxybutyrate).

The biodegradable polyester resin preferably has no long chain branches. From the viewpoint of biodegradability, the biodegradable polyester resin according to the present embodiment is preferably an aliphatic polyester resin.

The proportion of the aliphatic polyester resin is preferably 85 mass% or more, more preferably 90 mass% or more, and still more preferably 95 mass% or more, assuming that 100 mass% of the total biodegradable polyester resin contained in the resin composition is used.

The total biodegradable polyester resin contained in the resin composition is particularly preferably an aliphatic polyester resin.

Among these, the biodegradable polyester resin used in the present embodiment is particularly preferably polybutylene succinate.

The proportion of polybutylene succinate is preferably 85 mass% or more, more preferably 90 mass% or more, and still more preferably 95 mass% or more, based on 100 mass% of the total biodegradable polyester resin contained in the resin composition.

The biodegradable polyester resin contained in the resin composition is preferably polybutylene succinate in particular.

In the present embodiment, one of the biodegradable aliphatic polyester resins exemplified above may be selectively used, a plurality of the biodegradable aliphatic polyester resins exemplified above may be used in combination, or biodegradable aliphatic polyester resins other than those exemplified above may be used.

Examples of the additive to be contained in the resin composition include inorganic substances such as polymers other than biodegradable resins and inorganic fillers; various rubber/plastic chemicals, etc.

Examples of the polymer that can be contained in the resin composition other than the biodegradable resin include a polymer type antistatic agent, a fluorine-based resin used as a bubble control agent, a rubber-based modifier, and the like.

In order to exhibit excellent biodegradability in the biodegradable laminated foam sheet, the proportion of the biodegradable resin contained in the resin composition in the total polymer is preferably 85 mass% or more, more preferably 90 mass% or more, and still more preferably 95 mass% or more.

In order to exhibit excellent biodegradability in the biodegradable laminated foam sheet, the proportion of the biodegradable polyester resin contained in the resin composition in the total biodegradable resin is preferably 85 mass% or more, more preferably 90 mass% or more, and still more preferably 95 mass% or more.

The resin composition may optionally contain an additive such as a shrinkage inhibitor for the purpose of further improving the foam moldability.

The content of the additive is preferably in a range of 0.05 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the biodegradable resin.

Examples of the antishrinking agent include ester compounds of higher fatty acids and polyhydric alcohols such as lauric acid monoglyceride, palmitic acid monoglyceride, stearic acid monoglyceride, pentaerythritol monodecanoate, pentaerythritol monooleate, pentaerythritol monolaurate, dipentaerythritol distearate, sorbitan monooleate, sorbitan sesqui-sugar oil fatty acid ester, sorbitan monopalmitate, sorbitan monolaurate, sorbitan monostearate, mannan monooleate, and mannan monolaurate, and full esters of higher alkyl amines, fatty acid amides, and higher fatty acids.

The anti-shrinkage agent may be selected from one of the above-mentioned exemplified materials, may be used in combination with a plurality of the above-mentioned exemplified anti-shrinkage agents, or may be a known anti-shrinkage agent other than the above-mentioned exemplified materials.

Among them, stearic acid monoglyceride is particularly preferable.

The resin composition may use a commonly used cell regulator for the purpose of forming a good cell structure upon foaming.

Examples of the bubble control agent include fine powders of fluorine-based resins such as polytetrafluoroethylene, talc, aluminum hydroxide, and silica.

Further, the decomposition type foaming agent described later can be used in combination with a volatile foaming agent to adjust the foaming state, and can also be used as a cell regulator.

The blowing agent used in the resin composition is not particularly limited as long as it is a blowing agent used in ordinary extrusion foaming, and a volatile blowing agent that turns into a gas at normal temperature (23 ℃) and normal pressure (1 atm); examples of the volatile blowing agent include an inert gas, an aliphatic hydrocarbon, and an alicyclic hydrocarbon.

Examples of the inert gas include carbon dioxide and nitrogen, examples of the aliphatic hydrocarbon include propane, n-butane, isobutane, n-pentane and isopentane, and examples of the alicyclic hydrocarbon include cyclopentane and cyclohexane.

The content of the foaming agent is preferably 0.1 part by mass or more, more preferably 0.3 part by mass or more, and particularly preferably 0.6 part by mass or more, based on 100 parts by mass of the biodegradable resin contained in the resin composition.

The content of the foaming agent is preferably 2 parts by mass or less, more preferably 1.5 parts by mass or less, and further preferably 1.2 parts by mass or less.

Examples of the decomposition type blowing agent include azodicarbonamide, dinitrosopentamethylenetetramine, and a mixture of an organic acid such as sodium hydrogen carbonate or citric acid or a salt thereof and a hydrogen carbonate.

The resin composition for extrusion foaming may contain the biodegradable resin, and may further contain a crystal nucleating agent and a crystallization accelerator.

Examples of the crystal nucleus agent include organic crystal nucleus agents and inorganic crystal nucleus agents.

As the crystal nucleus agent, only one of an organic crystal nucleus agent and an inorganic crystal nucleus agent may be used, or an organic crystal nucleus agent and an inorganic crystal nucleus agent may be used in combination.

In addition, when only the inorganic crystal nucleating agent is used as the crystal nucleating agent, only one of the inorganic crystal nucleating agents listed below may be used, or two or more kinds may be used in combination.

Similarly, when only the organic crystal nucleating agent is used as the crystal nucleating agent, only one of the organic crystal nucleating agents listed below may be used, or two or more of them may be used in combination.

When the crystal nucleus agent is used in combination with an organic crystal nucleus agent and an inorganic crystal nucleus agent, a plurality of kinds of either or both of them may be used.

Examples of the inorganic crystal nucleating agent include talc, tin oxide, smectite, bentonite, dolomite, sericite, feldspar powder, kaolin, mica, and montmorillonite.

Among these, talc or tin oxide is preferable as the inorganic crystal nucleating agent from the viewpoints of improvement of crystallization rate, heat resistance, durability, and the like.

Examples of the organic crystal nucleating agent include organic amide compounds, organic hydrazide compounds, carboxylate compounds, organic sulfonate salts, phthalocyanine compounds, melamine compounds, and organic phosphonate salts.

As the organic sulfonate, various materials such as sulfoisophthalic acid salt can be used, and among them, dimethyl isophthalate 5-sulfonic acid metal salt is preferable from the viewpoint of the effect of promoting crystallization.

Further, barium salt, calcium salt, strontium salt, potassium salt, rubidium salt, sodium salt, and the like are preferable.

Examples of the organic amide compound include N, N ', N ″ -tricyclohexyltrimesic acid amide, N' -ethylenebis (12-hydroxystearic acid) amide, and the like.

The content of the crystal nucleating agent in the resin composition may be, for example, 0.5 parts by mass or more, when the content of the biodegradable resin in the resin composition is 100 parts by mass.

The content of the crystal nucleating agent in the resin composition is preferably 0.6 parts by mass or more, and more preferably 0.7 parts by mass or more.

The content of the crystal nucleating agent in the resin composition may be, for example, less than 3.0 parts by mass, when the content of the biodegradable resin in the resin composition is 100 parts by mass.

The content of the crystal nucleating agent in the resin composition is preferably 2.5 parts by mass or less, and more preferably 2.2 parts by mass or less.

Examples of the crystallization accelerator include phthalic acid derivatives such as di-n-octyl phthalate, di (2-ethylhexyl) phthalate, dibenzyl phthalate, diisodecyl phthalate, ditridecyl phthalate, and diundecyl phthalate; isophthalic acid derivatives such as dioctyl isophthalate; adipic acid derivatives such as di-n-butyl adipate and dioctyl adipate; maleic acid derivatives such as di-n-butyl maleate; citric acid derivatives such as tri-n-butyl citrate; itaconic acid derivatives such as monobutyl itaconate; oleic acid derivatives such as butyl oleate; ricinoleic acid derivatives such as glycerol monoricinoleate; phosphoric acid esters such as tricresyl phosphate and trixylyl phosphate; hydroxy polycarboxylic acid esters such as polyethylene glycol adipate, polyacrylate acetyl tributyl citrate and the like; polyol esters such as triacetin and tripropionic acid glycerol; polyalkylene glycol derivatives such as polyethylene glycol and polypropylene glycol; benzyl 2- (2-methoxyethoxy) ethyl adipate, polyglycerin fatty acid ester, and the like.

The crystallization accelerator is preferably a polyglycerin fatty acid ester.

Examples of the polyglycerol fatty acid esters include polyglycerol oleate, polyglycerol ricinoleate, polyglycerol laurate, polyglycerol stearate, and polyglycerol polyricinoleate.

Among these, polyglycerol stearate is preferably used as the crystallization accelerator.

The content of the crystallization accelerator in the resin composition may be, for example, 0.5 parts by mass or more, when the content of the biodegradable resin in the resin composition is 100 parts by mass.

The content of the crystallization promoter in the resin composition is preferably 0.6 parts by mass or more, and more preferably 0.7 parts by mass or more.

The content of the crystallization accelerator in the resin composition may be less than 5.0 parts by mass, assuming that the content of the biodegradable resin in the resin composition is 100 parts by mass.

The content of the crystallization accelerator in the resin composition is preferably 4.0 parts by mass or less, and more preferably 3.5 parts by mass or less.

Examples of the additives that can be contained in the resin composition include lubricants, antioxidants, antistatic agents, flame retardants, ultraviolet absorbers, light stabilizers, colorants, and inorganic fillers.

As described above, the present invention has been exemplified by using a biodegradable laminated foam sheet as a preferred embodiment of the present invention, but the laminated foam sheet of the present invention may not have biodegradability.

In this case, the resin constituting the resin foamed layer and the resin non-foamed layer is not necessarily a biodegradable resin, and for example, polyolefin-based resins such as polyethylene and polypropylene; polystyrene resins such as GPPS and HIPS; polyamide resins such as polyamide 12 and polyamide 66; polyester resins such as polyethylene terephthalate and polybutylene terephthalate; polycarbonate-based resins, and the like.

The present invention is not limited to the above-described examples, and appropriate modifications may be made to the examples.

Examples

The present invention will be described more specifically with reference to the following examples, but the present invention is not limited to the examples below.

(example 1)

As a biodegradable resin for forming a biodegradable resin foamed layer, a biodegradable polyester resin (product name "bioppbs FZ91 PM" manufactured by PTT MCC Biochem corporation) was prepared.

To 100 parts by mass of the biodegradable polyester resin, 2.0 parts by mass of "CROWN tal" manufactured by sonmura industries, inc.

In a tandem extruder equipped with a first extruder (upstream side) having a bore diameter of 50mm and a second extruder (downstream side) having a bore diameter of 65mm, the obtained resin composition was supplied to the first extruder having a bore diameter of 50mm through a hopper and heated and melted.

Thereafter, isobutane as a foaming agent was introduced into a first extruder, and melt-kneaded together with the resin composition to prepare a foamable resin composition in the extruder.

The foamable resin composition in a thermally melted state is flowed into a second extruder, and after the temperature of the foamable resin composition is lowered to a temperature suitable for foaming in the second extruder, the foamable resin composition is flowed into a confluence mold.

On the other hand, in order to form a non-foamed layer of a biodegradable resin, a biodegradable polyester resin (product name "BioPBS FZ91 PM" manufactured by PTT MCC Biochem) similar to the resin used in the above-mentioned foamed layer of a biodegradable resin was prepared.

The biodegradable polyester resin was supplied to a hopper of a single-screw extruder having a bore diameter of 32mm, and melt-kneaded, and then a melt-kneaded product (non-foamable resin composition) was poured into the confluence mold.

The foamable resin composition and the non-foamable resin composition merged in the merging mold are coextruded from the annular mold.

The co-extrusion was carried out so that the total discharge amount was 40kg/h from the die gap having an aperture of 70mm and an interval of 0.7mm, and the outer side was a non-foamed layer of a biodegradable resin and the inner side was a foamed layer of a biodegradable resin.

The co-extruded cylindrical foamed sheet was cooled and molded by a cooling plug, and then cut in the extrusion direction by a cutter attached to the rear portion of the cooling plug to produce a long band-shaped biodegradable laminated foamed sheet.

(example 2)

A biodegradable laminated foam sheet was produced in the same manner as in example 1, except that the resin composition for forming a non-foamed layer of a biodegradable resin was a mixture of 50 parts by mass of a biodegradable polyester resin (product name "BioPBS FZ91 PM", manufactured by PTT MCC Biochem) and 50 parts by mass of a "CROWN TALC", manufactured by sonmura industries.

Comparative example 1

A biodegradable laminated foamed sheet was produced in the same manner as in example 1, except that a biodegradable laminated foamed sheet having a single-layer structure in which only a biodegradable resin foamed layer was present was produced by not laminating a biodegradable resin non-foamed layer and setting the discharge amount at the time of extrusion to 30kg/h instead of 40 kg/h.

Comparative example 2

A biodegradable laminated foamed sheet having a single-layer structure was produced in the same manner as in comparative example 1, except that the discharge amount during extrusion was 37 kg/h.

Comparative example 3

A biodegradable laminated foamed sheet was produced in the same manner as in example 1, except that a biodegradable laminated foamed sheet having a three-layer structure in which biodegradable resin non-foamed layers were provided on both surfaces of a biodegradable resin foamed layer was produced.

< evaluation of moldability >

The biodegradable laminated foam sheet was thermoformed to prepare a container.

The thickness of the bottom surface and the thickness of the side wall of the container were measured, respectively, and the difference was confirmed.

The moldability was determined as follows.

O: a molded article having well-balanced wall thicknesses of the bottom surface and the side wall can be obtained

X: the wall thickness of the side wall is small, and the balance of the wall thickness of the molded product is poor

The evaluation results of the moldability are shown in table 1 together with other sheet properties.

[ Table 1]

The upper part of the numerical values of the surface roughness in examples 1 and 2 are values relating to the biodegradable resin foamed layer, and the lower part thereof is a numerical value relating to the biodegradable resin non-foamed layer.

As is clear from the above table, according to the present invention, a biodegradable laminated foam sheet having excellent moldability can be obtained.