JP5755934B2 - Method for producing polyolefin resin laminate foam and method for producing polyolefin resin foam - Google Patents

Description

  The present invention relates to a method for producing a polyolefin resin laminated foam and a polyolefin resin foam.

  Polyolefin resin foams such as non-crosslinked polyethylene foams have good buffer performance and are suitable as packing materials for various industrial products. In particular, a thick foam manufactured by extrusion foaming can be provided in any shape by punching, cutting, welding, etc., and since an expensive mold is not used, a foam with any shape can be made inexpensively. It is possible to provide.

Due to the recent emergence of environmental problems such as ozone layer destruction and global warming, it is difficult to use a fluorocarbon foaming agent when producing a polyolefin resin foam. Therefore, aliphatic hydrocarbons such as butane are used as a foaming agent when producing an uncrosslinked foam by an extrusion foaming method. However, when butane is used as the foaming agent, the gas permeation rate is faster than that of chlorofluorocarbon, and after extrusion foaming, the rapid foaming agent release from the foam reduces the pressure in the bubbles and causes the foam to shrink significantly. There was a problem. If the foam shrinks immediately after extrusion, even if air flows into the bubbles of the foam, it does not recover to the desired foaming ratio.
In order to solve this shrinkage problem, it has been proposed to add various compounds as shrinkage inhibitors in the production of polyolefin resin foams (Patent Documents 1 to 5). By adding a large amount of fatty acid esters such as glycerin monostearate and glycerin monopalmitate to the polyolefin resin as an anti-shrinkage agent and extrusion foaming, a rapid foaming agent (butane) is obtained after extrusion foaming. It is possible to prevent the foam from being diffused, and it is possible to suppress the shrinkage of the foam due to the foaming agent dispersion.

  The addition of the shrinkage inhibitor is effective in obtaining a sheet-like polyolefin resin foam having a relatively thin thickness. However, in the case of obtaining a thick plate-like polyolefin resin foam, if a large amount of an anti-shrinkage agent is added to the extent that the foam can be prevented from shrinking immediately after foaming, the foaming agent is delayed and the foaming agent is A large amount will remain in the foam for a long period of time. If a large amount of foaming agent remains, dimensional changes will occur after processing due to changes in the remaining amount of foaming agent and changes in the internal pressure of air bubbles caused by air flowing into the bubbles. In order to sufficiently dissipate the foaming agent from the body and stabilize the pressure in the bubbles, it has been necessary to take a long period of curing. Furthermore, when a foam is used for a package, the anti-shrink agent itself may migrate to the package, and when a large amount of the anti-shrink agent is added, the shrinkage inhibitor may migrate depending on the application. There was a problem.

  In order to disperse the foaming agent, for example, as disclosed in Patent Document 6, Patent Document 7 and the like, after producing a foam by adding an anti-shrink agent, the foam is subjected to needle hole processing or the foam is compressed. There is a technique for accelerating the replacement of the foaming agent with air by causing the film of the shrinkage-preventing agent to crack.

JP 54-81370 A Japanese Patent Laid-Open No. 54-111573 JP 54-127473 A JP-A-3-215534 JP-A-8-090626 JP 2003-53764 A JP 2005-297341 A

However, when the methods of Patent Document 6 and Patent Document 7 are used, there are problems that holes are formed in the bubble film or the foam is forcibly compressed, resulting in a decrease in physical properties such as compression strength of the foam. Moreover, the problem that the shrinkage preventing agent itself moves to the packaged body could not be solved.
That is, when producing a thick polyolefin resin foam using an aliphatic hydrocarbon such as butane as a foaming agent, long-term curing can be achieved while suppressing shrinkage immediately after foaming. The present condition is that the technique of obtaining the foam which is not required and was excellent in mechanical strength was not established.

  The present invention solves the above-mentioned problems, has low shrinkage of the foam after extrusion foaming and excellent dimensional stability, does not require long-term curing or high-temperature curing, and has mechanical strength such as compression strength. An object of the present invention is to provide a large polyolefin resin laminate foam having a large resistance to repeated compression and a polyolefin resin foam capable of solving the problem of migration of a shrinkage inhibitor to a package. And

As a result of intensive studies in view of the above problems, the present inventors have found that a surface layer having a polyolefin resin as a base resin is formed on the outer peripheral surface of a molten resin for forming a foam core layer containing a polyolefin resin and butane as a foaming agent. It has been found that a laminated foam having a thickness can be produced by solving a specific problem by blending and coextruding a specific amount of a specific shrinkage-preventing agent with a specific amount of an anti-shrink agent in the forming molten resin.
That is, the gist of the present invention is the invention described in the following (1) to (6).
(1) By laminating and coextruding a surface layer forming molten resin having a polyolefin resin as a base resin on the outer peripheral surface of a foamed core layer forming molten resin obtained by kneading a polyolefin resin and butane A method for producing a laminated foam comprising a foam core layer and a surface layer, wherein the thickness of the entire laminate foam is 30 mm or more and the apparent density of the foam core layer is 18 to 90 kg / m ³ , comprising: In the forming molten resin, a shrinkage inhibitor composed of a fatty acid ester, an aliphatic amine or a fatty acid amide is blended in an amount of 0.5 parts by mass or more based on 100 parts by mass of the polyolefin resin of the surface layer forming molten resin (A1). )
In the molten resin for forming the foam core layer, a shrinkage-preventing agent comprising a fatty acid ester, an aliphatic amine or a fatty acid amide is added to 100 parts by mass of the polyolefin resin of the molten resin for forming the foam core layer. A polyolefin-based resin characterized in that it is blended at a blending ratio less than the blending ratio (A1) of an anti-shrinkage agent or a shrinkage-preventing agent comprising a fatty acid ester, aliphatic amine or fatty acid amide is not blended. A method for producing a laminated foam.
(2) The blending ratio (A2) of the shrinkage inhibitor composed of a fatty acid ester, an aliphatic amine or an aliphatic amide to the molten resin for forming the foam core layer is 100 parts by mass of the polyolefin resin of the melt resin for forming the foam core layer. On the other hand, it is 0.3 mass part or less (however, 0 mass part is included), The manufacturing method of the polyolefin resin laminated foam as described in said (1) characterized by the above-mentioned.
(3) The method for producing a polyolefin resin laminated foam according to (1) or (2), wherein the apparent density of the surface layer is 18 to 180 kg / m ³ .
(4) The method for producing a polyolefin resin laminated foam according to any one of (1) to (3), wherein an organic physical foaming agent is blended in the molten resin for forming the surface layer.
(5) The ratio (m / t) between the basis weight m [g / m ² ] of the surface layer and the thickness t [mm] of the laminated foam is 0.5 or more, (1 ) To (4). A method for producing a polyolefin resin laminated foam according to any one of (4) to (4).
(6) The method for producing a polyolefin resin laminated foam according to any one of (1) to (5), wherein the polyolefin resin constituting the foam core layer is low density polyethylene.
(7) the (2) in excluding take surface layer from the resulting laminate foams by the method according method for producing a polyolefin resin foam.

In the production method of the present invention, a certain amount (0.5 parts by mass or more) is added to the polyolefin resin in the production of a polyolefin resin foam having a low apparent density that is likely to shrink immediately after foaming and having a large thickness. The outer peripheral surface of the foamed core layer-forming molten resin that contains a less amount of the shrinkage-preventing agent in the polyolefin-based resin than the surface layer, or contains no shrinkage-preventing agent. By laminating and coextrusion foaming, a laminated foam having a high blending ratio of the shrinkage inhibitor in the surface layer portion and a low blending ratio of the internal shrinkage inhibitor is obtained. Such a laminated foam can suppress or prevent the shrinkage of the foam immediately after extrusion foaming as well as the foam in which the necessary amount of the shrinkage inhibitor is added to the entire foam as in the prior art, and the foam as in the conventional case. The foaming agent release rate during curing is faster than that obtained by adding a necessary amount of an anti-shrink agent to the whole body, and the curing period can be shortened.
In addition, the polyolefin resin foam consisting only of the foam core layer from which the surface layer of the laminated foam obtained by the production method described in (2) above is removed is a transfer property of the shrinkage inhibitor to the packaged body. Is a foam with very little or no migration. Such a foam is particularly useful as a cushioning material for medical / electronic parts.

It is explanatory drawing which shows an example of the manufacturing method of the polyolefin resin laminated foam of this invention.

Below, the manufacturing method of polyolefin resin laminated foam is demonstrated. [1] Method for Producing Polyolefin-Based Resin Laminated Foam A method for producing a polyolefin-based resin laminated foam (hereinafter sometimes referred to as “laminated foam”) according to the first aspect of the present invention comprises a polyolefin resin and foam. By laminating and coextruding a melt resin for forming a surface layer using a polyolefin resin as a base resin on the outer peripheral surface of a melt resin for forming a foam core layer containing butane as an agent, the thickness of the entire laminated foam can be reduced. A method for producing a laminated foam comprising a foam core layer and a surface layer, wherein the apparent density of the foam core layer is 30 mm or more and 18 to 90 kg / m ³ ,
In the molten resin for forming the surface layer, a shrinkage inhibitor composed of a fatty acid ester, an aliphatic amine, or a fatty acid amide is blended in an amount of 0.5 part or more with respect to 100 parts by mass of the polyolefin resin of the molten resin for forming the surface layer ( A1)
In the molten resin for forming the foam core layer, a shrinkage-preventing agent comprising a fatty acid ester, an aliphatic amine or a fatty acid amide is added to 100 parts by mass of the polyolefin resin of the molten resin for forming the foam core layer. It is characterized in that it is blended at a blending ratio less than the blending ratio (A1) of the anti-shrinkage agent or a shrinkage-preventing agent composed of a fatty acid ester, aliphatic amine or fatty acid amide is not blended.

An example of the manufacturing method of the polyolefin resin laminated foam of this invention is shown in FIG.
The laminated foam 1 is manufactured by laminating the surface layer forming molten resin 5 on the outer peripheral surface of the foam core layer forming molten resin 9 and coextruding the foamed core layer forming molten resin.
A polyolefin-based resin 2 for forming a surface layer and a necessary amount of a shrinkage-preventing agent 3 are supplied to the inlet of the first extruder 11, melted and kneaded, and then an organic physical foaming agent as necessary. 4 is added in the middle of the extruder, and melted and kneaded to prepare a molten resin 5 for forming the surface layer. A polyolefin-based resin 6 for forming a foam core layer and, if necessary, an anti-shrink agent 7 are supplied to the inlet of the second extruder 12, and after melting and kneading them, the foaming agent 8 is introduced from the middle of the extruder. Addition and further melt-kneading to prepare a foamed core layer forming molten resin 9. In the merging die 13 provided downstream of the extruder, the surface layer forming molten resin 5 is laminated on the outer peripheral surface of the foamed core layer forming molten resin 9 adjusted to the foaming temperature. The polyolefin resin laminated foam 1 is produced by coextrusion under a lower pressure (usually under atmospheric pressure) to foam the molten resin 9 for forming the foam core layer.

(1) Shrinkage inhibitor In the present invention, the shrinkage inhibitor blended in the surface layer forming molten resin or both the surface layer forming molten resin and the foamed core layer forming molten resin is a fatty acid ester, an aliphatic amine or It is a fatty acid amide.
The fatty acid ester is preferably an ester of a fatty acid having 8 to 30 carbon atoms and a polyhydric alcohol having 3 to 7 hydroxyl groups. Examples of the fatty acid having 8 or more carbon atoms include lauric acid, oleic acid, stearic acid, behenic acid, lignoceric acid, serotic acid, heptacoic acid, montanic acid, mellicic acid, and laccelic acid. Examples of the polyhydric alcohol having 3 to 7 hydroxyl groups include glycerin, diglycerin, triglycerin, erythritol arabit, xylimaat, mannitol, sorbit, sorbitan and the like.
Among these ester compounds, partially esterified products, particularly monoesterified products, are more preferable than stearic acid monoglyceride, behenic acid monoglyceride, or stearic acid monoglyceride and behenic acid because they can provide a more remarkable shrinkage prevention effect. More preferred are mixtures of monoglycerides.
Examples of aliphatic amines include dodecylamine, tetradecylamine, hexadecylamine, octadecylamine, eicosylamine, docosylamine, N-methyloctadecylamine, N-ethyloctadecylamine, hexadecylpropylenediamine, octadecylpropylenediamine, and the like. Can be mentioned.
Examples of the fatty acid amide include lauric acid amide, myristic acid amide, palmitic acid amide, stearic acid amide, N-methyl stearic acid amide, N-ethyl stearic acid amide, N, N-dimethyl stearic acid amide, N, N- Examples include diethylstearic acid amide, dilauric acid amide, distearic acid amide, trilauric acid amide, and tristearic acid amide.

According to the production method of the present invention, the polyolefin resin 100 has a multilayer structure of a foam core layer and a surface layer, and the blending ratio (A1) of the shrinkage inhibitor to the molten resin for forming the surface layer is the molten resin for forming the surface layer. The blending ratio (A2) of the shrinkage-preventing agent to the molten resin for forming the foam core layer is 0.5 parts by weight or more with respect to the weight part, and the blending of the shrinkage-preventing agent to the molten resin for forming the surface layer It is possible to suppress or prevent rapid shrinkage of the foam immediately after extrusion foaming by reducing the ratio (A1) or not containing an anti-shrink agent, and to further suppress shrinkage immediately after foaming. Compared with a single-layer foam composed only of a conventional foam core layer containing a sufficient shrinkage-preventing agent, the foaming agent emission rate during curing is faster, and the curing period can be shortened.
In order to prevent shrinkage immediately after foaming, a shrinkage inhibitor should be present at a high concentration only on the surface portion to prevent sudden diffusion of the foaming agent from the entire foam. After the foam has cooled, the anti-shrink agent is present at a high concentration only on the surface portion, and since the concentration of the anti-shrink agent inside the foam is low, the anti-shrink agent is present at a high concentration throughout the foam. In comparison, the foaming agent is quickly released from the foam. It is assumed that the above effect can be obtained.

The blending ratio (A1) of the shrinkage inhibitor to the molten resin for forming the surface layer is 0.5 parts by mass or more with respect to 100 parts by mass of the polyolefin resin of the molten resin. If the blending ratio is too small, the effect of preventing the shrinkage of the foam immediately after foaming becomes insufficient. On the other hand, when the blending ratio is excessive, it is not particularly limited from the viewpoint of preventing shrinkage, but the cost-preventing advantage cannot be obtained because the shrinkage preventing effect reaches its peak. The upper limit is about 3 parts by mass.
On the other hand, the blending ratio (A2) of the shrinkage inhibitor to the molten resin for forming the foam core layer is the blending ratio (A1) of the shrinkage inhibitor to the molten resin for forming the surface layer in order to shorten the curing time after coextrusion. In order to prevent the shrinkage-preventing agent from being transferred from the foam after removing the surface layer to the packaged product, 100 parts by mass of a polyolefin-based resin as a foamed core layer-forming molten resin. 0.3 parts by mass or less (including 0 parts by mass) is more preferable, and 0 parts by mass, that is, no addition is further preferable.

(2) Polyolefin resin In the present invention, examples of the polyolefin resin used for the foam core layer and the surface layer include a polyethylene resin, a polypropylene resin, and a mixture of two or more thereof. As the polyethylene-based resin, a copolymer of ethylene and a comonomer such as high-density polyethylene, low-density polyethylene, linear low-density polyethylene, and ethylene-vinyl acetate copolymer having an ethylene component exceeding 50 mol%. Furthermore, the mixture of 2 or more types of these is mentioned. Examples of polypropylene resins include propylene homopolymers, propylene-ethylene copolymers, propylene-butene copolymers, propylene copolymers such as propylene-ethylene-butene copolymers, and mixtures of two or more of these. Is mentioned. Among the polyolefin resins, a polyethylene resin is preferably used from the viewpoint of flexibility such as low surface hardness and excellent surface protection performance of the package. In particular, a foam using low density polyethylene having a low elastic modulus as a base resin tends to shrink immediately after extrusion foaming, and the production method of the present invention is particularly effective when foaming low density polyethylene.

In the present invention, the polyolefin resin used for the foamed core layer and the surface layer may be a styrene resin such as polystyrene, a rubber such as ethylene propylene rubber, styrene-butadiene- or the like, as long as the object and effect of the present invention are not impaired. Polymers other than polyolefin-based resins such as elastomers such as styrene block copolymers can be added. In that case, it is preferable that the polyolefin resin is contained in an amount of 60% by mass or more, more preferably 80% by mass or more, and particularly 90% by mass or more.
A preferred polyolefin resin used for each of the foam core layer and the surface layer will be described later.

(3) Foaming agent (foam core layer)
In the present invention, the polyolefin-based resin laminate foam is formed by laminating and coextruding a foam core layer forming molten resin containing butane as a foaming agent and a surface layer forming molten resin.
As mentioned above, these fluorocarbon foaming agents have come to use aliphatic hydrocarbons from the fact that the use of these fluorocarbon foaming agents has become difficult due to the manifestation of environmental problems such as ozone layer destruction and global warming. Since it is easy to extrude and foam a polyolefin resin, butane is used as a foaming agent among aliphatic hydrocarbons. Examples of butane include normal butane, isobutane, or a mixture of normal butane and isobutane. Among these, isobutane or a mixture of normal butane and isobutane having an isobutane ratio of 30 mol% or more is preferable, and isobutane is particularly preferable because it is difficult to dissipate from the foam immediately after foaming.

(4) Organic physical foaming agent (surface layer)
In the present invention, when a polyolefin-based resin laminated foam is formed by laminating a molten resin for forming a foam core layer and a molten resin for forming a surface layer and coextruding it, a plasticizing effect is imparted to the molten resin for forming a surface layer Therefore, it is desirable to add an organic physical foaming agent.
When an organic physical foaming agent is blended in the molten resin for forming the surface layer and the molten resin is plasticized, it is possible to adjust the cooling to lower the resin temperature of the molten resin to a temperature that does not hinder foaming of the foam core layer. In addition, it is possible to impart extensibility following the foam core layer. Such means is particularly effective when the foam core layer has a high expansion ratio, and the surface layer can be laminated on the foam core layer without causing cracks or tears in the surface layer. Furthermore, it becomes possible to produce a laminated foam having a low open cell ratio of the foam core layer.
When a preferable organic physical blowing agent is exemplified, the hydrocarbon compound is selected from an aliphatic hydrocarbon having 2 to 7 carbon atoms, an aliphatic alcohol having 1 to 4 carbon atoms, or an aliphatic ether having 2 to 8 carbon atoms. 1 type (s) or 2 or more types can be used, and especially a C3-C6 aliphatic hydrocarbon is used preferably. The use of the hydrocarbon compound is preferable from the viewpoint of efficiently plasticizing the molten resin for forming the surface layer. Examples of the aliphatic hydrocarbon having 2 to 7 carbon atoms include ethane, propane, normal butane, isobutane, normal pentane, isopentane, isohexane, cyclohexane, heptane, etc. Among these, it is preferable to use butane. , Isobutane, or a mixture of normal butane and isobutane having an isobutane ratio of 30 mol% or more is more preferable, and isobutane is particularly preferable.

(5) Manufacturing method of polyolefin resin laminate foam As shown in FIG. 1, a polyolefin resin 2, an antishrink agent 3, and if necessary, an organic physical foaming agent 4 are kneaded in a first extruder 11. For forming a foam core layer obtained by kneading a molten resin 5 for forming a surface layer, a polyolefin-based resin 6, a butane 8 as a foaming agent and, if necessary, a cell regulator and / or a shrinkage-preventing agent 7 in a second extruder 12. A laminated foam is obtained by laminating the molten resin 9 and the molten resin 9 for surface layer formation on the outer peripheral surface of the molten resin 9 for forming the foam core layer in the merging die 13 and co-extrusion from the merging die. .

(5-1) Molten resin for forming foam core layer The melt resin for forming foam core layer contains the polyolefin-based resin and butane as a foaming agent, and further contains a cell regulator and a shrinkage inhibitor as necessary. The
(I) Base resin The base resin of the molten resin for forming the foam core layer is a polyolefin resin having a melt flow rate (MFR) at 190 ° C. of 0.05 to 10 g / 10 min, and further 0.1 to 8 A polyethylene resin having a melt tension (MT) at 190 ° C. of 3 g to 30 cN and further 3.5 to 25 cN is preferable for obtaining a polyolefin resin foam layer having a desired apparent density. . Furthermore, it is preferable that the base resin is mainly composed of a polyethylene resin having a density of 0.900 to 0.935 g / cm ³ .
The melt flow rate (MFR) is a test temperature of 190 ° C. and a load of 21.18 N in the case of a polyethylene resin and a test temperature of 230 in the case of a polypropylene resin in accordance with JIS K7210 (1999) A method. It is a value measured at ° C. and a load of 21.18 N.

  The melt tension (MT) is a value measured according to ASTM D1238, and can be measured by, for example, Capillograph 1D manufactured by Toyo Seiki Seisakusho. 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. The set temperature of the cylinder and the orifice is 190 in the case of polyethylene resin. ℃, in the case of polypropylene resin, set to 230 ℃, put the required amount of sample in the cylinder, let stand for 4 minutes, then extrude the molten resin from the orifice into a string with the piston speed of 10 mm / min. Hang the string-like object on a 45 mm diameter tension detection pulley and increase the take-up speed at a constant speed so that the take-up speed reaches from 0 m / min to 200 m / min in 4 minutes. Take the maximum value of the tension just before the string-like material is broken. Here, the reason why the time until the take-up speed reaches 0 m / min to 200 m / min is set to 4 minutes is to suppress the thermal deterioration of the resin and increase the reproducibility of the obtained value. Using a different sample for the above operation, measuring a total of 10 times, removing the three values in order from the largest value of the maximum value obtained in 10 times, and the three values in order from the smallest value of the maximum value, The value obtained by arithmetically averaging the remaining four local maximum values is the melt tension (cN).

However, when the melt tension is measured by the method described above and the string-like material is not cut even when the take-up speed reaches 200 m / min, the melt tension obtained by setting the take-up speed to a constant speed of 200 m / min. The value of (cN) is adopted. Specifically, in the same manner as in the above measurement, the molten resin is extruded into a string from the orifice, and this string is put on a tension detection pulley, and a constant speed increase is made so that the speed reaches 0 m / min to 200 m / min in 4 minutes. Rotate the take-up roller while increasing the take-up speed, and wait until the rotation speed reaches 200 m / min. When the rotational speed reaches 200 m / min, the data acquisition of the melt tension is started, and the data acquisition is finished after 30 seconds. The average value (Tave) of the maximum tension value (Tmax) and the minimum tension value (Tmin) obtained from the tension load curve with the vertical axis obtained during the 30 seconds and the melt tension on the vertical axis and time on the horizontal axis. It is set as the melt tension in this specification.
Here, the Tmax is a value obtained by dividing the total value of detected peak (peak) values in the tension load curve by the detected number, and the Tmin is detected in the tension load curve. It is a value obtained by dividing the total value of the dip (valley) values by the detected number. Of course, when the molten resin is extruded from the orifice into a string shape in the above measurement, bubbles are prevented from entering the string as much as possible.

(B) Blending of foaming agent Butane is used as the foaming agent in the molten resin for forming the foam core layer as described above.
The addition amount of the foaming agent in the molten resin for forming the foam core layer is adjusted according to the target apparent density. That is, in order to obtain a foamed core layer having an apparent density of 18 to 90 kg / m ³ , the amount of butane added is preferably 3 to 35 parts by mass per 100 parts by mass of the polyolefin resin.
(C) Formulation of anti-shrink agent Considering the transferability of the anti-shrink agent from the foam to the body to be packaged, etc., the melt resin for forming the foam core layer should contain substantially no anti-shrink agent. Is preferred. On the other hand, after forming a laminated foam by extrusion foaming, in order to balance the dissipation rate of the foaming agent and the inflow rate of air into the bubbles, and to minimize deformation such as shrinkage of the foam, the foam core layer It is preferable to add a small amount of shrinkage inhibitor to the forming molten resin.
The blending ratio (A2) of the shrinkage-preventing agent to the foamed core layer-forming molten resin is such that the shrinkage-preventing agent is blended into the surface layer-forming molten resin (A1) so that the curing period after foaming does not become long. The concentration is less than the above, and from the viewpoint of the above-mentioned transferability, it is 0.3 parts by mass or less (however, the blending ratio (A2) includes 0 part by mass) with respect to 100 parts by mass of the polyolefin resin of the molten resin. It is preferable that the amount is 0 parts by mass. If the blending ratio (A2) of the shrinkage inhibitor to the molten resin for forming the foam core layer is 0.3 parts by mass or less, the practical problem of transferability to the package is almost eliminated. On the other hand, in order to keep the deformation of the foam during curing very small, it is preferable to be more than 0.3 parts by mass and 0.7 parts by mass or less with respect to 100 parts by mass of the polyolefin resin of the molten resin. Preferably it is more than 0.3 parts by mass and 0.5 parts by mass or less.

(D) Chemical foaming of blended foam core layer forming resins such as air conditioners, such as inorganic substances such as talc and calcium carbonate, sodium bicarbonate, and a mixture of sodium bicarbonate and citric acid as necessary An agent or the like can be blended as a bubble regulator. These bubble regulators can be used in combination of two or more. You may mix | blend a bubble regulator in the form of the masterbatch which consists of the same type polyolefin resin as the base resin of a foam core layer, and a bubble regulator. The amount of the cell regulator added can be adjusted according to the target cell diameter, but is preferably 0.01 to 10 parts by mass, more preferably 0.03 to 8 parts by mass with respect to 100 parts by mass of the polyolefin resin. Part by mass.

(5-2) Molten resin for surface layer formation (a) Base resin In the present invention, as the polyolefin resin of the base resin forming the surface layer, the same resin as the base resin of the foam core layer is used. be able to. From the viewpoint of adhesiveness with the foam core layer, it is preferable to use the same type of polyolefin resin as the foam core layer.
(B) Compounding of shrinkage inhibitor The blending amount of the shrinkage inhibitor into the molten resin for forming the surface layer is 0.5 parts by mass or more with respect to 100 parts by mass of the polyolefin resin of the molten resin as described above. When the blending amount of the anti-shrink agent is less than the above range, the anti-shrinkage effect is insufficient. On the other hand, when it exceeds the above range, the anti-shrinkage effect reaches a peak. From this viewpoint, the amount of the shrinkage inhibitor is preferably 0.5 to 2.5 parts by mass, and more preferably 0.6 to 1.5 parts by mass with respect to 100 parts by mass of the polyolefin resin of the molten resin.

(C) Formulation of organic physical foaming agent etc. In the production method of the present invention, the organic physical foaming agent is preferably blended with the molten resin for forming the surface layer. By plasticizing the molten resin for forming the surface layer with the organic physical foaming agent, it is possible to adjust the cooling to lower the resin temperature of the molten resin to a temperature that does not hinder foaming of the foamed layer, and follow the foamed layer. It becomes possible to give the extensibility to do.
As described above, the organic physical foaming agent is preferably an aliphatic hydrocarbon having 3 to 6 carbon atoms, and the use of butane is particularly preferable because the molten resin for forming the surface layer is efficiently plasticized.

It is preferable that the compounding quantity of an organic physical foaming agent is 2-50 mass parts with respect to 100 mass parts of polyolefin resin. By setting the blending amount of the organic physical foaming agent to 2 parts by mass or more, the surface layer forming molten resin for forming the polyolefin resin layer can be prevented from excessively generating heat during extrusion. Since foaming of the foam core layer can be prevented from being broken during foaming, it is easy to obtain a foam core layer having a closed cell structure even when the apparent density is small. Further, since the melt elongation of the surface layer is increased and the film forming property is improved, a desired shrinkage prevention effect is easily obtained.
On the other hand, by setting the blending amount of the organic physical foaming agent to 50 parts by mass or less, the kneadability between the organic physical foaming agent and the resin of the surface layer becomes sufficient, so that the ejection of the organic physical foaming agent from the die lip can be prevented, A desired shrinkage-preventing effect can be easily obtained without making a hole in the surface layer of the laminated foam.
That is, by setting the blending amount of the organic physical foaming agent in the above range, it is possible to ensure the effect of lowering the melt viscosity and improving the extensibility of the surface layer forming molten resin at the time of coextrusion. From this viewpoint, the blending amount of the organic physical foaming agent is more preferably 2.5 to 40 parts by mass, still more preferably 3 to 35 parts by mass with respect to 100 parts by mass of the polyolefin resin.

In the production method of the present invention, it is preferable to foam the surface layer to an apparent density of 18 to 180 kg / m ³ . When the apparent density of the surface layer is within the above range, the change in the foaming agent permeation rate at the interface between the surface layer and the foamed core layer is alleviated, and swelling and the like are less likely to occur. From this point of view, the apparent density of the surface layer is more preferably 20~70kg / ^{m 3,} more preferably from 23~60kg / ^{m 3.}
The ratio of the apparent density of the surface layer to the apparent density of the foam core layer (surface layer density / foam core density) is preferably 0.4 to 2.5. When the ratio is within the above range, the difference in bubble growth rate between the surface layer and the foam core layer during extrusion foaming is reduced, so that cracks and irregularities are less likely to occur in the surface layer, and the shrinkage prevention effect is stably expressed. It becomes easy to do. From this viewpoint, the ratio is more preferably 0.5 to 2.0, and still more preferably 0.6 to 1.7.

By co-extrusion so that the basis weight of the surface layer is a specific amount or more, for example, 50 g / m ² or more, it becomes easy to obtain a laminated foam having an apparent density of 18 to 180 kg / m ³ of the surface layer. . Moreover, in order to obtain the laminated foam in which the surface layer was foamed, it is preferable that a foam regulator is blended in the molten resin for forming the surface layer. When the basis weight of the surface layer is too small, or when no cell regulator is blended, the surface layer may not foam, and in this case, the organic physical foaming agent acts as the plasticizer.
As the bubble adjusting agent, the same type as that used for the foam core layer can be used, and in order to adjust the apparent density to the above range, it is preferably 0 with respect to 100 parts by mass of the polyolefin resin of the surface layer. 0.01 to 10 parts by mass, more preferably 0.03 to 8 parts by mass.
(D) Blending of other additives Various additives may be blended in the molten resin for forming the surface layer as required. Examples of the various additives include crystal nucleating agents, antioxidants, heat stabilizers, weathering agents, ultraviolet absorbers, flame retardants, inorganic fillers, antibacterial agents, and the like. In that case, the blending amount is preferably 10% by mass or less, more preferably 5% by mass or less, and still more preferably 3% by mass or less in the molten resin for forming the surface layer. The lower limit is approximately 0.01% by mass.

(5-3) Method for Producing Polyolefin-Based Resin Laminated Foam The melt resin 5 for forming the surface layer and the melt resin 9 for forming the foam core layer are adjusted to an appropriate temperature in each of the extruders 11 and 12, and then merged. By laminating in the die 13 and co-extrusion from the die 13, a laminated foam in which the surface layer is laminated on the outer peripheral surface of the foam core layer is formed. As the shape of the lip opening at the tip of the die, a circular shape, an elliptical shape, a square shape, a rectangular shape, a star shape, a triangular shape, or the like can be used according to the desired foam shape.
The appropriate temperature in the extruder 12 of the molten resin 9 is a temperature at which the molten resin 9 exhibits optimum viscoelasticity for forming a foam core layer. The appropriate temperature of the molten resin 5 in the extruder 11 is a temperature at which the molten resin 5 exhibits good extensibility for forming the surface layer and does not hinder the formation of the foam core layer. Specifically, the appropriate temperature of the molten resins 9 and 5 is not less than [crystallization temperature + 5 ° C.] and not more than [crystallization temperature + 30 ° C.] of the olefin resin of each layer, and The appropriate temperature relationship is that the temperature of the molten resin 5 for forming the surface layer is not less than [temperature of the molten resin for forming the foam core layer −30 ° C.] or more and [temperature of the molten resin for forming the foam layer + 30 ° C.] or less. From the viewpoint of suppressing a decrease in the open cell ratio of the foam core layer and shrinkage of the resulting laminated foam, more preferably, the temperature of the molten resin 5 for forming the surface layer is [the temperature of the melt resin for forming the foam core layer -15 ° C. The above is [the temperature of the molten resin for forming the foam core layer + 15 ° C.] or less.

  In this specification, the crystallization temperature is JIS K7122 (1987) in accordance with JIS K7122 (1987) at a heating rate of 10 ° C./min. The vertex temperature of the crystallization heat amount peak of the DSC curve obtained when the temperature is lowered to 40 ° C. is defined as the crystallization temperature (° C.).

The production method of the present invention is particularly effective for polyolefin resin foams having an apparent density of 18 to 90 kg / m ³ and a thickness of 30 mm or more, which are likely to shrink immediately after foaming, and preferably an apparent density of 20 to 70 kg / m. ³ , more preferably effective for polyolefin resin foams having an apparent density of 23 to 60 kg / m ³ .

(Apparent density of foam core layer)
In the present invention, the apparent density of the foam core layer is obtained by removing the surface layer from the laminated foam, dividing the mass of the remaining foam core layer by the volume of the foam core layer, and converting the unit to [kg / m ³ ]. Can be sought. In addition, what is necessary is just to obtain | require the volume of a foam core layer from the submergence method or an external dimension.

(Total thickness of laminated foam)
When the shape of the laminated foam is plate-like, the total thickness of the laminated foam can be obtained by the following method. In the vertical cross section of the laminated foam in the width direction, the thickness [mm] of the laminated foam was measured at 10 points in the width direction at equal intervals, and the arithmetic average value of the thickness [mm] of the laminated foam at each measured point was laminated and foamed. The thickness of the body [mm].
In addition, when the shape of the laminated foam is an irregular shape such as a cylindrical shape or an elliptical column shape, the surface on the opposite side passes through the center of the laminated foam from one surface in a cross section perpendicular to the extrusion direction of the laminated foam. When the straight line is drawn, the distance of the straight line with the shortest distance is defined as the total thickness of the laminated foam.

(Apparent density of surface layer)
The apparent density of the surface layer can be determined by dividing the surface layer from the laminated foam, dividing the mass of the surface layer by the volume of the surface layer, and converting the unit to [kg / m ³ ]. Note that the volume of the surface layer may be obtained by a submerging method or the like.

(Ratio (m / t) between the basis weight m [g / m ² ] of the surface layer of the laminated foam and the thickness t [mm] of the laminated foam)
In the production method of the present invention, the ratio (m / t) between the basis weight m [g / m ² ] of the surface layer and the thickness t [mm] of the laminated foam is preferably 0.5 or more.
It is desirable that the basis weight (g / m ² ) as the amount of lamination of the surface layer is a certain amount or more with respect to the thickness of the entire laminated foam. This is because the time required to increase the air partial pressure at the center of the foam depends on the thickness of the entire laminated foam. The amount of the surface layer that adjusts the diffusion rate of the foaming agent depends on the overall thickness of the laminated foam. It is necessary to increase corresponding to the increase. The ratio (m / t) of the basis weight (m [g / m ² ]) of the surface layer to the thickness (t [mm]) of the entire laminated foam necessary to prevent shrinkage after foaming of the laminated foam is 0.00. 5 g / (m ² · mm) or more is desirable.
In addition, when the shrinkage inhibitor addition ratio of the foam core layer is 0.3% by mass or less, the ratio of the basis weight of the surface layer to the total thickness of the laminated foam necessary for preventing shrinkage after foaming (m / t) Is more preferably 1.0 g / (m ² · mm) or more, more preferably 1.2 or more, and particularly preferably 1.4 or more.

(Basis weight of surface layer)
The basis weight of the surface layer can be determined by the following formula from the discharge amount of the molten resin for forming the surface layer, the circumferential length of the laminated foam peripheral surface, and the take-up speed when producing the laminated foam.
Surface layer basis weight [g / m ² ] = discharge amount [g / hr] / (peripheral length [m] × take-off speed [m / hr])

(Average cell diameter ratio between surface layer and foam core layer)
When the surface layer is foamed, if there is a large difference in the average cell diameter between the surface layer and the foamed layer, voids are generated at the interface due to the difference in foaming speed, and the foaming agent flows into the voids. Prone to swelling during curing. In order to prevent the occurrence of such blistering, the ratio (a / b) of the bubble diameter a of the surface layer to the bubble diameter b of the foam core layer is preferably 0.3-3. 5 to 2 is more preferable, and 0.75 to 1.5 is even more preferable.
The average bubble diameter is a value measured as follows. The foam is cut in a cross section perpendicular to the extrusion direction, and the portion of the foam core layer on the cut surface is enlarged about 50 times with a microscope or the like to obtain an enlarged image. For all the bubbles in the foam core layer existing on the image, the length d [mm] of the longest part of each bubble is measured. This measurement is performed on arbitrary five points in the same cross section, and the average bubble diameter of the foam core layer is obtained by arithmetically averaging d [mm] measured for each bubble. This measurement is also performed on the surface layer, and the average bubble diameter of the surface layer is obtained in the same manner.

By the amount of the anti-shrinking agent to the foamed core layer is removed and the surface layer from a very small laminated foam, or migration of the anti-shrinking agent to the package is extremely small, or the migration is not a polyolefin resin foam You can get a body.
In particular, when the amount of the anti-shrinkage agent is 0% by mass, an ideal foam is obtained because the anti-shrinkage agent does not migrate to the package. Such a foam is particularly useful as a cushioning material for medical / electronic parts.
In addition, after making a foaming agent residual amount 1 mass% or less and making the air partial pressure in a bubble 0.95 atm or more, the foam which does not produce a dimensional change is obtained by excising a surface layer from a laminated foam. I can do it.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples.
The following are the raw materials used in the examples, polyolefin resins, shrinkage inhibitors, bubble regulators, and evaluation methods.
(1) Raw material (a) Polyolefin resin low density polyethylene (hereinafter sometimes referred to as LD1)
Product name: NUC8321 (density 922 g / L, MFR = 2.4 g / 10 min), manufactured by Nippon Unicar Co., Ltd.
(B) Polyolefin-based resin low density polyethylene (hereinafter sometimes referred to as LD2)
Product name: NUC8008 (density 918 g / L, MFR = 4.7 g / 10 min), manufactured by Nippon Unicar Co., Ltd.
(C) Shrinkage inhibitor stearic acid monoglyceride (d) Bubble regulator talc (manufactured by Matsumura Sangyo Co., Ltd., high filler # 12)

(2) Evaluation method (b) Thickness of laminated foam and apparent density immediately after coextrusion (total thickness of laminated foam)
The thickness of the laminated foam was cut vertically immediately calling foam after producing the laminated foam to the extrusion direction was measured thickness of the laminated foam by the method described above the cross-section as a target.
(Apparent density of foam core layer)
Immediately after producing the laminated foam, a measurement sample having a size of about 20 mm × 20 mm × 20 mm was cut out from the vicinity of the center of the foam core layer, and the volume of the measurement sample was determined from the outer dimensions, and the mass of the sample was determined. The apparent density of the foam core layer was calculated by dividing by volume.
(Apparent density of surface layer)
Immediately after producing the laminated foam, after cutting the surface layer portion from the laminated foam so as not to include the foam core layer, and measuring the mass of the cut surface layer portion, the volume is determined by a submerging method, The apparent density of the surface layer was calculated by dividing the mass by the volume.

(B) Bubble diameter ratio According to the above method, the average bubble diameter of the foam core layer and the surface layer was measured to obtain the bubble diameter ratio.
(C) Basis weight of the surface layer The basis weight of the surface layer was determined from the relationship between the discharge amount of the surface layer, the foam circumference, and the take-up speed.
(D) Specific volume retention The specific volume retention is the specific volume Vb of the laminated foam after curing for an arbitrary period in an atmosphere of 50 ° C. and 50% relative humidity with respect to the specific volume Va of the laminated foam immediately after foaming. Ratio. The specific volume of the laminated foam is the reciprocal of the apparent density of the laminated foam.
Specific volume retention [%] = (specific volume Vb [cm ³ / kg] after curing for an arbitrary period ÷ specific volume Va [cm ³ / kg] immediately after foaming) × 100
(E) Shrinkage ◎ when the specific volume retention is 90% or more after 3 days from production and after 1 week, ◎, when both are 60% or more and less than 90%, When either one was less than 60%, Δ was evaluated, and when either was less than 60%, the evaluation was ×.

(F) Days of foaming agent release completion The number of days of foaming agent release completed is 1 mass of the foaming agent remaining amount (butane) in the foam core layer when the laminated foam is cured under an atmosphere of 50 ° C. and 50% relative humidity. It is the number of days required to become less than%.
(G) About 1 g of a test piece was cut out from the center of the foaming agent remaining laminate foam. This test piece was immersed in a 45 cc solvent in which a known amount of cyclopentane was added to toluene in a closed container at room temperature for 24 hours, and the blowing agent (butane) remaining in the test piece was extracted into the solvent. The amount of butane extracted in the solvent was quantified by gas chromatography (internal standard method), and the amount of foaming agent remaining in the foam core layer was determined from the mass of the test piece measured in advance.
(H) Curing completion days Curing completion days are such that when the laminated foam is cured under an atmosphere of 50 ° C. and a relative humidity of 50%, the remaining amount of the foaming agent is 1% by mass or less and the specific volume retention of the foam is The number of days required to reach 90% or more.
(L) Apparent density and thickness after completion of curing After completion of curing, the apparent density of the foam core layer, the apparent density of the surface layer, and the thickness of the entire laminated foam were determined in the same manner as described above.

[Examples 1, 2, and 3]
As the foam core layer forming extruder, a single-screw first extruder having an inner diameter of 90 mm and a single-screw second extruder having an inner diameter of 120 mm were connected in series. A single-screw third extruder having an inner diameter of 115 mm was used as the surface layer forming extruder. A co-extrusion apparatus was used in which a co-extrusion die was attached to the outlet of the second extruder, and a third extruder was connected to the co-extrusion die. Low density polyethylene (LD1) as a polyolefin-based resin, a shrinkage inhibitor, and a cell regulator are added to the first extruder in the formulation shown in Table 1, and after melt-kneading, as a butane as a foaming agent in the extruder, Table 1 The amount of isobutane shown in FIG. 5 was injected and kneaded again, and then cooled in a second extruder to obtain a molten resin for forming a foam core layer having a target resin temperature. In addition, the compounding quantity of a shrinkage prevention agent, a bubble regulator, and butane is a value with respect to 100 mass parts of polyolefin resin of the molten resin for foaming core layer formation.
Similarly, low density polyethylene (LD2) as a polyolefin-based resin, an anti-shrinkage agent, and a cell regulator are supplied to the third extruder with the formulation shown in Table 1, and after melt-kneading, the organic physical foaming agent is shown in Table 1. The indicated amount of isobutane was injected, kneaded again, and then cooled to obtain a molten resin for forming a surface layer having a target resin temperature. In addition, the compounding quantity of a shrinkage inhibitor, a bubble regulator, and an organic physical foaming agent is a value with respect to 100 mass parts of polyolefin resin of the molten resin for surface layer formation.
The molten resin for forming the foam core layer and the molten resin for forming the surface layer are each extruded into the coextrusion die at the discharge amounts shown in Table 1, and the molten resin for forming the surface layer is laminated on the peripheral surface of the molten resin for forming the foam core layer. Then, it was extruded from a die lip having a hole diameter of 8.7 mm attached to the tip of the coextrusion die and foamed into a cylindrical shape. The obtained laminated foam was sandwiched by a conveyor and taken up to obtain a cylindrical laminated foam. The evaluation results are shown in Tables 2 and 3.

[Comparative Examples 1 and 2]
As Comparative Example 1, a laminated foam was obtained in the same manner as described in Example 2, except that the amount of the shrinkage-preventing agent shown in Table 1 was added to the molten resin for forming the foam core layer and the molten resin for forming the surface layer. It was.
As Comparative Example 2, a laminated foam was prepared in the same manner as described in Example 2, except that the shrinkage inhibitor was not added to the foamed core layer forming molten resin and the surface layer forming molten resin as shown in Table 1. Obtained.
The evaluation results are shown in Tables 2 and 3.

[Examples 4, 5, and 6]
As an extruder for forming a foam core layer, a single-screw first extruder having an inner diameter of 50 mm in which an accumulator A having an inner diameter of 90 mm is attached to the outlet of the extruder is used. As an extruder for forming a surface layer, an inner diameter is provided at the outlet of the extruder. A single-screw second extruder having an inner diameter of 45 mm, to which a 30 mm accumulator B was attached, was used. An accumulator B outlet is connected near the center of the accumulator A in the direction of extrusion, and a co-extrusion apparatus is used in the accumulator A that can laminate the surface layer forming molten resin on the peripheral surface of the foam core layer forming molten resin. It was.
Low density polyethylene (LD1) as a polyolefin-based resin, a shrinkage inhibitor, and a cell regulator are added to the first extruder in the formulation shown in Table 1, and after melt-kneading, as a butane as a foaming agent in the extruder, Table 1 The amount of isobutane shown in the above was injected, kneaded again, and cooled to obtain a foamed core layer forming molten resin having a target resin temperature. In addition, the compounding quantity of a shrinkage prevention agent, a bubble regulator, and butane is a value with respect to 100 mass parts of polyolefin resin of the molten resin for foaming core layer formation.
Similarly, low density polyethylene (LD2), an anti-shrinkage agent, and a cell regulator are charged into the third extruder with the formulation shown in Table 1, and after melt-kneading, the organic physical foaming agent is added to the extruder as shown in Table 1. The indicated amount of isobutane was injected, kneaded again, and then cooled to obtain a molten resin for forming a surface layer having a target resin temperature. In addition, the compounding quantity of a shrinkage inhibitor, a bubble regulator, and an organic physical foaming agent is a value with respect to 100 mass parts of polyolefin resin of the molten resin for surface layer formation.
The molten resin for forming the foam core layer is introduced into the accumulator A and the molten resin for forming the surface layer is introduced into the accumulator B and filled, and after filling the mass of the target foam, each gate is opened, A hole diameter of 15.15 is attached to the tip of the accumulator A by pressing at a speed that achieves the target instantaneous discharge amount, laminating the molten resin for forming the surface layer on the peripheral surface of the molten resin for forming the foam core layer at the intermediate portion of the accumulator. A cylindrical laminated foam was obtained by extruding from a 6 mm die lip and foaming in a cylindrical shape, and taking and cooling the resulting laminated foam sandwiched by a conveyor. The evaluation results are shown in Tables 2 and 3.

[Comparative Examples 3 and 4]
As Comparative Example 3, a laminated foam was molded in the same manner as described in Example 4 except that the shrinkage-preventing agent shown in Table 1 was added to the foamed core layer-forming molten resin and the surface layer-forming molten resin.
As Comparative Example 4, a laminated foam was obtained in the same manner as described in Example 4 except that the shrinkage inhibitor was not added to the foamed core layer-forming molten resin and the surface layer-forming molten resin as shown in Table 1. It was.
The evaluation results are shown in Tables 2 and 3.

[Examples 7, 8, and 9]
In the same manner as in Example 3 except that a slit-shaped die lip having a width of 70 mm and a clear 2.6 mm was used instead of the die lip having a hole diameter of 15.6 mm, a plate-like shape (width 300 mm, long Thickness of 1000 mm) was obtained. The evaluation results are shown in Tables 4 and 5.
Further, the surface contamination of the foam obtained by removing the surface layer from the laminated foam obtained in Example 8 was evaluated. The evaluation results are shown in Tables 4 and 5.

[Comparative Examples 5, 6, 7]
A laminated foam having a plate shape (width 300 mm, length 1000 mm) was obtained in the same manner as described in Example 8 under the conditions shown in Table 1. The evaluation results are shown in Tables 4 and 5.
Further, the surface contamination property of the foam obtained by removing the surface layer from the laminated foam obtained in Comparative Example 5 was evaluated.
First, 10 plate glasses having a thickness of 1 mm were stacked, and the haze of the glass plate laminate was measured in accordance with JIS K7136 (2000). This plate glass is divided into one piece, and for each plate glass, the plate glass is sandwiched between foams from which the surface layer is removed, and a load of 10 gf / cm ² is applied evenly from one foam side to 60 ° C., It left still in the atmosphere of humidity 50%. After 72 hours, the foam was removed, 10 plate glasses were stacked, and the haze of the glass plate laminate was measured in the same manner as described above. Subtract the haze of the glass plate laminate before sandwiching with the foam from the haze of the glass plate laminate after sandwiching with the foam, and if the difference is less than 1%, 1% or more and less than 5% The case was evaluated as Δ and 5% or more as x. It means that the smaller this difference is, the lower the surface contamination with respect to the package.
The evaluation results are shown in Table 6.

[Examples 10 and 11]
A laminated foam having a plate shape (width 300 mm, length 1000 mm) was obtained in the same manner as described in Example 8 except that the die lip clear was changed to 5.2 mm.
The evaluation results are shown in Tables 4 and 5.

[Comparative Examples 8 and 9]
Under the conditions shown in Table 1, a plate-like (width 300 mm, length 1000 mm) laminated foam was obtained in the same manner as described in Example 10. The evaluation results are shown in Tables 4 and 5.

DESCRIPTION OF SYMBOLS 1 Polyolefin resin laminated foam 2 Polyolefin resin 3 Shrinkage prevention agent 4 Organic physical foaming agent 5 Molten resin for surface layer formation 6 Polyolefin resin 7 Shrinkage prevention agent 8 Foaming agent 9 Molten resin 11 for foam core layer formation Surface layer formation Extruder 12 Foam core layer forming extruder 13 Coextrusion die

Claims (7)

Laminated foaming is performed by laminating and coextruding a melt resin for forming a surface layer using a polyolefin resin as a base resin on the outer peripheral surface of a melt resin for forming a foam core layer obtained by kneading a polyolefin resin and butane. A method for producing a laminated foam comprising a foam core layer and a surface layer, wherein the thickness of the whole body is 30 mm or more and the apparent density of the foam core layer is 18 to 90 kg / m ³ ,
In the molten resin for forming the surface layer, a shrinkage inhibitor composed of a fatty acid ester, an aliphatic amine or a fatty acid amide is blended in an amount of 0.5 parts by mass or more with respect to 100 parts by mass of the polyolefin resin of the molten resin for forming the surface layer. (A1) is blended,
In the molten resin for forming the foam core layer, a shrinkage-preventing agent comprising a fatty acid ester, an aliphatic amine or a fatty acid amide is added to 100 parts by mass of the polyolefin resin of the molten resin for forming the foam core layer. A polyolefin-based resin characterized in that it is blended at a blending ratio less than the blending ratio (A1) of an anti-shrinkage agent or a shrinkage-preventing agent comprising a fatty acid ester, aliphatic amine or fatty acid amide is not blended. A method for producing a laminated foam. The blending ratio (A2) of the shrinkage inhibitor composed of fatty acid ester, aliphatic amine or aliphatic amide to the molten resin for forming the foam core layer is 0 with respect to 100 parts by mass of the polyolefin resin of the melt resin for forming the foam core layer. The method for producing a polyolefin-based resin laminate foam according to claim 1, wherein the content is 3 parts by mass or less (including 0 part by mass). The method for producing a polyolefin-based resin laminate foam according to claim 1 or 2, wherein the apparent density of the surface layer is 18 to 180 kg / m ³ .   The method for producing a polyolefin-based resin laminate foam according to any one of claims 1 to 3, wherein an organic physical foaming agent is blended in the molten resin for forming the surface layer. 5. The ratio (m / t) between the basis weight m [g / m ² ] of the surface layer and the thickness t [mm] of the laminated foam is 0.5 or more. The manufacturing method of the polyolefin resin laminated foam in any one.   The method for producing a polyolefin resin laminated foam according to any one of claims 1 to 5, wherein the polyolefin resin of the foam core layer is low density polyethylene. Claim 2 production excluding take surface layer from the resulting laminate foams by the method described in method for producing a polyolefin resin foam.

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