JP5660676B2 - Method for producing recycled resin-containing polyolefin resin foam - Google Patents

Description

  The present invention relates to a method for producing a polyolefin resin foam containing a recycled resin. In particular, sufficient extrusion foaming is performed by effectively using waste such as defective products generated in the process of manufacturing extruded foam sheets or non-product parts generated in the slicing process of removing the skin from the manufactured foam sheets. The present invention relates to a method for producing a recycled resin-containing polyolefin resin foam that can be used.

  Conventionally, 5-40 parts by weight of a recycled resin composition obtained by recycling waste generated when foaming or processing an unused virgin raw material that is not a recycled resin composition is used with respect to 100 parts by weight of the virgin raw material. The one that forms a sheet is disclosed (Patent Document 1). According to Patent Document 1, it is said that a recycled resin-containing polyolefin resin foam with few pinholes can be produced by effectively utilizing the waste generated in the resin foam production process.

  However, Patent Document 1 has a problem that when the use of the recycled resin composition exceeds 40 parts by weight with respect to 100 parts by weight of the virgin raw material of the polyolefin-based resin composition, a good foam cannot be obtained. When the skin of the foam is removed by slicing and only the central part is used as a product, a large amount of waste of 30% by weight or more of the foamed sheet is generated, so that a larger amount of recycled resin composition may be used. It is desired.

JP 2006-225571 A

  An object of the present invention is to provide a recycled resin-containing polyolefin resin foam that can be sufficiently extruded and foamed even if the recycled resin composition exceeds 40 parts by weight with respect to 100 parts by weight of the polyolefin resin composition. The manufacturing method of is in place.

The present invention produces a recycled resin-containing polyolefin resin foam by adding a recycled resin composition obtained by regenerating waste generated when the foaming composition is subjected to foam molding or processing to the polyolefin resin foam composition. A method for producing a recycled resin-containing polyolefin resin foam, wherein the recycled resin composition has a weight average molecular weight (Mw) of 300 × 10 ³ or more and a melt tension of 2.0 cN or more. It is.

In the present invention, the recycled resin composition preferably has a Z average molecular weight (Mz) of 1300 × 10 ³ or more. In the present invention, the MFR at 230 ° C. of the recycled resin composition is preferably 2.0 g / 10 min or less. Moreover, it is preferable to add 10 to 250 parts by weight of a recycled resin composition obtained by regenerating waste generated when the foaming composition is foamed or processed with respect to 100 parts by weight of the polyolefin resin foaming composition.

The present invention improves the foamability of a recycled resin-containing polyolefin resin foam composition by using this recycled resin composition with respect to an unused polyolefin resin composition that is not a recycled resin composition. A good foam can be obtained even if a recycled resin in a ratio that cannot be obtained by the conventional method is used.
Therefore, in the present invention, even when the regenerated resin composition exceeds 40 parts by weight with respect to 100 parts by weight of the polyolefin-based resin composition, sufficient extrusion foaming can be performed, and a sheet can be formed. It is possible to provide a polyolefin resin foam containing a recycled resin that can effectively use the recycled resin composition as waste.

The present invention produces a recycled resin-containing polyolefin resin foam by adding a recycled resin composition obtained by regenerating waste generated when the foaming composition is subjected to foam molding or processing to the polyolefin resin foam composition. A method for producing a recycled resin-containing polyolefin resin foam, wherein the recycled resin composition has a weight average molecular weight (Mw) of 300 × 10 ³ or more and a melt tension of 2.0 cN or more. It is.

(Polyolefin resin foaming composition)
The polyolefin resin used as the virgin raw material (unused raw material) is not particularly limited as long as the melt flow rate (MFR) is about 0.2 to 5 g / 10 min. Specific examples include homopolypropylene and copolymers of propylene and other olefins.
The copolymer of propylene and another olefin may be either a random copolymer or a block copolymer, but a block copolymer is preferred because of excellent heat resistance.
Examples of other olefins copolymerized with propylene include, in addition to ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-nonene, 1-decene, etc. And α-olefins having 4 to 10 carbon atoms.
Of these, homopolypropylene having excellent foamability and heat resistance and block copolymer polypropylene are preferable, and homopolypropylene having excellent heat resistance is more preferable.

Moreover, as polyolefin resin used for this invention, since it is excellent in foamability, it is preferable to use a high melt tension polypropylene resin. High melt tension polypropylene resins include high melt tension polypropylene (HMS-PP) that has free-end long-chain branching in the molecular structure, such as electron beam crosslinking, and high molecular weight components to increase melt tension. There are things. Commercially available products can be used as the high melt tension polypropylene, and specific examples of commercially available products include “Newstrain SH9000” manufactured by Nippon Polypro Co., Ltd., and “DaployWB135HMS” manufactured by Borealis.
The polyolefin resin may be used alone or in a suitable combination of two or more.

If the MFR of the polyolefin resin is low, the load on the extruder increases and the productivity decreases, or the molten polyolefin resin composition containing the foaming agent cannot flow smoothly in the mold, On the other hand, unevenness occurs on the surface of the resulting polyolefin resin foam and the appearance is reduced. On the other hand, if it is high, the resin pressure in front of the annular die is lowered, and the resin pressure in the annular die bubble generating part is also lowered. In addition, bubbles are generated in front of the bubble generation part, and foam breakage is abruptly generated in the foam molding part, resulting in a decrease in foamability, and the appearance of the resulting foam is reduced or a foam cannot be obtained. .2 to 5 g / 10 min is preferable, 0.2 to 4 g / 10 min is more preferable, and 0.3 to 3.5 g / 10 min is particularly preferable.
In this specification, MFR of polyolefin resin means that measured at a test temperature of 230 ° C. and a test load of 21.18 N in accordance with JIS K7210: 1999, Method B.
The MFR of the polyolefin-based resin refers to a value obtained by measuring the MFR of the resin by the above method when one kind of the polyolefin-based resin is used alone.
In addition, when two or more types of polyolefin resin are used in combination, the MFR of each polyolefin resin is measured by the above measurement method, and calculated from the respective MFR values as follows: Say.
That is, when the polyolefin resin is a mixture of n types of polyolefin resins, MFR of polyolefin resin 1 is MFR ₁ , MFR of polyolefin resin 2 is MFR ₂ ,... MFR of polyolefin resin n Is MFR _n , the content of the polyolefin resin 1 is C1, the content of the polyolefin resin 2 is C2,... The content of the polyolefin resin n is Cn. In addition, content of polyolefin resin n shall remove | divide the weight of polyolefin resin n by the weight of the whole polyolefin resin. And MFR of the polyolefin-type resin of a virgin raw material is computed by a following formula.
Melt flow rate (g / 10min) = (MFR ₁ ) ^C1 x (MFR ₂ ) ^C2 x ... x (MFR _n ) ^Cn

  The polyolefin resin foaming composition used in the present invention contains a cell nucleating agent. The cell nucleating agent promotes the generation of cell nuclei when the polyolefin-based resin foaming composition forms cells, and has an effect on the refinement and uniformity of the cells. Examples of the cell nucleating agent include talc, mica, silica, diatomaceous earth, alumina, titanium oxide, zinc oxide, magnesium oxide, magnesium hydroxide, aluminum hydroxide, calcium hydroxide, potassium carbonate, calcium carbonate, magnesium carbonate, potassium sulfate, Inorganic compounds such as barium sulfate, sodium hydrogen carbonate and glass beads; organic compounds such as polytetrafluoroethylene, azodicarbonamide, a mixture of sodium hydrogen carbonate and citric acid, and inert gases such as nitrogen. Among them, talc is preferable for inorganic compounds, and polytetrafluoroethylene is preferable for organic compounds because it has a high effect on bubble miniaturization. Further, it is particularly preferable that the polytetrafluoroethylene becomes a fibril when dispersed to increase the melt tension of the resin.

  When the amount of the cell nucleating agent is small, it is difficult to increase the number of cells of the obtained polyolefin resin foam, and the surface smoothness of the resulting polyolefin resin foam may be lowered. On the other hand, if the amount is too high, secondary aggregation tends to occur, and the surface smoothness of the foam due to poor extrusion foaming may decrease, so the amount may be 0.01 to 15 parts by weight with respect to 100 parts by weight of the compounded resin composition. Preferably, it is 0.1 to 12 parts by weight.

The cell nucleating agent used in the present invention may be mixed with the compounded resin composition in its own form and supplied as a thermoplastic resin composition or separately into the extruder, and further as a masterbatch with the compounded resin composition They may be mixed and supplied as a thermoplastic resin composition or individually into the extruder.
The base resin of the masterbatch is not particularly limited as long as it has excellent compatibility with the compounded resin composition. For example, homopolypropylene, block polypropylene, random polypropylene, low density polyethylene, high density polyethylene and the like are preferable. Can be used.

In the polyolefin resin foaming composition used in the present invention, various additives usually used for foam molding can be blended as optional components in addition to the polyolefin resin and the cell nucleating agent. Examples of the additive include a weather resistance stabilizer, a light stabilizer, a pigment, a dye, a flame retardant, a crystal nucleating agent, a plasticizer, a lubricant, a surfactant, a dispersant, an ultraviolet absorber, an antioxidant, and a filler. , Reinforcing agents, antistatic agents and the like. Of these, the surfactant imparts slipperiness and anti-blocking property. Moreover, a dispersing agent improves the dispersibility of an inorganic filler, for example, higher fatty acid, higher fatty acid ester, higher fatty acid amide etc. are mentioned.
The addition amount of the additive can be appropriately selected within a range not impairing the formation of bubbles and the physical properties of the resulting foam, and the addition amount used for molding a normal thermoplastic resin can be adopted.
The cell nucleating agent and the additive can be used as a master batch for ease of handling and prevention of contamination of the production environment due to powder scattering, and for improving dispersibility in a thermoplastic resin. .
The masterbatch can be usually performed by kneading an additive or the like in a thermoplastic base resin at a high concentration to form a pellet. The base resin is not particularly limited as long as it has excellent compatibility with the compounded resin composition. For example, homopolypropylene, block polypropylene, random polypropylene, low density polyethylene, high density polyethylene, and the like are preferably used. Can do.

(Recycled resin composition)
The recycled resin composition refers to a recycled waste generated when the polyolefin resin foaming composition is foamed or processed.
Therefore, for example, an initial fluidized product described in JP-A-2006-225571 that does not wind up as a product until bubbles are stabilized, a surface portion (so-called skin layer) that is sliced to smooth the foam surface, and more specific Examples of the wastes such as unnecessary portions when punched into a shape can be given.
Also, the process of recycling waste usually comprises pulverization, melting, and pelletizing processes. Although each process may be performed individually, it is preferable to perform continuously as a series of processes using an apparatus capable of performing these processes continuously.

The molecular weight of the recycled resin composition refers to that measured as described below, but if the weight average molecular weight (Mw) of the recycled resin composition is small, it is difficult to obtain a good foamed sheet, so 300 × 10 ³ or more It is limited to. Moreover, since the range of the extrusion conditions from which a good foamed sheet can be obtained even if it is large may be narrow, 1500 × 10 ³ or less is preferable. A range of 350 × 10 ^{3 to} 1000 × 10 ³ is more preferable, and a range of 400 × 10 ^{3 to} 800 × 10 ³ is particularly preferable.
For the same reason, the Z-average molecular weight (Mz) of the recycled resin composition is preferably 1300 × 10 ³ or more. The range of 1300 × 10 ^{3 to} 5500 × 10 ³ is more preferable, the range of 1500 × 10 ^{3 to} 5000 × 10 ³ is more preferable, and the range of 1700 × 10 ^{3 to} 4500 × 10 ³ is preferable. Is particularly preferred.

  The melt tension of the recycled resin composition is measured as described below, but if it is low, the tension during foaming cannot be maintained, and it is difficult to obtain a sheet having a high foaming ratio, so it is limited to 2 cN or more. On the other hand, if it is too high, it is difficult to swell when bubbles are generated, and it may be difficult to obtain a sheet having a high expansion ratio. A range of 2 to 40 cN is more preferable, and a range of 2 to 30 cN is particularly preferable.

  The MFR of the recycled resin composition is measured as described below. If the MFR is large, the pressure at the tip of the mold cannot be maintained during extrusion, and a good foam may not be obtained. Preferably there is. On the other hand, even if it is too small, the pressure at the tip of the mold may increase too much, so 0.1 g / 10 min or more is preferable. A range of 0.1 to 1.8 g / 10 min is more preferable, and a range of 0.1 to 1.6 g / 10 min is particularly preferable.

(Foaming agent)
As the foaming agent, a known foaming agent that can be used for extrusion foaming can be used. Since it is easy to adjust the expansion ratio, a physical foaming agent supplied by being press-fitted into the extruder is preferable. In the present invention, it is particularly preferable to use carbon dioxide. Carbon dioxide can form finer bubbles than conventional foams by using supercritical, subcritical, or liquefied carbon dioxide, and the surface smoothness and flexibility of the resulting foams Can be improved. The amount of the foaming agent that is press-fitted into the extruder may be adjusted as appropriate according to the expansion ratio of the polyolefin resin foam. However, if the amount is small, the expansion ratio of the polyolefin resin foam is reduced, and the weight and On the other hand, heat insulation may decrease, but if it is large, foaming may occur in the mold, resulting in bubble breakage or large voids in the polyolefin resin foam. It is preferably about 1 to 10 parts by weight, more preferably about 2 to 8 parts by weight, more preferably 3 to 6 parts by weight with respect to 100 parts by weight of the composition or recycled resin composition-containing polyolefin resin foaming composition. It is particularly preferable that the amount is about 1 part.

(Recycled resin-containing polyolefin-based resin foaming composition)
The present invention produces a recycled resin-containing polyolefin resin foam by adding a recycled resin composition obtained by regenerating waste generated when the foaming composition is subjected to foam molding or processing to the polyolefin resin foam composition. Although it is a method, 10-250 weight part of regenerated resin composition which reproduced | regenerated the said waste can be added with respect to 100 weight part of said polyolefin resin foaming compositions.
When the recycled resin composition obtained by recycling the waste exceeds 250 parts by weight, the magnification and thickness are reduced, and a foam equivalent to the conventional product cannot be obtained. The amount is preferably 200 parts by weight or less.
Incidentally, the recycled resin composition recycled from the waste, the waste can be more effectively utilized (material recycling), leading to cost reduction, 100 parts by weight of the polyolefin resin foam composition, It is preferable to mix | blend exceeding 40 weight part, and it is more preferable to mix | blend exceeding 50 weight part.

(Extruder)
In the production method of the present invention, any of a single-screw extruder, a twin-screw extruder, and a tandem type extruder can be used as the extruder. In the present invention, among these, a tandem type extruder is preferable because it is easy to adjust the extrusion conditions.

  The mold used in the manufacturing method of the present invention has a bubble generation part formed by constricting the resin flow path, and a foam molding part for growing the generated bubbles and smoothing the foam surface. Consists of an annular die. Since the recycled resin-containing polyolefin resin foam according to the present invention has finer bubbles than conventional ones, when foamed using a conventional annular die, a large number of corrugates are generated on the surface of the foam. The surface smoothness of the obtained foam is deteriorated. However, the annular die of the foam forming part can suppress the generation of corrugation in the bubble generating part and obtain a foam with a smooth surface by an appropriate slip resistance in the foam molded part. The corrugated herein refers to a number of ridges and valleys formed by undulation of the foam from the annular die to absorb the linear expansion in the circumferential direction due to volume expansion.

In the production method of the present invention, it is preferable that the resin discharge speed V at the bubble generation unit is 50 to 300 kg / cm ² · hr and the resin pressure before the annular die is 7 MPa or more.
Discharge speed V is more preferably about 70~250kg / ^cm 2 · hr, and more preferably about 100~200kg / ^cm 2 · hr. In addition, the resin pressure before the annular die is preferably 7 MPa or more, and more preferably 8 MPa or more and 20 MPa or less. In addition to improving the foamability of the polyolefin-based resin by extrusion foaming under the above conditions, the bubbles can be refined and the strength of the cell membrane can be further increased. Under these conditions, the obtained foam is improved in workability in the case of secondary processing, and a sheet-like foam obtained by slicing is excellent in surface smoothness. When the discharge speed V is less than about 50 kg / cm ² · hr, it may be difficult to obtain finer bubbles or a foam with a high expansion ratio. On the other hand, when it is larger than about 300 kg / cm ² · hr, the resin generates heat at the mold bubble generation part, causing bubble breakage, and the foaming ratio is likely to be lowered, and a corrugated corrugate is likely to be generated. This is not preferable because the diameter becomes uneven and the surface smoothness of the foam decreases. The discharge speed V is appropriately adjusted according to the cross-sectional area of the annular die bubble generating unit and the extrusion discharge amount.

  The method of adjusting the cross-sectional area of the bubble generating part includes changing the length of the bubble generating part of the mold (in the case of a flat mold) and the diameter (in the case of an annular die) and the interval between the bubble generating parts of the mold. There are two methods including a method of changing (in the case of a flat die or an annular die).

If the resin pressure in front of the annular die is lower than 7 MPa, bubble generation starts before the annular die bubble generation part and a good foam cannot be obtained, which is not preferable. On the other hand, if the pressure is higher than 20 MPa, the load on the extruder becomes too high, or the injection pressure of the foaming agent becomes too high, so that it is not possible to press-fit.
The resin pressure in front of the annular die is appropriately adjusted by the molten resin viscosity, the extrusion discharge amount, and the sectional area of the annular die bubble generating part. Furthermore, the molten resin viscosity is appropriately adjusted depending on the viscosity of the blended resin composition, the amount of foaming agent added, and the molten resin temperature. In this specification, the molten resin temperature refers to the temperature measured by a thermocouple attached in a direct contact with the molten resin in a straight pipe mold for measuring the resin pressure before the annular die. say.

(Recycled resin-containing polyolefin resin foam)
When the average cell diameter of the recycled resin-containing polyolefin resin foam obtained by the method of the present invention is small, foam breakage increases, and the apparent density of the polyolefin resin foam may increase. Since physical properties such as time recovery and mechanical strength may be lowered, it is preferably about 0.02 to 0.2 mm, more preferably about 0.04 to 0.18 mm, and It is especially preferable that it is about 06-0.16 mm.

(Measuring method)
The measurement method is described below.
Average cell diameter In this specification, the average cell diameter of the recycled resin-containing polyolefin-based resin foam is measured as follows in accordance with the test method of ASTM D2842-69.
Specifically, the foamed sheet is cut along the MD direction (extrusion direction) and the TD direction (direction perpendicular to the extrusion direction), and the center of each cut surface is scanned by an electron microscope (manufactured by Hitachi, Ltd.). S-3000N) and enlarged.
Next, the photographed image is printed on A4 paper, and a straight line having a length of 60 mm is drawn on the image. The cut surface cut in the MD direction is parallel to the MD direction, the cut surface cut in the TD direction is parallel to the TD direction, and the VD direction (thickness direction) is perpendicular to the MD direction and the TD direction (sheet). Draw a straight line (perpendicular to). At this time, the magnification in the electron microscope was adjusted so that about 10 to 20 bubbles were formed on a straight line of 60 mm.
The average chord length (t) of the bubbles was calculated from the number of bubbles present on the straight line by the following formula, and the average chord length was defined as the average bubble diameter in each direction (MD direction, TD direction, and VD direction).
Average string length t = 60 / (number of bubbles × photo magnification)
When drawing a straight line, the straight line should be penetrated as much as possible without making point contact with the bubbles. Also, if some of the bubbles come into point contact with a straight line, this bubble is included in the number of bubbles, and if both ends of the straight line are located in the bubble without penetrating the bubbles Includes the bubbles in which both ends of the straight line are located in the number of bubbles.
Based on the average chord length t calculated by the above formula, the bubble diameter is calculated by the following formula.
Bubble diameter (mm) D = t / 0.616
Then, the arithmetic average value of the obtained bubble diameter in the MD direction (DMD), the bubble diameter in the TD direction (DTD), and the bubble diameter in the VD direction (DVD) is the average bubble diameter of the recycled resin-containing polyolefin resin foam. To do.
Average bubble diameter (mm) = (DMD + DTD + DVD) / 3

Apparent density In this specification, the apparent density of the recycled resin-containing polyolefin resin foam is measured by a method based on the method described in JIS K 7222-1999. Specifically, a test piece of 10 cm ³ or more (100 cm ³ or more in the case of semi-rigid and soft materials) is cut from the sample so as not to change the original cell structure of the sample, and its mass is measured. calculate.
Density (kg / m ³ ) = test piece mass (g) / test piece volume (cm ³ ) × 10 ³

When the apparent density of the recycled resin-containing polyolefin resin foam is small, the mechanical strength of the recycled resin-containing polyolefin resin foam may be reduced. On the other hand, when the apparent density is large, the cushioning property of the recycled resin-containing polyolefin resin foam is reduced. or because the flexibility may be reduced, it is preferably in the range of about 30~100kg / ^{m 3,} more preferably in the range of about ^{30~90kg / m 3, 35~70kg / m} 3 It is particularly preferred that it is within the range of the degree.

Molecular weight (GPC analysis)
In the present specification, the molecular weight of the recycled resin composition refers to that measured as follows. Specifically, after weighing about 10 mg of sample in a sample bottle, add about 4 mL of ODCB, seal it, heat and dissolve in an aluminum block for high-temperature GPC dissolution equipment at 160 ° C for about 2 hours, and after dissolution, high-temperature GPC filtration equipment The solution was transferred into a dedicated instrument, heated for about 30 minutes and filtered with a plastic syringe, and the filtrate was transferred again to a high-temperature GPC test tube to prepare a sample solution. The sample solution was measured at a column temperature of 145 ° C. and a flow rate of 1.0 mL / min, and the weight average molecular weight (Mw) and the Z average molecular weight (Mz) were calculated. TOSOH HLC-8121GPC / HT can be used as the measuring device, and UT-806M × 3 (Shodex) can be used as the column.

Melt tension In the present specification, the molecular weight of the regenerated resin composition is measured as follows. Specifically, the test temperature is set to 230 ° C, the capillary diameter is 15 mm, the die diameter is 2.095 mm, the die length is 8 mm, the extrusion speed is 0.0676 mm / s, and the initial winding speed is 4 mm / s to 12 mm / s. ² is acceleration. As a measuring apparatus, a twin bore capillary rheometer Rheologic 5000T manufactured by Chiast Corporation can be used.

MFR
In the present specification, the MFR of the recycled resin composition is measured by a method based on the method described in JIS K 7210: 1999 MFR and MVR test methods for thermoplastics. Specifically, the test is performed at a test temperature of 230 ° C. and a test load of 21.18N. As a measuring device, a semi-auto melt indexer manufactured by Toyo Seiki Co., Ltd. can be used.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the present invention is not limited by these. In each example, parts and% are based on weight in principle.

(Manufacture of polyolefin resin foam)
A tandem extruder was prepared by connecting a second extruder having a diameter of 75 mm to the tip of a first extruder having a diameter of 65 mm.
In the first extruder of this tandem type extruder, 100 parts by weight of a polyolefin-based resin (Newstor SH9000 MFR: 0.3 g / 10 min manufactured by Nippon Polypro Co., Ltd.) is heated to a heat which is an uncrosslinked ethylene-propylene-diene copolymer elastomer. A masterbatch containing 70% by weight of talc having an average particle size of 12 μm as a cell nucleating agent in 100 parts by weight of a compounded resin composition obtained by adding 67 parts by weight of a plastic elastomer (Thermolan Z101N MFR: 14 g / 10 min manufactured by Mitsubishi Chemical Corporation) A polyolefin resin foaming composition mixed with 10 parts by weight of Talpet 70P manufactured by Talc was supplied to the first extruder and melt-kneaded. 4.2 parts by weight of carbon dioxide in a supercritical state as a blowing agent is injected from the middle of the first extruder, and the foamed polyolefin resin foaming composition and carbon dioxide are uniformly mixed and kneaded. The molten resin composition containing the agent was continuously supplied to the second extruder and melted and kneaded while cooling to a resin temperature suitable for foaming. Thereafter, the diameter of the bubble generation part of the mold attached to the tip of the second extruder is 35 mm, the distance between the bubble generation parts of the mold is 0.25 mm (cross-sectional area of the bubble generation part: 0.275 cm ² ), and the distance between the foam molding parts Discharge rate of 30 mm / hr (discharge speed V = 109 kg / cm ² · hr) from an annular die having an outlet diameter φ70 of 3.4 mm and a foam molded part, a resin temperature of 175 ° C., and a resin pressure in front of the annular die Extruded and foamed under the condition of 8 MPa, and the cylindrical foam molded in the foam molding part of the annular die is attached onto the cooled mandrel, and the outer surface is cooled by blowing air from the air ring. The cylindrical foam was cut with a cutter at one point on the mandrel to obtain a sheet-like polyolefin resin foam.
The olefin-based resin foam obtained by the above method has no corrugation and excellent surface smoothness, and therefore has excellent secondary processability such as slicing. Moreover, the sheet | seat which maintained sufficient thickness for performing a secondary process was obtained.

(Manufacture of recycled resin composition)
Both surfaces of the obtained polyolefin-based resin foam were sliced by a splitting machine to remove the skin, and a sliced foamed sheet processed product was obtained. On the other hand, the removed epidermis was collected. The recovered skin was pulverized, melted and kneaded with an extruder, extruded into a strand, cooled with water, and a regenerated resin composition A molded into a cylindrical pellet was obtained. Since the speed of the rotating blade of the pelletizer can be adjusted freely, pellets of any size can be obtained. Recycled resin composition A has a weight average molecular weight (Mw) of 446 × 10 ³ , a Z average molecular weight (Mz) of 1865 × 10 ³ , a melt tension of 2.3 cN, and an MFR at 230 ° C. of 1.6 g / 10 min. Met.

(Manufacture of recycled resin composition-containing polyolefin resin foam)
[Example 1] (Recycled resin composition 30% by weight)
100 parts by weight of a polyolefin-based resin (New Poly SH SH9000 MFR: 0.3 g / 10 min manufactured by Nippon Polypro Co., Ltd.) and a thermoplastic elastomer which is a non-crosslinked ethylene-propylene-diene copolymer elastomer (thermolan Z101N MFR: 14 g manufactured by Mitsubishi Chemical Corporation) / 10 min) is added to 100 parts by weight of the compounded resin composition, and 10 parts by weight of a master batch (Talpet 70P, manufactured by Nippon Talc Co., Ltd.) containing 70% by weight of talc having an average particle size of 12 μm as a cell nucleating agent is mixed. The recycled resin-containing polyolefin resin composition prepared by mixing 43 parts by weight of the recycled resin composition A prepared above with 100 parts by weight of the polyolefin resin foaming composition was supplied to an extruder and melt-kneaded. 4.2 double supercritical carbon dioxide as a blowing agent from the middle of one extruder The molten regenerated resin-containing polyolefin resin composition and carbon dioxide are uniformly mixed and kneaded by injecting a certain amount, and the molten regenerated resin-containing polyolefin resin composition containing the blowing agent is continuously fed to the second extruder. The mixture was cooled to a resin temperature suitable for foaming while being melted and kneaded. Thereafter, the diameter of the bubble generation part of the mold attached to the tip of the second extruder is 35 mm, the distance between the bubble generation parts of the mold is 0.25 mm (cross-sectional area of the bubble generation part: 0.275 cm ² ), and the distance between the foam molding parts Discharge rate 30 kg / hr (discharge speed V = 109 kg / cm ² · hr), resin temperature 176 ° C., resin pressure in front of the ring die Extruded and foamed under the condition of 3 MPa, and the cylindrical foam formed in the foam molding part of the annular die is added onto the cooled mandrel, and the outer surface is cooled by blowing air from the air ring. At one point on the mandrel, a cylindrical foam was cut with a cutter to obtain a sheet-like recycled resin-containing polyolefin resin foam. The obtained foamed sheet had a thickness of 2.1 mm, an average cell diameter of 0.14 mm, and an apparent density of 54.2 kg / m ³ .

[Example 2] (Recycled resin composition 50% by weight)
In the same manner as in Example 1 except that 100 parts by weight of the recycled resin composition A was mixed with 100 parts by weight of the polyolefin resin foaming composition, 4.2 parts by weight of carbon dioxide in a supercritical state was injected. Extrusion foaming was performed under the conditions of a resin temperature of 175 ° C. and a resin pressure of 10.2 MPa in front of the annular die to obtain a sheet-like recycled resin-containing polyolefin resin foam. The obtained foamed sheet had a thickness of 1.7 mm, an average cell diameter of 0.12 mm, and an apparent density of 57.5 kg / m ³ .

[Comparative Example 1] (Virgin raw material not used)
Except that 100% of the recycled resin composition A was supplied to the extruder and melt-kneaded, 4.2 parts by weight of carbon dioxide in a supercritical state was injected, and the resin temperature was 172 ° C. Extrusion foaming was performed under a resin pressure of 12.6 MPa in front of the ring die.
When the recycled resin composition alone was 100%, the resin viscosity was low, and the resin pressure and mold clearance before the annular die could not be adjusted, so that a good foam could not be obtained.

[Comparative Example 2]
The waste generated when producing the recycled resin-containing polyolefin resin foam produced in Example 2 or the waste generated after processing is recovered, the recovered waste is pulverized, melt-kneaded in an extruder, After extruding into a strand, it was cooled with water to obtain a recycled resin composition B formed into a cylindrical pellet. Since the speed of the rotating blade of the pelletizer can be adjusted freely, pellets of any size can be obtained. Recycled resin composition B has a weight average molecular weight (Mw) of 421 × 10 ³ , a Z average molecular weight (Mz) of 1400 × 10 ³ , a melt tension of 1.9 cN, and an MFR at 230 ° C. of 1.8 g / 10 min. Met.
Next, in the same manner as in Example 1, 100 parts by weight of a polyolefin-based resin (Newstrain SH9000 MFR: 0.3 g / 10 min manufactured by Nippon Polypro Co., Ltd.) was added to a thermoplastic elastomer (non-crosslinked ethylene-propylene-diene copolymer elastomer ( A masterbatch (manufactured by Nippon Talc Co., Ltd.) containing 100% by weight of a compounded resin composition to which 67 parts by weight of Thermo-Lan Z101N MFR: 14 g / 10 min) manufactured by Mitsubishi Chemical Corporation is added, and 70% by weight of talc having an average particle size of 12 μm as a cell nucleating agent Recycled resin composition B-containing thermoplastic resin composition in which recycled resin composition B is mixed with 100 parts by weight of thermoplastic resin composition mixed with 10 parts by weight of Talpet 70P) is supplied to an extruder. And then melt-kneaded, and 4.2 parts by weight of carbon dioxide in a supercritical state is injected, and the resin temperature is 175 ° C. Extrusion foaming was performed under the condition of a resin pressure of 11.5 MPa before the die. In the recycled resin composition B, in addition to the difficulty of adjusting the resin pressure and the mold clearance in front of the annular die, it was difficult to foam because the tension was reduced, and a good foam was not obtained. .

[Comparative Example 3]
Except that 100 parts by weight of recycled resin composition B was mixed, 4.2 parts by weight of supercritical carbon dioxide was injected in the same manner as in Comparative Example 2, the resin temperature was 174 ° C., and the resin was in front of the ring die. Extrusion foaming was performed under conditions of a pressure of 9.7 MPa. As in Comparative Example 2, it was difficult to adjust the resin pressure and clearance, and the amount of the regenerated resin composition was increased. Therefore, since the tension was further lowered, foaming was difficult and a good foam was not obtained.

According to the present invention, it is possible to effectively use waste, and even when extrusion is performed using waste, it is possible to obtain a foam having the same thickness, magnification, and physical properties as a conventional foam. For example, it can be suitably used in fields that require high performance and followability, electronic equipment that requires sealing and dustproof properties, home appliances, and housing and automobiles that require cushioning.

Claims (2)

Polyolefin resin foaming composition containing a polypropylene resin as a virgin raw material having a melt flow rate (MFR) of 0.2 to 5 g / 10 min and an elastomer as a virgin raw material of a non-crosslinked ethylene-propylene-diene copolymer In the method for producing a recycled resin-containing polyolefin resin foam by adding a recycled resin composition obtained by recycling waste generated when the foaming composition is subjected to foam molding or processing to
The regenerated resin composition has a weight average molecular weight (Mw) of 300 × 10 ^{3 to} 1500 × 10 ³ ,
Z average molecular weight (Mz) is 1300 × 10 ^{3 to} 5500 × 10 ³ ,
The melt tension is 2.0 cN or more and the MFR at 230 ° C. is 2.0 g / 10 min or less,
A method for producing a recycled resin-containing polyolefin resin foam, comprising adding 10 to 250 parts by weight of a recycled resin composition to 100 parts by weight of a polyolefin resin foam composition . A recycled resin-containing polyolefin-based resin foam sheet obtained by the production method according to claim 1.